GB1120223A - Improvements in or relating to polyethers and polyurethanes derived therefrom - Google Patents

Abstract

The invention comprises a mixture of polyethers having a molecular weight of 1000 to 6000 and containing three or more hydroxyl groups which polyethers consist essentially of ethylene oxide and 1:2 propylene oxide residues and the residue of a polyhydric alcohol containing three or more hydroxyl groups, wherein from 4-20% by weight of the alkylene oxide residues are ethylene oxide residues, wherein at least 2% by weight of the alkylene oxide residues are ethylene oxide residues in a nonterminal position separated from a terminal block of ethylene oxide residues by a penultimate block of propylene oxide residues, and wherein from 15 to 50% of the hydroxyl groups present are primary hydroxyl groups. The mixture is prepared by (a) reacting 1,2-propylene oxide and ethylene oxide in turn or together with a polyhydric alcohol having three or more -OH groups, (b) reacting the product of step (a) with 1,2-propylene oxide and (c) reacting the product of (b) with ethylene oxide in an amount such that 15-50% of the -OH groups present are primary. Suitable polyhydric alcohols are glycerol, trimethylol propane, 1:2:6 - hexane triol, pentaerythritol, a -methyl glucoside and sorbitol. The reaction is preferably effected in the presence of an alkali metal catalyst. Polyurethanes are formed by reacting an organic polyisocyanate or polyisothiocyanate of formula R(NCX)n+1, wherein R is an organic radical, X is O or S and n is a positive integer with a mixture of polyethers according to the invention. Water and/or an auxiliary blowing agent may be incorporated into the reaction to form polyurethane foams and foam catalysts and stabilizers may also be present. Alternatively, the foams may be prepared by reacting the polyurethane prepolymer prepared as above with water in the presence of a foam catalyst and a foam stabilizer. The invention also comprises the moulding of polyurethane foams prepared as above.ALSO:A solution of a polyurethane prepolymer is used as a surface coating agent and is applied to wood, metal or leather to give clear top coats or varnishes. The solvent is preferably evaporated from the film applied to the surface to be coated. The polyurethane prepolymer (see Div. C3) is prepared from a mixture of polyethers having a molecular weight of 1000 to 6000 and containing three or more hydroxyl groups which polyethers consist essentially of ethylene oxide and 1, 2-propylene oxide residues and the residue of a polyhydric alcohol having 3 or more -OH groups, wherein from 4-20% of the alkylene oxide residues are ethylene oxide residues, wherein at least 2% of the alkylene oxide residues are ethylene oxide residues in a non-terminal position separated by a penultimate propylene oxide residue block from a terminal ethylene oxide block, and wherein 15 to 50% of the hydroxyl groups present are primary, by reactions with a polyfunctional isocyanate or isothiocyanate, and is cross-linked by the reaction of the terminal isocyanate groups with atmospheric moisture or reactive groups in the substrate.