Method for producing isocyanate compound

Abstract

To provide a method for producing an isocyanate compound capable of improving the thermal decomposition rate of a blocked isocyanate compound without accompanying an increase in the amount of by-products formed.SOLUTION: A method for producing an isocyanate compound comprises a reaction step in which a blocked isocyanate compound is thermally treated in the presence of a compound having a structure represented by the general formula (I) in the figure, to decompose the blocked isocyanate compound into a blocking agent and an isocyanate compound, thereby obtaining the isocyanate compound. (In the general formula (I), R1 and R2 each independently represent a monovalent organic group, or may independently form a ring structure through a carbon-carbon bond, a carbon-oxygen-carbon bond, or a carbon-nitrogen-carbon bond, provided that at least one of R1 and R2 has an aromatic group.)SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing an isocyanate compound. [Background technology]

[0002] Isocyanates are widely used as raw materials for the production of polyurethane foams, paints, adhesives, etc. The main industrial method for producing isocyanates is the reaction of an amine compound with phosgene (the phosgene process), and almost all of the isocyanates produced worldwide are produced by the phosgene process. However, the phosgene process has many problems related to the raw material phosgene and the by-product hydrogen chloride.

[0003] In light of this background, there is a demand for a method for producing an isocyanate without using phosgene. For example, Patent Document 1 describes a method for producing 1,6-hexamethylene diisocyanate by thermally decomposing a 1,6-hexamethylene dicarbamate ester in the presence of a specific catalyst. Furthermore, Patent Document 2 describes a method for producing a diisocyanate compound by reacting a diamine with dimethyl carbonate in the presence of an alkali catalyst to synthesize a urethane compound, and then thermally decomposing the urethane compound in the presence of a catalyst.

[0004] In addition, isocyanates are highly reactive and react easily with compounds such as water. Therefore, to improve stability, they are sometimes converted to blocked isocyanates, and when used, the blocking agent is dissociated by heating to regenerate the isocyanate. Blocked isocyanates have low reactivity with active hydrogen compounds, can be stored stably, and are less toxic than isocyanates, making them useful as one-component paints, adhesives, and molding compounds.

[0005] In addition, blocked isocyanates have the property of dissociating into an isocyanate and a blocking agent upon thermal decomposition. Therefore, blocked isocyanates can be decomposed into an isocyanate and a blocking agent by thermal decomposition, and the resulting isocyanate and blocking agent can be separated after or simultaneously with the thermal decomposition. The separated isocyanate and blocking agent are useful because they can also be used as raw materials in the production of isocyanates.

[0006] Various methods for producing blocked isocyanates are known, including, for example, a method of producing a blocked isocyanate by directly reacting an isocyanate with a blocking agent, a method of producing a blocked isocyanate by reacting a carbamic acid chloride obtained by reacting an amine with phosgene with the blocking agent, a method of producing a blocked isocyanate by reacting a carbamic acid with a blocking agent and a condensing agent, a method of producing a blocked isocyanate by reacting an amine with a carbonic acid derivative to produce a blocked isocyanate containing a compound derived from the carbonic acid derivative, and a method of producing a blocked isocyanate by reacting an amine with a carbonic acid derivative and a blocking agent.

[0007] When producing an isocyanate by thermal decomposition of a blocked isocyanate, it is desirable to carry out the process in the presence of a highly polar compound that is stable at the thermal decomposition temperature, from the viewpoints of promoting the reaction and suppressing the formation of precipitates. An example of a highly polar compound is formamide such as dimethylformamide, but since dimethylformamide decomposes at high temperatures, a more stable compound is desired. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 6-239826 [Patent Document 2] Japanese Unexamined Patent Publication No. 64-85956 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been made in view of the above circumstances, and provides a method for producing an isocyanate compound in high yield without increasing the amount of by-products produced by thermally decomposing a blocked isocyanate composition in the presence of a specific compound. [Means for solving the problem]

[0010] That is, the present invention includes the following aspects.

