Low-set fire-resistant synthetic hydraulic fluid and method of making same

Abstract

The application discloses a kind of low condensation fire-resistant synthetic hydraulic oil and preparation method thereof in the technical field of high-performance special lubricant, the hydraulic oil uses pentaerythritol oleate as base oil, and cooperates with multiple functional additives, key in that γ-ammonia propyl triethoxysilane surface modified layered zinc boron aluminate hydroxide and γ-ammonia propyl triethoxysilane surface modified hafnium-doped silicon dioxide coated titanium carbide nanohybrid are added.The preparation, first base oil and organic additives such as anti-oxidation, anti-wear, rust prevention are mixed, then two kinds of modified materials are uniformly added by shear dispersion process.Layered material uses coprecipitation and calcination reconstruction process to introduce boron element into layer, and nanohybrid is uniformly doped with hafnium in silica shell layer by sol-gel method.The hydraulic oil prepared by the application has excellent low-temperature fluidity, outstanding fire resistance, good thermal oxidation stability and excellent extreme pressure and wear resistance, and is suitable for harsh industrial environment with fire hazard.

Description

Technical Field

[0001] This invention relates to the field of high-performance specialty lubricants, specifically to a low-pour-point, flame-retardant synthetic hydraulic oil and its preparation method. Background Technology

[0002] As the core power and transmission carrier of modern industrial equipment, the reliability and durability of hydraulic systems largely depend on the comprehensive performance of hydraulic oil. With industrial technology advancing towards high pressure, high speed, high precision, and extreme temperature conditions, traditional hydraulic oils are struggling to meet increasingly stringent requirements. On the one hand, in applications such as aerospace, polar exploration, and outdoor engineering machinery in frigid regions, hydraulic systems must possess excellent low-temperature starting capabilities. This necessitates hydraulic oils with extremely low pour points and good low-temperature fluidity to ensure smooth pumping even at low temperatures, preventing start-up wear and a surge in energy consumption. On the other hand, in high-temperature or fire-prone industrial scenarios such as metallurgical continuous casting, underground coal mines, thermal power generation, and heat treatment near open flames, the risk of combustion caused by hydraulic oil leaks cannot be ignored. Therefore, excellent fire-resistant properties are a key indicator for ensuring the safety of personnel and equipment. Furthermore, thermal oxidation stability under long-term operation, wear protection capabilities, and compatibility with various metal materials are all indispensable dimensions for evaluating a high-performance hydraulic oil. An ideal hydraulic oil needs to achieve a delicate balance among multiple properties such as low pour point, flame retardancy, stability, and lubrication, which is precisely the core challenge and main focus of current technological research and development.

[0003] Currently, mainstream hydraulic oils on the market can be broadly categorized into mineral oil-based, synthetic, and flame-retardant types, each with significant limitations. Traditional mineral oils are widely available and inexpensive, but their molecular structure results in poor low-temperature fluidity, a high pour point, and limited flash and auto-ignition points. They are also prone to oxidation at high temperatures, forming carbon deposits and sludge, and their flame-retardant safety is insufficient. To improve flame resistance, a series of products have been developed, including water-glycol, water-in-oil emulsions, and phosphate ester synthetic fluids. However, water-based hydraulic fluids have a narrow operating temperature range, are prone to freezing at low temperatures and evaporation at high temperatures, exhibit strong corrosiveness to metals, and generally have poor lubrication performance. While phosphate ester-based hydraulic fluids offer excellent flame resistance, their poor biodegradability and swelling properties in various sealing materials pose risks to environmental friendliness and system compatibility. Synthetic ester-based hydraulic oils, represented by polyol esters, perform well in terms of high-temperature stability, viscosity characteristics, and biodegradability, but their inherent flame resistance still has room for improvement, especially in dealing with extreme high-temperature jet flames or ignition from hot surfaces. In recent years, research on introducing inorganic nanomaterials as functional additives into lubricating oil base oils to improve their anti-wear, thermal conductivity, or extreme pressure properties has become increasingly active. However, problems such as the long-term dispersion stability of nanoparticles in the oil phase, compatibility with composite additive systems, and how to design structures to simultaneously endow base oils with multiple functions (such as synergistic improvement of rheology and flame retardancy) have not yet been systematically solved, which limits their practical application in high-standard hydraulic oils.

[0004] To address the aforementioned technical bottlenecks, the present invention aims to provide a novel solution. Through molecular design and structural innovation, two inorganic nanocompounds with specific functions are synthesized and their surfaces are modified with organic compounds to solve the problem of dispersion stability in base oils. Furthermore, these two modified inorganic materials are scientifically compounded with selected synthetic ester base oils and various functional additives to synergistically improve the overall performance of hydraulic oils. This technical solution is particularly dedicated to overcoming the industry challenge of simultaneously achieving low pour point and high flame resistance, while significantly enhancing the thermal oxidation stability and lubrication protection capabilities under extreme pressures. This meets the comprehensive requirements of the most demanding industrial application environments for hydraulic media, representing an important development direction for high-performance synthetic hydraulic oils. Summary of the Invention

[0005] The purpose of this invention is to provide a low-pour-point, flame-retardant synthetic hydraulic oil and its preparation method, which overcomes the technical problem that existing hydraulic oils cannot simultaneously possess excellent low-temperature fluidity and high flame-retardant safety.

