Method for producing esters

Abstract

To provide a method for obtaining esters that have low odor and high stability over a long period of time. [Solution] The above method for producing the ester comprises the steps of reacting an alcohol and an aliphatic carboxylic acid to obtain a crude ester product, and treating the crude ester product with magnesium silicate at 60 to 120°C, wherein the magnesium silicate has a silicon dioxide content of 55 to 70% by mass, a magnesium oxide content of 10 to 25% by mass, and a specific surface area of ​​100 m². 2 It is 1 / g or more.

Description

Technical Field

[0001] The present invention relates to a method for producing an ester.

Background Art

[0002] Esters obtained by the reaction of various alcohols with carboxylic acids such as fatty acids are used in a wide range of applications, including industrial uses such as lubricating oils, metal working fluids, and plasticizers, as well as healthcare uses such as cosmetics and detergents. As an industrial production method for esters, a method of producing an ester by subjecting an alcohol and a carboxylic acid to a dehydration reaction at a high temperature is generally known. However, this reaction does not proceed completely, and the raw materials such as alcohol and carboxylic acid, or modified products thereof, remain in the ester. The residual impurities such as raw materials may accelerate the deterioration of the ester or may lead to insufficient inherent performance of the ester. Accordingly, a method for synthesizing an ester with few impurities and high purification degree is desired. Further, for esters produced by, for example, a transesterification method or the like, it is also desired to reduce impurities and increase the purification degree.

[0003] As a method for obtaining an ester with high purification degree, for example, Patent Document 1 describes a method in which ammonia or ammonium carbonate is added to a crude fatty acid ester to form fatty acid ammonium and the like, and these are separated and removed. According to this method, unreacted raw material fatty acids contained in the fatty acid ester can be removed. The ester purified in this manner is used as the above-mentioned lubricating oil and the like.

[0004] On the other hand, odor is cited as one of the indicators of the purification degree of an ester. Odor is susceptible to influence even when the residual amount of impurities is extremely small, and an ester with low odor can be judged to have a high purification degree. As a method for reducing the odor of an ester, for example, Patent Document 2 discloses a method of bringing a fat or oil into contact with a supercritical fluid to incorporate odor components into the supercritical fluid, thereby reducing the odor of the fat or oil. In this manner, the ester whose odor is suppressed as compared with the conventional ones can be used in applications that come into direct contact with the human body, such as the above-mentioned cosmetics. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 8-92159 [Patent Document 2] Japanese Patent Publication No. 2001-354991 [Overview of the project] [Problems that the invention aims to solve]

[0006] Among the various applications of esters, cosmetics, in particular, often have long storage periods between manufacturing and consumption. When stored for extended periods, esters can decompose or deteriorate, potentially altering their odor, physical properties, and other qualities. Therefore, it is desirable that the esters used in these applications maintain consistent quality over long periods. However, the aforementioned prior art did not adequately address long-term quality stability, often resulting in insufficient performance. In other words, there was a need for the development of a method capable of producing esters that are not only low-odor, meaning highly purified, but also highly stable over long periods.

[0007] This invention was made in view of the aforementioned problems. The object of this invention is to provide a method for obtaining an ester that has low odor and high quality stability over a long period of time. [Means for solving the problem]

[0008] As a result of diligent research by the inventors, we have discovered that by treating crude ester products with a specific magnesium silicate at a specific temperature, it is possible to produce esters with low odor and high quality stability over a long period of time.

[0009] In other words, the present invention provides the following method for producing esters. [1] The process includes a step of treating the crude ester product with magnesium silicate at 60-120°C, wherein the magnesium silicate has a silicon dioxide content of 55-70% by mass, a magnesium oxide content of 10-25% by mass, and a specific surface area of ​​100-700 m². 2 A method for producing esters, which is / g.

