METHOD FOR CONTROLLING SIZE DISTRIBUTION OF POLYMER PARTICLES DURING PREPARATION OF AQUEOUS POLYMER DISPERSION, AQUEOUS POLYMER DISPERSION AND ITS USE

摘要

The invention relates to a method for controlling size distribution of formed polymer particles during preparation of aqueous polymer dispersion. The method comprises obtaining a aqueous polysaccharide solution, which comprises 10 to 40 weight-% polysaccharide containing a free hydroxyl group, such as starch, and polymerising in the polysaccharide solution in the presence of a graft-linking, water-soluble redox system 30 to 60 weight-% of at least one optionally substituted styrene, 60 to 30 weight-% of at least one C1-C4-alkyl (meth)acrylate, and 0 to 10 weight-% of other ethylenically unsaturated copolymerizable monomers. The size distribution of the formed polymer particles is controlled by adjusting viscosity of the polysaccharide solution before the polymerisation to a level < 20 m Pas. The invention relates also to an aqueous polymer dispersion having the D(99) value < 160 nm for polymer particles in the polymer dispersion and its use.