COATING FOR ELASTOMERIC SUBSTRATES
CROSS REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. § 119(e) from U.S.
Provisional Patent Application Serial No. 61/039,446 filed March 26,2008, entitled
"COEXTRUDABLE COATING FOR EXTRUDABLE SUBSTRATES", the disclosure
of which is incorporated herein by reference.
FIELD OF THE INVENTION
The present invention relates to a low-friction coating for extruded elastomeric
materials. More particularly, the present invention relates to a coating for EPDM or
TPV profiles such as automotive weatherstrip, windshield wipers, door seals and the
like. The present invention also relates to a method of applying the coating
composition onto a substrate during the extrusion of the substrate.
BACKGROUND OF THE INVENTION
Weatherstrip and weatherstrip coatings are generally known in the art.
Weatherstrip often comprises EPDM or other elastomeric substrate and is employed
to affect a seal around doors, windows, trunks, hoods and other automotive closures.
The weatherstrip is often coated with a low-friction coating that provides slip to allow
a surface to slide against the weatherstrip and optionally provides ice release and
heat resistance for enhanced performance in extreme temperature conditions.
Typically, urethane based materials are employed for elastomer coating applications
due to their inherent flexibility abrasion resistance, and weatherability.
Weatherstrip is commonly formed by extrusion molding the weatherstrip,
cooling the elastomeric part, and then spray applying and curing the coating. While

thisprocess can be effective, it is often labor and time intensive requiring several
separate steps, and results in significant loss of coating through overspray.
It would therefore be desirable to provide a weatherstrip coating which can be
co-extruded with a substrate, and is also available for application through
conventional methods. Such a coating must provide high abrasion resistance, high
weather resistance, good ice release characteristics and low noise. The coating
must be capable of application on thermoplastic olefin compounds (TPO),
thermoplastic vulcanizate compounds (TPV) and ethylene-propylene-diene-
terpolymers (EPDM).
SUMMARY OF THE INVENTION
In a first aspect of the present invention, a coating for elastomers is provided
comprising, a rubber modified epoxy resin, an epoxy reactive diluent, and an epoxy
curative. In a preferred embodiment of the present invention, the epoxy resin is
modified with a carboxyl terminated butadiene acrylonitrile rubber. In a most
preferred embodiment of the present invention, the epoxy resin comprises bisphenol
A. In a further preferred embodiment of the present invention, the coating further
comprises a carboxylic acid terminated butadiene rubber modified epoxidized
neopentyl glycol.
In one embodiment of the present invention, the rubber modified epoxy resin
is present in an amount from 30 to 90 weight percent based on the total weight of the
formulation. In another embodiment of the present invention, the rubber modified
epoxy resin is present in an amount greater than 40 weight percent based on the
weight of the formulation.
In further alternate embodiments of the present invention, the coating is 100
percent solids, solvent free, and free of isocyanates, phenolic, and phenoxy
compounds.

In an additional embodiment of the present invention, the coating further
comprises a cure accelerator. In a preferred embodiment of the present invention,
the cure accelerator comprises methylene diphenyl bis (dimethyl urea).
On another embodiment of the present invention, the coating further
comprises a thixotrope. In a preferred embodiment of the present invention, the
thixotrope comprises fumed silica. In yet another embodiment of the present
inveniotnk the coating further comprises a slip agent, preferably
polytetrafluoroethylene powder or ultra high molecular weight polyethylene powder.
In still another embodiment of the present invention, the coating further
comprises a pigment, preferably carbon black. In another embodiment of the
present invention, the coating further comprises an adhesion promoter, preferably
dinitrosobenzene. In a further preferred embodiment of the present invention, the
epoxy curative comprises a dicyanamide curative.
In another embodiment of the present invention, the coating is co-extruded
onto substrate, preferably dense EPDM or alternatively sponge EPDM, and
preferably the substrate is weatherstrip material. In two alternate embodiment of the
present invention, the substrate comprises a thermoplastic olefin and a thermoplastic
vulcanizate. In a further embodiment of the present invention, the substrate is a
square EPDM tensile pad measuring 6 inches by 6 inches by 0.125 inches thick, and
when cured the coated pad can be bent at a 180 degree angle with no visible
cracking in the cured coating.
In a further aspect of the present invention, the coating comprises a two-part
coating, wherein the A-side comprises a rubber modified epoxy resin, and an epoxy
reactive diluent, and the B-side comprises an epoxy curative.
In an additional aspect of the present invention, an automotive weatherstrip is
provided comprising a substrate and a coating wherein the substrate and coating are
co-extruded to form the weatherstrip. In a preferred embodiment of the present
invention, the coating comprises at least 40 percent by weight of a modified epoxy
material, based on the total weight of the coating.

