A PROCESS FOR PRODUCING AN ALPHA-ALKYL-SUBSTITUTED AROMATIC VINYL COPOLYMER AND A THERMOPLASTIC RESIN COMPOSITION COMPRISING THE COPOLYMER

摘要

A process for producing an alpha -alkyl-substituted aromatic vinyl copolymer constituted of 60 to 85 parts by weight of the alpha -alkyl-substituted aromatic vinyl monomer, 15 to 35 parts by weight of a vinyl cyanide monomer, and 0 to 40 parts by weight of another vinyl monomer copolymerizable with these monomers, which process is characterized in that all the amount of the aromatic vinyl monomer necessary for the entire polymerization and such partial amounts of the vinyl cyanide monomer and another copolymerizable vinyl monomer as to give a predetermined copolymer composition with respect to the content of the aromatic vinyl monomer, are first charged and emulsified and the emulsion polymerization is then initiated and carried out by adding dropwise continuously the residual amounts of the vinyl cyanide monomer and another copolymerizable vinyl monomer in such a manner that the range of change in the content of the aromatic vinyl monomer in the copolymer during the polymerization reaction will not vary more than 2% in the range of conversion of 0 to 90%; and a thermoplastic resin composition comprising [A] 50 to 90% by weight of a copolymer constituted of 60 to 85 parts by weight of an alpha -alkyl-substituted aromatic vinyl monomer, 15 to 35 parts by weight of a vinyl cyanide monomer, and 0 to 40 parts by weight of another vinyl monomer copolymerizable with these monomers, the copolymer being produced in such a manner that the range of change in the content of the aromatic vinyl monomer in the copolymer during the polymerization reaction will not vary more than 2% in the range of conversion of 0 to 90, and [B] 10 to 50% by weight of a graft copolymer constituted of 30 to 85 parts by weight of a rubber polymer and 15 to 70 parts by weight of a grafted polymer consisting of a monovinyl aromatic monomer, vinyl cyanide monomer, and another monomer copolymerizable with them in respective proportions of 85-40:0-40:0-80, where the total amount of polymers [A] and [B] is 100% by weight.