JP6283552B2 - Water-soluble metalworking oil and coolant for metalworking - Google Patents

Description

  The present invention relates to a water-soluble metalworking oil and a metalworking coolant obtained by diluting it with water.

Metalworking fluids used in metalworking are classified into oil-based (oil-based) and water-based (water-based), but water-based types that are excellent in cooling and infiltration properties and do not pose a fire hazard are frequently used.
In particular, since the cooling property of the oil agent is important in grinding applications, a solution-based oil agent that does not contain mineral oil is frequently used (for example, see Patent Document 1). Solution oils have good cooling and rot resistance, but are inferior to non-water, emulsion, and solve systems in terms of lubricity. Insufficient lubricity causes deterioration of the machined surface roughness, reduction of the grinding wheel life, or grinding burn.
Then, in order to provide lubricity to a solution type oil agent, polyalkylene glycol (PAG) is mix | blended with an oil agent (refer patent document 2, 3).

Japanese Patent Publication No. 40-14480 Japanese Patent Laid-Open No. 10-324888 JP 2010-70736 A

  In the solution oils described in Patent Documents 2 and 3, the lubricity is improved by increasing the blending amount of PAG. However, there is a limit to improving the lubricity even if a large amount of PAG is blended. For this reason, under severe processing conditions, the coefficient of friction between the grindstone and the work material increases, resulting in a decrease in the grindstone life and grinding burn.

  An object of the present invention is to provide a water-soluble metal working oil that is excellent in lubricity and wear resistance even under severe working conditions, and a metal working coolant obtained by diluting it with water.

The present inventors use a water-soluble oil agent in combination with a dicarboxylic acid having a sulfide structure, a polyalkylene oxide adduct of a polyhydric alcohol such as PAG or pentaesitol, and a monocarboxylic acid, thereby improving lubricity and resistance. It has been found that the wearability can be improved, and the reduction of the grinding wheel life and grinding burn can be suppressed. The present invention has been completed based on this finding.
That is, the present invention provides the following water-soluble metalworking oil and metalworking coolant.
[1] A blend of (A) a dicarboxylic acid containing a sulfide structure, (B) a polyalkylene glycol, (C) a polyhydric alcohol polyalkylene oxide adduct, and (D) a monocarboxylic acid. Water-soluble metal processing oil.
[2] The water-soluble metalworking oil according to the above [1], wherein the component (A) is a compound of the following formula (1).
_{^{HOOC-R 1 -S n -R 2}} -COOH (1)
(R ¹ and R ² are each independently a hydrocarbon group having 1 to 5 carbon atoms, and n is an integer of 1 to 8)
[3] In the water-soluble metal processing oil according to [1] or [2], the blending amount of the component (A) is 0.1% by mass or more and 14% by mass or less based on the total amount of the processing oil. Water-soluble metalworking oil characterized by that.
[4] The water-soluble metalworking oil according to any one of [1] to [3] above, wherein the component (B) is a compound of the following formula (2) and a compound of the following formula (3) A water-soluble metalworking oil characterized by being at least one of the following.
HO- (EO) a- (PO) b- (EO) c-H (2)
(EO means an ethylene oxide unit, PO means a propylene oxide unit. A and c are each independently an integer of 1 to 30, and b is an integer of 5 to 100.)
^{R 3 O- (R'O) d-} H (3)
(R ³ is an alkyl group having 1 to 30 carbon atoms. R′O is an oxide unit selected from PO and EO and may be used in combination. However, the mole of EO in R′O (The fraction is less than 1. d is an integer from 1 to 50.)
[5] The water-soluble metal processing oil according to any one of [1] to [4] above, wherein the blending amount of the component (B) is 10% by mass or more and 60% by mass based on the total amount of the processing oil. % Water-soluble metalworking oil characterized by being less than or equal to%.
[6] The water-soluble metalworking oil according to any one of [1] to [5] above, wherein the component (C) is a compound of the following formula (7) from a compound of the following formula (4) Water-soluble metalworking oil characterized by being at least one of the above.

(R ¹¹ to R ¹⁴ are each independently an alkylene group having 1 to 5 carbon atoms. E to h are each independently an integer of 1 to 30.)

