TWI402255B - Process for preparing esters plasticizers - Google Patents

Description

Method for producing ester plasticizer

This invention relates to a process for making high purity, low hue ester plasticizers, and more particularly to a process for making ester plasticizers in the presence of a particular co-catalyst.

Plasticizers are widely used in polyvinyl chloride (PVC) products, plastic elastomers, and rubber products to exhibit good plasticity to polymer resins and impart different flexibility and performance to products. Polyvinyl butyral resin plasticized by a plasticizer is often used as an intermediate film of glued glass, whereby the intermediate film is then strengthened to bond the glass to withstand external impact without the risk of crushing and cracking, so it is widely used in automobiles and buildings. The curtain is applied. The plasticized intermediate film is mainly composed of polyvinyl butyral and a plasticizer, and is added with an adhesion promoter, an ultraviolet absorber, an antioxidant, and the like, so that the use of the bonded glass does not cause transparency during long-term use. Poor, thermal disintegration, and hydrolysis in high humidity environments cause glass atomization. The ester which is reacted with a diol or a dimer, a trimer or a tetramer thereof and a carboxylic acid is a plasticizer which is typically used in a polyvinyl butyral interlayer film because of its high boiling point, low vapor pressure, and heat resistance. Inferior solution and good water absorption resistance, so when the high temperature of the bonded glass is produced, the plasticizer vapor can be prevented from escaping from the intermediate film, and the adhesive force does not decrease even after long-term use. When the bonded glass maintains adhesion and transparency in a high temperature and high humidity environment for a long time, the purity of the plasticizer plays an important role. The synthesis of a glycol or a dimer, a trimer or a tetramer thereof and a carboxylic acid to form an ester is generally carried out using an organic sulfonate as a catalyst, and an organic sulfonate is used as a catalyst for the esterification process. The by-product is derivatized to produce a by-product of the monoester, so that the purity of the obtained ester is lowered, and as a result, the intermediate film formed is deteriorated due to high temperature and high humidity, resulting in accelerated hydrolysis, and the bonded glass is thus peeled off. On the other hand, organometallic compounds are often used as catalysts for the synthesis of ester plasticizers from diols or their dimers, trimers, tetramers and carboxylic acids, but due to impurities in the catalyst raw materials, The esterification process is often accompanied by the formation of a non-ferrous metal complex, which results in severe coloration of the plasticizer product, resulting in poor transparency of the produced glued glass.

The esterification reaction production process by a monocarboxylic acid or a polycarboxylic acid and an alcohol in the presence of a catalyst is a well-known technique for producing an ester plasticizer. However, the esterification reaction via a carboxylic acid or an alcohol, the presence of impurities and the by-products caused by the addition of a catalyst to promote the side reaction caused by the esterification must be eliminated by a cumbersome purification procedure, and also consume excessive energy and waste. The problem of impact on the environment. The impurity of the plasticizer is derived from the raw materials used and the process of the reaction. The impurities of the raw materials, such as aldehydes, unsaturated compounds, sulfur compounds, etc. in the alcohol, will produce coloring matter in the esterification reaction and reduce the purity of the product; In US00580310A, a low-color ester plasticizer product is obtained by a decompression process and by injecting inactive nitrogen to remove dissolved oxygen in the raw material alcohol to reduce the impurity coloring matter. U.S. Patent No. 4,018,708 discloses the use of two metal catalysts to first react to form a composite bimetallic catalyst which is used in the esterification reaction to shorten the reaction time and the resulting ester product has a lower hue. In JP2002-293758A, it is explained that the process for producing an ester plasticizer uses a sulfonate as a catalyst, and the side reaction product induced by the process can be treated by adding a solid alkaline substance, and the by-product sulfonate compound after decomposition is dissolved. The water can be removed by a water washing process; the product thus obtained is greatly reduced by by-products, and can maintain a good hue after high-temperature processing. US6423856B1 describes the addition of a low boiling point entraining agent having a boiling point of less than 120 ° C in the process of synthesizing an ester plasticizer. By azeotropically removing the water of the reaction, a high purity and high yield product can be obtained.

