A high-concentration oil-phase surfactant composition and its dispersion application

Abstract

This invention relates to the field of surfactant technology, specifically disclosing a high-concentration oil-phase surfactant composition and its dispersion application. The composition is an organic-inorganic hybrid structure, prepared by hybridizing an amphiphilic random copolymer with silica nanoparticles under specific conditions. The amphiphilic random copolymer provides dual affinity and anchoring to both the oil phase and the solid filler surface, while the silica nanoparticles act as rigid support points, binding with the polymer chains to synergistically construct a strong steric hindrance network. When applied to high-solids-content oil-based dispersion systems, this composition significantly improves the dispersion uniformity and long-term storage stability of filler particles, and exhibits excellent high-temperature shear resistance. This invention features a mild process, readily available raw materials, and is suitable for the preparation of high-performance oil-based formulations in fields such as lubrication, electronics, and composite materials.

Description

Technical Field

[0001] This invention relates to the field of surfactants and dispersants, specifically to a surfactant composition suitable for high-concentration nonpolar oil phase systems and its application in improving the dispersion stability of solid fillers in the oil phase. Background Technology

[0002] With the development of the energy, lubrication, electronics, and high-performance composite materials industries, the demand for high-concentration, uniform, and stable dispersion of various functional solid fillers (such as graphene, carbon nanotubes, molybdenum disulfide, and nano-metal oxides) in oil-phase media such as non-polar mineral oils and synthetic base oils is becoming increasingly urgent. Such dispersion systems are key to the preparation of high-performance greases, conductive / thermal greases, oil-based drilling fluids, and special composite materials.

[0003] Currently, commercially available surfactants for oil-phase dispersion mainly fall into the following categories: traditional nonionic surfactants (such as Span series and oleamide), polymeric dispersants (such as polyisobutylene succinimide and polyacrylate), and amphiphilic polymers obtained through chemical grafting modification. However, existing technologies generally suffer from the following defects and shortcomings: First, most traditional small-molecule surfactants have limited steric hindrance in high-concentration solid filler (>5wt%) systems, making it difficult to prevent particle aggregation and sedimentation caused by van der Waals forces, leading to phase separation during storage or high-shear applications. Second, while some polymeric dispersants can provide good steric stability, their molecular chains may degrade or undergo conformational changes under high temperatures (>120℃) or long-term shear, resulting in a decline in dispersion performance. Furthermore, the complex synthesis processes, harsh conditions, or high raw material costs of many modified polymers limit their application in food-grade or high-safety-requirement fields.

[0004] To address the aforementioned technical bottlenecks, the core idea of ​​this invention is to abandon simple physical mixing or conventional chemical modification approaches. For the first time, it proposes an in-situ hybrid assembly of amphiphilic random copolymers and silica nanoparticles via hydrogen bonding interactions, constructing a "polymer-inorganic nanoparticle" organic-inorganic hybrid structure. This structure is not a simple addition of components; the random copolymer provides dual affinity and anchoring to both the oil phase and the surface of the solid filler, while the silica nanoparticles act as rigid support points, binding to the polymer chains via hydrogen bonds. Together, they construct a strong and thermally stable steric network. This invention achieves superior synergistic effects compared to complex chemical grafting through a simple physical assembly method, effectively solving the problems of poor high-temperature stability of single polymers, poor dispersion of inorganic particles, and insufficient synergistic effects in traditional compounding methods. Summary of the Invention

[0005] This invention provides a high-concentration oil-phase surfactant composition and its preparation method, aiming to overcome the defects of existing technologies such as low dispersion efficiency, poor long-term stability, and insufficient high-temperature shear resistance of surfactants in high-concentration oil-phase systems.

[0006] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a high-concentration oil-phase surfactant composition comprising an amphiphilic random copolymer and silica nanoparticles, wherein the composition is an organic-inorganic hybrid structure formed by the hybrid assembly of the amphiphilic random copolymer and silica nanoparticles; wherein the amphiphilic random copolymer is copolymerized from the hydrophobic monomer octadecyl methacrylate and the hydrophilic monomer N-vinylpyrrolidone.

[0007] Preferably, the mass ratio of the amphiphilic random copolymer to silica nanoparticles is 2:1-6:1.

[0008] Preferably, the mass ratio of octadecyl methacrylate to N-vinylpyrrolidone is 2:1-3:1.

[0009] Preferably, the silica nanoparticles are prepared by hydrolysis and condensation of orthosilicate under alkaline conditions, and their particle size ranges from 10 to 50 nm.

[0010] Secondly, the present invention provides a method for preparing the above-described high-concentration oil-phase surfactant composition, comprising the following steps: S1. Preparation of amphiphilic random copolymer: Under an inert atmosphere, hydrophobic monomers, hydrophilic monomers and initiators are dissolved in toluene and reacted at 60-80℃ for 4-8 hours. After precipitation and drying, amphiphilic random copolymer is obtained. S2. Preparation of silica nanoparticle dispersion: Orthosilicate is added to an alcohol-water mixed solvent and hydrolyzed and polycondensed at 25-40℃ for 12-24 hours under the action of an alkaline catalyst to obtain silica nanoparticle dispersion. S3. Hybrid Assembly: The amphiphilic random copolymer obtained in step S1 is dissolved in a mixed solvent of toluene and isopropanol. The silica nanoparticle dispersion obtained in step S2 is added dropwise to the solvent under stirring. The mixture is reacted at 50-70°C for 2-4 hours. After removing the solvent, the surfactant composition is obtained.

