Metalworking fluid composition

Abstract

To provide a metalworking fluid composition that has a sufficiently high flash point and can extend the tool service life.SOLUTION: The present invention provides a metalworking fluid composition. The metalworking fluid composition includes: a lubricant base oil including a first ester, which is an ester derived from a saturated fatty acid and an alcohol, a second ester, which is an ester derived from an unsaturated fatty acid and an alcohol, and at least one selected from the group consisting of mineral oil and synthetic oil excluding esters; a thio phosphate; and an acid phosphate.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a metalworking oil composition. [Background technology]

[0002] In the field of metalworking, metalworking oils are used to lubricate the machining areas of workpieces. From the viewpoint of improving production efficiency, etc., metalworking oils with excellent cutting properties are being developed.

[0003] As a metal working oil, for example, a metal working oil containing a specific ester oil has been disclosed (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-272818 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, the performance requirements for metalworking fluids have been increasing, and conventional metalworking fluids have room for improvement in terms of tool life, flash point, etc. In particular, if a metalworking fluid has a sufficiently high flash point (e.g., 200°C or higher), tool life tends to be insufficient.

[0006] Therefore, a main object of the present invention is to provide a metalworking oil composition that has a sufficiently high flash point and is capable of extending tool life. [Means for solving the problem]

[0007] According to the investigations of the present inventors, it has been found that by combining a predetermined lubricating base oil, a thiophosphate ester, and an acidic phosphate ester, it is possible to achieve both a high level of flash point and a high level of tool life, and this has led to the completion of the present invention.

[0008] The present invention provides a metalworking oil composition. The metalworking oil composition contains a first ester, which is an ester of a saturated fatty acid and an alcohol; a second ester, which is an ester of an unsaturated fatty acid and an alcohol; a lubricating base oil containing at least one oil selected from the group consisting of mineral oils and synthetic oils other than esters; a thiophosphate ester; and an acidic phosphate ester. This metalworking oil composition has a sufficiently high flash point and can extend tool life.

[0009] The iodine value of the lubricating base oil is preferably 50 g I / 100 g or less. In this specification, the iodine value refers to the iodine value measured in accordance with JIS K 0070:1992 "Testing methods for acid value, saponification value, ester value, iodine value, hydroxyl value and unsaponifiable matter of chemical products." The iodine value is an index showing the degree of unsaturation derived from the second ester.

[0010] The total content of the first ester and the second ester is preferably 50 to 90 mass % based on the total amount of the lubricating base oil.

[0011] The mineral oil is preferably a Group III mineral oil of the API base oil classification.

[0012] The metalworking oil composition preferably has a kinematic viscosity at 40°C of 30 mm 2 In this specification, the 40°C kinematic viscosity and the 100°C kinematic viscosity refer to the kinematic viscosities measured in accordance with JIS K2283:2000.

[0013] The flash point of the metal working oil composition is preferably not less than 200° C. In this specification, the flash point means the flash point measured in accordance with JIS K2265-4:2007. [Effects of the Invention]

[0014] According to the present invention, there is provided a metalworking oil composition which has a sufficiently high flash point and is capable of extending tool life. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments.

[0016] In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In numerical ranges described in stages in this specification, the upper or lower limit of a numerical range in one stage may be replaced with the upper or lower limit of a numerical range in another stage. Furthermore, in numerical ranges described in this specification, the upper or lower limit of that numerical range may be replaced with a value shown in an example.

[0017] In this specification, unless otherwise specified, the materials exemplified below may be used alone or in combination of two or more within the range that meets the conditions. When the metal working oil composition contains multiple substances corresponding to each component, the content of each component in the metal working oil composition means the total amount of the multiple substances present in the metal working oil composition, unless otherwise specified.

[0018] In this specification, "skin sensitization" refers to a condition in which repeated contact with a substance causes the substance to act as an antigen, resulting in the production of antibodies in the body and an allergic reaction. This is a different concept from skin irritation, which is a condition in which a substance comes into contact with the skin and causes a direct toxic reaction on the skin, resulting in inflammation, etc.

[0019] [Metalworking oil composition] A metal working oil composition according to one embodiment contains a first ester which is an ester of a saturated fatty acid and an alcohol, a second ester which is an ester of an unsaturated fatty acid and an alcohol, a lubricating base oil containing a mineral oil, a thiophosphate ester, and an acidic phosphate ester.

