Hydraulic oil composition, method for producing the same, and use thereof

Abstract

The present application relates to the field of lubricating oil, disclose a kind of hydraulic oil composition and its preparation method and application.The hydraulic oil composition includes borate ester, polyethylene glycol methyl ether, polyethylene glycol butyl ether, polyethylene glycol and polyethylene oxide polypropylene oxide monobutyl ether and optional adjuvant;Wherein, the weight ratio of borate ester, polyethylene glycol methyl ether, polyethylene glycol butyl ether, polyethylene glycol and polyethylene oxide polypropylene oxide monobutyl ether is 10-20:1-6:1-5:0.5-4:1.The hydraulic oil prepared by the composition of the present application has good high and low temperature performance, and also has excellent antioxidant corrosion resistance and lubricating property.

Description

Technical Field

[0001] This invention relates to the field of lubricating oils, and more specifically to a hydraulic oil composition, its preparation method, and its application. Background Technology

[0002] The function of a vehicle's hydraulic braking system is to stop or slow down movement within the machine. Hydraulic oil is a functional fluid used in the hydraulic braking system to transmit pressure and stop wheel rotation. With the advancement of automotive technology, modern braking systems have higher requirements for weight, efficiency, driving force, noise, safety, and rapid response. To meet the demands of modern braking systems, the performance requirements for the hydraulic oil used are also more stringent. For example, the selected hydraulic oil needs to possess excellent high-temperature performance, good lubrication performance, good corrosion resistance, and excellent high and low temperature performance.

[0003] Currently, hydraulic oil base oils on the market are mainly divided into mineral base oils, synthetic base oils, and bio-based base oils. Synthetic base oils are mainly divided into two categories: synthetic ester base oils and synthetic hydrocarbon base oils. Ester oils have excellent viscosity-temperature properties, good heat resistance, less coking, and good oxidation stability, but poor compatibility with sealing materials and coatings, poor hydrolytic stability, and moderate corrosion resistance. Synthetic hydrocarbon base oils have good high-temperature resistance, good fluidity, and high flash point and ignition point, but unstable viscosity-temperature properties, poor oxidation corrosion resistance, and poor lubrication performance.

[0004] For example, CN109233954A discloses an energy-saving anti-wear hydraulic oil, which includes 100 parts of base oil, 1-10 parts of friction reducer, 0.5-5 parts of antioxidant, 0.1-0.5 parts of antifoaming agent, 0.1-0.5 parts of deemulsifier, and 0.1-0.5 parts of four-arm PEG sulfhydryl. The base oil is an ester synthetic oil and a Group III mineral oil. The hydraulic oil prepared has good fluidity at low temperature and a small viscosity difference between low and high temperature, but poor corrosion resistance.

[0005] CN114763502A discloses a hydraulic oil composition and its preparation method. Based on the hydraulic oil composition, it contains the following components in weight percentages: 0.1-0.3% extreme pressure anti-wear agent, 0.1-2% demulsifier, 0.1-1.5% friction modifier, 0.1-0.3% detergent-dispersant, 0.1-0.3% corrosion inhibitor, 0.1-0.5% pour point depressant, 0.005-0.035% antifoaming agent, and the balance being a composite base oil, wherein the composite base oil is a combination of coal-derived base oil and natural gas synthetic oil. The prepared hydraulic oil composition has good rubber compatibility, but poor anti-wear and anti-friction properties.

[0006] In summary, hydraulic fluids need to possess excellent resistance to oxidation and corrosion, lubrication properties, and high and low temperature performance to ensure the normal operation of vehicle braking systems. However, currently available commercially available synthetic hydraulic fluids do not fully meet these requirements, necessitating the development of a suitable product. Summary of the Invention

[0007] The purpose of this invention is to overcome the problem that existing hydraulic oils cannot simultaneously possess both antioxidant and lubricating properties, and to provide a hydraulic oil composition and its preparation method. The hydraulic oil prepared from the hydraulic oil composition of this invention has excellent antioxidant and lubricating properties, as well as good high and low temperature performance.

[0008] To achieve the above objectives, the present invention provides a hydraulic oil composition, characterized in that the hydraulic oil composition comprises: borate ester, polyethylene glycol methyl ether, polyethylene glycol butyl ether, polyethylene glycol and polyethylene oxide polypropylene oxide monobutyl ether and optional additives.

