Method for producing ester wax, and method for reducing the amount of free fatty acids and alkali metals contained in ester wax.

Abstract

This invention provides a method for producing ester wax in high yield with reduced content of free fatty acids and alkali metals. [Solution] A method for producing ester wax, comprising the steps of: (A) condensing a C14-28 linear saturated monofatty acid with at least one alcohol selected from the group consisting of C14-28 linear saturated monohydric alcohols and C2-10 dihydric-hexahydric alcohols in a specific equivalence ratio to obtain a crude ester product (10% by mass or less of free fatty acids); (B) adding methylcyclohexane to the crude ester product to obtain a crude ester solution having a specific specific gravity; (C) deoxidizing the crude ester solution using a specific aqueous solution to obtain a deoxidized ester solution; (D) washing the deoxidized ester solution with water under specific conditions to obtain a water-washed ester solution; and (E) removing the solvent from the water-washed ester solution to obtain a purified ester.

Description

[Technical Field]

[0001] The present invention relates to a method for producing ester wax, and a method for reducing the amount of free fatty acids and alkali metals contained in ester wax. [Background technology]

[0002] Common examples of waxes include paraffin and ester waxes. Waxes have traditionally been used in a wide range of applications, such as lubricants during the molding of resin materials, release agents for toners used in electronic printing, and thickeners for cosmetics. Among these, ester waxes have recently attracted attention as biomass materials because they can be formulated using plant-derived fatty acids as raw materials.

[0003] Furthermore, as demands in various fields diversify, highly refined ester waxes are needed, and methods for producing them are also being investigated. For example, Patent Document 1 discloses a method for producing ester wax for toner, characterized by neutralizing the ester wax obtained by a condensation reaction with an alkaline aqueous solution and removing the neutralized salt by centrifugation. However, in the production method of Patent Document 1, metal components derived from the neutralized salt may remain in the ester wax, and sufficient consideration has not been given to reducing the amount of metal components in the ester wax.

[0004] Patent Document 2 discloses a method for producing ester wax for toner, characterized by removing unreacted substances from the ester wax obtained by a condensation reaction using molecular distillation. However, the production method in Patent Document 2 results in a low yield of ester wax, and no efforts have been made to improve the yield. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2012-32479 [Patent Document 2] Japanese Patent Publication No. 2012-67043 [Overview of the project] [Problems that the invention aims to solve]

[0006] This invention has been made in view of the above problems, and aims to provide a method for producing ester wax in which the content of free fatty acids and alkali metals is reduced and which can be obtained in high yield. Furthermore, the present invention aims to provide a method for reducing the amount of free fatty acids and alkali metals in ester wax obtained by a condensation reaction. [Means for solving the problem]

[0007] The inventors of the present invention have discovered that ester waxes with low content of free fatty acids and alkali metals can be obtained in high yield by a specific manufacturing method, and have completed the present invention.

[0008] In other words, the present invention is as follows: [1] A method for producing ester wax, comprising the following steps (A), (B), (C), (D) and (E). Step (A): A step to obtain a crude esterification product containing 10% by mass or less of free fatty acids by condensing a fatty acid (component 1) and an alcohol (component 2) in an amount such that the equivalent ratio of the carboxyl groups of the fatty acid to the hydroxyl groups of the alcohol is 1.00 to 1.10. Component 1: At least one fatty acid selected from the group consisting of straight-chain saturated monofatty acids with 14 to 28 carbon atoms. Component 2: At least one alcohol selected from the group consisting of linear saturated monohydric alcohols with 14 to 28 carbon atoms and dihydric to hexahydric polyhydric alcohols with 2 to 10 carbon atoms. Step (B): Methylcyclohexane is added to the crude esterification product obtained in Step (A), and the specific gravity SG at 80°C is measured. B Steps to obtain a crude ester solution with a ratio of 0.74 to 0.86. Step (C): The crude ester solution obtained in step (B) is mixed with the following components 3 and 4 and has a specific gravity SG at 80°C. C A process to obtain a deoxidized ester solution by performing deoxidation using an aqueous solution with a concentration of 0.90 to 1.10. Component 3: 1.1 to 2.0 mol equivalents of potassium hydroxide relative to the carboxyl groups of the free fatty acids contained in the crude ester solution obtained in step (B) above. Component 4: At least one selected from the group consisting of n-propanol and isopropanol. Step (D): A step to obtain a water-washed ester solution by repeatedly washing the deoxidized ester solution obtained in step (C) with water until the pH of the wastewater reaches 6.5 to 7.4. Step (E): A step to obtain a purified ester by removing the solvent from the water-washed ester solution obtained in step (D).

