JPH03118362A - Production of n-substituted maleimide - Google Patents

Abstract

PURPOSE:To obtain the subject compound useful as an agent for improving heat-resistance of resins, etc., under mild condition at a low cost without causing corrosion of apparatus by using an N-substituted maleamic acid monoester as a raw material and cyclizing and imidating the material by the dealcoholation reaction in the presence of an acid catalyst and superheated steam. CONSTITUTION:An N-substituted maleamic acid monoester of formula I (R<1> is unsubstituted or substituted 1-20C alkyl, 3-12C cycloalkyl, phenyl or naphthyl; R<2> is 1-7C alkyl or 3-7C cycloalkyl) (e.g. methylmaleamic acid methyl ester) is used as a raw material and subjected to the cyclization and imidation by dealcoholation reaction in the presence of an acid catalyst while introducing superheated steam into the reaction system at a reaction temperature of 60-180 deg.C, preferably 80-160 deg.C to obtain the objective compound of formula II. The temperature of the superheated steam is 100-200 deg.C, preferably 100-180 deg.C and the introduction rate of the steam is preferably 20-2,000 pts.wt. per 100 pts.wt. of the raw material mixture per hour in the case of continuous reaction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an improved method for producing N-substituted maleimides.

N-substituted maleimide is a compound useful as a heat resistance improver for resins such as ABS, MMA, and PVC, and as an intermediate for pharmaceuticals and agricultural chemicals.

[Conventional technology]

Various methods for producing maleimides have been studied for a long time. For example, U.S. Patent No. 2444536, JP
No. 68770 and Japanese Patent Publication No. 51-40078 describe a method for producing N-substituted maleimide by dehydrating and imidizing maleamic acid.

Apart from these, Japanese Patent Publication No. 46-37588 also describes maleic acid half amide (maleamic acid).
No. 45339 describes a method for producing N-substituted maleimides by cyclodehydration of monoammonium salts of maleic acid in the presence of superheated steam. This method has the advantage that highly pure N-substituted maleimide can be obtained through simple steps. However, these methods involve the use of a large amount of a water desorbing agent such as phosphonic acid, and the high reaction temperature of 200 to 250° C., resulting in corrosion of the equipment.

Therefore, in JP-A No. 61-251658, instead of using a water-eliminating agent such as phosphonic acid, maleic acid is used to produce N-substituted maleimide by cyclization dehydration in the presence of superheated steam. A method has been proposed. However, as a result of follow-up tests by the present inventors, even with this method, a high temperature of 200 to 250°C is still required in order to increase the yield, which prevents corrosion of the equipment, but prevents deterioration of the equipment. I couldn't do it.

[Problem to be solved by the invention]

By the way, in recent years, among N-substituted maleimides, cycloalkyl substituted products or alkyl substituted products are colorless, and M
It is attracting attention from the viewpoint that even when added to transparent resins such as MA and PVC, it can improve the heat resistance of the resin without coloring the resin.

Therefore, an object of the present invention is to provide a method for producing high-purity N-substituted maleimide in high yield, which does not require high temperatures of 200 to 250°C, although superheated steam is used. .

A further object of the present invention is to provide a method for producing cycloalkyl-substituted and alkyl-substituted maleimides in high yield and high purity.

[Means to solve the problem]

Therefore, the present invention provides an N-substituted maleamic acid monoester represented by the general formula (1) (wherein R1 is unsubstituted or has a substituent and has 1 to 2 carbon atoms)
0 alkyl group, a cycloalkyl group having 3 to 12 carbon atoms that is unsubstituted or has a substituent, a phenyl group that is unsubstituted or has a substituent, or a naphthyl group that is unsubstituted or has a substituent, and R2 is unsubstituted or An alkyl group having 1 to 7 carbon atoms having a substituent, or a cycloalkyl group having 3 to 7 carbon atoms having an unsubstituted or substituent group) is ring-closed by a dealcoholization reaction in the presence of an acid catalyst and superheated steam. The present invention relates to a method for producing an N-substituted maleimide represented by the general formula (2), which is imidized.

The present invention will be explained in detail below.

In general formulas (1) and (2), R1 is an unsubstituted or substituted alkyl group having 1 to 20 carbon atoms, an unsubstituted or substituted cycloalkyl group having 3 to 12 carbon atoms, or an unsubstituted or substituted cycloalkyl group having 3 to 12 carbon atoms. Indicates a phenyl group having a substituent, or a naphthyl group that is unsubstituted or has a substituent.

