JP3338112B2 - Water-glycol hydraulic fluid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-glycol hydraulic fluid, and more particularly to a water-glycol flame-retardant hydraulic fluid capable of suppressing the occurrence of pitting in a rolling bearing.

[0002]

2. Description of the Related Art In recent years, hydraulic devices have been widely used in various fields in the industrial world, and have greatly contributed to improvement in productivity. Among these hydraulic systems, fire-resistant hydraulic fluids are used as hydraulic fluids because high-temperature metal processing equipment, electric spark generating equipment, heating furnaces and other hydraulic equipment involve fire hazards. ing. However, among the flame-retardant hydraulic oils, particularly, a hydrous hydraulic fluid has a problem in that the life of rolling bearings used in hydraulic pumps and motors is shortened. In other words, the hydrous hydraulic fluid greatly reduces the rolling bearing life and further damages the bearing as compared with the mineral oil-based and synthetic hydraulic fluids, and often hinders the normal operation of the entire hydraulic system. Until now, to prevent these bearing troubles, improvement of hydraulic equipment and installation of incidental equipment have been taken. For example, a method of using hydraulic equipment at a pressure lower than its rated specification pressure, a method of improving the size of a standard bearing part to a specially large one, or forcibly lubricating a bearing part where coupling or poor lubrication is likely to occur. In order to do this, a special hydraulic oil circulation circuit is installed. Changing the specifications of these devices and investing in equipment are measures that are not particularly necessary if the bearing life of the hydrous hydraulic oil, especially the water-glycol hydraulic fluid, which is the mainstream of the hydrous hydraulic oil, is improved.

[0003] Water-glycol-based hydraulic fluids that are currently commercially available have the following basic composition.

[0004]

[Table 1]

Examples of the solvent as a component include ethylene glycol, propylene glycol, dipropylene glycol, and the like. These solvents have a function of lowering the pour point and also have a role of increasing the compatibility of various additives. included. As the thickener, a polyalkylene glycol having an appropriate molecular weight is used. By adjusting the amount of the thickener to be added, it is possible to obtain a working fluid compatible with various ISO viscosity grades. Water is essential for maintaining flame retardancy. Thus, typically, a three-component mixed system of glycol-polyalkylene glycol-water is the base oil of the water-glycol hydraulic oil.
Examples of the lubricant to be added to the base oil include unsaturated fatty acids such as oleic acid, saturated fatty acids such as lauric acid and stearic acid, aromatic fatty acids, and carboxylic acids such as dimer acid. Examples of the rust preventive include organic amines, organic amine derivatives, alkali metal carboxylate and the like. In practice, the above-mentioned salt of carboxylic acid and organic amine or alkali metal carboxylate may be used as both a lubricant and a rust preventive. Some of these conventional water-glycol based hydraulic fluids are quite satisfactory in terms of sliding lubrication.

[0006] However, even with the conventional water-glycol hydraulic fluid, which is quite satisfactory in sliding lubrication, it actually reduces the rolling life of the rolling bearings used in hydraulic pumps and motors, and in the case of mineral oil hydraulic fluid, The problem is that the bearing is damaged in a much shorter time than in the case of the above. This is due to the fact that the conventional water-glycol based hydraulic fluid does not have sufficient rolling lubricity. In addition, when a water-glycol hydraulic fluid to which an unsaturated fatty acid such as oleic acid is added, which is conventionally used as a lubricant, is used, sludge is generated when divalent metal (zinc, lead, calcium, etc.) ions are mixed. However, there is a drawback that the rolling bearing is easily worn, which causes the filter to be blocked.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned state of the art, and does not impair the excellent flame retardancy of a water-glycol type hydraulic fluid, and also has various required performances. It is an object of the present invention to provide a water-glycol-based hydraulic fluid of a uniform solution that can suppress the occurrence of pitching of a rolling bearing without impairing and extend the life of the rolling bearing.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, have focused on polyoxyethylene fatty acid esters having a specific aliphatic hydrocarbon group. As a result, by mixing a small amount of the polyoxyethylene fatty acid ester having a specific structure into a water-glycol hydraulic fluid, the pitching of the rolling bearing can be performed without impairing various required performances of the hydraulic fluid. It has been found that generation can be suppressed and the life of the rolling bearing can be extended, and the present invention has been completed based on this finding.

