Vinyl compound plasma pre-treatment for promoting the adhesion between textiles and rubber compounds

This invention relates to a method of promoting the adhesion of textiles to rubber compounds through a vinyl compound plasma pre-treatment procedure and a subsequent application of resorcinol-formaldehyde latex (RFL) to the textile surface. The inventive method encompasses a process through which free radicals of compounds comprising strong carbon--carbon bonds form a film over textile films and then covalently bonded to the resin component of the RFL. Such a method thus produces an extremely strong and versatile adhesive that facilitates adhesion between rubber compounds and heretofore unusable or difficult-to-use textiles. The resultant textile/rubber composites are utilized as reinforcements within such materials as automobile tires, fan belts, conveyor belts, and the like. Such materials and composites are also contemplated within this invention.

FIELD OF THE INVENTION 
This invention relates to a method of promoting the adhesion of textiles to 
rubber compounds through a vinyl compound plasma pre-treatment procedure 
and a subsequent application of resorcinol-formaldehyde latex (RFL) to the 
textile surface. The inventive method encompasses a process through which 
free radicals of compounds comprising strong carbon--carbon bonds form a 
film over a textile substrate and then covalently bond the textile to the 
resin component of the RFL. Such a method thus produces an extremely 
strong and versatile adhesive that facilitates adhesion between rubber 
compounds and heretofore unusable or difficult-to-use textiles. The 
resultant textile/rubber composites are utilized as reinforcements within 
such materials as automobile tires, fan belts, conveyor belts, and the 
like. Such materials and composites are also contemplated within this 
invention. 
DISCUSSION OF THE PRIOR ART 
It has long been known that adhering a textile, particularly one composed 
of filaments having high tenacity to a rubber enhances the modulus and 
tensile strength of the rubber component and provides long-lasting 
durability, particularly in high friction applications. Examples of such 
applications include fan and timing belts within automobile engines; 
vehicle tires; conveyor belts; and the like. The main requirement of such 
textile-reinforced rubber articles has been the strength of adhesion 
between the textile and the rubber. Without any primer treatment, the 
textile will not effectively adhere to the rubber. A weak bond between the 
two components results in separation of the two layers and mechanical 
failure of the resulting composite. Thus, it has been and is necessary to 
provide a textile treatment to enhance the adhesion of these two distinct 
components. 
The primary method followed within the prior art of providing such 
adherence between rubber and textile layers includes coating or 
impregnating the textile layer with a formaldehyde latex, such as a 
resorcinol formaldehyde vinyl-pyridine rubber latex or RFL. This creates a 
resin layer which encapsulates the textile fibers and also has 
encapsulated within it rubber particles which can be adhered to the rubber 
compound through a curing process. Unfortunately, this process does not 
provide substantial adhesion between the resin encapsulating layer and the 
textile fibers. Various methods of promoting adhesion between the resin 
and the textile have been disclosed including pre-coating the textile with 
an RFL latex and an amino functional polyacrylate, as in U.S. Pat. No. 
5,654,099, to Pelton, and in European Patent Application 665,390, to 
Tsubakimoto Chain Company, or utilizing a pre-activated textile which has 
reactive pendant groups to facilitate adhesion between the fabric surface 
and the reactive sites on the rubber layer, all of the aforementioned 
references being herein entirely incorporated by reference. The RFL 
coating method results in a composition which does not always provide 
sufficient adhesion between layers. Pre-activated textiles, such as a 
polyester fibers coated with an epoxy adhesion enhancer, are typically 
used in combination with an RFL treatment to further improve the textile 
adhesion to rubbers. Although such pre-activated textiles perform well in 
many cases, there remains a need for less expensive methods and 
compositions for adhesion promotion between rubber and textile layers in 
order ultimately to produce a reinforced, long-lasting, and durable rubber 
product. Also worth mentioning are U.S. Pat. Nos. 5,064,876, to Hamada et 
al., and 5,082,738, to Swofford, both of which teach a primer composition 
for promoting adhesion for polymer films. 
