JP2593312B2 - Method for producing azobisamidine salts - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for producing azobisamidine salts useful as a water-soluble polymerization initiator in producing a polymer compound, and more particularly, to a method for preparing an acid alcohol prepared in advance. Azobisnitrile is successively added to the solution in a temperature range of 10 ° C. or more and less than 20 ° C. to react, and then the corresponding intermediate azobis imino ether salt is reacted with an amine to produce a corresponding azobisamidine salt. About the method.

[Conventional technology]

Conventionally, as this type of compound, U.S. Pat.
On issue (Where HX is an inorganic acid, R and R 'are linear alkyl groups having 1 to 4 carbon atoms, and R "is a group selected from the group consisting of hydrogen and monovalent saturated aliphatic groups having 1 to 6 carbon atoms. ), The preparation of which is accomplished by reacting the corresponding azonitrile with an alcohol, hydrogen halide and a compound of the formula
A method is described in which HNR ₂ (R is hydrogen or an organic group, preferably a hydrocarbon group having 1 to 6 carbon atoms) is reacted with a hydrogen-containing amine.

Japanese Patent Publication No. 42-12641 discloses the following method for producing an azo compound via an intermediate of the same kind as the intermediate in the present invention. That is, the expression (Where R is an alkyl group having 1 to 8 carbon atoms) is reacted with an alcohol in the presence of an acid catalyst, and the intermediate azodiimino ester salt is hydrolyzed with water to give the corresponding azodiimino ester. Converted to diester,
The azo diester is then selectively reduced to the corresponding azo dialcohol by reacting the azo diester with a hydride of aluminum or boron or a complex of these hydrides, and recovering the azo dialcohol from the reaction mixture. Feature, expression Wherein R is an alkyl group having 1 to 8 carbon atoms and X is an -OH group.

However, in these methods, when producing an intermediate imino ether such as an azobisamidine salt or an azobis alcohol from the azobisnitrile, a method of sequentially adding an acid to a solution of the azobisnitrile or a method of adding an acid to the azobisnitrile and the acid is used. Are added simultaneously, and the reaction tends to proceed rapidly.
Reaction for a long time at low temperature (for example, Example 1 of the second proposal)
In this case, the reaction must be carried out at a reaction temperature of 5 to 10 ° C. for about 2 hours and then left overnight at 0 ° C.), and the yield of the obtained target product is insufficient. On the other hand, if the reaction temperature is increased to about 20 ° C in order to shorten the reaction time, it is extremely difficult to control the reaction by cooling etc. even on a small experimental scale, and production on an industrial scale by scale-up is dangerous. It was big and impossible.

In order to solve the above problems, Japanese Patent Publication No. 58-2230 discloses a general formula (In the formula, R ¹ and R ² represent an alkyl or cycloalkyl group.)
Reacting the compound with an alcohol in the presence of hydrochloric acid gas to produce an imino ether, wherein the reaction is carried out in a solvent having low solubility in hydrochloric acid gas, (Wherein R ¹ and R ² are the same as above, and R ³ represents an alkyl group).

However, according to the study by the present inventors, the third
It was found that the following problems still existed in the proposal.

(A) As described in the above-mentioned third preferred embodiment, a mixed solvent of an alcohol such as methanol and a solvent having low solubility in hydrochloric acid gas such as toluene (hereinafter sometimes referred to as a diluting solvent) is used. When hydrochloric acid gas is blown, heat of dissolution of hydrochloric acid gas in the alcohol is generated, and the reaction system temperature is raised to 10 ° C.
In order to keep the temperature below, it is necessary to take a relatively long time to inject hydrochloric acid gas, and then it is necessary to react at a temperature of about room temperature for several hours, the total reaction time is still considerably long, and the control of the reaction is not necessarily performed Not easy.

(B) Separation and recovery of the diluting solvent, alcohol and hydrochloric acid gas is considerably complicated.

Since the reaction is started in a state where the whole amount of the starting azobisnitrile is present in the system, there is still a risk of side reaction and runaway reaction.

[Problems to be solved by the invention]

According to the study by the present inventors, it has been found that there is still a problem that needs to be solved even in the third proposal as described in (a) to (d) above.

The present inventors have intensively studied to solve these problems, and as a result, azobisnitrile is sequentially added in a temperature range of 10 ° C. or more and less than 20 ° C. in a solution of an alcohol of an acid prepared in advance. As a result, it has been found that these problems can be solved at once, and that a high-purity azobisamidine salt can be produced safely and in a short time in a high yield, and the present invention has been completed.

