A multi-purpose composite lithium-based grease and its preparation method

Abstract

The present invention relates to the technical field of grease preparation, specifically a multi-purpose composite lithium-based grease and a preparation method thereof. The composite lithium-based grease comprises a base oil, a composite lithium-based thickener, and an additive, and is prepared by wrapping the base oil in a composite lithium-based thickener skeleton structure through a high-temperature micro-pressure reactor. The present invention uses epoxy resin to modify epoxidized castor oil, and the grease prepared has a small change in cone penetration, good stability, and acid corrosion resistance; by compounding fatty acids with different types of auxiliary acids, the composite lithium-based grease prepared has a high dropping point and is resistant to high temperatures; by modifying graphene oxide with ionic liquids, the grease prepared has a low volume resistivity and high conductivity, and can be used for lubrication of electronic components; by compounding α-layered zirconium phosphate with calcium carbonate, the grease prepared has good anti-wear performance and is suitable for long-term lubrication work.

Description

[0001] The present invention relates to the technical field of grease preparation, in particular to a multi-purpose composite lithium-based grease and a preparation method thereof. Background Art

[0002] Friction and wear are the primary causes of energy consumption and equipment damage in mechanical equipment. As the world advances the concept of sustainable development, energy and material conservation are becoming increasingly important. Lubrication technology is the primary means of reducing friction and wear. With the development of modern industry, the increasingly demanding operating conditions and diverse working environments of mechanical equipment are placing increasingly stringent demands on lubricants, urging the development of lubricants that are compatible with these requirements.

[0003] Grease is a key component of industrial lubricants. Grease technology has continuously evolved since its inception, resulting in a comprehensive range of lubricant products. As machinery and equipment evolve towards larger, smaller, higher-speed, heavier-load, vacuum-capable, cryogenic, ultra-high-precision, automated, and intelligent equipment, the demand for new, high-performance lubricants is growing. Developing high-performance greases that can be used in multiple applications, offer long life, and provide reliable lubrication offers significant market potential and economic benefits.

[0004] Lithium-complex grease is a high-temperature, multi-effect grease developed in the 1960s. Compared to lithium-based grease, it is more suitable for use at high temperatures, exhibits excellent multi-effect properties, and has a strong thickening ability for various mineral and synthetic oils. However, with the development of modern industry, industries such as food, automotive, printing and dyeing, mining, metallurgy, and aerospace have placed increasingly stringent requirements on grease's antioxidant properties, high and low temperature resistance, extreme pressure and anti-wear properties, water resistance, and mechanical stability.

[0005] Patent CN109810748B reports a lithium-based grease and its preparation method. The grease comprises a base oil, an anti-wear agent, a rust inhibitor, an antioxidant, a lubricant, a thickener, and a saponifier. The thickener is dodecyl stearic acid, and the saponifier is selected from lithium hydroxide monohydrate. The resulting lithium-based grease exhibits excellent stability and wear resistance. However, this type of grease has a low dropping point, resulting in decreased adhesion and oil separation at high temperatures. Furthermore, the use of organic rust and antioxidants can cause the grease to separate from the equipment, leading to poor lubrication and damage, and potentially causing environmental pollution.

[0006] Patent CN112877121B reports a grease, its preparation method and application. The grease is prepared using mineral oil as a base oil, a lithium-based composite as a thickener, and antioxidants, rust inhibitors, and extreme pressure anti-wear agents. The grease has good low-temperature resistance, but has a large cone penetration and poor grease stability, which limits the further use of the grease.

[0007] Patent CN109536260B reports an environmentally friendly grease with high lubrication performance and a preparation method thereof, which comprises base oil, 12-hydroxystearic acid, lithium hydroxide powder, a composite thermal stabilizer, an auxiliary thermal stabilizer, carboxymethyl cellulose, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, an antioxidant, graphite and glycerin. The grease prepared by this invention uses environmentally friendly additives, which increases the biodegradability of the grease and causes less pollution to the environment. However, the addition of a large amount of additives leads to uneven particle size distribution, and there is a trend of decreasing the total surface area of the particle phase, thereby accelerating the surface hardening phenomenon of this type of grease, while reducing the wear resistance of the grease and reducing the lubrication effect.

[0008] Patent CN102051257B reports on a composite lithium-based grease and its production process. By uniformly mixing 12-hydroxystearic acid, sebacic acid, lithium hydroxide, composite calcium sulfonate grease, base oil, tackifier, multifunctional agent, antioxidant, and metal passivator, the composite lithium-based grease produced has good lubrication performance in water-rich and heavy-load situations, extending the life of bearings. The addition of additives changes the performance of the grease, but also reduces the corrosion resistance of the grease. The lubrication performance is reduced under long-term use conditions, limiting the use of the lubricant.

[0009] Grease forms a lubricating film between the inner and outer rings of a bearing and the rolling elements. When a shaft voltage is generated on both sides of the oil film and exceeds a threshold, the lubricating film breaks down, generating a large transient current, which can damage the rolling elements and raceway surfaces. This phenomenon is called "electrolytic corrosion." Industrial development has made the operating conditions of motor bearings and electronic components increasingly complex, resulting in a variety of failure modes, including electrolytic corrosion, pitting, plastic deformation, wear, and fatigue. However, bearings are one of the key components of mechanical equipment and play a vital role in precision machinery. Therefore, the lubrication of bearings and electronic components also requires grease with certain conductive properties.

[0010] Patent CN102618359B reports a silicone-based grease composition for electrical contacts and its preparation method, which includes a silicone-based base oil, a thickener, and additives. The thickener is a complex lithium soap. The addition of graphite or zinc oxide as a conductive material can improve the conductive properties of the grease. However, the addition of solid conductive materials can improve the high-temperature resistance and conductivity of the grease, but the fluidity and lubricity are poor. At the same time, the addition of a large amount of inorganic substances further improves the antioxidant and corrosion resistance of the grease.

