JP6825839B2 - N-Cyclohexylmaleimide composition and its production method - Google Patents

Description

The present invention relates to a highly stable N-cyclohexylmaleimide composition and a method for producing a highly stable N-cyclohexylmaleimide composition.

Providing N-cyclohexylmaleimide, which is widely used in the chemical field, in a stable state is an important industrial issue.
Malemic acid and maleamic acid amine salts are known as contained components that improve the stability of N-cyclohexylmaleimide (see, for example, Patent Document 1). However, even if these stabilizers are contained, when this N-cyclohexylmaleimide is used as a monomer for polymerization, a problem may occur in the performance of the resin. In order to solve such a problem, a method using cyclohexylaminosuccinic anhydride as a containing component is known (see, for example, Patent Document 2).
These contained substances are substances contained as by-products during the production of N-cyclohexylmaleimide, and by specifying the existence and content thereof, the stability of N-cyclohexylmaleimide and the physical characteristics of the resin using the same can be greatly increased. It turns out that it can be varied.
However, even in this method, there are problems in the stability of N-cyclohexylmaleimide and the physical characteristics of the resin made from N-cyclohexylmaleimide as a raw material.
In order to solve these problems, there is a strong demand for an additive that stabilizes N-cyclohexylmaleimide.

In addition, many methods for producing N-cyclohexylmaleimide are known (see, for example, Patent Documents 3 to 6). These disclose techniques for removing reaction intermediates, dehydration catalysts, and by-products when reacting cyclohexylamine with maleic anhydride.
However, N-cyclohexylmaleimide produced by using the production methods described in these documents also has a problem that it is not satisfactory in terms of stability, purity and the like.

Japanese Patent Application Laid-Open No. 62-234063 JP-A-9-151218 Japanese Unexamined Patent Publication No. 8-27107 Japanese Patent Application Laid-Open No. 2003-160557 Japanese Unexamined Patent Publication No. 8-245580 Japanese Patent Application Laid-Open No. 6-184103

An object of the present invention is to provide an N-cyclohexylmaleimide composition in which N-cyclohexylmaleimide can be present with excellent stability, and a method for producing the N-cyclohexylmaleimide composition.

As a result of diligent studies, the present inventors have found that the stability of N-cyclohexylmaleimide is improved when a specific component is present in a specific range as a component contained in N-cyclohexylmaleimide. In addition, they have found a method for producing the N-cyclohexylmaleimide composition and have come up with the present invention.

That is, the present invention relates to the following.
[1]
It contains 200% by mass or less of a phenolic stabilizer, and 0.06% or less of fumaric acid and 0.03 to 0. 3-hydroxy-N-cyclohexylsuccinic acid imide as measured by HPLC at a detection wavelength of 220 nm. An N-cyclohexylmaleimide composition comprising 14%.
[2]
In the method for producing an N-cyclohexylmaleimide composition according to [1] , a dehydration reaction is carried out in the presence of a phosphoric acid catalyst using cyclohexylamine and maleic anhydride as raw materials.
Prior to the addition of the raw material, the phosphoric acid catalyst was neutralized to a degree of neutralization of 0.1 to 0.8.
The cyclohexylamine and the maleic anhydride are added at the same time,
Here, the ratio of the molar amount of the phosphoric acid catalyst to the molar amount of the maleic anhydride is set to 1.0 to 4.0.
The reaction mixture after the dehydration reaction is washed with water or an aqueous sodium carbonate solution.
After the washing, N-cyclohexylmaleimide is removed from the reaction mixture by distillation.
A method for producing an N-cyclohexylmaleimide composition, which comprises the above.
[3]
The method for producing an N-cyclohexylmaleimide composition according to [2], wherein a phenolic stabilizer is added to the N-cyclohexylmaleimide after the distillation.

The present invention can provide an N-cyclohexylmaleimide composition in which N-cyclohexylmaleimide can be present with excellent stability, and a method for producing the N-cyclohexylmaleimide composition.

Hereinafter, embodiments for carrying out the present invention (hereinafter, simply referred to as “the present embodiment”) will be described in detail. The following embodiments are examples for explaining the present invention, and are not intended to limit the present invention to the following contents. The present invention can be appropriately modified and implemented within the scope of the gist thereof.

(N-Cyclohexylmaleimide composition)
The present invention is characterized in that the stability of N-cyclohexylmaleimide is improved by including a specific substance in a specific amount in the N-cyclohexylmaleimide composition.
Specifically, the N-cyclohexylmaleimide composition of the present embodiment contains a phenolic stabilizer of 200 mass ppm or less, and contains 0.06% or less of fumaric acid as an area percentage measured by HPLC at a detection wavelength of 220 nm. , Hydroxycyclohexylsuccinate imide 0.03 to 0.14%.
Further, the N-cyclohexylmaleimide composition of the present embodiment preferably contains 99.6% or more of N-cyclohexylmaleimide, preferably 99.7% or more, in terms of area percentage measured by HPLC at a detection wavelength of 220 nm. It is more preferable, and it is particularly preferable that the content is 99.8% or more.

-Phenolic stabilizer-
It is preferable that the phenolic stabilizer is contained in a larger amount in terms of preventing polymerization, but if it is contained in a large amount, there is a problem that the degree of coloring at the time of heating becomes deeper, and the content thereof in the N-cyclohexylmaleimide composition is high. , 200 mass ppm or less is preferable. More preferably, it is in the range of 40 to 150 mass pmm, and most preferably in the range of 60 to 120 mass ppm.
The phenolic stabilizer may be a compound having a hydroxy group bonded to the aromatic ring. Specifically, p-methoxyphenol, nonylphenol, tert-butyl-p-cresol, tert-butyl-m-cresol, butylhydroxyanisole, 6-tert-, which have one hydroxy group bonded to the aromatic ring. Butyl-2,4-xylenol, 2,6-di-tert-butyl-p-cresol, 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,4 , 6-Tri-tert-butylphenol, 4-hydroxymethyl-2,6-di-tert-butylphenol, n-octadecyl-3- (4-hydroxy 3', 5'-di-tert-butylphenyl) propionate, di Stearyl (4-hydroxy-3-methyl-5-tert-butyl) benzyl malonate, styrenated phenol, 2,6-diphenyl-4-octadecanoxy-phenol, etc .; two hydroxy groups bonded to the aromatic ring , Hydroquinone, catechol, resorcinol, tert-butylhydroquinone, 4-tert-butylcatechol, 2,5-di-tert-butylhydroquinone, 2,5-di-tert-amylhydroquinone, etc .; three hydroxy groups in the aromatic ring Examples thereof include propyl 3,4,5-trihydroxybenzoate, which has one or more bonds.
Among these, a stabilizer in which one hydroxy group is bonded to the aromatic ring and a stabilizer in which two hydroxy groups are bonded to the aromatic ring are preferable from the viewpoint of the effect of preventing polymerization, and coloring during heating is preferable. Considering the viewpoint of inhibitory effect, hydroxy groups are formed on aromatic rings such as tert-butyl-p-cresol, 2,6-di-tert-butyl-p-cresol, and 6-tert-butyl-2,4-xylenol. A stabilizer in which one of the above is bound is mentioned as a preferable compound.

-Fumaric acid-
Fumaric acid is generated when maleic acid is hydrolyzed and transferred to trans in the reaction step or purification step. This trans body is not returned to the cyclized monomer by intramolecular dehydration during heating, and leaves a highly reactive carboxylic acid even after the double bond is polymerized. Therefore, it causes various colorings during heating, so it should be as small as possible. preferable. Fumaric acid is contained in the N-cyclohexylmaleimide composition in an area percentage of 0.06% or less, preferably 0.04% or less, preferably 0.02% or less, as measured by HPLC at a detection wavelength of 220 nm. It is more preferably included.

