Polymer-coated magnetic powder, method for producing the same, and magnet

Abstract

The application discloses a kind of polymer coated magnetic powder and its preparation method, magnet, polymer coated magnetic powder includes magnetic powder, inorganic layer coated in the magnetic powder outside and polymer layer coated in the inorganic layer outside.The polymer coated magnetic powder includes magnetic powder, inorganic layer coated in the magnetic powder outside and polymer layer coated in the inorganic layer outside, and polymer layer enhances the mechanical strength and insulation strength of polymer coated magnetic powder.The polymer coated magnetic powder of the application is used as raw material to prepare magnet by high-performance casting process and injection molding method, due to the protection of polymer layer, the rupture of inorganic layer can be greatly avoided, thereby reducing the probability of problems in the mechanical properties and insulation of the finally prepared magnet.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of magnets, in particular to a polymer-coated magnetic powder, a polymer-coated magnetic powder prepared from the polymer-coated magnetic powder and a magnet comprising the polymer-coated magnetic powder. BACKGROUND

[0002] Traditional soft magnetic alloy materials have small resistance, and the eddy current loss increases rapidly with the increase of frequency, which greatly limits its use at higher frequencies, and cannot meet the development of high frequency, miniaturization and thinness of electronic equipment. The demand for high Bs (saturation magnetization), high mu (magnetic permeability), low Ps (eddy current loss) and low Hc (coercivity) of the magnetic powder core. The key to fully utilizing the high saturation magnetic induction and high magnetic permeability characteristics of soft magnetic alloy is how to solve the problem of low resistivity of the material.

[0003] In recent years, with the continuous growth of demand for high-power inverters, transformers and other new energy fields, soft magnetic alloy powder cores have been widely used as core components, but the high magnetic permeability characteristics of soft magnetic alloy powder cores have not been best utilized. Traditional magnetic powders generally use surface coating processes, such as coating magnetic powders with oxides, organic matter, phosphates and other high-resistance materials. Because the mechanical strength of the coating material of the traditional magnetic powder is relatively poor, especially when using high-performance casting process and injection molding method to prepare magnets with traditional magnetic powder as raw material, the mechanical properties and insulation of the prepared magnets are prone to problems due to the rupture of the coating material, which in turn leads to problems such as large eddy current loss with increasing frequency. SUMMARY

[0004] Therefore, it is necessary to provide a polymer-coated magnetic powder that can solve the above problems.

[0005] In addition, it is also necessary to provide a preparation method of the polymer-coated magnetic powder and a magnet comprising the polymer-coated magnetic powder.

[0006] A polymer-coated magnetic powder comprises a magnetic powder, an inorganic layer coated on the outside of the magnetic powder, and a polymer layer coated on the outside of the inorganic layer.

[0007] The inorganic layer is connected with a silane coupling agent, and the general formula of the silane coupling agent is NH2-R1-Si-(OCH2CH3)3, -R1- is -CH2-(CH2) n -(C6H4) m -CH2-, n is a natural number of 0-12, and m is 0 or 1.

[0008] The polymer layer is formed by polymerization of a polymer monomer, and the general formula of the polymer monomer is O=C=N-R2-N=C=O, -R2- is -(C6H3)(CH3)-, -C6H4-(CH2) k-C6H4-, -C6H 10 -CH2-C6H 10 -、-CH2-CH3-C6H 10 -(CH3)2-, -CH2-CH2-CH2-, wherein k is a natural number from 0 to 12;

[0009] The silane coupling agent and the polymer monomer are covalently bonded through -NH2 and -N=C=O to form -NH-CO-NH-.

[0010] In one embodiment, the polymer monomer is selected from at least one of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, hexamethylene diisocyanate, and lysine diisocyanate.

