JP7519351B2 - Metalworking Oil - Google Patents

Description

The present invention relates to metal processing oil.

Metalworking oils for plastic processing used when metal materials are subjected to processes such as pressing, drawing, ironing, bending, rolling, and cold forging are used under severe lubricating conditions, and therefore require lubrication properties such as seizure resistance.
For example, Patent Document 1 describes a lubricating oil composition for plastic working, such as press working and cold forging, which contains 5 to 99 mass % of a zinc dithiophosphate having a specific structure, 1 to 95 mass % of a metal salt of sulfonic acid, and 0 to 80 mass % of a base oil, for the purpose of providing a lubricating oil composition for plastic working, such as press working, cold forging, etc., which has excellent lubricity and can be used even under severe lubricating conditions.

JP 2013-173957 A

In this situation, new metalworking oils are needed.

（上記式中、Ｒ^１、Ｒ^２及びＲ^３は、それぞれ独立に、炭素数１０～４０のアルキル基であり、Ｒ^４は、炭素数１～１０のアルキル基である。）
［６］成分（Ｂ）の含有量が、前記金属加工油の全量基準で、０．１～５０質量％である、上記［１］～［５］のいずれか一項に記載の金属加工油。
［７］さらに硫黄系極圧剤（Ｃ）を含む、上記［１］～［６］のいずれか一項に記載の金属加工油。
［８］成分（Ｃ）の硫黄原子換算での含有量が、前記金属加工油の全量基準で、６．５質量％以上である、上記［１］～［７］のいずれか一項に記載の金属加工油。
［９］さらに、成分（Ｂ）には該当しない、脂肪酸及び脂肪酸エステルから選ばれる１種以上の化合物（Ｄ）を含む、上記［１］～［８］のいずれか一項に記載の金属加工油。
［１０］さらに流動点降下剤（Ｅ）を含む、上記［１］～［９］のいずれか一項に記載の金属加工油。
［１１］水の含有量が、前記金属加工油の全量基準で、１．０質量％未満である、上記［１］～［１０］のいずれか一項に記載の金属加工油。
［１２］金属材の冷間鍛造加工に適用する、上記［１］～［１１］のいずれか一項に記載の金属加工油。
［１３］上記［１］～［１２］のいずれか一項に記載の金属加工油を、金属材の冷間鍛造加工に用いる、金属加工油の使用。
［１４］上記［１］～［１２］のいずれか一項に記載の金属加工油を用いて、金属材の冷間鍛造加工を行う、金属加工方法。 The present invention provides a metalworking oil that contains a base oil and a compound that is liquid under normal pressure but undergoes a phase transition from liquid to solid upon increasing pressure.
That is, the present invention provides the following [1] to [14].
[1] A metal processing oil comprising: a base oil (A); and a compound (B) that is liquid under a pressure of 0.1 MPa but undergoes a phase transition from liquid to solid under an increase in pressure in the range of 0.1 MPa to 300 MPa.
[2] The metal working oil according to the above [1], wherein the metal working oil has a kinetic viscosity at 40°C of 100 mm ² /s or less.
[3] The metal working oil according to the above [1] or [2], wherein component (B) contains one or more of the phase-transition compounds selected from a carboxylic acid ester, a carboxylic acid, and an alcohol.
[4] The carboxylic acid ester is a saturated carboxylic acid ester,
the carboxylic acid is a saturated carboxylic acid,
The alcohol is a saturated alcohol.
The metal processing oil according to the above [3].
[5] The metal processing oil according to any one of the above [1] to [4], wherein component (B) contains the compound undergoing a phase transition represented by any one of the following general formulas (b-1) to (b-3).

(In the above formula, R ¹ , R ² and R ³ are each independently an alkyl group having 10 to 40 carbon atoms, and R ⁴ is an alkyl group having 1 to 10 carbon atoms.)
[6] The metal processing oil according to any one of the above [1] to [5], wherein the content of component (B) is 0.1 to 50 mass% based on the total amount of the metal processing oil.
[7] The metal processing oil according to any one of the above [1] to [6], further comprising a sulfur-based extreme pressure agent (C).
[8] The metal working oil according to any one of the above [1] to [7], wherein the content of component (C) in terms of sulfur atoms is 6.5 mass% or more based on the total amount of the metal working oil.
[9] The metal processing oil according to any one of the above [1] to [8], further comprising one or more compounds (D) selected from fatty acids and fatty acid esters, which do not fall under the category of component (B).
[10] The metal processing oil according to any one of the above [1] to [9], further comprising a pour point depressant (E).
[11] The metal processing oil according to any one of the above [1] to [10], wherein the water content is less than 1.0 mass% based on the total amount of the metal processing oil.
[12] The metal processing oil according to any one of the above [1] to [11], which is applied to cold forging of metal materials.
[13] Use of the metalworking oil according to any one of the above [1] to [12] for cold forging of a metal material.
[14] A metalworking method comprising cold forging a metal material using the metalworking oil according to any one of [1] to [12] above.

A preferred embodiment of the metalworking oil of the present invention has excellent workability for metal materials, and a more preferred embodiment of the metalworking oil has an excellent balance of low viscosity and seizure resistance, and can be particularly suitably used for cold forging of metal materials.

FIG. 1 is a schematic diagram of a high-pressure test apparatus for confirming phase transition behavior.

