Graphene oily slurry as well as preparation method and application thereof

Abstract

The invention discloses graphene oily slurry as well as a preparation method and application thereof, and relates to the technical field of lubricating oil additives. The preparation method of the graphene oily slurry comprises the following steps: firstly, taking a polymer monomer with good compatibility with graphene as a solvent, and dispersing the graphene in the polymer monomer solvent to prepare graphene polymer monomer slurry with good dispersion; and carrying out polymerization reaction by combining an in-situ polymerization method to obtain the graphene oily slurry. According to the technical scheme, the surface of graphene is coated with a polymer generated through in-situ polymerization, so that the dispersion stability of graphene is improved, the prepared graphene oily slurry can be uniformly dispersed in lubricating oil through simple mixing, and all components in the graphene oily slurry are common components in the lubricating oil, so that the graphene oily slurry can be uniformly dispersed in the lubricating oil. The graphene lubricating oil can be directly used as a lubricating oil additive, blending of the graphene lubricating oil can be realized by utilizing conventional equipment, equipment improvement is not needed, and the production cost is reduced.

Description

Technical Field

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

[0002] With economic development and the improvement of living standards, the number of fuel vehicles in my country ranks first in the world. During the operation of the internal combustion engine of an automobile, 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. At the same time, based on the requirements of environmental protection, higher requirements are put forward for fuel vehicle engines in terms of high efficiency, energy saving, near-zero emissions and low fuel consumption. Therefore, requirements are also put forward for the quality of lubricating oil. Lubricating oil is generally composed of base oil and additives. The addition of additives can enhance or add certain functions, thereby greatly improving the quality of lubricating oil.

[0003] Nanomaterials have optical, electrical, thermal, chemical or mechanical properties that are completely different from conventional materials. Nanoparticles of appropriate size can be used as lubricant additives, and they have shown better anti-wear and friction-reducing properties than traditional additives under extreme conditions such as high temperature, low temperature, dryness, and extreme pressure. Graphene has some 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.

[0004] In the prior art, when graphene is used as an additive in lubricating oil, it is usually added in the form of powder. However, the graphene powder has a soft agglomeration phenomenon, which makes it impossible to achieve good dispersion in the oil phase. In order to improve the dispersion stability of the graphene powder, the lubricating oil production line needs to be modified and additional dispersion equipment (such as shearing equipment) needs to be added, which greatly increases the production cost and production difficulty. At the same time, the dispersion process of the graphene powder is inevitably accompanied by a violent shearing action, which destroys the structure of macromolecular components such as base oil and tackifier in the lubricating oil, resulting in a decrease in the performance of the lubricating oil, such as a decrease in viscosity, a decrease in oxidation stability, and a decrease in service life. In addition, there is dust pollution in the process of adding the powder.

[0005] In order to solve the above problems, a method for preparing a graphene slurry is preferred, so that the graphene is in a good dispersed state, and the graphene is added to the lubricating oil, and the graphene is evenly mixed by simple dispersion, and the graphene is kept in a good dispersed state, so as to solve the problems of difficulty in adding graphene powder, difficulty in dispersion, and degradation of oil performance in the production process of graphene lubricating oil. The graphene slurry in the prior art is usually an aqueous slurry or an oily slurry, wherein the oily slurry uses an organic solvent with good compatibility with graphene, such as NMP (N-methylpyrrolidone), DMF (N, N-dimethylformamide), ethyl acetate, etc. as a medium, and NMP slurry is the most common. However, according to existing lubricant standards, such as the API (American Petroleum Institute) standard, the moisture content of automobile engine oil should be less than 0.2%, and the ISO6743 / 18 standard stipulates that the moisture content of industrial lubricants should be less than 0.05%. Therefore, the use of aqueous graphene slurry in lubricating oil will cause the water content to exceed the standard. In addition, aqueous graphene slurry usually contains dispersants, which are generally water-soluble and not applicable in lubricating oil. For NMP slurry, NMP is not a component allowed to exist in lubricating oil. The addition of NMP will lead to a decrease in the performance of lubricating oil, such as viscosity, flash point, rubber compatibility, etc. Therefore, the application of graphene slurry in lubricating oil in the prior art is limited.

[0006] In view of this, the present invention provides a method for dispersing graphene based on using a polymer monomer having good compatibility with graphene as a solvent, and then removing the polymer monomer after a polymerization reaction by an in-situ polymerization method to obtain a graphene oily slurry, thereby avoiding the introduction of components that cannot be added into the lubricating oil and directly using the graphene oily slurry as an additive for the lubricating oil, thereby solving the problems existing in the prior art. Summary of the invention

[0007] In order to solve the above problems, the present invention provides a graphene oily slurry and a preparation method and application thereof.