[0011] Preferably, the volume ratio of toluene to isopropanol is 1:1 to 4:1.

[0012] Preferably, the preparation method of the high-concentration oil-phase surfactant composition adopts the following preparation scheme: S1. Preparation of the amphiphilic random copolymer: Under inert gas protection, solvent A (toluene) 500-800 mL was added to a reaction vessel and heated to 60-80℃. Then, 50-80 g of the hydrophobic monomer octadecyl methacrylate, 20-40 g of the hydrophilic monomer N-vinylpyrrolidone, and 1.0-2.5 g of the initiator azobisisobutyronitrile were added sequentially. The stirring speed was controlled at 300-500 rpm, and the reaction was carried out at a constant temperature for 4-8 hours. After the reaction was completed, the reaction solution was dropped into excess anhydrous ethanol to precipitate the copolymer. The precipitate was filtered, and the resulting solid was dried in a vacuum drying oven at 40-60℃ for 6-12 hours to obtain a white powdery amphiphilic random copolymer. The purpose of this step is to synthesize a polymer dispersant with a uniform molecular structure containing long-chain alkyl groups (lipophilic / anchoring groups) and pyrrolidone rings (solidophilic / hydrogen bond acceptor groups).

[0013] S2. Preparation of silica nanoparticle dispersion: In another reaction vessel, add 200-400 mL of deionized water and 100-200 mL of ethanol, and add 10-20 mL of tetraethyl orthosilicate while stirring. Adjust the pH of the mixture to 8-10 with 10% ammonia solution, and react at 25-40℃ and 800-1200 rpm for 12-24 hours. After the reaction, centrifuge, wash the precipitate three times with deionized water, and finally disperse it in anhydrous ethanol to prepare a silica nanoparticle ethanol dispersion with a concentration of 20-50 mg / mL. The purpose of this step is to prepare inorganic nanoparticles with uniform particle size and a surface rich in silanol groups, which serve as a rigid component to enhance steric hindrance.

[0014] S3. Assembly of the hybrid surfactant composition: Take 20-40 g of the amphiphilic random copolymer obtained in step S1, dissolve it in 100-200 mL of toluene to form a clear solution, and then add 50-100 mL of isopropanol as a co-solvent. Under magnetic stirring, slowly add 50-150 mL of the silica nanoparticle ethanol dispersion obtained in step S2 to the above mixed solution, controlling the dropping rate to 1-3 mL / min. After the addition is complete, continue stirring at 50-70℃ for 2-4 hours. After the reaction is complete, remove toluene, ethanol and residual water by vacuum distillation at 60℃ and a vacuum degree of -0.08 to -0.09 MPa, and then dry in a vacuum drying oven at 60℃ for 12 hours to obtain a pale yellow to brownish-yellow viscous paste, which is the high-concentration oil-phase surfactant composition. This step, measured by variable-temperature Fourier transform infrared spectroscopy (VT-FTIR), showed that the characteristic peak of the C=O stretching vibration of the amide bond in the polymer shifted from 1655 cm⁻¹ in the free state. -1 Redshifted to 1642 cm -1This study demonstrated that strong hydrogen bonds were formed between the silica nanoparticles and the silanol groups on their surface. Acid-base titration revealed that the silanol content on the silica nanoparticle surface was 2.0 mmol / g, providing sufficient active sites for interfacial bonding. High-resolution X-ray photoelectron spectroscopy (XPS) of the Si 2p peak showed that the binding energy of the hybridized Si 2p peak shifted to a lower energy direction by 0.8 eV compared to pure silica, confirming the existence of electronic interactions at the inorganic-organic interface. Transmission electron microscopy (TEM) observation showed that the silica nanoparticles were uniformly anchored on the polymer chains without significant agglomeration, forming a stable organic-inorganic hybrid structure.

[0015] Preferably, in step S1, the mass ratio of the hydrophobic monomer octadecyl methacrylate to the hydrophilic monomer N-vinylpyrrolidone is 2.5:1.

[0016] Preferably, in step S1, the amount of the initiator azobisisobutyronitrile is about 1.2% of the total mass of the two monomers.

[0017] Preferably, in step S1, the polymerization reaction temperature is 70°C and the reaction time is 6 hours.

[0018] Preferably, in step S2, when preparing silica nanoparticles, the pH value adjusted by the ammonia water is 9.

[0019] Preferably, in step S2, the stirring reaction temperature is 30°C and the time is 18 hours.

[0020] Preferably, in step S3, the mass ratio of the amphiphilic random copolymer to the silica nanoparticles is 4:1.

