JP2010037278A - Method for producing dibenzylidene alditol - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a practical method for stably producing high-purity dibenzylidene alditols by an easily controllable reaction and enabling recycled use of the reaction liquid. <P>SOLUTION: The method for producing dibenzylidene alditols comprises condensation reaction of an aromatic aldehyde with alditol in an aqueous medium in the presence of an acid catalyst and neutralization of the reaction liquid to obtain dibenzylidene alditols. In the production method, a compatibilizer for the aromatic aldehyde and the alditol is added to the aqueous medium in an amount of 3-7 times weight based on the aromatic aldehyde. The production method enables easy recovery of the reaction liquid and recycled use of the reaction liquid. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing dibenzylidene alditols such as dibenzylidene sorbitol, which is used as a gelling agent for organic liquids, a transparent nucleating agent for polyolefins, and the like, and in particular, a method for producing water when using water as a solvent. About.

  Dibenzylidene alditols such as dibenzylidene sorbitol obtained by reacting aromatic aldehydes such as benzaldehyde and alditols such as sorbitol in the presence of an acid catalyst are organic liquid gelling agents and transparent nuclei of polyolefins. It is useful as an agent, a thickener for paints, and the like, and conventionally, there are two types of production methods based on the properties of the reaction medium.

  One is a production method called an “solvent method” using an organic solvent as a solvent, and the other is a production method called a “water method” using a water as a solvent.

  For example, Patent Document 1 discloses a solvent method using one or more organic solvents of cyclohexane and a saturated hydrocarbon having 6 to 10 carbon atoms as a reaction solvent, and Patent Document 2 discloses a mixed solvent of cyclohexane and hexane. As a solvent method using the above as a reaction solvent, Patent Document 3 describes a solvent method using a mixed solvent of cyclohexane and methanol.

  As described above, the solvent method uses cyclohexane as the main solvent. However, it is necessary to remove a large amount of the solvent and to remove the generated water because it is a condensation reaction. The azeotropic point of water and cyclohexane is 70 to 80. It is disadvantageous in terms of cost because it is necessary to react at a temperature of 0 ° C., which requires high risk and requires equipment for dealing with specific hazardous materials, and further requires equipment for recovering the solvent by distillation. Moreover, since cyclohexane has almost no odor at low concentrations, symptoms such as headache occur when inhaled without being aware of it, and there is a concern about the influence on the human body.

On the other hand, the manufacturing method called the water method is highly safe because it does not use a large amount of dangerous goods.
There is an advantage that the product can be produced without taking out the produced water out of the reaction system because the product dibenzylidene alditols are not dissolved in water and are precipitated without being affected by the human body. However, as a disadvantage, since it is carried out in an aqueous reaction medium in which an aromatic aldehyde that is hardly soluble in water and an aqueous alditol solution are heterogeneously mixed, there is a problem that the reaction solution is easily gelled. It is difficult to obtain high-purity dibenzylidene alditols.

  For example, Patent Document 4 discloses a two-stage reaction in which a reaction medium is diluted as a second stage after the gel characteristics are expressed in the first stage of the reaction, and then a water method in which an aging process is provided. However, the yield of the dibenzylidene sorbitol produced is 55% immediately after the reaction, 70% after the aging, the purity is limited to 90%, and the process is too complicated to be practical.

  Patent Document 5 discloses a water method of a one-step reaction, but there is no description of a solution for gelation, the yield is shown by the mass ratio of diacetal to the mass of alditol used, and the purity is also diacetal. And the mass ratio of diacetal to the total mass of triacetal. Based on Example 4 described in this document in which benzaldehyde and sorbitol are reacted with p-toluenesulfonic acid, the present inventors have confirmed by a manufacturing method trace experiment that the disclosed reaction time is 5.5 hours. Gelled. The yield of the product was 55%, and the purity of dibenzylidene sorbitol by HPLC (manufactured by Shimadzu Corporation, high performance liquid chromatography) analysis was as low as 77.6%.

