Metalworking fluid composition

Abstract

To provide a metalworking fluid composition that has a sufficiently high flash point and can mitigate dermal sensitization reactions.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, and a second ester, which is an ester derived from an unsaturated fatty acid and an alcohol; and a sulfur compound. The lubricant base oil has an iodine value of 50 gI2 / 100 g or less.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] In the field of metalworking, metalworking oils are used to lubricate the machining parts of workpieces. From the perspective of improving production efficiency and the like, the development of metalworking oils having excellent cutting performance has been underway.

[0003] As metalworking oils, for example, metalworking oils containing a predetermined ester oil are disclosed (for example, cited references 1 and 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, the required performance for metalworking oils has further increased, and conventional metalworking oils have room for improvement in terms of skin sensitization and flash point. In particular, when a metalworking oil has a sufficiently high flash point (for example, 250°C or higher), the skin sensitization tends to be insufficient.

[0006] Note that "skin sensitization" means that when a substance repeatedly contacts a certain substance, the substance becomes an antigen and antibodies are produced in the body, causing an allergic reaction, which is a different concept from skin irritation that causes a direct toxic reaction on the skin or the like and the appearance of inflammation when the substance touches the skin.

[0007] Therefore, the main object of the present invention is to provide a metalworking oil composition that has a sufficiently high flash point and can reduce skin sensitization.

Means for Solving the Problems

[0008] As a result of investigations by the present inventors, it has been found that by using specific esters and sulfur compounds in metalworking oils, it is possible to achieve both a high flash point and low skin sensitization at a high level, and the present invention has been completed.

[0009] The present invention provides a metalworking oil composition. The metalworking oil composition contains a lubricating base oil containing a first ester that is an ester of a saturated fatty acid and an alcohol and a second ester that is an ester of an unsaturated fatty acid and an alcohol, and a sulfur compound. The iodine value in the lubricating base oil is 50 gI2 / 100 g or less. According to such a metalworking oil composition, it has a sufficiently high flash point and can reduce skin sensitization.

[0010] In the present specification, the iodine value means the iodine value measured in accordance with JIS K 0070:1992 "Test Methods for Acid Value, Saponification Value, Ester Value, Iodine Value, Hydroxyl Value and Unsaponifiable Matter of Chemical Products". The iodine value is an index indicating the degree of unsaturation derived from the second ester.

[0011] The total content of the first ester and the second ester is preferably 50 to 90% by mass based on the total amount of the lubricating base oil. The content of the second ester is preferably 5 to 60% by mass based on the total amount of the lubricating base oil.

[0012] The flash point of the metalworking oil composition is preferably 250°C or higher. In the present specification, the flash point means the flash point measured in accordance with JIS K2265-4:2007.

Effects of the Invention

[0013] The present invention provides a metalworking oil composition that has a sufficiently high flash point and can reduce skin sensitization. [Modes for carrying out the invention]

[0014] Embodiments of the present invention will be described in detail below. However, the present invention is not limited to the following embodiments.

[0015] In this specification, numerical ranges indicated using "~" represent a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. In numerical ranges described in stages in this specification, the upper or lower limit of one stage of the numerical range may be replaced with the upper or lower limit of another stage of the numerical range. Furthermore, in numerical ranges described in this specification, the upper or lower limit of that numerical range may be replaced with the values ​​shown in the examples.

[0016] In this specification, unless otherwise specified, the materials exemplified below may be used individually or in combination of two or more, to the extent that the conditions are met. The content of each component in the metalworking oil composition means the total amount of multiple substances present in the metalworking oil composition if multiple substances corresponding to each component are present in the metalworking oil composition, unless otherwise specified.

[0017] [Metalworking oil composition] A metalworking oil composition according to one embodiment contains a lubricating oil base oil comprising a first ester which is an ester of a saturated fatty acid and an alcohol, and a second ester which is an ester of an unsaturated fatty acid and an alcohol, and a sulfur compound. The iodine value of the lubricating oil base oil is 50 gI2 / 100 g or less.

[0018] <Lubricant base oil> (First ester: Ester of saturated fatty acid and alcohol) The lubricating oil base oil contains a first ester. The saturated fatty acid constituting the first ester may be a monobasic acid or a polybasic acid.