[0011] In one embodiment, the silane coupling agent is selected from at least one of 3-aminopropyltrimethoxysilane, γ-dieithylenetriaminopropylmethyldimethoxysilane, N-aminoethyl-3-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltriethoxysilane, and 3-(acryloxy)propyltrimethoxysilane.

[0012] In one embodiment, the inorganic layer is externally modified with -OH, and the inorganic layer is bonded to the silane coupling agent through -OH.

[0013] In one embodiment, the magnetic powder is pure Fe powder, Fe-Ni-Co series metal powder, Fe-Ni series metal powder, Fe-Si-Al series metal powder, Fe-Co series metal powder, Fe-Si series metal powder, Fe-P series metal powder, Fe3O4 powder, or Fe-Cr series metal powder, and the particle size of the magnetic powder is 10 μm to 200 μm.

[0014] The material of the inorganic layer is silicon dioxide, silicate, phosphate, or borate, and the thickness of the inorganic layer is 30 nm to 300 nm.

[0015] A method for preparing the polymer-coated magnetic powder described above, comprising the following steps:

[0016] Providing an inorganic-coated magnetic powder, which comprises magnetic powder and an inorganic layer coated on the outside of the magnetic powder, and the inorganic layer is externally modified with -OH;

[0017] The inorganic coated magnetic powder, a silane coupling agent and an organic solvent are mixed and fully reacted so that the inorganic layer is combined with the silane coupling agent through -OH, to obtain a semi-finished product, wherein the general formula of the silane coupling agent is NH2-R1-Si(OCH2CH3)3, -R1- is -CH2-(CH2) n -(C6H4) m -CH2-, n is a natural number of 0-12, and m is 0 or 1;

[0018] The semi-finished product, a polymer monomer, a catalyst and a dispersion system are mixed and fully reacted so that the silane coupling agent and the polymer monomer are covalently combined through -NH2 and -N=C=O to form -NH-CO-NH-, to obtain the required polymer coated magnetic powder, wherein the general formula of the polymer monomer is O=C=N-R2-N=C=O, -R2- is -(C6H3)(CH3)-, -C6H4-(CH2) k -C6H4-, -C6H 10 -CH2-C6H 10 -, -CH2-CH3-C6H 10 -(CH3)2-, -CH2-CH2-CH2-, wherein k is a natural number of 0-12.

[0019] In one embodiment, in the operation of mixing the inorganic coated magnetic powder, the silane coupling agent and the organic solvent, the mass ratio of the inorganic coated magnetic powder and the silane coupling agent is 100-200:4.5;

[0020] The organic solvent is selected from at least one of acetone, methyl butanone, ethylene glycol monoethyl ether and N-methyl pyrrolidone, etc.

[0021] In one embodiment, the operation of mixing the semi-finished product, the polymer monomer, the catalyst and the dispersion system is that the semi-finished product and the catalyst are dispersed into the dispersion system, and then the polymer monomer is added;

[0022] The mass ratio of the semi-finished product, the polymer monomer and the catalyst is 100:0.48-1.5:1.2-5.

[0023] In one embodiment, the dispersion system is a solvent type dispersion system or an ionic liquid, the solvent type dispersion system is selected from at least one of xylene, isomeric alkanes, petroleum ether and tetrahydrofuran, and the ionic liquid is a fluorine-containing ionic liquid selected from at least one of 1-ethyl-3-methyl imidazole tetrafluoroborate, 1-ethyl-3-methyl imidazole trifluoroacetate, 1-pentyl-3-methyl imidazole tetrafluoroborate and 1-hexyl-3-methyl imidazole tetrafluoroborate;

[0024] The operation of dispersing the semi-finished product and the catalyst into the dispersion system is ultrasonic dispersion or high-speed dispersion.

[0025] The catalyst is at least one of bis(dimethylaminoethyl) ether, N-methylmorpholine, triethylenediamine, and diphenylamine.

[0026] A magnet comprising the polymer-coated magnetic powder described above.

