| 摘要 |
Polyurethanes are formed by reacting an organic di-isocyanate with a polyalkylene ether glycol and/or a hydroxyl-terminated polyester to produce an isocyanate-terminated polyurethane prepolymer and chain extending the resultant prepolymer by reacting it with a mixture of 5 to 50 mole per cent of a compound (A) of the formula H2N-R-NR1-R-NH2, wherein R is an alkylene group and R1 is an alkyl group, both R and R1 having 1 to 4 carbon atoms, and 95 to 50 mole per cent of a compound (B) containing two active hydrogen atoms each of which is bonded to a different aminonitrogen atom, compound (B) being different from compound (A), in order to obtain a substantially linear polyurethane having a molecular weight of 5000 to 300,000 which is soluble in dimethylformamide. Many polyester-forming reactants, polyalkylene ether glycols, and organic di-isocyanates are specified. Compounds (A) specified are N-methylaminobispropylamine, N - butylaminobispropylamine and N - methylaminobispropylamine and compounds (B) are hydrazine hydrate; monosubstituted hydrazines; 2,5-dimethylpiperazine; 4 - methyl - m - phenylenediamine; m - phenylenediamine; 4,41 - diaminodiphenylmethane; 1,4-diaminopiperazine and ethylenediamine. When compound (B) is not hydrazine the prepolymer must be added to the chain extender. The polyurethanes may be compounded with pigments, ultraviolet light screening agents and antioxidants. Specification 919,500 is referred to.ALSO:Vapour-permeable sheet material is prepared by applying to a porous, fibrous, flexible substrate, a layer of a solution of a polyurethane polymer formed by reacting an organic di-isocyanate with a polyalkylene ether glycol and/or a hydroxyl-terminated polyester to produce an isocynate terminated prepolymer and effecting chain extensions of the prepolymer by reacting it with a mixture of 5-50 mole per cent of a compound of the formula:- H2N-R-NR1-R-NH2 wherein R is an alkylene group and R1 an alkyl group, both R and R1 having 1-4 carbon atoms, and 95-50 mole per cent of a different compound containing two active hydrogen atoms each of which is bonded to a different amino-nitrogen atom (see Division C3), in an organic solvent therefor which is miscible with an inert liquid, bathing the layer with the inert liquid to coagulate it, render it microporous and to remove most or all of the organic solvent therefrom and drying the material obtained. In examples, a non-woven fabric obtained by needle-punching, heat-shrinking and impregnating with a hydrazine-extended polyurethane elastomer a batt of poly(ethylene terephthalate) fibres is coated, using a doctor-blade, with a solution consisting of a polyurethane elastomer as hereinbefore defined polyvinyl chloride and dimethylformamide. The coated fabric is immersed in water, removed, steamed and then dried at 100 DEG C. The coating solution may have had water added to give a colloidal dispersion. The products are useful as leather replacements in the manufacture of shoe uppers and garments. Specification 919,500 is referred to. |
