JP2016050217A - Water-containing hydraulic fluid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-containing hydraulic fluid that inhibits acid generation, suppresses a decrease in pH, and has excellent oxidation stability, when used for the long term, and moreover, prevents such effects from being greatly impaired even if a water-containing hydraulic fluid comprising the acids generated from the degradation.SOLUTION: A water-containing hydraulic fluid comprises one or more compounds of 0.01 mass%-1 mass% in total, the compounds selected from the compound group consisting of a C1-C3 aliphatic monocarboxylic acid, a C2-C5 aliphatic dicarboxylic acid and a C6 aliphatic tricarboxylic acid, and a carboxylic acid having a hydroxy group bound thereto.SELECTED DRAWING: None

Description

  The present invention relates to a hydrous working fluid.

  Hydraulic equipment is widely adopted in the industry and contributes to productivity improvement. In these hydraulic systems, hydraulic fluid is used as a power transmission medium. However, in the vicinity of high-temperature heat sources and equipment that generates electric sparks, various difficulties such as water-glycol hydraulic fluids are required for disaster prevention. Flammable water-containing hydraulic fluid is used.

It is desired that a hydrous hydraulic oil has little change in liquid properties with respect to oxidation and shear, and maintains its properties within a proper range over a long period of time.
For example, water-glycol hydraulic fluid has excellent performance, but generation of acid and viscosity reduction occur due to shear and oxidation during use. In order to maintain the performance, it is common to replenish the concentrate and use it while controlling the properties such as pH of the solution.

  In addition, when the water-glycol hydraulic fluid exceeds its proper value during use and deteriorates excessively to the extent that it is not appropriate to manage it by replenishing the concentrate, the working fluid is usually discarded. Replace with new solution. At this time, it is best to draw out the used solution sufficiently and perform flushing before replacing it with a new solution. However, water-glycol based hydraulic fluids are often used in dangerous locations such as near high-temperature heat sources, and the mechanical piping is complicated and the replacement of the fluid is costly. There are few things. Therefore, it is inevitable that the remaining liquid is mixed with the new liquid.

  Examples of performance improvement technologies such as pH reduction suppression and oxidative stability improvement of water-containing hydraulic fluid include, for example, polyoxyalkylene glycol diether compounds having a specific structure, polyoxyalkylene glycol monoether compounds having a specific structure, and polyoxyalkylene having a specific structure. Water-containing hydraulic fluid containing a propylene glycol monoether compound and a fatty acid salt having a specific structure (see Patent Literature 1), water-glycol flame-retardant hydraulic fluid containing a neutralized product of glycerol borate and base (Patent Literature) 2), water-glycol flame retardant hydraulic fluid containing a water-soluble polyether having a specific structure (see Patent Document 3), water-glycol flame retardant hydraulic fluid containing an alkylated morpholine having a specific structure (patent Reference 4), water-containing hydraulic fluid containing a cyclic amine having a specific structure (see Patent Document 5), and the like.

Japanese Patent Laid-Open No. 6-279979 JP-A-5-263096 JP 2000-26982 A JP 2007-39569 A JP 2014-051650 A

As described above, when using a hydrous working fluid, since the properties such as the pH of the fluid are generally managed, it takes time and cost to maintain and maintain the performance, so the pH is difficult to decrease during use. Is needed.
In addition, the acid contained in the remaining use liquid at the time of liquid replacement decreases the pH of the replaced new liquid and becomes a factor that accelerates the deterioration of the new liquid. For this reason, suppression of the pH fall of the water-glycol system hydraulic fluid when a use liquid is mixed with a new liquid and the improvement of oxidation stability are required.

  The present invention has been made in view of the above-described prior art, and suppresses acid generation over a long period of use, has a small pH drop, has excellent oxidation stability, and further contains an acid generated by deterioration. It is an object of the present invention to provide a water-containing working fluid that does not greatly impair such effects even when a water-containing working fluid is mixed.

  As a result of intensive studies to solve the above problems, the present inventor has found that by containing a specific amount of a compound having a specific structure, it is possible to suppress the decrease in pH of the aqueous hydraulic fluid and improve the oxidation stability. I found it. The present invention has been made based on these findings. That is, specific means for solving the above-described problems are as follows.