-Hydroxycyclohexyl succinate imide-
Hydroxycyclohexylsuccinateimide is a by-product purified by the hydration reaction of the product N-cyclohexylmaleimide. Although this substance can be removed in the purification step, it has been found that the heat-resistant coloring of N-cyclohexylmaleimide produced by removing the substance is very poor. On the other hand, if this substance is contained in a large amount, it does not participate in the subsequent polymerization reaction of the double bond and remains as a monomer in the polymer as it is, becoming a high boiling point volatile substance in the polymer and causing abnormal physical properties and process abnormalities. Become. Therefore, the hydroxysuccinate imide is contained in the N-cyclohexylmaleimide composition in the range of 0.03 to 0.14% in the area percentage measured by HPLC at the detection wavelength of 220 nm, and is 0.08 to 0. It is preferably contained in the range of 12%.

-Other impurities-
Examples of other impurities include dimers of maleic acid, N-cyclohexylmaleamic acid, N-cyclohexyl fumaric acid, and N-cyclohexylmaleimide.
Of course, it is preferable that these impurities are small, but it is very difficult to eliminate them. Therefore, the permissible range of the content of each substance in the N-cyclohexyl maleimide composition is the area percentage measured by HPLC at the detection wavelength of 220 nm. In the case of maleic acid, 0.01 to 0.07% and N-cyclohexyl. 0.001 to 0.07% for maleeamic acid, detection limit to 0.03% for N-cyclohexyl fumaluminic acid by high performance liquid chromatography analysis, N-cyclohexylmaleimide dimer The detection limit by gas chromatography analysis is ~ 0.6%. In particular, since the dimer of N-cyclohexylmaleimide has two highly reactive double bonds in the molecule, even if it is contained in a small amount in N-cyclohexylmaleimide, it acts as a cross-linking material during polymerization and polymerizes. There is a problem that the physical properties of an object are greatly changed. Therefore, the content of the dimer of N-cyclohexylmaleimide is preferably in the range of 0.001 to 0.02% in terms of area percentage as measured by gas chromatography analysis.

The area percentage of fumaric acid, hydroxycyclohexylsuccinimide, and other impurities measured by HPLC at a detection wavelength of 220 nm can be specifically measured by the method described in Examples described later, and is N-. The area percentage in the measurement of the dimer of cyclohexylmaleimide by gas chromatography analysis can be specifically measured by using the method described in Examples described later.

(Method for Producing N-Cyclohexyl Maleimide Composition)
The method for producing the N-cyclohexyl maleimide composition of the present embodiment is not particularly limited, and a reaction mixture is prepared by adding maleic anhydride, cyclohexylamine, a dehydration catalyst, a solvent and the like to the reaction vessel, and the reaction mixture is stirred. The dehydration reaction may proceed while proceeding, but in order to produce in a higher yield, the raw material input method, raw material concentration, dehydration catalyst state, dehydration catalyst amount, by-product removal method, etc. are limited as described later. It is preferable to do so.

In this reaction, maleic anhydride reacts with cyclohexylamine to produce N-cyclohexylmaleamide, and this N-cyclohexylmaleamic acid undergoes a dehydration reaction by the action of a dehydration catalyst to produce N-cyclohexylmaleimide. ..

-Dehydration catalyst-
The dehydration catalyst is not particularly limited as long as it is a catalyst capable of dehydrating N-cyclohexylmaleamic acid to produce N-cyclohexylmaleimide, and may be a solid catalyst or a fluid catalyst, and an acidic catalyst may be basic. It may be a catalyst.

Examples of the solid catalyst include cation exchange resins and zeolites.
As a fluid catalyst, sulfuric acid, benzene sulfonic acid, paratoluene sulfonic acid, xylene sulfonic acid, mesitylen sulfonic acid, chlorobenzene sulfonic acid, fluorobenzene sulfonic acid, ethylbenzene sulfonic acid, nitrobenzene sulfonic acid, naphthalene sulfonic acid, methane sulfon Examples thereof include acid, ethanesulfonic acid, vinylsulfonic acid, acetic acid, monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, phosphoric acid, metaphosphoric acid and pyrophosphate.

When a by-product of the reaction that is insoluble in the reaction mixture such as a polymer is produced, it is preferable to use a fluid acidic catalyst. Among the fluid acidic catalysts, sulfuric acid, phosphoric acid and methanesulfonic acid are preferable in that they can be layer-separable from the reaction mixture.

When a dehydration catalyst containing water is used, the reaction can be carried out with the water contained in the catalyst removed from the system with maleic anhydride, N-cyclohexylmaleamide acid, and N-cyclohexylmaleimide as raw materials. , It is preferable because it does not induce a side reaction with water.
When phosphoric acid is used as a fluid acidic catalyst, it is preferable to remove water contained in commercially available phosphoric acid from the system by azeotropic boiling with a solvent before the reaction.

Among the acidic catalysts and basic catalysts, acidic catalysts, particularly those showing Bronsted acidity and Lewis acidity, are preferable.

When an acidic catalyst is used, depending on its acidity, the desired reaction (intramolecular dehydration reaction of N-cyclohexylmaleamic acid) and side reaction (transfer reaction to N-cyclohexylhumalamide acid (isomerization reaction)) Selectivity varies between. Therefore, it is preferable to adjust the acidity of the acidic catalyst used in advance so that the selectivity of the desired reaction is high.

Specifically, when the acidic catalyst has an acidic functional group, it is preferable to neutralize a part of the acidic functional group of the acidic catalyst with a base and adjust the degree of neutralization.
The degree of neutralization here means the ratio of the molar amount of the basic substance used for neutralization to the molar amount of the acidic catalyst. For example, in the case of a fluid acidic catalyst in which a plurality of acidic functional groups are present in one molecule, the number of moles of the acidic functional group is the number of moles of the molecule. This is because when one of the plurality of acidic functional groups is neutralized, the neutralized product has a large acidity and moves to neutralization, and the acidity sufficiently exerts the side reaction suppressing effect.

The preferred degree of neutralization is 0.1 to 0.8. The degree of neutralization may be expressed as a percentage (%). In particular, when an acidic catalyst having Bronsted acidity is used, 0.3 to 0.8 is preferable, and when phosphoric acid is used even in a small amount, 0.4 to 0.8 is preferable.

The base used for neutralization is not particularly limited as long as it is a base that neutralizes Bronsted acid and Lewis acid.
Examples of the base include cyclohexylamine, methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, sec-butylamine, tert-butylamine, n-hexylamine, n-dodecylamine, allylamine, benzylamine, Cyclohexylamine, aniline, nitroaniline, aminophenol, aminobenzoic acid, anicidin, ethoxyphenylamine, monochloroaniline, dichloroaniline, toluidine, xylidine, ethylaniline, ethylenediamine, m-xylylene diamine, p-xylylene diamine, tetramethylene Typical examples are amines such as diamine, hexamethylenediamine, octamethylenediamine, decamethylenediamine, 4,4'-diaminodicyclohexylmethane, 4,4'-diaminodiphenylmethane, and bis-p- (4-aminophenoxycarbonyl) benzene. Among these bases, it is preferable to use a base that neutralizes brainstead acid, and it is most preferable to use cyclohexylamine as a raw material.

