JPH093073A - Method for producing 1,3-2,4-di (4-methylbenzylidene) sorbitol - Google Patents

Abstract

PURPOSE: To produce the subject compound useful as an improving agent, etc., for the transparency of a polyolefin resin by reacting sorbitol which is a solid substance with 4-methylbenzaldehyde in the presence of a catalyst in a mixed solvent of cyclohexane with hexane. CONSTITUTION: Sorbitol which is a solid substance having <=5wt.% moisture content and 4-methylbenzaldehyde are heated up in the presence of a catalyst comprising p-toluenesulfonic acid, etc., in a mixed solvent of cyclohexane with hexane at (5/95) to (50/50) mixing ratio expressed in terms of the volume ratio, and reaction thereof is then carried out for 6hr while separating water formed as a reactional product under heating and refluxing. An aqueous solution of sodium bicarbonate is then added thereto and the reactional mixture is further heated to form and distill away an azeotropic mixture of an organic solvent with water. The reactional product is solidified and methanol is then added to purify the product by recrystallization. A gelation phenomenon during the reaction is suppressed to stably afford the objective high-purity compound useful as an additive, etc., for resins capable of improving the transparency of a polyolefin resin in high yield.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing 1,3-2,4-di (4-methylbenzylidene) sorbitol. 1,3-2,4-di (4-methylbenzylidene) sorbitol (hereinafter abbreviated as PMBS) is used as a resin by adding a small amount of it to a polyolefin resin, particularly polyethylene, polypropylene or a copolymer containing them as a main component. It is a compound that has the effect of improving transparency and is useful as an additive for resins in the field of molding of various containers that require transparency. It is also a compound useful as a gelling agent for various organic solvents.

[0002]

2. Description of the Related Art Generally, as a method for producing dibenzylidene sorbitols, a method in which sorbitol and aldehydes are dehydrated and condensed in the presence of a catalyst (Pharmaceutical Journal, 79, 59).
8, 1958) is disclosed.

[0003]

However, even if this method is applied to the method for producing PMBS, in the production of PMBS having a gelling ability, the reaction mass gels during the reaction and stirring becomes impossible, so that the desired PMBS is not obtained. It is not possible to obtain high yield and high purity. The first reason is that 4-methylbenzaldehyde (hereinafter abbreviated as PMBA), sorbitol and the catalyst do not disperse uniformly due to gelation during the reaction, and as a result, the molar ratio of PMBA and sorbitol becomes uneven. Change to PM against sorbitol
This is because the amount of by-products such as a tri-adduct with three BAs added and a mono-adduct with one BA increases.

On the other hand, for example, an aqueous solution of sorbitol and benzaldehyde are mixed with cyclohexane and a carbon number of 6 to
A method for obtaining a target substance with high purity by reacting in a solvent of a mixture of 10 saturated hydrocarbons and suppressing the gelation phenomenon during the reaction is disclosed (Japanese Patent Publication No. 48-43748).
issue). However, simply performing the reaction under these conditions cannot suppress gelation during the reaction, and as water is removed to the outside of the reaction system during the dehydration reaction, sorbitol precipitates and solidifies as a large mass in the reaction vessel. To attach,
Since the molar ratio of sorbitol / PMBA is deviated, tri-adduct is produced remarkably, PMBS cannot be obtained in high yield and high purity, which is not always a satisfactory method.

[0005] As another manufacturing method, a method of condensing in an aqueous reaction medium (Japanese Patent Publication No. 61-17833) is disclosed. However, in this method, a hydrolysis reaction (reverse reaction) of PMBS formed is likely to occur, The conversion rate of PMBA does not improve and the extraction yield is about 50%, which is not a production method that is industrially satisfactory in terms of production efficiency.

As described above, at present, there is no efficient manufacturing method for obtaining PMBS with high yield and high purity.

