Composite magnetic materials and their preparation methods, refrigerant valves and motors

Abstract

This invention discloses composite magnetic granules and their preparation method, a refrigerant valve, and a motor, relating to the field of magnetic material production technology. The preparation method of the composite magnetic granules includes the following steps: dissolving a hindered phenol-grafted hyperbranched coupling agent in anhydrous ethanol and stirring it evenly with NdFeB magnetic powder, drying, crushing, and sieving to obtain surface-treated magnetic powder; mixing PPS resin powder and lubricant evenly to obtain a binder masterbatch; adding the binder masterbatch and the surface-treated magnetic powder to the first and second feed ports of a twin-screw extruder, respectively, with the second feed port being closer to the homogenization section than the first feed port; extruding into strips; cooling and granulating by a pelletizer to obtain the composite magnetic material. The composite magnetic material prepared by this invention has both good mechanical properties and processing performance, and has high practical value.

Description

Technical Field

[0001] This application relates to the field of magnetic materials technology, specifically to composite magnet granules and their preparation methods, refrigerant valves, and motors. Background Technology

[0002] Injection-molded NdFeB magnets, with their advantages of controllable shape, high processing precision, excellent magnetic properties, and ease of production, have been widely used in automotive motors, air conditioning appliances, and aerospace. The core components of this magnet are NdFeB magnetic powder and a polymer binder. However, because both the magnetic powder and the binder are in powder form, the particles are fine and easily dispersed, and contain a significant amount of gas and volatile substances, direct injection molding can easily lead to air bubbles within the product, thus affecting its overall quality. To ensure smooth subsequent processing and improve product quality, the mixture of magnetic powder and binder must be thoroughly mixed and granulated before injection. This process aims to improve the material's strength and density while reducing its internal porosity. However, for some high-viscosity, high-content magnetic materials, the mixing process can be challenging; poor mixing can affect the quality of the final product. Furthermore, the uniformity of mixing the magnetic powder with other materials during the mixing process is also a major problem. Inhomogeneous mixing can lead to stratification of the granules, which not only affects the product's appearance but, more importantly, severely damages its magnetic and mechanical properties. Therefore, it is necessary to provide a method for preparing magnetic injection molding masterbatch.

[0003] Current technologies have the following shortcomings: One of the key factors in improving the magnetic properties of composite magnets is increasing the NdFeB magnetic powder filling rate, typically aiming for a 70% volume ratio. However, during the mixing process, NdFeB magnetic powder may separate from PPS resin, causing inhomogeneity in the mixture. This negatively impacts the rheological properties and magnetic properties of the extruded granules, ultimately affecting the quality of the final product. Furthermore, given that the mixing step is conducted at temperatures above 300°C, direct mixing of NdFeB magnetic powder without anti-oxidation treatment will lead to rapid oxidation, further damaging the performance of the granules and the final product. Summary of the Invention

[0004] This application provides a method for preparing composite magnetic materials, which can improve the magnetic properties of composite magnetic materials.

[0005] This application also provides composite magnetic materials, refrigerant valves, and motors.

[0006] The first aspect of this application provides a method for preparing a composite magnetic material, the method comprising the following steps:

[0007] Step 1: Dissolve the hindered phenol-grafted hyperbranched coupling agent in anhydrous ethanol to obtain a modification solution. Stir the modification solution and NdFeB magnetic powder evenly, then dry, crush, and sieve to obtain surface-treated magnetic powder.

[0008] Step 2: Mix PPS resin powder and lubricant evenly to obtain bonding masterbatch;

[0009] Step 3: Add the binder masterbatch and the surface-treated magnetic powder to the first and second feed ports of the twin-screw extruder, respectively. The second feed port is closer to the homogenization section than the first feed port. Extrude the material into strips at 285-310℃, cool it, and then granulate it through a pelletizer to obtain the composite magnetic material.

[0010] Furthermore, in step one, the amount of hindered phenol-grafted hyperbranched coupling agent used is 0.5-2% of the mass of NdFeB magnetic powder, and the ratio of anhydrous ethanol to NdFeB magnetic powder is 1 mL: 1 g.

