Graphene oil slurry and preparation method and application thereof

Abstract

The application discloses a kind of graphene oily slurry and its preparation method and application, it is related to lubricating oil additive technical field.The preparation method of the graphene oily slurry includes first with the polymer monomer of good compatibility with graphene as solvent, graphene is dispersed in the polymer monomer solvent, and a well-dispersed graphene polymer monomer slurry is prepared, then in-situ polymerization is combined to obtain graphene oily slurry after polymerization reaction.The technical scheme of the application, the polymer generated by in-situ polymerization is coated on the surface of graphene, so as to improve the dispersion stability of graphene, and the graphene oily slurry prepared can be uniformly dispersed in lubricating oil by simple mixing, and the components in the graphene oily slurry are all commonly used components in lubricating oil, which can be directly used as a lubricating oil additive, and the graphene lubricating oil can be prepared using conventional equipment without improving the equipment, reducing the production cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lubricating oil additives, and particularly relates to a graphene oil slurry and a preparation method and application thereof. BACKGROUND

[0002] With the economic development and the improvement of living standards, the number of fuel vehicles in China ranks in the forefront of the world. In the operation process of automobile internal combustion engine, due to the existence of friction and wear, part of the energy of fuel is inevitably lost. Lubricating oil can effectively reduce the friction and wear between mechanical parts, and is one of the key factors affecting the mechanical efficiency and reliability of engine. At the same time, based on the requirement of environmental protection, higher requirements are put forward for the fuel vehicle engine in terms of high efficiency, energy saving, near zero emission and low fuel consumption, and therefore the quality of lubricating oil is also required. Lubricating oil is generally composed of base oil and additives, and the addition of additives can improve or add some functions, thereby greatly improving the quality of lubricating oil.

[0003] Nanomaterials have completely different optical, electrical, thermal, chemical or mechanical properties from conventional materials. Nanoparticles of suitable size can be used as lubricating oil additives, and show better anti-wear and friction-reducing performance 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 sensitivity, low shear strength, strong surface adhesion and layered structure, and therefore graphene has great application prospect in the field of lubricating oil 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, and the graphene powder has a soft agglomeration phenomenon, so that it cannot be well dispersed 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 difficulty; at the same time, the dispersion process of graphene powder is inevitably accompanied by severe shearing action, which destroys the structure of macromolecular components such as base oil and tackifier in lubricating oil, resulting in the performance of lubricating oil being reduced, such as viscosity reduction, oxidation stability reduction, service life reduction, etc. In addition, there is dust pollution in the process of adding powder.

[0005] To solve the above problems, by preparing a graphene slurry method, the graphene is in a good dispersion state, adding lubricating oil, through simple dispersion, can be uniformly mixed, and keep the good dispersion state of graphene, to solve the problem of graphene powder adding difficulty, not easy to disperse and oil performance decline in the production process of graphene lubricating oil. The graphene slurry of the prior art is usually aqueous slurry or oily slurry, wherein the oily slurry uses NMP (N-methyl pyrrolidone), DMF (N, N-dimethylformamide), ethyl acetate and other organic solvents with good compatibility with graphene as medium, and the NMP slurry is the most common. However, the existing lubricating oil standards, such as API (American Petroleum Institute) standard, the water content of automobile engine oil should be less than 0.2%, and the water content of industrial lubricating oil should be less than 0.05% according to ISO6743 / 18 standard, therefore, the application of aqueous graphene slurry in lubricating oil will cause the water content to exceed the standard, in addition, the aqueous graphene slurry usually contains dispersants, and these dispersants are generally water-soluble and not suitable for use in lubricating oil; and for NMP slurry, NMP is also not an allowed component in lubricating oil, the addition of NMP will cause the performance of lubricating oil to decrease, such as viscosity, flash point, rubber compatibility and the like. Therefore, the application of the graphene slurry in the prior art in lubricating oil is limited.

