Lubricating oil for a transmission and method for producing the same

Abstract

The application discloses a kind of lubricating oil for transmission and preparation method thereof, the lubricating oil for transmission, including raw material and its mass percentage as follows: extreme pressure agent 0.6%~1%, detergent 0.3%~0.5%, dispersant 6%~8%, antioxidant 0.5%~0.6%, rust inhibitor 0.1%~0.2%, metal passivator 0.01%~0.06%, stick agent 2~5% and the balance of base oil;Wherein, the extreme pressure agent includes component A, component A includes quaternary phosphonium cation a and phosphate anion b, the structure of quaternary phosphonium cation a and the phosphate anion b is as shown below: formula a n=8~16 and n is integer.In the lubricating oil for transmission according to the application, the performance of load-carrying capacity and bare copper corrosion protection can be balanced, and good material compatibility is obtained, and the problem of strong bare copper corrosion and poor material compatibility caused by high load of traditional lubricating oil is solved.

Description

Technical Field

[0001] This invention relates to the field of lubricating oil technology, and in particular to a lubricating oil for transmissions and its preparation method. Background Technology

[0002] In related technologies, the global development of new energy vehicles mainly focuses on pure electric vehicles and hybrid electric vehicles. Traditional transmission oil additives may damage the transmission system of electric vehicles. For example, a certain amount of active sulfur can corrode exposed copper or copper alloy components and precision circuits in motors. The protection of shafts and gears by lubricating oil is usually achieved through extreme pressure agents. Extreme pressure refers to the load-bearing capacity of lubricating oil under heavy loads and boundary lubrication. As the load increases, the thickness of the oil film between metal surfaces gradually decreases. When the load increases to a certain level, the lubricating oil film is destroyed by the peaks of the metal surface, resulting in localized direct contact between the metal surfaces. This type of lubrication is called boundary lubrication. When metal surfaces are subjected to high loads, a large number of metal surfaces come into direct contact, generating a large amount of heat. The film formed by anti-wear agents is also destroyed, no longer protecting the metal surface. For example, additives can react chemically with the metal surface to form a chemical protective film, providing lubrication and preventing scratches or even welding of the metal surface. This harsh boundary lubrication is usually called extreme pressure lubrication, and the additives are called extreme pressure additives. Among them, sulfur-based extreme pressure additives have a wide range of applications, but they are highly corrosive to metals, especially copper. In heavy-duty electric drive systems, lubricating oil requires more extreme pressure additives to protect the gears. However, the increasing use of traditional sulfur and phosphorus extreme pressure additives can corrode the exposed copper in the motor windings, leading to motor failure. Therefore, there is an urgent need for a low-activity sulfur lubricating oil to protect the gears of heavy-duty trucks while preventing corrosion of the exposed copper in the oil-cooled motor windings. Summary of the Invention

[0003] The present invention aims to at least solve one of the technical problems existing in the prior art. Therefore, one object of the present invention is to provide a transmission lubricant with good lubrication performance and high safety.

[0004] Another object of the present invention is to provide a method for preparing a lubricating oil for transmissions.

[0005] According to an embodiment of the first aspect of the present invention, the present invention provides a transmission lubricant comprising the following raw materials and their mass percentages as follows: extreme pressure agent 0.6% to 1%, detergent 0.3% to 0.5%, dispersant 6% to 8%, antioxidant 0.5% to 0.6%, rust inhibitor 0.1% to 0.2%, metal passivator 0.01% to 0.06%, viscosity index agent 2% to 5%, and the balance being base oil;

[0006] The extreme pressure agent includes component A, which comprises a quaternary phosphonium cation a and a phosphate anion b. The structures of the quaternary phosphonium cation a and the phosphate anion b are shown below:

[0007]

[0008] In formula a, n = 8 to 16 and n is an integer.

