A full synthetic gasoline engine oil for a hybrid engine and a method for preparing the same

Abstract

The present application relates to lubricating oil chemical technology field, specifically relates to a kind of full synthetic gasoline engine oil for hybrid engine and its preparation method, including base oil 50wt%~95wt%, is class III or class IV or its combination, viscosity index modifier 0.5wt%~25wt%, is star or comb polymethacrylate, functional additive 4wt%~30wt%, after 5wt% fuel dilution, 100 ℃ viscosity retention rate ≥80%, shear viscosity recovery rate ≥70%.The present application is by using star and or comb polymethacrylate as viscosity agent, under fuel dilution, molecular chain changes from tight to stretch, increase hydrodynamic volume, produce viscosity gain to offset dilution loss, realize viscosity self-compensation, by using star / comb polymethacrylate has multiple branched topological structure, under high shear stress, reversible elastic deformation occurs preferentially rather than main chain permanent rupture;After shear stress release, molecular chain is recovered to effective thickening conformation under the driving of entropy elasticity, and significant viscosity recovery characteristics is shown.

Description

Technical Field

[0001] This invention relates to the field of lubricating oil chemical technology, specifically to a fully synthetic gasoline engine oil for hybrid power engines and its preparation method. Background Technology

[0002] With the rapid development of hybrid vehicle technology, hybrid engines are placing higher demands on lubricating oil performance. Hybrid vehicle engines are characterized by frequent start-stop cycles and low-speed electric motor drive, resulting in prolonged operation under cold or partial load conditions, which can easily lead to fuel dilution issues. Existing lubricating oils still have shortcomings in addressing fuel dilution, high shear stability, and viscosity-temperature properties, making it difficult to meet the special operating conditions of hybrid engines.

[0003] CN109913304A discloses a method for preparing wear-resistant lubricating oil for chemical pumps. By adding a mixture of carbon-supported nano-diatomaceous earth and nano-tungsten disulfide, modifiers, and other components, the wear resistance and load-bearing capacity of the lubricating oil are improved. However, this technical solution mainly targets lubricating oils for chemical pumps and does not consider the special operating conditions of fuel dilution in hybrid engines. Its formulation design lacks optimization for viscosity retention after fuel dilution. Furthermore, the solid additives in this lubricating oil may precipitate during long-term use, affecting the stability of the lubrication system, and it does not address improvements in viscosity retention performance under high shear conditions.

[0004] CN107418672A discloses a lubricating oil that improves its viscosity index and stability by using a neutral base oil as the main component and adding a SHELL 260 viscosity index improver. However, the linear viscosity index improver in this technical solution is prone to mechanical fracture under high shear conditions, leading to permanent viscosity loss and failing to meet the high shear requirements of frequent start-stop operations in hybrid engines. Furthermore, this lubricating oil formulation does not consider the impact of fuel dilution on oil performance and lacks a functional design for viscosity recovery after fuel dilution.

[0005] The aforementioned problems indicate that existing lubricant technology still has significant shortcomings in addressing fuel dilution, high shear stability, and viscosity-temperature properties in hybrid engines. Therefore, there is an urgent need to develop a fully synthetic gasoline engine oil for hybrid engines that can effectively cope with fuel dilution, maintain high shear stability, and possess excellent viscosity-temperature properties. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a fully synthetic gasoline engine oil for hybrid engines and its preparation method.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] In a first aspect, the present invention provides a fully synthetic gasoline engine oil for hybrid engines, comprising, by gross weight, the following components:

[0009] S1: 50wt% to 95wt% of base oil, wherein the base oil includes at least one of Group III hydroisomerized base oil and Group IV polyalphaolefin base oil;

[0010] S2: 0.5wt% to 25wt% of a viscosity index improver, wherein the viscosity index improver is the following S21 and / or S22:

[0011] S21: Star-shaped polymethacrylate, which has 3 to 10 polymer arms and a weight-average molecular weight of 80,000 to 400,000;

[0012] S22: Comb-shaped polymethacrylate, which has side chains with an average number of carbon atoms of C6 to C30 and a weight-average molecular weight of 70,000 to 300,000;

[0013] S3: A functional additive system of 4wt% to 30wt%;

[0014] The fully synthetic gasoline engine oil for the hybrid engine, after adding 5wt% to 8wt% of a fuel-simulated diluent, retains a kinematic viscosity of no less than 80% at 100°C. The fuel-simulated diluent is a mixture of n-heptane and isooctane in a mass ratio of 40:60.

[0015] The fully synthetic gasoline engine oil for the hybrid engine, after undergoing the ASTM D6278 standard shear test, has a viscosity recovery rate of not less than 70% after being allowed to stand at 25°C for 30 minutes without shearing.

[0016] Furthermore, when the viscosity index improver contains star-shaped polymethacrylate, the star-shaped polymethacrylate has 4 to 8 arms, each arm is copolymerized from short-chain alkyl methacrylate units and long-chain alkyl methacrylate units, the short-chain alkyl units have C1 to C4 carbon atoms, the long-chain alkyl units have C8 to C18 carbon atoms, and the molar ratio of short-chain units to long-chain units is 2:8 to 5:5.

[0017] Furthermore, when the viscosity index improver comprises comb-shaped polymethacrylate, the side chain branch density of the comb-shaped polymethacrylate is 8 to 40 side chains per 100 main chain repeating units.

[0018] Furthermore, the viscosity index improver is a combination of the star-shaped polymethyl methacrylate and the comb-shaped polymethyl methacrylate, with a mass ratio of 20:80 to 80:20.

[0019] Furthermore, the base oil further comprises alkyl naphthalene and / or synthetic ester base oil, wherein the alkyl naphthalene and / or synthetic ester base oil has a mass percentage of 1wt% to 12wt%.

