United States
Environmental Protection
Agency
National Risk Management
Research Laboratory
Research Triangle Park, NC 27711
Research and Development
EPA/600/SR-98/043
May 1998
Project Summary
Low-VOC Coatings Using
Reactive Diluents
Demonstration Project
Gregory Roche
Reactive diluents are compounds that
might be used to replace organic sol-
vents in conventional high-VOC (vola-
tile organic compound) coatings.
Reactive diluents function like solvents
in adjusting coating viscosity for vari-
ous applications. However, rather than
evaporating like conventional solvents,
reactive diluents participate in a chemi-
cal reaction with the coating resin dur-
ing the curing process, and become
incorporated into the cured coating.
Earlier results had indicated that a natu-
ral vegetable oil derived from the ver-
nonia plant could serve as a reactive
diluent, but it is not grown commercially.
Further studies indicated that partially
epoxidized soy and linseed oils could
serve as low cost substitutes for ver-
nonia oil. This project investigated the
possibility of replacing a fraction of con-
ventional solvents with one-third, two-
thirds, and fully epoxidized vegetable
oils. Three applications were investi-
gated: in an aerosol product, in a 55 gal
(208L) drum refinishing operation, and
in a dry film lubricant. For the aerosol,
dry time was too extended. The drum
refinisher found that the reformulated
coating did not have sufficient corro-
sion resistance. The dry lubricant manu-
facturer could not get acceptable
chemical resistance with the new coat-
ing. There may be other, less demand-
ing applications where the reformulated,
lower VOC coating would be satisfac-
tory.
This Project Summary was developed
by EPA's National Risk Management Re-
search Laboratory, Research Triangle
Park, NC, to announce key findings of
the research project that is fully docu-
mented in a separate report of the same
title (see Project Report ordering infor-
mation at back).
Overview
Coatings and solvents are a significant
source of stationary and area volatile or-
ganic compound (VOC) emissions. Rules
promulgated by South Coast Air Quality
Management District (SCAQMD) and other
agencies have resulted in reduced VOC
content for many coatings. However, sig-
nificant additional reductions are required
to meet future air quality goals.
In addition, the production phase-out
of 1,1,1-trichloroethane due to ozone
depletion concerns has eliminated this
chemical solvent as a low-VOC technol-
ogy for coatings. The Clean Air Act
Amendments of 1990 have also created
incentives to reduce the hazardous air
pollutant (HAP) content of coatings and
solvents. Many HAP compounds are also
VOCs.
This project addressed VOC reductions
in coatings for metal substrates. While
many metal coating applicators have con-
verted to low-VOC technologies such as
powder and water-base, many others
have not been able to make this conver-
sion because of performance require-
ments, technology conversion issues, and
cost. A significant and broad range of
metal coating applicators are still in need
of low-VOC alternatives.
The SCAQMD, EPA, and others have
sponsored a series of research projects
that investigated vegetable-oil-based re-
active diluents as a means to reduce VOC
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content in traditional solvent coatings. The
general term "reactive diluents" refers to
compounds that undergo cross-linking re-
actions as part of the coating curing pro-
cess. In this document, "reactive diluents"
refers to vegetable-oil-based reactive
diluents unless otherwise specified. This
project, sponsored by the SCAQMD and
EPA, was the third and final phase of the
research program. A Technical Advisory
Committee (TAG), with representation
from coating companies, resin suppliers,
applicators, and other interested parties,
provided guidance to the project contrac-
tors.
Technology Description
Reactive diluents are compounds that
might be used to replace solvents in con-
ventional high-VOC coatings. Reactive
diluents function like solvents in adjust-
ing coating viscosity for various applica-
tions. However, rather than evaporating
like conventional solvents, reactive
diluents participate in a chemical reac-
tion with the coating during the curing
process. Coatings are extended since the
reactive diluent becomes part of the coat-
ing rather than evaporating like solvents.
It appears that reactive diluent coat-
ings could potentially be used by appli-
cators without major technology
conversion issues. This is in contrast to
other low-VOC technologies that can re-
quire significant changes to production
processes.