[0009] According to a specific embodiment of the transmission lubricant of the present invention, the extreme pressure agent component A includes a quaternary phosphonium cation a and a phosphate anion b. The phosphate anion b readily loses its alkyl group. After losing the alkyl group, the phosphate can react with metal or metal friction debris to form a phosphate friction film on the metal surface. This phosphate friction film prevents direct contact between surface roughness points and the transmission, thus reducing friction and preventing wear. Furthermore, it has the property of passivating metal activity, improving the corrosion resistance of the lubricant. This significantly enhances the protective effect of the lubricant on copper wires in the electric drive system. The quaternary phosphonium cation a includes an alkyl group with side chains. The alkyl group and its side chains can increase the compatibility between the components in the lubricant. Specifically, it can improve the oil solubility of the additives in the lubricant. Typically, the alkyl chain length is greater than 6-8 carbon atoms. Thus, the transmission lubricant of the present invention can balance load-bearing capacity and bare copper corrosion protection performance, and has good material compatibility, solving the problems of strong bare copper corrosion and poor material compatibility caused by traditional lubricants under high load conditions.

[0010] According to some embodiments of the present invention, the raw materials and their mass percentages are as follows: extreme pressure agent 0.8%, detergent 0.3%, dispersant 6%, antioxidant 0.5%, rust inhibitor 0.1%, metal passivator 0.04%, viscosity index enhancer 3.5%, and base oil 88.76%.

[0011] According to some embodiments of the present invention, the molar ratio of the quaternary phosphonium cation a to the phosphate anion b is 1:1.

[0012] According to some embodiments of the present invention, the quaternary phosphonium cation a comprises an alkyl group with a side chain.

[0013] According to some embodiments of the present invention, the preparation method of the extreme pressure agent includes the following steps: first, 30-40 parts by weight of component A are uniformly dispersed in 40-50 parts by weight of pentaerythritol, and ultrasonically dispersed for 30-40 minutes. Then, the mixture is stirred at 30-40°C, 10-30 parts by weight of di-n-butyl phosphite are added, and the mixture is stirred for 30-40 minutes. Finally, the supernatant is collected by centrifugation to obtain the extreme pressure agent.

[0014] According to some embodiments of the present invention, the base oil comprises at least one of mineral oil and synthetic oil; and / or

[0015] The adhesive includes at least one of polymethyl methacrylate, dispersed polymethyl methacrylate, styrene-diene copolymer, and styrene-isoprene copolymer; and / or

[0016] The detergent is a sulfonate and / or a phenolate; and / or

[0017] The dispersant is monosuccinimide and / or boronized succinimide.

[0018] According to some embodiments of the present invention, the antioxidant includes at least one of amine antioxidants and phenolic antioxidants.

[0019] According to some embodiments of the present invention, the rust inhibitor includes at least one of metal sulfonates, alkylamines, dodecenylsuccinic acid, and N,N3-bis(benzotriazolylmethylene)laurylamine.

[0020] According to some embodiments of the present invention, the metal passivating agent includes at least one of toluenetriazole derivatives and thiadiazole derivatives.

[0021] According to an embodiment of the second aspect of the present invention, the present invention provides a method for preparing a transmission lubricant according to an embodiment of the first aspect of the present invention, comprising the following steps: heating a base oil to 40°C to 50°C according to the stated mass percentage; adding a viscosity index enhancer, detergent, dispersant, antioxidant, rust inhibitor, metal passivator, and extreme pressure agent to the base oil under continuous stirring; stirring for 20 min to 40 min; cooling to 25°C to 35°C; continuing to stir for 20 min to 40 min; and filtering to obtain the transmission lubricant.

[0022] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Detailed Implementation

[0023] The embodiments of the present invention are described in detail below. These embodiments are exemplary, and the transmission lubricant of a specific embodiment of the present invention is described below.

[0024] The transmission lubricant comprises the following raw materials and their weight percentages: extreme pressure agent 0.6%–1%, detergent 0.3%–0.5%, dispersant 6%–8%, antioxidant 0.5%–0.6%, rust inhibitor 0.1%–0.2%, metal passivator 0.01%–0.06%, viscosity index improver 2%–5%, and the balance being base oil. With this configuration, the transmission lubricant of the present invention comprises a suitable weight percentage of base oil and additives, such as extreme pressure agents, detergents, and dispersants, which ensures the lubricating and protective functions of the lubricant. For example, the lubricant can protect the gears of heavy-duty trucks while preventing corrosion of exposed copper in oil-cooled motor windings.

