Stabilization of polyaddition products of polyhydroxyl compounds, polyisocyanates and hydrazine, hydrazine - derivatives and / or hydrazine compounds against discoloration

摘要

Polyurethanes containing no free NCO groups and prepared from polyhydroxy compounds, polyisocyanates and hydrazine and/or hydrazide compounds are protected against discoloration by adding to a solution of the polyurethane in an organic polar solvent that can form hydrogen bonds, a solution containing from 0.01 to 5%, based on the weight of polyurethane, of a salt or salts of tin and/or antimony and/or beryllium in a polar solvent. The following salts may be used singly or in admixture: stannous chloride, acetate, octoate, stearate, trichloracetate, formate and dibutyltin dilaurate and salts of formula Sn2O(CH3COO)2, SnO(CH3COO)2, SnCl2(CH3COO)2, Na2[Sn(CH3COO)6], SbCl3, SbOCl, SbCl5, Be(NO3)2, BeSO4, BeCl2, (CH3COO)2Be, and antimonyl potassium oxalate. Polar solvents specified are: water, dimethyl formamide, hexamethylene phosphoramide, dimethyl sulphoxide, N-methyl pyrrolidone and dimethyl acetamide. The polyurethanes may be prepared from: polyesters, polyesteramides, polyethers, polythioethers, polycarbonates and polyacetals having a linear structure. Many substituted hydrazines and hydrazides are listed. In examples: (1) a propolymer derived from toluylene diisocyanate and polyethylene adipate in solution in chlorobenzene and dimethyl formamide was reacted with carbodihydrazide and 0.2% of SnCl2.2H2O, SbCl3 or Be(NO3)2.3H2O added in dimethylformamide, (3) sulphur dioxide was added to a polyester derived from adipic acid, ethylene glycol and butylene-1,4-glycol, followed by diisocyanate, hydrazine hydrate and solutions of SnCl2 and Be(NO3)2. Specifications 917,450 and 972,029 are referred to.