[0010] [2] The method for producing an ester according to [1], wherein, prior to the processing step, one or more steps are further performed, selected from (1) a distillation step of distilling off an alcohol and / or aliphatic carboxylic acid from the crude ester product, (2) a neutralization step of neutralizing the crude ester product with an alkaline aqueous solution, and (3) an adsorption treatment step of mixing the crude ester product with an adsorbent. [Effects of the Invention]

[0011] According to the manufacturing method of the present invention, an ester with low odor and high stability over a long period of time can be obtained. [Modes for carrying out the invention]

[0012] The raw materials and manufacturing process used in the manufacturing method of the present invention will be described in detail below. In this specification, the method for producing the ester of the present invention may be simply referred to as the "manufacturing method." In this specification, numerical ranges defined using the symbol "~" include the values ​​at both ends (upper and lower limits) of "~". For example, "2~5" means 2 or more and 5 or less.

[0013] The present invention provides a method for producing esters, comprising at least a processing step of treating a crude ester product with a specific magnesium silicate at a specific temperature. However, the production method may further include other steps. For example, various purification steps may be included before the processing step of treating the crude ester product with magnesium silicate. Furthermore, the method for preparing the crude ester product to be treated in the processing step is not particularly limited. In the following description, an example will be given in which various purification steps are further included between the step of preparing the crude ester product and the step of treating it with magnesium silicate. However, the method for producing esters of the present invention is not limited to this method and may further include any other steps. Each step will be described in detail.

[0014] [Steps for preparing crude ester product] As mentioned above, the method for obtaining crude ester products is not particularly limited, but examples include methods for preparing esters from alcohols and aliphatic carboxylic acids, and methods using transesterification. The method for preparing esters from alcohols and aliphatic carboxylic acids will be described below.

[0015] <Alcohol> The alcohol used in the production method of the present invention may be a monohydric alcohol or a polyhydric alcohol of two or more hydric values. Furthermore, the alcohol may be a saturated alcohol or an unsaturated alcohol. In addition, the alcohol may be an aliphatic alcohol or an aromatic alcohol. If the alcohol is an aliphatic alcohol, the aliphatic chain may have a linear, branched, or cyclic structure. For the preparation of the crude ester product, one type of alcohol or a combination of two or more types can be used.

[0016] Monohydric alcohols include saturated aliphatic alcohols with linear structures such as methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, 1-decanol, 1-undecanol, 1-dodecanol, 1-tridecanol, 1-tetradecanol, 1-hexadecanol, 1-octadecanol, and 1-docosanol; and linear alcohols such as cis-9-hexadecene-1-ol (palmitrail alcohol), cis-9-octadecene-1-ol (oleyl alcohol), and cis,cis-9,12-octadecadiene-1-ol (linoleyl alcohol). Examples include unsaturated aliphatic alcohols having a chain-like structure; saturated (or unsaturated) aliphatic alcohols having a branched chain structure such as 2-propanol, 2-butanol, 2-ethyl-1-butanol, 2-ethyl-1-hexanol, 3,5,5-trimethyl-1-hexanol, 7-methyl-1-octanol, 11-methyl-1-dodecanol, and 16-methyl-1-heptecanol; saturated (or unsaturated) aliphatic alcohols having a cyclic structure such as cyclopropanol, cyclobutanol, cyclopentanol, cyclohexanol, and cycloheptanol; and aromatic alcohols such as phenol, benzyl alcohol, and phenethyl alcohol.

[0017] Examples of polyhydric alcohols with a valency of 2 or more include neopentyl glycol, 2-ethyl-2-methyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-n-butyl-2-ethyl-1,3-propanediol, trimethylolethane, trimethylolpropane, trimethylolnonane, pentaerythritol, and dipentaerythritol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, and diglycerin.

[0018] From the viewpoint of easy availability, the alcohol is preferably an alcohol having 1 to 22 carbon atoms, more preferably an alcohol having 1 to 18 carbon atoms. Further, from the viewpoint of reactivity, it is preferably a 1- to 6-hydric alcohol, more preferably a 1- to 4-hydric alcohol.

