Composite magnetic material and preparation method thereof, refrigerant valve and motor

Abstract

The invention discloses a composite magnet particle material and a preparation method thereof, a refrigerant valve and a motor, and relates to the technical field of magnetic material production, and the preparation method of the composite magnet particle material comprises the following steps: dissolving a hindered phenol grafted hyperbranched coupling agent with absolute ethyl alcohol, uniformly stirring the dissolved hindered phenol grafted hyperbranched coupling agent and NdFeB magnetic powder, drying, crushing, and screening to obtain surface-treated magnetic powder; uniformly mixing the PPS resin powder and the lubricant to obtain bonding master batch; the bonding master batch and the surface-treated magnetic powder are added into a first feeding port and a second feeding port of a double-screw extruder respectively, the second feeding port is closer to a homogenizing section than the first feeding port, the materials are extruded into strips, the strips are granulated through a granulator after being cooled, and the composite magnetic material is obtained. The composite magnetic material prepared by the invention has good mechanical properties and processability, and has high practical value.

Description

Technical Field

[0001] This application relates to the technical field of magnetic materials. Specifically, it relates to composite magnet pellets, a preparation method thereof, a refrigerant valve, and an electric motor. Background Art

[0002] Injection-molded NdFeB magnets have been widely used in fields such as automotive motors, air-conditioning appliances, and aerospace due to their many advantages, such as controllable shape, high processing accuracy, excellent magnetic properties, and easy production. The core components of such magnets are NdFeB magnetic powder and a polymer binder. However, since both the magnetic powder and the binder are in powder form, with fine particles and easy to loosen, and contain a relatively large amount of gas and volatile substances, directly performing injection molding processing is extremely likely to cause bubbles to form inside the product, thereby affecting the overall quality of the product. To ensure the smooth progress of subsequent processing and improve the product quality, the mixture of magnetic powder and binder must be fully kneaded and granulated before injection. This process aims to improve the strength and density of the material while reducing its internal porosity. However, for some magnetic materials with high viscosity and high content, the kneading process may face challenges, such as poor kneading effect, thus affecting the quality of the final product. In addition, the mixing uniformity of the magnetic powder and other materials during the kneading process is also a major problem. If the mixing is uneven, it may cause layering of the pellets, which not only affects the appearance quality of the product, but more critically, will seriously damage its magnetic properties and mechanical properties. Based on this, it is necessary to provide a preparation method for magnetic injection masterbatch.

[0003] The currently existing technologies have the following deficiencies: One of the key factors in improving the magnetic properties of composite magnets is to increase the filling rate of NdFeB magnetic powder, and a volume ratio of 70% is usually expected to be achieved. However, during the mixing process, separation of NdFeB magnetic powder and PPS resin may occur, resulting in non-uniformity of the mixture, which has a negative impact on the rheological properties and magnetic properties of the extruded and cut pellets, and thus affects the quality of the final product. Given that the kneading step is carried out in a high-temperature environment above 300°C, if the NdFeB magnetic powder is not subjected to antioxidant treatment and directly participates in the kneading, it will cause rapid oxidation of the magnetic powder, further damaging the properties of the pellets and the final product. Summary of the Invention

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

[0005] This application also provides composite magnetic materials, a refrigerant valve, and an electric motor.

[0006] The first aspect of this application provides a preparation method for composite magnetic materials, and the preparation method includes the following steps:

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

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

[0009] Step 3: Add the bonding masterbatch and the surface-treated magnetic powder into the first feeding port and the second feeding port of a twin-screw extruder respectively. The second feeding port is closer to the homogenization section than the first feeding port. Extrude into strips at 285 - 310 °C, and granulate by a pelletizer after cooling to obtain a composite magnetic material.

