JP2019199427A - Method for producing isocyanate - Google Patents

Abstract

To provide a method for producing isocyanate that suppresses a side reaction and continuously produces isocyanate.SOLUTION: The present invention provides a method for producing isocyanate by pyrolysis of carbamate, the method including: a pyrolysis step in which a liquid mixture containing carbamate and a cyclic compound of a specific structure is continuously introduced into a pyrolytic reactor for a pyrolytic reaction of carbamate; a low-boiling-point pyrolytic product recovery step in which a low-boiling-point pyrolytic product having a normal boiling point lower than that of the cyclic compound is continuously extracted in a gas state from the pyrolytic reactor; and a high-boiling-point component recovery step in which a liquid phase component, which has not been recovered in a gas state in the low-boiling-point pyrolytic product recovery step, is continuously extracted as a high-boiling-point component from the pyrolytic reactor.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing isocyanate.

  Isocyanates are widely used as raw materials for producing polyurethane foams, paints, adhesives and the like. The main industrial production method of isocyanate is a reaction between an amine compound and phosgene (phosgene method), and almost all of the world production is produced by the phosgene method. However, the phosgene method has many problems.

The first is to use a large amount of phosgene as a raw material. Phosgene is extremely toxic and requires special care in handling to prevent exposure to workers and special equipment to remove waste.
Secondly, in the phosgene method, a large amount of highly corrosive hydrogen chloride is by-produced, so a process for removing hydrogen chloride is required. Furthermore, the produced isocyanate often contains hydrolyzable chlorine. For this reason, when an isocyanate produced by the phosgene method is used, the weather resistance and heat resistance of the polyurethane product may be adversely affected.

  From such a background, a method for producing an isocyanate compound without using phosgene is desired. As one of the methods for producing an isocyanate compound that does not use phosgene, a method by thermal decomposition of a carbamic acid ester has been proposed. It is known that an isocyanate and a hydroxy compound can be obtained by thermal decomposition of a carbamic acid ester (see, for example, Non-Patent Document 1). The basic reaction is exemplified by the following general formula (1).

(In the general formula (1), R is an a-valent organic residue. R ′ is a monovalent organic residue. A is an integer of 1 or more.)

  Patent Document 1 discloses a method for producing an isocyanate by thermally decomposing carbamate in a flask in the presence of an inert solvent. Patent Document 2 discloses a method for producing an isocyanate by thermally decomposing a carbamate in the presence of an aromatic hydroxy compound and a carbonic acid derivative.

  On the other hand, in the thermal decomposition reaction of carbamic acid ester, various irreversible side reactions such as unfavorable thermal modification reaction of carbamic acid ester and condensation reaction of isocyanate generated by the thermal decomposition are likely to occur simultaneously (for example, non-patent documents). 1 and 2).

  These side reactions not only lead to a decrease in the yield and selectivity of the target isocyanate, but particularly in the production of polyisocyanates, long-term operations such as the precipitation of polymer solids and plugging of the reactor can occur. It could be difficult.

JP 2003-252846 A JP 2012-2333014 A

Berchte der Deutschen Chemischen Gesellschaft, 3, 653, 1870. Journal of American Chemical Society, 81, 2138, 1959.

The method of Patent Document 1 discloses a method in which carbamate is supplied to a reactor and thermal decomposition is performed while extracting the generated isocyanate, but since there is no mechanism for extracting a high-boiling component generated by a side reaction. It is difficult to produce isocyanate continuously over a long period of time.
In the method of Patent Document 2, although the isocyanate generated by the thermal decomposition of the carbamate is continuously extracted as a low boiling point decomposition product, the carbamate generated by the reaction between the generated isocyanate and the hydroxy compound falls to the bottom of the reactor. Since a high boiling point component is generated by a side reaction at the bottom of the reactor, the yield of isocyanate tends to decrease.

  This invention is made | formed in view of the said situation, Comprising: A side reaction is suppressed and the manufacturing method of the isocyanate which manufactures isocyanate continuously is provided.

That is, the present invention includes the following aspects.
The method for producing an isocyanate according to the first aspect of the present invention is a method for producing an isocyanate by thermal decomposition of a carbamate, comprising a mixed solution containing a carbamate and a cyclic compound represented by the following general formula (4). A pyrolysis step in which the carbamate is pyrolyzed and continuously introduced into the pyrolysis reactor, and a low-boiling cracking product having a lower standard boiling point than the cyclic compound is gaseous from the pyrolysis reactor. A low boiling point decomposition product recovery step that is continuously extracted at a high boiling point, and a liquid phase component that is not recovered in a gaseous state in the low boiling point decomposition product recovery step as a high boiling point component. And a component recovery step.

(In the formula, A represents a condensed ring, a heteromonocyclic ring, or a benzene ring, and R ⁴⁰¹ represents a hydrocarbon group, an alkoxy group, an acyl group, a dimethylaminoalkyl group, an oxo group, a cyano group, or a halogen atom. , N401 is an integer of 0 to 3. When n401 is 2 or 3, a plurality of R ⁴⁰¹ present in one molecule may be the same group or different groups.

  In the isocyanate production method according to the first aspect, A in the general formula (4) is morpholine ring, piperazine ring, pyridine ring, triazine ring, tetrahydroquinoline ring, quinoline ring, isoquinoline ring, acridine ring, chroman ring. , A xanthene ring, a benzene ring, a naphthalene ring, a tetrahydronaphthalene ring, a phenanthrene ring, an anthracene ring, a tetracene ring, or a pyrene ring.

In the isocyanate production method according to the first aspect, the mixed solution further contains an inert solvent, and in the low-boiling decomposition product recovery step, the low-boiling decomposition product and the inert solvent are subjected to the thermal decomposition. Continuously withdrawn from the reactor in gaseous form, and the inert solvent is substantially inert under the pyrolysis reaction conditions, and its normal boiling point is lower than the normal boiling point of the cyclic compound, It may be between the normal boiling points of the isocyanate and hydroxy compounds produced by decomposition.
In the isocyanate production method according to the first aspect, the carbamate may be a compound represented by the following general formula (2).

(In the formula (2), is n21, an integer of 1 or more ^{.R 21} is ^{.R 22} is n21 divalent organic group is a residue obtained by removing one hydroxyl group from the hydroxy compound.)

In the isocyanate production method according to the first aspect, the pyrolysis reactor may be a tubular reactor.
In the isocyanate production method according to the first aspect, the low-boiling point decomposition product contains the isocyanate, the low-boiling point decomposition product is supplied to the distillation column in a gaseous state, and the isocyanate is separated in the distillation column. A separation step may be further included.
In the isocyanate production method according to the first aspect, under the thermal decomposition reaction conditions, a substantially inert and gaseous carrier is introduced into the thermal decomposition reactor, and a gaseous component is converted into the thermal component. You may carry out from a decomposition reactor.

  According to the isocyanate production method of the above aspect, side reactions can be suppressed and isocyanate can be produced continuously.

1 is a schematic diagram showing the structure of an isocyanate production apparatus used in Example 1. FIG. 3 is a schematic diagram showing the structure of an isocyanate production apparatus used in Example 2. FIG.

  Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. The following embodiment is an exemplification for explaining the present invention, and the present invention is not limited to the following embodiment. The present invention can be appropriately modified within the scope of the gist.

≪Method for producing isocyanate≫
The isocyanate production method of the present embodiment is a method for producing an isocyanate by thermally decomposing a carbamate.
The isocyanate production method of the present embodiment is a method including a thermal decomposition step, a low boiling point decomposition product recovery step, and a high boiling point component recovery step.
In the pyrolysis step, a mixed solution containing carbamate and a cyclic compound represented by the following general formula (4) (hereinafter sometimes referred to as “cyclic compound (4)”) is placed in a pyrolysis reactor. It is continuously introduced to carry out a thermal decomposition reaction of carbamate.
In the low boiling point decomposition product recovery step, a low boiling point decomposition product having a standard boiling point lower than that of the cyclic compound is continuously withdrawn from the thermal decomposition reactor in a gaseous state.
In the high boiling point component recovery step, the liquid phase component that has not been recovered in the gaseous state in the low boiling point decomposition product recovery step is continuously extracted from the thermal decomposition reactor as a high boiling point component.

(In the formula, A represents a condensed ring, a heteromonocyclic ring, or a benzene ring, and R ⁴⁰¹ represents a hydrocarbon group, an alkoxy group, an acyl group, a dimethylaminoalkyl group, an oxo group, a cyano group, or a halogen atom. , N401 is an integer of 0 to 3. When n401 is 2 or 3, a plurality of R ⁴⁰¹ present in one molecule may be the same group or different groups.

According to the production method of the present embodiment, side reactions can be suppressed and isocyanate can be produced continuously.
Hereinafter, each step will be described.

[Pyrolysis process]
This step is a step of obtaining isocyanate by continuously introducing a mixed solution containing carbamate and the cyclic compound (4) into a thermal decomposition reactor and subjecting it to a thermal decomposition reaction. This thermal decomposition reaction is a reaction for generating an isocyanate and a hydroxy compound (preferably an aromatic hydroxy compound) from a carbamate. This step is preferably performed in a liquid phase.
The mixed solution may further contain an inert solvent. The inert solvent is substantially inert under the thermal decomposition reaction conditions, and its normal boiling point is lower than the normal boiling point of the cyclic compound (4), and is a standard for isocyanate and hydroxy compounds produced by thermal decomposition. Between the boiling points. That is, in the mixed solution, the standard boiling point of each component increases in the order of the hydroxy compound, the inert solvent, the isocyanate, and the cyclic compound (4).
In the present specification, “substantially inactive” means that it does not react or reacts with the carbamate and the isocyanate or hydroxy compound that is the thermal decomposition product under the conditions under which the carbamate is thermally decomposed. Even in this case, it means that the thermal decomposition of the carbamate is not greatly affected.
The carbamate used in this step is preferably a carbamate obtained by the production method described later.
Moreover, the inert solvent and cyclic compound (4) used at this process are mentioned later.

