Stable aqueous colloidal silica product, and methods to make and use same

Abstract

An aqueous colloidal silica product, a method of using the aqueous colloidal silica product, and a method of producing an aqueous colloidal silica product, are disclosed. The method of producing the aqueous colloidal silica product incorporates semi-batch addition of alkali metal silicate, which is capable of achieving an aqueous colloidal silica product having desirable physical and chemical characteristics. The aqueous colloidal silica product has been found to be particularly useful as an additive in a papermaking process.

1 . An aqueous colloidal silica product comprising water and from 16 to 18 weight percent colloidal silica solids, wherein the aqueous colloidal silica product has a viscosity ranging from about 4 to about 20 cps and an S-value ranging from 26 to 40%, wherein the colloidal silica solids have a specific surface area ranging from 700 to 850 m 2 /g. 
     
     
         2 . The aqueous colloidal silica product of  claim 1 , further comprising an alkali metal. 
     
     
         3 . The aqueous colloidal silica product of  claim 1 , wherein the alkali metal is present in an amount sufficient to provide a molar ratio of silica to alkali metal ranging from 50:1 to 5:1 
     
     
         4 . The aqueous colloidal silica product of  claim 1 , wherein the aqueous colloidal silica product has a viscosity ranging from about 4 to about 18 cps. 
     
     
         5 . The aqueous colloidal silica product of  claim 1 , wherein the aqueous colloidal silica product comprises from 17 to 18 weight percent colloidal silica solids. 
     
     
         6 . The aqueous colloidal silica product of  claim 1 , wherein the aqueous colloidal silica product has a ratio of weight percent colloidal silica solids to cps viscosity ranging from 1:2 to 4:1. 
     
     
         7 . The aqueous colloidal silica product of  claim 1 , wherein the aqueous colloidal silica product has a pH ranging from 9 to 11. 
     
     
         8 . The aqueous colloidal silica product of  claim 1 , wherein the aqueous colloidal silica product has a pH ranging from 10 to 11. 
     
     
         9 . A method of producing an aqueous colloidal silica product, the method comprising:
 first, adding a first quantity of alkali metal silicate to water and a partially regenerated cationic ion exchange resin under agitation, thereby forming a first intermediate composition comprising a first portion of aqueous colloidal silica product, wherein the first intermediate composition has a temperature ranging from 70 to 200 degrees Fahrenheit and a pH ranging from 8 to 14, and the first quantity of alkali metal silicate is added at a first rate sufficient to allow the first addition to last for 1 to 45 minutes;   second, after 0 to 90 minutes, adding a second quantity of alkali metal silicate to the first intermediate composition under agitation, thereby forming a second intermediate composition comprising a second portion of aqueous colloidal silica product, wherein the second intermediate composition has a temperature ranging from 70 to 200 degrees Fahrenheit and a pH ranging from 9 to 11, and the second quantity of alkali metal silicate is added at a second rate sufficient to allow the second addition to last for 5 to 120 minutes;   after 0 minutes to 24 hours, separating the first and second portions of aqueous colloidal silica products from the second intermediate composition, thereby producing the aqueous colloidal silica product;   wherein the first quantity and the second quantity comprise a total quantity, the first quantity ranging from 60 to 95 weight percent of the total quantity.   
     
     
         10 . The method of  claim 9 , wherein the first and second portions of aqueous silica products are separated from the second intermediate composition via filtration using a screen or slotted pipe. 
     
     
         11 . The method of  claim 9 , wherein the second intermediate composition is allowed to agitate at from 70 to 200 degrees Fahrenheit for a time ranging from 0 minutes to 75 minutes. 
     
     
         12 . The method of  claim 9 , wherein the first intermediate composition has a pH ranging from 9 to 11. 
     
     
         13 . The method of  claim 9 , wherein the first and second intermediate compositions have temperatures ranging from 100 to 160 degrees Fahrenheit. 
     
     
         14 . The method of  claim 9 , wherein the first rate is sufficient to allow the addition of the first quantity of alkali metal silicate to last from 2 to 10 minutes. 
     
     
         15 . The method of  claim 9 , wherein the second rate is sufficient to allow the addition of the second quantity of alkali metal silicate to last from 10 to 40 minutes. 
     
     
         16 . A method of making a cellulosic sheet, the method comprising:
 preparing a cellulosic furnish containing from 0.01 to 1.5 weight percent cellulosic fiber;   adding to the cellulosic furnish an amount of the aqueous colloidal silica product of  claim 1  sufficient to achieve a concentration of colloidal silica solids of from 0.00005 to 1.5 weight percent per dry weight of fiber in the cellulosic furnish, and an amount of a water soluble polymeric flocculant sufficient to achieve a concentration of water soluble polymeric flocculant of from 0.001 to 5 weight percent per dry weight of fiber in the cellulosic furnish, wherein the water soluble polymeric flocculant has a molecular weight ranging from 500,000 to 30 million daltons; and   dewatering the cellulosic furnish to obtain a cellulosic sheet.   
     
     
         17 . The method of  claim 16 , wherein the amount of the aqueous colloidal silica product added to the cellulosic furnish is sufficient to achieve a colloidal silica solids concentration of from about 0.005 to about 1 weight percent per dry weight of fiber in the cellulosic furnish. 
     
     
         18 . The method of  claim 16 , wherein the colloidal silica product has a first pass ash retention replacement ratio ranging from about 0.5 to about 0.8 relative to a batch aqueous colloidal silica product. 
     
     
         19 . The method of  claim 16 , wherein the colloidal silica product achieves a first pass ash retention of at least 90% relative to a batch aqueous colloidal silica product when dosing microparticles into the cellulosic furnish at a concentration of about 0.9 to 1.2 pounds per ton dry weight of fiber in the cellulosic furnish. 
     
     
         20 . The method of  claim 16 , wherein a cationic starch is added to the cellulosic furnish in an amount sufficient to achieve a concentration of cationic starch of from 0.005 to 5 weight percent cationic starch per dry weight of fiber in the cellulosic furnish.