Lubricant

Abstract

To provide a lubricant useful as a component of water-soluble cutting fluids, exhibiting excellent lubricity, defoaming properties, and low-temperature stability. [Solution] A lubricant comprising a polyether represented by the following formula (1) (the definition of the symbols in the formula is as described in the specification). JPEG2026050048000008.jpg15123

Description

Technical Field

[0001] The present invention relates to a lubricant composed of polyether.

Background Art

[0002] Polyethers produced by ring-opening addition polymerization with cyclic ethers such as ethylene oxide and propylene oxide, or by dehydration condensation of polyhydric alcohols, are used in various applications such as lubricants and defoamers because it is easy to control the balance between hydrophilicity and lipophilicity and the molecular weight.

[0003] For example, water-soluble cutting oils widely used in the field of plastic processing such as cutting, grinding, rolling, and quenching use polyethers for the purpose of imparting water solubility and lubricity. However, from the perspective of improving workability, there is an increasing demand for imparting defoaming properties. In view of such a situation, in Patent Documents 1 and 2, it has been reported that lubricants composed of specific polyethers are excellent in lubricity and defoaming properties.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the field of lubricants, particularly in the area of ​​water-soluble cutting fluids used for lubrication and cooling during machining, hydrophobic components such as mineral oils, fats and oils, and synthetic oils are sometimes used in combination with polyethers to improve lubricity. However, while water-soluble cutting fluids containing hydrophobic components offer excellent lubricity, they also require the inclusion of surfactants. As a result, foaming and other issues can occur due to the surfactants, leading to insufficient cooling and reduced machinability, which can worsen production efficiency. Furthermore, water-soluble cutting fluids are sometimes mixed with sliding oils to enhance lubricity. However, since the water-soluble cutting fluid is recovered and reused after use, it is necessary for the sliding oil to separate quickly from the water-soluble cutting fluid. However, when water-soluble cutting fluids contain surfactants, the sliding oil and water-soluble cutting fluid can emulsify, resulting in poor separation.

[0006] On the other hand, reducing the amount of surfactant in water-soluble cutting fluid could lead to problems with the low-temperature stability of water-soluble cutting fluid. Under low-temperature conditions below 0°C, such as those in winter, components of the water-soluble cutting fluid adhering to the machine may precipitate when the machine is stopped (on holidays, at night), causing cutting defects when the machine is restarted. Alternatively, if the water-soluble cutting fluid is stored below 0°C after preparation, the cutting fluid components may precipitate.

[0007] The problem that this invention aims to solve is to provide a lubricant that is useful as a component of water-soluble cutting fluid, exhibiting excellent lubricity, antifoaming properties, and low-temperature stability. [Means for solving the problem]

[0008] In view of the above circumstances, the inventors conducted diligent research and found that a polyether of a specific structure is a useful lubricant as a component of a water-soluble cutting fluid that is excellent in lubricity, defoaming properties, and low-temperature stability. Based on this finding, the present invention is as follows. [1] Equation (1):

[0009] [ka]

[0010] [wherein, R , R 2 , and a number of R 3 are each independently a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, (the number of hydrogen atoms in R 1 ~R 3 ) / (the number of hydrocarbon groups in R 1 ~R 3 ) is 20 or less, GL is a glycerin residue, CH2CH2O is an ethylene glycol residue, CH2CH2CH2O is a 1,3-propanediol residue, C n H 2n O is an alkanediol residue having 4 to 8 carbon atoms, a, b, c, and d are the average degrees of polymerization of GL, CH2CH2O, CH2CH2CH2O, and C n H 2n O, respectively, a is a number from 0 to 30, b is a number from 0 to 80, <00,00136>a + b is a number from 1 to 80, c is a number from 0 to 60, d is a number from 0 to 60, c + d is a number from 1 to 70, (a + b) / (c + d) is a number from 0.2 to 8, and n is a number from 4 to 8.] A lubricant comprising a polyether represented by

Advantages of the Invention

[0011] According to the present invention, a lubricant useful as a component of a water-soluble cutting oil excellent in lubricity, defoaming property, and low-temperature stability can be obtained.

Embodiments for Carrying Out the Invention

[0012] In this specification, a numerical range defined using "~" shall include the numerical values at both ends (upper limit and lower limit) of "~". For example, "2~5" represents 2 or more and 5 or less.

