KR102574282B1 - Method for purifying n-substituted maleimide - Google Patents

Abstract

1) preparing an N-substituted maleimide solution produced by the reaction of maleic anhydride and primary amine in the presence of an organic solvent and a catalyst; and 2) separating the crystallized N-substituted maleimide by cooling the N-substituted maleimide solution to 50 to 70 °C, wherein the organic solvent is an alkane-based solvent having 9 or more carbon atoms. It relates to a method for refining mead.

Description

N-substituted maleimide purification method {METHOD FOR PURIFYING N-SUBSTITUTED MALEIMIDE}

The present invention relates to a method for purifying N-substituted maleimides.

The maleimide compound is a compound useful as a resin material, a raw material for pharmaceuticals and pesticides, etc., and in particular, styrene-based resins such as ABS resins, AS resins, AB resins, ACS resins, AES resins, AAS resins, polyvinyl chloride resins, In order to improve the heat resistance of polymethyl methacrylate resins, phenol resins, etc., it is widely used as one of the copolymerization components. Among them, N-phenyl maleimide (hereinafter also referred to as PMI) is excellent in reactivity and heat resistance and is particularly widely used.

Regarding the method for producing the maleimide compound, (1) a method obtained by subjecting maleic anhydride (hereinafter also referred to as MAH) and a primary amine to a dehydration reaction in one step, (2) from maleic anhydride and a primary amine A method of producing maleamic acid and obtaining it by dehydration ring-closure imidation of maleamic acid, (3) a method of obtaining by ring-closure imidation of the corresponding maleamic acid monoester, etc. Many methods are known.

Among these methods, (1) in the method obtained from maleic anhydride and primary amines in one step, the yield is still low and productivity is poor, and (3) in the method obtained from maleamic acid monoesters, ring closure Since there is a problem that alcohol generated by the imidation reaction remains and is mixed in the product, industrially, a method of obtaining by (2) dehydration ring closure imidization of maleamic acid is generally performed.

On the other hand, when producing N-phenyl maleimide (PMI), primary amines are aniline (hereinafter also referred to as ANL), and maleamic acids are N-phenyl maleamic acid (hereinafter also referred to as PMA).

The prepared maleimide compound is purified through a purification process to remove impurities generated during the maleimide compound preparation process, so that a high-purity maleimide compound can be obtained.

The existing maleimide compound separation/purification process includes separation of the maleimide compound-generating solution and the catalyst used after the reaction, extraction of impurities using washing water to remove impurities in the maleimide compound-generating solution, and distillation to increase the purity of maleimide. done

However, in the impurity extraction process using washing water, the impurity extraction process using washing water was performed after a cooling process was performed due to a problem in that a high-temperature maleimide compound generating solution could not be directly applied to the washing process. Due to the cooling process of the front end, additional energy input due to reheating occurs for the temperature condition of the purification process through distillation at the rear end, and the polymerization of the maleimide compound, the main product, according to the high temperature condition during purification through the distillation process. There was a problem that the loss of the main product due to the possible occurrence.

Accordingly, the inventors of the present invention have researched to solve the above problems, and purified maleimide compounds capable of obtaining high-purity maleimide compounds without a distillation process by using the solubility of maleimide compounds in organic solvents used in preparing maleimide compounds. method was completed.

KR 2014-0005951 A (2014.01.15)

An object to be solved by the present invention is to obtain a high-purity N-substituted maleimide without performing a distillation process by using the solubility of the N-substituted maleimide compound in an organic solvent used in the preparation of the N-substituted maleimide compound. It is to provide a method for purifying N-substituted maleimide.

Another problem to be solved by the present invention is to use a zirconium hydrogen phosphate (Zirconium (IV) hydrogen phosphate) solid acid catalyst as a catalyst in the synthesis of N-substituted maleimide, thereby minimizing the loss of the catalyst and replenishing the catalyst during the synthesis reaction. An object of the present invention is to provide a method for purifying N-substituted maleimide that is unnecessary and has a simplified process because separation is possible only through simple filtration during purification of N-substituted maleimide.

