Isocyanate production method

Patent metadata

Field	Value
Publication number	US-10968168-B2
Application number	US-201816610404-A
Country	US
Kind code	B2
Filing date	May 15, 2018
Priority date	May 15, 2017
Publication date	Apr 6, 2021
Grant date	Apr 6, 2021

Abstract

An isocyanate production method according to the present invention is a method in which an isocyanate is produced by subjecting a carbamate to thermal decomposition, and includes: a step of preparing a mixture liquid containing the carbamate, an inactive solvent and a polyisocyanate compound; a step of conducting a thermal decomposition reaction of the carbamate by continuously introducing the mixture liquid into a thermal decomposition reactor; a step of collecting a low-boiling decomposition product by continuously extracting the low-boiling decomposition product in a gaseous state from the reactor, the low-boiling decomposition product having a boiling point lower than the polyisocyanate compound; and a step of collecting a high-boiling component by continuously extracting, from the reactor, a liquid phase component which is not collected in a gaseous state at the step of collecting the low-boiling decomposition product.

First claim

The invention claimed is:

1. An isocyanate production method in which an isocyanate is produced by thermal decomposition of a carbamate, comprising:
a step of preparing a mixture liquid comprising the carbamate and a polyisocyanate compound;
a step of conducting a thermal decomposition reaction of the carbamate by continuously introducing the mixture liquid into a thermal decomposition reactor:
a step of collecting a low-boiling decomposition product by continuously extracting the low-boiling decomposition product in a gaseous state from the thermal decomposition reactor, the low-boiling decomposition product having a standard boiling point lower than the polyisocyanate compound and comprising the isocyanate; and
a step of collecting a high-boiling component by continuously extracting, from the thermal decomposition reactor, a liquid phase component which is not collected in a gaseous state at the step of collecting the low-boiling decomposition product, as the high-boiling component.

2. The isocyanate production method according to claim 1 , wherein the mixture liquid comprises an inactive solvent,
the inactive solvent is continuously extracted in a gaseous state from the thermal decomposition reactor together with the low-boiling decomposition product having a boiling point lower than the polyisocyanate compound in the step of collecting the low-boiling decomposition product, and
the inactive solvent is substantially inactive under thermal decomposition reaction conditions, and has a boiling point between a boiling point of the isocyanate produced by thermal decomposition and a boiling point of a hydroxy compound.

3. The method according to claim 1 , wherein the carbamate is a carbamate of formula (20):

in the formula (20),
c represents an integer of 1 or more,
R 1 represents an aliphatic hydrocarbon group, an aromatic hydrocarbon group, or a group formed by bonding a single or plural of aliphatic hydrocarbon groups and/or aromatic hydrocarbon groups via an ether bond (—O—), a thioether bond (—S—), an ester bond (COO—), or an amide bond (—CONH—),
R 3 represents a C1-20 aliphatic hydrocarbon group or a C6-20 aromatic group, and plural R 3 are identical to or different from each other.

4. The method according to claim 1 , wherein the thermal decomposition reactor is a tubular reactor.

5. The method according to claim 1 , further comprising a step in which the low-boiling decomposition product is supplied in a gaseous state to a distillation column and the isocyanate is separated in the distillation column.

6. The method according to claim 2 , wherein the step of conducting the thermal decomposition reaction comprises:
a step of preparing the liquid phase component in which the mixture liquid is continuously introduced into a first reactor comprising a vertical tubular reactor to conduct a first decomposition reaction while allowing the mixture liquid to fall down inside the first reactor, and the liquid phase component is obtained from a bottom of the first reactor; and
a decomposition step in which the liquid phase component is introduced into a second reactor comprising a tank reactor and a second decomposition reaction is conducted to decompose the carbamate into the isocyanate and a hydroxy compound;
wherein, in the step of collecting the low-boiling decomposition product, the low-boiling decomposition product is extracted continuously in a gaseous state from the first reactor or both the first reactor and the second reactor,
in the step of collecting the high-boiling component, the liquid phase component comprises a high-boiling decomposition product having a standard boiling point higher than a standard boiling point of the low-boiling decomposition product, and the high-boiling decomposition product is extracted continuously from the second reactor together with the polyisocyanate compound,
the isocyanate is further comprised in the high-boiling decomposition product, and
a difference between a temperature in the first reactor and a temperature in the second reactor is 50° C. or lower.

