KR102224894B1 - Purification method of n-substituted maleimide - Google Patents

Abstract

The present invention provides a method for purifying N-substituted maleimide, particularly N-phenyl maleimide. The purification method of the present invention is to purify an N-substituted maleimide prepared by reaction of maleic anhydride and a primary amine from a reaction solution state dissolved in a non-polar solvent, wherein the N-substituted maleimide solution is used in a silica gel column. It is characterized by further purification through recrystallization after purification, and removal of impurities and residual solvents having a low boiling point through distillation. In the present invention, the reaction solution containing N-substituted maleimide produced by the production process of N-substituted maleimide is applied as it is to a silica gel column to remove red impurities that are polymerization oligomers or analogs thereof of N-substituted maleimide. Therefore, the purification method is simple, so that it can contribute to the improvement of the production rate of N-substituted maleimide, and can be applied industrially.

Description

Purification method of N-substituted maleimide {PURIFICATION METHOD OF N-SUBSTITUTED MALEIMIDE}

The present invention relates to a method for purifying an N-substituted maleimide prepared by the reaction of maleic anhydride and a primary amine, and more particularly, to a method for purifying N-substituted maleimide prepared by the reaction of maleic anhydride and a primary amine. -It relates to a method for purifying N-substituted maleimide in which a recrystallization process and a distillation process are performed after the primary purification of the substituted maleimide using a silica gel column.

Maleimide is, for example, a compound useful as an intermediate for medicines and pesticides in addition to the raw materials for thermoplastic resins requiring heat resistance. In particular, N-phenyl maleimide (PMI, N-phenyl maleimide) is used in various industrial fields, and is typically used in the manufacture of ABS resins with improved heat resistance.

Various methods of manufacturing maleimide are known, but the most common method is, for example, maleamic acid produced by reacting maleic anhydride and a primary amine disclosed in US Patent No. 2,444,536. acid) is dehydrated and cyclized in the presence of acetic anhydride and sodium acetate and imidized.

Another method is, as described in Japanese Patent Laid-Open Publication No. 53-68770, by reacting maleic anhydride and a primary amine in an organic solvent, and isolating the resulting maleamic acid, followed by dimethyl formamide, There is a method of dehydrating and cyclizing in the presence of a polar aprotic solvent such as dimethyl sulfoxide and a catalyst.

Another method, as disclosed in Japanese Patent Laid-Open No. 06-23195, is closed by heating maleamic acids in the presence of an acid catalyst in a water-insoluble or water-immiscible inert organic solvent. There is a method of producing maleimides by imidization.

Maleimide prepared in this way is obtained as high-purity maleimide through a purification process. In Japanese Patent Laid-Open No. 2001-302627, a hydrocarbon solution containing a crude N-alkyl maleimide is stirred and mixed with an aqueous solution containing aliphatic aldehydes to prevent impurities. The removal of phosphorus N-alkyl amino succinic anhydride is mentioned, and Japanese Patent Laid-Open No. 2003-160557 refers to removing impurities while washing with water using an aqueous solution containing ammonia. It is widely used to remove impurities by adding a specific substance to the aqueous solution in the process of washing the prepared maleimide solution with water. However, a large amount of wastewater is generated during the washing process, and the additional cost for purifying the wastewater decreases the economics of the PMI process.

In general, in the manufacturing process of N-phenyl maleimide, in addition to PMI, maleic acid (MA), fumaric acid (FA), 2-anilino-N-phenyl succinimide , APSI), N-(2,5-dioxo-1-phenyl-3-pyrrolidinyl)-N-phenylmaleamic acid (N-(2,5-dioxo-1-phneyl-3-pyrrolidinyl Impurities such as )-N-phenylmaleamic acid, PPMA) are generated. Among the impurities, MA and FA are extracted and removed into the water layer through a conventional washing process as mentioned above, but APSI and PPMA cannot be completely removed through the washing process. On the other hand, in addition to the above impurities, PMI generates an oligomeric PMI polymer during the reaction. The PMI polymer is present as a red color impurity in the product, thus limiting the application range of PMI, so it needs to be separated and removed. Therefore, in order to use PMI in the manufacture of heat-resistant ABS resin, impurities such as APSI, PPMA, and PMI polymer must be removed through an additional purification process.