[0019] <Aliphatic carboxylic acid> The aliphatic carboxylic acid (hereinafter also simply referred to as "carboxylic acid") used in the production method of the present invention may be any compound that has an aliphatic chain and one or more carboxy groups. The carboxylic acid may be a monovalent carboxylic acid or a divalent or higher polyvalent carboxylic acid, with a monovalent carboxylic acid or a divalent carboxylic acid being preferred. In addition, the aliphatic chain of the carboxylic acid may be saturated or unsaturated, linear, branched, or cyclic. For the preparation of the crude ester product, only one type of aliphatic carboxylic acid can be used, or two or more types can be used in combination.

[0020] Examples of the monovalent carboxylic acid include monovalent saturated carboxylic acids having a linear structure such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, heptanoic acid, caprylic acid, pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, stearic acid, and behenic acid; unsaturated carboxylic acids having a linear structure such as myristoleic acid, palmitoleic acid, oleic acid, linoleic acid, and linolenic acid; saturated (or unsaturated) carboxylic acids having a branched structure such as 2-methylpentanoic acid, 2-ethylhexanoic acid, 3,5,5-trimethylhexanoic acid, 7-methyloctanoic acid, 9,9-dimethyldecanoic acid, 11-methyldodecanoic acid, and 16-methylheptadecanoic acid; and saturated (or unsaturated) carboxylic acids having a cyclic structure such as cyclopropanecarboxylic acid, cyclobutanecarboxylic acid, cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, and cycloheptanecarboxylic acid.

[0021] Examples of the divalent carboxylic acid include succinic acid, adipic acid, azelaic acid, sebacic acid, and the like.

[0022] As the aliphatic carboxylic acid, from the viewpoint of easy availability, an aliphatic carboxylic acid having 1 to 22 carbon atoms is preferred, an aliphatic carboxylic acid having 1 to 18 carbon atoms is more preferred, and an aliphatic carboxylic acid having a linear or branched chain structure with 1 to 18 carbon atoms is even more preferred.

[0023] <Reaction of alcohol and aliphatic carboxylic acid> The preparation of the crude ester product is carried out by charging the above-mentioned alcohol and aliphatic carboxylic acid into a suitable reactor. At this time, the ratio of the alcohol to the aliphatic carboxylic acid is preferably such that the amount of aliphatic carboxylic acid groups is 0.6 to 1.5 (molar equivalents) relative to the amount of hydroxyl groups of the alcohol. In the present specification, the ratio of the amount (moles) of carboxylic acid groups of the aliphatic carboxylic acid to the amount (moles) of hydroxyl groups of the alcohol used in preparing the crude ester product is also referred to as "COOH / OH".

[0024] The reaction temperature of the above alcohol and aliphatic carboxylic acid is preferably in the range of 120°C to 250°C in order to efficiently remove the water generated as the esterification reaction proceeds. The atmosphere during the reaction is not particularly limited, but it is preferred to carry out the reaction under a nitrogen stream to suppress side reactions. Further, the pressure during the reaction is not particularly limited, but the reaction atmosphere may be depressurized in order to efficiently distill off water.

[0025] While there are no particular restrictions on the reaction time, from the viewpoint of the stability of the ester produced, a time that allows the esterification reaction to proceed sufficiently is preferable. The progress of esterification can be determined by the acid value and hydroxyl value. For example, if the amount of carboxylic acid groups of the aliphatic carboxylic acid relative to the amount of hydroxyl groups of the alcohol at the start of the reaction (COOH / OH) is 0.6 to 1.0 (molar equivalent), it is preferable to continue the reaction until the acid value of the crude ester product is 3.0 mgKOH / g or less. On the other hand, if the amount of carboxylic acid groups of the aliphatic carboxylic acid relative to the amount of hydroxyl groups of the alcohol at the start of the reaction (COOH / OH) is 1.0 to 1.5 (molar equivalent), it is preferable to continue the reaction until the hydroxyl value of the crude ester product is 5.0 mgKOH / g or less. The above acid value is a value measured in accordance with JIS C-2101, and the above hydroxyl value is a value measured in accordance with JIS K-0070.