[0020] Furthermore, the Noyak volatility of the base oil is not higher than 12 wt%.

[0021] Furthermore, the fully synthetic gasoline engine oil for the hybrid engine meets SAE viscosity grades of 0W-20, 0W-30, and 5W-30.

[0022] Furthermore, when the viscosity index improver is dissolved at 25°C in pure base oil and base oil containing 5 wt% fuel simulation diluent, the change rate of its intrinsic viscosity [η] is +10% to +50%. The intrinsic viscosity [η] is determined according to the standard method of GB / T1632 or ISO1628. The fuel simulation diluent is a mixture of n-heptane and isooctane in a mass ratio of 40:60.

[0023] Furthermore, the functional additive system includes a dispersant, a detergent, an antioxidant, an anti-wear agent, and a friction modifier, wherein the anti-wear agent is zinc dialkyl dithiophosphate.

[0024] Secondly, the present invention also provides a method for preparing a fully synthetic gasoline engine oil for a hybrid engine, used to prepare the fully synthetic gasoline engine oil for a hybrid engine as described in any of the above claims.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] This invention employs star-shaped polymethyl methacrylate and / or comb-shaped polymethyl methacrylate as viscosity index improvers. By utilizing the molecular chain conformational transformation that occurs under fuel dilution conditions, the polymer transforms from a relatively compressed state to a more fully extended state, thereby increasing the hydrodynamic volume. The resulting viscosity gain effectively offsets the viscosity loss caused by fuel dilution, achieving viscosity self-compensation.

[0027] The star-shaped / comb-shaped polymethacrylate used has a multi-branched topology, which preferentially undergoes reversible elastic deformation rather than permanent main chain breakage under high shear stress. After the shear stress is released, the molecular chain recovers to the effective viscosity-enhancing conformation under entropic elastic drive, exhibiting significant viscosity recovery characteristics.

[0028] By blending low-volatility base oils with special polymers, a stable liquid-phase environment is provided for polymer conformational adjustment, avoiding polymer precipitation or conformational instability caused by excessive volatility of base oil components, and further improving the stability of the oil under high-temperature conditions. Attached Figure Description

[0029] Figure 1 This is a schematic diagram showing the comparison of kinematic viscosity retention rate at 100℃ according to the present invention;

[0030] Figure 2 This is a schematic diagram comparing the viscosity recovery rates of the present invention;

[0031] Figure 3 This is a schematic diagram showing the relationship between the compounding ratio and the kinematic viscosity retention rate at 100°C according to the present invention;

[0032] Figure 4 This is a schematic diagram illustrating the effect of the amount of diluent added on the kinematic viscosity retention rate at 100°C.

[0033] Figure 5 This is a graph showing the relationship between the compounding ratio and the rate of change of intrinsic viscosity in this invention. Detailed Implementation

[0034] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0035] Raw material description:

[0036] Group III hydroisomerized base oil: kinematic viscosity at 100℃ is 4.0~4.5mm² / s, Noack volatility ≤10wt%.

[0037] PAO-4: Class IV polyalphaolefin base oil, with a kinematic viscosity of approximately 4 mm² / s at 100°C.

[0038] PAO-6: Class IV polyalphaolefin base oil, kinematic viscosity at 100°C is approximately 6 mm² / s.

[0039] Alkylnaphthalene: Commercially available alkylnaphthalene base oil, kinematic viscosity at 100℃ is approximately 5 mm² / s.

[0040] Synthetic ester: Commercially available polyol ester base oil, kinematic viscosity at 100℃ is approximately 4.5 mm² / s.

[0041] Group II base oil: kinematic viscosity at 100°C is approximately 6.5 mm² / s, Noack volatility is approximately 18 wt%, used for comparative analysis.

[0042] Star-shaped polymethyl methacrylate: Commercially available star-shaped polymethyl methacrylate can be used, or it can be prepared by conventional controlled free radical polymerization methods in the art. The star-shaped polymethyl methacrylate used in this embodiment has a pentaerythritol derivative core, 4 branches, and a weight-average molecular weight of 180,000. Each branch is formed by copolymerization of butyl methacrylate and dodecyl methacrylate, with a molar ratio of short-chain units to long-chain units of 35:65.

[0043] Comb-shaped polymethacrylate: Commercially available comb-shaped polymethacrylate can be used, or it can be prepared by copolymerization or graft polymerization of conventional methacrylate monomers in the art. In this embodiment, the main chain of the comb-shaped polymethacrylate is a methacrylate copolymer with a weight average molecular weight of 150,000, an average side chain carbon number of C12, and a side chain grafting density of 18 side chains per 100 main chain repeating units.

[0044] Linear OCP: Linear olefin copolymer with a weight-average molecular weight of approximately 150,000, used for comparative examples.

[0045] Linear PMA: Linear polymethacrylate with a weight-average molecular weight of approximately 160,000, used for comparative purposes.

[0046] Functional additive system: includes polyisobutylene succinimide dispersant, calcium sulfonate detergent, hindered phenol / diphenylamine antioxidant, zinc dialkyl dithiophosphate anti-wear agent, organic molybdenum friction modifier and antifoaming agent.

[0047] The overall Noack volatility of the base oil systems used in Examples 1 to 7 below is no higher than 12 wt%.

[0048] Engine oil testing method:

[0049] Fuel dilution simulation test: Add fuel simulation dilution medium to the oil sample. The fuel simulation dilution medium is a mixture of n-heptane and isooctane in a mass ratio of 40:60. The amount of fuel simulation dilution medium added is 5wt% to 8wt% of the oil sample mass, specifically 5wt%, 6wt%, 7wt% or 8wt%.

