JP6578902B2 - Hydraulic fluid composition - Google Patents

Description

  The present invention relates to a hydraulic fluid composition used as a power transmission medium in hydraulic equipment. More specifically, the present invention relates to a hydraulic fluid composition that is excellent in biodegradability and excellent in flame retardancy, abrasion resistance, oxidation stability, thermal stability, rust resistance, and demulsibility.

  In recent years, new efforts for environmental protection have become an important mission worldwide. Lubricating oil is no exception, and there is an increasing demand for lubricating oil that can reduce environmental impact. Under such circumstances, biodegradable lubricants that are easy to be decomposed in nature even when leaked and have little impact on the ecosystem are attracting attention as lubricants that can reduce environmental impact.

  Many biodegradable lubricants are used as hydraulic fluids as countermeasures against leakage into rivers, oceans, and soils, such as sluice switchgears such as dams and weirs, and pile pressers used around water. It is often used in hydraulic equipment such as excavators, pile pullers and construction machines. When used as a hydraulic oil in these applications, it is required that the general requirements for the hydraulic oil, such as oxidation stability, abrasion resistance, rust resistance, and demulsibility, be good.

  As the base oil of the above-described biodegradable hydraulic fluid, ester compounds are mainly used. Conventionally used base oils include, for example, fats and oils (triglycerides) described in Patent Document 1, diesters described in Patent Document 2, and those described in Patent Document 3. Examples include complete esters of neopentyl polyol, but from the viewpoints of performance, quality, and price, complete esters of neopentyl polyol and unsaturated fatty acids are mainly used at present.

  However, the above-mentioned complete ester of neopentyl polyol and unsaturated fatty acid has a double bond in the molecule, so that it is easily oxidized and has a drawback of low oxidation stability. In order to solve this problem, for example, Patent Document 4 describes that a thiobisphenol type antioxidant and an amine type antioxidant are used in combination, and Patent Document 5 describes alkylated phenol-α-naphthylamine dehydration condensation. In combination with 2,6-di-tert-butyl-p-cresol (BHT), but none of them has achieved sufficient oxidative stability.

  Further, as disclosed in Patent Document 6 and Patent Document 7, quinoline-based antioxidants have been used for lubricating oil for a long time. However, since the quinoline-based antioxidant has low heat resistance, there is a problem that precipitates are likely to be generated when the lubricating oil containing the quinoline-based antioxidant is heated to a high temperature for a long time.

On the other hand, hydraulic fluids are used in various applications, and may be used in applications where the hydraulic pressure is very high, such as construction machinery. When used under such severe pressure conditions, phosphorus-based or sulfur-based extreme pressure agents are often used for hydraulic fluids in order to prevent seizure, wear, and the like.
However, in the above-mentioned complete ester of neopentyl polyol and unsaturated fatty acid, when a quinoline antioxidant and a phosphorus-based or sulfur-based extreme pressure agent are used in combination, precipitates at higher temperatures are more likely to occur. There was a problem.

JP-A-6-240283 Japanese Patent Laid-Open No. 9-249889 JP-A-53-136170 JP 59-230094 JP-A-8-157853 JP 58-037092 A JP-A-5-078325

  The object of the present invention is to solve the above-mentioned problems. Specifically, it is excellent in biodegradability, and also excellent in flame retardancy, wear resistance, oxidation stability, thermal stability, rust resistance, and demulsibility. It is to provide a hydraulic fluid composition.

  As a result of intensive studies to solve the above problems, the present inventors have found that a specific ester compound, a quinoline derivative or a polymer thereof synthesized from neopentyl polyol and a linear unsaturated fatty acid, and a specific dithioline Hydraulic fluid composition containing acid ester derivatives has good biodegradability, flame retardancy, excellent wear resistance, high oxidation stability, excellent thermal stability, good rust resistance, excellent It has been found that it has demulsibility.