[0008] As one of the objects of the invention, the present invention provides a method for preparing graphene oily slurry, comprising using a polymer monomer having good compatibility with graphene as a solvent, dispersing graphene in the solvent; and then performing a polymerization reaction by an in-situ polymerization method to obtain a graphene oily slurry, namely the graphene oily slurry.

[0009] Specifically, the method for preparing the graphene oily slurry comprises the following steps:

[0010] S1. Providing a graphene polymer monomer slurry;

[0011] The polymer monomer is used as a solvent, and an inhibitor is added. Expanded graphite is homogenized in the solvent under high pressure to prepare graphene, and the graphene is evenly dispersed in the solvent to form the graphene polymer monomer slurry. The conditions in the process of preparing graphene are relatively severe. If an inhibitor is not added for control, the polymer monomer is very likely to self-polymerize, which will increase the viscosity of the slurry. In severe cases, the slurry will solidify due to direct explosive polymerization, and the graphene polymer monomer slurry cannot be obtained.

[0012] S2. Providing a graphene polymer slurry;

[0013] Add base oil to the graphene polymer monomer slurry provided by S1, mix evenly, add initiator under the atmosphere of protective gas, stir and carry out in-situ polymerization reaction, the polymer obtained by the reaction is wrapped on the surface of the graphene and evenly dispersed in the base oil.

[0014] S3. Providing graphene oily slurry;

[0015] The graphene polymer slurry provided in S2 is added to an oily dispersant and an antioxidant and dispersed evenly to obtain the graphene oily slurry.

[0016] In some specific embodiments, in S1, the polymer monomer includes a combination of one or more of styrene, acrylate compounds, and acrylamide compounds.

[0017] The present invention prepares the graphene polymer monomer slurry first because the molecular structure of the polymer monomer is simple and is hardly affected by shearing during the graphene dispersion process, and then removes the monomer by an in-situ polymerization method, thereby avoiding the influence of shearing on the structure of macromolecular components such as polymer, base oil, and tackifier in the graphene oily slurry during the dispersion process.

[0018] Preferably, the acrylate compound is a methacrylate compound.

[0019] More preferably, the acrylamide compounds include but are not limited to any one of N-alkyl substituted acrylamide, N-alkyl substituted methacrylamide, 4-acryloylmorpholine, 3-acryloyl-2-oxazolone, N-benzyl acrylamide, N-phenyl acrylamide, N-phenyl methacrylamide, N-benzyl methacrylamide, N,N-dibenzyl acrylamide, N-benzyl-N-methyl acrylamide and the like.

[0020] In some specific embodiments, the inhibitor includes but is not limited to any one of hydroquinone monomethyl ether (MEHQ), hydroquinone (HQ), para-benzoquinone (PBQ), methyl hydroquinone (THQ), para-hydroxyanisole (HQMME), 2-tert-butylhydroquinone (MTBHQ), 2,5-di-tert-butylhydroquinone (2,5-DTBHQ), etc.

[0021] As a preferred embodiment, the preparation method of the graphene polymer monomer slurry comprises: adding at least expanded graphite, the polymer monomer, and an inhibitor into a vacuum disperser, dispersing at a speed of 2000 to 3000 rpm and a temperature of 0 to 20° C. in a dry air atmosphere for 2 to 4 hours; then circulating the mixture at 8000 to 14000 rpm using an emulsifying pump, and finally circulating the mixture 2 to 4 times through a high-pressure homogenizer, so that the prepared graphene is uniformly and stably dispersed in the polymer monomer to form the graphene polymer monomer slurry; during the preparation process, the expanded graphite is physically exfoliated and converted into graphene, and a graphene polymer monomer slurry is formed.

[0022] Preferably, the mass ratio of the expanded graphite to the polymerization inhibitor is 1:0.01-0.1.

[0023] Preferably, the mass ratio of the expanded graphite to the polymer monomer is 1:(10-100).

[0024] Preferably, in S2, the base oil includes but is not limited to any one of Group II base oil, Group III base oil, and synthetic base oil, or a combination of several of them.

[0025] More preferably, the synthetic base oil includes but is not limited to any one of PAO base oil and alkyl naphthalene base oil or a combination of the two.

[0026] Preferably, the initiator is azobisisobutyronitrile or benzoyl peroxide.

