Methods For Enhancing Paper Strength

Abstract

Methods of making paper or paperboard having enhanced dry strength are provided. An enzyme and a polymer including at least one of a cationic water-soluble polymer and an amphoteric water-soluble polymer can be added to a papermaking pulp to yield a treated pulp. The treated pulp can then be formed into paper or paperboard having a dry strength greater than paper or paperboard formed from papermaking pulp without the addition of the enzyme and polymer. Any suitable enzyme can be used, for example, a laccase or a cellulase. Any suitable polymer can be used. For example, at least one of a glyoxylated polyacrylamide (gPAM), a polyvinylamine, a decarboxylated polyacrylamide, and a dimethylamine-epichlorohydrin (epi-DMA).

What is claimed is: 
     
         1 . A method of making paper or paperboard having enhanced dry strength comprising:
 adding at least one enzyme and at least one polymer comprising at least one cationic water-soluble polymer or at least one amphoteric water-soluble polymer, or both, to a papermaking pulp to yield a treated pulp; and   forming the treated pulp into paper or paperboard having a dry strength greater than paper or paperboard formed from papermaking pulp without the addition of the enzyme and polymer.   
     
     
         2 . The method of  claim 1 , wherein the dry strength is measured using a strength test that is a ring crush test (RCT) or a corrugating medium test (CMT). 
     
     
         3 . The method of  claim 1 , wherein the enzyme comprises at least one cellulose, or at least one laccase, or both. 
     
     
         4 . The method of  claim 3 , wherein the enzyme is laccase. 
     
     
         5 . The method of  claim 1 , wherein the polymer comprises a glyoxylated polyacrylamide (gPAM), a polyvinylamine, a decarboxylated polyacrylamide, or a dimethylamine-epichlorohydrin (epi-DMA), or any combination thereof. 
     
     
         6 . The method of  claim 1 , wherein the enzyme is laccase and the polymer is gPAM. 
     
     
         7 . The method of  claim 1 , wherein the enzyme and polymer are added stepwise. 
     
     
         8 . The method of  claim 1 , wherein the enzyme and the polymer are added as a composition. 
     
     
         9 . The method of  claim 8 , wherein the composition comprises from about 1.0 wt. % to about 99 wt. % enzyme and from about 99 wt. % to about 1.0 wt. % polymer, based on the total dry solids weight of the composition. 
     
     
         10 . The method of  claim 1 , wherein the enzyme and polymer are added in synergistic amounts, wherein the paper or paperboard has a dry strength greater than if either the enzyme or polymer alone were added. 
     
     
         11 . A method of making paper or paperboard having enhanced dry strength comprising:
 adding a laccase and a glyoxylated polyacrylamide to a papermaking pulp to yield a treated pulp; and   forming the treated pulp into paper or paperboard having a dry strength greater than paper or paperboard formed from papermaking pulp without the addition of the laccase and the glyoxylated polyacrylamide.