Preparation method and application of graphene oily slurry

Abstract

The invention provides a preparation method and application of graphene oily slurry. The preparation method comprises the following steps: converting aqueous graphene slurry into oily graphene slurry through a phase conversion method; the phase property conversion method comprises the following steps: adding an oily dispersant, base oil and a cosolvent into the graphene aqueous slurry to form a water-in-oil graphene emulsion; converting the water-in-oil emulsion into an oil-in-water emulsion through a reverse phase agent; and removing water and the cosolvent in the oil-in-water emulsion to obtain the graphene oily slurry. According to the technical scheme, the graphene oily slurry obtained through a phase property conversion method retains a good dispersion state of graphene in water-based slurry, and can be uniformly dispersed in base oil / lubricating oil through a simple mixing method, so that the problem that graphene powder is not easy to disperse when being directly added into the lubricating oil is avoided; the additive can be directly used as a lubricating oil additive, so that blending of the additive with good anti-wear and anti-friction performance can be realized by adopting conventional equipment.

Description

Technical Field

[0001] The invention relates to the technical field of lubricating oils, and in particular to a preparation method and application of graphene oily slurry. Background Art

[0002] With economic development and improved living standards, the number of fuel vehicles in my country ranks first in the world. During the operation of the automobile internal combustion engine, part of the energy of the fuel is inevitably lost due to friction and wear. Lubricating oil can effectively reduce friction and wear between mechanical parts and is one of the key factors affecting the mechanical efficiency and reliability of the engine. With the rapid increase in the use of automobiles, exhaust emissions have also increased, causing adverse effects on the environment and human health; and lubricating oil consumption is the main source of particulate matter in automobile exhaust. With the vigorous promotion of the "green development policy" and the continuous improvement of environmental requirements and usage requirements such as engine high efficiency and energy saving, near-zero emissions and low fuel consumption, higher requirements are placed on the quality of lubricants.

[0003] Lubricants are generally composed of base oils and additives. The addition of additives can enhance or increase certain functions, thereby greatly improving the quality of the lubricant.

[0004] Nanomaterials have optical, electrical, thermal, chemical or mechanical properties that are completely different from conventional materials. Nanoparticles of suitable size can be used as lubricant additives, and they show anti-wear and friction reduction properties that are superior to traditional additives under extreme conditions such as high temperature, low temperature, dryness, and extreme pressure. Graphene has a multilayer structure and possesses 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 lubricants. However, graphene is directly added to lubricating oil, usually in the form of powder, and graphene powder has a soft agglomeration phenomenon, and the formed dispersion system is an unstable state, which is not conducive to the anti-wear and friction reduction effect of graphene. The existing equipment of the lubricating oil production line cannot achieve good dispersion, and the production line needs to be modified to increase the supporting dispersion equipment, and there is dust pollution during the addition process. For example, a graphene oily slurry disclosed in Chinese invention patent CN106147295A can achieve its mechanical exfoliation in the oil phase system even by adding a high shear force emulsifier.

[0005] On the other hand, the graphene slurry in the prior art is generally water-based slurry and NMP slurry. The graphene in these two slurries can be in a good dispersion state and the dispersion state is still good after dilution. However, when it is applied to the field of lubricating oil, since lubricating oil cannot contain water, the introduction of NMP will also reduce the performance of lubricating oil, such as viscosity, flash point, rubber compatibility, etc. Therefore, the above two slurries cannot be directly applied to lubricating oil.

[0006] Therefore, how to provide an oily slurry of graphene and add it directly to lubricating oil to achieve a good dispersion effect without the need for additional modification of the lubricating oil production line, improve the dispersion stability of graphene in the oil phase, and give full play to the friction reduction and anti-wear effect of graphene, has become an urgent problem to be solved in the application of graphene additives in the field of lubricating oil in the prior art. Summary of the invention

[0007] To solve the above problems, the present invention provides a preparation method and application of graphene oily slurry, in which graphene aqueous slurry is converted into graphene oily slurry by a phase conversion method, and the graphene oily slurry can be directly added to lubricating oil. Good dispersion of graphene in lubricating oil can be achieved through conventional stirring equipment, without the need for additional modification of the lubricating oil production line.