（Ｒ_１及びＲ_２はそれぞれ独立して炭素数１〜５のアルキル基、Ｒ_３は水素原子又は炭素数１〜５のアルキル基、Ａは炭素数１〜５のアルキレン基を表す。） That is, this invention contains the following ester compound (A), the following quinoline derivative or its polymer (B), and the following dithiophosphoric acid ester derivative (C), and with respect to 100 mass parts of ester compounds (A). , A hydraulic fluid composition containing 0.5 to 1.5 parts by mass of a quinoline derivative or a polymer thereof (B) and 0.1 to 0.5 parts by mass of a dithiophosphate derivative (C).
(A) It is an ester compound of 5 to 10 carbon atoms, an alcohol valence of 3 to 6 neopentyl polyol, and a linear unsaturated fatty acid of 16 to 22 carbon atoms, and in the ester compound, The monoester (a1) is contained in an amount of 0.1 to 5% by mass, the diester (a2) is contained in an amount of 10 to 30% by mass, and the trivalent or higher ester (a3) is contained in an amount of 65 to 89.9%. Ester compound whose mass ratio of diester (a2) is 1/99 to 20/80 (B) 2,2,4-trimethyl-1,2-dihydroquinoline or a polymer thereof, 6-methoxy-2,2,4 -One or more quinoline derivatives selected from the group consisting of trimethyl-1,2-dihydroquinoline or polymers thereof and 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline or polymers thereof Or a polymer thereof (C) Dithiophosphate derivative represented by the following formula

(R ₁ and R ₂ each independently represents an alkyl group having 1 to 5 carbon atoms, R ₃ represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and A represents an alkylene group having 1 to 5 carbon atoms.)

  The hydraulic fluid composition of the present invention is excellent in biodegradability and is excellent in flame retardancy, wear resistance, oxidation stability, thermal stability, rust resistance, and demulsibility.

  Hereinafter, the hydraulic fluid composition of the present invention will be described. In addition, the numerical value range prescribed | regulated using the symbol "~" in this specification shall contain the numerical value of the both ends (upper limit and lower limit) of "~". For example, “2 to 5” represents 2 or more and 5 or less.

  The hydraulic fluid composition of the present invention contains the following ester compound (A), the following quinoline derivative or polymer thereof (B), and the following dithiophosphate derivative (C).

[Ester compound (A)]
The ester compound (A) is an ester compound of a neopentyl polyol having 5 to 10 carbon atoms and a valence of 3 to 6 alcohols and a linear unsaturated fatty acid having 16 to 22 carbon atoms.
Neopentyl polyol is an alcohol having a neopentyl skeleton having no hydrogen atom at the carbon at the β-position relative to the hydroxyl group. The neopentyl polyol in the present invention is a neopentyl polyol having 5 to 10 carbon atoms and 3 to 6 valences of alcohol. Examples of the trivalent neopentyl polyol include trimethylol ethane and trimethylol propane. Examples of the tetravalent neopentyl polyol include pentaerythritol. Examples of the hexavalent neopentyl polyol include For example, dipentaerythritol and the like can be mentioned. One of these neopentyl polyols can be used alone, or two or more can be used in combination.
Of the neopentyl polyols, trivalent or tetravalent neopentyl polyols can be preferably used, and trivalent trimethylolpropane and tetravalent pentaerythritol can be particularly preferably used.
In addition, when two or more of the above neopentyl polyols are used in combination as an alcohol for forming the ester compound (A), it is preferable to use trivalent trimethylolpropane and tetravalent pentaerythritol in combination. By containing the ester compound (A) obtained by using a polyol, it is possible to further improve the lubricity and oxidation stability of the hydraulic fluid composition. In the case of preparing both esters using trimethylolpropane and pentaerythritol in combination, the mass ratio of the ester of trimethylolpropane / the ester of pentaerythritol is preferably 95/5 to 50/50, particularly preferably. 95/5 to 60/40, more preferably 95/5 to 70/30.

The straight chain unsaturated fatty acid having 16 to 22 carbon atoms in the present invention is a monocarboxylic acid having a straight chain hydrocarbon chain and having one or more double bonds in the molecule. It is an acid. For example, palmitoleic acid, oleic acid, elaidic acid, erucic acid, linoleic acid, linolenic acid and the like can be mentioned.
Of the above linear unsaturated fatty acids, oleic acid, linoleic acid, and linolenic acid are preferable, and oleic acid is more preferable. One of these fatty acids can be used alone, or two or more can be used in combination.

