Weather resistant impact modifiers for thermoplastic resins

A weather resistant impact modifier for thermoplastic resins which comprises a graft copolymer having a multi-layered structure which is obtained by graft polymerization of

• a component (c) which is a combination of
• (i) 10-100 parts by weight of a monomer or a monomer mixture consisting of an aromatic vinyl monomer in a first stage selected from the group consisting of styrene, alpha-methylstyrene and vinyl toluene and
• (ii) 10-100 parts by weight of a monomer or a monomer mixture consisting of a methacrylic ester in a second stage selected from the group consisting of alkyl esters of methacrylic acid,
• to 100 parts by weight of an elastomer obtained by polymerizing a component (b) consisting of 98-60 parts by weight of a monomer mixture composed of
• (i) 60-99.95 wt % of a copolymerizable monomer selected from the group consisting of alkyl esters of acrylic acid,
• (ii) 0-49.95 wt % of another copolymerizable monomer consisting of a vinyl group containing unsaturated monomer and
• (iii) 0.05-5 wt % of a polyfunctional monomer,
• in the presence of 2-40 parts by weight of a component (a) composed of a butadiene elastomer having a degree of swelling of 5-40 and an average particle size not less than 0.15 .mu.m.