[0006] The present invention achieves the above objectives through the following technical solutions:

[0007] A method for preparing a low-pour-point, flame-retardant synthetic hydraulic oil, comprising the following steps:

[0008] S1. By weight, add 75.0-85.0 parts of pentaerythritol oleate to a mixing vessel, stir, and heat to 55-65℃; while stirring, add 0.8-1.5 parts of dialkyl dithiophosphate, 0.3-0.8 parts of alkylated diphenylamine, 0.2-0.5 parts of antioxidant, 0.05-0.15 parts of dodecenyl succinate half ester, 0.02-0.08 parts of benzotriazole, 0.1-0.5 parts of polymethacrylate, and 0.5-1.5 parts of polyisobutylene succinimide, stir, and obtain a mixture;

[0009] S2. Add 0.5-2.0 parts of γ-aminopropyltriethoxysilane-modified layered zinc boroaluminate hydroxide to the mixture and shear disperse; add 0.5-2.0 parts of γ-aminopropyltriethoxysilane-modified hafnium-doped silica-coated titanium carbide nano-hybrid and continue shear dispersion; add 0.5-1.2 parts of sulfurized olefin and stir; cool to 30-35℃, add defoamer and stir.

[0010] In this invention, the formation of the low-pour-point, flame-retardant synthetic hydraulic oil is a comprehensive embodiment of multi-component synergy and interface engineering. Using pentaerythritol oleate as the base oil, ashless anti-wear agents, a composite antioxidant system, rust inhibitors, metal deactivators, pour point depressants, and dispersants are dissolved sequentially under gentle heating to construct a basic lubrication framework. The core lies in the gradient introduction of two silane-modified nano-additives: under high-speed shearing, layered zinc boroaluminate hydroxide is uniformly dispersed, its layered structure stably suspended in the shear field, and can release borate to form a protective film under high-temperature conditions, significantly improving flame-retardant safety; hafnium-doped nano-hybrids simultaneously achieve nanoscale dispersion, the titanium carbide core provides hardness support, and the hafnium-doped silica shell enhances interfacial bonding, synergistically optimizing boundary lubrication performance. Sulfated olefins further enhance extreme pressure anti-wear capabilities, and polysiloxane defoamers are added after cooling to eliminate bubble interference. The entire process ensures that the interfaces of each component are compatible and the structure is stable. The final product is precision filtered to obtain a synthetic hydraulic medium that has excellent low-temperature fluidity, high flame retardancy, excellent anti-wear and friction reduction properties, and long-term storage stability, fully meeting the stringent requirements of high-end hydraulic systems for cleanliness, safety and reliability.

[0011] According to a preferred embodiment of the present invention, in step S1, the antioxidant is a phosphite antioxidant.

[0012] According to a preferred embodiment of the present invention, in step S2, the defoamer is a polysiloxane defoamer.

[0013] According to a preferred embodiment of the present invention, the method for preparing the γ-aminopropyltriethoxysilane surface-modified layered zinc boroaluminate hydroxide includes:

[0014] A1. By weight, dissolve 58-62 parts of zinc nitrate hexahydrate and 36-38 parts of aluminum nitrate nonahydrate in a mixed solvent of deionized water and anhydrous ethanol to obtain solution A; dissolve 14-16 parts of sodium carbonate and 6-10 parts of sodium hydroxide in deionized water to obtain solution B; under stirring and nitrogen protection, add solution B dropwise to solution A, adjust the pH to 9.8-10.2, and obtain a reaction mixture; subject the reaction mixture to hydrothermal crystallization at 115-125℃ to obtain the reaction product; wash and dry the reaction product to obtain a carbonate-intercalated zinc-aluminum hydrotalcite precursor.

[0015] A2. The carbonate-intercalated zinc-aluminum hydrotalcite precursor is calcined in air at 445-455℃ to obtain a zinc-aluminum composite metal oxide. 98-102 parts of the zinc-aluminum composite metal oxide are dispersed in a buffer solution with pH 9.3-9.7, consisting of 6-7 parts of boric acid and 2-4 parts of sodium hydroxide, and stirred at 58-62℃. After the reaction is complete, the solid is collected by centrifugation, washed, and dried to obtain a borate-intercalated zinc-aluminum hydrotalcite intermediate. 98-102 parts of the borate-intercalated zinc-aluminum hydrotalcite intermediate are dispersed with 1.8-2.2 parts of γ-aminopropyltriethoxysilane in a mixed solution of anhydrous ethanol and deionized water, and stirred in a water bath at 58-62℃ to obtain the reaction product. The reaction product is centrifuged, washed, and dried.

[0016] In this invention, the construction of the γ-aminopropyltriethoxysilane-modified layered zinc boroaluminate hydroxide relies on the structural memory effect and surface chemical modification principle of layered double hydroxides. First, using zinc and aluminum salts as metal sources, they are co-precipitated with a mixed alkaline solution of sodium carbonate and sodium hydroxide in a nitrogen atmosphere. The pH of the system is precisely controlled to a weakly alkaline window, promoting the simultaneous precipitation of zinc and aluminum ions to form a carbonate-stable intercalated hydrotalcite precursor. This precursor undergoes hydrothermal crystallization to perfect the layered crystal structure. The precursor is then transformed into a mixed metal oxide through appropriate heat treatment, activating its structural memory properties. A key step involves dispersing it in a buffer system prepared with boric acid and sodium hydroxide, with the pH strictly limited to a weakly alkaline range. This induces the layers to rebuild their layered configuration under the guidance of borate ions, allowing borate ions to be stably embedded in the interlayer in anionic form, endowing the material with high-temperature thermal stability and flame-retardant potential. Subsequently, an amino-containing silane coupling agent is introduced. In the ethanol aqueous phase, its alkoxy group hydrolyzes to generate silanol groups, which undergo dehydration condensation with the metal hydroxyl groups on the material surface to form a strong silicon-oxygen metal covalent bond. The amino group faces the oil phase, realizing the interface transformation from hydrophilic to lipophilic, which significantly improves its dispersion stability and compatibility in synthetic base oils.

[0017] According to a preferred embodiment of the present invention, in step A1, the reaction mixture is subjected to hydrothermal crystallization at 115-125°C for 24-30 hours.

[0018] According to a preferred embodiment of the present invention, in step A2, the calcination time at 445-455°C is 4-6 hours.

