JP5503066B2 - Hydraulic fluid composition - Google Patents

Description

  The present invention relates to a hydraulic fluid composition, and more particularly to a hydraulic fluid composition that is excellent in oxidation stability and lubrication performance under high pressure and can be used for a long period of time.

The hydraulic fluid is a power transmission fluid used for operations such as power transmission, force control, and buffering in hydraulic systems such as hydraulic equipment and devices, and also functions to lubricate sliding portions.
By the way, recent hydraulic equipment has been reduced in size and increased in output, and accordingly, the operating pressure has become higher (for example, what was conventionally 14 to 20 MPa is now 30 MPa or more). Oil tanks are becoming smaller. For this reason, the heat load received by the hydraulic oil has become more severe than ever, and problems such as premature deterioration, sludge generation, odor, chattering of the cylinder, malfunction, etc. have become problems.
Conventionally, zinc alkyldithiophosphate (ZnDTP) having both antioxidant ability and lubricating ability has been used for hydraulic fluid. However, in such hydraulic hydraulic fluid, the ZnDTP is thermally decomposed at a locally high temperature portion generated by the compression heat of the bubbles as the pressure is increased, resulting in the generation of sludge, malfunction due to this sludge, or a strange odor, etc. There was a problem of causing.

  Therefore, in order to solve such problems, the combined use of ZnDTP and a metal-based detergent has been studied, but it is not sufficient in terms of life, and there is also a problem of cylinder chatter during operation due to high pressure. It was unsolved.

  An object of the present invention is to provide a hydraulic fluid composition that can be used for a long period of time, in which early degradation of hydraulic fluid and sludge generation due to high pressure are effectively prevented under such circumstances. It is.

The inventors of the present invention have made extensive studies to develop a hydraulic fluid composition having the above-mentioned preferable properties. As a result, amine-based antioxidants, phenol-based antioxidants, and phosphate esters are added to base oils with specific properties at the specified ratios, respectively, and oxidation stability and lubrication performance under high pressure. Has been found to improve and achieve its purpose. The present invention has been completed based on such findings.
That is, the present invention relates to the following (1) to (10).
(1) Based on the total amount of the composition with respect to polyolefin having a kinematic viscosity at 40 ° C. of 10 to 100 mm ² / sec, (A) 0.01 to 5% by weight of amine-based antioxidant, (B) phenol-based antioxidant A hydraulic fluid composition comprising 0.01 to 5% by weight of an agent and (C) 0.01 to 5% by weight of a phosphate ester.
(2) The hydraulic fluid composition according to (1), wherein the polyolefin is an α-olefin homopolymer.
(3) The content ratio ((A) :( B) (weight ratio)) of (A) amine-based antioxidant and (B) phenol-based antioxidant is 1: 9 to 1: 1. The hydraulic fluid composition according to (1) or (2).
(4) The hydraulic fluid composition according to any one of the above (1) to (3), which does not contain zinc alkyldithiophosphate (ZnDTP).
(5) The (C) component phosphate ester is an aliphatic phosphate ester having an alkyl or alkenyl group having 3 to 30 carbon atoms, or an amine salt thereof, and an aromatic group having an aryl group having 6 to 30 carbon atoms. The hydraulic fluid composition according to any one of the above (1) to (4), which is one or more selected from group phosphate esters.
(6) The hydraulic fluid composition according to any one of (1) to (5), wherein the polyolefin has a viscosity index of 100 or more.
(7) The hydraulic fluid composition according to any one of (1) to (6), wherein the amine-based antioxidant as the component (A) is an alkylated diphenylamine having an alkyl group having 3 to 20 carbon atoms. .
(8) The hydraulic fluid composition according to any one of (1) to (7), wherein the phenolic antioxidant as the component (B) is a monocyclic phenol.
(9) The hydraulic fluid composition according to any one of (1) to (8), wherein the phosphate ester of component (C) is an aromatic phosphate ester.
(10) The hydraulic fluid composition according to any one of (1) to (9), which is used for a hydraulic device having an operating pressure of 30 MPa or more.