[0020] <Lubricant base oil> (First ester: ester of saturated fatty acid and alcohol) The lubricating base oil contains a first ester. The saturated fatty acid constituting the first ester may be a monobasic acid or a polybasic acid.

[0021] When a monobasic acid is used as the saturated fatty acid, the number of carbon atoms therein is preferably 6 to 24, more preferably 8 to 18. Such a monobasic acid may be a linear monobasic acid or a branched monobasic acid. When the monobasic acid has 6 or more carbon atoms, the metal working oil composition can have a higher flash point, and when the monobasic acid has 24 or less carbon atoms, the metal working oil composition can have a lower viscosity.

[0022] When a polybasic acid is used as the saturated fatty acid, the polybasic acid is preferably a dibasic acid having a carbon number of 2 to 16. Such a dibasic acid may be a linear dibasic acid or a branched dibasic acid.

[0023] The alcohol constituting the first ester may be a monohydric alcohol or a polyhydric alcohol.

[0024] The monohydric alcohol may be a linear monohydric alcohol or a branched monohydric alcohol. The number of carbon atoms in the monohydric alcohol is preferably 1 to 24, more preferably 3 to 16. When the carbon number in the monohydric alcohol is 1 or more, the metal working oil composition can have a higher flash point, and when the carbon number in the monohydric alcohol is 24 or less, the viscosity of the metal working oil composition can be reduced.

[0025] The polyhydric alcohol is preferably a dihydric to decahydric alcohol, more preferably a dihydric to hexahydric alcohol. Examples of the dihydric to decahydric alcohol include dihydric alcohols such as ethylene glycol, diethylene glycol, polyethylene glycol (trimer to pentagonal chain of ethylene glycol), propylene glycol, dipropylene glycol, polypropylene glycol (trimer to pentagonal chain of propylene glycol), 1,3-propanediol, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 2-methyl-1,2-propanediol, 2-methyl-1,3-propanediol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 1,5-pentanediol, and neopentyl glycol; glycerin, polyglycerin (dimer to octamer of glycerin, such as diglycerin, triglycerin, tetra ... trimethylolalkanes (e.g., trimethylolethane, trimethylolpropane, trimethylolbutane, etc.) and dimers to octamers thereof, pentaerythritol and dimers to tetramers thereof, 1,2,4-butanetriol, 1,3,5-pentanetriol, 1,2,6-hexanetriol, 1,2,3,4-butanetetrol, sorbitol, sorbitan, sorbitol glycerin condensates, adonitol, arabitol, xylitol, mannitol, and other polyhydric alcohols; xylose, arabinose, ribose, rhamnose, glucose, fructose, galactose, mannose, sorbose, cellobiose, maltose, isomaltose, trehalose, sucrose, and other sugars; and mixtures thereof. Among these, the polyhydric alcohol is preferably neopentyl glycol, glycerin, or trimethylolalkane, from the viewpoint of further increasing the flash point of the metal working oil composition.

[0026] In this embodiment, an ester obtained by combining any saturated fatty acid (monobasic acid or polybasic acid) and any alcohol (monohydric alcohol or polyhydric alcohol) can be used. Examples of the first ester include the esters shown in (i) to (vii) below. (i) Esters of monobasic acids and monohydric alcohols (ii) Esters of monobasic acids and polyhydric alcohols (iii) Esters of polybasic acids and monohydric alcohols (iv) Esters of polybasic acids and polyhydric alcohols (v) Esters of polybasic acids with mixed alcohols of monohydric and polyhydric alcohols (vi) Esters of mixed fatty acids of monobasic and polybasic acids with polyhydric alcohols (vii) Esters of mixed fatty acids of monobasic and polybasic acids with mixed alcohols of monohydric and polyhydric alcohols

[0027] When the alcohol constituting the first ester is a polyhydric alcohol, the first ester may be a complete ester in which all hydroxyl groups in the polyhydric alcohol are esterified, or a partial ester in which some hydroxyl groups are not esterified and remain as hydroxyl groups. When the saturated fatty acid constituting the first ester is a polybasic acid, the first ester may be a complete ester in which all carboxyl groups in the polybasic acid are esterified, or a partial ester in which some carboxyl groups are not esterified and remain as carboxyl groups.