[0019] When a monobasic acid is used as a saturated fatty acid, its carbon number is preferably 6 to 24, more preferably 8 to 18. Such a monobasic acid may be a linear or branched monobasic acid. If the monobasic acid has 6 or more carbon atoms, the flash point of the metalworking oil composition can be increased, and if the monobasic acid has 24 or fewer carbon atoms, the viscosity of the metalworking oil composition can be reduced.

[0020] When a polybasic acid is used as the saturated fatty acid, it is preferable that the polybasic acid is a dibasic acid having 2 to 16 carbon atoms. Such a dibasic acid may be a linear or branched dibasic acid.

[0021] The alcohol constituting the first ester may be a monohydric alcohol or a polyhydric alcohol.

[0022] The monohydric alcohol may be a linear or branched monohydric alcohol. The number of carbon atoms in the monohydric alcohol is preferably 1 to 24, more preferably 3 to 16. If the number of carbon atoms in the monohydric alcohol is 1 or more, the flash point of the metalworking oil composition can be made higher, and if the number of carbon atoms in the monohydric alcohol is 24 or less, the viscosity of the metalworking oil composition can be made lower.

[0023] The polyhydric alcohol is preferably a 2- to 10-hydric alcohol, more preferably a 2- to 6-hydric alcohol. Examples of 2- to 10-hydric alcohols include dihydric alcohols such as ethylene glycol, diethylene glycol, polyethylene glycol (3- to 15-mers of ethylene glycol), propylene glycol, dipropylene glycol, polypropylene glycol (3- to 15-mers 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, neopentyl glycol, and other dihydric alcohols; glycerin, polyglycerin (2- to 8-mers of glycerin, e.g., diglycerin, triglycerin, tetraglycerin) Examples include glycerin, trimethylol alkanes (e.g., trimethylolethane, trimethylolpropane, trimethylolbutane, etc.) and their dimethylol-octamers, pentaerythritol and its dimethylol-tetramers, 1,2,4-butanetriol, 1,3,5-pentanetriol, 1,2,6-hexanetriol, 1,2,3,4-butanetetrol, sorbitol, sorbitan, sorbitol-glycerol condensates, adonitol, arabitol, xylitol, mannitol, and other polyhydric alcohols; sugars such as xylose, arabinose, ribose, rhamnose, glucose, fructose, glastose, mannose, sorbose, cellobiose, maltose, isomaltose, trehalose, sucrose, and mixtures thereof. Among these, polyhydric alcohols are preferably neopentyl glycol, glycerin, or trimethylol alkanes, from the viewpoint of further increasing the flash point of the metalworking oil composition.

[0024] In this embodiment, esters formed by any combination of saturated fatty acids (monobasic acids and polybasic acids) and any alcohols (monohydric alcohols and polyhydric alcohols) 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

[0025] Furthermore, if 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 of the hydroxyl groups remain unesterified. If 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 of the carboxyl groups remain unesterified.

[0026] 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, from the viewpoint of further increasing the flash point of the metalworking oil composition.

[0027] The content of the first ester is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more, based on the total amount of lubricating oil base oil, from the viewpoint of further increasing the flash point of the metalworking oil composition. The content of the first ester is preferably 80% by mass or less, more preferably 75% by mass or less, and even more preferably 70% by mass or less, from the viewpoint of further suppressing the skin sensitization properties of the metalworking oil composition. In one embodiment, the content of the first ester is preferably 20 to 80% by mass, more preferably 30 to 75% by mass, and even more preferably 40 to 70% by mass, based on the total amount of lubricating oil base oil.

[0028] (Second ester: Ester of an unsaturated fatty acid and an alcohol) The lubricating oil base oil contains a second ester. The unsaturated fatty acid constituting the second ester may be a monobasic acid or a polybasic acid.

[0029] When a monobasic acid is used as the unsaturated fatty acid, its carbon number is preferably 6 to 24, more preferably 12 to 18. Such a monobasic acid may be a linear or branched monobasic acid. If the monobasic acid has 6 or more carbon atoms, the flash point of the metalworking oil composition can be made higher, and if the monobasic acid has 24 or fewer carbon atoms, the viscosity of the metalworking oil composition can be made lower.

