EPA-660/2-75-014
JUNE 1975
Environmental Protection Technology Series
Recycle of Synthetic Warp Sizes from
Textile Desizing Wastewater
National Environmental Research Center
Office of Research and Development
U.S. EhvOtinmental Protection Agency
Corvailis, Oregon 97330
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development,
U.S. Environmental Protection Agency, have been grouped into
five series. These five broad categories were established to
facilitate further development and application of environmental
technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in
related fields. The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL PROTECTION
TECHNOLOGY STUDIES series. This series describes research
performed to develop and demonstrate instrumentation, equipment
and methodology to repair or prevent environmental degradation from
point and non-point sources of pollution. This work provides the
new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
EPA REVIEW NOTICE
This report has been reviewed by the Office of Research and
Development, EPA, and approved for publication. Approval does
not signify that the contents necessarily reflect the views and
policies of the Environmental Protection Agency, nor does mention
of trade names or commercial products constitute endorsement or
recommendation for use.
-------
EPA-660/2-75-014
June 1975
RECYCLE OF SYNTHETIC WARP SIZES
FROM TEXTILE DESIZING WASTEWATER
Carl E. Bryan
Department of Textile Chemistry
North Carolina State University
Raleigh, North Carolina 27607
Grant S800294
Program Element 1BB036
ROAP Z1AZT, Task 006
Project Officer
Thomas N. Sargent
Southeast Environmental Research Laboratory
National Environmental Research Center
College Station Road
Athens, Georgia 30601
NATIONAL ENVIRONMENTAL RESEARCH CENTER
OFFICE OF RESEARCH AND DEVELOPMENT
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
CORVALLIS, OREGON 97330
For tale by the Superintendent of Document!, U.S. Government
Printing Office, Washington, D.C. 20402
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ABSTRACT
In an earlier project for the Environmental Protection Agency,
a process was developed on a small scale for precipitating car boxy-
methyl cellulose (CMC) from desizing wastewater with filter alum.
and recovering and dissolving the precipitate to give a solution suit-
able for reuse in sizing warp yarns. More extensive recovery trials
have now been made on plant desizing wastewater to give sufficient
material for weaving trials and for developing a practical procedure
for size recovery.
Weaving trials using warp yarns sized with CMC recovered from
plant desizing wastewater were as satisfactory as those using warps
sized with new CMC. Desizing and dyeing the woven fabrics showed
no difference in hand and shade that could be attributed to the recover-
ed CMC. The yarns were blends of polyester and cotton (65:35) and
polyester and rayon (65:35).
Sufficient dewatering of the precipitated CMC - to ten percent
solids or higher - was accomplished by centrifuging or by the use of
a Dual Cell Gravity (DCG) unit (Permutit Co.) alone or, preferably,
in combination with a Multi-Roll Press (MRP) unit (Permutit Co. ).
This report was submitted in fulfillment of Project S800E94 by
North Carolina State University under the partial sponsorship of the
Environmental Protection Agency. Work was completed as of April
1974.
11
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CONTENTS
Page
Abstract ii
List of Figures iv
List of Tables v
Acknowledgments vi
Sections
I Conclusions 1
II Recommendations 2
III Introduction 4
IV Experimental Studies and Discussion 8
Recovery of CMC from Plant Desizing Wastes 8
Weaving Trials with Recovered CMC 16
Dyeing of Fabrics Woven with Recovered CMC 20
Separating and Dewatering Precipitated CMC 28
Stability of CMC During Recovery and Storage 40
Economic Assessment of Recovery Process 42
Recovery of Polyvinyl Alcohol (PVA) from
Desizing Wastes 45
V References 48
VI Publications 50
VEI Appendix 51
111
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FIGURES
No. Page
1 Combinations of processes for treating fabrics 23
2 Total yardage of fabric in each treatment process 24
3 Diagrammatic cross-section of DCG unit 32
4 Diagrammatic cross-section of MRP unit 34
IV
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TABLES
No. Page
1 BOD, COD and TOD of common sizing agents 5
2 Total solids and CMC content in first desizing liquors 8
3 Slashing data for new and recovered CMC on 32/2
Dacron/Avril yarn 10
4 Warp-shed tester results on 32/2 Dacron/Avril yarn
sized with new and with recovered CMC 12
5 Total solids and CMC content of second desizing liquors 14
6 Total solids and CMC content of third desizing liquors 15
7 Weaving with new and recovered CMC: first trial 17
8 Weaving with new and recovered CMC: second trial 18
9 Weaving with new and recovered CMC: third trial 20
10 Process sequence for each two-yard sample of fabric 25
11 Plant desizing trials with fabrics sized with CMC 36
12 Total solids and CMC content of plant desizing liquors
used in precipitating and dewatering trials 37
13 Solids content of CMC-alum precipitates dewatered with
DCG and MRP units in sequence 39
14 COD of desizing liquors before and after precipitation
with alum 40
15 Warp-shed tester results on yarns sized with commercial
PVA and with modified PVA 47
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ACKNOWLEDGMENTS
This report was prepared by Carl E. Bryan, Project Director,
with the assistance of the other people engaged in work on the pro-
ject.
The major part of the bench-scale laboratory studies, including
the analytical work, was carried out by Peggy S. Harrison. The
warp-sizing experiments and the trials on the warp-shed tester were
performed by Charles D. Livengood and Gene G. Floyd. The warping,
slashing and weaving trials were made by Fred N. Watkins, Ada L.
Harvell and students, under the supervision of Joseph A. Porter and
Charles D. Livengood. The fabric preparation and dyeing trials were
made by Gene G. Floyd and students in Textile Chemistry.
The size recovery and dewatering trials were carried out at the
Wake Finishing Plant of Burlington Industries, Inc. , with the assis-
tance of laboratory and plant personnel there; Edward H. Teague,
Plant Manager, and John Apinis, Plant Chemist, provided consultative
and administrative support.
The Dual-Cell Gravity and Multi-Roll Press units, used in the
major part of the dewatering trials, were rented from the Permutit
Company (Division of Sybron Corporation) •whose personnel provided
advice and assistance.
The Hydrocyclonics Corporation, the Bauer Brothers Company,
and the Rexnord Company, in the exploratory stage of the dewatering
experiments, made trials for us or allowed us to use their equipment
without charge. Their cooperation was much appreciated and is
hereby acknowledged.
VI
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The copolymers of vinyl acetate and vinyl alcohol were prepared
by Samia G. Saad, a graduate student in Civil Engineering.
The support of the major part of the project by the United States
Environmental Protection Agency,' and the help provided by Thomas N.
Sargent, Project Officer, is gratefully acknowledged.
VLl
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SECTION I
CONCLUSIONS
A process developed earlier on a laboratory scale for precipita-
ting and recovering carboxymethyl cellulose (CMC) from desizing
wastes has been found to be applicable to plant -desizing wastes. As
in the earlier work, precipitation was accomplished with aluminum
sulfate (filter alum).
The CMC-alum precipitate was dewatered to a solids level (10-
15%) satisfactory for reuse as a warp size by means of the Dual Cell
Gravity (DCG) and Multi-Roll Press (MRP) units, in sequence, of the
Permutit Company.
Weaving trials using warp yarns sized with CMC recovered from
plant desizing wastes were as satisfactory as those using warp sized
with new CMC. Desizing and dyeing the woven fabrics showed that no
difference in hand and shade could be attributed to the use of recovered
CMC. The yarns were blends of polyester and cotton (65:35) and poly-
ester and rayon (65:35).
Several copolymers of polyvinyl alcohol (PVA) were prepared
which were precipitated from dilute solution by aluminum sulfate and
ferric chloride. Sizing trials with two of these copolymers followed
by tests of the sized yarns with the warp-shed tester, indicated that
these, or similar, copolymers may be effective, recoverable warp
sizes.
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SECTION II
RECOMMENDATIONS
Further work on the removal of warp sizes from textile -
desizing wastewater should be concerned with a careful technological
and economic evaluation of the several procedures already available.
The objective should be to obtain wastewater that is reusable and to
leave residues that can be disposed of without harm to the environ-
ment. A number of questions remain to be answered and further
studies are necessary.
