A composite resin-coated magnetic powder core, its preparation method and application

Abstract

This invention provides a composite resin-coated magnetic powder core, its preparation method, and its application. The composite resin-coated magnetic powder core includes soft magnetic powder and a composite coating layer covering the surface of the soft magnetic powder. The composite coating layer is prepared by combining benzoxazine with a thermoplastic-thermosetting resin binder. The thermoplastic-thermosetting resin binder is prepared by combining thermoplastic resin and thermosetting resin. The mass percentage of the composite coating layer in the composite resin-coated magnetic powder core is 1-10%, and the mass ratio of benzoxazine, thermoplastic resin, and thermosetting resin is (1-10):(1-10):(1-10). The composite coating layer has good coating uniformity and low porosity. The composite resin-coated magnetic powder core also has low eddy current loss and high effective permeability. The preparation method of the composite resin-coated magnetic powder core is simple, time-saving, easy to control, and environmentally friendly.

Description

Technical Field

[0001] This invention relates to the field of soft magnetic materials technology, and more specifically, to a composite resin-coated magnetic powder core, its preparation method, and its application. Background Technology

[0002] With the increasing frequency of electronic devices, higher demands are being placed on the performance of soft magnetic materials. Traditional soft magnetic materials, such as soft magnetic ferrites and metallic soft magnetic materials, can no longer meet the requirements of high-frequency, high-power applications. Magnetic powder cores, prepared by mixing magnetic powder, insulating media, and binders, have become a material of great interest due to their high saturation magnetic induction and excellent frequency stability. Eddy current loss is the main cause of power loss in composite materials with magnetic powders such as metals and alloys as the matrix. To reduce eddy current loss in magnetic powder cores, it is necessary to insulate and coat the magnetic powders such as metals and alloys.

[0003] Currently, commonly used coating methods include inorganic coating, organic coating, and organic-inorganic composite coating. While inorganic coating offers high thermal stability, it is prone to uneven coating or localized detachment. Organic coating, although improving the density of the magnetic powder core, suffers from resin decomposition, leading to decreased insulation, increased eddy current losses, and aging issues during long-term use. Organic-inorganic composite coating, while combining the advantages of both inorganic and organic coatings, still presents challenges such as difficult preparation, poor process stability, high environmental pollution, and susceptibility to coating layer cracking.

[0004] Therefore, developing a composite coated magnetic powder core that can simultaneously achieve high insulation and good coating uniformity, as well as its coating method, is of great significance for improving the overall performance of magnetic powder cores. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a composite resin-coated magnetic powder core, its preparation method, and its application. The composite resin-coated magnetic powder core has a uniform and dense composite coating layer with good coating uniformity and low porosity, enabling the composite resin-coated magnetic powder core to possess both low eddy current loss and high effective permeability.

[0006] The specific technical solution of this invention is as follows:

[0007] In a first aspect, the present invention 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 prepared by combining benzoxazine with a thermoplastic-thermosetting resin binder. The mass percentage of the composite coating layer in the composite resin-coated magnetic powder core is 1-10%. The thermoplastic-thermosetting resin binder is prepared by combining thermoplastic resin and thermosetting resin. The mass ratio of benzoxazine, thermoplastic resin and thermosetting resin in the composite coating layer is (1-10):(1-10):(1-10).

[0008] In one possible implementation, the benzoxazine is selected from at least one of bisphenol A benzoxazine, bisphenol F benzoxazine, MDA benzoxazine, DCPD benzoxazine, phenolphthalein benzoxazine, and cashew phenol-aniline benzoxazine.

[0009] In one possible implementation, the thermosetting resin is selected from at least one of epoxy resin, polyurethane resin, and phenolic resin.

[0010] In one possible implementation, the thermoplastic resin is selected from at least one of polyethylene resin, polypropylene resin, and polyvinyl butyral resin.

[0011] In one possible implementation, the epoxy resin is selected from at least one of bisphenol A type epoxy resin, polyphenol type glycidyl ether epoxy resin, glycidyl ester type epoxy resin, and glycidyl amine type epoxy resin.

[0012] In one possible implementation, 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.

[0013] In one possible implementation, the mass percentage of the composite coating layer in the composite resin-coated magnetic powder core is 1.2-1.6%.

[0014] In one possible implementation, the mass ratio of the benzoxazine to the thermoplastic-thermosetting resin adhesive in the composite coating layer is (1-3):(1-5).

[0015] In one possible implementation, the mass ratio of the thermoplastic resin to the thermosetting resin in the thermoplastic-thermosetting combined resin adhesive is (1-4):1.

[0016] Secondly, the present invention provides a method for preparing the above-mentioned composite resin-coated magnetic powder core, comprising the following steps:

[0017] S1. After cleaning, the soft magnetic powder is added to an organic solution containing benzoxazine and thermoplastic-thermosetting resin binder. The mixture is stirred evenly in an ultrasonic water bath to form a mixture. The mixture is then stirred until all the organic solvent evaporates to obtain composite resin-coated magnetic powder.