[0021] Preferably, in step S3, the temperature of the hybridization assembly reaction is 60°C and the time is 3 hours.

[0022] Preferably, the octadecyl methacrylate used in step S1 was purchased from Saen Chemical Technology (Shanghai) Co., Ltd.; N-vinylpyrrolidone was purchased from Beijing Bailingwei Technology Co., Ltd.; the tetraethyl orthosilicate used in step S2 was of analytical grade and purchased from Sinopharm Chemical Reagent Co., Ltd.; the polyisobutylene succinimide used was purchased from Wuhan Jiyesheng Chemical Co., Ltd.; and the Span 80 used was purchased from Shandong Xinheng Chemical Co., Ltd.

[0023] Thirdly, the present invention provides an application of the above-mentioned high-concentration oil-phase surfactant composition in the preparation of an oil-based dispersion, wherein the surfactant composition, solid filler and base oil are mixed and sheared to obtain an oil-based dispersion in which the solid filler is uniformly dispersed; wherein the amount of surfactant composition added is 5%-15% of the mass of the solid filler.

[0024] Preferably, in step S4, the dispersion application of the composition specifically involves: premixing the target solid filler (such as graphite powder, molybdenum disulfide powder, etc.) with a base oil (such as mineral oil 150SN, polyalphaolefin PAO6, etc.) at the desired total mass fraction (e.g., 5-20 wt%). The surfactant composition obtained in step S3 is then added to the premixed system at a ratio of 5-15% of the solid filler mass. The entire system is placed in a high-speed shear emulsifier and homogenized at 10,000-20,000 rpm for 10-30 minutes to obtain a uniform, stable, and long-term storable oil-based dispersion. This step demonstrates the application method of this composition; its hybrid structure can efficiently anchor to the filler surface under shear action and form strong steric hindrance in the oil phase, achieving stable dispersion.

[0025] Fourthly, the present invention provides an oil-based dispersion comprising a base oil, a solid filler, and the aforementioned high-concentration oil-phase surfactant composition; wherein the solid filler has a mass fraction of 5%-20% in the oil-based dispersion; and the sedimentation volume ratio of the oil-based dispersion after standing at room temperature for 60 days is not higher than 10%.

[0026] Advantages of this invention 1. This invention combines the amphiphilic anchoring function of polymers with the rigid support function of inorganic nanoparticles by designing a "polymer-inorganic nanoparticle" hybrid structure, which generates a significant synergistic steric hindrance effect in high-concentration oil-phase dispersion systems, effectively preventing secondary agglomeration and sedimentation of solid fillers, and significantly improving the long-term storage stability and dynamic shear stability of the dispersion system.

[0027] 2. The silica nanoparticles introduced in this invention act as rigid support points, binding with the polymer chains to form a stable physical network structure in the oil phase. This structure can effectively suppress excessive softening and conformational collapse of polymer chain segments at high temperatures, thereby compensating for the shortcomings of traditional polymeric dispersants in terms of steric hindrance attenuation under high-temperature shear conditions, and endowing the composition with superior high-temperature resistance.

[0028] 3. The preparation process of this invention is mild, requiring no complex chemical grafting or harsh post-processing. The raw materials used are all common chemical products, and the final product, after GC testing, has a toluene residue of <50 ppm, meeting environmental and safety requirements. The production process is economical and easy to scale up.

[0029] 4. The surfactant composition of the present invention has wide applicability and can be used to disperse inorganic or carbon fillers of various polarities in non-polar or weakly polar oil phases. It shows broad application prospects in the fields of grease thickening, heat transfer oil preparation, and conductive ink, and has achieved unexpected technical effects. Attached Figure Description

[0030] Figure 1 The graph is a line graph comparing the static sedimentation stability of graphite / PAO6 prepared in Examples 1-4 and Comparative Examples 1-5 of this invention.

[0031] Figure 2 This is a line graph comparing the high-temperature storage stability of the sample in Example 1 and the sample in Comparative Example 1 of the present invention.

[0032] Figure 3 Line graphs showing the rheological properties of samples from Example 1, Comparative Example 1, and Comparative Example 2 of this invention.

[0033] Figure 4 This is a comparison chart of the high-temperature shear stability of samples from Example 1, Comparative Example 1, and Comparative Example 2 of the present invention.

[0034] Figure 5 Characterization results of the interfacial interactions of organic-inorganic hybrid materials: (a) Variable temperature Fourier transform infrared (VT-FTIR) spectrum; (b) Bar chart of silanol content on the surface of silica nanoparticles determined by acid-base titration; (c) High-resolution Si 2p spectrum by X-ray photoelectron spectroscopy (XPS); (d) Transmission electron microscopy (TEM) image of the hybrid materials. Detailed Implementation

[0035] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0036] In this invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in this industry. Example

[0037] S1. Preparation of the amphiphilic random copolymer: Under nitrogen protection, 500 mL of toluene (solvent A) was added to a three-necked flask equipped with a stirrer, condenser, and thermometer, and heated to 70°C. Then, 60 g of octadecyl methacrylate, 24 g of N-vinylpyrrolidone (mass ratio 2.5:1), and 1.0 g of azobisisobutyronitrile (azobisisobutyronitrile) initiator were added sequentially. The stirring speed was controlled at 400 rpm, and the reaction was carried out at a constant temperature for 6 hours. After the reaction was completed, the reaction solution was slowly added dropwise to 2 L of ice-cold anhydrous ethanol, resulting in the precipitation of a white solid. The solid was filtered, and then dried in a vacuum drying oven at 50°C for 10 hours to obtain a white powdery amphiphilic random copolymer, denoted as P1.