The upper and lower limit values of the numerical ranges described in this specification can be arbitrarily combined. For example, when the numerical range is described as "preferably 30 to 100, more preferably 40 to 80", the ranges "30 to 80" and "40 to 100" are also included in the numerical ranges described in this specification. In addition, when the numerical range is described as "preferably 30 or more, more preferably 40 or more, and preferably 100 or less, more preferably 80 or less", the ranges "30 to 80" and "40 to 100" are also included in the numerical ranges described in this specification.
In addition, as for a numerical range described in this specification, for example, "60 to 100" means a range of "60 or more and 100 or less."

[Composition of metalworking oil]
Conventional metal processing oils for plastic working have been adjusted to have a high viscosity, for example, a kinetic viscosity of more than 100 ^mm2 /s at 40°C, to suppress seizure on metal materials. However, such high-viscosity metal processing oils have poor handleability, making it difficult to supply the oil to metal materials. In addition, when high-viscosity metal processing oils are used in low-temperature environments, the viscosity increases, reducing the fluidity, and in some cases, the oil may solidify when processing metal materials.
On the other hand, low-viscosity metal processing oils can suppress the above problems, but they have the problem of being prone to seizure on metal materials. In particular, when used in cold forging, the frequency of seizure on metal materials increases.

In order to solve such problems, the metal processing oil of the present invention is prepared to contain a base oil (A) and a compound (B) (hereinafter also referred to as a "phase transition compound") that is liquid under a pressure of 0.1 MPa but undergoes a phase transition from liquid to solid when the pressure is increased in the range of 0.1 MPa to 300 MPa.
The phase transition compound used as component (B) is liquid under normal pressure (under a pressure of 0.1 MPa), and therefore the metalworking oil can maintain good handleability. Even when a high-viscosity base oil is used as base oil (A), the phase transition compound of component (B) is liquid under normal pressure, and therefore the metalworking oil can be made to have good handleability by containing the phase transition compound.
It is believed that the phase transition compound used as component (B) solidifies on the surface of the metal material being processed when high pressure is applied during plastic processing, forming a strong oil film, and the metal processing oil of the present invention can effectively suppress the occurrence of seizure on the metal material.
Therefore, the metal working oil of one embodiment of the present invention has an excellent balance between low viscosity and seizure resistance, and can be used particularly favorably in cold forging of metal materials.

The kinetic viscosity at 40°C of the metal processing oil of one embodiment of the present invention is preferably 100 mm ² /s or less, more preferably 90 mm ² /s or less, even more preferably 80 mm ² /s or less, and even more preferably 70 mm ² /s or less, from the viewpoint of providing a metal processing oil with good handleability, and is preferably 10 mm ² /s or more, more preferably 20 mm ² /s or more, even more preferably 30 mm ² /s or more, and even more preferably 40 mm ² /s or more, from the viewpoint of maintaining a strong oil film and reducing evaporation loss.

From the same viewpoint as above, the kinematic viscosity at 100°C of one embodiment of the metal processing oil of the present invention is preferably 12.0 ^mm2 /s or less, more preferably 11.0 ^mm2 /s or less, even more preferably 10.0 ^mm2 /s or less, still more preferably 9.0 ^mm2 /s or less, and preferably 2.0 ^mm2 /s or more, more preferably 3.0 ^mm2 /s or more, even more preferably 4.0 ^mm2 /s or more, and still more preferably 4.5 ^mm2 /s or more.

The viscosity index of the metal working oil of one embodiment of the present invention is preferably 60 or more, more preferably 70 or more, even more preferably 80 or more, and still more preferably 85 or more.
In this specification, the kinematic viscosity and viscosity index refer to values measured and calculated in accordance with JIS K2283:2000.

The metal working oil of one embodiment of the present invention preferably further contains at least one selected from a sulfur-based extreme pressure agent (C), one or more compounds (D) selected from fatty acids and fatty acid esters not corresponding to component (B), and a pour point depressant (E), more preferably contains two or more selected from components (C), (D) and (E), and even more preferably contains all of components (C), (D) and (E).
Furthermore, the metal working oil of one embodiment of the present invention may contain components other than the above components (A) to (E) to the extent that the effects of the present invention are not impaired.

In addition, in one embodiment of the metal processing oil of the present invention, the total content of components (A) and (B) is preferably 25 to 100 mass%, more preferably 35 to 100 mass%, even more preferably 45 to 100 mass%, still more preferably 55 to 100 mass%, and particularly preferably 60 to 100 mass%, based on the total amount (100 mass%) of the metal processing oil.

In the metal processing oil of one embodiment of the present invention, the total content of the components (A), (B), (C), (D) and (E) is preferably 50 to 100 mass%, more preferably 60 to 100 mass%, even more preferably 70 to 100 mass%, still more preferably 80 to 100 mass%, and particularly preferably 90 to 100 mass%, based on the total amount (100 mass%) of the metal processing oil.
Hereinafter, each component contained in the metal processing oil according to one embodiment of the present invention will be described in detail.

<Component (A): Base oil>
The base oil (A) used in one embodiment of the present invention may be one or more selected from mineral oils and synthetic oils.
Examples of mineral oils include atmospheric residual oils obtained by atmospheric distillation of crude oils such as paraffinic crude oil, intermediate base crude oil, and naphthenic crude oil; and distillate oils obtained by vacuum distillation of these atmospheric residual oils. refined oils obtained by subjecting the distillate oil to one or more refining treatments such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining; and the like.

