Dimethicone for magnetic powder core, preparation method of dimethicone, coated magnetic powder core, preparation method of coated magnetic powder core and application of coated magnetic powder core

Abstract

The invention belongs to the technical field of magnetic material preparation, and particularly relates to dimethyl silicone oil for a magnetic powder core and a preparation method thereof, a coated magnetic powder core and a preparation method and application of the coated magnetic powder core. The invention provides a preparation method of dimethyl silicone oil for a magnetic powder core, which comprises the following steps: taking a dimethyl silicone oil crude product, and adding trimethylsilyl phosphate to obtain the dimethyl silicone oil, the purity of the trimethylsilyl phosphate is not less than 99%; on the basis of the total mass of monomers in the simethicone crude product raw material, the addition amount of the trimethylsilyl phosphate is 0.1-0.3%. The prepared coated magnetic powder core is provided with a single-layer insulating coating layer with inorganic matter properties and organic matter properties, the magnetic conductivity and the direct current superposition performance of the coated magnetic powder core are high, and the loss of the coated magnetic powder core is low.

Description

Technical Field

[0001] The invention belongs to the technical field of magnetic material preparation, and in particular relates to dimethyl silicone oil for magnetic powder cores and a preparation method thereof, and a coated magnetic powder core and a preparation method and application thereof. Background Art

[0002] With the rapid upgrading of electronic products, the demand, practicality and safety of small-volume, high-power inductor components have been put forward with higher requirements; among them, soft magnetic alloy inductors have gradually shown their possibility of being widely used under the trend of miniaturization of electronic products. Metal soft magnetic powder core is a new type of soft magnetic functional material obtained by pressing and forming, heat treatment and annealing with alloy powder as raw material and insulating material coated on the surface of magnetic powder. The insulating coating can improve the overall resistivity of the material, reduce eddy current loss and comprehensive electromagnetic performance.

[0003] Insulation coating is generally divided into organic coating and inorganic coating. Organic coating mainly includes thermosetting resin (such as epoxy resin, phenolic resin, silicone resin, etc.) and thermoplastic resin (such as polyethylene, polyamide, ethylene-vinyl acetate polymer, polypropylene, PBT, PPS, nylon, etc.). Organic matter has strong adhesion and can ensure that the magnetic powder core has sufficient strength. The organic insulation coating layer formed has the advantages of density, high resistivity and low loss. However, it has a low heat resistance temperature and is easy to decompose during high temperature annealing. It is difficult to maintain a complete insulation layer, which deteriorates the performance of the magnetic powder core and leads to poor magnetic properties. Inorganic coating mainly includes inorganic phosphate coating (zinc phosphate, iron phosphate and manganese phosphate), metal oxide coating (SiO2, MgO), ferrite coating and silicate coating, etc., which form a coating layer on the surface of the alloy powder that is resistant to high temperature, reduces high-frequency eddy current loss and has high DC superposition performance, but has poor fluidity and adhesion, resulting in poor mechanical properties of the magnetic powder core and difficult application, as well as reduced resistivity and overall pressing density of the magnetic powder core, resulting in weakened magnetic powder core loss and magnetic permeability performance. In order to overcome the defects of inorganic coating and organic coating, multiple coatings are usually used to obtain inorganic-organic composite coatings to avoid the shortcomings of a single organic or inorganic coating, but this will bring about the problem of weak adhesion and compatibility of the inorganic and organic coatings, as well as the overall coating layer being too thick and uneven, reducing the overall performance of the obtained magnetic powder core, and it is impossible to prepare a coated magnetic powder core with high magnetic permeability and DC superposition performance and low loss.

[0004] The prior art discloses a method for preparing a magnetic powder core, in which organic silicon resin is first decomposed at high temperature to generate SiO2 for coating during the coating process to improve the rust resistance, and then coupled coating is performed. The whole process requires multiple coatings, which inevitably reduces the performance of the magnetic powder core, and can only improve part of the coating layer, and cannot reduce the overall coating thickness and the uniformity of the coating layer. The prior art also discloses a method for preparing an iron-nickel magnetic powder core, which first uses calcium oxide, kaolin, magnesium oxide and glue for an insulation coating, then uses phosphoric acid passivation, adds insulation and adhesive for secondary insulation coating, and obtains the product through pressing and heat treatment. The process requires multiple annealing and multiple coatings, which easily leads to uneven coating layers, and also affects magnetic properties such as loss and DC superposition. It can be seen that when the prior art uses inorganic-organic composite coating, there are problems such as weak adhesion and compatibility of the coating layer, and the overall coating layer is too thick and uneven, which will also reduce the overall performance of the magnetic powder core, and it is impossible to prepare a coated magnetic powder core with high magnetic permeability and DC superposition performance and low loss. Therefore, it is necessary to provide a coated magnetic powder core having a single-layer insulating coating layer with inorganic and organic properties, which has high magnetic permeability and DC superposition performance and low loss. Summary of the invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the problem that the inorganic or organic coating layer in the prior art cannot achieve the good coating effect of the inorganic and organic composite coating layer, but the inorganic and organic composite coating layers have weak adhesion and poor compatibility, and the overall coating layer is too thick and uneven, which makes the overall performance of the prepared magnetic powder core low and cannot have the defects of high magnetic permeability, low loss and high DC superposition performance. Thus, a dimethyl silicone oil for magnetic powder core and a preparation method, a coated magnetic powder core and a preparation method and application are provided.

