Modified graphene and graphene composite oily slurry as well as preparation method and application thereof

Abstract

The invention discloses modified graphene and graphene composite oily slurry as well as a preparation method and application thereof. The preparation method comprises the following steps: sequentially adding a series of graphene oxides with different oxygen contents into water according to the oxygen contents from high to low, dispersing after adding each time, then adding graphene for dispersing, and carrying out high-pressure homogenization treatment to obtain graphene composite aqueous slurry; and uniformly dispersing the graphene composite aqueous slurry, the oily dispersant and modifier and the base oil, then carrying out reduced pressure distillation, and modifying the graphene oxide while removing water to prepare the modified graphene and graphene composite oily slurry. In the preparation process of the composite oily slurry disclosed by the invention, graphene is dispersed by virtue of graphene oxide, and an additional dispersing agent does not need to be used; modified graphene in the composite oily slurry improves the dispersion stability and anti-wear and anti-friction properties of graphene; when the composite oily slurry is used as a lubricating oil additive, the anti-wear and anti-friction performance and oil film toughness of lubricating oil can be improved at the same time.

Description

Technical Field

[0001] This invention relates to a graphene composite slurry, specifically to a modified graphene and graphene composite oily slurry and its preparation method, as well as its application in lubricating oil, belonging to the technical fields of nanomaterials and lubricating additives. Background Technology

[0002] With economic development and improved living standards, my country's ownership of gasoline-powered vehicles ranks among the highest in the world. During the operation of an internal combustion engine, some of the fuel's energy is inevitably lost due to friction and wear. Lubricating oil effectively reduces friction and wear between mechanical parts and is one of the key factors affecting engine mechanical efficiency and reliability. Furthermore, with the rapid increase in vehicle ownership, exhaust emissions have also increased, adversely affecting the environment and human health. Among these emissions, lubricating oil consumption is a major source of particulate matter in exhaust gases.

[0003] In recent years, the vigorous implementation of "dual-carbon" and green development policies, along with the urgent need for high-efficiency, energy-saving, near-zero-emission, and low-fuel-consumption engines, has placed higher demands on the quality of lubricating oils. Lubricating oils are generally composed of base oils and additives. The addition of additives can enhance or add certain functions, thereby greatly improving the quality of the lubricating oil.

[0004] Nanomaterials possess optical, electrical, thermal, chemical, and mechanical properties that are drastically different from conventional materials. Nanoparticles of suitable size can be used as lubricant additives, exhibiting superior friction-reducing and anti-wear properties compared to traditional additives under extreme conditions such as high temperature, low temperature, dryness, and extreme pressure.

[0005] Graphene possesses some of the basic properties of solid lubricants, such as thermal stability, low shear strength, strong surface adhesion, and layered structure. Therefore, graphene has great application prospects in the field of lubricant additives.

[0006] Currently, graphene is usually added to lubricating oil in powder form. However, graphene powder exhibits soft agglomeration, resulting in an unstable dispersion system that hinders the effective anti-wear and friction-reducing properties of graphene. Existing equipment in lubricating oil production lines cannot achieve good dispersion, requiring line modifications to add supporting dispersion equipment. Furthermore, dust pollution occurs during the addition process.

[0007] Graphene in graphene slurries exhibits good dispersion, which remains even after dilution. Existing graphene slurries are generally of two types: aqueous slurries and NMP (N-methylpyrrolidone) slurries. Both types of slurries maintain good graphene dispersion even after dilution. However, when applied to the lubricating oil industry, the direct addition of aqueous slurries, which specify water content limits in lubricating oil standards, leads to excessive water content. Furthermore, aqueous slurries typically contain dispersants, making them unsuitable for lubricating oil formulations. The introduction of NMP also degrades lubricating oil performance, affecting viscosity, flash point, and rubber compatibility. Therefore, neither of these two types of slurries can be directly used in lubricating oils. Summary of the Invention

[0008] The main objective of this invention is to provide a modified graphene and graphene composite oily slurry and its preparation method, so as to overcome the shortcomings of the prior art.

[0009] Another object of the present invention is to provide the application of the modified graphene and graphene composite oily slurry in lubricating oil.