[0011] [1] A method for producing an isocyanate compound, comprising a reaction step of decomposing a blocked isocyanate compound into a blocking agent and an isocyanate compound by heat treatment in the presence of a compound having a structure represented by the following general formula (I), thereby obtaining the isocyanate compound: [ka] (In general formula (I), R 1 and R 2 R is each independently a monovalent organic group. 1 and R 2 may be bonded to each other to form a ring structure via a carbon-carbon bond, a carbon-oxygen-carbon bond, or a carbon-nitrogen-carbon bond. 1 and R 2 At least one of the groups has an aromatic group. [2] In the general formula (I), R 1 and R 2 The method for producing an isocyanate compound according to [1], wherein one of the above has a structure represented by any one of the following general formulas (I-1) to (I-4), and the other has a structure represented by any one of the following general formulas (I-1) to (I-5). [ka] In formulas (I-1) to (I-6), an asterisk (*) represents a bond to a nitrogen atom. In formula (I-2), R 11 represents a saturated hydrocarbon group having 1 to 6 carbon atoms. In formula (I-3), n11 represents an integer of 1 to 3. In formula (I-4), R 12 and R 13each independently represents a hydrogen atom or a saturated hydrocarbon group having 1 to 6 carbon atoms which may have a ring structure. 14 represents a saturated hydrocarbon group having 1 to 6 carbon atoms. 15 represents a saturated hydrocarbon group having 1 to 6 carbon atoms. [3] The method for producing an isocyanate compound according to [1] or [2], wherein the blocking agent contains one or more compounds selected from the group consisting of hydroxy compounds, amine compounds, and ammonia. [4] The method for producing an isocyanate compound according to any one of [1] to [3], wherein the isocyanate compound is an isocyanate compound represented by the following general formula (II): [ka] (In general formula (II), R 21 is an organic group having a valence of n21, where n21 is an integer of 1 or more and 12 or less. [5] The method for producing an isocyanate compound according to any one of [1] to [4], wherein the blocking agent is an aromatic hydroxy compound represented by the following general formula (III): [ka] (In general formula (III), ring A 31 is an aromatic hydrocarbon ring having 6 to 20 carbon atoms. 31 is a hydrogen atom, a halogen atom, a carboxy group, an alkyl group having from 1 to 20 carbon atoms, an alkoxy group having from 1 to 20 carbon atoms, an alkyloxycarbonyl group having from 1 to 20 carbon atoms, an alkylcarbonyloxy group having from 1 to 20 carbon atoms, an aryl group having from 6 to 20 carbon atoms, an aryloxy group having from 6 to 20 carbon atoms, an aralkyl group having from 7 to 20 carbon atoms, or an aralkyloxy group having from 7 to 20 carbon atoms. 31 is ring A 31 may bond to form a ring structure, and n31 is an integer of 1 or more and 10 or less. [6] The method for producing an isocyanate compound according to any one of [1] to [5], wherein the blocking agent is an aliphatic hydroxy compound represented by the following general formula (IV): [ka] (In general formula (IV), R 41 is a substituted or unsubstituted aliphatic hydrocarbon group having 1 to 24 carbon atoms, which may have an ether group, a carbonyl group, or an ester group. [7] The method for producing an isocyanate compound according to any one of [1] to [6], wherein the blocking agent is a secondary amine compound represented by the following general formula (V): [ka] (In general formula (V), R 51 and R 52 R is each independently a monovalent organic group. 51 and R 52 may be bonded to each other to form a ring structure via a carbon-carbon bond, a carbon-oxygen-carbon bond, or a carbon-nitrogen-carbon bond. [8] The method for producing an isocyanate compound according to any one of [1] to [7], wherein in the reaction step, the amount of the compound having the structure represented by general formula (I) present is 1 ppm by mass or more relative to the total amount of the blocked isocyanate compound. [9] The compound having a structure represented by the general formula (I) is N,N-diphenylformanilide, N-phenyl-N-tolylformanilide (each isomer), N-(methoxyphenyl)-N-phenylformanilide (each isomer), N-(ethoxyphenyl)-N-phenylformanilide (each isomer), N-(butoxyphenyl)-N-phenylformanilide (each isomer), N-methylformanilide, N-ethylformanilide, The method for producing an isocyanate compound according to any one of [1] to [8], wherein the isocyanate compound is N-propylformanilide, N-butylformanilide, N-methyl-N-tolylformamide (each isomer), N-ethyl-N-tolylformamide, N-propyl-N-tolylformamide, N-butyl-N-tolylformamide, N-(methoxyphenyl)-N-methylformamide, or N-(ethoxyphenyl)-N-methylformamide. [Effects of the Invention]

[0012] According to the method for producing an isocyanate compound of the above aspect, it is possible to provide a method for producing an isocyanate compound in high yield without increasing the amount of by-products produced. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment for carrying out the present invention (hereinafter referred to as "the present embodiment") will be described in detail. The present embodiment is an example for explaining the present invention, and the present invention is not limited to the present embodiment. The present invention can be carried out by appropriately modifying it within the scope of its gist.

[0014] In this specification, the term "active hydrogen" refers to a hydrogen atom bonded to an oxygen atom, a sulfur atom, or a nitrogen atom, and a hydrogen atom of an active methylene group, such as a hydrogen atom contained in an atomic group such as an -OH group, a -C(=O)OH group, a -SH group, a -NH group, a -NH- group, or a -C(=O)-C(-H)-C(=O)- group.

[0015] <Method for producing isocyanate compounds> The present embodiment is a method for producing an isocyanate compound, which includes a reaction step of decomposing a blocked isocyanate compound into a blocking agent and an isocyanate compound by heat treatment in the presence of a compound having a structure represented by the following general formula (I), thereby obtaining the isocyanate compound. Hereinafter, a compound having a structure represented by the following general formula (I) will be referred to as "compound (I)".

[0016] [ka] (In general formula (I), R 1 and R 2 R is each independently a monovalent organic group. 1 and R 2 may each independently form a ring structure via a carbon-carbon bond, a carbon-oxygen-carbon bond, or a carbon-nitrogen-carbon bond. 1 and R 2 At least one of the groups has an aromatic group.

[0017] The present inventors have found that a method for producing an isocyanate compound in high yield without increasing the amount of by-products produced can be achieved by heat treating a blocked isocyanate compound in the presence of compound (I) to decompose it into a blocking agent and an isocyanate compound, thereby completing the present invention. The manufacturing method of the present invention will be described below.

[0018] <Reaction process> In the reaction step in the method for producing an isocyanate compound according to this embodiment, a blocked isocyanate compound is decomposed into a blocking agent and an isocyanate compound by heat treatment in the presence of compound (I), thereby obtaining an isocyanate compound.

[0019] In the reaction step, the amount of compound (I) present is preferably large from the viewpoint of improving the thermal decomposition rate. Specifically, the amount of compound (I) present is preferably 1 ppm by mass or more, more preferably 1000 ppm by mass or more, and even more preferably 1% by mass or more, based on the total amount of the blocked isocyanate compound. The upper limit of the amount present is not particularly limited, but is preferably 1000% by mass or less, more preferably 100% by mass or less, and even more preferably 10% by mass or less, based on the total amount of the blocked isocyanate compound.