Different, stronger textile/rubber composites have been formed through the 
utilization of plasma pre-treatment methods. Of particular interest are 
U.S. Pat. Nos. 5,501,880 to Parker et al., 5,283,119 to Shuttleworth et 
al., and 5,053,246 to Shuttleworth et al. Each of these references 
discloses a plasma pre-treatment of textiles in order to effectuate 
improved adhesion between the textile and a RFL rubber. Within these 
methods, the textile surface is cleaned with specific plasma gases 
(O.sub.2 /CF.sub.4) initially and then treated again with other plasma 
gases to provide a surface which facilitates adhesion between the textile 
and the RFL. Plasma cleaning and activation provide a pristine surface 
with a more favorable surface energy for coating with an RFL latex. This 
increases the adhesion to the rubber by providing more thorough (and thus 
better) contact between the textile and the resin component of the RFL. 
However, there is still no substantial covalent bonding between the 
textile and the RFL. U.S. Pat. Nos. 5,053,246 and 5,283,119, both to 
Shuttleworth et al., teach a subsequent step in which a CS.sub.2 plasma is 
utilized to plasma deposit a sulfur-containing film on the textile 
surface. This increases the adhesion further by allowing this film to 
cross-link with the rubber latex particles in the RFL. Unfortunately, the 
adhesion increase is relatively modest because the latex particles are 
substantially covered with the resin component of the RFL, blocking the 
creation of the desired covalent bonds. The chief benefit of these two 
patents are the availability of bonding rubber to a textile without 
utilizing an extra RFL component. However, the adhesion obtained is, 
again, unsatisfactory. Furthermore, sulfur-containing compounds present 
undesirable environmental hazards. 
Thus, resin encapsulation of textile fibers appears to produce the limiting 
degree of adhesiveness for the resultant textile/rubber composite because 
the resin component will more easily become disengaged from around such 
textile fibers than if an actual resin film adhered substantially 
uniformly over the textile surface. This same type of problem has been 
noticed in other previous teachings, as in U.S. Pat. Nos. 5,466,424 to 
Kusano et al., 5,316,739 to Yoshikawa et al., 5,160,592 to Spitsin et al., 
5,108,780 to Pitt et al., and 4,756,925 to Furukawa et al. 
This encapsulation characteristic has subsequently limited the types of 
textiles which may be employed within such prior methods. For instance, 
nylon (polyamide) is the primary (if not only) fabric available as a 
potential reinforcement material within the above-mentioned patent 
documents. This fabric permits strong adhesion between the resin of the 
RFL even through this encapsulation procedure and thus is readily utilized 
throughout the textile/rubber reinforcement composite industry. However, 
such a fabric suffers from a number of limitations itself. For example as 
compared with polyester, nylon is much more expensive to use. Polyester, 
however, is very difficult to adhere with RFL rubber and thus has not 
proven to be easy to combine with rubber to form a proper reinforcement 
material in the past. Also, polyaramid textiles, such as Kevlar.RTM. (from 
DuPont du Nemours), Twaron.TM. (from Akzo), and Technora.TM. (from 
Teijin), as merely non-limiting examples, are well known as providing very 
strong reinforcements and are particularly desirable as textiles within 
such textile/rubber composites. However, these fabrics suffer from the 
same adhesion difficulty problem as with polyester and thus have had 
limited utility in the past within the pertinent industries (i.e., tire 
reinforcement, conveyor belts, and the like). As such, there still exists 
a need to facilitate adhesion between RFL rubber and polyesters or 
polyaramids in order to provide cost-effective and/or extremely strong 
textile/rubber reinforcement composites within the target industries 
(i.e., automobile tires, fan belts, conveyor belts, and the like). 
DESCRIPTION OF THE INVENTION 
It is thus an object of the invention to provide improved adhesion for a 
long-lasting and durable textile-reinforced rubber product comprised of 
any type of textile. A further object is to provide a plasma pre-treatment 
method which itself provides versatility of selection of textiles. Another 
object of the invention is to provide a method of promoting adhesion which 
ultimately provides a textile-reinforced rubber product comprised of any 
type of textile which does not exhibit adhesive failure. Yet another 
object of this invention is to provide a method of plasma pre-treatment 
which ultimately produces vastly improved adhesive quailities within 
textile/rubber composites without incurring an appreciable amount of extra 
manufacturing costs. 
