GB1005852A - Foamed polyurethanes - Google Patents

Abstract

A foamed polyurethane is produced by interacting an organic polyisocyanate with water and a polyether containing at least 2 hydroxyl groups per molecule which is the reaction product of a polyalkylene glycol and an aromatic polycarboxylic acid having at least 3 carboxyl groups per molecule or its ester, chloride or anhydride. The polyether may be prepared at an elevated temperature under an inert atmosphere and in the presence of a catalyst, e.g. tetrabutyl-orthotitinate. The number of hydroxyl groups present per carboxyl group may be 0.01-0.6 for tricarboxylic acids and 0.01-0.5 for tetra-carboxylic acids. Specified acid are trimellitic, trimeric and pyromellitic. Mixtures may be used. Specified polyalkylene glycols may be prepared from one or more cyclic oxides, e.g. ethylene, propylene or butylene oxides, tetrahydrofuran or oxacyclobutane, using a catalyst, e.g. KOH, in the presence of an initiator having two active hydrogen atoms, e.g. water or diethylene glycol. Polyisocyanates specified for polyurethane formation are: hexamethylene diisocyanate, tolylene-2,4 and 2,6-diisocyanates, diphenylmethane - 4,41 - diisocyanate, 3 - methyldiphenylmethane - 4,41 - diisocyanate, m- and p-phenylene diisocyanates, chlorophenylene - 2,4 - diisocyanate, dicyclohexylmethane diisocyanate, 2,4,6-triisocyanatotoluene, 2,4,41 - triisocyanatodiphenyl ether and isocyanurate trimers and uretdione dimers of tolylene - 2,4 and 2,6 - diisocyanates. Mixtures of isocyanates may be used. 1-10% water is used. Other additives may be: catalysts, e.g. tertiary amines, iron and manganese acetylacetonates, dibutyltin dilaurate, and stannous octoate; surface-active agents, e.g. oxyethylated phenols and fatty alcohols, sulphonated methyl oleate, alkyl and aryl polysiloxanes and siloxane-oxy-alkylene copolymers, flame retardants, e.g. tri-b -chloroethyl phosphate and antimony oxide, plasticizers, e.g. tricresyl phosphate and dioctyl phthalate, colouring, fillers, e.g. carbon black, and silica, colour stabilizers, whitening agents and antioxidants, e.g. tert-butyl catechol and sterically hindered phenols. In Example (1) a polyether prepared by interacting polypropylene glycol and trimellitic acid under nitrogen in the presence of tetraorthobutyl titinate, was treated with water and tolylene-2,4 and 2,6-diisocyanate in the presence of 4-dimethylaminopyridine, dimethylbenzylamine, stannous octoate and a siloxane-oxyalkylene block copolymer. The reactants were allowed to foam in a mould. In Example (2) the carboxyl derivative used was pyromellitic dianhydride.