  In Patent Document 6, on the premise that the reaction medium is gelled, stirring is performed by vigorous forced stirring under the condition that the reaction is performed in a reaction system in which the theoretical amount of the generated diacetals is in the range of 15 to 50% by weight. Although a continuous water method is disclosed, this production method is practically a two-stage reaction under the above conditions, and requires a special stirrer having a ribbon blade, which is not practical because it requires high energy costs. Although 90% yield and purity of 95% or more of dibenzylidene sorbitol and the like are described, there is no description of their measuring method, and therefore their specific meaning is unknown.

Japanese Patent Publication No. 48-43748 Japanese Patent Laid-Open No. 9-12579 JP-A-10-204089 Japanese Patent Publication No. 61-17833 JP-A 63-267777 JP 2001-131183 A

  As described above, the water method has a strong tendency to gel the reaction solution, so that a practical production method can be provided which can stably produce high-purity dibenzylidene alditols and can be used for recycling the reaction solution. The current situation is not.

  Therefore, an object of the present invention is to provide a method for producing dibenzylidene alditols by condensing an aromatic aldehyde and an alditol in an aqueous medium in the presence of an acid catalyst, wherein the reaction control is simple and stable. Another object of the present invention is to provide a practical production method in which high-purity dibenzylidene alditols can be produced and the reaction solution can be used for recycling.

  In order to solve the above problems, the present inventors made the following inference. That is, as described in detail in Example 4 in Patent Document 5, "728 g of sorbitol aqueous solution containing 25% dry matter (1 mol), 215 g (1.25 mol) of paratoluenesulfonic acid and 190.8 g of benzaldehyde. (1.8 mol) while stirring, at the time of tracing the production method of reacting at 30 ° C. for 5 hours and 30 minutes ”, waxy material adheres to the bottom of the stirring blade or flask in about 1 to 2 hours after the start of the reaction. However, after 5.5 hours, it was felt that the wax-like substances gathered and gelled. As a result of HPLC analysis of the waxy material, the relatively soft surface layer portion was 26% dibenzylidene sorbitol and 44% benzaldehyde, and the waxy and hard inner layer portion was 0.4% dibenzylidene sorbitol and 96% benzaldehyde. .

  This analysis result suggests that when the reaction solution is stirred, benzaldehyde becomes large oil droplets, but the reaction proceeds from the surface layer portion of these oil droplets. Therefore, it was considered that gelation could be prevented if the oil droplets of benzaldehyde were made as fine as possible or made into a completely dissolved reaction solution.

  As a result of repeated research, the present inventors have found that if a certain amount of alcohol solvent and / or cellosolve solvent is added to the aqueous medium, a reaction solution in which benzaldehyde is completely dissolved, not oil droplets, can be obtained. I found.

  Therefore, when a certain amount of alcohol solvent and / or cellosolve solvent is added as a compatibilizing agent to an aqueous medium containing an aromatic aldehyde and alditol in the presence of an acid catalyst, it is hardly soluble in water. Although the reaction solution is completely dissolved in the aromatic aldehyde, this reaction solution is surprisingly capable of preventing gelation without causing gelation even when reacted up to 192 hours. As a result, high-purity dibenzylidene The inventors have found that sorbitols can be obtained, and have completed the present invention as a practical production method. In addition, since the gelation can be prevented, the acid catalyst contained in the mother liquor is recovered in an active state by filtering the product and recovering the unneutralized mother liquor. If the reaction liquid is adjusted by replenishing the raw materials contained outside the system, it can be recycled repeatedly.

  That is, the invention according to claim 1 is a dibenzylidene which obtains dibenzylidene alditols by subjecting an aromatic aldehyde and alditol to a condensation reaction in an aqueous medium in the presence of an acid catalyst and then neutralizing the reaction solution. In the method for producing alditols, in the aqueous medium, the compatibilizer of the aromatic aldehyde and the alditol is blended in an amount 3 to 7 times by weight with respect to the blended amount of the aromatic aldehyde. This is a method for producing dibenzylidene alditols represented by the following general formula (1).

（式中，Ｒ¹及びＲ²は、同一又は異なって、水素原子、炭素原子数１〜４のアルキル基または炭素原子数１〜３のアルコキシル基を表す。Ｘ及びＹは、同一又は異なって、１〜５を示し、ｎは0又は１を示す。）

Wherein R ¹ and R ² are the same or different and each represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms or an alkoxyl group having 1 to 3 carbon atoms. X and Y are the same or different. 1 to 5 and n represents 0 or 1.)