[0050] After thoroughly mixing the oil sample with the fuel-based simulated dilution medium, the kinematic viscosity of the oil sample at 100°C before and after dilution was determined according to ASTM D445, and the kinematic viscosity retention rate at 100°C was calculated using the following formula:

[0051] Kinematic viscosity retention at 100℃ = Kinematic viscosity at 100℃ after dilution / Kinematic viscosity at 100℃ before dilution × 100%.

[0052] Shear stability and viscosity recovery rate test: The oil sample was sheared according to the ASTM D6278 standard method. Immediately after shearing, a sample was taken and the kinematic viscosity at 100°C was measured according to ASTM D445, which was recorded as the viscosity at the moment of shearing. Subsequently, the sheared oil sample was kept at 25°C for 30 minutes, and the kinematic viscosity at 100°C was measured again according to ASTM D445, which was recorded as the recovered viscosity. The viscosity recovery rate was calculated according to the following formula:

[0053] Viscosity recovery rate = (viscosity after recovery - viscosity at the moment of shear termination) / (viscosity before shear termination - viscosity at the moment of shear termination) × 100%.

[0054] Intrinsic viscosity determination: According to the standard method of GB / T1632 or ISO1628, the viscosity index improver to be tested is dissolved in pure base oil and base oil containing 5 wt% fuel simulated diluent. The fuel simulated diluent is a mixture of n-heptane and isooctane in a mass ratio of 40:60.

[0055] The outflow time of solutions of various concentrations was measured using an Ubbelohde viscometer in a constant temperature water bath at 25±0.1℃. The intrinsic viscosity [η] was calculated, and the rate of change of intrinsic viscosity was calculated using the following formula:

[0056] The rate of change in intrinsic viscosity = ([η] in the base oil containing the fuel-simulated dilution medium - [η] in the pure base oil) / [η] in the pure base oil × 100%.

[0057] For the compound system of star-shaped polymethyl methacrylate and comb-shaped polymethyl methacrylate, the two are premixed according to the formula ratio and then dissolved in the base oil for testing.

[0058] Example 1

[0059] A fully synthetic gasoline engine oil for hybrid engines comprises the following components:

[0060] Group III hydroisomerized base oils 58 PAO-6 18 Alkylnaphthalene 4 Star-shaped polymethacrylate 6 Functional additive system 14

[0061] The above components, by mass percentage, include, among which, star-shaped polymethacrylate has: a central core of pentaerythritol derivative; 4 branches; a weight-average molecular weight of 180,000; each branch is copolymerized from butyl methacrylate and dodecyl methacrylate; and a molar ratio of short-chain units to long-chain units of 35:65.

[0062] In this embodiment, the base oil system includes Group III hydroisomerized base oil, PAO-6 and alkyl naphthalene, with an overall Noack volatility not exceeding 12 wt%, and the resulting oil meets the SAE 0W-20 viscosity grade.

[0063] A method for preparing a fully synthetic gasoline engine oil for a hybrid engine includes the following steps:

[0064] (1) The measured Group III hydroisomerized base oil, PAO-6 and alkyl naphthalene are added sequentially to the blending vessel equipped with a mechanical stirring and heating device. Stirring is started and the stirring speed is controlled at 200-300 rpm. At the same time, the mixture is heated to 60±2℃.

[0065] (2) Maintain stirring and temperature conditions, slowly add the metered star-shaped polymethyl methacrylate into the mixing tank, control the feeding time to 10-15 minutes, and continue stirring for 30 minutes after the feeding is completed to ensure that the polymer is fully dissolved and evenly dispersed in the base oil;

[0066] (3) Maintain stirring and temperature conditions, add the metered functional additive system into the mixing tank in sequence, and continue stirring for 60 minutes after the addition is completed until the mixture is transparent and homogeneous;

[0067] (4) Stop heating, continue stirring and cooling to room temperature 25±5℃, filter through a 1μm filter bag to obtain the fully synthetic gasoline engine oil product of Example 1.

[0068] Example 2

[0069] A fully synthetic gasoline engine oil for hybrid engines comprises the following components:

[0070] Group III hydroisomerized base oils 52 PAO-4 22 Synthetic esters 5 comb-shaped polymethacrylate 7 Functional additive system 14

[0071] The above components, by mass percentage, include comb-shaped polymethacrylate with the following characteristics: the main chain is a methacrylate copolymer; the weight average molecular weight is 150,000; the average number of carbon atoms in the side chains is C12; and the side chain branching density is 18 side chains per 100 main chain repeating units.

[0072] In this embodiment, the base oil system includes Group III hydroisomerized base oil, PAO-4 and synthetic ester, with an overall Noack volatility not exceeding 12 wt%, and the resulting oil meets the SAE 0W-30 viscosity grade.

[0073] A method for preparing a fully synthetic gasoline engine oil for a hybrid engine includes the following steps:

[0074] (1) The measured Group III hydroisomerized base oil, PAO-4 and synthetic ester are sequentially added to a blending vessel equipped with a mechanical stirring and heating device. Stirring is started, and the stirring speed is controlled at 200-300 rpm. At the same time, the mixture is heated to 60±2℃.

[0075] (2) Maintain stirring and temperature conditions, slowly add the metered comb-shaped polymethyl methacrylate into the mixing tank, control the feeding time to 10-15 minutes, and continue stirring for 30 minutes after the feeding is completed to ensure that the polymer is fully dissolved and evenly dispersed in the base oil;

[0076] (3) Maintain stirring and temperature conditions, add the metered functional additive system into the mixing tank in sequence, and continue stirring for 60 minutes after the addition is completed until the mixture is transparent and homogeneous;

[0077] (4) Stop heating, continue stirring and cooling to room temperature 25±5℃, filter through a 1μm filter bag to obtain the fully synthetic gasoline engine oil product of Example 2.