− Solvent −
The solvent is not particularly limited as long as it is a solvent that dissolves maleic anhydride, cyclohexylamine, and N-cyclohexylmaleimide.
In particular, as the solvent, a solvent that co-boils with water is preferable from the viewpoint of evaporating and removing water generated by the dehydration reaction, and it is possible to raise the temperature during the dehydration reaction to increase the evaporation rate of water. From the viewpoint, those having a relatively high boiling point are preferable, and from these viewpoints, aromatic solvents are particularly preferable.
As aromatic solvents, benzene, toluene, petroleum distillate having a boiling point of 50 to 120 ° C., xylene, ethylbenzene, isopropylbenzene, cumene, mesityrene, tert-butylbenzene, pseudocumene, chlorbenzene, m-dichlorobenzene, sec- Butylbenzene, p-dichlorobenzene, p-simene, o-dichlorobenzene, butylbenzene, decahydronaphthaline, tetrahydronaphthalin, naphthalin, cyclohexylbenzene and the like can be mentioned, among which benzene, toluene and xylene (o). -Xylene, m-xylene, p-xylene) is more preferable, and xylene having a high boiling point is most preferable.

As described above, in the reaction in the production method of the present embodiment, maleic anhydride and cyclohexylamine react to produce N-cyclohexylmaleamic acid, and this N-cyclohexylmaleamic acid is dehydrated by the action of a dehydration catalyst. Is generated, and N-cyclohexylmaleimide is produced.
Here, the side reaction is a reaction in which the cis form of N-cyclohexylmaleamic acid is transferred (isomerized) to the trans form of N-cyclohexylfumaric acid under acidic conditions, and this trans form is dehydrated and condensed to form polyimide. Is.
Therefore, in the system, it is preferable to cause intramolecular dehydration condensation almost at the same time as the formation of N-cyclohexylmaleamic acid and convert it to N-cyclohexylmaleimide, specifically, a mixture of maleic anhydride and cyclohexylamine. It is preferable to carry out the above in the presence of a dehydration catalyst, and more specifically, it is preferable to put maleic anhydride and cyclohexylamine as raw materials into the reactor to which the solution of the dehydration catalyst is added.

((Catalyst preparation))
When the solvent, cyclohexylamine, and maleic anhydride are added to the reactor to which the dehydration catalyst is added, water is distilled off from the catalyst and the inside of the reactor is brought to a boiling state so that the input raw materials are immediately dehydrated. It is preferable to keep it.

In the dehydration reaction, it is preferable to use a larger amount of dehydration catalyst because the dehydration rate is improved and the target reaction is promoted depending on the amount of dehydration catalyst used. On the other hand, since the reaction solution and the product may interact with the catalyst and it may be difficult to remove the reaction solution from the catalyst, the effect of improving the yield is lost even if a certain amount or more of the catalyst is added.
Therefore, the amount of the dehydration catalyst used is preferably in the range of 1.0 to 4.0, more preferably 1.5 to 2 in terms of molar amount with respect to the amount of maleic anhydride as a raw material. It is in the range of .5.

It is preferable to add a solvent to the catalyst in the reactor before the raw material is charged, depending on its properties. In particular, when a fluid acidic catalyst is used, it is preferable to use a solvent because it has the effect of lowering the viscosity. Specifically, as the amount of the solvent used, it is preferable to add the solvent to the catalyst in the range of 0.05 to 2.0 on a mass basis, and more preferably 0.1 to 0. It is in the range of 5.

((Raw material input))
In the situation where maleic anhydride and cyclohexylamine are in contact with each other, in the presence of a large excess of cyclohexylamine, the product N-cyclohexylmaleamic acid and / or N-cyclohexylmaleimide reacts with cyclohexylamine, and cyclohexylamine is formed in the double bond. There is a possibility that an adduct to which amine is added, a diamide form in which cyclohexylamine is dehydrated and condensed with the carboxylic acid of N-cyclohexylamine amidoic acid, etc. are by-produced. Further, in a situation where maleic anhydride and cyclohexylamine are in contact with each other, if maleic anhydride is present in a large excess, hydrolysis of the carboxylic acid anhydride proceeds by the water generated in the dehydration reaction, and maleic acid and fumaric acid are by-produced. There is a problem of doing.
Therefore, it is preferable to simultaneously add maleic anhydride and cyclohexylamine used as raw materials to a reaction system in which a dehydration catalyst is present, and here, it is preferable to simultaneously add the total amount of maleic anhydride and the total amount of cyclohexylamine. The simultaneous addition of maleic anhydride and cyclohexylamine means that the addition start time and the addition completion time of both are the same.

Since the amidation reaction by the reaction of maleic anhydride and cyclohexylamine is a very large exothermic reaction, there is a risk of bumping in the reaction vessel if they are added at the same time at the same time. Therefore, it is usually 0.5 to 50 hours. Put it in over a period of time.
Regarding the input rate of maleic anhydride and cyclohexylamine, the ratio of the input rate of maleic anhydride (mol / hour) to the input rate of cyclohexylamine (mol / hour) can be kept in the range of 0.3 to 3.0. preferable. It is more preferable to bring this ratio close to 1.0.

In particular, when the dehydration catalyst is partially neutralized with cyclohexylamine, which is also a raw material, in advance, cyclohexylamine is present in the reaction mixture. Therefore, even when only maleic anhydride is added, it reacts with cyclohexylamine for neutralizing the dehydration catalyst to suppress the production of maleic acid and fumaric acid to some extent, and cyclohexylamine is added first. Even if this is the case, it is neutralized by an unneutralized acid catalyst, and the nucleophilic addition reaction of cyclohexylamine to the double bond can be suppressed.
Therefore, in this case, when maleic anhydride and cyclohexylamine are added at the same time, the respective raw materials may be added intermittently, there is no problem even if the addition start time is different, and there is a problem even if the addition completion time is different. Absent.

During the reaction, water produced by dehydration of N-cyclohexylmaleic acid is present in the reactor, and direct addition of maleic anhydride into the reactor in such a state induces hydrolysis of maleic anhydride. It is easy and leads to an increase in by-products such as maleic anhydride and fumaric acid. Therefore, it is preferable that the maleic anhydride to be added contains a solvent to prevent contact with water.
Further, since maleic anhydride is a solid at room temperature, it is preferable to add it in a state of being dissolved in a solvent, and it is preferable that the concentration thereof is high. Specifically, it preferably contains a solvent having a mass of 0.01 to 5.0 with respect to the mass of maleic anhydride, and further contains a solvent having a mass of 0.6 to 2.0. preferable.

The cyclohexylamine to be added is also preferably at a high concentration, and it is a preferable method to add cyclohexylamine as it is without diluting it with a solvent.

((Dehydration reaction))
In the present embodiment, the reaction mixture is formed by the above-mentioned catalyst adjustment and the above-mentioned raw material input, and the dehydration reaction is carried out in the reaction mixture.
Hereinafter, the reaction mixture of the dehydration reaction will be similarly referred to as "reaction mixture" even when it has undergone the separation step, the filtration step, and the washing step described later.

The reaction time (time from the completion of charging of the raw material to the end of the reaction) may be 1 to 24 hours, preferably 2 to 8 hours.
The reaction temperature may be any temperature as long as it can evaporate and remove water. In particular, when the reaction is carried out at normal pressure using o-xylene as the reaction solvent, it may be 130 to 170 ° C., preferably 145 to 160 ° C. ℃.

In the production method of the present embodiment, the solvent is used for diluting maleic anhydride, diluting cyclohexylamine, and diluting the catalyst, and the total amount of the solvent is the total amount of maleic anhydride and cyclohexylamine added as raw materials. The amount is preferably in the range of 0.4 to 2.0, more preferably in the range of 0.6 to 1.2, based on the total mass of the solvent. ..

In the dehydration reaction, it is particularly preferable to add a polymerization inhibitor in order to suppress the polymerization of the double bond during the dehydration reaction.
The polymerization inhibitor may be either the above-mentioned phenol-based stabilizer (polymerization inhibitor) or copper-based stabilizer (polymerization inhibitor), and since it becomes a salt with an acidic catalyst and stays in the reaction vessel after charging, it is a copper-based stabilizer. Is particularly preferable.
Specific examples of the copper-based polymerization inhibitor include copper dimethyldithiocarbamate, copper dibutyldithiocarbamate, copper salicylate, copper chloride, copper phosphate and the like.