[0027] Preferably, the mass ratio of the expanded graphite to the initiator is 1:0.05-0.5.

[0028] The mass ratio of the expanded graphite to the base oil is 1:10-100.

[0029] Preferably, the stirring speed is 500-1000 rpm.

[0030] Preferably, the reaction temperature of the in-situ polymerization reaction is 60-80° C., and the reaction time is 4-6 hours.

[0031] Preferably, in S3, the dispersion conditions of the graphene polymer slurry include a stirring speed of 200 to 500 rpm, a dispersion time of 1 to 3 hours, and a temperature of 60 to 80°C.

[0032] Preferably, the oily dispersant includes but is not limited to at least one of polyisobutylene succinimide, boronated polyisobutylene succinimide, isopropyl titanate, sorbitan oleate, polyether, stearic acid, oleic acid, tallow amine, tallow amine polyoxyethylene ether, and the like.

[0033] Preferably, the antioxidant is any one of butyl diphenylamine, octyl diphenylamine, nonyl diphenylamine, and N-octylphenyl-α-naphthylamine, or a combination thereof. The antioxidant can not only capture free radicals and terminate the in-situ polymerization reaction, but also react with the initiator to remove the remaining initiator in the graphene polymer slurry, further reducing the residual amount of the initiator in the additive; and the residual polymer monomer and initiator in the present invention have almost no effect on the performance of the additive.

[0034] As a preferred embodiment, the mass ratio of expanded graphite: the polymer monomer: the inhibitor: the base oil: the initiator: the oily dispersant: the antioxidant is 1: (10-100): (0.01-0.1): (10-100): (0.05-0.5): (2-20): (1-10).

[0035] As one of the objects of the invention, the present invention also provides a graphene oily slurry obtained by the above-mentioned preparation method, which can be directly applied to lubricating oil as an additive.

[0036] As one of the objects of the invention, the present invention further provides a lubricating oil, comprising at least the graphene oily slurry provided by the above technical solution.

[0037] Polymer monomers (such as methacrylates, styrene, and N-substituted acrylamide) also have good compatibility with graphene, and graphene oily slurry with similar properties to the graphene NMP slurry in the prior art can be obtained; among them, PMA (polymethacrylate) obtained by polymerization of methacrylate monomers is a commonly used additive in lubricating oils, and methacrylate monomers can be miscible with most base oils. Therefore, graphene slurry is prepared using polymer monomers such as methacrylate as a solvent, and then dispersed into base oil, an initiator is added, methacrylate monomers are polymerized in situ to obtain PMA, and other lubricating oil additives are added to obtain graphene oily slurry, which can be directly used as a lubricating oil additive, thereby replacing graphene NMP slurry, solving the defect that graphene NMP slurry in the prior art cannot be directly used as a lubricating oil additive.

[0038] Beneficial technical effects obtained by the present invention:

[0039] 1. The technical solution of the present invention is to prepare a graphene polymer monomer slurry with a polymer monomer as a solvent, and then remove the polymer monomer components that cannot be added to the lubricating oil by an in-situ polymerization method, so as to prepare a graphene oily slurry that can be directly used as a lubricating oil additive.

[0040] 2. The technical solution of the present invention disperses graphene in shear-resistant polymer monomers to withstand the severe shearing effect in the graphene preparation process, and then polymerizes the polymer monomers to form a polymer to prepare a graphene oily slurry, thereby avoiding the severe shearing effect in the graphene preparation process to damage the polymer, base oil and other components in the graphene oily slurry, thereby affecting the performance of the lubricating oil.

[0041] 3. The technical solution of the present invention adopts a polymer monomer with good compatibility with graphene as a solvent, so that the graphene is well dispersed in the polymer monomer slurry, and then polymer-wrapped graphene is formed by an in-situ polymerization method to obtain a graphene oily slurry. While maintaining the good dispersibility of graphene in the graphene polymer monomer slurry, the dispersion stability of the graphene oily slurry in the lubricating oil is further improved.

[0042] 4. The graphene oily slurry provided by the technical solution of the present invention can be directly used as a lubricant additive. Through a simple dispersion operation, it can be evenly mixed with the base oil or the finished lubricant to achieve stable dispersion of graphene in the base oil or the finished lubricant, so that traditional lubricant blending plants can use existing equipment to produce graphene lubricants, and product upgrades can be achieved without equipment modification. DETAILED DESCRIPTION

[0043] 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 embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0044] The technical solution of the present invention is described in detail below through specific embodiments.

