Hydrotalcite nano composite material based on multi-carboxyl-hydroxyl structure and eutectic intercalation thereof, preparation method and application of hydrotalcite nano composite material as lubricating additive

Abstract

The invention provides a hydrotalcite nano composite material based on a multi-carboxyl-hydroxyl structure and a eutectic intercalation layer thereof, a preparation method and application of the hydrotalcite nano composite material as a lubricating additive. The method comprises the steps of multi-carboxyl-hydroxyl compound eutectic preparation, hydrotalcite precursor preparation and intercalation hydrotalcite nano composite material preparation. The interlayer spacing of hydrotalcite is increased from 0.76 nm to 1.01-1.21 nm through a coprecipitation-intercalation process, the intercalated hydrotalcite nanocomposite with the thickness of 50-100 nm is obtained, and the intercalated hydrotalcite nanocomposite provided by the invention is added into basic lubricating oil as a lubricating additive, so that the wear volume is remarkably reduced, the friction coefficient is reduced, a curve is stable, and the wear resistance of the lubricating oil is improved. The excellent antifriction and antiwear properties are shown.

Description

Technical Field

[0001] This application relates to the field of lubrication technology, and in particular to a nanocomposite material based on a polycarboxy-hydroxyl structure and its eutectic intercalation layered hydrotalcite, its preparation method, and its application as a lubricating additive. Background Technology

[0002] The energy loss, increased time and cost, and reduced productivity caused by friction and wear in the operation of current mechanical equipment remain unresolved. Therefore, designing a lubricant additive that is easy to synthesize, environmentally friendly, and highly stable is crucial for improving energy efficiency. In recent years, traditional lubricant additives have been found to decompose at high temperatures, producing harmful substances and being environmentally unfriendly, making them unsuitable for the requirements of "green and environmentally friendly" lubricants. Nanomaterials have come into focus. With their extremely small size, nanomaterials can fill depressions on worn surfaces, providing timely repair; they can form a uniform and dense friction film on worn surfaces; and they maintain stable lubrication performance at high temperatures. Among the many types of nanomaterials, layered materials, with their unique morphology and interaction forces, have become an important component of high-performance lubricants. Specifically, the layers of layered lubricants are bonded by weak van der Waals forces or other non-covalent bonds. This internal structure allows for interlayer slip during friction, resulting in excellent friction-reducing and anti-wear properties. Layered double hydroxides (LDHs), due to their unique layered structure and intercalation capability, have become an ideal carrier for solving the dispersion problem of nanomaterial additives.

[0003] The LDH layers carry positive charges, and the edge -OH groups readily form hydrogen bonds with functional groups such as carboxylic acids and phosphate esters. The interlayer spacing is adjustable, allowing for the quantitative insertion of substances such as MoS2, graphene, ionic liquids, and organic acids to achieve a two-dimensional composite structure. The raw materials are inorganic salts [Al(NO3)3•9H2O and Zn(NO3)2•6H2O], making it green, pollution-free, and low-cost. The performance of nanocomposites varies depending on the intercalating materials and preparation methods. To date, research on layered hydrotalcite materials is still expanding. There is considerable research on modified functionalized hydrotalcites for adsorption and catalysis, and some studies involve the intercalation of functionalized hydrotalcites with different ionic liquids. However, research on intercalated functionalized hydrotalcite composites in the field of tribology is limited. Based on the literature reviewed so far, research on intercalated hydrotalcites can be explored from aspects such as preparation methods, the physicochemical properties of the intercalated materials, and the intercalation mechanism, and innovations can be made in these areas. Summary of the Invention

[0004] This application provides a multi-carboxy-hydroxyl structure and its eutectic intercalated hydrotalcite nanocomposite material, its preparation method, and its application as a lubricating additive, in order to solve the problems mentioned in the background art.

[0005] In a first aspect, this application provides a method for preparing a hydrotalcite nanocomposite material based on a polycarboxy-hydroxyl structure and its low eutectic intercalation, the method comprising the following steps: (1) Preparation of hydrotalcite precursor: Al(NO3)3•9H2O and Zn(NO3)2•6H2O were mixed in a molar ratio of 1:1-3 and dissolved in a solvent to obtain a salt solution. Sodium carbonate solution and sodium hydroxide solution were mixed to obtain an alkaline solution. The alkaline solution was added dropwise to the salt solution until the pH value of the solution was 9-12 to obtain the first reaction solution. The first reaction solution was heated and reacted for 8-10 hours to obtain the hydrotalcite precursor. (2) Preparation of intercalated hydrotalcite nanocomposites: Take a polycarboxy-hydroxy compound or a polycarboxy-hydroxy compound eutectic, dissolve it in ethylene glycol, add hydrotalcite precursor to obtain a second reaction solution, heat the second reaction solution under stirring for 5-8 hours to obtain intercalated hydrotalcite nanocomposites, namely polycarboxy-hydroxy intercalated hydrotalcite nanocomposites or polycarboxy-hydroxy eutectic intercalated hydrotalcite nanocomposites; The polycarboxylated-hydroxy compound is obtained by reacting L-carnitine with the polycarboxylated-hydroxy compound.

[0006] Optionally, the carboxyl-hydroxy compound is selected from at least one of lactic acid, salicylic acid, gluconic acid, malic acid, 2-hydroxybutyric acid, tartaric acid, citric acid, and amino acids.

[0007] Optionally, the molar ratio of sodium carbonate to sodium hydroxide in the alkaline solution is 1:4, the mass fraction of both sodium carbonate and sodium hydroxide solutions is 0.5%, and the molar ratio of Al(NO3)3•9H2O to sodium carbonate is 1:100.

[0008] Optionally, the preparation steps of the hydrotalcite precursor also include a reaction temperature of 50-100℃, cooling to room temperature after the reaction, washing with water until neutral, and drying to obtain the hydrotalcite precursor.

[0009] Optionally, the alkaline solution can be added at a rate of 4-6 mL / min.

[0010] Optionally, in the second reaction solution, the mass ratio of the hydrotalcite precursor to the polycarboxylated-hydroxy compound, or the polycarboxylated-hydroxy compound in a low-melting state, is 1:0.4-1, and the mass-volume ratio of the hydrotalcite precursor to ethylene glycol is 1-10 g / 100 mL.

[0011] Optionally, the preparation steps of the intercalated hydrotalcite nanocomposite material also include: a reaction temperature of 100-150℃, cooling to room temperature after the reaction, washing with water until neutral, and drying to obtain the intercalated hydrotalcite nanocomposite material.

[0012] Optionally, the preparation method of the polycarboxy-hydroxy compound eutectic includes: mixing L-carnitine and the polycarboxy-hydroxy compound in a molar ratio of 1:1-3, stirring at a temperature of 50-100℃ until a clear, transparent and homogeneous liquid is formed to obtain the eutectic solvent, and then keeping the eutectic solvent under vacuum at 60℃ for 24h to obtain the polycarboxy-hydroxy compound eutectic.

[0013] Secondly, this application provides a multi-carboxy-hydroxyl structure and its eutectic intercalated hydrotalcite nanocomposite material, which is prepared by the above-mentioned method.

[0014] Thirdly, this application provides the application of the above-mentioned multi-carboxy-hydroxyl structure and its eutectic intercalated hydrotalcite nanocomposite material as a lubricating additive.

