Fatty acid esters and methods for producing the same

Abstract

To provide novel fatty acid esters. [Solution] A fatty acid ester is used, which contains 3% by mass or less of a lactone with 18 carbon atoms and has an acid value of 1 mgKOH / g or less.

Description

[Technical Field]

[0001] This invention relates to fatty acid esters and methods for producing the same. [Background technology]

[0002] Fatty acid esters are used in various applications, such as lubricants. For example, Patent Document 1 discloses a lubricant composition using fatty acid esters. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2017-165912 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The object of the present invention is to provide novel fatty acid esters.

[0005] Another object of the present invention is to provide a novel method for producing fatty acid esters. [Means for solving the problem]

[0006] Fatty acid esters are produced by esterifying fatty acids with alcohols, but the fatty acids used as raw materials may contain lactones.

[0007] The inventors anticipated that fatty acid esters obtained using lactone-containing fatty acids would have poor performance when used as lubricants.

[0008] Therefore, the inventors have repeatedly investigated methods for producing fatty acids with reduced lactone content [particularly fatty acids with 14 to 20 carbon atoms]. However, because the boiling points of fatty acids and lactones derived from fatty acids are close, it is difficult to efficiently remove only the lactones, and establishing such a production method has proven extremely challenging.

[0009] In this context, the inventor conceived the idea of ​​reducing the lactone content in the fatty acid ester after esterification, rather than reducing the lactone content in the fatty acid itself. The inventor then discovered that the lactone content in the fatty acid ester can be efficiently reduced through a specific process. Furthermore, the inventor found that reducing the lactone content in the fatty acid ester improves the heat resistance and / or viscosity index of the fatty acid ester, and through further diligent research, completed the present invention.

[0010] This invention relates to the following fatty acid esters, etc. [1] Fatty acid esters (or compositions containing fatty acid esters) having a content of 3% by mass or less (e.g., 0% by mass, 0.01% by mass or more and 3% by mass or less, 0.05% by mass or more and 3% by mass or less) of lactone {especially, lactones having 18 carbon atoms [e.g., lactones having a 5-membered ring and / or lactones having a 6-membered ring (e.g., one or more selected from γ-isooctadecalactone, γ-octadecalactone, δ-octadecalactone and δ-isooctadecalactone)]}. Such fatty acid esters (or compositions) may have an acid value of 1 mgKOH / g or less (e.g., 0.01 mgKOH / g or more and 1 mgKOH / g or less). Furthermore, such fatty acid esters (or compositions) may have an alcohol content of 0.001% by mass or more. [2] A step (A) of esterifying an alcohol with a composition (fatty acid composition) containing a lactone {in particular, a lactone having 18 carbon atoms [for example, a lactone having a 5-membered ring and / or a lactone having a 6-membered ring (for example, one or more selected from γ-isooctadecalactone, γ-octadecalactone, δ-octadecalactone and δ-isooctadecalactone)]} and a fatty acid, A method for producing a fatty acid ester (or a composition containing a fatty acid ester) having a lactone (particularly a lactone having 18 carbon atoms) content of 3% by mass or less (e.g., 0% by mass, 0.01% by mass or more and 3% by mass or less, 0.05% by mass or more and 3% by mass or less), comprising step (B) of treating the reaction mixture from step (A) under reduced pressure at 200 to 250°C and 0.1 to 500 Torr. [3] A method for producing the fatty acid ester (or composition) according to [2], wherein the acid value of the reaction mixture used in step (B) is 3 mg KOH / g or less. [4] The fatty acid ester (or composition) according to [1], wherein the fatty acid (fatty acid constituting the fatty acid ester) comprises a fatty acid having 14 to 20 carbon atoms (for example, 16 to 18 carbon atoms) (saturated fatty acid and / or unsaturated fatty acid). [5] The manufacturing method according to [2] or [3], wherein the fatty acid [fatty acid used in step (A)] is a fatty acid having 14 to 20 carbon atoms (for example, 16 to 18 carbon atoms) (saturated fatty acid and / or unsaturated fatty acid). [6] A fatty acid ester (or composition) according to [1] or [4], wherein the fatty acid (fatty acid constituting the fatty acid ester) comprises a branched fatty acid having 14 to 20 carbon atoms (e.g., 16 to 18 carbon atoms) (saturated branched fatty acid and / or unsaturated branched fatty acid) [e.g., a branched fatty acid having 18 carbon atoms (e.g., isostearic acid, isoleic acid)]. [7] A method of production according to any one of [2], [3], and [5], wherein the fatty acid [fatty acid used in step (A)] comprises a branched fatty acid having 14 to 20 carbon atoms (e.g., 16 to 18 carbon atoms) (saturated branched fatty acid and / or unsaturated branched fatty acid) [e.g., a branched fatty acid having 18 carbon atoms (e.g., isostearic acid, isoleic acid)]. [8] A fatty acid ester (or composition) according to any one of [1], [4], and [6], wherein the fatty acid (a fatty acid constituting the fatty acid ester) contains isostearic acid (or isoleic acid) (as the main component) (for example, the proportion of isostearic acid in a branched fatty acid having 18 carbon atoms is 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, etc.). [9] A method of production according to any one of [2], [3], [5] and [7], wherein the fatty acid [fatty acid used in step (A)] contains isostearic acid (or isoleic acid) (as the main component) (for example, the proportion of isostearic acid in a branched fatty acid having 18 carbon atoms is 50% by mass or more, 60% by mass or more, 70% by mass or more, or 80% by mass or more).

[10] A fatty acid ester (or composition) according to any one of [1], [4], [6], and [8], wherein the content of fatty acids having 16 to 18 carbon atoms in the total fatty acids (fatty acids constituting the fatty acid ester) is 80% by mass or more (for example, 90% by mass or more). In the fatty acid ester (or composition), the acid value of the fatty acid ester may be 0.5 mg KOH / g or less, and the alcohol content may be 0.1% by mass or less.

[11] A method for producing a fatty acid having 16 to 18 carbon atoms in the total fatty acid [fatty acid used in step (A)], wherein the content of fatty acids having 16 to 18 carbon atoms is 80% by mass or more (for example, 90% by mass or more) as described in any of [2], [3], [5], [7] and [9]. In the fatty acid ester (or composition) obtained by this method, the acid value of the fatty acid ester may be 0.5 mg KOH / g or less, and the alcohol content may be 0.1% by mass or less.

[12] A method of production according to any one of [2], [3], [5], [7], [9], and

[11] , wherein the composition (used in step (A)) contains 3% by mass or more (for example, more than 3% by mass) and 10% by mass or less.

[13] A manufacturing method according to any one of [2], [3], [5], [7], [9],

[11] , and

[12] , wherein the alcohol (the alcohol used in step (A)) comprises an alcohol having 20 or fewer carbon atoms or a dihydric or greater alcohol.

