JPH0356463A - Reducing method of acid component in maleimides - Google Patents

Abstract

PURPOSE:To readily obtain the subject compound of high quality containing small amount of acid component from an organic layer after washing by subjecting maleic amide acids obtained from maleic acid anhydride and primary amines to imidization reaction and washing the solution after the reaction with water in a specific condition. CONSTITUTION:Maleic amide acids obtained from maleic acid anhydride and primary amines is heated in a water-insoluble or water-incompatible inert organic solvent in the presence of an acid catalyst. An organic solvent layer containing the aimed compound obtained by ring-closing imidization while distilling away the generated water to outside of the system as a mixture with said organic solvent is washed with water at a temperature of >=70 deg.C. The amount of water used in washing is >=10wt.% based on the primary amines of raw material. After the washing, the system is allowed to stand to divide into two layers and the aimed compound is obtained from the organic solvent layer. Besides, as the practical method, at first, primary amines of raw material are added to a solution of maleic acid anhydride in the organic solvent and reacted, then the catalyst is added and reacted.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for producing maleimides.

Maleimide compounds are useful compounds as raw materials for resins, pharmaceuticals and agricultural chemicals, and the present invention provides an advantageous method for producing high-quality maleimides with a low content of acid components.

(Prior art) Maleimides are compounds that are particularly useful as raw materials for heat-resistant resins, and have recently been widely used as one of the copolymerization components to improve the heat resistance of ABS resins, polyvinyl chloride resins, polymethyl methacrylate resins, etc. ing.

In many cases, emulsion polymerization, dendritic polymerization, and the like are employed as methods for producing such maleimide resins. However, in these polymerization methods, it is known that the incorporation of acid components into the polymerization system is undesirable because it destabilizes the polymerization system and causes coagulation, coalescence, etc.

Further, the contamination of such acid components into the polymerization system is largely caused by the fact that maleimide products contain a large amount of impurities such as maleic acid and fumaric acid, which are produced as by-products during the maleimide manufacturing process.

In addition, if such acid components are mixed into resin products such as ABS resin or polymethyl methacrylate resin, the acid component will easily decompose by heating and may seriously damage the resin. There is a problem in that the commercial value of the resin itself is significantly lowered because it causes coloring and silver streaks in the resin product.

For these reasons, the content of acid components in maleimides is currently strictly regulated.

On the other hand, many methods for producing maleimides have been known since ancient times. Japanese Patent Publication No. 51-40078 describes the use of maleamic acid as a diluent, solvents such as toluene, xylene, and chlorobenzene with a boiling point of 800 C or higher, and chlorosulfonic acid, p-toluenesulfonic acid,
A method for producing maleimides by carrying out thermal dehydration ring closure together with an acid catalyst such as benzenesulfonic acid, orthophosphoric acid, pyrophosphoric acid, or phosphorous acid, and distilling the water produced at this time out of the system by azeotropy with a solvent. is disclosed.

In addition, JP-A No. 61-5066 discloses a method of reacting maleamic acid in an organic solvent capable of azeotroping with water in the coexistence of an acid catalyst, a metal compound, and a stabilizer while distilling the resulting water out of the system. discloses a method for producing maleimides.

(Problems to be Solved by the Invention) In order to remove acid components from maleimides produced in this manner, it has been proposed to wash the organic solvent layer containing maleimides with water. However, in the organic solvent layer of maleimides produced by the method described above, there is a small amount of impurities that are generated by-product during the reaction and are difficult to dissolve in both water and organic solvents. Since it has the effect of stabilizing the washing water particles in the organic solvent layer when the reaction solution is washed with water, there is a problem that the water layer and the organic solvent layer are completely mixed and emulsified. Therefore, depending on the conditions, it may become impossible to separate both the aqueous layer and the organic solvent layer, making washing with water impossible.

To solve these problems, usually after the imidization reaction, the organic solvent layer containing maleimides is filtered in advance to remove impurities that are insoluble in water and organic solvents in the reaction solution, and then washed with water. What is being done is being done. However, since the insoluble impurity is a sticky substance, it sticks to the filter surface of the filter like glue, making it impossible to filter the reaction solution in a short time.