[0006] Therefore, the present application provides a graphene oily slurry based on dispersing graphene with a polymer monomer having good compatibility with graphene as a solvent, and then removing the polymer monomer after in-situ polymerization to obtain the graphene oily slurry, which avoids introducing components that cannot be added in lubricating oil and can be directly used as an additive of lubricating oil, thereby solving the problems existing in the prior art. SUMMARY

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

[0008] As one of the purposes of the application, the present application provides a preparation method of a graphene oily slurry, which comprises dispersing graphene in a solvent with a polymer monomer having good compatibility with graphene as a solvent; and then obtaining a graphene oily slurry after in-situ polymerization to obtain the graphene oily slurry.

[0009] Specifically, the preparation method of 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 a polymerization inhibitor is added, and the expanded graphite is prepared into graphene by high-pressure homogenization in the solvent, and the graphene is uniformly dispersed in the solvent to form the graphene polymer monomer slurry; the conditions in the process of preparing the graphene are relatively severe, and if the polymer monomer is not controlled without adding the polymerization inhibitor, the polymer monomer is prone to self-polymerization, which can increase the viscosity of the slurry, and in a serious case, the slurry is directly solidified by explosive polymerization, and the graphene polymer monomer slurry cannot be obtained.

[0012] S2. providing the graphene polymer slurry;

[0013] The base oil is added to the graphene polymer monomer slurry provided by S1, and is uniformly mixed, and the initiator is added under the atmosphere of a protective gas, and the in-situ polymerization reaction is carried out by stirring, and the polymer obtained by the reaction is wrapped on the surface of the graphene and is uniformly dispersed in the base oil.

[0014] S3. providing the graphene oil slurry;

[0015] The oil dispersant and the antioxidant are added to the graphene polymer slurry provided by S2, and are uniformly dispersed to obtain the graphene oil slurry.

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

[0017] The graphene polymer monomer slurry is prepared first in the present application because the molecular structure of the polymer monomer is simple, and the graphene is hardly affected by the shearing action in the dispersion process, and then the monomer is removed by the in-situ polymerization method, so that the influence of the shearing action on the structure of the macromolecular components such as the polymer, the base oil and the tackifier in the graphene oil slurry is avoided.

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

[0019] More preferably, the acrylamide compound includes but is not limited to any one of N-alkyl-substituted acrylamide, N-alkyl-substituted methacrylamide, 4-acryloyl morpholine, 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 embodiments, the polymerization inhibitor includes, but is not limited to, any one of hydroquinone monomethyl ether (MEHQ), hydroquinone (HQ), p-benzoquinone (PBQ), methylhydroquinone (THQ), p-hydroxyanisole (HQMME), 2-tert-butylhydroquinone (MTBHQ), 2,5-di-tert-butylhydroquinone (2,5-DTBHQ), and the like.

[0021] As a preferred embodiment, the preparation method of the graphene polymer monomer slurry comprises: at least adding expanded graphite, the polymer monomer, and the polymerization inhibitor into a vacuum dispersion machine, dispersing under the condition of a dry air atmosphere, a rotation speed of 2000-3000 rpm, and a temperature of 0-20℃, and a dispersion time of 2-4 h; then circulating at 8000-14000 rpm using an emulsifying pump, and finally circulating 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; in the preparation process, the expanded graphite is physically exfoliated to form graphene, and the 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 or a combination of two or more of Group II base oil, Group III base oil, and synthetic base oil.

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

[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℃, and the reaction time is 4-6 h.

[0031] Preferably, in S3, the dispersion condition of the graphene polymer slurry includes a stirring speed of 200-500 rpm, a dispersion time of 1-3 h, and a temperature of 60-80℃.

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

[0033] Preferably, the antioxidant is any one or a combination of butyldiphenylamine, octyldiphenylamine, nonyldiphenylamine, N-octylphenyl-alpha-naphthylamine. The antioxidant not only can capture free radicals to play a role in terminating in-situ polymerization, but also can 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 application have little effect on the performance of the additive.

[0034] As a preferred embodiment, the mass ratio of the expanded graphite: the polymer monomer: the polymerization 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 purposes of the application, the present application also provides a graphene oily slurry obtained by the above preparation method, which can be directly applied as an additive in lubricating oil.

[0036] As one of the purposes of the application, the present application also provides a lubricating oil comprising at least the graphene oily slurry provided in the above technical solution.

