amp;agr;-Methylstyrene high-content copolymers, a process for their production and thermoplastic resin compositions containing amp;agr;- methylstyrene high-content copolymers blended with graft copolymers

摘要

An &agr;-methylstyrene high-content copolymer which is characterized by that it is a copolymer which comprises 65-90 parts by weight of &agr; -methylstyrene with 35-10 parts by weight of acrylonitrile and 0-5 parts by weight of a copolymerizable vinyl monomer or monomers and that a component having an &agr;-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 &agr;-methylstyrene and 10% by weight or less based on this . alpha.-methylstyrene of acrylonitrile and a vinyl monomer or monomers 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 a polymer produced has amounted to 50 parts by weight or more in such way that the ratio of the &agr;-methylstyrene monomer to the monomers other than &agr;- methylstyrene in the system is always maintained at 90/10 or higher on the weight basis. A thermoplastic resin composition comprises the above &agr;-methylstyrene high-content copolymer and a graft copolymer obtained by reacting a diene rubber with monomer comprising a monovinyl aromatic compound and an unsaturated nitrile compound, the diene rubber being present in an amount of 5-30 parts by weight. Molded products obtained from the composition of this invention have excellent heat resistance and impact resistance.