[0027] The polymer-coated magnetic powder comprises a magnetic powder, an inorganic layer coated on the magnetic powder, and a polymer layer coated on the inorganic layer, and the polymer layer enhances the mechanical strength, high-temperature resistance, and insulation strength of the polymer-coated magnetic powder.

[0028] When the magnet is prepared by using the polymer-coated magnetic powder of the present application as raw material by a high-performance casting process and an injection molding method, the polymer layer can greatly avoid the rupture of the inorganic layer, and the polymer layer also improves the high-temperature resistance of the polymer-coated magnetic powder, thereby reducing the probability of problems in the mechanical properties and insulation of the finally prepared magnet, and further reducing the problems of large eddy current loss at high frequency.

[0029] In addition, the key process for the magnet to obtain high density is high-temperature sintering, and the key to obtaining high resistivity is to improve the high-temperature resistance and resistivity of the coating layer on the surface of the magnetic powder. The polymer-coated magnetic powder of the present application has better mechanical strength, high-temperature resistance, and insulation strength than traditional magnetic powder, and the magnet prepared therefrom is more likely to obtain high density and high resistivity.

[0030] The polymer-coated magnetic powder of the present application can be used to prepare inductors and shielding materials. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0032] wherein:

[0033] Figure 1 It is a structural schematic diagram of the polymer-coated magnetic powder of an embodiment.

[0034] Figure 2 It is a preparation flowchart of the polymer-coated magnetic powder as shown in Figure 1 DETAILED DESCRIPTION

[0035] ​With reference to the accompanying drawings, the technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative efforts belong to the scope of the present application.

[0036] As shown in Figure 1 The present application discloses a polymer-coated magnetic powder in an embodiment, which comprises magnetic powder 10, inorganic layer 20 coated on the magnetic powder 10, and polymer layer 30 coated on the inorganic layer 20.

[0037] The inorganic layer 20 is connected with silane coupling agent, and the general formula of the silane coupling agent is NH2-R1-Si(OCH2CH3)3, -R1- is -CH2-(CH2) n -(C6H4) m -CH2-, n is a natural number from 0 to 12, and m is 0 or 1.

[0038] The polymer layer 30 is formed by polymerization of polymer monomer, and the general formula of the polymer monomer is O=C=N-R2-N=C=O, -R2- is -(C6H3)(CH3)-, -C6H4-(CH2) k -C6H4-, -C6H 10 -CH2-C6H 10 -, 10 -(CH3)2-, -CH2-CH2-CH2-, wherein k is a natural number from 0 to 12.

[0039] The silane coupling agent and the polymer monomer are covalently combined through -NH2 and -N=C=O to form -NH-CO-NH-.

[0040] The polymer-coated magnetic powder comprises magnetic powder 10, inorganic layer 20 coated on the magnetic powder 10, and polymer layer 30 coated on the inorganic layer 20, and the polymer layer 30 enhances the mechanical strength, high-temperature resistance and insulation strength of the polymer-coated magnetic powder.

[0041] When the polymer-coated magnetic powder in the present application is used as raw material to prepare a magnet by high-performance casting process and injection molding method, the rupture of the inorganic layer 20 can be greatly avoided due to the protection of the polymer layer 30, and the polymer layer also improves the high-temperature resistance of the polymer-coated magnetic powder, thereby reducing the probability of problems in the mechanical properties and insulation of the finally prepared magnet, and further reducing the problems of large frequency rise eddy current loss and the like.

[0042] In addition, the key process for the magnet to obtain high density is to realize high-temperature sintering, and the key to obtain high resistivity is to improve the high-temperature resistance and resistance of the surface coating layer of the magnetic powder, and the polymer-coated magnetic powder has better mechanical strength, high-temperature resistance and insulation strength, and the magnet prepared by the polymer-coated magnetic powder is easier to obtain high density and high resistivity.

[0043] The polymer-coated magnetic powder can be used to prepare inductance, shielding materials and the like.