[0009] [2] In an ester wax obtained by purifying a crude esterification product after a condensation reaction between a fatty acid and an alcohol, The crude esterification product is obtained by the following step (A), A method for reducing the amount of free fatty acids and alkali metals contained in the ester wax by purifying the crude esterification product by a method comprising the following steps (B), (C), (D), and (E). Step (A): A step to obtain a crude esterification product containing 10% by mass or less of free fatty acids by condensing a fatty acid (component 1) and an alcohol (component 2) in an amount such that the equivalent ratio of the carboxyl groups of the fatty acid to the hydroxyl groups of the alcohol is 1.00 to 1.10. Component 1: At least one fatty acid selected from the group consisting of straight-chain saturated monofatty acids with 14 to 28 carbon atoms. Component 2: At least one alcohol selected from the group consisting of linear saturated monohydric alcohols with 14 to 28 carbon atoms and dihydric to hexahydric polyhydric alcohols with 2 to 10 carbon atoms. Step (B): Methylcyclohexane is added to the esterification crude product obtained in the step (A), and a crude ester solution having a specific gravity SG at 80 °C B is 0.74 to 0.86 is obtained. Step (C): With respect to the crude ester solution obtained in the step (B), deacidification is performed using an aqueous solution containing the following component 3 and component 4 and having a specific gravity SG at 80 °C C is 0.90 to 1.10 to obtain a deacidified ester solution. Component 3: Potassium hydroxide in an amount of 1.1 to 2.0 mol equivalents relative to the carboxyl group of the free fatty acid contained in the crude ester solution obtained in the step (B) Component 4: At least one selected from the group consisting of normal propanol and isopropanol Step (D): The washed ester solution is obtained by repeatedly washing the deacidified ester solution obtained in the step (C) until the pH of the drained water becomes 6.5 to 7.4. Step (E): The purified ester is obtained by removing the solvent from the washed ester solution obtained in the step (D).

Advantages of the Invention

[0010] According to the method for producing an ester wax of the present invention, it is possible to obtain an ester wax with reduced contents of free fatty acid and alkali metal components in a high yield. Furthermore, the present invention can provide a method for reducing the amounts of free fatty acid and alkali metal components contained in an ester wax obtained by subjecting a crude esterification product obtained by subjecting a fatty acid and an alcohol to a condensation reaction to purification.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the embodiments described in this specification, and various modifications can be made without departing from the gist of the present invention. Furthermore, in this invention, a numerical range defined using the symbol "~" includes the numerical values ​​at both ends (upper and lower limits) of "~". For example, "2~10" represents the range of 2 to 10. Furthermore, within the numerical range described in the present invention, the upper or lower limit of that numerical range can be replaced with the values ​​shown in the examples or values ​​uniquely derived from the examples. Furthermore, among the numerical values ​​described to explain the present invention, the numerical values ​​that may include decimal places are, unless otherwise specified, obtained by rounding a digit that was one place smaller than the smallest digit included in the numerical value. Furthermore, in this invention, the notations C1, C2, C3, etc., relating to a compound represent the number of carbon atoms in the compound, and the range C1 to 20, etc., represents the range of carbon atoms in the compound.

[0012] The present invention provides a method for producing ester wax, which involves first obtaining a crude esterification product by condensing a fatty acid (component 1) with an alcohol (component 2), and then purifying the crude esterification product using a predetermined method in which methylcyclohexane (MCH) is used as a lipophilic solvent to form the oil layer during oil-water separation, and separation alcohol (component 4) is added together with an alkali (component 3), thereby producing ester wax. The present invention provides a method for producing ester wax that reduces the content of free fatty acids and alkali metals, and allows for the production of ester wax in high yield, with particularly excellent effectiveness in reducing the content of alkali metals. The present invention's production method reduces the amount of component 1 that remains without condensation reaction, thereby reducing the amount of potassium hydroxide (component 3) used for deoxidation. In this way, the amount of free fatty acids and alkali metals contained in the ester before purification is reduced, and further purification of the ester by a predetermined method makes the compatibility between the oil layer and the water layer appropriate during oil-water separation, thus facilitating oil-water separation. This allows for the easy removal of free fatty acids and alkali metals, and enables the production of ester wax in high yield. The following describes each step included in the manufacturing method of the present invention.

[0013] [Process (A)] Step A in the present invention is a step in which a fatty acid, which is component 1 below, and an alcohol, which is component 2 below, are condensed in an amount such that the equivalent ratio of the carboxyl groups of the fatty acid to the hydroxyl groups of the alcohol (COOH / OH) is 1.00 to 1.10, thereby obtaining a crude esterification product containing 10% by mass or less of free fatty acids. Component 1: At least one fatty acid selected from the group consisting of straight-chain saturated monofatty acids with 14 to 28 carbon atoms. Component 2: At least one alcohol selected from the group consisting of linear saturated monohydric alcohols with 14 to 28 carbon atoms and dihydric to hexahydric polyhydric alcohols with 2 to 10 carbon atoms.

[0014] Component 1, the fatty acid, is at least one selected from the group consisting of straight-chain saturated monofatty acids having 14 to 28 carbon atoms; that is, it may be just one fatty acid or a mixture of two or more fatty acids. Note that "straight-chain saturated monofatty acid" is a straight-chain saturated fatty acid that has only one carboxyl group in one molecule. Component 1 is not particularly limited, but it is preferably at least one fatty acid selected from the group consisting of straight-chain saturated monofatty acids having 14 to 24 carbon atoms, as this makes it easier to reduce the content of free fatty acids and alkali metals in the final ester wax. Specific examples of straight-chain saturated monofatty acids having 14 to 24 carbon atoms include myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, and lignoceric acid.

