Graphene-based lubricating oil for hydraulic drilling rig and preparation method thereof

Abstract

The application relates to the technical field of lubricants, and particularly discloses a graphene-based lubricating oil for a hydraulic drilling machine and a preparation method thereof.The graphene-based lubricating oil for the hydraulic drilling machine comprises the following raw materials in parts by weight: base oil 95-98 parts, sulfur-phosphorus type extreme pressure anti-wear agent 0.2-0.5 parts, quaternary ammonium salt ionic liquid 0.5-2 parts, hindered phenolic antioxidant 0.4-0.5 parts, temperature-sensitive microcapsules 0.1-0.3 parts, and graphene-boron nitride hybrid nanosheet 0.3-0.5 parts; the application has the advantages of solving the problems of poor dispersion stability of graphene, inability of the lubricant to release and continuously compensate for loss on demand.

Description

Technical Field

[0001] This application relates to the field of lubricant technology, and more specifically, to a graphene-based lubricant for hydraulic drilling rigs and a method for preparing the same. Background Technology

[0002] Under high-frequency impact loads, traditional lubricating oil films are prone to rupture, leading to lubrication failure and increased wear of friction pairs. Graphene, as a novel lubricating material, possesses excellent lubrication properties, but its poor dispersion stability makes it difficult to uniformly disperse in lubricating oil and maintain its activity over a long period. Conventional lubrication methods include: using high-viscosity base oils to increase oil film thickness to resist impact loads; adding solid lubricants such as molybdenum disulfide and graphite; and using microencapsulation of lubricants to achieve slow-release lubrication. In addition, existing technologies have also attempted to improve lubrication performance using graphene-boron nitride hybrid materials, as well as using ionic liquids to enhance the adsorption stability of the lubricating film.

[0003] However, existing technologies still have the following shortcomings: high-viscosity base oils are prone to failure at high temperatures, which can lead to increased energy consumption and difficulty in starting at low temperatures; solid lubricants have poor dispersibility and are prone to sedimentation; the microcapsule release mechanism is singular and cannot achieve gradient release or on-demand response, resulting in unsustainable lubrication effects or untimely response. In particular, under the high-frequency impact load conditions of hydraulic drilling rigs, traditional lubricating oil films are prone to rupture, and the dispersion stability problem of graphene has not been fundamentally solved. At the same time, there is a lack of a mechanism that can release lubricating components on demand and continuously replenish them according to changes in working conditions, such as temperature and pressure, resulting in short equipment maintenance cycles and high lubrication costs. Summary of the Invention

[0004] To address the issues of poor graphene dispersion stability, inability of lubricants to be released on demand, and continuous replenishment, this application provides a graphene-based lubricating oil for hydraulic drilling rigs and its preparation method.

[0005] In a first aspect, this application provides a graphene-based lubricating oil for hydraulic drilling rigs, employing the following technical solution: A graphene-based lubricating oil for a hydraulic drilling rig comprises the following raw materials in parts by weight: 95-98 parts base oil, 0.2-0.5 parts sulfur-phosphorus extreme pressure anti-wear agent, 0.5-2 parts quaternary ammonium salt ionic liquid, 0.4-0.5 parts hindered phenolic antioxidant, 0.1-0.3 parts temperature-sensitive microcapsules, and 0.3-0.5 parts graphene-boron nitride hybrid nanosheets.