[0009] The weight ratio of the borate ester, polyethylene glycol methyl ether, polyethylene glycol butyl ether, polydiol and polyethylene oxide polypropylene oxide monobutyl ether is 10-20:1-6:1-5:0.5-4:1.

[0010] A second aspect of the present invention provides a method for preparing hydraulic oil, characterized in that the method comprises:

[0011] Borate esters, polyethylene glycol methyl ether, polyethylene glycol butyl ether, polyethylene glycol and polyethylene oxide polypropylene monobutyl ether and optional additives are mixed.

[0012] The third aspect of the present invention provides the application of the aforementioned borate esters, polyethylene glycol methyl ether, polyethylene glycol butyl ether, polyethylene glycol and polyethylene oxide polypropylene oxide monobutyl ether as base oils in improving the antioxidant corrosion resistance, high and low temperature performance and lubrication performance of hydraulic oil compositions.

[0013] The advantages of this invention compared to the prior art are at least as follows:

[0014] (1) The hydraulic oil of the present invention has good high and low temperature performance, good viscosity-temperature performance and excellent stability, providing good energy transmission, sealing and heat dissipation functions for vehicle hydraulic braking system.

[0015] (2) The hydraulic oil of the present invention has particularly excellent anti-oxidation and corrosion properties and lubrication properties, providing better lubrication and anti-corrosion functions for vehicle hydraulic braking systems, better meeting the usage requirements of modern vehicle braking systems under harsh conditions, and providing a guarantee for the operation of the braking system. Detailed Implementation

[0016] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0017] The first aspect of the present invention provides a hydraulic oil composition, characterized in that the hydraulic oil composition comprises: borate ester, polyethylene glycol methyl ether, polyethylene glycol butyl ether, polyethylene glycol and polyethylene oxide polypropylene oxide monobutyl ether and optional additives.

[0018] The weight ratio of the borate ester, polyethylene glycol methyl ether, polyethylene glycol butyl ether, polydiol and polyethylene oxide polypropylene oxide monobutyl ether is 10-20:1-6:1-5:0.5-4:1.

[0019] In a preferred embodiment, the weight ratio of the borate ester, polyethylene glycol methyl ether, polyethylene glycol butyl ether, polydiol, and polyethylene oxide polypropylene oxide monobutyl ether is 12-17:2-5:1.5-4:1-2:1.

[0020] According to some embodiments of the present invention, the total content of the borate ester, polyethylene glycol methyl ether, polyethylene glycol butyl ether, polyethylene glycol and polyethylene oxide polypropylene oxide monobutyl ether is 90wt%-98.5wt% based on the total weight of the hydraulic oil composition.

[0021] In a preferred embodiment, the total content of the borate ester, polyethylene glycol methyl ether, polyethylene glycol butyl ether, polyethylene glycol, and polyethylene oxide polypropylene oxide monobutyl ether is 94wt%-97.5wt% based on the total weight of the hydraulic oil composition.

[0022] According to some embodiments of the present invention, the boronic ester has the structural formula: R1-O-[(CH2CH2-O)] n -B, n is an integer ≥2, R1 is a C1-C4 alkyl group, preferably n is an integer 2-4, and the borate ester is selected from at least one of polyethylene glycol methyl ether borate, polyethylene glycol ethyl ether borate and polyethylene glycol butyl ether borate.

[0023] According to some embodiments of the present invention, the structural formula of the polyethylene glycol methyl ether is: R2-O-(CH2CH2-O). m -H, m is an integer ≥2, R2 is methyl, and preferably m is an integer between 2 and 4.

[0024] According to some embodiments of the present invention, the structural formula of the polyethylene glycol butyl ether is: R3-O-(CH2CH2-O).p -H, p is an integer ≥2, R3 is n-butyl, and preferably p is an integer between 2 and 4.

[0025] According to some embodiments of the present invention, the structural formula of the polyethylene glycol is: H-(O-CH2CH2) q -OH, q is an integer ≥2, preferably an integer between 2 and 5, and the polyethylene glycol is selected from at least one of diethylene glycol, triethylene glycol, polyethylene glycol 200 and polyethylene glycol 400.

[0026] According to some embodiments of the present invention, the structural formula of the polyethylene oxide polypropylene oxide monobutyl ether is: R4O-(CH2CH2-O). r -[CH2CH(CH3)-O] s -H, r and s are both non-zero integers, R4 is n-butyl, and preferably r is an integer of 3-6 and s is an integer of 4-7.

