Curable solid polyester resins

DETAILED DESCRIPTION OF THE INVENTION Ingredients Crystalline Polyester Crystalline polyesters for use in this invention have an X-ray structure and a fairly sharp melting point.
They are solids which at room temperature are insoluble or have a low solubility (for example, up to about 5 wt.
%) in the crosslinking agent used in the composition, but which at elevated temperatures are readily soluble in the crosslinking agent.
The crystalline polyester must be soluble in the crosslinking agent at a temperature below that at which the resin would cure.
Crystalline polyesters, which contains ethylenic unsaturation that is reactable with the ethylenic unsaturation of the crosslinking agent, and processes for preparing them are well known.
For example, the crystalline polyester can be prepared by polyesterifying a symmetrical, aliphatic diol with fumaric acid, or lower alkyl esters of fumaric acid.
Maleic anhydride or maleic acid or lower alkyl esters of maleic acid may also be used in the presence of a maleatefumarate isomerization catalyst such as piperidine or iodine or any of the other known isomerization catalysts.
Mixtures of fumaric acid or its esters, with maleic anhydride or maleic acid or its esters, may be used provided that the amount of maleate present in the polyester is not large enough to prevent crystallization.
Part of the ethylenically unsaturated acid may be replaced wiith saturated dicarboxylic acids such as adipic, sebacic, isophthalic or terephthalic acid.
This will generally have the effect of reducing the melting point of the polyester, decreasing its solution temperature and increasing its solubility.
The maximum ratio of saturated acid to the ethylenically unsaturated dicarboxylic acid that can be used will be dependent on the melting point and solution temperature desired and the melting point and solubility characteristics of the polyester of the saturated acid as compared to the unsaturated polyester.
Part of the symmetrical diol may be replaced with an unsymmetrical diol such as propylene or dipropylene glycol