The alkyl group may be a straight chain or branched alkyl group. Preferred alkyl groups include methyl, ethyl, n
-propyl, isopropyl, n-butyl, isobutyl,
5ec-butyl, tert-butyl, n-hexyl, n-
Octyl, n-decyl, n-dodecyl, n-octadecyl and the like can be mentioned.

Preferred cycloalkyl groups include cyclopropyl,
Examples include cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, and cyclododecyl.

The above alkyl group, cycloalkyl group, phenyl group and naphthyl group may all be unsubstituted or substituted. Examples of substituents include alkyl groups having 1 to 10 carbon atoms, phenyl groups, and halogens (fluorine, chlorine,
Bromine) can be exemplified.

Examples of phenyl groups having substituents include methylphenyl group, dimethylphenyl group, trimethylphenyl group, p
-ethylphenyl group, p-isopropylphenyl group, hydroxyphenyl group, p-methoxyphenyl group, p-ethoxyphenyl group, phenyl chloride group, phenyl bromide group,
Examples include fluorinated phenyl groups.

In general formula (1), R2 represents an alkyl group having 1 to 7 carbon atoms, which is unsubstituted or has a substituent, or a cycloalkyl group, which is unsubstituted or has a substituent, and has 3 to 7 carbon atoms.

The alkyl group may be a straight chain or branched alkyl group. Preferred alkyl groups include methyl, ethyl, n
-propyl, n-butyl, isobutyl, n-hexyl and the like.

Preferred cycloalkyl groups include cyclohexyl,
Examples include cycloheptyl.

The above alkyl group and cycloalkyl group may be unsubstituted or may have a substituent.

Examples of the substituent include an alkyl group having 1 to 6 carbon atoms and a phenyl group. An example of an alkyl group having a phenyl group as a substituent is a benzyl group.

Next, specific examples of maleamic acid monoesters represented by general formula (1) are shown: Methyl maleamic acid methyl ester, ethyl maleamic acid methyl ester, n-propyl maleamic acid methyl ester, isopropyl maleamic acid methyl ester Methyl ester, n-butyl maleamic acid methyl ester, cyclohexyl maleamic acid methyl ester, n-octadecyl maleamic acid methyl ester,
Phenylmaleamide acid methyl ester, p-nitrophenylmaleamide acid methyl ester, O-)ruylmaleamide acid methyl ester, p-tolylmaleamide acid methyl ester, p-chloro-phenylmaleamide acid methyl ester, dichloro-phenyl maleamic acid methyl ester, methyl maleamic acid ethyl ester, ethyl maleamic acid ethyl ester, n-propyl maleamic acid ethyl ester,
Isopropyl maleamic acid ethyl ester, n-butyl maleamic acid ethyl ester, cyclohexyl maleamic acid ethyl ester, n-octadecyl maleamic acid ethyl ester, phenyl maleamic acid ethyl ester, p-nitrophenyl maleamic acid ethyl ester Esters, o-toluylmaleamide acid ethyl ester, p-toluylmaleamide acid ethyl ester, p-chloro-phenylmaleamide acid ethyl ester, dichloro-phenylmaleamide acid ethyl ester, methylmaleamide acid n-propyl ester, ethyl Maleamic acid n-propyl ester, n
-Propylmaleamide acid n-propyl ester, isopropylmaleamide acid n-propyl ester, n
-butyl maleamic acid n-propyl ester, cyclohexyl maleamic acid n-propyl ester, n
-octadecylmaleamide acid n-propyl ester, phenylmaleamide acid n-propyl ester, p
-Nitrophenylmaleamide acid n-propyl ester, 0-toluylmaleamide acid n-propyl ester, p-toluylmaleamide acid n-propyl ester, p-chloro-phenylmaleamide acid n-propyl ester, dichloro-phenylmaleic acid Amic acid n-
Propyl ester, methyl maleamic acid 1so-butyl ester, ethyl maleamic acid is.

Butyl ester, n-propyl maleamic acid 1so
-Butyl ester, isopropyl maleamic acid 1s
o-butyl ester, n-butyl maleamic acid 1s
o-butyl ester, cyclohexyl maleamic acid iso-butyl ester, n-octadecyl maleamic acid is.

