A high-temperature antioxidant for lubricating oil, a lubricating oil and a preparation method thereof

Abstract

This application relates to the field of lubricating oil antioxidants, and specifically discloses a high-temperature antioxidant for lubricating oil, a lubricating oil and a preparation method thereof. A high-temperature antioxidant for lubricating oil, calculated by weight percentage, is composed of the following components: 10-50% of diisooctyl diphenylamine; 25-40% of sulfur ether-modified phenolic antioxidant; the balance is a mixture composed of one or two of hindered phenolic antioxidants and phosphite esters. The high-temperature antioxidant for lubricating oil of this application can be used to prepare lubricating oil, improve the oxidation stability of lubricating oil, extend the oxidation induction period, and significantly improve the high-temperature stability of lubricating oil, so that the high-temperature evaporation amount of lubricating oil is reduced.

Description

Technical Field

[0001] The present application relates to the field of lubricant antioxidants, and more specifically, it relates to a high-temperature antioxidant for lubricants, a lubricant, and a preparation method thereof. Background Art

[0002] During the use and storage of lubricants, the ability to resist oxidative degradation and deterioration under the catalytic action of heat, oxygen, and metal is called the antioxidant stability of the lubricant, which is an important index for evaluating the quality of lubricants. Therefore, in order to improve the antioxidant property of lubricants, antioxidants are generally added.

[0003] Chain oil is one type of lubricant, mainly used for lubricating chains at high temperatures, reducing the noise during chain operation, and playing roles such as anti-corrosion and anti-rust for chains, and is widely used in precision instruments, such as heat setting machines, automotive factory painting lines, and printing setting machines.

[0004] Generally, the temperature in a high-temperature chain drive system will be maintained in a relatively high temperature range of 210 - 230 °C for a long time, and some even reach up to 250 °C. Most of the current chain oils on the market have poor high-temperature performance, resulting in large evaporation losses. Therefore, developing an antioxidant to improve the high-temperature stability of lubricants and reduce the evaporation amount has broad application prospects. Summary of the Invention

[0005] In order to improve the high-temperature stability of lubricants and reduce the evaporation amount, the present application provides a high-temperature antioxidant for lubricants, a lubricant, and a preparation method thereof.

[0006] In the first aspect, the present application provides a high-temperature antioxidant for lubricants, adopting the following technical solution:

[0007] A high-temperature antioxidant for lubricants, by weight percentage, consists of the following components:

[0008] Diisooctyl diphenylamine 10 - 50%;

[0009] Sulfide-modified phenolic antioxidant 25 - 40%;

[0010] The balance is a mixture composed of one or two of hindered phenolic antioxidants and phosphite esters.

[0011] By adopting the above technical solution, thio-phenols and amines are used as the main antioxidants to exert the main antioxidant effect. At the same time, hindered phenol antioxidants, phosphite antioxidants or their compound are used as co-antioxidants to further enhance the antioxidant efficacy. Through the above compounding, the antioxidant components work synergistically, enabling the antioxidant prepared in this application to have excellent antioxidant performance and outstanding thermal stability, prolonging the oxidation induction period and reducing the evaporation loss of lubricating oil at high temperatures. The performance of the antioxidant is similar to that of high-end antioxidants, but the components are simpler and more easily available.

[0012] The antioxidant prepared in this application is added to the base oil, and the performance of the obtained lubricating oil is tested. When only two of diisooctyl diphenylamine, sulfur ether-modified phenolic antioxidant and phosphite are used as the antioxidant, the oxidation induction period of the prepared lubricating oil at 240 °C is only 14.89 - 16.06 min, the evaporation amount in 9 h is as high as 3.45 - 3.66%, and the evaporation amount in 18 h is as high as 6.59 - 6.74%. The performance of the lubricating oil is significantly insufficient. However, when the antioxidant uses the compound of diisooctyl diphenylamine, sulfur ether-modified phenolic antioxidant and phosphite, the oxidation induction period of the prepared lubricating oil at 240 °C is as high as 25.43 min, reducing its evaporation amount in 9 h to 2.89% and the evaporation amount in 18 h to 5.61%.

[0013] Optionally, the hindered phenol antioxidant is one or a mixture of two of pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and N,N-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexanediamine.

