Injection molding rare earth permanent magnet material, preparation method thereof and injection molding magnet

Abstract

The invention relates to the technical field of rare earth permanent magnet materials, and discloses an injection molding rare earth permanent magnet material, a preparation method of the injection molding rare earth permanent magnet material and an injection molding magnet. 3.5-15 wt% of a binder, wherein the binder is at least one of PA6 and PA12; 0.5-3 wt% of functional resin, wherein the functional resin is at least one of PE (Polyethylene) and PVDC (Polyvinyl Dichloride); 0.5-2 wt% of a coupling agent; 0.2 to 1.5 wt% of an auxiliary agent; the functional resin in the permanent magnet material serves as a protective layer and wraps the neodymium iron boron magnetic powder and the binding agent, and the adding weight of the functional resin accounts for 0.6%-3% of the total weight of the neodymium iron boron magnetic powder and the binding agent. The rare earth permanent magnet material has good corrosion resistance, a magnet prepared from the permanent magnet material is not rusted when used in a high-humidity environment, the magnetic performance is greatly utilized, and the loss of the magnetic performance is reduced. By adjusting the adding proportion of the raw materials, the injection molding magnet material has good fluidity, and the cost of the raw materials is low.

Description

Technical Field

[0001] The invention relates to the technical field of rare earth permanent magnetic materials, and in particular to an injection-molded rare earth permanent magnetic material and a preparation method thereof, and an injection-molded magnet. Background Art

[0002] Injection molded ferrite permanent magnet materials are used in various fields because of their low price; however, the highest magnetic properties of injection molded ferrite permanent magnet materials on the current market can only reach 2.3MGOe, which cannot meet the market demand. The magnetic properties of isotropic NdFeB permanent magnet materials on the market can reach 9MGOe, and the magnetic properties of anisotropic NdFeB permanent magnet materials can reach 15MGOe. Injection molded rare earth permanent magnets such as samarium cobalt (SmCo) and neodymium iron boron (NdFeB) magnets have higher magnetic properties. However, NdFeB rare earth permanent magnet materials contain rare earth active metals, which are very easy to react with water and oxygen in the air. When used in a high humidity environment, they will rust, thereby affecting the magnetic properties and mechanical properties of the magnet.

[0003] In order to improve the corrosion resistance of NdFeB rare earth permanent magnet materials, the prior art uses surface coatings, steel parts or plastic coatings on the magnet body to block water vapor from entering the interior of the magnet, thereby solving the problem of magnet corrosion in a high humidity environment and improving the corrosion resistance of rare earth permanent magnet materials. However, the coating will have defects, and water will enter the interior of the magnet from the defects, causing the magnet to rust. The use of surface coatings not only cannot achieve complete density, but also increases process costs during production. The treatment method of coating the surface with steel or plastic can effectively improve the corrosion resistance of the magnet, but sealing welding technology and secondary plastic coating will greatly increase the manufacturing cost, and higher requirements are placed on the magnetic properties of the magnetic material.

[0004] Patent document CN111696740A discloses a method for improving the hygroscopicity of a magnetic composite material. The raw materials for preparing the magnetic composite material include, by weight: 85-90 parts of anisotropic strontium ferromagnetic powder, 40-50 parts of ethanol, 0.1-0.3 parts of isopropyl tri(dioctyl pyrophosphate) titanate, 3-5 parts of nylon 6, 1-2 parts of talc, 0.05-0.1 parts of γ-aminopropyl trimethoxysilane, 0.1-0.3 parts of phthalic acid diester, 0.5-1.5 parts of polyethylene grafted maleic anhydride, 4-10 parts of polyethylene, 1-3 parts of silica glass fiber and 0.5-1 parts of stearic acid monoglyceride. By selecting nylon 6 and polyethylene as the composite material, the hygroscopicity of the magnetic composite material is improved. The invention discloses a composite magnetic material which has good mechanical properties and avoids the problem of hygroscopicity of nylon 6. However, the strontium iron magnetic powder targeted by the patent will not reduce the mechanical properties in a high humidity environment. The patent solves the hygroscopicity of nylon 6 and prevents nylon from becoming brittle, resulting in cracks and falling off of magnetic blocks. The strontium iron magnetic powder material itself does not have the problem of rust. The above method will not improve the magnetic properties of the magnetic powder. More importantly, the composite magnetic material adopts a secondary mixing and extrusion process, which increases the complexity of the process. Therefore, the method cannot be applied to neodymium iron boron magnet materials.

[0005] Therefore, it is necessary to propose a method to improve the corrosion resistance of NdFeB rare earth permanent magnet materials, so as to promote the application environment of NdFeB rare earth permanent magnet materials. Summary of the invention

[0006] The purpose of the present invention is to solve the problems of the existing method that the corrosion resistance cannot be effectively improved and the process complexity is increased, and to provide an injection molded rare earth permanent magnet material and a preparation method thereof, and an injection molded magnet.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] An injection-molded rare earth permanent magnetic material, wherein the raw materials for preparing the permanent magnetic material include, by weight:

[0009] NdFeB magnetic powder 80-95wt%;

[0010] 3.5-15wt% binder, wherein the binder is at least one of PA6 and PA12;

[0011] 0.5-3wt% of functional resin, wherein the functional resin is at least one of PE and PVDC;

[0012] Coupling agent 0.5-2wt%;

[0013] Additives 0.2-1.5wt%;

[0014] In the permanent magnetic material, the functional resin is used as a protective layer to cover the NdFeB magnetic powder and the binder, wherein the added weight of the functional resin accounts for 0.6% to 3% of the total weight of the NdFeB magnetic powder and the binder.

