Aqueous silica-containing composition

Abstract

The present invention relates to an aqueous silica-containing composition comprising an anionic organic polymer having at least one aromatic group and anionic silica-based particles. The aqueous silica-containing composition contains the anionic organic polymer having at least one aromatic group and the anionic silica-based particles in an amount of at least 0.01% by weight of the total weight of the aqueous silica-containing composition. The aqueous silica-containing composition contains substantially no cellulose-reactive sizing agent and the anionic organic polymer having at least one aromatic group is not an anionic naphthalene sulphonate formaldehyde condensate. The invention further relates to methods for the preparation of the aqueous silica-containing composition and the use of the aqueous silica-composition as a drainage and retention aid in a process for the production of paper. The invention also relates to a process for the production of paper from an aqueous suspension containing cellulosic fibres, and optionally filler, in which the aqueous silica-containing composition and at least one charged organic polymer are added to the cellulosic suspension.

1 . A process for the production of paper from a suspension containing cellulosic fibres, and optionally fillers, comprising adding to the suspension at least one cationic organic polymer and an aqueous silica-containing composition comprising an anionic organic polymer having at least one aromatic group and aggregated or microgel formed anionic silica-based particles, the aqueous silica-containing composition containing the anionic organic polymer having at least one aromatic group and total amount of anionic silica-based particles in an amount of at least 0.01% by weight based on the total weight of the aqueous silica-containing composition, with the proviso that the composition contains substantially no cellulose-reactive sizing agent and the anionic organic polymer having at least one aromatic group is not an anionic naphthalene sulphonate formaldehyde condensate.  
     
     
         2 . The process according to  claim 1  wherein the cationic organic polymer is cationic starch or cationic polyacrylamide.  
     
     
         3 . The process according to  claim 1  wherein the cationic organic polymer has at least one aromatic group.  
     
     
         4 . The process according to  claim 2  wherein the cationic organic polymer has at least one aromatic group.  
     
     
         5 . The process according to  claim 1  wherein the silica-based particles have a specific surface area from about 300 to about 1300 m 2 /g.  
     
     
         6 . The process according to  claim 1  wherein the silica-based particles have an average particle size ranging from about 1 nm up to about 10 nm.  
     
     
         7 . The process according to  claim 1  wherein pH of the aqueous solution of the anionic organic polymer having at least one aromatic group is adjusted to a pH of at least 8 prior to mixing with the silica-based particles.  
     
     
         8 . The process according to  claim 1  wherein the anionic organic polymer having at least one aromatic group polymer is a polyurethane, lignosulphonate, Kraft lignin or oxylignin.  
     
     
         9 . The process according to  claim 1  wherein the aqueous silica-containing composition has a negative charge density within the range of from 0.1 to 6 meq/g.  
     
     
         10 . The process according to  claim 1  with the proviso that the composition contains substantially no sizing agent.  
     
     
         11 . A process for the production of paper from a suspension containing cellulosic fibres, and optionally fillers, comprising adding to the suspension at least one cat ionic organic polymer and an aqueous silica-containing composition obtainable by mixing an anionic organic polymer having at least one aromatic group with an aqueous alkali stabilised silica sol containing aggregated or microgel formed silica-based particles having an S-value in the range of from about 5 up to about 50%, to provide an aqueous silica-containing composition containing the anionic organic polymer having at least one aromatic group and total amount of silica-based particles in an amount of at least 0.01% by weight, based on the total weight of the aqueous silica-containing composition, with the proviso that the composition contains substantially no cellulose-reactive sizing agent and that the anionic organic polymer having at least one aromatic group is not an anionic naphthalene sulphonate formaldehyde condensate.  
     
     
         12 . The process according to  claim 12  wherein the cationic organic polymer is cationic starch or cationic polyacrylamide.  
     
     
         13 . The process according to  claim 12  wherein the cationic organic polymer has at least one aromatic group.  
     
     
         14 . The process according to  claim 12  wherein the cationic organic polymer having at least one aromatic group.  
     
     
         15 . The process according to  claim 12  wherein the silica-based particles have a specific surface area from about 300 to about 1300 m 2 /g.  
     
     
         16 . The process according to  claim 12  wherein the silica-based particles have an average particle size ranging from about 1 nm up to about 10 nm.  
     
     
         17 . The process according to  claim 12  wherein pH of the aqueous solution of the anionic organic polymer having at least one aromatic group is adjusted to a pH of at least 8 prior to mixing with the silica-based particles.  
     
     
         18 . The process according to  claim 12  wherein the anionic organic polymer having at least one aromatic group polymer is a polyurethane, lignosulphonate, Kraft lignin or oxylignin.  
     
     
         19 . The process according to  claim 12  wherein the aqueous silica-containing composition has a negative charge density within the range of from 0.1 to 6 meq/g.  
     
     
         20 . The process according to  claim 12  with the proviso that the composition contains substantially no sizing agent.