Polymer dispersion for coating wood for blocking migratable compounds

An aqueous polymer dispersion wherein said polymer comprises, in its structure, monomer units incorporated from a composition of monomers comprising:

• a) at least one (meth)acrylic monomer which is a C1-C18 alkyl or C6-C18 cycloalkyl (meth)acrylic ester, without any ionic group,
• b) at least one ethylenically unsaturated monomer carrying at least one carboxylic acid group, and
• c) at least one ethylenically unsaturated monomer carrying a tertiary amine,
• wherein said polymer additionally comprises grafted silane groups in a form of —Si(OR1)3 or —Si—R2(OR1)2 or —Si—(R2)2(OR1), with R1, R2 being an identical or different C1 to C4 alkyl,
• wherein the composition of monomers comprises less than 25% by weight of vinylaromatic monomers, and
• wherein said grafted silane groups are incorporated by at least one of the following two routes or their combination:
• (i) presence with the monomers a), b) and c) of at least one ethylenically unsaturated comonomer d) comprising, in addition to said ethylenic unsaturation, at least one blocked silane group as defined above, and/or
• (ii) presence with the monomers a), b) and c) of, or post-treatment of the aqueous dispersion with, at least one silane compound e) comprising at least one silane group and at least one functional group selected from:
• epoxy, amino, thio, hydroxyl and isocyanate, the latter functional group being capable of reacting, at least in part, with the carboxylic groups of said monomer b).