Metalworking oil, metalworking fluid, metal corrosion inhibition method, and metalworking method

Abstract

To provide a metalworking oil solution that satisfactorily suppresses metal corrosion.SOLUTION: A metalworking oil solution contains at least one kind of monocarboxylic acid having 1 to 9 carbon atoms and / or a salt thereof and a base oil, and does not substantially contain monocarboxylic acids having 10 or more carbon atoms (in which a monocarboxylic acid having an ester bond is excluded) and / or a salt thereof.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a metalworking oil, a metalworking fluid, a method for inhibiting corrosion of metals, and a metalworking method, and more particularly to a metalworking oil, a metalworking fluid, a method for inhibiting corrosion of metals, particularly ferrous metals, and a metalworking method. [Background technology]

[0002] Water-soluble metalworking fluids are used in metalworking fields such as cutting and grinding. Water-soluble metalworking fluids are generally formulated with base oil, surfactant, antioxidant, water, and other ingredients depending on the purpose, and are often diluted with water, for example, as in coolant fluids. This presents a problem of susceptibility to corrosion of the workpiece.

[0003] Metalworking fluids have traditionally contained corrosion inhibitors to prevent corrosion of workpieces. These inhibitors have the effect of preventing the metal in the workpiece from dissolving as ions into the water contained in the metalworking fluid.

[0004] Non-Patent Document 1 discloses an adsorption-type corrosion inhibitor containing an alkylamine. The unshared electron pair of the alkylamine is shared with the metal atom, causing the corrosion inhibitor molecules to adsorb to the metal. This forms a film on the metal surface, preventing the elution of metal ions into the metalworking fluid. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Kunitsugu Aramaki, Action of Corrosion Inhibitors (Part 1), Vol. 56, No. 6, Materials and Environment, June 15, 2007, pp. 243-251 Summary of the Invention [Problem to be solved by the invention]

[0006] When the corrosion inhibitor of Non-Patent Document 1 is used in a metalworking fluid for iron-based metals, the corrosion inhibitor molecules are not strongly adsorbed to the iron, and the corrosion inhibitor molecules are desorbed from the iron during use of the metalworking fluid, causing the film to break down, resulting in a problem of insufficient corrosion inhibition effect.

[0007] The present invention has been made in view of the above-mentioned current state of the prior art, and its main object is to provide a metalworking fluid that effectively inhibits metal corrosion. [Means for solving the problem]

[0008] The present inventors have conducted extensive research to solve the above problems. As a result, they have found that a metalworking oil containing a specific monocarboxylic acid can suppress the elution of metals into the metalworking oil or a diluted solution of the metalworking oil. The present invention was completed based on this finding.

[0009] That is, a metalworking oil according to one embodiment of the present invention contains a base oil and at least one monocarboxylic acid having 1 to 9 carbon atoms and / or a salt thereof, and is substantially free of a monocarboxylic acid having 10 or more carbon atoms (excluding monocarboxylic acids having an ester bond) and / or a salt thereof.

[0010] The above-mentioned metalworking oil may contain a monocarboxylic acid having an ester bond.

[0011] In the metalworking oil agent, the monocarboxylic acid having an ester bond may have 50 or more carbon atoms.

[0012] In the metalworking oil agent described above, the monocarboxylic acid having 1 to 9 carbon atoms may include octanoic acid or nonanoic acid.

[0013] In the metalworking oil agent described above, the monocarboxylic acid having 1 to 9 carbon atoms may be linear.

[0014] A metalworking fluid according to one aspect of the present invention is prepared by diluting any of the metalworking oils described above with water.

[0015] A method for inhibiting corrosion of a metal according to one aspect of the present invention comprises supplying any of the metalworking oils or metalworking fluids described above to a surface of a metal.

[0016] A metalworking method according to one aspect of the present invention involves working a metal using any of the metalworking oils or metalworking fluids described above. [Effects of the Invention]

[0017] According to the present disclosure, it is possible to provide a metalworking oil agent that effectively inhibits metal corrosion. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 shows the structural formula of a tetramer of (9Z,12R)-12-hydroxyoctadec-9-enoic acid. [Figure 2] 1 is a graph showing the amount of iron eluted when each monocarboxylic acid is blended. [Figure 3] 1 is a graph showing the amount of iron elution in Example 3 and Modifications 1 and 2. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described in detail.

