US20230357663A1

US20230357663A1 - Water-soluble metalworking fluid

Info

Publication number: US20230357663A1
Application number: US18/042,787
Authority: US
Inventors: Tomoaki Okano; Tomohiko Kitamura; Hideto Kamimura
Original assignee: Idemitsu Kosan Co Ltd
Current assignee: Idemitsu Kosan Co Ltd
Priority date: 2020-08-31
Filing date: 2021-07-09
Publication date: 2023-11-09
Also published as: CN115989312A; CN115989312B; WO2022044566A1; JPWO2022044566A1

Abstract

Provided is a water-soluble metalworking oil comprising a base oil (A) comprising oil-soluble polyalkylene glycol (A1), wherein a total content of water-soluble polyalkylene glycol and methoxypolyethylene glycol is less than 60% by mass based on the total amount excluding water.

Description

TECHNICAL FIELD

The present invention relates to a water-soluble metalworking oil, a metalworking fluid obtained by blending the water-soluble metalworking oil with dilution water, and a metalworking method comprising processing a workpiece comprising metal by application of the metalworking fluid.

BACKGROUND ART

In the art of metalworking such as cutting and grinding, metalworking fluids are used to increase workability for workpieces and to suppress wear of working tools.
Metalworking fluids include oil-based metalworking fluids containing oils such as mineral oils, synthetic oils, and animal and vegetable oils as main components, and water-soluble metalworking fluids provided with water solubility by blending an oil with a surface-active compound. Recently, water-soluble metalworking fluids are increasingly used for safety reasons such as a reduced risk of catching fire.
For example, Patent Literature 1 discloses an invention which relates to a concentrated metalworking fluid comprising from 60 to 90 percent by weight of base oil selected from the group consisting of water-soluble polyalkylene glycols, methoxypolyethylene glycols, and combinations of two or more thereof; from 5 to 20 percent by weight of glycol ether; 0.01 to 5 percent by weight of oil-soluble polyalkylene glycol; and from 0.2 to 6 percent by weight of additives.
Moreover, Patent Literature 2 discloses an invention which relates to a water-soluble working oil comprising methyldicyclohexylamine.

CITATION LIST

Patent Literature

Patent Literature 1
International Publication No. WO 2014/089766
Patent Literature 2
International Publication No. WO 2010/113594

SUMMARY OF INVENTION

Technical Problem

Under such circumstances, the demand exists for novel water-soluble metalworking oils, e.g., also as emulsion-type and soluble-type oils, that have various improved characteristics so as to be more readily applicable to metalworking than conventional metalworking oils.

Solution to Problem

The present invention provides a water-soluble metalworking oil containing oil-soluble polyalkylene glycol as a base oil and having a content of water-soluble polyalkylene glycol and methoxypolyethylene glycol that is equal to or less than a predetermined amount. Specifically, the present invention provides, for example, the following embodiments [1] to [16]:
[1] A water-soluble metalworking oil comprising a base oil (A) comprising oil-soluble polyalkylene glycol (A1), wherein a total content of water-soluble polyalkylene glycol and methoxypolyethylene glycol is less than 60% by mass based on the total amount excluding water.
[2] The water-soluble metalworking oil according to [1], wherein the total content of water-soluble polyalkylene glycol and methoxypolyethylene glycol is less than 10 parts by mass based on 100 parts by mass of the total amount of component (A1).
[3] The water-soluble metalworking oil according to [1] or [2], which is substantially free of a sulfuric extreme pressure agent.
[4] The water-soluble metalworking oil according to any one of [1] to [3], further comprising water (B).
[5] The water-soluble metalworking oil according to any one of [1] to [4], wherein the content of component (A1) in component (A) is 10 to 100% by mass based on the total amount of component (A) contained in the water-soluble metalworking oil.
[6] The water-soluble metalworking oil according to any one of [1] to [5], wherein the content of component (A1) is 0.01% by mass or more based on the total amount of the water-soluble metalworking oil excluding water.
[7] The water-soluble metalworking oil according to any one of [1] to [6], further comprising an amine compound (C).
[8] The water-soluble metalworking oil according to any one of [1] to [7], further comprising a fatty acid (D).
[9] The water-soluble metalworking oil according to any one of [1] to [8], further comprising a nonionic surfactant (E).
[10] The water-soluble metalworking oil according to any one of [1] to [9], which is an emulsion-type oil classified as A1 as stipulated in JIS K 2241:2017.
[11] The water-soluble metalworking oil according to any one of [1] to [9], which is a soluble-type oil classified as A2 as stipulated in JIS K 2241:2017.
[12] A water-soluble metalworking oil comprising a base oil (A) comprising oil-soluble polyalkylene glycol (A1), wherein a total content of water-soluble polyalkylene glycol and methoxypolyethylene glycol is less than 10 parts by mass based on 100 parts by mass of the total amount of component (A).
[13] A metalworking fluid obtained by blending the water-soluble metalworking oil of any one of [1] to [12] with dilution water.
[14] A metalworking method comprising processing a workpiece comprising metal by application of the metalworking fluid according to [13].
[15] The metalworking method according to [14], wherein the workpiece has a member comprising at least iron or aluminum.
[16] The metalworking method according to [14] or [15], wherein corrosion of a copper-containing member constituting a processing machine used in processing of the workpiece is suppressed.

Advantageous Effects of Invention

The water-soluble metalworking oil of one preferable embodiment of the present invention can be prepared into a metalworking fluid having a variety of excellent characteristics such as workability by being diluted with dilution water.

DESCRIPTION OF EMBODIMENT

Concerning the numerical ranges described herein, the upper limits and the lower limits can be suitably combined. For example, when a numerical range is described as being “preferably 30 to 100, and more preferably 40 to 80”, the range of “30 to 80” and the range of “40 to 100” are also included in the numerical range described herein. Moreover, for example, when a numerical range is described as being “preferably 30 or more and more preferably 40 or more, and preferably 100 or less and more preferably 80 or less”, the range of “30 to 80” and the range of “40 to 100” are also included in the numerical range described herein.
In addition, for example, “60 to 100” as a numerical range described herein means the range of “60 or more and 100 or less”.
Herein, the “metalworking oil” is a stock solution of a metalworking fluid before being diluted with dilution water to provide a metalworking fluid, and is in a form suitable for transportation and storage before being used in metalworking. The “metalworking fluid” is what is obtained by adding dilution water to a stock solution of a metalworking oil to dilute the stock solution, and is in a form suitable when used in metalworking.
The “metalworking oil” and the “metalworking fluid” can be distinguished according to, for example, the water content as follows:

- “Metalworking oil”: the water content is 0 parts by mass or more and 400 parts by mass or less based on 100 parts by mass of the total amount of components other than water; and
- “Metalworking fluid”: the water content is more than 400 parts by mass based on 100 parts by mass of the total amount of components other than water.

[Configuration of Water-Soluble Metalworking Oil]

The water-soluble metalworking oil of the present invention is an oil that contains a base oil (A) containing oil-soluble polyalkylene glycol (hereinafter also referred to as “oil-soluble PAG”) (A1), and that is regulated such that the total content of water-soluble polyalkylene glycol (hereinafter also referred to as “water-soluble PAG”) and methoxypolyethylene glycol (hereinafter also referred to as “MPEG”) is a predetermined content.
Herein, the term “water-soluble” means a component that the amount of the component soluble in 100 g of water at 25° C. is 20 g or more, and the total light transmittance of a solution at 25° C. prepared by adding 20 g of the component to 100 g of water at 25° C. is 90% or more.
In the following description of the present specification, the component described as being “water-soluble” is a component having the above characteristics.
In the water-soluble metalworking oil of one embodiment of the present invention, the total content of water-soluble PAG and MPEG may be less than 60% by mass, less than 50% by mass, less than 40% by mass, less than 30% by mass, less than 20% by mass, less than 10% by mass, less than 5% by mass, less than 1% by mass, or less than 0.1% by mass based on the total amount (100% by mass) excluding water.
Moreover, in the water-soluble metalworking oil of one embodiment of the present invention, the total content of water-soluble PAG and MPEG may be less than 10 parts by mass, less than 5 parts by mass, less than 1 part by mass, less than 0.1 parts by mass, less than 0.01 parts by mass, or less than 0.001 parts by mass based on 100 parts by mass of the total amount of component (A1).
The above water-soluble metalworking oil of one embodiment of the present invention may further contain water (B). By regulating the content of water (B), the water-soluble metalworking oil can be prepared into an emulsion-type oil classified as A1 or a soluble-type oil classified as A2 as stipulated in JIS K 2241:2017.
Moreover, the above water-soluble metalworking oil of one embodiment of the present invention preferably contains one or more selected from an amine compound (C), a fatty acid (D), and a nonionic surfactant (E), more preferably contains at least components (C) and (D), and even more preferably contains all components (C), (D), and (E).
The water-soluble metalworking oil of one embodiment of the present invention may contain a further component other than the components (A) to (E) as long as the effects of the present invention are not impaired.
In the water-soluble metalworking oil of one embodiment of the present invention, the total content of the components (A) and (B) is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, yet more preferably 45% by mass or more, and particularly preferably 50% by mass or more, and may be 100% by mass or less, 95% by mass or less, 90% by mass or less, 85% by mass or less, 80% by mass or less, 75% by mass or less, 70% by mass or less, 65% by mass or less, or 60% by mass or less based on the total amount (100° by mass) of the water-soluble metalworking oil.
In the water-soluble metalworking oil of one embodiment of the present invention, the total content of the components (A) to (D) is preferably 30% by mass or more, more preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, yet more preferably 70% by mass or more, and particularly preferably 80% by mass or more, and may be 100% by mass or less, 98% by mass or less, 95% by mass or less, 93% by mass or less, or 90% by mass or less based on the total amount (100% by mass) of the water-soluble metalworking oil.
In the water-soluble metalworking oil of one embodiment of the present invention, the total content of the components (A) to (E) is preferably 35% by mass or more, more preferably 45% by mass or more, even more preferably 55% by mass or more, yet more preferably 65% by mass or more, further preferably 75% by mass or more, and particularly preferably 85% by mass or more, and may be 100% by mass or less, 98% by mass or less, 96% by mass or less, or 94% by mass or less based on the total amount (100% by mass) of the water-soluble metalworking oil.
Below, the respective components contained in the water-soluble metalworking oil of one embodiment of the present invention will now be described.

