Engine oil and preparation method thereof

Abstract

The invention relates to the technical field of engine oil, in particular to engine oil which comprises the following components in parts by weight: 100 parts of hydrogenated base oil, 5-10 parts of a purification dispersant, 0.2-1.2 parts of an antioxidant, 2-8 parts of an anti-wear agent and 1.7-4.2 parts of a metal deactivator, the purification dispersant is styrene modified polyisobutene phenol Mannich base quaternary ammonium salt. The lubricating oil can effectively reduce generation of sediments, prevents engine abrasion, and is low in viscosity and not prone to blockage.

Description

Technical Field

[0001] This invention relates to the field of engine oil technology, and more particularly to an engine oil and its preparation method. Background Technology

[0002] Engine oil is a specialized lubricant used to lubricate the moving parts inside an internal combustion engine. When an engine runs at high speed, intense friction and high temperatures occur between metal parts. Without lubrication, this can lead to instantaneous wear, scoring, and even welding. During operation, engines produce deposits, which are solid, insoluble substances that adhere to the engine's metal walls, formed by the high-temperature oxidation of fuel oil and lubricating oil. With continuous use of gasoline engines, these deposits accumulate, becoming increasingly dense and difficult to clean. The accumulation of engine deposits significantly impacts engine lifespan and makes the engine more prone to malfunctions.

[0003] To address the issue of deposits, existing technologies often add detergent-dispersants to engine oil. These dispersants work by suspending the deposits in a colloidal state, preventing insoluble substances from settling on the surface of components and forming sludge. Currently, the most commonly used detergent-dispersant is polyisobutylene amine (POI). However, PPI has drawbacks, including excessively high decomposition temperatures and large molecular particles that can easily clog electronic fuel injector components used in modern gasoline engines. This can lead to serious problems such as poor fuel intake at the injectors, reduced engine power, or even complete engine failure. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art. This invention provides an engine oil that can effectively reduce the formation of deposits, prevent engine wear, and has low viscosity, making it less prone to clogging.

[0005] To address the above problems, the present invention provides an engine oil comprising the following components in parts by weight: 100 parts hydrogenated base oil, 5-10 parts detergent-dispersant, 0.2-1.2 parts antioxidant, 2-8 parts anti-wear agent, and 1.7 parts metal passivator. 4.2 copies; The cleaning and dispersing agent is a styrene-modified polyisobutylene phenol Mannich base quaternary ammonium salt.

[0006] As an improvement to the above technical solution, the styrene-modified polyisobutylene phenol Mannich base quaternary ammonium salt is prepared from the following raw materials in parts by weight: 25-45 parts of polyisobutylene phenol Mannich base, 18-30 parts of styrene, 5-13 parts of benzyl chloride, 100-200 parts of toluene, 3-8 parts of potassium persulfate, 100-200 parts of anhydrous ethanol, and 1-3 parts of sodium iodide.

[0007] As an improvement to the above technical solution, the polyisobutylene phenol Mannich base is prepared from the following raw materials in parts by weight: 40-55 parts of polyisobutylene phenol, 8-18 parts of N,N-dimethylethanolamine, 7-15 parts of formaldehyde solution with a mass fraction of 30%-40%, and 28-45 parts of n-hexane.

[0008] As an improvement to the above technical solution, the preparation method of the styrene-modified polyisobutylene phenol Mannich base quaternary ammonium salt includes the following steps: (1) Under a nitrogen atmosphere, polyisobutylene phenol and N,N-dimethylethanolamine are added sequentially and mixed evenly. Then formaldehyde solution is added dropwise over a period of 0.5h to 2h. After the addition is complete, the temperature is heated to 100℃ to 125℃ and stirred for 5h to 7h to obtain the mixture to be treated. (2) Add n-hexane to the mixture to be treated for dilution, wash it multiple times with deionized water until the pH is 6.8~7.2, separate the deionized water and retain the n-hexane solution, and then distill and vacuum dry the n-hexane solution to obtain polyisobutylene phenol Mannich base; (3) Under a nitrogen atmosphere, the polyisobutylene phenol Mannich base was dissolved in toluene, potassium persulfate was added and stirred to dissolve, styrene was added dropwise at a rate of 0.3 ml / min to 0.8 ml / min, and the temperature was raised to 70°C to 80°C. The mixture was stirred for 4 h to 6 h, then cooled to 25°C to 30°C. Methanol was added at a predetermined time to terminate the reaction. The mixture was filtered, washed, and vacuum dried to obtain the product to be quaternized. (4) Dissolve the product to be quaternized in anhydrous ethanol, then add benzyl chloride and sodium iodide, heat to 45℃~60℃, stir for 4h~6h, evaporate under reduced pressure after the reaction, wash with ether 2~5 times, and dry under vacuum to obtain the styrene-modified polyisobutylene phenol Mannich base quaternary ammonium salt.

