Polyuréthanes cellulaires

A process for the preparation of a polyurethane foam comprises reacting an organic compound having at least two reactive hydrogen atoms, a molecular weight of at least 500, a hydroxyl number of not more than 225 and an acid number of not more than 10 with an organic polyisocyanate and if necessary or if desired (the latter being the case when carboxyl groups are present) a blowing agent, in the presence of a stabilizer having the formula in which R represents a monovalent alkyl radical having from 1 to 5 carbon atoms, R1 and R11 each represent hydrogen atoms or monovalent alkyl radicals having 1 to 5 carbon atoms, x is a whole number greater than 3, y is a whole number greater than 2 and n is 3 or 4. The organic compound with reactive hydrogens can be a polyether, polyester, polyesteramide, polythioether, or polyacetal. The silicon compounds can be prepared by the method of Specification 926,914. As polyisocyanates there are listed aliphatic, aromatic, alicyclic and heterocyclic di- and tri-isocyanates, including compounds with halogen, azo, sulphone and furfurylidene radicals. Suitable catalysts for the reaction are tertiary amines, alkalis such as sodium hydroxide, phenolates, alcoholates, alkaline earth metal oxides, salts of amines and organic acids tin salts, organo tin compounds, the non-basic metal compounds of Specification 769,681 and the metal catalysts disclosed in U.S.A. Specification 2,916,464. Emulsifiers, fillers, paraffin oil dyestuffs can also be used. Carbon dioxide, dichlorofluoromethane or trichloromethane can be added as blowing agents to the reaction mixture. In the examples foams are prepared from polypropylene ethers (obtained by reacting trimethylolpropane and propylene oxide), toluylene 2,4- and 2,6-diisocyanates and catalysts in the presence of (1) tris[butoxy dipropyleneoxy diethyleneoxy tri(dimethylsiloxy) methylene] propane; (2) tris(butoxy decapropyleneoxy-decaethyleneoxy hexa-(dimethylsiloxy) methylene) ethane; (3) tetra-(butoxy monopropyleneoxy-triethyleneoxy-deka(dimethylsiloxy) methylene) methane. As catalysts there are used mixtures of dimethylbenzylamine and dibutyl tin di-laurate or di-hexoate or of dibutyl tin di-laurate and permethylated aminoethyl piperazine. Specifications 769,682 and 804,369 also are referred to.ALSO:A process for the preparation of a polyurethane foam comprises reacting an organic compound having at least two reactive hydrogen atoms, a molecular weight of at least 500, a hy