[0006] By employing the above-mentioned technical solution, graphene is hybridized with boron nitride to form nanosheets, significantly improving the dispersion stability of two-dimensional materials in base oils and avoiding the problems of easy aggregation and precipitation of traditional graphene. The graphene-boron nitride hybrid nanosheets combine the low friction properties of graphene with the high thermal conductivity and high oxidation resistance of boron nitride, enabling the formation of a stable physical isolation layer on the surface of friction-prone objects; the anions of quaternary ammonium salt ionic liquids, such as [BF4], are also used. - It can form coordination bonds with metal surfaces, enhancing the adsorption strength and thermal stability of the lubricating film; sulfur-phosphorus extreme pressure anti-wear agents react with metal surfaces under high temperature and pressure to form a chemical reaction film, further protecting the friction objects; the introduction of temperature-sensitive microcapsules allows the lubricant to release active lubricating components when the temperature rises to a set threshold, achieving on-demand lubrication; hindered phenolic antioxidants effectively delay the thermal oxidative degradation of ionic liquids and base oils, extending the service life of lubricating oils; the dispersion stability, lubricating film strength, high-temperature oxidation resistance, and on-demand release of graphene-based lubricating oils have all been significantly improved, making them suitable for high-frequency impact conditions in hydraulic drilling rigs.

[0007] Preferably, the core of the temperature-sensitive microcapsule is an ionic lubricating liquid, the capsule wall is polydopamine, and the core rupture temperature of the temperature-sensitive microcapsule is 115-130℃.

[0008] By adopting the above technical solution, the polydopamine capsule wall softens and ruptures at 115-130℃, releasing an ionic lubricating liquid. This ionic liquid has low volatility and excellent high-temperature lubrication performance, and can quickly replenish the friction interface to form a new lubricating film, preventing dry friction. Compared with a single release mechanism, the temperature-sensitive microcapsule achieves intelligent release based on temperature changes, avoiding ineffective consumption and premature failure. The rupture temperature covers the typical operating temperature range of hydraulic drilling rigs, improving operating condition adaptability and service life.

[0009] Preferably, the method for preparing the temperature-sensitive microcapsules includes the following steps: uniformly dispersing cellulose nanocrystals in water using ultrasound as the aqueous phase, using 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid as the oil phase, mixing the oil phase and the aqueous phase, and emulsifying at high speed at 8000-10000 r / min for 5-7 min to obtain a stable emulsion, adding dopamine hydrochloride monomer to the stable emulsion, adjusting the pH of the system to 8-9 using Tris-HCl buffer, reacting for 8-10 h, centrifuging, separating, and washing to obtain the temperature-sensitive microcapsules.

[0010] By adopting the above technical solution, cellulose nanocrystals are used as an aqueous phase stabilizer to form a physical barrier to prevent droplet aggregation. High-speed emulsification yields uniform micron-sized oil droplets. Dopamine self-polymerizes under weakly alkaline conditions to generate polydopamine, which is deposited at the oil-water interface to form a dense capsule wall. By controlling the reaction time and pH, the capsule wall thickness and rupture temperature can be precisely adjusted. The prepared microcapsules have controllable particle size and high encapsulation efficiency.

[0011] Preferably, the concentration of the cellulose nanocrystals in the emulsion is 0.5-0.8 wt%, and the mass ratio of the oil phase to the water phase is 1:(19-21).

[0012] By adopting the above technical solution, the controlled concentration of cellulose nanocrystals can form a complete physical barrier layer at the oil-water interface, avoiding droplet aggregation due to excessively low concentration or emulsification difficulties due to excessively high concentration. The oil-water ratio ensures an appropriate loading of ionic liquid, avoiding uneven capsule wall thickness or decreased encapsulation efficiency. The prepared microcapsules have a concentrated particle size distribution and uniform capsule walls, ensuring consistency and reliability in mass production.

[0013] Preferably, the preparation method of the graphene-boron nitride hybrid nanosheets includes the following steps: dispersing graphene oxide and aminated boron nitride in water at a mass ratio of 7:3, adding a reducing agent to carry out a hydrothermal reaction, carrying out the hydrothermal reaction at 140-160℃ for 8-10 hours, centrifuging, separating, washing, and drying to obtain graphene-boron nitride hybrid nanosheets.

[0014] By adopting the above technical solution, aminated boron nitride and graphene oxide undergo chemical bonding under hydrothermal conditions. Controlling the mass ratio can ensure that boron nitride is uniformly distributed on the graphene sheets, avoiding the re-stacking and agglomeration of graphene. The resulting hybrid nanosheets have a large specific surface area, are easy to disperse, and have a thermal stability that is about 50°C higher than that of single graphene. They still maintain structural integrity at a high temperature of 200°C, thus improving the high-temperature performance of lubricants.

