Abstract: A flame retardant for thermoplastic resins comprising polyorganosiloxane crosslinked particles having a toluene-insoluble matter content of at least 50% by weight and an average particle size of 0.01 to 2,000 &mgr;m, which provides flame retardant resin compositions of low environmental load generating no harmful gas at the time of burning and having an excellent impact resistance by the incorporation thereof into thermoplastic resins.

Abstract: There is provided graft copolymer particles prepared by graft-polymerizing a vinyl monomer to a coagglomerated rubber, wherein said rubber is prepared by coagglomerating rubber particles of mixed latexes obtained by mixing (A) a silicone rubber latex with (B) an acrylic rubber latex and/or a conjugated diene rubber latex in such an amount as a silicone content is from 1 to 90% by weight based on the total rubber component. A physical property of a thermoplastic resin is improved using the graft copolymer particles. The thermoplastic resin composition using the graft copolymer particles is excellent in impact resistance, weather resistance, processability, thermal discoloration resistance and appearance of molded products.