[0030] When using a polybasic acid as an unsaturated fatty acid, it is preferable that the polybasic acid is a dibasic acid having 2 to 16 carbon atoms and possessing a double bond. Such a dibasic acid may be a linear or branched dibasic acid.

[0031] Examples of alcohols constituting the second ester include those exemplified as alcohols constituting the first ester. When a monohydric alcohol is used as the alcohol constituting the second ester, the monohydric alcohol is the same as the preferred examples of monohydric alcohols 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 trimethylol alkane, and more preferably neopentyl glycol.

[0032] In this embodiment, esters formed by any combination of unsaturated fatty acids (monobasic acids and polybasic acids) and any alcohols (monohydric alcohols and polyhydric alcohols) 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

[0033] Furthermore, if 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 of the hydroxyl groups remain unesterified. If 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 of the carboxyl groups remain unesterified.

[0034] 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, from the viewpoint of further reducing the viscosity of the metalworking oil composition.

[0035] The total iodine value of the second ester is not particularly limited, but is preferably 10 gI2 / 100g or more, more preferably 30 gI2 / 100g or more, even more preferably 50 gI2 / 100g or more, preferably 140 gI2 / 100g or less, more preferably 120 gI2 / 100g or less, and even more preferably 100 gI2 / 100g or less.

[0036] The content of the second ester is preferably 5 to 60% by mass, based on the total amount of lubricating oil base oil. When the content of the second ester is 5% by mass or more, based on the total amount of lubricating oil base oil, the flash point of the metalworking oil composition can be made higher. When the content of the second ester is 60% by mass or less, based on the total amount of lubricating oil base oil, the skin sensitization properties of the metalworking oil composition tend to be within an acceptable range. The content of the second ester is more preferably 7% by mass or more, even more preferably 10% by mass, more preferably 50% by mass or less, and even more preferably 40% by mass or less, based on the total amount of lubricating oil base oil. In one embodiment, the content of the second ester is more preferably 7 to 50% by mass, and even more preferably 10 to 40% by mass, based on the total amount of lubricating oil base oil.

[0037] The iodine value in the total amount of the first and second esters is preferably 50 gI2 / 100g or less. When the iodine value is within this range, the skin sensitization properties of the metalworking oil composition can be further reduced. The iodine value is more preferably 40 gI2 / 100g or less, and even more preferably 20 gI2 / 100g or less. The lower limit of the iodine value in the total amount of the first and second esters may be, for example, 1 gI2 / 100g or more, or 3 gI2 / 100g or more.

[0038] The iodine value is an indicator of the degree of unsaturation derived from the second ester. Therefore, the iodine value in the total amount of the first and second esters can be adjusted to the above range by reducing the proportion of the second ester or by using a second ester with a lower iodine value.

[0039] The total content of the first ester and the second ester is preferably 50 to 90% by mass, based on the total amount of lubricating oil base oil. When the total content of the first ester and the second ester is within this range, the flash point of the metalworking oil composition can be made higher and the skin sensitization of the metalworking oil composition can be further reduced. The total content of the first ester and the second ester is more preferably 55% by mass or more, even more preferably 60% by mass or more, more preferably 85% by mass or less, and even more preferably 80% by mass or less, based on the total amount of lubricating oil base oil. In one embodiment, the total content of the first ester and the second ester is more preferably 55 to 85% by mass, and even more preferably 60 to 80% by mass.

[0040] (Other base oils: base oils other than the first and second esters) To further enhance the effects of the present invention, the lubricating oil base oil may, if necessary, further contain, in addition to the first ester and the second ester, at least one other base oil selected from the group consisting of mineral oil and synthetic oils other than esters.

[0041] Examples of mineral oils include those belonging to API base oil classification groups I, II, or III. Note that each group in the API classification refers to the lubricant grade classification of the American Petroleum Institute (API).

