Bonded ferrite magnetic powder for injection molding and preparation method and application thereof
阅读说明：本技术 一种注射成型用粘结铁氧体磁粉及其制备方法与应用 (Bonded ferrite magnetic powder for injection molding and preparation method and application thereof ) 是由 王峰 熊君 胡国辉 周超 邢献虎 王继全 唐大为 刘辉 贾立颖 孙威 于 2021-10-29 设计创作，主要内容包括：本发明公开了一种注射成型用粘结铁氧体磁粉及其制备方法与应用,该注射成型用粘结铁氧体磁粉是将平均粒度为0.5～1.2微米的细粒铁氧体磁粉和平均粒度为3.0～6.0微米的粗粒铁氧体磁粉,按照所述细粒铁氧体磁粉占10～35wt％的重量比,加入到球磨机中进行球磨,从而得到的粗细混合磁粉。该注射成型用粘结铁氧体磁粉可与橡胶类粘结剂、增塑剂、稳定剂混合制备注射成型柔性粘结磁体。本发明能使磁粉的流动性和磁体的磁性能均得到大幅提升,超过现有同类产品的水平,而且能够使注射成型柔性粘结磁体的使用温度上限从80℃提高到125℃,这拓宽了其应用领域,增加了该注射成型柔性粘结磁体的稳定性和可靠性。(The invention discloses bonded ferrite magnetic powder for injection molding and a preparation method and application thereof, wherein the bonded ferrite magnetic powder for injection molding is prepared by adding fine-grain ferrite magnetic powder with the average particle size of 0.5-1.2 micrometers and coarse-grain ferrite magnetic powder with the average particle size of 3.0-6.0 micrometers into a ball mill for ball milling according to the weight ratio of the fine-grain ferrite magnetic powder accounting for 10-35 wt%. The bonded ferrite magnetic powder for injection molding can be mixed with rubber binder, plasticizer and stabilizer to prepare injection molding flexible bonded magnet. The invention can greatly improve the fluidity of magnetic powder and the magnetic performance of the magnet, and exceed the level of the existing similar products, and can improve the upper limit of the use temperature of the injection molding flexible bonded magnet from 80 ℃ to 125 ℃, thereby widening the application field and increasing the stability and reliability of the injection molding flexible bonded magnet.)
1. A bonded ferrite magnetic powder for injection molding is characterized in that a fine ferrite magnetic powder having an average particle size of 0.5 to 1.2 μm and a coarse ferrite magnetic powder having an average particle size of 3.0 to 6.0 μm are added to a ball mill in a weight ratio of 10 to 35 wt% of the fine ferrite magnetic powder to be ball-milled, thereby obtaining a coarse and fine mixed magnetic powder.
2. The bonded ferrite magnetic powder for injection molding according to claim 1, wherein the ball milling comprises: adding a ball milling auxiliary agent into a ball mill for ball milling; the ball-milling auxiliary agent is prepared by mixing triethanolamine, ethylene glycol and water according to the mass ratio of 0.5:0.5: 10.
3. A bonded ferrite magnetic powder for injection molding according to claim 1 or 2, wherein the fine ferrite magnetic powder contains 0.2 to 0.4 wt% bismuth oxide, and the coarse ferrite magnetic powder also contains 0.2 to 0.4 wt% bismuth oxide.
4. The bonded ferrite magnetic powder for injection molding according to claim 1 or 2, wherein 15 g of the bonded ferrite magnetic powder for injection molding is placed in a cylinder mold having a diameter of 25 mm, a molding pressure of 80KN is applied to press a cylindrical compact, the thickness of the compact is measured, and a compression density calculation is performed to obtain a compression density of 3.55g/cm of the bonded ferrite magnetic powder for injection molding3The above.
5. The bonded ferrite magnetic powder for injection molding according to claim 1 or 2, wherein the bonded ferrite magnetic powder for injection molding has a melt flow rate of 100g or more per 10 minutes when subjected to a flowability test in the following steps 1 to 3;
step 1, stirring and mixing 92 parts by weight of the bonded ferrite magnetic powder for injection molding, 1.0 part by weight of a stabilizer, 1.0 part by weight of a plasticizer and 6.0 parts by weight of a rubber binder by a stirrer; wherein the rubber adhesive is prepared by mixing polyvinyl chloride, thermoplastic polyurethane elastomer and thermoplastic polyester elastomer according to the weight ratio of 25:60: 15;
step 2, mixing the mixture obtained in the step 1 at 170-180 ℃ to prepare mixed particles with the average particle size of 3-4 mm;
and 3, placing the mixed particles obtained in the step 2 on a melt flow index tester, measuring the extrusion weight within 10 minutes under the conditions of 190 ℃ and 10kg load, and taking the extrusion weight as the melt flow rate.
6. The bonded ferrite magnetic powder for injection molding according to claim 1 or 2, wherein the bonded ferrite magnetic powder for injection molding is characterized in that an injection-molded flexible bonded magnet produced using the bonded ferrite magnetic powder for injection molding has an intrinsic coercive force of 190kA/m or more and a residual magnetic induction strength of 296mT or more when subjected to an intrinsic coercive force test and a residual magnetic induction strength test in the following steps 1, 2, and 4;
step 1, stirring and mixing 92 parts by weight of the bonded ferrite magnetic powder for injection molding, 1.0 part by weight of a stabilizer, 1.0 part by weight of a plasticizer and 6.0 parts by weight of a rubber binder by a stirrer; wherein the rubber adhesive is prepared by mixing polyvinyl chloride, thermoplastic polyurethane elastomer and thermoplastic polyester elastomer according to the weight ratio of 25:60: 15;
step 2, mixing the mixture obtained in the step 1 at 170-180 ℃ to prepare mixed particles with the average particle size of 3-4 mm;
and 4, injection molding the mixed particles obtained in the step 2 into a cylindrical injection molding flexible bonded magnet with the diameter of 20mm multiplied by 10mm in an orientation magnetic field of 8.0kGS at the temperature of 190 ℃, wherein the orientation magnetic field is parallel to the central axis of the cylinder, and the intrinsic coercive force and the residual magnetic induction strength of the magnetic field are measured by a permanent magnet measuring instrument.
7. A method for preparing a bonded ferrite magnetic powder for injection molding, comprising: adding fine ferrite magnetic powder with an average particle size of 0.5-1.2 micrometers and coarse ferrite magnetic powder with an average particle size of 3.0-6.0 micrometers into a ball mill according to a weight ratio of 10-35 wt% of the fine ferrite magnetic powder for ball milling to obtain coarse and fine mixed magnetic powder, namely the bonded ferrite magnetic powder for injection molding according to any one of claims 1-6.
8. The method of making a bonded ferrite magnetic powder for injection molding of claim 7, wherein the ball milling comprises: adding a ball milling auxiliary agent into a ball mill for ball milling; the ball-milling auxiliary agent is prepared by mixing triethanolamine, ethylene glycol and water according to the mass ratio of 0.5:0.5: 10.
9. The injection molding flexible bonded magnet is characterized by comprising the following raw materials in parts by weight:
92 to 93 parts of the bonded ferrite magnetic powder for injection molding according to any one of claims 1 to 6,
5-6 parts of a rubber binder,
1 to 1.5 parts of a plasticizer,
0.5-1 part of a stabilizer;
the rubber binder is prepared by blending 20-25 parts by weight of polyvinyl chloride, 60-70 parts by weight of thermoplastic polyurethane elastomer and 10-15 parts by weight of thermoplastic polyester elastomer.
