Isocyanate production process

Patent metadata

Field	Value
Publication number	US-9233918-B2
Application number	US-99162508-A
Country	US
Kind code	B2
Filing date	May 15, 2008
Priority date	May 15, 2008
Publication date	Jan 12, 2016
Grant date	Jan 12, 2016

Abstract

An object of the present invention is to provide a process that enables isocyanate to be produced stably over a long period of time and at high yield without encountering problems of the prior art during production of isocyanate without using phosgene. The present invention discloses a process for producing an isocyanate by subjecting a carbamic acid ester to a thermal decomposition reaction, including the steps of: recovering a low boiling point component in a form of a gaseous phase component from a thermal decomposition reaction vessel in which the thermal decomposition reaction is carried out; recovering a liquid phase component containing a carbamic acid ester from a bottom of the thermal decomposition reaction vessel; and supplying all or a portion of the liquid phase component to an upper portion of the thermal decomposition reaction vessel.

First claim

We claim:

1. A process for producing an isocyanate by subjecting a carbamic acid ester to a thermal decomposition reaction, comprising the steps of:
recovering a low boiling point component by distillation in a thermal decomposition reaction vessel in a form of a gaseous phase component from the thermal decomposition reaction vessel in which the thermal decomposition reaction is carried out;
recovering a liquid phase component containing the carbamic acid ester from a bottom of the thermal decomposition reaction vessel; and
supplying all or a portion of the liquid phase component to an upper portion of the thermal decomposition reaction vessel;
wherein the thermal decomposition reaction is carried out in a liquid phase, and
the step for recovering the low boiling component is carried out in the thermal decomposition reaction vessel in which the thermal decomposition reaction is carried out.

2. The process according to claim 1 , wherein the carbamic acid ester is supplied to the thermal decomposition reaction vessel within a temperature range of from 50 to 180° C.

3. The process according to claim 1 , wherein the carbamic acid ester is supplied to the thermal decomposition reaction vessel in a form of a liquid.

4. The process according to claim 1 , wherein the carbamic acid ester is a carbamic acid ester produced by reacting a carbonic acid ester with an amine compound.

5. The process according to claim 4 , wherein the reaction vessel for producing the carbamic acid ester and the thermal decomposition reaction vessel may be the same or different, and the reaction vessel for producing the carbamic acid ester and the thermal decomposition reaction vessel are at least one reaction vessel selected from the group consisting of a column-type reaction vessel and a tank-type reaction vessel.

6. The process according to claim 1 , wherein the thermal decomposition reaction vessel is composed of at least one reaction vessel selected from the group consisting of an evaporator, a continuous multistage distillation column, a packed column, a thin film evaporator and a falling film evaporator.

7. The process according to claim 4 , wherein a mixture, in which all or a portion of a hydroxy compound and/or all or a portion of the carbonic acid ester has been separated from a mixture containing the carbamic acid ester produced by reacting a carbonic acid ester and an amine compound, is supplied to a thermal decomposition reaction apparatus.

8. The process according to claim 7 , wherein the separation is carried out by distillative separation, and the distillative separation is carried out at 180° C. or lower.

9. The process according to claim 1 , wherein all or a portion of the liquid phase component recovered from the bottom of the thermal decomposition reaction vessel is supplied to the upper portion of the thermal decomposition reaction vessel within a temperature range of from 50 to 180° C.

10. The process according to claim 4 , wherein the carbonic acid ester is used at a stoichiometric ratio of 1 time or more based on amino groups constituting the amine compound.

11. The process according to claim 1 , further comprising cleaning a high boiling point by-product adhered to the thermal decomposition reaction vessel, with an acid.

12. The process according to claim 11 , wherein the acid is an aromatic hydroxy compound.

13. The process according to claim 4 , wherein the carbonic acid ester is a compound represented by the following formula (1):

(wherein R 1 represents an aliphatic group having 1 to 12 carbon atoms or an aromatic group having 6 to 12 carbon atoms).

14. The process according to claim 13 , wherein the carbonic acid ester contains a metal atom at from 0.001 ppm to 10%.

15. The process according to claim 14 , wherein the metal atom is one type or a plurality of types of metal atoms selected from the group consisting of iron, nickel, cobalt, zinc, tin, copper and titanium atoms.

16. The process according to claim 13 , wherein R 1 in the carbonic acid ester represents an aliphatic group having 5 to 7 carbon atoms or an aromatic group having 6 to 7 carbon atoms.

17. The process according to claim 4 , wherein the amine compound is a compound represented by the following formula (2):

(wherein R 2 represents a group selected from the group consisting of an aliphatic group having 1 to 20 carbon atoms and an aromatic group having 6 to 20 carbon atoms, the above group containing an atom selected from carbon and oxygen atoms, and having a valence equal to n, and
n represents an integer of from 2 to 10).

18. The process according to claim 17 , wherein the amine compound is a diamine compound represented by formula (2) in which n is 2.

19. The process according to claim 1 , wherein a low boiling point component is supplied to a distillation column in a form of a gaseous component from the low boiling point component formed by the thermal decomposition reaction and recovered in a form of a gaseous phase component, and a hydroxy compound originating from the carbamic acid ester and an isocyanate originating from the carbamic acid ester are separated in the distillation column.

20. The process according to claim 1 , wherein a hydroxy compound originating from the carbamic acid ester and an isocyanate originating from the carbamic acid ester are recovered separately from a low boiling point component formed by the thermal decomposition reaction and recovered in a form of a gaseous component by a thin film evaporator.

21. The process according to claim 1 , wherein the isocyanate is recovered from the liquid phase component by distillative separation.

22. The process according to claim 13 , wherein R 1 in the carbonic acid ester in formula (1) represents an aliphatic group having 1 to 12 carbon atoms, and the carbonic acid ester is produced according to a process which comprises the following steps (1) and (2):
step (1): obtaining a reaction mixture containing a dialkyl carbonate by reacting an organic tin compound having a tin-oxygen-carbon bond and carbon dioxide; and
step (2): obtaining a dialkyl carbonate and a residue liquid by separating the reaction mixture.

23. The process according to claim 13 , wherein R 1 in the carbonic acid ester in formula (1) represents an aromatic group having 6 to 12 carbon atoms, and the carbonic acid ester is produced according to a process which comprises the following step (3) in addition to the steps (1) and (2):
step (3): obtaining a diaryl carbonate by reacting the dialkyl carbonate separated in step (2) and an aromatic hydroxy compound A followed by recovering a by-product alcohol.

24. The process according to claim 22 or 23 , wherein the carbonic acid ester is a carbonic acid ester produced by a process which comprises the following steps (4) and (5) in addition to the steps (1) and (2) or the steps (1) to (3):
step (4): forming an organic tin compound having a tin-oxygen-carbon bond and water by reacting the residue liquid obtained in step (2) with an alcohol followed by removing the water from a reaction system; and
step (5): reusing the organic tin compound having the tin-oxygen-carbon bond obtained in step (4) as the organic tin compound having the tin-oxygen-carbon bond of step (1).

Assignees

• Shinohata Masaaki
• Miyake Nobuhisa
• Asahi Kasei Chemicals Corp

Inventors

• Shinohata Masaaki
• Miyake Nobuhisa

Classifications

• C07C263/18

  Separation; Purification; Stabilisation; Use of additives · CPC title

• C07C263/04 Primary

  from or via carbamates or carbamoyl halides · CPC title

• C07C265/14

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

• C07C2101/14

  Chemistry & Metallurgy · mapped topic

• C07C263/00

  Preparation of derivatives of isocyanic acid · CPC title