  Since the fatty acid is usually commercially available as a fatty acid mixture (the content of the linear unsaturated fatty acid is 60% by mass or more), other fatty acids such as saturated fatty acids and branched fatty acids can be used as long as the effects are not impaired. Fatty acids may be included. The content of the linear unsaturated fatty acid in the fatty acid mixture containing other fatty acids is preferably 60% by mass or more, particularly preferably 65% by mass or more, and further preferably 70% by mass or more.

  The ester compound (A) can be produced by a known method such as a method of directly reacting a neopentyl polyol and a linear unsaturated fatty acid or a method of synthesis by transesterification. Moreover, after esterification, you may use removal methods, such as a water-washing process after pressure reduction distillation and alkali neutralization, for the purpose of removing unreacted linear unsaturated fatty acid etc. as needed.

The ester compound (A) obtained by esterifying the above-mentioned neopentyl polyol and linear unsaturated fatty acid contains a monoester (a1), a diester (a2), and a trivalent or higher valent ester (a3). .
Here, monoester (a1) means that one of the hydroxyl groups in neopentyl polyol is esterified with a linear unsaturated fatty acid. The diester (a2) means that two of the hydroxyl groups in the neopentyl polyol are esterified with a linear unsaturated fatty acid. The trivalent or higher valent ester (a3) means that three or more hydroxyl groups of neopentyl polyol are esterified with a linear unsaturated fatty acid.

  Content of monoester (a1) in ester compound (A) is 0.1-5 mass%, Preferably it is 0.15-4 mass%, Most preferably, it is 0.2-2 mass%. When there is too little content of monoester (a1), rust prevention performance may be inferior. On the other hand, when there is too much content of monoester (a1), demulsification performance may deteriorate remarkably.

  Content of diester (a2) in ester compound (A) is 10-30 mass%, Preferably it is 11-25 mass%, Most preferably, it is 12-20 mass%. When the content of the diester (a2) is too small, the thermal stability of the hydraulic fluid composition of the present invention may be significantly reduced. On the other hand, when there is too much content of diester (a2), in addition to demulsibility and oxidation stability falling, lubricity may also fall.

  The content of the trivalent or higher valent ester (a3) in the ester compound (A) is 65 to 89.9% by mass, preferably 67 to 89% by mass, and particularly preferably 70 to 88% by mass. When there is too little content of trivalent or more ester (a3), demulsibility and oxidation stability may fall. On the other hand, when the content of the trivalent or higher valent ester (a3) is too large, the thermal stability of the hydraulic fluid composition of the present invention may be significantly reduced.

  The ester compound (A) is a mass ratio of the content of the monoester (a1) to the content of the diester (a2), that is, a mass ratio of the monoester (a1) / diester (a2) (hereinafter referred to as (a1) / (Also referred to as (a2)) is 1/99 to 20/80, preferably 1.5 / 98.5 to 17.5 / 82.5, particularly preferably 2/98 to 15/85. More preferably, it is 3/97 to 10/90. When (a1) / (a2) is too small, rust prevention properties may be deteriorated. On the other hand, if (a1) / (a2) is too large, the demulsibility may be significantly reduced.

When the content and mass ratio of the various esters (a1) to (a3) contained in the ester compound (A) are within the above ranges, a method for controlling the reaction conditions for esterification, and various esters synthesized separately ( The method etc. which mix | blend a1)-(a3) are employable.
When controlling the reaction conditions for esterification so that the mass ratio is the above ratio, for example, adopting a method of adjusting the feed ratio of raw materials, a method of controlling the heating rate and final reaction temperature, a method of using a catalyst, etc. can do.
In the method of blending various esters (a1) to (a3) synthesized separately, monoester (a1), diester (a2), trivalent or higher ester (a3) are separately synthesized in advance, and the above contents are contained. Or an ester compound (A) by blending so as to obtain a mass ratio.

