Impact-resistant methacrylic resin composition

An impact-resistant methacrylic resin composition comprising a multilayer structure methacrylic resin [II] is provided. The resin [II] is obtained by the following sequential four polymerization stages (i) through (iv):(i) forming 5-50 wt. parts of a hard crosslinked resin (A) containing at least 80 wt.% of methyl methacrylate units;(ii) obtaining 100 wt. parts of a multilayer structure acrylic elastomer [I] by forming on the periphery of resin (A) 95-50 wt. parts of a crosslinked acrylic acid ester copolymer (B) by polymerizing a monomer mixture comprising 69.9-89.9 wt.% of at least one alkyl (C1-8) acrylate, 10-30 wt.% of styrene or a mixture of styrene and a derivative thereof and 0.1 -10 wt.% ofand/or(iii) forming on the periphery of elastomer [I] 5-100 wt. parts of a hard crosslinked resin (C) by polymerizing a crosslinkable monomer mixture comprising 80-99.9 wt.% of methyl methacrylate, 0-19.9 wt.% of at least one alkyl (Ci-8) acrylate, 0-10 wt.% of other copolymerizable vinyl monomer and 0.1-10 wt.% of a copolymerizable polyfunctional monomer having at least two C-C double bonds in the molecule; and then(iv) forming on the periphery of resin (C) 5-1000 wt. parts of a hard non-crosslinked resin (D) by polymerizing a non-crosslinkable monomer or non-crosslinkable monomer mixture comprising 80-100 wt.% of methyl methacrylate, 0-20 wt.% of at least one alkyl (C1-8) acrylate and 0-10 wt.% of another copolymerizable vinyl monomer, the resin (D)/resin (C) weight ratio being from 0.5 to 200. The resin [II] may be blended with a methacrylic resin [III] formed by polymerizing 80-100 wt.% of methyl methacrylate and 0-20 wt.% of a vinyl or vinylidene monomer in such a proportion that the content of the acrylic elastomer [I] is 1-70 wt.% based on the total composition.