Composite resin coated magnetic powder core and preparation method and application thereof

Abstract

The invention provides a composite resin coated magnetic powder core and a preparation method and application thereof.The composite resin coated magnetic powder core comprises soft magnetic powder and a composite coating layer coating the surface of the soft magnetic powder, and the composite coating layer is prepared by compounding benzoxazine and a thermoplastic-thermosetting combined resin binder; the thermoplastic-thermosetting combined resin binder is prepared by compounding thermoplastic resin and thermosetting resin, the mass ratio of the composite coating layer in the composite resin coated magnetic powder core is 1-10%, and the mass ratio of benzoxazine to the thermoplastic resin to the thermosetting resin is (1-10): (1-10): (1-10). The composite coating layer has good coating uniformity and low porosity, and the composite resin coated magnetic powder core has low eddy current loss and high effective magnetic conductivity. The preparation method of the composite resin coated magnetic powder core has the characteristics of being simple in process, short in time consumption, easy in condition control and environment-friendly.

Description

Technical Field

[0001] The present invention relates to the technical field of soft magnetic materials, in particular to a composite resin-coated magnetic powder core and a preparation method and application thereof. Background Art

[0002] With the development of high-frequency electronic devices, higher requirements are being placed on the performance of soft magnetic materials. Traditional soft magnetic materials such as soft ferrites and metallic soft magnetic materials can no longer meet the requirements in high-frequency and high-power applications. Magnetic powder cores, which are made by mixing magnetic powder, insulating medium, and binder, have high saturation magnetic induction intensity and excellent frequency stability, making them a material of great interest. Eddy current loss is the main cause of power loss in composite materials based on magnetic powders such as metals and alloys. In order to reduce the eddy current loss of magnetic powder cores, the metal and alloy magnetic powders need to be insulated and coated.

[0003] Currently, commonly used coating methods include inorganic coating, organic coating, and organic-inorganic composite coating. Although inorganic coating has high thermal stability, it is prone to problems such as uneven coating or localized shedding. Although organic coating can improve the density of magnetic powder cores, its resin is easily decomposed, resulting in reduced insulation, increased eddy current loss, and prone to aging during long-term use. Although organic-inorganic composite coating combines the advantages of inorganic and organic coatings, it still has problems such as difficulty in preparation, poor process stability, high environmental pollution, and easy rupture of the coating layer.

[0004] Therefore, developing a composite coated magnetic powder core and its coating method that can simultaneously take into account high insulation and good coating uniformity is of great significance for improving the comprehensive performance of the magnetic powder core. Summary of the Invention

[0005] In response to the deficiencies in the prior art, the present invention provides a composite resin-coated magnetic powder core, a preparation method thereof, and an application thereof. The composite resin-coated magnetic powder core has a uniform and dense composite coating layer, and the composite coating layer has good coating uniformity and low porosity, so that the composite resin-coated magnetic powder core has both low eddy current loss and high effective magnetic permeability.

[0006] The specific technical solutions of the present invention are: In a first aspect, the present invention provides a composite resin-coated magnetic powder core, comprising a soft magnetic powder and a composite coating layer coated on the surface of the soft magnetic powder, wherein the composite coating layer is composited by benzoxazine and a thermoplastic-thermosetting combined resin binder, the mass proportion of the composite coating layer in the composite resin-coated magnetic powder core is 1-10%, the thermoplastic-thermosetting combined resin binder is composited by a thermoplastic resin and a thermosetting resin, and the mass ratio of the benzoxazine, the thermoplastic resin and the thermosetting resin in the composite coating layer is (1-10):(1-10):(1-10).

[0007] In one possible embodiment, the benzoxazine is selected from at least one of bisphenol A benzoxazine, bisphenol F benzoxazine, MDA benzoxazine, DCPD benzoxazine, phenolphthalein benzoxazine and cardanol-aniline benzoxazine.

[0008] In one possible implementation, the thermosetting resin is selected from at least one of epoxy resin, polyurethane resin and phenolic resin.

[0009] In one possible implementation, the thermoplastic resin is selected from at least one of polyethylene resin, polypropylene resin and polyvinyl butyral resin.

[0010] In one possible embodiment, the epoxy resin is selected from at least one of bisphenol A epoxy resin, polyphenol glycidyl ether epoxy resin, glycidyl ester epoxy resin and glycidyl amine epoxy resin.

[0011] In one possible embodiment, the soft magnetic powder is selected from at least one of pure carbonyl iron powder, Fe-Si powder, Fe-Si-Al powder, Fe-Si-Cr powder, Fe-Ni powder, Fe-Ni-Mo powder, iron-based amorphous nanocrystalline soft magnetic powder and cobalt-based amorphous nanocrystalline soft magnetic powder.

[0012] In a possible implementation, the mass proportion of the composite coating layer in the composite resin-coated magnetic powder core is 1.2-1.6%.

[0013] In one possible embodiment, the mass ratio of the benzoxazine to the thermoplastic-thermosetting combined resin binder in the composite coating layer is (1-3):(1-5).

[0014] In one possible implementation, the mass ratio of the thermoplastic resin to the thermosetting resin in the thermoplastic-thermosetting combined resin binder is (1-4):1.

[0015] In a second aspect, the present invention provides a method for preparing the composite resin-coated magnetic powder core, comprising the following steps: S1. After cleaning, the soft magnetic powder is added to an organic solution containing benzoxazine and a thermoplastic-thermosetting combined resin binder, mixed uniformly in an ultrasonic water bath to form a mixed solution, and then stirred until the organic solvent is completely evaporated to obtain a composite resin-coated magnetic powder; S2. The composite resin coated magnetic powder in step S1 is pressed and annealed to obtain a composite resin coated magnetic powder core.

[0016] In one possible embodiment, the organic solvent in step S1 is selected from at least one of chloroform, acetone, ethanol, isopropanol, ether, dichloromethane and methyl ethyl ketone.

