Preparation method of composite flexible rare earth magnetic strip

Abstract

The application discloses a preparation method of a composite flexible rare earth magnetic strip and belongs to the technical field of flexible rare earth permanent magnet material preparation. The method comprises the following steps: after the surface of rare earth permanent magnet powder with magnetic crystal anisotropy is activated, the activated rare earth permanent magnet powder is mixed with a flexible bonding system to obtain a flexible magnetic material; the flexible magnetic material is preformed into a continuous magnetic strip blank, and an orientation magnetic field and calendering or extrusion setting are synchronously applied when the blank is in an orientation viscosity window, so that the easy magnetization axis of the rare earth permanent magnet powder is arranged along a predetermined direction; then the blank is cooled and locked in the state of the orientation magnetic field, and finally, the composite flexible rare earth magnetic strip is obtained through heat setting and magnetization. The application can generate an anisotropic orientation structure in situ during the preparation process, and the magnetic attraction force, flexibility and orientation stability of the magnetic strip are improved.

Description

Technical Field

[0001] This invention relates to the field of flexible rare earth permanent magnet material preparation technology, specifically a method for preparing composite flexible rare earth magnetic strips. Background Technology

[0002] Flexible magnetic strips are a type of magnetic functional material that can be used in bent, coiled, or attached states. They are widely used in door seals, adsorption positioning, flexible sensing, electronic device fixing, automotive interior fixing, and industrial flexible connections. Traditional flexible magnetic strips are mostly made by combining ferrite magnetic powder with rubber or thermoplastic elastomers, which has the advantages of low cost and easy processing. However, their remanence and magnetic energy product are relatively low, making it difficult to meet the requirements of thin-film, high-adsorption-force, or small-size assembly scenarios.

[0003] Rare earth permanent magnet materials, especially neodymium iron boron, samarium iron nitrogen, and samarium cobalt, possess high magnetic properties. Combining rare earth permanent magnet powder with a flexible polymer matrix can produce flexible rare earth magnetic strips with magnetic properties superior to ordinary ferrite rubber magnetic strips. However, the high density and strong surface activity of rare earth magnetic powder, especially in a highly filled state, significantly increase the viscosity of the system, making the magnetic strips prone to processing difficulties, reduced flexibility, bending cracks, and magnetic powder shedding.

[0004] Furthermore, for rare-earth permanent magnet powders with magnetocrystalline anisotropy, if the easily magnetized axes are not effectively oriented during the preparation process, even with subsequent magnetization, only flexible magnetic strips with low orientation can be obtained, and their magnetic properties cannot be fully utilized. Some existing processes only perform magnetization after the magnetic strips are formed, but magnetization itself cannot change the spatial orientation of the magnetic powder particles in the matrix; other processes introduce a magnetic field but do not systematically control the softening viscosity of the flexible magnetic material, the rotational resistance of the magnetic powder interface, and the temporal relationship between magnetic field orientation and forming, resulting in insufficient rotatability of the magnetic powder in the matrix, or relaxation and rotation after orientation before cooling and setting.

[0005] Therefore, there is an urgent need to develop a method for preparing composite flexible rare earth magnetic strips, so that rare earth permanent magnet powder can be oriented in situ during the preparation of the magnetic strip and be stably locked in the molding stage, thereby taking into account high magnetic performance, flexibility and long-term orientation stability. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing composite flexible rare earth magnetic strips, which can align the easy magnetization axis of rare earth permanent magnet powder along a predetermined direction during the preparation process, thereby generating an anisotropic orientation structure in situ, and maintaining the stability of the orientation structure through cooling locking and heat setting, so as to solve the problems of insufficient orientation degree, insufficient magnetic performance, and difficulty in balancing flexibility and high filling amount in existing flexible rare earth magnetic strips.