[14] A manufacturing method according to any one of [2], [3], [5], [7], [9] and

[11] to

[13] , wherein step (B) comprises step (B-1) of treating the reaction mixture of step (A) at 200 to 250°C under reduced pressure at 10 to 50 Torr, and step (B-2) of treating the fatty acid ester obtained in step (B-1) at the temperature of step (B-1) (i.e., maintaining the temperature of step (B-1)) under reduced pressure at 0.1 to 10 Torr.

[15] Further, it includes a step (C) of transesterifying a fatty acid ester (or a composition) with an alcohol or polyhydric alcohol having 21 or more carbon atoms, and the production method according to any one of [2], [3], [5], [7], [9], and

[11] to

[14] .

[16] A method for improving the heat resistance and / or viscosity index of a fatty acid ester, which includes a step of reducing the content of lactone (for example, lactone having 18 carbon atoms) in the fatty acid ester (for example, to 3% by mass or less).

Advantages of the Invention

[0011] According to the present invention, a novel fatty acid ester can be provided. Since the fatty acid ester of the present invention has a high viscosity index, it can be suitably used for lubricant applications and the like.

[0012] According to another aspect of the present invention, a method for producing a novel fatty acid ester can be provided. According to such a production method, a fatty acid ester with a reduced lactone content can be efficiently produced Among fatty acids, branched fatty acids can be industrially produced by a catalytic or thermal isomerization step of unsaturated fatty acids. However, in the isomerization step, it is known that impurities such as lactone corresponding to the starting unsaturated fatty acid are by-produced, and it has been difficult to obtain high-purity branched fatty acids For example, commercially available isostearic acid usually contains a large amount of lactone. On the other hand, according to the production method of the present invention, since the lactone content in the fatty acid ester after esterification can be reduced, even when using a branched fatty acid containing lactone, a fatty acid ester with a reduced lactone content can be efficiently produced Also, when a branched fatty acid ester using a branched fatty acid containing lactone is used as a lubricant, its performance may not be satisfactory in some cases. However, according to the present invention, since a fatty acid ester with a reduced lactone content can be produced, a fatty acid ester suitable for lubricant applications can be produced

[0013] Another aspect of the present invention can provide a method for producing fatty acid esters with a high viscosity index.

[0014] According to another aspect of the present invention, a fatty acid ester with excellent heat resistance and a method for producing the same can be provided.

[0015] Another aspect of the present invention may provide a method for improving the heat resistance and / or viscosity index of fatty acid esters. [Modes for carrying out the invention]

[0016] [Method for producing fatty acid esters] The method for producing fatty acid esters of the present invention typically includes specific steps [A (a) of esterifying a composition containing lactone and fatty acid with an alcohol, and B (b) of treating the reaction mixture from step (A) under reduced pressure under specific conditions]. The fatty acid ester obtained by the production method of the present invention may be a composition containing fatty acid esters.

[0017] (Process (A)) In step (A), a composition containing lactones and fatty acids (hereinafter sometimes simply referred to as "fatty acid composition") is typically esterified with an alcohol. The reaction mixture obtained in step (A) may be a composition containing fatty acid esters.

[0018] fatty acid composition The lactones included in the fatty acid composition are not particularly limited, and the number of carbon atoms in the lactones may be, for example, 2 or more (e.g., 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, 10 or more, 11 or more, 12 or more, 13 or more, 14 or more, 15 or more, 16 or more, 17 or more, 18 or more), or 25 or less (e.g., 24 or less, 23 or less, 22 or less, 21 or less, 20 or less, 19 or less, 18 or less), etc.

[0019] The number of carbon atoms in the lactone may be such that, from the viewpoint of efficiently removing lactone and unreacted fatty acids (from step (A)) in step (B), the difference between the number of carbon atoms in the lactone and the number of carbon atoms in the fatty acid is, for example, 10 or less (e.g., 9 or less, 8 or less, 7 or less), preferably 6 or less (e.g., 5 or less, 4 or less, 3 or less, 2 or less), etc. The lactone may preferably contain a lactone with the same number of carbon atoms as the fatty acid contained in the fatty acid composition. For example, if the fatty acid composition contains a fatty acid with 18 carbon atoms, the lactone may contain a lactone with 18 carbon atoms (e.g., γ-isooctadecalactone, γ-octadecalactone, δ-isooctadecalactone, δ-octadecalactone, etc.).

[0020] The boiling point of the lactone may be such that the difference in boiling point with that of the fatty acid (the fatty acid contained in the fatty acid composition) is, for example, 20°C or less (for example, 15°C or less), preferably 10°C or less, and more preferably 5°C or less. According to the manufacturing method of the present invention, even when the difference in boiling points between fatty acids and lactones is not so large, fatty acid esters with reduced lactone content can be efficiently produced.

[0021] The ring structure of the lactone is not particularly limited, but may be, for example, a five-membered ring, a six-membered ring, etc. In other words, examples of lactones include lactones with a five-membered ring (γ-lactones) and lactones with a six-membered ring (δ-lactones). The ring structure of the lactone may have an aliphatic hydrocarbon group (e.g., a C1-C16 aliphatic saturated hydrocarbon group such as a C1-C16 alkyl group, or a C2-C16 aliphatic unsaturated hydrocarbon group such as a C2-C16 alkenyl group). The aliphatic hydrocarbon group may be substituted on a carbon atom of the lactone ring. The ring structure of the lactone may have one or more aliphatic hydrocarbon groups. The aliphatic hydrocarbon group may be a straight chain or a branched chain. The number of branches in a branched chain is not particularly limited; it may be one or two or more. The position of the branches in the branched chain is also not particularly limited. Typical lactones include, for example, lactones having a five-membered ring [e.g., γ-tetradecalactone (γ-hydroxytetradecanoic acid γ-lactone), γ-pentadecalactone (γ-hydroxypentadecanoic acid γ-lactone), γ-hexadecalactone (γ-hydroxyhexadecanoic acid γ-lactone), γ-heptadecalactone (γ-hydroxyheptadecanoic acid γ-lactone), γ-octadecalactone (γ-hydroxyoctadecanoic acid γ-lactone), γ-isooctadecalactone, and other γ-C14~C20 lactones, preferably γ-C16~C18 lactones]. Examples include lactones, lactones having a 6-membered ring, such as δ-tetradecalactone (δ-5-hydroxytetradecanoic acid δ-lactone), δ-pentadecalactone (δ-5-hydroxypentadecanoic acid δ-lactone), δ-hexadecalactone (δ-5-hydroxyhexadecanoic acid δ-lactone), δ-heptadecalactone (δ-5-hydroxyheptadecanoic acid δ-lactone), δ-octadecalactone (δ-5-hydroxyoctadecanoic acid δ-lactone), δ-isooctadecalactone, and other δ-C14~C20 lactones, preferably δ-C16~C18 lactones. Furthermore, γ-isooctadecalactone may also be γ-lactone 4-hydroxyisostearate, or an isomer of γ-lactone 4-hydroxyisostearate. δ-isooctadecalactone may also be δ-lactone 5-hydroxyisostearate, or an isomer of δ-lactone 5-hydroxyisostearate.