[0008] In order to achieve the above-mentioned purpose, the present invention provides a method for preparing graphene oily slurry, wherein graphene water-based slurry is converted into graphene oily slurry by a phase conversion method; the phase conversion method comprises compatibilizing the graphene water-based slurry with a base oil to form an oil-in-water graphene emulsion; and then converting the oil-in-water graphene emulsion into a water-in-oil graphene emulsion to achieve phase reversal, wherein the graphene enters the oil phase from the water phase, and the graphene oily slurry is obtained by post-treatment.

[0009] Preferably, the phase conversion method includes making the base oil compatible with the graphene aqueous slurry under the action of a cosolvent and an oily dispersant to form an oil-in-water graphene emulsion; then converting the oil-in-water graphene emulsion into an oil-in-water graphene emulsion by a phase inversion agent to achieve phase reversal and allow the graphene to enter the oil phase from the water phase; finally, removing the water and the cosolvent from the water-in-oil graphene emulsion through post-treatment to obtain the graphene oily slurry, thereby achieving a phase conversion of the graphene slurry from water-based to oily.

[0010] In some specific embodiments, the phase conversion method includes: adding an oily dispersant, a base oil and the co-solvent to the graphene aqueous slurry, and obtaining the oil-in-water graphene emulsion after the first dispersion treatment; then, adding an inverting agent to the oil-in-water graphene emulsion, and performing a second dispersion treatment under high-speed shearing to obtain the water-in-oil graphene emulsion; the water-in-water graphene emulsion is post-treated to remove water and the co-solvent to obtain the graphene oily slurry.

[0011] In some specific embodiments, based on the graphene material in the graphene aqueous slurry, the mass ratio of the graphene aqueous slurry: the oily dispersant, the base oil and the co-solvent is 1:(2-10):(10-30):(1-5).

[0012] In some specific embodiments, the conditions of the first dispersion treatment include a dispersion speed of 200 to 500 rpm and a dispersion time of 1 to 3 hours.

[0013] In some specific embodiments, the base oil is one or a combination of group I mineral oil, group II mineral oil, group III mineral oil, PAO base oil, ester base oil, polyether base oil, and alkyl naphthalene base oil.

[0014] In some specific embodiments, the co-solvent is an alcohol compound or an ether compound that is slightly soluble in water.

[0015] Preferably, the alcohol compound is any one of n-butanol, sec-butanol, n-pentanol, isopentanol, 3-pentanol, tert-pentanol, n-hexanol, benzyl alcohol, phenylethyl alcohol and citronellol, or a combination of several thereof.

[0016] Preferably, the ether compound is one or a combination of ethylene glycol phenyl ether, ethylene glycol monobutyl ether, and diethylene glycol monobutyl ether.

[0017] In some specific embodiments, the oily dispersant is any one of polyisobutylene succinimide, polyisobutylene succinic anhydride, Span 80, boronated polyisobutylene succinimide, isopropyl titanate, sorbitan oleate, polyether, stearic acid, oleic acid, tallow amine, and tallow amine polyoxyethylene ether.

[0018] In some specific embodiments, the reverse agent is nonylphenol polyoxyethylene ether, octylphenol polyoxyethylene ether-10, and cardanol polyoxyethylene ether, and the number of polyoxyethylene ether chain segments is 7-10.

[0019] In some specific embodiments, based on the graphene material in the graphene aqueous slurry, the mass ratio of the graphene aqueous slurry to the reverse agent is 1:(0.1-0.5).

[0020] In some specific embodiments, the conditions for the second dispersion include: a dispersion speed of 1000 to 3000 rpm and a dispersion time of 1 to 3 hours.

[0021] In some specific embodiments, the graphene material in the graphene aqueous slurry is at least one of pure graphene, fluorinated graphene, oxidized graphene or doped graphene.

[0022] As a preferred embodiment, the graphene material in the graphene aqueous slurry may also be replaced by a graphene-like material.

[0023] Preferably, the graphene-like material includes but is not limited to carbon nanotubes.

[0024] Furthermore, the present invention makes the base oil and the graphene aqueous slurry compatible by adding a cosolvent and an oily dispersant, thereby obtaining a graphene emulsion of an oil-in-water system, which provides a basis for finally achieving the inversion of the oil-water two-phase of the liquid phase through the action of an inverting agent.