The water-soluble metalworking oil of the present invention contains a base oil (A) containing oil-soluble PAG (A1).
Containing oil-soluble PAG as a base oil, the water-soluble metalworking oil of the present invention is capable of enhancing the workability of a metalworking fluid obtained by blending the water-soluble metalworking oil with dilution water.
Generally, to form a metalworking fluid having excellent workability (especially workability for an iron-containing workpiece), the water-soluble metalworking oil, which is a stock solution thereof, contains a sulfuric extreme pressure agent. However, the sulfuric extreme pressure agent causes corrosion of a copper-containing member that constitutes a processing machine used during metalworking of a workpiece. On the other hand, by containing component (A1), the water-soluble metalworking oil of the present invention can be prepared into a metalworking fluid having excellent workability while being substantially free of a sulfuric extreme pressure agent and, also, can avoid the problem of corroding the copper-containing member.
Component (A) used in one embodiment of the present invention may contain another base oil (A2) other than component (A1).
However, in the water-soluble metalworking oil of one embodiment of the present invention, the content of component (A1) in component (A), from the viewpoint of providing a water-soluble metalworking oil capable of becoming a metalworking fluid having excellent workability, may be 10 to 100% by mass, 20 to 100% by mass, 30 to 100% by mass, 40 to 100% by mass, 50 to 100% by mass, 60 to 100% by mass, 70 to 100% by mass, 75 to 100% by mass, 80 to 100% by mass, 85 to 100% by mass, 90 to 100% by mass, 95 to 100% by mass, or 98 to 100% by mass based on the total amount (100% by mass) of component (A) contained in the water-soluble metalworking oil.
In the water-soluble metalworking oil of one embodiment of the present invention, the content of component (A), from the viewpoint of providing a water-soluble metalworking oil capable of becoming a metalworking fluid having excellent workability, may be preferably 0.01% by mass or more, more preferably 0.05% by mass or more, more preferably 0.1% by mass or more, more preferably 0.5% by mass or more, more preferably 1.0% by mass or more, even more preferably 1.5% by mass or more, even more preferably 2.0% by mass or more, even more preferably 2.5% by mass or more, even more preferably 3.0% by mass or more, yet more preferably 4.0% by mass or more, yet more preferably 5.0% by mass or more, yet more preferably 6.0° by mass or more, yet more preferably 7.0% by mass or more, yet more preferably 8.0% by mass or more, particularly preferably 9.0% by mass or more, moreover, 9.5% by mass or more, 10.0% by mass or more, 11.0% by mass or more, or 12.0% by mass or more, and may be 100% by mass or less, 99% by mass or less, 95% by mass or less, 90% by mass or less, 85% by mass or less, 80% by mass or less, 75% by mass or less, or 70% by mass or less based on the total amount (100% by mass) of the water-soluble metalworking oil excluding water.
When providing an emulsion-type oil classified as A1 as stipulated in JIS K 2241:2017, the content of component (A) may be 10° by mass or more, 15° by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, 45% by mass or more, or 50% by mass or more based on the total amount (100% by mass) of the oil excluding water, and the upper limit is as described above.
When providing a soluble-type oil classified as A2 as stipulated in JIS K 2241:2017, the content of component (A) may be 60% by mass or less, 50% by mass or less, 40% by mass or less, 30% by mass or less, 25% by mass or less, or 20% by mass or less based on the total amount (100% by mass) of the oil excluding water, and the lower limit is as described above.
Moreover, in the water-soluble metalworking oil of one embodiment of the present invention, the content of component (A), from the viewpoint of providing a water-soluble metalworking oil capable of becoming a metalworking fluid having excellent workability, may be preferably 0.01% by mass or more, more preferably 0.05% by mass or more, more preferably 0.1% by mass or more, more preferably 0.3% by mass or more, more preferably 0.5% by mass or more, even more preferably 0.7% by mass or more, even more preferably 1.0% by mass or more, even more preferably 1.5% by mass or more, even more preferably 2.0% by mass or more, yet more preferably 2.5% by mass or more, yet more preferably 3.0% by mass or more, yet more preferably 3.5° by mass or more, particularly preferably 4.0% by mass or more, moreover, 4.5% by mass or more, 5.0% by mass or more, 5.5% by mass or more, 6.0% by mass or more, 6.5% by mass or more, or 7.0% by mass or more, and is 100% by mass or less, but in consideration of the content of other components, may be 99% by mass or less, 95% by mass or less, 90% by mass or less, 85% by mass or less, 80% by mass or less, 75% by mass or less, 70% by mass or less, 65% by mass or less, or 60% by mass or less based on the total amount (100% by mass) of the water-soluble metalworking oil.
When forming an emulsion-type oil classified as A1 as stipulated in JIS K 2241:2017, the content of component (A) may be 10% by mass or more, 15% by mass or more, 20° by mass or more, 30° by mass or more, 40° by mass or more, 45% by mass or more, or 50% by mass or more based on the total amount (100% by mass) of the oil, and the upper limit is as described above.
When forming a soluble-type oil classified as A1 as stipulated in JIS K 2241:2017, the content of component (A) may be 60% by mass or less, 50% by mass or less, 40% by mass or less, 30% by mass or less, 25% by mass or less, 20% by mass or less, 15% by mass or less, or 10% by mass or less based on the total amount (100% by mass) of the oil, and the lower limit is as described above.

<<Component (A1): Oil-Soluble Polyalkylene Glycol (Oil-Soluble PAG)>>

Component (A1) used in one embodiment of the present invention is not particularly limited as long as it has a structural unit derived from alkylene oxide and is polyalkylene glycol (PAG) that demonstrates oil solubility.
Herein, whether the PAG of interest is oil-soluble or not is determined by its miscibility with a mineral oil that is classified into Group 1 of the API (American Petroleum Institute) base oil category. Specifically, the PAG of interest is determined as oil-soluble PAG when a sample having a mass ratio of the content of the PAG of interest to the content of a mineral oil classified into Group 1 [PAG/mineral oil] of 10/90 or 90/10 is prepared, then the total light transmittances at 25° C. of the sample and a standard are measured, and the following criteria (i) and (ii) are satisfied:

- (i) When a sample has a content ratio [PAG/mineral oil]=10/90, [Total light transmittance of the sample (%)]−[Total light transmittance of mineral oil only (%)]≤20%; and
- (ii) When a sample has a content ratio [PAG/mineral oil]=90/10, [Total light transmittance of the sample (%)]−[Total light transmittance of PAG (%)]≤20%.