[0022] Furthermore, the lactone may be one type or two or more types.

[0023] The lactone may preferably be a lactone derived from a fatty acid contained in the fatty acid composition. For example, if the fatty acid composition contains branched fatty acids with 18 carbon atoms (e.g., isostearic acid, isoleic acid), the lactone may contain a branched-chain lactone with 18 carbon atoms (e.g., γ-hydroxyisostearate).

[0024] Typically, the lactone content may be such that the amount of lactone with the same number of carbon atoms as the fatty acid contained in the fatty acid composition is, for example, 50% or more by mass, 60% or more by mass, 70% or more by mass, 80% or more by mass, 90% or more by mass, 95% or more by mass, etc., relative to the total amount of lactone.

[0025] The lactones may typically consist of C14-C20 lactones (e.g., γ-C14-C20 lactones, δ-C14-C20 lactones) or C16-C18 lactones (e.g., γ-C16-C18 lactones, δ-C16-C18 lactones) in amounts of, for example, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, 95% or more, etc., relative to the total lactone content.

[0026] The lactones may typically consist of γ-isooctadecalactone, γ-octadecalactone, δ-isooctadecalactone, and δ-octadecalactone, and their total content may be, for example, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, 95% or more, etc., relative to the total amount of lactones (especially lactones with 18 carbon atoms).

[0027] If the lactone contains γ-isooctadecalactone, the γ-isooctadecalactone may contain two or more isomers (for example, isomers with different branching positions, number of branches, etc.), and may contain at least γ-lactone 4-hydroxyisostearate.

[0028] If the lactone contains δ-isooctadecalactone, the δ-isooctadecalactone may contain two or more isomers (for example, isomers with different branching positions, number of branches, etc.), and may contain at least δ-lactone 5-hydroxyisostearate.

[0029] The lactone content in the fatty acid composition may be, for example, 3% by mass or more (e.g., more than 3% by mass, 4% by mass or more, 5% by mass or more) relative to the total fatty acid composition, or it may be, for example, 15% by mass or less (e.g., 13% by mass or less), 10% by mass or less (e.g., 9% by mass or less, 8% by mass or less), etc.

[0030] The method for measuring the lactone content in a fatty acid composition (and further, fatty acid esters described later) is not particularly limited, but may be measured using, for example, gas chromatography, GC-MS, etc. The measurement method for gas chromatography and GC-MS is not particularly limited, but for example, the conditions described in the examples can be used.

[0031] fatty acid The fatty acids contained in the fatty acid composition (or fatty acids that constitute fatty acid esters, or fatty acids that serve as raw materials for fatty acid esters) may be monovalent or polyvalent (divalent or more). Furthermore, fatty acids may be in any form, such as linear (straight-chain or branched-chain) or cyclic, and may be saturated or unsaturated. In unsaturated fatty acids, the number of unsaturated bonds (carbon-carbon double bonds, carbon-carbon triple bonds, etc.) is not particularly limited; for example, it is sufficient if there is one or more (e.g., 1 to 21, 1 to 10, 1 to 5, 1 to 4, 1 to 3, etc.).

[0032] The number of carbon atoms in a fatty acid is not particularly limited, but is usually two or more, for example, three or more (for example, four or more, five or more, six or more, seven or more, eight or more, nine or more, ten or more, eleven or more, twelve or more, thirteen or more, fourteen or more, fifteen or more, sixteen or more, seventeen or more), etc. The upper limit of the number of carbon atoms in a fatty acid is not particularly limited, but may be, for example, 50 (e.g., 45, 40, 35, 30, 25, 22, 20, 18).

[0033] The number of carbon atoms in fatty acids may be selected by appropriately combining these ranges (upper and lower limits), for example, 12 to 22 (e.g., 14 to 20, 16 to 18).

[0034] Specific fatty acids include, for example, ethane acid (acetic acid), propanoic acid (propionic acid), butanoic acid (butyric acid), pentanoic acid (valeric acid), hexanoic acid (caproic acid), heptanoic acid (enanthic acid), octanoic acid (caprylic acid), nonanoic acid (pelargonic acid), isononanoic acid, decanoic acid (capric acid), dodecanoic acid (lauric acid), tetradecanoic acid (myristic acid), pentadecanoic acid (pentadecyl acid), hexadecanoic acid (palmitic acid), 9-Hexadecenoic acid (palmitoleic acid), heptadecanoic acid (margaric acid), octadecanoic acid (stearic acid), isostearic acid, cis-9-octadecenoic acid (oleic acid), isoleic acid, 11-octadecenoic acid (vaccenic acid), cis,cis-9,12-octadecadienoic acid (linoleic acid), 9,12,15-octadecantrienoic acid ((9,12,15)-linolenic acid), 6,9,12-octadecadienoic acid ((6,9,12)-linolenic acid), 9,11,13-octadecatrienoic acid (eleostearic acid), eicosanoic acid (arachidic acid), 8,11-eicosadienoic acid, 5,8,11-eicosatrienoic acid (medic acid), 5,8,11-eicosatetraenoic acid (arachidonic acid), docosanoic acid (behenic acid), tetracosanoic acid (lignoceric acid), cis-15-tetracosanoic acid (nervonic acid), hexacosanoic acid (cerotic acid), o Examples include monounsaturated or unsaturated monounsaturated fatty acids with 2 to 30 carbon atoms (preferably 12 to 22, 14 to 20, 16 to 18, etc.), straight-chain or branched-chain monounsaturated fatty acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, and pimelic acid (for example, straight-chain or branched-chain polyunsaturated fatty acids with 2 to 30 carbon atoms (for example, diunsaturated fatty acids)). The fatty acids should consist of at least monounsaturated fatty acids, and both monounsaturated and polyunsaturated fatty acids may be used.

[0035] Fatty acids may be commercially available or synthesized (manufactured). The synthesis method is not particularly limited, and conventional methods may be used.

[0036] Furthermore, the fatty acids may contain small amounts of dimer acids, trimer acids, etc., as long as they achieve the effects of the present invention.

[0037] Furthermore, fatty acids may be used individually or in combination of two or more types.

[0038] The fatty acid may typically be a fatty acid having 14 to 20 carbon atoms (preferably a fatty acid having 16 to 18 carbon atoms, more preferably a branched fatty acid having 18 carbon atoms). The content of fatty acids having 14 to 20 carbon atoms (preferably fatty acids having 16 to 18 carbon atoms, more preferably branched fatty acids with 18 carbon atoms) in the fatty acids may be, for example, 50% or more by mass, 60% or more by mass, 70% or more by mass, 80% or more by mass, 90% or more by mass, 95% or more by mass, etc., relative to the total amount of fatty acids.