[0006] To this end, the present invention provides the following technical solutions.

[0007] The present invention provides a method for preparing dimethyl silicone oil for magnetic powder cores, comprising taking crude dimethyl silicone oil, adding trimethylsilyl phosphate, and obtaining the dimethyl silicone oil;

[0008] The purity of the trimethylsilyl phosphate is not less than 99%;

[0009] Based on the total mass of monomers in the crude dimethyl silicone oil raw material, the added amount of the trimethylsilyl phosphate is 0.1-0.3%.

[0010] After adding trimethylsilyl phosphate for reaction, vacuum degassing is also included to obtain dimethyl silicone oil.

[0011] The vacuum degassing means that low molecular weight impurities in the reaction system are removed by vacuuming, which can make the process safe and stable and improve the purity of the product. The vacuum degassing is carried out according to a method known in the art, and the present invention does not make any specific limitation on this.

[0012] In an optional embodiment, the trimethylsilyl phosphate includes at least one of tris(trimethylsilyl)phosphate, trimethylsilyl dihydrogenphosphate and bistrimethylsilyl hydrogen phosphate;

[0013] In an optional embodiment, the trimethylsilyl phosphate includes tris(trimethylsilyl)phosphate;

[0014] Preferably, the trimethylsilyl phosphate further comprises at least one of trimethylsilyl dihydrogen phosphate and bistrimethylsilyl hydrogen phosphate;

[0015] Preferably, the method for preparing the crude dimethyl silicone oil comprises: mixing methylsiloxane, a capping agent and a catalyst and reacting them.

[0016] In an optional embodiment, the reaction temperature is 140-150°C;

[0017] In an optional embodiment, the reaction time is 3-4h; as an example, the reaction temperature is 140°C, 142°C, 144°C, 146°C, 148°C, 150°C or in the range of any two of the above values; the reaction time is 3h, 3.3h, 3.9h, 4h or in the range of any two of the above values.

[0018] In an optional embodiment, the mass ratio of tris(trimethylsilyl)phosphate to trimethylsilyl dihydrogenphosphate and / or bistrimethylsilyl hydrogen phosphate is (0.25-4.5):1;

[0019] Preferably, the mass ratio of tris(trimethylsilyl)phosphate to trimethylsilyl dihydrogenphosphate and / or bistrimethylsilyl hydrogen phosphate is 0.25:1, 0.67:1, 1:1, 4:1, etc.;

[0020] In an optional embodiment, the mass ratio of the methylsiloxane, the capping agent and the catalyst is 2000:(20-40):(1-2);

[0021] In an optional embodiment, the catalyst includes at least one of potassium hydroxide, sodium hydroxide, lithium hydroxide and cesium hydroxide;

[0022] In an optional embodiment, the methylsiloxane includes at least one of dimethylsiloxane mixed ring (DMC), hexamethylcyclotrisiloxane (D3), dodecamethylcyclohexasiloxane (D6), octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5); it is understandable that the methylsiloxane is preferably methylcyclosiloxane.

[0023] In an optional embodiment, the capping agent includes at least one of tetramethyldisiloxane, hexamethyldisiloxane and octamethyltrisiloxane.

[0024] The present invention provides a dimethyl silicone oil prepared by the above preparation method;

[0025] Preferably, the dimethyl silicone oil has a viscosity of 1000-20000 mPa.s / 25°C.

[0026] The present invention provides a method for preparing a coated magnetic powder core, comprising the following steps:

[0027] (1) adding dimethyl silicone oil and a solvent to an iron-nickel alloy powder to obtain coated magnetic powder; the dimethyl silicone oil is prepared by the above-mentioned preparation method or is selected from dimethyl silicone oils prepared by the above-mentioned preparation method;

[0028] (2) adding a release agent to the coated magnetic powder, pressing and heat treating the powder.

[0029] In an optional embodiment, the solvent includes at least one of ethanol, acetone and butanol;

[0030] In an optional embodiment, the iron-nickel alloy powder is heated to 100-140° C. and then dimethyl silicone oil and a solvent are added;

[0031] As an example, the pre-firing temperature of the present invention may be 100°C, 105°C, 110°C, 120°C, 130°C, 140°C or within a range formed by any two of the above values;

[0032] In an optional embodiment, in the step (1), based on the mass of the iron-nickel alloy powder, the content of the dimethyl silicone oil is 0.8-1.4%;

[0033] As an example, the content of dimethicone can be 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4% or within the range of any two of the above values;

[0034] In an optional embodiment, based on the mass of the iron-nickel alloy powder, the solvent content is 6-14%;

[0035] As an example, the content of the solvent may be 6%, 7%, 9%, 10%, 11%, 13%, 14%, or within a range consisting of any two of the above values;

[0036] In an optional embodiment, the method for preparing the iron-nickel alloy powder comprises: preparing an iron-nickel alloy raw powder by a gas atomization method, sieving the raw powder, and annealing the powder to prepare the iron-nickel alloy powder;

[0037] Preferably, in terms of mass percentage, the iron content of the iron-nickel alloy powder is 46-54%, and the nickel content of the iron-nickel alloy powder is 46-54%;

[0038] As an example, the iron content in the iron-nickel alloy powder may be 46%, 47%, 48%, 50%, 51%, 52%, 53%, 54%, or within a range formed by any two of the above values; the nickel content in the iron-nickel alloy powder may be 46%, 47%, 48%, 50%, 51%, 52%, 53%, 54%, or within a range formed by any two of the above values;

[0039] The ideal sum of the mass percentages of iron and nickel is equal to 100%; it is understandable that there are inevitable impurities in the iron-nickel alloy powder.