[0042] Examples of mineral oils include paraffinic base oils and naphthenic base oils, which are obtained by applying one or more refining methods, such as solvent delamination, solvent extraction, solvent dewaxing, catalytic dewaxing, hydrorefining, sulfuric acid washing, and clay treatment, to a lubricating oil fraction obtained by atmospheric or vacuum distillation of crude oil. Mineral oils in API Group II and API Group III are usually produced through a hydrorefining process. Other examples of mineral oils include wax isomerized base oils; base oils produced by methods of isomerizing GTL WAX (gas-to-liquid wax).

[0043] The viscosity index of the mineral oil is preferably 80 or higher, more preferably 90 or higher, and even more preferably 100 or higher. The upper limit of the viscosity index of the mineral oil is not particularly limited, but may be, for example, 150 or lower. In this specification, viscosity index refers to the viscosity index measured in accordance with JIS K2283:2000.

[0044] 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, sulfur content refers to the sulfur content measured by the ultraviolet fluorescence method specified in JIS K2541-6:2013.

[0045] 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 mineral oil. The naphthene content of the mineral oil is preferably 10% by mass or more, more preferably 20% by mass or more, and also preferably 60% by mass or less, more preferably 40% by mass or less, based on the total amount of 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 mineral oil. In this specification, the paraffin content, naphthene content, and aromatic content of the mineral oil refer to values ​​measured by the method (ndm ring analysis) in accordance with ASTM D3238-95 (2010).

[0046] Examples of synthetic oils other than esters include poly-α-olefins, alkylbenzenes, alkylnaphthalenes, polyoxyalkylene glycols, polyphenyl ethers, dialkyldiphenyl ethers, fluorine-containing compounds, silicone oils, and the like.

[0047] When the lubricant base oil contains other base oils, the content of the other base oils is preferably 1 to 50% by mass, more preferably 5 to 40% by mass, and still more preferably 10 to 30% by mass, based on the total amount of the lubricant base oil.

[0048] The kinematic viscosity of the lubricant base oil at 40 °C is preferably , ,

[0051] 5 mm 2 / s or more, more preferably 2 7 mm 2 / s or more, still more preferably 2 10 mm 2 / s or more, and preferably

[0049] 100 mm 2 / s or less, more preferably 2 60 mm 2 / s or less, still more preferably 2 40 mm 2 / s or less. 2 [[ID=۳۸]]

[0050] In this specification, the kinematic viscosity at 40 °C and the kinematic viscosity at 100 °C mean the kinematic viscosity measured in accordance with JIS K2283:2000.

[0051] [[ID=4۳]] The iodine value of the lubricating oil base oil is 50 gI2 / 100g or less. Having an iodine value within this range can reduce the skin sensitization potential of the metalworking oil composition. Preferably, the iodine value is 40 gI2 / 100g or less, more preferably 30 gI2 / 100g or less, and even more preferably 15 gI2 / 100g or less. The lower limit of the iodine value in the lubricating oil base oil may be, for example, 1 gI2 / 100g or more, or 3 gI2 / 100g or more.

[0052] The iodine value in the above lubricating oil base oil can be adjusted to the above range by 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 low iodine value.

[0053] The lubricating oil base oil is the main component of the metalworking oil composition and constitutes the remainder of the content of the additives listed below. The content of the lubricating oil base oil may be, for example, 70% or more by mass, 80% or more by mass, 90% or more by mass, or 95% or more by mass, based on the total amount of the metalworking oil composition.

[0054] <Additives> (Sulfur compounds) The metalworking oil composition contains a sulfur compound. The sulfur compound is preferably one selected from the group consisting of thiophosphate esters, dithiophosphate esters, sulfur esters, sulfurized olefins, and thiobisphenols.

[0055] Examples of thiophosphate esters include compounds represented by the following formula (1).

[0056] [ka]

[0057] In formula (1), R 11 , R 12 , and R 13 Each of these independently represents a hydrogen atom, an alkyl group, an alkenyl group, or an aryl group. However, R 11 , R12 , and R 13 At least one of these 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 may be 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 aryl groups as described later.

[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 aryl groups as described later.

[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 of the aryl group may be substituted with the alkyl or alkenyl groups mentioned above.