10. An injection molded flexible bonded magnet as claimed in claim 9, wherein said polyvinyl chloride is model SG9 in accordance with GB/T5761-2006, having an average degree of polymerization of less than 650; the plasticizer is a long-chain chlorinated paraffin environment-friendly plasticizer; the stabilizer is an ultraviolet light absorber UV 531.
Technical Field
The invention relates to the field of injection molding flexible bonded magnets, in particular to bonded ferrite magnetic powder for injection molding and a preparation method and application thereof.
Background
Injection molding magnets require high fluidity of magnetic powder to fill a mold for injection molding into a magnetic device with a complicated shape, and the fluidity of the magnetic powder is generally improved by decreasing the powder content to decrease the volume ratio of the magnetic powder to the magnet and increasing the volume ratio of the binder to the magnet, but this decreases the magnetic performance of the injection molded magnet. The magnetic performance is improved to a certain extent by simply increasing the powder content, but the fluidity is reduced, the mechanical properties of the magnet are deteriorated, and the problem that the magnet cannot be molded is caused.
In order to solve the above-mentioned problems in terms of fluidity and magnetic properties, some prior patent documents disclose a coarse powder and fine powder mixing process, in which coarse ferrite powder and fine ferrite powder are mixed together to form ferrite powder for injection molding, which enables the fine ferrite powder to fill the pores of the coarse ferrite powder, thereby increasing the filling rate of the powder in the injection molded magnet, and achieving the purpose of improving the performance of the magnet to a certain extent. In the prior art, many patent documents are disclosed in the mixing process of coarse powder and fine powder, and the following examples are provided:
(1) chinese patent application CN200410034695.1 discloses a bonded magnet and ferrite magnetic powder for the bonded magnet, wherein the average grain size of coarse powder is 2.5-5.0 microns, the average grain size of fine powder is 0.5-1.0 micron, the weight of the fine powder is 15-40% of the mixed powder, the coarse powder and the fine powder are mixed by a wet method, the bonded magnet uses nylon 6 as a binder, and the shape of the magnet is rigid.
(2) Chinese patent application CN200880108680.1 discloses a ferrite powder for bonded magnet and its manufacturing method, and a bonded magnet using the same, wherein the ferrite powder adopts a coarse powder with an average particle size of 1.0-5.0 microns, a fine powder with an average particle size of 0.2-1.0 microns, the fine powder accounts for 15-40% of the weight of the mixed powder, the bonded magnet uses nylon 6 as binder, and the magnet is rigid in shape.
(3) Chinese patent application CN201080016639.9 discloses a ferrite powder for bonded magnets, a method for producing the same, and a bonded magnet using the same, wherein coarse powder and fine powder are mixed, the average particle size range of the coarse powder and the fine powder is not specified, the fine powder accounts for 15 to 40% of the weight of the mixed powder, the bonded magnet uses nylon 6 as a binder, and the shape of the magnet is rigid.
It can be seen from the above documents that the coarse powder and fine powder mixing process in the prior art has at least the following problems:
(1) in the prior art, the coarse powder and fine powder mixing process is used for preparing a bonded magnet with a rigid magnet form, and the bonding agents used by the bonded magnet are nylon bonding agents, so that the bonded magnet cannot be bent and deformed to be matched with a complex part for use, and the application field is greatly limited.
(2) In the prior art, coarse powder and fine powder are respectively prepared firstly, and then the coarse powder and the fine powder are mixed by adopting a dry mixing method or a wet mixing method, the fine powder and the coarse powder cannot be densely combined after the mixing by the method, so that the volume of the coarse and fine mixed magnetic powder is increased, and when high powder content molding is carried out subsequently, due to the resistance action of a binder in a molten state, the difficulty of filling the fine powder in the coarse and fine mixed magnetic powder into gaps between the coarse powder and the fine powder in the binder is increased, so that the volume ratio of the magnetic powder in a magnet is increased, and the improvement of the fluidity and the magnetic performance is not favorable.
(3) In the prior art, the formula of the magnetic powder adopted by the coarse powder and fine powder mixing process is unreasonable, so that the particle size uniformity of the coarse ferrite magnetic powder and the fine ferrite magnetic powder is poor, a large number of oversize magnetic powder particles and undersize magnetic powder particles are generated, the sizes of the magnetic powder particles are dispersed, the filling of the fine particle magnetic powder is not facilitated, and the magnetic performance of a magnet is reduced.
In view of the above, the present invention is particularly proposed.
Disclosure of Invention
The invention aims to provide bonded ferrite magnetic powder for injection molding and a preparation method and application thereof, so as to solve the technical problems in the prior art. The invention can be used for preparing the injection molding flexible bonded magnet, so that the fluidity of the bonded ferrite magnetic powder for injection molding and the magnetic performance of the injection molding flexible bonded magnet can be greatly improved and exceed the level of similar products in the prior art, and the upper limit of the use temperature of the prepared injection molding flexible bonded magnet can be improved to 125 ℃ from 80 ℃ in the prior art, thereby widening the application field of the injection molding flexible bonded magnet and increasing the stability and reliability of the injection molding flexible bonded magnet.
The purpose of the invention is realized by the following technical scheme:
a bonded ferrite magnetic powder for injection molding is a coarse and fine mixed magnetic powder obtained by adding a fine ferrite magnetic powder having an average particle size of 0.5 to 1.2 μm and a coarse ferrite magnetic powder having an average particle size of 3.0 to 6.0 μm to a ball mill in a weight ratio of 10 to 35 wt% of the fine ferrite magnetic powder.
Preferably, the ball milling comprises: adding a ball milling auxiliary agent into a ball mill for ball milling; the ball-milling auxiliary agent is prepared by mixing triethanolamine, ethylene glycol and water according to the mass ratio of 0.5:0.5: 10.
Preferably, the fine ferrite magnetic powder contains 0.2 to 0.4 wt% of bismuth oxide, and the coarse ferrite magnetic powder also contains 0.2 to 0.4 wt% of bismuth oxide.
Preferably, the bonded iron for injection molding is used15 g of ferrite magnetic powder is put into a cylinder die with the diameter of 25 mm, the forming pressure of 80KN is applied to press the ferrite magnetic powder into a cylindrical pressed compact, the thickness of the pressed compact is measured, and the compression density is calculated, so that the compression density of the bonded ferrite magnetic powder for injection molding is 3.55g/cm3The above.
Preferably, the bonded ferrite magnetic powder for injection molding has a melt flow rate of 100g or more per 10 minutes when subjected to a flowability test in the following steps 1 to 3;
step 1, stirring and mixing 92 parts by weight of the bonded ferrite magnetic powder for injection molding, 1.0 part by weight of a stabilizer, 1.0 part by weight of a plasticizer and 6.0 parts by weight of a rubber binder by a stirrer; wherein the rubber adhesive is prepared by mixing polyvinyl chloride, thermoplastic polyurethane elastomer and thermoplastic polyester elastomer according to the weight ratio of 25:60: 15;
step 2, mixing the mixture obtained in the step 1 at 170-180 ℃ to prepare mixed particles with the average particle size of 3-4 mm;
and 3, placing the mixed particles obtained in the step 2 on a melt flow index tester, measuring the extrusion weight within 10 minutes under the conditions of 190 ℃ and 10kg load, and taking the extrusion weight as the melt flow rate.