[0013] <Lubricant> The lubricant of the present invention is defined by the following formula (1):

[0014] [ka]

[0015] It consists of a polyether represented by . The lubricant of the present invention may be used alone or in combination of two or more types. The definitions of the symbols in formula (1) will be explained in order below.

[0016] In equation (1), R 1 , R 2 , and a number of R 3 Each of these is independently a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms. Polyethers having hydrocarbon groups with 21 or more carbon atoms may have reduced antifoaming properties or reduced low-temperature stability of water-soluble cutting fluids.

[0017] Examples of hydrocarbon groups include alkyl groups, alkenyl groups, cycloalkyl groups, aryl groups, and aralkyl groups. The hydrocarbon group is preferably an alkyl group or an alkenyl group. Both alkyl and alkenyl groups may be linear or branched.

[0018] The hydrocarbon group having 1 to 20 carbon atoms is preferably an alkyl group having 1 to 12 carbon atoms or an alkenyl group having 1 to 12 carbon atoms, and more preferably an alkyl group having 1 to 6 carbon atoms. Examples of alkyl groups having 1 to 6 carbon atoms include methyl, ethyl, propyl, butyl, sec-butyl, tert-butyl, and hexyl groups. The hydrocarbon group having 1 to 20 carbon atoms is most preferably a methyl group.

[0019] (R 1 ~R 3 (Number of hydrogen atoms inside) / (R) 1 ~R 3The ratio of hydrogen atoms to hydrocarbon groups (hereinafter sometimes referred to as "hydrogen atom / hydrocarbon group") is 20 or less, preferably 15 or less, and more preferably 10 or less, from the viewpoint of lubricity, defoaming properties, and low-temperature stability of the water-soluble cutting fluid. Note that the hydrogen atom / hydrocarbon group ratio may be 0. Also, in this specification, R 1 ~R 3 When the number of hydrocarbon groups inside is 0, the hydrogen atom / hydrocarbon group ratio is interpreted as ∞ (infinity).

[0020] As described in the Examples section below, the hydrogen atom / hydrocarbon group of the polyether (i.e., (R 1 ~R 3 (Number of hydrogen atoms inside) / (R) 1 ~R 3 The number of hydrocarbon groups inside is determined when a polyether is acetylated. 13 From the integrated signal of the carbonyl carbon derived from the acetyl group and the integrated signal of the terminal CH3 derived from the hydrocarbon group, obtained by 13C-NMR measurement, the following formula is derived: Hydrogen atom / hydrocarbon group = Integral value of the signal from the carbonyl carbon derived from the acetyl group / Integral value of the signal from the terminal CH3 derived from the hydrocarbon group It can be calculated by [method].

[0021] The acetylation method described above is not particularly limited, and known methods can be used, but the method using pyridine and acetic anhydride, as described in the Examples section below, is preferred. 13 1C-NMR measurement can be performed as described in the Examples section below.

[0022] as needed, 13 In addition to CNMR measurement 1 By combining measurements such as H-NMR, DEPT135, and 2D NMR (HHCOSY, HMQC, HMBC, NOESY), it is possible to calculate the number of hydrogen atoms / hydrocarbon groups.

[0023] In formula (1), GL is a glycerol residue. Here, "glycerol residue" refers to a compound in formula (2) or formula (3):

[0024] [ka]

[0025] (In the formula, * represents R 3 This is the bonding position. This refers to the group represented by formula (1) or (3). Note that the glycerol residue may be a group formed from a compound other than glycerol, as long as it has the structure represented by formula (1) or (3).

[0026] In formula (1), CH2CH2O is an ethylene glycol residue. Here, "ethylene glycol residue" means a group having a structure obtained by removing one hydroxyl group (HO-) and the hydrogen atom (H) from the other hydroxyl group (-OH) of ethylene glycol (HO-CH2CH2-OH). Note that the ethylene glycol residue may be a group formed from a compound other than ethylene glycol (e.g., ethylene oxide), as long as it has the above structure.

