JPH10204089A - Purification of dibenzylidene sorbitols - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for purifying dibenzylidene sorbitol, capable of reducing the content of impurities such as monobenzylidene sorbitols, tribenzylidene sorbitols, benzaldehydes and hydrophobic organic solvents into <=0.1wt.%. SOLUTION: A benzaldehyde is condensed with sorbitol in the presence of an acid catalyst and a 1-4C aliphatic alcohol in a hydrophobic organic solvent to give a reaction mixture solution, which is mixed with a 1-4C aliphatic alcohol, adjusted to pH7-1 and distilled. The hydrophobic organic solvent is removed and the solution is filtered to purify a dibenzylidene sorbitol.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying dibenzylidene sorbitol useful as a crystal nucleating agent for polyalkylene, which is widely used in food containers, garment cases, medical equipment, home electric appliances and the like.

[0002]

2. Description of the Related Art As a method for purifying dibenzylidene sorbitol, for example, (1) Japanese Patent Publication No. Sho 61-14150 discloses that a crude dibenzylidene sorbitol is mixed with a lower aliphatic alcohol while hot, and monobenzylidene sorbitol and / or A method of separating dibenzylidene sorbitol from a solution in which tribenzylidene sorbitol is dissolved, a method of purification by recrystallization from N-methylpyrrolidone or dimethylformamide, (2)
JP-B-61-17835 discloses that a slightly alkaline aqueous solution having a pH of 7.1 to 9.0 is added to a reaction solution obtained by dehydration condensation of an aromatic aldehyde and sorbitol in a hydrophobic organic solvent, followed by heating. Is distilled off as an azeotrope with water, and the resulting di (alkylbenzylidene) sorbitol is separated as a solid powder, (3) Tokuho 2-5
No. 0909 discloses that a reaction product obtained by subjecting sorbitol and benzaldehyde or alkylbenzaldehyde to dehydration condensation in the presence of an acid catalyst is subjected to a heat treatment at pH 7 or higher in the coexistence of a lower aliphatic ketone to obtain a purified diamine. A method for separating benzylidene sorbitol, (4) JP-A-3-120284 and JP-A-3-120285 disclose a reaction crude obtained by dehydrating and condensing a polyhydric alcohol and an aromatic aldehyde in the presence of an acid catalyst. To the reaction product, a hydrophobic organic solvent solution of an aliphatic tertiary amine and an aqueous solution of an alkali metal hydroxide such as sodium hydroxide are added and uniformly mixed, and then filtered, washed with water, and dried to obtain a reaction product. (5) Pharmaceutical Magazine Vol. 79, No. 5, pp. 595-598, describes the method for reducing benzene and methyl alcohol. (6) Japanese Patent Application Laid-Open No. 60-198991 discloses a method of treating crude dibenzylidene sorbitol with a fluid in a subcritical or supercritical state. And purification methods are known.

[0003]

A sorbitol crystal nucleating agent effective for clearing polypropylene resin and the like, for example, dibenzylidene sorbitol, di (alkylbenzylidene)
In the case of dibenzylidene sorbitols such as sorbitol, if the content of impurities is large, the transparency of the polypropylene resin is significantly reduced, and an odor of benzaldehydes is generated at the time of molding. Required.

However, the methods described in the prior art section, for example, the methods described in JP-A-61-14150, JP-B-61-17835 and JP-B-2-50909, disclose monobenzylidene sorbitol. , Tribenzylidene sorbitols, unreacted benzaldehydes and other impurities contained in an amount of 2% by weight or more,
In any case, there is a problem that the purity of dibenzylidene sorbitol is 98% by weight or less.

An object of the present invention is to provide dibenzylidene sorbitol which reduces the content of impurities such as monobenzylidene sorbitols, tribenzylidene sorbitols, benzaldehydes and hydrophobic organic solvents to 0.1% by weight or less. To provide a purification method of

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies on a method for purifying dibenzylidene sorbitols such as dibenzylidene sorbitol, di (alkylbenzylidene) sorbitol and the like. In the obtained reaction mixture containing the crude dibenzylidene sorbitols, an aliphatic alcohol having 1 to 4 carbon atoms is allowed to coexist, and the pH in the system is adjusted to 7 to 11; While adding the aliphatic alcohol of 4, distillation, preferably azeotropic distillation, distills off the hydrophobic organic solvent, and then, when filtered, the aliphatic alcohol having 1 to 4 carbon atoms is obtained upon heating during the distillation. Benzaldehydes, monobenzylidene sorbitols, tribenzylidene sorbitols and the like are dissolved and distilled, and then filtered to obtain a carbon number of 1-4. Since it is removed together with the aliphatic alcohol, the content of impurities such as monobenzylidene sorbitols, tribenzylidene sorbitols, benzaldehydes, and hydrophobic organic solvents is less than 0.10% by weight, which is 1/10 of the prior art method. The inventors have found that dibenzylidene sorbitols that can be reduced to a high degree and can be easily purified can be obtained with high purity, and have completed the present invention.

That is, the present invention relates to (1) a reaction mixture obtained by dehydrating and condensing benzaldehydes and sorbitol in a hydrophobic organic solvent in the presence of an acid catalyst and an aliphatic alcohol having 1 to 4 carbon atoms. An aliphatic alcohol having 1 to 4 carbon atoms is allowed to coexist in the liquid, and the pH in the system is adjusted to 7-1.
(1) A method for purifying dibenzylidene sorbitols, which comprises distilling off a hydrophobic organic solvent after adjusting to 1, followed by filtration. (2) The above (1), wherein the benzaldehydes are alkylbenzaldehydes. (3) the purification method according to the above (1) or (2), wherein the distillation is azeotropic distillation; and (4) an aliphatic alcohol having 1 to 4 carbon atoms in the reaction mixture during the distillation. The purification method according to the above (1), (2) or (3) to be added. Is provided.

[0008]

DETAILED DESCRIPTION OF THE INVENTION The process of the present invention is preferably applied to the purification of dibenzylidene sorbitols, for example, dibenzylidene sorbitol and di (alkylbenzylidene) sorbitol having an alkyl group having 1 to 4 carbon atoms. Examples of the di (alkylbenzylidene) sorbitol include di (p-methylbenzylidene) sorbitol, di (p-ethylbenzylidene) sorbitol, di (3,4-dimethylbenzylidene) sorbitol, and di (2,4-dimethylbenzylidene) sorbitol. And di (alkylbenzylidene) sorbitol.

The hydrophobic organic solvent used in the present invention includes:
For example, cyclohexane, methylcyclohexane, ethylcyclohexane, hexane, heptane, cyclooctane, octane and the like can be mentioned, and among them, cyclohexane is particularly preferable. The amount of the hydrophobic organic solvent used is 5 parts by weight based on 100 parts by weight of the raw material sorbitol.
The range which becomes 00-3000 weight part is preferable.

The acid catalyst used in the present invention includes, for example,
Examples thereof include p-toluenesulfonic acid, sulfuric acid, phosphoric acid, benzenesulfonic acid, and alkylbenzenesulfonic acid having 2 to 9 carbon atoms. The amount of the acid catalyst used is preferably in the range of 0.1 to 10 parts by weight based on 100 parts by weight of the raw material sorbitol.

In the method of the present invention, the acid catalyst is usually added after the addition of the hydrophobic organic solvent. The order in which the hydrophobic organic solvent, the acid catalyst, the aliphatic alcohol having 1 to 4 carbon atoms, benzaldehydes and sorbitol are added is added. Is not important to the invention.

The benzaldehydes used in the present invention include, for example, benzaldehyde, p-tolualdehyde,
Examples thereof include o-tolualdehyde, 3,4-dimethylbenzaldehyde, 2,4-dimethylbenzaldehyde, p-ethylbenzaldehyde and the like. The amount of the benzaldehyde used is usually in the range of 1.5 to 3.0 mol with respect to 1.0 mol of sorbitol as a raw material, and among them, the range of 1.8 to 2.5 mol is preferable. Is preferred.

Examples of the aliphatic alcohol having 1 to 4 carbon atoms used for dehydrating and condensing benzaldehydes and sorbitol include methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butyl alcohol and 2-butyl alcohol. Of these, methyl alcohol is particularly preferred. 1 to 1 carbon atoms
The amount of the aliphatic alcohol to be used is preferably in the range of 50 to 2,000 parts by weight based on 100 parts by weight of the raw material sorbitol.

The temperature and time for the dehydration condensation of benzaldehydes and sorbitol are usually 40 to 100 ° C.
It is 2 to 20 hours, particularly preferably 50 to 80 ° C and 4 to 15 hours. During the heating, the reaction mixture is preferably stirred. The pressure at this time is usually normal pressure,
The pressure may be reduced from 10 kPa to less than normal pressure.

Examples of aliphatic alcohols having 1 to 4 carbon atoms which coexist in a reaction mixture obtained by dehydrating and condensing benzaldehydes and sorbitol include methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butyl alcohol, and the like. Examples thereof include 2-butyl alcohol, and among them, methyl alcohol is particularly preferable. These aliphatic alcohols may contain up to 40% by weight of water. The amount of the aliphatic alcohol used is preferably in the range of 500 to 3000 parts by weight based on 100 parts by weight of the raw material sorbitol.

The aliphatic alcohol used for dehydrating and condensing benzaldehydes and sorbitol and the aliphatic alcohol coexisting in the reaction mixture may be the same or different.

In the method of the present invention, the reaction mixture obtained by dehydrating and condensing benzaldehydes and sorbitol together with an aliphatic alcohol having 1 to 4 carbon atoms has a pH of 7 to 11, preferably 8 to 8. Adjust to ~ 10,
This pH adjustment is usually performed by adding a basic compound. The addition of the basic compound at this time is usually performed by adding a solution in which the basic compound is dissolved in an aliphatic alcohol having 1 to 4 carbon atoms for coexistence in the reaction mixture to the reaction mixture. Basic compound and carbon atom number 1-4
May be added alone.
In addition, when adding each independently, it is preferable to add a basic compound first.

The basic compound used herein includes, for example, sodium hydrogen carbonate, potassium hydrogen carbonate, sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide, triethylamine, diethylamine, triethanolamine, diethanolamine and the like.

When the basic compound and the aliphatic alcohol having 1 to 4 carbon atoms are added, the temperature of the reaction mixture is from room temperature to
80 ° C. is preferred. In addition, it is preferable to stir when heating the reaction mixture.

In the method of the present invention, the hydrophobic organic solvent is distilled off, but usually, the hydrophobic organic solvent and the aliphatic alcohol having 1 to 4 carbon atoms form an azeotropic mixture. By distillation, the hydrophobic organic solvent has 1 to 4 carbon atoms.
It is distilled off together with the aliphatic alcohol. However, only the hydrophobic organic solvent may be distilled off using a hydrophobic organic solvent that does not form an azeotrope and an aliphatic alcohol having 1 to 4 carbon atoms.

The temperature and time of distillation, especially azeotropic distillation, are 40
C. to 90.degree. C. for 1 to 15 hours are preferred, and particularly 60.degree. To 80.degree. C. for 3 to 10 hours.
In the distillation, the reaction mixture is preferably heated while stirring.

In the present invention, the reaction mixture at the end of distillation contains an aliphatic alcohol having 1 to 4 carbon atoms, in which most of benzaldehydes, monobenzylidene sorbitols, tribenzylidene sorbitols and the like are dissolved. It is necessary that an aliphatic alcohol having 1 to 4 carbon atoms be added to the reaction mixture during the distillation, if necessary. In the case of performing azeotropic distillation, it is preferable that the aliphatic alcohol having 1 to 4 carbon atoms distilled off together with the hydrophobic organic solvent is separated, returned to the reaction mixture, and reused.

In the reaction mixture after distillation, benzaldehydes, monobenzylidene sorbitols, tribenzylidene sorbitols and the like are dissolved, and this is filtered, washed and dried to reduce the amount of impurities to 0.1% by weight. The following dibenzylidene sorbitols are obtained.

The temperature of the above-mentioned filtration and washing is preferably in the range of room temperature to 90 ° C. The washing is usually carried out by coexistence of a C 1-4 carbon atom in a reaction mixture obtained by dehydrating and condensing benzaldehydes and sorbitol. Using aliphatic alcohols. Further, the temperature and pressure when drying the wet cake obtained after filtration and washing are normal temperature to 120 ° C. and normal pressure to 1 ° C.
A range of 0 kPa is preferred.

[0025]

The present invention will be specifically described below with reference to examples and comparative examples. In addition,% in an example represents weight%.

Example 1 1000 m equipped with a stirrer, thermometer, cooler and water separator
l, 392 g of cyclohexane, 266 g of methyl alcohol, and 22.4 g of powdered sorbitol (0.
12 mol), 29.5 g (0.24 p-tolualdehyde)
Mol) and 0.7 g of p-toluenesulfonic acid. Next, the mixture was heated to raise the temperature of the raw material mixture to 55 to 60 ° C., and was subjected to dehydration condensation for 4 hours, and the distilled methyl alcohol and produced water were discharged to a 300 ml receiver. At the stage where the distilling amounts of methyl alcohol and produced water were reduced, the temperature of the reaction mixture was increased to 70 to 72 ° C., and dehydration condensation was further performed for 1 hour to distill methyl alcohol and produced water.

Next, the obtained reaction mixture was cooled to room temperature, and 0.8 g of sodium hydrogen carbonate and 200 g of methyl alcohol were added to adjust the pH of the reaction mixture to 8.5. The liquid was heated to 55 to 60 ° C., azeotropic distillation was started, and azeotropic distillation was performed for 3 hours. The cyclohexane distilled at this time was withdrawn to a 1000 ml receiver, and the methyl alcohol distilled at the same time was returned to the reaction vessel. Every time the amount of cyclohexane distilled other than this methyl alcohol reaches 20 ml, more methyl alcohol 20
ml, and a total of 500 g of methyl alcohol was added. The temperature of the reaction mixture at the end of the azeotropic distillation was 63 ° C. Next, the mixture was cooled to 40 ° C., filtered, washed with methyl alcohol, and dried under vacuum to obtain 40.0 g of a white powder.

This was analyzed by gas chromatography to find that di (p-methylbenzylidene) sorbitol was 9%.
9.9%, tri (p-methylbenzylidene) sorbitol less than 0.01%, mono (p-methylbenzylidene)
Sorbitol 0.05%, p-tolualdehyde 14%
ppm.

Example 2 1000 m equipped with a stirrer, thermometer, cooler and water separator
560 g of cyclohexane, 140 g of methyl alcohol, and 32.0 g of powdered sorbitol (0.
18 mol), 42.2 g (0.35 p-tolualdehyde)
Mol) and 1.0 g of p-toluenesulfonic acid. Next, the mixture was heated to raise the temperature of the raw material mixture to 55 to 60 ° C. and dehydrated and condensed for 3 hours. The distilled methyl alcohol and generated water were discharged to a 300 ml receiver. At the stage where the distilling amount of methyl alcohol and produced water decreased, the temperature of the reaction mixture was raised to 70 ° C. for 2 hours and 73 kP.
Under the reduced pressure of a, dehydration condensation was performed at 69 to 71 ° C. for 3 hours to distill off methyl alcohol and produced water.

Then, the pressure was returned to normal pressure, the obtained reaction mixture was cooled to room temperature, and 1.2 g of sodium hydrogen carbonate and 200 g of methyl alcohol were added to adjust the pH of the reaction mixture to 8.8. Heat to bring the reaction mixture to 55-55
The azeotropic distillation was started by increasing the temperature to 60 ° C., and the azeotropic distillation was performed for 3 hours. The cyclohexane distilled at this time is 1000
The methyl alcohol was withdrawn from the reactor, and the methyl alcohol distilled off was returned to the reaction vessel. Every time the amount of cyclohexane distilled other than this methyl alcohol reached 20 ml, 20 ml of methyl alcohol was further added, and a total of 400 g of methyl alcohol was added. The temperature of the reaction mixture at the end of the azeotropic distillation was 63 ° C. Then, cool down to 40 ° C,
After filtration, the precipitate was washed with methyl alcohol and dried under vacuum to obtain 56.2 g of a white powder.

As a result of analyzing this by gas chromatography, di (p-methylbenzylidene) sorbitol 99.
9%, tri (p-methylbenzylidene) sorbitol was less than 0.01%, mono (p-methylbenzylidene) sorbitol was 0.03%, and p-tolualdehyde was 9 ppm.

Example 3 32.0 g (0.18 mol) of sorbitol and 42.2 g (0.35 mol) of p-tolualdehyde were subjected to dehydration condensation in the same manner as in Example 2 to obtain a reaction mixture.

Then, the pressure was returned to normal pressure, and the obtained reaction mixture was cooled to normal temperature.
After adding 200 g of a 0% aqueous methyl alcohol solution to adjust the pH of the reaction mixture to 9.3, heating was performed to raise the reaction mixture to 55 to 60 ° C., and azeotropic distillation was started. An azeotropic distillation was performed. The cyclohexane distilled at this time was withdrawn to a 1000 ml receiver, and the methyl alcohol and water distilled at the same time were returned to the reaction vessel. Cyclohexane distilled off besides this methyl alcohol and water is 1
Every time the volume reached 00 ml, 100 ml of a 70% aqueous methyl alcohol solution was further added, and a total of 500 g of a 70% aqueous methyl alcohol solution was added. The temperature of the reaction mixture at the end of the azeotropic distillation was 71 ° C. Then 50
After cooling to 0 ° C., the solution was filtered, washed with a 70% aqueous solution of methyl alcohol, and dried under vacuum to obtain 57.2 g of a white powder.

As a result of analyzing this by gas chromatography, di (p-methylbenzylidene) sorbitol was found to be 9%.
9.9%, tri (p-methylbenzylidene) sorbitol 0.01%, mono (p-methylbenzylidene) sorbitol 0.04%, p-tolualdehyde 23pp
m.

Example 4 32.0 g (0.18 mol) of sorbitol and 42.2 g (0.35 mol) of p-tolualdehyde were subjected to dehydration condensation in the same manner as in Example 2 to obtain a reaction mixture.

Then, the pressure was returned to normal pressure, and the obtained reaction mixture was cooled to normal temperature.
After adding 200 g of a methyl alcohol aqueous solution having a concentration of 200% to adjust the pH of the reaction mixture to 8.2, heating was performed to raise the reaction mixture to 55 to 60 ° C., and azeotropic distillation was started.
The azeotropic distillation was performed for 5 hours. The cyclohexane distilled at this time was withdrawn to a 1000 ml receiver, and the methyl alcohol and water distilled at the same time were returned to the reaction vessel. 20 m of cyclohexane distilled off besides this methyl alcohol and water
Each time the volume reached 1 l, 20 ml of a 90% aqueous methyl alcohol solution was further added, and a total of 500 g of a 90% aqueous methyl alcohol solution was added. The temperature of the reaction mixture at the end of the azeotropic distillation was 66 ° C. Next, the mixture was cooled to 40 ° C., filtered, washed with a 90% strength aqueous methyl alcohol solution, and dried under vacuum to obtain 56.4 g of a white powder. As a result of analyzing this by gas chromatography, di (p
-Methylbenzylidene) sorbitol is 99.9%, and tri (p-methylbenzylidene) sorbitol is 0.01%.
%, Mono (p-methylbenzylidene) sorbitol was 0.06%, and p-tolualdehyde was 21 ppm.

Example 5 In the same manner as in Example 2 except that the amount of cyclohexane used was changed to 450 g, 32.0 g (0.18 mol) of sorbitol and 42.2 g (0.35 mol) of p-tolualdehyde were used.
Was subjected to dehydration condensation to obtain a reaction mixture.

Next, the pressure was returned to normal pressure, the obtained reaction mixture was cooled to room temperature, and 200 g of methyl alcohol in which 0.9 g of triethanolamine was dissolved was added to adjust the pH of the reaction mixture to 8.7. After that, the mixture was heated to raise the temperature of the reaction mixture to 55 to 60 ° C. to start azeotropic distillation, and azeotropic distillation was performed for 3 hours. The cyclohexane distilled at this time was withdrawn to a 1000 ml receiver, and the methyl alcohol distilled at the same time was returned to the reaction vessel. Each time the amount of cyclohexane distilled out other than this methyl alcohol reaches 100 ml, 100 ml of methyl alcohol is further added, and a total of 3
An additional 50 g of methyl alcohol was added. The temperature of the reaction mixture at the end of the azeotropic distillation was 63 ° C. Then, at 50 ° C
, Filtered, washed with methyl alcohol, and dried under vacuum to obtain 57.1 g of a white powder.

As a result of analyzing this by gas chromatography, di (p-methylbenzylidene) sorbitol was found to be 9%.
9.9%, tri (p-methylbenzylidene) sorbitol less than 0.01%, mono (p-methylbenzylidene)
Sorbitol is 0.02% and p-tolualdehyde is 16%.
ppm.

Example 6 1000 m equipped with a stirrer, thermometer, cooler and water separator
l, 392 g of cyclohexane, 266 g of methyl alcohol, and 22.4 g of powdered sorbitol (0.
12 mol), 29.5 g (0.24 p-tolualdehyde)
Mol) and 0.7 g of p-toluenesulfonic acid. Next, the mixture was heated to raise the temperature of the raw material mixture to 55 to 60 ° C., and was subjected to dehydration condensation for 4 hours, and the distilled methyl alcohol and produced water were discharged to a 500 ml receiver. At the stage where the distilling amounts of methyl alcohol and produced water were reduced, the temperature of the reaction mixture was increased to 71 to 73 ° C., and dehydration condensation was further performed for 2 hours to distill methyl alcohol and produced water.

Then, the obtained reaction mixture was cooled to room temperature, 15.5 g of a 1% aqueous sodium hydroxide solution and 200 g of methyl alcohol were added to adjust the pH of the reaction mixture to 8.5, and then heated. To 55 to 55
The azeotropic distillation was started by increasing the temperature to 60 ° C., and the azeotropic distillation was performed for 3 hours. The cyclohexane distilled at this time is 1000
The methyl alcohol and water distilled out at the same time were returned to the reaction vessel. Every time the amount of cyclohexane distilled out other than this methyl alcohol and water reaches 20 ml, an additional 20 ml of methyl alcohol is added, and a total of 400 g
Of methyl alcohol was added. The temperature of the reaction mixture at the end of the azeotropic distillation was 63 ° C. Next, the mixture was cooled to 40 ° C., filtered, washed with methyl alcohol, and dried under vacuum to obtain 39.6 g of a white powder.

As a result of analyzing this by gas chromatography, di (p-methylbenzylidene) sorbitol was found to be 9%.
9.9%, tri (p-methylbenzylidene) sorbitol less than 0.01%, mono (p-methylbenzylidene)
Sorbitol 0.03%, p-tolualdehyde 19
ppm.

Example 7 1000 m equipped with a stirrer, thermometer, cooler and water separator
l-reaction vessel, n-heptane 420 g, methyl alcohol 140 g, powdered sorbitol 32.0 g (0.1
8 mol), 47.1 g of p-ethylbenzaldehyde
(0.35 mol) and 1.0 g of p-toluenesulfonic acid
Was weighed. Next, heating is performed to reduce the mixture of the raw materials to 60 to
The temperature was raised to 65 ° C., and the mixture was dehydrated and condensed for 3 hours, and the distilled methyl alcohol and produced water were discharged to a 300 ml receiver. At the stage where the distilling amounts of methyl alcohol and produced water were reduced, the temperature of the reaction mixture was raised to 73 to 75 ° C. and dehydration-condensed for 3 hours to distill methyl alcohol and produced water.

Then, the obtained reaction mixture was cooled to room temperature, and 1.2 g of sodium hydrogen carbonate and 200 g of a 80% strength aqueous methyl alcohol solution were added thereto.
Was adjusted to 8.9, heating was performed to bring the reaction mixture to 60
The azeotropic distillation was started by increasing the temperature to ６５65 ° C., and the azeotropic distillation was performed for 3 hours. The n-heptane distilled at this time is 1000
The methyl alcohol and water distilled out at the same time were returned to the reaction vessel. Every time the amount of n-heptane distilled out other than the methyl alcohol and water reaches 100 ml, 100 ml of an 80% aqueous methyl alcohol solution is further added, and an 80% aqueous methyl alcohol solution is added to a total of 3 ml.
50 g was added. The temperature of the reaction mixture at the end of the azeotropic distillation was 68 ° C. Next, the mixture was cooled to 50 ° C., filtered, and washed with an aqueous 80% methyl alcohol solution.
Vacuum drying yielded 58.6 g of a white powder.

As a result of analyzing this by gas chromatography, di (p-ethylbenzylidene) sorbitol was found to be 9%.
9.9%, tri (p-ethylbenzylidene) sorbitol was 0.02%, mono (p-ethylbenzylidene) sorbitol was 0.04%, and p-ethylbenzaldehyde was 36 ppm.

Example 8 1000 m equipped with a stirrer, thermometer, cooler and water separator
n-heptane (350 g), 2-butyl alcohol (266 g), powdered sorbitol (22.4 g)
(0.12 mol), 33.0 g (0.24 mol) of 2,4-dimethylbenzaldehyde and 0.7 g of p-toluenesulfonic acid were weighed. Next, after reducing the pressure to 47 kPa, the mixture was heated to raise the temperature of the raw material mixture to 65 to 70 ° C., and dehydration-condensed for 5 hours. At the stage where the amount of distilled 2-butyl alcohol and produced water decreased, the temperature of the reaction mixture was increased to 73 to 75 ° C., and the mixture was further dehydrated and condensed for 3 hours to distill 2-butyl alcohol and produced water. Was.

Then, the pressure was returned to normal pressure, the obtained reaction mixture was cooled to room temperature, and 15.5 g of 1% aqueous sodium hydroxide solution and 90% aqueous methyl alcohol solution 2 were added.
After the pH of the reaction mixture was adjusted to 8.8 by adding 00 g, the reaction mixture was heated to 60 to 65 ° C. to start azeotropic distillation, and azeotropic distillation was performed for 3 hours. The n-heptane distilled off at this time was withdrawn to a 1000 ml receiver. At the same time, the methyl alcohol and water distilled off were returned to the reaction vessel. Every time the amount of distilled n-heptane other than methyl alcohol reaches 20 ml, 20 ml of a 90% aqueous methyl alcohol solution was further added, and a total of 400 g of a 90% aqueous methyl alcohol solution was added. The temperature of the reaction mixture at the end of the azeotropic distillation was 66 ° C. Then
The mixture was cooled to 40 ° C., filtered, washed with a 90% aqueous methyl alcohol solution, and dried under vacuum to obtain 41.5 g of a white powder.

This was analyzed by gas chromatography to find that 99.9% of di (2,4-dimethylbenzylidene) sorbitol and tri (2,4-dimethylbenzylidene)
Sorbitol was 0.02%, mono (2,4-dimethylbenzylidene) sorbitol was 0.03%, and 2,4-dimethylbenzaldehyde was 41 ppm.

Example 9 1000 m equipped with a stirrer, thermometer, cooler and water separator
560 g of cyclohexane, 140 g of isopropyl alcohol, 32.0 g of powdered sorbitol
(0.18 mol), 42.2 g of p-tolualdehyde
(0.35 mol) and 1.0 g of p-toluenesulfonic acid
Was weighed. Then, the raw material mixture was heated to 72 to
The temperature was raised to 74 ° C. and the mixture was dehydrated and condensed for 3 hours. At the stage where the distilling amount of isopropyl alcohol and produced water was reduced, dehydration condensation was performed for 3 hours while maintaining the temperature of the reaction mixture at 72 to 74 ° C. under a reduced pressure of 80 kPa,
Isopropyl alcohol and product water were distilled off.

Then, the pressure was returned to normal pressure, and the obtained reaction mixture was cooled to normal temperature.
After adjusting the pH of the reaction mixture to 8.9 by adding 200 g of 0% isopropyl alcohol aqueous solution, heating was performed to raise the reaction mixture to 65 to 70 ° C., and azeotropic distillation was started. An azeotropic distillation was performed. The cyclohexane distilled at this time was withdrawn to a 1000 ml receiver, and the isopropyl alcohol and water distilled at the same time were returned to the reaction vessel. Each time the distilled cyclohexane reaches 100 ml, an 80% isopropyl alcohol aqueous solution 100
ml, and a total of 400 g of an 80% isopropyl alcohol aqueous solution was added. The temperature of the reaction mixture at the end of the azeotropic distillation was 75 ° C. Next, the mixture was cooled to 40 ° C., filtered, washed with an 80% isopropyl alcohol aqueous solution, and dried under vacuum to obtain 54.6 g of a white powder.

As a result of analyzing this by gas chromatography, di (p-methylbenzylidene) sorbitol was found to be 9%.
9.9%, tri (p-methylbenzylidene) sorbitol 0.01%, mono (p-methylbenzylidene) sorbitol 0.04%, p-tolualdehyde 28 pp
m.

Example 10 1000 m equipped with a stirrer, thermometer, cooler and water separator
In a 1 l reaction vessel, cyclohexane 400 g, methyl alcohol 10 g, powdered sorbitol 32.0 g (0.1
8 mol), 42.2 g (0.35 mol) of p-tolualdehyde and 1.0 g of p-toluenesulfonic acid were weighed.
Then, the mixture was heated to raise the temperature of the raw material mixture to 55 to 60 ° C., and was subjected to dehydration condensation for 1 hour. At the stage where the amount of distilled methyl alcohol and produced water is reduced, 60 kPa
The reaction mixture was subjected to dehydration condensation at a temperature of 60 to 64 ° C. for 2 hours under reduced pressure to distill off methyl alcohol and produced water. Then, after the pressure was returned to normal pressure, 10 g of methyl alcohol was added, and the temperature of the reaction mixture was kept at 55 to 60 ° C. for 1 hour and further 60 hours.
Under reduced pressure of kPa, the reaction mixture was dehydrated and condensed at a temperature of 60 to 64 ° C. for 2 hours to distill off methyl alcohol and produced water. The pressure was returned to normal pressure again, 10 g of methyl alcohol was added, and the temperature of the reaction mixture was kept at 55 to 60 ° C. for one hour,
Under reduced pressure of kPa, the reaction mixture was dehydrated and condensed at a temperature of 60 to 64 ° C. for 2 hours to distill off methyl alcohol and produced water.

Next, the pressure was returned to normal pressure, the obtained reaction mixture was cooled to room temperature, and 200 g of a 70% aqueous methyl alcohol solution in which 1.2 g of sodium hydrogen carbonate was dissolved.
Was added to adjust the pH of the reaction mixture to 8.6, followed by heating to raise the reaction mixture to 55 to 60 ° C. to start azeotropic distillation, followed by azeotropic distillation for 3 hours. The cyclohexane distilled at this time was withdrawn to a 1000 ml receiver, and the methyl alcohol and water distilled at the same time were returned to the reaction vessel. Each time the amount of cyclohexane distilled out other than the methyl alcohol and water reaches 100 ml, 100 ml of a 70% strength aqueous methyl alcohol solution is added, and a total of 400 g of 7
A 0% aqueous methyl alcohol solution was added. The temperature of the reaction mixture at the end of the azeotropic distillation was 71 ° C. Next, the mixture was cooled to 40 ° C., filtered, washed with a 70% aqueous methyl alcohol solution, and dried in vacuo to obtain 56.7.
g of a white powder were obtained.

As a result of analyzing this by gas chromatography, di (p-methylbenzylidene) sorbitol was found to be 9%.
9.9%, tri (p-methylbenzylidene) sorbitol 0.01%, mono (p-methylbenzylidene) sorbitol 0.01%, p-tolualdehyde 18 pp
m.

Comparative Example 1 In a 1000 ml reaction flask equipped with a stirrer, thermometer and reflux condenser, 540.0 g of methyl alcohol was weighed. To this was added 95% pure di (p-methylbenzylidene) containing 0.6% tri (p-methylbenzylidene) sorbitol, 2.9% mono (p-methylbenzylidene) sorbitol and 1.4% p-tolualdehyde. ) 60.0 g of sorbitol dry powder was added and heated, and the temperature of the raw material mixture was raised to 65 ° C and slightly boiled.
Stirred for hours.

Next, the obtained reaction mixture was cooled to 60 ° C., filtered, washed with methyl alcohol, and dried under vacuum to obtain 57.4 g of a white powder.

