JPH0535141B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides N, which is useful as a heat resistance improver for resins such as ABS, MMA, and PVC, and as an intermediate raw material for pharmaceuticals and agricultural chemicals.
- An improved method for producing substituted maleimides. [Prior Art] Conventionally, as a method for producing N-substituted maleimide from maleic anhydride and a primary amine via dicarphonic acid monoamide, the latter half of the dehydration reaction was (1)
A method of applying a dehydrating agent such as acetic anhydride (for example,
(Japanese Patent Publication No. 46-29140, USP 2444536), (2) A method in which a base is used as a catalyst and the produced water is azeotropically dehydrated with a solvent (for example, Japanese Patent Publication No. 47-24024), (3) An acid is used as a catalyst and the produced water is dehydrated with a solvent. Boiling dehydration method (e.g.,
46394, JP-A-60-100554, JP-A-60-112758)
etc. are known. However, method (1) consumes an equimolar amount of dehydrating agent with respect to the produced water, which is economically disadvantageous, and method (2) generally requires high temperatures and has insufficient yield and quality. be. On the other hand, as method (3), an aprotic polar solvent such as N,N-dimethylacetamide or N-methylpyrrolidone is used as the solvent,
Adding an onium salt with a specific structure (Japanese Patent Application No. 60-213154 = JP-A No. 62-72663) improves the solubility of the catalyst and intermediate dicarboxylic acid monoamide, allowing the reaction to proceed smoothly. The process has been tried and the desired N-substituted maleimides have been obtained in relatively high yields. However, high purity N-
It is not always sufficient to separate and purify substituted maleimides with good yield. Separation and purification techniques for N-substituted maleimides include:
For example, there is a method in which a reactant is added to a large amount of water to precipitate it as crystals, but this method results in a large loss of solvent and N-substituted maleimide. In a method in which the reactant is used as it is, or all or part of the solvent is distilled off, cooled, and the precipitated crystals are filtered out, catalyst remaining in the reaction solution, unreacted dicarboxylic acid monoamide, and various side reactions are removed. The adhesion and contamination of substances to the crystals is unavoidable, and complicated steps such as recrystallization using a new solvent are required to obtain a high-purity product. Furthermore, a method of purifying the reactants by distillation has also been reported (Japanese Patent Application Laid-Open No. 1989-1999).
112758). In this method, after the reaction using a phosphorus-based dehydrating agent, most of the solvent is evaporated, the solution phase of the phosphorus compound is separated by liquid separation, and the N-substituted maleimide is then distilled. However, if only liquid separation is used, strong acidic phosphorus compounds such as phosphoric acid remain, so there are limitations regarding the material used to prevent corrosion of the equipment. Furthermore, if the intermediate dicarboxylic acid monoamide is present in the reaction product, and residual acidic compounds such as phosphoric acid are present, decomposition products such as maleic anhydride will be generated during distillation, resulting in the formation of the desired N-substituted maleimide. This method has disadvantages such as a significant decrease in purity, and is not necessarily an industrially satisfactory method. [Problems to be Solved by the Invention] The present inventors dehydrated dicarboxylic acid monoamide in the presence of an acid or a compound that reacts with water to produce an acid (hereinafter referred to as "acid catalyst etc."). Regarding the method for producing N-substituted maleimide, the above-mentioned drawbacks are improved, high-purity N-substituted maleimide can be obtained in good yield through a simple process, and the quality can be improved even if dicarboxylic acid monoamide, which is a reaction intermediate, remains. We investigated ways to find more advantageous methods, such as those that do not become a hindrance.
