U.S. patent application number 14/337632 was filed with the patent office on 2014-11-13 for fabric adhesion improvement for epdm based low cost timing belt.
This patent application is currently assigned to VEYANCE TECHNOLOGIES, INC.. The applicant listed for this patent is Thomas George Burrowes, Michael John William Gregg. Invention is credited to Thomas George Burrowes, Michael John William Gregg.
Application Number | 20140332144 14/337632 |
Document ID | / |
Family ID | 36095724 |
Filed Date | 2014-11-13 |
United States Patent
Application |
20140332144 |
Kind Code |
A1 |
Burrowes; Thomas George ; et
al. |
November 13, 2014 |
FABRIC ADHESION IMPROVEMENT FOR EPDM BASED LOW COST TIMING BELT
Abstract
The present invention is directed to timing belts having
improved fabric adhesion to the tooth facing which can be achieved
by the use of a combination of a RFL treated fabric and an EPDM
body provided the RFL treatment or the body include ZDA or the RF
latex is an X-HNBR latex.
Inventors: |
Burrowes; Thomas George; (N.
Canton, OH) ; Gregg; Michael John William; (Lincoln,
NE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Burrowes; Thomas George
Gregg; Michael John William |
N. Canton
Lincoln |
OH
NE |
US
US |
|
|
Assignee: |
VEYANCE TECHNOLOGIES, INC.
FAIRLAWN
OH
|
Family ID: |
36095724 |
Appl. No.: |
14/337632 |
Filed: |
July 22, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13024624 |
Feb 10, 2011 |
8795456 |
|
|
14337632 |
|
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|
|
11026786 |
Dec 31, 2004 |
7909720 |
|
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13024624 |
|
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Current U.S.
Class: |
156/138 |
Current CPC
Class: |
B32B 2262/062 20130101;
B32B 2264/10 20130101; B32B 9/045 20130101; B32B 9/04 20130101;
B32B 37/12 20130101; F16G 1/28 20130101; B32B 9/048 20130101; B32B
9/043 20130101; B32B 2264/102 20130101 |
Class at
Publication: |
156/138 |
International
Class: |
B32B 37/12 20060101
B32B037/12; B32B 9/04 20060101 B32B009/04 |
Claims
1. A method of making a toothed belt comprising: (1) forming a body
having a length, laterally spaced sides, and inside and an outside
surface, and defining a plurality of teeth spaced in a lengthwise
direction on one of the inside or the outside of the body, said
body defining at least in part by a rubber composition comprising
at least an ethylene propylene diene monomer terpolymer, (2)
applying a cloth layer on the teeth on one of the inside or outside
of the body and bonding said cloth layer to said body whereby the
cloth layer is disposed on the surface of and adhered to the teeth,
wherein the cloth layer is comprised of a cloth fabric selected
from cotton fabrics, polyester fabrics, and polyamide fabrics, said
cloth layer being treated with a solution of
resorcin-formalin-latex, wherein the solution of
resorcin-formalin-latex consists of a reaction product of resorcin
and formalin, a carboxylated hydrogenated nitrile rubber latex,
ammonia, optionally a wax, optionally urea, and optionally an
antioxidant, wherein the mole ratio of the resorcin to the formalin
is within the range of 1:1 to 1:3, and wherein the rubber
composition and the solution for treating said cloth layer are void
of metal salts of .alpha.,.beta.-unsaturated organic acids.
2. The method of claim 1 wherein the rubber composition includes at
least one reinforcing filler.
3. The method of claim 2 wherein the cloth layer is comprised of a
cotton fabric.
4. The method of claim 1 wherein the cloth layer is comprised of a
polyester fabric.
5. The method of claim 1 wherein the cloth layer is comprised of a
polyamide fabric.
6. The method of claim 1 wherein the cloth layer is comprised of a
nylon-66 fabric.
7. The method of claim 1 wherein the cloth fabric is made by plain
weaving.
8. The method of claim 1 wherein the cloth fabric is made by twill
weaving.
9. The method of claim 1 wherein the cloth fabric is made by satin
weaving.
10. The method of claim 1 wherein the solution of
resorcin-formalin-latex has a pH of at least 9.0.
11. The method of claim 2 wherein the reinforcing filler is present
at a level which is within the range of 25 phr to 250 phr.