[0014] Optionally, the phosphite is one or a mixture of two of tris[2,4-di-tert-butylphenyl]phosphite and bis(2,4-dicumylphenyl)pentaerythritol diphosphite.

[0015] By adopting the above technical solution, by preferably using hindered phenol antioxidants and phosphites and compounding them with thio-phenols and amines, the antioxidant has a more excellent antioxidant effect, and at the same time, the oxidation induction period of the lubricating oil is prolonged and the evaporation loss at high temperatures is further reduced.

[0016] Optionally, by weight percentage, it consists of the following components:

[0017] Diisooctyl diphenylamine 15 - 30%;

[0018] Sulfur ether-modified phenolic antioxidant 25 - 35%;

[0019] Tris[2,4-di-tert-butylphenyl]phosphite 25 - 35%;

[0020] Pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] balance.

[0021] By adopting the above technical scheme, using tris(2,4-di-tert-butylphenyl) phosphite and pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and compounding with thioether phenols and amines, it is found that when the usage amounts of the four are within the above ranges, they can work synergistically, significantly prolonging the oxidation induction period of the lubricating oil at high temperature and reducing the evaporation amount at high temperature.

[0022] The antioxidant prepared in this application is added to the base oil, and the performance of the obtained lubricating oil is tested. When the usage amounts of the four are outside the above ranges, the oxidation induction period of the prepared lubricating oil at 240 °C is maintained at 26.75 - 26.77 min, its 9-hour evaporation amount is maintained at 2.76 - 2.80%, and its 18-hour evaporation amount is maintained at 5.57 - 5.59%, which is similar to the performance of the compound antioxidant using only phosphite, thioether phenols, and amines, indicating that the four do not have any impact on the performance of the lubricating oil. When the usage amounts of the four are within the above ranges, the oxidation induction period of the prepared lubricating oil at 240 °C is increased to 32.27 - 33.58 min, the 9-hour evaporation amount is reduced to 2.32 - 2.43%, and the 18-hour evaporation amount is reduced to 4.88 - 5.13%. The prepared antioxidant significantly improves the performance of the lubricating oil.

[0023] Optionally, by weight percentage, it consists of the following components:

[0024] Diisooctyl diphenylamine 35 - 50%;

[0025] Thioether-modified phenolic antioxidant 25 - 35%;

[0026] Bis(2,4-dicumylphenyl)pentaerythritol diphosphite balance.

[0027] By adopting the above technical scheme, using bis(2,4-dicumylphenyl)pentaerythritol diphosphite, and compounding with thioether phenols and amines, it is found that only when the usage amounts of the three are within the above ranges, they can work synergistically, significantly prolonging the oxidation induction period of the lubricating oil at high temperature and significantly reducing the evaporation amount of the lubricating oil at high temperature.

[0028] The antioxidant prepared in this application was added to the base oil, and the performance of the obtained lubricating oil was tested. When the usage amounts of the three were outside the above ranges, the oxidation induction period of the lubricating oil at 240°C was maintained at 26.73 min, its 9-hour evaporation loss was maintained at 2.82%, and its 18-hour evaporation loss was maintained at 5.62%. The performance was similar to that of the antioxidant compounded with only ST-626, thioether phenols, and amines, indicating that the three did not have any impact on the performance of the lubricating oil. When the usage amounts of the three were within the above ranges, the oxidation induction period of the prepared lubricating oil at 240°C was increased to 32.58 - 33.35 min, the 9-hour evaporation loss was reduced by 2.36 - 2.46%, and the 18-hour evaporation loss was reduced by 5.05 - 5.18%. The prepared antioxidant significantly improved the performance of the lubricating oil.

[0029] Optionally, by weight percentage, it consists of the following components:

[0030] Diisooctyl diphenylamine 10 - 15%;

[0031] Thioether-modified phenolic antioxidant 25 - 40%;

[0032] Bis(2,4-dicumylphenyl)pentaerythritol diphosphite 25 - 35%;

[0033] Pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] 5 - 20%;

[0034] N,N-Bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexanediamine the balance.