Preferably, when the bonded ferrite magnetic powder for injection molding is subjected to the intrinsic coercive force test and the residual magnetic induction strength test in the following steps 1, 2 and 4, the intrinsic coercive force of the injection-molded flexible bonded magnet made of the bonded ferrite magnetic powder for injection molding is 190kA/m or more and the residual magnetic induction strength is 296mT or more;
step 1, stirring and mixing 92 parts by weight of the bonded ferrite magnetic powder for injection molding, 1.0 part by weight of a stabilizer, 1.0 part by weight of a plasticizer and 6.0 parts by weight of a rubber binder by a stirrer; wherein the rubber adhesive is prepared by mixing polyvinyl chloride, thermoplastic polyurethane elastomer and thermoplastic polyester elastomer according to the weight ratio of 25:60: 15;
step 2, mixing the mixture obtained in the step 1 at 170-180 ℃ to prepare mixed particles with the average particle size of 3-4 mm;
and 4, injection molding the mixed particles obtained in the step 2 into a cylindrical injection molding flexible bonded magnet with the diameter of 20mm multiplied by 10mm in an orientation magnetic field of 8.0kGS at the temperature of 190 ℃, wherein the orientation magnetic field is parallel to the central axis of the cylinder, and the intrinsic coercive force and the residual magnetic induction strength of the magnetic field are measured by a permanent magnet measuring instrument.
A method of making a bonded ferrite magnetic powder for injection molding, comprising: adding fine ferrite magnetic powder with the average particle size of 0.5-1.2 micrometers and coarse ferrite magnetic powder with the average particle size of 3.0-6.0 micrometers into a ball mill for ball milling according to the weight ratio of the fine ferrite magnetic powder accounting for 10-35 wt% to obtain coarse and fine mixed magnetic powder, namely the bonded ferrite magnetic powder for injection molding.
Preferably, the ball milling comprises: adding a ball milling auxiliary agent into a ball mill for ball milling; the ball-milling auxiliary agent is prepared by mixing triethanolamine, ethylene glycol and water according to the mass ratio of 0.5:0.5: 10.
An injection molding flexible bonded magnet comprises the following raw materials in parts by weight:
the rubber binder is prepared by blending 20-25 parts by weight of polyvinyl chloride, 60-70 parts by weight of thermoplastic polyurethane elastomer and 10-15 parts by weight of thermoplastic polyester elastomer.
Preferably, the polyvinyl chloride is an SG9 model product conforming to GB/T5761-2006, and the average polymerization degree of the polyvinyl chloride is less than 650; the plasticizer is a long-chain chlorinated paraffin environment-friendly plasticizer; the stabilizer is an ultraviolet light absorber UV 531.
Compared with the prior art, the invention combines the coarse ferrite magnetic powder and the fine ferrite magnetic powder with specific average particle size with ball milling to prepare the bonded ferrite magnetic powder for injection molding, and the bonded ferrite magnetic powder is matched with the rubber binder, the plasticizer and the stabilizer with special formula according to specific proportion for use, thereby preparing the injection molding flexible bonded magnet, greatly improving the fluidity of the bonded ferrite magnetic powder for injection molding and the magnetic performance of the injection molding flexible bonded magnet, both exceeding the level of similar products at home and abroad, and improving the upper limit of the use temperature of the prepared injection molding flexible bonded magnet from 80 ℃ of the existing flexible bonded magnet to 125 ℃, thereby widening the application field of the injection molding flexible bonded magnet and increasing the stability and the reliability of the injection molding flexible bonded magnet.
Detailed Description
The technical scheme in the embodiment of the invention is clearly and completely described below; it is to be understood that the described embodiments are merely exemplary of the invention, and are not intended to limit the invention to the particular forms disclosed. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
The terms that may be used herein are first described as follows:
the term "and/or" means that either or both can be achieved, for example, X and/or Y means that both cases include "X" or "Y" as well as three cases including "X and Y".
The terms "comprising," "including," "containing," "having," or other similar terms of meaning should be construed as non-exclusive inclusions. For example: including a feature (e.g., material, component, ingredient, carrier, formulation, material, dimension, part, component, mechanism, device, process, procedure, method, reaction condition, processing condition, parameter, algorithm, signal, data, product, or article of manufacture), is to be construed as including not only the particular feature explicitly listed but also other features not explicitly listed as such which are known in the art.
The term "consisting of … …" is meant to exclude any technical feature elements not explicitly listed. If used in a claim, the term shall render the claim closed except for the inclusion of the technical features that are expressly listed except for the conventional impurities associated therewith. If the term occurs in only one clause of the claims, it is defined only to the elements explicitly recited in that clause, and elements recited in other clauses are not excluded from the overall claims.
The term "parts by weight" is intended to indicate the relationship of mass proportions between the various components, for example: if the X component is described as X parts by weight and the Y component is described as Y parts by weight, the mass ratio of the X component to the Y component is represented as X: Y; 1 part by weight may represent any mass, for example: 1 part by weight may be expressed as 1kg or 3.1415926 kg. The sum of the parts by weight of all components is not necessarily 100 parts and may be greater than 100 parts, less than 100 parts or equal to 100 parts. Parts, ratios and percentages described herein are by mass unless otherwise indicated.
When concentrations, temperatures, pressures, dimensions, or other parameters are expressed as ranges of values, the ranges are to be understood as specifically disclosing all ranges formed from any pair of upper, lower, and preferred values within the range, regardless of whether ranges are explicitly recited; for example, if a numerical range of "2 ~ 8" is recited, then the numerical range should be interpreted to include ranges of "2 ~ 7", "2 ~ 6", "5 ~ 7", "3 ~ 4 and 6 ~ 7", "3 ~ 5 and 7", "2 and 5 ~ 7", and the like. Unless otherwise indicated, the numerical ranges recited herein include both the endpoints thereof and all integers and fractions within the numerical range.
The bonded ferrite magnetic powder for injection molding provided by the present invention, and the preparation method and application thereof will be described in detail below. Details not described in the present invention are well known to those skilled in the art. Those not specifically mentioned in the examples of the present invention were carried out according to the conventional conditions in the art or conditions suggested by the manufacturer. The reagents or instruments used in the examples of the present invention are not specified by manufacturers, and are all conventional products available by commercial purchase.
Bonded ferrite magnetic powder for injection molding
The invention provides bonded ferrite magnetic powder for injection molding, which is prepared by adding fine-grain ferrite magnetic powder with the average particle size of 0.5-1.2 micrometers and coarse-grain ferrite magnetic powder with the average particle size of 3.0-6.0 micrometers into a ball mill for ball milling according to the weight ratio of the fine-grain ferrite magnetic powder accounting for 10-35 wt%.
Wherein the weight ratio of the fine-grained ferrite magnetic powder to 10 to 35 wt% means that the fine-grained ferrite magnetic powder accounts for 10 to 35 wt% of the total of the fine-grained ferrite magnetic powder and the coarse-grained ferrite magnetic powder.