[0025] The extreme pressure agent includes component A, which comprises a quaternary phosphonium cation a and a phosphate anion b. The structures of the quaternary phosphonium cation a and the phosphate anion b are shown below:

[0026]

[0027] In formula a, n = 8 to 16, and n is an integer. This configuration results in a low-sulfur lubricating oil that can protect the gears of heavy-duty trucks while preventing corrosion of exposed copper in oil-cooled motor windings. Specifically, the quaternary phosphonium cation a, phosphate anion b, and di-n-butyl phosphate in extreme pressure agent component A exhibit excellent synergistic effects, further improving the lubricating oil's fluidity, anti-wear properties, stability, and corrosion resistance. Furthermore, the quaternary phosphonium cation a and phosphate anion b in extreme pressure agent component A possess the ability to passivate metal activity. Under boundary lubrication, component A does not easily form a friction film at low temperatures, and the friction film formed at high temperatures has a layered structure, providing low shear strength and thus resulting in lower friction. Dibutyl phosphate in extreme pressure agents has poor thermal stability and high activity, which can easily cause corrosion and wear. However, the friction film formed by dibutyl phosphite at low temperatures has good load-bearing capacity and anti-wear properties. Component A and dibutyl phosphite form a synergistic and complementary effect at high and low temperatures, which can further improve anti-wear and extreme pressure properties and further improve corrosion resistance.

[0028] According to a specific embodiment of the transmission lubricant of the present invention, the extreme pressure agent component A includes a quaternary phosphonium cation a and a phosphate anion b. The phosphate anion b readily loses its alkyl group. After losing the alkyl group, the phosphate can react with metal or metal friction debris to form a phosphate friction film on the metal surface. This phosphate friction film prevents direct contact between surface roughness points and the transmission, thus reducing friction and preventing wear. Furthermore, it has the property of passivating metal activity, improving the corrosion resistance of the lubricant. This significantly enhances the protective effect of the lubricant on copper wires in the electric drive system. The quaternary phosphonium cation a includes an alkyl group with side chains. The alkyl group and its side chains can increase the compatibility between the components in the lubricant. Specifically, it can improve the oil solubility of the additives in the lubricant. Typically, the alkyl chain length is greater than 6-8 carbon atoms. Thus, the transmission lubricant of the present invention can balance load-bearing capacity and bare copper corrosion protection while having good material compatibility, solving the problems of strong bare copper corrosion and poor material compatibility caused by traditional lubricants under high load conditions.

[0029] According to some embodiments of the present invention, the raw materials and their mass percentages are as follows: extreme pressure agent 0.8%, detergent 0.3%, dispersant 6%, antioxidant 0.5%, rust inhibitor 0.1%, metal passivator 0.04%, viscosity index improver 3.5%, and base oil 88.76%. This configuration results in a more suitable ratio of base oil and additives in the lubricating oil, leading to superior lubricating oil performance.

[0030] According to some embodiments of the present invention, the molar ratio of quaternary phosphonium cation a to phosphate anion b is 1:1. This configuration ensures that the quaternary phosphonium cation a and phosphate anion are well-matched, achieving a balance between cations and anions in the system.

[0031] According to some embodiments of the present invention, the quaternary phosphonium cation a comprises an alkyl group with a side chain. This arrangement allows the alkyl group with the side chain to improve the compatibility between the components of the lubricating oil.

[0032] According to some embodiments of the present invention, the preparation method of the extreme pressure agent includes the following steps: first, 30-40 parts by weight of component A are uniformly dispersed in 40-50 parts by weight of pentaerythritol, then ultrasonically dispersed for 30-40 minutes; then, 10-30 parts by weight of di-n-butyl phosphite are added under stirring at 30-40°C, and stirring is continued for 30-40 minutes. The supernatant is then collected by centrifugation to obtain the extreme pressure agent. This configuration ensures thorough mixing of the components of the extreme pressure agent, which is beneficial for improving the lubrication and corrosion resistance properties of the lubricating oil.

