GB947483A - Non-linear polyurethane prepolymers and methods of forming polyurethane foam therefrom - Google Patents

Abstract

A non-linear polyurethane prepolymer adapted for foam formation comprises the reaction product of an aliphatic or aromatic diisocyanate with a hydroxyl-terminated ployether, said polyether having a molecular weight of from 200 to 7500 and being formed by interaction of an alkylene oxide with a polyhydric alcohol having at least four hydroxyl groups said diisocyanate being present in a stoichiometric excess corresponding to a free -NCO content of from 8% to 30%. The prepolymer can be converted to a foam by reaction with compounds having active hydrogen atoms, such as water or a polyether. A volatile physical foamant may also be present in the reaction mixture suitable polyhydric alcohols a pentaerythritol, i-erythritol, adonitol, oxylitol, arabitol, mannitol, sorbitol, dulcitol, iditol, perseitol, volemitol, glucose, fructose, bioses, dipentaerythritol, 2,2 - dimethylol - 1,5 - dihydroxypentane and 1,3,6,9,12 - pentahydroxy dodecane. Alkylene oxides referred to are ethylene and propylene oxides. Oxygen atoms may be replaced by sulphur atoms, and aryl, cycloaliphatic, chloroformate and butene groups may be present. Diepoxy compounds may also be used. In the prepolymer there may be incorporated antioxidants, stabilizing and emulsifying agents, acceleratiors, dyestuffs, fillers, softeners, titanium dioxide, carbon black, sulphur or sulphur-containing materials; The prepolymers can be used also in the preparation of coatings which can be air-dried in the presence of a catalyst such as a tertiary amine. In example (1) a prepolymer from a pentaerythritol propylene oxide condensate and toluene - 2,4 - diisocyanate is converted to foam by reaction with water, more polyetherpentaerythritol, siloxane and triethylenediamine; (3) sorbitol/polypropylene oxide condensate is used in a similar process.