Ultralow-temperature degradable aviation hydraulic oil and preparation method thereof

Abstract

The invention discloses ultralow-temperature degradable aviation hydraulic oil and a preparation method thereof, and belongs to the technical field of lubricating oil. The hydraulic oil is prepared from the following raw materials: 79 to 90 percent of base oil, 8 to 20 percent of a viscosity index improver, 0.05 to 0.3 percent of an antioxidant, 0.1 to 1 percent of an extreme pressure anti-wear agent, 0.01 to 0.2 percent of an anti-rust agent, 0.005 to 0.1 percent of a metal deactivator, 0.1 to 1 percent of a pour point depressant, 0.005 to 0.03 percent of an anti-foaming agent and 0.001 to 0.005 percent of a blue dye agent. The functional agents adopted by the invention have a synergistic effect, so that the wear resistance, oxidation resistance and other properties of the oil product can be effectively improved; the base oil has excellent low-temperature performance such as low pour point and the like, and also has good degradability, so that the problem that hydraulic oil in the current market is non-degradable is effectively solved; the formula system is moderate in cost, the production process is simple and easy to operate, and rapid development of current aviation equipment hydraulic systems can be well met.

Description

Technical Field

[0001] The invention belongs to the technical field of lubricating oils, and in particular relates to an ultra-low temperature degradable aviation hydraulic oil and a preparation method thereof. Background Art

[0002] Due to the large size of aircraft, human power can no longer directly operate the various components of the aircraft through the joystick, pedals, etc., which requires the help of a power assist mechanism - a hydraulic transmission power assist system.

[0003] Hydraulic oil is the working medium for the transmission and conversion of mechanical energy in the aircraft control system. It is mainly used in hydraulic systems of aviation equipment such as retractable landing gear, speed brakes, automatic control equipment, brakes and other hydraulic systems using synthetic sealing materials. It realizes energy conversion, transmission and control in the hydraulic transmission system. It also plays the role of lubrication, cooling, rust prevention, damping and shock absorption. It can be divided into plant-based hydraulic oil (blue oil), mineral-based hydraulic oil (red oil) and phosphate-based hydraulic oil (purple oil). The hydraulic system of aviation equipment has the characteristics of high working pressure, wide operating temperature range, high shear force, etc., so the hydraulic oil is required to have good thermal stability and corrosion resistance, oxidation stability, low temperature performance, shear resistance and anti-foaming properties. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide an ultra-low temperature degradable aviation hydraulic oil and a preparation method thereof. The hydraulic oil uses a homemade tackifier as a viscosity index improver, and has excellent low temperature performance and good degradability. At the same time, the hydraulic oil formula system of the present invention has moderate cost, simple production process and easy operation, which effectively solves the problem of non-degradability and ineffective balance of low temperature performance of hydraulic oil in the current market, and can well adapt to the rapid development of hydraulic systems of current aviation equipment.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] An ultra-low temperature biodegradable aviation hydraulic oil comprises the following raw materials by mass fraction: 79-90% base oil, 8-20% viscosity index improver, 0.05-0.3% antioxidant, 0.1-1% extreme pressure anti-wear agent, 0.01-0.2% rust inhibitor, 0.005-0.1% metal deactivator, 0.1-1% pour point depressant, 0.005-0.03% anti-foaming agent, and 0.001-0.005% blue dye.

[0007] Furthermore, the base oil is one or both of synthetic ester and polyalphaolefin.

[0008] Furthermore, the synthetic ester is one or more of monoester, diester, and polyol ester.

[0009] Furthermore, the viscosity index improver is one or both of a polymethacrylate viscosity index improver and a homemade tackifier.

[0010] Furthermore, the homemade tackifier is prepared by the following steps:

[0011] (1) reacting oleic acid, isooctyl alcohol and concentrated sulfuric acid at 80-120° C. for 4-6 hours, removing impurities and drying to obtain an esterification product;

[0012] (2) adding hydrogen peroxide to the esterification product obtained in step (1), reacting at 40 to 100° C. for 6 to 12 hours, removing impurities, and drying to obtain an epoxidation product;

[0013] (3) adding 0.5-5% of a ring-opening polymerization catalyst to the epoxidation product obtained in step (2), reacting at 90-150° C. for 4-6 hours to obtain a high-viscosity substance, i.e., a homemade tackifier.

