JP2001354638A - Method for producing azoalkyl ester compound and method for purifying the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide both a method for safely producing an azoalkyl ester compound in a high yield and a method for purifying the same in a high purity. SOLUTION: This method for producing the azoalkyl ester compound comprises reacting an azonitrile compound with an alcohol and hydrogen chloride in the presence of an organic solvent having a low solubility of hydrogen chloride and then hydrolyzing the reaction product. This method for purifying the azoalkyl ester compound comprises adding water to the azoalkyl ester, removing the organic solvent by azeotrope, then bringing a mixture of the azoalkyl ester compound and water into contact with a member at a temperature higher than the melting point of the azoalkyl ester compound and lower than the melting point of water, freezing water in the mixture and removing water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing an azoalkyl ester compound and a method for purifying the compound.

[0002]

2. Description of the Related Art An azo compound is a compound useful as a polymerization initiator for a high molecular weight polymer, a resin foaming agent, a radical generator used in a halogenation reaction of an organic hydrocarbon compound, and the like. Among them, certain aliphatic azo compounds are liquid at room temperature, and have the following advantages as compared with many other azo compounds which are in the form of solid powder.

(1) Solid powdery compounds have the problem of dust generation during handling, and it is essential to install local exhaust equipment and wear protective masks and protective gloves so that workers do not inhale. However, if it is a liquid, such a problem of dust generation does not occur.

(2) The azo compound in the form of a solid powder often has a problem that it hardens when stored for a long period of time, so that it is difficult to take out the azo compound from a container or it has to be crushed before use. However, if it is a liquid, such a problem does not occur.

(3) The azo compound in the form of solid powder may clog valves and pipes. However, if it is a liquid, there is no such danger.

(4) When the azo compound in the form of solid powder is continuously added little by little or supplied automatically in a fixed amount, a dissolving vessel equipped with a stirrer is required to dissolve the azo compound in the solvent as necessary. However, such equipment and labor are unnecessary for a liquid material.

(5) Azo compounds are highly reactive, and solid powders are difficult to measure with an automatic weighing machine because of the risk of promoting self-decomposition due to frictional heat. It was necessary to pay attention to static elimination in order to prevent the danger. However, in the case of a liquid material, dangers such as self-decomposition due to frictional heat and electrification ignition can be greatly reduced, and it can be handled safely.

As the aliphatic azo compound which is liquid at normal temperature,
For example, the general formula (4) (R ¹ ) (R ² ) (COOR ³ ) CN = NC (R ¹ ) (R ² ) (COOR ³ ) [wherein, R ¹ represents a methyl group, and R ² represents a carbon atom having 1 carbon atom. And represents an alkyl group or a carboxyethyl group. R ³ has 1 to 1 carbon atoms
4 represents an alkyl group. However, when R ² is an alkyl group having 1 to 4 carbon atoms, R ³ represents an alkyl group having 2 to 4 carbon atoms. An azoalkyl ester compound represented by the following formula is known. However, such azoalkyl ester compounds have not yet been produced on an industrial scale. One of the causes is that it was difficult to produce the azoalkyl ester compound.

As methods for producing the azoalkyl ester compound of the general formula (4), the following methods A and B have been known to date. Method A: In this method, a hydrazobisalkyl nitrile compound is reacted with an alcohol and hydrogen chloride to form a hydrazobisalkyliminoalkyl ether hydrogen chloride salt, which is then hydrolyzed by adding water to the hydrazobisalkyl nitrile compound. And oxidizing the hydrazoalkyl compound to obtain an azoalkyl ester compound (Thie
le and Hauser; Ann. 290 1 (1896), IAFBickel and Wat
er; Rec.trav.chim. 69 312-20 (1950)).

[0010]

Embedded image Wherein R ¹ , R ² and R ³ are the same as above. However, in the method A, the yield of the target azoalkyl ester compound is low (about 45 to 50%) and cannot be used industrially. The hydrazobisalkylnitrile compound as a raw material is usually produced in a state containing water, but in the method A, if water is present, the reaction with the alcohol and hydrogen chloride does not proceed. Therefore, when the method A is performed, the hydrazobisalkylnitrile compound as a raw material needs to be in an anhydrous state, but a great deal of labor is required to remove water. Method B: Method B comprises reacting an azobisalkyl nitrile compound with hydrogen chloride in an alcohol solvent to form an azobisalkyliminoalkyl ether hydrogen chloride, and then adding water to the hydrogen chloride to hydrolyze the azobisalkyliminoalkyl ether. This is a method for obtaining an alkyl ester compound (German Published Patent Application No. 2254572).

[0011]

Embedded image Wherein R ¹ , R ² and R ³ are the same as above. However, in this method, alcohol is used as a reaction solvent, and hydrogen chloride is absorbed by the alcohol, so that a much larger amount of hydrogen chloride than the theoretical amount must be used. Since it is discarded after processing, it has the disadvantage that the cost increases and the burden on the environment is great. In addition, according to the method B, the state of the reaction solution becomes unstable due to the high concentration of hydrogen chloride being dissolved in the alcohol, and there is a danger of a sudden rise in the reaction temperature or the ejection of steam due to boiling. Have difficulty.