  The invention according to claim 2 is characterized in that the compatibilizer is at least one alcohol solvent selected from methanol, ethanol, isopropanol, and 1-propanol, and / or at least selected from methyl cellosolve, ethyl cellosolve, and butyl cellosolve. The method for producing dibenzylidene alditols according to claim 1, which is a cellosolve-type solvent, and the invention according to claim 3 is characterized in that the dibenzylidene alditols produced before the neutralization are produced. The mother liquor is recovered by filtration, and the condensation reaction is repeatedly performed using an aromatic aldehyde, alditol, acid catalyst, compatibilizing agent, etc. contained in the mother liquor, and then used for recycling. 2. The method for producing dibenzylidene alditols according to 2.

（式中，Ｒ¹は、水素原子、炭素原子数１〜４のアルキル基または炭素原子数１〜３のアルコキシル基を表し、Ｘは１〜５を示す。）
で表されるものであるが、好ましくは炭素数１〜４のアルキル基を有するアルキルベンズアルデヒドを用いるとよい。具体的には、ベンズアルデヒド、o−トルアルデヒド、m−トルアルデヒド、p−トルアルデヒド、o−エチルベンズアルデヒド、m−エチルベンズアルデヒド、p−エチルベンズアルデヒド、２，３−ジメチルベンズアルデヒド、２，4−ジメチルベンズアルデヒド、２，５−ジメチルベンズアルデヒド、３，４−ジメチルベンズアルデヒド、３，５−ジメチルベンズアルデヒド、２，４，５−トリメチルベンズアルデヒド等が例示される。芳香族アルデヒドの配合割合は、アルジトール１モルに対して１．５〜１．９モルにするのが好ましく、より好ましくは１．７〜１．８モルである。１．５モル未満では収率が低下し、１．９モルを超えるとトリベンジリデンアルジトール類（トリアセタール体）が増え、純度が低下する傾向にあるからである。 As an aromatic aldehyde used by this invention, general formula (2)

(In the formula, R ¹ represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an alkoxyl group having 1 to 3 carbon atoms, and X represents 1 to 5).
However, it is preferable to use an alkylbenzaldehyde having an alkyl group having 1 to 4 carbon atoms. Specifically, benzaldehyde, o-tolualdehyde, m-tolualdehyde, p-tolualdehyde, o-ethylbenzaldehyde, m-ethylbenzaldehyde, p-ethylbenzaldehyde, 2,3-dimethylbenzaldehyde, 2,4-dimethylbenzaldehyde 2,5-dimethylbenzaldehyde, 3,4-dimethylbenzaldehyde, 3,5-dimethylbenzaldehyde, 2,4,5-trimethylbenzaldehyde and the like. The blending ratio of the aromatic aldehyde is preferably 1.5 to 1.9 mol, more preferably 1.7 to 1.8 mol with respect to 1 mol of alditol. If the amount is less than 1.5 mol, the yield decreases, and if it exceeds 1.9 mol, tribenzylidene alditols (triacetal form) increase and the purity tends to decrease.

  The alditol used in the present invention is sorbitol or xylitol. A preferable concentration of the alditol aqueous solution is 30% or less, more preferably 15 to 25%, in order to allow the reaction to proceed gradually and reliably.

  The compatibilizer used in the present invention refers to a solvent that homogenizes the aromatic aldehyde and the alditol in an aqueous medium, and is not particularly limited as long as it contributes to the object of the present invention. It is preferable to use a solvent and / or a cellosolve solvent. Specifically, as in the invention of claim 2, at least one alcohol solvent selected from methanol, ethanol, isopropanol, 1-propanol, and / or It is preferable to use at least one cellosolve solvent selected from methyl cellosolve, ethyl cellosolve, and butyl cellosolve.

  A preferable blending ratio of the alcohol solvent and / or cellolb solvent as the compatibilizer is 3 to 7 times by weight with respect to the weight of the aromatic aldehyde, more preferably 3. 5 to 5.0 times the amount. If the amount is less than 3 times, turbidity remains in the reaction solution and the compatibility is insufficient. If the amount exceeds 7 times, the reaction becomes extremely slow, the safety becomes disadvantageous, and the cost becomes too high.