In the prior art, the particle size distribution of the traditional bonded ferrite magnetic powder for injection molding is normally distributed, the waveform of the laser particle size distribution shows a single peak value, and the compression density is generally 3.3g/cm3Left and right; the three patent applications mentioned in the background of the present application are ferrite magnetic powder prepared by mixing coarse powder and fine powder, and the waveform of the laser particle size distribution has multiple peaks, and the compression density can reach 3.5g/cm3. The inventor researches and discovers that: performing ball milling on fine ferrite magnetic powder with the average particle size of 0.5-1.2 microns and coarse ferrite magnetic powder with the average particle size of 3.0-6.0 microns as raw materials to obtain coarse and fine mixed magnetic powder with high compression density, wherein the compression density of the coarse and fine mixed magnetic powder is at least 3.55g/cm3The volume percentage of the magnetic powder with the same mass percentage in the binder can be smaller, so that the volume ratio of the binder can be relatively increased, the fluidity of the coarse and fine mixed magnetic powder and the magnetic performance of the injection molding flexible bonded magnet prepared from the coarse and fine mixed magnetic powder can be greatly improved, and the dual-high magnetic performance and fluidity can be effectively realized.
In a typical but non-limiting embodiment of the invention, the fine ferrite magnetic powder having an average particle size of 0.5 to 1.2 μm is a fine ferrite magnetic powder having an average particle size of 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1 or 1.2 μm.
In a typical but non-limiting embodiment of the invention, the coarse ferrite magnetic powder having an average particle size of 3.0 to 6.0 microns is a coarse ferrite magnetic powder having an average particle size of 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, or 6.0 microns.
In a typical but non-limiting embodiment of the present invention, the weight ratio of the fine ferrite magnetic powder to 10 to 35 wt% is 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, 30 wt%, 31 wt%, 32 wt%, 33 wt%, 34 wt%, or 35 wt% of the fine ferrite magnetic powder to the total of the fine ferrite magnetic powder and the coarse ferrite magnetic powder.
In a preferred embodiment of the present invention, the ball milling comprises: adding fine ferrite magnetic powder with the average particle size of 0.5-1.2 microns, coarse ferrite magnetic powder with the average particle size of 3.0-6.0 microns and a ball-milling auxiliary agent into a ball mill for ball milling to obtain coarse and fine mixed magnetic powder; the ball milling auxiliary agent can be a ball milling auxiliary agent in the prior art, but the ball milling auxiliary agent which is prepared by mixing triethanolamine, ethylene glycol and water according to the mass ratio of 0.5:0.5:10 and is provided by the invention is preferably adopted; different from the prior art, the invention combines the coarse ferrite magnetic powder and the fine ferrite magnetic powder with specific average particle size with ball milling to prepare coarse and fine mixed magnetic powder, and adds the ball milling auxiliary agent provided by the invention in the ball milling process (the ball milling auxiliary agent is formed by mixing triethanolamine, ethylene glycol and water according to the mass ratio of 0.5:0.5: 10), thereby enabling the coarse ferrite magnetic powder and the fine ferrite magnetic powder to be mixed and dispersed more uniformly in the ball milling process, reducing the friction resistance among the magnetic powders, being beneficial to the self-adaptive optimization improvement of the joint surface morphology and the integral average particle size of the coarse ferrite magnetic powder and the fine ferrite magnetic powder, eliminating the pores between the coarse ferrite magnetic powder and the fine ferrite magnetic powder to the greatest extent, enabling the coarse ferrite magnetic powder and the fine ferrite magnetic powder to be more closely and organically combined, further reducing the volume of the coarse and fine mixed magnetic powder, improving the compression density of the coarse and fine mixed magnetic powder, the minimum value of the compressed density also exceeds the level of the prior three patent applications mentioned in the background of the present application.
In a typical but non-limiting embodiment of the invention, the ball milling time of the ball mill is 0.5 to 1.0 hour.
In a typical but non-limiting embodiment of the invention, the ball milling is accomplished using a prior art JM-2L wet ball mill.
In a preferred embodiment of the invention, the fine ferrite magnetic powder contains 0.2 to 0.4 wt% bismuth oxide, and/or the coarse ferrite magnetic powder also contains 0.2 to 0.4 wt% bismuth oxide; preferably, the fine ferrite magnetic powder and the coarse ferrite magnetic powder each contain 0.2 to 0.4 wt% of bismuth oxide; that is, bismuth oxide is added to the composition of the fine-grained ferrite magnetic powder in an amount of 0.2 to 0.4 wt% based on the total weight of the fine-grained ferrite magnetic powder, and bismuth oxide is also added to the composition of the coarse-grained ferrite magnetic powder in an amount of 0.2 to 0.4 wt% based on the total weight of the coarse-grained ferrite magnetic powder. Besides bismuth oxide, the other components of the fine ferrite magnetic powder may be those of ferrite magnetic powder in the prior art, and the other components of the coarse ferrite magnetic powder may also be those of ferrite magnetic powder in the prior art. According to the invention, the bismuth oxide with a specific proportion is added into the composition formula of the fine-grain ferrite magnetic powder and the coarse-grain ferrite magnetic powder, so that the grain sizes of the fine-grain ferrite magnetic powder and the coarse-grain ferrite magnetic powder are more refined and more uniform, the generation of oversize magnetic powder particles and undersize magnetic powder particles is reduced, the grain sizes of the magnetic powder are concentrated, the average grain size is more accurately controlled, the fine-grain ferrite magnetic powder is favorably filled into gaps of the coarse-grain ferrite magnetic powder, the magnetic performance of the flexible bonded magnet prepared from the magnetic powder is improved, and the flowability of the magnetic powder can be improved at the same time.
In typical but non-limiting embodiments of the invention, the fine-grained ferrite magnetic powder contains 0.20%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, 0.30%, 0.31%, 0.32%, 0.33%, 0.34%, 0.35%, 0.36%, 0.37%, 0.38%, 0.39%, or 0.40% by weight bismuth oxide.
In typical but non-limiting embodiments of the invention, the coarse ferrite magnetic powder contains 0.20%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, 0.30%, 0.31%, 0.32%, 0.33%, 0.34%, 0.35%, 0.36%, 0.37%, 0.38%, 0.39%, or 0.40% by weight bismuth oxide.
In a preferred embodiment of the present invention, the fine ferrite magnetic powder can be produced by a magnetic powder production method of the related art; for example: the fine ferrite magnetic powder can adopt the' raw material mixing->Balling>Drying->Sintering->Crushing->Ball milling>Annealing material>PH value treatment>Drying and crushing. In a preferred embodiment of the present invention, the coarse ferrite magnetic powder can be prepared by a magnetic powder preparation method in the prior art; for example: the coarse ferrite magnetic powder can adopt' raw material mixing->Balling>Drying->Sintering->Crushing->Ball milling>Annealing material>PH value treatment>Drying and crushing. In a preferred embodiment of the present invention, 15 g of the bonded ferrite magnetic powder for injection molding provided by the present invention is placed in a cylinder mold having a diameter of 25 mm, a molding pressure of 80KN is applied to press the powder into a cylindrical compact, the thickness of the compact is measured, and a compression density calculation is performed, whereby the bonded ferrite magnetic powder for injection molding has a Compression Density (CD) of 3.55g/cm3The above.
In a preferred embodiment of the present invention, the bonded ferrite magnetic powder for injection molding provided by the present invention has a melt flow rate of 100g/10 min or more when subjected to a flowability test in the following steps 1 to 3:
step 1, stirring and mixing 92 parts by weight of the bonded ferrite magnetic powder for injection molding, 1.0 part by weight of a stabilizer, 1.0 part by weight of a plasticizer and 6.0 parts by weight of a rubber binder by a stirrer; the rubber adhesive is prepared by mixing polyvinyl chloride, a thermoplastic polyurethane elastomer and a thermoplastic polyester elastomer according to the weight ratio of 25:60: 15.
And 2, mixing the mixture obtained in the step 1 at 170-180 ℃ to prepare mixed particles with the average particle size of 3-4 mm.