[0028] From the viewpoint of further increasing the flash point of the metal working oil composition, the first ester is preferably (i) an ester of a monobasic acid and a monohydric alcohol or (ii) an ester of a monobasic acid and a polyhydric alcohol, and more preferably (ii) an ester of a monobasic acid and a polyhydric alcohol.

[0029] From the viewpoint of further increasing the flash point of the metal working oil composition, the content of the first ester is preferably 50% by mass or more, more preferably 55% by mass or more, and even more preferably 60% by mass or more, based on the total amount of the lubricating base oil. From the viewpoint of improving the metal workability of the metal working oil composition, the content of the first ester is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less. In one embodiment, the content of the first ester is preferably 50 to 90% by mass, more preferably 55 to 85% by mass, and even more preferably 60 to 80% by mass, based on the total amount of the lubricating base oil.

[0030] (Second ester: ester of unsaturated fatty acid and alcohol) The lubricating base oil includes a second ester. The unsaturated fatty acid constituting the second ester may be a monobasic acid or a polybasic acid.

[0031] When a monobasic acid is used as the unsaturated fatty acid, the number of carbon atoms therein is preferably 6 to 24, more preferably 12 to 18. Such a monobasic acid may be a linear monobasic acid or a branched monobasic acid. When the monobasic acid has 6 or more carbon atoms, the metal working oil composition can have a higher flash point, and when the monobasic acid has 24 or less carbon atoms, the metal working oil composition can have a lower viscosity.

[0032] When a polybasic acid is used as the unsaturated fatty acid, the polybasic acid is preferably a dibasic acid having a double bond and having 2 to 16 carbon atoms. Such a dibasic acid may be a linear dibasic acid or a branched dibasic acid.

[0033] Examples of the alcohol constituting the second ester include the alcohols exemplified as the alcohol constituting the first ester. When a monohydric alcohol is used as the alcohol constituting the second ester, the monohydric alcohol may be the same as the preferred examples of the monohydric alcohol constituting the first ester. When a polyhydric alcohol is used as the alcohol constituting the second ester, the polyhydric alcohol is preferably neopentyl glycol, glycerin, or a trimethylolalkane, and more preferably neopentyl glycol.

[0034] In this embodiment, an ester obtained by combining any unsaturated fatty acid (monobasic acid or polybasic acid) and any alcohol (monohydric alcohol or polyhydric alcohol) can be used. Examples of the second ester include the esters shown in (i) to (vii) below. (i) Esters of monobasic acids and monohydric alcohols (ii) Esters of monobasic acids and polyhydric alcohols (iii) Esters of polybasic acids and monohydric alcohols (iv) Esters of polybasic acids and polyhydric alcohols (v) Esters of polybasic acids with mixed alcohols of monohydric and polyhydric alcohols (vi) Esters of mixed fatty acids of monobasic and polybasic acids with polyhydric alcohols (vii) Esters of mixed fatty acids of monobasic and polybasic acids with mixed alcohols of monohydric and polyhydric alcohols

[0035] When the alcohol constituting the second ester is a polyhydric alcohol, the second ester may be a complete ester in which all hydroxyl groups in the polyhydric alcohol are esterified, or a partial ester in which some hydroxyl groups are not esterified and remain as hydroxyl groups.When the unsaturated fatty acid constituting the second ester is a polybasic acid, the second ester may be a complete ester in which all carboxyl groups in the polybasic acid are esterified, or a partial ester in which some carboxyl groups are not esterified and remain as carboxyl groups.

[0036] From the viewpoint of further reducing the viscosity of the metal working oil composition, the second ester is preferably (i) an ester of a monobasic acid and a monohydric alcohol or (ii) an ester of a monobasic acid and a polyhydric alcohol.

[0037] The iodine value of the total amount of the second ester is not particularly limited, but is preferably 10 gI2 / 100 g or more, more preferably 30 gI2 / 100 g or more, even more preferably 50 gI2 / 100 g or more, and is preferably 140 gI2 / 100 g or less, more preferably 120 gI2 / 100 g or less, even more preferably 100 gI2 / 100 g or less.