Butyl ester, phenylmaleamide acid 1sO-butyl ester, p-nitrophenylmaleamide acid 1
so-butyl ester, 0-toluylmaleamide acid 1so-butyl ester, p-toluylmaleamide acid 1so-butyl ester, p-chloro-phenylmaleamide acid 1SO-butyl ester, dichloro-phenylmaleamide acid 1so-butyl ester, Methyl maleamic acid n-hexyl ester, ethyl maleamic acid n-hexyl ester, n-propyl maleamic acid n-hexyl ester, isopropyl maleamic acid n-hexyl ester, n-butyl maleamic acid n-hexyl ester Esters, cyclohexylmaleamide acid n-hexyl ester, n-octadecylmaleamide acid n-hexyl ester, phenylmaleamide acid n-hexyl ester, p-nitrophenylmaleamide acid n-hexyl ester, o-toluylmaleamide acid n-hexyl ester, 1)-toluylmaleamidic acid n-hexyl ester, p-chloro-phenylmaleamidic acid n
-hexyl ester, dichloro-phenylmaleamidic acid n-hexyl ester.

Next, the maleimides represented by the general formula (2) are illustrated below: methylmaleimide, ethylmaleimide, n-propylmaleimide, isopropylmaleimide, n-butylmaleimide, isobutylmaleimide, 5ec-butylmaleimide, jet-butylmaleimide, n-hexylmaleimide, n-octylmaleimide, n-decylmaleimide,
n-dodecylmaleimide, n-octadecylmaleimide, cyclohexylmaleimide, 2-methyl-cyclohexylmaleimide, 4-methyl-cyclohexylmaleimide,
Allylmaleimide, benzylmaleimide, phenylmaleimide, p-nitrophenylmaleimide, o-tolylmaleimide, p-)ruylmaleimide, quizyridylmaleimide, p-ethyl-phenylmaleimide, ethoxyphenylmaleimide, p-isopropylphenylmaleimide, p-chloro -phenylmaleimide, dichloro-phenylmaleimide.

The method of the present invention will be explained in detail below.

In the method of the present invention, maleamic acid monoester of general formula (1) is treated in the presence of an acid catalyst and superheated steam,
Ring-closing imidization is performed by dealcoholization reaction.

This reaction can be carried out either continuously or batchwise.

In the case of a continuous method, a mixture of maleamic acid monoester and an acid catalyst is introduced into a reactor maintained at a predetermined temperature and brought into contact with it while being mixed with superheated steam. At this time, the mixture of maleamic acid monoester and acid catalyst may be heated and melted, or may be dissolved in a solvent and supplied as a solution. Dissolving or suspending the mixture of maleamic acid monoester and acid catalyst using a solvent may be preferable because it facilitates the feeding of raw materials to the reactor.

Examples of the solvent include hydrocarbon compounds with relatively low boiling points, alcohols, water, and the like.

Examples of hydrocarbon compounds include aliphatic hydrocarbons having 8 or less carbon atoms (e.g., hexane, heptane, octane, isooctane, etc.), alicyclic hydrocarbons (e.g., cyclohexane, etc.)
, aromatic hydrocarbons (eg, benzene, toluene, xylene, etc.). Examples of alcohols include methanol, ethanol, propatool, isoproptool, butanol, isobutanol, and the like, each having 4 or less carbon atoms. If desired, two or more types of solvents can be used in combination.

The appropriate amount of solvent to be used is such that the concentration of the raw material mixture is approximately 20 to 480% by weight in order to obtain a viscosity suitable for supply.

In the case of a batch method, a mixture of a maleamic acid monoester and an acid catalyst is placed in a reactor, heated to a predetermined temperature, and superheated steam is introduced and brought into contact with it. In addition, in the case of a batch method, a solvent may or may not be used. however,
The esterification reaction solution containing the solvent can be directly introduced into the reaction apparatus and subjected to ring-closing imidization.

In the present invention, superheated steam is defined as under a certain pressure,
Steam that has been heated above a certain temperature necessary to maintain equilibrium between steam and water. For example, under 1 atmosphere, 1
Steam heated to 00°C or above, under 2 atmospheres, 12
Steam heated to 0°C or higher is superheated steam.

Raising the reaction temperature will increase the reaction rate, but side reactions such as isomerization and polymerization to fumaramic acid etc. will occur.
Selectivity decreases. Therefore, the reaction temperature is 60-180℃
, preferably in the range of 80 to 1600C.