[Quinoline derivative or polymer thereof (B)]
A quinoline derivative or a polymer thereof (B) is 2,2,4-trimethyl-1,2-dihydroquinoline or a polymer thereof, 6-methoxy-2,2,4-trimethyl-1,2-dihydroquinoline or a polymer thereof. A polymer, and 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline or one or more quinoline derivatives or a polymer thereof selected from the group consisting of polymers thereof.
The quinoline derivative or the polymer (B) thereof is generally used as a quinoline antioxidant, and for example, those commercially available as an antioxidant for lubricating oil or an antioxidant for rubber can be used. For example, 2,2,4-trimethyl-1,2-dihydroquinoline or a polymer thereof (TMDQ) includes R.I. T. T. et al. Vanlube manufactured by Vandervirt
RD, Nouchi 224 manufactured by Ouchi Shinsei Chemical Co., Ltd., Antage RD manufactured by Kawaguchi Chemical Industry Co., Ltd., Nonflex RD manufactured by Seiko Chemical Co., Ltd., Nonflex QS, and the like.
Examples of 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline or a polymer thereof include Nocrack AW, Nocrack AW-N manufactured by Ouchi Shinsei Chemical Co., Ltd. Non-flex AW, non-flex AW-S, etc. manufactured by Kagaku Co., Ltd. may be mentioned.
In the present invention, it is preferable to use 2,2,4-trimethyl-1,2-dihydroquinoline or a polymer thereof (TMDQ) from the viewpoint that excellent oxidation stability can be imparted to the ester compound (A). .

  The content of the quinoline derivative or the polymer (B) thereof in the hydraulic fluid composition of the present invention is 0.5 to 1.5 parts by mass, preferably 0.6 with respect to 100 parts by mass of the ester compound (A). It is -1.4 mass part, Most preferably, it is 0.7-1.3 mass part. When there is too little content of a quinoline derivative or its polymer (B), it may become difficult to obtain sufficient oxidation stability. On the other hand, when the content of the quinoline derivative or its polymer (B) is too large, not only the antioxidant ability commensurate with the content may not be obtained, but also when exposed to extreme pressure agents, it is exposed to high temperatures. If this occurs, sludge and precipitates may be generated, and the thermal stability may be significantly reduced.

[Dithiophosphate derivative (C)]
The dithiophosphate derivative (C) is a dithiophosphate derivative represented by the following formula.

R ₁ and R ₂ each independently represents an alkyl group having 1 to 5 carbon atoms. The alkyl group may be linear or branched. R ₁ and R ₂ are preferably a propyl group, an isopropyl group, a butyl group, an isobutyl group, and a t-butyl group, and particularly preferably an isopropyl group or an isobutyl group. R ₁ and R ₂ are preferably the same alkyl group.
R ₃ represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. The alkyl group may be linear or branched. R ₃ is preferably a hydrogen atom, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, or t-butyl group, and particularly preferably a hydrogen atom, methyl group, ethyl group, propyl group, isopropyl group. More preferably a hydrogen atom, a methyl group or an ethyl group.
A represents an alkylene group having 1 to 5 carbon atoms, and includes a linear or branched alkylene group. Examples of A include a methylene group, an ethylene group, a propylene group, a trimethylene group, an isopropylidene group, a tetramethylene group, and a pentamethylene group, and preferably a methylene group, an ethylene group, a propylene group, a trimethylene group, and an isopropylidene group. Particularly preferred are a methylene group, an ethylene group, a propylene group, and a trimethylene group.

As the dithiophosphate derivative (C), commercially available products can be used as extreme pressure agents for lubricants, antiwear agents, and the like. For example, examples of the compound in which R ₁ and R ₂ in the above formula are an isobutyl group, R ₃ is a hydrogen atom, and A is a propylene group include IRGALUBE 353 manufactured by BASF, HiTEC 511, HiTEC 511T manufactured by AFTON, and the like. Examples of the compound in which R ₁ and R ₂ in the above formula are isopropyl groups, R ₃ is an ethyl group, and A is an ethylene group include IRGALUBE 63 manufactured by BASF.