As a result, if the acidic substance remaining in the reaction product is distilled after neutralizing it with an alkali metal compound such as sodium hydroxide or potassium hydroxide, the N-substituted maleimide will polymerize during the distillation and the yield will drop significantly. On the other hand, when an alkaline earth metal hydroxide is added or neutralized with an alkaline earth metal hydroxide and then distilled, the polymerization reaction does not occur as in the case of alkali metal compounds, and further distillation The present inventors have discovered that even when digalboxylic acid monoamide coexists in the raw materials, impurities such as maleic anhydride are not generated, so that extremely pure N-substituted maleimides can be obtained in high yields, leading to the completion of the present invention. That is, in the present invention, when separating and purifying the N-substituted maleimide obtained by dehydrating dicarboxylic acid monoamide obtained from maleic anhydride and a primary amine in the presence of an acid catalyst, the remaining acidic substance is treated with a specific base. The purpose of the present invention is to provide a method for obtaining N-substituted maleimide of extremely high purity in a high yield through a simple process, which is characterized by purifying the N-substituted maleimide by contacting it with a sexual substance before and/or during distillation. . [Means for Solving the Problems] As the primary amine applied in the present invention, a compound represented by the following general formula is recommended. RNH ₂ (wherein R is an alkyl group, a halogen atom, an alkoxy group, a carboxyl group, an alkyl group having 1 to 20 carbon atoms which may have a substituent such as a nitro group or a hydroxyl group, a cycloalkyl group, phenyl or naphthyl group) Specifically, methylamine, ethylamine, n-
Butylamine, n-octylamine, 2-ethylhexylamine, n-dodecylamine, n-octadecylamine, cyclohexylamine, aniline, triidine, xylidine, ethylaniline,
Isopropylaniline, dodecylaniline, p-
Examples include chloroaniline, 2,4-dichloroaniline, anisidine, phenetidine, aminobenzoic acid, nitroaniline, and aminophenol. Acid catalysts used in the reaction of the present invention include inorganic acids such as sulfuric acid, phosphoric acid, phosphorous acid, hypophosphorous acid, metaphosphoric acid, pyrophosphoric acid, tripolyphosphoric acid, polyphosphoric acid, methanesulfonic acid, p - Organic acids such as toluenesulfonic acid, benzelsulfonic acid, and naphthalenesulfonic acid, and oxides such as phosphorus pentoxide, phosphorus sesquioxide, sulfur trioxide, and sulfur dioxide are exemplified. The following acid catalysts include onium compounds such as trimethyldodecyl ammonium bromide, benzyltrimethylammonium chloride, etc.
In some cases, it may be even more preferable to use grade amines as cocatalysts. Specific examples of the above compounds are provided by Tokuhan Sho.
Learn more about No. 60-213154 (Japanese Unexamined Patent Publication No. 62-72663). The basic substance used in dispersing and purifying N-substituted maleimide from the reactant is an oxide of an alkaline earth metal, a hydroxide thereof, or a carbonate thereof, and among these, magnesium, calcium, or barium is used, but is not particularly limited. The oxides, hydroxides or carbonates of are preferred. These basic substances can be used alone or in a mixture of two or more. The amount of these basic substances to be used is preferably 0.5 to 100 times equivalent to the acidic substance in the distillation raw material. If the amount is less than 0.5 times equivalent, the quality of the N-substituted maleimide obtained by distillation will be poor, and the effect of preventing corrosion by acidic substances will be insufficient. On the other hand, if 100 times the equivalent or more is used, it will only be economically disadvantageous and no industrial advantage will be observed. However, this upper limit does not apply, for example, when a packed column is filled with molded articles or crushed pieces of the basic substance and a process is performed in which the distillation raw material is passed therethrough. When a basic substance is used, it is preferable that water coexist with the basic substance, as this will promote the reaction with the acidic substance in the distillation raw material. In this case, the amount of water added is 1 to 1
50% by weight is preferred. As the solvent used in the reaction, any of hydrocarbons, halogen-containing hydrocarbons, and aprotic polar solvents can be used. Specifically, toluene, xylene, ethylbenzene, cumene, hexane, octane, decane, cyclohexane, methylcyclohexane, ethylcyclohexane, light oil, chlorobenzene, dichloroethane, trichloroethane, perchloroethane, N,N-dimethylformamide,