[0026] When alcohols react with aliphatic carboxylic acids, catalysts can be used to ensure the reaction proceeds efficiently and sufficiently. There are no particular restrictions on the catalyst used, as long as it has a catalytic effect on the esterification reaction. Common catalysts include Brønsted acids and Lewis acids. Examples of Brønsted acids include sulfuric acid, p-toluenesulfonic acid, and methanesulfonic acid. Examples of Lewis acid catalysts include titanium, zirconium, and hafnium, which possess Lewis acidity.

[0027] [Various purification processes] After the reaction of the alcohol and aliphatic carboxylic acid described above, any of the following steps (1) to (3) may be carried out. The choice of which step to carry out should be appropriately selected according to the method for preparing the crude ester product. These steps may be carried out individually or in combination of two or more steps. By carrying out at least one of these steps, it becomes easier to obtain an ester that is more stable over a longer period of time. It is more preferable to carry out two of the steps (1) to (3), and even more preferable to carry out all three steps. There is no particular order in which the three steps are carried out, but it is more preferable to carry them out in the order of (1), (2), and (3) below, or in the order of (2), (1), and (3).

[0028] <Process (1): Distillation of raw material alcohol and carboxylic acid (Distillation process)> Step (1) is a step in which any alcohols or aliphatic carboxylic acids remaining in the crude ester product are removed by distillation under reduced pressure. The temperature and degree of reduced pressure used for removing the alcohols and aliphatic carboxylic acids can be appropriately selected depending on the amount and type of alcohols and aliphatic carboxylic acids remaining in the crude ester product. For example, it can be carried out at a temperature range of 150°C to 250°C and a reduced pressure of 100 Torr or less. Furthermore, it is preferable to carry out the process under a nitrogen atmosphere in order to prevent oxidative degradation of the ester in the crude ester product as much as possible. The time for removing the alcohols and carboxylic acids can be appropriately selected, but it is usually preferable to be between 0.5 hours and 5 hours.

[0029] <Step (2): Neutralization treatment with alkaline aqueous solution (neutralization step)> Step (2) is a step in which an alkaline aqueous solution is added to the crude ester product to neutralize it. More specifically, a specified amount of alkaline aqueous solution is added to the crude ester product, stirred, and allowed to stand to separate into layers, after which the alkaline aqueous solution is discharged. The alkaline component in the alkaline aqueous solution used is preferably sodium hydroxide, potassium hydroxide, sodium carbonate, or potassium carbonate, and one of these can be used alone or in combination of two or more. Furthermore, the concentration of the alkaline component in the alkaline aqueous solution is preferably 5 to 30% by mass, taking into consideration the processing efficiency and the hydrolysis of the ester by the alkaline aqueous solution.

[0030] The amount of alkaline aqueous solution added to the crude ester product is preferably adjusted so that the amount of alkaline component is 1 to 2 molar equivalents relative to the acid value of the crude ester product. The temperature for the neutralization treatment is preferably in the range of 60°C to 90°C. At this time, the alkaline aqueous solution may be heated to the above temperature before being mixed with the crude ester product, or the crude ester product and the alkaline aqueous solution may be mixed first and then heated to the above temperature. In step (2), it is preferable to stir the mixture of the crude ester product and the alkaline aqueous solution. The stirring method is not particularly limited and any known method may be used. The stirring time can be selected as appropriate, but is usually preferably 0.01 hours or more and 3 hours or less.

[0031] Afterward, stirring is stopped and the mixture is allowed to stand and separate into layers to remove the lower layer of alkaline aqueous solution. If alkaline components remain in the ester, the heat resistance of the ester may decrease. Therefore, it is preferable to wash with water to thoroughly remove the alkaline components. For example, 5 to 30% by mass of water is added to the amount of crude ester product after removal of the alkaline aqueous solution, and the mixture is stirred. Then, stirring is stopped and the mixture is allowed to stand and separate into layers to remove the lower layer of water. It is preferable to repeat this series of operations until the pH of the treated water is 7 to 9. Finally, dehydration is performed to remove water from the crude ester product. There are no particular restrictions on the method of dehydration, but stirring under reduced pressure at 60 to 150°C can sufficiently reduce the amount of water in the ester.

