Water-glycol based hydraulic fluid composition and supplementary additive therefor

Abstract

To provide a water-glycol-based hydraulic liquid having excellent gas phase rust-prevention and good properties.SOLUTION: A water-glycol-based hydraulic liquid composition includes N,N-dibutylaminoethanol, includes 20-60 mass% of water, 20-60 mass% of glycols, 0.6-1.2 mass% of fatty acid lubricants, 0.01-0.06 mass% of an alkali hydroxide selected from potassium hydroxide and / or sodium hydroxide, and has a preliminary alkalinity based on a measuring method regulated by JISK2234-1994 of 10-25, wherein the fatty acid lubricant includes at least one of capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, oleic acid, linoleic acid, linolenic acid, dimer acid, or sodium salts of these.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a water-glycol based hydraulic fluid composition and a supplemental additive therefor. [Background technology]

[0002] Hydraulic fluids are used as power transmission media in hydraulic systems. Petroleum-based hydraulic fluids are widely used, and commonly used general hydraulic fluids are those that use mineral oil-based base oils such as highly refined paraffin-based base oils.

[0003] However, various hydraulic equipment, aluminum die casting, extrusion processing machines, etc. used within steelworks premises, etc., are operated under high temperatures and pressures, which increases the risk of fire. To avoid this risk of fire, water-glycol-based hydraulic fluids are used as hydraulic fluids for such equipment instead of those using the mineral oil-based base oils mentioned above.

[0004] When using such water-glycol-based hydraulic fluids, it is important to ensure smooth hydraulic operation and to extend the life of hydraulic equipment, which requires rust prevention. In particular, it is necessary to add a volatile alkaline rust inhibitor to prevent rust on wall and ceiling surfaces that are not in contact with the hydraulic fluid. Furthermore, although water-glycol based hydraulic fluids have excellent performance, their performance deteriorates due to a decrease in pH during use and oxidation. Therefore, as a technology for improving performance such as inhibiting pH decrease and oxidative stability, for example, a water-containing hydraulic fluid composition containing a polyoxyalkylene glycol diether compound of 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] Furthermore, this water-glycol-based hydraulic fluid is a hydraulic fluid whose main components are water and glycol, but when hydraulic equipment using this fluid experiences the phenomenon of water evaporating from the fluid during use. Water-glycol-based hydraulic fluids generally contain liquid or vapor-phase rust inhibitors as additives, but as the water evaporates during use, the additives also evaporate, causing the properties of the water-glycol-based hydraulic fluid to exceed the appropriate range.

[0006] In such cases, it is common to add or replenish additional additives to maintain the performance of the water-glycol-based hydraulic fluid, thereby managing the fluid's properties to maintain them within the appropriate range. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 3233490 Summary of the Invention [Problem to be solved by the invention]

[0008] For these reasons, the present invention aims to improve the performance of water-glycol-based hydraulic fluids filled in hydraulic equipment and to provide an effective supplemental additive for maintaining the performance, particularly the vapor phase rust prevention performance. [Means for solving the problem]

[0009] A water-glycol-based working fluid is one that 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 corrosion inhibitor, an antifoaming agent, etc. The present inventors have conducted extensive research to solve the above-mentioned problems and have found that the use of a specific alkanolamine compound can significantly improve the vapor phase rust prevention properties of water-glycol-based working fluids, and that this alkanolamine compound can also be effectively used as a supplementary additive.The present invention was completed based on these findings.

[0010] That is, the present invention provides a compound represented by the following general formula: [ka] (In the above general formula, R1 and R2 are hydrocarbon groups having 1 to 8 carbon atoms, and R3 is a hydrocarbon group having 2 or more carbon atoms.) Alkanolamine compounds represented by the formula: The alkanolamine compound has a specific gravity at 20°C of 0.86 to 0.89. is mixed into a water-glycol based hydraulic fluid. The alkanolamine compound is also used as a supplementary additive in a water-glycol based hydraulic fluid composition. [Effects of the Invention]

[0011] According to the present invention, a water-glycol-based hydraulic fluid with excellent rust prevention properties can be obtained by blending a specific alkanolamine compound. Furthermore, when the water in a water-glycol-based hydraulic fluid used in hydraulic equipment evaporates, the use of this alkanolamine compound as a supplementary additive can improve the vapor-phase rust prevention properties of the water-glycol-based hydraulic fluid, which decrease with water evaporation, to their initial performance. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is an explanatory diagram showing an outline of an apparatus for vapor phase rust prevention testing according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] The alkanolamine compound of the present invention is [ka] It is a compound represented by the general formula: The above R1 and R2 represent hydrocarbon groups having 1 to 8 carbon atoms, preferably 1 to 4 carbon atoms, and most preferably 3 or 4 carbon atoms. The carbon numbers of R1 and R2 may be the same or different, but are usually preferably the same. The above R3 is a hydrocarbon having 2 or more carbon atoms, and preferably has about 2 to 4 carbon atoms, since the water solubility of the compound tends to decrease as the carbon number increases.