5. The temperature of the superheated steam is not appropriate because if it is too high, side reactions such as isomerization and polymerization to fumaramic acid etc. will occur. Furthermore, it is necessary to control the temperature and flow rate of superheated steam depending on the reaction temperature setting, but the temperature of superheated steam can be set in the range of 100 to 200°C, preferably 100 to 180°C. Appropriate.

Furthermore, if the amount of superheated steam introduced is too large, the average residence time inside the reactor will be shortened, and unreacted substances will flow out of the reactor before the reaction has sufficiently progressed, which is not appropriate. On the other hand, if the amount is too small, a reaction mixture that cannot be distilled out of the reactor is formed, and as a result, side reactions such as polymerization occur within the reactor, reducing the yield.

Therefore, in the case of a continuous system, the amount of superheated steam introduced is 1 part per hour per 100 parts by weight of the reaction raw material mixture introduced.
A suitable amount is 0 to 3,000 parts by weight, preferably 20 to 2,000 parts by weight.

In the case of a batch method, it is appropriate to introduce 10 to 3,000 parts by weight, preferably 20 to 2,000 parts by weight of superheated steam per hour to 100 parts by weight of the reaction raw material mixture until the reaction is completed. .

The reaction time (residence time in the case of a continuous method) varies depending on the reaction temperature, the type of maleamic acid monoester, etc., but it is appropriate to set it to, for example, about 1 to 7 hours, preferably 1 to 4 hours. be.

The N-substituted maleimide produced by the reaction is led out of the reactor as a hot reaction gas. By cooling this hot reaction gas, it is separated into steam condensed water and crude products.

As the acid catalyst, Brønsted acids such as sulfuric acid, sulfuric anhydride, p-toluenesulfonic acid, metasulfonic acid, benzenesulfonic acid, ethylsulfonic acid, octylsulfonic acid, phosphoric acid, maleic acid, and acidic ion exchange resins are used. be able to.

If the amount of acid catalyst used is too small, the progress of the reaction will be slow and the reaction time will be prolonged. On the other hand, if the amount is too large, a large amount of side reaction products tend to be produced, which is not preferable. Therefore, it is appropriate to use 0.5 to 30 parts by weight, preferably 2 to 20 parts by weight, per 100 parts by weight of maleamic acid monoester.

The reaction pressure may be normal pressure, increased pressure, or reduced pressure as long as it is within the above temperature range.

〔Effect of the invention〕

According to the method of the present invention, a highly purified cycloalkyl-substituted maleimide, etc. can be produced in high yield from maleamic acid monoester.

Furthermore, according to the method of the present invention, cycloalkyl-substituted maleimides can be produced at a relatively low temperature compared to conventional methods, so corrosion of production equipment can be avoided even though an acid catalyst is used. Can be effectively prevented. Furthermore, since the reaction temperature is low, there is no fear of cracks in the glass even if a glass-lined reaction apparatus is used.

The present invention will be explained in more detail below using examples. However, the present invention is not limited to these examples.

〔Example〕

Reference Example (Preparation of N-cyclohexylmaleamidic acid 8 1so-butyl ester) 2 equipped with a thermometer, a cooling tube equipped with a water separator, and a stirrer
157.6 g (0°8 mol) of N-cyclohexyl maleamic acid, 177.9 g (2.4 mol) of 1so-butyl alcohol, 7 benzene
20- and concentrated sulfuric acid 4.0- were charged and heated to 80°C with stirring.
The esterification reaction was carried out for 1 hour while the water produced by the reaction was distilled off from the system together with benzene.

This esterification reaction solution was washed twice with 600 yd of a saturated aqueous sodium bicarbonate solution and 600 yd of water, dried over anhydrous sodium sulfate, and then the solvent was distilled off under reduced pressure.

The obtained product was vacuum dried at 40° C. for one day and night to obtain 222.6 g of N-cyclohexyl maleamic acid 1so-butyl ester in the form of a white powder.

As a result of analysis by high performance liquid chromatography, this white powdery N-cyclohexyl maleamic acid 1so
The purity of the -butyl ester was 86.5% and the yield was 94.3%.