[0010] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0011] This invention provides a method for preparing a modified graphene and graphene composite oily slurry, comprising:

[0012] A range of graphene oxides with different oxygen contents are available;

[0013] A series of graphene oxides with different oxygen contents were added to water in descending order of oxygen content. Each addition was followed by dispersion, and then more graphene was added and dispersed. The mixture was then subjected to high-pressure homogenization to obtain a graphene composite aqueous slurry.

[0014] The graphene composite aqueous slurry, oily dispersant / modifier, and base oil are uniformly dispersed, and then subjected to vacuum distillation while the graphene oxide is modified to obtain a modified graphene and graphene composite oily slurry.

[0015] The present invention also provides a modified graphene and graphene composite oily slurry prepared by the aforementioned preparation method, comprising a base oil, and modified graphene and graphene uniformly dispersed in the base oil.

[0016] The present invention also provides the application of the modified graphene and graphene composite oily slurry in the field of lubricating oil.

[0017] Accordingly, embodiments of the present invention also provide a lubricating oil additive, which includes the aforementioned modified graphene and graphene composite oily slurry.

[0018] Furthermore, embodiments of the present invention also provide a lubricating oil, comprising at least the aforementioned modified graphene and graphene composite oily slurry.

[0019] Compared with the prior art, the beneficial effects of the present invention include at least the following:

[0020] 1) The modified graphene and graphene composite oily slurry provided by this invention involves adding graphene oxide with different oxygen contents sequentially to water according to the oxygen content from high to low during the preparation process. The graphene oxide disperses the graphene, eliminating the need for additional dispersants. Therefore, when used as a lubricating oil additive, it does not introduce ash dispersants that could affect the performance indicators of the lubricating oil. At the same time, stable dispersion in base oil / lubricating oil can be achieved using conventional dispersion equipment. Traditional lubricating oil blending plants can produce graphene lubricating oil without modifying their equipment.

[0021] 2) When the modified graphene and graphene composite oily slurry of the present invention are applied to lubricating oil, since graphene has better anti-wear and friction-reducing properties than modified graphene, while modified graphene can better improve the oil film toughness of lubricating oil compared to graphene, the composite slurry has both properties. Moreover, the modified graphene component in the composite slurry can improve the dispersion stability of the graphene component in the oil phase, making the dispersion stability of the graphene component close to that of modified graphene. Furthermore, while improving the dispersion stability of the graphene component in the oil phase, the modified graphene component in the composite slurry also improves the anti-wear and friction-reducing properties of the graphene component in the lubricating oil. Detailed Implementation

[0022] In view of the deficiencies of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The main purpose is to provide a method that, without adding additional dispersants, utilizes the differences in oil-water affinity between graphene and graphene oxide with different oxygen contents, as well as the affinity between graphene and graphene oxide due to structural similarity, to achieve dispersion in an aqueous phase, thus obtaining a graphene composite aqueous slurry; then, the graphene composite aqueous slurry is transformed into an oil-based slurry, and in this process, the graphene oxide is simultaneously modified, resulting in a modified graphene and graphene composite oil-based slurry.

[0023] The following will further explain the technical solution, its implementation process, and its principles. However, it should be understood that within the scope of this invention, the above-mentioned technical features of this invention and the technical features specifically described below (in embodiments) can be combined with each other to form new or preferred technical solutions. Due to space limitations, they will not be described in detail here.

[0024] As one aspect of the technical solution of this invention, the preparation method of a modified graphene and graphene composite oily slurry includes:

[0025] A range of graphene oxides with different oxygen contents are available;

[0026] A series of graphene oxides with different oxygen contents were added to water in descending order of oxygen content. Each addition was followed by dispersion, and then more graphene was added and dispersed. The mixture was then subjected to high-pressure homogenization to obtain a graphene composite aqueous slurry.

[0027] The graphene composite aqueous slurry, oily dispersant / modifier, and base oil are uniformly dispersed, and then subjected to vacuum distillation while the graphene oxide is modified to obtain a modified graphene and graphene composite oily slurry.

[0028] In some embodiments, the oxygen content of the series of graphene oxides with different oxygen contents is 15% to 55%.

[0029] In some preferred embodiments, the series of graphene oxides with different oxygen contents includes graphene oxides with an oxygen content of 15-25%, 25-35%, 35-45%, and 45-55%. The purpose of using a series of graphene oxides with different oxygen contents in this invention is to disperse hydrophobic graphene in water without adding additional dispersants. This objective cannot be achieved by using graphene oxides with a single oxygen content; the graphene cannot be dispersed in water, and a graphene composite aqueous slurry cannot be obtained.