[0014] Furthermore, in step (1), the molar ratio of oleic acid to isooctyl alcohol is 1:1-5.

[0015] Furthermore, in step (2), the molar ratio of the esterification product to hydrogen peroxide is 1:1-10.

[0016] Furthermore, the concentration of hydrogen peroxide in step (2) is 30%.

[0017] Furthermore, in step (3), the catalyst is one or more of tertiary amine, tert-butyl alcohol, and potassium hydroxide.

[0018] Furthermore, the antioxidant is one or more of 2,6-di-tert-butyl-p-methylphenol, 4,4'-methylenebis(2,6-di-tert-butylphenol), N-phenyl-α-naphthylamine, and N,N-di-sec-butyl-p-phenylenediamine.

[0019] Furthermore, the extreme pressure anti-wear agent is one or more of tricresyl phosphate, triphenyl phosphate, triethyl phosphate, tributyl phosphate, di-n-butyl phosphite, triphenylthiophosphate, dialkyl dithiophosphate, and butyl triphenylthiophosphate.

[0020] Furthermore, the rust inhibitor is one or more of dodecenylsuccinic acid, alkenyl succinate, sorbitan oleate, and sodium petroleum sulfonate.

[0021] Furthermore, the metal deactivator is one or more of benzotriazole derivatives, heterocyclic derivatives, and thiadiazole derivatives.

[0022] Furthermore, the metal deactivator is one or more of T551, T553, and T561.

[0023] Furthermore, the pour point depressant is one or more of polymethacrylate pour point depressants.

[0024] Pour point depressants can significantly improve the low-temperature fluidity of oil products.

[0025] Furthermore, the antifoaming agent is one or more of an organic silicon antifoaming agent, a polyether antifoaming agent, and a polyether-modified silicon antifoaming agent.

[0026] A method for preparing ultra-low temperature degradable aviation hydraulic oil comprises the following steps:

[0027] (1) Stir and heat the base oil to 70-80° C. in a reactor;

[0028] (2) adding a viscosity index improver, a pour point depressant, an antioxidant, an extreme pressure anti-wear agent, a rust inhibitor, a metal deactivator, an anti-foaming agent and a blue dye agent in sequence, stirring at 70° C. for 2 h, and curing at temperature to obtain a semi-finished hydraulic oil;

[0029] (3) The semi-finished hydraulic oil after temperature curing is cooled to 60°C, positive pressure filtered, and naturally cooled to room temperature to obtain the finished hydraulic oil.

[0030] This hydraulic oil has excellent low-temperature performance and good biodegradability. At the same time, the formula system has moderate cost and the production process is simple and easy to operate, which can well meet the rapid development of hydraulic systems in current aviation equipment.

[0031] The hydraulic oil uses a self-made tackifier as a viscosity index improver, and shows excellent low-temperature performance and good degradability compared to the hydraulic oil in the prior art. The remaining performance indicators are comparable to the physical and chemical properties of similar oils in the world, and can well meet the needs of flight hydraulic systems. At the same time, the hydraulic oil formula system of the present invention has moderate cost, simple production process and easy operation, which fully meets the needs of the current market.

[0032] Beneficial effects of the present invention:

[0033] 1. The functional agents used in the present invention have a synergistic effect and can effectively improve the anti-wear and anti-oxidation properties of the oil.

[0034] 2. The base oil used in the present invention has excellent low-temperature properties such as a low pour point, and also has good degradability, which effectively solves the problem of non-degradability of hydraulic oil in the current market.

