Fatty acid composition

Abstract

To provide a fatty acid composition containing ricinoleic acid in a high content, reduced in thickening accompanied by heating, and improved in oxidation stability and dispersion stability in a solvent.SOLUTION: The fatty acid composition contains (A) a fatty acid having 18 carbon atoms, a double bond at the 9-position, and a hydroxyl group at the 12-position, and (B) a fatty acid having 18 carbon atoms, a double bond at the 9-position, and a carbonyl group at the 12-position, wherein the content ratio of the component (A) and the component (B) [(A): (B)] is 99.9:0.1 to 90:10 by mass ratio.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a fatty acid composition having a high content of ricinoleic acid. [Background technology]

[0002] Conventionally, fatty acid compositions containing ricinoleic acid have been used as dispersants for metal powders for conductive pastes, raw materials for rubber compositions for tires, deinking agents for waste paper, etc. Furthermore, it is generally known that ricinoleic acid, having a hydroxyl group in its molecule, undergoes dehydration condensation at high temperatures to form ricinoleic acid condensates. For example, Patent Document 1 describes that a rubber composition for tires containing ricinoleic acid and one or more acids selected from the group consisting of linoleic acid, oleic acid, palmitic acid, and dihydroxystearic acid has excellent reinforcement properties, fuel economy, ozone resistance, discoloration resistance, and appearance. The composition is produced by kneading ricinoleic acid and other raw materials using a rubber kneading device such as an open roll or a Banbury mixer, and vulcanizing the mixture at a temperature such as 160°C. Patent Document 2 describes a silver particle dispersion liquid that is composed of silver powder and a solvent, with ricinoleic acid attached to the surface of the silver powder, and describes that the silver particle dispersion liquid can be used as a slurry for inkjet printing. Furthermore, Patent Document 3 describes a water-insoluble metalworking oil composition containing at least one carboxylic acid dehydration condensate selected from the group consisting of a dehydration condensate of ricinoleic acid and a dehydration condensate of ricinoleic acid and a fatty acid other than ricinoleic acid, and a base oil such as a mineral oil, as a water-insoluble metalworking oil composition with reduced use of sulfur-based compounds. Patent Document 3 also describes that when the dehydration condensation of ricinoleic acid progresses and the acid value of the carboxylic acid dehydration condensate falls below 5 mgKOH / g, the viscosity of the water-insoluble metalworking oil composition itself increases, which may result in processing defects.

[0003] That is, ricinoleic acid undergoes dehydration condensation at high temperatures, resulting in an increase in viscosity. Therefore, when a rubber composition is produced or a ricinoleic acid condensate is used as a lubricant, the viscosity increases as a result of the production of a high polymer of ricinoleic acid, which can affect the performance and productivity of the rubber composition, etc. Therefore, there is a need for a fatty acid composition containing ricinoleic acid that exhibits reduced thickening upon heating. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-232089 [Patent Document 2] Japanese Patent Application Publication No. 2018-80402 [Patent Document 3] International Publication No. 2017 / 171069 Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, an object of the present invention is to provide a fatty acid composition that contains a high content of ricinoleic acid, yet exhibits reduced thickening upon heating, and has improved oxidation stability and dispersion stability in solvents. [Means for solving the problem]

[0006] As a result of intensive research conducted by the present inventors to solve the above-mentioned problems, they found that by preparing a fatty acid composition containing (A) a fatty acid having 18 carbon atoms, a double bond at position 9, and a hydroxyl group at position 12, and (B) a fatty acid having 18 carbon atoms, a double bond at position 9, and a carbonyl group at position 12, in a mass ratio [(A):(B)] of 99.9:0.1 to 90:10, thickening due to heating is reduced and oxidation stability and dispersion stability in a solvent are improved. Further research led to the completion of the present invention.

