Patent ID: 6184307
Filing Date: 2001-02-06
Classification: C08F,C08L

Abstract:
A process for selectively hydrogenating a block copolymer having at least one butadiene polymer block and at least one isoprene polymer block with a hydrogenation catalyst that hydrogenates isoprene blocks and butadiene blocks at a different rate, comprising:a) choosing a desired polymer molecular weight and a desired level of residual unsaturation in the isoprene block(s) and in the butadiene block(s) and determining molecular weights of the butadiene block(s) and isoprene block(s) such that times required to hydrogenate the butadiene block(s) and isoprene block(s) with the hydrogenation catalyst to the desired levels of residual unsaturation are substantially the same;b) anionically polymerising butadiene and isoprene to form a block copolymer as determined in step (a), wherein the block copolymer comprises from about 40% to about 60% by weight of butadiene incorporated by 1.2-addition; andc) selectively hydrogenating the block copolymer with the hydrogenation catalyst until the butadiene block(s) and the isoprene block(s) have reached the desired levels of residual unsaturation wherein the desired level of residual unsaturation in the butadiene block is about 0.2 to 0.5 milliequivalents per gram of the block copolymer.