United States Office of Pollution EPA 744-B-97-001
Environmental Protection Prevention and Toxics June 1997
Agency (7406)
&EPA Polymer Exemption
Guidance Manual
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POLYMER EXEMPTION GUIDANCE MANUAL
5/22/97
A technical manual to accompany, but not supersede the
"Premanufacture Notification Exemptions; Revisions of Exemptions
for Polymers; Final Rule" found at 40 CFR Part 723, (60) FR
16316-16336, published Wednesday, March 29, 1995
Environmental Protection Agency
Office of Pollution Prevention and Toxics
401 M St., SW.,
Washington, DC 20460-0001
Copies of this document are available through the TSCA
Assistance Information Service at (202) 554-1404 or by faxing
requests to (202) 554-5603.
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LIST
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TABLE OF CONTENTS
OF EQUATIONS
OF FIGURES
OF TABLES
INTRODUCTION
HISTORY
DEFINITIONS
ELIGIBILITY REQUIREMENTS
4.1. MEETING THE DEFINITION OF A POLYMER AT 40 CFR §723. 250 (b) . . .
4.2. SUBSTANCES EXCLUDED FROM THE EXEMPTION AT 40 CFR §723. 250 (d)
4.2.1. EXCLUSIONS FOR CATIONIC AND POTENTIALLY CATIONIC
POLYMERS
4.2.1.1. CATIONIC POLYMERS NOT EXCLUDED FROM EXEMPTION
4.2.2. EXCLUSIONS FOR ELEMENTAL CRITERIA
4.2.3. EXCLUSIONS FOR DEGRADABLE OR UNSTABLE POLYMERS ....
4.2.4. EXCLUSIONS BY REACTANTS
4.2.5. EXCLUSIONS FOR WATER-ABSORBING POLYMERS
4.3. CATEGORIES WHICH ARE NO LONGER EXCLUDED FROM EXEMPTION ....
4.4. MEETING EXEMPTION CRITERIA AT 40 CFR §723. 250 (e)
4.4.1. THE (e) (1) EXEMPTION CRITERIA
4.4.1.1. LOW- CONCERN FUNCTIONAL GROUPS AND THE (e) (1)
EXEMPTION
4.4.1.2. MODERATE -CONCERN FUNCTIONAL GROUPS AND THE (e)
EXEMPTION
4.4.1.3. HIGH-CONCERN FUNCTIONAL GROUPS AND THE
(e) (1) EXEMPTION
4.4.2. THE (e) (2) EXEMPTION CRITERIA
4.4.3. THE (e) (3) EXEMPTION CRITERIA
NUMERICAL CONSIDERATIONS
5.1. CALCULATING NUMBER-AVERAGE MOLECULAR WEIGHT
5.1.1. GEL PERMEATION CHROMATOGRAPHY
5.1.2. MEMBRANE OSMOMETRY
5.1.3. VAPOR- PHASE OSMOMETRY
5.1.4. VAPOR PRESSURE LOWERING
5.1.5. EBULLIOMETRY
5.1.6. CRYOSCOPY
5.1.7. END-GROUP ANALYSIS
5.2. THE TWO PERCENT RULE AND CHEMICAL IDENTITY
5.2.1. PERCENT CHARGED METHOD
5.2.2. PERCENT INCORPORATED METHOD
5.2.3. METHODS FOR DETECTION OF POLYMER COMPOSITION
5.2.3.1. MASS SPECTROMETRY
5.2.3.2. GAS CHROMATOGRAPHY
5.2.3.3. INFRARED SPECTROSCOPY
5.2.3.4. NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY . . .
5.2.3.5. X-RAY DIFFRACTION ANALYSIS
5.3. CALCULATING FUNCTIONAL GROUP EQUIVALENT WEIGHT
5.3.1. END-GROUP ANALYSIS
5.3.2. MORE COMPLEX FGEW CALCULATIONS
5.3.3. DETERMINING FGEW BY NOMOGRAPH
OTHER REGULATIONS AND REQUIREMENTS
COMMON QUESTIONS AND ANSWERS
REFERENCES
FEDERAL REGISTER REFERENCES
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(1)
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LIST OF EQUATIONS
1. NUMBER AVERAGE MOLECULAR WEIGHT 16
2. WEIGHT AVERAGE MOLECULAR WEIGHT 16
3. PERCENT BY WEIGHT CHARGED 20
4. RATIO A (WEIGHT PERCENT OF FRAGMENT / MOLECULAR WEIGHT OF FRAGMENT) 22
5. WEIGHT PERCENT OF REACTANT INCORPORATED 22
6. MONOMER EQUIVALENT WEIGHT 27
7. DEGREE OF BRANCHING 27
8. TOTAL NUMBER OF POLYMER END GROUPS (FOR BRANCHED POLYMERS) .... 28
9. FUNCTIONAL GROUP EQUIVALENT WEIGHT (BASIC EQUATION) 29
10. WEIGHT PERCENT OF REACTIVE GROUP 29
11. FUNCTIONAL GROUP EQUIVALENT WEIGHT (FUNCTION OF NUMBER OF GROUPS IN
MONOMER) 30
12. COMBINED FUNCTIONAL GROUP EQUIVALENT WEIGHT 30
LIST OF FIGURES
1.
2.
3.
4.
5 .
6 .
7 .
8.
9 .
10.
11.
12.
SEQUENCE CRITERIA EXAMPLE 1: ETHOXYLATED BENZENETETROL
SEQUENCE CRITERIA EXAMPLE 2 : ETHOXYLATED HYDROQUINONE
SEQUENCE CRITERIA EXAMPLE 3 : ETHOXYLATED GLYCEROL
SEQUENCE CRITERIA EXAMPLE 4 : GLYCEROL TRIESTER
SEQUENCE CRITERIA EXAMPLE 5: EPOXY RESIN
POLYVINYL ALCOHOL AND WEIGHT PERCENT
ISOCYANATE-TERMINATED URETHANE AND FUNCTIONAL GROUP EQUIVALENT WEIGHT
EPOXIDE-CAPPED NOVOLAK AND FUNCTIONAL GROUP EQUIVALENT WEIGHT . . .
ACRYLATE WITH MULTIPLE FUNCTIONAL GROUPS
UNCONSUMED AMINES AND COMBINED FUNCTIONAL GROUP EQUIVALENT WEIGHT .
REPEATING UNITS, A POLYAMINE AND FUNCTIONAL GROUP EQUIVALENT WEIGHT
NOMOGRAPH FOR DETERMINING FUNCTIONAL GROUP EQUIVALENT WEIGHT . . .
5
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6
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LIST OF TABLES
1. DISTRIBUTION CRITERIA EXAMPLES 6,7 AND 8: ETHOXYLATED ALCOHOLS
2. COMBINED FUNCTIONAL GROUP EQUIVALENT WEIGHT SUMMARY
3. (e)(3) MONOMER AND REACTANT LIST
4. ALLOWABLE THRESHOLDS FOR REACTIVE FUNCTIONAL GROUPS
7
12
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1. INTRODUCTION
The Environmental Protection Agency (EPA) published a series of proposed
rules (USEPA 1993a-1993d) in the Federal Register on February 8, 1993 to
announce the Agency's plan to amend premanufacture notification (PMN)
regulations for new chemical substances under §5 of the Toxic Substances
Control Act (TSCA). Included were proposed amendments to the polymer
exemption rule originally published on November 21, 1984 (USEPA 1984) under
the auspices of § 5(h)(4) of TSCA and entered into the Code of Federal
Regulations (CFR), the administrative rules under which the U.S. Government
operates, at 40 CFR Chapter I, Subchapter R, part 723.250.
After the proposed polymer exemption rule was published, the Agency
considered public comments, consulted with European counterparts, and utilized
the experience gained in the review of over 12,000 polymers in publishing its
new final rule for polymer exemptions on March 29, 1995, amending 40 CFR
§723.250 (USEPA 1995). The new polymer exemption rule is notably different
from that originally published in 1984 and it is the purpose of this technical
manual to provide the regulated community with additional insight, so that
manufacturers and importers will be able to determine if their new chemical
substances are eligible for the polymer exemption under the new rule.
Substances submitted before May 30, 1995 are subject to the original rule
(USEPA 1984) and its requirements. On or after that date, all polymer
exemptions are subject to the new rule and its requirements.
A few notable features of the 1995 Polymer Exemption are as follows:
• Manufacturers and importers are no longer required to submit notice
prior to manufacture or import. However, manufacturers and importers
must submit an annual report for those exempt polymers whose manufacture
or import has commenced for the first time during the preceding calendar
year, as stipulated in §723.250(f), and the manufacturer or importer of
an exempt polymer must comply with all recordkeeping requirements at
§723.250(j).
• A new method can be used for determining which monomers and reactants
are considered part of the polymer's chemical identity
(modification of the so-called "Two Percent Rule").
• More polymers are now eligible for exemption because previous exclusions
have been modified or eliminated. Some of the changes are in
regard to halogens, cyano groups, biopolymers and reactive group
limitations.
• Certain high molecular weight polymers once considered eligible for
submission under the 1984 exemption are not eligible for this
exemption.
The EPA hopes this technical manual will: (1) assist the chemical
manufacturer or importer in determining whether the PMN substance is a polymer
as defined by the polymer exemption rule, (2) guide the manufacturer or
importer in determining whether the polymer meets the exemption criteria of
the rule and (3) assist the manufacturer or importer in determining whether
the polymer is excluded from exemption by certain factors. In addition, this
manual provides technical guidance and numerous pertinent examples of
decision-making rationales.
The Agency hopes that after reviewing this document prospective
manufactures and importers will be able to decide easily whether the polymer
exemption is applicable to any of their new substances. This technical
guidance manual is not intended to substitute for or supersede the regulations
as found at 40 CFR §723.250 and the Federal Register (USEPA 1995).
Manufacturers and importers must read those provisions to assure compliance
with all the procedural and recordkeeping requirements of the polymer
exemption.
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2. HISTORY
Section 5 of TSCA contains provisions that allow the Agency to review
new chemical substances before they are manufactured or imported. Section
5(a)1 of TSCA requires that persons notify EPA at least 90 days prior to the
manufacture or import of a new chemical substance for commercial purposes. A
"new" chemical substance is one that is subject to TSCA but is not already
included on the TSCA Chemical Substance Inventory. If the Agency determines
that a new chemical substance may present an unreasonable risk of injury to
human health or the environment or if there is insufficient information to
establish that no such risk exists, the Agency may limit the manufacture,
processing, distribution in commerce, use, or disposal of the new chemical
substance under the authority provided in TSCA §5(e).
From the beginning of the PMN program in 1979 until 1984 all new
chemical substances, including polymers, were subject to the full reporting
requirements of the premanufacture notification process. Under §5(h)(4) the
Agency has authority to promulgate rules granting exemptions from some or all
of the premanufacture requirements for new chemicals if the Agency determines
that the manufacturing, processing, distribution in commerce, use, or disposal
of a new chemical substance will not present an unreasonable risk of injury to
human health or the environment.
Through its experience in reviewing new chemical substances, the Agency
identified certain criteria to determine which polymers were most unlikely to
present an unreasonable risk of injury to human health or the environment.
This experience led to the original polymer exemption rule under §5(h)(4)
allowing polymers that met certain criteria under these conservative
guidelines to be exempt from some of the reporting requirements for new
chemicals (USEPA 1984) .
Since the EPA published the 1984 TSCA polymer exemption rule, the Agency
has reviewed over 10,000 polymer submissions under the standard 90 day PMN
review process and an additional 2,000 polymer exemption notices. With the
experience gained by the review of this large number of submissions, the
Agency reevaluated the criteria used to identify those polymers which were
unlikely to present unreasonable risks. This led to the proposal of a revised
polymer exemption rule that would increase the number of polymers qualifying
for exemption and enable the Agency to concentrate its limited resources on
those polymers that do not meet the polymer exemption criteria and on non-
polymeric new chemical substances that may present greater risks. The
amendments are expected to result in resource savings for industry as well as
the EPA.
The new polymer exemption rule amends appropriate sections of
40 CFR 723.250 to allow certain polymers to be exempt from the reporting
requirements for new chemicals and imposes new restrictions on a limited set
of polymers that were previously eligible for the exemption (USEPA 1993d). To
be eligible for the exemption, a new chemical substance must: 1) meet the
polymer definition, 2) meet one of three exemption criteria and 3) not be
excluded. The definition of polymer, for purposes of the new exemption, is
found at 40 CFR §723.250(b). There are now three exemption types, located at
40 CFR §723.250(e)(1), (e)(2), and (e)(3), subsequently referred to as the
(e)(1), (e)(2), and (e)(3) criteria. Excluded categories are listed at
40 CFR §723.250(d) of the new rule.
The definition of polymer, the key components of each of the three
exemption types, and the categories excluded from the exemption are discussed
below. The remainder of this technical manual provides prospective submitters
with information helpful for establishing whether or not their new chemical
substances meet the exemption criteria.
The (e)(1) exemption concerns polymers with a number-average molecular
weight (NAVG MW) in a range that is greater than or equal to 1,000 (> 1000)
daltons and less than 10,000 (<10,000) daltons.
Dalton - precisely 1.0000 atomic mass unit or 1/12 the mass of a carbon
atom of mass 12. Hence, a polymer with a molecular weight of 10,000
atomic mass units has a mass of 10,000 daltons.
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For the (e)(1) exemption, oligomer content must be less than 10 percent
by weight below 500 daltons and less than 25% by weight below 1,000 daltons.
The polymer must also meet functional group criteria to be described in a
later section of this manual.
Oligomer (in the context of the rule and this manual) - a low molecular
weight species derived from the polymerization reaction. The
Organization for Economic Cooperation and Development (OECD) has a draft
guidelines document1 for determining the low molecular weight polymer
content.
For the (e)(2) exemption, the NAVG MW for eligible polymers must be
greater than or equal to 10,000 daltons and these polymers must have oligomer
content less than two percent below 500 daltons and less than 5 percent below
1,000 daltons.
The (e)(3) exemption concerns certain polyester polymers (as defined at
§723.250(b)) composed solely of monomers and reactants from the list as found
at §723.250(e) (3) .
In addition to meeting the specific criteria of one of the three
exemption types described above, the new polymer must not fall into any of the
prohibited categories listed at §723.250(d) of the new rule. This section of
the amended rule specifically excludes certain polymers from the reduced
reporting requirements of the polymer exemption: certain cationic polymers;
polymers that do not meet elemental restrictions; polymers that degrade,
decompose, or depolymerize; and polymers that are produced from monomers
and/or other reactants that are not on the TSCA inventory or otherwise
exempted from full PMN reporting under a §5 exemption. Some highly water-
absorbing, high molecular weight polymers are also specifically prohibited.
Any new chemical polymer substance that does not meet the polymer definition,
does not meet any of the (e)(1), (e)(2), or (e)(3) exemptions, or is
specifically excluded from the polymer exemption is subject to the full PMN
reporting requirements.
3. DEFINITIONS
For a new polymer to be eligible for the exemption it must meet distinct
criteria set forth in the 1995 polymer exemption rule. Much of the
terminology used in these criteria is explained in this and subsequent
sections of the guidance manual. Note that the definitions provided herein
are those used in the new polymer exemption rule, and that these terms may not
necessarily have the same meaning as commonly used in an academic or
industrial setting. Careful attention must be paid to the definitions
contained in the new polymer exemption rule when determining eligibility.
The polymer definition has been revised to conform with the
international definition recently adopted by the OECD as a result of the
Experts on Polymers Meetings held in Toronto, Canada (January 1990), Paris,
France (October 1991), and Tokyo, Japan (April 1993), in which the Agency
participated. The definition was agreed upon in May 1993 by the OECD member
countries, including the United States, Canada, Japan, and member nations of
the European Union. The definitions of polymer and other important terms as
used in the new polymer exemption rule are:
Polymer - a chemical substance consisting of molecules
characterized by the sequence of one or more types of monomer
units and comprising a simple weight majority of molecules
containing at least 3 monomer units which are covalently bound to
at least one other monomer unit or other reactant and which
consists of less than a simple weight majority of molecules of the
same molecular weight. Such molecules must be distributed over a
range of molecular weights wherein differences in the molecular
weight are primarily attributable to differences in the number of
monomer units.
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Monomer - a chemical substance that is capable of forming covalent
bonds with two or more like or unlike molecules under the
conditions of the relevant polymer-forming reaction used for the
particular process.
Monomer unit - the reacted form of the monomer in a polymer.
Sequence - a continuous string of monomer units within the molecule that
are covalently bonded to one another and are uninterrupted by units
other than monomer units.
Reactant - a chemical substance that is used intentionally in the
manufacture of a polymer to become chemically a part of the
polymer composition. (Reactants include monomers, chain transfer
and crosslinking agents, monofunctional groups that act as
modifiers, other end groups or pendant groups incorporated into
the polymer. For example, sodium hydroxide is considered a
reactant when the sodium ion becomes part of the polymer molecule
as a counter ion.)
