Modified pressure sensitive adhesive

Abstract

A modified pressure sensitive adhesive (PSA) is produced by polymerizing at least one ethylenically unsaturated monomer to form a base polymer and reacting the base polymer with a modifying polymer comprising units derived from a n-vinyl lactam to thereby produce a modified polymer. The modified polymer can be used to form modified PSAs having improved adhesion properties over PSAs formed from the unmodified base polymer.

1 - 25 . (canceled)  
     
     
         26 . A method of making a pressure sensitive adhesive comprising: forming a monomer mixture comprising an ethylenically unsaturated acid ester having a glass transition temperature of less than about 0° C. and an ethylenically unsaturated acid; emulsion polymerizing said ethylenically unsaturated acid ester and said ethylenically unsaturated acid to thereby form an acidic polymerized mixture comprising a base copolymer, wherein said base copolymer comprises about 60 to about 98 weight percent of units derived from said ethylenically unsaturated acid ester and about 0.2 to about 5 weight percent of units derived from said ethylenically unsaturated acid; after at least about 80 weight percent of said ethylenically unsaturated acid ester has been polymerized, adding polyvinyl pyrrolidone to said acidic polymerized mixture to thereby form a modified mixture comprising a modified polymer; and neutralizing said modified mixture to a pH of at least about 7.0 to thereby form a neutralized mixture:  
     
     
         27 . The method of  claim 26  wherein said ethylenically unsaturated acid ester has a glass transition temperature of less than about −20° C. in homopolymerized form.  
     
     
         28 . The method of  claim 27  wherein said ethylenically unsaturated acid ester is n-butyl acrylate and said ethylenically unsaturated acid is acrylic acid.  
     
     
         29 . The method of  claim 28  wherein said monomer mixture further comprises an ethylenically unsaturated acid ester having a glass transition temperature of at least 20° C. in homopolymerized form.  
     
     
         30 . The method of  claim 26  further comprising reacting said polyvinyl pyrrolidone with said base copolymer to thereby form said modified polymer.  
     
     
         31 . The method of  claim 30  wherein said emulsion polymerizing step includes employing a free-radical initiator to initiate polymerization.  
     
     
         32 . The method of  claim 31  wherein said reacting step includes using said free-radical initiator to facilitate ring-opening of said polyvinyl pyrrolidone.  
     
     
         33 . The method of  claim 32  wherein said free-radical initiator is an inorganic persulfate.  
     
     
         34 . The method of  claim 30  wherein said reacting step includes chemically binding said polyvinyl pyrrolidone with said base copolymer.  
     
     
         35 . The method of  claim 26  wherein said adding step includes adding about 0.2 to about 2.0 weight percent, based on the total weight of monomers in said monomer mixture, of said polyvinyl pyrrolidone to said acidic polymerized mixture.  
     
     
         36 . The method of  claim 26  wherein said adding step includes adding 0.075 to 0.5 weight percent, based on the total weight of monomers in said monomer mixture, of said polyvinyl pyrrolidone to said acidic polymerized mixture.  
     
     
         37 . The method of  claim 26  further comprising adding polyvinyl pyrrolidone to said neutralized mixture.  
     
     
         38 . A pressure sensitive adhesive composition produced by the method of  claim 26 .  
     
     
         39 . A method of making a pressure sensitive adhesive comprising: copolymerizing a main monomer and a functional monomer via emulsion polymerization to thereby form a polymeric backbone having a carboxylic functional group; and after substantial completion of said copolymerization step, reacting a polyvinyl pyrrolidone polymer with said polymeric backbone to thereby chemically bind said polyvinyl pyrrolidone polymer to said backbone at said carboxylic functional group.  
     
     
         40 . The method of  claim 39  wherein said copolymerizing and reacting steps are carried out in the presence of a free-radical initiator.  
     
     
         41 . The method of  claim 40  wherein said free-radical initiator is a peroxide.  
     
     
         42 . The method of  claim 41  wherein said free-radical initiator is ammonium persulfate.  
     
     
         43 . The method of  claim 39  wherein said reacting step includes ring-opening of said polyvinyl pyrrolidone polymer.  
     
     
         44 . The method of  claim 39  wherein said reacting step includes grafting said polyvinyl pyrrolidone polymer onto said polymeric backbone.  
     
     
         45 . The method of  claim 39  wherein said reacting step includes crosslinking said polymeric backbone with said polyvinyl pyrrolidone polymer.  
     
     
         46 . The method of  claim 39  wherein said polymeric backbone comprises about 60 to about 98 weight percent of units derived from said main monomer and about 0.2 to about 5 weight percent of units derived from said functional monomer.  
     