[0020] The reaction temperature in the reaction step (thermal decomposition temperature of the blocked isocyanate compound) is not particularly limited and is appropriately selected depending on the rate at which the blocked isocyanate compound decomposes into a blocking agent and an isocyanate compound, and the degree of thermal denaturation and coloration. From the viewpoint of suppressing denaturation of the isocyanate compound, the reaction temperature is preferably 350°C or lower, more preferably 300°C or lower, and even more preferably 260°C or lower. On the other hand, if the reaction temperature is low, it may be necessary to set the condenser temperature at a low temperature, which may require new equipment. From this viewpoint, the reaction temperature is preferably 50°C or higher, more preferably 80°C or higher, and even more preferably 100°C or higher.

[0021] The reaction pressure in the reaction step varies depending on the type of compound used and the reaction temperature, but may be reduced pressure, normal pressure, or increased pressure. Generally, the absolute pressure is 20 Pa or more and 2×10 7 It is performed in the range of Pa or less.

[0022] The reaction step may be carried out in the presence of oxygen. When the reaction step is carried out in the presence of oxygen, the amount of oxygen present in the thermal decomposition apparatus for the blocked isocyanate compound is preferably reduced, since thermal denaturation and coloration of the isocyanate compound may occur. On the other hand, when considering a large-scale production facility, reducing the amount of oxygen present in the thermal decomposition apparatus for the blocked isocyanate compound requires reducing air leakage into the production facility, which results in stricter design standards for the facility and increased facility costs. From this perspective, the oxygen concentration in the gas supplied to the reaction step is preferably controlled at a high level, preferably greater than 0% by volume, more preferably greater than 0.0001% by volume, and even more preferably greater than 0.001% by volume.

[0023] In the reaction step, any solvent may be used in any proportion. The solvent is preferably an inert solvent that does not have reactivity with the blocked isocyanate compound, etc. Such a solvent is preferably an ester solvent, an ether solvent, a phosphate ester solvent, a hydrocarbon solvent, an aromatic hydrocarbon solvent, or a carbonic acid derivative solvent.

[0024] In the reaction step, the reaction solution may contain any metal in any proportion. The metal may be in the form of a complex or a solid. While the metal reduces the thermal decomposition temperature of the blocked isocyanate compound, it may cause thermal denaturation, deterioration, and coloration. The metal content is preferably less than 10% by mass, more preferably less than 1% by mass, and even more preferably less than 0.1 ppm by mass, relative to the mass of the blocked isocyanate compound.

[0025] In the reaction step, the reaction solution may contain any compound other than compound (I) that exhibits catalytic activity.

[0026] The thermal decomposition apparatus for the blocked isocyanate compound is not particularly limited, and known thermal decomposition apparatuses can be used. For example, an apparatus that places a composition containing a blocked isocyanate compound in a container connected to a condenser, heats the container to thermally decompose the blocked isocyanate compound, and then introduces vapor containing a blocking agent produced thereafter or simultaneously with the thermal decomposition into a condenser to separate the isocyanate compound and the blocking agent in a batchwise manner; an apparatus that continuously introduces a composition containing a blocked isocyanate compound into a distillation column heated to a temperature equal to or higher than the thermal decomposition temperature of the blocked isocyanate compound, and then separates the blocking agent and the isocyanate compound produced simultaneously with the thermal decomposition of the blocked isocyanate compound, thereby continuously obtaining free isocyanate compound and the blocking agent; an apparatus that introduces a blocked isocyanate compound into an evaporator or thin film heated to a temperature equal to or higher than the thermal decomposition temperature of the blocked isocyanate compound, introduces vapor containing the blocking agent and the isocyanate compound produced by thermal decomposition into a distillation column, and separates the blocking agent and the isocyanate compound in the distillation column.

[0027] In the thermal decomposition apparatus for a blocked isocyanate compound, the material of the portion that comes into contact with the composition containing the blocked isocyanate compound and the blocking agent, isocyanate compound, and other components that are generated during thermal decomposition may be any known material as long as it does not adversely affect the denaturation of the blocked isocyanate compound, the blocking agent, the isocyanate compound, and other components. Specific examples of such materials include steel, stainless steel, ceramic, carbon, and materials lined with these materials.

[0028] ≪Compound (I)≫ Compound (I) is represented by the following general formula (I).

[0029] [ka] (In general formula (I), R 1 and R 2 R is each independently a monovalent organic group. 1 and R 2may each independently form a ring structure via a carbon-carbon bond, a carbon-oxygen-carbon bond, or a carbon-nitrogen-carbon bond. 1 and R 2 At least one of the groups has an aromatic group.

[0030] R 1 and R 2 The structure of R 1 and R 2 It is more preferable that one of them has a structure represented by any one of the following general formulas (I-1) to (I-5), and the other has a structure represented by any one of the following general formulas (I-1) to (I-6). [ka] In formulas (I-1) to (I-6), an asterisk (*) represents a bond to a nitrogen atom. In formula (I-2), R 11 represents a saturated hydrocarbon group having 1 to 6 carbon atoms. In formula (I-3), n11 represents an integer of 1 to 3. In formula (I-4), R 12 and R 13 each independently represents a hydrogen atom or a saturated hydrocarbon group having 1 to 6 carbon atoms which may have a ring structure. 14 represents a saturated hydrocarbon group having 1 to 6 carbon atoms. 15 represents a saturated hydrocarbon group having 1 to 6 carbon atoms.

