Hot melt adhesive based on acrylic block copolymers

Abstract

High performance, low viscosity hot melt adhesives are obtained using acrylic block copolymers. The level of acrylic block copolymer in the adhesive formulation is less than 50% by weight.

1 . A hot melt adhesive composition comprising an acrylic block copolymer, wherein the acrylic block copolymer is present in the composition in amounts of less than about 50% by weight based on the weight of the adhesive composition.  
     
     
         2 . The adhesive of  claim 1  wherein the adhesive further comprises a tackifier and/or diluent.  
     
     
         3 . The adhesive of  claim 1  wherein the block copolymers have the formula:  
       -[A1]-[B]-[A2]-  
       wherein A1 and A2 each represents a polymer block having a glass transition temperature (Tg) of greater than about 30° C., and B represents a polymer block having a Tg of less than about 20° C.  
     
     
         4 . The adhesive of  claim 3  wherein polymer block B is present in amounts of at least about 50 weight %.  
     
     
         5 . The adhesive of  claim 3  where in A1 and A2 is methyl methacrylate and B is n-butyl acrylate.  
     
     
         6 . The adhesive of  claim 2  wherein said diluent is polypropylene glycol  
     
     
         7 . The adhesive of  claim 2  comprising from about 20 to about 35 wt % of an acrylic block copolymer, from about 35 to about 80 wt % of a tackifier, and from about 10 to about 45 wt % of a diluent, and up to about 2 wt % of an antioxidant.  
     
     
         8 . The adhesive of  claim 1  comprising a block copolymer prepared by anionic polymerization.  
     
     
         9 . An article of manufacture comprising the adhesive of  claim 1 .  
     
     
         10 . The article of  claim 9  which is an adhesive tape.  
     
     
         11 . The article of  claim 10  which is a medical tape.  
     
     
         12 . The article of  claim 11  which is a transdermal drug delivery device.