JPH07278056A - Production of organic acid ester - Google Patents

Abstract

PURPOSE:To efficiently and readily produce an organic acid ester compound free from a residual catalyst, excellent in volume resistivity value-and useful as, e.g. a plasticizer for PVC-based resin by reacting an organic acid with an alcohol and treating the resultant reaction product containing a catalyst with an aqueous solution of a polyhydric alcohol. CONSTITUTION:An organic acid (anhydride) is reacted with an alcohol in the presence of (A) an organometallic compound catalyst such as tetraisopropyl titanate, tetrabutyl titanate or tetra-2-ethylhexyl titanate and the resultant esterification reaction product containing the component (A) is treated with (B) an aqueous solution of a polyhydric alcohol, e.g. an aqueous solution of pentaerythritol, thus producing the objective compound. In addition, the amount of the polyhydric alcohol as the component (B) is preferably 1/10 to 1/1 of RV value represented by the formula [A and B are respectively the molar number and the valence number of the component (A); C and M are respectively the valence number and the molecular weight of the polyhydric alcohol in the component (B)] on weight base.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for industrially advantageously producing a high-quality organic acid ester containing a small amount of impurities such as catalyst residues by an easy operation. Specifically, when an organic acid ester used as a plasticizer for vinyl chloride resin is produced using an organometallic compound catalyst such as a titanate catalyst, the catalyst is efficiently removed in the purification step after the reaction, The present invention relates to a method for improving the purity of ester.

[0002]

2. Description of the Related Art As an advantageous method for producing an ester from an organic acid or its anhydride and an alcohol, a titanate type organometallic compound such as tetraisopropyl titanate, tetrabutyl titanate or tetra-2-ethylhexyl titanate is used as a catalyst. The method of doing so is widely known. In order to purify the esterification reaction product by these methods to obtain the product ester, it is necessary to separate and remove the used titanate-based catalyst and the catalyst residue. Wet method and dry method are known as methods therefor. ing.

In the wet method, the titanate catalyst is hydrolyzed by adding water to the reaction product and heating it, and then an alkali is added to neutralize the unreacted organic acid. After washing with water and recovering excess alcohol by steam stripping or vacuum distillation, it is adsorbed and filtered with activated carbon, activated clay or the like (for example, JP-A-55-130937).

As a dry method, a method in which the esterification reaction product is subjected to a heat contact treatment with a solid alkali such as sodium carbonate in the absence of water, or simultaneously, is subjected to an adsorption treatment with an adsorbent such as activated clay ( JP-A-54-76517
No.) or a compound such as a phosphite compound or ethanolamine prior to steam stripping to remove the titanate catalyst (USP 4,506,
No. 091) is known.

However, the former wet method has a drawback that the process is complicated, the refining process requires a long time, and the consumption of cleaning water and heat energy is large. Also, the latter dry method using solid alkali is a solid-liquid reaction, so the treatment time is long, and since it is a heat treatment at high temperature, alteration of the ester is likely to occur, and further solid alkali for neutralization and catalyst removal is used. However, the treatment with phosphites and ethanolamines is highly effective, but the treatment of the treatment agent and the volume resistivity of the product ester obtained are lower than with other methods. , Etc.

On the other hand, the present inventor first made a high-quality ester containing few impurities industrially advantageous by contacting the esterification reaction product with a polyhydric alcohol under heating to remove the catalyst. A method of manufacturing has been found (JP-A-3-31239).

[0007]

However, even in the above-mentioned treatment method using polyhydric alcohol, a large amount of polyhydric alcohol must be used in order to lower the treatment temperature, and conversely, in order to reduce this amount. Was required to be treated at a high temperature, but in this case, it was found that there was a problem that the amount of by-products generated from the polyhydric alcohol increased.

In view of the situation of the prior art as described above, the present inventor has made earnest studies to solve the problems in the treatment with the polyhydric alcohol, and as a result, by using the polyhydric alcohol as an aqueous solution, it can be used alone. The present invention has been completed by finding that the amount of alcohol is smaller than that in the case of the above treatment and the treatment can be performed at a low temperature. That is, the present invention enables treatment with a polyhydric alcohol to be carried out efficiently at a lower temperature and in a small amount, and a high-quality ester having a low content of impurities such as a catalyst and a catalyst residue can be industrially produced by an easy operation. It is intended to be manufactured advantageously.

[0009]

The gist of the present invention is to provide a method for producing an organic acid ester by reacting an organic acid or its anhydride with an alcohol in the presence of an organometallic compound catalyst, which comprises a catalyst. A method for producing an organic acid ester, which comprises treating the esterification reaction product with a polyhydric alcohol aqueous solution.

The present invention will be described in detail below. Examples of the organic acid in the present invention include aromatic polycarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid, trimellitic acid and pyromellitic acid, and aliphatic polycarboxylic acids such as adipic acid, azelaic acid and sebacic acid. , Maleic acid, aliphatic unsaturated polycarboxylic acids such as fumaric acid, oleic acid, aliphatic monocarboxylic acids such as stearic acid, aromatic monocarboxylic acids such as benzoic acid, and the like, as an organic acid anhydride. Include the anhydrides of the above organic acids.

