HEAT RESISTANT EMULSION POLYMER DISPERSION

The invention relates to an aqueous polymer dispersion obtainable by emulsion copolymerization of vinyl ester monomers (a) in the presence of fully hydrolyzed polyvinyl alcohol (PVOH) (c), using comonomers (b), wherein the vinyl ester monomers (a) comprise a first component (a1) of versatic acid ester(s) and a second component (a2) of vinyl acetate, wherein the comonomer(s) (b) comprise a (meth)acryl amide derivative (b1) of the general formula CH2 = CX - CO - NHY, wherein X is hydrogen or a methyl group, Y is the group - (CH2)n - O - Z, wherein n is an integer in the range of 1 to 6, and Z is hydrogen or an alkyl or acyl group having up to 4 carbon atoms, and a (meth)acryl amide derivative (b2), different from (b1), of the general formula CH2 = CX - CO - NHY, wherein X is hydrogen or a methyl group, Y is hydrogen or the group - (CH2)n - O - Z, wherein n is an integer in the range of 1 to 6, and Z is an alkyl or acyl group having up to 4 carbon atoms, wherein the fully hydrolyzed polyvinyl alcohol (PVOH) (c) comprises a blend of fully hydrolyzed Standard-PVOH (S-PVOH) having an average degree of hydrolysis above 95 mol% and of fully hydrolyzed modified PVOH (X-PVOH) having an average degree of hydrolysis above 95 mol%. The invention further relates to an adhesive formulation comprising the aqueous polymer dispersion and the use of the aqueous polymer dispersion to provide to an adhesive formulation a water resistance, measured as a D3/3 value and D4/5 value of a wood bond according to DIN EN 204/205 of at least 4 N/mm2 and/or to provide to an adhesive formulation a heat resistance measured as WATT 91 value of a wood bond according to DIN EN 14257 of at least 6 N/mm2 and/or to provide to an adhesive formulation a long term processibility or workability, useful in various applications. The invention furthermore provides a process of making the aqueous polymer dispersion L'invention concerne une dispersion polymère aqueuse, qui peut être obtenue par copolymérisation en émulsion de monomères d'ester de vinyle (a) en présence d'alcool polyvinylique complètement hydrolysé (PVOH) (c), en utilisant des monomères (b). Selon l'invention, les monomères d'ester de vinyle (a) comprennent un premier composant (a1) constitué d'un ou de plusieurs esters de l'acide versatique et un second composant (a2) constitué d'acétate de vinyle, le ou les comonomères (b) comprennent un dérivé de (méth)acrylamide (b1) de formule générale CH2=CX-CO-NHY, dans laquelle X représente l'hydr