Water-glycol based hydraulic fluid

Abstract

To provide a water-glycol hydraulic fluid which has improved wear resistance.SOLUTION: A water-glycol hydraulic fluid contains as fatty acid lubricants 0.2 to 0.6 mass% of dimer acid and more than 0.10 mass% and 0.20 mass% or less of the following phosphate so that a sum of the dimer acid and the phosphate is more than 0.35 mass% (where, R1 and R2, which may be the same or different, each represent a hydrogen atom or a C1-C30 hydrocarbon group, R3 represents a C1-C20 hydrocarbon group, R4 represents a hydrogen atom or a C1-C30 hydrocarbon group, and X1, X2, X3, and X4, which may be the same or different, each represent an oxygen atom or a sulfur atom).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an improvement in water-glycol based hydraulic fluids. [Background technology]

[0002] Hydraulic devices are widely used in industry, contributing to improved productivity, and are also widely adopted in society. These hydraulic devices use hydraulic fluid as a power transmission medium, and generally, petroleum-based hydraulic fluid using mineral oil-based base oils such as highly refined paraffin-based base oils is used as the hydraulic fluid.

[0003] However, petroleum-based hydraulic oils cannot be used as hydraulic fluids for various hydraulic devices in iron and steel making facilities in the steel industry, where fire resistance is required, mechanical equipment such as die casting machines and forging presses, and hydraulic devices for indoor facilities such as amusement and stage equipment, where fire safety is important. Instead, fire-resistant water-containing hydraulic fluids such as water-glycol-based hydraulic fluids are used.

[0004] When using such a water-glycol-based hydraulic fluid, which is an aqueous hydraulic fluid, it is important that hydraulic operation is performed smoothly and that the life of the hydraulic equipment is extended, and for these reasons it is necessary to improve the wear resistance and lubricity. As a material for improving the lubricity and wear resistance of water-glycol based hydraulic fluids, for example, a water-containing hydraulic fluid composition containing a polyoxyalkylene glycol diether compound having a specific structure, a polyoxyalkylene glycol monoether compound, a polyoxypropylene glycol monoether compound, and a fatty acid salt in water is known (Patent Document 1).

[0005] Also, among water-glycol based hydraulic fluids, those containing a small amount of a neutralization product of glycerol borate, obtained by reacting glycerol with boric anhydride or boron trichloride, and a base, are known (Patent Document 2). Furthermore, it is also known to incorporate a water-glycol based hydraulic fluid containing a water-soluble polyether having a specific structure derived from a water-soluble polyoxyalkylene polyol and a glycidyl ether (Patent Document 3). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 3233490 [Patent Document 2] Patent No. 2646308 [Patent Document 3] Japanese Patent Application Publication No. 7-233391 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention aims to obtain a water-glycol-based working fluid with good performance by blending a specific additive with the water-glycol-based working fluid, thereby significantly improving the wear resistance without impairing the various performance properties of the water-glycol-based working fluid. [Means for solving the problem]

[0008] A water-glycol-based hydraulic fluid contains, out of a total of 100% by mass, 20 to 60% by mass of water, 20 to 60% by mass of glycols, a fatty acid-based lubricant, an alkali hydroxide compound, a thickener, a rust inhibitor, a corrosion inhibitor, an antifoaming agent, etc. As described above, the present inventors have been conducting research and development aimed at improving the performance of water-glycol-based hydraulic fluids, and have found that the wear resistance of water-glycol-based hydraulic fluids can be greatly improved by using a dimer acid as a fatty acid lubricant and also containing a phosphoric acid ester with a special structure, and have completed the present invention based on this finding.

[0009] That is, the present invention provides a water-glycol based working fluid containing 20 to 60 mass% water, 0.2 mass% or more and 0.6 mass% or less of dimer acid, and more than 0.10 mass% and 0.20 mass% or less of phosphate, with the sum of the dimer acid and phosphate exceeding 0.35 mass%, and this phosphate has the following structure.

[0010] [ka] (In the formula, R1 and R2 may be the same or different and each represents a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms, R3 represents a hydrocarbon group having 1 to 20 carbon atoms, R4 represents a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms, and X1, X2, X3, and X4 may be the same or different and each represents an oxygen atom or a sulfur atom.) Effect of the Invention

[0011] According to the present invention, by adopting the above-mentioned configuration, it is possible to easily obtain a water-glycol-based working fluid that is easy to use and has significantly improved wear resistance without impairing the various performance properties that the water-glycol-based working fluid possesses. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] In the water-glycol hydraulic fluid of the present invention, a fatty acid lubricant is used, and dimer acid is used as the fatty acid lubricant. This dimer acid is a dimer of unsaturated fatty acid having 18 carbon atoms, and is a liquid fatty acid containing monobasic acid and tribasic acid as the main component, which is a dibasic acid of C36 dicarboxylic acid produced by dimerization of C18 unsaturated fatty acid derived from vegetable oil.