(R ⁴ is an alkyl group having 1 to 30 carbon atoms. R ²¹ to R ²³ are each independently an alkylene group having 1 to 5 carbon atoms. Each of i to k is independently 1 It is an integer of 30 or more.)

(R ⁵ and R ⁶ are each independently an alkyl group having 1 to 30 carbon atoms. R ³¹ and R ³² are each independently an alkylene group having 1 to 5 carbon atoms. Each is independently an integer of 1-30.)

(R ⁷ to R ⁹ are each independently an alkyl group having 1 to 30 carbon atoms. R ⁴¹ is an alkylene group having 1 to 5 carbon atoms. N is an integer of 1 to 30. is there.)
[7] In the water-soluble metalworking oil according to any one of [1] to [6], the blending amount of the component (C) is 5% by mass or more and 30% by mass based on the total amount of the processing oil. % Water-soluble metalworking oil characterized by
[8] The water-soluble metalworking oil according to any one of [1] to [7] above, wherein the component (D) is a compound of the following formula (8) Metal processing oil.
R ¹⁰ -COOH (8)
(R ¹⁰ is a hydrocarbon group having 11 or more carbon atoms.)
[9] The water-soluble metal processing oil according to any one of [1] to [8] above, wherein the blending amount of the component (D) is 1% by mass or more and 20% by mass based on the total amount of the processing oil. % Water-soluble metalworking oil characterized by being less than or equal to%.
[10] The water-soluble metalworking oil according to any one of [1] to [9] above, further comprising (E) an acetylene glycol surfactant. Metal processing oil.
[11] The water-soluble metalworking oil according to the above [10], wherein the component (E) is an acetylene glycol ethylene oxide adduct.
[12] The water-soluble metal processing oil according to [10] or [11] above, wherein the blending amount of the component (E) is 1% by mass or more and 15% by mass or less based on the total amount of the processing oil. Features a water-soluble metalworking oil.
[13] The water-soluble metalworking oil according to any one of [1] to [12] above is a stock solution in which water is blended in an amount of 15% by mass to 75% by mass. Water-soluble metal processing oil.
[14] A metal obtained by diluting the water-soluble metalworking oil according to any one of [1] to [13] above with water to 2 to 200 times (volume) Coolant for processing.
[15] A coolant for metal processing, wherein the coolant for metal processing described in [14] is for grinding.

  The water-soluble metalworking oil (stock solution) of the present invention exhibits good lubricity and wear resistance when diluted with water to form a metalworking coolant. Therefore, when the coolant for metal processing of the present invention is used for grinding, it is difficult to cause deterioration of the machined surface roughness even under severe processing conditions, and it is possible to sufficiently suppress grinding burn and a decrease in the life of the grindstone.

  The water-soluble metal processing oil of the present invention (hereinafter also referred to as “the present processing oil”) includes (A) a dicarboxylic acid containing a sulfide structure, (B) a polyalkylene glycol, and (C) a polyhydric alcohol polyalkylene oxide adduct. And (D) a monocarboxylic acid. This processing oil is a stock solution, which is diluted with water to obtain the metal processing coolant of the present invention. Hereinafter, the present invention will be described in detail.

[Component (A)]
The component (A) in the present processing oil is a dicarboxylic acid containing a sulfide structure and has an effect of improving lubricity.
As the component (A), a dicarboxylic acid having a structure represented by the following formula (1) is particularly excellent from the viewpoint of improving lubricity.
_{^{HOOC-R 1 -S n -R 2}} -COOH (1)
Here, R ¹ and R ² are hydrocarbon groups having 1 to 5 carbon atoms, and n is an integer of 1 to 8 inclusive. If the carbon number of R ¹ or R ² is 6 or more, the water solubility may decrease.

The total carbon number in the dicarboxylic acid of the above formula (1) is 4 or more and 12 or less, but 6 or more and 10 or less is preferable from the viewpoint of water solubility and lubricity. R ¹ and R ² are preferably alkylene groups, and examples thereof include a methylene group, an ethylene group, a methylethylene group, a propylene group, and a butylene group. An ethylene group is particularly preferable from the viewpoints of water solubility and lubricity.
Further, when n is 9 or more, the structure becomes unstable and may be decomposed. Therefore, n is preferably 6 or less, more preferably 2 or less, and even more preferably 1.

