Abstract: The invention relates to a process for the continuous preparation of organic isocyanates, preferably polyisocyanates, through the reaction of organic amines, preferably polyamines, with phosgene in the presence of organic solvents under pressure, for example from 5 to 100 bar, at elevated temperatures, for example from 100 to 220.degree. C., whereby the reaction mixture is partially recycled, preferably using natural circulation, and the hydrogen chloride content in the reaction mixture prior to the addition of the amine is less than 0.5 percent by weight based on the total weight of the reaction mixture and the molar ratio of phosgene to NH.sub.2 group in the organic amines is from 12:1 to 200:1.

Abstract: A process for the manufacture of 4,4'-diphenylmethane diisocyanate and a mixture of diphenylmethane diisocyanate isomers containing a controllable amount of uretdione and hydrolizable chlorine which comprises feeding crude MDI to an evaporator, condensing a head fraction in two stages in the presence of an inert gas, feeding the first stage condensate to a distillation column, producing a mixture of diphenylmethane diisocyanate isomers as an overhead, producing 4,4'-diphenylmethane diisocyanate as a side draw, and condensing each of the overhead and side draw in two stages in the presence of an inert gas.

Abstract: Storage-stable, liquid carbodiimide-modified polyisocyanates are prepared by condensation of polyisocyanates in the presence of catalytic amounts of phospholine, phospholidine, phospholine oxides and/or phospholidine oxides, said condensation terminated and the products stabilized by means of perchloric acid or trifluoromethanesulfonic acid.