The content of carbamate in the mixed solution is usually 1% by mass to 50% by mass, preferably 3% by mass to 40% by mass, and preferably 5% by mass to 30% by mass with respect to the total mass of the mixed solution. The following is more preferable.
When the carbamate content is not less than the above lower limit, the space-time yield of isocyanate is further improved, which tends to be advantageous in industrial implementation. Moreover, it exists in the tendency for a side reaction to be suppressed more at the time of thermal decomposition by being below the said upper limit.

The reaction temperature is usually in the range of 100 ° C. or higher and 300 ° C. or lower, and a high temperature is preferable to increase the reaction rate, but side reactions caused by at least one of the carbamate and the product isocyanate are further suppressed. From the viewpoint, a range of 150 ° C. or higher and 250 ° C. or lower is preferable.
In order to keep the reaction temperature constant, a known cooling device and heating device may be installed in the pyrolysis reactor.

The reaction pressure varies depending on the kind and the reaction temperature of the compound to be used, reduced pressure may be either normal pressure and a pressure is carried out at 1 × 10 6 ^Pa or less in the range of usually 1 Pa.
There is no restriction | limiting in particular in reaction time (residence time), Usually 0.001 to 100 hours are preferable, 0.005 to 50 hours are more preferable, 0.01 to 10 hours are further more preferable.

Although there is no particular limitation on the type of the pyrolysis reactor, it is preferable to use a known distillation apparatus in order to efficiently recover the gas phase components. Evaporator, continuous multistage distillation column, packed column, thin film evaporator And at least one reactor selected from the group consisting of a falling film evaporator.
In addition to these, for example, any of a distillation column, a multistage distillation column, a multitubular reactor, a reactor having a support inside, a forced circulation reactor, a falling film evaporator and a drop evaporator is included. Various known methods such as a method using a reactor and a method combining these are used.
From the viewpoint of quickly removing low boiling point decomposition products having a lower normal boiling point than the cyclic compound (4) from the reaction system, a packed tower or a tubular reactor is preferable, a tubular reactor is more preferable, and a tubular thin film. A method using a tubular reactor such as an evaporator or a tubular falling film evaporator is more preferable. Further, as the internal structure of these reactors, a structure having a large gas-liquid contact area capable of promptly moving the produced low boiling point decomposition product to the gas phase is preferable.

In the case of using a packed tower, as a solid filler provided in the packed tower, a filler generally used in a distillation tower or an absorption tower can be appropriately used. Specific examples of preferred solid fillers include Raschig rings, Lessing rings, spiral rings, ball rings, Interlocks saddles, Steadman packing, McMahon packing, Dixon packing, helix packing, coil packing, heat pipe packing, and the like.
The material of the solid filler is not particularly limited, such as magnetic or metal. Especially, as a material of a solid filler, a material with high heat conductivity is preferable.

  As the material for the pyrolysis reactor and the line, known materials that do not adversely affect the carbamate, its product hydroxy compound, isocyanate and the like can be appropriately selected and used. For example, SUS304, SUS316, SUS316L, etc. It is inexpensive and can be used preferably.

In this step, a catalyst is not always necessary, but a catalyst can be used for the purpose of lowering the reaction temperature and for completing the reaction at an early stage.
The amount of the catalyst used is preferably 0.01% by mass or more and 30% by mass or less, and more preferably 0.5% by mass or more and 20% by mass or less with respect to the mass of the carbamate.
Examples of the catalyst include Lewis acids and transition metal compounds that generate Lewis acids, organotin compounds, compounds containing copper group metals, compounds containing lead, compounds containing zinc, compounds containing iron group metals, amines, and the like. Can be mentioned.
Specific examples of the Lewis acid and the transition metal compound that generates the Lewis acid include AlX ₃ , TiX ₃ , TiX ₄ , VOX ₃ , VX ₅ , ZnX ₂ , FeX ₃ , and SnX ₄ . Here, “X” is a halogen, an acetoxy group, an alkoxy group or an aryloxy group.
Specific examples of the organic tin compound include (CH ₃ ) ₃ SnOCOCH ₃ , (C ₂ H ₅ ) SnOCOC ₆ H ₅ , Bu ₃ SnOCOCH ₃ , Ph ₃ SnOCOCH ₃ , Bu ₂ Sn (OCOCH ₃ ) ₂ , Bu ₂ Sn (OCOC ₁₁ H ₂₃ ) ₂ (dibutyltin dilaurate), Ph ₃ SnOCH ₃ , (C ₂ H ₅ ) ₃ SnOPh, Bu ₂ Sn (OCH ₃ ) ₂ , Bu ₂ Sn (OC ₂ H ₅ ) ₂ , Bu ₂ Sn (OPh) ₂ , Ph ₂ Sn (CH ₃ ) ₂ , (C ₂ H ₅ ) ₃ SnOH, PhSnOH, Bu ₂ SnO, (C ₈ H ₁₇ ) ₂ SnO, Bu ₂ SnCl ₂ , BuSnO (OH), Examples include tin octylate. Here, “Bu” is a butyl group and “Ph” is a phenyl group.
Specific examples of the compound containing a copper group metal include, for example, CuCl, CuCl ₂ , CuBr, CuBr ₂ , CuI, CuI ₂ , Cu (OAc) ₂ , Cu (acac) ₂ , copper olefinate, Bu ₂ Cu, ( CH ₃ O) ₂ Cu, AgNO ₃ , AgBr, silver picrate, AgC ₆ H ₆ ClO _{4 and the} like. Here, “acac” is an acetylacetone chelate ligand.
Specific examples of the compound containing lead include, for example, lead octylate.
Specific examples of the compound containing zinc include Zn (acac) _{2 and the} like.
Specific examples of the compound containing an iron group metal include, for example, Fe (C ₁₀ H ₈ ) (CO) ₅ , Fe (CO) ₅ , Fe (C ₄ H ₆ ) (CO) ₃ , Co (mesitylene) ₂ ( PEt ₂ Ph ₂ ), CoC ₅ F ₅ (CO) ₇ , ferrocene and the like.
Specific examples of amines include 1,4-diazabicyclo [2,2,2] octane, triethylenediamine, and triethylamine.
Among them, as the catalyst, dibutyltin dilaurate, lead octylate or tin octylate is preferable. These catalysts may be used alone or in combination of two or more.

[Low boiling point decomposition product recovery process]
In this step, the low boiling point decomposition product generated by the carbamate pyrolysis reaction is continuously withdrawn from the pyrolysis reactor in a gaseous state. The “low boiling point decomposition product” here refers to a compound having a standard boiling point lower than that of the cyclic compound (4) among the isocyanate and hydroxy compounds generated by the thermal decomposition reaction of carbamate. As the low boiling point decomposition product, at least one of a hydroxy compound and an isocyanate is preferable, and a hydroxy compound and an isocyanate are preferable. Moreover, when a liquid mixture contains an inert solvent, in this process, a low boiling point decomposition product and an inert solvent are continuously extracted in a gaseous state from a thermal decomposition reactor.

  In order to recover these components in a gaseous state, it is preferable to set conditions such as temperature and pressure for carrying out the step according to the compound used and the compound produced by the thermal decomposition reaction of carbamate.

Moreover, in order to collect | recover a low boiling point decomposition product rapidly, a carrier can be introduce | transduced into a thermal decomposition reactor and the gaseous component containing a carrier can also be carried out from a thermal decomposition reactor. The term “carrier” as used herein refers to a substance that is substantially inert and in a gaseous state under the thermal decomposition reaction conditions.
Specific examples of such a carrier include inert gas and hydrocarbon gas. Examples of the inert gas include nitrogen, argon, helium, carbon dioxide gas, methane, ethane, and propane. Among these, an inert gas such as nitrogen is preferable as the carrier.
Low boiling organic solvents may be used as the same effect. Examples of the low boiling point organic solvents include halogenated hydrocarbons, lower hydrocarbons, ethers and the like. Examples of halogenated hydrocarbons include dichloromethane, chloroform, carbon tetrachloride and the like. Examples of lower hydrocarbons include pentane, hexane, heptane, benzene and the like. Examples of ethers include tetrahydrofuran and dioxane.
These carrier agents may be used alone or in combination of two or more. Moreover, it is preferable to use these carriers by heating them in advance.

  The gaseous low boiling point decomposition product recovered from the thermal decomposition reactor, or the low boiling point decomposition product and the inert solvent are introduced into the cooler as they are, and a part or all of them are recovered in liquid form. Also good. Further, purification and separation may be performed by supplying to a distillation tower in a gaseous state or in a state of being introduced into a cooler to form a liquid.