[0027] In formula (1), CH2CH2CH2O is a 1,3-propanediol residue. Here, a "1,3-propanediol residue" means a group having the structure obtained by removing one hydroxyl group (HO-) and the hydrogen atom (H) from the other hydroxyl group (-OH) of 1,3-propanediol (HO-CH2CH2CH2-OH). Note that the 1,3-propanediol residue may be a group formed from a compound other than 1,3-propanediol, as long as it has the above structure.

[0028] In equation (1), C n H 2n O is an alkanediol residue with 4 to 8 carbon atoms. Here, "alkanediol residue with 4 to 8 carbon atoms" means "an alkanediol (HO-C) with 4 to 8 carbon atoms." n H 2nThis refers to a group having a structure obtained by removing one hydroxyl group (HO-) from a -OH group (n=4~8) and removing a hydrogen atom (H) from the other hydroxyl group (-OH). The alkanediol may be linear or branched. Note that the alkanediol residue with 4 to 8 carbon atoms may be a group formed from a different compound than the alkanediol with 4 to 8 carbon atoms, as long as it has the above structure. The "1,2-butanediol residue" and the like described later have the same meaning as the "alkanediol residue with 4 to 8 carbon atoms".

[0029] Examples of alkanediol residues with 4 to 8 carbon atoms include 1,2-butanediol residues, 1,3-butanediol residues, 1,4-butanediol residues, 1,2-pentanediol residues, 1,3-pentanediol residues, 1,4-pentanediol residues, 1,5-pentanediol residues, neopentyl glycol residues, 1,2-hexanediol residues, 1,3-hexanediol residues, 1,4-hexanediol residues, 1,5-hexanediol residues, 1,6-hexanediol residues, 3-methyl-1,5-pentanediol residues, 1,2-heptanediol residues, 1,7-heptanediol residues, and 1,8-octanediol residues.

[0030] C n H 2n O is, from the viewpoint of the lubricity and low-temperature stability of water-soluble cutting fluids, Preferably, it is an alkanediol residue having 4 to 6 carbon atoms. More preferably, the residues are 1,2-butanediol residues, 1,3-butanediol residues, 1,4-butanediol residues, 1,5-pentanediol residues, or 1,6-hexanediol residues. More preferably, the residues are 1,3-butanediol residues, 1,4-butanediol residues, or 1,6-hexanediol residues. Particularly preferred are 1,3-butanediol residues or 1,6-hexanediol residues.

[0031] Polyethers containing alkanediol residues with 9 or more carbon atoms may have reduced lubricity and low-temperature stability in water-soluble cutting fluids containing them.

[0032] In equation (1), a, b, c, and d are GL, CH2CH2O, CH2CH2CH2O, and C, respectively. n H 2n This represents the average degree of polymerization of O. Therefore, these values ​​may all be decimals.

[0033] From the viewpoint of the lubricity and low-temperature stability of the water-soluble cutting fluid, a is a number from 0 to 30, preferably a number from 0 to 15, and more preferably a number from 0 to 10. Here, "a is 0" means that GL is not present. If b is 0, from the viewpoint of lubricity, a is preferably a number from 3 to 10.

[0034] From the viewpoint of the defoaming properties of the water-soluble cutting fluid, b is a number from 0 to 80, preferably from 0 to 50, and more preferably from 0 to 30. Here, "b is 0" means that CH2CH2O is not present. If a is 0, from the viewpoint of the defoaming properties of the water-soluble cutting fluid, b is preferably a number from 4 to 50.

[0035] a+b is a number from 1 to 80, preferably a number from 2 to 70, and more preferably a number from 3 to 60, from the viewpoint of the lubricity and defoaming properties of the water-soluble cutting fluid.

[0036] c is a number between 0 and 60, preferably between 0 and 40, and more preferably between 0 and 30, from the viewpoint of the lubricity of the water-soluble cutting fluid. Here, "c is 0" means that CH2CH2CH2O is not present. When d is 0, c is preferably a number between 2 and 30, from the viewpoint of the lubricity and low-temperature stability of the water-soluble cutting fluid.

[0037] From the viewpoint of the lubricity of the water-soluble cutting fluid, d is a number from 0 to 60, preferably a number from 0 to 40, and more preferably a number from 0 to 30. Here, "d is 0" means C n H 2nThis means that O is not present. When c is 0, d is preferably a number between 2 and 30 from the viewpoint of lubricity and low-temperature stability of the water-soluble cutting fluid.

