Curing synthetic elastomers

Copolymers of butadiene and an alkyl acrylate or an alkyl acrylate having an electrophilic substituent in the alkyl group are cured by heating in the presence of a basic oxide or hydroxide of a polyvalent metal and a neutral or basic organic hydroxy compound. The copolymers may contain 5-60% by weight of monomers of alkyl acrylate which preferably contains up to 4 carbon atoms in the alkyl group. Suitable negative substituents in the alkyl group are chlorine, bromine, cyano, nitro-, or sulphonic groups. The copolymer may contain up to 30% of a third monomer containing a vinylidene group such as methyl methacrylate, vinylidene chloride, methyl isopropenyl ketone, methyl vinyl ketone, acrylonitrile and styrene. The copolymers are prepared by emulsion polymerization using a persulphate or redox catalyst. The preferred organic hydroxy compounds are those which will dissolve at least 0,1% of the basic oxide or hydroxide used and are preferably aliphatic or have a predominantly aliphatic nature, preferably have a boiling point above the curing temperature, and include starches, glucose, sorbitol, mannitol, ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, glycerol, tetramethylol cyclohexanol, transquinitol, 1,5-bis(2-hydroxyethyl) naphthalene cyclohexanol, benzyl alcohol and lauryl alcohol. It is used in an amount of 1-15% by weight of the copolymer. The basic oxide or hydroxide is preferably one of a divalent metal such as an alkaline earth metal and is used in an amount of 5-10% by weight of the copolymer. Curing times are 30 minutes to 4 hours at about 150 DEG C. Carbon black or titanium dioxide fillers may be added but acidic ingredients should be avoided. Specification 808,913 is referred to.