((Separation))
In the production method of the present embodiment, after the reaction is completed, the reaction mixture is separated to separate the product and the catalyst.

If a solid catalyst is used, sedimentation separation, filtration separation is used to remove the catalyst from the reaction mixture to give an organic layer.
Hereinafter, the organic layer will be similarly referred to as an "organic layer" even after undergoing the filtration step and the cleaning step described later.

When a fluid catalyst is used, the reaction mixture is allowed to stand and separated into two layers, an organic layer containing the product N-cyclohexylmaleimide and a catalyst layer (aqueous layer) containing a dehydration catalyst. ..
When the two-layer separation is performed, the amount of the reaction solution dissolved in the catalyst layer varies depending on the temperature, so it is preferable to carry out the two-layer separation at a constant temperature. Specifically, it is preferable to separate in the range of 80 to 160 ° C., and when the temperature is higher, the number of organic layers dissolved in the catalyst layer is reduced, and the loss of the organic layer containing the product can be suppressed. Most preferably, the separation is in the range of 120 to 160 ° C.

((filtration))
In the reaction mixture of the dehydration reaction, substances insoluble in the reaction mixture may be generated, and it is preferable to remove all or a part of such substances before the washing operation described later.
The operation of removing the insoluble substance may be performed on the organic layer in the two-layer state during separation, may be performed on the organic layer after separation, or both of them. ..
If the subsequent washing step is carried out without removing the insoluble matter, the insoluble matter acts as a surfactant between the organic layer and the aqueous layer, the layer separation state becomes very poor, and the organic layer is also removed at the same time as the aqueous layer is removed, resulting in a yield. There is a problem of lowering.

As the substance insoluble in the reaction mixture to be removed by filtration, a substance having a diameter of 1 cm or less is preferable, a substance having a diameter of 200 μm or less is more preferable, and a substance having a diameter of more than 10 μm is preferable.
The removal of the substance insoluble in the reaction mixture having a diameter exceeding the predetermined value may be specifically carried out by passing the reaction mixture through a filter filtration device having the opening and pore size of the predetermined value. For example, when removing a substance having a diameter of more than 10 μm among substances insoluble in the reaction mixture, a filter filtration device having a pore diameter of 10 μm is used.
The filter filtration device may be a filter filtration device commonly used in solid-liquid separation, and may be appropriately selected based on the values described in the catalog such as opening, pore size, and particle size that can be collected.
Here, for an insoluble solid that passes through a pore size of 10 μm, the oil-water separation interface in the cleaning step is not deteriorated, so that it is not highly necessary to separate the fine particles. Further, insoluble particles having a diameter of more than 1 cm are insoluble in the next step and do not deteriorate the interfacial separation between the organic layer and the aqueous layer, so that there is no high need to remove them.

In the production method of the present embodiment, for example, the reaction mixture containing the insoluble substance may be sequentially passed through a filter having a pore size of 100 μm, 50 μm, 30 μm, or 10 μm to remove the insoluble substance.

In order to enable the organic layer and the aqueous layer to be easily separated in the cleaning operation described later, the content of the insoluble substance in the organic layer after the dehydration reaction described above and before the cleaning described later is 100. The mass% is preferably 0.5% by mass or less, and more preferably 0.2% by mass or less.
The substance insoluble in the reaction mixture after the dehydration reaction means a substance having a diameter of more than 0.2 μm.
Within the above range, the operation of the cleaning step described later can be performed accurately, and the yield can be increased.

((Washing))
Since the taken-out reaction solution contains an acidic catalyst, it is preferable to wash (wash with water) the reaction solution in order to remove it.
Here, water or an aqueous solution is added to the organic layer, these are mixed well, and two layers are separated. Accurate operation of the two-layer separation in washing is essential for obtaining the N-cyclohexylmaleimide of the present embodiment.

As the water or aqueous solution used in washing, when the Bronsted acidic catalyst is used as the dehydration catalyst, water and a neutral to alkaline aqueous solution are preferable.
Since the hydroxysuccinate imide is removed from the organic layer under strong alkaline conditions, it is preferable to use an aqueous solution in the range of pH 6 to 11 as the neutral to alkaline aqueous solution, and more preferably pH 6.5. Use an aqueous solution in the range of ~ 8.0.
Examples of substances that can be included in the neutral to alkaline aqueous solution include sodium carbonate, potassium carbonate, ammonium carbonate, calcium carbonate, barium carbonate, magnesium carbonate, lithium carbonate, sodium hydrogen carbonate and the like, and sodium carbonate in particular. preferable.

The amount of water or aqueous solution used is preferably in the range of 0.05 to 0.5, more preferably 0.1 to 0.3, based on the mass of the reaction mixture.

The higher the temperature during washing with water, the larger the amount of the target substance dissolves in the aqueous layer and the lower the yield. At low temperatures, there is a risk that the target substance will precipitate from the organic layer. Therefore, 30 to 90 The temperature range is preferably in the range of 50 to 80 ° C.

The number of washings with water is preferably in the range of 1 to 5, and more preferably 2 to 4 times.

((distillation))
In the production method of the present embodiment, first, xylene may be distilled and removed from the reaction solution washed with water, and then N-cyclohexylmaleimide may be distilled and taken out.

At the time of distillation, it is preferable to put a polymerization inhibitor into the distillation pot in order to suppress the polymerization of N-cyclohexylmaleimide by heating. As the polymerization inhibitor to be added, a copper-based stabilizer (polymerization inhibitor) is preferable.

The structure of a phenolic stabilizer (polymerization inhibitor) changes by participating in a polymerization inhibitory reaction and becomes an impurity that is distilled at the same time as N-cyclohexylmaleimide. Therefore, after N-cyclohexylmaleimide evaporates and vaporizes, N -Preferably mixed with cyclohexyl maleimide.
The amount of the phenolic stabilizer to be mixed is particularly preferably in the range of the content of the phenolic stabilizer in the N-cyclohexylmaleimide composition of the present embodiment.

In the method for producing the N-cyclohexylmaleimide composition of the present embodiment, the yield of N-cyclohexylmaleimide is preferably 80 to 100%, more preferably 85 to 95%.

The N-cyclohexylmaleimide contained in the N-cyclohexylmaleimide composition of the present embodiment can be suitably used as a monomer for polymerization and / or copolymerization, and makes it possible to obtain a heat-resistant resin having excellent physical properties. ..

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto.

The measuring devices and measuring conditions for high performance liquid chromatography (HPLC) and gas chromatography (GC) used in Examples and Comparative Examples are as follows.

