JP2002293758A - Method for producing ester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an ester having an extremely small content of a residual sulfur compound in the case of using an organic sulfonic acid as a catalyst for producing the ester. SOLUTION: This method for producing the ester in which a carboxylic acid (preferably 2-ethylhexanoic acid) or its anhydride is reacted with an alcohol such as triethylene glycol, etc., in the presence of a catalyst is provided by using an organic sulfonic acid as the catalyst, adding a solid alkali such as powdery sodium carbonate into a reaction system after the reaction, treating at preferably >100 deg.C and then neutralizing by adding water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an ester, and more particularly, to a method for producing an ester in which an organic sulfonic acid is used as a catalyst and in which almost no sulfur compound remains.

[Prior art]

A method for producing an ester by reacting a carboxylic acid or its anhydride with an alcohol in the presence of a catalyst has been known for a long time. However, depending on the type of the catalyst, a side reaction or a by-product may be generated, and may remain in the ester without being removed by the subsequent neutralization with an aqueous alkali solution, thereby deteriorating the product quality.

[0003] On the other hand, plasticized polyvinyl butyral is known as an interlayer film of laminated glass sandwiched between plate glasses because of its excellent transparency and adhesiveness to glass. Since the glass is hardly scattered even when subjected to an impact and has excellent penetration resistance, it is widely used for window glasses of automobiles and buildings.

[0004] The plasticized polyvinyl butyral contains a polyvinyl butyral resin and a plasticizer as main components, and further contains additives such as an ultraviolet absorber, an antioxidant, and an adhesion regulator. The composition is determined. For this purpose, it is important to balance the compatibility between the polyvinyl butyral resin as the main component and the plasticizer and the overall performance. Examples of the plasticizer for polyvinyl butyral include glycols having an ether bond such as triethylene glycol di-2-ethylbutanoate, triethylene glycol di-2-ethylhexanoate, and tetraethylene glycol diheptanoate; Examples include diesters with acids and diesters of adipic acids such as dihexyl adipate with alcohols.

[0005] Apart from the quality aspects, these esters are
It can be manufactured by a known method. In general, as a catalyst for producing an ester by a reaction between a carboxylic acid and an alcohol, for example, organic sulfonic acids such as paratoluenesulfonic acid are known as those having a high reaction activity and capable of causing an esterification reaction in a short time. I have. But,
When an acid catalyst such as an organic sulfonic acid is used, a side reaction is apt to occur, and thus the synthesized ester product is considered to be inferior in quality when used as a plasticizer (Japanese Patent Publication No. 1-381515). Reference).

[0006]

SUMMARY OF THE INVENTION The present inventors have studied various methods for producing esters, and when an organic sulfonic acid is used as a catalyst in the production of the above-mentioned ester which can be used as a plasticizer for polyvinyl butyral, the organic sulfonic acid and raw material As a result of side reaction between the alcohol and the by-product remaining in the product ester, the intermediate film composition containing polyvinyl butyral and this ester and other additives is subjected to a high-temperature history, for example, by extrusion molding. When given and formed into a film,
It was confirmed that the above by-products were further decomposed to produce aldehydes and ketones, which became the cause of coloring of the polyvinyl butyral film, and ultimately the transparency of laminated glass was significantly impaired. The by-product at the time of the production of the ester is presumed to be an organic sulfonic acid ester, but the present invention has been completed based on the findings of the present inventors when an organic sulfonic acid is used as a catalyst at the time of the production of the ester. It is an object of the present invention to provide a method for producing an ester having an extremely small amount of residual sulfur compounds.

[0007]

In order to achieve the above object, the present invention relates to a method for producing an ester by reacting a carboxylic acid or its anhydride with an alcohol in the presence of a catalyst. Provided is a method for producing an ester, characterized in that a solid alkali is added to a reaction system after the reaction using an acid, followed by treatment, followed by neutralization by adding water. The present invention also provides a method for producing an ester, wherein the temperature at which the solid alkali is added and treated exceeds 100 ° C. Further, the present invention provides a method for producing an ester in which the solid alkali is powdery sodium carbonate.