[0015] This application provides a multi-carboxy-hydroxyl structure and its eutectic intercalated hydrotalcite nanocomposite material, its preparation method, and its application as a lubricating additive. This achieves the preparation of multi-carboxy-hydroxyl structure and its eutectic intercalated hydrotalcite nanocomposite material, and has the following advantages compared to existing technologies: (1) The intercalated hydrotalcite nanocomposite material provided in this application firstly uses a co-precipitation method to prepare a hydrotalcite precursor, and controls the Al 3+ With Zn 2+ The ratio of aluminum ions to sodium hydroxide solution is carefully controlled to ensure effective intercalation into the layered structure, forming a stable LDH phase. A solution of sodium carbonate and sodium hydroxide is added dropwise to create a uniform layered structure in the hydrotalcite precursor, which is beneficial for intercalation into polycarboxy-hydroxy compounds or their eutectic processes. The hydrotalcite precursor is then reacted with polycarboxy-hydroxy compounds or their eutectic processes to prepare intercalated hydrotalcite nanocomposites. These compounds act as interlayer support points and hydrogen bond points, increasing the interlayer spacing of the hydrotalcite and providing more space for subsequent oil molecule adsorption and shear slip. When used as a lubricant additive, this facilitates interlayer slip during friction, thereby improving lubrication performance.

[0016] (2) In this application, by controlling the molar ratio of Al(NO3)3•9H2O to Zn(NO3)2•6H2O and the molar ratio of L-carnitine to malic acid in the low-melting synthesis of the polycarboxy-hydroxyl structure during the preparation of intercalated hydrotalcite nanocomposites, an intercalated hydrotalcite nanocomposites with a layered structure are prepared, thereby increasing the interlayer spacing of hydrotalcite from 0.76 nm to 1.01-1.21 nm and obtaining nanosheets of 50-100 nm. When used as a lubricating additive for base oil PAO10 and base oil 500SN, the appropriate layered structure and particle size are beneficial to the interlayer slip of the intercalated hydrotalcite nanocomposites during the friction process, which is conducive to the timely filling of the intercalated hydrotalcite nanocomposites between the friction pairs. At the same time, it helps the nanomaterials to be uniformly and stably dispersed during the friction process. Under the synergistic influence of multiple factors, the lubricating film always remains continuous and stable, thereby allowing the intercalated hydrotalcite nanocomposites to fully exert their excellent lubrication performance.

[0017] (3) The preparation method of the polycarboxy-hydroxy structure and its low eutectic intercalated hydrotalcite nanocomposite material provided in this application is simple, low cost, environmentally friendly, and can be mass-produced, providing a new attempt for the application of nanolayered materials in the field of lubrication. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Explanation of reference numerals in the attached figures: Figure 1 These are electron micrographs of the intercalated hydrotalcite nanocomposites obtained in Examples 3, 4, 7, and 8 of this application. Figure 1 Image (A) is a morphology diagram of the unmodified hydrotalcite precursor (LDH) obtained in Example 3. Figure 1 (a) in the text is the malic acid intercalated hydrotalcite nanocomposite material obtained in Example 3. Figure 1 (b) in Example 4 shows the malic acid eutectic intercalated hydrotalcite nanocomposite material. Figure 1 (c) in the text refers to the tartaric acid-intercalated hydrotalcite nanocomposite material obtained in Example 7. Figure 1 (d) in Example 8 refers to the tartaric acid eutectic intercalated hydrotalcite nanocomposite material obtained in Example 8; Figure 2The images show the XRD patterns of the intercalated hydrotalcite nanocomposites and the unmodified hydrotalcite precursors obtained in Examples 3, 4, 7 and 8 of this application. Figure 3 The infrared spectra of the intercalated hydrotalcite nanocomposites and the unmodified hydrotalcite precursors prepared in Examples 3, 4, 7 and 8 are shown. Figure 4 The graphs show the tribological wear of Example 3 (P-LDH) at different addition amounts in 500SN. Figure 4 (a) is a graph showing the coefficient of friction of Example 3 (P-LDH) in 500SN at different addition amounts. Figure 4 (b) is a graph showing the average wear volume of Example 3 (P-LDH) in 500SN at different addition amounts; Figure 5 The graphs show the tribological wear of Example 4 (PD-LDH) at different addition amounts in 500SN. Figure 5 (a) is a graph showing the coefficient of friction of Example 4 (PD-LDH) at different addition amounts in 500SN. Figure 5 (b) is a graph showing the average wear volume of Example 4 (PD-LDH) in 500SN at different addition amounts; Figure 6 The graphs show the tribological wear of Example 7 (J-LDH) at different addition amounts in 500SN. Figure 6 (a) is a graph showing the coefficient of friction of Example 7 (J-LDH) in 500SN at different addition amounts. Figure 6 (b) is a graph showing the average wear volume of Example 7 (J-LDH) in 500SN at different addition amounts; Figure 7 The graphs show the tribological wear of Example 8 (JD-LDH) when added to 500SN at concentrations of 0.1%, 0.5%, 1%, and 2%. Figure 7 (a) is a graph showing the coefficient of friction of Example 8 (JD-LDH) in 500SN at different addition amounts. Figure 7 (b) is a graph showing the average wear volume of Example 8 (JD-LDH) in 500SN at different addition amounts; Figure 8 Tribological diagrams of unmodified hydrotalcite precursor (LDH) in 500SN at different addition amounts. Figure 8 (a) is a graph showing the coefficient of friction of unmodified hydrotalcite precursor (LDH) in 500SN at different addition amounts. Figure 8 (b) is the average wear volume plot for different amounts of unmodified hydrotalcite precursor (LDH) in 500SN; Figure 9The friction coefficient curves of the intercalated hydrotalcite nanocomposites prepared in Examples 3, 4, 7, and 8 when added to base oil 500SN at an addition amount of 2% are shown. Figure 10 The average wear volume diagram is shown for the intercalated hydrotalcite nanocomposites prepared in Examples 3, 4, 7 and 8 when the addition amount in base oil 500SN is 2%.

[0020] Figure 11 The wear track profile curves of the intercalated hydrotalcite nanocomposites prepared in Examples 3, 4, 7 and 8 when the addition amount of 500SN is 2% are shown. Figure 12 The friction coefficient curves of the intercalated hydrotalcite nanocomposites prepared in Examples 3, 4, 7, and 8 when the amount of PAO10 added is 2% are shown. Figure 13 The average wear volume diagram is shown for the intercalated hydrotalcite nanocomposites prepared in Examples 3, 4, 7 and 8 when the amount of PAO10 added is 2%. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are also within the scope of protection of this application.

[0022] In a first aspect, this application provides a method for preparing a hydrotalcite nanocomposite material based on a polycarboxy-hydroxyl structure and its low eutectic intercalation, the method comprising the following steps: (1) Preparation of hydrotalcite precursor: Al(NO3)3•9H2O and Zn(NO3)2•6H2O were mixed in a molar ratio of 1:1-3 and dissolved in a solvent to obtain a salt solution. Sodium carbonate solution and sodium hydroxide solution were mixed to obtain an alkaline solution. The alkaline solution was added dropwise to the salt solution until the pH value of the solution was 9-12 to obtain the first reaction solution. The first reaction solution was heated and reacted for 8-10 hours to obtain the hydrotalcite precursor. (2) Preparation of intercalated hydrotalcite nanocomposites: Take a polycarboxy-hydroxy compound or a polycarboxy-hydroxy compound eutectic, dissolve it in ethylene glycol, add hydrotalcite precursor to obtain a second reaction solution, heat the second reaction solution under stirring for 5-8 hours to obtain intercalated hydrotalcite nanocomposites, namely polycarboxy-hydroxy intercalated hydrotalcite nanocomposites or polycarboxy-hydroxy eutectic intercalated hydrotalcite nanocomposites; The polycarboxylated-hydroxy compound is obtained by reacting L-carnitine with the polycarboxylated-hydroxy compound.