Since the impurities have a boiling point higher than that of PMI, a distillation process is generally used for PMI purification, but the boiling point of PMI is relatively high at about 190 degrees at 30 Torr, so a high energy cost is required when purifying PMI through distillation. In addition, since the PMI polymer among the impurities generates a PMI polymer when exposed to a high temperature, purification of the product through distillation must be performed at a low pressure. This reduces the economics of the PMI manufacturing process.

Therefore, there is a need for research on the development of a process for economically and efficiently removing impurities in the manufacturing process of N-substituted maleimide and purifying and recovering high-purity N-substituted maleimide.

The present invention removes various impurities generated during the production of N-substituted maleimide, in particular, N-phenyl maleimide, through a silica gel column and a recrystallization and distillation process under predetermined conditions. -To provide a method for purifying substituted maleimide.

According to one embodiment of the invention, in the method for purifying an N-substituted maleimide in the presence of a non-polar solvent prepared by reaction of maleic anhydride and a primary amine, the N-substituted maleimide solution having a size of 30 to 400 mesh Adsorbing a first impurity on the silica gel by passing it through a column filled with silica gel, and first eluting an N-substituted maleimide, and passing the non-polar solvent through a silica gel column to pass the N-substituted maleimide remaining in the silica gel column to 2 Primary elution step, by performing a crystallization process of refrigerating the N-substituted maleimide eluate separated from the silica gel column at a temperature of 0 °C to 30 °C to precipitate N-substituted maleimide-containing crystals, and the N- The volume of the N-substituted maleimide solution applied to the silica gel column, including the step of distilling the substituted maleimide-containing crystals under a pressure of 100 torr to 200 torr and a temperature condition of 50 to 100 °C to remove the second impurity. Is not more than 2 times the volume of silica gel, and in the first elution step and the second elution step, the silica gel column is maintained at 40° C. to 90° C., and purification of N-substituted maleimide is performed under pressure conditions of 450 torr to 720 torr. Provides a way.

In addition, according to another embodiment of the present invention, in a method for purifying an N-substituted maleimide in the presence of a non-polar solvent prepared by reaction of maleic anhydride and a primary amine, 0.5 times the volume of silica gel in a silica gel column To 1 times of the non-polar solvent, and then passing the N-substituted maleimide solution through a column filled with silica gel having a size of 30 to 400 mesh to adsorb the first impurity (heavy impurity) to the silica gel, and then N-substituted maleimide. The step of eluting the mid, by performing a crystallization process of refrigerating the N-substituted maleimide eluate separated from the silica gel column at a temperature of 0 °C to 30 °C to precipitate crystals containing N-substituted maleimide, and the N -Comprising the step of distilling the substituted maleimide-containing crystal under a pressure of 100 torr to 200 torr and a temperature of 50 to 100 °C to remove a second impurity (light impurity), and N- applied to the silica gel column The volume of the substituted maleimide solution is not more than twice the volume of the silica gel, and the elution step is a method of purifying N-substituted maleimide performed under pressure conditions of 450 torr to 720 torr by maintaining the silica gel column at 40°C to 90°C. Provides.

As an example, the non-polar solvent may be at least one selected from the group consisting of toluene, xylene, benzene, ethylbenzene, cumene, mesitylene, t-butylbenzene, octane, nonane, decane, and chlorobenzene.

The first impurity (heavy impurity) is 2-anilino-N-phenyl succinimide (APSI), N-(2,5-dioxo-1-phenyl-3- Pyrrolidinyl)-N-phenylmaleic acid (N-(2,5-dioxo-1-phneyl-3-pyrrolidinyl)-N-phenylmaleamic acid, PPMA), fumaric acid (FA), and N- It may be one or more selected from the group consisting of substituted maleimide polymerization oligomers or analogs thereof.