Other reactant - a molecule linked to one or more sequences of
monomer units but which under the relevant reaction conditions
used for the particular process cannot become a repeating unit in
the polymer structure. (This term is used primarily in applying
the concept of sequence in the definition of a polymer).
Polymer molecule - a molecule that contains a sequence of at least
3 monomer units, which are covalently bound to at least one other
monomer unit or other reactant.
Internal monomer unit - a monomer unit of a polymer molecule that
is covalently bonded to at least two other molecules. Internal
monomer units of polymer molecules are chemically derived from
monomer molecules that have formed covalent bonds between two or
more other monomer molecules or other reactants.
Number-Average Molecular Weight - the arithmetic average (mean) of
the molecular weights of all molecules in a polymer. (This value
should not take into account unreacted monomers and other
reactants, but must include oligomers.)
4. ELIGIBILITY REQUIREMENTS
In order for a new chemical substance to be eligible for exemption under
the amended rule, it must meet the following requirements:
• The substance must meet the definition of a polymer as defined in
§723.250 (b) ;
• The substance must not be specifically excluded from the polymer
exemption by §723.250(d); and
• The substance must meet one of the (e)(1), (e)(2), or (e)(3)
criteria.
4.1 MEETING THE DEFINITION OF A POLYMER AT 40 CFR §723.250(b)
For deciding if a substance meets the definition of a polymer these
sequence and distribution criteria must be met:
• > 50 percent of molecules must be composed of a sequence of at
least 3 monomer units plus at least one additional monomer unit or
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other reactant. (In other words, > 50 percent of the substance
must be polymer molecules.)
• The amount of polymer molecules of any one molecular weight cannot
exceed 50 weight percent.
The following examples illustrate the analysis of substances with regard
to the polymer definition criteria mentioned above. Some of these have been
taken from the Chairman's Report2 of the Chemicals Group and Management
Committee at the Third Meeting of OECD Experts on Polymers (Tokyo, April 14-16
1993) in which the Agency participated. In the figures, 'o.r.' refers to
'other reactant,' and 'm.u.' refers to 'monomer unit.' Examples 1-5 illustrate
the sequence criteria for defining a polymer molecule. In Examples 1-3 the
relevant polymer-forming reaction is ethoxylation with ethylene oxide.
Example 1:
Figure 1
Ethoxylated Benzenetetrol:
o.r.
m.u.
HOCH2CH2O.
2 m.u.
O(CH2CH2O)2H
OCH2CH2OH
m.u.
Example 1 does not meet the sequence criterion and is therefore not a polymer
molecule. Under the reaction conditions, the phenol hydroxy group can neither
react with another phenol hydroxy nor an opened epoxide. Therefore, phenolic
precursor is an 'other reactant,' (o.r.). In the molecule shown, there is no
sequence of three monomer units (m.u.) from ethylene oxide.
Example 2:
Figure 2
Ethoxylated Hydroquinone:
O(CH2CH2O)nH
o.r.
m.u.
The Example 2 molecule, produced from the ethoxylation of hydroquinone, would
meet the sequence criterion if n > 3 and therefore would be a polymer
molecule. Hydroquinone would be an 'other reactant' because the phenol
hydroxyl can react with neither another phenol hydroxyl nor an opened epoxide,
under the reaction conditions.
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Example 3:
Figure 3
Ethoxylated Glycerol:
o.r.
2 m.u.
m.u.
CH2O—(CH2CH2O)2H
CHO (CH2CH2O)2H
CH2O—(CH2CH2O)2—CH2CH2OH
Example 3 meets the sequence criterion and would be considered a polymer
molecule. If polymer formation is desired, at least 7 equivalents of EO
should be charged to the reactor. With less EO charged, each hydroxyl may only
be ethoxylated twice or less, which would not satisfy the sequence criterion.
Example 4:
Figure 4
Glycerol Triester:
o.r.
o.r.
CH20-CO(CH2)16_18CH3
CHO—CO(CH2)16.18CH3
CH20-CO(CH2)16.18CH3
Example 4 does not meet the sequence criterion. There are no repeating units.
Neither the glycerol other reactant nor the fatty acid other reactant can
repeat under the reaction conditions. Methylene (CH2) is not a monomer unit,
because it is not the reacted form of a monomer present in the polymer.
Example 5:
Figure 5
Epoxy Resin:
o
OH
I
H3C—C—O—CH2-CH-CH2-
o.r.
m.u.
O
/\
O-CH2-CH-CH2
m.u.
m.u.
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Example 5 meets the sequence criterion and therefore would be a polymer
molecule. It has an unbroken chain of three monomer units and one other
reactant.
Examples 6, 7, and 8:
Examples 6-8 illustrate the sequence and distribution criterion of the new
polymer exemption rule.
Table 1
Distribution Criteria Examples 6, 7, and 8: Ethoxylated Alcohols
SPECIES
RO.EO.H
RO.EO.EO.H
RO.EO.EO.EO.H
RO.EO.EO.EO.EO.H
RO . EO . EO . EO . EO . EO . H
o . r . + m.u .
1 + 1
1 + 2
1 + 3
1 + 4
1 + 5
EXAMPLE 6
5%
20%
30%
40%
5%
EXAMPLE 7
25%
35%
20%
10%
10%
EXAMPLE 8
8%
20%
52%
10%
10%
For these examples, 'EO' is a monomer unit derived from ethylene oxide, and
'RO' is an other reactant derived from an alcohol. Example 6 meets the
definition of a polymer because >50 percent of the substance has molecules of
at least 3 monomer units in sequence and <50 percent of each species (same
molecular weight components) is present. Example 7 does not meet the
definition of polymer because <50 percent of substance has molecules of at
least 3 monomer units plus at least one additional monomer unit or other
reactant. Example 8 does not meet the definition of polymer because >50
percent of one molecular weight species is present.
Example 9:
Consider the enzyme pepsin and the sequence and distribution criteria of
the new polymer exemption rule's definition of a polymer substance. Although
pepsin meets the sequence requirements of the polymer definition, the
molecules will always have the same distinct molecular weight, corresponding
to the sum of the molecular weights of the amino acid monomer units which
comprise the specific protein sequence of the enzyme. As such it has a
majority of molecules having identical weight and will not meet that portion
of the new rule's definition of a polymer.
On the other hand, a lipoprotein or mucoprotein with its attachments
intact might satisfy the sequence and distribution criteria. The lipo- or
muco- portions can be quite variable in quantity and this could cause enough
variation in weight of the polymer molecules.
4.2.
SUBSTANCES EXCLUDED FROM THE EXEMPTION AT 40 CFR §723.250(d)
Certain categories of polymers are ineligible for exemption under the
new polymer exemption rule because the Agency cannot determine whether these
substances can be reasonably anticipated to present an unreasonable risk of
injury to human health or the environment. For a discussion of the history
behind the selection of these categories consult the preamble to the 1995
polymer exemption rule (USEPA 1995). The following sections discuss the
excluded categories.
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4.2.1. EXCLUSIONS FOR CATIONIC AND POTENTIALLY CATIONIC POLYMERS
Cationic polymers and those polymers which are reasonably anticipated to
become cationic in the natural aquatic environment are excluded from the
exemption and may not be manufactured under it. The principal concern is the
toxicity toward aquatic organisms.
Cationic polymer - a polymer that contains a net positively
charged atom(s) or associated group(s) of atoms covalently linked
to the polymer molecule. This includes, but is not limited to
phosphonium, sulfonium, and ammonium cations.
Potentially cationic polymer - a polymer containing groups that are
reasonably anticipated to become cationic. This includes, but is not
limited to, all amines (primary, secondary, tertiary, aromatic, etc.)
and all isocyanates (which hydrolyze to form carbamic acids, then
decarboxylate to form amines).
Reasonably anticipated means that a knowledgeable person would expect a
given physical or chemical composition or characteristic to occur, based
on such factors as the nature of the precursors used to manufacture the
polymer, the type of reaction, the type of manufacturing process, the
products produced in the polymerization, the intended uses of the
substance, or associated use conditions.
4.2.1.1. CATIONIC POLYMERS NOT EXCLUDED FROM EXEMPTION
Through its experience reviewing thousands of polymers, the Agency has
determined that two categories of cationic and potentially cationic polymers
would not pose an unreasonable risk of injury to human health or the
environment. These two types are not excluded from consideration for the
exemption and are as follows:
• Cationic or potentially cationic polymers that are solids, are
neither water soluble nor dispersible in water, are only to be used in
the solid phase, and are not excluded from exemption by other factors,
and
• Cationic or potentially cationic polymers with low cationic
density (the percent of cationic or potentially cationic species with
respect to the overall weight of polymer) which would not be excluded
from the exemption by other factors.
For a polymer to be considered to have low cationic density, the concentration
of cationic functional groups is limited to a functional group equivalent
weight of greater than or equal to 5,000 daltons.
Functional group equivalent weight (FGEW) - the weight of polymer
that contains one equivalent of the functional group; or the ratio
of number-average molecular weight (NAVG MW) to the number of
functional groups in the polymer. The methods for calculating the
FGEW are described in a later section.
Example 10:
As an example of the cationic density requirement, consider the reaction
of precisely equal molar amounts of ethanediamine and phthalic acid, resulting
in a polyamide (polymer) with an equal number of unreacted amine and unreacted
carboxylic acid groups. This would be equivalent to a sample of polymer
molecules that would have (on average) one end group that was an unreacted
amine (potentially cationic) and the other end group an unreacted carboxylic
acid. For this polymer to be eligible for the exemption it must have a
minimum NAVG MW of 5,000 daltons which would give the amine FGEW as 5,000
daltons (1 amine termination per 5,000 MW of polymer).
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4.2.2. EXCLUSIONS FOR ELEMENTAL CRITERIA
A polymer manufactured under the 1995 rule must contain as an integral
part of its composition at least two of the atomic elements of carbon,
hydrogen, nitrogen, oxygen, sulfur, or silicon (C, H, N, O, S, Si).
In addition to the six elements listed above, only certain other
elements are permitted either as counterions or as an integral part of the
polymer. These additional elements are as follows: fluorine, chlorine,
bromine and iodine (F, Cl, Br and I) when covalently bonded to carbon, and the
monatomic counterions chloride, bromide, and iodide (C1-, Br- and I-). The
fluoride anion, (F-) is not permitted. This decision was based on data
obtained by the Agency. Other permitted monatomic cations are sodium,
magnesium, aluminum, potassium, and calcium (Na+, Mg+2, Al+3, K+ and Ca+2).
Allowed at less than 0.20 weight percent total (in any combination) are the
atomic elements lithium, boron, phosphorus, titanium, manganese, iron, nickel,
copper, zinc, tin and zirconium (Li, B, P, Ti, Mn, Fe, Ni, Cu, Zn, Sn, and
Zr) . No other elements are permitted, except as impurities.
4.2.3. EXCLUSIONS FOR DEGRADABLE OR UNSTABLE POLYMERS
A polymer is not eligible to be manufactured under the new exemption
rule if the polymer is designed or reasonably anticipated to substantially
degrade, decompose, or depolymerize, including those polymers that could
substantially decompose after manufacture and use, even though they are not
actually intended to do so. For purposes of this section the following
definition applies:
Degradation, decomposition, or depolymerization - a type of chemical
change in which a polymeric substance breaks down into simpler, smaller
weight substances as the result of (for example) oxidation, hydrolysis,
heat, sunlight, attack by solvents or microbial action.
4.2.4. EXCLUSIONS BY REACTANTS
A polymer may contain at more than two percent by weight only those
reactants and monomers that are either: on the TSCA Chemical Substance
Inventory, granted a §5 exemption, (a low-volume exemption; a polymer
exemption under the 1984 rule; etc.), excluded from reporting or a non-
isolated intermediate. Monomers and reactants that do not fit one of these
categories would render a polymer ineligible for the polymer exemption. This
applies to both manufactured and imported polymers. (See section 5.2. of this
manual for a discussion of the so-called "Two Percent Rule").
Monomers and reactants incorporated or charged at greater than two
percent in a polymer are considered part of the chemical identity of the new
polymer. (See Section 5.2. on the "Two Percent Rule.") Monomers and
reactants which are not on the Inventory and do not have a §5 exemption may be
used at less than or equal to two percent provided that those monomers and
reactants will not introduce into the polymer any elements, properties, or
functional groups that would render the polymer ineligible for the exemption.
However, in practice, the use of non-Inventory monomers or reactants at two
percent or less applies only to imported polymers since domestic manufacturers
may not distribute or use any substance unless it is on the TSCA Inventory or
exempt from TSCA reporting requirements. In other words, non-Inventory
monomers and reactants may be handled domestically only if they are
intermediates made in situ and are not isolated, or if they are already
exempt.
-------
4.2.5. EXCLUSIONS FOR WATER-ABSORBING POLYMERS
Water-absorbing polymers with number-average molecular weight (NAVG MW)
of 10,000 daltons and greater are excluded from exemption. A history
describing how the EPA came to select this NAVG MW and the level of water
absorptivity to be excluded is given in the preamble to the new rule. The
Agency's definition of water-absorbing is given below:
Water-absorbing polymer means a polymeric substance that is
capable of absorbing its weight of water.
4.3. CATEGORIES WHICH ARE NO LONGER EXCLUDED FROM EXEMPTION
Three exclusions have been dropped from the new polymer exemption rule
because the Agency now believes that other provisions of the new rule will
exclude any polymers that would pose an unreasonable risk of injury to human
health or the environment. The three types of polymers that are no longer
automatically excluded from the exemption are: (1) polymers containing less
than 32 percent carbon; (2) polymers manufactured from reactants containing
halogen atoms (see section 4.2.2 of this manual) or cyano groups; and (3)
biopolymers. To be manufactured under the exemption these polymers must meet
all of the criteria of the new rule. For example, in the biopolymer category,
most enzymes and polypeptides will not meet the polymer definition because of
the requirement that the molecular weight of the polymer must be distributed
over a range (no one molecular weight species can be present in a simple
majority). Some DNA, RNA or polysaccharide substances may meet the molecular
weight distribution criterion but fail because of reactivity (reactive group
content, degradability, etc.), cationic potential, or water-absorbing
properties .
4.4. MEETING EXEMPTION CRITERIA at 40 CFR §723.250(e)
Providing the new polymer meets the definition of a polymer at
§723.250(b) and the polymer is not automatically excluded by section
§723.250(d), the polymer must also meet one or more of the criteria listed in
§723.250 (e)(1), (e)(2), or (e)(3) to be manufactured or imported under a
polymer exemption.
4.4.1. THE (e)(1) EXEMPTION CRITERIA
In order to be manufactured or imported under §723.250(e)(1), the
polymer must have a NAVG MW equal to or greater than 1,000 daltons and less
than 10,000 daltons. (See section 5.1., for determining NAVG MW.) The
polymer also must contain less than 10 percent oligomer content of molecular
weight below 500 daltons and less than 25 percent oligomer content of
molecular weight below 1,000 daltons. In addition, (e)(1) polymers have
reactivity constraints. The polymer must have either: no reactive functional
groups; only low-concern functional groups; or it must have a functional group
equivalent weight (FGEW) above threshold levels for moderate- and high-concern
functional groups in order to remain eligible for the exemption. (See section
5.3., "Calculating Functional Group Equivalent Weight," in this manual.)
Reactive functional group - an atom or associated group of atoms in a
chemical substance that is intended or can be reasonably anticipated to
undergo facile chemical reaction.
The following sections describe the reactive functional groups in the low-
concern, moderate-concern and high-concern categories.
10
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4.4.1.1. LOW-CONCERN FUNCTIONAL GROUPS AND THE (e)(1) EXEMPTION
Low-concern functional groups defined in §723.250(e)(1)(ii)(A) may be
used without limit. These groups are so categorized because they generally
lack reactivity in biological settings. The low-concern reactive functional
groups are: carboxylic acid groups; aliphatic hydroxyl groups; unconjugated
olefinic groups that are considered "ordinary;" butenedioic acid groups; those
conjugated olefinic groups contained in naturally-occurring fats, oils, and
carboxylic acids; blocked isocyanates (including ketoxime-blocked
isocyanates); thiols; unconjugated nitrile groups; and halogens (not including
reactive halogen-containing groups such as benzylic or allylic halides).
Ordinary olefinic groups - unconjugated olefinic groups that are not
specifically activated either by being part of a larger functional
group, such as a vinyl ether, or by other activating influences, such as
the strongly electron-withdrawing sulfone functionality (in a vinyl
sulfone system).
In addition, carboxylic esters, ethers, amides, urethanes and sulfones
are implicitly permitted because polyesters, polyethers, polyamides,
polyurethanes, and polysulfones are among the types of polymers allowed under
the exemption, as long as these functional groups have not been modified to
enhance their reactivity. One such group that would not be allowed is the
dinitrophenyl ester of a carboxylic acid, which is far more reactive due to
the activating functionality.