[0045] Example 1

[0046] This embodiment provides a graphene oily slurry, and the specific preparation steps include:

[0047] 1. Preparation of graphene polymer monomer slurry

[0048] 1 part of expanded graphite, 20 parts of ethyl methacrylate and 0.1 part of hydroquinone are added into the kettle of a vacuum disperser with a jacket. Dry air is passed through the kettle and 5°C cooling water is passed through the jacket. The disperser speed is 2000rpm. The mixture is circulated through an emulsifier pump connected to the vacuum disperser. The speed of the emulsifier pump is 10000rpm and the processing time is 2h. Finally, a high-pressure homogenizer is used for three cycles to obtain graphene polymer monomer slurry 1#.

[0049] 2. Preparation of graphene oily slurry

[0050] The graphene polymer monomer slurry 1# is returned to the vacuum disperser, and 20 parts of polyα-olefin (PAO-4) are added. Under nitrogen protection, 0.2 parts of benzoyl peroxide are added as an initiator, the stirring speed is 800 rpm, the reaction temperature is 70°C, and the reaction time is 5 hours; then 3 parts of boronated polyisobutylene succinimide and 2 parts of N-octylphenyl-α-naphthylamine are added, the stirring speed is 200 rpm, the treatment temperature is 70°C, and the treatment time is 1 hour to obtain graphene oily slurry 1#.

[0051] Example 2

[0052] This embodiment provides a graphene oily slurry, and the specific preparation steps include:

[0053] 1. Preparation of graphene polymer monomer slurry

[0054] 1 part of expanded graphite, 10 parts of ethyl methacrylate, 10 parts of styrene, and 0.1 part of p-benzoquinone are added to the kettle of a vacuum disperser with a jacket. Dry air is passed through the kettle, and 5°C cooling water is passed through the jacket. The disperser speed is 2000rpm, and the emulsification pump connected to the vacuum disperser is used for circulation treatment. The emulsification pump speed is 10000rpm, and the treatment time is 2h. Finally, a high-pressure homogenizer is used for three cycles to obtain graphene polymer monomer slurry 2#.

[0055] 2. Preparation of graphene oily slurry

[0056] Graphene polymer monomer slurry 2# is returned to the kettle of the vacuum disperser, 20 parts of PAO-4 are added, and under nitrogen protection, 0.2 parts of benzoyl peroxide is added as an initiator, the stirring speed is 800 rpm, the reaction temperature is 70°C, and the reaction time is 5 hours; then 3 parts of polyisobutylene succinimide and 2 parts of butyl diphenylamine are added, the stirring speed is 200 rpm, the treatment temperature is 70°C, and the treatment time is 1 hour to obtain graphene oily slurry 2#.

[0057] Example 3

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

[0059] 1. Preparation of graphene polymer monomer slurry

[0060] 1 part of expanded graphite, 15 parts of ethyl methacrylate, 5 parts of N,N-dimethylacrylamide, and 0.1 part of hydroquinone monomethyl ether are added to the kettle of a vacuum disperser with a jacket. Dry air is passed through the kettle, and 5°C cooling water is passed through the jacket. The disperser speed is 2000rpm, and the emulsification pump connected to the vacuum disperser is used for circulation treatment. The emulsification pump speed is 10000rpm, and the treatment time is 2h. Finally, a high-pressure homogenizer is used for three cycles to obtain graphene polymer monomer slurry 3#.

[0061] 2. Preparation of graphene oily slurry

[0062] The graphene polymer monomer slurry 3# is returned to the kettle of the vacuum disperser, 20 parts of PAO-4 are added, and under nitrogen protection, 0.2 parts of benzoyl peroxide are added as an initiator, the stirring speed is 800 rpm, the reaction temperature is 70°C, and the reaction time is 5 hours; then 3 parts of isopropyl titanate and 2 parts of octyl diphenylamine are added, the stirring speed is 200 rpm, the treatment temperature is 70°C, and the treatment time is 1 hour to obtain graphene oily slurry 3#.

[0063] Comparative Example 1

[0064] This comparative example provides a graphene NMP slurry, and the specific preparation steps include:

[0065] 1 part of expanded graphite and 20 parts of NMP were added to the kettle of a vacuum disperser with a jacket. Dry air was passed through the kettle and 5°C cooling water was passed through the jacket. The disperser speed was 2000rpm. The emulsification pump connected to the vacuum disperser was circulated at a speed of 10000rpm for 2h. Finally, a high-pressure homogenizer was used for 3 cycles to obtain graphene NMP slurry.

