Scorch-safe acceleration of urethane vulcanization of unsaturated rubbers.

摘要

The invention relates to a method of curing an unsaturated rubber which is a conjugated diene homopolymer or a copolymer containing at least 50% by weight of a conjugated diene. The method involves the heating of the rubber in admixture with an adduct of nitrosophenol and methylene bis(4-phenylisocyanate) of the formula
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to form urethane cross-links, a scorch delay cure catalyst being added to the rubber prior to curing and the catalyst being a derivative of dithiophosphoric acid of the formula
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wherein R1 and R2 are alkyl groups having at least 12 carbon atoms or are connected together and form an alkylene group having at least 2 carbon atoms, and R3 is hydrogen or phenethyl.
<??>Use of the invention is found to improve scorch times of natural and synthetic rubber compositions in urethane cross-linking systems.