[0023] Specifically, this application uses a co-precipitation method to prepare the hydrotalcite precursor, with Al(NO3)3•9H2O providing the trivalent metal cation Al. 3+ Zn(NO3)2•6H2O provides divalent metal cations Zn 2+ These are the two essential metal ions in terms of valence that constitute the layers of the hydrotalcite precursor (LDH). Simultaneously, the molar ratio of Al(NO3)3•9H2O to Zn(NO3)2•6H2O is 1:1-3. 3+ With Zn 2+ The ratio of aluminum ions to zinc ions is a key parameter in the LDH structure, determining the charge density of the laminations and the number of interlayer anions. This helps ensure that aluminum ions can be effectively embedded in the lamination structure to form a stable LDH phase, avoiding the formation of aluminum hydroxide gel alone. Both Al(NO3)3•9H2O and Zn(NO3)2•6H2O are nitrates, which can be better dissolved and are conducive to the efficient reaction.

[0024] The solvent is a mixture of deionized water and methanol in a volume ratio of 1:1, and the total mass of Al(NO3)3•9H2O and Zn(NO3)2•6H2O is 5-15 g / 100 mL in mass-volume ratio to the solvent.

[0025] A sodium carbonate (Na₂CO₃) solution is mixed with a sodium hydroxide (NaOH) solution to obtain an alkaline solution. Sodium hydroxide primarily acts as a precipitating agent, reacting with metal ions to form hydroxide precipitates, while sodium carbonate provides CO₃²⁻. 2- Introducing interlayer anions during LDH formation, CO3 2- Due to its high charge density and strong affinity for LDH structures, it easily enters the interlayer region, balancing the positively charged lamellar charges and promoting the structural stability of the hydrotalcite precursor. Slowly adding the alkaline solution avoids excessive local alkali supersaturation, preventing the formation of amorphous or non-LDH phase precipitates. Simultaneously, it promotes the synchronous and uniform precipitation of aluminum and zinc ions, stabilizing the LDH crystal structure. Furthermore, the slow addition facilitates nucleus formation and growth control, resulting in a uniform layered structure in the hydrotalcite precursor. This is beneficial for its intercalation into polycarboxy-hydroxy compounds or in the eutectic layer of polycarboxy-hydroxy compounds, contributing to the better friction-reducing and wear-resistant effects of intercalated hydrotalcite nanocomposites as lubricating additives.

[0026] During the dripping process, the amount of alkaline solution added is such that the dripping is stopped when the pH value of the solution is 9-12. Controlling the appropriate pH value is beneficial to the stable formation of the LDH structure.

[0027] In the preparation steps of intercalated hydrotalcite nanocomposites, a polycarboxylated hydroxyl compound or a polycarboxylated hydroxyl compound eutectic is dissolved in ethylene glycol, and then a hydrotalcite precursor is added to obtain a second reaction solution, which is then heated to react. The polycarboxylated hydroxyl compound or the polycarboxylated hydroxyl compound eutectic serves as an intercalator, containing both carboxyl groups (-COOH) and hydroxyl groups (-OH). The carboxyl groups can dissociate into negatively charged carboxylate ions (-COO₂). - The interaction between the compound and the positively charged laminae of LDH allows it to intercalate between layers and balance the core driving force of the charge. The hydroxyl groups can form hydrogen bonds with hydroxyl groups or metal ions on the laminae, contributing to the stability of the intercalation structure and resulting in intercalated hydrotalcite nanocomposites. The polycarboxylated-hydroxyl compounds or their eutectic properties simultaneously act as interlayer support points and hydrogen bond connection points, increasing the interlayer spacing of the hydrotalcite and providing more space for subsequent oil molecule adsorption and shear slip. When used as a lubricating additive, this promotes interlayer slip during friction, thereby improving lubrication performance.

[0028] Furthermore, LDH with polycarboxy-hydroxy compounds undergoing eutectic intercalation has a lower melting point or softening point. When used as a lubricating additive, it is more sensitive to the temperature and shear force generated by friction under the local high temperature. The intercalating agent will partially soften, melt, or even partially volatilize, making it easier to release from the LDH interlayer and quickly diffuse into the friction contact area. This allows for the faster formation of a stable and continuous lubricating film on the friction pair surface, thereby improving the friction reduction and anti-wear performance of the base lubricating oil.

[0029] The method for preparing intercalated hydrotalcite nanocomposites provided in this application is simple and the conditions are easy to control, improving the dispersibility of nanocomposites in base oils and thus obtaining a lubricating oil system containing intercalated hydrotalcite nanocomposites. This application first uses a co-precipitation method to prepare the hydrotalcite precursor, with Al(NO3)3•9H2O providing the trivalent metal cation Al. 3+ Zn(NO3)2•6H2O provides divalent metal cations Zn 2+ and control Al 3+ With Zn 2+The ratio of sodium carbonate to sodium hydroxide solution is carefully controlled to ensure effective intercalation of aluminum ions into the layered structure, forming a stable LDH phase. An alkaline solution is added dropwise, with sodium hydroxide acting primarily as a precipitant, resulting in a uniform layered structure in the hydrotalcite precursor. This facilitates its intercalation into polycarboxy-hydroxy compounds or their eutectic processes. The obtained hydrotalcite precursor is then reacted with polycarboxy-hydroxy compounds or their eutectic processes to prepare intercalated hydrotalcite nanocomposites. These compounds act as interlayer support points and hydrogen bond points, increasing the interlayer spacing of the hydrotalcite and providing more space for subsequent oil molecule adsorption and shear slip. When used as a lubricant additive, this facilitates interlayer slip during friction, thereby improving lubrication performance.

[0030] Optionally, the carboxyl-hydroxy compound is selected from at least one of lactic acid, salicylic acid, gluconic acid, malic acid, 2-hydroxybutyric acid, tartaric acid, citric acid, and amino acids.

[0031] Optionally, the molar ratio of sodium carbonate to sodium hydroxide in the alkaline solution is 1:4, the mass fraction of both sodium carbonate and sodium hydroxide solutions is 0.5%, and the molar ratio of Al(NO3)3•9H2O to sodium carbonate is 1:100.

[0032] Specifically, the molar ratio of sodium carbonate to sodium hydroxide in the alkaline solution is 1:4, which helps to introduce interlayer anions CO32-. 2- This balances the positively charged layer charge, which in turn contributes to the structural stability of the hydrotalcite precursor.

[0033] Optionally, the preparation steps of the hydrotalcite precursor also include a reaction temperature of 50-100℃, cooling to room temperature after the reaction, washing with water until neutral, and drying to obtain the hydrotalcite precursor.

[0034] Specifically, controlling the reaction temperature to 50-100℃ promotes the crystallization and increases the crystallinity of the hydrotalcite precursor. Microcrystals or primary precipitates undergo a dissolution-recrystallization process, which facilitates the dissolution of fine, unstable particles or disordered phases, followed by recrystallization onto larger, more stable LDH crystals. This significantly improves the crystallinity, crystal size, and phase purity of the product. Simultaneously, it contributes to the ordered arrangement of the lamellar structure and the formation of interlayer anions (CO3). 2- Stable embedding.