[0011] In summary, composite lithium-based grease is used in the prior art to improve the performance of grease and can be used in different lubrication occasions, but there are still some shortcomings; the grease has poor high-temperature resistance, low adhesion, the grease is easy to separate from the equipment, and the high-temperature lubrication performance is poor; the residual alkali in the preparation process of the grease has poor oxidation stability, which affects the corrosion resistance of the grease and has low stability, which is not conducive to the long-term effect of the grease; at the same time, it has the disadvantages of hardening tendency, poor rust resistance, large changes in high-temperature cone penetration, poor wear resistance, and poor lubrication effect; at the same time, it is used in different mechanical fields, such as motor bearings and electronic components, and while having good lubrication properties, it still needs to have certain electrical conductivity. The base oil or thickener used in the prior art is not environmentally friendly, and there are certain application restrictions in industries with environmental protection requirements.

[0012] Therefore, a multi-purpose composite lithium-based grease and a preparation method thereof are proposed. Summary of the Invention

[0013] The present invention aims to provide a multi-purpose composite lithium-based grease and a preparation method thereof. The modified castor oil is obtained by oxidizing castor oil and modifying it with epoxy resin, thereby increasing the hydrogen bonding force in the grease. The composite lithium-based grease has a working cone penetration of 242 / 0.1 mm and an extended working cone penetration of 275 / 0.1 mm, thereby improving stability. By compounding 12-hydroxystearic acid with stearic acid and changing the amount of auxiliary acid and fatty acid, the composite lithium-based grease has a dropping point of 326°C, a steel mesh oil separation rate of 1.28%, and improved heat resistance. By modifying the epoxidized castor oil and controlling the amount of modifier, the composite lithium-based grease has copper sheet acid corrosion resistance of 1a and steel sheet acid corrosion resistance of 1a, respectively, thereby improving acid corrosion resistance. Graphene oxide is modified with ionic liquid to increase the compatibility of solid graphene in the grease. The volume resistivity of the composite lithium-based grease is 0.82×10 9 Ω·cm, can be used for the lubrication of electronic components; by using α-layered zirconium phosphate and calcium carbonate in combination, the composite lithium-based grease produced has a steel ball wear spot diameter of 0.35mm, an average friction coefficient of 0.091, and good anti-wear performance.

[0014] To achieve the above object, the present invention provides the following technical solutions:

[0015] In one aspect, the present invention provides a method for preparing a multi-purpose composite lithium-based grease, characterized in that: the composite lithium-based grease comprises 75-100 parts of base oil, a composite lithium-based thickener, and additives;

[0016] The composite lithium-based thickener comprises 5-10 parts of 12-hydroxystearic acid, 1.5-4 parts of stearic acid, auxiliary acid, and 0.8-2 parts of lithium hydroxide;

[0017] The additives include 5-15 parts of modified graphene oxide, 4-13 parts of anti-wear agent, antioxidant, and rust inhibitor;

[0018] The modified graphene is prepared by modifying graphene oxide and ionic liquid in a ratio of 1-4:6-9;

[0019] The preparation method of the multi-purpose composite lithium-based grease comprises the following steps:

[0020] The lithium hydroxide is added to deionized water and stirred to obtain a lithium hydroxide solution; 50% of the base oil, the 12-hydroxystearic acid, and the stearic acid are added to a flask to obtain a dissolving system; the lithium hydroxide solution is added to the dissolving system, the temperature is raised to 95-100° C., and saponification is performed for 2 hours to obtain a system 1; the auxiliary acid is added to the system 1, the remaining amount of the lithium hydroxide solution is heated to 120-130° C., and saponification is performed for 1 hour to obtain a system 2; the system 2 is heated to 180-190° C., stirred and mixed for 3 hours. 0min to obtain system three; add 25% of the base oil in total to the system three, slowly raise the temperature to 220-225°C, and refine for 20min to obtain system four; add the remaining base oil to the system four, cool to 120°C, and keep warm for 10min to obtain a composite grease; add the modified graphene oxide, the anti-wear agent, the antioxidant, and the rust inhibitor to the composite grease, stir at 90°C for 30min to obtain a mixture; transfer the mixture to a degassing kettle for degassing, filter, and then package to obtain the composite lithium-based grease.

[0021] Preferably, the base oil is selected from modified castor oil, white oil, naphthenic oil, and polyalphaolefin oil.

[0022] Preferably, the preparation method of the modified castor oil comprises the following steps:

[0023] Castor oil, glacial acetic acid, and phosphoric acid are added to a three-necked flask to prepare a mixture; the mixture is stirred, the temperature is raised to 70° C., a 30% H2O2 solution is slowly added dropwise to the mixture, and the mixture is kept warm for 4 hours to obtain a reaction solution; the reaction solution is extracted with petroleum ether, rotary evaporated, and vacuum dried to obtain epoxidized castor oil; the epoxidized castor oil has an epoxidation degree of 0.5-2.2 mol / kg;

[0024] The modifier was added to a three-necked flask, and 50 ml of ethanol was added and stirred to dissolve to prepare a solution; 100 parts of the epoxidized castor oil was slowly added to the solution, and the mixture was reacted at 50° C. for 2 hours to prepare a reaction liquid; the reaction liquid was cooled to room temperature, the solvent was removed by rotary evaporation, and vacuum dried at 80° C. for 2 hours to prepare the modified castor oil.

[0025] Preferably, the modifier is selected from one of polymethacrylate, polyethylene, epoxy resin E42, epoxy resin E44, and bisphenol F; and the amount of the modifier is 1-5 parts.

[0026] Preferably, the auxiliary acid is selected from azelaic acid, adipic acid, boric acid, terephthalic acid, and dodecanedioic acid.

[0027] Preferably, the ionic liquid is selected from one of 1-butyl-3-methylimidazolium hexafluorophosphate, 1-decyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-decyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and bis(trifluoromethylsulfonyl)imide.

[0028] Preferably, the preparation method of modified graphene oxide comprises the following steps:

[0029] Concentrated sulfuric acid and concentrated nitric acid are mixed in a volume ratio of 3:1 to obtain a mixed acid solution; graphite and a 30% hydrogen peroxide solution are added to the mixed acid solution, and ultrasonic reaction is performed for 2 hours to obtain a graphene solution; the graphene solution is centrifuged to obtain a solid separator; the solid separator is washed with a 10% volume fraction hydrochloric acid solution, washed with deionized water, and vacuum dried at 80°C to obtain graphene oxide; the graphene oxide is added to anhydrous acetone, the ionic liquid is added under stirring, and ultrasonic dispersion is performed to obtain a mixed solution; the mixed solution is ground at room temperature for 4 hours to obtain a grind; the grind is placed in a vacuum drying oven at 80°C and dried for 24 hours to obtain the modified graphene oxide.

