Water-glycol hydraulic fluid

Abstract

The present invention provides a water-glycol hydraulic fluid containing 0.2 to 0.6 mass% of a dimer acid as a fatty acid lubricant, and more than 0.10 mass% and 0.20 mass% or less of a phosphate ester of formula (1), wherein the total of the dimer acid and the phosphate ester is more than 0.35 mass%, wherein R1 and R2 can be the same or different, each representing 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 can be the same or different, each representing an oxygen atom or a sulfur atom.

Description

Technical Field

[0001] This invention relates to an improved water-diol hydraulic fluid. Background Technology

[0002] Hydraulic equipment is widely used in industry, where it helps improve productivity, and it is also widely used by the general public. Hydraulic fluid is used as the power transmission medium in hydraulic equipment, and petroleum-based hydraulic oils, such as highly refined alkane-based oils, are commonly used as hydraulic fluids.

[0003] However, hydraulic equipment used in mechanical equipment such as die casting machines, forging presses, steelmaking equipment in the steel industry that requires fire resistance, and stage equipment in amusement park equipment and indoor facilities where fire safety is important cannot use petroleum-based hydraulic oils. Therefore, water-glycol hydraulic fluids are used because they are flame-retardant water-based hydraulic fluids.

[0004] When water-glycol hydraulic fluids are used as water-based hydraulic fluids, good wear resistance and lubricity are required to ensure smooth hydraulic operation and extend the service life of hydraulic equipment. Therefore, as described in JP3233490 B2, water-based hydraulic fluid compositions obtained by adding, for example, polyoxyethylene glycol diether compounds, polyoxyethylene glycol monoether compounds, polyoxypropylene glycol monoether compounds, and fatty acid salts having specific structures to water are used to improve performance in terms of lubricity and wear resistance.

[0005] Some water-glycol hydraulic fluids also contain small amounts of borate glycerol ester neutralization products and bases obtained by reacting glycerol with boric anhydride or boron trichloride, see, for example, JP2646308 B2. (Patent Document 2) Other water-glycol hydraulic fluids, such as those described in JP H07-233391A, contain water-soluble polyethers having specific structures derived from water-soluble polyoxyethylene polyols and glycidyl ethers.

[0006] One object of the present invention is to obtain a high-performance water-glycol hydraulic fluid that has greatly improved wear resistance without impairing any other type of performance provided by water-glycol hydraulic fluids provided by including specific additives. Summary of the Invention

[0007] Specifically, the present invention is a water-diol hydraulic fluid comprising 20% ​​to 60% by mass of water, 0.2% to 0.6% by mass of a dimer acid as a fatty acid lubricant, and more than 0.10% by mass and 0.20% by mass or less of a phosphate ester, wherein the sum of the dimer acid and the phosphate ester of structure [Formula 1] is more than 0.35% by mass.

[0008]

[0009] In this formula, R1 and R2 can be the same or different, each representing 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 can be the same or different, each representing an oxygen atom or a sulfur atom. Detailed Implementation

[0010] This invention provides a water-glycol hydraulic fluid comprising 20% ​​to 60% by mass of water and 20% to 60% by mass of glycol, as well as, for example, a fatty acid-based lubricant, an alkaline hydroxide compound, a thickener, a rust inhibitor, a corrosion inhibitor, and a defoamer, totaling 100% by mass. As a result of extensive research and development to address this problem, the inventors have discovered that the use of dimer acids as fatty acid-based lubricants and phosphate esters having specific structures can significantly improve the wear resistance of water-glycol hydraulic fluids. This invention is based on this discovery.

[0011] By using this construction, the present invention enables the easy acquisition of a water-glycol hydraulic fluid with significantly improved wear resistance without compromising any other type of performance provided by the water-glycol hydraulic fluid.

[0012] The water-diol hydraulic fluid of the present invention uses a fatty acid lubricant, and a dimer acid is used as this fatty acid lubricant. This dimer acid is a dimer of an unsaturated fatty acid having 18 carbon atoms, and is primarily composed of a dicarboxylic acid having 36 carbon atoms, derived from the dimerization of unsaturated fatty acids having 18 carbon atoms based on plant fats and oils. It is a liquid fatty acid containing both monocarboxylic and tricarboxylic acids.

[0013] The dimer acid is included in an amount of 0.2% by mass or more and 0.6% by mass or less relative to the total mass of the water-diol hydraulic fluid composition. Insufficient abrasion resistance cannot be obtained when less than 0.2% by mass is used. Sludge formation is more likely when more than 0.6% by mass is used.

[0014] This water-diol hydraulic fluid also contains a phosphate ester. This phosphate ester is represented by the following formula (1):

[0015]

[0016] In this general formula, R1 and R2 each represent a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms. R1 and R2 may be the same or different. 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 may be the same or different, and each represents an oxygen atom or a sulfur atom.

