Isocyanate-modified epoxy-functional polyester

A modified epoxy functional polyester produced by reacting epihalohydrin in the presence of a base, with at least one carboxyl functional polyester resin (II) produced by reacting:

• (a) at least one aromatic, aliphatic or cycloaliphatic dicarboxylic acid A comprising two aromatic or secondary aliphatic carboxyl groups;
• or the anhydride thereof;
• (b) at least one diol compound B comprising two aliphatic hydroxyl groups, which are independently a primary or a secondary hydroxyl group;
• optionally,
• (c) compound C1 comprising one monofunctional primary or secondary hydroxyl group and/or at least one compound C2 comprising one primary or secondary hydroxyl group and one tertiary aliphatic carboxyl group;
• optionally
• (d) a dihydroxymonocarboxylic acid D comprising a tertiary aliphatic carboxyl group and two aliphatic hydroxyl groups, which each independently are a primary or secondary hydroxyl;
• and optionally,
• (e) a trihydroxyalkane (E1) or tetrahydroxyalkane (E2),
• the molar ratio of compounds A:B:C1:C2:D:E1:E2 being
• (X+Y+1):X:M:N:Y:Z:Q
• wherein M+N is in the range of from 0 to 2, X ranges from 2 to 8 and Y ranges from 0 to 8, Z ranges from 0 to 2 and Q ranges from 0 to 2, at a temperature of from 100 to 220° C. until a predominant part of the non-tertiary carboxyl groups initially present in the reaction mixture have been reacted, thereby producing an epoxy-functional polyester (III) having an epoxy group content of from 500 to 3000 and a number average molecular weight Mn of from 500 to 10,000, and subsequently reacting said epoxy functional polyester (III) with an isocyanate (IV), in a molar ratio of III:IV such that at least all the present terminal hydroxyl groups are reacted.