In an additional aspect of the present invention, a coated article is provided
comprising, an elastomeric substrate, a coating comprising at least 15 weight
percent of a rubber epoxy resin, and an epoxy curative, wherein the coating covers
at least a portion of the substrate. In preferred embodiments of the present
invention, the coating is substantially isocyanate free, and/or 100 percent solids.
In one embodiment of the present invention, the substrate is extruded and the
coating is co-extruded with the substrate, preferably an EPDM substrate, and
preferably the substrate comprises weatherstrip. In an additional embodiment of the
present invention, the coating further comprises an epoxy curative. In another
embodiment of the present invention, the coating further comprises a cure
accelerator.
As will be realized by those of skill in the art, many different embodiments of a
coating according to the present invention are possible. Additional uses, objects,
advantages, and novel features of the invention are set forth in the detailed
description that follows and will become more apparent to those skilled in the art
upon examination of the following or by practice of the invention.
Thus, there has been outlined, rather broadly, the more important features of
the invention in order that the detailed description that follows may be better
understood and in order that the present contribution to the art may be better
appreciated. There are, obviously, additional features of the invention that will be
described hereinafter and which will form the subject matter of the claims appended
hereto. In this respect, before explaining several embodiments of the invention in
detail, it is to be understood that the invention is not limited in its application to the
details and construction and to the arrangement of the components set forth in the
following description or illustrated in the drawings. The invention is capable of other
embodiments and of being practiced and carried out in various ways.
It is also to be understood that the phraseology and terminology herein are for
the purposes of description and should not be regarded as limiting in any respect.
Those skilled in the art will appreciate the concepts upon which this disclosure is

based and that it may readily be utilized as the basis for designating other structures,
methods and systems for carrying out the several purposes of this development. It is
important that the claims be regarded as including such equivalent constructions
insofar as they do not depart from the spirit and scope of the present invention.
DETAILED DESCRIPTION
In one embodiment of the present invention, the coating is capable of co-
extrusion with an elastomeric substrate, such as a weatherstrip, thereby eliminating
the need for additional processing steps to coat the elastomer.
The coatings of the present invention possess many features and advantages
as compared to coating of the prior art. The coatings of the present invention
comprise high-solids coatings, preferably greater than 95% and most preferably
100% solids. A high solids coating allows for co-extrusion onto a substrate and
reduces or eliminates emissions associated with solvent-based coatings. Further a
high-solids coating applied via coextrusion approaches 100% transfer efficiency
thereby reducing or eliminating waste associated with spray applied coatings.
In one preferred embodiment of the present invention, the coating
composition is essentially free of isocyanates, and more preferably the composition
is isocyanate free. Though isocyanates are often used in coatings for elastomers, it
is preferable to construct a coating composition which is free of isocyanates to
reduce health and environmental concerns.
The embodiments of the present invention provide coatings that have a low
coefficient of friction, which is desirable in many applications including, for example,
coatings for weatherstrip used in automobiles. For example, the weatherstrip used
to provide a seal between window glass and a door frame typically has a coating
with a low friction surface to allow lowering or raising of the window glass with
minimum resistance. The coating on the weatherstrip also provides resistance to
degradation by abrasion from movement of the window glass. In addition to having a
low coefficient of friction, the coating on the weatherstrip must also remain flexible
over a wide range of temperatures in order to provide a seal at temperatures of -40