In the following description of the present specification, the component described as being “oil-soluble” is a component that satisfies the above criteria (i) and (ii) unless specified otherwise.
Examples of component (A1) used in one embodiment of the present invention include polymers having a structural unit derived from at least one of propylene oxide and butylene oxide, such as a propylene oxide homopolymer, a butylene oxide homopolymer, and a propylene oxide/butylene oxide copolymer.
One component (A1) may be used singly, or two or more may be used in combination.
From the viewpoint of providing a water-soluble metalworking oil capable of becoming a metalworking fluid having excellent workability, the kinematic viscosity at 40° C. of component (A1) used in one embodiment of the present invention is preferably 9 to 800 mm²/s, more preferably 15 to 350 mm²/s, more preferably 20 to 250 mm²/s, even more preferably 23 to 180 mm²/s, yet more preferably 25 to 100 mm²/s, yet more preferably 28.8 to 90 mm²/s, and particularly preferably 40 to 80 mm²/s.
From the viewpoint of providing a water-soluble metalworking oil capable of becoming a metalworking fluid having excellent workability, the viscosity grade as stipulated in ISO 3448 of component (A1) used in one embodiment of the present invention is preferably VG10, VG15, VG22, VG32, VG46, VG68, VG100, VG150, VG220, VG320, VG460, or VG680, more preferably VG22, VG32, VG46, VG68, or VG100, even more preferably VG32, VG46, or VG68, yet more preferably VG46 or VG68, and particularly preferably VG68.
In the water-soluble metalworking oil of one embodiment of the present invention, the content of component (A1), from the viewpoint of providing a water-soluble metalworking oil capable of becoming a metalworking fluid having excellent workability, may be preferably 0.01% by mass or more, more preferably 0.05% by mass or more, more preferably 0.1° by mass or more, more preferably 0.5% by mass or more, more preferably 1.0% by mass or more, even more preferably 1.5% by mass or more, even more preferably 2.0% by mass or more, even more preferably 2.5% by mass or more, even more preferably 3.0% by mass or more, yet more preferably 4.0% by mass or more, yet more preferably 5.0% by mass or more, yet more preferably 6.0% by mass or more, yet more preferably 7.0% by mass or more, yet more preferably 8.0% by mass or more, particularly preferably 9.0% by mass or more, moreover, 9.5% by mass or more, 10.0% by mass or more, 11.0% by mass or more, or 12.0% by mass or more, and is 100% by mass or less, but in consideration of the content of other components, may be 95° by mass or less, 90% by mass or less, 85% by mass or less, 80% by mass or less, 75% by mass or less, 70% by mass or less, or 65% by mass or less based on the total amount (100% by mass) of the water-soluble metalworking oil excluding water.
When providing an emulsion-type oil classified as A1 as stipulated in JIS K 2241:2017, the content of component (A1) may be 10% by mass or more, 15% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, 45% by mass or more, or 50% by mass or more based on the total amount (100% by mass) of the oil excluding water, and the upper limit is as described above.
When providing a soluble-type oil classified as A2 as stipulated in JIS K 2241:2017, the content of component (A1) may be 60% by mass or less, 50% by mass or less, 40% by mass or less, 30% by mass or less, 25% by mass or less, or 20% by mass or less based on the total amount (100% by mass) of the oil excluding water, and the lower limit is as described above.
<<Component (A2): Base Oil Other than Component (A1)>>
The base oil (A2) other than component (A1) used in one embodiment of the present invention may be at least one selected from mineral oils and synthetic oils other than oil-soluble PAG.
Herein, the above water-soluble polyalkylene glycol (water-soluble PAG) and methoxypolyethylene glycol (MPEG) are also included in component (A2), and the total content of water-soluble PAG and MPEG is regulated as described above.
Examples of mineral oils include atmospheric residue obtained by performing atmospheric distillation on crude oil such as paraffinic crude oil, intermediate crude oil, and naphthenic crude oil; distillate obtained by performing vacuum distillation on such atmospheric residue; and refined oil obtained by performing on such distillate one or more refining treatments such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining.
Examples of synthetic oils include polyα-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); isoparaffin; ester oils such as polyol esters, dibasic acid esters, and phosphoric acid esters; ether oils such as polyphenyl ether; alkylbenzene; alkyl naphthalene; synthetic oils (GTL) obtained by isomerizing wax (GTL wax (Gas-To-Liquids WAX)) produced from natural gas by Fischer-Tropsch process or the like.
From the viewpoint of providing a water-soluble metalworking oil capable of becoming a metalworking fluid having excellent workability, the kinematic viscosity at 40° C. of component (A2) used in one embodiment of the present invention is preferably 2.0 to 150 mm²/s, more preferably 3.0 to 120 mm²/s, even more preferably 5.0 to 100 mm²/s, yet more preferably 6.0 to 90 mm²/s, and particularly preferably 7.0 to 80 mm²/s.
The viscosity index of component (A2) used in one embodiment of the present invention is preferably 70 or more, more preferably 80 or more, even more preferably 90 or more, yet more preferably 100 or more, and particularly preferably 105 or more.

The water-soluble metalworking oil of one embodiment of the present invention may further contain water (B). Containing water, the water-soluble metalworking oil becomes flame retardant and thus has good handleability as a non-hazardous material during storage.
Water, which is component (B) used in one embodiment of the present invention, is not particularly limited, and may be, for example, distilled water, ion exchanged water, tap water, or water for industrial use.
In the water-soluble metalworking oil of one embodiment of the present invention, the content of component (B) is 400 parts by mass or less, preferably 1 to 350 parts by mass, more preferably 2 to 300 parts by mass, more preferably 3 to 250 parts by mass, and even more preferably 5 to 200 parts by mass based on 100 parts by mass of the total amount of components other than water of the water-soluble metalworking oil.
When providing an emulsion-type oil classified as A1 as stipulated in JIS K 2241:2017, the content of component (B) may be 150 parts by mass or less, 100 parts by mass or less, 70 parts by mass or less, 50 parts by mass or less, 40 parts by mass or less, 30 parts by mass or less, 20 parts by mass or less, or 15 parts by mass or less based on 100 parts by mass of the total amount of components excluding water in the water-soluble metalworking oil, and the lower limit is as described above.
When providing a soluble-type oil classified as A2 as stipulated in JIS K 2241:2017, the content of component (B) may be 10 parts by mass or more, 30 parts by mass or more, 50 parts by mass or more, 60 parts by mass or more, 70 parts by mass or more, 80 parts by mass or more, 90 parts by mass or more, or 100 parts by mass or more based on 100 parts by mass of the total amount of components excluding water in the water-soluble metalworking oil, and the upper limit is as described above.
In the water-soluble metalworking oil of one embodiment of the present invention, the content of component (B) is preferably 1 to 99° by mass, more preferably 2 to 90% by mass, even more preferably 3 to 85% by mass, and yet more preferably 5 to 80% by mass based on the total amount (100% by mass) of the water-soluble metalworking oil.
When providing an emulsion-type oil classified as A1 as stipulated in JIS K 2241:2017, the content of component (B) may be 70% by mass or less, 60% by mass or less, 50% by mass or less, 40% by mass or less, 30% by mass or less, 25% by mass or less, 20% by mass or less, or 15% by mass or less based on the total amount (100% by mass) of the water-soluble metalworking oil, and the lower limit is as described above.
When providing a soluble-type oil classified as A2 as stipulated in JIS K 2241:2017, the content of component (B) may be 10° by mass or more, 15° by mass or more, 20% by mass or more, 25% by mass or more, 30° by mass or more, 35% by mass or more, 40% by mass or more, 45% by mass or more, or 50% by mass or more based on the total amount (100% by mass) of the water-soluble metalworking oil, and the upper limit is as described above.