[0032] <Process (3): Adsorption treatment using adsorbent (Adsorption treatment process)> Step (3) is a step in which an adsorbent is added to the crude ester product to adsorb alcohols and / or aliphatic carboxylic acids. Examples of adsorbents that can be used include activated clay, acid clay, activated carbon, zeolite, activated alumina, diatomaceous earth, silicon dioxide, aluminum oxide, and hydrotalcite. These may be used individually or in combination of two or more. The amount of adsorbent used is preferably 0.1 to 5% by mass relative to the amount of crude ester product. Furthermore, the adsorption treatment is preferably carried out at a temperature range of 60 to 120°C under reduced pressure conditions of 100 Torr or less and under a nitrogen stream. After the adsorption treatment, the adsorbent is removed by filtration or the like.

[0033] [Processing step using magnesium silicate (processing step)] After preparing the crude ester product as described above, or after performing steps (1) to (3) described above, the crude ester product is treated with a specific magnesium silicate at a specific temperature.

[0034] The magnesium silicate used may be hydrated magnesium silicate. This magnesium silicate may be naturally derived or synthesized. The magnesium silicate has a silicon dioxide content of 55-70% by mass and a magnesium oxide content of 10-25% by mass. When the silicon dioxide and magnesium oxide content in the magnesium silicate is within this range, substances that cause odor and deterioration are easily incorporated into the magnesium silicate. Furthermore, from this viewpoint, it is more preferable that the silicon dioxide content in the magnesium silicate is 57-62% by mass and the magnesium oxide content is 15-20% by mass. In this specification, the silicon dioxide and magnesium oxide content in the magnesium silicate is measured by methods such as X-ray fluorescence.

[0035] Furthermore, the specific surface area of ​​magnesium silicate is 100-700 m². 2 It is / g. The specific surface area is 100m². 2When the concentration is above 1 / g, substances that cause odor and deterioration are efficiently incorporated into magnesium silicate, and the treatment effect is fully achieved. From this perspective, the specific surface area is 200 m². 2 It is preferable that the amount is 1 / g or more. Also, from the standpoint of availability, the specific surface area should be 700 m². 2 It is preferable that it be less than / g, and 500m 2 It is more preferable that the amount is less than or equal to / g. The specific surface area of ​​magnesium silicate in this specification is measured by methods such as the BET method.

[0036] There are no particular restrictions on the shape of the magnesium silicate mentioned above. For example, it may be in powder form, spherical form, flake form, or irregular shape. It may also be in the form of pellets, flakes, or beads that have been molded with a binder component. When the magnesium silicate is molded with a binder component, the specific surface area shall be the value measured for the pellets, etc., after molding. Furthermore, when the magnesium silicate is molded with a binder component, the silicon dioxide content and magnesium oxide content shall be measured after removing these binders according to conventional methods.

[0037] The average particle size of magnesium silicate is not particularly limited, but from the viewpoint of ease of processing the crude ester product, it is preferable that the average particle size measured by a laser diffraction / scattering method such as the microtrac method be between 5 μm and 50 μm, and more preferably between 8 μm and 20 μm.

[0038] On the other hand, the acid value of the crude ester product when treated with magnesium silicate is preferably 0.50 mg KOH / g or less. When the acid value of the crude ester product is 0.50 mg KOH / g or less, the stability during treatment with magnesium silicate is enhanced. From this viewpoint, the acid value of the crude ester product when treated with magnesium silicate is more preferably 0.35 mg KOH / g or less, even more preferably 0.20 mg KOH / g or less, and particularly preferably 0.10 mg KOH / g or less. This acid value is measured by the method described above. Furthermore, the acid value of the crude ester product can be adjusted by the various purification processes described above.