(1) The most commonly used warp sizes - starch, polyvinyl
alcohol (PVA), carboxymethyl cellulose (CMC) - have been shown to
be biodegradable under the proper conditions. Is biological treat-
ment the most economical method for disposing of these materials?
In regard to PVA and CMC particularly, what are the "proper"
conditions?
(2) The synthetic warp sizes, CMC and PVA (or a modified PVA),
can be removed or recovered from wastewater by several procedures,
including precipitation, hyperfiltration, and evaporation. What is the
most economic (in the broad sense) method of removal? Should they
be removed for disposal (incineration or land disposal) or is it econo-
mically favorable to recover them for reuse?
(3) The commercial PVA currently used for sizing warp yarns is
not practicably recoverable from desizing wastewater by precipitation.
Results on this project show that development of a modified PVA
recoverable by precipitation is possible. Is this procedure a "good"
way of removing PVA from desizing wastewater?
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(4) A large proportion of the COD of CMC-desizing wastewater
remains after the CMC is precipitated and removed. Can the mater-
ials responsible for this COD be removed economically to leave a
reusable wastewater?
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SECTION in
INTRODUCTION
The major warp size used in the textile industry is starch which
must be removed (scoured) from a fabric before dyeing and contri-
butes heavily to the biochemical oxygen demand (BOD) of textile
wastewater. In recent years certain synthetic polymers have been
introduced for use as warp sizes; of these materials, polyvinyl alcohol
(PVA) and carboxymethyl cellulose (CMC) have gained the widest use.
Although the cost of these materials is higher than that of starch, they
have certain advantages in performance, particularly with yarns of
the synthetics and cotton-synthetic blends, which tend to offset this
cost differential.
Besides giving increased operating efficiencies, the synthetic
warp sizes, having a low 5-day BOD (BODg) have been promoted also
as a means of reducing the water-pollution potential of desizing wastes.
According to one report, CMC has an essentially negligible BODg but
shows a steady consumption of oxygen up to the ultimate level of 25%
of its weight in about 30 days. According to another report, the
BODC for CMC is 4% and the BODon is 15%, while the BOD. of PVA
14
is negligible (1%) and the BOD3Q is only about 3%. The Federal
Water Pollution Control Act Amendments (PL 92-500) of 1972 and the
effluent limitation guidelines proposed by the United States Environ-
mental Protection Agency now indicate that BOD5 is becoming inade-
quate as the sole measure of organic pollution. Instead the more
stringent measure of chemical oxygen demand (COD), or perhaps
total organic carbon (TOC), may be required.
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The COD of CMC is nearly as high as the COD of starch, however,
and the COD of PVA is much higher than that of starch (see Table 1).
Therefore, for reducing water pollution as measured by COD, these
materials offer no advantage over starch - unless they are more
effective than starch and can be used in smaller amounts or unless
they can be recovered and reused.
TABLE 1. BOD, COD AND TODa OF COMMON SIZING AGENTS
Sizing Agent
Starch
Carboxymethyl cellulose (CMC)
Polyvinyl alcohol (PVA)
BOD5
64
4
1
BOD3Q
95
25
3
COD
118
93
175
TOD
118
103
182
Theoretical oxygen demand
Starch is readily biodegradable and is removed to a high degree
in a well-operating biological waste-treatment system. Previously,
CMC and PVA, having a low BOD5, were assumed to be only slowly
and incompletely biodegradable and apparently to pass unchanged
through these treatment systems or to be only partially removed by
adsorption on the biological mass. Recent investigations on another
project sponsored by the United States Environmental Protection
Agency, have shown that activated-sludge microorganisms can be-
come acclimated to CMC and PVA, respectively, and effect ahigh
degree of removal of these substances from influents containing
"3 A
them. A process was developed on pilot scale for precipitating
CMC from desizing wastes with filter alum and recovering and redis-
solving the precipitate to give a solution potentially suitable for reuse
•3
in sizing warp yarns. On the other hand, the recovered CMC may
be disposed of as a solid waste without further treatment.
5
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The CMC was carried through five cycles of sizing, desizing, and
size recovery, continuing with only the material recovered from the
previous step. The trials were carried out on a blended yarn of poly-
ester and cotton (65:35) with an add-on of size of approximately 10% of
yarn weight. Nearly quantitative recovery of CMC was obtained by
precipitation from the dilute desizing wastewater with filter alum.
The precipitated CMC was dewatered by centrifuging, dissolved in
dilute sodium hydroxide, and reused. Performance of the recovered
CMC on the Callaway slasher was satisfactory. The results obtained
with the sized yarns on a warp-shed tester were comparable to those
obtained with yarns sized with new CMC for four cycles. On the fifth
cycle, however, the results were slightly poorer with the recovered
CMC; the shed was higher, the clinging was greater, and there were
more "stops". Some of the natural impurities of the cotton and pro-
bably the spinning oil used on the polyester were retained by the CMC
during recovery, gradually accumulating in each cycle, and undoubt-
edly were the major if not the sole cause of the final decrease in per-
formance of the recovered CMC as a warp size. They did not affect
four cycles of operation, however, and they were not retained by the
yarns in any step.
Other researchers have shown that PVA can be recovered in a
28 13
reusable form from desizing wastewater by hyperfiltration.
Precipitation techniques have not been found applicable to commer-
cial warp-size-grade PVA but are applicable to certain PVA modifi-
Q
cations. On the other hand, hyperfiltration might be used with CMC
desizing wastewater. The two processes therefore should be compared
to find out if one is better or if they might be complimentary.
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The results, summarized above, obtained on the earlier EPA
project and elsewhere, indicated that more extensive trials should be
made in a textile plant to develop a practical procedure for size
recovery and to obtain sufficient amounts of recovered material for
weaving trials. The Wake Finishing Plant of Burlington Industries
agreed to cooperate with us in these trials.
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SECTION IV
EXPERIMENTAL STUDIES AND DISCUSSION
RECOVERY OF CMC FROM PLANT DESIZING WASTES
A preliminary trial of size recovery from desizing wastes was
carried out at the Wake Finishing Plant of Burlington Industries.
Some 3700 yards (3100 Ib. , approx. ) of polyester/rayon (65/35)
fabric, woven from warps sized with sodium carboxymethyl cellulose
(CMC), was desized continuously in a beck which was divided into
three compartments, twelve feet, three feet, and three feet, respec-
tively, in width. The fabric passed first through the twelve-foot
section which contained a solution of soda ash (0. 1%) and non-ionic
surfactant (0. 1%), and then through the two three-foot sections,
which contained only water. All three compartments were heated to
180°F. Analysis, after desizing, of the liquors in the three compart-
ments for total solids, amount precipitated by alum, and CMC content
gave the values shown in Table 2.
TABLE 2. TOTAL SOLIDS AND CMC CONTENT
IN FIRST DESIZING LIQUORS
Analysis
Total solids (%)
Alum precipitate (%)
CMC analysis (%)
Compartment
1
0.72
0.40
0.32
2
0.36
0. 18
0. 13
3
0.22
0. 12
0.09
Spectrophotometric determination
8
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The CMC in the desizing liquors was flocculated by the addition
of a 50% solution of filter alum. The alum solution was added until
the pH was lowered to 3. 5, a condition found previously to insure
complete flocculation of the CMC. Because of the presence of the
surfactant, an attempt to pump the CMC slurry from the beck produced
an emulsion from which the CMC could not be settled. A portion of
the flocculated CMC was collected manually from the first compart-
ment of the desizing beck and taken to North Carolina State University
(NCSU) for dewatering by centrifuging. Approximately 200 pounds of
water-swollen, salmon-colored material (approx. 20 Ib. , dry weight)
was obtained.
Part (approx. 17.5 Ib. ) of the recovered, dewatered CMC was
dissolved by the addition of sodium hydroxide solution with vigorous
stirring using a laboratory homogenizer (Eppenbach). About 2.5
gallons of a smooth, opaque, salmon-colored solution was formed,
with a solids content of 10% (by weight), a viscosity of 400 centipoises
(160°F) and a pH of 7. 9.
Warps containing 252 ends of 32/2 Dacron/Avril (65/35) yarn,
identical to the warps in the desized fabric, were sized on a Callaway
Slasher with the solution of recovered CMC and, as a control, with a
solution of new CMC. Three add-on levels were applied with each of
the CMC solutions. A small build-up of size and fiber on the first
drying cylinder was noted near the end of the slashing trial with the
recovered CMC.