[High Performance Liquid Chromatography]
Liquid Chromatography Pump: PU-2089 manufactured by JASCO Corporation
Autosampler: AS-2057 manufactured by JASCO Corporation (internal temperature 4-10 ° C)
Column oven: CO-2060 manufactured by JASCO Corporation
Detector: MD-2018 manufactured by JASCO Corporation
Column: Tosoh TSK-GEL ODS-80TM
(ID: 4.6 x 150 mm → ID: 4.6 x 250 mm 2 connections)
Mobile phase: water / acetonitrile = 3/4 (mass / mass)
(KH ₂ PO ₄ = 0.008 mol / kg-H ₂₀ ) Prepare to pH 3.0 with phosphoric acid.
Flow velocity: 0.6 mL / min
Column temperature: 50 ° C
Detection conditions: UV (wavelength 220 nm)
Internal standard substance: Isopropyl benzoate Injection amount: 10 μL
Sample concentration: 0.3% by mass
Retention time:
・ Maleic acid ・ ・ ・ 6.9 minutes ・ Fumaric acid ・ ・ ・ 7.4 minutes ・ Hydroxycyclohexylsuccinic acidimide ・ ・ ・ 10.1 minutes ・ N-cyclohexylmaleamic acid ・ ・ ・ 11.2 minutes ・ N- Cyclohexyl fumaric acid ・ ・ ・ 9.2 minutes ・ N-cyclohexylmaleimide ・ ・ ・ 17.5 minutes ・ o-xylene ・ ・ ・ 27.3 minutes

[Gas chromatography]
Equipment: GC-2014 manufactured by Shimadzu Corporation
Column: Agilent J & W GC column manufactured by Agilent Technologies, Inc. HP-5ms (Length: 30m, ID: 0.25mm, film thickness: 0.25μm)
Carrier gas: Helium inlet temperature: 325 ° C
Detector temperature: 325 ° C
Detector: FID
Oven temperature conditions: 40 ° C (hold for 5 minutes) → temperature rise at 20 ° C / min → 325 ° C (hold for 10 minutes)
Control mode: Pressure Pressure: 100kPa
Total flow rate: 16.3 mL / min
Column flow rate: 1.33 mL / min
Linear velocity: 30.8 cm / sec
Purge flow rate: 3.0 mL / min
Injection volume: 0.4 μL
Split ratio: 10: 1
Sample concentration: 10% by mass
The concentration of 6-tert-butyl-2,4-xylenol (phenolic stabilizer) was calculated by the absolute calibration curve method.

<(1) Measurement of the content of trace components in the composition>
The concentration of the trace component contained in the N-cyclohexyl maleimide composition obtained in Examples and Comparative Examples was measured by using high performance liquid chromatography (HPLC) and gas chromatography (GC), and the content of the trace component was measured. It was measured. Fumaric acid and hydroxycyclohexylsuccinic acid imide were measured by HPLC, and phenolic stabilizers were measured by GC.

<(2) Heat resistance test of N-cyclohexylmaleimide composition>
Approximately 1 g of a sample of the N-cyclohexylmaleimide composition obtained in Examples and Comparative Examples was placed in a heat-resistant glass container, immersed in an oil bath adjusted to 200 ° C. for 1 hour, and the color tone of the composition after heating for 1 hour was as follows. It was evaluated visually according to the standard.
<Criteria>
○: No coloring ×: Colored

<(3) Calculation of yield of N-cyclohexylmaleimide>
The amount of N-cyclohexylmaleimide contained in the organic layer and the catalyst layer was determined by high performance liquid chromatography in the stage after the dehydration reaction of Examples and Comparative Examples and before separation, and the yield (%) was determined by the following formula (A). Calculated from.
(Yield of N-cyclohexylmaleimide) (%) = 100 × {(mass of organic layer) × (concentration of N-cyclohexylmaleimide in organic layer (%)) + (mass of catalyst layer) × (in catalyst layer) Concentration of N-cyclohexylmaleimide (%))} / {number of moles of maleic anhydride charged) × 179.22)} ... (A)
In formula (A), the mass of the organic layer is the mass of the charged o-xylene, maleic anhydride, and cyclohexylamine used in the reaction minus the amount of water removed from the system during the reaction; the mass of the catalyst layer. The mass is the mass of 85% phosphoric acid charged and the mass of cyclohexylamine used for phosphoric acid neutralization minus the amount of water removed from the system in the dehydration step before the reaction; 179.22 is the mass. The molecular weight of N-cyclohexylmaleimide.

<(4) Measurement of the content of substances with a diameter of more than 0.2 μm that are insoluble in the organic layer>
In Examples and Comparative Examples, about 20 g of the organic layer at a predetermined stage such as the stage after the dehydration reaction and before washing was taken, and about 20 g of this taken amount was heated to 60 ° C., and a pore size of 0.2 μm PTFE membrane filter (pore size 0.2 μm PTFE membrane filter). An Omnipore membrane filter manufactured by Merck Millipore, product number: JGWP04700) was poured into a stainless steel pressure filter incorporated as a filter medium, the container was pressurized with nitrogen gas, and the insoluble components in the organic layer were filtered off. ..
Next, the insoluble component remaining on the filter medium was washed with o-xylene, and the soluble component adhering to the insoluble component was washed away. The insoluble component remaining on the filter medium was dried under reduced pressure at 60 ° C. to remove the adhering o-xylene to obtain an insoluble component.
The mass of the insoluble component was measured, and the content (mass%) of the insoluble substance in the organic layer was calculated based on the mass of the organic layer.

[Example 1]
A 10L cylindrical round bottom separable flask (manufactured by AS ONE Co., Ltd., product number: 1-8492-06, specification DN150), equipped with a stirring blade, a baffle plate, a thermometer, a Dean Stark apparatus, and a cooling tube with 85% phosphoric acid ( 2697 g (manufactured by Sigma Aldrich), 957 g of o-xylene (manufactured by Sigma Aldrich) and 0.38 g of copper dibutyldithiocarbamate (product name CB-WG manufactured by Kawaguchi Chemical Industry Co., Ltd.), and the temperature inside the flask while stirring. The temperature was 130 ° C., o-xylene and water were distilled off, and the water was extracted from the system by Dean Stark.
At the same time, 1414 g of cyclohexylamine was added dropwise to the flask in 1 hour and 30 minutes using a metering pump to neutralize the phosphoric acid. Further heating was continued and 446 g of water was taken out of the system.
While maintaining the jacket temperature of the 10 L flask at 160 ° C., separately charge 1044 g of o-xylene and 1044 g of maleic anhydride in a 3 L four-necked flask and heat to 70 ° C. to provide a uniform solution (hereinafter, “xylene / anhydrous”). It is called "maleic anhydride solution").
Then, a xylene / maleic anhydride solution and 1056 g of cyclohexylamine were simultaneously added dropwise to a 10 L flask over 2 hours using a metering pump. The dropping lines were separated from each other, and after the dropping was completed, the lines were flushed into a 10 L flask with 10 g of o-xylene for washing.
The reaction was continued for 5 hours while keeping the jacket temperature at 160 ° C. and removing water from the system. After that, the temperature in the 10 L flask was lowered to 140 ° C., stirring was stopped, and the mixture was allowed to stand for 1 hour, and it was confirmed that the catalyst layer and the organic layer were separated into two layers.
At this time, the organic layer and the catalyst layer were subjected to component analysis according to the above (3) using high performance liquid chromatography (HPLC), and the yield of N-cyclohexylmaleimide was calculated.
2997 g of the upper organic layer was taken out into a 5 L 4-diameter flask using a decant rod.
Next, the internal temperature of the 5 L 4-diameter flask was set to 60 ° C., and the mixture was filtered through a stainless steel pressure filter incorporating a nylon mesh having a mesh size of 59 μm as a filter medium, and the insoluble components in the organic layer were filtered off.
The organic layer from which the insoluble components have been removed is collected in a 5 L 4-diameter flask equipped with a stirring blade and a thermometer, the temperature inside the flask is set to 60 ° C., ion-exchanged water is added in an amount of 20% by mass based on the mass of the organic layer, and the temperature is 60 ° C. The organic layer was washed with stirring for 30 minutes. Then, the stirring was stopped, the mixture was allowed to stand for 30 minutes, and the lower aqueous layer was separated using a decant rod. The same amount of ion-exchanged water was charged again, and the organic layer was purified by washing, standing, and separating the aqueous layer under the same conditions.
In order to distill off o-xylene under reduced pressure, a concentrator equipped with a distilling head, a condenser, and a receiver was assembled in a 5 L 4-diameter flask, and 1000 mass ppm of copper dibutyldithiocarbamate was added to the charged liquid. O-xylene was distilled off at an internal temperature of 70 to 100 ° C. and a pressure of 35 to 10 kPa to obtain a concentrated solution.
Next, in order to obtain N-cyclohexylmaleimide by simple distillation, the concentrated solution was transferred to a 2 L 4-diameter flask, and the flask was filled with a thermometer, a distilling head, a single tube with a heater, and 1.5 L as a receiver. 4 diameter flask was attached. Here, 0.082 g of 6-tert-butyl-2,4-xylenol was charged into the receiver. Then, the fraction was received in the receiver while being immersed in a 100 ° C. bath and heated. The simple distillation was carried out at an internal temperature of 101 to 130 ° C. and a pressure of 0.5 to 1.0 kPa to obtain an N-cyclohexylmaleimide composition. The single tube around which the heater was wound was kept at 100 ° C.
The content of trace components in the obtained N-cyclohexylmaleimide composition was determined by HPLC and GC according to the above (1).
Moreover, the heat resistance test was performed on the obtained N-cyclohexylmaleimide composition according to the above (2).