[0066] Comparative Example 2

[0067] This comparative example provides a graphene oily slurry, which directly disperses graphene, polymethacrylate (PMA) and other components into a base oil. The specific preparation steps include:

[0068] 1 part of graphene powder (the graphene powder is obtained by drying graphene polymer monomer slurry 1#), 20 parts of PMA, 20 parts of PAO-4, 3 parts of boronated polyisobutylene succinimide, and 2 parts of N-octylphenyl-α-naphthylamine are added to the kettle of a jacketed vacuum disperser at a disperser speed of 800 rpm, a processing temperature of 70°C, and a processing time of 6 hours to obtain graphene oily slurry 4#.

[0069] Comparative Example 3

[0070] This comparative example provides a graphene oily slurry, which directly disperses expanded graphite, polymethacrylate (PMA) and other components into base oil, and converts the expanded graphite into graphene. The specific preparation steps include:

[0071] 1 part of expanded graphite, 20 parts of PMA, 20 parts of PAO-4, 3 parts of boronated polyisobutylene succinimide, and 2 parts of N-octylphenyl-α-naphthylamine are added to the kettle of a vacuum disperser with a jacket. Dry air is passed through the kettle, and 5°C cooling water is passed through the jacket. The disperser speed is 2000rpm, and the emulsifier pump connected to the vacuum disperser is used for circulation treatment. The emulsifier pump speed is 10000rpm, and the treatment time is 2h. Finally, a high-pressure homogenizer is used for three cycles to obtain graphene oily slurry 5#.

[0072] Comparative Example 4

[0073] This comparative example provides a graphene oily slurry, in which graphene, polymethacrylate (PMA) and other components are directly dispersed in a base oil, and the graphene is fully dispersed by a shearing operation. The specific preparation steps include:

[0074] 1 part of graphene powder (the graphene powder is obtained by drying graphene polymer monomer slurry 1#), 20 parts of PMA, 20 parts of PAO-4, 3 parts of boronated polyisobutylene succinimide, and 2 parts of N-octylphenyl-α-naphthylamine are added to the kettle of a vacuum disperser with a jacket, the kettle is passed through dry air, 5°C cooling water is passed through the jacket, the disperser speed is 2000rpm, and the emulsifier pump connected to the vacuum disperser is used for circulation treatment, the emulsifier pump speed is 10000rpm, and the treatment time is 2h; finally, a high-pressure homogenizer is used for three cycles to obtain graphene oily slurry 6#.

[0075] Comparative Example 5

[0076] This comparative example provides a graphene oily slurry, and the specific preparation steps include:

[0077] 1 part of graphene powder (the graphene powder is obtained by drying graphene polymer monomer slurry 1#), 20 parts of ethyl methacrylate, and 20 parts of PAO-4 are added to the kettle of a jacketed vacuum disperser. Under nitrogen protection, 0.2 parts of benzoyl peroxide are added as an initiator. The disperser speed is 800 rpm, the reaction temperature is 70°C, and the reaction time is 5 hours. Then, 3 parts of boronated polyisobutylene succinimide and 2 parts of N-octylphenyl-α-naphthylamine are added. 5°C cooling water is passed through the jacket. The disperser speed is 2000 rpm, and the emulsification pump connected to the vacuum disperser is used for circulation treatment. The emulsification pump speed is 10000 rpm and the treatment time is 2 hours. Finally, a high-pressure homogenizer is used for three cycles to obtain graphene oily slurry 7#.

[0078] Performance Test:

[0079] Fineness scraper test:

[0080] The fineness of the graphene polymer monomer slurry 1# to graphene polymer monomer slurry 3#, graphene oily slurry 1# to graphene polymer monomer slurry 3# of the embodiment and the graphene NMP slurry and graphene oily slurry 4# to graphene oily slurry 6# of comparative example 1 were tested using a scraper fineness meter. The test results are shown in Table 1.

[0081] From the results in Table 1, it can be seen that the fineness of graphene NMP slurry and graphene polymer monomer slurry 1# to graphene polymer monomer slurry 3# are similar. This shows that graphene has good compatibility with some polymer monomers, and the polymer monomers used in Examples 1 to 3 can be used as carriers for preparing graphene by physical methods.

[0082] After in-situ polymerization, the fineness of graphene polymer monomer slurry 1# to graphene polymer monomer slurry 3# did not change significantly compared with before and after polymerization, indicating that the dispersion state of the graphene slurry was not destroyed.

[0083] Graphene oily slurry 4# (Comparative Example 2) Compared with graphene oily slurry 1# (Example 1), graphene oily slurry 4# directly disperses graphene powder into base oil to prepare oily slurry. Since graphene undergoes soft agglomeration during the pulverization process, it is not easy to disperse, resulting in a larger fineness of the slurry.