Accordingly, the present invention is a polyoxyethylene fatty acid ester represented by the following following general formula (1) 0.05
The present invention provides a water-glycol type hydraulic fluid characterized by containing about 5% by weight. General formula (1):

[0010]

Embedded image RCOO (CH ₂ CH ₂ O) _n H

(Wherein, R represents an aliphatic hydrocarbon group having 12 to 18 carbon atoms, and n represents an integer of 4 to 9 ). Hereinafter, the present invention will be described in detail.

The water-glycol hydraulic fluid of the present invention contains the polyoxyethylene fatty acid ester represented by the general formula (1). R in the general formula (1) has 1 carbon atom.
And 2 to 18 aliphatic hydrocarbon groups. When the number of carbon atoms is less than 12, there is a disadvantage that an oil film is poorly formed and lubricity is inferior. When the number of carbon atoms exceeds 18 , there is a disadvantage that compatibility stability is deteriorated. Specific examples of these aliphatic hydrocarbon groups include, for example, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl , oleyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl,
Examples include a hexadecenyl group, a heptadecenyl group, an octadecenyl group , a linoleyl group, and a linolenyl group.

[0013] n in one general formula (1) is an integer representing the number of moles of added oxyethylene group, an integer from 4-9
There is . The polyoxyethylene fatty acid ester may be used alone or in combination of two or more. This polyoxyethylene fatty acid ester can be prepared by addition polymerization of fatty acid with ethylene oxide.

The content of the polyoxyethylene fatty acid ester contained in the water-glycol hydraulic fluid of the present invention is 0.1.
It is from 0.5 to 5% by weight, preferably from 1 to 1.8% by weight. When the content of the polyoxyethylene fatty acid ester is less than 0.05% by weight, the lubricating property is not sufficient, and even if it is added in excess of 5% by weight, the effect of the rolling lubricating property is saturated. Disadvantageous. In the case of hydraulic oil, the operating environment is a closed system, and the initial concentration is maintained without any lubricating oil additive being taken out of the system as seen in the case of cutting oil, rolling oil and the like. Excessive addition has no merit in cost.

The base oil of the water-glycol-based hydraulic oil of the present invention may be any commonly used water-glycol-based hydraulic fluid, and is usually about 25 to 50% by weight of glycols, about 10% by weight.
Consist of ２０20% by weight of thickener and about 35-50% by weight of water. Further, in this base oil, additives usually used in this type of hydraulic fluid, for example, an oil agent, a lubricant, a liquid phase rust inhibitor, a gas phase rust inhibitor, a metal deactivator, a pH adjuster, Antifoam,
Colorants and other additives may be appropriately added in appropriate amounts.

The glycols include ethylene glycol, propylene glycol, dipropylene glycol,
Glycols such as tripropylene glycol and hexylene glycol and monoalkyl ethers of these glycols are exemplified, and propylene glycol and dipropylene glycol are preferred. These glycols may be used alone or in combination of two or more.

As the thickener, a polyether type thickener such as polyalkylene glycol or its alkyl ether derivative is usually used.
Polyoxyalkylene polyol of polyhydric alcohol, for example, polyoxyalkylene glycol such as Newpol 75H90000 (Sanyo Chemical), Newpol V-
Polyoxyalkylene triols such as 10-C (Sanyo Chemical), polyoxyalkylene polyols described in JP-A-54-105653; polyoxyalkylene polyols of polyamides, such as polyoxyalkylene glycols described in JP-B-51-44275. And
Preferred is polyoxyalkylene glycol. These thickeners may be used alone or in a combination of two or more.

The water-glycol-based working fluid of the present invention has excellent rolling lubrication without adding a conventionally added lubricant, but a conventional lubricant may be used in combination.
Examples of the lubricant that can be used in combination include unsaturated fatty acids such as oleic acid, lauric acid, stearic acid, aromatic fatty acids, and dimer acid.

