JPH0132815B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a carboxylic acid ester, and more specifically, the present invention relates to a method for producing a carboxylic acid ester, and more specifically, it reduces the amount of pollution in wastewater discharged from a reaction process using a specific organic sulfonic acid compound as a catalyst, and improves product quality. The present invention relates to an improved method for producing carboxylic acid esters which has excellent properties and a short reaction time.

As catalysts for producing esters by reacting carboxylic acids or their anhydrides with alcohols, acid catalysts such as sulfuric acid and para-toluenesulfonic acid, and metal catalysts such as metal oxides and organometallic compounds are widely known. .

Among these, acid catalysts generally have high reaction activity and can carry out esterification reactions at relatively low temperatures in a short time, but on the other hand, side reactions are likely to occur, and for this reason, ester products synthesized with these catalysts have poor thermal stability. It has a low volume resistivity value and is inferior in quality when used as a plasticizer.

Therefore, steps such as water washing or total distillation are required to remove various substances generated by side reactions from the produced ester, and washing with water has the disadvantage of increasing the amount of wastewater pollution.

In addition, metal catalysts generally have very few side reactions compared to acid catalysts, and the resulting products have high volume resistivity and good thermal stability, and are effective in removing various substances caused by side reactions from the produced ester. This method has the advantage of omitting steps such as washing with water or total distillation for esterification, but has a major disadvantage in industrial production in that the reaction rate is slow and the esterification reaction must be carried out at a relatively high temperature for a long time.

The present invention aims to eliminate the drawbacks of the conventional methods described above, and was completed by discovering an acid catalyst that has both the advantages of conventional catalysts used in the production of carboxylic acid esters. A method characterized in that a compound represented by the general formula R(SO ₃ H) ₂ (where R represents a lower alkylene group) is used as a catalyst when producing an ester from an acid or carboxylic acid anhydride and an alcohol. It consists in a method for producing a carboxylic acid ester.

The carboxylic acids in the present invention include aromatic polycarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, and trimethic acid, aromatic monocarboxylic acids such as benzoic acid, and aliphatic saturated polycarboxylic acids such as adipic acid and sepacic acid. Carboxylic acids, aliphatic unsaturated polycarboxylic acids such as maleic acid and fumaric acid, and aliphatic monocarboxylic acids such as oleic acid and stearic acid are used. Among these organic acids and their anhydrides, aromatic polyhydric carboxylic acids and their acid anhydrides are preferably used, and phthalic acid and phthalic anhydride are particularly preferably used.

Examples of alcohol include n-butyl alcohol, isobutyl alcohol, secondary butyl alcohol, isoheptyl alcohol, neopentyl alcohol, n-octyl alcohol,
Aliphatic saturated monohydric alcohols such as 2-ethylhexyl alcohol, isooctyl alcohol, nonyl alcohol, and decyl alcohol, and aliphatic polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, and pentaerythritol are used,
Mixtures of these alcohols may also be used. Among these alcohols, aliphatic saturated monohydric alcohols having 4 to 10 carbon atoms are particularly preferably used.

Examples of the compound represented by the above general formula used as a catalyst in the present invention include methanedisulfonic acid, ethanedisulfonic acid, propanedisulfonic acid, etc., and ethanedisulfonic acid is particularly preferred.

Even if these catalysts are dissolved in waste water containing monoester neutralized products in the reaction system, they hardly increase the chemical oxygen consumption of the waste water; When the number of carbon atoms is large, the degree of pollution of the wastewater becomes even greater.

These compounds may be used alone or in combination, and the amount used is usually 0.01 to 3.0 parts by weight, preferably 0.1 to 3.0 parts by weight, per 100 parts by weight of carboxylic acid.
It is assumed to be 1.0 part by weight.

In the esterification reaction, an amount of alcohol is added to the carboxylic acid or carboxylic anhydride in an amount slightly larger than the amount of alcohol to be reacted with the carboxylic acid or carboxylic acid anhydride, and then the predetermined amount of catalyst is added, and the mixture is heated under reduced pressure to
The reaction is carried out at a temperature of 250°C. The reaction is terminated when the acid value of the reaction system becomes 1.5 or less, but the reaction time is only 1 to 4 hours.

When using a polycarboxylic acid, in order to remove unreacted monoester generated in the reaction system, after cooling the reaction system to 50 to 100°C, add 0.003 to the crude ester.
Add ~3% by weight of an alkali such as sodium hydroxide or an alkali salt such as sodium carbonate, and then add 5~25% of water based on the crude ester for 30 minutes ~
Stir for 3 hours and extract unreacted monoester into water.

The added water is separated from the crude ester and disposed of as wastewater outside the system. After that, the crude ester is washed with water, the excess alcohol in the reaction system is removed by distillation, and the reaction system is cooled and treated with activated carbon or activated clay to adsorb and remove the catalyst remaining in the reaction system. It is made into a product.

The method for producing a carboxylic acid ester of the present invention is configured as described above, and the compound represented by the above general formula is used as a catalyst. Compared to the above, there is almost no progress of side reactions, so the process of water washing or total distillation to remove various substances generated by side reactions from the produced ester can be omitted, and the amount of wastewater pollution is small. The product obtained has the advantage of having a large volume resistivity and good thermal stability, and also has the advantage that a reaction product can be obtained in a shorter time than with conventional metal catalysts.