[0007] That is, the present invention relates to the following. [1] A fatty acid composition comprising (A) a fatty acid having 18 carbon atoms, a double bond at position 9, and a hydroxyl group at position 12, and (B) a fatty acid having 18 carbon atoms, a double bond at position 9, and a carbonyl group at position 12, wherein the content ratio of component (A) to component (B) [(A):(B)] is 99.9:0.1 to 90:10 by mass. [2] The fatty acid composition according to [1], containing component (A) and component (B) in a total amount of 60% by mass or more based on the total amount of the fatty acid composition. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a fatty acid composition that contains a high content of ricinoleic acid, in which thickening due to heating is reduced and the oxidation stability and dispersion stability in solvents are improved. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Fatty acid composition containing ricinoleic acid] The present invention provides a fatty acid composition containing ricinoleic acid (hereinafter also referred to as "the composition of the present invention" in this specification). The composition of the present invention contains (A) a fatty acid having 18 carbon atoms, a double bond at position 9, and a hydroxyl group at position 12, and (B) a fatty acid having 18 carbon atoms, a double bond at position 9, and a carbonyl group at position 12, in the following content ratio:

[0010] An example of a fatty acid having 18 carbon atoms, a double bond at position 9, and a hydroxyl group at position 12, which is contained as component (A) in the composition of the present invention, is (Z,R)-12-hydroxy-9-octadecenoic acid (ricinoleic acid). Furthermore, an example of a fatty acid having 18 carbon atoms, a double bond at position 9, and a carbonyl group at position 12, which is contained as component (B) in the composition of the present invention, is (Z)-12-oxo-9-octadecenoic acid (12-oxoleic acid).

[0011] The content ratio of component (A) to component (B) in the composition of the present invention [(A):(B)] is 99.9:0.1 to 90:10 in mass ratio. When the content ratio of component (A) to component (B) in the composition of the present invention is within the above range, thickening of the fatty acid composition containing ricinoleic acid due to heating is reduced and oxidation stability is improved. On the other hand, when the total content of components (A) and (B) is taken as 100, if the ratio of the content of component (B) to said total exceeds 10 by mass, the dispersion stability of the fatty acid composition containing ricinoleic acid decreases. From the viewpoints of reducing thickening due to heating and of oxidative stability and dispersion stability, the content ratio of component (A) to component (B) [(A):(B)] is preferably 99.9:0.1 to 92:8 by mass, more preferably 99.9:0.1 to 95:5, and even more preferably 99.9:0.1 to 97:3.

[0012] For the purposes of the present invention, the total content of component (A) and component (B) in the composition of the present invention is 60 mass % or more, preferably 70 mass % or more, and more preferably 75 mass % or more, based on the total amount of the composition of the present invention.

[0013] In addition to components (A) and (B), the composition of the present invention may contain, as component (C), a fatty acid having 16 to 20 carbon atoms. Examples of fatty acids that may be contained as component (C) include saturated fatty acids having 16 to 20 carbon atoms, such as hexadecanoic acid (palmitic acid), heptadecanoic acid (margaric acid), octadecanoic acid (stearic acid), and eicosanoic acid (arachidic acid); monounsaturated fatty acids, such as (Z)-9-hexadecenoic acid (palmitoleic acid), (E)-9-hexadecenoic acid (palmitoeladic acid), (Z)-9-octadecenoic acid (oleic acid), and (E)-11-octadecenoic acid (trans-vaccenic acid); and (9Z,12Z)-9,12-octadecenoic acid (trans-vaccenic acid). Examples of polyunsaturated fatty acids include cadienoic acid (linoleic acid), (9Z,12Z,15Z)-9,12,15-octadecanetrienoic acid (α-linolenic acid), (6Z,9Z,12Z)-6,9,12-octadecatrienoic acid (γ-linolenic acid), (8Z,11Z)-8,11-icosadienoic acid, (5Z,8Z,11Z)-5,8,11-icosatrienoic acid (mead acid), and (5Z,8Z,11Z,14Z)-5,8,11,14-icosatetraenoic acid (arachidonic acid), and fatty acids having 16 to 18 carbon atoms are preferred. From the viewpoints of oxidation stability and dispersion stability, the content of component (C) in the composition of the present invention is preferably 15% by mass or less, more preferably 12% by mass or less, and even more preferably 10% by mass or less, based on the total content of fatty acids in the composition of the present invention. Also, from the viewpoints of oxidation stability and dispersion stability, the content of component (C) in the composition of the present invention is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, based on the total content of fatty acids in the composition of the present invention. Furthermore, the ratio of the saturated fatty acids to the unsaturated fatty acids (saturated fatty acids:unsaturated fatty acids) in component (C) is preferably 1:1 to 1:10 by mass, more preferably 1:1 to 1:5, and even more preferably 1:1 to 1:3.

