Lubricant composition

Abstract

To provide an aqueous lubricant composition with excellent lubricity.SOLUTION: There is provided a lubricant composition, comprising: a poly-oxyalkylene glycol (A) represented by the following general formula (1); a polyethylene glycol (B); a carboxylic acid (C); and water. General formula (1): R1O-[(CH2CH2O)m(CH2CH(CH3)O)n]-R2, in which R1 is an alkyl group having 1 to 8 carbon atoms, R2 is a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, m is an integer of 1 or more, and n is an integer of 1 or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to lubricant compositions. [Background technology]

[0002] Mineral oils, greases, and the like are widely used as lubricants in metal working, including plastic working. On the other hand, water-based lubricants have been studied from the viewpoint of cleanability and the like.

[0003] For example, Patent Document 1 discloses a water-soluble lubricant for wire drawing, which is an aqueous solution containing a specific nonionic surfactant. This water-soluble lubricant is said to solve problems caused by the lubricant remaining on the wire after wire drawing.

[0004] Furthermore, Patent Document 2 discloses a lubricating composition for metalworking containing a specific polyalkylene glycol, which is said to be capable of suppressing contamination of workpieces. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-241782 [Patent Document 2] Japanese Patent Publication No. 2023-042264 Summary of the Invention [Problem to be solved by the invention]

[0006] Traditionally, mineral oils have been widely used in metalworking fluids due to their lubricity. However, from the perspective of realizing a sustainable, recycling-oriented society, as exemplified by the recent SDGs, mineral oils are finite and their disposal generates carbon dioxide, so it is desirable to replace them. On the other hand, water is highly sustainable and safe for workers, so even a partial switch to water could help alleviate the aforementioned issues. However, achieving the same lubricity as current oil-based fluids while maintaining the stability of the original solution in a water-containing composition is an extremely difficult task.

[0007] An object of the present disclosure is to provide a lubricant composition having excellent lubricity. [Means for solving the problem]

[0008] One aspect of the lubricant composition according to the present disclosure comprises: A polyoxyalkylene glycol (A) represented by the following general formula (1), Polyethylene glycol (B), a carboxylic acid (C); and water. R 1 O-[(CH2CH2O) m (CH2CH(CH3)O) n ]-R 2 …(1) however, R 1 is an alkyl group having 1 to 8 carbon atoms, R 2 is a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, m is an integer equal to or greater than 1, n is an integer of 1 or greater. [Effects of the Invention]

[0009] The present disclosure provides a lubricant composition with excellent lubricity. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, a lubricant composition according to an embodiment of the present disclosure will be described. The symbol "to" indicating a range of values ​​includes the lower and upper limits unless otherwise specified.

[0011] [Lubricant composition] The lubricant composition of the present disclosure comprises: A polyoxyalkylene glycol (A) represented by the following general formula (1), Polyethylene glycol (B), a carboxylic acid (C); and water. R 1 O-[(CH2CH2O) m (CH2CH(CH3)O) n ]-R 2 …(1) however, R 1 is an alkyl group having 1 to 8 carbon atoms, R 2 is a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, m is an integer equal to or greater than 1, n is an integer of 1 or greater.

[0012] The lubricant composition has excellent lubricity due to the use of a specific polyoxyalkylene glycol (A) and a polyethylene glycol (B) different from (A), and further a combination with a carboxylic acid (C). The lubricant composition contains at least a polyoxyalkylene glycol (A), a polyethylene glycol (B), a carboxylic acid (C), and water, and may further contain other components. Each component that may be contained in the lubricant composition is described below.

[0013] <Polyoxyalkylene glycol (A)> The polyoxyalkylene glycol (A) is a compound represented by the above formula (1). The polyoxyalkylene glycol (A) has oxyethylene (CH2CHO; hereinafter also referred to as "EO") and oxypropylene (CH2CH(CH3)O; hereinafter also referred to as "PO") as structural units, and further has an alkyl group at least on one end. A lubricant composition containing such a polyoxyalkylene glycol (A) has excellent lubricity and excellent stability at low temperatures.

