Patent ID: 7824486

Claim:
A process for making a decorative base paper for a paper laminate comprising impregnating a base paper with a pigment mixture of titanium dioxide and water wherein the titanium dioxide pigment is made by: (a) contacting titanium dioxide pigment with water to form a mixture having a pigment concentration of from about 14 to 40 weight percent based on the weight of the mixture then adjusting the pH of this mixture to about 7 with aqueous sodium hydroxide; (b) heating the mixture to a temperature of about 40° C.; (c) adding to the heated mixture at a rate such that the pH of the resulting mixture is maintained at about 7 throughout this step (c) from about 0.15 to 0.65 moles of phosphoric acid per kilogram of dry pigment and at least a portion of sodium aluminate aqueous solution required to react with the phosphoric acid to form aluminum phosphate; (d) adding any remaining aqueous sodium aluminate solution required to react with unreacted phosphoric acid to complete the formation of aluminum phosphate simultaneously with a solution of hydrochloric acid wherein the rate of addition of aluminate solution and that of the acid solution is adjusted so that that the pH of the resulting mixture from and in this step (d) is maintained in a range from 5 to 8; (e) drying the mixture to form a dried treated pigment; and (f) thermally treating the dried treated pigment for at least about 0.25 hour at a temperature of about 300° C. to about 800° C. to form a thermally treated pigment; whereby the thermally treated pigment exhibits an improvement in light fastness corresponding to a decrease in delta E* (color change) of at least about 40%, based on the delta E* value of the dried treated pigment of step (e).