[0078] Example 3

[0079] This example is an equal-volume control example of star-shaped polymethyl methacrylate used alone, used together with Examples 4-6 and Example 7 to evaluate the effect of the compounding ratio of star-shaped polymethyl methacrylate and comb-shaped polymethyl methacrylate on oil performance.

[0080] A fully synthetic gasoline engine oil for hybrid engines comprises the following components:

[0081] Group III hydroisomerized base oils 50 PAO-6 20 Alkylnaphthalene 5 Star-shaped polymethacrylate 6 Functional additive system 19

[0082] The above components, by mass percentage, include star-shaped polymethyl methacrylate, which is the same as the star-shaped polymethyl methacrylate used in Example 1.

[0083] In this embodiment, the total amount of the base oil system, functional additive system, and viscosity index improver added is consistent with that in Examples 4 to 7, only the specific composition of the viscosity index improver is different, and the resulting oil meets the SAE 5W-30 viscosity grade.

[0084] A method for preparing a fully synthetic gasoline engine oil for a hybrid engine includes the following steps:

[0085] (1) The measured Group III hydroisomerized base oil, PAO-6 and alkyl naphthalene are added sequentially to the blending vessel equipped with a mechanical stirring and heating device. Stirring is started and the stirring speed is controlled at 200-300 rpm. At the same time, the mixture is heated to 60±2℃.

[0086] (2) Maintain stirring and temperature conditions, slowly add the metered star-shaped polymethyl methacrylate into the mixing tank, control the feeding time to 10-15 minutes, and continue stirring for 30 minutes after the feeding is completed to ensure that the polymer is fully dissolved and evenly dispersed in the base oil;

[0087] (3) Maintain stirring and temperature conditions, add the metered functional additive system into the mixing tank in sequence, and continue stirring for 60 minutes after the addition is completed until the mixture is transparent and homogeneous;

[0088] (4) Stop heating, continue stirring and cooling to room temperature 25±5℃, filter through a 1μm filter bag to obtain the fully synthetic gasoline engine oil product of Example 3.

[0089] Example 4

[0090] A fully synthetic gasoline engine oil for hybrid engines comprises the following components:

[0091] Group III hydroisomerized base oils 50 PAO-6 20 Alkylnaphthalene 5 Star-shaped polymethacrylate 4.2 comb-shaped polymethacrylate 1.8 Functional additive system 19

[0092] The components mentioned above, by mass percentage, include star-shaped polymethyl methacrylate, which is the same as the star-shaped polymethyl methacrylate used in Example 1, and comb-shaped polymethyl methacrylate, which is the same as the comb-shaped polymethyl methacrylate used in Example 2.

[0093] In this embodiment, the mass ratio of star-shaped polymethyl methacrylate to comb-shaped polymethyl methacrylate is 70:30, and the total addition amount of the two is 6wt%, and the resulting oil meets the SAE 5W-30 viscosity grade.

[0094] A method for preparing a fully synthetic gasoline engine oil for a hybrid engine includes the following steps:

[0095] (1) The measured Group III hydroisomerized base oil, PAO-6 and alkyl naphthalene are added sequentially to the blending vessel equipped with a mechanical stirring and heating device. Stirring is started and the stirring speed is controlled at 200-300 rpm. At the same time, the mixture is heated to 60±2℃.

[0096] (2) Maintain stirring and temperature conditions, and slowly add the metered star-shaped polymethyl methacrylate and comb-shaped polymethyl methacrylate into the mixing tank in sequence. The feeding time is controlled at 15-20 minutes. After the feeding is completed, continue stirring for 40 minutes to ensure that the two polymers are fully dissolved and evenly dispersed in the base oil.

[0097] (3) Maintain stirring and temperature conditions, add the metered functional additive system into the mixing tank in sequence, and continue stirring for 60 minutes after the addition is completed until the mixture is transparent and homogeneous;

[0098] (4) Stop heating, continue stirring and cooling to room temperature 25±5℃, filter through a 1μm filter bag to obtain the fully synthetic gasoline engine oil product of Example 4.

[0099] Example 5

[0100] A fully synthetic gasoline engine oil for hybrid engines comprises the following components:

[0101] Group III hydroisomerized base oils 50 PAO-6 20 Alkylnaphthalene 5 Star-shaped polymethacrylate 3 comb-shaped polymethacrylate 3 Functional additive system 19

[0102] The components mentioned above, by mass percentage, include star-shaped polymethyl methacrylate, which is the same as the star-shaped polymethyl methacrylate used in Example 1, and comb-shaped polymethyl methacrylate, which is the same as the comb-shaped polymethyl methacrylate used in Example 2.

[0103] In this embodiment, the mass ratio of star-shaped polymethyl methacrylate to comb-shaped polymethyl methacrylate is 50:50, and the total addition amount of the two is 6wt%, and the resulting oil meets the SAE 5W-30 viscosity grade.

[0104] A method for preparing a fully synthetic gasoline engine oil for a hybrid engine includes the following steps:

[0105] (1) The measured Group III hydroisomerized base oil, PAO-6 and alkyl naphthalene are added sequentially to the blending vessel equipped with a mechanical stirring and heating device. Stirring is started and the stirring speed is controlled at 200-300 rpm. At the same time, the mixture is heated to 60±2℃.

[0106] (2) Maintain stirring and temperature conditions, and slowly add the metered star-shaped polymethyl methacrylate and comb-shaped polymethyl methacrylate into the mixing tank in sequence. The feeding time is controlled at 15-20 minutes. After the feeding is completed, continue stirring for 40 minutes to ensure that the two polymers are fully dissolved and evenly dispersed in the base oil.

[0107] (3) Maintain stirring and temperature conditions, add the metered functional additive system into the mixing tank in sequence, and continue stirring for 60 minutes after the addition is completed until the mixture is transparent and homogeneous;

[0108] (4) Stop heating, continue stirring and cooling to room temperature 25±5℃, filter through a 1μm filter bag to obtain the fully synthetic gasoline engine oil product of Example 5.