[0033] According to some embodiments of the present invention, the base oil includes at least one of mineral oil and synthetic oil. Specifically, the base oil according to specific embodiments of the present invention is typically a highly refined mineral oil, synthetic oil, or a mixture of mineral and synthetic oils. The mineral oil is generally a Group III base oil produced by atmospheric and vacuum distillation of paraffinic crude oil, intermediate-based crude oil, or naphthenic crude oil, followed by high-level hydrocracking and hydroisomerization; or it is a GTL (Gas-to-Liquid) base oil produced from natural gas via Fischer-Tropsch synthesis, or a CTL (Chemical-to-Liquid) base oil produced from coal gas via Fischer-Tropsch synthesis. The synthetic oil is generally a polyalphaolefin, polyvinyl ether, saturated polyol, etc., and one or more of these synthetic oils can be used. This arrangement results in a wide availability and low cost of base oils.

[0034] According to some embodiments of the present invention, the adhesive includes at least one of polymethacrylate, dispersed polymethacrylate, styrene-diene copolymer, and styrene-isoprene copolymer.

[0035] According to some embodiments of the present invention, the detergent is a sulfonate and / or a phenolate.

[0036] According to some embodiments of the present invention, the dispersant is monosuccinimide and / or boronized succinimide.

[0037] According to some embodiments of the present invention, the antioxidant includes at least one of amine antioxidants and phenolic antioxidants. The amine antioxidants include at least one of monooctyldiphenylamine, 4,4-dibutyldiphenylamine, 4,4-dipentyldiphenylamine, 4-diheptyldiphenylamine, tetrabutyldiphenylamine, tetraoctyldiphenylamine, α-naphthylamine, and phenyl-α-naphthylamine.

[0038] Among them, phenolic antioxidants include at least one of 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, and 4,4-methylenebis(2,6-di-tert-butylphenol).

[0039] According to some embodiments of the present invention, the rust inhibitor includes at least one of metal sulfonates, alkylamines, dodecenylsuccinic acid, and N,N3-bis(benzotriazolylmethylene)laurylamine. This configuration allows the lubricating oil additive to better form an adsorption film on the metal surface, inhibiting the contact between the metal and water and oxygen, reducing metal corrosion, and further improving the rust-preventive performance of the lubricating oil additive.

[0040] According to some embodiments of the present invention, the metal passivating agent includes at least one of toluene-triazole derivatives and thiadiazole derivatives. With this configuration, the obtained lubricating oil additive can better form a chemical protective film on the metal surface, preventing the metal from becoming ionic, thereby preventing metal ions from catalytically oxidizing the oil, extending the service life of the lubricating oil additive, and the formed chemical protective film can also prevent sulfur and organic acids from corroding the metal, improving the corrosion resistance of the lubricating oil additive.

[0041] According to an embodiment of a second aspect of the present invention, the present invention provides a method for preparing a transmission lubricant, comprising the following steps: heating a base oil to 40°C to 50°C by the stated mass percentage; adding a viscosity index enhancer, detergent, dispersant, antioxidant, rust inhibitor, metal passivator, and extreme pressure agent to the base oil under continuous stirring; stirring for 20 min to 40 min; cooling to 25°C to 35°C; continuing to stir for 20 min to 40 min; and filtering to obtain the transmission lubricant.

[0042] According to a specific embodiment of the present invention, a method for preparing transmission lubricating oil involves adding various additives, such as viscosity index enhancers, detergents, dispersants, antioxidants, rust inhibitors, metal passivators, and extreme pressure agents, to a base oil at a suitable temperature and mixing them thoroughly to obtain the transmission lubricating oil of the present invention.

[0043] Specific exemplary embodiments

[0044] It should be noted that, unless otherwise stated, the raw materials used in the specific embodiments of the present invention are all commercially available products. Among them, the source of extreme pressure agent component A is not particularly limited, and it can be purchased through commercial channels or prepared by methods known to those skilled in the art (Christine J. Bradaric, Andrew Downard, Christine Kennedy, et al. Industrial preparation of phosphonium ionic liquids[J]. Green Chemistry, 2003, 5(2): 143-152).