[0025] In some specific embodiments, the method for removing water and the co-solvent from the oil-in-water graphene comprises vacuum distillation. In the present invention, water and the co-solvent are low-boiling point substances, and their boiling points are much higher than those of water and the co-solvent compared to other components in the system, so water and the co-solvent can be completely removed by vacuum distillation.

[0026] Specifically, the conditions of the reduced pressure distillation include: vacuum treatment for 2 to 5 hours at a temperature of 60 to 80°C.

[0027] In some specific embodiments, the post-treatment further comprises adding a viscosity modifier and / or an alkaline agent.

[0028] Specifically, after the reduced pressure distillation, the viscosity modifier and / or the alkaline agent is added and then a third dispersion treatment is performed to obtain the graphene oily slurry.

[0029] Preferably, the speed of the third dispersion is 200-500 rpm, and the dispersion time is 1-3 hours.

[0030] Preferably, based on the graphene material in the aqueous graphene slurry, the mass ratio of the aqueous graphene slurry: the viscosity improver is 1:(2-10).

[0031] Preferably, the viscosity improver is any one of propylene copolymer, PMA polymethacrylate, polyisobutylene, polystyrene isoprene copolymer or a combination of several thereof.

[0032] Preferably, based on the graphene material in the graphene aqueous slurry, the mass ratio of the graphene aqueous slurry: the alkaline agent is 1:(0.2-1).

[0033] Preferably, the alkaline agent is any one or a combination of polyisobutylene amine, polyisobutylene succinimide, polyether amine, synthetic calcium sulfonate, magnesium sulfonate, alkyl phenol calcium sulfide, alkyl salicylate calcium or diphenylamine compounds.

[0034] More preferably, the diphenylamine compound is selected from any one or a combination of butyl diphenylamine, octyl diphenylamine, nonyl diphenylamine.

[0035] The role of the viscosity improver is to improve the stability of the slurry, and the alkaline agent is added to adjust the pH of the slurry. The pH of the commercially available graphene aqueous slurry is adjusted according to the different pH values. The present invention does not limit the pH of the graphene aqueous slurry.

[0036] As one of the purposes of the invention, the present invention also provides a graphene oily slurry, which is prepared by the above-mentioned preparation method.

[0037] The graphene oily slurry provided by the above technical solution can be used as an additive in the field of lubricating oil; in particular, the graphene oily slurry can be directly added to the lubricating oil.

[0038] As one of the purposes of the invention, the present invention provides a lubricating oil, which at least comprises the graphene oily slurry provided by the aforementioned technical solution added to the base oil and mixed.

[0039] Beneficial technical effects obtained by the present invention:

[0040] 1. The technical solution of the present invention is adopted to transform the graphene aqueous slurry into the graphene oily slurry through the equipment and process conditions of the prior art by the phase conversion method, and the graphene in the oily slurry retains its dispersion state in the aqueous slurry, so that the graphene oily slurry can be evenly dispersed in the lubricating oil by simple mixing, avoiding the problem of difficult dispersion due to powder agglomeration when the graphene powder is directly added to the lubricating oil.

[0041] 2. The graphene oily slurry provided by the technical solution of the present invention has good dispersibility in base oil and / or lubricating oil. At the same time, the components in the graphene oily slurry are all commonly used components in lubricating oil, and can be directly used as an additive in the production process of lubricating oil, thereby providing a lubricating oil additive with good anti-wear and friction reduction. In addition, there is no need to modify the graphene, the process is simple, the production cost is low, and it is suitable for large-scale promotion and application.

[0042] 3. The technical solution of the present invention is used to prepare graphene oily slurry without the need for additional production line modification. The preparation of graphene lubricating oil can be achieved through conventional equipment and process conditions of the prior art, thereby saving equipment modification costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a comparison chart of dispersion stability test of Example 2 of the present invention, Comparative Example 1 and pure lubricating oil.

[0044] Figure 2 Wear spot diameter test chart of pure lubricating oil.

[0045] Figure 3This is a test diagram of the wear spot diameter of the lubricating oil to which the graphene oily slurry provided in Example 1 of the present invention is added.