[0030] In some more preferred embodiments, the graphene composite aqueous slurry comprises the following components by weight: 1 part graphene, 0.1 to 0.3 parts graphene oxide with an oxygen content of 15 to 25%, 0.2 to 0.6 parts graphene oxide with an oxygen content of 25 to 35%, 0.2 to 0.6 parts graphene oxide with an oxygen content of 35 to 45%, 0.5 to 1.5 parts graphene oxide with an oxygen content of 45 to 55%, and 80 to 200 parts water.

[0031] In some embodiments, the preparation method specifically includes: adding a series of graphene oxides with different oxygen contents sequentially to water according to the oxygen content from high to low, performing a first dispersion after each addition, then adding graphene for a second dispersion, and then performing high-pressure homogenization to obtain a graphene composite aqueous slurry.

[0032] This invention utilizes the structural gradient similarity between graphene and graphene oxide with different oxygen contents, as well as the hydrophilicity of graphene oxide with high oxygen content. The higher oxygen content of graphene oxide promotes the dispersion of graphene oxide with lower oxygen content in the aqueous phase, ultimately dispersing the hydrophilic graphene in the aqueous phase. The specific mechanism is explained as follows: graphene is a hydrophobic material and cannot achieve stable dispersion in water without a dispersant, while graphene oxide is hydrophilic due to the presence of oxygen-containing functional groups. At the same time, the dispersibility of graphene oxide in water increases with the increase of oxygen content (when the oxygen content is about 50%, graphene oxide can be easily dispersed in water by shaking it by hand). The lower the oxygen content of graphene oxide, the closer its structure is to that of graphene, and the better its affinity. Therefore, graphene oxide with lower oxygen content can promote the dispersion of graphene in water by virtue of its hydrophilicity and structural similarity with graphene. However, graphene oxide with lower oxygen content itself cannot disperse well in water, and is insufficient to achieve the dispersion of graphene in water. On the other hand, the closer the oxygen content of graphene oxide is to that of graphene oxide, the higher the structural similarity and the better its affinity. When graphene oxide with higher oxygen content has already achieved good dispersion in water, adding graphene oxide with lower oxygen content can also achieve good dispersion of the latter. Therefore, when a type of graphene oxide with a high oxygen content is well dispersed in water, adding multiple types of graphene oxide with decreasing oxygen content in sequence can achieve a good overall dispersion. Finally, graphene is added to achieve good dispersion of graphene, resulting in an aqueous graphene slurry without the addition of additional dispersants. This successfully avoids the use of additional dispersants in the traditional preparation process of aqueous graphene slurries. At the same time, adding an oily dispersant and modifier to modify the graphene oxide to be oleophilic and removing the water yields an oily slurry composed of modified graphene and graphene composite. The components of this oily slurry are all beneficial to the performance of lubricating oil, thus avoiding the possible impact of additional dispersants on the performance of lubricating oil.

[0033] Furthermore, the first dispersion is carried out at a rotation speed of 3000-8000 rpm, and the time for the first dispersion of graphene oxide added each time is 0.5-1 h.

[0034] Furthermore, the second dispersion is carried out at a rotation speed of 3000–8000 rpm and the dispersion time is 3–5 hours.

[0035] In some implementations, the high-pressure homogenization process is carried out at a pressure of 80–100 MPa, and the process is repeated 5–10 times.

[0036] In some embodiments, the oily dispersant / modifier may include any one or more combinations of polyisobutylene amine, polyisobutylene succinimide, polyether amine, tallow amine, tallow amine polyoxyethylene ether, etc., but is not limited thereto. This invention modifies graphene oxide using an oily dispersant / modifier. After grafting lipophilic groups from the oily dispersant / modifier onto the surface of the graphene oxide, it becomes modified graphene, changing from hydrophilic to lipophilic, thus allowing it to enter the oil phase along with the graphene. Without the addition of the oily dispersant / modifier, the composite aqueous slurry cannot be uniformly mixed with the oil phase substances, making subsequent operations impossible.

[0037] In some implementations, the base oil may include any one or more combinations of Group II base oils, Group III base oils, Group IV base oils, Group V base oils, etc., but is not limited to this.

[0038] In some embodiments, the preparation method specifically includes: adding an oily dispersant / modifier and a base oil to the graphene composite aqueous slurry, and performing a third dispersion to obtain a mixed slurry.