<1> Selected from a compound group consisting of an aliphatic monocarboxylic acid having 1 to 3 carbon atoms, an aliphatic dicarboxylic acid having 2 to 5 carbon atoms and an aliphatic tricarboxylic acid having 6 carbon atoms, and a carboxylic acid having a hydroxyl group bonded thereto. A water-containing hydraulic fluid containing at least 0.01% by mass to 1% by mass of one or more types.
<2> The water-containing working fluid according to <1>, wherein the compound group includes formic acid, acetic acid, malonic acid, maleic acid, and citric acid.
<3> The water-containing working fluid according to <1>, wherein the compound group includes malonic acid and maleic acid.
<4> The hydrous hydraulic fluid according to any one of <1> to <3>, wherein the hydrous hydraulic fluid is a water-glycol hydraulic fluid.

  According to the present invention, over long-term use, acid generation is suppressed, pH drop is small, oxidation stability is excellent, and even when a water-containing hydraulic fluid containing an acid generated by deterioration is mixed, this is required. A water-containing working fluid that does not significantly impair the effect is provided.

  Hereinafter, the water-containing working fluid of the present invention will be described in detail. In addition, in this specification, "-" showing a numerical range represents the range containing the numerical value of the upper limit and the minimum. Further, in the present specification, the amount of each component in the water-containing hydraulic fluid is the amount of each component present in the water-containing hydraulic fluid unless there is a specific indication when there are a plurality of substances corresponding to each component in the water-containing hydraulic fluid. Means the total amount of substances.

  The water-containing hydraulic fluid of the present invention comprises an aliphatic monocarboxylic acid having 1 to 3 carbon atoms, an aliphatic dicarboxylic acid having 2 to 5 carbon atoms, an aliphatic tricarboxylic acid having 6 carbon atoms, and a carboxylic acid having a hydroxyl group bonded thereto. The total amount of one or more carboxylic acids selected from the compound group consisting of: 0.01% by mass to 1% by mass.

(1) Carboxylic acid The hydrous hydraulic fluid of the present invention comprises an aliphatic monocarboxylic acid having 1 to 3 carbon atoms, an aliphatic dicarboxylic acid having 2 to 5 carbon atoms, an aliphatic tricarboxylic acid having 6 carbon atoms, and a hydroxyl group. 1 or more types chosen from the compound group which consists of carboxylic acid which these couple | bonded. These may be compounds having an unsaturated bond in the carbon chain.

  Examples of the aliphatic monocarboxylic acid having 1 to 3 carbon atoms include formic acid, acetic acid, propionic acid and the like, and examples of the aliphatic monocarboxylic acid having 1 to 3 carbon atoms to which a hydroxyl group is bonded include hydroxyacetic acid and 2-hydroxypropane. An acid, glyceric acid, etc. are mentioned. Examples of the aliphatic dicarboxylic acid having 2 to 5 carbon atoms include oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, methylmalonic acid, and the like. Examples of the group dicarboxylic acid include malic acid, tartaric acid, 2-hydroxymalonic acid, hydroxysuccinic acid, and hydroxyglutaric acid. Examples of the aliphatic tricarboxylic acid having 6 carbon atoms include 1,2,3-propanetricarboxylic acid, and examples of the aliphatic tricarboxylic acid having 6 carbon atoms to which a hydroxyl group is bonded include citric acid and isocitric acid.

Among the above compound groups, by using one or more selected from formic acid, acetic acid, propionic acid, malonic acid, maleic acid, fumaric acid, tartaric acid and citric acid, the decrease in pH over a long period of use is small, and the oxidation stability The effect of the present invention that it is excellent in this can be further enhanced. Further, by using one or more selected from malonic acid and maleic acid, in addition to the above effects, better wear resistance can be obtained.
The content of the compound group consisting of an aliphatic monocarboxylic acid having 1 to 3 carbon atoms, an aliphatic dicarboxylic acid having 2 to 5 carbon atoms and an aliphatic tricarboxylic acid having 6 carbon atoms, and a carboxylic acid having a hydroxyl group bonded thereto. The total amount is 0.01% by mass to 1% by mass, preferably 0.05% by mass to 0.98% by mass, more preferably 0.2% by mass to 0% by mass with respect to the total mass of the hydrous hydraulic fluid. It is 0.95 mass%, Most preferably, it is 0.3 mass%-0.7 mass%. When the total content of the carboxylic acid is less than 0.01% by mass, the effect of the present invention that the decrease in pH is small and the oxidation stability is excellent over a long period of use cannot be sufficiently obtained. If it exceeds the upper limit, the wear resistance may decrease, which is not preferable. In addition, in the hydrous system hydraulic fluid of this invention, you may contain only 1 type chosen from an above described compound group, and may contain 2 or more types. The total amount in the water-containing working fluid of the compound in the case of containing two or more types needs to be 0.01% by mass to 1% by mass with respect to the total mass of the water-containing working fluid.

