JPH11349531A - Method for producing ester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively suppress the production of peroxides and simply, economically and advantageously produce an ester by reacting an acid with an alcohol in at least an atmosphere under a reduced pressure or a vacuum or an inert gas atmosphere in the whole production process. SOLUTION: An acid (e.g. a monocarboxylic acid, a dicarboxylic acid, a polyvalent carboxylic acid or a carboxylic acid anhydride) is reacted with an alcohol (e.g. a monoalcohol, a polyhydric alcohol or glycols) in at least an atmosphere under a reduced pressure or a vacuum or an atmosphere of an inert gas (e.g. nitrogen gas as a preferred one) in the whole production process (an esterifying reactional step, a neutralizing step, a water washing step, a dehydrating step, a filtering step, a drying step, a distilling step, etc.), at about 50-300 deg.C preferably by using a catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing an ester.

[0002]

2. Description of the Related Art Hitherto, esters obtained by reacting an acid with an alcohol have been widely used in various industrial applications, for example, as a plasticizer.

As an example of the industrial use of the plasticizer, for example, a polyvinyl acetal resin such as a polyvinyl butyral resin is mixed with a plasticizer, and further, an adhesion regulator,
A resin film (hereinafter, referred to as “intermediate film”) obtained by forming a plasticized polyvinyl acetal resin obtained by adding various additives such as an antioxidant and an ultraviolet absorber is interposed between at least a pair of glasses. Such laminated glass is widely used for windshields of automobiles, window glasses of buildings, and the like.

[0004] The above-mentioned interlayer film and laminated glass are required to be excellent in various properties such as transparency, adhesion, impact absorption, penetration resistance, weather resistance, etc., in accordance with the use.

On the other hand, as a plasticizer for an intermediate film for plasticizing a polyvinyl acetal resin, for example, Japanese Unexamined Patent Publication No.
As disclosed in JP-A-186250, the compound has an ether bond such as triethylene glycol-di-2-ethylbutanoate, triethylene glycol-di-2-ethylhexanoate, and tetraethylene glycol-di-heptanoate. Diesters obtained by an esterification reaction of glycols and carboxylic acids, and diesters obtained by an esterification reaction of adipic acids such as dihexyl adipate and alcohols, and the like, which have been widely used conventionally. .

[0006] However, in general, the plasticizer contains, as a by-product, a peroxide by-produced by contact of the produced ester with air at a high temperature in the production process.

[0007] When the above-mentioned peroxide-containing plasticizer is used for the intermediate film, the peroxide is decomposed by the high temperature at the time of forming the plasticized polyvinyl acetal resin, and aldehydes and ketones are generated, thereby obtaining However, there is a problem that the resulting intermediate film becomes a causative substance and the transparency of the finally obtained laminated glass is significantly impaired.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned conventional problems, the present invention provides a simple and economically advantageous method for reducing the production of peroxide by using an acid and an alcohol. It is an object of the present invention to provide a method for producing an ester.

[0009]

The process for producing an ester according to the present invention is a process for producing an ester by reacting an acid with an alcohol, wherein the entire production process is performed at least under reduced pressure or a vacuum atmosphere or under an inert gas atmosphere. It is characterized by performing.

The term "all production steps" used herein means ester production steps such as an esterification reaction step in which an ester is brought into contact with an acid, a neutralization step, a washing step, a dehydration step, a filtration step, a drying step or a distillation step. All steps.

The acid used in the present invention is not particularly limited. For example, acetic acid, propionic acid,
Linear monocarboxylic acids such as butanoic acid (butyric acid), caproic acid, caprylic acid, capric acid, and succinic acid; 2-ethylbutanoic acid (2-ethylbutyric acid), 2-ethylhexanoic acid,
Conventionally known branched monocarboxylic acids such as ethylheptanoic acid; dicarboxylic acids such as adipic acid and sebacic acid; polycarboxylic acids such as trimellitic acid and pyromellitic acid; and carboxylic anhydrides such as phthalic anhydride. Examples of the acid include an acid, which is preferably used. When an ester suitable as a plasticizer for an intermediate film is produced, a branched monocarboxylic acid is more preferably used.

The above acids may be used alone or
More than one type may be used in combination.

The alcohol used in the present invention is not particularly restricted but includes, for example, butanol, hexanol, heptanol, n-octanol,
Monoalcohols such as 2-ethylhexanol; polyhydric alcohols such as pentaerythritol; ethylene glycol, diethylene glycol, triethylene glycol,
Conventionally known alcohols such as glycols such as tetraethylene glycol are exemplified and are preferably used. In the case of producing an ester suitable as a plasticizer for an intermediate film, glycols are more preferably used.

The alcohols may be used alone or in combination of two or more.

In the method for producing an ester according to the present invention, the esterification reaction between the acid and the alcohol may be carried out using a catalyst or without a catalyst. In consideration of easiness, it is preferable to use a catalyst.