[0018] S2. The composite resin-coated magnetic powder described in step S1 is pressed and annealed to obtain a composite resin-coated magnetic powder core.

[0019] In one possible implementation, the organic solvent in step S1 is selected from at least one of chloroform, acetone, ethanol, isopropanol, diethyl ether, dichloromethane, and methyl ethyl ketone.

[0020] In one possible implementation, the temperature of the ultrasonic water bath in step S1 is 60-100 ℃ and the time is 20-120 min.

[0021] In one possible implementation, the pressing pressure in step S2 is 200-2000 MPa, and the annealing temperature is 200-1800 °C.

[0022] Thirdly, the present invention also provides the application of the above-mentioned composite resin-coated magnetic powder core in inductors.

[0023] The positive and progressive effects of this invention are as follows:

[0024] The composite resin-coated magnetic powder core provided by this invention employs a composite resin insulating coating layer formed by benzoxazine and a thermoplastic-thermosetting resin binder. This combines the advantages of both benzoxazine and thermoplastic-thermosetting resin binders, forming a dense insulating coating layer that retains a relatively intact insulating resin layer even after high-temperature annealing. This effectively reduces the conductivity between soft magnetic powders, enabling the composite resin-coated magnetic powder core to exhibit both low eddy current loss and dielectric loss, while also improving its effective permeability. The preparation method of the composite resin-coated magnetic powder core provided by this invention is characterized by its simple process, short preparation time, easily controllable conditions, and environmental friendliness. Attached Figure Description

[0025] Figure 1 The images show 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.

[0026] 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 cores prepared in Comparative Example 1.

[0027] Figure 3 The graph shows 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.

[0028] Figure 4 The graph shows the core loss 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.

[0029] Figure 5 The graph shows the Q-value 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.

[0030] Figure 6 The thermogravimetric analysis results are shown for the composite resin prepared in Example 2 and the epoxy resin prepared in Comparative Example 1.

[0031] Figure 7 The graph shows the thermogravimetric analysis results of bisphenol A type epoxy resin.

[0032] Figure 8 The graph shows the thermogravimetric analysis results of bisphenol A type benzoxazine. Detailed Implementation

[0033] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only used to illustrate the implementation methods and typical parameters of the present invention, and are not intended to limit the parameter range described in the present invention. Reasonable variations derived therefrom are still within the protection scope of the claims of the present invention.

[0034] It should be noted that the endpoints and any values ​​of the ranges 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 endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0035] Unless otherwise defined, all terms, symbols, and other scientific terms used herein are intended to have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In some instances, terms having a conventional meaning are defined herein for clarification or ease of reference, and such definitions should not be construed as indicating a significant difference from conventional understanding in the art. The technical methods described or referenced herein are generally well understood by those skilled in the art and employed by conventional methods. Unless otherwise stated, the use of commercially available kits, reagents, and instruments shall be performed according to the manufacturer's instructions and parameters.

[0036] Terminology Explanation

[0037] Eddy current loss: When the external magnetic field changes with frequency, an induced current will be generated in the material due to electromagnetic induction, resulting in eddy current loss. The higher the frequency of the alternating magnetic field, the greater the eddy current. The insulating coating can block the eddy current inside the magnetic powder particles, thereby reducing the eddy current between the magnetic powder particles and thus reducing the eddy current loss of the composite resin-coated magnetic powder core.

[0038] Thermogravimetric analysis (TGA): Thermogravimetric analysis measures the change in weight of a substance as the temperature increases, by heating the substance and causing it to gradually evaporate and decompose. TGA can be used to determine certain physical properties of substances, such as decomposition temperature and melting point.

[0039] Magnetic permeability is a physical quantity characterizing the magnetism 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 changes in permeability. In addition, the use of insulating coatings and magnetic binders in the composite resin-coated magnetic powder core can introduce non-magnetic phases, leading to a decrease in permeability. Therefore, it is necessary to minimize the content of binders or insulating coating materials while ensuring the insulating effect of the composite resin-coated magnetic powder core.

[0040] The specific technical solution of this invention is as follows:

[0041] In a first aspect, the present invention 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 prepared by combining benzoxazine with a thermoplastic-thermosetting resin binder. The mass percentage of the composite coating layer in the composite resin-coated magnetic powder core is 1-10%. The thermoplastic-thermosetting resin binder is prepared by combining thermoplastic resin and thermosetting resin. 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).

