A polyol is an alcohol that contains a plurality of hydroxyl groups, and includes diols such as the glycols (dihydric alcohols) ethylene glycol, propylene glycol and trimethylene glycol; triols such as glycerin (1,2,3-propanetriol); and polyhydroxy or polycarboxylic acid compounds such as tartaric acid or ascorbic acid (vitamin C): ##STR7## Hydroxy acid binders are acids that contain a hydroxyl gr