[0038] S2. Preparation of silica nanoparticle dispersion: In another beaker, 300 mL of deionized water and 150 mL of anhydrous ethanol were added and stirred until homogeneous. 25 mL of tetraethyl orthosilicate was slowly added while stirring. The pH of the mixture was adjusted to 9 with 10% ammonia solution, and the mixture was stirred at 1000 rpm for 18 hours at 30°C. After the reaction, the mixture was centrifuged at 8000 rpm for 10 minutes, the supernatant was discarded, and the precipitate was washed three times with deionized water. Finally, it was redispersed in 160 mL of anhydrous ethanol to obtain an ethanol dispersion of silica nanoparticles with a concentration of approximately 38.1 mg / mL, denoted as SiO2-1. Dynamic light scattering (DLS) characterization showed that the average particle size of the obtained silica nanoparticles was 25 ± 5 nm, with a narrow particle size distribution.

[0039] S3. Assembly of the hybrid surfactant composition: 24 g of the amphiphilic random copolymer P1 obtained in step S1 was dissolved in 150 mL of toluene to form a clear solution. Then, 75 mL of isopropanol was added as a co-solvent, and the solution was kept warm in a 60°C water bath. Under magnetic stirring, 160 mL of the SiO2-1 dispersion obtained in step S2 (containing approximately 6.1 g of SiO2, with a polymer to SiO2 mass ratio of 4:1) was slowly added dropwise to the above toluene solution, controlling the dropping rate at 2 mL / min. After the addition was complete, the reaction was continued at 60°C for 3 hours. After the reaction was complete, toluene, ethanol, and residual water were removed by rotary evaporation under reduced pressure at 60°C and a vacuum degree of -0.08 MPa, yielding a pale yellow viscous paste, which is the surfactant composition of this invention, denoted as HS-1. Figure 5 As shown, this step, as measured by variable-temperature Fourier transform infrared spectroscopy (VT-FTIR), revealed that the characteristic peak of the C=O stretching vibration of the amide bond in the polymer decreased from 1655 cm⁻¹ in the free state. -1 Redshifted to 1642 cm -1The results showed that strong hydrogen bonds were formed between the silica nanoparticles and the silanol groups on the surface of the silica nanoparticles. The silanol content on the surface of the silica nanoparticles was 2.0 mmol / g, which provided sufficient active sites for interfacial bonding. High-resolution Si 2p spectra obtained by X-ray photoelectron spectroscopy (XPS) showed that the binding energy of the Si 2p peak after hybridization shifted to a lower energy direction by 0.8 eV compared with pure silica, which confirmed the existence of electronic interactions at the inorganic-organic interface. Transmission electron microscopy (TEM) showed that the silica nanoparticles were uniformly anchored on the polymer chains without obvious agglomeration, forming a stable organic-inorganic hybrid structure. Example

[0040] S1. Preparation of the amphiphilic random copolymer: Under nitrogen protection, 500 mL of toluene (solvent A) was added to a three-necked flask equipped with a stirrer, condenser, and thermometer, and heated to 60 °C. Then, 60 g of octadecyl methacrylate, 24 g of N-vinylpyrrolidone (mass ratio 2.5:1), and 1.0 g of azobisisobutyronitrile (AIB) initiator were added sequentially. The stirring speed was controlled at 400 rpm, and the reaction was carried out at a constant temperature for 8 hours. After the reaction was completed, the reaction solution was slowly added dropwise to 2 L of ice-cold anhydrous ethanol, resulting in the precipitation of a white solid. The solid was filtered, and then dried in a vacuum drying oven at 50 °C for 10 hours to obtain a white powdery amphiphilic random copolymer, denoted as P2.

[0041] S2. Preparation of silica nanoparticle dispersion: In another beaker, 300 mL of deionized water and 150 mL of anhydrous ethanol were added and stirred until homogeneous. 15 mL of tetraethyl orthosilicate was slowly added while stirring. The pH of the mixture was adjusted to 9 with 10% ammonia solution, and the mixture was stirred at 1000 rpm for 18 hours at 30°C. After the reaction, the mixture was centrifuged at 8000 rpm for 10 minutes, the supernatant was discarded, and the precipitate was washed three times with deionized water. Finally, it was redispersed in 100 mL of anhydrous ethanol to obtain a silica nanoparticle ethanol dispersion with a concentration of approximately 36.6 mg / mL, denoted as SiO2-2. DLS characterization showed an average particle size of 22 ± 4 nm.