[0014] R in formula (1) 1 is an alkyl group having 1 to 8 carbon atoms. The alkyl group may be linear or branched. Specific examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a 1,1-diethylpropyl group, an n-hexyl group, a 2,2-dimethylbutyl group, an n-heptyl group, and an n-octyl group. From the viewpoints of lubricity and low-temperature stability, the number of carbon atoms in the alkyl group is preferably 1 to 6, more preferably 2 to 4, and even more preferably 4. Furthermore, from the viewpoints of lubricity and low-temperature stability, the alkyl group is preferably a linear alkyl group.

[0015] R 2 The alkyl group having 1 to 8 carbon atoms in the above R 1 In terms of lubricity and low temperature stability, R 2 is preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom or a straight-chain alkyl group having 1 to 6 carbon atoms, and even more preferably a hydrogen atom or a straight-chain alkyl group having 2 to 4 carbon atoms.

[0016] [(CH2CH2O) m (CH2CH(CH3)O) n The symbol [ ] does not represent the bonding order of EO and PO, and the bonding order of EO and PO is arbitrary. That is, EO and PO may be random copolymerized, may be alternate copolymerized, or may be a block copolymer having a block where EO is linked and a block where PO is linked.

[0017] m and n represent the number of EO and PO, respectively. From the viewpoints of lubricity and low-temperature stability, m is preferably 1 to 100, more preferably 1 to 80, and more preferably 1 to 50. From the viewpoints of lubricity and low-temperature stability, n is preferably 1 to 100, more preferably 1 to 80, and more preferably 1 to 50. From the viewpoint of lubricity and low-temperature stability, the EO ratio (m / (m+n)) in all structural units is preferably 0.42 to 0.95, more preferably 0.45 to 0.90, and even more preferably 0.48 to 0.85.

[0018] The weight average molecular weight (Mw) of the polyoxyalkylene glycol (A) is preferably from 250 to 5,000, more preferably from 280 to 3,000, and even more preferably from 300 to 2,000, from the viewpoints of lubricity and low-temperature stability. The weight average molecular weight Mw is a value measured by GPC (gel permeation chromatography).

[0019] From the viewpoint of low temperature stability, the polyoxyalkylene glycol (A) preferably has a melting point of 0° C. or lower, more preferably −5° C. or lower, and even more preferably −8° C. or lower. The lower limit of the melting point is not particularly limited, but is usually −100° C. or higher.

[0020] In terms of lubricity, the kinematic viscosity of the polyoxyalkylene glycol (A) at 20°C in accordance with JIS K 2283 is 10 to 1,500 mm 2 / sec is preferable, 10 to 1,200 mm 2 / sec is more preferable, 10 to 500 mm 2 / second is even better.

[0021] The polyoxyalkylene glycol (A) may be synthesized or a commercially available product may be used. The synthesis method is not particularly limited, but for example, 1 The polyoxyalkylene glycol (A) can be obtained by mixing OH, ethylene oxide, and propylene oxide in a desired ratio and subjecting them to addition polymerization.

[0022] <Polyethylene glycol (B)> Polyethylene glycol (B) is HO-(CH2CH2O) p -H (where p is an integer of 2 or more), and also includes diethylene glycol. By including polyethylene glycol (B), the lubricant composition has excellent liquid stability. Furthermore, by adjusting the molecular weight and content of polyethylene glycol (B), the kinematic viscosity of the lubricant composition can be easily adjusted.

[0023] In the present lubricant composition, the molecular weight of the polyethylene glycol (B) is preferably relatively small. Specifically, the molecular weight of the polyethylene glycol (B) is preferably 80 to 600, more preferably 90 to 500, and even more preferably 100 to 400. Furthermore, the pH in the above formula is preferably 2 to 10, more preferably 2 to 9, and even more preferably 2 to 8. Two or more polyethylene glycols (B) having different molecular weights may be used in combination.