[0040] Preferably, the average particle size of the raw powder after sieving is 10-20 μm;

[0041] Preferably, the annealing treatment is performed under an inert atmosphere;

[0042] Preferably, the temperature of the annealing treatment is 600-700° C., and the time of the annealing treatment is 30-90 min.

[0043] As an example, the temperature of the annealing treatment of the present invention can be 600°C, 620°C, 640°C, 660°C, 680°C, 700°C, or within the range of any two of the above values; the time of the annealing treatment can be 30min, 40min, 50min, 60min, 70min, 80min, 90min, or within the range of any two of the above values;

[0044] In an optional embodiment, in the step (2), the content of the release agent is 0.2-1% based on the mass of the coated magnetic powder;

[0045] In an optional embodiment, the release agent includes at least one of zinc stearate, calcium stearate and aluminum stearate;

[0046] In an optional embodiment, the pressing pressure is 1200-2000 MPa;

[0047] In an optional embodiment, the heat treatment is carried out under a protective atmosphere or a reducing atmosphere;

[0048] As examples, the protective atmosphere may be nitrogen, argon, helium, etc.; the reducing atmosphere may be hydrogen, carbon monoxide, decomposed ammonia, etc.

[0049] In an optional embodiment, the heat treatment temperature is 650-800° C., and the heat treatment time is 30-90 min.

[0050] As an example, the heat treatment temperature of the present invention can be 650°C, 680°C, 700°C, 730°C, 760°C, 800°C, or within the range of any two of the above values; the heat treatment time can be 30min, 40min, 50min, 60min, 70min, 80min, 90min, or within the range of any two of the above values;

[0051] The invention provides a coated magnetic powder core prepared by the preparation method.

[0052] The present invention provides an application of a coated magnetic powder core prepared by the preparation method in the field of magnetic materials.

[0053] The technical solution of the present invention has the following advantages:

[0054] 1. The preparation method of dimethyl silicone oil for magnetic powder core provided by the present invention comprises taking crude dimethyl silicone oil, adding trimethyl silyl phosphate, and obtaining the dimethyl silicone oil; the purity of the trimethyl silyl phosphate is not less than 99%; the addition amount of the trimethyl silyl phosphate is 0.1-0.3% based on the total mass of monomers in the dimethyl silicone oil raw material. The present invention can prepare dimethyl silicone oil with a viscosity of 1000-20000mPa.s / 25℃, which is used to prepare magnetic powder cores, plays the role of a binder in the coating process, helps to simplify the process steps and reduce the variables between the steps, wherein the purity of the trimethyl silyl phosphate is limited so that when the obtained dimethyl silicone oil is used to coat the magnetic powder core, the obtained dimethyl silicone oil coating layer of the coated magnetic powder core has both the inorganic properties of phosphate and the organic properties of silicone oil, effectively improving the performance of the coated magnetic powder core.

[0055] 2. The preparation method of the coated magnetic powder core provided by the present invention comprises (1) adding dimethyl silicone oil and a solvent to an iron-nickel alloy powder to obtain a coated magnetic powder; the dimethyl silicone oil is prepared by the above-mentioned dimethyl silicone oil preparation method; (2) adding a release agent to the coated magnetic powder, pressing and heat treating. The present invention can prepare a coated magnetic powder core with high magnetic permeability, low loss and good DC superposition performance. The present invention does not require more complicated steps such as multiple coatings when preparing the coated magnetic powder core, thereby simplifying the process flow. The coated magnetic powder core of the present invention comprises a dimethyl silicone oil coating layer, and the dimethyl silicone oil coating layer has both the inorganic properties of phosphate and the organic properties of silicone oil, and is a coating layer in which inorganic and organic are fused with each other, thereby improving the magnetic permeability and DC superposition performance of the magnetic powder core, reducing losses, and effectively improving the performance of the coated magnetic powder core, avoiding the defects of single-layer coating and multi-layer coating in the prior art. Therefore, the dimethyl silicone oil prepared by the present invention is used to coat the magnetic powder core, which can ensure the performance of the magnetic powder core. In addition, the use of the dimethyl silicone oil containing an appropriate amount of phosphoric acid plasma as the magnetic powder core coating layer of the present invention can also reduce process costs and difficulty, and does not require high equipment accuracy.

