Viscosity index improver for lubricating oil

Abstract

The invention discloses a viscosity index improver for lubricating oil, and relates to the technical field of lubricating oil additives. Comprising the following components in parts by weight: 8 to 15 parts of a methacrylate monomer, 5 to 10 parts of a poly (N-isopropylacrylamide) monomer, 3 to 8 parts of a benzoxazine monomer, 0.05 to 0.2 part of azodiisobutyronitrile, 8 to 15 parts of methyl oleate, 5 to 12 parts of polyisobutene, 2 to 5 parts of molybdenum disulfide nanoparticles, 1 to 3 parts of a silane coupling agent, 0.05 to 0.15 part of benzoyl peroxide, 6 to 12 parts of dimethyl carbonate, 1 to 3 parts of nano montmorillonite, 10 to 18 parts of castor oil and 5 to 10 parts of epoxy chloropropane. 0.2 to 0.8 part of boron trifluoride diethyl etherate complex, 5 to 10 parts of ethanol and 0.05 to 0.2 part of dodecanethiol. The problems that lubricating oil is difficult to degrade, soil and water are polluted, and the ecological environment is harmed are solved.

Description

Technical Field

[0001] This invention relates to the field of lubricant additives, specifically to a viscosity index improver for lubricants. Background Technology

[0002] Viscosity index improvers for lubricating oils are used to improve the viscosity-temperature characteristics of lubricating oils. That is, by changing the morphology of their molecules at different temperatures, they enable lubricating oils to maintain a low viscosity at low temperatures to ensure fluidity, and maintain sufficient viscosity at high temperatures to ensure the strength of the lubricating film. This widens the applicable temperature range of the lubricating oil and ensures that equipment can obtain stable and effective lubrication protection under different operating conditions.

[0003] Existing technologies for viscosity index improvers of lubricating oils suffer from problems such as poor environmental performance, unsatisfactory anti-wear effects, and insufficient compatibility with base oils. Many improvers use mineral-based raw materials with low biodegradability, easily causing environmental pollution after disposal. Some improvers containing anti-wear components have unstable anti-wear performance due to uneven dispersion, failing to provide long-term effective equipment protection. Furthermore, the organic solvents used in traditional preparation processes easily cause the improvers to separate or precipitate in the lubricating oil, affecting their performance stability and consequently impacting the overall performance and applicability of the lubricating oil. Therefore, this invention provides a viscosity index improver for lubricating oils. Summary of the Invention

[0004] The purpose of this invention is to provide a viscosity index improver for lubricating oil. By combining various functional components and optimizing the preparation process, this invention achieves a comprehensive improvement in the environmental performance, anti-wear performance, and compatibility with base oil of lubricating oil, thereby solving the problems existing in the prior art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A viscosity index improver for lubricating oil comprises the following components in parts by weight: 8-15 parts of methacrylate monomers, 5-10 parts of poly(N-isopropylacrylamide) monomers, 3-8 parts of benzoxazine monomers, 0.05-0.2 parts of azobisisobutyronitrile, 8-15 parts of methyl oleate, 5-12 parts of polyisobutylene, 2-5 parts of molybdenum disulfide nanoparticles, 1-3 parts of silane coupling agent, 0.05-0.15 parts of benzoyl peroxide, 6-12 parts of dimethyl carbonate, 1-3 parts of nano-montmorillonite, 10-18 parts of castor oil, 5-10 parts of epichlorohydrin, 0.2-0.8 parts of boron trifluoride ether complex, 5-10 parts of ethanol, and 0.05-0.2 parts of dodecyl mercaptan.

[0006] Preferably, the preparation steps are as follows: S1: Prepare smart responsive polymers, self-healing anti-wear polymers, and bio-based polymers respectively; S2: Mix the smart responsive polymer, the self-healing anti-wear polymer and the bio-based polymer in a certain proportion, add the dispersion medium supercritical carbon dioxide, the amount of supercritical carbon dioxide is 50% to 80% of the total volume of the reaction system, and then add 0.05 to 0.2 parts of the chain transfer agent dodecyl mercaptan. S3: Control the reaction conditions to carry out the mixing reaction and obtain the viscosity index improver of the lubricating oil.

