Acrylic pressure-sensitive adhesives with acylaziridine crosslinking agents

Abstract

A pre-adhesive composition is described comprising an acid-functional (meth)acrylate copolymer and an acylaziridine crosslinking agent, which when crosslinked provides a pressure-sensitive adhesive and pressure-sensitive adhesive articles.

1 . A crosslinkable composition comprising an acid-functional (meth)acrylate copolymer and an acylaziridine crosslinking agent of the formula: 
       
         
           
           
               
               
           
         
         wherein 
         R 1  is H or CH 3 ; 
         X 1  is —O— or —NH—; 
         R 2  is a (hetero)hydrocarbyl group, 
         X 2  is —O— or —NH—; 
         x is 0 or 1; 
         each R 3  is independently —H or a C 1 -C 4  alkyl group, 
         y is 0, 1 or 2. 
       
     
     
         2 . The crosslinkable composition of  claim 1  wherein the acid-functional (meth)acrylate copolymer comprises:
 i. 85 to 99.5 parts by weight of an (meth)acrylic acid ester monomer; 
 ii. 0.5 to 15 parts by weight of an acid functional ethylenically unsaturated monomer; 
 iii. 0 to 10 parts by weight of a non-acid functional, ethylenically unsaturated polar monomer; 
 iv. 0 to 5 parts vinyl monomer; and 
 v. 0 to 5 parts of a multifunctional (meth)acrylate; 
 based on 100 parts by weight total monomer. 
 
     
     
         3 . The crosslinkable composition of  claim 1  comprising 0.005 to 5.0 parts by weight of an acylaziridine crosslinking agent, relative to 100 parts of monomers. 
     
     
         4 . The polymer composition of  claim 1  comprising 0.5 to 10 parts by weight of acid functional monomers. 
     
     
         5 . The polymer composition of  claim 1  comprising 0.5 to 5 parts by weight of a non-acid functional, ethylenically unsaturated polar monomers. 
     
     
         6 . The crosslinkable composition of  claim 1  wherein the acid functional monomer is selected from acrylic acid, methacrylic acid, itaconic acid, fumaric acid, crotonic acid, citraconic acid, maleic acid, oleic acid, β-carboxyethyl(meth)acrylate, 2-sulfoethyl methacrylate, styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, vinyl phosphonic acid, and mixtures thereof. 
     
     
         7 . The crosslinkable composition of  claim 1  comprising 90 to 95 parts by weight of units of (meth)acrylic acid ester monomers. 
     
     
         8 . The crosslinkable composition of  claim 5  wherein said non-acid functional, ethylenically unsaturated polar monomer is selected from 2-hydroxyethyl(meth)acrylate; N-vinylpyrrolidone; N-vinylcaprolactam; acrylamide; t-butyl acrylamide; dimethylamino ethyl acrylamide; N-octyl acrylamide; poly(alkoxyalkyl)(meth)acrylates; poly(vinyl methyl ether); and mixtures thereof. 
     
     
         9 . The crosslinkable composition of  claim 1  wherein said copolymer comprises 0.5 to 5 parts by weight of acrylic acid and 1 to 5 parts by weight of a non-acid functional, ethylenically unsaturated polar monomers. 
     
     
         10 . The crosslinkable composition of  claim 1  comprising 1 to 5 parts of a vinyl monomer selected from vinyl esters, styrene, substituted styrene, vinyl halide, vinyl propionate, and mixtures thereof. 
     
     
         11 . The crosslinkable composition of  claim 1  with the average number of carbon atoms of the alcohol of said (meth)acrylic acid ester monomers being from about 4 to about 12. 
     
     
         12 . The crosslinkable composition of  claim 1  wherein said alcohol of said (meth)acrylic acid ester is selected from 2-octanol, citronellol or dihydrocitronellol. 
     
     
         13 . The crosslinkable composition of  claim 1  wherein (meth)acrylic acid ester monomer component comprises a high T g  monomer, have a T g  of at least 25° C. 
     
     
         14 . The crosslinkable composition of  claim 13  wherein (meth)acrylic acid ester monomer component comprises a high T g  monomer, have a T g  of at least 50° C. 
     
     
         15 . The crosslinkable composition of  claim 13  wherein the high Tg monomer comprises up to 30 parts by weight, of the 85 to 99.5 parts by weight of (meth)acrylate ester monomer component. 
     
     
         16 . The crosslinkable composition of  claim 13  comprising:
 i. 55 to 69.5 parts by weight of an (meth)acrylic acid ester of non-tertiary alcohol; 
 ii. 1 to 30 parts by weight of an (meth)acrylic acid ester having a T g  of greater than 25° C.; 
 iii. 0.5 to 15 parts by weight of an acid functional ethylenically unsaturated monomer; 
 iv. 0 to 10 parts by weight of a non-acid functional, ethylenically unsaturated polar monomer; 
 v. 0 to 5 parts vinyl monomer; and 
 vi. 0 to 5 parts of a multifunctional (meth)acrylate; 
 based on 100 parts by weight total monomer. 
 
     
     
         17 . The crosslinkable composition of  claim 1  further comprising a chain transfer agent. 
     
     
         18 . The crosslinkable composition of  claim 1  further comprising a surfactant. 
     
     
         19 . The crosslinkable composition of  claim 1  further comprising a tackifier 
     
     
         20 . The crosslinkable composition of  claim 1  comprising an emulsion comprising:
 (a) 30 to about 70 weight percent, based on the total weight of the emulsion, of the crosslinkable composition of  claim 1 , and 
 (b)  30  to  70  weight percent of an aqueous phase comprising a surfactant, based on the total weight of the emulsion. 
 
     
     
         21 . The crosslinkable composition of  claim 1  comprising a syrup polymer composition comprising:
 a) first component solute copolymer comprising:
 i. 85 to 99.5 parts by weight of an (meth)acrylic acid ester of non-tertiary alcohol; 
 ii. 0.5 to 15 parts by weight of an acid functional monomer; 
 iii. 0 to 10 parts by weight of a non-acid functional, ethylenically unsaturated polar monomer; 
 iv. 0 to 5 parts vinyl monomer, and 
 
 b) a second component comprising at least one free-radically polymerizable solvent monomer, and 
 c) 0.005 to 5.0 parts by weight of an acylaziridine crosslinking agent of the formula: 
 
       
         
           
           
               
               
           
         
       
       wherein 
       R 1  is H or CH 3 ; 
       X 1  is —O— or —NH—; 
       R 2  is a divalent alkylene, optionally substituted by one or more catenary ester groups, urea groups and/or urethane groups, 
       X 2  is —O— or —NH—; 
       x is 0 or 1; 
       each R 3  is independently —H or a C 1 -C 4  alkyl group, and 
       y is 0, 1 or 2.