[Example 2]
A device equipped with a 2L cylindrical round bottom separable flask equipped with a stirring blade, a baffle plate, a thermometer, a Dean Stark apparatus, and a cooling tube, 85% phosphoric acid (manufactured by Sigma Aldrich) 531.67 g, o-xylene (manufactured by Sigma Aldrich). 185.93 g and 0.0021 g of copper dibutyldithiocarbamate (product name CB-WG manufactured by Kawaguchi Chemical Industry Co., Ltd.) were charged, and the temperature inside the flask was set to 130 ° C. while stirring to retain o-xylene and water. The water was pulled out of the system by Dean Stark.
At the same time, 277.82 g of cyclohexylamine was added dropwise to the flask in 1 hour and 30 minutes using a metering pump to neutralize the phosphoric acid. Further heating was continued and 69.87 g of water was taken out of the system.
While maintaining the jacket temperature of the 2L flask at 180 ° C., separately charge 205.18 g of o-xylene and 207.35 g of maleic anhydride in a 500 mL four-necked flask and heat to 70 ° C. to provide a uniform solution (xylene /). Maleic anhydride solution).
Then, a xylene / maleic anhydride solution and 212.83 g of cyclohexylamine were simultaneously added dropwise to a 2 L flask over 2 hours using a metering pump. The dropping lines were separated from each other, and after the dropping was completed, the lines were flushed into a 2 L flask with 8 g of o-xylene for washing.
The reaction was continued for 5 hours while keeping the jacket temperature at 180 ° C. and removing water from the system. After that, the temperature in the 2L flask was lowered to 140 ° C., stirring was stopped, and the mixture was allowed to stand for 1 hour, and it was confirmed that the catalyst layer and the organic layer were separated into two layers.
At this time, the organic layer and the catalyst layer were subjected to component analysis according to the above (3) using high performance liquid chromatography (HPLC), and the yield of N-cyclohexylmaleimide was calculated.
590.8 g of the upper organic layer was taken out into a 1 L glass bottle using a decant rod.
Next, the internal temperature of the 1 L glass bottle was set to 60 ° C., and the nylon mesh having a mesh opening of 59 μm was poured into a stainless steel pressure filter incorporated as a filter medium, and the insoluble components in the organic layer were filtered off.
In particular, the filtrate obtained here is referred to as filtrate A.
100 g of the filtrate A was collected in a 300 mL 4-diameter flask equipped with a stirring blade and a thermometer, the temperature inside the flask was adjusted to 60 ° C., 20 g of ion-exchanged water was added, and the mixture was stirred at 60 ° C. for 30 minutes to wash the organic layer. Then, the stirring was stopped, and the mixture was allowed to stand for 30 minutes, and the lower aqueous layer was separated by using a decant rod. The same amount of ion-exchanged water was charged again, and the organic layer was purified by washing, standing, and separating the aqueous layer under the same conditions.
In order to distill off o-xylene under reduced pressure, a concentrator equipped with a distilling head, a condenser, and a receiver was assembled in a 300 mL 4-diameter flask, 0.1 g of copper dibutyldithiocarbamate was added, and the internal temperature was 70 to 100. O-xylene was distilled off at ° C. and a pressure of 35 to 10 kPa to obtain a concentrated solution. Next, in order to obtain N-cyclohexylmaleimide by simple distillation, the concentrated solution was transferred to a 200 mL 4-diameter flask, and the flask was filled with a thermometer, a distilling head, a single tube with a heater, and 100 mL 4 as a receiver. A diameter flask was attached. Then, the receiver was immersed in a 100 ° C. bath and heated while receiving the distillate. Simple distillation was carried out at an internal temperature of 101 to 150 ° C. and a pressure of 0.5 to 1.0 kPa to obtain N-cyclohexylmaleimide. The single tube around which the heater was wound was kept at 100 ° C.
The content of trace components in the obtained N-cyclohexylmaleimide composition was determined by HPLC and GC according to the above (1).
Further, the obtained N-cyclohexylmaleimide composition was subjected to a heat resistance test according to (2) above.

[Example 3]
The same operation as in Example 2 except that the first washing of the filtrate A obtained in Example 2 was carried out with 20 g of a 9.0 mass% sodium hydrogen carbonate (NaHCO ₃ ) aqueous solution instead of 20 g of ion-exchanged water. To obtain an N-cyclohexylmaleimide composition.
The content of trace components in the obtained N-cyclohexylmaleimide composition was determined by HPLC and GC according to the above (1).
Further, the obtained N-cyclohexylmaleimide composition was subjected to a heat resistance test according to (2) above.

[Example 4]
61.850 kg of 85% phosphate, 24.708 kg of o-xylene, and copper dibutyldithiocarbamate (Kawaguchi Chemical Industry Co., Ltd.) in a 200 L glass lining tank equipped with a stirring blade, baffle plate, thermometer, Dean Stark and cooling tube. 17 g of product name CB-WG) was charged, the temperature inside the flask was adjusted to 130 ° C. while stirring, o-xylene and water were distilled off, and water was extracted from the system by Dean Stark.
At the same time, 32.564 kg of cyclohexylamine was added dropwise using a metering pump over 2 hours to neutralize the phosphoric acid. Further heating was continued for 17 hours, and 9.316 kg of water was taken out of the system.
While maintaining the jacket temperature of the 200 L glass lining tank at 180 ° C, 24.066 kg of o-xylene and 23.582 kg of maleic anhydride were separately charged in a SUS container and heated to 70 ° C to provide a uniform solution (xylene / maleic anhydride). Acid solution).
Then, a xylene / maleic anhydride solution and 23.648 kg of cyclohexylamine were simultaneously added dropwise to a 200 L glass lining tank over 2 hours using a metering pump. The dropping lines were separated from each other, and after the dropping was completed, the lines were washed by flushing them into a 200 L glass lining tank with 337.5 g of o-xylene.
The reaction was continued for 5 hours while keeping the jacket temperature at 180 ° C. and removing water from the system. After that, the internal temperature of the tank was lowered to 140 ° C., stirring was stopped, and the mixture was allowed to stand for 1 hour to separate the catalyst layer and the organic layer.
Then, the organic layer, which is the upper layer, was taken out into a SUS container using a decant rod.
The content of the insoluble substance in the organic layer after separation was calculated according to (4) above and found to be 0.3% by mass.
A SUS container is heated to 80 ° C. and pressurized and pumped at 0.1 MPa to form a cotton filter medium with a nominal pore diameter of 50 μm (ADVANTEC cotton wind cartridge filter, product name: TCW-50-CSD) and a nominal pore diameter of 10 μm. Insoluble components were filtered off by a cartridge filter attached with a cotton filter medium (cotton wind cartridge filter manufactured by ADVANTEC, product name: TCW-10-CSS), and the filtrate was collected in a 200 L glass lining tank.
The content of the insoluble substance in the filtrate (organic layer after the above filtration operation) at this time was calculated according to the above (4) and found to be 0.09% by mass.
Next, the internal temperature of the 200 L glass lining tank was maintained at 60 ° C., 20% by mass of ion-exchanged water was charged with respect to the filtrate, and the mixture was stirred and washed for 30 minutes to wash the organic layer. After that, the stirring is stopped, the mixture is allowed to stand for 30 minutes, the lower aqueous layer is pulled out from the bottom of the kettle while checking the layer separation state with a sight glass, and the same amount of ion-exchanged water is charged again, and the same stirring and washing is performed. The organic layer was purified by setting and separating the aqueous layer.
In each of the two-layer separation operations, the layer separation state of the organic layer and the aqueous layer was good.
In order to distill off o-xylene under reduced pressure, the above-mentioned water-washed and refined organic layer was charged in a 50 L SUS stirring tank equipped with a thermometer, a cooler, and a receiver, and copper dibutyldithiocarbamate was charged to the charged liquid. Was added in an amount of 1000 mass ppm, and o-xylene was distilled off at an internal temperature of 70 to 100 ° C. and a pressure of 3.5 to 1.0 kPa.
Subsequently, in order to obtain N-cyclohexylmaleimide by simple distillation, xylene distilled from the receiver was extracted, the receiver was heated to 100 ° C., and 2.505 g of 6-tert-butyl-2,4-xylenol was charged and placed. I received a distillate. The simple distillation was carried out at an internal temperature of 102 to 122 ° C. and a pressure of 0.6 kPa to obtain an N-cyclohexylmaleimide composition.
The content of trace components in the obtained N-cyclohexylmaleimide composition was determined by HPLC and GC according to the above (1).
Further, the obtained N-cyclohexylmaleimide composition was subjected to a heat resistance test according to (2) above.