[0017] In one possible embodiment, the temperature of the ultrasonic water bath in step S1 is 60-100° C. and the time is 20-120 min.

[0018] In a possible implementation manner, the pressure of the press molding in step S2 is 200-2000 MPa, and the temperature of the annealing is 200-1800°C.

[0019] In a third aspect, the present invention further provides use of the composite resin-coated magnetic powder core in an inductor.

[0020] The positive progress effect of the present invention is: The composite resin-coated magnetic powder core provided by the present invention utilizes a composite resin insulation coating formed by benzoxazine and a thermoplastic-thermosetting combined resin binder. This combines the advantages of benzoxazine and a thermoplastic-thermosetting combined resin binder to form a dense insulation coating. After high-temperature annealing, a relatively complete insulating resin layer can still be retained. This can effectively reduce the conductivity between soft magnetic powders, allowing the composite resin-coated magnetic powder core to have both low eddy current loss and dielectric loss, while also improving the effective magnetic permeability of the composite resin-coated magnetic powder core. The preparation method of the composite resin-coated magnetic powder core provided by the present invention has the characteristics of simple process, short time consumption, easily controllable conditions, and environmental friendliness. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 These are SEM images of the composite resin-coated magnetic powder core prepared in Example 1 and the epoxy resin-coated magnetic powder core prepared in Comparative Example 1.

[0022] Figure 2 This is a density comparison chart of the composite resin coated magnetic powder cores prepared in Examples 1-3 and the epoxy resin coated magnetic powder core prepared in Comparative Example 1.

[0023] Figure 3 Graph showing the effective magnetic permeability data of the composite resin coated magnetic powder cores prepared in Examples 1-3 and the epoxy resin coated magnetic powder cores prepared in Comparative Example 1.

[0024] Figure 4 This is a graph showing the core loss data of the composite resin-coated magnetic powder cores prepared in Examples 1-3 and the epoxy resin-coated magnetic powder core prepared in Comparative Example 1.

[0025] Figure 5 Graph showing the Q value of the composite resin-coated magnetic powder cores prepared in Examples 1-3 and the epoxy resin-coated magnetic powder cores prepared in Comparative Example 1.

[0026] Figure 6 Graphs showing thermogravimetric analysis results of the composite resin prepared in Example 2 and the epoxy resin prepared in Comparative Example 1.

[0027] Figure 7 This is the thermogravimetric analysis result of bisphenol A epoxy resin.

[0028] Figure 8 This is the thermogravimetric analysis result of bisphenol A type benzoxazine. DETAILED DESCRIPTION

[0029] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only intended to illustrate the implementation methods and typical parameters of the present invention, and are not intended to limit the parameter ranges described in the present invention. Reasonable variations derived therefrom are still within the scope of protection of the claims of the present invention.

[0030] It should be noted that the endpoints of the ranges and any values disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed herein.

[0031] Unless otherwise defined, all terms, symbols and other scientific terms used herein are intended to have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. In some cases, terms with conventional meanings are defined herein for the purpose of clarification or ease of reference, and such definitions herein should not be construed as indicating significant differences from conventional understandings in the art. The technical methods described or cited herein are generally well understood by those skilled in the art and are adopted by conventional methods. Unless otherwise stated, the use of commercially available kits, reagents and instruments was carried out in accordance with the protocols and parameters given by the manufacturers.

[0032] Explanation of terms Eddy current loss: When the external magnetic field changes with frequency, electromagnetic induction generates induced currents in the material, causing eddy current losses. The higher the frequency of the alternating magnetic field, the greater the eddy currents. The insulating coating can block the eddy currents within the magnetic powder particles, thereby reducing the eddy currents between the magnetic powder particles and thus reducing the eddy current losses of the composite resin-coated magnetic powder core.

[0033] Thermal gravimetry: Thermal gravimetry involves heating a substance, causing it to gradually volatilize and decompose, and measuring the change in weight as the temperature rises. Thermal gravimetry can be used to determine certain physical properties of a substance, such as decomposition temperature and melting point.

[0034] Magnetic permeability is a physical quantity that characterizes the magnetic properties of a magnetic medium. For magnetic powder materials, factors such as the particle size of the soft magnetic powder and the molding density, porosity, internal stress, and dislocation defects of the composite resin-coated magnetic powder core can cause variations in magnetic permeability. Furthermore, the insulating coating and magnetic binder used in composite resin-coated magnetic powder cores introduce non-magnetic phases, resulting in a decrease in magnetic permeability. Therefore, it is necessary to minimize the binder or insulating coating material content while maintaining the insulation performance of the composite resin-coated magnetic powder core.

[0035] The specific technical solutions of the present invention are: In a first aspect, the present invention provides a composite resin-coated magnetic powder core, comprising a soft magnetic powder and a composite coating layer coated on the surface of the soft magnetic powder, wherein the composite coating layer is composited by benzoxazine and a thermoplastic-thermosetting combined resin binder, and the mass proportion of the composite coating layer in the composite resin-coated magnetic powder core is 1-10%, the thermoplastic-thermosetting combined resin binder is composited by a thermoplastic resin and a thermosetting resin, and the mass ratio of the benzoxazine, the thermoplastic resin and the thermosetting resin in the composite coating layer is (1-10):(1-10):(1-10).