[0014] The composition of fatty acids contained in the composition of the present invention can be determined by gas chromatography-time of flight mass spectrometry (GC-TOFMS). For example, 10 mg of the composition of the present invention can be mixed with 0.2 mL of acetonitrile, 0.1 mL of pyridine, and 0.2 mL of N,O-bis(trimethylsilyl)trifluoroacetamide, heated on a hot plate at 120°C for 2 hours, cooled, and then toluene is added to prepare a sample, which can then be subjected to gas chromatography-time-of-flight mass spectrometry (GC-TOFMS). The analysis can be performed using a gas chromatograph-time-of-flight mass spectrometer such as the "JMS-T2000GC AccuTOF GC-Alpha" (JEOL Ltd.).

[0015] Furthermore, the composition of the present invention may contain an oil-soluble additive such as an oil-soluble antioxidant or a condensate of a fatty acid, within a range that does not impair the characteristics of the present invention. The content of the oil-soluble additive or the condensate of a fatty acid in the composition of the present invention is preferably 40% by mass or less, more preferably 30% by mass or less, based on the total amount of the composition of the present invention.

[0016] The content of each fatty acid in the composition of the present invention can be determined by liquid chromatography-mass spectrometry (LC-MS). For example, a sample can be prepared by adding methanol to 10 mg of the composition of the present invention to a concentration of 200 μg / mL, and then subjected to liquid chromatography-mass spectrometry (LC-MS). The analysis can be performed using a liquid chromatograph-mass spectrometer such as the Agilent 6430 (Agilent Technologies).

[0017] In the composition of the present invention, thickening due to heating is reduced, and oxidation stability and dispersion stability in a solvent are improved. From the viewpoint of dispersion stability and dissolution stability in a solvent, it is preferable that the viscosity increase rate upon heating of the composition of the present invention, i.e., the ratio of the viscosity after heat treatment to the viscosity at the start of heat treatment [(viscosity after heat treatment) / (viscosity at the start of heat treatment)], is 1.5 or less. In this specification, the "viscosity increase rate upon heating" refers to the ratio of the viscosity at the end of a heat treatment in which the composition of the present invention is heated at 100°C for 30 minutes while stirring at 60 rpm to the viscosity at the start of the treatment. Specifically, the viscosity increase rate can be determined by using a Brookfield viscometer, setting the measurement temperature to 100°C and the rotation speed to 60 rpm, and measuring the viscosity at the start and end of 30 minutes of stirring.

[0018] The composition of the present invention can be produced by producing component (A) and component (B) by a method known per se, or by using commercially available products as component (A) and component (B), mixing them so that the content ratio of component (A) and component (B) falls within the above-mentioned range, and adding and mixing other fatty acids, oil-soluble additives, etc., as necessary so that the contents fall within the above-mentioned ranges, to produce a homogeneous composition.

[0019] The component (A) can be produced by decomposing natural fats and oils to liberate fatty acids containing ricinoleic acid, followed by purification. Examples of natural fats and oils include animal fats and oils, vegetable fats and oils, and fish oil. However, vegetable fats and oils are preferred because they contain a large amount of ricinoleic acid as a fatty acid constituting the fats and oils, and castor oil is particularly preferred. Methods for liberating fatty acids from natural fats and oils include continuous high-pressure decomposition, catalytic decomposition, saponification decomposition, enzymatic decomposition, etc. Any of these methods may be used in producing the composition of the present invention, but the enzymatic decomposition method using lipase is preferably used because it can liberate fatty acids in a substrate-specific manner under mild reaction conditions. As a method for purifying ricinoleic acid, which is component (A), from a mixture of fatty acids released from natural fats and oils, general purification methods such as distillation and column chromatography can be used. Alternatively, it can be produced by reducing a commercially available product such as 12-Oxo-9(Z)-octadecenoic acid (product number: 13-1820, purity >98%, Larodan) using the Meerwein-Ponndorf-Valley reduction method using isopropyl alcohol and aluminum isopropoxide, or the hydride reduction method using sodium borohydride.