And 3, placing the mixed particles obtained in the step 2 on a melt flow index tester, and measuring the extrusion weight within 10 minutes under the conditions of 190 ℃ and 10kg load, wherein the extrusion weight is used as the melt flow rate (unit: g/10 minutes).
In a preferred embodiment of the present invention, the bonded ferrite magnetic powder for injection molding provided by the present invention, when subjected to the intrinsic coercive force test and the residual magnetic induction test in the following steps 1, 2, and 4, an injection-molded flexible bonded magnet produced using the bonded ferrite magnetic powder for injection molding has an intrinsic coercive force (iHc) of 190kA/m or more and a residual magnetic induction (Br) of 296mT or more:
step 1, stirring and mixing 92 parts by weight of the bonded ferrite magnetic powder for injection molding, 1.0 part by weight of a stabilizer, 1.0 part by weight of a plasticizer and 6.0 parts by weight of a rubber binder by a stirrer; the rubber adhesive is prepared by mixing polyvinyl chloride, a thermoplastic polyurethane elastomer and a thermoplastic polyester elastomer according to the weight ratio of 25:60: 15.
And 2, mixing the mixture obtained in the step 1 at 170-180 ℃ to prepare mixed particles with the average particle size of 3-4 mm.
And 4, injection molding the mixed particles obtained in the step 2 into a cylindrical injection molding flexible bonded magnet with the diameter of 20mm multiplied by 10mm in an orientation magnetic field of 8.0kGS at the temperature of 190 ℃, wherein the orientation magnetic field is parallel to the central axis of the cylinder, and the intrinsic coercive force and the residual magnetic induction strength of the magnetic field are measured by a permanent magnet measuring instrument.
(II) preparation method of bonded ferrite magnetic powder for injection molding
The invention provides a preparation method of bonded ferrite magnetic powder for injection molding, which is used for preparing the bonded ferrite magnetic powder for injection molding and specifically comprises the following steps: adding fine ferrite magnetic powder with the average particle size of 0.5-1.2 micrometers and coarse ferrite magnetic powder with the average particle size of 3.0-6.0 micrometers into a ball mill for ball milling according to the weight ratio of the fine ferrite magnetic powder accounting for 10-35 wt% to obtain coarse and fine mixed magnetic powder, namely the bonded ferrite magnetic powder for injection molding provided by the invention.
In a preferred embodiment of the present invention, the ball milling comprises: adding fine ferrite magnetic powder with the average particle size of 0.5-1.2 microns, coarse ferrite magnetic powder with the average particle size of 3.0-6.0 microns and a ball-milling auxiliary agent into a ball mill for ball milling to obtain coarse and fine mixed magnetic powder; the ball milling auxiliary agent can be a ball milling auxiliary agent in the prior art, but the ball milling auxiliary agent provided by the invention and formed by mixing triethanolamine, ethylene glycol and water according to the mass ratio of 0.5:0.5:10 is preferably adopted.
In a preferred embodiment of the invention, the fine ferrite magnetic powder contains 0.2 to 0.4 wt% bismuth oxide, and/or the coarse ferrite magnetic powder also contains 0.2 to 0.4 wt% bismuth oxide; preferably, the fine ferrite magnetic powder and the coarse ferrite magnetic powder each contain 0.2 to 0.4 wt% of bismuth oxide; that is, bismuth oxide is added to the composition of the fine-grained ferrite magnetic powder in an amount of 0.2 to 0.4 wt% based on the total weight of the fine-grained ferrite magnetic powder, and bismuth oxide is also added to the composition of the coarse-grained ferrite magnetic powder in an amount of 0.2 to 0.4 wt% based on the total weight of the coarse-grained ferrite magnetic powder. Besides bismuth oxide, the other components of the fine ferrite magnetic powder may be those of ferrite magnetic powder in the prior art, and the other components of the coarse ferrite magnetic powder may also be those of ferrite magnetic powder in the prior art.
In a preferred embodiment of the present invention, the fine ferrite magnetic powder can be produced by a magnetic powder production method of the related art; for example: the fine ferrite magnetic powder can be prepared by adopting the processes of raw material mixing- > pelletizing- > drying- > sintering- > crushing- > ball milling- > tempering- > PH value treatment- > drying and crushing in the prior art.
In a preferred embodiment of the present invention, the coarse ferrite magnetic powder can be prepared by a magnetic powder preparation method in the prior art; for example: the coarse ferrite magnetic powder can be prepared by adopting the processes of raw material mixing- > pelletizing- > drying- > sintering- > crushing- > ball milling- > tempering- > PH value treatment- > drying and crushing in the prior art.
(III) an injection-molded flexible bonded magnet
The invention also provides an injection molding flexible bonded magnet which comprises the following raw materials in parts by weight: 92-93 parts of bonded ferrite magnetic powder for injection molding, 5-6 parts of rubber binder, 1-1.5 parts of plasticizer and 0.5-1 part of stabilizer.
In a preferred embodiment of the present invention, the rubber-based binder is prepared by blending 20 to 25 parts by weight of polyvinyl chloride (PVC), 60 to 70 parts by weight of thermoplastic polyurethane elastomer (TPU), and 10 to 15 parts by weight of thermoplastic polyester elastomer (TPEE). The invention creatively develops the rubber adhesive with the special formula, the rubber adhesive with the special formula is matched with the bonded ferrite magnetic powder for injection molding according to a specific proportion for use, the injection-molded flexible bonded magnet can be prepared, the upper limit of the use temperature of the prepared injection-molded flexible bonded magnet can be increased, the upper limit of the use temperature of the flexible bonded magnet is increased from 80 ℃ in the prior art to 125 ℃, the application field of the injection-molded flexible bonded magnet is widened, and the stability and the reliability of the injection-molded flexible bonded magnet are increased.
In a preferred embodiment of the invention, the polyvinyl chloride (PVC) is a product of model SG9 which conforms to the GB/T5761-2006 standard, and the average polymerization degree of the product is less than 650; the melt fluidity of the magnet can be greatly improved by adopting the polyvinyl chloride.
In a preferred embodiment of the invention, the thermoplastic polyurethane elastomer (TPU) is a prior art thermoplastic polyurethane elastomer with the type H570; the thermoplastic polyurethane elastomer (TPU) and the thermoplastic polyester elastomer (TPEE) are mixed to be used as the binder, so that the heat resistance of the flexible bonding magnet can be improved, and the service temperature of the flexible bonding magnet can reach 125 ℃.
In a preferred embodiment of the present invention, the thermoplastic polyester elastomer (TPEE) is a prior art thermoplastic polyester elastomer with model number H2525; the thermoplastic polyester elastomer (TPEE) and the thermoplastic polyurethane elastomer (TPU) are mixed to be used as the binder, so that the heat resistance of the flexible bonding magnet can be improved, and the service temperature of the flexible bonding magnet can reach 125 ℃.
In a preferred embodiment of the invention, the plasticizer is a long-chain chlorinated paraffin environment-friendly plasticizer; the plasticizer plays roles of plasticization and lubrication.
In a preferred embodiment of the present invention, the stabilizer is an ultraviolet absorber UV 531; the stabilizer improves aging resistance of the magnet.
