GB837120A - Trimerisation of organic isocyanates - Google Patents

Abstract

Organic isocyanates are converted into their trimeric iso cyanurate form by contacting them with at least one organic base containing an hydroxyl ion. Such bases may be quaternary hydroxides derived from nitrogen, phosphorus, arsenic or antimony or a ternary hydroxide derived from selenium or sulphur. Temperatures from -10 DEG C. to the decomposition temperature of the catalyst may be used. Inert solvents may be present. The polymerization may be inhibited at any stage by addition of an acidic substance such as HCl, acetic acid or acetyl chloride. Unchanged monomers may be separated from the trimer by distillation or by precipitation of the polymer from a solution of the mixture by addition of a non-solvent for the polymer. Examples describe the trimerization of phenyl isocyanate, p-tolyl isocyanate, p- and o-methoxy phenyl isocyanates, p- and o-chloro phenyl isocyanates, p-nitro phenyl isocyanate, 2 : 4-toluene di iso cyanate, chloro phenylene-2 : 4-di-isocyanate and n-hexadecyl isocyanate, the reactions generally being carried out in dimethyl sulphoxide using tetraethyl ammonium hydroxide, benzyl triethyl ammonium hydroxide, trimethyl sulphonium hydroxide, tetraethyl phosphonium hydroxide or tri-a : a 1-di-pyridyl ferrous dihydroxide as catalyst. Numerous other monomeric isocyanates are mentioned including 3 : 31-dimethyl-4 : 41-di-iso-cyanato-diphenyl methane, 4 : 41-diisocyanato-diphenyl ether, naphthylene-1 : 5-diisocyanate, hexamethylene diisocyanate, diisocyanato-di-cyclohexyl methane, toluene-2 : 4 : 6-triisocya-nate and 2 : 4 : 41-triisocyanato-diphenyl. The trimers and their reaction products with phenols, diphenylamine, aceto acetic esters and malonic esters may be used as curing agents for resins (see Group IV (a)).