[0015] Secondly, this application provides a method for preparing graphene-based lubricating oil for hydraulic drilling rigs, employing the following technical solution: A method for preparing a graphene-based lubricating oil for a hydraulic drilling rig includes the following steps: The graphene-boron nitride hybrid nanosheets and thermosensitive microcapsules were prepared. After pretreatment of the thermosensitive microcapsules with some graphene-boron nitride hybrid nanosheets, a nanosheet-thermosensitive microcapsule composite material was obtained. The nanosheet-thermosensitive microcapsule composite material, the remaining graphene-boron nitride hybrid nanosheets, and the hindered phenolic antioxidant are dispersed in a base oil and mixed evenly to obtain a graphene-based lubricating oil.

[0016] By adopting the above technical solution, a composite material is formed by pretreating some hybrid nanosheets with temperature-sensitive microcapsules. The nanosheets are attached to the surface of the microcapsules to prevent mechanical damage and improve storage stability. When the microcapsules rupture, the nanosheets are released together with the capsule core to achieve synergistic lubrication. The distribution of nanosheets can regulate the rupture behavior of the microcapsules, and the remaining nanosheets are freely dispersed to provide continuous lubrication enhancement, realizing the dual mechanism of "continuous lubrication + intelligent release" and improving the adaptability to complex working conditions.

[0017] Preferably, the pretreatment includes the following steps: aminated graphene-boron nitride hybrid nanosheets, then the aminated graphene-boron nitride hybrid nanosheets are mixed with thermosensitive microcapsules and dispersed in Tris-HCl buffer solution with pH 8-8.5. After standing at 40-60℃ for 6-8 hours, the mixture is centrifuged, separated, washed, and dried to obtain the nanosheet-thermosensitive microcapsule composite material.

[0018] By adopting the above technical solution, -NH2 active groups are introduced on the surface of the nanosheets after amination modification. Under weakly alkaline conditions, these groups are covalently linked to the catechol groups of the polydopamine capsule wall, making the nanosheets firmly anchored on the microcapsule surface, thereby ensuring the stability and release reliability of the lubricant during use.

[0019] Preferably, the mass ratio of the aminated graphene-boron nitride hybrid nanosheets to the temperature-sensitive microcapsules is 1:(1-1.5).

[0020] By adopting the above technical solution, the mass ratio is controlled to form a single-layer or multi-layer coating structure of nanosheets on the surface of microcapsules. If the proportion is too high, the nanosheets will agglomerate, hinder the release of lubricating liquid and delay the temperature-sensitive response; if the proportion is too low, the coverage will be insufficient and the synergistic lubrication effect will be weakened. Limiting the mass ratio ensures that the temperature-sensitive rupture characteristics of microcapsules are not suppressed, and achieves synergistic lubrication of hybrid nanosheets and ionic liquid during release.

[0021] In summary, this application has the following beneficial effects: By hybridizing graphene with boron nitride to form nanosheets, and combining them with quaternary ammonium salt ionic liquids and temperature-sensitive microcapsules, the dispersion stability of graphene in base oils was significantly improved, solving the problem of easy agglomeration and precipitation of traditional graphene.

[0022] The temperature-sensitive microcapsules, which use polydopamine as the capsule wall and ionic liquid as the capsule core, achieve intelligent release within a temperature range of 115-130℃. They can automatically replenish lubricating components according to the local temperature rise of the friction pair, thus achieving on-demand lubrication.