[High boiling point recovery process]
In this step, the liquid phase component that has not been recovered in the gaseous state in the low boiling point decomposition product recovery step is continuously extracted and recovered as a high boiling point component from the reactor. In the low boiling point decomposition product recovery step, the low boiling point decomposition product having a lower standard boiling point than the cyclic compound (4) supplied to the thermal decomposition reactor, or the low boiling point decomposition product and the inert solvent are gaseous. It is collected at. Therefore, the high boiling point component recovered in this step is a liquid phase component that has not been recovered in the gaseous state in the low boiling point decomposition product recovery step, and the cyclic compound (4) supplied to the thermal decomposition reaction and the standard It is understood that the components have the same boiling point or a higher standard boiling point than the cyclic compound (4). The high-boiling components are produced by further reaction of side reaction products of isocyanate and carbamate generated by thermal decomposition of carbamate, side reaction products of isocyanate, side reaction products of carbamate, and these side reaction products. In many cases, compounds are included. These compounds are often not recovered in the gaseous state in the low boiling point decomposition product recovery step, but often adhere to the surface of the reactor and cause clogging or the like. Therefore, by continuously recovering as a liquid phase component from the thermal decomposition reactor together with the cyclic compound (4) supplied to the thermal decomposition reaction, there is an effect of preventing adhesion to the reactor surface.

  The thermal decomposition step, the low boiling point decomposition product recovery step, and the high boiling point component recovery step shown above may be performed individually using a plurality of devices or may be performed simultaneously using a single device. Good.

[Other processes]
The isocyanate production method of the present embodiment may further include, for example, a separation step, a carbamate production step, and the like in addition to the thermal decomposition step, the low boiling point decomposition product recovery step, and the high boiling point component recovery step.

(Separation process)
In the separation step, the isocyanate contained in the low boiling point decomposition product recovered in the low boiling point decomposition product recovery step is separated and purified. Specifically, the low boiling point decomposition product recovered in the low boiling point decomposition product recovery step is supplied in a gaseous state to a distillation tower, and the isocyanate and the hydroxy compound are separated to obtain a highly purified isocyanate. . Distillation conditions, distillation apparatuses, and the like can be appropriately selected from known conditions and apparatuses according to the types of isocyanate and hydroxy compounds.

(Carbamate manufacturing process)
The carbamate used in the pyrolysis step is preferably produced using the method shown below. Further, from the viewpoint of the quality and yield of the resulting isocyanate, a carbamate derived from an amino acid ester that gives a hydroxyl compound as a low boiling point decomposition product and an isocyanate as a high boiling point decomposition product is preferable.

  In this step, a carbonate ester is reacted with an amine compound to contain a carbamate that is a reaction product of the carbonate ester and the amine compound, a hydroxy compound that is a reaction byproduct of the carbonate ester, and a carbonate ester. A mixture is obtained.

  The reaction between the carbonate ester and the amine compound may be performed in a reaction solvent. Further, the carbonate ester used in excess relative to the molar amount of the amino group of the amine compound is preferably used as a solvent in the reaction.

  Although the reaction conditions of the carbonate ester and the amine compound vary depending on the compound to be reacted, the molar amount of the carbonate ester with respect to the molar amount of the amino group of the amine compound can be 1 or more times in terms of the stoichiometric ratio. From the viewpoint of increasing the speed and completing the reaction at an early stage, the molar amount of the carbonate ester relative to the molar amount of the amino group of the amine compound is preferably an excess amount, more preferably in the range of 1 to 1000 times, and the size of the reactor. In view of the above, a range of 1.1 times to 50 times is more preferable, and a range of 1.5 times to 10 times is particularly preferable.

  The reaction temperature can usually be in the range of 0 ° C. or higher and 150 ° C. or lower, and a high temperature is preferable for increasing the reaction rate. On the other hand, an unfavorable reaction may occur at a high temperature. A range of 100 ° C. or lower is preferable. In order to keep the reaction temperature constant, a known cooling device and heating device may be installed in the reactor.

The reaction pressure varies depending on the type of compound used and the reaction temperature, but may be any of reduced pressure, normal pressure, and increased pressure, and is usually performed in the range of 20 Pa or more and 1 × 10 ⁶ Pa or less. The reaction time (retention time in the case of a continuous method) is not particularly limited, and is usually preferably 0.001 hour to 50 hours, more preferably 0.01 hours to 20 hours, and more preferably 0.1 hours to 10 hours. Further preferred. In addition, the reaction solution can be collected and the reaction can be terminated after confirming that a desired amount of carbamate has been generated by, for example, liquid chromatography.

In the reaction between the carbonate ester and the amine compound, a catalyst may or may not be used. When a catalyst is not used, thermal modification of the carbamate due to the influence of the metal component derived from the catalyst can be prevented.
When a catalyst is used, the reaction can be completed in a short time and the reaction temperature can be lowered.

In particular, when the compound to be used forms a salt with an inorganic acid or an organic acid, a basic compound can be used.
The basic compound may be an inorganic base or an organic base. Examples of the inorganic base include alkali metal hydroxide, alkaline earth metal hydroxide, ammonia and the like. Examples of the organic base include amine and phosphazene. Among these, as the basic compound, an amine is preferable, an aliphatic amine is more preferable, and a secondary aliphatic amine or a tertiary aliphatic amine is more preferable.

  The amount of the basic compound used is appropriately selected depending on the compound used, but the molar amount of the basic compound relative to the molar amount of the amino group of the amine compound forming the salt is 0.001 times the stoichiometric ratio. The above is preferable, and the range of 0.01 times to 100 times is more preferable.

  As the reactor used in the reaction between the carbonate ester and the amine compound, a known tank reactor, tower reactor, or distillation tower can be used. As the material of the reactor and the line, known materials can be appropriately selected and used as long as they do not adversely affect the starting materials and the reactants, but SUS304, SUS316, SUS316L, etc. are inexpensive and can be preferably used.

<Each raw material and reaction product>
Hereinafter, each raw material and reaction product used in the production method of the present embodiment will be described.

[Carbamate]
The carbamate used in the production method of the present embodiment is preferably a carbamate represented by the following general formula (2) (hereinafter sometimes referred to as “carbamate (2)”). The “carbamate” mentioned here is not limited to the carbamate obtained by the above “carbamate production process”, but includes any carbamate that can be used in the production method of the present embodiment.

In general formula (2), n21 is an integer of 1 or more. R ²¹ is an n21 valent organic group. R ²² is a residue obtained by removing one hydroxy group from a hydroxy compound.

(N21)
In general formula (2), in view of ease of production and ease of handling, n21 is preferably an integer of 1 to 5, more preferably 2 or 3, and even more preferably 3.

(R ²¹ )
In general formula (2), R ²¹ is preferably an organic group having 3 to 85 carbon atoms, and more preferably an organic group having 3 to 30 carbon atoms. The organic group for R ²¹ is an aliphatic hydrocarbon group, an aromatic hydrocarbon group, or a group formed by bonding an aliphatic hydrocarbon group and an aromatic hydrocarbon group. Specific examples of R ²¹ include a cyclic hydrocarbon group, an acyclic hydrocarbon group, a group in which an acyclic hydrocarbon group and one or more cyclic groups are bonded, and these groups are specific. And a group covalently bonded to the nonmetallic atom. Examples of the cyclic group include a cyclic hydrocarbon group, a heterocyclic group, a heterocyclic spiro group, and a hetero bridged ring group. Examples of the cyclic hydrocarbon group include a monocyclic hydrocarbon group, a condensed polycyclic hydrocarbon group, a bridged cyclic hydrocarbon group, a spiro hydrocarbon group, a ring assembly hydrocarbon group, and a cyclic group having a side chain. A hydrocarbon group etc. are mentioned. Examples of the nonmetallic atom include carbon, oxygen, nitrogen, sulfur, silicon and the like.

(R ²² )
In General Formula (2), R ²² is a residue obtained by removing one hydroxy group from a hydroxy compound, a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms, or 6 to 20 carbon atoms. The following monovalent aromatic hydrocarbon groups are preferred. The monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms and the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms may have a substituent.

The monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms in R ²² may be a chain or a ring.
Examples of the chain aliphatic hydrocarbon group include a linear alkyl group and a branched alkyl group. The linear alkyl group preferably has 1 to 5 carbon atoms, more preferably 1 to 4 carbon atoms, and still more preferably 1 or 2. Specific examples of the linear alkyl group include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, and an n-pentyl group. The number of carbon atoms of the branched alkyl group is preferably 3 or more and 10 or less, and more preferably 3 or more and 5 or less. Specific examples of the branched alkyl group include isopropyl group, isobutyl group, tert-butyl group, isopentyl group, neopentyl group, 1,1-diethylpropyl group, 2,2-dimethylbutyl group, and the like. .
The cyclic aliphatic hydrocarbon group (that is, alicyclic hydrocarbon group) may be monocyclic or polycyclic. Specific examples of the monocyclic alicyclic hydrocarbon group include cyclopentane and cyclohexane. Specific examples of the polycyclic alicyclic hydrocarbon group include adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane.

The aromatic hydrocarbon group for R ²² preferably has 6 to 20 carbon atoms, and more preferably 6 to 12 carbon atoms. R ²² may be an aromatic hydrocarbon group having 21 or more carbon atoms, but from the viewpoint of facilitating separation from isocyanate generated by a thermal decomposition reaction of carbamate, the number of carbon atoms constituting R ²² is 20 or less. Is preferred.

Examples of the aromatic hydrocarbon group in R ²² include a phenyl group, a methylphenyl group (each isomer), an ethylphenyl group (each isomer), a propylphenyl group (each isomer), and a butylphenyl group (each isomer). ), Pentylphenyl group (each isomer), hexylphenyl group (each isomer), dimethylphenyl group (each isomer), methylethylphenyl group (each isomer), methylpropylphenyl group (each isomer), methyl Butylphenyl group (each isomer), methylpentylphenyl group (each isomer), diethylphenyl group (each isomer), ethylpropylphenyl group (each isomer), ethylbutylphenyl group (each isomer), dipropyl Phenyl group (each isomer), trimethylphenyl group (each isomer), triethylphenyl group (each isomer), naphthyl group (each isomer), etc. It is.