[0013] The dimer acid is contained in an amount of 0.2% by mass or more and 0.6% by mass or less based on the total amount of the water-glycol based working fluid composition. If the content is less than 0.2% by mass, sufficient wear resistance cannot be obtained, whereas if it exceeds 0.6% by mass, sludge tends to be generated.

[0014] The water-glycol based hydraulic fluid also contains a phosphate ester. The phosphate ester is represented by the following general formula: [ka]

[0015] In the above general formula, R1 and R2 each represent a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms, and R1 and R2 may be the same or different. The above R3 represents a hydrocarbon group having 1 to 20 carbon atoms, and R4 represents a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms. X1, X2, X3 and X4 each represent an oxygen atom or a sulfur atom, and may be the same or different.

[0016] The content of this phosphate ester is more than 0.10 mass % and not more than 0.20 mass % based on the total amount of the water-glycol based working fluid composition, and at the same time, the sum of the dimer acid and the phosphate ester is more than 0.35 mass %. The above phosphoric acid ester is preferably used in an amount of 0.12% by mass or more, and more preferably 0.15% by mass or more.

[0017] Examples of glycols for the water-glycol based working fluid include ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, diethylene glycol, dipropylene glycol, dibutylene glycol, dihexylene glycol, trimethylene glycol, triethylene glycol, and tripropylene glycol. The glycols may be used alone or in combination of two or more of the above. Propylene glycol or dipropylene glycol is preferably used. The glycols are used in an amount of 20 to 60% by mass, more preferably 30 to 50% by mass, based on the total amount of the water-glycol based working fluid composition.

[0018] Furthermore, alkanolamines can be used as rust inhibitors, such as methanolamine, ethanolamine, propanolamine, diethanolamine, triethanolamine, dimethylethanolamine, N-methylethanolamine, N-methyldiethanolamine, N,N-dimethylaminoethanol, N,N-diethylaminoethanol, N,N-dipropylaminoethanol, N,N-dibutylaminoethanol, N,N-dipentylaminoethanol, N,N-dihexylaminoethanol, N,N-diheptylaminoethanol, and N,N-dioctylaminoethanol. The alkanolamine is contained in an amount of 1.0 to 5.0% by mass based on the total amount of the composition.

[0019] The alkali hydroxide compound may be potassium hydroxide or sodium hydroxide, which may be used alone or in combination as appropriate. The alkali hydroxide compound is contained in an amount of 0.01 to 0.12% by mass, more preferably 0.04 to 0.06% by mass, based on the total amount of the composition.

[0020] In addition, such water-glycol based hydraulic fluids may contain known additives, such as thickeners, lubricants, metal deactivators, anti-wear agents, extreme pressure agents, dispersants, metal detergents, friction modifiers, corrosion inhibitors, demulsifiers, anti-foaming agents, and other various additives, either alone or in combination. In this case, an additive package for water-glycol based hydraulic fluids may be used. EXAMPLES

[0021] EXAMPLES The water-glycol based hydraulic fluid of the present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited thereto in any way. The components were thoroughly mixed based on the blending amounts shown in Tables 1 and 2 to obtain the water-glycol based working fluids of Examples 1 to 7.

[0022] Example 1 A water-glycol based working fluid was obtained by mixing 0.20% by mass of dimer acid, 0.20% by mass of 3-(di-isobutoxy-thiophosphoryl sulfanyl)-2-methyl-propionic acid as a phosphate ester, 38.628% by mass of propylene glycol as a glycol, 16.10% by mass of a water-soluble polymer as a thickener, 2.565% by mass of other additives including sodium hydroxide, corrosion inhibitors, and antifoaming agents, and 42.307% by mass of water. This water-glycol based working fluid had a reserve alkalinity of 20 according to JIS K 2234-1994 and a kinetic viscosity of 46 mm at 40°C. 2 / s and pH was 10.6.

[0023] The phosphate ester used in Example 1 above has the following structural formula: [ka]

[0024] Example 2 A water-glycol based working fluid was obtained by using 0.30 mass% of dimer acid, 0.15 mass% of the above phosphoric ester, and 42.257 mass% of water in the same manner as in Example 1. This water-glycol based working fluid had a reserve alkalinity of 20 according to JIS K 2234-1994 and a kinetic viscosity of 46 mm at 40°C. 2 / s.

[0025] Example 3 A water-glycol based working fluid was obtained in the same manner as in Example 1, except that 0.30% by mass of dimer acid, 0.20% by mass of phosphoric ester, and 42.207% by mass of water were used. The reserve alkalinity according to JIS K 2234-1994 was 20, and the kinetic viscosity at 40°C was 46mm. 2 / s.

