Ambient or low-temperature curable coatings

An ambient or low-temperature curable polymer composition adapted to coat a rigid substrate comprising:

• a. a polymer polymerized from a monomer mixture comprising (1) from about 0.25% to about 35% by weight of a polymerizable aldehyde, and (2) at least one copolymerizable mono-ethylenically unsaturated monomer selected from the group consisting of .alpha.,.beta.-ethylenically unsaturated carboxylic acid, (C.sub.1 -C.sub.24)alkyl methacrylates, (C.sub.1 -C.sub.24)alkyl acrylates, vinylidene halides, vinyl halides, (meth)acrylonitrile, vinyl esters, ethylene and alpha-olefins, acrylic and methacrylic acid esters of alcohol-ethers, vinyl ether, styrene and alkyl-substituted styrenes and vinyl aromatics, the combination of monomers being selected to provide a T.sub.g of the polymer of greater than about 0.degree. C.;
• and
• b. a curing agent comprising a member selected from the group consisting of a dicarboxylic acid bis-hydrazide represented by the formula, H.sub.2 N--NH--C(O)--R--C(O)--NH--NH.sub.2, and a dicarboxylic acid bis-hydrazone represented by the formula R.sup.1 R.sup.2 C.dbd.N--NH--C(O)--R--C(O)--NH--N.dbd.CR.sup.1 R.sup.2, and acrylic oligomers and low molecular weight acrylic solution polymers containing a plurality of pendant hydrazide groups of the formula --C(O)--NH--NH.sub.2 or hydrazone groups of the formula --(O)--NH--N.dbd.CR.sup.1 R.sup.2, wherein R is a member selected from the group consisting of a divalent alkylene group or alicyclic group having from 0 to 34 carbon atoms and a divalent aromatic ring and R.sup.1 and R.sup.2 are selected from the group consisting of H and (C.sub.1 -C.sub.6) alkyl and alicyclic groups, the amount of hydrazide or hydrazone compound being selected to provide a ratio of hydrazide or of hydrazone groups to aldehyde groups of the polymer in the dispersion of from about 1:2 to 2:1.