Further, as related inventions of the present invention, the following (1A) to (7A) are mentioned.
(1A)% CA 5 or less base oil, based on the total amount of the composition, (A) amine antioxidant 0.01-5 wt%, (B) phenolic antioxidant 0.01-5 wt% And (C) a hydraulic fluid composition comprising 0.01 to 5% by weight of a phosphate ester.
(2A) The phosphate ester of component (C) is an aliphatic phosphate ester having an alkyl group or alkenyl group having 3 to 30 carbon atoms, or an amine salt thereof, and an aromatic group having an aryl group having 6 to 30 carbon atoms. The hydraulic fluid composition according to the above (1A), which is one or more selected from group phosphate esters.
(3A) The hydraulic fluid composition according to the above (1A) or (2A), wherein the base oil has a kinematic viscosity at 40 ° C. of ^{2 to} 500 mm ² / sec and a viscosity index of 100 or more.
(4A) The hydraulic fluid composition according to any one of (1A) to (3A), wherein the amine-based antioxidant as the component (A) is an alkylated diphenylamine having an alkyl group having 3 to 20 carbon atoms.
(5A) The hydraulic fluid composition according to the above (1A) to (4A), wherein the phenolic antioxidant as the component (B) is a monocyclic phenol.
(6A) The hydraulic fluid composition according to the above (1A) to (5A), wherein the phosphate ester of component (C) is an aromatic phosphate ester.
(7A) The hydraulic fluid composition according to the above (1A) to (6A), which is used for hydraulic equipment having an operating pressure of 30 MPa or more.

Since the hydraulic fluid composition of the present invention is excellent in oxidation stability and lubrication performance under high pressure, it can be used over a long period of time, effectively preventing early deterioration of hydraulic fluid and sludge generation accompanying high pressure. it can.
Therefore, the hydraulic fluid composition of the present invention is suitably used as a hydraulic fluid for, for example, hydraulic devices for construction machinery and general industrial machinery, or hydraulic equipment such as sluices and hydraulic power generators.

In the composition of the present invention, a base oil having% CA of 5 or less is used. When this% CA is more than 5, the oxidation stability, particularly the stability against instantaneous local high temperature heat history is poor. In view of such oxidation stability, those having a% CA of 3 or less are particularly preferred. In addition, this% CA is a value measured by the ndM ring analysis method.
The base oil is preferably in the range of kinematic viscosity at 40 ° C. of ^{2 to} 500 mm ² / sec. If the kinematic viscosity is less than 2 mm ² / sec, the lubrication performance is inferior, abnormal wear or seizure may occur, and the risk of fire is high. On the other hand, if it exceeds 500 mm ² / sec, the viscous resistance at a low temperature increases, which makes it difficult to suck into the pump and may cause malfunction of the machine. From the viewpoints of lubrication performance, fire hazard and viscous resistance at low temperatures, a more preferable kinematic viscosity is in the range of 10 to 100 mm ² / sec.
In the composition of the present invention, it is particularly preferable from the viewpoint of the performance of the hydraulic oil composition to use a base oil having a kinematic viscosity at% CA and 40 ° C. that satisfies the above conditions and having a viscosity index of 100 or more. If the viscosity index is less than 100, the viscosity becomes low at high temperature and the lubricating performance is lowered, while the viscosity becomes high at low temperature, resulting in poor suction of the pump. When the viscosity index is 100 or more, there is little change in viscosity due to temperature, and the usable temperature range from low temperature to high temperature is widened. This effect is noticeable with a base oil having a viscosity index of 110 or more. When a polymer is blended with a normal base oil to increase the viscosity index, the polymer is cut during use and the viscosity index decreases, but such a phenomenon is not observed in the base oil.
As such base oils, for example, atmospheric distillation residue and residual oil obtained in the desulfurization process of fuel oil are used as raw materials, subjected to vacuum distillation, solvent removal and dewaxing treatment, and further hydrofinishing and hydrogenation modification. Paraffinic base oil or paraffinic high viscosity index base oil obtained by solvent extraction, sulfuric acid treatment, clay treatment, etc., and paraffinic high viscosity index base oil obtained by hydrocracking slack wax. And so on.
In the composition of the present invention, a synthetic oil-based base oil can be used in addition to the mineral oil-based base oil. Examples of the synthetic oil include polybutene, polyolefin [α-olefin homopolymer and copolymer (eg, ethylene-α-olefin copolymer)], and various esters (eg, polyol ester, dibasic acid ester, etc.). ), Various ethers, polyglycols and the like. Of these, polyolefin and polyol ester are particularly preferable.
These base oils may be used alone or in combination of two or more.