[0035] By adopting the above technical solution, using bis(2,4-dicumylphenyl)pentaerythritol diphosphite, pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], N,N-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexanediamine, and compounding with thioether phenols and amines, it was found that only when the usage amounts of the five were within the above ranges, they could work synergistically, significantly prolonging the oxidation induction period of the lubricating oil at high temperature and significantly reducing the evaporation loss of the lubricating oil at high temperature.

[0036] The antioxidant prepared in this application is added to the base oil, and the performance of the obtained lubricating oil is tested. When the usage amounts of the three are outside the above range, the oxidation induction period of the prepared lubricating oil at 240 °C is maintained at 26.80 - 26.81 min, its 9-hour evaporation amount is maintained at 2.72 - 2.74%, and the 18-hour evaporation amount is maintained at 5.50 - 5.52%. The performance is similar to that of the composite antioxidant using only ST-626, thioether phenols, and amines, indicating that the three do not have any impact on the performance of the lubricating oil. When the usage amounts of the five are within the above range, the oxidation induction period of the prepared lubricating oil at 240 °C is increased to 33.20 - 34.26 min, the 9-hour evaporation amount is reduced to 2.02 - 2.38%, and the 18-hour evaporation amount is reduced to 4.67 - 4.98%. The prepared antioxidant significantly improves the performance of the lubricating oil.

[0037] In a second aspect, this application provides a lubricating oil, adopting the following technical solution:

[0038] A lubricating oil includes a base oil and the above antioxidant, and the addition amount of the antioxidant is 1.2 - 1.8%.

[0039] By adopting the above technical solution, as the usage amount of the antioxidant increases, the oxidation induction period of the lubricating oil is extended. When the addition amount of the antioxidant is within the above range, the oxidation induction period of the prepared lubricating oil is in a better range; when it is outside the above range, further increasing the usage amount of the antioxidant may cause a significant increase in the average particle size of the lubricating oil after use due to excessive precipitation of the antioxidant.

[0040] Preferably, it further includes alkaline pectinase, and the addition amount of the alkaline pectinase is 0.5 - 0.7%.

[0041] By adopting the above technical solution, using alkaline pectinase has the following two effects:

[0042] (1) Increase the viscosity of the antioxidant, improve its compatibility with the base oil, improve the effect of the antioxidant, make the lubricating oil have better antioxidant stability, and lower high-temperature evaporation amount; when the lubricating oil prepared in this application is tested for performance, compared with when alkaline pectinase is not added, the 9-hour evaporation amount of the lubricating oil is reduced by 0.12 - 0.26%, and the 18-hour evaporation amount is further reduced by 0.22 - 0.38%.

[0043] (2) During the use of the oil fluid, fibrous particles will be generated due to decay and accumulate in the oil fluid system, affecting the performance of the chain. By adding alkaline pectinase, it can decompose and remove the colloid on the fiber surface, reducing the formation of particles due to fiber aggregation. When the lubricating oil prepared in this application was subjected to performance testing, the average particle size difference before and after use of the lubricating oil without adding alkaline pectinase was as high as 15.355 μm. For the lubricating oil added with alkaline pectinase, the average particle size difference before and after use was significantly reduced to 10.805 - 10.843 μm.

[0044] Thirdly, this application provides a preparation method of lubricating oil, adopting the following technical solution:

[0045] A preparation method of lubricating oil includes the following steps:

[0046] S1. Add alkaline pectinase to the antioxidant and stir to mix to obtain a mixed solution;

[0047] S2. Add the mixed solution to the base oil and disperse it by ultrasonic wave to obtain the lubricating oil.

[0048] By adopting the above technical solution, the process steps are fewer, and the preparation process of the lubricating oil is simple and efficient.

[0049] Moreover, the prepared lubricating oil has good antioxidant stability, extremely low evaporation loss at high temperature, and strong high-temperature stability.

