Patent GB-795276-A (GB)
Title: Elastic foam
IPC: C08G79/02
Filed: 1956-06-11
Abstract: A process for the production of polyurethane foam comprises reacting with excess polyisocyanate and water a polyether or polythioether, which polyether or polythioether contains at least two hydroxy groups, and from 1 to 10 per cent by weight, based on the weight of the polyether or polythioether, of a tertiary amine containing at least two functional groups capable of reacting with isocyanate groups.  Preferably the reaction is carried out in two steps, in the first of which the polyether and the tertiary amine are reacted with an amount of diisocyanate less than that calculated to react with the reactive groups in the polyether and the tertiary amine (leaving 0.3 to 3 per cent of free OH groups) and in the second of which cross-linking and foaming are effected by adding water and further diisocyanate.  Alternatively the polyether and tertiary amine are reacted with excess diisocyanate and the product is cross-linked and foamed by adding water in a second stage.  As additional accelerators tertiary amines with no groups reactive with isocyanato groups can be added.  Other polymeric compounds such as hydroxypolyesters and hydrogenation products of polymeric ketones can also be added to the reaction mixture.  The hydroxypolyethers or polythioethers preferably contain ethylene, (iso)propylene or (iso)butylene groups.  The divalent groups may also be cycloaliphatic or aromatic, e.g. p-xylylene or dimethyldiphenylene methane.  The molecular weight can be in the range 500 to 3000.  Suitable are linear or branched polymers obtained by polymerization of tetrahydrofuran in the presence of acetic anhydride and perchloric acid and subsequent saponification or by copolymerization of tetrahydrofuran and epichlorhydrin in the presence of iron chloride and sulphuryl chloride and subsequent reaction with butanediol.  Hydroxy polythioethers may be those obtained by the reaction of polyhydric alcohols with thioether glycols at 100 DEG  to 300 DEG  using a dehydration catalyst.  Alternatively a compound of the formula HO-R-(S-R1)n-S-R1-XH (in which R is ethylene or propylene, R1 is a divalent organic radical which may be interrupted by hetero atoms such as O or Sn and may also be branched and have terminal XH groups, n is an integer and X is oxygen or sulphur) is self condensed or condensed with another polyhydric alcohol or thioether alcohol. Preferred tertiary amines are those of the formula R1N(ROH)2 in which R is alkylene and R1 is alkyl, cycloalkyl or a substituted radical, e.g. hydroxyethyl.  Also suitable are compounds with several tertiary amino groups such as alkoxylation products of diethylene triamine and triethylene tetramine 2,4- and 2,6-toluylene, 4,41-diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate and 4,41 - dicyclohexyl - dimethyl methane diisocyanate are specified polyisocyanates. Amine salts of fatty acids or alkali salts of turkey red oil are suitable surface-active agents.  Specified as additional accelerators are hexahydromethylaniline, diethanolamine adipic ester, sodium phenolate and iron acetonylacetone.  In Example (1) a mixture of linear tetrahydrofuran polymer with terminal OH groups and triethanolamine are reacted with mixed 2,4- and 2,6-toluylene diisocyanates.  The product, still containing free OH groups, is mixed with N-diethanolamine adipic ester, diethylamine oleate and water, followed by more of the diisocyanate mixture to give a foamed product.  In a similar manner foam products are prepared from (2) a branched polyether (obtained by copolymerization of tetrahydrofuran and epichlorhydrin and subsequent reaction with 1,4-butanediol), methyl diethanolamine, the mixed toluylene diisocyanates, N-ethylethanolamine adipic ester, diethylamine oleate; (3) and (4) a polythioether (from the condensation of equimolecular amounts of 1,4-butanediol and thiodiglycol), triethanolamine, the same mixed toluylene diisocyanates, N-diethylethanolamine adipic ester, diethyl amine oleate and water.  In Example (5) the polythioether of Example (3) mixed with a polyester from adipic acid, diethylene glycol and trimethylol propane, is stirred with a mixture of N-diethyl ethanolamine adipic ester, diethylamine oleate and water, and then with the further addition of the toluylene diisocyanate to give a foamed product.