The cause of this build-up is not known but it may indicate the
presence of a small amount of water-soluble impurities in the recov-
ered size. Slashing data are presented in Table 3.
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TABLE 3. SLASHING DATA FOR NEW AND RECOVERED CMC
ON 32/2 DACRON/AVRIL YARN
Test
no?
1
2
3
4
5
6
Viscosity
(Centi poises)
400
at
160°F
430
at
180°F
Foaming in
size box
No
No
No
No
No
No
Dry can
sticking
No
No
No
Nob
Nob
Nob
Shedding
at split -
rods
Slight
Slight
Slight
Slight0
Slight0
Slight0
Bath
solids
(%)
10.5
10.5
10.5
7.6
7.6
7.6
Tests 1-3 were made using recovered CMC.
Tests 4-6 were made using new CMC.
There was shedding on the first drying cylinder. This shed brushed off easily.
The yarn was separating poorly at the split rods. Also, there were broken
yarns at this point as a result of the hard split.
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The sized warps were tested on a warp-shed tester, a laboratory
machine that simulates the action of a loom. The results given in
Table 4 indicate that at equivalent add-ons, there was less shedding
with warps sized with new CMC. The fibrous content of the shed,
however, was lower for the warps sized with recovered CMC. There
was no difference in number of stops but clinging was slightly less with
warps sized with new CMC. With the recovered CMC, it was found
that the higher the add-on, the higher the percent shed after testing.
The fibrous content decreased with increasing add-on, suggesting
that the recovered CMC contained an appreciable amount of water -
soluble impurities which loosely adhered to the sized yarn.
A second trial of size recovery from, desizing wastes was
carried out at the Wake Finishing Plant. Some 3200 yards of poly-
ester-rayon-spand ex (59:37:4) fabric, woven from warps sized with
sodium craboxymethyl cellulose (CMC), was desized continuously as
a rope in a beck which was divided into three compartments, twelve
feet, three feet, and three feet, respectively, in width. Desizing in
this case differed from that previously reported in that all the com-
partments of the beck contained only water, heated to 180 F.
The desizing liquor was pumped from the first compartment of
the beck into six cylindrical tanks (total capacity, 500 gal.). As soon
as a tank was filled, the proper amount of concentrated (50%) alum
solution was added to precipitate the CMC. When the CMC-alum
precipitate had settled the supernatant was pumped to a floor drain
and the sludge remaining was transferred to a container for storage
and transportation to NCSU for recycling. The tanks were filled
again with desizing liquor from the beck and the operations of preci-
pitation with alum, settling, removal of supernatant, and transfer of
11
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TABLE 4. WARP-SHED TESTER RESULTS ON 32/2 DACRON/AVRIL YARN
SIZED WITH NEW AND WITH RECOVERED CMC
Test
Noa
1
2
3
4
5
6
Add-on
(%)
10.4
9.0
8.8
9.0
7.2
6.3
Shed
(%)
2.8
2.4
2.2
1.8
1.9
1.9
Fiber in
Shed
(%)
31
34
38
64
80
85
Cling
Rating
(%)
25 +
50-
50-
25
50
25 +
Stops
20 yds.
(No.)
0
1
0
0
1
0
Tests 1-3 were made with recovered CMC.
Tests 4-6 were made with new CMC.
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CMC-alum sludge were repeated. Each tank was used four times,
a total of 24 precipitations, in recovering the CMC from the desizing
liquor in the first (12-ft. ) compartment of the beck. Because the
liquors in the other two compartments had smaller volumes, as well
as a lower concentration of CMC, they were not collected for further
processing. Small-scale experiments have shown, however, that
CMC is precipitated essentially quantitatively by alum from solutions
of these low concentrations. The results of analysis of the liquors in
the three compartments, after desizing, are shown in Table 5.
13
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TABLE 5. TOTAL SOLIDS AND CMC CONTENT
OF SECOND DESIZING LIQUORS
Analysis
Total solids (%)
Alum precipitate (%)
CMC content {%)*
Compartment
1 2 3
0.72
0.68
0.50
0.27
0.17
0.13
0. 18
0. 11
0. 10
c*
Spectrophotometric analysis
The precipitated CMC was taken to NCSU for dewatering by
centrifuging. Approximately 350 pounds of water-swollen, gray
material was obtained, with a dry weight of approximately 35 pounds.
The desized and dried fabric had a slightly stiff hand (feel), indi-
cating that it still retained a small amount of the sizing material.
Extraction of a sample of the fabric with Freon showed that the
material retained was primarily composed of the wax which was used
in small amount in the CMC sizing composition. Scouring with a
detergent will most likely be necessary for complete removal of such
a size in a rapid, commercial desizing operation. The use of a deter-
gent in CMC desizing, however, will be of consequence in the CMC
recovery process only if the CMC-alum sludge must be passed through
a pump during recovery and dewatering. There is also some contro-
versy as to whether wax is necessary in CMC sizing compositions.
A third trial of size recovery from desizing wastes was carried
out at the Wake Finishing Plant. Some 3000 yards (approx. 2000 Ibs.)
of rayon-acetate-nylon (47:33:20) fabric, woven from warps sized
with CMC and kettle wax, was desized continuously, as a rope, in a
beck which was divided into three compartments, twelve feet, three
14
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feet, and three feet, respectively, in width. The fabric passed first
through the twelve-foot section which contained a solution of non-
ionic detergent (0. 1%) and then through the two three-foot sections
which contained only water. The first compartment was heated to
170°F, the second to 150 F, and the third to 100 F. Analyses, after
desizing, of the liquors in the three compartments for total solids,
amount precipitated by alum, and CMC content are shown in Table 6.
TABLE 6. TOTAL SOLIDS AND CMC CONTENT
OF THIRD DESIZING LIQUORS
Analysis
Total solids (%)
Alum precipitate (%)
CMC content (%)
C ompa r tme nt
1
0.43
O.Z2
0.21
2 3
0. 19
0. 10
0. 08
0. 09
0. 04
0. 03
The desizing liquor in the first compartment of the beck was
pumped into several large cylindrical tanks (capacities: 50 and 150
gallons). Tanks containing about half of the liquor were treated with
a concentrated alum solution in the amount found previously to be sat-
isfactory for precipitation of the CMC. The precipitated material was
taken to NCSU for further experimentation. Tanks containing the other
half - some still hot (140 F) and some that had been allowed to stand
and cool to room temperature - were treated with varying amounts of
concentrated ferric chloride solution. In every case the precipitate
that formed -was finely dispersed and slow to settle in comparison with
15
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that produced with alum. This result substantiates earlier jar tests
in the NCSU laboratory.
WEAVING TRIALS WITH RECOVERED CMC
A weaving trial was made using warp yarns sized with the CMC
recovered from the desizing wastes. A similar trial was made with
warps sized with new, commercial, warp-size-grade CMC (Hercules)
as a control. The CMC, dewatered by centrifuging but still highly
swollen with water (10-15% dry weight CMC),was dissolved by the
addition of sodium hydroxide solution (40%) with good agitation (Eppen-
bach homogenizer) and heating in a hot-water bath. Approximately
eight pounds of dewatered CMC was dissolved in this way to give about
eight gallons of solution with a total solids content of 12% and a pH
of 8.5. Hot water was added to the concentrated solution to give appro-
ximately 15 gallons of sizing solution with a total solids content of
7. 3% (CMC content, 5. 8%) and a pH of 8. 5.
The yarns used in the weaving trials were the same as those com-
prising the commercial fabric (Burlington) from which the CMC was
recovered. The warp yarn was a 35/2 polyester-rayon (65:35) blend;
the filling yarn was a 16/1 polyester-rayon (65:35) blend.
Although a number of mechanical steps are involved, weaving may
be divided into three operations: warping, i. e. placing the required
number of yarns of the required length on a beam; slashing (sizing),
i.e. coating the warp yarns with a protective, polymeric film; and
the weaving, i.e. formation of a fabric. Data regarding the sizing
solutions and the sizing operation are shown in Table 7.
16
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Results of the weaving trials indicate weaving with warp yarns sized
with recovered CMC was as satisfactory as that with warp yarns sized
with new CMC.