[0009] As an improvement to the above technical solution, in step (3), the stirring reaction is continuously carried out at a stirring speed of not less than 500 rpm. After the stirring reaction is completed, methanol is added dropwise at a predetermined time to terminate the reaction. The dropwise time is 30 min to 45 min. During washing, methanol and deionized water are mixed in a 1:1 volume ratio to obtain a washing solution, and the reaction product is washed 2 to 3 times. Then, it is vacuum dried at 35℃ to 45℃ for 12 to 15 hours to obtain the product to be quaternized.

[0010] As an improvement to the above technical solution, in step (4), the product washed with ether is vacuum dried at 48℃~55℃ for 8h~13h to obtain the styrene-modified polyisobutylene phenol Mannich base quaternary ammonium salt.

[0011] As an improvement to the above technical solution, the hydrotreated base oil includes Group II hydrotreated base oil 500SN, Group III hydrotreated base oil 500SN, and Group III hydrotreated base oil 500N in a weight ratio of (1.5~2):(1.5~2):1. The anti-wear agent is a mixture of zinc dialkyl dithiophosphate and molybdenum dithiocarbamate, with a weight ratio of 1:(0.2~0.4).

[0012] As an improvement to the above technical solution, the antioxidant includes 2,6-di-tert-butyl-p-cresol and / or alkylated diphenylamine; The metal passivating agent includes benzotriazole and / or 2,5-bisoctyldithiothiadiazole.

[0013] As an improvement to the above technical solution, the weight ratio of detergent-dispersant to hydrogenated base oil is 1:(13~16).

[0014] Accordingly, the present invention also provides an engine oil, comprising the following steps: The hydrotreated base oil is heated to 50℃~60℃ and stirred for 10 min~30 min. Then, detergent-dispersant, antioxidant, anti-wear agent and metal passivator are added in sequence. Stirring is continued at 50℃~60℃ for 1~3 h to obtain a mixed oil. The mixed oil is filtered at a pressure of 0.1 MPa to 0.2 MPa to obtain the engine oil.

[0015] The implementation of this invention has the following beneficial effects: This invention provides an engine oil comprising the following components by weight: hydrotreated base oil, detergent-dispersant, antioxidant, anti-wear agent, and metal passivator; wherein the detergent-dispersant is a styrene-modified polyisobutylene phenol Mannich base quaternary ammonium salt. The aforementioned detergent-dispersant, through styrene modification, has a narrower molecular weight distribution, significantly smaller than traditional PIBA, avoiding the formation of large molecular micelles that clog precision fuel injector valve bodies at high temperatures. The quaternary ammonium salt structure improves oil solubility, reduces the risk of high-temperature precipitation, and decreases the incidence of fuel injector clogging. Furthermore, the phenolic hydroxyl and amine groups in the Mannich base synergistically neutralize acidic combustion products, reducing carbon deposits in the piston ring grooves; the quaternary ammonium salt cations stabilize suspended carbon deposit particles through electrostatic repulsion, improving dispersion efficiency and delaying sludge formation. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in further detail below.

[0017] This invention provides an engine oil comprising the following components in parts by weight: 100 parts hydrogenated base oil, 5-10 parts detergent-dispersant, 0.2-1.2 parts antioxidant, 2-8 parts anti-wear agent, and 1.7 parts metal passivator. 4.2 copies; The cleaning and dispersing agent is a styrene-modified polyisobutylene phenol Mannich base quaternary ammonium salt.