  The content of the dithiophosphate ester derivative (C) in the hydraulic fluid composition of the present invention is 0.1 to 0.5 parts by mass, preferably 0.12 to 0 parts per 100 parts by mass of the ester compound (A). .45 parts by mass, particularly preferably 0.15 to 0.40 parts by mass. When the content of the dithiophosphate derivative (C) is too small, sufficient extreme pressure performance and wear resistance performance may not be obtained. On the other hand, when the content of the dithiophosphate ester derivative (C) is too large, not only extreme pressure performance and wear resistance performance corresponding to the content may not be obtained, but sludge and precipitates may be formed when exposed to high temperatures. May occur and thermal stability may be significantly degraded.

  In addition to the ester compound (A), the quinoline derivative or polymer thereof (B), and the dithiophosphate derivative (C), the hydraulic fluid composition of the present invention can be used in various ways that are usually used. Additives can be blended. Additives that can be blended include rust inhibitors, antioxidants, metal deactivators, antifoaming agents, extreme pressure / antiwear agents, pour point depressants, viscosity index improvers, thickeners, detergents, Examples include ash dispersants.

Examples of the rust inhibitor (D) that can be blended in the hydraulic fluid composition of the present invention include alkenyl succinic acid or derivatives thereof, amine salts of phosphate esters, imidazoline derivatives such as carboxyimidazoline, and the like. One of these rust inhibitors can be used alone or in combination of two or more. In the present invention, an imidazoline derivative such as an amine salt of a phosphate ester or carboxyimidazoline can be more preferably used because it can impart high rust prevention performance to the ester compound (A). Furthermore, imidazoline derivatives such as carboxyimidazoline can be most preferably used from the viewpoint that high oxidative stability can be maintained.
Content of a rust inhibitor (D) is 0.01-1 mass part with respect to 100 mass parts of ester compounds (A), Preferably it is 0.05-0.5 mass part, Most preferably, it is 0.00. 1 to 0.3 parts by mass.

In the hydraulic fluid composition of the present invention, examples of other antioxidants that can be further blended with the component (B) that functions as an antioxidant include, for example, phenol-based antioxidants, amine-based antioxidants, sulfur And system antioxidants.
Examples of the phenolic antioxidant include dibutylhydroxytoluene (BHT), 2,6-di-t-butylparacresol, 4,4-methylenebis (2,6-di-t-butylphenol), 4,4- Examples thereof include thiobis (2-methyl-6-tert-butylphenol) and 4,4-bis (2,6-di-tert-butylphenol).
Examples of amine antioxidants include phenyl naphthylamine antioxidants such as phenyl-α-naphthylamine, phenyl-β-naphthylamine, alkylphenyl-α-naphthylamine, alkylphenyl-β-naphthylamine, and bis (alkylphenyl) amine. , Phenothiazine, monooctyldiphenylamine, and the like.
Examples of the sulfur-based antioxidant include alkyl disulfides and benzodiazoles.

The quinoline derivative or polymer (B) used in the present invention can impart further excellent antioxidant ability when used in combination with the above-mentioned amine-based antioxidant and phenol-based antioxidant. For example, one or more phenyl naphthylamine antioxidants and phenolic antioxidants selected from the group consisting of phenyl-α-naphthylamine, phenyl-β-naphthylamine, alkylphenyl-α-naphthylamine and alkylphenyl-β-naphthylamine In combination with alkylphenyl-α-naphthylamine and / or alkylphenyl-β-naphthylamine and a phenolic antioxidant are particularly preferred, and alkylphenyl-α-naphthylamine and / or alkylphenyl-β-naphthylamine The combined use with 2,6-di-t-butylparacresol is more preferable.
The preferred blending ratio of the quinoline derivative or its polymer (B), the phenyl naphthylamine-based antioxidant, and the phenol-based antioxidant is 100 parts by mass of the quinoline derivative or its polymer (B). A phenyl naphthylamine antioxidant is 25-100 mass parts, for example, and a phenolic antioxidant is 25-100 mass parts, for example.

  In the hydraulic fluid composition of the present invention, other extreme pressure / antiwear agents that can be further blended together with the component (C) that functions as an extreme pressure / antiwear agent include, for example, sulfurized olefins, sulfurized oils and fats, and sulfides. , Phosphate ester, phosphite ester, thiophosphate ester, phosphate ester amine salt, zinc dialkyldithiophosphate, dialkyl polysulfide and the like.