Therefore, in order to prevent such troubles, filtration is carried out using a filter aid such as diatomaceous earth, but since a large amount of filter aid is required to maintain filtration in good condition, the result However, there is a problem in that the manufacturing cost becomes high.

Thus, it is no exaggeration to say that there is currently no established method for industrially producing maleimites with a low acid content at low cost.

Therefore, the object of the present invention is to heat maleamic acid obtained from maleic anhydride and primary amines in a water-insoluble or water-immiscible inert organic solvent in the presence of an acid catalyst, and to generate water. It is an object of the present invention to provide a method for obtaining maleimides with a low acid component content when producing maleimides by carrying out a ring-closing imidization reaction while distilling them out of the system as a mixture with the organic solvent. Provided is a method for obtaining maleimides with a low content of acid components by an easy and inexpensive improved water washing treatment method that does not require complicated pretreatment steps such as filtration when washing the reaction solution after the reaction. It's about doing.

(Means for Solving the Problems) As a result of studies to achieve the above object, the present inventors have found that impurities that are insoluble or poorly soluble in water and organic solvents, which are by-produced in the imidization reaction, are produced at relatively high temperatures. It was discovered that the compound easily decomposes in water and turns into a water-soluble compound, and based on this knowledge, the present invention was completed.

That is, the present invention heats maleamidic acids obtained from maleic anhydride and primary amines in a water-insoluble or water-immiscible inert organic solvent in the presence of an acid catalyst, and then converts the resulting water into The organic solvent layer containing the maleimide obtained by ring-closing imidization while being distilled out of the system as a mixture with the organic solvent is washed with water at a temperature of 70°C or higher, and then the organic solvent layer and the aqueous layer are separated. This is a method for reducing acid components in maleimides, which is characterized by separating them.

The most distinctive feature of the present invention is that the water washing treatment after the imidization reaction is carried out at a temperature of 70°C or higher, and side reaction products that are insoluble in both water and organic solvents can be easily converted into water-soluble compounds. It is in the place where it is broken down into.

The present invention will be explained in detail below.

The maleamic acid used in the present invention is usually easily obtained by the reaction of maleic anhydride and primary amines. Examples of the primary amines include methylamine, ethylamine, n-propylamine, , isopropylamine, n-butylamine, sec-butylamine, t
ert-butylamine, n-hexylamine, n-dodecylamine, allylamine, penzylamine, cyclohexylamine, aniline, nitroaniline, aminophenol, ami7benzoic acid, anisidine, ethoxyphenylamine, monochloroaniline, dichloroaniline, toluidine, xylidine , ethylaniline, ethylenediamine, m-xylylenediamine, p-xylylenediamine, tetramethylenediamine, hexamethylenediamine, octamethylenediamine, decamethylenediamine, 4
．． 4'-diaminodicyclohexylmethane, 4.4'-
Examples include diaminodiphenylmethane, bis-p-(4-aminophenoxycarbonyl)benzene, and the like, but are not limited to these.

The organic solvent used in the present invention is preferably a solvent that is insoluble or immiscible in water, inert, and does not participate in the reaction, such as benzene, toluene, and
℃ petroleum distillates, xylenes, ethylbenzene, isoprobylbenzene, cumene, mesitylene, tert-butylbenzene, butoidcumene, trimethylhexane, octane, tetrachloroethane, nonane, chlorobenzene,
Ethylcyclohexane, petroleum distillate with a boiling point of 120-170°C, m-dichlorobenzene, sec-butylbenzene,
Examples include p-dichlorobenzene, decane, p-cymene, 0-dichlorobenzene, butylbenzene, decahydronaphthalene, tetrahydronaphthalene, dodecane, naphthalene, cyclohexylbenzene, and petroleum fractions with a boiling point of 170 to 250°C. The amount of this solvent to be used is 0.5 to 20 times (by weight), preferably 1 to 7 times the amount of maleamic acid, in order to conduct the reaction smoothly and satisfy economic conditions.
Double amount used.