In summary, if a substance (1) meets the definition of a polymer, (2) is
not excluded by §723.250(d), (3) has a NAVG MW greater than or equal to 1000
daltons and less than 10,000 daltons, (4) contains only the low-concern
reactive functional groups, and (5) meets oligomer content criteria (<10
percent below 500 daltons and <25 percent below 1000 daltons), the new
substance may be manufactured under a polymer exemption.
4.4.1.2. MODERATE-CONCERN FUNCTIONAL GROUPS AND THE (e)(1) EXEMPTION
Moderate-concern groups defined in §723.250 (e) (1) (ii) (B) may be used
with functional group equivalent weight (FGEW) constraints. Each functional
group present from category (B) must have a FGEW of greater than or equal to
1,000 daltons. For a polymer containing no type (C) groups (see section
4.4.1.3 for when type (C) groups are present), the FGEWcomblned must be greater
than or equal to 1,000 daltons. (The method for calculating a FGEWcomblned is
covered in section 5.3. of this manual). The moderate-concern reactive
functional groups are: acid halides; acid anhydrides; aldehydes; hemiacetals;
methylolamides; methylolamines; methylolureas; alkoxysilanes bearing alkoxy
groups greater than C2; allyl ethers; conjugated olefins (except those in
naturally-occurring fats, oils, and carboxylic acids); cyanates; epoxides;
imines (ketimines and aldimines); and unsubstituted positions ortho- and para-
to a phenolic hydroxyl group.
In summary, if a substance (1) meets the definition of a polymer, (2) is
not excluded by any of the provisions of §723.250(d), (3) has a NAVG MW
greater than or equal to 1000 daltons and less than 10,000 daltons, (4) has
individual FGEWs and a FGEWcomblned greater than or equal to 1,000 daltons for
moderate-concern groups (when high-concern groups are not present, but low-
concern groups may be present without limit), and (5) meets oligomer content
criteria (<10 percent below 500 daltons and <25 percent below 1000 daltons),
the new substance may be manufactured under a polymer exemption.
4.4.1.3. HIGH-CONCERN FUNCTIONAL GROUPS AND THE (e)(1) EXEMPTION
Reactive groups not defined by (e)(1)(ii)(A) or (B) fall into category
(e)(1)(ii)(C), the high-concern reactive functional groups. These may be used
with more restriction than moderate-concern groups alone. If a polymer
contains type (C) reactive functional groups, each type (C) functional group
present must meet a 5,000 dalton minimum permissible limit, each type (B)
group present must meet the 1,000 dalton limit and the polymer must have a
11
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FGEWcomblned of greater than or equal to 5,000 daltons. A FGEWcomblned calculation
takes into account all type (C) and type (B) reactive groups. (This type of
calculation is covered in section 5.3. of this manual.) Therefore, if a
substance containing category (e)(1)(ii)(C) functional groups meets the
definition of a polymer, is not excluded by any of the provisions of
§723.250(d), has a NAVG MW greater than or equal to 1,000 daltons and less
than 10,000 daltons, has a FGEWcomblned greater than 5,000 daltons, meets the
individual type (B) and (C) FGEW limits of 1,000 and 5,000, respectively, and
the polymer meets oligomer content criteria (<10 percent below 500 daltons and
<25 percent below 1000 daltons) the new substance may be manufactured under a
polymer exemption.
Table 2 summarizes the FGEWcomblned minimum permissible levels as discussed
in the preceding (e)(1) exemption criteria section of this manual. In the
table, the 'X' marks which type of group (or groups) is present from the
categories: low-concern, moderate-concern, and high-concern.
Table 2
FGEWCOIIt)ined Summary
Low-
Concern
Moderate-
Concern
High-
Concern
Minimum
FGEWcomblned
X
None*
X
1,000
X
5,000
X
X
1,000"
X
X
5,000"
X
X
5,000
X
X
X
5,000"
* There are no FGEW limits for polymers containing only low-concern (type
A, also known as (e)(1)(ii)(A) ) functional groups.
** When calculating FGEWcomblned for substances with moderate (Type (B) )
and/or high-concern (Type (C)) functional groups, low-concern groups (Type
(A)) are not included in the calculation.
4.4.2.
THE (e)(2) EXEMPTION CRITERIA
Those polymers having NAVG Mws exceeding the limits of §723.250 (e) (1)
are subject to §723.250(e)(2). Hence, this section covers polymers with NAVG
Mws greater than or equal to 10,000 daltons. The oligomeric content of these
higher molecular weight polymers must be less than two percent for species
with molecular weight less than 500 daltons, and must be less than 5 percent
for species of molecular weight less than 1,000 daltons. There are no
functional group restrictions for the (e)(2) exemption, but the substance must
not be excluded from exemption by any of the provisions found at §723.250(d).
For example, water-absorbing polymers and cationic or potentially cationic
polymers in this weight range are excluded from exemption by §723.250(d).
Therefore, if a substance meets the definition of a polymer, is not
excluded by any of the provisions of §723.250(d), has a NAVG MW greater than
or equal to 10,000, and meets the oligomer content criteria (less than two
percent below 500 daltons and <5 percent below 1,000 daltons), the new
substance may be manufactured under a polymer exemption.
4.4.3.
THE (e)(3) EXEMPTION CRITERIA
Section 723.250(e)(3) provides for the exemption of manufactured or
imported polyesters which have been prepared exclusively from a list of
feedstocks identified in section (e)(3) of the new rule. To qualify for this
exemption, each monomer or reactant in the chemical identity of the polymer
(charged at any level) must be on the list. At this writing (5/22/97), six
entries on the list are not on the TSCA Inventory. Therefore, these six
monomers and reactants are not allowed for use in domestic manufacture.
12
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Just as for all other exempted polymers, polyesters that are allowed an
exemption under (e)(3) must meet the definition of a polymer and must not be
excluded from exemption by §723.250(d). For example, excluded from an (e)(3)
exemption are biodegradable polyesters and highly water-absorbing polyesters
with number-average molecular weights (NAVG MW) greater than 10,000 daltons.
The following is the list from which all monomers and reactants in
(e)(3)-exempted polymers must be taken. They are listed by Chemical Abstracts
Index Names and Registry Numbers (where available). A "V" identifies the six
substances not on the TSCA Inventory, as of this writing.
Table 3
The (e)(3) Monomer and Reactant List
(in order by CAS Registry Number)
[56-81-5] 1,2,3-Propanetriol
[57-55-6] 1,2-Propanediol
[65-85-0] Benzoic acid
[71-36-3]** 1-Butanol
[77-85-0] 1,3-Propanediol, 2-(hydroxymethyl)-2-methyl-
[77-99-6] 1,3-Propanediol, 2-ethyl-2-(hydroxymethyl)-
[80-04-6] Cyclohexanol, 4,4'-(1-methylethylidene)bis-
[88-99-3] 1,2-Benzenedicarboxylic acid
[100-21-0] 1,4-Benzenedicarboxylic acid
[105-08-8] 1,4-Cyclohexanedimethanol
[106-65-0] Butanedioic acid, dimethyl ester
[106-79-6] Decanedioic acid, dimethyl ester
[107-21-1] 1,2-Ethanediol
[107-88-0] 1,3-Butanediol
[108-93-0] Cyclohexanol
[110-15-6] Butanedioic acid
[110-17-8] 2-Butenedioic acid (E)-
[110-40-7] Decanedioic acid, diethyl ester
[110-63-4] 1,4-Butanediol
[110-94-1] Pentanedioic acid,
[110-99-6] Acetic acid, 2,2'-oxybis-
[111-14-8] Heptanoic acid
[111-16-0] Heptanedioic acid
[111-20-6] Decanedioic acid
[111-27-3] 1-Hexanol
[111-46-6] Ethanol, 2,2'-oxybis-
[112-05-0] Nonanoic acid
[112-34-5] Ethanol, 2 -(2-butoxyethoxy)-
[115-77-5] 1,3-Propanediol, 2,2-bis(hydroxymethyl)-
[120-61-6] 1,4-Benzenedicarboxylic acid, dimethyl ester
[121-91-5] 1,3-Benzenedicarboxylic acid
[123-25-1] Butanedioic acid, diethyl ester
[123-99-9] Nonanedioic acid
[124-04-9] Hexanedioic acid
[126-30-7] 1,3-Propanediol, 2,2-dimethyl-
[141-28-6] Hexanedioic acid, diethyl ester
[142-62-1] Hexanoic acid
[143-07-7] Dodecanoic acid
[144-19-4] 1,3-Pentanediol, 2,2,4-trimethyl-
[505-48-6] Octanedioic acid
[528-44-9] 1,2,4-Benzenetricarboxylic acid
[624-17-9] Nonanedioic acid, diethyl ester
[627-93-0] Hexanedioic acid, dimethyl ester
[629-11-8] 1,6-Hexanediol
[636-09-9] 1,4-Benzenedicarboxylic acid, diethyl ester
[693-23-2] Dodecanedioic acid
[818-38-2] Pentanedioic acid, diethyl ester
[1119-40-0] Pentanedioic acid, dimethyl ester
[1459-93-4] 1,3-Benzenedicarboxylic acid, dimethyl ester
13
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[1732-
[1732-
[1732-
[1852-
[2163-
[3302-
[8001-
[8001-
[8001-
[8001-
[8001-
[8001-
[8001-
[8001-
[8002-
[8016-
[8023-
[8024-
[13393
08-7]
09-8]
10-1]
04-6]
42-0]
10-1]
20-5]*
21-6]*
22-7]*
23-8]*
26-1]*
29-4]*
30-7]*
31-8]*
50-4]*
35-1]*
79-8]*
09-7]*
-93-6]
[25036-25-3]
[25119-
[25618-
[61788-
[61788-
[61788-
[61789-
[61789-
[61790-
[67701-
[67701-
[68037-
[68132-
[68153-
[68308-
[68424-
[68440-
62-4]
55-7]
47-4]*
66-7]*
89-4]*
44-4]*
45-5]*
12-3]*
08-0]*
30-8]*
90-1]*
21-8]*
06-0]*
53-2]*
45-3]*
65-3]*
[68957-04-0]*
[68957-06-2]*
[72318-84-4]*
[84625-38-7]*
[68649-95-6]*
[68953-27-5]*
[91078-92-1]* V
[93165-34-5]* V
[93334-41-9]* V
[120962-03-0]*
[128952-11-4]* V
[No Registry #]*
[No Registry #]*
3,3, 5-trimethy1-
Heptanedioic acid, dimethyl ester
Octanedioic acid, dimethyl ester
Nonanedioic acid, dimethyl ester
Undecanedioic acid
1,3-Propanediol, 2-methyl
Hexanoic acid,
Tung oil
Sunflower oil
Soybean oil
Safflower oil
Linseed oil
Cottonseed oil
Corn oil
Coconut oil
Fats and glyceridic oils, menhaden
Fats and glyceridic oils, oiticica
Palm kernel oil
Oils, walnut
1-Phenanthrenemethanol, tetradecahydro-1,4a-dimethyl-7-(1-
methylethyl)-
Phenol, 4,4'-(1-methylethylidene)bis-, polymer with 2,2'-
[(1-methylethylidene)bis(4,1-phenyleneoxymethylene)]-
bis[oxirane]
2-Propen-l-ol, polymer with ethenylbenzene
1,2,3-Propanetriol, homopolymer
Fatty acids, coco
Fatty acids, vegetable-oil
Fatty acids, C18-unsatd., dimers
Fatty acids, castor oil
Fatty acids, dehydrated castor oil
Fatty acids, tall-oil
Fatty acids, C16-18 and C18-unsatd.
Glycerides, C16-18 and C18-unsatd.
Silsesquioxanes, Ph Pr
Oils, perilla
Fats and glyceridic oils, herring
Fatty acids, soya
Fatty acids, linseed oil
Siloxanes and silicones, di-Me, di-Ph,
Silsesquioxanes, methoxy-terminated
Siloxanes and silicones, di-Me, methoxy Ph, polymers with Ph
Silsesquioxanes, methoxy-terminated
Siloxanes and silicones, Me Ph, methoxy Ph, polymers with Ph
Silsesquioxanes, methoxy- and Ph-terminated
Methanol, hydrolysis products with trichlorohexylsilane and
trichlorophenylsilane
Fatty acids, sunflower-oil
Linseed oil, oxidized
Fatty acids, sunflower-oil, conjugated
Fats and glyceridic oils, babassu
Fatty acids, safflower-oil
Fats and glyceridic oils, sardine
Canola oil
Fats and glyceridic oils, anchovy
v Fatty acids, tall-oil, conjugated
s/ Oils, cannabis
polymers with Ph
* Designates chemical substances of unknown or variable composition,
complex reaction products, or biological materials (UVCB substances). The CAS
Registry Numbers for UVCB substances are not used in Chemical Abstracts and
its indexes.
14
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** 1-Butanol may not be used in a substance manufactured from fumaric
or maleic acid because of potential risks associated with esters which may be
formed by reaction of these reactants.
5. NUMERICAL CONSIDERATIONS
There are several numerical criteria to consider when deciding if a
polymer is eligible for an exemption:
1). Number-average molecular weight (NAVG MW) is one of the criteria defining
whether an eligible polymer fits an (e)(1) or (e)(2) exemption; in the case of
a water-absorbing polymer, NAVG MW defines whether or not the polymer will be
excluded from exemption due to the 10,000 dalton restriction. Section 5.1.,
expounds on NAVG MW determination.
2). The "Two Percent Rule" governs whether a monomer or other reactant is part
of the chemical identity. Substances that are considered by the Agency as
automatically part of the chemical identity of the polymer (those monomers or
reactants used at greater than two percent composition) must be on the TSCA
Inventory, excluding from reporting or otherwise exempt under section 5 of
TSCA. For (e)(1) and (e)(2) exemptions, imported polymers may have monomers
or reactants at less than or equal to 2 percent which are not on the
Inventory; whereas in the case of domestic manufacture under an (e)(1) or
(e)2) exemption, all monomers and reactants must either be: on the Inventory;
a non-isolated intermediate; otherwise exempt; or excluded from reporting.
For (e)(3) polymers, all monomers and reactants, regardless of charge must be
from the (e)(3) list, but only those charged at greater than 2 percent will be
part of the identity. Section 5.2. explains the so-called "Two Percent Rule"
and its determination.
3). The functional group equivalent weight (FGEW) is a measure of the
concentration of functional groups of moderate- and high-concern in the
polymer. This is an important factor in determining eligibility for polymers
with NAVG MW greater than or equal to 1,000 daltons and less than 10,000
daltons. It is also important in determining whether a cationic polymer is
excluded. Section 5.3., below, explains the determination of FGEW.
5.1. CALCULATING NUMBER-AVERAGE MOLECULAR WEIGHT
The rationale and theoretical basis for determining number-average
molecular weight (NAVG MW) and brief summaries of the preferred analytical
methods for determining the value follow.
The Agency uses number-average molecular weight (NAVG MW) instead of the
weight-average molecular weight (WAVG MW) for defining polymer exemption
categories and criteria. The NAVG MW takes into account the number of
molecules of various molecular weights in the polymer sample and therefore is
representative of the average weight of the typical (major) components of a
polymer sample. The WAVG MW takes into account the total weight of all
molecules, placing no emphasis on the number of molecules at each individual
weight. When the WAVG MW is calculated, a small percentage of large molecules
can bias the average and give a false representation of the majority of
molecules in the sample.
The equations for determining NAVG MW (Mn) and WAVG MW (MJ are taken
from the OECD guidelines draft proposal entitled "Determination of the Number-
Average Molecular Weight and the Molecular Weight Distribution of Polymers
using Gel Permeation Chromatography"3 and "Determination of the Low Molecular
Weight Polymer Content."1 In the equations, N1 is the number of molecules at
a given molecular weight (which in gel permeation Chromatography (GPC) is
proportional to the detector signal for the retention volume VJ . M± is the
molecular weight of the polymer fraction at the retention volume V±.
15
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Equation 1:
Equation 2:
M,., =
Example 11:
The reason for using the NAVG MW instead of the WAVG MW in the criteria
is best demonstrated by an example. Suppose a polymer contains 200 molecules
that weigh 1,000 daltons, 300 molecules that weigh 1,500 daltons, 400
molecules that weigh 2,000 daltons and 2 molecules that weigh 1,000,000
daltons. In this case 99.8 percent of the molecules in this sample weigh <
2000 daltons. Clearly, one might say that typically, the polymer has a
molecular weight from 1,000 to 2,000 daltons. The NAVG MW and the WAVG MW are
calculated below:
M = ^= = 1503
" 200 + 300 + 400 + 2
1000 1500 2000 1,000,000
_ 200,000 + 450,000 + 800,000 + 2,000,000 _ -DOI-
= - - = 3825
Of these two calculations, the Mn at 1503 daltons more accurately represents
99.8 percent of the molecules in the polymer batch. The Mw is biased by the
two incidental 1,000,000 dalton molecules to the extent that the Mw average is
a considerably greater weight than 99.8 percent of the sample.