[0019] According to a preferred embodiment of the present invention, the method for preparing the γ-aminopropyltriethoxysilane-modified hafnium-doped silica-coated titanium carbide nanocomposite includes:

[0020] B1. By weight, disperse 98-102 parts of titanium carbide nanoparticles in a mixed solution of deionized water and anhydrous ethanol, and sonicate. Under stirring, add 5-10 parts of ammonia and 0.5-1.0 parts of tetraethyl orthosilicate sequentially, and stir at room temperature to obtain a suspension. Dissolve 20-40 parts of hafnium tetrachloride in anhydrous ethanol and add glacial acetic acid to obtain a hafnium precursor solution. Under continuous stirring, add the hafnium precursor solution to the suspension and add 2.0-4.0 parts of tetraethyl orthosilicate. Adjust the pH to 3.8-4.2 with dilute acetic acid, heat in a water bath at 58-62℃, and stir under reflux to obtain the reaction product.

[0021] B2. The reaction product is centrifuged, washed, and dried to obtain a dried product. Under argon protection, the dried product is calcined in a tube furnace at 595-605℃ to obtain hafnium-doped silica-coated titanium carbide nanocomposite. 98-102 parts of the hafnium-doped silica-coated titanium carbide nanocomposite and 1.5-2.5 parts of γ-aminopropyltriethoxysilane are dispersed in a mixed solution of anhydrous ethanol and deionized water, and the mixture is stirred and reacted in a water bath at 58-62℃ to obtain a reaction mixture. The reaction mixture is centrifuged, washed, and dried.

[0022] In this invention, the synthesis of the γ-aminopropyltriethoxysilane-modified hafnium-doped silica-coated titanium carbide nanohybrids is based on a sol-gel co-condensation and surface functionalization strategy. Titanium carbide nanoparticles are uniformly dispersed by ultrasound and then reacted with a silicon source under ammonia catalysis to construct an initial silica coating layer on their surface. Hafnium tetrachloride is pre-dissolved in anhydrous ethanol and glacial acetic acid is added to form a stable complex, effectively inhibiting the hydrolysis and precipitation of the metal precursor. This solution, along with a supplementary silicon source, is introduced into the system and heated under reflux in a weakly acidic environment. The hafnium species and silicon source undergo molecular-level co-hydrolysis and co-condensation, resulting in hafnium atoms uniformly doped into the silica network via hafnium-oxysilicon chemical bonds, forming a dense composite shell. Heat treatment under an inert atmosphere further enhances the crystallinity and structural integrity of the shell. Finally, an amino-containing silane coupling agent was used for surface modification. Its hydrolysis products condensed and grafted with the hydroxyl groups on the surface of the nanoparticles to form an organic-inorganic interface bridge. The exposed amino groups endowed the particles with excellent oil solubility, ensuring their long-term stable suspension in hydraulic media and synergistically playing the role of anti-wear and enhancing oil film strength.

[0023] According to a preferred embodiment of the present invention, in step B1, the stirring and reflux reaction time is 12-14 hours.

[0024] According to a preferred embodiment of the present invention, in step B2, the stirring reaction in a water bath at 58-62°C is carried out for 2-4 hours.

[0025] The present invention also provides a low-pour-point, flame-retardant synthetic hydraulic oil prepared according to the preparation method of the low-pour-point, flame-retardant synthetic hydraulic oil.

[0026] The beneficial effects of this invention are as follows:

[0027] The low-pour-point, flame-retardant synthetic hydraulic oil and its preparation method provided by this invention achieve a breakthrough improvement in the comprehensive performance of hydraulic oil through innovative formulation system and material design. Its technical effects are significant and comprehensive, specifically reflected in the following closely related aspects.

[0028] First, the most direct technical effect of this invention lies in endowing the hydraulic oil with superior and balanced key performance characteristics. This hydraulic oil exhibits exceptional low-temperature fluidity, maintaining low viscosity and smooth pumping even in extremely cold environments, ensuring smooth cold starts and effectively preventing wear and energy consumption surges caused by low-temperature solidification or poor fluidity. Simultaneously, its flame retardancy and safety reach an extremely high level. Not only are its flash point and auto-ignition point significantly higher than conventional synthetic ester oils, but it also effectively resists direct ignition from high-temperature jet flames or hot surfaces, greatly reducing the risk of fire in high-temperature or near-fire conditions, providing a solid guarantee for equipment and personnel safety. In terms of lubrication protection, this oil combines excellent anti-wear and extreme pressure carrying capacity, forming a robust protective film on the friction pair surfaces under high load and boundary lubrication conditions, significantly reducing wear and extending the service life of core hydraulic components. Furthermore, the oil possesses outstanding thermal oxidation stability, effectively resisting oxidative deterioration during long-term high-temperature operation, inhibiting the formation of sludge and carbon deposits, thereby keeping the system clean and extending oil change intervals.

[0029] Secondly, the superior performance mentioned above stems from the core inorganic functional material design and synergistic mechanism of this invention. Two surface-modified inorganic nanomaterials are key to achieving the technical effects. The layered zinc aluminoborate hydroxide material possesses a unique nanosheet structure, which effectively intervenes in the crystallization tendency of base oil molecules at low temperatures, improving rheology. During friction, its layered structure itself provides lubrication, while the zinc, boron, and other elements it contains participate in forming a tough protective film with self-healing capabilities on the friction surface, thus providing excellent friction reduction and wear resistance in the medium- and low-temperature range. The other hafnium-doped silica-coated titanium carbide core-shell nanohybrid material primarily serves high-temperature protection. Its highly thermally conductive core helps dissipate local hot spots, while the outer doped silica shell undergoes a ceramic transformation when exposed to extreme temperatures, forming a dense physical barrier on the metal surface, fundamentally blocking the combustion chain. This is the core mechanism for achieving exceptional flame resistance. These two materials have a clear division of labor and complement each other in time and space. Together with a carefully selected network of organic additives, they create a synergistic effect, forming a comprehensive and robust performance guarantee system that covers everything from low to high temperatures and from normal lubrication to extreme protection.