Examples of synthetic oils include poly-α-olefins such as α-olefin homopolymers or α-olefin copolymers (e.g., α-olefin copolymers having 8 to 14 carbon atoms, such as ethylene-α-olefin copolymers); isoparaffins; polyalkylene glycols; ester-based oils such as polyol esters, dibasic acid esters, and phosphate esters; ether-based oils such as polyphenyl ether; alkylbenzenes; alkylnaphthalenes; and synthetic oils (GTL) obtained by isomerizing wax produced from natural gas by the Fischer-Tropsch process or the like (GTL wax (Gas To Liquids WAX)).

From the viewpoint of obtaining a metal processing oil with further improved seizure resistance, the kinematic viscosity at 40°C of the base oil (A) used in one embodiment of the present invention is preferably 10 mm ² /s or more, more preferably 20 mm ² /s or more, more preferably 30 mm ² /s or more, more preferably 40 mm ² /s or more, even more preferably 100 mm ² /s or more, even more preferably 200 mm ² /s or more, still more preferably 300 mm ² /s or more, still more preferably 350 mm ² /s or more, and particularly preferably 400 mm ² /s or more.
In addition, even if the metal processing oil of the present invention uses as base oil (A) a base oil having a kinetic viscosity of 100 ^mm2 /s or more at 40°C, since it contains a phase transition compound of component (B) that is liquid under normal pressure (under a pressure of 0.1 MPa), the kinetic viscosity of the resulting metal processing oil can be appropriately adjusted, and a metal processing oil with good handleability can be obtained.
On the other hand, the kinematic viscosity at 40°C of the base oil (A) used in one embodiment of the present invention is preferably ¹⁰⁰⁰ mm2/s or less, more preferably 900 ^mm2 /s or less, even more preferably 800 ^mm2 /s or less, still more preferably 700 ^mm2 /s or less, and particularly preferably 600 ^mm2 /s or less.

From the same viewpoints as above, the kinematic viscosity at 100°C of the base oil (A) used in one embodiment of the present invention is preferably 2.0 ^mm2 /s or more, more preferably 3.0 ^mm2 /s or more, more preferably 4.0 ^mm2 /s or more, more preferably 4.5 ^mm2 /s or more, even more preferably 7.0 ^mm2 /s or more, even more preferably 10.0 ^mm2 /s or more, still more preferably 12.5 ^mm2 /s or more, particularly preferably 15.0 ^mm2 /s or more, and preferably 40.0 ^mm2 /s or less, more preferably 35.0 ^mm2 /s or less, even more preferably 30.0 ^mm2 /s or less, still more preferably 27.0 ^mm2 /s or less, particularly preferably 25.0 ^mm2 /s or less.

The viscosity index of the base oil (A) used in one embodiment of the present invention is preferably 2 or more, more preferably 5 or more, even more preferably 10 or more, still more preferably 20 or more, and particularly preferably 30 or more.
In one embodiment of the present invention, when a mixed oil of two or more base oils is used as the base oil (A), the kinematic viscosity and viscosity index of the mixed oil are preferably within the above-mentioned ranges.

In one embodiment of the metal processing oil of the present invention, the content of component (A) is preferably 20 to 99.9 mass%, more preferably 30 to 95 mass%, even more preferably 35 to 90 mass%, still more preferably 40 to 80 mass%, and particularly preferably 45 to 70 mass%, based on the total amount (100 mass%) of the metal processing oil.

<Component (B): Phase transition compound>
The metal working oil of the present invention contains a compound (B) that undergoes a phase transition from liquid to solid under an elevated pressure in the range of 0.1 MPa to 300 MPa.
Component (B) is liquid under normal pressure (0.1 MPa), but undergoes a phase transition to a solid when pressure is increased to 300 MPa. Therefore, when pressure is increased during plastic processing, component (B) contained in the metal processing oil solidifies on the surface of the metal material to be processed, forming a strong oil film. As a result, the metal processing oil of the present invention is believed to be able to effectively exhibit excellent seizure resistance during plastic processing.
In this specification, whether or not a compound corresponds to the "phase transition compound" of component (B) can be confirmed by using, for example, a high-pressure test apparatus for confirming phase transition behavior as shown in Fig. 1. A specific confirmation method can be based on the method described in the Examples below.

Component (B) used in one embodiment of the metal processing oil of the present invention may be any compound that undergoes a phase transition from liquid to solid under a pressure increase in the range of 0.1 MPa to 300 MPa, but it is preferable that the component (B) contains one or more of the phase-transition compounds selected from carboxylic acid esters, carboxylic acids, and alcohols.

In one embodiment of the metal processing oil of the present invention, the content of the phase-transition compound selected from carboxylic acid esters, carboxylic acids, and alcohols is preferably 60 to 100 mass%, more preferably 70 to 100 mass%, even more preferably 80 to 100 mass, still more preferably 90 to 100 mass%, and particularly preferably 95 to 100 mass%, relative to the total amount (100 mass%) of component (B) contained in the metal processing oil.

The phase transition tends to occur more easily in saturated compounds than in unsaturated compounds.
Therefore, it is preferable that the carboxylate ester is a saturated carboxylate ester, the carboxylic acid is a saturated carboxylic acid, and the alcohol is a saturated alcohol.

From the viewpoint of the ease with which the phase transition occurs, component (B) preferably contains a compound having an alkyl group having 10 to 40 carbon atoms, and more preferably contains a compound having an alkyl group having 10 to 40 carbon atoms selected from saturated carboxylate esters, saturated carboxylic acids, and saturated alcohols.
In other words, it is more preferable that the component (B) used in the metal working oil of one embodiment of the present invention contains a compound that undergoes a phase transition and is represented by any one of the following general formulas (b-1) to (b-3).