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

[0038] The present application has the following beneficial technical effects:

[0039] 1. The technical scheme of the present application prepares a graphene polymer monomer slurry with polymer monomer as solvent first, and then removes the polymer monomer component that cannot be added in lubricating oil by in-situ polymerization method, to realize the preparation of graphene oil slurry that can be directly used as lubricating oil additive.

[0040] 2. The technical scheme of the present application disperses graphene in shear-resistant polymer monomer to withstand the severe shearing action in the preparation of graphene, and then polymerizes the polymer monomer to form a polymer, to obtain graphene oil slurry, which avoids the damage of the severe shearing action in the preparation of graphene to the components such as polymer and base oil in the graphene oil slurry, and further affects the performance of lubricating oil.

[0041] 3. The technical scheme of the present application uses polymer monomer with good compatibility with graphene as solvent, so that graphene is well dispersed in the polymer monomer slurry, and then forms graphene wrapped by polymer through in-situ polymerization method to obtain graphene oil slurry, which further improves the dispersion stability of graphene oil slurry in lubricating oil while maintaining the good dispersion of graphene in graphene polymer monomer slurry.

[0042] 4. The graphene oil slurry provided by the technical scheme of the present application can be directly used as lubricating oil additive, and can be uniformly mixed with base oil or finished lubricating oil through simple dispersion operation, to realize the stable dispersion of graphene in base oil or finished lubricating oil, so that the traditional lubricating oil blending plant can produce graphene lubricating oil using existing equipment, and product upgrading can be realized without equipment modification. DETAILED DESCRIPTION

[0043] To make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all the embodiments.

[0044] The technical scheme of the present application will be described in detail below through specific embodiments.

[0045] Embodiment 1

[0046] The present embodiment provides a graphene oil 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, 0.1 part of hydroquinone were added into the kettle body of a jacketed vacuum disperser, dry air was passed through the kettle body, 5℃ cooling water was passed through the jacket, the disperser rotated at 2000 rpm, and circulation treatment was performed through an emulsifying pump connected with the vacuum disperser, the emulsifying pump rotated at 10000 rpm, and the treatment time was 2 h; finally, circulation was performed 3 times using a high-pressure homogenizer to obtain graphene polymer monomer slurry 1#.

[0049] 2. Preparation of graphene oily slurry

[0050] The graphene polymer monomer slurry 1# was returned to the kettle body of the vacuum disperser, 20 parts of poly-alpha-olefin (PAO-4) was added, 0.2 parts of benzoyl peroxide was added as an initiator under nitrogen protection, the stirring speed was 800 rpm, the reaction temperature was 70℃, and the reaction time was 5 h; then 3 parts of polyisobutylene succinimide and 2 parts of N-octylphenyl-alpha-nitrile were added, the stirring speed was 200 rpm, the treatment temperature was 70℃, and the treatment time was 1 h to obtain graphene oily slurry 1#.

[0051] Example 2

[0052] The embodiment provides a kind of graphene oily slurry, and 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, 0.1 part of p-benzoquinone were added into the kettle body of a jacketed vacuum disperser, dry air was passed through the kettle body, 5℃ cooling water was passed through the jacket, the disperser rotated at 2000 rpm, and circulation treatment was performed through an emulsifying pump connected with the vacuum disperser, the emulsifying pump rotated at 10000 rpm, and the treatment time was 2 h; finally, circulation was performed 3 times using a high-pressure homogenizer to obtain graphene polymer monomer slurry 2#.

[0055] 2. Preparation of graphene oily slurry

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

[0057] Example 3

[0058] The embodiment provides a kind of graphene oily slurry, and 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- dimethyl acrylamide, 0.1 part of hydroquinone monomethyl ether were added into the kettle body of a jacketed vacuum dispersion machine, dry air was passed through the kettle body, 5℃ cooling water was passed through the jacket, the rotation speed of the dispersion machine was 2000 rpm, and the circulation treatment was carried out through the emulsifying pump connected with the vacuum dispersion machine, the rotation speed of the emulsifying pump was 10000 rpm, and the treatment time was 2h; finally, the high-pressure homogenizer was circulated for 3 times to obtain graphene polymer monomer slurry 3#.