[0027] In this invention, when the types and amounts of the borate ester, polyethylene glycol methyl ether, polyethylene glycol butyl ether, polydiol, and polyethylene oxide polypropylene oxide monobutyl ether meet the above-mentioned ranges, the hydraulic oil composition possesses excellent high and low temperature performance and lubrication performance.

[0028] In this invention, in order to further improve the anti-oxidation and corrosion properties, high and low temperature properties and lubrication properties of the hydraulic oil composition, the additives include at least one of corrosion inhibitors, metal passivators and pH adjusters. Preferably, the additives include antioxidants, corrosion inhibitors, metal passivators and pH adjusters.

[0029] More preferably, based on the total weight of the hydraulic oil composition, the content of the antioxidant is 0.2wt%-4wt%, the content of the corrosion inhibitor is 0.03wt%-2.5wt%, the content of the metal passivator is 0.02wt%-1.0wt%, and the content of the pH adjuster is 1.25wt%-2.5wt%.

[0030] According to some embodiments of the present invention, the antioxidant is selected from at least one of organic phenolic antioxidants, organic amine antioxidants, phosphite antioxidants, and organic sulfur antioxidants. Preferably,

[0031] The antioxidant is an organic phenolic antioxidant and an organic sulfur antioxidant. More preferably, the weight ratio of the organic phenolic antioxidant to the organic sulfur antioxidant is 1:1-3.

[0032] According to some embodiments of the present invention, the organic sulfur antioxidant is selected from at least one of dialkyl dithiocarbamate, dithiodipropionic acid and dialkyl dithiodipropionic acid; the organic phenolic antioxidant is selected from at least one of 2,6-di-tert-butyl-4-methylphenol, 2,2-di(4-hydroxyphenyl)propane and p-hydroxyanisole.

[0033] According to some embodiments of the present invention, the corrosion inhibitor is selected from at least one of sulfonates, fatty acids, fatty acid derivatives and complex phosphate compounds. Preferably, the corrosion inhibitor is selected from at least one of sodium dinonylnaphthalenesulfonate, dodecenyl succinic acid, dodecenyl succinic acid half ester and polyethylene glycol phosphate.

[0034] According to some embodiments of the present invention, the metal passivating agent is selected from at least one of benzotriazole derivatives, thiadiazole derivatives and purines. Preferably, the metal passivating agent is a benzotriazole derivative and a thiadiazole derivative. More preferably, the weight ratio of the benzotriazole derivative to the thiadiazole derivative is 1-5:1.

[0035] According to some embodiments of the present invention, preferably, the benzotriazole derivative is selected from at least one of benzotriazole, methylbenzotriazole, 1,2,4-triazole and 1,2,3-triazole; and the thiadiazole derivative is selected from di(tert-dodecyl dithio)-1,3,4-thiadiazole and / or sodium dimercaptothiadiazole.

[0036] According to some embodiments of the present invention, the pH adjuster is selected from at least one of organic amines and their derivatives, and preferably, the pH adjuster is selected from at least one of diethanolamine, triethanolamine, n-butylamine, methyldiethanolamine and tri-n-butylamine.

[0037] In this invention, when the types and amounts of the antioxidant, corrosion inhibitor, metal passivator and pH adjuster meet the above-mentioned ranges, the hydraulic oil composition has excellent antioxidant and corrosion resistance.

[0038] A second aspect of the present invention provides a method for preparing hydraulic oil, characterized in that the method comprises:

[0039] Borate esters, polyethylene glycol methyl ether, polyethylene glycol butyl ether, polyethylene glycol and polyethylene oxide polypropylene monobutyl ether and optional additives are mixed.

[0040] In this invention, there are no particular limitations on the mixing method of the borate ester, polyethylene glycol methyl ether, polyethylene glycol butyl ether, polyethylene glycol, polyethylene oxide polypropylene oxide monobutyl ether and the additives; any mixing method conventional in the art can be used.

[0041] According to some embodiments of the present invention, the mixing includes: a temperature of 90-130°C, a pressure of -0.092MPa to -0.095MPa, and a time of 0.5-5h; preferably, the temperature is 100-110°C, the pressure is -0.092MPa to -0.095MPa, and the time is 1-2h.