[0036] Because high density and low porosity are key factors in obtaining high-performance magnetic powder cores, the composite resin-coated magnetic powder core provided by the present invention adopts an insulating coating layer made of a composite of benzoxazine and a thermoplastic-thermosetting resin binder. By utilizing the characteristic that the benzoxazine resin does not release small molecules during the curing process, the solid-state shrinkage of the insulating coating layer is reduced, the porosity is significantly reduced, and the density is increased, thereby effectively reducing the eddy current loss between the soft magnetic powder particles; in the thermoplastic-thermosetting resin binder, the insulation of the thermosetting resin is stable after curing, and the thermoplastic resin can fill the micro-gaps that may be generated during the curing process of the benzoxazine by virtue of a certain fluidity, further optimizing the insulation coating layer. Continuity; by controlling the mass proportion of the insulating coating in the composite resin-coated magnetic powder core to be 1-10% and the usage ratio of benzoxazine resin to thermoplastic resin and thermosetting resin to be (1-10):(1-10):(1-10), benzoxazine is coordinated with thermoplastic resin and thermosetting resin to form a uniform and dense insulating coating on the surface of the magnetic powder particles, effectively reducing the conductivity between soft magnetic powders, effectively reducing the magnetic resistance and eddy current loss inside the composite resin-coated magnetic powder core, reducing electromagnetic coupling between particles, and thereby improving the effective magnetic permeability of the composite resin-coated magnetic powder core, so that the composite resin-coated magnetic powder core can still maintain stable magnetic properties under high-frequency conditions.

[0037] In one possible embodiment, the benzoxazine is selected from at least one of bisphenol A-type benzoxazine, bisphenol F-type benzoxazine, MDA-type benzoxazine, DCPD-type benzoxazine, phenolphthalein-type benzoxazine, and cardanol-aniline-type benzoxazine. Bisphenol A-type benzoxazine, bisphenol F-type benzoxazine, MDA-type benzoxazine, DCPD-type benzoxazine, phenolphthalein-type benzoxazine, and cardanol-aniline-type benzoxazine have higher glass transition temperatures and better temperature stability, which helps further improve the temperature stability of the composite resin-coated magnetic powder core.

[0038] In one possible embodiment, the thermosetting resin is selected from at least one of epoxy resin, polyurethane resin, and phenolic resin. Epoxy resin, polyurethane resin, and phenolic resin have excellent chemical stability. They maintain the stability of their chemical structures in complex operating environments, whether exposed to acids, bases, organic solvents, or other corrosive media. This chemical stability enables the composite resin-coated magnetic powder core to maintain effective protection of the coating layer for the soft magnetic powder during long-term use. Furthermore, these three thermosetting resins have excellent compatibility with benzoxazine and thermoplastic resins. During the preparation of the composite coating layer, they can be uniformly mixed with benzoxazine and thermoplastic resin to form a stable composite system, ensuring that the various components are evenly dispersed in the coating layer, resulting in a dense structure and uniform performance of the composite coating layer.

[0039] In one possible embodiment, the thermoplastic resin is selected from at least one of polyethylene resin, polypropylene resin, and polyvinyl butyral resin. Polyethylene resin, polypropylene resin, and polyvinyl butyral resin can all be melted and plasticized at relatively low temperatures, have good fluidity, and are easily mixed evenly with benzoxazine, thermosetting resin, and soft magnetic powder. Subsequent molding processes, whether extrusion, injection, or compression molding, can be successfully completed, reducing the complexity and difficulty of the production process. In addition, polyethylene, polypropylene, and polyvinyl butyral resins can all impart a certain degree of flexibility to the composite coating layer, effectively buffering stress when the composite resin-coated magnetic powder core is deformed by external forces or changes in ambient temperature, thereby preventing cracking of the coating layer or damage to the composite resin-coated magnetic powder core structure.

[0040] In one possible embodiment, the epoxy resin is selected from at least one of bisphenol A epoxy resin, polyphenol glycidyl ether epoxy resin, glycidyl ester epoxy resin, and glycidyl amine epoxy resin. Bisphenol A epoxy resin, polyphenol glycidyl ether epoxy resin, glycidyl ester epoxy resin, and glycidyl amine epoxy resin have high viscosity and high temperature resistance, which helps improve the modulus and strength of the composite coating layer.

[0041] In one possible embodiment, the soft magnetic powder is selected from at least one of pure carbonyl iron powder, Fe-Si powder, Fe-Si-Al powder, Fe-Si-Cr powder, Fe-Ni powder, Fe-Ni-Mo powder, iron-based amorphous nanocrystalline soft magnetic powder, and cobalt-based amorphous nanocrystalline soft magnetic powder. Due to surface chemical activity, residual residues from the preparation process, and environmental interactions, these soft magnetic powders contain active groups such as hydroxyl groups on their surfaces, which readily bond with benzoxazine or thermoplastic-thermosetting combined resin binders through hydrogen bonds or chemical bonds.

[0042] In one possible embodiment, the composite coating layer in the composite resin-coated magnetic powder core accounts for 1.2-1.6% by weight. When the composite coating layer accounts for 1.2-1.6% by weight in the composite resin-coated magnetic powder core, the composite resin-coated magnetic powder core, while using less coating material, can still achieve lower core loss than a magnetic powder core using a larger amount of epoxy resin binder as a coating layer, which is more conducive to obtaining a composite resin-coated magnetic powder core with high magnetic permeability and low core loss.

[0043] In one possible embodiment, the mass ratio of benzoxazine to the thermoplastic-thermosetting combined resin binder in the composite coating layer is (1-3):(1-5). When the mass ratio of benzoxazine to the thermoplastic-thermosetting combined resin binder is within the above range, the benzoxazine and thermoplastic-thermosetting combined resin binder have better compatibility, and the coating layer will not fail due to softening at high temperatures. Instead, the benzoxazine can buffer thermal stress at high temperatures through micro-motion of the molecular chains, preventing cracking of the composite coating layer, thereby broadening the operating temperature range of the composite resin-coated magnetic powder core.