[0007] Preferably, the preparation method of the smart responsive polymer in step S1 is as follows: adding methacrylate monomers, poly-N-isopropylacrylamide monomers, benzoxazine monomers, azobisisobutyronitrile and methyl oleate into a reaction vessel, and stirring at 150-250 r / min at 60-80°C for 4-6 hours to obtain the smart responsive polymer.

[0008] Preferably, when preparing the smart responsive polymer, after the reaction is completed, some of the bio-based solvent methyl oleate is removed by vacuum distillation until the polymer solid content reaches 60% to 70%.

[0009] Preferably, the preparation method of the self-healing anti-wear polymer in step S1 is as follows: polyisobutylene, molybdenum disulfide nanoparticles, silane coupling agent, benzoyl peroxide, dimethyl carbonate and nano-montmorillonite are added to a reaction vessel and reacted at 70-90°C with a stirring rate of 150-250 r / min for 3-5 hours to obtain the self-healing anti-wear polymer.

[0010] Preferably, when preparing the self-healing and wear-resistant polymer, the molybdenum disulfide nanoparticles need to be ultrasonically dispersed first, with an ultrasonic power of 300-500W and an ultrasonic time of 20-30 minutes, before being added to the reaction vessel to participate in the reaction.

[0011] Preferably, the preparation method of the bio-based polymer in step S1 is as follows: castor oil, epichlorohydrin, and boron trifluoride diethyl ether complex are added to a reaction apparatus and reacted at 50-70°C for 5-7 hours. Then ethanol is added and the mixture is stirred at 40-50°C at a stirring rate of 100-200 r / min for 1-2 hours. The mixture is then allowed to stand and separate into layers. The upper liquid is taken as the purified bio-based polymer.

[0012] Preferably, the mixing weight ratio of the smart responsive polymer, the self-healing anti-wear polymer and the bio-based polymer in step S2 is: 1-2 parts of smart responsive polymer, 1-1.5 parts of self-healing anti-wear polymer and 1.5-2.5 parts of bio-based polymer.

[0013] Preferably, the mixing reaction conditions in step S3 are: temperature 80-100℃, pressure 15-20MPa, reaction time 2-4 hours, and continuous stirring during the reaction, with a stirring rate of 200-300r / min.

[0014] Preferably, the viscosity index improver is added to the lubricating oil at a weight percentage of 3% to 8%.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention prepares a bio-based polymer using castor oil as a raw material, and mixes it with a smart responsive polymer and a self-healing anti-wear polymer in a ratio of 1-2 parts smart responsive polymer, 1-1.5 parts self-healing anti-wear polymer, and 1.5-2.5 parts bio-based polymer. This improves the biodegradability of lubricating oil. Compared with existing technologies, this significantly enhances the environmental performance of lubricating oil. The introduction of the bio-based polymer makes the lubricating oil more easily decomposed by microorganisms in the environment after disposal, effectively solving the problem of traditional lubricating oils being difficult to degrade, causing pollution to soil and water, and harming the ecological environment.

[0016] 2. This invention achieves uniform dispersion of molybdenum disulfide nanoparticles in the polymer by subjecting them to ultrasonic dispersion treatment at 300-500W for 20-30 minutes during the preparation of the self-healing anti-wear polymer, allowing them to fully react with components such as polyisobutylene and silane coupling agents. Compared with existing technologies, this significantly improves the self-healing and anti-wear performance of lubricating oil. The uniformly dispersed molybdenum disulfide nanoparticles can quickly and effectively form a tough protective film on the friction surface, promptly repairing surface damage when wear occurs. This solves the problem of accelerated wear of components due to continuous friction accumulation during long-term use of existing lubricating oils, thus reducing equipment lifespan.