[0031] Among them, R is the most popular due to its high thermal stability. 1 and R 2It is more preferable that one of them has a structure represented by any one of the general formulas (I-1), (I-2), and (I-5), and the other has a structure represented by any one of the general formulas (I-1), (I-2), (I-5), and (I-6). Compound (I) is preferably N,N-diphenylformanilide, N-phenyl-N-tolylformanilide (each isomer), N-(methoxyphenyl)-N-phenylformanilide (each isomer), N-(ethoxyphenyl)-N-phenylformanilide (each isomer), N-(butoxyphenyl)-N-phenylformanilide (each isomer), N-methylformanilide, N-ethylformanilide, N-propylformanilide, N-butylformanilide, N-methyl-N-tolylformamide (each isomer), N-ethyl-N-tolylformamide, N-propyl-N-tolylformamide, N-butyl-N-tolylformamide, N-(methoxyphenyl)-N-methylformamide, or N-(ethoxyphenyl)-N-methylformamide.

[0032] <Blocked isocyanate compounds> The blocked isocyanate compound is a compound that can be dissociated into a blocking agent and an isocyanate compound by heat, as shown in the following reaction formula.

[0033] R a -(NH-C(=O)-BL) na → BL-H + R a -(N=C=O) na

[0034] In the above reaction formula, BL-H is a blocking agent having active hydrogen. a is an organic group with a valence of na, where na is an integer of 1 or greater. BL- is a residue obtained by removing active hydrogen from a blocking agent.

[0035] <Isocyanate compounds> As the isocyanate compound in the reaction step, an isocyanate compound represented by the following general formula (II) (hereinafter, sometimes referred to as "isocyanate compound (II)") is preferably used.

[0036] [ka]

[0037] (In general formula (II), R 21 is an organic group having a valence of n21, where n21 is an integer of 1 or more and 12 or less.

[0038] R 21 Although R is not particularly limited as long as it is an organic group with a valence of 1 to 12, it is preferably an organic group (hydrocarbon group) consisting of carbon atoms and hydrogen atoms or an organic group consisting of carbon atoms, oxygen atoms, and hydrogen atoms, and more preferably an organic group without active hydrogen. 21 The oxygen atom contained in preferably constitutes an ether group or an ester group.

[0039] R 21 The aliphatic hydrocarbon group in is preferably an alkyl group, an alkylene group, an alkanetriyl group, a cycloalkyl group, a cycloalkylene group, a cycloalkanetriyl group, or a group composed of two or more of these.

[0040] R 21 The aromatic hydrocarbon group in is preferably a substituted or unsubstituted group having an aromatic ring with 6 to 13 carbon atoms. Examples of the substituent include an alkyl group, an aralkyl group, an aryl group, an alkoxy group, an alkoxycarbonyl group, and an alkylcarbonyloxy group.

[0041] The isocyanate compound (II) may be a monofunctional isocyanate compound, a bifunctional isocyanate compound, or a polyfunctional isocyanate compound.

[0042] In monofunctional isocyanate compounds, R 21 Examples of the monovalent organic group include a substituted or unsubstituted alkyl group, cycloalkyl group, aralkyl group, and aryl group.

[0043] In bifunctional isocyanate compounds, R 21 Examples of the divalent organic group include a substituted or unsubstituted alkylene group, a cycloalkylene group, an arylene group, an arylene dialkylene group, an alkylenediarylene group, an alkylenedicycloalkylene group, etc. The bifunctional isocyanate compound may be a compound having an isocyanatoalkyl group such as isophorone diisocyanate, a compound having an isocyanatocycloalkyl group such as dicyclohexylmethane 4,4'-diisocyanate, a compound having an isocyanatoaryl group such as diphenylmethane diisocyanate, or a compound having a carbonyl group such as lysine diisocyanate.

[0044] In polyfunctional isocyanate compounds, R 21 Examples of the polyvalent organic group include a substituted or unsubstituted alkanetriyl group, a cycloalkanetriyl group, an arenetriyl group, etc. The polyfunctional isocyanate compound may be a compound having an isocyanatoalkyl group such as 4-isocyanatomethyl-1,8-octamethylene diisocyanate, or a compound having a carbonyl group such as lysine triisocyanate.

[0045] <Blocking agent> The blocking agent is a compound having active hydrogen. The blocking agent used in the reaction step preferably contains one or more compounds selected from the group consisting of hydroxy compounds, amine compounds, and ammonia. The hydroxy compounds include one or more compounds selected from the group consisting of aromatic hydroxy compounds and aliphatic hydroxy compounds.

[0046] [Blocking agent, aromatic hydroxy compound] Aromatic hydroxy compounds preferred as blocking agents include aromatic hydroxy compounds represented by the following general formula (III).

[0047] [ka]

[0048] (In general formula (III), ring A 31 is an aromatic hydrocarbon ring having 6 to 20 carbon atoms. 31 R is a hydrogen atom, a halogen atom, a carboxy group, an alkyl group having from 1 to 20 carbon atoms, an alkoxy group having from 1 to 20 carbon atoms, an alkyloxycarbonyl group having from 1 to 20 carbon atoms, an alkylcarbonyloxy group having from 1 to 20 carbon atoms, an aryl group having from 6 to 20 carbon atoms, an aryloxy group having from 6 to 20 carbon atoms, an aralkyl group having from 7 to 20 carbon atoms, or an aralkyloxy group having from 7 to 20 carbon atoms. 31 is ring A 31 may bond to form a ring structure, and n31 is an integer of 1 or more and 10 or less.

[0049] Ring A 31 may be a monocyclic ring or a polycyclic ring such as a condensed ring. 31 Specific examples of the ring A include a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, a naphthacene ring, a chrysene ring, a pyrene ring, a triphenylene ring, a pentalene ring, an azulene ring, a heptalene ring, an indacene ring, a biphenylene ring, an acenaphthylene ring, an aceanthrylene ring, and an acephenanthrylene ring. 31 As the ring, a benzene ring, a naphthalene ring, or an anthracene ring is preferable, and a benzene ring is more preferable.