Preferably, the water-soluble metalworking oil of one embodiment of the present invention further contains an amine compound (C). When the water-soluble metalworking oil containing component (C) is combined with dilution water to be formed into a metalworking fluid, the metalworking fluid can have a good emulsion state and more increased antibacterial properties, antirust properties, workability, and the like.
One component (C) may be used singly, or two or more may be used in combination.
From the same viewpoint as above, in the water-soluble metalworking oil of one embodiment of the present invention, the content of component (C) may be preferably 3 to 70% by mass, more preferably 5 to 60% by mass, even more preferably 7 to 50% by mass, yet more preferably 10 to 45% by mass, particularly preferably 12 to 40% by mass, moreover, 15% by mass or more, 17% by mass or more, 20% by mass or more, 22% by mass or more, or 24% by mass or more, and may be 37° by mass or less, 35° by mass or less, 33% by mass or less, 31% by mass or less, 27% by mass or less, or 25% by mass or less based on the total amount (100% by mass) of the water-soluble metalworking oil.
From the same viewpoint as above, in the water-soluble metalworking oil of one embodiment of the present invention, the content of component (C) may be preferably 2 to 40% by mass, more preferably 4 to 35% by mass, even more preferably 6 to 30% by mass, yet more preferably 8 to 25% by mass, particularly preferably 10 to 20% by mass, moreover, 11% by mass or more, or 12% by mass or more, and may be 18° by mass or less or 16° by mass or less based on the total amount (100% by mass) of the water-soluble metalworking oil.
Moreover, in the water-soluble metalworking oil of one embodiment of the present invention, the mass ratio of the content of component (C) to the content of component (A1) [(C)/(A1)] may be preferably 0.01 to 30, more preferably 0.05 to 25, even more preferably 0.10 to 20, yet more preferably 0.20 to 15, particularly preferably 0.25 to 9.0, moreover, 0.28 or more, 0.30 or more, 0.40 or more, 0.50 or more, 0.60 or more, 0.70 or more, 0.80 or more, 0.90 or more, 1.00 or more, 1.20 or more, 1.40 or more, or 1.60 or more, and may be 8.0 or less, 7.0 or less, 6.0 or less, 5.0 or less, 4.5 or less, 4.0 or less, 3.5 or less, 3.0 or less, 2.9 or less, 2.8 or less, 2.7 or less, 2.6 or less, 2.5 or less, or 2.4 or less.
Component (C) used in one embodiment of the present invention may be any of monoamine having one amino nitrogen atom within one molecule, diamine having two amino nitrogen atoms within one molecule, and polyamine having 3 or more amino nitrogen atoms within one molecule.
However, from the viewpoint of providing a water-soluble metalworking oil capable of becoming a metalworking fluid having more increased antibacterial properties, antirust properties, workability, and the like, component (C) used in one embodiment of the present invention preferably contains monoamine.
The content of monoamine is preferably 50 to 100% by mass, more preferably 60 to 100% by mass, more preferably 70 to 100% by mass, more preferably 75 to 100% by mass, even more preferably 80 to 100% by mass, even more preferably 85 to 100% by mass, yet more preferably 90 to 100% by mass, yet more preferably 95 to 100% by mass, and particularly preferably 98 to 100% by mass based on the total amount (100% by mass) of component (C) contained in the water-soluble metalworking oil.
Monoamine used as component (C) in one embodiment of the present invention is classified according to the number of substituents R into primary monoamine represented by the following formula (i), secondary monoamine represented by the following formula (ii), and tertiary monoamine represented by the following formula (iii).
From the viewpoint of providing a water-soluble metalworking oil capable of becoming a metalworking fluid having a good emulsion state and more increased antibacterial properties, antirust properties, workability, and the like when combined with dilution water, component (C) used in one embodiment of the present invention preferably contains at least tertiary monoamine, more preferably contains tertiary monoamine and at least one of primary monoamine and secondary monoamine, and even more preferably contains at least secondary monoamine and tertiary monoamine.
In the above formulae, R each independently represents a substituent. A plurality of R may be the same or may be different from each other. Examples of the substituent include an alkyl group, a hydroxyalkyl group, an alkenyl group, a cycloalkyl group, a phenyl group, and a benzyl group.
Examples of the alkyl group that can be selected as a substituent R include a methyl group, an ethyl group, a propyl group (a n-propyl group, an i-propyl group), a butyl group (a n-butyl group, an i-butyl group, a s-butyl group, a t-butyl group), a pentyl group (a n-pentyl group, an i-pentyl group, a neopentyl group), a hexyl group, a heptyl group, an octyl group, a 2-ethylhexyl group, a nonyl group, a decyl group, a undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, and an octadecyl group.
The alkyl group may be a linear alkyl group or may be a branched alkyl group.
The number of carbon atoms of the alkyl group is preferably 1 to 30, more preferably 1 to 20, even more preferably 1 to 10, yet more preferably 1 to 6, and particularly preferably 1 to 4.
Examples of the hydroxyalkyl group that can be selected as a substituent R include groups obtained by replacing at least one hydrogen atom of the above alkyl groups with a hydroxyl group.
The alkyl group that constitutes the hydroxyalkyl group may also be a linear alkyl group or may be a branched alkyl group.
The number of carbon atoms of the hydroxyalkyl group is preferably 1 to 30, more preferably 1 to 20, even more preferably 1 to 10, yet more preferably 1 to 6, and particularly preferably 2 to 4.
Examples of the alkenyl group that can be selected as a substituent R include an ethenyl group (a vinyl group), a propenyl group, a butenyl group, a pentenyl group, a hexenyl group, a heptenyl group, an octenyl group, a nonenyl group, a decenyl group, a dodecenyl group, a tridecenyl group, a tetradecenyl group, a pentadecenyl group, a hexadecenyl group, and an octadecenyl group.
The alkenyl group may be a linear alkenyl group or may be a branched alkenyl group.
The number of carbon atoms of the alkenyl group is preferably 1 to 30, more preferably 1 to 20 carbon atoms, even more preferably 1 to 10 carbon atoms, yet more preferably 1 to 6 carbon atoms, and particularly preferably 1 to 3 carbon atoms.
Examples of the cycloalkyl group that can be selected as a substituent R include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, and an adamantyl group.
From the viewpoint of providing a water-soluble metalworking oil capable of becoming a metalworking fluid having a good emulsion state and more increased antibacterial properties, antirust properties, workability, and the like, when combined with dilution water, component (C) used in one embodiment of the present invention preferably contains alkanolamine having at least one hydroxyalkyl group.
Examples of alkanolamine include primary alkanolamine in which R in the above formula (i) is a hydroxyalkyl group, secondary alkanolamine in which at least one R in the above formula (ii) is a hydroxyalkyl group, and tertiary alkanolamine in which at least one R in the above formula (iii) is a hydroxyalkyl group.
Examples of primary alkanolamine include ethanolamine, propanolamine, butanolamine, and 2-amino-2-methyl-1-propanol.
Examples of secondary alkanolamine include monoethanolamine such as N-methylethanolamine, N-ethylethanolamine, N-propylethanolamine, N-butylethanolamine, N-octylethanolamine, N-stearylethanolamine, N-oleylethanolamine, N-cyclohexylethanolamine, N-phenylethanolamine, and N-benzylethanolamine; monopropanolamine such as N-methylpropanolamine, N-ethylpropanolamine, N-propylpropanolamine, N-butylpropanolamine, N-octylpropanolamine, N-stearylpropanolamine, N-oleylpropanolamine, N-cyclohexylpropanolamine, N-phenylpropanolamine, and N-benzylpropanolamine; diethanolamine, and dipropanolamine.
Examples of tertiary alkanolamine include monoethanolamine such as N-dimethylethanolamine, N-diethylethanolamine, N-dipropylethanolamine, N-dibutylethanolamine, N-dioctylethanolamine, N-distearylethanolamine, N-dioleylethanolamine, N-dicyclohexylethanolamine, N-diphenylethanolamine, and N-dibenzylethanolamine; monopropanolamine such as N-dimethylpropanolamine, N-diethylpropanolamine, N-dipropylpropanolamine, N-dibutylpropanolamine, N-dioctylpropanolamine, N-distearylpropanolamine, N-dioleylpropanolamine, N-dicyclohexylpropanolamine, N-diphenylpropanolamine, and N-dibenzylpropanolamine; diethanolamine such as N-methyldiethanolamine, N-ethyldiethanolamine, N-propyldiethanolamine, N-butyldiethanolamine, N-octyldiethanolamine, N-stearyldiethanolamine, N-oleyldiethanolamine, N-cyclohexyldiethanolamine, N-phenyldiethanolamine, and N-benzyldiethanolamine; dipropanolamine such as N-methyldipropanolamine, N-ethyldipropanolamine, N-propyldipropanolamine, N-butyldipropanolamine, N-octyldipropanolamine, N-stearyldipropanolamine, N-oleyldipropanolamine, N-cyclohexyldipropanolamine, N-phenyldipropanolamine, and N-benzyldipropanolamine; triethanolamine, and tripropanolamine (such as triisopropanolamine).
Among these, from the viewpoint of providing a water-soluble metalworking oil capable of becoming a metalworking fluid having a good emulsion state and more increased antibacterial properties, antirust properties, workability, and the like, when combined with dilution water, component (C) used in one embodiment of the present invention preferably contains at least tertiary alkanolamine, more preferably contains tertiary alkanolamine and at least one of primary alkanolamine and secondary alkanolamine, and even more preferably contains at least secondary alkanolamine and tertiary alkanolamine.
The content of alkanolamine may be preferably 5% by mass or more, more preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, yet more preferably 35% by mass or more, particularly preferably 40% by mass or more, moreover, 45% by mass or more, 50% by mass or more, or 55% by mass or more, and may be 100% by mass or less, 95% by mass or less, 90% by mass or less, 85% by mass or less, 80% by mass or less, 75% by mass or less, 70% by mass or less, or 65% by mass or less based on the total amount (100% by mass) of component (C) contained in the water-soluble metalworking oil.
Component (C) used in one embodiment of the present invention preferably contains alicyclic amine.
Examples of alicyclic amine include primary alicyclic amine wherein R in the above formula (i) is a cycloalkyl group, secondary alicyclic amine wherein at least one R in the above formula (ii) is a cycloalkyl group; and tertiary alicyclic amine wherein at least one R in the above formula (iii) is a cycloalkyl group.
Examples of primary alicyclic amine include N-cyclohexylamine.
Examples of secondary alicyclic amine include monocyclohexylamine such as N-methylcyclohexylamine, N-ethylcyclohexylamine, N-propylcyclohexylamine, and N-oleylcyclohexylamine; monocyclohexylalkanolamine such as N-cyclohexylethanolamine and N-cyclohexylpropanolamine; and N-dicyclohexylamine.
Examples of tertiary alicyclic amine include dialkylmonocyclohexylamine such as N-dimethylcyclohexylamine, N-diethylcyclohexylamine, N-dipropylcyclohexylamine, N-dioleylcyclohexylamine, and N-dicyclohexylamine; monocyclohexyldialkanolamine such as N-cyclohexyldiethanolamine and N-cyclohexyldipropanolamine; monoalkyldicyclohexylamine such as N-methyldicyclohexylamine, N-ethyldicyclohexylamine, N-propyldicyclohexylamine, and N-oleyldicyclohexylamine; dicyclohexylalkanolamine such as N-dicyclohexylethanolamine and N-dicyclohexylpropanolamine; and tricyclohexylamine.
When providing an emulsion-type oil classified as A1 as stipulated in JIS K 2241:2017, component (C) preferably contains one or more selected from dialkylmonocyclohexylamine and monoalkyldicyclohexylamine, and more preferably contains monoalkyldicyclohexylamine.
When providing a soluble-type oil classified as A2 as stipulated in JIS K 2241:2017, component (C) preferably contains one or more selected from monocyclohexyldialkanolamine and dicyclohexyldialkanolamine, and more preferably contains monocyclohexyldialkanolamine.
The content of alicyclic amine may be preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 25% by mass or more, yet more preferably 30% by mass or more, particularly preferably 35% by mass or more, moreover, 37% by mass or more, or 40% by mass or more, and may be 100% by mass or less, 95% by mass or less, 90% by mass or less, 85% by mass or less, 80% by mass or less, 75% by mass or less, 70% by mass or less, 65% by mass or less, 60% by mass or less, 55% by mass or less, or 50% by mass or less based on the total amount (100% by mass) of component (C) contained in the water-soluble metalworking oil.
The water-soluble metalworking oil of one embodiment of the present invention may contain another amine (including diamine and polyamine) other than alkanolamine and alicyclic amine as component (C).
The content of another amine may be 0 to 50% by mass, 0 to 40% by mass, 0 to 30% by mass, 0 to 20% by mass, 0 to 10% by mass, 0 to 5.0% by mass, 0 to 2.0% by mass, 0 to 1.0% by mass, 0 to 0.10% by mass, 0 to 0.01% by mass, 0 to 0.001% by mass, 0 to 0.0001% by mass, or 0 to 0.00001% by mass based on the total amount (100% by mass) of component (C) contained in the water-soluble metalworking oil.