[0035] Optionally, the alkaline solution can be added at a rate of 4-6 mL / min.

[0036] Specifically, controlling the dropping rate during the dropping process avoids excessively high local pH values ​​or excessive dropping, which is conducive to the stable formation of the LDH structure.

[0037] Optionally, in the second reaction solution, the mass ratio of the hydrotalcite precursor to the polycarboxylated-hydroxy compound, or the polycarboxylated-hydroxy compound in a low-melting state, is 1:0.4-1, and the mass-volume ratio of the hydrotalcite precursor to ethylene glycol is 1-10 g / 100 mL.

[0038] Specifically, the intercalation of polycarboxy-hydroxy compounds, or polycarboxy-hydroxy compounds in a eutectic state, is an anion exchange reaction, in which negatively charged carboxylate ions (i.e., from polycarboxy-hydroxy compounds, or polycarboxy-hydroxy compounds in a eutectic state) replace the original CO3 anions in the interlayer of the hydrotalcite. 2- To control the ratio of hydrotalcite precursor to intercalated material, it is essential to first ensure sufficient intercalated material to guarantee enough carboxylate groups to replace the original CO3 in the interlayer. 2- To ensure successful intercalation, the maximum mass ratio of the hydrotalcite precursor to the intercalated product in this application is 1:1, with the intercalated product being more abundant than the hydrotalcite precursor. This provides a high concentration of carboxylate ions, which is beneficial for driving the ion exchange reaction towards the formation of the intercalated product and maximizing the removal of CO3 from the interlayer. 2- This achieves a high intercalation rate or near-saturation intercalation, thereby improving the quality of intercalated hydrotalcite nanocomposites and enhancing the lubrication performance of lubricants when used as lubricant additives.

[0039] Optionally, the preparation steps of the intercalated hydrotalcite nanocomposite material also include: a reaction temperature of 100-150℃, cooling to room temperature after the reaction, washing with water until neutral, and drying to obtain the intercalated hydrotalcite nanocomposite material.

[0040] Optionally, the preparation method of the polycarboxy-hydroxy compound eutectic includes: mixing L-carnitine and the polycarboxy-hydroxy compound in a molar ratio of 1:1-3, stirring at a temperature of 50-100℃ until a clear, transparent and homogeneous liquid is formed to obtain the eutectic solvent, and then keeping the eutectic solvent under vacuum at 60℃ for 24h to obtain the polycarboxy-hydroxy compound eutectic.

[0041] Specifically, L-carnitine acts as a hydrogen bond acceptor, and polycarboxy-hydroxy compounds act as hydrogen bond donors. The two react to form ionic hydrogen bonds, resulting in the low-melting-point polycarboxy-hydroxy compound. The synthesis of the low-melting-point polycarboxy-hydroxy compound is used as an intercalator to intercalate the hydrotalcite precursor. Compared with the intercalation of polycarboxy-hydroxy compounds, the intercalation efficiency is higher and the intercalation structure is more stable. That is, the hydrogen bond network formed by L-carnitine and polycarboxy-hydroxy compounds is directly intercalated into the LDH interlayer during intercalation, avoiding structural defects caused by random molecular insertion. At the same time, when used as a lubricating additive, the hydrogen bond network formed by L-carnitine and polycarboxy-hydroxy compounds undergoes reversible bonding and recombination in the interlayer, realizing the self-healing function of the friction interface.

[0042] During the vacuum holding process, the vacuum level is -0.1 to -1 MPa.

[0043] Secondly, this application provides a multi-carboxy-hydroxyl structure and its eutectic intercalated hydrotalcite nanocomposite material, which is prepared by the above-mentioned method.

[0044] Thirdly, this application provides the application of the above-mentioned multi-carboxy-hydroxyl structure and its eutectic intercalated hydrotalcite nanocomposite material as a lubricating additive.

[0045] Specifically, the intercalated hydrotalcite nanocomposite material provided in this application is added as a lubricating additive to a base lubricating oil. Its multi-carboxyl-hydroxyl structure and eutectic properties simultaneously act as interlayer support points and hydrogen bond connection points, providing more space for subsequent oil molecule adsorption and shear slip, thereby improving the lubrication performance of the base lubricating oil. The base lubricating oil is selected from at least one of PAO10, 500SN, and base oil 5750.

[0046] The technical solutions of this application are illustrated in detail below with specific embodiments, but they should not be construed as limiting the scope of protection of this invention. Example 1

[0047] A method for preparing hydrotalcite nanocomposites based on a polycarboxylated-hydroxyl structure and its eutectic intercalation, the method comprising the following steps: (1) Preparation of hydrotalcite precursor: Al(NO3)3•9H2O and Zn(NO3)2•6H2O were mixed in a molar ratio of 1:1 and dissolved in a mixed solvent of deionized water and methanol in a volume ratio of 1:1 to obtain a salt solution. Sodium carbonate solution and sodium hydroxide solution were mixed to obtain an alkaline solution. The alkaline solution was added to the salt solution at a dropping rate of 4 mL / min until the pH value of the solution was 9 to obtain the first reaction solution. The first reaction solution was reacted at 50℃ for 8 h under stirring. After the reaction was completed, it was cooled to room temperature, washed with water until neutral (pH value of 7-7.5), and freeze-dried to obtain the hydrotalcite precursor.

[0048] The total mass of Al(NO3)3•9H2O and Zn(NO3)2•6H2O is 5 g / 100 mL in mass-volume ratio to the solvent. The molar ratio of sodium carbonate to sodium hydroxide in the alkaline solution is 1:4. The mass fraction of both sodium carbonate and sodium hydroxide solutions is 0.5%. The molar ratio of Al(NO3)3•9H2O to sodium carbonate is 1:100.

[0049] (2) Preparation of intercalated hydrotalcite nanocomposite material: Malic acid was dissolved in ethylene glycol, and hydrotalcite precursor was added to obtain a second reaction solution. The second reaction solution was stirred and reacted at 100℃ for 5 hours. After the reaction was completed, it was cooled to room temperature, washed with water until neutral (pH value 7-7.5), and freeze-dried to obtain malic acid intercalated hydrotalcite nanocomposite material. The mass ratio of hydrotalcite precursor to malic acid was 1:0.4, and the mass-to-volume ratio of hydrotalcite precursor to ethylene glycol was 1 g / 100 mL. Example 2

[0050] A method for preparing hydrotalcite nanocomposites based on a polycarboxylated-hydroxyl structure and its eutectic intercalation, the method comprising the following steps: (1) Preparation method of malic acid eutectic: L-carnitine and malic acid are mixed in a molar ratio of 1:1 and stirred at 50°C until a clear, transparent and homogeneous liquid is formed to obtain a eutectic solvent. The eutectic solvent is then kept under vacuum at 60°C for 24 hours to obtain malic acid eutectic.

[0051] (2) Preparation of hydrotalcite precursor: Al(NO3)3•9H2O and Zn(NO3)2•6H2O were mixed in a molar ratio of 1:1 and dissolved in a mixed solvent of deionized water and methanol in a volume ratio of 1:1 to obtain a salt solution. Sodium carbonate solution and sodium hydroxide solution were mixed to obtain an alkaline solution. The alkaline solution was added to the salt solution at a dropping rate of 4-6 mL / min until the pH value of the solution was 9 to obtain the first reaction solution. The first reaction solution was reacted at 50℃ for 8 hours under stirring. After the reaction was completed, it was cooled to room temperature, washed with water until neutral (pH value of 7-7.5), and freeze-dried to obtain the hydrotalcite precursor.