°C. Additionally, the coatings of the various embodiments of the present invention
impart other desirable properties including itch/squeak resistance, and improved
weathering resistance to the coated elastomeric weatherstrip.
In an embodiment of the present invention, the coating is applied to an
elastomeric substrate. The elastomeric substrate may comprise a variety of
materials including thermoplastic or thermosetting materials, including but not limited
to TPE, EPDM or any combination thereof. However, in a preferred embodiment of
the present invention, the coating is applied to an extrudable material.
In a preferred embodiment of the present invention, the coating comprises an
epoxy-based EPDM coating. In the past, epoxy type coatings have been considered
too brittle for elastomer coatings. However, the coatings of the present invention
overcome this limitation through the use of a rubber modified epoxy resin. In a
preferred embodiment of the present invention, the epoxy resin comprises a
carboxylic acid terminated butadiene rubber modified epoxy resin.
. The CTBN rubber-modified epoxy resin is produced by reacting the
conventional epoxy resin as mentioned above with a CTBN rubber having a carboxyl
group. The CTBN rubber having a carboxyl group includes various commercially
available products. In one embodiment of the present invention, the reaction ratio of
the epoxy resin and the CTBN rubber is in the range of 1/0.5 to 1/2.0 by weight
(epoxy resin/CTBN rubber). The reaction is usually carried out at a temperature of
120 °C. to 150 °C. for 3 to 8 hours.
The epoxy resin comprises includes any conventional epoxy resins, such as
glycidyl ether type epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type
epoxy resins, linear aliphatic epoxide type epoxy resins, alicyclic epoxide type epoxy
resins, and the like, which are used alone or in combination of two or more thereof.
In a preferred embodiment of the present invention, the epoxy resin comprises
bisphenol A type epoxy resins and the glycidyl ether type epoxy resins.
In one embodiment of the present invention, the rubber modified epoxy rein is
present in an amount from 10 to 90 weight percent based on the weight of the

coating composition. In a preferred embodiment of the present invention, the rubber
modified epoxy resin is present in an amount greater than 30 weight percent based
on the weight of the coating composition.
In one embodiment of the present invention, the composition further
comprises an epoxy reactive diluent. The epoxy reactive diluent comprises one or
more compounds which have at least one oxide ring reactive with the polymerizable
epoxy. In one preferred embodiment of the present invention, the reactive diluent
comprises a mono-epoxy functional glycidyl ether. In one embodiment of the
present invention, the diluent is added in amounts from 0 to about 25 weight percent,
preferably from about 10 to about 20 weight percent of the coating composition.
In an additional embodiment of the invention, the coating composition further
comprises a cure agent. The cure agent comprises a crosslinker for the epoxy resin,
which can be selected from various known compounds used for cure of epoxy
resins, including aliphatic amine compounds, aromatic amine compounds, polyamide
compounds, acid anhydride compounds, dicyandiamide, complexes of boron
trifluoride and an amine compound, phenolic and novolac resins, and the like. The
cure agent can be used either singly or as a combination of multiple agents. The
cure agent is present in an amount of about 2 to about 50 weight percent, preferably,
about 5 to about 35 weight percent of the total composition.
In a further embodiment of the present invention, the composition further
comprises a catalyst or cure accelerator to speed the reaction of the epoxy resin with
the epoxy curative compound. Such catalysts are well known to those skilled in the
art, and include those described in U.S. Pat. No. 5,344,856. In a preferred
embodiment of the present invention, the cure accelerator comprises ureas,
imidazoles, and boron trihalides with the ureas being the most preferred. In a most
preferred embodiment of the present invention, the accelerator comprises methylene
diphenyl bisdimethyl urea.
In further embodiments of the present invention, the cure accelerator amount
may vary depending upon the desired reactivity and shelf stability. In a most

