Coating compositions from polyurethanes containing a molecular sieve of the sodium aluminum silicate type

A process for preparing substantially solvent-free fast low temperature curing coating compositions with long shelf-life comprising

• (a) forming hydroxyl bearing prepolymer from:
• (i) a polyisocyanate,
• (ii) about 50 to 85 wt.%, based on the weight of ii to v, of a branched polyether having an average hydroxyl functionality of between about 2.5 and 3.0 and a Mn of between about 2000 and 4000,
• (iii) about 0 to 10 wt.%, based on the weight of ii to v, of a polyester polyol having a Mn of between about 500 and 2000,
• (iv) about 10 to 30wt.%, based on the weight of ii to v, of a glycol having a molecular weight of between about 62 and 250, and
• (v) about 0.5 to 5 wt.%, based on the weight of ii to v, of a compound containing at least two primary or secondary amino groups,
• said polyisocyanate being present in sufficient quantity to give a NCO to achieve hydrogen ratio of between about 0.25 and 0.65,
• (b) combining said prepolymer either before or after its synthesis with
• (i) about 1 to 4 wt.%, based on the weight of said prepolymer, of a molecular sieve of the aluminum silicate type, and
• (ii) about 0.1 to 5 wt.%, based on the weight of said prepolymer of a catalyst for isocyanate addition reactions, and
• (c) after synthesis of said prepolymer mixing it with about 5 to 30 wt.%, based on the weight of prepolymer and this component, of a polyisocyanate having a melt point above about 100.degree. C.