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

[0011] Furthermore, in Step 1, the stirring equipment is a vacuum mixing blender with a rotation speed of 750 rpm and a stirring time of 30 min. 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 stirring, so as to achieve the expected mixing effect. If the stirring speed is too low, the magnetic powder may not be fully and evenly 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 1, the drying equipment is an electrothermal blast drying oven, the drying temperature is 110 ± 5 °C, and the drying duration is 5 h. This temperature range setting can ensure that the moisture and absolute ethanol in the magnetic powder can be effectively removed, while avoiding incomplete drying caused by too low temperature or damage to the performance of the magnetic powder caused by too high temperature. An overly long drying time may cause aggregation between magnetic powder particles, which will affect the dispersibility and uniformity of the magnetic powder. On the contrary, if the drying time is set too short, the moisture or solvent in the magnetic powder may not be fully volatilized, resulting in problems such as moisture absorption and caking of the magnetic powder during use. Only by reasonably setting the drying time can the quality and performance of the magnetic powder reach the best state and meet the requirements of practical applications.

[0013] Furthermore, in Step 1, the screening is through a 40-mesh sieve.

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

[0015] Further, the preparation steps of the hindered phenol grafted hyperbranched coupling agent are as follows:

[0016] Mix the hyperbranched coupling agent, 2,6 - di - tert - butyl - 4 - mercapto - phenol, benzoin dimethyl ether and tetrahydrofuran evenly, react under ultraviolet light for 30 min, and remove tetrahydrofuran under reduced pressure to obtain the hindered phenol grafted hyperbranched coupling agent.

[0017] Further, the mass ratio of the hyperbranched coupling agent to 2,6 - di - tert - butyl - 4 - mercapto - phenol is 6.0 - 6.2:2.4, and the dosage of benzoin dimethyl ether is 2% of the mass of the hyperbranched coupling agent.

[0018] Further, the power of the ultraviolet lamp is 300 - 600 W, and the wavelength is 365 nm.

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

[0020] Add trimethylolpropane triacrylate and 3 - aminopropyltriethoxysilane into tetrahydrofuran, react at 50 °C for 12 h under nitrogen protection, and remove tetrahydrofuran under reduced pressure to obtain the hyperbranched coupling agent.

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

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

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

[0024] Further, in step two, the stirring device is a vacuum mixing blender, the rotation speed is 300 - 50 rpm, and the stirring time is 10 - 20 min.

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

[0026] The third aspect of this application provides a refrigerant valve, which includes a valve body, a valve core, and a driving part. At least part of the valve core is located inside the valve body, and the valve core is connected to the driving part;

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

[0028] The driving part can drive the valve core to change from the first state to the second state, and the driving part can drive the valve core to change from the second state to the first state;

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

[0030] The refrigerant valve provided in the third aspect of the present application includes a driving part, the driving part includes a composite magnetic material, the composite magnetic material includes surface-treated magnetic powder and a binder masterbatch, the binder masterbatch can firmly bond with the surface-treated magnetic powder, and can also improve the antioxidant performance of the magnetic particles, which is beneficial to reducing the non-magnetic components of the composite magnet, improving the magnetic performance of the composite magnet, and further improving the magnetic performance of the driving part of the refrigerant valve.

[0031] The fourth aspect of the present application provides a motor, including a rotor, and the rotor includes a composite magnetic material.

[0032] The beneficial effects of the present invention:

[0033] The present invention successfully prepares NdFeB / PPS injection molding granule materials. During mixing, the phenomenon of separation between NdFeB magnetic powder and PPS resin during mixing is not likely to occur. During the granulation process, the binder masterbatch and the surface-treated magnetic powder are respectively added to the first feeding port and the second feeding port of the twin-screw extruder. This setting is because the flowability of additives such as PPS resin is much greater than that of magnetic powder. The PPS resin and other additive powders are premixed before the magnetic powder, which is beneficial for the magnetic powder to directly mix with the molten PPS resin through the feeding port to achieve uniform mixing. This greatly improves the performance of the NdFeB / PPS injection molding granule materials and lays a good foundation for preparing injection molding NdFeB / PPS composite magnets with excellent performance; at the same time, this preparation method is simple and easy to operate, and has high practical value.