preferred embodiment of the present invention, the cure accelerator is present in an
amount of 0 to 5 weight percent based on the weight of the coating composition.
In a further embodiment of the present invention, a nitroso compound is
added to the composition as an adhesion promoter. The nitroso compound can be
any aromatic hydrocarbon, such as benzenes, naphthalenes, anthracenes,
biphenyls, and the like, containing at least two nitroso groups attached directly to
non-adjacent ring carbon atoms. More particularly, such nitroso compounds are
described as poly-C-nitroso aromatic compounds having from 1 to 3 aromatic nuclei,
including fused aromatic nuclei, having from 2 to 6 nitroso groups attached directly to
non-adjacent nuclear carbon atoms. The nuclear hydrogen atoms of the aromatic
nucleus can be replaced by alkyI, alkoxy, cycloalkyl, aryl, aralkyl, alkaryl, arylamine,
arylnitroso, amino, halogen, and like groups. The presence of such substituents on
the aromatic nuclei has little effect on the activity of the poly-C-nitroso compounds in
the present invention. As far as is presently known, there is no limitation as to the
character of the substituent, and such substituents can be organic or inorganic in
nature. Thus, where reference is made to "DNB", this collectively refers to poly-C-
nitroso or di-C-nitroso aromatic compound, benzenes, or naphthalenes, and is
understood to include both substituted and unsubstituted nitroso compounds, unless
otherwise specified.
The preferred poly-C-nitroso materials are the di-nitroso aromatic compounds,
especially the dinitrosobenzenes and dinitrosonaphthalenes, such as the meta- or
para-dinitrosobenzenes and the meta- or para-dinitrosonaphthalenes. Particularly
preferred poly-C-nitroso compounds are characterized by the formula (R).sub.m -Ar-
-(NO).sub.2 wherein Ar is selected from the group consisting of phenylene and
naphthalene; R is a monovalent organic radical selected from the group consisting of
alkyl, cycloalkyl, aryl, aralkyl, alkaryl, arylamine and alkoxy radicals having from 1 to
20 carbon atoms, amino, or halogen, and is preferably an alkyl group having from 1
to 8 carbon atoms; and m is zero, 1, 2,3, or 4. Preferably m is zero. DNB is
incorporated into the adhesive composition by addition as a solvent dispersion. The
nitroso compound may be replaced by the corresponding oxime or the
corresponding nitro compound with the appropriate oxidation/reduction agent.

Exemplary non-limiting embodiments of poly-C-nitroso compounds which are
suitable for use in the practice of the invention include m-dinitrosobenzene, p-
dinitrosobenzene, m-dinitrosonaphthalene, p-dinilrosonaphthalene, 2,5-dinitroso-p-
cymeme, 2-methyl-1,4-dinitrosobenzene, 2-methyl-5-chloro-1,4-dinitrosobenzene, 2-
fluoro-1,4-dinitrosobenzene, 2-methoxy-1-3-dinitrosobenzene, 5-chloro-1,3-
dinitrosobenzene, 2-benzyl-1,4-dinitrobenzene, and 2-cyclohexyl-1,4-
dinitrosobenzene. Amount of aromatic dinitroso compound used in the adhesive may
be from 1 to 200 parts by weight per 100 parts of halogenated polyolefin and
preferably from 50 to 150 parts. Nitroso compounds are typically provided as 20-45
wt. % dispsersion in aromatic or chlorinated aromatic solvent.
In an additional embodiment of the present invention, other constituents may
be added to provide faster curing, slip properties, viscosity control, and enhanced
adhesion. Various additives such as fillers, ceramic spheres, gloss control agents,
pigments, rheology modifiers, wetting agents, and the like can be used to impart
various properties to the aqueous dispersion coating composition and/or the cured
coating thereof.
In an embodiment of the present invention, an epoxy functional silicone is
added as a friction reducing agent. Epoxy functional silicones, or epoxy silicones,
such as those described in U.S. Patent No. 4,279,717, and others are available
commercially. In one preferred embodiment of the present invention, the epoxy
functional silicone is present in the coating composition in an amount from 0 to about
20 weight percent based on the total weight of the composition.
In one embodiment of the present invention, one or more polyolefins and
preferably polyethylenes such as powdered crystalline high temperature resistant
polyethylenes are added to the composition. These materials are particularly
desirable in embodiments to be used on automotive weatherstrip since they lower
both the dry and wet noise level when applied to a vehicle seal. The amount of the
polyolefins such as the noted polyethylene generally ranges from 0 to about 15, and
preferably about 2 to about 10 weight percent based on the total weight of the
composition.