[0039] In some preferred embodiments, the mixed slurry comprises the following components by weight: 1 part of a mixture of graphene and graphene oxide in the graphene composite aqueous slurry, 8 to 20 parts of an oily dispersant and modifier, and 10 to 30 parts of a base oil.

[0040] Furthermore, the third dispersion is carried out at a rotation speed of 200–500 rpm and for a duration of 1–3 hours.

[0041] In some embodiments, the preparation method specifically includes: adding a low-boiling-point alcohol compound to the mixed slurry, performing vacuum distillation to remove water and the low-boiling-point alcohol compound, and modifying the graphene oxide in this process to obtain the modified graphene and graphene composite slurry.

[0042] In some preferred embodiments, the low-boiling-point alcohol compound is miscible with water to form an azeotrope, thereby accelerating the distillation rate and speeding up the water removal process.

[0043] Furthermore, the low-boiling-point alcohol compound may include one or more combinations of methanol, ethanol, n-propanol, isopropanol, etc., but is not limited to these.

[0044] In some more preferred embodiments, the mass ratio of the graphene composite aqueous slurry to the low-boiling-point alcohol compound is 1:(2-4), based on the solid portion of the graphene composite aqueous slurry.

[0045] In some embodiments, the conditions for vacuum distillation include: a temperature of 80–120°C, vacuum treatment for 6–10 hours, and a vacuum degree of -0.095–-0.1 MPa.

[0046] In some preferred embodiments, a method for preparing a modified graphene and graphene composite oily slurry includes the following steps:

[0047] (1) Preparation of graphene composite aqueous slurry

[0048] The allocation ratios for each group are as follows:

[0049]

[0050]

[0051] The preparation process is as follows: graphene oxide powders with different oxygen contents are added to deionized water in descending order of oxygen content. The first dispersion is carried out using a disperser at a speed of 3000-8000 rpm, and the dispersion time for each addition is 0.5-1 h. Finally, graphene is added for the second dispersion, and the dispersion time is 3-5 h. Then, a high-pressure homogenizer is used to cycle the process 5-10 times under a pressure of 80-100 MPa.

[0052] (2) Adding an oily dispersant / modifier and base oil to graphene composite aqueous slurry

[0053] The allocation ratios for each group are as follows:

[0054] One part of graphene composite aqueous slurry (calculated based on the total mass of graphene and graphene oxide in the slurry).

[0055] 8-20 parts of oily dispersant / modifier

[0056] 10-30 parts base oil

[0057] The preparation process is as follows: graphene composite aqueous slurry is added to an oily dispersant / modifier and base oil for third dispersion. The dispersion speed is 200-500 rpm and the dispersion time is 1-3 h.

[0058] (3) Water is removed by vacuum distillation, and graphene oxide is modified in the process to obtain a graphene composite oily slurry, which can be used as a lubricating oil additive. The vacuum distillation includes the addition of low-boiling-point alcohol compounds, which are miscible with water to form an azeotrope and accelerate the distillation rate.

[0059] The preparation process is as follows: vacuum treatment for 6 to 10 hours at a temperature of 80 to 120°C, with a vacuum degree of -0.095 to -0.1 MPa.

[0060] As another aspect of the technical solution of the present invention, it also relates to a modified graphene and graphene composite oily slurry prepared by the aforementioned preparation method.

[0061] This invention simultaneously modifies graphene oxide during the conversion of aqueous slurry to oil-based slurry, resulting in a final composite slurry product that is a mixture of graphene and modified graphene. Compared to graphene, modified graphene exhibits better dispersion stability in the oil (base oil / lubricating oil) phase. Furthermore, due to their structural similarity, modified graphene can act as a dispersant for graphene, improving its dispersion stability in the oil phase (to a level close to that of modified graphene). This results in excellent overall dispersion stability of the composite slurry in the oil phase. Simultaneously, the improved dispersibility of graphene further enhances its anti-wear and friction-reducing properties in lubricating oil. In other words, modified graphene in the composite oil-based slurry improves both the dispersibility and anti-wear and friction-reducing properties of graphene (the dispersion stability of graphene directly affects its anti-wear and friction-reducing performance).