[0018] The aforementioned detergent-dispersant, modified with styrene, has a narrower molecular weight distribution, significantly smaller than traditional PIBA, thus preventing the formation of large molecular micelles that clog precision fuel injector valve bodies at high temperatures. The quaternary ammonium salt structure improves oil solubility, reducing the risk of high-temperature precipitation and decreasing the incidence of fuel injector clogging. Furthermore, the phenolic hydroxyl and amine groups in the Nishi base synergistically neutralize acidic combustion products, reducing carbon deposits in the piston ring grooves; the quaternary ammonium salt cations stabilize suspended carbon deposit particles through electrostatic repulsion, improving dispersion efficiency and delaying sludge formation.

[0019] It should be noted that hydrotreated base oils are lubricating oil base oils refined through a hydrotreating process. They exhibit superior performance compared to traditional mineral oils, particularly in terms of oxidation resistance, wear resistance, and low-temperature fluidity. Examples include Group II, Group III, Group IV, and Group V hydrotreated base oils, but are not limited to these.

[0020] Preferably, the styrene-modified polyisobutylene phenol Mannich base quaternary ammonium salt is prepared from the following raw materials in parts by weight: 25-45 parts of polyisobutylene phenol Mannich base, 18-30 parts of styrene, 5-13 parts of benzyl chloride, 100-200 parts of toluene, 3-8 parts of potassium persulfate, 100-200 parts of anhydrous ethanol, and 1-3 parts of sodium iodide.

[0021] More preferably, the polyisobutylene phenol Mannich base is prepared from the following raw materials in parts by weight: 40-55 parts of polyisobutylene phenol, 8-18 parts of N,N-dimethylethanolamine, 7-15 parts of formaldehyde solution with a mass fraction of 30%-40%, and 28-45 parts of n-hexane.

[0022] The optimal method for preparing the styrene-modified polyisobutylene phenol Mannich base quaternary ammonium salt includes the following steps: (1) Under a nitrogen atmosphere, polyisobutylene phenol and N,N-dimethylethanolamine are added sequentially and mixed evenly. Then formaldehyde solution is added dropwise over a period of 0.5h to 2h. After the addition is complete, the temperature is heated to 100℃ to 125℃ and stirred for 5h to 7h to obtain the mixture to be treated. Specifically, nitrogen gas is introduced into the reaction chamber to fill it with nitrogen. Polyisobutylene phenol and N,N-dimethylethanolamine are then added and stirred until homogeneous. After thorough stirring, formaldehyde solution is slowly added dropwise to control the heat release during the reaction. If the dropwise addition time is less than 0.5 hours, the heat release becomes concentrated, leading to the formation of byproducts; if the dropwise addition time is greater than 2 hours, the reaction cycle is prolonged, reducing efficiency.

[0023] (2) Add n-hexane to the mixture to be treated for dilution, wash it multiple times with deionized water until the pH is 6.8~7.2, separate the deionized water and retain the n-hexane solution, and then distill and vacuum dry the n-hexane solution to obtain polyisobutylene phenol Mannich base; Specifically, the mixture to be treated, diluted with n-hexane, is washed with deionized water to extract impurities, and the washing continues until the pH of the separated deionized water is 6.8–7.2. The washed n-hexane solution is then vacuum dried at 40–50°C.

[0024] (3) Under a nitrogen atmosphere, the polyisobutylene phenol Mannich base was dissolved in toluene, potassium persulfate was added and stirred to dissolve, styrene was added dropwise at a rate of 0.3 ml / min to 0.8 ml / min, and the temperature was raised to 70°C to 80°C. The mixture was stirred for 4 h to 6 h, then cooled to 25°C to 30°C. Methanol was added at a predetermined time to terminate the reaction. The mixture was filtered, washed, and vacuum dried to obtain the product to be quaternized. Examples of styrene addition rates include 0.3 ml / min, 0.4 ml / min, 0.5 ml / min, 0.6 ml / min, 0.7 ml / min, and 0.8 ml / min, but are not limited to these. Slow addition prevents excessively high instantaneous styrene concentrations, which could lead to a rapid increase in the free radical polymerization rate and trigger explosive polymerization. The reaction is exothermic; localized overheating can accelerate chain growth, resulting in excessively broad molecular weight distributions or cross-linking byproducts, and even causing safety accidents. Controlling the dropping rate ensures a smooth release of reaction heat, maintaining the system temperature within the designed range of 70–80°C. When the dropping rate is less than 0.3 ml / min, the reaction cycle is prolonged, increasing energy consumption without significantly improving purity. When the dropping rate is greater than 0.8 ml / min, the amount of oligomers generated during the termination reaction increases, leading to the loss of the target product in subsequent filtration steps.