12. The method of claim 2 wherein the reinforcing filler is present
at a level which is within the range of 25 phr to 100 phr.
13. The method of claim 12 wherein the reinforcing filler is carbon
black.
14. The method of claim 12 wherein the reinforcing filler is
calcium carbonate.
15. The method of claim 12 wherein the reinforcing filler is
talc.
16. The method of claim 12 wherein the reinforcing filler is
clay.
17. The method of claim 12 wherein the reinforcing filler is
hydrated silica.
18. The method of claim 1 wherein the rubber composition defining
the body of the belt consists of the ethylene propylene diene
terpolymer.
19. The method of claim 18 wherein the cloth layer is comprised of
is a single ply polyamide fabric.
20. The method of claim 18 wherein the cloth layer is comprised of
is a single ply nylon-66 fabric.
Description
[0001] This is a continuation of U.S. patent application Ser. No.
13/024,624, filed on Feb. 10, 2011, which is a divisional of U.S.
patent application Ser. No. 11/026,786, filed on Dec. 31, 2004, now
issued as U.S. Pat. No. 7,909,720. The teachings of U.S. patent
application Ser. No. 13/024,624 and U.S. patent application Ser.
No. 11/026,786 are incorporated herein by reference in their
entirety.
BACKGROUND OF THE INVENTION
[0002] This invention is directed to belting for use as timing
belts, which incorporate a cloth or fabric layer on the teeth of
the belt, and to improved fabric adhesion, when the belt is an
ethylene-alpha-olefin elastomeric composition, such as EPDM
(ethylene propylene diene terpolymer, by the use of, preferably, a
combination of the use of a resorcinol formaldehyde lates (RFL)
treatment for the fabric and the use of zinc diacrylate (ZDA).
[0003] Ethylene-alpha-olefin elastomeric compositions, which are
readily processed, should have adequate mechanical properties in
dynamic applications and acceptable adhesion to textile
reinforcement materials to enable its use as the primary base
elastomeric composition in applications such as belting including
power transmission and flat belting, air springs, engine mounts.
But they have not found much success.
[0004] The use of salts of alpha, beta-unsaturated organic acids in
elastomeric compositions is known. For example, Yarnell et al (U.S.
Pat. No. 5,610,217), teaches an elastomeric material for use as the
primary elastomeric composition in articles subject to dynamic
loading, which comprises an ethylene-alpha-olefin elastomers
composition capable of maintaining excellen abrasion resistance,
pilling resistance, tensile strength, cut-growth resistance,
modulus and adhesion to reinforcement materials under high and low
temperature dynamic loading conditions. The elastomeric material is
cured using a free radical promoting material, and comprises the
reaction product of 100 parts by weight of an ethylene-alpha-olefin
elastomers which serves as the primary elastomers of the
composition, from about 1 to about 30 parts per hundred weight of
the elastomers (phr) of a metal salt of an
.alpha.-.beta.-unsaturated organic acid, which includes zinc
diacrylate, although zinc dimethacrylate is most preferred, and
from about 25 to about 250 phr of a reinforcing filler.
[0005] The use or resorcinol-formaldehyde latex is known also for
use in treating fabrics. For example, Knuston (U.S. Pat. No.
6,695,733) teaches treating carbon fiber tensile cord with RFL in
making low growth power transmission belts. Fujumoto et al, U.S.
Pat. No. 6,641,905, also teaches RFL treated polyester fiber cords
for use in power transmission belts wherein the rubber latex is a
chlorosulfonated polyethylene and alkylated chlorosulfonated
polyethylene. Fujita et al, U.S. Pat. No. 5,609,243, teaches RFL
treated fabric for toothed conveying belts. Takada et al, U.S. Pat.
No. 6,294,600, teaches ethylene-a-olefin elastomers and N,
N'-m-phenylene dimaleimide compositions surfaced by RFL treated
canvas cloth for use as power transmission belting. Hasaka et al,
U.S. Pat. No. 6,524,417 teaches the use of RFL treated fiber
material for use in ethylene-.alpha.-olefin elastomers latex which
is cured by vulcanization bonding and used in power transmission
belts. Di Meco et al, U.S. Pat. No. 6,656,073, teaches a toothed
belt where the toothed portion is covered with a cloth having a
specific weft and warp design for the cloth, but where the cloth is
treated with a RFL composition.