In addition, the second impurity (light impurity) may be at least one selected from the group consisting of maleic anhydride (MAH) and maleic acid (MA).

Meanwhile, in the step of secondary eluting the N-substituted maleimide in the silica gel column purification process, the volume of the non-polar solvent may be 0.5 to 1 times the volume of the silica gel.

In the purification method of the present invention, the purity of the N-substituted maleimide measured after completing the distillation process may be 98% or more.

In the present invention, a product solution containing N-substituted maleimide produced by the production process of N-substituted maleimide is applied as it is to a silica gel column to remove heavy impurities, and a crystallization process and a low-temperature distillation process Since all impurities having a low boiling point are removed through the method, the purification method is simple, thus contributing to the improvement of the production rate of N-substituted maleimide, and has the advantage that it can be applied industrially.

In the present invention, terms such as first and second are used to describe various components, and the terms are used only for the purpose of distinguishing one component from other components.

In addition, terms used in the present specification are only used to describe exemplary embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present specification, terms such as "comprise", "include", or "have" are intended to designate the existence of a feature, number, step, element, or combination of the implemented features, but one or more other features or It is to be understood that the possibility of the presence or addition of numbers, steps, elements, or combinations thereof is not preliminarily excluded.

The present invention will be described in detail below and exemplify specific embodiments, as various modifications can be made and various forms can be obtained. However, this is not intended to limit the present invention to a specific form disclosed, it should be understood to include all changes, equivalents, and substitutes included in the spirit and scope of the present invention.

Hereinafter, a method for purifying N-phenyl maleimide according to a preferred embodiment of the present invention will be described in more detail.

According to an embodiment of the present invention, there is provided a method for purifying N-substituted maleimide, particularly N-phenyl maleimide. In particular, in the purification method of the present invention, the resulting solution containing N-substituted maleimide is applied as it is to a silica gel column to remove heavy impurities, and the light has a low boiling point through a crystallization process and a low-temperature distillation process. ) It is characterized by removing all impurities.

First, as a first preferred aspect of the method for purifying an N-substituted maleimide according to the present invention, in the method of purifying an N-substituted maleimide in the presence of a non-polar solvent prepared by reaction of maleic anhydride and a primary amine, Adsorbing the first impurity to the silica gel by passing an N-substituted maleimide solution through a column filled with silica gel having a size of 30 to 400 mesh and first eluting the N-substituted maleimide, passing the non-polar solvent through a silica gel column Secondly eluting the N-substituted maleimide remaining in the silica gel column by performing a crystallization process of refrigerating the N-substituted maleimide eluate separated from the silica gel column at a temperature of 0°C to 30°C, thereby N-substituted Precipitating a maleimide-containing crystal, and distilling the N-substituted maleimide-containing crystal under a pressure of 100 torr to 200 torr and a temperature condition of 50 to 100 °C to remove a second impurity, the The volume of the N-substituted maleimide solution applied to the silica gel column is not more than twice the volume of silica gel, and the first elution step and the second elution step maintain the silica gel column at 40° C. to 90° C., and 450 torr to 720 torr. It is mentioned that it is carried out under pressure conditions of.

In addition, as a second preferred aspect of the method for purifying an N-substituted maleimide according to the present invention, in the method for purifying an N-substituted maleimide in the presence of a non-polar solvent prepared by reaction of maleic anhydride and a primary amine, After filling the silica gel column with 0.5 to 1 times of the non-polar solvent based on the volume of silica gel, the N-substituted maleimide solution is passed through a column filled with silica gel having a size of 30 to 400 mesh. One impurity) adsorbing and eluting the N-substituted maleimide, and performing a crystallization process of refrigerating the N-substituted maleimide eluate separated from the silica gel column at a temperature of 0°C to 30°C. Precipitating the containing crystal, and distilling the N-substituted maleimide-containing crystal under a pressure of 100 torr to 200 torr and a temperature of 50 to 100°C to remove a second impurity (light impurity) And, the volume of the N-substituted maleimide solution applied to the silica gel column is not more than twice the volume of the silica gel, and the elution step maintains the silica gel column at 40° C. to 90° C., and under a pressure condition of 450 torr to 720 torr. Something to practice.

