Styrene-isoprene-styrene block copolymer composition and adhesives made therefrom

Abstract

A linear styrene-isoprene-styrene block copolymer composition comprised of linear polymeric blocks wherein the block copolymer composition has a coupling efficiency of 25 to 82 percent, a polystyrene content of from 19 to 27 percent by weight, a polystyrene block molecular weight (peak polystyrene equivalent molecular weight as determined by gel permeation chromatography) of 12,000 to 18,000, and an overall molecular weight (peak polystyrene equivalent molecular weight as determined by gel permeation chromatography) of from 170,000 to 280,000. The invention also contemplates adhesive formulations comprising these block copolymer compositions and a tackifying resin.

We claim: 
     
       1. A linear styrene-isoprene-styrene block copolymer composition comprised of linear polymeric blocks, said block polymer composition characterized in that it has a coupling efficiency from 25 to 82%, a polystyrene content of from 19 to 17% by weight, a polystyrene block molecular weight of from 12,000 to 18,000 and an overall molecular weight of from 170,000 to 280,000, both molecular weights being peak polystyrene equivalent molecular weights as determined by gel permeation chromatography. 
     
     
       2. A hot melt adhesive comprising the block copolymer composition of claim 1 and a tackifying resin. 
     
     
       3. The block copolymer composition of claim 1 wherein the polystyrene content ranges from 19 to 26% by weight, the polystyrene block molecular weight ranges from 12,000 to 17,000 and the overall molecular weight ranges from 170,000 to 240,000, both molecular weights being peak polystyrene equivalent molecular weights as determined by gel permeation chromatography. 
     
     
       4. A hot melt adhesive comprising the block copolymer composition of claim 3 and a tackifying resin.