[0039] If the fatty acids contain saturated fatty acids, the content of saturated fatty acids (total amount) may be, for example, 0.1% by mass or more (for example, 1% by mass or more, 5% by mass or more, 10% by mass or more, 15% by mass or more, 20% by mass or more, 25% by mass or more, 30% by mass or more, 35% by mass or more, 40% by mass or more, 45% by mass or more, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more), or for example, 99% by mass or less (for example, 98% by mass or less, 97% by mass or less, 96% by mass or less, 95% by mass or less, 90% by mass or less, 85% by mass or less, 80% by mass or less, 75% by mass or less, 70% by mass or less, 65% by mass or less, 60% by mass or less), etc.

[0040] Furthermore, the saturated fatty acid content may be selected by appropriately combining these ranges (upper and lower limits) (for example, 50-90% by mass).

[0041] Typically, the fatty acids may contain saturated fatty acids with 14 to 20 carbon atoms (for example, saturated fatty acids with 16 to 18 carbon atoms such as isostearic acid) in an amount of 0.1% or more by mass, 1% or more by mass, 5% or more by mass, 10% or more by mass, 20% or more by mass, 30% or more by mass, 40% or more by mass, 50% or more by mass, 60% or more by mass, etc., relative to the total amount of fatty acids.

[0042] In particular, if the fatty acid contains a branched fatty acid with 18 carbon atoms, the branched fatty acid with 18 carbon atoms may have isostearic acid as its main component, and the isostearic acid content in the branched fatty acid with 18 carbon atoms may be, for example, 50% by mass or more (for example, 60% by mass or more, 70% by mass or more, 80% by mass or more), or 99% by mass or less, 95% by mass or less, 90% by mass or less, etc.

[0043] If the fatty acid contains isostearic acid, the isostearic acid may contain two or more isomers (for example, isomers with different branching positions, number of branches, etc.), and may contain at least 16-methylheptadecanoic acid.

[0044] If the fatty acid contains unsaturated fatty acids, the content of unsaturated fatty acids (total amount) may be, for example, 0.1% by mass or more (for example, 0.5% by mass or more, 1% by mass or more, 2% by mass or more, 3% by mass or more, 4% by mass or more, 5% by mass or more, 7% by mass or more, 10% by mass or more, 15% by mass or more, 20% by mass or more, 25% by mass or more, 30% by mass or more, 35% by mass or more, 40% by mass or more, 45% by mass or more, 50% by mass or more), or for example, 70% by mass or less (for example, 65% by mass or less, 60% by mass or less, 55% by mass or less, 50% by mass or less, 45% by mass or less, 40% by mass or less), etc.

[0045] Furthermore, the content of unsaturated fatty acids may be selected by appropriately combining these ranges (upper and lower limits) (for example, 0.1 to 40% by mass).

[0046] Typically, the fatty acids may contain unsaturated fatty acids with 14 to 20 carbon atoms (for example, unsaturated fatty acids with 16 to 18 carbon atoms such as isoleic acid) in amounts of, for example, 0.1% by mass or more (for example, 2% by mass or more, 3% by mass or more, 4% by mass or more, 5% by mass or more, 7% by mass or more, 10% by mass or more) relative to the total amount of fatty acids. In particular, when the fatty acid contains a branched fatty acid with 18 carbon atoms, the content of the unsaturated fatty acid with 18 carbon atoms (e.g., isoleic acid) in the branched fatty acid with 18 carbon atoms may be, for example, 50% by mass or more, 60% by mass or more, 70% by mass or more, or 50% by mass or less, 40% by mass or less, 30% by mass or less. Furthermore, depending on the manufacturing method, unsaturated fatty acids may be particularly prone to containing (or generating) lactones, making it difficult to efficiently produce fatty acid esters with reduced lactone content. However, according to the present invention, even when using unsaturated fatty acids containing lactones, fatty acid esters with reduced lactone content can be efficiently produced.

[0047] If the fatty acid contains isoleic acid, the isoleic acid may contain two or more isomers (for example, isomers with different positions of double bonds, etc.), and may contain at least isocis-9-octadecenoic acid.

[0048] The fatty acid may have a boiling point difference with the lactone such that it can efficiently remove the lactone and unreacted fatty acid (from step (A)) in step (B), for example, 20°C or lower (for example, 15°C or lower), preferably 10°C or lower, and more preferably 5°C or lower. The fatty acid may contain fatty acids with a boiling point difference of 5°C or less from lactones, for example, 50% by mass or more (for example, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more) in the total fatty acid composition.

[0049] The method for measuring the fatty acid content in a fatty acid composition is not particularly limited, but may be measured using, for example, gas chromatography. The method for measuring using gas chromatography is not particularly limited, and known methods can be used.

[0050] alcohol The alcohol (or the alcohol that constitutes the fatty acid ester, or the alcohol that is a raw material for the fatty acid ester) is not particularly limited and includes, for example, aliphatic alcohols (including alicyclic alcohols) and non-aliphatic alcohols (for example, aromatic alcohols), but may be aliphatic alcohols in particular.

[0051] The alcohol may be a monool (monohydric alcohol) or a polyol (polyhydric alcohol). The alcohol may be primary, secondary, or tertiary, linear (linear or branched), or cyclic, and may be saturated or unsaturated (in particular, saturated is also acceptable).

[0052] The number of carbon atoms in the alcohol is not particularly limited and may be, for example, 1 or more, 2 or more, 3 or more, 4 or more, 5 or more, etc., or it may be 30 or less, 28 or less, 26 or less, 24 or less, 22 or less, 20 or less, etc.

[0053] Typical alcohols include monohydric alcohols such as aliphatic monools [e.g., alkanols (e.g., methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, amyl alcohol, 2-ethylhexanol, lauryl alcohol, nonanol, isononanol, tridecanol, decyl alcohol, oleyl alcohol, arachidyl alcohol, behenyl alcohol, etc.)], aromatic monools (e.g., phenol, etc.); aliphatic diols [e.g., alkanediols (e.g., ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, hexanediol, etc.)] Examples include dihydric alcohols such as polyalkylene glycols (e.g., diethylene glycol, polyethylene glycol, polypropylene glycol, etc.), alkane polyols (e.g., alkanetriols (e.g., glycerin, trimethylolethane, trimethylolpropane, etc.), alkanetetraols (e.g., pentaerythritol, etc.)), condensates of alkane polyols (e.g., polyalkanetriols to hexaols (e.g., diglycerin, ditrimethylolpropane, dipentaerythritol, etc.), sugar alcohols (e.g., glucose, maltose, sorbitol, maltitol, trehalose, etc.)), and trihydric or higher alcohols.

[0054] The alcohol can be of one type or a combination of two or more types.

