Process of high-surface-activity nanoscale calcium hydroxide for lubricating oil

Abstract

The invention relates to the technical field of nano materials, and discloses a process of high-surface-activity nanoscale calcium hydroxide for lubricating oil, which comprises the following steps: S1, constructing a stable oil-water emulsion dispersion system under a high shear condition; s2, introducing a surface modifier and completing pre-distribution in the system; s3, adding a calcium-containing precursor solution at a constant rate; s4, CO2 is introduced, and the pH slow change process is regulated and controlled; s5, inducing calcium hydroxide precipitation in a confinement interface and synchronously coating; s6, completing reaction aging and removing by-products; and S7, separating, washing and drying to obtain the functionalized nano calcium hydroxide. Through high-shear construction of an oil-water interface emulsion system and a micro-scale space confinement strategy, directional regulation and control of the particle size in the early stage of nucleation are realized, the technical effects of concentrated particle size distribution, low agglomeration rate and high structural integrity of the product are achieved, and the problems of disordered particle growth and violent particle size fluctuation are solved.

Description

Technical Field

[0001] The invention relates to the technical field of nano materials, in particular to a process for producing nano-scale calcium hydroxide with high surface activity for lubricating oil. Background Art

[0002] Calcium hydroxide has broad application prospects in the fields of rubber, lubrication, environmental treatment, etc. due to its alkaline sustained-release properties, adsorption capacity and material compatibility. At present, the preparation of nano-scale calcium hydroxide mostly adopts the liquid phase co-precipitation method, which controls the crystal formation process by adjusting the reactant concentration, pH, temperature and other parameters, and at the same time uses surface modifiers to improve its dispersibility in organic media. In some technical solutions, in order to optimize the morphology and distribution of particles, ultrasound, mechanical stirring or the addition of surfactants are also introduced to achieve the goals of small particle size, narrow distribution and less agglomeration. In specific applications, such as lubricating oil systems, modified coating is often used to improve the oil phase affinity of the particles so that they can maintain a good dispersion state under working conditions.

[0003] However, existing methods still face certain bottlenecks in terms of particle size control and dispersion performance improvement. Since most precipitation reaction processes lack spatial structural constraints, crystals grow freely in the entire liquid phase system, and nucleation and particle aggregation often occur simultaneously, resulting in large fluctuations in particle size and easy agglomeration between particles; at the same time, surface coating is mostly processed after the reaction is completed, and the bonding strength between the coating layer and the crystal is limited, making it difficult to maintain structural integrity under heat or shear conditions. In terms of oil phase dispersion, some systems are sensitive to temperature or shear, and the modification effect is time-dependent. Especially in high-temperature lubrication environments, particle sedimentation and coating layer rupture are still common. Therefore, how to establish an effective interface induction mechanism in the early stage of crystal formation, synergistically complete particle size control and surface coating, and improve the dispersion stability of the product in complex media has become a direction that urgently needs in-depth research in this technical field. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the present invention provides a process for producing high-surface-activity nano-scale calcium hydroxide for lubricating oil, which solves the problems of difficult particle size control, uneven coating, and poor dispersion stability of nano-calcium hydroxide in non-polar media.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions: A process for producing high-surface-active nano-scale calcium hydroxide for lubricating oil comprises the following steps:

[0006] S1, constructing an oil-water emulsion system, mixing the oil phase and the water phase, and forming an emulsion dispersion system under high shear conditions;

[0007] S2. Introducing a surface modifier into the system and performing a pre-distribution treatment;

[0008] S3, injecting a solution containing a calcium precursor into the emulsion system at a controlled rate;

[0009] S4, introducing CO2 gas into the system and controlling the pH change rate;

[0010] S5. Precipitation reaction of calcium hydroxide is carried out under the confinement of the oil-water interface and the microbubble interface, and in-situ coating of the crystal surface is achieved simultaneously;

[0011] S6. performing aging treatment on the reaction system and separating by-products;

[0012] S7, separating, washing and drying the product to obtain nano-scale calcium hydroxide with enhanced surface activity;

[0013] Furthermore, the present invention employs a multi-step synergistic reaction strategy, organically integrating gas-liquid shear reaction, confined precipitation control, dynamic feedback of pH adjustment, and in-situ surface coating processes to construct a preparation system with a clear interfacial reaction pathway and structural evolution logic. The entire process encompasses the entire process from raw material dispersion, reaction environment establishment, dynamic transport control of reactants, precipitation reaction micro-zone induction, and the simultaneous occurrence of crystal formation and modification, forming a complete system for the controllable nanocrystal formation and surface functionalization coupling.

