Polymer dispersion for coating wood for blocking migratable compounds

A wood substrate coated with at least one coating layer, wherein the coating layer comprises a coating composition, wherein the coating composition comprises at least one polymer dispersion, wherein the polymer dispersion is an aqueous polymer dispersion of a polymer comprising, 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
• (i-a) preparing an aqueous dispersion comprising monomers (a), (b), (c) and silane graft compound (e) and simultaneously
• polymerizing monomers (a), (b), and (c) and grafting to their polymerization product silane compound (e) or
• (i-b) post-treating an aqueous dispersion comprising the polymerization product of monomers (a), (b), and (c) with graft silane compound (e);
• wherein the silane compound (e) comprises at least one silane group and at least one functional group capable of reacting, at least in part, with the carboxylic groups of monomer (b) selected from the group consisting of epoxy-, amino-, thiol-, hydroxyl-, and isocyanate groups.