  A preferred example of the method for producing dibenzylidene alditols represented by the general formula (1) according to the present invention is an aromatic aldehyde of the general formula (2) in an aqueous medium in the presence of an acid catalyst. Are mixed with an aqueous solution of sorbitol or xylitol and the compatibilizer in an amount of 3 to 7 times by weight with respect to the blended amount of the aromatic aldehyde, and condensed at a temperature of about 30 ° C. for a predetermined time. Dibenzylidene alditols are produced by the reaction, and after neutralizing the reaction solution, the product can be obtained through the steps of filtration, washing with water, and drying. In this case, since the reaction solution before neutralization does not gel even when the condensation reaction reaches a state where it does not proceed any more, the aromatic aldehyde, alditol, acid catalyst contained in the reaction solution as in the invention of claim 3 The condensation reaction can be repeatedly performed using a compatibilizing agent and the like, and can be used for recycling.

  In the production method of the present invention, as described above, an aromatic aldehyde and alditol are condensed in an aqueous medium in the presence of an acid catalyst, and then the reaction solution is neutralized to obtain dibenzylidene alditols. In the method for producing the obtained dibenzylidene alditols, an alcohol-based solvent and / or a cellosolve-based solvent or the like is blended as a compatibilizing agent for an aromatic aldehyde that is hardly soluble in water and an alditol that is easily soluble in water. It is a practical production method that can be produced only by ordinary stirring without gelation of the reaction solution, and that can produce dibenzylidene alditols of very simple and stable high purity. It is also a production method that can be recycled by collecting the reaction solution before neutralization. The produced dibenzylidene alditols are useful as organic liquid gelling agents, polyolefin transparent nucleating agents, paint thickeners, and the like because high purity products can be obtained.

(1) aromatic aldehydes as benzaldehyde, p-tolualdehyde, p-ethylbenzaldehyde, 3,4-dimethylbenzaldehyde or 2,4-dimethylbenzaldehyde; (2) alditol as sorbitol or xylitol; and (3) acid. Examples of the catalyst include p-toluenesulfonic acid, benzenesulfonic acid, naphthalenesulfonic acid, dodecylbenzenesulfonic acid, sulfuric acid or hydrochloric acid, (3) water, and (4) compatibilizers such as methanol, ethanol, isopropanol, 1 -Using one or more of propanol, methyl cellosolve, ethyl cellosolve or butyl cellosolve,
(1) is 1.5 to 1.9 moles per mole of (2),
(4) is 3 to 7 times the weight ratio of (1),
(1) to (4) may be respectively charged into a reaction vessel, and the reaction temperature may be maintained at 30 ± 2 ° C. while stirring at a rotational speed of 500 to 700 rpm, and the reaction may be performed for a predetermined time.

  In this case, the reaction solution reaches equilibrium without gelation, and the reaction does not proceed any further, so that the wet product is filtered and separated from the mother liquor, neutralized, washed with water and dried. Dibenzylidene sorbitol or dibenzylidene xylitol, di (p-methylbenzylidene) sorbitol or di (p-methylbenzylidene) xylitol, di (p-ethylbenzylidene) sorbitol or di (p-ethylbenzylidene) xylitol, di (3,4 -Product (powder) of dimethylbenzylidene) sorbitol or di (3,4-dimethylbenzylidene) xylitol, di (2,4-dimethylbenzylidene) sorbitol or di (2,4-dimethylbenzylidene) xylitol is about 50% or more. Yield (actual yield relative to theoretical yield) Obtained by the ratio).

  Then, the unneutralized mother liquor can be easily supplied to the recycle reaction by supplementing the reaction components corresponding to the amount removed as a wet product.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

  Benzaldehyde or p-tolualdehyde is used as aromatic aldehyde, sorbitol is commonly used as alditol, p-toluenesulfonic acid monohydrate is commonly used as catalyst, and methanol or ethyl cellosolve is used as compatibilizer. In Comparative Examples 1 and 2 in which the blending components of Examples 1 to 6 and the compatibilizing agent are not used, those blending components, reaction time, product yield, and purity are summarized in a table. As shown in FIG.

