Patent ID: 7393898

Claim:
A block copolymer composition which is a block copolymer composition comprising, as monomer units, from 55 to 95 mass % of a vinyl aromatic hydrocarbon and from 5 to 45 mass % of a conjugated diene, which composition contains the following components A and B in a blend ratio within a range of component A/component B=20 to 80/80 to 20 (mass ratio): Component A is a block copolymer (1) which comprises, as monomer units, from 55 to 95 mass % of a vinyl aromatic hydrocarbon and from 5 to 45 mass % of a conjugated diene, (2) which is constituted by a hard segment block made mainly of the vinyl aromatic hydrocarbon and a soft segment block made mainly of the conjugated diene, (3) wherein the hard segment block comprises blocks S 1 and S 2 made mainly of a vinyl aromatic hydrocarbon having two types of different molecular weights, and when the number average molecular weights of S 1 and S 2 are represented by M 1 and M 2 , respectively, M 1 is within a range of from 75,000 to 170,000 and M 2 is within a range of from 14,000 to 30,000, and their ratio M 1 /M 2 is within a range of from 4 to 9, and the ratio of S 1 to S 2 is within a range of S 1 /S 2 =6 to 35/65 to 94 (molar ratio), and (4) which is produced by a coupling reaction; and component B is a block copolymer (1) which comprises, as monomer units, from 55 to 95 mass % of a vinyl aromatic hydrocarbon and from 5 to 45 mass % of a conjugated diene, (2) which is constituted by a hard segment block made mainly of the vinyl aromatic hydrocarbon and a soft segment block made mainly of the conjugated diene, (3) wherein the hard segment block comprises blocks S 3 and S 4 made mainly of a vinyl aromatic hydrocarbon having two types of different molecular weights, and when the number average molecular weights of S 3 and S 4 are represented by M 3 and M 4 , respectively, M 3 is within a range of from 80,000 to 160,000 and M 4 is within a range of from 4,000 to 12,000 and their ratio M 3 /M 4 is within a range of from 13 to 22, and the ratio of S 3 to S 4 is within a range of S 3 /S 4 =5 to 30/70 to 95 (molar ratio), and (4) which is produced by a coupling reaction.