[0052] The total mass of Al(NO3)3•9H2O and Zn(NO3)2•6H2O is 5 g / 100 mL in mass-volume ratio to the solvent. The molar ratio of sodium carbonate to sodium hydroxide in the alkaline solution is 1:4. The mass fraction of both sodium carbonate and sodium hydroxide solutions is 0.5%. The molar ratio of Al(NO3)3•9H2O to sodium carbonate is 1:100.

[0053] (3) Preparation of intercalated hydrotalcite nanocomposite material: malic acid was dissolved in ethylene glycol in a low eutectic state, and then hydrotalcite precursor was added to obtain a second reaction solution. The second reaction solution was stirred and reacted at 100℃ for 5 hours. After the reaction was completed, it was cooled to room temperature, washed with water until neutral (pH value 7-7.5), and freeze-dried to obtain malic acid low eutectic intercalated hydrotalcite nanocomposite material. The mass ratio of hydrotalcite precursor to malic acid was 1:0.4, and the mass-to-volume ratio of hydrotalcite precursor to ethylene glycol was 1 g / 100 mL. Example 3

[0054] A method for preparing hydrotalcite nanocomposites based on a polycarboxylated-hydroxyl structure and its eutectic intercalation, the method comprising the following steps: (1) Preparation of hydrotalcite precursor: Al(NO3)3•9H2O and Zn(NO3)2•6H2O were mixed in a molar ratio of 1:2 and dissolved in a mixed solvent of deionized water and methanol in a volume ratio of 1:1 to obtain a salt solution. Sodium carbonate solution and sodium hydroxide solution were mixed to obtain an alkaline solution. The alkaline solution was added to the salt solution at a dropping rate of 5 mL / min until the pH value of the solution was 10 to obtain the first reaction solution. The first reaction solution was reacted at 80℃ for 9 h under stirring. After the reaction was completed, it was cooled to room temperature, washed with water until neutral (pH value of 7-7.5), and freeze-dried to obtain the hydrotalcite precursor.

[0055] The total mass of Al(NO3)3•9H2O and Zn(NO3)2•6H2O is 10 g / 100 mL in mass-volume ratio to the solvent. The molar ratio of sodium carbonate to sodium hydroxide in the alkaline solution is 1:4. The mass fraction of both sodium carbonate and sodium hydroxide solutions is 0.5%. The molar ratio of Al(NO3)3•9H2O to sodium carbonate is 1:100.

[0056] (2) Preparation of intercalated hydrotalcite nanocomposite material: Malic acid was dissolved in ethylene glycol, and hydrotalcite precursor was added to obtain a second reaction solution. The second reaction solution was stirred and reacted at 120℃ for 7h. After the reaction was completed, it was cooled to room temperature, washed with water until neutral (pH value 7-7.5), and freeze-dried to obtain malic acid intercalated hydrotalcite nanocomposite material. The mass ratio of hydrotalcite precursor to malic acid was 1:0.7, and the mass-to-volume ratio of hydrotalcite precursor to ethylene glycol was 5 g / 100 mL. Example 4

[0057] A method for preparing hydrotalcite nanocomposites based on a polycarboxylated-hydroxyl structure and its eutectic intercalation, the method comprising the following steps: (1) Preparation method of malic acid eutectic: L-carnitine and malic acid are mixed in a molar ratio of 1:2 and stirred at 80°C until a clear, transparent and homogeneous liquid is formed to obtain a eutectic solvent. The eutectic solvent is then kept under vacuum at 60°C for 24 hours to obtain malic acid eutectic.

[0058] (2) Preparation of hydrotalcite precursor: Al(NO3)3•9H2O and Zn(NO3)2•6H2O were mixed in a molar ratio of 1:2 and dissolved in a mixed solvent of deionized water and methanol in a volume ratio of 1:1 to obtain a salt solution. Sodium carbonate solution and sodium hydroxide solution were mixed to obtain an alkaline solution. The alkaline solution was added to the salt solution at a dropping rate of 5 mL / min until the pH value of the solution was 10 to obtain the first reaction solution. The first reaction solution was reacted at 80℃ for 9 h under stirring. After the reaction was completed, it was cooled to room temperature, washed with water until neutral (pH value of 7-7.5), and freeze-dried to obtain the hydrotalcite precursor.

[0059] The total mass of Al(NO3)3•9H2O and Zn(NO3)2•6H2O is 10 g / 100 mL in mass-volume ratio to the solvent. The molar ratio of sodium carbonate to sodium hydroxide in the alkaline solution is 1:4. The mass fraction of both sodium carbonate and sodium hydroxide solutions is 0.5%. The molar ratio of Al(NO3)3•9H2O to sodium carbonate is 1:100.

[0060] (3) Preparation of intercalated hydrotalcite nanocomposite material: malic acid was dissolved in ethylene glycol in a low eutectic state, and then hydrotalcite precursor was added to obtain a second reaction solution. The second reaction solution was stirred and reacted at 120℃ for 7 hours. After the reaction was completed, it was cooled to room temperature, washed with water until neutral (pH value 7-7.5), and freeze-dried to obtain malic acid low eutectic intercalated hydrotalcite nanocomposite material. The mass ratio of hydrotalcite precursor to malic acid was 1:0.7, and the mass-to-volume ratio of hydrotalcite precursor to ethylene glycol was 5 g / 100 mL.

[0061] Example 5 A method for preparing hydrotalcite nanocomposites based on a polycarboxylated-hydroxyl structure and its eutectic intercalation, the method comprising the following steps: (1) Preparation of hydrotalcite precursor: Al(NO3)3•9H2O and Zn(NO3)2•6H2O were mixed in a molar ratio of 1:3 and dissolved in a mixed solvent of deionized water and methanol in a volume ratio of 1:1 to obtain a salt solution. Sodium carbonate solution and sodium hydroxide solution were mixed to obtain an alkaline solution. The alkaline solution was added to the salt solution at a dropping rate of 4-6 mL / min until the pH value of the solution was 12 to obtain the first reaction solution. The first reaction solution was reacted at 100℃ for 10 h under stirring. After the reaction was completed, it was cooled to room temperature, washed with water until neutral (pH value of 7-7.5), and freeze-dried to obtain the hydrotalcite precursor.

[0062] The total mass of Al(NO3)3•9H2O and Zn(NO3)2•6H2O is 15 g / 100 mL in mass-volume ratio to the solvent. The molar ratio of sodium carbonate to sodium hydroxide in the alkaline solution is 1:4. The mass fraction of both sodium carbonate and sodium hydroxide solutions is 0.5%. The molar ratio of Al(NO3)3•9H2O to sodium carbonate is 1:100.

[0063] (2) Preparation of intercalated hydrotalcite nanocomposite material: Malic acid was dissolved in ethylene glycol, and hydrotalcite precursor was added to obtain a second reaction solution. The second reaction solution was stirred and reacted at 150℃ for 8 hours. After the reaction was completed, it was cooled to room temperature, washed with water until neutral (pH value 7-7.5), and freeze-dried to obtain malic acid intercalated hydrotalcite nanocomposite material. The mass ratio of hydrotalcite precursor to malic acid was 1:1, and the mass-to-volume ratio of hydrotalcite precursor to ethylene glycol was 10 g / 100 mL.

