Diphenylmethane diisocyanate → Benzylbenzene diisocyanate

Participants

Reaction Steps

1.5 g of tributyl phosphine were added at room temperature to a solution of 1,000 g (4.0 mols) of diphenylmethane-4,4'-diisocyanate (MDI) in 2,000 g of toluene. After a short time, the dimeric MDI separated out of the solution and the temperature gradually rose to from 30° to 35° C. The reaction mixture was stirred for an additional 4 hours and the dimerization catalyst was then stopped by adding 1.5 g of toluene sulfonic acid methyl ester. The solid MDI "dimer" which formed was filtered by suction. After drying for about 5 hours at from 70° to 80° C., about 800 g of MDI "dimer" were obtained in the form of a fine powder. This powder was insoluble in practically all solvents. The decomposition point was above 250° C.

Provenance & Evidence