Vapor-phase cure of coating compositions containing an aliphatic polyisocyanate and a tertiary amine polyahl

DETAILED DESCRIPTION OF THE INVENTION Unless otherwise stated, the numerical limitations used herein are not critical.
That is, they may be read as if prefaced with the term "about" or "substantially".
One essential component of the invention is an aliphatic polyisocyanate.
The precise character of the aliphatic polyisocyanate is not critical, and generally, any aliphatic polyisocyanate which is suitable for use in other urethane coatings will be suitable for use in the instant invention.
The polyisocyanate may be a simple aliphatic compound terminated with two or more isocyanate moieties, such as a C.
sub.
4 to C.
sub.
12, preferably a C.
sub.
5 to C.
sub.
8 diisocyanate, for example, 1,6-hexamethylene diisocyanate (1,6-diisocyanatohexane) and adducts thereof.
Another class of suitable polyisocyanates are cycloaliphatic isocyanates such as 1,3-diisocyanatomethyl-3,5,5-trimethylcyclohexane (also known as isophorone diisocyanate) and various isomers of dicyclopentadiene diisocyanate.
Another class of suitable polyisocyanates includes the biurets of aliphatic (e.
g.
, C.
sub.
4 to C.
sub.
12, especially C.
sub.
5 to C.
sub.
8) diisocyanates, such as the biuret of 1,6-diisocyanatohexane.
This class is especially preferred because of its low cost, ready availability, and excellent performance.
Yet another suitable form of the aliphatic polyisocyanate is that of a polymer of an ethylenically unsaturated isocyanate.
Suitable polymers include those of isocyanatoalkyl esters of ethylenically unsaturated carboxylic acids, especially those of 2-isocyanatoethyl methacrylate.
Furthermore, the practice of the invention includes the use of aliphatic isocyanates attached to an aromatic ring.
Isocyanate compounds having both aliphatic and aromatic character have long reaction times in conventional vapor-cure systems (similar to compounds of entirely aliphatic character), but their performance is improved in the practice of the invention, and they are within the scope of the invention.
Such compounds may be virtually any compound having an aromatic ring and more than one isocyanate moiety, where the isocyanate moieties are separated from the aromatic ring by at least one carbon atom