[0042] The third aspect of the present invention provides the application of the aforementioned borate esters, polyethylene glycol methyl ether, polyethylene glycol butyl ether, polyethylene glycol and polyethylene oxide polypropylene oxide monobutyl ether as base oils in improving the antioxidant corrosion resistance, high and low temperature performance and lubrication performance of hydraulic oil compositions.

[0043] Unless otherwise specified, all pressures mentioned in this invention are gauge pressures.

[0044] According to a particularly preferred embodiment of the present invention, the preparation method of the hydraulic oil composition includes: mixing borate ester, polyethylene glycol methyl ether, polyethylene glycol butyl ether, polyethylene glycol, polyethylene oxide polypropylene oxide monobutyl ether, antioxidant, corrosion inhibitor, metal passivator and pH adjuster, and stirring evenly at 100-110°C and a pressure of -0.092MPa to -0.095MPa to obtain the hydraulic oil composition;

[0045] The weight ratio of the borate ester, polyethylene glycol methyl ether, polyethylene glycol butyl ether, polydiol and polyethylene oxide polypropylene oxide monobutyl ether is 12-17:2-5:1.5-4:1-2:1.

[0046] The hydraulic oil composition obtained according to this preferred embodiment has good high and low temperature performance, as well as excellent anti-oxidation and corrosion performance and lubrication performance.

[0047] Example

[0048] To further illustrate the present invention, the following embodiments will be described in detail.

[0049] In the following embodiments of the present invention, unless otherwise specified, all raw materials are commercially available products.

[0050] Example 1

[0051] This embodiment illustrates the preparation of a hydraulic oil composition using the method described in this invention. The method includes: mixing borate ester, polyethylene glycol methyl ether, polyethylene glycol butyl ether, polyethylene glycol, polyethylene oxide polypropylene oxide monobutyl ether, antioxidant, corrosion inhibitor, metal passivator, and pH adjuster, stirring until homogeneous, and dehydrating at 105°C and -0.095 MPa for 1.5 h to obtain the hydraulic oil composition A1. The types and amounts of each raw material are shown in Table 1.

[0052] The structural formulas of the polyethylene glycol methyl ether, polyethylene glycol butyl ether, and polyethylene oxide polypropylene oxide monobutyl ether are CH3-O-(CH2CH2-O)3-H, CH3(CH2)3-O-(CH2CH2-O)3-H, and CH3(CH2)3O-(CH2CH2-O)6-[CH2CH(CH3)-O]7-H, respectively.

[0053] Example 2

[0054] This embodiment illustrates the preparation of hydraulic oil using the method described in this invention. The method includes: mixing borate ester, polyethylene glycol methyl ether, polyethylene glycol butyl ether, polyethylene glycol, polyethylene oxide polypropylene oxide monobutyl ether, antioxidant, corrosion inhibitor, metal passivator and pH adjuster, stirring evenly, and dehydrating at 100°C and -0.092 MPa for 1 hour to obtain the hydraulic oil composition A2. The types and amounts of each raw material are shown in Table 1.

[0055] The structural formulas of the polyethylene glycol methyl ether, polyethylene glycol butyl ether, and polyethylene oxide polypropylene oxide monobutyl ether are CH3-O-(CH2CH2-O)2-H, CH3(CH2)3-O-(CH2CH2-O)2-H, and CH3(CH2)3O-(CH2CH2-O)3-[CH2CH(CH3)-O]7-H, respectively.

[0056] Example 3

[0057] This embodiment illustrates the preparation of hydraulic oil using the method described in this invention. The method includes: mixing borate ester, polyethylene glycol methyl ether, polyethylene glycol butyl ether, polyethylene glycol, polyethylene oxide polypropylene oxide monobutyl ether, antioxidant, corrosion inhibitor, metal passivator and pH adjuster, stirring evenly, and dehydrating at 110°C and -0.095 MPa for 2 hours to obtain the hydraulic oil composition A3. The types and amounts of each raw material are shown in Table 1.

[0058] The structural formulas of the polyethylene glycol methyl ether, polyethylene glycol butyl ether, and polyethylene oxide polypropylene oxide monobutyl ether are CH3-O-(CH2CH2-O)2-H, CH3(CH2)3-O-(CH2CH2-O)4-H, and CH3(CH2)3O-(CH2CH2-O)6-[CH2CH(CH3)-O]4-H, respectively.

