JPH04295462A - Production of n-phenylmaleimide - Google Patents

Abstract

PURPOSE:To inexpensively obtain the title compound useful as a raw material for various kinds of resins, agricultural chemicals and medicines, etc., by reacting maleic anhydride with hydrous aniline to give N-phenylmaleinamic acid, and then imidating through dehydration. CONSTITUTION:An excessive amount of maleic anhydride is reacted with hydrous aniline containing 0.1-10wt.% water in an organic solvent (e.g. xylene) azeotropic with water or in a mixed solvent of the organic solvent azeotropic with water and an organic aprotic polar solvent (e.g. DMF) at 0-140 deg.C, to give N-phenylmaleinamic acid. Then, N-phenylmaleinamic acid is dehydrated and imidated by using metal tin and a tin element-containing compound (e.g. stannous chloride) as a dehydrating catalyst in the mixed solvent of the organic solvent azeotropic with water and the organic aprotic polar solvent at 50-200 deg.C to give the objective compound.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing N-phenylmaleimide by reacting maleic anhydride with hydrated aniline to obtain N-phenylmaleamidic acid, and then dehydrating and imidizing the mixture.

N-phenylmaleimide is useful as a raw material for various resins, agricultural chemicals, medicines, etc. In recent years, it has been used in large quantities to improve the heat resistance of styrenic resins, and it has also been used as a comonomer and polymer for improving other resins. It is expected to be used as a copolymer for blending.

0003

BACKGROUND OF THE INVENTION A general method for producing N-phenylmaleamic acid is to react maleic anhydride and aniline in an organic solvent to form N-phenylmaleamic acid. For example, Organic Synthesis Volume 41,
In Item 93, maleic anhydride and aniline are reacted in ethyl ether to produce N-phenylmaleamic acid. The aniline used here is reagent grade. Until now, there has been no example of using hydrous aniline in a method for producing N-phenylmaleamic acid.

Several methods have long been known for producing N-phenylmaleimide. A general method for producing N-substituted maleimides is to react maleic anhydride with a primary amine to obtain maleamic acid, which is then dehydrated and ring-closed to imidize it. Broadly speaking, there are methods using dehydrating agents and methods using catalysts. In the method using a dehydrating agent, the reaction is carried out using equimolar or more of a dehydrating agent such as acetic anhydride, as is known, for example, in US Pat. No. 244,453 and Organic Synthesis, Vol. 41, Section 93. Although this method is excellent because the reaction conditions are mild and the reaction yield is relatively high, it requires the use of large amounts of expensive dehydrating agents and complicated product separation treatment after the reaction. This increases the cost of the maleimide product, making it difficult to use as an economical mass production method.

[0005] In comparison, the catalytic dehydration imidization method does not consume large amounts of expensive auxiliary raw materials, and therefore can basically be an excellent economical production method. As a method for this, there is known a method disclosed in Japanese Patent Publication No. 51-40078, in which maleamic acids are dehydrated with an acid catalyst, and the resulting water is azeotropically removed while ring-closing within the molecule to imidize. As an acid catalyst, an inorganic acid such as sulfuric acid or phosphoric acid, or a strong acid with a pKa of 3 or less such as organic para-toluenesulfonic acid is used. In this case, Japanese Patent Publication No. 55-46394 uses a solvent system in which an aprotic polar solvent is mixed with an azeotropic solvent in order to increase the solubility of maleamic acids. Directly by using a strong acid type ion exchanger as an acid catalyst as in JP-A-60-11465, or by reacting maleic anhydride with a primary amine in the presence of a strong acid catalyst as described above. Methods for obtaining maleimides are also known. Furthermore, in Japanese Patent Publication Nos. 51-40078, 61-50066, and 62-63562, polymerization inhibitors and alcohols are added as stabilizers in the presence of an acid catalyst, and the reaction is carried out in the presence of an acid catalyst. A trace amount of a metal compound is added and reacted in the presence of. An essential element common to these known catalytic dehydration imidization methods is a strong Bronsted acid catalyst, such as inorganic protonic acids such as sulfuric acids, phosphoric acids, hydrobromic acid, fluorosulfonic acid, etc. Alternatively, a Brønsted acid with strong acid strength, typified by organic protonic acids such as chloroacetic acid, fluoroacetic acid, trifluoromethanesulfonic acid, and sulfone type ion exchange resin, is used as the acid catalyst.