[0044] In one possible embodiment, the mass ratio of thermoplastic resin to thermosetting resin in the thermoplastic-thermosetting combined resin binder is (1-4):1. When the mass ratio of thermoplastic resin to thermosetting resin is (1-4):1, the thermoplastic resin acts as a "tough matrix" and can absorb external stresses (such as mechanical stress during the pressing of the composite resin-coated magnetic powder core and thermal expansion and contraction stress during operation) through molecular chain deformation, alleviating the brittle fracture tendency of the thermosetting resin due to excessive rigidity. The thermosetting resin, acting as a "rigid skeleton," can provide basic bonding strength for the combined resin, ensuring that the coating layer can firmly bond to the soft magnetic powder.

[0045] In a second aspect, the present invention provides a method for preparing the composite resin-coated magnetic powder core, comprising the following steps: S1. After cleaning, the soft magnetic powder is added to an organic solution containing benzoxazine and a thermoplastic-thermosetting combined resin binder, mixed uniformly in an ultrasonic water bath to form a mixed solution, and then stirred until the organic solvent is completely evaporated to obtain a composite resin-coated magnetic powder; S2. The composite resin coated magnetic powder in step S1 is pressed and annealed to obtain a composite resin coated magnetic powder core.

[0046] In the preparation method of the composite resin-coated magnetic powder core provided by the present invention, benzoxazine and a thermoplastic-thermosetting combined resin are used as raw materials for the coating layer, and the benzoxazine monomer and the thermoplastic-thermosetting combined resin undergo a self-polymerization reaction on the surface of the soft magnetic powder to form a uniform, dense, stable and insulating composite resin coating layer. The coating process is simple, does not require complex instruments and steps, and the coating conditions are easy to achieve and control. The coating process is also short in time, has the advantages of low energy consumption and environmental friendliness.

[0047] In one possible embodiment, the organic solvent in step S1 is selected from at least one of chloroform, acetone, ethanol, isopropyl alcohol, ether, dichloromethane, and methyl ethyl ketone. Chloroform, acetone, ethanol, isopropyl alcohol, ether, dichloromethane, and methyl ethyl ketone are organic solvents. On the one hand, they can effectively dissolve benzoxazine and the thermoplastic-thermosetting combined resin binder to form a uniform resin solution. During ultrasonic mixing, the soft magnetic powder can be fully infiltrated to ensure that a thin and uniform coating layer is formed on the surface of the magnetic powder. On the other hand, during the coating process, the organic solvent does not chemically react with the soft magnetic powder, benzoxazine, and the thermoplastic-thermosetting combined resin, but only acts as a medium. It can evaporate rapidly during the stirring process, and the dielectric properties and magnetic permeability of the composite resin-coated magnetic powder core will not be affected by residual solvent.

[0048] In one possible embodiment, the ultrasonic water bath in step S1 is maintained at a temperature of 60-100°C for 20-120 minutes. The 60-100°C temperature removes adsorbed water or oxides from the surface of the soft magnetic powder, exposing more polar sites that form hydrogen bonds or chemical bonds with polar groups in the resin (such as hydroxyl groups in epoxy resins and nitrogen-oxygen bonds in benzoxazine), thereby enhancing the binding force between the coating and the magnetic powder. The combined effect of continuous ultrasonication for 20-120 minutes and high temperature allows the resin molecules to fully penetrate the pores and crevices of the magnetic powder particles through thermal motion, thereby enhancing the binding force between the coating and the magnetic powder.

[0049] In one possible embodiment, the pressing pressure in step S2 is 200-2000 MPa, and the annealing temperature is 200-1800°C. The pressure range of 200-2000 MPa can control the air gap volume fraction within the composite resin-coated magnetic powder core to a relatively low range, avoiding a decrease in magnetic permeability caused by an excessively large air gap, while also preventing a surge in eddy current losses caused by an excessively small air gap. Annealing within the temperature range of 200-1800°C promotes the formation of a stable insulating coating layer between benzoxazine and the thermoplastic-thermosetting combined resin on the surface of the magnetic powder, thereby increasing the insulation resistance and reducing eddy current losses of the composite resin-coated magnetic powder core.

[0050] In a third aspect, the present invention further provides use of the composite resin-coated magnetic powder core in an inductor.

[0051] The technical solutions of the present invention are further illustrated below with reference to specific examples and comparative examples. All reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further treatment. The instruments used in the examples are commercially available.

[0052] Example 1

[0053] This embodiment provides a composite resin-coated magnetic powder core, comprising soft magnetic powder and a composite coating layer coated on the surface of the soft magnetic powder. The composite coating layer is made by compounding bisphenol A-type benzoxazine, bisphenol A-type epoxy resin, and polyethylene resin. The mass proportion of the composite coating layer in the composite resin-coated magnetic powder core is 1.2%, and the mass ratio of benzoxazine to bisphenol A-type epoxy resin and polyethylene resin in the composite coating layer is 1:4:1.

[0054] The composite resin coated magnetic powder core of this embodiment is prepared by the following preparation method: M1. Weigh 0.2 g of bisphenol A benzoxazine powder, 0.8 g of bisphenol A epoxy resin, and 0.2 g of polyethylene resin and dissolve them in 80 mL of chloroform to prepare an organic solution; M2, use anhydrous ethanol to clean the soft magnetic powder FeSiBCCr (Fe 73 Si 11 B 11 C3Cr2) surface grease and oxides, then adding 98.8 g of soft magnetic powder to the organic solution in step M1, mixing them evenly under ultrasonic water bath conditions at a water bath temperature of 80°C for 30 min to obtain a mixed solution, and mechanically stirring the mixed solution until the chloroform is completely volatilized to obtain a composite resin-coated magnetic powder; M3. The composite resin-coated magnetic powder in step M2 is pressed under a pressure of 1800 MPa and annealed at 480° C. to obtain a composite resin-coated magnetic powder core.