[0039] Treatment of crude ester products with magnesium silicate is carried out under a nitrogen atmosphere at 60-120°C. At temperatures above 60°C, the magnesium silicate becomes sufficiently active, and the treatment effect is fully obtained. However, at temperatures above 120°C, excessive release of adsorbed components from the magnesium silicate and components originally contained in the adsorbent may occur, resulting in insufficient treatment effect, or causing odor and deterioration of the ester quality. At temperatures below 120°C, however, the treatment effect is fully obtained. Treatment with magnesium silicate is preferably carried out at 70°C or higher, more preferably at 80°C or higher. Furthermore, it is preferably carried out at 110°C or lower, and more preferably at 100°C or lower.

[0040] Furthermore, this process is most effective when carried out under reduced pressure to enhance the effects of magnesium silicate treatment. A lower degree of reduced pressure is preferable, but it is preferable to carry it out at 100 Torr or less. The treatment time is preferably 30 minutes to 6 hours under the above conditions.

[0041] The method for treating the crude ester product with magnesium silicate is not particularly limited, as long as sufficient contact between the two is possible. For example, a predetermined amount of magnesium silicate may be added directly to the reactor containing the crude ester product. Alternatively, the crude ester product may be passed through a cylindrical column packed with magnesium silicate and controlled to a predetermined temperature. When adding a predetermined amount of magnesium silicate directly to the reactor, the amount of magnesium silicate added is preferably 0.1% by mass or more and 10% by mass or less relative to the amount of crude ester product. When the amount of magnesium silicate added is 0.1% by mass or more, the treatment effect of magnesium silicate is likely to be fully realized. On the other hand, even if more than 10% by mass is added, the effect commensurate with the amount added may not be obtained, so the upper limit is preferably around 10% by mass. Also, when adding a predetermined amount of magnesium silicate directly to the reactor containing the crude ester product, the magnesium silicate is removed after treatment by filtration or other means.

[0042] [Uses of esters] The esters obtained by the manufacturing method of the present invention can be used in a wide range of applications, such as cosmetics, lubricants, metalworking oils, textile lubricants, plasticizers, detergents, emulsifiers, and reaction solvents, and are particularly suitable for use in cosmetics. [Examples]

[0043] The present invention will be described in more detail below with reference to examples and comparative examples.

[0044] [Preparation and purification of crude ester products] <Synthesis Example 1> (Reaction process between alcohol and aliphatic carboxylic acid) A 3L four-necked flask equipped with a thermometer, nitrogen inlet tube, stirrer, condenser, and oil-water separator tube was charged with 1100.0 g (7.0 mol) of 7-methyloctanoic acid (isononanoic acid) and 1053.2 g (7.3 mol) of 7-methyl-1-octanol (isononanol) (COOH / OH = 0.95). The alcohol and carboxylic acid were then reacted at 180°C under a nitrogen atmosphere until the acid value was 0.5 mg KOH / g or less.

[0045] (neutralization process) The reactor was then cooled to 85°C. Meanwhile, 1.5 equivalents of sodium hydroxide, calculated from the above acid value and necessary for neutralization, were diluted with deionized water to prepare a 10% by mass sodium hydroxide aqueous solution. This sodium hydroxide aqueous solution was added to the reaction mixture and stirred for 1 hour. After stopping the stirring, the mixture was allowed to stand for 30 minutes, and the aqueous layer separated at the bottom was removed. Next, an amount of deionized water equivalent to 20% by mass of the reaction mixture was added, stirred at 85°C for 10 minutes, allowed to stand for 15 minutes, and the separated aqueous layer was removed. This process was repeated 5 times. After that, the mixture was dehydrated by stirring at 100°C and 30 Torr for 1 hour.

[0046] (Removal process) Next, excess alcohol was removed by stirring under a nitrogen stream at 150°C and 30 Torr for 1 hour.