[0038] c+d is a number from 1 to 70, preferably a number from 2 to 50, and more preferably a number from 3 to 40, from the viewpoint of the lubricity of the water-soluble cutting fluid.

[0039] (a+b) / (c+d) is a number between 0.2 and 8, preferably between 0.25 and 5, and more preferably between 0.33 and 4, from the viewpoint of the defoaming properties and low-temperature stability of the water-soluble cutting fluid. In this specification, when c+d is 0, (a+b) / (c+d) is interpreted as ∞ (infinity).

[0040] In equation (1), n ​​is C n H 2n n is the number of carbon atoms in oxygen, and is between 4 and 8. From the viewpoint of low-temperature stability of water-soluble cutting fluids, n is preferably between 4 and 6.

[0041] In equation (1), the slash " / " represents GL, CH2CH2O, CH2CH2CH2O, and C n H 2n This indicates that there is no restriction on the order of O, that is, they can exist in any order. Therefore, (i)GL, CH2CH2O, CH2CH2CH2O, and C n H 2n O may be bonded to each other randomly, (ii) GL, CH2CH2O, CH2CH2CH2O, and C n H 2n One or more of the O molecules may form blocks with each other, (iii) GL, CH2CH2O, CH2CH2CH2O, and C n H 2n O may be bonded to include both embodiments of (i) and (ii) above. For example, multiple CH2CH2O may form a block, and this block, GL, CH2CH2CH2O, and C n H 2nO may be randomly bonded. If there are three or more CH2CH2O molecules in one molecule, it is preferable that a (CH2CH2O)3 block is formed.

[0042] The weight-average molecular weight (Mw) of the polyether lubricant of the present invention, calculated from the chromatogram obtained by gel permeation chromatography (GPC), is preferably 300 to 10000, and more preferably 500 to 8000, from the viewpoint of the lubricity of the water-soluble cutting fluid.

[0043] The polyether lubricant of the present invention can be produced by known methods. For example, (i) a reaction intermediate can be produced by a dehydration condensation reaction of a polyhydric alcohol at 80°C to 130°C and atmospheric pressure in the presence of an acid catalyst such as sulfuric acid, and (ii) thereafter, the polyether lubricant of the present invention can be produced by carrying out an etherification reaction between the obtained reaction intermediate and an alkyl halide or alkenyl halide at 80°C to 130°C in the presence of a catalyst such as potassium hydroxide.

[0044] The water-soluble lubricant of the present invention is useful as a component of water-soluble cutting fluids with excellent lubricity and defoaming properties, and it can relatively reduce the amount of surfactant used in combination with the lubricant of the present invention in water-soluble cutting fluids. The content of the lubricant of the present invention in water-soluble cutting fluids is not particularly limited as long as it does not impair the effects of the present invention, but it is preferably 0.1 to 50% by mass of the total water-soluble cutting fluid.

[0045] Examples of aqueous components that can be used in combination with the lubricant of the present invention include (i) water, (ii) lower alcohols such as ethanol and propyl alcohol, and (iii) mixtures of water and lower alcohols.

[0046] The lubricant of the present invention can also be used as a component (base oil, etc.) in sliding surface lubricants; rolling oils; drawing oils; pressing oils; forging oils; metalworking oils used for processing such as polishing and cutting of aluminum discs and silicon wafers; and water-based lubricants such as water-glycol-based hydraulic oils.

[0047] The lubricant of the present invention may be used in combination with other components as needed, such as detergent dispersants, antioxidants, oiliness agents, emulsifiers, extreme pressure agents, metal deactivators, rust inhibitors, viscosity index improvers, and pour point depressants.

[0048] <Antifoaming agent> The polyether represented by formula (1) above has excellent defoaming properties and can therefore be used as an antifoaming agent. Accordingly, the present invention also provides an antifoaming agent comprising the polyether represented by formula (1) above. The antifoaming agent of the present invention may be used alone or in combination of two or more types. Furthermore, the explanation of formula (1) in the present invention is the same as above. [Examples]

[0049] The present invention will be described in detail below with reference to examples and comparative examples. Unless otherwise specified, "%" in the component amounts below refers to "mass%".