[0025] Specifically, during the reaction, the mixture is continuously stirred at a speed of not less than 500 rpm to prevent localized gelation. After the reaction is complete, methanol is added dropwise at predetermined intervals to terminate the reaction, with the addition time being 30 min to 45 min; examples of addition times are 30 min, 35 min, 40 min, and 45 min, but are not limited to these.

[0026] During washing, methanol and deionized water are mixed in a 1:1 volume ratio to obtain a washing solution, and the reaction product is washed 2 to 3 times. Then, it is vacuum dried at 35℃ to 45℃ for 12 to 15 hours to obtain the product to be quaternized.

[0027] (4) Dissolve the product to be quaternized in anhydrous ethanol, then add benzyl chloride and sodium iodide, heat to 45℃~60℃, stir for 4h~6h, evaporate under reduced pressure after the reaction, wash with ether 2~5 times, and dry under vacuum to obtain the styrene-modified polyisobutylene phenol Mannich base quaternary ammonium salt.

[0028] Specifically, the product washed with ether is vacuum dried at 48℃~55℃ for 8h~13h to obtain the styrene-modified polyisobutylene phenol Mannich base quaternary ammonium salt.

[0029] Preferably, the hydrotreated base oil comprises Group II hydrotreated base oil 500SN, Group III hydrotreated base oil 500SN, and Group III hydrotreated base oil 500N, with a mass ratio of (1.5~2):(1.5~2):1. The synergistic effect of Group III hydrotreated base oil 500N with the Group II and Group III 500SN in terms of oxidation stability effectively inhibits the oxidative deterioration of the engine oil under high temperature and high pressure, extends the oil change interval, and reduces deposit formation. The compounded base oil, in synergy with styrene-modified polyisobutylene phenol Mannich base quaternary ammonium salt, reduces the catalytic activity of acidic combustion products inside the engine, reduces carbon deposits in the piston ring grooves, and ensures long-term clean engine operation. The extremely low volatility of the Group III base oil complements the low-temperature fluidity of the Group II base oil, preventing the engine oil from thickening during cold starts or decreasing in viscosity at high temperatures.

[0030] Preferably, the weight ratio of the detergent-dispersant to the hydrotreated base oil is 1:(13~16). Examples include 1:13, 1:14, 1:15, and 1:16, but are not limited to these. When the ratio is between 1:13 and 1:16, the quaternary ammonium salt can be uniformly dispersed in the base oil, effectively neutralizing acidic substances and inhibiting the formation of sludge and varnish. When the ratio is less than 1:17, the quaternary ammonium salt content is insufficient, leading to decreased cleaning efficiency, making the oil prone to deposits and acid corrosion, and shortening its service life. When the ratio is greater than 1:13, excessive quaternary ammonium salt may cause gelation or incompatibility problems, increasing oil viscosity and clogging the filtration system, affecting equipment operating safety.

[0031] Preferably, the anti-wear agent is a mixture of zinc dialkyl dithiophosphate and molybdenum dithiocarbamate, with a weight ratio of 1:(0.5~0.9). A phosphate / sulfophosphorus glass film is formed on the metal surface, and a nano-molybdenum disulfide layer is generated through thermal decomposition. The two layers are superimposed to form a composite friction reaction film with low shear strength, thereby reducing the coefficient of friction. Examples of ratios are 1:0.5, 1:0.6, 1:0.8, and 1:0.9, but are not limited thereto.