[0046] Figure 4 The figures are comparison diagrams showing the change of friction coefficient of pure lubricating oil and lubricating oil added with graphene oily slurry provided in Example 1 over time. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0048] The invention provides a method for preparing graphene oily slurry, wherein a graphene water-based slurry is converted into a graphene oily slurry by a phase conversion method; the phase conversion method comprises the following steps: making a base oil compatible with the graphene water-based slurry under the action of a cosolvent and an oily dispersant to form an oil-in-water graphene emulsion; then converting the oil-in-water graphene emulsion into an oil-in-water graphene emulsion by a phase inversion agent to achieve phase inversion, so that the graphene enters the oil phase from the water phase; and finally, removing water and the cosolvent from the water-in-oil graphene emulsion to obtain the graphene oily slurry, thereby achieving phase conversion of the graphene slurry from water-based to oily.

[0049] Specifically, an oily dispersant, a base oil and the co-solvent are added to the graphene aqueous slurry, and the water-in-oil graphene emulsion is obtained after the first dispersion treatment;

[0050] The inverting agent is added to the water-in-oil graphene, and a second dispersion treatment is performed under the action of high-speed shearing to obtain the oil-in-water graphene emulsion.

[0051] Finally, after a post-treatment step, water and the co-solvent are removed, and the viscosity and acidity of the slurry are adjusted to obtain a graphene oily slurry.

[0052] Technical principle of phase conversion method: in graphene aqueous slurry, graphene is stably dispersed in the aqueous phase; then, under the action of co-solvent and oily dispersant, base oil and graphene aqueous slurry are compatible, and after dispersion treatment, base oil wraps graphene-containing aqueous phase droplets to form a graphene emulsion of oil-in-water system; further, under the coordinated action of inverting agent and disperser with high-speed shear, inverting agent realizes the oil-water phase inversion of emulsion system, graphene emulsion is converted from oil-in-water system to water-in-oil system, and graphene enters oil phase from aqueous phase; finally, after treatment with reduced pressure distillation, water and co-solvent in water-in-oil graphene emulsion are removed, and viscosity improver and alkaline agent are added to adjust the viscosity and alkalinity of graphene oily slurry to obtain graphene oily slurry, and graphene slurry is converted from aqueous to oily.

[0053] The present invention adopts a phase conversion method to convert graphene water-based slurry into graphene oil-based slurry. There is no need to modify the graphene or modify the equipment. The existing water-based slurry and existing equipment in the prior art can be selected to directly perform phase conversion, which greatly saves preparation costs.

[0054] The graphene aqueous slurry used in the examples and comparative examples of the present invention was purchased from Ningbo Zhaoxi Technology Co., Ltd., model G3S5, solid content 5%, particle size D503-6 μm.

[0055] It should be noted that, except for the water contained in the graphene aqueous slurry, other components that are not removed and retained in the graphene oily slurry are all common components in lubricating oils and can be directly used as lubricating oil additives without affecting the anti-wear and friction-reducing properties of the lubricating oil.

[0056] The technical solution of the present invention is described in detail below through specific embodiments.

[0057] Example 1

[0058] This embodiment provides a method for preparing graphene oily slurry, and the specific steps include:

[0059] A graphene aqueous slurry containing 1 part of graphene, 2 parts of Span 80, 10 parts of polyalphaolefin base oil PAO-4, and 1 part of n-butanol were added into the reactor and dispersed at a speed of 300 rpm for 2 hours.

[0060] Then, 0.1 parts of OP-10 (octylphenol polyoxyethylene ether-10) was added and dispersed at 2000 rpm for 2 hours.

[0061] Next, 2 parts of isopropanol were added, the mixture was heated to 80°C and vacuumed for 3 h to remove low-boiling substances.

[0062] Finally, 2 parts of polymethacrylate and 0.4 parts of butyl diphenylamine were added, and the mixture was dispersed at a speed of 300 rpm for 1 hour to obtain graphene oily slurry 1-1#.

[0063] The above-mentioned graphene oily slurry 1-1# can be used as a lubricating oil additive.

[0064] Example 2

[0065] This embodiment provides a method for preparing graphene oily slurry, and the specific steps include:

[0066] A graphene aqueous slurry containing 1 part of graphene, 6 parts of polyisobutylene succinimide, 20 parts of AN-5 alkyl naphthalene base oil, and 3 parts of n-butanol were added into a reactor and dispersed at a speed of 400 rpm for 1 hour.