[0042] S3. Assembly of the hybrid surfactant composition: Take 22 g of the amphiphilic random copolymer P2 obtained in step S1, dissolve it in 100 mL of toluene to form a clear solution, then add 50 mL of isopropanol as a co-solvent and keep it in a 60°C water bath. Under magnetic stirring, slowly add 100 mL of the SiO2-2 dispersion obtained in step S2 (containing approximately 3.66 g of SiO2, with a polymer to SiO2 mass ratio of 6:1) to the above toluene solution, controlling the dropping rate at 2 mL / min. After the addition is complete, continue stirring at 50°C for 4 hours. After the reaction is complete, remove toluene, ethanol, and residual water by rotary evaporation under reduced pressure at 60°C and a vacuum degree of -0.08 MPa, then dry in a 60°C vacuum drying oven for 12 hours to obtain a pale yellow to brownish-yellow viscous paste, which is the surfactant composition of this invention, denoted as HS-2. Example

[0043] S1. Preparation of the amphiphilic random copolymer: Under nitrogen protection, 500 mL of toluene (solvent A) was added to a three-necked flask equipped with a stirrer, condenser, and thermometer, and heated to 80 °C. Then, 60 g of octadecyl methacrylate, 24 g of N-vinylpyrrolidone (mass ratio 2.5:1), and 1.0 g of azobisisobutyronitrile (azobisisobutyronitrile) initiator were added sequentially. The stirring speed was controlled at 400 rpm, and the reaction was carried out at a constant temperature for 4 hours. After the reaction was completed, the reaction solution was slowly added dropwise to 2 L of ice-cold anhydrous ethanol, resulting in the precipitation of a white solid. The solid was filtered, and then dried in a vacuum drying oven at 50 °C for 10 hours to obtain a white powdery amphiphilic random copolymer, denoted as P3.

[0044] S2. Preparation of silica nanoparticle dispersion: In another beaker, 200 mL of deionized water and 200 mL of anhydrous ethanol were added and stirred until homogeneous. 35 mL of tetraethyl orthosilicate was slowly added while stirring. The pH of the mixture was adjusted to 8 with 10% ammonia solution, and the mixture was stirred at 1000 rpm for 24 hours at 25°C. After the reaction, the mixture was centrifuged at 8000 rpm for 10 minutes, the supernatant was discarded, and the precipitate was washed three times with deionized water. Finally, it was redispersed in 220 mL of anhydrous ethanol to obtain a silica nanoparticle ethanol dispersion with a concentration of approximately 38.8 mg / mL, denoted as SiO2-3. DLS characterization showed an average particle size of 30 ± 6 nm.

[0045] S3. Assembly of the hybrid surfactant composition: 42.5 g of the amphiphilic random copolymer P3 obtained in step S1 was dissolved in 200 mL of toluene to form a clear solution. Then, 100 mL of isopropanol was added as a co-solvent, and the solution was kept warm in a 60°C water bath. Under magnetic stirring, 220 mL of the SiO2-3 dispersion obtained in step S2 (containing approximately 8.54 g of SiO2, with a polymer to SiO2 mass ratio of 5:1) was slowly added dropwise to the above toluene solution, controlling the dropping rate at 2 mL / min. After the addition was complete, the mixture was stirred at 70°C for 2 hours. After the reaction was complete, toluene, ethanol, and residual water were removed by rotary evaporation under reduced pressure at 60°C and a vacuum degree of -0.09 MPa. The mixture was then dried in a 60°C vacuum drying oven for 12 hours to obtain a pale yellow to brownish-yellow viscous paste, which is the surfactant composition of this invention, denoted as HS-3. Example

[0046] S1. Preparation of the amphiphilic random copolymer: Under nitrogen protection, 500 mL of toluene (solvent A) was added to a three-necked flask equipped with a stirrer, condenser, and thermometer, and heated to 70°C. Then, 80 g of octadecyl methacrylate, 26.7 g of N-vinylpyrrolidone (mass ratio 3:1), and 1.6 g of azobisisobutyronitrile (azobisisobutyronitrile) initiator were added sequentially. The stirring speed was controlled at 400 rpm, and the reaction was carried out at a constant temperature for 6 hours. After the reaction was completed, the reaction solution was slowly added dropwise to 2 L of ice-cold anhydrous ethanol, resulting in the precipitation of a white solid. The solid was filtered, and then dried in a vacuum drying oven at 50°C for 10 hours to obtain a white powdery amphiphilic random copolymer, denoted as P4.

[0047] S2. Preparation of silica nanoparticle dispersion: In another beaker, 400 mL of deionized water and 100 mL of anhydrous ethanol were added and stirred until homogeneous. 45 mL of tetraethyl orthosilicate was slowly added while stirring. The pH of the mixture was adjusted to 10 with 10% ammonia solution, and the mixture was stirred at 1000 rpm for 12 hours at 40°C. After the reaction, the mixture was centrifuged at 8000 rpm for 10 minutes, the supernatant was discarded, and the precipitate was washed three times with deionized water. Finally, it was redispersed in 280 mL of anhydrous ethanol to obtain a silica nanoparticle ethanol dispersion with a concentration of approximately 39.2 mg / mL, denoted as SiO2-4. DLS characterization showed an average particle size of 35 ± 7 nm.