[0059] Example 4

[0060] The hydraulic oil composition was prepared according to the method of Example 1, except that the amounts of each raw material were as shown in Table 1, and the hydraulic oil composition A4 was obtained.

[0061] Example 5

[0062] The hydraulic oil composition A5 was prepared according to the method of Example 1, except that the antioxidant was diphenylamine, and the other conditions were the same.

[0063] Example 6

[0064] The hydraulic oil composition A6 was prepared according to the method of Example 1, except that the metal passivating agent was adenine, and the other conditions were the same.

[0065] Example 7

[0066] The hydraulic oil composition was prepared according to the method of Example 1, except that the weight ratio of phenolic antioxidant to organic sulfur antioxidant was 2.5:1, and the other conditions were the same, to obtain hydraulic oil composition A7.

[0067] Example 8

[0068] The hydraulic oil composition was prepared according to the method of Example 1, except that the weight ratio of the benzotriazole derivative to the thiadiazole derivative was 9:1, and the other conditions were the same, to obtain hydraulic oil composition A8.

[0069] Comparative Examples 1-2

[0070] The hydraulic oil composition was prepared according to the method of Example 1, except that the amount of each raw material was as shown in Table 1, and the hydraulic oil compositions D1-D2 were obtained.

[0071] Comparative Example 3

[0072] Hydraulic oil was prepared according to the method of Example 1, except that borate ester was replaced with sebacate ester, while the other conditions were the same, to obtain hydraulic oil composition D3.

[0073] Comparative Example 4

[0074] Hydraulic oil was prepared according to the method of Example 1, except that polyethylene oxide polypropylene oxide monobutyl ether was replaced with polyalkylene trihydroxy ether, while the other conditions were the same, and hydraulic oil composition D4 was prepared.

[0075] Comparative Example 5

[0076] Hydraulic oil was prepared according to the method of Example 1, except that polyethylene glycol methyl ether was replaced with polyethylene glycol ethyl ether, while the other conditions were the same, and hydraulic oil composition D5 was prepared.

[0077] Comparative Example 6

[0078] Hydraulic oil was prepared according to the method of Example 1, except that polyethylene glycol butyl ether was replaced with polyethylene glycol glycerol ether, while the other conditions were the same, and hydraulic oil composition D6 was prepared.

[0079] Comparative Example 7

[0080] Hydraulic oil was prepared according to the method of Example 1, except that polyethylene glycol was replaced with glycerol, while the other conditions were the same, and hydraulic oil composition D7 was prepared.

[0081] Comparative Example 8

[0082] Hydraulic oil was prepared according to the method of Example 1, except that the amounts of borate ester, polyethylene glycol methyl ether, polyethylene glycol butyl ether, polyethylene glycol, and polyethylene oxide polypropylene oxide monobutyl ether were different. Specifically, the amounts were 56.8 g borate ester, 18.4 g polyethylene glycol methyl ether, 13.2 g polyethylene glycol butyl ether, 6.6 g polyethylene glycol, and 2.42 g polyethylene oxide polypropylene oxide monobutyl ether, while the other conditions remained the same, to prepare hydraulic oil composition D8.

[0083] Test case

[0084] The properties of the hydraulic oil compositions prepared in the examples and comparative examples were tested, and the test results are shown in Tables 1-4.

[0085] The low-temperature kinematic viscosity of hydraulic oil was determined according to the method of GB / T 265, using an instrument model ST-1506.

[0086] The equilibrium reflux boiling point of hydraulic oil was determined according to the SH / T 0430 method, using an instrument model JF0430.

[0087] The wet equilibrium reflux boiling point of hydraulic oil was determined according to the method in Appendix C of GB 12981, using an instrument model JF0430.

[0088] The stability test of the hydraulic oil was conducted according to the SH / T 0091 method, using an instrument model AT-710B.

[0089] The mass change of different metal sheets after oxidation and corrosion of hydraulic oil (100℃×240h, 100mL / min air) was determined according to the SH / T 0450 method, using an instrument model FDH-3001.

[0090] The coefficient of friction of the hydraulic oil was determined according to the ASTM G99 method using an instrument model UFW 200.