The catalyst is not particularly restricted but includes, for example, inorganic acids such as sulfuric acid, hydrochloric acid and phosphoric acid; organic sulfonic acids such as paratoluenesulfonic acid and methanesulfonic acid; tetraisopropyl titanate and tetrabutyl titanate Organic metals such as 12-tungstophosphoric acid;
12-tungstosilicic acid, 12-tungstoboric acid, 12-
Conventionally known catalysts such as heteropolyacids such as molybdophosphoric acid and 12-molybdosilicic acid are mentioned, and are preferably used.

The above catalyst may be used alone,
Two or more types may be used in combination.

The amount of the catalyst used is not particularly limited, but is generally 0.01 to 5% by weight of the total reactants.
Is preferably an amount corresponding to

In the method for producing an ester according to the present invention, an organic solvent may be used at the time of the esterification reaction between the acid and the alcohol.

The organic solvent is not particularly limited, but is preferably inert to the reactants and capable of forming an azeotropic mixture with water produced during the esterification reaction. Conventionally known organic solvents such as benzene, xylene, benzene and the like can be mentioned, and are preferably used.

The above-mentioned organic solvents may be used alone or in combination of two or more.

In the method for producing an ester according to the present invention, the esterification reaction between the acid and the alcohol can be carried out at normal temperature and normal pressure.
Considering the removability of water generated by the reaction, 50 to 30
The reaction is preferably performed at a temperature of about 0 ° C., particularly preferably at a temperature equal to the boiling point of an azeotropic mixture with an organic solvent used in the reaction.

The water generated by the reaction between the acid and the alcohol is used to increase the reaction rate to complete the reaction quickly or to measure the amount of generated water to grasp the progress of the reaction. It is preferred to remove it quickly during the reaction.

The removal of water is preferably carried out by distillation of an azeotropic mixture of water and an acid or an organic solvent.

In the method for producing an ester according to the present invention, in the method for producing an ester in which an acid is reacted with an alcohol, it is necessary that all the production steps are performed at least under reduced pressure, a vacuum atmosphere, or an inert gas atmosphere. .

In any one of the above manufacturing steps, peroxide production cannot be sufficiently suppressed if performed in an atmosphere other than a reduced pressure or vacuum atmosphere or an inert gas atmosphere, in other words, in the atmosphere. .

The higher the degree of pressure reduction for obtaining the above-mentioned reduced pressure or vacuum atmosphere, the greater the effect of suppressing the generation of peroxides, which is preferable. However, in practice, it is not necessary to increase the degree of pressure reduction more than necessary. Considering the difficulty and cost,
It is preferable to set an appropriate degree of reduced pressure.

The inert gas for obtaining the above-mentioned inert gas atmosphere is not particularly restricted but includes, for example, nitrogen gas and rare gases such as helium, neon, argon, krypton, xenon and radon. Nitrogen gas, which has a good balance between performance and cost, is most preferably used.

The inert gas may be used alone or in combination of two or more.

The reduced pressure or vacuum atmosphere and the inert gas atmosphere may be set independently, or may be set in a state where both are used together.

Furthermore, when an inert gas atmosphere is set, the degree of reduced pressure may be relatively low, and in some cases, each step of ester production may be performed under normal pressure.

[0032]

In the method for producing an ester according to the present invention, all of the steps for producing the ester are performed at least under reduced pressure, a vacuum atmosphere, or an inert gas atmosphere. Can be suppressed.

[0033]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto. In the examples, “parts” means “parts by weight”.

(Example 1)

(1) Synthesis of ester 360 g (2.5 mol) of 2-ethylhexanoic acid was placed in a reaction vessel equipped with a Gene Stark type oil-water separator and a stirrer.
150 g (1 mol) of triethylene glycol and 1 g of sulfuric acid as a catalyst were charged, the degree of reduced pressure was adjusted so as to slowly reflux, and the esterification reaction was carried out at a temperature of 100 ° C. while stirring. During the esterification reaction, the reaction solution was sampled at predetermined intervals, and the conversion to ester was determined using a gas chromatograph. After completion of the esterification reaction, unreacted acid was removed by distillation, and then sodium carbonate was added to the reaction solution to perform a neutralization treatment. The neutralization treatment was performed under normal pressure while flowing nitrogen gas over the surface of the reaction solution.
After completion of the neutralization treatment, a water washing treatment was performed under a normal pressure while flowing nitrogen gas over the surface of the reaction solution. Next, after dehydration treatment under reduced pressure, activated carbon was added to the reaction solution, and filtration was performed while flowing nitrogen gas under normal pressure to obtain an ester.

(2) Production of Intermediate Film For 100 parts of polyvinyl butyral resin, 40 parts of the ester (plasticizer) obtained above and an antioxidant (trade name “Sumilyzer BHT”, manufactured by Sumitomo Chemical Co., Ltd.) 0.2 Parts, a mixture obtained by adding 0.2 parts of an ultraviolet absorber (trade name “Tinuvin 328”, manufactured by Ciba Geigy) and 0.08 parts of magnesium 2-ethylhexanoate as an adhesive force adjuster were melt-kneaded with a mixing roll. Using a press molding machine at a temperature of 150 ° C. and a pressure of 100 kg / cm ² ,
Press molding was performed for 0 minutes to obtain an intermediate film having a thickness of 0.8 mm.