[0042] High density and low porosity are key factors for obtaining high-performance magnetic powder cores. The composite resin-coated magnetic powder core provided by this invention utilizes an insulating coating layer made of benzoxazine and a thermoplastic-thermosetting combined resin binder. Taking advantage of the characteristic that benzoxazine resin does not release small molecules during curing, the solid-state shrinkage of the insulating coating layer is reduced, porosity is significantly decreased, and density is increased, thereby effectively reducing eddy current losses between soft magnetic powder particles. In the thermoplastic-thermosetting combined resin binder, the thermosetting resin has stable insulation after curing, while the thermoplastic resin, with its certain fluidity, can fill the micro-gaps that may be generated during the curing process of benzoxazine, further optimizing the insulating coating layer. Continuity; by controlling the mass ratio of the insulating coating layer in the composite resin-coated magnetic powder core to 1-10% and the ratio of benzoxazine resin to thermoplastic resin and thermosetting resin to (1-10):(1-10):(1-10), benzoxazine, thermoplastic resin and thermosetting resin are coordinated to form a uniform and dense insulating coating layer on the surface of 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 the electromagnetic coupling between particles, and thus improving the effective 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.

[0043] In one possible implementation, 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 cashew phenol-aniline-type benzoxazine. Bisphenol A-type benzoxazine, bisphenol F-type benzoxazine, MDA-type benzoxazine, DCPD-type benzoxazine, phenolphthalein-type benzoxazine, and cashew phenol-aniline-type benzoxazine have higher glass transition temperatures and better temperature stability, which is beneficial for further improving the temperature stability of the composite resin-coated magnetic powder core.

[0044] In one possible implementation, the thermosetting resin is selected from at least one of epoxy resin, polyurethane resin, and phenolic resin. Epoxy resin, polyurethane resin, and phenolic resin possess excellent chemical stability. In complex operating environments, whether exposed to acids, alkalis, organic solvents, or other corrosive media, they maintain the stability of their chemical structure. This chemical stability allows the composite resin-coated magnetic powder core to maintain effective protection of the soft magnetic powder during long-term use. Furthermore, these three thermosetting resins have good compatibility with benzoxazine and thermoplastic resins. During the preparation of the composite coating layer, they can be uniformly mixed with benzoxazine and thermoplastic resins to form a stable composite system, ensuring uniform dispersion of each component in the coating layer, resulting in a dense and uniform composite coating layer structure.

[0045] In one possible implementation, 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 melt and plasticize at relatively low temperatures, exhibiting good fluidity and easy uniform mixing with benzoxazine, thermosetting resin, and soft magnetic powder. Subsequent processing, whether using extrusion, injection molding, or compression molding, can be successfully completed, reducing the complexity and difficulty of the production process. Furthermore, polyethylene, polypropylene, and polyvinyl butyral resins can impart a certain degree of flexibility to the composite coating layer, effectively buffering stress when the composite resin-coated magnetic powder core is subjected to external forces or deformation due to changes in ambient temperature, thus preventing cracking of the coating layer or damage to the composite resin-coated magnetic powder core structure.

[0046] In one possible embodiment, the epoxy resin is selected from at least one of bisphenol A type epoxy resin, polyphenol type glycidyl ether epoxy resin, glycidyl ester type epoxy resin, and glycidylamine type epoxy resin. Bisphenol A type epoxy resin, polyphenol type glycidyl ether epoxy resin, glycidyl ester type epoxy resin, and glycidylamine type epoxy resin have the characteristics of high viscosity and high temperature resistance, which is beneficial for improving the modulus and strength of the composite coating layer.

[0047] In one possible implementation, 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, process residues, and environmental interactions, the aforementioned soft magnetic powders possess active groups such as hydroxyl groups on their surface, making them readily bonded to benzoxazine or thermoplastic-thermosetting resin binders via hydrogen bonds or chemical bonds.

[0048] In one possible implementation, the mass percentage of the composite coating layer in the composite resin-coated magnetic powder core is 1.2-1.6%. When the mass percentage of the composite coating layer in the composite resin-coated magnetic powder core is 1.2-1.6%, the composite resin-coated magnetic powder core can achieve lower core loss than the magnetic powder core using more epoxy resin binder as the coating layer, even with less coating material. This is more conducive to obtaining a composite resin-coated magnetic powder core with high permeability and low core loss.

[0049] In one possible implementation, the mass ratio of benzoxazine to thermoplastic-thermosetting resin binder in the composite coating layer is (1-3):(1-5). When the mass ratio of benzoxazine to thermoplastic-thermosetting resin binder is within the above range, the compatibility between benzoxazine and thermoplastic-thermosetting resin binder is better, and the coating layer will not fail due to softening at high temperatures. On the contrary, the micro-movement of molecular chains can buffer the thermal stress at high temperatures, avoid cracking of the composite coating layer, and help to broaden the working temperature range of the composite resin-coated magnetic powder core.