[0050] The hydroxy group shown in general formula (III) is 31 The ring A is bonded to an aromatic carbon atom and has phenolic properties. 31 and n31 R 31 The aromatic hydrocarbon group having the formula may be a substituted or unsubstituted monovalent aromatic hydrocarbon group such as an aryl group.

[0051] R 31 is the ring A except for the hydrogen atom. 31 is a substituent of Ring A. 31 As shown in general formula (III), it is a group consisting of one hydroxy group and n31 R31 It has n31 R 31 are each independently, R 31 Different rings may be selected from the group exemplified in the above, or two or more of the same rings may be selected. 31 is the above R 31 Besides, Ring A 31 The ring A may have a hydrogen atom and / or a substituent bonded to the carbon atom constituting the ring A. 31 The hydrogen atoms, substituents, and functional groups bonded to the carbon atoms constituting the formula (III) are one hydroxy group and n31 R 31Specific compounds include phenol, methylphenol (each isomer), ethylphenol (each isomer), propylphenol (each isomer), butylphenol (each isomer), pentylphenol (each isomer), hexylphenol (each isomer), heptylphenol (each isomer), octylphenol (each isomer), nonylphenol (each isomer), decylphenol (each isomer), undecylphenol (each isomer), tridecylphenol (each isomer), tetradecylphenol (each isomer), octadecylphenol (each isomer), nonadecylphenol, phenol (each isomer), icosylphenol (each isomer), cyclopentylphenol (each isomer), cyclohexylphenol (each isomer), dimethylphenol (each isomer), methylethylphenol (each isomer), diethylphenol (each isomer), methylpropylphenol (each isomer), ethylpropylphenol (each isomer), dipropylphenol (each isomer), methylbutylphenol (each isomer), ethylbutylphenol (each isomer), propylbutylphenol (each isomer), dibutylphenol (each isomer), trimethylphenol phenol (each isomer), methyldiethylphenol (each isomer), dimethylethylphenol (each isomer), triethylphenol (each isomer), methyldipropylphenol (each isomer), dimethylpropylphenol (each isomer), tripropylphenol (each isomer), ethyldipropylphenol (each isomer), diethylpropylphenol (each isomer), methyldibutylphenol (each isomer), dimethylbutylphenol (each isomer), ethyldibutylphenol (each isomer), diethylbutylphenol (each isomer), propyldibutylphenol phenol (each isomer), dipropylbutylphenol (each isomer), tributylphenol (each isomer), naphthol (each isomer), methylnaphthol (each isomer), ethylnaphthol (each isomer), propylnaphthol (each isomer), butylnaphthol (each isomer), tetrahydronaphthalen-1-ol, tetrahydronaphthalen-2-ol, hydroxyphenylphenylmethane (each isomer), hydroxyphenylphenylethane (each isomer), hydroxyphenylphenylpropane (each isomer), hydroxyphenylphenylbutane (each isomer),Phenol-based blocking agents having a hydrocarbon group such as 4-α-cumylphenol and 2,4-di-α-cumylphenol; methoxyphenol (each isomer), ethoxyphenol (each isomer), propoxyphenol (each isomer), butoxyphenol (each isomer), pentoxyphenol (each isomer), hexoxyphenol (each isomer), heptoxyphenol (each isomer), octoxyphenol (each isomer), methoxymethylphenol (each isomer), methoxyethylphenol (each isomer), methoxypropylphenol (each isomer), methoxybutylphenol Examples of the blocking agent include phenol-based blocking agents having an ether bond, such as butylphenol (each isomer), ethoxymethylphenol (each isomer), ethoxyethylphenol (each isomer), ethoxypropylphenol (each isomer), ethoxybutylphenol (each isomer), propoxymethylphenol (each isomer), propoxyethylphenol (each isomer), propoxypropylphenol (each isomer), butoxymethylphenol (each isomer), butoxyethylphenol (each isomer), butoxypropylphenol (each isomer), and butoxybutylphenol.

[0052] [Aliphatic hydroxy compound blocking agent] The aliphatic hydroxy compound preferably used as a blocking agent includes an aliphatic hydroxy compound represented by the following general formula (IV).

[0053] [ka]

[0054] (In general formula (IV), R 41 is a substituted or unsubstituted aliphatic hydrocarbon group having 1 to 24 carbon atoms, which may have an ether group, a carbonyl group, or an ester group.

[0055] R 41 is a monovalent aliphatic hydrocarbon group. 41 The number of carbon atoms in the aliphatic hydrocarbon group in R is 1 or more and 24 or less, preferably 1 or more and 20 or less, and more preferably 1 or more and 12 or less.41 The aliphatic hydrocarbon group in may be saturated or unsaturated. One hydroxy group shown in general formula (IV) is R 41 Specific compounds include alcohol-based blocking agents having saturated hydrocarbon groups such as methanol, ethanol, propanol (each isomer), butanol (each isomer), pentanol (each isomer), hexanol (each isomer), heptanol (each isomer), octanol (each isomer), nonanol (each isomer), cyclopentanol, and cyclohexanol, as well as 1-methoxyethanol, 1-ethoxyethanol, 1-propoxyethanol, 1-butoxyethanol, 1-pentoxyethanol, 1-hexoxyethanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, and 1- Examples of the blocking agent include alcohol-based blocking agents having an ether group, such as propoxy-2-propanol, 1-butoxy-2-propanol, 1-pentoxy-2-propanol, 1-butoxy-2-propanol, polyethylene oxide monomethyl ether, polyethylene oxide monoethyl ether, polyethylene oxide monopropyl ether, polyethylene oxide monobutyl ether, polypropylene oxide monomethyl ether, polypropylene oxide monoethyl ether, polypropylene oxide monopropyl ether, and polypropylene oxide monobutyl ether.

