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

Abstract

The invention discloses modified graphene oily slurry as well as a preparation method and application thereof. The preparation method comprises the following steps: forming a first dispersion liquid from graphene oxide and a switch type microemulsion; enabling the modifier, the base oil and the switching type microemulsion to form second dispersion liquid; mixing the two dispersions, heating to carry out a modification reaction, changing graphene oxide into modified graphene, then adding a first switching substance, carrying out a switching reaction on the switching type microemulsion to change into a water phase system, enabling the modified graphene to enter an oil phase system, and realizing oil-water separation, wherein the oil phase system is the product, namely the modified graphene oily slurry. According to the invention, hydrophilic graphene oxide and an oil-soluble modifier are effectively mixed by utilizing the amphipathicity of the switch type microemulsion, so that the generation of a modification reaction is promoted, and the modification of graphene oxide is realized; oil-water separation can be easily realized by utilizing a switch reaction to obtain a product, and a water-phase system can be recycled; the product can be used as a lubricating oil additive, and has good antiwear and antifriction effects and dispersion stability.

Description

Technical Field

[0001] This invention relates to a method for preparing modified graphene oily slurry, and more particularly to a method for preparing modified graphene oily slurry using a switch-type microemulsion, and its application in lubricating oil, belonging to the technical fields of nanomaterials and lubricating additives. Background Technology

[0002] In recent years, graphene and its derivatives (such as graphene oxide, GO) have shown great potential in the field of lubricant additives due to their ultra-high mechanical strength, excellent thermal conductivity, and extremely low coefficient of friction. Studies have shown that the introduction of trace amounts of GO can significantly improve the anti-wear and friction-reducing properties and load-carrying capacity of base oils, and is expected to meet the urgent needs of high-end equipment for long-term lubrication and protection under extreme operating conditions.

[0003] However, the practical application of graphene oxide faces fundamental challenges. Graphene oxide is hydrophilic, with its surface rich in hydrophilic groups such as hydroxyl and carboxyl groups, making it prone to agglomeration and precipitation in hydrophobic lubricating oils, and difficult to disperse stably. Therefore, graphene oxide needs to be modified to be lipophilic when used in lubricating oils. Current technologies generally use oil-soluble modifiers (such as long-chain alkylamines) to functionalize the surface of graphene oxide to enhance its compatibility with base oils. However, this process has significant drawbacks: the modification reaction must be carried out in an oily solvent, but hydrophilic graphene oxide is difficult to disperse in oily solvents, greatly reducing preparation efficiency and effectiveness; moreover, it must rely on long-term high-speed shearing, which is not only energy-intensive and complex, but also damages the molecular structure of the base oil, reducing the bulk performance of the lubricating oil. Furthermore, the separation and purification process after modification consumes a large amount of organic solvent, and the modifier is difficult to recycle, leading to high production costs and increased environmental pollution risks.

[0004] Therefore, developing an efficient and environmentally friendly graphene oxide modification and dispersion process to achieve stable compatibility with lubricating oils while avoiding damage to base oil performance and secondary pollution has become a critical technical bottleneck that urgently needs to be overcome in this field. Summary of the Invention

[0005] The main objective of this invention is to provide a modified graphene oily slurry and its preparation method, so as to overcome the shortcomings of the prior art.

[0006] Another object of the present invention is to provide the application of the modified graphene oily slurry in lubricating oil.

[0007] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0008] This invention provides a method for preparing a modified graphene oily slurry, comprising:

[0009] A switchable microemulsion is provided, comprising an organic tertiary amine, a surfactant, a soluble salt, and water, wherein the organic tertiary amine is a combination of an oil-soluble first organic tertiary amine and a water-slightly soluble second organic tertiary amine;

[0010] Graphene oxide is mixed with the switch-type microemulsion to form a first dispersion;

[0011] The modifier, base oil, and the switch-type microemulsion are mixed to form a second dispersion;

[0012] The first dispersion and the second dispersion are mixed evenly and heated to undergo a modification reaction, transforming graphene oxide into modified graphene; the modifier is a substance capable of reacting with the hydroxyl, carboxyl, or epoxy groups contained in graphene oxide.

[0013] A first switching substance is added to the reaction system after the modification reaction is completed. The first switching substance can react with the switching microemulsion to make the organic tertiary amine in the switching microemulsion water-soluble, and the switching microemulsion is transformed into an aqueous phase system. The modified graphene enters the oil phase system, realizing oil-water separation. The oil phase system is the modified graphene oily slurry. The first switching substance is an acid corresponding to the soluble salt.