(2) Water The water-containing working fluid of the present invention contains water. As the water to be used, for example, ion exchange water can be used. The water content is preferably 20% by mass to 60% by mass and more preferably 20% by mass to 50% by mass with respect to the total mass of the water-containing hydraulic fluid. When the water content is 20% by mass or more, the flame retardancy that is the merit of the water-containing working fluid is sufficiently exhibited. Further, when the content is 60% by mass or less, it is advantageous for obtaining an abrasion resistance effect.

  The water-containing hydraulic fluid of the present invention can be applied to various water-containing hydraulic fluids such as water-glycol hydraulic fluid, W / O emulsion type and O / W emulsion hydraulic fluid. Applicable optimally.

The water-glycol hydraulic fluid is a hydraulic fluid containing water and glycols (glycol compound) in the fluid.
Examples of the glycols contained in the water-glycol hydraulic fluid include ethylene glycol, diethylene glycol, trimethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, hexylene glycol, and dihexylene glycol. And monoalkyl ethers of these glycols. Here, as for carbon number of the alkyl group in the said monoalkyl ether, 1-8 are preferable. Among these, it is more preferable to use ethylene glycol, propylene glycol or dipropylene glycol.
The content of glycols in the water-glycol hydraulic fluid is preferably 20% by mass to 60% by mass and more preferably 25% by mass to 50% by mass with respect to the total amount of the hydrous hydraulic fluid. The glycols may be used alone or in combination of two or more, but when two or more types are used in combination, the total content is preferably within the above range.

(3) Alkaline agent In the water-containing hydraulic fluid of the present invention, for example, an alkali metal or alkaline earth metal hydroxide such as potassium hydroxide or sodium hydroxide may be used as an alkali agent for pH adjustment. . In that case, the content of the alkaline agent is preferably 0.1% by mass to 3% by mass, and more preferably 0.2% by mass to 2% by mass with respect to the total mass of the water-containing hydraulic fluid.

The hydrous working fluid of the present invention may contain a pH adjuster other than the alkaline agent.
As a pH adjuster, in addition to the alkali agent, it can be mentioned as a liquid phase and a gas phase rust preventive agent to be described later. It is preferable to adjust the pH of the hydraulic fluid to about 8 to 11 by blending these pH adjusters. When the pH is within this range, the solubility of the lubricant is increased, so that the solubility of the entire water-containing working fluid is easily maintained, and the wear resistance effect of the water-containing working fluid is easily obtained.

(4) Thickener The water-containing working fluid of the present invention preferably contains a thickener.
Examples of the thickener preferably used in the water-containing working fluid of the present invention include water-soluble polyoxyalkylene polyols or alkyl ether derivatives thereof.

  Examples of water-soluble polyoxyalkylene polyols include polyoxyalkylene glycol and polyoxyalkylene triol. Specifically, a copolymer of polyhydric alcohol with ethylene oxide (EO) homopolymer, EO and other alkylene oxides (for example, propylene oxide, 1,2-butylene oxide, tetrahydrofuran, α-olefin oxide, etc.) The compound obtained by adding is mentioned. When using a compound obtained by adding a copolymer of EO and another alkylene oxide to a polyhydric alcohol, the other alkylene oxide is preferably polyoxyethylene (PO), and EO / etc. The alkylene oxide has a molar ratio of preferably 25/75 to 90/10, more preferably 50/50 to 85/15. It is preferable to set the molar ratio of EO to 25% or more because it becomes easy to ensure appropriate solubility in the working fluid. Further, the addition mode of EO and other alkylene oxide copolymers may be random addition or block addition.

  Examples of the alkyl ether derivative of the water-soluble polyoxyalkylene polyol include the above-described alkyl ether derivatives of the water-soluble polyoxyalkylene polyol, that is, polyoxyalkylene glycol monoether, polyoxyalkylene glycol diether and the like. 1-4 are preferable and, as for carbon number of the alkyl group in the alkyl ether group in an alkyl ether derivative, 1-3 are especially preferable.