[0014] A key step in the present invention is to first construct an oil-water emulsion system. By selecting an oil and water phase system of appropriate polarity, supplemented by a surfactant, a network of emulsified droplets is formed under high shear conditions, achieving a preliminary homogenization of the distribution of the reaction precursors. This emulsion structure not only provides a stable dispersed phase environment but also forms a multiphase interface framework for the subsequent precipitation reaction.

[0015] More importantly, the emulsion structure, combined with high shear conditions, enables control over the distribution of microscale droplets, thereby spatially confining the calcium hydroxide nuclei and inhibiting agglomeration. This shear-induced emulsion platform lays the physical foundation for regulating reaction system structure.

[0016] Subsequently, a surface modifier is introduced into the system and pre-distributed. This invention prefers stearic acid or long-chain organic compounds such as organophosphates as modifiers. Their amphiphilic structure, consisting of polar groups and hydrophobic carbon chains, allows them to form stable micromicelles and achieve uniform distribution at the oil-water interface. Compared to traditional post-coating methods, this approach ensures that the modifier is enriched at the interface before precipitation occurs, thus facilitating instantaneous surface adsorption for subsequent crystal nucleation.

[0017] This pre-set "interface preloading mechanism" allows the modifier to selectively bind to the crystal surface during the reaction, forming a stable, continuous coating layer, avoiding problems such as uneven coating and structural damage that can occur in post-processing methods. This mechanism simultaneously ensures coating efficiency and crystal integrity at the molecular scale.

[0018] In the subsequent calcium source precursor rate-controlled injection process, 0.1–0.5 mol / L Ca was slowly injected by constant current. 2+ The solution is then injected and combined with high-shear stirring to maintain a dynamic equilibrium between the injection rate and the mixing state within the system. This "injection-mixing-nucleation" process operates within a nonlinear response region, avoiding the problems of rapid nucleation and coarse particle growth caused by local high concentrations.

[0019] By precisely controlling the calcium source delivery rate, the nucleation time window can be significantly extended, further matching the subsequent CO2-induced precipitation conditions to achieve effective convergence of the particle size range. This step demonstrates the present invention's ability to control the nucleation kinetics and enhances the size controllability of the final product.

[0020] In the core step, CO2 gas is introduced into the system and introduced into the emulsion structure in the form of microbubbles. CO2 is gradually hydrolyzed in the water phase to generate OH - , achieving controllable alkaline conditions. By controlling the bubble size (50–200 nm) and the flow rate (50–300 mL / min), a uniform and sustained-release pH-regulating environment can be created within the system. Specifically, the pH change rate (ΔpH / Δt) in the system is precisely controlled within the range of 0.2–0.4 units / min, keeping the reaction within the control window where nucleation takes precedence over growth.

[0021] More importantly, the microbubbles themselves have an obvious confinement effect at the oil-water interface, forming a concentrated area of CO2 and Ca 2+ The localized reaction micro-zones induce the formation of calcium hydroxide precipitation nuclei in the interface region, further restricting their free expansion and growth. This "interface + microbubble" composite confinement mechanism is introduced for the first time in this invention, solving the technical problem of uncontrollable crystal agglomeration in conventional precipitation methods.

[0022] During the confined precipitation process, the surface modifier participates in the coating reaction in situ, forming a surface organic layer. Because the modifier exists in the form of micelles before nucleation and possesses strong interfacial affinity during the initial nucleation phase, it rapidly adsorbs at the moment of crystal formation, establishing a stable organic-inorganic composite interface. This "simultaneous precipitation and modification" process significantly improves modification efficiency and creates a surface structure with a high affinity for the oil phase, meeting the performance requirements for particle dispersibility in lubricants.