[0055] Among the alcohols mentioned above, alcohols with 20 or fewer carbon atoms (for example, monohydric alcohols with 20 or fewer carbon atoms, or dihydric or more alcohols with 20 or fewer carbon atoms) may be preferably used, from the viewpoint of efficiently removing lactones and unreacted alcohols (from step (A)) in step (B).

[0056] Furthermore, among the alcohols mentioned above, alcohols with a boiling point of 60°C or higher (for example, 100°C or higher, 200°C or higher, or 300°C or higher) may be suitably used, from the viewpoint of efficiently removing lactones and unreacted alcohols (in step (A)) in step (B). The boiling point of the alcohol may preferably be 300°C or lower (for example, 200°C or lower, or 100°C or lower).

[0057] Note that the boiling point of alcohol can be selected by appropriately combining these ranges (upper and lower limits) (for example, 100-300°C).

[0058] Esterification The esterification method in step (A) is not particularly limited as long as it is a method of esterification using the fatty acid composition and an alcohol, and known esterification methods can be used. For example, esterification may be carried out by condensation of the fatty acid composition and the alcohol under an acid catalyst or a metal catalyst.

[0059] The reaction conditions for the esterification reaction are not particularly limited and can be appropriately set depending on the fatty acid composition, alcohol, etc. used. In the esterification reaction, the ratio of the fatty acid composition to the alcohol can be set as appropriate, but for example, the molar ratio of the fatty acid composition to the alcohol may be, for example, 1:10 to 10:1. The reaction temperature is not particularly limited, but may be, for example, 100 to 250°C. The pressure during the reaction is not particularly limited, but may be, for example, 0.1 to 500 Torr. The reaction time can be set appropriately depending on the reaction temperature, pressure, etc., but for example, it may be 1 to 50 hours.

[0060] The reaction mixture obtained by the above esterification reaction may have an acid value of, for example, 5 mg KOH / g or less (for example, 4.5 mg KOH / g or less), preferably 3 mg KOH / g or less (for example, 2.5 mg KOH / g or less, 2 mg KOH / g or less, 1.5 mg KOH / g or less, 1 mg KOH / g or less).

[0061] The method for measuring the acid value is not particularly limited, and conventional methods (for example, JIS K 0070-1992) may be used.

[0062] (Process (B)) In step (B), the reaction mixture from step (A) is typically subjected to reduced pressure under specific conditions (temperature and pressure).

[0063] The temperature in step (B) may be, for example, 200-250°C, from the viewpoint of efficiently removing lactones contained in the reaction mixture of step (A), as well as unreacted fatty acids and alcohols (in step (A)).

[0064] The pressure in step (B) may be, for example, 0.1 to 500 Torr, from the viewpoint of efficiently removing lactones contained in the reaction mixture of step (A), as well as unreacted fatty acids and alcohols (in step (A)).

[0065] The depressurization time in process (B) can be set appropriately depending on the temperature, pressure, etc., but may be, for example, 1 to 20 hours. Furthermore, it is preferable to continue the process in step (B) until the lactone content in the fatty acid ester obtained by step (B) is 3% by mass or less.

[0066] The fatty acid ester obtained in step (B) may have a lactone (particularly a lactone with 18 carbon atoms) content of, for example, 3% by mass or less (e.g., 2.8% by mass or less, 2.5% by mass or less, 2.3% by mass or less), preferably 2% by mass or less (e.g., 1.8% by mass or less, 1.5% by mass or less), and more preferably 1% by mass or less (e.g., 0.5% by mass or less) in the total fatty acid ester. The lower limit of the lactone (especially 18-carbon lactone) content is not particularly limited and may be 0% by mass in the total fatty acid ester, or it may be a finite value (for example, 0.01% by mass, 0.05% by mass, 0.1% by mass, 0.25% by mass, 0.5% by mass, 1% by mass, etc.).

[0067] Furthermore, the lactone content (especially lactones with 18 carbon atoms) may be selected by appropriately combining these ranges (upper and lower limits) (for example, 0.01 to 3% by mass, 0.1 to 3% by mass, etc.).

[0068] When the lactone content in the fatty acid composition used in step (A) is X by mass and the lactone content in the fatty acid ester obtained in step (B) is Y by mass, X and Y may be, for example, 1% by mass or more (for example, 1.5% by mass or more), preferably 2% by mass or more (for example, 2.5% by mass or more, 3% by mass or more, 3.5% by mass or more), etc.

[0069] In the present invention, the lactone content in fatty acid esters can be efficiently reduced by going through step (B).

[0070] Step (B) may be carried out in two stages, (B-1) and (B-2), from the viewpoint of being able to more efficiently reduce the lactone content in the fatty acid ester.

[0071] Step (B-1) may be, for example, a step of treating the reaction mixture from step (A) (a composition containing fatty acid esters) under reduced pressure at 200-250°C and 10-50 Torr.

[0072] The depressurization time in process (B-1) can be set appropriately depending on the temperature, pressure, etc., but may be, for example, 1 to 20 hours. Furthermore, it is preferable to continue the process in step (B-1) until the content of (unreacted) alcohol in the fatty acid ester obtained in step (B-1) is 0.1% by mass or less. Step (B-1) can efficiently remove unreacted fatty acids and alcohols from step (A).

[0073] Step (B-2) may be, for example, a step in which the fatty acid ester obtained in step (B-1) is subjected to reduced pressure at the temperature of step (B-1), 0.1 to 10 Torr.

[0074] The depressurization time in process (B-2) can be set appropriately depending on the temperature, pressure, etc., but may be, for example, 1 to 20 hours. Furthermore, it is preferable to perform the reduced-pressure treatment in step (B-2) until the lactone content in the fatty acid ester obtained in step (B-2) becomes 3% by mass or less. Step (B-2) can efficiently remove lactones from fatty acid esters.

[0075] Furthermore, the manufacturing method of the present invention may include further steps (for example, a purification step) after steps (A) and (B), and the method of such steps is not particularly limited, and known methods may be used.

[0076] A further step may be, for example, a step (C) in which the fatty acid ester obtained in step (B) is transesterified with an alcohol.

[0077] Examples of alcohols used in step (C) include the alcohols exemplified above, but it is preferable to use an alcohol different from the one used in step (A). For example, if an alcohol with 20 or fewer carbon atoms is used in step (A), an alcohol with 21 or more carbon atoms, or a polyhydric alcohol, may be suitably used in step (C).

[0078] As the alcohol used in step (C), for example, an alcohol with a boiling point of 60°C or higher (e.g., 100°C or higher, 200°C or higher, 300°C or higher) may be suitably used. The boiling point of the alcohol may preferably be 300°C or lower (for example, 200°C or lower, or 100°C or lower).

[0079] Furthermore, the boiling point of the alcohol used in process (C) may be selected by appropriately combining these ranges (upper and lower limits), for example, 60 to 300°C.

[0080] The method of transesterification is not particularly limited, and known transesterification methods can be used.

