COPOLYMERS WITH A HIGH CONTENT OF ALPHA-METHYLSTYRENE, A PROCESS FOR THEIR PRODUCTION AND THERMOPLASTIC RESIN COMPOSITIONS CONTAINING THESE COPOLYMERS

摘要

The invention relates to a copolymer with a high content of alpha -methylstyrene which is characterized in that it is a copolymer comprising 65 to 90 parts by weight of alpha -methylstyrene with 35 to 10 parts by weight of acrylonitrile and 0 to 5 parts by weight of at least one copolymerizable vinyl monomer and that a component having an alpha -methylstyrene content of 82% or higher is contained in an amount of 30 parts by weight or more. Such a copolymer may be produced by a process which comprises charging 65 parts by weight or more of alpha -methylstyrene and 10% by weight or less based on this alpha -methylstyrene of acrylonitrile and at least one vinyl monomer all in one portion at the initial stage, making the system fully emulsified, gradually adding 35 parts by weight or less of acrylonitrile and the vinyl monomer or monomers, and carrying out emulsion polymerization until the amount of the polymer produced has reached 50 parts by weight or more in such way that the ratio of the alpha -methylstyrene monomer to the monomers other than alpha -methylstyrene in the system is always maintained at 90/10 or higher on the weight basis.
The invention further relates to a thermoplastic resin composition which comprises the above copolymer with high content of alpha -methylstyrene and a graft copolymer obtained by reacting a diene rubber with monomers comprising an aromatic monovinyl compound and an unsaturated nitrile compound, the diene rubber being present in an amount of 5 to 30 parts by weight.
Molded products obtained from the composition of this invention have excellent heat resistance and impact resistance.