[0032] Preferably, the antioxidant comprises 2,6-di-tert-butyl-p-cresol and / or alkylated diphenylamine; 2,6-di-tert-butyl-p-cresol acts as the primary antioxidant, terminating the oxidation chain reaction by capturing free radicals. Alkylated diphenylamine remains active at high temperatures, decomposing peroxide free radicals and compensating for the high-temperature failure defects of phenols.

[0033] The metal passivating agent includes benzotriazole and / or 2,5-bis(octyl)dithiothiadiazole. Benzotriazole complexes with copper ions to form a passivation film, inhibiting metal-catalyzed oil oxidation. 2,5-bis(octyl)dithiothiadiazole forms a sulfide film on the metal surface, blocking active sulfur corrosion and the metal ion catalytic pathway.

[0034] Accordingly, the present invention also provides an engine oil, comprising the following steps: The hydrotreated base oil is heated to 50℃~60℃ and stirred for 10 min~30 min. Then, detergent-dispersant, antioxidant, anti-wear agent and metal passivator are added in sequence. Stirring is continued at 50℃~60℃ for 1~3 h to obtain a mixed oil. The mixed oil is filtered at a pressure of 0.1 MPa to 0.2 MPa to obtain the engine oil.

[0035] The present invention will now be described with reference to specific embodiments: Example 1 An engine oil comprising the following components in parts by weight: 100 parts hydrogenated base oil, 7.5 parts detergent-dispersant, 0.7 parts antioxidant, 5 parts anti-wear agent, and 3.4 parts metal passivator; The cleaning and dispersing agent is styrene-modified polyisobutylene phenol Mannich base quaternary ammonium salt; The styrene-modified polyisobutylene phenol Mannich base quaternary ammonium salt is prepared from the following raw materials in parts by weight: 40 parts of polyisobutylene phenol Mannich base, 25 parts of styrene, 9 parts of benzyl chloride, 150 parts of toluene, 5.5 parts of potassium persulfate, 150 parts of anhydrous ethanol, and 2 parts of sodium iodide. The polyisobutylene phenol Mannich base is prepared from the following raw materials in parts by weight: 50 parts of polyisobutylene phenol, 15 parts of N,N-dimethylethanolamine, 11 parts of formaldehyde solution with a mass fraction of 37%, and 40 parts of n-hexane; The preparation method of the styrene-modified polyisobutylene phenol Mannich base quaternary ammonium salt includes the following steps: (1) Under a nitrogen atmosphere, polyisobutylene phenol and N,N-dimethylethanolamine were added and mixed evenly in sequence, and then formaldehyde solution was added dropwise over a period of 1.5 h. After the addition was completed, the temperature was heated to 110 °C and stirred for 6 h to obtain the mixture to be treated. (2) Add n-hexane to the mixture to be treated for dilution, wash it multiple times with deionized water until the pH is 6.8~7.2, separate the deionized water and retain the n-hexane solution, and then distill and vacuum dry the n-hexane solution to obtain polyisobutylene phenol Mannich base; (3) Under a nitrogen atmosphere, the polyisobutylene phenol Mannich base was dissolved in toluene, potassium persulfate was added and stirred to dissolve, styrene was added dropwise at a rate of 0.55 ml / min, and the temperature was raised to 75°C. The reaction was stirred for 5 h, then cooled to 25°C, and methanol was slowly added dropwise to terminate the reaction. The addition time was controlled at 40 min. The product to be quaternized was obtained by filtration, washing and vacuum drying. During washing, methanol and deionized water were mixed at a volume ratio of 1:1 to obtain a washing solution, and the reaction product was washed three times. Then the product was vacuum dried at 40°C for 14 h to obtain the product to be quaternized.

[0036] (4) Dissolve the product to be quaternized in anhydrous ethanol, then add benzyl chloride and sodium iodide, heat to 55°C, stir for 6 hours, evaporate under reduced pressure after the reaction, wash with ether 2 to 5 times, and dry the product after washing with ether under vacuum at 50°C for 10 hours to obtain the styrene-modified polyisobutylene phenol Mannich base quaternary ammonium salt.