[0015] In the above technical solution, the formula of the injection molding permanent magnet material is: NdFeB magnetic powder, binder, functional resin, coupling agent and additive, the binder is at least one of PA6 (nylon 6) and PA12 (nylon 12); the functional resin is at least one of PE (polyethylene) and PVDC (polyvinylidene chloride); the formula contains two types of resins, the first type of resin is a binder for bonding effect, which has good affinity with the magnetic powder, so in the injection molding preparation process, the first type of resin will be mixed evenly with the NdFeB magnetic powder to form a molten state; the second type of resin is a functional resin, and the compatibility between the first type of resin and the second type of resin is poor. , the processing temperature is equivalent. In the formula of the permanent magnetic material of the present invention, not only the amount of NdFeB magnetic powder, binder and functional resin is limited, but also the added weight of the functional resin is limited to the proportion of the total weight of NdFeB magnetic powder and binder to 0.6% to 3%. In the subsequent injection molding preparation process, the functional resin will gather on the surface of the injection molded magnet to form a protective layer. Through the above-mentioned limitation, the protective layer formed by the functional resin can better cover the NdFeB magnetic powder and the binder. As a protective layer, it has good toughness and waterproof performance, thereby blocking water vapor from entering the magnet, avoiding rust caused by reaction with NdFeB magnetic powder, thereby improving the corrosion resistance of rare earth permanent magnetic materials.

[0016] The rare earth permanent magnetic material of the present invention has good corrosion resistance. The magnet prepared by using the permanent magnetic material does not rust when used in a high humidity environment, greatly utilizes the magnetic performance, reduces the loss of the magnetic performance, and by adjusting the addition ratio between the raw materials, the injection molding magnet material has good fluidity and low raw material cost. In addition, in the preparation process of the rare earth permanent magnetic material, the binder and the functional resin can be added at the same time to reduce the complexity of the process.

[0017] As a preferred embodiment of the present invention, the coupling agent is at least one of a silane coupling agent, a titanate coupling agent, an aluminum zirconate coupling agent, and a titanate coupling agent; the silane coupling agent used is one or more of KH550 silane coupling agent, KH560 silane coupling agent, and KH570 silane coupling agent; the titanate coupling agent used is isopropyl tri(dioctyl) pyrophosphate titanate; the aluminum zirconate coupling agent is, for example, a titanate coupling agent is, for example, a monoalkoxy pyrophosphate type.

[0018] As a preferred embodiment of the present invention, the auxiliary agent is at least one of a lubricant, a dispersant, a plasticizer, a heat stabilizer, and an antioxidant. Lubricants include stearic acid, zinc stearate, paraffin, etc.; dispersants include sodium hexametaphosphate, sodium polyacrylate, etc.; heat stabilizers include stearates, etc.; antioxidants include 168, 1010, 1076, etc.; plasticizers include modified citrate, epoxy soybean oil, phthalates, etc.

[0019] As a preferred embodiment of the present invention, the molecular weight of PA6 is 10,000 to 25,000, and the molecular weight of PA12 is 10,000 to 35,000.

[0020] As a preferred embodiment of the present invention, the binder is PA12.

[0021] As a preferred embodiment of the present invention, the molecular weight of PE is 2000-200000, and the molecular weight of PVDC is 1000-20000.

[0022] As a preferred embodiment of the present invention, the raw materials for preparing the permanent magnetic material include, by weight: 87.5-93wt% NdFeB magnetic powder, 4.5-8wt% binder, 0.7-2.7wt% functional resin, 0.5-1.5wt% coupling agent, and 0.3-1.5wt% auxiliary agent.

[0023] As a preferred solution of the present invention, the added weight of the binder accounts for 4-10% of the weight of the NdFeB magnetic powder.

[0024] As a preferred embodiment of the present invention, in the above structure, the functional resin is used as a protective layer, and the thickness of the protective layer is 5 to 30 μm. More preferably, the thickness of the protective layer is 10 to 20 μm.

[0025] As a preferred embodiment of the present invention, the added weight of the functional resin accounts for 1.5-2.1% of the total weight of the NdFeB magnetic powder and the binder. The functional resin forms a protective layer, and by adjusting the added weight ratio of the functional resin to the total weight of the system, the thickness of the surface protective layer can be adjusted, which can improve the corrosion resistance of the rare earth permanent magnet on the one hand, and minimize the loss of magnetic properties on the other hand.