[0007] A method for preparing a composite flexible rare earth magnetic strip includes the following steps: Modified rare earth magnetic powder is obtained by drying and surface activation of rare earth permanent magnet powder with magnetocrystalline anisotropy. Modified rare earth magnetic powder and flexible binder system are mixed in a low oxygen environment to obtain a partially shaped flexible magnetic material. The flexible magnetic material is pre-formed into a continuous magnetic strip blank; The continuous magnetic strip blank is heated until the flexible bonding system is in a softened and flowing state, so that the continuous magnetic strip blank enters the orientation viscosity window; When the continuous magnetic strip blank is in the orientation viscosity window, an orientation magnetic field is applied to the continuous magnetic strip blank, and calendering or extrusion shaping is performed simultaneously to make the easy magnetization axis of the rare earth permanent magnet powder align along a predetermined direction, thereby generating an anisotropic orientation structure inside the continuous magnetic strip blank. The continuous magnetic strip blank after forming an anisotropic orientation structure is subjected to cooling, locking and heat setting treatment. The continuous magnetic strip blank after heat setting is magnetized to obtain a composite flexible rare earth magnetic strip.

[0008] As a further aspect of the present invention, the rare earth permanent magnet powder is selected from one or more of HDDR neodymium iron boron magnetic powder, anisotropic fast-quenching neodymium iron boron magnetic powder, samarium iron nitrogen magnetic powder, and samarium cobalt magnetic powder. These magnetic powders themselves possess magnetocrystalline anisotropy and can undergo easy magnetization axis directional alignment under the action of an applied orientation magnetic field, making them suitable for preparing anisotropic flexible rare earth magnetic strips.

[0009] As a further aspect of the present invention, the particle size of the rare earth permanent magnet powder is 1μm to 100μm. By controlling the particle size range within the above range, the problems of difficulty in rotation during the orientation process and rough surface after molding caused by excessively large magnetic powder particles can be avoided, while also taking into account the magnetic powder filling density, dispersion uniformity, and magnetic performance output. Specifically, when the rare earth permanent magnet powder is samarium iron nitrogen magnetic powder, its particle size can be 1μm to 40μm, and more specifically, 1μm to 20μm; when the rare earth permanent magnet powder is HDDR neodymium iron boron magnetic powder, its particle size can be 20μm to 100μm, and more specifically, 40μm to 100μm; when the rare earth permanent magnet powder is samarium cobalt magnetic powder or anisotropic fast-quenched neodymium iron boron magnetic powder, its particle size can be selected within the range of 1μm to 100μm according to the material morphology and molding requirements.

[0010] As a further aspect of the present invention, the rare earth permanent magnet powder undergoes a multi-stage surface activation treatment, which includes passivation treatment, coupling treatment, and lubrication and compatibility treatment. Passivation treatment reduces the oxidation activity of the rare earth magnetic powder surface, coupling treatment improves the interfacial bonding between the magnetic powder and the flexible bonding system, and lubrication and compatibility treatment reduces the rotational resistance of the magnetic powder in the softened matrix, making it easier for the magnetic powder to undergo directional rotation in the orientation magnetic field.

[0011] As a further embodiment of the present invention, the passivation treatment uses one or more of phosphate, phytate or silicate; the coupling treatment uses one or more of silane coupling agent, titanate coupling agent or aluminate coupling agent; and the lubrication compatibility treatment uses one or more of stearate, polyethylene wax, maleic anhydride grafted elastomer or isocyanate-terminated polyurethane prepolymer.

[0012] As a further aspect of the present invention, the orientation viscosity window is such that the apparent viscosity of the flexible magnetic material is within a certain range. The apparent viscosity is below a certain range, resulting in insufficient dimensional stability of the magnetic strip blank, making it prone to collapse or deformation during casting. Conversely, when the apparent viscosity is above this range, the rare earth magnetic powder is difficult to rotate within the matrix, reducing orientation efficiency. By controlling the orientation viscosity window, the magnetic powder can have sufficient rotational freedom while maintaining the continuous forming stability of the magnetic strip blank.

[0013] As a further aspect of the present invention, the orientation magnetic field is performed simultaneously with calendering or extrusion shaping. The orientation magnetic field provides the orientation direction for the easy magnetization axis of the rare earth magnetic powder, and the shearing action generated during the calendering or extrusion process assists in the rearrangement of the magnetic powder particles, thereby improving the orientation degree and the uniformity of magnetic powder packing.