TABLE 7. WEAVING WITH NEW AND RECOVERED CMC:
FIRST TRIAL
Sizing and Weaving Data
Solids in sizing solution (%)
CMC content of solids in size (%)
3,
Viscosity of sizing solution (cps)
pH of sizing solution
Add-on of size (% of yarn weight)
Fiber in shed during weaving (%)
New
CMC
5.4
98
180
8.0
5.0
60
Recovered
CMC
7. 3
79
400
8.5
7.2
70
a Centipoises at 170-175°F
A second weaving trial was made on commercial looms using
warp yarns sized with another batch of CMC recovered from plant
desizing wastes. In this case, fabric desizing had been carried out
with hot water without any auxiliary chemicals. Solution of the recov-
ered and dewatered CMC was effected as before by the addition of the
proper amount of sodium hydroxide solution (40%), with good agitation
and heating in a hot-water bath. Approximately ten pounds of dewater-
ed CMC was dissolved in this way to give about ten gallons of solution
with a total solids content of 12% and a pH of 8. 0. Hot water was
added to the concentrated solution to give approximately 18 gallons of
sizing solution with a total solids content of 6. 8% (CMC content, 5. 1%)
and a pH of 8.0.
17
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The yarns used in the -weaving trials were, as before, the same
as those comprising the commercial fabric (Burlington) from which
the CMC was recovered. The warp yarn was a. 35/2 poly ester-rayon
(65:35) blend; the filling yarn was a 16/1 poly ester-rayon (65:35) blend.
The results obtained from the second weaving trial are shown in
Table 8. For comparison, the results obtained from the first •weaving
trial are shown again, along with those obtained from the control. The
performance of the recovered CMC was as good as, if not better than,
that of the. new CMC used as a control. The construction of the fabric
woven was very tight, placing great strain on the warp yarns, and pro-
bably accounted for the warp-end breakage.
TABLE 8. WEAVING WITH NEW AND RECOVERED CMC:
SECOND TRIAL
Sizing and Weaving Data
Solids in sizing solution (%)
CMC content of solids in size (%)
b
Viscosity of sizing solution (cps)
pH of sizing solution
Add-on of size (% of yarn weight)
Number of warp stops during weaving
Fiber in shed during weaving (%)
Fabric woven (yd. )
New CMCa
5.4
98
180
8.0
5.0
12
57
53
Recovered
CMC
1 2
7.3
80
400
8.5
7.2
10
70
51
6.8
74
170
8.5
10.5
6
72
44
Control, with warp-size grade CMC (Hercules)
Centipoises at 170-175°F
18
-------
Further weaving trials were made using warp yarns sized with
CMC recovered from plant desizing wastes as previously described.
The yarn, both warp and filling, was a 40/1 polyester-cotton (65:35)
blend, a composition widely used in the textile industry. This yarn
was finer than that used in previous weaving trials and hence provided
a more strenous test of the performance of the recovered CMC as a
warp size. A similar trial was made with warps sized with new,
commercial CMC (Hercules) as a control.
Solution of the recovered and dewatered CMC was effected as
in previous experiments by the addition of the proper amount of
sodium hydroxide solution (40%), with good agitation and heating in a
hot-water bath. In one case, approximately 10. 5 pounds of dewatered
CMC was dissolved in this way to give about 10 gallons of solution
with a total solids content of 7.4% (CMC content, 5.2%) and a pH of
7.5. In the other case, approximately nine pounds of dewatered CMC
was dissolved with sodium hydroxide to give eight gallons of solution
with a total solids content of 13% and a pH of 8. 2. This solution was
diluted with hot water to give approximately 10 gallons of sizing solu-
tion with a total solids content of 10. 7% (CMC content, 8.2%) and a
pH of 8.2.
The results obtained from these weaving trials are shown in
Table 9. The better performance of the warps in the second trial
with recovered CMC apparently can be attributed to the higher add-on
of size.
19
-------
TABLE 9. WEAVING WITH NEW AND RECOVERED CMC:
THIRD TRIAL
(Yarn: 40/1 Poly ester-cotton (65:35) blend)
Sizing and Weaving Data
Solids in sizing solution (%)
CMC content of solids in size (%)
pH of sizing solution
Add-on of size (% of yarn weight)
Number of warp stops during weaving
Fiber in shed during weaving (%)
Fabric woven (yd)
New CMCa
7.2
98
7.5
Recovered
CMC
1
7.4
70
8.0
7.1 to. 4
10
85
70
85
61
47
2
10.7
77
8.2
12.3
11
54
39
a Control with warp-size-grade CMC (Hercules)
DYEING OF FABRICS WOVEN WITH RECOVERED CMC
Weaving trials with a poly ester-rayon (65:35) blended yarn, both
warp and filling, were described in the preceding part. Portions
(25 yd) of the fabrics from each of the three weaving trials, two with
recovered CMC and one with new CMC, were desized together in a
small beck. The desizing bath was a solution of soda ash (0. 1%) and
Triton X-100 (0. 1%) in water (80 gal). The fabrics were scoured in
this bath at 170°F for 20 minutes; then the bath was discharged and the
fabrics were rinsed twice in successive baths of warm (130 F) water.
Samples of the three desized fabrics were dyed and heatset in
accordance with the following sequences.
20
-------
A. Polyester dyed only
B. Polyester dyed, heat-set
C. Polyester dyed, heat-set, rayon dyed
D. Rayon dyed only
E. Heat-set, rayon dyed
The polyester component of the fabrics was dyed (A, B, C) with
Latyl Blue FLW (C. I. Disperse Blue 27, No. 60767); the rayon compo-
nent of fabrics was dyed (C, D, E) with Diphenyl Billiant Blue FF (C. I.
Direct Blue 1, No. 24410). Fabrics dyed with these dyes tend to show
dyeing defects readily. Standard dyeing procedures recommended by
dye and fabric manufacturers, and well-known in the trade, were used
throughout.
o
Some of the fabric samples were heat-set (B, C, E) at 390 F
for 45 seconds on a tenter frame.
Fifteen different fabric samples were obtained from the dyeing
and heat-setting sequences --five from the fabric (1) woven with new
CMC, five from the fabric (2) woven with the first batch of recovered
CMC, and five from the fabric (3) woven with the second batch of
recovered CMC. Swatches (8" x 12") were cut from each of the 15
fabric samples and sewn into five test panels, representing each of
the five processing sequences. These panels are represented schema-
tically below.
A
B
C
1
1
1
2
2
2
1
1
1
3
3
3
2
2
2
D
1
2
1
3
2
E
1
2
1
3
2
21
-------
A cursory examination of the panels by members of the NCSU
staff indicated that there was no difference in hand among any of the
swatches, nor was there any difference in shade or uniformity of
color among the swatches in any panel that could be attributed to the
size.
A weaving trial with a 40/1 poly ester-cotton (65:35) blend, both
warp and filling yarns, using CMC recovered from plant desizing
wastes as a warp size, was described above. A similar trial was
made at the same time with warps sized with new, commercial CMC
as a control. Portions (32 yd) were taken from each of the woven
fabrics and split into two-yard samples. These samples were put
through serial combinations of two, three, four or five of the pro-
cesses of desizing, bleaching, cotton dyeing, polyester dyeing, and
heat setting. The desizing process, however, was a component of
each treatment combination as represented in Table 10. To insure
validity of comparison, corresponding experimental samples, woven
with recovered CMC, and control samples, woven with new CMC,
were always treated together. In addition the two-yard samples were
sewn together before each treatment process so that all samples
received a given treatment at the same time. The only exception to
this procedure was heat setting, which had to be done in two separate
batches.
The combinations and sequences of processes used in finishing
the fabric samples are shown diagramatically in Figures 1 and 2.
The final results are given in Table 10.
Procedures for each of the processes are given as follows:
22
-------
^-Polyester Dyed
(4)
Heat Set
(12)
• Desized.
(12)
• Bleached —
(6)
-Polyester Dyed
(4)
ro
u>
^-Polyester Dyed
(6)
Desized—
(20)
-Bleached
(10)
-Polyester Dyed-
(6)
-Heat Set-
(4)
-Heat Set-
(2)
Cotton Dyed
(2)
Cotton Dyed
(2)
Cotton Dyed
(2)
Cotton Dyed
(2)
Cotton Dyed
(2)
Cotton Dyed
(2)
Cotton Dyed
(2)
Cotton Dyed
(2)
Cotton Dyed
(2)
Cotton Dyed
(2)
Figure 1. Combinations of processes for treating fabrics.