[0030] Preferably, the anti-wear agent is selected from a mixture of α-layered zirconium phosphate and calcium carbonate; the amount of the α-layered zirconium phosphate is 1-10 parts, and the particle size is 600-800 nm; the amount of the calcium carbonate is 1-5 parts.

[0031] Preferably, the antioxidant is selected from tert-butyl-4-hydroxyanisole, and the rust inhibitor is selected from zinc naphthenate.

[0032] Another aspect of the present invention provides a multi-purpose composite lithium-based grease, characterized in that: the composite lithium-based grease comprises the base oil, the composite lithium-based thickener, the modified graphene oxide, the anti-wear agent, the antioxidant, and the rust inhibitor; the composite lithium-based grease has a working cone penetration of 242 / 0.1 mm and an extended working cone penetration of 275 / 0.1 mm; the composite lithium-based grease has a dropping point of 326° C. and a steel mesh oil separation rate of 1.28%; the composite lithium-based grease has a copper sheet acid corrosion resistance and a steel sheet acid corrosion resistance of 1a and 1a, respectively; and the composite lithium-based grease has a volume resistivity of 0.82×10 9Ω·cm; the steel ball wear spot diameter of the composite lithium-based grease is 0.35mm, and the average friction coefficient is 0.091.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The present invention obtains epoxidized castor oil by oxidizing castor oil under acidic conditions, controls the epoxidation degree to improve the viscosity of the epoxidized castor oil, and modifies the castor oil to obtain an innovative method of modified castor oil. The presence of epoxy bonds is utilized to enhance the hydrogen bonding effect in the grease, increase the cohesion of the grease molecules, and fully wrap the base oil in a three-dimensional skeleton structure, thereby reducing the difference in the working cone penetration of the grease. The stability of the composite lithium-based grease is enhanced and improved. At the same time, the base oil used is a food-grade base oil. The grease has broad application prospects in industries that have color requirements or environmental protection requirements for the appearance of the grease, and is suitable for use in the food processing industry.

[0035] 2. The present invention uses a compound of 12-hydroxystearic acid and stearic acid, utilizes the electrostatic attraction between the carboxyl oxygen atoms in the stearic acid crystals and the auxiliary acid lithium crystals and the lithium ions, and generates a strong interaction to form a co-crystal, thereby producing an innovative means of producing a composite lithium-based thickener with a stable skeleton structure. The food-grade grease thickener achieves the high-temperature resistance of the composite lithium-based grease, as well as the improvement and enhancement of the oil separation rate of the steel mesh, and is suitable for use in food processing and high-temperature lubrication conditions.

[0036] 3. The present invention enhances the viscosity of the modified castor oil by modifying epoxidized castor oil with epoxy resin. At the same time, the introduction of polar groups can achieve better compatibility with the composite lithium-based thickener. At the same time, the epoxy resin can form a covalent bond with -OH, thereby enhancing the intermolecular force. The innovative means of forming a three-dimensional network cross-linked structure achieves the improvement of the corrosion resistance of the composite lithium-based grease, especially the acid corrosion resistance, and is suitable for use under acidic conditions.

[0037] 4. The present invention increases the electrical conductivity of grease by adding graphene oxide, and increases the compatibility of graphene oxide with grease base oil by modifying graphene oxide with ionic liquid. The innovative method of modifying graphene oxide with ionic liquid achieves improvement and enhancement of the electrical conductivity of composite lithium-based grease. The enhanced conductivity is suitable for lubrication of electronic components and electronic products.

[0038] 5. The present invention uses a compound of α-layered zirconium phosphate and calcium carbonate and adds them to a composite lithium-based grease. Through the innovative method of compounding the layered zirconium phosphate and calcium carbonate, the average friction coefficient of the composite lithium-based grease and the diameter of the wear spot of the steel ball are improved, thereby improving the anti-wear performance of the grease, facilitating the long-term operation of the grease under high-pressure and acidic working conditions, and reducing the cost of using the grease. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a SEM image of the α-layered zirconium phosphate prepared in Example 56;

[0040] Figure 2 This is a graph showing the change in volume wear of the steel disc and the wear spot diameter of the steel ball with the amount of α-layered zirconium phosphate used in the present invention. DETAILED DESCRIPTION

[0041] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0042] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or those recommended by the manufacturer. All reagents or instruments used, if the manufacturer is not specified, are commercially available conventional products.

[0043] The white oil of the present invention is selected from food grade white oil produced by Mobil Corporation of the United States.

[0044] The naphthenic oil of the present invention is selected from naphthenic oil 100SN, produced by Mobil Corporation of the United States.

[0045] The polyalphaolefin oil of the present invention is selected from PAO40, which is purchased from ExxonMobil.

[0046] See also Figures 1 to 2 The present invention provides a multi-purpose composite lithium-based grease and a preparation method thereof, and the technical solution is as follows:

[0047] Examples 1-5

[0048] Preparation of epoxidized castor oil:

[0049] 60 parts of castor oil, 9 parts of glacial acetic acid, and 0.6 parts of phosphoric acid were added to a three-necked flask equipped with a thermometer, a reflux condenser, and a dropping funnel to prepare a mixture. The mixture was stirred until the oil bath temperature reached 70° C. 6-48 parts of a 30% H 2 O 2 solution were slowly added dropwise to the mixture, and the mixture was kept warm for 4 hours to prepare a reaction solution. The reaction solution was extracted with petroleum ether, rotary evaporated, and vacuum dried to prepare epoxidized castor oil. The degree of epoxidation of the epoxidized castor oil was quantified according to ISO 3001:1999, and the epoxidation degree is shown in Table 1.