  The weight average molecular weight of water-soluble polyoxyalkylene polyols and alkyl ether derivatives thereof is preferably in the range of 3,000 to 75,000, more preferably in the range of 10,000 to 55,000. By increasing the weight average molecular weight to 3,000 or more, it is easy to secure a thickening effect and can be suppressed to an appropriate blending amount, so that the blending ratio of glycols does not decrease relatively and the system dissolves. It is preferable because the nature does not change. Moreover, it is preferable to make the weight average molecular weight 75,000 or less because it is easy to ensure the stability of the thickener against heat and shear, and it is easy to suppress property changes accompanying the decomposition of the thickener.

The content of the thickener is preferably from the viewpoint of blending balance of the glycols as described above, and 5% to 40% by weight relative to the total mass of the water-containing hydraulic fluid, 10% by weight More preferably, it is -30 mass%. In addition, only 1 type of thickener may be used or 2 or more types may be used together, but when using 2 or more types together, it is preferable that the total content is in said range.
The water based hydraulic fluid preferably has 40 ° C. kinematic viscosity of 20.0mm ² /sec~75.0mm ² / ^sec, particularly preferably 30.0mm ² /sec~55.0mm 2 / sec.

  The kinematic viscosity is a value obtained in the kinematic viscosity test method of JIS K2283 (crude oil and petroleum products-kinematic viscosity test method and viscosity index calculation method, 1956 (revised in 2000)).

(5) Other additives In the water-containing hydraulic fluid of the present invention, as other additives, lubricant, liquid phase rust preventive agent, gas phase rust preventive agent, metal deactivator, antifoaming agent, colorant , And other optional additives can be blended as required.

  Examples of the lubricant include saturated fatty acids such as myristic acid, palmitic acid, lauric acid and stearic acid, unsaturated fatty acids such as oleic acid, linoleic acid and linolenic acid, aromatic fatty acids and dimer acids. These fatty acids may be used alone or in combination of two or more.

  Liquid phase or gas phase rust inhibitors include piperazine, 1-methylpiperazine, 2-methylpiperazine, 1,4-dimethylpiperazine, 1,2-dimethylpiperazine, 1,3-dimethylpiperazine, 2,5-dimethylpiperazine. 2,6-dimethylpiperazine, 1-ethylpiperazine, 2-ethylpiperazine, 1,4-diethylpiperazine, 1,2-diethylpiperazine, 1,3-diethylpiperazine, 2,5-edethylpiperazine, 2,6 -Diethylpiperazine, hydroxymethylpiperazine, dihydroxymethylpiperazine, piperidine, 1-methylpiperidine, 2-methylpiperidine, 3-methylpiperidine, 1,2-dimethylpiperidine, 1,3-dimethylpiperidine, 1-ethylpiperidine, 2- Ethylpiperidine, 3-ethylpiperidine, 1 , 2-diethylpiperidine, 1,3-diethylpiperidine, morpholine, methylmorpholine, ethylmorpholine, propylmorpholine, hydroxymethylmorpholine, hydroxyethylmorpholine, hydroxypropylmorpholine, hydroxybutylmorpholine, monoethanolamine, diethanolamine, triethanolamine, 3-amino-1-propanol, 1-amino-2-propanol, 3-methoxypropylamine, 3-ethoxypropylamine, ethylenediamine, diethylenetriamine, cyclohexylamine, N-methylethanolamine, N-methyldiethanolamine, N-ethylethanol Amine, N-ethyldiethanolamine, Nn-butylethanolamine, Nn-butyldiethanolamine, dimethyl Examples include organic amines such as butanolamine, diethylethanolamine, dibutylethanolamine, N- (β-aminoethyl) ethanolamine, 1,4-bis (2-hydroxyethyl) imidazoline and derivatives thereof, and alkali metal carboxylates. It is done. These liquid phase or vapor phase rust preventives may be used alone or in combination of two or more.

Examples of the metal deactivator include benzotriazole compounds such as benzotriazole, tolyltriazole, carboxybenzotriazole, and alkali metal salts or amine salts thereof, mercaptobenzothiazole, and alkali metal salts thereof.
Examples of the antifoaming agent include silicone compounds, and examples of the coloring agent include alcohol-based coloring agents and metal-based coloring agents.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, this invention is not restrict | limited at all by these examples.