[0084] Graphene oily slurry 5# (Comparative Example 3) uses expanded graphite as raw material, and directly prepares graphene in base oil to obtain graphene oily slurry. Since the viscosity of the polymer (PMA) is much higher than that of the polymer monomer, and the molecular weight of the polymer is originally greater than that of the polymer monomer, the expanded graphite cannot be fully sheared, and the exfoliation efficiency of the expanded graphite is greatly reduced, resulting in a significantly larger fineness of the slurry.

[0085] Graphene oily slurry 1# (Example 1) and graphene oily slurry 6# (Comparative Example 4) are prepared by directly dispersing graphene powder into base oil. Through strong shearing action, the soft agglomerates of graphene powder can be opened and fully dispersed, and the fineness of the slurry is not much different.

[0086] Table 1 Comparison of fineness test results

[0087] sample Fineness(μm) Example 1 Graphene polymer monomer slurry 1# 15 Example 2 Graphene polymer monomer slurry 2# 16 Example 3 Graphene polymer monomer slurry 3# 16 Comparative Example 1 Graphene NMP slurry 14 Example 1 Graphene oily slurry 1# 16 Example 2 Graphene oily slurry 2# 17 Example 3 Graphene oily slurry 3# 15 Comparative Example 2 Graphene oily slurry 4# 30 Comparative Example 3 Graphene oily slurry 5# 50 Comparative Example 4 Graphene oily slurry 6# 17

[0088] Particle size and specific surface area test:

[0089] Graphene polymer monomer slurry 1# (Example 1), graphene NMP slurry (Comparative Example 1), and graphene oily slurry 5# (Comparative Example 3) are dried or washed and then dried to obtain graphene powder, and the specific surface area is tested. The graphene powder is dispersed in NMP to test the particle size. The particle size is obtained by using a laser particle size analyzer, and the specific surface area is obtained by using the BET method. The test results are shown in Table 2.

[0090] Table 2 Comparison of particle size and specific surface area test results

[0091] sample D50 / μm <![CDATA[Specific surface area / m 2 / g]]> Example 1 Graphene polymer monomer slurry 1# 10.5 55.7 Comparative Example 1 Graphene NMP slurry 9.3 64.2 Comparative Example 3 Graphene oily slurry 5# 24.6 31.7

[0092] As can be seen from Table 2, the graphene polymer monomer slurry 1# provided in Example 1 has a similar particle size and specific surface area as the graphene NMP slurry provided in Comparative Example 1, indicating that graphene has good compatibility with some polymer monomers, and these polymer monomers can be used as carriers for preparing graphene by physical methods.

[0093] Compared with the graphene polymer monomer slurry 1# provided in Example 1, the graphene oily slurry 5# provided in Comparative Example 3 has a larger particle size and a smaller specific surface area, indicating that when graphene is prepared directly in the base oil using expanded graphite to obtain the graphene oily slurry, the viscosity of the carrier is much higher than that of the polymer monomer and the molecular weight of the component is large, so that the expanded graphite cannot receive sufficient shearing action, and the exfoliation efficiency of the expanded graphite is greatly reduced.

[0094] Kinematic viscosity test:

[0095] Graphene oily slurry 1# (Example 1), graphene oily slurry 4# (Comparative Example 2), graphene oily slurry 6# (Comparative Example 4), and graphene oily slurry 7# (Comparative Example 5) were tested for kinematic viscosity at 100°C according to standard GB / T 265. The test results are shown in Table 3.

[0096] Table 3 Comparison of kinematic viscosity test results at 100°C

[0097]

[0098] Referring to Table 3, by comparing the 100°C kinematic viscosities of graphene oily slurry 1# (Example 1) and graphene oily slurry 4# (Comparative Example 2), it can be seen that due to the addition of polymer PMA, the viscosity of graphene oily slurry 4# increases, but due to the soft agglomeration effect, the dispersion effect of graphene directly dispersed in the base oil is poor.

