Process for improving water-whitening resistance of pressure sensitive adhesives

Abstract

Pressure sensitive adhesive compositions having enhanced resistance to water-whitening comprising an aqueous emulsion polymer are disclosed. The polymer comprises the polymerization reaction product of a polymerizable aqueous emulsion comprising: (i) a hydrophobic monomer mixture of at least one alkyl acrylate or alkyl methacrylate ester of an alcohol wherein the alkyl portion of the alcohol is linear or branched and contains at least 4 carbon atoms, and at least one styrenic monomer, wherein the styrenic monomer is up to about 30 wt. % of the total hydrophobic monomer mixture, (ii) at least about 1 wt. % of at least one hydrophilic monomer, (iii) at least about 5 wt. % of at least one partially hydrophilic monomer selected from alkyl acrylate or alkyl methacrylate esters of an alcohol wherein the alkyl portion of the alcohol has 1 to 2 carbon atoms, N-vinyl-2-pyrrolidone, or mixtures thererof, and (iv) a water-soluble or water-dispersible polymerizable surfactant selected from compounds having a terminal allyl amine moiety, polyoxyalkylene-1-(allyloxymethyl)alkyl ether sulfate salts, or mixtures thereof, and the average particle size of the polymer is less than or equal to 200 nm. Also disclosed are processes for preparing same.

1 - 39 . (canceled)  
     
     
         40 . Original) A pressure sensitive adhesive composition having enhanced resistance to water-whitening comprising an aqueous emulsion polymer, said polymer comprising the polymerization reaction product of a polymerizable aqueous emulsion comprising: (i) a hydrophobic monomer mixture of at least one alkyl acrylate or alkyl methacrylate ester of an alcohol wherein the alkyl portion of the alcohol is linear or branched and contains at least 4 carbon atoms, and at least one styrenic monomer, wherein the styrenic monomer is up to about 30 wt. % of the total hydrophobic monomer mixture, (ii) at least about 1 wt. % of at least one hydrophilic monomer, (iii) at least about 5 wt. % of at least one partially hydrophilic monomer selected from alkyl acrylate or alkyl methacrylate esters of an alcohol wherein the alkyl portion of the alcohol has 1 to 2 carbon atoms, N-vinyl-2-pyrrolidone, or mixtures thererof, and (iv) a water-soluble or water-dispersible polymerizable surfactant selected from compounds having a terminal allyl amine moiety, polyoxyalkylene-1-(allyloxymethyl)alkyl ether sulfate salts, or mixtures thereof, wherein the wt. % of monomers (i), (ii) and (iii) are based on the total weight of monomers (i), (ii) and (iii) in said emulsion; 
 wherein after said polymerization the pH of said polymer is adjusted to a pH of about 6.5 to about 9, and the average particle size of said polymer is less than or equal to 200 nm.    
     
     
         41 . The composition of  claim 40  wherein the amount of monomer (i) in said emulsion is about 70 to about 90 wt. %.  
     
     
         42 . The composition of  claim 41  wherein the amount of monomer (i) in said emulsion is about 75 to about 85 wt. %.  
     
     
         43 . The composition of  claim 40  wherein the amount of monomer (ii) in said emulsion is about 3 to about 10 wt. %.  
     
     
         44 . The composition of  claim 43  wherein the amount of monomer (ii) in said emulsion is about 4 to about 8 wt. %.  
     
     
         45 . The composition of  claim 40  wherein the amount of monomer (iii) in said emulsion is about 5 to about 20 wt. %.  
     
     
         46 . The composition of  claim 45  wherein the amount of monomer (iii) in said emulsion is about 5 to about 18 wt. %.  
     
     
         47 . The composition of  claim 40  wherein said pressure sensitive adhesive has an average particle size of less than or equal to 100 nm.  
     
     
         48 . The composition of  claim 40  wherein said monomer (i) is at least one hydrophobic alkyl acrylate or alkyl methacrylate ester of an alcohol wherein the alkyl portion contains at least 4 carbon atoms.  
     
     
         49 . The composition of  claim 48  wherein said monomer (i) is selected from isooctyl acrylate, 4-methyl-2-pentyl acrylate, 2-methylbutyl acrylate, isoamyl acrylate, sec-butyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, isodecyl methacrylate, isononyl acrylate, isodecyl acrylate, or mixtures thereof.  
     
     
         50 . The composition of  claim 49  wherein said monomer (i) is selected from n-butyl acrylate, 2-ethylhexyl acrylate, or mixtures thereof.  
     
     
         51 . The composition of  claim 40  wherein said monomer (ii) is selected from a monoolefinic monocarboxylic acid, a monoolefinic dicarboxylic acid, or mixtures thereof.  
     
     
         52 . The composition of  claim 51  wherein said monomer (ii) is selected from acrylic acid, methacrylic acid, fumaric acid, maleic acid, itaconic acid, crotonic acid, or mixtures thereof.  
     
     
         53 . The composition of  claim 52  wherein said monomer (ii) is selected from acrylic acid, methacrylic acid, or mixtures thereof.  
     
     
         54 . The composition of  claim 40  wherein said monomer (iii) is selected from methyl acrylate, methyl methacrylate, ethyl acrylate, or mixtures thereof.  
     