[0023] In the later stages of the reaction, the system is aged by maintaining low-speed stirring or static conditions. The turbulence caused by bubble collapse helps migrate byproducts and interfacial residues to the edges of the system, simplifying the separation process and improving the purity of the main product. Finally, the products are separated by low-temperature centrifugation or sedimentation, and dried under mild conditions to obtain nano-calcium hydroxide powder with enhanced surface activity.

[0024] Preferably, in step S1, the volume ratio of the oil phase to the water phase is 1:3-1:5;

[0025] The high shear conditions are a shear rate of 10000 rpm to 20000 rpm and a shear time of 10 min to 20 min.

[0026] Preferably, in step S2, the surface modifier is stearic acid, and after introduction, ultrasonic treatment is performed to form uniformly distributed micromicelles.

[0027] Preferably, in step S3, the concentration of the calcium-containing precursor solution is 0.1 mol / L-0.5 mol / L, the injection method is constant flow injection, the injection rate is 0.5 mL / min-2.0 mL / min, and the injection process is carried out under high shear stirring conditions.

[0028] Preferably, in the step S4, the CO2 gas is introduced in the form of microbubbles, the bubble particle size is 50nm-200nm, the gas flow rate is 50mL / min-300mL / min, and the pH value change rate ΔpH / Δt is controlled at 0.2-0.4.

[0029] Preferably, in step S4, the reaction temperature of the system is controlled between 25°C and 40°C.

[0030] Preferably, in the step S5, calcium hydroxide precipitation occurs in the confined area at the interface between CO2 microbubbles and the oil-water emulsion, and the surface modifier is in situ adsorbed on the crystal surface during the crystal nucleation process to achieve synchronous coating.

[0031] Preferably, in step S5, the precipitation of calcium hydroxide and the in-situ coating of the surface modifier are carried out simultaneously, and the modifier is distributed in the interface region in a micro-micelle state before precipitation begins, and is adsorbed on the crystal surface to form a stable coating layer at the moment of crystal nucleation.

[0032] Preferably, in the step S6, the duration of the aging treatment is 20 min to 40 min, low-speed stirring is maintained during the treatment, and the disturbance generated by the bubble collapse is used to drive the by-products to migrate to the edge of the system.

[0033] Preferably, in the step S7, the separation is centrifugal separation, and the drying process is carried out at 40° C. to 60° C., and the drying time is 6 h to 12 h.

[0034] The present invention provides a process for producing high-surface-activity nanoscale calcium hydroxide for lubricating oil. It has the following beneficial effects:

[0035] 1. This invention utilizes high shear to construct an oil-water interface emulsion system and a microscale spatial confinement strategy to achieve targeted control of particle size during the initial nucleation phase, resulting in a concentrated product particle size distribution, low agglomeration rate, and high structural integrity. Compared to the conventional emulsification and dispersion methods commonly used in existing technologies under conventional stirring and no shear conditions, this approach solves the problems of disordered particle growth and drastic particle size fluctuations.

[0036] 2. The present invention utilizes a synergistic control mechanism of constant-flow calcium source injection and dynamic CO2 microbubble aeration to form a stable precipitation reaction interface, achieving the technical benefits of predictable pH control, stable precipitation rate, and regular crystal structure. Existing solutions, such as direct calcium source addition or free gas aeration, are prone to violent reactions and interface disturbances. The present invention effectively avoids drawbacks such as coarsening of crystal nuclei and uncontrolled nucleation time.

[0037] 3. By pre-distributing the surface modifier and designing a simultaneous adsorption pathway for instantaneous nucleation, this invention achieves the technical benefits of complete crystal surface coating, excellent oil-phase dispersion, and stable system zeta potential. Unlike existing post-modification or physical adsorption strategies, this significantly addresses the issues of localized coating cracking and rapid dispersant failure, ensuring the product's extended stability in lubricating media.