The Agency requires that the manufacturer of an exempt polymer keep
records of the "lowest" number-average molecular weight at which the polymer
is to be made. This is not the value for the lowest MW species in a sample,
but rather the lowest value of the NAVG MW obtained from polymer samples taken
from a series of batches in the production of the polymer.
There are several analytical techniques for determining NAVG MW. Two
literature references4'5 as well as OECD's guidelines document for testing of
chemicals3 discuss methodologies in some detail and provide additional
references. Brief summaries of the information provided in these references
are given below. The techniques are based on molecular size (a function of
the NAVG MW) ; colligative properties of polymer solutions (osmotic pressure,
boiling point, freezing point, vapor pressure, etc.); or the number of
chemically reactive groups present in the polymer. Any method that can be
verified is acceptable for purposes of the polymer exemption. The following
are most commonly used:
Gel permeation chromatography (polymer size) ,
Membrane osmometry (colligative property) ,
Vapor-phase osmometry (colligative property) ,
Vapor pressure lowering (colligative property) ,
Ebulliometry (colligative property) ,
Cryoscopy (colligative property) , and
End-group analysis (chemical reactivity) .
16
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5.1.1. GEL PERMEATION CHROMATOGRAPHY
Gel permeation chromatography (GPC), the most frequently used and
generally most reliable method for determining NAVG MW of polymers and
oligomer content below 500 and 1000 daltons, is suitable for substances
ranging from very low to very high molecular weights. In an ideal situation,
separation of the polymer sample is governed by hydrodynamic radius (size) of
each molecular species as it passes through a column filled with porous
material, typically an organic gel. Smaller molecules penetrate the pores and
thereby travel a longer path and elute after larger molecules. The GPC column
must be calibrated using polymers of known weight and, ideally, similar
structure. Polystyrenes are used quite extensively as internal standards.
Detection techniques used for GPC are refractive index and UV-absorption.
One potential problem with GPC is band broadening, especially when
measuring low molecular weight polymers, or as the result of unevenly packed
columns or dead volumes. Empirical calibrations of the instrument can be made
to minimize broadening6, but become unimportant when the ratio of the WAVG MW
to the NAVG MW is greater than two. Another limitation with GPC is that many
high molecular polymers are insoluble in usable solvents, and therefore can't
be analyzed by GPC.
5.1.2. MEMBRANE OSMOMETRY
Membrane osmometry exploits the principle of osmosis for determining
NAVG MW7. Polymer is placed in a membrane osmometer on one side of a semi-
permeable membrane while a solvent is placed on the other. Solvent is drawn
through the membrane as the system progresses toward equilibrium, creating a
pressure differential that is dependent on the concentration difference and
the molecular weight of the polymer.
The major disadvantage to this method is that accuracy and reliability
may be compromised by diffusion of low weight oligomers through the membrane.
Generally, diffusion is absent for unfractionated polymers with NAVG MWs
greater than 50,000 daltons. The upper limit of the NAVG MW that may be
measured with confidence is generally 200,000 daltons (OECD guidelines3).
5.1.3. VAPOR-PHASE OSMOMETRY
This method is based on the comparison of evaporation rates for a
solvent aerosol and at least three other aerosols with varying polymer
concentration in the same solvent. The technique is most accurate for
polymers with NAVG MW less than 20,000 daltons (OECD guidelines3). This
method is best applied to samples with molecular weight too low to be measured
in a membrane osmometer.
5.1.4. VAPOR PRESSURE LOWERING
For this technique the basic principle is similar to vapor phase
osmometry, however, vapor pressure is measured instead of the rate of aerosol
evaporation. The vapor pressure of a reference solvent is compared against
the vapor pressure of at least three concentrations of the polymer mixed with
the solvent. Theoretically this technique may be applicable for polymers of
up to 20,000 dalton NAVG Mws. In practice, however, it is of limited value.
5.1.5. EBULLIOMETRY
This technique exploits the boiling point elevation of a solution of a
polymer to determine NAVG MW8. This method makes accurate determinations for
polymers with NAVG MW approaching 30,000 daltons; however, it is limited by
the tendency of polymer solutions to foam upon boiling. The polymer may even
concentrate in the foam due to the foam's greater surface area, making the
observed concentration of the polymer in solution less than the actual. It is
customary to calibrate the ebulliometer with a substance of known molecular
weight. Octacosane, with a molecular weight of 396 daltons, is a common
choice.
17
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5.1.6. CRYOSCOPY
Freezing point depressions of polymer solutions can also be used to
determine NAVG MW. Although the limitations associated with cryoscopy are
fewer than those of ebulliometry, care must be taken to avoid supercooling.
The use of a nucleating agent to provide controlled crystallization of the
solvent is helpful. Reliable results may be obtained for molecular weights of
up to 30,000 daltons. As with ebulliometry, calibration with a substance of
known molecular weight is customary.
5.1.7. END-GROUP ANALYSIS
This method is generally the least useful since a fair amount of prior
knowledge, such as overall structure and the nature of the chain-terminating
end groups, is needed about the polymer. Basically, end-group analysis
methods take into account the number of molecules in a given weight of a
sample, which in turn, yields the NAVG MW. End-group analysis is best suited
to linear condensation polymers. For branched condensation polymers or
addition polymers no general procedures can be established because of the
variety and origin of the end-groups. However, when the polymerization
kinetics are well known, the degree of branching may be estimated based on the
amount of feedstock charged. For addition polymerization, end-group analysis
can be used to determine molecular weight by analyzing for specific initiator
fragments containing identifiable functional groups, elements, or radioactive
atoms; for chain terminating groups arising from transfer reactions with
solvent; or for unsaturated end groups such as in polyethylene and poly-oc-
olefins.
The analytical method used must distinguish the end groups from the main
polymer skeleton. The most widely used methods are NMR, titration, or
derivatization. For example, carboxyl groups in polyesters are usually
titrated directly with a base in an alcoholic or phenolic solvent. Infrared
spectroscopy is used when the polymer cannot be titrated due to insolubility
in certain solvents. This technique is useful for NAVG MWs up to 50,000
daltons (with decreasing reliability as the NAVG is increased).
5.2. THE TWO PERCENT RULE AND CHEMICAL IDENTITY
According to the polymer exemption rule at §723.250(d)(4), a polymer is
not eligible for exemption if it contains at greater than two weight percent
monomers and/or reactants that are not: included on the TSCA Inventory,
manufactured under an applicable TSCA §5 exemption, excluded from exemption,
or an non-isolated intermediate. Monomers and reactants at greater than two
percent make up the "chemical identity" of the polymer. For an exempt
polymer, monomers and reactants at less than or equal to two weight percent
are not considered part of the "chemical identity" of the polymer; and the use
of these monomers and reactants creates a different set of issues, which are
discussed below.
A manufacturer or importer must carefully decide at what weight percent
level each monomer or other reactant is to be used in the preparation of the
exempt polymer. This choice (which must be obvious from the manufacturing
data kept by the manufacturer or importer) limits the manufacturer or importer
of an exempt polymer in two major ways. First, if a certain monomer or
reactant is used in an exempt polymer at less than or equal to two weight
percent, the manufacturer may not later use that reactant at greater than two
weight percent (under the exemption for the same polymer). The new polymer
substance that results when the reactant is increased to greater than two
weight percent is different, by definition, from the polymer that contains the
reactant at less than or equal to two weight percent. Second, if a reactant
or monomer is used at greater than two weight percent in an exempt polymer,
the reactant or monomer must not be eliminated completely from the polymer (if
the manufacturer is trying to satisfy the exemption for the same polymer). If
either of these "identity-changing" events occur, the manufacturer must do one
of the following: 1) find the new polymer identity on the TSCA Inventory, 2)
submit a PMN at least 90 days prior to manufacture if the new polymer is not
18
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on the Inventory, or 3) meet the conditions of a PMN exemption to cover the
new polymer identity.
Non-Inventory monomers and reactants cannot be used in domestic
manufacture (unless they are subject to another §5 exemption or are non-
isolated intermediates). Therefore, a manufacturer cannot use such monomers
and reactants for an exemption even at levels of two percent or less. A
manufacturer will be able to exchange Inventory-listed monomers and reactants
at less than or equal to two weight percent under one exemption, as long as
such changes do not affect the eligibility of the polymer and records for such
changes are maintained as stated in the rule. An exempt imported polymer
under the new rule may contain non-Inventory monomers and reactants at two
percent or less as long as they do not introduce into the polymer elements,
properties, or groups that would render the polymer ineligible for the polymer
exemption. The exception to this last statement is the (e)(3) type exempted
polymer, for which monomers and reactants must only come from the (e)(3) list,
even if at levels less than or equal to two percent. For all polymer types,
restrictions unique to the polymer exemption must be applied in addition to
the "Two Percent Rule."
Percent by weight has been defined as the weight of the monomer or
other reactant used expressed as a percentage of the dry weight of
polymer.
The Agency has long recognized that when calculating the percentage of
each reactant, it is a matter of convenience rather than a matter of science
to use the amount charged to the reactor, rather than the amount of a monomer
incorporated into the polymer. EPA believes that the actual content of a
polymer (what is actually incorporated into the polymer) is a better indicator
of its physical, chemical, and toxicological properties, but has accepted
calculations based upon the amount charged to the reaction vessel in order to
facilitate PMN reporting for industry. Under the 1995 PMN rule revisions, the
Agency now accepts two methods for determining the "percent by weight" of each
reactant for the purpose of establishing the chemical identity of a polymer:
1). The Percent Charged Method: The percent composition of each monomer or
reactant is established by the amounts charged to the reaction vessel.
2). The Percent Incorporated Method: The percent composition is based on the
minimum theoretical amount of monomer or reactant needed to be charged to the
reactor in order to account for the amount analytically determined to be
incorporated in the polymer. The percent composition of each whole monomer or
reactant whose fragment is present in the polymer should be established by
analytical determination of the incorporated fragment, or may be established
by theoretical calculations if it can be documented that an analytical
determination cannot or need not be made to demonstrate compliance with the
new polymer exemption rule.
At 40 CFR §723.250(g) the Agency specifies what identity information is
required to be kept by the manufacturer or importer. By paragraph (1) of
section (g), the Agency requires that a manufacturer or importer must
identify, to the extent known or reasonably ascertainable, the specific
chemical identity and CAS Registry Number (or EPA Accession Number) for each
"reactant" used at any weight in the manufacture of an exempt polymer. This
criterion is considered reasonable by the Agency based on the requirement that
any reactant used at greater than two percent must already be listed on the
TSCA Inventory or otherwise exempt under an appropriate §5 rule. There may be
cases where a monomer or reactant was the subject of a previous PMN, exempted
or excluded from exemption, hence the requirement to have a CAS registry
number for such a monomer or reactant may not be necessary. However,
manufacturers and importers should maintain in their records the CAS registry
number for the monomer or reactant, if one exists for that substance).
At paragraph (2) of section (g) , the Agency requests that a structural
diagram be provided if possible, to further clarify the identity of an exempt
polymer. The Agency believes it is possible to provide a representative
19
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chemical structure diagram for nearly all polymers. It is often the structure
that best illustrates the intended identity of a substance. For instance, if
2,2-bis(hydroxymethyl)propionic acid and an amine are among the feedstocks,
would these two feedstocks react in such a way as to form amides or carboxylic
acid salts? A structure makes clear the intent of the manufacturer or
importer. All monomers and reactants at greater than two percent by weight in
the polymer should be represented by the polymer structural diagram kept in
the records.
5.2.1. PERCENT CHARGED METHOD
The calculations required to determine the percent by weight of a
reactant charged to the reaction vessel are straightforward. The weight
percent of the reactant is the weight of the material charged to the reactor
(weighed before addition into the reaction), expressed as a percentage of the
dry weight of the manufactured polymer (weighed after isolation from the
reaction). The following equation applies, where 'GFC' is grams of feedstock
charged, and 'GPF' is grams of dry polymer formed:
Equation 3:
Percent by weight charged = —, x 100
a a (GPF)
Calculations by percent charged to the reaction vessel can cause
confusion if monomers or reactants lose a substantial portion of their
molecular structure when incorporated into a polymer. Under these
circumstances, the sum of the weights of reactants charged significantly
exceeds, 100 percent. This type of calculation is demonstrated by Example 12,
the formation of polyvinyl alcohol (PVA) produced from the polymerization of
vinyl acetate followed by hydrolysis.
Example 12:
Figure 6
Polyvinyl Alcohol and Weight Percent:
o
Jj 1. Polymerization _(CH2_rH)x
^ 2. Hydrolysis OH
The molecular weight of vinyl acetate is 86 daltons, and the molecular weight
of the repeating unit for PVA [-CH2-CH (OH) -] is 44 daltons. In this example,
because only one monomer is used to form the polymer, and one monomer fragment
is present in the polymer, the ratio of (GFC/GPF) is the same as (Feedstock
MW/Fragment MW) , so the equation can be simplified as follows:
Wt. % of vinyl acetate = |86| x 100 = 195
(44)
The weight percent of the vinyl acetate charged to the reactor is 195 percent!
20
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5.2.2. PERCENT INCORPORATED METHOD
In the percent incorporated method, as stated in the 1995 PMN rule
amendments, "the weight percent is based on...the minimum weight of monomer or
other reactant required in theory to account for the actual weight of monomer
or other reactant molecule or fragments chemically incorporated (chemically
combined) in the polymeric substance manufactured." Therefore, if a percent
incorporated is to be calculated for a monomer or reactant, the degree of
incorporation of the fragment resulting from the monomer or reactant must be
measured.
It is not always possible or feasible to determine analytically the
degree of incorporation for every type of reactant, especially for random
polymerizations where no repeating subunits exist and for polymerizations
using chemical reactants where the structures are not completely specified
(such a reactant as conjugated sunflower-oil fatty acids, for example).
Complete or efficient incorporation cannot be assumed, even if the reaction
equilibrium and kinetics predict a certain result. It is also necessary to
identify a structural unit within the polymer that corresponds to the specific
monomer from which it came. Often the same monomer unit may originate from
more than one monomer. For example, empirically determining the exact
chemical incorporation of oxirane, methyloxirane, ethylene diamine, and
epichlorohydrin in a polymer would require a complicated study, perhaps using
radioisotope-labeled reactants. If the percent incorporated cannot be deduced
by measurement or reliably estimated, the manufacturer must use the percent
charged method.
In order to calculate a weight percent incorporated for a reactant,
certain data must be known: the molecular weight of the reactant charged; the
molecular weight of the fragment that is incorporated into the polymer (if the
feedstock is not entirely incorporated); and the analytically determined
amount of the incorporated reactant that is present in the polymer (the weight
percent of the polymer that consists of the fragment). From these data the
number of moles of fragment present in the polymer can be calculated, which is
proportional to the amount of feedstock that reacted to form the polymer. The
following ratio is useful:
Equation 4:
Wt.
MW of Frag. (lOOg Polym. ) (gFrag.) lOOg of Polym.
Wt. % Fiag. _ (g Frag.) „ (mol Frag.) _ Moles of Frag. _ „-,<-,-„
— v — It a UJ-O
The weight percentage of reactant incorporated is calculated by converting
moles of incorporated fragment per 100 g of polymer (Ratio A), to moles of
reactant and then multiplying by the reactant molecular weight. (The specific
units used are irrelevant; gram-moles per 100 grams or ton-moles per 100 tons
are equally valid for the calculation.) This is accomplished by the following
equation:
Equation 5:
Wt. % React. Incorp. = (Ratio A) x ^oles React.) x ^ Qf Reactant) x 100
(Moles Frag.)
Example 13:
For an example of the calculation for the percent incorporated method
consider the polymerization of ethylene glycol with a dialkyl terephthalate.
It is known that both oxygen atoms of the glycol are incorporated into the
resulting polyester while two alkoxy groups of the terephthalate ester are
lost in the process. The following calculation determines the weight
21
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percentage incorporated for dialkyl terephthalate: The polymer was
empirically shown to contain 13.2 percent by weight of the terephthaloyl unit
t-C(=0)-C6H4-C(=0)-], which has a MW of 132 daltons. Ratio A for
terephthaloyl is calculated as follows:
Ratio A = (13 . 2 g) (1 mole) _ (0.10 moles terephthaloyl)
(100 g polymer) (132 g) (100 g polymer)
The weight percent of reactant incorporated is calculated as shown below.
Each mole of parent dialkyl terephthalate ester would result in one mole of
fragment, so the molar conversion factor is 1. If the dialkyl terephthalate
charged is dimethyl terephthalate, the MW used for the calculation is
194 g/mole.
