Coating composition

An aqueous coating composition comprising a multi-aziridine compound and a carboxylic acid functional polymer, wherein

• (i) the aqueous coating composition is an aqueous dispersion having a pH ranging from 8 to 14,
• (ii) the aqueous dispersion comprises particles X which particles X comprise multi-aziridine compound and particles Y which particles Y comprise carboxylic acid functional polymer, whereby the carboxylic acid functional polymer contains carboxylic acid groups and/or carboxylate groups, and
• (iii) said multi-aziridine compound has:
• a) from 2 to 6 of the following structural units A:
• whereby
• R1 is H,
• R2 and R4 are independently chosen from H or an aliphatic hydrocarbon group containing from 1 to 4 carbon atoms,
• R3 is an aliphatic hydrocarbon group containing from 1 to 4 carbon atoms,
• m is an integer from 1 to 6,
• R′ and R″ are according to (1) or (2):
• (1) R′=H or an aliphatic hydrocarbon group containing from 1 to 14 carbon atoms, and
• R″=an aliphatic hydrocarbon group containing from 1 to 14 carbon atoms, a cycloaliphatic hydrocarbon group containing from 5 to 12 carbon atoms, an aromatic hydrocarbon group containing from 6 to 12 carbon atoms, CH2—O—(C═O)—R′″, CH2—O—R″″, or CH2—(OCR′″″HCR′″″H)n—OR″″″, whereby R′″ is an aliphatic hydrocarbon group containing from 1 to 14 carbon atoms and R″″ is an aliphatic hydrocarbon group containing from 1 to 14 carbon atoms or an aromatic hydrocarbon group containing from 6 to 12 carbon atoms, n being from 1 to 35, R′″″ independently being H or an aliphatic hydrocarbon group containing from 1 to 14 carbon atoms and R″″″ being an aliphatic hydrocarbon group containing from 1 to 4 carbon atoms,
• (2) R′ and R″ form together a saturated cycloaliphatic hydrocarbon group containing from 5 to 8 carbon atoms,
• t is an integer from 0 to 3,
• R5 is H or CH3,
• X and Y are according to (I), (II) or (III):
• (I) X and Y are both N—R6;
• (II) X is O and Y is N—R6;
• (III) X is N—R6 and Y is O,
• whereby R6 is H or a linear or branched hydrocarbon group containing from 1 to 4 carbon atoms;
• b) one or more linking chains wherein each one of these linking chains links two of the structural units A, whereby a linking chain is the shortest chain of consecutive atoms that links two structural units A;
• and
• c) a calculated molecular weight in the range from 500 to 10000 Daltons, wherein the calculated molecular weight is the sum of the atomic masses of all atoms present in the structural formula of the multi-aziridine compound.