[0064] Example 6 A method for preparing hydrotalcite nanocomposites based on a polycarboxylated-hydroxyl structure and its eutectic intercalation, the method comprising the following steps: (1) Preparation method of malic acid eutectic: L-carnitine and malic acid are mixed in a molar ratio of 1:3 and stirred at 100°C until a clear, transparent and homogeneous liquid is formed to obtain a eutectic solvent. The eutectic solvent is then kept under vacuum at 60°C for 24 hours to obtain malic acid eutectic.

[0065] (2) Preparation of hydrotalcite precursor: Al(NO3)3•9H2O and Zn(NO3)2•6H2O were mixed in a molar ratio of 1:3 and dissolved in a mixed solvent of deionized water and methanol in a volume ratio of 1:1 to obtain a salt solution. Sodium carbonate solution and sodium hydroxide solution were mixed to obtain an alkaline solution. The alkaline solution was added to the salt solution at a dropping rate of 6 mL / min until the pH value of the solution was 12 to obtain the first reaction solution. The first reaction solution was reacted at 100℃ for 10 h under stirring. After the reaction was completed, it was cooled to room temperature, washed with water until neutral (pH value of 7-7.5), and freeze-dried to obtain the hydrotalcite precursor.

[0066] The total mass of Al(NO3)3•9H2O and Zn(NO3)2•6H2O is 15 g / 100 mL in mass-volume ratio to the solvent. The molar ratio of sodium carbonate to sodium hydroxide in the alkaline solution is 1:4. The mass fraction of both sodium carbonate and sodium hydroxide solutions is 0.5%. The molar ratio of Al(NO3)3•9H2O to sodium carbonate is 1:100.

[0067] (3) Preparation of intercalated hydrotalcite nanocomposite material: malic acid was dissolved in ethylene glycol in a low eutectic state, and then hydrotalcite precursor was added to obtain a second reaction solution. The second reaction solution was stirred and reacted at 150℃ for 8 hours. After the reaction was completed, it was cooled to room temperature, washed with water until neutral (pH value 7-7.5), and freeze-dried to obtain malic acid low eutectic intercalated hydrotalcite nanocomposite material. The mass ratio of hydrotalcite precursor to malic acid was 1:1, and the mass-to-volume ratio of hydrotalcite precursor to ethylene glycol was 10 g / 100 mL.

[0068] Example 7 A method for preparing hydrotalcite nanocomposites based on a polycarboxylated-hydroxyl structure and its eutectic intercalation, the method comprising the following steps: (1) Preparation of hydrotalcite precursor: Al(NO3)3•9H2O and Zn(NO3)2•6H2O were mixed in a molar ratio of 1:2 and dissolved in a mixed solvent of deionized water and methanol in a volume ratio of 1:1 to obtain a salt solution. Sodium carbonate solution and sodium hydroxide solution were mixed to obtain an alkaline solution. The alkaline solution was added to the salt solution at a dropping rate of 5 mL / min until the pH value of the solution was 10 to obtain the first reaction solution. The first reaction solution was reacted at 80℃ for 9 h under stirring. After the reaction was completed, it was cooled to room temperature, washed with water until neutral (pH value of 7-7.5), and freeze-dried to obtain the hydrotalcite precursor.

[0069] The total mass of Al(NO3)3•9H2O and Zn(NO3)2•6H2O is 10 g / 100 mL in mass-volume ratio to the solvent. The molar ratio of sodium carbonate to sodium hydroxide in the alkaline solution is 1:4. The mass fraction of both sodium carbonate and sodium hydroxide solutions is 0.5%. The molar ratio of Al(NO3)3•9H2O to sodium carbonate is 1:100.

[0070] (2) Preparation of intercalated hydrotalcite nanocomposite material: Tartaric acid was dissolved in ethylene glycol, and hydrotalcite precursor was added to obtain a second reaction solution. The second reaction solution was stirred and reacted at 120℃ for 7 hours. After the reaction was completed, it was cooled to room temperature, washed with water until neutral (pH value 7-7.5), and freeze-dried to obtain tartaric acid intercalated hydrotalcite nanocomposite material. The mass ratio of hydrotalcite precursor to tartaric acid was 1:0.7, and the mass-to-volume ratio of hydrotalcite precursor to ethylene glycol was 5 g / 100 mL.

[0071] Example 8 A method for preparing hydrotalcite nanocomposites based on a polycarboxylated-hydroxyl structure and its eutectic intercalation, the method comprising the following steps: (1) Preparation method of tartaric acid eutectic: L-carnitine and tartaric acid are mixed in a molar ratio of 1:2 and stirred at 80°C until a clear, transparent and homogeneous liquid is formed to obtain a eutectic solvent. The eutectic solvent is then kept under vacuum at 60°C for 24 hours to obtain tartaric acid eutectic.

[0072] (2) Preparation of hydrotalcite precursor: Al(NO3)3•9H2O and Zn(NO3)2•6H2O were mixed in a molar ratio of 1:2 and dissolved in a mixed solvent of deionized water and methanol in a volume ratio of 1:1 to obtain a salt solution. Sodium carbonate solution and sodium hydroxide solution were mixed to obtain an alkaline solution. The alkaline solution was added to the salt solution at a dropping rate of 5 mL / min until the pH value of the solution was 10 to obtain the first reaction solution. The first reaction solution was reacted at 80℃ for 9 h under stirring. After the reaction was completed, it was cooled to room temperature, washed with water until neutral (pH value of 7-7.5), and freeze-dried to obtain the hydrotalcite precursor.

[0073] The total mass of Al(NO3)3•9H2O and Zn(NO3)2•6H2O is 10 g / 100 mL in mass-volume ratio to the solvent. The molar ratio of sodium carbonate to sodium hydroxide in the alkaline solution is 1:4. The mass fraction of both sodium carbonate and sodium hydroxide solutions is 0.5%. The molar ratio of Al(NO3)3•9H2O to sodium carbonate is 1:100.

[0074] (3) Preparation of intercalated hydrotalcite nanocomposite material: Tartaric acid was dissolved in ethylene glycol in a low eutectic state, and then hydrotalcite precursor was added to obtain a second reaction solution. The second reaction solution was stirred and reacted at 120℃ for 7 hours. After the reaction was completed, it was cooled to room temperature, washed with water until neutral (pH value 7-7.5), and freeze-dried to obtain tartaric acid low eutectic intercalated hydrotalcite nanocomposite material. The mass ratio of hydrotalcite precursor to tartaric acid was 1:0.7, and the mass-to-volume ratio of hydrotalcite precursor to ethylene glycol was 5 g / 100 mL.

[0075] Experimental Example 1 Characterization of intercalated hydrotalcite nanocomposites Malic acid-intercalated hydrotalcite nanocomposites were successfully synthesized using the methods provided in Examples 1, 3, and 5. Malic acid eutectic intercalated hydrotalcite nanocomposites were successfully synthesized using Examples 2, 4, and 6. Taking the malic acid-intercalated hydrotalcite nanocomposites obtained in Example 3 (named P-LDH), the malic acid eutectic intercalated hydrotalcite nanocomposites obtained in Example 4 (named PD-LDH), the tartaric acid-intercalated hydrotalcite nanocomposites obtained in Example 7 (named J-LDH), and the tartaric acid eutectic intercalated hydrotalcite nanocomposites obtained in Example 8 (named JD-LDH) as examples, the morphology of the above-mentioned intercalated hydrotalcite nanocomposites was characterized by electron microscopy. The results are as follows: Figure 1 As shown, Figure 1 The images shown are electron microscope images of the intercalated hydrotalcite nanocomposites obtained in Examples 3, 4, 7, and 8.

