GB971171A - Foamed polyurethane resins having low moisture vapor transmission - Google Patents

Abstract

Polyurethane foams are manufactured by reacting a polyoxyalkylene polyol urethane prepolymer having at least two isocyanate groups per molecule with a polyoxyalkylene polyol cross-linking agent in the presence of a catalyst, a volatile organic blowing agent and a hydrophobic polyoxyalkylene glycol or polyoxyalkylene glycerol emulsifier for the reactants, which emulsifier is added to the reaction mixture just prior to carrying out the foaming reaction in a proportion to provide a foam of the required cell size. The emulsifier may be a polyoxypropylene glycol having a molecular weight of at least 2000, a polyoxybutylene glycol having a molecular weight of at least 1000, a tris(hydroxypolyoxypropylene) ether of glycerol, a higher polyoxyalkylene glycol in which the alkylene radicals contain 4 to 7 carbon atoms or their ethers e.g. their methyl, ethyl, butyl, octyl, dodecyl, isobutyl, sec-amyl, t-butyl, phenyl, alkylphenyl and halophenyl ethers. The emulsifier may also contain a small proportion of oxyalkylene radicals derived from ethylene oxide or glycidol. In examples a prepolymer, prepared by reacting tris(2-hydroxypropyl) glycerol with tolylene di-isocyanate which was added in two portions, is reacted with a cross-linking agent which is the reaction product of propylene oxide with a mixture of sucrose and glycerol in the presence of triethylene-diamine, trichlorofluoromethane, and an emulsifier which is (1) an ethylene oxide tipped tris (polyoxypropyelne) ether of glycerol, (2) a polyoxypropylene glycol or (3) a polyoxybutylene glycol, to give a foam.