In the method B, it is difficult to completely react the azobisalkylnitrile compound as the raw material, and the azobisalkylnitrile compound as the raw material is contained in the target substance at a ratio of about 0.3 to 1%. Since the azobisalkylnitrile compound is inevitable to remain, and it is difficult to remove the azobisalkylnitrile compound, the target product cannot be produced with high purity.

Further, German Published Patent Application No. 22545
No. 72, by adding a small amount of a good solvent of hydrogen chloride such as dioxane and tetrahydrofuran to alcohol,
There is a disclosure that the purity of the target product can be improved, but the purity of the obtained target product cannot be said to be sufficient yet.

[0014]

An object of the present invention is to provide a method for producing an azoalkyl ester compound in a safe and high yield.

Another object of the present invention is to provide a method for purifying an azoalkyl ester compound.

[0016]

[Means for Solving the Problems] The present invention provides a compound represented by the following general formula (1): (R ¹ ) (R ² ) (CN) CN = NC (R ¹ ) (R ² ) (CN) wherein R ¹ and R ² are as defined above. The azonitrile compound represented by the general formula (2) R ³ OH in the presence of an organic solvent having a solubility of hydrogen chloride at 20 ° C. and 1 atm of 5 g or less with respect to 100 g of the organic solvent is represented by the formula: ³ is the same as above. Reaction with an alcohol and hydrogen chloride represented by the following formula (3): (R ¹ ) (R ² ) (C (= NH.HCl) -OR ³ ) CN = NC (R ¹ ) (R ² ) (C (= NH ・ HC
l) -OR ³ ) wherein R ¹ , R ² and R ³ are as defined above. The azobisalkyliminoalkyl ether hydrochloride represented by the formula (4) is hydrolyzed to give a compound of the general formula (4) (R ¹ ) (R ² ) (COOR ³ ) CN = NC (R ¹ ) (R ² ) (COOR ³ Wherein R ¹ , R ² and R ³ are as defined above. ] (Hereinafter, this method is referred to as "method C"). 2. The present invention has the general formula ^{(5) (R 1) (} R 2) (CN) C-NH-NH-C (R 1) (R 2) (CN) [ wherein, R ¹ represents a methyl radical, R ² represents an alkyl group having 1 to 4 carbon atoms or a carboxyethyl group. ], And 0.
A hydrazonitrile compound containing 5 to 50% by weight of water,
Water solubility at 20 ° C and 1 atm is 100 g of organic solvent
Is dissolved in an organic solvent having a solubility of 0.5 g or less with respect to 100 g of the hydrazonitrile compound with respect to 100 g of the organic solvent, and is separated into two layers of an organic solvent layer and an aqueous layer. Is added to the organic solvent layer of the general formula (2) R ³ OH wherein R ³ represents an alkyl group having 1 to 4 carbon atoms. However, when R ² in the general formula (5) is an alkyl group having 1 to 4 carbon atoms, R ³ represents an alkyl group having 2 to 4 carbon atoms. ] After adding the alcohol represented by
A hydrazonitrile compound is oxidized by treating with chlorine, and the resulting general formula (1) (R ¹ ) (R ² ) (CN) CN = NC (R ¹ ) (R ² ) (CN) R ¹ and R ² are the same as above. The azonitrile compound represented by the following formula is reacted with hydrogen chloride, and finally obtained formula (3): (R ¹ ) (R ² ) (C (= NH.HCl) -OR ³ ) CN = NC (R ¹ ) (R ² ) (C (= NHHC
l) -OR ³ ) wherein R ¹ , R ² and R ³ are as defined above. The azobisalkyliminoalkyl ether hydrochloride represented by the formula (4) is hydrolyzed to give a compound of the general formula (4) (R ¹ ) (R ² ) (COOR ³ ) CN = NC (R ¹ ) (R ² ) (COOR ³ Wherein R ¹ , R ² and R ³ are as defined above. ] (Hereinafter referred to as "method D"). 3. The present invention, (a) the general formula containing an organic solvent ^{(4) (R 1) (} R 2) (COOR 3) CN = NC (R 1) (R 2) (COOR 3) [ In the formula, R ¹ , R ² and R ³ are the same as above. (B) adding water to the azoalkyl ester compound represented by the general formula (4) and removing the organic solvent by azeotropic distillation to obtain a mixture of the azoalkyl ester compound represented by the general formula (4) and water; The mixture of the azoalkyl ester compound represented by the general formula (4) obtained in the above step (a) and water is brought into contact with a member having a temperature higher than the melting point of the azoalkyl ester compound and lower than the melting point of water. A method for purifying an azoalkyl ester compound represented by the general formula (4), comprising a step of freezing water in the mixture to remove water from the mixture.

[0017]

DETAILED DESCRIPTION OF THE INVENTION Preparation of azoalkyl ester compound
Production method C: In method C, an azonitrile compound represented by the above general formula (1) is used as a raw material.

The starting azonitrile compounds are all known compounds, and corresponding azonitrile compounds are used depending on the target compounds.