[0014] As a further aspect of the present invention, the continuous magnetic strip blank is cooled and locked while maintaining the orientation magnetic field, so that when the flexible bonding system changes from a softened and flowing state to a fixed state, the rare earth magnetic powder is still constrained by the orientation magnetic field, thus preventing the magnetic powder from rotating or loosening its orientation before being removed from the field.

[0015] As a further aspect of the present invention, the continuous magnetic strip blank includes a magnetic core layer and a flexible protective layer covering the outside of the magnetic core layer. The magnetic core layer is used to provide the main magnetic properties, and the flexible protective layer is used to improve bending resistance, wear resistance and moisture resistance, so that the magnetic strip still has good flexibility and stability in use even in a high magnetic powder filling state.

[0016] Compared with the prior art, the beneficial effects of the present invention are: I. This invention does not obtain magnetism solely through subsequent magnetization, but rather through the orientation of rare earth permanent magnet powder with magnetocrystalline anisotropy during the preparation process, thereby generating an anisotropic orientation structure in situ inside the magnetic strip, which can more fully utilize the magnetic properties of rare earth permanent magnet powder.

[0017] Second, this invention controls the particle size of rare earth permanent magnet powder to 1μm to 100μm, and sets a more suitable particle size selection range for small-particle rare earth magnetic powders such as samarium iron nitrogen magnetic powder, which is beneficial to improving the dispersibility and orientation response of magnetic powder in flexible bonding systems.

[0018] Third, this invention avoids using magnetic powder with excessively large particle size, which can reduce the rotational resistance of large magnetic powder particles during the magnetic field orientation process, improve the surface smoothness of the magnetic strip after forming, and reduce the risk of rough surface, exposed particles, or local stress concentration of the magnetic strip.

[0019] Fourth, this invention controls the orientation viscosity window, enabling the flexible magnetic material to have both the rotatability of magnetic powder and the shape stability of magnetic strips during the orientation stage, avoiding insufficient orientation due to an overly rigid system or deformation of the magnetic strip blank due to an overly soft system.

[0020] V. This invention reduces the interfacial frictional resistance of rare earth magnetic powder in a flexible matrix through surface activation treatment, improves the response capability of magnetic powder in an orientation magnetic field, and enhances the bonding strength between magnetic powder and matrix, thereby reducing the risk of magnetic powder shedding and bending cracking.

[0021] VI. This invention synchronizes the orientation magnetic field with calendering or extrusion molding, and utilizes the magnetic force and molding shear to promote the alignment of the easily magnetized axes of the magnetic powder, thereby improving the orientation uniformity of the magnetic strip.

[0022] VII. The present invention performs cooling and locking while maintaining the orientation magnetic field, and stabilizes the orientation structure through subsequent heat setting, which can reduce the probability of orientation relaxation, warping or delamination during winding, attachment and long-term use.

[0023] Other features and advantages of the present invention will be disclosed in detail in the following detailed description and accompanying drawings. Attached Figure Description

[0024] Figure 1 This is a schematic flowchart of the preparation method in an embodiment of the present invention. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] In this embodiment of the invention, a method for preparing a composite flexible rare earth magnetic strip is described below. Figure 1 As shown, the process mainly includes steps such as surface activation treatment of rare earth permanent magnet powder, low-oxygen mixing, preforming, orientation viscosity window control, magnetic field-assisted orientation and shaping, cooling and locking, heat shaping, and magnetization. It should be noted that the anisotropy described in this invention does not simply refer to the subsequent magnetization direction, but rather to the fact that the easy magnetization axes of the rare earth permanent magnet powder within the flexible matrix are already aligned along a predetermined direction.

