Use of zirconium salts to improve the surface sizing efficiency in paper making

摘要

This invention relates to an improved process of surface sizing of paper and paperboard. The process consists of: a) Preparing an aqueous surface sizing compound by combining and mixing an aqueous solution of at least one water soluble or dispersible polymer or interpolymer, a solution or dispersion of auxiliary materials, and an aqueous solution of a metal salt, selected from the group of metals consisting of zirconium, hafnium or titanium, to the polymer solution; b) Adjusting the pH of the aqueous sizing compound from about 5 to about 10.5 by the addition of alkali, thereby increasing the molecular weight of the polymer or interpolymer by chemically or physically reacting the polymer or interpolymer with the salt of zirconium, hafnium or titanium, resulting in an increase in viscosity of the aqueous sizing compound; c) Applying the aqueous surface sizing compound to the surface of the paper or paperboard by means of a coating device, where the aqueous surface sizing compound is immobilized in the wet state, thereby preventing penetration of the aqueous surface sizing compound into the paper or paperboard; and d) Drying and curing the aqueous surface sizing compound by applying heat to the treated paper or paperboard thereby crosslinking the polisher or interpolymer contained in the surface sizing compound, and also forming bonds with the pigment particles and fiber present at the surface of the paper or paperboard, and thereby anchoring the polymer or interpolymer to the surface of the paper or paperboard.