[0055] Example 2

[0056] This embodiment provides a composite resin-coated magnetic powder core, comprising soft magnetic powder and a composite coating layer coated on the surface of the soft magnetic powder. The composite coating layer is made by compounding bisphenol A-type benzoxazine, bisphenol A-type epoxy resin, and polypropylene resin. The mass proportion of the composite coating layer in the composite resin-coated magnetic powder core is 1.6%, and the mass ratio of benzoxazine to bisphenol A-type epoxy resin and polypropylene resin in the composite coating layer is 3:3:2.

[0057] The composite resin coated magnetic powder core of this embodiment is prepared by the following preparation method: M1. Weigh 0.6 g of bisphenol A benzoxazine powder, 0.6 g of bisphenol A epoxy resin, and 0.4 g of polypropylene resin and dissolve them in 80 mL of chloroform to prepare an organic solution; M2, use anhydrous ethanol to clean the soft magnetic powder FeSiBCCr (Fe 73 Si 11 B 11C3Cr2) surface grease and oxides, then adding 98.4 g of soft magnetic powder to the organic solution in step M1, mixing them evenly under ultrasonic water bath conditions at a water bath temperature of 80°C for 30 min to obtain a mixed solution, and mechanically stirring the mixed solution until the chloroform is completely volatilized to obtain a composite resin-coated magnetic powder; M3. The composite resin-coated magnetic powder in step M2 is pressed under a pressure of 1800 MPa and annealed at 480° C. to obtain a composite resin-coated magnetic powder core.

[0058] Example 3

[0059] This embodiment provides a composite resin-coated magnetic powder core, comprising soft magnetic powder and a composite coating coated on the surface of the soft magnetic powder. The composite coating is made by compounding bisphenol A-type benzoxazine, bisphenol A-type epoxy resin, and polyvinyl butyral resin (PVB). The composite coating accounts for 2% by weight of the composite resin-coated magnetic powder core, and the mass ratio of bisphenol A-type benzoxazine, bisphenol A-type epoxy resin, and PVB in the composite coating is 1:0.5:0.5. It is prepared by the following preparation method: M1. Weigh 1 g of bisphenol A benzoxazine powder, 0.5 g of bisphenol A epoxy resin, and 0.5 g of PVB and dissolve them in 80 mL of chloroform to prepare an organic solution. M2, use anhydrous ethanol to clean the soft magnetic powder FeSiBCCr (Fe 73 Si 11 B 11 C3Cr2) surface grease and oxides, then add 98 g of soft magnetic powder to the organic solution in step M1, mix them evenly under ultrasonic water bath conditions, the water bath temperature is 80 ° C, and the mixing time is 30 min to obtain a mixed solution, and the mixed solution is mechanically stirred until the chloroform is completely volatilized to obtain a composite resin-coated magnetic powder; M3. The composite resin-coated magnetic powder in step M2 is pressed under a pressure of 1800 MPa and annealed at 480° C. to obtain a composite resin-coated magnetic powder core.

[0060] Comparative Example 1 This comparative example provides an epoxy resin-coated magnetic powder core comprising soft magnetic powder and a coating layer coated on the surface of the soft magnetic powder. The coating layer is made of bisphenol A epoxy resin, and the composite coating layer accounts for 2% by weight of the bisphenol A epoxy resin-coated magnetic powder core. The core is prepared by the following method: M1. Weigh 2 g of bisphenol A epoxy resin and dissolve it in 800 mL of chloroform to prepare an organic solution; M2, use anhydrous ethanol to clean the soft magnetic powder FeSiBCCr (Fe 73 Si 11 B11 C3Cr2) surface grease and oxides, etc., then add 98 g of soft magnetic powder to the organic solution in step M1, mix them evenly under ultrasonic water bath conditions, the water bath temperature is 80 ° C, and the mixing time is 30 min to obtain a mixed solution, and the mixed solution is mechanically stirred until the chloroform is completely volatilized to obtain epoxy resin-coated magnetic powder; M3. The epoxy resin-coated magnetic powder in step M2 is pressed under a pressure of 1800 MPa and annealed at 480° C. to obtain an epoxy resin-coated magnetic powder core.

[0061] Example 4

[0062] This embodiment provides a composite resin-coated magnetic powder core, comprising soft magnetic powder and a composite coating layer coated on the surface of the soft magnetic powder. The composite coating layer is made by compounding bisphenol A-type benzoxazine, polyphenol-type glycidyl ether epoxy resin, and polyethylene resin. The mass proportion of the composite coating layer in the composite resin-coated magnetic powder core is 1.2%, and the mass ratio of benzoxazine to polyphenol-type glycidyl ether epoxy resin and polyethylene resin in the composite coating layer is 1:4:1.

[0063] The composite resin coated magnetic powder core of this embodiment is prepared by the following preparation method: M1. Weigh 0.2 g of bisphenol A benzoxazine powder, 0.8 g of polyphenol glycidyl ether epoxy resin, and 0.2 g of polyethylene resin and dissolve them in 80 mL of chloroform to prepare an organic solution; M2, use anhydrous ethanol to clean the soft magnetic powder FeSiBCCr (Fe 73 Si 11 B 11 C3Cr2) surface grease and oxides, then adding 98.8 g of soft magnetic powder to the organic solution in step M1, mixing them evenly under ultrasonic water bath conditions at a water bath temperature of 100°C for 20 min to obtain a mixed solution, and mechanically stirring the mixed solution until the chloroform is completely volatilized to obtain a composite resin-coated magnetic powder; M3. The composite resin-coated magnetic powder in step M2 is pressed under a pressure of 1500 MPa and annealed at 480° C. to obtain a composite resin-coated magnetic powder core.

[0064] Example 5

[0065] This embodiment provides a composite resin-coated magnetic powder core, comprising soft magnetic powder and a composite coating layer coated on the surface of the soft magnetic powder. The composite coating layer is made by compounding bisphenol A-type benzoxazine, glycidyl ester epoxy resin, and polypropylene resin. The mass proportion of the composite coating layer in the composite resin-coated magnetic powder core is 1.6%, and the mass ratio of benzoxazine to glycidyl ester epoxy resin and polypropylene resin in the composite coating layer is 3:3:2.