In the method C, the azonitrile compound of the general formula (1) is treated with the compound of the general formula (2) in the presence of an organic solvent having a solubility of hydrogen chloride at 20 ° C. and 1 atm. And hydrogen chloride.

As the organic solvent having a solubility of hydrogen chloride at 20 ° C. and 1 atm of 5 g or less with respect to 100 g of the organic solvent, conventionally known organic solvents can be widely used, for example, n-hexane, cyclohexane, petroleum ether, isooctane and the like. Aliphatic hydrocarbons, benzene, toluene, xylene, ethylbenzene, aromatic hydrocarbons such as cumene, trichloroethylene, perchrene, 1,2-dichloroethane,
Examples thereof include halogenated hydrocarbons such as 1,1,1-trichloroethane, chloroform, carbon tetrachloride, dichloromethane, and chlorobenzene. Among these organic solvents, toluene, 1,2-dichloroethane and dichloromethane are preferred.

The amount of the organic solvent to be used is generally about 10 to 10 times the total weight of the starting azonitrile compound and the alcohol of the formula (2).

If the amount of the organic solvent is too small, the reaction system may not be maintained stably, which is not preferable. On the other hand, if the amount of the organic solvent is too large, the reaction rate may be reduced, and the cost is required for isolating the target azoalkyl ester compound of the general formula (4), which is economically disadvantageous. Is not preferred.

In the method C, the amount of the organic solvent used is preferably about 2 to 5 times the total weight of the raw material azonitrile compound and the alcohol of the formula (2).

As the alcohol of the general formula (2), conventionally known alcohols can be widely used, and examples thereof include methanol, ethanol, isopropanol, propanol, n-butanol and isobutanol. When the azonitrile compound of the general formula (1) used as a raw material has R ² having 1 carbon atom,
In the case of an azonitrile compound which is an alkyl group of (1) to (4), when the alcohol of the general formula (2) is methanol,
Since the target substance becomes solid and the object of the present invention cannot be solved, the alcohol represented by the general formula (2) is represented by R
It is important that ³ is an alcohol having 2 to 4 carbon atoms.

In the method C, the alcohol of the general formula (2) is not used as a reaction solvent, but is used for the reaction with the azonitrile compound of the general formula (1). The use amount of the alcohol of the general formula (2) is usually
Is preferably about 2 to 10 moles per mole of the azonitrile compound. If the amount of the alcohol is too small, unreacted azonitrile compound remains, which is not preferable. On the other hand, if the amount of the alcohol used is too large, it becomes difficult to isolate the target substance, and the amount of hydrogen chloride which is absorbed by the alcohol and does not contribute to the reaction increases. . In the present invention, the alcohol of the general formula (2) is preferably used in an amount of about 2.1 to 5 mol per 1 mol of the azonitrile compound of the general formula (1).

In the method C, it is preferable to use anhydrous hydrogen chloride gas as the hydrogen chloride and to blow it into the reaction system to cause the reaction. The amount of hydrogen chloride to be used is usually based on 1 mol of the azonitrile compound of the general formula (1).
The amount is preferably about 2 to 20 mol. If the amount of hydrogen chloride used is too small, unreacted azonitrile compounds remain unpreferably. In addition, if the amount of hydrogen chloride used is too large, only the amount of neutralized waste increases, which is not preferable in terms of economy and environment. In the present invention, hydrogen chloride is used in an amount of 2 to 2 mol per mol of the azonitrile compound of the general formula (1).
It is preferable to use about 10 moles.

The blowing of hydrogen chloride is usually performed for 10 minutes to 12 hours.
It is possible to carry out the reaction for about a time, and then it is preferable to continue stirring for about 1 to 48 hours to complete the reaction. The blowing of hydrogen chloride may be continuous or intermittent, but is preferably continuous.

The above reaction is carried out usually while maintaining the reaction system at a temperature of 40 ° C. or lower, preferably 5 to 25 ° C.

Thus, the azobisalkyliminoalkyl ether hydrogen chloride represented by the general formula (3) is produced.

In the method C, the reaction product is converted to a compound of the general formula (3)
The azobisalkyliminoalkyl ether hydrochloride may be isolated and subjected to the next hydrolysis reaction, or may be subjected to the next hydrolysis reaction without isolation as a reaction product. In consideration of workability, it is desirable that the azobisalkyliminoalkyl ether hydrochloride of the general formula (3) is not isolated from the reaction product and is used as it is for the next hydrolysis reaction.

In the method C, the desired azoalkyl ester compound of the general formula (4) can be produced by hydrolyzing the reaction product obtained by the above reaction.

The hydrolysis is carried out by adding water to the reaction product. At this time, it is preferable to remove the used organic solvent and unreacted alcohol by distillation or the like, and then add water to the residue. The distillation of the used organic solvent and unreacted alcohol is
It is preferably performed at about 30 ° C. The amount of water to be added for the hydrolysis is preferably about 0.5 to 10 times, more preferably about 1 to 5 times the weight of the residue. The temperature of the water to be added is preferably low, usually about 0 to 30 ° C.
Preferably, it is about 0 to 10 ° C.