Examples of such dicarboxylic acids include thiodipropionic acid, dithiodipropionic acid, thiodiacetic acid, thiodisuccinic acid, dithiodiacetic acid, and dithiodibutyric acid.
(A) As a compounding quantity of a component, 0.1 mass% or more and 14 mass% or less are preferable on the basis of the stock solution whole quantity, 1 mass% or more and 10 mass% or less are more preferable, and 2 mass% or more and 5 mass% or less are more preferable. . When there are too many compounding quantities of (A) component, there exists a possibility that the rust prevention property at the time of diluting a stock solution with water may fall.

[(B) component]
(B) component in this processing oil is polyalkylene glycol, and contributes to improvement of lubricity similarly to (A) component, but also contributes to improvement of abrasion resistance. As such a component (B), it is preferable to use at least one of polyalkylene glycols represented by the following formulas (2) and (3) from the viewpoint of improving lubricity and wear resistance.
HO- (EO) a- (PO) b- (EO) c-H (2)
^{R 3 O- (R'O) d-} H (3)

In the formula (2), EO means an ethylene oxide unit, and PO means a propylene oxide unit. a and c are each independently an integer of 1 to 30, and b is an integer of 5 to 100. The total number of EO structures in formula (2) is preferably 10 or more and 30 or less, and the total number of PO structures is preferably 10 or more and 50 or less, more preferably 20 or more and 40 or less. If the total number of EO structures exceeds 60, the lubricity when diluted with water may be reduced. Further, if the total number of PO structures exceeds 100, the water solubility may decrease.
In Formula (3), R ³ is an alkyl group having 1 to 30 carbon atoms. If the number of carbon atoms in R ³ exceeds 30, water solubility may be reduced. R′O is an oxide unit selected from PO and EO and may be used as a mixture. However, the molar fraction of EO in R′O is preferably less than 1 from the viewpoint of defoaming properties when diluted with water. d is an integer of 1 to 50. If the number of carbon atoms in R ³ exceeds 30, water solubility may be reduced.

The mass average molecular weight of the component (B) described above is preferably 500 or more and 10,000 or less, and more preferably 1000 or more and 5000 or less. In any case where the mass average molecular weight is less than 500 or more than 10,000, there is a possibility that the lubricity when diluted with water is lowered.
The (B) component polyalkylene glycols of the formulas (2) and (3) may be used alone or in combination. In addition, the polyalkylene glycols of the formulas (2) and (3) may be used in a mixture of various structures having different EO structures and PO unit numbers.
(B) The preferable compounding quantity of a component is 10 mass% or more and 60 mass% or less on the basis of the undiluted | stock solution whole quantity, A more preferable compounding quantity is 20 mass% or more and 40 mass% or less, Furthermore, a more preferable compounding quantity is 20 mass% or more. 30% by mass or less. If the amount is too large, the lubricity becomes too high at a normal dilution rate, and the biting ability of the grindstone may be lowered during grinding.

[Component (C)]
(C) component in this processing oil is at least any one from the compound of following formula (4) to the compound of following formula (7). Component (C) contributes to improvement of wear resistance.

In the above formula (4), R ¹¹ to R ¹⁴ are each independently an alkylene group having 1 to 5 carbon atoms. e to h are each independently an integer of 1 to 30.
In the above formula (5), R ⁴ is an alkyl group having 1 to 30 carbon atoms. R ²¹ to R ²³ are each independently an alkylene group having 1 to 5 carbon atoms. i to k are each independently an integer of 1 to 30.
In the above formula (6), R ⁵ and R ⁶ are each independently an alkyl group having 1 to 30 carbon atoms. R ³¹ and R ³² are each independently an alkylene group having 1 to 5 carbon atoms. l and m are each independently an integer of 1 to 30.
In the above formula (7), R ⁷ to R ⁹ are each independently an alkyl group having 1 to 30 carbon atoms. R ⁴¹ is an alkylene group having 1 to 5 carbon atoms. n is an integer of 1-30.