[0050] (Manufacturing Example 1: Synthesis of Example Compound 1) A four-necked flask equipped with a stirrer, nitrogen inlet tube, thermocouple, and condenser was charged with 540 g of triethylene glycol (manufactured by Kanto Chemical Co., Ltd.), 500 g of 1,3-propanediol (manufactured by Kanto Chemical Co., Ltd.) as polyhydric alcohols, and 13.8 g of sulfuric acid (manufactured by Kanto Chemical Co., Ltd.) as a catalyst. After nitrogen purging, the temperature was raised to 130°C, and a dehydration condensation reaction was carried out under nitrogen bubbling conditions. Subsequently, an adsorbent (manufactured by Kyowa Chemical Industry Co., Ltd.) was added, and the mixture was adsorbed at a temperature of 90°C and a pressure of -0.097 MPa (gauge pressure) or less under nitrogen bubbling for 1 hour. The reaction intermediate was then filtered to obtain a reaction intermediate (hydroxyl value: 105 (mg KOH / g)). The hydroxyl value of this reaction intermediate was calculated according to JIS K-1557-1. The hydroxyl values ​​of compounds other than this reaction intermediate were calculated in the same manner.

[0051] Subsequently, the reaction intermediate and 120 g of potassium hydroxide were charged into an autoclave equipped with a thermometer, pressure gauge, safety valve, nitrogen gas injection pipe, stirrer, vacuum exhaust pipe, cooling coil, and steam jacket. After purging with nitrogen, 120 g of methyl chloride was injected under pressure at a temperature of 80°C to 130°C, and the etherification reaction was carried out for 5 hours. After that, the crude product was removed from the autoclave, treated with an adsorbent (manufactured by Kyowa Chemical Industry Co., Ltd.), and then filtered to obtain Example Compound 1 (hydroxyl value: 50 (mg KOH / g)).

[0052] (Production Example 2: Synthesis of Example Compounds 2-12 and Comparative Example Compounds 1-9) Example compounds 2-12 and Comparative Examples 1-9 were synthesized using the same method as in Production Example 1. The polyhydric alcohols used in the dehydration condensation reaction and the alkyl or alkenyl halides used in the subsequent etherification reaction are shown in Tables 1 and 2.

[0053] (Manufacturing Example 3: Synthesis of Comparative Example Compound 10) In an autoclave equipped with a thermometer, pressure gauge, safety valve, nitrogen gas inlet, agitator, vacuum exhaust pipe, cooling coil, and steam jacket, 100 g of 1,2-propanediol and 6.0 g of potassium hydroxide as a catalyst were charged. After purging with nitrogen, the temperature was raised to 115°C, and a mixture of 1626 g of propylene oxide and 1258 g of ethylene oxide was added over 8 hours under conditions of 0.5 MPa or less. After the addition was complete, the mixture was reacted at 115°C for 1 hour, and then treated under reduced pressure at 75-85°C for 1 hour to obtain a reaction intermediate (hydroxyl value: 106 (mg KOH / g)).

[0054] Next, 110 g of potassium hydroxide was placed in the autoclave, and after purging with nitrogen, 50 g of methyl chloride was injected under pressure at a temperature of 80°C to 130°C, and the etherification reaction was carried out for 5 hours. After that, the reaction composition was removed from the autoclave, treated with adsorption using two adsorbents (Kyoward #700 and #1000), and then filtered to obtain comparative example compound 10 (hydroxyl value: 5.0 (mg KOH / g)).

[0055] The R of the obtained example compounds 1-12 and comparative example compounds 1-10 1 ~R 3 , hydrogen atom / hydrocarbon group (i.e., (R 1 ~R 3 (Number of hydrogen atoms inside) / (R) 1 ~R 3 (Ratio of the number of hydrocarbon groups inside), a-d, a+b, c+d, n, C n H 2n Tables 1 and 2 show the raw materials for O, (a+b) / (c+d), and weight-average molecular weight (hereinafter referred to as "Mw"). The hydrogen atom / hydrocarbon group and Mw were calculated as follows.