[0109] Example 6

[0110] A fully synthetic gasoline engine oil for hybrid engines comprises the following components:

[0111] Group III hydroisomerized base oils 50 PAO-6 20 Alkylnaphthalene 5 Star-shaped polymethacrylate 1.8 comb-shaped polymethacrylate 4.2 Functional additive system 19

[0112] The components mentioned above, by mass percentage, include star-shaped polymethyl methacrylate, which is the same as the star-shaped polymethyl methacrylate used in Example 1, and comb-shaped polymethyl methacrylate, which is the same as the comb-shaped polymethyl methacrylate used in Example 2.

[0113] In this embodiment, the mass ratio of star-shaped polymethyl methacrylate to comb-shaped polymethyl methacrylate is 30:70, and the total addition amount is 6 wt%. The resulting oil meets the SAE 5W-30 viscosity grade.

[0114] A method for preparing a fully synthetic gasoline engine oil for a hybrid engine includes the following steps:

[0115] (1) The measured Group III hydroisomerized base oil, PAO-6 and alkyl naphthalene are added sequentially to the blending vessel equipped with a mechanical stirring and heating device. Stirring is started and the stirring speed is controlled at 200-300 rpm. At the same time, the mixture is heated to 60±2℃.

[0116] (2) Maintain stirring and temperature conditions, and slowly add the metered star-shaped polymethyl methacrylate and comb-shaped polymethyl methacrylate into the mixing tank in sequence. The feeding time is controlled at 15-20 minutes. After the feeding is completed, continue stirring for 40 minutes to ensure that the two polymers are fully dissolved and evenly dispersed in the base oil.

[0117] (3) Maintain stirring and temperature conditions, add the metered functional additive system into the mixing tank in sequence, and continue stirring for 60 minutes after the addition is completed until the mixture is transparent and homogeneous;

[0118] (4) Stop heating, continue stirring and cooling to room temperature 25±5℃, filter through a 1μm filter bag to obtain the fully synthetic gasoline engine oil product of Example 6.

[0119] Example 7

[0120] This example is an equal-volume control example of comb-shaped polymethyl methacrylate used alone, used together with Examples 3-6 to evaluate the effect of the ratio of star-shaped polymethyl methacrylate to comb-shaped polymethyl methacrylate on oil performance.

[0121] A fully synthetic gasoline engine oil for hybrid engines comprises the following components:

[0122] Group III hydroisomerized base oils 50 PAO-6 20 Alkylnaphthalene 5 comb-shaped polymethacrylate 6 Functional additive system 19

[0123] The above components, by mass percentage, include comb-shaped polymethyl methacrylate, which is the same as the comb-shaped polymethyl methacrylate used in Example 2.

[0124] In this embodiment, the total amount of the base oil system, functional additive system, and viscosity index improver added is consistent with that in Examples 3 to 6, only the specific composition of the viscosity index improver is different, and the resulting oil meets the SAE 5W-30 viscosity grade.

[0125] A method for preparing a fully synthetic gasoline engine oil for a hybrid engine includes the following steps:

[0126] (1) The measured Group III hydroisomerized base oil, PAO-6 and alkyl naphthalene are added sequentially to the blending vessel equipped with a mechanical stirring and heating device. Stirring is started and the stirring speed is controlled at 200-300 rpm. At the same time, the mixture is heated to 60±2℃.

[0127] (2) Maintain stirring and temperature conditions, slowly add the metered comb-shaped polymethyl methacrylate into the mixing tank, control the feeding time to 10-15 minutes, and continue stirring for 30 minutes after the feeding is completed to ensure that the polymer is fully dissolved and evenly dispersed in the base oil;

[0128] (3) Maintain stirring and temperature conditions, add the metered functional additive system into the mixing tank in sequence, and continue stirring for 60 minutes after the addition is completed until the mixture is transparent and homogeneous;

[0129] (4) Stop heating, continue stirring and cooling to room temperature 25±5℃, filter through a 1μm filter bag to obtain the fully synthetic gasoline engine oil product of Example 7.

[0130] The oils obtained in Examples 1-7 were subjected to performance tests according to the above testing methods, and the results are shown in Table 1:

[0131] Table 1 Performance test results of Examples 1-7

[0132] Example 1 Star-shaped PMA 6wt% 88 5wt% 82 0W-20 Example 2 Comb-shaped PMA 7wt% 85 8wt% 78 0W-30 Example 3 Star-shaped PMA 6wt% 88 5wt% 82 5W-30 Example 4 Star-shaped PMA: Comb-shaped PMA = 70:30 91 5wt% 85 5W-30 Example 5 Star-shaped PMA: Comb-shaped PMA = 50:50 92 5wt% 86 5W-30 Example 6 Star-shaped PMA: Comb-shaped PMA = 30:70 90 5wt% 84 5W-30 Example 7 Comb-shaped PMA 6wt% 85 5wt% 78 5W-30

[0133] As shown in Table 1, the kinematic viscosity retention rate at 100°C of the oils obtained in Examples 1 to 7 is not less than 80%, and the viscosity recovery rate after shearing is not less than 70%.

[0134] Examples 1, 2, and 3-7 cover SAE 0W-20, 0W-30, and 5W-30 viscosity grades, respectively, and correspond to the viscosity grade range defined in claim 7.

[0135] To further verify the viscosity retention capability of the oil of the present invention within the range of 5wt% to 8wt% of fuel simulated diluent addition, Example 4, Example 5 and Example 6 were selected to conduct kinematic viscosity retention rate tests at 100°C under different fuel simulated diluent addition amounts.

