Filler for papermaking process

Abstract

The present invention relates to a filler comprising calcium salt and cellulose derivative having a degree of substitution of net ionic groups up to about 0.65, wherein the filler is substantially free from fibres or fibrils of cellulose or lignocellulose. The invention also relates to a filler comprising calcium salt and a cellulose derivative having a degree of substitution of net ionic groups up to about 0.65, wherein the cellulose derivative contains cationic groups.

1 . A filler comprising calcium salt and water-soluble cellulose derivative having a degree of substitution of net anionic groups up to about 0.65, wherein the filler is substantially free from fibers or fibrils of cellulose or lignocellulose, wherein at least about 30 by weight of the cellulose derivative is absorbed on or attached to the calcium salt. 
     
     
         2 . The filler according to  claim 1 , wherein the degree of substitution is at least about 0.15. 
     
     
         3 . The filler according to  claim 1 , wherein the degree of substitution is up to about 0.60. 
     
     
         4 . The filler according to  claim 1 , wherein the degree of substitution is up to about 0.50. 
     
     
         5 . The filler according to  claim 1 , wherein the cellulose derivative contains carboxymethyl groups. 
     
     
         6 . The filler according to  claim 1 , wherein the cellulose derivative contains quaternary ammonium groups. 
     
     
         7 . The filler according to  claim 1 , wherein the cellulose derivative is anionic. 
     
     
         8 . The filler according to  claim 1 , wherein the cellulose derivative is amphoteric. 
     
     
         9 . The filler according to  claim 1 , wherein the calcium salt is calcium carbonate. 
     
     
         10 . The filler according to  claim 1 , wherein the calcium salt is precipitated calcium carbonate. 
     
     
         11 . The filler according to  claim 1 , wherein the calcium salt is ground calcium carbonate. 
     
     
         12 . The filler according to  claim 1 , wherein at least about 45% by weight of the cellulose derivative is absorbed on or attached to the calcium salt. 
     
     
         13 . The filler according to  claim 1 , wherein at least about 60% by weight of the cellulose derivative is absorbed on or attached to the calcium salt. 
     
     
         14 . The filler according to  claim 14 , wherein at least about 30% by weight of the cellulose derivative is absorbed on or attached to the calcium salt. 
     
     
         15 . A filler comprising a calcium salt which is precipitated calcium carbonate and a water-soluble cellulose derivative which is carboxymethyl cellulose having a degree of substitution of carboxymethyl groups up to about 0.65. 
     
     
         16 . The filler according to  claim 15 , wherein the degree of substitution is at least 0.15. 
     
     
         17 . The filler according to  claim 15 , wherein the degree of substitution is up to about 0.60. 
     
     
         18 . The filler according to  claim 15 , wherein the degree of substitution is up to about 0.50. 
     
     
         19 . A filler comprising a calcium salt which is calcium carbonate and a water-soluble cellulose derivative having a degree of substitution of carboxyalkyl groups up to about 0.65, wherein the calcium salt is precipitated calcium carbonate having a specific surface area of from about 2 to about 20 m 2 /g, and wherein the filler has a calcium salt content of at least 0.0001% by weight and a cellulose derivative content of at least 0.01 by weight, based on the weight of solids of the filler. 
     
     
         20 . The filler of  claim 19 , wherein the precipitated calcium carbonate has a specific surface area of from about 7 to 12 m 2 /g.