Moreover, as a metal deactivator which can be mix | blended with the hydraulic fluid composition of this invention, benzotriazole or its derivative (s), an alkenyl succinic acid ester, etc. are mentioned, for example.
Content of a metal deactivator is 0.01-0.1 mass part with respect to 100 mass parts of ester compounds (A), Preferably it is 0.02-0.08 mass part, Most preferably, it is 0. 0.03 to 0.06 parts by mass.

  Examples of the antifoaming agent that can be blended in the hydraulic fluid composition of the present invention include silicone compounds.

  In the hydraulic fluid composition of the present invention, a predetermined amount of each of the quinoline derivative or a polymer thereof (B) and the dithiophosphate ester derivative (C) is blended with the ester compound (A). It can manufacture by mix | blending an additive. The method of blending, mixing, and adding each additive is not particularly limited, and various methods can be employed. The order of blending, mixing, and addition is not particularly limited, and various methods can be employed. For example, a method in which various additives are directly added to the ester compound (A) that is a base oil and heated and mixed, a method in which a high concentration solution of the additive is prepared in advance, and these are mixed with the base oil It may be used.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples.

[Synthesis of ester mixture I]
1200 g (8.94 mol) of trimethylolpropane (TMP), manufactured by NOF Corporation, NAA-34 for industrial use, in a 5 L four-necked flask equipped with a thermometer, a nitrogen inlet tube, a stirrer, and a condenser tube (Unsaturated acid content: 90% by mass) was charged with 2486 g (8.94 mol), and reacted under atmospheric pressure while distilling off the reaction water at 220 ° C. under a nitrogen stream. The acid value was 0.1 mgKOH / g or less. The reaction was continued until After cooling the reaction product, most of the unreacted trimethylolpropane was removed by filtration. Thereafter, about 2500 g of partial ester I was obtained by distillation.
After the obtained partial ester I was silylated (TMS converted) and analyzed by gas chromatography under the following conditions, it was a partial ester mixture containing 98.1% by mass of TMP monoester and 1.9% by mass of TMP diester. It was.

<Gas chromatography analysis conditions>
Column: Packed column OV-1 (0.4 m)
Temperature rising condition: The temperature is raised from 150 ° C. to 350 ° C. at a heating rate of 5 ° C./min and held at 350 ° C. for 10 minutes. Injection temperature: 375 ° C.
Detector temperature: 375 ° C
Helium flow rate: 50 mL / min

(Synthesis of ester mixture II)
In a synthesizer similar to that used in partial ester I, 600 g (4.47 mol) of trimethylolpropane (TMP), manufactured by NOF Corporation, industrial oleic acid NAA-34 (unsaturated acid content: 90% by mass) 3108 g (11.18 mol) was charged and reacted at 220 ° C. under a nitrogen stream while distilling off the water of reaction at normal pressure until the acid value was 0.1 mgKOH / g or less. After completion of the reaction, the low molecular weight component was removed at 300 ° C. and 5 torr to obtain an ester.
As a result of analyzing the obtained ester under the conditions of gas chromatography analysis using partial ester I, it was a mixture of partial ester and complete ester of 41.5% by mass of TMP diester and 58.5% by mass of TMP triester.

(Synthesis of ester mixture III)
In a synthesis apparatus similar to the apparatus used in partial ester I, 400 g (2.98 mol) of trimethylolpropane (TMP), manufactured by NOF Corporation, industrial oleic acid NAA-34 (unsaturated acid content: 90% by mass) 3315 g (11.93 mol) was charged and reacted at 220 ° C. under a nitrogen stream while distilling off the reaction water at normal pressure until the hydroxyl value was 0.1 mgKOH / g or less. After the reaction was completed, potassium hydroxide was added and deacidified water washing was performed for the purpose of removing free fatty acids.
In addition, deoxidation water washing was implemented in several times in order to prevent emulsification, and the same operation was repeatedly performed until the deoxidation waste liquid became neutral. The solution after washing with deoxidized water was depressurized at 95 ° C. and 5 torr to remove water to obtain an ester.
As a result of analyzing the obtained ester under the conditions of gas chromatography analysis using Partial Ester I, it was a mixture of a partial ester and a complete ester of 0.5% by mass of TMP diester and 99.5% by mass of TMP triester. It was.