[0024] From the viewpoint of the stability of the lubricant composition, the freezing point of the polyethylene glycol (B) is preferably 15° C. or lower, more preferably 10° C. or lower, and even more preferably 7° C. or lower. The lower limit of the freezing point is not particularly limited, but is usually −100° C. or higher.

[0025] <Carboxylic acid (C)> The lubricant composition of the present invention has excellent lubricity, particularly boundary lubricity, and is therefore suitable for difficult machining processes, due to the use of a carboxylic acid (C) in combination with the above components (A) and (B). Furthermore, the lubricant composition containing the carboxylic acid (C) also has excellent rust prevention properties for the workpiece and the machining machinery.

[0026] In the present lubricant composition, the carboxylic acid (C) is preferably a monocarboxylic acid, and R 11 COOH (where R 11 is a hydrocarbon group) is more preferred. R 11Examples of the hydrocarbon group in include an aliphatic hydrocarbon group and an aromatic hydrocarbon group, and from the viewpoint of lubricity, an aliphatic hydrocarbon group is preferred. The aliphatic hydrocarbon group may be saturated or unsaturated. Furthermore, the aliphatic hydrocarbon group may be linear or branched. As the carboxylic acid (C), saturated fatty acid (R 11 is a straight-chain saturated aliphatic hydrocarbon group), unsaturated fatty acids (R 11 is a straight-chain unsaturated aliphatic hydrocarbon group), or R 11 Carboxylic acids in which the alkyl group is a branched aliphatic hydrocarbon group are preferred. Specific examples of the carboxylic acid (C) include saturated fatty acids such as hexanoic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, and stearic acid; unsaturated fatty acids such as undecenoic acid, oleic acid, and linoleic acid; and carboxylic acids having a branched alkyl group such as isononanoic acid and neodecanoic acid. From the viewpoint of lubricity, the number of carbon atoms in the carboxylic acid (C) is preferably 8 to 18. The carboxylic acid (C) may be used alone or in combination of two or more.

[0027] <Content ratio> The amount of each component in the lubricant composition may be adjusted appropriately taking into consideration the viscosity and other factors that correspond to the metal processing method used. The content of the polyoxyalkylene glycol (A) is preferably 5 to 90 mass %, more preferably 40 to 90 mass %, and even more preferably 50 to 90 mass %, based on the total amount of the lubricant composition. The content of polyethylene glycol (B) is preferably 1 to 70 mass %, more preferably 2 to 60 mass %, and even more preferably 4 to 40 mass %, based on the total amount of the lubricant composition. The content of the carboxylic acid (C) is preferably 0.1 to 10 mass %, more preferably 0.2 to 8 mass %, and even more preferably 0.5 to 5 mass %, based on the total amount of the lubricant composition. The content of water is preferably 1 to 50 mass %, more preferably 2 to 40 mass %, and even more preferably 5 to 30 mass %, based on the total amount of the lubricant composition.

[0028] The lubricant composition has a kinematic viscosity (40°C) of 1 to 300 mm in accordance with JIS K 2283. 2 / sec is preferred. It is also preferred that the lubricant composition does not solidify at 0°C, preferably at -5°C.

[0029] <Optional ingredients> The lubricant composition may further contain other components as needed, such as extreme pressure agents, antioxidants, rust inhibitors, anticorrosive agents, surfactants, amine compounds, preservatives, and antifoaming agents.