[0050] In one possible implementation, 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, as a "tough matrix," can absorb external stress (such as mechanical stress during the pressing of the composite resin-coated magnetic powder core, and thermal expansion and contraction stress during operation) through the deformation of its molecular chains, thus alleviating the tendency of the thermosetting resin to crack due to excessive rigidity. Meanwhile, the thermosetting resin, as a "rigid skeleton," can provide basic bonding strength for the combined resin, ensuring that the coating layer can firmly bond the soft magnetic powder.

[0051] Secondly, the present invention provides a method for preparing the above-mentioned composite resin-coated magnetic powder core, comprising the following steps:

[0052] S1. After cleaning, the soft magnetic powder is added to an organic solution containing benzoxazine and thermoplastic-thermosetting resin binder. The mixture is stirred evenly in an ultrasonic water bath to form a mixture. The mixture is then stirred until all the organic solvent evaporates to obtain composite resin-coated magnetic powder.

[0053] S2. In step S1, the composite resin-coated magnetic powder is pressed and annealed to obtain a composite resin-coated magnetic powder core.

[0054] The method for preparing composite resin-coated magnetic powder core provided by this invention uses benzoxazine and thermoplastic-thermosetting composite resin as raw materials for the coating layer. The benzoxazine monomer and the thermoplastic-thermosetting composite 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. Moreover, the coating process is short and has the advantages of low energy consumption and environmental friendliness.

[0055] In one possible implementation, the organic solvent in step S1 is selected from at least one of chloroform, acetone, ethanol, isopropanol, diethyl ether, dichloromethane, and methyl ethyl ketone. As organic solvents, chloroform, acetone, ethanol, isopropanol, diethyl ether, dichloromethane, and methyl ethyl ketone effectively dissolve benzoxazine and the thermoplastic-thermosetting resin binder, forming a uniform resin solution. During ultrasonic mixing, the soft magnetic powder is fully wetted, ensuring a thin and uniform coating layer is formed on the surface of the magnetic powder. Furthermore, during the coating process, the solvent does not chemically react with the soft magnetic powder, benzoxazine, or the thermoplastic-thermosetting resin; it only acts as a medium. It evaporates rapidly during stirring, preventing solvent residue from affecting the dielectric properties and magnetic permeability of the composite resin-coated magnetic powder core.

[0056] In one possible implementation, the ultrasonic water bath in step S1 is at a temperature of 60-100 °C for 20-120 min. 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 the hydroxyl groups of epoxy resin and the nitrogen-oxygen bonds of benzoxazine), thus enhancing the bonding force between the coating layer and the magnetic powder. The continuous ultrasonic action for 20-120 min, combined with the temperature, allows resin molecules to fully penetrate into the pores and gaps of the magnetic powder particles through thermal motion, further enhancing the bonding force between the coating layer and the magnetic powder.

[0057] In one possible implementation, the pressing pressure in step S2 is 200-2000 MPa, and the annealing temperature is 200-1800 ℃. The pressure range of 200-2000 MPa allows for control of the air gap volume fraction within the composite resin-coated magnetic powder core within a low range, avoiding a decrease in magnetic permeability due to excessively large air gaps, while also preventing a surge in eddy current losses caused by excessively small air gaps. Annealing within the temperature range of 200-1800 ℃ promotes the formation of a stable insulating coating layer between benzoxazine and the thermoplastic-thermosetting composite resin on the magnetic powder surface, thereby increasing the insulation resistance and reducing eddy current losses of the composite resin-coated magnetic powder core.

[0058] Thirdly, the present invention also provides the application of the above-mentioned composite resin-coated magnetic powder core in inductors.

[0059] The technical solution of the present invention will be further described below with reference to specific embodiments and comparative examples. All reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing. The instruments used in the embodiments are also commercially available.

[0060] Example 1

[0061] 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 of bisphenol A type benzoxazine, bisphenol A type epoxy resin and polyethylene resin. The mass percentage 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.

[0062] The composite resin-coated magnetic powder core of this embodiment is prepared by the following method:

[0063] M1. Weigh 0.2 g of bisphenol A type benzoxazine powder, 0.8 g of bisphenol A type epoxy resin and 0.2 g of polyethylene resin and dissolve them in 80 mL of chloroform to prepare an organic solution;

[0064] M2, The soft magnetic powder FeSiBCCr (Fe) was removed by cleaning with anhydrous ethanol. 73 Si 11 B 11 The oil and oxides on the surface of C3Cr2) were removed, and then 98.8 g of soft magnetic powder was added to the organic solution in step M1. The mixture was mixed evenly under ultrasonic water bath conditions. The water bath temperature was 80 ℃ and the mixing time was 30 min to obtain a mixture. The mixture was stirred under mechanical stirring until the chloroform was completely evaporated to obtain composite resin coated magnetic powder.

[0065] In steps M3 and M2, the composite resin-coated magnetic powder is pressed into shape under a pressure of 1800 MPa and annealed at 480 ℃ to obtain a composite resin-coated magnetic powder core.