[0038] The content of the second ester is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass, based on the total amount of the lubricating base oil, from the viewpoint of further increasing the flash point of the metal working oil composition. The content of the second ester is preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less, from the viewpoint of further improving the metal workability of the metal working oil composition and reducing skin sensitization. In one embodiment, the content of the second ester is preferably 1 to 30% by mass, more preferably 3 to 25% by mass, and even more preferably 5 to 20% by mass, based on the total amount of the lubricating base oil.

[0039] The iodine value of the total amount of the first ester and the second ester is preferably 50 gI2 / 100 g or less. When the iodine value is in this range, the skin sensitization of the metal working oil composition can be further reduced. The iodine value is more preferably 40 gI2 / 100 g or less, and even more preferably 20 gI2 / 100 g or less. The lower limit of the iodine value of the total amount of the first ester and the second ester may be, for example, 1 gI2 / 100 g or more or 3 gI2 / 100 g or more.

[0040] The iodine value is an index showing the degree of unsaturation derived from the second ester. Therefore, the iodine value of the total amount of the first ester and the second ester can be adjusted to fall within the above range by reducing the proportion of the second ester, using a second ester with a low iodine value, or the like.

[0041] The total content of the first ester and the second ester is preferably 50 to 90 mass% based on the total amount of the lubricating base oil. When the total content of the first ester and the second ester is within this range, the metalworking oil composition can have a higher flash point and be less susceptible to skin sensitization. Furthermore, when the total content of the first ester and the second ester is within this range, the metalworking oil composition has excellent compatibility with resins, making it less likely to deteriorate resin materials used in machine tools and the like, even when the metalworking oil composition adheres to the resin materials. The total content of the first ester and the second ester is more preferably 55 mass% or more, even more preferably 60 mass% or more, and more preferably 87 mass% or less, even more preferably 85 mass% or less, based on the total amount of the lubricating base oil. In one embodiment, the total content of the first ester and the second ester is more preferably 55 to 7 mass%, even more preferably 60 to 85 mass%.

[0042] (Other base oils: base oils other than the first ester and the second ester) In addition to the first ester and the second ester, the lubricating base oil further contains, as other base oils, at least one selected from the group consisting of mineral oils and synthetic oils other than esters.

[0043] Examples of mineral oils include mineral oils of Group I, Group II, or Group III of the API base oil classification, where each group in the API classification refers to the classification of lubricating oil grades by the American Petroleum Institute (API).

[0044] Examples of mineral oils include paraffinic base oils and naphthenic base oils obtained by subjecting lubricating oil fractions obtained by atmospheric or vacuum distillation of crude oil to one or more refining processes, such as solvent deasphalting, solvent extraction, solvent dewaxing, catalytic dewaxing, hydrorefining, sulfuric acid washing, and clay treatment, in appropriate combination. API base oil Group II mineral oils and API base oil Group III mineral oils are typically produced via hydrorefining processes. Other examples of mineral oils include wax isomerized base oils, such as base oils produced by isomerizing GTL wax (gas-to-liquid wax). From the perspective of achieving a high flash point, it is preferable to use Group III mineral oils.

[0045] The viscosity index of the mineral oil is preferably at least 80, more preferably at least 90, and even more preferably at least 100. There is no particular upper limit to the viscosity index of the mineral oil, but it may be, for example, not more than 150. In this specification, viscosity index refers to the viscosity index measured in accordance with JIS K2283:2000.

[0046] The sulfur content of the mineral oil is preferably 10,000 ppm by mass or less, more preferably 5,000 ppm by mass or less, and even more preferably 1,000 ppm by mass or less. In this specification, the sulfur content refers to the sulfur content measured by the ultraviolet fluorescence method specified in JIS K2541-6:2013.

[0047] The paraffin content of the mineral oil is preferably 50% by mass or more, more preferably 70% by mass or more, based on the total amount of the mineral oil. The naphthene content of the mineral oil is preferably 10% by mass or more, more preferably 20% by mass or more, and preferably 60% by mass or less, more preferably 40% by mass or less, based on the total amount of the mineral oil. The aromatic content of the mineral oil is preferably 10% by mass or less, more preferably 5% by mass or less, based on the total amount of the mineral oil. In this specification, the paraffin content, naphthene content, and aromatic content of the mineral oil each refer to values ​​measured by a method (NDM ring analysis) in accordance with ASTM D3238-95(2010).