[0066] The composite resin coated magnetic powder core of this embodiment is prepared by the following preparation method: M1. Weigh 0.6 g of bisphenol A benzoxazine powder, 0.6 g of glycidyl ester epoxy resin, and 0.4 g of polypropylene resin and dissolve them in 80 mL of chloroform to prepare an organic solution; M2, use anhydrous ethanol to clean the soft magnetic powder FeSiBCCr (Fe 73 Si 11 B 11 C3Cr2) surface grease and oxides, then adding 98.4 g of soft magnetic powder to the organic solution in step M1, mixing them evenly under ultrasonic water bath conditions at a water bath temperature of 90°C for 60 min to obtain a mixed solution, and mechanically stirring the mixed solution until the chloroform is completely volatilized to obtain composite resin-coated magnetic powder; M3. The composite resin-coated magnetic powder in step M2 is pressed under a pressure of 2000 MPa and annealed at 1000° C. to obtain a composite resin-coated magnetic powder core.

[0067] Example 6

[0068] This embodiment provides a composite resin-coated magnetic powder core, comprising soft magnetic powder and a composite coating coated on the surface of the soft magnetic powder. The composite coating is made by compounding bisphenol A-type benzoxazine with glycidylamine-type epoxy resin and polyvinyl butyral resin (PVB). The composite coating accounts for 2% by weight of the composite resin-coated magnetic powder core, and the mass ratio of bisphenol A-type benzoxazine to glycidylamine-type epoxy resin and polyvinyl butyral resin in the composite coating is 1:0.5:0.5. It is prepared by the following preparation method: M1. Weigh 1 g of bisphenol A benzoxazine powder, 0.5 g of glycidylamine epoxy resin, and 0.5 g of PVB and dissolve them in 80 mL of chloroform to prepare an organic solution. M2, use anhydrous ethanol to clean the soft magnetic powder FeSiBCCr (Fe 73 Si 11 B 11 C3Cr2) surface grease and oxides, then adding 98 g of soft magnetic powder to the organic solution in step M1, mixing them evenly under ultrasonic water bath conditions at a water bath temperature of 60°C for 120 min to obtain a mixed solution, and mechanically stirring the mixed solution until the chloroform is completely volatilized to obtain composite resin-coated magnetic powder; M3. The composite resin-coated magnetic powder in step M2 is pressed under a pressure of 800 MPa and annealed at 480° C. to obtain a composite resin-coated magnetic powder core.

[0069] Example 7

[0070] This embodiment provides a composite resin-coated magnetic powder core, comprising a soft magnetic powder and a composite coating coated on the surface of the soft magnetic powder. The composite coating is made by compounding bisphenol F-type benzoxazine with a polyphenol glycidyl ether epoxy resin and a polyethylene resin. The composite coating accounts for 2.2% by weight of the composite resin-coated magnetic powder core, and the mass ratio of bisphenol F-type benzoxazine to the polyphenol glycidyl ether epoxy resin and the polyethylene resin in the composite coating is 5:4:2. It is prepared by the following preparation method: M1. Weigh 1 g of bisphenol F-type benzoxazine, 0.8 g of polyphenol glycidyl ether epoxy resin, and 0.4 g of polyethylene resin and dissolve them in 80 mL of chloroform to prepare an organic solution; M2, use anhydrous ethanol to clean the soft magnetic powder FeSiBCCr (Fe 73 Si 11 B 11 C3Cr2) surface grease and oxides, etc., then 97.8 g of soft magnetic powder was added to the organic solution in step M1, and mixed evenly under ultrasonic water bath conditions at a water bath temperature of 80°C for 30 min to obtain a mixed solution, which was mechanically stirred until the chloroform was completely volatilized to obtain a composite resin-coated magnetic powder; M3. The composite resin-coated magnetic powder in step M2 is pressed under a pressure of 1800 MPa and annealed at 480° C. to obtain a composite resin-coated magnetic powder core.

[0071] Example 8 This embodiment provides a composite resin-coated magnetic powder core, which differs from Example 1 in that bisphenol F benzoxazine is used instead of bisphenol A benzoxazine, PVB is used instead of polyethylene resin, and phenolic resin is used instead of bisphenol A epoxy resin. All other aspects are the same as Example 1.

[0072] Example 9

[0073] This embodiment provides a composite resin-coated magnetic powder core, which differs from Example 2 in that bisphenol A benzoxazine is replaced by bisphenol F benzoxazine and polypropylene resin is replaced by PVB. Other aspects are the same as Example 2.

[0074] Example 10

[0075] This embodiment provides a composite resin-coated magnetic powder core, which differs from the third embodiment in that bisphenol A benzoxazine is replaced by bisphenol F benzoxazine and PVB is replaced by polypropylene resin. Other aspects are the same as the third embodiment.

[0076] Example 11

[0077] This embodiment provides a composite resin-coated magnetic powder core, which differs from the first embodiment in that bisphenol A-type benzoxazine is replaced by MDA-type benzoxazine. Other aspects are the same as the first embodiment.

[0078] Example 12

[0079] This embodiment provides a composite resin coated magnetic powder core, which differs from Example 2 in that MDA benzoxazine is used instead of bisphenol A benzoxazine, and phenolic resin is used instead of bisphenol A epoxy resin. Other aspects are the same as Example 2.

[0080] Example 13

[0081] This embodiment provides a composite resin-coated magnetic powder core, which differs from the embodiment 3 in that MDA-type benzoxazine is used instead of bisphenol A-type benzoxazine. Other aspects are the same as those of the embodiment 3.