[0020] Component (B) in the composition of the present invention can be produced by decomposing natural fats and oils to liberate a fatty acid mixture, and then oxidizing the fatty acids having a hydroxyl group at the 12th position in the fatty acid mixture to fatty acids having a carbonyl group at the 12th position by, for example, Oppenauer oxidation, in which the mixture is heated and stirred with acetone and aluminum isopropoxide, or Jones oxidation, in which chromic anhydride is used, and then separating component (B). From the viewpoint of suppressing coloration and high molecular weight of fatty acids, Oppenauer oxidation is preferably employed.

[0021] Methods for separating component (B) from a mixture of fatty acids containing a fatty acid having a carbonyl group at the 12-position include the Emersol method, in which fractional crystallization is performed at low temperatures using methanol as a solvent, and the Henkel method, in which solid fatty acids are cooled to below their melting point for crystallization, followed by separation by centrifugation. [Example]

[0022] The present invention will be described in more detail below by showing specific examples of the present invention, but the present invention is not limited to these examples.

[0023] The fatty acid compositions of Examples 1 to 4 and Comparative Examples 1 and 2 were prepared using the following commercially available products as various fatty acids. The fatty acid compositions of the products used as various fatty acids are shown in Table 1. Each fatty acid composition of the Examples and Comparative Examples was obtained by mixing various fatty acids according to the composition shown in Table 2 until homogeneous. (i) component (A); (a-1): "Ricinoleic acid" (product code R7257, purity ≥ 95%, Merck) (a-2): "Ricinoleic Acid" (product code: R0027, purity >80.0%, Tokyo Chemical Industry Co., Ltd.) (ii) component (B); (b-1); “12-Oxo-9(Z)-octadecenoic acid” (Product No.: 13-1820, purity >98%, Larodan) (iii) component (C); (c-1) Palmitic acid; "NAA-160" (NOF Corporation) (c-2) Stearic acid; "NAA-180" (NOF Corporation) (c-3) Oleic acid; "EXTRA OLEIN 99" (NOF Corporation) (C-4) Linoleic acid; "Extra Linoleic 90" (NOF Corporation)

[0024] [Table 1]

[0025] [Table 2]

[0026] The fatty acid composition of each of the fatty acid compositions of Examples 1 to 4 and Comparative Examples 1 and 2 was analyzed as follows, and the thickening caused by heating, dispersion stability, and oxidation stability were evaluated. The analytical and evaluation results are summarized in Table 3.

[0027] (1) Analysis of fatty acid composition 0.2 mL of acetonitrile, 0.1 mL of pyridine, and 0.2 mL of N,O-bis(trimethylsilyl)trifluoroacetamide were added to 10 mg of each of the fatty acid compositions of Examples 1 to 4 and Comparative Examples 1 and 2, mixed, and heated on a hot plate at 120°C for 2 hours. After cooling, 2.0 mL of toluene was added to prepare analytical samples. The samples were applied to a gas chromatograph-time-of-flight mass spectrometer ("JMS-T2000GC AccuTOF GC-Alpha" (JEOL Ltd.)) and the fatty acid composition was analyzed. The content of each fatty acid in each fatty acid composition of Examples 1 to 4 and Comparative Examples 1 and 2 was determined by adding methanol to 10 mg of each fatty acid composition to prepare an analytical sample with a concentration of 200 μg / mL, and analyzing it using a liquid chromatograph-mass spectrometer (Agilent 6430 (Agilent Technologies)).