In the above invention, the use of reduced pressure deoxidation and the incorporation of nitrogen gas can alleviate the coloring opportunity of high temperature esterification, but it is still insufficient to avoid by-products caused by the raw material impurities and the catalyst, thereby making the purity of the product too low. The composite bimetallic catalyst formed by the reaction of two kinds of metal catalysts has high reactivity, and the esterification reaction produces a high purity of the ester compound, but the complex coloring body produced by the metal catalyst and the alcohol impurity is The high hue of the esterified article is imparted, thereby reducing the range of use and commercial value of the article. The addition of toluenesulfonic acid catalyst in the esterification reaction is mainly due to its high activity and short esterification time. However, the use of such a sulfonate catalyst is highly prone to side reactions, resulting in too low purity and poor quality of the plasticizer product. problem. It is a conventional technique to add a dehydration entrainer to accelerate the reaction in the esterification reaction, but the low boiling point solvent causes excessive energy consumption and the alcohol impurity causes the product to form a high hue of by-products, which is used for polyvinyl condensate. In the production of a glass interlayer film, the aldehyde plasticizer decomposes the above-mentioned by-products into aldehydes or ketones due to high temperature extrusion, resulting in coloration of the polyvinyl butyral interlayer film, so that the transparency of the bonded glass is impaired.

In order to further improve the ester purity caused by the use of a sulfonate catalyst or other catalyst to produce an ester plasticizer, and the use of an organometallic compound catalyst to produce a colored metal complex, the chromatographic product has a higher hue. The invention has extensively studied the process conditions of the ester plasticizers, and found that the diol or its dimer, trimer, tetramer, etc. are in contact with the aliphatic saturated linear or branched monocarboxylic acid. The esterification is carried out in the presence of a medium to obtain an ester plasticizer of high purity and low hue, and thus the present invention has been completed.

The invention provides a method for producing an ester plasticizer obtained by esterifying a diol, a dimer or a trimer thereof, a tetramer and a carboxylic acid with high purity and low hue. Specifically, the ester plasticizer is an ester plasticizer produced by esterification reaction of a dihydric alcohol or a dimer, a trimer or a tetramer thereof with a monocarboxylic acid (hereinafter, this is derived from a glycol or The ester obtained by esterification of a dimer, a trimer or a tetramer with a carboxylic acid is simply referred to as an "ester plasticizer"). Further, the ester plasticizer produced by the method of the present invention is characterized by a purity of ≧98.0%, hue ≦APHA 20, which can exhibit high commercial value, and improve the conventional low-purity ester as a plasticizer for polyethylene. The butyral butyral film causes the problem of poor heat resistance and moisture resistance of the bonded glass; the low hue ester plasticizer of the present invention can improve the transparency of the polyvinyl butyral interlayer film used for the bonded glass.

The main object of the present invention is to provide a process for producing a high purity, low hue ester plasticizer comprising saturating a linear or branched diol or a dimer or a trimer or a tetramer thereof with an aliphatic C4-C10. The monocarboxylic acid is obtained by esterification in the presence of a cocatalyst composed of a phosphorus-containing polyproton acid and an organometallic compound and a reactive activated carbon.

A further object of the present invention is to provide an ester plasticizer characterized by a purity of 8.098.0% and a hue of APHA 20 (the same applies hereinafter) as measured in accordance with ASTM D-1209.

According to the method for producing an ester plasticizer of the present invention, since no solvent is used as a solvent in the esterification reaction process, the volatilization of the organic gas can be greatly reduced, and the impact on environmental pollution can be reduced, and the obtained ester plasticizer has The characteristics of high purity and low hue are used to improve the transparency of the polyvinyl butyral interlayer film used in the bonded glass when the intermediate film of the laminated glass is produced by using polyvinyl butyral as a plasticizer.