Compared with the prior art, the bonded ferrite magnetic powder for injection molding, the preparation method of the bonded ferrite magnetic powder for injection molding and the injection molding flexible bonded magnet provided by the invention have the following advantages:
(1) different from the prior art, the invention combines the coarse ferrite magnetic powder with specific average grain size and the fine ferrite magnetic powder with ball milling to prepare the coarse and fine mixed magnetic powder, and adds the ball milling auxiliary agent creatively researched by the invention in the ball milling process, thereby enabling the coarse ferrite magnetic powder and the fine ferrite magnetic powder to be mixed and dispersed more uniformly in the ball milling process, reducing the frictional resistance between the magnetic powders, being beneficial to the self-adaptive optimization and improvement of the appearance of the joint surface and the integral average granularity of the coarse ferrite magnetic powder and the fine ferrite magnetic powder, eliminating the pores between the coarse ferrite magnetic powder and the fine ferrite magnetic powder to the greatest extent, enabling the coarse ferrite magnetic powder and the fine ferrite magnetic powder to be combined more closely and organically, further reducing the volume of the coarse and fine mixed magnetic powder, improving the compression density of the coarse and fine mixed magnetic powder, the minimum value of the compressed density also exceeds the level of the prior three patent applications mentioned in the background of the present application.
(2) According to the invention, the bismuth oxide with a specific proportion is added into the composition formula of the fine-grain ferrite magnetic powder and the coarse-grain ferrite magnetic powder, so that the grain sizes of the fine-grain ferrite magnetic powder and the coarse-grain ferrite magnetic powder are more refined and more uniform, the generation of oversize magnetic powder particles and undersize magnetic powder particles is reduced, the grain sizes of the magnetic powder are concentrated, the average grain size is more accurately controlled, and the filling of the fine-grain ferrite magnetic powder is facilitated, thereby improving the magnetic performance of the flexible bonded magnet prepared from the magnetic powder, and simultaneously improving the fluidity of the magnetic powder.
(3) The mixing process of coarse powder and fine powder in the prior art is used for preparing rigid magnets and is not used for preparing flexible magnets, and particularly, the injection molding flexible bonded magnet with excellent magnetic performance prepared by adopting coarse and fine mixed magnetic powder with high compression density and high melt flowability is a technical blank. The invention combines the coarse ferrite magnetic powder and the fine ferrite magnetic powder with specific average particle size with ball milling to prepare the bonded ferrite magnetic powder for injection molding with high compression density and high melt flowability, and the bonded ferrite magnetic powder is matched with a rubber binder, a plasticizer and a stabilizer with a special formula according to a specific proportion for use, so that the injection molding flexible bonded magnet with excellent magnetic performance can be prepared, the flowability of the bonded ferrite magnetic powder for injection molding and the magnetic performance of the injection molding flexible bonded magnet can be greatly improved and exceed the level of similar products at home and abroad, the upper limit of the service temperature of the prepared injection molding flexible bonded magnet can be improved to 125 ℃ from 80 ℃ of the existing flexible bonded magnet, the application field of the injection molding flexible bonded magnet is widened, and the stability and the reliability of the injection molding flexible bonded magnet are improved.
In conclusion, the embodiment of the invention can be used for preparing the injection molding flexible bonded magnet, so that the flowability of the bonded ferrite magnetic powder for injection molding and the magnetic performance of the injection molding flexible bonded magnet can be greatly improved and exceed the level of similar products in the prior art, and the upper limit of the service temperature of the prepared injection molding flexible bonded magnet can be increased to 125 ℃ from 80 ℃ in the prior art, thereby widening the application field of the injection molding flexible bonded magnet and increasing the stability and reliability of the injection molding flexible bonded magnet.
In order to more clearly show the technical solutions and the technical effects provided by the present invention, the following detailed descriptions of the bonded ferrite magnetic powder for injection molding, the preparation method and the application thereof are provided in the following embodiments.
Example 1
An injection molded flexible bonded magnet, the method of making which may include the steps of:
step A1, preparation of fine ferrite magnetic powder: weighing iron oxide and strontium carbonate according to the mol ratio of 5.78: 1; adding 0.2 wt% of bismuth oxide and 2.98 wt% of strontium chloride to the total weight of the iron oxide and the strontium carbonate to the iron oxide and the strontium carbonate, mixing, granulating with water to obtain pellets having a diameter of 5-10 mm, drying in an oven at 130 ℃, sintering the dried pellets in an electric furnace at 1250 ℃ for 2 hours, crushing with a jaw crusher, and ball-milling with a JM-2L wet ball mill for 6 hours to obtain fine-grained ferrite magnetic powder having an average particle size of 0.5 μm.
Step A2, preparation of coarse ferrite magnetic powder: weighing iron oxide and strontium carbonate according to the mol ratio of 5.78: 1; adding bismuth oxide accounting for 0.2 wt% of the total weight of the iron oxide and the strontium carbonate and strontium chloride accounting for 2.98 wt% of the total weight of the iron oxide and the strontium carbonate into the iron oxide and the strontium carbonate, mixing the materials together, granulating the mixture by using water to prepare a material ball with the diameter of 5-10 mm, drying the material ball in a 130 ℃ oven, sintering the dried material ball in an electric furnace at 1250 ℃ for 2 hours, and crushing the material ball by using a jaw crusher to obtain coarse-grained ferrite magnetic powder with the average grain size of 3.0 microns.
Step A3, preparation of coarse and fine mixed magnetic powder: the fine ferrite magnetic powder with the average particle size of 0.5 micron in step a1 and the coarse ferrite magnetic powder with the average particle size of 3.0 micron in step a2 are added into a ball mill according to the weight ratio of 35 wt% of the fine ferrite magnetic powder to 65 wt% of the coarse ferrite magnetic powder, a ball milling aid (the ball milling aid is formed by mixing triethanolamine, ethylene glycol and water according to the mass ratio of 0.5:0.5: 10) is added into the ball mill for ball milling for 1.0 hour, then the mixed powder is washed with water, dried, placed in an electric furnace for tempering at 950 ℃, then washed with 2 wt% hydrochloric acid solution to make the pH value of the mixed powder reach 6-7, and then dried and crushed to obtain coarse and fine mixed ferrite magnetic powder, namely the bonded ferrite magnetic powder for injection molding prepared in embodiment 1 of the invention.
Step A4, preparation of injection molding flexible bonded magnet: and (2) stirring and mixing 92 parts by weight of the coarse and fine mixed magnetic powder obtained in the step A3, 6 parts by weight of rubber binder, 1 part by weight of plasticizer and 1 part by weight of stabilizer together by using a stirrer, then extruding and granulating by using a double-screw extruder, and performing injection molding on the obtained granules on an injection machine, wherein the injection temperature is 175-190 ℃, and the size of a molded sample is phi 20 x 10mm, so that the injection molded flexible bonded magnet is obtained.
Wherein the rubber adhesive is prepared by blending 25 parts by weight of polyvinyl chloride (PVC), 65 parts by weight of thermoplastic polyurethane elastomer (TPU) and 10 parts by weight of thermoplastic polyester elastomer (TPEE). The heat resistance of the flexible bonding magnet can be improved by using the thermoplastic polyurethane elastomer (TPU) and the thermoplastic polyester elastomer (TPEE) as the bonding agent in a mixed way, and the use temperature of the flexible bonding magnet can reach 125 ℃. The polyvinyl chloride (PVC) is an SG9 product meeting GB/T5761-2006 standard, the average polymerization degree of the polyvinyl chloride (PVC) is less than 650, and the melt fluidity of the magnet can be greatly improved by adopting the polyvinyl chloride. The plasticizer is a long-chain chlorinated paraffin environment-friendly plasticizer, and can play a role in plasticization and lubrication. The stabilizer is an ultraviolet absorbent UV531, and the aging resistance of the magnet can be improved by adopting the stabilizer.
