Improvements relating to processes for bonding rubber to metal and to articles produced thereby

摘要

In bonding rubber to metal, a thin coating of an adherence layer, devoid of rubber, comprising a low molecular weight substance having an affinity for metals and a nitrogenous substance reactable therewith at raised temperature to form a resin is applied to clean metal, over the coating of adherence layer is applied a thin coating of an adhesive solution comprising rubber and a nitrogenous substance reactable at raised temperature with the substance having an affinity for metals to form a resin, the coatings on the metal are heated in an oxygen-containing gas, e.g. heated at 100-180 DEG C. in air of humidity not more than 80 per cent., to transform the non-rubber constituents of the coatings to an infusible, metal-adherent resin, a vulcanizable rubber compound is applied to the so-treated metal and is then vulcanized under pressure on the metal. The substance having an affinity for metals may be a phenol or thiophenol in the molecule of which are at least two labile hydrogen atoms and a plurality of substituents formed by halogen atoms or sulphurated or nitrogenous groups, e.g. the monosulphide, disulphide or mercapto derivative of resorcinol, the reaction products of resorcinol with sulphur at 220-225 DEG C., produced, if desired, in the presence of hydroquinone; 1, 3-dimercaptobenzene; the reaction products of a phenol with thionyl chloride obtained in the presence of anhydrous aluminium chloride and freed from the aluminium choride and its transformation products; diresorcinol sulphoxide; resorcinol sulphonium chloride; resorcinol; p-nitrophenol; p-bromophenol. 4-chlororesorcinol. The nitrogenous substance of the adherence layer may be a condensation product obtained by reacting ammonia or a primary amine with an aliphatic, aromatic or heterocyclic aldehyde, e.g. hexamethylene tetramine. the nitrogenous substance of the adhesive solution may be an N-substituted aldehydimine in the molecule of which are two azomethynic groups, R (- N=CH-R1)11, where n is 2 or more, R an organic radical of n valency, e.g. a polymethylenic chain of at least four terms, in which atoms of oxygen or sulphur may be inserted, and R1 is hydrogen, a monovalent olefinic radical, furyl or other monovalent radical having one furnace nucleus, such N-substituted aldehydimines being exemplified by monomeric difurfurylidenehexamethylenediamine, N-methylene - N1 - furfurylidene - hexamethylenediamine and difurfurylidene?p-phenylene-diamine. The rubbers referred to are natural rubber, butadiene-styrene copolymers, butadiene-acrylonitrile copolymers, copolymers of butadiene or isoprene with isobutylene, polymers or copolymers of chlorobutadiene, thioplasts. The adhesive solution does not necessarily contain the same rubber as that on which is based the rubber compound to be bonded; for heat-vulcanizable rubber compounds based on butadiene-styrene copolymers or thioplasts the adhesive solution may contain natural rubber.