[0045] Example 1

[0046] A transmission fluid for transmissions, by weight, comprises the following raw materials: 88.975 parts base oil, 3.5 parts viscosity index enhancer, 0.3 parts detergent, 6 parts dispersant, 0.5 parts antioxidant, 0.1 parts rust inhibitor, 0.025 parts metal passivator, and 0.6 parts extreme pressure agent; wherein the extreme pressure agent includes component A, which comprises equimolar amounts of quaternary phosphonium cation a and phosphate anion b, the structures of which are shown below:

[0047]

[0048] In formula a, n = 10, and the alkyl group has a side chain.

[0049] The preparation method of the extreme pressure agent includes the following steps:

[0050] First, 30 parts by weight of component A are uniformly dispersed in 40 parts by weight of pentaerythritol, and then ultrasonically dispersed for 30 minutes. During stirring at 30°C, 10 parts by weight of di-n-butyl phosphite are added. After stirring for 30 minutes, the supernatant is collected by centrifugation to obtain the extreme pressure agent.

[0051] The base oil is a III+ base oil with a kinematic viscosity of 6.5-8.5 cst at 100℃; the viscosity indexer is polymethyl methacrylate; the dispersant is boronized succinimide; the detergent is calcium sulfonate; the antioxidant is a mixture of tetrabutyldiphenylamine and 2,6-di-tert-butyl-4-methylphenol in a 1:1 weight ratio; the rust inhibitor is dodecenylsuccinic acid; and the metal passivator is a thiadiazole derivative.

[0052] The preparation method of the transmission lubricant includes the following steps: 89 parts by weight of base oil are heated to 40°C, and under continuous stirring, 3.5 parts of viscosity index enhancer, 0.3 parts of detergent, 6 parts of dispersant, 0.5 parts of antioxidant, 0.1 parts of rust inhibitor, 0.025 parts of metal passivator, and 0.6 parts of extreme pressure agent are added to the base oil. After stirring for 30 minutes, the mixture is cooled to 25°C and stirred for another 30 minutes. After filtration and packaging, the transmission lubricant is obtained.

[0053] Example 2

[0054] A transmission fluid for transmissions, by weight, comprises the following raw materials: 88.76 parts base oil, 3.5 parts viscosity index enhancer, 0.3 parts detergent, 6 parts dispersant, 0.5 parts antioxidant, 0.1 parts rust inhibitor, 0.04 parts metal passivator, and 0.8 parts extreme pressure agent;

[0055] The extreme pressure agent includes component A, which comprises equimolar amounts of quaternary phosphonium cation a and phosphate anion b. The structures of quaternary phosphonium cation a and phosphate anion b are shown below:

[0056]

[0057] In formula a, n = 10, and the alkyl group has a side chain.

[0058] The types of base oil and various additives are basically the same as in Example 1;

[0059] The preparation method of the extreme pressure agent is basically the same as that in Example 1;

[0060] The preparation method of the transmission lubricant is basically the same as that in Example 1.

[0061] Example 3

[0062] A transmission fluid for transmissions, by weight, comprises the following raw materials: 88.54 parts base oil, 3.5 parts viscosity index enhancer, 0.3 parts detergent, 6 parts dispersant, 0.5 parts antioxidant, 0.1 parts rust inhibitor, 0.06 parts metal passivator, and 1 part extreme pressure agent;

[0063] The extreme pressure agent includes component A, which comprises equimolar amounts of quaternary phosphonium cation a and phosphate anion b. The structures of quaternary phosphonium cation a and phosphate anion b are shown below:

[0064]

[0065] In formula a, n = 10, and the alkyl group has a side chain.

[0066] The types of base oil and various additives are basically the same as in Example 1;

[0067] The preparation method of the extreme pressure agent is basically the same as that in Example 1;

[0068] The preparation method of the transmission lubricant is basically the same as that in Example 1.