[0015] Component 2, the alcohol, is at least one selected from the group consisting of linear saturated monohydric alcohols with 14 to 28 carbon atoms and dihydric to hexahydric polyhydric alcohols with 2 to 10 carbon atoms. In other words, it may be just one alcohol or a mixture of two or more alcohols. A "linear saturated monohydric alcohol" is a linear saturated aliphatic alcohol having only one hydroxyl group per molecule, while a "polyhydric alcohol" is an alcohol having two or more hydroxyl groups per molecule. While there are no particular limitations on the polyhydric alcohol, it is preferable to use an aliphatic polyhydric alcohol, and more preferably a saturated aliphatic polyhydric alcohol, as this makes it easier to obtain the effects of the production method of the present invention. Component 2 is not particularly limited, but it is preferably at least one alcohol selected from the group consisting of linear saturated monohydric alcohols having 14 to 24 carbon atoms and dihydric saturated aliphatic polyhydric alcohols having 2 to 10 carbon atoms, as this makes it easier to reduce the content of free fatty acids and alkali metals in the final ester wax. Specific examples of straight-chain saturated monohydric alcohols with 14 to 24 carbon atoms include myristyl alcohol, palmityl alcohol, stearyl alcohol, arachidyl alcohol, behenyl alcohol, and lignoceryl alcohol. Specific examples of saturated aliphatic polyhydric alcohols with 2 to 10 carbon atoms and a valency of 2 to 6 include ethylene glycol, propylene glycol, butylene glycol, glycerin, pentaerythritol, dipentaerythritol, and dimers and trimers of glycerin.

[0016] The method for the condensation reaction between component 1, a fatty acid, and component 2, an alcohol, can be any known method and is not particularly limited. For example, a method can be used in which component 1 and component 2 are mixed and reacted at a temperature of 130°C to 260°C. A catalyst may be used during the condensation reaction. As a catalyst, it is preferable to use an organic acid, as it is preferably removed along with the free fatty acid or alkali metal component in steps (C) to (D) described later. Examples of organic acids that can be preferably used include phosphoric acid, sulfuric acid, methanesulfonic acid, and p-toluenesulfonic acid.

[0017] In step (A), the ratio of component 1 to component 2 to undergo the condensation reaction is such that the equivalent ratio of carboxyl groups to hydroxyl groups, i.e., the ratio of the molar equivalents of carboxyl groups of component 1 (fatty acid) to 1.00 molar equivalents of hydroxyl groups of component 2 (alcohol) (COOH / OH) is 1.00 to 1.10. By keeping the equivalent ratio within the above range, the amount of unreacted component 1 or component 2 can be reduced. Therefore, the yield of the final ester wax can be improved, and oil-water separation in steps (C) and (D) becomes easier, making it easier to reduce the content of free fatty acids and alkali metals in the final ester wax. Furthermore, by keeping the equivalent ratio below 1.10, the content of free fatty acids in the resulting crude esterification product can be reduced, thus further reducing the content of free fatty acids in the final ester wax. In addition, by reducing the amount of free fatty acids, deoxidation can be performed with a smaller amount of potassium hydroxide, thus reducing the content of alkali metals in the final ester wax. From this perspective, the above equivalent ratio is preferably 1.01 or higher as a lower limit, more preferably 1.02 or higher, and preferably 1.08 or lower as an upper limit, more preferably 1.06 or lower.

[0018] The crude esterification product obtained in step (A) contains free fatty acids at a rate of 10% by mass or less, when the crude esterification product is considered as 100% by mass. Having a free fatty acid content of 10% by mass or less in the crude esterification product makes it easier to reduce the free fatty acid content in the final ester wax, and also allows for deoxidation with a small amount of potassium hydroxide, thus making it easier to reduce the alkali metal content in the final ester wax. From this viewpoint, it is preferable that the free fatty acid content in the crude esterification product obtained in step (A) is 7% by mass or less. On the other hand, in order to easily exhibit the effects of the manufacturing method of the present invention, the free fatty acid content in the crude esterification product may be 2% by mass or more, or 5% by mass or more. Free fatty acids are components that remain unreacted without undergoing the condensation reaction. The free fatty acid content is expressed as a percentage relative to the crude esterification product after the removal of solvents such as water, with the crude esterification product being 100% by mass. In step (A), the content of free fatty acids in the esterification crude product can be reduced by adjusting the conditions of the condensation reaction, such as the reaction temperature or the equivalent ratio of carboxyl groups of the fatty acid to the hydroxyl groups of the alcohol, or by adjusting the number of carbon atoms in the fatty acid used as component 1, the type or number of carbon atoms of the alcohol used as component 2, or the combination of component 1 and component 2.

[0019] [Process (B)] Step (B) of the present invention involves adding methylcyclohexane to the crude esterification product obtained in step (A), and measuring the specific gravity SG at 80°C. B This is a step to obtain a crude ester solution in which the ratio is 0.74 to 0.86.

[0020] The methylcyclohexane added in step (B) is a lipophilic solvent, and therefore forms an oil layer when oil-water separation is performed in steps (C) and (D) described later. In this invention, by using methylcyclohexane as a lipophilic solvent, the compatibility between the oil layer and the water layer is appropriately adjusted in steps (C) and (D), making it easier to reduce the content of free fatty acids and alkali metals in the ester wax obtained in the final product.

[0021] The amount of methylcyclohexane added in step (B) is not particularly specified, but it is preferably 5 to 40 parts by mass, and more preferably 10 to 30 parts by mass, per 100 parts by mass of the crude esterification product, as this facilitates oil-water separation in steps (C) and (D), thereby increasing the yield of the final ester wax, and also helps to reduce the content of free fatty acids and alkali metals in the final ester wax.

[0022] Specific gravity SG of the crude ester solution obtained in step (B) at 80°C B The specific gravity SG is 0.74 to 0.86. Btends to increase as the addition amount of methylcyclohexane decreases and to decrease as the addition amount of methylcyclohexane increases. The specific gravity SG B When B is within the above range, the amount of methylcyclohexane becomes appropriate, facilitating oil-water separation in steps (C) and (D). This makes it easier to increase the yield of the finally obtained ester wax and to reduce the contents of free fatty acids and alkali metals in the finally obtained ester wax. From this perspective, the specific gravity SG B is preferably 0.78 to 0.83.