(Yards of each fabric shown in parentheses.)
-------
Bleached
(32)
\
Cotton Dyed
(40)
Heat Set
(24)
Polyester Dyed
(40)
ro
Figure 2. Total yardage of fabric in each treatment process.
(Experimental and control)
-------
TABLE 10. PROCESS SEQUENCE FOR EACH TWO-YARD
SAMPLE OF FABRIC
to
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Size
control
control
control
control
control
control
control
control
control
control
recovered
recovered
recovered
recovered
recovered
recovered
recovered
desized,
desized,
desized,
desized,
desized,
desized,
desized,
desized,
desized,
desized,
desized,
desized,
desized,
desized,
desized,
desized,
desized,
bleached, polyester dyed
bleached, polyester dyed, heatset
bleached, polyester dyed, heatset, cotton dyed
bleached, cotton dyed
bleached, heatset, cotton dyed
left unbleached, polyester dyed
left unbleached, polyester dyed, heatset
left unbleached, polyester dyed, heatset, cotton dyed
left unbleached, cotton dyed
left unbleached, heatset, cotton dyed
bleached, polyester dyed
bleached, polyester dyed, heatset
bleached, polyester dyed, heatset, cotton dyed
bleached, cotton dyed
bleached, heatset, cotton dyed
left unbleached, polyester dyed
left unbleached, polyester dyed, heatset
-------
TABLE 10 (continued). PROCESS SEQUENCE FOR EACH TWO-YARD
SAMPLE OF FABRIC
18
19
20
21
23
23
24
25
26
27
28
29
30
31
32
recovered
recovered
recovered
control
control
control
control
control
control
recovered
recovered
recovered
recovered
recovered
recovered
desized,
desized,
desized,
heatset,
heatset,
heatset,
heatset,
heatset,
heatset,
heatset,
heatset,
heatset,
heatset,
heatset,
heatset,
left unbleached, polyester dyed, heatset, cotton dyed
left unbleached, cotton dyed
left unbleached, heatset, cotton dyed
desize, bleach, polyester dyed
desize, bleach, polyester dyed, cotton dyed
desize, bleach, cotton dyed
desize, left unbleached, polyester dyed
desize, left unbleached, polyester dyed, cotton dyed
desize, left unbleached, cotton dyed
desisse, bleached, polyester dyed
desize, bleached, polyester dyed, cotton dyed
desize, bleached, cotton dyed
desize, left unbleached, polyester dyed
desize, left unbleached, polyester dyed, cotton dyed
desize, left unbleached, cotton dyed
-------
Heat-Setting: The fabric samples were heat set on a tenter
frame at 390 F for 45 seconds. The fabric width was held at 38
inches.
Desizing: The fabric samples were desized in a small laboratory
beck with a bath solution of soda ash (0. 1%) and Triton X-100 (0. 1%);
the bath ratio was 60:1 (bath to fabric by weight). The bath was held
at 170 F for 20 minutes; then it was discharged to the drain and the
fabric was given two rinses with hot (130 F) water.
Bleaching: The fabric samples were bleached in a. small beck
with a solution of hydrogen peroxide (8. 0%, on weight of fabric (owf)
of 35% H O ) sodium silicate (6. 0%, owf) and caustic soda (0.8% owf);
the bath ratio was 120:1. The bleaching bath was held at 200 F for
90 minutes; then it was discharged and the fabric was rinsed once
with hot (140°F) water, once with a solution of Triton X-100 (0. 8%
owf) and twice with warm 120 F water.
Dyeing - Disperse Dye: Dyeing was carried out in a jig with a
bath ratio of 30:1. A bath solution containing Carolid (0. 5%) and Avi-
tone T (0. 05%) was heated to 140°F and the fabric was run through
four ends (times). The dye stuff (Latyi Blue FLW, C. I. Disperse
Blue 27, No. 60767) (1. 5% owf) were added to the bath, the tempera-
ture was raised to 210 F over a 45-minute period, and dyeing was
continued for 60 minutes. The dye bath was discharged and the fabric
was rinsed once with water at 140 F, once with a solution of Alkanol
H. C.S. (1.0%) at 180°F, and again with water at 140 F. Finally, the
fabric was dried on a tenter frame.
27
-------
Dyeing - Direct Dye: Dyeing was carried out in a jig with a bath
ratio of 33:1. The fabric was wet out in the bath solution containing
Sequestrene (1.0% owf) and the dyestuff (Diphenyl Brilliant Blue FF,
C. I. Direct Blue 1, No. 24410, 1.0% owf) was added. The bath
temperature was raised to 210°F over a 30-minute period and dyeing
was continued for 45 minutes. Then salt (30%, owf) was added and dye-
ing was continued for a further 15 minutes before the dye bath was
discharged. The fabric was rinsed once with water at 140 F and dried
on a tenter frame.
Corresponding pairs of dyes samples, obtained from weaving with
new and recovered CMC, were sewn together and examined by several
members of the NCSU staff. The opinion was that there was no differ-
ence in shade or uniformity of color between the pairs of samples that
could be attributed to the size. This result substantiates that reported
earlier for dyeing fabric samples woven similarly from polyester-rayon
(65:35) blended yarns.
SEPARATING AND DEWATERING PRECIPITATED CMC
In the earlier work on the recovery and reuse of CMC from textile
desizing wastes, the CMC-alum floe was allowed to settle, the super-
natant was decanted, and the settled Hoc was dewatered by centrifuga-
tion. Satisfactory batch dewatering was obtained with a basket-type
centrifuge, 26 inches in diameter (United States Hoffman Machinery
Corp.), operating at 1800 rpm. Consultations with other staff
members of NCSU as well as industrial representatives leave little
doubt that a large, continuous centrifuge would be suitable for
dewatering the CMC-alum floe in the plant. Continuous centrifuges
are expensive, however.
28
-------
There are a number of firms that have already developed other
equipment for separating and dewatering sludges from biological treat-
ment and from chemical coagulation and trials on the CMC-alum floe
were made with some of the equipment of this type. Four types of
equipment were evaluated on the pilot scale and are discussed in the
following paragraphs.
Rotostrainer® (Hydrocyclonics Corp.)
A sample of CMC desizing waste, from Wake Finishing plant, was
shipped to Hydrocyclonics Corporation of Lake Bluff, Illinois, together
with instructions for precipitating the CMC with alum. The quantity of
this precipitate retained by the Rotostrainer, a rotating screening
device, was less than 10% of the quantity recovered in the laboratory
by filtration or centrifugation. The openings in the Rotostrainer
apparently are too large to retain this type of precipitate.
Hydrasieve® (Bauer Bros. Co. )
The Hydrasieve is a commercial apparatus for continuously and
rapidly separating solid particles from most of the liquid phase of a
solid-water mixture. It consists of a stationary, slanting screen or
sieve over which the mixture is passed in a thin but rapidly flowing
layer. The water phase passes through the screen on the way down
while the solid particles are retained to fall down the screen into a
trough at the bottom.
A small, portable Hydrasieve with a stainless steel screen (6
inches wide, 0. 030 - inch mesh), obtained on loan from American
Pollution Control, Inc. , retained about 50% of the solids from a CMC-
alum suspension after one pass. The solids content of the suspension
was 0. 5% while that of the material retained was 1. 8%. The solids
29
-------
retention with this screen is inadequate and the solids content of the
material retained is much too low for preparing a solution suitable for
warp sizing.
Trials with another small Hydrasieve (Model 552-3, stainless
steel, 6-^ inches wide, 0. 020-inch mesh screen) gave better results
in that 80-90% of the solids from a CMC-alum suspension was retained
by the screen upon a single pass. The solids content of the material
retained by the screen from a 1% suspension was 4. 0-4. 5%; this is too
low for our purpose and further dewatering would be required.