[0011] Furthermore, in step one, the stirring equipment is a vacuum mixer with a speed of 750 rpm and a stirring time of 30 minutes. The stirring speed affects the mixing uniformity of the magnetic powder. An appropriate stirring speed can ensure that the magnetic powder and the hindered phenol-grafted hyperbranched coupling agent are fully mixed during the stirring process, thereby achieving the expected mixing effect. If the stirring speed is too low, the magnetic powder may not be completely and uniformly dispersed, resulting in uneven mixing; while if the stirring speed is too high, excessive shear force may be generated, damaging the magnetic powder particles or affecting their performance.

[0012] Furthermore, in step one, the drying equipment is an electrically heated forced-air drying oven with a drying temperature of 110±5℃ and a drying time of 5 hours. This temperature range ensures that moisture and anhydrous ethanol in the magnetic powder are effectively removed, while avoiding incomplete drying due to excessively low temperatures or damage to the magnetic powder performance due to excessively high temperatures. Excessive drying time may cause aggregation between magnetic powder particles, affecting the dispersion and uniformity of the magnetic powder. Conversely, if the drying time is set too short, moisture or solvents in the magnetic powder may not evaporate sufficiently, leading to problems such as moisture absorption and clumping during use. Only by setting a reasonable drying time can the quality and performance of the magnetic powder be ensured to reach optimal levels, meeting the needs of practical applications.

[0013] Furthermore, in step one, the sieving is performed through a 40-mesh sieve.

[0014] Furthermore, the hindered phenol-grafted hyperbranched coupling agent is obtained by reacting a hyperbranched coupling agent with 2,6-di-tert-butyl-4-mercaptophenol via a mercapto-alkene click reaction. The hyperbranched coupling agent is prepared by the addition reaction of trimethylolpropane tris(3-mercaptopropionate) and 3-aminopropyltriethoxysilane via a Maciatell addition reaction, and contains acrylate groups, amino groups, and siloxane structures.

[0015] Furthermore, the specific preparation steps for the hindered phenol-grafted hyperbranched coupling agent are as follows:

[0016] The hyperbranched coupling agent, 2,6-di-tert-butyl-4-mercaptophenol, benzoin dimethyl ether and tetrahydrofuran were mixed evenly and reacted under ultraviolet light for 30 min. The tetrahydrofuran was then removed under reduced pressure to obtain the hindered phenol-grafted hyperbranched coupling agent.

[0017] Furthermore, the mass ratio of the hyperbranched coupling agent to 2,6-di-tert-butyl-4-mercaptophenol is 6.0-6.2:2.4, and the amount of benzoin dimethyl ether used is 2% of the mass of the hyperbranched coupling agent.

[0018] Furthermore, the ultraviolet lamp has a power of 300-600W and a wavelength of 365nm.

[0019] Furthermore, the hyperbranched coupling agent is prepared through the following steps:

[0020] Trimethylolpropane triacrylate and 3-aminopropyltriethoxysilane were added to tetrahydrofuran and reacted at 50°C for 12 h under nitrogen protection. The tetrahydrofuran was then removed under reduced pressure to obtain the hyperbranched coupling agent.

[0021] Furthermore, the molar ratio of trimethylolpropane tris(3-mercaptopropionate) to 3-aminopropyltriethoxysilane is 1:1.

[0022] Furthermore, the amount of PPS resin powder used is 7.5% of the mass of the surface-treated magnetic powder, and the amount of lubricant used is 0.2% of the mass of the surface-treated magnetic powder.

[0023] Furthermore, the lubricant is specifically selected from at least one of paraffin wax, magnesium stearate, zinc stearate, and calcium stearate, preferably calcium stearate.

[0024] Furthermore, in step two, the mixing equipment is a vacuum mixer with a speed of 300-50 rpm and a mixing time of 10-20 min.

[0025] The second aspect of this application provides a composite magnetic material prepared by the above-described preparation method.

[0026] A third aspect of this application provides a refrigerant valve, including a valve body, a valve core, and a drive unit, wherein the valve core is at least partially located within the valve body and is connected to the drive unit;

[0027] The valve body has a first cavity and a second cavity, and the valve core has a first state and a second state. In the first state, the flow area between the first cavity and the second cavity is a first flow area, which is greater than or equal to the first flow area. In the second state, the flow area between the first cavity and the second cavity is a second flow area, which is greater than the first flow area.

[0028] The driving unit is capable of driving the valve core to change from the first state to the second state, and the driving unit is also capable of driving the valve core to change from the second state to the first state.

[0029] The driving unit includes a composite magnetic material.