[0136] The test results are shown in Table 2:

[0137] Table 2. Kinematic viscosity retention at 100℃ under different amounts of simulated fuel diluent added.

[0138] Example 4 70:30 91 89 87 85 Example 5 50:50 92 90 88 86 Example 6 30:70 90 88 86 84

[0139] As shown in Table 2, within the range of 5wt% to 8wt% of the fuel simulation dilution medium added, the kinematic viscosity retention rate at 100°C of the oils obtained in Examples 4 to 6 is not less than 80%. This result indicates that when the mass ratio of star-shaped polymethyl methacrylate to comb-shaped polymethyl methacrylate is 30:70 to 70:30, the obtained fully synthetic gasoline engine oil for hybrid engines can maintain good kinematic viscosity retention at 100°C under different degrees of fuel simulation dilution conditions.

[0140] To verify the synergistic effect of star-shaped polymethyl methacrylate and comb-shaped polymethyl methacrylate when used in combination within a mass ratio range of 30:70 to 70:30, Examples 3 to 7 were compared using the same amount of base oil system, functional additive system and viscosity index improver.

[0141] Among them, Example 3 is a sample of star-shaped polymethyl methacrylate used alone, Example 7 is a sample of comb-shaped polymethyl methacrylate used alone, and Examples 4 to 6 are compound samples of star-shaped polymethyl methacrylate and comb-shaped polymethyl methacrylate in different mass ratios.

[0142] In Examples 3-7, the base oil system consisted of 50 wt% Group III hydroisomerized base oil, 20 wt% PAO-6, and 5 wt% alkyl naphthalene. The functional additive system consisted of 19 wt% of each, and the total amount of viscosity index improver added was 6 wt%. Therefore, the performance differences between Examples 3-7 mainly stemmed from the specific composition of the viscosity index improver and the variation in the compounding ratio of star-shaped polymethyl methacrylate to comb-shaped polymethyl methacrylate.

[0143] Table 3 Performance test results of star-shaped PMA and comb-shaped PMA at different compounding ratios

[0144] Example 3 100:0 88 88.0 0 82 82.0 0 Example 4 70:30 91 87.1 +3.9 85 80.8 +4.2 Example 5 50:50 92 86.5 +5.5 86 80.0 +6.0 Example 6 30:70 90 85.9 +4.1 84 79.2 +4.8 Example 7 0:100 85 85.0 0 78 78.0 0

[0145] The above linear expected value is calculated according to the following formula:

[0146] Linear expected value = Performance value of star-shaped polymethacrylate used alone × Mass percentage of star-shaped polymethacrylate + Performance value of comb-shaped polymethacrylate used alone × Mass percentage of comb-shaped polymethacrylate.

[0147] For example, in Example 5, the mass ratio of star-shaped polymethyl methacrylate to comb-shaped polymethyl methacrylate is 50:50, then the linear expected value of the kinematic viscosity retention rate at 100°C is:

[0148] 88% × 50% + 85% × 50% = 86.5%;

[0149] The measured kinematic viscosity retention rate at 100°C in Example 5 was 92%, which was 5.5 percentage points higher than the expected linear value.

[0150] Similarly, the expected linear value for viscosity recovery in Example 5 is:

[0151] 82% × 50% + 78% × 50% = 80.0%;

[0152] The measured viscosity recovery rate of Example 5 was 86%, which was 6.0 percentage points higher than the expected linear value.

[0153] As shown in Table 3, when star-shaped polymethyl methacrylate and comb-shaped polymethyl methacrylate are blended in a mass ratio of 30:70 to 70:30, the resulting oil exhibits higher kinematic viscosity retention at 100°C and viscosity recovery after shear than the theoretically expected values ​​obtained by linear weighted calculation based on the performance of star-shaped polymethyl methacrylate and comb-shaped polymethyl methacrylate used alone. This result indicates that the performance of star-shaped polymethyl methacrylate and comb-shaped polymethyl methacrylate within this blending ratio range is not simply additive, but rather exhibits a synergistic effect in fire-resistant oil dilution and viscosity recovery after shear.

[0154] The reason may be that star-shaped polymethacrylate has a multi-arm topology, which can absorb some shear energy through the reversible compression and extension of the arms under high shear conditions, thereby reducing the risk of irreversible breakage of the main chain; comb-shaped polymethacrylate has more alkyl side chains, which can enhance the interaction between polymer segments and base oil and diluent in the presence of fuel-based dilution media, promoting the transformation of molecular chain conformation from a compressed state to an extended state. When the two are combined, the star structure provides shear elastic recovery capability, and the comb structure provides conformational response capability under fuel dilution environment. The two complement each other in the same oil system, thus exhibiting a synergistic effect higher than the linear weighted expected value.

[0155] This set of data supports the use of a combination of star-shaped polymethyl methacrylate and comb-shaped polymethyl methacrylate as viscosity index improvers, with a mass ratio of 30:70 to 70:30.

[0156] According to the aforementioned intrinsic viscosity determination method, the intrinsic viscosity of the viscosity index improvers used in Examples 3 to 7 was determined. For the compound system, star-shaped polymethyl methacrylate and comb-shaped polymethyl methacrylate were premixed according to the corresponding formulation ratio and then dissolved in the base oil for determination.

[0157] The test results are shown in the table below:

[0158] Table 4. Change rate of intrinsic viscosity of viscosity index improver

[0159] Example 3 100:0 0.45 0.56 +24.4 Example 4 70:30 0.43 0.55 +27.9 Example 5 50:50 0.41 0.53 +29.3 Example 6 30:70 0.40 0.51 +27.5 Example 7 0:100 0.38 0.46 +21.1

[0160] As shown in Table 4, the intrinsic viscosity change rates of the star-shaped polymethyl methacrylate, comb-shaped polymethyl methacrylate and their compound systems used in Examples 3 to 7 in base oil containing 5 wt% fuel oil as a simulated diluent are all within the range of +10% to +50%.