[0048] S3. Assembly of the hybrid surfactant composition: Take 33g of the amphiphilic random copolymer P4 obtained in step S1, dissolve it in 120 mL of toluene to form a clear solution, then add 60 mL of isopropanol as a co-solvent and keep it in a 60℃ water bath. Under magnetic stirring, slowly add 280 mL of the SiO2-4 dispersion obtained in step S2 (containing about 10.98 g of SiO2, with a polymer to SiO2 mass ratio of 3:1) to the above toluene solution, controlling the dropping rate at 2 mL / min. After the addition is complete, continue stirring at 55℃ for 3.5 hours. After the reaction is complete, remove toluene, ethanol and residual water by rotary evaporation under reduced pressure at 60℃ and a vacuum degree of -0.09 MPa, then dry in a 60℃ vacuum drying oven for 12 hours to obtain a pale yellow to brownish-yellow viscous paste, which is the surfactant composition of this invention, denoted as HS-4.

[0049] Comparative Example 1: Except for omitting the hybrid assembly in step S3 and not adding silica nanoparticles, all other steps were the same as in Example 1. Only the amphiphilic random copolymer P1 obtained in step S1 of Example 1 was used as a dispersant, and the resulting product was designated CP-1.

[0050] Comparative Example 2: Except for step S3, which uses simple mechanical stirring and mixing and does not control the hybrid assembly conditions, all other steps are the same as in Example 1. The resulting product is denoted as CP-2.

[0051] Comparative Example 3: Except that the surfactant composition in step S3 was replaced with commercially available standard polyisobutylene succinimide, and the amount added was the same as in Example 1 (10% of the filler mass), all other steps were the same. The resulting product was designated CP-3.

[0052] Comparative Example 4: Except for not preparing and adding the amphiphilic random copolymer, and only adding silica nanoparticles (i.e., 6.1 g) with the same mass as the silica nanoparticles contained in the hybrid composition HS-1 in Example 1, all other steps were the same as in Example 1. The resulting product was designated CP-4.

[0053] Comparative Example 5: Except that the surfactant composition in step S3 was replaced with commercially available Span 80, and the amount added was the same as in Example 1 (10% of the filler mass), all other steps were the same. The resulting product was designated CP-5.

[0054] To verify the technical effect of the surfactant composition of the present invention, graphite was selected as a representative solid filler and PAO6 (polyalphaolefin) synthetic oil was selected as the base oil to prepare a high-concentration dispersion system and conduct performance tests.

[0055] Weigh out 78 g of PAO6 base oil, 20 g of graphite powder (particle size D50 = 10 μm), and 2.0 g of dispersant equivalent to 10% of the graphite mass. The specific groupings are as follows: Experimental group: HS-1, HS-2, HS-3, and HS-4 prepared in Examples 1-4 were used respectively.

[0056] Control group: CP-1, CP-2, CP-3, CP-4, and CP-5 from comparative examples 1-3 were used respectively.

[0057] The above raw materials were placed in a 250 mL beaker, and after initial stirring, homogenized and dispersed at 15,000 rpm for 20 minutes using an IKA T25 digital high-speed shear emulsifier to obtain a graphite / PAO6 dispersion with a mass fraction of 20%. All samples were prepared under the same conditions.

[0058] I. Dispersion Stability Test The sedimentation stability of the dispersion system was tested according to GB / T 41316-2022, "Guiding Principles for Characterizing the Stability of Dispersion Systems". The prepared dispersion was stirred evenly with a glass rod and then filled into graduated 25 mL stoppered colorimetric tubes to the mark (recorded as the initial height H0), and sealed. The tubes were then allowed to stand vertically at room temperature (25 ± 1℃) without vibration. The height Ht of the upper clear oil phase was recorded on days 7, 30, and 60. The volume ratio of the upper clear liquid (Φ, representing the degree of sedimentation) was calculated using the formula: Φ = Ht / H0 × 100%. A smaller Φ value indicates less upper clear liquid, less sedimentation, and better dispersion stability.

[0059] Table 1. Static sedimentation volume ratio (Φ, %) of graphite / PAO6 dispersions prepared with different dispersants