[0037] The hydrotreated base oils include Group II hydrotreated base oil 500SN, Group III hydrotreated base oil 500SN, and Group III hydrotreated base oil 500N, with a mass ratio of 1.5:1.5:1. The anti-wear agent is a mixture of zinc dialkyl dithiophosphate and molybdenum dithiocarbamate, with a weight ratio of 1:0.3. The antioxidant includes 2,6-di-tert-butyl-p-cresol; The metal passivating agent includes benzotriazole.

[0038] Example 2 The difference between this embodiment and Embodiment 1 is that: The detergent-dispersant is 10 parts, and the weight ratio of the detergent-dispersant to the hydrogenated base oil is 1:10.

[0039] Example 3 The difference between this embodiment and Embodiment 1 is that: The detergent-dispersant is 5 parts, and the weight ratio of the detergent-dispersant to the hydrogenated base oil is 1:20.

[0040] Example 4 The difference between this embodiment and Embodiment 1 is that: The hydrotreated base oils include Group II hydrotreated base oil 500SN, Group III hydrotreated base oil 500SN, and Group III hydrotreated base oil 500N, with a mass ratio of 1:1:1. The anti-wear agent is a mixture of zinc dialkyl dithiophosphate and molybdenum dithiocarbamate in a weight ratio of 1:1.

[0041] Example 5 The difference between this embodiment and Embodiment 1 is that: The antioxidant comprises a mixture of 2,6-di-tert-butyl-p-cresol and alkylated diphenylamine, which are mixed in a 1:1 weight ratio; The antioxidant comprises 2,6-di-tert-butyl-p-cresol and alkylated diphenylamine, which are mixed in a 1:1 weight ratio.

[0042] Comparative Example 1 The difference between this comparative example and Example 1 is that: The detergent dispersant is succinate.

[0043] Comparative Example 2 The difference between this comparative example and Example 1 is that: The hydrotreated base oil is only Group II hydrotreated base oil 500SN, and the detergent-dispersant is succinate.

[0044] Comparative Example 3 The difference between this comparative example and Example 1 is that: The amount of detergent-dispersant added is 0.

[0045] Engine oils were prepared in Examples 1-5 and Comparative Examples 1-3 by the following methods: The hydrotreated base oil was heated to 55°C and stirred for 30 minutes. Then, detergent-dispersant, antioxidant, anti-wear agent and metal passivator were added in sequence. Stirring was continued at 55°C for 2 hours to obtain the mixed oil. The mixed oil is filtered at a pressure of 0.2 MPa to obtain the engine oil.

[0046] For the engine oils prepared in Examples 1-5 and Comparative Examples 1-3, refer to SH / T 0189 The standards 2017, GB / T 511 and GB / T 1995 are used to test the coefficient of friction, mechanical impurities and viscosity index in sequence.

[0047]

[0048] The test results above show that adding styrene-modified polyisobutylene phenol Mannich base quaternary ammonium salt as a detergent dispersant avoids the formation of large molecular micelles that clog the precision fuel injector valve body at high temperatures. The quaternary ammonium salt structure improves oil solubility, reduces the risk of high-temperature precipitation, and decreases the incidence of fuel injector clogging. In addition, the phenolic hydroxyl groups and amine groups in the Mannich base synergistically neutralize acidic combustion products, reducing carbon deposits in the piston ring grooves; the quaternary ammonium salt cations stabilize suspended carbon deposit particles through electrostatic repulsion, improving dispersion efficiency and delaying sludge formation.

[0049] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. An engine oil, characterized in that, Includes the following components, calculated in parts by weight: 100 parts hydrogenated base oil, 5-10 parts detergent-dispersant, 0.2-1.2 parts antioxidant, 2-8 parts anti-wear agent, and 1.7-4.2 parts metal passivator; The cleaning and dispersing agent is a styrene-modified polyisobutylene phenol Mannich base quaternary ammonium salt.

2. The engine oil as described in claim 1, characterized in that, The styrene-modified polyisobutylene phenol Mannich base quaternary ammonium salt is prepared from the following raw materials in parts by weight: 25-45 parts of polyisobutylene phenol Mannich base, 18-30 parts of styrene, 5-13 parts of benzyl chloride, 100-200 parts of toluene, 3-8 parts of potassium persulfate, 100-200 parts of anhydrous ethanol, and 1-3 parts of sodium iodide.