Vacuum Filter (Rexnord)
A sample of settled CMC-alum sludge (about 1.5% solids), obtained
from plant desizing wastes, was shipped to the Rexnord Technical Center
in Milwaukee, Wisconsin for trials with a rotary vacuum filter. The
results showed that the sludge is filterable but that the resultant filter
cake is quite high in moisture content. The best conditions gave a
cake with 94% moisture (6% solids). Further dewatering of the cake
would be necessary for our purpose. Cake thicknesses were one-
fourth inch to five-sixteenth inch and were satisfactory for discharge
from the filter cloth.
Dual Cell Gravity (DCG) and Multi-Roll Press (MRP) Units
(Permutit Company)
Sufficient dewatering (to 10% solids or higher) of the CMC-alum
precipitate was obtained with the Dual Cell Gravity (DCG) and the
Multi-roll Press (MRP) dewatering units of the Permutit Company,
Division of Sybron Corporation.
30
-------
The DCG Sludge Dewatering Unit has been used for dewatering all
types of sanitary sewage sludges, a wide range of industrial waste
sludges, both biological and chemical, and water treatment sludges
from clarification and softening. It consists of two separate compart-
ments or cells, a dewatering cell and a cake-forming cell, which are
formed by a fine-mesh nylon filter cloth traveling continuously over
front and rear guide wheels. A drive-roll and sprocket assembly
rotates the cloth and also serves as the separator between the two cells.
(Figure 3).
The sludge is pumped into the first cell where the initial dewatering
occurs. The water drains rapidly through the filter cloth and the
partially dewatered solids are carried from the first cell over the
drive-roll separator into the second cell. Here they are rolled con-
tinuously and formed into a cylindrical cake of lower water content.
The weight of this sludge cake itself presses out additional water. When
the cake grows to sufficient size, the excess tumbles over the rim of
the second cell to a conveyor belt which carries it to a disposal point.
Dewatering in the DCG unit is accomplished entirely by gravity
and the maximum force applied is only that of a few inches of hydro-
static head. This unit can be used with fragile floes, such as the CMC-
alum precipitate, which may be difficult to handle in devices employing
larger forces (pressure or vacuum).
"Blinding" of the filter cloth or screen is minimized, both
because of the low pressures applied and because of the tendency of
the sludge particles to adhere to one another and separate cleanly
from the cloth as a cake.
31
-------
NYLON
FILTER CLOTH
DRIVE ROLL AND
SPROCKET ASSEMBLE/
FILTRATE DISCHARGE
DEWATERING
CELL
SLUDGE
INLET
CONVEYOR
Figure 3, Diagrammatic cross-section of DCG unit.
-------
The Multi-Roll Press (MRP) is a secondary dewatering unit
developed for use in combination with the DCG unit and produces
cakes with a still higher solids content. It consists of two sets of
continuous monofilament-nylon filter belts backed by two neoprene
compression belts. The space between the belts and, hence, the
pressure applied to the sludge traveling between them, is controlled
by four sets of tension rollers which can be adjusted to produce the
maximum solids for the type of sludge being dewatered (Figure 4).
The partially dewatered sludge from the DCG unit is discharged
directly into the receiving hopper of the MRP Unit where a metering
blade volumetrically feeds the cake to the moving filter belts at a rate
synchronized with the speed of the belts. The sludge enters a. gradual
compression area prior to full compression in order to remove the
water by degrees; thus maximum pressure can be applied without
squeezing the sludge outside the compression area. The belts are
inclined, allowing the displaced water to run down to a drip pan. The
neoprene compression belts backing the filter belts contain V-shaped
treads through which the displaced water travels to the drip pan. A
second function of these treads is to allow the sludge to move slightly
during compression, facilitating water removal and attaining higher
solids content. Removal of the compressed cake at the discharge
point is accomplished with a doctor blade. Strategically located
sprays backwash the filter and compression belts and any possible
solids accumulation points.
In the beginning, it was established in the laboratory by a proce-
dure recommended by the manufacturer, that the DCG unit would
probably be suitable for dewatering the CMC-alum sludge. A small
33
-------
CAKE DISCHARGE
SLUDGE INLET
EFFLUENT
Figure 4. Diagrammatic cross-section of MRP unit.
-------
amount of the sludge was poured onto a piece of coarse nylon fabric
held suspended in a U-shape between the two hands. The sludge was
rocked or rolled by raising and lowering each end of the fabric alter-
nately. The water phase passed through the fabric while the sludge
particles coalesced to form a roll on the fabric. Further dewatering
of the sludge continued as the rolling action of the sludge roll was
continued. This simple experiment simulates the operation of the DCG
unit.
Fabric desizing (Table 11) for the DCG trials was carried out in
a beck in the same manner as that described for the preliminary
recovery trials. Desizing wastewater for the recovery trials were
taken from the first compartment of the beck, which contained the
major part of size (Table 12). It was pumped into a 500-gallon tank
on the trailer upon which the DCG unit was mounted. The CMC in the
desizing wastewater was flocculated -by the addition of 50% alum solu-
tion, with gentle stirring, to a pH of 3. 3-3.5. The mixture in the
flocculating tank was then pumped at a suitable rate onto the DCG
screens. When the flocculating tank was empty, more desizing waste-
water was pumped in and the sequence of flocculation and dewatering
was repeated.
A certain amount of trial-and-error experimentation was neces-
sary before the best operating conditions for the DCG unit were found.
The variables involved were the concentration of the CMC sludge, the
rate of pumping the sludge onto the DCG screens, the porosity of the
DCG screens, the rate of rotation of the screens.
35
-------
TABLE 11. PLANT DESIZING TRIALS WITH FABRICS SIZED WITH CMC
OJ
Run no.
1
2
3
4
5
6
7
8
9
Fabric composition
Polyester-rayon-spandex (68:30:2)
Polyester- rayon -spandex (59:37:4)
Rayon-acetate-nylon (47:33:20)
Polyester-rayon (65:35)
Polyester -rayon (65:35)
Polyester-rayon-acrylic (62:36:2)
Polyester -rayon -acrylic (62:36:2)
Polyester-rayon-acrylic (62 :36 :2)
Poly ester -ray on -acrylic (62:36:2)
Yards fabric
3720
3165
3020
3710
2220
2080
4860
9210
5720
-------
TABLE 12. TOTAL SOLIDS (TS) AND CMC CONTENT OF PLANT
DESIZING LIQUORS USED IN PRECIPITATING AND
DEWATERING TRIALS (PER CENT)
Run no.
1
2
3
4
5
6
7
8
9
Beck Compartment
1
TS
0.72
0.72
0.43
0.69
0.45
0.36
0.28
0.69
0.52
CMC
0.32
0. 50
0.21
0.29
0. 18
2
TS CMC
0.36
0.27
0.19
0.36
0.16
0.08
0.07
0.46
0.16
0.13
0.13
0.08
0.12
0.06
3
TS
0.22
0. 18
0.09
0. 33
0. 11
0. 03
0. 12
0.32
0. 13
CMC
0.09
0. 10
0.08
0.07
0.03
a 59
Determined .spectrophotometrically '
-------
The following observations were made regarding the operation of
the DCG unit.
(1) A sufficient amount of solid material to form a roll must be
on the screens before they begin to function properly. Smaller amounts
tend to cling to the screens and cause "blinding".
(2) The optimum rate of addition of the solid-liquid mixture from
the precipitating tank to the DCG screens in six-to-eight gallons per
minute. Faster rates cause over-flowing without permitting the water
to pass through the screens.
(3) Eighty-mesh or 100-mesh screens are better for dewatering
the CMC-alum precipitate than a 40-mesh screen.
When the rolls of partially dewatered CMC-alum precipitate become
large enough, the excess tumbles over onto a conveyor belt which dis-
charges it to the MRP unit for further dewatering. The operation of
this unit was described above but the following observations were made
in the trials with this particular material.
(1) If the degree of dewatering of the solid introduced is not high
enough (8-9% solids in the present case) the MRP unit is not effective
and gives essentially no further dewatering.
(2) The pressure on the rolls is important and must be adjusted
to fit the nature of the solid to be dewatered. The CMC-alum precipi-
tate is fragile and too much pressure, in attempts to attain higher
degrees of dewatering, only causes "blinding" of the screens, re-
sults in little or no dewatering and requires cleansing of the screen.
The solids contents of the CMC-alum precipitates after
dewatering with the DCG and the MRP units in sequence are given
in Table 13.