The hydrolysis reaction is carried out for 5 minutes after adding water.
The stirring is performed efficiently for about 120 minutes.
The stirring may be performed at the temperature as it is, or may be performed by heating the temperature of the reaction solution to about 30 ° C. For stirring,
Any conventionally known means can be applied.

Thus, the desired azoalkyl ester compound of the general formula (4) is produced. Since the azoalkyl ester compound of the general formula (4) is insoluble in water, it is separated into two layers, an aqueous layer and an organic layer, at the end of the hydrolysis reaction. Therefore, in the present invention, the target azoalkyl ester compound of the general formula (4) can be isolated by removing the aqueous layer and then removing the hydrogen chloride remaining in the organic layer according to a conventional means. it can.

The removal of hydrogen chloride may be carried out according to a conventionally known means. For example, the organic layer may be washed with 5% aqueous sodium bicarbonate or the like. In this way, the desired azoalkyl ester compound of the general formula (4) can be produced. However, since the compound contains a small amount of an organic solvent or water, the compound is purified by the purification method described below. It is sufficient to purify the azoalkyl ester compound of the general formula (4) with high purity.

Method D: In method D, the hydrazonitrile compound represented by the above general formula (5) is used as a raw material.

As the hydrazonitrile compound as a raw material,
All are known compounds, and corresponding hydrazonitrile compounds are used depending on the target compound. Such a hydrazonitrile compound usually contains 0.5 to 50% by weight of water, but it is not necessary to isolate water in the method D.
It is used as a raw material while containing water.

In the method D, the water-containing hydrazonitrile compound represented by the general formula (5) is converted into a hydrazonitrile having a water solubility of 0.5 g or less at 20 ° C. and 1 atm with respect to 100 g of the organic solvent. The compound is dissolved in an organic solvent having a solubility of 5 g or more per 100 g of the organic solvent.

The solubility of water at 20 ° C. and 1 atm is 0.5 g or less with respect to 100 g of the organic solvent, and the solubility of the hydrazonitrile compound is 5 g with respect to 100 g of the organic solvent.
As the organic solvent having a weight of at least g, widely known organic solvents can be used, for example, aliphatic hydrocarbons such as n-hexane, cyclohexane, petroleum ether, and isooctane; and aromatics such as benzene, toluene, xylene, ethylbenzene, and cumene. Hydrocarbons, trichlorethylene, perchrene,
Examples thereof include halogenated hydrocarbons such as 1,2-dichloroethane, 1,1,1-trichloroethane, chloroform, carbon tetrachloride, dichloromethane, and chlorobenzene. Among these organic solvents, toluene, 1,2
Dichloroethane, dichloromethane is preferred.

The amount of the organic solvent to be used is preferably about 0.5 to 30 times the weight of the hydrated hydrazonitrile compound as a raw material.

If the amount of the organic solvent used is too small, the hydrazonitrile compound may not be dissolved, the reaction may proceed rapidly and the exothermic runaway may occur, or the azobisalkyliminoalkyl may precipitate. Stirring may be difficult due to the ether hydrogen chloride salt, which is not preferable. If the amount of the organic solvent is too large, the reaction becomes slow, or it takes time to evaporate the organic solvent,
It is not preferable because the production efficiency is deteriorated.

In the method D, the amount of the organic solvent to be used is 3 to 3 with respect to the hydrated hydrazonitrile compound as the raw material.
The weight is preferably about 15 times the weight.

In the method D, when the water-containing hydrazonitrile compound represented by the general formula (5) is dissolved in the above organic solvent, it is separated into two layers, an organic solvent layer and an aqueous layer.
Remove the aqueous layer. As means for removing water, conventionally known means can be widely applied, and examples thereof include decantation and a method using a separating funnel.

In the method D, an alcohol represented by the general formula (2) is added to the organic solvent layer, and the resultant is treated with chlorine to oxidize the hydrazonitrile compound.
An azonitrile compound represented by

As the alcohol of the general formula (2), the same alcohol as the alcohol of the general formula (2) used in the method C can be used. For example, methanol, ethanol, isopropanol, propanol, n-butanol, isobutanol and the like can be used. No. General formula (5) used as a raw material
In the case where the hydrazonitrile compound of formula (1) is an azonitrile compound in which R ² is an alkyl group having 1 to 4 carbon atoms, if the alcohol of the general formula (2) is methanol, the final target product becomes a solid, and Since the problem of the invention cannot be solved, it is important that the alcohol of the general formula (2) is an alcohol in which R ³ is an alkyl group having 2 to 4 carbon atoms.

The amount of the alcohol represented by the general formula (2) is preferably about 2 to 10 mol per 1 mol of the hydrazonitrile compound represented by the general formula (5).

If the amount of alcohol used is too small, the yield of the desired product tends to decrease, which is not preferable. If the amount of the alcohol used is too large, it becomes difficult to isolate the target substance, and the amount of hydrogen chloride absorbed by the alcohol and not contributing to the reaction increases, so that a large amount of hydrogen chloride is required, which is not preferable.

