A thickening modification and blending process of a silicone oil-based carrier liquid for preparing a shock absorber magnetorheological liquid

Abstract

The application discloses a silicon oil-based carrier liquid thickening modification and deployment process for preparing a shock absorber magnetorheological liquid, and relates to the technical field of magnetorheological liquid preparation, and comprises the following steps: S1. Magnetic particle pretreatment: selecting carbonyl iron powder as the magnetic particle, after grinding and screening, the magnetic particle is ultrasonically cleaned with anhydrous ethanol for 20-30 min, surface impurities are removed, and then the magnetic particle is vacuum dried at 80-100 DEG C for 1-2 h to obtain pretreated magnetic particles. In use, the process of in-situ coating and grafting is adopted, a siloxane layer is coated on the surface of the magnetic particle at the same time, and in-situ grafting of the thickening chain segment is realized, so that the particle has a "thickening side chain", the system thickening is realized from the particle interface, a large amount of thickening agent does not need to be additionally added, the problem of poor compatibility of the traditional thickening agent with the silicon oil and easy separation and oil analysis of the thickening agent is fundamentally solved, and the stability of the silicon oil-based carrier liquid is significantly improved.

Description

Technical Field

[0001] This invention relates to the field of magnetorheological fluid preparation technology, specifically to a silicone oil-based carrier fluid thickening and modification formulation process for preparing magnetorheological fluid for shock absorbers. Background Technology

[0002] Magnetorheological fluids are intelligent fluids composed of magnetic particles, a carrier fluid, and additives. Their rheological properties can be reversibly controlled in milliseconds via an external magnetic field, making them promising for applications in the field of shock absorbers. Among these, silicone oil is the most commonly used carrier fluid type for shock absorbers due to its excellent high-temperature resistance, aging resistance, and strong chemical stability.

[0003] However, in practical applications, silicone oil-based carrier fluids have obvious technical defects: ordinary silicone oil has a low viscosity, which results in insufficient suspension stability when used as a carrier fluid for magnetorheological fluids, and magnetic particles are prone to sedimentation, leading to a decrease in the damping performance of the magnetorheological fluid; at the same time, temperature changes cause the viscosity of silicone oil to fluctuate drastically. At high temperatures, silicone oil becomes thinner and cannot effectively suspend magnetic particles, while at low temperatures, the viscosity of silicone oil increases sharply, resulting in stiff start-up of the shock absorber and uncontrollable damping, which seriously affects the working stability of the shock absorber under high and low temperature conditions.

[0004] To address the aforementioned issues, existing technologies typically employ the addition of thickeners to increase the viscosity of silicone oil-based carrier fluids. However, conventional thickeners exhibit poor compatibility with silicone oils, and phase separation and oil precipitation are prone to occur after prolonged standing or shearing, leading to decreased stability of the magnetorheological fluid and shortening the lifespan of the shock absorber. Furthermore, simply adding thickeners increases the zero-field viscosity of the carrier fluid, reducing the magnetic field response speed of the magnetorheological fluid, making it difficult to balance suspension stability and rheological response performance.

[0005] Other technologies attempt to modify the surface of magnetic particles by coating to improve their compatibility with silicone oil. However, coating modification alone cannot fundamentally improve the overall viscosity of the carrier fluid, and it still requires the addition of external thickeners. This fails to solve the core problems of poor compatibility between thickeners and silicone oil and insufficient system stability. A common method is to coat magnetic particles with SiO2 aerogel and graft fluorosilanes, which mainly improves the low-temperature performance of magnetorheological fluids, but does not involve in-situ thickening modification of the carrier fluid. It still requires the addition of dispersants, anticoagulants and other components, and cannot achieve a synergistic improvement in viscosity and stability. Therefore, we propose a silicone oil-based carrier fluid thickening and modification formulation process for the preparation of magnetorheological fluids for shock absorbers. Summary of the Invention