Details of each example and comparative example are described below.
Example 1
A 2L separable flask equipped with a three-motor 600G (manufactured by Shinto Kagaku Co., Ltd.), a general-purpose stirrer, and a bowl-shaped stirring blade, was charged with 234 g of pure water and 130 g (0.5 mol) of 70% sorbitol and rotated. The sorbitol was dissolved by stirring at several 500 rpm. Next, with stirring, 119 g (0.625 mol) of p-toluenesulfonic acid monohydrate was added and dissolved, the gas phase was replaced with nitrogen, the temperature was raised to 30 ° C., and 380 g of methanol (weight ratio) And 4 times the amount of benzaldehyde) was added to obtain a uniform solution. Finally, 95 g (0.9 mol) of benzaldehyde was added to start the reaction. The reaction was carried out at a reaction temperature of 30 ° C. while maintaining the condition of a rotation speed of 500 rpm. After 6 hours, the reaction was in a slurry state, and continued for 24 hours as it was, thereby completing the reaction.

  The liquid state after the reaction for 24 hours was a slurry having a viscosity of 3.3 Pa · s. Subsequently, the reaction liquid was subjected to suction filtration to separate the product and the mother liquor. The product separated by filtration was resuspended in 5 times the amount of water, neutralized with 20% sodium hydroxide solution, heated to 60 ° C. and stirred for 2 hours. The material was washed with warm water at 60 ° C. for 2 hours. Thereafter, the mixture was filtered again with suction, and the product having a wetness of about 67% was dried at 90 ° C. for 12 hours and pulverized to obtain 80.4 g of dibenzylidene sorbitol as a white powder (yield 50.1% based on the theoretical yield). Obtained.

The yield calculation method in this case is as follows.
When benzaldehyde is BA, sorbitol is Sor, dibenzylidene sorbitol is DBS, and molecular weight is shown in parentheses, this reaction formula is
Since 2 × BA (106) + Sor (182) => DBS (358) + 2H ₂ O (18) and the amount of BA charged is 95 g, the theoretical yield of DBS is (95/212) × 358 g = 160.4 g.
However, since the yield of DBS is 80.4 g, the yield with respect to the theoretical yield (hereinafter simply referred to as “yield”) is (80.4 / 160.4) × 100 = 50.1%. The purity of dibenzylidene sorbitol was 97.7% (calculated by area ratio) from a chart (FIG. 1) of HPLC (manufactured by Shimadzu Corporation, high performance liquid chromatography) analysis.

(Example 2)
The reaction was conducted in the same manner as in Example 1 except for the reaction time, and the effect was examined by extending the reaction time from that in Example 1. As shown below, even if the reaction is extended to a maximum of 192 hours, the liquid state after the reaction is a slurry having a viscosity of 3.1 Pa · s and no gelation tendency is observed. It was almost the same as the case of 1.

(Example 3)
A non-neutralized mother liquor 716.8g recovered from Example 1 was charged into a 2 L separable flask equipped with a three-purpose motor 600G (manufactured by Shinto Kagaku Co., Ltd.) and a bowl-shaped stirring blade, and rotated. While stirring at several 500 rpm, 21.9 g of pure water, 71.6 g of 70% sorbitol, and 21.8 g of p-toluenesulfonic acid monohydrate were replenished and dissolved, and then the gas phase was replaced with nitrogen. After the temperature was increased to 69.6 g of methanol, a uniform solution was obtained. Finally, 56.3 g of benzaldehyde was added, and the raw material that had flowed out of the system by filtration of the wet product was replenished. The liquid was adjusted. The reaction was carried out at a reaction temperature of 30 ° C. while maintaining the condition of a rotation speed of 500 rpm. After 6 hours, the reaction was in a slurry state, and continued for 24 hours as it was, thereby completing the reaction.

  The liquid state after the reaction for 24 hours was a slurry having a viscosity of 3.2 Pa · s. The reaction solution was then filtered with suction to separate the product and mother liquor. The product was resuspended in 5 volumes of water, neutralized with 20% sodium hydroxide solution, heated to 60 ° C. and stirred for 2 hours. After filtering the product, the product was again filtered. Washed with warm water at 60 ° C. for 2 hours. Thereafter, the mixture was filtered again with suction, and the product having a wetness of about 67% was dried at 90 ° C. for 12 hours and pulverized to obtain 82.6 g (yield 51.5%) of white powder of dibenzylidene sorbitol.

