Flexible foamed polyurethane products

Flexible, cellular polyurethanes are prepared by reacting an alkyd resin and a diisocyanate in weight proportions between 4 : 1 and 5 : 4, the resin being made from a dicarboxylic acid, a glycol, and a polyhydric alcohol with more than two hydroxyl groups. The molar ratio of glycol to polyhydric alcohol is between 30 : 1 and 5 : 1 and the ratio of carboxyl groups to hydroxyl groups is between 1 : 1 and 1 : 2. Water may be added to the reaction mixture if there is any scarcity or absence of free carboxyl groups. Suitable reactants for the alkyd are: phthalic anhydride, fumaric acid, maleic anhydride, succinic, adipic, tartaric or malic acid; ethylene, diethylene, 1,4-butylene, 1,3-butylene, 1.2-propylene, or polyethylene glycol, hexane diol; glycerol, trimethylol propane, pentaerythritol, hexane triol. Toluylene diisocyanate is the preferred isocyanate. A cellulose derivative, e.g. ethyl cellulose or cellulose acetate butyrate may be added to control bubble growth and also accelerators, e.g. tertiary amines, or hydrolysable salts of organic acids (see Specification 770,526), e.g. sodium lactate, acetate or naphthenate. Preferably, the alkyd, water, modifier and accelerator are mixed before addition of the isocyanate. Cellulose acetate butyrate or modifier dissolves in the alkyd at 130-180 DEG C. and remains dissolved on cooling. Many examples are given, e.g. (1) An alkyd was made by condensing 1.5 mol. adipic acid, 1.5 mol. sebacic acid, 2.75 mol. diethylene glycol and 0.5 mol. glycerol until the acid number was 2. Re-heated to 150 DEG C. it dissolved 1 per cent of low viscosity cellulose acetate butyrate. 100 gms. of the resulting solution was mixed with 30 grams of toluylene diisocyanate and 2 c.cs. of 25 per cent aqueous sodium acetate to yield a light, soft, flexible foamed product. Foams with a wide variety of physical properties and good chemical resistance were prepared. By performing the reaction in a mould shaped, foamed products could be prepared. The products are useful as heat and sound insulators, vibration dampers, packaging materials, flooring underfelt, upholstery, sponges and surgical appliances. Specification 754,502 also is referred to.