Among the components (C) described above, an EO adduct of pentaerythritol or an EO adduct of trimethylolpropane is more preferable from the viewpoint of improving wear resistance.
The blending amount of component (C) is preferably 5% by mass or more and 30% by mass or less based on the total amount of processing oil from the viewpoint of wear resistance at a normal dilution rate.

[Component (D)]
(D) component in this processing oil is monocarboxylic acid, and contributes to improvement of lubricity and abrasion resistance. As such a monocarboxylic acid, a so-called long-chain carboxylic acid is preferable, and specifically, a compound of the following formula (8) is preferable.
R ¹⁰ -COOH (8)
Here, R ¹⁰ is a hydrocarbon group having 11 or more carbon atoms. The hydrocarbon group may be linear or branched and may be saturated or unsaturated. From the viewpoints of lubricity and wear resistance, tall oil fatty acids are preferred.
Specific examples of the long chain carboxylic acid include lauric acid, stearic acid, oleic acid, linoleic acid, linolenic acid, erucic acid, palmitic acid, ricinoleic acid, hydroxy fatty acids (eg, ricinoleic acid, 12-hydroxystearic acid, etc. ), Arachidic acid, behenic acid, melissic acid, isostearic acid, soybean oil fatty acid extracted from oil and fat, coconut oil fatty acid, rapeseed oil fatty acid, tall oil fatty acid (C18) and the like.
The blending amount of component (D) is preferably 1% by mass or more and 20% by mass or less based on the total amount of processing oil from the viewpoint of lubricity and wear resistance at a normal dilution rate.

This processing oil mix | blends above-mentioned (A) component to (D) component with water, and makes it a stock solution. This processing oil (stock solution) is preferably 40% by mass or more and 90% by mass or less, and more preferably 60% by mass, based on the total amount of processing oil based on the total amount of processing oil (A) to (D). % To 80% by mass.
When the blending amount of the component (A) to the component (D) is less than 40% by mass, when the dilution ratio with water is too high when the processing oil is used in the field, the lubricity decreases (the friction coefficient) Rise). On the other hand, if the blending amount of the component (A) to the component (D) exceeds 90% by mass, the stock solution stability may be lowered. Here, the stock solution stability means that the stock solution is not uniform due to phase separation, solid insolubility, precipitation, or the like.

The proportion of water for preparing the stock solution is preferably 15% by mass or more and 75% by mass or less based on the total amount of processing oil. When the proportion of water is less than 15% by mass, it becomes difficult to dissolve the components (A) and (B), and the preparation of the stock solution becomes complicated. Moreover, when the ratio of the water for stock solution preparation exceeds 75 mass%, the storage amount and transport amount as stock solution will become excessive, and handling property will fall.
The processing oil (stock solution) may be used as it is, but is preferably diluted with water to a ratio (volume ratio) of 2 to 200 times, more preferably 5 to 100 times. Used as coolant for metal processing.

[Other ingredients]
It is preferable that a nonionic surfactant is further blended in the processing oil as the component (E). By blending such a surfactant, the wettability of the processing oil is improved and the processing oil can easily penetrate between the grindstone and the work material.
As the component (E), an acetylene glycol surfactant is particularly preferable from the viewpoint of its effect. As such an acetylene glycol-based surfactant, for example, acetylene glycol and its alkylene oxide adduct described in JP2011-12249A can be suitably used. For example, an acetylene glycol EO adduct is suitable. Examples of commercially available products include DYNOL 604, SURFINOL 420, SURFINOL 465 and the like manufactured by Air Products and Chemicals.
(E) As a compounding quantity of a component, it is preferable that it is 0.1 mass% or more and 20 mass% or less on the basis of the undiluted solution whole quantity, and it is more preferable that it is 1 mass% or more and 10 mass% or less. When there are too many compounding quantities of (E) component, the defoaming property at the time of dilution will deteriorate.

The processing oil preferably further contains alkanolamine as the component (F). This alkanolamine reacts with the above-mentioned component (A) or component (D) to become an alkanolamine carboxylate and further improve the lubricity. Alkanolamine also functions as a rust inhibitor.
The alkanolamine is not particularly limited, and primary, secondary, and tertiary amines can be used in combination. However, if only a primary amine is used, the amine is highly volatile, and the working environment may be deteriorated in terms of odor. Therefore, when a primary amine is used, it is preferable to combine a secondary amine or a tertiary amine. A tertiary amine is preferred from the viewpoint of odor.