Wt. % React, incorp. - , (0.10 m°les} , x (,X molf of Feedstock) x Ig4 x 100 = 19.4
(lOOg Polymer) (1 mole of Fragment)
Example 14:
For a comparison to Example 13, consider if the dialkyl terephthalate
charged were diethyl terephthalate. The MW for the diethyl terephthalate is
222 g/mole. The calculation would show a weight percent of reactant
incorporated as 22.2 percent. This would mean that diethyl terephthalate
would have to be charged to the reaction vessel at 22.2 percent for the
terephthaloyl fragment to be incorporated into the polymer at 13.2 percent;
whereas dimethyl terephthalate would have to be charged at only 19.4 percent
to have the terephthaloyl fragment incorporated at 13.2 percent. These
percentage values make sense because a larger alkoxy group is lost when the
diethyl terephthalate is the source of the terephthaloyl group than when
dimethyl terephthaloyl is the source of the terephthaloyl groups and the
methoxy group is lost. Therefore, to provide the same fragment incorporated
in the polymer, more weight of diethyl terephthalate would have to be charged
in comparison to dimethyl terephthalate.
Example 15:
Neutralizers are often used in considerable excess over the amount
actually incorporated into the polymer. If the amount of incorporation is two
percent or less, neutralizer may be omitted from the identity of the polymer.
A sample calculation of the "weight percent incorporated" for a neutralizing
base is given below:
A polymer containing free carboxylic acid functional groups was
neutralized using a large excess of sodium hydroxide (NaOH; formula weight =
40); the total amount of base charged to the reactor was 10 percent. Analysis
of the resulting polymer salt revealed that the polymer contained 0.92 weight
percent of sodium (atomic weight = 23), coming only from the base. This amount
of sodium corresponds to 0.04 moles of sodium per hundred grams of polymer, or
1.6 grams of NaOH per hundred grams of polymer -- that is, 1.6 weight percent
NaOH incorporated, despite the large excess charged. Because the weight
percent of NaOH is not greater than two percent, the polymer substance would
not have to be described as the sodium salt.
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P . . , f ., _ (0.92 g Na) (1 mo 2 Na ) _ (0.04 moles Na)
Ratio A tor Na (100 g Polym.) x (23 g Na) (100 g Polym.)
Vt. % inc. NaOH = (0-O^molNa) (40 g NaOH) ±QQ =
(100 g Polym. ) (1 /nol NaOH)
If sodium bicarbonate (NaHC03; formula weight = 86) had been the
neutralizing agent, the same number of moles of sodium per hundred grams of
polymer would have corresponded to 3.36 weight percent of NaHC03. Because the
weight percent of NaHC03 is greater than two percent, the polymer substance
must be described as the sodium salt.
(0 04 mol Na) (84 g NaHCO-)
Wt. % Inc. NaHCO, = lu-u^ mo± Na> _^ y 3^ x 100 = 3i36
3 (100 g Polym. ) (1 mol NaHCO3 )
If a combination of bases is used for neutralization, the amounts
incorporated should be prorated according to the mole ratios of the
neutralizing agents charged if the reactivities are similar. Otherwise,
assume the most reactive neutralizing agents is consumed first, etc.
Example 16:
For calculating the weight percent incorporated of an initiator, the
computation will be similar to that for an excess neutralizing base.
Initiator may be charged to the reaction vessel at a higher percentage than
what is actually incorporated into the polymer. If the amount of
incorporation is consistently below two percent, the initiator will not be in
the chemical identity of an exempted polymer. (For polymers with PMNs and
NOCs, the submitter has the option of leaving the initiator out of the
identity, or including it.) In the case where initiator is not in the
identity of the either an exempted polymer or in the identity of a polymer
covered by a PMN and NOC, a change in initiator could be made without having
to establish another polymer exemption or PMN for the change in the polymer
manufacture, as long as the alternate initiator remained at or under two
percent and in the case of the exemption, the initiator did not exclude the
polymer in other ways. A sample calculation of the "weight percent
incorporated" for an initiator is given below:
A polyolefin with a NAVG MW of 9,000 daltons was produced using
azobis[isobutyronitrile] (AIBN, MW = 164) charged at 3 percent. This class of
initiator is known to produce radicals that contain the nitrile moiety (CN, FW
= 26), which can be analytically determined. The polymer sample was found to
contain 0.29 weight percent nitrile, which was assumed to originate only from
AIBN. This 0.29 g of fragment in 100 g of polymer corresponds to 0.011 moles
of fragment [(0.29 g / 26 g/mol) = 0.011 moles] in 100 g of polymer. Since
every 1 mole of AIBN reactant produces 2 moles of fragment, a molar conversion
factor of 1/2 is used to relate the amount of fragment present to the amount
of reactant incorporated. The weight percent of reactant incorporated is
calculated as follows:
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Wt. % React. Inc. = (Ratio A) x ^oles of React.} x (M? of React.) x (100)
(Moles of Frag.)
or
Wt. % AIBN incorp. - (0.011 moles Frag.) (1 Mole React.) ( } ( } = 0_g
(lOOg Polym.) (2 Moles Frag.)
As stated at the beginning of this example, AIBN was charged to the reaction
vessel at 3 weight percent, but only 0.9 percent was actually incorporated
into the polymer. After establishing that the weight percent of AIBN
incorporated is less than or equal to two percent, the submitter need not
include it in the polymer identity.
5.2.3. METHODS FOR DETECTION OF POLYMER COMPOSITION
There are many methods available for chemical analysis of polymers and
for detecting weight percent of fragments incorporated. Although any
analytical method that can be verified is acceptable, this section explores
some of the more common approaches. The following list of options is not
meant to be exhaustive:
Classical chemical analysis (elemental analysis, titration, etc.),
Mass spectrometry,
Gas chromatography,
Infrared spectroscopy,
Nuclear magnetic resonance spectroscopy, and
X-ray diffraction analysis.
A brief description for each of the non-chemical methods of analysis
follows.
5.2.3.1. MASS SPECTROMETRY
In mass spectrometry, an electron beam bombards a sample and creates
from it positive ion fragments that are separated by mass to charge ratio in
an electromagnetic field and measured quantitatively. From the abundance of
the various ionic species found, the structure and composition of the original
substance can be inferred. When mass spectrometry is used for analyzing
polymers, the polymer is usually thermally degraded first to form fragments of
low molecular weight. These fragments are volatized, ionized and then
separated as per the standard technique.
5.2.3.2. GAS CHROMATOGRAPHY
In gas chromatography (GC) gaseous or vaporized components of the sample
are distributed between a moving gas phase and a fixed liquid phase or solid
absorbent. By a continuous succession of elution steps, occurring at
different rates for each species, separation is achieved. In the resulting
gas chromatogram the peaks are proportional to the instantaneous concentration
of the components. Therefore, information about the number, nature, and
weight percentages of the components can be derived.
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5.2.3.3. INFRARED SPECTROSCOPY
Infrared frequencies are in the wavelength range of 1 to 50 microns and
are associated with molecular vibration and vibration-rotation spectra. Often
for polymers, the infrared absorption spectra are surprisingly simple. This
is because many of the normal vibrations have the same frequency and the
strict selection rules for absorption prevent many of the vibrations from
causing absorption peaks in the spectrum. Rarely can infrared be used for
quantitative analysis of polymer composition.
5.2.3.4. NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY
Nuclear magnetic resonance (NMR) spectroscopy is a powerful tool in the
study of chain configuration, sequence distribution, and microstructures in
polymers. NMR spectroscopy utilizes the property of spin angular momentum
possessed by nuclei whose atomic number and mass number are not both even.
Irradiation of the sample by a strong magnetic field splits the energy level
into two: one corresponding to alignment of electrons with the field and the
other with an antiparallel alignment. Transitions between these states lead
to spectra. Peak intensity is proportional to concentration for proton NMR.
5.2.3.5. X-RAY DIFFRACTION ANALYSIS
X-ray diffraction is a useful method for detecting the presence of
structures that are arranged in an orderly array or lattice. The
interferences that result from the lattice interaction with electromagnetic
radiation provides information regarding the geometry of the structures.
Since single crystals of polymer as now prepared are too small for x-ray
diffraction experiments, the crystal structure is generally derived from a
fiber drawn from the polymer.
5.3. CALCULATING FUNCTIONAL GROUP EQUIVALENT WEIGHT
Reactive functional groups that come from monomers and reactants at
greater than or equal to two percent in a polymer must meet the minimum FGEW
requirements for the exemption category under which the polymer is
manufactured or imported. Polymers that are exempt under the (e)(1) criteria
must meet or exceed the minimum permissible equivalent weights for reactive
functional groups (FGEW). There are no functional group restrictions for
polymers meeting the (e)(2) exemption except for cationic and potentially
cationic group concerns, as specified in §723.250(d). For (e)(3) polymers,
reactive functional groups of moderate and high concern would not be present
in any polymer derived from monomers on the allowed list. In addition, the
monomers on the list are not expected to bear reactive functional groups of
moderate or high concern once they are incorporated into the polymer. Hence,
the (e)(3) section of the new polymer exemption rule does not have any FGEW
requirements.
For (e)(1) polymers the allowable thresholds for certain reactive
functional groups are listed in the Table 4. Note: this is not an exhaustive
list. Consult the 1995 polymer exemption rule for groups not mentioned. Note
that if a functional group is not mentioned in the rule among the low-
(e) (1) (ii) (A) or moderate-concern groups (e) (1) (ii) (B) , it is considered to be
a high-concern functional group. Low-concern reactive groups may be used
without limit, and no thresholds have been set for them.
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Table 4
Allowable Thresholds for Reactive Functional Groups
Moderate-Concern: The minimum permissible FGEW is 1,000 daltons.
Acid halides
Acid anhydrides
Aldehydes
Alkoxysilanes where alkyl is greater than C2
Allyl ethers
Conjugated olefins
Cyanates
Epoxides
Hemiacetals
Hydroxymethylamides
Imines
Methylolamides
Methylolamines
Methylolureas
Unsubstituted position ortho- or para- to phenolic hydroxyl
High-Concern: The minimum permissible FGEW is 5,000 daltons.*
Acrylates
Alkoxysilanes where alkyl = methyl or ethyl
Amines
Aziridines
Carbodiimides
Halosilanes
Hydrazines
Isocyanates
Isothiocyanates
.alpha.-Lactones; .beta.-Lactones
Methacrylates
Vinyl sulfones
* For polymers containing high-concern functional groups, the FGEWcomblned must
be greater than or equal to 5,000 daltons taking into account high-concern
(e) (1) (ii) (c) and, if present, moderate-concern (e) (1) (ii) (b) functional
groups.
Unless a functional group equivalent weight can be determined
empirically by recognized, scientific methodology (typically titration) , a
worst-case estimate must be made for the FGEW, in which all moderate- and
high-concern functional moieties must be factored. A generalized approach for
performing equivalent weight estimations with specific methods and examples is
provided below. The following is limited guidance on how to calculate
functional group equivalent weights. The methods discussed are end-group
analysis (Section 5.3.1), calculation based on percent charged (Section
5.3.2.) , and nomograph use (Section 5.3.3.) .
5.3.1. END-GROUP ANALYSIS
Most condensation polymers (polyesters, polyamides, etc.) contain
reactive functional groups only at the chain ends, because all other reactive
functionality in the monomers is consumed to produce the condensation polymer
backbone in the final product. For this type of polymer, FGEW determination
may be as simple as theoretical end group analysis and can be performed
regardless of the reactive group type.
For a linear polymer (two reactive groups per monomer) with either the
nucleophilic or electrophilic reagents in excess, the FGEW is half the NAVG
MW, as described.
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EXAMPLE 17:
A polyamide with a NAVG MW of 1000 daltons, made from excess ethylene
diamine (two nucleophiles) and adipic acid (two electrophiles), would be
anticipated to be amine-terminated at both ends, assuming a worst case
scenario (the greatest content of reactive functional groups present). The
amine equivalent weight would be 1/2 the NAVG molecular weight, or 500
daltons.
For simple, branched condensation polymers (having only one monomer
possessing more than 2 reactive sites), the FGEW must be calculated from the
total number of end groups present in the polymer. This is calculated from an
estimated degree of branching, which is derived by knowing the number of
reactive groups in the polyfunctional monomer. If reasonable, it should be
assumed that the monomer responsible for the branching will be incorporated in
its entirety to form the polymer.
The mathematics for estimating the FGEW for simple branched condensation
polymers follows. The equivalent weight of the monomer is the molecular
weight of the monomer divided by the weight percent charged to the reaction
vessel. The monomer equivalent weight of 1000 daltons means that there is one
mole of monomer for every 1000 daltons of polymer.
Equation 6:
Monomer Equivalent Wt. = (Monomer molecular weight)
(Weight Percent Charged)
The degree of branching is calculated by dividing the NAVG MW value by the
monomer equivalent weight, multiplied by the number of reactive groups that
are not used to make the polymer backbone, which is (NRG - 2). (The NRG value
is the number of reactive groups originally in the monomer.)
Equation 7:
Degree of Branching = -. (NAVG m x (NRG-2)
(Monomer Eg. Wt.)
The total number of end-groups in the polymer is the degree of branching value
plus two, where the two in this equation is the number of end-groups of the
polymer backbone.
Equation 8:
Total number of Polymer End Groups = Degree of Branching + 2
The FGEW is then derived by simply dividing the NAVG MW by the number of end-
groups in the polymer.
Example 18:
Consider the polymerization of pentaerythritol (PE, 4 reactive groups)
with polypropylene glycol (PPG, 2 reactive groups) and an excess of isophorone
diisocyanate (2 reactive groups). The polyfunctional feedstock (PE) is added
to the reaction at 10 percent by weight to produce an isocyanate-terminated
polymer having a NAVG molecular weight equal to 2720 daltons. The monomer
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equivalent weight of pentaerythritol is 1360, obtained by dividing the monomer
molecular weight by the weight percent charged (136 H- 0.10) . PE has four
reactive alcohol moieties, two are used to form the polymer backbone and the
other two form branches. Following the equations given above, the degree of
branching for this polymer example is [(2720 H- 1360) x (4 - 2)] = 4. The
total number of end-groups is [4+2] =6. Due to the excess of isophorone
diisocyanate, we assume that each end-group is an isocyanate group. Finally,
the FGEW can be calculated by simply dividing the NAVG MW by the total number
of end groups theoretically present. Therefore, FGEW = (2720 H- 6) = 453
daltons.
Figure 7
Isocyanate-Teriminated Urethane and Functional Group Equivalent Weight:
HO
OH
0=C=N
N=C=O
0]X-H
CH3
OCN-Chain—O
OCN-Chain—O.
O-C-N
II
O
O—Chain-NCO
OCN-Chain—O.
OCN-Chain—
O—Chain-NCO
For condensation polymers derived from a more complex mixture of feedstocks,
computer programs that simplify the complicated FGEW calculations may be used.
(There are a few commercial programs which perform a "Monte Carlo" simulation
of a random condensation polymerization that directly estimates the NAVG MW
and FGEW from the types of data described earlier.) Analytical data should be
used periodically to confirm computer estimates and verify eligibility.
5.3.2.
MORE COMPLEX FGEW CALCULATIONS
Some condensation and addition reactions create polymers where not all
reactive functional groups along the backbone of the polymer are consumed
during the reaction, so a simple end-group analysis will not suffice for
determining an accurate FGEW. In many of these cases the equations in this
section may be used to estimate FGEWs. These equations aid in calculating
FGEWs for elements (for example, basic nitrogen), for reactive groups that are
unchanged under the reaction conditions and for multiple types of functional
groups that remain in the polymer molecule.
Equation 9 can be used for any reactive functional group in a polymer.
This may even be an atom, such as basic nitrogen, as in an example that
follows. In the equation, 'FWG' is the formula weight of the group; and 'W%G'
is the weight percent of the group:
28
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Equation 9:
wrww - (^WG) x 100
FGEW
Example 19:
To calculate the amine FGEW for a polymer containing 2.8 weight percent
basic nitrogen (using 14.0, the atomic weight of nitrogen, as the formula
weight of the group), the equation becomes:
FGEW = 14-0*100 = 500
Functional groups are typically introduced into polymers from the
precursor monomers. Using Equation 10 one may calculate the weight percent of
the functional group in the polymer, as long as the monomer is included in its
entirety and the functional groups are introduced unchanged. In Equation 10,
'FWG' is formula weight of the group, 'NGM' is the number of groups in the
monomer, 'W%M' is the weight percent of the monomer, and 'FWM' is the formula
weight of the monomer:
Equation 10:
Weight % of Group = -I™® x (NGM] x (W*M}
(FWM)
Substituting Equation 10 into Equation 9, FGEW Equation 11 is obtained, where
'FWM' is the formula weight of the monomer, 'W%M' is the weight percent of the
monomer, and 'NGM' is the number of groups in the monomer:
Equation 11:
FGEW-- (FWM}
(W%M) x (NGM)
Example 20:
For an acrylic polymer containing 5.4 weight percent of acryloyl
chloride (formula weight 90.5) as a monomer, the FGEW of acid chloride groups
in the polymer is:
- (90.5) (100) _
(5.4) (1) ~
If the various moderate- and high-concern functional groups in the
polymer arise from more than a single monomer, the FGEWcomblned may be calculated
using Equation 12. Also, if several different monomers contain the same
groups, for example, if three monomers contribute epoxides which remain intact
in the polymer, Equation 12 may be used to calculate the epoxide FGEW. This
combined epoxide FGEW should be compared to the minimum permissible FGEW for
epoxides when determining eligibility of the polymer.