[0030] The refrigerant valve provided in the third aspect of this application includes an actuation unit, which includes a composite magnetic material. The composite magnetic material includes surface-treated magnetic powder and a binder masterbatch. The binder masterbatch can be firmly bonded to the surface-treated magnetic powder and can also improve the oxidation resistance of the magnetic particles. This helps to reduce the non-magnetic components of the composite magnet, improves the magnetic properties of the composite magnet, and thus improves the magnetic properties of the refrigerant valve actuation unit.

[0031] A fourth aspect of this application provides an electric motor including a rotor comprising a composite magnetic material.

[0032] The beneficial effects of this invention are:

[0033] This invention successfully prepared NdFeB / PPS injection-molded granules. During mixing, the separation of NdFeB magnetic powder and PPS resin is less likely to occur. In the granulation process, the binder masterbatch and surface-treated magnetic powder are added to the first and second feed ports of a twin-screw extruder, respectively. This arrangement is because the flow properties of PPS resin and other additives are much greater than those of the magnetic powder. The PPS resin and other additive powders are mixed before the magnetic powder, which facilitates direct mixing of the magnetic powder with the molten PPS resin through the feed port, achieving uniform mixing. This significantly improves the performance of the NdFeB / PPS injection-molded granules, laying a solid foundation for preparing high-performance injection-molded NdFeB / PPS composite magnets. Furthermore, this preparation method is simple, easy to implement, and convenient to operate, possessing high practical value.

[0034] To address the issues of NdFeB magnetic powder being easily oxidized and having poor affinity when combined with PPS resin, this invention utilizes a hindered phenol-grafted hyperbranched coupling agent to modify the surface of NdFeB magnetic powder. This hindered phenol-grafted hyperbranched coupling agent acts as a "molecular bridge" between inorganic and organic matter, reacting with the hydroxyl groups in NdFeB magnetic powder and interacting with the long molecular chains of PPS resin. This enhances the compatibility and affinity between NdFeB magnetic powder and PPS resin. Simultaneously, a coating film is formed on the surface of NdFeB magnetic powder, improving its oxidation resistance and reducing high-temperature loss of magnetic properties.

[0035] Compared with existing coupling agents, the presence of numerous hindered phenol groups and thioether bonds in the hindered phenol-grafted hyperbranched coupling agent significantly improves the antioxidant properties of NdFeB magnetic powder. This hindered phenol-grafted hyperbranched coupling agent is also a hyperbranched polymer with less intermolecular entanglement, effectively reducing the viscosity of the composite material and thus improving its flowability. It also reduces defects such as voids in the composite material after injection molding, facilitating the large-scale production of injection-molded permanent magnet composites. Furthermore, when subjected to external forces, the voids within the hindered phenol-grafted hyperbranched coupling agent molecules can undergo cavitation, absorbing and dispersing impact energy, thereby slowing crack propagation and improving the impact resistance of the composite material.

[0036] Compared with existing antioxidants, hindered phenol-grafted hyperbranched coupling agents connect the hindered phenol structure with antioxidant function to NdFeB magnetic powder through chemical bonds, overcoming the problems of easy migration and precipitation of small molecule antioxidants, and maintaining a long-lasting and good antioxidant effect. Attached Figure Description

[0037] The invention will now be further described with reference to the accompanying drawings.

[0038] Figure 1 A cross-sectional structural schematic diagram of a refrigerant valve provided in one embodiment of this application;

[0039] Figure 2 A cross-sectional structural diagram of a refrigerant valve provided for another embodiment of this application. Detailed Implementation

[0040] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0041] The first aspect of this application provides a method for preparing a composite magnetic material, the method comprising the following steps:

[0042] Step 1: Dissolve the hindered phenol-grafted hyperbranched coupling agent in anhydrous ethanol to obtain a modification solution. Stir the modification solution and NdFeB magnetic powder evenly, then dry, crush, and sieve to obtain surface-treated magnetic powder.

[0043] Step 2: Mix PPS resin powder and lubricant evenly to obtain bonding masterbatch;

[0044] Step 3: Add the binder masterbatch and the surface-treated magnetic powder to the first and second feed ports of the twin-screw extruder, respectively. The second feed port is closer to the homogenization section than the first feed port. Extrude the material into strips at 285-310℃, cool it, and then granulate it through a pelletizer to obtain the composite magnetic material.

[0045] In some embodiments, the amount of hindered phenol-grafted hyperbranched coupling agent used in step one is 0.5-2% of the mass of NdFeB magnetic powder, and the ratio of anhydrous ethanol to NdFeB magnetic powder is 1 mL: 1 g.