[0066] Example 2

[0067] 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 combining bisphenol A type benzoxazine with bisphenol A type epoxy resin and polypropylene resin. The mass percentage 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.

[0068] The composite resin-coated magnetic powder core of this embodiment is prepared by the following method:

[0069] M1. Weigh 0.6 g of bisphenol A type benzoxazine powder, 0.6 g of bisphenol A type epoxy resin and 0.4 g of polypropylene resin and dissolve them in 80 mL of chloroform to prepare an organic solution;

[0070] M2, The soft magnetic powder FeSiBCCr (Fe) was removed by cleaning with anhydrous ethanol. 73 Si 11 B 11The oil and oxides on the surface of C3Cr2) were removed, and then 98.4 g of soft magnetic powder was added to the organic solution in step M1. The mixture was mixed evenly under ultrasonic water bath conditions. The water bath temperature was 80 ℃ and the mixing time was 30 min to obtain a mixture. The mixture was stirred under mechanical stirring until the chloroform was completely evaporated to obtain composite resin coated magnetic powder.

[0071] In steps M3 and M2, the composite resin-coated magnetic powder is pressed into shape under a pressure of 1800 MPa and annealed at 480 ℃ to obtain a composite resin-coated magnetic powder core.

[0072] Example 3

[0073] 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 prepared by combining bisphenol A type benzoxazine with bisphenol A type epoxy resin and polyvinyl butyral resin (PVB). The mass percentage of the composite coating layer in the composite resin-coated magnetic powder core is 2%, and the mass ratio of bisphenol A type benzoxazine to bisphenol A type epoxy resin and PVB in the composite coating layer is 1:0.5:0.5. It is prepared by the following method:

[0074] M1. Weigh 1 g of bisphenol A type benzoxazine powder, 0.5 g of bisphenol A type epoxy resin and 0.5 g of PVB and dissolve them in 80 mL of chloroform to prepare an organic solution;

[0075] M2, The soft magnetic powder FeSiBCCr (Fe) was removed by cleaning with anhydrous ethanol. 73 Si 11 B 11 The oil and oxides on the surface of C3Cr2) were removed, and then 98 g of soft magnetic powder was added to the organic solution in step M1. The mixture was mixed evenly under ultrasonic water bath conditions. The water bath temperature was 80 ℃ and the mixing time was 30 min to obtain a mixture. The mixture was stirred under mechanical stirring until the chloroform was completely evaporated to obtain composite resin coated magnetic powder.

[0076] In steps M3 and M2, the composite resin-coated magnetic powder is pressed into shape under a pressure of 1800 MPa and annealed at 480 ℃ to obtain a composite resin-coated magnetic powder core.

[0077] Comparative Example 1

[0078] This comparative example provides an epoxy resin-coated magnetic powder core, comprising soft magnetic powder and a coating layer covering the surface of the soft magnetic powder. The coating layer is made of bisphenol A type epoxy resin, and the mass percentage of the composite coating layer in the bisphenol A type epoxy resin-coated magnetic powder core is 2%. It is prepared by the following method:

[0079] M1. Weigh 2 g of bisphenol A type epoxy resin and dissolve it in 800 mL of chloroform to prepare an organic solution;

[0080] M2, The soft magnetic powder FeSiBCCr (Fe) was removed by cleaning with anhydrous ethanol. 73 Si 11 B 11 Oils and oxides on the surface of C3Cr2) were removed, and then 98 g of soft magnetic powder was added to the organic solution in step M1. The mixture was stirred evenly under ultrasonic water bath conditions. The water bath temperature was 80 ℃ and the mixing time was 30 min to obtain a mixture. The mixture was stirred under mechanical stirring until the chloroform was completely evaporated to obtain epoxy resin coated magnetic powder.

[0081] In steps M3 and M2, the epoxy resin-coated magnetic powder is pressed into shape under a pressure of 1800 MPa and annealed at 480 ℃ to obtain an epoxy resin-coated magnetic powder core.

[0082] Example 4

[0083] 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 combining bisphenol A type benzoxazine with polyphenol type glycidyl ether epoxy resin and polyethylene resin. The mass percentage 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.

[0084] The composite resin-coated magnetic powder core of this embodiment is prepared by the following method:

[0085] M1. Weigh 0.2 g of bisphenol A type benzoxazine powder, 0.8 g of polyphenol type glycidyl ether epoxy resin and 0.2 g of polyethylene resin and dissolve them in 80 mL of chloroform to prepare an organic solution;

[0086] M2, The soft magnetic powder FeSiBCCr (Fe) was removed by cleaning with anhydrous ethanol. 73 Si 11 B 11 The oil and oxides on the surface of C3Cr2) were removed, and then 98.8 g of soft magnetic powder was added to the organic solution in step M1. The mixture was mixed evenly under ultrasonic water bath conditions. The water bath temperature was 100 ℃ and the mixing time was 20 min to obtain a mixture. The mixture was stirred under mechanical stirring until the chloroform was completely evaporated to obtain composite resin coated magnetic powder.