[0056] (Calculation of hydrogen atoms / hydrocarbon groups) Hydrogen atom / hydrocarbon group (i.e., (R 1 ~R 3 (Number of hydrogen atoms inside) / (R) 1 ~R 3 The number of hydrocarbon groups in the compound when it is acetylated. 13 From the integrated signal of the carbonyl carbon derived from the acetyl group and the integrated signal of the terminal CH3 derived from the hydrocarbon group, obtained by 13C-NMR measurement, the following formula is derived: Hydrogen atom / hydrocarbon group = Integral value of the signal from the carbonyl carbon derived from the acetyl group / Integral value of the signal from the terminal CH3 derived from the hydrocarbon group It was calculated using the following method. The specific steps are as follows:

[0057] <Acetylation> 4.0 mL of pyridine and 1.0 mL of acetic anhydride were weighed into a flask and shaken well. Then 1 g of the compound was added and shaken well, and the mixture was heated for 1 hour. After that, 1 mL of water was added and the mixture was heated for 10 minutes, and the acetic anhydride was removed to obtain the acetylated product of the compound.

[0058] < 13 C-NMR measurement> Regarding the obtained acetylated product 13¹¹C-NMR measurements were performed to calculate the integrated signal of the carbonyl carbon derived from the acetyl group at around 170 ppm and the integrated signal of the terminal CH3 derived from the hydrocarbon group at around 10-15 ppm (around 60 ppm if the hydrocarbon group is a methyl group). Using these, the above formula was derived from hydrogen atom / hydrocarbon group (i.e., (R 1 ~R 3 (Number of hydrogen atoms inside) / (R) 1 ~R 3 The number of hydrocarbon groups inside was calculated. 13 The conditions for the 1C-NMR measurement were as follows: • JNM-ECA600 (JEOL-NMR) • Solvent: CDCl3 • Sample concentration: 40 mg / 0.6 mL ·Temperature: 25℃ • Total number of times: 4096

[0059] (Calculation of Mw) Mw was calculated from gel permeation chromatography (GPC) under the following conditions: The GPC system consisted of a SHODEX® GPC101 dedicated GPC system, a SHODEX RI-71s differential refractometer, a SHODEX KF-G guard column, and three SHODEX KF804L columns mounted in sequence. The column temperature was 40°C, and tetrahydrofuran was flowed at a flow rate of 1 ml / min as the developing solvent. 0.1 ml of a 0.1% tetrahydrofuran solution of the obtained example compound or comparative example compound was injected, and the Mw was calculated from the chromatogram, which represents the refractive index intensity and elution time, using the BORWIN GPC calculation program.

[0060] [Table 1]

[0061] [Table 2]

[0062] (a) Evaluation of lubricity Lubricity tests were conducted using 5% aqueous solutions of the example compounds or comparative example compounds, and the SRV Lubricant and Material Test System (manufactured by Optimal). Specifically, the tests were performed using balls and discs, with SUJ-2 specimens used for each. After dropping 1.0 ml of the 5% aqueous solution onto the disc, the coefficient of friction (μ) was measured at a temperature of 50°C, a load of 40 N, an amplitude of 1 mm, and a vibration frequency of 50 Hz. Lubricity was evaluated according to the following criteria. The results are shown in Table 3. <Evaluation Criteria> ◎: Friction coefficient (μ) is 0.11 or less ○: Friction coefficient (μ) greater than 0.11 and 0.12 or less. △: Friction coefficient (μ) greater than 0.12 and less than or equal to 0.14 ×: Friction coefficient (μ) greater than 0.14

[0063] (b) Evaluation of antifoaming properties 200 mL of a 5% aqueous solution of the example compound or comparative example compound was placed in a 1000 mL graduated cylinder, and air bubbles were blown through the 5% aqueous solution at 100 mL / min for 10 minutes while maintaining the 5% aqueous solution at 20°C. The volume from the bottom of the graduated cylinder to the highest point of the bubbles was defined as the "volume of the 5% aqueous solution after air bubbles," and using this and the "volume of the 5% aqueous solution before air bubbles (i.e., 200 mL)," the following formula was used: Volume increase rate (%) = (Volume of 5% aqueous solution after air bubbling - Volume of 5% aqueous solution before air bubbling) (mL) / Volume of 5% aqueous solution before air bubbling (mL) × 100 The volume increase rate was calculated, and the defoaming properties were evaluated according to the following criteria. A smaller volume increase rate indicates superior defoaming performance. <Evaluation Criteria> ◎: Volume increase rate is less than 110% ○: Volume increase rate of 110% or more, but less than 200% △: Volume increase rate is 200% or more, but less than 300%. ×: Volume increase rate is 300% or more