[0056] 3. The preparation method of the coated magnetic powder core provided by the present invention, the present invention raises the temperature to 100-140°C so that the dimethyl silicone oil can be completely coated to obtain the coated magnetic powder core without high temperature decomposition. The present invention only needs dimethyl silicone oil for one-step coating, which simplifies the multi-step coating process of phosphoric acid coating, coupling agent coating and resin coating commonly used in the prior art; the viscosity of the prepared dimethyl silicone oil is 1000-20000mPa.s / 25°C, which can act as a binder to help the stability of the one-step coating process; the one-step coating process makes the process flow shorter and more controllable, and reduces the variables and external influences between the processes in the multi-step coating process. The present invention adds a solvent, and the solvent includes at least one of ethanol, acetone and butanol; the solvent can dissolve the prepared dimethyl silicone oil, so that the dimethyl silicone oil is fully and evenly coated, and the performance of the prepared coated magnetic powder core is improved. DETAILED DESCRIPTION

[0057] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0058] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0059] Example 1

[0060] This embodiment provides a method for preparing dimethyl silicone oil, comprising the following steps:

[0061] (1) 1 kg of hexamethylcyclotrisiloxane, 10 g of hexamethyldisiloxane, and 0.5 g of potassium hydroxide catalyst were mixed, reacted at 140° C. for 4 h, 1 g of tris(trimethylsilyl)phosphate (purity: 99%) was added for reaction, and vacuum degassing was performed to obtain dimethyl silicone oil; the obtained dimethyl silicone oil had a viscosity of 10000 Pa.s / 25° C.

[0062] This embodiment also provides a method for preparing a coated magnetic powder core, comprising the following steps:

[0063] (2) placing an iron ingot and a nickel ingot in a smelting furnace to remove impurities, obtaining a raw powder by a gas atomization method, sieving to obtain a raw powder with an average particle size of 20 μm, and annealing at 650° C. for 60 min in a nitrogen atmosphere to obtain an iron-nickel alloy powder; in terms of mass percentage, the iron content of the iron-nickel alloy powder is 46%, and the nickel content is 54%;

[0064] (3) Based on the mass of the iron-nickel alloy powder, the iron-nickel alloy powder is heated to 120° C., 0.8% dimethyl silicone oil and 10% ethanol are added, and the mixture is stirred evenly until dry to obtain coated magnetic powder;

[0065] (4) Based on the mass of the coated magnetic powder, 0.2% zinc stearate was added, and the magnetic powder core was molded at 2000 MPa. The molded magnetic powder core was heat treated at 800° C. for 30 minutes in an argon atmosphere to obtain a coated magnetic powder core.

[0066] Example 2

[0067] This embodiment provides a method for preparing dimethyl silicone oil, comprising the following steps:

[0068] (1) 1 kg of octamethylcyclotetrasiloxane, 20 g of tetramethyldisilane, and 0.5 g of potassium hydroxide catalyst were mixed, reacted at 140° C. for 4 h, 3 g of bistrimethylsilyl hydrogen phosphate (purity: 99%) was added for reaction, and vacuum degassing was performed to obtain dimethyl silicone oil; the obtained dimethyl silicone oil had a viscosity of 5000 Pa.s / 25° C.

[0069] This embodiment also provides a method for preparing a coated magnetic powder core, comprising the following steps:

[0070] (2) placing an iron ingot and a nickel ingot in a smelting furnace to remove impurities, obtaining a raw powder by a gas atomization method, sieving to obtain a raw powder with an average particle size of 10 μm, and annealing at 650° C. for 60 min in an argon atmosphere to obtain an iron-nickel alloy powder; in terms of mass percentage, the iron content of the iron-nickel alloy powder is 54% and the nickel content is 46%;

[0071] (3) Based on the mass of the iron-nickel alloy powder, the iron-nickel alloy powder is heated to 120° C., 1.4% dimethyl silicone oil and 10% ethanol are added, and the mixture is stirred evenly until dry to obtain coated magnetic powder;

[0072] (4) Based on the mass of the coated magnetic powder, 1.0% zinc stearate was added, and the powder core was molded at 1200 MPa. The molded magnetic powder core was heat treated at 650° C. for 90 minutes in a hydrogen atmosphere to obtain a coated magnetic powder core.

[0073] Example 3

[0074] This embodiment provides a method for preparing dimethyl silicone oil, comprising the following steps:

[0075] (1) 1 kg of decamethylcyclopentasiloxane, 15 g of octamethyltrisiloxane, and 0.5 g of potassium hydroxide catalyst were mixed, reacted at 140° C. for 4 h, 2 g of trimethylsilyl dihydrogen phosphate (purity of 99%) was added for reaction, and vacuum degassing was performed to obtain dimethyl silicone oil; the viscosity of the obtained dimethyl silicone oil was 15000 Pa.s / 25° C.

[0076] This embodiment also provides a method for preparing a coated magnetic powder core, comprising the following steps:

[0077] (2) placing an iron ingot and a nickel ingot in a smelting furnace to remove impurities, obtaining a raw powder by a gas atomization method, sieving to obtain a raw powder with an average particle size of 15 μm, and annealing at 650° C. for 60 min in a nitrogen atmosphere to obtain an iron-nickel alloy powder; in terms of mass percentage, the iron content of the iron-nickel alloy powder is 50% and the nickel content is 50%;

[0078] (3) Based on the mass of the iron-nickel alloy powder, the iron-nickel alloy powder is heated to 120° C., 1.1% dimethyl silicone oil and 10% ethanol are added, and the mixture is stirred evenly until dry to obtain coated magnetic powder;

[0079] (4) Based on the mass of the coated magnetic powder, 0.5% zinc stearate was added, and the powder core was molded at 1600 MPa. The molded magnetic powder core was heat treated at 720° C. for 60 min in a hydrogen atmosphere to obtain a coated magnetic powder core.