[0046] In some embodiments, the stirring equipment in step one is a vacuum mixer with a rotation speed of 750 rpm and a stirring time of 30 minutes. The stirring speed affects the mixing uniformity of the magnetic powder. An appropriate stirring speed can ensure that the magnetic powder and the hindered phenol-grafted hyperbranched coupling agent are fully mixed during the stirring process, thereby achieving the expected mixing effect. If the stirring speed is too low, the magnetic powder may not be completely and uniformly dispersed, resulting in uneven mixing; while if the stirring speed is too high, excessive shear force may be generated, damaging the magnetic powder particles or affecting their performance.

[0047] In some implementations, the drying equipment in step one is an electrically heated forced-air drying oven with a drying temperature of 110±5℃ and a drying time of 5 hours. This temperature range ensures that moisture and anhydrous ethanol in the magnetic powder are effectively removed, while avoiding incomplete drying due to excessively low temperatures or damage to the magnetic powder performance due to excessively high temperatures. Excessive drying time may cause aggregation between magnetic powder particles, affecting the dispersion and uniformity of the magnetic powder. Conversely, if the drying time is set too short, moisture or solvents in the magnetic powder may not evaporate sufficiently, leading to problems such as moisture absorption and clumping during use. Properly setting the drying time ensures that the quality and performance of the magnetic powder reach their optimal state, meeting the needs of practical applications.

[0048] In some implementations, the sieving in step one involves passing the material through a 40-mesh sieve.

[0049] In some embodiments, the hindered phenol-grafted hyperbranched coupling agent is obtained by a hyperbranched coupling agent and 2,6-di-tert-butyl-4-mercaptophenol via a mercapto-alkene click reaction. The hyperbranched coupling agent is prepared by a Miachail addition reaction of trimethylolpropane tris(3-mercaptopropionate) and 3-aminopropyltriethoxysilane, and contains acrylate groups, amino groups, and siloxane structures.

[0050] In some embodiments, the specific preparation steps of the hindered phenol-grafted hyperbranched coupling agent are as follows:

[0051] The hyperbranched coupling agent, 2,6-di-tert-butyl-4-mercaptophenol, benzoin dimethyl ether and tetrahydrofuran were mixed evenly and reacted under ultraviolet light for 30 min. The tetrahydrofuran was then removed under reduced pressure to obtain the hindered phenol-grafted hyperbranched coupling agent.

[0052] In some embodiments, the mass ratio of the hyperbranched coupling agent to 2,6-di-tert-butyl-4-mercaptophenol is 6.0-6.2:2.4, and the amount of benzoin dimethyl ether used is 2% of the mass of the hyperbranched coupling agent.

[0053] In some implementations, the ultraviolet lamp has a power of 300-600W and a wavelength of 365nm.

[0054] In some embodiments, the hyperbranched coupling agent is prepared by the following steps:

[0055] Trimethylolpropane triacrylate and 3-aminopropyltriethoxysilane were added to tetrahydrofuran and reacted at 50°C for 12 h under nitrogen protection. The tetrahydrofuran was then removed under reduced pressure to obtain the hyperbranched coupling agent.

[0056] In some embodiments, the molar ratio of trimethylolpropane tris(3-mercaptopropionate) to 3-aminopropyltriethoxysilane is 1:1.

[0057] In some embodiments, the amount of PPS resin powder used is 7.5% of the mass of the surface-treated magnetic powder, and the amount of lubricant used is 0.2% of the mass of the surface-treated magnetic powder.

[0058] In some embodiments, the lubricant is specifically selected from at least one of paraffin wax, magnesium stearate, zinc stearate, and calcium stearate, preferably calcium stearate.

[0059] In some embodiments, the stirring equipment in step two is a vacuum mixer with a speed of 300-50 rpm and a stirring time of 10-20 min.

[0060] The second aspect of this application provides a composite magnetic material prepared by the above-described preparation method.

[0061] A fourth aspect of this application provides a refrigerant valve, including a valve body 1, a valve core 2 and a drive unit 3, wherein the valve core 2 is at least partially located within the valve body 1 and the valve core 2 is connected to the drive unit 3.

[0062] The valve body 1 has a first cavity 11 and a second cavity 12, and the valve core 2 has a first state and a second state. In the first state, the flow area between the first cavity 11 and the second cavity 12 is the first flow area, which is greater than or equal to 0. In the second state, the flow area between the first cavity 11 and the second cavity 12 is the second flow area, which is greater than the first flow area.