[0038] 4. This invention integrates the microbubble-induced confined precipitation mechanism with the crystal growth path at the oil-water interface and applies it to high-temperature systems. This achieves the technical effect of maintaining slow particle size growth and zero sedimentation at temperatures above 80°C. Compared to the severe particle agglomeration observed at conventional high-temperature conditions, this overcomes the key shortcomings of existing functional lubricating materials, such as rapid dispersibility degradation and poor thermal stability under high-temperature shear. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a flow chart of the process steps of the present invention. DETAILED DESCRIPTION

[0040] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the present specification. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0041] Please see the attached Figure 1 , Example 1:

[0042] Oil-water emulsion system construction:

[0043] Take 30 mL of mineral base oil as the oil phase and 90 mL of deionized water as the aqueous phase (volume ratio 1:3), add 1 wt% of the non-ionic surfactant Span-80, and stir at 12000 rpm for 15 min in a high shear emulsifier (Ultra-Turrax-T25) to obtain a stable emulsion system.

[0044] Surface modifier pretreatment:

[0045] 0.5 g of stearic acid was added to the emulsion system in the previous step, and ultrasonic treatment was performed for 10 min using an ultrasonic oscillator with a power of 150 W to form micromicelles of stearic acid and evenly distribute them in the emulsion.

[0046] Calcium source precursor rate-controlled injection:

[0047] Prepare a 0.2 mol / L aqueous solution of CaCl2 and slowly inject it into the emulsion at a rate of 1.0 mL / min using a constant-flow syringe pump. The injection process lasts for 30 minutes while stirring at 12,000 rpm to maintain a uniform system.

[0048] CO2 gas injection and pH control:

[0049] A nanobubble generator was used to generate CO2 microbubbles with an average particle size of approximately 100 nm at a rate of 150 mL / min. A pH meter was used to dynamically monitor the pH of the system, keeping the ΔpH / Δt ratio within 0.3 units / min. This process lasted for 40 minutes, with the reaction temperature maintained at 30°C.

[0050] Confined precipitation and in-situ coating:

[0051] During the CO2 injection process, white turbidity was observed on the surface of the microemulsion droplets, indicating in situ precipitation of calcium hydroxide crystals at the interface between the emulsion and the microbubbles. The surface modifier was simultaneously adsorbed on the crystal surface, achieving coating.

[0052] Aging treatment and by-product separation:

[0053] After the reaction was completed, the stirring rate was maintained at 300 rpm and the aging was continued for 30 min. The disturbance induced by the collapse of microbubbles was used to migrate the by-products to the boundary.

[0054] Product recovery:

[0055] The product was recovered by centrifugation at 8000 rpm for 10 min, washed twice with ethanol and twice with deionized water, and dried at 50°C for 8 h to obtain a white powder with a particle size distribution of 80–120 nm and good dispersibility.

[0056] Example 2:

[0057] Emulsion Construction:

[0058] The oil phase was white oil (20 mL) and the aqueous phase was distilled water (100 mL), with a volume ratio of 1:5. 2 wt% Tween-80 was added, and the emulsification condition was a shear rate of 10,000 rpm for 20 min.

[0059] Modifier treatment:

[0060] 0.3 g of sodium-caprylate was added as a surfactant and ultrasonic treatment was performed for 8 min to form a micromicelle distribution with a smaller particle size.

[0061] Calcium source injection:

[0062] A 0.1 mol / L Ca(NO3)2 solution was used with an injection rate of 0.5 mL / min, and constant flow injection was maintained for 40 min, with the stirring rate maintained at 10,000 rpm.

[0063] CO2 injection:

[0064] The CO2 gas introduction rate was 100 mL / min, the microbubble particle size was about 80 nm, the system temperature was controlled at 25°C, and the pH change rate was about 0.2 units / min.

[0065] Precipitation and modification:

[0066] Calcium hydroxide precipitates at the oil-water interface and is rapidly adsorbed by the active agent in the micelles to form coated particles with a primary particle size of approximately 70 nm.