In the N-substituted maleimide purification method according to the present invention, preferred first and second embodiments are, respectively, after applying the N-substituted maleimide solution to a silica gel column in a silica gel column process, further performing an elution step (first Embodiment), only performing the step of filling a non-polar solvent in a silica gel-filled column before applying the N-substituted maleimide solution to the silica gel column (second mode), in addition to the silica gel column purification process and crystallization process, distillation All of the processes can be performed in the same way.

The purification method of the present invention is to purify an N-substituted maleimide prepared by reaction of maleic anhydride and a primary amine from a reaction solution dissolved in a non-polar solvent. These N-substituted maleimide solutions, especially N-phenyl maleimide solutions, are maleic acid (MA), fumaric acid (FA), and 2-anilino-N-phenyl produced during the reaction process for their preparation. Succinimide (2-anilino-N-phenyl succinimide, APSI), N-(2,5-dioxo-1-phenyl-3-pyrrolidinyl)-N-phenylmaleic acid (N-(2, It contains impurities such as 5-dioxo-1-phneyl-3-pyrrolidinyl)-N-phenylmaleamic acid, PPMA). In addition, the N-substituted maleimide produced during the reaction for preparing the N-substituted maleimide partially polymerizes, and the polymer contains impurities such as oligomers or analogs thereof having a small molecular weight. If these impurities remain with the N-substituted maleimide, they are eluted in the process of processing the heat-resistant polymer containing N-substituted maleimide, making the surface of the polymer unsmooth, and causing the color change of the heat-resistant polymer after processing. Substituted maleimide can be a factor that renders it unusable to produce heat-resistant polymers, such as heat-resistant ABS resins. Therefore, it is desirable that these impurities are removed. In general, a distillation process is used to remove such impurities, but since the boiling point of N-substituted maleimide is high, high energy cost is required when purifying N-substituted maleimide through simple distillation. For example, the boiling point of N-phenyl maleimide (PMI) is about 190 degrees at 30 Torr. In addition, in the case of N-substituted maleimide, an impurity having a higher boiling point than N-substituted maleimide, for example, N-phenyl maleimide (PMI), is generated because N-substituted maleimide polymers are generated through polymerization when heated at 150 degrees or more It is difficult to perform distillation stably in the state where it is contained. Accordingly, the present invention is characterized in that the product of the N-substituted maleimide production process is effectively purified without using a distillation process carried out at low pressure or high temperature. In particular, the present invention obtains the N-substituted maleimide-containing crystal from which the first impurity having a high boiling point (heavy impurity) has been removed through a silica gel column purification process, and then the pressure of 100 torr to 200 torr and 50 to 100 °C Since the second impurity (light impurity) is removed by distillation under temperature conditions, the energy cost incurred in the distillation step of the N-substituted maleimide manufacturing process can be reduced by keeping the temperature of the distillation column low. Problems caused by the generation of N-substituted maleimide polymers can be prevented in advance.

In the purification method of the present invention, first, the product solution itself containing N-substituted maleimide dissolved in a non-polar solvent, the solution after washing it with water, or a solution from which the solid catalyst or other solid is removed by filtration is passed through a silica gel column. When the N-substituted maleimide solution is passed through a silica gel column, all of the first impurities (heavy impurities) are adsorbed on the silica gel, and a part of the N-substituted maleimide is adsorbed on the silica gel and the rest is dissolved in a non-polar solvent and eluted.

In the silica gel column process, before applying the N-substituted maleimide solution, a silica gel column may be first filled with a non-polar solvent, and then a column separation process may be performed. When the non-polar solvent is first filled in this way, the non-polar solvent may be 0.5 to 1 times the volume of the silica gel. Here, when the amount of the non-polar solvent is too large, it is not economical to use the solvent unnecessarily, and impurities may be eluted. On the other hand, when the amount of the non-polar solvent is too small, the recovery rate of the N-substituted maleimide decreases when passing through the silica gel column.