[0027] In this embodiment, the rare earth permanent magnet powder is a rare earth magnetic powder with magnetic anisotropy. The rare earth magnetic powder can be one or more of HDDR neodymium iron boron magnetic powder, anisotropic fast-quenching neodymium iron boron magnetic powder, samarium iron nitrogen magnetic powder, and samarium cobalt magnetic powder. The particle size of the rare earth permanent magnet powder is 1 μm to 100 μm. By selecting magnetic powder within the above particle size range, the magnetic powder can have better dispersibility and rotational response in the flexible bonding system, and the surface roughness and orientation difficulties caused by large magnetic powder particles can be reduced.

[0028] In this embodiment, the particle size of HDDR NdFeB magnetic powder can be 20μm to 100μm, and more specifically 40μm to 100μm. HDDR NdFeB magnetic powder has high magnetic properties and magnetocrystalline anisotropy, and can undergo easy magnetization axis orientation alignment under the action of an applied orientation magnetic field. For cases where it is necessary to further improve the magnetic powder packing density and the surface flatness of the magnetic strip, HDDR NdFeB magnetic powder can also be compounded with samarium iron nitrogen magnetic powder with a particle size of 1μm to 40μm at a mass ratio of 7:3 to 9:1, so that the small-particle-size samarium iron nitrogen magnetic powder fills the spaces between the larger-particle-size NdFeB magnetic powder, thereby improving the uniformity of magnetic powder filling and the consistency of orientation.

[0029] In this embodiment, the particle size of the samarium iron nitrogen magnetic powder can be 1 μm to 40 μm, and more specifically 1 μm to 20 μm. Since samarium iron nitrogen magnetic powder can usually be prepared into small particle size magnetic powder, it has good dispersibility and surface smoothness advantages in flexible bonding systems, making it suitable for preparing thin composite flexible rare earth magnetic strips with high flexibility or high surface quality requirements.

[0030] In this embodiment, the rare earth permanent magnet powder is first placed in a vacuum drying oven and dried at 70℃~90℃ for 2h~4h to remove the moisture adsorbed on the surface of the magnetic powder. Then, the dried rare earth permanent magnet powder is added to a treatment solution containing phosphate or phytate for passivation treatment, so that an antioxidant passivation layer is formed on the surface of the magnetic powder. Then, a silane coupling agent is added for coupling treatment, so that an interfacial bonding layer capable of bonding with a flexible adhesive system is formed on the surface of the magnetic powder. Finally, zinc stearate, polyethylene wax or maleic anhydride-grafted SEBS is added for lubrication and compatibility treatment to reduce the rotational resistance of the magnetic powder in the softened matrix.

[0031] In this embodiment, the flexible bonding system includes TPU, SEBS, hydrogenated nitrile butadiene rubber, plasticizer, lubricant, antioxidant, and crosslinking agent. TPU and SEBS form a heat-processable elastic network, hydrogenated nitrile butadiene rubber improves oil resistance and aging resistance, and the crosslinking agent further stabilizes the system during subsequent heat setting. The flexible bonding system should be selected to allow it to soften and flow at 80°C to 130°C and recover a stable elastic state upon cooling.

[0032] In this embodiment, the flexible bonding system is pre-plasticized in a mixer for 3-8 minutes, then modified rare earth magnetic powder is added in two batches, and low-oxygen mixing is carried out under nitrogen protection. The mixing temperature is controlled at 70℃-120℃, preferably 85℃-105℃; the mixing time is 10-25 minutes; and the oxygen content in the mixing environment is not higher than 5%. The mass fraction of modified rare earth magnetic powder in the flexible magnetic material is 85wt%-96wt%, preferably 90wt%-94wt%. By adding powder in stages and mixing under low oxygen conditions, the agglomeration and oxidation of magnetic powder can be reduced, and the uniformity of the magnetic material can be improved.

[0033] In this embodiment, the mixed flexible magnetic material is preformed into a continuous magnetic strip blank using an extruder or calender. The continuous magnetic strip blank can be in sheet, strip, or bar shape, with a thickness of 0.5 mm to 5 mm and a width of 3 mm to 50 mm. The preforming stage is mainly used to form a continuous and stable blank shape, and does not require the magnetic powder to have reached its final orientation state.