SUMMARY OF THE INVENTION
[0006] The present invention is the result of the discovery that
timing belts having improved fabric adhesion to the tooth facing
can be achieved by the use of a combination of a RFL treated fabric
and an EPDM body provided the RFL treatment or the body include ZDA
or the RF latex is an X-HNBR latex.
[0007] The present invention more specifically discloses a method
of making a toothed belt comprising: (1) forming a body having a
length, laterally spaced sides, and inside and an outside surface,
and defining a plurality of teeth spaced in a lengthwise direction
on one of the inside or the outside of the body, said body defining
at least in part by a rubber composition comprising at least an
ethylene propylene diene monomer terpolymer, and (2) applying a
cloth layer on the teeth on one of the inside or outside of the
body, and bonding said cloth layer to said body whereby the cloth
layer is disposed on the surface of and adhered to the teeth, said
cloth layer being treated with a solution of
resorcin-formalin-latex, wherein the mole ratio of the resorcin to
formalin is within the range of 1:1 to 1:3, wherein the latex in
the resorcin-formalin-latex consists of a carboxylated hydrogenated
nitrile rubber latex, and wherein the rubber composition and the
solution for treating said cloth layer are void of metal salts of
.alpha.,.beta.-unsaturated organic acids.
DETAILED DESCRIPTION OF THE INVENTION
[0008] A typical synchronous belt includes an elastomeric main belt
body portion and a sheave contact portion positioned along the
inner periphery of the main belt body portion. The word "sheave" in
this context includes normal pulleys and sprockets used with power
transmission belts, and also pulleys, rollers and like mechanisms
used with conveyor and flat belting. Examples of a sheave and belt
system are illustrated in U.S. Pat. Nos. 4,956,036 and 5,610,217,
and the contents of which are hereby incorporated by reference. The
particular sheave contact portion can take the form of alternating
teeth and land portions. A tensile layer is positioned within the
main belt body portion for providing support and strength to the
belt, and can be, for example, in the form of a plurality of
strain-resisting cords aligned longitudinally along the length of
the main belt body portion. But, any type of tensile layer known to
the art may be utilized and any desired material may be used as the
tensile member, such as cotton, rayon, nylon, polyester, aramid,
steel, fiberglass, carbon and even discontinuous fibers oriented
for load carrying capability.
[0009] The main belt body portion is a flex fatigue resistant,
abrasion resistant, high tensile strength, high modulus elastomeric
composition. The main belt body portion is prepared from an
ethylene-alpha-olefin elastomer which has been cured with a
free-radical promoting material. A tensile member is disposed
within the body portion, and a sheave contact portion is integral
with the main belt body portion. The elastomeric composition is
formed by mixing and milling together in accordance with
conventional rubber processing practice a resin mixture comprising,
by weight, 100 parts of an ethylene-alpha-olefin elastomer which
serves as the primary elastomer of the composition, from about 1 to
about 30 phr of a metal salt of an .alpha.,.beta.-unsaturated
organic acid, and from about 25 to about 250 phr of a reinforcing
filler. This elastomeric material when cured exhibits excellent
adhesion to the belt's tensile member in the substantial absence of
additional adhesion promoters.
[0010] The ethylene-alpha-olefin elastomeric compositions may
optionally contain other conventional additives which are commonly
utilized in elastomer compositions. Such additives may include
process and extender oils, antioxidants, waxes, pigments,
plasticizers, softeners and the like. These additives may be
employed in amounts conventionally used in standard rubber
compounds.
[0011] A reinforcing fabric is utilized and intimately fits along
the alternating teeth and land portions of the belt to form a face
cover therefor. This fabric may be of any desired configuration
such as a conventional weave consisting of warp and weft threads at
any desired angle or may consist of warp threads held together by
spaced pick cords, or of a knitted or braided configuration, and
the like. The fabric may be friction- or skim-coated with the same
or different elastomer composition of the body. More than one ply
of fabric may be employed. If desired, the fabric may be cut on a
bias so that the strands form an angle with the direction of travel
of the belt. Conventional fabrics may be employed using such
materials as cotton, polyester, polyamide, hemp, jute, fiberglass
and various other natural and synthetic fibers. In a preferred
embodiment of the invention, the fabric layer consists of an
expansible wear-resistant fabric in which at least one of the warp
or weft threads is made of nylon. In the most preferred form, the
fabric layer is made of nylon 66 stretch fabric.