[Means for solving the problem]

The present invention has the following general formula The azobisnitrile represented by is sequentially added and reacted in a temperature range of 10 ° C. or more and less than 20 ° C. in an alcohol solution of an acid prepared in advance, and then reacted. HNR ³ R ⁴ …… Characterized by reacting amines represented by
The following general formula And a method for producing an azobisamidine salt represented by the formula:

 Hereinafter, the present invention will be described in more detail.

The azobisnitrile used as a starting material in the present invention is a compound represented by the above general formula,
R ¹ and R ² in the formula are each independently C _{1 to} C ₁₀ , preferably
C ₁ -C _8, more preferably an alkyl group of C ₁ -C _4, for example,
Methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, ter
t-butyl group, n-pentyl group, isopentyl group, n-
Hexyl, n- heptyl, n- octyl, 2-ethylhexyl group and the like; C ₃ -C _8, preferably a cycloalkyl group having C ₃ -C _7, for example, cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl Group, 2-methylcyclopentyl group, cycloheptyl group, 3-methylcyclohexyl group and the like; one alkylene group of C _{2 to} C ₇ , preferably C _{2 to} C ₆ formed by R ¹ and R ² , for example, Ethylene, trimethylene, tetramethylene, pentamethylene, hexamethylene and the like. Examples of such azobisnitrile include, for example, 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis-2-methylvaleroyl Nitrile, 2,2'-azobis-2,3-dimethylbutyronitrile, 2,2'-azobis-2-cyclopropylpropionitrile, 2,2'-azobis-2-methylcapronitrile, 2,2 '-Azobis-2,4-dimethylvaleronitrile, 2,2'-azobis-2-ethylbutyronitrile, 2,
2'-azobis-2-ethylvaleronitrile, 2,2'-
Azobis-2-n-propyl valeronitrile, 2,2 '
-Azobis-2-n-butylcapronitrile, 2,2'-
n-butylcaprinonitrile, 2,2'-azobis-2-
n-pentylenanthonitrile, 2,2'-azobis-2
-N-hexylcaprylonitrile, 2,2'-azobis-
Nitrile of 2-n-heptylperalgo, 2,2'-azobis-2-n-octylcapronitrile, 2,2'-azobiscyclohexane-1-carbonitrile and the like can be mentioned. Particularly preferred starting materials for the process of the invention are 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis-2, 4-dimethylvaleronitrile, 2,2'-azobis-2-methylhexylonitrile,
2,2'-azobis-2-cyclopropylpropionitrile and the like can be mentioned.

The production method of the present invention is to prepare the azobisnitrile as described above in an alcohol solution of an acid prepared in advance at 10 ° C.
An alcohol addition reaction step (hereinafter, may be referred to as a first step) as described below for sequentially adding and reacting in a temperature range of less than 20 ° C. to produce an intermediate azobisimino ether.

The acid (HX) can be appropriately selected according to the kind of the azobisamidine salt which is the object of the present invention. As these acids, for example, strong acids such as hydrochloric acid, nitric acid, phosphoric acid, benzenesulfonic acid, p-toluenesulfonic acid, trichloroacetic acid and the like can be used. Since the excess acid component can be removed only by distilling off the alcohol solution of the reaction system (hereinafter sometimes referred to as reaction solution) after the step is completed under reduced pressure, the intermediate azobisimino ether salt can be used simply. It is particularly preferable because the condensation reaction with the following amines can be carried out using the reaction solution after the distillation under reduced pressure without separation and without using an anion exchange resin or the like. The amount of these acids to be used is generally 2 to 10 mol, preferably 4 to 8 mol, per 1 mol of the azobisnitrile used from the viewpoint of the reaction rate and the like.