The present invention is to solve the above problems,

1) preparing an N-substituted maleimide solution produced by the reaction of maleic anhydride and primary amine in the presence of an organic solvent and a catalyst; and

2) separating the crystallized N-substituted maleimide by cooling the N-substituted maleimide solution to 50 to 70 °C;

The organic solvent provides a method for purifying N-substituted maleimide, wherein the organic solvent is an alkane-based solvent having 9 or more carbon atoms.

The method for purifying N-substituted maleimide of the present invention has an effect of being able to purify into high-purity N-substituted maleimide without performing a distillation process.

In addition, the present invention does not perform a distillation process on the N-substituted maleimide solution, so additional energy input for cooling and reheating is unnecessary, and polymerization loss of the N-substituted maleimide due to high temperature conditions of the distillation process can be minimized. There are possible effects.

In addition, the present invention uses a Zirconium (IV) hydrogen phosphate solid acid catalyst as a catalyst in the synthesis of N-substituted maleimide, thereby minimizing the loss of the catalyst and eliminating the need for supplementation of the catalyst during the synthesis reaction. - There is an effect that can be separated through simple filtration when purifying substituted maleimide.

The following drawings attached to this specification illustrate specific embodiments of the present invention, and serve to further understand the technical idea of the present invention together with the contents of the above-described invention, so the present invention is limited to those described in the drawings. It should not be construed as limiting.
1 is a graph showing the solubility of squalane used in Example 1 of the present invention.

Hereinafter, the present invention will be described in more detail to aid understanding of the present invention. At this time, the terms or words used in this specification and claims should not be construed as being limited to ordinary or dictionary meanings, and the inventor appropriately defines the concept of terms in order to explain his/her invention in the best way. It should be interpreted as meaning and concept consistent with the technical idea of the present invention based on the principle that it can be done.

the present invention

1) preparing an N-substituted maleimide solution produced by the reaction of maleic anhydride and primary amine in the presence of an organic solvent and a catalyst; and

2) separating the crystallized N-substituted maleimide by cooling the N-substituted maleimide solution to 50 to 70 °C;

The organic solvent provides a method for purifying N-substituted maleimide, wherein the organic solvent is an alkane-based solvent having 9 or more carbon atoms.

Hereinafter, the N-substituted maleimide purification method of the present invention will be described in detail for each step.

Step 1)

Step 1) according to an embodiment of the present invention is a step for preparing an N-substituted maleimide solution to be purified, and N-substituted maleimide is obtained by reacting maleic anhydride and primary amine in the presence of an organic solvent and a catalyst. It is characterized in that the mid is synthesized.

Regarding the method for producing the N-substituted maleimide compound, (1) a method obtained by subjecting maleic anhydride and primary amine to a dehydration reaction in one step, (2) maleic acid produced from maleic anhydride and primary amine and (3) a method obtained by ring closure imidation of the corresponding maleamic acid monoester, and the like.

However, (1) in the method of obtaining from maleic anhydride and primary amine in one step, the yield is still low and productivity is poor, and (3) in the method of obtaining from maleic acid monoester, ring closure imidation reaction Since there is a problem that the alcohol generated by the residual mixing in the product, etc., the method for preparing N-substituted maleimide of the present invention is (2) synthesizing N-substituted maleimide by dehydration ring closure imidation of maleamic acid. The form is explained in detail.

The N-substituted maleimide of the present invention is subjected to an acylation reaction by heating maleic anhydride and a primary amine in one step to obtain an intermediate N-substituted maleamic acid, and in a second step, the N-substituted maleimide on the surface of the catalyst An N-substituted maleimide can be synthesized by a method of subjecting leamic acid to dehydration ring closure imidation.

In addition, in the process of obtaining N-substituted maleamic acid from the maleic anhydride and primary amine, maleic anhydride or primary amine may be used as it is, but used in the form of a solution dissolved in an organic solvent It is desirable to do On the other hand, when maleic anhydride or primary amine is used in the form of a solution dissolved in an organic solvent, the following dehydration ring closure imidization reaction of N-substituted maleamic acid can be carried out as it is in a solution (organic solvent).