[0050] Table 1 Epoxy degree results of Examples 1-5

[0051]

[0052] Example 6

[0053] 3 parts of epoxy resin were added to a three-necked flask, and 50 ml of ethanol was added and stirred to dissolve to prepare a resin solution; 100 parts of the epoxidized castor oil prepared in Example 1 was weighed and slowly added to the resin solution, and the mixture was reacted at 50° C. and 400 rpm for 2 hours to prepare a reaction solution; the reaction solution was cooled to room temperature, the solvent was removed by rotary evaporation, and the mixture was vacuum dried at 80° C. for 2 hours to prepare the modified castor oil.

[0054] Add 1.5 parts of lithium hydroxide to 15 ml of deionized water and stir evenly to prepare a lithium hydroxide solution; add half of the total amount of the modified castor oil, 8 parts of 12-hydroxystearic acid, and 1.5 parts of stearic acid to a three-necked flask, heat to 80°C, and keep warm for 30 minutes to prepare a dissolution system; add 1 part of the lithium hydroxide solution to the dissolution system, heat to 100°C, and saponify at a constant temperature for 2 hours to prepare a saponification system 1; add 2.5 parts of azelaic acid to the saponification system 1, and heat 0.5 parts of the lithium hydroxide solution to 120°C, and saponify at a constant temperature for 1 hour to prepare a saponification system 2; heat the saponification system 2 to 180°C, mix at a constant temperature for 30 minutes, and accelerate stirring. Stir to obtain saponification system three; add 25% of the modified castor oil to the saponification system three, slowly raise the temperature to 210° C., and keep it warm for 20 minutes to obtain saponification system four; add the remaining modified castor oil to the saponification system four, cool it to 120° C., and keep it warm for 10 minutes to obtain a composite grease; add 10 parts of modified graphene oxide, 5 parts of α-layered zirconium phosphate, 3 parts of calcium carbonate, 0.5 parts of tert-butyl-4-hydroxyanisole, and 0.5 parts of zinc cyclohexane to the composite grease, stir at 90° C. for 30 minutes, and stir evenly to obtain a mixture; transfer the mixture to a degassing kettle for degassing, filter, and then package to obtain the composite lithium-based grease.

[0055] Examples 7-10 The preparation method and parameter conditions described in Example 6 were referred to, except that the modified castor oil prepared in Examples 2-5 was used respectively.

[0056] Examples 11-19 were prepared according to the preparation method and parameter conditions described in Example 6, with the differences shown in Table 2.

[0057] Comparative Example 1 The preparation method and parameter conditions described in Example 6 were used with the exception that castor oil was used as the base oil.

[0058] Comparative Example 2 The preparation method and parameter conditions described in Example 6 were referred to, except that epoxidized castor oil was used as the base oil.

[0059] Example 20 Stability Performance Determination

[0060] The greases prepared in Examples 6-19 and Comparative Examples 1-2 were tested for working cone penetration and extended cone penetration, respectively, to evaluate the stability of the prepared greases. The test results are shown in Table 2.

[0061] Working cone penetration: Place the grease sample in a standard working device and, at 25°C, after 60 shear cycles, measure the cone penetration to be 0.1 mm. This is determined in accordance with GT / T269-1991.

[0062] Extended working cone penetration: The cone penetration value of the grease after 100,000 shear cycles in a standard working device at 25°C is 0.1mm; it is measured in accordance with GT / T269-1991 standard.

[0063] The cone penetration tester model is BF-38A.

[0064] Table 2 Stability performance determination of Examples 6-19

[0065]

[0066] The results in Table 2 show that the unmodified castor oil used in Comparative Example 1 exhibits a significantly reduced viscosity, and the prepared grease has a high working penetration, but the grease is in a liquid state and has poor bonding properties, making it unsuitable for lubricating daily mechanical bearings. In Comparative Example 2, the epoxidized castor oil modified with epoxy resin is not added, and the working penetration of the prepared grease is significantly reduced compared to that in Comparative Example 1, and the grease has good stability. Since the epoxy resin contains a large number of epoxy bonds, the force of its hydrogen bonds can be enhanced. In addition, the epoxy resin forms a covalent bond with the -OH in the epoxidized castor oil, thereby enhancing the intermolecular force and improving the The working cone penetration and extended cone penetration of the grease; the results of Examples 6-15 show that the use of different base oils as the base oil of the grease results in significant differences in the stability of the grease due to the differences in the properties of the prepared lubricating oils. The cone penetration of the grease synthesized from paraffin oil is significantly smaller than that of the grease synthesized from polyalphaolefin oil. Since polyalphaolefin oil has a highly polymerized molecular chain and weak polarity, it is difficult for the polar groups in the complex lithium group to bond to form a skeleton structure, which reduces its thickening ability and improves the working cone penetration; the same cycloalkyl oil has a reduced thickening ability due to the interaction of the rigid cycloalkyl groups; as the cycloalkyl groups The increase in oxygen value shows a significantly improved cone penetration, which improves the application of grease in mechanical lubrication. Due to the increase in oxidation value, the cross-linking of modified castor oil in the composite lithium-based thickener is increased. The presence of epoxy bonds enhances the hydrogen bonding effect in the grease, increases the cohesion of the grease molecules, and fully wraps the base oil in the three-dimensional skeleton structure, thereby improving the working cone penetration of the grease and enhancing the stability of the grease. The results of Examples 16-19 and Example 10 show that with the increase in the amount of base oil, the working cone penetration gradually increases; the low base oil content and the rigid network structure reduce the viscosity of the grease. Grease is relatively hard, with poor lubrication effect and low stability. Increasing the base oil content can increase the viscosity of the grease and increase the cross-linking degree with the thickener. However, excessively high viscosity leads to high fluidity of the grease, which cannot be fully adsorbed by the skeleton structure, resulting in poor lubrication. At the same time, the exposed epoxy groups are easily affected by the environment, reducing the stability of the grease. Based on the results in Table 2, it can be seen that by using epoxy resin to modify castor oil and controlling the amount of base oil, the composite lithium-based grease prepared has a working cone penetration of 242 / 0.1mm and an extended working cone penetration of 275 / 0.1mm, enhanced shear resistance, and significantly improved stability.