[0014] Examples of such alkanolamine compounds include N,N-dimethylaminoethanol, N,N-diethylaminoethanol, N,N-dipropylaminoethanol, N,N-dibutylaminoethanol, N,N-dipentylaminoethanol, N,N-dihexylaminoethanol, N,N-diheptylaminoethanol, N,N-dioctylaminoethanol, N,N-dimethylaminopropanol, N,N-diethylaminopropanol, N,N-dipropylaminopropanol, N,N-dibutylaminopropanol, N,N-dipentylaminopropanol, N,N-dihexylaminopropanol, N,N-diheptylaminopropanol, N, Examples include N-dioctylaminopropanol, N,N-dimethylaminobutanol, N,N-diethylaminobutanol, N,N-dipropylaminobutanol, N,N-dibutylaminobutanol, N,N-dipentylaminobutanol, N,N-dihexylaminobutanol, N,N-diheptylaminobutanol, N,N-dioctylaminobutanol, N-butyl(N-pentyl)aminoethanol, N-butyl(N-hexyl)aminoethanol, N-butyl(N-heptyl)aminoethanol, N-butyl(N-pentyl)aminopropanol, N-butyl(N-hexyl)aminopropanol, and N-butyl(N-heptyl)aminopropanol. Such alkanolamine compounds are blended so that the reserve alkalinity of the water-glycol based working fluid as specified in JIS K 2234-1994 is 10 to 25, more preferably 15 to 23, and even more preferably 18 to 21. In addition, the 20°C alkalinity of such alkanolamine compounds is 10 to 25, more preferably 15 to 23, and even more preferably 18 to 21. specific gravity A value of 0.86 to 0.89 is recommended. specific gravity If the value exceeds 0.89, the volatility decreases and the vapor phase rust prevention effect against the reserve alkalinity decreases, which is not preferable.

[0015] Such alkanolamine compounds are used by being blended with a water-glycol based working fluid. There are no particular limitations on the type of water-glycol based working fluid, but it is preferable that the fluid have the following composition, for example. Of the total 100% by mass, the composition contains 20 to 60% by mass, more preferably 30 to 50% by mass, water, 0.6 to 1.2% by mass of a fatty acid-based lubricant, 0.01 to 0.12% by mass of an alkali hydroxide compound, and 20 to 60% by mass of glycols.

[0016] Examples of the glycols 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. Preferably, propylene glycol or dipropylene glycol is used. The glycol is used in an amount of 20 to 60 mass %, more preferably 30 to 50 mass %, based on the total amount of the water-glycol based working fluid composition.

[0017] Examples of the fatty acid-based lubricants include saturated fatty acids such as capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, and stearic acid, and unsaturated fatty acids such as oleic acid, linoleic acid, and linolenic acid. Sodium salts of these fatty acids can also be used, such as sodium caprate, sodium undecylate, sodium laurate, sodium tridecylate, sodium myristate, sodium pentadecylate, sodium palmitate, sodium margarate, sodium stearate, sodium oleate, sodium linoleate, and sodium linolenate.

[0018] Other examples include aromatic fatty acids and dimer acids. Dimer acids are liquid fatty acids that contain monobasic and tribasic acids, primarily consisting of dibasic C36 dicarboxylic acids produced by dimerization of C18 unsaturated fatty acids derived from vegetable oils. These fatty acid-based lubricants, such as fatty acids, sodium salts of fatty acids, and dimer acids, may be used singly or in appropriate mixtures of two or more of the above-mentioned types.

[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 mass %, more preferably 0.04 to 0.06 mass %, based on the total amount of the composition.

[0020] Additionally, specific phosphate ester compounds may be used as anti-wear agents, and these phosphate esters have the following structure: [ka] (In the formula, R1 and R2 may be the same or different and each represent 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 represent an oxygen atom or a sulfur atom.)

[0021] Furthermore, such water-glycol-based hydraulic fluids may contain, as needed, 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.