When passing the N-substituted maleimide solution through a silica gel column in the purification method of the present invention, the volume of the N-substituted maleimide solution applied to the silica gel column is less than or equal to 2 times or 0.5 to 2 times the volume of the silica gel, preferably Can be from 0.8 times to 1.5 times. The volume ratio of the N-substituted maleimide solution and silica gel should be 2 times or less in terms of achieving excellent purification efficiency, but may be 0.5 times or more in terms of realizing high productivity of the entire process. If the volume of the N-substituted maleimide solution is too large, all of the red first impurities exceeding the adsorption capacity of the silica gel are not adsorbed to the silica gel, so that the removal of the heavy first impurities is not complete. This is because it may not be possible.

The non-polar solvent used in the present invention may be used to prepare an N-substituted maleimide and any one capable of dissolving the N-substituted maleimide may be used.In particular, the non-polar solvent is toluene, xylene, benzene, and ethylbenzene. , Cumene, mesitylene, t-butylbenzene, octane, nonane, decane, and may be one or more selected from the group consisting of chlorobenzene, or a mixture thereof.

In the purification method of the present invention, after first eluting the N-substituted maleimide by passing an N-substituted maleimide solution through a silica gel column, an N-substituted maleimide remaining in the silica gel column was further passed through a non-polar solvent through a silica gel column. A process of secondary eluting may be performed. In particular, as in the first aspect of the present invention, in the case of applying the N-substituted maleimide solution to the silica gel column without prior treatment of a non-polar solvent, excellent purification efficiency can be implemented by performing such a secondary elution process. .

In the case of performing the second elution of the N-substituted maleimide remaining in the silica gel column, the non-polar solvent is used to elute and separate the adsorbed N-substituted maleimide without eluting the impurities adsorbed on the silica gel. Pass through a silica gel column. As the non-polar solvent, those described above may be used, and it is preferable to use the same solvent as the solvent of the N-substituted maleimide solution, but this is not necessary. In this case, the volume of the non-polar solvent used in this step may be about 0.5 to 1 times the volume of the silica gel. If the amount of non-polar solvent is too much at this stage, it is possible to elute impurities, but it is not economical because the solvent is used unnecessarily. If the amount of non-polar solvent is too little, N adsorbed on silica gel -The dissolution of substituted maleimide becomes unsatisfactory.

The silica gel used in the present invention may have a size of 30 to 400 mesh, preferably 50 to 200 mesh, more preferably 70 to 150 mesh. The size of the silica gel should be 30 mesh or more in terms of impurity adsorption efficiency, and 400 mesh or less in terms of productivity. The smaller the size of the silica gel, the larger the surface area for adsorbing impurities, and thus the retention efficiency increases. However, if the size of the silica gel is too small, the time for the product solution in the PMI manufacturing process to pass through the silica gel column is lengthened, so that productivity is degraded.

The N-substituted maleimide solution used in the present invention can be applied to silica gel at the temperature at which the reaction for its preparation is completed. Thus, the solution can be applied to silica gel at a temperature of 50 to 140 °C, in particular at a temperature of 70 to 110 °C. When the temperature of the solution is too low, a problem of precipitation of PMI crystals present in the resulting solution of the PMI manufacturing process may occur, and when the temperature of the solution is too high, a problem of lowering the adsorption efficiency of silica gel may occur.

Here, in the purification process using the silica gel column, the silica gel column is maintained at 40 to 90 °C, and is performed under pressure conditions of 450 torr to 720 torr. Preferably, the silica gel column may be maintained at a temperature of 70 to 90° C. to perform a purification process. If the internal temperature of the silica gel column is too low, a problem of precipitation of PMI crystals present in the resulting solution of the PMI manufacturing process may occur, and if the temperature of the solution is too high, a problem of lowering the adsorption efficiency of silica gel may occur. In addition, the silica gel column process may be preferably performed under a pressure condition of 500 torr to 680 torr. The silica gel column purification process may be performed under reduced pressure conditions optimized as described above in terms of effectively recovering high-purity N-substituted maleimide and improving the efficiency of the purification process.