[0026] Example 4 A water-glycol based working fluid was obtained in the same manner as in Example 1, except that 0.40% by mass of dimer acid, 0.15% by mass of phosphoric ester, and 42.157% by mass of water were used. The reserve alkalinity according to JIS K 2234-1994 was 20, and the kinetic viscosity at 40°C was 46mm. 2 / s.

[0027] Example 5 A water-glycol based working fluid was obtained in the same manner as in Example 1, except that 0.40% by mass of dimer acid, 0.20% by mass of phosphoric ester, and 42.107% by mass of water were used. The reserve alkalinity according to JIS K 2234-1994 was 20, and the kinetic viscosity at 40°C was 46mm. 2 / s.

[0028] Example 6 A water-glycol based working fluid was obtained in the same manner as in Example 1, except that 0.60% by mass of dimer acid, 0.15% by mass of phosphoric ester, and 41.957% by mass of water were used. The reserve alkalinity according to JIS K 2234-1994 was 20, and the kinetic viscosity at 40°C was 46mm. 2 / s.

[0029] Example 7 A water-glycol based working fluid was obtained in the same manner as in Example 1, except that 0.60% by mass of dimer acid, 0.20% by mass of phosphoric ester, and 41.907% by mass of water were used. The reserve alkalinity according to JIS K 2234-1994 was 20, and the kinetic viscosity at 40°C was 46mm. 2 / s.

[0030] Comparative Example 1 A water-glycol based working fluid was obtained in the same manner as in Example 1, except that 0.20% by mass of dimer acid, 0.05% by mass of phosphoric ester, and 42.457% by mass of water were used. The reserve alkalinity according to JIS K 2234-1994 was 20, and the kinetic viscosity at 40°C was 46mm. 2 / s.

[0031] (Comparative Examples 2 to 5) The components were thoroughly mixed based on the blending amounts shown in Table 3, and water-glycol based working fluids were obtained in the same manner as in Example 1. The water-glycol based working fluids of Comparative Examples 2 to 5 all had a reserve alkalinity of 20 according to JIS K 2234-1994 and a kinetic viscosity of 46 mm at 40°C. 2 / s.

[0032] [test] The following tests were carried out to evaluate the wear resistance and lubricity of the above-mentioned Examples and Comparative Examples. (Shell four-ball test) In accordance with ASTM D4172, the test was carried out at a spindle speed of 1500 rpm, a load of 40 kgf, and room temperature for 30 minutes, and the wear scar diameter (mm) of the steel ball after the test was measured. Evaluation criteria: Wear mark diameter 0.65 mm or less... Pass (〇) Wear mark diameter exceeds 0.65mm...Fail (×)

[0033] (Test Results) The test results are shown in Tables 1 to 3.

[0034] (Consideration) As shown in Tables 1 and 2, in Examples 1 to 7 in which the dimer acid was 0.20 mass% to 0.60 mass% and the phosphate ester was 0.15 mass% to 0.20 mass%, and the sum of the dimer acid and the phosphate ester exceeded 0.35 mass%, the wear scar diameter after the Shell four-ball test was 0.65 mm or less in all cases, demonstrating excellent wear resistance and lubricity.

[0035] On the other hand, as shown in Table 3, in Comparative Examples 1, 2, 4, and 5, in which the amount of dimer acid was 0.2% by mass or more and 0.6% by mass or less, but the amount of phosphate was 0.10% by mass or less, and in Comparative Example 3, in which the amount exceeded 0.10% by mass but the sum of the amounts of dimer acid and phosphate was 0.35% by mass or less, the wear scar diameter after the Shell four-ball test was 0.681 mm or more, which was a failure. Furthermore, in Comparative Example 1, a seizure phenomenon was observed, and it is clear that no good effect was obtained.

[0036]

Table 1

[0037]

Table 2

[0038]

Table 3

Claims

1. A water-glycol-based hydraulic fluid comprising 20 to 60 mass % of water, 0.2 mass % or more and 0.6 mass % or less of a dimer acid as a fatty acid lubricant, and more than 0.10 mass % but not more than 0.20 mass % of a phosphate ester represented by the following general formula (1), the sum of the dimer acid and the phosphate ester exceeding 0.35 mass %. 【Chemistry 1】 (In the formula, R １ and R ２ may be the same or different, each represents a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms; R ３ is —CH(CH 3 )— or —CH 2 —CH 2 —, R ４ represents a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms, X 1 and X 2 are oxygen atoms, and X 3 and X 4 are sulfur atoms.

2. 2. The water-glycol based hydraulic fluid according to claim 1, wherein the content of the phosphate ester is 0.15% by mass to 0.20% by mass.

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