1.1 Functional Carbamate When the carbamate (2) is a monofunctional carbamate in which n21 is 1 (that is, a compound having one carbamate group in one molecule), preferred carbamate (2) is, for example, A carbamate represented by the following general formula (2-1a) (hereinafter sometimes referred to as “carbamate (2-1a)”), a carbamate represented by the following general formula (2-1b) (hereinafter referred to as “carbamate”). (2-1b) may be referred to).
In addition, these compounds are only examples of preferable carbamate (2), and preferable carbamate (2) is not limited thereto.

In the general formula (2-1a), R ²¹¹ is a hydrocarbon group having 3 to 85 carbon atoms. R ²¹² is the same as R ²² described above.

In the general formula (2-1b), X ²¹¹ is an oxygen atom or a secondary amino group (—NH—). R ²¹³ is the same as R ²² described above. R ²¹⁴ is a hydrogen atom, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, or an aromatic hydrocarbon group having 6 to 10 carbon atoms. The aliphatic hydrocarbon group having 1 to 10 carbon atoms and the aromatic hydrocarbon group having 6 to 10 carbon atoms may include at least one selected from the group consisting of a sulfur atom, an oxygen atom, and a halogen atom. . R ²¹⁵ is a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 10 carbon atoms.

The carbamate (2-1b) is a carbamate having an α-amino acid skeleton.
In α-amino acids, there are two steric combinations of amino groups, carboxyl groups and the like to the α carbon, which are distinguished as D-type and L-type optical isomers, respectively. The amino acid (and the compound having an amino acid skeleton) used for the production of the carbamate (3-1b) may be D-type, L-type, a mixture thereof or a racemate. Many amino acids that can be obtained industrially at low cost are amino acids that are produced by fermentation and are mostly L-type, but they can be preferably used. In this specification, the configuration is not shown, but either the D-type or the L-type is shown.

( ^R211 )
R ²¹¹ represents a hydrocarbon group having 85 or less carbon number of 3 or more. The hydrocarbon group for ^R211 may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group. As the hydrocarbon group for R ^211, the same hydrocarbon groups as those exemplified for R ²¹ above can be mentioned.

(R ²¹⁴ and R ²¹⁵ )
Specific examples of the monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms in R ²¹⁴ and R ²¹⁵ include, for example, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, and a decyl group. Is mentioned. Specific examples of the monovalent aromatic hydrocarbon group having 6 to 10 carbon atoms in R ²¹⁴ and R ²¹⁵ include, for example, a phenyl group, a methylphenyl group, an ethylphenyl group, a butylphenyl group, a dimethylphenyl group, and diethylphenyl. Groups and the like. In addition, the aliphatic hydrocarbon group having 1 to 10 carbon atoms and the aromatic hydrocarbon group having 6 to 10 carbon atoms in R ²¹⁴ include at least one selected from the group consisting of a sulfur atom, an oxygen atom, and a halogen atom. May be included. In addition, when it contains a sulfur atom or an oxygen atom, the carbon atom constituting the aliphatic hydrocarbon group having 1 to 10 carbon atoms and the aromatic hydrocarbon group having 6 to 10 carbon atoms is an oxygen atom or an oxygen atom. Has been replaced.

( ^X211 )
X ²¹¹ is an oxygen atom or a secondary amino group (-NH-). When X ²¹¹ is an oxygen atom, an ester bond is formed with an adjacent carbonyl group. When X ²¹¹ is a secondary amino group (—NH—), an amide bond is formed with an adjacent carbonyl group.

Among these, as the monofunctional carbamate, carbamate (2-1b) is preferable.
As preferable carbamate (2-1b), for example, a compound represented by the following formula (2-1b-1), a compound represented by the following formula (2-1b-2), and the following formula (2-1b-3) ), A compound represented by the following formula (2-1b-4), and the like.

2.2 Functional Carbamate When the carbamate (2) is a bifunctional carbamate in which n21 is 2 (that is, a compound having two carbamate groups in one molecule), preferred carbamate (2) is, for example, A carbamate represented by the following general formula (2-2a) (hereinafter sometimes referred to as “carbamate (2-2a)”), a carbamate represented by the following general formula (2-2b) (hereinafter referred to as “carbamate”). (2-2b) ”, carbamates represented by the following general formula (2-2c) (hereinafter sometimes referred to as“ carbamate (2-2c) ”), and general formulas (2- 2d) (hereinafter sometimes referred to as “carbamate (2-2d)”) and the like.
In addition, these compounds are only examples of preferable carbamate (2), and preferable carbamate (2) is not limited thereto.

In the general formula (2-2a), R ²²¹ is the same as R ²¹¹ described above. R ²²² is the same as R ²² described above.

In the general formula (2-2b), X ²²¹ is the same as X ²¹¹ described above. R ²²³ is the same as R ²² described above. R ²²⁴ is the same as R ²¹⁴ described above. R ²²⁵ is a divalent aliphatic hydrocarbon group having 1 to 10 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 10 carbon atoms.

In general formula (2-2c), X ²²² is the same as X ²¹¹ described above. R ²²⁶ and R ²²⁷ are the same as R ²² described above. Y ²²¹ is a polyalkylene chain having 1 to 5 carbon atoms. R ²²⁸ is the same as R ²¹⁵ described above.

In general formula (2-2d), X ²²³ is the same as X ²¹¹ described above. R ²²⁹ and R ²³⁰ are the same as R ²² described above. Y ²²² is the same as Y ²²¹ described above. R ²³¹ is the same as R ²¹⁴ described above.

(R ²²⁵ )
Examples of the divalent aliphatic hydrocarbon group having 1 to 10 carbon atoms in R ^225, for example, methylene group, ethylene group, trimethylene group, tetramethylene group, pentamethylene group, hexamethylene group and the like. Examples of the divalent aromatic hydrocarbon group having 6 to 10 carbon atoms in R ^225, e.g., a phenylene group, naphthalene - like diyl group.

(Y ²²¹ )
Y ²²¹ and Y ²²² are each independently a polyalkylene chain having 1 to 5 carbon atoms. That is, Y ²²¹ and Y ²²² are divalent groups represented by the following general formula (II).
_{- (CH 2) n221 - (} II)

  In general formula (II), n221 is an integer of 1 or more and 5 or less.

  Examples of the polyalkylene chain having 1 to 5 carbon atoms include a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, and a pentamethylene group.

  Specific examples of preferable carbamate (2-2a), carbamate (2-2b), carbamate (2-2c) and carbamate (2-2d) include, for example, aliphatic dicarbamate having 4 to 30 carbon atoms, carbon number Examples thereof include alicyclic dicarbamates having 8 to 30 carbon atoms, dicarbamates containing an aromatic group having 8 to 30 carbon atoms, and the like.

  Specific examples of the aliphatic dicarbamate having 4 to 30 carbon atoms include 1,5-pentamethylene di (carbamic acid methyl ester), 1,6-hexamethylene di (carbamic acid methyl ester), and lysine ethyl ester. Di (carbamic acid methyl ester), 1,5-pentamethylene di (carbamic acid ethyl ester), 1,6-hexamethylene di (carbamic acid ethyl ester), lysine ethyl ester di (carbamic acid ethyl ester), 1,5 -Pentamethylene di (carbamic acid phenyl ester), 1,6-hexamethylene di (carbamic acid phenyl ester), lysine ethyl ester di (carbamic acid phenyl ester), ethyl-2,6-bis ((phenoxycarbonyl) amino) Examples include hexonate.

  Specific examples of the alicyclic dicarbamate having 8 to 30 carbon atoms include, for example, isophorone di (carbamic acid methyl ester), 1,3-bis ((carbamic acid methyl ester) methyl) -cyclohexane, 4,4′- Dicyclohexylmethane di (carbamic acid methyl ester), hydrogenated tetramethylxylylene di (carbamic acid methyl ester), norbornene di (carbamic acid methyl ester), isophorone di (carbamic acid ethyl ester), 1,3-bis ((ethyl carbamate) Ester) ethyl) -cyclohexane, 4,4'-dicyclohexylmethane di (carbamic acid ethyl ester), hydrogenated tetraethylxylylene dicarbamate (ethyl carbamate), norbornene di (carbamic acid ethyl ester), isophorone di (carbamic acid) Phenyl ester), 1,3-bis ((carbamic acid phenyl ester) phenyl) -cyclohexane, 4,4′-dicyclohexylmethane di (carbamic acid phenyl ester), hydrogenated tetraphenylxylylene dicarbamate (phenyl ester), norbornene Examples include di (carbamic acid phenyl ester), 3- (phenoxycarbonylamino-methyl) -3,5,5-trimethylcyclohexylcarbamic acid phenyl ester, and the like.

  Specific examples of the dicarbamate containing an aromatic group having 8 or more and 30 or less carbon atoms include, for example, 4,4′-diphenylmethane di (carbamic acid methyl ester), 2,6-tolylene di (carbamic acid methyl ester), and xylylene diene. (Methyl carbamate), tetramethylxylylene dicarbamate (methyl ester), naphthalene dicarbamate (methyl ester), 4,4'-diphenylmethane di (ethyl carbamate), 2,6-tolylene dicarbamate (ethyl carbamate) Ester), xylylene di (carbamic acid ethyl ester), tetraethyl xylylene di (carbamic acid ethyl ester), naphthalene di (carbamic acid ethyl ester), 4,4'-diphenylmethane di (carbamic acid phenyl ester), 2,6-tolylene (Carbamic acid phenyl ester), Kishirirenji (carbamic acid phenyl ester), tetraphenyl xylylene (carbamic acid phenyl ester), and naphthalenedicarboxylic (carbamic acid dimethyl phenyl ester) is.