[0006] The purpose of this invention is to provide a thickening and modification process for a silicone oil-based carrier fluid used in the preparation of magnetorheological fluids for shock absorbers, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a thickening, modification, and formulation process for a silicone oil-based carrier fluid used in the preparation of magnetorheological fluids for shock absorbers, comprising the following steps: S1. Pretreatment of magnetic particles: Carbonyl iron powder is selected as magnetic particles. After grinding and sieving, it is ultrasonically cleaned with anhydrous ethanol for 20-30 minutes to remove surface impurities. Then, it is vacuum dried at 80-100℃ for 1-2 hours to obtain pretreated magnetic particles. S2. Preparation of in-situ modified system: Add the pretreated magnetic particles to the reaction vessel, and then add the silicone oil-based carrier liquid, siloxane coating agent, thickening segment monomer, initiator and dispersant in sequence. Stir evenly to obtain a mixed reaction system. The components are as follows by weight: 100 parts silicone oil-based carrier liquid, 40-60 parts pretreated magnetic particles, 5-10 parts siloxane coating agent, 3-8 parts thickening segment monomer, 0.2-0.5 parts initiator, and 1-3 parts dispersant. S3. In-situ coating and grafting reaction: The mixed reaction system is heated to 60-80℃ and stirred at 200-300r / min for 3-5h under nitrogen protection, so that the siloxane coating agent forms a siloxane coating layer on the surface of the magnetic particles. At the same time, the thickening chain monomer is in-situ grafted on the surface of the siloxane coating layer to form modified magnetic particles with thickening side chains. S4. Post-processing: After the reaction is completed, the reaction product is cooled to room temperature and degassed under vacuum for 20-30 minutes to remove bubbles and trace volatiles from the system. Then, unreacted impurities and agglomerated particles are removed by precision filtration to obtain the thickened and modified silicone oil-based carrier liquid, which is the silicone oil-based carrier liquid for preparing magnetorheological fluid for shock absorbers.

[0008] Furthermore, the carbonyl iron powder mentioned in step S1 has a particle size of 1-10 μm, and after grinding, it is sieved using a 200-500 mesh sieve, and the ultrasonic cleaning power is 150-200W.

[0009] Furthermore, the silicone oil-based carrier liquid in step S2 is a compound system of dimethyl silicone oil and methylphenyl silicone oil, with a weight ratio of 7:3-8:2, and the kinematic viscosity of the silicone oil-based carrier liquid at 25°C is 100-500 mm² / s.

[0010] Furthermore, the siloxane coating agent in step S2 is one or a combination of two of methyltrimethoxysilane and vinyltriethoxysilane, and the weight ratio of the two is 1:1-2:1 when they are combined; the thickening segment monomer is one of polymethyl methacrylate and polysiloxane block copolymer, and the number average molecular weight of the thickening segment monomer is 5000-20000.

[0011] Furthermore, the initiator in step S2 is one of azobisisobutyronitrile and benzoyl peroxide; the dispersant is a silicone-based block copolymer, which has one end affinity for silicone oil-based carrier liquid and the other end affinity for the surface of magnetic particles.

[0012] Furthermore, in step S3, the nitrogen protection flow rate is 50-100 mL / min, the stirring speed is 250 r / min, the reaction temperature is 70℃, and the reaction time is 4 h.

[0013] Furthermore, the vacuum degree of vacuum degassing in step S4 is -0.08 to -0.1 MPa, and the precision filtration uses a 1000-1200 mesh filter membrane with a filtration pressure of 0.1-0.2 MPa.

[0014] Furthermore, the thickness of the siloxane coating layer on the surface of the modified magnetic particles is 50-100 nm, and the grafting rate of the thickening side chains is 15-25%.

[0015] Furthermore, the thickened and modified silicone oil-based carrier fluid has a zero-field viscosity of 0.8-1.2 Pa·s at 25°C, a viscosity fluctuation rate of ≤5% in the range of -40°C to 150°C, and a 30-day sedimentation rate of ≤8%.

