Aqueous adhesive for bonding elastomers

#The present invention relates to compositions of matter useful for bonding various substrates such as elastomeric materials. More specifically, the present invention relates to environmentally resistant aqueous adhesive compositions based on polyvinyl alcohol-stablized butadiene polymer latices and methylene donor compounds.

#In light of the increasing awareness for environmental protection and workplace safety, a current major thrust of the adhesives industry is to develop an adhesive composition which avoids the use of highly volatile organic solvents which can cause damage to the environment and potentially affect the health of workers exposed to the solvent. It has thus far been relatively difficult to develop an aqueous adhesive which performs at a level equal to traditional solvent-based adhesives. One major problem associated with bonds formed from aqueous adhesives is the relative susceptibility of the bonds to high temperature fluids and corrosive materials. In applications involving the bonding of elastomeric substrates to surfaces such as metal surfaces, an aqueous adhesive must exhibit an affinity for the elastomeric substrate as well as possess the ability to withstand degradation by high temperature fluids or corrosive materials.

#Various aqueous adhesives for bonding elastomeric materials have been developed in a continuing effort to obtain the ultimate aqueous adhesive for bonding elastomeric substrates. For example, U.S. Pat. No. 4,167,500 describes an aqueous adhesive composition that contains a water dispersible novolak phenolic resin, a methylene donor such as an acetal homopolymer or acetal copolymer, and water. The phenolic resins described are primarily derived from resorcinol and alkylphenols such as p-nonylphenol although various other polyhydroxy phenols are mentioned, such as phloroglucinol and pyrogallol.

#Preparation of Polyvinyl Alcohol-Stabilized Latex

#A polyvinyl alcohol-stabilized dichlorobutadiene/.alpha.-bromoacrylonitrile copolymer latex is prepared with the following ingredients (PHM=parts per hundred parts monomer):

#______________________________________ Ingredient Weight (g) PHM ______________________________________ 2,3-dichloro-1,3-butadiene (90% in CH.sub.2 Cl.sub.2) 656.0 82.0 .alpha.-bromoacrylonitrile 144.0 18.0 Polyvinyl alcohol 56.0 7.0 Deionized water 1056.0 132.0 Methanol 400.0 50.0 (NH.sub.4).sub.2 S.sub.2 O.sub.8 4.0 0.5 Na.sub.2 S.sub.2 O.sub.5 4.0 0.5 ______________________________________