The maleic anhydride exists in a solid state at room temperature and has very low solubility in an organic solvent as a reaction solvent. Accordingly, it is preferable to raise the temperature at which the maleic anhydride can be in a molten state so as to completely form a mixture with the organic solvent and use it in a liquid state.

The organic solvent should be insoluble or immiscible with water, inert to the reaction, and not participate in the reaction, so that water produced by the dehydration ring closure reaction of the N-substituted maleamic acid can be released out of the system through azeotropic distillation.

In addition, the present invention provides a method for obtaining high-purity N-substituted maleimide without performing a distillation process by naturally cooling the N-substituted maleimide solution to crystallize and separate the N-substituted maleimide dissolved in the organic solvent. As an object of providing a method for purifying N-substituted maleimide, an organic solvent having low solubility for N-substituted maleimide at low temperature should be used.

Specifically, the organic solvent usable in the present invention is characterized by being an alkane-based solvent having 9 or more carbon atoms, preferably an alkane-based solvent having 9 to 30 carbon atoms. Alkane-based solvents having 8 or less carbon atoms have a low boiling point and are not suitable as N-substituted maleimide synthesis reaction solvents.

During the N-substituted maleimide synthesis reaction, water is generated as a product of the dehydration ring closure reaction, and the water can react with the already produced N-substituted maleimide or with maleamic acid as an intermediate product, so it must be quickly removed to suppress side reactions. can do.

The method of removing water generated during the reaction is to bring the reaction temperature higher than the boiling point of water and remove the generated water as water vapor. This is because water cannot be removed effectively.

The higher the carbon number, the lower the polarity and the lower the solubility of the N-substituted maleimide. Therefore, the lower the polarity in the crystallization process, the higher the recovery rate of the N-substituted maleimide due to the lower solubility of the N-substituted maleimide.

On the other hand, aromatic hydrocarbon-based solvents have a limited number of carbon atoms, whereas linear alkane-based hydrocarbon solvents have a wide range of carbon atoms and are more stable than alkenes and alkynes even if they are linear. desirable.

The organic solvent of the present invention is characterized in that the solubility of the N-substituted maleimide at 50 to 70 ° C., more specifically at 50 to 60 ° C., is 0.4 to 1.4% by weight, more specifically 0.4 to 1.0% by weight, based on the weight of the organic solvent. do. When the above range is satisfied, the residual amount of the N-substituted maleimide remaining on the organic solvent generated in the crystallization and purification process may be reduced. If the amount is less than the above range, the recovery rate of the N-substituted maleimide may decrease due to an increase in the ratio of the N-substituted maleimide that is not crystallized in the organic solvent and exists in a dissolved state during the crystallization process.

The organic solvent may have a boiling point of 110 to 350 °C or 150 to 340 °C, of which 150 to 340 °C is preferred. When the above-mentioned range is satisfied, the reaction can be performed smoothly, and the purity of the obtained N-substituted maleimide can be increased. If the above range is not satisfied, specifically below the above range, the reaction may not be performed smoothly or the purity of the obtained N-substituted maleamide may be low.

The organic solvent may be at least one selected from the group consisting of nonane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, heptadecane, octadecane, nonadecane, eicosane, and squalane. can In contrast, aromatic organic solvents such as ethylbenzene or o-xylene have high solubility in N-substituted maleimides even at low temperatures, and thus are not suitable as organic solvents for the present invention.

The primary amine of the present invention is selected from saturated or unsaturated alkylamines having 1 to 20 carbon atoms, cycloalkylamines having 5 to 20 carbon atoms, cycloalkylamines having 6 to 20 carbon atoms, or aromatic alkylamines having 6 to 20 carbon atoms. One type of primary amine can be used, specifically methyl amine, ethyl amine, n-propyl amine, isopropyl amine, n-butyl amine, sec-butyl amine, iso-butyl amine, tert-butylamine, n -At least one selected from the group consisting of hexyl amine, n-octyl amine, n-decyl amine, n-dodecyl amine, cyclohexyl amine and aniline may be used, and in order to synthesize N-phenyl maleimide, primary amine Aniline can be used as

In the present invention, the mole ratio of maleic anhydride and primary amine used in the synthesis of N-substituted maleimides is preferably 1:1 to 1.3:1. When maleic anhydride is used in an amount less than the above-mentioned range, problems of yield reduction and by-product increase occur, and when it is used in excess of the above-mentioned range, an excessive amount of unreacted maleic anhydride remains after synthesizing N-substituted maleimide. This is undesirable from an economic point of view.