[0082] Example 14

[0083] This embodiment provides a composite resin-coated magnetic powder core, which differs from Embodiment 2 in that MDA-type benzoxazine is used instead of bisphenol A-type benzoxazine. Other aspects are the same as those of Embodiment 2.

[0084] Example 15

[0085] This embodiment provides a composite resin coated magnetic powder core, which differs from Example 3 in that MDA benzoxazine is used instead of bisphenol A benzoxazine, and phenolic resin is used instead of bisphenol A epoxy resin. Other aspects are the same as Example 3.

[0086] Example 16

[0087] This embodiment provides a composite resin-coated magnetic powder core, which differs from the first embodiment in that bisphenol A-type benzoxazine is replaced by DCPD-type benzoxazine. Other aspects are the same as the first embodiment.

[0088] Example 17

[0089] This embodiment provides a composite resin-coated magnetic powder core, which differs from Example 2 in that bisphenol A-type benzoxazine is replaced by DCPD-type benzoxazine, and is otherwise the same as Example 2.

[0090] Example 18

[0091] This embodiment provides a composite resin-coated magnetic powder core, which differs from the embodiment 3 in that bisphenol A-type benzoxazine is replaced by DCPD-type benzoxazine, and is otherwise the same as the embodiment 3.

[0092] Example 19

[0093] This embodiment provides a composite resin coated magnetic powder core, which differs from the first embodiment in that bisphenol A benzoxazine is replaced by phenolphthalein benzoxazine and bisphenol A epoxy resin is replaced by phenolic resin. Other aspects are the same as the first embodiment.

[0094] Example 20

[0095] This embodiment provides a composite resin coated magnetic powder core, which differs from Example 2 in that bisphenol A benzoxazine is replaced by phenolphthalein benzoxazine, and bisphenol A epoxy resin is replaced by phenolic resin. Other aspects are the same as Example 2.

[0096] Example 21

[0097] This embodiment provides a composite resin coated magnetic powder core, which differs from the third embodiment in that bisphenol A benzoxazine is replaced by phenolphthalein benzoxazine and bisphenol A epoxy resin is replaced by phenolic resin. Other aspects are the same as the third embodiment.

[0098] Example 22

[0099] This embodiment provides a composite resin-coated magnetic powder core, which differs from Embodiment 1 in that bisphenol A-type benzoxazine is replaced by cardanol-aniline-type benzoxazine, and is otherwise the same as Embodiment 1.

[0100] Example 23

[0101] This embodiment provides a composite resin-coated magnetic powder core, which differs from Example 2 in that bisphenol A-type benzoxazine is replaced by cardanol-aniline-type benzoxazine, and is otherwise the same as Example 2.

[0102] Example 24

[0103] This embodiment provides a composite resin-coated magnetic powder core, which differs from Example 3 in that bisphenol A-type benzoxazine is replaced by cardanol-aniline-type benzoxazine, and is otherwise the same as Example 3.

[0104] The composite resin coated magnetic powder cores prepared in Examples 1-24 and the epoxy resin coated magnetic powder core prepared in Comparative Example 1 were characterized and tested, and the results are as follows: Figure 1 These are SEM images of the composite resin-coated magnetic powder core prepared in Example 1 and the epoxy resin-coated magnetic powder core prepared in Comparative Example 1. Figure 1 (a) is a SEM image of the surface of the composite resin-coated magnetic powder core prepared in Example 1. It can be seen that there is no excess resin agglomeration between the magnetic powders of the composite resin-coated magnetic powder core prepared in Example 1. Figure 1(b) is an SEM image of the surface of the epoxy resin coated magnetic powder core prepared in Comparative Example 1. The area marked with a red dotted line in the figure is the resin agglomeration area. The agglomerated resin will increase the hysteresis effect of the epoxy resin coated magnetic powder core, thereby increasing the hysteresis loss and reducing the magnetic permeability. Figure 1 (c) is a partial enlarged view of (a), in which it can be seen that tiny resin particles attached to the magnetic powder play a role of bonding and insulation; Figure 1 (d) is a partial enlargement of Figure (b). It can be seen that the pores between the magnetic powders are occupied by resin and the surface of the magnetic powders is rough and uneven. These signs will cause the soft magnetic properties to deteriorate.

[0105] Figure 2 The following is a density comparison chart of the composite resin-coated magnetic powder cores prepared in Examples 1-3 and the epoxy resin-coated magnetic powder core prepared in Comparative Example 1. As can be seen from the chart, the density of the composite resin-coated magnetic powder cores prepared in Examples 1-3 is higher than that of the epoxy resin-coated magnetic powder core in Comparative Example 1, and the density of the magnetic powder core increases as the overall amount of the composite coating layer decreases.

[0106] Figure 3 The following is a graph showing the effective magnetic permeability data for the composite resin-coated magnetic powder cores prepared in Examples 1-3 and the epoxy resin-coated magnetic powder core prepared in Comparative Example 1. As can be seen from the graph, the effective magnetic permeabilities of the composite resin-coated magnetic powder cores prepared in Examples 1-3 are significantly higher than those of the epoxy resin-coated magnetic powder core prepared in Comparative Example 1, with the composite resin-coated magnetic powder core prepared in Example 2 having the highest effective magnetic permeability.

[0107] Figure 4 The core loss data of the composite resin coated magnetic powder cores prepared in Examples 1-3 and the epoxy resin coated magnetic powder core prepared in Comparative Example 1 are shown. As can be seen from the figure, the core losses of the composite resin coated magnetic powder cores prepared in Examples 1 and 2 are significantly lower than the core loss of the epoxy resin coated magnetic powder core prepared in Comparative Example 1. In other words, the composite resin coated magnetic powder core provided by the present invention, while using less coating layer material, also obtains a composite resin coated magnetic powder core with lower core loss than the composite resin coated magnetic powder core using more coating layers in Comparative Example 1. The core loss of the composite resin coated magnetic powder core prepared in Example 3 is slightly higher than that of the epoxy resin coated magnetic powder core in Comparative Example 1 at low frequencies, but is comparable to that of the epoxy resin coated magnetic powder core in Comparative Example 1 at high frequencies.

