A flexible magnetic material, its preparation method and application

Abstract

This invention belongs to the field of flexible magnetic materials technology, specifically relating to a flexible magnetic material, its preparation method, and its application. The flexible magnetic material comprises the following components in parts by weight: 80-90 parts magnetic powder, 10-15 parts binder, 1-2 parts plasticizer, 0.4-0.9 parts vulcanizing agent, and 0.5-1.0 parts antioxidant; the magnetic powder is selected from at least one of modified NdFeB magnetic powder, ferrite, samarium iron nitrogen, and samarium cobalt; the modified NdFeB magnetic powder is prepared by modification with bis[3-(triethoxysilyl)propyl]tetrasulfide; the binder comprises NBR rubber A, NBR rubber B, and natural rubber in a mass ratio of (1.3-1.5):(0.4-0.6):(0.8-1.0). The flexible magnetic material of this invention possesses both excellent magnetic and mechanical properties, and exhibits good stability.

Description

Technical Field

[0001] This invention belongs to the field of flexible magnetic materials technology, specifically relating to a flexible magnetic material, its preparation method, and its application. Background Technology

[0002] With the rapid development of high-tech industries such as modern electronics, automation control, new energy vehicles, and intelligent equipment, the demand for permanent magnet materials that are lightweight, highly designable, easy to process and form, and possess excellent magnetic properties is increasing. While traditional sintered NdFeB magnets have excellent magnetic energy product and coercivity, they are inherently brittle metallic materials, facing challenges such as difficult processing, shape limitations, and poor impact resistance, making them unsuitable for applications requiring complex structures and flexible assembly. Therefore, novel permanent magnet composite materials that combine good magnetic properties with mechanical flexibility have become an important direction in current functional materials research.

[0003] Against this backdrop, flexible bonded magnets have emerged and gradually developed into an important class of functional structural materials. Among them, rubber-based bonded magnets, using rapidly quenched NdFeB as the magnetic filler and rubber-based elastomers (such as nitrile rubber, silicone rubber, and EPDM rubber) as the continuous phase matrix, have attracted widespread attention due to their unique comprehensive properties. This type of material, by uniformly dispersing high-remanence, high-coercivity rare-earth permanent magnet powder in a flexible polymer network and utilizing rubber processing techniques such as mixing, open milling, calendering, extrusion, or molding, can produce various forms of products, including magnetic plates, magnetic strips, magnetic rings, and irregularly shaped magnetic components. It boasts advantages such as high production efficiency, low cost, and high design freedom, and is widely used in fields such as micro-motors, encoders, sensors, magnetic seals, consumer electronics, and automotive parts.

[0004] Despite the significant advantages of existing composite magnets in terms of process adaptability and shape flexibility, they still face two major technological challenges in practical applications, hindering further performance improvements and the expansion of their application scope. First, insufficient mechanical properties are a critical issue that urgently needs to be addressed. Due to the low modulus of the rubber matrix itself, and the need to introduce high-volume-fraction hard NdFeB particles into the system to obtain higher magnetic properties, the continuous polymer phase is severely fragmented, resulting in weak interfacial bonding between the filler and the matrix and low stress transfer efficiency. Under external forces, stress concentration easily occurs within the material, and microcracks propagate rapidly. Macroscopically, this manifests as low tensile strength, low elongation at break, and poor fatigue resistance. Especially under bending, stretching, or repeated deformation conditions, brittle fracture or delamination failure is likely to occur, severely affecting product durability and assembly reliability. Second, performance stability during long-term service is also a crucial factor determining the material's practical value. Besides magnetic parameters (such as coercivity and energy product) needing to meet specific application requirements, the material's weather resistance in complex environments is equally important. However, the overall performance, especially the stability, of existing flexible rubber neodymium iron boron magnets cannot meet market demands. Summary of the Invention

[0005] To address the aforementioned problems, the purpose of this invention is to provide a flexible magnetic material, its preparation method, and its applications.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A flexible magnetic material comprising the following components in parts by weight: 80-90 parts magnetic powder, 10-15 parts binder, 1-2 parts plasticizer, 0.4-0.9 parts vulcanizing agent and 0.5-1.0 parts antioxidant.

[0008] Preferably, the magnetic powder is selected from at least one of modified NdFeB magnetic powder, ferrite, samarium iron nitrogen, and samarium cobalt.