As the rust preventive, organic amines (monoethanolamine, triethanolamine, ethylenediamine, diethylenetriamine, cyclohexylamine, morpholine, 1,4-bis (2-aminoethyl) piperazine, 2-heptadecyl-1- (2 -Hydroxyethyl)
Imidazoline), organic amine derivatives (such as the above-mentioned amine alkylene oxide adducts), alkali metal salts of carboxylic acids, and cyclohexylamine nitrite.

Examples of the antifoaming agent include an emulsion of a silicon compound. Furthermore, sulfur compounds and phosphorus compounds as extreme pressure agents, hydroxides of alkali metals and amines as pH adjusters, metal salts and amine salts of nitrogen-containing compounds such as mercaptobenzothiazole and triazole as corrosion inhibitors, sequestration of metal ions. Examples of the agent include metal salts of aminocarboxylic acids such as ethylenediaminetetraacetic acid.

The water-containing working fluid composition of the present invention can be prepared by appropriately mixing and mixing predetermined amounts of the above components. The mixing method and the addition method in this adjustment are not particularly limited, and can be performed by various methods, and the mixing order and the addition order of each component can also be performed in various mixing orders and the addition order.

The hydraulic device in which the hydrous hydraulic fluid composition of the present invention can be used is not particularly limited.
Machine tools, die casting machines, transfer machines,
Press machine, forging machine, cargo handling machine, civil engineering machine,
Plant control devices, automobiles, ships, aircraft, various hydraulic devices used for various machines including rockets, high-temperature metal processing equipment, especially with the danger of fire,
It is effective in a hydraulic device used near a heat source such as a device that generates an electric spark, a heating furnace, a continuous casting device, a hot rolling mill, and an aluminum die casting machine. Also, the hydraulic pump used in the hydraulic device is not particularly limited, and can be used for various hydraulic pumps.
For example, vane pump, gear pump, plunger pump,
And a screw pump. The hydrous hydraulic fluid composition of the present invention is particularly effective for the fatigue life of a plunger pump bearing.

[0023]

[Action] is not clear for the action, polyoxyethylene fatty acid esters of the general formula dissolved in the solution (1) is, with an increase in temperature of the lubricating surface, deposited on the rolling surface of the bearing surface, the oil film It is considered to make the formation more dense.

[0024]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples. The present invention is not limited by these examples. Examples 1 to 8 The polyoxyethylene fatty acid ester shown in Table 3 was added to the base oil I shown in Table 2 below and mixed to prepare a water-glycol-based working fluid. The polyoxyethylene fatty acid ester used in Examples 1 to 8 was a mixture of those having a saturated aliphatic hydrocarbon group having the carbon number shown in Table 3 and those having an unsaturated aliphatic hydrocarbon group. Was.

[0025]

[Table 2]

Comparative Examples 1 to 3 Three commercially available water-glycol-based hydraulic fluids A, B and C (hereinafter sometimes abbreviated as W / G) and a base oil I (polyoxyethylene) shown in Table 2 No fatty acid monoester added)
Was used. In addition, A of commercially available W / G contains lauric acid, and B of commercially available W / G contains about 1% by weight of oleic acid. In addition, C of commercially available W / G
Contains dimer acid (a dimer of oleic acid).

[0027]

[Table 3]

The results of the 10% life and 50% life in Table 3 are the results of the Uni-steel rolling life test. The rolling life was measured using a Uni-steel rolling test life tester (IP305 / compliant) under the following conditions. Was evaluated. (Uni-steel rolling life test) Test conditions Rotation speed: 1500 rpm Load: 660 lbs Test bearing: thrust ball bearing # 2910P5 (NAC
HI) Test piece: SUJ-2 Test ball: 5 Lubrication method: Dropping method (10 drops / min) Stopping level: 1.5G Number of tests: 5 to 7 times

For the evaluation, the ball bearing was rotated on a washer-shaped test piece under the set conditions. As the operation is continued, small holes of wear due to fatigue, ie, pitting, occur on the track of the test piece. When pitching occurs, vibration occurs in the test section. Therefore, a rotation stop vibrometer prepared so as to stop at 1.5 G or more beforehand was operated to stop the testing machine. The fatigue life time (hr) was obtained as an integrated time up to this time. The test was performed 5 to 7 times, data was accumulated, and plotted on Weibull probability paper to obtain 10% life and 50% life.