In Phase 1, work by the Eastern Michi-
gan University (EMU) Coatings Research
Institute (CRI) found that reactive diluents
formulated from vernonia oil offered VOC
reductions and some property improve-
ments. Vernonia oil is obtained from a
rare plant so that commercial supplies
are not currently available. Further work
by CRI in the Phase 2 research program
suggested that readily available soybean
and linseed oils could be partially
epoxidized to imitate vernonia oil proper-
ties. In Phase 3, this project continued
the research and development of par-
tially epoxidized soybean and linseed oils
as reactive diluents. This report focuses
on Phase 3 work, but includes brief sum-
maries of the work completed under
Phases 1 and 2.
Results
In Phase 3, project subcontractor PRA
Laboratories performed applied labora-
tory development studies (Task 1) to ad-
vance the basic academic research
performed by CRI. This work investigated
partially epoxidized soybean and linseed
oils to formulate both alkyd and epoxy
coatings. The purpose of this effort was to
transfer the technology from the academic
research environment to the applied re-
search arena. Laboratory development
and testing was performed on alkyd and
epoxy systems. Pigmented and clear coat-
ings were tested. Testing involved substi-
tuting solvents in standard coating
systems. Test variables included the
amount of solvent replaced, types of re-
active diluents used, pigment types, and
performance additives. Solvent substitutes
were one-third, two-thirds, and fully
epoxidized soy and linseed oils. Results
from the PRA work indicated that it is
feasible to use partially epoxidized veg-
etable oil as a reactive diluent in alkyd
and epoxy coatings.
Initially five companies, all TAG mem-
bers, volunteered to participate in Task 2.
All five received samples of fully or par-
tially epoxidized linseed or soybean oil.
For various business reasons, only three
companies actually reported working on
the samples obtained.
A diverse group of products were evalu-
ated in Task 4. One company was very
interested in being able to lower the VOC
of aerosol products. Another company
was interested in developing new busi-
ness in the drum finishing market. The
third company was interested in dry film
lubricants. These company interests rep-
resented three distinct product types. The
aerosol product was a quick air dry prod-
uct. The drum coating was to be a black,
forced-air dry alkyd coating. The dry film
lubricant was a baked epoxy coating.
The aerosol manufacturer was unable
to obtain an acceptable dry time of the
applied product. After numerous attempts
using various drier combinations and
seeking help from drier suppliers, they
were not able to obtain an acceptable
product.
The company developing a drum
enamel was initially encouraged that their
work might lead to a viable product with
lower VOC. However, upon further test-
ing it was found that corrosion resistance
was not acceptable and their work was
discontinued.
The dry film lubricant manufacturer
found that the inclusion of the epoxidized
oil in epoxy systems lowered the chemi-
cal resistance to an unacceptable level. It
was necessary for them to evaluate ex-
empt solvents. They remain convinced
that the basic concept of a reactive diluent
is viable. But, at least for their require-
ments, epoxidized vegetable oils are not
acceptable.
It appears that competing technologies
(e.g., exempt solvents) provide a quicker/
better solution at the present level of de-
velopment. Even commercially available
reactive diluents are not finding success
in the market place.
For differing reasons, none of the par-
ticipating companies was able to develop
a commercially viable product using the
epoxidized vegetable oils. While the ba-
sic research and development efforts ap-
pear to indicate that this approach to
formulating lower VOC products has merit,
in practical product development it has
not proven to be acceptable at this time.
Conclusions
Reactive diluents trade VOC reductions
for property changes. In practical formu-
lations, reactive diluents exhibit increased
dry times and reduced hardness. While
the significance of property changes de-
pends on the specific coating application,
these changes are generally undesirable.
Because of these limitations, the com-
mercial coating companies that partici-
pated in this project determined that the
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G. Roche is with Ecotek, Seal Beach, CA 90740.
Robert C. McCrillis is the EPA Project Officer (see below).
The complete report, entitled "Low-VOC Coatings Using Reactive Diluents
Demonstration Project," (Order No. PB98-137383; Cost: $41.00, subject to
change) will be available only from
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at
Air Pollution Prevention and Control Division
National Risk Management Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection Agency
CenterforEnvironmental Research Information
Cincinnati, OH 45268
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POSTAGES FEES PAID
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EPA/600/SR-98/043
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