[0044] Preferably, in the embodiment, the polymer monomer is selected from at least one of toluene diisocyanate, isophorone diisocyanate, diphenyl methane diisocyanate, dicyclohexyl methane diisocyanate, polymethylene polyphenyl polyisocyanate, hexamethylene diisocyanate and lysine diisocyanate.

[0045] Preferably, in the embodiment, the silane coupling agent is selected from at least one of 3-aminopropyl trimethoxysilane, γ-diatheylene triamine propyl methyl dimethoxysilane, N-aminoethyl-3-aminopropyl methyl dimethoxysilane, γ-aminopropyl triethoxysilane, N-(β-aminoethyl)-γ-aminopropyl triethoxysilane and 3-(acryloyloxy) propyl trimethoxysilane.

[0046] Preferably, in the embodiment, the inorganic layer 20 is externally modified with -OH, and the inorganic layer 20 is combined with the silane coupling agent through -OH.

[0047] The combination of -OH and the silane coupling agent makes the silane coupling agent play a role in connecting the inorganic layer 20 and the polymer layer 30, so that the polymer layer 30 can be tightly coated outside the inorganic layer 20, and the coating strength of the polymer layer 30 is high and not easy to fall off.

[0048] Preferably, in the embodiment, the magnetic powder 10 is pure Fe powder, Fe-Ni-Co system metal powder, Fe-Ni system metal powder, Fe-Si-Al system metal powder, Fe-Co system metal powder, Fe-Si system metal powder, Fe-P system metal powder, Fe3O4 powder or Fe-Cr system metal powder, and the particle size of the magnetic powder 10 is 10 μm-500 μm.

[0049] Preferably, in the embodiment, the material of the inorganic layer 20 is silica, silicate, phosphate or borate, and the thickness of the inorganic layer 20 is 30-300 nm.

[0050] As shown in an embodiment of the above polymer-coated magnetic powder preparation method, Figure 2 The method comprises the following steps:

[0051] S10, providing inorganic coated magnetic powder.

[0052] The inorganic coated magnetic powder comprises magnetic powder 10 and inorganic layer 20 coated on the magnetic powder 10, and the inorganic layer 20 is externally modified with -OH.

[0053] Preferably, in the embodiment, the magnetic powder 10 is pure Fe powder, Fe-Ni-Co system metal powder, Fe-Ni system metal powder, Fe-Si-Al system metal powder, Fe-Co system metal powder, Fe-Si system metal powder, Fe-P system metal powder, Fe3O4 powder or Fe-Cr system metal powder, and the particle size of the magnetic powder 10 is 10 μm-500 μm.

[0054] Preferably, in the embodiment, the material of the inorganic layer 20 is silicon dioxide, silicate, phosphate or borate, and the thickness of the inorganic layer 20 is 30-300 nm.

[0055] The inorganic coated magnetic powder with -OH externally modified on the inorganic layer 20 can be prepared by itself or purchased.

[0056] Specifically, the inorganic coated magnetic powder is Changsha Hualuo's iron-silicon-aluminum powder D25.

[0057] S20, the inorganic coated magnetic powder obtained in S10, silane coupling agent and organic solvent are mixed and fully reacted to make the inorganic layer 20 combined with the silane coupling agent through -OH, thereby obtaining a semi-finished product.

[0058] The general formula of the silane coupling agent is NH2-R1-Si(OCH2CH3)3, -R1- is -CH2-(CH2) n -(C6H4) m -CH2-, n is a natural number of 0-12, and m is 0 or 1.

[0059] The reaction of the inorganic coated magnetic powder and the silane coupling agent is as follows:

[0060] ○-OH + NH2-R1-Si(OCH2CH3)3→ ○-O-Si-R1(CH3)2-NH2, wherein ○ is the inorganic coated magnetic powder.