N,N-diethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, N-methylcaprolactam, tetramethylurea, N,N
-dimethylpiperidinone, dimethylsulfoxide, sulfolane, methylisobutylketone, hexamethylphosphoramide, 1,3-dimethyl-2
-Imidazolidinone etc. can be used alone or in a mixture of two or more. A general method of carrying out the invention is described below. In the presence of the above-mentioned solvent, maleic anhydride and a primary amine are reacted at 150° C. or lower, preferably at 20 to 80° C. to produce the corresponding dicarboxylic acid monoamide, and then an acid catalyst or the like is added to the resulting reaction mixture. Generally, the reaction is carried out by stirring and heating at 90 to 150°C, preferably 100 to 140°C, and removing water produced by the reaction. However, maleic anhydride and a primary amine are reacted in a different solvent than the dehydration reaction of dicarboxylic acid monoamide, such as acetone, the intermediate dicarboxylic acid monoamide is once separated, and then the dehydration imidization reaction is performed in the above solvent. You can also do that. Furthermore, when only a nonpolar solvent such as a hydrocarbon or a halogen-containing hydrocarbon is used as a solvent, it is preferable to use an acid catalyst or the like together with the above-mentioned onium compound and/or tertiary amine. Next, the distillation raw material is brought into contact with the above-mentioned specific basic substance, and various methods can be employed for this purpose. For example, the basic substance can be added alone or together with water to the reaction product and distilled directly.
After heating and stirring at a temperature of 150° C. or lower, distillation may be performed, or further, unreacted basic substances may be filtered off and then distilled. Alternatively, the distillation raw material can be passed through a tower filled with molded products or crushed pieces of the basic substance. It is preferable to add water in these cases as well. Depending on the type of acid catalyst, solvent, primary amine used, etc., the acidic substance may be separated by cooling the reaction solution. In this case, it is particularly preferable to add the basic substance after separating and removing the acidic substance, since a sufficient effect can be obtained with a small amount of the basic substance. Furthermore, if the reaction mixture containing only a non-polar solvent or a non-polar solvent is sufficiently cooled, N-
Substituted maleimide may precipitate as crystals. In this case as well, it is preferable to treat the filtered crystals with a basic substance. Distillation is preferably carried out under reduced pressure at a liquid temperature of 200° C. or less. At temperatures above 200℃, the product deteriorates,
Yield and quality will decrease. [Example] The present invention will be explained in detail with reference to Examples below. Example 1 Maleic anhydride was placed in a four-necked flask equipped with a condenser with a water separator, a dropping funnel, a thermometer, and a stirrer.
47.5g (0.50mol), xylene 145g, toluene 27
Charge 35g of g and n-octane, and set the reaction temperature to 50°C.
While stirring, 44.7 g (0.48 mol) of aniline was added dropwise little by little over 1 hour, and the reaction was continued for an additional 30 minutes at the same temperature. To the resulting reaction mixture were added 2.5 g of sulfuric acid and 0.9 g of benzyltrimethylammonium chloride, heated at reflux temperature (125 to 135° C.) with stirring, and reacted for about 3 hours while removing produced water. After the reaction was completed, the acidic compound was cooled and separated into a lower layer, and 2.8 g of potassium hydroxide (2.0 times equivalent to the remaining acidic substance) and 6.5 g of water were added to the upper layer and stirred at 80°C for 1 hour. . Next, excess solids such as calcium hydroxide were filtered off at 70°C, the aqueous layer was separated, and the oil layer was transferred to a 500 ml Claisen flask with a side arm and distilled under reduced pressure. As a result, 75.6 g (yield 91% based on the charged aniline) of a yellow crystalline product was obtained. This product has a melting point of 91-91.5℃, a purity of N-phenylmaleimide of 99% or more by GPC, and an acid value.
It had extremely high purity of less than 0.1. Example 2 In a reactor similar to Example 1, 47.5% maleic anhydride was added.