[0067] Examples 21-36

[0068] 0.8-2 parts of lithium hydroxide were added to 15 ml of deionized water and stirred to obtain a lithium hydroxide solution; 45 parts of the modified castor oil obtained in Example 5 were taken, 5-10 parts of 12-hydroxystearic acid and 1.5-4 parts of stearic acid were weighed, and the mixture was added to a three-necked flask, heated to 80° C., and kept warm for 30 minutes to obtain a dissolution system; half of the total amount of the lithium hydroxide solution was added to the dissolution system, the temperature was raised to 100° C., and the saponification system was saponified at a constant temperature for 2 hours to obtain a saponification system 1; 1.5-5 parts of an auxiliary acid were added to the saponification system 1, and the remaining amount of the lithium hydroxide solution was heated to 120° C. and saponified at a constant temperature for 1 hour to obtain a saponification system 2; the saponification system 2 was heated to 180° C. and kept warm. The mixture was mixed at room temperature for 30 minutes with accelerated stirring to obtain saponification system three; 20 parts of the modified castor oil were added to the saponification system three, the temperature was slowly raised to 210° C., and the mixture was kept warm for 20 minutes to obtain saponification system four; 20 parts of the modified castor oil were added to the saponification system four, the temperature was lowered to 120° C., and the mixture was kept warm for 10 minutes to obtain a composite grease; 10 parts of modified graphene oxide, 5 parts of α-layered zirconium phosphate, 3 parts of calcium carbonate, 0.5 parts of tert-butyl-4-hydroxyanisole, and 0.5 parts of zinc cyclohexane were added to the composite grease, and the mixture was stirred at 90° C. for 30 minutes to obtain a mixture; the mixture was transferred to a degassing kettle for degassing, filtered, and then packaged to obtain the composite lithium-based grease.

[0069] The specific differences are shown in Table 3.

[0070] Table 3 Differences in the dosage of components in Examples 21-36

[0071]

[0072] Comparative Example 3 The preparation method and parameter conditions are the same as those in Example 21, except that only 12-hydroxystearic acid is added.

[0073] Comparative Example 4 The preparation method and parameter conditions are the same as those in Example 21, except that only stearic acid is added.

[0074] Example 37 Grease Temperature Resistance Test

[0075] The dropping points of the greases prepared in Examples 19-31 were measured using a wide temperature range dropping point tester for grease (SYD-3498-I), and the test standard was GT / T3498-2008.

[0076] The oil separation rate of the grease steel mesh prepared in Examples 19-31 was measured using a grease cone mesh oil separation tester (BF-54B) according to the SH / TT0324-2004 standard. The test results are shown in Table 4.

[0077] Table 4 Temperature resistance test of Examples 21-36

[0078]

[0079] The results in Table 4 show that the dropping point of the composite lithium-based grease generated by saponification reaction of 12-hydroxystearic acid as a long-chain acid with lithium hydroxide in Comparative Example 3 is significantly higher than that of the grease formed by saponification of only stearic acid and lithium hydroxide in Comparative Example 4, but the oil separation rate of the steel mesh is also significantly improved; since the hydroxyl group can make the organic chain force stronger, thereby forming a more stable soap fiber structure, the composite lithium-based grease generates electrostatic attraction between the carboxyl oxygen atoms in the 12-hydroxystearic acid crystals and the lithium azelaic acid crystals and the lithium ions, resulting in strong interaction to form co-crystallization, resulting in a stable skeleton structure, making the lubricant The grease obtains high-temperature heat resistance, and the excess hydroxyl groups cross-link with the base oil and are easily destroyed under high temperature, thereby increasing the oil separation rate of the steel mesh. The results of Examples 21-26 show that as the proportion of 12-hydroxystearic acid increases, the dropping point of the grease gradually increases, the oil separation rate of the steel mesh gradually increases, and the colloidal stability of the grease gradually decreases. As the content of stearic acid increases, the dropping point of the grease does not increase significantly, but the oil separation rate of the steel mesh gradually decreases. The introduction of stearic acid reduces the interaction between the base oil and the saponified lithium, while reducing the content of hydroxyl groups, thereby avoiding the loss of base oil under high temperature conditions. Increase colloid stability; The results of Examples 22 and 27-33 show that with the change of the type of auxiliary acid, the dropping point of the composite lithium-based grease and the oil separation rate of the steel mesh change significantly. The preparation mechanism of the composite lithium-based grease is that long-chain fatty acids and small molecule acids associate through hydrogen bonds, and long-chain fatty acids associate through lithium bond saponification to form a composite lithium-based grease, and cross-link with the base oil to change the viscosity of the base oil. Therefore, the longer the hydrogen bond length formed by the composite lithium-based grease, the higher the dropping point, and vice versa. The adipic acid composite lithium soap has a longer hydrogen bond length than other organic dibasic acid composite lithium soaps, so the dropping point is significantly reduced; according to the unit cell structure By calculating the bulk modulus based on the structural change, it can be found that the bulk modulus of the lithium soap azelaic acid complex is large due to the small rate of molecular shape change under heat or external influences. Therefore, the soap fiber structure formed is very adsorbent and the base oil is not easily lost, resulting in a high dropping point of the grease. However, the bulk modulus of the lithium soap azelaic acid and terephthalic acid complex is small, and the base oil in the unit cell is easily squeezed out, so the dropping point is low and the steel mesh oil separation rate is high. The results of Examples 22 and 34-36 show that with the increase of lithium hydroxide dosage, the dropping point gradually increases, the associative saponification increases, and the internal force of the grease is strong. However, excessive lithium hydroxide will affect the thickening degree of the grease. Comprehensively considering the results in Table 4, it can be seen that the use of 12-hydroxystearic acid and stearic acid in combination, the selection of azelaic acid as the auxiliary acid, and the control of the acid dosage can produce a lithium-based composite grease with a dropping point of 326°C and a steel mesh oil separation rate of 1.28%, which has significantly improved high temperature resistance.