[0080] Example 4

[0081] This embodiment provides a method for preparing dimethyl silicone oil, comprising the following steps:

[0082] (1) 1 kg of hexamethylcyclotrisiloxane, 15 g of tetramethyldisilane, and 1 g of sodium hydroxide catalyst were mixed and reacted at 150° C. for 3 h, and 1.6 g of trimethylsilyl dihydrogen phosphate (purity: 99%) and 0.4 g of bistrimethylsilyl hydrogen phosphate (purity: 99%) were added and reacted, and the mixture was vacuum-desorbed to obtain dimethyl silicone oil; the viscosity of the obtained dimethyl silicone oil was 2000 Pa.s / 25° C.

[0083] This embodiment also provides a method for preparing a coated magnetic powder core, comprising the following steps:

[0084] (2) placing an iron ingot and a nickel ingot in a smelting furnace to remove impurities, obtaining a raw powder by a gas atomization method, sieving to obtain a raw powder with an average particle size of 15 μm, and annealing at 600° C. for 90 min in an argon atmosphere to obtain an iron-nickel alloy powder; in terms of mass percentage, the iron content of the iron-nickel alloy powder is 50% and the nickel content is 50%;

[0085] (3) Based on the mass of the iron-nickel alloy powder, the iron-nickel alloy powder is heated to 100° C., 0.8% dimethyl silicone oil and 6% acetone are added, and the mixture is stirred evenly until dry to obtain coated magnetic powder;

[0086] (4) Based on the mass of the coated magnetic powder, 0.5% zinc stearate was added, and the powder core was molded at 1600 MPa. The molded magnetic powder core was heat treated at 720° C. for 60 min in a nitrogen atmosphere to obtain a coated magnetic powder core.

[0087] Example 5

[0088] This embodiment provides a method for preparing dimethyl silicone oil, comprising the following steps:

[0089] (1) 1 kg of octamethylcyclotetrasiloxane, 10 g of octamethyltrisiloxane, and 1 g of sodium hydroxide catalyst were mixed, reacted at 150° C. for 3 h, and 2.4 g of tris(trimethylsilyl)phosphate (purity: 99%) and 0.6 g of bis(trimethylsilyl) hydrogen phosphate (purity: 99%) were added and vacuum degassing was performed to obtain dimethyl silicone oil; the viscosity of the obtained dimethyl silicone oil was 8000 Pa.s / 25° C.

[0090] This embodiment also provides a method for preparing a coated magnetic powder core, comprising the following steps:

[0091] (2) placing an iron ingot and a nickel ingot in a smelting furnace to remove impurities, obtaining a raw powder by a gas atomization method, sieving to obtain a raw powder with an average particle size of 15 μm, and annealing at 600° C. for 90 min in a nitrogen atmosphere to obtain an iron-nickel alloy powder; in terms of mass percentage, the iron content of the iron-nickel alloy powder is 50% and the nickel content is 50%;

[0092] (3) Based on the mass of the iron-nickel alloy powder, the iron-nickel alloy powder is heated to 100° C., 1.4% dimethyl silicone oil and 6% acetone are added, and the mixture is stirred evenly until dry to obtain coated magnetic powder;

[0093] (4) Based on the mass of the coated magnetic powder, 0.5% zinc stearate was added, and the powder core was molded at 1600 MPa. The molded magnetic powder core was heat treated at 720° C. for 60 min in a hydrogen atmosphere to obtain a coated magnetic powder core.

[0094] Example 6

[0095] This embodiment provides a method for preparing dimethyl silicone oil, comprising the following steps:

[0096] (1) 1 kg of decamethylcyclopentasiloxane, 20 g of hexamethyldisiloxane and 1 g of sodium hydroxide catalyst were mixed and reacted at 150° C. for 3 h, 0.2 g of tris(trimethylsilyl)phosphate (purity: 99%) and 0.8 g of trimethylsilyl dihydrogenphosphate (purity: 99%) were added and reacted, and the mixture was vacuum-desorbed to obtain dimethyl silicone oil; the viscosity of the obtained dimethyl silicone oil was 18000 Pa.s / 25° C.

[0097] This embodiment also provides a method for preparing a coated magnetic powder core, comprising the following steps:

[0098] (2) placing an iron ingot and a nickel ingot in a smelting furnace to remove impurities, obtaining a raw powder by a gas atomization method, sieving to obtain a raw powder with an average particle size of 15 μm, and annealing at 600° C. for 90 min in an argon atmosphere to obtain an iron-nickel alloy powder; in terms of mass percentage, the iron content of the iron-nickel alloy powder is 50% and the nickel content is 50%;

[0099] (3) Based on the mass of the iron-nickel alloy powder, the iron-nickel alloy powder is heated to 100° C., 1.1% dimethyl silicone oil and 6% acetone are added, and the mixture is stirred evenly until dry to obtain coated magnetic powder;

[0100] (4) Based on the mass of the coated magnetic powder, 0.5% zinc stearate was added, and the powder core was molded at 1600 MPa. The molded magnetic powder core was heat treated at 720° C. for 60 min in a hydrogen atmosphere to obtain a coated magnetic powder core.