[0006] The catalytic dehydration imidization method is a direct reaction that does not consume large amounts of expensive auxiliary raw materials, so it can basically be an excellent economical production method. however,
Judging from the industrial use of N-phenylmaleimide, none of the conventionally known methods is still technically or economically satisfactory for the following reasons. (1) Even when the above-mentioned known inorganic or organic strong acids are used as catalysts, the reaction selectivity or yield is insufficient. (2) Inorganic acids and expensive organic acids that are used in large amounts as catalysts have poor separation properties from the organic phase, so it is not easy to separate and recover them after the reaction. (3) Acid catalysts tend to contaminate products, and because of their relatively low selectivity, many by-products are mixed in. In order to remove this from products, complicated purification such as washing with water and separation is essential. (4) Because of (3) above, a large amount of washing water must be treated as wastewater. (5) Since the strong acid of the catalyst is used in large amounts at high temperatures, the reactor and peripheral equipment are made of corrosion-resistant materials, making them expensive.

The present inventors discovered the above-mentioned 5 properties of conventional acid catalysts.
We conducted a catalyst search to fundamentally solve the problems in the item. As a result, it was found that dehydration imidization can be carried out according to the purpose without using the aforementioned acid catalyst, simply by adding at least one catalyst selected from metal tin and compounds containing the tin element. Miidashi filed a patent application prior to the present invention (Japanese Patent Application No. 1-152432 and Japanese Patent Application No. 2-1
08769).

[0008]

[Problem to be solved by the invention] Conventionally, industrially, N-
Phenylmaleamic acid was produced by reacting maleic anhydride with distilled aniline in a nonpolar organic solvent. If hydrated aniline is used instead of distilled aniline, water will be present in the reaction system. The raw material maleic anhydride is hydrolyzed by this water and becomes maleic acid or fumaric acid, resulting in a decrease in yield and the formation of impurities.

Furthermore, if water is present in the reaction system for producing N-phenylmaleimide by dehydrating and imidizing N-phenylmaleamic acid, N-phenylmaleamic acid undergoes hydrolysis and becomes maleic acid. It becomes aniline, resulting in lower yields and the formation of impurities.

[0010] If inexpensive industrial hydrous aniline could be used as a raw material for producing N-phenylmaleimide instead of distilled aniline, which has conventionally been used, it would become an economical production method from an industrial perspective.

[0011]

[Means for Solving the Problems] In order to solve the above problems, the present inventors conducted intensive studies using industrial hydrous aniline. As a result, the molar ratio of maleic anhydride and hydrated aniline is set to 1.01 or more in an organic solvent that is azeotropic with water or in a mixed solvent consisting of an organic solvent that is azeotropic with water and an organic aprotic polar solvent. This enables the amidation process to produce N-phenylmaleamic acid in high yield even when using hydrated aniline, and the reaction solution containing N-phenylmaleamic acid is combined with an organic solvent that is azeotropic with water. In a mixed solvent consisting of an aprotic polar solvent, at least one catalyst selected from metal tin and compounds containing the tin element is added, and N-phenylmaleimide is produced in high yield by dehydration imidization. The inventors have discovered that the desired N-phenylmaleimide can be produced in high yield by combining the dehydration and imidization steps, and have completed the present invention.