[0026] Another aspect of the present invention provides a method for preparing an injection-molded rare earth permanent magnetic material, comprising the following steps:

[0027] S1, spraying the coupling agent onto the NdFeB magnetic powder under stirring, stirring, then adding the binder, the functional resin, and the auxiliary agent, and continuing to stir evenly to obtain a mixed material;

[0028] S2. The obtained mixture is put into a twin-screw extruder, melt-extruded into wire at 220° C. to 260° C., cooled, and pelletized to obtain an injection-molded rare earth permanent magnet material.

[0029] In the above technical scheme, the NdFeB magnetic powder is first modified with a coupling agent, and then the modified magnetic powder is mixed with a binder, a functional resin, and an additive, and then extruded and granulated at 220°C to 260°C to obtain a rare earth permanent magnet material. The rare earth permanent magnet material of the present invention is prepared by a one-time extrusion process, which is simple and easy to operate. While reducing the complexity of the process, the cost can also be reduced. The subsequent injection molding rare earth permanent magnet material can give the injection molded rare earth permanent magnet a good appearance after one-time injection molding. The magnet will not rust when used in a high humidity environment, and no electrophoresis or spraying is required to form a protective film. The preparation method is simple and convenient for industrial promotion.

[0030] As a preferred embodiment of the present invention, in step S1, the coupling agent is dissolved in a diluent, dissolved evenly, and then sprayed on the NdFeB magnetic powder under stirring.

[0031] As a preferred embodiment of the present invention, in step S2, the temperature in the twin-screw extruder is controlled to be 230° C. to 240° C., and the granulation is performed by melt extrusion at 230° C. to 240° C. In the mixing process of the magnet material, the temperature has a direct relationship with the final performance of the product. If the temperature is too low, the uniformity of the material is poor, and if the temperature is too high, the strength and magnetic properties of the material will be affected. Therefore, the present invention adopts melt extrusion granulation at 230° C. to 240° C.

[0032] The present invention also provides an injection-molded magnet, which is obtained by injection molding the above-mentioned injection-molded rare earth permanent magnet material through an injection molding machine. The injection-molded magnet prepared by the rare earth permanent magnet material of the present invention not only has high magnetic properties and strength, but also has good corrosion resistance, low manufacturing cost, and is easy to promote and apply.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The present invention provides an injection-molded rare earth permanent magnet material, in which the functional resin in the material will gather on the surface of the injection-molded magnet to form a protective layer. The functional resin as the protective layer has good toughness and waterproof properties, thereby blocking water vapor from entering the magnet and preventing the neodymium iron boron magnetic powder from reacting and rusting, thereby improving the corrosion resistance of the rare earth permanent magnet material. The rare earth permanent magnet material of the present invention has good corrosion resistance, and the magnet prepared by the permanent magnet material does not rust when used in a high humidity environment, greatly reducing the loss of magnetic properties. By adjusting the addition ratio between the raw materials, the injection-molded magnet material has good fluidity and low raw material cost.

[0035] 2. The rare earth permanent magnet material of the present invention is prepared by a one-time extrusion process, which is simple in process. While reducing the complexity of the process, the cost can also be reduced. The subsequent injection molding of the rare earth permanent magnet material can give the injection molded rare earth permanent magnet a good appearance after one-time injection molding. The magnet will not rust when used in a high humidity environment, and no electrophoresis or spraying is required to form a protective film. The preparation method is simple and is convenient for industrial promotion.

[0036] 3. The rare earth permanent magnet material prepared by the present invention has good tensile strength, impact strength, and material fluidity after testing, and has good processability. It does not rust in constant temperature and humidity tests and salt spray tests, has a good appearance, and is dimensionally stable, and can meet the requirements for use in high humidity environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a schematic diagram of the structure of the rare earth permanent magnetic material prepared by the present invention, in which A is a protective layer formed by a functional resin; B is a composition of a binder and magnetic powder;

[0038] Figure 2 The following are 10× photos of the comparative rare earth permanent magnet materials after constant temperature and humidity test: (1) comparative example 1; (2) comparative example 2; (3) comparative example 3; (4) comparative example 4; (5) comparative example 5; (6) comparative example 6; (8) comparative example 8; (9) comparative example 9; (10) comparative example 10; (12) comparative example 12.

[0039] Figure 3 The following are 10× photos of the comparative rare earth permanent magnet materials after salt spray test: (1) comparative example 1; (2) comparative example 2; (3) comparative example 3; (4) comparative example 4; (5) comparative example 5; (6) comparative example 6; (8) comparative example 8; (12) comparative example 12. DETAILED DESCRIPTION

[0040] In order to more clearly describe the invention purpose, technical scheme and technical effect advantages in the specific implementation case of the present invention, the scheme in the specific embodiment will be described in detail in combination with the drawings of the specification of the present invention. The specific technical scheme involved in the following specific embodiments is only for a clear and complete description of the innovative technical scheme of the present invention. It is only a part of the specific implementation scheme that can be adopted by the present invention, not all embodiments, and should not be understood as a limitation on the innovative scheme of the present invention. Any scheme adopting the same inventive concept of the present invention should be included in the protection scope of the present invention.