(0.05 mol) was charged with 200 g of toluene and 20 g of N-methylpyrrolidone, and while stirring at a reaction temperature of 40°C, 44.7 g (0.48 mol) of aniline was added dropwise in small portions over 1 hour, and the reaction was continued for an additional 30 minutes at the same temperature. Ta. 7.0 g of phosphoric acid was added to the resulting reaction mixture, and the mixture was stirred and reacted at 110° C. for 2.5 hours while removing produced water.
After the reaction was completed, the mixture was cooled to separate the acidic substance in the lower layer, and 5.0 g of magnesium hydroxide (6 times equivalent to the acidic component) and 10.0 g of water were added to the upper layer, followed by stirring at 70°C for 1 hour. Next, excess solids such as magnesium hydroxide were filtered off, and the mixture was distilled under reduced pressure in the same manner as in Example 1. As a result, melting point 90.5-91.5℃, GPC purity 99
% or more, N-phenylmaleimide with acid value 0.2 78.0
g (94% yield based on aniline) was obtained. Example 3 In a reactor similar to Example 1, 47.5% maleic anhydride was added.
g (0.05 mol) and toluene 109 g and xylene
108 g of aniline was charged, and while stirring at a reaction temperature of 50° C., 44.7 g (0.48 mol) of aniline was added dropwise little by little over 1 hour, and the reaction was continued at the same temperature for an additional 30 minutes. Add 6.8 g of phosphorus pentoxide and 1.5 g of dimethylstearylamine to the resulting reaction mixture and heat to 120-130°C with stirring.
The reaction was continued for 5 hours while removing the produced water. After the reaction was completed, the mixture was cooled and distilled in the same manner as in Example 1 together with 6.9 g of barium carbonate (3.0 times equivalent to the acidic component in the distillation raw material) and 15 g of water. As a result, the melting point is 89.5~
74.7 g of N-phenylmaleimide (yield based on aniline: 90%) was obtained at 90.5°C, with a GPC purity of 99% or more and an acid value of 0.3. Examples 4 to 7 In Example 1, 0.48 mol of various primary amines shown in Table 1 and a basic compound were used instead of aniline.
The reaction and distillation were carried out in the same manner as in Example 1 except that 5.0g was used. The yield and analysis results of the obtained N-phenylmaleimide are shown in Table 1. Comparative Example 1 The same operation as in Example 1 was carried out without adding any basic compound. The yield of the obtained N-phenylmaleimide based on aniline was 91%, but the melting point was 84.5~
The quality was poor, at 86.5°C, with a purity of 95.5% by GPC and an acid value of 6.3. Comparative Example 2 In Example 1, 3.1 g of sodium hydroxide was used instead of calcium hydroxide (based on the remaining acidic substances).
2.0 times equivalent) was added, stirred at 80℃ for 1 hour, and left to stand.
When the oil layer separated at 70°C was distilled, polymerization occurred during the distillation, resulting in a low yield of less than 10% of the target N-phenylmaleimide. [Effects of the Invention] Since the decomposition of dicarboxylic acid monoamide and the polymerization of N-substituted maleimide during distillation can be prevented, extremely high purity N-substituted maleimide can be obtained in high yield with simple operations. Furthermore, since the acidic compounds remaining in the distillation raw material are neutralized, there is no fear of corrosion of the equipment during distillation. 【table】

Claims (1)

[Claims] 1. Purification of an N-substituted maleimide obtained by dehydrating a dicarboxylic acid monoamide obtained from maleic anhydride and a primary amine in the presence of an acid or a compound that generates an acid by reacting with water. When distilling, the remaining acidic substance is brought into contact with one or more basic substances selected from the group consisting of alkaline earth metal acid additions, hydroxides, and carbonates before and/or during distillation. 1. A method for producing a highly pure N-substituted maleimide, the method comprising purifying it by: 2. The method for producing a high purity N-substituted maleimide according to claim 1, which comprises bringing the remaining acidic substance and basic substance into contact in the presence of water.