[0061] Preferably, in S20, the mass ratio of the inorganic coated magnetic powder and the silane coupling agent is 100-200:4.5.

[0062] Preferably, the organic solvent is selected from at least one of acetone, methyl butanone, ethylene glycol monoethyl ether and N-methyl pyrrolidone.

[0063] Specifically, S20 is: after mixing the inorganic coated magnetic powder, silane coupling agent and organic solvent obtained in S10, heating to boiling of the organic solvent under negative pressure, and after removing the organic solvent, retaining the powder, the powder is reacted for 12h-36h in constant temperature and humidity of 40℃-60℃, 80%RH-90%RH, to obtain a semi-finished product.

[0064] S30, mixing the semi-finished product obtained in S20, polymer monomer, catalyst and dispersion system, and fully reacting to make the silane coupling agent and polymer monomer covalently bond through -NH2 and -N=C=O to form -NH-CO-NH-, to obtain the required polymer coated magnetic powder.

[0065] The general formula of the polymer monomer is O=C=N-R2-N=C=O, -R2- is -(C6H3)(CH3)-, -C6H4-(CH2) k -C6H4-, -C6H 10 -CH2-C6H 10 -, -CH2-CH3-C6H 10 -(CH3)2-, -CH2-CH2-CH2-, wherein k is a natural number of 0-12.

[0066] The reaction of the semi-finished product and the polymer monomer is as follows:

[0067] ○-O-Si-R1(CH3)2-NH2+O=C=N-R2-N=C=O→○-O-Si-R1(CH3)2-NH-CO-NH-R2-N=C=O, wherein ○ is the inorganic coated magnetic powder.

[0068] Preferably, in S30, the mass ratio of the semi-finished product, polymer monomer and catalyst is 100:0.48-1.5:1.2-5.

[0069] Preferably, the operation of mixing the semi-finished product, polymer monomer, catalyst and dispersion system is: dispersing the semi-finished product and catalyst into the dispersion system, and then adding the polymer monomer.

[0070] Preferably, the dispersion system can be a solvent type dispersion system or an ionic liquid, the solvent type dispersion system is selected from at least one of xylene, isomeric alkanes, petroleum ether and tetrahydrofuran, and the ionic liquid can be a fluorine-containing ionic liquid. The fluorine-containing ionic liquid is selected from at least one of 1-ethyl-3-methylimidazole tetrafluoroborate, 1-ethyl-3-methylimidazole trifluoroacetate, 1-pentyl-3-methylimidazole tetrafluoroborate and 1-hexyl-3-methylimidazole tetrafluoroborate.

[0071] In the operation of dispersing the semi-finished product and catalyst into the dispersion system, the dispersion is ultrasonic dispersion or high-speed dispersion.

[0072] The catalyst is selected from at least one of bis(dimethylaminoethyl) ether, N-methylmorpholine, triethylenediamine and diphenylamine.

[0073] Specifically, S30 involves dispersing the semi-finished product and catalyst into a dispersion system, adding polymer monomers, heating to 60℃~80℃ under a protective gas atmosphere, adding polymer monomers at this temperature, and then raising the temperature to 100℃~120℃ to react for 2h~10h, so that the silane coupling agent and polymer monomers covalently combine through -NH2 and -N=C=O to form -NH-CO-NH-, thereby obtaining the desired polymer-coated magnetic powder.

[0074] Preferably, the preparation method of polymer-coated magnetic powder also includes operations such as precipitation filtration and solvent recovery performed after S30.

[0075] The present invention also discloses a magnet according to one embodiment, comprising the above-described polymer-coated magnetic powder.

[0076] The following are specific examples.

[0077] Example 1

[0078] Step 1: Treat magnetic powder with inorganic coating layer using active siloxane coupling agent

[0079] Add 150g of iron-silicon-aluminum spherical magnetic powder (Changsha Hualiu's iron-silicon-aluminum powder D25), 200mL of n-hexane, and 4.50g of NH2(CH2)3Si(OCH2CH3)3 silane coupling agent to a 500mL four-necked flask equipped with a stirrer, reflux condenser, constant pressure dropping funnel, and thermometer. Disperse the powder ultrasonically for 30min and stir at high speed for 2 hours.