[0030] Finally, the technical effects of this invention extend to superior product stability, wide applicability, and good environmental friendliness. By covalently grafting inorganic nanoparticles onto their surface, the long-term dispersion stability problem in the oil phase is fundamentally solved, ensuring consistent and stable performance throughout the product's lifespan and meeting the stringent requirements of hydraulic systems for high media cleanliness. This oil uses high-performance synthetic esters as its base oil, exhibiting good compatibility with common metal and sealing materials, avoiding the material compatibility risks associated with some fire-resistant hydraulic fluids. From an environmental perspective, its base oil components possess excellent biodegradability potential, and the functional inorganic materials used are chemically stable, containing no environmentally harmful heavy metals or halogens, reflecting an advanced design concept that combines high performance with green technology. In summary, this invention successfully overcomes the industry's technical bottleneck of balancing low pour point and high fire resistance, while significantly improving the overall performance and reliability of the oil. It provides a safe, long-lasting, and reliable high-end hydraulic transmission medium solution for high-end equipment fields such as metallurgy, mining, power, aviation, and engineering machinery operating in extreme environments, possessing significant practical value and broad application prospects. Detailed Implementation

[0031] The following detailed embodiments are only used to further illustrate this application and should not be construed as limiting the scope of protection of this application. Those skilled in the art can make some non-essential improvements and adjustments to this application based on the above application content.

[0032] Example 1

[0033] This embodiment provides a method for preparing a low-pour-point, flame-retardant synthetic hydraulic oil, the steps of which include:

[0034] Preparation of layered zinc boroaluminate hydroxide surface-modified with γ-aminopropyltriethoxysilane:

[0035] Step A1: In a 2000 mL three-necked flask equipped with a stirrer, thermometer, and constant-pressure dropping funnel, add 800 mL of deionized water and 100 mL of anhydrous ethanol as a mixed solvent. Under nitrogen protection and vigorous stirring, add 60.0 g of zinc nitrate hexahydrate and 37.5 g of aluminum nitrate nonahydrate to the solvent sequentially, stirring until completely dissolved to form solution A. In another beaker, dissolve 15.9 g of sodium carbonate and 8.0 g of sodium hydroxide in 200 mL of deionized water to obtain solution B. Under continuous vigorous stirring and nitrogen protection, slowly add solution B dropwise to solution A through a constant-pressure dropping funnel, monitoring the addition rate in real time with a pH meter to ensure the pH of the system eventually stabilizes at 10.0. After the addition is complete, transfer the resulting white gel-like reaction mixture to a polytetrafluoroethylene-lined high-pressure reactor and carry out a hydrothermal crystallization reaction in an oven at 120 °C for 24 h. After the reaction was completed, the product was naturally cooled to room temperature. The product was then washed 5 times each by centrifugation with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven at 80°C for 12 hours. The product was then gently ground in an agate mortar to obtain the carbonate intercalated zinc aluminum hydrotalcite precursor.

[0036] Step A2: Take 100.0 g of the above-mentioned dried precursor powder, place it in a muffle furnace, and calcine it at 450 °C for 4 h in air atmosphere to obtain zinc-aluminum composite metal oxide (LDO). Weigh 100.0 g of the LDO powder and disperse it in 1000 mL of boric acid-sodium hydroxide buffer solution with a pH of 9.5 (this buffer solution is prepared by dissolving 6.2 g of boric acid and 3.0 g of sodium hydroxide in deionized water), and stir the reaction in a constant temperature water bath at 60 °C for 6 h. After the reaction is complete, collect the solid by centrifugation, wash it three times with deionized water, and dry it at 80 °C to obtain a borate-intercalated zinc-aluminum hydrotalcite intermediate. Weigh 100.0 g of this intermediate and 2.0 g of γ-aminopropyltriethoxysilane (KH-550), disperse them in a mixed solution of 100 mL of anhydrous ethanol and 3 mL of deionized water, and stir the reaction in a water bath at 60 °C for 2 h. After the reaction was completed, the solid was collected by centrifugation, washed three times with anhydrous ethanol, and dried under vacuum at 80°C for 12 h to obtain layered zinc boroaluminate hydroxide modified with γ-aminopropyltriethoxysilane, denoted as modified ZBAOH powder.

[0037] Preparation of Hafnium-doped silica-coated titanium carbide nanohybrids modified with γ-aminopropyltriethoxysilane

[0038] Step B1: Weigh 100.0 g of titanium carbide (TiC, average particle size 50 nm) nanoparticles and disperse them in 2000 mL of a mixed solution of deionized water and anhydrous ethanol in a volume ratio of 1:4. Sonicate the solution for 30 min to form a homogeneous suspension. Under mechanical stirring, add 8.0 mL of ammonia (28% concentration) and 0.8 mL of tetraethyl orthosilicate (TEOS) sequentially to the suspension. Stir and react at room temperature (25℃) for 6 h to initially coat the TiC particles with a layer of SiO2. Separately weigh 30.0 g of hafnium tetrachloride (HfCl4), add 2 mL of glacial acetic acid, and dissolve in 20 mL of anhydrous ethanol. Stir until completely dissolved to obtain a clear hafnium precursor solution. Slowly add this hafnium precursor solution to the above suspension under continuous stirring, followed by the addition of 3.0 mL of TEOS. Adjust the pH of the mixture to 4.0 with dilute acetic acid, transfer the mixture to a flask equipped with a reflux condenser, and heat and reflux in a 60°C water bath for 12 hours with stirring.

