HIGH-SOLIDS NONAQUEOUS DISPERSION COATINGS BASED ON CRYSTALLINE OLIGOESTERS

Nonaqueous dispersions (NADs) of a crystalline oligoester diol were pr epared by crystallization in a medium consisting of amorphous diol, re active diluent (RD), and a solvent. The crystalline diol (6GT) was pre pared from terephthalic acid and 1,6-hexanediol; RD was prepared from terephthalic acid and glycidyl neodecanoate. The dispersions are opaqu e, thixotropic liquids with low viscosities at solids of 60-70 wt%. X- ray and calorimetry studies show that the dispersed particles are crys talline. Microscopy shows that they have a narrow distribution of diam eters, varying from 5 to 20 mum depending on process conditions. When formulated with crosslinkers (melamine or isocyanate resins) and baked at temperatures above the melting point of the crystalline diol, thes e NADs gave transparent coatings. Glossy pigmented coatings were also prepared. As high-solids coatings, these materials provide excellent a pplication properties (resistance to sagging) and a good balance of fi lm physical properties. While some of the formulated coatings stratify on standing, they can be restored to homogeneous, free-flowing liquid s by stirring gently.