[0080] The mixture was transferred to a rotary evaporator under a vacuum of -0.07 to -0.08 MPa and heated until the hexane solvent boiled. The solvent was then condensed and recovered. The resulting powder was placed in a constant temperature and humidity chamber at 50°C and 85% RH for 24 hours and then dried for later use.

[0081] Step Two:

[0082] 100g of activated silane-treated iron-silicon-aluminum spherical magnetic powder, 220mL of xylene, and 0.54g of diphenylamine were added to a 500mL four-necked flask equipped with a stirrer, reflux condenser, constant pressure dropping funnel, and thermometer. The mixture was stirred thoroughly and the temperature inside the flask was raised to 70℃ under nitrogen protection. At this temperature, a xylene solution of 1.75g ​​of MDI (diphenylmethane diisocyanate) was slowly added dropwise to the flask through the constant pressure dropping funnel. The temperature was then raised to 80℃ and reacted for 5h. After cooling and filtration, polymer-coated iron-silicon-aluminum magnetic powder was obtained.

[0083] Example 2

[0084] First step: active siloxane coupling agent treatment of magnetic powder with inorganic coating layer

[0085] In a 500 mL four-necked flask equipped with a stirrer, reflux condenser, constant pressure dropping funnel, thermometer, 150 g of iron-silicon-aluminum spherical magnetic powder (iron-silicon-aluminum powder D25 from Changsha Hualai), 200 mL of n-hexane, and 4.50 g of NH2(CH2)3Si(OCH2CH3)3 silane coupling agent were added, and ultrasonic dispersion was performed for 30 min, followed by high-speed stirring for 2 h.

[0086] The mixture was transferred into a rotary evaporator, the vacuum degree was -0.07 to -0.08 MPa, heating was performed until the n-hexane solvent boiled, and the solvent was recovered by condensation. The obtained powder was placed in a constant temperature and humidity box at 50°C and 85% RH for reaction for 24 h, and the powder was dried for use.

[0087] Second step:

[0088] In a 500 mL four-necked flask equipped with a stirrer, reflux condenser, constant pressure dropping funnel, thermometer, 100 g of active silane treated iron-silicon-aluminum spherical magnetic powder, 220 mL of dimethylbenzene, and 1.08 g of diphenylamine were added, and stirring was performed, the temperature in the flask was increased to 70°C under nitrogen protection, 3.50 g of (diphenylmethane diisocyanate) toluene solution was slowly added into the flask from the constant pressure dropping funnel at the temperature, and then the temperature was increased to 80°C for reaction for 5 h, and cooling and suction filtration were performed to obtain polymer coated iron-silicon-aluminum magnetic powder.

[0089] Example 3

[0090] First step: active siloxane coupling agent treatment of magnetic powder with inorganic coating layer

[0091] In a 500 mL four-necked flask equipped with a stirrer, reflux condenser, constant pressure dropping funnel, thermometer, 150 g of iron-silicon-aluminum spherical magnetic powder (iron-silicon-aluminum powder D25 from Changsha Hualai), 200 mL of n-hexane, and 4.50 g of NH2(CH2)3Si(OCH2CH3)3 silane coupling agent were added, and ultrasonic dispersion was performed for 30 min, followed by high-speed stirring for 2 h.

[0092] The mixture was transferred into a rotary evaporator, the vacuum degree was -0.07 to -0.08 MPa, heating was performed until the n-hexane solvent boiled, and the solvent was recovered by condensation. The obtained powder was placed in a constant temperature and humidity box at 50°C and 85% RH for reaction for 24 h, and the powder was dried for use.