The alcohol (ROH) is not particularly limited as long as it is a primary or secondary alcohol, that is, an alcohol in which at least one hydrogen atom is attached to a carbon atom to which a hydroxyl group is attached. Alcohols such as alkyl, (alkyl) cycloalkyl, and aralkyl can be used. Among them, C _{1 to} C ₁₈ alcohols are preferable, and for example, methanol, ethanol, 1- and 2-propanol, 1- and 2-butanol, 2-methyl-1-propanol, 1- and 2-pentanol , 1-octanol, 2-ethyl-1
Alcohols of a linear or branched alkyl group such as hexanol, 1-decanol and 1-dodecanol; cyclohexanol, 2-methylcyclohexanol, 1-butylcyclohexylmethanol, 1- (2'-methylcyclohexyl) -1- Alcohols of a cycloalkyl group or an alkylcycloalkyl group such as ethanol; benzyl alcohol, 2-phenyl-1-ethanol, 1-phenyl-1-ethanol, 3-phenyl-1-propanol, 1-phenyl-1-decanol, 8-phenyl-
1-octanol, 2-methylbenzyl alcohol, 3
- methylbenzyl alcohol, 2,4-alcohols of dimethyl aralkyl group benzyl alcohol; a can Reikyo, inter alia, low boiling point of methanol, ethanol, 2-propanol, C ₁ and 1-butanol- It is particularly preferable to use an alcohol having a C ₄ alkyl group because the resulting azobisamidine salt can be easily separated and recovered in a short time by a method such as drying under reduced pressure. These alcohols can be used alone or in combination of two or more. The amount of these alcohols to be used is generally 2 mol or more, preferably 3 to 10 mol, per 1 mol of the azobisnitrile starting material. By using alcohols in the above range, there is no problem such as a tendency to decrease the reaction rate when the amount is too small, and a tendency to decrease productivity such as an increase in energy required for recovery of the target product azobisamidine salts when the amount is too small. Therefore, it is preferable that the alcohols are appropriately selected and used in accordance with the kind within the above range.

Further, the concentration of the acid used in the first step of the production method of the present invention is generally 5% by weight or more as a solution of the above-mentioned alcohols, and the reaction rate and the amount of energy required on the apparatus and in the recovery of the target product azobisamidine salts From the viewpoint of the above, the acid concentration is preferably in the range of 20 to 70% by weight. When hydrochloric acid is used as the acid, the upper limit of the acid concentration is the saturated concentration of hydrochloric acid with respect to alcohols. Since the saturation concentration varies depending on the type of alcohol, it is preferable to determine the concentration in advance by experiments.

The most important feature of the production method of the present invention is that the azobisnitrile is sequentially added to the above-mentioned acid alcohol solution in the first step.

By this sequential addition method, (i) the exothermic reaction can be easily controlled by controlling the sequential addition rate of the azobisnitrile, so that mass production is possible.

(Ii) Since there is no need to use a diluent solvent to control heat generation,
When isolating the intermediate azobisimino ether salt and / or separating and recovering the target azobisamidine salt, complicated operations can be avoided.

(Iii) Since an alcohol solution of an acid prepared in advance is used, the heat of dissolution generated at the time of dissolving the acid into the alcohol, which is a serious problem in the conventional method for maintaining the temperature of the reaction system, does not become a problem. In addition, since the heat generated by this method is only reaction heat, the temperature can be easily maintained and the reaction time can be shortened.

And so on.

The azobisnitrile is usually preferably added successively in the form of a powder, but if necessary, or using alcohols or other solvents within a range that does not impair the above-described excellent effects of the present invention. The azobisnitrile can be added in the form of a solution or a slurry.

In the production method of the present invention, the reaction temperature in the first step is generally set to about 1 to avoid thermal decomposition of azobisnitrile.
The temperature is preferably 50 ° C. or lower, and is preferably in the range of 10 to 20 ° C. from the viewpoints of a high reaction rate, a good crude yield of the azobisamidine salt obtained, a high purity, and the like. Therefore, the rate of sequential addition of the azobisnitrile may be appropriately selected within a range where the above reaction system does not deviate from the above temperature range.

The reaction time in the first step is usually about 2 to 2.
About 8 hours.

By the reaction in the first step described above, the azobisimino ether salts, which are intermediates according to the present invention, are produced in a high yield in the reaction solution.

According to the production method of the present invention, the intermediate azobisimino ether salts thus obtained are added to the following general formula HNR ³ R ^4. By reacting amines represented by the following general formula To produce azobisamidine salts represented by the formula:

The above-mentioned intermediate azobisimino ether salts can be reacted with the above-mentioned amines, if necessary, by isolating the reaction solution by concentrating, cooling and passing it by a conventional method. However, in general, the above-mentioned intermediate has high hygroscopicity and is unstable, so that the intermediate is isolated by distilling off the reaction solution under reduced pressure or by ion exchange using an anion exchange resin without isolating the intermediate. This makes it possible to employ a method of removing the excess acid component and subsequently introducing and reacting the amines. According to this method, the step of isolating the intermediate can be omitted, the separation / recovery of the target azobisamidine salt is easier, and the crude yield and purity of the obtained azobisamidine salt are high.
It is preferable to employ this method. Among them, when the target azobisamidine salt is a salt of a volatile acid such as hydrochloride, the excess acid component can be easily removed only by distilling the reaction solution under reduced pressure. The method of the present invention can be used very suitably.

