Patent NZ-614963-A (NZ)
Title: Aqueous multistage polymer dispersion, process for its preparation and use thereof as binder for coating substrates
Inventor: BALK ROELOF
IPC: C08F2/22
Filed: 2012-03-22
Abstract: The disclosure relates to a process for preparing a polymer dispersion obtained by at least two-stage emulsion polymerization. The first stage comprises forming in an aqueous medium a first polymer having a glass transition temperature of more than 50°C and a weight-average molecular weight of between 5 and 100 kDa is prepared by free-radical emulsion polymerization from a first composition comprising hydrophilic and hydrophobic monomers, comprising (A1) at least one (meth)acrylic acid alkyl ester, (B1) optionally at least one vinylaromatic having up to 20 C atoms, (C1) optionally at least one free-radically polymerizable compound selected from the 15 group consisting of ethylenically unsaturated nitriles having up to 20 C atoms, vinyl esters of carboxylic acids comprising up to 20 C atoms, vinyl halides having up to 10 C atoms, and vinyl ethers of alcohols containing 1 to 10 C atoms, (D1) at least one a,B-ethylenically unsaturated carboxylic acid, or a vinyl monomer with latent ionic groups, (E1) optionally at least one crosslinker, (F1) at least one compound selected from the group consisting of 2-(2-oxoimidazolidin-1-yl)ethyl (meth)acrylate, 2-ureido(meth)acrylate, acetoacetoxyethyl acrylate, acetoacetoxypropyl methacrylate, acetoacetoxybutyl methacrylate, 2-(acetoacetoxy)ethyl methacrylate, diacetoneacrylamide (OAAM), and 25 diacetonemethacrylamide, (G1) optionally at least one compound having a (meth)acrylate group and an epoxy group, and (H1) optionally at least one a,B-ethylenically unsaturated carboxamide, in the presence of at least one initiator, at least one emulsifier, and at least one chain transfer agent, neutralization to a pH of at least 4.5 of the particles thus formed, using a base (neutralizing agent), followed by free-radical polymerization of hydrophobic and hydrophilic monomers in a following stage, in the presence of the copolymer prepared in the first stage, from (A2) at least one (meth)acrylic acid alkyl ester, (B2) optionally at least one vinylaromatic having up to 20 C atoms, (C2) optionally at least one free-radically polymerizable compound selected from the group consisting of ethylenically unsaturated nitriles having up to 20 C atoms, vinyl esters of carboxylic acids comprising up to 20 C atoms, vinyl halides having up to 10 C atoms, and vinyl ethers of alcohols containing 1 to 10 C atoms, (02) optionally at least one a,B-ethylenically unsaturated carboxylic acid, or a vinyl monomer with latent ionic groups, (E2) optionally at least one crosslinker, and (F2) optionally at least one compound selected from the group consisting of 2-(2- 5 oxoimidazolidin-1-yl)ethyl (meth)acrylate, 2-ureido(meth)acrylate, acetoacetoxyethyl acrylate, acetoacetoxypropyl methacrylate, acetoacetoxybutyl methacrylate, 2-(acetoacetoxy)ethyl methacrylate, diacetoneacrylamide (OAAM), anddiacetonemethacrylamide, (G2) optionally at least one compound having a (meth)acrylate group and an epoxy group, and (H2) optionally at least one a,B-ethylenically unsaturated carboxamide, with the proviso that the polymer of the 2nd stage is more hydrophobic than that of the 1st stage, and the glass transition temperature of the second stage is at least 50°C lower than that of the first stage.