[0081] [Fatty acid esters] Fatty acid esters can be obtained by the above manufacturing method. Furthermore, fatty acid esters may contain small amounts (e.g., 3% by mass or less) of other components (e.g., alcohols, unreacted fatty acids, lactones, etc.), and even in such cases, they are still included in the category of fatty acid esters. In other words, fatty acid esters may also be compositions containing fatty acid esters. The other components may be one type or two or more types. The present invention also includes such fatty acid esters [in particular, fatty acid esters with a lactone content (especially a lactone having 18 carbon atoms) of 3% by mass or less].

[0082] The fatty acid ester may contain lactones (particularly C18 lactones) in a quantity of, for example, 3% by mass or less (e.g., 2.8% by mass or less, 2.5% by mass or less, 2.3% by mass or less), preferably 2% by mass or less (e.g., 1.8% by mass or less, 1.5% by mass or less), and more preferably 1% by mass or less (e.g., 0.5% by mass or less) in the total fatty acid ester.

[0083] The lower limit of the lactone (especially the 18-carbon lactone) content in the fatty acid ester is not particularly limited and may be 0% by mass in the entire fatty acid ester, or it may be a finite value (for example, 0.01% by mass, 0.05% by mass, 0.1% by mass, etc.).

[0084] Furthermore, the lactone content (especially lactones with 18 carbon atoms) in fatty acid esters may be selected by appropriately combining these ranges (upper and lower limits) (for example, 0.01 to 3% by mass, 0.1 to 3% by mass, etc.).

[0085] In this invention, lactones are not typically included in the category of fatty acid esters (or fatty acid esters obtained by the production method of this invention) of the present invention.

[0086] Fatty acid esters may typically be esters of fatty acids having 14 to 20 carbon atoms (preferably fatty acids having 16 to 18 carbon atoms, such as isostearic acid and isoleic acid).

[0087] If the fatty acid ester contains an ester of a branched fatty acid having 18 carbon atoms, the ester of the branched fatty acid having 18 carbon atoms may be mainly composed of isostearate ester or isoleate ester. The isostearate ester content in the ester of a branched fatty acid having 18 carbon atoms may be, for example, 50% by mass or more (for example, 60% by mass or more, 70% by mass or more, 80% by mass or more), or for example, 50% by mass or less, 40% by mass or less, or 30% by mass or less. Furthermore, the ester of a branched fatty acid having 18 carbon atoms may contain, for example, 50% or more by mass, 60% or more by mass, 70% or more by mass of an unsaturated fatty acid ester having 18 carbon atoms (e.g., isoleic acid ester), or for example, 50% or less by mass, 40% or less by mass, or 30% or less by mass.

[0088] The fatty acid ester may be a total ester or a partial ester.

[0089] The esterification rate of fatty acid esters may be, for example, 100% or less, 98% or less, 96% or less, 94% or less, 92% or less, 90% or less, 88% or less, 86% or less, 84% or less, 82% or less, 80% or less, etc. The lower limit of the esterification rate of fatty acid esters is not particularly limited and may be, for example, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, etc.

[0090] The esterification rate may be selected by appropriately combining these ranges (upper and lower limits) (for example, 30-100%).

[0091] The method for measuring the esterification rate is not particularly limited, and conventional methods (for example, JIS K 0070-1992) may be used. The esterification rate can be calculated using the following formula. The ester value in the formula below is calculated according to JIS K 0070-1992. Esterification rate (%) = {Ester value / (Ester value + Hydroxyl value)} × 100

[0092] The acid value of the fatty acid ester may be, for example, 5 mg KOH / g or less (e.g., 4 mg KOH / g or less, 3 mg KOH / g or less, 2 mg KOH / g or less), and preferably 1 mg KOH / g or less (e.g., 0.5 mg KOH / g or less). The lower limit of the acid value of fatty acid esters is not particularly limited and may be 0 mgKOH / g, or a finite value (for example, 0.01 mgKOH / g, 0.02 mgKOH / g, 0.03 mgKOH / g, 0.04 mgKOH / g, 0.05 mgKOH / g, 0.06 mgKOH / g, 0.07 mgKOH / g, 0.08 mgKOH / g, 0.09 mgKOH / g, 0.1 mgKOH / g).

[0093] The acid value may be selected by appropriately combining these ranges (upper and lower limits) (for example, 0.01 to 1 mg KOH / g).

[0094] The method for measuring the acid value is not particularly limited, and conventional methods (for example, JIS K 0070-1992) may be used.

[0095] In fatty acid esters, the alcohol content is not particularly limited, but may be small, for example, 1% by mass or less (e.g., 0.8% by mass or less, 0.6% by mass or less), preferably 0.5% by mass or less (0.4% by mass or less, 0.3% by mass or less, 0.2% by mass or less, 0.1% by mass or less) in the total fatty acid ester. According to the manufacturing method of the present invention, the alcohol content in the fatty acid ester can be efficiently reduced by going through step (B).

[0096] The lower limit of the alcohol content in the fatty acid ester is not particularly limited and may be 0% by mass in the entire fatty acid ester, or it may be a finite value (for example, 0.001% by mass, 0.005% by mass, 0.01% by mass, 0.025% by mass, 0.05% by mass, etc.).

[0097] In addition, the alcohol content in the fatty acid ester may be selected within a range by appropriately combining these ranges (upper limit and lower limit) (for example, 0 to 0.5% by mass, etc.).

[0098] The fatty acid ester may contain, for example, 90% by mass or more (for example, 95% by mass or more, 98% by mass or more) of a fatty acid ester having a boiling point difference of 10°C or more (for example, 20°C or more, 30°C or more) from the lactone.

[0099] The kinematic viscosity of the fatty acid ester at 100°C depends on the type of fatty acid, etc., but for example, it may be 50 mm 2 , 2 / s or less (for example, 40 mm 2 / s or less), preferably 30 mm 2 / s or less (for example, 20 mm 2 / s or less, 15 mm 2 / s or less). The lower limit value of the kinematic viscosity of the fatty acid ester at 100°C is not particularly limited, but for example, it may be 1 mm 2 / s, 2 mm 2 / s, 3 mm 2 / s, 4 mm 2 / s, 5 mm 2 / s or the like.

[0100] In addition, the kinematic viscosity at 100°C may be selected within a range by appropriately combining these ranges (upper limit and lower limit) (for example, 1 to 30 mm 2 / s or the like).

[0101] The kinematic viscosity of the fatty acid ester at 40°C depends on the type of fatty acid, etc., but for example, it may be 300 mm 2 / s or less (for example, 250 mm 2 / s or less), preferably 200 mm 2 / s or less (for example, 150 mm 2 / s or less, 100 mm 2 / s or less). The lower limit value of the kinematic viscosity of the fatty acid ester at 40°C is not particularly limited, but for example, it may be 1 mm 2 / s, 3 mm<00 / s, 5mm 2 / s, 7mm 2 / s, 9mm 2 You can also use / s, etc.