  There is no restriction | limiting in particular about the amine antioxidant of (A) component in the composition of this invention, A conventionally well-known thing can be used. Examples of the amine-based antioxidant include diphenylamine-based compounds, specifically diphenylamine, monooctyldiphenylamine; monononyldiphenylamine; 4,4′-dibutyldiphenylamine; 4,4′-dihexyldiphenylamine; 4,4 ′. -Dioctyldiphenylamine; 4,4'-dinonyldiphenylamine; tetrabutyldiphenylamine; tetrahexyldiphenylamine; tetraoctyldiphenylamine; , Specifically α-naphthylamine; phenyl-α-naphthylamine, further butylphenyl-α-naphthylamine; hexylphenyl-α-naphthylamine; Butylphenyl -α- naphthylamine; and alkyl-substituted phenyl -α- naphthylamine having 3 to 20 carbon atoms such as nonylphenyl -α- naphthylamine.

Among these, the diphenylamine system is more effective than the naphthylamine system for the instantaneous high-temperature heat history, and is particularly an alkylated diphenylamine having an alkyl group having 3 to 20 carbon atoms, particularly 4,4′-di (C3-3). C20 alkyl) diphenylamine is preferred.
These amine antioxidants may be used alone or in combination of two or more. The blending amount is selected in the range of 0.01 to 5% by weight based on the total amount of the composition. If this amount is less than 0.01% by weight, the effect of blending the antioxidant may not be sufficiently exerted. On the other hand, if it exceeds 5% by weight, the improvement of the effect is not recognized for the amount, but rather low temperature. Sometimes this precipitates and is also economically disadvantageous. From the viewpoints of the effect as an antioxidant, the suppression of precipitation at low temperatures, and the economy, the preferred blending amount of this amine-based antioxidant is in the range of 0.1 to 2% by weight based on the total amount of the composition. .

There is no restriction | limiting in particular about the phenolic antioxidant of (B) component in the composition of this invention, A conventionally well-known thing can be used. Examples of the phenolic antioxidant include 2,6-di-tert-butyl-4-methylphenol; 2,6-di-tert-butyl-4-ethylphenol; 2,4,6-tri-tert- 2,6-di-tert-butyl-4-hydroxymethylphenol; 2,6-di-tert-butylphenol; 2,4-dimethyl-6-tert-butylphenol; 2,6-di-tert-butyl- 4- (N, N-dimethylaminomethyl) phenol; 2,6-di-tert-amyl-4-methylphenol; n-octadecyl-3- (4′-hydroxy-3 ′, 5′-di-tert- Monocyclic phenols such as butylphenyl) propionate, 4,4′-methylenebis (2,6-di-tert-butylphenol); Sopropylidenebis (2,6-di-tert-butylphenol); 2,2′-methylenebis (4-methyl-6-tert-butylphenol); 4,4′-bis (2,6-di-tert-butylphenol) 4,4′-bis (2-methyl-6-tert-butylphenol); 2,2′-methylenebis (4-ethyl-6-tert-butylphenol); 4,4′-butylidenebis (3-methyl-6) -Tert-butylphenol); 2,2'-thiobis (4-methyl-6-tert-butylphenol); polycyclic phenols such as 4,4'-thiobis (3-methyl-6-tert-butylphenol) It is done.
Among these, monocyclic phenols are preferable because they are highly effective against instantaneous high-temperature heat history under high pressure.

These phenolic antioxidants may be used alone or in combination of two or more. The blending amount is selected in the range of 0.01 to 5% by weight based on the total amount of the composition. If this amount is less than 0.01% by weight, the effect of blending the antioxidant may not be sufficiently exerted. On the other hand, if it exceeds 5% by weight, the improvement of the effect is not recognized for the amount, but rather low temperature. Sometimes this precipitates and is also economically disadvantageous. From the viewpoints of the effect as an antioxidant, the suppression of precipitation at low temperatures, and the economy, the preferred blending amount of this phenolic antioxidant is in the range of 0.1 to 2% by weight based on the total amount of the composition. .
In the present invention, it is necessary to use the amine-based antioxidant and the phenol-based antioxidant in combination, whereby the instantaneous high-temperature thermal stability under high pressure is dramatically improved. The use ratio of the amine-based antioxidant and the phenol-based antioxidant is preferably selected as appropriate within a weight ratio of 1: 9 to 9: 1.
In the composition of this invention, phosphate ester is used as (C) component. This phosphate ester is for improving the lubrication performance, and there is no particular limitation on the type thereof, and a known one that has been conventionally used as an extreme pressure agent or the like can be used. Examples of such an alkyl group or alkenyl group having 3 to 30 carbon atoms such as triisopropyl phosphate, tributyl phosphate, trihexyl phosphate, tri-2-ethylhexyl phosphate, trilauryl phosphate, tristearyl phosphate, trioleyl phosphate. An aliphatic phosphate ester having an aryl group, or an amine salt thereof, and further an aromatic phosphate ester having an aryl group having 6 to 30 carbon atoms such as triphenyl phosphate, tricresyl phosphate, and trixylenyl phosphate. .