The main object of the present invention is to provide a process for producing a high purity, low hue ester plasticizer comprising a glycol or a dimer thereof or a terpolymer thereof, a tetramer and an aliphatic saturated linear or branched monocarboxylic acid. In the presence of a cocatalyst composed of a phosphorus-containing polyproton acid and an organometallic compound and a reactive activated carbon, the esterification reaction is carried out to a purity of 8.098.0%; and an intermediate phase of ≦APHA 20 is an ester plasticizer. The ester plasticizer obtained by the method of the present invention is characterized in that the purity is 8.098.0%, and the hue is ≦APHA 20, so that when the laminated glass is used as a plasticizer in polyvinyl butyral, high transparency and coloring can be obtained. Low and stable products.

The method of producing a paper plasticizer of the present invention will be described in more detail later.

The diol used in the production of the present invention or its dimer, trimer, and tetramer raw materials (hereinafter collectively referred to as "diols") are chemicals which can be easily produced industrially or commercially. The diol may be a linear or branched chain aliphatic saturated diol, and representative aliphatic saturated diols such as ethylene glycol, 1,2-propanediol, and 1,3-propanediol. An aliphatic diol having 2 to 10 carbon atoms such as diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, tetraethylene glycol or pentaethylene glycol. It is preferably an aliphatic diol having 4 to 8 carbon atoms, more preferably a diol having 6 to 8 carbon atoms which repeats 2 alkyl ether groups. These diols may be used singly or in combination of two or more.

The aliphatic straight-chain or branched monocarboxylic acid which is the starting constituent of the ester plasticizer of the present invention may be exemplified by: butyric acid, isobutyric acid, valeric acid, 2-methylbutyric acid, 3-methyl group. Butyric acid, 2-methyl valeric acid, cyclohexanoic acid, heptanoic acid, 2-methylhexanoic acid, octanoic acid, isooctanoic acid, 2-ethylhexanoic acid, citric acid, isodecanoic acid, 2-methyloctanoic acid, etc. 4 to 10 carbon atoms, more preferably a saturated monocarboxylic acid having 6 to 9 carbon atoms. These monocarboxylic acids may be used singly or in combination of two or more.

The ratio of the use of the diol and the aliphatic saturated monocarboxylic acid in the ester plasticizer of the present invention may be a stoichiometric amount, for example, the equivalent ratio of the aliphatic saturated monocarboxylic acid to the diol is 2/1 1/1, in order to facilitate the smooth progress of the reaction, it is more preferable that the equivalent ratio of the monocarboxylic acid to the glycol is 1.5/1-1.1/1.

According to the method of the present invention, the phosphorus-containing polyprotic acid used in the co-catalyst composed of the phosphorus-containing polyprotic acid and the organometallic compound is a phosphorus-containing polyprotic acid having a chemical formula of H ₃ P(O) _n , wherein n represents an integer of 2-4, preferably an integer of 2-3, more preferably n=2. The phosphorus-containing polyprotonic acid may be present as a solid substance or in a solution state; when the phosphorus-containing polyprotonic acid is present in a solution, the solvent may be water or an alcohol, and the alcohol may be a unit alcohol or two. The alcohol is preferably an aqueous solution of a phosphorus-containing polyproton acid. The phosphorus-containing polyprotic acid is used in an amount of usually 0.01 to 1.0% by weight, based on the total amount of the reactants, preferably 0.01 to 0.5% by weight, more preferably 0.01 to 0.2% by weight. The phosphorus-containing polyprotic acid in the present invention may be used alone or in combination of two or more.

According to the method of the present invention, the organometallic compound used in the co-catalyst composed of the phosphorus-containing polyprotic acid and the organometallic compound can be exemplified by, for example, an organic cerium compound, an organotin compound, an organozirconium compound, or an organotitanium compound. Among them, an organic titanium compound and an organotin compound are preferred catalyst components. These organometallic compounds may be used alone or in combination of two or more. The organometallic compound is used in an amount of usually 0.01 to 1.0% by weight based on the total of the reactants, preferably 0.02 to 0.5% by weight, more preferably 0.02 to 0.2% by weight. When used in plural, the amount used means the total amount of various organometallic compounds.