That is, in the present invention, in producing N-phenylmaleimide, (A) excess maleic anhydride and hydrated aniline containing 0.1 to 10 wt% of water are reacted in an organic solvent to produce N-phenylmaleimide. Amidation step to obtain amic acid, and (B
) A dehydration imidization step of obtaining N-phenylmaleimide by dehydration imidization of the reaction solution containing N-phenylmaleamic acid produced in the above (A) in the presence of a dehydration catalyst. A method for producing N-phenylmaleimide is provided. The method of the present invention will be specifically explained below.

The amidation step in the present invention consists of a step for producing N-phenylmaleamic acid by reacting maleic anhydride with hydrous aniline.

The hydrous aniline used as a raw material in the amidation step may be produced by any production method, and has a water content of 0.1 to 10 wt%, preferably 0.1 to 10 wt%.
5 wt% (the hydrated aniline referred to here refers to aniline containing dissolved water, and the separated water is used as a liquid).

The molar ratio of maleic anhydride and amino groups in the hydrous aniline in the amidation step is naturally desirable to be stoichiometric, but the former is 1.01 to 1.5, preferably 1.0.
It is important to use it within the range of 15 to 1.4, more preferably 1.02 to 1.3. Maleic anhydride having a molar ratio of 1.5 or more may be used, but this is economically disadvantageous. Incidentally, this excess amount of maleic anhydride can be recovered and reused later.

The organic solvent used in the amidation step is an organic solvent that is azeotropic with water, or a mixed solvent consisting of an organic solvent that is azeotropic with water and an organic aprotic polar solvent, preferably an organic solvent that is azeotropic with water. A mixed solvent consisting of an organic aprotic polar solvent and an organic aprotic polar solvent is preferred, and the same solvent as used in the subsequent dehydration imidization step is preferred. The organic solvent that is azeotropic with water may be one that is inert to the reaction, but the same solvent as the organic solvent that is azeotropic with water used in the subsequent dehydration imidization step is preferably used. Examples include benzene, toluene, ethylbenzene, xylenes, cumene, chlorobenzene, anisole, dichloroethane, diethoxyethane, cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, trioxane, etc., and at least one or two of these organic solvents are azeotropic with water.
More than one species may be used. Preferably, xylenes are often used.

Although it is not necessary to use an organic aprotic polar solvent, it is preferable to use it, and the same solvent as used in the subsequent dehydration imidization step is preferable. For example, dimethylformamide, dimethylacetamide, dimethylsulfoxide,
Sulfolane, methyl isobutyl ketone, γ-butyrolactone, hexamethylphosphoramide, N-methylpyrrolidone, tetramethylurea, 1,3-dimethyl-2-imidazolidinone, etc. are used, but dimethylformamide and dimethylacetamide are preferably used. , dimethyl sulfoxide, etc. are used. When using a mixed solvent consisting of an organic solvent that is azeotropic with water and an organic aprotic polar solvent, the composition of the organic aprotic polar solvent is usually 0.1 to 0.1 in volume.
50%, preferably from 1 to 20%. The amount of solvent to be used is 0.1 to 5 mol/L, preferably in terms of the concentration of N-phenylmaleamic acid produced.
It is in the range of 0.5 to 4 mol/L.

The reaction temperature in the amidation step is 0 to 1
The temperature is 40°C, preferably 10 to 100°C. When the reaction temperature is less than 0°C, the reaction rate is low and the reaction takes a long time. Furthermore, when the temperature exceeds 100°C, the double bond of N-phenylmaleamic acid is thermally activated, producing undesirable side reaction products. The reaction pressure in the amidation step is not particularly limited, and the reaction is usually preferably carried out at normal pressure. The reaction time in the amidation step is usually 1 minute to 10 minutes.
The practical optimum time is determined depending on the selection of other reaction conditions, but is preferably in the range of 10 minutes to 3 hours.