[0028] (2) Viscosity increase due to heating Using a Brookfield viscometer (VISCOMETER "LVDV-I Prime", Brookfield), the thermosel was set to 100°C, and each fatty acid composition from the Examples and Comparative Examples was heated to 100°C. The viscosity at the start of the heat treatment was determined from the measured value after 30 seconds of rotation at a spindle of LV-1 and a rotation speed of 60 rpm. Next, the viscosity was measured in the same manner after 30 minutes of rotation at 100°C and 60 rpm. The ratio of the viscosity after 30 minutes of heating to the viscosity at the start of the heat treatment [(viscosity after 30 minutes of heating) / (viscosity at the start of the heat treatment)] was calculated to determine the viscosity increase rate. A viscosity increase rate of 1.5 or less was evaluated as a reduction in viscosity increase due to heating.

[0029] (3) Evaluation of dispersion stability 10 g of each fatty acid composition of the Examples and Comparative Examples was added to 50 g of mineral oil (liquid paraffin (Fujifilm Wako Pure Chemical Industries, Ltd.)) and shaken for 30 seconds to obtain a dispersion. The transmittance of each dispersion was measured every minute using an ultraviolet-visible spectrophotometer ("UV-1900i", Shimadzu Corporation), and the time until the transmittance reached 80% or more was defined as the time until the uniform dispersion separated into layers. The longer the time until the uniform dispersion separated into layers, the better the dispersion stability, and the evaluation was performed according to the following evaluation criteria. <Evaluation criteria> The time required for stratification is 30 minutes or more. Time to stratification is 15 minutes or more but less than 30 minutes; Time until layer separation is 5 minutes or more but less than 15 minutes; △ Time to layer separation is less than 5 minutes; ×

[0030] (4) Evaluation of oxidation stability 5.0 g of each fatty acid composition of the Examples and Comparative Examples was placed in a test tube and stored at 50°C for one month. The Gardner color index of each fatty acid composition before and after storage was determined in accordance with Japanese Industrial Standards (JIS) K 0071-2:1998. The smaller the color change before and after storage at high temperature (50°C), the better the oxidation stability, and the storage stability was evaluated according to the following evaluation criteria. <Evaluation criteria> The change in Gardner color scale is less than 2; ◎ The Gardner color change is 2 or more but less than 4; The change in Gardner color scale is 4 or more but less than 6; △ The change in Gardner color scale is 6 or more; ×

[0031] [Table 3]

[0032] As shown in Table 3, in the compositions of Examples 1 to 4, in which the content ratio of component (A) to component (B) [(A):(B)] was in the range of 99.9:0.1 to 90:10 by mass, the viscosity increase rate upon heating was 1.5 or less, and the viscosity increase upon heating was sufficiently reduced, and the dispersion stability and oxidation stability were evaluated as good or very good. In particular, in the composition of Example 3, in which the content ratio of component (A) to component (B) [(A):(B)] was 99.5:0.5 by mass, the viscosity increase upon heating was sufficiently reduced, and the dispersion stability and oxidation stability were evaluated as very good.

[0033] On the other hand, the composition of Comparative Example 1, in which the content of component (A) was 90 mass% or more of the total amount of the fatty acid composition but did not contain component (B), had a high viscosity increase rate upon heating of 1.9, and was evaluated as having insufficient dispersion stability and poor oxidative stability. The composition of Comparative Example 2, in which the content ratio of components (A) to (B) [(A):(B)] was 89.6:10.4 by mass, had a viscosity increase rate upon heating of 1.6, and the thickening upon heating was not sufficiently reduced, and was evaluated as having poor dispersion stability and insufficient oxidative stability. [Industrial Applicability]

[0034] As described above in detail, the present invention can provide a fatty acid composition that contains a high content of (Z,R)-12-hydroxy-9-octadecenoic acid (ricinoleic acid), exhibits reduced thickening upon heating, and has improved oxidation stability and dispersion stability in solvents.

Claims

1. 1. A fatty acid composition comprising (A) a fatty acid having 18 carbon atoms, a double bond at position 9, and a hydroxyl group at position 12, and (B) a fatty acid having 18 carbon atoms, a double bond at position 9, and a carbonyl group at position 12, wherein the content ratio of component (A) to component (B) [(A):(B)] is 99.9:0.1 to 90:10 by mass.

2. 2. The fatty acid composition according to claim 1, wherein the total amount of component (A) and component (B) is 60% by mass or more based on the total amount of the fatty acid composition.

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