Specifically, the parameters of the injection molding such as the temperature gradient in step a4 are shown in table 1 below:
TABLE 1
A segment of
Two segment
Three sections
Magnetizing current
Cooling and pressure maintaining
190℃
185℃
175℃
70A
Operation cycle 100S
Further, the comparison of the performance and the temperature aging resistance of the prior art product 1 (the prior art product 1 employs the injection magnetic powder BMZR-3D produced by north mineral magnet science and technology limited and the flexible magnet BMZR-Y3 produced from the injection magnetic powder BMZR-3D) with the injection molding bonded ferrite magnetic powder produced in step A3 of example 1 of the present invention and the injection molding flexible bonded magnet produced in step a4 was examined, and the results are shown in the following table 2 and table 3:
TABLE 2
Characteristics of
Unit of
Example 1
Prior art product 1
Remanence (Br)
mT
296
290
Coercive force (bHc)
kA/m
176
170
Intrinsic coercivity (iHc)
kA/m
210
205
Maximum magnetic energy product ((BH) max)
kJ/m3
16.8
15.9
Flow MFR
g/10min
105
85
Compressed density of magnetic powder
g/cm3
3.57
3.38
TABLE 3
As can be seen from table 2 above: the compressed density of the traditional ferrite magnetic powder is generally 3.3g/cm3About, the compression density of the prior art product 1 in Table 2 reached 3.38g/cm3The bonded ferrite magnetic powder for injection molding obtained in example 1 of the present invention had a compressed density of 3.57g/cm3Meanwhile, the fluidity and the magnetic performance of the injection molding flexible bonded magnet prepared by the embodiment 1 of the invention are both better than those of the product 1 in the prior art. As can be seen from table 3 above: the product 1 in the prior art is seriously deformed and cracked under the temperature-resistant aging condition of 125 ℃ for 96 hours, but the volume of the injection-molded flexible bonded magnet prepared in the embodiment 1 of the invention is hardly changed under the temperature-resistant aging condition of 125 ℃ for 96 hours, which shows that the upper limit of the use temperature of the injection-molded flexible bonded magnet prepared in the embodiment 1 of the invention is increased from 80 ℃ in the prior art to 125 ℃, thus widening the application field of the injection-molded flexible bonded magnet and increasing the stability and reliability of the injection-molded flexible bonded magnet.
Example 2
An injection molded flexible bonded magnet, the method of making which may include the steps of:
step B1, preparation of fine ferrite magnetic powder: weighing iron oxide and strontium carbonate according to the mol ratio of 5.78: 1; adding 0.2 wt% of bismuth oxide and 2.98 wt% of strontium chloride to the total weight of the iron oxide and the strontium carbonate to the iron oxide and the strontium carbonate, mixing, granulating with water to obtain pellets having a diameter of 5-10 mm, drying in an oven at 130 ℃, sintering the dried pellets in an electric furnace at 1250 ℃ for 2 hours, crushing with a jaw crusher, and ball-milling with a JM-2L wet ball mill for 4 hours to obtain fine-grained ferrite magnetic powder having an average particle size of 0.8 μm.
Step B2, preparation of coarse ferrite magnetic powder: weighing iron oxide and strontium carbonate according to the mol ratio of 5.78: 1; adding bismuth oxide accounting for 0.2 wt% of the total weight of the iron oxide and the strontium carbonate and strontium chloride accounting for 2.98 wt% of the total weight of the iron oxide and the strontium carbonate into the iron oxide and the strontium carbonate, mixing the materials together, granulating the mixture by using water to prepare a material ball with the diameter of 5-10 mm, drying the material ball in a 130 ℃ oven, sintering the dried material ball in an electric furnace at 1250 ℃ for 2 hours, and crushing the material ball by using a jaw crusher to obtain the coarse-grained ferrite magnetic powder with the average grain size of 4.0 microns.
Step B3, preparation of coarse and fine mixed magnetic powder: adding the fine ferrite magnetic powder with the average particle size of 0.8 micron in the step B1 and the coarse ferrite magnetic powder with the average particle size of 4.0 micron in the step B2 into a ball mill according to the weight ratio of 25 wt% of the fine ferrite magnetic powder to 75 wt% of the coarse ferrite magnetic powder, adding a ball milling aid (the ball milling aid is formed by mixing triethanolamine, ethylene glycol and water according to the mass ratio of 0.5:0.5: 10) into the ball mill for ball milling for 1.0 hour, washing and drying the mixed powder, tempering the mixed powder in an electric furnace at 950 ℃, then washing the mixed powder with 2 wt% hydrochloric acid solution to make the pH value of the mixed powder reach 6-7, and drying and crushing the washed mixed powder to obtain coarse and fine mixed ferrite magnetic powder, namely the bonded ferrite magnetic powder for injection molding prepared in the embodiment 2 of the invention.
Step B4, preparation of injection molding flexible bonded magnet: and B, stirring and mixing 92 parts by weight of the coarse and fine mixed magnetic powder obtained in the step B3, 6 parts by weight of rubber binder, 1 part by weight of plasticizer and 1 part by weight of stabilizer together by using a stirrer, then extruding and granulating by using a double-screw extruder, and performing injection molding on the obtained granules on an injection machine, wherein the injection temperature is 175-190 ℃, and the size of a molded sample is phi 20 x 10mm, so that the injection molded flexible bonded magnet is obtained.
Wherein the rubber adhesive is prepared by blending 20 parts by weight of polyvinyl chloride (PVC), 70 parts by weight of thermoplastic polyurethane elastomer (TPU) and 10 parts by weight of thermoplastic polyester elastomer (TPEE). The heat resistance of the flexible bonding magnet can be improved by using the thermoplastic polyurethane elastomer (TPU) and the thermoplastic polyester elastomer (TPEE) as the bonding agent in a mixed way, and the use temperature of the flexible bonding magnet can reach 125 ℃. The polyvinyl chloride (PVC) is an SG9 product meeting GB/T5761-2006 standard, the average polymerization degree of the polyvinyl chloride (PVC) is less than 650, and the melt fluidity of the magnet can be greatly improved by adopting the polyvinyl chloride. The plasticizer is a long-chain chlorinated paraffin environment-friendly plasticizer, and can play a role in plasticization and lubrication. The stabilizer is an ultraviolet absorbent UV531, and the aging resistance of the magnet can be improved by adopting the stabilizer.
Specifically, the parameters of the injection molding such as temperature gradient in step B4 are shown in table 4 below:
TABLE 4
A segment of
Two segment
Three sections
Magnetizing current
Cooling and pressure maintaining
190℃
185℃
175℃
70A
Operation cycle 100S
Further, a comparison test of the performance and the temperature aging resistance was carried out on the prior art product 2 (the prior art product 2 was made of the injection magnetic powder BMZR-3C produced by north mineral magnet technology ltd and the flexible magnet BMZR-Y2 produced from the injection magnetic powder BMZR-3C) with the injection molding bonded ferrite magnetic powder produced in step B3 of example 2 of the present invention and the injection molding flexible bonded magnet produced in step B4, and the results are shown in the following table 5 and table 6:
TABLE 5
TABLE 6
As can be seen from table 5 above: the compressed density of the traditional ferrite magnetic powder is generally 3.3g/cm3About, the compression density of prior art product 2 in Table 5 reached 3.39g/cm3The bonded ferrite magnetic powder for injection molding obtained in example 2 of the present invention had a compressed density of 3.59g/cm3Meanwhile, the fluidity and the magnetic performance of the injection molding flexible bonded magnet prepared by the embodiment 2 of the invention are both superior to those of the product 2 in the prior art. As can be seen from table 6 above: the product 2 in the prior art is seriously deformed and cracked under the temperature-resistant aging condition of 125 ℃ for 96 hours, but the volume of the injection-molded flexible bonded magnet prepared in the embodiment 2 of the invention is hardly changed under the temperature-resistant aging condition of 125 ℃ for 96 hours, which shows that the upper limit of the use temperature of the injection-molded flexible bonded magnet prepared in the embodiment 2 of the invention is increased from 80 ℃ in the prior art to 125 ℃, thus widening the application field of the injection-molded flexible bonded magnet and increasing the stability and reliability of the injection-molded flexible bonded magnet.