In Equation 12, FGEWn is the FGEW for each particular functional group
in the polymer:
29
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Equation 12:
FGEWi FGEW2 FGEWn
Example 21:
This calculation of FGEW demonstrates the use of end-group analysis and
equation estimations.
Some condensation polymers contain unreacted reactive functional groups
in addition to the end groups of interest; for example, an epoxide-capped
phenol-formaldehyde novolak resin. The FGEW for each type of reactive group
present in the molecule (end groups and unreacted groups) should be calculated
separately and then summed using Equation 12. Assume a para-cresol and
formaldehyde copolymerization produced a condensation polymer that was reacted
with one percent epichlorohydrin. The NAVG MW of this product was determined
Figure 8
Epoxide-capped Novolak and Functional Group Equivalent Weight:
CH2]y-H
by GPC to be 8,000 daltons. It would be difficult to show empirically that
the polymer would not be phenol-terminated. Therefore, the polymer is assumed
to be phenol-terminated as a worst case scenario. This would mean phenol
groups with reactive ortho positions reside at the polymer backbone termini.
The FGEW for the terminal phenolic ortho positions is (NAVG MW / 2), or 4,000
daltons. This is above the minimum permissible functional group equivalent
weight for the phenol reactive group which is of moderate concern (1000
daltons minimum permissible weight). If the terminals are the only reactive
groups in the polymer, this polymer would be eligible for exemption. However,
epoxy rings from the epichlorohydrin are also present, so the FGEW for epoxide
must also be considered. Even though epichlorohydrin would not be included in
the chemical identity of the polymer being considered for exemption, (it is
charged at less than two percent by weight), the FGEW for the epoxide must be
included for the FGEWcomblned calculation. Following Equation 11, the epoxide
FGEW is calculated to be 9,250. (The molecular weight for epichlorohydrin,
92.5 was used; along with 1 percent for the amount charged, and 1 as the
number of reactive epoxides.) The FGEW of 9,250 means that there is one
epoxide moiety present for every 9,250 daltons of polymer. If epoxide were
the only reactive group in the polymer the minimum equivalent weight
requirement for moderate concern groups would be exceeded and the polymer
would meet the FGEW criteria for exemption. However, for a polymer with more
than one type of reactive group of concern, a FGEWcomblned must be calculated to
determine exemption eligibility.
For the polymer, the phenolic FGEW is 4,000 and for epoxides the FGEW is
9,250. The FGEWcomblned would be calculated following Equation 12, as follows:
30
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=2792
4000 9250
With a FGEWcomblned of 2,792 daltons, this polymer would be eligible for
exemption because the FGEW comblned is greater than the required 1,000 minimum
permissible equivalent weight (threshold level). Although there are two
reactive functional groups from the moderate-concern list, there are no high-
concern groups present.
However, note that if instead of epichlorohydrin, 1 percent of acryloyl
chloride (high-concern reactant with a molecular weight 90.5) had been used,
the same type of calculation would produce a polymer that is excluded from the
exemption. In this further example, groups from (e)(1)(ii)(B) and
(e) (1) (ii) (C) are both present and give a FGEW comblned of 2,774 daltons. The
threshold of 5,000 is daltons is not satisfied.
FGEWcomblned = — 1 — =2774
4000 + 9050
Example 22:
Similar calculations may be done for addition reaction polymers.
Consider a radical polymerization of acrylates, which react via the alkene
leaving reactive functionality in the molecule. In this case it would be
reasonable to assume that each monomer charged to the reaction vessel will be
incorporated in its entirety to form polymer.
Assume that polyacrylate was produced from 10 percent glycidyl
methacylate (MW = 142), two percent hydroxymethyl acrylamide (MW = 101) and 88
percent acrylic acid. (See Figure 9). The reactive functional groups of
concern are the epoxide (1,000 dalton threshold) from glycidyl methacrylate
and the hydroxymethyl amide from the acrylamide (1,000 dalton threshold). The
carboxylic acid moiety from acrylic acid may be used without limit. (See the
rule, section (e)(1)(A); and also the tables in this manual.)
Using Equation 11, one can calculate the FGEW for the epoxide to be
1,420 daltons (142 / 0.10), and the FGEW for hydroxymethyl amide to be 5,050
daltons (101 / 0.02). (If either of these monomers had been used separately
in the stated proportions, the polymer FGEW eligibility restrictions would
have been met.) The FGEWcomblned for the polymer calculated using Equation 12 is
1,108 daltons ( 1 / [(1/1420) + (1/5050)] ). This polymer would be eligible
for the exemption because the 1,000 dalton threshold for two or more moderate-
concern reactants was met. Because 1,108 daltons is fairly close to the 1,000
dalton threshold, the manufacturer will not have a lot of flexibility to
increase the epoxide or amide in future batches. Also, each batch must meet
the exemption. If it is anticipated that some batches will not qualify for
the exemption, the manufacturer or importer must file a regular PMN 90 days
prior to the manufacture of the commercial product, to cover those particular
production runs.
31
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Figure 9
Acrylate with Multiple Functional Groups:
10% Charged 2% Charged 88% Charged
CH3
CH,
Chain-[CH2-C]-[CH2-CH]-[CH2-CH]-Chain
)=° >=°
O HN HO
OH
In some addition reactions the reactive groups that effect the desired
polymerization reaction are consumed and in others they are not. Examples 23
and 24 contrast these two types.
Example 23:
An example of an addition reaction that consumes the reactive functional
groups is the addition of an amine to an isocyanate molecule. The reactive
amine adds to the isocyanate to produce a "urea" polymeric backbone which is
unreactive. Typically, an end-group analysis would be used to determine if
the FGEW falls within the allowable limits for the exemption.
Example 24:
An addition reaction where the reactive group involved in the
polymerization is not consumed (is still considered reactive) involves a more
complicated calculation of FGEW.
Figure 10
Unconsumed Amines and Combined Functional Group Equivalent Weight:
30% Charged
c
70% Charged
H OH
OH
Consider the reaction between ethanediamine (MW = 60) charged at 30 percent,
and diglycidyl ether (MW = 130) charged at 70 percent. In the reaction, amine
nitrogens react with the epoxides. This results in consumption of the epoxide
to form an aliphatic alcohol, which is on the low-concern list and may be
present in any quantity. The amine functionality remains intact and the FGEW
32
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for the amine is proportional to the amount of feedstock containing the amine
charged to the reaction vessel. The FGEW for the amines in this type of
reaction is estimated using Equation 11, the molecular weight of the feedstock
(60) , the percent of the monomer charged to the reaction vessel (30) , and the
number of reactive functional groups in the feedstock (2) :
FGEW = 60 = 100
30x2
The minimum permissible equivalent weight for amines is 5,000 daltons.
Because adding more groups to the FGEWcomblned calculation can only lower the
value, no further calculation would be necessary since the polymer would not
be eligible by amine content alone. This is demonstrated by factoring in the
epoxide contribution. The polymer would likely be epoxide-terminated because
of the excess molar amount of glycidyl ether charged. If this polymer had a
NAVG MW = 5,000 daltons, the epoxide FGEW would be 2,500 daltons by end group
analysis, assuming linear polymerization. The epoxide-terminated polymer
containing reactive amines would have a FGEWcomblned equal to 96 daltons
[1 4- [(1/100) + (1/2500)] ] .
In some addition polymer processes one reactant (or group of reactants)
is used in large excess compared to the other reactants. The reporting of
residual amounts of monomers or other reactants is not required under the new
rule. (The amount of reactant that does not form polymer is not regulated by
the new polymer exemption rule, since these residual, unreacted materials must
be on the TSCA inventory and are covered by different Agency authority, as
existing chemicals.) For polymers made under these conditions, a simple
repeating unit of known molecular weight can be assumed. The FGEW can be
calculated by dividing the unit molecular weight by the number of groups in
the unit .
Example 25:
A polyamine was made from the addition of 70 weight percent 1,2-
benzenediamine (MW = 108) to 30 weight percent of diglycidyl ether (MW = 130) .
The diamine :diepoxide ratio equals about 3:1, as charged to the reaction
vessel. A linear polymer of a 1:1 adduct (MW = 238) is the most likely
Figure 11
Repeating Units, A Polyamine and Functional Group Equivalent Weight:
-Chain
'2 ^/ H OH OH
3:1 Mole Ratio 1:1 Linear Adduct
representative repeating unit. The amine FGEW would be 119 daltons (the
repeating unit MW of 238 daltons divided by two, the number of reactive amines
in the repeating unit). The FGEW will not change regardless of the number of
repeating units in the polymer or the amount of excess diamine monomer.
33
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5.3.3. DETERMINING FGEW BY NOMOGRAPH
The nomograph in Figure 12 has been developed to aid in the estimation
of FGEW. The logarithmic axes on the nomograph are "Formula weight of group
or monomer," "FGEW," and "Weight percent of group or monomer in the polymer."
Choosing the axis points for the first and last of these data and drawing a
line between the two points will intersect the FGEW axis at the point
representing the FGEW for the monomer or group being estimated. For monomers
containing several identical groups, the FGEW should be divided by the number
of identical groups in the monomer. For the case of several different
monomers containing the same groups use FGEW equation 4 instead of the
nomograph.
6. OTHER REGULATIONS AND REQUIREMENTS
Please consult the new rule at 60 FR 16316-16336 (USEPA 1995) for any of
the following topics:
Exemption Report and Requirements
Chemical Identity Information
Certification
Exemptions Granted Under Superseded Regulations
Recordkeeping
Inspections
Submission Information
Compliance
Inspections
Confidentiality
34
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Figure 12
Nomograph for Determining FGEW
10,000
5,000
1,000
500
100
50
10
100,000,000
50,000,000
10,000,000
5,000,000
100,000
50,000
10,000
5,000
1,000
500
100
50
10
0.01
0.05
0.1
0.5
1
5
10
50
100
Formula Weight of
Group or Monomer
FGEW Weight Percent Group
or Monomer in Polymer
35
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7. COMMON QUESTIONS AND ANSWERS
POLYMER DEFINITION:
1. In determining whether a polymer is on the Inventory, does the "new"
polymer definition under the polymer exemption apply? For example, if I
manufacture a substance of the type R(OCH2CH2)nOSO3Na where n = an
average of 7, will I have to submit a PMN even though >3 units of
consecutive monomer are present? The Inventory currently considers all
the ethoxylates with >3 units as polymeric, and therefore as the same
substance. What if n = exactly 7? Exactly 15?
The alkyl ethoxylate sulfates with definite numbers of repeating units
that you describe would not meet the polymer definition, because they would
consist of molecules of a single molecular weight. Chemical Abstracts
nomenclature rules and the TSCA Inventory nevertheless does treat some of
these as though they were polymers. For example, "laureth sulfate", which
corresponds to the formula above where R = C12H25 and n = x, is on the
Inventory (CASRN 9004-82-4). Variations in the number of ethylene oxide
units, as long as n is either >10 or variable or represents an average value,
will not produce a new (that is, non-Inventory) substance. Thus laureth
sulfate with n averaging 7 is considered an existing substance, as is laureth
sulfate with n = exactly 15. However, the case where n = exactly 7 is
considered a discrete chemical substance, not a polymer, and would not be
considered the same. It would have a different name and CASRN, and would be a
new chemical if it is not already on the Inventory elsewhere. This has always
been true, and is unchanged by the polymer exemption.
The "new" polymer definition does not affect the Inventory status of
existing polymers or of new polymers submitted under the PMN rule. The
polymer definition, which applies only to polymers manufactured under the
polymer exemption, therefore does not have the effect of creating a set of "no
longer polymers".
2. Would the following example count as a "polymer molecule?" (The longest
straight chain is 1+1+2=3+1.)
H(oxypropylene)-O-sorbitol-O-(propyleneoxy)2-H
No. Sorbitol cannot be a repeating unit under the conditions of the
relevant polymerization reaction (propoxylation), so it is considered an
"other reactant". Therefore the longest sequence of monomer units (considered
as derived from propylene oxide) is two. A continuous string of at least
three monomer units is required, plus one additional monomer unit or other
reactant.
3. How do you apply the molecular weight distribution requirement of the
polymer definition (i.e., <50 percent of any one MW) to highly cross-
linked polymers of essentially infinite MW?
For polymers of "essentially infinite" MW, unless the entire mass of
polymer produced were in one continuous phase, the actual molecular weight
would be limited by the size of the individual droplets, beads, pellets,
flakes, etc. No two of these would be likely to have exactly the same mass,
and the distribution criterion would be met. For that matter, the molecular
weight determination itself would produce a range of values because of the
finite precision of the instrument.
ELEMENTAL EXCLUSIONS:
4. Regarding elemental limitations, why was fluorine not included in
723.250(d)(2)(B) but included in ii(C)?
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Fluoride ion (F~) has a high acute toxicity, and would therefore be
unacceptable as a counterion in a substance that is supposed to present no
unreasonable risk to human health. Fluorine covalently bound to carbon is
either unreactive and thus not available in the form of F", or is part of a
reactive functional group such as acyl fluoride (COF) and subject to the
reactive functional group criteria.
5. Can you give an example of F- (anion) that is not allowed?
Consider a cationic ion exchange resin that would otherwise have been
eligible (because it meets the criterion of insolubility). If the counterion
is fluoride (F") , it will be ineligible.
6. Ammonium is not listed as an acceptable monatomic counterion. Does this
mean a polymer may be made under the exemption, but not its ammonium
salt?
No; Ammonium may be used as a counterion. It is not monatomic, and is
not excluded under section (d)(2)(ii).
7. Are only monatomic counterions allowed? What about CO32", HCO3", NO3",
etc.?
Monatomic counterions are allowed only if they are on a list of
specifically allowed ones. All other monatomic counterions are excluded. The
polymer exemption says nothing whatsoever about polyatomic counterions as
such; they are permitted if they do not otherwise render the polymer
ineligible. Carbonate (C032~) is allowed, for example; perchlorate (C104~) is
not, because the chlorine is neither a monatomic ion nor is it covalently
bound to carbon; trichloroacetate (CC13C02~) is allowed.
8. Are monomers that have CF2 or CF3 groups allowed?
Monomers that contain CF2 or CF3 groups are acceptable, provided that
the groups are not part of a reactive functional group. -CF2- is not
generally a monomer unit because it is not "the reacted form of the monomer in
the polymer"; however, -CF2CF2- groups derived from the polymerization of
tetrafluoroethylene certainly could be monomer units.
EXCLUSION FOR DEGRADABLE POLYMERS:
9. What is the time frame for "polymers that do not degrade, decompose or
depolymerize?" Does EPA want us to synthesize polymers that
bioaccumulate in the environment? Does the term "degrade" apply to
biodegradation or other degradation in waste treatment systems?
This restriction is essentially unchanged from the 1984 polymer
exemption. While EPA recognizes in principle the beneficial effects of
biodegradability, it commented in the discussion section of that rule that the
Agency "...has little experience reviewing the mechanism by which breakdown
may occur, the decomposition products that may result, and the potential uses
of such polymers. ... Because of the complexity of review necessary for many
of these polymers and the lack of EPA review experience, the Agency did not
believe that an expedited review period was sufficient to adequately
characterize risk."
The Agency acknowledged in that discussion that essentially all polymers
degrade or decompose to a limited degree over time. It gave as examples the
normal fate of polymers in landfills and the weathering of paint, and
specifically stated that the exclusion was not intended to address such
degradation. Substantial biodegradation in a waste treatment system would
render a polymer ineligible for the exemption.
37
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10. How does EPA define "degrade," "decompose," and "depolymerize?" If
these are by-product minor reactions of a polymer, can the polymer still
be eligible for the exemption, assuming other criteria are met?
The definitions are provided at §723.250(d)(3), and read: "For the
purposes of this section, degradation, decomposition, or depolymerization mean
those types of chemical change that convert a polymeric substance into
simpler, smaller substances, through processes including but not limited to
oxidation, hydrolysis, attack by solvents, heat, light, or microbial action."
Minor byproduct degradative reactions will not exclude a polymer from the
exemption; see the answer to the previous question, for example.
11. Starch is a polymer that readily degrades in the environment. If it
were not listed on the TSCA Inventory, would starch be eligible for the
exemption?
No; polymers that readily degrade are excluded from the exemption.
12. What does the Agency mean by "substantially" in the phrase
"substantially degrade..."? Does this refer to any specific conditions
(e.g., sunlight, water, low pressure) or under normal environmental
conditions?
By "substantially," the Agency means considerably; meaningfully; to a
significantly large extent. The restriction refers to polymers that undergo
considerable degradation, under normally anticipated conditions of use or
disposal, and in a reasonable length of time.