The organotitanium compound can be, for example, a tetraalkyl titanate compound which is commercially available. Suitable tetraalkyl titanate is a compound represented by Ti(OR) ₄ wherein R may be the same or different from each other and represents 1 to 16 carbon atoms, preferably 1 to 12 carbon atoms, and more preferably 2 An alkyl group of 8 carbon atoms, a cycloalkyl group having 3 to 16 carbon atoms, preferably 4 to 12 carbon atoms, more preferably 5 to 8 carbon atoms, or an alkyl group having 7 to 15 carbon atoms Aryl. Preferably, R is a tetraalkyl titanate having an alkyl group of 2 to 8 carbon atoms, mainly because of its universality and ease of stability in the form of a solution. Specific examples of suitable tetraalkyl titanate compounds include, but are not limited to, titanium tetraethoxide, titanium tetrapropylene oxide, titanium tetraisopropoxide, titanium tetra-n-butylene oxide, titanium tetraisobutyloxide, titanium tetrahexoxide, and tetra-octyl oxide. Titanium, tetra-ethylhexyltitanium oxide, and the tetraalkyl titanate may be used singly or in combination of two or more. The above organotitanium compound as a catalyst is usually added in an amount of from 0.01 to 1.0% by weight based on the total amount of the reactants, more preferably from 0.02 to 0.5% by weight, still more preferably from 0.02 to 0.2% by weight. If the amount of addition is too small, the promotion efficiency of the esterification reaction is poor, and if the amount of addition is too large, the ester product may easily leave too much titanium complex to cause coloration.

The organotin compound may, for example, be dibutyltin diacetate, dibutyltin laurate, tributyltin oxide, dibutyltin oxide or monobutyltin oxide. These may be used singly or in combination of two or more. The organotin compound catalyst may be added alone or in combination with the organotitanium compound in an amount of from 0.01 to 1.0% by weight based on the total reactants, more preferably from 0.02 to 0.5% by weight, still more preferably from 0.02 to 0.2% by weight. The amount of addition is too small to promote the esterification reaction, and the excessive addition amount is limited and uneconomical to promote the esterification reaction.

According to the method of the present invention, since the esterification reaction is carried out in the presence of the reactive activated carbon in addition to the above-mentioned cocatalyst, yellowing of the esterified product at the time of high temperature esterification or oxidation can be prevented. The raw material of the activated carbon may be any activated carbon, and examples thereof include wood carbon, bamboo carbon, coconut shell carbon, and palm shell carbon, which can be produced by a known method known to those skilled in the art, and thus will not be described herein. The reactive activated carbon of the present invention preferably has a specific surface area of from 1,500 to 2,500 m ² /g, preferably from 1,800 to 2,500 m ² /g; and the activated iodine has an iodine value of from 1,000 to 2,000 mg/g. The adsorption iodine value is 1200-1800 mg/g. In the method of the present invention, the activated carbon is preferably added in an amount of from 0.1 to 10.0% by weight, preferably from 0.2 to 2.0% by weight, more preferably from 0.2 to 1.0% by weight, based on the total reactants; Insufficiently, the esterified product is easily colored, and if the amount of addition is too high, the process is lengthy due to poor filtration.

The apparatus for carrying out the method of the present invention may be a single reactor or two or three reactors in series, and the reactors are equipped with a stirring device for a good mixing and esterification of the reactants; A condenser is provided; the reactor may be provided with a water-oil separator, and the device of the oil-water separator may be used for refluxing the upper layer of the reaction into the reactor to continue the reaction, and the esterified dewatering water of the collected lower layer may be collected in the storage tank by the pipeline.