[Example 5]
After the reaction in Example 4, the catalyst layer separated by standing was reused to carry out a dehydration reaction.
After taking out the upper organic layer in the 200L glass lining tank using a decant rod in Example 4, 24.759 kg of o-xylene was charged into the catalyst layer remaining in the 200L glass lining tank, and the jacket temperature was set to 180 ° C. The internal temperature was raised to 148 ° C. At this time, the reflux of o-xylene was started.
Then, in the same manner as in Example 4, a xylene / maleic anhydride solution and cyclohexylamine were simultaneously added dropwise, and the reaction was further continued to allow the organic layer to stand and separate.
The operation from the dehydration reaction in which the catalyst layer was reused to the static separation of the organic layer was repeated twice more to collect the organic layer.
The content of the insoluble substance in the organic layer after separation was calculated according to (4) above and found to be 0.9% by mass.
For the organic layer taken out, the filter media for filtering the insoluble components were a cotton filter medium having a nominal pore size of 100 μm (cotton wind cartridge filter manufactured by ADVANTEC, product name: TCW-100-CSD) and a cotton filter medium having a nominal pore diameter of 50 μm. The filtration operation was carried out in the same manner as in Example 4 except that the cartridge filter was changed to a cartridge filter equipped with (cotton wind cartridge filter manufactured by ADVANTEC, product name: TCW-50-CSS), and the filtrate containing the N-cyclohexylmaleimide composition was carried out. Got
The organic layer was washed with ion-exchanged water in the same manner as in Example 4.
The content of the insoluble substance in the filtrate (organic layer after the above filtration operation) obtained by the filtration at this time was calculated according to the above (4) and found to be 0.14% by mass.
The layer separation state between the organic layer and the aqueous layer during washing and purification was good.
Distillation of o-xylene under reduced pressure and distillation of N-cyclohexylmaleimide were the same as in Example 4.
The content of trace components in the obtained N-cyclohexylmaleimide composition was determined by HPLC and GC according to the above (1).
Further, the obtained N-cyclohexylmaleimide composition was subjected to a heat resistance test according to (2) above.

[Comparative Example 1]
152.6 g of 85% phosphoric acid (manufactured by Sigma Aldrich) and 164.68 g of o-xylene (manufactured by Sigma Aldrich) in a device equipped with a stirring blade, a thermometer, Dean Stark and a cooling tube in a 2 L round bottom 4-diameter flask. And 6-tert-butyl-2,4-xylenol (manufactured by Tokyo Kasei Kogyo Co., Ltd.) was charged in 0.0159 g, the temperature in the flask was adjusted to 130 ° C. with stirring, o-xylene and water were distilled off, and Dean Stark was used. Water was extracted from the system.
At the same time, 79.44 g of cyclohexylamine was added dropwise to the flask in 1 hour and 30 minutes using a metering pump to neutralize the phosphoric acid. Further heating was continued and 25.18 g of water was taken out of the system.
While maintaining the jacket temperature of the 2L flask at 180 ° C., separately charge 160.78 g of o-xylene and 157.57 g of maleic anhydride in a 500 mL four-necked flask and heat to 70 ° C. to obtain a uniform solution (xylene / maleic anhydride solution). To say).
Then, a xylene / maleic anhydride solution and 158.94 g of cyclohexylamine were simultaneously added dropwise to a 2 L flask over 2 hours using a metering pump. The dropping lines were separated from each other, and after the dropping was completed, the lines were flushed into a 2 L flask with 8 g of o-xylene for washing.
The reaction was continued for 5 hours while keeping the jacket temperature at 180 ° C. and removing water from the system. After that, the temperature in the 2L flask was lowered to 140 ° C., stirring was stopped, and the mixture was allowed to stand for 1 hour, and it was confirmed that the catalyst layer and the organic layer were separated into two layers.
510.2 g of the upper organic layer was taken out into a 1 L4 diameter flask using a decant rod.
Next, the internal temperature of the 1L4 diameter flask was maintained at 60 ° C., 102.04 g of ion-exchanged water was added, and the mixture was stirred at 60 ° C. for 30 minutes to wash the organic layer. Then, the stirring was stopped, and the mixture was allowed to stand for 30 minutes, and the lower aqueous layer was separated by using a decant rod. The same operation was performed two more times to purify the organic layer.
In order to distill off o-xylene under reduced pressure, a concentrator equipped with a distilling head, a condenser, and a receiver was assembled in a 1 L4 diameter flask, 0.46 g of copper dibutyldithiocarbamate was added, and the internal temperature was 70 to 100 ° C. O-xylene was distilled off at 3.5 to 1.0 kPa to obtain a concentrated solution.
Next, in order to obtain N-cyclohexylmaleimide by simple distillation, the concentrated solution was transferred to a 300 mL 4-diameter flask, and a thermometer, a distilling head, a single tube with a heater, and a 200 mL 4-diameter flask as a receiver were attached to the flask. .. Here, 0.02 g of 6-tert-butyl-2,4-xylenol was charged in the receiver, immersed in a 100 ° C. bath and heated to receive a fraction in the receiver. The simple distillation was carried out at an internal temperature of 101 to 150 ° C. and a pressure of 0.5 to 1.0 kPa to obtain an N-cyclohexylmaleimide composition. The single tube around which the heater was wound was kept at 100 ° C.
The content of trace components in the obtained N-cyclohexylmaleimide composition was determined by HPLC and GC according to the above (1).
Further, the obtained N-cyclohexylmaleimide composition was subjected to a heat resistance test according to (2) above.