[0039] Step B2: After the reaction was complete, the product was washed three times with anhydrous ethanol by centrifugation and dried in an oven at 80°C. The dried powder was placed in a tube furnace and calcined at 600°C for 2 hours under argon protection to obtain gray-black hafnium-doped silica-coated titanium carbide nanocomposite (Hf-STC) powder. 100.0 g of this Hf-STC powder and 2.0 g of γ-aminopropyltriethoxysilane (KH-550) were weighed and dispersed in a mixed solution of 100 mL anhydrous ethanol and 3 mL deionized water, and stirred in a water bath at 60°C for 2 hours. After the reaction was complete, the solid was collected by centrifugation, washed three times with anhydrous ethanol, and dried under vacuum at 80°C for 12 hours to obtain γ-aminopropyltriethoxysilane-modified hafnium-doped silica-coated titanium carbide nanocomposite, denoted as modified Hf-STC powder.

[0040] Preparation of Low-Pour-Point Anti-Flame Synthetic Hydraulic Oil

[0041] Step S1: In a clean mixing vessel, add 800g of pentaerythritol oleate, start stirring and slowly heat to 60°C. Under medium shear rate stirring, slowly add 12g of dialkyl dithiophosphate (ashless), 5g of alkylated diphenylamine, 3g of phosphite antioxidant, 1g of dodecenyl succinate half-ester, 0.5g of benzotriazole, 3g of polymethacrylate pour point depressant and 10g of high molecular weight polyisobutylene succinimide dispersant in sequence. After each addition, continue stirring for at least 15 minutes until completely dissolved and mixed evenly to obtain the basic mixture.

[0042] Step S2: Start the high-shear emulsifier, set the speed to 5000 rpm, and slowly add 10g of modified ZBAOH powder to the base mixture obtained in Step S1, continuously dispersing at high speed for 1 hour. Then, at the same speed, slowly add 10g of modified Hf-STC powder to the system, continuing high-speed shear dispersion for another 1 hour. Afterward, restore the stirring speed to medium, add 8g of sulfurized olefin, and continue stirring for 30 minutes. Finally, circulate cooling water through the blending vessel jacket to cool the oil temperature to 35°C, add 0.05g of polysiloxane defoamer pre-diluted with 10g of base oil, and slowly stir for at least 1 hour to ensure uniform distribution of the defoamer. Samples are taken for testing of kinematic viscosity, pour point, flash point, and other indicators. After passing the tests, filter using a 5μm precision filtration system, and fill into the final product: low-pour-point, flame-retardant synthetic hydraulic oil.

[0043] Example 2

[0044] The specific implementation method is the same as in Example 1, except that the preparation of the layered zinc boroaluminate hydroxide modified with γ-aminopropyltriethoxysilane is as follows:

[0045] Step A1: In a 2000mL three-necked flask, add 800mL of deionized water and 100mL of anhydrous ethanol. Under nitrogen protection, add 62.0g of zinc nitrate hexahydrate and 38.0g of aluminum nitrate nonahydrate sequentially, stirring to dissolve them into solution A. Dissolve 16.0g of sodium carbonate and 10.0g of sodium hydroxide in 200mL of deionized water to obtain solution B. Add solution B dropwise to solution A, controlling the final pH to 9.8. Transfer the reaction mixture to a high-pressure reactor and hydrothermally crystallize at 125℃ for 26h. Wash the product and dry it under vacuum at 80℃ for 12h to obtain the precursor.

[0046] Step A2: Take 100.0 g of the precursor and calcine it at 455 °C for 5 h in air to obtain LDO. Disperse the LDO in 1000 mL of pH 9.4 buffer solution prepared with 6.5 g boric acid and 3.5 g sodium hydroxide, and stir the reaction at 58 °C for 6 h. Centrifuge, wash with water, and dry the product to obtain the intermediate. Take 100.0 g of the intermediate and 1.9 g of KH-550, and react them in 100 mL of anhydrous ethanol and 3 mL of deionized water in a water bath at 62 °C for 2 h. Centrifuge, wash with ethanol, and vacuum dry at 80 °C for 12 h to obtain modified ZBAOH powder.

[0047] Preparation of γ-aminopropyltriethoxysilane-modified hafnium-doped silica-coated titanium carbide nanohybrids:

[0048] Step B1: Disperse 102.0 g of titanium carbide nanoparticles in 2000 mL of a mixture of deionized water and anhydrous ethanol (1:4, v / v) and sonicate for 30 min. Add 5.0 mL of ammonia and 1.0 mL of LTEOS and stir at room temperature for 6 h. Dissolve 40.0 g of hafnium tetrachloride in 2 mL of glacial acetic acid in 20 mL of anhydrous ethanol to obtain a precursor solution. Add this to the suspension, followed by 4.0 mL of LTEOS. Adjust the pH to 3.9 and reflux at 62 °C for 13 h.

[0049] Step B2: The product was washed with ethanol, dried at 80°C, and calcined at 595°C for 2 hours under argon protection to obtain Hf-STC powder. 100.0 g of this powder and 2.5 g of KH-550 were reacted in a water bath at 58°C for 3 hours in 100 mL of anhydrous ethanol and 3 mL of deionized water. The product was centrifuged, washed with ethanol, and vacuum dried at 80°C for 12 hours to obtain modified Hf-STC powder.

[0050] Preparation of low-pour-point, flame-retardant synthetic hydraulic oil:

[0051] Step S1: Add 820g pentaerythritol oleate to a mixing vessel and heat to 62℃. Then, add 15g dialkyl dithiophosphate, 8g alkylated diphenylamine, 5g phosphite antioxidant, 1.5g dodecenyl succinate half-ester, 0.8g benzotriazole, 5g polymethacrylate, and 15g polyisobutylene succinimide sequentially, stirring for 15 minutes after each addition until homogeneous.

