Oligocarbodiimides for the formation of crosslinked latex films

A curable composition curable thermally and by UV radiation comprising a carbodiimide and a film-forming water-dispersible polymer, wherein the carbodiimide comprises a reaction product of

• a) at least one of an aliphatic C4 to C20 polyisocyanate and an araliphatic C4 to C20 polyisocyanate,
• b) at least one of a mono-hydroxyl-functional carboxylic acid and a mono-hydroxyl-functional carboxylic salt,
• c) optionally, a further compound carrying groups able to react with isocyanate groups in an addition reaction,
• d) optionally, at least one other isocyanate, and
• carbodiimide units in the carbodiimide being derived essentially exclusively from the isocyanate groups of component a), wherein the carbodiimide is represented by the structure
• R1—CO—NH—X—N═C═N—X—[—N═C═N—X—]n—NH—CO—R2
• wherein X is at least one of an aliphatic hydrocarbon radical having 4 to 12 carbon atoms, a cycloaliphatic hydrocarbon radical having 6 to 15 carbon atoms, and an araliphatic hydrocarbon radical having 7 to 15 carbon atoms;
• n is an integer from 0 to 10;
• and R1 and R2 are radicals derived from component b) by abstraction therefrom of a hydrogen atom attached to a hydroxyl group, wherein the carbodiimide is free from units derived from macropolyols having a molecular weight of more than 400, and
• the water-dispersible film-forming polymer comprises a reaction product of an ethylenically unsaturated carboxylic acid and at least one of a C1 to C20 alkyl (meth)acrylate, a vinyl ester of a carboxylic acid containing up to 20 carbon atoms, a vinyl aromatic compound having up to 20 carbon atoms, an ethylenically unsaturated nitrile, a vinyl halide, an aliphatic hydrocarbon having 2 to 8 carbon atoms and 1 or 2 double bonds, and a free-radically polymerizable monomer and the polymer comprises carboxylic acid groups in amounts of from 0.01 to 2 mol/kg and
• wherein, under cure conditions, the carbodiimide undergoes a crosslinking reaction with the carboxylic acid to form acylurea groups.