Preferably, the water-soluble metalworking oil of one embodiment of the present invention further contains a fatty acid (D).
Containing component (D), the water-soluble metalworking oil is capable of becoming a metalworking fluid having more increased emulsion stability, antirust properties, workability, and the like.
In the water-soluble metalworking oil of one embodiment of the present invention, one component (D) may be used singly, or two or more may be used in combination.
From the same viewpoint as above, in the water-soluble metalworking oil of one embodiment of the present invention, the content of component (D) may be preferably 5 to 70% by mass, more preferably 7 to 60% by mass, even more preferably 10 to 50% by mass, yet more preferably 13 to 45% by mass, particularly preferably 16 to 40% by mass, moreover, 18% by mass or more, 20% by mass or more, 22% by mass or more, or 25% by mass or more, and may be 38% by mass or less, 35% by mass or less, or 32% by mass or less based on the total amount (100% by mass) of the water-soluble metalworking oil excluding water.
Also, from the same viewpoint as above, in the water-soluble metalworking oil of one embodiment of the present invention, the content of component (D) may be preferably 2 to 60% by mass, more preferably 3 to 50% by mass, even more preferably 5 to 40% by mass, yet more preferably 7 to 30% by mass, particularly preferably 9 to 25% by mass, moreover, 10% by mass or more, 12% by mass or more, or 14% by mass or more, and may be 22% by mass or less, 20% by mass or less, or 18% by mass or less based on the total amount (100% by mass) of the water-soluble metalworking oil.
Moreover, in the water-soluble metalworking oil of one embodiment of the present invention, the mass ratio of the content of component (D) to the content of component (A1) [(D)/(A1)] may be preferably 0.01 to 30, more preferably 0.05 to 25, more preferably 0.10 to 20, even more preferably 0.20 to 15, yet more preferably 0.25 to 12.0, particularly preferably 0.30 to 8.0, moreover, 0.32 or more, 0.35 or more, 0.50 or more, 0.70 or more, 0.90 or more, 1.00 or more, 1.20 or more, 1.40 or more, or 1.50 or more, and may be 7.0 or less, 6.0 or less, 5.0 or less, 4.5 or less, 4.0 or less, 3.8 or less, 3.6 or less, 3.4 or less, 3.2 or less, 3.0 or less, 2.8 or less, 2.6 or less, or 2.4 or less.
In the water-soluble metalworking fluid of one embodiment of the present invention, from the viewpoint of providing a water-soluble metalworking oil that has a good stock solution stability and is capable of becoming a metalworking fluid having more increased workability, the mass ratio of the content of component (C) to the content of component (D) [(C)/(D)] may be preferably 0.01 to 5.0, more preferably 0.05 to 4.0, more preferably 0.1 to 3.0, even more preferably 0.2 to 2.5, yet more preferably 0.3 to 2.0, particularly preferably 0.5 to 1.5, moreover, 0.6 or more, 0.65 or more, 0.7 or more, 0.75 or more, or 0.8 or more, and may be 1.4 or less, 1.3 or less, 1.2 or less, or 1.15 or less.
Examples of component (D) used in one embodiment of the present invention include fatty acid, hydroxy fatty acid, aliphatic dicarboxylic acid, dimer acid of fatty acid, and polymerized fatty acid of hydroxy unsaturated fatty acid.
Examples of the fatty acid include saturated aliphatic monocarboxylic acid such as octanoic acid, 2-ethylhexanoic acid, decanoic acid, neodecanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, pentadecanoic acid, heptadecanoic acid, nonadecanic acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, and isostearic acid, and unsaturated aliphatic monocarboxylic acid such as octenoic acid, nonenoic acid, decenoic acid, undecenoic 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.
A mixture of unsaturated fatty acid may be used, such as tall oil fatty acid, soybean oil fatty acid, palm oil fatty acid, linseed oil fatty acid, rice bran oil fatty acid, and cottonseed oil fatty acid.
The number of carbon atoms in the fatty acid is preferably 8 to 30, more preferably 10 to 25, and even more preferably 10 to 20.
Examples of the hydroxy fatty acid include hydroxylauric acid, hydroxymyristic acid, hydroxypalmitic acid, hydroxystearic acid, hydroxyarachic acid, hydroxybehenic acid, and hydroxyoctadecenoic acid.
The number of carbon atoms of the hydroxy fatty acid is preferably 8 to 30, more preferably 10 to 25, and even more preferably 10 to 20 carbon atoms.
Examples of the aliphatic dicarboxylic acid include saturated aliphatic dicarboxylic acid such as sebacic acid, dodecanedioic acid, dodecylsuccinic acid, laurylsuccinic acid, stearylsuccinic acid, and isostearylsuccinic acid.
The number of carbon atoms of the aliphatic dicarboxylic acid is preferably 8 to 30, more preferably 10 to 25, and even more preferably 10 to 20 carbon atoms.
Examples of the hydroxy unsaturated fatty acid constituting a polymerized fatty acid of the hydroxy unsaturated fatty acid include ricinoleic acid (12-hydroxyoctadec-9-enoic acid). A fatty acid mixture containing recinoleic acid, such as castor oil, may be used.
Examples of the polymerized fatty acid of the hydroxy unsaturated fatty acid include condensed fatty acid that is a dehydrative polycondensation product of hydroxy unsaturated fatty acid (such as castor oil polymerized fatty acid that is a dehydrative condensation product of a fatty acid mixture containing ricinoleic acid as a main component), and condensed fatty acid obtained by dehydratively condensing an alcoholic hydroxyl group of condensed fatty acid that is a dehydrative polycondensation product of hydroxy unsaturated fatty acid and monocarboxylic acid.
Component (D) used in one embodiment of the present invention preferably contains one or more (preferably two or more, and more preferably three or more) selected from unsaturated aliphatic monocarboxylic acid, saturated aliphatic dicarboxylic acid, and polymerized fatty acid of hydroxy unsaturated fatty acid, and more preferably contains all of the unsaturated aliphatic monocarboxylic acid, saturated aliphatic dicarboxylic acid, and polymerized fatty acid of hydroxy unsaturated fatty acid.
From the viewpoint of providing a water-soluble metalworking oil capable of becoming a metalworking fluid having more increased workability, the acid value of component (D) is usually 0 mgKOH/g or more, preferably 10 to 100 mgKOH/g, more preferably 20 to 90 mgKOH/g, and even more preferably 30 to 80 mgKOH/g.
The hydroxyl value of component (D) is preferably 0 to 80 mgKOH/g, more preferably 0 to 60 mgKOH/g, and even more preferably 0 to 40 mgKOH/g.
From the above viewpoint, the ratio of the acid value to the hydroxyl value of component (D) [acid value/hydroxyl value] is preferably 1.5 to 15, more preferably from 2.0 to 10, and even more preferably from 2.5 to 9.5.
The saponification value of component (D) is preferably 180 to 220 mgKOH/g, more preferably 190 to 210 mgKOH/g, and even more preferably 195 to 205 mgKOH/g.
Herein, the acid value means a value measured in accordance with JIS K 2501:2003 (indicator photometric titration method), the hydroxyl value means a value measured in accordance with JIS K 0070:1992, and the saponification value means a value measured in accordance with JIS K 2503:1996.

Preferably, the water-soluble metalworking oil of one embodiment of the present invention further contains a nonionic surfactant (E). Containing the nonionic surfactant (E), the water-soluble metalworking oil is capable of becoming a metalworking fluid having more increased emulsion stability and workability.
In the water-soluble metalworking oil of one embodiment of the present invention, one nonionic surfactant (E) may be used singly, or two or more may be used in combination.
From the above viewpoint, in the water-soluble metalworking oil of one embodiment of the present invention, the content of component (E) is preferably 0.5 to 35.0% by mass, more preferably 1.0 to 30.0% by mass, even more preferably 1.2 to 25.0% by mass, and yet more preferably 1.5 to 20.0% by mass based, and particularly preferably 1.7 to 16.0% by mass based on the total amount (100% by mass) of the water-soluble metalworking oil excluding water.
When providing an emulsion-type oil classified as A1 as stipulated in JIS K 2241:2017, the content of component (E) may be 15.0% by mass or less, 12.0% by mass or less, 10.0% by mass or less, 8.0% by mass or less, 6.0% by mass or less, 5.0% by mass or less, 4.0% by mass or less, or 3.5% by mass or less based on the total amount (100% by mass) of the water-soluble metalworking oil excluding water, and the lower limit is as described above.
When providing a soluble-type oil classified as A2 as stipulated in JIS K 2241:2017, the content of component (E) may be 2.0% by mass or more, 3.0% by mass or more, 4.0% by mass or more, 5.0% by mass or more, 6.0% by mass or more, 7.0° by mass or more, 8.0° by mass or more, 9.0% by mass or more, or 10.0% by mass or more based on the total amount (100% by mass) of the water-soluble metalworking oil excluding water, and the upper limit is as described above.
From the above viewpoint, in the water-soluble metalworking oil of one embodiment of the present invention, the content of component (E) is preferably 0.1 to 15.0% by mass, more preferably 0.2 to 12.0% by mass, even more preferably 0.3 to 10.0% by mass, yet more preferably 0.5 to 8.0% by mass, and particularly preferably 0.7 to 6.0% by mass based on the total amount (100% by mass) of the water-soluble metalworking oil.
When providing an emulsion-type oil classified as A1 as stipulated in JIS K 2241:2017, the content of component (E) may be 5.0% by mass or less, 4.5% by mass or less, 4.0% by mass or less, 3.5% by mass or less, 3.0% by mass or less, or 2.5% by mass or less based on the total amount (100% by mass) of the water-soluble metalworking oil, and the lower limit is as described above.
When providing a soluble-type oil classified as A2 as stipulated in JIS K 2241:2017, the content of component (E) may be 1.0% by mass or more, 1.2% by mass or more, 1.5% by mass or more, 2.0% by mass or more, 2.5% by mass or more, 3.0% by mass or more, 3.5% by mass or more, or 4.0% by mass or more based on the total amount (100° by mass) of the water-soluble metalworking oil, and the upper limit is as described above.
From the viewpoint of providing a water-soluble metalworking oil capable of becoming a metalworking fluid having more increased emulsion stability and workability, the HLB of component (E) used in one embodiment of the present invention is preferably 6.0 or more, more preferably 7.0 or more, even more preferably 8.0 or more, yet more preferably 9.0 or more, and particularly preferably 10.0 or more, and is 18.0 or less, preferably 17.0 or less, more preferably 16.0 or less, even more preferably 15.0 or less, and yet more preferably 14.5 or less.
Herein, HLB means a value calculated by Griffin's method.
Examples of component (E) used in one embodiment of the present invention include alkylene glycol, polyoxyalkylene alkyl ether, polyoxyalkylene aryl ether, polyoxyalkylenealkylamine (a cocoamine alkylene oxide adduct), an alkylphenol alkylene oxide adduct, a higher alcohol alkylene oxide adduct, a polyoxyalkylene fatty acid ester, a fatty acid ester of glycerin and pentaerythritol, a fatty acid ester of sucrose, a fatty acid ester of a polyoxyalkylene adduct of polyhydric alcohol, alkyl polyglycoside, and fatty acid alkanolamide.
Among these, from the viewpoint of providing a water-soluble metalworking oil capable of becoming a metalworking fluid having more increased emulsion stability and workability, component (E) used in one embodiment of the present invention preferably contains one or more selected from polyoxyalkylene alkyl ether and polyoxyalkylenealkylamine.
The total content of polyoxyalkylene alkyl ether and polyoxyalkylene alkylamine is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, even more preferably 80 to 100% by mass, yet more preferably 90 to 100% by mass, and particularly preferably 95 to 100% by mass based on the total amount (100% by mass) of component (E) contained in the water-soluble metalworking oil.