[0093] Second step:

[0094] In a 500 mL four-necked flask equipped with a stirrer, reflux condenser, constant pressure dropping funnel, thermometer, 100 g of active silane treated iron-silicon-aluminum spherical magnetic powder was added, 220 mL of dimethylbenzene, 0.54 g of diphenylamine was added, and stirred thoroughly. The temperature in the flask was raised to 70°C under nitrogen protection. A solution of 1.75 TDI (toluene diisocyanate) in dimethylbenzene was slowly dropped into the flask from the constant pressure dropping funnel at the temperature, and then the temperature was raised to 110°C for 5 h of reaction. After cooling and suction filtration, the polymer-coated iron-silicon-aluminum magnetic powder was obtained.

[0095] Test Example

[0096] Preparation of inductance by injection molding

[0097] The polymer-coated magnetic powder prepared above was taken respectively, and the iron-silicon-aluminum spherical magnetic powder without polymer coating was taken as a comparative example. The magnetic powder, epoxy adhesive and lubricant were mixed by internal mixing to form a magnetic adhesive mixture, wherein the magnetic powder was 95 wt%, the epoxy adhesive was 4.5 wt%, and the lubricant was 0.5 wt%. The lubricant was zinc stearate wax powder.

[0098] The magnetic adhesive mixture was removed from the internal bubbles under vacuum environment to obtain a magnetic adhesive base material.

[0099] The magnetic adhesive was injected into a fixed mold, and baked at 125°C for 1 h to form a cured magnetic body, and the performance thereof was measured.

[0100] The granular material was injection molded to obtain a magnetic ring (outer diameter x inner diameter x height: 62 mm x 33 mm x 25 mm), and the injection molding temperature was set to 295°C-310°C. According to the relevant test standard, the copper coil wire diameter was φ0.6 mm, and the number of turns was 75 turns. The inductance of different frequencies was measured respectively to obtain Table 1.

[0101] Table 1: Inductance test of different types of magnetic rings

[0102]

[0103]

[0104] As can be seen from Table 1, the high frequency inductance of Example 1, Example 2 and Example 3 is higher than that of the comparative example, and better high frequency characteristics are obtained.

[0105] The above examples only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as limiting the scope of the application. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of the present application. Therefore, the protection scope of the present application patent should be subject to the appended claims.

Claims

1. A polymer-coated magnetic powder, characterized in that, It includes magnetic powder, an inorganic layer covering the magnetic powder, and a polymer layer covering the inorganic layer; The inorganic layer is externally connected to a silane coupling agent, the general formula of which is NH2-R1-Si-(OCH2CH3)3, where -R1- is -CH2-(CH2). n -(C6H4) m -CH2-, where n is a natural number from 0 to 12, and m is 0 or 1; The polymer layer is formed by polymerizing polymer monomers under the action of a catalyst. The general formula of the polymer monomers is O=C=N-R2-N=C=O, where -R2- is -(C6H3)(CH3)- or -C6H4-(CH2). k -C6H4-、-C6H 10 -CH2-C6H 10 -,-CH2-CH3-C6H 10 -(CH3)2-, -CH2-CH2-CH2-, where k is a natural number from 0 to 12; The silane coupling agent and the polymer monomer are covalently bonded by -NH2 and -N=C=O to form -NH-CO-NH-; The mass ratio of the magnetic powder with an inorganic layer treated with the silane coupling agent, the polymer monomer, and the catalyst is 100:0.48~1.5:1.2~5; the catalyst is selected from at least one of bis(dimethylaminoethyl) ether, N-methylmorpholine, triethylenediamine, and diphenylamine.

2. The polymer-coated magnetic powder according to claim 1, characterized in that, The polymer monomer is selected from at least one of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, hexamethylene diisocyanate, and lysine diisocyanate.