[0034] Aiming at the problems that NdFeB magnetic powder is easily oxidized and has poor affinity when combined with PPS resin, the present invention uses a hindered phenol grafted hyperbranched coupling agent to perform surface modification on NdFeB magnetic powder. As a "molecular bridge" between inorganic and organic substances, the hindered phenol grafted hyperbranched coupling agent can not only react with the hydroxyl groups in NdFeB magnetic powder, but also interact with the long molecular chains of PPS resin, thereby enhancing the compatibility and affinity between NdFeB magnetic powder and PPS resin. At the same time, a coating film is formed on the surface of NdFeB magnetic powder to improve the antioxidant performance of NdFeB magnetic powder and reduce the high-temperature loss of magnetic properties;

[0035] Compared with existing coupling agents, the presence of numerous hindered phenol groups and thioether bonds in the molecular chain of the hindered phenol grafted hyperbranched coupling agent significantly improves the antioxidant performance of NdFeB magnetic powder; the hindered phenol grafted hyperbranched coupling agent also belongs to hyperbranched polymers, with less intermolecular entanglement, which can effectively reduce the viscosity of the composite material and thus improve the fluidity of the composite material, reduce defects such as voids in the composite material after injection, and contribute to the large-scale production of injection permanent magnet composite materials; in addition, when subjected to external forces, the cavities in the molecules of the hindered phenol grafted hyperbranched coupling agent can undergo cavitation, absorb and disperse impact energy, thereby slowing down the propagation of cracks and improving the impact resistance of the composite material;

[0036] Compared with existing antioxidants, the hindered phenol grafted hyperbranched coupling agent connects the hindered phenol structure with antioxidant function to NdFeB magnetic powder through chemical bonds, overcomes the problems of easy migration and precipitation of small molecule antioxidants, and exhibits good antioxidant effects for a long time. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0038] Figure 1 It is a schematic cross-sectional structure diagram of a refrigerant valve provided by an embodiment of the present application;

[0039] Figure 2 It is a schematic cross-sectional structure diagram of a refrigerant valve provided by another embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0041] The first aspect of the present application provides a method for preparing a composite magnetic material, and the preparation method includes the following steps:

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

[0043] Step 2: Mix the PPS resin powder and the lubricant evenly to obtain a binder masterbatch.

[0044] Step 3: Add the binder masterbatch and the surface-treated magnetic powder into the first feeding port and the second feeding port of a twin-screw extruder respectively. The second feeding port is closer to the homogenization section than the first feeding port. Extrude into strips at 285 - 310 °C, cool, and pelletize with a pelletizer to obtain a composite magnetic material.

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

[0046] In some embodiments, the stirring device in Step 1 is a vacuum mixing blender with a rotation speed of 750 rpm and a stirring time of 30 min. 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 stirring, thus achieving the expected mixing effect. If the stirring speed is too low, the magnetic powder may not be completely and evenly 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 embodiments, the drying device in Step 1 is an electrothermal blast drying oven with a drying temperature of 110 ± 5 °C and a drying duration of 5 h. This temperature range setting can ensure that the moisture and absolute ethanol in the magnetic powder can be effectively removed, while avoiding incomplete drying due to too low temperature or damage to the magnetic powder performance due to too high temperature. An overly long drying time may cause aggregation between the magnetic powder particles, which will affect the dispersibility and uniformity of the magnetic powder. On the contrary, if the drying time is set too short, the moisture or solvent in the magnetic powder may not be fully volatilized, resulting in problems such as moisture absorption and caking of the magnetic powder during use. Only by reasonably setting the drying time can the quality and performance of the magnetic powder reach the best state and meet the requirements of practical applications.

[0048] In some embodiments, the screening in Step 1 is through a 40-mesh sieve.

[0049] In some embodiments, the hindered phenol grafted hyperbranched coupling agent is obtained by the thiol-ene click reaction of a hyperbranched coupling agent and 2,6-di-tert-butyl-4-mercaptophenol. The hyperbranched coupling agent is prepared by Michael addition of trimethylolpropane tri(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] Mix the hyperbranched coupling agent, 2,6-di-tert-butyl-4-mercaptophenol, benzoin dimethyl ether, and tetrahydrofuran evenly, react under ultraviolet light for 30 min, and remove tetrahydrofuran 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 embodiments, the power of the ultraviolet lamp is 300 - 600 W, and the wavelength is 365 nm.