[0017] 3. This invention utilizes supercritical carbon dioxide as the dispersion medium, accounting for 50%–80% of the total volume of the reaction system, and combines it with the chain transfer agent dodecyl mercaptan to regulate the polymerization reaction, achieving a molecular-level uniform mixture of the three polymers. Compared with existing technologies, this improves the dispersion stability of the modifier in lubricating oil and avoids the stratification or precipitation problems caused by traditional solvent methods. Therefore, it can solve the problems of insufficient compatibility between the modifier and base oil and performance degradation after long-term use. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention have been clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] This embodiment provides a viscosity index improver for lubricating oil, comprising the following components in parts by weight: 8-15 parts of methacrylate monomers, 5-10 parts of poly(N-isopropylacrylamide) monomers, 3-8 parts of benzoxazine monomers, 0.05-0.2 parts of azobisisobutyronitrile, 8-15 parts of methyl oleate, 5-12 parts of polyisobutylene, 2-5 parts of molybdenum disulfide nanoparticles, 1-3 parts of silane coupling agent, 0.05-0.15 parts of benzoyl peroxide, 6-12 parts of dimethyl carbonate, 1-3 parts of nano-montmorillonite, 10-18 parts of castor oil, 5-10 parts of epichlorohydrin, 0.2-0.8 parts of boron trifluoride diethyl ether complex, 5-10 parts of ethanol, and 0.05-0.2 parts of dodecyl mercaptan.

[0020] In some embodiments, the preparation steps are as follows: S1: Prepare smart responsive polymers, self-healing anti-wear polymers, and bio-based polymers respectively; S2: Mix the smart responsive polymer, the self-healing anti-wear polymer and the bio-based polymer in a certain proportion, add the dispersion medium supercritical carbon dioxide, the amount of supercritical carbon dioxide is 50% to 80% of the total volume of the reaction system, and then add 0.05 to 0.2 parts of the chain transfer agent dodecyl mercaptan. S3: Control the reaction conditions to carry out the mixing reaction and obtain the viscosity index improver of the lubricating oil.

[0021] In some embodiments, the preparation method of the smart responsive polymer in step S1 is as follows: adding methacrylate monomers, poly-N-isopropylacrylamide monomers, benzoxazine monomers, azobisisobutyronitrile and methyl oleate into a reaction vessel, and stirring at 150-250 r / min at 60-80°C for 4-6 hours to obtain the smart responsive polymer.

[0022] In some embodiments, when preparing the smart responsive polymer, after the reaction is completed, a portion of the bio-based solvent methyl oleate is removed by vacuum distillation until the polymer solid content reaches 60% to 70%.

[0023] In some embodiments, the preparation method of the self-healing anti-wear polymer in step S1 is as follows: polyisobutylene, molybdenum disulfide nanoparticles, silane coupling agent, benzoyl peroxide, dimethyl carbonate and nano-montmorillonite are added to a reaction vessel and reacted at 70-90°C with a stirring rate of 150-250 r / min for 3-5 hours to obtain the self-healing anti-wear polymer.

[0024] In some embodiments, when preparing the self-healing and wear-resistant polymer, the molybdenum disulfide nanoparticles need to be ultrasonically dispersed first, with an ultrasonic power of 300-500W and an ultrasonic time of 20-30 minutes, before being added to the reaction vessel to participate in the reaction.

[0025] In some embodiments, the preparation method of the bio-based polymer in step S1 is as follows: castor oil, epichlorohydrin, and boron trifluoride diethyl ether complex are added to a reaction apparatus and reacted at 50-70°C for 5-7 hours. Then ethanol is added and the mixture is stirred at 40-50°C at a stirring rate of 100-200 r / min for 1-2 hours. The mixture is then allowed to stand and separate into layers. The upper liquid is taken as the purified bio-based polymer.

[0026] In some embodiments, the mixing weight ratio of the smart responsive polymer, the self-healing anti-wear polymer, and the bio-based polymer in step S2 is: 1-2 parts of smart responsive polymer, 1-1.5 parts of self-healing anti-wear polymer, and 1.5-2.5 parts of bio-based polymer.

[0027] In some embodiments, the mixing reaction conditions in step S3 are: temperature 80-100°C, pressure 15-20 MPa, reaction time 2-4 hours, and continuous stirring during the reaction at a stirring rate of 200-300 r / min.

[0028] In some embodiments, the viscosity index improver is added to the lubricating oil at a weight percentage of 3% to 8%.