[0067] Aging and recycling:

[0068] The product was aged for 40 minutes with gentle stirring to promote the aggregation and sedimentation of by-products. Centrifugation was performed at 9000 rpm and dried at 45°C for 12 hours. The product was a light grey powder with fine particle size suitable for use in high shear lubricant systems.

[0069] Example 3:

[0070] Emulsion preparation:

[0071] The oil phase was composed of base oil plus 5 wt% polyisobutylene dispersant (PIB), and the aqueous phase was RO water, with a volume ratio of 1:4. Span-60 was added as an emulsifier, and the emulsification shear rate was 20,000 rpm for 10 minutes to form a microemulsion.

[0072] Modifier introduction:

[0073] 1.0 g of sodium dodecylbenzenesulfonate (SDBS) was added as a surface modifier and dispersed naturally under stirring conditions without using ultrasound.

[0074] Calcium source injection:

[0075] 0.5 mol / L Ca(CH3COO)2 solution was injected at 2.0 mL / min, and the injection time was only 15 minutes. The shear condition was still 20000 rpm.

[0076] CO2 treatment:

[0077] CO2 was introduced at a rate of 300 mL / min, and a ceramic microporous vaporizer was used to prepare bubbles with a particle size of 50–80 nm. The pH change rate was controlled at 0.4 units / min, and the system temperature was set at 40 °C.

[0078] Reaction and coating:

[0079] Precipitation occurs rapidly, and the modifier is adsorbed at the moment of crystal nucleation to form a thicker organic coating layer, which is beneficial for maintaining dispersion in high-temperature lubrication systems.

[0080] Aging and recycling:

[0081] The aging time is 20 minutes, followed by high-speed centrifugation at 10,000 rpm and drying at 60°C for 6 hours. The final product particle size is about 100-150 nm, and the surface organic layer thickness is about 5-8 nm, which is suitable for stable dispersion in a high-temperature lubrication environment.

[0082] Comparative Example 1:

[0083] Compared with Example 1, the difference is that high shear treatment is not used in the emulsion construction process, but conventional stirring (500 rpm) is used to mix the oil and water phases. The rest are the same.

[0084] The results show that the dispersed particle size of the emulsion in the system is uneven, the oil-water interface structure is unstable, there is no clear nucleation area for the crystals during the reaction, and large particle precipitates are formed. The final product is severely agglomerated, the particle size exceeds 300nm, and the surface coating is incomplete.

[0085] Comparative Example 2:

[0086] Compared with Example 1, the difference is that the calcium source solution is added to the reaction system by a one-time rapid pouring method instead of constant flow injection. The rest is the same.

[0087] During the experiment, the system quickly became turbid, and local Ca 2+ The sudden increase in concentration triggers uncontrolled precipitation, crystal nucleation and growth overlap, particle size enlargement, irregular morphology, inability to form nano-scale particles, and uneven coating.

[0088] Comparative Example 3:

[0089] Compared with Example 2, the difference is that the flow rate and time of CO2 introduction process were not controlled, and the actual pH change rate reached 0.9 units / min, exceeding the recommended upper limit. The rest were the same.

[0090] The results showed that too rapid precipitation led to large-scale crystal aggregation, rough nucleation, loose surface structure, inability of modifier to be effectively and synchronously adsorbed, significant increase in product particle size, and decreased dispersibility.

[0091] Comparative Example 4:

[0092] Compared with Example 2, the difference is that the reaction temperature is set to 50° C. (higher than the recommended upper limit), and the rest are the same.

[0093] Under this condition, the crystals grow rapidly, the adsorption of the coating agent lags, and local uncoated areas are formed. The final product shows agglomeration and caking, and the oil phase dispersion is poor.

[0094] Comparative Example 5:

[0095] Compared with Example 3, the difference is that the emulsion is constructed by low-speed homogenization (3000 rpm), which does not reach a high shear level. The rest are the same.

[0096] The results show that the oil droplets are large in size and unevenly dispersed, and the precipitation reaction diffuses to the entire liquid phase area, making it impossible to achieve confined nucleation. The crystal particle size expands and the coating layer structure is damaged.

