Optical brightener for paper

摘要

Optical brightening of non-textile cellulose substrates comprises the use of bis-2-triazinylaminostilbene cpds of formula: in which R1 is H, opt. OH- or alkoxy-substd alkyl, alkoxyalkyl or alkylaminoalkyl or opt. lower alkyl-substd. cycloalkyl; R2 is H or opt OH- or alkoxy-substd alkyl or alkoxy-alkyl; R1 and R2 together with the N and opt. with O form a non-aromatic heterocycle; R3 is H or halogen with at no =35; M is a cation selected from H, alkali(ne earth) metal, opt. substd ammonium or Al). These cpds are used brightening viscose films and paper. They show no redn in bath strength i.e. constant brightening effect in surface brightening of paper and have good compatibility with the binders and white pigments used in surface coatings. They also have good resistance to acid and Al salts in pulp brightening and show no underisable discolouration by detergents.