[0029] Based on the foregoing embodiments, the following sets of experiments were conducted: It should be noted that the raw materials used in the following embodiments are all commercially available.

[0030] Example 1: A viscosity index improver for lubricating oil, comprising the following components in parts by weight: 10 parts methacrylate monomers, 7 parts poly(N-isopropylacrylamide) monomers, 5 parts benzoxazine monomers, 0.1 parts azobisisobutyronitrile, 12 parts methyl oleate, 8 parts polyisobutylene, 3 parts molybdenum disulfide nanoparticles, 2 parts silane coupling agent, 0.1 parts benzoyl peroxide, 9 parts dimethyl carbonate, 2 parts nano-montmorillonite, 15 parts castor oil, 7 parts epichlorohydrin, 0.5 parts boron trifluoride ether complex, 7 parts ethanol, and 0.1 parts dodecyl mercaptan. The preparation steps are as follows: S1: Prepare smart responsive polymers, self-healing anti-wear polymers, and bio-based polymers respectively; S2: Mix the smart responsive polymer, the self-healing anti-wear polymer and the bio-based polymer in a certain proportion, add the dispersion medium supercritical carbon dioxide, the amount of supercritical carbon dioxide is 65% of the total volume of the reaction system, and then add 0.1 parts of chain transfer agent dodecyl mercaptan. S3: Control the reaction conditions to carry out the mixing reaction and obtain the viscosity index improver of the lubricating oil. The preparation method of the smart responsive polymer in step S1 is as follows: methacrylate monomers, poly-N-isopropylacrylamide monomers, benzoxazine monomers, azobisisobutyronitrile and methyl oleate are added to a reaction vessel, and the mixture is stirred at 200 r / min for 5 hours at 70°C to obtain the smart responsive polymer. When preparing the smart responsive polymer, after the reaction is completed, some of the bio-based solvent methyl oleate is removed by vacuum distillation until the polymer solid content reaches 65%. The preparation method of the self-healing anti-wear polymer in step S1 is as follows: polyisobutylene, molybdenum disulfide nanoparticles, silane coupling agent, benzoyl peroxide, dimethyl carbonate and nano-montmorillonite are added to the reaction vessel and reacted at 80°C with a stirring rate of 200 r / min for 4 hours to obtain the self-healing anti-wear polymer.

[0031] When preparing self-healing and wear-resistant polymers, molybdenum disulfide nanoparticles need to be ultrasonically dispersed first, with an ultrasonic power of 400W and an ultrasonic time of 25 minutes, before being added to the reaction vessel to participate in the reaction. The preparation method of the bio-based polymer in step S1 is as follows: castor oil, epichlorohydrin, and boron trifluoride diethyl ether complex are added to the reaction apparatus and reacted at 60°C for 6 hours. Then ethanol is added and stirred at 45°C at a stirring rate of 150 r / min for 1.5 hours. After standing and separating into layers, the upper liquid is taken as the purified bio-based polymer. In step S2, the mixing weight ratio of the smart responsive polymer, the self-healing anti-wear polymer, and the bio-based polymer is: 1.5 parts of smart responsive polymer, 1.2 parts of self-healing anti-wear polymer, and 2 parts of bio-based polymer. The conditions for the mixing reaction in step S3 are: temperature 90℃, pressure 18MPa, reaction time 3 hours, and continuous stirring during the reaction at a stirring rate of 250r / min. The viscosity index improver is added to the lubricating oil at a rate of 5% by weight.