Containing oil-soluble PAG (A1) as the base oil (A), the water-soluble metalworking oil of the present invention is capable of being prepared into a metalworking fluid having excellent workability even without containing a sulfuric extreme pressure agent that causes corrosion of a copper-containing member. Accordingly, from the viewpoint of providing a water-soluble metalworking oil capable of becoming a metalworking fluid that is highly effective for suppressing corrosion of a copper-containing member, the water-soluble metalworking oil of one embodiment of the present invention is preferably substantially free of a sulfuric extreme pressure agent.
Examples of the sulfuric extreme pressure agent include sulfurized olefin, sulfurized lard, alkyl polysulfide, and sulfurized fatty acid.
Herein, the expression “substantially free of a sulfuric extreme pressure agent” is a provision obviating an embodiment wherein a sulfuric extreme pressure agent is contained for a specific purpose, but is not a provision obviating an embodiment wherein a sulfuric extreme pressure agent is inadvertently contained as an impurity of other components. However, even in consideration of an embodiment wherein a sulfuric extreme pressure agent is inadvertently contained, the content of a sulfuric extreme pressure agent is preferably as small as possible from the viewpoint of providing a water-soluble metalworking oil capable of becoming a metalworking fluid that is highly effective for suppressing corrosion of a copper-containing member.
A specific content of a sulfuric extreme pressure agent is preferably less than 10 parts by mass, more preferably less than 1 part by mass, more preferably less than 0.1 parts by mass, even more preferably less than 0.01 parts by mass, and particularly preferably less than 0.001 parts by mass based on 100 parts by mass of the total amount of component (A1) contained in the water-soluble metalworking oil.

The water-soluble metalworking oil of one embodiment of the present invention may further contain, as necessary, other various additives other than the above components (A) to (E) as long as the effects of the present invention are not impaired.
Examples of such other various additives include anionic surfactants, cationic surfactants, petroleum sulfonates, non-sulfuric extreme pressure agents, metal deactivators, emulsification aids, antibacterial agents, antifoaming agents, antioxidants, and oily agents.
One of these various additives may be used singly, or two or more may be used in combination.
In the water-soluble metalworking oil of one embodiment of the present invention, the content of each of these various additives is suitably set according to the type and the function of each component, and is preferably 0.001 to 50% by mass, more preferably 0.01 to 40% by mass, even more preferably 0.07 to 30% by mass, and yet more preferably 0.1 to 20% by mass based on the total amount (100% by mass) of the water-soluble metalworking oil excluding water.
In the water-soluble metalworking oil of one embodiment of the present invention, the content of each of these various additives is suitably set according to the type and the function of each component, and is preferably 0.001 to 25% by mass, more preferably 0.01 to 20% by mass, even more preferably 0.03 to 15% by mass, and yet more preferably 0.05 to 10% by mass based on the total amount (100% by mass) of the water-soluble metalworking oil.
Examples of the anionic surfactant include polyoxyethylene alkyl ether carboxylic acids, polyoxyethylene alkyl ether phosphoric acids, alkylbenzene sulfonic acids, α-olefinsulfonic acids, and salts thereof.
The acid value of anionic surfactants is preferably 20 to 250 mgKOH/g, more preferably 30 to 200 mgKOH/g, even more preferably 40 to 190 mgKOH/g, and yet more preferably 50 to 180 mgKOH/g.
Examples of cationic surfactants include alkyltrimethylammonium salts, dialkyldimethylammonium salts, and alkyldimethylbenzylammonium salts.
Examples of petroleum sulfonates include calcium sulfonate, sodium sulfonate, and magnesium sulfonate.
Examples of non-sulfuric extreme pressure agents include chloric extreme pressure agents such as chlorinated paraffin, chlorinated fatty acids, and chlorinated fatty oils; and phosphoric extreme pressure agents such as phosphoric esters, phosphorous esters, thiophosphoric esters, salts thereof, phosphines, and tricresyl phosphate.
Examples of metal deactivators include benzotriazoles, imidazolines, pyrimidine derivatives, and thiadiazoles.
Examples of emulsifying aids include unsaturated fatty acid esters such as methyl oleate, ethyl oleate, and propyl oleate; and aromatic alcohols such as 2-phenoxyethanol and 2-phenylethyl alcohol.
Examples of antibacterial agents include isothiazoline compounds, triazine compounds, alkylbenzimidazole compounds, and metal pyrithione salts.
Examples of antifoaming agents include silicone antifoaming agents, fluorosilicone antifoaming agents, and polyacrylates.
Examples of antioxidants include amine antioxidants such as alkylated diphenylamine, phenylnaphthylamine, and alkylated phenylnaphthylamine; and phenolic 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.
Examples of oily agents include alcohols such as lauryl alcohol, myristyl alcohol, palmityl alcohol, stearyl alcohol, and oleyl alcohol.

The method for producing a water-soluble metalworking oil of one embodiment of the present invention is not particularly limited, and is preferably a method comprising the step of blending the above component (A) and, optionally, the components (B) to (E) and various other additives. The order of blending the respective components can be suitably set.

[Properties of Water-Soluble Metalworking Oil]

The acid value of the water-soluble metalworking oil of one embodiment of the present invention is preferably 10 to 70 mgKOH/g, more preferably 15 to 60 mgKOH/g, even more preferably 20 to 50 mgKOH/g, and yet more preferably 25 to 40 mgKOH/g.
The base value of the water-soluble metalworking oil of one embodiment of the present invention is preferably 10 to 100 mgKOH/g, more preferably 20 to 90 mgKOH/g, even more preferably 30 to 80 mgKOH/g, and yet more preferably 40 to 70 mgKOH/g.
Herein, the base value means a value measured in accordance with JIS K 2501:2003 (HCl method).
The ratio of the base value to the acid value [base value/acid value] of the water-soluble metalworking oil of one embodiment of the present invention is preferably 1.0 to 4.0, more preferably 1.1 to 3.5, even more preferably 1.3 to 3.2, yet more preferably 1.5 to 3.0, and particularly preferably 1.7 to 2.8.
When the ratio is 1.0 or more, a water-soluble metalworking oil having good decay resistance can be provided. On the other hand, when the ratio is 4.0 or less, irritation to the human skin can be small, and thus the water-soluble metalworking oil is preferable in terms of handleability.

[Form of Metalworking Fluid]

The metalworking fluid of the present invention is obtained by using the above metalworking oil of one embodiment of the present invention as a stock solution, and adding dilution water to the metalworking oil.
Dilution water may be any of, for example, distilled water, ion exchanged water, tap water, or water for industrial use.
The amount of dilution water added when preparing the metalworking fluid is more than 400 parts by mass based on 100 parts by mass of the total amount of components other than water of the water-soluble metalworking oil and, preferably, is suitably regulated so as to attain a desired dilute concentration.
The dilute concentration of the metalworking fluid of one embodiment of the present invention is preferably 1 to 50% by volume, more preferably 3 to 40% by volume, and even more preferably 5 to 20% by volume.
Herein, the “dilute concentration of the metalworking fluid” means a value calculated from the following equation:
“Dilute concentration of metalworking fluid (% by volume)”=[Volume of metalworking oil before dilution]/[[Volume of metalworking oil before dilution]+[Volume of dilution water]]×100.