[0009] Preferably, the adhesive comprises NBR rubber A, NBR rubber B and natural rubber in a mass ratio of (1.3-1.5):(0.4-0.6):(0.8-1.0).

[0010] Preferably, the Mooney viscosity of NBR rubber A is 68-72 MU under the test conditions of ML1+4 and 100℃, and the acrylonitrile content is 26-29 wt%.

[0011] Further preferably, the Mooney viscosity of NBR rubber A is 70 MU under the test conditions of ML1+4 and 100°C, and the acrylonitrile content is 28 wt%. The model of NBR rubber A is Perbunan® 2865. It is manufactured by BAYER GmbH, Germany.

[0012] Preferably, the Mooney viscosity of NBR rubber B is 58-62 MU under the test conditions of ML1+4 and 100℃, and the acrylonitrile content is 37-40 wt%.

[0013] Further preferably, the Mooney viscosity of NBR rubber B is 60 MU under the test conditions of ML1+4 and 100°C, and the acrylonitrile content is 39 wt%. The grade of NBR rubber B is Europrene® N39.60. It is manufactured by Eni, Italy.

[0014] Preferably, the Mooney viscosity of natural rubber is 55-67 MU under the test conditions of ML1+4 and 100°C.

[0015] Further preferred is the natural rubber type STR20CV60, manufactured by China United Rubber Co., Ltd.

[0016] This invention improves the mechanical strength of flexible magnetic materials by compounding NBR rubber A, NBR rubber B, and natural rubber. Furthermore, using specific parameters for the compounding of NBR rubber A, NBR rubber B, and natural rubber enhances the stability of the flexible magnetic materials. Analysis shows that the compounding and vulcanization of NBR rubber A, NBR rubber B, and natural rubber forms a highly regular and complete network structure, providing the flexible magnetic materials with extremely high tensile strength and elasticity. Moreover, the specific Mooney viscosity of the rubber compound increases the degree of entanglement between molecular chains, and by adjusting the acrylonitrile units, it makes chain segment movement difficult. Through these two effects, the stability of the flexible magnetic materials is improved.

[0017] Preferably, the modified NdFeB magnetic powder is prepared by modification with bis[3-(triethoxysilyl)propyl]tetrasulfide.

[0018] Preferably, the preparation method of the modified NdFeB magnetic powder includes the following steps:

[0019] (1) Mix bis[3-(triethoxysilyl)propyl]tetrasulfide, water and anhydrous ethanol in a volume ratio of (4-5):10:(45-50), stir well, adjust the pH to 4-6 with glacial acetic acid, and hydrolyze at 25℃ for 10-15h to obtain a solution.

[0020] (2) Add neodymium iron boron magnetic powder to the solution. The mass of bis[3-(triethoxysilyl)propyl]tetrasulfide in step (1) accounts for 1-1.5% of the mass of neodymium iron boron magnetic powder. Heat to 60-65℃ and stir at 250-300 rpm for 4-5 hours. After the reaction is completed, centrifuge at 2000 rpm for 4 minutes, wash twice with ethanol and water respectively, and dry at 60℃ to constant weight to obtain modified neodymium iron boron magnetic powder.

[0021] This invention modifies neodymium iron boron magnetic powder by using bis[3-(triethoxysilyl)propyl]tetrasulfide. The modified neodymium iron boron magnetic powder improves the bonding strength with the specific binder of this invention, which can better solve the problem of magnetic powder particles falling off the binder surface, and further improve the magnetic and mechanical properties of the material.

[0022] Preferably, the antioxidant includes at least one of antioxidant MB, antioxidant RD, and antioxidant 445.

[0023] Preferably, the plasticizer is selected from plasticizer TP-95. Brand: Rohm and Haas Hallstar. From distributor: Hubei Guangcheng New Materials Co., Ltd.

[0024] This invention provides a method for preparing the flexible magnetic material, comprising the following steps:

[0025] (1) Mix the components of the flexible magnetic material and run them on a two-roll mill at 70-80℃ for 5-15 minutes;

[0026] (2) Put the material after open milling into the internal mixer for internal mixing. The internal mixing pressure is 0.1-0.5 MPa, the internal mixing temperature is 80-90℃, and the internal mixing time is 5-10 min.