On the other hand, most of the catalysts used in the conventional N-substituted maleimide synthesis method directly used a homogeneous liquid catalyst or a supported catalyst having a homogeneous active component supported on a support. However, in the case of using the homogeneous liquid catalyst, loss of the catalyst may occur in the process of separating the product and the catalyst through layer separation due to the difference in polarity after the completion of the synthesis reaction, and in the case of using the supported catalyst, N-substituted maleimide It was necessary to continuously supplement the loss of active ingredients due to the loss of active ingredients due to water, a by-product generated during the synthesis process, and the supplementation of the active ingredients was also possible after separating and drying the supported catalyst. Due to this complexity, there was a problem that it was not easy to replenish the active ingredient.

In the N-substituted maleimide production step of the present invention, unlike conventional production methods, N-substituted maleimide is synthesized using a heterogeneous solid acid catalyst rather than a homogeneous liquid catalyst or a supported catalyst. It is characterized by being able to solve. Meanwhile, in the present invention, the homogeneous system means that the reactants and the catalyst in the N-substituted maleimide synthesis reaction are in the same phase, and the heterogeneous system means that the reactants and the catalyst are in different states.

More specifically, the heterogeneous solid acid catalyst used in the present invention is characterized in that it is zirconium (IV) hydrogen phosphate (Zr(H ₂ PO ₄ ) ₂ ).

Zirconium hydrogen phosphate is an acidic, inorganic cation exchange material with a layered structure, characterized by high thermal and chemical stability, solid ionic conductivity, resistance to ionizing radiation, and the ability to introduce different types of molecules of different sizes into their layers. have etc. The zirconium hydrogen phosphate can exist in various states with various interlayer spaces and crystal structures, and the most widely known zirconium hydrogen phosphate is the alpha form of Zr(HPO ₄ ) ₂ H ₂ O and Zr(PO ₄ ) (H It is the gamma form of ₂ PO ₄ )·2H ₂ O.

In the case of the present invention, the zirconium hydrogen phosphate used as the solid acid catalyst is an amorphous zirconium hydrogen phosphate rather than the alpha-type and gamma-type crystalline structures, and the degree of hydration may vary depending on the reaction conditions. can be displayed

[Formula 1]

Zr _x (H _a PO _b ) _c

(In Formula 1, 0.5≤x≤1.5, 0≤a≤8, 0≤b≤8, 1≤c≤4.)

As described above, the N-substituted maleimide of the present invention can minimize the possibility of catalyst loss by using a heterogeneous solid acid catalyst having a different state from the reactant of the N-substituted maleimide synthesis reaction, and among the solid acid catalysts, zirconium hydrogen By using phosphate, it is characterized in that the synthesis yield of N-substituted maleimide is high.

Specifically, since the catalyst of the present invention is a solid in a state different from that of the reactants, loss of active components due to water, a by-product generated during the synthesis of N-substituted maleimide, and loss of the catalyst during layer separation after completion of the synthesis reaction. In addition, since the zirconium hydrogen phosphate used in the present invention is structurally very stable and has low reactivity with water, replenishment and regeneration of the catalyst are not necessarily required during the reaction, so that N-substituted maleimide manufacturing process It also has a simplification effect.

Meanwhile, depending on the case, a metal-containing compound or a stabilizer may be allowed to coexist in the reaction system and reacted. The metal-containing compound used at this time is not particularly limited, but is at least one metal oxide selected from the group consisting of zinc, chromium, palladium, cobalt, nickel, iron and aluminum, acetate, maleate, succinate salt (salt of succinic acid), nitrate, phosphate, chloride and sulfate. Among these, zinc acetate is particularly effective. Their amount is 0.005 to 0.5 mol% as a metal, preferably 0.01 to 0.1 mol%, based on maleic anhydride and/or primary amine as raw materials.