[0012] The wear resistant fabric is disposed at the peripheral
surface of the belt teeth for promoting tooth sheer strength and,
in castable belt constructions in particular, for reducing
aggressiveness of the belt teeth when entering grooves of a
sprocket, any suitable or conventional material may be employed,
including crimped nylon, cotton, hemp, jute, aramid, polyester, and
fiberglass. More than one ply of fabric may be employed. If desired
the fabric may be cut on a bias so that the strands form an angle
with the direction of travel of the belt. The fabric may be of any
desired configuration such as a conventional weave consisting of
warp and weft threads at any desired angle, or may consist of pick
cords, or of a knitted or braided configuration or the like.
[0013] The ethylene-alpha-olefin elastomers useful in the present
invention include but are not limited to copolymers composed of
ethylene and propylene units (EPM), ethylene and butene units,
ethylene and pentene units, or ethylene and octene units (EOM), and
terpolymers composed of ethylene and propylene units and an
unsaturated component (EPDM), as well as mixtures thereof. As the
unsaturated component of EPDM, any appropriate non-conjugated diene
may be used, including for example, 1,4-hexadiene,
dicyclopentadiene or ethylidenenorbomene (ENB). The
ethylene-alpha-olefin elastomer preferred in the present invention
contains from about 35% by weight to about 80% by weight of the
ethylene unit, from about 65% by weight to about 25% by weight of
the propylene or octene unit, and 0-10% by weight of the
unsaturated component. In a more preferred embodiment, the
ethylene-alpha-olefin elastomer contains from about 55% to about
78% by weight of the ethylene unit, and in a most preferred
embodiment, the ethylene-alpha-olefin elastomer contains from about
65% to about 75% of the ethylene unit. At these more preferred
ethylene unit content levels, endless belts incorporating as their
main belt body portions the ethylene-alpha-olefin elastomer
compositions of this preferred embodiment of the present invention
exhibit improved pilling resistance. The most preferred
ethylene-alpha-olefin elastomer is EPDM.
[0014] To form the elastomer composition of the present invention
the ethylene-alpha-olefin elastomer may optionally be blended with
less than 50% by weight, more preferably up to about 25%, and most
preferably from about 5% to about 10% based on the total
elastomeric content of the composition of a second elastomeric
material including but not limited to silicone rubber,
polychloroprene, epichlorohydrin, hydrogenated nitrile butadiene
rubber, natural rubber, ethylene-vinyl-acetate copolymer, ethylene
methacrylate copolymers and terpolymers, styrene butadiene rubber,
nitrile rubber, chlorinated polyethylene, chlorosulfonated
polyethylene, alkylated chlorosulfonated polyethylene,
transpolyoctenamer, polyacrylic rubbers, butadiene rubber, and
mixtures thereof, to fine-tune certain mechanical properties such
as high temperature performance and tack.
[0015] The ethylene-alpha-olefin elastomeric compositions useful in
the endless belts of the present invention further comprise from
about 25 phr to about 250 phr and preferably from about 25 phr to
about 100 phr of a reinforcing filler such as carbon black, calcium
carbonate, talc, clay or hydrated silica, or mixtures of the
foregoing. The incorporation of from 1 phr to 30 phr of a metal
salt of an unsaturated organic acid and from about 25 phr to about
250 phr and preferably about phr 25 to about 100 phr of reinforcing
filler in the peroxide-cured ethylene-alpha-olefin elastomeric
composition preserves the heat stability of conventional
peroxide-cured elastomers, while providing the tear strength and
dynamic properties usually associated with sulfur cured
elastomers.
[0016] The free-radical producing curatives useful in the present
invention are those suitable for curing ethylene-alpha-olefin
elastomers and include for example, organic peroxides and ionizing
radiation. The preferred curative is an organic peroxide, including
but not limited to dicumyl peroxide, bis-(t-butyl
peroxy-diisopropyl benzene, t-butyl perbenzoate, di-t-butyl
peroxide, 2,5-dimethyl-2,5-di-t-butylperoxyhexane,
.alpha.,.alpha.-bis(t-butylperoxy) diisopropylbenzene. The
preferred organic peroxide curative is a-a-bis(t-butylperoxy)
diisopropylbenzene. Cure-effective amounts of organic peroxide for
purposes of the present invention are typically from about 2 phr to
about 10 phr. Preferred levels of organic peroxide are from about 4
phr to about 6 phr. Sulfur may optionally be added to the organic
peroxide curative as part of a mixed cure system in an amount of
from about 0.01 phr to about 1.0 phr, to improve the cured
elastomer's Young's modulus without negatively affecting its tear
resistance.
