CONCENTRATED SOLUTIONS OF OPTICAL BRIGHTENER Russian patent published in 2010 - IPC C07D251/68 D06L3/12 D21H21/30 

FIELD: chemistry.

SUBSTANCE: invention relates to concentrated aqueous solutions of hexa-sulfonated stilbene used optical brighteners. Description is given of an aqueous solution of hexa-sulfonated stilbene optical brightener which is stable during storage with over 0.214 mol/kg content thereof in the solution. The solution does not contain a soluble agent, for example urea. By removing salts formed during synthesis of the optical brightener, its concentration of up to 0.35 mol/kg can be achieved without losing stability during storage. Also described is a method of preparing an aqueous solution of the said optical brightener and its use for bleaching paper or cellulose materials.

EFFECT: high concentration solutions of the said optical brightener do not show crystallisation signs after 2 weeks at 5°C and enables formation of coating compositions with low water content, which reduces energy consumption on drying and reduces penetration of water and adhesive into the paper layer.

10 cl, 1 dwg, 1 tbl, 3 ex