[0035] 3. The formula system of the present invention has moderate cost, simple and easy-to-operate production process, and can well meet the rapid development of hydraulic systems of current aviation equipment. DETAILED DESCRIPTION

[0036] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] Example 1

[0038] Prepare the homemade tackifier as follows:

[0039] (1) reacting oleic acid, isooctyl alcohol and concentrated sulfuric acid at 80° C. for 4 h, removing impurities and drying to obtain an esterification product; wherein the molar ratio of oleic acid to isooctyl alcohol is 1:1;

[0040] (2) adding 30% hydrogen peroxide to the esterification product obtained in step (1), reacting at 40° C. for 6 h, removing impurities, and drying to obtain an epoxidation product; wherein the molar ratio of the esterification product to the hydrogen peroxide is 1:1;

[0041] (3) adding 0.5% triethanolamine to the epoxidation product obtained in step (2), and reacting at 90° C. for 4 h to obtain a high-viscosity substance, i.e., a homemade tackifier.

[0042] Example 2

[0043] Prepare the homemade tackifier as follows:

[0044] (1) reacting oleic acid, isooctyl alcohol and concentrated sulfuric acid at 120° C. for 6 h, removing impurities and drying to obtain an esterification product; wherein the molar ratio of oleic acid to isooctyl alcohol is 1:5;

[0045] (2) adding 30% hydrogen peroxide to the esterification product obtained in step (1), reacting at 100° C. for 12 h, removing impurities, and drying to obtain an epoxidation product; wherein the molar ratio of the esterification product to the hydrogen peroxide is 1:10;

[0046] (3) adding 5% potassium tert-butoxide to the epoxidation product obtained in step (2), reacting at 150° C. for 6 h to obtain a high-viscosity substance, i.e., a homemade tackifier.

[0047] Example 3

[0048] Prepare the homemade tackifier as follows:

[0049] (1) reacting oleic acid, isooctyl alcohol and concentrated sulfuric acid at 100° C. for 5 h, removing impurities and drying to obtain an esterification product; wherein the molar ratio of oleic acid to isooctyl alcohol is 1:3;

[0050] (2) adding 30% hydrogen peroxide to the esterification product obtained in step (1), reacting at 90° C. for 8 h, removing impurities, and drying to obtain an epoxidation product; wherein the molar ratio of the esterification product to the hydrogen peroxide is 1:6;

[0051] (3) Add 3% potassium hydroxide to the epoxidation product obtained in step (2), and react at 120° C. for 5 hours to obtain a high-viscosity substance, i.e., a homemade viscosity enhancer.

[0052] Example 4

[0053] Prepare hydraulic oil, the specific steps are as follows:

[0054] 96 kg of ExxonMobil's esterex a32 diester was added to a reactor, mechanically stirred and heated to 70°C; then 10 kg of the homemade tackifier prepared in Example 1, 8 kg of VISCOPLEX 0-051 viscosity index improver from Evonik, 0.2 kg of 2,6-di-tert-butyl-p-methylphenol and N,N-di-sec-butyl-p-phenylenediamine, 0.8 kg of tributyl phosphate, 0.1 kg of sorbitan oleate, 0.02 kg of metal deactivator T551, 0.25 kg of VISCOPLEX 1-180, 0.025 kg of T901 methyl silicone antifoaming agent, and 0.006 kg of blue dye were added in sequence, and stirred at 70°C for 2 hours to obtain a semi-finished hydraulic oil. After the oil product was cooled to about 60°C, it was filtered and naturally cooled to room temperature to obtain an ultra-low temperature hydraulic oil.

[0055] Example 5

[0056] Prepare hydraulic oil, the specific steps are as follows:

[0057] 40 kg of isooctyl oleate and 56 kg of amyl oleate were added to the reactor, mechanically stirred and heated to 70 ° C; then 7 kg of VISCOPLEX 8-310 viscosity index improver from Evonik, Germany, 13 kg of VISCOPLEX 0-051 from Evonik, Germany, 0.1 kg of 2,6-di-tert-butyl-p-methylphenol, 0.1 kg of N-phenyl-α-naphthylamine, 0.8 kg of tricresol phosphate, 0.05 kg of sodium petroleum sulfonate, 0.05 kg of dodecenyl succinic acid, 0.02 kg of metal deactivator T553, and 0.25 kg of VISCOPLEX pour point depressant from Evonik were added in sequence. 1-248, 0.025kg T901 methyl silicone antifoaming agent, 0.006kg blue dye, stirred at 70℃ for 2 hours to obtain semi-finished hydraulic oil, wait for the oil to cool to about 60℃, filter, and naturally cool to room temperature to obtain ultra-low temperature hydraulic oil.