The first impurities may be removed through a silica gel column process, and generally may be impurities having a high boiling point, such as materials having a boiling point of 250 degrees or more or 260 degrees or more. The first impurity is 2-anilino-N-phenyl succinimide (APSI), N-(2,5-dioxo-1-phenyl-3-pyrrolidinyl)- Polymerization of N-phenylmaleic acid (N-(2,5-dioxo-1-phneyl-3-pyrrolidinyl)-N-phenylmaleamic acid, PPMA), fumaric acid (FA), and N-substituted maleimide It may be one or more selected from the group consisting of oligomers or analogs thereof.

In addition, the purification method of the present invention may further include the step of eluting the impurities adsorbed on the silica gel by passing a polar solvent through the silica gel column, separating from the silica gel column, and regenerating the silica gel column. In particular, after the elution of the N-substituted maleimide adsorbed on the silica gel is completed, in order to regenerate the used silica gel and use it again, the first impurity (heavy impurity) adsorbed on the silica gel is eluted with a polar solvent from the silica gel. Can be removed. Any polar solvent used may be used as long as it can be eluted from silica gel by dissolving the above impurities, but preferably in the group consisting of acetone, methanol, acetonitrile, dimethyl sulfoxide, tetrahydrofuran, and dimethylformamide. It may be one or more selected or a mixed solvent thereof. In particular, when acetone is used as the non-polar solvent, the above-described impurities can be sufficiently eluted by using acetone having a volume equal to the volume of silica gel. In order to remove the polar solvent remaining in the silica gel column after elution of the impurities, the column is heated to close to the boiling point of the polar solvent, and nitrogen or air is passed through the column to regenerate the silica gel. The silica gel thus regenerated can be used again in the method of the present invention.

Meanwhile, in the purification method of the present invention, a purification process using crystallization is performed on the separated N-substituted maleimide eluate after removing the first impurities (heavy impurities) through the silica gel column process.

Impurities remaining in the liquid product that is first purified through the silica gel column are removed through a crystallization step, which is a second purification step. When the first purified liquid product is cooled, crystals are precipitated, and crystals can be obtained by removing the liquid product through filtration after the crystals are precipitated. In particular, crystals containing N-substituted maleimide are precipitated by performing a crystallization process in which the N-substituted maleimide eluate separated from the silica gel column is refrigerated at a temperature of 0°C to 30°C. The crystallization process may preferably be performed at a temperature of 0 to 30 degrees, and more preferably at a temperature of 10 to 20 degrees. The refrigeration temperature of the crystallization process may be performed at a temperature of 0°C or more in terms of energy efficiency, and may be performed at a temperature of 30°C or less in terms of recrystallization generation efficiency. When crystals containing N-substituted maleimide are precipitated through such a crystallization process, crystals containing N-substituted maleimide can be recovered by removing the remaining liquid product through filtration.

In addition, in the purification method of the present invention, in order to remove the second impurity (light impurity) and residual non-polar solvent contained in the N-substituted maleimide-containing crystal after filtration, a pressure of 100 torr to 200 torr and 50 degrees Celsius. The distillation process is carried out under a temperature condition of to 100 degrees. In particular, the distillation process is not performed at a low pressure or high temperature like a conventional purification process, and thus energy costs that may be excessively generated during PMI purification can be reduced.

The second impurities may be removed through a crystallization process and a distillation process, and may generally be impurities having a low boiling point, such as materials having a boiling point of less than 250 degrees or less than 230 degrees. The second impurity may be at least one selected from the group consisting of maleic anhydride (MAH) and maleic acid (MA).