[0014] The present invention also provides a modified graphene oily slurry prepared by the preparation method, which comprises at least a base oil and modified graphene and unreacted modifier uniformly dispersed in the base oil.

[0015] This invention also provides the application of the modified graphene oily slurry in the field of lubricating oil.

[0016] Accordingly, embodiments of the present invention also provide a lubricating oil additive, which includes the aforementioned modified graphene oily slurry.

[0017] Compared with the prior art, the beneficial effects of the present invention include at least the following:

[0018] 1) The method for preparing modified graphene oily slurry provided by the present invention utilizes the amphiphilicity of the switch-type microemulsion to achieve good dispersion of both hydrophilic graphene oxide and oil-soluble modifier, and to effectively mix the two, thereby promoting the modification reaction and achieving the modification of graphene oxide. At the same time, due to the amphiphilicity of the switch-type microemulsion, after the hydrophilic graphene oxide is transformed into oleophilic modified graphene, the modified graphene can also achieve good dispersion in the switch-type microemulsion. Therefore, the graphene oxide / modified graphene always maintains a good dispersion state during the modification reaction.

[0019] 2) This invention utilizes a switching reaction to easily integrate modified graphene into the oil phase system while maintaining its good dispersion, resulting in a modified graphene oily slurry. It also achieves separation of the oil and aqueous phases, simplifying the entire process. The aqueous phase system can be regenerated using the switching reaction, allowing the microemulsion used as the reaction medium to be recycled, reducing costs and minimizing waste solvent generation.

[0020] 3) The modified graphene oily slurry of the present invention exists in liquid form and can be conveniently added to lubricating oil as a graphene lubricating oil additive to exert the good anti-wear and friction-reducing effect of modified graphene. At the same time, during the addition process, the modified graphene is transferred from one well-compatible liquid phase to another well-compatible liquid phase without destroying the good dispersion state of the modified graphene in the modified graphene oily slurry. Therefore, the modified graphene has good dispersion stability in lubricating oil. Detailed Implementation

[0021] Given the shortcomings of existing technologies where the modification reaction must be carried out in an oily solvent, and the fact that hydrophilic graphene oxide is not easily dispersed in an oily solvent, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The main feature is that the amphiphilicity of the switch-type microemulsion enables the hydrophilic graphene oxide to be effectively mixed with the oil-soluble modifier and react fully, thereby achieving both the modification and good dispersion of graphene oxide. Furthermore, the switch-type reaction is used to separate the oil phase system and the aqueous phase system, with the oil phase system being the modified graphene oily slurry.

[0022] The following will further explain the technical solution, its implementation process, and its principles. However, it should be understood that within the scope of this invention, the above-mentioned technical features of this invention and the technical features specifically described below (in embodiments) can be combined with each other to form new or preferred technical solutions. Due to space limitations, they will not be described in detail here.

[0023] As one aspect of the technical solution of this invention, a method for preparing a modified graphene oily slurry includes:

[0024] A switchable microemulsion is provided, the switchable microemulsion comprising an organic tertiary amine, a surfactant, a soluble salt and water, wherein the organic tertiary amine is a combination of an oil-soluble first organic tertiary amine and a water-slightly soluble second organic tertiary amine;

[0025] Graphene oxide is mixed with the switch-type microemulsion to form a first dispersion;

[0026] The modifier, base oil, and the switch-type microemulsion are mixed to form a second dispersion;

[0027] The first dispersion and the second dispersion are mixed evenly and heated to undergo a modification reaction, transforming graphene oxide into modified graphene; the modifier is a substance capable of reacting with the hydroxyl, carboxyl, or epoxy groups contained in graphene oxide.

[0028] A first switching substance is added to the reaction system after the modification reaction is completed. The first switching substance can react with the switching microemulsion to make the organic tertiary amine in the switching microemulsion water-soluble, and the switching microemulsion is transformed into an aqueous phase system. The modified graphene enters the oil phase system, realizing oil-water separation. The oil phase system is the modified graphene oily slurry. The first switching substance is an acid corresponding to the soluble salt.

[0029] In some implementations, the switchable microemulsion is converted into an aqueous phase system by adding a first switchable substance, and the aqueous phase system is converted into a switchable microemulsion by adding a second switchable substance.