The carboxylic acid in the present invention includes, for example, butyric acid, valeric acid, caproic acid, 2-ethylbutanoic acid,
Aliphatic monocarboxylic acids such as hexanoic acid, 2-ethylhexanoic acid, octanoic acid, heptanoic acid, lauric acid, and myristic acid, and aliphatic polycarboxylic acids such as adipic acid, succinic acid, sebacic acid, maleic acid, and fumaric acid In addition to acids and the like, anhydrides of polycarboxylic acids such as succinic anhydride, maleic anhydride, phthalic anhydride and trimellitic anhydride can be mentioned. Preferably, 2-ethylhexanoic acid is used.

[0009] Examples of the alcohol include glycols having an ether bond such as ethylene glycol, diethylene glycol, triethylene glycol and tetraethylene glycol. Preferably, triethylene glycol is used.

Examples of the organic sulfonic acids for the catalyst include organic monosulfonic acids such as paratoluenesulfonic acid, methanesulfonic acid and ethanesulfonic acid. The amount used will normally be an amount corresponding to about 0.01-5.0% by weight of the total reactants.

In the present invention, in order to carry out a condensation reaction between a carboxylic acid or an anhydride thereof and an alcohol in the presence of an organic sulfonic acid, the alcohol is contacted with the carboxylic acid according to a conventional method which has been conventionally carried out. I just need. If necessary, a solvent may be used in addition to the reactants. The solvent must be inert to the reactants and preferably form an azeotrope with the water formed during the reaction, and preferably includes organic solvents such as toluene, xylene, and benzene.

Generally, the reaction is carried out at a high temperature of 50 to 300 ° C. in order to accelerate the reaction and facilitate the removal of water generated in the reaction, preferably at a temperature equal to the boiling point of the azeotrope with the solvent used in the reaction. Done in Water generated by the two-component reaction is preferably removed during the reaction to increase the reaction rate to complete the reaction and to monitor its progress by measuring the amount of water generated. Water is conveniently removed by an azeotrope of water and an acid or solvent.

After completion of the reaction, a pulverulent alkali such as sodium carbonate, sodium hydrogen carbonate and calcium carbonate is added to the reaction solution, and it is usually at room temperature to 300 ° C., preferably at 50 to 300 ° C.
300 ° C., more preferably a temperature exceeding 100 ° C. to 30 ° C.
The treatment is performed at a high temperature of 0 ° C. Before the addition of the alkali, it is desirable that the acid content in the reaction solution is reduced as much as possible by distillation so that the acid content in the reaction solution does not react with the alkali. In the case of a high-temperature treatment, it is preferable to keep the atmosphere as low as possible in an inert atmosphere.

In the method of the present invention, since no water is present at the time of addition of the solid alkali, the alkali treatment can be performed at high temperature and reduced pressure, and the by-products can be decomposed. After the alkali treatment, the reaction system is neutralized by adding water, and washed with water, dehydrated, dried under reduced pressure, or subjected to distillation to purify the ester to produce a product.

(Effect) In the conventional general ester synthesis, an aqueous alkali solution is added to the reaction system after the ester condensation reaction to neutralize an excessively charged acid under uniform conditions. However, the present inventors presume that the temperature cannot exceed 100 ° C. in the presence of water, and the residual organic sulfonic acid compound could not be decomposed. Further, when neutralization is performed at a high temperature using an aqueous alkali solution, hydrolysis of the product ester may occur depending on the alkali concentration.

On the other hand, the method of the present invention is a heterogeneous system in which water is not present when a solid alkali is added, so that alkali treatment can be performed under high temperature and reduced pressure conditions, and the organic sulfonic acid as a by-product The ester can be decomposed. Further, the decomposed organic sulfonic acid compound becomes an alkali salt and can be easily extracted and removed to the aqueous layer by a neutralization treatment or the like, so that the amount of the residual sulfur compound in the ester can be extremely efficiently reduced.
Therefore, if the plasticized polyvinyl butyral using the ester obtained by the production method of the present invention is molded into an intermediate film, there is no increase in the hue of the ester at the time of heating, so that a non-colored intermediate film can be obtained.