[0032] Example 2: A viscosity index improver for lubricating oil, comprising the following components in parts by weight: 8 parts methacrylate monomers, 5 parts poly(N-isopropylacrylamide) monomers, 3 parts benzoxazine monomers, 0.05 parts azobisisobutyronitrile, 8 parts methyl oleate, 5 parts polyisobutylene, 2 parts molybdenum disulfide nanoparticles, 1 part silane coupling agent, 0.05 parts benzoyl peroxide, 6 parts dimethyl carbonate, 1 part nano-montmorillonite, 10 parts castor oil, 5 parts epichlorohydrin, 0.2 parts boron trifluoride ether complex, 5 parts ethanol, and 0.05 parts dodecyl mercaptan. The preparation steps are as follows: S1: Prepare smart responsive polymers, self-healing anti-wear polymers, and bio-based polymers respectively; S2: Mix the smart responsive polymer, the self-healing anti-wear polymer and the bio-based polymer in a certain proportion, add the dispersion medium supercritical carbon dioxide, the amount of supercritical carbon dioxide is 50% of the total volume of the reaction system, and then add 0.05 parts of chain transfer agent dodecyl mercaptan. S3: Control the reaction conditions to carry out the mixing reaction and obtain the viscosity index improver of the lubricating oil. The preparation method of the smart responsive polymer in step S1 is as follows: methacrylate monomers, poly-N-isopropylacrylamide monomers, benzoxazine monomers, azobisisobutyronitrile and methyl oleate are added to a reaction vessel, and the mixture is stirred at 150 r / min for 4 hours at 60°C to obtain the smart responsive polymer. When preparing the smart responsive polymer, after the reaction is completed, some of the bio-based solvent methyl oleate is removed by vacuum distillation until the polymer solid content reaches 60%. The preparation method of the self-healing anti-wear polymer in step S1 is as follows: polyisobutylene, molybdenum disulfide nanoparticles, silane coupling agent, benzoyl peroxide, dimethyl carbonate and nano-montmorillonite are added to the reaction vessel and reacted at 70°C with a stirring rate of 150 r / min for 3 hours to obtain the self-healing anti-wear polymer.

[0033] When preparing self-healing and wear-resistant polymers, molybdenum disulfide nanoparticles need to be ultrasonically dispersed first, with an ultrasonic power of 300W and an ultrasonic time of 20 minutes, before being added to the reaction vessel to participate in the reaction. The preparation method of the bio-based polymer in step S1 is as follows: castor oil, epichlorohydrin, and boron trifluoride diethyl ether complex are added to the reaction apparatus and reacted at 50°C for 5 hours. Then ethanol is added and stirred at 40°C at a stirring rate of 100 r / min for 1 hour. After standing and separating into layers, the upper liquid is taken as the purified bio-based polymer. In step S2, the mixing weight ratio of the smart responsive polymer, the self-healing anti-wear polymer, and the bio-based polymer is: 1 part smart responsive polymer, 1 part self-healing anti-wear polymer, and 1.5 parts bio-based polymer. The conditions for the mixing reaction in step S3 are: temperature 80℃, pressure 15MPa, reaction time 2 hours, and continuous stirring during the reaction at a stirring rate of 200r / min. The viscosity index improver is added to the lubricating oil at a rate of 3% by weight.

[0034] Example 3: A viscosity index improver for lubricating oil, comprising the following components in parts by weight: 15 parts methacrylate monomers, 10 parts poly(N-isopropylacrylamide) monomers, 8 parts benzoxazine monomers, 0.2 parts azobisisobutyronitrile, 15 parts methyl oleate, 12 parts polyisobutylene, 5 parts molybdenum disulfide nanoparticles, 3 parts silane coupling agent, 0.15 parts benzoyl peroxide, 12 parts dimethyl carbonate, 3 parts nano-montmorillonite, 18 parts castor oil, 10 parts epichlorohydrin, 0.8 parts boron trifluoride ether complex, 10 parts ethanol, and 0.2 parts dodecyl mercaptan. The preparation steps are as follows: S1: Prepare smart responsive polymers, self-healing anti-wear polymers, and bio-based polymers respectively; S2: Mix the smart responsive polymer, the self-healing anti-wear polymer and the bio-based polymer in a certain proportion, add the dispersion medium supercritical carbon dioxide, the amount of supercritical carbon dioxide is 80% of the total volume of the reaction system, and then add 0.2 parts of chain transfer agent dodecyl mercaptan. S3: Control the reaction conditions to carry out the mixing reaction and obtain the viscosity index improver of the lubricating oil. The preparation method of the smart responsive polymer in step S1 is as follows: methacrylate monomers, poly-N-isopropylacrylamide monomers, benzoxazine monomers, azobisisobutyronitrile and methyl oleate are added to a reaction vessel, and the mixture is stirred at 250 r / min for 6 hours at 80°C to obtain the smart responsive polymer. When preparing the smart responsive polymer, after the reaction is completed, some of the bio-based solvent methyl oleate is removed by vacuum distillation until the polymer solid content reaches 70%. The preparation method of the self-healing anti-wear polymer in step S1 is as follows: polyisobutylene, molybdenum disulfide nanoparticles, silane coupling agent, benzoyl peroxide, dimethyl carbonate and nano-montmorillonite are added to the reaction vessel and reacted at 90°C with a stirring rate of 250 r / min for 5 hours to obtain the self-healing anti-wear polymer.