[0023] Step (B) is not particularly limited. From the perspective of increasing the yield of ester wax, it is preferably carried out at a temperature higher than the freezing point of the crude ester product, for example, it may be carried out at 70°C or higher, or may be carried out at 80°C or higher. On the other hand, from the perspective of suppressing the volatilization of methylcyclohexane, considering the boiling point of methylcyclohexane, step (B) is preferably carried out at 90°C or lower.

[0024] 〔Step (C)〕 In step (C) of the present invention, deacidification is carried out on the crude ester solution obtained in step (B) using an aqueous solution containing component 3 and component 4 and having a specific gravity SG C of 0.90 to 1.10 at 80°C to obtain a deacidified ester solution. Component 3: Potassium hydroxide at 1.1 to 2.0 mol equivalents relative to the carboxyl groups of the free fatty acids contained in the crude ester solution obtained in step (B) Component 4: At least one selected from the group consisting of normal propanol and isopropanol

[0025] The deacidification carried out in step (C) refers to an operation for removing free fatty acids in the crude ester solution. Potassium hydroxide, which is component 3, solubilizes in water by neutralizing the free fatty acids in the crude ester solution. Therefore, by adding component 3 together with water to the crude ester solution, performing oil-water separation, and removing the aqueous layer, the free fatty acids in the crude ester solution can be removed. In the present invention, by further using component 4, oil-water separation becomes easier. In step (C), an aqueous solution containing component 3 and component 4 may be prepared and added to the crude ester solution obtained in step (B), or component 3, component 4, and water may be added to the crude ester solution obtained in step (B) in any order to form an aqueous solution in the system. In either case, step (C) may be a step in which the crude ester solution obtained in step (B) and the aqueous solution containing component 3 and component 4 (which may be referred to as "mixture C" in this invention) are stirred and allowed to stand to separate the oil and water, and then the lower aqueous layer is removed to remove the free fatty acids contained in the crude ester solution.

[0026] In step (C), the amount of potassium hydroxide added as component 3 is 1.1 mol equivalent or more relative to the carboxyl groups of the free fatty acids contained in the crude ester solution obtained in step (B), from the viewpoint of sufficiently neutralizing the free fatty acids contained in the crude ester solution. On the other hand, from the viewpoint of reducing the amount of potassium hydroxide added for deoxidation and thereby reducing the alkali metal content in the final ester wax, the amount is 2.0 mol equivalent or less relative to the carboxyl groups of the free fatty acids contained in the crude ester solution. Preferably, the amount of potassium hydroxide is 1.3 to 1.7 mol equivalent relative to the carboxyl groups of the free fatty acids contained in the crude ester solution, as this makes it easier to reduce the content of free fatty acids and alkali metals in the final ester wax.

[0027] The amount of free fatty acids contained in the crude ester solution obtained in step (B) is calculated from the acid value and volume of the crude ester solution using the following formula (1). In formula (1) below, "56.11" is the molecular weight of potassium hydroxide (KOH). The acid value is measured according to [2.3.1-2013 Acid Value] in "Standard Test Methods for Analysis of Fats and Oils (I) 2013 Edition" compiled by the Japan Oil Chemists' Society. Since the free fatty acids contained in the crude ester solution are component 1 (straight-chain saturated monofatty acids with 14 to 28 carbon atoms) used in step (A), the amount of free fatty acids can be considered equal to the amount of carboxyl groups of the free fatty acids.

[0028]

number

[0029] Component 4 is a separation alcohol used to facilitate oil-water separation in step (C) and step (D) described later. In the present invention, adding component 4 in step (C) makes oil-water separation even easier. As a result, the yield of the final ester wax is increased, and the content of free fatty acids and alkali metals in the final ester wax is reduced. From this viewpoint, component 4 may be at least one selected from the group consisting of n-propanol (NPA) and isopropanol (IPA), and isopropyl alcohol is preferred.

[0030] The amount of component 4 added in step (C) is not particularly limited, but in order to facilitate oil-water separation in steps (C) and (D), it is preferably 0.5 to 20 parts by mass, and more preferably 1 to 15 parts by mass, when the crude esterification product obtained in step (A) is 100 parts by mass.

[0031] The amount of water added in step (C) is not particularly limited, but the specific gravity SG of the aqueous solution at 80°C is important. C As this tends to fall within the range described later, when the crude esterification product obtained in step (A) above is 100 parts by mass, it is preferably 1 to 20 parts by mass, and more preferably 5 to 15 parts by mass. Furthermore, it is preferable that the water used in step (C) is deionized water.

[0032] Specific gravity SG of the aqueous solution used in process (C) at 80°C C The specific gravity SG is 0.90 to 1.10. C The specific gravity SG tends to increase as the proportion of water in the aqueous solution increases, and decrease as the proportion of water in the aqueous solution decreases. CWhen the specific gravity SG is within the above range, the amount of water becomes appropriate, which facilitates oil-water separation in steps (C) and (D), making it easier to increase the yield of the final ester wax and to reduce the content of free fatty acids and alkali metals in the final ester wax. From this perspective, the specific gravity SG C The value is preferably between 0.92 and 1.08.