[0027] (3) Use a crusher to crush the intensively mixed material to a size of less than 2 mm;

[0028] (4) Press the crushed material into 1.0-2.0 mm thin sheets using a calender at 70-80℃.

[0029] (5) The plate vulcanization method is used for vulcanization. The vulcanization temperature is 160-170℃ and the vulcanization time is 80-120s. The vulcanization is then allowed to cool naturally to room temperature.

[0030] (6) The sulfided sheet is heat-treated to obtain a flexible magnetic material.

[0031] Preferably, the heat treatment step (6) is as follows: the temperature is increased from room temperature to 80-90℃ at a rate of 1-2℃ / min and held for 0.5-1h; the temperature is further increased to 100-110℃ at a rate of 5-7℃ / min and held for 2-3h; after the holding period, the temperature is gradually reduced to room temperature at a rate of 1-2℃ / min.

[0032] This invention employs a segmented temperature-controlled heat treatment process to improve the mechanical properties of flexible magnetic materials. The process involves first achieving uniform temperature throughout the material and initial stress relaxation; then, promoting cross-linking reactions at a higher temperature to further eliminate internal stress; finally, slow cooling effectively avoids the re-accumulation of thermal stress during the cooling process. This process significantly improves the internal structural uniformity of the flexible magnetic material, thereby enhancing its mechanical properties.

[0033] This invention provides the application of the flexible magnetic material in the preparation of permanent magnet materials.

[0034] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0035] 1. The present invention can improve the mechanical strength of flexible magnetic materials by using NBR rubber A, NBR rubber B and natural rubber in a compound; and when NBR rubber A, NBR rubber B and natural rubber are compounded with specific parameters, the stability of flexible magnetic materials can be improved.

[0036] 2. By using bis[3-(triethoxysilyl)propyl]tetrasulfide to modify NdFeB magnetic powder, the present invention can better solve the problem of magnetic powder particles falling off the binder surface, and further improve the magnetic and mechanical properties of the material.

[0037] 3. The present invention adopts a segmented temperature-controlled heat treatment process, which improves the mechanical properties of flexible magnetic materials. Attached Figure Description

[0038] Figure 1 This is a physical image of the flexible magnetic material prepared in Example 1. Detailed Implementation

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0040] All raw materials used in the following embodiments of the present invention are commercially available products:

[0041] The antioxidant is antioxidant MB, manufactured by Chengming Chemical (Shandong) Co., Ltd.

[0042] The plasticizer is TP-95. Brand: Rohm and Haas Hallstar. From distributor: Hubei Guangcheng New Materials Co., Ltd.

[0043] Neodymium iron boron magnetic powder, Jiangmen Xinhui District Yuhong Technology Co., Ltd., model YMM-8-5.

[0044] The sulfiding agent is sulfur.

[0045] Bis[3-(triethoxysilyl)propyl]tetrasulfide, CAS: 40372-72-3.

[0046] Example 1

[0047] This embodiment provides a flexible magnetic material comprising the following components in parts by weight: 85 parts modified neodymium iron boron magnetic powder, 12 parts binder, 1.5 parts plasticizer, 0.5 parts vulcanizing agent, and 0.8 parts antioxidant.

[0048] The binder comprises NBR rubber A, NBR rubber B, and natural rubber in a mass ratio of 1.4:0.5:1. NBR rubber A has a Mooney viscosity of 70 MU under ML1+4 testing conditions at 100°C and an acrylonitrile content of 28 wt%. NBR rubber A is designated Perbunan® 2865 and is manufactured by BAYER GmbH, Germany. NBR rubber B has a Mooney viscosity of 60 MU under ML1+4 testing conditions at 100°C and an acrylonitrile content of 39 wt%. NBR rubber B is designated Europrene® N39.60 and is manufactured by Eni GmbH, Italy. The natural rubber has a Mooney viscosity of 60 MU under ML1+4 testing conditions at 100°C; the natural rubber is designated Special Natural Rubber STR20CV60 and is manufactured by China United Rubber Co., Ltd.