Accordingly, this invention encompasses a method for promoting the adhesion 
between a textile and a rubber comprising the treatment of a textile in a 
vinyl compound plasma followed by coating the resultant textile with a 
resorcinol-formaldehyde latex and subsequently contacting said textile 
with a rubber compound. With greater particularity, this inventive method 
comprises the following steps 
(a) providing a textile, at least a portion of which is comprised of fibers 
selected from the group consisting of polyaramids, polyesters, nylon and 
any mixtures thereof; 
(b) plasma cleaning the textile surface, thereby attaching amino or 
carbonyl groups to the textile surface; 
(c) treating the resultant textile of step "b" in a medium selected from 
the group consisting of a vinyl compound plasma and a plasma gas 
containing a vinyl compound, thereby attaching various carbon-bonded 
compounds having exposed free radicals to the textile; 
(d) optionally coating the resultant textile of step "c" with a resin; 
(e) coating the resultant textile of either of steps "c" or "d" with a 
resorcinol-formaldehyde latex (RFL); 
(f) optionally coating the resultant latex-coated textile of step "e" with 
at least one adhesive compound selected from the group consisting of a 
cement, a tackifier, an overcoat, a resin, and mixtures thereof; 
(g) providing a rubber compound; and 
(h) contacting the RFL-coated textile of either of steps "e" or "f" with 
the rubber compound of step "g". 
Nowhere within the prior art has such a specific vinyl compound plasma 
treatment step been utilized to form a textile/rubber composite. 
Furthermore, nor has such a specific composition or method of utilizing 
such a specific plasma treatment been taught or fairly suggested. Such 
methods provide significant advantages over the standard adhesion methods 
of the state of the art. 
The inventive method does not add an appreciable amount to the relative 
cost of preparing the target textile/rubber composite. In fact, the major 
costs involved in this inventive process are incurred from the rubber 
and/or textile components. The ability of this inventive method to provide 
polyaramid/rubber composites at relatively low cost as well as the ability 
of this method to produce polyester/rubber composites, again at very low 
cost, is thus highly unexpected and greatly desired within the suitable 
industries. 
Such a method generally permits the application of very strong 
carbon-bonded groups to the textile surface through the treatment of the 
textile with a vinyl compound plasma. Without intending to be limited to 
any scientific theory, it is believed that the plasma generated with vinyl 
compounds produces a vast array of compounds having myriad different chain 
lengths and structures which easily bond to the surface of the substrate 
textile. As the plasma-generating process cleaves the vinyl compounds in 
random fashion, the resultant textile surface treatment appears to be 
highly tackified, most likely due to the formation of carbon-containing 
compounds having large amounts of freely exposed free radicals. This tacky 
composition thus appears to form an actual film layer on the textile 
surface. Apparently, the exposed free radicals produced on the textile 
surface through the vinyl compound plasma or plasma gas treatment bond to 
the RFL resin component themselves, thereby providing increasing bonding 
and adhesion between the textile substrate and the RFL. Since the degree 
of free radical generation is extremely high, the tacky vinyl compound 
plasma-generated composition thus adheres to a very large surface area of 
RFL. Combined with the very strong carbon bonds attached to the textile 
surface, the complete degree of adhesiveness between the textile and the 
RFL is very high. In addition, since the plasma polymerized vinyl film and 
the rubber latex of the RFL are very similar chemically, there will be 
increased mixing/solubility between the RFL and the textile, thereby 
providing increased adhesive properties. The RFL is then left exposed to 
produce very strong bonds with the rubber compound contacted with the 
resultant RFL-textile to form a very strong textile/rubber composite which 
exhibits rubber from rubber tearing before the textile and rubber exhibit 
any disengagement due to the very strong bond formed between the two 
components. 
This inventive process also encompasses a plasma pre-treatment prior to 
vinyl compound plasma treatment in order to "clean" the textile surface 
and theoretically apply other potentially strong bonding materials to the 
substrate. For example, an oxygen/tetrafluoromethane (O.sub.2 /CF.sub.4) 
or an ammonia (NH.sub.3) pre-treatment provides both a mechanism to remove 
unwanted debris and impurities from the textile surface, but also produces 
carboxy or amino linkages, respectively, on the target substrate. These 
linkages react with the vinyl compounds generated from such plasma, again, 
to form very strong bonds which enhance the adhesive qualities of the 
overall textile/rubber composite structure. Such a pre-treatment is highly 
preferred but is not required to effectuate a desired degree of 
adhesiveness between the vast array of plasma-generated vinyl compounds 
and the resin component of the RFL. 