[0101] Example 7

[0102] This embodiment provides a method for preparing dimethyl silicone oil, comprising the following steps:

[0103] (1) 1 kg of dimethylsiloxane mixed ring body, 20 g of octamethyltrisiloxane, and 0.75 g of lithium hydroxide catalyst were mixed and reacted at 145° C. for 3.5 h, and 1.8 g of tris(trimethylsilyl)phosphate (purity: 99%), 0.6 g of bistrimethylsilyl hydrogenphosphate (purity: 99%), and 0.6 g of trimethylsilyl dihydrogenphosphate (purity: 99%) were added and reacted, and vacuum degassing was performed to obtain dimethyl silicone oil; the obtained dimethyl silicone oil has a viscosity of 14000 Pa.s / 25° C.

[0104] This embodiment also provides a method for preparing a coated magnetic powder core, comprising the following steps:

[0105] (2) placing an iron ingot and a nickel ingot in a smelting furnace to remove impurities, obtaining a raw powder by a gas atomization method, sieving to obtain a raw powder with an average particle size of 15 μm, and annealing at 700° C. for 30 min in an argon atmosphere to obtain an iron-nickel alloy powder; in terms of mass percentage, the iron content of the iron-nickel alloy powder is 50% and the nickel content is 50%;

[0106] (3) Based on the mass of the iron-nickel alloy powder, the iron-nickel alloy powder is heated to 140° C., 0.8% dimethyl silicone oil and 14% butanol are added, and the mixture is stirred evenly until dry to obtain coated magnetic powder;

[0107] (4) Based on the mass of the coated magnetic powder, 0.5% zinc stearate was added, and the powder core was molded at 1600 MPa. The molded magnetic powder core was heat treated at 720° C. for 60 min in an argon atmosphere to obtain a coated magnetic powder core.

[0108] Example 8

[0109] This embodiment provides a method for preparing dimethyl silicone oil, comprising the following steps:

[0110] (1) 1 kg of dimethylsiloxane mixed ring body, 10 g of tetramethyldisilane, and 0.75 g of lithium hydroxide catalyst were mixed and reacted at 145° C. for 3.5 h, 0.4 g of tris(trimethylsilyl)phosphate (purity: 99%) and 0.6 g of trimethylsilyl dihydrogenphosphate (purity: 99%) were added and reacted, and the mixture was vacuum-desorbed to obtain dimethyl silicone oil; the viscosity of the obtained dimethyl silicone oil was 6000 Pa.s / 25° C.

[0111] This embodiment also provides a method for preparing a coated magnetic powder core, comprising the following steps:

[0112] (2) placing an iron ingot and a nickel ingot in a smelting furnace to remove impurities, obtaining a raw powder by a gas atomization method, sieving to obtain a raw powder with an average particle size of 15 μm, and annealing at 700° C. for 30 min in a nitrogen atmosphere to obtain an iron-nickel alloy powder; in terms of mass percentage, the iron content of the iron-nickel alloy powder is 50% and the nickel content is 50%;

[0113] (3) Based on the mass of the iron-nickel alloy powder, the iron-nickel alloy powder is heated to 140° C., 1.4% dimethyl silicone oil and 14% butanol are added, and the mixture is stirred evenly until dry to obtain coated magnetic powder;

[0114] (4) Based on the mass of the coated magnetic powder, 0.5% zinc stearate was added, and the powder core was molded at 1600 MPa. The molded magnetic powder core was heat treated at 720° C. for 60 min in a nitrogen atmosphere to obtain a coated magnetic powder core.

[0115] Example 9

[0116] This embodiment provides a method for preparing dimethyl silicone oil, comprising the following steps:

[0117] (1) 1 kg of dimethylsiloxane mixed ring body, 15 g of hexamethyldisiloxane, and 0.75 g of cesium hydroxide catalyst were mixed and reacted at 145° C. for 3.5 h, and 1 g of tris(trimethylsilyl)phosphate (purity: 99%), 0.6 g of bistrimethylsilyl hydrogenphosphate (purity: 99%), and 0.4 g of trimethylsilyl dihydrogenphosphate (purity: 99%) were added and reacted, and vacuum degassing was performed to obtain dimethyl silicone oil; the obtained dimethyl silicone oil has a viscosity of 12000 Pa.s / 25° C.

[0118] This embodiment also provides a method for preparing a coated magnetic powder core, comprising the following steps:

[0119] (2) placing an iron ingot and a nickel ingot in a smelting furnace to remove impurities, obtaining a raw powder by a gas atomization method, sieving to obtain a raw powder with an average particle size of 15 μm, and annealing at 700° C. for 30 min in an argon atmosphere to obtain an iron-nickel alloy powder; in terms of mass percentage, the iron content of the iron-nickel alloy powder is 46%, and the nickel content is 54%;

[0120] (3) Based on the mass of the iron-nickel alloy powder, the iron-nickel alloy powder is heated to 140° C., 1.1% dimethyl silicone oil and 14% butanol are added, and the mixture is stirred evenly until dry to obtain coated magnetic powder;

[0121] (4) Based on the mass of the coated magnetic powder, 0.2% zinc stearate was added, and the powder core was molded at 2000 MPa. The molded magnetic powder core was heat treated at 720° C. for 30 min in a hydrogen atmosphere to obtain a coated magnetic powder core.