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

[0055] Add trimethylolpropane triacrylate and 3-aminopropyltriethoxysilane to tetrahydrofuran, react at 50 °C for 12 h under nitrogen protection, and remove tetrahydrofuran under reduced pressure to obtain the hyperbranched coupling agent.

[0056] In some embodiments, the molar ratio of trimethylolpropane tri(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, magnesium stearate, zinc stearate, and calcium stearate, and preferably calcium stearate.

[0059] In some embodiments, the stirring device in step two is a vacuum mixing blender, the rotation speed is 300 - 50 rpm, and the stirring time is 10 - 20 min.

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

[0061] The fourth aspect of the present application provides a refrigerant valve, which includes a valve body 1, a valve core 2, and a driving part 3. At least a part of the valve core 2 is located inside the valve body 1, and the valve core 2 is connected to the driving part 3;

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

[0063] The driving part 3 can drive the valve core 2 to change from the first state to the second state, and the driving part 3 can drive the valve core 2 to change from the second state to the first state;

[0064] The driving part 3 includes a composite magnetic material.

[0065] The refrigerant valve 10 provided in the third aspect of the present application includes a driving part 3. The driving part 3 includes a composite magnetic material. The composite magnetic material includes surface-treated magnetic powder and a bonding masterbatch. The bonding masterbatch can firmly combine with magnetic particles and can also improve the antioxidant performance of magnetic particles, which is beneficial to reducing the non-magnetic components of the composite magnet and improving the magnetic performance of the composite magnet. Furthermore, it can improve the magnetic performance of the driving part 3 of the refrigerant valve 10.

[0066] In some embodiments, 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 driving part 3 can drive the valve core 2 to change from the first state to the second state, and the driving part 3 can 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 switching valve or a stop valve. In Figure 1 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 in communication with the third chamber 13, or rather, the first chamber 11 and the second chamber 12 are in communication through the third chamber 13, as in the Figure 1 state shown. In the second state, both the first chamber 11 and the second chamber 12 are fluidly isolated from the third chamber 13, thereby realizing the fluid isolation between the first chamber 11 and the second chamber 12.

[0067] In other embodiments, for example Figure 2As shown, the valve body 1 has a first chamber 11, a second chamber 12, and a communication port. The communication 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 communication port is the first flow area; in the fourth state, the flow area of the communication port is the second flow area, and the second flow area is larger than the first flow area. The driving part 3 can drive the valve core 2 to change from the third state to the fourth state, and the driving part 3 can drive the valve core 2 to change from the fourth state to the third state. That is, the refrigerant valve 10 serves as a throttle valve.

[0068] In some embodiments of the present application, the refrigerant valve 10 is a globe valve or a throttle valve (for example, an electronic expansion valve). The valve core is spherical, and the refrigerant valve 10 is a ball valve; or, the valve core is needle-shaped, and the refrigerant valve 10 is a needle valve.

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

[0070] The technical solutions of the present application will be described below through specific examples and comparative examples.

[0071] Some of the raw materials used in the present application are sourced as follows:

[0072] NdFeB magnetic powder, model XQP15-10 rapidly quenched alloy magnetic powder, purchased from Shenyang New Oak Magnetic Materials Co., Ltd.;

[0073] PPS resin powder, model P-4, manufactured by Phillips in the United States.

[0074] Example 1

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

[0076] Dissolve 0.5 kg of a hindered phenol-grafted hyperbranched coupling agent in 100 L of absolute ethanol to obtain a modification solution. Add the modification solution and 100 kg of NdFeB magnetic powder to a vacuum mixing blender, with a rotation speed of 750 rpm and a stirring time of 30 min. Then place it in an electrothermal blast drying oven for drying, with a drying temperature of 105 °C and a drying duration of 5 h. Crush and pass through a 40-mesh sieve to obtain the surface-treated magnetic powder.

[0077] The specific preparation steps of the hindered phenol-grafted hyperbranched coupling agent are as follows:

[0078] 6.0 kg of hyperbranched coupling agent, 2.4 kg of 2,6 - di - tert - butyl - 4 - mercapto - phenol, benzoin dimethyl ether and 80 L of tetrahydrofuran were added to a reaction kettle, 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 an ultraviolet lamp (power 300 W, wavelength 365 nm) for 30 min, and then tetrahydrofuran was removed under reduced pressure to obtain the hindered phenol - grafted hyperbranched coupling agent.