[0022] The above-described alkanolamine compound can be used as a supplementary additive when a water-glycol-based working fluid is being used. For example, when a new water-glycol-based working fluid is being used, evaporation of water occurs, and the additive evaporates along with the water, resulting in a decrease in vapor-phase rust inhibitory properties. Measurement of the reserve alkalinity as specified in JIS K 2234-1994 is one example of a measure of vapor-phase rust inhibitory properties, and the reserve alkalinity decreases with evaporation. In such cases, the above-described alkanolamine compound can be added to the water-glycol-based working fluid as a supplementary additive to restore the initial reserve alkalinity and maintain the vapor-phase rust inhibitory properties, thereby enabling stable long-term use.

[0023] Among the above alkanolamine compounds, both dimethylethanolamine and diethylethanolamine are designated as hazardous substances, and therefore require strict handling control. Therefore, when used as a supplementary additive, R1 and R2 preferably have 3 or 4 carbon atoms. Such compounds are easy to handle as supplementary additives, and can be safely replenished by on-site workers into hydraulic fluids for hydraulic equipment. [Example]

[0024] The water-glycol based hydraulic fluid containing the alkanolamine compound of the present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples in any way.

[0025] The above-mentioned "reserve alkalinity" is measured using the reserve alkalinity measurement method specified in JIS K 2234-1994 to measure the basic components in a water-glycol-based working fluid. This reserve alkalinity is expressed in ml as the amount of 0.1 N hydrochloric acid required to neutralize the basic components contained in 10 ml of sample oil to a pH of 5.5.

[0026] Example 1 The following components were used: 1.90% by mass of N,N-dibutylaminoethanol as an alkanolamine compound, 37.73% by mass of propylene glycol as a glycol, 16.10% by mass of a water-soluble polymer as a thickener, 0.80% by mass of equal amounts of dimer acid and lauric acid as a fatty acid lubricant, 0.06% by mass of sodium hydroxide as an alkali hydroxide compound, 1.57% by mass of other additives including corrosion inhibitors and antifoaming agents, and 41.84% by mass of water. These components were thoroughly mixed to obtain a water-glycol based working fluid. The reserve alkalinity obtained according to JIS K 2234-1994 was 20. The kinematic viscosity at 40°C was 46mm. 2 / s and pH was 11. The molecular weight of the compounded N,N-dibutylaminoethanol is 173, and the specific gravity The viscosity is 0.860, the flash point is 90°C, and the boiling point is 226°C.

[0027] Example 2 The following components were used: 1.00 mass% N,N-dimethylaminoethanol as an alkanolamine compound, 38.63 mass% glycol, 16.10 mass% thickener, 0.80 mass% fatty acid lubricant, 0.06 mass% alkali hydroxide compound, 1.57 mass% other additives, and 41.84 mass% water. These components were mixed well to obtain a water-glycol based working fluid. The reserve alkalinity obtained according to JIS K 2234-1994 was 20, and the kinematic viscosity at 40°C was 46mm. 2 / s. The molecular weight of the compounded N,N-dimethylaminoethanol is 89, and the specific gravity The viscosity is 0.888, the flash point is 40°C, and the boiling point is 134°C.

[0028] (Comparative Example 1) The following compounds were used: 1.40% by mass of N-ethyldiethanolamine as an alkanolamine compound, 38.23% by mass of glycol, 16.10% by mass of a thickener, 0.80% by mass of a fatty acid lubricant, 0.06% by mass of an alkali hydroxide compound, 1.57% by mass of other additives, and 41.84% by mass of water. These were thoroughly mixed to obtain a water-glycol based working fluid. The reserve alkalinity obtained according to JIS K 2234-1994 was 20, and the kinematic viscosity at 40°C was 46mm. 2 / s. The molecular weight of the compounded N-ethyldiethanolamine is 133, and the specific gravity The viscosity is 1.07, the flash point is 124°C, and the boiling point is 251°C.

[0029] (Comparative Example 2) The following compounds were used: 1.00 mass% N-methylethanolamine as an alkanolamine compound, 38.63 mass% glycol, 16.10 mass% thickener, 0.80 mass% fatty acid lubricant, 0.06 mass% alkali hydroxide compound, 1.57 mass% other additives, and 41.84 mass% water. These were mixed well to obtain a water-glycol based hydraulic fluid. The reserve alkalinity obtained according to JIS K 2234-1994 was 20, and the kinematic viscosity at 40°C was 46mm. 2 / s. The molecular weight of the compounded N-ethyldiethanolamine is 75, and the temperature is 20°C. specific gravity The viscosity is 0.940, the flash point is 73°C, and the boiling point is 156°C.