In addition, as a stabilizer, methoxybenzoquinone, p-methoxyphenol, phenothiazine, hydroquinone, alkylated diphenyl amines, methylene blue, tert-butyl catechol, tert-butyl hydroquinone, dimethyldithiocarba Mate zinc, copper dimethyldithiocarbamate, copper dibutyldithiocarbamate, copper salicylate, thiodipropionic acid esters, mercaptobenzimidazole, triphenyl phosphite, alkyl phenols, alkyl bisphenols, etc. are used. The effect of these stabilizers serves to stably exist the N-substituted maleimide produced by the dehydration ring closure imidation reaction without being altered even under the high temperature of the imidation reaction. The addition amount is not particularly limited, but may be 0.001 to 0.5 mol% based on maleic anhydride and/or primary amine as raw materials. Here, with such an added amount, the above-mentioned stabilizing effect can be sufficiently exhibited, and the problem of mixing in the product can be avoided.

The reaction temperature of the N-substituted maleimide synthesis reaction in step 1) of the present invention is generally 50 to 200°C, more specifically preferably 100 to 140°C. When the synthesis reaction temperature is less than the above range, the yield decreases, and when it exceeds the above range, the purity and yield of the N-substituted maleimide synthesized as a side reaction decreases.

In the present invention, the reaction pressure is not particularly limited, and may be selected from a wide range of pressure, normal pressure and pressure. The reaction may vary depending on conditions such as the type of solvent, input amount of raw materials, catalyst amount, and reaction temperature, but is generally about 1 to 16 hours, and more preferably within 1 to 10 hours.

Under these reaction conditions, the dehydration ring closure imidation reaction of N-substituted maleamic acid proceeds efficiently, and N-substituted maleimide can be obtained efficiently.

The N-substituted maleimide of the present invention prepared by the above method is N-methyl maleimide, N-ethyl maleimide, N-hexyl maleimide, N-octyl maleimide, N-dodecyl maleimide, and the like. alkyl maleimide; N-benzylmaleimide; N-cycloalkyl maleimides such as N-cyclohexyl maleimide; N-phenyl maleimide; and N-nitrophenyl maleimide, N-methoxyphenyl maleimide, N-methylphenyl maleimide, N-carboxyphenyl maleimide, N-hydroxyphenyl maleimide, N-chlorophenyl maleimide, N-dimethylphenyl maleimide , N-dichlorophenyl maleimide, N-bromophenyl maleimide, N-dibromophenyl maleimide, N-trichlorophenyl maleimide, N-tribromophenyl maleimide, nitro groups, alkoxy groups, alkyl groups such as , N-substituted phenyl maleimides in which a carboxyl group, a hydroxyl group, and a halogen group are substituted with a phenyl group may be at least one selected from the group consisting of.

Step 2)

Step 2) according to an embodiment of the present invention is characterized by separating the crystallized N-substituted maleimide by cooling the N-substituted maleimide solution prepared in step 1).

Specifically, the N-substituted maleimide purification method included in the present invention is characterized by naturally cooling the N-substituted maleimide solution to 50 to 70 °C, more specifically to 50 to 60 °C. This is because the alkane series having 9 or more carbon atoms used in the present invention has low solubility of N-substituted maleimide in the low-temperature range, making it easy to crystallize and separate the N-substituted maleimide.

On the other hand, if the cooling temperature is lower than the above range, there may be a problem of purity deterioration due to simultaneous precipitation of unreacted residue, maleic anhydride, and if the cooling temperature is higher than the above range, the crystallization reaction of N-substituted maleimide may occur. This may not be done sufficiently, and thus the recovery rate of N-substituted maleimide may decrease.