[0061] Specific examples of thiophosphate esters include monobutyl phosphorothionate, monohexyl phosphorothionate, monooctyl phosphorothionate, monodecyl phosphorothionate, monododecyl phosphorothionate, monotetradecyl phosphorothionate, monohexadecyl phosphorothionate, monooctadecyl phosphorothionate, monooleyl phosphorothionate, monophenyl phosphorothionate, monocrezyl phosphorothionate, monoxylenyl phosphorothionate, and other mono(alkyl, alkenyl, or aryl) thiophosphates; dibutyl phosphorothionate, dihexyl phosphorothionate, dioctyl phosphorothionate, didecyl phosphorothionate, didodecyl phosphorothionate, ditetradecyl phosphorothionate, dihexadecyl phosphorothionate, and dioctadecyl phosphorothionate. Examples include di(alkyl, alkenyl, or aryl) thiophosphates such as dioleyl phosphorothionate, diphenyl phosphorothionate, dicresyl phosphorothionate, and dixylenyl phosphorothionate; and tri(alkyl, alkenyl, or aryl) thiophosphates such as tributyl phosphorothionate, trihexyl phosphorothionate, trioctyl phosphorothionate, tridecyl phosphorothionate, tridodecyl phosphorothionate, tritetradecyl phosphorothionate, trihexadecyl phosphorothionate, trioctadecyl phosphorothionate, trioleyl phosphorothionate, triphenyl phosphorothionate (TPPT), tricresyl phosphorothionate, trixylenyl phosphorothionate, cresyldiphenyl phosphorothionate, and xylenyldiphenyl phosphorothionate. Among these, thiophosphate esters are preferably thiophosphate triesters. Thiophosphate triesters are preferably triphenyl phosphorothionate (TPPT).

[0062] Examples of dithiophosphate esters include compounds represented by the following formula (2) and compounds represented by the following formula (3).

[0063] [ka]

[0064] In formula (2), R 21 , R 22 , and R 23 Each of these independently represents a hydrogen atom, an alkyl group, an alkenyl group, or an aryl group. However, R 21 , R 22 , and R 23 At least one of these is an alkyl group, an alkenyl group, or an aryl group.

[0065] R 21 , R 22 , and R 23 In R, the alkyl group, alkenyl group, or aryl group is R 11 , R 12 , and R 13 The preferred examples of alkyl groups, alkenyl groups, or aryl groups in the above may be the same as those in the above.

[0066] Specific examples of compounds represented by formula (2) include mono(alkyl, alkenyl, or aryl) dithiophosphates such as butyl dithiophosphate, hexyl dithiophosphate, octyl dithiophosphate, and phenyl dithiophosphate; di(alkyl, alkenyl, or aryl) dithiophosphates such as dibutyl dithiophosphate, dihexyl dithiophosphate, dioctyl dithiophosphate, and diphenyl dithiophosphate; and tri(alkyl, alkenyl, or aryl) dithiophosphates such as tributyl dithiophosphate, trihexyl dithiophosphate, trioctyl dithiophosphate, and triphenyl dithiophosphate.

[0067] [ka]

[0068] In formula (3), R 31 and R 32 Each of these independently represents an alkyl group or an alkenyl group, R 33 represents an alkylene group.

[0069] R 31 and R32 The alkyl or alkenyl group in R 11 , R 12 , and R 13 The preferred examples of alkyl or alkenyl groups may be the same as those in the above.

[0070] R 33 The number of carbon atoms in the alkylene group may be 1 or more, 2 or more, and 8 or less, 6 or less, or 4 or less. The alkylene group may be linear or branched.

[0071] Examples of sulfurized esters include sulfurized fats and oils obtained by sulfurizing animal and vegetable oils and fats such as beef tallow, pork tallow, fish oil, rapeseed oil, and soybean oil by any method; esters obtained by sulfurizing unsaturated fatty acid esters (such as methyl unsaturated fatty acids) obtained by reacting unsaturated fatty acids with alcohols by any method; and esters obtained by sulfurizing a mixture of animal and vegetable oils and unsaturated fatty acid esters by any method.