[0034] In this embodiment, a continuous magnetic strip blank is fed into an orientation forming zone, which is sequentially arranged along the material conveying direction as a heating section, an orientation magnetic field section, a calendering and thickness fixing section, and a cooling and locking section. The heating section heats the continuous magnetic strip blank to 80℃~130℃, causing the flexible bonding system to enter a softened and flowing state, and setting the apparent viscosity of the flexible magnetic material to a certain level. Within the orientation viscosity window.

[0035] In this embodiment, when the continuous magnetic strip blank is within the orientation viscosity window, an orientation magnetic field of 0.5T to 3.0T is applied to it. The orientation magnetic field direction can be the thickness direction, width direction, or length direction of the magnetic strip. For magnetic strips that require frontal adsorption, it is preferable to make the orientation magnetic field direction perpendicular to the width and thickness plane of the magnetic strip, so that the easy magnetization axis of the rare earth permanent magnet powder is arranged along the thickness direction of the magnetic strip; for magnetic strips that require lateral adsorption or embedded adsorption, the orientation magnetic field direction can also be set along the width direction of the magnetic strip.

[0036] In this embodiment, while applying an orientation magnetic field, the continuous magnetic strip blank is rolled 2 to 5 times, with a reduction rate of 10% to 35% per pass. The orientation magnetic field causes the rare earth permanent magnet powder to align along the magnetic field direction due to the magnetic field torque. The shearing and thickness-fixing effects generated by rolling reduce local stacking resistance and promote the rearrangement of magnetic powder particles. Through the synergistic effect of magnetic field orientation and rolling shearing, the uniformity of magnetic powder orientation can be improved, and the fluctuation of magnetic properties caused by local agglomeration can be reduced.

[0037] In this embodiment, after the continuous magnetic strip blank has completed orientation and calendering, it remains within the orientation magnetic field as it enters the cooling and locking section. The cooling and locking section cools the continuous magnetic strip blank to below 40°C using cooling rollers, cold air, or cooling plates, causing the flexible bonding system to change from a softened, flowing state to a shaped state. Because the orientation magnetic field is not removed during the cooling process, the rare earth permanent magnet powder remains under orientation constraint before the matrix solidifies or sets, thereby reducing orientation relaxation and powder rotation.

[0038] In this embodiment, the continuous magnetic strip blank after cooling and locking is subjected to heat setting. The heat setting temperature is 90℃~150℃, and the holding time is 3min~30min. For systems containing rubber phase and crosslinking agent, heat setting can further crosslink the system; for thermoplastic elastomer systems, heat setting can release calendering stress and improve dimensional stability. Slow cooling after heat setting further releases the internal stress of the magnetic strip, reducing the probability of warping and edge cracking during subsequent winding.

[0039] In this embodiment, the continuous magnetic strip blank can be further configured as a composite layer structure. Specifically, the composite layer structure includes a magnetic core layer and a flexible protective layer covering the outside of the magnetic core layer. The magnetic core layer contains 85wt% to 96wt% modified rare earth magnetic powder to provide the main magnetic properties; the flexible protective layer can be made of TPU, SEBS, polyurethane elastomer, or their composite materials to improve the wear resistance, bending resistance, and moisture resistance of the magnetic strip surface. The flexible protective layer can be bonded to the magnetic core layer by co-extrusion, lamination calendering, or hot-pressing.

[0040] In this embodiment, the heat-set continuous magnetic strip blank is magnetized. The magnetization direction is consistent with the orientation direction of the easy magnetization axis of the rare earth permanent magnet powder, and the magnetization method can be unipolar magnetization, bipolar magnetization, or multipolar magnetization. Since the easy magnetization axis of the magnetic powder has already been aligned along a predetermined direction during the preparation process, subsequent magnetization can make fuller use of the magnetocrystalline anisotropy of the rare earth magnetic powder, thereby improving the surface magnetic induction intensity and magnetic adsorption force of the composite flexible rare earth magnetic strip.