The intermediate azobisimino ether salts are considered to react with the amines as follows (second step).

R ³ and R ⁴ of the above amines (HNR ³ R ⁴ ) are each independently H; a C _{1 to} C ₁₀ , preferably a C _{1 to} C ₈ alkyl group, for example, a methyl group, an ethyl group, an n- Propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, t
ert-butyl group, n-pentyl group, isopentyl group, n
-Hexyl group, n-heptyl group, n-octyl group, 2-
Ethylhexyl group and the like; C ₁ -C _10, preferably hydroxyalkyl group C ₂ -C _6, for example, hydroxyethyl group, hydroxypropyl group, 1-methyl - hydroxyethyl group,
1-ethyl-hydroxyethyl group, 1,1-dimethyl-hydroxymethyl group, 1-methyl-1,1-dihydroxymethyl group, 1-methyl-1-hydroxymethyl-2-hydroxybutyl group, etc .; C ₃ -C ₈ alkyl group, for example, a cyclohexyl group; an aralkyl group of C ₇ -C _12, for example, benzyl group, 1-methyl - benzyl group or the like; an aryl group of C ₆ -C _12, for example, a phenyl group, a naphthyl group, etc. ; C ₂ with R ³ and R ⁴
-C ₈ , preferably those forming one alkylene group of C ₂ -C ₆ , for example, ethylene group, trimethylene group, tetramethylene group, pentamethylene group, hexamethylene group and the like. Examples of such amines include ammonia, methylamine, dimethylamine, ethylamine, diethylamine, propylamine, dipropylamine, isopropylamine, diisopropylamine, butylamine, dibutylamine, isobutylamine, diisobutylamine, t-butylamine, 2-aminoethanol, diethanolamine, 2-amino-1-butanol, 2-aminoethanol
Amino-2-methyl-1-propanol, 2-amino-
2-ethyl-1,3-propanediol, 2-amino-2
-Methyl-1,3-pentanediol, cyclohexylamine, benzylamine, α-methylbenzylamine, aniline, 1-naphthylamine, 2-naphthylamine, aziridine, azetidine, pyrrolidine, piperidine and the like. Among these, ammonia, methylamine, dimethylamine, ethylamine, diethylamine,
Amines having a boiling point of 100 ° C. or less, such as propylamine, isopropylamine, diisopropylamine, butylamine, isobutylamine, and t-butylamine, particularly ammonia, are reacted with intermediate azobisimino ether salts to form azobisamidine salts, especially When it is desired to obtain an azobisamidinopropane salt, the azobisamidine salt can be obtained in a high yield and a high purity, so that the method of the present invention can be particularly suitably used.

The amount of the amines used is usually 2 to 25 mol, preferably 5 to 20 mol per mol of the azobisnitrile used.
Is a mole. The amines can be added alone or appropriately diluted with the above-mentioned solvents such as alcohols as long as the excellent effects of the method of the present invention are not impaired.

The reaction in the second step is carried out in a solution obtained by removing excess acid from the reaction solution after the completion of the first step, or in a solution of the above-mentioned alcohols of the intermediate isolated from the reaction solution. The method is carried out by introducing the amines alone or by appropriately diluting them with a solvent having a kind and an amount such as the alcohols which do not impair the excellent effects of the method of the present invention. The concentration of the intermediate in the solution in the above-mentioned second step reaction is usually about 10 to 30% by weight, preferably about 15 to 20% by weight. The temperature at the time of the introduction of the amines and the reaction temperature of the second step are generally about 50 ° C. or less in order to avoid thermal decomposition of the intermediate, and the reaction rate is high and the yield of the obtained azobisamidine salts is coarse. The temperature is preferably in the range of 10 to 30 ° C. from the viewpoint of good rate and high purity. The reaction time in this reaction is usually about 4 to about 15 hours.

Azobisamidine salts, which are the object of the method of the present invention,
After the reaction solution of the second step reaction is dried under reduced pressure, the obtained solid is appropriately washed with a solvent such as methanol, ethanol, 2-propanol, diethyl ether, chloroform, toluene, or the like to remove excess amines. Can be obtained by removing Here, when amines having a boiling point of 100 ° C. or less, particularly ammonia, are used as the amines, it is very preferable that excess amines can be almost completely removed only by drying the reaction solution under reduced pressure to dryness. .