[0108] Figure 5The figure shows the quality factor Q value data of the composite resin-coated magnetic powder cores prepared in Examples 1-3 and the epoxy resin-coated magnetic powder core prepared in Comparative Example 1. As can be seen from the figure, the Q value of the composite resin-coated magnetic powder core prepared in Example 1 is significantly higher than that of the epoxy resin-coated magnetic powder core prepared in Comparative Example 1, while the quality factor Q values of the composite resin-coated magnetic powder cores prepared in Examples 2 and 3 are comparable to the Q value of the epoxy resin-coated magnetic powder core prepared in Comparative Example 1.

[0109] Figure 6 The thermogravimetric analysis results of the composite resin prepared in Example 2 and the epoxy resin prepared in Comparative Example 1 are shown in FIG. Figure 7 This is the thermogravimetric analysis result of bisphenol A epoxy resin. Figure 8 The figure shows the thermogravimetric analysis results of bisphenol A type benzoxazine monomer. Figure 6 、 Figure 7 and Figure 8 It can be seen that the epoxy resin loses weight most rapidly at 263°C, and the bisphenol A-type benzoxazine loses weight most rapidly at 485°C. However, the composite resin prepared in Example 2 loses weight slowly at 360°C, and its retention rate at temperatures exceeding 500°C is higher than that of the epoxy resin-coated magnetic powder core in Comparative Example 1. This indicates that the composite resin provided by the present invention has higher thermal stability.

[0110] Table 1 shows the coating materials and soft magnetic properties of the composite resin coated magnetic powder cores prepared in Examples 1-24. The data in the table show that the magnetic permeability of the composite resin coated magnetic powder cores prepared in Examples 1-24 is between 30.2 and 43.1, and the density is between 4.59 and 5.33 g / cm 3 The core loss at 50 mT and 100 kHz is between 101.29-210.3 mW / cm 3 between; .

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some or all of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite resin coated magnetic powder core, characterized in that: The invention comprises a soft magnetic powder and a composite coating layer coated on the surface of the soft magnetic powder, wherein the composite coating layer is composited by benzoxazine and a thermoplastic-thermosetting combined resin binder, the mass proportion of the composite coating layer in the composite resin-coated magnetic powder core is 1-10%, the thermoplastic-thermosetting combined resin binder is composited by a thermoplastic resin and a thermosetting resin, and the mass ratio of the benzoxazine, the thermoplastic resin and the thermosetting resin in the composite coating layer is (1-10):(1-10):(1-10).

2. The composite resin coated magnetic powder core according to claim 1, characterized in that: The benzoxazine is at least one selected from bisphenol A benzoxazine, bisphenol F benzoxazine, MDA benzoxazine, DCPD benzoxazine, phenolphthalein benzoxazine and cardanol-aniline benzoxazine.

3. The composite resin coated magnetic powder core according to claim 1, characterized in that: The thermosetting resin is selected from at least one of epoxy resin, polyurethane resin and phenolic resin.

4. The composite resin coated magnetic powder core according to claim 1, characterized in that: The thermoplastic resin is at least one selected from polyethylene resin, polypropylene resin and polyvinyl butyral resin.

5. The composite resin coated magnetic powder core according to claim 3, characterized in that: The epoxy resin is selected from at least one of bisphenol A epoxy resin, polyphenol glycidyl ether epoxy resin, glycidyl ester epoxy resin and glycidyl amine epoxy resin.

6. The composite resin coated magnetic powder core according to claim 1, characterized in that: The soft magnetic powder is selected from at least one of carbonyl iron powder, Fe-Si powder, Fe-Si-Al powder, Fe-Si-Cr powder, Fe-Ni powder, Fe-Ni-Mo powder, iron-based amorphous nanocrystalline soft magnetic powder and cobalt-based amorphous nanocrystalline soft magnetic powder.

7. The composite resin coated magnetic powder core according to claim 1, characterized in that: The mass proportion of the composite coating layer in the composite resin-coated magnetic powder core is 1.2-1.6%.

8. The composite resin coated magnetic powder core according to claim 1, characterized in that: The mass ratio of the benzoxazine to the thermoplastic-thermosetting combined resin binder in the composite coating layer is (1-3):(1-5).

9. The composite resin coated magnetic powder core according to claim 1, characterized in that: The mass ratio of the thermoplastic resin to the thermosetting resin in the thermoplastic-thermosetting combined resin binder is (1-4):

1.

10. A method for preparing a composite resin-coated magnetic powder core according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1. After cleaning, the soft magnetic powder is added to an organic solution containing benzoxazine and a thermoplastic-thermosetting combined resin binder, mixed uniformly in an ultrasonic water bath to form a mixed solution, and then stirred until the organic solvent is completely evaporated to obtain a composite resin-coated magnetic powder; S2. The composite resin coated magnetic powder in step S1 is pressed and annealed to obtain a composite resin coated magnetic powder core.

11. The method for preparing a composite resin coated magnetic powder core according to claim 10, wherein: The organic solvent in step S1 is selected from at least one of chloroform, acetone, ethanol, isopropanol, ether, dichloromethane and methyl ethyl ketone.

12. The method for preparing a composite resin coated magnetic powder core according to claim 10, wherein: The temperature of the ultrasonic water bath in step S1 is 60-100° C. and the time is 20-120 min.

13. The method for preparing a composite resin coated magnetic powder core according to claim 10, wherein: The pressure of the press molding in step S2 is 200-2000 MPa, and the temperature of the annealing is 200-1800°C.

14. Use of the composite resin coated magnetic powder core according to any one of claims 1 to 9 in an inductor.

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