[0087] In steps M3 and M2, the composite resin-coated magnetic powder is pressed into shape under a pressure of 1500 MPa and annealed at 480 ℃ to obtain a composite resin-coated magnetic powder core.

[0088] Example 5

[0089] 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 combining bisphenol A type benzoxazine with glycidyl ester type epoxy resin and polypropylene resin. The mass percentage 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 type epoxy resin and polypropylene resin in the composite coating layer is 3:3:2.

[0090] The composite resin-coated magnetic powder core of this embodiment is prepared by the following method:

[0091] M1. Weigh 0.6 g of bisphenol A type benzoxazine powder, 0.6 g of glycidyl ester type epoxy resin and 0.4 g of polypropylene resin and dissolve them in 80 mL of chloroform to prepare an organic solution;

[0092] M2, The soft magnetic powder FeSiBCCr (Fe) was removed by cleaning with anhydrous ethanol. 73 Si 11 B 11 The grease and oxides on the surface of C3Cr2) were removed, and then 98.4 g of soft magnetic powder was added to the organic solution in step M1. The mixture was mixed evenly under ultrasonic water bath conditions. The water bath temperature was 90 ℃ and the mixing time was 60 min to obtain a mixture. The mixture was stirred under mechanical stirring until the chloroform was completely evaporated to obtain composite resin coated magnetic powder.

[0093] In steps M3 and M2, the composite resin-coated magnetic powder is pressed into shape under a pressure of 2000 MPa and annealed at 1000 ℃ to obtain a composite resin-coated magnetic powder core.

[0094] Example 6

[0095] This embodiment provides a composite resin-coated magnetic powder core, comprising soft magnetic powder and a composite coating layer covering the surface of the soft magnetic powder. The composite coating layer is prepared by combining bisphenol A type benzoxazine with glycidylamine type epoxy resin and polyvinyl butyral resin (PVB). The mass percentage of the composite coating layer in the composite resin-coated magnetic powder core is 2%, and the mass ratio of bisphenol A type benzoxazine to glycidylamine type epoxy resin and polyvinyl butyral resin in the composite coating layer is 1:0.5:0.5. It is prepared by the following method:

[0096] M1. Weigh 1 g of bisphenol A type benzoxazine powder, 0.5 g of glycidylamine type epoxy resin and 0.5 g of PVB and dissolve them in 80 mL of chloroform to prepare an organic solution;

[0097] M2, The soft magnetic powder FeSiBCCr (Fe) was removed by cleaning with anhydrous ethanol. 73 Si 11 B11 The oil and oxides on the surface of C3Cr2) were removed, and then 98 g of soft magnetic powder was added to the organic solution in step M1. The mixture was mixed evenly under ultrasonic water bath conditions. The water bath temperature was 60 ℃ and the mixing time was 120 min to obtain a mixture. The mixture was stirred under mechanical stirring until the chloroform was completely evaporated to obtain composite resin coated magnetic powder.

[0098] In steps M3 and M2, the composite resin-coated magnetic powder is pressed into shape under a pressure of 800 MPa and annealed at 480 °C to obtain a composite resin-coated magnetic powder core.

[0099] Example 7

[0100] This embodiment provides a composite resin-coated magnetic powder core, comprising soft magnetic powder and a composite coating layer covering the surface of the soft magnetic powder. The composite coating layer is prepared by combining bisphenol F benzoxazine with polyphenolic glycidyl ether epoxy resin and polyethylene resin. The mass percentage of the composite coating layer in the composite resin-coated magnetic powder core is 2.2%, and the mass ratio of bisphenol F benzoxazine to polyphenolic glycidyl ether epoxy resin and polyethylene resin in the composite coating layer is 5:4:2. It is prepared by the following method:

[0101] M1. Weigh 1 g of bisphenol F type benzoxazine, 0.8 g of polyphenol type glycidyl ether epoxy resin and 0.4 g of polyethylene resin and dissolve them in 80 mL of chloroform to prepare an organic solution;

[0102] M2, The soft magnetic powder FeSiBCCr (Fe) was removed by cleaning with anhydrous ethanol. 73 Si 11 B 11 Oils and oxides on the surface of C3Cr2) were removed, and then 97.8 g of soft magnetic powder was added to the organic solution in step M1. The mixture was stirred evenly under ultrasonic water bath conditions. The water bath temperature was 80 ℃ and the mixing time was 30 min to obtain a mixture. The mixture was stirred under mechanical stirring until the chloroform was completely evaporated to obtain composite resin coated magnetic powder.