[0076] Figure 1 Image (A) is a morphology diagram of the unmodified hydrotalcite precursor (LDH) obtained in Example 3. Figure 1 (a) in the text is the malic acid intercalated hydrotalcite nanocomposite material obtained in Example 3. Figure 1 (b) in Example 4 shows the malic acid eutectic intercalated hydrotalcite nanocomposite material. Figure 1 (c) in the text refers to the tartaric acid-intercalated hydrotalcite nanocomposite material obtained in Example 7. Figure 1 In Example 8, (d) represents the tartaric acid eutectic intercalated hydrotalcite nanocomposite material obtained. Figure 1 It can be seen that the intercalated hydrotalcite has a better layered structure compared with the unmodified hydrotalcite precursor. Moreover, the low eutectic intercalation of polycarboxy-hydroxy compounds has a smaller particle size and a more obvious plate-like structure compared with the intercalation of polycarboxy-hydroxy compounds. Such a structure is conducive to interlayer sliding and forming a friction film during the friction process.

[0077] Experiment Example 2 Characterization of intercalated hydrotalcite nanocomposites XRD analysis was performed on the intercalated hydrotalcite nanocomposites obtained in Examples 3 (P-LDH), 4 (PD-LDH), 7 (J-LDH), and 8 (JD-LDH), as well as the unmodified hydrotalcite precursor (LDH). The results are as follows: Figure 2 As shown.

[0078] from Figure 2As can be seen from the XRD patterns, LDH, J-LDH, JD-LDH, P-LDH, and PD-LDH all exhibited typical hydrotalcite (003), (006), and (009) characteristic diffraction peaks. The peak intensity is directly related to the crystallinity. The XRD patterns show that these four intercalated functional hydrotalcites have good crystallinity, with sharp and complete peak shapes. The diffraction angle 2θ corresponding to the (003) crystal plane of LDH is 11.68°, and the interlayer spacing is calculated to be d = 0.7571 nm using Bragg's formula. The 003 characteristic diffraction peaks of the modified hydrotalcites (J-LDH, JD-LDH, P-LDH, and PD-LDH) show a significant forward shift. The calculated values ​​are dJ-LDH=1.2035, dJD-LDH=1.0128, dP-LDH=1.2102, and dPD-LDH=1.1662. The data shows that the interlayer spacing (d-value) of the four modified LDHs has increased, indicating that tartaric acid, tartaric acid eutectic, malic acid, and malic acid eutectic have been successfully inserted into the hydrotalcite precursor.

[0079] Experimental Example 3 Characterization of intercalated hydrotalcite nanocomposites FTIR analysis was performed on the intercalated hydrotalcite nanocomposites obtained in Examples 3 (P-LDH), 4 (PD-LDH), 7 (J-LDH), and 8 (JD-LDH), as well as the unmodified hydrotalcite precursor (LDH). The results are as follows: Figure 3 As shown, Figure 3 The infrared spectra of the intercalated hydrotalcite nanocomposites and the unmodified hydrotalcite precursors prepared in Examples 3, 4, 7 and 8 are shown.

[0080] Depend on Figure 3 It was observed that 3450cm in the figure -1 A broad absorption peak appears nearby, corresponding to the stretching vibration of HOH in interlayer water molecules and the hydroxyl group OH. - Symmetrical contraction. LDH's 1369cm -1 The strong absorption peak at this point is a characteristic absorption peak of nitrate ions, corresponding to NO. 3- Symmetric stretching vibration; in the range of 400-900 cm -1 The peaks within this range are vibrational absorption peaks caused by the horizontal and vertical movement of Zn / Al-O and O-Zn / Al-O layers in the layered material. J-LDH, JD-LDH, P-LDH, and PD-LDH peaks are at 1550 cm⁻¹. -1 and 1370cm -1 The absorption peak at 1064 cm⁻¹ is due to the stretching vibration of the carbonyl C=O group of -COOH in tartaric acid, malic acid, and synthetic eutectic L-carnitine; -1The moderate intensity peak at the point indicates the presence of CO bonds. These results suggest that tartaric acid, malic acid, tartaric acid eutectic, and malic acid eutectic have been successfully inserted into the hydrotalcite precursor.

[0081] Experiment Example 4 The intercalated hydrotalcite nanocomposites and unmodified hydrotalcite precursors (LDH) obtained in Examples 3 (P-LDH), 4 (PD-LDH), 7 (J-LDH), and 8 (JD-LDH) of this application were added to base oil as lubricating additives and stably dispersed. The lubricating performance of the obtained intercalated hydrotalcite nanocomposites as lubricating additives was evaluated using an SRV-V micro-vibration friction and wear tester manufactured by Optimol Grease GmbH, Germany. The wear volume and wear track profile curve of the samples were measured by a BRUKER-NPFLEX three-dimensional optical profilometer.

[0082] The intercalated hydrotalcite nanocomposites obtained in Examples 3 (P-LDH), 4 (PD-LDH), 7 (J-LDH), and 8 (JD-LDH), along with the unmodified hydrotalcite precursor (LDH), were added to base oil 500SN at mass concentrations of 0.1%, 0.5%, 1%, and 2%, respectively. Friction tests were conducted, with each experiment performed in at least three parallel trials, and the average value was taken. The test results are as follows: Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 As shown.

[0083] The test conditions were: load 200 N, temperature 25℃, frequency 25 Hz, amplitude 1 mm, and test time 30 min; the test ball was a Φ10 mm AISI 52100 steel ball; in the steel / steel friction pair, the lower sample was a Φ24 mm, 7.9 mm thick AISI 52100 steel block with a hardness of 750-850 HV.

[0084] By comparison Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 The friction and wear graphs shown indicate that when the addition amount is 2%, the lubricant exhibits good friction coefficient and wear volume, and the friction coefficient curve is significantly more stable compared to base oil 500SN. Therefore, the lubrication performance of intercalated hydrotalcite nanocomposite material and unmodified hydrotalcite precursor in base oil 500SN with an addition amount of 2% was plotted, and the results are as follows. Figure 9 , Figure 10 and Figure 11 As shown, Figure 9 This is a graph showing the coefficient of friction when 2% of 500SN is added. Figure 10 This is a plot of the average wear volume when the addition amount is 2% in 500SN. Figure 11 The wear track profile is shown when 2% of 500SN is added.

[0085] observe Figure 9 , Figure 10 and Figure 11 It is evident that the polycarboxylated-hydroxyl structure and its eutectic intercalated hydrotalcite nanocomposite material provided in this application, when used as an additive for base oil 500SN, significantly reduce both the coefficient of friction and wear volume compared to base oil 500SN, and the lubrication performance of the intercalated hydrotalcite nanocomposite material provided in Example 3 (P-LDH) is significantly improved. Meanwhile, observations... Figure 11 It is known that when the polycarboxy-hydroxy structure and its eutectic intercalated hydrotalcite nanocomposite material provided in this application are used as an additive for base oil 500SN, the depth and width of the wear tracks are significantly smaller than those of base oil 500SN and the unmodified hydrotalcite precursor. This indicates that when polycarboxy-hydroxy compounds or polycarboxy-hydroxy compound eutectic intercalated hydrotalcite are used, they simultaneously act as interlayer support points and hydrogen bond connection points, increasing the interlayer spacing of the hydrotalcite and providing more space for subsequent oil molecule adsorption and shear slip. When used as a lubricating additive, it facilitates interlayer slip during friction, thereby significantly improving the lubrication performance of base oil 500SN.

