Patent GB-849405-A (GB)
Title: Improvements in or relating to polyurethane resins
Inventor: MERCER ALEC VICTOR
IPC: C08G18/54
Filed: 1959-02-11
Abstract: A process for the preparation of a polyurethane resin comprises reacting an organic isocyanate or isothiocyanate of the general formula R(NCX)n, where R represents an organic radical, X represents an oxygen or sulphur atom and n is a positive integer greater than 1, with a condensate having at least two hydroxyl groups in the molecule and obtained by reacting a polyhydric aromatic compound with propylene oxide, the relative amounts of isocyanate or isothiocyanate and condensate being such that the ratio of total (-NCX) groups to total hydroxy groups present in the reaction mixture is greater than 1:1.  The resin obtained can be reacted with a compound containing a plurality of active hydrogen atoms to form polyurethane plastics. The polyhydroxy aromatic compound may be a mononuclear compound such as pyrogallol, hydroquinone, phloroglucinol or resorcinol, a polynuclear compound such as diphenylol methane or propane, a condensation product of an aldehyde and a phenol or a condensed ring compound ; the hydroxyl groups need not be nuclear, e.g. the aromatic compound can be styrene glycol or dimethylol benzene. Mixtures of polypropylene oxide with other alkylene oxides can be condensed with the aromatic compound or a mixture of polyhydroxy compounds can be condensed with polypropylene oxide alone.  The preferred condensate has a molecular weight of 1000 to 3000, although with novolacs molecular weights of 20,000 are possible. A number of polymethylene, alkylidene, cycloalkylene, cycloalkylidene, aromatic and aliphatic aromatic diisocyanates and diisothiocyanates are listed.  The cross-linking of the resin go give a foam or rubber can be effected by heating in the presence of a basic catalyst and advantageously also a difunctional compound such as a glycol, amine, dicarboxylic acid, hydroxy amine, hydroxy acid or amino acid.  Foam plastics can be obtained by reacting the resin with water, hydrogen sulphide, a carboxylic acid or an ester containing carboxylic groups, preferably in the presence of an emulsifying agent and a catalyst. The polyurethane resin can also be prepared in the presence of an organic solvent such as benzene, toluene, xylene, solvent naphtha, gasoline, carbon tetrachloride or ethyl or amyl acetate ; a film of the solution then reacts with atmospheric water or an organic compound containing active hydrogen to give a polyurethane plastic.ALSO:A polyurethane resin obtained by reacting an organic isocyanate or isothiocyanate of the general formula R(NCX)n, where R represents an organic radical, X represents an oxygen or sulphur atom and n is a positive integer greater than 1, with a condensate having at least two hydroxyl groups in the molecule and obtained by reacting a polyhydric aromatic compound with propylene oxide, the relative amounts of isocyanate or isothiocyanate and condensate being such that the ratio of total -NCX groups to total hydroxy groups is greater than 1 : 1 is converted to a foamed plastic by reaction with water, hydrogen sulphide, a carboxylic acid or an ester containing carboxyl groups, preferably in the presence of an emulsifying agent and a catalyst.  The polyhydroxy compound may be a mononuclear compound such as pyrogallol, hydroquinore, phloroglucinol or resorcinal, a polynuclear compound such as diphenylol methane or propane, a condensation product of an aldehyde and a phenol, or a condensed ring compound; the hydroxyl groups need not be nuclear, e.g. the compound may be styrene glycol or dimethylol benzene. Mixtures of propylene oxide with other alkylene oxide or mixed aromatic compounds can be used.  A number of polymethylene, alkylidene, cycloalkylene, cycloalkylidene, aromatic and alkylaromatic diisocyanates and diisothiocyanates are listed.