(3) Production of laminated glass The interlayer film obtained above was placed in a thermo-hygrostat (20 ° C.-65%
RH) so as to adjust the moisture content to 0.4 to 0.5% by weight, and then sandwiched between two pieces of float glass (thickness: 2.4 mm) and placed in a vacuum bag (rubber bag). After holding at a vacuum of 20 Torr for 20 minutes, pre-adhesion was carried out by holding the vacuum at 90 ° C. for 30 minutes in an oven to perform lamination. Next, the laminate taken out of the vacuum bag was heated in an autoclave at a temperature of 150 ° C. and a pressure of 1 ° C.
The main bonding was performed under the condition of 3 kg / cm ² to obtain a laminated glass.

(4) Evaluation The peroxide value of the ester obtained in (1), and
The yellowness (YI value) of the laminated glass obtained in (3) was evaluated by the following method. The results were as shown in Table 1.

Peroxide value: 15 ml of acetic acid and 10 ml of chloroform were placed in a stoppered Erlenmeyer flask, sealed with carbon dioxide, and a sample of the ester was weighed and placed in the Erlenmeyer flask. Next, a potassium iodide aqueous solution (10
% By weight) and 5 ml in a freezer at −30 ° C.
After standing for minutes, titration was performed with sodium thiosulfate (0.025 N), and the peroxide value (meq / kg) was measured.

Yellowness (YI value): JIS R-321
2 The yellowness (YI value) of the laminated glass was measured using a spectrometer in accordance with "Test Method for Safety Glass for Automobiles".

(Example 2) In the synthesis of ester, tetrabutyl titanate was used instead of sulfuric acid as a catalyst, and the reaction temperature of the esterification reaction was set to 300 ° C. An ester, an interlayer and a laminated glass were obtained.

Comparative Example 1 In the synthesis of an ester, an ester, an intermediate film and a laminated glass were obtained in the same manner as in Example 1 except that only the neutralization step in the production process was performed in the air.

Comparative Example 2 An ester, an intermediate film and a laminated glass were obtained in the same manner as in Example 1 except that in the synthesis of the ester, the washing step and the filtration step in the production step were performed in the atmosphere.

Comparative Example 3 In the synthesis of an ester, an ester, an intermediate film and a laminated glass were produced in the same manner as in Example 1 except that the neutralization step, the washing step and the filtration step in the production process were performed in the atmosphere. I got

Comparative Example 4 An ester, an intermediate film and a laminated glass were obtained in the same manner as in Example 2 except that in the synthesis of the ester, only the neutralization step in the production process was performed in the air.

Comparative Example 5 An ester, an intermediate film and a laminated glass were obtained in the same manner as in Example 2 except that in the synthesis of the ester, the water washing step and the filtration step in the production step were performed in the atmosphere.

Comparative Example 6 In the synthesis of an ester, an ester, an intermediate film and a laminated glass were produced in the same manner as in Example 2 except that the neutralization step, the washing step and the filtration step in the production step were performed in the atmosphere. I got

The peroxide values of the seven types of esters obtained in Example 2 and Comparative Examples 1 to 6, and the yellowness (YI) of the seven types of laminated glass obtained in Example 2 and Comparative Examples 1 to 6 Value) was evaluated in the same manner as in Example 1. The results were as shown in Table 1.

[0049]

[Table 1]

As is clear from Table 1, the esters of Examples 1 and 2 produced by the production method of the present invention had a low peroxide value and hardly produced any peroxide. Example 1
The laminated glasses of Examples 1 and 2 produced using the interlayer films produced using the esters of Examples 1 and 2 had low yellowness (YI value) and were excellent in transparency.

On the other hand, in the synthesis of the esters, the esters of Comparative Examples 1 to 6 in which some of the steps in the production process were carried out in the air had a high peroxide value, and produced many peroxides. Was. Further, Comparative Examples 1 to 6 produced using the intermediate films produced using the esters of Comparative Examples 1 to 6 were used.
All of the laminated glasses have high yellowness (YI value),
Transparency was poor.

[0052]

As described above, according to the method for producing an ester of the present invention, a high-quality ester having almost no peroxide as a by-product can be obtained easily and economically.

The laminated glass produced by using the interlayer according to the present invention using the ester as a plasticizer has excellent transparency and is suitably used for automobiles and buildings.

Further, the ester according to the present invention is suitably used not only for the above-mentioned intermediate film but also as a plasticizer for various products requiring a high degree of transparency.

Claims (1)

[Claims] 1. A method for producing an ester, which comprises reacting an acid with an alcohol, wherein all the production steps are performed at least under reduced pressure, a vacuum atmosphere, or an inert gas atmosphere.