The plasma treatment and pre-treatment require a certain degree of power 
and pressure in order to be effective within this inventive method. Also, 
fiber speed and thus exposure time for the target textile also appear to 
be of importance to the performance of the ultimate textile/rubber 
composite. For instance, generally acceptable conditions for the vinyl 
compound plasma treatment are from about 5 to about 1,000 millitorr (mT) 
pressure, from about 5 watts to about 2.5 kilowatts power, for an exposure 
time of from about 5 seconds to about 5 minutes. Preferred conditions and 
exposures times are from about 10 to about 500 mT, most preferred from 
about 50 to about 250 mT; from about 10 watts to about 1 kilowatt, most 
preferred from about 60 to about 250 watts; and from about 10 seconds to 
about 2 minutes, most preferred from about 30 seconds to about 1 minutes. 
Generally acceptable, and well known, conditions and exposures times for 
the plasma "cleaning" procedure are from about 10 to about 10,000 mT, 
preferred from about 50 to about 5,000 mT, and most preferred from about 
100 to about 1,000 mT; 10 watts to about 10 kilowatts, preferred from 
about 100 watts to about 2.5 kilowatts, and most preferred from about 250 
watts to about 1 kilowatt; and exposure times of from about 5 seconds to 
about 5 minutes, preferred from about 10 seconds to about 2 minutes, and 
most preferred from about 30 seconds to about 1 minute. In actuality, 
these conditions and exposure times may vary according to the type of 
plasma generator utilized. These conditions and exposure times were the 
optima for the PS1010 cord treater from Plasma Science (which is an air to 
air system). More specific conditions are listed below in the EXAMPLEs. 
It has been found that the inventive methods can be utilized with any 
rubber compositions and with any type of smooth filament textile normally 
utilized as a rubber reinforcement material, not to mention any other type 
of smooth filament textile which has proven difficult to use in such 
applications in the past (i.e., polyaramids, polyesters). Examples of 
rubber compositions include, but are not limited to, natural rubber, 
polyurethane rubber, neoprene rubber, ascium, viton, hypalon, 
styrene-butadiene rubber (SBR), carboxylated SBR, acrylonitrile-butadiene 
rubber (NBR), butyl rubber, fluorinated rubber, chlorobutyl rubber, 
bromobutyl rubber, and ethylene-propylene-diene rubber (EPDM), and any 
mixtures thereof. Modified rubbers which are potentially useful, though 
more expensive, include hydrogenated SBR, hydrogenated NBR, and 
carboxylated NBR. Suitable textiles include, and are not limited to, those 
comprising polyester, polyester/cotton blends, polyamides, such as nylon-6 
or -6,6, polyaramids (such as Kevlar.RTM., available from DuPont), 
polypropylene, boron derivatives, glass fibers, polyvinyl alcohols fibers, 
polypropylene oxide fibers, and carbon fibers. Of particular interest are 
polyesters and polyaramids since adhesion between these fibers and rubber 
has proven to be very difficult in the past. The textile component may be 
dyed or colored various shades and hues in order to facilitate 
categorizing the different widths, lengths, etc., of products such as, 
without limitation, timing belts, V-belts, and the like, for tires and for 
utilization in automobiles. Finally, the inventive methods, when utilized 
and/or practiced as intended, result in a textile-reinforced rubber 
product which does not exhibit textile/rubber adhesive failure. 
Preferably, the inventive methods utilize any plasma treatment involving 
vinyl compound plasma generation. As noted above, the vast array of 
differing carbon-bonded compounds produced within such a specific 
treatment are highly desired, particularly since free radicals (which bond 
extremely well with the RFL resin) are easily produced in great quantities 
as a film on the textile surface. Thus, acrylic acid, ethylene, butadiene, 
vinyl pyridine, and any other such vinyl-group containing compounds (as 
well as any mixtures of such vinyl-group containing compounds) are useful 
as compounds for the plasma-treatment in this inventive method. The 
specifically named ones above are those which are most highly preferred 
due to their relatively low cost and their very effective performance. The 
plasma pre-treatment may utilize any "cleaning" plasma compound, such as 
O.sub.2 /CF.sub.4 and NH.sub.3, as merely examples which removes debris, 
etc., from the substrate surface and preferably provides a potentially 
strong bonding linkage on the cleaned textile as well. Such plasma 
compounds are well known in the art. 