[0161] Among them, the intrinsic viscosity change rate of the compound system in Examples 4-6 is higher than that of star-shaped polymethyl methacrylate or comb-shaped polymethyl methacrylate alone, which further illustrates that the compound can enhance the conformational response of the polymer in the fuel simulated dilution medium, and support the improvement of its anti-fuel dilution performance and viscosity recovery performance after shear at the molecular level.

[0162] Comparative Example 1

[0163] The same base oil and functional additive system as in Example 1 were used, except that the star-shaped polymethacrylate was replaced with an equal amount of linear olefin copolymer. The linear olefin copolymer was OCP, with a weight-average molecular weight of approximately 150,000. The specific formulation is as follows:

[0164] Group III hydroisomerized base oils 58 PAO-6 18 Alkylnaphthalene 4 Linear OCP 6 Functional additive system 14

[0165] The preparation method is as follows:

[0166] (1) The measured Group III hydroisomerized base oil, PAO-6 and alkyl naphthalene are added sequentially to the blending vessel equipped with a mechanical stirring and heating device. Stirring is started and the stirring speed is controlled at 200-300 rpm. At the same time, the mixture is heated to 60±2℃.

[0167] (2) Maintain stirring and temperature conditions, slowly add the metered linear OCP into the mixing tank, control the feeding time to 10-15 minutes, and continue stirring for 30 minutes after the feeding is completed to ensure that the polymer is fully dissolved and evenly dispersed in the base oil;

[0168] (3) Maintain stirring and temperature conditions, add the metered functional additive system into the mixing tank in sequence, and continue stirring for 60 minutes after the addition is completed until the mixture is transparent and homogeneous;

[0169] (4) Stop heating, continue stirring and cooling to room temperature 25±5℃, filter through a 1μm filter bag to obtain the gasoline engine oil product of Comparative Example 1.

[0170] Comparative Example 2

[0171] The same base oil and functional additive system as in Example 1 were used, except that the star-shaped polymethacrylate was replaced with an equal amount of linear polymethacrylate. The weight-average molecular weight of the linear polymethacrylate was approximately 160,000. The specific formulation is as follows:

[0172] Group III hydroisomerized base oils 58 PAO-6 18 Alkylnaphthalene 4 Linear PMA 6 Functional additive system 14

[0173] The preparation method is as follows:

[0174] (1) The measured Group III hydroisomerized base oil, PAO-6 and alkyl naphthalene are added sequentially to the blending vessel equipped with a mechanical stirring and heating device. Stirring is started and the stirring speed is controlled at 200-300 rpm. At the same time, the mixture is heated to 60±2℃.

[0175] (2) Maintain stirring and temperature conditions, slowly add the metered linear PMA into the mixing tank, control the feeding time to 10-15 minutes, and continue stirring for 30 minutes after the feeding is completed to ensure that the polymer is fully dissolved and evenly dispersed in the base oil;

[0176] (3) Maintain stirring and temperature conditions, add the metered functional additive system into the mixing tank in sequence, and continue stirring for 60 minutes after the addition is completed until the mixture is transparent and homogeneous;

[0177] (4) Stop heating, continue stirring and cooling to room temperature 25±5℃, filter through a 1μm filter bag to obtain the gasoline engine oil product of Comparative Example 2.

[0178] Comparative Example 3

[0179] Compared with Example 1, while keeping the type and amount of star-shaped polymethacrylate, the amount of alkyl naphthalene, and the type and amount of functional additives unchanged, only some Group III hydroisomerized base oil and PAO-6 were replaced with Group II base oil to investigate the effect of increased base oil volatility on the anti-dilution performance and viscosity recovery performance after shear of fully synthetic gasoline engine oil for hybrid engines.

[0180] The kinematic viscosity of the Group II base oil at 100°C is approximately 6.5 mm² / s, and the Noack volatility is approximately 18 wt%. The specific formulation is as follows:

[0181] Group III hydroisomerized base oils 38 PAO-6 15 Group II base oils 23 Alkylnaphthalene 4 Star-shaped polymethacrylate 6 Functional additive system 14

[0182] The star-shaped polymethyl methacrylate is the same as in Example 1, and the functional additive system is the same as in Example 1.

[0183] In this comparative example, the types and amounts of functional additives were kept consistent with those in Example 1, as were the types and amounts of star-shaped polymethyl methacrylate. The only difference was the introduction of a Group II base oil with a Noack volatility of approximately 18 wt% to replace part of the low-volatility Group III hydroisomerized base oil and PAO-6, thus creating a difference in base oil volatility. This eliminated the influence of changes in the amount of functional additives on the test results, allowing for a more direct evaluation of the impact of base oil volatility on the viscosity retention and viscosity recovery of the oil.

[0184] The preparation method is as follows:

[0185] (1) The measured Group III hydroisomerized base oil, PAO-6, Group II base oil and alkyl naphthalene are sequentially added to the blending vessel equipped with a mechanical stirring and heating device. Stirring is started and the stirring speed is controlled at 200-300 rpm. At the same time, the mixture is heated to 60±2℃.

[0186] (2) Maintain stirring and temperature conditions, slowly add the metered star-shaped polymethyl methacrylate into the mixing tank, control the feeding time to 10-15 minutes, and continue stirring for 30 minutes after the feeding is completed to ensure that the polymer is fully dissolved and evenly dispersed in the base oil;

[0187] (3) Maintain stirring and temperature conditions, add the metered functional additive system into the mixing tank in sequence, and continue stirring for 60 minutes after the addition is completed until the mixture is transparent and homogeneous;

[0188] (4) Stop heating, continue stirring and cooling to room temperature 25±5℃, filter through a 1μm filter bag to obtain the gasoline engine oil product of Comparative Example 3.