[0016] This invention provides a thickening and modification process for silicone oil-based carrier fluid used in the preparation of magnetorheological fluids for shock absorbers, which has the following advantages: It employs a process that simultaneously performs in-situ coating and grafting. While coating the surface of magnetic particles with a siloxane layer, thickening segments are grafted in-situ, giving the particles their own "thickening side chains." This achieves thickening of the system from the particle interface, eliminating the need for adding large amounts of thickener. This fundamentally solves the problems of poor compatibility and easy oil separation between traditional thickeners and silicone oil, significantly improving the stability of the silicone oil-based carrier fluid.

[0017] Meanwhile, the siloxane coating on the surface of the modified magnetic particles in this invention improves the compatibility between the magnetic particles and the silicone oil-based carrier liquid. The thickening side chains form an entangled network with the silicone oil molecules. This dual effect effectively improves the overall viscosity and suspension stability of the carrier liquid, avoids the sedimentation of magnetic particles, and simultaneously takes into account both zero-field viscosity and magnetic field response speed, thus solving the technical contradiction of "difficulty in balancing thickening and response speed" in the prior art. Attached Figure Description

[0018] Figure 1 This is a process flow diagram of a silicone oil-based carrier fluid thickening and modification formulation process for preparing magnetorheological fluid for shock absorbers according to the present invention. Detailed Implementation

[0019] Example 1 A thickening and modification process for a silicone oil-based carrier fluid used in the preparation of magnetorheological fluids for shock absorbers includes the following steps: (1) Pretreatment of magnetic particles: Select carbonyl iron powder with a particle size of 1-5μm, grind it and then sieve it with a 200-mesh sieve. Then, use anhydrous ethanol to ultrasonically clean it with a power of 150W for 20min to remove surface impurities. Then, vacuum dry it at 80℃ for 2h to obtain pretreated magnetic particles. (2) Preparation of in-situ modified system: 40 parts by weight of pretreated magnetic particles were added to the reaction vessel, and 100 parts by weight of silicone oil-based carrier liquid (the weight ratio of dimethyl silicone oil to methylphenyl silicone oil was 7:3, and the kinematic viscosity at 25℃ was 100 mm² / s), 5 parts by weight of methyltrimethoxysilane, 3 parts by weight of polymethyl methacrylate (number average molecular weight 5000), 0.2 parts by weight of azobisisobutyronitrile, and 1 part by weight of silicone block copolymer dispersant were added in sequence. The mixture was stirred evenly to obtain a mixed reaction system. (3) In-situ coating and grafting reaction: The mixed reaction system was heated to 60°C and stirred at 200 r / min for 5 h under nitrogen protection (flow rate 50 mL / min) to form a siloxane coating layer on the surface of the magnetic particles with methyltrimethoxysilane. At the same time, polymethyl methacrylate was in-situ grafted on the surface of the siloxane coating layer to form modified magnetic particles with thickening side chains. (4) Post-processing: After the reaction is completed, the reaction product is cooled to room temperature and degassed under a vacuum of -0.08MPa for 30 minutes. Then, it is filtered precisely with a 1000-mesh filter membrane under a pressure of 0.1MPa to remove unreacted impurities and agglomerated particles, and the thickened and modified silicone oil-based carrier liquid is obtained.

[0020] According to the test results, the silicone oil-based carrier liquid prepared in this embodiment has a zero-field viscosity of 0.8 Pa·s at 25°C, a viscosity fluctuation rate of 4.8% in the range of -40°C to 150°C, a sedimentation rate of 7.5% after 30 days, a siloxane coating thickness of 50 nm on the surface of the modified magnetic particles, and a thickening side-linking branching rate of 15%.