[0091] Table 1

[0092]

[0093] Table 2

[0094]

[0095] Table 3

[0096]

[0097] Table 4

[0098]

[0099] As can be seen from the data in Tables 1-4, compared with Comparative Examples 1-2, changing the amount of each substance in the hydraulic oil composition in Example 1 resulted in a decrease in the equilibrium reflux boiling point and wet equilibrium reflux boiling point, an increase in the change in reserve alkalinity, an increase in the mass change of brass and copper after oxidation and corrosion, and a slight increase in the coefficient of friction, leading to a deterioration in the low-temperature performance, oxidation and corrosion resistance, and lubrication performance of the hydraulic oil composition. Compared with Comparative Example 3, replacing borate ester with sebacic acid ester in Example 1 resulted in a decrease in the wet equilibrium reflux boiling point and an increase in the mass change of brass and copper after oxidation and corrosion, leading to a deterioration in the high-temperature performance and oxidation and corrosion resistance of the hydraulic oil composition. Compared with Comparative Example 4, replacing polyethylene oxide polypropylene oxide monobutyl ether with polyalkylene trihydroxy ether in Example 1 resulted in an increase in the coefficient of friction, leading to a deterioration in the lubrication performance of the hydraulic oil composition. Compared with Comparative Example 5, replacing polyethylene glycol methyl ether with polyethylene glycol ethyl ether in Example 1 resulted in an increase in the change in reserve alkalinity, an increase in the mass change of brass and copper after oxidation and corrosion, and a slight increase in the coefficient of friction. The high alkalinity leads to a deterioration in the antioxidant and lubricating properties of the hydraulic oil composition. In Example 1, compared to Comparative Example 6, replacing polyethylene glycol butyl ether with polyethylene glycol glycerol ether resulted in a higher reserve alkalinity change, increased mass changes in brass and copper after oxidation and corrosion, and a slightly higher coefficient of friction, all of which worsened the antioxidant and lubricating properties of the hydraulic oil composition. In Example 1, compared to Comparative Example 7, replacing polyethylene glycol with glycerol resulted in a higher reserve alkalinity change, increased mass changes in brass and copper after oxidation and corrosion, and a slightly higher coefficient of friction, all of which worsened the antioxidant and lubricating properties of the hydraulic oil composition. In Example 1, compared to Comparative Example 8, the weight ratio of borate ester, polyethylene glycol methyl ether, polyethylene glycol butyl ether, polyethylene glycol, and polyethylene oxide polypropylene oxide monobutyl ether was outside the range specified in this invention, resulting in a higher reserve alkalinity change, increased mass changes in brass and copper after oxidation and corrosion, and a slightly higher coefficient of friction, all of which worsened the antioxidant and lubricating properties of the hydraulic oil composition.

[0100] In summary, the hydraulic oil prepared using the composition of the present invention has good high and low temperature performance, as well as excellent anti-oxidation and corrosion performance and lubrication performance. It provides good heat dissipation, lubrication and anti-corrosion functions for vehicle hydraulic braking systems, better meets the usage requirements of modern vehicle braking systems under harsh conditions, and provides a guarantee for the operation of the braking system.

[0101] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A hydraulic oil composition, characterized in that, The hydraulic fluid composition comprises: borate ester, polyethylene glycol methyl ether, polyethylene glycol butyl ether, polyethylene glycol, and polyethylene oxide polypropylene oxide monobutyl ether, and additives; wherein the borate ester is selected from at least one of triethylene glycol methyl ether borate ester, triethylene glycol ethyl ether borate ester, and triethylene glycol butyl ether borate ester; The weight ratio of the borate ester, polyethylene glycol methyl ether, polyethylene glycol butyl ether, polydiol and polyethylene oxide polypropylene oxide monobutyl ether is 10-20:1-6:1-5:0.5-4:1; Based on the total weight of the hydraulic oil composition, the total content of the borate ester, polyethylene glycol methyl ether, polyethylene glycol butyl ether, polyethylene glycol, and polyethylene oxide polypropylene oxide monobutyl ether is 90wt%-98.5wt%. The polyethylene glycol is selected from at least one of diethylene glycol, triethylene glycol, polyethylene glycol 200, and polyethylene glycol 400; The structural formula of the poly(ethylene oxide) poly(propylene oxide) monobutyl ether is as follows: r is an integer from 3 to 6, s is an integer from 4 to 7, and R4 is a n-butyl group.