[0067] Then, 0.3 parts of NP-10 (nonylphenol polyoxyethylene ether-10) was added and dispersed at 1000 rpm for 3 hours.

[0068] Next, 3 portions of ethanol were added, heated to 70°C and vacuumed for 4 h to remove low-boiling substances.

[0069] Finally, 6 parts of ethylene-propylene copolymer and 0.3 parts of synthetic calcium sulfonate were added, and the mixture was dispersed at 200 rpm for 2 hours to obtain graphene oily slurry 1-2#.

[0070] The above-mentioned graphene oily slurry 1-2# can be used as a lubricating oil additive.

[0071] Example 3

[0072] This embodiment provides a method for preparing graphene oily slurry, and the specific steps include:

[0073] A graphene aqueous slurry containing 1 part of graphene, 10 parts of polyisobutylene succinic anhydride, 30 parts of Class III mineral oil, and 5 parts of n-butanol were added into a reactor and dispersed at a speed of 200 rpm for 3 hours.

[0074] Then, 0.5 parts of NSF-10 (cardanol polyoxyethylene ether-10) was added and dispersed at a speed of 3000 rpm for 1 hour.

[0075] Next, 4 portions of methanol were added, the mixture was heated to 60°C and vacuumed for 5 hours to remove low-boiling substances.

[0076] Finally, 10 parts of polyisobutylene and 0.3 parts of calcium alkyl salicylate were added, and the mixture was dispersed at 200 rpm for 2 h to obtain graphene oily slurry 1-3#.

[0077] The above-mentioned graphene oily slurry 1-3# can be used as a lubricating oil additive.

[0078] Example 4

[0079] This embodiment provides a method for preparing graphene oily slurry, and the specific steps include:

[0080] A graphene aqueous slurry containing 1 part of graphene, 2 parts of polyisobutylene succinic anhydride, 30 parts of AN-5 base oil, and 5 parts of n-butanol were added into a reactor and dispersed at a speed of 400 rpm for 3 hours.

[0081] Then, 0.5 parts of NSF-10 (cardanol polyoxyethylene ether-10) was added and dispersed at a speed of 3000 rpm for 1 hour.

[0082] Next, 3 parts of n-propanol were added, the mixture was heated to 60°C and vacuumed for 5 hours to remove low-boiling substances.

[0083] Finally, 2 parts of ethylene-propylene copolymer and 0.3 parts of butyl diphenylamine were added, and the mixture was dispersed at 200 rpm for 2 h to obtain graphene oily slurry 1-4#.

[0084] The above-mentioned graphene oily slurry 1-4# can be used as a lubricating oil additive.

[0085] Comparative Example 1

[0086] This comparative example provides a method for preparing a graphene oily slurry, wherein graphene powder is directly dispersed in an oil phase system to obtain a graphene oily slurry, and the specific steps include:

[0087] 1 part of graphene powder, 2 parts of polyisobutylene succinimide, 30 parts of AN-5 base oil, 2 parts of ethylene propylene copolymer, and 0.4 parts of butyl diphenylamine were added into a reactor and dispersed at 3000 rpm for 3 hours to obtain graphene oily slurry 2-1#.

[0088] The graphene powder is obtained by drying the graphene aqueous slurry, and has the same material parameters as those of the graphene in the graphene aqueous slurry in Example 1.

[0089] Comparative Example 2

[0090] This comparative example provides a method for preparing a graphene oily slurry, which is different from Example 4 in that water and solvent are directly removed without phase inversion in the obtained water-in-oil graphene state, and the specific steps include:

[0091] A graphene aqueous slurry containing 1 part of graphene, 2 parts of polyisobutylene succinimide, 30 parts of AN-5 base oil, and 5 parts of n-butanol were added to a reactor and dispersed at 400rpm for 3 hours; 3 parts of n-propanol were added, the materials in the reactor were heated to 60°C, vacuumed, and treated for 5 hours to remove low-boiling substances; 2 parts of ethylene propylene copolymer and 0.3 parts of butyl diphenylamine were added, and dispersed at 200rpm for 2 hours to obtain graphene oily slurry 2-2#.