[0061] 2. Preparation of graphene oil slurry

[0062] The graphene polymer monomer slurry 3# was returned to the kettle body of the vacuum dispersion machine, 20 parts of PAO-4 were added, 0.2 parts of benzoyl peroxide were added as an initiator under the condition of nitrogen protection, the stirring speed was 800 rpm, the reaction temperature was 70℃, and the reaction time was 5h; then 3 parts of isopropyl titanate and 2 parts of octyl diphenylamine were added, the stirring speed was 200 rpm, the treatment temperature was 70℃, and the treatment time was 1h to obtain graphene oil 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 into the kettle body of a jacketed vacuum dispersion machine, dry air was passed through the kettle body, 5℃ cooling water was passed through the jacket, the rotation speed of the dispersion machine was 2000 rpm, and the circulation treatment was carried out through the emulsifying pump connected with the vacuum dispersion machine, the rotation speed of the emulsifying pump was 10000 rpm, and the treatment time was 2h; finally, the high-pressure homogenizer was circulated for 3 times to obtain graphene NMP slurry.

[0066] Comparative Example 2

[0067] This comparative example provides a graphene oil slurry, and the graphene, polymethacrylate (PMA) and other components are directly dispersed into base oil, and the specific preparation steps include:

[0068] 1 part of graphene powder (obtained by drying graphene polymer monomer slurry 1#), 20 parts of PMA, 20 parts of PAO-4, 3 parts of boronized polyisobutylene succinimide, and 2 parts of N-octyl phenyl-α-nitrile were added into the kettle body of a jacketed vacuum dispersion machine, the rotation speed of the dispersion machine was 800 rpm, the treatment temperature was 70℃, and the treatment time was 6h to obtain graphene oil slurry 4#.

[0069] Comparative Example 3

[0070] The comparative example provides a graphene oily slurry, and expanded graphite, polymethacrylate (PMA) and other components are directly dispersed into base oil to convert 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 boronized polyisobutylene succinimide and 2 parts of N-octylphenyl-alpha-nitrile are added into a kettle of a jacketed vacuum disperser, dry air is passed through the kettle, 5°C cooling water is passed through the jacket, the disperser rotates at 2000 rpm, and circulation treatment is performed through an emulsifying pump connected with the vacuum disperser, the emulsifying pump rotates at 10000 rpm, and the treatment time is 2 h; finally, a high-pressure homogenizer is used for circulation for 3 times to obtain graphene oily slurry 5#.

[0072] Comparative example 4

[0073] The comparative example provides a graphene oily slurry, and graphene, polymethacrylate (PMA) and other components are directly dispersed into base oil, and the graphene is fully dispersed through 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 boronized polyisobutylene succinimide and 2 parts of N-octylphenyl-alpha-nitrile are added into a kettle of a jacketed vacuum disperser, dry air is passed through the kettle, 5°C cooling water is passed through the jacket, the disperser rotates at 2000 rpm, and circulation treatment is performed through an emulsifying pump connected with the vacuum disperser, the emulsifying pump rotates at 10000 rpm, and the treatment time is 2 h; finally, a high-pressure homogenizer is used for circulation for 3 times to obtain graphene oily slurry 6#.

[0075] Comparative example 5

[0076] The comparative example provides a graphene oily slurry. 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 PMA, 20 parts of PAO-4, 3 parts of boronized polyisobutylene succinimide and 2 parts of N-octylphenyl-alpha-nitrile are added into a kettle of a jacketed vacuum disperser, dry air is passed through the kettle, 5°C cooling water is passed through the jacket, the disperser rotates at 2000 rpm, and circulation treatment is performed through an emulsifying pump connected with the vacuum disperser, the emulsifying pump rotates at 10000 rpm, and the treatment time is 2 h; finally, a high-pressure homogenizer is used for circulation for 3 times to obtain graphene oily slurry 6#.

[0078] Performance test:

[0079] Fineness doctor blade test:

[0080] The fineness of the graphene polymer monomer slurry 1#-3#, graphene oil slurry 1#-3# and the graphene NMP slurry of the comparative example 1, graphene oil slurry 4#-6# were tested by using the doctor blade fineness meter, and the test results are shown in Table 1.