38
-------
TABLE 13. SOLIDS CONTENT OF CMC-ALUM PRECIPITATES
DEWATERED WITH DCG AND MRP UNITS
IN SEQUENCE
Run no.
6
7
7
7
7
7
8
8
9
9
9
9
9
9
Solids in cake (%)
DCG
9.0
8.4
8.7
9.0
9.7
9.6
9.1
8.9
7.3
6.5
7.2
9.8
6.4
8.6
MRP
14.6
10.5
11.5
12.0
12.1
11.8
14.3
14.1
11.5
10.8
10.4
15'. 4
13.3
13. 1
The fabrics desized in the series of trials made in this work had
been sized with a mixture of CMC and kettle wax. Desizing was accom-
plished with a hot solution of non-ionic detergent (0. 1%) and sodium
carbonate (0. 1%). The desizing liquors therefore consisted of a
solution of CMC and the detergent and a suspension of the wax. Pre-
cipitation of the CMC with alum left the detergent and the wax, as well
as the spinning oils, in solution or suspension in the supernatant.
39
-------
Determination of chemical oxygen demand (COD) showed that while a
sizable portion of the organic material was removed from the desizing
liquor by precipitation of the CMC the major portion remained.
(Table 14).
TABLE 14. COD OF DESIZING LIQUORS BEFORE AND
AFTER PRECIPITATION WITH ALUM
Run no.
6
7
COD (mg/1)
Before
Precipitation
4710
4300
After
Precipitation
3820
2980
STABILITY OF CMC DURING RECOVERY AND STORAGE
In any recycling process, attention must be given to the accumu-
lation of impurities which, entering each cycle in only small amounts,
may eventually reach harmful proportions. A good example is the
natural impurities of cotton which are removed from fabrics of cotton
and cotton blends during desizing and are partially precipitated with
the CMC during size recovery.
The instability of the size itself under the conditions of recycling
could also introduce impurities in the recovered size. A partially
degraded material would be less active of course and the degradation
products, unless removed, would sooner or later render the recycled
material useless as a warp size. The prime example is starch which
is always degraded during desizing, either biologically (enzymatically)
or chemically, and cannot be recycled at all.
40
-------
In the case of the synthetic size CMC, both the biological and
chemical stability during recovery and storage must also be considered.
The hydrolysis of cellulose and cellulose derivatives under the
influence of strong acids and alkalis, particularly at elevated tempera-
tures, is well known, of course, and must receive attention in any
process for recycling CMC.
When work on this project was begun, several papers had appeared
on the biodegradation of CMC under laboratory conditions. Freeman,
7
Baillie, and Macinnes found that solutions of CMC in tap water under-
went a loss in viscosity upon standing at room temperature for a month
in the absence of a bacteriostat. They isolated gram-negative bacteria
which grew rapidly in aqueous media containing CMC as the only carbon
source, again with a resultant loss of solution viscosity.
In a study of the susceptibility of cellulose derivatives to attack by
a fungus, Myrothecium verrucaria, Siu, Darby, Burkholder and Barg-
hoorn found that CMC of low degree of substitution (DS) was metabo-
lized.
Reese, Siu, and Levinson, using a number of strains of bacteria
and fungi, found that the growth of most microorganisms was very
good on CMC preparations of low DS; when the DS was above 1. 0, how-
ever, growth was slight.
Accelerated enzymic degradation studies by Wyrick of a series
of six CMC's varying in DS from 0.41 to 2.45 showed that stability
improves with increasing substitution and that the sample with DS of
2.45 was essentially refractory to enzymic attack.
41
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Thus, the published work indicates that CMC solutions, or moist
CMC, of warp-size grade (DS 0. 7), should not be stored for lengthy
periods in the absence of a bacteriostat nor should the pH be allowed
to rise too high by too rapid addition of sodium hydroxide when the
recovered CMC is redissolved with heating for reuse.
That CMC from desizing wastewater can be recovered and reused
without significant degradation is evidenced by the work reported here.
When the recovered CMC was dissolved to give a sizing solution with a
solids concentration approximately the same as that of the original CMC
sizing solution, the viscosity of the two solutions was approximately the
same also.
4
Polyvinyl alcohol (PVA) is also biodegradable , although perhaps
less readily than CMC, and similar considerations apply to its recovery
for reuse.
ECONOMIC ASSESSMENT OF RECOVERY PROCESS
The power requirement for each DCG-100 unit is 2. 5 horsepower
(hp). Since 500 gallons of precipitated-CMC sludge can be dewatered
in 90 minutes, 1000 gallons can be dewatered in 180 minutes, or three
hours. Thus, dewatering 1000 gallons of sludge requires
3 x 2.5 x 750 = 5595 watt-hours =5.6 kilowatt-hour s (kwh) (1)
The power requirement for an MRP-100 unit is 0. 75 horsepower
so that further dewatering of the cake produced by the DCG unit from
1000 gallons of sludge, assuming three hours of continuous operation,
requires
3 x 0. 75 x 750 = 1688 watt-hours -1.7 kwh (2)
42
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Thus, the electrical energy reqaired to operate the DCG and MRP
units in tandem for three hours to dewater 1000 gallons of precipitated-
CMC sludge is:
5. 6 + 1. 7 = 7. 3 kwh (3)
The cost of additional electrical energy to a plant already using a
large amount is a little difficult to calculate since it depends on the
total amount used as well as on the peak power demand. A rate
schedule in effect at present by the Carolina Power and Light Company
for plants using 50-1000 kw of power is as follows:
$120. 00 for first 50 kw of billing demand (4)
2. 15 per lew for each addition kw of billing demand (5)
1. 10£ per kwh for first 50, 000 kwh (6)
1. 02£ per kwh for next 400, 000 kwh (7)
0. 90£ per kwh for all additional kwh (8)
The additional billing demand for a relatively large plant like
Wake Finishing would be:
(2. 50 + 0. 75) x 750 = 2438 watts = 2. 5 kw (9)
The additional billing-demand cost would be:
3 x 2. 15 = $6.45 per month (10)
If the dewatering units were used eight hours per day for a 22-day
month the pro rata increase would obviously be less than 7£ per hour
of operation.
43
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Thus, the cost of electrical energy could be set at approximately
7£ per hour, or conservatively, at X)£ per hour. The cost for
dewatering 1000 gallons of precipitated-CMC sludge would then be:
0.10 x 7.3 = $0.73 (11)
Approximately 6000 ml of alum solution (17% A12°3 basis) is
required for 500 gallons of desizing liquor, or 12, 000 ml for 1000
gallons. This amount of alum solution weighs:
12,000 x 1.4/454 = 37 pounds (Ibs) (12)
The cost of liquid alum (17% Al O ) in carload lots at present
(January 1975) is $62 per ton or $0. 031 per pound. Thus, the cost of
the alum required for recovering the CMC from 1000 gallons of desizing
liquor is:
37 x 0.031 = $1. 15 (13)
A reasonable average value for the concentration of CMC in
desizing liquor is 0. 3 per cent and, since it has been shown that the
CMC can be precipitated quantitatively from such dilute solutions, the
amount of CMC (dry basis) that can be recovered from 1000 gallons of
desizing liquor is:
1000 x 8. 34 x 0. 003 = 25 Ibs. (14)
The cost of warp-size grade CMC is currently (January 1975)
about $0. 54 per pound, so that the CMC recovered from 1000 gallons
of desizing liquor can be used in place of new CMC costing:
25 x 0.54 = $13.50 (15)
44
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The operating costs in recovering and dewatering the CMC from
1000 gallons of desizing liquors is therefore:
$1. 15 + 0.73 = $1.88 (l6)
Thus, there appears to be a considerable economic incentive for
recycling the CMC in desizing wastes, even if it is recycled only once.
RECOVERY OF POLYVINYL ALCOHOL (PVA) FROM
DESIZING WASTES
The work with polyvinyl alcohol (PVA) has not progressed as far as
that with CMC. An attractive procedure was not found for precipitating
and recovering the conventional warp-size-grade PVA from desizing
wastes. A number of materials that will insolubilize PVA are reported
in the literature but larger amounts of precipitant are required than
are practical.