[0030] Specifically, the reaction process and mechanism of this invention are explained as follows: A switchable microemulsion is selected as the reaction medium. All components of the switchable microemulsion are substances that do not participate in the modification reaction. The switchable microemulsion is amphiphilic, and before the modification reaction, it can effectively disperse hydrophilic graphene oxide and oil-soluble modifiers, allowing for effective mixing of graphene oxide and modifiers. The amino, carboxyl, anhydride, or hydroxyl groups on the modifier can fully contact the hydroxyl, carboxyl, or epoxy groups on the graphene oxide, promoting the modification reaction and achieving efficient modification of graphene oxide. Simultaneously, due to the amphiphilic nature of the switchable microemulsion, the switchable microemulsion... The emulsion can also effectively disperse lipophilic modified graphene. After graphene oxide is converted into modified graphene, the dispersion state of modified graphene in the switch-type microemulsion does not change. During the modification reaction, graphene oxide / modified graphene always maintains a good dispersion state. Furthermore, after the modification reaction is completed, taking advantage of the reaction and phase switching characteristics between the switch-type microemulsion and the switch substance, the first switch substance is added to cause a switch reaction with the switch-type microemulsion. The organic tertiary amine in the switch-type microemulsion becomes water-soluble, and the switch-type microemulsion is converted into an aqueous phase system. Meanwhile, the modified graphene, due to its lipophilicity, enters the oil phase system and is stably dispersed.

[0031] In some embodiments, the oxygen content of the graphene oxide is 20% to 50%.

[0032] In some embodiments, the mass ratio of the graphene oxide to the sum of the components in the switchable microemulsion other than water is 1:(2-4).

[0033] In some embodiments, the preparation method includes: mixing graphene oxide with the switch-type microemulsion and performing a first dispersion treatment to obtain a first dispersion.

[0034] Furthermore, the rotation speed of the first dispersion treatment is 6000 rpm to 10000 rpm, and the time is 2 h to 4 h.

[0035] In some embodiments, the modifier is a substance that can react with the hydroxyl, carboxyl, or epoxy groups on graphene oxide.

[0036] In some preferred embodiments, the modifier includes, but is not limited to, one or more of amino modifiers, carboxyl-containing modifiers, anhydride-containing modifiers, hydroxyl-containing modifiers, etc.

[0037] Furthermore, the modifier may specifically be one or more of fatty acids such as tallow amine polyoxyethylene ether, polyisobutylene succinimide, polyisobutylene amine, polyether amine, polyisobutylene succinic anhydride, and oleic acid, but is not limited to these.

[0038] In some implementations, the base oil may include one or more of Group II base oils, Group III base oils, Group IV base oils, Group V base oils, etc., but is not limited to this.

[0039] In some embodiments, when preparing the second dispersion, the mass ratio of the modifier, base oil and the sum of the components other than water in the switch-type microemulsion is (5-20):(20-50):(2-4).

[0040] In some embodiments, the preparation method includes: mixing a modifier, a base oil, and the switch-type microemulsion, and performing a second dispersion treatment to obtain a second dispersion.

[0041] Furthermore, the rotation speed of the second dispersion treatment is 1000 rpm to 3000 rpm, and the time is 2 h to 4 h.

[0042] In some embodiments, the modification reaction is carried out at a temperature of 80°C to 100°C for 6 to 10 hours. During this process, different modifiers can react with the hydroxyl, carboxyl, or epoxy groups on graphene oxide to modify the graphene oxide.

[0043] In some embodiments, the preparation method specifically includes: slowly adding the first switching substance to the reaction system after the modification reaction is completed, controlling the addition to be completed within 0.5 to 1 hour. The first switching substance reacts with the switching microemulsion during addition, and the pH value of the reaction system is adjusted to 5.6 to 6.6. During the switching reaction, the organic tertiary amine in the switching microemulsion becomes water-soluble. The reason for controlling the addition of the first switching substance within 0.5 to 1 hour in this invention is: (1) if the addition rate of the first switching substance is too fast, it will cause the oil-water separation to be too fast, which will lead to the destruction of the dispersion state of the modified graphene during the process of entering the oil phase system; (2) to take into account efficiency.

[0044] The first switching substance may include one or more combinations of oxalic acid, carbonic acid, maleic acid, citric acid, etc., and the second switching substance includes calcium salt, preferably calcium hydroxide, but is not limited thereto.