The operation of esterification of a diol with a monocarboxylic acid is generally carried out by introducing an inert gas such as nitrogen or carbon dioxide to prevent the reactant from being oxidized. Therefore, the inert gas is introduced into the method of the present invention. It is good to introduce nitrogen. Since the method of the present invention uses the above-mentioned co-catalyst, the reaction operation is easy and the reaction rate is fast, so that the reaction can be carried out directly using the reactant as a solvent without adding a solvent. The above esterification reaction can be carried out under normal pressure, pressure, and reduced pressure. In order to promote the progress of the reaction, the method of the present invention first performs esterification under normal pressure, and then removes the esterification of the reaction system under reduced pressure. water.

The reactants and the catalyst may be put into a suitable esterification reactor once or in batches, preferably in one feeding; in the initial stage of the reaction, the esterification reaction is carried out at a heating temperature in the range of 150-250 ° C at a normal pressure, preferably a reaction. The temperature is 150-220 ° C; thereafter, the removal of water generated by the accelerated esterification reaction proceeds smoothly, and a reduced pressure reaction can be applied, and the degree of vacuum is in the range of 200-700 mmHg, preferably 400-660. Mm mercury range. After the above-mentioned atmospheric pressure esterification reaction and water removal under reduced pressure, it is preferred to further carry out vacuum distillation at a reaction temperature of 200-250 ° C and an absolute pressure from 2-50 mmHg until the esterification is removed. Water and other small molecule volatiles with excess monocarboxylic acid.

After the reaction is stopped, the esterified crude product can be further neutralized, washed with water, dehydrated, dried under reduced pressure or distilled, decolorized by activated carbon, and filtered to obtain a purity of 98.0%; low color phase ≦APHA 20 high quality ester plasticizer .

The invention will be described in detail by the following examples, which are intended to be illustrative only and not to limit the scope of the invention.

Example 1

In a 3L four-necked round bottom flask equipped with a stirrer, thermometer, distillation tube and condenser, and oil and water glass, 1296 g (9.0 mol) of 2-ethylhexanoic acid, triethylene glycol 450克 (3.0 mol), 1.4 g of a 50% aqueous solution of phosphorous acid, 0.7 g of monobutyltin oxide, and an activated carbon having a specific surface area of 2000 m ² /g and an adsorption iodine value of 1500 mg/g, 7 g, were sequentially placed in the round bottom flask. . The reactor is thoroughly stirred and warmed under a nitrogen gas stream, and the reaction is dehydrated and dehydrated at 150-200 ° C. The upper 2-ethylhexanoic acid flows into the reactor through the oil-water separator to continue to participate in the reaction, and the lower layer water is discharged through the discharge valve. The cylinder is metered. When the reaction temperature reaches 200 ° C, in order to accelerate the dehydration of the esterification, the pressure is reduced and the pressure is reduced from 660 mm Hg to 460-400 mm Hg. At this time, the reactor is continuously warmed to 220. °C, the journey is about 7 hours. During this reduced pressure esterification reaction, the hydroxyl value of the reaction liquid was monitored by timed sampling until the hydroxyl value of the reaction liquid was 3.9. After the esterification reaction, the excess 2-ethylhexanoic acid in the crude esterified product is recovered by distillation, and the reaction liquid is neutralized with a 10% aqueous sodium hydroxide solution, and then subjected to a water washing treatment, dehydration treatment, and the product obtained by filtration is passed through a gas phase. The chromatographic analysis of the purity of 98.3%, the color phase of APHA10 (platinum-cobalt 10, determined according to ASTM D1209) of triethylene glycol di-2-ethylhexanate plasticizer .

Example 2

The reaction equipment, process, and formulation were the same as in Example 1 except that the catalyst monobutyltin was replaced by 1.4 g of tetra-n-butyl titanate. The reaction was also carried out under reduced pressure for 8 hours until the hydroxyl value of the reaction mixture was 3.6. The same procedure as in Example 1 was carried out, such as neutralization and the like, and the purity was 98.6% after gas chromatography, and the high quality di-2-ethylhexanoate triacetate was obtained in the form of APHA 10 (platinum-cobalt 10). Alcohol ester plasticizer.