[0048] Examples of synthetic oils other than esters include poly-α-olefins, alkylbenzenes, alkylnaphthalenes, polyoxyalkylene glycols, polyphenyl ethers, dialkyldiphenyl ethers, polyphenyl ethers, dialkyldiphenyl ethers, fluorine-containing compounds, and silicone oils.

[0049] The content of the other base oil is preferably 1 to 50 mass %, more preferably 5 to 40 mass %, and even more preferably 10 to 30 mass %, based on the total amount of the lubricating base oil.

[0050] The kinematic viscosity of the lubricating base oil at 40°C is preferably 5mm 2 / s or more, preferably 7mm 2 / s or more, more preferably 10 mm 2 / s or more, preferably 100 mm 2 / s or less, preferably 60 mm 2 / s or less, more preferably 40 mm 2 / s or less.

[0051] The kinematic viscosity at 100°C of the lubricating base oil is preferably 1mm 2 / s or more, preferably 2 mm 2 / s or more, more preferably 3 mm 2 / s or more, preferably 12 mm 2 / s or less, preferably 9mm 2 / s or less, more preferably 7 mm 2 / Below is.

[0052] The iodine value of the lubricating base oil is preferably 50 gI2 / 100 g or less. When the iodine value is within this range, the skin sensitization of the metal working oil composition can be reduced. The iodine value is more preferably 40 gI2 / 100 g or less, even more preferably 30 gI2 / 100 g or less, and particularly preferably 15 gI2 / 100 g or less. The lower limit of the iodine value of the lubricating base oil may be, for example, 1 gI2 / 100 g or more or 3 gI2 / 100 g or more.

[0053] The iodine value of the lubricating base oil can be adjusted to fall within the above range by, for example, reducing the proportion of the second ester (increasing the proportion of the first ester, mineral oil, or synthetic oil other than ester), or by using a second ester with a lower iodine value.

[0054] The lubricating base oil is the main component of the metal working oil composition and constitutes the remainder of the content of the additives described below. The content of the lubricating base oil may be, for example, 70 mass % or more, 80 mass % or more, 90 mass % or more, or 95 mass % or more based on the total amount of the metal working oil composition.

[0055] <Additives> (thiophosphate ester) An example of the thiophosphate ester is a compound represented by the following formula (1).

[0056] [ka]

[0057] In formula (1), R 11 , R 12 , and R 13 each independently represents a hydrogen atom, an alkyl group, an alkenyl group, or an aryl group, provided that R 11 , R 12 , and R 13 At least one of the groups is an alkyl group, an alkenyl group, or an aryl group.

[0058] The number of carbon atoms in the alkyl group may be, for example, 1 or more, 3 or more, or 6 or more, and 20 or less, 18 or less, or 16 or less. The alkyl group may be linear or branched. Some of the hydrogen atoms in the alkyl group may be substituted with an aryl group described below.

[0059] The number of carbon atoms in the alkenyl group may be, for example, 2 or more, 3 or more, or 6 or more, and may be 20 or less, 18 or less, or 16 or less. The alkenyl group may be linear or branched. Some of the hydrogen atoms in the alkenyl group may be substituted with an aryl group described below.

[0060] The number of carbon atoms in the aryl group may be, for example, 6 or more, 8 or more, or 10 or more, and may be 30 or less, 24 or less, or 18 or less. Some of the hydrogen atoms in the aryl group may be substituted with the above-mentioned alkyl or alkenyl group.