[0058] Example 6

[0059] Prepare hydraulic oil, the specific steps are as follows:

[0060] 96 kg of ExxonMobil's esterex a32 diester was added to the reactor, mechanically stirred and heated to 70°C; then 8 kg of VISCOPLEX 0-120 viscosity index improver from Evonik of Germany, 12 kg of the homemade tackifier prepared in Example 2, 0.1 kg of 2,6-di-tert-butyl-p-methylphenol, 0.1 kg of N-phenyl-α-naphthylamine, 0.5 kg of tricresol phosphate, 0.5 kg of triphenylthiophosphate, 0.1 kg of rust inhibitor sodium petroleum sulfonate, 0.02 kg of metal deactivator T561, and 0.25 kg of VISCOPLEX pour point depressant from Evonik of Germany were added in sequence. 1-180, 0.025kg T901 methyl silicone antifoaming agent, 0.006kg blue dye, stirred at 70℃ for 2 hours to obtain semi-finished hydraulic oil, wait for the oil to cool to about 60℃, filter, and naturally cool to room temperature to obtain ultra-low temperature hydraulic oil.

[0061] Example 7

[0062] Prepare hydraulic oil, the specific steps are as follows:

[0063] 76 kg of ExxonMobil's esterex a32 diester and 20 kg of PAO2 were added to a reactor, mechanically stirred and heated to 70°C; then 12 kg of VISCOPLEX 0-120 viscosity index improver from Evonik of Germany, 8 kg of the homemade tackifier obtained in Example 3, 0.1 kg of antioxidant 2,6-di-tert-butyl-p-methylphenol, 0.1 kg of N-phenyl-α-naphthylamine, 0.5 kg of di-n-butyl phosphite, 0.5 kg of dialkyl dithiophosphate, 0.15 kg of sodium petroleum sulfonate, 0.025 kg of metal deactivator T553, and 0.2 kg of VISCOPLEX pour point depressant from Evonik of Germany were added in sequence. 1-248, 0.025kg T901 methyl silicone antifoaming agent, 0.006kg blue dye, stirred at 70℃ for 2 hours to obtain semi-finished hydraulic oil, wait for the oil to cool to about 60℃, filter, and naturally cool to room temperature to obtain ultra-low temperature hydraulic oil.

[0064] Example 8

[0065] Prepare hydraulic oil, the specific steps are as follows:

[0066] 60 kg of isooctyl oleate and 36 kg of PAO2 were added to the reactor, mechanically stirred and heated to 70 ° C; then 18.5 kg of the homemade tackifier prepared in Example 3, 0.1 kg of antioxidant 2,6-di-tert-butyl-p-methylphenol, 0.08 kg of N-phenyl-α-naphthylamine, 1.0 kg of butyl triphenyl thiophosphate, 0.1 kg of sodium petroleum sulfonate, 0.025 kg of metal deactivator T551, 0.15 kg of pour point depressant VISCOPLEX 1-248 of EVONIK, Germany, 0.025 kg of antifoaming agent, 0.006 kg of blue dye were added in sequence, and stirred at 70 ° C for 2 hours to obtain semi-finished hydraulic oil. When the oil product is cooled to about 60 ° C, it is filtered and naturally cooled to room temperature to obtain ultra-low temperature hydraulic oil.

[0067] Example 9

[0068] Prepare hydraulic oil, the specific steps are as follows:

[0069] 70 kg of trimethylolpropane trioleate and 26 kg of PAO2 were added to the reactor, mechanically stirred and heated to 70 ° C; then 15 kg of the homemade tackifier prepared in Example 3, 5 kg of VISCOPLEX0-051 viscosity index improver from Evonik, 0.10 kg of 2,6-di-tert-butyl-p-methylphenol, 0.08 kg of N-phenyl-α-naphthylamine, 0.85 kg of tricresol phosphate, 0.05 kg of sodium petroleum sulfonate, 0.05 kg of dodecenylsuccinic acid, 0.02 kg of metal deactivator T553, and 0.2 kg of VISCOPLEX pour point depressant from Evonik were added in sequence. 1-148, 0.025kg T901 methyl silicone antifoaming agent, 0.006kg blue dye, stirred at 70℃ for 2 hours to obtain semi-finished hydraulic oil, wait for the oil to cool to about 60℃, filter, and naturally cool to room temperature to obtain ultra-low temperature hydraulic oil.