In the method D, it is preferable to use the alcohol of the general formula (2) in an amount of about 2.1 to 5 mol per 1 mol of the hydrazonitrile compound of the general formula (5).

In the method D, chlorine is represented by the general formula (5)
Is used to oxidize the hydrazonitrile compound of formula (1) to obtain an azonitrile compound represented by the general formula (1).

When the present inventor makes chlorine act on the hydrazonitrile compound of the general formula (5) to lead to the azonitrile compound represented by the general formula (1), the above-mentioned general formula (2) It has been found that the presence of the alcohol promotes the oxidation reaction by chlorine, and the oxidation reaction proceeds rapidly.

The amount of chlorine used is usually about 1 to 2 moles per 1 mole of the hydrazonitrile compound of the general formula (5).

If the amount of chlorine used is too small, the yield of the desired product is lowered, and unreacted materials tend to remain, which tends to lower the purity of the desired product. If the amount of chlorine used is too large, a large amount of by-products such as organic chlorine compounds is generated, and the purity of the target product tends to decrease, which is not preferable.

In the method D, it is preferable to use chlorine in an amount of about 1 to 1.2 mol per 1 mol of the hydrazonitrile compound of the general formula (5).

In the method D, the reaction of the azonitrile compound represented by the general formula (1) obtained above with hydrogen chloride, and the subsequent azobisalkyliminoalkyl ether hydrogen chloride represented by the general formula (3) The salt hydrolysis reactions are carried out under the same reaction conditions as those reactions in Method C.

That is, in the reaction of the azonitrile compound represented by the general formula (1) with hydrogen chloride in the method D, the alcohol of the general formula (2) is already present in the reaction system. It is not necessary to add the alcohol of the general formula (2). Of course, the alcohol of the general formula (2) may be further added. In the reaction at this stage, the alcohol of the general formula (2) is used for the reaction with the azonitrile compound of the general formula (1).

In the method D, it is preferable to use anhydrous hydrogen chloride gas as the hydrogen chloride and to blow it into the reaction system to cause the reaction. When the hydrazonitrile compound of the general formula (5) is oxidized with chlorine, hydrogen chloride is produced as a by-product, and this by-produced hydrogen chloride can be used in this reaction. Therefore, the amount of hydrogen chloride blown into the reaction system may be smaller than the theoretical amount required for the reaction. The amount is
Although it depends on the amount of chlorine used in the pre-reaction and the like, it cannot be said unconditionally, it is usually preferably about 0 to 18 moles per mole of the azonitrile compound of the general formula (1),
It is particularly preferable that the amount is about 0 to 8 mol.

The blowing of hydrogen chloride is usually performed for 10 minutes to 12 minutes.
It is possible to carry out the reaction for about a time, and then it is preferable to continue stirring for about 1 to 48 hours to complete the reaction. The blowing of hydrogen chloride may be continuous or intermittent, but is preferably continuous.

The above reaction is carried out usually while maintaining the reaction system at a temperature of 40 ° C. or lower, preferably 5 to 25 ° C.

Thus, the azobisalkyliminoalkyl ether hydrogen chloride represented by the general formula (3) is produced.

In the method D, the reaction product is converted to a compound of the general formula (3)
The azobisalkyliminoalkyl ether hydrochloride may be isolated and subjected to the next hydrolysis reaction, or may be subjected to the next hydrolysis reaction without isolation as a reaction product. In consideration of workability, it is desirable that the azobisalkyliminoalkyl ether hydrochloride of the general formula (3) is not isolated from the reaction product and is used as it is for the next hydrolysis reaction.

In the method D, the desired azoalkyl ester compound of the general formula (4) can be produced by hydrolyzing the reaction product obtained by the above reaction.

The hydrolysis is carried out by adding water to the reaction product. At this time, it is preferable to remove the used organic solvent and unreacted alcohol by distillation or the like, and then add water to the residue. The distillation of the used organic solvent and unreacted alcohol is
It is preferably performed at about 30 ° C. The amount of water to be added is preferably about 0.5 to 10 times, more preferably about 1 to 5 times the weight of the residue. The temperature of the water to be added is desirably low, usually about 0 to 30 ° C., preferably 0 to 1 ° C.
About 0 ° C is good.

The hydrolysis reaction is carried out for 5 minutes after adding water.
The stirring is performed efficiently for about 120 minutes.
The stirring may be performed at the temperature as it is, or may be performed by heating the temperature of the reaction solution to about 30 ° C. For stirring,
Any conventionally known means can be applied.

Thus, the desired azoalkyl ester compound of the general formula (4) is produced. Since the azoalkyl ester compound of the general formula (4) is insoluble in water, it is separated into two layers, an aqueous layer and an organic layer, at the end of the hydrolysis reaction. Therefore, in the present invention, the target azoalkyl ester compound of the general formula (4) can be isolated by removing the aqueous layer and then removing the hydrogen chloride remaining in the organic layer according to a conventional means. it can.

The removal of hydrogen chloride may be carried out according to a conventionally known method. For example, the organic layer may be washed with 5% aqueous sodium bicarbonate or the like. In this way, the desired azoalkyl ester compound of the general formula (4) can be produced. However, since the compound contains a small amount of an organic solvent or water, the compound is purified by the purification method described below. It is sufficient to purify the azoalkyl ester compound of the general formula (4) with high purity.