The replenishment amount of benzaldehyde and the like was calculated as follows using the amount of benzaldehyde and the like contained in the product having a wet rate of 67% removed by filtration as a replenishment amount, and the amount was replenished.
That is,
In the reaction formula of 2 × BA (106) + Sor (182) => DBS (358) + 2H ₂ O (18), in Example 1, the DBS yield was 50% and the wet DBS wet rate was 67%. The solid content weight is 160.4 g × 0.5 = 80.2 g, and the wet weight of 67% DBS is 80.2 × 3 = 240.6 g. Therefore, the residual coefficient of the mother liquor from which the wet DBS was separated by suction filtration was (958 (initial amount) −80.2 × 3 (wet DBS weight)) / (958-80.2 (dry DBS weight)) = 0. 817, and using this, the replenishment amount of each component was calculated as shown in the following table. In the following table, MeOH represents methanol, and PTS represents p-toluenesulfonic acid monohydrate.

  According to HPLC analysis, the purity of dibenzylidene sorbitol was 97.8%. Therefore, the purity and yield of dibenzylidene sorbitol produced by the present recycling method were equivalent to those obtained in Example 1, which is a reaction before recycling.

The total yield when this recycling reaction is repeated for 5 cycles reaches 84% as shown below.
That is, the yield is 50%, the wet DBS wet rate is 67%, and the residual coefficient of the mother liquor from which the wet DBS was separated by suction filtration is 0.817. Since the total yield is 135 g as follows, this is divided by the theoretical yield of DBS of 160.4 g and the yield is calculated to be 84.2%.

First time 160.4g × 0.5 = 80.2g
Recycle 1 80.2g x 0.817 x 0.5 = 32.8g
Recycle 2 32.8g × 0.817 × 0.5 = 13.4g
Recycle 3 13.4g x 0.817 x 0.5 = 5.5g
Recycle 4 5.5g x 0.817 x 0.5 = 2.2g
Recycle 5 2.2g x 0.817 x 0.5 = 0.9g

  The purity of the dibenzylidene sorbitol obtained in Examples 1 to 3 was 97% or more, and the purity of the commercial product of dibenzylidene sorbitol analyzed by the inventors under the same analysis conditions by HPLC, ie, API Corporation. Compared to the EC 9 (trade name) manufactured by Corporation and the gelall D (trade name) manufactured by Shin Nippon Rika Co., Ltd., the purity is 94.9% and the purity is 94.9%, respectively.

Example 4
A 2L separable flask equipped with a three-motor 600G (manufactured by Shinto Kagaku Co., Ltd.), a general-purpose stirrer, and a bowl-shaped stirring blade, was charged with 234 g of pure water and 130 g (0.5 mol) of 70% sorbitol and rotated. The sorbitol was dissolved by stirring at several 500 rpm. Next, with stirring, 119 g (0.625 mol) of p-toluenesulfonic acid monohydrate was added and dissolved, the gas phase was replaced with nitrogen, the temperature was raised to 30 ° C., and 378 g of ethyl cellosolve (weight) In ratio, 3.5 times the amount of p-tolualdehyde) was added to obtain a uniform solution. Finally, 108 g (0.9 mol) of p-tolualdehyde was added to start the reaction. The reaction was carried out at a reaction temperature of 30 ° C. while maintaining the condition of a rotation speed of 500 rpm. After 2 hours, the reaction was in a slurry state and continued for 48 hours as it was before the reaction was terminated.