In the dehydration imidization step of the present invention, N-phenylmaleamide acid is mixed with metallic tin and a compound containing tin element in a mixed solvent consisting of an organic solvent azeotropic with water and an organic aprotic polar solvent. It consists of a process for producing N-phenylmaleimide by dehydration imidization in the presence of at least one catalyst selected from among them. As the dehydration imidization catalyst used in the dehydration imidization step, at least one selected from metal tin and compounds containing the tin element is used, and the following can be exemplified. There are no restrictions on the shape of metal tin, but fine powder is preferred. Compounds containing the tin element include divalent and tetravalent tin oxides, hydroxides, carboxylates,
Examples include alkoxides, halides, mineral acid salts, and organic tin compounds. As the tin oxide and hydroxide, stannous oxide, stannous oxide, stannous hydroxide, and stannous hydroxide can be used. The organic tin carboxylate is a tin salt of an aliphatic, alicyclic or aromatic monovalent or polyvalent carboxylic acid. Typical examples of such carboxylic acids include acetic acid, propionic acid, butyric acid,
2-ethylhexanoic acid, octylic acid, lauric acid, stearic acid, glycine, lactic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, maleic acid, fumaric acid, citric acid, cyclohexylcarboxylic acid, naphthenic acid, benzoic acid, Examples include tolylic acid, chlorobenzoic acid, phthalic acid, and terephthalic acid.

Examples of tin alkoxide include tin methoxide, ethoxide, n-propoxide, i-propoxide, n-butoxide, sec-butoxide, t-
Examples include ert-butoxide, pentaoxide, hexoxide, phenoxide, and benzyloxide. Tin halides include stannous chloride, stannic chloride, stannous bromide, stannic bromide, stannous iodide, stannic iodide, dichlorotin bisacetylacetonate, dichlorodi-n- These are halogen-containing tin compounds such as butyltin, dichloro-tert-butyltin, dichlorodimethyltin, dichlorodivinyltin, trichloromethyltin, trichlorphenyltin, triethylbromotin, and trimethylbromotin. Examples of organic tin compounds include allyltriphenyltin, bis(trimethyltin)acetylene, hexamethylditin, tetramethyltin, tetra-i-propyltin, tri-n-butylcyclopentadienyltin, and triphenyltin hydroxide. Organotin compounds can also be used. Among these compounds containing metallic tin and the element tin, stannous oxide, stannous hydroxide, stannic hydroxide, stannous chloride, stannic chloride, and divalent tin organic carboxylates Acid salts and alkoxides are preferred. These catalysts are usually used alone, but two or more types can be used in combination if necessary. The amount of catalyst used is not particularly limited, but it is usually 0.1 to 20 mol% (0.001 to 20 mol% as tin) per 1 mol of raw maleamic acid.
0.2 gram atom), preferably 0.5-10 mol% (
(0.005 to 0.1 gram atom of tin).

In the dehydration imidization step, a solvent is used in which an organic aprotic polar solvent is added or mixed with an organic solvent that is azeotropic with water. The organic solvent that is azeotropic with water is used to azeotropically remove water produced by the reaction from the reaction system. This azeotropic solvent may be one that can azeotropically distill water at a temperature in the range of 50 to 200°C and is inert to the reaction. Examples include benzene, toluene, ethylbenzene, xylenes, cumene, chlorobenzene, anisole, dichloroethane, diethoxyethane, cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, trioxane, etc. Preferably, xylene is used in consideration of solvent properties and price. types are often used. In addition, organic aprotic polar solvents are used to increase the solution concentration of maleamic acid and catalyst, such as dimethylformamide, dimethylacetamide, dimethylsulfoxide, sulfolane,
Methyl isobutyl ketone, γ-butyrolactone, hexamethylphosphoramide, N-methylpyrrolidone, tetramethylurea, 1,3-dimethyl-2-imidazolidinone, etc. are used, but preferably dimethylformamide, dimethylacetamide, dimethyl Sulfoxide etc. are used. The amount of the mixed solvent of an organic solvent azeotropic with water and an organic aprotic polar solvent used is usually 0.1 to 5 mol/L, preferably 0.5 to 4 mol/L, as the raw material concentration of maleamic acid. This is within the range of L. The composition of the polar solvent in the mixed solvent is usually selected from the range of 0.1 to 50%, preferably 1 to 20% by volume.