In the above formula, R ¹ , R ² and R ³ are each independently an alkyl group having 10 to 40 carbon atoms, and R ⁴ is an alkyl group having 1 to 10 carbon atoms.

The alkyl group that can be selected as R ¹ , R ² and R ³ may be a linear alkyl group or a branched alkyl group, but is preferably a linear alkyl group from the viewpoint of ease of occurrence of the phase transition.
The number of carbon atoms of the alkyl group that can be selected as R ¹ , R ² and R ³ is preferably 9 to 39, more preferably 9 to 29, even more preferably 10 to 23, and still more preferably 11 to 19, from the viewpoint of the ease with which the phase transition occurs.

Specific examples of R ¹ , R ² and R ³ include a decyl group, an undecyl group, a dodecyl group (a lauryl group), a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group (a stearyl group), an icosyl group, and a tetracosyl group.
Among these, from the viewpoint of the ease with which the phase transition occurs, R ¹ , R ² and R ³ are each independently preferably an undecyl group, a dodecyl group (lauryl group), a tridecyl group, a tetradecyl group, a hexadecyl group, a heptadecyl group, or an octadecyl group (stearyl group), and more preferably a heptadecyl group.

The alkyl group that can be selected as ^R4 may be a linear alkyl group or a branched alkyl group, but is preferably a linear alkyl group from the viewpoint of ease of occurrence of the phase transition.
The number of carbon atoms in the alkyl group that can be selected as ^R4 is 1 to 10, more preferably 1 to 6, even more preferably 1 to 4, still more preferably 1 to 2, and particularly preferably 1, from the viewpoint of the ease with which the phase transition occurs.

Specific examples of ^R4 include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an s-butyl group, a t-butyl group, an isobutyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a 2-ethylhexyl group, a nonyl group, and a decyl group.
Among these, from the viewpoint of the ease with which the phase transition occurs, R ⁴ is preferably a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, or an n-octyl group, more preferably a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, or an n-hexyl group, even more preferably a methyl group, an ethyl group, an n-propyl group, or an n-butyl group, even more preferably a methyl group or an ethyl group, and particularly preferably a methyl group.

In one embodiment of the metal processing oil of the present invention, the content of the compound undergoing a phase transition represented by any one of the general formulas (b-1) to (b-3) is preferably 60 to 100 mass%, more preferably 70 to 100 mass%, even more preferably 80 to 100 mass, still more preferably 90 to 100 mass%, and particularly preferably 95 to 100 mass%, relative to the total amount (100 mass%) of component (B) contained in the metal processing oil.

Moreover, the melting point of component (B) used in the metal processing oil of one embodiment of the present invention is, from the viewpoint of the ease with which the phase transition occurs, preferably 10 to 70°C, more preferably 14 to 60°C, even more preferably 17 to 55°C, and still more preferably 25 to 50°C.
In this specification, the melting point is a value measured using a differential scanning calorimeter (DSC), and specifically, is measured by the following method.
[Method of measuring melting point using a differential scanning calorimeter]
The sample is held at -10°C for 5 minutes in a nitrogen atmosphere, then heated to 190°C at 10°C/min and held at 190°C for 5 minutes. The temperature is then lowered to -10°C at 5°C/min and held at -10°C for 5 minutes. The peak observed in the melting endothermic curve obtained by subsequently raising the temperature to 190°C at 10°C/min is taken as the melting point (Tm).

In one embodiment of the metal processing oil of the present invention, the content of component (B) is preferably 0.1 to 50 mass%, more preferably 1.0 to 40 mass%, even more preferably 3.0 to 35 mass%, still more preferably 5.0 to 30 mass%, and particularly preferably 7.5 to 25 mass%, based on the total amount (100 mass%) of the metal processing oil.

<Component (C): Sulfur-based extreme pressure agent>
From the viewpoint of providing a metal working oil having improved anti-seizure properties, the metal working oil of one embodiment of the present invention preferably further contains a sulfur-based extreme pressure agent (C).
Examples of the sulfur-based extreme pressure agent (C) used in one embodiment of the present invention include sulfurized olefins, polysulfides, sulfurized esters, thiazoles, thiadiazoles, zinc dithiophosphates, molybdenum dithiophosphates, molybdenum dithiocarbamates, and powdered sulfur.
These sulfur-based extreme pressure agents (C) may be used alone or in combination of two or more kinds.
Among these, the sulfur-based extreme pressure agent (C) preferably contains a polysulfide.

The sulfur chain length of the polysulfide used in one embodiment of the present invention is preferably 2 or more, more preferably 3 or more, further preferably 5 or more, and is preferably 10 or less.
Specific examples of polysulfides include dimethyl trisulfide, diethoxy disulfide, ethyl hydrodisulfide, diacetyl disulfide, and di-t-dodecyl trisulfide.

In one embodiment of the metal processing oil of the present invention, the content of component (C) is preferably 7 to 50 mass%, more preferably 10 to 45 mass%, even more preferably 12 to 40 mass%, still more preferably 15 to 35 mass%, and particularly preferably 17 to 35 mass%, based on the total amount (100 mass%) of the metal processing oil, from the viewpoint of providing a metal processing oil with improved seizure resistance and from the viewpoint of avoiding deterioration of the working environment due to odor generation, etc.