[0099] By comparing the kinematic viscosity of graphene oily slurry 1# (Example 1), graphene oily slurry 6# (Comparative Example 4) and graphene oily slurry 7# (Comparative Example 5) at 100°C, it can be seen that under the premise of similar components, the difference is that the viscosity of graphene oily slurry 6# and graphene oily slurry 7# is significantly reduced under different shear conditions, indicating that after severe shearing, although the graphene powder can be fully dispersed, the structure of the base oil and the polymer is destroyed, resulting in a decrease in viscosity, which will affect the performance of the lubricating oil. In the prior art, if graphene powder is used to produce graphene lubricating oil, traditional lubricating oil blending equipment cannot achieve full dispersion of graphene, and it is necessary to increase shearing equipment. Although the shearing equipment can achieve full dispersion of graphene, it will damage the quality of the oil. Therefore, the technical solution of the present invention is adopted, and the full dispersion of graphene can be achieved by directly adopting a simple stirring method, avoiding the damage of the structure of the base oil and the polymer by the shearing action.

[0100] Dispersion stability test:

[0101] 1. Take graphene NMP slurry, graphene polymer monomer slurry 1# and graphene oily slurry 1#, place them for 7 days, and record the dispersion conditions every day. The test results are shown in Table 4.

[0102] Table 4 Dispersion stability test results

[0103]

[0104] It can be seen from Table 4 that although ethyl methacrylate has good compatibility with graphene, the stability of graphene polymer monomer slurry 1# is still poorer than that of graphene NMP slurry, while graphene oily slurry 1# also has good stability, indicating that the stability of the slurry is improved after ethyl methacrylate is polymerized into PMA through in-situ polymerization.

[0105] 2. Graphene oily slurry 1# (Example 1), graphene oily slurry 4# (Comparative Example 2) and graphene oily slurry 6# (Comparative Example 4) were added to the finished lubricating oil GL-585W-140 at a weight ratio of 100 ppm of modified graphene, and simply dispersed by manual stirring.

[0106] Centrifuge at a centrifugal force of 1440g (1440 times the acceleration of gravity) for 30 minutes (equivalent to natural sedimentation for about one month), pause for 30 minutes, and then centrifuge for 30 minutes, repeat this process for a total of 3 hours. See Table 5 for the test results.

[0107] Table 5 Dispersion stability test results

[0108]

[0109]

[0110] As can be seen from Table 5, graphene oily slurry 1# can maintain good dispersion stability of graphene in lubricating oil through simple dispersion operation, indicating that graphene oily slurry 1# can be directly used as a lubricating oil additive.

[0111] The graphene oily slurry 6# can maintain good dispersion stability of graphene in lubricating oil through simple dispersion operation, which means that the soft agglomerates of graphene powder can be opened and fully dispersed through strong shearing action.

[0112] The dispersion stability of graphene oily slurry 1# is better than that of graphene oily slurry 6#, indicating that the polymer-wrapped graphene structure obtained by in-situ polymerization can improve the dispersion stability of graphene in lubricating oil.

[0113] However, the dispersion stability of graphene oily slurry 4# in lubricating oil is poor, which means that the graphene powder is directly dispersed in the base oil to prepare the oily slurry without undergoing strong shearing action. Due to the existence of soft agglomerates of graphene powder, under conventional equipment conditions, graphene cannot be fully dispersed in the lubricating oil.

[0114] Friction performance test

[0115] Graphene oily slurry 1# (Example 1), graphene oily slurry 4# (Comparative Example 2) and graphene oily slurry 6# (Comparative Example 4) were used as additives and added into the finished lubricant oil Morun SP / 0W-40 at a graphene weight ratio of 10 ppm to test the friction and wear properties of the lubricant, including the friction coefficient and the wear spot diameter.

[0116] The oil samples and finished lubricants after graphene oily slurry 1#, graphene oily slurry 4#, graphene oily slurry 6# were compounded with finished lubricants and the finished lubricants 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, speed 1200r / min, oil temperature 75℃, long grinding 60min, 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. The results are shown in Table 6.

[0117] Table 6 Friction coefficient and wear spot diameter test results

[0118] sample Friction coefficient Wear spot diameter (mm) Finished lubricants 0.1145 0.43 Graphene oily slurry 1# 0.0778 0.36 Graphene oily slurry 4# 0.1287 0.47 Graphene oily slurry 6# 0.0781 0.37

[0119] It can be seen from Table 6 that when graphene oily slurry 1# and graphene oily slurry 6# are used as lubricating oil additives, the anti-wear and friction reducing properties of the lubricating oil can be significantly improved, while when graphene oily slurry 4# is used as a lubricating oil additive, the anti-wear and friction reducing properties of the lubricating oil decrease. This shows that graphene can only play a role in improving the anti-wear and friction reducing properties if it is fully dispersed, but if it is not fully dispersed, it will have a counterproductive effect.