[0041] Secondly, the description of the drawings in the specific embodiments of the present invention is only for the convenience of technical personnel to understand the solution of the present invention. The partial details in the drawings are for the convenience of clearly presenting the technical solution. It should not be considered that all technical features in the drawings must be included in the specific implementation cases, and the detailed features in the drawings should not be identified as additional limitations on the innovative technical solution of the present invention. The components in the various embodiments described and shown in the drawings can be combined and arranged according to different configurations, and these changes in combination and arrangement should be identified as part of the entire embodiment of the innovative solution of the present invention and included in the scope of protection of the present invention.

[0042] In summary, the schemes or descriptions presented in the specific embodiments and drawings of the present invention are not intended to limit the scope of protection claimed, but are merely selected embodiments / cases to help technicians understand the relevant innovative solutions. Based on these embodiments, all other equivalent or parallel embodiments obtained by those skilled in the art without creative work are within the scope of protection claimed by the present invention.

[0043] Example 1

[0044] The present embodiment provides an injection-molded rare earth permanent magnet material, wherein the raw materials include, by weight: 87.5wt% of NdFeB magnetic powder; 8wt% of PA12, 2.7wt% of PVDC, 1.5wt% of silane coupling agent, and 0.3% of auxiliary agent; wherein the molecular weight of the PA12 used is 15000-20000, the molecular weight of the PVDC is 5000-10000, and the auxiliary agent is 0.1wt% of lubricant zinc stearate and 0.2wt% of antioxidant hindered phenol antioxidant.

[0045] The preparation method of injection molded rare earth permanent magnet material is as follows:

[0046] S1. Dissolve the coupling agent in ethanol and dissolve it evenly, then spray it on the NdFeB magnetic powder under stirring, then add a binder, a functional resin, and an additive, continue to stir evenly, and obtain a mixed material;

[0047] S2. The obtained mixture is put into a twin-screw extruder, melt-extruded into a wire at 245±5°C, cooled, and pelletized to obtain an injection-molded rare earth permanent magnet material, in which the functional resin is used as a protective layer to coat the NdFeB magnetic powder and the binder, such as Figure 1 shown.

[0048] Example 2

[0049] The present embodiment provides an injection-molded rare earth permanent magnet material, wherein the raw materials include, by weight: 90wt% of NdFeB magnetic powder; 6.7wt% of PA12, 1.5wt% of HDPE, 1wt% of titanate coupling agent, and 0.8% of additives; wherein the molecular weight of the PA12 used is 15000-20000, the molecular weight of the HDPE is 20000-30000, and the additives are 0.4wt% of lubricant ethylene bisstearamide and 0.4wt% of phosphite antioxidant.

[0050] The preparation method of the injection molded rare earth permanent magnet material is the same as that in Example 1.

[0051] Example 3

[0052] The present embodiment provides an injection-molded rare earth permanent magnet material, wherein the raw materials include, by weight: 93wt% of NdFeB magnetic powder; 4.5wt% of PA12, 0.7wt% of LLDPE, 0.6wt% of silane coupling agent, and 1.2% of auxiliary agent; wherein the molecular weight of the PA12 used is 15000-20000, the molecular weight of the LLDPE is 20000-30000, and the auxiliary agent is 0.5wt% of lubricant ethylene bis stearamide, 0.5wt% of phosphite antioxidant, and 0.2wt% of phosphorus flame retardant.

[0053] The preparation method of the injection molded rare earth permanent magnet material is the same as that in Example 1.

[0054] Example 4

[0055] The present embodiment provides an injection-molded rare earth permanent magnet material, wherein the raw materials include, by weight: 87.5wt% of NdFeB magnetic powder; 8wt% of PA6, 2.7wt% of PVDC, 1.5wt% of titanate coupling agent, and 0.3% of auxiliary agent; the molecular weight of PA6 is 15000-20000, the molecular weight of PVDC is 5000-10000, and the auxiliary agent is 0.2wt% of lubricant zinc stearate and 0.1wt% of plasticizer modified citrate.

[0056] The preparation method of the injection molded rare earth permanent magnet material is the same as that in Example 1.

[0057] Example 5

[0058] The present embodiment provides an injection-molded rare earth permanent magnet material, wherein the raw materials include, by weight: 90wt% of NdFeB magnetic powder; 6.7wt% of PA6, 1.5wt% of HDPE, 1wt% of titanate coupling agent, and 0.8% of additives; the molecular weight of PA6 is 15000-20000, the molecular weight of HDPE is 20000-30000, and the additives are 0.4wt% of lubricant zinc stearate and 0.4wt% of plasticizer modified citrate.

[0059] The preparation method of the injection molded rare earth permanent magnet material is the same as that in Example 1.

[0060] Example 6

[0061] The present embodiment provides an injection-molded rare earth permanent magnet material, wherein the raw materials include, by weight: 93wt% of NdFeB magnetic powder; 4.5wt% of PA6, 2.7wt% of LLDPE, 0.6wt% of silane coupling agent, and 1.2% of auxiliary agent; the molecular weight of PA6 is 15000-20000, the molecular weight of LLDPE is 20000-30000, and the auxiliary agent is 0.6wt% of lubricant zinc stearate and 0.6wt% of plasticizer modified citrate.

