GB802189A - Process for the production of rubber-like polyurethane plastics of high molecular weight - Google Patents

Abstract

A process for the production of rubber-like polyurethanes comprises reacting a linear condensation or polymerization product containing free terminal hydroxyl groups and having a molecular weight above 1000 with a dimeric diisocyanate and a cross-linking agent having a molecular weight below 1000 at a temperature lower than that required to split the dimeric dissocyanate into the corresponding monomeric diisocyanate. The process can be carried out in one embodiment by reacting the linear condensation or polymerization product with an amount of the dimeric diisocyanate sufficient to provide an excess of free NCO groups over the hydroxyl groups in the condensation or polymerization product, and the product obtained is reacted with the cross-linking agent in an amount of 1 to 10 per cent by weight based on the weight of the condensation or polymerization product. In another embodiment the linear condensation or polymerization product is reacted with an amount of the dimeric diisocyanate insufficient to react with all the hydroxyl groups and the product obtained is reacted with the cross-linking agent and with a further amount of the dimeric diisocyanate. Suitable compounds with terminal hydroxyl groups are hydroxypolyesters obtained by esterifying, for example, adipic and phthalic acids with, for example, glycol, diethylene glycol, propylene glycol and butylene glycol-1,3 or -1,4. Also suitable are polymerization products of alkylene oxides and condensation products of glycols with themselves or thiodiglycols. Specified cross-linking agents are diamines, such as o-dichloro-benzidine and 2,5-dichloro-p-phenylene diamine, diand trihydric alcohols such as butanediol-1,3 or -1,4, trimethylol propane, quimtol, tetra- and pentabutylene glycols, hydroxypolyesters and hydroxypolyethers. Suitable dimeric diisocyanates are dimerization products of 2,4-toluylene diisocyanate, chloro-p-phenylene diisocyanate and 1-ethylbenzene-2,4-diisocyanate. In examples: (1) a glycol/adipic acid hydroxypolyester is reacted at 130-140 DEG C. with excess dimeric 2,4-toluylene diisocyanate, butane-1,4-diol is mixed in and the melt poured into moulds. Reaction is completed by heating the mouldings at 100 DEG C.; (2) a similar process is employed, using a mixture of tetra- and pentabutylene glycols as cross-linking agent; (3) in a similar process water is used as the cross-linking agent. Specifications 700,608 and 700,609 are referred to.