GB821158A - Polymerisation of organic isocyanates - Google Patents

Abstract

Aryl isocyanates containing at least one isocyanate group preferably having no substituents ortho thereto are polymerized to the dimeric and/or trimeric form by contacting with a 3- and/or 4-substituted pyridine of such basicity that, when substituted in benzoic acid in the meta- or para-position respectively, said 3- and/or 4-substituent increases the pKa value of the substituted benzoic acid, measured in water at 25 DEG C. to greater than 4.35. The process is preferably conducted at a temperature of between - 40 DEG and 140 DEG C. and in presence of an inert solvent. Specified pyridine catalysts are 4-alkoxy or -aryloxy pyridines (e.g. 4-ethoxypyridine), 3- and 4-dialkylamino pyridines (e.g. 3- and 4-dimethylaminopyridines), 3- and 4-alkylarylaminopyridines and pyridines containing a 3- or 4-substituent of the type: <FORM:0821158/IV (a)/1> where X represents an aliphatic chain with or without a hetero-link, such substituents being exemplified by 3- or 4-morpholino- or -piperidino-. Between 0.005 to 15% of catalyst based on weight of isocyanate and temperatures between 0 DEG and 100 DEG C. facilitate the formation of the dimer, while between 0.05 to 15% of catalyst and 0 DEG to 140 DEG C. facilitates the formation of the trimer. The polymerization may be terminated by addition of acyl halides or Friedel-Crafts catalysts such as boron trifluoride or its complexes in substantially equimolecular amounts with respect to the catalyst. Specified isocyanates are phenyl isocyanate, para-chlorophenyl isocyanate, para-nitrophenyl isocyanate, 2 : 4 - toluenediisocyanate, 4 - chloro - 1 : 3 - phenylenediisocyanate, 2 - chloro - 1 : 4 - phenylenediisocyanate, para - tolyl isocyanate, 2 - nitro - 4 - isocyanatotoluene, anisole - 2 : 4 - diisocyanate, 3 - alkoxy - 1 : 4 - phenylene diisocyanates and 4-alkoxy-1 : 3-phenylene diisocyanates such as 4-methoxy-1 : 3-phenylene diisocyanate. The examples describe the preparation of N : N1-diphenyl uretedione, N : N1-bis - (4 - methyl - 3 - isocyanatophenyl) - uretedione, N : N1 : N11 - tris - (4 - methyl - 3 - isocyanatophenyl) - isocyanurate, N : N1 : N11 - tris - (para - tolyl) - isocyanurate, N : N1 : N11-tris-(para-nitrophenyl)-isocyanurate, N : N1 : N11-tris - (3 - nitro - 4 - methylphenyl) - isocyanurate and N : N1 : N11 - tris - (4 - methoxy - 3 - isocyanatophenyl) - isocyanurate. 4 - N - morpholinopyridine is prepared by reacting 4-chloropyridine-N-oxide with boiling morpholine in presence of hydrated copper sulphate.