[0020] (metalworking oil) The metalworking oil of the present invention contains at least one monocarboxylic acid having 1 to 9 carbon atoms and / or a salt thereof, and a base oil, and is substantially free of monocarboxylic acids having 10 or more carbon atoms (excluding monocarboxylic acids having an ester bond) and / or salts thereof. The composition of the metalworking oil will be specifically described below.

[0021] The metalworking oil of the embodiment contains a monocarboxylic acid having 1 to 9 carbon atoms and / or a salt thereof. In this specification, "monocarboxylic acid" refers to a compound having one carboxyl group in the molecule. By containing a monocarboxylic acid having a relatively small number of carbon atoms, such as 1 to 9 carbon atoms, the elution of metals (metal ions) into the metalworking oil or a diluted solution of the metalworking oil can be effectively suppressed, resulting in excellent metal corrosion inhibition properties and improved stability of the metalworking oil or a diluted solution of the metalworking oil.

[0022] The monocarboxylic acid having 1 to 9 carbon atoms may be either a saturated monocarboxylic acid or an unsaturated monocarboxylic acid, and is preferably a saturated monocarboxylic acid. The monocarboxylic acid having 1 to 9 carbon atoms preferably has a chain structure. When the monocarboxylic acid having 1 to 9 carbon atoms has a chain structure, it may be either a linear or branched chain structure, and is preferably a linear chain structure. The monocarboxylic acid having 1 to 9 carbon atoms preferably has a linear or branched alkyl group, and preferably has a linear alkyl group. From the viewpoint of improving corrosion inhibition properties, the monocarboxylic acid preferably has 8 to 9 carbon atoms, and more preferably has 9 carbon atoms.

[0023] Specific examples of monocarboxylic acids having 1 to 9 carbon atoms include nonanoic acid, octanoic acid, heptanoic acid, and hexanoic acid. Among these, from the viewpoint of improving corrosion inhibition, nonanoic acid and octanoic acid are preferred, and nonanoic acid is more preferred. Examples of salts of monocarboxylic acids include alkali metal salts selected from sodium and potassium. The monocarboxylic acids having 1 to 9 carbon atoms may be used alone or in combination of two or more.

[0024] The content of the monocarboxylic acid having 1 to 9 carbon atoms and / or its salt in the metalworking oil of the embodiment is not limited, but is preferably 1% by mass or more and 4% by mass or less. When two or more types are used in combination, the content refers to the total amount. Within the above range, metal elution can be more effectively suppressed, corrosion inhibition can be excellent, and the stability of the metalworking oil can be improved. The content of the monocarboxylic acid having 1 to 9 carbon atoms and / or its salt is more preferably 1.5% by mass or more, even more preferably 2% by mass or more, and more preferably 3.5% by mass or less, even more preferably 3% by mass or less.

[0025] The metal working oil of the embodiment contains a base oil. The base oil may be a natural product or a synthetic product. Examples of the base oil include mineral oil and vegetable oil. Among them, mineral oil is preferred, and paraffinic mineral oil is more preferred. The base oil may be used alone or in combination of two or more types.

[0026] The content of base oil in a metalworking oil can be set appropriately depending on the type of base oil, the types and content ratios of other blended ingredients, etc. For example, the content of base oil in a metalworking oil according to an embodiment is preferably 5% by mass or more and 50% by mass or less. When two or more types are used in combination, the content refers to the total amount. Within the above range, metal elution can be more effectively suppressed, corrosion inhibition can be excellent, and the stability of the metalworking oil can be improved. The content of base oil is more preferably 7% by mass or more, and more preferably 30% by mass or less, and even more preferably 20% by mass or less.