13. Will a polymer that is designed to be pyrolyzed or burned when it
functions as intended be excluded from the exemption by the "degrade,
decompose or depolymerize" conditions?
Yes, if that is the normal way it is used. A polymer propellant or
explosive would be excluded. However, a plastic used for (say) garbage bags
would not be excluded merely because it might under some circumstances be
incinerated.
14. A manufacturer produces a polymer that is otherwise eligible for the
exemption. It is readily biodegradable by the OECD test. There are two
uses for the product. In one use, the manufacturer can reasonably
anticipate that the polymer will eventually find itself in aqueous
systems where it may degrade. In the second use, the polymer will be
formulated into articles at a low percentage such that the articles
themselves would not be anticipated to degrade once they are disposed of
in a landfill. Provided that the manufacturer could control customer
sales to assure that the polymer would only be used in the second use,
could the polymer exemption apply?
Yes; provided that the use is restricted to conditions under which the
polymer would not be expected to degrade, decompose or depolymerize, it would
not be excluded from the exemption.
15. Will EPA specify testing conditions for evaluating "degradation"? Will
manufacturers using the exemption have to test to prove their polymers
don't degrade? Can we rely on intent to degrade?
This guidance document does not specify test conditions for
degradability; there is no testing requirement to establish nondegradability;
and, as the rule says in section (d)(3), polymers are excluded "...that could
substantially decompose after manufacture and use, even though they are not
actually intended to do so." In other words, it is what can actually be
expected to happen to the substance, rather than just the intent of the
manufacturer, that determines whether this criterion is met.
16. Are Diels-Alder polymers (for example, dicyclopentadiene polymers)
considered degradable?
38
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There are no specific constraints on structure or method of
polymerization. If Diels-Alder polymers are "designed or reasonably
anticipated to substantially degrade, decompose, or depolymerize," they would
be excluded; if not, they would be eligible if the other exemption criteria
are met.
EXCLUSION OF WATER-ABSORBING POLYMERS:
17. How are water-soluble, water-dispersible, and water-absorbing polymers
distinguished with regard to the polymer exemption? Are they treated the
same? Is dispersibility considered degradation?
Water-soluble and water-dispersible (that is, self-dispersing or already
dispersed) polymers are not considered to be water-absorbing substances. Only
water-insoluble, non-dispersible water-absorbing polymers are excluded. The
distinction is based on an assumed mechanism for lung damage by water-
absorbing polymers, which involves a failure of the lungs to clear particles
of these materials. Water-soluble or water-dispersible materials are expected
to be cleared, and are thus not excluded. Dispersibility is not considered to
be degradation.
A water-absorbing polymer that is manufactured or imported in water and
is sold in water at concentrations allowing full water-absorption is not
excluded from exemption provided that it meets all other criteria of the
exemption and is not otherwise specifically excluded.
18. Why are high MW water-absorbing polymers excluded from the polymer
exemption?
EPA excluded this category of polymers from the exemption based on TSCA
section 8(e) inhalation study, designated 8(e)-1795 and FYI-470, on a water-
absorbing polyacrylate polymer with a MW in excess of 1 million daltons that
indicated a potential cancer concern for this type of high MW water-absorbing
polymer. The Agency concluded that exposure to respirable fractions of these
polymers might present an unreasonable risk to human health. (For a
discussion of this issue also see pages 16319-16320 in the rule which this
document compliments).
19. If a polymer is partly ionized on use by a pH change which increases its
water absorption to greater than 100 percent by weight, is the polymer
no longer eligible for the exemption? What if the neutralizing agent is
less than two weight percent of the polymer? Does the so-called
"(h)(7)" pH neutralizer exclusion apply to polymers > 10,000 MW that
absorb more than 100 percent of their weight of water upon
neutralization? Does the "(h)(7)" exclusion take precedence over the
polymer exemption, or vice versa, or what?
If the polymer becomes water-absorbing upon use in neutral water, it is
a water-absorbing polymer, whether or not ionization is involved.
If it is deliberately converted to a water-absorbing polymer by
neutralization, that constitutes manufacture for commercial purposes as a
chemical substance per se, rather than processing. The resulting substance
would be a different polymer that would be considered water-absorbing and
consequently not eligible for the exemption. (Even if the neutralizing agent
used is less than or equalt to two percent, a polymer must still meet the
eligibility requirements in order to be exempt.) The unneutralized starting
polymer could still be eligible for the exemption, if it met the other
exemption criteria.
On the other hand, if the neutralization results in a substance excluded
from reporting under 40 CFR §720.30(h)(7) (which basically covers processing
rather than manufacture), that substance remains excluded from reporting even
if it would have been ineligible under the polymer exemption. (See the
Agency's published clarification on this issue available through the TSCA
Assistance Information Service (202) 554-1404: the package from Joseph Carra,
Deputy Director, Office of Pollution Prevention and Toxics, to the regulated
community, dated June 29, 1994.) If an exempt polymer is converted into a
water-absorbing substance as a result of a chemical process or reaction that
39
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produces a substance excluded from reporting under (h)(7), the starting
polymer remains exempt. Both the polymer exemption and 40 CFR §720.30(h)(7)
apply, independently, to the respective substances.
20. I have an acidic resin that is eligible for a polymer exemption. Would
the salt of this resin automatically be eligible for exemption?
A salt of an exempt polymer would not automatically be eligible for
exemption. However, if the conversion of the resin to its salt introduces no
properties (for example, water-absorption) or constituents (for example,
certain elements in amounts greater than permitted) that would cause it to be
excluded from the exemption, the resulting polymer salt should also be
eligible for the exemption. The manufacturer must ensure that the polymer
salt does in fact meet all requirements for exemption and that the reaction
making the salt has not caused a change in the polymer which could exclude it
from exemption. (Bear in mind that the conversion of a polymer to its salt
does not always produce a reportable substance; see the answer to question
19.)
LIMITATION ON CATIONIC PROPERTIES:
21. If you have a very "non-basic" amine (such as dialkyl aniline) is it
anticipated to become cationic in the environment? Suppose you can
calculate from the pKa of the amine and the concentration of amine
groups in the polymer that the functional group equivalent weight of the
protonated form of the amine will be >5000 in a natural aquatic
environment. Could the polymer be eligible for the exemption?
If a manufacturer or importer can establish by pKa data, or otherwise,
that the amine groups in a polymer are "non-basic" and therefore would not
become cationic in the environment, the polymer would not be excluded from
exemption on the basis of potentially cationic character. However, amine
groups are still considered reactive functional groups whether they are
protonated or not. In other words, neither pKa nor the "non-basic" character
of amines affects the calculated reactive functional group equivalent weight.
See the discussion under that section.
22. Does the phrase "used only in the solid phase" mean end use, as opposed
to processing where the polymer may be melt extruded, injection molded,
etc.?
"Used only in the solid phase" does refer to end use; a solid material
melted during the course of processing does not have to be considered a liquid
if it is solidified at the end of the processing step.
23. A polymer contains a potentially cationic group. The polymer is neither
water soluble nor water dispersible but is manufactured by emulsion
polymerization and therefore exists as particles dispersed in water. Is
the polymer ineligible for the exemption?
Cationic polymers and potentially cationic polymers (see definitions in
section 4.2.1 of this manual) are excluded from the exemption except for two
types: 1) those that are solids, are neither water soluble nor dispersible in
water, are only used in the solid phase and are not excluded by other factors;
and 2) those that have low cationic density and are not excluded by other
factors. If your polymer is neither water soluble not water dispersible,
manufacture by emulsion polymerization alone would not render it ineligible.
See also the answer to question 17.
24. What exactly is meant by water-insoluble with respect to cationic
polymers that qualify for exemption? Does the phrase "[T]he polymer is
a solid material that is not soluble or dispersible in water" relate to
a specific test? Is this a drop in water test or formulating test?
The phrase in section (d)(1)(i) does not relate to a specific test, and
the Agency has not prescribed any specific test for water-solubility of
40
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polymers. Whatever standard is used, however, should be applied to the
commercial material as manufactured and sold. If an aqueous emulsion is the
commercial form of the substance, the solubility criterion should be applied
to that, rather than to a dried film of the final, end-use product. (An
aqueous emulsion is a water-dispersed material, and a substance in that form
would be considered to be soluble or dispersible; it therefore would not
qualify.)
REACTIVE FUNCTIONAL GROUPS:
25. Please confirm that amine salts are permitted, as well as confirming
that sulfonic and sulfuric acids (-SO3H and -OSO3H) and their salts are
considered non-reactive.
Amine counterions are permitted for anionic polymers. Sulfonate salts
are not considered reactive. However, sulfonic and sulfuric acids are
considered reactive (they were specifically designated as such in the 1984
polymer exemption rule, and the interpretation has not been changed in the new
rule) .
26. Regarding (e)(1) criteria, what are a few examples of "high concern" and
"low concern" functional groups. Would acrylate, epoxide or isocyanate
groups be considered "high" or "low" concern?
Epoxides are listed in (e)(1)(ii)(B), the list of "moderate concern"
groups for which concerns exist at a functional group equivalent weight of
1,000 or less. Acrylate and isocyanate are not listed either in (e)(1)(ii)(B)
or in (e)(1)(ii)(A), the "low concern" group list; they are therefore
considered "high concern" groups and fall under (e)(1)(ii)(C), for which the
functional group equivalent weight concern level is 5,000 or less. Sections
(e)(1)(ii)(A) and (B) contain lists of all the "low concern" and "moderate
concern" groups, respectively. Any reactive group not on either list is
considered to be "high concern."
27. The nitro group does not appear on the low- or moderate- concern list of
reactive functional groups. Does this mean that nitro would fall into
the high-concern category by default? This is counter-intuitive,
because I wouldn't consider the nitro group to be very reactive and of
much concern.
Numerous groups were not listed because they were not considered to be
reactive functional groups (for example, ester and ether groups). Nitro
groups are also not considered to be reactive functional groups, unless they
are specially activated (certain aromatic nitro groups are readily displaced
by nucleophilic substitution reactions).
28. Is the amine group considered a high-concern reactive functional group?
It is not listed specifically at either 40 CFR §723.250(e)(ii)(A) or
(B), which would by default place it in category (C). However, because
the criteria for a substance that "may become cationic in the
environment" appears to address the concerns that EPA would have for
amine groups in limiting the amount of amine in a polymer to one in
5,000 daltons, it does not seem that the amine group, in and of itself,
should be regarded as a reactive functional group. Would the amine group
be used in the calculation for FGEWcomblned?
The amine group is considered a high-concern reactive functional group
and therefore should be used in the calculation. It is reactive in undergoing
condensation reactions to form polyamides and polyimides and, unlike the
aliphatic hydroxyl group, was not identified as a low-concern functional
(category (A)) group. The Agency has concern for this group as a reactive
functional group unrelated to considerations of its aquatic toxicity. For
polymers that are not water-soluble or -dispersible and that will be used only
in the solid phase, the limitation on cationic functional groups (such as
quaternary ammonium) would not apply; but the limit on amine groups as
reactive groups would still apply.
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29. Regarding FGEW of high concern groups vs. low concern
groups, does one need to combine all high concern groups and
separately combine all low concern groups - or add both together?
If any "high concern" (that is, (e)(1)(ii)(C)) groups are present, one
needs to calculate the combined functional group equivalent weight of any
"moderate concern" (that is, (e)(1)(ii)(B)) and "high concern" groups
together. To meet the criterion, the resulting FGEW must be no less than
5,000. "Low concern" (that is, (e)(1)(ii)(A)) groups are not included in the
computation.
30. If a polymer with a number-average molecular weight >10,000 meets the
reactive functional group and oligomer content criteria of (e)(1), but
not the more stringent oligomer content criterion of (e)(2) , it seems to
fall into a gap between (e)(1) and (e)(2). Is it therefore not eligible
for the exemption? If is isn't, does the Agency plan to amend the
(e)(1) criterion to omit the phrase "and less than 10,000 daltons"?
The (e)(1) and (e)(2) exemptions are indeed mutually exclusive.
Polymers with molecular weight of more than 10,000 are eligible only for the
(e)(2) exemption, which has lower allowable concentrations of oligomer than
does (e)(1). A polymer like the one described would not be eligible for
either the (e)(1) or (e)(2) exemption. The Agency received no comment on this
issue from the time the rule was proposed on February 8, 1993 until after the
final rule became effective on May 30, 1995. A modification of the criteria
seems reasonable, but additional rulemaking rather than a simple correction
would be required. The issue is under discussion, and Agency resource
constraints may rule out near-term action.
THE TWO PERCENT RULE (AND NON-INVENTORY REACTANTS):
31. Please explain the changes in the "Two Percent Rule" for polymers.
The "Two Percent Rule," which has been in effect since 1977, allows
manufacturers and importers of polymers to add monomers or other reactants to
an Inventory-listed polymer at levels of two percent or less (based on the dry
weight of the manufactured polymer) without making a polymer with a different
chemical identity than the Inventory-listed polymer. It also serves as a
basis for determining the identity of a polymer. Before May 30, 1995, the
effective date of the PMN Rule amendments, the monomer content of a polymer
was always calculated based on the weight percentage of monomer or other
reactant "charged" to the reaction vessel. The 1995 amendments allow persons
greater flexibility in determining the percentage composition and whether
monomers and other reactants are present at more than two percent. In
addition to being able to use the "charged" method, the 1995 amendments allow
persons to use an alternative method, i.e., to determine the amount of monomer
or other reactant that is present "in chemically combined form" (incorporated)
in a polymer and to report the minimum weight percent of that monomer or
reactant that is needed in theory to account for the amount incorporated. A
manufacturer is free to use either method to determine a two percent level;
however the "incorporated" method, while providing more flexibility, also
requires supporting analytical data or theoretical calculations.
This change in the "Two Percent Rule" applies to all polymers under
TSCA, including Inventory listings, PMN submissions, and polymer exemptions.
32. If I use the "chemically combined" method and claim that two percent or
less of a reactant is incorporated in my polymer even though I charge a
higher level to the reaction vessel, what records am I required to
maintain to support this claim?
Your records must contain analytical data or appropriate theoretical
calculations, if such an analysis is not feasible, to demonstrate that the
minimum weight of monomer/reactant required to account for the
monomer/reactant fragments chemically incorporated is two percent or less.
Your records should take into account potential batch-to-batch variation.
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33. It appears from the polymer exemption rule and the technical guidance
manual that a person does not have the option of including a
reactant/monomer at less than or equal to two percent in the polymer
identity. Is this true?
Yes, this statement is true. Polymers covered by a polymer exemption do
not have a formal name. The "identity" is established by the percentages of
monomers/reactants charged or incorporated in the polymer, as cited in the
exemption-holder's records. If a polymer has less than or equal to two
percent of a monomer/reactant, the identity does not contain that
monomer/reactant. If an otherwise identical polymer is made, and the same
monomer/reactant is a greater than two percent, the identity of the second
polymer is different from the first. Two exemptions would have to be claimed
to cover both polymers.
For polymers for which a PMN is submitted, the submitter does have the
option of including a reactant/monomer at less than or equal to two percent in
the polymer identity.
34. Does a manufacturer need to test every batch of polymer to prove that
less than two percent is incorporated, or would one documented test on a
typical batch be sufficient?
A company is not required to test every batch but is required to
maintain in its records analytical data or theoretical calculations to
demonstrate compliance with the "Two Percent Rule" when using the
"incorporated" method. If the amount normally incorporated is expected to be
close enough to two percent that occasional batches might exceed that level,
either more frequent testing, or always considering the reactant to be part of
the chemical identity, or manufacturing a separate exempt polymer with the
reactant present at greater than two percent and included in the polymer
identity, might be appropriate.
35. I use a prepolymer that is on the Inventory to make my polymer. The
prepolymer contains a non-Inventory monomer, and the final polymer
contains greater than two percent of that monomer. Will my polymer be
ineligible for the exemption?
Not on the basis of the non-Inventory monomer; §(d)(4) bars the use of
"monomers and/or other reactants... that are not already included on the TSCA
Chemical Substance Inventory...", but the prepolymer is a reactant that is on
the Inventory. The identity of the final polymer will probably include the
non-Inventory monomer, though; see the answers to related questions in the
section on Inventory Status of Reactants (questions 45-49) .
36. If an initiator is incorporated at no more than two percent, does it
have to be on the TSCA Inventory?
An initiator or other reactant present at no more than two percent does
not have to be on the Inventory for a polymer to be eligible for the
exemption. However, if the reactant is not on the Inventory, it cannot be
used for commercial manufacture in the United States. Consequently, this
provision will for all practical purposes be applicable only to imported
polymers.
37. Can I use less than or equal to two percent of any monomer that is on
the Inventory?
Yes, as long as that monomer doesn't introduce elements, groups or
properties that would render the polymer ineligible at the concentration of
monomer used. Note, though, that for the (e)(3) "polyester" exemption, all
components of the polymer must be on the list of allowable reactants. In this
case the use of non-listed monomers, even at two percent or less, would render
the polymer ineligible for the (e)(3) exemption.