[0080] Example 38

[0081] The modifier methacrylate was added to a three-necked flask, and 50 ml of ethanol was added and stirred to dissolve to prepare a resin solution. 100 parts of the epoxidized castor oil prepared in Example 5 was weighed and slowly added to the resin solution. The mixture was reacted at 400 rpm at 50° C. for 2 h to obtain a reaction solution. The reaction solution was cooled to room temperature, the solvent was removed by rotary evaporation, and vacuum dried at 80° C. for 2 h to obtain the modified castor oil.

[0082] The preparation method and parameter conditions of the composite lithium-based grease are prepared with reference to Example 20.

[0083] Examples 39-45 The preparation methods and parameter conditions of Example 33 are referred to, with the differences shown in Table 5.

[0084] Comparative Example 5 The preparation method and parameter conditions are the same as those in Example 33, except that no modifier is added to modify the castor oil.

[0085] Example 46 Acid resistance test

[0086] The corrosion resistance of the grease was tested using a copper sheet / steel sheet with a size of 20×50×3mm. Before the experiment, the copper sheet / steel sheet was polished, ultrasonically cleaned several times and dried. The grease prepared in Examples 33-40 and Comparative Example 5 was evenly applied to the dry copper sheet with a spoon to a thickness of 2mm. The copper sheet was placed obliquely in a beaker, and a 3% by mass HCl solution was added to the beaker and placed at 100°C for 48h. After the experiment, the grease on the metal surface was thoroughly cleaned and dried, and compared with the standard copper sheet corrosion color chart according to GB / T7326-1987. The experimental results are shown in Table 5.

[0087] Among them, 1a is a copper / steel sheet with a light yellow color, 1b is a light orange color, 2a is an orange-red color, and 2b is a purple-red color.

[0088] Table 5 Acid resistance test of Examples 38-45 and Comparative Example 5

[0089]

[0090] The results in Table 5 show that the acid corrosion resistance of the composite lithium-based grease obtained by not using a modifier to modify the epoxy resin in Comparative Example 5 is significantly lower than that of Examples 38-45. Since the epoxidized castor oil base oil contains polar epoxy groups, the hydroxyl groups are freed on the surface of the grease during the saponification process, which increases the hydrophilicity of the grease. Under acidic conditions, water molecules combine with the polar groups and release active H +, enters the interior of the grease, affects the thickening performance of the lithium soap, and causes the acid resistance of the grease to decrease; the results of Examples 38-42 show that the type of modifier has a greater influence on the acid resistance. The use of polymethyl methacrylate contains more C=O bonds, and a small amount can enhance the colloidal structure of the lithium grease, but the polarity of the C=O bond is strong. After reaching a certain amount, the strong polarity will affect the colloidal structure of the grease and lower its dropping point; in addition, the interaction between polymethyl methacrylate and lithium grease is a relatively weak interatomic interaction force, and no covalent bond is formed, which cannot achieve the strong interaction force to fix the colloidal structure of the lithium grease; the 12-hydroxystearic acid lithium soap contains The colloidal structure formed by the base oil contains a large number of -OH groups, which strengthens the hydrogen bonding force between molecules. The epoxy resin contains a large number of -O- bonds, which can enhance the hydrogen bonding force. In addition, the epoxy resin can form covalent bonds with -OH, thereby also enhancing the intermolecular force. The three-dimensional cross-linked network structure formed can effectively improve the corrosion resistance of the grease. However, excessive -OH structures will increase the oil separation rate of the grease steel mesh, and the epoxy degree of the epoxy resin should be controlled. Comparing the results of Example 38 and Examples 43-45, it can be seen that with the increase of epoxy resin content, the acid corrosion resistance of the grease gradually increases, and all show a level of 1a. Comprehensive Table 5 shows that using epoxy resin E42 as a modifier to modify epoxidized castor oil, the composite lithium-based grease obtained has a copper sheet acid corrosion resistance of 1a and a steel sheet acid corrosion resistance of 1a, respectively, showing significantly improved acid corrosion resistance.

[0091] Example 47

[0092] Preparation of modified graphene oxide:

[0093] Concentrated sulfuric acid and concentrated nitric acid are mixed in a volume ratio of 3:1 to obtain a mixed acid solution; 15 parts of graphite powder and 5 parts of 30% hydrogen peroxide solution are added to 10 ml of the mixed acid solution, and ultrasonic reaction is performed for 2 hours to obtain a graphene solution; the graphene solution is centrifuged to obtain a solid separator; the solid separator is washed with a 10% volume fraction hydrochloric acid solution, washed with deionized water, and vacuum dried at 80°C to obtain graphene oxide; 9 parts of the graphene oxide are added to anhydrous acetone, 1 part of an ionic liquid is added under stirring, and ultrasonic dispersion is performed to obtain a mixed solution; the mixed solution is ground at room temperature for 4 hours to obtain a grind; the grind is placed in a vacuum drying oven at 80°C and dried for 24 hours to obtain the modified graphene oxide.

[0094] The preparation method and parameter conditions of the composite lithium-based grease are prepared with reference to Example 40.

[0095] Examples 47-57 The preparation methods and parameter conditions are similar to those of Example 42, with the differences shown in Table 6.

[0096] Comparative Example 6 The preparation method and parameter conditions are similar to those of Example 42, except that no ionic liquid modification treatment is added.

[0097] Example 58 Conductive Performance Measurement

[0098] The volume resistivity of the composite lithium-based greases prepared in Examples 47-57 and Comparative Example 6 was measured using a GEST-121 volume resistivity tester produced by Beijing Guanshi Precision Instrument Equipment Co., Ltd. The test current was 100 A and the indoor test time was 10 s.

[0099] ρ=R×A / h

[0100] Where: ρ (Ω·cm) is the volume resistivity of the grease; R (Ω) is the volume resistance; A (cm 2 ) is the contact area; h (cm) is the average thickness of the sample. The measurement results are shown in Table 6.