Purification of Azoalkyl Ester Compound The azoalkyl ester compound of the general formula (4) obtained by the above-mentioned method is slightly mixed with an organic solvent and water.

Since the azoalkyl ester compound of the general formula (4) has a property of decomposing by heating, it is difficult to employ a means for removing an organic solvent or water by heating.

In carrying out the purification method of the present invention, it is desirable to remove the organic solvent from the azoalkyl ester compound of the general formula (4) as much as possible in advance. The removal of the organic solvent can be performed, for example, by distillation under reduced pressure. However, in the vacuum distillation step without heating, the organic solvent cannot be sufficiently removed, and about 1 to 10% by weight of the organic solvent cannot be distilled off with respect to the azoalkyl ester compound of the general formula (4). It is unavoidable to remain in

In the purification method of the present invention, first, water is added to the azoalkyl ester compound of the general formula (4) containing an organic solvent, and the organic solvent is removed by azeotropic distillation with water (step (a)). . The amount of water to be added may be an amount sufficient to remove the organic solvent by azeotropic distillation with water, and it is generally preferable to add 0.1 to 10 times by weight of water to the organic solvent.

The azeotropic distillation of the organic solvent with water is preferably performed under reduced pressure without heating. The degree of decompression is usually 13.3.
About Pa to 26.6 kPa, preferably 133 to 665
It may be about Pa. Thus, most of the organic solvent can be removed from the azoalkyl ester compound of the general formula (4). In the step (a), a mixture of the azoalkyl ester compound of the general formula (4) and water can be obtained.

In the purification method of the present invention, the mixture of the azoalkyl ester compound represented by the general formula (4) obtained in the above step (a) and water is heated to a temperature lower than the melting point of the azo alkyl ester compound. The water in the mixture is frozen by contacting a member having a temperature higher than the melting point of water to remove frozen water from the mixture (step (b)).

Here, specific examples of the member include a container for containing the azoalkyl ester compound of the general formula (4),
A stirrer for stirring the object to be processed can be exemplified. Further, the temperature of the member is set to a temperature higher than the melting point of the compound of the general formula (4) and lower than the melting point of water, because only the water is maintained while maintaining the fluidity of the azoalkyl ester compound of the general formula (4). This is because water and the azoalkyl ester compound of the general formula (4) are separated by freezing and fixing to the member. Such a temperature is about −20 ° C. to 0 ° C. at normal pressure.

More specifically, the container containing the mixture of the azoalkyl ester compound of the general formula (4) and water is cooled to about -10 ° C. After freezing the water contained in the water, the container is tilted to allow only the azoalkyl ester compound of the general formula (4) to flow out, whereby the water can be separated from the azoalkyl ester compound of the general formula (4). .

In another embodiment, an object to be treated comprising a mixture of an azoalkyl ester compound of the general formula (4) and water is stirred with a stirring rod cooled to about -10 ° C. By freezing the water contained in the stirring rod, water in the object to be treated can be removed.

The azoalkyl ester compound of the general formula (4) purified as described above has a purity of 99
% Or more, and more preferably 99.5% or more.

The high-purity aliphatic azoester compound is particularly useful as a polymerization initiator or a radical initiator for a high-molecular polymer, which is required to have a high purity, as another azo compound raw material, and the like.

[0077]

According to the present invention, there is provided a method for producing an azoalkyl ester compound of the general formula (4) in a safe and high yield.

According to the present invention, there is provided a method for purifying an azoalkyl ester compound of the general formula (4) with high purity.

Since the production method of the present invention uses an organic solvent having low solubility in hydrogen chloride as a reaction solvent, it is not necessary to use a large amount of hydrogen chloride, and it is economically and environmentally excellent.

In the production method of the present invention, the state of the reaction solution becomes unstable due to the high concentration of hydrogen chloride being dissolved in the alcohol, and there is a danger of a sudden rise in the reaction temperature or the ejection of steam due to boiling. The absence of disadvantages facilitates implementation on an industrial scale.

[0081]

The present invention will be further clarified with reference to the following examples. In the following, simply “%” means “% by weight”.

Example 1 (1) Preparation of 2,2'-azobis (2-methyl-ethylpropionate) 16.4 g of 2,2'-azobisisobutyronitrile
(0.10 mol), 110 g of toluene and ethanol 3
To 6.9 g (0.80 mol) of the mixture was added 29.2 g (0.8%) of dry hydrochloric acid at a temperature of 10 to 15 ° C. over 4.5 hours.
(0 mol). After that, keep the same temperature, 24
Stirring was continued for an hour to complete the reaction, and the mixture was concentrated under reduced pressure at the same temperature to distill a mixed solution of 20 g of ethanol and 90 g of toluene by azeotropic distillation.

100 g of water cooled to 3 ° C. was quickly added to the remaining liquid while stirring. After stirring at 20 ° C. for 60 minutes, the hydrolysis reaction was terminated.