Incidentally, the flame-retardant hydraulic oil acts not only as a pressure transmission medium used for a long time under severe conditions, but also as a lubricant for sliding parts of hydraulic pumps and hydraulic motors. In addition, compatibility with various materials (metal materials, rubber, etc.) used in the hydraulic system is required. Therefore, a vane pump durability test was performed. (Vane Pump Endurance Test) The suitability of Example 5 as a hydraulic oil was comprehensively evaluated by conducting an actual pump test.
Table 4 shows the results. Test pump: PV2R-26 vane pump manufactured by Yuken Kogyo Test conditions: Rotation speed 1200 rpm Discharge pressure 250 kgf / cm ² Oil temperature 50 ° C Oil amount 50 l

[0031]

[Table 4]

As is clear from Table 4, the amount of wear is saturated after normal initial wear. No discoloration of the cartridge, no corrosion of sludge, and the like were recognized at all, and changes in the general properties (viscosity, pH, preliminary alkalinity, etc.) of the hydraulic oil were very slight, indicating sufficient compatibility. A metal material immersion test (JIS K 2234) conducted simultaneously
Compliant) and rubber material immersion test (JIS K6301)
Compliance), it was confirmed that the fluid had sufficient compatibility as a working oil without any problem. In addition, when the water-glycol hydraulic oil of the example was operated using the plunger pump, it had a remarkable effect on the fatigue life of the bearing of the plunger pump.

The water of the present invention - glycol-based hydraulic fluid, since by blending a specific polyoxyethylene fatty acid ester into its components, excellent in rolling lubricity, can suppress the pitching occurrence of rolling bearings, the rolling bearing life Can be extended. In addition, even if divalent metal (zinc, lead, calcium, etc.) ions are mixed, sludge is not generated and there is no blockage of the filter. Furthermore, the water-glycol-based hydraulic fluid of the present invention does not impair any of the inherent properties (flammability, low-temperature fluidity, metal compatibility, etc.) of the water-glycol-based hydraulic fluid. As a result, there are secondary effects such as no need to change the specifications of the hydraulic equipment, capital investment, and the like, and because the high pressure can be used, the apparatus can be made compact. Therefore, the water-glycol hydraulic fluid of the present invention is extremely useful in practical use.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI C10N 30:00 C10N 40:02 40:02 40:08 40:08 (56) References JP-A-4-18492 (JP, A JP-A-4-136097 (JP, A) JP-A-57-105491 (JP, A) JP-A-57-105492 (JP, A) JP-A-59-38295 (JP, A) 105653 (JP, A) JP-B-51-44275 (JP, B2) JP-B-48-39205 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C10M 173/02 C10M 105 / 14 C10M 105/18 C10M 105/40 C10M 107/34 C10M 129/08 C10M 129/16 C10M 129/76 C10M 145/26-145/38 C10N 30:00 C10N 40:02 C10N 40:08

Claims (2)

(57) [Claims] 1. A lower following general formula (1) water, characterized in that it contains 0.05 to 5% by weight of polyoxyethylene fatty acid ester represented by - glycol based hydraulic fluid. General formula (1): embedded image RCOO (CH ₂ CH ₂ O) _n H (wherein, R represents an aliphatic hydrocarbon group having 12 to 18 carbon atoms, and n represents an integer of 4 to 9) . ) 2. The base oil of a water-glycol hydraulic oil is glyco-based.
25-50% by weight, thickener 10-20% by weight, and
2. The water-jet according to claim 1, comprising 35 to 50% by weight of water.
Recall hydraulic fluid.