[0023] By covalently bonding aminated hybrid nanosheets with temperature-sensitive microcapsules to form a composite material, the integrity of the microcapsules is protected, and a synergistic lubrication effect is achieved during release. Detailed Implementation

[0024] The present application will be further described in detail below with reference to the embodiments. Examples of preparation of thermosensitive microcapsules 1-8

[0025] Preparation Example 1 The method for preparing thermosensitive microcapsules includes the following steps: cellulose nanocrystals are ultrasonically and uniformly dispersed in water as the aqueous phase, and 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid is used as the oil phase. The oil phase and aqueous phase are mixed at a mass ratio of 1:19 and emulsified at 8000 r / min for 7 min to obtain a stable emulsion. The concentration of cellulose nanocrystals in the emulsion is 0.5 wt%. Dopamine hydrochloride monomer is added to the stable emulsion, and the concentration of dopamine hydrochloride monomer in the emulsion is 0.5 mg / mL. After adjusting the pH of the system to 8 with Tris-HCl buffer, the reaction is carried out for 10 h. The mixture is then centrifuged, separated, and washed to obtain thermosensitive microcapsules.

[0026] Preparation Example 2 The method for preparing thermosensitive microcapsules includes the following steps: cellulose nanocrystals are ultrasonically and uniformly dispersed in water as the aqueous phase, and 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid is used as the oil phase. The oil phase and aqueous phase are mixed at a mass ratio of 1:21 and emulsified at 10000 r / min for 5 min to obtain a stable emulsion. The concentration of cellulose nanocrystals in the emulsion is 0.8 wt%. Dopamine hydrochloride monomer is added to the stable emulsion, and the concentration of dopamine hydrochloride monomer in the emulsion is 0.7 mg / mL. After adjusting the pH of the system to 9 using Tris-HCl buffer, the reaction is carried out for 8 h. The mixture is then centrifuged, separated, and washed to obtain thermosensitive microcapsules.

[0027] Preparation Example 3 The difference between Preparation Example 3 and Preparation Example 1 is that in Preparation Example 3, the mass ratio of the oil phase to the water phase is 1:15.

[0028] Preparation Example 4 The difference between Preparation Example 4 and Preparation Example 1 is that in Preparation Example 4, the mass ratio of the oil phase to the water phase is 1:25.

[0029] Preparation Example 5 The difference between Preparation Example 5 and Preparation Example 1 is that in Preparation Example 5, the concentration of cellulose nanocrystals in the emulsion is 0.3 wt%.

[0030] Preparation Example 6 The difference between Preparation Example 6 and Preparation Example 1 is that in Preparation Example 6, the concentration of cellulose nanocrystals in the emulsion is 1.2 wt%.

[0031] Preparation Example 7 The difference between Preparation Example 7 and Preparation Example 1 is that in Preparation Example 7, the concentration of dopamine hydrochloride monomer in the emulsion is 0.3 mg / mL.

[0032] Preparation Example 8 The difference between Preparation Example 8 and Preparation Example 1 is that in Preparation Example 8, the concentration of dopamine hydrochloride monomer in the emulsion is 1.2 mg / mL. Example of preparation of graphene-boron nitride hybrid nanosheets

[0033] Preparation Example 9 The preparation method of graphene-boron nitride hybrid nanosheets includes the following steps: dispersing graphene oxide and aminated boron nitride in water at a mass ratio of 7:3, adding a reducing agent to carry out a hydrothermal reaction, carrying out the hydrothermal reaction at 140℃ for 10h, centrifuging, separating, washing, and drying to obtain graphene-boron nitride hybrid nanosheets. The mass ratio of reducing agent to graphene oxide is 1:1, and L-ascorbic acid is selected as the reducing agent. Example

[0034] Example 1 A graphene-based lubricating oil for a hydraulic drilling rig comprises the following raw materials in parts by weight: 95 kg of base oil, 0.2 kg of sulfur-phosphorus type extreme pressure anti-wear agent, 0.5 kg of quaternary ammonium salt ionic liquid, 0.4 kg of hindered phenolic antioxidant, 0.1 kg of temperature-sensitive microcapsules, and 0.3 kg of graphene-boron nitride hybrid nanosheets. The temperature-sensitive microcapsules are selected from those prepared in Preparation Example 1, and the graphene-boron nitride hybrid nanosheets are selected from those prepared in Preparation Example 9.