[0017] The phosphate ester is contained in an amount of more than 0.10% by mass and less than 0.20% by mass relative to the total mass of the water-diol hydraulic fluid composition, and the sum of the dimer acid and the phosphate ester is more than 0.35% by mass. The phosphate ester is preferably used in an amount of 0.12% by mass or more, more preferably 0.15% by mass or more.

[0018] The diol in this water-diol hydraulic fluid composition may be, for example, ethylene glycol, propylene glycol, butanediol, hexanediol, diethylene glycol, dipropylene glycol, dibutylene glycol, dihexanediol, trimethylene glycol, triethylene glycol, and tripropylene glycol. A single type of diol may be used, or a mixture of two or more types of diols may be used. Propylene glycol or dipropylene glycol is preferred. These diols are included in an amount of 20 to 60% by mass, preferably 30 to 50% by mass, relative to the total mass of the water-diol hydraulic fluid composition.

[0019] Alkanolamines can be used as rust inhibitors. Examples of alkanolamines include 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. Based on the total mass of the composition, the alkanolamine is included in an amount from 1.0% by mass to 5.0% by mass.

[0020] The aforementioned alkaline hydroxide compounds are potassium hydroxide and sodium hydroxide, which can be used alone or together. The alkaline hydroxide compounds are included in an amount of 0.01% to 0.12% by mass, preferably 0.04% to 0.06% by mass, relative to the total mass of the composition.

[0021] If desired, well-known additives may be included in water-glycol hydraulic fluids. Examples include thickeners, lubricants, metal passivators, anti-wear agents, extreme pressure agents, dispersants, metal detergents, friction modifiers, corrosion inhibitors, demulsifiers, and defoamers. These additives may be used alone or in combination of more than one additive. Additive packages for water-glycol hydraulic fluids are also available.

[0022] Example

[0023] The water-diol hydraulic fluid of the present invention will now be described in detail with reference to the embodiments and comparative examples. The present invention is not limited to these embodiments. The components were thoroughly mixed together in the amounts shown in Tables 1 and 2 to obtain the water-diol hydraulic fluids of Examples 1 to 7.

[0024] Example 1

[0025] A water-glycol hydraulic fluid is obtained by thoroughly mixing the following components: 0.20 wt% dimer acid, 0.20 wt% 3-(diisobutoxy-thiophosphorylsulfonyl)-2-methylpropionic acid as a phosphate ester, 38.628 wt% propylene glycol as a glycol, 16.10 wt% a water-soluble polymer as a thickener, a total of 2.565 wt% other additives such as sodium hydroxide, corrosion inhibitors, and defoamers, and 42.307 wt% water. The water-glycol hydraulic fluid obtained according to JIS K2234-1994 has an alkali reserve of 20 and a kinematic viscosity of 46 mmHg at 40°C. 2 / s, and the pH is 10.6.

[0026] The phosphate ester used in Example 1 is represented by the following structural formula:

[0027]

[0028] Example 2

[0029] A water-diol hydraulic fluid was obtained using 0.30% by mass of dimer acid, 0.15% by mass of the aforementioned phosphate ester, and 42.257% by mass of water, in the same manner as in Example 1. The water-diol hydraulic fluid obtained according to JIS K2234-1994 had an alkali content of 20 and a kinematic viscosity of 46 mm at 40°C. 2 / s.

[0030] Example 3

[0031] A water-diol hydraulic fluid was obtained using 0.30% by mass of dimer acid, 0.20% by mass of the aforementioned phosphate ester, and 42.207% by mass of water, in the same manner as in Example 1. The water-diol hydraulic fluid obtained according to JIS K2234-1994 had an alkali content of 20 and a kinematic viscosity of 46 mm at 40°C. 2 / s.

[0032] Example 4

[0033] A water-diol hydraulic fluid was obtained using 0.40% by mass of dimer acid, 0.15% by mass of the aforementioned phosphate ester, and 42.157% by mass of water, in the same manner as in Example 1. The water-diol hydraulic fluid obtained according to JIS K2234-1994 had an alkali reserve of 20 and a kinematic viscosity of 46 mm at 40°C. 2 / s.

[0034] Example 5

[0035] A water-diol hydraulic fluid was obtained using 0.40% by mass of dimer acid, 0.20% by mass of the aforementioned phosphate ester, and 42.107% by mass of water, in the same manner as in Example 1. The water-diol hydraulic fluid obtained according to JIS K2234-1994 had an alkali content of 20 and a kinematic viscosity of 46 mm at 40°C. 2 / s.

[0036] Example 6

[0037] A water-diol hydraulic fluid was obtained using 0.60% by mass of dimer acid, 0.15% by mass of the aforementioned phosphate ester, and 41.957% by mass of water, in the same manner as in Example 1. The water-diol hydraulic fluid obtained according to JIS K2234-1994 had an alkali content of 20 and a kinematic viscosity of 46 mm at 40°C. 2 / s.

