Elastomer composition and pressure-sensitive adhesives made by using the same

Abstract

The invention provides an elastomer composition which comprises 33.5 to 95% by weight of an aromatic vinyl-isoprene block copolymer (a) having two or more poly(aromatic vinyl) blocks, 0 to 47.5% by weight of an aromatic vinyl-isoprene diblock copolymer (b), and 5 to 33% by weight of polyisoprene (c) having a weight average molecular weight of 20,000 to 100,000, and which has a content of aromatic vinyl monomer unit of 14 to 50% by weight based on the total amount of the components (a), (b) and (c). The invention further provides a pressure-sensitive adhesive composition comprising the elastomer composition and a tackifier resin. The invention intends to provide a pressure-sensitive adhesive composition which is excellent in the tackiness at low temperatures, peel strength at ordinary temperatures and holding power at high temperatures, and which is, when applied to pressure-sensitive adhesive labels, excellent in both the pressure-sensitive adhesive properties and die-cuttability, and further intends to provide an elastomer composition for producing the pressure-sensitive adhesive composition.

What is claimed is:  
     
         1 . An elastomer composition which comprises 33.5 to 95% by weight of an aromatic vinyl-isoprene block copolymer (a) having two or more poly(aromatic vinyl) blocks, 0 to 47.5% by weight of an aromatic vinyl-isoprene diblock copolymer (b), and 5 to 33% by weight of polyisoprene (c) having a weight average molecular weight of 20,000 to 100,000, and which has a content of aromatic vinyl monomer unit of 14 to 50% by weight based on the total amount of the components (a), (b) and (c).  
     
     
         2 . The elastomer composition according to  claim 1 , wherein a weight average molecular weight of the aromatic vinyl-isoprene block copolymer (a) is 120,000 to 1,200,000.  
     
     
         3 . The elastomer composition according to  claim 1 , wherein a content of aromatic vinyl monomer unit in the aromatic vinyl-isoprene block copolymer (a) is 17 to 50% by weight.  
     
     
         4 . The elastomer composition according to  claim 1 , wherein a weight average molecular weight of the aromatic vinyl-isoprene diblock copolymer (b) is 60,000 to 250,000.  
     
     
         5 . The elastomer composition according to  claim 1 , wherein a content of aromatic vinyl monomer unit in the aromatic vinyl-isoprene diblock copolymer (b) is 16 to 55% by weight.  
     
     
         6 . The elastomer composition according to  claim 1 , wherein a content of vinyl bond in isoprene unit of the polyisoprene (c) is 20% by weight or less.  
     
     
         7 . A pressure-sensitive adhesive composition comprising an elastomer composition as defined in  claim 1  and a tackifier resin.  
     
     
         8 . The pressure-sensitive adhesive composition according to  claim 7 , wherein the tackifier resin is contained in an amount of 10 to 500 parts by weight based on 100 parts by weight of the elastomer composition.  
     
     
         9 . The pressure-sensitive adhesive composition according to  claim 7 , wherein the tackifier resin is a petroleum resin.  
     
     
         10 . The pressure-sensitive adhesive composition according to  claim 7 , which is used for producing a pressure-sensitive adhesive label.