[0062] The preparation method of the injection molded rare earth permanent magnet material is the same as that in Example 1.

[0063] Example 7

[0064] The present embodiment provides an injection-molded rare earth permanent magnet material, wherein the raw materials include, by weight: 90 wt% of NdFeB magnetic powder; 6.7 wt% of PA12, 2 wt% of HDPE, 1 wt% of titanate coupling agent, and 0.3% of additives; the molecular weight of PA12 is 15,000 to 20,000, the molecular weight of HDPE is 20,000 to 30,000, and the additives are 0.1 wt% of lubricant ethylene bisstearamide, 0.1 wt% of plasticizer modified citrate, and 0.1 wt% of phosphite antioxidant.

[0065] The preparation method of the injection molded rare earth permanent magnet material is the same as that in Example 1.

[0066] Example 8

[0067] The present embodiment provides an injection-molded rare earth permanent magnet material, wherein the raw materials include, by weight: 90wt% of NdFeB magnetic powder; 5.5wt% of PA12, 1.5wt% of HDPE, 1.5wt% of titanate coupling agent, and 1.5% of additives; the molecular weight of PA12 is 15000-20000, the molecular weight of HDPE is 20000-30000, and the additives are 0.6wt% of lubricant ethylene bisstearamide, 0.6wt% of plasticizer modified citrate, and 0.3wt% of phosphite antioxidant.

[0068] The preparation method of the injection molded rare earth permanent magnet material is the same as that in Example 1.

[0069] Example 9

[0070] The present embodiment provides an injection-molded rare earth permanent magnet material, wherein the raw materials include, by weight: 90wt% of NdFeB magnetic powder; 6.7wt% of PA12, 1.5wt% of HDPE, 1wt% of titanate coupling agent, and 0.8% of additives; the molecular weight of PA12 is 15000-20000, the molecular weight of HDPE is 20000-30000, and the additives are 0.3wt% of lubricant ethylene bisstearamide, 0.3wt% of plasticizer modified citrate, and 0.2wt% of phosphite antioxidant.

[0071] The preparation method of injection molded rare earth permanent magnet material is as follows:

[0072] S1. Dissolve the coupling agent in ethanol and dissolve it evenly, then spray it on the NdFeB magnetic powder under stirring, then add a binder, a functional resin, and an additive, continue to stir evenly, and obtain a mixed material;

[0073] S2. The obtained mixture is put into a twin-screw extruder, melt-extruded into a wire at 230±5°C, cooled, and pelletized to obtain an injection-molded rare earth permanent magnet material.

[0074] Comparative Example 1

[0075] This embodiment is an injection molded rare earth permanent magnet material, which differs from the embodiment 1 in that no functional resin is added, and the raw materials include by weight: 87.5wt% of NdFeB magnetic powder; 128wt% of PA, 1.5wt% of coupling agent, and 0.3% of auxiliary agent. The preparation method of the injection molded rare earth permanent magnet material is the same as that of the embodiment 1. It should be noted that in the comparative example, the total proportion of all raw materials may be less than or more than 100%, but it does not affect the proportion between different raw materials.

[0076] Comparative Example 2

[0077] This embodiment is an injection molded rare earth permanent magnet material, which differs from the embodiment 2 in that no functional resin is added, and the raw materials include by weight: 90wt% of NdFeB magnetic powder; 6.7wt% of PA12, 1wt% of coupling agent, and 0.8% of auxiliary agent. The preparation method of the injection molded rare earth permanent magnet material is the same as that of the embodiment 1.

[0078] Comparative Example 3

[0079] This embodiment is an injection molded rare earth permanent magnet material, which differs from the embodiment 3 in that no functional resin is added, and the raw materials include by weight: 93wt% of NdFeB magnetic powder; 4.5wt% of PA12, 0.6wt% of ester coupling agent, and 1.2% of auxiliary agent. The preparation method of the injection molded rare earth permanent magnet material is the same as that of the embodiment 1.

[0080] Comparative Example 4

[0081] This embodiment is an injection molded rare earth permanent magnet material, which differs from the embodiment 4 in that no functional resin is added, and the raw materials include by weight: 87.5wt% of NdFeB magnetic powder; 8wt% of PA6, 1.5wt% of coupling agent, and 0.3% of auxiliary agent. The preparation method of the injection molded rare earth permanent magnet material is the same as that of the embodiment 1.

[0082] Comparative Example 5

[0083] This embodiment is an injection molded rare earth permanent magnet material, which differs from the embodiment 5 in that no functional resin is added, and the raw materials include by weight: 90wt% NdFeB magnetic powder; 6.7wt% PA6, 1wt% coupling agent, and 0.8% auxiliary agent. The preparation method of the injection molded rare earth permanent magnet material is the same as that of the embodiment 1.

[0084] Comparative Example 6

[0085] This embodiment is an injection molded rare earth permanent magnet material, which differs from the embodiment 6 in that no functional resin is added, and the raw materials include by weight: 93wt% NdFeB magnetic powder; 4.5wt% PA6, 0.6wt% coupling agent, and 1.2% auxiliary agent. The preparation method of the injection molded rare earth permanent magnet material is the same as that of the embodiment 1.