Examples of the method of the present invention will be described below.

Note that the volume resistivity value and hue Hazen value shown below were measured in accordance with JIS-K-6751 (phthalate ester test method). Further, the amount of pollution in the wastewater was measured in accordance with JIS-K-102 (method for measuring oxygen consumption using potassium dichromate), and the chemical oxygen consumption was simply expressed as COD.

Example 1 222 g (1.5 mol) of phthalic anhydride, 449 g (3.45 mol) of 2-ethylhexanol, and 2.28 g (12 mmol) of ethanedisulfonic acid were added to the pressure-resistant glass reactor equipped with an electromagnetic rotary stirrer from 1, and the mixture was stirred at 160°C under reduced pressure.
The temperature rose to The esterification reaction was carried out at a reaction tank temperature of 160° C. for 1 hour, and the water produced by the reaction was azeotroped with the alcohol. After condensing it in a condenser, the water and alcohol were separated, and only the alcohol was refluxed to the reaction system. After the reaction was completed, the acid value was measured and found to be 1.41.

After that, the crude ester was cooled to 90°C, and an aqueous solution of 5g of sodium carbonate dissolved in 90g of water was added.
The mixture was stirred for 1 hour to neutralize unreacted monoester and extracted into water as a sodium salt. The reaction solution was transferred to a separatory funnel, the crude ester layer was separated from the water tank, and the amount of wastewater pollution in the separated water was measured.
COD was 3248PPm. The separated crude ester is washed with 270 g of water, the excess alcohol in the crude ester is distilled under reduced pressure and recovered outside the system, steam is further blown for 1 hour to completely remove the remaining alcohol, and all water is distilled under reduced pressure at 150°C. After completely removing 1.9 g of activated clay, the mixture was treated at 80°C for 30 minutes and filtered off. The product thus obtained had an acid value of 0.0051, a hue Hazen value of 10, a volume resistivity value (30℃) of 2.99×10 ¹² Ωcm, and an acid value and hue value after heating at 125℃ for 3 hours. are 0.06 and 10 respectively
It was hot.

Example 2 Isodecyl alcohol 546.1 as alcohol
The esterification reaction was carried out at 160° C. for 1 hour and 15 minutes in the same manner as in Example 1, except that g (3.45 mol) was used.
The acid value after the completion of the reaction was 1.39. Also, Example 1
The wastewater separated after the same post-treatment as
COD was 3190PPm. The obtained product had an acid value of 0.0048, a hue Hazen value of 10, a volume resistivity value (30℃) of 3.14×10 ¹² Ωcm, and an acid value and hue of 0.07 and 10 after heating at 125℃ for 3 hours, respectively. Ta.

Comparative Example 1 4.08 g (12
According to Example 1 except for using
The esterification reaction was carried out at 160°C for 4 hours and 30 minutes.

The acid value after the completion of the reaction was 1.02. After the reaction was completed, the crude ester was cooled to 90°C, and then an aqueous solution of 10g of sodium carbonate dissolved in 90g of water was added to neutralize the unreacted monoester at 90°C for 30 minutes to remove the unreacted monoester. The sodium salt was extracted into water. Thereafter, the same post-treatment as in Example 1 was carried out, and the COD of the separated wastewater was 3390 PPm. The acid value of the obtained product is 0.0056, the hue Hazen value is 10, and the volume resistivity value (30℃) is 2.51×
The acid value and hue after heating at 10 ¹² Ωcm and 125° C. for 3 hours were 0.07 and 10, respectively.

Comparative Example 2 An esterification reaction was carried out at 160° C. for 1 hour and 45 minutes in the same manner as in Example 1, except that 1.18 g (12 mmol) of sulfuric acid was used as a catalyst. The acid value after the completion of the reaction was 1.31. Furthermore, the COD of the wastewater separated after performing the same post-treatment as in Example 1 was 12,300 PPm, which was a large value compared to the example. The acid value of the obtained product is
0.0072, the hue Hazen value was 10, the volume resistivity value (30°C) was 2.09×10 ¹² Ωcm, and the acid value and hue after heating at 125°C for 3 hours were 0.09 and 10, respectively.

Comparative Example 3 2.07 g of para-toluenesulfonic acid (12
160 mmol) according to Example 1 except that 160
The esterification reaction was carried out at ℃ for 2 hours and 30 minutes. The acid value after the completion of the reaction was 1.16. In addition, the COD of wastewater separated by the same post-treatment as in Example 1 is
The value was 34000PPm, which was larger than that of the example.
The acid value of the obtained product was 0.0079, and the hue Hazen value was
10, Volume resistivity value (30℃) is 1.69×10 ¹² Ωcm,
The acid value and hue after heating at 125℃ for 3 hours are respectively
They were 0.09 and 10.

Claims (1)

[Claims] 1. When producing an ester from a carboxylic acid or carboxylic acid anhydride and an alcohol, the general formula R
A method for producing a carboxylic acid ester, characterized in that a compound represented by (SO ₃ H) ₂ (wherein R represents a lower alkylene group) is used as a catalyst. 2 The first carboxylic acid anhydride is phthalic anhydride
Manufacturing method described in section. 3. The manufacturing method according to item 1 or 2, wherein the compound is ethanedisulfonic acid.