Specific examples of the primary amine include, for example, 1-amino-2-propanol, 2-amino-2-methyl-1-propanol, 1-amino-2-butanol, 2-amino-1-propanol, and 3-amino- Examples include 2-butanol. Among these, 1-amino-2-propanol and 2-amino-2-methyl-1-propanol are particularly preferable from the viewpoint of rust prevention against iron. In this processing oil, the above-described components may be used singly or in combination of two or more.
Specific examples of the secondary amine include, for example, diethanolamine, di (n-propanol) amine, diisopropanolamine, N-methylmonoethanolamine, N-ethylmonoethanolamine, N-cyclomonoethanolamine, Nn-propyl. Examples thereof include monoethanolamine, Ni-propyl monoethanolamine, Nn-butyl monoethanolamine, Ni-butyl monoethanolamine, and Nt-butyl monoethanolamine. In this processing oil, the above-described components may be used singly or in combination of two or more.

  Specific examples of the tertiary amine include N-methyldiethanolamine, N-ethyldiethanolamine, triethanolamine, N-cyclohexyldiethanolamine, Nn-propyldiethanolamine, Ni-propyldiethanolamine, Nn-butyldiethanolamine, N -I-butyldiethanolamine, Nt-butyldiethanolamine and the like. One kind of the above-described components may be used, or two or more kinds may be used.

The blending amount of the component (F) is preferably 20% by mass or more and 55% by mass or less based on the total amount of processing oil (stock solution). When the blending amount of the component (F) is less than 20% by mass, if the dilution ratio with water is too high when the processing oil is used in the field, the rust prevention property may be lowered. On the other hand, when the blending amount of the component (F) exceeds 55% by mass, the stock solution stability is lowered.
Here, in order to improve rust prevention property, it is preferable to use together with (F) component carboxylic acid which does not contain sulfur as a rust preventive agent. Examples of such carboxylic acids include caproic acid, nonanoic acid, isononanoic acid, trimethylhexanoic acid, neodecanoic acid, and decanoic acid having 8 to 10 carbon atoms from the viewpoint of defoaming property and stability of hard water. Preferred are monocarboxylic acids such as these, and dicarboxylic acids such as nonanedioic acid having 9 to 12 carbon atoms, undecanedioic acid, sebacic acid, and dodecanedioic acid.
In particular, the above-described trimethylhexanoic acid is excellent in the effect (hard water stability) of reducing the formation of a solid on the liquid surface when the processing oil (stock solution) is diluted with water.
Moreover, as an alkyl group which comprises the principal chain of carboxylic acid, what has a branched structure is preferable at the point of decay resistance. As the carboxylic acid, dibasic acid is superior in rust prevention when used as a salt, but from the viewpoint of stability of the stock solution (hard to insolubilize), dibasic acid and monobasic acid are mixed. Are preferably used.

Moreover, various well-known additives can be suitably mix | blended with this processing oil in the range which does not inhibit the objective of this invention. For example, extreme pressure agents, oily agents, bactericides (preservatives), metal deactivators, and antifoaming agents.
Examples of the extreme pressure agent include a sulfur-based extreme pressure agent, a phosphorus-based extreme pressure agent, an extreme pressure agent containing sulfur and a metal, and an extreme pressure agent containing phosphorus and a metal. These extreme pressure agents can be used singly or in combination of two or more. Any extreme pressure agent may be used as long as it contains a sulfur atom or a phosphorus atom in the molecule and can exhibit load resistance and wear resistance. Examples of extreme pressure agents containing sulfur in the molecule include sulfurized fats and oils, sulfurized fatty acids, sulfurized esters, sulfurized olefins, dihydrocarbyl polysulfides, thiadiazole compounds, alkylthiocarbamoyl compounds, triazine compounds, thioterpene compounds, dialkylthiodipropionate compounds, etc. Can be mentioned. The blending amount of these extreme pressure agents is blended in the stock solution so as to be about 0.05% by mass or more and 0.5% by mass or less on the basis of the final diluent (coolant) from the viewpoint of the blending effect.