[0022] The reaction temperature in the dehydration imidization step is 50°C.
A range of from 80 to 180°C is used, preferably from 80 to 180°C. The reaction pressure in the dehydration imidization step is not particularly limited, and it is usually preferably carried out at normal pressure. The reaction time in the dehydration imidization step is usually in the range of 0.5 to 10 hours, preferably in the range of 1 to 5 hours. In the process of the invention, the reaction can be carried out batchwise, semi-continuously or continuously. Usually, maleic anhydride, an organic solvent azeotropic with water, and an organic aprotic polar solvent are mixed prior to the reaction, or maleic anhydride is fed into the reactor together with hydrous aniline.

[0023] The N-phenylmaleamide acid reaction solution is transferred to the reactor as it is or to another reactor, a catalyst is supplied and heated, and the water produced is removed from the reactor while heating and refluxing the solvent for a predetermined period of time. The dehydration reaction proceeds by azeotropic separation and conversion to N-phenylmaleimide. After both solvents are evaporated and recovered from the resulting reaction mixture using a distiller, a crude product of maleimide is obtained by simple extraction, crystallization, or distillation. On the other hand, the residue from extraction, crystallization, or distillation can be reused as a recovered catalyst after undergoing treatment such as regeneration as necessary. The crude product of maleimide can be easily converted into a high-purity product suitable for practical use through conventional purification operations such as suitable extraction, crystallization, washing, and distillation. If necessary, it can be dissolved in an appropriate solvent for practical use. Further, the tin metal catalyst of the present invention does not exhibit corrosivity, unlike conventional strong acid catalysts. Therefore, since ordinary inexpensive device materials can be used, the manufacturing equipment becomes extremely economical.

[0024]

EXAMPLES Next, the present invention will be explained in detail with reference to Examples, but the present invention is not limited thereto. Example 1 Maleic anhydride 108.1 was added to a flask equipped with a thermometer, a condenser with a water separator, a dropping funnel and a stirrer.
g (1.1025 mol) and mixed xylene 630 m
It was dissolved in l. Place this flask in an oil bath controlled at 40℃, and when the internal temperature reaches 40℃,
Hydrated aniline (contains 5.0 wt% water) 102.9 g (
1.05 mol of aniline) was gradually added under stirring while keeping the temperature below 90°C. Finish the addition in 15 minutes, and
The reaction is aged for 15 minutes at 0°C to yield N-phenylmaleamic acid.

Next, after adding 70 ml of dimethylformamide and 7.07 g (0.0525 mol) of stannous oxide to this flask, the temperature inside the flask was raised to 135-143 ml.
The temperature was raised to .degree. C., xylene was refluxed, and the reaction was carried out for 150 minutes while water was distilled out of the system together with xylene. After the reaction was completed, the reaction solution was filtered, and the solvent was distilled off from the filtrate under reduced pressure to obtain 187.9 g of a yellow solid. When this solid was analyzed by liquid chromatography, the yield of N-phenylmaleimide was 86.9% based on the aniline charged in the reaction.
It was 0 mol%.

Comparative Example 1 A reaction was carried out in the same manner as in Example 1, except that 103.0 g (1.05 mol) of maleic anhydride was used. After the reaction was completed, 163.8 g of yellow solid was obtained in the same manner as in Example 1. When this solid was analyzed by liquid chromatography, the yield of N-phenylmaleimide was 78.9 mol % based on the aniline charged in the reaction.