In particular, a solvent generally used in the reaction for producing N-substituted maleimide is an organic solvent having a boiling point (bp) of 150° C. or less, and is easily removed through distillation. In the distillation process, the low boiling point (light) MAH and MA are also removed, and finally, a high purity N-substituted maleimide can be obtained.

In the purification method of the present invention, the purity of the N-substituted maleimide measured after completing the distillation process, for example, the purity of PMI after purification may be 98% or more, preferably 99% or more.

Hereinafter, a preferred embodiment is presented to aid the understanding of the present invention. However, the following examples are provided for easier understanding of the present invention, and the contents of the present invention are not limited thereto.

Example One

The N-phenyl maleimide solution (solvent: ortho-xylene, o-xylene) obtained by applying the preparation method of N-phenyl maleimide (PMI) was passed through a 150 mesh silica gel column. At this time, the N-phenyl maleimide solution was used in the same volume (1:1) as the volume of silica gel. Here, the temperature of the silica gel column was maintained at 90° C., and the pressure was applied in the range of 650 torr. After passing the first solution through silica gel, the solvent used to prepare N-phenyl maleimide was passed through silica gel in an amount equal to the volume of silica gel (1:1) to elute N-phenyl maleimide. Finally, the first impurities (heavy impurities) including the upper red impurities remaining in the silica gel were eluted with acetone equal to the volume of silica gel and removed from the silica gel, and the silica gel was regenerated by heating the silica gel column to 50 degrees in a nitrogen atmosphere. I did.

In addition, impurities remaining in the liquid product that was first purified through a silica gel column were removed through a crystallization step, which is a second purification step. When the first purified liquid product was refrigerated at a temperature of 10° C., crystals containing N-substituted maleimide precipitated, and after the crystals were precipitated, the liquid product was removed through filtration to recover the crystals containing N-substituted maleimide. After filtration, a small amount of liquid substances contained in the crystal are the solvent used in the PMI manufacturing process, maleic anhydride (MAH), maleic acid (MA), etc., which are a small amount of second impurities (light impurities). As a result, the N-substituted maleimide-containing crystals were distilled under a pressure of 100 torr and a temperature of 100°C to remove residual solvents and second impurities (light impurities), MAH and MA, and finally obtain high purity PMI. Could.

Purified PMI was quantified and dissolved in tetrahydrofuran (THF), and the purity of PMI was analyzed using high-performance liquid chromatography (HPLC).

The purity of PMI before purification was 89.1 wt%, and the purity of PMI after purification measured after performing the purification method was 99.2 wt%.

Example 2

After filling the same amount of solvent as the volume of silica gel in the silica gel column, that is, ortho-xylene, the PMI synthesis reaction product is passed through a silica gel column. After passing through the resulting solution, N- A purification process for N-phenyl maleimide was performed in the same manner as in Example 1, except that a separate process for eluting phenyl maleimide was not performed. After purification, the PMI purity became 98%.

Example 3

As in Example 1, except that ethylbenzene was used as a solvent for the PMI synthesis reaction, and the solvent was used to elute the N-substituted maleimide remaining in the silica gel column after the first impurity was adsorbed. In the same manner, a purification process for N-phenyl maleimide was performed. After purification, the PMI purity was 98.8%.

Example 4

A purification process for N-phenyl maleimide was performed in the same manner as in Example 3, except that the volume ratio (PMI solution/silica gel) of the resulting solution obtained from the synthesis reaction of silica gel and PMI was set to 2. After purification, the PMI purity was 99.2%.

Example 5

After passing the PMI synthesis reaction solution through a silica gel column, N in the same manner as in Example 1, except that the volume ratio (solvent/silica gel) of the non-polar solvent and silica gel for secondary elution of N-phenyl maleimide is 0.5. -A purification process for phenyl maleimide was carried out. After purification, the PMI purity was 98.6%.

Example 6

A purification process for N-phenyl maleimide was performed in the same manner as in Example 1, except that the silica gel column temperature was maintained at 40°C. After purification, the PMI purity was 98.8%.