[0035] The preparation method of the graphene-based lubricating oil for the aforementioned hydraulic drilling rig includes the following steps: Graphene-boron nitride hybrid nanosheets and thermosensitive microcapsules were prepared. After pretreatment of the thermosensitive microcapsules with some graphene-boron nitride hybrid nanosheets, a nanosheet-thermosensitive microcapsule composite material was obtained. The pretreatment includes the following steps: Amination modification of graphene-boron nitride hybrid nanosheets; dispersion of graphene-boron nitride hybrid nanosheets in anhydrous ethanol at a mass ratio of 1:10; ultrasonic treatment for 30 min to ensure uniform dispersion; addition of 5% (by mass) 3-aminopropyltriethoxysilane to the dispersion; adjustment of pH to 4 with glacial acetic acid; stirring and reflux reaction at 60℃ for 8 h; centrifugation after reaction; washing three times with anhydrous ethanol and twice with water; vacuum drying at 60℃ for 12 h to obtain amination-modified graphene-boron nitride hybrid nanosheets; mixing and dispersing the amination-modified graphene-boron nitride hybrid nanosheets with thermosensitive microcapsules in Tris-HCl buffer solution at pH 8; static reaction at 40℃ for 8 h; centrifugation, separation, washing, and drying to obtain nanosheet-thermosensitive microcapsule composite material; the mass ratio of amination-modified graphene-boron nitride hybrid nanosheets to thermosensitive microcapsules is 1:1. The nanosheet-thermosensitive microcapsule composite material, the remaining graphene-boron nitride hybrid nanosheets, and the hindered phenolic antioxidant were dispersed in the base oil and mixed evenly to obtain graphene-based lubricating oil.

[0036] Example 2

[0037] A graphene-based lubricating oil for a hydraulic drilling rig comprises the following raw materials in parts by weight: 98 kg of base oil, 0.5 kg of sulfur-phosphorus type extreme pressure anti-wear agent, 2 kg of quaternary ammonium salt ionic liquid, 0.5 kg of hindered phenolic antioxidant, 0.3 kg of temperature-sensitive microcapsules, and 0.5 kg of graphene-boron nitride hybrid nanosheets. The temperature-sensitive microcapsules are selected from those prepared in Preparation Example 2, and the graphene-boron nitride hybrid nanosheets are selected from those prepared in Preparation Example 9.

[0038] The preparation method of the graphene-based lubricating oil for the aforementioned hydraulic drilling rig includes the following steps: Graphene-boron nitride hybrid nanosheets and thermosensitive microcapsules were prepared. After pretreatment of the thermosensitive microcapsules with some graphene-boron nitride hybrid nanosheets, a nanosheet-thermosensitive microcapsule composite material was obtained. The pretreatment includes the following steps: Amination modification of graphene-boron nitride hybrid nanosheets is performed by dispersing the graphene-boron nitride hybrid nanosheets in anhydrous ethanol at a mass ratio of 1:10, and ultrasonic treatment for 30 min to ensure uniform dispersion. 3-Aminopropyltriethoxysilane (10% of the nanosheet mass) is added to the dispersion, the pH is adjusted to 5 with glacial acetic acid, and the mixture is stirred and refluxed at 80 °C for 6 h. After the reaction was completed, the nanosheets were centrifuged, washed three times with anhydrous ethanol, and then washed twice with water. They were then vacuum dried at 60°C for 12 hours to obtain aminated graphene-boron nitride hybrid nanosheets. The aminated graphene-boron nitride hybrid nanosheets were then mixed with thermosensitive microcapsules and dispersed in Tris-HCl buffer solution at pH 8.5. After standing at 60°C for 6 hours, the nanosheets were centrifuged, separated, washed, and dried to obtain the nanosheet-thermosensitive microcapsule composite material. The mass ratio of the aminated graphene-boron nitride hybrid nanosheets to the thermosensitive microcapsules was 1:1.5. The nanosheet-thermosensitive microcapsule composite material, the remaining graphene-boron nitride hybrid nanosheets, and the hindered phenolic antioxidant were dispersed in the base oil and mixed evenly to obtain graphene-based lubricating oil.