[0056] [Secondary amine compound blocking agent] The secondary amine compound preferably used as a blocking agent includes a secondary amine compound represented by the following general formula (V).

[0057] [ka]

[0058] (In general formula (V), R 51 and R 52 R is each independently a monovalent organic group. 51 and R 52may be bonded to each other to form a ring structure via a carbon-carbon bond, a carbon-oxygen-carbon bond, or a carbon-nitrogen-carbon bond.

[0059] Among them, R 51 and R 52 R is preferably a substituted or unsubstituted monovalent aliphatic hydrocarbon group having 1 to 70 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 70 carbon atoms, which may have an ether group, a carbonyl group, or an ester group. 51 and R 52 is preferably an organic group that does not contain active hydrogen, and more preferably an organic group that does not contain a substituted or unsubstituted amino group.

[0060] R 51 and R 52 Examples of the aliphatic hydrocarbon group in R include an alkyl group and a cycloalkyl group. 51 and R 52 The number of carbon atoms in the aliphatic hydrocarbon group in R is preferably 1 or more and 70 or less, more preferably 1 or more and 20 or less, even more preferably 1 or more and 12 or less, and particularly preferably 1 or more and 10 or less. 51 and R 52 Examples of the substituent on the aliphatic hydrocarbon group in the formula include a hydroxyl group, a cyano group, and a halogen atom.

[0061] R 51 and R 52 Examples of the aromatic hydrocarbon group in R include an aryl group and an aralkyl group. 51 and R 52 The number of carbon atoms in the aromatic hydrocarbon group in R is preferably 6 or more and 70 or less, more preferably 6 or more and 20 or less, even more preferably 6 or more and 12 or less, and particularly preferably 6 or more and 10 or less. 51 and R 52 Examples of the substituent on the aromatic hydrocarbon group in the formula (I) include an aliphatic hydrocarbon group, a hydroxyl group, a cyano group, and a halogen atom.

[0062] R 51 and R 52 When they are bonded to each other to form a ring structure, R 51and R 52 The group formed by bonding together is a divalent organic group. 51 and R 52 Examples of groups formed by bonding together include substituted or unsubstituted ether groups, carbonyl groups, ester groups, and substituted imino groups (-N(-R 53 )-), -CH=N- group, substituted amide group (-C(=O)-N(-R 54 )-) or a substituted imido group (-C(=O)-N(-R 55 Examples of suitable divalent aliphatic hydrocarbon groups include divalent aliphatic hydrocarbon groups having 1 to 70 carbon atoms and divalent aromatic hydrocarbon groups having 6 to 70 carbon atoms, which may have a substituent R 53 , R 54 and R 55Examples of the alkyl group include monovalent aliphatic hydrocarbon groups and aromatic hydrocarbon groups. Specific compounds include secondary amine compounds having a saturated aliphatic hydrocarbon group, such as dimethylamine, methylethylamine, diethylamine, methylpropylamine (each isomer), ethylpropylamine (each isomer), dipropylamine (each isomer), methylbutylamine (each isomer), ethylbutylamine (each isomer), propylbutylamine (each isomer), dibutylamine (each isomer), dihexylamine (each isomer), dioctylamine (each isomer), didecylamine (each isomer), and didodecylamine (each isomer); compounds such as pyrrolidine, piperidine, azepane, imidazole, methylpiperazine, and pyrrole; N-methylaniline, N-ethylaniline, N-propylaniline (each isomer), N-butylaniline (each isomer), N-pentylaniline (each isomer), and N-hexylaniline (each isomer); ), N-heptylaniline (each isomer), N-octylaniline (each isomer), N-nonylaniline (each isomer), N-decylaniline (each isomer), and other N-alkylaniline compounds; N-methyltoluidine (each isomer), N-ethyltoluidine (each isomer), N-propyltoluidine (each isomer), N-butyltoluidine (each isomer), N-pentyltoluidine (each isomer), N-hexyltoluidine ( N-alkyltoluidine compounds such as N-heptyltoluidine (each isomer), N-octyltoluidine (each isomer), N-nonyltoluidine (each isomer), and N-decyltoluidine (each isomer); or aromatic cyclic amine compounds such as indoline, methylindoline (each isomer), 1,2,3,4-tetrahydroquinoline, and methyl 1,2,3,4-tetrahydroquinoline (each isomer). [Example]

[0063] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. All of the reagents used as raw materials were purified products.

[0064] [Example of manufacturing a blocked isocyanate compound] 20 parts by mass of hexamethylene diisocyanate and 80 parts by mass of phenol were mixed and reacted at 150°C for 20 hours to synthesize diphenylhexane-1,6-diyldicarbamate. Subsequently, excess phenol was distilled off under reduced pressure at 100°C and 1 Pa. 1 As a result of HNMR analysis, it was found that a blocked isocyanate composition BL-1 containing 99 mol % of blocked isocyanate groups was obtained.

[0065] Blocked isocyanate compositions BL-2 to BL-11 were also prepared in the same manner, and the results are summarized in Table 1. The abbreviations for the isocyanate compounds and blocking agents used, and the content of blocked isocyanate (BL-NCO) groups are shown.