[0092] Comparative Example 3

[0093] This comparative example provides a method for preparing a graphene oily slurry, which is different from Example 4 in that an inverting agent is added to the obtained water-in-oil graphene state without high-speed shearing, and then water and solvent are directly removed. The specific steps include:

[0094] Add 1 part of graphene aqueous slurry containing 1 part of graphene, 2 parts of polyisobutylene succinimide, 30 parts of AN-5 base oil, and 5 parts of n-butanol into the reactor and treat at 400rpm for 3 hours; add 0.4 parts of NSF-10, dispersing device 50rpm, and treat for 1 hour; add 3 parts of n-propanol, heat the materials in the reactor to 60°C, evacuate, and treat for 5 hours to remove low-boiling substances; add 2 parts of ethylene propylene copolymer and 0.3 parts of butyl diphenylamine, and disperse at 200rpm for 2 hours to obtain graphene oily slurry 2-3#.

[0095] Comparative Example 4

[0096] This comparative example provides a method for preparing a graphene oily slurry, which is different from Example 4 in that no inverting agent is added to the obtained water-in-oil graphene state, only high-speed shearing is performed, and then water and solvent are directly removed. The specific steps include:

[0097] Add graphene aqueous slurry containing 1 part of graphene, 2 parts of polyisobutylene succinimide, 30 parts of AN-5 base oil, 2 parts of ethylene propylene copolymer, and 5 parts of n-butanol into the reactor and treat at 3000rpm for 1h; the dispersion device is 3000rpm and treated for 1h; 3 parts of n-propanol are added, the materials in the reactor are heated to 60°C, vacuumed, and treated for 6h to remove low-boiling point substances; 2 parts of ethylene propylene copolymer and 0.3 parts of butyl diphenylamine are added, and the dispersion treatment is carried out at 200rpm for 2h to obtain graphene oily slurry 2-4#.

[0098] Performance Test:

[0099] 1. Fineness scraper test

[0100] The fineness of the graphene aqueous slurry and the graphene oily slurry provided in the embodiment and the comparative example was tested using a scraper fineness meter, respectively. The test results are shown in Table 1.

[0101] As can be seen from Table 1, from Examples 1 to 4, there is no significant change in the fineness of the graphene slurry before and after the phase conversion, indicating that the graphene oily slurry obtained by the phase conversion method retains the stable dispersion performance of the graphene of the graphene aqueous slurry raw material. The fineness of the graphene oily slurry 1-2# of Example 2 is basically unchanged after being placed for 2 months, indicating that the graphene oily slurry obtained by the phase conversion method has good dispersion stability.

[0102] It can be seen from Example 4 and Comparative Example 1 that the fineness of the obtained graphene oily slurry is significantly increased by directly dispersing the graphene powder into the oil phase, indicating that the graphene powder cannot be well dispersed into the oil phase using conventional dispersing equipment and the graphene agglomerates.

[0103] It can be seen from Example 4 and Comparative Example 2 that without the phase inversion of the graphene emulsion, the fineness of the obtained graphene oily slurry becomes significantly larger, indicating that without the phase inversion, the graphene enters the oil phase from the water phase during the vacuum distillation process, and agglomeration occurs in this process.

[0104] It can be seen from Example 4 and Comparative Examples 3 and 4 that the graphene emulsion is phase-reversed by a single means (addition of an inverting agent or high-speed shearing), and the fineness of the obtained graphene oily slurry varies greatly, indicating that the phase reversal by a single means is not complete, and the graphene has not completely entered the oil phase from the water phase, while the graphene retained in the water phase enters the oil phase from the water phase during the vacuum distillation process, and the graphene agglomerates in this process.

[0105] Table 1 Particle size and specific surface area of ​​Examples and Comparative Examples

[0106]

[0107]

[0108] 2. Dispersion stability test

[0109] The samples of graphene oily slurry prepared in Example 4 and Comparative Example 1 were respectively added to commercially available finished lubricant SP / 0W-30 (Merruns), and the addition ratio of the graphene oily slurry was 0.05% based on the mass of graphene. After addition, a simple dispersion treatment was performed by manual stirring. After being placed in a transparent test tube for 1 week, the dispersion stability was observed.

