Process for Enhancing Dry Strength of Paper by Treatment with Vinylamine-Containing Polymers and Acrylamide-Containing Polymers

Abstract

A process is disclosed for the production of paper with enhanced dry strength comprising adding to the wet end of a paper machine, (a) a vinylamine-containing aqueous solution polymer having a molecular weight of from 75,000 daltons to 750,000 daltons and (b) an amphoteric or cationic acrylamide-containing aqueous solution polymer having a molecular weight of from 75,000 daltons to 1,500,000 daltons, wherein the sum of the anionic and cationic monomers comprises at least 5% on a molar basis of the composition of the acrylamide-containing polymer.

1 . A process for the production of paper, board, and cardboard with enhanced dry strength comprising adding to the wet end of a paper machine (a) a vinylamine-containing aqueous solution polymer having a molecular weight of from 75,000 daltons to 750,000 daltons and (b) an amphoteric or cationic acrylamide-containing aqueous solution polymer having a molecular weight of from 75,000 daltons to 1,500,000 daltons, wherein the sum of the anionic and cationic monomers comprises at least 5% on a molar basis of the composition of the acrylamide-containing monomer. 
     
     
         2 . The process according to  claim 1  wherein the active polymer content of the vinylamine containing aqueous solution polymer is from 5% to 30% on a dry weight basis and wherein the vinylamine-containing polymer has an N-vinylformamide content of at least 50% on a molar basis of the total monomer charged prior to hydrolysis, and at least 10% of the N-vinylformamide has been hydrolyzed in the final polymer. 
     
     
         3 . The process according to  claim 1  wherein the vinylamine-containing polymer has a molecular weight of from 150,000 daltons to 500,000 daltons. 
     
     
         4 . The process according to  claim 1  wherein the acrylamide-containing aqueous solution polymer contains a sum cationic and/or amphoteric monomer charge of from 5% to 50% on a molar basis, and has an active polymer content of from 5% to 50% on a weight basis. 
     
     
         5 . The process according to  claim 1  wherein the acrylamide-containing aqueous solution polymer is cationic and has a molecular weight of from 75,000 daltons to 750,000 daltons. 
     
     
         6 . The process according to  claim 1  wherein the acrylamide-containing aqueous solution polymer is an aqueous dispersion polymer. 
     
     
         7 . The process according to  claim 6  wherein the acrylamide-containing aqueous solution polymer is an aqueous dispersion polymer having a molecular weight of from 300,000 daltons to 1,500,000 daltons. 
     
     
         8 . The process according to  claim 6  wherein the acrylamide-containing aqueous solution polymer is an aqueous dispersion polymer having a molecular weight of from 400,000 daltons to less than 1,250,000 daltons. 
     
     
         9 . The process according to  claim 1 , wherein the acrylamide-containing aqueous solution polymer contains a cationic monomer charge of from 5% to 50% on a molar basis, has an active polymer content of from 5% to 50% on a weight basis, and comprises a least one cationic monomer selected from the group consisting of: diallyldimethylammonium chloride (DADMAC), 2-(dimethylamino)ethyl acrylate, 2-(dimethylamino)ethyl methacrylate, 2-(diethylaminoethyl) acrylate, 2-(diethylamino)ethyl methacrylate, 3-(dimethylamino)propyl acrylate, 3-(dimethylamino)propyl methacrylate, 3-(diethylamino)propyl acrylate, 3-(diethylamino)propyl methacrylate, N-[3-(dimethylamino)propyl]acrylamide, N-[3-(dimethylamino)propyl]methacrylamide, N-[3-(diethylamino)propyl]acrylamide, N-[3-(diethylamino)propyl]methacrylamide, [2-(acryloyloxy)ethyl]trimethylammonium chloride, [2-(methacryloyloxy)ethyl]trimethylammonium chloride, [3-(acryloyloxy)propyl]trimethylammonium chloride, [3-(methacryloyloxy)propyl]trimethylammonium chloride, 3-(acrylamidopropyl)trimethylammonium chloride, and 3-(methacrylamidopropyl)trimethylammonium chloride. 
     
     
         10 . The process according to  claim 4 , wherein the acrylamide-containing aqueous solution polymer has an overall amphoteric charge. 
     
     
         11 . The process according to  claim 10  wherein the acrylamide-containing aqueous solution polymer is amphoteric and has a molecular weight of from 75,000 daltons to 750,000 daltons. 
     
     
         12 . The process according to  claim 10 , wherein the amphoteric acrylamide-containing aqueous solution is comprised of a polyelectrolyte complex consisting of an acrylamide-containing aqueous solution polymer and a cofactor carrying a complementary charge. 
     
     
         13 . The process according to  claim 12 , wherein the amphoteric acrylamide-containing aqueous solution is comprised of a polyelectrolyte complex having a molecular weight of from 100,000 daltons to less than 1,000,000 daltons. 
     
     
         14 . The process according to  claim 1 , wherein the vinylamine-containing polymer and the acrylamide-containing polymer are added to the papermachine as a single product blend. 
     
     
         15 . The process according to  claim 14 , wherein the cationic portion of the acrylamide-containing polymer is generated by at least one monomer selected from the group consisting of diallyldimethylammonium chloride (DADMAC), N-[3-(dimethylamino)propyl]acrylamide, N-[3-(dimethylamino)propyl]methacrylamide, N-[3-(diethylamino)propyl]acrylamide, N-[3-(diethylamino)propyl]methacrylamide, 3-(acrylamidopropyl)trimethylammonium chloride, and 3-(methacrylamidopropyl)trimethylammonium chloride. 
     
     
         16 . The process according to  claim 15 , wherein the cationic portion of the acrylamide-containing polymer is generated by at least one monomer selected from the group consisting of diallyldimethylammonium chloride (DADMAC), N-[3-(dimethylamino)propyl]acrylamide, N-[3-(dimethylamino)propyl]methacrylamide, 3-(acrylamidopropyl)trimethylammonium chloride, and 3-(methacrylamidopropyl)trimethylammonium chloride. 
     
     
         17 . The process according to  claim 1 , wherein the vinylamine-containing polymer and the acrylamide-containing polymer are added to the wet end of a paper machine in a ratio of vinylamine-containing polymer to acrylamide-containing polymer of from 10:1 to 1:50 up to a sum total of 1.25% on a weight basis of the dry pulp, based on the active polymer solids of the polymeric products. 
     
     
         18 . A paper product produced by the process of  claim 1 .