[0033] Step (C) is preferably carried out at 80°C or below from the viewpoint of suppressing the volatilization of component 4, and is preferably carried out at 60°C or above from the viewpoint of solubilizing the neutralized free fatty acid, i.e., fatty acid soap, in the aqueous solution.

[0034] [Process (D)] Step (D) of the present invention is a step of obtaining a water-washed ester solution by repeatedly washing the deoxidized ester solution obtained in step (C) with water until the pH of the wastewater reaches 6.5 to 7.4. The washing in step (D) refers to the operation of adding water to the deoxidized ester solution and mixing it, then separating the oil and water from the resulting mixture and removing the water layer. The purpose is to remove water-soluble components such as alkali metals contained in the deoxidized ester solution. The washing in step (D) may also be the operation of separating the oil and water from the mixture of the deoxidized ester solution and water (sometimes referred to as "mixture D" in this invention) by stirring and letting it stand, and then removing the lower water layer. For example, washing five times means repeating the above operation five times.

[0035] In step (D), the deoxidized ester solution is repeatedly washed with water until the pH of the wastewater reaches 6.5 to 7.4, thereby sufficiently removing water-soluble components such as alkali metals contained in the deoxidized ester solution. From this viewpoint, it is preferable to repeat the washing in step (D) until the pH of the wastewater reaches 7.3 or lower, and more preferably until it reaches 7.2 or lower. In step (D), the pH of the wastewater in the final wash may be 6.8 or higher, or 7.0 or higher. Furthermore, in step (D), the number of times the rinsing is repeated is not particularly limited, but for example, it may be 3 to 6 times.

[0036] In step (D), the amount of water added at once to the deoxidized ester solution during washing is not particularly limited, but from the viewpoint of obtaining ester wax in good yield, it is preferably 5 to 30 parts by mass, and more preferably 15 to 25 parts by mass, when the crude esterification product obtained in step (A) is 100 parts by mass. For example, from the viewpoint of obtaining ester wax in good yield, it is preferable to wash with 20 parts by mass of water five times rather than washing with 100 parts by mass of water once. Furthermore, it is preferable that the water used in step (D) is deionized water.

[0037] Step (D) is not particularly limited, but it is preferable to carry it at 70°C or higher in order to suppress the solidification of the crude ester and increase the yield of ester wax. On the other hand, from the viewpoint of suppressing the volatilization of methylcyclohexane, it is preferable to carry out step (D) at 90°C or lower, taking into account the boiling point of methylcyclohexane.

[0038] [Process (E)] Step (E) of the present invention is a step of obtaining a purified ester by removing the solvent from the water-washed ester solution obtained in step (D). Here, the solvent includes organic solvents and water. The solvent removed in step (E) may be at least one selected from the group consisting of methylcyclohexane added in step (B), component 4 added in step (C), and water remaining after washing with water in step (D), or it may be a different solvent.

[0039] In step (E), the method for removing the solvent is not particularly limited, and may be, for example, by distilling off the solvent from the ester solution after washing with water obtained in step (D). When distilling off the solvent, there are no particular limitations, but from the viewpoint of sufficiently distilling off the solvent from the ester solution after washing with water, it is preferable to distill it off under reduced pressure at a temperature of 100°C or higher.

[0040] [Other processes] The method for producing ester wax of the present invention may further include, as necessary, other steps different from steps (A) to (E) described above. Other steps include, for example, repeating steps (A) to (E) described above to obtain two or more purified esters, and then mixing these two or more purified esters. The mixing of the two or more purified esters may be done by, for example, melt mixing.

[0041] In the present invention, the purified ester obtained by the above-described steps (A) to (E) may be used as the ester wax produced by the method of the present invention, or a mixture of two or more purified esters may be used as the ester wax produced by the method of the present invention.

[0042] According to the manufacturing method of the present invention, the yield of ester wax can be, for example, 95% or more, and in some cases, 98% or more.

[0043] According to the manufacturing method of the present invention, the amount of free fatty acids contained in the resulting ester wax can be, for example, 700 ppm or less, and in some cases, 300 ppm or less.

[0044] According to the manufacturing method of the present invention, the amount of alkali metal content in the resulting ester wax can be, for example, 100 ppb or less, and in some cases, 50 ppb or less. The alkali metal content that may be contained in the ester wax obtained by the manufacturing method of the present invention is usually the alkali metal contained in component 3 used for deoxidation treatment, the alkali metal contained as an impurity in component 1, or a mixture thereof. In the ester wax obtained by the manufacturing method of the present invention, alkali metal elements other than Na and K are unlikely to be contained unless intentionally added. Therefore, the alkali metal content contained in the ester wax obtained by the manufacturing method of the present invention is usually at least one selected from the group consisting of Na and K. In the manufacturing method of the present invention, from the viewpoint of keeping the amount of alkali metal content in the ester wax below the above upper limit, it is preferable that among the materials used, only at least one selected from the group consisting of component 1 and component 3 is a material that could cause the contamination of the ester wax with alkali metal content.

[0045] [Ester wax] In order to easily obtain the effects of the manufacturing method of the present invention, the ester wax produced by the method of the present invention preferably has a solidification point of 85°C or lower, and more preferably 80°C or lower. On the other hand, the solidification point of the ester wax produced by the method of the present invention is not particularly limited, but may be 30°C or higher, 50°C or higher, or 60°C or higher. The freezing point of the ester wax obtained can be adjusted by adjusting the number of carbon atoms in components 1 and 2 used in step (A). Generally, esters tend to have higher freezing points as the number of carbon atoms increases, and higher freezing points tend to result in a higher retention rate of free fatty acids and alkali metals. In the manufacturing method of the present invention, even ester waxes with a freezing point above the above lower limit can be obtained in high yield while reducing the content of free fatty acids and alkali metals.