Example 3
An injection molded flexible bonded magnet, the method of making which may include the steps of:
step C1, preparation of fine ferrite magnetic powder: weighing iron oxide and strontium carbonate according to the mol ratio of 5.78: 1; adding 0.2 wt% of bismuth oxide and 2.98 wt% of strontium chloride to the total weight of the iron oxide and the strontium carbonate to the iron oxide and the strontium carbonate, mixing, granulating with water to obtain pellets having a diameter of 5-10 mm, drying in an oven at 130 ℃, sintering the dried pellets in an electric furnace at 1250 ℃ for 2 hours, crushing with a jaw crusher, and ball-milling with a JM-2L wet ball mill for 2.5 hours to obtain fine-grained ferrite magnetic powder having an average particle diameter of 1.2 μm.
Step C2, preparation of coarse ferrite magnetic powder: weighing iron oxide and strontium carbonate according to the mol ratio of 5.78: 1; adding bismuth oxide accounting for 0.2 wt% of the total weight of the iron oxide and the strontium carbonate and strontium chloride accounting for 2.98 wt% of the total weight of the iron oxide and the strontium carbonate into the iron oxide and the strontium carbonate, mixing the materials together, granulating the mixture by using water to prepare a material ball with the diameter of 5-10 mm, drying the material ball in a 130 ℃ oven, sintering the dried material ball in an electric furnace at 1250 ℃ for 2 hours, and crushing the material ball by using a jaw crusher to obtain the coarse-grained ferrite magnetic powder with the average grain size of 6.0 microns.
Step C3, preparation of coarse and fine mixed magnetic powder: the fine ferrite magnetic powder with the average particle size of 1.2 microns obtained in the step C1 and the coarse ferrite magnetic powder with the average particle size of 6.0 microns obtained in the step C2 are added into a ball mill according to the weight ratio of 10 wt% of the fine ferrite magnetic powder to 90 wt% of the coarse ferrite magnetic powder, a ball milling aid (the ball milling aid is formed by mixing triethanolamine, ethylene glycol and water according to the mass ratio of 0.5:0.5: 10) is added into the ball mill for ball milling for 1.0 hour, then the mixed powder is washed with water, dried, placed in an electric furnace for tempering at 950 ℃, then washed with 2 wt% hydrochloric acid solution to make the pH value of the mixed powder reach 6-7, and then dried and crushed to obtain coarse and fine mixed ferrite magnetic powder, namely the bonded ferrite magnetic powder for injection molding prepared in the embodiment 3 of the present invention.
Step C4, preparation of injection molded flexible bonded magnet: and C, stirring and mixing 93 parts by weight of the coarse and fine mixed magnetic powder obtained in the step C3, 6 parts by weight of rubber binder, 1 part by weight of plasticizer and 1 part by weight of stabilizer together by using a stirrer, then extruding and granulating by using a double-screw extruder, and performing injection molding on the obtained granules on an injection machine, wherein the injection temperature is 175-190 ℃, and the size of a molded sample is phi 20 x 10mm, so that the injection molded flexible bonded magnet is obtained.
Wherein the rubber adhesive is prepared by blending 20 parts by weight of polyvinyl chloride (PVC), 65 parts by weight of thermoplastic polyurethane elastomer (TPU) and 15 parts by weight of thermoplastic polyester elastomer (TPEE). The heat resistance of the flexible bonding magnet can be improved by using the thermoplastic polyurethane elastomer (TPU) and the thermoplastic polyester elastomer (TPEE) as the bonding agent in a mixed way, and the use temperature of the flexible bonding magnet can reach 125 ℃. The polyvinyl chloride (PVC) is an SG9 product meeting GB/T5761-2006 standard, the average polymerization degree of the polyvinyl chloride (PVC) is less than 650, and the melt fluidity of the magnet can be greatly improved by adopting the polyvinyl chloride. The plasticizer is a long-chain chlorinated paraffin environment-friendly plasticizer, and can play a role in plasticization and lubrication. The stabilizer is an ultraviolet absorbent UV531, and the aging resistance of the magnet can be improved by adopting the stabilizer.
Specifically, the parameters of the injection molding such as temperature gradient in step C4 are shown in table 7 below:
TABLE 7
A segment of
Two segment
Three sections
Magnetizing current
Cooling and pressure maintaining
190℃
185℃
175℃
70A
Operation cycle 100S
Further, a comparison test of the performance and the temperature aging resistance was carried out on the prior art product 3 (the prior art product 3 was made of the injection magnetic powder BMZR-3A produced by north mineral magnet science and technology ltd and the flexible magnet BMZR-Y1 produced from the injection magnetic powder BMZR-3A) with the bonded ferrite magnetic powder for injection molding produced in step C3 of example 3 of the present invention and the injection-molded flexible bonded magnet produced in step C4, and the results are shown in the following table 8 and table 9:
TABLE 8
TABLE 9
As can be seen from table 8 above: the compressed density of the traditional ferrite magnetic powder is generally 3.3g/cm3About, the compression density of prior art product 3 in Table 8 reached 3.48g/cm3The injection molding adhesive prepared in example 3 of the present inventionThe compressed density of the ferrite magnetic powder reaches 3.62g/cm3Meanwhile, the fluidity and the magnetic performance of the injection molding flexible bonded magnet prepared by the embodiment 3 of the invention are both superior to those of the product 3 in the prior art. As can be seen from table 9 above: the product 3 in the prior art is seriously deformed and cracked under the temperature-resistant aging condition of 125 ℃ for 96 hours, but the volume of the injection-molded flexible bonded magnet prepared in the embodiment 3 of the invention is hardly changed under the temperature-resistant aging condition of 125 ℃ for 96 hours, which shows that the upper limit of the use temperature of the injection-molded flexible bonded magnet prepared in the embodiment 3 of the invention is increased from 80 ℃ in the prior art to 125 ℃, thus widening the application field of the injection-molded flexible bonded magnet and increasing the stability and reliability of the injection-molded flexible bonded magnet.
In conclusion, the embodiment of the invention can be used for preparing the injection molding flexible bonded magnet, so that the flowability of the bonded ferrite magnetic powder for injection molding and the magnetic performance of the injection molding flexible bonded magnet can be greatly improved and exceed the level of similar products in the prior art, and the upper limit of the service temperature of the prepared injection molding flexible bonded magnet can be increased to 125 ℃ from 80 ℃ in the prior art, thereby widening the application field of the injection molding flexible bonded magnet and increasing the stability and reliability of the injection molding flexible bonded magnet.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims. The information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.