In the metal working oil of one embodiment of the present invention, the content of component (C) in terms of sulfur atoms is, from the above viewpoints, preferably 6.5 to 30 mass%, more preferably 7.0 to 20 mass%, even more preferably 7.5 to 17 mass%, still more preferably 8.0 to 15 mass%, and particularly preferably 8.5 to 12 mass%, based on the total amount (100 mass%) of the metal working oil.
In this specification, the content of sulfur atoms means a value measured in accordance with JIS K2541-6:2013.

<Component (D): Fatty Acids and Fatty Acid Esters>
From the viewpoint of providing a metal working oil with improved lubricity, the metal working oil of one embodiment of the present invention preferably contains one or more compounds (D) selected from fatty acids and fatty acid esters which do not fall under component (B).
In this specification, fatty acids and fatty acid esters that undergo a phase transition from liquid to solid under a pressure increase in the range of 0.1 MPa to 300 MPa are included in the above-mentioned component (B). In other words, component (D) refers to fatty acids and fatty acid esters that do not fall under the category of phase transition compounds.

In one embodiment of the present invention, examples of the fatty acid used as component (D) include saturated aliphatic monocarboxylic acids, unsaturated aliphatic monocarboxylic acids, saturated aliphatic dicarboxylic acids, and unsaturated aliphatic dicarboxylic acids.
These fatty acids may be used alone or in combination of two or more kinds.
The number of carbon atoms in these fatty acids is preferably 10 to 30, more preferably 12 to 24, and even more preferably 14 to 20.

Among these, in one embodiment of the present invention, the fatty acid used as component (D) preferably contains an unsaturated aliphatic monocarboxylic acid, from the viewpoint of providing a metal processing oil with improved lubricity in combination with component (B).
Examples of the unsaturated aliphatic monocarboxylic acid include undecylenic acid, dodecenoic acid, oleic acid, elaidic acid, erucic acid, nervonic acid, linoleic acid, γ-linolenic acid, arachidonic acid, α-linolenic acid, stearidonic acid, eicosapentaenoic acid, and docosahexaenoic acid, with oleic acid being preferred.
The unsaturated aliphatic monocarboxylic acid may be a hydroxy unsaturated fatty acid such as ricinoleic acid (12-hydroxyoctadec-9-enoic acid).

In one embodiment of the present invention, the fatty acid ester used as component (D) includes an ester of a polyhydric alcohol and a fatty acid.
The number of ester bonds in the molecule of the fatty acid ester is preferably 2 to 6.
The fatty acid ester may be a complete ester or an incomplete ester, but is preferably a complete ester.

Examples of the polyhydric alcohol constituting the fatty acid ester include ethylene glycol, 1,3-propanediol, propylene glycol, 1,4-butanediol, 1,2-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 2-ethyl-2-methyl-1,3-propanediol, 1,7-heptanediol, 2-methyl-2-propyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, and 1,12-dodeca. trimethylolethane, trimethylolpropane, trimethylolbutane, ditrimethylolpropane, tri-(trimethylolpropane), pentaerythritol, dipentaerythritol, tripentaerythritol, glycerin, polyglycerin (glycerin dimer to trimer), 1,3,5-pentanetriol, sorbitol, sorbitan, sorbitol glycerin condensate, adonitol, arabitol, xylitol, mannitol, and other trivalent or higher alcohols; xylose, arabinose, ribose, rhamnose, glucose, fructose, galactose, mannose, sorbose, cellobiose, and the like.
These polyhydric alcohols may be used alone or in combination of two or more kinds.

On the other hand, examples of the fatty acid constituting the fatty acid ester include saturated aliphatic monocarboxylic acids, unsaturated aliphatic monocarboxylic acids, saturated aliphatic dicarboxylic acids, and unsaturated aliphatic dicarboxylic acids, and one or more selected from saturated aliphatic monocarboxylic acids and unsaturated aliphatic monocarboxylic acids are preferred.
Examples of saturated aliphatic monocarboxylic acids include caproic acid, enanthic acid, caprylic acid, 2-ethylhexanoic acid, pelargonic acid, isononanoic acid, capric acid, neodecanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, and lignoceric acid.
The unsaturated aliphatic monocarboxylic acid may be the same as the "fatty acid" that may be selected as component (D) described above.

In one embodiment of the metal processing oil of the present invention, the content of component (D) is preferably 0.1 to 30 mass%, more preferably 0.5 to 25 mass%, even more preferably 1.0 to 20 mass%, still more preferably 1.5 to 15 mass%, and particularly preferably 2.0 to 10 mass%, based on the total amount (100 mass%) of the metal processing oil, from the viewpoint of providing a metal processing oil with improved lubricity.

In addition, in one embodiment of the metal processing oil of the present invention, the content of component (D) relative to 100 parts by mass of the total amount of component (B) is, from the same viewpoint as above, preferably 1 to 200 parts by mass, more preferably 5 to 150 parts by mass, even more preferably 10 to 100 parts by mass, still more preferably 15 to 70 parts by mass, and particularly preferably 20 to 50 parts by mass.

<Component (E): Pour Point Depressant>
The metal working oil of one embodiment of the present invention preferably contains a pour point depressant (E) from the viewpoint of providing a metal working oil with good low-temperature fluidity.
In the metal working oil according to one embodiment of the present invention, even if the pour point depressant (E) is contained, the anti-seizure property can be well maintained.