[0049] The preparation method of the modified NdFeB magnetic powder includes the following steps:

[0050] (1) Mix bis[3-(triethoxysilyl)propyl]tetrasulfide, water and anhydrous ethanol in a volume ratio of 4.5:10:45, stir well, adjust the pH to 5 with glacial acetic acid, and hydrolyze at 25°C for 12 h to obtain a solution;

[0051] (2) Add NdFeB magnetic powder with a mesh size of less than 100 to the solution. The mass of bis[3-(triethoxysilyl)propyl]tetrasulfide in step (1) accounts for 1.2% of the mass of NdFeB magnetic powder. Heat to 60°C and stir at 300 rpm for 4 h. After the reaction is completed, centrifuge at 2000 rpm for 4 min, wash twice with ethanol and water respectively, and dry at 60°C to constant weight to obtain modified NdFeB magnetic powder.

[0052] The method for preparing the flexible magnetic material includes the following steps:

[0053] (1) Mix the components of the flexible magnetic material and run them on a two-roll mill at 75°C for 10 min;

[0054] (2) Put the material after open milling into the internal mixer for internal mixing. The internal mixing pressure is 0.2 MPa, the internal mixing temperature is 90℃, and the internal mixing time is 10 min.

[0055] (3) Use a crusher to crush the intensively mixed material to a size of less than 2 mm;

[0056] (4) Press the crushed material into 1.0 mm thin sheets using a calender at 80°C.

[0057] (5) The plate vulcanization method is used for vulcanization. The vulcanization temperature is 165℃ and the vulcanization time is 100s. The vulcanization is then allowed to cool naturally to room temperature.

[0058] (6) The sulfided sheet is heat-treated to obtain a flexible magnetic material.

[0059] The heat treatment steps in step (6) are as follows: the temperature is increased from room temperature to 80°C at a rate of 2°C / min and held for 1 hour; the temperature is further increased to 110°C at a rate of 5°C / min and held for 2 hours; after the holding period, the temperature is gradually reduced to room temperature at a rate of 2°C / min.

[0060] Example 2

[0061] This embodiment provides a flexible magnetic material comprising the following components in parts by weight: 90 parts modified neodymium iron boron magnetic powder, 15 parts binder, 1 part plasticizer, 0.9 parts vulcanizing agent, and 1.0 part antioxidant.

[0062] The binder comprises NBR rubber A, NBR rubber B, and natural rubber in a mass ratio of 1.3:0.6:0.8. NBR rubber A has a Mooney viscosity of 70 MU under ML1+4 testing conditions at 100°C and an acrylonitrile content of 28 wt%. NBR rubber A is designated Perbunan® 2865 and is manufactured by BAYER GmbH, Germany. NBR rubber B has a Mooney viscosity of 60 MU under ML1+4 testing conditions at 100°C and an acrylonitrile content of 39 wt%. NBR rubber B is designated Europrene® N39.60 and is manufactured by Eni GmbH, Italy. The natural rubber has a Mooney viscosity of 60 MU under ML1+4 testing conditions at 100°C; the natural rubber is designated Special Natural Rubber STR20CV60 and is manufactured by China United Rubber Co., Ltd.

[0063] The preparation method of the modified NdFeB magnetic powder includes the following steps:

[0064] (1) Mix bis[3-(triethoxysilyl)propyl]tetrasulfide, water and anhydrous ethanol in a volume ratio of 4:10:50, stir well, adjust the pH to 6 with glacial acetic acid, and hydrolyze at 25°C for 15 h to obtain a solution;

[0065] (2) Add NdFeB magnetic powder with a mesh size of less than 100 to the solution. The mass of bis[3-(triethoxysilyl)propyl]tetrasulfide in step (1) accounts for 1.5% of the mass of NdFeB magnetic powder. Heat to 65°C and stir at 250 rpm for 5 h. After the reaction is completed, centrifuge at 2000 rpm for 4 min, wash twice with ethanol and water respectively, and dry at 60°C to constant weight to obtain modified NdFeB magnetic powder.

[0066] The method for preparing the flexible magnetic material includes the following steps:

[0067] (1) Mix the components of the flexible magnetic material and run them on a two-roll mill at 75°C for 10 min;

[0068] (2) Put the material after open milling into the internal mixer for internal mixing. The internal mixing pressure is 0.2 MPa, the internal mixing temperature is 90℃, and the internal mixing time is 10 min.

[0069] (3) Use a crusher to crush the intensively mixed material to a size of less than 2 mm;

[0070] (4) Press the crushed material into 1.0 mm thin sheets using a calender at 80°C.

[0071] (5) The plate vulcanization method is used for vulcanization. The vulcanization temperature is 165℃ and the vulcanization time is 100s. The vulcanization is then allowed to cool naturally to room temperature.