[0063] The drive unit 3 can drive the valve core 2 to change from the first state to the second state, and the drive unit 3 can also drive the valve core 2 to change from the second state to the first state.

[0064] The drive unit 3 includes a composite magnetic material.

[0065] The refrigerant valve 10 provided in the third aspect of this application includes a drive part 3, which includes a composite magnetic material. The composite magnetic material includes surface-treated magnetic powder and a binder masterbatch. The binder masterbatch can be firmly bonded to the magnetic particles and can also improve the oxidation resistance of the magnetic particles. This helps to reduce the non-magnetic components of the composite magnet, improves the magnetic properties of the composite magnet, and thus improves the magnetic properties of the drive part 3 of the refrigerant valve 10.

[0066] In some implementations, for example Figure 1 As shown, in the first state, the first chamber 11 and the second chamber 12 are in fluid communication; in the second state, the first chamber 11 and the second chamber 12 are fluidly isolated. The drive unit 3 can drive the valve core 2 to change from the first state to the second state, and the drive unit 3 can also drive the valve core 2 to change from the second state to the first state. That is, the refrigerant valve 10 is used as a switch valve or a shut-off valve. Figure 1 In the ball valve shown, the valve core has a third chamber 13. In the first state, both the first chamber 11 and the second chamber 12 are connected to the third chamber 13, or in other words, the first chamber 11 and the second chamber 12 are connected through the third chamber 13. Figure 1 In the state shown. In the second state, both the first cavity 11 and the second cavity 12 are fluidly isolated from the third cavity 13, thereby achieving fluid isolation between the first cavity 11 and the second cavity 12.

[0067] In other implementations, for example Figure 2As shown, the valve body 1 has a first chamber 11, a second chamber 12, and a connecting port. The connecting port can be used to connect the first chamber 11 and the second chamber 12. The valve core 2 has a third state and a fourth state. In the third state, the flow area of ​​the connecting port is the first flow area; in the fourth state, the flow area of ​​the connecting port is the second flow area, which is larger than the first flow area. The drive unit 3 can drive the valve core 2 to change from the third state to the fourth state, and the drive unit 3 can also drive the valve core 2 to change from the fourth state to the third state. That is, the refrigerant valve 10 is used as a throttling valve.

[0068] In some embodiments of this application, the refrigerant valve 10 is a shut-off valve or a throttle valve (e.g., an electronic expansion valve). The valve core is spherical, making the refrigerant valve 10 a ball valve; or the valve core is needle-shaped, making the refrigerant valve 10 a needle valve.

[0069] The motor provided in the fourth aspect of this application includes a rotor, and the rotor includes a composite magnetic material.

[0070] The technical solution of this application will be illustrated below through specific embodiments and comparative examples.

[0071] The sources of some of the raw materials used in this application are as follows:

[0072] NdFeB magnetic powder, model XQP15-10 fast quenched alloy magnetic powder, was purchased from Shenyang Xinxiangshu Magnetic Materials Co., Ltd.

[0073] PPS resin powder, model P-4, manufactured by Philips, USA.

[0074] Example 1

[0075] A surface-treated magnetic powder is prepared by the following steps:

[0076] 0.5 kg of hindered phenol-grafted hyperbranched coupling agent was dissolved in 100 L of anhydrous ethanol to obtain a modified solution. The modified solution and 100 kg of NdFeB magnetic powder were added to a vacuum mixer at 750 rpm for 30 min. The mixture was then placed in an electric heating oven for drying at 105 °C for 5 h. After drying, the powder was crushed and passed through a 40-mesh sieve to obtain surface-treated magnetic powder.

[0077] The specific preparation steps for hindered phenol-grafted hyperbranched coupling agents are as follows:

[0078] 6.0 kg of hyperbranched coupling agent, 2.4 kg of 2,6-di-tert-butyl-4-mercaptophenol, benzoin dimethyl ether, and 80 L of tetrahydrofuran were added to a reaction vessel and stirred at 500 rpm for 30 min. The amount of benzoin dimethyl ether was 2% of the mass of the hyperbranched coupling agent. The reaction was carried out under ultraviolet light (power 300 W, wavelength 365 nm) for 30 min. The tetrahydrofuran was removed under reduced pressure to obtain the hindered phenol-grafted hyperbranched coupling agent.