Examples of the component (E) used in one embodiment of the present invention include ethylene-vinyl acetate copolymers, condensates of chlorinated paraffin and naphthalene, condensates of chlorinated paraffin and phenol, polymethacrylates, and polyalkylstyrenes.
These components (E) may be used alone or in combination of two or more.
Of these, it is preferable that component (E) contains at least one selected from ethylene-vinyl acetate copolymers and polymethacrylates.
The mass average molecular weight (Mw) of these components (E) is usually 50,000 to 150,000.

In one embodiment of the metal processing oil of the present invention, the content of component (E) is preferably 0.001 to 7.0 mass%, more preferably 0.01 to 5.0 mass%, even more preferably 0.1 to 3.0 mass%, and even more preferably 0.3 to 2.0 mass%, based on the total amount (100 mass%) of the metal processing oil, from the viewpoint of providing a metal processing oil that has good low-temperature fluidity and can maintain good seizure resistance.

<Other Ingredients>
The metal processing oil of one embodiment of the present invention may further contain other components in addition to the above components (A) to (E) as necessary, within the range that does not impair the effects of the present invention.
Examples of such other components include antioxidants, extreme pressure agents other than component (C), oiliness improvers other than component (D), degreasers, and antifoaming agents.

Examples of the antioxidant include amine-based antioxidants such as alkylated diphenylamine, phenylnaphthylamine, and alkylated phenylnaphthylamine; and phenol-based antioxidants such as 2,6-di-t-butylphenol, 4,4'-methylenebis(2,6-di-t-butylphenol), isooctyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, and n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate.
In the metal working oil of one embodiment of the present invention, the content of the antioxidant is preferably 0.01 to 10 mass %, more preferably 0.05 to 5 mass %, and even more preferably 0.1 to 2 mass %, based on the total amount (100 mass %) of the metal working oil.

Examples of extreme pressure agents other than component (C) include phosphate esters (tricresyl phosphate, trioleyl phosphate, etc.), acid phosphate esters (monooleyl acid phosphate, dioleyl acid phosphate, etc.), acid phosphate amine salts (oleylamine salt of monooleyl acid phosphate, etc.), phosphites (dioleyl acid phosphite, tridecyl phosphite, trisnonylphenyl sulfite, etc.), oils and fats (beef tallow, lard, soybean oil, rapeseed oil, rice bran oil, coconut oil, palm oil, etc.), and the like.
In the metal working oil of one embodiment of the present invention, the content of the extreme pressure agent other than component (C) is preferably 0.01 to 10 mass%, more preferably 0.05 to 5 mass%, and even more preferably 0.1 to 3 mass%, based on the total amount (100 mass%) of the metal working oil.

Examples of oiliness improvers other than component (D) include polymers of polymerized fatty acids such as dimer acid and hydrogenated dimer acid; aliphatic saturated or unsaturated monoalcohols such as lauryl alcohol and oleyl alcohol; aliphatic saturated or unsaturated monoamines such as stearylamine and oleylamine; aliphatic saturated or unsaturated monocarboxylic acid amides such as lauric acid amide and oleic acid amide; and the like.
In the metal working oil of one embodiment of the present invention, the content of the oiliness improver other than component (D) is preferably 0.01 to 10 mass %, more preferably 0.05 to 5 mass %, and even more preferably 0.1 to 3 mass %, based on the total amount (100 mass %) of the metal working oil.

The degreasing agent may, for example, be alkenylsulfosuccinic acid.
In the metal processing oil of one embodiment of the present invention, the content of the degreaser is preferably 0.001 to 5 mass % based on the total amount (100 mass %) of the metal processing oil.

Examples of the antifoaming agent include methyl silicone oil, fluorosilicone oil, polyacrylate, and the like.
In the metal processing oil of one embodiment of the present invention, the content of the antifoaming agent is preferably 0.0001 to 2 mass %, more preferably 0.001 to 1 mass %, based on the total amount (100 mass %) of the metal processing oil.

<Metalworking oil manufacturing method>
The method for producing a metal processing oil according to one embodiment of the present invention is not particularly limited, and is preferably a method having a step of blending components (A) to (B) and, if necessary, components (C) to (E) and other components. The order of blending the components can be appropriately set.

<Various properties of metalworking oil>
In the metal processing oil of one embodiment of the present invention, the content of sulfur atoms, based on the total amount (100 mass%) of the metal processing oil, is preferably 6.5 mass% or more, more preferably 7.0 mass% or more, even more preferably 7.5 mass% or more, still more preferably 8.0 mass% or more, and particularly preferably 8.5 mass% or more, from the viewpoint of obtaining a metal processing oil with further improved anti-seizure properties, and is preferably 30 mass% or less, more preferably 20 mass% or less, even more preferably 17 mass% or less, still more preferably 15 mass% or less, and particularly preferably 12 mass% or less, from the viewpoint of avoiding deterioration of the working environment due to the generation of odors, etc.

The metalworking oil of one embodiment of the present invention is preferably used as is, and in this respect is distinguished from water-soluble metalworking oils which are used after being diluted with water.
Therefore, in the metal processing oil of one embodiment of the present invention, the water content is preferably as low as possible from the viewpoints of stability and suppressing corrosion of the metal material to be processed. Specifically, the water content is preferably less than 1.0 mass%, more preferably less than 0.1 mass%, even more preferably less than 0.01 mass%, and even more preferably less than 0.001 mass%, based on the total amount (100 mass%) of the metal processing oil.

In one embodiment of the metal processing oil of the present invention, the maximum area reduction rate in a ball-passing test conducted based on the method of the examples described below is preferably 5% or more, more preferably 6% or more, and even more preferably 8% or more.