[0086] Comparative Example 7

[0087] This embodiment is an injection-molded rare earth permanent magnet material, which is different from the embodiment 2 in that the addition amount of the functional resin exceeds 0.5-3wt%, and the raw materials include by weight: 90wt% of NdFeB magnetic powder; 6.7wt% of PA12, 4wt% of HDPE, 1wt% of coupling agent, and 0.8% of auxiliary agent. The preparation method of the injection-molded rare earth permanent magnet material is the same as that of the embodiment 1.

[0088] Comparative Example 8

[0089] This embodiment is an injection-molded rare earth permanent magnet material, which is different from the embodiment 2 in that the amount of functional resin added is less than 0.5-3wt%, and the raw materials include by weight: 90wt% of NdFeB magnetic powder; 6.7wt% of PA12, 0.3wt% of HDPE, 1wt% of coupling agent, and 0.8% of auxiliary agent. The preparation method of the injection-molded rare earth permanent magnet material is the same as that of the embodiment 1.

[0090] Comparative Example 9

[0091] This embodiment is an injection molded rare earth permanent magnet material, which is different from the embodiment 2 in that the amount of coupling agent added exceeds 0.5-2wt%, and the raw materials include by weight: 90wt% of NdFeB magnetic powder; 6.7wt% of PA12, 1.5wt% of HDPE, 2.1wt% of coupling agent, and 0.8% of auxiliary agent. The preparation method of the injection molded rare earth permanent magnet material is the same as that of the embodiment 1.

[0092] Comparative Example 10

[0093] This embodiment is an injection-molded rare earth permanent magnet material, which is different from the embodiment 2 in that the amount of coupling agent added is less than 0.5-2wt%, and the raw materials include by weight: 90wt% of NdFeB magnetic powder; 6.7wt% of PA12, 1.5wt% of HDPE, 0.3wt% of coupling agent, and 0.8% of auxiliary agent. The preparation method of the injection-molded rare earth permanent magnet material is the same as that of the embodiment 1.

[0094] Comparative Example 11

[0095] This embodiment is an injection-molded rare earth permanent magnet material, which is different from the embodiment 1 in that the functional resin accounts for more than 3%, and the raw materials include by weight: 87.5wt% of NdFeB magnetic powder; 28wt% of PA1, 3wt% of PVDC, 1.5wt% of silane coupling agent, and 0.3% of auxiliary agent. The preparation method of the injection-molded rare earth permanent magnet material is the same as that of the embodiment 1.

[0096] Comparative Example 12

[0097] This embodiment is an injection-molded rare earth permanent magnet material, which is different from the embodiment 3 in that the functional resin accounts for less than 0.6%, and the raw materials include by weight: 93wt% of NdFeB magnetic powder; 4.5wt% of PA12, 0.5wt% of PVDC, 0.6wt% of silane coupling agent, and 1.2% of auxiliary agent. The preparation method of the injection-molded rare earth permanent magnet material is the same as that of the embodiment 1.

[0098] Comparative Example 13

[0099] This embodiment is an injection-molded rare earth permanent magnet material. The raw materials are the same as those in Embodiment 2. The difference from Embodiment 2 is that the processing temperature is too high. The preparation method of the injection-molded rare earth permanent magnet material is as follows:

[0100] S1. Dissolve the coupling agent in ethanol and dissolve it evenly, then spray it on the NdFeB magnetic powder under stirring, then add a binder, a functional resin, and an additive, continue to stir evenly, and obtain a mixed material;

[0101] S2. The obtained mixture is put into a twin-screw extruder, melt-extruded into a wire at 265±5°C, cooled, and pelletized to obtain an injection-molded rare earth permanent magnet material.

[0102] Comparative Example 14

[0103] This embodiment is an injection-molded rare earth permanent magnet material. The raw materials are the same as those in Embodiment 2. The difference from Embodiment 2 is that the processing temperature is too low. The preparation method of the injection-molded rare earth permanent magnet material is as follows:

[0104] S1. Dissolve the coupling agent in ethanol and dissolve it evenly, then spray it on the NdFeB magnetic powder under stirring, then add a binder, a functional resin, and an additive, continue to stir evenly, and obtain a mixed material;

[0105] S2. The obtained mixture is put into a twin-screw extruder, melt-extruded into a wire at 215±5°C, cooled, and pelletized to obtain an injection-molded rare earth permanent magnet material.

[0106] The raw materials used in the rare earth permanent magnet materials of Examples 1-9 and Comparative Examples 1-14 are summarized in Table 1, wherein the binder ratio is the ratio of the added weight of the binder to the added weight of the NdFeB magnetic powder, and the functional resin ratio is the ratio of the added weight of the functional resin to the total weight of the NdFeB magnetic powder and the binder.

[0107] Table 1 Raw materials of rare earth permanent magnet materials of Examples 1-9 and Comparative Examples 1-14

[0108]

[0109] Test Example 1

[0110] The rare earth permanent magnet materials prepared in Examples 1-9 and Comparative Examples 1-14 were made into standard samples, the size of which was a cylinder of Φ10×10, and then the remanence (Br) and the maximum magnetic energy product (BH) were tested. max .