[0027] The ratio of the content of base oil to the monocarboxylic acid and / or salt thereof having 1 to 9 carbon atoms is preferably 2.0 to 50 in mass ratio (base oil / monocarboxylic acid and / or salt thereof having 1 to 9 carbon atoms).With a content within this range, metal elution is more effectively suppressed, corrosion inhibition is excellent, and the stability of the metalworking oil can be improved.The mass ratio is more preferably 2.5 or more, and more preferably 20 or less, and even more preferably 7.5 or less.

[0028] The metalworking oil of this embodiment is substantially free of monocarboxylic acids having 10 or more carbon atoms and / or salts thereof, except for monocarboxylic acids having an ester bond. Monocarboxylic acids having a relatively large number of carbon atoms, such as monocarboxylic acids having 10 or more carbon atoms, generally have the effect of enhancing the stability of metalworking oils or their diluted solutions, and are therefore used as stabilizers in many metalworking oils. On the other hand, the metalworking oil of this embodiment contains a monocarboxylic acid having 1 to 9 carbon atoms and / or a salt thereof, and can improve the stability of metalworking oils or their diluted solutions and effectively suppress metal elution, even without using a monocarboxylic acid having 10 or more carbon atoms (excluding monocarboxylic acids having an ester bond) and / or a salt thereof.

[0029] As used herein, the term "monocarboxylic acid having an ester bond" refers to a compound having one carboxyl group and at least one ester bond in the molecule.

[0030] In this specification, "substantially free" means that monocarboxylic acids having 10 or more carbon atoms (excluding monocarboxylic acids having an ester bond) and / or salts thereof are not actively added to the metalworking oil of the embodiment, and does not mean that monocarboxylic acids having 10 or more carbon atoms (excluding monocarboxylic acids having an ester bond) and / or salts thereof are not contained at all. Preferably, this means that the content of monocarboxylic acids having 10 or more carbon atoms (excluding monocarboxylic acids having an ester bond) and / or salts thereof in the metalworking oil is 0.1 mass% or less.

[0031] The metalworking oil of the embodiment preferably contains a monocarboxylic acid having an ester bond. By using a monocarboxylic acid having an ester bond in combination with a monocarboxylic acid having 1 to 9 carbon atoms and / or a salt thereof, it is possible to effectively suppress metal elution and further improve the stability of the metalworking oil or its diluted solution. The monocarboxylic acid having an ester bond may be used alone or in combination of two or more.

[0032] From the viewpoints of improving stability and enhancing synergistic effects with monocarboxylic acids having 1 to 9 carbon atoms and / or salts thereof, the monocarboxylic acid having an ester bond preferably has 50 to 90 carbon atoms, more preferably 70 to 90 carbon atoms, and even more preferably 72 carbon atoms. The monocarboxylic acid having an ester bond is preferably a polymer containing unsaturated fatty acid monomers as polymerization units. The monomers may be used alone or in combination of two or more. A preferred example of such a monocarboxylic acid having an ester bond is a polymer obtained by polymerizing a monomer of (9Z,12R)-12-hydroxyoctadec-9-enoic acid, and in particular, a tetramer of (9Z,12R)-12-hydroxyoctadec-9-enoic acid (72 carbon atoms). Figure 1 shows the structural formula of the tetramer of (9Z,12R)-12-hydroxyoctadec-9-enoic acid.

[0033] The content of the monocarboxylic acid having an ester bond in the metalworking oil of the embodiment is not limited, but is preferably 5% by mass or more and 15% by mass or less. When two or more types are used in combination, the content refers to the total amount. Within the above range, metal elution can be more effectively suppressed, corrosion inhibition can be excellent, and the stability of the metalworking oil or its diluted solution can be improved. The content of the monocarboxylic acid having an ester bond is more preferably 8% by mass or more, more preferably 12% by mass or less, and even more preferably 10% by mass or less. The content of the monocarboxylic acid having an ester bond is most preferably 9% by mass.

[0034] The ratio of the content of monocarboxylic acid having an ester bond to monocarboxylic acid having 1 to 9 carbon atoms and / or its salt is preferably 2.5 to 7.5 by mass ratio (monocarboxylic acid having an ester bond / monocarboxylic acid having 1 to 9 carbon atoms and / or its salt). When a monocarboxylic acid having 1 to 9 carbon atoms and / or its salt is used in combination with a monocarboxylic acid having an ester bond within the above ratio range, a synergistic effect is enhanced, metal elution is more effectively suppressed, and the stability of the metalworking oil can be improved. The mass ratio is more preferably 3.0 or more, even more preferably 4.0 or more, and more preferably 7.0 or less, even more preferably 6.0 or less.

