| abstract |
Aqueous optical brightener compositions consisting essentially of: (a) at least one optical brightener of formula <IMAGE> in which R1 is hydrogen or -SO3M; R2 is hydrogen or -SO3M; R3 is hydrogen, C2-3-hydroxyalkyl, C1-4-alkyl, -CH2-CH2-CN or -CH2-CH2-CONH2; R4 is hydrogen, C1-4-alkyl, C2-3-hydroxyalkyl, hydroxy-ethoxy-ethyl, N,N-Bis-(C1-3-alkyl)-amino-C2-6-alkyl or benzyl; or R3 and R4 together with the neighboring nitrogen atom signify a morpholine, pyrrolidine, piperidine or N-methylpiperazine ring; and M is hydrogen or a colorless cation; provided that at most one of R3 and R4 is hydrogen; (b) polyethylene glycol with an average molecular weight in the range of 1000 to 3000; and (c) water; 10 to 500 parts by weight of component (b) being present per 100 parts by weight of component (a), and component (c) constituting at least 20% of the composition, are storage stable optical brightener compositions, which are eminently suitable for the formulation of aqueous coating compositions especially such in which at least some of the binder is a synthetic latex; with these coating compositions there may be obtained very white coated papers which are optically brightened at least in the coating. |