[0041] Example 1: A magnetic core material was prepared by taking 92 parts of HDDR NdFeB magnetic powder with a particle size of 40μm to 100μm, 4 parts of TPU, 2 parts of SEBS, 1 part of hydrogenated nitrile rubber, and 1 part of additives. The magnetic powder was passivated with phosphate, coupled with silane, and lubricated with polyethylene wax, and then mixed under nitrogen protection. The mixture was preformed into a continuous magnetic strip blank with a thickness of 1.5mm, entered the orientation viscosity window at 110℃, and underwent three-pass calendering in a 2.0T thickness-direction orientation magnetic field. It was then cooled to 35℃ while maintaining the magnetic field, followed by heat setting at 120℃ for 10 minutes and magnetization in the thickness direction to obtain a highly adsorption-type composite flexible rare earth magnetic strip.

[0042] Example 2: A magnetic core material was prepared by taking 75 parts of HDDR NdFeB magnetic powder with a particle size of 40μm to 100μm, 15 parts of Samarium Iron Nitrogen magnetic powder with a particle size of 1μm to 40μm, 5 parts of TPU, 3 parts of SEBS, and 2 parts of additives. A flexible TPU / SEBS protective layer was then laminated onto the upper and lower surfaces of the magnetic core. In this example, the Samarium Iron Nitrogen magnetic powder, as a small-particle-size rare earth magnetic powder, fills the spaces between the HDDR NdFeB magnetic powder, which helps to improve the uniformity of magnetic powder packing, improve the surface smoothness of the magnetic strip, and enhance the overall response of the magnetic powder in the orientation magnetic field. The protective layer mainly provides bending resistance and moisture protection, while the magnetic core mainly provides magnetic output. After forming the composite preform through co-extrusion, it is simultaneously calendered and shaped in a 1.5T thickness-direction orientation magnetic field to obtain a composite flexible rare earth magnetic strip that combines flexibility and high magnetic adsorption force.

[0043] Example 3: A heat-resistant magnetic material was prepared by taking 88 parts of samarium iron nitrogen magnetic powder with a particle size of 1μm to 20μm, 6 parts of TPEE, 4 parts of chlorinated polyethylene rubber, and 2 parts of additives. The magnetic material was heated to about 120°C to enter the orientation viscosity window, and then extruded and shaped under a 1.0T orientation magnetic field in the width direction. Subsequently, it was cooled and locked while maintaining the orientation magnetic field to obtain a composite flexible rare earth magnetic strip suitable for lateral adsorption or embedding fixation. Because this example uses small-particle-size samarium iron nitrogen magnetic powder, it can improve the surface smoothness and bending stability of the magnetic strip while ensuring magnetic performance.

[0044] It is understood that the type of rare earth magnetic powder, particle size range, flexible bonding system, magnetic field direction, magnetic field strength, rolling passes, and magnetization method in the above embodiments can be adjusted according to specific application scenarios. As long as it uses rare earth permanent magnet powder with magnetocrystalline anisotropy and a particle size of 1μm to 100μm, and when the flexible magnetic material is in the orientation viscosity window, the technical concept of aligning the easy magnetization axis of the rare earth permanent magnet powder along a predetermined direction and locking it by cooling through the combination of orientation magnetic field and molding is applied, it should fall within the protection scope of this invention.

[0045] This invention provides a method for preparing composite flexible rare earth magnetic strips, which can generate anisotropic orientation structures in situ during the magnetic strip preparation process, has high reliability, and is suitable for continuous production.

[0046] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0047] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a composite flexible rare earth magnetic strip, characterized in that, Includes the following steps: S1. The rare earth permanent magnet powder with magnetocrystalline anisotropy is dried and surface activated to obtain modified rare earth magnetic powder. S2. The modified rare earth magnetic powder and the flexible bonding system are mixed in a low oxygen environment to obtain an incompletely shaped flexible magnetic material. S3. Pre-form the flexible magnetic material into a continuous magnetic strip blank; S4. Heat the continuous magnetic strip blank until the flexible bonding system is in a softened and flowing state, so that the continuous magnetic strip blank enters the orientation viscosity window; S5. When the continuous magnetic strip blank is in the orientation viscosity window, an orientation magnetic field is applied to the continuous magnetic strip blank, and calendering or extrusion is performed simultaneously to make the easy magnetization axis of the rare earth permanent magnet powder align along a predetermined direction, thereby generating an anisotropic orientation structure inside the continuous magnetic strip blank. S6. Cooling, locking and heat-setting treatment are performed on the continuous magnetic strip blank after the anisotropic orientation structure is formed. S7. Magnetize the continuous magnetic strip blank after heat setting to obtain a composite flexible rare earth magnetic strip.