[0079] The hyperbranched coupling agent was prepared through the following steps:

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

[0081] Example 2

[0082] A surface - treated magnetic powder was prepared through the following steps:

[0083] 2 kg of the hindered phenol - grafted hyperbranched coupling agent was dissolved in 100 L of absolute ethanol to obtain a modifier solution. The modifier solution and 100 kg of NdFeB magnetic powder were added to a vacuum mixing blender, stirred at 750 rpm for 30 min, then placed in an electro - thermal blast drying oven for drying. The drying temperature was 115 °C and the drying duration was 5 h. After crushing and passing through a 40 - mesh sieve, the surface - treated magnetic powder was obtained.

[0084] The specific preparation steps of the hindered phenol - grafted hyperbranched coupling agent are as follows:

[0085] 6.2 kg of hyperbranched coupling agent, 2.4 kg of 2,6 - di - tert - butyl - 4 - mercapto - phenol, benzoin dimethyl ether and 80 L of tetrahydrofuran were added to a reaction kettle, 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 an ultraviolet lamp (power 600 W, wavelength 365 nm) for 30 min, and then tetrahydrofuran was removed under reduced pressure to obtain the hindered phenol - grafted hyperbranched coupling agent.

[0086] The hyperbranched coupling agent was prepared through the following steps:

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

[0088] Comparative Example 1

[0089] A surface - treated magnetic powder was prepared through the following steps:

[0090] Dissolve 0.5 kg of hyperbranched coupling agent in 100 L of absolute ethanol to obtain a modification solution. Add the modification solution and 100 kg of NdFeB magnetic powder to a vacuum mixing blender, with a rotation speed of 750 rpm and a stirring time of 30 min. Then place it in an electrothermal blast drying oven for drying, with a drying temperature of 105 °C and a drying duration of 5 h. Crush and pass through a 40-mesh sieve to obtain surface-treated magnetic powder. The preparation process of the hyperbranched coupling agent is the same as that in Example 1.

[0091] Comparative Example 2

[0092] On the basis of Comparative Example 1, replace the hyperbranched coupling agent in Comparative Example 1 with an equal mass of coupling agent KH-550.

[0093] Comparative Example 3

[0094] On the basis of Comparative Example 1, replace the hyperbranched coupling agent in Comparative Example 1 with an equal mass of coupling agent KH-560.

[0095] Place the surface-treated magnetic powder and NdFeB magnetic powder obtained in Examples 1-2 and Comparative Examples 1-3 respectively in a box-type atmosphere furnace for an oxidation weight gain test at 300 °C in an air atmosphere. Weigh them with a thermogravimetric analyzer every 30 min and calculate their oxidation weight gain rates. The test results are shown in Table 1:

[0096] Table 1

[0097]

[0098]

[0099] It can be seen from the data recorded in Table 1 that compared with the surface-treated magnetic powder prepared in Comparative Example 1, Comparative Example 2, and Comparative Example 3, the surface-treated magnetic powder obtained in Example 1 and Example 2 has higher antioxidant performance.

[0100] Example 3

[0101] A preparation method of a composite magnetic material, comprising the following steps:

[0102] Add 7.5 kg of PPS resin powder and 0.2 kg of calcium stearate to a vacuum mixing blender, and stir at 300 rpm for 10 min to obtain a bonding masterbatch;

[0103] Add the bonding masterbatch and 100 kg of the surface-treated magnetic powder of Example 1 to the first feeding port and the second feeding port of the twin-screw extruder respectively. The second feeding port is closer to the homogenization section than the first feeding port. The temperatures of each section of the extruder are as follows: Zone 1: 285 °C, Zone 2: 295 °C, Zone 3: 310 °C, Zone 4: 310 °C, Zone 5: 305 °C, and the head temperature is 300 °C. After cooling, granulate through a pelletizer to obtain the composite magnetic material.

