De-inking of waste paper

Abstract

In the production of pulp and paper from starch-containing paper, the deinking effect can be improved by including treatment with both a starch-degrading enzyme and a pectate lyase. The process comprises enzyme treatment during or after disintegration of the paper to produce pulp, followed by separation of ink particles.

1 . A process for producing a papermaking pulp from starch-containing printed paper, comprising: 
 a) disintegrating the paper to produce a pulp,    b) treating with a starch-degrading enzyme and a pectate lyase during or after step a), and    c) separating ink particles from the pulp after steps a) and b).    
     
     
         2 . The process according to  claim 1  wherein the starch-degrading enzyme is an alkaline stable enzyme.  
     
     
         3 . The process according to  claim 1  wherein the starch-degrading enzyme is an Δ-amylase.  
     
     
         4 . The process according to  claim 1  wherein the starch-degrading enzyme is derived from a strain of Bacillus.  
     
     
         5 . The process according to  claim 4  wherein the starch-degrading enzyme is derived from  B. amyloliquefaciens, B. licheniformis  or  B. stearothermophilus.    
     
     
         6 . The process according to any of  claims 1  to  4  wherein the enzymatic treatment is performed with an amount of starch-degrading enzyme in the range 0.01-10 KNU/g of dry matter.  
     
     
         7 . The process according to  claim 1  wherein the pectate lyase is derived from or produced by a strain of Bacillus.  
     
     
         8 . The process according to  claim 7  wherein the pectate lyase is derived from or produced by  B. licheniformis.    
     
     
         9 . The process according to any of claims  1 ,  6  and  7  wherein the enzymatic treatment is performed with an amount of pectate lyase in the range 0.01-10 APSU/g of dry matter.  
     
     
         10 . The process according to  claim 1  wherein the enzymatic treatment is performed at a pH in the range 6-10.  
     
     
         11 . The process according to  claim 10  wherein the enzymatic treatment is performed at a pH in the range 8-10.  
     
     
         12 . The process according to  claim 1  wherein the starch-containing paper is mixed office waste.  
     
     
         13 . The process of  claim 1  wherein the enzyme treatment is performed simultaneously with the disintegration.  
     
     
         14 . The process according to  claim 13  wherein the enzyme treatment and disintegration are performed in the presence of a surfactant.  
     
     
         15 . The process according to claim  13 - 14  wherein the enzyme treatment is continued after the disintegration.  
     
     
         16 . The process according to any of claims  1  and  13 - 15  wherein said c) comprises the following sequential steps after the disintegration and the enzyme treatment: 
 separation of ink particles,  
 bleaching, and  
 separation of ink particles.  
 
     
     
         17 . The process according to  claim 1  wherein the enzyme treatment is performed after the disintegration.  
     
     
         18 . The process of any of the preceding claims wherein the enzyme treatment is performed simultaneously with bleaching.  
     
     
         19 . The process according to  claim 18  wherein the enzyme treatment and bleaching are performed in the presence of hydrogen peroxide and a surfactant.  
     
     
         20 . A process for making new paper or tissue from starch-containing printed paper, comprising producing papermaking pulp by the process of any preceding claim, and making new paper or tissue from the pulp.