[0079] Hyperbranched coupling agents are prepared through the following steps:

[0080] 11 mol of trimethylolpropane triacrylate and 11 mol of 3-aminopropyltriethoxysilane were added to 70 L of tetrahydrofuran. The mixture was reacted at 50 °C for 12 h under nitrogen protection. The tetrahydrofuran was then removed under reduced pressure to obtain the hyperbranched coupling agent.

[0081] Example 2

[0082] A surface-treated magnetic powder is prepared by the following steps:

[0083] 2 kg of hindered phenol-grafted hyperbranched coupling agent was dissolved in 100 L of anhydrous ethanol to obtain a modified solution. The modified solution and 100 kg of NdFeB magnetic powder were added to a vacuum mixer at 750 rpm for 30 min. The mixture was then placed in an electric heating oven for drying at 115 °C for 5 h. The powder was then crushed and passed through a 40-mesh sieve to obtain surface-treated magnetic powder.

[0084] The specific preparation steps for hindered phenol-grafted hyperbranched coupling agents are as follows:

[0085] 6.2 kg of hyperbranched coupling agent, 2.4 kg of 2,6-di-tert-butyl-4-mercaptophenol, benzoin dimethyl ether, and 80 L of tetrahydrofuran were added to a reaction vessel and stirred at 500 rpm for 30 min. The amount of benzoin dimethyl ether was 2% of the mass of the hyperbranched coupling agent. The reaction was carried out under ultraviolet light (power 600 W, wavelength 365 nm) for 30 min. The tetrahydrofuran was removed under reduced pressure to obtain the hindered phenol-grafted hyperbranched coupling agent.

[0086] Hyperbranched coupling agents are prepared through the following steps:

[0087] 11 mol of trimethylolpropane triacrylate and 11 mol of 3-aminopropyltriethoxysilane were added to 70 L of tetrahydrofuran. The mixture was reacted at 50 °C for 12 h under nitrogen protection. The tetrahydrofuran was then removed under reduced pressure to obtain the hyperbranched coupling agent.

[0088] Comparative Example 1

[0089] A surface-treated magnetic powder is prepared by the following steps:

[0090] 0.5 kg of hyperbranched coupling agent was dissolved in 100 L of anhydrous ethanol to obtain a modified solution. The modified solution and 100 kg of NdFeB magnetic powder were added to a vacuum mixer at 750 rpm for 30 min. The mixture was then placed in an electric heating oven to dry at 105 °C for 5 h. After drying, the powder was crushed and passed through a 40-mesh sieve to obtain surface-treated magnetic powder. The preparation process of the hyperbranched coupling agent was the same as in Example 1.

[0091] Comparative Example 2

[0092] Based on Comparative Example 1, the hyperbranched coupling agent in Comparative Example 1 was replaced with an equal mass of coupling agent KH-550.

[0093] Comparative Example 3

[0094] Based on Comparative Example 1, the hyperbranched coupling agent in Comparative Example 1 was replaced with an equal mass of coupling agent KH-560.

[0095] The surface-treated magnetic powders and NdFeB magnetic powders obtained in Examples 1-2 and Comparative Examples 1-3 were placed in a box furnace and subjected to oxidation weight gain tests at 300°C in an air atmosphere. The weights were measured every 30 minutes using a thermogravimetric analyzer, and the oxidation weight gain rate was calculated. The test results are shown in Table 1.

[0096] Table 1

[0097]

[0098]

[0099] As can be seen from the data recorded in Table 1, the surface-treated magnetic powders obtained in Examples 1 and 2 have higher antioxidant properties compared to the surface-treated magnetic powders prepared in Comparative Examples 1, 2 and 3.

[0100] Example 3

[0101] The preparation method of composite magnetic materials includes the following steps:

[0102] 7.5 kg of PPS resin powder and 0.2 kg of calcium stearate were added to a vacuum mixer and stirred at 300 rpm for 10 minutes to obtain the binder masterbatch.

[0103] The binder masterbatch and 100 kg of surface-treated magnetic powder from Example 1 were added to the first and second feed ports of a twin-screw extruder, respectively. The second feed port was closer to the homogenization section than the first feed port. The temperatures of each section of the extruder were: Zone 1 285°C, Zone 2 295°C, Zone 3 310°C, Zone 4 310°C, Zone 5 305°C, and the die head temperature was 300°C. After cooling, the material was granulated by a pelletizer to obtain the composite magnetic material.

