Reducing residual monomer content in aqueous polymer dispersion

摘要

The residual monomer content of aqueous polymer dispersions is reduced by further treatment with an initiator system containing a peroxide, a saturated alpha - hydroxycarboxylic acid and, optionally, multivalent ions of a variable-valency metal. A method for reducing the residual monomer content in aqueous polymer dispersions comprises post-treatment by addition of an initiator system essentially containing: (a) 0.01-5 wt% (based on total amount of monomers used to make the dispersion) of a compound of formula: R<1>-O-O-R<2> (a1), and/or a compound which liberates hydrogen peroxide (H2O2) in aqueous medium (a2); (b) 0.01-30 wt% alpha -hydroxy- carboxylic acid with no polymerisable carbon-carbon double bonds or a salt thereof; and (c) 0-1000 ppm multivalent metal ions of variable valency. R<1> and R<2> = H, 1-8 C alkyl or 6-12 C aryl, at least one of these groups being H;