Acrylic polymer having multilayer structure and methacrylic resin composition containing the same

A multilayered acrylic polymer comprising:

• an innermost layer polymer (A) obtained by polymerizing a mixture composed of 100 parts by weight of a monomer or monomer mixture comprising
• 40 to 100% by weight of an alkyl methacrylate having an alkyl group of 1 to 4 carbon atoms,
• 0 to 60% by weight of an alkyl acrylate having an alkyl group of 1 to 8 carbon atoms, and
• 0 to 20% by weight of another copolymerizable monomer,
• and 0.1 to 10 parts by weight of a multifunctional monomer;
• an intermediate layer polymer (B) obtained by polymerizing a mixture composed of 100 parts by weight of a monomer mixture comprising
• 70 to 90% by weight of an alkyl acrylate having an alkyl group of 1 to 8 carbon atoms, 10 to 30% by weight of an aromatic vinyl monomer, and
• 0 to 20% by weight of another copolymerizable monomer,
• and 0.1 to 5 parts by weight of a multifunctional monomer, in the presence of the innermost layer polymer (A);
• and
• an outermost layer polymer (C) obtained by polymerizing a monomer or monomer mixture comprising 50 to 100% by weight of an alkyl methacrylate having an alkyl group of 1 to 4 carbon atoms, 0 to 50% by weight of an alkyl acrylate having an alkyl group of 1 to 8 carbon atoms, and 0 to 20% by weight of another copolymerizable monomer, in the presence of the innermost layer polymer (A) and the intermediate layer polymer (B);
• and wherein the average value of the coating ratio as defined by the following equation is not less than 30%:
• Coating ratio={(minimum thickness of the intermediate layer)÷(maximum thickness of the intermediate layer)}×100 (%).