OPTICAL BRIGHTENER AND METHOD OF PREPARING IT

摘要

The present invention relates generally to an improved method of preparing aqueous coating compositions including an optical brightener and a polyvinyl alcohol resin, the improvement being directed to cooking a slurry to dissolve the polyvinyl alcohol resin subsequent to the addition of optical brightener and polyvinyl alcohol resin to the slurry at a temperature above about 160‹F for at least about 5 minutes. The invention enables preparation with lower water content without compromising brightness and color. Particularly preferred is the addition of dry resin and/or dry brightener to provide high solids mixtures. Another aspect of the invention is a dry, particulate blend of brightener and PVOH resin. Disclosed is a method of preparing an optical brightener/PVOH aqueous concentrate comprising the sequential steps of: (a) providing an aqueous brightener composition including water and optical brightener active ingredient, wherein the optical brightener active ingredient is typically present in the aqueous brightener composition in an amount of from about 10% to about 25%; (b) admixing a polyvinyl alcohol resin with said aqueous optical brightener composition in an amount of about 1 part of dry polyvinyl alcohol resin per 0.5 to 10 wet parts of aqueous brightener composition to provide a nascent aqueous concentrate of polyvinyl alcohol resin and optical brightener; and (c) cooking the aqueous concentrate to dissolve the solids typically at a temperature of from about 175‹F to about 210‹F for a time of from about 10 minutes to about 120 minutes to provide a conked brightener/polyvinyl alcohol concentrate. ® KIPO & WIPO 2007