[Applications of Metalworking Fluid, and Metalworking Method]

The metalworking fluid of one suitable embodiment of the present invention has better workability than conventional metalworking fluids, and can be suitably used in metalworking. The metalworking fluid of one suitable embodiment of the present invention can exhibit excellent workability even without containing a sulfuric extreme pressure agent. Accordingly, corrosion of copper-containing members constituting a processing machine caused by a sulfuric extreme pressure agent can be effectively suppressed.
The workpiece to be processed using the metalworking fluid of one embodiment of the present invention is not particularly limited, and the metalworking fluid is particularly suitable for workpieces composed of metals selected from the group consisting of iron, titanium, aluminum, titanium alloy, alloy steel, nickel-based alloy, niobium alloy, tantalum alloy, molybdenum alloy, tungsten alloy, stainless steel, aluminum alloy, and high-manganese steel. Among these, the metalworking fluid is particularly suitable for a workpiece having a member containing at least iron or aluminum.
Accordingly, the present invention can also provide [1] and [2] below:
[1] A method of use comprising applying the above metalworking fluid of one embodiment of the present invention to processing of a metal workpiece.
[2] A metalworking method comprising applying the above metalworking fluid of one embodiment of the present invention to process a metal workpiece.
The workpiece set forth in [1] and [2] is as described above, and is suitably a workpiece having a member containing at least iron or aluminum.
Moreover, according to the methods set forth in [1] and [2], corrosion of copper-containing members constituting a processing machine used to process the workpiece can be suppressed.
In [1] and [2], examples of processing of the workpiece include cutting, grinding, punching, polishing, spinning, drawing, and rolling.
In the method of use according to [1] and the metalworking method according to [2], the metalworking fluid is used such that the above water-soluble metalworking oil of one embodiment of the present invention is blended with dilution water and then fed to, and thus brought into contact with, the workpiece. The metalworking fluid provides lubrication between the workpiece and the work tool. Moreover, the metalworking fluid is also used to remove swarf, prevent rust of the workpiece, cool the tool and the work piece, and the like.

EXAMPLES

Next, the present invention will now be described in more detail by way of Examples, but the present invention is not limited to these Examples in any way.
In the following Examples, the methods for measuring and calculating the following physical property values are as follows:

(1) Kinematic Viscosity, Viscosity Index

Measured and calculated in accordance with JIS K 2283:2000.

(2) HLB

Calculated based on Griffin's method.

(3) Acid Value (Indicator Photometric Titration Method)

Measured in accordance with JIS K 2501:2003 (indicator photometric titration method).

(4) Base Value (HCl Method)

Measured in accordance with JIS K 2501:2003 (HCl method).

Examples 1 to 8, Comparative Examples 1 to 4

Various components of the types shown in Tables 2 and 3 were added and mixed in the amounts shown in Tables 2 and 3 to prepare respective water-soluble metalworking oils. Details of each component used in the preparation of the water-soluble metalworking oils are as follows.

- Oil-soluble PAG (a-1): Oil-soluble polyalkylene glycol corresponding to viscosity grade VG32 stipulated in ISO 3448.
- Oil-soluble PAG (a-2): Oil-soluble polyalkylene glycol corresponding to viscosity grade VG46 stipulated in ISO 3448.
- Oil-soluble PAG (a-3): Oil-soluble polyalkylene glycol corresponding to viscosity grade VG68 stipulated in ISO 3448.

- Paraffinic mineral oil: Paraffinic mineral oil having kinematic viscosity at 40° C.=7.117 mm²/s, viscosity index=109.

- Water: Ion exchanged water

- Amine (c-1): N-Methylethanolamine, secondary monoamine
- Amine (c-2): N-Cyclohexyldiethanolamine, tertiary monoamine
- Amine (c-3): N-Methyldiethanolamine, tertiary monoamine
- Amine (c-4): Triisopropanolamine, tertiary monoamine
- Amine (c-5): N-Methyldicyclohexylamine, tertiary monoamine

- Fatty acid (d-1): Neodecanoic acid
- Fatty acid (d-2): Tall oil fatty acid
- Fatty acid (d-3): Dodecanedioic acid
- Fatty acid (d-4): Castor oil polymerized fatty acid (ricinoleic acid hexamer, acid value: 31.6 mgKOH/g, hydroxyl value: 9.4 mgKOH/g, acid value/hydroxyl value=3.36)

- Nonionic surfactant (e-1): Cocoamine ethylene oxide 2-mol adduct, HLB=6.3
- Nonionic surfactant (e-2): Polyoxyalkylene alkyl ether, HLB=12.7

- Dioctylpolysulfide

- Anionic surfactant: Polyoxyethylene oleyl ether carboxylic acid, acid value=69.3 mgKOH/g.
- Metal deactivator: Benzotriazole
- Emulsifying aid: 2-Phenoxyethanol
- Antibacterial agent: 1,2-Benzoisothiazolin-3-on
- Antifoaming agent: Silicone defoaming agent

The acid value, the base value, and the ratio of base value/acid value of the prepared water-soluble metalworking oils were measured and calculated and, also, the following evaluations were made using the water-soluble metalworking oils. The results thereof are shown in Tables 2 and 3.

(1) Classification of Oil Type

In accordance with the provisions of JIS K 2241:2017, the water-soluble metalworking oils were classified as emulsion-type oils A1 or soluble-type oils A2 of this standard. In Tables 2 and 3, “E” is given when classified as an emulsion-type oil A1, and “S” is given when classified as a soluble-type oil A2.

(2) Copper Plate Corrosion Test

A test was conducted under 50° C. oil temperature and 48-hour conditions by a test method in accordance with JIS K 2513, then the degree of discoloration of a copper plate was visually inspected, and the degree of corrosion of the copper plate was evaluated based on “Table 1 Classification of Corrosion by Copper Plate Corrosion Standard” of JIS K 2513 shown in Table 1 below. Tables 2 and 3 provide “discoloration numbers (subclassification symbols)”, and the discoloration numbers indicate the degree of corrosion of a copper plate by way of numerical values of 1 to 4, with a greater numerical value indicating severer corrosion.

TABLE 1

Discoloration	Degree of
number	discoloration	State of discoloration

Copper plate	—		For a copper plate corrosion
immediately			standard, the state of a copper
after being			plate surface immediately
polished			after being polished is
			indicated, but such a state is
			unlikely obtained after testing
			even from a sample with
			completely no corrosion.
1	Slightly	(a)	Pale orange (almost the same
	discolored		color as copper plate
			immediately after being
			polished)
		(b)	Dark orange
2	Mildly	(a)	Pink
	discolored	(b)	Pale pink with purple hue
		(c)	Multi-colored pattern with
			dark pink, blue with purple
			hue, etc. over orange
		(d)	Silver with pale gold hue
		(e)	Brass or gold
3	Severely	(a)	Reddish brown pattern over
			brass
	discolored	(b)	Multi-colored pattern with
			red and green (peacock
			pattern)
4	Corroded	(a)	Greenish blue purple or black
			to such an extent that the
			underlayer is visible
		(b)	Graphite-like black or matte
			black
		(c)	Glossy black

(3) Evaluation of Workability

A water-soluble metalworking oil was diluted with ion exchanged water to prepare a metalworking fluid having a dilute concentration of 5° by volume. Using the prepared metalworking fluid, a pilot hole was drilled under the following conditions, and then a tapping torque test was performed to measure the maximum tapping torque during processing. Measurement was performed three times, and the average value and the maximum value of the results are shown in Tables 2 and 3.
It can be said that the smaller the average value and the maximum value are, the better the metal workability of the metalworking fluid used is.

- Machine used: Tapping Center MTV-T350 (manufactured by Mectron Inc.)
- Drill: SG-ESS (manufactured by Nachi-Fujikoshi Corporation), drill diameter: 5.56 mm
  - Cutting speed: 31 m/min
  - Rotational speed: 1798 min-1
  - Feeding speed: 260 ram/min
  - Feed per revolution: 0.145 mm/rev
  - Depth: 15 mm

- Tester used: Megatap II (micro-electronische Gerate GmbH)
- Tap: Nu-Roll Tap VP-NRT B M6×1 (manufactured by OSG Corporation)
  - Cutting speed: 10 m/min
  - Feed: 1.0 mm/rev
  - Depth: 12 mm
  - Number of processed samples n: 3
  - Material to be cut: SCM440 (JIS standard) (chrome molybdenum steel)

TABLE 2

							Com-	Com-
							parative	parative
	Ex-	Ex-	Ex-	Ex-	Ex-	Ex-	Ex-	Ex-
	ample	ample	ample	ample	ample	ample	ample	ample
	1	2	3	4	5	6	1	2