As shown in FIG. 1, for example, it can be confirmed that squalane has a solubility of 0 wt% in N-phenyl maleimide (PMI) at 40 °C. Accordingly, when the N-phenyl maleimide solution is cooled to 40 ° C., all N-phenyl maleimide dissolved in squalane can be obtained by precipitating as a solid, but maleic acid, which is an unreacted impurity contained in the N-phenyl maleimide solution, is present. The freezing point of the anhydride is about 50 ° C., and when cooled to a temperature lower than 50 ° C., the maleic anhydride is precipitated and high-purity N-phenyl maleimide cannot be obtained. Therefore, in order to prevent the precipitation of the maleic anhydride, the cooling temperature of the present invention is preferably maintained at 50 ° C. or higher.

On the other hand, even in the cooling temperature range of 50 to 70 ℃, more specifically, 50 to 60 ℃ of the present invention, organic acid impurities such as maleic anhydride, which is an unreacted material, may be partially precipitated, but the average of the crystallized N-substituted maleimide While the particle diameter is 1 to 100 mm, more specifically 5 to 80 mm, the average particle diameter of the crystallized organic acid impurities is very different in the precipitated properties as very fine particles in the micrometer unit, a mesh network having a diameter of 1 mm or more It is possible to separate only the crystallized N-substituted maleimide with high purity through a filtration device such as a large particle size.

In addition, the present invention may further include a step of washing impurities with washing water before or after step 2) to obtain a higher purity N-substituted maleimide by removing impurities, and before step 2), N-substituted maleimide A step of separating the catalyst from the substituted maleimide solution may be further included.

Meanwhile, a drying step such as distillation may be additionally performed on the separated crystallized N-substituted maleimide to completely remove some of the solvent or washing water.

When the catalyst for producing N-substituted maleimide is a solid acid catalyst of zirconium hydrogen phosphate (Zr(H ₂ PO ₄ ) ₂ ), it can be separated by a simple process such as filtration, washing or There may be an advantage of being able to regenerate the catalyst through the calcination process.

*

The method for purifying N-substituted maleimide of the present invention is characterized in that a distillation process is not performed on the N-substituted maleimide production solution, and the high temperature of 100 to 140 ° C. produced by the synthesis reaction of N-substituted maleimide There is no need for additional input of energy required in the process of cooling the N-substituted maleimide solution and reheating it for the distillation process, and the effect of minimizing the polymerization loss of the N-substituted maleimide due to the high-temperature conditions of the distillation process there is.

The method for purifying N-substituted maleimide of the present invention can secure high-purity N-substituted maleimide with a purity of 95.0 wt% or more, specifically 98 wt% or more, which is equivalent to or similar to that of the distillation process, and N-substituted maleimide Polymerization loss caused by the polymerization of maleimide into an oligomer at a high temperature is minimized, thereby securing higher purity and higher yield of N-substituted maleimide.

Example One

In a 100 ml reactor equipped with a stirrer, thermometer, water separator and condenser, 20 ml of squalane, 2.5 g of aniline and 2.9 g of liquid maleic anhydride (maleic anhydride) melted at 80 ° C. ) hydrogen phosphate) After adding 1.249 g of a solid acid catalyst, the temperature of the reaction system was raised to 125 °C to synthesize N-phenyl maleimide. During the reaction, water produced by dehydration ring closure was removed from the reaction system together with squalane through azeotropic distillation. Squalane (boiling point: 285 °C, C ₃₀ H ₆₂ ) removed from the reaction system was re-injected into the reaction system while a synthesis reaction was further performed for 4 hours. After completion of the synthesis reaction, the solid acid catalyst was separated through simple filtration, and a solution containing N-phenyl maleimide and squalane was naturally cooled to 50 °C. Thereafter, the crystallized N-phenyl maleimide was separated by filtration, and highly pure N-phenyl maleimide was purified by extracting impurities from the crystallized N-phenyl maleimide using washing water.

Example 2

N-phenyl maleimide was purified in the same manner as in Example 1, except that the mixture was naturally cooled to 60 °C in Example 1.

Example 3

N-phenyl maleimide was purified in the same manner as in Example 1, except that it was naturally cooled to 70 °C in Example 1.