[0103] In steps M3 and M2, the composite resin-coated magnetic powder is pressed into shape under a pressure of 1800 MPa and annealed at 480 ℃ to obtain a composite resin-coated magnetic powder core.

[0104] Example 8

[0105] This embodiment provides a composite resin-coated magnetic powder core, which differs from Embodiment 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 in Embodiment 1.

[0106] Example 9

[0107] This embodiment provides a composite resin-coated magnetic powder core, which differs from Embodiment 2 in that bisphenol F benzoxazine is used instead of bisphenol A benzoxazine and PVB is used instead of polypropylene resin. All other aspects are the same as in Embodiment 2.

[0108] Example 10

[0109] This embodiment provides a composite resin-coated magnetic powder core, which differs from Embodiment 3 in that bisphenol F benzoxazine is used instead of bisphenol A benzoxazine and polypropylene resin is used instead of PVB. All other aspects are the same as in Embodiment 3.

[0110] Example 11

[0111] This embodiment provides a composite resin-coated magnetic powder core, which differs from Embodiment 1 in that it uses MDA-type benzoxazine instead of bisphenol A-type benzoxazine, while all other aspects are the same as in Embodiment 1.

[0112] Example 12

[0113] 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, and phenolic resin is used instead of bisphenol A-type epoxy resin. All other aspects are the same as in Embodiment 2.

[0114] Example 13

[0115] This embodiment provides a composite resin-coated magnetic powder core, which differs from Embodiment 3 in that it uses MDA-type benzoxazine instead of bisphenol A-type benzoxazine, while all other aspects are the same as in Embodiment 3.

[0116] Example 14

[0117] This embodiment provides a composite resin-coated magnetic powder core, which differs from Embodiment 2 in that it uses MDA-type benzoxazine instead of bisphenol A-type benzoxazine, while all other aspects are the same as in Embodiment 2.

[0118] Example 15

[0119] This embodiment provides a composite resin-coated magnetic powder core, which differs from Embodiment 3 in that MDA-type benzoxazine is used instead of bisphenol A-type benzoxazine, and phenolic resin is used instead of bisphenol A-type epoxy resin. All other aspects are the same as in Embodiment 3.

[0120] Example 16

[0121] This embodiment provides a composite resin-coated magnetic powder core, which differs from Embodiment 1 in that it uses DCPD type benzoxazine instead of bisphenol A type benzoxazine, while all other aspects are the same as in Embodiment 1.

[0122] Example 17

[0123] This embodiment provides a composite resin-coated magnetic powder core, which differs from Embodiment 2 in that it uses DCPD type benzoxazine instead of bisphenol A type benzoxazine, while all other aspects are the same as in Embodiment 2.

[0124] Example 18

[0125] This embodiment provides a composite resin-coated magnetic powder core, which differs from Embodiment 3 in that it uses DCPD type benzoxazine instead of bisphenol A type benzoxazine, while all other aspects are the same as in Embodiment 3.

[0126] Example 19

[0127] This embodiment provides a composite resin-coated magnetic powder core, which differs from Embodiment 1 in that phenolphthalein-type benzoxazine is used instead of bisphenol A-type benzoxazine, and phenolic resin is used instead of bisphenol A-type epoxy resin. All other aspects are the same as in Embodiment 1.

[0128] Example 20

[0129] This embodiment provides a composite resin-coated magnetic powder core, which differs from Embodiment 2 in that phenolphthalein-type benzoxazine is used instead of bisphenol A-type benzoxazine, and phenolic resin is used instead of bisphenol A-type epoxy resin. All other aspects are the same as in Embodiment 2.

[0130] Example 21

[0131] This embodiment provides a composite resin-coated magnetic powder core, which differs from Embodiment 3 in that phenolphthalein-type benzoxazine is used instead of bisphenol A-type benzoxazine, and phenolic resin is used instead of bisphenol A-type epoxy resin. All other aspects are the same as in Embodiment 3.

[0132] Example 22

[0133] This embodiment provides a composite resin-coated magnetic powder core, which differs from Embodiment 1 in that it uses cashew phenol-aniline type benzoxazine instead of bisphenol A type benzoxazine, while all other aspects are the same as in Embodiment 1.

[0134] Example 23

[0135] This embodiment provides a composite resin-coated magnetic powder core, which differs from Embodiment 2 in that it uses cashew phenol-aniline type benzoxazine instead of bisphenol A type benzoxazine, while all other aspects are the same as in Embodiment 2.

[0136] Example 24

[0137] This embodiment provides a composite resin-coated magnetic powder core, which differs from Embodiment 3 in that it uses cashew phenol-aniline type benzoxazine instead of bisphenol A type benzoxazine, while all other aspects are the same as in Embodiment 3.