[0104] Example 4

[0105] A method for preparing a composite magnetic material, comprising the following steps:

[0106] Add 7.5 kg of PPS resin powder and 0.2 kg of magnesium stearate to a vacuum mixing and stirring machine, stir at a speed of 40 rpm for 15 min to obtain the bonding masterbatch;

[0107] Add the bonding masterbatch and 100 kg of the surface-treated magnetic powder of Example 2 to the first feeding port and the second feeding port of the twin-screw extruder respectively. The second feeding port is closer to the homogenization section than the first feeding port. The temperatures of each section of the extruder are as follows: Zone 1: 285 °C, Zone 2: 295 °C, Zone 3: 310 °C, Zone 4: 310 °C, Zone 5: 305 °C, and the head temperature is 300 °C. After cooling, granulate through a pelletizer to obtain the composite magnetic material.

[0108] Example 5

[0109] A method for preparing a composite magnetic material, comprising the following steps:

[0110] Add 7.5 kg of PPS resin powder and 0.2 kg of paraffin to a vacuum mixing and stirring machine, stir at a speed of 50 rpm for 20 min to obtain the bonding masterbatch;

[0111] Add the bonding masterbatch and 100 kg of the surface-treated magnetic powder of Example 2 to the first feeding port and the second feeding port of the twin-screw extruder respectively. The second feeding port is closer to the homogenization section than the first feeding port. The temperatures of each section of the extruder are as follows: Zone 1: 285 °C, Zone 2: 295 °C, Zone 3: 310 °C, Zone 4: 310 °C, Zone 5: 305 °C, and the head temperature is 300 °C. After cooling, granulate through a pelletizer to obtain the composite magnetic material.

[0112] Comparative Example 4

[0113] A method for preparing a composite magnetic material. On the basis of Example 3, replace the surface-treated magnetic powder in Example 3 with the product prepared in Comparative Example 1, and the other raw materials and preparation methods are the same as those in Example 3.

[0114] Comparative Example 5

[0115] Preparation method of composite magnetic material. On the basis of Example 3, replace the surface-treated magnetic powder in Example 3 with the product prepared in Comparative Example 2, and the other raw materials and preparation method are the same as those in Example 3.

[0116] Comparative Example 6

[0117] Preparation method of composite magnetic material. On the basis of Example 3, replace the surface-treated magnetic powder in Example 3 with the product prepared in Comparative Example 3, and the other raw materials and preparation method are the same as those in Example 3.

[0118] Comparative Example 7

[0119] Preparation method of composite magnetic material. On the basis of Example 3, replace the sentence "Add the binder masterbatch and 100 kg of the surface-treated magnetic powder of Example 2 into the first feeding port and the second feeding port of the twin-screw extruder respectively, and the second feeding port is closer to the homogenization section than the first feeding port" in Example 3 with "Add the binder masterbatch and 100 kg of the surface-treated magnetic powder of Example 2 into the first feeding port of the twin-screw extruder together", and the other raw materials and preparation method are the same as those in Example 3.

[0120] Test Example

[0121] (1) Use an XNR-400C type melt flow rate instrument. The test conditions are 310 °C and 10 kg pressure. According to the test standard ASTM D 1238, measure the melt index of each group of composite magnetic materials, characterized by MFR, with the unit of g / min. MFR = m / t × 600, where: m is the extrusion mass (g) of the composite magnetic material within a certain time; t is the time (s);

[0122] (2) Inject each group of composite magnetic materials into a magnetic field through a fully automatic injection molding machine. The injection temperature is 310 °C and the holding pressure is 45 MPa. Use a pendulum impact (cantilever beam experiment) to measure the impact strength performance. The impact performance is tested according to the GB / T 1843-1993 standard. The experimental results are the average values of 5 specimens. The impact strength of the specimen in the cantilever beam experiment is represented by A (kJ / m 2 )), then A = (E - EO) / (b × d) × 1000, where E is the impact energy absorbed by the specimen (J), EO is the empty pendulum absorption work (J), b is the width of the specimen (mm), and d is the thickness of the specimen (mm);

[0123] (3) Inject each group of composite magnetic materials into a magnetic field through a fully automatic injection molding machine to obtain a cylindrical bonded NdFeB magnet with Ф10mm x 10mm. Use a permanent magnet measuring instrument AMT-4 to measure the magnetic properties, such as remanence (Br) (kGs), coercivity (Hcb) (Koe), intrinsic coercivity (Hcj) (Koe), and maximum magnetic energy product (BH)max (MGoe);

[0124] The results are shown in Table 2 as follows:

[0125] Table 2

[0126] Item 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 can be seen from Table 2, compared with ratios 4-7, the composite magnetic materials obtained by implementations 3-5 have better comprehensive properties. It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device.