Of these, aromatic phosphates are particularly preferred from the standpoint of excellent high-temperature thermal stability and anti-wear effects.
This phosphate ester may be used independently and may be used in combination of 2 or more type. The blending amount is selected in the range of 0.01 to 5% by weight based on the total amount of the composition. If this amount is less than 0.01% by weight, there is a risk that the effect of preventing seizure or wear will not be sufficiently exhibited. Disadvantageous. From the standpoints of seizure prevention, wear prevention effect and economic efficiency, the preferable blending amount of the phosphate ester is in the range of 0.1 to 2% by weight based on the total amount of the composition.
In the composition of the present invention, a fatty acid amide and / or a polyhydric alcohol ester may be further used as the component (D) as necessary. This component (D) mainly has an action to prevent the chatter phenomenon of the cylinder. Examples of fatty acid amides include isostearic acid triethylenetetramide, isostearic acid tetraethylenepentamide, oleic acid diethylenetriamide, and oleic acid diethanolamide. And a reaction product of a saturated or unsaturated fatty acid having 1 to 24 carbon atoms with an aliphatic amine, aromatic amine, polyalkylene polyamine, and the like. On the other hand, as polyhydric alcohol ester, for example, trimethylolpropane monooleate, trimethylolpropane dioleate, pentaerythritol monooleate, pentaerythritol tetraoleate, oleic acid monoglyceride, sorbitan monooleate, sorbitan sesquioleate, etc. And complete or partial esters of polyhydric alcohols such as neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol, sorbitan, sorbitol, glycerin and saturated or unsaturated fatty acids having 1 to 24 carbon atoms. .

In the composition of the present invention, as the component (D), the above fatty acid amide may be used alone or in combination of two or more, or a polyhydric alcohol ester may be used alone. Two or more kinds may be used in combination. Furthermore, one or more fatty acid amides and one or more polyhydric alcohol esters may be used in combination.
The blending amount of the component (D) is selected in the range of 0.001 to 5% by weight based on the total amount of the composition. If this amount is less than 0.001% by weight, the effect of preventing the chatter phenomenon of the cylinder may not be sufficiently exerted. On the other hand, if it exceeds 5% by weight, the improvement of the effect is not recognized for the amount, but rather oxidation stability. Will also be economically disadvantageous. From the viewpoints of the cylinder chattering prevention effect, oxidation stability, economic efficiency, and the like, the preferred amount of component (D) is in the range of 0.01 to 2% by weight based on the total amount of the composition. As the component (D), a combination of a fatty acid amide and a polyhydric alcohol ester is preferable from the viewpoint of preventing the chatter phenomenon of the cylinder. At this time, the ratio of the fatty acid amide to the polyhydric alcohol ester is suitably selected within a polymerization ratio range of 5:95 to 95: 5.

The hydraulic fluid composition of the present invention for the purpose is not impaired scope of the present invention, other additives as necessary, for example, polymethacryloylacetones relay bets of which viscosity index improvers, polymethacrylates and, chlorinated paraffin Pour point depressants such as condensates of phthalates and naphthalene, oily agents such as various fatty acids, alcohols and esters, alkali metal or alkaline earth metal sulfonates, phenates, phosphonates, salicylates and other metal detergents, succinic acid Ashless dispersants such as imides, boron-containing succinimides, benzylamines, and boron-containing benzylamines, extreme pressure agents such as sulfurized fats and oils, polysulfides, alkyl phosphate ester amine salts, chlorinated paraffins, alkenyl succinics Rust inhibitors such as acid esters and sulfonates, benzotriazole derivatives and thiadiazo Metal deactivators such as Le derivatives, silicone oils, polyacrylates, can be appropriately compounded defoaming agent such as an organic fluorine compound.
The amount of each additive is usually 0.01 to 5% by weight, preferably 0.01 to 2% by weight, based on the total amount of the composition.
The hydraulic fluid composition of the present invention is excellent in oxidation stability and lubrication performance under high pressure, and is particularly suitably used for hydraulic equipment having an operating pressure of 30 MPa or more. And it can be used for a long period of time by effectively preventing early deterioration of hydraulic oil and sludge generation accompanying high pressure.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.