[0062] Furthermore, the modified graphene and graphene composite oily slurry prepared by this invention can be directly added to lubricating oil, and good and stable dispersion can be achieved by conventional dispersion equipment; at the same time, the addition of the composite oily slurry will not introduce additional components that are detrimental to the performance of the lubricating oil.

[0063] As another aspect of the technical solution of the present invention, it also relates to the application of the aforementioned modified graphene and graphene composite oily slurry in the field of lubricating oil.

[0064] Correspondingly, another aspect of the technical solution of the present invention also provides a lubricating oil additive, which includes the aforementioned modified graphene and graphene composite oily slurry.

[0065] Furthermore, another aspect of the technical solution of the present invention provides a lubricating oil, which at least comprises the aforementioned modified graphene and graphene composite oily slurry.

[0066] By means of the above technical solution, the composite oily slurry of the present invention can be used as a lubricating oil additive without introducing ash dispersants, thus affecting the performance indicators of the lubricating oil. When applied to lubricating oil, graphene has better anti-wear and friction reduction properties than modified graphene, while modified graphene can better improve the oil film toughness of the lubricating oil compared to graphene. Therefore, the composite slurry has both properties.

[0067] The technical solution of the present invention will be further described in detail below with reference to several preferred embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. It should be noted that the following embodiments are intended to facilitate the understanding of the present invention, and do not constitute any limitation thereof. 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. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or according to the conditions recommended by the manufacturer.

[0068] Example 1

[0069] S1. Add 0.5 parts of graphene oxide with an oxygen content of 55% to 80 parts of deionized water and disperse at 4000 rpm for 0.75 h. Then add 0.2 parts of graphene oxide with an oxygen content of 35% and disperse at 4000 rpm for another 0.75 h. Next, add 0.2 parts of graphene oxide with an oxygen content of 25% and disperse at 4000 rpm for another 0.75 h. Then add 0.1 parts of graphene oxide with an oxygen content of 20% and disperse at 4000 rpm for another 0.75 h. Finally, add 1 part of graphene, increase the speed to 6000 rpm, and disperse for another 5 h. Then, use a high-pressure homogenizer to homogenize at 80 MPa 10 times to obtain graphene composite aqueous slurry.

[0070] S2. Take a composite aqueous slurry containing 1 part solid (a mixture of graphene and graphene oxide), add 8 parts tallow amine and 10 parts Group IV base oil PAO to the reactor, and disperse at 300 rpm for 2 hours.

[0071] Next, add 2 parts isopropanol, heat to 120°C and vacuum, and process for 6 hours to remove low-boiling-point substances. At the same time, modify the graphene oxide to obtain a modified graphene and graphene composite oily slurry (which can be named composite oily slurry 1#).

[0072] The composite oily slurry 1# prepared in this embodiment can be used as a lubricating oil additive.

[0073] Example 2

[0074] S1. Add 1 part of graphene oxide with an oxygen content of 50% to 150 parts of deionized water and disperse at 3000 rpm for 1 hour. Then add 0.4 parts of graphene oxide with an oxygen content of 45% and continue dispersing at 3000 rpm for 1 hour. Next, add 0.4 parts of graphene oxide with an oxygen content of 35% and continue dispersing at 3000 rpm for 1 hour. Then add 0.2 parts of graphene oxide with an oxygen content of 15% and continue dispersing at 3000 rpm for 1 hour. Finally, add 1 part of graphene, increase the speed to 7000 rpm, and continue dispersing for 4 hours. Then, use a high-pressure homogenizer to homogenize at 90 MPa 7 times to obtain graphene composite aqueous slurry.

[0075] S2. Take a composite aqueous slurry containing 1 part solid (a mixture of graphene and graphene oxide), add 15 parts polyisobutylene succinimide and 20 parts Class V base oil oil-soluble polyether OSP to the reactor, and disperse at 500 rpm for 1 hour.

[0076] Next, 3 parts of ethanol were added, heated to 100°C and vacuumed for 8 hours to remove low-boiling-point substances. At the same time, the graphene oxide was modified to obtain a modified graphene and graphene composite oily slurry (which can be named composite oily slurry 2#).

[0077] The composite oily slurry No. 2 prepared in this embodiment can be used as a lubricating oil additive.