[0070] Example 10

[0071] Prepare hydraulic oil, the specific steps are as follows:

[0072] 70 kg of amyl oleate and 26 kg of PAO2 were added to a reactor, mechanically stirred and heated to 70 ° C; then 5.53 kg of the homemade tackifier prepared in Example 3, 3 kg of VISCOPLEX 0-051 viscosity index improver from EVONIK, Germany, 0.053 kg of 4,4'-methylenebis(2,6-di-tert-butylphenol), 1.07 kg of triphenyl phosphate, 0.011 kg of alkenyl succinate, 0.0053 kg of metal deactivator T553, 1.07 kg of VISCOPLEX 1-148 pour point depressant from EVONIK, Germany, 0.0053 kg of polyethylene glycol, and 0.0011 kg of blue dye were added in sequence, and stirred at 70 ° C for 2 hours to obtain a semi-finished hydraulic oil. When the oil product is cooled to about 60 ° C, it is filtered and naturally cooled to room temperature to obtain an ultra-low temperature hydraulic oil.

[0073] Embodiment 11

[0074] Prepare hydraulic oil, the specific steps are as follows:

[0075] 70 kg of trimethylolpropane trioleate and 26 kg of PAO2 were added to the reactor, mechanically stirred and heated to 70 ° C; then 18 kg of the homemade tackifier prepared in Example 3, 6.3 kg of VISCOPLEX 0-051 viscosity index improver from Evonik, 0.2 kg of 4,4'-methylenebis(2,6-di-tert-butylphenol), 0.16 kg of N-phenyl-α-naphthylamine, 0.12 kg of triethyl phosphate, 0.24 kg of alkenyl succinate, 0.12 kg of metal deactivator T553, 3.15 kg of VISCOPLEX pour point depressant from Evonik, Germany were added in sequence. 1-148, 3.65kg polyethylene glycol and 0.006kg blue dye are stirred at 70℃ for 2 hours to obtain semi-finished hydraulic oil. When the oil product is cooled to about 60℃, it is filtered and naturally cooled to room temperature to obtain ultra-low temperature hydraulic oil.

[0076] Comparative Example 1

[0077] It uses the French Nyco Hydraunycoil FH51 hydraulic oil on the market, which meets the standard of MIL-PRF-5606H.

[0078] Comparative Example 2

[0079] It uses Royco 719 ultra-low temperature hydraulic oil from Royal Company in the United States on the market, which meets the standard of MIL-PRF-81019.

[0080] The hydraulic oils of Examples 4-9 and Comparative Examples 1-2 were tested for kinematic viscosity at different temperatures according to GB / T265, flash point according to GB / T3536, pour point according to GB / T3535, acid value according to GB / T7304, rubber expansion rate according to SH / T0691, evaporation loss according to GB / T7325, copper corrosion according to GB / T5096, shear stability according to SH / T0505, and biodegradability according to GB / T21856. The test results are shown in the following table:

[0081]

[0082] The ultra-low temperature degradable hydraulic oil of the present invention is prepared by the synergistic effect of various components, especially preferably suitable base oil and high shear stable viscosity index improver, and preferably antioxidant, extreme pressure anti-wear agent, rust inhibitor, metal deactivator, pour point depressant and anti-foaming agent, adding blue dye agent, and adopting appropriate preparation process technology. The hydraulic oil of the present invention has good viscosity-temperature performance, low temperature flow performance, antioxidant stability, anti-wear and anti-corrosion properties, degradability, etc., and meets the requirements of the rapid development of hydraulic systems of current aviation equipment. Compared with similar products on the market, the low temperature viscosity and shear stability performance are better, and it has good degradability, and has achieved good technical effects.