Examples of alcohols used in the production of esters together with these organic acids include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, heptanol, n-octanol, 2 -Aldol condensation of oxo reaction product of n-butene, isononyl alcohol produced by oxo reaction of dimer of ethylhexanol, isooctanol and mixed butene, isodecyl alcohol produced by oxo reaction of propylene trimer and mixed C ₁₀ alcohols as a main component 2-propylheptanol made by hydrogenation, undecanol, aliphatic saturated monohydric alcohols such as tridecanol, ethylene glycol, propylene glycol, diethylene glycol Aliphatic polyhydric alcohols, or aromatic monohydric alcohol such as benzyl alcohol and the like, may be used by mixing these alcohols.

Examples of the organometallic compound catalyst of the present invention include alkyl titanate compounds which exhibit activity as an esterification catalyst at a temperature of 180 ° C. or higher. Examples thereof include tetraisopropyl titanate, tetrabutyl titanate and tetra-2-ethylhexyl. Titanate or the like is used. The esterification reaction of an organic acid or its anhydride with an alcohol is carried out according to a known method, for example, by mixing a raw material organic acid in a predetermined ratio with an alcohol, adding an organometallic compound catalyst thereto, and heating at a temperature of about 180 ° C. or higher. It is carried out by heating.

A feature of the present invention is that the reaction product containing the catalyst obtained by the above esterification reaction is treated with an aqueous polyhydric alcohol solution, whereby the amount of polyhydric alcohol used is reduced. At least, it is possible to obtain the effect that the catalyst can be efficiently removed at a low temperature. The polyhydric alcohol used in the present invention is 3 in the molecule.
It is a compound having only one or more hydroxyl groups and composed only of carbon, hydrogen and oxygen elements. The polyhydric alcohol is required to be water-soluble, but it is preferable that the polyhydric alcohol can give an aqueous solution having a concentration of 0.1% by weight or more at room temperature.

As the polyhydric alcohol which can be used here, for example, polyhydric alcohols such as pentaerythritol, trimethylolpropane, dipentaerythritol, erythritol, sorbitol and sugars are particularly preferable. These polyhydric alcohols may be used alone or in combination of two or more. The amount of polyhydric alcohol used is the value given by the following formula (RV)
1/10 to 1/1, preferably 1/5 to 4/5.

[0015]

[Equation 2] However, A: number of moles of organometallic compound catalyst B: valence of organometallic compound catalyst (refers to valence of metal element) C: valence of polyhydric alcohol M: molecular weight of polyhydric alcohol

The amount of polyhydric alcohol used is 1/10 of RV.
If it is less than, the organometallic compound catalyst cannot be removed efficiently,
Alternatively, the treatment tends to require a high temperature, and even if an amount exceeding RV is used, its effect is not increased in proportion to the added amount and it is uneconomical, and the residue after the treatment causes tackiness. In addition to being easily charged, the product ester tends to have a low volume resistivity.

The concentration of the polyhydric alcohol aqueous solution used is 0.
It is preferably in the range of 5% to 10% (weight / volume%). If this concentration is too low, the catalyst residue becomes sticky and separation / removal becomes difficult, and if it is too high,
A sufficient effect may not be obtained unless the treatment temperature is raised. The treatment with this polyhydric alcohol aqueous solution is 100
℃ or more, preferably 110 ℃ or more, more preferably 12
The temperature is preferably 0 ° C. or higher and 150 ° C. or lower, preferably 145 ° C. or lower, more preferably 140 ° C. or lower. If the treatment is performed at a temperature lower than 100 ° C, it takes a long time to remove the organometallic catalyst. On the other hand, if the treatment is performed at a temperature higher than 150 ° C, a lot of impurities derived from the polyhydric alcohol may occur, which may adversely affect the product quality. There is.

This treatment can be carried out by adding a predetermined amount of the polyhydric alcohol aqueous solution to the reaction liquid containing the catalyst after the esterification reaction and stirring and mixing at the treatment temperature for 5 minutes or more. By this treatment, the organometallic compound catalyst reacts with the polyhydric alcohol to form a solid reaction product, which can be easily removed by filtration or the like, so that a good-quality ester can be industrially advantageously produced. .

The treatment with this polyhydric alcohol aqueous solution is
After the esterification reaction and before the filtration step, it can be carried out without any particular limitation, for example, immediately after the esterification reaction or before the filtration step immediately before commercialization, but the excess After removing the alcohol by distillation and before removing a trace amount of residual alcohol by steam distillation, it is possible to remove the alcohol including the alcohol produced by the slight decomposition of the ester that may occur due to the addition of water in this process. It is particularly preferable because the possibility of odor to be eliminated.

