An aqueous polymer dispersion wherein said polymer comprises polymerized units issued from the monomers of the following monomeric composition comprising in weight proportions per 100 parts of monomers a) +b) as defined below: a) 50 to 90 %, preferably from 60 to 80% of at least one monoethylenically unsaturated non-ionic monomer having a homopolymer with a Tg (as measured by DSC at 10°C/min) lower than 0°C, preferably lower than -20°C, preferably said monomer a) being selected in the group consisting of alkyl (meth)acrylates or vinylic monomers and their mixtures, more preferably in the group consisting of alkyl (meth)acrylates and even more preferably of alkyl acrylates, b) 10 to 50%, preferably from 20 to 40% of at least one monomer having a homopolymer Tg higher than 80°C, preferably of at least 90°C, preferably said monomer selected from vinyl aromatic monomers, more preferably selected from styrene and styrene derivatives or from methyl methacrylate or mixtures thereof, c) 1 to 5%, preferably from 1 to 4% of at least one hydroxyl-containing (meth)acrylate, preferably at least one hydroxy alkyl (meth)acrylate monomer, more preferably with said alkyl being in C2-C4 and their combinations, d) 0.1 to 3%, preferably from 0.2 to 2% of at least one acid monomer selected from: either d1) at least one acid monomer selected from a monocarboxylic acid monomer, a dicarboxylic acid monomer and their mixtures, or d2) at least one acid monomer selected from phosphorous-based or sulfur-based strong acid monomers or/and their salts, or from the mixtures of the above-defined d1) and d2), e) 0.001 to 2%, preferably from 0.001 to 1.5%, more preferably 0.005 to 1% of at least one chain transfer agent, and f) 0 to 1%, preferably from 0 to 0.5% of at least one internal crosslinker bearing at least two copolymerisable ethylenic unsaturations, preferably selected from multifunctional (meth)acrylates bearing at least two (meth)acrylic groups or from polyvinyl monomers, the said polymer having a Tg by DSC at 10°C/min from -30 to 0 °C, preferably from - 20 to 0 °C and a gel content determined by the method mentioned in the specification of 0 to 60%, preferably from 0 to lower than 55% formed during the polymerization. a) 50 to 90 %, preferably from 60 to 80% of at least one monoethylenically unsaturated non-ionic monomer having a homopolymer with a Tg (as measured by DSC at 10°C/min) lower than 0°C, preferably lower than -20°C, preferably said monomer a) being selected in the group consisting of alkyl (meth)acrylates or vinylic monomers and their mixtures, more preferably in the group consisting of alkyl (meth)acrylates and even more preferably of alkyl acrylates, b) 10 to 50%, preferably from 20 to 40% of at least one monomer having a homopolymer Tg higher than 80°C, preferably of at least 90°C, preferably said monomer selected from vinyl aromatic monomers, more preferably selected from styrene and styrene derivatives or from methyl methacrylate or mixtures thereof, c) 1 to 5%, preferably from 1 to 4% of at least one hydroxyl-containing (meth)acrylate, preferably at least one hydroxy alkyl (meth)acrylate monomer, more preferably with said alkyl being in C2-C4 and their combinations, d) 0.1 to 3%, preferably from 0.2 to 2% of at least one acid monomer selected from: either d1) at least one acid monomer selected from a monocarboxylic acid monomer, a dicarboxylic acid monomer and their mixtures, or d2) at least one acid monomer selected from phosphorous-based or sulfur-based strong acid monomers or/and their salts, or from the mixtures of the above-defined d1) and d2), either d1) at least one acid monomer selected from a monocarboxylic acid monomer, a dicarboxylic acid monomer and their mixtures, or d2) at least one acid monomer selected from phosphorous-based or sulfur-based strong acid monomers or/and their salts, or from the mixtures of the above-defined d1) and d2), e) 0.001 to 2%, preferably from 0.001 to 1.5%, more preferably 0.005 to 1% of at least one chain transfer agent, and f) 0 to 1%, preferably from 0 to 0.5% of at least one internal crosslinker bearing at least two copolymerisable ethylenic unsaturations, preferably selected from multifunctional (meth)acrylates bearing at least two (meth)acrylic groups or from polyvinyl monomers, the said polymer having a Tg by DSC at 10°C/min from -30 to 0 °C, preferably from - 20 to 0 °C and a gel content determined by the method mentioned in the specification of 0 to 60%, preferably from 0 to lower than 55% formed during the polymerization.