[0081] As can be seen from the results in Table 1, the fineness of the graphene NMP slurry and the graphene polymer monomer slurry 1#-3# is similar. It shows that the graphene has good compatibility with the partial polymer monomer, and the polymer monomer used in the examples 1-3 can be used as a carrier for preparing graphene by physical method.

[0082] After the graphene polymer monomer slurry 1#-3# is polymerized in situ, the fineness of the slurry has no obvious change before and after polymerization, which shows that the dispersion state of the graphene slurry is not destroyed.

[0083] The graphene oil slurry 4# (comparative example 2) is compared with the graphene oil slurry 1# (example 1). The graphene oil slurry 4# is prepared by directly dispersing the graphene powder into the base oil. The graphene is not easy to disperse because of the soft agglomeration in the powderization process, which leads to the fineness of the slurry being too large.

[0084] The graphene oil slurry 5# (comparative example 3) is prepared by directly dispersing the expanded graphite into the base oil. The viscosity of the polymer (PMA) is much higher than that of the polymer monomer, and the molecular weight of the polymer is much larger than that of the polymer monomer, which makes the expanded graphite not be subjected to sufficient shearing action, and the exfoliation efficiency of the expanded graphite is greatly reduced, which leads to the fineness of the slurry being obviously too large.

[0085] The graphene oil slurry 1# (example 1) and the graphene oil slurry 6# (comparative example 4) are prepared by directly dispersing the graphene powder into the base oil. Through the strong shearing action, the soft agglomeration of the graphene powder can be opened, and the graphene powder is fully dispersed, so that the fineness of the slurry is not much different.

[0086] Table 1 comparison of fineness test results

[0087] Sample Fineness (pm) 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] The graphene polymer monomer slurry 1# (Example 1), the graphene NMP slurry (Comparative Example 1), the graphene oily slurry 5# (Comparative Example 3) were dried or washed and dried to obtain graphene powder, the specific surface area was tested, and the particle size of the graphene powder was tested by dispersing the graphene powder in NMP, the particle size was tested by a laser particle size analyzer, and the specific surface area was tested by a BET method, and the test results are shown in Table 2.

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

[0091] Sample D50 / pm 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 by Example 1 has a particle size and specific surface area close to that of the graphene NMP slurry provided by Comparative Example 1, indicating that the graphene has good compatibility with the polymer monomers, and these polymer monomers can be used as a carrier for physically preparing graphene.

[0093] The graphene oily slurry 5# provided by Comparative Example 3 has a larger particle size and a smaller specific surface area compared to the graphene polymer monomer slurry 1# provided by Example 1, indicating that when graphene is prepared from expanded graphite directly in base oil, the expanded graphite cannot be subjected to sufficient shearing due to the high viscosity of the carrier and the large molecular weight of the components, greatly reducing the efficiency of the expanded graphite exfoliation.

[0094] Kinematic viscosity test:

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

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

[0097]

[0098] As can be seen from Table 3, the kinematic viscosity at 100°C of the graphene oily slurry 1# (Example 1) and the graphene oily slurry 4# (Comparative Example 2) was compared, and it was found that due to the addition of the polymer PMA, the viscosity of the graphene oily slurry 4# increased, but the dispersion effect of the graphene dispersed directly in the base oil was poor due to the soft agglomeration.

[0099] Comparing the kinematic viscosity at 100℃ of graphene oily slurry 1# (Example 1), graphene oily slurry 6# (Comparative Example 4) and graphene oily slurry 7# (Comparative Example 5) can be known that, under the premise of similar components, the difference lies in different shearing conditions, the viscosity of graphene oily slurry 6# and graphene oily slurry 7# is significantly reduced, which shows 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. If graphene powder is used to produce graphene lubricating oil in the prior art, the traditional lubricating oil blending equipment cannot achieve the full dispersion of graphene, and a shearing device needs to be added, but the shearing device can achieve the full dispersion of graphene, but will damage the quality of the oil. Therefore, by adopting the technical scheme of the present application, the full dispersion of graphene can be achieved by directly using simple stirring, which avoids the damage of shearing to the structure of the base oil and the polymer.