[0030] (Comparative Example 3) 1.00 mass% of 2-ethylaminoethanol as an alkanolamine compound, 38.63 mass% of glycol, 16.10 mass% of a thickener, 0.80 mass% of a fatty acid lubricant, 0.06 mass% of an alkali hydroxide compound, 1.57 mass% of other additives, and 41.84 mass% of water were used and thoroughly mixed to obtain a water-glycol based working fluid. The reserve alkalinity obtained according to JIS K 2234-1994 was 20, and the kinematic viscosity at 40°C was 46mm. 2 / s. The molecular weight of the compounded 2-ethyldiaminoethanol was 117, and the specific gravity The viscosity is 0.918, the flash point is 77°C, and the boiling point is 199°C.

[0031] Comparative Example 4 The following compounds were used: 1.23% by mass of mono-n-butylethanolamine as an alkanolamine compound, 38.40% by mass of glycol, 16.10% by mass of a thickener, 0.80% by mass of a fatty acid lubricant, 0.06% by mass of an alkali hydroxide compound, 1.57% by mass of other additives, and 41.84% by mass of water. These were thoroughly mixed to obtain a water-glycol based working fluid. The reserve alkalinity obtained according to JIS K 2234-1994 was 20, and the kinematic viscosity at 40°C was 46mm. 2 / s. The molecular weight of the compounded N-mono-n-butylethanolamine is 117, and the specific gravity The viscosity is 0.893, the flash point is 77°C, and the boiling point is 199°C.

[0032] (Comparative Example 5) A water-glycol based hydraulic fluid was obtained by thoroughly mixing 39.63 mass% glycol, 16.10 mass% thickener, 0.80 mass% fatty acid lubricant, 0.06 mass% alkali hydroxide compound, 1.57 mass% other additives, and 41.84 mass% water. Because no alkanolamine compound was added, the reserve alkalinity obtained according to JIS K 2234-1994 was 9, and the kinematic viscosity at 40°C was 46mm. 2 / s.

[0033] 〔test〕 The following tests were carried out to evaluate the vapor phase rust prevention properties of the above-mentioned Examples and Comparative Examples. (Gas-phase corrosion prevention test) As shown in Figure 1, 100 g of the water-glycol-based working fluid of the Example or Comparative Example was placed in a hard glass test tube with a height of 600 mm and an outer diameter of 50 mm, which is used in the turbine oil oxidation stability test of JIS K2514-2, and two test pieces of general structural rolled steel (SS-400) measuring 80 × 30 × 2 mm were hung so that they were positioned at the top and bottom of the test tube. The top opening of the test tube was covered with a cooler, and the bottom of the test tube was placed in a thermostatic bath at 50°C. After leaving it to stand for 200 hours, the test piece was visually inspected for the presence or absence of rust. Evaluation criteria: No rust on either side of the test piece... Pass Rust is found on either or both test pieces...Fail

[0034] (Test results) The test results are shown in Table 1.

[0035] (Consideration) As shown in Table 1, in Examples 1 and 2, an alkanolamine compound was blended so that the reserve alkalinity was 20.0, and in both cases no rust was observed in the vapor phase rust prevention test, resulting in a passing result. Comparative Example 5 shown in Table 2 does not contain any alkanolamine compound and has a low reserve alkalinity of 9.0. Rust was observed in the vapor phase rust prevention test, resulting in a failure, which indicates that it is not preferable. In Comparative Examples 2 to 4, an alkanolamine compound was blended so that the reserve alkalinity was 20.0. However, since this alkanolamine compound was not a dialkylaminoalkanol as defined in the present invention, rust was observed in the vapor-phase rust prevention test, resulting in failure, and it is clear that this is not preferable.

[0036] [Table 1]

[0037] [Table 2]

Claims

[Claim 1] A water-glycol based hydraulic fluid composition comprising an alkanolamine compound represented by the following general formula, said alkanolamine compound having a specific gravity at 20°C of 0.86 to 0.89; 20 to 60 mass% water, 20 to 60 mass% glycols, 0.6 to 1.2 mass% fatty acid lubricant, and 0.01 to 0.06 mass% alkali hydroxide compound selected from potassium hydroxide and / or sodium hydroxide; and having a reserve alkalinity of 10 to 25 as measured by the method specified in JIS K 2234-1994: 【Chemical 1】 (In the above general formula, R 1 and R 2 are hydrocarbon groups having 1 to 8 carbon atoms, and R 3 is a hydrocarbon group having 2 or more carbon atoms.)

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