ASPHALT COMPOSITION CONTAINING STYRENE-BUTADIENE-STYRENE BLOCK COPOLYMERS HAVING UNSYMMETRIC POLYSTYRENE BLOCK

摘要

Provided is an asphalt composition comprising a styrene-butadiene-styrene block copolymer formed of asymmetric styrene blocks, which has significantly improved elongation property at low temperature, and thus is useful for road pavement materials, waterproofing sheets and modified asphalt for a sealant. The modified asphalt composition comprises: 100 parts by weight of pure asphalt and 0.5-40 parts by weight of an asymmetric triblock copolymer having a number average molecular weight of 20,000-1,000,000 and represented by the formula of A-B-A'. In the above formula, A is an aromatic vinyl monomer and represents a polymer block having a number average molecular weight of 8,000-30,000; B is a polymer block comprising conjugated diene monomers or a conjugated diene-based block copolymer containing a small amount of an aromatic vinyl monomer; and A' is a polymer block comprising an aromatic vinyl monomer and having a number average molecular weight of 500-5,000, wherein the blocks A and A' is present in an amount of 5-40 wt% based on the total weight of the A-B-A' block copolymer and shows a block ratio of 50-98%.