[0030] The lubricant composition may contain an extreme pressure agent from the viewpoint of further improving the lubricating effect during metal processing and preventing seizure. Examples of the extreme pressure additive include sulfur-based extreme pressure agents, phosphorus-based extreme pressure agents, and chlorine-based extreme pressure agents. Specific examples of the sulfur-based extreme pressure agent include polysulfides such as dibenzyl polysulfide, dinonyl polysulfide, didodecyl polysulfide, dibutyl polysulfide, dioctyl polysulfide, and diphenyl polysulfide; sulfurized fatty oils such as sulfurized lard, sulfurized rapeseed oil, sulfurized castor oil, sulfurized soybean oil, and sulfurized rice bran oil; sulfurized fatty acids such as sulfurized oleic acid; sulfurized esters such as sulfurized methyl oleate and sulfurized octyl oleate; and sulfurized mineral oils in which elemental sulfur is dissolved in various mineral oils. Specific examples of the phosphorus-based extreme pressure agent include zinc dialkyldithiophosphate; phosphate esters such as tricresyl phosphate, trioleyl phosphate, tributyl phosphate, trihexyl phosphate, and tridecyl phosphate; phosphites such as trioleyl phosphite and triisodecyl phosphite; thiophosphate esters such as trilauryl trithiophosphite; and amine salts and alkali metal salts thereof. Specific examples of the chlorine-based extreme pressure agent include chlorinated paraffin, chlorinated fatty oil, polyvinylidene chloride, polyvinyl chloride, vinylidene chloride-acrylic copolymer, and the like. When an extreme pressure agent is used, the content of the extreme pressure agent is preferably 0.1 to 40 mass %, more preferably 0.5 to 30 mass %, based on the total amount of the lubricant composition.

[0031] Examples of the antioxidant include phenol-based antioxidants and amine-based antioxidants. Specific examples of the phenolic antioxidant include monocyclic phenols such as 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,4,6-tri-tert-butylphenol, 2,6-di-tert-butyl-4-hydroxymethylphenol, 2,6-di-tert-butylphenol, 2,4-dimethyl-6-tert-butylphenol, 2,6-di-tert-butyl-4-(N,N-dimethylaminomethyl)phenol, 2,6-di-tert-amyl-4-methylphenol, and n-octadecyl-3-(4-hydroxy-3,5-di-tert-butylphenyl)propionate; 4,4'-methylenebis(2,6-di-tert-butylphenol), 4,4'-isopropylidenebis(2,6-di-tert-butylphenol), Examples include polycyclic phenols such as 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 4,4'-bis(2,6-di-tert-butylphenol), 4,4'-bis(2-methyl-6-tert-butylphenol), 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), 4,4'-butylidenebis(3-methyl-6-tert-butylphenol), 2,2'-thiobis(4-methyl-6-tert-butylphenol), and 4,4'-thiobis(3-methyl-6-tert-butylphenol). Specific examples of the amine antioxidant include diphenylamines such as diphenylamine, monooctyldiphenylamine, monononyldiphenylamine, 4,4'-dibutyldiphenylamine, 4,4'-dihexyldiphenylamine, 4,4'-dioctyldiphenylamine, 4,4'-dinonyldiphenylamine, tetrabutyldiphenylamine, tetrahexyldiphenylamine, tetraoctyldiphenylamine, and tetranonyldiphenylamine; and naphthylamines such as α-naphthylamine, phenyl-α-naphthylamine, butylphenyl-α-naphthylamine, hexylphenyl-α-naphthylamine, octylphenyl-α-naphthylamine, and nonylphenyl-α-naphthylamine. When an antioxidant is used, the content of the antioxidant is preferably 0.01 to 5 mass %, more preferably 0.05 to 3 mass %, based on the total amount of the lubricant composition.

[0032] Examples of the rust inhibitor include inorganic bases such as potassium hydroxide and sodium hydroxide, and acid salts such as carboxylates, phosphates, polyphosphates, tungstates, molybdates, and sulfonates. When a rust inhibitor is used, the content of the rust inhibitor is preferably 0.01 to 5 mass %, more preferably 0.05 to 3 mass %, based on the total amount of the lubricant composition.

[0033] Examples of the anticorrosive agent include benzotriazole compounds, tolyltriazole compounds, thiadiazole compounds, imidazole compounds, etc. When a rust inhibitor is used, the content of the rust inhibitor is preferably 0.01 to 5 mass %, more preferably 0.05 to 3 mass %, based on the total amount of the lubricant composition.