[0111] Test Example 2

[0112] The rare earth permanent magnet materials prepared in Examples 1-9 and Comparative Examples 1-14 were sampled into standard specimens, and the tensile strength and impact strength of the materials were tested using a universal material testing machine and an impact testing machine, respectively. The test standard for tensile strength was GB / T 1040, and the test standard for impact strength was GB / T1843.

[0113] Test Example 3

[0114] The melting index of the rare earth permanent magnet materials prepared in Examples 1-9 and Comparative Examples 1-14 was tested using a melt index meter. During the test, the test conditions for the rare earth permanent magnet materials whose binder was PA6 were 270°C×10kg, and the test conditions for the rare earth permanent magnet materials whose binder was PA12 were 270°C×5kg. The test standard was GB / T 3682.

[0115] Test Example 4

[0116] The rare earth permanent magnetic materials prepared in Examples 1-9 and Comparative Examples 1-14 were made into magnetic rings with a size of Φ8.1×Φ2×3, and environmental tests were conducted under the following experimental conditions: (1) Constant temperature and humidity test conditions: the product was stored at 80±2°C and a relative humidity of 90%-95% for 100 hours, and the product was observed to be rusted after the constant temperature and humidity test; (2) Salt spray test conditions: the product was stored at 35°C and 5% sodium chloride salt spray for 38 hours, and the product was observed to be rusted after the salt spray test. The above test results are summarized in Table 2.

[0117] Table 2 Test results of rare earth permanent magnet materials performance of Examples 1-9 and Comparative Examples 1-14

[0118]

[0119]

[0120] Analyzing from the above results:

[0121] (1) Compared with Comparative Example 1, Example 2 with Comparative Example 2, Example 3 with Comparative Example 3, Example 4 with Comparative Example 4, Example 5 with Comparative Example 5, and Example 6 with Comparative Example 6, the magnetic properties (Br, (BH)) of Example 1, Example 2 with Comparative Example 2, Example 3 with Comparative Example 3, Example 4 with Comparative Example 4, Example 5 with Comparative Example 5, and Example 6 with Comparative Example 6 are different because the amount of magnetic powder added in the formula is unchanged and the functional resin is missing. max ) is almost unchanged compared with the comparative example, and the tensile strength, impact strength, and fluidity (MFR) of the magnetic material are basically unchanged. The products of comparative examples 1-6 show slight rust or corrosion after the constant temperature and humidity test, and rust after the salt spray test, indicating that the addition of the functional resin will not affect the magnetic properties, strength (tensile strength, impact strength) and fluidity of the magnetic powder. In summary, the addition of the functional resin to the formula has basically no effect on the rare earth permanent magnet material, and the rare earth permanent magnet material has good moisture resistance and good anti-corrosion performance after adding the functional resin. The obtained magnet has a good appearance and stable size, which can meet the use requirements of high humidity environment.

[0122] Among them, in Example 1 & Comparative Example 1, Example 2 & Comparative Example 2, and Example 3 & Comparative Example 3, the binder used is PA12, and the products of Comparative Example 1-3 without adding functional resin have slight rust on the surface after the constant temperature and humidity test, and the products of Example 1-3 with adding functional resin have no rust and are in good appearance; after the salt spray test, the products of Comparative Example 1-3 without adding functional resin have rust on the surface after the constant temperature and humidity test; the products of Example 1-3 with adding functional resin have no rust and are in good appearance. The binder used in Example 4 & Comparative Example 4, Example 5 & Comparative Example 5, Example 6 & Comparative Example 6 is PA6. The products of Comparative Examples 4, 5, and 6 without adding functional resin have rust on their surfaces after the constant temperature and humidity test, while the products of Example 4, 5, and 6 with adding functional resin have no rust and are in good appearance. After the salt spray test, the products of Comparative Examples 4, 5, and 6 without adding functional resin have rust on their surfaces after the constant temperature and humidity test; the products of Example 4, 5, and 6 with adding functional resin have no rust and are in good appearance, which shows that the use of PA12 has better moisture resistance than PA6.

[0123] (2) Compared with Comparative Example 7, Example 2 and Example 1 are compared with Comparative Example 11. When the weight of the functional resin added is too much (>3wt%) or the proportion of the functional resin is too high (>3%), the thickness of the surface protective layer formed by the functional resin is very thick. When the amount of magnetic powder added is the same, the melt viscosity of the magnetic powder and the binder is large, thereby reducing the fluidity of the rare earth permanent magnet material, which is not conducive to product injection molding and leads to reduced magnetic properties. Compared with Comparative Example 8, Example 2 and Example 3 are compared with Comparative Example 12. When the weight of the functional resin added is too little (<0.5wt%) or the proportion of the functional resin is too low (<0.6%), the surface protective layer formed by the functional resin is defective, thereby reducing the corrosion resistance of the product. Therefore, in the raw materials of the rare earth permanent magnet material of the present invention, the amount of functional resin is limited to 0.5-3wt%, and the added weight of the functional resin is limited to 0.6%-3% of the total weight of the NdFeB magnetic powder and the binder. Through the above-mentioned limitation, the functional resin forms a protective layer that can better cover the NdFeB magnetic powder and the binder. The protective layer has good toughness and waterproof properties, thereby blocking water vapor from entering the magnet, avoiding rust caused by reaction with the NdFeB magnetic powder, thereby improving the corrosion resistance of the rare earth permanent magnet material.