[0061] Specific examples of thiophosphate esters include mono(alkyl, alkenyl, or aryl) thiophosphates such as monobutyl phosphorothioate, monohexyl phosphorothioate, monooctyl phosphorothioate, monodecyl phosphorothioate, monododecyl phosphorothioate, monotetradecyl phosphorothioate, monohexadecyl phosphorothioate, monooctadecyl phosphorothioate, monooleyl phosphorothioate, monophenyl phosphorothioate, monocresyl phosphorothioate, and monoxylenyl phosphorothioate; dibutyl phosphorothioate, dihexyl phosphorothioate, dioctyl phosphorothioate, didecyl phosphorothioate, didodecyl phosphorothioate, ditetradecyl phosphorothioate, dihexadecyl phosphorothioate, and dioctadecyl phosphorothioate. di(alkyl, alkenyl, or aryl) thiophosphates such as dioleyl phosphorothioate, diphenyl phosphorothioate, dicresyl phosphorothioate, and dixylenyl phosphorothioate; and tri(alkyl, alkenyl, or aryl) thiophosphates such as tributyl phosphorothioate, trihexyl phosphorothioate, trioctyl phosphorothioate, tridecyl phosphorothioate, tridodecyl phosphorothioate, tritetradecyl phosphorothioate, trihexadecyl phosphorothioate, trioctadecyl phosphorothioate, trioleyl phosphorothioate, triphenyl phosphorothioate (TPPT), tricresyl phosphorothioate, trixylenyl phosphorothioate, cresyl diphenyl phosphorothioate, and xylenyl diphenyl phosphorothioate. Among these, the thiophosphate ester is preferably a thiophosphate triester. The thiophosphate triester is preferably a thiophosphate triester having an aryl group, more preferably triphenylphosphorothionate (TPPT).

[0062] The content of the thiophosphate ester is preferably 100 ppm by mass or more, more preferably 300 ppm by mass or more, and even more preferably 500 ppm by mass or more, and preferably 8000 ppm by mass or less, more preferably 6000 ppm by mass or less, and even more preferably 4000 ppm by mass or less, in terms of phosphorus, based on the total amount of the metal working oil composition. When the content of the thiophosphate ester is 100 ppm by mass or more, in terms of phosphorus, based on the total amount of the metal working oil composition, tool life can be extended, and when it is 8000 ppm by mass or less, the metal working oil composition can have a high flash point. In one embodiment, the content of the thiophosphate ester is preferably 100 to 8000 ppm by mass, more preferably 300 to 6000 ppm by mass, and even more preferably 500 to 4000 ppm by mass, in terms of phosphorus, based on the total amount of the metal working oil composition.

[0063] (acid phosphate ester) An example of the acidic phosphate ester is a compound represented by the following formula (2).

[0064] [ka]

[0065] In formula (2), R 21 and R 22 each independently represents a hydrogen atom, an alkyl group, an alkenyl group, or an aryl group, provided that R 21 and R 22 At least one of the groups is an alkyl group, an alkenyl group, or an aryl group.

[0066] R 21 and R 22 The alkyl group, alkenyl group, or aryl group in R 11 , R 12 , and R 13 The alkyl group, alkenyl group, or aryl group may be the same as the preferred examples of the alkyl group, alkenyl group, or aryl group in the above.

[0067] Specific examples of acidic phosphate esters include monobutyl acid phosphate, monopentyl acid phosphate, monohexyl acid phosphate, monoheptyl acid phosphate, monooctyl acid phosphate, monononyl acid phosphate, monodecyl acid phosphate, monoundecyl acid phosphate, monododecyl acid phosphate, monotridecyl acid phosphate, monotetradecyl acid phosphate, monopentadecyl acid phosphate, monohexadecyl acid phosphate, monoheptadecyl acid phosphate, monoocta ... Examples of the acidic phosphate include oleyl acid phosphate, dibutyl acid phosphate, dipentyl acid phosphate, dihexyl acid phosphate, diheptyl acid phosphate, dioctyl acid phosphate, dinonyl acid phosphate, didecyl acid phosphate, diundecyl acid phosphate, didodecyl acid phosphate, ditridecyl acid phosphate, ditetradecyl acid phosphate, dipentadecyl acid phosphate, dihexadecyl acid phosphate, diheptadecyl acid phosphate, dioctadecyl acid phosphate, and dioleyl acid phosphate. Among these, the acidic phosphate ester is preferably a thiophosphate triester having an alkyl or alkenyl group, and more preferably an acidic phosphate ester having an alkyl or alkenyl group having 10 to 20 carbon atoms.