[0072] Sulfurized oils may have a cross-linked structure formed by sulfur atoms. Sulfurized oils with four or more sulfur atoms forming the cross-linked structure are classified as active sulfurized oils that are highly likely to cause copper plate corrosion, while sulfurized oils with three or fewer sulfur atoms can be classified as inert sulfurized oils that are less likely to cause copper plate corrosion. Therefore, when using a copper alloy as the workpiece, and when the copper alloy is applied to the part of the processing equipment to which the processing oil adheres, it is preferable to use sulfurized oils with three or fewer sulfur atoms.

[0073] Examples of sulfurized olefins include compounds represented by the following formula (4).

[0074] [ka]

[0075] In formula (4), R 41 and R 42 Each of these independently represents an alkyl group, and n represents an integer greater than or equal to 1.

[0076] R 41 and R 42 The number of carbon atoms in the alkyl group may be 3 or more, 5 or more, or 7 or more, and may be 16 or less, 12 or less, 10 or less, or 8 or less. The alkyl group may be linear or branched. n may be an integer of 2 or more, or 3 or more, and may be an integer of 10 or less, 9 or less, or 8 or less.

[0077] Examples of thiobisphenols include compounds represented by the following formula (5).

[0078] [ka]

[0079] In formula (2), R 51 R represents a hydrogen atom or an alkyl group. 52 and R 53 Each of these independently represents a divalent alkylene group, and x represents an integer from 1 to 3.

[0080] R 51 The number of carbon atoms in the alkyl group may be 1 or more, 2 or more, or 3 or more, and may be 16 or less, 12 or less, 10 or less, or 8 or less. The alkyl group may be linear or branched.

[0081] R 52 and R 53 The alkylene group may have 1 or more carbon atoms or 2 or more carbon atoms. The alkyl group may have 8 or fewer carbon atoms or 6 or fewer carbon atoms. The alkylene group may be linear or branched.

[0082] x can be 1 or 2, or it can be 1.

[0083] The sulfur content of sulfur compounds in terms of sulfur atoms (sulfur content derived from additives) based on the total amount of the metalworking oil composition is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, even more preferably 0.4% by mass or more, preferably 2.0% by mass or less, more preferably 1.5% by mass or less, and even more preferably 1.0% by mass or less. When the sulfur content derived from additives is 0.1% by mass or more, the metalworkability of the metalworking oil composition is improved, and when it is 2.0% by mass or less, the flash point of the metalworking oil composition can be further increased.

[0084] (Phosphate ester) Metalworking oil compositions may contain phosphate esters. Examples of phosphate esters include mono(alkyl, alkenyl, or aryl) phosphates such as monobutyl phosphate, monohexyl phosphate, monooctyl phosphate, monodecyl phosphate, monododecyl phosphate, monooleyl phosphate, monophenyl phosphate, and monocresyl phosphate; di(alkyl, alkenyl, or aryl) phosphates such as dibutyl phosphate, dihexyl phosphate, dioctyl phosphate, didecyl phosphate, didodecyl phosphate, dioleyl phosphate, diphenyl phosphate, and dicresyl phosphate; and tri(alkyl, alkenyl, or aryl) phosphates such as tributyl phosphate, trihexyl phosphate, trioctyl phosphate, tridecyl phosphate, tridodecyl phosphate, trioleyl phosphate, triphenyl phosphate, and tricresyl phosphate. Mono(alkyl, alkenyl, or aryl) phosphates and di(alkyl, alkenyl, or aryl) phosphates can be called acidic phosphate esters. The alkyl or alkenyl group may be linear or branched.

[0085] The phosphate ester content is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, preferably 2% by mass or less, and more preferably 1% by mass or less, based on the total amount of the metalworking oil composition. When the phosphate ester content is 0.01% by mass or more, based on the total amount of the metalworking oil composition, metalworkability is improved, and when it is 2% by mass or less, the flash point of the metalworking oil composition can be further increased.