The weight average molecular weight of the preferred polyethylene is
generally very high and ranges from about 2 million to about 5 million and desirably
from about 3 million to about 4 million and thus can be classified as an ultra high
molecular weight polyethylene. The size of the polyethylene powder can vary with a
mean or average particle diameter of from about 20 to about 70 microns.
Fillers are utilized to lower costs and often to lower COF and noise. Desirably
the fillers are various polymers such as nylon, fumed silica, polytetrafluoroethylene,
polyolefins, and silicone rubber powder. These fillers aid in reducing the coefficient
of friction of the coatings of the present invention. However, with regard to noise
reduction, they generally only show improved results with regard to dry noise
properties.
Another class of fillers includes ceramic spheres which are generally utilized
as an extender and the same are known to the art and to the literature. Suitable
spheres include ceramic beads that have an average diameter of from about 1 to
about 12 microns. The amount thereof is generally from about 10 or about 20 to
about 35 or about 40 parts by weight per 100 parts by weight of said one or more
polysiloxanes per se and said one or more polyurethanes per se.
Various gloss control agents can be utilized to lower the gloss of the cured
coating. A suitable gloss control agent are known to the art and to the literature such
as various synthetic wax coated silicas.
It is often desired to use various pigments so that the applied coating can
generally match the color of the polymer substrate. Since weatherstrip seals are
often black, various black pigment dispersions can be utilized the majority of which
are various carbon blacks that are well known to the art and to the literature. The
amount of such pigments can vary as from about C.1 to about 5.0 percent by weight
of the total composition.
The coatings of the embodiments of the present invention have generally
been described as one-part formulations. In a further embodiment of the present
invention, the coating may be packaged and sold as a two-part formulation wherein

the A-side comprises the epoxy resin and the B-side comprises the cure agent. To
the extent other constituents are employed with the epoxy and curative, they are
generally added to the A-side, though could be included in either the A-side or B-side
so long as the mixtures are shelf stable.
Although the present invention has been described with reference to particular
embodiments, it should be recognized that these embodiments are merely illustrative
of the principles of the present invention. Those of ordinary skill in the art will
appreciate that the compositions, apparatus and methods of the present invention
may be constructed and implemented in other ways and embodiments. Accordingly,
the description herein should not be read as limiting the present invention, as other
embodiments also fall within the scope of the present invention as defined by the
appended claims.

EXAMPLES
Table 1 and Table 2 provide exemplary formulations of two embodiments of
the present invention that are particularly well suited for coating onto dense EPDM
substrates.



In embodiments of the present invention comprising a two-part system, the
ratio of A-side to B-side may vary according to a particular application ranging from
about 100:20 A-side to B-side to 100:50 A-side to B-side. Additionally, the
crosslinker may be tailored to suit the particular needs of a particular application as
will be understood by those skilled in the art.
Table 3 provides a specific exemplary formulation of an embodiment of the
present invention that is particularly well suited for coating onto a sponge EPDM
substrate, as well as ranges for alternate exemplary embodiments.

The coated EPDM pads were then subjected to standard weatherstrip tests
with the following results:

The ingredients of Formulation B were mixed together and coated on EPDM
pads heated to 200 °F to simulate extruder conditions.

To 100 grams of the above, 29.5 grams of polyamide curative were added.
The coated EPDM pads were then subjected to standard weatherstrip tests with the
following results:



Although the present invention has been described with reference to particular
embodiments, it should be recognized that these embodiments are merely illustrative
of the principles of the present invention. Those of ordinary skill in the art will
appreciate that the compositions, apparatus and methods of the present invention
may be constructed and implemented in other ways and embodiments. Accordingly,
the description herein should not be read as limiting the preseni invention, as other
embodiments also fall within the scope of the present invention as defined by the
appended claims.