[0068] The content of the acidic phosphate ester is, based on the total amount of the metal working oil composition, preferably 1 ppm by mass or more, more preferably 5 ppm by mass or more, even more preferably 10 ppm by mass or more, and preferably 600 ppm by mass or less, more preferably 400 ppm by mass or less, and even more preferably 200 ppm by mass or less, in terms of elemental phosphorus. When the content of the acidic phosphate ester is 1 ppm by mass or more, based on the total amount of the metal working oil composition, in terms of elemental phosphorus, tool life can be extended, and when it is 600 ppm by mass or less, the metal working oil composition can have a high flash point. In one embodiment, the content of the acidic phosphate ester is, based on the total amount of the metal working oil composition, preferably 1 to 600 ppm by mass, more preferably 5 to 400 ppm by mass, and even more preferably 10 to 200 ppm by mass, in terms of elemental phosphorus.

[0069] The mass ratio of the thiophosphate content to the acid phosphate content, in terms of elemental phosphorus (thiophosphate content (in terms of elemental phosphorus) / acid phosphate content (in terms of elemental phosphorus)) is preferably 1 or more, more preferably 10 or more, even more preferably 20 or more, and is preferably 700 or less, more preferably 500 or less, even more preferably 300 or less.

[0070] In addition to the thiophosphate ester and acid phosphate ester, the metalworking oil composition may contain other additives, provided that the effects of the present invention are not significantly impaired. Examples of such additives include antioxidants (phenolic compounds such as 2,6-di-tert.butyl-p-cresol (DBPC) and aromatic amines such as phenyl-α-naphthylamine), metal deactivators (benzotriazole, etc.), mist suppressants (hydrocarbon polymers such as polyisobutylene and ethylene-propylene copolymers), sulfur compounds such as sulfurized esters, sulfurized olefins, and thiobisphenols, antiwear agents other than thiophosphate esters and acid phosphate esters (phosphites, their amine salts, metal salts, and derivatives), and friction modifiers (amine-based agents such as ditridecylamine, amide-based agents, imide-based agents, fatty acid-based agents, aliphatic alcohol-based agents, aliphatic ether-based agents, etc.). The total content of such additives is not particularly limited, but is preferably 5 mass% or less based on the total mass of the metalworking oil composition.

[0071] <Metalworking oil composition> The metalworking oil composition preferably has a kinematic viscosity at 40°C of 30 mm 2 The kinematic viscosity at 40°C of the metalworking oil composition is more preferably 28 mm / s or less. 2 / s or less, more preferably 25 mm 2 The kinematic viscosity at 40°C of the metalworking oil composition is preferably 8 mm / s or less. 2 / s or more, preferably 13 mm 2 / s or more, preferably 16 mm 2 / s or more.

[0072] The flash point of the metal working oil composition is preferably 200°C or higher. When the flash point of the metal working oil composition is 200°C or higher, safety during handling of the metal working oil composition is improved. The flash point of the metal working oil composition is more preferably 220°C or higher, even more preferably 240°C or higher, and particularly preferably 260°C or higher. The upper limit of the flash point of the metal working oil composition may be, for example, 300°C or lower.

[0073] The metal working oil composition according to this embodiment can be suitably used, for example, in metal cutting. The metal working oil composition according to this embodiment can also be called a metal cutting oil composition. The material of the workpiece in metal working is not particularly limited, but examples thereof include iron, stainless steel, aluminum or its alloy, nickel or its alloy, chromium or its alloy, copper or its alloy, zinc or its alloy, and titanium or its alloy.

[0074] The metal working oil composition according to this embodiment has a high flash point and can extend the tool life. [Example]

[0075] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.

[0076] [Lubricant base oil] (A) First Ester A1: Esters of n-octanoic acid and n-decanoic acid with glycerin (iodine value: 0gI2 / 100g) (B) a second ester B1: Ester of oleic acid (9-cis-octadecenoic acid) and neopentyl glycol (iodine value: 82.6 g I2 / 100 g) (C) Mineral oil C1: API Classification Group III mineral oil (40°C kinematic viscosity: 34.79 mm) 2 / s, 100℃ kinematic viscosity: 6.46mm 2 / s, viscosity index: 141) C2: API Classification Group III GTL mineral oil (40°C kinematic viscosity: 44.43 mm 2 / s, 100℃ kinematic viscosity: 7.61mm 2 / s, viscosity index: 139)