In addition, when a structural isomer exists in the compound illustrated above, the structural isomer is also included in a preferable carbamate (2).
Moreover, these compounds are only examples of preferable carbamate (2), and preferable carbamate (2) is not limited thereto.

3.3 Trifunctional Carbamate In the carbamate (2), when it is a trifunctional carbamate in which n31 is 3 (that is, a compound having three carbamate groups in one molecule), preferred carbamate (2) is, for example, A carbamate represented by the following general formula (2-3a) (hereinafter sometimes referred to as “carbamate (2-3c)”), a carbamate represented by the following general formula (2-3a) (hereinafter referred to as “carbamate”). (Sometimes referred to as “(2-3b)”), carbamates represented by the following general formula (2-3c) (hereinafter, sometimes referred to as “carbamate (2-3c)”), and the like.
In addition, these compounds are only examples of preferable carbamate (2), and preferable carbamate (2) is not limited to these.

In general formula (2-3a), X ²⁵¹ is the same as X ²¹¹ described above. R ²⁵¹ is the same as R ²² described above. R ²⁵² is the same as R ²¹⁴ described above. R ²⁵³ is a trivalent aliphatic hydrocarbon group having 1 to 10 carbon atoms or a trivalent aromatic hydrocarbon group having 6 to 10 carbon atoms.

In general formula (2-3b), n251, n252 and n253 are each independently an integer of 1 or more and 4 or less. n254, n255, and n256 are each independently an integer of 0 or more and 5 or less. m251, m225, and m253 are each independently 0 or 1. R ²⁵⁴ , R ²⁵⁵ and R ²⁵⁶ are each independently the same as R ²² described above.

In General Formula (2-3c), a plurality of Y ²⁵¹ each independently include a single bond or one or more selected from the group consisting of an ester group and an ether group, and may have 1 to 20 carbon atoms. It is a divalent hydrocarbon group. A plurality of R ²⁵⁸ are the same as R ²² described above. A plurality of Y ²⁵¹ and R ²⁵⁸ may be the same or different. R ²⁵⁷ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms. The divalent hydrocarbon group having 1 to 20 carbon atoms and the hydrocarbon group having 1 to 20 carbon atoms may have a substituent.

( ^R253 )
R ²⁵³ is a trivalent aliphatic hydrocarbon group having 1 to 10 carbon atoms or a trivalent aromatic hydrocarbon group having 6 to 10 carbon atoms.
Examples of the trivalent aliphatic hydrocarbon group having 1 to 10 carbon atoms in R ²⁵³ include a methanetriyl group, ethanetriyl group, and propanetriyl group. Examples of the trivalent aromatic hydrocarbon group having 6 to 10 carbon atoms in R ²⁵³ include a benzenetriyl group and a naphthalenetriyl group.

(Y ²⁵¹ )
Preferred examples of Y ²⁵¹ include a divalent aliphatic hydrocarbon group having 1 to 20 carbon atoms, a divalent aromatic hydrocarbon group having 6 to 20 carbon atoms, and a fatty acid having 2 to 20 carbon atoms. A divalent group in which an aromatic hydrocarbon group and an aliphatic hydrocarbon group are bonded via an ester group, and having 2 to 20 carbon atoms, and the aliphatic hydrocarbon group and the aliphatic hydrocarbon group are bonded via an ether group A divalent group having 7 to 20 carbon atoms and a divalent group in which an aliphatic hydrocarbon group and an aromatic hydrocarbon group are bonded via an ester group, and having 7 to 20 carbon atoms. A divalent group in which an aliphatic hydrocarbon group and an aromatic hydrocarbon group are bonded via an ether group, and an ester group in which the aromatic hydrocarbon group and the aromatic hydrocarbon group have 14 to 20 carbon atoms. A divalent group bonded via a carbon atom having 14 to 20 carbon atoms. And a divalent group in which an aromatic hydrocarbon group and an aromatic hydrocarbon group are bonded via an ether group.

(R ²⁵⁷ )
R ²⁵⁷ is preferably an aliphatic hydrocarbon group having 1 to 10 carbon atoms or an aromatic hydrocarbon group having 6 to 10 carbon atoms. Examples of the aliphatic hydrocarbon group having 1 to 10 carbon atoms and the aromatic hydrocarbon group having 6 to 10 carbon atoms in R ²⁵⁷ include the same as those exemplified in the above R ²¹⁴ and R ²¹⁵ .

  Preferable carbamate (2-3b) includes, for example, a compound represented by the following general formula (2-3b-1) (hereinafter sometimes referred to as “compound (2-3b-1)”). .

(In General Formula (2-3b-1), a plurality of R ²⁵⁹ are the same as R ²² above. N257 is an integer of 2 or more and 4 or less.)

Preferred examples of the compound (2-3b-1) include those shown below.
In the general formula (2-3b-1), n257 = 2
2,2- (carbamic acid methyl ester) ethyl-2,6-di (carbamic acid methyl ester) hexanoate (in general formula (2-3b-1), R ²⁵⁹ is a methyl group)
2- (carbamic acid ethyl ester) ethyl-2,6-di (carbamic acid ethyl ester) hexanoate (in formula (2-3b-1), R ²⁵⁹ is an ethyl group)
2- (carbamic acid butyl ester) ethyl-2,6-di (carbamic acid butyl ester) hexanoate (in formula (2-3b-1), R ²⁵⁹ is a butyl group)
2- (carbamic acid phenyl ester) ethyl-2,6-di (carbamic acid phenyl ester) hexanoate (in formula (2-3b-1), R ²⁵⁹ is a phenyl group)
2- (carbamic acid dimethylphenyl ester) ethyl-2,6-di (carbamic acid dimethylphenyl ester) hexanoate (in formula (2-3b-1), R ²⁵⁹ is a dimethylphenyl group)

Preferred carbamates (2-3c), for ^example, compound ^{Y 251} represents a divalent aliphatic hydrocarbon group having 1 to 20 carbon ^{atoms, Y 251} is a divalent aromatic having 6 to 20 carbon carbonized Examples thereof include compounds that are hydrogen groups.

Specific examples of the compound in which Y ²⁵¹ is a divalent aliphatic hydrocarbon group having 1 to 20 carbon atoms include, for example, 1,8-di (carbamic acid methyl ester) -4- (carbamic acid methyl ester) methyl. Octane, 1,8-di (carbamic acid ethyl ester) 4- (carbamic acid ethyl ester) methyl octane, 2- (carbamic acid ethyl ester) ethyl-2,5-di (carbamic acid ethyl ester) pentanoate, 2- ( Carbamic acid methyl ester) ethyl-2,5-di (carbamic acid methyl ester) pentanoate, 2- (carbamic acid methyl ester) ethyl-2,6-di (carbamic acid methyl ester) hexanoate, 2- (carbamic acid ethyl ester) ) Ethyl-2,6-di (carbamic acid ethyl ester) hexanoate, Bis (2- (carbamic acid ethyl ester) ethyl) -2- (carbamic acid ethyl ester) pentanedioate, bis (2- (carbamic acid methyl ester) ethyl) -2- (carbamic acid methyl ester) pentanedioate, Bis (2- (carbamic acid butyl ester) ethyl) -2- (carbamic acid butyl ester) pentanedioate, 1,3,5-tri (carbamic acid methyl ester) benzene, 1,3,5-tri (carbamic acid) Ethyl ester) benzene and the like.

Specific examples of the compound in which Y ²⁵¹ is a divalent aromatic hydrocarbon group having 6 to 20 carbon atoms include, for example, 1,8-di (carbamic acid phenyl ester) 4- (carbamic acid phenyl ester) methyloctane. 2- (carbamic acid phenyl ester) ethyl-2,5-di (carbamic acid phenyl ester) pentanoate, 2- (carbamic acid phenyl ester) ethyl-2,6-di (carbamic acid phenyl ester) hexanoate, bis (2 Examples include-(phenyl carbamate) ethyl) -2- (phenyl carbamate) pentanedioate, 1,3,5-tri (phenyl carbamate) benzene, and the like.

[Inert solvent]
The inert solvent used in the production method of the present embodiment is practically inert under the reaction conditions, the normal boiling point is lower than that of the cyclic compound (4), and the normal boiling point of the isocyanate and hydroxyl compound to be produced. If it exists in between, it will not specifically limit.
Examples of such an inert solvent include aliphatics, alicyclics, aromatics optionally having a substituent, unsubstituted hydrocarbons, and mixtures thereof.
Further, it may be a compound which may have an oxygen atom such as ether, ketone or ester, or a compound which may have a sulfur atom such as thioether, sulfoxide or sulfone.