Example 3

The reaction equipment, process and formulation were the same as in Example 1 except that the catalyst monobutyltin was replaced by 1.4 g of tetrapropyl titanate and 0.35 g of 50% aqueous hypophosphite was added. The reaction was also carried out under reduced pressure for 10 hours until the hydroxyl value of the reaction mixture was 5.2. Through the process of neutralization and the like in Example 1, a gas chromatograph was used to analyze the purity of 98.5%; the hue of APHA 18 (platinum-cobalt 18) was high quality di-2-ethylhexanoate triethylene glycol ester. Plasticizer.

Example 4

As described in Example 1, except that 2-ethylhexanoic acid was substituted with 1170 g of n-heptanoic acid, 0.35 g of an aqueous solution of 50% hypophosphorous acid was added, and 0.7 g of dibutyltin laurate was added. The other reaction equipment, process, and formulation were as Example 1. The reaction course was refluxed for 11 hours under reduced pressure until the hydroxyl value of the reaction mixture was 5.2. The process of neutralization and the like in Example 1 was carried out to obtain a purity of 98.3% by gas chromatography, and a diheptyl glycolate plasticizer having a hue of APHA 20 (platinum-cobalt 20).

Example 5

The reaction equipment, process, and formulation were the same as in Example 1 except that the catalyst was replaced with 50% phosphorous phosphite. The reaction course was refluxed for 8 hours under reduced pressure until the hydroxyl value of the reaction mixture was 5.4. The same procedure as in Example 1 was carried out, such as neutralization and the like, to obtain a purity of 98.4% by gas chromatography, and a high quality di-2-ethylhexanoic acid triethylene glycol having a hue of APHA 17 (platinum-cobalt 10). Ester plasticizer.

Comparative example 1

As in the apparatus and the synthesis process of Example 1, 1080 g (9.0 mol) of 2-ethylhexanoic acid, 450 g (3.0 mol) of triethylene glycol, 2.3 g of p-toluenesulfonic acid and a specific surface area of 2000 m ² /g. 6.1 g of activated carbon containing 52% of high-pressure steam was separately charged into the reactor, and 100 g of xylene was added as a solvent. The reaction was also carried out under reduced pressure for 5 hours until the hydroxyl value of the reaction mixture was 5.2. After the process of vacuum distillation, neutralization, etc. of Example 1, a gas chromatograph was used to analyze the purity of 92.2%; the hue of APHA 15 (platinum-cobalt 15) was di-2-ethylhexanoic acid triacetate. Alcohol ester plasticizer.

Comparative example 2

The formulation and process of Comparative Example 1 were followed except that the catalyst was substituted with p-toluenesulfonic acid with 0.3 g of monobutyltin oxide and 0.6 g of tetra-n-butyl titanate. The reaction course was refluxed for 14 hours under reduced pressure until the hydroxyl value of the reaction mixture was 5.1. After the process of vacuum distillation, neutralization, etc. of Example 1, a gas chromatograph was used to analyze the purity of 98.9%; the hue of APHA 300 (platinum-cobalt 300) was di-2-ethylhexanoate triacetate. Alcohol ester plasticizer.

Comparative example 3

The reaction equipment, process and formulation were the same as in Example 1 except that the catalyst oxidation of monobutyltin and hypophosphorous acid was replaced by 0.6 g of p-toluenesulfonic acid and 0.3 g of tetra-n-butyl titanate. The reaction was also carried out under reduced pressure for 12 hours until the hydroxy value of the reaction mixture was > The same procedure as in Example 1 was used for the same neutralization and the like, and the purity of the gas chromatograph was 96.0%; the color of the phase was APHA 50 (platinum-cobalt 50) of di-2-ethylhexanoic acid triethylene glycol ester. Agent.