     
         47 . The method of  claim 46  wherein said main monomer is an ethylenically unsaturated acid ester and said functional monomer is an ethylenically unsaturated acid.  
     
     
         48 . The method of  claim 46  wherein said main monomer is a (meth)acrylate monomer having a glass transition temperature less than about 0° C. in homopolymerized form and said functional monomer is a carboxylic acid.  
     
     
         49 . The method of  claim 46  wherein said main monomer is n-butyl acrylate and said functional monomer is acrylic acid.  
     
     
         50 . The method of  claim 39  wherein said copolymerizing step includes copolymerizing a modifying monomer having a glass transition temperature of at least about 0° C. in homopolymerized form with said main monomer and said functional monomer.  
     
     
         51 . The method of  claim 50  wherein said polymeric backbone comprises about 60 to about 98 weight percent of units derived from said main monomer, about 2 to about 30 weight percent of units derived from said modifying monomer, and about 0.2 to about 5 weight percent of units derived from said functional monomer.  
     
     
         52 . The method of  claim 51  wherein said modifying monomer is a (meth)acrylate monomer having a glass transition temperature of at least 20° C.  
     
     
         53 . The method of  claim 51  wherein said main monomer is n-butyl acrylate, said functional monomer is acrylic acid, and said modifying monomer is butyl methacrylate or methyl methacrylate.  
     
     
         54 . The method of  claim 39  wherein said reacting step is performed in an acidic environment.  
     
     
         55 . A pressure sensitive adhesive composition produced by the method of  claim 39 .  
     
     
         56 . A modified polymer composition suitable for use in pressure sensitive adhesives, said modified polymer composition comprising: a polymeric backbone comprising main units derived from a main monomer having a glass transition temperature of less than about 0° C. in homopolymerized form and functional units derived from a functional monomer having a carboxylic functionality; and a modifying polymeric moiety that has been chemically bound to at least one of said functional units of said polymeric backbone, wherein prior to being chemically bound to said at least one functional unit said modifying polymeric moiety was a modifying polymer comprising units derived from a n-vinyl lactam.  
     
     
         57 . The modified polymer composition of  claim 56  wherein said n-vinyl lactam is selected from the group consisting of n-vinyl pyrrolidone, n-vinyl caprolactam, and n-vinyl piperidone.  
     
     
         58 . The modified polymer composition of  claim 56  wherein said modifying polymer is a poly(n-vinyl lactam) homopolymer.  
     
     
         59 . The modified polymer composition of  claim 56  wherein said modifying polymer comprises at least about 50 mole percent of units derived from n-vinyl pyrrolidone.  
     
     
         60 . The modified polymer composition of  claim 56  wherein said modifying polymer is a polyvinyl pyrrolidone homopolymer.  
     
     
         61 . The modified polymer composition of  claim 56  wherein said polymeric backbone and said modifying polymer were each formed in separate polymerization procedures.  
     
     
         62 . The modified polymer composition of  claim 61  wherein said polymeric backbone was formed via emulsion polymerization.  
     
     
         63 . The modified polymer composition of  claim 56  wherein said polymeric backbone comprises about 60 to about 98 weight percent of units derived from said main monomer and about 0.2 to about 5 weight percent of units derived from said functional monomer.  
     
     
         64 . The modified polymer composition of  claim 63  wherein said main monomer is n-butyl acrylate and said functional monomer is acrylic acid.  
     
     
         65 . The modified polymer composition of  claim 56  wherein said copolymerizing step includes copolymerizing a modifying monomer having a glass transition temperature of at least about 0° C. in homopolymerized form with said main monomer and said functional monomer.  
     
     
         66 . The modified polymer composition of  claim 65  wherein said polymeric backbone comprises about 60 to about 98 weight percent of units derived from said main monomer, about 2 to about 30 weight percent of units derived from said modifying monomer, and about 0.2 to about 5 weight percent of units derived from said functional monomer.  
     
     
         67 . The modified polymer composition of  claim 66  wherein said modifying monomer is a (meth)acrylate monomer having a glass transition temperature of at least 20° C.  
     
     
         68 . The modified polymer composition of  claim 66  wherein said main monomer is n-butyl acrylate, said functional monomer is acrylic acid, and said modifying monomer is butyl methacrylate or methyl methacrylate.  
     
     
         69 . The modified polymer composition of  claim 56  having a glass transition temperature of less than about −10° C.  
     
     
         70 . The modified polymer composition of  claim 69  having a glass transition temperature of −60° C. to −20° C.