Example 4

N-phenyl maleimide was purified in the same manner as in Example 1, except that tetradecane (C ₁₄ H ₃₀ , boiling point: 253 °C) was used instead of squalane in Example 1.

Example 5

N-phenyl maleimide was purified in the same manner as in Example 1, except that dodecane (C ₂₃ H ₂₆ , boiling point: 216.2 °C) was used instead of squalane in Example 1.

comparative example One

In a 100 mL reactor equipped with a stirrer, thermometer, water separator and condenser, 20 ml of ethylbenzene as solvent, 2.5 g of aniline and 2.9 g of maleic anhydride melted at 80 °C, Zirconium(IV) hydrogen phosphate solid acid After adding 1.249 g of the catalyst, the temperature of the reaction system was raised to 125°C to synthesize N-phenyl maleimide. During the reaction, water generated by the dehydration ring closure reaction was removed from the reaction system together with ethylbenzene through azeotropic distillation. Ethylbenzene removed from the reaction system was re-injected into the reaction system, and the synthesis reaction was further conducted for 4 hours. After completion of the synthesis reaction, N-phenyl maleimide was purified by separating only the solvent through distillation under reduced pressure.

comparative example 2

N-phenyl maleimide was purified in the same manner as in Comparative Example 1, except that o-xylene was used instead of ethylbenzene.

comparative example 3

N-phenyl maleimide was purified in the same manner as in Example 1, except that octane (C ₈ H ₁₈ , boiling point: 125 °C) was used instead of squalane in Example 1.

reference example One

20 ml of ethylbenzene, 2.5 g of aniline and 2.9 g of maleic anhydride (maleic anhydride) melted at 80 °C, zirconium hydrogen phosphate (Zirconium(IV) After adding 1.249 g of hydrogen phosphate) solid acid catalyst, the temperature of the reaction system was raised to 125 °C to synthesize N-phenyl maleimide. During the reaction, water produced by dehydration ring closure was removed from the reaction system along with ethylbenzene through azeotropic distillation. Ethylbenzene removed from the reaction system was re-injected into the reaction system, and the synthesis reaction was further conducted for 4 hours. After completion of the synthesis reaction, the solid acid catalyst was separated through simple filtration, and the solution containing N-phenyl maleimide and ethylbenzene was washed with washing water, and the temperature was raised to 80° C. under a reduced pressure of 10 mmHg to obtain ethylbenzene through distillation under reduced pressure. In order to increase the purity of the N-phenyl maleimide product, distillation was performed at a feed rate of 6.7 to 9 g/min per minute, an evaporation section of 145 °C, a condensation section of 100 °C, and a pressure of 3 mmHg using a thin-film distiller with an inner diameter of 2 inches to increase the purity of the N-phenyl maleimide product. A further run was performed to purify the N-phenyl maleimide.

Experimental example

N-phenyl maleimide purified in the above Examples, Comparative Examples, and Reference Examples is obtained as a solid. For purity analysis, it is dissolved in a tetrahydrofuran solvent and the purity is measured using LC (liquid chromatography) analysis to obtain the following It is shown in Table 1 and Table 2.

On the other hand, Example 1 and Comparative Examples 1 and 2 may contain some of the squalane solvent, so for direct comparison of purity with Reference Example 1, the weight of the solvent was subtracted for the total weight of dissolved solid components in the solution obtained. The wt% of each dissolved solid component was calculated and displayed.

(wt%) Example 1 Example 2 Example 3 Example 4 Example 5 MA+MAH - - - 0.15 0.15 ANL 0.23 0.23 0.25 0.46 0.46 PMA 0.20 0.21 0.21 0.59 0.59 PMI 98.79 98.75 98.72 97.45 97.30 PPMA 0.05 0.05 0.06 0.36 0.51 PPFA - - - - - APSI 0.21 0.21 0.21 0.25 0.25 Others 0.53 0.55 0.55 0.74 0.74 Solvent - - - - -