The reaction solution was transferred to a separating funnel, the lower layer (aqueous layer) was discarded, and then washed with 50 ml of 5% aqueous sodium bicarbonate to give 2,2'-
Azobis (2-methyl-ethyl propionate) was obtained.

(2) Purification of 2,2′-azobis (2-methyl-ethylpropionate) The 2,2′-azobis (2-methyl-propionate) obtained in the above (1) was obtained.
Ethyl propionate) was washed three times with 50 ml of deionized water. Transfer the oil layer to a flask and add deionized water 2
0 ml was added, and the mixture was concentrated under reduced pressure at 10 to 15 ° C. By this operation, toluene remaining in the oil layer azeotropes with water,
Removed.

Thereafter, the flask was cooled to −10 ° C., the remaining water was frozen on the flask, and the liquid was separated by decantation.

As a result of chemical analysis, it was confirmed that the product was 2,2′-azobis (2-methyl-ethylpropionate). Further, the purity was measured by liquid chromatography.

The yield was 23.7 g, the yield was 87%, and the purity was 99.
6%, less than 0.1% residual azobisisobutyronitrile.

Example 2 Reaction and purification were carried out in the same manner as in Example 1 except that the amount of ethanol used was 27.6 g (0.6 mol) and the amount of dry hydrochloric acid was 17.7 g (0.48 mol). To obtain a liquid material.

As a result of chemical analysis, it was confirmed that the product was 2,2'-azobis (2-methyl-ethylpropionate). Further, the purity was measured by liquid chromatography.

The yield was 24.0 g, the yield was 89%, and the purity was 99.
8%, less than 0.1% residual azobisisobutyronitrile.

Example 3 (1) Production of 2,2'-azobis (2-methyl-ethylpropionate) Hydrous 2,2'-hydrazobisisobutyronitrile 17.
8 g (0.10 mol, water content 7.2%) was added to 110 g of toluene at 25 ° C., dissolved by stirring, allowed to stand, and the lower layer of water was separated and removed.

Next, ethyl alcohol 1 was added to the mixture.
0.1 g (0.22 mol) was added, and chlorine 7.5 at 10 ° C.
By blowing in 1 g (0.11 mol) for 3 hours, 2,2′-hydrazobisisobutyronitrile was oxidized.

Next, this mixture was added at 10 to 15 ° C. for 2.
After 5 hours, 6.20 g (0.17 mol) of dry hydrochloric acid was blown, and then stirring was continued at the same temperature for 24 hours to complete the reaction.

Further, 100 g of water was added to this reaction product for 10 to 10 minutes.
The mixture was added at 15 ° C with stirring, and further stirred at 10 to 15 ° C for 1 hour to complete the hydrolysis reaction.

After the completion of the hydrolysis reaction, the stirring was stopped, and the mixture was allowed to stand. The water in the lower layer was separated and removed.
Washed once with 1 and twice with 100 ml of water. Collect the oil reservoir,
The bath temperature was controlled to 25 ° C. or lower, and the mixture was concentrated under reduced pressure using a rotary evaporator to give 2,2′-azobis (2-
Methyl-ethyl propionate) was obtained.

(2) Purification of 2,2′-azobis (2-methyl-ethylpropionate) The 2,2′-azobis (2-methyl-propionate) obtained in the above (1) was obtained.
Ethyl propionate), add 30 g of deionized water,
It concentrated under reduced pressure using a rotary evaporator. By this operation, toluene mixed in 2,2′-azobis (2-methyl-ethylpropionate) was removed by azeotropic distillation with water.

When the distillation of toluene and water stopped, the container (flask) was removed, and the container was cooled to -20 ° C., and water was frozen on the inner wall of the container. The container was tilted to leave only the icing water in the flask, and the content was transferred to another container as it was.

As a result of chemical analysis, it was confirmed that the product was 2,2'-azobis (2-methyl-ethylpropionate). Further, the purity was measured by liquid chromatography.

The yield was 22.2 g, the yield was 86%, the purity was 99.
7%, less than 0.1% residual azobisisobutyronitrile.

Comparative Example 1 1,2 g of 2,2'-azobisisobutyronitrile
(0.10 mol) and 56 g (1.5 mol) of dry hydrochloric acid were blown into a mixture of 66.6 g (1.4 mol) of ethanol at a temperature of 10 to 15 ° C. over 2 hours. The solution temperature was maintained at 10 to 15 ° C. to ripen the reaction. After about 12 hours, the solution temperature rose rapidly to nearly 70 ° C., and despite rapid cooling, hydrochloric acid gas was blown out from the tip of the cooler. Was. After 19 hours, the reaction was terminated, and hydrochloric acid and ethanol were removed with an aspirator.
0 g was added and hydrolyzed at 20 ° C. for 60 minutes. The reaction solution was transferred to a separating funnel, and the lower layer was discarded.
And then 3 times with 50 ml of deionized water.

The oil layer was transferred to a flask and concentrated under reduced pressure at 10 to 15 ° C. to obtain a liquid.

As a result of chemical analysis, it was confirmed that the product was 2,2′-azobis (2-methyl-ethylpropionate). Further, the purity was measured by liquid chromatography.

