Abstract: A process for continuous preparation of oligomeric or polymeric isocyanates by catalytic modification of monomeric di- and/or triisocyanates, characterized in that at least one isocyanate component A and at least one catalyst component B are combined continuously in a reaction apparatus and conducted through the reaction apparatus as a reaction mixture, the residence time distribution being characterized according to the dispersion model by Bo (Bodenstein number) above 40, preferably above 60 and most preferably above 80.

Abstract: A process for continuous preparation of oligomeric or polymeric isocyanates by catalytic modification of monomeric di- and/or triisocyanates, characterized in that at least one isocyanate component A and at least one catalyst component B are combined continuously in a reaction apparatus and conducted through the reaction apparatus as a reaction mixture, the residence time distribution being characterized according to the dispersion model by Bo (Bodenstein number) above 40, preferably above 60 and most preferably above 80.

Abstract: The present invention relates to a process for obtaining adipic acid from the aqueous nitric acid mother liquors that arise during industrial adipic acid production by(i) removing nitric acid from the aqueous mother liquor by evaporation to a concentrate having a residual content of at most about 2.5 wt. % of HNO.sub.3,(ii) mixing the concentrate obtained according to step (i) with water or dilute aqueous nitric acid in a quantity corresponding to a weight ratio of solid to liquid of about 1:2.1 to about 1:1.2,(iii) allowing the water added in step (ii) or the nitric acid added in step (ii) to act upon the concentrate for at least about 10 minutes at about 20.degree. to about 80.degree. C., and(iv) separating adipic acid as crystals that are formed (1) during step (iii) at temperatures of no more than about 35.degree. C. or (2) after step (iii) by cooling the mixture from step (iii) to about 10.degree. to about 35.degree. C.