  The liquid state after the reaction for 48 hours was a slurry having a viscosity of 2.7 Pa · s. The reaction solution was then filtered with suction to separate the product and mother liquor. The product was resuspended in 5 times the amount of water, neutralized with 20% sodium hydroxide solution, heated to 60 ° C. and stirred for 2 hours, the product was filtered off, and the product was filtered again. Washed with warm water at 0 ° C. for 2 hours. Thereafter, the mixture was filtered again with suction, and the product having a wetness of about 67% was dried at 90 ° C. for 12 hours, pulverized, and 117.4 g of a white powder of di (p-methylbenzylidene) sorbitol (yield 67.6%). )

  According to HPLC analysis, the purity of di (p-methylbenzylidene) sorbitol was 94.9%. Next, the white powder having a purity of 94.9% was washed in a mixed solvent of water / ethyl cellosolve (weight ratio 40/60) at a concentration of 5% by weight at 60 ° C. for 24 hours, filtered, dried and pulverized. After rewashing, the purity of di (p-methylbenzylidene) sorbitol by HPLC analysis was 98.9%.

(Example 5)
The reaction was conducted in the same manner as in Example 4 except for the reaction time, and the reaction was continued until 167 hours, and then the reaction was terminated. Even if the reaction was continued up to 167 hours, the liquid state after the reaction was a slurry with a viscosity of 2.6 Pa · s, and no gelation tendency was observed. 117.6 g (yield 67.7%) of white powder was obtained. According to HPLC analysis, the purity of di (p-methylbenzylidene) sorbitol was 94.5%.

Example 6
A non-neutralized mother liquor recovered from Example 4 was charged in a 2 L separable flask equipped with a three-motor 600G (manufactured by Shinto Kagaku Co., Ltd.), a general-purpose stirrer, and a bowl-shaped stirring blade, and the rotational speed was 500 rpm. After stirring, the solution was replenished with 39.5 g of pure water, 93.3 g of 70% sorbitol, and 32.9 g of p-toluenesulfonic acid monohydrate, and the gas phase was replaced with nitrogen and the temperature was raised to 30 ° C. After heating, 104.6 g of ethyl cellosolve is replenished to make a uniform solution, and finally 82.7 g of p-tolualdehyde is replenished to replenish the raw materials that have come out of the system by filtration of the wet product. To prepare a reaction solution. The reaction was performed at a reaction temperature of 30 ° C. while maintaining the condition of a rotation speed of 500 rpm. After 3 hours, the reaction was in a slurry state and continued for 48 hours as it was before the reaction was terminated. Note that the replenishment amount of p-tolualdehyde and the like was calculated in the same manner as described in Example 3.

  The liquid state after the reaction for 48 hours was a slurry having a viscosity of 2.8 Pa · s. Subsequently, the reaction liquid was subjected to suction filtration to separate the product and the mother liquor. The product was resuspended in 5 volumes of water, neutralized with 20% sodium hydroxide solution, heated to 60 ° C. and stirred for 2 hours. After filtering the product, the product was again filtered. Washed with warm water at 60 ° C. for 2 hours. Thereafter, the mixture was filtered again with suction, and the product having a wetness of about 67% was dried at 90 ° C. for 12 hours and pulverized to obtain 114.6 g (yield 66.0%) of a white powder. According to HPLC analysis, the purity of di (p-methylbenzylidene) sorbitol was 94.4%. Therefore, the purity and yield of di (p-methylbenzylidene) sorbitol produced by the present recycling method were equivalent to those obtained in Example 4, which is a reaction before recycling. Further, when this recycling reaction is repeated 5 cycles, the total yield reaches 90% when calculated in the same manner as described in Example 3.

  The purity of di (p-methylbenzylidene) sorbitol obtained in Examples 4 to 6 was 94% or higher, and the obtained white powder having a purity of 94% or higher was mixed with water / ethyl cellosolve (weight ratio 40). / 60) in a mixed solvent at a concentration of 5% by weight at 60 ° C. for 24 hours, purified di (p-methylbenzylidene) sorbitol with a purity close to 99% is obtained.

  This is the purity of a commercial product of di (p-methylbenzylidene) sorbitol analyzed by the inventors under the same analysis conditions by HPLC, that is, the purity of Yoshiclear MS (trade name) manufactured by API Corporation 96.6%. Compared to, it is a high purity product.