[0102] Furthermore, the kinematic viscosity at 40°C may be selected by appropriately combining these ranges (upper and lower limits) (for example, 1 to 100 mm²). 2 / s etc.).

[0103] The method for measuring kinematic viscosity is not particularly limited, and conventional methods (for example, JIS K 2283-2000) may be used.

[0104] The viscosity index of a fatty acid ester depends on the type of fatty acid, but may be, for example, 100 or higher, preferably 110 or higher, and more preferably 120 or higher. The upper limit of the viscosity index of the fatty acid ester is not particularly limited, but may be, for example, 100, 150, 200, etc.

[0105] Note that the viscosity index may be selected by appropriately combining these ranges (upper and lower limits) (for example, 100-200 mm). 2 / s etc.).

[0106] The method for measuring viscosity index is not particularly limited, and conventional methods (for example, JIS K 2283-2000) may be used.

[0107] [Uses of fatty acid esters, etc.] The fatty acid esters obtained by the manufacturing method of the present invention, as well as the fatty acid esters of the present invention, can be used in a variety of applications [for example, lubricating oils, resin additives, cosmetics, surfactants, processing oils, greases, etc.].

[0108] The present invention also includes a method for improving the heat resistance and / or viscosity index of a fatty acid ester, which includes a step of reducing the lactone content in the fatty acid ester. In this method, the step of reducing the lactone content in the fatty acid ester may be step (B) described above, and the fatty acid ester and lactone may be those described above. The lactone content in the fatty acid ester may be, for example, 3% by mass or less (for example, 0.01 to 3% by mass, 0.1 to 3% by mass). In this method, the improvement in viscosity index is defined as the viscosity index of the fatty acid ester containing lactone and the fatty acid ester with reduced lactone content (viscosity index measured according to JIS K 2283-2000) being V and V', respectively, where the value of V'-V is greater than 0, for example, 0.1 or more (for example, 0.1 to 10), 2 or more, 3 or more, etc. In this method, the improvement in heat resistance is achieved when the mass reduction rate (%) of the fatty acid ester containing lactone and the fatty acid ester with reduced lactone content is M and M' respectively when heated at 150°C for 24 hours, and the value of M-M' is greater than 0, for example, 0.1 or more (for example, 0.1 to 0.9), 0.2 or more, 0.3 or more, 0.4 or more, etc. [Examples]

[0109] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited in any way by these examples, and many modifications are possible within the technical concept of the present invention by those with ordinary skill in the art.

[0110] [Esterification rate] In this invention, the esterification rate (%) of the fatty acid ester is the value calculated by the following formula. The ester value in the following formula is calculated based on JIS K 0070-1992. Esterification rate (%) = {Ester value / (Ester value + Hydroxyl value)} × 100

[0111] [Hydroxyl value] The measurement was performed according to JIS K 0070-1992 (neutralization titration method).

[0112] [Acid value] The measurement was performed according to JIS K 0070-1992 (neutralization titration method).

[0113] [Method for measuring lactones] The lactone content in fatty acid esters was measured by gas chromatography and GC-MS analysis. The GC measurement conditions are shown below. The measurement results are shown in Table 2 below. (GC measurement conditions) Equipment: Shimadzu Corporation's "GC-2014" Column: Agilent Technologies' "DB-1HT" Column temperature: 70°C (2 mins) → heating rate 10°C / min → 350°C (5 mins) Sample volume: 1 μL Carrier gas: Nitrogen (total flow rate 57.8 mL / min) Injection conditions: Split (split ratio 50) Injection temperature: 350℃ Detector: FID (GC-MS measurement conditions) Equipment: GCMS―QP-2000 Column: Agilent Technologies' "DB-1HT" Column temperature: 150°C (10 minutes) → heating rate 3°C / min → 300°C Sample volume: 1 μL Carrier gas: Helium. Injection conditions: Split (split ratio 50). Injection temperature: 300℃ MS ion source temperature: 200℃ Interface temperature: 250℃

[0114] [Method for measuring alcohol content] The alcohol content was determined by gas chromatography analysis and hydroxyl value. The GC measurement conditions were the same as those for lactone measurement.

[0115] [Kinematic viscosity] The kinematic viscosity of fatty acid esters was measured in accordance with JIS K 2283-2000.

[0116] [Viscosity index] The viscosity index refers to the viscosity index measured according to JIS K 2283-2000.

[0117] [Heat resistance test] A cup made of borosilicate glass with an inner diameter of φ21.5 mm, a body diameter of φ24 mm, and a total length of 40 mm was placed in a container and heated at 150°C for 24 hours. The amount of fatty acid ester was measured before and after heating. Heat resistance was evaluated by calculating the mass loss rate as -(amount of fatty acid ester after heating - amount of fatty acid ester before heating) / amount of fatty acid ester before heating × 100 (%). A lower mass loss rate indicates better heat resistance.

[0118] (Example 1) In a 2 L four-necked flask equipped with a stirrer, thermometer, and Dean-Stark tube with condenser, 983 g (3.3 mol) of TFA-45 (manufactured by Tsukuno Oleochemicals Co., Ltd., composition listed in Table 1), 573 g (4.4 mol) of 2-ethylhexanol (manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.05% by mass of tin oxide (Tokyo Chemical) as a catalyst were charged, and the mixture was heated to 230°C under a nitrogen atmosphere. After reaching 230°C, the pressure was reduced to 500 Torr, and the esterification reaction was carried out while removing the distilled product water using a Dean-Stark tube. After confirming that the acid value of the resulting reaction mixture was 1.0 mg KOH / g or less, the pressure was reduced to 30 Torr, and unreacted 2-ethylhexanol was removed. After confirming that the content of the remaining 2-ethylhexanol was 0.1% by mass or less, fatty acid ester A was obtained. The lactone content of fatty acid ester A was 2.5% by mass. Furthermore, the mixture was subjected to reduced pressure from 0.1 to 10 Torr while maintaining a temperature of 230°C. After confirming that the lactone content was 0.1% by mass, the reduced pressure treatment was terminated to obtain fatty acid ester A'. The 2-ethylhexanol content in fatty acid ester A' was 0.1% by mass or less. Various analyses were performed on the obtained fatty acid esters A and A'. The results are shown in Table 2. The esterification rate of fatty acid esters A and A' was 99.9%.