Furthermore, a maleimide having a boiling point suitable for the reaction conditions is selected while taking into consideration the solubility, price, ease of handling, etc. of the maleimide. Furthermore, when considering the separation of the maleimides from the solvent after the reaction is completed, it may be advantageous to use a low boiling point solvent and carry out the reaction under pressure.

As a catalyst, monobasic or polybasic acids such as sulfuric acid, ornephosphoric acid, metaphosphoric acid, birophosphoric acid, etc. and/or amines obtained by neutralizing the acids and amines used as raw materials for the production of maleimides can be used. Salt is used.

Further, these catalysts may be supported on a solid carrier.

Solid carriers include natural minerals such as kaolins, clays, talc, chalk, quartz, bentonite, montmorillonite, diatomaceous earth, etc.; synthetic minerals such as highly dispersed silicic acid, alumina, silicates, activated carbon, gypsum, red iron, oxides, etc. Titanium, silica, silica alumina, zirconium oxide, etc.; natural rocks such as calcite, marble, pumice, sepiolite, dolomite, etc. are used. These inorganic carriers are used in the form of a powder, granules obtained by granulating or classifying the carrier, or a honeycomb shape.

It is also possible to use organic carriers, and particulate carriers such as polyfluorocarbon, polystyrene, and phenolic resins can also be used.

Particularly good results can be obtained when the carrier is porous, such as diatomaceous earth, silica gel, etc. For example, examples of commercially available diatomaceous earth include Radiolite (trade name, manufactured by Showa Kagaku Kogyo Co., Ltd.), and examples of silica gel include Caract, Thyroid, and Micropeas Silica Gel (
Product name. manufactured by Fuji Davison Chemical Co.), Wakogel (manufactured by Fuji Davison Chemical Company),
Product name. (manufactured by Wako Pure Chemical Industries, Ltd.), etc.

The amount of these catalysts used is 1 to 20 C mol %, preferably 10 to 1 C mol %, based on the maleamic acid contained in the acid content.
The range is 0.00 mol%. Further, part or all of the acid serving as a catalyst may be neutralized with an amine.

Further, depending on the case, a metal-containing compound or a stabilizer may be allowed to coexist in the reaction system for the reaction. The metal-containing compounds used at this time include at least one metal oxide, acetate, maleate, succinate from the group consisting of zinc, chromium, palladium, cobalt, nickel, iron and aluminum; It is selected from nitrates, phosphates, chlorides and sulfates, among which zinc acetate is particularly effective. The amount of these used is 0.0 as metal per 1 mole of maleamic acid. 0.005 to 0.5 mol%, preferably 0.01 to 0.1 mol%.

Furthermore, as stabilizers, methoxybenzoquinone, p-methoxyphenol, phenothiazine, hydroquinone, alkylated diphenylamines, methylene blue, ter
t-Butylcatechol, tert-butylhydroquinone, zinc dimethyldithiocarbamate, copper dimethyldithiocarbamate, copper dibutyldithiocarbamate, copper salicylate, thiodipropionate esters, mercabutobenzimidazole, triphenylphosphite, alkylphenols, alkylbisphenols etc. are used.

The effects of these stabilizers play a role in allowing the maleimide produced by the imidization reaction to exist stably without deterioration even under the high temperature of the imidization reaction.

As for the amount added, adding a trace amount will have little effect, and conversely, adding an excessive amount is not desirable because it may cause a problem of mixing into the product. Therefore, the amount of these used is 0.001 to 0.5 mol% based on 1 mol of maleamic acid.
It is.

As a method of carrying out the present invention, first, primary amines are added to a solution of maleic anhydride in an organic solvent, and the temperature is lower than 150°C.
Maleamic acid is obtained by reacting preferably at 30 to 120°C for 15 to 120 minutes.

In this case, the molar ratio of the total amount of maleic anhydride added to the reaction system to the total amount of primary amines added to the reaction system is more than 1 and less than 2, preferably more than 1 and less than 1.3.