[0035] When preparing self-healing and wear-resistant polymers, molybdenum disulfide nanoparticles need to be ultrasonically dispersed first, with an ultrasonic power of 500W and an ultrasonic time of 30 minutes, before being added to the reaction vessel to participate in the reaction. The preparation method of the bio-based polymer in step S1 is as follows: castor oil, epichlorohydrin, and boron trifluoride diethyl ether complex are added to the reaction apparatus and reacted at 70°C for 7 hours. Then ethanol is added and stirred at 50°C with a stirring rate of 200 r / min for 2 hours. After standing and separating into layers, the upper liquid is taken as the purified bio-based polymer. In step S2, the mixing weight ratio of the smart responsive polymer, the self-healing anti-wear polymer, and the bio-based polymer is: 2 parts smart responsive polymer, 1.5 parts self-healing anti-wear polymer, and 2.5 parts bio-based polymer. The conditions for the mixing reaction in step S3 are: temperature 100℃, pressure 20MPa, reaction time 4 hours, and continuous stirring during the reaction at a stirring rate of 300r / min. The viscosity index improver is added to the lubricating oil at a weight percentage of 8%.

[0036] Comparative Example 1 differs from Example 1 in that: castor oil is not used to prepare the bio-based polymer; instead, an equal part by weight of mineral oil is used.

[0037] Comparative Example 2 differs from Example 1 in that the molybdenum disulfide nanoparticles are not ultrasonically dispersed during the preparation of the self-healing and wear-resistant polymer.

[0038] Comparative Example 3 differs from Example 1 in that it does not use supercritical carbon dioxide as the dispersion medium, but instead uses an equal volume of the traditional organic solvent toluene.

[0039] Comparative Example 4 differs from Example 1 in that the smart responsive polymer, self-healing anti-wear polymer, and bio-based polymer are mixed in a ratio of 3 parts: 0.5 parts: 1 part.

[0040] Performance testing: Performance tests were conducted on the viscosity index improvers of the lubricating oils treated in Examples 1, 2, 3, 1, 2, 3, and 4. The test data are recorded in Table 1 below: project Biodegradation rate (%, 28 days) Wear scar diameter (mm, 392N, 60min) Dispersion stability (%, no stratification after 30 days) Viscosity index improvement value Example 1 64 0.35 94 46 Example 2 58 0.39 89 41 Example 3 68 0.33 97 50 Comparative Example 1 21 0.36 94 43 Comparative Example 2 63 0.52 92 35 Comparative Example 3 64 0.37 60 38 Comparative Example 4 58 0.41 86 32 In the performance test, the biodegradability rate was determined according to GB / T19203~2003 "Determination of Biodegradability of Lubricating Oils", the wear scar diameter was determined using a four-ball friction and wear tester according to GB / T3142~1982 "Determination of Carrying Capacity of Lubricants", and the dispersion stability was determined by observing whether the sample separated into layers within 30 days and calculating the proportion of the stable part. The viscosity index improvement value was the difference between the viscosity index of the lubricating oil and the viscosity index of the base oil after the addition of the improver.

[0041] As can be seen, the lubricating oil viscosity index improver provided in the embodiments of the present invention exhibits comprehensive advantages in environmental performance, anti-wear performance, dispersion stability and viscosity index improvement through the synergistic effect of multiple components and the optimization of the preparation process. These advantages can be clearly demonstrated through the performance comparison of the embodiments and comparative examples.