(Synthesis of ester mixture IV)
550 g (4.04 mol) of pentaerythritol (PE), manufactured by NOF Corporation, industrial oleic acid NAA-34 (unsaturated acid content: 90% by mass) 3369 g (12.12 mol) was charged, and the reaction water was reacted at 220 ° C. under a nitrogen stream while distilling off the reaction water at normal pressure, and the reaction was carried out until the acid value became 0.1 mgKOH / g or less to obtain an ester.
As a result of analyzing the obtained ester under the conditions of gas chromatography analysis using partial ester I, PE monoester 4.8% by mass, PE diester 27.8% by mass, PE triester 36.3% by mass, PE tetraester It was a mixture of partial ester and complete ester of 31.1% by mass of ester (total content other than PE monoester and PE diester: 67.4% by mass).

[Synthesis of ester mixture V]
350 g (2.57 mol) of pentaerythritol (PE), manufactured by NOF Corporation, industrial oleic acid NAA-34 (unsaturated acid content: 90% by mass) 3573 g (12.85 mol) was charged and reacted under a nitrogen stream at 220 ° C. while distilling off the water of reaction at normal pressure until the hydroxyl value was 0.1 mgKOH / g or less. After the reaction was completed, potassium hydroxide was added and deacidified water washing was performed for the purpose of removing free fatty acids. In addition, deoxidation water washing was implemented in several times in order to prevent emulsification, and the same operation was repeated until the deoxidation waste liquid became neutral. The solution after washing with deoxidized water was depressurized at 95 ° C. and 5 torr to remove water to obtain an ester.
As a result of analyzing the obtained ester under the conditions of gas chromatography analysis using partial ester I, PE triester 1.2% by mass, PE tetraester 98.8% by mass (total content other than PE monoester and PE diester) Amount: 100.0%).

[Preparation of ester base oils 1 to 12]
Ester mixtures I to V synthesized above were mixed at the blending ratios shown in Table 1 to prepare ester base oils 1 to 12. Table 1 also shows the monoester, diester, and trivalent or higher ester ratio of the prepared ester base oil.

(Preparation of hydraulic fluid composition)
Predetermined amounts of the following additives were blended with the ester base oils 1 to 12 prepared above to prepare hydraulic fluid compositions shown in Tables 2 to 5.
(B-1) 2,2,4-Trimethyl-1,2-dihydroquinoline polymer (Vanrube RD manufactured by RT Vandervirt)
(B-2) 6-Ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline (Nonflex AW manufactured by Seiko Chemical Co., Ltd.)
(C) Propanoic acid, bis (2-methylpropoxy) phosphinothiolthio-2-methyl (IRGALUBE 353 manufactured by BASF)

(D-1) amine, C11-14-side chain alkyl, monohexyl and dihexyl phosphate (phosphate ester rust inhibitor: IRGALUBE 349 manufactured by BASF)
(D-2) Carboxyimidazoline mixture (Carboxyimidazoline rust inhibitor: HiTEC536 manufactured by AFTON)
(Phenol antioxidant) Dibutylhydroxytoluene (BHT)
(Amine-based antioxidant) N-phenyl-1,1,3,3-tetramethylbutylnaphthalen-1-amine (IRGANOX L06 manufactured by BASF)
(Metal deactivator) N, N-bis (2-ethylhexyl)-(4 or 5) -methyl-1H-benzotriazole-1-methylamine (BASF's Irgamet 39)

[Evaluation of hydraulic fluid composition]
The following evaluation was performed about the prepared hydraulic fluid composition, and the result was described in Tables 2-5.

(RBOT test)
A turbine oil oxidation stability test (RBOT) was carried out in accordance with Japanese Industrial Standard JIS K2514 (1996). The numbers shown in the table represent the time (minutes) required to drop 175 kPa from the maximum pressure, and the larger the value, the higher the oxidation stability.