[0045] In some embodiments, the preparation method further includes: adding a second switching substance to the aqueous phase system obtained by oil-water separation, adjusting the pH value to 7.5-8.5, regenerating the switching microemulsion, and allowing it to be recycled after solid-liquid separation.

[0046] Specifically, the organic tertiary amine includes a combination of an oil-soluble first organic tertiary amine and a water-slightly soluble second organic tertiary amine. The present invention selects organic tertiary amines to avoid their reaction with graphene oxide. In addition, both organic tertiary amines are indispensable, otherwise a stable microemulsion cannot be formed.

[0047] In some embodiments, the oil-soluble first organic tertiary amine may include one or more combinations of N,N-dimethylcyclohexylamine, N,N-dimethylhexylamine, N,N-dimethylheptylamine, N,N-dimethyln-octylamine, etc., but is not limited thereto.

[0048] In some embodiments, the slightly water-soluble second organic tertiary amine may include one or more combinations of tetramethylethylenediamine, tetraethylethylenediamine, N,N-dimethylbutylamine, triethylamine, tri-n-propylamine, etc., but is not limited thereto.

[0049] In some embodiments, the soluble salt directly corresponds to the substance that implements the switch, and may include, but is not limited to, one or more combinations of oxalate, bicarbonate, carbonate, maleate, and citrate, preferably oxalate.

[0050] In some preferred embodiments, the soluble salt may include one or more combinations of soluble potassium salts, soluble sodium salts, soluble ammonium salts, etc., but is not limited thereto.

[0051] Furthermore, the oxalate can be obtained by neutralizing oxalic acid with a base.

[0052] In some preferred embodiments, the oxalate may include one or more combinations of ammonium oxalate, sodium oxalate, potassium oxalate, etc., but is not limited thereto.

[0053] In some embodiments, the surfactant is an anionic surfactant, preferably including one or more combinations of sulfonate surfactants, sulfate surfactants, and carboxylate surfactants.

[0054] In some more preferred embodiments, the anionic surfactant may include, but is not limited to, one or more of the following: sodium α-alkenyl sulfonate and its copolymers, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, triethanolamine dodecylbenzene sulfonate, sodium secondary alkyl sulfonate, sodium dodecyl diphenyl ether disulfonate, fatty alcohol polyoxyethylene ether sulfate, fatty alcohol polyoxyethylene ether sulfonate, alkylphenol polyoxyethylene ether carboxylate, and fatty alcohol polyoxyethylene ether carboxylate.

[0055] In some embodiments, the molar ratio of the organic tertiary amine to the soluble salt is 1:(1 to 1.05) based on the number of amino groups. In other words, based on the molar ratio, 1 part of the organic tertiary amine (based on the number of amino groups) corresponds to 1 to 1.05 parts of the soluble salt.

[0056] In some embodiments, the mass ratio of the organic tertiary amine to the surfactant is 1:(0.2 to 0.5), that is, in other words, by mass, 1 part of organic tertiary amine corresponds to 0.2 to 0.5 parts of anionic surfactant.

[0057] In some embodiments, the water comprises 60% to 80% of the total mass of the switchable microemulsion.

[0058] In some embodiments, the molar ratio of the first organic tertiary amine to the second organic tertiary amine is 1:(0.1 to 0.2).

[0059] As another aspect of the technical solution of the present invention, it also relates to a method for preparing the switch-type microemulsion, which includes: adding an organic tertiary amine, a surfactant, and an acid corresponding to a soluble salt to water, and then adding an alkali to form the switch-type microemulsion.

[0060] In some preferred embodiments, the preparation method of the switchable microemulsion specifically includes: adding an organic tertiary amine, an anionic surfactant, and an acid corresponding to a soluble salt (such as oxalic acid) to water (the organic tertiary amine reacts with oxalic acid and dissolves in water), and then adding an alkaline solution while stirring (the alkali reacts with oxalic acid, and the organic tertiary amine is converted into an oil-soluble form) to form a switchable microemulsion, and adjusting the pH value to 7.5-8.5.