     
         55 . The composition of  claim 54  wherein said monomer (iii) is selected from methyl acrylate, methyl methacrylate, or mixtures thereof.  
     
     
         56 . The composition of  claim 40  wherein the total amount of water-soluble or water-dispersible polymerizable surfactant present during the polymerization is about 0.1 to about 5 wt. % of the total weight of monomers (i), (ii) and (iii) in said emulsion.  
     
     
         57 . The composition of  claim 56  wherein the total amount of water-soluble or water-dispersible polymerizable surfactant present during the polymerization is about 0.5 to about 2 wt. % of the total weight of monomers (i), (ii) and (iii) in said emulsion.  
     
     
         58 . The composition of  claim 56  wherein the amount of water-soluble or water-dispersible polymerizable surfactant added with said monomers (i), (ii) and (iii) is less than about 80 wt. % of the total amount of water-soluble or water-dispersible polymerizable surfactant present during the polymerization.  
     
     
         59 . The composition of  claim 40  wherein said polymerizable surfactant has a hydrophilic portion selected from a sulfonate allyl amine moiety, a sulfate allyl amine moiety, or a phosphate allyl amine moiety, and a hydrophobic portion selected from —R, or a group having the formula RO—(CH 2 CH 2 O) n —; wherein R is an alkyl group or an alkyl-substituted phenyl group wherein the alkyl group has 1 to 20 carbon atoms, and n is an integer from 2 to 100.  
     
     
         60 . The composition of  claim 59  wherein n is an integer from 2 to 15.  
     
     
         61 . The composition of  claim 40  wherein said polymerizable surfactant is an allyl amine salt of an alkyl benzene sulfonate having the formula  
       
         
           
           
               
               
           
         
         wherein R 1  is an alkyl group having 1 to 20 carbon atoms, and X +  is selected from  + NH 3 ,  + NH 2 R 4 , or  + NHR 4 R 5 , wherein R 4  and R 5  are independently selected from C 1 -C 4  alkyl or hydroxyalkyl groups.  
       
     
     
         62 . The composition of  claim 61  wherein said polymerizable surfactant is an allyl amine salt of dodecylbenzene sulfonate.  
     
     
         63 . The composition of  claim 40  wherein said polymerizable surfactant is an allyl amine salt of an alkyl ether sulfate having the formula  
       
         
           
           
               
               
           
         
         wherein R 2  is an alkyl group having 1 to 20 carbon atoms, n is an integer from 2 to 100, and X +  is selected from  + NH 3 ,  + NH 2 R 4 , or  + NHR 4 R 5 , wherein R 4  and R 5  are independently selected from C 1 -C 4  alkyl or hydroxyalkyl groups.  
       
     
     
         64 . The composition of  claim 63  wherein n is an integer from 2 to 15.  
     
     
         65 . The composition of  claim 64  wherein said polymerizable surfactant is an allyl amine salt of laureth sulfate.  
     
     
         66 . The composition of  claim 40  wherein said polymerizable surfactant is an allyl amine salt of a phosphate ester having the formula  
       
         
           
           
               
               
           
         
         wherein R 3  is an alkyl or alkyl-substituted phenyl group wherein the alkyl group has 1 to 20 carbon atoms, n is an integer from 2 to 100, and X +  is selected from  + NH 3 ,  + NH 2 R 4 , or  + NHR 4 R 5 , wherein R 4  and R 5  are independently selected from C 1 -C 4  alkyl or hydroxyalkyl groups.  
       
     
     
         67 . The composition of  claim 66  wherein n is an integer from 2 to 15.  
     
     
         68 . The composition of  claim 67  wherein said polymerizable surfactant is an allyl amine salt of nonylphenol ethoxylate (9 moles EO) phosphate ester.  
     
     
         69 . The composition of  claim 40  wherein said polymerizable surfactant is an allyl amine salt of a sulfate having the formula  
         R 6 —SO 3   −   + X—CH 2 —CH═CH 2    wherein R 6  is an alkyl group having 6 to 20 carbon atoms, and X +  is selected from  + NH 3 ,  + NH 2 R 4 , or  + NHR 5 , wherein R 4  and R 5  are independently selected from C 1 -C 4  alkyl or hydroxyalkyl groups.    
     
     
         70 . The composition of  claim 69  wherein R 6  is an alkyl group having 10 to 18 carbon atoms.  
     
     
         71 - 72 . (canceled)  
     
     
         73 . The composition of  claim 40  wherein the total amount of said polymerization initiator added is about 0.01 to about 0.5 wt. % of the total weight of monomers (i), (ii) and (iii) in said emulsion.  
     
     
         74 . The composition of  claim 40  wherein the polymerization reaction product further comprises a vinyl ester of a C 2  to C 12  carboxylic acid that is added to said polymerization reaction product after the conversion of monomers (i), (ii) and (iii) is greater than 90%.  
     
     
         75 . The composition of  claim 74  wherein the polymerization reaction product further comprises a vinyl ester of a C 2  to C 12  carboxylic acid that is added to said polymerization reaction product after the conversion of monomers (i), (ii) and (iii) is greater than 95%.  
     
     
         76 - 117 . (canceled)