Method for improving papermaking or board making process, use of a polysaccharide and paper

Abstract

The invention relates to a method for improving papermaking or board making process. The method comprises forming a fibre stock, and leading the fibre stock to a headbox and feeding it to a wire to form a wet fibrous web. A at least one polysaccharide having 1,4-β-anomeric configuration in linkages between saccharide units of the polysaccharide backbone or the main polysaccharide backbone is applied to the fibre stock after machine chest or on the wet fibrous web. The invention relates also to paper made by the method and to the use of polysaccharide.

1 . Method for improving papermaking or board making process, comprising
 forming a fibre stock,   leading the fibre stock to a headbox and feeding it to a wire to form a wet fibrous web, characterised in applying at least one polysaccharide having 1,4-β-anomeric configuration in linkages between saccharide units of the polysaccharide backbone or the main polysaccharide backbone to the fibre stock after machine chest or on the wet fibrous web.   
     
     
         2 . Method according to  claim 1 , characterised in selecting the polysaccharide from a group comprising water soluble cellulose derivatives; galactomannans, such as guar gum or locust bean gum; galactoglucomannans; carboxymethyl cellulose; xylan and substituted glucans, such as xyloglucans; other suitable hydrocolloids, such as tamarind gum; chitosan; chitin; or their derivatives. 
     
     
         3 . Method according to  claim 1 , characterised in applying the polysaccharide as a solution. 
     
     
         4 . Method according to  claim 1 , characterised in that the concentration of the polysaccharide in the polysaccharide solution is <60 weight-%, more typically 0.02-5 weight-%, preferably 0.05-3 weight-%, more preferably 0.05-2 weight-%. 
     
     
         5 . Method according to  claim 1 , characterised in applying a mixture of different polysaccharides to the fibre stock after machine chest or on the wet fibrous web. 
     
     
         6 . Method according to  claim 1 , characterised in that the at least one polysaccharide having 1,4-β-anomeric configuration in linkages between saccharide units of the polysaccharide backbone or the main polysaccharide backbone is guar gum. 
     
     
         7 . Method according to  claim 1 , characterised in that the at least one polysaccharide having 1,4-β-anomeric configuration in the linkages between saccharide units of the polysaccharide backbone or the main polysaccharide backbone is a polysaccharide with high degree of polymerisation (DP). 
     
     
         8 . Method according to  claim 1 , characterised in applying the polysaccharide in amount ≦0.1-10 kg/(ton paper), preferably 0.3-3 kg/(ton paper). 
     
     
         9 . Method according to  claim 1 , characterised in applying the polysaccharide to the fibre stock between the last pump preceding the paper machine headbox and the outlet of the paper machine headbox. 
     
     
         10 . Method according to  claim 9 , characterised in applying the polysaccharide into the fibre stock together with a retention or drainage agent. 
     
     
         11 . Method according to  claim 10 , characterised in selecting the retention agent from a group comprising anionic or cationic polyacrylamide, polyvinylamine, polyethyleneimine, cationic starch, bentonite or silica, especially from anionic or cationic polyacrylamide, polyvinylamine or polyethyleneimine. 
     
     
         12 . Method according to  claim 10 , characterised in adding the polysaccharide and the retention agent as single solution. 
     
     
         13 . Method according to  claim 1 , characterised in applying the polysaccharide on the wet fibre web between the headbox and the last nip of the press section. 
     
     
         14 . Method according to  claim 13 , characterised in applying the polysaccharide on the fibre web by spraying, by coating, by film transfer or by foam layer application. 
     
     
         15 . Method according to  claim 14 , characterised in applying the polysaccharide by spraying as a solution with a concentration in the range of 0.2-20 weight-%, preferably 0.3-3 weight-%. 
     
     
         16 . Method according to  claim 14 , characterised in applying the polysaccharide by spraying in amount ≦2 g/m 2 , most typically 0.05-1.5 g/m 2 , preferably 0.05-0.5 g/m 2 , on the wet paper web. 
     
     
         17 . Method according to  claim 14 , characterised in applying the polysaccharide by foam coating, whereby the polysaccharide is applied as a foam having an air content of 60-95%. 
     
     
         18 . Method according to  claim 14 , characterised in applying the polysaccharide solution on the wet paper web when the dryness of the web is <50%, preferably 8-15%. 
     
     
         19 . Paper or board produced by using method according to  claim 18 . 
     
     
         20 . Use of a polysaccharide which has 1,4-β-anomeric configuration in linkages between saccharide units of the polysaccharide backbone or the main polysaccharide backbone for increasing filler content of the paper or board, for reducing basis weight, and/or improving runnability of a wet paper or board web. 
     
     
         21 . Use according to  claim 20 , characterised in that the filler, content of which is increased, is clay, calcium carbonate, calcium sulphate, titanium dioxide or talc, or their mixtures. 
     
     
         22 . Use according to  claim 20 , characterised in improving runnability of a wet paper or board web by improving strength of the wet paper or board web when producing wood-free uncoated paper, wood-free coated paper, super calendered (SC) paper, ultralight weight coated (ULWC) paper, light weight coated (LWC) paper or newsprint paper. 
     
     
         23 . Use according to  claim 20 , characterised in increasing filler content of the paper or board, whereby the ash content in the wet paper or board web is
 >25% for wood-free uncoated paper,   >25% for wood-free coated paper base paper,   >34% for super calendered (SC) paper,   >13% for coated mechanical base paper,   >15% for newsprint paper, fluting board or testliner board,   the ash content being measured by burning the stock sample in 525° C.