Optionally, a pre-RFL treatment of the textile surface may be performed 
after the plasma treatment wherein various types of resins may be adhered 
to the newly created tacky textile surface in order to improve the 
adhesive characteristics of the overall target textile/rubber composite. 
Thus, resins such as epoxy resins, isocyanates (in toluene), piperazines, 
silanes, and the like (including mixtures of such resins), may be reacted 
with the plastma-treated textile surface thereby creating a film of resin 
bonded to the textile-surface free radicals generated from the plasma 
treatment. After such a film is produced, the desired RFL would then be 
brought into contact with the resultant resin-coated textile whereupon the 
resin component of the RFL would form a film on the previously produced 
resin film surface. Such a resin/resin bond thus provides the necessary 
bond strength to effectuate the desired adhesion to the overall composite 
structure. 
Similarly, upon completion of the contacting between the plasma-treated 
textile and the RFL, such a resultant coated textile may also be coated 
with an adhesive compound which provides improved adhesion between the RFL 
and the rubber compound. Such compounds are selected from cements (such 
as, as merely an example, a solution of rubber in toluene), tackifiers 
(such as, again as merely examples, polysiloxanes), overcoats (such as, 
again as merely examples, compositions such as Chemlock.TM., available 
from Lord Corporation, and Chemosil.TM., available from Henkel 
Corporation), resins, such as those noted above for the pre-RFL treatment 
of the textile surface (i.e., epoxies, silanes, piperazines, isocyanates, 
and the like), and any mixtures thereof. 
Any standard rubber additives, including ultraviolet absorbers, 
antioxidants, dyes, colorants, curing agents, perfumes, antistatic agents, 
fillers (such as carbon black), silanes, and the like may be added to the 
rubber. To the textile substrate may be added any other standard textile 
additives, such as dyes, colorants, pigments, ultra violet absorbers, 
antioxidants, and the like. To the inventive composition and/or RFL used 
in combination with the inventive composition may be added wetting agents, 
antioxidants, and filler dispersions (such as carbon black, carbon fibers, 
tackifiers, UV absorbers, silica, ZnO dispersions, and flame retardant 
compounds). 
Furthermore, any well known RFL composition may be utilized within the 
inventive method. Such are extremely well known to the ordinarily skilled 
practitioner within the pertinent art and include combinations of 
resorcinol and formaldehyde in varying ratios and at varying temperatures 
and pH levels and solids. Furthermore, such resorcinol and formaldehyde 
compositions are combined with any number of rubber latex compounds and 
other additives, including, as merely examples, epoxies, urethanes, and 
the like. Such RFL compositions are very well known in the art and the 
utilization of such types of compositions (any number of which may be used 
in the inventive method) would be well appreciated by the ordinarily 
skilled, artisan in the textile/rubber reinforcement composite art. One 
particularly preferred RFL comprises the epoxy adhesive composition of 
U.S. Pat. No. 5,565,507 to Marco et al. 
Additionally, the curing step between the RFL-coated textile and the rubber 
compound is performed in any conventional manner, such as through 
heat-activated vulcanization in the presence of a curing agent (such as 
organic peroxide). Again, such a step should be well within the purview of 
the ordinarily skilled artisan in this field.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The Examples below are indicative of the particularly preferred embodiment 
within the scope of the present invention: 
EXAMPLES 1-2; Comparative Examples 3-14 
In each EXAMPLE below, Twaron.TM. yarn (polyaramid) of approximately 1,000 
denier was twisted two-for-one into a cord of approximately 2,000 denier. 