The yield was 14.6 g, the yield was 57%, and the purity was 97.
2%, 1.1% residual azobisisobutyronitrile.

From these results, it was found that the method of Comparative Example 1 in which alcohol was used as a reaction solvent without using a solvent having low solubility of hydrochloric acid was accompanied by danger in the reaction and that the yield and purity of the target product were low. Understand.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Akihiko Goto 615, Satoura, Satoura-cho, Satoura-cho, Naruto-shi, Tokushima Prefecture F-term in the Naruto Plant of Otsuka Chemical Co., Ltd.

Claims (3)

[Claims] 1. A compound of the general formula (1): (R ¹ ) (R ² ) (CN) CN = NC (R ¹ ) (R ² ) (CN) wherein R ¹ is a methyl group, R ² is carbon It represents an alkyl group or a carboxyethyl group of the formulas 1 to 4. The azonitrile compound represented by the general formula (2) R ³ OH in the presence of an organic solvent having a solubility of hydrogen chloride at 20 ° C. and 1 atm of 5 g or less with respect to 100 g of the organic solvent is represented by the formula: ³ represents an alkyl group having 1 to 4 carbon atoms. However, when R ² in the general formula (1) is an alkyl group having 1 to 4 carbon atoms, R ³ represents an alkyl group having 2 to 4 carbon atoms. Reaction with an alcohol and hydrogen chloride represented by the following formula (3): (R ¹ ) (R ² ) (C (= NH.HCl) -OR ³ ) CN = NC (R ¹ ) (R ² ) (C (= NH ・ HC
l) -OR ³ ) wherein R ¹ , R ² and R ³ are as defined above. The azobisalkyliminoalkyl ether hydrochloride represented by the formula (4) is hydrolyzed to give a compound of the general formula (4) (R ¹ ) (R ² ) (COOR ³ ) CN = NC (R ¹ ) (R ² ) (COOR ³ Wherein R ¹ , R ² and R ³ are as defined above. A method for producing an azoalkyl ester compound, characterized by obtaining an azoalkyl ester compound represented by the formula: 2. A compound of the general formula (5): (R ¹ ) (R ² ) (CN) C-NH-NH-C (R ¹ ) (R ² ) (CN) wherein R ¹ is a methyl group, R ² represents an alkyl group having 1 to 4 carbon atoms or a carboxyethyl group. ], And 0.
A hydrazonitrile compound containing 5 to 50% by weight of water,
Water solubility at 20 ° C and 1 atm is 100 g of organic solvent
Is dissolved in an organic solvent having a solubility of 0.5 g or less with respect to 100 g of the hydrazonitrile compound with respect to 100 g of the organic solvent, and is separated into two layers of an organic solvent layer and an aqueous layer. Is added to the organic solvent layer of the general formula (2) R ³ OH wherein R ³ represents an alkyl group having 1 to 4 carbon atoms. However, when R ² in the general formula (5) is an alkyl group having 1 to 4 carbon atoms, R ³ represents an alkyl group having 2 to 4 carbon atoms. ] After adding the alcohol represented by
A hydrazonitrile compound is oxidized by treating with chlorine, and the resulting general formula (1) (R ¹ ) (R ² ) (CN) CN = NC (R ¹ ) (R ² ) (CN) R ¹ and R ² are the same as above. The azonitrile compound represented by the following formula is reacted with hydrogen chloride, and finally obtained formula (3): (R ¹ ) (R ² ) (C (= NH.HCl) -OR ³ ) CN = NC (R ¹ ) (R ² ) (C (= NHHC
l) -OR ³ ) wherein R ¹ , R ² and R ³ are as defined above. The azobisalkyliminoalkyl ether hydrochloride represented by the formula (4) is hydrolyzed to give a compound of the general formula (4) (R ¹ ) (R ² ) (COOR ³ ) CN = NC (R ¹ ) (R ² ) (COOR ³ Wherein R ¹ , R ² and R ³ are as defined above. A method for producing an azoalkyl ester compound, characterized by obtaining an azoalkyl ester compound represented by the formula: (A) a general formula (4) containing an organic solvent: (R ¹ ) (R ² ) (COOR ³ ) CN = NC (R ¹ ) (R ² ) (COOR ³ ) ¹ represents a methyl group, and R ² represents an alkyl group having 1 to 4 carbon atoms or a carboxyethyl group. R ³ has 1 to 1 carbon atoms
4 represents an alkyl group. However, when R ² is an alkyl group having 1 to 4 carbon atoms, R ³ represents an alkyl group having 2 to 4 carbon atoms. (B) adding water to the azoalkyl ester compound represented by the general formula (4) and removing the organic solvent by azeotropic distillation to obtain a mixture of the azoalkyl ester compound represented by the general formula (4) and water; The mixture of the azoalkyl ester compound represented by the general formula (4) obtained in the above step (a) and water is brought into contact with a member having a temperature higher than the melting point of the azoalkyl ester compound and lower than the melting point of water. A step of freezing water in the mixture to remove water from the mixture.
A method for purifying an azoalkyl ester compound represented by the formula: