JPH1059976A - Method for purifying di (alkylbenzylidene) sorbitol - Google Patents

Abstract

(57) Abstract: Di (alkylbenzylidene) for reducing the amount of impurities such as mono (alkylbenzylidene) sorbitol, tri (alkylbenzylidene) sorbitol, aromatic aldehyde, and hydrophobic organic solvent to 0.1% by weight or less. To provide a method for purifying sorbitol. SOLUTION: A crude di (alkylbenzylidene) sorbitol obtained by dehydrating and condensing an aromatic aldehyde and sorbitol in a hydrophobic organic solvent in the presence of an acid catalyst and a lower aliphatic alcohol is converted to a lower aliphatic alcohol aqueous solution. A method for purifying di (alkylbenzylidene) sorbitol, which comprises heating and dissolving in a lower aliphatic nitrile aqueous solution or lower aliphatic ketone aqueous solution, and then cooling to collect crystals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for purifying di (alkylbenzylidene) sorbitol useful as a crystal nucleating agent for polyalkylene widely used in food containers, garment cases, medical equipment, home electric appliances and the like. About.

[0002]

2. Description of the Related Art As a method for purifying di (alkylbenzylidene) sorbitol, for example, (1) Japanese Patent Publication No. 61-14 / 1986
No. 150 discloses a method of hot-mixing crude dibenzylidene sorbitol with a lower aliphatic alcohol to separate a solution in which monobenzylidene sorbitol and / or tribenzylidene sorbitol is dissolved from crude dibenzylidene sorbitol, and N-methylpyrrolidone. Or a method of purification by recrystallization with dimethylformamide,
(2) Japanese Patent Publication No. 50909/1990 discloses that a reaction product obtained by dehydrating and condensing sorbitol with benzaldehyde or alkylbenzaldehyde in the presence of an acid catalyst is heated at pH 7 or higher in the presence of a lower aliphatic ketone. And separating the purified dibenzylidene sorbitol, (3) JP-A-3-120284 and JP-A-3-
JP-A-120285 discloses that a reaction product obtained by dehydrating and condensing a polyhydric alcohol and an aromatic aldehyde in the presence of an acid catalyst is added with an aliphatic tertiary amine and an alkali metal hydroxide such as sodium hydroxide. And (4) Pharmaceutical Magazine Vol. 79, No. 5, pp. 595-598, which discloses a method for preparing crude dibenzylidene sorbitol utilizing the difference in solubility in benzene and methanol. (5) JP-A-60-1998
No. 91 discloses a method of purifying crude dibenzylidene sorbitol by treating it with a fluid in a subcritical or supercritical state.

[0003]

In the case of a sorbitol-based crystal nucleating agent which is effective for clearing a polypropylene resin or the like, if the content of impurities in di (alkylbenzylidene) sorbitol is large, the transparency of the propylene resin is significantly reduced. Since odors of aromatic aldehydes are generated at the time of molding, sorbitol crystal nucleating agents used for this purpose are required to be of high purity.

However, in the methods described in the prior art section, for example, in the methods described in JP-A-61-14150 and JP-B-2-50909, mono (alkylbenzylidene) sorbitol, tri (alkylbenzylidene) Ii) There was a problem that the purity of di (alkylbenzylidene) sorbitol was 98% by weight or less in all cases, such as containing 2% by weight or more of impurities such as sorbitol and aromatic aldehyde.

An object of the present invention is to reduce the amount of impurities such as mono (alkylbenzylidene) sorbitol, tri (alkylbenzylidene) sorbitol, aromatic aldehyde and hydrophobic organic solvent to 0.1% by weight or less. To provide a method for purifying di (alkylbenzylidene) sorbitol.

[0006]

The present inventors have conducted intensive studies on a method for purifying di (alkylbenzylidene) sorbitol. As a result, the present inventors have found that aromatic compounds can be used in a hydrophobic organic solvent in the presence of an acid catalyst and a lower aliphatic alcohol. Di (alkylbenzylidene) sorbitol obtained by dehydration-condensation of aliphatic aldehyde and sorbitol is dissolved in a lower aliphatic alcohol aqueous solution, lower aliphatic nitrile aqueous solution or lower aliphatic ketone aqueous solution by heating and then cooled. When the crystals to be crystallized are separated, the content of the impurities mono (alkylbenzylidene) sorbitol, tri (alkylbenzylidene) sorbitol, aromatic aldehyde and hydrophobic organic solvent is less than 0.10% by weight according to the prior art method. 1/1 compared to
It has been found that it can be reduced to 0 or less, and that di (alkylbenzylidene) sorbitol can be produced with high purity, and the present invention has been completed.

That is, in order to solve the above-mentioned problems, the present invention provides a crude di (d) obtained by dehydrating and condensing an aromatic aldehyde and sorbitol in a hydrophobic organic solvent in the presence of an acid catalyst and a lower aliphatic alcohol. Alkylbenzylidene)
Di (alkylbenzylidene) sorbitol, characterized in that sorbitol is heated and dissolved in a lower aliphatic alcohol aqueous solution, lower aliphatic nitrile aqueous solution or lower aliphatic ketone aqueous solution, and then cooled to collect crystals. And a method for purifying the same.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The purification method of the present invention comprises dibenzylidene sorbitol, di (p-methylbenzylidene) sorbitol, di (p-ethylbenzylidene) sorbitol, di (3,4-dimethylbenzylidene) sorbitol, di (2 , 4-dimethylbenzylidene) sorbitol and the like.

The crude di (alkylbenzylidene) sorbitol used in the purification method of the present invention is prepared in a hydrophobic organic solvent such as cyclohexane in the presence of an acid catalyst such as p-toluenesulfonic acid and a lower aliphatic alcohol such as methanol. After dehydrating and condensing the aromatic aldehyde and sorbitol with, the reaction mixture is made weakly alkaline at about pH 7 to 9, and then the reaction mixture is filtered by a conventional method, and the residue is washed with water.
It can be manufactured by drying.

The purity of the crude di (alkylbenzylidene) sorbitol used in the purification method of the present invention is from 80 to 98.
A range of weight% is preferred.

In the purification method of the present invention, the crude di (alkylbenzylidene) sorbitol is heated and dissolved in a lower aliphatic alcohol aqueous solution, lower aliphatic nitrile aqueous solution or lower aliphatic ketone aqueous solution. By cooling this solution, crystals of di (alkylbenzylidene) sorbitol are crystallized. The crystallized crystals are filtered, sufficiently washed with a lower aliphatic alcohol aqueous solution, a lower aliphatic nitrile aqueous solution or a lower aliphatic ketone aqueous solution, and then dried under vacuum.
Thus, di (alkylbenzylidene) sorbitol having an impurity amount of 0.1% by weight or less is obtained.

The lower aliphatic alcohol used in the purification method of the present invention includes, for example, methanol, ethanol, n
-Propyl alcohol, isopropyl alcohol, n-
Butyl alcohol, isobutyl alcohol,
Among these, methanol and ethanol are particularly preferred.

The lower aliphatic nitrile used in the purification method of the present invention includes, for example, acetonitrile, propionitrile, n-butyronitrile and isobutyronitrile, and among these, acetonitrile is particularly preferred.

The lower aliphatic ketone used in the purification method of the present invention includes, for example, acetone, methyl ethyl ketone,
Examples thereof include n-propyl methyl ketone and isopropyl methyl ketone, and among them, acetone and methyl ethyl ketone are particularly preferable.

Among these lower aliphatic alcohols, lower aliphatic nitriles and lower aliphatic ketones used in the purification method of the present invention, lower aliphatic nitriles are particularly preferred.

The water content of the lower aliphatic alcohol aqueous solution, lower aliphatic nitrile aqueous solution and lower aliphatic ketone aqueous solution used in the present invention is preferably 80% by weight or less, and 10 to 6% by weight.
A range of 0% by weight is particularly preferred.

The amount of the aqueous solution of lower aliphatic alcohol, aqueous solution of lower aliphatic nitrile, and aqueous solution of lower aliphatic ketone used in the present invention is 500 to 3000 parts by weight based on 100 parts by weight of crude di (alkylbenzylidene) sorbitol. A range is preferred.

The temperature at which the crude di (alkylbenzylidene) sorbitol is dissolved in the lower aliphatic alcohol aqueous solution, lower aliphatic nitrile aqueous solution, or lower aliphatic ketone aqueous solution used in the present invention is in the range of 50 ° C to 160 ° C. The range of 70 ° C to 130 ° C is particularly preferred.

The pressure at which crude di (alkylbenzylidene) sorbitol is dissolved in the aqueous solution of lower aliphatic alcohol, aqueous solution of lower aliphatic nitrile, or aqueous solution of lower aliphatic ketone used in the present invention is normal pressure to 10 kg / cm ² gauge. A pressure range is preferred.

[0020]

The present invention will be specifically described below with reference to examples and comparative examples. In the following Examples and Comparative Examples, “%” represents “% by weight”.

Example 1 In a 1000 ml reactor equipped with a stirrer, thermometer, cooler and water separator, cyclohexane 600 g, methanol 100 g, powdered sorbitol 32.8 g (0.18 mol), p -After charging 43.2 g (0.36 mol) of tolualdehyde and 1.0 g of p-toluenesulfonic acid, the content was heated to reflux temperature, and while heating and refluxing for 10 hours, distilled methanol and produced water were removed. It was withdrawn into a 300 ml receiver. After completion of the reaction, the reaction mixture was cooled, and the pH of the reaction mixture was adjusted to 7.5 by adding a 1% aqueous sodium hydrogen carbonate solution.
The contents were filtered, the residue was washed with water and dried to give crude di (p-methylbenzylidene) sorbitol. As a result of analysis, the purity of the crude product was 92%, and the tri (p-
Methylbenzylidene) sorbitol 0.9%, mono (p
-Methylbenzylidene) sorbitol 5.6%, p-tolualdehyde 1.0%.

Capacity 2 equipped with stirrer, thermometer and pressure gauge
800.0 g of methanol in a 000 ml pressurized reaction vessel
After charging 160.0 g of ion-exchanged water, the crude di (p-methylbenzylidene) sorbitol having a purity of 92% obtained above was added. After stirring the content at room temperature, the content is heated in a sealed state, the temperature of the content is increased to 120 ° C., and stirring is continued at the same temperature for 1 hour to dissolve all the solids. Was crystallized.

After cooling the content to room temperature, the crystallized crystals were collected by filtration and dried in vacuo to obtain 56.
1 g of a white powder was obtained. This was analyzed by gas chromatography to find that 99.9% of di (p-methylbenzylidene) sorbitol, 0.01% of tri (p-methylbenzylidene) sorbitol, 0.03% of mono (p-methylbenzylidene) sorbitol, 12 pp for tolaldehyde
m.

Example 2 In a 1000 ml reactor equipped with a stirrer, thermometer, cooler and water separator, cyclohexane 600 g, methanol 100 g, powdered sorbitol 32.8 g (0.18 mol), benzaldehyde After charging 38.2 g (0.36 mol) and 1.0 g of p-toluenesulfonic acid, the content was heated to reflux temperature, and while heating and refluxing for 10 hours, 300 ml of distilled methanol and produced water were received. I pulled it out of the bowl. After the reaction,
After cooling the reaction mixture and adding 1% aqueous sodium hydrogen carbonate solution to adjust the pH of the content to 7.3, the content was filtered, the residue was washed with water and dried to remove crude dibenzylidene sorbitol. Obtained. As a result of analysis, the purity of the crude product was 94%, and tribenzylidene sorbitol 0.1% was obtained.
It contained 5%, 4.3% monobenzylidene sorbitol and 0.5% benzaldehyde.

Acetonitrile 80 was added to a 2000 ml reaction flask equipped with a stirrer, thermometer and reflux condenser.
After charging 0.0 g and ion-exchanged water 160.0 g,
The crude dibenzylidene sorbitol of 94% purity obtained above was added. After stirring the contents at room temperature, the temperature of the contents was increased to 80 ° C. by heating, and stirring was continued at the same temperature for 1 hour to dissolve all the solids. I let it.

After cooling the content to room temperature, the crystallized crystals were collected by filtration and dried in vacuo to form 52.
6 g of a white powder were obtained. As a result of analyzing this by gas chromatography, dibenzylidene sorbitol 99.9%,
Tribenzylidene sorbitol 0.01%, monobenzylidene sorbitol 0.03%, benzaldehyde 1
It was 0 ppm.

Example 3 600 g of cyclohexane, 100 g of methanol, 32.8 g (0.18 mol) of powdery sorbitol, p-type sorbitol were placed in a 1000 ml-capacity reaction vessel equipped with a stirrer, thermometer, cooler and water separator. -After charging 43.2 g (0.36 mol) of tolualdehyde and 1.0 g of p-toluenesulfonic acid, the content was heated to reflux temperature, and while heating and refluxing for 10 hours, distilled methanol and produced water were removed. It was withdrawn into a 300 ml receiver. After the completion of the reaction, the mixture was cooled, and the pH of the content was adjusted to 7.1 by adding a 1% aqueous solution of potassium hydrogen carbonate. Then, the content was filtered, the residue was washed with water, dried, and the crude di ( (p-Methylbenzylidene) sorbitol was obtained. As a result of analysis, the purity of the crude product was 92%, and 0.6% of tri (p-methylbenzylidene) sorbitol, 6.2% of mono (p-methylbenzylidene) sorbitol and 0.4% of p-tolualdehyde were used. Included.

Volume 2 equipped with stirrer, thermometer and pressure gauge
Acetonitrile 800.000 ml.
After charging 0 g and 160.0 g of ion-exchanged water, the crude di (p-methylbenzylidene) sorbitol having a purity of 92% obtained above was added. After stirring the contents at room temperature, the contents are heated in a sealed state, the temperature of the contents is increased to 120 ° C,
After stirring was continued for 1 hour at the same temperature to dissolve all the solids, crystals were crystallized while gradually cooling.

After cooling the content to room temperature, the crystallized crystals are filtered and dried under vacuum to obtain 55.
7 g of a white powder were obtained. This was analyzed by gas chromatography to find that 99.9% of di (p-methylbenzylidene) sorbitol, 0.01% of tri (p-methylbenzylidene) sorbitol, 0.03% of mono (p-methylbenzylidene) sorbitol, 15 pp for tolaldehyde
m.

Example 4 A 1000 ml pressurized reaction vessel equipped with a stirrer, a thermometer and a pressure gauge was charged with 500.0 g of ethanol and 150.0 g of ion-exchanged water. To this was added 93% pure di (p-methyl) containing 0.6% tri (p-methylbenzylidene) sorbitol, 4.9% mono (p-methylbenzylidene) sorbitol and 0.6% p-tolualdehyde. After adding 25.0 g of benzylidene) sorbitol dry powder and stirring at room temperature, the pH of the content was measured to be 6.2.
Add 1% aqueous potassium carbonate solution to the contents and p
After adjusting H to 7.5, the temperature of the content was increased to 130 ° C. by heating under airtightness, and stirring was continued for 1 hour at the same temperature to dissolve all the solids. Was crystallized.

After cooling the content to room temperature, the crystallized crystals were filtered and dried under vacuum to obtain 22.
6 g of a white powder were obtained. This was analyzed by gas chromatography to find that 99.9% of di (p-methylbenzylidene) sorbitol, 0.01% of tri (p-methylbenzylidene) sorbitol, 0.03% of mono (p-methylbenzylidene) sorbitol, Tolualdehyde is 21pp
m.

Example 5 In a 1000 ml reactor equipped with a stirrer, thermometer, cooler and water separator, cyclohexane 600 g, methanol 100 g, powdered sorbitol 32.8 g (0.18 mol), p -After charging 43.2 g (0.36 mol) of tolualdehyde and 1.0 g of p-toluenesulfonic acid, the content was heated to reflux temperature, and while heating and refluxing for 10 hours, distilled methanol and produced water were removed. It was withdrawn into a 300 ml receiver. After completion of the reaction, the reaction mixture was cooled, and the pH of the reaction mixture was adjusted to 7.5 by adding a 1% aqueous sodium hydrogen carbonate solution.
The contents were filtered, the residue was washed with water and dried to give crude di (p-methylbenzylidene) sorbitol. As a result of analysis, the purity of the crude product was 93%, and
Methylbenzylidene) sorbitol 1.1%, mono (p
-Methylbenzylidene) sorbitol 4.5% and p-tolualdehyde 0.5%.

Capacity 2 equipped with stirrer, thermometer and pressure gauge
In a 000 ml pressurized reaction vessel, propionitrile 120
After charging 0.0 g and 300.0 g of ion-exchanged water,
25.0 g of the crude powder of di (p-methylbenzylidene) sorbitol having a purity of 93% obtained above was added. After stirring the contents at room temperature, the contents are heated in a sealed state, the temperature of the contents is increased to 130 ° C., and stirring is continued at the same temperature for 1 hour to dissolve all the solids. Was crystallized.

After cooling the content to room temperature, the crystallized crystals were collected by filtration and dried in vacuo to obtain 21.
8 g of a white powder was obtained. This was analyzed by gas chromatography to find that 99.9% of di (p-methylbenzylidene) sorbitol, 0.01% of tri (p-methylbenzylidene) sorbitol, 0.03% of mono (p-methylbenzylidene) sorbitol, 12 pp for tolaldehyde
m.

Example 6 In a 1000 ml reactor equipped with a stirrer, thermometer, cooler and water separator, cyclohexane 600 g, methanol 100 g, powdered sorbitol 32.8 g (0.18 mol), benzaldehyde After charging 38.2 g (0.36 mol) and 1.0 g of p-toluenesulfonic acid, the content was heated to reflux temperature, and while heating and refluxing for 10 hours, 300 ml of distilled methanol and produced water were received. I pulled it out of the bowl. After the reaction,
After the reaction mixture was cooled and the pH of the reaction mixture was adjusted to 7.9 by adding 1% aqueous sodium carbonate solution, the contents were filtered, the residue was washed with water and dried to obtain crude dibenzylidene sorbitol. Was. As a result of analysis, the purity of the crude product was 93%, and tribenzylidene sorbitol 1.
It contained 1%, 4.5% monobenzylidene sorbitol and 0.5% benzaldehyde.

Volume 2 equipped with stirrer, thermometer and pressure gauge
Methyl ethyl ketone 10
After charging 00.0 g and ion-exchanged water 400.0 g, 25.0 g of the crude dibenzylidene sorbitol dry powder having a purity of 93% obtained above was added. After stirring the contents at room temperature, the contents were heated in a sealed state and the temperature of the contents was reduced to 120.
C., stirring was continued at the same temperature for 1 hour to dissolve all the solids, and then crystals were crystallized while gradually cooling.

After cooling the content to room temperature, the crystallized crystals were collected by filtration and dried in vacuo to obtain 21.
1 g of a white powder was obtained. As a result of analyzing this by gas chromatography, dibenzylidene sorbitol 99.9%,
Tribenzylidene sorbitol 0.01%, monobenzylidene sorbitol 0.02%, benzaldehyde 1
It was 2 ppm.

Example 7 500.0 g of n-butyronitrile and 150.0 g of ion-exchanged water were charged into a 1000 ml pressurized reaction vessel equipped with a stirrer, a thermometer and a pressure gauge. To this, tribenzylidene sorbitol 0.1.
After adding 15.0 g of a crude dibenzylidene sorbitol dry powder having a purity of 92% containing 9%, monobenzylidene sorbitol 5.6% and benzaldehyde 0.8%, and stirring at room temperature, the pH of the content was measured. 5.6
Met. After adjusting the pH of the content to 7.5 by adding a 1% aqueous sodium hydroxide solution to the content, the content is heated in a sealed state, the temperature of the content is increased to 130 ° C., and stirring is continued at the same temperature for 1 hour. After dissolving the entire amount of the solid by heating, crystals were crystallized while gradually cooling.

After the content was cooled to room temperature, the crystallized crystals were collected by filtration and dried under vacuum.
6 g of a white powder were obtained. As a result of analyzing this by gas chromatography, dibenzylidene sorbitol 99.9%,
Tribenzylidene sorbitol 0.01%, monobenzylidene sorbitol 0.01%, benzaldehyde 1
It was 7 ppm.

Example 8 A 1000 ml pressurized reaction vessel equipped with a stirrer, a thermometer and a pressure gauge was charged with 600.0 g of acetonitrile and 100.0 g of ion-exchanged water. To this, 4.1% tri (p-ethylbenzylidene) sorbitol, 3.8% mono (p-ethylbenzylidene) sorbitol and 0.1% p-ethylbenzaldehyde.
After adding 15.0 g of crude di (p-ethylbenzylidene) sorbitol dry powder having a purity of 91% containing 7% and stirring at room temperature, the pH of the content was measured to be 5.6.
Met. After adjusting the pH of the content to 7.5 by adding a 1% aqueous sodium hydroxide solution to the content, the content is heated in a sealed state, the temperature of the content is increased to 130 ° C., and stirring is continued at the same temperature for 1 hour. After dissolving the entire amount of the solid, the crystals were crystallized while gradually cooling.

After cooling the content to room temperature, the crystallized crystals were collected by filtration and dried under vacuum to obtain 12.
4 g of a white powder were obtained. As a result of gas chromatographic analysis, 99.9% of di (p-ethylbenzylidene) sorbitol, 0.01% of tri (p-ethylbenzylidene) sorbitol, 0.03% of mono (p-ethylbenzylidene) sorbitol, Ethylbenzaldehyde was 19 ppm.

Example 9 A 1000 ml pressurized reaction vessel equipped with a stirrer, a thermometer and a pressure gauge was charged with 600.0 g of acetonitrile and 100.0 g of ion-exchanged water. In addition, tri (3,5-dimethylbenzylidene)
Crude di (3,5-dimethylbenzylidene) sorbitol dry powder of 94% purity containing sorbitol 3.1%, mono (3,5-dimethylbenzylidene) sorbitol 1.6% and 3,5-dimethylbenzaldehyde 0.9% 15.0 g was added, and the mixture was stirred at room temperature.
When H was measured, it was 6.0. After adjusting the pH of the content to 8.1 by adding a 1% aqueous sodium hydroxide solution to the content, the content is heated in a sealed state, and the temperature of the content is increased to 130 ° C.
After stirring at the same temperature for 1 hour to dissolve all the solids, the crystals were crystallized while gradually cooling.

After cooling the content to room temperature, the crystallized crystals were collected by filtration and dried in vacuo to obtain 13.
0 g of a white powder was obtained. This was analyzed by gas chromatography, and as a result, di (3,5-dimethylbenzylidene) sorbitol 99.9%, tri (3,5-dimethylbenzylidene) sorbitol 0.01%, mono (3,5-dimethylbenzylidene) sorbitol 0 0.04% and 3,5-dimethylbenzaldehyde were 23 ppm.

Comparative Example 1 540.0 g of methyl alcohol was charged into a 1000-ml reaction flask equipped with a stirrer, a thermometer, and a reflux condenser. 60.0 g of crude 95% pure dibenzylidene sorbitol dry powder containing 0.8% tribenzylidene sorbitol, 2.6% monobenzylidene sorbitol and 1.0% benzaldehyde was added thereto, and the temperature of the content was lowered. Heat to 65 ° C. and boil slightly. Further, after stirring at the same temperature for 1 hour, the content was filtered at 60 ° C., the residue obtained by filtration was washed with methanol, and then dried under vacuum to obtain 57.1 g of a white powder. As a result of analysis by gas chromatography, dibenzylidene sorbitol was 97.5%, tribenzylidene sorbitol was 0.6%, monobenzylidene sorbitol was 1.3%, and benzaldehyde was 0.5%.

Comparative Example 2 29.2 g (0.16 mol) of sorbitol and 38.4 (0.32 mol) of p-tolualdehyde were placed in a 1000-ml reaction flask equipped with a stirrer, thermometer and reflux condenser. ) After charging 560 g of cyclohexane and 1.0 g of p-toluenesulfonic acid, the mixture was heated until the cyclohexane was refluxed under stirring, and then heated at the same temperature for 6 hours.
While reacting for an hour, generated water was separated by a water separator and extracted to a receiver. Next, the content was filtered, the residue collected by filtration was washed with water, and the obtained wet cake was sufficiently washed with 2% sodium hydrogen carbonate. As a result of the analysis, the purity of the crude di (p-methylbenzylidene) sorbitol from which water was removed was 90%, tri (p-methylbenzylidene) sorbitol 1.1%, and mono (p-methylbenzylidene) sorbitol.
It contained 6.0% sorbitol and 1.6% p-tolualdehyde.

480.0 g of methyl ethyl ketone was charged into a 1000 ml-capacity reaction flask equipped with a stirrer, a thermometer and a reflux condenser, and the above-obtained crude 90% pure di (p-methylbenzylidene) sorbitol was added thereto. The mixture was stirred at room temperature. The content was heated to the boiling point of methyl ethyl ketone and kept at the same temperature for 1 hour, then the content was cooled to room temperature, the content was filtered, the residue collected was washed with methyl eyl ketone, and dried in vacuo. 57.
0 g of a white powder was obtained. As a result of gas chromatographic analysis, 94.1% of di (p-methylbenzylidene) sorbitol, 1.0% of tri (p-methylbenzylidene) sorbitol, 3.5% of mono (p-methylbenzylidene) sorbitol, 3.5% of p-methyl Tolualdehyde was 1.0%.

[0047]

According to the purification method of the present invention, the amount of impurities such as mono (alkylbenzylidene) sorbitol, tri (alkylbenzylidene) sorbitol, aromatic aldehyde, and hydrophobic organic solvent is 2.0% of that of the conventional method. % To less than 0.10% by weight, which is 1/10 of the conventional method.
It can be reduced to:

Claims (3)

[Claims] A crude di (alkylbenzylidene) sorbitol obtained by dehydrating and condensing an aromatic aldehyde with sorbitol in a hydrophobic organic solvent in the presence of an acid catalyst and a lower aliphatic alcohol, is used as an aqueous solution of lower aliphatic alcohol. A method for purifying di (alkylbenzylidene) sorbitol, comprising heating and dissolving in an aqueous solution of lower aliphatic nitrile or aqueous solution of lower aliphatic ketone, cooling, and collecting crystals that crystallize. 2. A crude di (alkylbenzylidene) sorbitol obtained by dehydrating an aromatic aldehyde and sorbitol in the presence of an acid catalyst and a lower aliphatic alcohol in a hydrophobic organic solvent to obtain a lower aliphatic nitrile aqueous solution. A method for purifying di (alkylbenzylidene) sorbitol, comprising heating and dissolving the solution therein, cooling the solution, and collecting crystals. 3. The method for purifying di (alkylbenzylidene) sorbitol according to claim 1, wherein the aromatic aldehyde is benzaldehyde or p-tolualdehyde.