We Claim:
1. A coating for elastomers comprising:
a rubber modified epoxy resin;
an epoxy reactive diluent; and,
an epoxy curative.
2. The coating of claim 1. wherein the epoxy resin is modified with a carboxyl
terminated butadiene acrylonitrile rubber.
3. The coating of claim 2, wherein the epoxy resin comprises bisphenol A.
4. The coating of claim 3, further comprising a carboxylic acid terminated
butadiene rubber modified epoxidized neopentyl glycol.
5. The coating of claim 1, wherein the rubber modified epoxy resin is present in
an amount from 30 to 90 weight percent based on the total weight of the formulation.
6. The coating of claim 1, wherein the rubber modified epoxy resin is present in
an amount greater than 40 weight percent based on the weight of the formulation.
7. The coating of claim 1, wherein the coaling is 100 percent solids.
8. The coating of claim 1, wherein the coating is solvent Tree.
9. The coating of claim 1, wherein the coating is free of isocyanates.
10. The coaling of claim 1, further comprising a cure accelerator.
11. The coaling of claim 10, wherein the cure accelerator comprises methylene
diphenyl bis (dimethyl urea).

12. The coating of claim 1, further comprising a thixotrope.
13. The coating of claim 12, wherein the thixotrope comprises fumed silica.
14. The coating of claim 1, further comprising a slip agent.
15. The coating of claim 14, wherein the slip agent comprises
polytetrafluoroethylene powder or ultra high molecular weight polyethylene powder.
16. The coating of claim 1, further comprising a pigment.
17. The coating of claim 16, wherein the pigment comprises carbon black.
18. The coating of claim 1, further comprising an adhesion promoter.
19. The coating of claim 18, where in the adhesion promoter comprises
dinitrosobenzene.
20. The coating of claim 1, wherein the epoxy curative comprises a dicyanamide
curative.
21. The coating of claim 1, wherein the coating is free of phenolic and phenoxy
compounds.
22. The coating of claim 1, co-extruded onto substrate.
23. The coating of claim 22, wherein the substrate comprises dense EPDM.
24. The coating of claim 22, wherein the substrate comprises sponge EPDM.
25. The coating of claim 22, wherein the substrate is weatherstrip material.
26. The coating of claim 22, wherein the substrate comprises a thermoplastic
olefin.

27. The coating of claim 22, wherein the substrate comprises a thermoplastic
vulcanizate.
28. The coating of claim 22, wherein the substrate is a square EPDM tensile pad
measuring 6 inches by 6 inches by 0.125 inches thick, and when cured the coated
pad can be bent at a 180 degree angle with no visible cracking in the cured coating.
29. A two-part coating according to claim 1, wherein the A-side comprises:
a rubber modified epoxy resin; and,
an epoxy reactive diluent; and,
wherein the B-side comprises an epoxy curative.
30. An automotive weatherstrip comprising a substrate and a coating wherein the
substrate and coating are co-extruded to form the weatherstrip.
31. The weatherstrip of claim 29, wherein said coating comprises at least 40
percent by weight of a modified epoxy material, based on the total weight of the
coating.
32. A coated article comprising:
an elastomeric substrate;
a coating comprising at least 15 weight percent of a rubber epoxy resin; and,
an epoxy curative;
wherein the coating covers at least a portion of the substrate.
33. The article of claim 32, wherein the coating is substantially isocyanate free.
34. The article of claim 32, wherein the coating is 100 percent solids.

35. The article of claim 32, wherein the substrate is extruded and the coating is
co-extruded with the substrate.
36. The article of claim 32, wherein the substrate comprises EPDM.

37. The article of claim 32, wherein the substrate comprises weatherstrip.
38. The article of claim 32, wherein the coating further comprises an epoxy
curative.
39. The article of claim 32, wherein the coating further comprises a cure
accelerator.

A coating for elastomers is provided comprising, a
rubber modified epoxy resin, an epoxy reactive diluent,
and an epoxy curative. The epoxy resin is modified with
a carboxyl terminated butadiene acrylonitrile rubber,
and the coating is capable of co-extrusion with an
elastomeric substrate, such as a weatherstrip.