3. The engine oil as described in claim 2, characterized in that, The polyisobutylene phenol Mannich base is prepared from the following raw materials in parts by weight: 40-55 parts of polyisobutylene phenol, 8-18 parts of N,N-dimethylethanolamine, 7-15 parts of formaldehyde solution with a mass fraction of 30%-40%, and 28-45 parts of n-hexane.

4. The engine oil as described in claim 3, characterized in that, The preparation method of the styrene-modified polyisobutylene phenol Mannich base quaternary ammonium salt includes the following steps: (1) Under a nitrogen atmosphere, polyisobutylene phenol and N,N-dimethylethanolamine are added sequentially and mixed evenly. Then formaldehyde solution is added dropwise over a period of 0.5h to 2h. After the addition is complete, the temperature is heated to 100℃ to 125℃ and stirred for 5h to 7h to obtain the mixture to be treated. (2) Add n-hexane to the mixture to be treated for dilution, wash it multiple times with deionized water until the pH is 6.8~7.2, separate the deionized water and retain the n-hexane solution, and then distill and vacuum dry the n-hexane solution to obtain polyisobutylene phenol Mannich base; (3) Under a nitrogen atmosphere, the polyisobutylene phenol Mannich base was dissolved in toluene, potassium persulfate was added and stirred to dissolve, styrene was added dropwise at a rate of 0.3 ml / min to 0.8 ml / min, and the temperature was raised to 70°C to 80°C. The mixture was stirred for 4 h to 6 h, then cooled to 25°C to 30°C. Methanol was added at a predetermined time to terminate the reaction. The mixture was filtered, washed, and vacuum dried to obtain the product to be quaternized. (4) Dissolve the product to be quaternized in anhydrous ethanol, then add benzyl chloride and sodium iodide, heat to 45℃~60℃, stir for 4h~6h, evaporate under reduced pressure after the reaction, wash with ether 2~5 times, and dry under vacuum to obtain the styrene-modified polyisobutylene phenol Mannich base quaternary ammonium salt.

5. The engine oil as described in claim 4, characterized in that, In step (3), the stirring reaction is carried out continuously at a stirring speed of not less than 500 rpm. After the stirring reaction is completed, methanol is added dropwise at a predetermined time to terminate the reaction. The dropwise addition time is 30 min to 45 min. During washing, methanol and deionized water are mixed in a 1:1 volume ratio to obtain a washing solution, and the reaction product is washed 2 to 3 times. Then, it is vacuum dried at 35℃ to 45℃ for 12 to 15 hours to obtain the product to be quaternized.

6. The engine oil as described in claim 4, characterized in that, In step (4), the product washed with ether is vacuum dried at 48℃~55℃ for 8h~13h to obtain the styrene-modified polyisobutylene phenol Mannich base quaternary ammonium salt.

7. The engine oil as described in claim 1, characterized in that, The hydrotreated base oils include Group II hydrotreated base oil 500SN, Group III hydrotreated base oil 500SN, and Group III hydrotreated base oil 500N, with an addition weight ratio of (1.5~2):(1.5~2):1; The anti-wear agent is a mixture of zinc dialkyl dithiophosphate and molybdenum dithiocarbamate, with a weight ratio of 1:(0.2~0.4).

8. The engine oil as described in claim 1, characterized in that, The antioxidants include 2,6-di-tert-butyl-p-cresol and / or alkylated diphenylamine; The metal passivating agent includes benzotriazole and / or 2,5-bisoctyldithiothiadiazole.

9. The engine oil as described in claim 7, characterized in that, The weight ratio of detergent-dispersant to hydrotreated base oil is 1:(13~16).

10. An engine oil as described in any one of claims 1 to 9, characterized in that, Includes the following steps: The hydrotreated base oil is heated to 50℃~60℃ and stirred for 10 min~30 min. Then, detergent-dispersant, antioxidant, anti-wear agent and metal passivator are added in sequence. Stirring is continued at 50℃~60℃ for 1~3 h to obtain a mixed oil. The mixed oil is filtered at a pressure of 0.1 MPa to 0.2 MPa to obtain the engine oil.

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