[0052] Step S2: Using a high-shear emulsifier (5000 rpm), first add 15 g of modified ZBAOH powder and shear at high speed for 1 hour; then add 15 g of modified Hf-STC powder and shear at high speed for 1 hour. Return to medium stirring, add 12 g of sulfurized olefin, and stir for 30 minutes. Cool to 32°C, add 0.08 g of polysiloxane defoamer (pre-diluted), and stir slowly for 1 hour. Filter and fill.

[0053] Example 3

[0054] The specific implementation method is the same as in Example 1, except that the preparation of the layered zinc boroaluminate hydroxide modified with γ-aminopropyltriethoxysilane is as follows:

[0055] Step A1: In a 2000mL three-necked flask, add 800mL of deionized water and 100mL of anhydrous ethanol. Under nitrogen protection, add 58.0g of zinc nitrate hexahydrate and 36.0g of aluminum nitrate nonahydrate sequentially, stirring to dissolve them into solution A. Dissolve 14.0g of sodium carbonate and 6.0g of sodium hydroxide in 200mL of deionized water to obtain solution B. Add solution B dropwise to solution A, controlling the final pH to 10.2. Transfer the reaction mixture to a high-pressure reactor and hydrothermally crystallize at 115℃ for 28h. Wash the product and dry it under vacuum at 80℃ for 12h to obtain the precursor.

[0056] Step A2: Take 100.0 g of the precursor and calcine it at 445 °C for 6 h in air to obtain LDO. Disperse the LDO in 1000 mL of pH 9.6 buffer solution prepared with 7.0 g of boric acid and 4.0 g of sodium hydroxide, and stir the reaction at 62 °C for 6 h. Centrifuge, wash with water, and dry the product to obtain the intermediate. Take 100.0 g of the intermediate and 2.1 g of KH-550, and react them in 100 mL of anhydrous ethanol and 3 mL of deionized water in a water bath at 58 °C for 2 h. Centrifuge, wash with ethanol, and vacuum dry at 80 °C for 12 h to obtain modified ZBAOH powder.

[0057] Preparation of γ-aminopropyltriethoxysilane-modified hafnium-doped silica-coated titanium carbide nanohybrids:

[0058] Step B1: Disperse 98.0 g of titanium carbide nanoparticles in 2000 mL of a mixture of deionized water and anhydrous ethanol (1:4, v / v) and sonicate for 30 min. Add 10.0 mL of ammonia and 0.5 mL of LTEOS and stir at room temperature for 6 h. Dissolve 20.0 g of hafnium tetrachloride in 2 mL of glacial acetic acid in 20 mL of anhydrous ethanol to obtain a precursor solution. Add this to the suspension, followed by 2.0 mL of LTEOS. Adjust the pH to 4.1 and reflux at 58 °C for 14 h.

[0059] Step B2: After washing with ethanol and drying at 80°C, the product was calcined at 605°C for 2 hours under argon protection to obtain Hf-STC powder. 100.0 g of this powder and 1.8 g of KH-550 were reacted in a water bath at 62°C for 4 hours in 100 mL of anhydrous ethanol and 3 mL of deionized water. The product was then centrifuged, washed with ethanol, and vacuum dried at 80°C for 12 hours to obtain modified Hf-STC powder.

[0060] Preparation of low-pour-point, flame-retardant synthetic hydraulic oil:

[0061] Step S1: Add 780g of pentaerythritol oleate to a mixing vessel and heat to 58°C. Then, add 8g of dialkyl dithiophosphate, 3g of alkylated diphenylamine, 2g of phosphite antioxidant, 0.5g of dodecenyl succinate half-ester, 0.2g of benzotriazole, 1g of polymethacrylate, and 5g of polyisobutylene succinimide sequentially, stirring for 15 minutes after each addition until homogeneous.

[0062] Step S2: Using a high-shear emulsifier (5000 rpm), first add 5g of modified ZBAOH powder and shear at high speed for 1 hour; then add 5g of modified Hf-STC powder and shear at high speed for 1 hour. Return to medium stirring, add 5g of sulfurized olefin, and stir for 30 minutes. Cool to 30°C, add 0.03g of polysiloxane defoamer (pre-diluted), and stir slowly for 1 hour. Filter and fill.

[0063] Comparative Example 1

[0064] The specific implementation method is the same as in Example 1, except that no modified ZBAOH powder and modified Hf-STC powder are added in this comparative example, and the rest is the same as in Example 1.

[0065] Comparative Example 2

[0066] The specific implementation method is the same as in Example 1, except that this comparative example only adds an equal mass of the carbonate-intercalated zinc-aluminum hydrotalcite precursor prepared in step A1 of Example 1. Hydraulic oil is prepared according to steps S1-S2 of Example 1, but the added modified ZBAOH powder and modified Hf-STC powder are replaced with an equal mass of the carbonate-intercalated zinc-aluminum hydrotalcite precursor prepared in step A1 of Example 1.

[0067] Comparative Example 3

[0068] The specific implementation method is the same as in Example 1, except that two unmodified intermediate materials are added in this comparative example. A borate-intercalated zinc-aluminum hydrotalcite intermediate and a calcined hafnium-doped silica-coated titanium carbide nanocomposite (Hf-STC) were prepared according to the method in Example 1, but the final step of surface modification reaction with KH-550 was omitted. In the hydraulic oil preparation step S2, 10g of each of these two unmodified intermediates were added, and the remaining steps were exactly the same as in Example 1.

[0069] Performance testing

[0070] The low-pour-point, flame-retardant synthetic hydraulic oils prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests according to the following method, which included the following steps:

[0071] Kinematic viscosity testing was performed using a calibrated glass capillary viscometer in a constant temperature bath. First, the time it took for the oil sample to flow through a designated capillary was measured and the viscosity was calculated at a constant temperature of 40.0℃. Then, the same operation was repeated in a low-temperature constant temperature bath at -40.0℃. Viscosity results were reported in mm² / s.