As a result of analyzing this by gas chromatography, di (p-methylbenzylidene) sorbitol was found to be 9%.
7.3%, tri (p-methylbenzylidene) sorbitol 0.48%, mono (p-methylbenzylidene) sorbitol 1.63%, p-tolualdehyde 0.59
%Met.

Comparative Example 2 In a 1000 ml reaction flask equipped with a stirrer, thermometer and reflux condenser, 280 g of cyclohexane, 18.2 g (0.10 mol) of powdered sorbitol, and 24.0 (0. 20 mol) and 0.2 g of p-toluenesulfonic acid. Next, the mixture was heated to raise the temperature of the raw material mixture to 70 to 75 ° C. and dehydrated and condensed for 6 hours, and the distilled water was extracted into a 100 ml receiver.

Then, the obtained reaction mixture was cooled to room temperature, and an aqueous solution in which 0.5 g of sodium hydrogen carbonate was dissolved in 260 g of water was added to adjust the pH of the reaction mixture to 8.9. The reaction mixture was heated to 70 to 72 ° C. to start azeotropic distillation, and azeotropic distillation was performed for 4 hours. The cyclohexane distilled at this time was withdrawn to a 500 ml receiver, and the distilled water was returned to the reaction vessel. The temperature of the reaction mixture at the end of the azeotropic distillation was 75 ° C. Then
After cooling to room temperature, filtration, washing with water, and vacuum drying, 31.3 g of a white powder was obtained.

As a result of analyzing this by gas chromatography, di (p-methylbenzylidene) sorbitol was found to be 9%.
7.4%, tri (p-methylbenzylidene) sorbitol 0.19%, mono (p-methylbenzylidene) sorbitol 1.34%, p-tolualdehyde 0.96%
%Met.

Comparative Example 3 Cyclohexane (560 g), powdered sorbitol (29.2 g, 0.16 mol) and p-tolualdehyde (38.4) were added to a 1000 ml reaction flask equipped with a stirrer, thermometer and reflux condenser. 32 mol) and 1.0 g of p-toluenesulfonic acid. Next, the mixture was heated to raise the temperature of the raw material mixture to 70 to 75 ° C. and dehydrated and condensed for 6 hours, and the distilled water was extracted into a 100 ml receiver.

Next, the obtained reaction mixture was cooled to room temperature, filtered, washed with water, and further sufficiently washed with a 2% aqueous sodium hydrogen carbonate solution. As a result of analyzing the wet cake by gas chromatography, the purity of crude di (p-methylbenzylidene) sorbitol from which water was removed was 90%.
%, Containing 1.1% tri (p-methylbenzylidene) sorbitol, 6.0% mono (p-methylbenzylidene) sorbitol, and 1.6% p-tolualdehyde.

A 10 equipped with a stirrer, thermometer and reflux condenser
In a 00 ml reaction flask, add methyl ethyl ketone 48
After weighing 0.0 g, the above crude di-p (p-
(Methylbenzylidene) sorbitol was added, and the mixture was stirred at room temperature. Next, heating is performed to reduce the raw material mixture to 75 to 80.
After the mixture was heated to ℃ and stirred for 1 hour, the obtained mixture was cooled to room temperature, filtered, washed with methyl ethyl ketone, and dried under vacuum to obtain 57.0 g of a white powder.

As a result of analyzing this by gas chromatography, di (p-methylbenzylidene) sorbitol was found to be 9%.
4.1%, tri (p-methylbenzylidene) sorbitol was 1.0%, mono (p-methylbenzylidene) sorbitol was 3.5%, and p-tolualdehyde was 1.0%.

[0065]

The content of impurities such as monobenzylidene sorbitols, tribenzylidene sorbitols, benzaldehydes and hydrophobic organic solvents is reduced to less than 0.10% by weight, which is less than 1/10 of that of the prior art method. And highly purified dibenzylidene sorbitols can be easily obtained.

Claims (4)

[Claims] 1. A reaction mixture obtained by dehydrating and condensing benzaldehydes and sorbitol in a hydrophobic organic solvent in the presence of an acid catalyst and an aliphatic alcohol having 1 to 4 carbon atoms. A method for preparing dibenzylidene sorbitols, comprising coexisting an aliphatic alcohol of 1 to 4 and adjusting the pH of the system to 7 to 11, distilling off a hydrophobic organic solvent, and then filtering. Purification method. 2. The method according to claim 1, wherein the benzaldehyde is an alkylbenzaldehyde. 3. The purification method according to claim 1, wherein the distillation is azeotropic distillation. 4. The reaction mixture during distillation contains 1 to 4 carbon atoms.
4. The purification method according to claim 1, wherein the aliphatic alcohol is added.