[Metalworking oil applications and metalworking methods]
The metal working oil according to a preferred embodiment of the present invention has an excellent balance between low viscosity and anti-seizure property, and is therefore suitable for the plastic working of metal materials.
The metal material to be processed using the metal processing oil of one embodiment of the present invention is not particularly limited, and examples thereof include ferrous alloys such as steel, stainless steel, alloy steel, and surface-treated steel, and non-ferrous alloys such as aluminum alloys, copper, titanium, titanium alloys, nickel-based alloys, niobium alloys, tantalum alloys, molybdenum alloys, and tungsten alloys.

The metal processing oil of one embodiment of the present invention can be suitably used in the press processing, drawing, ironing, bending, rolling, and cold forging of the above-mentioned metal materials, and is particularly preferably used in the cold forging of metal materials.

Therefore, the present invention also provides the following aspects.
[1] Use of the metalworking oil according to one embodiment of the present invention in cold forging of metal materials.
[2] A metalworking method comprising cold forging a metal material using the metalworking oil according to one embodiment of the present invention.

The details of the metal material and the metal processing oil described in [1] and [2] above are as described above.
In the above-mentioned use [1] and the above-mentioned metalworking method [2], the metalworking oil is used by contacting it with the metal material to be worked.

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The methods for measuring various physical properties and the method for confirming the presence or absence of a phase transition from liquid to solid under increased pressure are as follows.

(1) Kinematic Viscosity and Viscosity Index Measured and calculated in accordance with JIS K2283:2000.
(2) Sulfur atom content: Measured in accordance with JIS K2541-6:2013.
(3) Melting point: The melting point was measured by the following method using a differential scanning calorimeter (DSC).
The sample was held at -10°C for 5 minutes under a nitrogen atmosphere, then heated to 190°C at 10°C/min and held at 190°C for 5 minutes. The temperature was then lowered to -10°C at 5°C/min and held at -10°C for 5 minutes. The peak observed in the melting endothermic curve obtained by subsequently raising the temperature to 190°C at 10°C/min was taken as the melting point (Tm).
(4) Pour point: Measured in accordance with JIS K2269.
(5) Confirmation of the Presence or Absence of a Phase Transition from Liquid to Solid Under Increased Pressure Using a high-pressure testing device for confirming phase transition behavior as shown in FIG. 1, confirmation was made of the presence or absence of a phase transition from liquid to solid under increased pressure of the target components.
The high-pressure test apparatus 1 for confirming phase transition behavior shown in Fig. 1 has two observation windows 11, 12 on the side of a cylindrical space 10 in which a compound to be measured is placed, facing each other in a horizontal line, and an LED light source 20 is installed outside the space 10 of one observation window 11, and an optical microscope 30 is installed outside the cylindrical space 10 of the other observation window 12. The LED light source 20, the observation windows 11, 12, and the optical microscope 30 are installed in a line so as to be parallel to the horizontal direction. In addition, a plunger 40 movable in the vertical direction is provided above the cylindrical space 10, and is designed so that pressure can be applied to the compound to be measured placed in the cylindrical space 10 by applying a load in the vertical direction.
Using such a high-pressure test apparatus 1 for confirming phase transition behavior, a compound to be measured was first placed in the cylindrical space 10. Then, at 30° C., the plunger 40 was lowered and the compound was observed with the optical microscope 30, and a video of the state of the compound as pressure was applied to the compound was taken. From the video, the pressure at which the compound started to change from a liquid to a solid was determined as the "phase transition pressure (MPa)," and the presence or absence of a phase transition was confirmed.

Examples 1 to 4, Comparative Examples 1 to 6
Components (A) to (D) and a pour point depressant were blended in the types and amounts shown in Table 1 to prepare metal processing oils.
The details of each component used in preparing these metalworking oils are as follows:
[Component (A): Base oil]
Naphthenic base oil (a-1): a naphthenic base oil having a kinetic viscosity at 40° C. of 484.7 mm ² /s and a viscosity index of 36.
Naphthenic base oil (a-2): a naphthenic base oil having a kinetic viscosity at 40° C. of 27.77 mm ² /s and a viscosity index of 2.
Naphthenic base oil (a-3): a naphthenic base oil having a kinetic viscosity at 40° C. of 45.40 mm ² /s and a viscosity index of 27.
[Component (B): Phase transition compound]
Methyl stearate: a compound represented by the general formula (b-1) in which R ¹ is a C17 alkyl group and R ⁴ is a methyl group. A phase transition compound that is liquid at 0.1 MPa, but has been confirmed to undergo a phase transition from liquid to solid at a phase transition pressure of 75 MPa. Melting point: 37 to 41°C.
Butyl stearate: a compound in which R ¹ is a C17 alkyl group and R ⁴ is an n-butyl group in the general formula (b-1). A phase transition compound that is liquid at 0.1 MPa, but has been confirmed to undergo a phase transition from liquid to solid at a phase transition pressure of 160 MPa. Melting point: 17 to 22°C.
[Component (C): Sulfur-based extreme pressure agent]
Powdered sulfur polysulfide: A polysulfide with an average sulfur chain length of 5.
[Component (D): Fatty acids and fatty acid esters not corresponding to phase transition compounds]
・Oleic acid: A component that is liquid under pressure of 0.1 to 300 MPa and does not undergo phase transition. Melting point = 13.4°C.
Dipentaerythritol ester: A component that is liquid under pressure of 0.1 to 300 MPa and no phase transition has been confirmed. Pour point: 2.5°C.
Triglyceride: A component that is liquid under a pressure of 0.1 to 300 MPa and no phase transition has been confirmed. Pour point: 7.5°C.
[Component (E): Pour Point Depressant]
・Polymethacrylate

The kinematic viscosity, viscosity index, and sulfur atom content of the prepared metalworking oil at 40°C and 100°C were measured or calculated, and a ball-passing test was performed according to the procedure described below to evaluate the seizure resistance. The results are shown in Table 1.