[0078] Example 3

[0079] S1. Add 1.5 parts of graphene oxide with an oxygen content of 45% to 200 parts of deionized water and disperse at 5000 rpm for 0.5 h. Then add 0.6 parts of graphene oxide with an oxygen content of 40% and disperse at 5000 rpm for another 0.5 h. Next, add 0.6 parts of graphene oxide with an oxygen content of 30% and disperse at 5000 rpm for another 0.5 h. Then add 0.3 parts of graphene oxide with an oxygen content of 25% and disperse at 5000 rpm for another 0.5 h. Finally, add 1 part of graphene, increase the speed to 8000 rpm, and disperse for another 3 h. Then, homogenize at 100 MPa for 5 times using a high-pressure homogenizer to obtain graphene composite aqueous slurry.

[0080] S2. Take a composite aqueous slurry containing 1 part solid (a mixture of graphene and graphene oxide), add 20 parts polyetheramine and 30 parts Group III base oil to the reactor, and disperse at 200 rpm for 3 hours.

[0081] Next, 4 parts of methanol were added, heated to 80°C and vacuumed for 10 hours to remove low-boiling-point substances. At the same time, the graphene oxide was modified to obtain a modified graphene and graphene composite oily slurry (which can be named composite oily slurry 3#).

[0082] The composite oily slurry No. 3 prepared in this embodiment can be used as a lubricating oil additive.

[0083] Comparative Example 1 (Aqueous slurry consisting of graphene and dispersant)

[0084] S1. Add 0.25 parts of dispersant PVP to 40 parts of deionized water. Each time it is added, disperse at 4000 rpm for 0.75 h. Finally, add 1 part of graphene, increase the speed to 6000 rpm, and continue to disperse for 5 h. Then, use a high-pressure homogenizer to process it 10 times at 80 MPa to obtain graphene aqueous slurry.

[0085] S2. Take 1 part of the aqueous slurry containing graphene prepared in step S1, add 8 parts of tallow amine and 10 parts of Group IV base oil PAO into the reactor, and disperse at 300 rpm for 2 hours.

[0086] Next, add 2 parts isopropanol, heat to 120°C and vacuum, and process for 6 hours to remove low-boiling-point substances, thus obtaining graphene oily slurry (which can be named graphene oily slurry 4#).

[0087] The graphene oily slurry No. 4 prepared in this comparative example can be used as a lubricating oil additive.

[0088] Comparative Example 2 (Water-based slurry without graphene)

[0089] S1. Add 0.5 parts of graphene oxide with an oxygen content of 55% to 80 parts of deionized water and disperse at 4000 rpm for 0.75 h. Then add 0.2 parts of graphene oxide with an oxygen content of 35% and continue dispersing at 4000 rpm for another 0.75 h. Next, add 0.2 parts of graphene oxide with an oxygen content of 25% and continue dispersing at 4000 rpm for another 0.75 h. Then add 0.1 parts of graphene oxide with an oxygen content of 20% and continue dispersing at 4000 rpm for another 0.75 h. Finally, increase the speed to 6000 rpm and continue dispersing for 5 h. Then, use a high-pressure homogenizer to homogenize at 80 MPa 10 times to obtain an aqueous slurry of graphene oxide.

[0090] S2. Take an aqueous slurry containing 1 part of graphene oxide prepared in step S1, add 8 parts of tallow amine and 10 parts of Group IV base oil PAO to the reactor, and disperse at 300 rpm for 2 hours.

[0091] Next, add 2 parts isopropanol, heat to 120°C and vacuum, and process for 6 hours to remove low-boiling-point substances. At the same time, the graphene oxide is modified to obtain modified graphene oily slurry (which can be named modified graphene oily slurry 5#).

[0092] The modified graphene oily slurry No. 5 prepared in this comparative example can be used as a lubricating oil additive.

[0093] Test Example 1: Dispersion Stability Test

[0094] Composite oily slurry 1#, composite oily slurry 2#, composite oily slurry 3#, graphene oily slurry 4#, and modified graphene oily slurry 5# are added as additives to the finished lubricating oil Merbühne SP 0W-40 at a weight ratio of 100 ppm of graphene or composite graphene (modified graphene and graphene) or modified graphene. The mixture is then dispersed by manual stirring using conventional methods.

[0095] Centrifuge at 1440g (1440 times the acceleration of gravity) for 30 minutes (approximately equivalent to one month of natural settling), pause for 30 minutes, then centrifuge again for 30 minutes, repeating this process for a total of 3 hours. The test results are shown in Table 1.

