Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2000-04-28
2002-12-24
Morris, Terrel (Department: 1771)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C152S903000, C152S451000, C152S565000, C156S110100, C156S272200
Reexamination Certificate
active
06497954
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a method of promoting the adhesion of textiles to rubber compounds through a vinyl compound plasma pretreatment procedure and a subsequent application of resorcinol-for aldehyde 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. No. 5,064,876, to Hamada et al., and U.S. Pat. No. 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. No. 5,501,880 to Parker et al., U.S. Pat. No. 5,283,119 to Shuttleworth et al., and U.S. Pat. No. 5,053,246 to Shuttleworth et al. Each of these references discloses a plasma pretreatment 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
2
/CF
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
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 is 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. No. 5,466,424 to Kusano et al., U.S. Pat. No. 5,316,739 to Yoshikawa et al., U.S. Pat. No. 5,160,592 to Spitsin et al., U.S. Pat. No. 5,108,780 to Pitt et al., and U.S. Pat. No. 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® (from DuPont du Nemours), Twaron™ (from Akzo), and Technora™ (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 pretreatment method which itself provides versatility of selection of textiles. Another object of the invention is to pro
Maria Michiels Dany Felix
Morin Brian G.
Wentz Brenda D.
Milliken & Company
Morris Terrel
Moyer Terry T.
Parks William S.
Wachtel Alexis
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