[0077] [Additives] (D) Thiophosphate ester D1: Triphenylphosphorothionate (TPPT) (phosphorus content: 8.9% by mass) (E) Acidic phosphate ester E1: A mixture of monooleyl acid phosphate and dioleyl acid phosphate in a mass ratio of 1:1 (phosphorus content: 6.6 mass%) (e) Phosphate triester e1: Tricresyl phosphate (phosphorus content: 9.2% by mass)

[0078] [Metalworking oil composition] (Examples 1 to 5 and Comparative Examples 1 to 3) Using the above lubricating base oils and additives, metal working oil compositions having the compositions shown in Table 1 were prepared. In the table, the numerical values ​​for the lubricating base oils refer to the content (mass%) based on the total amount of the lubricating base oil, and the numerical values ​​for the additives refer to the content (mass%) based on the total amount of the metal working oil composition. The numerical values ​​in parentheses for the additives refer to the content (ppm by mass) in terms of phosphorus element based on the total amount of the metal working oil composition.

[0079] [Evaluation of Metalworking Oil Compositions] (Measurement of kinematic viscosity at 40°C) The kinematic viscosity at 40°C was measured in accordance with JIS K2283:2000. The results are shown in Table 1.

[0080] (Tool life evaluation) A turning test was carried out using a lathe under the following conditions, and the wear width of the tool was evaluated. Testing machine: Okuma Corporation LCC-15 Work material: SUS430 Test tool: Sandvik CP-A1108-L5 Cutting speed: 140m / min Cutting amount: 0.5 mm Feed rate: 0.2 mm / rev Test temperature: Room temperature (25°C) Processing distance: 3695m Evaluation item: Wear width per unit time (μm / min) The wear width per unit time (μm / min) was determined by measuring the wear width (μm) periodically every hour. The results are shown in Table 1. In the table, the smaller the wear width per unit time (μm / min), the better the tool life.

[0081] (Flash point measurement) The flash point was measured in accordance with JIS K2265-4:2007, and the results are shown in Table 1.

[0082] (Evaluation of compatibility with resin) A resin (HIPS (high impact polystyrene)) was immersed in the sample oil at 60°C for 336 hours, and the volume change, mass change, and hardness change were measured. The volume change and mass change were measured in accordance with JIS K7114:2001, and the hardness change was measured in accordance with JIS K6253-3:2012. A volume change and mass change of ±5% or less was considered acceptable, and a hardness change of ±5 or less was considered acceptable.

[0083] [Table 1]

[0084] As shown in Table 1, the metalworking oil compositions of Examples 1 to 5, which contained the specified lubricating base oil, thiophosphate ester, and acidic phosphate ester, had flash points of 200°C or higher and longer tool lives than the metalworking oil compositions of Comparative Examples 1 to 3. These results confirmed that the metalworking oil composition according to the present invention has a sufficiently high flash point and is capable of extending tool life.

Claims

1. a lubricating base oil comprising a first ester which is an ester of a saturated fatty acid and an alcohol, a second ester which is an ester of an unsaturated fatty acid and an alcohol, and at least one selected from the group consisting of mineral oils and synthetic oils other than esters; a thiophosphate ester; an acid phosphate ester; Contains the saturated fatty acid constituting the first ester is a monobasic acid having 8 to 18 carbon atoms, the alcohol constituting the first ester is a dihydric to hexahydric alcohol, The content of the first ester is 60 to 80 mass% based on the total amount of the lubricating base oil, the unsaturated fatty acid constituting the second ester is a monobasic acid having 12 to 18 carbon atoms, the alcohol constituting the second ester is a dihydric to hexahydric alcohol, The metal working oil composition, wherein the content of the second ester is 5 to 20 mass % based on the total amount of the lubricating base oil.

2. The iodine value of the total amount of the lubricating base oil is 50 g / L ２ 2. The metal working oil composition according to claim 1, wherein the total weight of the oil is 100g or less.

3. 3. The metalworking oil composition of claim 1, wherein the mineral oil is a Group III mineral oil of the API base oil classification.

4. 40℃ kinematic viscosity 30mm ２ 3. The metal working oil composition according to claim 1, wherein the viscosity of the metal working oil composition is 1 / s or less.

5. 3. The metal working oil composition according to claim 1, which has a flash point of 200°C or higher.

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