[0104] Example 4

[0105] The preparation method of composite magnetic materials includes the following steps:

[0106] 7.5 kg of PPS resin powder and 0.2 kg of magnesium stearate were added to a vacuum mixer and stirred at 40 rpm for 15 min to obtain the binder masterbatch.

[0107] The binder masterbatch and 100 kg of surface-treated magnetic powder from Example 2 were added to the first and second feed ports of a twin-screw extruder, respectively. The second feed port was closer to the homogenization section than the first feed port. The temperatures of each section of the extruder were: Zone 1 285°C, Zone 2 295°C, Zone 3 310°C, Zone 4 310°C, Zone 5 305°C, and the die head temperature was 300°C. After cooling, the material was granulated by a pelletizer to obtain the composite magnetic material.

[0108] Example 5

[0109] The preparation method of composite magnetic materials includes the following steps:

[0110] 7.5 kg of PPS resin powder and 0.2 kg of paraffin were added to a vacuum mixer and stirred at 50 rpm for 20 minutes to obtain the binder masterbatch.

[0111] The binder masterbatch and 100 kg of surface-treated magnetic powder from Example 2 were added to the first and second feed ports of a twin-screw extruder, respectively. The second feed port was closer to the homogenization section than the first feed port. The temperatures of each section of the extruder were: Zone 1 285°C, Zone 2 295°C, Zone 3 310°C, Zone 4 310°C, Zone 5 305°C, and the die head temperature was 300°C. After cooling, the material was granulated by a pelletizer to obtain the composite magnetic material.

[0112] Comparative Example 4

[0113] The method for preparing composite magnetic materials is based on Example 3, except that the surface-treated magnetic powder in Example 3 is replaced with the product prepared in Comparative Example 1, and the other raw materials and preparation methods are the same as in Example 3.

[0114] Comparative Example 5

[0115] The preparation method of the composite magnetic material is based on Example 3, except that the surface-treated magnetic powder in Example 3 is replaced with the product prepared in Comparative Example 2, and the other raw materials and preparation methods are the same as in Example 3.

[0116] Comparative Example 6

[0117] The method for preparing composite magnetic materials is based on Example 3, except that the surface-treated magnetic powder in Example 3 is replaced with the product prepared in Comparative Example 3, and the other raw materials and preparation methods are the same as in Example 3.

[0118] Comparative Example 7

[0119] The method for preparing composite magnetic materials is based on Example 3, except that in Example 3, "the binder masterbatch and 100 kg of surface-treated magnetic powder from Example 2 are added to the first feed port and the second feed port of the twin-screw extruder, respectively, with the second feed port being closer to the homogenization section than the first feed port" is replaced with "the binder masterbatch and 100 kg of surface-treated magnetic powder from Example 2 are added together to the first feed port of the twin-screw extruder". The other raw materials and preparation methods are the same as in Example 3.

[0120] Test case

[0121] (1) The XNR-400C melt flow rate tester was used. The test conditions were 310℃ and 10kg pressure. The melt flow rate of each group of composite magnetic materials was determined according to the test standard ASTMD 1238. The MFR was used to characterize the composite magnetic materials. The unit was g / min. MFR = m / t × 600, where: m is the mass of composite magnetic material extruded in a certain time (g); t is the time (s).

[0122] (2) The composite magnetic materials of each group were magnetically injected into the mold using a fully automatic injection molding machine at an injection temperature of 310℃ and a holding pressure of 45MPa. The impact strength was determined by a pendulum bending impact test (cantilever beam test). The impact performance was tested according to GB / T 1843-1993 standard. The experimental result was the average value of 5 samples. The cantilever beam impact strength of the samples was expressed as A (KJ / m). 2 If ) represents the impact performance absorbed by the sample (J), EO represents the energy absorbed by the pendulum (J), b represents the sample width (mm), and d represents the sample thickness (mm).

[0123] (3) Each group of composite magnetic materials was magnetically injected into a fully automatic injection molding machine to obtain a cylindrical bonded NdFeB magnet with a diameter of Ф10mm x 10mm. The magnetic properties, such as remanence (Br) (kGs), coercivity (Hcb) (Koe), intrinsic coercivity (Hcj) (Koe), and maximum energy product (BH)max (MGoe), were measured using a permanent magnet measuring instrument AMT-4.