[0034] The surfactant may be any of nonionic surfactants, anionic surfactants, amphoteric surfactants, and cationic surfactants. Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyalkylene (ethylene and / or propylene) alkylphenyl ethers, polyoxyethylene alkyl esters composed of polyethylene glycol (or ethylene oxide) and higher fatty acids (e.g., linear or branched fatty acids having 12 to 18 carbon atoms), and polyoxyethylene sorbitan alkyl esters composed of sorbitan, polyethylene glycol, and higher fatty acids (e.g., linear or branched fatty acids having 12 to 18 carbon atoms). Examples of anionic surfactants include fatty acid salts, sulfate ester salts, sulfonate salts, phosphate ester salts, and dithiophosphate ester salts. Examples of amphoteric surfactants include amino acid-type and betaine-type carboxylate salts, sulfate ester salts, sulfonate salts, and phosphate ester salts. Examples of cationic surfactants include aliphatic amine salts and quaternary ammonium salts. When a surfactant is used, the content of the surfactant is preferably 0.01 to 5 mass %, more preferably 0.05 to 3 mass %, based on the total amount of the lubricant composition.

[0035] The amine compound is preferably an alkanolamine, more preferably a tertiary alkanolamine, such as butyldiisopropanolamine, dibutylmonoisopropanolamine, triethanolamine, triisopropanolamine, dibutylethanolamine, cyclohexyldiethanolamine, N-methyldiethanolamine, hydroxypropylamine, N-hydroxyethyl-N,N-di(2-hydroxypropyl)amine, or cyclohexyldiethanolamine. When an amine compound is used, the content of the amine compound is preferably equal to or greater than the neutralization equivalent of the carboxylic acid (C), i.e., preferably equal to or greater than 1.0 equivalent, more preferably equal to or greater than 1.05 equivalent, and even more preferably 1.1 to 2.0 equivalents relative to the carboxylic acid (C).

[0036] Examples of the preservative include isothiazolinone compounds, iodine compounds, parabens, and phenolic compounds such as isopropylmethylphenol. The antifoaming agent is preferably a polymeric silicone antifoaming agent, and examples of the polymeric silicone antifoaming agent include organopolysiloxane and fluorine-containing organopolysiloxane.

[0037] On the other hand, from the viewpoint of cleansing properties, etc., it is desirable that the content of oily components be low. Specifically, the total content of triglycerides contained in vegetable oils and the like and hydrocarbons having 18 or more carbon atoms contained in mineral oils and the like is preferably 1% by mass or less, more preferably 0.1% by mass or less, and even more preferably 0.05% by mass or less.

[0038] <Method for preparing lubricant composition> The method for preparing the lubricant composition is not particularly limited. For example, the lubricant composition can be obtained by mixing the polyoxyalkylene glycol (A), the polyethylene glycol (B), the carboxylic acid (C), and, if necessary, other components in water until homogeneous. Alternatively, a high-concentration lubricant composition may be prepared and then diluted with water before use.

[0039] <Uses of the lubricant composition> The present lubricant composition can be suitably used as a lubricant for metal working, particularly for plastic working of metals, and is effective by forming a lubricating coating on at least one surface of the material to be worked or a die or the like that comes into contact with the metal. The present lubricant composition can be suitably used as a lubricant for drawing, among other plastic workings, and further for wire drawing. The material to be processed may be metals, and among these, non-ferrous metals, particularly copper and aluminum, are preferred. [Example]

[0040] EXAMPLES The present invention will be specifically explained below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0041] [Example 1] The lubricant composition of Example 1 was prepared by adding 50 parts by mass of the following polyoxyalkylene glycol (A1), 13 parts by mass of the following polyethylene glycol (B1), 3.5 parts by mass of the following carboxylic acid (C1), and 3.5 parts by mass of the following carboxylic acid (C2) to 30 parts by mass of water and mixing them.

[0042] [Examples 2 to 11, Comparative Examples 1 to 7] Each lubricant composition was obtained in the same manner as in Example 1, except that the components were changed so as to obtain the formulation shown in Table 1.