[0086] The metalworking oil composition may contain other additives in addition to the above-mentioned sulfur compounds and phosphate esters, to the extent that they do not significantly impair the effects of the present invention. Examples of other additives include antioxidants (phenolic compounds such as 2,6-di-tert-butyl-p-cresol (DBPC), aromatic amines such as phenyl-α-naphthylamine, etc.), metal deactivators (benzotriazole, etc.), mist inhibitors (hydrocarbon polymer compounds such as polyisobutylene and ethylene-propylene copolymer, etc.), anti-wear agents other than sulfur compounds and phosphate esters (phosphite esters, etc., their amine salts, metal salts, and derivatives, etc.), friction modifiers (amine-based such as ditridecylamine, amide-based, imide-based, fatty acid-based, aliphatic alcohol-based, aliphatic ether-based, etc.). The total amount of other additives is not particularly limited, but is preferably 5% by mass or less based on the total amount of the metalworking oil composition.

[0087] <Metalworking oil composition> The kinematic viscosity of the metalworking fluid composition at 40°C is preferably 30 mm². 2 The kinematic viscosity of the metalworking oil composition at 40°C is preferably 28 mm². 2 / s or less, more preferably 25 mm 2 The kinematic viscosity of the metalworking oil composition at 40°C is preferably 8 mm². 2 / s or more, more preferably 13 mm 2 / s or more, more preferably 16mm 2 It is / s or greater.

[0088] The flash point of the metalworking oil composition is preferably 250°C or higher. A flash point of 250°C or higher improves the safety of handling the metalworking oil composition. The flash point of the metalworking oil composition is more preferably 254°C or higher, and even more preferably 256°C or higher. The upper limit of the flash point of the metalworking oil composition may be, for example, 300°C or lower.

[0089] The metalworking fluid composition according to this embodiment can be suitably used, for example, in metal cutting processes. The metalworking fluid composition according to this embodiment can also be called a metal cutting fluid composition. The material of the workpiece in metalworking is not particularly limited, but examples include iron, stainless steel, aluminum or its alloys, nickel or its alloys, chromium or its alloys, copper or its alloys, zinc or its alloys, titanium or its alloys, etc.

[0090] The metalworking oil composition according to this embodiment has a high flash point and can reduce skin sensitization. [Examples]

[0091] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

[0092] [Lubricant base oil] (A) First ester A1: Esters of n-octanoic acid and n-decanoic acid with trimethylolpropane (iodine value: 0gI2 / 100g) A2: Esters of n-octanoic acid and n-decanoic acid with glycerol (iodine value: 0gI2 / 100g) (B) Second ester B1: Ester of oleic acid (9-cis-octadecenoic acid) and neopentyl glycol (iodine value: 82.6 gI2 / 100g) B2: Ester of oleic acid (9-cis-octadecenoic acid) and 1-tridecanol (iodine value: 54.6 gI2 / 100g) (C) Mineral oil C1: API classification Group III mineral oil (kinematic viscosity at 40°C: 34.79 mm) 2 / s, 100℃ kinematic viscosity: 6.46mm 2 / s, viscosity index: 141)

[0093] [Additives] (D) Sulfur compounds D1: Sulfurized oil (manufactured by DIC Corporation, DAILUBE GS-245, sulfur content: 16.3% by mass) D2: Sulfur ester (methyl oleate sulfide, sulfur content: 17.0% by mass) D3: Thiophosphate ester (triphenylphosphorothionate (TPPT), sulfur content: 9.0% by mass) D4: Thiobisphenol (BASF, IRGANOX L115, sulfur content: 5.0% by mass) (E) Phosphate ester E1: Tricresyl phosphate E2: A mixture of monooleyl phosphate and dioleyl phosphate in a mass ratio of 1:1.

[0094] [Metalworking oil composition] (Examples 1-4 and Comparative Example 1) Using the above-mentioned lubricating oil base oils and additives, metalworking oil compositions having the compositions shown in Tables 2 and 3 were prepared. In the tables, the values ​​for each lubricating oil base oil represent the content (mass%) relative to the total amount of lubricating oil base oil, and the values ​​for each additive and the sulfur content derived from the additives represent the content (mass%) relative to the total amount of the metalworking oil composition.