[0021] Example 2 A thickening and modification process for a silicone oil-based carrier fluid used in the preparation of magnetorheological fluids for shock absorbers includes the following steps: (1) Pretreatment of magnetic particles: Carbonyl iron powder with a particle size of 3-8 μm was selected, ground and sieved with a 300-mesh sieve, then ultrasonically cleaned with anhydrous ethanol at 180W power for 25 min to remove surface impurities, and vacuum dried at 90℃ for 1.5 h to obtain pretreated magnetic particles. (2) Preparation of in-situ modified system: 50 parts by weight of pretreated magnetic particles were added to the reaction vessel, and 100 parts by weight of silicone oil-based carrier liquid (the weight ratio of dimethyl silicone oil to methylphenyl silicone oil was 7.5:2.5, and the kinematic viscosity at 25℃ was 300 mm² / s), 8 parts by weight of siloxane coating agent (the weight ratio of methyltrimethoxysilane to vinyltriethoxysilane was 1.5:1), 5 parts by weight of polysiloxane block copolymer (number average molecular weight 12000), 0.3 parts by weight of benzoyl peroxide, and 2 parts by weight of silicone block copolymer dispersant were added. The mixture was stirred evenly to obtain a mixed reaction system. (3) In-situ coating and grafting reaction: The mixed reaction system was heated to 70°C and stirred at 250 r / min for 4 h under nitrogen protection (flow rate 80 mL / min) to form a siloxane coating layer on the surface of the magnetic particles. At the same time, the polysiloxane block copolymer was in-situ grafted on the surface of the siloxane coating layer to form modified magnetic particles with thickening side chains. (4) Post-processing: After the reaction is completed, the reaction product is cooled to room temperature and degassed under a vacuum of -0.09MPa for 25 minutes. Then, it is filtered precisely with an 1100-mesh filter membrane under a pressure of 0.15MPa to remove unreacted impurities and agglomerated particles, and the thickened and modified silicone oil-based carrier liquid is obtained.

[0022] According to the test results, the silicone oil-based carrier liquid prepared in this embodiment has a zero-field viscosity of 1.0 Pa·s at 25°C, a viscosity fluctuation rate of 3.2% in the range of -40°C to 150°C, a sedimentation rate of 6.2% after 30 days, a siloxane coating thickness of 80 nm on the surface of the modified magnetic particles, and a thickening side-linking branching rate of 20%.

[0023] Example 3 A thickening and modification process for a silicone oil-based carrier fluid used in the preparation of magnetorheological fluids for shock absorbers includes the following steps: (1) Pretreatment of magnetic particles: Select carbonyl iron powder with a particle size of 5-10 μm, grind it and then sieve it with a 500 mesh screen. Then, use anhydrous ethanol to ultrasonically clean it with a power of 200W for 30 min to remove surface impurities. Then, vacuum dry it at 100℃ for 1 h to obtain pretreated magnetic particles. (2) Preparation of in-situ modified system: 60 parts by weight of pretreated magnetic particles were added to the reaction vessel, followed by 100 parts by weight of silicone oil-based carrier liquid (the weight ratio of dimethyl silicone oil to methylphenyl silicone oil was 8:2, and the kinematic viscosity at 25℃ was 500 mm² / s), 10 parts by weight of vinyltriethoxysilane, 8 parts by weight of polymethyl methacrylate (number average molecular weight 20000), 0.5 parts by weight of azobisisobutyronitrile, and 3 parts by weight of silicone-based block copolymer dispersant. The mixture was stirred evenly to obtain a mixed reaction system. (3) In-situ coating and grafting reaction: The mixed reaction system was heated to 80°C and stirred at 300 r / min for 3 h under nitrogen protection (flow rate 100 mL / min) to form a siloxane coating layer on the surface of the magnetic particles. At the same time, polymethyl methacrylate was in-situ grafted on the surface of the siloxane coating layer to form modified magnetic particles with thickening side chains. (4) Post-processing: After the reaction is completed, the reaction product is cooled to room temperature and degassed under a vacuum of -0.1MPa for 20 minutes. Then, it is filtered precisely with a 1200-mesh filter membrane under a pressure of 0.2MPa to remove unreacted impurities and agglomerated particles, and the thickened and modified silicone oil-based carrier liquid is obtained.

[0024] According to the test results, the silicone oil-based carrier liquid prepared in this embodiment has a zero-field viscosity of 1.2 Pa·s at 25°C, a viscosity fluctuation rate of 2.5% in the range of -40°C to 150°C, a sedimentation rate of 5.8% after 30 days, a siloxane coating thickness of 100 nm on the surface of the modified magnetic particles, and a thickening side-linking branching rate of 25%.