[0035] The metalworking oil of the embodiment preferably contains water. The water used may be tap water, industrial water, ion-exchanged water, distilled water, or the like, and may be hard or soft. The water content in the metalworking oil can be appropriately set depending on the type and content of other ingredients. For example, the water content in the metalworking oil of the embodiment is preferably 10% by mass or more and 60% by mass or less, and more preferably 30% by mass or more and 60% by mass or less. Within the above range, excellent corrosion inhibition properties, increased stability of the metalworking oil, and easy preparation of the metalworking oil can be achieved. When the metalworking oil of the embodiment contains water, it is preferable that an emulsifier be also contained. The emulsifiers described below can be suitably used. Note that the water contained in the metalworking oil refers to the water as a constituent component of the metalworking oil as a stock solution, and is different from the water as a diluent described below.

[0036] In addition to the above components, the metalworking oil may contain various additives, such as emulsifiers, rust inhibitors, lubricants, preservatives, and antifoaming agents, as needed, provided that the effects of the present invention are not impaired.

[0037] Examples of emulsifiers include surfactants such as nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants, as well as organic amines such as alkanolamines. These emulsifiers may be used alone or in combination of two or more. The content of the emulsifier in the metalworking oil may be, for example, 0.01% by mass or more and 20% by mass or less. Within the above range, the emulsion stability of the metalworking oil can be improved, and corrosion inhibition performance can be effectively exhibited. As the emulsifier, from the viewpoint of improving the emulsion stability of the monocarboxylic acid having 1 to 9 carbon atoms and / or its salt, nonionic surfactants, alkanolamines, and combinations thereof are preferred, and polyoxyalkylene ethers, N-methylethanolamine, triisopropanolamine, triethanolamine, and combinations thereof are more preferred.

[0038] Examples of rust inhibitors include dibasic acids, benzotriazoles, and organic amines. Rust inhibitors may be used singly or in combination of two or more. The content of the rust inhibitor in the metalworking oil may be, for example, 0.001% by mass or more and 6% by mass or less. Within the above range, the rust prevention properties of metals can be improved, and corrosion inhibition performance can be effectively exhibited. As the rust inhibitor, from the viewpoint of rust prevention, dibasic acids, benzotriazoles, and combinations thereof are preferred, and dodecanedioic acid, dimer acids, benzotriazoles, and combinations thereof are more preferred.

[0039] Examples of preservatives include aliphatic amines, triazine compounds, thiazoline compounds, and phenolic compounds. These preservatives may be used singly or in combination of two or more. The content of the preservative in the metalworking oil may be, for example, 0.01% by mass or more and 10% by mass or less. Within the above range, decay of the metalworking oil can be effectively inhibited, and corrosion-inhibiting performance can be effectively exhibited. As the preservative, from the viewpoint of corrosion inhibition, aliphatic amines, triazine compounds and combinations thereof are preferred, and dicyclohexylamine, hexahydro-1,3,5-tris(2-hydroxyethyl)-1,3,5-triazine and combinations thereof are more preferred.

[0040] Examples of antifoaming agents include silicone-based antifoaming agents such as polyorganosiloxanes having a molecular weight of 100 to 1,000. Antifoaming agents may be used singly or in combination of two or more. The content of the antifoaming agent in the metalworking oil may be, for example, 0.001% by mass or more and 1% by mass or less. Within the above range, the antifoaming properties of the metalworking oil can be improved, and corrosion inhibition performance can be effectively exhibited.

[0041] The pH of the metalworking oil according to the present embodiment is preferably 8.5 to 11.0, more preferably 9.5 to 10.7, and even more preferably 9.7 to 10.5. Within the above range, the metalworking oil can be effectively prevented from decaying and exhibits corrosion-inhibiting performance.