[0007]

Means for Solving the Problems The present inventors obtain 1,3-2,4-di (4-methylbenzylidene) sorbitol by reacting sorbitol and PMBA in a hydrocarbon organic solvent in the presence of a catalyst. As a result of extensive studies on the method, it was found that PMBS can be obtained in high yield and high purity by using a specific sorbitol and a reaction solvent, and further by controlling the reaction concentration and the molar ratio of benzaldehyde and sorbitol. Has been completed. That is, sorbitol and 4-methylbenzaldehyde are reacted in the presence of a catalyst in an organic solvent to give 1,3-2,4-di (4
-Methylbenzylidene) sorbitol, wherein 1,3-2,4-di (4-methylbenzylidene) is characterized in that sorbitol is a solid substance and the organic solvent is a mixed solvent of hexane and cyclohexane. ) A method for producing sorbitol.

Regarding the solid substance of sorbitol, which is one of the features of the method of the present invention, it is necessary to control the water content first and the particle size secondly. For the first water content,
The content is preferably 5% by weight or less, preferably 3% by weight or less, more preferably 2% by weight or less, further preferably 1% by weight or less. When it is more than 5% by weight, as in the above-mentioned example (Japanese Patent Publication No. 48-43748), the reaction mass is apt to gel, so that a disproportionation reaction occurs and a disproportionation of the molar ratio of PMBA and sorbitol occurs. Therefore, the amount of tri-adducts and the like tends to increase, which is not preferable. Regarding the second particle size, its shape is powder,
It may take various forms such as granules, granules, lumps, and blocks, and the shape is not limited in the method of the present invention, but the particle size is 2 mm or less, preferably 1.0 mm.
The following is more preferable, and 0.5 mm or less is more preferable. The reason for this is that, under the present reaction conditions, the solid substance of sorbitol is insoluble in the reaction solvent, so that a solid-liquid reaction occurs, and therefore the particle size of sorbitol is large (larger than 2 mm).
The more it is, the more the amount of sorbitol substantially involved in the reaction is apparently decreased, the molar ratio of PMBA / sorbitol is increased, and the amount of triadducts and the like is increased, which is not preferable.

The amount of sorbitol solid and PMBA used in the method of the present invention is such that when sorbitol satisfies the above conditions, the PMBA / sorbitol molar ratio is from 1.5 to 2.0, preferably. 1.6 to 1.9, more preferably 1.7 to 1.8, is preferable, and the target PMBS can be obtained with high purity and efficiency within this range. When the molar ratio is more than 2.0, a triadduct in which three PMBAs are added to sorbitol is likely to be produced, and the purity of the target PMBS tends to be lowered, which is not preferable. On the contrary, when the molar ratio is less than 1.5, not only the production efficiency is deteriorated, but also the sorbitol contains P
This is not preferable because a mono-adduct in which one MBA is added is produced, and the purity of the target PMBS tends to decrease.

The organic solvent, which is one of the features of the method of the present invention, is that a mixed solvent of cyclohexane and hexane is used. By using this mixed solvent, gelation during the reaction is suppressed and the reaction This enables stable and reproducible operation.

Both cyclohexane and hexane used in the method of the present invention are easily available. Hexane can be used as a reagent or as a mixture having a narrow boiling range centered on a commercially available C ₆ hydrocarbon.

The mixing ratio of cyclohexane and hexane is
Volume ratio of 5/95 to 50/50, preferably 10/90
-40/60, particularly preferably 20 / 80-30 / 70
Range. When a mixed solvent in which the volume ratio of cyclohexane exceeds 50 is used, the reaction rate is fast, but gelation (disproportionation reaction) occurs as the reaction progresses, and by-products such as tri-adducts are produced, and thus obtained. It is not preferable because the purity of PMBS tends to decrease. Conversely, when a mixed solvent with a cyclohexane volume ratio of less than 5 is used, the reaction rate and PMB
It is not preferable because the reproducibility of the A conversion rate tends to decrease.

The amount of the organic solvent used in the method of the present invention is preferably such that the reaction concentration is such that PMBS formed during the reaction does not extremely solidify (gel).
-20% (g / ml), more preferably 7-15% (g
/ Ml), more preferably 9 to 13% (g / ml) in the reaction concentration. The reaction concentration mentioned here is the ratio of the amount of the organic solvent used to the theoretical amount of PMBS, and is expressed in g / ml.