[0050] In summary, this application has the following beneficial effects:

[0051] 1. By controlling the compounding of antioxidant components in this application, the antioxidant components work synergistically, so that the prepared antioxidant has both excellent antioxidant performance and outstanding thermal stability, prolonging the induction period of the lubricating oil and reducing the evaporation loss of the lubricating oil at high temperature;

[0052] 2. By controlling the usage amounts of the antioxidant components in this application, the components of the antioxidant work synergistically, further improving the antioxidant property and high-temperature stability of the lubricating oil, prolonging the oxidation induction period of the lubricating oil, and reducing the high-temperature evaporation amount; 3. The lubricating oil of this application, by adding alkaline pectinase, on the one hand, improves the compatibility between the antioxidant and the base oil, promotes the antioxidant to better exert its effect, and further reduces the high-temperature evaporation amount of the lubricating oil; on the other hand, during the use of the lubricating oil, it continuously decomposes the fiber colloid, reduces the occurrence of fiber aggregation into particles, reduces blockage, and improves the quality of the lubricating oil. Specific Embodiments

[0053] The following further elaborates on this application in combination with embodiments.

[0054] Preparation Examples

[0055] Preparation Example 1-17, Comparative Preparation Example 1-5

[0056] A lubricating oil high-temperature antioxidant, wherein the components and their corresponding weights are shown in Table 1, and the components are added into a mixer and stirred for 45 minutes to obtain;

[0057] Among them, the brand of diisooctyl diphenylamine is BASF (China) Co., Ltd., and the brand is IRGANOX L01; the brand of thioether modified phenolic antioxidant is BASF (China) Co., Ltd., and the brand is IRGANOX L115; bis(2,4-di-tert-butylphenol) pentaerythritol diphosphite, branded by Shanghai Petrochemical Senior Chemical Technology Co., Ltd., with the trademark ST-626; tris[2,4-di-tert-butylphenyl] phosphite, branded by Shanghai Petrochemical Senior Chemical Technology Co., Ltd., with the trademark ST-168; pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, branded by Shanghai Petrochemical Senior Chemical Technology Co., Ltd., with the trademark ST-1010; bis(2,4-dicumylphenyl) pentaerythritol diphosphite, branded by Shanghai Petrochemical Senior Chemical Technology Co., Ltd., with the trademark ST-9228; N,N-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine, branded by Shanghai Petrochemical Senior Chemical Technology Co., Ltd., with the trademark ST-1098;

[0058] In Table 1, only the brand names are used to replace the ingredients.

[0059] Table 1-1 Components and their weights (kg) in Preparation Examples 1-3 and Comparative Preparation Examples 1-5

[0060]

[0061] Table 1-2 Components and weights (kg) in Preparation Example 4-17

[0062]

[0063]

[0064] Example

[0065] Examples 1-3, Comparative Examples 1-2

[0066] A lubricating oil is prepared by conventionally mixing a base oil and an antioxidant, wherein the base oil is obtained from Shanxi Feilite Trading Co., Ltd., industrial closed gear oil L-CKC 150, and the antioxidant is prepared according to Preparation Example 1;

[0067] The usage of base oil and antioxidant is as follows:

[0068] Example 1: 98.8 kg of base oil and 1.2 kg of antioxidant.

[0069] Example 2: 98.5 kg of base oil and 1.5 kg of antioxidant.

[0070] Example 3: 98.2 kg of base oil and 1.8 kg of antioxidant.

[0071] Comparative Example 1: 99.2 kg of base oil and 0.8 kg of antioxidant.

[0072] Comparative Example 2: 98.0 kg of base oil and 2 kg of antioxidant.

[0073] Examples 4 - 19

[0074] A lubricating oil, different from Example 2 in that the usage of the antioxidant is shown in Table 2.

[0075] Table 2 Usage of antioxidant in Examples 4 - 19

[0076] Example 2 4 5 6 7 8 9 10 11 Preparation Example of Antioxidant 1 2 3 4 5 6 7 8 9 Example 12 13 14 15 16 17 18 19 \ Preparation Example of Antioxidant 10 11 12 13 14 15 16 17 \ Comparative Example 3 4 5 6 7 \ \ \ \ Comparative Preparation Example of Antioxidant 1 2 3 4 5 \ \ \ \

[0077] Examples 20 - 23

[0078] A lubricating oil, different from Example 17 in that the usage amounts of each component are shown in Table 3 and are obtained by the following steps:

[0079] S1. Add alkaline pectinase to the antioxidant, stir and mix at 15 r / min for 1 h to obtain a mixed solution;

[0080] S2. Add the mixed solution to the base oil and disperse it by ultrasonic wave for 20 min to obtain the product.