2. The method for preparing a composite flexible rare earth magnetic strip according to claim 1, characterized in that, The rare earth permanent magnet powder is one or more of HDDR neodymium iron boron magnetic powder, anisotropic fast-quenched neodymium iron boron magnetic powder, samarium iron nitrogen magnetic powder, and samarium cobalt magnetic powder, and the particle size of the rare earth permanent magnet powder is 1μm to 100μm.

3. The method for preparing a composite flexible rare earth magnetic strip according to claim 1, characterized in that, The surface activation treatment includes passivation, coupling, and lubrication compatibility treatment performed sequentially; the passivation treatment is used to form an anti-oxidation passivation layer on the surface of the rare earth permanent magnet powder, the coupling treatment is used to form an interface connection layer that is bonded to the flexible bonding system, and the lubrication compatibility treatment is used to reduce the rotational resistance of the rare earth permanent magnet powder in the flexible bonding system.

4. The method for preparing a composite flexible rare earth magnetic strip according to claim 3, characterized in that, The passivation treatment uses one or more of phosphates, phytates, or silicates; the coupling treatment uses one or more of silane coupling agents, titanate coupling agents, or aluminate coupling agents; the lubrication compatibility treatment uses one or more of stearates, polyethylene wax, maleic anhydride grafted elastomers, or isocyanate-terminated polyurethane prepolymers.

5. The method for preparing a composite flexible rare earth magnetic strip according to claim 1, characterized in that, The flexible bonding system includes a thermoplastic elastomer, a rubber phase, a plasticizer, a lubricant, an antioxidant, and a crosslinking agent. The thermoplastic elastomer is one or more of TPU, SEBS, and TPEE, and the rubber phase is one or more of nitrile rubber, hydrogenated nitrile rubber, chlorinated polyethylene rubber, and ethylene propylene rubber.

6. The method for preparing a composite flexible rare earth magnetic strip according to claim 1, characterized in that, The modified rare earth magnetic powder has a mass fraction of 85wt% to 96wt% in the flexible magnetic material, the oxygen content in the low-oxygen environment is not higher than 5%, and the mixing temperature is 70℃ to 120℃.

7. The method for preparing a composite flexible rare earth magnetic strip according to claim 1, characterized in that, The orientation viscosity window is when the apparent viscosity of the flexible magnetic material is within a certain range. The continuous magnetic strip blank is in a state where the temperature when it enters the orientation viscosity window is 80℃~130℃.

8. The method for preparing a composite flexible rare earth magnetic strip according to claim 1, characterized in that, The magnetic field strength of the orientation magnetic field is 0.5T to 3.0T, and the direction of the orientation magnetic field is one of the thickness direction, width direction or length direction of the composite flexible rare earth magnetic strip.

9. The method for preparing a composite flexible rare earth magnetic strip according to claim 1, characterized in that, While applying the orientation magnetic field, the continuous magnetic strip blank is rolled in 2 to 5 passes, with a reduction rate of 10% to 35% per pass; and while maintaining the orientation magnetic field, the continuous magnetic strip blank is cooled to below 40°C to lock the anisotropic orientation structure.

10. The method for preparing a composite flexible rare earth magnetic strip according to claim 1, characterized in that, The continuous magnetic strip blank includes a magnetic core layer and a flexible protective layer covering the outside of the magnetic core layer. The magnetic core layer contains the modified rare earth magnetic powder. The direction of magnetization is consistent with the orientation direction of the easy magnetization axis of the rare earth permanent magnet powder. The magnetization is unipolar magnetization, bipolar magnetization, or multipolar magnetization.

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