[0097] Comparative Example 6:

[0098] Compared with Example 3, the difference is that the CO2 introduction method adopts conventional bubble aeration (bubble particle size>1μm) and the microbubble system is not used. The rest are the same.

[0099] The experiment observed that the precipitation had no specific interface, the crystals were dispersed in the aqueous phase, there was a lack of micro-area induction, and the coating agent was not completely attached, resulting in uneven surface structure of the particles and weak hydrophobicity.

[0100] Comparative experiment:

[0101] Experiment 1:

[0102] This experiment aimed to evaluate the effects of different preparation methods on the particle size uniformity of calcium hydroxide. Example 1 and its two comparative examples were selected as experimental subjects. Standard wet dispersion and particle size testing were performed to analyze the ability of process parameters to control the product size and distribution range.

[0103] The experimental steps are as follows:

[0104] Sample weighing and pre-dispersion:

[0105] 0.10 g of the dried product powder was taken from each group and placed in a clean 100 mL conical flask. 50 mL of deionized water was added, to which 0.05 wt% of the non-ionic dispersant Tween-80 was added, and the mixture was premixed with magnetic stirring for 5 minutes.

[0106] Sonication:

[0107] Each group of samples was placed in a 40 kHz water bath ultrasonic cleaner, maintained at 30 °C, and ultrasonicated for 10 min to ensure that the particles were evenly dispersed and no agglomerates were visible to the naked eye.

[0108] Particle size test:

[0109] The test was performed using a laser particle size analyzer (Malvern-Mastersizer-3000). The mixture was thoroughly mixed before testing. Each group was tested three times in succession, and the average value was taken. The particle size distribution range (D10, D50, D90) was also recorded.

[0110] Data recording and analysis:

[0111] All test data were recorded as mean + standard deviation, with the distribution width additionally noted, and the differences between groups were analyzed in combination with the particle size distribution curve (see Table 1 for details).

[0112] Table 1

[0113]

[0114] Summarize:

[0115] In Example 1, a uniform and stable emulsion interface system was constructed under high shear conditions, combined with a process path of injecting a calcium source at a constant flow rate, to achieve controlled nucleation and confined growth of calcium hydroxide particles. The resulting product had a concentrated particle size, a D50 value that was stable at around 100 nm, a narrow particle size distribution range, and good repeatability. In contrast, Comparative Example 1 lacked a shear-induced interface, resulting in a loose interface in the reaction system, disordered distribution of the nucleation area, and large fluctuations in particle size. In Comparative Example 2, Ca 2+ Rapid injection induces non-uniform instantaneous nucleation and uncontrolled precipitation, resulting in serious loss of control of product particle size and failure of surface modification.

[0116] This demonstrates that by incorporating a dual control mechanism of "shear confinement + dynamic injection" into the process, the present invention successfully confines particle formation to the interface space and time window, avoiding premature aggregation and the formation of coarse particles. This process control model significantly improves the precision of particle size control and the consistency of the finished product, providing a key guarantee for the stable production of nanoscale products.

[0117] Experiment 2:

[0118] This experiment aims to observe the performance of calcium hydroxide particles prepared by three different methods in lubricating oil systems.

[0119] Materials preparation:

[0120] Lubricant base: mineral oil (SN500);

[0121] Sample sources: Example 2, Comparative Example 3, Comparative Example 4;

[0122] The amount of particles added was unified to 1.0 wt%;

[0123] Dispersion treatment: stirring at 8000 rpm for 10 min + water bath ultrasound for 5 min;

[0124] Experimental steps:

[0125] Configuration of suspension system:

[0126] Add the three groups of products to the lubricating oil separately, weigh them, and emulsify them directly. Stir and ultrasonicate until they are visually uniform and free of sediment. Leave them for observation and start timing.

[0127] Static sedimentation test:

[0128] Place the samples in transparent colorimetric tubes and place them on a 25°C bench for observation. Record the change in the particle sinking interface height at regular intervals up to 72 hours.