[0083] In the description of the specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0084] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. An ultra-low temperature biodegradable aviation hydraulic oil, characterized in that: The raw materials include the following by mass fraction: 79-90% base oil, 8-20% viscosity index improver, 0.05-0.3% antioxidant, 0.1-1% extreme pressure anti-wear agent, 0.01-0.2% rust inhibitor, 0.005-0.1% metal deactivator, 0.1-1% pour point depressant, 0.005-0.03% anti-foaming agent, 0.001-0.005% blue dye agent; Wherein, the viscosity index improver is one or both of a polymethacrylate viscosity index improver and a homemade tackifier; The homemade tackifier is prepared by the following steps: (1) reacting oleic acid, isooctyl alcohol and concentrated sulfuric acid at 80-120° C. for 4-6 hours, removing impurities and drying to obtain an esterification product; (2) adding hydrogen peroxide to the esterification product obtained in step (1), reacting at 40 to 100° C. for 6 to 12 hours, removing impurities, and drying to obtain an epoxidation product; (3) adding 0.5-5% of a ring-opening polymerization catalyst to the epoxidation product obtained in step (2), reacting at 90-150° C. for 4-6 hours to obtain a high-viscosity substance, i.e., a homemade tackifier.

2. The ultra-low temperature degradable aviation hydraulic oil according to claim 1, characterized in that: In the step (1), the molar ratio of oleic acid to isooctyl alcohol is 1:1-5; in the step (2), the molar ratio of the esterification product to hydrogen peroxide is 1:1-10; in the step (2), the concentration of hydrogen peroxide is 30%; in the step (3), the catalyst is one or more of tertiary amine, tert-butyl alcohol, and potassium hydroxide.

3. The ultra-low temperature biodegradable aviation hydraulic oil according to claim 1, characterized in that: The base oil is one or both of synthetic ester and polyalphaolefin.

4. The ultra-low temperature degradable aviation hydraulic oil according to claim 3, characterized in that: The synthetic ester is one or more of monoester, diester and polyol ester.

5. The ultra-low temperature degradable aviation hydraulic oil according to claim 1, characterized in that: The antioxidant is one or more of 2,6-di-tert-butyl-p-methylphenol, 4,4'-methylenebis(2,6-di-tert-butylphenol), N-phenyl-α-naphthylamine, and N,N-di-sec-butyl-p-phenylenediamine; the extreme pressure anti-wear agent is one or more of tricresyl phosphate, triphenyl phosphate, triethyl phosphate, tributyl phosphate, di-n-butyl phosphite, triphenyl thiophosphate, dialkyl dithiophosphate, and butyl triphenyl thiophosphate.

6. The ultra-low temperature biodegradable aviation hydraulic oil according to claim 1, characterized in that: The rust inhibitor is one or more of dodecenylsuccinic acid, alkenylsuccinate, sorbitan oleate, and sodium petroleum sulfonate.

7. The ultra-low temperature biodegradable aviation hydraulic oil according to claim 1, characterized in that: The metal deactivator is one or more of benzotriazole derivatives, heterocyclic derivatives and thiadiazole derivatives.

8. The ultra-low temperature biodegradable aviation hydraulic oil according to claim 7, characterized in that: The metal deactivator is one or more of T551, T553 and T561.

9. The ultra-low temperature biodegradable aviation hydraulic oil according to claim 1, characterized in that: The pour point depressant is one or more polymethacrylate pour point depressants; the antifoaming agent is one or more organic silicon antifoaming agent, polyether antifoaming agent, polyether modified silicon antifoaming agent.

10. The method for preparing an ultra-low temperature degradable aviation hydraulic oil according to claim 1, characterized in that: The following steps are involved: (1) Stir and heat the base oil to 70-80° C. in a reactor; (2) adding a viscosity index improver, a pour point depressant, an antioxidant, an extreme pressure anti-wear agent, a rust inhibitor, a metal deactivator, an anti-foaming agent and a blue dye, stirring at 70° C. for 2 h, and curing at room temperature to obtain a semi-finished hydraulic oil; (3) The semi-finished hydraulic oil after temperature curing is cooled to 60°C, positive pressure filtered, and naturally cooled to room temperature to obtain the finished hydraulic oil.

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