[0017] Other conventional ethylene-alpha-olefin elastomer
additives, process and extender oils, antioxidants, waxes,
pigments, plasticizers, softeners and the like may be added
according to common rubber processing practice without departing
from the present invention. For example, in a preferred embodiment
of the present invention, the elastomeric composition also contains
from about 0.5 phr to about 1.5 phr of an antiozonant or
antioxidant and from about 5 phr to about 15 phr of a paraffinic
petroleum oil plasticizer/softener.
[0018] The ethylene-alpha-olefin elastomeric compositions useful in
the present invention may be prepared by any conventional procedure
such as for example, by mixing the ingredients in an internal mixer
or on a mill.
[0019] The RFL composition, i.e., an elastomer latex composition
further comprising a resorcinol-formaldehyde reaction product, is
applied as a cord treatment to at least a portion of the yarn
and/or one or more of its carbon filaments. Throughout the present
disclosure, the term, "cord treatment" is used to denote a material
applied to a yarn and/or yarn filament (which may or may not
include a sizing) and located at least on a portion of the yarn
and/or yarn filament surface and within at least a portion of one
or more interstices formed between such filaments and yarn(s) of a
cord formed through the bundling and/or twisting and/or other
combination or configuration of such cord-treated yarn; and being
applied to such yarn and/or yarn filament at a level greater than
2.0% based on the final weight of the so treated cord.
[0020] As the RFL constituents, any suitable materials may be
employed. The RFL solid solution is made up of solid RF and latex
resin, were the RFL solution is an initial condensate of resorcin
and formalin mixed in latex, with the mole ratio of the resorcin
and the formalin being 1 to 1 to 3. The weight percent ratio of the
initial condensate of resorcin and formalin and the latex is 1 to 1
to 10. The resorcinol-formaldehyde resin fraction in the RFL
solution preferably represents from about 2 to about 40% by weight
dry basis, with the latex fraction representing from about 60 to
about 98%. Preferably, the resorcinol-formaldehyde resin fraction
represents from 5 to 40% by weight dry basis, and the latex
fraction represents from 70 to 95%.
[0021] The latex component in the RFL solution may be of any
suitable type, including hydrogenated nitrile rubber (HNBR),
nitrile rubber (NBR), carboxylated HNBR (X-HNBR), carboxylated NBR,
vinyl pyridine/styrene butadiene rubber ("VP/SBR"), carboxylated
VP/SBR, SBR, chlorosulfonated polyethylene ("CSM"), ethylene
alpha-olefin-type elastomer such as ethylene propylene diene
terpolymer ("EPDM") and ethylene propylene copolymer ("EPM"), or a
combination of any two or more of the foregoing. In a preferred
embodiment, the latex component is a carboxylated HNBR type, and
may include minor to up to equal amounts or proportions by weight
or more of other elastomer types, including ethylene
alpha-olefin-type elastomers such as EPDM or EPM. Ethylene alpha
olefin elastomer may be utilized singly or in combination of any
two or more thereof to improve low temperature performance
properties of the resultant belt, such as low temperature
flexibility.
[0022] To make the X-HNBR RFL, aqueous ammonia was added to the
water and stirred until blending was complete. Then,
resorcinol/formaldehyde resin was added to the thus-formed solution
and was mixed until the resin was completely dissolved. The
resulting resin mixture was adjusted as required with additional
aqueous ammonia to a final pH of at least 9.0. This resin mixture
was then added to carboxylated HNBR latex and mixed until blending
was complete. At that point the formaldehyde was added to the
solution with stirring and the resultant solution was mixed well.
The mixture was then aged for at least two hours, and the pH of the
solution was adjusted as necessary with aqueous ammonia to a final
pH of 9.0.
[0023] In addition, X-HNBR RFL may include 4.3% by wet weight (18
parts by weight) of a 45% solids HEVEAMUL M-111b wax dispersion by
Heveatex, 6.50% by wet weight (27.2 parts by weight) of a 41%
aqueous urea solution, and 2% by wet weight (8.4 parts by weight)
of an antioxidant available under the name, AQUANOX 29 by Goodyear
Chemical Co. These three constituents, i.e., wax, urea and
antioxidant, are not required in the RFL solutions in accordance
with the present invention, but may optionally be employed as
process aids and/or, in the case of the antioxidant, to modify
material handling and properties not related to the scope of the
present invention.