[0072] (6) The sulfided sheet is heat-treated to obtain a flexible magnetic material.

[0073] The heat treatment steps in step (6) are as follows: the temperature is increased from room temperature to 90°C at a rate of 1°C / min and held for 0.5h; the temperature is further increased to 100°C at a rate of 7°C / min and held for 3h; after the holding period, the temperature is gradually reduced to room temperature at a rate of 1°C / min.

[0074] Comparative Example 1

[0075] The difference between this comparative example and Example 1 is that the Mooney viscosity of NBR rubber A is 30 MU under the test conditions of ML1+4 and 100°C, and the acrylonitrile content is 34 wt%. The model of NBR rubber A is Perbunan® 3430. It is manufactured by BAYER GmbH, Germany.

[0076] Comparative Example 2

[0077] The difference between this comparative example and Example 1 is that the Mooney viscosity of NBR rubber A is 45 MU under the test conditions of ML1+4 and 100°C, and the acrylonitrile content is 18 wt%. The type of NBR rubber A is Perbunan® 1845. It is manufactured by BAYER GmbH, Germany.

[0078] Comparative Example 3

[0079] The difference between this comparative example and Example 1 is that the Mooney viscosity of NBR rubber B under the test conditions of ML1+4 and 100°C is 80 MU, and the acrylonitrile content is 33 wt%. The type of NBR rubber B is Europrene® N39.60. It is manufactured by Eni, Italy.

[0080] Comparative Example 4

[0081] The difference between this comparative example and Example 1 is that the Mooney viscosity of NBR rubber B under the test conditions of ML1+4 and 100°C is 19 MU, and the acrylonitrile content is 45 wt%. The type of NBR rubber B is Europrene® N19.45. It is manufactured by Eni, Italy.

[0082] Comparative Example 5

[0083] The difference between this comparative example and Example 1 is that the adhesive comprises NBR rubber A and natural rubber in a mass ratio of 1.4:1.

[0084] Comparative Example 6

[0085] The difference between this comparative example and Example 1 is that the adhesive comprises NBR rubber A, NBR rubber B and natural rubber in a mass ratio of 1:1:1.

[0086] Comparative Example 7

[0087] The difference between this comparative example and Example 1 is that the preparation method of the modified NdFeB magnetic powder includes the following steps:

[0088] (1) Mix silane coupling agent 550, water and anhydrous ethanol in a volume ratio of 4.5:10:45, stir well, adjust the pH value to 5 with glacial acetic acid, and hydrolyze at 25℃ for 12h to obtain a solution;

[0089] (2) Add NdFeB magnetic powder with a mesh size of less than 100 to the solution, add 1.2% of the mass of silane coupling agent 550 in step (1), heat to 60°C, stir at 300 rpm for 4 h, after the reaction is completed, centrifuge at 2000 rpm for 4 min, wash twice with ethanol and water respectively, dry at 60°C to constant weight, and obtain modified NdFeB magnetic powder.

[0090] Performance testing

[0091] The flexible magnetic materials of Examples 1-2 and Comparative Examples 1-7 were cut into 20mm×10mm×1.0mm pieces for performance testing.

[0092] 1. Intrinsic coercivity (Hcj) and maximum energy product (BH): These were determined using a BH hysteresis loop plotter under a pulsed magnetic field, in accordance with GB / T3217-2013 "Standard for Magnetic Test Methods of Permanent Magnet (Hard Magnetic) Materials".

[0093] 2. Tensile strength and elongation were measured using a rubber tensile testing machine.

[0094] 3. Thermal stability: In Examples 1-2 and Comparative Examples 1-7, 20 magnet material samples of 20mm×10mm×1.0mm were selected and kept at 100℃ for 300h. The number of samples that warped was counted.

[0095] The results are shown in Table 1.