[0110] See also Figure 1 , from left to right, they are pure lubricating oil, lubricating oil added with graphene oily slurry 2-1# prepared in Comparative Example 1, and lubricating oil added with graphene oily slurry 1-2# prepared in Example 2. Obviously, the lubricating oil added with graphene oily slurry 2-1# has obvious precipitation, while the lubricating oil added with graphene oily slurry 1-2# and the pure lubricating oil are both clear and transparent.

[0111] The results show that the graphene oily slurry 2-1# prepared using graphene powder has poor dispersion state of graphene in the slurry, and the dispersion stability of graphene when dispersed in lubricating oil is also poor, indicating that graphene powder cannot be directly used in lubricating oil under conventional equipment.

[0112] 3. Friction and wear test

[0113] The graphene oily slurry prepared in the examples and comparative examples was added as an additive to finished lubricating oil, and the friction and wear properties of the lubricating oil were tested, including the friction coefficient and the wear spot diameter.

[0114] The commercially available finished lubricant SP / 0W-30 (Merrun) and the commercially available finished lubricant SP / 0W-30 (Merrun) with graphene oily slurry 1-1# (Example 1) added were evaluated by a four-ball friction tester to test their anti-friction and anti-wear properties (industry standard SH / TO189-92). The test conditions include: GCr15 steel ball, rotation speed 1200r / min, oil temperature 75°C, long grinding time 60min, and load 392N. The data given by the four-ball friction tester test include wear spot diameter and friction coefficient. The smaller the wear spot diameter, the higher the anti-wear ability, the smaller the friction coefficient, and the better the anti-friction performance.

[0115] See also Figure 2 The wear spot diameter of the finished lubricant SP / 0W-30 is 0.44mm, and the wear marks are obvious. Figure 3 The wear spot diameter of the lubricating oil added with graphene oily slurry 1-1# is 0.34 mm, and there is almost no wear mark. Obviously, after adding graphene oily slurry 1-1#, the wear spot diameter and wear marks of the lubricating oil are reduced, and the anti-wear performance is improved.

[0116] See also Figure 4 , is a graph showing the change in friction coefficient over time of the finished lubricant SP / 0W-30 and the lubricant with graphene oily slurry 1-1# added. It can be seen from the figure that the friction coefficient of the lubricant with graphene oily slurry 1-1# added remains stable over time, and compared with the finished lubricant, it has better stability and a lower friction coefficient.

[0117] The above are only preferred embodiments of the present invention, which do not limit the protection scope of the present invention. For those skilled in the art, the present invention may have various modifications and changes. Within the spirit and principle of the present invention, changes, modifications, replacements, integrations and parameter changes to these embodiments by conventional substitutions or capable of achieving the same functions without departing from the principles and spirit of the present invention all fall within the protection scope of the present invention.

Claims

1. A method for preparing graphene oily slurry, characterized in that: The graphene aqueous slurry is transformed into the graphene oily slurry by a phase conversion method; The phase conversion method comprises compatibilizing the graphene aqueous slurry with base oil to form an oil-in-water graphene emulsion; then converting the oil-in-water graphene emulsion into a water-in-oil graphene emulsion to achieve phase reversal, whereby the graphene enters the oil phase from the water phase, and the graphene oily slurry is obtained after post-treatment.

2. The preparation method according to claim 1, characterized in that: The phase conversion method comprises: adding an oily dispersant, a base oil and a cosolvent to the graphene aqueous slurry, and obtaining the water-in-oil graphene emulsion through a first dispersion treatment; Adding an inverting agent to the water-in-oil graphene emulsion, and performing a second dispersion treatment under high-speed shearing to obtain the oil-in-water graphene emulsion; The oil-in-water graphene emulsion is subjected to the post-treatment to remove water and the co-solvent, thereby obtaining the graphene oily slurry.