Example 2 Aniline is hydrated aniline (contains 1.4 wt% water)97
．． The reaction was carried out in the same manner as in Example 1, except that 8 g (1.035 mol as aniline) was used. After the reaction was completed, 188.5 g of yellow solid was obtained in the same manner as in Example 1. When this solid was analyzed by liquid chromatography, the yield of N-phenylmaleimide was 89.9 mol % based on the aniline charged in the reaction.

Comparative Example 2 The reaction was carried out in the same manner as in Example 2, except that 101.5 g (1.035 mol) of maleic anhydride was used. After the reaction was completed, 174.9 g was obtained in the same manner as in Example 2.
A yellow solid was obtained. When this solid was analyzed by liquid chromatography, the yield of N-phenylmaleimide was 84.9 mol % based on the aniline charged in the reaction.

Example 3 The same reactor as used in Example 1 was used. 108.1 g (1.1025 mol) of maleic anhydride was dissolved in a mixed solvent of 630 ml of mixed xylene and 70 ml of dimethylformamide. When the internal temperature reached 40°C, add 102 hydrated aniline (containing 5.0 wt% water) to this solution.
．． 9 g (1.05 mol as aniline) was stirred at 90
Add gradually while keeping the temperature below ℃. The addition is completed in 15 minutes, and the reaction is aged at 90° C. for 15 minutes to give N-phenylmaleamic acid.

After adding 7.07 g (0.0525 mol) of stannous oxide, the temperature inside the flask was increased to 135-143 °C.
The temperature was raised to .degree. C., xylene was refluxed, and the reaction was carried out for 150 minutes while water was distilled out of the system together with xylene. After the reaction was completed, the reaction solution was filtered, and the solvent was distilled off from the filtrate under reduced pressure to obtain 185.7 g of a yellow solid. When this solid was analyzed by liquid chromatography, the yield of N-phenylmaleimide was 92% based on the aniline charged in the reaction.
．． It was 0 mol%.

Comparative Example 3 The reaction was carried out in the same manner as in Example 3, except that 103.0 g (1.05 mol) of maleic anhydride was used. After the reaction was completed, 181.6 g of yellow solid was obtained in the same manner as in Example 3. When this solid was analyzed by liquid chromatography, the yield of N-phenylmaleimide was 88.9 mol % based on the aniline charged in the reaction.

[0032]

Effects of the Invention The present invention provides a process for producing N-phenylmaleamide acid using inexpensive industrial hydrous aniline, and a process for isolating N-phenylmaleamide acid produced using hydrous aniline. The imide is dehydrated in a mixed solvent consisting of an organic solvent azeotropic with water and an organic aprotic polar solvent by adding at least one catalyst selected from metal tin and compounds containing the tin element. This is a method for producing N-phenylmaleimide, which comprises a step of obtaining N-phenylmaleimide in high yield. According to the present invention, N-phenylmaleimide can be produced industrially at low cost because industrial aniline, which is cheaper than the conventional method for producing N-phenylmaleimide, can be used as a raw material, that is, hydrated aniline can be used. It is possible to make a significant contribution to industry.

Claims (4)

[Claims] Claim 1: In producing N-phenylmaleimide, (A) excess maleic anhydride and water 0.1 to 10 wt.
% of hydrated aniline in an organic solvent to form N-
Amidation step to obtain phenylmaleamide acid; and (B) N-phenylmaleimide is obtained by dehydrating and imidizing the reaction solution containing N-phenylmaleamide acid produced in (A) above in the presence of a dehydration catalyst. A method for producing N-phenylmaleimide, comprising a dehydration imidization step to obtain N-phenylmaleimide. 2. The method according to claim 1, wherein the dehydration catalyst is at least one selected from metal tin and compounds containing elemental tin. 3. The method according to claim 1, wherein the organic solvent used in the amidation step is a mixed solvent consisting of an organic solvent that is azeotropic with water and an organic aprotic polar solvent. 4. The method according to claim 1, wherein the organic solvent used in the dehydration imidization step is a mixed solvent consisting of an organic solvent that is azeotropic with water and an organic aprotic polar solvent.