[0039] Example 3

[0040] The difference between Example 3 and Example 1 is that in Example 3, the temperature-sensitive microcapsules are the same as those prepared in Preparation Example 3.

[0041] Example 4

[0042] The difference between Example 4 and Example 1 is that in Example 4, the temperature-sensitive microcapsules are the same as those prepared in Preparation Example 4.

[0043] Example 5

[0044] The difference between Example 5 and Example 1 is that in Example 5, the temperature-sensitive microcapsules are the same as those prepared in Example 5.

[0045] Example 6

[0046] The difference between Example 6 and Example 1 is that in Example 6, the temperature-sensitive microcapsules are the same as those prepared in Preparation Example 6.

[0047] Example 7

[0048] The difference between Example 7 and Example 1 is that in Example 7, the temperature-sensitive microcapsules are the same as those prepared in Preparation Example 7.

[0049] Example 8

[0050] The difference between Example 8 and Example 1 is that in Example 8, the temperature-sensitive microcapsules are the same as those prepared in Preparation Example 8. Comparative Example

[0051] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that no temperature-sensitive microcapsules were added in Comparative Example 1.

[0052] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that no graphene-boron nitride hybrid nanosheets were added in Comparative Example 2.

[0053] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that in Comparative Example 3, the thermosensitive microcapsules and graphene-boron nitride hybrid nanosheets were not pretreated and were directly dispersed in the base oil with the hindered phenolic antioxidants. Performance testing

[0054] Graphene-based lubricating oils were prepared according to Examples 1-8 and Comparative Examples 1-3, and were tested. The results are recorded in Table 1. The coefficient of friction of steel balls at 25°C and 120°C was measured according to ASTM D5183 (four-ball method). Measure the wear volume of the wear scar according to ASTM D7755; Its dispersion stability was determined according to ASTM D7065. After centrifugation at 3000 rpm for 30 min, the ratio of the height of the sedimentation layer to the height of the original liquid was measured and expressed as sedimentation rate. According to ASTM D2893 (rotating bomb oxidation method), the lubricating oil was oxidized at 120°C for 72 hours, and the increase in the kinematic viscosity of the lubricating oil at 40°C before and after the test was measured as the thermal oxidation stability. Differential scanning calorimetry (DSC) was used to observe the endothermic peak caused by the glass transition or rupture of the polydopamine capsule wall at a heating rate of 10 °C / min, and the temperature-sensitive release temperature was recorded.

[0055] Table 1. Lubricating oil performance test results Example 1 0.062 0.071 0.023 1.2 2.1 118 Example 2 0.058 0.067 0.021 1.0 1.9 116 Example 3 0.065 0.078 0.027 1.8 2.4 112 Example 4 0.067 0.082 0.029 2.1 2.6 135 Example 5 0.066 0.080 0.028 2.0 2.5 110 Example 6 0.068 0.083 0.030 2.3 2.8 138 Example 7 0.069 0.085 0.031 2.4 2.9 108 Example 8 0.071 0.088 0.033 2.6 3.1 142 Comparative Example 1 0.085 0.112 0.058 3.5 4.2 —— Comparative Example 2 0.092 0.108 0.065 8.7 4.5 120 Comparative Example 3 0.078 0.096 0.042 4.2 3.6 119 As can be seen from Table 1, Examples 1-2 and Comparative Examples 1-2, the graphene-based lubricating oil for hydraulic drilling rigs prepared in Examples 1-2 has a low coefficient of friction and a small wear volume at both 25°C and 120°C, and exhibits excellent dispersion stability and thermal oxidation stability. The lubricating oils in Examples 1-2 contain graphene-boron nitride hybrid nanosheets. Through chemical bonding, the graphene-boron nitride hybrid nanosheets ensure uniform distribution of boron nitride on the graphene sheets, effectively preventing graphene recombination and agglomeration, and significantly improving the dispersion stability of the two-dimensional material in the base oil. Simultaneously, the quaternary ammonium salt ionic liquid forms strong adsorption coordination bonds with the metal surface, synergistically forming a chemical reaction film with the sulfur-phosphorus extreme pressure anti-wear agent, jointly constructing a high-strength, high-temperature resistant lubricating protective layer. This significantly reduces the friction coefficient and wear volume under high-frequency impact conditions. In contrast, Comparative Example 1, lacking the addition of temperature-sensitive microcapsules and an intelligent damage compensation mechanism at high temperatures, resulted in a significant increase in the high-temperature friction coefficient and wear volume. Comparative Example 2, also lacking graphene-boron nitride hybrid nanosheets, lacked the physical isolation and load-bearing function of the nanosheet layers. This not only worsened the friction coefficient and wear volume but also significantly reduced dispersion stability due to the absence of a stable framework provided by the hybrid nanosheets, further confirming the crucial role of the hybrid nanosheets in improving the overall lubrication performance of the system.