[0072] The pour point test is performed according to the standard laboratory method. Pour about 45 mL of oil sample into a clean test tube, preheat it under the specified conditions, and then place it in an automatic pour point tester. Cool the test tube at 3°C ​​intervals and remove it to check the fluidity. When the test tube is placed horizontally for 5 seconds and the oil surface no longer moves, record the temperature and add 3°C as the reported pour point. The unit is °C.

[0073] The flash point test adopts the Cleveland open cup method. The oil sample is poured into a standard brass cup to the specified mark. Under a strictly controlled opening rate, a standard test flame is periodically swept across the mouth of the cup. The temperature at which the oil vapor first flashes is recorded as the flash point, and the unit is ℃.

[0074] The auto-ignition point test is conducted in a dedicated heating furnace. A small amount of oil sample is injected into a hot surface dish that has been preheated to a certain temperature and placed inside the furnace. The test is then repeated at different temperatures to determine the lowest temperature at which auto-ignition occurs. The result is reported as the auto-ignition point, in °C.

[0075] The thermal oxidation stability test was conducted using the rotating oxygen bomb method. A 50.0g oil sample, 5.0mL distilled water, and a copper catalyst coil were placed in a specially designed oxygen bomb. After being filled with oxygen at a pressure of 620kPa, the bomb was placed in an oil bath at 150.0℃ and kept rotating continuously. The time taken from the start of the test to the pressure drop of 175kPa inside the oxygen bomb was recorded and reported as the oxidation induction period, in minutes.

[0076] Extreme pressure performance testing was performed using a four-ball extreme pressure testing machine. At a speed of 1760 rpm and room temperature, a progressively increasing load was applied to a set of four standard steel balls (one on top and three on the bottom), with each run lasting 10 seconds, until sintering occurred. The load at the level before sintering occurred was reported as the maximum non-seizing load, and the load at which sintering occurred was reported as the sintering load. The data in the table are the sintering loads, and the unit is kgf.

[0077] The wear resistance test was performed using a four-ball wear tester. The test was conducted for 60 minutes under a fixed load of 392N, an oil temperature of 75.0℃, and a speed of 1200rpm. After the test, the diameter of the wear marks on the three bottom steel balls was measured, and the arithmetic mean was calculated as the reported wear mark diameter in mm.

[0078] The copper sheet corrosion test involves immersing a polished standard copper sheet completely in an oil sample at 100.0°C for 3 hours. After removal, the sheet is cleaned and compared with the ASTM corrosion standard color chart. The degree of color change is rated and reported.

[0079] The liquid phase corrosion test is divided into Method A (distilled water) and Method B (artificial seawater). The polished steel rod is immersed in a mixture of oil and water and stirred at 1000 rpm at 60.0℃ for 24 hours. The steel rod is then removed and the surface corrosion is visually inspected. No rust means it passes, and rust means it fails.

[0080] Foam characteristics were tested using a foam characteristics analyzer. Under three conditions—Sequence I (24.0℃), Sequence II (93.5℃), and Sequence III (cooling the Sequence II sample back to 24.0℃)—dry air was introduced into the oil sample at a constant flow rate for 5 minutes. The foam volume was measured at the moment the air flow stopped and after standing for 10 minutes. The results were reported in the form of "foam volume at the moment of stopping / foam volume after standing for 10 minutes," with the unit being mL.

[0081] Test results:

[0082] Table 1: Test results of each embodiment and comparative example

[0083]

[0084] As can be seen from Table 1, the low-pour-point and flame-retardant synthetic hydraulic oils prepared in Examples 1 to 3, compared with Comparative Examples 1 to 3, systematically and significantly solve the core contradiction in the prior art that hydraulic oils cannot simultaneously possess excellent low-temperature fluidity and high flame-retardant safety, and achieve synergistic improvement in thermal oxidation stability and extreme pressure anti-wear properties.

[0085] Specifically, in terms of low-temperature performance, the kinematic viscosity of Examples 1-3 at -40℃ is only 2920-3050 mm² / s, which is much lower than that of Comparative Example 1 (4250 mm² / s). At the same time, the pour point is as low as -49~-52℃, which is significantly improved compared to -42℃ of Comparative Example 1. This proves that the present invention effectively improves the rheological properties of oil under severe cold by introducing a specific modified layered zinc boroaluminate hydroxide, ensuring pumping and start-up performance in extremely cold environments.

[0086] Regarding the crucial aspect of fire resistance and safety, the auto-ignition point of the embodiment is as high as 562-570°C, which is a significant improvement of more than 67°C compared to Comparative Example 1 (495°C) without any added functional nanomaterials. It is also significantly better than Comparative Example 2 (508°C) with only ordinary layered materials and Comparative Example 3 (530°C) with unmodified functional materials. This strongly confirms that the unique mechanism by which specially designed hafnium-doped core-shell nano-hybrids form a ceramic barrier when exposed to high temperatures is the key to giving the oil excellent fire resistance.

[0087] In characterizing the thermal oxidation stability of long-term use, the rotating oxygen bomb time of the example was as long as 1480-1600 min, far exceeding the 820 min of Comparative Example 1, indicating that the two modified nanomaterials and the composite antioxidant system produced a significant synergistic antioxidant effect.

[0088] In terms of extreme pressure anti-wear protection, the four-ball solder joint load of Examples 1-3 reached 1240-1280 kgf, and the wear scar diameter was as small as 0.35-0.38 mm, which was superior to all comparative examples. In particular, the wear scar diameter data clearly showed that the dispersibility and anti-wear effect of Comparative Example 3 decreased due to the lack of surface modification, which confirmed that surface organic modification is indispensable for nano-additives to give full play to their friction reduction and anti-wear functions.

[0089] In summary, the test data fully demonstrates that this invention, through the synergistic design of two innovative inorganic functional materials and a refined surface modification process, not only successfully overcomes the traditional technical bottleneck of the difficulty in simultaneously achieving low pour point and flame retardancy, but also realizes a comprehensive performance leap in lubrication protection and oxidation stability.