[0042] The metalworking oil of the embodiment can be obtained by mixing and stirring the above-mentioned components. The metalworking oil of the embodiment is water-soluble and can be used as is for metalworking.

[0043] (metal processing fluid) The metalworking fluid of the embodiment is obtained by diluting the metalworking oil of the above embodiment as a stock solution with water. The metalworking fluid (diluted solution) can be used as a coolant for metal processing. The water used may be tap water, industrial water, ion-exchanged water, distilled water, or the like, and the water may be hard water or soft water.

[0044] When diluting a metalworking oil with water, the dilution ratio can be adjusted as appropriate depending on the composition of the metalworking oil and the performance required during metalworking. The dilution ratio is not limited, but is usually preferably 1.5 to 100 times before use. From the viewpoint of further enhancing the effects of the present invention and improving processing characteristics, the dilution ratio is more preferably 5 times or more, even more preferably 10 times or more, and more preferably 50 times or less, and even more preferably 30 times or less. When using a diluted metalworking oil, it is preferable that the undiluted metalworking oil solution contains an emulsifier. The emulsifiers described above can be suitably used.

[0045] The metalworking oil (undiluted solution) and metalworking fluid (diluted solution) of the embodiments have excellent corrosion inhibition properties and processability, and can therefore be suitably used in metalworking, such as cutting, grinding, polishing, and cutting of metals. Examples of metals to be processed include iron-based metals and their alloys, and non-ferrous metals such as aluminum, magnesium, and copper and their alloys, with iron-based metals and their alloys being preferred. In particular, when the metalworking oil and metalworking fluid of the embodiments are applied to iron-based metals and their alloys, which have low corrosion inhibition effects with conventional corrosion inhibitors, a good metal elution inhibition effect is exhibited.

[0046] (Metal corrosion inhibition method) In the metal corrosion suppression method of the embodiment, a metalworking oil (undiluted solution) or a metalworking fluid (diluted solution) of the embodiment is supplied to a metal surface. In the metal corrosion suppression method of the embodiment, the metalworking oil or metalworking fluid described above is used, and thus metal elution can be effectively suppressed. Examples of the metal to be supplied include the metals described above, with iron-based metals and their alloys being preferred. Supplying to a metal surface may refer to supplying to either a portion or the entire metal surface, with supplying to the entire metal surface being preferred. The method for supplying the metalworking oil or metalworking fluid to a metal surface is not particularly limited, and may include, for example, spraying or applying the metalworking oil or metalworking fluid to the metal surface. Examples of methods for applying the metalworking oil or metalworking fluid to a metal surface include immersion coating, shower coating, spray coating, and jet coating.

[0047] (Metal processing method) In the metalworking method of the embodiment, a metal material is processed using the metalworking oil (undiluted solution) or metalworking fluid (diluted solution) of the embodiment. The metalworking method can be suitably used for various metalworking processes, such as cutting, grinding, polishing, and cutting. When the metalworking oil or metalworking fluid is supplied to the processing point, for example, in liquid or mist form, it can exhibit the effect of suppressing metal elution into the metalworking oil or metalworking fluid. The metalworking oil or metalworking fluid can be supplied to the processing point using, for example, the techniques described above. Examples of the types of metals to be processed include the metals described above, with iron-based metals and their alloys being preferred. In the metalworking method of the embodiment, the metalworking oil described above is used, thereby suppressing metal elution and enabling good processing. [Example]

[0048] The present invention will be explained in more detail below based on examples and comparative examples, but it is not intended that the present invention be limited to these examples.

[0049] 1. Preparation of Metalworking Fluid [Example 1] The following components shown in Table 1 were weighed out to obtain the compositions (in mass %) shown in the table: (A) monocarboxylic acid (n-octanoic acid having 8 carbon atoms), (B) base oil, (C) monocarboxylic acid having an ester bond, (D) water, (E) emulsifier, (F) rust inhibitor, (G) preservative, and (H) antifoaming agent. These components were mixed in a mixer until uniform, yielding the metalworking fluid of Example 1. The pH of the resulting metalworking fluid was 10.3 (20°C). pH was measured using a pH meter ("F-52" manufactured by HORIBA, Ltd.). The (C) monocarboxylic acid having an ester bond in Table 1 is the tetramer of the aforementioned (9Z,12R)-12-hydroxyoctadec-9-enoic acid (see Figure 1), which has 72 carbon atoms. Note that the molar number of the (A) monocarboxylic acid used in each of the examples and comparative examples in Table 1 is the same.