The cord was then continuously run through a vacuum chamber with a plasma 
created therein. The gas, gas pressure, and power were controllable plasma 
conditions and were adjusted as noted below for each EXAMPLE. The speed of 
the yarn dictated the residence time of the cord within the plasma chamber 
and was also adjusted for each EXAMPLE as noted below. Upon exiting the 
plasma chamber, the yarn was wound up thereby providing a continuous 
plasma process. EXAMPLES 1-7 encompassed a two-step plasma treatment for 
the subject cord, the initial being an O.sub.2 /CF.sub.4 plasma 
pre-treatment cleaning procedure, followed by the subject cord being wound 
up and subsequently exposed to a second plasma treatment, the plasma gases 
and conditions being specified in the table below. In all of the EXAMPLEs 
the cord was wound into a bobbin, from which individual pieces of yarn 
were cut by hand approximately 15 minutes after the respective final 
plasma treatment, dipped in a RFL mixture and dried in a forced air oven 
at about 350.degree. F. for about 4 minutes. All of the EXAMPLEs were 
coated from the same batch of RFL at the same time after plasma treatment 
was completed. The RFL coated yarn samples were then sealed in 
polyethylene bags and stored under normal conditions (room temperature and 
pressure) for two months. After this time, the coated yarns were removed 
from the bags and placed between two same-size samples of 
styrene-butadiene rubber (SBR) and cured, at a temperature of about 
350.degree. F. and a pressure of about 5 tons/square foot, into a single 
structure having yarn protruding from the front and back of the resultant 
composite. The plasma treatment conditions of these textile/rubber 
composites are more fully described in TABLE 1 below, with EXAMPLEs 1 
through 7 having been initially subjected to a plasma pre-treatment 
cleaning procedure, as discussed above, under the following conditions: 
______________________________________ 
PLASMA O.sub.2 /CF.sub.4 PRE-TREATMENT CLEANING CONDITIONS 
Pressure 
Power Yarn Speed 
Exposure Time 
(mTorr) (watts) (feet/min) 
(min) 
______________________________________ 
200 500 50 2 
______________________________________ 
TABLE 1 
______________________________________ 
Plasma Treatment Conditions 
Yarn 
Speed Exposure 
Treatment Pressure 
Power (feet/ 
Time 
Example # Gas (mTorr) (watts) 
min) (min) 
______________________________________ 
1 Acrylic Acid 
200 200 50 2 
2 Acrylic Acid 
200 100 50 2 
3 (Comparative) 
NH.sub.3 200 400 100 1 
4 (Comparative) 
NH.sub.3 400 400 100 1 
5 (Comparative) 
NH.sub.3 200 400 50 2 
6 (Comparative) 
CH.sub.3 OH 
200 400 100 1 
7 (Comparative) 
CH.sub.3 OH 
200 400 50 2 
8 (Comparative) 
NH.sub.3 200 400 50 2 
9 (Comparative) 
NH.sub.3 200 400 25 4 
10 (Comparative) 
NH.sub.3 400 400 50 2 
11 (Comparative) 
O.sub.2 /CF.sub.4 
200 500 50 2 
12 (Comparative) 
O.sub.2 /CF.sub.4 
400 500 50 2 
13 (Comparative) 
Air.sup.1 760,000 0 50 2 
14 (Comparative) 
O.sub.2 /CF.sub.4.sup.2 
200 0 50 2 
______________________________________ 
.sup.1 Comparative EXAMPLE 13 included the coating of the yarn with an RF 
without any vacuum or plasma processing after running through the inactiv 
plasma chamber. 
.sup.2 Comparative EXAMPLE 14 included vacuum treatment of the yarn 
through the plasma chamber without any power applied. 
Each of these EXAMPLEs was then tested for the 1/4" pull-out strength of 
the yarn embedded within the textile/rubber composite structure. The 
numbers reported in TABLE 2, below are actually an average of test 
measurements for three samples subjected to the same conditions. A ten 
percent (10%) increase of about 1 pound of force for these pull-out tests 
is considered significant. 
TABLE 2 
______________________________________ 
Test Measurements for 
Adhesive Characteristics Between Textile and Rubber 
Example # Pull-Out Force (Pounds) 
______________________________________ 
1 16.9 
2 16.7 
3 (Comparative) 
13.2 
4 (Comparative) 
13.5 
5 (Comparative) 
13.6 
6 (Comparative) 
11.1 
7 (Comparative) 
12.9 
8 (Comparative) 
12.7 
9 (Comparative) 
13.0 
10 (Comparative) 
11.0 
11 (Comparative) 
12.6 
12 (Comparative) 
13.2 
13 (Comparative) 
11.1 
14 (Comparative) 
10.5 
______________________________________ 
It is evident from these tests that the preferred embodiment EXAMPLEs (1 
and 2) exhibited far superior rubber to textile adhesion than the 
Comparatives EXAMPLEs. Thus, the utilization of vinyl-compound plasma 
treatments provided vast improvements in the desired adhesive effects of 
the textile/rubber composite structures. In fact, the plasma chamber 
itself felt tacky to the touch upon completion of plasma treatment with 
the acrylic acid (vinyl compound). The other treatments did not produce 
such a result within the chamber and the O.sub.2 /CF.sub.4 gas was 
utilized to clean the plasma chamber after the vinyl compound plasma 
treatment. 