Specific examples of the inert solvent include alkanes, aromatic hydrocarbons and alkyl-substituted aromatic hydrocarbons, aromatic compounds substituted with a nitro group or halogen, polycyclic hydrocarbon compounds, and alicyclic groups. Examples thereof include hydrocarbons, ketones, esters, ethers and thioethers, sulfoxides, sulfones, and silicone oil.
Examples of alkanes include hexane, heptane, octane, nonane, decane, n-hexadecane, n-octadecane, eicosane, squalane and the like.
Examples of aromatic hydrocarbons and alkyl-substituted aromatic hydrocarbons include benzene, toluene, xylene, ethylbenzene, cumene, diisopropylbenzene, dibutylbenzene, naphthalene, lower alkyl-substituted naphthalene, dodecylbenzene, and the like.
Examples of aromatic compounds substituted with a nitro group or halogen include chlorobenzene, dichlorobenzene, bromobenzene, dibromobenzene, chloronaphthalene, bromnaphthalene, nitrobenzene, nitronaphthalene and the like.
Examples of the polycyclic hydrocarbon compounds include diphenyl, substituted diphenyl, diphenylmethane, terphenyl, anthracene, phenanthrene, benzyltoluene, isomers of benzyltoluene, and triphenylmethane.
Examples of the alicyclic hydrocarbons include cyclohexane and ethylcyclohexane.
Examples of ketones include methyl ethyl ketone and acetophenone.
Examples of the esters include dibutyl phthalate, dihexyl phthalate, and dioctyl phthalate.
Examples of ethers and thioethers include diphenyl ether and diphenyl sulfide.
Examples of the sulfoxides include dimethyl sulfoxide and diphenyl sulfoxide. Examples of the sulfones include dimethyl sulfone, diethyl sulfone, diphenyl sulfone, and sulfolane.
Among them, the inert solvent is preferably an aromatic compound substituted with a nitro group or halogen such as chlorobenzene, dichlorobenzene, bromobenzene, dibromobenzene, chloronaphthalene, bromnaphthalene, nitrobenzene, nitronaphthalene, and the like. More preferred is benzene substituted with halogen such as benzene or dichlorobenzene.

[Cyclic compound (4)]
The cyclic compound used in the production method of the present embodiment is a compound (cyclic compound (4)) represented by the following general formula (4).

In general formula (4), A is a condensed ring, a heteromonocyclic ring, or a benzene ring, -R ⁴⁰¹ represents a substituent substituted with one of the hydrogen atoms constituting A, and n401 is 0 or more. It is an integer of 3 or less. That is, the cyclic compound (4) is, N401 pieces of the hydrogen atoms constituting the ring A is a cyclic compound substituted with -R ^401. When n401 is 0, the cyclic compound (4) is a ring A having no substituent.

  When A is a condensed ring, the condensed ring may be a hydrocarbon group or a heterocyclic ring having a nitrogen atom or an oxygen atom. Further, the rings constituting the condensed ring may be the same ring or different rings. The condensed ring is preferably a condensed ring composed of 2 or more and 6 or less rings selected from the group consisting of 4-membered rings, 5-membered rings, and 6-membered rings. A condensed ring composed of 2 or more and 4 or less rings selected from the group consisting of membered rings is more preferred, and a condensed ring composed of 2 or more and 4 or less rings selected from the group consisting of 5 or 6 membered rings Rings are more preferred.

  As the condensed ring, a heterocyclic condensed ring having at least one nitrogen atom, a heterocyclic condensed ring having at least one oxygen atom, or a condensed cyclic hydrocarbon is preferable. Examples of the heterocyclic condensed ring having at least one nitrogen atom include, for example, a ring in which two 6-membered rings such as a quinoline ring, an isoquinoline ring, a tetrahydroquinoline ring, a naphthyridine ring, and a pteridine ring are condensed; a pyridine ring, an indole ring, Rings in which 6-membered and 5-membered rings such as isoindole ring, benzimidazole ring, indazole ring, benzotriazole ring, and purine ring are condensed; acridine ring, phenanthridine ring, phenanthroline ring, phenazine ring, carbazole ring, carboline ring And a ring in which three or more rings such as a phenoxazine ring are condensed. Examples of the heterocyclic condensed ring having at least one oxygen atom (excluding those having a nitrogen atom) include, for example, a ring in which two 6-membered rings such as a benzopyran ring and a dihydrobenpyran ring are condensed; a benzofuran ring, Examples thereof include a ring in which a 6-membered ring and a 5-membered ring such as a dihydrobenzofuran ring are condensed; a ring in which three or more rings such as a xanthene ring and an oxanthrene ring are condensed. The condensed cyclic hydrocarbon includes three rings such as a naphthalene ring, a pentalene ring and an indene ring; three rings such as an anthracene ring, a phenanthrene ring, an indacene ring, a biphenylene ring, an acenaphthylene ring and a fluorene ring Condensed ring consisting of 4 rings such as tetracene ring, tetraphen ring, pyrene ring, triphenylene ring, chrysene ring; pentacene ring, picene ring, perylene ring, pentaphen ring, hexacene ring, tetraphenylene ring, etc. And a condensed ring composed of 5 or more rings.

  When A is a heteromonocycle, the heteromonocycle may be a monocycle having at least one nitrogen atom, oxygen atom, or sulfur atom. The number of atoms constituting the ring is not particularly limited as long as it is a ring of 3 to 8 members. The heteromonocycle is preferably a heteromonocycle having at least one nitrogen atom or oxygen atom, more preferably a 5-membered or 6-membered heterocycle having at least one nitrogen atom or oxygen atom, and at least 1 More preferred are 6-membered heterocycles having one nitrogen or oxygen atom. Examples of the heterocyclic monocycle having at least one nitrogen atom include 5-membered heterocycles such as pyrrolidine ring, pyrrole ring, imidazole ring, pyrazole ring, oxazole ring; piperidine ring, pyridine ring, pyrazine ring, piperazine ring, morpholine ring, Examples thereof include 6-membered heterocycles such as a pyrimidine ring, a pyridazine ring, and a triazine ring. Examples of the heterocyclic monocycle having at least one oxygen atom (excluding those having a nitrogen atom) include, for example, 5-membered heterocycles such as tetrahydrofuran ring, dioxolane ring, furan ring; tetrahydropyran ring, pyran ring, dioxane And 6-membered heterocycles such as rings.

  As the cyclic compound (4), A is preferably a condensed ring obtained by condensing at least two 6-membered rings, a 6-membered heteromonocyclic ring, or a benzene ring. Is more preferably a condensed ring in which at least two 6-membered rings and one or two 5-membered rings are condensed, a 6-membered heteromonocycle containing at least a nitrogen atom, or a benzene ring. Specifically, as the cyclic compound (4), A is a morpholine ring, piperazine ring, pyridine ring, triazine ring, tetrahydroquinoline ring, quinoline ring, isoquinoline ring, acridine ring, chroman ring, xanthene ring, benzene ring. , A cyclic compound that is a naphthalene ring, a tetrahydronaphthalene ring, a phenanthrene ring, an anthracene ring, a tetracene ring, or a pyrene ring is preferable.

In general formula (4), R ⁴⁰¹ is a hydrocarbon group, an alkoxy group, an acyl group, a dimethylaminoalkyl group, an oxo group, a cyano group, or a halogen atom. When n401 is 2 or 3, a plurality of R ⁴⁰¹ present in one molecule may be the same group or different groups.

When R ⁴⁰¹ is a hydrocarbon group, the hydrocarbon group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group. The aliphatic hydrocarbon group may be a saturated aliphatic hydrocarbon group or an unsaturated aliphatic hydrocarbon group. Further, it may be a chain or a ring, but a chain is preferred.

When R ⁴⁰¹ is a chain aliphatic hydrocarbon group, the chain aliphatic hydrocarbon group is not particularly limited, but a chain aliphatic hydrocarbon group having 1 to 20 carbon atoms is preferable. . Examples of the chain saturated aliphatic hydrocarbon group having 1 to 20 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group. Group, n-pentyl group, isopentyl group, neopentyl group, tert-pentyl group, 1-methylbutyl group, n-hexyl group, 2-methylpentyl group, 3-methylpentyl group, 2,2-dimethylbutyl group, 2, 3-dimethylbutyl group, n-heptyl group, 2-methylhexyl group, 3-methylhexyl group, 2,2-dimethylpentyl group, 2,3-dimethylpentyl group, 2,4-dimethylpentyl group, 3,3 -Dimethylpentyl group, 3-ethylpentyl group, 2,2,3-trimethylbutyl group, n-octyl group, isooctyl group, 2-ethylhexyl group, Group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, eicosyl group and the like. As the chain unsaturated aliphatic hydrocarbon group having 1 to 20 carbon atoms, a group having a saturated bond between 1 or 2 carbon atoms of the chain saturated aliphatic hydrocarbon group listed above as an unsaturated bond Is preferred.

When A is a benzene ring, R ⁴⁰¹ is preferably a chain saturated aliphatic hydrocarbon group having 10 to 20 carbon atoms, and more preferably a chain saturated aliphatic hydrocarbon group having 10 to 16 carbon atoms. On the other hand, when A is a condensed ring or a heteromonocycle, R ⁴⁰¹ is preferably a chain saturated aliphatic hydrocarbon group having 1 to 14 carbon atoms, and a chain saturated aliphatic hydrocarbon having 1 to 10 carbon atoms. Group is more preferable, chain saturated aliphatic hydrocarbon group having 1 to 6 carbon atoms is more preferable, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group Or a tert-butyl group is even more preferred.

When R ⁴⁰¹ is an alkoxy group, the alkoxy group is preferably an alkoxy group in which the alkyl group portion is a linear or branched alkyl group having 1 to 10 carbon atoms. As the linear or branched alkyl group having 1 to 10 carbon atoms, the same as those listed for the chain saturated aliphatic hydrocarbon group of R ⁴⁰¹ can be used. As the cyclic compound (4), R ⁴⁰¹ is preferably an alkoxy group in which the alkyl group part is a linear or branched alkyl group having 1 to 6 carbon atoms, and is a methoxy group, an ethoxy group, or a propoxy group. Is more preferable.