[0119] (Example 2) In a 2 L four-necked flask equipped with a stirrer, thermometer, and Dean-Stark tube with condenser, 731 g (2.4 mol) of TFA-80MS (manufactured by Tsukuno Oleochemicals Co., Ltd., composition listed in Table 1), 626 g (3.4 mol) of lauryl alcohol (manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.05% by mass of tin oxide (Tokyo Chemical) as a catalyst were charged, and the mixture was heated to 230°C under a nitrogen atmosphere. After reaching 230°C, the pressure was reduced to 100 Torr, and the esterification reaction was carried out while removing the distilled product water using a Dean-Stark tube. After confirming that the acid value of the obtained reaction mixture was 1.0 mg KOH / g or less, the pressure was reduced to 30 Torr, and unreacted lauryl alcohol was removed. After confirming that the content of the remaining lauryl alcohol was 0.1% by mass or less, fatty acid ester B was obtained. The lactone content of fatty acid ester B was 2.1% by mass. Furthermore, the mixture was subjected to reduced pressure from 0.1 to 10 Torr while maintaining a temperature of 230°C. After confirming that the lactone content was 0.1% by mass, the reduced pressure treatment was terminated to obtain fatty acid ester B'. The lauryl alcohol content in fatty acid ester B' was 0.1% by mass or less. Various analyses were performed on the obtained fatty acid esters B and B'. The results are shown in Table 2. The esterification rate of fatty acid esters B and B' was 99.9%.

[0120] (Example 3) TFA-80MS was subjected to a hydrogenation reaction in the presence of a hydrogenation catalyst. The hydrogenated TFA-80MS was then separated into solid and liquid acids using the difference in melting points. The resulting liquid acid was distilled to obtain hydrogenated and fractionated TFA-80MS (compositions listed in Table 1).

[0121] In a 2L four-necked flask equipped with a stirrer, thermometer, and Dean-Stark tube with condenser, 1222g (4.0 mol) of TFA-80MS hydrogenated and fractionated, 214g (1.6 mol) of trimethylolpropane (manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.1% by mass of tin oxide (Tokyo Chemical) as a catalyst were charged, and the mixture was heated to 230°C under a nitrogen atmosphere. After reaching 230°C, the pressure was reduced to 50 Torr, and the esterification reaction was carried out while removing the distillate-produced water using a Dean-Stark tube. The acid value of the resulting reaction mixture was confirmed to be 1.0 mg KOH / g or less, and the trimethylolpropane content was confirmed to be 0.1% by mass or less to obtain fatty acid ester C. The lactone content of fatty acid ester C was 2.8% by mass. Furthermore, the mixture was subjected to reduced pressure from 0.1 to 10 Torr while maintaining the temperature at 230°C. After confirming that the lactone content was 1.5% by mass, the reduced pressure treatment was terminated to obtain fatty acid ester C'. The trimethylolpropane content in fatty acid ester C' was 0.1% by mass or less. Various analyses were performed on the obtained fatty acid esters C and C'. The results are shown in Table 2. The esterification rate of fatty acid esters C and C' was 83.7%.

[0122] [Table 1]

[0123] In Table 1, C18 branched fatty acids contain isostearic acid and isoleic acid, with isostearic acid or isoleic acid as the main component. C18 lactones include γ-lactone of 4-hydroxyoctadecanoic acid, γ-isooctadecalactone, δ-lactone of 5-hydroxyoctadecanoic acid, δ-isooctadecalactone, and other C18 lactones. Furthermore, the boiling points of each fatty acid are as follows: palmitic acid: 351°C, stearic acid: 361°C, oleic acid: 360°C, linoleic acid: 230°C (16 Torr), isostearic acid: 369.5°C, and 4-hydroxyoctadecanoic acid: 365.1°C.

[0124] [Table 2]

[0125] As shown in Table 2, the fatty acid esters A-C and A'-C' obtained in Examples 1-3 had high viscosity indices. Furthermore, the fatty acid esters A-C and A'-C' exhibited good heat resistance. Fatty acid esters A' to C', which had particularly low lactone content, also exhibited particularly high viscosity indices and excellent heat resistance.

[0126] The composition of fatty acid esters A' to C' is shown in Table 3. In Table 3, C18 lactones include 4-hydroxyoctadecanoic acid γ-lactone, γ-isooctadecalactone, 5-hydroxyoctadecanoic acid δ-lactone, δ-isooctadecalactone, and other C18 lactones.

[0127] [Table 3] [Industrial applicability]

[0128] The present invention provides novel fatty acid esters and methods for producing the same. The fatty acid esters of the present invention can be used in various applications, such as lubricants.

Claims

1. A fatty acid ester having a lactone content of 3% by mass or less with 18 carbon atoms and an acid value of 1 mgKOH / g or less.

2. A step (A) of esterifying an alcohol with a composition containing a lactone having 18 carbon atoms and a fatty acid, A method for producing fatty acid esters having a lactone content of 3% by mass or less, comprising step (B) of treating the reaction mixture from step (A) under reduced pressure at 200 to 250°C and 0.1 to 500 Torr.

3. The manufacturing method according to claim 2, wherein the acid value of the reaction mixture used in step (B) is 3 mg KOH / g or less.

4. The fatty acid ester according to claim 1, wherein the fatty acid constituting the fatty acid ester includes a fatty acid having 14 to 20 carbon atoms.

5. The method for producing a fatty acid according to claim 2, wherein the fatty acid comprises a fatty acid having 14 to 20 carbon atoms.

6. The fatty acid ester according to claim 1, wherein the fatty acid constituting the fatty acid ester includes a branched fatty acid having 18 carbon atoms.

7. The method for producing a product according to claim 2, wherein the fatty acid comprises a branched fatty acid having 18 carbon atoms.

8. The fatty acid ester according to claim 1, wherein the fatty acid constituting the fatty acid ester contains isostearic acid.

9. The method for producing a fatty acid according to claim 2, wherein the fatty acid is isostearic acid.

10. The fatty acid ester according to claim 1, wherein the content of fatty acids having 16 to 18 carbon atoms in the total fatty acids constituting the fatty acid ester is 80% by mass or more.

11. The manufacturing method according to claim 2, wherein the content of fatty acids having 16 to 18 carbon atoms in the total fatty acids contained in the fatty acid is 80% by mass or more.

12. The manufacturing method according to claim 2, wherein the content of a lactone having 18 carbon atoms in the fatty acid is more than 3% by mass and 10% by mass or less.

13. The method for producing alcohol according to claim 2, wherein the alcohol comprises an alcohol having 20 or fewer carbon atoms or a dihydric or higher alcohol.

14. The manufacturing method according to claim 2, wherein step (B) comprises step (B-1) of treating the reaction mixture of step (A) at 200 to 250°C and under reduced pressure at 10 to 50 Torr, and step (B-2) of treating the fatty acid ester obtained in step (B-1) at the temperature of step (B-1) and under reduced pressure at 0.1 to 10 Torr.

15. Furthermore, the manufacturing method according to claim 2, comprising the step (C) of transesterifying the fatty acid ester with an alcohol or polyhydric alcohol having 21 or more carbon atoms.

16. A method for improving the heat resistance and / or viscosity index of a fatty acid ester, comprising the step of reducing the lactone content in the fatty acid ester.

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