[0061] In some preferred embodiments, a method for preparing a modified graphene oily slurry includes the following steps:

[0062] (1) GO (graphene oxide with an oxygen content of 20% to 50%) was mixed evenly with a switch-type microemulsion (disperser, speed of 6000 rpm to 10000 rpm, time of 2 h to 4 h);

[0063] (2) The modifier, base oil and switch-type microemulsion are mixed evenly (disperser, speed 1000rpm~3000rpm, time 2h~4h);

[0064] (3) Mix the two dispersions from step (1) and step (2) evenly, place them in a reaction vessel and heat them to undergo a modification reaction (temperature is 80℃~100℃, time is 6h~10h), and GO is converted into modified graphene.

[0065] (4) Slowly add oxalic acid (calculated by molar number, the ratio of oxalic acid to amino group in organic tertiary amine is 0.5:(0.95~1.05)), adjust the pH value to 5.6~6.6, and continue the addition process for 0.5h~1h, during which a switching reaction occurs (oxalic acid reacts with organic tertiary amine, making the organic tertiary amine water-soluble).

[0066] (5) After centrifugation, the oil and water are separated, and the modified graphene enters the oil phase system. The main components of the oil phase system are a combination of modified graphene, remaining modifier, and base oil, which is the graphene lubricating oil additive; the aqueous phase system can be regenerated into a switch-type microemulsion.

[0067] (6) Add calcium hydroxide to the aqueous phase obtained from oil-water separation and adjust the pH to 7.5-8.5 to regenerate the switch-type microemulsion. After solid-liquid separation, the switch-type microemulsion used as the reaction medium can be recycled, which reduces costs and reduces the generation of waste solvents.

[0068] The graphene lubricant additive produced by this invention is easily separated from the switch-type microemulsion, making the entire operation process simpler.

[0069] As another aspect of the technical solution of the present invention, it also relates to a modified graphene oily slurry prepared by the aforementioned preparation method, wherein the modified graphene oily slurry comprises at least a base oil and modified graphene uniformly dispersed in the base oil, as well as an incompletely reacted modifier.

[0070] As another aspect of the technical solution of the present invention, it also relates to the application of the aforementioned modified graphene oily slurry in the field of lubricating oil.

[0071] Accordingly, another aspect of the present invention provides a lubricating oil additive comprising the aforementioned modified graphene oily slurry. This modified graphene oily slurry exists in liquid form and can be easily added to lubricating oils, exhibiting good anti-wear and friction-reducing effects as well as good dispersion stability.

[0072] The technical solution of the present invention will be further described in detail below with reference to several preferred embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. It should be noted that the following embodiments are intended to facilitate the understanding of the present invention, and do not constitute any limitation thereof. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or according to the conditions recommended by the manufacturer.

[0073] Example 1

[0074] S1. Preparation of the switch-type microemulsion. 31.96 g of sodium α-alkenylsulfonate, 148.02 g of N,N-dimethylcyclohexylamine, 11.77 g of triethylamine, and 115.18 g of oxalic acid were dissolved in 1227.72 g of water. 465.35 g of 20% sodium hydroxide solution was added, and the mixture was stirred until homogeneous to obtain the switch-type microemulsion. The pH value of the switch-type microemulsion at this point was 8.0.

[0075] S2. Graphene Modification. 1 part by mass of GO (oxygen content 20%) and 2 parts by mass of switch-type microemulsion (based on the portion after water removal) were added to a disperser and dispersed at 10,000 rpm for 2 hours. The mixture was then transferred to a reaction vessel. 5 parts by mass of tallow amine polyoxyethylene ether, 50 parts by mass of Group IV base oil PAO, and 2 parts by mass of switch-type microemulsion (based on the portion after water removal) were added to a disperser and dispersed at 1,000 rpm for 4 hours. The mixture was then transferred to the same reaction vessel, mixed thoroughly, and modified at 100°C for 6 hours.

[0076] S3. Separation of graphene lubricating oil additive. Oxalic acid is added to the reactor, with the addition completed within 0.5 hours, and the pH value is adjusted to 6.6. Centrifugation separates the oil and water phases. The oil phase is modified graphene oily slurry #1, which can be used as a graphene lubricating oil additive, while the aqueous phase can be regenerated into a switchable microemulsion.

[0077] Example 2

[0078] S1. Preparation of the switch-type microemulsion. 31.96 g of sodium α-alkenylsulfonate, 148.02 g of N,N-dimethylcyclohexylamine, 11.77 g of triethylamine, and 115.18 g of oxalic acid were dissolved in 1227.72 g of water. 465.35 g of 20% sodium hydroxide solution was added, and the mixture was stirred until homogeneous to obtain the switch-type microemulsion. The pH value of the switch-type microemulsion at this point was 8.0.