[0024] The metal salts of .alpha.,.beta.-unsaturated organic acids
useful in the present invention are metal salts of acids such as
for example, acrylic, methacrylic, maleic, fumaric, ethacrylic,
vinyl-acrylic, itaconic, methyl itaconic, aconitic, methyl
aconitic, crotonic, alpha-methylcrotonic, cinnamic, and
2,4-dihydroxy cinnamic acids. These salts may be of zinc, cadmium,
calcium, magnesium, sodium or aluminum, and are preferably those of
zinc. The preferred metal salts of .alpha.,.beta.-unsaturated
organic acids are zinc diacrylate and zinc dimethacrylate. The most
preferred metal salt of unsaturated organic acid is zinc
dimethacrylate. Amounts of the metal salt useful in the present
invention may range from about 1 to about 30 phr, and are
preferably from about 5 to about 20 phr. In the most preferred
embodiment, the metal salt is zinc dimethacrylate used in an amount
of about 5 phr when used in conjunction with EPDM mixed with up to
about 10% of silicone rubber, and from about 10 to about 20 phr and
more preferably about 15 phr when used in conjunction with the
other ethylene-alpha-olefin elastomers useful in the present
invention.
[0025] The cloth canvas layers may be cloth made by plain weaving,
twill weaving, satin weaving, or the like, using threads formed
from cotton, polyamide fiber, polyethylene terephthalate fiber, or
aramid fiber.
[0026] The cloth is treated preferably as follows. The cloth is
immersed in the RFL solution using a dip treatment for about 0.1 to
20 seconds and excess solution is removed by squeezing the cloth
between a pair of rollers at a squeezing pressure of approximately
0.3 to 0.8 kgf/cm (gauge pressure). The cloth is then dried at
about 100 to 200.degree. C. for about 30 to 600 seconds. Additional
RFL solution treatment is carried out until the solid adhered
amount of RFL solution is 30 to 50 weight percent.
[0027] It has been found that when the RFL solution is less than 30
weight percent, the contacting portions of the warp and weft on the
cloth tend to move to expand the openings bounded by the warp and
weft. The openings between the warp and weft tend to expand, as a
result of which the rubber surface becomes exposed. On the other
hand, when the solid adhered amount of RFL solution exceeds 50
weight percent, the teeth lose their original, desired shape.
EXAMPLE
[0028] In order to illustrate the present invention, fabric
adhesion studies were conducted in which fabrics impregnated with
RFL solution were adhered to EPDM rubber bodies. In these examples,
a RFL impregnated fabric was adhered to an EPDM elastomeric sheet,
and then tested to determine the bonding characteristics.
[0029] A single ply cotton canvas layer was laminated on the outer
surface of an EPDM rubber layer. Prior to lamination the fabric was
treated with an RFL solution (100 parts of hydrogenated nitrile
(HNBR), about 20 parts of condensate of resorcin and formaldehyde,
and zinc diacrylate (ZDA). The results are set forth in Table 1
which follows.
TABLE-US-00001 TABLE 1 Treatment of Example fabric as Treatment
applied No. received to fabric Adhesion Evaluation 1 None None
Inadequate Fabric Adhesion 2 RFL/HNBR RFL and ZDA Press 40 Min. @
345.degree. F.; Complete Rubber Tear, Chemical Adhesion 3 RFL/HNBR
RFL and 31 phr ZDA PD Belt Build, 1 mil HDPE on madrel; Tooth
formation acceptable; Lief 461, 466, 477, 502 Hours
[0030] The foregoing embodiments of the present invention have been
presented for the purposes of illustration and description. These
descriptions and embodiments are not intended to be exhaustive or
to limit the invention to the precise form disclosed, and obviously
many modifications and variations are possible in light of the
above disclosure. The embodiments were chosen and described in
order to best explain the principle of the invention and its
practical applications to thereby enable others skilled in the art
to best utilize the invention in its various embodiments and with
various modifications as are suited to the particular use
contemplated. It is intended that the invention be defined by the
following claims.
* * * * *