[0122] Comparative Example 1

[0123] This comparative example provides a method for preparing dimethyl silicone oil. Compared with Example 9, the difference is that in step (1), 2 g of phosphoric acid (purity of 98%) is used instead of tris(trimethylsilyl) phosphate (purity of 99%), bis(trimethylsilyl) hydrogen phosphate (purity of 99%) and trimethylsilyl dihydrogen phosphate (purity of 99%) for reaction.

[0124] This comparative example provides a method for preparing a coated magnetic powder core. Compared with Example 9, the difference is that the dimethyl silicone oil prepared in this comparative example is used to prepare the coated magnetic powder core according to the method of Example 9.

[0125] Comparative Example 2

[0126] This comparative example provides a method for preparing a coated magnetic powder core. Compared with Example 9, the difference is that phosphoric acid and silicone resin (manufacturer: Shin-Etsu Japan; model: KR-220L silicone resin) are used to replace the dimethyl silicone oil in step (3); based on the mass of the iron-nickel alloy powder, the amount of phosphoric acid used is 0.1%, and the amount of silicone used is 1%.

[0127] Comparative Example 3

[0128] This comparative example provides a method for preparing a coated magnetic powder core. Compared with Example 9, the difference is that silicone resin (manufacturer: Japan Shin-Etsu; model: KR-220L silicone resin) of equal quality is used instead of dimethyl silicone oil.

[0129] Test example

[0130] This test example provides the properties of the materials prepared in each embodiment and comparative example, as follows:

[0131] Magnetic permeability test method: measured at 50kHz, 1V, using the equipment IWATSU SY-8218, the results are shown in Table 1;

[0132] The test method of loss 1 is: measured at 50kHz, magnetic field strength of 100mT, temperature of 25℃, using the equipment IWATSU SY-8218, the results are shown in Table 1;

[0133] The test method of loss 2 is: measured at 1MHz, magnetic field strength of 50mT, temperature of 25℃, using the equipment IWATSU SY-8218, the results are shown in Table 1;

[0134] Test method for DC superposition performance: Under 100Oe, the inductance is measured by the device Chroma 11300, and the DC superposition performance x is calculated according to the calculation formula: x = (inductance (100Oe) / inductance (0Oe)) × 100%; the results are shown in Table 1;

[0135] Table 1 Performance test results of various embodiments and comparative examples

[0136] Magnetic permeability (H / m) <![CDATA[Loss 1 (Kw / m 3 )]]> <![CDATA[Loss 2 (Kw / m 3 )]]> DC superposition (%) Example 1 111 181 2335 47.4％ Example 2 99 163 1933 50.4％ Example 3 101 168 2001 50.1％ Example 4 100 167 1978 50.3％ Example 5 118 173 2069 50.1％ Example 6 107 149 1813 53.6％ Example 7 116 170 1987 51.6％ Example 8 108 150 1823 53.5％ Example 9 115 151 1843 53.5％ Comparative Example 1 98 183 2363 46.8％ Comparative Example 2 91 209 2639 47.2％ Comparative Example 3 97 216 2777 45.6％

[0137] It can be seen from the above results that the coated magnetic powder core prepared by the present invention has the characteristics of high magnetic permeability, low loss and good DC superposition performance.

[0138] Comparison between Examples 1-3 and Comparative Examples 1-3 shows that after preparing dimethyl silicone oil with one of tris(trimethylsilyl)phosphate, trimethylsilyl dihydrogen phosphate and bistrimethylsilyl hydrogen phosphate, the coated magnetic powder core is prepared. The prepared coated magnetic powder core has higher magnetic permeability, lower loss and better DC superposition performance than the dimethyl silicone oil coated magnetic powder core prepared without using the present invention.

[0139] Comparison between Examples 1-4 and 5-9 shows that when tris(trimethylsilyl)phosphate is mixed with trimethylsilyl dihydrogenphosphate and / or bistrimethylsilyl hydrogen phosphate and dimethyl silicone oil is neutralized, and then prepared into a coated magnetic powder core according to the method of the present invention, the magnetic permeability and DC superposition performance are high, the loss is low, and the coating effect is the best.

[0140] It can be seen from the above embodiments that the dimethyl silicone oil obtained by mixing two or three of trimethylsilyl dihydrogen phosphate, bistrimethylsilyl hydrogen phosphate and tris(trimethylsilyl) phosphate has a more appropriate purity and contains more moderate phosphate ions, so that the performance of the inorganic-organic composite coating layer is better, and the performance of the magnetic powder core is effectively improved. In general, when two or three of trimethylsilyl dihydrogen phosphate, bistrimethylsilyl hydrogen phosphate and tris(trimethylsilyl) phosphate are used in combination, the comprehensive performance of the magnetic powder core is more excellent.

[0141] Example 9 is compared with Comparative Example 1. Dimethyl silicone oil is prepared by neutralization with phosphoric acid. The magnetic permeability of the coated magnetic powder core prepared by using dimethyl silicone oil as a raw material decreases, the loss increases, and the DC superposition performance is poor, which further indicates that the dimethyl silicone oil prepared by neutralization with trimethylsilyl phosphate has better quality and coating effect.