[0066] [Example 1-1] The blocked isocyanate compound of the above-mentioned Production Example, Compound (I), and solvent were added to a 300 mL glass vessel equipped with a pressure reducing device at the end of condenser tube 1 (the condensate from condenser tube 1 enters the 300 mL glass vessel) and condenser tube 2 (the condensate from condenser tube 2 does not enter the 300 mL glass vessel but is collected as the TOP liquid), both filled with a filler. The temperature inside the 300 mL glass vessel (reaction temperature), the degree of vacuum, the temperature of condenser tube 1, and the temperature of condenser tube 2 were set as shown in the reaction conditions in Table 2. The absolute pressure inside the reaction vessel was adjusted to 380 mmHg using the pressure reducing device, and the reaction was carried out for the time shown in Table 2. The weight of the reaction solution remaining in the 300 mL glass vessel after the reaction (referred to as the post-reaction BTM weight) is also shown in Table 2.

[0067] The content of blocked isocyanate groups (BL-NCO groups: mol%), the yield of isocyanate groups (NCO groups: mol%), and the sum of the content of BL-NCO groups and the yield of isocyanate groups (MB: mol%) were determined for the resulting reaction solution.

[0068] The blocked isocyanate group content (BL-NCO group: mol%) was calculated from the molar amount of blocked isocyanate functional groups at the time of charging and the molar amount of blocked isocyanate functional groups after the reaction according to the following formula. Note that each molar amount was calculated by 1H NMR. "Blocked isocyanate group content (BL-NCO group: mol%)" = (molar amount of blocked isocyanate functional groups after reaction) / (molar amount of blocked isocyanate functional groups at the time of charging)

[0069] The yield of isocyanate groups (NCO group: mol %) was calculated from the molar amount of blocked isocyanate functional groups at the time of charging and the molar amount of isocyanate groups after the reaction according to the following formula, where each molar amount was calculated by 1H NMR. "Isocyanate group yield (NCO group: mol%)" = (molar amount of isocyanate groups after reaction) / (molar amount of blocked isocyanate functional groups at the time of charging)

[0070] The sum of the BL-NCO group content and the isocyanate group yield (MB: mol %) was calculated according to the following formula. "MB mol%" = (Blocked isocyanate group content (BL-NCO group: mol%)) + (Isocyanate group yield (NCO group: mol%))

[0071] [Examples 1-2 to 1-11] [Comparative Examples 1-1 to 1-8] For Examples 1-2 to 1-11 and Comparative Examples 1-1 to 1-8, the reaction was carried out in the same manner as in Example 1-1, and the results are shown in Tables 2 and 3.

[0072] In the following table, the abbreviations represent the following compounds.

[0073] (Isocyanate compounds) HDI: 1,6-hexamethylene diisocyanate IPDI: Isophorone diisocyanate (mixture of isomers) TDI: Diisocyanatotoluene (mixture of isomers) MDI: Diphenylmethane diisocyanate (mixture of isomers) HMDI: Dicyclohexylmethane 4,4'-diisocyanate

[0074] (blocking agent) PhOH: Phenol o-cresol: o-cresol m-cresol p-cresol n-BuOH: normal butanol DBA: Dibutylamine NMA: N-methylaniline (solvent) Naphthene: Naphthenic solvent (EXXOL TM D80)

[0075] In the table below, the structure of compound (I) is as follows:

[0076] [ka]

[0077] [Table 1]

[0078] [Table 2]

[0079] [Table 3]

[0080] From Examples 1-1 to 1-11 in Table 2, when a blocked isocyanate compound was thermally decomposed in the presence of compound (I), the BL-NCO group after the reaction was 5 mol % or less, the NCO group was 88 mol % or more, and the MB was 92 mol % or more, and thus the modification was slight despite the large amount of NCO groups.

[0081] On the other hand, from Comparative Examples 1-1 to 1-8 in Table 3, when thermal decomposition was performed in the presence of N,N-dibutylformamide, the BL-NCO group after the reaction was 6 mol% or more, the NCO group was 35 mol% or less, and the MB was 42 mol% or less, indicating a small amount of NCO group and a large amount of modification.

[0082] [Example 2-1] [Comparative Example 2-1] The reaction in Example 2-1 and Comparative Example 2-1 was carried out in the same manner as in Example 1-1, and the results are shown in Table 4.

[0083] [Table 4]

[0084] From Example 2-1 in Table 4, when a blocked isocyanate compound was thermally decomposed in the presence of compound (I), the BL-NCO group content after the reaction was 12 mol%, the NCO group content was 53 mol%, and the MB content was 65 mol%, and thus the modification was slight despite the large amount of NCO groups.

[0085] On the other hand, from Comparative Example 2-1 in Table 4, when thermal decomposition was performed in the presence of N,N-dibutylformamide, the BL-NCO group was 14 mol%, the NCO group was 35 mol%, and the MB was 49 mol%, indicating a small amount of NCO group and a large amount of modification.

[0086] [Example 3-1] [Comparative Example 3-1] The reaction in Example 3-1 and Comparative Example 3-1 was carried out in the same manner as in Example 1-1, and the results are shown in Table 5.

[0087] [Table 5]

[0088] From Example 3-1 in Table 5, when the blocked isocyanate compound was thermally decomposed in the presence of compound (I), the NCO group content after the reaction was 35 mol %, which was high, and no gelation of the reaction solution was observed.

[0089] On the other hand, from Comparative Example 3-1 in Table 5, when thermal decomposition was carried out in the presence of N,N-dibutylformamide, the reaction solution gelled and the amount of modification was large.