Then, without isolating the maleamic acid, the above catalyst is added and the temperature is increased to 100-250° C1, preferably 110-2
The reaction is carried out while the water produced at a temperature of 20'C is distilled out of the system as a mixture with a solvent.

It is also possible to additionally add a portion of maleic anhydride during the reaction.

The reaction solution containing maleimides produced in this manner is separated from the acid catalyst and washed with water at a temperature of 70° C. or higher.

The separation methods used at this time include static separation,
Alternatively, any known method such as cyclone, centrifugal separation, thickener, etc. can be used.

Further, the water used for the washing treatment is not limited to sewage water, pure water, or tap water, and may be weakly alkaline or weakly acidic. The amount of water used varies depending on the type of maleimide to be produced and the liquid concentration, but it needs to be at least 10% by weight based on the primary amine used as a raw material.

The temperature of the water washing treatment must be 70° C. or higher in order to decompose insoluble substances generated during the reaction and make them soluble in water. If the temperature is lower than this, a long time is required for solubilization, which is not a good idea.

The water washing treatment can be carried out either batchwise or continuously.

After washing with water, the mixture of the aqueous layer and the organic layer is allowed to stand to separate into two layers, and the aqueous layer is separated from the organic solvent layer.
Thereafter, by distilling off the organic solvent from the organic layer, maleimides with a significantly low acid content can be obtained.

(Effects of the Invention) The present invention has been described above. By carrying out the present invention, it is possible to easily and safely reduce the acid component in maleimides without the need for a complicated process, thereby reducing the acid content at an extremely low cost. This makes it possible to produce high-quality maleimides.

(Examples) Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

Example 1 20 g of orthophosphoric acid was added to a 200 cc beaker, and then a granular silica gel carrier (Carryact 30, manufactured by Fuji Depison Chemical Co., Ltd.) was added to support orthophosphoric acid.

A solution prepared by dissolving 55 g of maleic anhydride in 50 g of xylene was charged into a flask equipped with a thermometer, a cooling tube equipped with a water separator, a dropping funnel, and a stirrer. Next, the temperature inside the flask was adjusted to 80 DEG C., and a solution prepared by dissolving 50 g of aniline in 400 g of xylene was added little by little over 30 minutes to synthesize a xylene slurry of N-phenylmaleamic acid.

The slurry liquid thus obtained was mixed with the catalyst prepared in advance in a beaker and 0.0% copper dibutyldithiocarpamate.
1 g was added and the reaction was carried out at 140° C. for 3 hours.

After the reaction was completed, the reaction solution was separated from the catalyst layer.

The separated reaction solution was cooled to 85-90°C and heated to 15°C at 87°C.
0 g of pure water was added to this reaction solution and stirred for 5 minutes.

Next, when stirring was stopped, the reaction liquid layer and the aqueous layer were immediately separated. Moreover, the interface between these two layers was extremely clear, and separation of both layers was easy.

Subsequently, this operation was repeated once more, and then xylene was distilled off from the reaction liquid layer to obtain 92 g of yellow crystals.

Next, the crystals were distilled at 160°C under a reduced pressure of 3 mmHg to obtain 85 g of bright yellow crystals.

When this crystal was analyzed by liquid chromatography, it was found to have the following structure.

Tophenylmaleimide 99.5% by weight or more Maleic anhydride 0.01% by weight or less Fumaric acid
0.01 “N-phenylmaleamic acid 0
．． 01 "Comparative Example 1 The same operation as in Example 1 was carried out except that the water washing temperature was changed to 50'C. During the water washing process, the reaction liquid layer and the aqueous layer 7 were emulsified and the two layers were completely separated. However, this condition did not change even if I left it for a day and night.

Comparative Example 2 In Example 1, when the amount of water used for washing was 500 g and the washing temperature was 60° C., both layers were completely emulsified during the washing and could not be separated.

Example 2 A solution prepared by dissolving 47 g of maleic anhydride in 200 g of ortho-xylene was charged into a flask equipped with a thermometer, a cooling tube equipped with a water separator, a dropping funnel, and a stirrer.