[Comparative Example 2]
22.90 kg of 85% phosphoric acid, 24.733 kg of o-xylene and 6-tert-butyl-2,4-xylenol 2 in a 200 L glass lining tank equipped with a stirring blade, baffle plate, thermometer, Dean Stark and cooling tube. .39 g was charged, the temperature in the 200 L glass lining tank was adjusted to 130 ° C. while stirring, o-xylene and water were distilled off, and water was extracted from the system by Dean Stark.
At the same time, 11.948 kg of cyclohexylamine was added dropwise over 2 hours using a metering pump to neutralize the phosphoric acid. Further heating was continued for 8 hours, and 3.686 kg of water was taken out of the system.
While keeping the jacket temperature of the 200L glass lining tank at 180 ° C., separately put 23.958 kg of o-xylene, 23.482 kg of maleic anhydride, and 2.40 g of 6-tert-butyl-2,4-xylenol in a SUS container. The mixture was heated to 70 ° C. to prepare a uniform solution (xylene / maleic anhydride solution).
Then, a xylene / maleic anhydride solution and 23.519 kg of cyclohexylamine were simultaneously added dropwise to a 200 L glass lining tank using a metering pump over 2 hours. The dropping lines were separated from each other, and after the dropping was completed, the lines were washed by flushing them into a 200 L glass lining tank with 631 g of o-xylene.
The reaction was continued for 5 hours while keeping the jacket temperature at 180 ° C. and removing water from the system. After that, the internal temperature was lowered to 140 ° C., stirring was stopped, and the mixture was allowed to stand for 1 hour to separate the catalyst layer and the organic layer.
Then, the organic layer, which is the upper layer, was taken out into a SUS container using a decant rod.
The content of the insoluble substance in the organic layer after separation was calculated according to (4) above and found to be 0.6% by mass.
Next, the organic layer taken out in a SUS container was charged into a 200 L glass lining tank, 20% by mass of ion-exchanged water was charged to the charged organic layer, and the mixture was stirred and washed for 30 minutes to wash the organic layer. After that, the stirring is stopped, the mixture is allowed to stand for 30 minutes, the lower aqueous layer is pulled out from the bottom of the kettle while checking the separation surface with a sight glass, and the same stirring washing, standing, and separation are performed twice, and the organic layer is formed. Was purified.
In any of the two-layer separation operations, the layer separation state of the organic layer and the aqueous layer was poor, and there was an intermediate layer.
In order to distill off o-xylene under reduced pressure, the above-mentioned water-washed and refined organic layer was charged in a 50 LSUS stirring tank equipped with a thermometer, a cooler, and a receiver, and 1000 copper dibutyldithiocarbamate was added to the charged liquid. Mass ppm was added, and o-xylene was distilled off at an internal temperature of 70 to 100 ° C. and a pressure of 3.5 to 1.0 kPa.
Subsequently, xylene distilled off from the receiver was extracted from the receiver in order to obtain N-cyclohexylmaleimide by simple distillation, and the receiver was heated to 100 ° C. to receive a fraction. The simple distillation was carried out at an internal temperature of 102 to 122 ° C. and a pressure of 0.6 kPa to obtain an N-cyclohexylmaleimide composition.
The content of trace components in the obtained N-cyclohexylmaleimide composition was determined by HPLC and GC according to the above (1).
Further, the obtained N-cyclohexylmaleimide composition was subjected to a heat resistance test according to (2) above.

[Comparative Example 3]
N-cyclohexylmaleimide was carried out in the same manner as in Example 2 except that the first washing of the filtrate A obtained in Example 2 was carried out with 20 g of a 4.3 mass% NH ₃ aqueous solution instead of 20 g of ion-exchanged water. The composition was obtained.
The content of trace components in the obtained N-cyclohexylmaleimide composition was determined by HPLC and GC according to the above (1).
Further, the obtained N-cyclohexylmaleimide composition was subjected to a heat resistance test according to (2) above.

[Comparative Example 4]
The N-cyclohexylmaleimide composition was carried out in the same manner as in Example 2 except that the first washing of the filtrate A obtained in Example 2 was carried out with 20 g of a 10.0 mass% NaOH aqueous solution instead of 20 g of ion-exchanged water. I got something.
The content of trace components in the obtained N-cyclohexylmaleimide composition was determined by HPLC and GC according to the above (1).
Further, the obtained N-cyclohexylmaleimide composition was subjected to a heat resistance test according to (2) above.

[Comparative Example 5]
A 2L round bottom 4-diameter flask equipped with a stirring blade, a thermometer, a Dean-Stark apparatus, and a cooling tube, 85% phosphoric acid (manufactured by Sigma Aldrich) 273.9 g, o-xylene (manufactured by Sigma Aldrich) 280. 03 g was charged, the temperature in the flask was adjusted to 138 to 144 ° C. with stirring, o-xylene and water were distilled off, and water was extracted from the system by Dean Stark. Heating was continued for 6 hours and 45.11 g of water was taken out of the system.
While maintaining the jacket temperature of the 2L flask at 180 ° C., separately charge 300.68 g of o-xylene and 294.69 g of maleic anhydride in a 1L 4-necked flask and heat to 70 ° C. to provide a uniform solution (xylene / maleic anhydride). Acid solution).
Then, a xylene / maleic anhydride solution and 297.94 g of cyclohexylamine were simultaneously added dropwise to a 2 L flask over 2 hours using a metering pump. The dropping lines were separated from each other, and after the dropping was completed, the lines were flushed into a 2 L flask with 12 g of o-xylene for washing.
The reaction was continued for 5 hours while keeping the jacket temperature at 180 ° C. and removing water from the system. After that, the temperature in the 2L flask was lowered to 140 ° C., stirring was stopped, and the mixture was allowed to stand for 1 hour, and it was confirmed that the catalyst layer and the organic layer were replaced by two layers.
At this time, the organic layer and the catalyst layer were subjected to component analysis according to the above (3) using high performance liquid chromatography (HPLC), and the yield of N-cyclohexylmaleimide was calculated.
952.3 g of the upper organic layer was taken out into a 1 L4 diameter flask using a decant rod.
No further operations such as filtration and cleaning were performed.

[Comparative Example 6]
274 g of 85% phosphoric acid (manufactured by Sigma Aldrich) and 280 g of o-xylene (manufactured by Sigma Aldrich) were charged into a device equipped with a stirring blade, a thermometer, Dean-Stark and a cooling tube in a 2 L round bottom 4-diameter flask. The temperature inside the flask was adjusted to 130 ° C. with stirring, o-xylene and water were distilled off, and water was extracted from the system by Dean Stark.
At the same time, 236 g of cyclohexylamine was added dropwise to the flask using a metering pump to neutralize the phosphoric acid, but in the latter half of the addition, the catalyst layer solidified and stirring became impossible.
No further operations such as dehydration reaction were performed.

The present invention can provide a highly stable N-cyclohexylmaleimide composition, and provides a heat-resistant resin having excellent physical properties when the N-cyclohexylmaleimide composition is used as a monomer for polymerization and / or copolymerization. can do.

Claims (3)

Containing a phenolic stabilizer of 200 mass ppm or less,
It contains 0.06% or less of fumaric acid and 0.03 to 0.14% of 3-hydroxy-N-cyclohexylsuccinic acid imide in terms of area percentage measured by HPLC at a detection wavelength of 220 nm.
An N-cyclohexylmaleimide composition, characterized in that. The method for producing an N-cyclohexylmaleimide composition according to claim 1 , wherein a dehydration reaction is carried out using cyclohexylamine and maleic anhydride as raw materials in the presence of a phosphoric acid catalyst.
Prior to the addition of the raw material, the phosphoric acid catalyst was neutralized to a degree of neutralization of 0.1 to 0.8.
The cyclohexylamine and the maleic anhydride are added at the same time,
Here, the ratio of the molar amount of the phosphoric acid catalyst to the molar amount of the maleic anhydride is set to 1.0 to 4.0.
The reaction mixture after the dehydration reaction is washed with water or an aqueous sodium carbonate solution.
After the washing, N-cyclohexylmaleimide is removed from the reaction mixture by distillation.
A method for producing an N-cyclohexylmaleimide composition, which comprises the above. The method for producing an N-cyclohexylmaleimide composition according to claim 2, wherein a phenolic stabilizer is added to the N-cyclohexylmaleimide after the distillation.