1. As preparation examples and comparative examples of water-containing hydraulic fluid (water-glycol hydraulic fluid), the components shown in Table 1 and Table 2 below were mixed in the blending amounts (% by mass) shown in the table, and water- A glycol-based working fluid was prepared.
Moreover, each water-glycol type | system | group hydraulic fluid of Table 1 and Table 2 contains what is shown below as a thickener, glycols, a lubricant, an alkali agent, a gaseous-phase rust preventive agent, and a metal deactivator. Each water-glycol-based hydraulic fluid was adjusted so as to have a pH of 10.8 and a 40 ° C. kinematic viscosity of 49.0 mm ² / sec depending on the blending amount thereof.
The kinematic viscosity was measured according to the kinematic viscosity test method of JIS K2283 (crude oil and petroleum products—kinematic viscosity test method and viscosity index calculation method, 1956 (revised 2000)).

Thickener: Polyoxyethylene / oxypropylene glycol, EO / PO molar ratio of 75/25 random copolymer (weight average molecular weight 29,000)
・ Glycols: Propylene glycol ・ Lubricant: Oleic acid ・ Alkaline agent: Potassium hydroxide ・ Gas phase rust preventive agent: Morpholine ・ Metal deactivator: Tolyltriazole

2. Evaluation Method (A) Oxidation Stability For each of the water-glycol hydraulic fluids shown in Tables 1 and 2, the following oxidation stability test was conducted for 14 hours, and the oxidation stability was evaluated by pH measurement. The results are shown in Tables 1 and 2.
In addition, pH measurement was performed about following (1)-(3), and the result was described in each table | surface. The higher the numerical values of “pH after mixing of deteriorated hydraulic fluid” and “pH after test”, the better the stability of the water-glycol hydraulic fluid.
(1) pH immediately after preparing the water-glycol hydraulic fluid
(2) pH of “deteriorated working fluid mixture” after mixing 30% by mass of the following “degraded working fluid” separately prepared
(3) pH after conducting the oxidation stability test on the “degraded hydraulic fluid mixture” in (2) above

(A-1) Oxidation stability test Rotating cylinder type defined in paragraph 6 of JIS K2514-3 (Lubricating oil-Determination of oxidation stability-Part 3: Rotational pressure vessel type oxidation stability, 2013) Using an oxidation stability tester, an oxidation stability test was performed under the following conditions.
Test solution volume: 80g
Catalyst; None Test temperature: 120 ° C
Enclosed oxygen pressure: 620 kPa (25 ° C.)

(A-2) Preparation method of “degraded hydraulic fluid” A product obtained by degrading Cosmo Fluid GS46, which is a commercially available water-glycol hydraulic fluid, using the rotary cylinder type oxidation stability tester until pH 8.0. Used as “degraded hydraulic fluid”.

(B) Abrasion resistance test Among the water-glycol based hydraulic fluids listed in Tables 1 and 2, the water glycol hydraulic fluids of Examples 3 to 5 and Comparative Example 1 were tested using JP-5S-32-90 “Lubrication”. A wear resistance test was performed under the following conditions using a four-ball wear tester specified in “Oil Wear Resistance Test Method (Shell Four-ball Method)” to evaluate the wear resistance. The results are shown in Tables 1 and 2.
The smaller the wear scar diameter, the better the wear resistance.
Test load: 294N
Test temperature: Room temperature Rotation speed: 1200rpm
Time: 30 minutes

  From the results shown in Table 1 and Table 2, it can be seen that the water-containing hydraulic fluid according to the present invention has a small pH drop over a long period of use and is excellent in oxidation stability. It can also be seen that even better abrasion resistance can be obtained when maleic acid or malonic acid is selected in the hydrous working fluid according to the present invention.

Claims (4)

  One kind selected from a compound group consisting of an aliphatic monocarboxylic acid having 1 to 3 carbon atoms, an aliphatic dicarboxylic acid having 2 to 5 carbon atoms and an aliphatic tricarboxylic acid having 6 carbon atoms, and a carboxylic acid having a hydroxyl group bonded thereto. A hydrous hydraulic fluid containing 0.01% by mass to 1% by mass of the above in total.   The water-containing working fluid according to claim 1, wherein the compound group comprises formic acid, acetic acid, malonic acid, maleic acid, and citric acid.   The hydrous working fluid according to claim 1, wherein the compound group includes malonic acid and maleic acid.   The water-containing working fluid according to any one of claims 1 to 3, wherein the water-containing working fluid is a water-glycol working fluid.