[0086] In this application, by controlling the molar ratio of Al(NO3)3•9H2O to Zn(NO3)2•6H2O and the molar ratio of L-carnitine to malic acid in the low-melting synthesis of the polycarboxy-hydroxyl structure during the preparation of intercalated hydrotalcite nanocomposites, a layered hydrotalcite nanocomposites with a layered structure are prepared. This increases the interlayer spacing of the hydrotalcite from 0.76 nm to 1.01-1.21 nm, resulting in nanosheets of 50-100 nm. When used as a lubricating additive, the appropriate layered structure and particle size during friction facilitate interlayer slippage of the intercalated hydrotalcite nanocomposites, allowing them to fill the friction pairs in a timely manner. Simultaneously, it contributes to the uniform and stable dispersion of nanomaterials during friction. Under the synergistic influence of multiple factors, the lubricating film remains continuous and stable, thereby allowing the intercalated hydrotalcite nanocomposites to fully exert their excellent lubrication performance.

[0087] Experimental Example 5 The test method was the same as in Experiment 4. The intercalated hydrotalcite nanocomposites and unmodified hydrotalcite precursors (LDH) obtained in Examples 3 (P-LDH), 4 (PD-LDH), 7 (J-LDH), and 8 (JD-LDH) were added to base oil PAO10 at mass concentrations of 0.1%, 0.5%, 1%, and 2%, respectively. Friction tests were conducted, with at least three parallel experiments for each experiment, and the average value was taken. It was found that the lubricating performance of the intercalated hydrotalcite nanocomposites as an additive to base oil PAO10 was basically consistent with that in base oil 500SN. That is, when the addition amount was 2%, the coefficient of friction and wear volume of the lubricant were both good. The test results are as follows: Figure 12 , Figure 13 As shown. Figure 12 This is a graph showing the coefficient of friction when 2% of PAO10 base oil is added. Figure 13 The average wear volume diagram is shown when 2% of PAO10 base oil is added.

[0088] observe Figure 12 , Figure 13 It is known that when the polycarboxy-hydroxy structure and its low eutectic intercalated hydrotalcite nanocomposite material provided in this application are used as an additive for base oil PAO10, the coefficient of friction and wear volume are significantly reduced compared to base oil PAO10. Moreover, in base oil PAO10, the intercalated hydrotalcite nanocomposite material (JD-LDH) provided in Example 8 has better lubrication performance.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing a hydrotalcite nanocomposite material based on a polycarboxylated-hydroxyl structure and its eutectic intercalation, characterized in that, The preparation method includes the following steps: (1) Preparation of hydrotalcite precursor: Al(NO3)3•9H2O and Zn(NO3)2•6H2O are mixed in a molar ratio of 1:1-3 and dissolved in a solvent to obtain a salt solution. Sodium carbonate solution and sodium hydroxide solution are mixed to obtain an alkaline solution. The alkaline solution is added dropwise to the salt solution until the pH value of the solution is 9-12 to obtain the first reaction solution. The first reaction solution is heated and reacted for 8-10 hours to obtain the hydrotalcite precursor. (2) Preparation of intercalated hydrotalcite nanocomposite material: Take a polycarboxy-hydroxy compound or a polycarboxy-hydroxy compound eutectic, dissolve it in ethylene glycol, and then add the hydrotalcite precursor to obtain a second reaction solution. Heat the second reaction solution under stirring for 5-8 hours to obtain the intercalated hydrotalcite nanocomposite material, namely, polycarboxy-hydroxy intercalated hydrotalcite nanocomposite material or polycarboxy-hydroxy eutectic intercalated hydrotalcite nanocomposite material; The polycarboxylated-hydroxy compound is obtained by reacting L-carnitine with the polycarboxylated-hydroxy compound.

2. The preparation method of the hydrotalcite nanocomposite material based on the polycarboxy-hydroxyl structure and its eutectic intercalation according to claim 1, characterized in that, The carboxyl-hydroxy compound is selected from at least one of lactic acid, salicylic acid, gluconic acid, malic acid, 2-hydroxybutyric acid, tartaric acid, citric acid, and amino acids.

3. The preparation method of the hydrotalcite nanocomposite material based on the polycarboxy-hydroxyl structure and its eutectic intercalation according to claim 1, characterized in that, The molar ratio of sodium carbonate to sodium hydroxide in the alkaline solution is 1:4, the mass fraction of both the sodium carbonate solution and the sodium hydroxide solution is 0.5%, and the molar ratio of Al(NO3)3•9H2O to sodium carbonate is 1:

100.

4. The preparation method of the hydrotalcite nanocomposite material based on the polycarboxy-hydroxyl structure and its eutectic intercalation according to claim 1, characterized in that, The preparation steps of the hydrotalcite precursor also include a reaction temperature of 50-100℃, cooling to room temperature after the reaction, washing with water until neutral, and drying to obtain the hydrotalcite precursor.

5. The preparation method of the hydrotalcite nanocomposite material based on the polycarboxy-hydroxyl structure and its eutectic intercalation according to claim 1, characterized in that, The alkaline solution is added at a rate of 4-6 mL / min.

6. The preparation method of the hydrotalcite nanocomposite material based on the polycarboxy-hydroxyl structure and its eutectic intercalation according to claim 1, characterized in that, In the second reaction solution, the mass ratio of the hydrotalcite precursor to the polycarboxylated-hydroxy compound, or the polycarboxylated-hydroxy compound in a low-melting state, is 1:0.4-1, and the mass-volume ratio of the hydrotalcite precursor to the ethylene glycol is 1-10 g / 100 mL.

7. The preparation method of the hydrotalcite nanocomposite material based on the polycarboxy-hydroxyl structure and its eutectic intercalation according to claim 1, characterized in that, The preparation steps of the intercalated hydrotalcite nanocomposite material also include a reaction temperature of 100-150℃, cooling to room temperature after the reaction, washing with water until neutral, and drying to obtain the intercalated hydrotalcite nanocomposite material.

8. The preparation method of the hydrotalcite nanocomposite material based on the polycarboxy-hydroxyl structure and its eutectic intercalation according to any one of claims 1-7, characterized in that, The method for preparing the polycarboxy-hydroxy compound eutectic solvent includes: mixing L-carnitine with the polycarboxy-hydroxy compound in a molar ratio of 1:1-3, stirring at a temperature of 50-100°C until a clear, transparent, and homogeneous liquid is formed to obtain a eutectic solvent, and then maintaining the eutectic solvent under a vacuum at 60°C for 24 hours to obtain the polycarboxy-hydroxy compound eutectic solvent.

9. A nanocomposite material based on a polycarboxylated-hydroxyl structure and its eutectic intercalation layered double hydroxide, characterized in that, The intercalated hydrotalcite nanocomposite material is prepared by the method described in any one of claims 1-8.

10. The application of the hydrotalcite nanocomposite material based on the polycarboxy-hydroxy structure and its eutectic intercalation as described in claim 9 as a lubricating additive.

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