[0100] Dispersion stability test:

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

[0102] Table 4 Dispersion stability test results

[0103]

[0104] As can be seen from Table 4, although ethyl methacrylate has good compatibility with graphene, the stability of graphene polymer monomer slurry 1# is still poor compared with graphene NMP slurry, and graphene oily slurry 1# also has good stability, which shows that after in-situ polymerization of ethyl methacrylate into PMA, the stability of the slurry is improved.

[0105] 2. Add graphene oily slurry 1# (Example 1), graphene oily slurry 4# (Comparative Example 2) and graphene oily slurry 6# (Comparative Example 4) to the finished lubricating oil Murunsi GL-585W-140 at a weight ratio of 100 ppm of modified graphene, and perform simple dispersion treatment by manual stirring.

[0106] Centrifugal force 1440g (1440 times gravitational acceleration) centrifugation for 30min (about equal to natural sedimentation for one month), pause for 30min, centrifugation for another 30min, repeat, total centrifugation time is 3h. The test results are shown in Table 5.

[0107] Table 5 Dispersion stability test results

[0108]

[0109]

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

[0111] The graphene oily slurry 6# can keep the graphene in the lubricating oil in good dispersion stability through simple dispersion operation, indicating that the soft agglomeration of the graphene powder can be opened through strong shearing action to obtain sufficient dispersion.

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

[0113] The dispersion stability of the graphene oily slurry 4# in the lubricating oil is poor, indicating that the graphene powder is directly dispersed into the base oil to prepare the oily slurry without strong shearing action, and due to the existence of the soft agglomeration of the graphene powder, the graphene cannot be fully dispersed into the lubricating oil under the conditions of the conventional equipment.

[0114] Friction performance test

[0115] The graphene oily slurry 1# (Example 1), the graphene oily slurry 4# (Comparative Example 2) and the graphene oily slurry 6# (Comparative Example 4) are used as additives, and are added into the finished lubricating oil Murunsi SP / 0W-40 at 10 ppm of graphene by weight, to test the friction and wear performance of the lubricating oil, including the friction coefficient and the wear scar diameter.

[0116] The oil samples and the finished lubricating oil after compounding of the graphene oily slurry 1#, the graphene oily slurry 4# and the graphene oily slurry 6# with the finished lubricating oil are respectively evaluated by a four-ball friction tester to test the friction-reducing and wear-resistant performance (industry standard SH / T 0189-92). The test conditions include GCr15 steel balls, a rotation speed of 1200 r / min, an oil temperature of 75°C, a long grinding of 60 min, and a load of 392 N. The data given by the four-ball friction tester include the wear scar diameter and the friction coefficient, and the smaller the wear scar diameter and the friction coefficient, the better the friction-reducing and wear-resistant performance. The results are shown in Table 6.

[0117] Table 6 Test results of friction coefficient and wear scar diameter

[0118] Sample Coefficient of friction Wear scar diameter (mm) Finished lubricating oil 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] As can be seen from Table 6, the graphene oily slurry 1# and the graphene oily slurry 6# used as lubricating oil additives can obviously improve the anti-wear and friction-reducing performance of the lubricating oil, while the graphene oily slurry 4# used as a lubricating oil additive, the anti-wear and friction-reducing performance of the lubricating oil is decreased, which shows that the graphene can only play a role in improving the anti-wear and friction-reducing performance when it is fully dispersed, and if it is not fully dispersed, it will have the opposite effect.

[0120] The above are only preferred embodiments of the present application, and are not intended to limit the protection scope of the present application. For those skilled in the art, the present application can have various changes and modifications. Any changes, modifications, replacements, integrations and parameter changes made to these embodiments within the spirit and principles of the present application by conventional substitutions or capable of realizing the same functions without departing from the principles and spirit of the present application all fall within the protection scope of the present application.