[0064] (c) Evaluation of low-temperature stability An aqueous solution was prepared using 5% of the example compound or comparative example compound, 20% triethanolamine, 2% caprylic acid, 1% sebacic acid, and the remainder as water. This solution was then packed into a 50 mL glass container and stored in a light-free -4°C constant temperature bath for 3 months. After returning to room temperature, the aqueous solution was observed, and its low-temperature stability was evaluated according to the following criteria. The results are shown in Table 3. <Evaluation Criteria> ○: The aqueous solution remained transparent. ×: Precipitation or separation occurred in the aqueous solution.

[0065] [Table 3]

[0066] As is clear from Table 3 above, the example compounds exhibited excellent lubricity, defoaming properties, and low-temperature stability. In contrast, as is clear from Table 3 above, comparative examples 1 to 10 were inferior in some or all of the lubricity, defoaming properties, and low-temperature stability.

[0067] R 1 ~R 3 Comparative compound 1, in which the group consists of a hydrogen atom and the hydrogen atom / hydrocarbon group ratio is infinite, exhibited inferiority compared to the example compound in terms of lubricity, defoaming properties, and low-temperature stability. Comparative example compound 2, in which a+b exceeded 80, exhibited inferior lubricity and defoaming properties compared to the example compound.

[0068] Comparative example compound 3, in which (a+b) / (c+d) was less than 0.2, exhibited inferior defoaming properties and low-temperature stability compared to the example compound. Comparative example compound 4, in which (a+b) / (c+d) exceeded 8, was inferior to the example compound in all aspects: lubricity, defoaming properties, and low-temperature stability.

[0069] Comparative compound 5, in which a+b was less than 1, was inferior to the example compound in all aspects: lubricity, defoaming properties, and low-temperature stability. Comparative compound 6, which had more than 20 hydrogen atoms / hydrocarbon groups, more than 60 d, and more than 70 c+d, was inferior to the example compound in all aspects: lubricity, defoaming properties, and low-temperature stability.

[0070] Comparative example compound 7, in which both c and d are 0 and (a+b) / (c+d) is ∞ (=1 / 0), was inferior to the example compound in all aspects: lubricity, defoaming properties, and low-temperature stability. R 1 ~R 3 Comparative example compound 8, in which the hydrocarbon group has more than 20 carbon atoms, was inferior to the example compound in all aspects: lubricity, defoaming properties, and low-temperature stability.

[0071] Comparative example compound 9, in which n exceeded 8, exhibited inferior lubricity and low-temperature stability compared to the example compound. Comparative example compound 10, a copolymer of ethylene oxide and propylene oxide, and having a different structure from the polyether represented by formula (1), was inferior to the example compound in all aspects: lubricity, defoaming properties, and low-temperature stability. [Industrial applicability]

[0072] The lubricant of the present invention can be used as a component of water-soluble cutting fluids, etc.

Claims

[Claim 1] Formula (1): 【Chemistry 1】 [In the formula, R １ , R ２ , and a number of R ３ Each of these is independently a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms. (R １ ~R ３ (Number of hydrogen atoms inside) / (R) １ ~R ３ The ratio of the number of hydrocarbon groups inside is 20 or less. GL is a glycerol residue, CH ２ CH ２ O is an ethylene glycol residue, CH ２ CH ２ CH ２ O is a 1,3-propanediol residue, C ｎ H ２ｎ O is an alkanediol residue with 4 to 8 carbon atoms. a, b, c, and d are GL and CH, respectively. ２ CH ２ O, CH ２ CH ２ CH ２ O, and C ｎ H ２ｎ This is the average degree of polymerization of O. a is a number between 0 and 30. b is a number between 0 and 80. a + b is a number between 1 and 80. c is a number between 0 and 60. d is a number between 0 and 60. c + d is a number between 1 and 70. (a+b) / (c+d) is a number between 0.2 and 8, and n is a number between 4 and 8. A lubricant consisting of a polyether represented by [the formula].

Images