[0060] From Table 1 and Figure 1As can be seen, HS-1 prepared in Example 1 of this invention exhibits the best sedimentation stability in the graphite / PAO6 dispersion system, with a sedimentation volume ratio of only 5.0% after 60 days of standing, significantly better than the comparative examples. Comparative Example 4, which only added silica nanoparticles, showed extremely poor dispersion. Due to the fact that unmodified hydrophilic silica is prone to severe agglomeration and rapid precipitation in the nonpolar oil phase, the sedimentation volume ratio reached as high as 45.0% after 7 days of standing, and it completely precipitated after 30 days, indicating that silica alone cannot play an effective dispersing role in the oil phase. Comparative Example 5, which used Span 80, showed slightly better stability than commercially available dispersants, but the sedimentation volume ratio was still as high as 75.0% after 60 days, indicating that traditional small molecule surfactants could not maintain the long-term stability of high-concentration oil phase systems. The stability of Comparative Example 1, which used only amphiphilic random copolymers, and Comparative Example 2, which was physically blended, was far lower than that of the hybrid product of this invention. Comparative Example 3, which used commercially available dispersants, showed severe sedimentation in a short period of time and completely failed after 30 days. The above data confirms that the organic-inorganic synergistic structure constructed by in-situ hybrid assembly in this invention can form a stable steric hindrance network, effectively solving the problem of solid filler agglomeration and sedimentation in high-concentration oil phase systems. II. High-Temperature Storage Stability Test To investigate the thermal stability of the dispersant, the graphite / PAO6 dispersions prepared in Example 1 (using HS-1) and Comparative Example 1 (using CP-1) were placed in a forced-air drying oven at 120 ± 1℃ for continuous heating and high-temperature accelerated storage experiments. Samples were removed every 24 hours, allowed to cool naturally to room temperature, and then allowed to stand for 24 hours. The sedimentation volume ratio (Φ value after 24 hours of standing) was then measured according to the aforementioned static sedimentation test method.

[0061] Table 2. Changes in sedimentation stability of dispersions after high-temperature storage

[0062] From Table 2 and Figure 2 As can be seen, the HS-1 prepared in Example 1 of this invention exhibits excellent thermal stability under continuous storage at 120°C. After 14 days, the sedimentation volume ratio only slowly increased from the initial 0.5% to 3.0%, and the system remained uniform and stable. In contrast, the sample of Comparative Example 1, which only used an amphiphilic random copolymer, rapidly failed at high temperatures, with the sedimentation volume ratio rising to 28.5% after 3 days and completely settling (≥90%) after 7 days. The above data confirm that the silica nanoparticles introduced by the in-situ hybrid assembly of this invention serve as rigid support points, effectively suppressing the excessive softening and conformational collapse of molecular chain segments of a single polymer at high temperatures, compensating for the poor thermal stability of traditional polymeric dispersants, and endowing the system with excellent high-temperature storage stability.

[0063] III. Rheological Performance Testing Steady-state shear tests were performed on the dispersion samples of Example 1, Comparative Example 1, and Comparative Example 2 using a rotational rheometer. A 40 mm diameter flat plate fixture was used, and the test gap was set to 1.0 mm. The test temperature was 25 °C. The test time ranged from 0.1 to 100 s. -1 Logarithmic scans were performed within the range of shear rates to record the apparent viscosity as a function of shear rate. Special attention was paid to low shear rates (0.1 s⁻¹). -1 The viscosity at zero shear (η0) reflects the strength of the network structure of the dispersion system in resisting particle settling.

[0064] Furthermore, after shearing the sample of Example 1 at 10,000 rpm for 30 minutes at 120°C and then cooling it to room temperature, its sedimentation volume ratio (after standing for 24 hours) increased from 0.5% to 1.2%, which was still significantly better than the 15.0% of the sample of Comparative Example 1 under unsheared conditions. This indicates that the hybrid structure of the present invention can still maintain a strong spatial steric network after high-temperature shearing, exhibiting excellent high-temperature shear resistance.

[0065] Table 3. Rheological properties of different dispersion systems at 25℃

[0066] *Note: A power-law model was used within the tested shear rate range. Fitting the rheological curve, = Shear stress, = Shear rate, K = Consistency coefficient, n = Shear-thinning index; n < 1 indicates shear-thinning, and the smaller n is, the higher the sensitivity of the system to the shear rate and the stronger the internal network structure.

[0067] From Table 3 and Figure 3 It can be seen that the sample in Example 1 has the highest zero-shear viscosity ( This indicates that it forms the most robust three-dimensional network structure, effectively locking in the oil phase and resisting the gravitational settling of graphite particles, which is consistent with the static settling test results. Comparative Example 1 sample has the lowest zero-shear viscosity and weakest structural strength. Comparative Example 2 sample falls between the two. Meanwhile, the sample in Example 1 has the smallest shear thinning index n, indicating that its network structure has good reversible disassembly and reconstruction capabilities under shear, combining good storage stability and ease of application (easy to stir and coat). This further confirms the excellent effect of the hybrid structure of this invention in constructing a strong spatial steric network.

[0068] IV. High-Temperature Shear Stability Test To quantitatively evaluate the high-temperature shear resistance of the surfactant composition of the present invention, the following tests were conducted: 50g of each of the graphite / PAO6 dispersion samples prepared in Example 1, Comparative Example 1, and Comparative Example 2 were placed in 100mL beakers. The beakers were placed in an oil bath, and the oil bath temperature was controlled at 120±1℃. An IKA T25 digital high-speed shear emulsifier was used to continuously shear the samples at 10000rpm for 30 minutes. After shearing, the samples were allowed to cool naturally to room temperature (25±1℃) and allowed to stand for 24 hours to equilibrate. Referring to the method in "I. Dispersion Stability Test," the sedimentation volume ratio (Φ_shear) after standing for 24 hours was tested. Simultaneously, a rotational rheometer was used to test the sheared samples at 25℃ and a shear rate of 0.1 s⁻¹. -1 The apparent viscosity (η_shear) was calculated, and its viscosity retention relative to the zero-shear viscosity (η0) before shearing was calculated (η_retention = η_shear / η0 × 100%). The results are shown in Table 4.