[0079] S2. Graphene Modification. 1 part by mass of GO (oxygen content 35%) and 4 parts by mass of switch-type microemulsion (based on the portion after water removal) were added to a disperser and dispersed at 6000 rpm for 4 hours. The mixture was then transferred to a reaction vessel. 10 parts by mass of polyisobutylene succinic anhydride, 40 parts by mass of Group III base oil GTL, and 4 parts by mass of switch-type microemulsion (based on the portion after water removal) were added to a disperser and dispersed at 2000 rpm for 3 hours. The mixture was then transferred to the same reaction vessel, mixed thoroughly, and modified at 90℃ for 8 hours.

[0080] S3. Separation of graphene lubricating oil additive. Oxalic acid is added to the reactor, with the addition completed within 1 hour, and the pH value is adjusted to 6.0. Centrifugation separates the oil and water phases. The oil phase is modified graphene oily slurry #2, which can be used as a graphene lubricating oil additive. The aqueous phase can be regenerated into a switchable microemulsion.

[0081] Example 3

[0082] S1. Preparation of the switch-type microemulsion. 31.96 g of sodium α-alkenylsulfonate, 148.02 g of N,N-dimethylcyclohexylamine, 11.77 g of triethylamine, and 115.18 g of oxalic acid were dissolved in 1227.72 g of water. 465.35 g of 20% sodium hydroxide solution was added, and the mixture was stirred until homogeneous to obtain the switch-type microemulsion. The pH value of the switch-type microemulsion at this point was 8.0.

[0083] S2. Graphene Modification. 1 part by mass of GO (50% oxygen content) and 3 parts by mass of the switch-type microemulsion (based on the portion after water removal) were added to a disperser and dispersed at 8000 rpm for 3 hours. 20 parts by mass of polyetheramine, 20 parts by mass of Class V base oil oil-soluble polyether OSP, and 3 parts by mass of the switch-type microemulsion (based on the portion after water removal) were added to a disperser and dispersed at 3000 rpm for 2 hours. The mixtures were then transferred to the same reactor, mixed thoroughly, and modified at 80°C for 10 hours.

[0084] S3. Separation of graphene lubricating oil additive. Oxalic acid is added to the reactor, with the addition completed within 0.5 hours, and the pH value is adjusted to 5.6. Centrifugation separates the oil and water phases. The oil phase is modified graphene oily slurry #3, which can be used as a graphene lubricating oil additive, while the aqueous phase can be regenerated into a switchable microemulsion.

[0085] Comparative example: 1GO + modifier + base oil reaction

[0086] 1 part by mass of GO (oxygen content of 50%), 10 parts by mass of tallow amine polyoxyethylene ether and 10 parts by mass of Group IV base oil PAO were added to a disperser and dispersed at 10,000 rpm for 2 hours. The mixture was then transferred to a reactor and modified at 100°C for 6 hours to obtain modified graphene oily slurry #4.

[0087] Comparative example: 2GO + water + modifier + base oil reaction

[0088] 1 part by mass of GO (oxygen content of 20%) and 25 parts by mass of water were added to a disperser and dispersed at 10,000 rpm for 2 hours. 10 parts by mass of tallow amine polyoxyethylene ether and 10 parts by mass of Group IV base oil PAO were added and transferred to a reactor. The mixture was modified and reacted at 100°C for 6 hours under vacuum to obtain modified graphene oily slurry No. 5.

[0089] Test Example 1: Dispersion Stability Test

[0090] Modified graphene oily slurry 1#, modified graphene oily slurry 2#, modified graphene oily slurry 3# prepared in Examples 1-3, modified graphene oily slurry 4# prepared in Comparative Example 1, and modified graphene oily slurry 5# prepared in Comparative Example 2 were added to the finished lubricating oil Merrenz SP 0W-30 at a graphene weight ratio of 100 ppm, and were simply dispersed by manual stirring.

[0091] Centrifuge at 1440g (1440 times the acceleration of gravity) for 30 minutes (approximately equivalent to one month of natural settling), pause for 30 minutes, then centrifuge again for 30 minutes, repeating this process for a total of 3 hours. The test results are shown in Table 1.