Several modified PVA's have been prepared which are precipitated
from dilute solution by filter alum. These materials were prepared
by the alkaline hydrolysis of copolymers of vinyl acetate with relatively
small amounts of acidic monomers or of easily hydrolyzed derivatives
of acidic monomers. The copolymers of vinyl acetate were prepared
by the emulsion copolymerization of vinyl acetate with the selected
comonomer s.
Two of the modified PVA's, which were precipitated quantitatively
from solution by filter alum, were evaluated as warp sizes on the
Callaway slasher and the warp-shed tester. These two PVA's were
obtained from the alkaline hydrolysis of (1) the copolymer of vinyl
acetate and methyl crotonate (90:10 monomer feed) and (2) the ter-
polymer of vinyl acetate, methyl acrylate and dibutyl maleate (90:5:5
45
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monomer feed). The performance of the modified PVA's during
slashing was satisfactory and the results obtained with the sized
yarns on a warp-shed tester were equivalent to those obtained with
yarns sized with a commercial warp-size grade PVA (see Table 15).
46
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TABLE 15. WARP-SHED TESTER RESULTS ON YARNS SIZED WITH
COMMERCIAL PVA AND WITH MODIFIED PVA
Warp size
Concentration of size (%)
Size Add-on (%)
Shed (%)
Fiber in shed (%)
Stops
-J Clinging ratio (%)
Warp tested (%)
Commercial PVA
__ (Vinol 540)
5.0
4.8
1.0
80
0
25
20
6.6
7.4
0.6
50
1
50 +
20
Modified PVA
(Vinyl alcohol-crotonic
acid copolymer)
3.8
3.5
0.8
73
0
25
20
5.0
5.3
0.7
51
0
50
20
6.4 n
7.3
0.6
40
0
50+
20
(Vinyl alcohol -acrylic
acid-dibutyl maleate
copolymer)
4.4
4.0
1. 1
81
1
25
20
5.1
5.4
1.0
69
0
50+
20
6.3
7.5
0.7
50
0
50 +
20
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SECTION V
REFERENCES
1. Baird, G. S. and A. L. Griffith. The Advantages of CMC as a
Warp Size. Modern Textiles Magazine. 6(6):34, June, 1965.
2. Brandon, C. A. Hyperfiltration (Reverse Osmosis) Pilot Plant
for Textile Wastewater Renovation. A paper presented at the
Conference of Textile Wastewater Treatment and Air Pollution
Control. Hilton Head Island, South Carolina. January 24-26,
1973.
3. Bryan, C. E. Water Pollution Reduction through Recovery of
Desizing Wastes. A report prepared for the U. S. Environmental
Protection Agency on Project 12090 EOE, January 1972.
4. Bryan, C. E. and P. S. Harrison. Biodegradation of Synthetic
Warp Sizes. Textile Chemist and Colorist. 5_(5):37-109, May
1973.
5. Eyler, R. W. and R. T Hall. Determination of CMC in Paper.
Paper Trade Journal. 125(15);59, October 9, 1947.
6. Federal Register. 39(130):24736, July 1974.
7. Freeman, G. G. , A. J. Baillie, and C. A. Macinnes. Bacterial
Degradation of Sodium CarboxymethylceHulose and Methyl Ethyl
Cellulose. Chemistry and Industry (London). May 1, 1948.
8. Gaston County Dyeing Machine Company. The Reuse of Poly vinyl
Alcohol in Textile Processing. A paper presented at a special
meeting in Charlotte, North Carolina. July 30, 1974.
9. Hercules, Inc. Technical Bulletin. Analytical Procedures for the
Assay of CMC and Its Determinations in Formulations. Wilmington,
Delaware. 1966.
48
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10. Permutit Company, Division of Sybron Corporation. The Separa-
tion and Dewatering of Industrial Sludges. Technical Seminar.
Paramus, New Jersey. 1972.
11. Reese, E. T. , R. G. H. Siu, and H. S. Levinson. The Biologi-
cal Degradation of Soluble Cellulose Derivatives and Its Relation-
ship to the Mechanism of Cellulose Hydrolysis. Journal of
Bacteriology. 5_9_(4):485, April 1950.
12. Siu, R. G. H. , R. T. Darby, P. R. Burkholder, and E. S.
Barghoorn. .Specificity of Microbiological Attack on Cellulose
Derivatives. Textile Research Journal. 1^(8):484, August 1949.
13. Textile Industries Staff Report. Stevens Reclaims PVA for Warp
Sizing. Textile Industries. 137(10);47, October 1974.
14. Wenner, J. H. Reducing Biochemical Oxygen Demand in Streams
by Using New Textile Warp Sizing Agents. A paper presented at a
Symposium of the American Association of Textile Chemists and
Colorists. Atlanta, Georgia. March 31-April 1, 1971.
15. Wirick, M. G. A Study of the Enzymic Degradation of CMC and
Other Cellulose Ethers. Journal of Polymer Science. Part A-l,
6{7):1965, July 1968.
49
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SECTION VI
PUBLICATIONS
A preliminary report of the work on this project was presented
at a Symposium of the American Association of Textile Chemists and
Colorists on the Textile Industry and the Environment in Washington,
D. C. , May 22-24, 1973. It was published in the proceedings of that
symposium.
50
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SECTION VII
APPENDIX
Conversion Factors
1 inch (in) = 2.540 centimeters (cm)
1 foot (ft) = 30.48 cm
1 yard (yd) = 0.914 meters (m) = 91.44 cm
1 cm = 0. 394 in
1 m = 1. 094 yd = 3.281 ft = 39.37 in
1 pound (Ib) = 0.454 kilograms (kg) = 453.6 grams
1 kg = 2.205 Ib
1 gallon (gal) = 3.785 liters (1)
11 = 0.264 gal
°F = 9/5 (°C) + 32°
°C = 5/9(°F-32°)
51
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing}
. REPORT NO.
EPA-660/2-75-014
2.
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
5. REPORT DATE
Recycle of Synthetic Warp Sizes from Textile
De sizing Waste water
May 1975
6. PERFORMING ORGANIZATION CODE
. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
Carl E. Bryan
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Department of Textile Chemistry
North Carolina State University
Raleigh, North Carolina 27607
10. PROGRAM ELEMENT NO.
1BB036
11. CONTRACT/GRANT NO.
S800Z94
12. SPONSORING AGENCY NAME AND ADDRESS
United States Environmental Protection Agency
National Environmental Research Center -Corvallis
Southeast Environmental Research Laboratory
p» Station RnaH, Athena, Georgia 30601
13. TYPE OF REPORT AND PERIOD COVERED
JEinaL
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
In an earlier project for the Environmental Protection Agency, a process was
developed on a small scale for precipitating carboxymethyl cellulose (CMC) from
desizing wastewater with filter alum and recovering and dissolving the precipitate
to give a solution suitable for reuse in sizing warp yarns. More extensive
recovery trials have now been made on plant desizing wastewater to give sufficient
material for weaving trials and for developing a practical procedure for size
recovery.
Weaving trials using warp yarns sized with CMC recovered from plant
desizing wastewater were as satisfactory as those using warps sized with new
CMC. Desizing and dyeing the woven fabrics showed no difference in hand and
shade that could be attributed to the recovered CMC. The yarns were blends of
polyester and cotton (65:35) and polyester and rayon (65:35).
Sufficient dewatering of the precipitated CMC - to ten percent solids or higher
was accomplished by centrifuging or by the use of a Dual Cell Gravity (DCG) unit
(Permutit Co. ) alone or, preferably, in combination with a Multi-Roll Press
(MRP) unit (Permutit Co. ).
17.
KEY WORDS AND DOCUMENT ANALYSIS
a.
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COS AT I Field/Group
*Textiles, coagulation, filtration,
flotation, *recycling, *pollution,
*abatement, dewatering, industrial
wastes, chemical wastes
aluminum sulfate,
carboxymethyl cellu-
lose, polyvinyl
alcohol, warp sizes
11/05, 13/02
18. DISTRIBUTION STATEMENT
Release Unlimited
19. SECURITY CLASS (ThisReport)'
Unclassified
•1. NO. OF PAGES
60
20. SECURITY CLASS (Thispage}
Unclassified
22. PRICE
EPA Form 222O-1 (9-73)
U.S. GOVERNMENT PRINTING OFFICE: I975—698-824 II72 REGION 10
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