[0056] Compared with Example 1, Examples 3-6 show a slight increase in the coefficient of friction, an increase in wear volume, and a decrease in dispersion stability and thermal oxidation stability. Examples 3-6 changed the oil-water ratio or cellulose nanocrystal concentration in the preparation process of the temperature-sensitive microcapsules. The increase in the oil-water ratio in Example 3 or the decrease in the oil-water ratio in Example 4 both led to a decrease in emulsion stability, a decrease in capsule wall encapsulation rate or uneven thickness, and the microcapsules were prone to premature rupture or precipitation in the base oil. In Example 5, the low concentration of cellulose nanocrystals resulted in insufficient interfacial physical barrier, and droplets were prone to coalescence. In Example 6, the high concentration made emulsification difficult and the capsule wall too thick. Both the oil-water ratio and the concentration of cellulose nanocrystals damaged the structural integrity of the temperature-sensitive microcapsules, reduced their storage stability and temperature-sensitive response accuracy, and made it impossible for the ionic liquid released on demand to effectively replenish the friction interface at the high-temperature critical point, thereby weakening the anti-wear and anti-oxidation ability of the lubricating oil in the high-temperature range.

[0057] Compared with Example 1, Examples 7-8 showed a significant decrease in friction coefficient, wear volume, and dispersion stability. Examples 7-8 changed the concentration of dopamine hydrochloride monomer in the preparation of temperature-sensitive microcapsules. In Example 7, the monomer concentration was too low, resulting in a thin polydopamine capsule wall with poor mechanical strength, which was prone to breakage under long-term circulating shear of lubricating oil, leading to premature leakage and failure of the capsule core ionic liquid. In Example 8, the monomer concentration was too high, resulting in a thick capsule wall and a high crosslinking density, causing the temperature-sensitive rupture temperature to rise to 142°C, which exceeded the temperature rise range of typical hydraulic drilling rig conditions. This caused a delay in high-temperature lubrication repair, preventing the timely formation of an effective lubricating film and thus losing the intelligent response capability.

[0058] Compared with Example 1, Comparative Example 3 showed an increase in friction coefficient and wear volume, and a decrease in dispersion stability. In Comparative Example 3, the temperature-sensitive microcapsules and graphene-boron nitride hybrid nanosheets were not pretreated to form a composite material. Due to the lack of protection of the hybrid nanosheets on the surface of the microcapsules, the microcapsules were directly exposed to mechanical shear and frictional heat in the base oil, which easily led to agglomeration and physical damage. At the same time, when the microcapsules ruptured, the hybrid nanosheets could not be released in synergy with them, resulting in a lack of nano-reinforcing phase in the repair film layer of the friction interface, which weakened the synergistic lubrication effect. This indicates that the pretreatment step anchored the nanosheets to the surface of the microcapsules through covalent bonding, which not only improved the storage and use stability of the microcapsules, but also achieved the synchronous release of the nano-reinforcing phase and the ionic lubricating liquid at the moment of rupture, which is beneficial to maintaining long-term low-friction performance under complex working conditions.