[0025] Comparative Example 1 The silicone oil-based carrier liquid was prepared by the traditional method of adding external thickeners. The specific steps are as follows: 100 parts by weight of dimethyl silicone oil (kinematic viscosity of 300 mm² / s at 25℃) was added to the reaction vessel, 5 parts by weight of organic bentonite thickener and 2 parts by weight of dispersant were added, and the mixture was stirred evenly. Then, 50 parts by weight of unmodified carbonyl iron powder was added, and the mixture was ultrasonically dispersed for 30 min and vacuum degassed for 25 min to obtain the silicone oil-based carrier liquid.

[0026] Testing revealed that the silicone oil-based carrier fluid prepared in this comparative example had a zero-field viscosity of 0.9 Pa·s at 25°C, a viscosity fluctuation rate of 12.3% in the range of -40°C to 150°C, a sedimentation rate of 28.5% after 30 days, and exhibited stratification and oil separation after standing for 7 days.

[0027] Comparative Example 2 Modified magnetic particles were prepared using a step-by-step process of coating followed by grafting, and then a silicone oil-based carrier liquid was prepared. Specific steps are as follows: (1) Pretreatment of magnetic particles: Same as in Example 2; (2) Magnetic particle coating: 50 parts by weight of pretreated magnetic particles are added to a reaction vessel, 8 parts by weight of siloxane coating agent are added, the temperature is raised to 70°C, and the reaction is stirred for 2 hours to form siloxane-coated magnetic particles. (3) Grafting of magnetic particles: Add 5 parts by weight of polysiloxane block copolymer and 0.3 parts by weight of benzoyl peroxide to the above system, and continue stirring for 2 hours to obtain modified magnetic particles; (4) Preparation of carrier liquid: 100 parts by weight of silicone oil-based carrier liquid (same as in Example 2) were added to the reaction vessel, along with the above-mentioned modified magnetic particles and 2 parts by weight of dispersant. The mixture was stirred evenly, vacuum degassed for 25 minutes, and then filtered precisely to obtain the silicone oil-based carrier liquid.

[0028] Testing revealed that the silicone oil-based carrier fluid prepared in this comparative example had a zero-field viscosity of 0.95 Pa·s at 25°C, a viscosity fluctuation rate of 6.8% in the range of -40°C to 150°C, a 30-day sedimentation rate of 13.2%, and a thickening side grafting rate of 12.3%. The grafting effect and stability were lower than those of Example 2.

[0029] A comparison of Examples 1-3 and Comparative Examples 1-2 shows that the silicone oil-based carrier fluid prepared by the present invention, which uses a process of simultaneous in-situ coating and grafting, is superior to traditional processes in terms of viscosity stability, suspension stability, and high and low temperature adaptability. Moreover, the process is simple and highly controllable, which can effectively solve the technical defects of the prior art and meet the requirements for the use of magnetorheological fluid in shock absorbers.

[0030] It should be noted that, in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0031] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only for the purpose of helping to understand the method and core ideas of the present invention. The above descriptions are only preferred embodiments of the present invention. It should be noted that due to the limitations of textual expression, while there are objectively infinite specific structures, those skilled in the art can make several improvements, modifications, or changes without departing from the principles of the present invention, and can also combine the above technical features in an appropriate manner. These improvements, modifications, changes, or combinations, or the direct application of the inventive concept and technical solution to other situations without modification, should all be considered within the scope of protection of the present invention.