[0069] Table 4 Comparison of dispersion stability and rheological properties before and after high-temperature shearing

[0070] From Table 4 and Figure 4 As can be seen, after undergoing high-temperature and high-speed shearing at 120℃, the sedimentation volume ratio of the sample in Example 1 of this invention only increased slightly from 0.5% to 1.2%, while the viscosity retention rate was as high as 84.7%, indicating that the steric network formed by its hybrid structure has excellent heat resistance and shear failure resistance. In contrast, the samples of Comparative Example 1 (polymer only) and Comparative Example 2 (physical mixture) showed a sharp decrease in stability after shearing, with significantly aggravated sedimentation and very low viscosity retention rates. This fully demonstrates that the rigid support network formed by the hybrid assembly of silica nanoparticles and polymer chains can effectively inhibit the softening, entanglement failure, or conformational collapse of polymer chains at high temperatures, thereby endowing the dispersion system with excellent high-temperature shear stability.

[0071] Based on the above test results, the surfactant composition prepared by the in-situ hybrid assembly technology of "amphiphilic random copolymer-silica nanoparticles" in this invention exhibits significantly better long-term static stability, superior high-temperature storage stability, and stronger internal network structure strength in high-concentration oil-phase dispersion systems compared to single polymer dispersants, simple physical mixtures, or commercial dispersants. These unexpected technical effects fully verify the effectiveness and inventiveness of the "synergistic steric hindrance" mechanism proposed in this invention, demonstrating that this composition has outstanding advantages in solving the problem of dispersion stability in high-concentration oil phases.

[0072] The above-described embodiments are merely illustrative of specific implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of protection of the present invention. It should be noted that for those skilled in the art, any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention should be considered equivalent substitutions and are included within the scope of protection of the present invention.

Claims

1. A high-concentration oil-phase surfactant composition comprising an amphiphilic random copolymer and silica nanoparticles, characterized in that, The composition is an organic-inorganic hybrid structure formed by the hybrid assembly of an amphiphilic random copolymer and silica nanoparticles; the amphiphilic random copolymer is copolymerized from the hydrophobic monomer octadecyl methacrylate and the hydrophilic monomer N-vinylpyrrolidone.

2. The high-concentration oil-phase surfactant composition according to claim 1, characterized in that, The mass ratio of the amphiphilic random copolymer to silica nanoparticles is 2:1-6:

1.

3. The high-concentration oil-phase surfactant composition according to claim 1, characterized in that, The mass ratio of octadecyl methacrylate to N-vinylpyrrolidone is 2:1-3:

1.

4. The high-concentration oil-phase surfactant composition according to claim 1, characterized in that, The silica nanoparticles are prepared by hydrolysis and condensation of orthosilicate under alkaline conditions, and their particle size ranges from 10 to 50 nm.

5. A method for preparing a high-concentration oil-phase surfactant composition according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Preparation of amphiphilic random copolymer: Under an inert atmosphere, hydrophobic monomers, hydrophilic monomers and initiators are dissolved in toluene and reacted at 60-80℃ for 4-8 hours. After precipitation and drying, amphiphilic random copolymer is obtained. S2. Preparation of silica nanoparticle dispersion: Orthosilicate is added to an alcohol-water mixed solvent and hydrolyzed and polycondensed at 25-40℃ for 12-24 hours under the action of an alkaline catalyst to obtain silica nanoparticle dispersion. S3. Hybrid Assembly: The amphiphilic random copolymer obtained in step S1 is dissolved in a mixed solvent of toluene and isopropanol. The silica nanoparticle dispersion obtained in step S2 is added dropwise to the solvent under stirring. The mixture is reacted at 50-70°C for 2-4 hours. After removing the solvent, the surfactant composition is obtained.

6. The preparation method according to claim 5, characterized in that, The volume ratio of toluene to isopropanol is 1:1 to 4:

1.

7. The use of a high-concentration oil-phase surfactant composition as described in any one of claims 1-4 in the preparation of an oil-based dispersion, characterized in that, The surfactant composition, solid filler, and base oil are mixed and sheared to prepare an oil-based dispersion in which the solid filler is uniformly dispersed; wherein the amount of surfactant composition added is 5%-15% of the mass of the solid filler.

8. An oil-based dispersion, characterized in that, The mixture comprises a base oil, solid fillers, and a high-concentration oil-phase surfactant composition as described in any one of claims 1-4; wherein the solid fillers constitute 5%-20% by mass in the oil-based dispersion; and the sedimentation volume ratio of the oil-based dispersion after standing at room temperature for 60 days is not higher than 10%.

Images