Claims

1. A method of preparing a graphene oily paste, characterized by, The graphene oil slurry is prepared by dispersing graphene in a polymer monomer which has good compatibility with graphene, and then performing polymerization reaction by in-situ polymerization method to obtain the graphene oil slurry. Specifically, the method comprises the following steps: S1. providing a graphene polymer monomer slurry; at least adding expanded graphite, the polymer monomer and a polymerization inhibitor into a vacuum dispersion machine, and dispersing under the atmosphere of dry air at a rotating speed of 2000-3000 rpm and a temperature of 0-20℃ for 2-4 hours; then circulating at 8000-14000 rpm by using an emulsifying pump, and finally circulating 2-4 times by using a high-pressure homogenizer, so that the graphene is uniformly and stably dispersed in the polymer monomer to form the graphene polymer monomer slurry; S2. providing a graphene polymer slurry; adding base oil into the graphene polymer monomer slurry provided in S1 and mixing uniformly, adding an initiator under the atmosphere of protective gas, and stirring to perform in-situ polymerization reaction, so that the polymer is wrapped on the surface of the graphene and uniformly dispersed in the base oil; S3. providing a graphene oil slurry; adding an oil dispersant and an antioxidant into the graphene polymer slurry provided in S2 and mixing uniformly, so that the graphene is in a uniformly dispersed state, and the graphene oil slurry is obtained. In S1, the polymer monomer comprises any one or a combination of styrene, an acrylate compound and an acrylamide compound. The polymerization inhibitor comprises any one of hydroquinone monomethyl ether, hydroquinone, p-benzoquinone, methylhydroquinone, p-hydroxyanisole, 2-tert-butyl hydroquinone and 2,5-di-tert-butyl hydroquinone. The oil dispersant is at least one of polyisobutylene succinimide, boronized polyisobutylene succinimide, isopropyl titanate, sorbitan oleate, polyether, stearic acid, oleic acid, tallow amine and tallow amine polyoxyethylene ether. The acrylate compound is a methacrylate compound. The acrylamide compound comprises any one or a combination of two or more of alkyl-substituted acrylamide, alkyl-substituted methacrylamide, 4-acryloyl morpholine, 3-acryloyl-2-oxazolone, N-methyl acrylamide, N-phenyl acrylamide, N-phenyl methacrylamide, N-benzyl methacrylamide, N,N-dibenzyl acrylamide and N-benzyl-N-methyl acrylamide.

2. The method of claim 1, wherein the graphene oil-based slurry is prepared by the steps of: In S2, the base oil comprises a group II base oil, a group III base oil or a synthetic base oil.

3. The method for preparing graphene oily slurry according to claim 1, characterized in that, The synthetic base oil is polyalphaolefin or alkyl naphthalene base oil.

4. The method for preparing graphene oily slurry according to claim 1, characterized in that, The protective gas is an inert gas.

5. The method of claim 4, wherein the graphene oil-based slurry is prepared by the steps of: The initiator is azobisisobutyronitrile or peroxobenzoyl.

6. The method of claim 1, wherein the graphene oil-based slurry is prepared by the steps of: The stirring speed is 500-1000 rpm.

7. The method for preparing graphene oily slurry according to claim 1, characterized in that, The in-situ polymerization reaction is performed at a reaction temperature of 60-80℃ for 4-6 hours.

8. The method for preparing graphene oily slurry according to claim 1, characterized in that, In S3, the dispersion condition of the graphene polymer slurry comprises a stirring speed of 200-500 rpm, a dispersion time of 1-3 hours and a temperature of 60-80℃.

9. The method for preparing graphene oily slurry according to claim 1, characterized in that, ​ 10. The method for preparing graphene oily slurry according to claim 1, characterized in that, ​ 11. The method for preparing graphene oily slurry according to claim 1, characterized in that, The antioxidant is any one or a combination of butyldiphenylamine, octyldiphenylamine, nonyldiphenylamine, N-octylphenyl-alpha-naphthylamine.

12. The method of claim 1-11, wherein the graphene oil-based slurry is prepared by the steps of: The mass ratio of the expanded graphite, the polymer monomer, the polymerization inhibitor, the base oil, the initiator, the oily dispersant, and the antioxidant is 1:(10-100):(0.01-0.1):(10-100):(0.05-0.5):(2-20):(1-10).

13. A graphene oily slurry obtained by the preparation method of any one of claims 1-12; the graphene oily slurry is directly applied to lubricating oil as an additive.

14. A lubricating oil characterised in that, At least comprising the graphene oily slurry of claim 13.

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