(Shell 4-ball wear test)
In a high-speed shell 4-ball tester, the test was carried out at a load of 294 N (30 kg), a rotation speed of 1200 rpm, a rotation time of 60 minutes, and a temperature of 75 ° C., and the wear scar diameter (μm) of three steel balls was measured. Values are listed. The smaller the wear scar diameter (μm), the better the wear resistance.

(Rust prevention performance test)
Lubricating oil rust prevention performance test (distilled water) was performed according to Japanese Industrial Standard JIS K2510.

(Thermal stability test)
A lubricating oil thermal stability test was conducted at 170 ° C. for 24 hours using a turntable tester described in Japanese Industrial Standard JIS K2540. In this test, when precipitates and sludge were not generated, it is described in the table as “no sludge”, indicating that the thermal stability is high. On the other hand, when precipitates and sludge are generated, it is described in the table as “with sludge”, indicating that the thermal stability is low.

(Flash point)
According to Japanese Industrial Standard JIS K2565, the flash point was measured by the Cleveland open type. The higher the flash point in this test, the better the flame retardancy.

(Burn point)
According to Japanese Industrial Standard JIS K2565, the burning point was measured by the Cleveland open type. The higher the burning point in this test, the better the flame retardancy.

(Demulsibility test)
In accordance with Japanese Industrial Standard JIS K2520, a demulsibility test was performed. The numerical values shown in the table indicate oil layer (ml) -water layer (ml) -emulsified layer (ml) (elapsed time), and the shorter the elapsed time, the better the demulsibility.

(Biodegradability test)
A biodegradability test was performed according to OECD301C. In addition, the Eco Mark Secretariat of the Japan Environment Association has a biodegradability of 60% or more in this test and satisfies the standards as a biodegradable lubricant. In this test, those with biodegradability of 60% or more were accepted and those with less than 60% were rejected.

  From the results of Tables 2 to 5, the ester compound (A) defined in the present invention is used, and the quinoline derivative or its polymer (B) and the dithiophosphate derivative (C) are blended in the content defined in the present invention. It can be seen that a hydraulic fluid composition having excellent oxidation stability, abrasion resistance, rust resistance, thermal stability, flame retardancy, demulsibility, and biodegradability can be obtained.

The hydraulic fluid composition of the present invention is excellent in biodegradability and also excellent in flame retardancy, abrasion resistance, oxidation stability, thermal stability, rust resistance, and anti-emulsification properties. It can be suitably used for hydraulic devices such as sluice gate opening and closing devices, pile press-in machines, excavators, pile pullers and construction machines used around water.

Claims (1)

The following ester compound (A), the following quinoline derivative or polymer thereof (B) and the following dithiophosphoric acid ester derivative (C) are contained, and the quinoline derivative or the polymer thereof is polymerized relative to 100 parts by mass of the ester compound (A). Hydraulic fluid composition containing 0.5 to 1.5 parts by mass of product (B) and 0.1 to 0.5 parts by mass of dithiophosphate ester derivative (C).
(A) It is an ester compound of 5 to 10 carbon atoms, an alcohol valence of 3 to 6 neopentyl polyol, and a linear unsaturated fatty acid of 16 to 22 carbon atoms, and in the ester compound, The monoester (a1) is contained in an amount of 0.1 to 5% by mass, the diester (a2) is contained in an amount of 10 to 30% by mass, and the trivalent or higher ester (a3) is contained in an amount of 65 to 89.9%. Ester compound whose mass ratio of diester (a2) is 1/99 to 20/80 (B) 2,2,4-trimethyl-1,2-dihydroquinoline or a polymer thereof, 6-methoxy-2,2,4 -One or more quinoline derivatives selected from the group consisting of trimethyl-1,2-dihydroquinoline or polymers thereof and 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline or polymers thereof Or a polymer thereof (C) Dithiophosphate derivative represented by the following formula

(R ₁ and R ₂ each independently represents an alkyl group having 1 to 5 carbon atoms, R ₃ represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and A represents an alkylene group having 1 to 5 carbon atoms.)