2. The hydraulic oil composition according to claim 1, wherein, The weight ratio of the borate ester, polyethylene glycol methyl ether, polyethylene glycol butyl ether, polydiol and polyethylene oxide polypropylene oxide monobutyl ether is 12-17:2-5:1.5-4:1-2:

1.

3. The hydraulic oil composition according to claim 1, wherein, Based on the total weight of the hydraulic oil composition, the total content of the borate ester, polyethylene glycol methyl ether, polyethylene glycol butyl ether, polyethylene glycol and polyethylene oxide polypropylene oxide monobutyl ether is 94wt%-97.5wt%.

4. The hydraulic oil composition according to claim 1, wherein, The structural formula of the polyethylene glycol methyl ether is: m is an integer ≥ 2, and R2 is a methyl group; And / or, the structural formula of the polyethylene glycol butyl ether is: p is an integer ≥ 2, and R3 is n-butyl.

5. The hydraulic oil composition according to claim 4, wherein, m is an integer between 2 and 4; And / or, p is an integer between 2 and 4.

6. The hydraulic oil composition according to claim 1, wherein, The additives include at least one of antioxidants, corrosion inhibitors, metal passivators, and pH adjusters.

7. The hydraulic oil composition according to claim 6, wherein, The additives include antioxidants, corrosion inhibitors, metal passivators, and pH adjusters.

8. The hydraulic oil composition according to claim 7, wherein, Based on the total weight of the hydraulic oil composition, the content of the antioxidant is 0.2wt%-4wt%, the content of the corrosion inhibitor is 0.03wt%-2.5wt%, the content of the metal passivator is 0.02wt%-1.0wt%, and the content of the pH adjuster is 1.25wt%-2.5wt%.

9. The hydraulic oil composition according to claim 7, wherein, The antioxidant is selected from at least one of organic phenolic antioxidants, organic amine antioxidants, phosphite antioxidants, and organic sulfur antioxidants; And / or, the corrosion inhibitor is selected from at least one of sulfonates, fatty acids, fatty acid derivatives and complex phosphate compounds; And / or, the metal passivating agent is selected from at least one of benzotriazole derivatives, thiadiazole derivatives, and purines; And / or, the pH adjuster is selected from at least one of organic amines and their derivatives.

10. The hydraulic oil composition according to claim 9, wherein, The antioxidants are organic phenolic antioxidants and organic sulfur antioxidants; And / or, the metal passivating agent is a benzotriazole derivative and a thiadiazole derivative.

11. The hydraulic oil composition according to claim 10, wherein, The weight ratio of the organic phenolic antioxidant to the organic sulfur antioxidant is 1:1-3.

12. The hydraulic oil composition according to claim 10, wherein, The weight ratio of the benzotriazole derivative to the thiadiazole derivative is 1-5:

1.

13. The hydraulic oil composition according to claim 10, wherein, The organic sulfur antioxidant is selected from at least one of dialkyl dithiocarbamate, dithiodipropionic acid and dialkyl dithiodipropionic acid; And / or, the organic phenolic antioxidant is selected from at least one of 2,6-di-tert-butyl-4-methylphenol, 2,2-di(4-hydroxyphenyl)propane and p-hydroxyanisole; And / or, the corrosion inhibitor is selected from at least one of sodium dinonylnaphthalenesulfonate, dodecenyl succinic acid, dodecenyl succinate half ester and polyethylene glycol phosphate; And / or, the benzotriazole derivative is selected from benzotriazole and / or methylbenzotriazole; the thiadiazole derivative is selected from di(tert-dodecyl dithio)-1,3,4-thiadiazole and / or sodium salt of dimercaptothiadiazole; And / or, the pH adjuster is selected from at least one of diethanolamine, triethanolamine, n-butylamine, methyldiethanolamine, and tri-n-butylamine.

14. A method for preparing the hydraulic oil composition according to any one of claims 1-13, characterized in that, The method includes mixing borate ester, polyethylene glycol methyl ether, polyethylene glycol butyl ether, polyethylene glycol, polyethylene oxide polypropylene oxide monobutyl ether, and additives.

15. The method according to claim 14, wherein, The mixing process includes: a temperature of 90-130℃, a pressure of -0.092MPa to -0.095MPa, and a time of 0.5-5h.

16. The method according to claim 15, wherein, The mixing process includes: a temperature of 100-110℃, a pressure of -0.092MPa to -0.095MPa, and a time of 1-2 hours.

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