Aluminium derivatives as stabilisers for polyurethane foam manufacture

A process for the preparation of polyurethane foams by reaction of conventional hydroxy containing polymers and polyisocyanates, in the presence of a foaming agent, is characterised by the presence in the reaction mixture of the product of a reaction between an aluminium alkoxide, a carboxylic acid, a polyoxyalkylene alcohol, and, optionally, at least one other hydroxy compound. Preferred aluminium alkoxides are those derived from secondary alcohols, such as sec. butanol; suitable carboxylic acids may be aliphatic, aromatic, or substituted aromatic acids. Poly-alkylene alcohols include hydroxy ended polymers and copolymers of cyclic oxides such as ethylene-and propylene-oxide, with compounds having a single hydrogen atom reactive to cyclic oxides, e.g. butanol, isooctanol, or having two or more such hydrogen atoms. Preferred polyoxyalkylene alcohols are those with a single hydroxyl end group. As optional second hydroxy compounds may be used: phenols, aromatic or aliphatic substituted or unsubstituted alcohols; primary, secondary or tertiary straight or branched chain, or cyclic alcohols, polyfunctional hydroxyl compounds, and hydroxy compounds derived from naturally occurring oils and fats. The preferred compounds are higher aliphatic alcohols. The proportions of the above reactants used per 1 mole of appropriate aluminium alkoxide may vary from 0.5-2.0 moles carboxylic acid, and 0.1-2.0 moles of total hydroxy compounds, the proportions being such that the total acid plus -OH compound is from 1-3 moles/1 mole aluminium alkoxide; preferred quantities are: acid, 0.6-1.2 moles; -OH compounds, 0.7-1.4 moles; total 1.5-2.5 moles, per 1 mole of aluminium alkoxide. The aluminium alkoxides may be prepared by known methods, such as primary heating of all the reactants together to a suitable temperature, to drive off lower boiling point alcohols, followed by stronger heating to effect further condensation. Polyurethane foam preparation is by conventional procedure, using such components as are already employed in the art, as suitable polyethers, polyesters or their amides, with organic polyisocyanates, and water and/or fluorinated alkanes as blowing agents, in the presence of 0.01%-5%, preferably 0.25%-2% of the aluminium derivatives, based upon the weight of the hydroxy components of the polyurethane reaction mixture. The aluminium derivatives act as foam stabilizers, where they prevent collapse and consequent loss of gas of the prepolymerized foam. They are partic