[0129] Centrifugal stability test:

[0130] After 24 hours, samples were taken and centrifuged at low speed (3000 rpm, 30 min). The stratification of the samples was recorded by taking photos, and the transmittance of the upper layer was measured by a spectrophotometer (500 nm wavelength).

[0131] Zeta potential determination:

[0132] A diluted sample was taken from the oil phase, and the charge characteristics of the particles in the oil were measured using a Zeta potential analyzer as a reference indicator of the electrostatic stability of the system (see Table 2 for details).

[0133] Table 2

[0134]

[0135] Summarize:

[0136] Dispersion stability tests in the oil phase system show that the sample in Example 2 exhibits good dispersion and strong anti-settling ability in the lubricating oil. It remains suspended and transparent even after 72 hours of stasis, with a zeta potential of -38 mV, indicating sufficient interparticle repulsion and high system stability. In contrast, in Comparative Example 3, where pH change rate control was not performed, the reaction process was intense, resulting in rough crystal nucleation, an uneven particle surface structure, and rapid sedimentation. In Comparative Example 4, due to the reaction temperature exceeding the control range, the crystal growth rate was too rapid, and the capping agent failed to be adsorbed synchronously, resulting in turbidity and severe stratification.

[0137] Mechanistic analysis reveals that the gradual introduction of CO2 microbubbles and the gradual pH control employed in the examples effectively prolong the crystal nucleation phase, providing ample reaction time for the in-situ adsorption of the surface modifier. Simultaneously, temperature control maintains the slow growth of the crystal interface, resulting in a uniform surface coating and stable surface electrical properties. This significantly enhances the stable distribution of particles in the nonpolar oil phase, demonstrating the core interface control advantage of the present invention.

[0138] Experiment 3:

[0139] In this experiment, a simulated hot-load lubrication system environment was constructed to test the dispersion durability, anti-agglomeration ability and particle size evolution of calcium hydroxide particles obtained by different preparation processes in an oil phase at 80°C.

[0140] Materials and dispersion systems:

[0141] Base oil: synthetic lubricant PAO (low viscosity type);

[0142] Samples: Example 3, Comparative Example 5, Comparative Example 6;

[0143] Addition amount per group: 0.8wt%;

[0144] Dispersion method: high-speed shearing (10000 rpm × 8 min) + water bath ultrasound (10 min);

[0145] Experimental steps:

[0146] Oil configuration and pretreatment:

[0147] After dispersion under the above conditions, the mixture was placed in a glass thermostated reaction bottle (about 60 mL per bottle), sealed, set to magnetic stirring (200 rpm), and placed in an 80°C oil bath.

[0148] Thermal aging process and sampling rhythm:

[0149] The total treatment time was set to 12 h, and 3 mL of sample solution was taken out every 4 h (3 times in total). The particle size was measured after cooling to room temperature.

[0150] Particle size change analysis:

[0151] Each sample was diluted 20 times (using a mixture of deionized water and ethanol), and the D50 change was measured using a laser particle size analyzer to observe whether the particle size increase was drastic.

[0152] Visual settlement auxiliary observation:

[0153] The remaining oil samples were left to stand for 12 h after treatment to observe whether there were any changes in appearance such as aggregation and precipitation, oil phase turbidity, and stratification (see Table 3 for details).

[0154] Table 3

[0155]

[0156] Summarize:

[0157] Thermal aging test results show that the sample in Example 3 maintained minimal particle size fluctuation (D50 increase <20 nm) even after prolonged stirring at 80°C, with no noticeable sedimentation or stratification, demonstrating excellent suspension stability. However, in Comparative Example 5, which lacked shear emulsion formation, the system initially exhibited large and uneven particle sizes, exhibiting significant agglomeration and a rapid increase in particle size after heat treatment. Furthermore, in Comparative Example 6, due to uncontrolled CO2 injection (non-microbubble-forming), the crystal precipitation region diffused throughout the liquid phase, preventing a confined reaction. The coating failed during heat treatment, leading to complete disintegration of the dispersed system.

