Aq. polymer dispersions, useful as binders for coating materials - are prepd. by two=stage emulsion copolymerisation of N-butyl acrylate with other monomers, esp. N-methylol-(meth)acrylamide and (meth)acrylamide

摘要

Aq. polymer dispersions (I) are claimed; (I) are obtd. by emulsion polymerisation of a mixt. of (A) 50-99.5wt.% n-butyl acrylate; (B) 0.5-10wt.% N-alkylolamide(s) of 3-10C alpha,beta- mono-unsatd. acids or corresp. 1-4C alkyl ethers or monomer(s) with 2 double bonds, and (C) 0-49.5wt.% other mono-unsatd. monomers, in the presence of surfactants and radical initiators; the process is carried out at 0-60 deg.C, the polymer obtd. (II) has Tg (-10) to (-5) deg.C, and the polymerisation is carried out in 2 consecutive stages, involving polymerisation of 40-99.5wt.% of the total amt. of monomers in stage 1 and 0.5-60wt.% in stage 2, with addn. of the whole of monomer (B) in stage 2 and with n-butyl acrylate making up at least half of the monomers used in stage 1. Also claimed is the above process as such. More specifically, the monomer mixt. contains at least 75 (pref. 90-97.5) wt.% N-methylol- (meth)acrylamide and 1-5wt.% (meth)acrylamide; stage 2 is carried out with monomer (B) only, or with (B) and above 10wt.% (A) and/or (C) (at 0-30 deg.C), or with (B) and below 10wt.% (A) and/or (C) (at 40-60 deg.C). USE/ADVANTAGE - (I) are useful as binders for coating materials (claimed). W.r.t. prior-art materials, (I) enable the prodn. of coating materials with increased elongation at tear and low surface tackiness, and are therefore esp. useful in paint and plaster for use on cracked exterior surfaces