[0059] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A graphene-based lubricating oil for a hydraulic drilling rig, characterized by: The raw materials include the following parts by weight: 95-98 parts base oil, 0.2-0.5 parts sulfur-phosphorus type extreme pressure anti-wear agent, 0.5-2 parts quaternary ammonium salt ionic liquid, 0.4-0.5 parts hindered phenolic antioxidant, 0.1-0.3 parts temperature-sensitive microcapsules, and 0.3-0.5 parts graphene-boron nitride hybrid nanosheets.

2. The graphene-based lubricating oil for a hydraulic drilling rig according to claim 1, characterized in that: The core of the temperature-sensitive microcapsule is an ionic lubricating liquid, and the capsule wall is polydopamine. The core rupture temperature of the temperature-sensitive microcapsule is 115-130℃.

3. The graphene-based lubricating oil for a hydraulic drilling rig according to claim 1, characterized in that: The method for preparing the temperature-sensitive microcapsules includes the following steps: uniformly dispersing cellulose nanocrystals in water using ultrasound as the aqueous phase, using 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid as the oil phase, mixing the oil phase and the aqueous phase, and emulsifying at high speed at 8000-10000 r / min for 5-7 min to obtain a stable emulsion, adding dopamine hydrochloride monomer to the stable emulsion, adjusting the pH of the system to 8-9 using Tris-HCl buffer, reacting for 8-10 h, centrifuging, separating, and washing to obtain the temperature-sensitive microcapsules.

4. The graphene-based lubricating oil for a hydraulic drilling rig according to claim 1, characterized in that: The concentration of the cellulose nanocrystals in the emulsion is 0.5-0.8 wt%, and the mass ratio of the oil phase to the water phase is 1:(19-21).

5. The graphene-based lubricating oil for a hydraulic drilling rig according to claim 1, characterized in that: The preparation method of the graphene-boron nitride hybrid nanosheets includes the following steps: dispersing graphene oxide and aminated boron nitride in water at a mass ratio of 7:3, adding a reducing agent to carry out a hydrothermal reaction, carrying out the hydrothermal reaction at 140-160℃ for 8-10 hours, centrifuging, separating, washing, and drying to obtain graphene-boron nitride hybrid nanosheets.

6. A method for preparing graphene-based lubricating oil for a hydraulic drilling rig according to any one of claims 1-5, characterized in that: Includes the following steps: The graphene-boron nitride hybrid nanosheets and thermosensitive microcapsules were prepared. After pretreatment of the thermosensitive microcapsules with some graphene-boron nitride hybrid nanosheets, a nanosheet-thermosensitive microcapsule composite material was obtained. The nanosheet-thermosensitive microcapsule composite material, the remaining graphene-boron nitride hybrid nanosheets, and the hindered phenolic antioxidant are dispersed in a base oil and mixed evenly to obtain a graphene-based lubricating oil.

7. The method for preparing graphene-based lubricating oil for hydraulic drilling rigs according to claim 6, characterized in that: The pretreatment includes the following steps: aminated graphene-boron nitride hybrid nanosheets, then the aminated graphene-boron nitride hybrid nanosheets are mixed with thermosensitive microcapsules and dispersed in Tris-HCl buffer solution with pH 8-8.

5. After standing at 40-60℃ for 6-8 hours, the mixture is centrifuged, separated, washed, and dried to obtain the nanosheet-thermosensitive microcapsule composite material.

8. The method for preparing graphene-based lubricating oil for hydraulic drilling rigs according to claim 7, characterized in that: The mass ratio of the aminated graphene-boron nitride hybrid nanosheets to the thermosensitive microcapsules is 1:(1-1.5).