3. The preparation method according to claim 2, characterized in that: Based on the graphene material in the graphene aqueous slurry, the mass ratio of the graphene aqueous slurry: the oily dispersant, the base oil and the co-solvent is 1:(2-10):(10-30):(1-5); The conditions of the first dispersion treatment include a dispersion speed of 200 to 500 rpm and a dispersion time of 1 to 3 hours; The base oil is one or a combination of Class I mineral oil, Class II mineral oil, Class III mineral oil, PAO base oil, ester base oil, polyether base oil, and alkyl naphthalene base oil; The cosolvent is an alcohol compound and / or an ether compound that is slightly soluble in water; preferably, the alcohol compound is any one of n-butanol, sec-butanol, n-pentanol, isopentanol, 3-pentanol, tert-pentanol, n-hexanol, benzyl alcohol, phenylethyl alcohol, and citronellol, or a combination thereof; the ether compound is any one of ethylene glycol phenyl ether, ethylene glycol monobutyl ether, and diethylene glycol monobutyl ether, or a combination thereof; The oily dispersant is any one or a combination of polyisobutylene succinimide, polyisobutylene succinic anhydride, Span 80, boronated polyisobutylene succinimide, isopropyl titanate, sorbitan oleate, polyether, stearic acid, oleic acid, tallow amine, and tallow amine polyoxyethylene ether; And / or, the graphene material in the graphene aqueous slurry is at least one of pure graphene, fluorinated graphene, oxidized graphene or doped graphene; Alternatively, the graphene material in the graphene aqueous slurry is a graphene-like material; preferably, the graphene-like material includes carbon nanotubes.

4. The preparation method according to claim 2 or 3, characterized in that: The reverse phase agent is nonylphenol polyoxyethylene ether, octylphenol polyoxyethylene ether, cardanol polyoxyethylene ether, and the number of polyoxyethylene ether chain segments is 7 to 10; And / or, based on the graphene material in the graphene aqueous slurry, the mass ratio of the graphene aqueous slurry to the reverse agent is 1:(0.1-0.5); And / or, the conditions for the second dispersion include: a dispersion speed of 1000 to 3000 rpm and a dispersion time of 1 to 3 hours.

5. The preparation method according to any one of claims 1 to 3, characterized in that: The post-treatment includes vacuum distillation; The conditions of the reduced pressure distillation include: vacuum treatment for 2 to 5 hours at a temperature of 60 to 120°C; Preferably, the reduced pressure distillation includes adding a low-boiling alcohol compound, wherein the low-boiling alcohol is miscible with water and the co-solvent to form an azeotrope, thereby accelerating the distillation speed; Preferably, the low boiling point alcohol includes one or a combination of methanol, ethanol, n-propanol or isopropanol; Based on the graphene material in the graphene aqueous slurry, the mass ratio of the graphene aqueous slurry to the low-boiling point alcohol is 1:(2-10).

6. The preparation method according to claim 5, characterized in that: The post-treatment also includes adding a viscosity modifier and / or an alkaline agent; After the reduced pressure distillation, the viscosity modifier and / or the alkaline agent are added, and then a third dispersion treatment is performed to obtain the graphene oily slurry; The speed of the third dispersion is 200-500 rpm, and the dispersion time is 1-3 hours; And / or, based on the graphene material in the graphene aqueous slurry, the mass ratio of the graphene aqueous slurry: the viscosity modifier is 1:(2-10); The viscosity improver is any one or a combination of ethylene propylene copolymer, polymethacrylate, polyisobutylene, polystyrene isoprene copolymer; And / or, based on the graphene material in the graphene aqueous slurry, the mass ratio of the graphene aqueous slurry: the alkaline agent is 1: (0.2-1); The alkaline agent is any one or a combination of polyisobutylene amine, polyisobutylene succinimide, polyether amine, synthetic calcium sulfonate, magnesium sulfonate, alkyl phenol calcium sulfide, alkyl salicylate calcium or diphenylamine compounds; preferably, the diphenylamine compound is selected from any one or a combination of butyl diphenylamine, octyl diphenylamine, nonyl diphenylamine.

7. A graphene oily slurry prepared by the preparation method according to any one of claims 1 to 6.

8. The graphene oily slurry prepared by the preparation method according to any one of claims 1 to 6, or the use of the graphene oily slurry according to claim 7 as an additive in the field of lubricating oil; the graphene oily slurry can be directly added to the lubricating oil.

9. A graphene oily slurry, comprising at least the graphene oily slurry prepared by the preparation method according to any one of claims 1 to 6, or the graphene oily slurry according to claim 7; wherein: The graphene oily slurry is compatible with base oil.

10. A lubricating oil comprising at least the graphene oily slurry according to claim 9.

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