Patent ID: 7557160

Claim:
An impact-resistant vinyl aromatic hydrocarbon resin, the hydrocarbon resin being produced by radical polymerization of 75 to 98 parts by mass of a vinyl aromatic hydrocarbon monomer (A-1) or a mixture of a vinyl aromatic hydrocarbon monomer and a monomer copolymerizable therewith (A-2) and 2 to 25 parts by mass of a modified block copolymer (B), wherein the total amount of the vinyl aromatic hydrocarbon monomer (A-1) or the mixture (A-2) and the modified block copolymer (B) is 100 parts by mass, the modified block copolymer (B) comprises: (B-1) a base block copolymer comprising conjugated diene monomer units and vinyl aromatic hydrocarbon monomer units, the base block copolymer containing at least one polymer block of vinyl aromatic hydrocarbon monomer units (H); (B-2) at least one primary modifier group comprising at least one functional group, bonded to the base block copolymer; and the modified block copolymer (B) has the following characteristics: (i) the content of the vinyl aromatic hydrocarbon monomer units is 12 to 50 mass % based on the mass of the modified block copolymer (B); (ii) the content of the at least one polymer block (H) is 12 to 45 mass % based on the mass of the modified block copolymer (B); and (iii) the polymer block ratio defined as the mass % of the at least one polymer block of vinyl aromatic hydrocarbon monomer units (H) based on the total mass of vinyl aromatic hydrocarbon monomer units contained in the modified block copolymer (B) is more than 50 mass %.