[0101] Table 6 Conductivity test of Examples 47-57 and Comparative Example 6

[0102]

[0103] As shown in Table 6, the volume resistivity of the graphene oxide modified without ionic liquid in Comparative Example 6 is significantly improved compared with that of Examples 47-57, indicating that the addition of ionic liquid can synergistically reduce the volume resistivity of the composite lithium-based grease with graphene oxide, thereby improving the conductivity of the lubricant. As shown in the results of Examples 47-50, the type of ionic liquid has a significant effect on the volume resistivity. The use of graphene oxide modified with ionic liquid greatly reduces the volume resistivity of the grease, indicating that conductive ionic liquids can greatly improve the conductivity of the grease. In addition, under the same cation conditions, the volume resistivity of the graphene oxide modified with trifluoromethanesulfonyl is lower than that of the graphene oxide modified with hexafluorophosphate. When the anions are the same, the volume resistivity of the grease increases with the increase of the length of the alkyl carbon chain of the cation. Since the anions are the same, the van der Waals force and the associative force are relatively reduced, and the conductivity increases with the increase of the cation chain length; for ionic liquids with the same cations, smaller anions have more dispersed charges, resulting in weaker hydrogen bonds and binding with cations, thereby increasing the conductivity of the grease; it can be seen from the results of Examples 51-54 that with the increase of the ionic liquid content, the volume resistivity of the composite lithium-based grease slowly decreases, but the decrease is small; the results of Examples 51 and Examples 55-57 show that with the increase of the amount of modified graphene oxide, the volume resistivity shows a trend of first increasing and then decreasing. Compared to traditional ionic liquids, bis(trifluorosulfonate) ionic liquids coordinate the polarity and conductivity of ionic liquids. While meeting the conductivity requirements, they also improve oil solubility, allowing ionic liquids to be stably dispersed in greases for a long time. The addition of graphene oxide solids makes it difficult to enter the oil film at the lubrication interface, and increasing the amount hinders its conductive effect. However, the addition of ionic liquids can enter the oil film, significantly reducing interfacial resistance and reducing friction and wear. However, the addition of excessive ionic liquids reduces the viscosity of composite lithium-based greases, reducing the basic performance of the grease. The results in Table 6 show that the volume resistivity of the composite lithium-based grease prepared by using bis(trifluorosulfonate) modified graphene oxide and controlling the amount is 0.82×10 9 Ω·cm, with significantly improved conductivity.

[0104] Example 59

[0105] Preparation of α-layered zirconium phosphate:

[0106] 5 parts of sodium chloride, 10 parts of zirconium oxychloride octahydrate and 300 ml of distilled water are fully stirred and dissolved in a reactor to obtain a dissolution solution; 20 parts of phosphoric acid are added to the dissolution solution, stirred evenly and aged at room temperature for 24 hours to obtain a mixture; the mixture is placed in an oven and reacted at 160° C. for 36 hours to obtain a reactant; the reactant is washed with distilled water until neutral, naturally air-dried and ground to obtain the α-layered zirconium phosphate; the particle size of the α-layered zirconium phosphate is 600 nm.

[0107] The preparation method and parameter conditions of the complex lithium-based grease are prepared with reference to Example 35.

[0108] Example 60

[0109] 8 parts of sodium chloride, 10 parts of zirconium oxychloride octahydrate and 300 ml of distilled water are fully stirred and dissolved in a reactor to obtain a dissolution solution; 20 parts of phosphoric acid are added to the dissolution solution, stirred evenly and aged at room temperature for 24 hours to obtain a mixture; the mixture is placed in an oven and reacted at 180° C. for 36 hours to obtain a reactant; the reactant is washed with distilled water until neutral, naturally air-dried and ground to obtain the α-layered zirconium phosphate; the particle size of the α-layered zirconium phosphate is 700 nm.

[0110] The preparation method and parameter conditions of the complex lithium-based grease are prepared with reference to Example 35.

[0111] Example 61

[0112] 10 parts of sodium chloride, 10 parts of zirconium oxychloride octahydrate and 300 ml of distilled water were fully stirred and dissolved in a reactor to obtain a solution; 20 parts of phosphoric acid were added to the solution, stirred evenly and aged at room temperature for 24 hours to obtain a mixture; the mixture was placed in an oven and reacted at 200° C. for 36 hours to obtain a reactant; the reactant was washed with distilled water until neutral, naturally air-dried and ground to obtain the α-layered zirconium phosphate; the particle size of the α-layered zirconium phosphate was 800 nm; the SEM image of the α-layered zirconium phosphate is shown as follows Figure 1 shown.

[0113] The preparation method and parameter conditions of the complex lithium-based grease are prepared with reference to Example 35.

[0114] Examples 62-68 were prepared according to the method and parameters of Example 54, with the differences shown in Table 7.

[0115] Table 7 Component dosage of Examples 59-68

[0116]

[0117] Comparative Example 7 The preparation method and parameter conditions were similar to those of Example 59, except that α-layered zirconium phosphate and calcium carbonate were not added.

[0118] Comparative Example 8 The preparation method and parameter conditions were the same as those in Example 59, except that calcium carbonate was not added.

[0119] Example 69 Friction Resistance Measurement

[0120] The composite lithium-based greases prepared in Examples 59-68 and Comparative Examples 7-8 were subjected to wear and friction reduction tests using a German OPTIMOL SRV-V friction and wear tester. The test was carried out at a load of 300 N, a frequency of 50 Hz, a stroke of 1 mm, a temperature of 80°C, and a time of 60 min. The results are shown in Table 8. The volume wear of the steel disc and the wear spot diameter of the steel ball changed with the amount of α-layered zirconium phosphate used. Figure 2 shown.