[0046] The ester wax obtained by the manufacturing method of the present invention may be used in mixture with other waxes. Examples of other waxes include paraffin wax, microcrystalline wax, and hydrocarbon waxes such as Fischer-Tropsch wax. The mixing of the ester wax obtained by the manufacturing method of the present invention with other waxes may be done by, for example, melt mixing.

[0047] [Method for reducing the amount of free fatty acids and alkali metals contained in ester waxes] In the ester wax obtained by purifying a crude esterification product obtained by condensing a fatty acid and an alcohol, the amount of free fatty acids and alkali metals contained in the resulting ester wax can be reduced by obtaining the crude esterification product by step (A) described above and purifying the crude esterification product by the method including steps (B), (C), (D), and (E) described above. In other words, the present invention relates to an ester wax obtained by purifying a crude esterification product obtained by condensing a fatty acid and an alcohol, The crude esterification product is obtained by the following step (A), The present invention provides a method for reducing the amount of free fatty acids and alkali metals contained in the ester wax by purifying the crude esterification product by a method comprising the following steps (B), (C), (D), and (E). Step (A): A step to obtain a crude esterification product containing 10% by mass or less of free fatty acids by condensing a fatty acid (component 1) and an alcohol (component 2) in an amount such that the equivalent ratio of the carboxyl groups of the fatty acid to the hydroxyl groups of the alcohol is 1.00 to 1.10. Component 1: At least one fatty acid selected from the group consisting of straight-chain saturated monofatty acids with 14 to 28 carbon atoms. Component 2: At least one alcohol selected from the group consisting of linear saturated monohydric alcohols with 14 to 28 carbon atoms and dihydric to hexahydric polyhydric alcohols with 2 to 10 carbon atoms. Step (B): Methylcyclohexane is added to the crude esterification product obtained in Step (A), and the specific gravity SG at 80°C is measured. B Steps to obtain a crude ester solution with a ratio of 0.74 to 0.86. Step (C): The crude ester solution obtained in step (B) is mixed with the following components 3 and 4 and has a specific gravity SG at 80°C. C A process to obtain a deoxidized ester solution by performing deoxidation using an aqueous solution with a concentration of 0.90 to 1.10. Component 3: 1.1 to 2.0 mol equivalents of potassium hydroxide relative to the carboxyl groups of the free fatty acids contained in the crude ester solution obtained in step (B) above. Component 4: At least one selected from the group consisting of n-propanol and isopropanol. Step (D): A step to obtain a water-washed ester solution by repeatedly washing the deoxidized ester solution obtained in step (C) with water until the pH of the wastewater reaches 6.5 to 7.4. Step (E): A step to obtain a purified ester by removing the solvent from the water-washed ester solution obtained in step (D). Detailed descriptions of steps (A), (B), (C), (D), and (E) in the method for reducing the amount of free fatty acids and alkali metals contained in ester wax are the same as detailed descriptions of steps (A), (B), (C), (D), and (E) in the method for producing ester wax of the present invention described above. Furthermore, reducing the amount of free fatty acids and alkali metals contained in the ester wax means, for example, that the amount of free fatty acids contained in the ester wax is 700 ppm or less, and the amount of alkali metals contained in the ester wax is 100 ppb or less. Also, the ester wax in which the amount of free fatty acids and alkali metals are each below the above upper limits may be the purified ester obtained by the above step (E). [Examples]

[0048] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. Unless otherwise specified, parts and percentages are by mass.

[0049] The component 1 (fatty acid) used in each example and comparative example is shown in Table 1 below, and the component 2 (alcohol) used in each example and comparative example is shown in Table 2 below.

[0050] [Example 1] Process (A): Component 1-A (1363.40 g, 4.00 mol) and component 2-A (1244.23 g, 3.81 mol) were placed in a 3 L flask and dissolved at 90°C under a nitrogen atmosphere. The temperature was then raised to 260°C and the condensation reaction was carried out for 9 hours. All water produced by the condensation reaction was removed from the system by distillation. The obtained crude esterification product was 2539.5 g, and the free fatty acid content in the crude esterification product was 3.0% by mass.

[0051] Process (B): The crude esterification product obtained in step (A) was cooled to 85°C, and 507.9 g of methylcyclohexane (specific gravity at 80°C is 0.71) was added to the cooled crude esterification product and mixed to obtain a crude ester solution. The specific gravity SG of the obtained crude ester solution at 80°C was determined. B The value was 0.78.

[0052] Process (C): To the crude ester solution obtained in step (B), an aqueous solution consisting of component 3, potassium hydroxide (16.05 g, 0.29 mol, 1.3 mol equivalent relative to free fatty acids), component 4, isopropyl alcohol (115.6 g, specific gravity at 80°C is 0.72), and water (144.45 g, specific gravity at 80°C is 0.97) was added at 80°C to obtain mixed solution C. Mixed solution C was stirred for 30 minutes while maintaining the temperature in the system at 70°C to 80°C, then allowed to stand for 30 minutes to separate the oil and water, and the lower aqueous layer was completely removed to deoxidize the crude ester solution and obtain the deoxidized ester solution. The specific gravity SG of the added aqueous solution at 80°C is also noted. CThe value was 0.94.