(wt%) Comparative Example 1 Comparative Example 2 Comparative Example 3 Reference example 1 MA+MAH 0.3 0.21 0.2 0.00 ANL - - 0.5 0.00 PMA 0.9 1.07 0.7 0.65 PMI 94 91.6 94.21 98.92 PPMA 1.00 1.42 0.6 0.00 PPFA 0.3 0.73 - 0.00 APSI 0.3 0.49 0.3 0.00 Others 3.2 4.48 3.49 0.43 Solvent - - - 0.00

* ANL: Aniline; PMA: N-phenyl maleamic acid; PMI: N-phenyl maleimide; PPMA: N-(2,5-dioxo-1-phenyl-3-pyrrolidinyl)-N-phenyl maleamic acid; PPFA: N-(2,5-dioxo-1-phenyl-3-pyrrolidinyl)-N-phenyl fumaranilic acid; APSI: 2-anilino-N-phenyl succinimide

As shown in Table 1 above, Examples 1 to 5 purified by cooling to 50 to 70 ° C using an alkane-based solvent having 9 or more carbon atoms show that high-purity PMI equivalent to or similar to that of Reference Example 1 in which the distillation process was performed can be purified without a distillation process. I was able to confirm.

On the other hand, Comparative Examples 1 and 2 using aromatic organic solvents could not purify PMI with high purity. This is because the solubility of impurities other than PMI in aromatic-based organic solvents is higher than that of alkane-based solvents having 9 or more carbon atoms, and impurities are contained in a dissolved state in the solvent included in the PMI crystal phase formed in the form of hollow needles. am.

On the other hand, Comparative Example 3 using octane as an organic solvent also could not purify PMI with high purity.

The above description of the present invention is for illustrative purposes, and those skilled in the art can understand that it can be easily modified into other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, the embodiments described above should be understood as illustrative in all respects and not limiting.

Claims (10)

1) preparing an N-substituted maleimide solution produced by the reaction of maleic anhydride and primary amine in the presence of an organic solvent and a solid acid catalyst; and
2) separating the crystallized N-substituted maleimide by cooling the N-substituted maleimide solution to 50 to 70 °C;
The N-substituted maleimide is N-phenyl maleimide, N-nitrophenyl maleimide, N-methoxyphenyl maleimide, N-methylphenyl maleimide, N-carboxyphenyl maleimide, N-hydroxyphenyl maleimide, N-hydroxyphenyl maleimide, -Chlorophenyl maleimide, N-dimethylphenyl maleimide, N-dichlorophenyl maleimide, N-bromophenyl maleimide, N-dibromophenyl maleimide, N-trichlorophenyl maleimide, and N-tribro At least one selected from the group consisting of mophenyl maleimide;
The organic solvent is an N-substituted maleimide purification method that is an alkane-based solvent having 9 or more carbon atoms.
According to claim 1,
The organic solvent is an alkane-based solvent having 9 to 30 carbon atoms. N-substituted maleimide purification method.

According to claim 1,
The organic solvent is N- containing at least one selected from the group consisting of nonane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, heptadecane, octadecane, nonadecane, eicosan, and squalane. Substituted maleimide purification method.
According to claim 1,
The organic solvent has a boiling point of 110 to 350 ° C. N-substituted maleimide purification method.
According to claim 1,
The solid acid catalyst is a zirconium hydrogen phosphate (Zirconium (IV) hydrogen phosphate, Zr (H ₂ PO ₄ ) ₂ ) N-substituted maleimide purification method that is a solid acid catalyst.
According to claim 1,
N-substituted maleimide purification method further comprising the step of separating the catalyst from the N-substituted maleimide solution before step 2).
According to claim 1,
N-substituted maleimide purification method, wherein the purity of the N-substituted maleimide purified by the above purification method is 95.0 wt% or more.
According to claim 1,
The maleic anhydride is a liquid N-substituted maleimide purification method.
According to claim 1,
The primary amine is methyl amine, ethyl amine, n-propyl amine, isopropyl amine, n-butyl amine, sec-butyl amine, iso-butyl amine, tert-butylamine, n-hexyl amine, n-octyl amine, A method for purifying N-substituted maleimide, which is at least one selected from the group consisting of n-decyl amine, n-dodecyl amine, cyclohexyl amine and aniline.
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