[0017]

EXAMPLES Examples will be described below, but the present invention is not limited to only the following examples. (Example 1) (1) Synthesis of plasticizer In a reactor equipped with a Gene Stark type oil-water separator, 360.0 g (2.50 mol) of 2-ethylhexanoic acid and 150.0 g (1.00 mol) of triethylene glycol were added. Mol) and 1.0 g of p-toluenesulfonic acid, adjusting the degree of reduced pressure so as to slowly reflux, and stirring at a set temperature of 90 °.
C., and the esterification reaction was carried out at 90.degree. C. for 5 hours.
The crude ester was obtained. During the esterification reaction, the reaction solution is sampled every predetermined time, and using a gas chromatograph,
The conversion to ester was determined.

After completion of the reaction, excess acid in the crude ester was removed by distillation, and 1.9 g of powdered sodium carbonate was obtained.
(0.017 mol) was added to the reaction solution, and alkali treatment was performed by stirring at 110 ° C. under reduced pressure for 1 hour.
After the alkali treatment, water was added to the reaction solution to perform a neutralization treatment. After the neutralization treatment, water washing treatment and dehydration treatment were performed, activated carbon was added to perform decolorization, and the crude ester was purified and commercialized.
The residual sulfur content in the obtained purified ester was 11 ppm. The results and the following thermal stability evaluation results are shown in Table 1 together with other examples and comparative examples.

(2) Evaluation of thermal stability of ester The amount of sulfur compounds remaining in the purified ester and the coloring during heating of the ester were evaluated by the following methods. Evaluation method: The ester before heating was sampled, and the hue was measured according to JIS K-6751. The ester was heated at 180 ° C for 1 hour. After cooling, the ester was sampled, and the hue was measured according to JIS K-6751. The hues of the ester were compared before and after heating. If no increase in the hue was observed, the ester was judged to be acceptable.

Example 2 In the alkali treatment step in Example 1, the amount of sodium carbonate added was 59.4 g.
(0.56 mol), except that the ester was commercialized and evaluated in the same manner as in Example 1. (Embodiment 3) In the step of alkali treatment in Embodiment 1,
5.7 g (0.053 mol) of sodium carbonate added
Example 1 except that the processing temperature was set to 130 ° C.
The ester was commercialized in the same manner as described above and evaluated.

Example 4 In the alkaline treatment step in Example 1, the amount of sodium carbonate added was 5.7 g (0.
053 mol), and the esterification was carried out in the same manner as in Example 1 except that the treatment temperature was 150 ° C., and the evaluation was carried out.

Comparative Example 1 In Comparative Example 1, Example 1
, An ester was produced and evaluated in the same manner as in Example 1 except that the alkali treatment with sodium carbonate was not performed during the ester production process. Comparative Example 2 In Comparative Example 2, an ester was commercialized and evaluated in the same manner as in Example 2 except that the alkali treatment with sodium carbonate was not performed during the ester production step.

Comparative Example 3 In Comparative Example 3, Example 3
, An ester was commercialized and evaluated in the same manner as in Example 3, except that the alkali treatment with sodium carbonate was not performed during the ester production process. (Comparative Example 4) In Comparative Example 4, an ester was commercialized and evaluated in the same manner as in Example 4 except that the alkali treatment with sodium carbonate was not performed during the ester production step.

[0024]

[Table 1]

[0025]

The process for producing an ester according to the present invention is constituted as described above. Since an organic sulfonic acid is used as a catalyst and a solid alkali is added to the reaction system after the reaction, the reaction is carried out. A certain organic sulfonic acid compound can be effectively decomposed, and then neutralized by adding water, so that the decomposed organic sulfonic acid compound becomes an alkali salt. Can be removed. Therefore, according to the present invention, it is possible to provide a high-quality ester having an extremely small amount of residual sulfur compounds and little increase in hue upon heating. If the temperature at which the solid alkali is added exceeds 100 ° C., the decomposition of by-products can be performed more reliably, and thus, it is possible to provide an ester having no increase in hue even when a high-temperature history is given. Become.

Claims (3)

[Claims] 1. A method for producing an ester by reacting a carboxylic acid or an anhydride thereof with an alcohol in the presence of a catalyst, wherein an organic sulfonic acid is used as a catalyst, and a solid alkali is added to the reaction system after the reaction. A method for producing an ester, which comprises neutralizing by adding water after the treatment. 2. The method according to claim 1, wherein the temperature for adding and treating the solid alkali is a temperature exceeding 100 ° C.
The method for producing the ester described in the above. 3. The method for producing an ester according to claim 1, wherein the solid alkali is powdery sodium carbonate.