Com-	Component (A1)	Oil-soluble PAG (a-1)	% by mass	1.00	3.00	5.00	7.00
position		Oil-soluble PAG (a-2)	% by mass					5.00
of		Oil-soluble PAG (a-3)	% by mass						5.00
water-	Component (A2)	Paraffinic mineral oil	% by mass							5.00
soluble	Component (B)	Water	% by mass	62.25	60.25	58.25	56.25	58.25	58.25	58.25	58.25
metal-	Component (C)	Amine (c-1)	% by mass	3.50	3.50	3.50	3.50	3.50	3.50	3.50	3.50
working		Amine (c-2)	% by mass	6.00	6.00	6.00	6.00	6.00	6.00	6.00	6.00
oil		Amine (c-3)	% by mass	3.50	3.50	3.50	3.50	3.50	3.50	3.50	3.50
		Amine (c-4)	% by mass
		Amine (c-5)	% by mass
	Component (D)	Fatty acid (d-1)	% by mass	2.00	2.00	2.00	2.00	2.00	2.00	2.00	2.00
		Fatty acid (d-2)	% by mass	2.00	2.00	2.00	2.00	2.00	2.00	2.00	2.00
		Fatty acid (d-3)	% by mass	1.50	1.50	1.50	1.50	1.50	1.50	1.50	1.50
		Fatty acid (d-4)	% by mass	6.00	6.00	6.00	6.00	6.00	6.00	6.00	6.00
	Component (E)	Nonionic surfactant (e-1)	% by mass	4.00	4.00	4.00	4.00	4.00	4.00	4.00	4.00
		Nonionic surfactant (e-2)	% by mass	1.00	1.00	1.00	1.00	1.00	1.00	1.00	1.00
	Sulfuric extreme	Dioctylpolysulfide	% by mass								5.00
	pressure agent
	Other	Anionic surfactant	% by mass	2.00	2.00	2.00	2.00	2.00	2.00	2.00	2.00
	components	Metal deactivator	% by mass	1.00	1.00	1.00	1.00	1.00	1.00	1.00	1.00
		Emulsifying aid	% by mass	4.00	4.00	4.00	4.00	4.00	4.00	4.00	4.00
		Antibacterial agent	% by mass	0.20	0.20	0.20	0.20	0.20	0.20	0.20	0.20
		Antifoaming agent	% by mass	0.05	0.05	0.05	0.05	0.05	0.05	0.05	0.05

Total

% by mass

100.00

Content of each	Component (A1) + (A2)	% by mass	2.6	7.5	12.0	16.0	12.0	12.0	0	0
component	Component (B)	% by mass	165	152	140	129	140	140	140	140
based on total	Component (C)	% by mass	34.4	32.7	31.1	29.7	31.1	31.1	31.1	31.1
amount (100%	Component (D)	% by mass	30.5	28.9	27.5	26.3	27.5	27.5	27.5	27.5
by mass) of oil	Component (E)	% by mass	13.2	12.6	12.0	11.4	12.0	12.0	12.0	12.0
excluding water	Sulfuric extreme	% by mass	0	0	0	0	0	0	0	12.0
	pressure agent
	Water-soluble	% by mass	0	0	0	0	0	0	0	0
	PAG + MPEG

	Component (C)/Component (A1)	—	13.00	4.33	2.60	1.86	2.60	2.60	—	—
	Component (D)/Component (A1)	—	11.50	3.83	2.30	1.64	2.30	2.30	—	—
	Component (C)/Component (D)	—	1.13	1.13	1.13	1.13	1.13	1.13	1.13	1.13
Properties	Acid value of water-soluble	mgKOH/g	26.11	26.11	26.11	26.11	26.11	26.11	26.11	26.12
	metalworking oil
	Base value of water-soluble	mgKOH/g	67.16	67.16	67.16	67.16	67.16	67.16	67.16	67.16
	metalworking oil
	Base value/acid value	—	2.57	2.57	2.57	2.57	2.57	2.57	2.57	2.57
Evaluation	(1) Classification of oil type	—	S	S	S	S	S	S	S	S
item	(2) Copper plate corrosion test JIS K2513	—	1(b)	1(1b)	1(1b)	1(1b)	1(1b)	1(1b)	1(1b)	4(4c)

(3) Evaluation	Average value	N · cm	249	233	230	229	225	222	291	235
of workability	of tap torque
	Maximum value	N · cm	360	340	340	340	335	335	425	345
	of tap torque

TABLE 3

			Com-	Com-
			parative	parative
	Ex-	Ex-	Ex-	Ex-
	ample	ample	ample	ample
	7	8	3	4

Composition	Component (A1)	Oil-soluble PAG (a-1)	% by mass	51.65	20.00
of		Oil-soluble PAG (a-2)	% by mass
water-soluble		Oil-soluble PAG (a-3)	% by mass
metalworking	Component (A2)	Paraffinic mineral oil	% by mass		31.65	51.65	31.65
oil	Component (B)	Water	% by mass	8.00	8.00	8.00	8.00
	Component (C)	Amine (c-1)	% by mass	1.00	1.00	1.00	1.00
		Amine (c-2)	% by mass
		Amine (c-3)	% by mass	3.50	3.50	3.50	3.50
		Amine (c-4)	% by mass	4.50	4.50	4.50	4.50
		Amine (c-5)	% by mass	6.50	6.50	6.50	6.50
	Component (D)	Fatty acid (d-1)	% by mass	1.85	1.85	1.85	1.85
		Fatty acid (d-2)	% by mass	5.00	5.00	5.00	5.00
		Fatty acid (d-3)	% by mass	1.00	1.00	1.00	1.00
		Fatty acid (d-4)	% by mass	11.00	11.00	11.00	11.00
	Component (E)	Nonionic surfactant (e-1)	% by mass
		Nonionic surfactant (e-2)	% by mass	1.90	1.90	1.90	1.90
	Sulfuric extreme	Dioctylpolysulfide	% by mass				20.00
	pressure agent
	Other	Anionic surfactant	% by mass
	components	Metal deactivator	% by mass	0.80	0.80	0.80	0.80
		Emulsifying aid	% by mass	3.00	3.00	3.00	3.00
		Antibacterial agent	% by mass	0.20	0.20	0.20	0.20
		Antifoaming agent	% by mass	0.10	0.10	0.10	0.10

Total

% by mass

100.00

Content of each	Component (A1) + (A2)	% by mass	56.1	21.7	0	0
component	Component (B)	% by mass	8.7	8.7	8.7	8.7
based on total	Component (C)	% by mass	16.8	16.8	16.8	16.8
amount (100%	Component (D)	% by mass	20.5	20.5	20.5	20.5
by mass) of oil	Component (E)	% by mass	2.1	2.1	2.1	2.1
excluding water	Sulfuric extreme pressure agent	% by mass	0	0	0	21.7
	Water-soluble PAG + MPEG	% by mass	0	0	0	0

	Component (C)/Component (A1)	—	0.30	0.78	—	—
	Component (D)/Component (A1)	—	0.36	0.94	—	—
	Component (C)/Component (D)	—	0.82	0.82	0.82	0.82
Properties	Acid value of water-soluble metalworking oil	mgKOH/g	28.20	28.20	28.20	28.26
	Base value of water-soluble metalworking oil	mgKOH/g	52.52	52.52	52.52	52.52
	Base value/acid value	—	1.86	1.86	1.86	1.86
Evaluation	(1) Classification of oil type	—	E	E	E	E
item	(2) Copper plate corrosion test JIS K2513	—	1(1b)	1(1b)	1(1b)	4(4c)

(3) Evaluation of	Average value of tap torque	N · cm	224	245	292	231
workability	Maximum value of tap torque	N · cm	340	360	430	350

From Tables 2 and 3, the metalworking fluids prepared by diluting the water-soluble metalworking oils of Examples 1 to 8, irrespective of being a soluble type or an emulsion type, suppressed corrosion of a copper plate and also had good workability. On the other hand, the metalworking fluids prepared by diluting the water-soluble metalworking oils of Comparative Examples 1 to 4 were inferior with respect to at least one of the copper plate corrosion suppressing effect and workability.

Claims

1. A water-soluble metalworking oil comprising a base oil (A) comprising oil-soluble polyalkylene glycol (A1), wherein a total content of water-soluble polyalkylene glycol and methoxypolyethylene glycol is less than 60% by mass based on the total amount excluding water.

2. The water-soluble metalworking oil according to claim 1, wherein the total content of water-soluble polyalkylene glycol and methoxypolyethylene glycol is less than 10 parts by mass based on 100 parts by mass of the total amount of component (A1).

3. The water-soluble metalworking oil according to claim 1, which is substantially free of a sulfuric extreme pressure agent.

4. The water-soluble metalworking oil according to claim 1, further comprising water (B).

5. The water-soluble metalworking oil according to claim 1, wherein the content of component (A1) in component (A) is 10 to 100% by mass based on the total amount of component (A) contained in the water-soluble metalworking oil.

6. The water-soluble metalworking oil according to claim 1, wherein the content of component (A1) is 0.01% by mass or more based on the total amount of the water-soluble metalworking oil excluding water.

7. The water-soluble metalworking oil according to claim 1, further comprising an amine compound (C).

8. The water-soluble metalworking oil according to claim 1, further comprising a fatty acid (D).

9. The water-soluble metalworking oil according to claim 1, further comprising a nonionic surfactant (E).

10. The water-soluble metalworking oil according to claim 1, which is an emulsion-type oil classified as A1 as stipulated in JIS K 2241:2017.

11. The water-soluble metalworking oil according to claim 1, which is a soluble-type oil classified as A2 as stipulated in JIS K 2241:2017.

12. A water-soluble metalworking oil comprising a base oil (A) comprising oil-soluble polyalkylene glycol (A1), wherein a total content of water-soluble polyalkylene glycol and methoxypolyethylene glycol is less than 10 parts by mass based on 100 parts by mass of the total amount of component (A).

13. A metalworking fluid obtained by blending the water-soluble metalworking oil of claim 1 with dilution water.

14. A metalworking method comprising processing a workpiece comprising metal by application of the metalworking fluid according to claim 13.

15. The metalworking method according to claim 14, wherein the workpiece has a member comprising at least iron or aluminum.

16. The metalworking method according to claim 14, wherein corrosion of a copper-containing member constituting a processing machine used in processing of the workpiece is suppressed.