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

Claims

1. Preparation method of composite magnetic material, characterized in that, It includes the following steps: Step 1: Dissolve the hindered phenol grafted hyperbranched coupling agent in absolute ethanol to obtain a modification solution. Stir the modification solution and NdFeB magnetic powder evenly, dry, crush and screen to obtain surface-treated magnetic powder; Step 2: Mix the PPS resin powder and the lubricant evenly to obtain a bonding masterbatch; Step 3: Add the bonding masterbatch and the surface-treated magnetic powder to the first feeding port and the second feeding port of the twin-screw extruder respectively. The second feeding port is closer to the homogenization section than the first feeding port. Extrude into strips at 285-310 °C, cool and granulate with a granulator to obtain a composite magnetic material.

2. The preparation method of the composite magnetic material according to claim 1, characterized in that In Step 1, the dosage of the hindered phenol grafted hyperbranched coupling agent is 0.5-2% of the mass of the NdFeB magnetic powder, and the dosage ratio of absolute ethanol to NdFeB magnetic powder is 1 mL: 1 g.

3. The preparation method of the composite magnetic material according to claim 1, wherein In Step 1, the stirring equipment is a vacuum mixing blender with a rotation speed of 750 rpm and a stirring time of 30 min. The drying equipment is an electrothermal blast drying oven with a drying temperature of 110±5 °C and a drying duration of 5 h.

4. The preparation method of the composite magnetic material according to claim 1, characterized in that, The specific preparation steps of the hindered phenol grafted hyperbranched coupling agent are as follows: Mix the hyperbranched coupling agent, 2,6-di-tert-butyl-4-mercaptophenol, benzoin dimethyl ether and tetrahydrofuran evenly, react under ultraviolet light for 30 min, and remove tetrahydrofuran under reduced pressure to obtain the hindered phenol grafted hyperbranched coupling agent.

5. The preparation method of the composite magnetic material according to claim 4, characterized in that, 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 dosage of benzoin dimethyl ether is 2% of the mass of the hyperbranched coupling agent.

6. The preparation method of the composite magnetic material according to claim 4, wherein, The hyperbranched coupling agent is prepared through the following steps: Add trimethylolpropane triacrylate and 3-aminopropyltriethoxysilane to tetrahydrofuran, react at 50 °C for 12 h under nitrogen protection, and remove tetrahydrofuran under reduced pressure to obtain the hyperbranched coupling agent.

7. The preparation method of the composite magnetic material according to claim 6, wherein The molar ratio of trimethylolpropane tris(3-mercaptopropionate) to 3-aminopropyltriethoxysilane is 1:

1.

8. Composite magnetic material, characterized in that, Prepared by the preparation method according to any one of claims 1-7.

9. A refrigerant valve, characterized in that, It includes a valve body (1), a valve core (2) and a driving part (3), the valve core (2) is at least partially located within the valve body (1), and the valve core (2) is connected to the driving part (3); The valve body (1) has a first chamber (11) and a second chamber (12), the valve core (2) has a first state and a second state. In the first state, the flow-through area between the first chamber (11) and the second chamber (12) is a first flow-through area, and the first flow-through area is greater than or equal to 0; in the second state, the flow-through area between the first chamber (11) and the second chamber (12) is a second flow-through area, and the second flow-through area is greater than the first flow-through area; The driving part (3) can drive the valve core (2) to change from the first state to the second state, and the driving part (3) can drive the valve core (2) to change from the second state to the first state; The driving part (3) includes a composite magnetic material.

10. An electric motor, comprising a rotor, characterized in that, The rotor includes a composite magnetic material.

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