[0081] Table 3 Components and their weights (kg) in Examples 17, 20 - 23

[0082]

[0083] Among them, the base oil and antioxidant used in this example are the same as those used in Example 17; the alkaline pectinase is from Novozymes (China) Biotechnology Co., Ltd., model BIOPREP FUSION.

[0084] Performance testing

[0085] Perform the following performance testing on the lubricating oils prepared in the examples and comparative examples, and record the test results in Table 4.

[0086] Testing method

[0087] 1. Oxidation induction period: According to the standard SH / T 0719 - 2002, test the oxidation induction period of the lubricating oil at 240 °C.

[0088] 2. High-temperature evaporation: According to GB / T 7325-1987, the evaporation of the lubricating oil is detected under the conditions of 250°C for 9 hours and 250°C for 18 hours.

[0089] 3. Particle size: According to the method described in "Research on Detection Methods of Lubricating Oil Particle Size Distribution" by Chen Yuhui et al., the lubricating oil prepared in the examples and comparative examples (i.e., the lubricating oil before use), and then after adding the lubricating oil to the engine and running (i.e., the lubricating oil after use) are detected. The average particle diameter of the same lubricating oil before and after use is recorded, and the difference is calculated. The smaller the difference indicates that the growth rate of the particle size of the lubricating oil after use is lower and the quality is better.

[0090] Table 4 Performance test results

[0091]

[0092]

[0093] In Example 1, due to the use of the antioxidant prepared in Preparation Example 1, since there is a synergistic effect among diisooctyl diphenylamine, sulfur ether modified phenolic antioxidant, and phosphite, the oxidation induction period of the lubricating oil at 240°C is significantly extended to 25.43 minutes, and the high-temperature stability of the lubricating oil is improved, with its 9-hour evaporation being only 2.89% and 18-hour evaporation being only 5.61%.

[0094] In Comparative Examples 5-7, the antioxidants prepared in the comparative preparation examples are used respectively. The antioxidant is only composed of two of diisooctyl diphenylamine, sulfur ether modified phenolic antioxidant, and phosphite, resulting in the oxidation induction period of the prepared lubricating oil at 240°C being only 14.89 - 16.06 minutes, 9-hour evaporation being as high as 3.45 - 3.66%, and 18-hour evaporation being as high as 6.59 - 6.74%. The performance of the lubricating oil is significantly insufficient in all aspects.

[0095] Combined with Table 4, comparing Examples 1-3 and Comparative Examples 1-2, it can be seen that as the dosage of the antioxidant increases, the oxidation induction period of the lubricating oil can be extended and the evaporation can be reduced. However, when the antioxidant is in excess, the above-mentioned gains begin to become insignificant, and the difference in average particle diameter increases significantly. Considering all factors, the dosage of the antioxidant in the lubricating oil should be within the range of Examples 1-3; comparing Examples 2, 4, 5 and Comparative Examples 3-4, it can be seen that the dosage of each component of the antioxidant should be within the range of Examples 2, 4, 5; and Example 2 is the best example.

[0096] The differences between Examples 6 - 10 and Example 2 are that a mixture of ST-168 and ST-1010 is used instead of ST-626. Combining Table 4, comparing Example 6 and Example 2, the various properties of the lubricating oil are similar, indicating that within the dosage range of Example 2, using a mixture of ST-168 and ST-1010 instead of ST-626 does not directly affect the various properties of the lubricating oil.

[0097] When the usage amounts of ST-168, ST-1010, L01, and L115 are within the ranges of Examples 7 - 9, compared with Example 2, the properties of the lubricating oil change abruptly. Its oxidation induction period at 240°C increases by 6.1 - 7.3 min, the 9-hour evaporation loss decreases by 0.32 - 0.43%, and the 18-hour evaporation loss decreases by 0.46 - 0.65%, which can significantly improve the various properties of the lubricating oil.

[0098] The differences between Examples 11 - 14 and Example 2 are that ST-9228 is used instead of ST-168. Combining Table 4, comparing Example 11 and Example 2, the various properties of the lubricating oil are similar, indicating that within the dosage range of Example 2, using ST-9228 instead of ST-168 does not directly affect the various properties of the lubricating oil.