[0020]

EXAMPLES Next, the method of the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. In the examples and comparative examples, “%” means “weight / volume (w /
v)% ". <Esterification reaction and polyhydric alcohol aqueous solution treatment>

Example 1 74 g (0.5 mol) of phthalic anhydride, 163 g (1.25 mol) of 2-ethylhexanol, and 0.36 g (0.001 mol) of tetraisopropyl titanate were used as a thermometer, a nitrogen introducing tube, Stirrer, Dean-Stark type water divider (hereinafter,
(Simply referred to as "water divider"), and charged into a flask with an internal volume of 1 liter equipped with a reflux condenser, heated while stirring under a nitrogen stream, and maintaining the reaction liquid temperature at 190 to 215 ° C to produce water. The esterification reaction was carried out for 3 hours while continuously removing C. by a water separator. The acid value of the reaction solution is 0.
After confirming that the pressure was 1 mgKOH / g or less, the system was depressurized and the internal pressure of 6 to 54 hPa (5 to 40 mmHg) was used to remove excess 2
-Ethylhexanol was distilled off.

1 ml of a 13% aqueous solution of pentaerythritol (0.
001 mol) and stirred at 140 ° C. for 20 minutes,
After cooling to 120 ° C., 0.2 g of magnesium oxide and 0.1 g of activated carbon were added, dehydration and filtration were performed at the same temperature to remove solids, and di-2-ethylhexyl phthalate (hereinafter referred to as “DOP”) was added. Obtained. Acid value for this DOP,
The volume resistivity, hue and titanium content were measured. The measurement results are summarized in Table-1. In the table, “PE” means “pentaerythritol”.

Example 2 The concentration of the pentaerythritol aqueous solution used for the treatment was 1.
An esterification reaction and treatment were carried out in the same manner as in Example 1 except that the amount was 3% and the addition amount was 1 ml (0.0001 mol) to obtain DOP. The evaluation results of the products are also shown in Table-1. Example 3 A DOP was obtained by carrying out the esterification reaction / treatment in the same manner as in Example 1 except that the treatment temperature was 100 ° C. and then the temperature was raised to 120 ° C. for magnesium oxide treatment. The evaluation results of the products are also shown in Table-1.

Example 4 The treatment temperature was 80 ° C., the treatment time was 60 minutes, and then 12
An esterification reaction / treatment was carried out in the same manner as in Example 1 except that the temperature was raised to 0 ° C. and the magnesium oxide treatment was carried out to obtain DOP. The evaluation results of the products are also shown in Table-1. Example 5 The concentration of the pentaerythritol aqueous solution used for the treatment was 26
%, The esterification reaction / treatment was carried out in the same manner as in Example 1 except that the addition amount was 1 ml (0.0002 mol) to obtain DOP. The evaluation results of the products are also shown in Table-1.

Comparative Example 1 The esterification reaction / treatment was carried out in the same manner as in Example 1 except that 0.13 g (0.001 mol) of pentaerythritol was used in place of the pentaerythritol aqueous solution.
P was obtained. The evaluation results of the products are also shown in Table-1. Comparative Example 2 Esterification reaction / treatment was carried out in the same manner as in Example 1 except that 0.13 g (0.001 mol) of pentaerythritol was used in place of the pentaerythritol aqueous solution, and the treatment temperature was 180 ° C. Obtained. The evaluation results of the products are also shown in Table-1. <Plasticizer evaluation method>

[0026]

[Table 1] (1) Acid value Based on JIS K6751. (2) Volume resistivity same as above (3) Hue same as above (4) Titanium content It was measured by ICP (emission spectrometry).

[0027]

[Table 2]

[0028]

EFFECT OF THE INVENTION By treating the esterification reaction product by the method of the present invention, the organometallic compound catalyst can be efficiently removed at a low temperature with a small amount of polyhydric alcohol as compared with the conventional polyhydric alcohol treatment method. The ester can be purified economically and energetically. Moreover, the obtained ester has a higher volume resistivity than that obtained by the conventional method, and other properties are equal to or higher than those of the conventional method. Pentaerythritol is suitable as the polyhydric alcohol.

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Claims (5)

[Claims] 1. A method for producing an organic acid ester by reacting an organic acid or its anhydride with an alcohol in the presence of an organometallic compound catalyst, wherein the esterification reaction product containing the catalyst is an aqueous polyhydric alcohol solution. A method for producing an organic acid ester, which comprises treating with an organic acid ester. 2. The weight of the polyhydric alcohol in the polyhydric alcohol aqueous solution used for the treatment is a value (R
The method for producing an organic acid ester according to claim 1, wherein the range is 1/10 to 1/1 of V). [Equation 1] However, A: number of moles of organometallic compound catalyst B: valence of organometallic compound catalyst C: valence of polyhydric alcohol M: molecular weight of polyhydric alcohol 3. The treatment with an aqueous solution of polyhydric alcohol is performed 10 times.
The method for producing an organic acid ester according to claim 1 or 2, which is performed at 0 to 150 ° C. 4. The method for producing an organic acid ester according to claim 1, wherein pentaerythritol is used as the polyhydric alcohol. 5. An organometallic catalyst, tetraisopropyl titanate, tetrabutyl titanate, or tetra-
Any one of 2-ethylhexyl titanate or 2
The method for producing an organic acid ester according to claim 1, wherein a mixture of one or more kinds is used.