Stock material or miscellaneous articles – Composite – Of polyamide
Reexamination Certificate
2000-02-16
2001-06-19
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of polyamide
C156S307500, C442S063000, C428S483000
Reexamination Certificate
active
06248450
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an adhesive composition that is used for bonding a variety of rubber compounds to textiles. More specifically, the present invention relates to a single adhesive composition that bonds more than one class of elastomeric polymer to fabric to produce end-products such as diaphragms, molded articles, V-belt covers, conveyor belts, hose wrap and the like.
BACKGROUND OF THE INVENTION
For many products such as diaphragms, molded articles, bead wraps for tires, V-belt covers and the like, stringent requirements exist for the bond between the rubber and the substrate to which it is attached. It is only by using special adhesives that sufficient adhesion is obtained between rubber and synthetic fibers, since synthetic fibers have a low affinity for the rubber compound due to the lack of binding sites in the fibers.
Developed in 1935, the resorcinol-formaldehyde resins are among the oldest adhesives to achieve rubber to textile adhesion. They are used in an aqueous phase in conjunction with latex, hence they are commonly referred to as resorcinol-formaldehyde latex (RFL) compounds. Commonly used RFL compounds are limited in several respects. First, some RFLs are able to bond to only one type of fabric. For example, a latex based on butadiene-styrene-2-vinyl-pyridine (“vinylpyridine latex) was developed for bonding rubber to polyamide fibers. This adhesive composition, however, is insufficient for bonding polyester fibers to rubber. Second, typical RFLs are formulated to bond only one class of elastomeric or rubber polymer to fabric. Consequently, to achieve strong adhesion of a particular rubber to fabric using an RFL formulation, that particular rubber should be included in the RFL formulation. For example, to bind nitrile rubber to fabric, nitrile is typically used as a component in the RFL formulation.
Because of the inability of existing RFL formulations to bind more than one class of rubber polymer, it is necessary to prepare different RFL formulations during the fabric finishing process. The RFL formulations that are prepared will depend on the rubber compound that is to be ultimately bound to the fabric. Such production of specifically tailored adhesives is both time-consuming and costly. Changeovers with different adhesive formulations are inefficient and time-consuming. Moreover, preparation of multiple adhesive formulations poses an increased risk in the selection of the improper RFL formulation for treating the fabric.
While obtaining good adhesion between the desired rubber and treated fabric is of paramount importance, there is a real need for the development of a single adhesive composition which can be used to bond more than one class of elastomeric polymer to textiles.
SUMMARY OF THE INVENTION
The present invention is directed to a single adhesive composition for use in bonding or reinforcing a variety of rubber polymers to textiles, in particular woven fabric. The composition comprises an aqueous mixture of a) a polychloroprene latex; b) at least one prepolymer of resorcinol with formaldehyde; c) at least one blocked diisocyanate compound, and d) sufficient water to adjust the solids content of the aqueous mixture from about 15 to about 40% by weight. The novelty of the present invention is based on the ability of the adhesive composition to bond more than one class of rubber polymer to fabric.
The adhesive composition further includes additional formaldehyde which enhances the chemical reaction of the aqueous mixture. A non-ionic surfactant is also contained in the composition, and functions to lower the surface tension of the aqueous mixture. Sufficient alkaline such as caustic soda is included as a catalyst and also to adjust the pH of the final composition between about 9 and about 11. If desired, carbon black may be added to the aqueous mixture to provide color.
The adhesive composition of the present invention overcomes the disadvantages of current adhesive formulations by being compatible with a variety of natural and synthetic rubber polymers. Regardless of the rubber that is bound to the fabric, a single adhesive composition has been discovered which is capable of providing strong adhesion between a variety of rubbers and fabric substrates including, but not limited to nylon, polyester, and blends thereof.
For purposes of this invention, the elastomers or rubber polymers include, but are not limited to, polychloroprene, more commonly known as neoprene, nitrile, natural rubber, fluoroelastomer, hypalon, and EPDM (ethylene-propylene terpolymer). The end-products that are contemplated by the present invention include, but are not limited to, diaphragms, molded articles, V-belt covers, conveyor belts, hose wrap, bead wraps for tires, dodge couplings and the like.
In one embodiment of the present invention, the adhesive composition for bonding a variety of rubber compounds to fabric, comprises an aqueous mixture of: a) about 85 to about 90 weight % polychloroprene latex; b) about 2 to about 6 weight % of at least one prepolymer of resorcinol with formaldehyde; c) about 4 to about 8 weight % of at least one blocked diisocyanate compound; and d) sufficient water to adjust the solids content of the mixture to about 15 to about 40 weight %, wherein the percentage of solids add-on on fabric treated with the adhesive composition ranges between about 5 and about 20% based on the untreated fabric weight.
In yet one preferred embodiment, the blocked diisocyanate compound is caprolactam blocked methylene-bis-(4-phenylisocyanate).
In another embodiment, the non-ionic surfactant is present in an amount of approximately 0.5 weight %.
A process is disclosed for adhering rubber compounds to synthetic fabric, comprising the steps of:
a) impregnating or dipping fabric in an aqueous mixture comprising a polychloroprene latex, a resorcinol-formaldehyde reaction product, at least one blocked diisocyanate compound, and sufficient water to adjust the solids content of the mixture to about 15 to about 40% by weight, wherein the percentage of solids add-on on fabric treated with the mixture ranges between about 5 and about 20% based on the weight of the untreated fabric;
b) drying the treated fabric at temperatures ranging between about 220° and 270° F. for approximately 1 minute;
c) curing the dried fabric for about 2 minutes at approximately 375° F. to bond the mixture to the fabric;
d) applying at least one rubber polymer to the cured fabric; and thereafter
e) vulcanizing the rubber to the fabric for a sufficient time and at sufficient pressure.
Additional features and advantages of the present invention are further described, and will be apparent from the detailed description from the presently preferred embodiments.
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“My Experience with Grilbond IL-6. Improved Adhesion on Pes Cord Fabrics with Processing Cost Reduction”; Lucien Hennicot; Mar. 20, 1995.
Smith Benny B.
Voss Gary D.
Aylward D.
Dawson Robert
Highland Industries, Inc.
Rhodes & Mason P.L.L.C.
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