GB971168A - Organic isocyanates - Google Patents

Abstract

The invention comprises diisocyanates of the formula:-<FORM:0971168/C1/1> in which X1 and X2, which may be the same or different, are hydrogen, chlorine or bromine. Preferred compounds are the 3,31-dibromo-, 3,31,5,51-tetrabromo-, and 3,31-dibromo-5, 51-dichloro-4,41-diisocyanato-diphenyl methane. The isocyanates may be made by brominating the corresponding 4,41-diisocyanatodiphenyl methane in the absence of actinic light to introduce at least one bromine atom into each of the aromatic nuclei. They may also be obtained by brominating the corresponding 4,41-di-amino-diphenyl-methane, the amino groups being protected by acylation during bromination, and then, after removal of the protective groups by hydrolysis, converting the amino groups to isocyanate by reaction with phosgene. Bromination is preferably effected in the presence of a halogen carrier, such as iodine, and an inert solvent, such as carbon tetrachloride at temperatures up to 100 DEG C. The bromine-substituted product may be chlorinated or chlorination may precede the bromination. The chlorination may be effected at temperatures up to 80 DEG C., preferably 10-30 DEG C. An example describes the bromination of 4,41-diisocyanate diphenyl methane in carbon tetrachloride in the presence of iodine to give 3,31-dibromo-4,41-diisocyanato-diphenyl methane.ALSO:Polyurethane materials may be made from a mixture of diisocyanates including one or more of the formula: <FORM:0971168/C3/1> in which X1 and X2, which may be the same or different, are hydrogen, chlorine or bromine, in admixture with unbrominated diisocyanates for example by adding such a mixture to a polyol catalyst system together with antimony oxide and water. The proportion of brominated diisocyanate may be up to 50%, usually 20 to 25% by weight of the unbrominated diisocyanate. The resultant composition, after stirring is poured into a mould and cured, either at room or an elevated temperature.