[0038] Example 7

[0039] A water-diol hydraulic fluid was obtained using 0.60% by mass of dimer acid, 0.20% by mass of the aforementioned phosphate ester, and 41.907% by mass of water, in the same manner as in Example 1. The water-diol hydraulic fluid obtained according to JIS K2234-1994 had an alkali content of 20 and a kinematic viscosity of 46 mm at 40°C. 2 / s.

[0040] Comparative Example 1

[0041] A water-diol hydraulic fluid was obtained using 0.20% by mass of dimer acid, 0.05% by mass of the aforementioned phosphate ester, and 42.457% by mass of water, in the same manner as in Example 1. The water-diol hydraulic fluid obtained according to JIS K2234-1994 had an alkali content of 20 and a kinematic viscosity of 46 mm at 40°C. 2 / s.

[0042] Comparative Examples 3 to 5

[0043] The components were thoroughly mixed together in the amounts shown in Table 3 to obtain a water-diol hydraulic fluid in the same manner as in Example 1. The water-diol hydraulic fluids of Comparative Examples 2 to 5, obtained according to JIS K2234-1994, had an alkali content of 20 and a kinematic viscosity of 46 mm at 40°C. 2 / s.

[0044] The following tests were conducted on the examples and comparative examples to evaluate wear resistance and lubricity.

[0045] Shell four-ball lubrication test

[0046] According to ASTM D4172, the spindle speed was 1,500 rpm and the load was 40 kgf, and the test was conducted for 30 minutes at room temperature. Afterwards, the diameter (mm) of the wear marks on the steel balls was measured. The test results are shown in Tables 1 to 3.

[0047] Evaluation criteria:

[0048] Wear mark diameter ≤ 0.65mm …………Pass (○)

[0049] Wear mark diameter > 0.65mm ... Failure (×)

[0050] Observation results

[0051] As shown in Tables 1 and 2, in Examples 1 to 7, which contain 0.20% by mass or more and 0.60% by mass or less of dimer acid and more than 0.15% by mass and 0.20% by mass or less of phosphate ester, and the total of dimer acid and phosphate ester is more than 0.35% by mass, the wear trace diameter in the Shell four-ball lubrication test is 0.65 mm or less, which indicates excellent wear resistance and lubricity.

[0052] As shown in Table 3, in Comparative Examples 1, 2, 4, and 5, which contained 0.2% or more and 0.6% or less of dimer acid but less than 0.10% of phosphate ester, and in Comparative Example 3, which contained more than 0.10% of phosphate ester but the sum of dimer acid and phosphate ester was less than 0.35% by mass, the wear trace diameter in the Shell four-ball lubrication test was 0.681 mm or greater, indicating a poor result. In the case of Comparative Example 1, scorching occurred.

[0053] Table 1

[0054]

[0055]

[0056] Table 2

[0057] Example 4 Example 5 Example 6 Example 7 dimer acid 0.40 0.40 0.60 0.60 Phosphate 0.15 0.20 0.15 0.20 Diol 38.628 38.628 38.628 38.628 Thickener 16.100 16.100 16.100 16.100 Other additives 2.565 2.565 2.565 2.565 water 42.157 42.107 41.957 41.907 Diameter of the wear mark (mm) 0.535 0.547 0.526 0.484 evaluate ○ ○ ○ ○

[0058] Table 3

[0059]

Claims

1. A water-glycol hydraulic fluid comprising: 20 to 60 mass% of water and 20 to 60 mass% of a glycol; 0.2 mass% or more and 0.6 mass% or less of a dimer acid as a fatty acid lubricant, wherein the dimer acid is a diacid of a dicarboxylic acid having 36 carbon atoms; and 0.15 to 0.20 mass% of a phosphate ester represented by the following general formula (1), wherein R1and R2may be the same or different, each representing a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms, R3represents a hydrocarbon group having 1 to 20 carbon atoms, R4represents a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms, and X1, X2, X3and X4may be the same or different, each representing an oxygen atom or a sulfur atom, and wherein the total of the dimer acid and the phosphate ester is more than 0.35 mass%.

2. The water-glycol hydraulic fluid according to claim 1, wherein X1and X2in the phosphate ester are oxygen atoms, X3and X4are sulfur atoms, and R3is -CH(CH3)- or -CH2-CH2-.

3. The water-glycol hydraulic fluid according to claim 1 or 2, wherein the glycol is selected from ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, diethylene glycol, dipropylene glycol, dibutylene glycol, dihexylene glycol, triethylene glycol, tripropylene glycol, or a combination thereof.

4. The water-glycol hydraulic fluid according to claim 1 or 2, wherein the glycol is propylene glycol or dipropylene glycol.

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