Japan Elastomer Co., Ltd.

Toda Keiichi

Nakamichi Yukinori

A block copolymer composition for modifying asphalt, which comprises a mixture of: (A) a block copolymer comprising: at least two polymer blocks each mainly comprising a monoalkenyl aromatic compound; and at least one polymer block mainly comprising a conjugated diene compound; and (B) a block copolymer comprising: at least one polymer block mainly comprising a monoalkenyl aromatic compound; and at least one copolymer block mainly comprising a conjugated diene compound, and having a molecular weight equivalent to 1/3 to 2/3 of the molecular weight of block copolymer (A), wherein (a) the total bonding alkenyl aromatic compound content in the mixture of block copolymers (A) and (B) is from 10 to 50% by weight, wherein (b) the vinyl bond content in the conjugated diene polymer blocks is not greater than 70% by weight, and wherein the block copolymer composition has: (c) a content of (A) component is from 98 to 20% by weight and a content of (B) component is from 2 to 80% by weight; (d) a melt index value of from 0.3 to 15.0 g/10 min; (e) a bulk density of from 0.1 to 0.7; (f) a particle size distribution such that the content of constituents remaining on a 5-mesh sieve is not greater than 30% by weight and the content of constituents passing through a 20-mesh sieve is not greater than 30% by weight; and (g) a total pore volume of from 100 to 2,000 mm.sup.3 /g.

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Ooita, Japan

Toda Keiichi