[0069] Example 4

[0070] A transmission fluid for transmissions, by weight, comprises the following raw materials: 88.76 parts base oil, 3.5 parts viscosity index enhancer, 0.3 parts detergent, 6 parts dispersant, 0.5 parts antioxidant, 0.1 parts rust inhibitor, 0.04 parts metal passivator, and 0.8 parts extreme pressure agent; wherein the extreme pressure agent includes component A, which comprises equimolar amounts of quaternary phosphonium cation a and phosphate anion b, the structures of which are shown below:

[0071]

[0072] In formula a, n = 10, and the alkyl group has a side chain.

[0073] The types of base oil and various additives are basically the same as in Example 1;

[0074] The preparation method of the extreme pressure agent is basically the same as that in Example 1;

[0075] The preparation method of the transmission lubricant is basically the same as that in Example 1.

[0076] Example 5

[0077] A transmission fluid for transmissions, by weight, comprises the following raw materials: 88.01 parts base oil, 2 parts viscosity index enhancer, 0.5 parts detergent, 8 parts dispersant, 0.6 parts antioxidant, 0.2 parts rust inhibitor, 0.03 parts metal passivator, and 0.66 parts extreme pressure agent;

[0078] The extreme pressure agent includes component A, which comprises a quaternary phosphonium cation a and a phosphate anion b. The structures of the quaternary phosphonium cation a and the phosphate anion b are shown below:

[0079]

[0080] In formula a, n = 8.

[0081] The preparation method of the extreme pressure agent includes the following steps: First, 40 parts by weight of component A are uniformly dispersed in 50 parts by weight of pentaerythritol, and then ultrasonically dispersed for 40 min. Then, 30 parts by weight of di-n-butyl phosphite are added under stirring at 40°C. After stirring for another 40 min, the supernatant is collected by centrifugation to obtain the extreme pressure agent.

[0082] The base oil is Group II, Group III, or a mixture of both, with a viscosity of 6.5 cSt-8.5 cSt at 100°C; the viscosity indexer includes equal parts by weight of styrene-diene copolymer and styrene-isoprene copolymer; the detergent is calcium phenol; the dispersant is boronized succinimide; the antioxidant includes equal parts by weight of 4,4-dibutyldiphenylamine and 2,6-di-tert-butyl-4-ethylphenol; the rust inhibitor includes equal parts by weight of dodecenylsuccinic acid and N,N3-bis(benzotriazolemethylene)laurylamine; and the metal passivator is a toluenetriazole derivative.

[0083] The preparation method of transmission lubricant includes the following steps: according to the above mass percentage, the base oil is heated to 50°C, and under continuous stirring, viscosity index enhancer, detergent, dispersant, antioxidant, rust inhibitor, metal passivator and extreme pressure agent are added to the above base oil. After stirring for 40 minutes, the mixture is cooled to 35°C and stirred for another 40 minutes. After filtration and packaging, transmission lubricant is obtained.

[0084] Example 6

[0085] A transmission fluid for transmissions, by weight, comprises the following raw materials: 86.29 parts base oil, 5 parts viscosity index enhancer, 0.4 parts detergent, 7 parts dispersant, 0.55 parts antioxidant, 0.15 parts rust inhibitor, 0.01 parts metal passivator, and 0.6 parts extreme pressure agent;

[0086] The extreme pressure agent includes component A, which comprises a quaternary phosphonium cation a and a phosphate anion b. The structures of the quaternary phosphonium cation a and the phosphate anion b are shown below:

[0087]

[0088] In formula a, n = 16.

[0089] The preparation method of the extreme pressure agent includes the following steps: First, 35 parts by weight of component A are uniformly dispersed into 45 parts of pentaerythritol, and then ultrasonically dispersed for 35 minutes. Then, 20 parts of di-n-butyl phosphite are added under stirring at 35°C. After stirring for another 35 minutes, the supernatant is collected by centrifugation to obtain the extreme pressure agent.