Claims

1. A thickening, modification, and formulation process for a silicone oil-based carrier fluid used in the preparation of magnetorheological fluids for shock absorbers, characterized in that, Includes the following steps: S1. Pretreatment of magnetic particles: Carbonyl iron powder is selected as magnetic particles. After grinding and sieving, it is ultrasonically cleaned with anhydrous ethanol for 20-30 minutes to remove surface impurities. Then, it is vacuum dried at 80-100℃ for 1-2 hours to obtain pretreated magnetic particles. S2. Preparation of in-situ modified system: Add the pretreated magnetic particles to the reaction vessel, and then add the silicone oil-based carrier liquid, siloxane coating agent, thickening segment monomer, initiator and dispersant in sequence. Stir evenly to obtain a mixed reaction system. The components are as follows by weight: 100 parts silicone oil-based carrier liquid, 40-60 parts pretreated magnetic particles, 5-10 parts siloxane coating agent, 3-8 parts thickening segment monomer, 0.2-0.5 parts initiator, and 1-3 parts dispersant. S3. In-situ coating and grafting reaction: The mixed reaction system is heated to 60-80℃ and stirred at 200-300r / min for 3-5h under nitrogen protection, so that the siloxane coating agent forms a siloxane coating layer on the surface of the magnetic particles. At the same time, the thickening chain monomer is in-situ grafted on the surface of the siloxane coating layer to form modified magnetic particles with thickening side chains. S4. Post-processing: After the reaction is completed, the reaction product is cooled to room temperature and degassed under vacuum for 20-30 minutes to remove bubbles and trace volatiles from the system. Then, unreacted impurities and agglomerated particles are removed by precision filtration to obtain the thickened and modified silicone oil-based carrier liquid, which is the silicone oil-based carrier liquid for preparing magnetorheological fluid for shock absorbers.

2. The silicone oil-based carrier fluid thickening and modification formulation process for preparing magnetorheological fluid for shock absorbers according to claim 1, characterized in that, The carbonyl iron powder mentioned in step S1 has a particle size of 1-10 μm, and after grinding, it is sieved using a 200-500 mesh sieve. The ultrasonic cleaning power is 150-200W.

3. The silicone oil-based carrier fluid thickening and modification formulation process for preparing magnetorheological fluid for shock absorbers according to claim 1, characterized in that, The silicone oil-based carrier liquid mentioned in step S2 is a compound system of dimethyl silicone oil and methylphenyl silicone oil, with a weight ratio of 7:3-8:

2. The kinematic viscosity of the silicone oil-based carrier liquid at 25°C is 100-500 mm² / s.

4. The silicone oil-based carrier fluid thickening and modification formulation process for preparing magnetorheological fluid for shock absorbers according to claim 1, characterized in that, The siloxane coating agent in step S2 is one or a combination of two of methyltrimethoxysilane and vinyltriethoxysilane, and the weight ratio of the two is 1:1-2:1 when they are combined; the thickening segment monomer is one of polymethyl methacrylate and polysiloxane block copolymer, and the number average molecular weight of the thickening segment monomer is 5000-20000.

5. The silicone oil-based carrier fluid thickening and modification formulation process for preparing magnetorheological fluid for shock absorbers according to claim 1, characterized in that, The initiator in step S2 is one of azobisisobutyronitrile and benzoyl peroxide; the dispersant is a silicone-based block copolymer, which has one end affinity for silicone oil-based carrier liquid and the other end affinity for the surface of magnetic particles.

6. The silicone oil-based carrier fluid thickening and modification formulation process for preparing magnetorheological fluid for shock absorbers according to claim 1, characterized in that, In step S3, the nitrogen protection flow rate is 50-100 mL / min, the stirring speed is 250 r / min, the reaction temperature is 70℃, and the reaction time is 4 h.

7. The silicone oil-based carrier fluid thickening and modification formulation process for preparing magnetorheological fluid for shock absorbers according to claim 1, characterized in that, The vacuum degree of vacuum degassing in step S4 is -0.08 to -0.1 MPa, and the precision filtration uses a 1000-1200 mesh filter membrane with a filtration pressure of 0.1-0.2 MPa.

8. The silicone oil-based carrier fluid thickening and modification formulation process for preparing magnetorheological fluid for shock absorbers according to claim 1, characterized in that, The thickness of the siloxane coating layer on the surface of the modified magnetic particles is 50-100 nm, and the grafting rate of the thickening side chains is 15-25%.

9. The silicone oil-based carrier fluid thickening and modification formulation process for preparing magnetorheological fluid for shock absorbers according to claim 1, characterized in that, The thickened and modified silicone oil-based carrier fluid has a zero-field viscosity of 0.8-1.2 Pa·s at 25℃, a viscosity fluctuation rate of ≤5% in the range of -40℃ to 150℃, and a 30-day sedimentation rate of ≤8%.

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