When R ⁴⁰¹ is an acyl group, the acyl group is preferably an acyl group in which the alkyl group portion is a linear or branched alkyl group having 1 to 8 carbon atoms. As the linear or branched alkyl group having 1 to 8 carbon atoms, the same as those listed for the chain saturated aliphatic hydrocarbon group of R ⁴⁰¹ can be used. As the cyclic compound (4), R ⁴⁰¹ is preferably an acyl group in which the alkyl group part is a linear or branched alkyl group having 1 to 6 carbon atoms, and is an acetyl group, a propanoyl group, or a butanoyl group. Is more preferable.

When R ⁴⁰¹ is a dimethylaminoalkyl group, the dimethylaminoalkyl group is preferably a dimethylaminoalkyl group in which the alkyl group portion is a linear or branched alkyl group having 1 to 8 carbon atoms. As the linear or branched alkyl group having 1 to 8 carbon atoms, the same as those listed for the chain saturated aliphatic hydrocarbon group of R ⁴⁰¹ can be used. As the cyclic compound (4), R ⁴⁰¹ is preferably a dimethylaminoalkyl group in which the alkyl group part is a linear or branched alkyl group having 1 to 6 carbon atoms, such as a dimethylaminomethyl group, dimethylamino An ethyl group or a dimethylaminopropyl group is more preferable.

When R ⁴⁰¹ is a halogen atom, R ⁴⁰¹ is preferably a fluorine atom, a chlorine atom, or a bromine atom, more preferably a fluorine atom or a chlorine atom, and even more preferably a chlorine atom.

  Specifically, the following compounds are preferable as the cyclic compound (4).

(boiling point)
The cyclic compound (4) functions to extract a high-boiling component produced by the side reaction. The normal boiling point of the cyclic compound (4) is preferably 10 ° C. or higher, more preferably 30 ° C. or higher, and 50 ° C. or higher higher than the standard boiling points of the isocyanate and hydroxy compound produced by the thermal decomposition of carbamate. Is more preferable. Thus, the boiling point of the cyclic compound (4) can be appropriately selected according to the type of carbamate to be used, but the cyclic compound (4) preferably has a high boiling point, for example, the boiling point is 280 ° C. or higher. The thing of 300 degreeC or more is more preferable.

[Carbonate ester]
As the carbonate used for the production of carbamate, a compound represented by the following general formula (3) (hereinafter sometimes referred to as “compound (3)”) is preferred.

In the general formula (3), a plurality of R ³¹ are each independently an aliphatic hydrocarbon group having 1 to 20 carbon atoms or an aromatic hydrocarbon group having 6 to 20 carbon atoms. A plurality of R ³¹ may be the same as or different from each other. Among them, R ³¹ there are a plurality, preferably the same.

(R ³¹ )
Examples of the aliphatic hydrocarbon group having 1 to 20 carbon atoms and the aromatic hydrocarbon group having 6 to 20 carbon atoms in R ³¹ are the same as those exemplified in R ²² above.

  Preferred examples of the compound (3) include diaryl carbonates represented by the following general formula (3-1) (hereinafter sometimes referred to as “diaryl carbonate (3-1)”). In addition, this compound is only an example of a preferable compound (3), and a preferable compound (3) is not limited to this.

In General Formula (3-1), a plurality of R ³¹¹ are each independently an aromatic hydrocarbon group having 6 to 20 carbon atoms.

(R ³¹¹ )
In General Formula (3-1), R ³¹¹ is an aromatic hydrocarbon group having 6 to 20 carbon atoms, preferably an aromatic hydrocarbon group having 6 to 12 carbon atoms, and having 6 to 8 carbon atoms. The aromatic hydrocarbon group is more preferable. Specific examples of such R ⁸¹¹ include those similar to those exemplified as the aromatic hydrocarbon group having 6 to 20 carbon atoms in R ²² above.

Preferable examples of diaryl carbonate (3-1) include diaryl carbonate in which R ³¹¹ is an aromatic hydrocarbon group having 6 to 8 carbon atoms. Specific examples of such diaryl carbonate (3-1) include, for example, diphenyl carbonate, di (methylphenyl) carbonate (each isomer), di (diethylphenyl) carbonate (each isomer), and di (methylethyl carbonate). Phenyl) (each isomer) and the like.
In addition, these compounds are only examples of preferable diaryl carbonate (3-1), and preferable diaryl carbonate (3-1) is not limited to this.

Further, the carbonate ester may contain a metal atom. The metal atom content relative to the mass of the carbonate ester is preferably in the range of 0.001 ppm to 100,000 ppm, more preferably in the range of 0.001 ppm to 50,000 ppm, and in the range of 0.002 ppm to 30,000 ppm. Further preferred.
Further, the metal atom may exist as a metal ion or may exist as a single metal atom. Especially, as a metal atom, the metal atom which can take the valence of 2 valence or more and 4 valence or less is preferable, and 1 or more types of metals chosen from the group which consists of iron, cobalt, nickel, zinc, tin, copper, and titanium are more. preferable.

  As a method for producing the carbonate ester, a known method can be used. Among them, an aliphatic carbonic acid ester is produced by reacting an organic tin compound having a tin-oxygen-carbon bond and carbon dioxide described in International Publication No. 2009/139061 (Reference 1). A method for producing an aromatic carbonate (that is, diaryl carbonate) from a carbonate and an aromatic hydroxy compound is preferred. Moreover, the said carbonate ester can be manufactured, for example using the manufacturing apparatus as described in international publication 2009/139061 (reference document 1).

[Amine compound]
As the amine compound used for the production of carbamate, those in which the carbamate group of the carbamate is substituted with an amino group are preferable. That is, the carbamate represented by the general formula (2), the carbamate represented by the general formula (2-1a), the carbamate represented by the general formula (2-1b), and the general formula (2-2a). The carbamate represented by the general formula (2-2b), the carbamate represented by the general formula (2-2c), the carbamate represented by the general formula (2-2d), and the general The carbamate represented by Formula (2-3a), the carbamate represented by Formula (2-3b), the carbamate represented by Formula (2-3c), or the Formula (2-3b- In the carbamate represented by 1), those in which the carbamate group is substituted with an amino group (—NH ₂ ) are preferable.

[Isocyanate]
The isocyanate obtained by the production method of the present embodiment is one in which the carbamate group of the carbamate is substituted with an isocyanate group. Among them, the carbamate represented by the general formula (2), the general formula (2-1a) The carbamate represented by the general formula (2-1b), the carbamate represented by the general formula (2-2a), the carbamate represented by the general formula (2-2b), and the general Carbamate represented by formula (2-2c), carbamate represented by general formula (2-2d), carbamate represented by general formula (2-3a), represented by general formula (2-3b) A carbamate group represented by the general formula (2-3c) or a carbamate represented by the general formula (2-3b-1) Those substituted in the isocyanate group (-NCO) is preferred. That is, a compound represented by the following general formula (2) ′, a compound represented by the following general formula (2-1a) ′, a compound represented by the following general formula (2-1b) ′, and the following general formula (2 -2a) ', a compound represented by the following general formula (2-2b)', a compound represented by the following general formula (2-2c) ', and the following general formula (2-2d)' A compound represented by the following general formula (2-3a) ′, a compound represented by the following general formula (2-3b) ′, a compound represented by the following general formula (2-3c) ′, Or the compound represented by general formula (2-3b-1) 'is preferable.

In the general formula (2) ', each of n21 and ^{R 21,} the same as n21 and ^{R 21} in the general formula (2).
In General Formula (2-1a) ′, R ²¹¹ is the same as R ²¹¹ in General Formula (2-1a).
In General Formula (2-1b) ′, X ²¹¹ , R ²¹⁴ and R ²¹⁵ are the same as X ²¹¹ , R ²¹⁴ and R ²¹⁵ in General Formula (2-1b), respectively.
In general formula (2-2a) ′, R ²²¹ is the same as R ²²¹ in general formula (2-2a).
In general formula (2-2b) ′, X ²²¹ , R ²²⁴ and R ²²⁵ are the same as X ²²¹ , R ²²⁴ and R ²²⁵ in general formula (2-2b), respectively.
In general formula (2-2c) ′, X ²²² , Y ²²¹ and R ²²⁸ are the same as X ²²² , Y ²²¹ and R ²²⁸ in general formula (2-2c), respectively.
In general formula (2-2d) ′, X ²²³ , Y ²²² and R ²³¹ are the same as X ²²³ , Y ²²² and R ²³¹ in general formula (2-2d), respectively.
In general formula (2-3a) ′, X ²⁵¹ , R ²⁵² and R ²⁵³ are the same as X ²⁵¹ , R ²⁵² and R ²⁵³ in general formula (2-3a), respectively.
In general formula (2-3b) ′, n251, n252, n253, n254, n255, n256, m251, m252 and m253 are respectively n251, n252, n253, n254, n255, n256 in general formula (2-3b), The same as m251, m252, and m253.
In the general formula (2-3c) ^', respectively, ^{Y 251 where R 257} and plurality of the same as ^{R 257} and ^{Y 251} in formula (2-3c).
In General Formula (2-3b-1) ′, n257 is the same as n257 in General Formula (2-3b-1).

  Hereinafter, the present embodiment will be described more specifically with specific examples and comparative examples. However, the present embodiment is not limited to the following examples unless it exceeds the gist.

