1365506 Chain terminators in the preparation of acrylonitrile copolymers IMPERIAL CHEMICAL INDUSTRIES Ltd 17 May 1972 [17 May 1971] 15265/71 Heading C3P Copolymers of acrylonitrile containing 50-95 mole per cent of acrylonitrile units and 50-5 mole per cent of randomly distributed units of at least one olefine having aromatic character, are obtained by polymerization of the monomers in the presence of at least one alkane thiol of boiling point 100‹ C. or less at atmospheric pressure and also at least one thiol of boiling point greater than 100‹ C. at atmospheric pressure, the first mentioned thiol being continuously added with monomer feed at a rate determined by the rate of polymerization. Thiols of B.Pt. 100‹ C. or less are methane-, ethane-, 1-propane-, 2-propane-, 1-butane-, and 2-butanethiols; those with a B.Pt. greater than 100‹ C. are 1-, 2-, or 3-pentane-, 1-hexane-, 1-heptane-, primary-, secondary- and tertiary octane-, tertiary non- ane-, 1-decane-, secondary undecane-, and primary and secondary dodecane thiols. Examples of olefins having an aromatic character are styrene, and its alphamethyl-, o-methyl-, m-methyl-, p-methyl-, m-hydroxy-, p-trimethylsilyl-, 2,5-dimethyl-, p-methoxy-, p-dimethylamino-, or -dibromo-, and p-acetamido derivatives; 1-vinyl naphthalene, 2-vinyl thiophene, 3-vinylphenanthrene, 2-methyl-5-vinyl pyridine and N-vinylcarbazole. The copolymers are mouldable and since they are odourless and tasteless, are useful for packaging foodstuffs, and medicines. In the example, acrylonitrile and styrene are copolymerized in aqueous emulsion using ammonium persulphate as initiator and ammonium dodecyl benzene sulphonate as emulsifier. The two thiols are octane-1-thiol and propane-1-thiol, the latter being continuously supplied with styrene. Sodium dimethyl dithiocarbamate is used as a moderator. The reaction is short stopped. Bottles are moulded from the resultant polymers.