GB773991A - Improvements in and relating to the production of polymeric materials from bifunctional polyisocyanates and polyesters, polyesteramides and polyethers - Google Patents

Abstract

Polyesters, polyesteramides and polyethers are reacted with an excess of polyisocyanates in the presence of stabilisers which are tertiary alcohols, secondary aromatic amines, mercaptans, monohydric phenols, imides or compounds containing enolisable hydrogen. The polyester &c. should have a molecular weight greater than 1000 and not more than 0.5 mol. of stabiliser should be present per mol. of polyisocyanate. As polyisocyanates diisocyanates may be used or compounds containing more than two isocyanate groups provided that they react in a predominantly bifunctional manner. The products, which may be cellular or solid, may be cured by heating in the presence of a basic catalyst or a polyfunctional compound reactive with isocyanate groups, e.g. water, and compounds containing a plurality of hydroxyl, amino and/or carboxyl groups. Such water may be present, fortuitously taken up from the air, or acquired by steam treatment. Some of the stabilizers form adducts with the polyisocyanate which dissociate at the higher temperatures at which the cure takes place. The stabilizer enables the uncured polymer to be stored for long periods of time, preferably out of contact with air. The polyester &c.-polyisocyanate reaction may be retarded by the presence of acidic substances. The curing reaction is accelerated by the use, as stabilizer, of succinimide or 2-mercaptobenzothiazole. The stabilized materials are in general soluble and may be used in varnishes as well as for moulding. For extrusion some cross-linking may be present. In examples: (1) 3 parts succinimide were added at 130 DEG C. to 100 parts polyethylene adipate of molecular weight 1700 and 15.4 parts naphthalene diisocyanate added and stirred for 15 minutes. The mixture was cast as a sheet and stored for two weeks, retaining its solubility in chloroform, and was then cross-linked by heating for 10 minutes at 150 DEG C. A similar material but without succinimide became insoluble after 6 days and could not then be moulded. (2) Similar to (1) but with the addition of cobaltous chloride hexahydrate to provide water for cross-linking. (3) 2.4 parts diphenylamine and 14.4 parts 1.5 naphthalene diisocyanate were heated to 140 DEG C. and added at 130 DEG C. to 100 parts dry polyethylene adipate of molecular weight 1800, the mix being then cast and heated at 100 DEG C. for 16 hours. The product was soluble and could be moulded after storing for 10 days by pressing for 1 hour at 160 DEG followed by baking at 150 DEG C. for 7 hours. (4) Similar to (1) but using mercaptobenzthiazole instead of succinimide. (5) Similar to (1) but using tertiary amyl alcohol. (6) Similar to (1) but using phenol. (7) Similar to (1) but using acetylacetone.