[0050] [Example 2] The metalworking oil of Example 2 was prepared in the same manner as in Example 1, except that n-nonanoic acid having 9 carbon atoms was blended as the (A) monocarboxylic acid, and the blending ratio of each component was as shown in Table 1. The pH of the obtained metalworking oil was 10.3 (20°C).

[0051] [Comparative Example 1] A metalworking oil of Comparative Example 1 was prepared in the same manner as in Example 1, except that n-dodecanoic acid having 12 carbon atoms was blended as the (A) monocarboxylic acid and the blending ratio of each component was as shown in Table 1. The pH of the obtained metalworking oil was 10.3 (20°C).

[0052] Comparative Example 2 A metalworking oil of Comparative Example 2 was prepared in the same manner as in Example 1, except that n-octadecanoic acid having 18 carbon atoms was blended as the (A) monocarboxylic acid and the blending ratio of each component was as shown in Table 1. The pH of the obtained metalworking oil was 10.3 (20°C).

[0053] Comparative Example 3 A metalworking oil of Comparative Example 3 was prepared in the same manner as in Example 1, except that (9Z)-octadecenoic acid having 18 carbon atoms was blended as the (A) monocarboxylic acid, and the blending ratio of each component was as shown in Table 1. The pH of the obtained metalworking oil was 10.3 (20°C).

[0054] Comparative Example 4 A metalworking fluid of Comparative Example 4 was prepared in the same manner as in Example 1, except that (9Z,12R)-12-hydroxyoctadec-9-enoic acid having 18 carbon atoms was blended as the (A) monocarboxylic acid, and the blending ratios of the respective components were as shown in Table 1. The pH of the obtained metalworking fluid was 10.3 (20°C).

[0055] [Table 1]

[0056] 2.Performance evaluation [Corrosion inhibition] The test fluids used were prepared by diluting each metalworking fluid (stock solution) with water to 10%. 10 g of cast iron chips (FC250) were added to 40 g of each diluted solution of the above Examples and Comparative Examples, and the mixture was allowed to stand at 50°C for one week. After standing, the iron concentration in the test solution was measured using an atomic absorption spectrophotometer, and the iron concentration (mg / L) in the test solution was recorded as the amount of iron elution (mg / L). Each test solution was vigorously stirred when adding the cast iron chips and before measurement with the atomic absorption spectrophotometer, and was allowed to stand for the rest of the time. The amount of elution was measured using an atomic absorption spectrophotometer (AA240FS, manufactured by Agilent Technologies) using the atomic absorption method. Corrosion inhibition was judged to be good when the amount of iron elution was less than 30 mg / L. The results for Examples 1 and 2 and Comparative Examples 1 to 4 are shown in Table 2 below. Figure 2 was created based on Table 2. Figure 2 is a graph showing the amount of iron eluted when each monocarboxylic acid was blended. The vertical axis of Figure 2 represents the amount of iron eluted (unit: mg / L). Each bar graph in Figure 2 represents the amount of iron eluted in Examples 1 and 2 and Comparative Examples 1 to 4, from left to right.

[0057] [Table 2]

[0058] As is clear from Table 2 and FIG. 2, the test fluids of Examples 1 and 2, which contained a monocarboxylic acid having 1 to 9 carbon atoms but not a monocarboxylic acid having 10 or more carbon atoms (excluding monocarboxylic acids having an ester bond) and / or a salt thereof, exhibited reduced iron elution into diluted solutions of the metalworking oil, demonstrating good corrosion inhibition. In contrast, the test fluids of Comparative Examples 1 to 4, which contained a monocarboxylic acid having 10 or more carbon atoms, did not exhibit a sufficient effect of inhibiting iron elution and showed poor corrosion inhibition. The monocarboxylic acid having 1 to 9 carbon atoms is preferably n-octanoic acid or n-nonanoic acid, and more preferably n-nonanoic acid. Each metalworking oil (stock solution) separated without the addition of the monocarboxylic acid (A), but a stable stock solution was obtained when the monocarboxylic acid (A) was added, confirming that the addition of the monocarboxylic acid (A) improves stability.