Next, the temperature inside the flask was adjusted to 80° C., and 50 g of aniline was added little by little over 30 minutes to synthesize a yellow-white ortho-xylene slurry of N-phenylmaleamic acid.

20 g of orthophosphoric acid (
(containing 3 g of water) was added thereto, and the reaction was carried out at 133° C. for 2 hours while distilling the water produced by the reaction out of the system together with ortho-xylene. After 2 hours, the amount of water produced was 10.
7g, which is 89% of the amount of water that should theoretically come out when all of the added maleic acid is converted to maleimide.
It corresponds to %.

An additional 11 g of maleic anhydride was then added and the reaction continued for 4 hours. After 4 hours of reaction, the stirrer was stopped to separate the catalyst layer and ortho-xylene layer, and then the ortho-xylene layer was extracted.

Subsequently, this ortho-xylene layer was cooled to 85°C and heated to 85°C.
Too much pure water at 5°C was added and stirred for 20 minutes at an internal temperature of 80-85°C.

When the stirring was stopped, the reaction liquid layer and the aqueous layer were immediately separated. Moreover, the interface between these two layers was extremely clear, and separation of both layers was easy.

Subsequently, this operation was repeated once more, and then xylene was distilled off from the reaction liquid layer to obtain 90 g of yellow crystals. Next, the crystals were distilled at 160° C. under a reduced pressure of 3 mmWg to obtain 84 g of bright yellow crystals.

When this crystal was analyzed by liquid chromatography, it was found to have the following composition.

N-phenylmaleimide 99.5% by weight or more Maleic anhydride 0. Ol weight% or less fumaric acid
0. Ol weight% or less N-phenylmaleamic acid 0.01 // Example 3 Add 100 g of sulfuric acid to a 500 cc beaker, add 200 g of silica gel (Wako Gel-C 100, manufactured by Wako Pure Chemical Industries, Ltd.) and stir, and add the acid catalyst to the silica gel. I was made to carry it. On the other hand, a reactor was prepared in which a 1Q glass flask was equipped with a thermometer, a stirrer, and a water separator.

Next, 53 g of maleic anhydride powder was added to 50 g of ethylbenzene.
The solution dissolved in g was charged into the above reactor.

Next, the temperature inside the reactor was adjusted to 130°C, and a solution of 40 g of n-butylamine dissolved in 400 g of ethylbenzene was added dropwise over 30 minutes to produce N-(n-butyl).
A slurry solution of maleamic acid was combined.

To the slurry liquid thus obtained, the entire amount of the above-mentioned supported catalyst and 0.0% of zinc acetate were added. (H4g and p-methoxyphenol 0.
065 g of ethylbenzene was added thereto, and the mixture was reacted for 1 hour at a temperature of 1° C. while distilling off the produced water together with ethylbenzene.

After the reaction was completed, the catalyst layer and the reaction liquid layer were separated.

Subsequently, the separated reaction liquid layer was cooled to 80°C, 100 g of 80°C pure water was added to this reaction liquid layer, and the mixture was stirred for 10 minutes. During this time, the internal temperature was 75-80°C. When the stirring was stopped after washing with water, the reaction liquid layer and the aqueous layer were immediately separated. Furthermore, the interface between the two layers was extremely clear, and separation of the two layers was quite easy.

After washing with water, the reaction liquid layer was separated by gas chromatography, and it was found that maleic acid was 0.0.0% by weight or less of OI, indicating that it had been sufficiently removed.

Comparative Example 3 The same procedure as in Example 3 was carried out except that the washing temperature was 60'C and the washing time was 60 minutes, but both layers emulsified during the washing process and it was impossible to separate the two layers. .

Claims (1)

[Claims] 1. Maleamidic acids obtained from maleic anhydride and primary amines are heated in a water-insoluble or water-immiscible inert organic solvent in the presence of an acid catalyst, and the resulting water is mixed with the organic solvent. The organic solvent layer containing maleimides obtained by ring-closing imidization was distilled out of the system as a mixture of
A method for reducing acid components in maleimides, which comprises separating an organic layer and an aqueous layer after washing with water at a temperature of 0° C. or higher.