[0090] The base oil is Group II, Group III, or a mixture of both, with a viscosity of 6.5 cSt-8.5 cSt at 100°C; the viscosity indexer includes equal parts by weight of polymethyl methacrylate and dispersed polymethyl methacrylate; the detergent is equal parts by weight of calcium sulfonate and calcium phenolate; the dispersant is equal parts by weight of monosuccinimide and boronized succinimide; the antioxidant includes equal parts by weight of 4-diheptyldiphenylamine and 4,4-methylenebis(2,6-di-tert-butylphenol); the rust inhibitor includes equal parts by weight of alkylamine, dodecenylsuccinic acid, and N,N3-bis(benzotriazolemethylene)laurylamine; and the metal passivator includes equal parts by weight of toluene-triazole derivatives and thiadiazole derivatives.

[0091] The preparation method of transmission lubricant includes the following steps: according to the above mass percentage, the base oil is heated to 45°C, and under continuous stirring, viscosity index enhancer, detergent, dispersant, antioxidant, rust inhibitor, metal passivator and extreme pressure agent are added to the above base oil. After stirring for 30 minutes, the mixture is cooled to 30°C and stirred for another 30 minutes. After filtration and packaging, transmission lubricant is obtained.

[0092] Comparative Example 1

[0093] Comparative Example 1 is essentially the same as Example 1, except that the extreme pressure agent is Vanlube SB from Vanderbilt.

[0094] Comparative Example 2

[0095] Comparative Example 2 is basically the same as Example 1, except that the extreme pressure agent is a phosphate ester amine salt (such as Vanlube 672).

[0096] Comparative Example 3

[0097] Comparative Example 3 is basically the same as Example 1, except that the amount of extreme pressure agent used is 0.3 parts.

[0098] Comparative Example 4

[0099] Comparative Example 4 is basically the same as Example 1, except that the extreme pressure agent is used in an amount of 3 parts.

[0100] 1. The raw material usage amounts for each embodiment and comparative example are shown in Table 1 below:

[0101] Table 1. Comparison of raw material consumption for lubricating oils in the examples and comparative examples

[0102]

[0103]

[0104] 2. Performance Testing:

[0105] The performance of the lubricating oils of Examples 1-6 and Comparative Examples 1-4 was tested. The test methods and results are shown in Table 2.

[0106] Table 2. Performance test results of the lubricating oils in the examples and comparative examples

[0107]

[0108] Based on the specific embodiments of the present invention, the comparative examples, and the test results in Table 2, it can be seen that when the lubricating oil of the present invention is applied to the transmission, it can ensure high load-bearing capacity of the gears and fully protect the hardware.

[0109] Specifically, as can be seen from Examples 1-6 and Comparative Example 1, the lubricating oil of the present invention, by improving the composition of the extreme pressure agent and adopting a low-sulfur formula, achieves the goal of not causing corrosion to copper components, thereby protecting the bare copper of the motor and electrical components. In contrast, the active sulfur in conventional lubricating oils or the lubricating oil of Comparative Example 1 increases the probability of pitting corrosion, which may cause corrosion of electrical components.

[0110] Based on Examples 1-6 and Comparative Example 2 and their performance test results, it can be seen that the difference between the extreme pressure agent of the present invention and phosphorus-based extreme pressure agents, especially phosphate ester amine salts, lies in the different mechanisms resulting from the chemical properties of the extreme pressure agents. Extreme pressure agent component A of the present invention contains quaternary phosphonium cation a and phosphate anion b. Phosphate anion b readily loses its alkyl group and reacts with the metal surface or friction debris to form a phosphate friction film. This phosphate friction film prevents direct contact between surface rough points, thus reducing friction and reducing wear. Furthermore, it has the property of passivating metal activity, improving the corrosion resistance of the lubricating oil, and can significantly enhance the corrosion resistance of the lubricating oil to copper wires in electric drive systems. Moreover, extreme pressure agent component A can achieve excellent synergistic effects with other components, further improving the fluidity, anti-wear properties, stability, and corrosion resistance of the lubricating oil. Phosphate ester amine salts are a type of phosphorus-containing extreme pressure anti-wear agent. Generally speaking, phosphorus-based extreme pressure anti-wear agents have poor thermal stability and good anti-wear properties, but their anti-wear durability will decrease, leading to an increased rate of additive consumption. Under boundary lubrication conditions, the phosphide undergoes C-O bond breakage, generating a mixture of iron phosphite, which plays an anti-wear role. The extreme pressure anti-wear properties of phosphate ester amine salts are greatly affected by the main structure of the compound. For example, some phosphate esters have straight-chain alkyl groups that can form the tightest adsorption film, and the structure of the amine will not affect the extreme pressure anti-wear performance. However, some phosphate esters have increased alkyl group volume, making their adsorption film quite loose. Straight-chain amines can penetrate into the gaps between these adsorption films, resulting in an uneven phosphate ester adsorption film, which will affect the anti-wear performance of the phosphate ester adsorption film.