[0043] [Comparative Examples 8 to 9] As Comparative Examples 8 and 9, rapeseed oil and mineral oil were prepared, respectively.

[0044] <Ingredients> The components in Table 1 are as follows: (Polyoxyalkylene glycol (A)) (A1)R 1 is a butyl group, R 2 is a hydrogen atom, EO ratio is 50%, Mw is 300, melting point is -50°C or less, and kinematic viscosity at 20°C is 16mm 2 / sec polyoxyalkylene glycol represented by formula (1). (A2)R 1 is a butyl group, R 2 is a hydrogen atom, EO ratio is 50%, Mw is 970, melting point is -49 ° C, kinematic viscosity at 20 ° C is 119 mm 2 / sec polyoxyalkylene glycol represented by formula (1). (A3)R 1 is a butyl group, R 2 is a hydrogen atom, EO ratio is 50%, Mw is 1,800, melting point is -45°C, kinematic viscosity at 20°C is 343mm 2 / sec polyoxyalkylene glycol represented by formula (1). (A4)R 1 is a butyl group, R 2 is a hydrogen atom, EO ratio is 50%, Mw is 3,200, melting point is -35°C, and kinematic viscosity at 20°C is 1,004mm2 The polyoxyalkylene glycol represented by the formula (1) per second. (A5) A polyoxyalkylene glycol having hydroxyl groups at both ends, an EO ratio of 50%, a Mw of 4,500, and a melting point of 40 °C, which does not satisfy the formula (1). (A6) R 1 is an n-hexadecyl group, R 2 is a hydrogen atom, and the polyoxyalkylene glycol having an EO ratio of 50% does not satisfy the formula (1). (A7) A polyoxyalkylene glycol having hydroxyl groups at both ends, an EO ratio of 40%, a Mw of 2,800, and a melting point of 3 °C, which does not satisfy the formula (1).

[0045] (Polyethylene glycol (B)) (B1) Diethylene glycol (Mw is 106, freezing point is -8 °C). (B2) Polyoxyethylene glycol (Mw is 200, freezing point is -35 °C or lower). (B3) Polyoxyethylene glycol (Mw is 300, freezing point is -10 °C). (B4) Polyoxyethylene glycol (Mw is 400, freezing point is 7 °C). (B5) Polyoxyethylene glycol (Mw is 600, freezing point is 20 °C).

[0046] (Carboxylic acid (C)) (C1) Caprylic acid (C2) Isononanoic acid (C3) Oleic acid

[0047] [Evaluation] <pH measurement> The pH of each composition was measured at 25 °C based on JIS K0102 12 (glass electrode method). The results are shown in a table.

[0048] <Kinematic viscosity measurement> The kinematic viscosity at 40 °C of the lubricant compositions of the above Examples and Comparative Examples was measured by a method in accordance with JIS K 2283. The results are shown in a table.

[0049] <Room temperature appearance evaluation> The lubricant compositions of the above Examples and Comparative Examples were visually observed at room temperature (25° C.), and the results are shown in the table below. (Evaluation criteria) A: No turbidity was observed. B: Slight turbidity was observed. C: Turbidity was observed. D: It had gelled. E: Separation or partial precipitation was observed.

[0050] <Low temperature stability evaluation> The lubricant compositions of the above Examples and Comparative Examples were visually observed in an environment of −5° C. The results are shown in the table. (Evaluation criteria) A: No turbidity and fluidity confirmed. B: Slight turbidity was observed. C: The fluidity was significantly reduced and the product became semi-solid. D: Gelled or solidified. E: Separation or partial precipitation was observed.