(Comparative Example 1)
A 1 L separable flask equipped with a general-purpose stirrer Three One Motor 600G (manufactured by Shinto Kagaku Co., Ltd.) and a bowl-shaped stirring blade was charged with 234 g of pure water and 130 g (0.5 mol) of 70% sorbitol and rotated. The sorbitol was dissolved by stirring at several 500 rpm. Next, with stirring, 119 g (0.625 mol) of p-toluenesulfonic acid monohydrate was added and dissolved, the gas phase was replaced with nitrogen, the temperature was raised to 30 ° C., and 95 g (0.9 g) of benzaldehyde was added. Mol) was added to initiate the reaction. The reaction was carried out at a reaction temperature of 30 ° C. while maintaining the condition of a rotation speed of 500 rpm. However, the reaction solution gelled after 5.5 hours, and thus the reaction was terminated due to the impossibility of stirring. The gelled product was then removed, the flask deposits were washed out and suction filtered to separate the product.

  The separated product was resuspended in 5 times the amount of water, neutralized with 20% sodium hydroxide solution, heated to 60 ° C. and stirred for 2 hours. The product was filtered off and filtered again. Washed with warm water at 0 ° C. for 2 hours. Thereafter, the mixture was filtered again with suction, and the product having a wetness of about 67% was dried at 90 ° C. for 12 hours and pulverized to obtain 88.7 g (yield 55.3%) of a white powder. According to HPLC analysis, the purity of dibenzylidene sorbitol was 77.6%, which was low.

(Comparative Example 2)
A 1 L separable flask equipped with a general-purpose stirrer Three One Motor 600G (manufactured by Shinto Kagaku Co., Ltd.) and a bowl-shaped stirring blade was charged with 234 g of pure water and 130 g (0.5 mol) of 70% sorbitol and rotated. The sorbitol was dissolved by stirring at several 500 rpm. Next, with stirring, 119 g (0.625 mol) of p-toluenesulfonic acid monohydrate was added and dissolved, the gas phase was replaced with nitrogen, the temperature was raised to 30 ° C., and 108 g of p-tolualdehyde was added ( 0.9 mol) was added to initiate the reaction. The reaction was carried out at a reaction temperature of 30 ° C. while maintaining the condition of a rotational speed of 500 rpm. However, the reaction solution gelled after 6 hours, so that the reaction became impossible and stirring was terminated. The gel was then removed, the flask deposits washed out and suction filtered to separate the product.

  The separated product was resuspended in 5 times the amount of water, neutralized with 20% sodium hydroxide solution, heated to 60 ° C. and stirred for 2 hours. The material was washed with warm water at 60 ° C. for 2 hours. Thereafter, the mixture was filtered again with suction, and the cake having a wetness of about 67% was dried at 90 ° C. for 12 hours and pulverized to obtain 107.2 g (yield 61.7%) of a white powder. According to HPLC analysis, the purity of di (p-methylbenzylidene) sorbitol was 15.3%, which was very low purity.

These are the charts when the HPLC analysis of the dibenzylidene sorbitol (elution time: 32.175) obtained in Example 1 is carried out. Monobenzylidene sorbitol and tribenzylidene sorbitol were not detected.

Explanation of symbols

1: Dibenzylidene sorbitol 2: Benzaldehyde 3: Unidentified impurity

Claims (3)

In the method for producing dibenzylidene alditols, an aromatic aldehyde and alditol are subjected to a condensation reaction in an aqueous medium in the presence of an acid catalyst, and then the reaction solution is neutralized to obtain dibenzylidene alditols. In the medium, the compatibilizer of the aromatic aldehyde and the alditol is blended in an amount of 3 to 7 times by weight with respect to the blending amount of the aromatic aldehyde. A process for producing dibenzylidenealditols represented by the formula (1).

(In the formula, R ¹ and R ² are the same or different and each represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an alkoxyl group having 1 to 3 carbon atoms. X and Y are the same or different. 1 to 5 and n represents 0 or 1.) The compatibilizer is at least one alcohol solvent selected from methanol, ethanol, isopropanol, and 1-propanol, and / or at least one cellosolve solvent selected from methyl cellosolve, ethyl cellosolve, and butyl cellosolve. The method for producing dibenzylidene alditols according to claim 1, Before the neutralization, the produced dibenzylidene alditols are filtered to recover the mother liquor, and the condensation reaction is repeated using aromatic aldehyde, alditol, acid catalyst, compatibilizing agent, etc. contained in the mother liquor. The method for producing dibenzylidene alditols according to claim 1 or 2, wherein the method is used for recycling.

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