[0096] Table 1. Dispersion stability test results

[0097]

[0098]

[0099] Table 1 shows that modified graphene exhibits significantly better dispersion stability in lubricating oil than graphene alone. A simple mixture of graphene and modified graphene shows the same overall dispersion stability as graphene alone. However, the composite of graphene and modified graphene shows a significantly improved overall dispersion stability compared to graphene alone, approaching that of modified graphene. This indicates that during the composite process of graphene and modified graphene, the modified graphene enhances the dispersion stability of graphene in the composite slurry.

[0100] Test Example 2 Friction and Wear Test

[0101] The composite oily slurry 1#, composite oily slurry 2#, composite oily slurry 3# prepared in Examples 1-3, the graphene oily slurry 4# prepared in Comparative Example 1, and the modified graphene oily slurry 5# prepared in Comparative Example 2 were added as additives to the finished lubricating oil. The friction and wear performance of the lubricating oil, including the coefficient of friction and the wear scar diameter, was tested. The test results are shown in Table 2.

[0102] Commercially available finished lubricating oil SP 0W-30 (Merlux) and commercially available finished lubricating oil SP 0W-30 (Merlux) with additives were evaluated using a four-ball friction tester to test their friction-reducing and anti-wear properties (industry standard SH / TO189-92). Test conditions included: GCr15 steel balls, rotation speed of 1200 r / min, oil temperature of 75℃, long-wear time of 60 min, and load of 392 N. The data provided by the four-ball friction tester included the wear scar diameter and coefficient of friction. A smaller wear scar diameter indicates higher anti-wear capability, and a smaller coefficient of friction indicates better friction-reducing performance.

[0103] Table 2. Tribological and Wear Properties of Lubricating Oils

[0104]

[0105] As can be seen from Table 2:

[0106] 1. Comparing oil samples 1, 5, and 6, under the experimental conditions, modified graphene had almost no effect on improving the anti-wear and friction-reducing properties of the lubricating oil, while the effect of graphene on improving the anti-wear and friction-reducing properties of the lubricating oil was significantly better than that of modified graphene. After standing for 7 days, the effect of graphene on improving the anti-wear and friction-reducing properties of the lubricating oil also decreased. Combined with the dispersion stability test results, due to the poor dispersion stability of graphene, after standing for 7 days, graphene will inevitably settle slightly, resulting in a decrease in the anti-wear and friction-reducing effect. This indicates that the dispersion state of graphene plays a decisive role in the performance of its anti-wear and friction-reducing properties.

[0107] 2. Comparing oil samples 5, 6 and 7, the simple mixing of graphene and modified graphene, regardless of whether it was left to stand, had the same effect on improving the anti-wear and friction-reducing properties of the lubricating oil as graphene, indicating that modified graphene had no effect in the mixture.

[0108] 3. Comparing oil samples 1, 2, 3, 4, 5, and 7, the overall effect of graphene combined with modified graphene on improving the anti-wear and friction-reducing properties of lubricating oil is further enhanced compared to graphene alone. The effect remains basically unchanged before and after standing. This indicates that during the process of combining graphene with modified graphene, the modified graphene improves the dispersion state of graphene, thereby enhancing the anti-wear and friction-reducing effect. However, simply mixing graphene with modified graphene does not change the dispersion state of graphene, so the anti-wear and friction-reducing effect remains unchanged.

[0109] Test Example 3: High Temperature High Shear Viscosity Test

[0110] The composite oily slurry 1#, composite oily slurry 2#, and composite oily slurry 3# prepared in Examples 1-3, the graphene oily slurry 4# prepared in Comparative Example 1, and the modified graphene oily slurry 5# prepared in Comparative Example 2 were added as additives to the finished lubricating oil SP 0W-30 (Morunshi). High-temperature, high-shear viscosity tests were conducted according to standard NB / SH / T 0703-2020, with test conditions of 150℃ and 10... 6 s -1 The test results are shown in Table 3.

[0111] Table 3. Results of High Temperature and High Shear Viscosity Test

[0112]

[0113] Table 3 shows that modified graphene can significantly improve the high-temperature high-shear viscosity of engine oil, while graphene can only slightly improve it. Combined with the conclusions in Table 2, it can be concluded that the combined use of graphene and modified graphene can achieve both good anti-wear and friction-reducing effects, and also improve high-temperature high-shear viscosity (i.e., improve oil film toughness).