Examples 1-5 and Comparative Examples 1-4
As the base oil, base oils I to III having the following properties were used.
Base oil I: hydrogenated modified oil; kinematic viscosity at 40 ° C. 46 mm ² / sec, viscosity index 120,% CA 0.1
Base oil II: hydrogenated finishing oil; kinematic viscosity at 40 ° C. 46 mm ² / sec, viscosity index 105,% C A 2.5
Base oil III: solvent refined oil; kinematic viscosity at 40 ° C. 46 mm ² / sec, viscosity index 98,% CA 7.0
(% CA: by ndM ring analysis method)
A hydraulic fluid having the composition shown in Table 1 was prepared and its performance was evaluated according to the following method. The results are shown in Table 1.

<Performance evaluation>
(1) High-pressure thermal stability test In a hydraulic circuit using a high-pressure pump, air is blown into the tank, and the oil containing bubbles is instantly pressurized to 35 MPa, giving a thermal history locally by the compression heat of the bubbles. It was. The thermal stability of the hydraulic oil at high pressure was evaluated by measuring the amount of sludge (millipore value) generated in the oil after 720 hours.
(2) Wear test of pump Using a vane pump (V-104C, manufactured by Vickers), the wear amount of the vane and the cam ring after 250 hours was measured.

〔note〕
Amine-based antioxidant: 4,4′-dioctyldiphenylamine Phenol-based antioxidant: 2,6-di-tert-butyl-4-methylphenol Phosphate ester: tricresyl phosphate Fatty acid amide: Triethylenetetramide isostearate Monohydric alcohol ester: Sorbitan monooleate Other: Rust preventive agent, metal deactivator, viscosity index improver, ashless dispersant, etc.

From Table 1, it can be seen that: That is, Examples 1-5 are excellent in high-pressure thermal stability (low sludge amount) and have good wear resistance as compared with Comparative Examples 1, 2, and 3. In Comparative Example 4, the wear resistance of the pump is poor.
Example 5 uses% CA 2.5 base oil, but the high pressure thermal stability is relatively good. On the other hand, Comparative Example 1 using a base oil of% CA 7.0 is extremely inferior in high-pressure thermal stability.

Comparative Example 5
The performance of the commercially available ZnDTP-based wear resistant hydraulic oil was evaluated in the same manner as described above. As a result, the amount of sludge in the high-pressure thermal stability test was 300 mg / 100 ml, and the amount of wear in the pump wear test was 5 mg. That is, it can be seen that this hydraulic oil has a particularly large amount of sludge due to the thermal decomposition of ZnDTP in the high-pressure thermal stability test.

Claims (8)

Based on the total amount of the composition, (A) 0.01 to 5% by weight of an amine-based antioxidant and (B) a phenol-based antioxidant of 0.1% by weight based on the total amount of the polyolefin having a kinematic viscosity at 40 ° C. of 10 to 100 mm ² / sec. Hydraulic pressure with an operating pressure of 30 MPa or more selected from construction machines, general industrial machines, sluices, and hydroelectric generators, comprising 01-5 wt% and (C) 0.01-5 wt% phosphate ester. A hydraulic fluid composition used in equipment,
(A) content of the amine antioxidant and (B) a phenolic antioxidant ((A) :( B) (weight ratio)) is from 1: 9 to 1: Ri 1 der, (B) The hydraulic fluid composition, wherein the component phenolic antioxidant is a monocyclic phenol and does not contain zinc alkyldithiophosphate (ZnDTP) . The hydraulic fluid composition according to claim 1, wherein the polyolefin is an α-olefin homopolymer. The hydraulic fluid composition according to claim 1 or 2, wherein a blending amount of the ashless dispersant based on the total amount of the hydraulic fluid composition is 2% by weight or less. The hydraulic fluid composition according to any one of claims 1 to 3 , wherein a blending amount of the viscosity index improver based on the total amount of the hydraulic fluid composition is 5% by weight or less. (C) An aliphatic phosphoric acid ester in which the phosphoric acid ester of the component has an alkyl group or an alkenyl group having 3 to 30 carbon atoms, or an amine salt thereof, and an aryl group having 6 to 30 carbon atoms The hydraulic fluid composition according to any one of claims 1 to 4 , which is one or more selected from esters. The viscosity index of the polyolefin is 100 or more, the hydraulic fluid composition according to any one of claims 1-5. The hydraulic fluid composition according to any one of claims 1 to 6 , wherein the amine-based antioxidant as the component (A) is an alkylated diphenylamine having an alkyl group having 3 to 20 carbon atoms. The hydraulic fluid composition according to any one of claims 1 to 7 , wherein the phosphate ester of component (C) is an aromatic phosphate ester.