[0124] The results are shown in Table 2:

[0125] Table 2

[0126] project MFR (g / min) <![CDATA[A(KJ / m 2 )]]> Br(kGs) Hcj(kOe) (BH)max(MGOe) Example 3 133.1 6.4 5.33 11.05 5.74 Example 4 133.8 6.8 5.38 11.17 5.86 Example 5 134.2 6.7 5.30 11.11 5.81 Comparative Example 4 133.0 6.3 5.21 10.56 5.42 Comparative Example 5 122.7 4.5 5.11 10.35 5.22 Comparative Example 6 122.9 4.3 5.13 10.32 5.19 Comparative Example 7 125.6 6.2 5.19 11.02 5.59

[0127] As shown in Table 2, the composite magnetic material obtained in Embodiments 3-5 exhibits better overall performance compared to Embodiments 4-7. It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, 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 a process, method, article, or apparatus.

[0128] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing composite magnetic materials, characterized in that, Includes the following steps: Step 1: Dissolve the hindered phenol-grafted hyperbranched coupling agent in anhydrous ethanol to obtain a modification solution. Stir the modification solution and NdFeB magnetic powder evenly, dry, crush and sieve to obtain surface-treated magnetic powder. Step 2: Mix PPS resin powder and lubricant evenly to obtain bonding masterbatch; Step 3: Add the binder masterbatch and the surface-treated magnetic powder to the first feed port and the second feed port of the twin-screw extruder, respectively. The second feed port is closer to the homogenization section than the first feed port. Extrude the material into strips at 285-310℃, cool it, and then granulate it through a pelletizer to obtain the composite magnetic material. The specific preparation steps for hindered phenol-grafted hyperbranched coupling agents are as follows: The hyperbranched coupling agent, 2,6-di-tert-butyl-4-mercaptophenol, benzoin dimethyl ether and tetrahydrofuran were mixed evenly and reacted under ultraviolet light for 30 min. The tetrahydrofuran was removed under reduced pressure to obtain the hindered phenol-grafted hyperbranched coupling agent. Hyperbranched coupling agents are prepared through the following steps: Trimethylolpropane triacrylate and 3-aminopropyltriethoxysilane were added to tetrahydrofuran and reacted at 50°C for 12 h under nitrogen protection. The tetrahydrofuran was then removed under reduced pressure to obtain the hyperbranched coupling agent.

2. The method for preparing the composite magnetic material according to claim 1, characterized in that, In step one, the amount of hindered phenol-grafted hyperbranched coupling agent used is 0.5-2% of the mass of NdFeB magnetic powder, and the ratio of anhydrous ethanol to NdFeB magnetic powder is 1 mL: 1 g.

3. The method for preparing the composite magnetic material according to claim 1, characterized in that, In step one, the mixing equipment is a vacuum mixer with a speed of 750 rpm and a mixing time of 30 min. The drying equipment is an electric heating oven with a drying temperature of 110±5℃ and a drying time of 5 h.

4. The method for preparing the composite magnetic material according to claim 1, characterized in that, The mass ratio of hyperbranched coupling agent to 2,6-di-tert-butyl-4-mercaptophenol is 6.0-6.2:2.4, and the amount of benzoin dimethyl ether used is 2% of the mass of hyperbranched coupling agent.

5. The method for preparing the composite magnetic material according to claim 1, characterized in that, The molar ratio of trimethylolpropane tris(3-mercaptopropionate) to 3-aminopropyltriethoxysilane is 1:

1.

6. A composite magnetic material, characterized in that, It is prepared by the preparation method described in any one of claims 1-5.

7. A refrigerant valve, characterized in that, It includes a valve body (1), a valve core (2) and a drive unit (3), wherein the valve core (2) is at least partially located inside the valve body (1) and the valve core (2) is connected to the drive unit (3); The valve body (1) has a first cavity (11) and a second cavity (12), and the valve core (2) has a first state and a second state. In the first state, the flow area between the first cavity (11) and the second cavity (12) is a first flow area, which is greater than or equal to 0. In the second state, the flow area between the first cavity (11) and the second cavity (12) is a second flow area, which is greater than the first flow area. The drive unit (3) is capable of driving the valve core (2) to change from the first state to the second state, and the drive unit (3) is capable of driving the valve core (2) to change from the second state to the first state; The driving part (3) includes the composite magnetic material as described in claim 6.

8. An electric motor, comprising a rotor, characterized in that, The rotor comprises the composite magnetic material as described in claim 6.

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