Polyester resin carrying at least two functional groups from hydroxyl and/or carboxyl, characterized in that it has a branched structure and has, as components: A) a polyol component comprising: a1) at least one C 3 to C 6 diol carrying at least two C 2 to C 4 alkyl side substituents, in particular with said alkyls being different, said diol preferably being a C 3 or C 4 diol, a2) at least one C 3 to C 6 diol carrying at least one methyl side substituent, in particular two methyl side substituents, said diol preferably being a C 3 or C 4 diol, a3) at least one linear C 2 to C 6 diol, carrying no (alkyl) side substituent, a4) at least one polyol of functionality > 2 and preferably of functionality 3 or 4, more preferentially of 3, and B) a polyacid component comprising: b1) at least one aromatic diacid or its anhydride, preferably representing from 20% to 75% by weight of said resin, b2) at least one linear C 4 to C 10, preferably C 4 to C 8, aliphatic diacid, b3) optionally a cycloaliphatic diacid, preferably with the b1/b2 molar ratio ranging from 1/1 to 4/1, said resin being devoid of any unsaturated fatty monoacid and of any unsaturated fatty monoalcohol and having a glass transition temperature, measured by DSC at 10°C/min, from -10°C to 50°C, preferably from 0°C to 30°C, and a (calculated) Mn ranging from 500 to 10000, said resin having a hydroxyl number ranging from 10 to 200 mg KOH/g, said diol a1) representing from 5% to 15% by weight of said resin. A) a polyol component comprising: a1) at least one C 3 to C 6 diol carrying at least two C 2 to C 4 alkyl side substituents, in particular with said alkyls being different, said diol preferably being a C 3 or C 4 diol, a2) at least one C 3 to C 6 diol carrying at least one methyl side substituent, in particular two methyl side substituents, said diol preferably being a C 3 or C 4 diol, a3) at least one linear C 2 to C 6 diol, carrying no (alkyl) side substituent, a4) at least one polyol of functionality > 2 and preferably of functionality 3 or 4, more preferentially of 3, and a1) at least one C 3 to C 6 diol carrying at least two C 2 to C 4 alkyl side substituents, in particular with said alkyls being different, said diol preferably being a C 3 or C 4 diol, a2) at least one C 3 to C 6 diol carrying at least one methyl side substituent, in particular two methyl side substituents, said diol preferably being a C 3 or C 4 diol, a3) at least one linear C 2 to C 6 diol, carrying no (alkyl) side substituent, a4) at least one polyol of functionality > 2 and preferably of functionality 3 or 4, more preferentially of 3, B) a polyacid component comprising: b1) at least one aromatic diacid or its anhydride, preferably representing from 20% to 75% by weight of said resin, b2) at least one linear C 4 to C 10, preferably C 4 to C 8, aliphatic diacid, b3) optionally a cycloaliphatic diacid, preferably with the b1/b2 molar ratio ranging from 1/1 to 4/1, said resin being devoid of any unsaturated fatty monoacid and of any unsaturated fatty monoalcohol and having a glass transition temperature, measured by DSC at 10°C/min, from -10°C to 50°C, preferably from 0°C to 30°C, and a (calculated) Mn ranging from 500 to 10000, said resin having a hydroxyl number ranging from 10 to 200 mg KOH/g, said diol a1) representing from 5% to 15% by weight of said resin. b1) at least one aromatic diacid or its anhydride, preferably representing from 20% to 75% by weight of said resin, b2) at least one linear C 4 to C 10, preferably C 4 to C 8, aliphatic diacid, b3) optionally a cycloaliphatic diacid, preferably with the b1/b2 molar ratio ranging from 1/1 to 4/1, said resin being devoid of any unsaturated fatty monoacid and of any unsaturated fatty monoalcohol and having a glass transition temperature, measured by DSC at 10°C/min, from -10°C to 50°C, preferably from 0°C to 30°C, and a (calculated) Mn ranging from 500 to 10000,