[0092] Table 1. Dispersion stability test results

[0093]

[0094] As shown in Table 1, the modified graphene prepared by this invention exhibits good dispersion stability in lubricating oil. Specifically, the modified graphene prepared in Examples 1-3 shows good modification effect due to the good mixing of graphene oxide and the modifier under the action of the switch-type emulsion. However, in Comparative Example 1, the high oxygen content of graphene oxide leads to strong hydrophilicity and poor dispersion in the base oil, resulting in poor contact between graphene oxide and the modifier, and thus poor modification effect. The modified graphene product also exhibits poor dispersion in the lubricating oil. In Comparative Example 2, the low oxygen content of graphene oxide results in insufficient hydrophilicity and poor dispersion in water, leading to poor contact between graphene oxide and the modifier, and also poor modification effect. The modified graphene product also exhibits poor dispersion in the lubricating oil. Comparative Examples 1 and 2 demonstrate that the switch-type microemulsion used in this application can adapt to graphene oxide with different oxygen contents for modification.

[0095] Test Example 2 Friction Performance Test

[0096] Modified graphene oily slurry 1#, modified graphene oily slurry 2#, modified graphene oily slurry 3# prepared in Examples 1-3, modified graphene oily slurry 4# prepared in Comparative Example 1, and modified graphene oily slurry 5# prepared in Comparative Example 2 were used as additives and added to the finished lubricating oil Merrenz SP 0W-30 at a graphene weight ratio of 10 ppm. The friction and wear performance of the lubricating oil, including the coefficient of friction and the wear scar diameter, was tested.

[0097] The oil samples and finished lubricating oils obtained by compounding modified graphene oily slurries 1#, 2#, and 3# prepared in Examples 1-3, modified graphene oily slurries 4# prepared in Comparative Example 1, and modified graphene oily slurries 5# prepared in Comparative Example 2 were evaluated using a four-ball friction tester to test their friction-reducing and anti-wear properties (industry standard SH / TO189-92). The test conditions included: GCr15 steel balls, a rotation speed of 1200 r / min, an oil temperature of 75℃, a long-term grinding time of 60 min, and a load of 392 N. The data provided by the four-ball friction tester included the wear scar diameter and the coefficient of friction. A smaller wear scar diameter indicates higher anti-wear ability, and a smaller coefficient of friction indicates better friction-reducing performance. The results are shown in Table 2.

[0098] Table 2. Tribological properties of lubricating oils

[0099] sample coefficient of friction Wear scar diameter (mm) Finished lubricating oil 0.1145 0.43 Example 1 0.0697 0.35 Example 2 0.0743 0.36 Example 3 0.0770 0.37 Comparative Example 1 0.1157 0.44 Comparative Example 2 0.1129 0.45

[0100] As shown in Table 2, the modified graphene prepared by the present invention has good anti-wear and friction reduction effects, while the modified graphene of Comparative Example 1 and Comparative Example 2 has no effect on improving anti-wear and friction reduction performance due to poor dispersion.

[0101] Furthermore, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the foregoing embodiments, and obtained relatively ideal results. For example, in the case of the switch-type microemulsion, using acids other than oxalic acid, oil-soluble first organic tertiary amines other than N,N-dimethylcyclohexylamine, water-slightly soluble second organic tertiary amines other than triethylamine, and surfactants other than sodium α-alkenylsulfonate, the resulting switch-type microemulsions have the same technical effects as those in Examples 1-3, all of which can form stable microemulsions and achieve the switching function.

[0102] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a modified graphene oily slurry, characterized in that, include: A switchable microemulsion is provided, comprising an organic tertiary amine, a surfactant, a soluble salt, and water, wherein the organic tertiary amine is a combination of an oil-soluble first organic tertiary amine and a water-slightly soluble second organic tertiary amine; Graphene oxide is mixed with the switch-type microemulsion to form a first dispersion; The modifier, base oil, and the switch-type microemulsion are mixed to form a second dispersion; The first dispersion and the second dispersion are mixed evenly and heated to undergo a modification reaction, transforming graphene oxide into modified graphene; the modifier is a substance capable of reacting with the hydroxyl, carboxyl, or epoxy groups contained in graphene oxide. A first switching substance is added to the reaction system after the modification reaction is completed. The first switching substance can react with the switching microemulsion to make the organic tertiary amine in the switching microemulsion water-soluble, and the switching microemulsion becomes an aqueous phase system. The modified graphene enters the oil phase system, realizing oil-water separation. The oil phase system is the modified graphene oily slurry. The first switching substance is an acid corresponding to the soluble salt.