[0096] Table 1 Performance Test Results

[0097] Tensile strength (MPa) Elongation (%) Hcj (kA / m) BH (kJ / m³) stability Example 1 5.61 71.6 586 38.7 0 Example 2 5.53 70.2 579 37.1 0 Comparative Example 1 4.42 72.4 539 35.1 1 Comparative Example 2 4.27 73.7 541 34.8 2 Comparative Example 3 5.15 60.5 540 45.5 1 Comparative Example 4 4.24 57.8 475 30.9 4 Comparative Example 5 4.48 59.3 518 32.4 5 Comparative Example 6 4.36 63.4 561 34.8 3 Comparative Example 7 4.60 65.1 534 33.2 1

[0098] From Table 1 and Figure 1 It can be seen that the flexible magnetic materials of Examples 1-2 possess both excellent magnetic and mechanical properties, as well as good stability. Comparative Examples 1-6 illustrate that the composition, ratio, and parameters of the binder have a significant impact on the magnetic and mechanical properties of the flexible magnetic materials. Only by using the formulations of Examples 1-2 can flexible magnetic materials with excellent comprehensive performance be obtained.

[0099] In Comparative Example 7, modification with silane coupling agent 550 resulted in a decrease in the magnetic and mechanical properties of the flexible magnetic material. Analysis shows that the present invention, through modification with bis[3-(triethoxysilyl)propyl]tetrasulfide, not only allows for bonding with the magnetic powder via silanol groups, but also enables the polysulfide bonds at its organic ends to directly participate in the vulcanization and crosslinking reaction of the rubber, forming a strong chemical covalent bond. Therefore, the bonding strength between the NdFeB magnetic powder modified with bis[3-(triethoxysilyl)propyl]tetrasulfide and the binder of this invention is higher.

[0100] The above description of flexible magnetic materials represents a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles described herein, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A flexible magnetic material, characterized in that, It comprises the following components in parts by weight: 80-90 parts magnetic powder, 10-15 parts binder, 1-2 parts plasticizer, 0.4-0.9 parts vulcanizing agent, and 0.5-1.0 parts antioxidant; The magnetic powder is modified neodymium iron boron magnetic powder; The preparation method of the modified NdFeB magnetic powder includes the following steps: (1) Mix bis[3-(triethoxysilyl)propyl]tetrasulfide, water and anhydrous ethanol, stir well, adjust the pH, and hydrolyze to obtain a solution; (2) Add neodymium iron boron magnetic powder to the solution, heat to 60-65℃, stir and react for 4-5 hours. After the reaction is complete, centrifuge, wash, and dry to constant weight to obtain modified neodymium iron boron magnetic powder. The adhesive comprises NBR rubber A, NBR rubber B, and natural rubber in a mass ratio of (1.3-1.5):(0.4-0.6):(0.8-1.0); NBR rubber A has a Mooney viscosity of 68-72 MU and an acrylonitrile content of 26-29 wt%; NBR rubber B has a Mooney viscosity of 58-62 MU and an acrylonitrile content of 37-40 wt%. The Mooney viscosity of natural rubber is 55-67 MU.

2. The flexible magnetic material according to claim 1, characterized in that, Antioxidants include at least one of antioxidant MB, antioxidant RD, and antioxidant 445.

3. The flexible magnetic material according to claim 1, characterized in that, The plasticizer is selected from plasticizer TP-95.

4. A method for preparing the flexible magnetic material according to any one of claims 1-3, characterized in that, Includes the following steps: (1) Mix the components of the flexible magnetic material and run them on a two-roll mill at 70-80℃ for 5-15 minutes; (2) Put the material after open milling into the internal mixer for internal mixing. The internal mixing pressure is 0.1-0.5 MPa, the internal mixing temperature is 80-90℃, and the internal mixing time is 5-10 min. (3) Use a crusher to crush the intensively mixed material to a size of less than 2 mm; (4) Press the crushed material into 1.0-2.0 mm thin sheets using a calender at 70-80℃. (5) The plate vulcanization method is used for vulcanization. The vulcanization temperature is 160-170℃ and the vulcanization time is 80-120s. The vulcanization is then allowed to cool naturally to room temperature. (6) The sulfided sheet is heat-treated to obtain a flexible magnetic material.

5. The method for preparing the flexible magnetic material according to claim 4, characterized in that, The heat treatment steps in step (6) are as follows: the temperature is increased from room temperature to 80-90℃ at a rate of 1-2℃ / min and held for 0.5-1h; the temperature is further increased to 100-110℃ at a rate of 5-7℃ / min and held for 2-3h; after the holding period, the temperature is gradually reduced to room temperature at a rate of 1-2℃ / min.

6. The application of the flexible magnetic material according to any one of claims 1-3 in the preparation of permanent magnet materials.

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