38. I wish to import a substance containing greater than two percent of a
reactant not on the public TSCA inventory, but which may be on the
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confidential inventory. On what do I file a Bona Fide, if all I plan to
import is the final polymer, to know whether it now qualifies for the
new polymer exemption criteria or if I need to file a PMN for the
polymer?
There is really no way to find out whether a substance is on the
Inventory unless you intend to import or manufacture that substance itself.
You may not file a Notice of Bona Fide Intent to Manufacture ("Bona Fide") on
the reactant unless you have a bona fide intent to manufacture or import it.
(Your supplier, if in the U.S., could file a Bona Fide on the monomer,
however.) Therefore, the only substance for which you can file a Bona Fide is
the final polymer. If the polymer is on the Inventory, no PMN will be needed.
If not, you will need to file a PMN for the polymer; unless you have a real
intent to import or manufacture the monomer, you cannot file a PMN or an
exemption for the monomer. If the monomer is on the Inventory, your polymer
may be eligible for exemption. If it is not, completing the review process
for the monomer and commencing its manufacture or import will allow it to be
used in an otherwise exemptible polymer.
39. Can the polymer exemption be used for import of a polymer made with a
non-TSCA listed chemical? If not, why?
The polymer cannot be imported under the polymer exemption if the non-
TSCA reactant is used at greater than two percent. The reason is that the
Agency cannot make the determination that no unreasonable risk will be
incurred by a polymer that contains residual amounts of a monomer or other
reactant that it has never reviewed. If the reactant is present at less than
or equal to two percent, and if its presence does not otherwise render the
polymer ineligible, the polymer may be imported (if eligible). A polymer may
not be manufactured domestically if any reactant is not on the Inventory.
40. If a polymer is on the Inventory but contains a non-Inventory monomer,
can you import it?
Yes. If the polymer is on the Inventory, it is an existing chemical, and
no PMN or other notice or exemption is required. The exclusion of non-
Inventory monomers and other reactants applies only to the polymer exemption.
As in the answer to the previous question, you may not manufacture it
domestically unless all the reactants are on the Inventory.
41. What if the non-Inventory-listed monomer is charged or incorporated at
less than or equal to two percent?
A polymer containing a non-Inventory-listed monomer at less than or
equal to two percent may be eligible for the exemption provided that the
monomer does not "introduce into the polymer elements, properties, or
functional groups that would render the polymer ineligible for the exemption".
Language at §(g)(1) says that such reactants are not allowed "at any level";
but to the extent that below certain levels they do not render the polymer
ineligible, they are not such reactants when used below those levels. Note
again that a non-Inventory-listed monomer that is not on the list of permitted
reactants for the (e)(3) exemption will render it ineligible for that
exemption. There are in fact reactants on that list that are not on the
Inventory. These are not subject to the two percent limitation, since they
have already been reviewed by the Agency and are considered to be not of
concern; see the answer to Question 50. However, if a monomer or other
reactant is not on the Inventory or otherwise excluded from reporting or
exempted from section 5 requirements, it cannot be used for domestic
manufacture, regardless of its concentration in the product polymer.
42. Can polymers that utilize less than or equalt to two percent of non-
Inventory listed monomers be eligible for the exemption?
Such polymers would be eligible for exemption as long as they meet all
the other exemption criteria. However, a monomer used at any concentration
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must be on the Inventory or exempt before it can be used in the domestic
manufacture of the polymer.
43. If a polymer contains any amount of a component that is not on the TSCA
inventory, it cannot be manufactured domestically under the polymer
exemption. Does that mean that a PMN for the polymer is necessary, or
does it mean the reactant must be put on the Inventory first before the
polymer exemption can be used?
To use a substance domestically for any reason, it must be on the
Inventory, excluded from reporting, or exempted under an applicable section 5
exemption (for example, low volume exemption, low release and exposure
exemption, pre-1995 polymer exemption, current polymer exemption). Therefore,
a PMN (or applicable section 5 exemption) is required for the new reactant,
and the reactant must be on the Inventory or exempt before it can be used in
the domestic manufacture of the polymer. Once the reactant is on the
Inventory, a polymer containing it would not be automatically excluded from
the exemption, as long as it was otherwise eligible.
44. If you have a TSCA-listed brominated flame retardant mixed at greater
than two percent in a polymer base, is the polymer subject to PMN
requirements or is it exempt?
The material is considered to be a mixture of polymer and the flame
retardant. Mixtures are not subject to reporting under TSCA, provided that
there is no intended reaction between the components of the mixture. The
components of the mixture are separately subject to reporting if they are not
on the Inventory. If they are both on the Inventory, no reporting is
required. If the polymer is eligible for the exemption, the presence of the
other component will not render it ineligible.
45. Are all of the exclusions under 40 CFR §720.30 ("Chemicals not subject
to notification requirements") applicable to the polymer exemption?
Yes; however, a manufacturer must comply with the conditions of the
exclusions even though the substances are being used in connection with the
polymer exemption. For example, a substance subject to the low-volume
exemption could be used as a monomer for an eligible polymer, but only if the
supplier is a holder of the exemption and if the appropriate production
ceiling is adhered to.
INVENTORY STATUS OF REACTANTS; CHEMICAL IDENTITY OF POLYMERS:
46. How do I find out whether:
(a) my polymer is on the confidential TSCA Inventory?
(b) a reactant in my polymer is on the confidential Inventory?
You can determine the Inventory status of your polymer by filing a
Notice of Bona Fide Intent to Manufacture (or a PMN). You may not file a Bona
Fide on the reactant unless you have a bona fide intent to manufacture or
import it. It is the responsibility of the manufacturer or importer (your
supplier, in this case) of the reactant to determine the Inventory status of
the reactant.
47. When a prepolymer is one of the precursors of a polymer, what should be
considered to be the constituents of the final polymer: the ultimate
reactants from which the prepolymer was manufactured, the prepolymer
itself, or what?
The choice should follow Chemical Abstracts (CA) nomenclature rules and
conventions for its Ninth Collective Index (9CI). In general, polymers are
named on the basis of their ultimate monomers. Thus the name of a prepolymer
derived from dimethyl terephthalate and 1,4-butanediol would be based on those
reactants. However, there are some exceptions to this generalization. For
example, although polyethylene glycol may be thought of as a homopolymer of
ethylene oxide, it is not named as a homopolymer under CA naming practices,
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but rather according to the structural repeating unit (SRU) and end groups
present: a-Hydro-CO-hydroxy-poly(oxy-1,2-ethanediyl). Similarly,
polydimethylsiloxane is named on the basis of its SRU: di-Me Siloxanes and
Silicones (and is considered to be end-capped with trimethylsilyl groups). If
a prepolymer is named so as to represent a certain structural feature or
definite repeating unit, its name cannot be decomposed into ultimate monomers
for the purpose of naming the final polymer. The Agency's conventions for
representation of polymeric substances are discussed in greater detail in a
1995 paper, "Toxic Substances Control Act Inventory Representation for
Polymeric Substances," available from the TSCA Hotline: phone (202) 554-1404;
fax (202) 554-5603.
48. Does the "Two Percent Rule" apply to the actual reactants used, or to
the ultimate or putative reactants?
Consistent with the answer above, the ultimate reactants should be the
basis of the chemical identity of the polymer. Thus, if a new polymer is made
from the polymer in the answer above, plus additional dimethyl terephthalate
and ethylene glycol, the final polymer name would be based on three
constituents, and the total amount of dimethyl terephthalate would be the sum
of the separate contributions. Ultimate reactants that contribute no more
than two percent by weight to the final polymer may be omitted from the
identity. If a homopolymer is used as a prepolymer constituent, the identity
of the derived polymer should be based on the ultimate monomer, except where
CA practice differs due to the applicability of SRU nomenclature (see the
paper referenced in the answer to the previous question). Although
calculation of the percentage composition of a polymer may be based on
analysis (that is, "incorporated"), the identity should be based on the
ultimate precursors.
49. In light of the modified "Two Percent Rule," which now allows reporting
of polymers as incorporated as well as charged, can all polymer listings
on the Inventory now be read either as incorporated or as charged?
Yes; polymers on the Inventory can be interpreted either as incorporated
or as charged. Remember that "incorporated" means the minimum amount that
theory requires to be charged in order to account for the amount monomer or
reactant molecules or fragments found in the polymer itself.
50. If I import a polymer that is described as a sodium salt and I can
determine analytically that sodium is present at two percent or less,
can I assume that sodium hydroxide was the neutralizing agent used to
produce that material, and should I use the sodium hydroxide molecular
weight in determining the percent incorporated (and hence the chemical
identity)?
Yes; in the absence of information about the source of the sodium ion,
sodium hydroxide should be used as the default source and the calculations
should be based on the molecular weight of sodium hydroxide. The hydroxides
of magnesium, aluminum, potassium and calcium should also be used as the
default sources of the respective ions.
POLYESTER CRITERION:
51. Some of the reactants on the polyester list are not on the TSCA
Inventory. Am I allowed to use these to manufacture a polyester under
the polymer exemption?
Yes, for imported polymers. Under the 1984 exemption those reactants
were placed on the polyester ingredients list, even though they were not on
the Inventory, because there was no exclusion for non-Inventory reactants.
The Agency is continuing to allow these specific reactants , because the
Agency has already made the determination that no unreasonable risk will be
incurred by a polymer that contains residual amounts of these reactants.
For domestic manufacture, you may use only substances that are on the
Inventory or are otherwise exempt or excluded from reporting.
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52. If a monomer in my polyester is used at less than or equal to two
percent and is not on the (e)(3) list, is the polymer eligible for the
exemption if it meets all the other criteria and is not otherwise
excluded from the (e)(3) exemption?
No, the polyester would not be eligible for the exemption. Only
monomers and reactants on the (e)(3) list may be used for this category of
polymer regardless of the percentage charged or incorporated.
53. Is there to be a mechanism to add new reactants to the polyester
reactants list? If so, what is expected to be required?
The list of permissible ingredients in the present exemption has already
been enlarged since the 1984 version. To quote from the Agency's response to
a comment addressing this specific issue in the preamble to the final rule,
"The Agency believes that it would be appropriate in the future to propose
amendments to this section to allow expansion of the list of eligible
precursors, when additional candidates have been identified. To support
requests for additional reactants, petitioners should provide health and
environmental effects information on the candidate reactants, which must be
already on the Inventory." No specific mechanism has yet been put in place.
The Agency would prefer not to deal with such reactants piecemeal, but rather
as part of a systematic process, perhaps initiated by trade organizations or
consortia of interested companies.
OTHER ISSUES:
54. If a polymer contains a gel fraction (presumably high MW>10,000) of 10
to 20 percent and the MW of the soluble fraction is <10,000, is it no
longer exempt? Or is the gel fraction an impurity? Or by-product?
Since the two polymeric fractions have the same chemical identity and
are not separately prepared, they would usually be considered as a single
substance, for which one (not two) number-average molecular weight would be
measured. However, impurities are not considered part of a polymer
composition; if the 10-20 percent gel portion is undesirable, it may be
considered an impurity. In that case, the appropriate number-average
molecular weight would be for the portion below 10,000, and the polymer would
have to meet the (e)(1) criteria. Whether the gel portion is considered an
impurity does not depend upon whether it is a minor component; it depends upon
whether it is not intended to be present.
55. Are inventory-listed monomers which have allowed groups, and a 5(e)
order attached, eligible for the new polymer exemption?
Yes, as long as the use of the monomer is in accordance with the
conditions of the 5(e) order.
56. There is no guidance on measurement of oligomer content. Is accumulated
weight fraction on a GPC trace an adequate determination? In the absence
of GPC, how can this be done?
Cumulative weight fraction is a commonly accepted method. The Agency has
not prescribed any analytical methodology; others may be acceptable, depending
on circumstances.
57. Do polymers made by "reactive processing" of two or more other polymers
(both on TSCA) fall under the polymer exemption?
If not otherwise excluded, yes, as long as they meet the necessary
criteria. There is no exclusion for polymers made from other polymers, nor is
there any restriction on method of preparation.
58. What are the analytical requirements with respect to insoluble polymers?
Can inference from melt flow data and comparison to other polymers be
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adequate? Can I use Monte Carlo simulation methods (such as Oligo 5) to
estimate the MW of an insoluble polymer theoretically?
The Agency does not require any specific analytical methodology.
Inference from physical behavior, from comparison to close analogues, and from
theoretical calculation is acceptable where appropriate or where other methods
are inapplicable. Monte Carlo methods, while widely used, have not been
subjected to much experimental verification; if your polymer is expected to
have values of MW or oligomer content near the allowable thresholds, you
should probably not rely too strongly on such methods. For a discussion of
analytical methods in general, see the relevant section of this guidance
manual.
59. For persons who choose to use the "chemically combined" method for
determining the amount incorporated in a manufactured polymer, does EPA
prescribe a specific analytical method for this determination?
No. The rule does not specify any particular method. Guidance on this
issue is found in this guidance manual.
60. If you make a new polymer in the laboratory which meets the
exemption rule, do you need to send a research and development
letter to the customer?
Substances considered to be research and development (R&D) chemicals are
subject to the Research and Development Exemption, and must follow the
conditions of that exemption. Polymers should be handled according to the R&D
requirements until they reach the stage of being commercial products eligible
for the polymer exemption. When the commercial activity is no longer R&D,
provisions of that exemption no longer apply.
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8. REFERENCES
1. OECD. 1994. (May). Organization for Economic Co-operation and
Development. OECD Guidelines for the Testing of Chemicals,
Determination of the Low Molecular Weight Polymer Content (Draft
Proposal).
2. OECD. 1994. (May 10) . Organization for Economic Co-operation and
Development. Chemicals Group and Management Committee. Chairman's
Report, Third Meeting of OECD Experts on Polymers, Tokyo, 14-16
April 1993.
3. OECD. 1994. (May). Organization for Economic Co-operation and
Development. OECD Guidelines for the Testing of Chemicals,
Determination of the Low Molecular Weight Polymer Content (Draft
Proposal).
4. IUPAC Physical Chemistry Division, Engl. Pure Appl. Chem. 1976, 48(2),
241-6 .
5. Glover, C.A. Tech. Methods. Polym. Eval. 1975, 4, Pt.1, 79-159.
6. Tung, L.H.; Runyon J.R. J. Appl. Polym. Sci. 1973, 17(5), 1589-96.
7. Wagner, H.L.; Verdier, P.H. J. Res. Natl. Bur. Stand. (U.S.) 1978,
83(2), 179-84.
8. Glover, C.A. Advan. Chem. Ser. 1973, Volume date 1971, No. 125, 1-8.
9. FEDERAL REGISTER REFERENCES
TSCA. 1976. The Toxic Substance Control Act, 15 U.S.C. §§ 2601-2629 (1982 &
Supp. Ill 1985) .
USEPA. 1983a. (May 13). U.S. Environmental Protection Agency.
Premanufacture Notification; Premanufacture Notice Requirements and Review
Procedures; Final Rule and Notice Form. (48 FR 21742).
USEPA. 1983b. (September 13). U.S. Environmental Protection Agency.
Premanufacture Notification; Revision of Regulation and Partial Stay of
Effective Date. (48 FR 41132).
USEPA. 1984. (November 21). U.S. Environmental Protection Agency.
Premanufacture Notification Exemptions; Exemptions for Polymers; Final Rule.
(49 FR 46066). see also 40 CFR part 273.
USEPA. 1986. (April 22). U.S. Environmental Protection Agency.
Toxic Substances; Revisions of Premanufacture Notice Regulations; Final Rule.
(51 FR 15096-15103). see also 40 CFR part 720.
USEPA. 1991. U.S. Environmental Protection Agency.
Premanufacture Notice for New Chemical Substances. EPA Form 7710-25.
USEPA. 1993a. (February 08). U.S. Environmental Protection Agency.
Premanufacture Notice; Revision of Exemption for Chemical Substances
Manufactured in Quantities of 1,000 Kg or Less Per Year; Proposed Rule. (58
FR 7646-7661). See also 40 CFR parts 721 and 723.
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USEPA. 1993b. (February 08). U.S. Environmental Protection Agency.
Premanufacture Notification; Revision of Notification Regulations; Proposed
Rule. (58 FR 7661-7676). See also 40 CFR part 720.
USEPA. 1993c. (February 08). U.S. Environmental Protection Agency.
Toxic Substances; Significant New Use Rules; Proposed Amendment to Expedited
Process for Issuing Significant New Use Rules; Proposed Rule. (58 FR 7676-
7679). See also 40 CFR part 721.
USEPA. 1993d. (February 08). U.S. Environmental Protection Agency.
Premanufacture Notification; Exemptions for Polymers; Proposed Rule. (58 FR
7679-7701). See also 40 CFR part 723
USEPA. 1995. (March 29). U.S. Environmental Protection Agency.
Premanufacture Notification Exemptions; Revisions of Exemptions for Polymers;
Final Rule. (60 FR 16316-16336) .
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