Noncaking vinyl chloride-vinyl ester copolymer powders - by drying aqueous dispersions of vinyl chloride copolymer and styrene copolymer, for use in hydraulic binders

摘要

Non-caking copolymer powders are prepd. by drying a mixt. of an aq. dispersion of (A) a copolymer of 20-80 (35-55) wt.% vinyl chloride and 80-20 (65-45) wt.% vinyl acetate and/or vinyl propionate, and a minor amt. of an aq. dispersion of (B) a copolymer of 60-90 wt.% styrene, 5-35 (5-30) wt.% (meth)acrylonitrile, (m)ethyl or tert, butyl acrylate, methyl methacrylate, vinyl acetate and/or vinyl propionate, 5-10 wt.% of an alpha, beta-alkenically unsatd. carboxylic acid and 0-5 wt.% of (meth)acrylamide and/or vinylpyrrolidone, and possibly a minor amt. of an aq. dispersion of (C) a vinyl-pyrrolidone polymer. The powders are added to concrete, cement and plaster; the powder does not cake during drying, nor agglomerate on prolonged storage; high throughput is achieved in the drier; and pre-dried air is not needed.