Comparative example 4

As in Example 2, activated carbon was replaced by 7 g of activated carbon having a specific surface area of 1300 m ² /g and an adsorbed iodine value of 930 mg/g. Other reaction equipment, processes, and formulations were as in Example 1. The reaction was also carried out under reduced pressure for 11.5 hours until the hydroxy value of the reaction mixture was 5.9. The same procedure as in Example 1 was carried out, such as neutralization and the like, to obtain a purity of 98.0% by gas chromatography, and a diethylene glycol di-2-ethylhexanoate of APHA 55 (platinum-cobalt 55). Plasticizer.

The comparison results of these examples and comparative examples are shown together in Table 1 below.

From the above, in the method for producing an ester plasticizer of the present invention, the glycol is carried out by combining a phosphorus-containing polyproton acid and an organometallic compound as a co-catalyst and in the presence of a reactive carbon which provides oxidation resistance. Esterification with a monocarboxylic acid gives a high purity, low hue ester plasticizer. Due to the high purity and low hue of the obtained ester plasticizer, when it is used for a plasticizer of polyvinyl butyral, a plasticized product excellent in heat resistance, moisture resistance, and transparency can be obtained.

Claims (11)

A method for producing a high-purity, low-color ester plasticizer from a glycol and a monocarboxylic acid, comprising at least one selected from the group consisting of glycols, dimers, trimers, and tetramers thereof The diol is aliphatic or C4-C10 saturated linear or branched monocarboxylic acid, and the equivalent ratio of aliphatic saturated monocarboxylic acid to diol is 2/1-1/1, in the presence of phosphorus-containing protons. It is obtained by esterification reaction in the presence of a cocatalyst composed of an acid and an organometallic compound and a reactive activated carbon; wherein the reactive activated carbon has a specific surface area of 1500-2500 m ² /g and an adsorption iodine value of 1000- 2000 mg/g. The method of claim 1, wherein the diol or a dimer or trimer or tetramer thereof is an aliphatic diol having 2 to 10 carbon atoms. The method of claim 1, wherein the aliphatic C4-C10 saturated linear or branched monocarboxylic acid is selected from the group consisting of butyric acid, isobutyric acid, valeric acid, 2-methylbutyric acid, 3-methyl Butyric acid, 2-methylpentanoic acid, cyclohexanoic acid, heptanoic acid, 2-methylhexanoic acid, octanoic acid, isooctanoic acid, 2-ethylhexanoic acid, decanoic acid, isophthalic acid, 2-methyloctanoic acid Or a variety. The method of claim 1, wherein the phosphorus-containing polyprotic acid is a phosphorus-containing polyprotic acid having a chemical formula of H ₃ P(O) _n , wherein n represents an integer of 2-4. The method of claim 4, wherein the phosphorus-containing polyprotic acid is used in an amount of from 0.01 to 1.0% by weight based on the total reactants. The method of claim 1, wherein the organometallic compound is selected from one or more of an organotellurium compound, an organotin compound, an organozirconium compound, or an organotitanium compound. The method of claim 6, wherein the organometallic compound is used in an amount of from 0.01 to 1.0% by weight based on the total reactants. The method of claim 6, wherein the organometallic compound is a compound represented by Ti(OR) ₄ , wherein R may be the same or different from each other, and represents an alkyl group having 1 to 16 carbon atoms, and 3 A cycloalkyl group of 16 carbon atoms, an alkaryl group having 7 to 15 carbon atoms. For example, the method of claim 6 wherein the organometallic compound is selected An organotin compound of one or more of dibutyltin diacetate, dibutyltin laurate, tributyltin oxide, dibutyltin oxide, and monobutyltin oxide. The method of claim 1, wherein the reactive activated carbon is used in an amount of from 0.1 to 10.0% by weight based on the total reactants. An ester plasticizer prepared by the method of claim 1, which is characterized by a purity of 8.098.0% and a hue of APHA 20 measured according to ASTM D1209.