〔Example〕

 Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1 164 g (1 mol) of azobisisobutyronitrile (hereinafter abbreviated as AIBN) was added to 388 g (5 mol of hydrochloric acid) of a 47% by weight methanol solution of hydrochloric acid under cooling at 15 ° C. while stirring.
Add sequentially over 5 hours. During this period, the temperature of the reaction system is kept at 20 ° C. or lower, and after the addition of AIBN, stirring is continued under the same conditions for 2.5 hours to complete the reaction. After the excess hydrochloric acid was distilled off under reduced pressure together with a little methanol, 170 g (10 mol) of ammonia gas was blown in at 20 ° C. or lower, and after aging overnight, dried under reduced pressure to give a white solid of azobisamidinopropane hydrochloride.
0 g (0.7 mol) were obtained. Crude yield 70%, purity 90% by weight, melting point 170 ° C.

Example 2 A reaction was carried out in the same manner as in Example 1 except that a 47% by weight ethanolic hydrochloric acid solution was used instead of the 47% by weight methanolic hydrochloric acid solution in Example 1, and 203 g (0.75 mol) of azobisamidinopropane hydrochloride white solid was obtained. Obtained. Crude yield 75%, purity 92
Wt%, melting point 170 ° C.

Example 3 In place of AIBN in Example 1, 248 g (1 mol) of 2,2'-azobis-2,4-dimethylvaleronitrile (ABVN) was used, and the reaction was carried out in the same manner as in Example 1. '-
231 g (0.65 mol) of azobis-4,4'-methyl-2,2'-amidinopentane hydrochloride were obtained. Crude yield 65%, purity 87% by weight.

〔The invention's effect〕

The method for producing azobisamidine salts of the present invention has the following outstanding effects.

(I) In the first step, the exothermic reaction can be easily controlled by controlling the sequential addition rate of the azobisnitrile, so that mass production is possible.

(Ii) In the first step, since it is not necessary to use a diluting solvent for controlling heat generation, complicated operations can be avoided in separating and recovering the target azobisamidine salts.

(Iii) In the first step, a previously prepared solution of an acid in an alcohol is used. Therefore, the heat of dissolution generated when the acid is dissolved in the alcohol, which was a serious problem in maintaining the temperature of the reaction system in the conventional method, was used. However, since the heat generated by this method is only reaction heat, the temperature can be easily maintained and the reaction time can be shortened.

(Iv) The excess acid component can be removed by distilling the reaction solution after completion of the first step under reduced pressure or by ion-exchange using an anion exchange resin, so that the hygroscopicity is high and the The step of isolating the stable intermediate azobisimino ether salt can be omitted. In particular,
When volatile hydrochloric acid is used as the acid, the excess acid component can be removed very easily only by distilling off the reaction solution after completion of the first step under reduced pressure. By introducing amines into the solution containing the intermediate thus obtained,
Subsequently, the reaction of the second step can be performed.

(V) When volatile acids and alcohols are used in the first step, the solid obtained by drying under reduced pressure after completion of the reaction in the second step is washed with an appropriate solvent such as methanol or ethanol. Thereby, a crude product can be easily obtained, and a complicated operation of separation and recovery can be avoided. Above all, when volatile amines such as ammonia are used as the amines, a crude product can be obtained extremely easily only by drying under reduced pressure.

Claims (6)

(57) [Claims] 1. The following general formula Azobisnitrile represented by the following is added and reacted sequentially in a temperature range of 10 ° C. or more and less than 20 ° C. in an alcohol solution of an acid prepared in advance, and then the obtained intermediate azobis imino ether salt is reacted with the following general formula HNR ³ R ⁴ …… Characterized by reacting amines represented by
The following general formula A method for producing an azobisamidine salt represented by the formula: 2. The method according to claim 1, wherein said alcohol is an alcohol having a C ₁ -C ₄ alkyl group. 3. The method according to claim 1, wherein said acid is hydrochloric acid. 4. The production method according to claim 1, wherein the amine of the general formula is an amine having a boiling point of 100 ° C. or less. 5. The method according to claim 4, wherein the amine of the general formula is ammonia. 6. The azobisnitrile of the above general formula, wherein R ¹ and R ² are each independently a C ₁ -C ₄ alkyl group. (5)
The production method according to any one of the above items.