[0051] <Lubricity evaluation> A test plate (aluminum plate) was washed with a solvent and then fixed to a Bowden tester. The lubricant composition prepared above was applied to the test plate. A steel ball (SUJ-2) was pressed against the test plate with a load of 1 kg, and the average dynamic friction coefficient was calculated when the ball reciprocated 10 times at a speed of 4 mm / sec. The results are shown in the table. (Evaluation criteria) A: The average dynamic friction coefficient was less than 0.10. B: The average dynamic friction coefficient was 0.10 or more and less than 0.15. C: The average dynamic friction coefficient was 0.15 or more and less than 0.20. D: The average dynamic friction coefficient was 0.20 or more and less than 0.25. E: The average dynamic friction coefficient was 0.25 or more or was not measurable.

[0052] <Cleaning performance evaluation> The test plate (steel plate) was washed with a solvent, dried, and its initial weight W0 was measured. The lubricant compositions of the above examples and comparative examples were placed in a petri dish, and the steel plate was immersed therein. The steel plate was left suspended overnight and dried at room temperature. The weight W1 of the steel plate after drying was measured, and the amount of adhered lubricant composition W2 (= W1 - W0) was calculated. The steel plate with the adhered lubricant composition was placed in a beaker containing pure water and left suspended for 60 seconds. The steel plate was then removed and left in a thermostatic chamber at 60°C for 30 minutes to remove moisture (final drying). The weight W3 of the steel plate after final drying was measured, and the amount of remaining lubricant composition W4 (= W1 - W3) on the steel plate was calculated. The cleaning rate was then calculated using the following formula (1). The results are shown in the table. Cleaning rate = (W2-W4) / W4×100 …(1) (Evaluation criteria) A: The cleaning rate was over 90%. B: The cleaning rate was 80% or more but less than 90%. C: The cleaning rate was 50% or more but less than 80%. D: The cleaning rate was 25% or more but less than 50%. E: The cleaning rate was less than 25%.

[0053] [Table 1]

[0054] [Table 2]

[0055] [Summary of results] The compositions of Comparative Examples 1 to 3, which used polyoxyalkylene glycols (A5) to (A7) that did not satisfy formula (1), showed gelation, separation, or precipitation and were not suitable as lubricants. No other evaluations were performed on these compositions of Comparative Examples 1 to 3. Comparative Examples 4 and 5, which did not contain polyoxyalkylene glycol (A) or carboxylic acid (C), were homogeneous compositions, but had insufficient lubricity. The compositions of Examples 1 to 12, which combined polyoxyalkylene glycol (A) represented by the above general formula (1), polyethylene glycol (B), and carboxylic acid (C), were found to have lubricity equivalent to or better than that of rapeseed oil (Comparative Example 6) and mineral oil (Comparative Example 7), and also to have excellent detergency.

Claims

1. A polyoxyalkylene glycol (A) represented by the following general formula (1), Polyethylene glycol (B), a carboxylic acid (C); and water. R １ O-[(CH ２ CH ２ O) ｍ (CH ２ CH(CH ３ )O) ｎ ]-R ２ …(1) however, R １ is an alkyl group having 1 to 8 carbon atoms, R ２ is a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, m is an integer of 1 or greater; n is an integer of 1 or more.

2. Dynamic viscosity (40°C) according to JIS K 2283 is 1 to 300 mm ２ 10. The lubricant composition of claim 1, wherein the lubricant composition has a viscosity of 1000 psi / sec.

3. R of the polyoxyalkylene glycol (A) １ 2. The lubricant composition according to claim 1, wherein is an alkyl group having 4 carbon atoms.

4. The polyoxyalkylene glycol (A) is 5% by mass or more and 90% by mass or less, The polyethylene glycol (B) is 1% by mass or more and 70% by mass or less, The carboxylic acid (C) is 0.1% by mass or more and 10% by mass or less, The lubricant composition according to claim 1, further comprising: 1% by mass or more and 50% by mass or less of the water.

5. 2. The lubricant composition according to claim 1, wherein the content of triglycerides and hydrocarbons having 18 or more carbon atoms is 1 mass % or less.

6. The lubricant composition of claim 1, which is for metalworking.

7. The lubricant composition according to claim 1, which is used for plastic working.

8. The lubricant composition of claim 1, which is for non-ferrous metal working.

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