[0124] (3) Compared with Comparative Example 9, when the weight of coupling agent added in Example 2 is too much (>2wt%), the surface modification layer of magnetic powder is thicker and the binding force between magnetic powder and binder is very large, so that the fluidity of rare earth permanent magnet material is significantly reduced; when the weight of coupling agent added in Example 2 is too little (<0.5wt%), the surface modification of magnetic powder is insufficient, the compatibility between magnetic powder and binder is reduced, the dispersibility of magnetic powder is reduced, and the magnetic properties, strength and fluidity of rare earth permanent magnet material are reduced. Therefore, the amount of coupling agent used in the raw materials of rare earth permanent magnet material of the present invention is limited to 0.5-2wt%.

[0125] (4) Compared with Example 13, Example 2 has a processing temperature that is too high, and the strength and magnetic properties of the material will be reduced. Compared with Example 14, Example 2 has a processing temperature that is too low, and the material uniformity is poor, and the processing performance is not good, resulting in reduced strength and magnetic properties. Therefore, the temperature has a direct relationship with the final performance of the product. In the preparation process of the rare earth permanent magnet material of the present invention, the processing temperature is limited to 220°C to 260°C.

[0126] For those skilled in the art, when understanding the solutions described in the specific embodiments of the present invention, they can refer to the conventional technical manuals in the field. At the same time, for the places where the above-mentioned terms appear, they can make appropriate understandings or adjustments for reference, and deduce the implementation of the same or similar technical solutions without paying any creative work.

[0127] The above embodiments describe only the basic principles, main features and / or advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and the invention content of the specification only describe the principles or specific cases of the present invention. Without departing from the essence of the innovative idea of ​​the present invention, the innovative scheme of the present invention may be subject to various changes and improvements, and these changes and improvements all fall within the scope of protection claimed by the present invention.

Claims

1. An injection molded rare earth permanent magnet material, characterized in that: The raw materials for preparing the permanent magnetic material include, by weight: NdFeB magnetic powder 80-95wt%; 3.5-15wt% binder, wherein the binder is at least one of PA6 and PA12; 0.5-3wt% of functional resin, wherein the functional resin is at least one of PE and PVDC; Coupling agent 0.5-2wt%; Additives 0.2-1.5wt%; In the permanent magnetic material, the functional resin is used as a protective layer to cover the NdFeB magnetic powder and the binder, wherein the added weight of the functional resin accounts for 0.6-3% of the total weight of the NdFeB magnetic powder and the binder.

2. The injection molded rare earth permanent magnet material according to claim 1, characterized in that: The molecular weight of PA6 is 10,000-25,000, the molecular weight of PA12 is 10,000-35,000; the molecular weight of PE is 2,000-200,000, and the molecular weight of PVDC is 1,000-20,000.

3. The injection molded rare earth permanent magnet material according to claim 1, characterized in that: The binder is PA12.

4. The injection molded rare earth permanent magnet material according to claim 1, characterized in that: The raw materials for preparing the permanent magnetic material include, by weight: 87.5-93wt% of NdFeB magnetic powder, 4.5-8wt% of binder, 0.7-2.7wt% of functional resin, 0.5-1.5wt% of coupling agent, and 0.3-1.5wt% of auxiliary agent.

5. The injection molded rare earth permanent magnet material according to any one of claims 1 to 4, characterized in that: The thickness of the protective layer is 5 to 30 μm.

6. The injection molded rare earth permanent magnet material according to any one of claims 1 to 4, characterized in that: The added weight of the binder accounts for 4-10% of the weight of the NdFeB magnetic powder.

7. The injection molded rare earth permanent magnet material according to any one of claims 1 to 4, characterized in that: The added weight of the functional resin accounts for 1.5-2.1% of the total weight of the NdFeB magnetic powder and the binder.

8. A method for preparing the injection-molded rare earth permanent magnetic material according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1, spraying the coupling agent onto the NdFeB magnetic powder under stirring, stirring, then adding the binder, the functional resin, and the auxiliary agent, and continuing to stir evenly to obtain a mixed material; S2. The obtained mixture is put into a twin-screw extruder, melt-extruded into wire at 220° C. to 260° C., cooled, and pelletized to obtain an injection-molded rare earth permanent magnet material.

9. The method for preparing the injection molded rare earth permanent magnetic material according to claim 8, characterized in that: In step S2, the temperature in the twin-screw extruder is controlled at 230°C to 240°C.

10. An injection molded magnet, characterized in that: The magnet is obtained by injection molding the injection-molded rare earth permanent magnet material according to any one of claims 1 to 7 through an injection molding machine.

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