Modified nonflammable resin composition

A modified nonflammable resin composition comprising 100 parts by weight of a nonflammable resin composition (A) composed of 30 to 80% by weight of a styrene resin comprising a rubber portion, a cross-linked portion and a non-rubber portion, said styrene resin having a methyl ethyl (keton-soluble) ketone-soluble portion having a reduced viscosity in the range of from 0.2 to 0.5 dl/g in N,N-dimethylformamide at 30.degree. C. at a concentration of 0.3 g/dl, and 70 to 20% by weight of a vinyl chloride resin having a polymerization degree of 400 to 800;

• and
• 0. 5 to 15 parts by weight of a copolymer (B) prepared by copolymerizing (a) a vinyl cyanide, (b) an alkyl methacrylate, (c) an aromatic vinyl compound, and (d) another copolymerizable vinyl monomer in amounts specified by the equation below, and having a reduced viscosity of not less than 1.8 dl/g in N,N-dimethylformamide at 30.degree. C. at a concentration of 0.3 g/dl;
• 15.ltoreq.a+b/4.ltoreq.40
• d=100-a-b-c
• a.gtoreq.0, b.gtoreq.0
• 0.ltoreq.c .ltoreq.85, and
• 0.ltoreq.d.ltoreq.20
• with proviso that when a is zero, b is not zero and when b is zero, both a and c are not zero;
• wherein a, b, c, and d, respectively, denote percentage by weight of the vinyl cyanide compound (a), the alkyl methacrylate (b), the aromatic vinyl compound (c), and the copolymerizable vinyl monomer (d).