[0120] 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 method comprises using a polymer monomer having good compatibility with graphene as a solvent, dispersing graphene in the polymer monomer; and then performing a polymerization reaction by combining an in-situ polymerization method to obtain a graphene oily slurry, namely the graphene oily slurry.

2. The method for preparing the graphene oily slurry according to claim 1, characterized in that: The following steps are involved: S1. Providing a graphene polymer monomer slurry; Adding expanded graphite and a polymerization inhibitor to the polymer monomer, and preparing graphene by high-pressure homogenization, wherein the graphene is evenly dispersed in the polymer monomer to form the graphene polymer monomer slurry; S2. Providing a graphene polymer slurry; Add base oil to the graphene polymer monomer slurry provided by S1, mix evenly, add initiator under a protective gas atmosphere, stir to carry out in-situ polymerization reaction, and the polymer obtained by the reaction is wrapped on the surface of the graphene and evenly dispersed in the base oil; S3. Providing graphene oily slurry; An oily dispersant and an antioxidant are added to the graphene polymer slurry provided by S2, and the mixture is evenly mixed to make the graphene in a uniformly dispersed state, thereby obtaining the graphene oily slurry.

3. The method for preparing the graphene oily slurry according to claim 2, characterized in that: In S1, the polymer monomer includes any one or more combinations of styrene, acrylate compounds, and acrylamide compounds; The polymerization inhibitor includes any one of hydroquinone monomethyl ether, hydroquinone, p-benzoquinone, methyl hydroquinone, p-hydroxyanisole, 2-tert-butylhydroquinone, and 2,5-di-tert-butylhydroquinone; The acrylic acid ester compound is a methacrylic acid ester compound.

4. The method for preparing the graphene oily slurry according to claim 3, characterized in that: The acrylamide compounds include any one of alkyl-substituted acrylamide, alkyl-substituted methacrylamide, 4-acryloylmorpholine, 3-acryloyl-2-oxazolone, N-benzyl acrylamide, N-phenyl acrylamide, N-phenyl methacrylamide, N-benzyl methacrylamide, N,N-dibenzyl acrylamide, and N-benzyl-N-methyl acrylamide, or a combination of two or more thereof.

5. The method for preparing the graphene oily slurry according to any one of claims 2 to 4, characterized in that: The preparation method of the graphene polymer monomer slurry comprises: adding at least expanded graphite, the polymer monomer and the polymerization inhibitor into a vacuum disperser, dispersing at a speed of 2000-3000 rpm and a temperature of 0-20° C. in a dry air atmosphere for 2-4 hours; then circulating the mixture at 8000-14000 rpm using an emulsifying pump, and finally circulating the mixture 2-4 times through a high-pressure homogenizer, so that the prepared graphene is uniformly and stably dispersed in the polymer monomer to form the graphene polymer monomer slurry.

6. The method for preparing graphene oily slurry according to claim 2, characterized in that: In S2, the base oil includes Group II base oil, Group III base oil, and synthetic base oil; preferably, the synthetic base oil is polyalphaolefin or alkyl naphthalene base oil; The protective gas is nitrogen or an inert gas; The initiator is azobisisobutyronitrile or benzoyl peroxide; The stirring speed is 500-1000 rpm; The reaction temperature of the in-situ polymerization reaction is 60-80° C., and the reaction time is 4-6 hours.

7. The method for preparing graphene oily slurry according to claim 2, characterized in that: In S3, the dispersion conditions of the graphene polymer slurry include a stirring speed of 200 to 500 rpm, a dispersion time of 1 to 3 hours, and a temperature of 60 to 80° C.; The oily dispersant is at least one of polyisobutylene succinimide, boronated polyisobutylene succinimide, isopropyl titanate, sorbitan oleate, polyether, stearic acid, oleic acid, tallow amine, and tallow amine polyoxyethylene ether; The antioxidant is any one of butyl diphenylamine, octyl diphenylamine, nonyl diphenylamine, and N-octylphenyl-α-naphthylamine, or a combination of several of them.

8. The method for preparing the graphene oily slurry according to any one of claims 2-4, 6-7, characterized in that: The mass ratio of expanded graphite: the polymer monomer: the inhibitor: the base oil: the initiator: the oily dispersant: the antioxidant is 1: (10-100): (0.01-0.1): (10-100): (0.05-0.5): (2-20): (1-10).

9. A graphene oily slurry obtained by the preparation method according to any one of claims 1 to 8; the graphene oily slurry can be directly applied to lubricating oil as an additive.

10. A lubricating oil, characterized in that: At least comprising the graphene oily slurry as claimed in claim 9.

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