  Examples of the oily agent include aliphatic compounds such as aliphatic alcohols and fatty acid metal salts, and ester compounds such as polyol esters, sorbitan esters, and glycerides. The blending amount of these oil-based agents is blended in the stock solution so as to be about 0.2% by mass or more and 2% by mass or less based on the coolant from the viewpoint of the blending effect.

  As a bactericidal agent, 2-pyridylthio-1-oxide salt is mentioned, for example. Specific examples include sodium 2-pyridylthio-1-oxide, bis (2-pyridyldithio-1-oxide) zinc, and bis (2-sulfidepyridine-1-olato) copper. The blending amount of these bactericides is blended in the stock solution so as to be about 0.01% by mass or more and 5% by mass or less based on the coolant from the viewpoint of blending effect.

Examples of the metal deactivator include benzotriazole, benzotriazole derivatives, imidazoline, pyrimidine derivatives, and thiadiazole. One of these may be used alone, or two or more may be used in combination. The blending amount of the metal deactivator is blended in the stock solution so as to be about 0.01% by mass or more and 3% by mass or less based on the coolant from the viewpoint of blending effect.
Examples of the antifoaming agent include methyl silicone oil, fluorosilicone oil, and polyacrylate. The blending amount of these antifoaming agents is blended in the stock solution so as to be about 0.004 mass% or more and 0.08 mass% or less on the basis of the blending effect.

  As described above, the water-soluble metalworking oil of the present invention is appropriately diluted with water so as to have an appropriate concentration according to the purpose of use, and includes grinding, cutting, polishing, drawing, drawing, rolling, etc. It can be suitably used in various metal processing fields. Grinding includes cylindrical grinding, internal grinding, surface grinding, centerless grinding, tool grinding, honing, super-finishing, and special curved grinding (eg screw grinding, gear grinding, cam grinding) , Roll grinding).

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
[Examples 1-5, Comparative Examples 1-7]
After preparing a water-soluble metalworking oil (stock solution) according to the formulation shown in Table 1, each stock solution was diluted 20 times (volume) with tap water to obtain each sample oil. Each sample oil was subjected to a block-on-ring test to evaluate lubricity and wear resistance. Test conditions and evaluation items (evaluation methods) are as follows. The results are shown in Table 1.

<Block-on-ring test>
Testing machine: Block-on-ring testing machine (manufactured by Maruhishi Engineering Co., Ltd.)
Load: 100N
Rotation speed: 500rpm (53m / min)
Time: 10min
Ring: SAE 4620STEEL
Block: S45C

<Evaluation item (evaluation method)>
・ Lubricity Evaluation was made based on friction force (N) according to the following criteria.
○: 13.5 N or less ×: Exceeding 13.5 N ・ Abrasion resistance Evaluation was made according to the following criteria from the wear scar width (μm).
○: 1000 μm or less △: Over 1000 μm and 1100 μm or less ×: 1 Over 100 μm

1) Tall oil fatty acid (C18)
2) HO (EO) _8.5- (PO) _30.2- (EO) _8.5 H: Sanyo Chemical 3) HO (EO) _13.2- (PO) _30- (EO) _13.2 H : Sanyo Chemical 4) CH ₃ O (PO) a ((EO) b / (PO) c) (PO) dH: Sanyo Chemical's Brember LUB82
5) Pentaerythritol polyoxyethylene ether: PNT-60U made by Nippon Emulsifier
6) Pentaerythritol polyoxyethylene ether: Nippon Emulsifier PNT-40
7) Trimethylolpropane tripolyoxyethylene ether: Nippon Emulsifier TMP-60
8) Acetylene glycol surfactant: used by mixing Dinol 604, Surfynol 420 and Surfynol 465 manufactured by Air Products and Chemicals 9) Other components: 30% by mass aqueous solution of (polyethyleneimine (molecular weight 1000)): 0.3 mass%, benzotriazole: 1.0 mass%, 35 mass% aqueous solution of benzoisothiazoline: 0.2 mass%, sodium pyrithione: 0.2 mass%, silicone-based antifoaming agent: 0.4 mass%)

〔Evaluation results〕
Since the coolant obtained by diluting the stock solutions of Examples 1 to 5 is composed of the components (A) to (D) of the present invention, both have excellent lubricity and wear resistance.
On the other hand, since the coolant obtained by diluting the stock solutions of Comparative Examples 1 to 6 lacks any of the components (A) to (D), it is possible to achieve both lubricity and wear resistance. Can not.