[0047] (Adsorption treatment process) Finally, activated clay equivalent to 0.5% by mass of the reaction mixture was added, and the mixture was stirred at 80°C and 30 Torr for 1 hour. The activated clay was then removed by filtration. This yielded ester compound A-1 (crude ester product) with an acid value of 0.05 mg KOH / g.

[0048] <Synthesis Example 2> The reaction was carried out under the same conditions as in Synthesis Example 1 until the acid value reached 0.25 mg KOH / g (preparation of crude ester product). Subsequently, without performing the neutralization step with sodium hydroxide as in Synthesis Example 1, the excess alcohol was removed by stirring under a nitrogen stream at 150°C and 30 Torr for 1 hour (distillation step). Finally, an amount of activated clay equivalent to 0.5% by mass of the reaction solution was added, and the mixture was stirred at 80°C and 30 Torr for 1 hour, followed by filtration to remove the activated clay (adsorption treatment step). This yielded ester compound A-2 (crude ester product) with an acid value of 0.18 mg KOH / g.

[0049] <Synthesis Example 3> Except for shortening the reaction time compared to Synthesis Example 2 and terminating the reaction when the acid value reached 0.40 mg KOH / g, the same procedure as in Synthesis Example 2 was used to obtain ester compound A-3 (crude ester product) with an acid value of 0.28 mg KOH / g.

[0050] <Synthesis Example 4> A 3L four-necked flask equipped with a thermometer, nitrogen inlet tube, stirrer, condenser, and oil-water separator tube was charged with 1800.0 g (10.4 mol) of 2-ethylhexanoic acid and 354.2 g (2.6 mol) of pentaerythritol (COOH / OH = 1.20). The alcohol and carboxylic acid were then reacted at 240°C under a nitrogen atmosphere until the hydroxyl value was 3.0 mg KOH / g or less.

[0051] (Removal process) Subsequently, excess carboxylic acid was removed by stirring under a nitrogen stream at 160°C and 30 Torr for 1 hour.

[0052] (neutralization process) Next, the reactor was cooled to 85°C and the acid value was determined. Meanwhile, 1.5 equivalents of sodium hydroxide, the amount of sodium hydroxide needed for neutralization calculated from the acid value, were diluted with deionized water to prepare a 10% by mass sodium hydroxide aqueous solution. This sodium hydroxide aqueous solution was added to the reaction mixture and stirred for 1 hour. After stopping the stirring, the mixture was allowed to stand for 30 minutes and the aqueous layer separated at the bottom was removed. Next, an amount of deionized water equivalent to 20% by mass of the reaction mixture was added, stirred at 85°C for 10 minutes, allowed to stand for 15 minutes, and the separated aqueous layer was removed. This process was repeated 5 times. After that, the mixture was dehydrated by stirring at 100°C and 30 Torr for 1 hour.

[0053] (Adsorption treatment process) Finally, activated clay equivalent to 0.5% by mass of the reaction mixture was added, and the mixture was stirred at 80°C and 30 Torr for 1 hour. The activated clay was then removed by filtration. This yielded ester compound A-4 (crude ester product) with an acid value of 0.05 mg KOH / g.

[0054] <Synthesis Example 5> Except for not treating with activated clay, the same procedure as in Synthesis Example 4 was used to obtain ester compound A-5 (crude ester product) with an acid value of 0.35 mg KOH / g. The acid values ​​of the ester compounds (crude ester products) obtained in the above synthesis examples are summarized in Table 1.

[0055] [Table 1]

[0056] The acid value, hydroxyl value, and acid value of the ester compound in the above synthesis example were measured by the following methods. Acid value: Measured in accordance with JIS K 0070. Hydroxyl value: Measured in accordance with JIS K-0070.

[0057] [Preparation of magnesium silicate and other porous materials] The magnesium silicate and other porous materials used for comparison are shown in Table 2 below.

[0058] [Table 2]

[0059] Measurements of magnesium silicate and other porous materials were performed using the following methods. Specific surface area: Measured in accordance with JIS Z-8830. Composition: Calculated using the calibration curve method of X-ray fluorescence analysis under the following measurement conditions.