[0121] Table 8 Friction resistance test of Examples 59-68 and Comparative Examples 7-8

[0122]

[0123] From the results in Table 8, it can be seen that in Comparative Example 7, no α-layered zirconium phosphate and calcium carbonate were added as extreme pressure and anti-wear agents, and the friction coefficient of the composite lithium grease obtained was high, and the wear amount and wear spot diameter were significantly increased compared with Examples 59-68; Comparative Example 8 added α-layered zirconium phosphate, and no calcium carbonate was added as an auxiliary, and the pressure reduction and anti-wear performance of the grease obtained was significantly improved compared with Comparative Example 8, but there was still a gap compared with the Examples, indicating that calcium carbonate can synergize with zirconium phosphate to change the extreme pressure and anti-wear performance of the grease; From the results of Examples 59-61, it can be seen that with the change of the particle size of α-layered zirconium phosphate, there is almost no effect on the friction performance of the grease, because the addition of composite calcium carbonate compensates for the friction deterioration caused by pitting corrosion; From the results of Examples 59 and Examples 62-65, it can be seen that with the increase of the amount of α-layered zirconium phosphate, the volume wear amount of the steel disc increases. It shows a significant reduction, the wear spot diameter and friction coefficient are significantly reduced, and the friction resistance is improved; zirconium phosphate has a layered structure, and during the friction process, it produces slippage between layers on the friction surface, which hinders the direct contact of the metal surface, effectively reduces the friction and wear of the metal, and increases the load-bearing capacity of the grease. At the same time, the presence of phosphorus can effectively improve the anti-wear ability of the grease and reduce the friction of the metal surface under medium load conditions; the results of Examples 59 and 66-68 show that changing the amount of calcium carbonate has a certain effect on the friction coefficient and average wear spot diameter of the grease. By compounding two calcium carbonates with different particle sizes, the lubrication performance of the grease can be improved according to the needs under different working conditions. Once pitting occurs on the tooth surface, the two calcium carbonates can fill and remedy the pitting site in time to avoid expansion, thereby extending the service life of the machine. Comprehensive Table 8 and Figure 2The results show that the composite lithium-based grease prepared by combining α-layered zirconium phosphate and calcium carbonate has a steel ball wear spot diameter of 0.35 mm and an average friction coefficient of 0.091, with significantly improved pressure relief and anti-wear performance.

[0124] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a multi-purpose composite lithium-based grease, characterized in that: The composite lithium-based grease comprises 75-100 parts of base oil, a composite lithium-based thickener, and additives; The composite lithium-based thickener comprises 5-10 parts of 12-hydroxystearic acid, 1.5-4 parts of stearic acid, 2.5 parts of auxiliary acid, and 0.8-2 parts of lithium hydroxide; The additives include 5-15 parts of modified graphene oxide, 4-13 parts of anti-wear agent, 0.5 parts of tert-butyl-4-hydroxyanisole, and 0.5 parts of zinc naphthenate; The modified graphene oxide is prepared by modifying graphene oxide and ionic liquid in a ratio of 1-4:6-9; The preparation method of the multi-purpose composite lithium-based grease comprises the following steps: The lithium hydroxide is added to deionized water and stirred to obtain a lithium hydroxide solution; 50% of the base oil, the 12-hydroxystearic acid, and the stearic acid are added to a flask to obtain a dissolving system; the lithium hydroxide solution is added to the dissolving system, the temperature is raised to 95-100° C., and saponification is performed for 2 hours to obtain a system 1; the auxiliary acid is added to the system 1, the remaining amount of the lithium hydroxide solution is heated to 120-130° C., and saponification is performed for 1 hour to obtain a system 2; the system 2 is heated to 180-190° C., stirred and kneaded for 30 minutes, Prepare system three; add 25% of the base oil to the system three, slowly raise the temperature to 220-225°C, and refine for 20 minutes to prepare system four; add the remaining base oil to the system four, cool to 120°C, and keep warm for 10 minutes to prepare a composite grease; add the modified graphene oxide, the antiwear agent, the tert-butyl-4-hydroxyanisole, and the zinc cyclohexane to the composite grease, stir at 90°C for 30 minutes to prepare a mixture; transfer the mixture to a degassing kettle for degassing, filter, and package to prepare the composite lithium-based grease; The auxiliary acid is azelaic acid; the ionic liquid is bistrifluorosulfonate; The anti-wear agent is selected from a mixture of α-layered zirconium phosphate and calcium carbonate; the amount of the α-layered zirconium phosphate is 1-10 parts, and the particle size is 600-800nm; the amount of the calcium carbonate is 1-5 parts; The base oil is modified castor oil; The preparation of the modified castor oil comprises the following steps: Castor oil, glacial acetic acid, and phosphoric acid are added to a three-necked flask to prepare a mixture; the mixture is stirred, the temperature is raised to 70° C., a 30% H2O2 solution is slowly added dropwise to the mixture, and the mixture is kept warm for 4 hours to obtain a reaction solution; the reaction solution is extracted with petroleum ether, rotary evaporated, and vacuum dried to obtain epoxidized castor oil; the epoxidized castor oil has an epoxidation degree of 0.5-2.2 mol / kg; Epoxy resin E42 was added to a three-necked flask, and 50 ml of ethanol was added and stirred to dissolve to prepare a solution; 100 parts of the epoxidized castor oil was slowly added to the solution, and the mixture was reacted at 50° C. for 2 hours to prepare a reaction liquid; the reaction liquid was cooled to room temperature, the solvent was removed by rotary evaporation, and vacuum dried at 80° C. for 2 hours to prepare the modified castor oil.

2. The method for preparing a multi-purpose composite lithium-based grease according to claim 1, wherein: The preparation method of the modified graphene oxide comprises the following steps: Concentrated sulfuric acid and concentrated nitric acid are mixed in a volume ratio of 3:1 to obtain a mixed acid solution; graphite and a 30% hydrogen peroxide solution are added to the mixed acid solution, and ultrasonic reaction is performed for 2 hours to obtain a graphene solution; the graphene solution is centrifuged to obtain a solid separator; the solid separator is washed with a 10% volume fraction hydrochloric acid solution, washed with deionized water, and vacuum dried at 80°C to obtain the graphene oxide; the graphene oxide is added to anhydrous acetone, and the bistrifluorosulfonic acid ester is added under stirring, and ultrasonic dispersion is performed to obtain a mixed solution; the mixed solution is ground at room temperature for 4 hours to obtain a grind; the grind is placed in a vacuum drying oven and dried at 80°C for 24 hours to obtain the modified graphene oxide.

3. A multi-purpose lithium-based composite grease, characterized by: The composite lithium-based grease includes modified castor oil, a composite lithium-based thickener, modified graphene oxide, a mixture of α-layered zirconium phosphate and calcium carbonate, tert-butyl-4-hydroxyanisole and zinc cyclohexane; the composite lithium-based grease is prepared by the preparation method according to any one of claims 1 to 2.

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