[0095] [Evaluation of metalworking fluid compositions] (Evaluation of skin sensitization) An Adjuvant and Patch Test (APT) was performed. First, as a primary sensitization treatment, an adjuvant was administered intradermally to the sensitization site. For the following four days, a small wound was made in the sensitization site with a needle each day, and the sensitizing substance (each metalworking oil composition from Examples 1-4 and Comparative Example 1) was applied. As a secondary sensitization treatment, the sensitizing substance was applied as an occlusive patch for 48 hours starting on the 8th day after the start of sensitization. On the 24th day after the start of sensitization (14 days after the completion of the secondary sensitization treatment), the inducing substance (each metalworking oil composition from Examples 1-4 and Comparative Example 1) was applied to the inducing site, and the skin condition at the application site was observed 24 hours later. The degree of erythema and edema formation was judged according to the criteria in Table 1 below.

[0096] [Table 1]

[0097] For each test substance, tests were conducted with n=5 triggers. In the sensitized group, the maximum skin reaction score was assigned to each individual based on the following formula. Similarly, the maximum skin reaction score shown in the non-sensitized group was assigned and used as the baseline score. Individuals showing a score higher than the baseline score were classified as sensitized positive animals. Score = (1) Score for erythema formation + (2) Score for edema formation

[0098] The percentage of sensitized animals (positive rate (%)) was calculated based on the following formula. The results are shown in Tables 2 and 3. Positive rate (%) = (number of sensitizing positive animals / number of attracting animals) × 100

[0099] (Measuring the flash point) The flash point was measured in accordance with JIS K2265-4:2007. The results are shown in Tables 2 and 3.

[0100] (Evaluation of metalworkability (machinability)) Tapping tests were conducted using each of the metalworking oil compositions from Examples 1-4 and Comparative Example 1, alternately with diisodecyl adipate, a comparative standard oil, under the conditions described below. When supplying the metalworking oil compositions to the workpiece, they were sprayed directly onto the workpiece at a rate of 6 L / hour. Tapping test conditions: Work material: JIS S25C (carbon mesh) Tool diameter: 8mm Tap pitch: 1.25mm Tap rake angle: 8 degrees Tap engagement angle: 60 degrees Tap pilot hole diameter: 6.8mm Rotation speed: 360 rpm Standard oil: Diisodecyl adipate

[0101] The tapping energy in the above test was measured, and the tapping energy efficiency (%) was calculated using the following formula. The results are shown in Tables 2 and 3. In the tables, a higher tapping energy efficiency indicates better metalworkability (cutting performance). Tapping energy efficiency (%) = (Tapping energy using comparative standard oil) / (Tapping energy using metalworking oil composition) × 100

[0102] [Table 2]

[0103] [Table 3]

[0104] As shown in Tables 2 and 3, the metalworking oil compositions of Examples 1 to 4, in which the iodine value of the lubricating oil base oil was 50 gI2 / 100 g or less, had a flash point of 250°C or higher and exhibited superior skin sensitization compared to the metalworking oil composition of Comparative Example 1. Furthermore, it was confirmed that the metalworking oil compositions of Examples 1 to 4 possessed sufficient metalworking properties. From these results, it was confirmed that the metalworking oil compositions according to the present invention have a sufficiently high flash point and can reduce skin sensitization.

Claims

1. A lubricating oil base oil comprising a first ester which is an ester of a saturated fatty acid monobasic acid and a polyhydric alcohol, and a second ester which is an ester of an unsaturated fatty acid monobasic acid and an alcohol, Sulfur compounds, It contains, The content of the first ester is 30% by mass or more, based on the total amount of lubricating oil base oil. The content of the second ester is 5% by mass or more, based on the total amount of lubricating oil base oil. The iodine value of the lubricating oil base oil is 50 gI ２ / 100g or less, A metalworking oil composition having a flash point of 250°C or higher.

2. The metalworking oil composition according to claim 1, wherein the total amount of the first ester and the second ester is 50 to 90% by mass, based on the total amount of the lubricating oil base oil.

3. The metalworking oil composition according to claim 1 or 2, wherein the content of the second ester is 5 to 60% by mass based on the total amount of lubricating oil base oil.

4. The metalworking oil composition according to claim 1 or 2, wherein the lubricating oil base oil further comprises at least one selected from the group consisting of mineral oil and synthetic oils other than esters.

5. The metalworking oil composition according to claim 1 or 2, wherein the sulfur compound is at least one selected from the group consisting of sulfur esters, sulfurized oils and fats, thiophosphate esters, and thiobisphenols.

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