[0158] This experiment fully demonstrated the high-temperature adaptability of the "shear interface induction + microbubble confined precipitation" mechanism employed in the present invention. Submicron-scale bubbles provide a uniform, confined nucleation interface, effectively suppressing the disordered growth of crystals at high temperatures. Furthermore, the simultaneous adsorption of the modifier during the precipitation phase forms a stable organic coating structure, maintaining particle dimensional stability and dispersion synergy under high-temperature lubrication conditions. This approach offers significant technical advantages for enhancing the thermally stable dispersion performance of the product in practical lubrication systems.

[0159] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A process for producing high-surface-active nano-scale calcium hydroxide for lubricating oil, characterized in that: The following steps are involved: S1, constructing an oil-water emulsion system, mixing the oil phase and the water phase, and forming an emulsion dispersion system under high shear conditions; S2. Introducing a surface modifier into the system and performing a pre-distribution treatment; S3, injecting a solution containing a calcium precursor into the emulsion system at a controlled rate; S4, introducing CO2 gas into the system and controlling the pH change rate; S5. Precipitation reaction of calcium hydroxide is carried out under the confinement of the oil-water interface and the microbubble interface, and in-situ coating of the crystal surface is achieved simultaneously; S6. performing aging treatment on the reaction system and separating by-products; S7. Separating, washing and drying the product to obtain nano-scale calcium hydroxide with enhanced surface activity.

2. The high-surface-activity nanoscale calcium hydroxide process for lubricating oil according to claim 1, characterized in that: In step S1, the volume ratio of the oil phase to the water phase is 1:3-1:5; The high shear conditions are a shear rate of 10000 rpm to 20000 rpm and a shear time of 10 min to 20 min.

3. The high-surface-activity nanoscale calcium hydroxide process for lubricating oil according to claim 1, characterized in that: In the step S2, the surface modifier is stearic acid, and after introduction, ultrasonic treatment is performed to form micromicelles for uniform distribution.

4. The process for producing high-surface-activity nano-scale calcium hydroxide for lubricating oil according to claim 1, wherein: In the step S3, the concentration of the calcium-containing precursor solution is 0.1 mol / L-0.5 mol / L, the injection method is constant flow injection, the injection rate is 0.5 mL / min-2.0 mL / min, and the injection process is carried out under high shear stirring conditions.

5. The process for producing high-surface-activity nano-scale calcium hydroxide for lubricating oil according to claim 1, wherein: In the step S4, CO2 gas is introduced in the form of microbubbles with a bubble particle size of 50nm-200nm, a gas flow rate of 50mL / min-300mL / min, and the pH value change rate ΔpH / Δt is controlled at 0.2-0.

4.

6. The process for producing high-surface-activity nano-scale calcium hydroxide for lubricating oil according to claim 1, characterized in that: In the step S4, the reaction temperature of the system is controlled between 25°C and 40°C.

7. The process for producing high-surface-activity nano-scale calcium hydroxide for lubricating oil according to claim 1, characterized in that: In the step S5, calcium hydroxide precipitation occurs in the confined area at the interface between CO2 microbubbles and the oil-water emulsion, and the surface modifier is in situ adsorbed on the crystal surface during the crystal nucleation process to achieve synchronous coating.

8. The process for producing high-surface-activity nano-scale calcium hydroxide for lubricating oil according to claim 1, wherein: In step S5, the precipitation of calcium hydroxide and the in-situ coating of the surface modifier are carried out simultaneously, and the modifier is distributed in the interface region in a micro-micelle state before the precipitation begins, and is adsorbed on the crystal surface to form a stable coating layer at the moment of crystal nucleation.

9. The process for producing high-surface-activity nano-scale calcium hydroxide for lubricating oil according to claim 1, characterized in that: In the step S6, the duration of the aging treatment is 20 min to 40 min, low-speed stirring is maintained during the treatment, and the disturbance generated by the bubble collapse is used to drive the by-products to migrate to the edge of the system.

10. The process for producing high-surface-activity nano-scale calcium hydroxide for lubricating oil according to claim 1, characterized in that: In the step S7, the separation is centrifugal separation, and the drying process is carried out at 40° C. to 60° C. for 6 h to 12 h.

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