[0090] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a low-pour-point, flame-retardant synthetic hydraulic oil, characterized in that the steps include... include: S1. By weight, add 75.0-85.0 parts of pentaerythritol oleate to a mixing vessel, stir, and heat to 55-65℃; while stirring, add 0.8-1.5 parts of dialkyl dithiophosphate, 0.3-0.8 parts of alkylated diphenylamine, 0.2-0.5 parts of antioxidant, 0.05-0.15 parts of dodecenyl succinate half ester, 0.02-0.08 parts of benzotriazole, 0.1-0.5 parts of polymethacrylate, and 0.5-1.5 parts of polyisobutylene succinimide, stir, and obtain a mixture; S2. Add 0.5-2.0 parts of γ-aminopropyltriethoxysilane-modified layered zinc boroaluminate hydroxide to the mixture and shear disperse; add 0.5-2.0 parts of γ-aminopropyltriethoxysilane-modified hafnium-doped silica-coated titanium carbide nano-hybrid and continue shear dispersion; add 0.5-1.2 parts of sulfurized olefin and stir. Cool to 30-35℃, add defoamer, and stir; The preparation method of the γ-aminopropyltriethoxysilane-modified layered zinc boroaluminate hydroxide includes: A1. By weight, dissolve 58-62 parts of zinc nitrate hexahydrate and 36-38 parts of aluminum nitrate nonahydrate in a mixed solvent of deionized water and anhydrous ethanol to obtain solution A; dissolve 14-16 parts of sodium carbonate and 6-10 parts of sodium hydroxide in deionized water to obtain solution B; under stirring and nitrogen protection, add solution B dropwise to solution A, adjust the pH to 9.8-10.2, and obtain a reaction mixture; subject the reaction mixture to hydrothermal crystallization at 115-125℃ to obtain the reaction product; wash and dry the reaction product to obtain a carbonate-intercalated zinc-aluminum hydrotalcite precursor. A2. The carbonate-intercalated zinc-aluminum hydrotalcite precursor is calcined in air at 445-455℃ to obtain a zinc-aluminum composite metal oxide. 98-102 parts of the zinc-aluminum composite metal oxide are dispersed in a buffer solution with pH 9.3-9.7, consisting of 6-7 parts of boric acid and 2-4 parts of sodium hydroxide, and stirred at 58-62℃. After the reaction is complete, the solid is collected by centrifugation, washed, and dried to obtain a borate-intercalated zinc-aluminum hydrotalcite intermediate. 98-102 parts of the borate-intercalated zinc-aluminum hydrotalcite intermediate are dispersed with 1.8-2.2 parts of γ-aminopropyltriethoxysilane in a mixed solution of anhydrous ethanol and deionized water, and stirred in a water bath at 58-62℃ to obtain the reaction product. The reaction product is centrifuged, washed, and dried.

2. The method for preparing the low-pour-point, flame-retardant synthetic hydraulic oil according to claim 1, characterized in that, In step S1, the antioxidant is a phosphite antioxidant.

3. The method for preparing the low-pour-point, flame-retardant synthetic hydraulic oil according to claim 1, characterized in that, In step S2, the defoamer is a polysiloxane defoamer.

4. The method for preparing low-pour-point, flame-retardant synthetic hydraulic oil according to claim 1, characterized in that, In step A1, the reaction mixture is subjected to hydrothermal crystallization at 115-125°C for 24-30 hours.

5. The method for preparing low-pour-point, flame-retardant synthetic hydraulic oil according to claim 1, characterized in that, In step A2, the calcination time at 445-455℃ is 4-6 hours.

6. The method for preparing low-pour-point, flame-retardant synthetic hydraulic oil according to claim 1, characterized in that, The preparation method of the γ-aminopropyltriethoxysilane-modified hafnium-doped silica-coated titanium carbide nano-hybrid includes: B1. By weight, disperse 98-102 parts of titanium carbide nanoparticles in a mixed solution of deionized water and anhydrous ethanol, and sonicate. Under stirring, add 5-10 parts of ammonia and 0.5-1.0 parts of tetraethyl orthosilicate sequentially, and stir at room temperature to obtain a suspension. Dissolve 20-40 parts of hafnium tetrachloride in anhydrous ethanol and add glacial acetic acid to obtain a hafnium precursor solution. Under continuous stirring, add the hafnium precursor solution to the suspension and add 2.0-4.0 parts of tetraethyl orthosilicate. Adjust the pH to 3.8-4.2 with dilute acetic acid, heat in a water bath at 58-62℃, and stir under reflux to obtain the reaction product. B2. The reaction product is centrifuged, washed, and dried to obtain a dried product. Under argon protection, the dried product is calcined in a tube furnace at 595-605℃ to obtain hafnium-doped silica-coated titanium carbide nanocomposite. 98-102 parts of the hafnium-doped silica-coated titanium carbide nanocomposite and 1.5-2.5 parts of γ-aminopropyltriethoxysilane are dispersed in a mixed solution of anhydrous ethanol and deionized water, and the mixture is stirred and reacted in a water bath at 58-62℃ to obtain a reaction mixture. The reaction mixture is centrifuged, washed, and dried.

7. The method for preparing the low-pour-point, flame-retardant synthetic hydraulic oil according to claim 6, characterized in that, In step B1, the stirring and reflux reaction time is 12-14 hours.

8. The method of producing a synthetic low pour point fire resistant hydraulic fluid according to claim 6, wherein In step B2, the reaction is carried out in a water bath at 58-62℃ for 2-4 hours with stirring.

9. A low-pour-point, flame-retardant synthetic hydraulic oil, characterized in that, The low-pour-point, flame-retardant synthetic hydraulic oil is prepared by the method according to any one of claims 1-8.

Images