[0042] From the perspective of the role of bio-based components, Examples 1, 2, and 3 all used castor oil to prepare bio-based polymers, and the biodegradability rate was significantly higher than that of Comparative Example 1, which used an equal amount of mineral oil to replace castor oil. This is because castor oil, as a renewable biological raw material, has ester groups and unsaturated bonds in its molecular structure that are more easily decomposed by microorganisms, while the long-chain alkane structure of mineral oil is difficult to degrade, resulting in a significant decrease in the biodegradability rate. Meanwhile, the bio-based polymers showed good compatibility with other components; the viscosity index improvement value of Example 1 was slightly higher than that of Comparative Example 1, indicating that the bio-based components not only improved environmental friendliness but also enhanced system stability through intermolecular forces, thus assisting in improving the viscosity adjustment effect.

[0043] Regarding the dispersion process of the self-healing anti-wear component, the wear scar diameters of Examples 1, 2, and 3 were significantly smaller than those of Comparative Example 2 without ultrasonic dispersion of the molybdenum disulfide nanoparticles. This is because after ultrasonic dispersion at 300–500 W for 20–30 minutes, the molybdenum disulfide nanoparticles are more uniformly dispersed in the polymer matrix, enabling them to more efficiently fill micro-pits on the friction surface and form a continuous lubricating film. Without ultrasonic treatment, the nanoparticles tend to agglomerate, weakening the anti-wear effect. Furthermore, the viscosity index increases of Examples 1 and 3 were higher than those of Comparative Example 2, indicating that uniformly dispersed nanoparticles can reduce friction within the system. Combined with the thickening effect of polyisobutylene, this further optimizes the viscosity-temperature characteristics.

[0044] Regarding the dispersion advantages of supercritical carbon dioxide, the dispersion stability of Examples 1, 2, and 3 is significantly better than that of Comparative Example 3 when an equal volume of toluene was used instead of supercritical carbon dioxide as the dispersion medium. Supercritical carbon dioxide combines the diffusivity of a gas with the solubility of a liquid, enabling the three polymers to mix uniformly under high pressure without solvent residue issues. In contrast, toluene, as a traditional organic solvent, tends to separate due to its volatility and compatibility with the polymers, thus affecting the viscosity index improvement. The viscosity index improvement values ​​of Examples 1, 2, and 3 are higher than those of Comparative Example 3. Furthermore, as a green solvent, supercritical carbon dioxide avoids the toxicity and environmental pollution of toluene, synergistically enhancing the environmental attributes of the product with the bio-based components.

[0045] Regarding the synergistic effect of polymer formulation, Examples 1, 2, and 3 showed better viscosity index improvement, dispersion stability, and anti-wear performance than Comparative Example 4. This is attributed to the optimized formulation of the smart responsive polymer, the self-healing anti-wear polymer, and the bio-based polymer. The smart responsive polymer contains poly(N-isopropylacrylamide), which can adjust the molecular chain morphology to stabilize viscosity with temperature changes. The self-healing anti-wear polymer contains molybdenum disulfide and nano-montmorillonite, which can provide anti-wear support. The bio-based polymer is derived from castor oil, which can enhance the system's compatibility. In contrast, the formulation of Comparative Example 4 was unbalanced, resulting in the inability of the components to function synergistically and a comprehensive decline in performance.

[0046] By comparing and analyzing the relevant data in the table, it can be seen that by rationally selecting the raw material composition, optimizing the preparation process parameters, and controlling the mixing ratio of each polymer, the prepared lubricating oil viscosity index improver exhibits excellent performance in terms of environmental protection, anti-wear properties, dispersion stability, and viscosity index improvement. This indicates that the lubricating oil viscosity index improver provided by this invention has a broader market prospect and is more suitable for widespread application.

[0047] In the description of this specification, references to terms such as "an experiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that experiment or example is included in at least one experiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same experiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more experiments or examples.