[0138] The composite resin-coated magnetic powder cores prepared in Examples 1-24 and the epoxy resin-coated magnetic powder cores prepared in Comparative Example 1 were characterized and tested, and the results are as follows:

[0139] Figure 1 The images show 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 Image (a) is an 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 powder particles in the composite resin-coated magnetic powder core prepared in Example 1. Figure 1 In Figure (b), the SEM image of the epoxy resin-coated magnetic powder core obtained in Comparative Example 1 is shown. The area marked by the red dashed line in the figure is the resin agglomeration area. Agglomerated resin will increase the hysteresis effect of the epoxy resin-coated magnetic powder core, which will increase the hysteresis loss and reduce the permeability. Figure 1 (c) is a magnified view of part of (a), which shows that tiny resin particles attached to the magnetic powder play a role in bonding and insulation. Figure 1 In the middle (d), which is a magnified view of part of (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 deterioration of the soft magnetic properties.

[0140] 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 cores prepared in Comparative Example 1. As shown in 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.

[0141] Figure 3 The graph shows 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. As can be seen from the graph, the effective magnetic permeability of the composite resin-coated magnetic powder cores prepared in Examples 1-3 is significantly higher than that of the epoxy resin-coated magnetic powder cores prepared in Comparative Example 1, and the composite resin-coated magnetic powder core prepared in Example 2 has the highest effective magnetic permeability.

[0142] Figure 4The figures show the core loss 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 figures, the core losses of the composite resin-coated magnetic powder cores prepared in Examples 1 and 2 are significantly lower than those 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 this invention achieves lower core loss than the composite resin-coated magnetic powder core prepared in Comparative Example 1 by using fewer coating layers. 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 comparable to that of the epoxy resin-coated magnetic powder core in Comparative Example 1 at high frequencies.

[0143] Figure 5 The figures show the quality factor Q values ​​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. As can be seen from the figures, 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 those of the epoxy resin-coated magnetic powder core prepared in Comparative Example 1.

[0144] Figure 6 The graph shows the thermogravimetric analysis results of the composite resin prepared in Example 2 and the epoxy resin prepared in Comparative Example 1. Figure 7 This is a graph showing the thermogravimetric analysis results of bisphenol A type epoxy resin. Figure 8 This is a graph showing the thermogravimetric analysis results of bisphenol A type benzoxazine monomers. Figure 6 , Figure 7 and Figure 8 It can be seen that epoxy resin loses weight most rapidly at 263 °C, and bisphenol A benzoxazine loses weight most rapidly at 485 °C. In contrast, the composite resin prepared in Example 2 loses weight slowly at 360 °C, and its retention rate is higher than that of the epoxy resin-coated magnetic powder core in Comparative Example 1 above 500 °C. This indicates that the composite resin provided by the present invention has higher thermal stability.

[0145] Table 1 shows the coating material 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 / cm³. 3 Between 50 mT and 100 kHz, the core loss ranges from 101.29 to 210.3 mW / cm. 3 between;

[0146] .

[0147] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions 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 product comprises soft magnetic powder and a composite coating layer covering the surface of the soft magnetic powder. The composite coating layer is made by combining benzoxazine with a thermoplastic-thermosetting resin binder. The mass percentage of the composite coating layer in the composite resin-coated magnetic powder core is 1-10%. The thermoplastic-thermosetting resin binder is made by combining thermoplastic resin and thermosetting resin. The mass ratio of benzoxazine, thermoplastic resin and 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 selected from at least one of bisphenol A type benzoxazine, bisphenol F type benzoxazine, MDA type benzoxazine, DCPD type benzoxazine, phenolphthalein type benzoxazine and cashew phenol-aniline type 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 selected from at least one of 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 type epoxy resin, polyphenol type glycidyl ether epoxy resin, glycidyl ester type epoxy resin and glycidyl amine type 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 composite coating layer in the composite resin-coated magnetic powder core accounts for 1.2-1.6% of the total mass.

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 resin adhesive 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 adhesive is (1-4):

1.

10. A method for preparing a composite resin-coated magnetic powder core according to any one of claims 1-9, characterized in that, Includes the following steps: S1. After cleaning, the soft magnetic powder is added to an organic solution containing benzoxazine and thermoplastic-thermosetting resin binder. The mixture is stirred evenly in an ultrasonic water bath to form a mixture. The mixture is then stirred until all the organic solvent evaporates to obtain composite resin-coated magnetic powder. S2. The composite resin-coated magnetic powder described 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, characterized in that, The organic solvent mentioned in step S1 is selected from at least one of chloroform, acetone, ethanol, isopropanol, diethyl ether, dichloromethane and methyl ethyl ketone.

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

13. The method for preparing a composite resin-coated magnetic powder core according to claim 10, characterized in that, The pressing pressure in step S2 is 200-2000 MPa, and the annealing temperature is 200-1800 ℃.

14. The application of the composite resin-coated magnetic powder core as described in any one of claims 1-9 in an inductor.

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