ALKALI-SOLUBLE RESIN (ASR) SHELL EPOXY RDP WITH DIVALENT METAL IONS EXHIBITING IMPROVED POWDER REDISPERSIBILITY

摘要

The present invention provides multilayer polymer redispersible powder (RDP) particles comprising a major proportion of from 50 to 90 wt. %, preferably, from 60 to 85 wt. %, based on total polymer solids, of epoxy resin resins having a calculated glass transition temperature (Tg) of from 0 to 40° C., a methacrylic acid containing alkali soluble polymer outer layer, and a divalent metal, such as zinc powder, having an aqueous pKa of 9.55 or more, or its acid salt having a pH of 7.0 or less, such as strong acid salts, e.g., chlorides, sulfates or phosphates, or organic acid salts, e.g., acetates, succinates and citrates, as well as to methods of making the same.

主权项

1. A redispersible polymer powder composition comprising as powder or an aqueous dispersion multilayer polymer particles of (i) from 50 to 90 wt. %, based on total polymer solids, of epoxy resin compositions having a calculated glass transition temperature (calculated Tg) of from 0 to 40° C., and (ii) from 10 to 50 wt. %, based on polymer solids, of an alkali soluble polymer shell around the epoxy resin, which polymer shell is the copolymerized product of from 5 to 40 wt. % of methacrylic acid or its anhydride, based on the total weight of monomers copolymerized to form the polymer shell, and the remainder of one or more ethylenically unsaturated comonomer, and (iv) an additive chosen from a divalent metal ion (M2+) having a pKa of 9.55 or higher and its strong acid (acid pKa<3.5) or organic acid salt having a pH in water of 7.0 or less, wherein the molar ratio of M2+ ions to the carboxyl groups in the alkali soluble resin shell is from 10 to 200 mole %.