[0111] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example.

[0112] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A lubricating oil for transmissions, characterized in that, The raw materials and their weight percentages are as follows: extreme pressure agent 0.6%–1%, detergent 0.3%–0.5%, dispersant 6%–8%, antioxidant 0.5%–0.6%, rust inhibitor 0.1%–0.2%, metal passivator 0.01%–0.06%, viscosity index improver 2%–5%, and the balance being base oil; The extreme pressure agent includes component A, which comprises a quaternary phosphonium cation a and a phosphate anion b. The structures of the quaternary phosphonium cation a and the phosphate anion b are shown below: ， In formula a, n = 8 to 16 and n is an integer; The preparation method of the extreme pressure agent includes the following steps: first, 30-40 parts by weight of component A are uniformly dispersed in 40-50 parts by weight of pentaerythritol, and ultrasonically dispersed for 30-40 minutes. Then, the mixture is stirred at 30-40°C, 10-30 parts by weight of di-n-butyl phosphite are added, and the mixture is stirred for 30-40 minutes. Finally, the supernatant is collected by centrifugation to obtain the extreme pressure agent.

2. The transmission lubricant according to claim 1, characterized in that, The raw materials and their weight percentages are as follows: extreme pressure agent 0.8%, detergent 0.3%, dispersant 6%, antioxidant 0.5%, rust inhibitor 0.1%, metal passivator 0.04%, viscosity index improver 3.5%, and base oil 88.76%.

3. The transmission lubricant according to claim 1, characterized in that, The molar ratio of the quaternary phosphonium cation a to the phosphate anion b is 1:

1.

4. The transmission lubricant according to claim 1, characterized in that, The quaternary phosphonium cation a includes alkyl groups with side chains.

5. The transmission lubricant according to claim 1, characterized in that, The base oil includes at least one of mineral oil and synthetic oil; and / or The adhesive finger comprises at least one of polymethyl methacrylate and styrene-diene copolymer, wherein the polymethyl methacrylate comprises dispersed polymethyl methacrylate, and the styrene-diene copolymer comprises styrene-isoprene copolymer; and / or The detergent is a sulfonate and / or a phenolate; and / or The dispersant is monosuccinimide and / or boronized succinimide.

6. The transmission lubricant according to claim 1, characterized in that, The antioxidants include at least one of amine antioxidants and phenolic antioxidants.

7. The transmission lubricant according to claim 1, characterized in that, The rust inhibitor includes metal sulfonates, alkylamines, dodecenylsuccinic acid, and N,N'-carboxylic acid. At least one of bis(benzotriazolemethylene)lauramine.

8. The transmission lubricant according to claim 1, characterized in that, The metal passivating agent includes at least one of toluenetriazole derivatives and thiadiazole derivatives.

9. A method for preparing a transmission lubricating oil according to any one of claims 1-8, characterized in that, Includes the following steps: According to the stated mass percentage, the base oil is heated to 40℃~50℃, and under continuous stirring, the viscosity index enhancer, detergent, dispersant, antioxidant, rust inhibitor, metal passivator and extreme pressure agent are added to the base oil. After stirring for 20min~40min, the mixture is cooled to 25℃~35℃ and stirred for another 20min~40min. After filtration, the transmission lubricating oil is obtained.

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