GB798209A - Process for the production of high molecular weight polyurethane plastics - Google Patents

Abstract

A process for the production of a high molecular weight polyurethane plastic comprises reacting a polyisocyanate with a polyhydroxy compound obtained by the condensation of an aldehyde with a polyalcohol which does not form cyclic acetals with formaldehyde. The condensation of the aldehyde and the polyalcohol is preferably effected in an organic solvent with azeotropic distillation of the water formed. As aldehydes there may be used formaldehyde, which gives acetals with the grouping -O-CH2-O-; other aldehydes such as acetaldehyde, benzaldehyde, crotonaldehyde or b -ethyl-a -methyl acrolein give acetals with the grouping -O-CHR-O in which R represents an aliphatic or aromatic hydrocarbon radical which can be unsaturated and/or branched. Suitable polyalcohols are hexanediol, butane - bis - b - hydroxyethyl ether (HOCH2CH2OC4H8OCH2CH2OH), trimethylol propane dihydroxyethyl ether and di-, tri- and polyethylene glycols. Also suitable are aromatic polyalcohols obtained by the reaction of aromatic polyhydroxy compounds with glycol chlorhydrin, for example compounds of the formul <FORM:0798209/IV (a)/1> Also suitable are polyesters, polyethers and polythioethers containing hydroxyl groups, and monomeric glycols containing carbonamide and urethane groups, for example adipic acid diethanolamide and hexamethylene - b - dihydroxyethyl urethane. As polyisocyanates there may be used hexamethylene, toluylene, 1,5-naphthylene and diphenylmethane diisocyanates, diisocyanates with urethdione groups, reaction products of an excess of diisocyanate with polyvalent alcohols (including the specified polyalcohol/aldehyde condensates) or polyesters and masked polyisocyanates. The reaction may be effected using excess polyisocyanate and with simultaneous or subsequent reaction with water (which gives foamed products), glycols, polyamines or aminoalcohols. Alternatively, the reaction is initially effected with a smaller amount of diisocyanate than that equivalent to the OH groups in the condensate, suitably with methyl diethanolamine or triethanolamine as catalyst, and the products, still containing free OH groups, are then reacted with additional polyiso-cyanates, if necessary with the use also of the specified cross-linking agents. In examples: (1) butanediol-1,4-dimethylmethanediphenyl - 4,41 - bis - b - dihydroxyethyl ether and paraformaldehyde are heated in benzene in the presence of p-toluenesulphonic acid to give a polyacetal. This is reacted with N-methyldiethanolamine, triethanolamine and tolulyene diisocyanate. The product obtained (of hydroxyl number 54) is mixed with an aqueous mixture of oleic acid and N-diethyl diethanolamine and then with toluylene diisocyanate to give a foamed product; (2) a condensation product from butanediol and paraformaldehyde is mixed with butanediol and trimethylol propane and reacted with toluylene diisocyanate. The product (of hydroxyl number 49) is converted to a foam by adding an aqueous mixture of oleic acid and N-diethylethanolamine and then mixing in toluylene diisocyanate; (3) a condensation product from butane-dihydroxyethyl glycol, naphthalene-1,5-b -dihydroxyethylether and paraformaldehyde is reacted with toluylene diisocyanate to give a product of hydroxyl number 47 which is converted to a foam by reaction with water and toluylene diisocyanate in the presence of diethylamine oleate and an ester of adipic acid and N-diethyldiethanolamine; (4) a condensation product of hydroxyl number 190 from trihydroxyethyl trimethylol propane, dimethyldiphenylmethane - 4,41 - di - b - hydroxyethyl ether and paraformaldehyde is mixed in ethyl acetate solution with a triisocyanate prepared by reacting one mol. of trimethylol propane with three mols. of toluylene diisocyanate and the mixture is coated on to plates; (5) a condensation product of hydroxyl number 56 from butane - dihydroxyethyl glycol, dimethylmethanediphenyl - 4,41 - bis - p - hydroxyethyl ether and formaldehyde is dehydrated and then heated with 1,5-naphthylene diisocyanate. The product is heated further with butanediol and the melt is poured into moulds and heated to give an elastomer.