GB829564A - Bonding rubber to polyurethane - Google Patents

Abstract

A bonding material comprising an organic isocyanate, an aromatic nitroso compound, and a polymeric film-forming agent selected from synthetic resins and natural and synthetic elastomers is interposed between an olefinic rubber and a polyurethane body and the assembly is heated under pressure to bond the rubber to the polyurethane, the isocyanate being at least available at the interface between the bonding material and the polyurethane, the nitroso compound being at least available at the interface between the bonding material and the rubber, and the isocyanate and/or the nitroso compound being incorporated in the film-forming agent. The olefinic rubber may comprise natural rubber, polybutadiene, butadiene-styrene or butadiene-acrylonitrile or butadiene-vinyl pyridine copolymer, a copolymer of polychloroprene and an ethylenically unsaturated compound, polychloroprene, or butyl rubber. The isocyanate included in the bonding material may be an alkyl or aryl isocyanate, or a polymethylene, alkylene, alkylidene, cycloalkylidene, or aromatic di-, tri-, tetra-, or other olyisocyanate. The nitroso compound is preferably aromatic, and a dinitroso compound is particularly preferred, e.g. a meta- or paradinitroso benzene or naphthalene. The aromatic nitroso compound may also be substituted by a radical or radicals selected from alkyl, arylalkyl, arylamine, arylnitrosamine, and halogen groups. Numerous examples of isocyanate and nitroso compounds are specified. The nitroso compound may be applied to the rubber surface and the isocyanate to the polyurethane or firstly the isocyanate and then the nitroso compound may be applied to the polyurethane, or firstly the nitroso compound and then the isocyanate may be applied to the rubber surface, or an isocyanate-dinitroso compound mixture is applied to the substrate and/or to the rubber. Alternatively the bonding material may be applied as a preformed sheet containing the film-forming agent. Several film-forming materials are specified including polychloroprene, brominated poly-2,3-dichlorobutadiene-1,3, phenolic resins, epoxy resins, polyurethane, and phosgenated aniline-aldehyde resin, the two latter substances serving also to provide the isocyanate component of the bonding material. A catalyst such as a tertiary amine may also be included in the bonding material for accelerating the action of the isocyanate. Preferably the isocyanate component constitutes 50 to 60% by weight and the nitroso groups in the nitroso compound about 0.9 to 22% of the solids in the bonding material. In one of the many examples a surface of an uncured polyurethane rubber is coated with a mixture comprising 100 parts by weight polyurethane, 50 parts polyisocyanate produced by phosgenation of aniline-formaldehyde resin, 25 parts p-nitroso diphenyl amine, and 567 parts methylethyl ketone. Unvulcanized GRS synthetic rubber compound is applied to the coated polyurethane surface and the assembly is vulcanized under pressure and then heated in an oven. Specification 822,725 is referred to.