[0114] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0115] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a modified graphene and graphene composite oily slurry, characterized in that, include: A range of graphene oxides with different oxygen contents are available; A series of graphene oxides with different oxygen contents were added to water in descending order of oxygen content. Each addition was followed by dispersion, and then more graphene was added and dispersed. The mixture was then subjected to high-pressure homogenization to obtain a graphene composite aqueous slurry. The graphene composite aqueous slurry, oily dispersant / modifier, and base oil are uniformly dispersed, and then subjected to vacuum distillation while the graphene oxide is modified to obtain a modified graphene and graphene composite oily slurry.

2. The preparation method according to claim 1, characterized in that: The oxygen content of the series of graphene oxides with different oxygen contents is 15-55%. Preferably, the series of graphene oxides with different oxygen contents includes graphene oxide with an oxygen content of 15-25%, graphene oxide with an oxygen content of 25-35%, graphene oxide with an oxygen content of 35-45%, and graphene oxide with an oxygen content of 45-55%. Preferably, the graphene composite aqueous slurry comprises the following components by weight: 1 part graphene, 0.1 to 0.3 parts graphene oxide with an oxygen content of 15 to 25%, 0.2 to 0.6 parts graphene oxide with an oxygen content of 25 to 35%, 0.2 to 0.6 parts graphene oxide with an oxygen content of 35 to 45%, 0.5 to 1.5 parts graphene oxide with an oxygen content of 45 to 55%, and 80 to 200 parts water.

3. The preparation method according to claim 2, characterized in that, include: A series of graphene oxides with different oxygen contents were added to water in descending order of oxygen content. Each addition was followed by a first dispersion, and then a second dispersion was performed. The mixture was then subjected to high-pressure homogenization to obtain a graphene composite aqueous slurry. Preferably, the first dispersion is carried out at a rotation speed of 3000-8000 rpm, and the first dispersion time for each addition of graphene oxide is 0.5-1 h. Preferably, the second dispersion is carried out at a rotation speed of 3000-8000 rpm and the second dispersion time is 3-5 hours; Preferably, the pressure of the high-pressure homogenization treatment is 80-100 MPa, and the treatment is repeated 5-10 times.

4. The preparation method according to claim 1, characterized in that: The oily dispersant / modifier includes any one or more combinations of polyisobutylene amine, polyisobutylene succinimide, polyether amine, tallow amine, and tallow amine polyoxyethylene ether; and / or, the base oil includes any one or more combinations of Group II base oil, Group III base oil, Group IV base oil, and Group V base oil.

5. The preparation method according to claim 1, characterized in that, include: An oily dispersant / modifier and base oil are added to the graphene composite aqueous slurry, and a third dispersion is carried out to obtain a mixed slurry. Preferably, the mixed slurry comprises the following components calculated by weight: 1 part of a mixture of graphene and graphene oxide in the graphene composite aqueous slurry, 8-20 parts of an oily dispersant and modifier, and 10-30 parts of base oil. Preferably, the third dispersion is carried out at a rotation speed of 200-500 rpm and the third dispersion time is 1-3 hours.

6. The preparation method according to claim 5, characterized in that, include: Low-boiling-point alcohol compounds are added to the mixed slurry, and vacuum distillation is performed to remove water and low-boiling-point alcohol compounds while modifying graphene oxide to obtain the modified graphene and graphene composite slurry. Preferably, the low-boiling-point alcohol compound includes one or more combinations of methanol, ethanol, n-propanol, and isopropanol; Preferably, based on the solid portion of the graphene composite aqueous slurry, the mass ratio of the graphene composite aqueous slurry to the low-boiling-point alcohol compound is 1:(2-4). And / or, the conditions for vacuum distillation include: a temperature of 80–120°C, vacuum treatment for 6–10 h, and a vacuum degree of -0.095–-0.1 MPa.

7. A modified graphene and graphene composite oily slurry prepared by any one of claims 1-6, comprising a base oil, and modified graphene and graphene uniformly dispersed in the base oil.

8. The application of the modified graphene and graphene composite oily slurry according to claim 7 in the field of lubricating oil.

9. A lubricating oil additive, characterized in that, Including the modified graphene and graphene composite oily slurry as described in claim 7.

10. A lubricating oil comprising at least the modified graphene and graphene composite oily slurry as described in claim 7.

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