EXAMPLES 15-25; COMATIVE EXAMPLES 26-29 
Different vinyl compounds were also utilized within a plasma treatment step 
for the yarn which was subsequently coated with a RFL, and contacted and 
cured with a SBR sample (as followed within the procedure outlined above 
for the previous EXAMPLEs. Each of the EXAMPLEs listed below were 
subjected to the plasma pre-treatment discussed above as well. The 
pull-out test measurement was made for each EXAMPLE, below, as performed 
for the previous EXAMPLES, too. EXAMPLEs 15 through 17 and 26-28 tested 
the pull-out force on plasma-treated polyaramid fibers (the Twaron.TM. 
yarn as discussed previously). EXAMPLES 18-25 and 29 tested the pull-out 
force on plasma-treated polyester fibers. Such polyesters are available 
from Akzo and are 1,000 denier polyethylene terephthalate twisted 2-ply, 
then twisted 3-ply, fibers, exhibiting a total denier of about 6,000. 
These were treated in the same manner as those of EXAMPLEs 15-17. 
TABLE 3 
______________________________________ 
Plasma Treatment Conditions and 
Textile/Rubber Adhesive Test Measurements 
Exposure 
Pull-Out 
Ex. Pressure 
Power Speed Time Force 
# Plasma Gas (mTorr) (watts) 
(ft/min) 
(minutes) 
(pounds) 
______________________________________ 
15 Acrylic Acid 
250 200 100 1 19.5 
16 Ethylene 250 200 100 1 21.1 
17 Butadiene 250 200 100 1 17.1 
18 Acrylic Acid 
250 200 50 2 15.8 
19 Ethylene 250 200 50 2 15.0 
20 Butadiene 250 200 50 2 13.8 
21 Vinyl Pyridine 
250 200 50 2 17.9 
22 Acrylic Acid 
250 200 100 1 18.3 
23 Ethylene 250 200 100 1 14.6 
24 Butadiene 250 200 100 1 18.5 
25 Vinyl Pyridine 
250 200 100 1 18.0 
26 O.sub.2 /CF.sub.4 
400 500 50 2 16.8 
27 NH.sub.3 400 400 100 1 17.6 
28 *Air 760,000 0 100 1 13.7 
29 *Air 760,000 0 100 1 12.2 
______________________________________ 
*Comparative EXAMPLEs 28 and 29 were run through to the plasma chamber 
without any vacuum or power utilized. 
It has been discovered that the optimum levels of power and pressure 
required to effectuate proper adhesive characteristics to the textile 
substrate through the use of vinyl compound plasma or plasma gas is 
relatively low as compared with the "cleaning" plasma treatments. In fact, 
the necessary levels for the "cleaning" plasma treatments must be 
relatively high; if conditions used were at too low a pressure and at too 
low a power level, a reduced degree of "cleaning" of the textile surface 
would occur which would substantially and deleteriously affect the 
adhesive characteristics of the ultimate textile/rubber composite. Were 
the power level and/or pressure level too high for the inventive 
treatments, the vinyl compound would be susceptible to degradation or the 
vinyl polymerization would run too fast. In such an instance, the compound 
fragments generated from such plasma treatment would be too small to 
properly polymerize or would create small "dust" particles on the textile 
substrate and the walls of the plasma chamber which would inhibit adhesion 
as well. Thus, although the power and pressure levels are different in 
TABLE 3 above, such differences actually compare the optimum levels for 
the specific plasma treatments tested. Clearly, the resultant adhesive 
measurements for the inventive method are either vastly improved over the 
comparative examples or evince procedures which produce comparable results 
from the other standard plasma treatments. 
There are, of course, many alternative embodiments and modifications of the 
present invention which are intended to be included within the spirit and 
scope of the following claims.