GB821342A - Polyurethane foams and method of making same - Google Patents

Abstract

A method of making polyurethane foam from a dihydroxy terminated polyester or polyether having a molecular weight of at least 500 and an organic polyisocyanate having 2 or 3 functional isocyanate groups, comprises the steps of uniformly distributing a liquefied halogen substituted alkane containing at least one fluorine atom in its molecule, having a boiling-point at one atmosphere pressure of not lower than - 60 DEG F. and not higher than 80 DEG F. in one of the foam-forming reactants, said liquefied gas being chemically inert to the reactants under the conditions of reaction, mixing the reactants and permitting the temperature of the mixture to rise during the ensuing reaction above the boiling-point of said liquefied gas whereby a porous polyurethane foam is produced by expansion of the gas. If water is present, blowing action is also produced by its reaction with isocyanate groups. The gas is preferably one which is soluble in the reactants, the higher its solubility the lower being the boiling-point which it may possess. Examples of suitable gases are methyl chloride, dichlorodifluoromethane, monochlorodifluoromethane, monofluorodichloromethane and dichlorotetrafluoroethane. Such liquefied gas may also contain dissolved hydrocarbons of up to 3 carbon atoms, or inorganic gases such as carbon dioxide and nitrous oxide. The type of polyester (linear or cross-linked, of molecular weight between about 1500 and about 4000) to be used, depends on whether a flexible or a rigid product is to be prepared. All or part of the polyester can be replaced by polyethers, such as ethylene, mixed ethylene propylene, polytri- or tetramethylene ether, polyneopentylene ether and polypentamethylene ether glycols. Cross-linking of the product can be effected by the use of tri-isocyanates in admixture with diisocyanates and by the use of cross-linking agents such as trimethylol propane and aliphatic or aromatic glycols. In an example, an adipic acid/diethylene glycol/trimethylolpropane polyester has dichlorodifluoromethane dissolved in it and is then reacted with mixed 2,4- and 2,6-diisocyanates (in a continuous process) in the presence of water, an emulsifier and the bisdiethylaminoethyl ester of adipic acid. Paraffin oil may be added to control pore size.ALSO:A method of making polyurethane foam from a dihydroxy terminated polyester or polyether having a molecular weight of at least 500 and an organic polyisocyanate having 2 or 3 functional isocyanate groups, comprises the steps of uniformly distributing a liquefied halogen substituted alkane containing at least one fluorine atom in its molecule, having a boiling point at one atmosphere pressure of not lower than -60 DEG F. and not higher than 80 DEG F. in one of the foam-forming reactant, said liquefied gas being chemically inert to the reactants under the conditions of reaction, mixing the reactants and permitting the temperature of the mixture to rise during the ensuing reaction above the boiling point of said liquefied gas whereby a porous polyurethane foam is produced by expansion of the gas. If water is present, blowing action is also produced by its reaction with isocyanate groups. The gas is preferably one which is soluble in the reactants, the higher its solubility the lower being the boiling point which it may possess. Examples of suitable gases are methyl chloride, dichlorodifluoromethane, monochlorodifluoromethane, monofluorodichloro methane and dichlorotetrafluoro ethane. Such liquefied gas may also contain dissolved hydrocarbons of up to 3 carbon atoms, or inorganic gases such as carbon dioxide and nitrous oxide. The type of polyester (linear or cross-linked, of molecular weight between about 1500 and about 4000) to be used, depends on whether a flexible or a rigid product is to be prepared. All or part of the polyester can be replaced by polyethers, such as ethylene, mixed ethylene propylene, polytri- or tetramethylene ether, polyneopentylene ether and polypentamethylene ether glycols. Cross-linking of the product can be effected by the use of tri-isocyanates in admixture with diisocyanates and by the use of cross-linking agents such as trimethylol propane and aliphatic or aromatic glycols. In an example, an adipic acid/diethylene glycol/trimethylolpropane polyester has dichlorodifluoromethane dissolved in it and is then reacted with mixed 2, 4- and 2, 6- diisocyanates (in a continuous process) in the presence of water, an emulsifier and the bis, diethylaminoethyl ester of adipic acid. Paraffin oil may be added to control pore size.