7. The isocyanate production method according to claim 6 , further comprising a recycle step in which, in the step of collecting the low-boiling decomposition product, an inactive solvent vapor is extracted continuously in a gaseous state together with the low-boiling decomposition product from the first reactor or both the first reactor and the second reactor,
the gas component extracted continuously is introduced into a partial condenser in which a temperature thereof is maintained at a temperature which allows partial or entire condensation of the inactive solvent vapor but does not allow partial or entire condensation of the low-boiling decomposition product to separate the gas component into a gaseous component mainly comprising the low-boiling decomposition product and a liquid-form component mainly comprising the inactive solvent, and then the liquid-form component is partially or entirely returned to the first reactor or both the first reactor and the second reactor.

8. The isocyanate production method according to claim 7 , wherein a tubular reactor, an inside of which is filled with either a solid filler content or a solid catalyst or both thereof, is used as the first reactor.

9. The isocyanate production method according to claim 7 , wherein a tubular reactor in which a tray is placed is used as the first reactor.

10. The isocyanate production method according to claim 7 , wherein a tubular reactor in which a tray is placed, the tubular reactor being filled with either a solid filler content or a solid catalyst or both thereof, is used as the first reactor.

11. The isocyanate production method according to claim 6 , wherein the gas component generated in the second reactor is introduced into the first reactor from a bottom thereof.

12. The isocyanate production method according to claim 6 , wherein a carrier agent in a gaseous state, which is substantially inactive under thermal decomposition reaction conditions, is introduced into either the first reactor or the second reactor or both thereof from a bottom thereof, and a gas component is extracted from a top thereof.

13. The isocyanate production method according to claim 12 , wherein the carrier agent is introduced into a liquid in the second reactor.

14. The method according to claim 3 , wherein R 1 is the aliphatic hydrocarbon group having 3 to 85 carbon atoms.

15. The method according to claim 3 , wherein R 1 is the aromatic hydrocarbon group having 6 to 20 carbon atoms.

16. The method according to claim 3 , wherein R 1 is the group formed by bonding a single or plural of aliphatic hydrocarbon groups and/or aromatic hydrocarbon groups via an ether bond (—O—), a thioether bond (—S—), an ester bond (COO—), or an amide bond (—CONH—).

17. The method according to claim 16 , wherein R 1 is a group represented by formula (20-1) or (20-2) when c is 1:

wherein:
R 211 , R 212 , R 221 , and R 222 each independently represent an oxygen atom or a secondary amino group (—NH—).

18. The method according to claim 16 , wherein R 1 is a group represented by formula (20-3), (20-4), (20-5), or (20-6) when c is 2:

wherein:
R 231 , R 232

Assignees

• Asahi Chemical Ind

Inventors

• Miyake Nobuhisa
• Nakaoka Koichi
• UEMATSU Tsubasa
• Sakurai Yusuke
• Ishii Yusuke
• Takagaki Kazuhiro
• Sasaki Takeharu
• Kosugi Yuji
• Ohkubo Atsushi
• Shinohata Masaaki

Classifications

• C07C263/04 Primary

  from or via carbamates or carbamoyl halides · CPC title

• C07C319/20

  by reactions not involving the formation of sulfide groups · CPC title

• C07D209/20

  substituted additionally by nitrogen atoms, e.g. tryptophane · CPC title

• C07C263/20

  Separation; Purification · CPC title

• C07D233/64

  with substituted hydrocarbon radicals attached to ring carbon atoms, e.g. histidine · CPC title