[0059] Next, the corrosion inhibition effect was investigated when the content of monocarboxylic acid having an ester bond was changed. Modifications 1 and 2 are examples for reference.

[0060] [Example 3] A metalworking oil of Example 3 was prepared in the same manner as in Example 1, except that (E) triethanolamine was used instead of triisopropanolamine as the emulsifier, and the blending ratios of each component were as shown in Table 3. The pH of the obtained metalworking oil was 10.3 (20°C). [Variations 1-2] Metalworking oils of Modifications 1 and 2 were prepared in the same manner as in Example 3, except that the blending ratio of (C) monocarboxylic acid having an ester bond was as shown in Table 3. The pH of the obtained metalworking oils was 10.4 (20°C) for Modification 1 and 10.1 (20°C) for Modification 2.

[0061] The amount of eluted iron (mg / L) was measured for Example 3 and Modifications 1 and 2 using the same method as in the above-mentioned Examples and Comparative Examples. The measurement results are shown in Table 3 below. Figure 3 was created based on Table 3. Figure 3 is a graph showing the amount of eluted iron in Example 3 and Modifications 1 and 2. The vertical axis of Figure 3 represents the amount of eluted iron (unit: mg / L). Each bar graph in Figure 3 represents the amount of eluted iron in Example 3 and Modifications 1 and 2, respectively, from left to right.

[0062] [Table 3]

[0063] 3, the amount of iron eluted into the diluted solution of the metalworking oil in Example 3 was lower than in Modifications 1 and 2, confirming improved corrosion inhibition. The content of monocarboxylic acid having an ester bond in the metalworking oil is more preferably 8% by mass or more and 12% by mass or less, even more preferably 8% by mass or more and 10% by mass or less, and most preferably 9% by mass.

[0064] From the above, it was confirmed that the metalworking oil agent of the present disclosure suppresses metal elution and effectively suppresses metal corrosion.

[0065] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The technical features described in each embodiment can be combined with each other, and the scope of the present invention is intended to include all modifications within the scope of the claims and the scope equivalent to the claims.

Claims

1. The oil composition contains 1% by mass or more and 4% by mass or less of at least one monocarboxylic acid having 1 to 9 carbon atoms and / or a salt thereof, 5% by mass or more and 50% by mass or less of a base oil, and 8% by mass or more and 12% by mass or less of a monocarboxylic acid having an ester bond and having 50 or more carbon atoms, and is substantially free of a monocarboxylic acid having 10 or more carbon atoms (excluding monocarboxylic acids having an ester bond) and / or a salt thereof. Metalworking oil.

2. The number of carbon atoms of the monocarboxylic acid having an ester bond is 72. The metalworking oil according to claim 1.

3. The ratio of the content of the monocarboxylic acid having an ester bond to the monocarboxylic acid having 1 to 9 carbon atoms and / or a salt thereof is 2.5 to 7.5 by mass. The metalworking oil according to claim 1 or 2.

4. The monocarboxylic acid having 1 to 9 carbon atoms includes octanoic acid or nonanoic acid. The metalworking oil according to any one of claims 1 to 3.

5. The monocarboxylic acid having 1 to 9 carbon atoms is linear. The metalworking oil according to any one of claims 1 to 3.

6. The metalworking oil according to any one of claims 1 to 3 diluted with water. Metalworking fluid.

7. The metalworking oil according to any one of claims 1 to 3 is supplied to a metal surface. Methods for inhibiting corrosion of metals.

8. The metalworking fluid according to claim 6 is supplied to a metal surface. Methods for inhibiting corrosion of metals.

9. Metal is processed using the metalworking oil according to any one of claims 1 to 3. Metal processing methods.

10. Metal is processed using the metalworking fluid according to claim 6. Metal processing methods.

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