The reaction temperature in the production of PMBS depends on the organic solvent used and the reaction pressure conditions therefor (it may be under reduced pressure, normal pressure or increased pressure, and there is no particular limitation), but it is from 40 ° C to 40 ° C. 100 [deg.] C., more preferably 60-80 [deg.] C. is good and is determined by the temperature at which the organic solvent used refluxes under the conditions. Industrially, the temperature at which the organic solvent is refluxed at atmospheric pressure is preferable.

Examples of the catalyst used in the method of the present invention include mineral acids such as hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid, and p-toluenesulfonic acid, with p-toluenesulfonic acid being particularly preferable. The usage is 1,3-2,4
0.05 to 10 parts by weight, preferably 0.1 to 100 parts by weight of di (4-methylbenzylidene) sorbitol
~ 3.0 parts by weight is preferable.

The PMBS produced under such conditions is
A known technique, for example, an isolation method disclosed in Japanese Patent Publication No. 61-17835, in which an aqueous alkali solution is charged, an organic solvent is distilled off, and solid-liquid separation is carried out from a slurry, JP-A-57-171.
It can be easily taken out and purified by the purification method of contacting with a hydrophilic organic solvent disclosed in JP-B-85287 and JP-B-61-14150.

[0017]

The present invention will be described below in more detail with reference to Examples and Comparative Examples. Example 1 Sorbitol 2 was placed in a 1.5 liter reaction kettle equipped with a Dean Stack having a cooling tube on the top, a thermometer, and a stirring bar.
6.7 g (0.15 mol), 4-methylbenzaldehyde 30.8 g (0.26 mol), p-toluenesulfonic acid 0.5 g, and a mixed solvent of cyclohexane and hexane (the volume ratio of cyclohexane and hexane is 20/8
0) After charging 500 ml, the temperature was raised and the mixture was heated under reflux (about 72 ° C.) for 6 hours. At this time, a mixture of cyclohexane, hexane, and water produced by the reaction was distilled off by a Dean Stack, and only cyclohexane and hexane were returned to the reaction vessel. Next, remove the cooling tube and Dean stack, attach a Liebig type cooling tube,
An aqueous solution prepared by dissolving 1.1 g of sodium bicarbonate in 500 g of water was charged into a reaction kettle and then heated, and cyclohexane and water were azeotropically distilled. At this time, as cyclohexane and hexane were distilled off, the reaction product gradually solidified into powder and became a slurry. After cyclohexane and hexane were almost completely distilled off, the obtained 1,3-2,4-di (4-methylbenzylidene) sorbitol and water slurry was filtered off. Next, add 500 ml of methanol to the obtained filter cake, sludge at room temperature for 1 hour, and then filter.
Repeated times. The obtained filter cake is dried to give a white powder 1,
45.4 g of 3-2,4-di (4-methylbenzylidene) sorbitol was obtained. The yield was 91.0% (yield based on methylbenzaldehyde) and the purity was 99.7%.

Examples 2 to 4 / and Comparative Examples 1 to 4 The results obtained by changing the reaction conditions (the composition ratio of the solvent, the reaction concentration, the molar ratio of 4-methylbenzaldehyde to sorbitol, and the amount of sorbitol) are shown in Table 1. Shown in.

[0019]

[Table 1] * Hex ... Hexane * CH ... Cyclohexane * PMBA ... 4-Methylbenzaldehyde * Sor ... Sorbitol

[0020]

INDUSTRIAL APPLICABILITY The method of the present invention suppresses the gelation phenomenon during the reaction by using a specific reaction solvent and sorbitol, so that 1,3-2,4-di (4-methylbenzylidene)
This is a method for producing sorbitol stably with high yield and high purity.

Claims (3)

[Claims] 1. A sorbitol and 4-methylbenzaldehyde are reacted in an organic solvent in the presence of a catalyst to give 1,3-2,
In the method for obtaining 4-di (4-methylbenzylidene) sorbitol, sorbitol is a solid substance, and the organic solvent is a mixed solvent of cyclohexane and hexane. Method for producing (4-methylbenzylidene) sorbitol. 2. The method according to claim 1, wherein the water content of the sorbitol solid substance is 5% by weight or less. 3. The mixing ratio of cyclohexane and hexane is
The method according to claim 1 or 2, wherein the volume ratio is 5/95 to 50/50.