3. The polymer-coated magnetic powder according to claim 2, characterized in that, The silane coupling agent is selected from at least one of 3-aminopropyltrimethoxysilane, γ-diethylenetriaminepropylmethyldimethoxysilane, N-aminoethyl-3-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltriethoxysilane, and 3-(acryloyloxy)propyltrimethoxysilane.

4. The polymer-coated magnetic powder according to any one of claims 1 to 3, characterized in that, The inorganic layer is modified with -OH, and the inorganic layer is bonded to the silane coupling agent through the -OH.

5. The polymer-coated magnetic powder according to claim 4, characterized in that, The magnetic powder is pure Fe powder, Fe-Ni-Co metal powder, Fe-Ni metal powder, Fe-Si-Al metal powder, Fe-Co metal powder, Fe-Si metal powder, Fe-P metal powder, Fe3O4 powder, or Fe-Cr metal powder, and the particle size of the magnetic powder is 10μm to 200μm. The inorganic layer is made of silicon dioxide, silicate, phosphate or borate, and the thickness of the inorganic layer is 30 nm to 300 nm.

6. A method for preparing polymer-coated magnetic powder as described in claim 4 or 5, characterized in that, Includes the following steps: An inorganic coated magnetic powder is provided, the inorganic coated magnetic powder comprising magnetic powder and an inorganic layer coated on the outside of the magnetic powder, the inorganic layer being modified with -OH; The inorganic coated magnetic powder, silane coupling agent, and organic solvent are mixed and reacted thoroughly so that the inorganic layer is bonded to the silane coupling agent through -OH groups, yielding a semi-finished product. The general formula of the silane coupling agent is NH2-R1-Si(OCH2CH3)3, and -R1- is -CH2-(CH2). n -(C6H4) m -CH2-, where n is a natural number from 0 to 12, and m is 0 or 1; The semi-finished product, polymer monomer, catalyst, and dispersion system are mixed and reacted thoroughly so that the silane coupling agent and the polymer monomer covalently bond through -NH2 and -N=C=O to form -NH-CO-NH-, thereby obtaining the desired polymer-coated magnetic powder. The polymer monomer has the general formula O=C=N-R2-N=C=O, and -R2- is either -(C6H3)(CH3)- or -C6H4-(CH2). k -C6H4-、-C6H 10 -CH2-C6H 10 -,-CH2-CH3-C6H 10 -(CH3)2-, -CH2-CH2-CH2-, where k is a natural number from 0 to 12.

7. The method for preparing polymer-coated magnetic powder according to claim 6, characterized in that, In the operation of mixing the inorganic coated magnetic powder, silane coupling agent and organic solvent, the mass ratio of the inorganic coated magnetic powder to the silane coupling agent is 100~200:4.5; The organic solvent is selected from at least one of acetone, methyl ethyl ketone, ethylene glycol monoethyl ether, and N-methylpyrrolidone.

8. The method for preparing polymer-coated magnetic powder according to claim 6, characterized in that, The operation of mixing the semi-finished product, polymer monomer, catalyst and dispersion system is as follows: the semi-finished product and the catalyst are dispersed into the dispersion system, and then the polymer monomer is added.

9. The method for preparing polymer-coated magnetic powder according to claim 8, characterized in that, The dispersion system is a solvent-based dispersion system or an ionic liquid. The solvent-based dispersion system is selected from at least one of xylene, isoalkanes, petroleum ether, and tetrahydrofuran. The ionic liquid is a fluorinated ionic liquid, and the fluorinated ionic liquid is selected from at least one of 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium trifluoroacetate, 1-pentyl-3-methylimidazolium tetrafluoroborate, and 1-hexyl-3-methylimidazolium tetrafluoroborate. In the operation of dispersing the semi-finished product and the catalyst into the dispersion system, the dispersion is ultrasonic dispersion or high-speed dispersion.

10. A magnet, characterized in that, It includes polymer-coated magnetic powder as described in any one of claims 1 to 5.

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