[0053] Process (D): Water (507.9 g) was added to the deoxidized ester solution obtained in step (C) at 80°C to obtain mixture D. Mixture D was stirred for 30 minutes while maintaining the system temperature at 70°C to 80°C, then allowed to stand for 30 minutes to separate the oil and water, and washed with water to completely remove the lower water layer. The same washing procedure was repeated three more times (a total of four washes) to obtain the ester solution after washing. The pH of the wastewater from the final wash was 7.2.

[0054] Process (E): The ester solution obtained in step (D) after washing with water was heated to 150°C under a nitrogen atmosphere, and the system was further reduced to 100 Torr and stirred for 1 hour to remove the solvent contained in the ester solution after washing with water. After purification, the ester was obtained, which was used as the ester wax of Example 1. The amount of ester wax obtained was 2436.2 g.

[0055] [Examples 2-25 and Comparative Examples 1-12] Ester waxes of Examples 2-25 and Comparative Examples 1-12 were obtained in the same manner as in Example 1, except that at least one of the following was modified according to Tables 3-6, and in Examples 2, 8, 10, and 16, the reaction temperature in step (A) was further changed from 260°C to 220°C. Component 1, Component 2, or both of these used in process (A) The equivalent ratio (COOH / OH) of component 1 and component 2 reacted in step (A) Amount of free fatty acids at the end of the reaction in step (A) Amount of methylcyclohexane added in step (B) Molar equivalent of potassium hydroxide added in step (C) relative to free fatty acids The type, amount, or both of the four components used in step (C). Specific gravity SG of the aqueous solution added in step (C) at 80°C C pH of wastewater at the end of rinsing in process (D) The amount of component 1 used was set at 4.00 mol, and when the equivalent ratio (COOH / OH) of component 1 and component 2 was changed, the amount of substance of component 2 was also changed. The amount of free fatty acids at the end of the reaction in step (A) was adjusted by adjusting the equivalent ratio (COOH / OH) of component 1 and component 2, and by adjusting the reaction temperature of the condensation reaction. Specific gravity SG of the aqueous solution added in step (C) at 80°C C The adjustment was made by adjusting the amount of water contained in the aqueous solution. In process (D), the pH of the wastewater at the end of rinsing was adjusted by repeating the rinsing process until the wastewater reached the desired pH.

[0056] The following measurements were performed on the ester waxes obtained in each example and comparative example.

[0057] [Theoretical molecular weight] The theoretical molecular weight of the ester wax was calculated using the theoretical molecular weights of component 1 and component 2.

[0058] [Freezing point] The temperature of the maximum point Pc during cooling in the DSC curve of ester wax was determined and defined as the freezing point of the ester wax. This maximum point Pc was confirmed using a differential scanning calorimeter (Hitachi High-Tech Science Corporation, DSC7000X) by performing the following procedure. First, 10 mg of the measurement sample (ester wax) was weighed into an aluminum sample pan. The weighed measurement sample was heated to 120°C at a heating rate of 2°C per minute in a measurement folder into which nitrogen was blown at a flow rate of 60 ml per minute, and then held at 120°C for 1 minute to ensure uniform thermal history between measurement samples. Subsequently, the measurement sample was cooled from 120°C to 30°C at a cooling rate of 2°C per minute to obtain the DSC curve of the measurement sample during cooling. An exothermic peak was observed during this cooling. At the exothermic peak in this DSC curve, the inflection point of the DDSC (derivative value of DSC) curve, i.e., the point where the DDSC value is 0, was defined as the freezing point. The measurement results were analyzed using the standard analysis software included with the device (DSC7000X).

[0059] 〔yield〕 The yield of ester wax was calculated according to the following formula (2).

[0060]

number

[0061] [Free fatty acids] The acid value of the ester wax was measured according to section [2.3.1-2013 Acid Value] of "Standard Test Methods for Analysis of Fats and Oils (I) 2013 Edition" compiled by the Japan Oil Chemists' Society. Using the acid value of the ester wax and the theoretical molecular weight of component 1 used in the production of the ester wax, the free fatty acid content (ppm) in the ester wax was calculated according to the following formula (3).

[0062]

number

[0063] [Alkali metal content] The total amount of alkali metals in ester wax, specifically Na and K (ppb), was measured using an ICP emission spectrometer (Shimadzu Corporation, ICPE-9800) by acid decomposition-inductively coupled plasma emission spectroscopy (ICP-AES method). Since other alkali metal elements are unlikely to be present, only the Na and K content was measured.

[0064] [Table 1]

[0065] [Table 2]

[0066] [Table 3]

[0067] [Table 4]

[0068] [Table 5]

[0069] [Table 6]

[0070] In Comparative Example 1, the equivalent ratio (COOH / OH) of component 1 and component 2 reacted in step (A) was greater than 1.10, and the crude esterification product obtained in step (A) had a free fatty acid content of more than 10% by mass. As a result, the final ester wax obtained had a low yield and a high content of free fatty acids and alkali metals. In Comparative Example 7, the equivalent ratio (COOH / OH) of component 1 and component 2 reacted in step (A) was less than 1.00, and the ester wax ultimately obtained had a low yield and a high alkali metal content.

[0071] Comparative Example 2 is the specific gravity SG of the crude ester solution obtained in step (B) at 80°C. B The ratio was less than 0.74, and the ester wax obtained ultimately had a high content of free fatty acids and alkali metals. Comparative Example 8 is the specific gravity SG of the crude ester solution obtained in step (B) at 80°C. B The ratio was over 0.86, and the ester wax ultimately obtained had a low yield and high content of free fatty acids and alkali metals.