[0090] [Example 4-1] [Comparative Example 4-1] The reaction in Example 4-1 and Comparative Example 4-1 was carried out in the same manner as in Example 1-1, and the results are shown in Table 6.

[0091] [Table 6]

[0092] From Example 4-1 in Table 6, when a blocked isocyanate compound was thermally decomposed in the presence of compound (I), the BL-NCO group content after the reaction was 8 mol%, the NCO group content was 76 mol%, and the MB content was 84 mol%, and thus the modification was slight despite the large amount of NCO groups.

[0093] On the other hand, from Comparative Example 4-1 in Table 6, when thermal decomposition was performed in the presence of N,N-dibutylformamide, the BL-NCO group was 9%, the NCO group was 30 mol%, and the MB was 39 mol%, indicating a small amount of NCO group and a large amount of modification. [Industrial Applicability]

[0094] According to the method for producing an isocyanate compound of the present embodiment, it is possible to provide a method for producing an isocyanate compound that can improve the thermal decomposition rate of a blocked isocyanate compound without increasing the amount of by-products produced.

Claims

1. A method for producing an isocyanate compound, comprising a reaction step of decomposing a blocked isocyanate compound into a blocking agent and an isocyanate compound by heat treatment in the presence of a compound having a structure represented by the following general formula (I), thereby obtaining the isocyanate compound: 【Chemical 1】 (In general formula (I), R １ and R ２ are each independently a monovalent organic group. １ and R ２ may each independently form a ring structure via a carbon-carbon bond, a carbon-oxygen-carbon bond, or a carbon-nitrogen-carbon bond. １ and R ２ At least one of the groups has an aromatic group.

2. In the general formula (I), R １ and R ２ wherein one of the above has a structure represented by any one of the following general formulas (I-1) to (I-5), and the other has a structure represented by any one of the following general formulas (I-1) to (I-6). 【Chemistry 2】 (In formulas (I-1) to (I-6), an asterisk (*) represents a bond to a nitrogen atom. In formula (I-2), R １１ represents a saturated hydrocarbon group having 1 to 6 carbon atoms. In formula (I-3), n11 represents an integer of 1 to 3. In formula (I-4), R １２ and R １３ each independently represents a hydrogen atom or a saturated hydrocarbon group having 1 to 6 carbon atoms which may have a ring structure. １４ represents a saturated hydrocarbon group having 1 to 6 carbon atoms. １５ represents a saturated hydrocarbon group having 1 to 6 carbon atoms.

3. 3. The method for producing an isocyanate compound according to claim 1, wherein the blocking agent comprises one or more compounds selected from the group consisting of hydroxy compounds, amine compounds, and ammonia.

4. The method for producing an isocyanate compound according to claim 1 or 2, wherein the isocyanate compound is an isocyanate compound represented by the following general formula (II): 【Chemistry 3】 (In general formula (II), R ２１ is an n21-valent organic group, where n21 is an integer of 1 or more and 12 or less.

5. The method for producing an isocyanate compound according to claim 1 or 2, wherein the blocking agent is an aromatic hydroxy compound represented by the following general formula (III): 【Chemistry 4】 (In general formula (III), ring A ３１ is an aromatic hydrocarbon ring having 6 to 20 carbon atoms. ３１ is a hydrogen atom, a halogen atom, a carboxy group, an alkyl group having from 1 to 20 carbon atoms, an alkoxy group having from 1 to 20 carbon atoms, an alkyloxycarbonyl group having from 1 to 20 carbon atoms, an alkylcarbonyloxy group having from 1 to 20 carbon atoms, an aryl group having from 6 to 20 carbon atoms, an aryloxy group having from 6 to 20 carbon atoms, an aralkyl group having from 7 to 20 carbon atoms, or an aralkyloxy group having from 7 to 20 carbon atoms. ３１ is ring A ３１ may bond to form a ring structure. n31 is an integer of 1 or more and 10 or less.

6. The method for producing an isocyanate compound according to claim 1 or 2, wherein the blocking agent is an aliphatic hydroxy compound represented by the following general formula (IV): 【Chemistry 5】 (In general formula (IV), R ４１ represents a substituted or unsubstituted aliphatic hydrocarbon group having 1 to 24 carbon atoms, which may have an ether group, a carbonyl group, or an ester group.

7. The method for producing an isocyanate compound according to claim 1 or 2, wherein the blocking agent is a secondary amine compound represented by the following general formula (V): 【Chemistry 6】 (In general formula (V), R ５１ and R ５２ are each independently a monovalent organic group. ５１ and R ５２ may be bonded to each other to form a ring structure via a carbon-carbon bond, a carbon-oxygen-carbon bond, or a carbon-nitrogen-carbon bond.)

8. 3. The method for producing an isocyanate compound according to claim 1, wherein in the reaction step, the amount of the compound having the structure represented by general formula (I) present is 1 ppm by mass or more relative to the total amount of the blocked isocyanate compound.

9. The compound having a structure represented by the general formula (I) is N,N-diphenylformanilide, N-phenyl-N-tolylformanilide (each isomer), N-(methoxyphenyl)-N-phenylformanilide (each isomer), N-(ethoxyphenyl)-N-phenylformanilide (each isomer), N-(butoxyphenyl)-N-phenylformanilide (each isomer), N-methylformanilide, N-ethylformanilide, N-propylformanilide, N-butylformanilide, N-methyl-N-tolylformamide (each isomer), N-ethyl-N-tolylformamide, N-propyl-N-tolylformamide, N-butyl-N-tolylformamide, N-(methoxyphenyl)-N-methylformamide, or N-(ethoxyphenyl)-N-methylformamide. The method for producing an isocyanate compound according to claim 1 or 2.

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