[Ball passing test]
A ball passing test was carried out in accordance with the method described in "Plasticity and Processing," Journal of the Japan Society for Engineering Plasticity, Vol. 34 (No. 393), pp. 1178-1183 (1993).
First, the metalworking oil prepared in the Examples and Comparative Examples was applied to the inside of a cylindrical test piece, and a steel ball was forced into the tube from one end, and the condition of seizure on the inner wall of the test piece was observed. The inner diameter of the test piece tube was adjusted so that the reduction in area (the area changed after insertion, with the initial area taken as the reference in the direction in which the steel ball is inserted into the test piece) was 4%, 6%, and 8%.
Then, a ball-passing test was performed using test pieces with surface area reduction rates of 4%, 6%, and 8%, respectively, and the state of seizure in the tube after the test was observed and compared with a standard seizure sample to confirm the presence or absence of seizure. Note that, among the test pieces in which seizure was confirmed when using each metalworking oil, the one with the smallest surface area reduction rate was determined as the "maximum surface area reduction rate in the ball-passing test" for that metalworking oil. The larger the maximum surface area reduction rate, the more excellent the metalworking oil's seizure resistance.
The conditions for the ball passing test are as follows:
・Test piece: outer diameter = 30.00 mm, inner diameter = 15.00 mm (area reduction rate 4%), 14.50 mm (area reduction rate 6%), 15.00 mm (area reduction rate 8%), material = S10C
・Steel ball: Outer diameter = 15.88 mm (area reduction rate 4% or 6%), 16.67 mm (area reduction rate 8% or 10%), material = SUJ2
Speed at which the steel ball is pushed into the mouth of the test piece = 200 mm/s

As can be seen from Table 1, the metalworking oils prepared in Examples 1 to 4 had low viscosities, but the maximum area reduction rate in the ball threading test was high at 6% or more, resulting in excellent seizure resistance. In addition, the metalworking oils of Examples 3 and 4 contain a pour point depressant, but it can be seen that they can maintain good seizure resistance compared to Examples 1 and 2.
On the other hand, the metal processing oils prepared in Comparative Examples 1 to 6 were inferior in at least one of low viscosity and anti-seizure properties.

1 High pressure test device for confirming phase transition behavior 10 Cylindrical space 11, 12 Observation window 20 LED light source 30 Optical microscope 40 Plunger

Claims (15)

A base oil (A) having a kinematic viscosity at 40°C of 200 ^mm2 /s or more;
A metal processing oil comprising: a compound (B) which is liquid at 30°C under a pressure of 0.1 MPa, but undergoes a phase transition from liquid to solid under an increase in pressure in the range of 0.1 MPa to 300 MPa;
The metal processing oil has a kinetic viscosity at 40°C of ¹⁰⁰ mm2/s or less;
A metal processing oil, wherein component (B) is a compound represented by the following general formula (b-1) or (b-3):

(In the above formula, ^R1 and ^R3 are each independently an alkyl group having 10 to 40 carbon atoms, and ^R4 is an alkyl group having 1 to 10 carbon atoms.) The metal working oil according to claim 1, wherein the metal working oil has a kinetic viscosity at 40°C of 40 mm ² /s or more and 100 mm ² /s or less. The metal working oil according to claim 1 or 2, wherein the component (A) has a kinetic viscosity at 40°C of 200 mm ² /s or more and 1000 mm ² /s or less. The metal processing oil according to any one of claims 1 to 3, wherein the content of component (A) is 20 to 99.9 mass% based on the total amount of the metal processing oil. The metal processing oil according to any one of claims 1 to 4, wherein the total content of components (A) and (B) is 25 to 100 mass% based on the total amount of the metal processing oil. The metalworking oil according to any one of claims 1 to 5, wherein the content of component (B) is 0.1 to 50 mass% based on the total amount of the metalworking oil. The metalworking oil according to any one of claims 1 to 6, further comprising a sulfur-based extreme pressure agent (C). The metalworking oil according to any one of claims 1 to 7, wherein the content of component (C) in terms of sulfur atoms is 6.5 mass% or more based on the total amount of the metalworking oil. The metalworking oil according to any one of claims 1 to 8 further contains one or more compounds (D) selected from fatty acids and fatty acid esters, which do not fall under component (B). The metalworking oil according to any one of claims 1 to 9, further comprising a pour point depressant (E). The metalworking oil according to any one of claims 1 to 10, wherein the water content is less than 1.0 mass% based on the total amount of the metalworking oil. Kinematic viscosity at 40°C is 200 mm ² /s or more, and
methyl stearate,
The metal processing oil has a kinetic viscosity of 100 mm at 40°C. ² /s or less. The metalworking oil according to any one of claims 1 to 12 , which is used in cold forging of metal materials. Use of the metalworking oil according to any one of claims 1 to 13 in cold forging of a metal material. A metalworking method comprising cold forging a metal material using the metalworking oil according to any one of claims 1 to 13 .

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