Patent ID: 7439301

Claim:
A selectively hydrogenated block copolymer having an S block and an E or E 1 block and having the general formula: S-E-S, (S-E 1 ) n , (S-E 1 ) n S, (S-E 1 ) n X or mixtures thereof, wherein: (a) prior to hydrogenation the S block is a polystyrene block; (b) prior to hydrogenation the E block is a polydiene block, selected from the group consisting of polybutadiene, polyisoprene and mixtures thereof, having a molecular weight of from 40,000 to 70,000; (c) prior to hydrogenation the E 1 block is a polydiene block, selected from the group consisting of polybutadiene, polyisoprene and mixtures thereof, having a molecular weight of from 20,000 to 35,000; (d) n has a value of 2 to 6 and X is a coupling agent residue; (e) the styrene content of the block copolymer is from 13 percent to 25 weight percent; (f) the vinyl content of the polydiene block prior to hydrogenation is from 70 to 85 mol percent; (g) the block copolymer includes less than 15 weight percent diblock having the general formula: S-E or S-E 1 wherein S, E and E 1 are as already defined; (h) subsequent to hydrogenation about 0-10% of the styrene double bonds have been hydrogenated and at least 80% of the conjugated diene double bonds have been hydrogenated; (i) the molecular weight of each of the S blocks is from 5,000 to 7,000; and (j) the melt index of the block copolymer is greater than or equal to 12 grams/10 minutes according to ASTM D1238 at 230° C. and 2.16 kg weight (k) the order-disorder temperature of the block copolymer is less than 250° C.