Comparative example One

The purification process for N-phenyl maleimide was performed in the same manner as in Example 1, except that normal pressure was applied without decompression when purifying a silica gel column. After purification, the PMI purity was 94.9%.

Comparative example 2

A purification process for N-phenyl maleimide was performed in the same manner as in Comparative Example 1, except that the volume ratio of the resulting solution obtained from the synthesis reaction of silica gel and PMI (PMI solution/silica gel) was reduced to 2, and the volume of silica gel was reduced. I did. After purification, the PMI purity was 93.5%.

Comparative example 3

Except that the PMI synthesis reaction product solution is passed through a silica gel column without additionally filling the silica gel column with a non-polar solvent, and after passing the product solution in this way, the process of eluting N-phenyl maleimide using a solvent is not performed. Was performed in the same manner as in Example 1 to purify N-phenyl maleimide. After purification, the PMI purity was 93.9%.

Claims (7)

In the method of purifying an N-substituted maleimide in the presence of a non-polar solvent prepared by reaction of maleic anhydride and a primary amine,
Adsorbing a first impurity on the silica gel by passing the N-substituted maleimide solution through a column filled with silica gel having a size of 30 to 400 mesh, and first eluting the N-substituted maleimide,
Secondly eluting the N-substituted maleimide remaining in the silica gel column by passing the non-polar solvent through a silica gel column,
Precipitating crystals containing N-substituted maleimide by performing a crystallization process of refrigerating the N-substituted maleimide eluate separated from the silica gel column at a temperature of 0°C to 30°C, and
Removing the second impurity by distilling the N-substituted maleimide-containing crystal under a pressure of 100 torr to 200 torr and a temperature of 50 to 100°C
Including,
The volume of the N-substituted maleimide solution applied to the silica gel column is not more than twice the volume of silica gel,
The first elution step and the second elution step are carried out under a pressure condition of 450 torr to 720 torr, maintaining the silica gel column at 40 to 90 ℃,
In the step of secondary eluting the N-substituted maleimide, the volume of the non-polar solvent is 0.5 to 1 times the volume of the silica gel,
Method for purifying N-substituted maleimide.
In the method of purifying an N-substituted maleimide in the presence of a non-polar solvent prepared by reaction of maleic anhydride and a primary amine,
After filling the silica gel column with 0.5 to 1 times of the non-polar solvent based on the volume of silica gel, the N-substituted maleimide solution is passed through a column filled with silica gel having a size of 30 to 400 mesh to adsorb the first impurity to the silica gel And eluting the N-substituted maleimide,
Precipitating crystals containing N-substituted maleimide by performing a crystallization process of refrigerating the N-substituted maleimide eluate separated from the silica gel column at a temperature of 0°C to 30°C, and
Removing the second impurity by distilling the N-substituted maleimide-containing crystal under a pressure of 100 torr to 200 torr and a temperature of 50 to 100°C
Including,
The volume of the N-substituted maleimide solution applied to the silica gel column is not more than twice the volume of silica gel,
The elution step is performed under a pressure condition of 450 torr to 720 torr and maintaining the silica gel column at 40 to 90 °C,
Method for purifying N-substituted maleimide.
The method according to claim 1 or 2,
The non-polar solvent is at least one selected from the group consisting of toluene, xylene, benzene, ethylbenzene, cumene, mesitylene, t-butyl benzene, octane, nonane, decane, and chlorobenzene.
The method according to claim 1 or 2,
The first impurity is 2-anilino-N-phenyl succinimide, N-(2,5-dioxo-1-phenyl-3-pyrrolidinyl)-N-phenylmaleic acid, fumaric acid, and N -A method for purifying N-substituted maleimide, which is one or more selected from the group consisting of polymerized oligomers or analogs thereof of substituted maleimide.
The method according to claim 1 or 2,
The second impurity is at least one selected from the group consisting of maleic anhydride and maleic acid.
delete The method according to claim 1 or 2,
A method for purifying an N-substituted maleimide in which the purity of the N-substituted maleimide measured after completing the distillation process is 98% or higher.