[0189] The test results are shown in Table 5:

[0190] Table 5 Comparison of Performance Test Results between Examples and Comparative Examples

[0191] Example 1 88 5wt% 82 0W-20 Example 2 85 8wt% 78 0W-30 Example 3 88 5wt% 82 5W-30 Example 4 91 5wt% 85 5W-30 Example 5 92 5wt% 86 5W-30 Example 6 90 5wt% 84 5W-30

[0192] As shown in Table 5, Examples 1 to 7 all meet the requirements of kinematic viscosity retention of not less than 80% and viscosity recovery after shear of not less than 70% at 100°C. Comparative Examples 1 and 2 use linear OCP and linear PMA to replace the star-shaped polymethyl methacrylate or comb-shaped polymethyl methacrylate of the present invention, respectively. Their kinematic viscosity retention of 100°C and viscosity recovery after shear are significantly reduced, indicating that the linear polymer has a weak conformational response under fuel dilution environment and insufficient viscosity recovery after high shear.

[0193] Comparative Example 3, while maintaining the same star-shaped polymethyl methacrylate and functional additive system as Example 1, introduced only a Group II base oil with high Noack volatility, resulting in a decrease in the kinematic viscosity retention rate at 100°C to 78%. This result indicates that increased base oil volatility can disrupt the stable liquid phase environment of the oil system, which is not conducive to maintaining the effective viscosity-enhancing conformation of the star-shaped polymethyl methacrylate. Therefore, a base oil Noack volatility of no more than 12 wt% is beneficial for maintaining the polymer conformation adjustment function, viscosity compensation effect, and viscosity recovery performance after shearing.

[0194] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art 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 appended claims and their equivalents.

Claims

1. A fully synthetic gasoline engine oil for hybrid engines, characterized in that, Based on total mass, it includes the following components: S1: 50wt% to 95wt% of base oil, wherein the base oil includes at least one of Group III hydroisomerized base oil and Group IV polyalphaolefin base oil; S2: 0.5wt% to 25wt% of a viscosity index improver, wherein the viscosity index improver is the following S21 and / or S22: S21: Star-shaped polymethacrylate, which has 3 to 10 polymer arms and a weight-average molecular weight of 80,000 to 400,000; S22: Comb-shaped polymethacrylate, which has side chains with an average number of carbon atoms of C6 to C30 and a weight-average molecular weight of 70,000 to 300,000; S3: A functional additive system of 4wt% to 30wt%; The fully synthetic gasoline engine oil for the hybrid engine, after adding 5wt% to 8wt% of a fuel-simulated diluent, retains a kinematic viscosity of no less than 80% at 100°C. The fuel-simulated diluent is a mixture of n-heptane and isooctane in a mass ratio of 40:

60. The fully synthetic gasoline engine oil for the hybrid engine, after undergoing the ASTM D6278 standard shear test, has a viscosity recovery rate of not less than 70% after being allowed to stand at 25°C for 30 minutes without shearing.

2. The fully synthetic gasoline engine oil for a hybrid engine according to claim 1, characterized in that, When the viscosity index improver contains star-shaped polymethacrylate, the star-shaped polymethacrylate has 4 to 8 arms, each arm is copolymerized from short-chain alkyl methacrylate units and long-chain alkyl methacrylate units, the short-chain alkyl units have C1 to C4 carbon atoms, the long-chain alkyl units have C8 to C18 carbon atoms, and the molar ratio of short-chain units to long-chain units is 2:8 to 5:

5.

3. The fully synthetic gasoline engine oil for a hybrid engine according to claim 1, characterized in that, When the viscosity index improver contains comb-shaped polymethacrylate, the side chain branch density of the comb-shaped polymethacrylate is 8 to 40 side chains per 100 main chain repeating units.

4. The fully synthetic gasoline engine oil for a hybrid engine according to claim 1, characterized in that, The viscosity index improver is a combination of the star-shaped polymethyl methacrylate and the comb-shaped polymethyl methacrylate, with a mass ratio of 20:80 to 80:

20.

5. A fully synthetic gasoline engine oil for a hybrid engine according to any one of claims 1 to 4, characterized in that, The base oil further comprises alkyl naphthalene and / or synthetic ester base oil, wherein the alkyl naphthalene and / or synthetic ester base oil has a mass percentage of 1wt% to 12wt%.

6. A fully synthetic gasoline engine oil for a hybrid engine according to any one of claims 1 to 4, characterized in that, The Noyak volatility of the base oil is no higher than 12 wt%.

7. A fully synthetic gasoline engine oil for a hybrid engine according to any one of claims 1 to 4, characterized in that, The fully synthetic gasoline engine oil used in the hybrid engine meets SAE viscosity grades of 0W-20, 0W-30, and 5W-30.

8. A fully synthetic gasoline engine oil for a hybrid engine according to any one of claims 1 to 4, characterized in that, When the viscosity index improver is dissolved at 25°C in pure base oil and base oil containing 5 wt% fuel simulation diluent, the change rate of its intrinsic viscosity [η] is +10% to +50%. The intrinsic viscosity [η] is determined according to the standard method of GB / T1632 or ISO1628. The fuel simulation diluent is a mixture of n-heptane and isooctane in a mass ratio of 40:

60.

9. A fully synthetic gasoline engine oil for a hybrid engine according to any one of claims 1 to 4, characterized in that, The functional additive system includes dispersants, detergents, antioxidants, anti-wear agents, and friction modifiers, wherein the anti-wear agent is zinc dialkyl dithiophosphate.

10. A method for preparing a fully synthetic gasoline engine oil for a hybrid engine, characterized in that, Used to prepare a fully synthetic gasoline engine oil for a hybrid engine as described in any one of claims 1-9.

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