[0048] The preferred experiments disclosed above are merely illustrative of the invention. These preferred experiments do not exhaustively describe all details, nor do they limit the invention to the specific embodiments described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these experiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize it. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A viscosity index improver for lubricating oil, characterized in that, It comprises the following components by weight: 8-15 parts of methacrylate monomers, 5-10 parts of poly(N-isopropylacrylamide) monomers, 3-8 parts of benzoxazine monomers, 0.05-0.2 parts of azobisisobutyronitrile, 8-15 parts of methyl oleate, 5-12 parts of polyisobutylene, 2-5 parts of molybdenum disulfide nanoparticles, 1-3 parts of silane coupling agent, 0.05-0.15 parts of benzoyl peroxide, 6-12 parts of dimethyl carbonate, 1-3 parts of nano-montmorillonite, 10-18 parts of castor oil, 5-10 parts of epichlorohydrin, 0.2-0.8 parts of boron trifluoride diethyl ether complex, 5-10 parts of ethanol, and 0.05-0.2 parts of dodecyl mercaptan.

2. The viscosity index improver for lubricating oil according to claim 1, characterized in that, The preparation steps are as follows: S1: Prepare smart responsive polymers, self-healing anti-wear polymers, and bio-based polymers respectively; S2: Mix the smart responsive polymer, the self-healing anti-wear polymer and the bio-based polymer in a certain proportion, add the dispersion medium supercritical carbon dioxide, the amount of supercritical carbon dioxide is 50% to 80% of the total volume of the reaction system, and then add 0.05 to 0.2 parts of the chain transfer agent dodecyl mercaptan. S3: Control the reaction conditions to carry out the mixing reaction and obtain the viscosity index improver of the lubricating oil.

3. The viscosity index improver for lubricating oil according to claim 2, characterized in that, The preparation method of the smart responsive polymer in step S1 is as follows: add methacrylate monomers, poly-N-isopropylacrylamide monomers, benzoxazine monomers, azobisisobutyronitrile and methyl oleate into a reaction vessel, and stir at 150-250 r / min at 60-80℃ for 4-6 hours to obtain the smart responsive polymer.

4. The viscosity index improver for lubricating oil according to claim 2, characterized in that, When preparing the smart responsive polymer, after the reaction is completed, some of the bio-based solvent methyl oleate is removed by vacuum distillation until the polymer solid content reaches 60% to 70%.

5. The viscosity index improver for lubricating oil according to claim 2, characterized in that, The preparation method of the self-healing anti-wear polymer in step S1 is as follows: polyisobutylene, molybdenum disulfide nanoparticles, silane coupling agent, benzoyl peroxide, dimethyl carbonate and nano-montmorillonite are added to a reaction vessel and reacted at 70-90℃ with a stirring rate of 150-250 r / min for 3-5 hours to obtain the self-healing anti-wear polymer.

6. The viscosity index improver for lubricating oil according to claim 2, characterized in that, When preparing self-healing and wear-resistant polymers, molybdenum disulfide nanoparticles need to be ultrasonically dispersed first, with an ultrasonic power of 300-500W and an ultrasonic time of 20-30 minutes, before being added to the reaction vessel to participate in the reaction.

7. The viscosity index improver for lubricating oil according to claim 2, characterized in that, The preparation method of the bio-based polymer in step S1 is as follows: castor oil, epichlorohydrin, and boron trifluoride diethyl ether complex are added to the reaction apparatus and reacted at 50-70°C for 5-7 hours. Then ethanol is added and stirred at 40-50°C at a stirring rate of 100-200 r / min for 1-2 hours. After standing and separating into layers, the upper liquid is taken as the purified bio-based polymer.

8. The viscosity index improver for lubricating oil according to claim 2, characterized in that, In step S2, the mixing weight ratio of the smart responsive polymer, the self-healing anti-wear polymer, and the bio-based polymer is: 1-2 parts of smart responsive polymer, 1-1.5 parts of self-healing anti-wear polymer, and 1.5-2.5 parts of bio-based polymer.

9. The viscosity index improver for lubricating oil according to claim 2, characterized in that, The conditions for the mixing reaction in step S3 are: temperature 80-100℃, pressure 15-20MPa, reaction time 2-4 hours, and continuous stirring during the reaction at a stirring rate of 200-300r / min.

10. A viscosity index improver for lubricating oil according to claim 1, characterized in that, The viscosity index improver is added to the lubricating oil at a rate of 3% to 8% by weight.