[0142] Example 9 is compared with Comparative Example 2. Comparative Example 2 uses phosphoric acid and silicone resin to perform multi-layer coating of inorganic and organic substances to form an inorganic-organic composite coating layer, but the inorganic and organic coating layers have weak adhesion and compatibility. This further illustrates that the inorganic-organic composite coating layer formed by coating with dimethyl silicone oil prepared by the present invention has good adhesion and compatibility, and the prepared coated magnetic powder core has high magnetic permeability and DC superposition performance and low loss.

[0143] Example 9 is compared with Comparative Example 3. Comparative Example 3 uses silicone resin alone to form an organic coating layer. The magnetic permeability and DC superposition performance of the coated magnetic powder core made according to the method of the present invention are significantly reduced, and the loss is greatly increased. This further indicates that the inorganic-organic composite coating layer can significantly reduce the loss and improve the magnetic permeability and DC superposition performance of the coated magnetic powder core.

[0144] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the scope of protection of the invention.

Claims

1. A method for preparing dimethyl silicone oil for magnetic powder cores, characterized in that: The method comprises taking crude dimethyl silicone oil, adding trimethylsilyl phosphate, and obtaining the dimethyl silicone oil; The purity of the trimethylsilyl phosphate is not less than 99%; Based on the total mass of monomers in the crude dimethyl silicone oil raw material, the added amount of the trimethylsilyl phosphate is 0.1-0.3%.

2. The preparation method according to claim 1, characterized in that: The trimethylsilyl phosphate includes at least one of tris(trimethylsilyl)phosphate, trimethylsilyl dihydrogenphosphate and bistrimethylsilyl hydrogen phosphate; Preferably, the method for preparing the crude dimethyl silicone oil comprises: mixing methylsiloxane, a capping agent and a catalyst and reacting them.

3. The preparation method according to claim 2, characterized in that: The reaction temperature is 140-150°C; and / or, The reaction time is 3-4h; and / or, The mass ratio of tris(trimethylsilyl)phosphate to trimethylsilyl dihydrogenphosphate and / or bistrimethylsilyl hydrogen phosphate is (0.25-4.5):1; and / or, The mass ratio of the methylsiloxane, the capping agent and the catalyst is 2000:(20-40):(1-2); and / or, The catalyst comprises at least one of potassium hydroxide, sodium hydroxide, lithium hydroxide and cesium hydroxide; and / or, The methylsiloxane comprises at least one of a dimethylsiloxane mixed ring, dodecamethylcyclohexasiloxane, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane and decamethylcyclopentasiloxane; and / or, The capping agent includes at least one of tetramethyldisiloxane, hexamethyldisiloxane and octamethyltrisiloxane.

4. A dimethyl silicone oil prepared according to the preparation method according to any one of claims 1 to 3; Preferably, the dimethyl silicone oil has a viscosity of 1000-20000 mPa.s / 25°C.

5. A method for preparing a coated magnetic powder core, characterized in that: The following steps are involved: (1) adding dimethyl silicone oil and a solvent to an iron-nickel alloy powder to obtain coated magnetic powder; the dimethyl silicone oil is prepared by the preparation method according to any one of claims 1 to 3 or is selected from claim 4; (2) adding a release agent to the coated magnetic powder, pressing and heat treating the powder.

6. The preparation method according to claim 5, characterized in that: The solvent comprises at least one of ethanol, acetone and butanol; and / or, The iron-nickel alloy powder is heated to 100-140° C. and then dimethyl silicone oil and a solvent are added; and / or, In the step (1), based on the mass of the iron-nickel alloy powder, the content of the dimethyl silicone oil is 0.8-1.4%; and / or, Based on the mass of the iron-nickel alloy powder, the solvent content is 6-14%.

7. The preparation method according to claim 5, characterized in that: The method for preparing the iron-nickel alloy powder comprises: preparing the iron-nickel alloy raw powder by gas atomization, sieving the raw powder, and annealing to prepare the iron-nickel alloy powder; Preferably, in terms of mass percentage, the iron content of the iron-nickel alloy powder is 46-54%, and the nickel content of the iron-nickel alloy powder is 46-54%; Preferably, the average particle size of the raw powder after sieving is 10-20 μm; Preferably, the annealing treatment is performed under an inert atmosphere; Preferably, the temperature of the annealing treatment is 600-700° C., and the time of the annealing treatment is 30-90 min.

8. The preparation method according to claim 5, characterized in that: In the step (2), based on the mass of the coated magnetic powder, the content of the release agent is 0.2-1%; and / or, The demoulding agent comprises at least one of zinc stearate, calcium stearate and aluminum stearate; and / or, The pressing pressure is 1200-2000 MPa; and / or, The heat treatment is carried out under a protective atmosphere or a reducing atmosphere; and / or, The temperature of the heat treatment is 650-800° C., and the time of the heat treatment is 30-90 minutes.

9. The coated magnetic powder core obtained by the preparation method according to any one of claims 5 to 8.

10. Application of the coated magnetic powder core prepared by the preparation method according to any one of claims 5 to 8 in the field of magnetic materials.