[0060] <Measurement conditions> • Equipment: Rigaku ZSX Primus III+ ·Tube:Rh tube Current / Voltage: 50kV, 50kA • Sample chamber: Vacuum

[0061] [Example 1] (Processing steps) In a 1 L four-necked flask equipped with a thermometer, nitrogen inlet tube, stirrer, and condenser, 700.0 g of the ester compound (crude ester product) A-1 obtained in Synthesis Example 1 and 7.0 g of magnesium silicate B-1 were charged, and the mixture was stirred at 85°C for 1 hour under reduced pressure of 30 Torr. After that, the magnesium silicate was removed by filtration.

[0062] [Examples 2-11 and Comparative Examples 1-7] (Processing steps) The same procedure as in Example 1 was followed, except that the type of ester compound (crude ester product), the type of magnesium silicate (or porous material), and the processing temperature were changed as shown in Table 3 or Table 4.

[0063] [evaluation] <Evaluation of odor and acid value before accelerated testing> (Odor evaluation) 100g of the ester to be evaluated was placed in a 145mL wide-mouthed glass bottle, and five monitors evaluated the odor according to the following criteria. The intensity of the odor is indicated on a 7-point scale from 0 to 6 (0 being odorless, and 6 being the strongest odor). Furthermore, the odor evaluation of the crude ester products before treatment shown in Table 1 is all rated as 6.

[0064] <Evaluation of odor and acid value after accelerated testing> The wide-mouthed glass bottles containing the ester were stored at 40°C for 3 months. The odor of the ester oil after storage was evaluated in the same manner as described above. Tables 3 and 4 also show the acid values ​​before and after the accelerated stability test. In this test, if the odor is kept low even after the accelerated stability test, and the acid value remains below a certain value even after the accelerated stability test, it can be said that the product has high stability. The evaluation results are shown in Tables 3 and 4.

[0065] [Table 3]

[0066] [Table 4]

[0067] [result] As is clear from the results shown in Table 3 above, the silicon dioxide content is 55-70% by mass, the magnesium acid content is 10-25% by mass, and the specific surface area is 100 m². 2 When treated with magnesium silicate at a concentration of 1 / g or higher, the odor evaluation before and after the accelerated testing was good (4 or less), and the acid value remained sufficiently low even after the heating test (Examples 1-11). In other words, these examples demonstrate that esters with low odor and high long-term stability could be produced. On the other hand, as shown in Table 4, even when magnesium silicate was used, if the treatment temperature was too low, the odor evaluation after the accelerated testing was poor and the stability was low (Comparative Examples 1 and 3). Also, if the treatment temperature was too high, the odor evaluation was very poor both before and after the accelerated testing, and low odor could not be achieved (Comparative Example 2).

[0068] Furthermore, when the silicon dioxide content in magnesium silicate was low, the odor evaluation after accelerated testing deteriorated, indicating low stability (Comparative Example 4). In addition, when adsorbents other than magnesium silicate were used, odor stability was low both before and after accelerated testing, and low odor could not be achieved (Comparative Examples 5-7). [Industrial applicability]

[0069] The esters obtained by this invention have low odor and high quality stability. Therefore, they can be used in a variety of fields, including industrial and healthcare applications.

Claims

1. The process includes a step of treating the crude ester product with magnesium silicate at 60 to 120°C. The magnesium silicate has a silicon dioxide content of 55 to 70% by mass, a magnesium oxide content of 10 to 25% by mass, and a specific surface area of ​​100 to 700 m². ２ / g is A method for producing esters.

2. Before the aforementioned processing step, (1) A distillation step in which alcohols and / or aliphatic carboxylic acids are removed from the crude ester product. (2) A neutralization step in which the crude ester product is neutralized with an alkaline aqueous solution, (3) An adsorption treatment step in which the crude ester product and the adsorbent are mixed. Selected from, perform one or more further steps. A method for producing an ester according to claim 1.

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