2. The preparation method according to claim 1, characterized in that: The oxygen content of the graphene oxide is 20% to 50%. Preferably, the mass ratio of the graphene oxide to the sum of the other components in the switchable microemulsion, excluding water, is 1:(2-4). And / or, the preparation method includes: mixing graphene oxide with the switch-type microemulsion, performing a first dispersion treatment, and obtaining a first dispersion; Preferably, the rotation speed of the first dispersion treatment is 6000 rpm to 10000 rpm, and the time is 2 h to 4 h.

3. The preparation method according to claim 1, characterized in that: The modifier includes one or more of amino modifiers, carboxyl-containing modifiers, acid anhydride modifiers, and hydroxyl-containing modifiers; preferably, the modifier includes one or more of tallow amine polyoxyethylene ether, polyisobutylene succinimide, polyisobutylene amine, polyether amine, polyisobutylene succinic anhydride, and oleic acid. And / or, the base oil includes one or more combinations of Group II base oils, Group III base oils, Group IV base oils, and Group V base oils.

4. The preparation method according to claim 1, characterized in that: When preparing the second dispersion, the mass ratio of the modifier, base oil and the sum of the other components in the switch-type microemulsion except water is (5-20):(20-50):(2-4); And / or, the preparation method includes: mixing the modifier, base oil and the switch-type microemulsion, and performing a second dispersion treatment to obtain a second dispersion; Preferably, the second dispersion treatment is carried out at a rotation speed of 1000 rpm to 3000 rpm for 2 hours to 4 hours.

5. The preparation method according to claim 1, characterized in that: The temperature of the modification reaction is 80℃~100℃, and the time is 6h~10h; And / or, the preparation method includes: slowly adding the first switching substance to the reaction system after the modification reaction is completed, controlling the addition to be completed in 0.5 to 1 hour, wherein the first switching substance reacts with the switching microemulsion during addition, and adjusting the pH value of the reaction system to 5.6 to 6.

6.

6. The preparation method according to claim 1, characterized in that: The soluble salt includes one or more combinations of oxalate, bicarbonate, carbonate, maleate, and citrate, preferably oxalate; And / or, the soluble salt includes one or more combinations of soluble potassium salts, soluble sodium salts, and soluble ammonium salts; Preferably, the oxalate is obtained by neutralizing oxalic acid with a base; preferably, the oxalate comprises one or more combinations of ammonium oxalate, sodium oxalate, and potassium oxalate. And / or, the first organic tertiary amine includes one or more combinations of N,N-dimethylcyclohexylamine, N,N-dimethylhexylamine, N,N-dimethylheptylamine, and N,N-dimethyln-octylamine; And / or, the second organic tertiary amine includes one or more combinations of tetramethylethylenediamine, tetraethylethylenediamine, N,N-dimethylbutylamine, triethylamine, and tri-n-propylamine; And / or, the surfactant is an anionic surfactant, preferably including one or more combinations of sulfonate surfactants, sulfate surfactants, and carboxylate surfactants; particularly preferably, the anionic surfactant includes one or more combinations of sodium α-alkenyl sulfonate and its copolymers, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, triethanolamine dodecylbenzene sulfonate, secondary alkyl sulfonate, sodium dodecyl diphenyl ether disulfonate, fatty alcohol polyoxyethylene ether sulfate, fatty alcohol polyoxyethylene ether sulfonate, alkylphenol polyoxyethylene ether carboxylate, and fatty alcohol polyoxyethylene ether carboxylate.

7. The preparation method according to claim 1, characterized in that: The molar ratio of the organic tertiary amine to the soluble salt, calculated based on the number of amino groups, is 1:(1-1.05); And / or, the mass ratio of the organic tertiary amine to the surfactant is 1:(0.2-0.5); And / or, the water accounts for 60% to 80% of the total mass of the switch-type microemulsion; And / or, the molar ratio of the first organic tertiary amine to the second organic tertiary amine is 1:(0.1 to 0.2).

8. A modified graphene oily slurry prepared by any one of claims 1-7, wherein the modified graphene oily slurry comprises at least a base oil and modified graphene and unreacted modifier uniformly dispersed in the base oil.

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

10. A lubricating oil additive, characterized in that, Including the modified graphene oily slurry as described in claim 8.

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