[0099] When the usage amounts of ST-9228, L01, and L115 are within the ranges of Examples 12 - 14, compared with Example 2, the properties of the lubricating oil change abruptly. Its oxidation induction period at 240°C increases by 5.8 - 6.57 min, the 9-hour evaporation loss decreases by 0.29 - 0.39%, and the 18-hour evaporation loss decreases by 0.35 - 0.48%, which can significantly improve the various properties of the lubricating oil.

[0100] The differences between Examples 15 - 19 and Example 2 are that a mixture of ST-9228 and ST-1010 is used instead of ST-168. Combining Table 4, when the usage amounts of ST-9228, ST-1010, L01, and L115 are within the ranges of Examples 16 - 18, compared with Example 2, the properties of the lubricating oil change abruptly. Its oxidation induction period at 240°C increases by 6.42 - 7.48 min, the 9-hour evaporation loss decreases by 0.37 - 0.73%, and the 18-hour evaporation loss decreases by 0.55 - 0.86%, which can significantly improve the various properties of the lubricating oil. Comparing Examples 15, Example 19, and Example 2, the various properties of the lubricating oil are similar, indicating that outside the ranges of Examples 16 - 18, it does not directly affect the various properties of the lubricating oil.

[0101] The difference between Examples 20-23 and Example 17 is that the lubricating oil further contains alkaline pectinase. Combining Table 4, the 9h evaporation loss of the lubricating oil is further reduced by 0.12-0.26%, and the 18h evaporation loss is further reduced by 0.22-0.38%. The average particle size difference is significantly reduced to 10.805-10.843μm;

[0102] The reason may be that the use of alkaline pectinase improves the compatibility between the antioxidant and the base oil and the antioxidant property of the lubricating oil, thereby reducing the high-temperature evaporation loss of the lubricating oil. On the other hand, alkaline pectinase decomposes and removes the colloid on the fiber surface, reducing the occurrence of fiber agglomeration to form microparticles, and further reducing the growth rate of the detectable fiber particle size in the lubricating oil.

[0103] This specific embodiment is only an explanation of the present application, and it does not limit the present application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A lubricating oil, characterized in that: Including base oil and antioxidant, alkaline pectinase, The amount of antioxidant added is 1.2-1.8%; the amount of alkaline pectinase added is 0.5-0.7%; The antioxidant is composed of the following components by weight percentage: Diisooctyldiphenylamine 10-50%; Thioether modified phenolic antioxidant 25-40%; The balance is one or a mixture of hindered phenol antioxidant and phosphite.

2. The lubricating oil according to claim 1, characterized in that: The hindered phenol antioxidant is one or a mixture of two of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentaerythritol ester and N,N-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexanediamine.

3. The lubricating oil according to claim 1, wherein: The phosphite is one or a mixture of tris[2,4-di-tert-butylphenyl]phosphite and bis(2,4-dicumylphenyl)pentaerythritol diphosphite.

4. A lubricating oil according to any one of claims 1 to 3, characterized in that: The antioxidant is composed of the following components by weight percentage: Diisooctyldiphenylamine 15-30%; Thioether modified phenolic antioxidant 25-35%; Tris[2,4-di-tert-butylphenyl]phosphite 25-35%; The balance is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

5. A lubricating oil according to any one of claims 1 to 3, characterized in that: The antioxidant is composed of the following components by weight percentage: Diisooctyldiphenylamine 35-50%; Thioether modified phenolic antioxidant 25-35%; Bis(2,4-dicumylphenyl)pentaerythritol diphosphite balance.

6. A lubricating oil according to any one of claims 1 to 3, characterized in that: The antioxidant is composed of the following components by weight percentage: Diisooctyldiphenylamine 10-15%; Thioether modified phenolic antioxidant 25-40%; Bis(2,4-dicumylphenyl)pentaerythritol diphosphite 25-35%; Pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] 5-20%; N,N-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexanediamine balance.

7. A method for preparing the lubricating oil according to claim 6, characterized in that: The following steps are involved: S1. adding alkaline pectinase to the antioxidant, stirring and mixing to obtain a mixed solution; S2. Add the mixed liquid to the base oil and disperse it by ultrasonic.

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