Process for preparing polyisocyanates

Patent metadata

Field	Value
Publication number	US-2018179150-A1
Application number	US-201615736485-A
Country	US
Kind code	A1
Filing date	Jun 27, 2016
Priority date	Jun 29, 2015
Publication date	Jun 28, 2018
Grant date	—

Abstract

The present invention relates to a continuous process for preparing a polyisocyanate, in which a polyamine and phosgene are first converted predominantly to carbamoyl chloride and amine hydrochloride and only in minor proportions to polyisocyanate, and a portion of the carbamoyl chloride- and amine hydrochloride-containing reaction mixture thus obtained is recycled into the reaction with phosgene, wherein polyamine, phosgene and the carbamoyl chloride- and amine hydrochloride-containing reaction mixture are mixed intimately in a mixing unit. The portion of the carbamoyl chloride- and amine hydrochloride-containing reaction mixture which is not recycled into the phosgenation is worked up to give the polyisocyanate.

First claim

1 . A continuous process for liquid phase preparation of a polyisocyanate by reaction of a corresponding polyamine with phosgene, with a corresponding carbamoyl chloride and a corresponding amine hydrochloride occurring as intermediates, comprising:
(i) mixing a phosgene-containing stream, polyamine-containing stream and a stream containing carbamoyl chloride and amine hydrochloride a mixing device to obtain a mixed stream, where phosgene is used in a stoichiometric excess of from >0% to 50% of theory, based on the amine groups of the polyamine present in the polyamine-containing stream; (ii) conveying mixed stream obtained in step i) through a reactor in which an absolute pressure of from 20 bar to 60 bar and a temperature of from 80° C. to 200° C., prevail, thereby forming a stream containing carbamoyl chloride and amine hydrochloride; (iii) optionally discharging a gaseous urge stream from the stream containing carbamoyl chloride and amine hydrochloride which is formed in step (ii), giving a stream which contains carbamoyl chloride and amine hydrochloride and has been depleted in gaseous components, and (iv) dividing the stream containing carbamoyl chloride obtained in step (ii) the stream which contains carbamoyl chloride and amine hydrochloride and has been depleted in gaseous components obtained in step (iii) into two substreams, where
(a) one substream is used as the stream containing carbarnoyl chloride and amine hydrochloride in step (i) and
(b) the other substream is converted into the desired polyisocyanate.

2 . The process of claim 1 , wherein the reactor in step (ii) is operated adiabatically.

3 . The process of claim 1 , wherein the reactor in step (ii) is operated isothermally.

4 . The process as of claim 1 , wherein, in step (iv) (b), the other substream is converted into the desired polyisocyanate by a process comprising:
(1) conveying the substream through an isothermally operated reactor and then (2) through a cascade of separators with gradually decreasing pressure.

5 . The process as of claim 3 , wherein, in step (iv) (b), the other substream is conveyed directly through a cascade of separators with gradually decreasing pressure.

6 . The process of claim 1 , wherein step (iv) (b) is carried out without addition of phosgene.

7 . The process of claim 1 , wherein
the phosgene-containing stream comprises a proportion by mass of from 10% to 90% of phosgene and a proportion by mass of from 90% to 10% of an inert solvent, in each case based on the total mass of the stream, the polyamine-containing stream comprises a proportion by mass of from 10% to 50% of polyamine and a proportion by mass of from 90% to 50% of an inert solvent, in each case based on the total mass of the stream.

8 . The process of claim 7 , wherein the inert solvent in the phosgene-containing stream and in the polyamine-containing stream is selected independently from the group consisting-of chlorobenzene, dichlorobenzene, toluene, dioxane, dimethyl sulfoxide and a mixture of two or more of the abovementioned solvents.

9 . The process of claim 1 , wherein the stream containing carbamoyl chloride and amino hydrochloride comprises a ratio of the molar amount of carbamoyl chloride and amine hydrochloride to polyisocyanate of from 2:1 to 100:1.

10 . The process of claim 1 , wherein the mixing device used in step (i) is a dynamic mixer.

11 . The process of claim 1 , wherein, in step (i), phosgene is used in a stoichiometric excess of from >0% to 20% of theory, based on the amine groups of the polyamine present in the polymine-containing stream.

12 . The process of claim 11 , wherein, in step (i), phosgene is used in a stoichiometric excess of from >0% to 15% of theory, based on the amine groups of the polyamine present in the polyamine-containing stream.

13 . The process of claim 12 , wherein, in step (i), phosgene is used in a stoichiometric excess of from >0% to 10% of theory, based on the amine groups of the polyamine present in polyamine-containing stream.

14 . The process of claim 1 , wherein unreacted phosgene is recovered by means of condensation by indirect cooling.

15 . The process claim 1 , wherein the isocyanate is selected from the group consisting of methylenedi(phenyl isocyanate) as pure isomer or as isomer mixture, polymethylenepolyphenyl polyisocyanate, mixtures of methylene(phenyl diisocyanate) and polymethylenepolyphenyl polyisocyanate, tolylene diisocyanate as pure isomer or isomer mixture, isomers of xylylene diisocyanate, isomers of diisocyanatobenzene, xylene 2,6-diisocyanate and naphthalene 1,5-diisocyanate.

Assignees

• Covestro Deutschland Ag

Inventors

• Arras Jürgen
• Busch Jan
• Steffens Christian
• Wastian Dietmar
• Keller-Killewald Manfred
• Conzelmann Holger

Classifications

• C07C265/14

  containing at least two isocyanate groups bound to the same carbon skeleton · CPC title

• C07C263/10 Primary

  by reaction of amines with carbonyl halides, e.g. with phosgene · CPC title

• B01J2219/00033

  Continuous processes · CPC title

• B01J19/0066

  Stirrers (mixing per se B01F) · CPC title