[0072] In Comparative Examples 3 and 9, the amount of component 3 (potassium hydroxide) added in step (C) was less than 1.1 mol equivalent relative to the carboxyl groups of the free fatty acids, resulting in a low yield and a high content of free fatty acids in the final ester wax. In Comparative Examples 4 and 10, the amount of component 3 (potassium hydroxide) added in step (C) exceeded 2.0 mol equivalents relative to the carboxyl groups of the free fatty acids, resulting in a low yield and high alkali metal content of the final ester wax.

[0073] Comparative Example 5 is the specific gravity SG of the aqueous solution added in step (C) at 80°C. C The ratio was less than 0.90, and the resulting ester wax had a low yield and high content of free fatty acids and alkali metals. Comparative Example 11 is the specific gravity SG of the aqueous solution added in step (C) at 80°C. C The ratio was over 1.10, and the resulting ester wax had a low yield and high content of free fatty acids and alkali metals.

[0074] In Comparative Examples 6 and 12, the washing in step (D) was only carried out until the pH of the wastewater reached 7.8, resulting in a low yield and high content of free fatty acids and alkali metals in the final ester wax.

[0075] In contrast, in Examples 1 to 25, the ester wax obtained by performing steps (A) to (E) described above had a high yield and low content of free fatty acids and alkali metals. Therefore, it was demonstrated that the manufacturing method of the present invention can produce ester wax with reduced content of free fatty acids and alkali metals in high yield. Furthermore, Examples 1 to 25 demonstrate that after obtaining the crude esterification product by step (A) described above, purifying the crude esterification product by the method including steps (B) to (E) described above can reduce the amount of free fatty acids and alkali metals contained in the ester wax.

Claims

1. A method for producing ester wax, comprising the following steps (A), (B), (C), (D), and (E). Step (A): A step to obtain a crude esterification product containing 10% by mass or less of free fatty acids by condensing a fatty acid (component 1 below) and an alcohol (component 2 below) in an amount such that the equivalent ratio of the carboxyl groups of the fatty acid to the hydroxyl groups of the alcohol is 1.00 to 1.

10. Component 1: A fatty acid selected from the group consisting of straight-chain saturated monofatty acids with 14 to 28 carbon atoms. Component 2: At least one alcohol selected from the group consisting of linear saturated monohydric alcohols with 14 to 28 carbon atoms and dihydric to hexahydric polyhydric alcohols with 2 to 10 carbon atoms. Step (B): Methylcyclohexane is added to the crude esterification product obtained in Step (A), and the specific gravity SG at 80°C is measured. Ｂ Steps to obtain a crude ester solution having a ratio of 0.74 to 0.

86. Step (C): The crude ester solution obtained in step (B) is mixed with the following components 3 and 4 and has a specific gravity SG at 80°C. Ｃ A process to obtain a deoxidized ester solution by performing deoxidation using an aqueous solution having a concentration of 0.90 to 1.

10. Component 3: 1.1 to 2.0 mol equivalents of potassium hydroxide relative to the carboxyl groups of the free fatty acids contained in the crude ester solution obtained in step (B) above. Component 4: At least one selected from the group consisting of n-propanol and isopropanol. Step (D): A step to obtain a water-washed ester solution by repeatedly washing the deoxidized ester solution obtained in step (C) with water until the pH of the wastewater reaches 6.5 to 7.

4. Step (E): A step to obtain a purified ester by removing the solvent from the water-washed ester solution obtained in step (D).

2. In an ester wax obtained by purifying a crude esterification product after a condensation reaction between a fatty acid and an alcohol, The crude esterification product is obtained by the following step (A), A method for reducing the amount of free fatty acids and alkali metals contained in the ester wax by purifying the crude esterification product by a method comprising the following steps (B), (C), (D), and (E). Step (A): A step to obtain a crude esterification product containing 10% by mass or less of free fatty acids by condensing a fatty acid (component 1 below) and an alcohol (component 2 below) in an amount such that the equivalent ratio of the carboxyl groups of the fatty acid to the hydroxyl groups of the alcohol is 1.00 to 1.

10. Component 1: A fatty acid selected from the group consisting of straight-chain saturated monofatty acids with 14 to 28 carbon atoms. Component 2: At least one alcohol selected from the group consisting of linear saturated monohydric alcohols with 14 to 28 carbon atoms and dihydric to hexahydric polyhydric alcohols with 2 to 10 carbon atoms. Step (B): Methylcyclohexane is added to the crude esterification product obtained in Step (A), and the specific gravity SG at 80°C is measured. Ｂ Steps to obtain a crude ester solution having a ratio of 0.74 to 0.

86. Step (C): The crude ester solution obtained in step (B) is mixed with the following components 3 and 4 and has a specific gravity SG at 80°C. Ｃ A process to obtain a deoxidized ester solution by performing deoxidation using an aqueous solution having a concentration of 0.90 to 1.

10. Component 3: 1.1 to 2.0 mol equivalents of potassium hydroxide relative to the carboxyl groups of the free fatty acids contained in the crude ester solution obtained in step (B) above. Component 4: At least one selected from the group consisting of n-propanol and isopropanol. Step (D): A step to obtain a water-washed ester solution by repeatedly washing the deoxidized ester solution obtained in step (C) with water until the pH of the wastewater reaches 6.5 to 7.

4. Step (E): A step to obtain a purified ester by removing the solvent from the water-washed ester solution obtained in step (D).

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