AQUEOUS SOLUTIONS OF OPTICAL BRIGHTENERS Russian patent published in 2012 - IPC C08L29/04 C08K5/00 D21H21/30 

FIELD: chemistry.

SUBSTANCE: described is an aqueous solution of an optical brightener, containing (a) 10-50 wt % optical brightener of formula (I): where: M is hydrogen, an alkali metal atom, ammonia or an amine cation; R¹ is hydrogen, C₁-C₄-alkyl or C₂-C₄-hydroxyalkyl; R² - C₁-C₄-alkyl which can be substituted with -CN- or -CONH₂-group or C₂-C₄-hydroxyalkyl; or R¹ and R² together with a nitrogen atom close a morpholine ring; (b) 0.5-9 wt % polyvinyl alcohol, having degree of hydrolysis 71-85.2% and Brookfield viscosity 3-5.4 mPa·s; and (c) water. The invention also describes use of said solution in a coating composition for paper and a method of obtaining paper coated with said coating composition.

EFFECT: disclosed aqueous solutions of optical brighteners have low viscosity, can be used directly by paper manufacturers and can be fed by a pump directly into the coating composition to provide a coating on paper with high whiteness.

10 cl, 2 tbl, 5 ex