9 Example 1 A cylindrical titanium autoclave with an internal capacity of 1007 nl and having an inlet tube for a mixture of superheated steam and raw materials and an outlet for a hot reaction gas in the upper part was used as a reaction apparatus. The inlet pipe for the superheated steam and raw material mixture was installed so that it reached near the bottom of the reactor. Further, the outlet of the hot reaction gas was connected to the receiver via an 80° C. glue-Big cooling pipe.

5.07 g of solid maleic acid was added to 50.7 g of N-cyclohexylmaleamidic acid 1so-butyl ester prepared in Reference Example and melted at 60 to 80°C. The resulting mixture was introduced over a period of 3 hours into a reactor maintained at 125-145° C. together with superheated steam at 120° C. in the amount of 50 g per hour. The hot reaction gas was passed through a cooling tube at 80° C., and the precipitated white crystals were received in a receiver along with a steam condensate. The obtained white crystalline substance was filtered and vacuum-dried at 40°C overnight to obtain 25.43 g of N-cyclohexylmaleimide (white crystalline substance).

As a result of analysis by high performance liquid chromatography, the purity of this white powdery N-cyclohexylmaleimide was 90.1%, and the yield was 73.9%.

Example 2 5 equipped with thermometer, cooling tube with water separator and stirrer
00-39.4 g (0.2 mol) of N-cyclohexyl maleamic acid obtained in the reference example, 180 benzene, and 43.0 iso-butyl alcohol in a three-necked flask. 4
g (0.6 mol) and concentrated sulfuric acid 1.0-,
The esterification reaction was carried out for 1 hour while maintaining the temperature at 80° C. with heating and stirring and azeotropically distilling the water produced by the reaction together with benzene.

After concentrating the obtained esterification reaction solution under reduced pressure, concentrated sulfuric acid 1.1- was added to this concentrated solution.

This mixture was mixed with 1 N-cyclohexyl maleamic acid.
The same procedure as in Example 1 was carried out except that the mixture of so-butyl ester and solid maleic acid was used instead, to obtain 31.47 g of white powdery N-cyclohexylmaleimide. As a result of analysis by high performance liquid chromatography, the purity of this white powdery N-1 cyclohexylmaleimide was 79.5%, and the yield was 69.8%.

Examples 3 and 4 Orthophosphoric acid (Example 3) or p-)luenesulfonic acid (Example 4) was used instead of solid maleic acid as an acid catalyst.
) was used in the same manner as in Example 1 to obtain white powdery N-cyclohexylmaleimide. The yield and purity of the product are shown in Table 1.

Comparative Example 29.02 g (0.25 mol) of maleic acid was placed in a 200-3-necked flask equipped with a thermometer, dropping funnel, and stirring device.
And 36m7 of water! I prepared it. While stirring this liquid,
While maintaining the temperature at °C, 24.8 g (0.25 mol) of cyclohexylamine was added dropwise from the dropping funnel over 30 minutes. After the dropwise addition was completed, the mixture was stirred for an additional 30 minutes.

5.3 g of solid maleic acid was added and dissolved in the obtained monoammonium salt aqueous solution of maleic acid.

This aqueous solution was used in the same manner as in Example 1, except that the mixture of N-cyclohexylma 2 leamic acid 1so-butyl ester and solid maleic acid in Example 1 was used, and a pale yellow viscous solid was obtained. N-cyclohexylmaleimide (18.97 g) was obtained.

As a result of analysis by high performance liquid chromatography, the purity of this pale yellow viscous solid N-cyclohexylmaleimide was 35.8%, and the yield was 15.2%.

The results of Examples 1 to 4 and Comparative Example are collectively shown in Table 1.

Table 1

Claims (1)

[Claims] (1) General formula (1) ▲There are mathematical formulas, chemical formulas, tables, etc.▼
20 alkyl group, a cycloalkyl group having 3 to 12 carbon atoms that is unsubstituted or has a substituent, a phenyl group that is unsubstituted or has a substituent, or a naphthyl group that is unsubstituted or has a substituent, and R^2 is nothing. A substituted or substituted alkyl group having 1 to 7 carbon atoms, or an unsubstituted or substituted cycloalkyl group having 3 to 7 carbon atoms) is subjected to a dealcoholization reaction in the presence of an acid catalyst and superheated steam. A method for producing N-substituted maleimide represented by the general formula (2) ▲ Numerical formula, chemical formula, table, etc. ▼ which undergoes ring-closing imidization.