Claims (12)

(A) a dicarboxylic acid containing a sulfide structure, (B) a compound of the following formula (2) and / or a compound of the following formula (3) , (C ) a compound of the following formula (4) to the following formula (7) And (D) a monocarboxylic acid which is a compound represented by the following formula (8) .
HO- (EO) a- (PO) b- (EO) c-H (2)
(EO means an ethylene oxide unit, PO means a propylene oxide unit. A and c are each independently an integer of 1 to 30, and b is an integer of 5 to 100.)
^{R 3 O- (R'O) d-} H (3)
(R ³ is an alkyl group having 1 to 30 carbon atoms. R′O is an oxide unit selected from PO and EO and may be used in combination. However, the mole of EO in R′O (The fraction is less than 1. d is an integer from 1 to 50.)

(R ¹¹ to R ¹⁴ are each independently an alkylene group having 1 to 5 carbon atoms. E to h are each independently an integer of 1 to 30.)

(R ⁴ is an alkyl group having 1 to 30 carbon atoms. R ²¹ to R ²³ are each independently an alkylene group having 1 to 5 carbon atoms. Each of i to k is independently 1 30 or more
The following integers. )

(R ⁵ and R ⁶ are each independently an alkyl group having 1 to 30 carbon atoms. R ³¹ and R ³² are each independently an alkylene group having 1 to 5 carbon atoms. Each is independently an integer of 1-30.)

(R ⁷ to R ⁹ are each independently an alkyl group having 1 to 30 carbon atoms. R ⁴¹ is an alkylene group having 1 to 5 carbon atoms. N is an integer of 1 to 30. is there.)
R ¹⁰ -COOH (8)
(R ¹⁰ is a hydrocarbon group having 11 or more carbon atoms.) In the water-soluble metalworking oil according to claim 1,
The said (A) component is a compound of following formula (1). Water-soluble metalworking oil characterized by the above-mentioned.
_{^{HOOC-R 1 -S n -R 2}} -COOH (1)
(R ¹ and R ² are each independently a hydrocarbon group having 1 to 5 carbon atoms, and n is an integer of 1 to 8) In the water-soluble metalworking oil according to claim 1 or 2,
The water-soluble metalworking oil, wherein the blending amount of the component (A) is 0.1% by mass or more and 14% by mass or less based on the total amount of the processing oil. In the water-soluble metalworking oil according to any one of claims 1 to 3 ,
The amount of the component (B) is 10% by mass or more and 60% by mass or less based on the total amount of the processing oil. In the water-soluble metalworking oil according to any one of claims 1 to 4 ,
The amount of the component (C) is 5% by mass or more and 30% by mass or less based on the total amount of the processing oil. In the water-soluble metalworking oil according to any one of claims 1 to 5 ,
The blending amount of the component (D) is 1% by mass or more and 20% by mass or less based on the total amount of the processing oil. In the water-soluble metalworking oil according to any one of claims 1 to 6 ,
(E) A water-soluble metalworking oil characterized by comprising an acetylene glycol surfactant. In the water-soluble metalworking oil according to claim 7 ,
The water-soluble metalworking oil, wherein the component (E) is an acetylene glycol ethylene oxide adduct. In the water-soluble metalworking oil according to claim 7 or 8 ,
The amount of the component (E) is 1% by mass or more and 15% by mass or less based on the total amount of the processing oil. The water-soluble metalworking oil according to any one of claims 1 to 9 , wherein the water-soluble metalworking oil is a stock solution in which water is blended in an amount of 15% by mass to 75% by mass. . A coolant for metalworking, wherein the water-soluble metalworking oil according to any one of claims 1 to 10 is diluted to 2 to 200 times (volume) with water. The coolant for metal processing according to claim 11 is for grinding.