Method and system using low fatty acid starches in paper sizing composition to inhibit deposition of multivalent fatty acid salts

Abstract

A method for inhibiting deposition of multivalent saturated fatty acids on paper sizing equipment and/or devices which use a paper surface sizing composition containing higher starch solids levels of surface sizing starches and a source of multivalent cations, such as a multivalent metal drying salt, by including (wholly or partially) one or more low fatty acid surface sizing starches in the paper surface sizing composition. Also, a paper surface sizing system for carrying out this method.

What is claimed is: 
     
         1 . A method comprising the following steps of:
 (a) providing a cooked paper surface sizing composition comprising above about 10% cooked surface sizing starch solids and no more than about 300 ppm C 16  or higher saturated fatty acids, wherein the cooked surface sizing starch solids comprise from 0 to about 95% high fatty acid surface sizing starch and from about 5 to 100% low fatty acid surface sizing starch; and   (b) treating at least one surface of a paper substrate with the cooked paper surface sizing composition to thereby provide a surface sizing coating on the at least one surface, wherein the at least one surface is also treated with a source of multivalent cations at a level of at least about 1000 ppm.   
     
     
         2 . The method of  claim 1 , wherein the cooked surface sizing starch solids of step (a) comprise from 0 to about 90% high fatty acid surface sizing starch and from about 10 to 100% low fatty acid surface sizing starch. 
     
     
         3 . The method of  claim 1 , wherein the cooked surface sizing starch solids of step (a) comprise from about 15 to about 85% high fatty acid surface sizing starch and from about 15 to about 85% low fatty acid surface sizing starch. 
     
     
         4 . The method of  claim 3 , wherein the cooked surface sizing starch solids of step (a) comprise from about 30 to about 70% high fatty acid surface sizing starch and from about 30 to about 70% low fatty acid surface sizing starch. 
     
     
         5 . The method of  claim 1 , which comprises the further step (c) of adding a monovalent hydroxide to the cooked paper surface sizing composition prior to adding the source of multivalent cations to thereby neutralize and convert the total fatty acids to monovalent fatty acid salts. 
     
     
         6 . The method of  claim 1 , wherein the high fatty acid surface sizing starch of step (a) comprises one or more surface sizing non-waxy cereal starches. 
     
     
         7 . The method of  claim 6 , wherein the non-waxy cereal starches of step (a) comprises one or more of non-waxy maize (corn) starch and non-waxy wheat starch. 
     
     
         8 . The method of  claim 1 , wherein the low fatty acid surface sizing starch of step (a) comprise one or more of tapioca starch and waxy cereal starch. 
     
     
         9 . The method of  claim 8 , wherein the low fatty acid surface sizing starch of step (a) comprises one or more of waxy maize (corn) starch, waxy rice starch, and waxy potato starch. 
     
     
         10 . The method of  claim 1 , wherein the source of multivalent cations of step (b) comprises a multivalent metal drying salt. 
     
     
         11 . The method of  claim 1 , wherein the cooked paper surface sizing composition comprises above about 12% cooked surface sizing starch solids. 
     
     
         12 . The method of  claim 1 , which comprises the further step (c) of adding a monovalent hydroxide to the cooked paper surface sizing composition and prior to introducing a source of multivalent cations to thereby neutralize and convert fatty acids liberated from the cooked surface sizing starch solids to monovalent C 16  or higher saturated fatty acid salts. 
     
     
         13 . The method of  claim 12 , wherein the cooked paper surface sizing composition is raised to a pH of from about 6 to about 9. 
     
     
         14 . A system comprising:
 a source of a paper surface sizing composition comprising above about 10% surface sizing starch solids, wherein the surface sizing starch solids comprise from 0 to about 95% high fatty acid surface sizing starch and from about 5 to 100% low fatty acid surface sizing starch;   a starch cooking stage which cooks the surface sizing starch solids in the paper surface sizing composition and thus liberates no more than about 300 ppm C 16  or higher saturated fatty acids;   a fatty acid neutralization stage which neutralizes and converts the liberated total fatty acids in the cooked paper surface sizing composition to monovalent fatty acid salts;   a source of a multivalent metal drying salt; and   a paper surface sizing device wherein at least one surface of a paper substrate is treated with the neutralized paper surface sizing composition and the multivalent metal drying salt, wherein the multivalent metal drying salt is in an amount which provides multivalent cations at a level of at least about 1000 ppm.   
     
     
         15 . The system of  claim 14 , wherein the surface sizing starch solids in the paper surface sizing composition comprise from 0 to about 95% high fatty acid surface sizing starch and from about 10 to 100% low fatty acid surface sizing starch. 
     
     
         16 . The system of  claim 14 , wherein the surface sizing starch solids in the paper surface sizing composition comprise from about 15 to about 85% high fatty acid surface sizing starch and from about 15 to about 85% low fatty acid surface sizing starch. 
     
     
         17 . The system of  claim 16 , wherein the surface sizing starch solids in the paper surface sizing composition comprise from about 30 to about 70% high fatty acid surface sizing starch and from about 30 to about 70% low fatty acid surface sizing starch. 
     
     
         18 . The system of  claim 14 , wherein the high fatty acid surface sizing starch solids comprise one or more surface sizing non-waxy cereal starches. 
     
     
         19 . The system of  claim 18 , wherein the non-waxy cereal starches comprise one or more of non-waxy maize (corn) starch and non-waxy wheat starch. 
     
     
         20 . The system of  claim 14 , wherein the low fatty acid surface sizing starch comprises one or more of tapioca starch and waxy starch. 
     
     
         21 . The system of  claim 20 , wherein the low fatty acid surface sizing starch comprises one or more of waxy maize (corn) starch, waxy rice starch, and waxy potato starch. 
     
     
         22 . The system of  claim 14 , wherein the source of the paper surface sizing composition comprises above about 12% surface sizing starch solids. 
     
     
         23 . The system of  claim 14 , wherein the multivalent metal drying salt is added to the paper surface sizing composition prior to treating the at least one surface at the paper surface sizing device. 
     
     
         24 . The system of  claim 14 , wherein the paper substrate has two surfaces and wherein each surface is treated with the paper surface sizing composition and the multivalent metal drying salt at the paper surface sizing device. 
     
     
         25 . The system of  claim 14 , wherein the paper surface sizing device comprises a size press.