[Example 1]
1. Preparation of mixed liquid 30 kg of toluene-2,4-dicarbamic acid dibutyl ester, 30 kg of o-dichlorobenzene and 30 kg of xanthene were mixed in a stirring tank heated to 120 ° C. under atmospheric pressure nitrogen to obtain a uniform mixed liquid. It was.

2. Thermal decomposition of carbamate The mixed solution prepared in “1.” was charged into the storage tank 101 of the isocyanate production apparatus 1A shown in FIG. Xanthene and o-dichlorobenzene are charged into a reactor 100 having a heating medium jacket, the temperature of the heating medium passing through the heating medium jacket is set to 270 ° C., and the pressure inside is adjusted, and the reactor is provided at the upper part of the packed bed 108. The state in which o-dichlorobenzene is refluxed is formed via the line 16, the condenser 115, the storage tank 103, and the line 17.
The above mixed solution was supplied from the storage tank 101 to the reactor 100 via the line 10 at 1 kg / hr, and toluene-2,4-dicarbamic acid dibutyl ester was thermally decomposed. A liquid mixture containing n-butanol and o-dichlorobenzene produced by pyrolysis is recovered in the storage tank 103 via a line 16 and a condenser 115 provided on the upper part of the packed bed 108, and produced by pyrolysis 2 , 4-Toluene diisocyanate, o-dichlorobenzene, and xanthene were collected in the storage tank 104 via the line 14 and the condenser 114 provided on the upper part of the packed bed 107. On the other hand, the reaction liquid was extracted from the bottom of the reactor 100 via the line 11 so that the liquid level in the reactor 100 was constant, and collected in the storage tank 102. The yield of 2,4-toluene diisocyanate recovered in the storage tank 104 was 63%. In addition, the above operation could be continued for 200 hours.

[Example 2]
1. Preparation of Mixed Liquid 10 kg of a compound represented by the following formula (2-1b-1) (compound (2-1b-1)), 20 kg of triethylbenzene and 70 kg of acridine are heated to 120 ° C. under atmospheric pressure nitrogen. Were mixed in a stirred tank to obtain a uniform mixed solution.

2. Thermal decomposition of carbamate The mixed solution prepared in “1.” was charged into the storage tank 201 of the isocyanate production apparatus 2A shown in FIG. Triethylbenzene is charged into the distillation column 210, the temperature of the reboiler 206 is set to 200 ° C., and the internal pressure is adjusted while passing through the line 23, the condenser 205, the storage tank 203, and the line 24 provided in the upper portion of the distillation column 210. A state in which triethylbenzene was refluxed was formed.
Here, the above mixed solution is supplied at 1 kg / hr from the storage tank 201 via the line 20 to the falling film reactor 200 heated to 250 ° C. in advance to thermally decompose the compound (2-1b-1). went. Gaseous components containing phenol produced by pyrolysis, methyl 2-isocyanato-4-methylvalerate and triethylbenzene were supplied to distillation column 210 via line 22. On the other hand, acridine containing by-products was recovered in the storage tank 202 via the line 21 from the bottom of the falling film type reactor. The gaseous component recovered via the line 22 was separated by distillation in the distillation column 210, and a mixed liquid containing phenol and triethylbenzene was recovered in the storage tank 203 via the line 23 and the condenser 205. On the other hand, a mixed liquid containing methyl 2-isocyanato-4-methylvalerate and triethylbenzene was collected in the storage tank 204 via the line 27. The yield of methyl 2-isocyanato-4-methylvalerate recovered in the storage tank 204 was 89%. Moreover, the said driving | operation was able to be performed continuously for 200 hours.

[Comparative Example 1]
1. Preparation of Mixed Liquid 30 kg of toluene-2,4-dicarbamic acid dibutyl ester and 30 kg of o-dichlorobenzene were mixed in a stirring tank heated to 120 ° C. under nitrogen at atmospheric pressure to obtain a uniform mixed liquid.

2. Carbamate Thermal Decomposition The mixed solution prepared in “1.” was charged into the storage tank 101 of the isocyanate production apparatus 1A shown in FIG. 1, and o-dichlorobenzene was charged into the reactor 100 equipped with a heat medium jacket. “2. Thermal decomposition of carbamate” in Example 1 except that a state in which dichlorobenzene is refluxed is formed and the mixed solution is supplied from the storage tank 101 via the line 10 to the reactor 100 at 0.4 kg / hr. Pyrolysis was performed in the same manner as above, and a mixed liquid containing 2,4-toluene diisocyanate and o-dichlorobenzene produced by pyrolysis was recovered in the storage tank 104. The yield of 2,4-toluene diisocyanate recovered in the storage tank 104 was 18%. Further, when the above operation was continued for 2 days, the line 11 was blocked and it was difficult to continue the operation.

[Comparative Example 2]
1. Preparation of liquid mixture Compound (2-1b-1) 40 kg and triethylbenzene 80 kg were mixed in a stirring tank heated to 120 ° C. under atmospheric pressure nitrogen to obtain a uniform liquid mixture.

2. Thermal decomposition of carbamate The mixed liquid prepared in “1.” is put into the storage tank 201 of the isocyanate production apparatus 2A shown in FIG. 2, and triethylbenzene is put into the distillation column 210 to form a state in which triethylbenzene is refluxed. The mixed liquid is supplied at 0.3 kg / hr from the storage tank 201 via the line 20 to the falling film reactor 200 heated to 250 ° C. in advance to thermally decompose the compound (2-1b-1). Except for the above, pyrolysis was carried out in the same manner as in “2. Thermal decomposition of carbamate” in Example 2, and a mixed solution containing methyl 2-isocyanato-4-methylvalerate and triethylbenzene was passed via line 27. And collected in the storage tank 204. The yield of methyl 2-isocyanato-4-methylvalerate recovered in the storage tank 204 was 35%. Further, when the above operation was continued for 2 days, the line 21 was blocked and it was difficult to continue the operation.

  According to the isocyanate production method of this embodiment, side reactions can be suppressed and isocyanate can be produced continuously.

100: reactor,
101, 102, 103, 104, 105: storage tanks 106, 107, 108: packed beds 109, 110, 111, 112, 116: liquid feed pumps 113, 114, 115: condensers 10, 11, 12, 13, 14, 15, 16, 17: Line 1A: Isocyanate production apparatus 200: Falling film reactors 201, 202, 203, 204: Storage tank 205: Condenser 206: Reboiler 207, 208, 209: Liquid feed pump 210: Distillation tower 20, 21, 22, 23, 24, 25, 26, 27: Line 2A: Isocyanate production apparatus

Claims (7)

A process for producing isocyanate by thermal decomposition of carbamate,
A thermal decomposition step of continuously introducing a mixed liquid containing a carbamate and a cyclic compound represented by the following general formula (4) into a thermal decomposition reactor to perform a thermal decomposition reaction of the carbamate;
A low boiling point decomposition product recovery step of continuously extracting a low boiling point decomposition product having a standard boiling point lower than that of the cyclic compound in a gaseous state from the thermal decomposition reactor;
A high boiling point component recovery step for continuously extracting the liquid phase component that has not been recovered in the gaseous state in the low boiling point decomposition product recovery step as a high boiling point component from the thermal decomposition reactor;
A process for producing isocyanates comprising

(In the formula, A represents a condensed ring, a heteromonocyclic ring, or a benzene ring, and R ⁴⁰¹ represents a hydrocarbon group, an alkoxy group, an acyl group, a dimethylaminoalkyl group, an oxo group, a cyano group, or a halogen atom. , N401 is an integer of 0 to 3. When n401 is 2 or 3, a plurality of R ⁴⁰¹ present in one molecule may be the same group or different groups.
  A in the general formula (4) is morpholine ring, piperazine ring, pyridine ring, triazine ring, tetrahydroquinoline ring, quinoline ring, isoquinoline ring, acridine ring, chroman ring, xanthene ring, benzene ring, naphthalene ring, tetrahydronaphthalene The manufacturing method of isocyanate of Claim 1 which is a ring, a phenanthrene ring, an anthracene ring, a tetracene ring, or a pyrene ring. The mixture further comprises an inert solvent;
In the low boiling point decomposition product recovery step, the low boiling point decomposition product and the inert solvent are continuously withdrawn in a gaseous state from the thermal decomposition reactor,
The inert solvent is substantially inert under thermal decomposition reaction conditions, and its normal boiling point is lower than the normal boiling point of the cyclic compound, and the normal boiling point of isocyanate and hydroxy compound produced by thermal decomposition. The process for producing an isocyanate according to claim 1 or 2, which is between The said carbamate is a compound represented by following General formula (2), The manufacturing method of the isocyanate as described in any one of Claims 1-3.

(In the formula (2), is n21, an integer of 1 or more ^{.R 21} is ^{.R 22} is n21 divalent organic group is a residue obtained by removing one hydroxyl group from the hydroxy compound.)   The method for producing isocyanate according to any one of claims 1 to 4, wherein the pyrolysis reactor is a tubular reactor.   The said low boiling-point decomposition product contains the said isocyanate, The said low-boiling-point decomposition product is gaseous, and is supplied to the distillation column, The separation process which further isolate | separates the said isocyanate in the said distillation column is included. The manufacturing method of the isocyanate as described in any one.   The pyrolysis reaction condition is substantially inert and a gaseous carrier is introduced into the pyrolysis reactor, and gaseous components are carried out of the pyrolysis reactor. The manufacturing method of the isocyanate as described in any one.

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