JP2005268352A - Resin bonded magnet and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin bonded magnet in which not only corrosion resistance against high temperature and high humidity but also excellent corrosion resistance against salt water can be improved, and high magnetic characteristics capable of reducing not only the generation of rust due to oxidation but also the deterioration of magnetic characteristics can be obtained. <P>SOLUTION: Rare-earth magnetic powder and bonding resin are mixed with each other by a mixing process 1, the surface of a resin bonded magnet body molded by a compression molding process 2 is etched by alkalescent etching process 3, the etched resin bonded magnet body is treated with phosphate by a phosphate treatment process 4 using zinc phosphate group or manganese phosphate group phosphate, and then a resin film is formed on the surface of the resin bonded magnet body after the phosphate treatment. Consequently, a resin bonded magnet of high corrosion resistance can be obtained in which Zn<SB>3</SB>(PO<SB>4</SB>)<SB>2</SB>/4H<SB>2</SB>O and/or Zn<SB>2</SB>M(PO<SB>4</SB>)<SB>2</SB>/4H<SB>2</SB>O (where M contains Mn as an essential element and contains one element out of Ni and Fe) exists on the surface of the resin bonded magnet body and a resin film is formed on the surface. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a resin-bonded magnet using a rare earth-based magnetic powder (rare earth magnet powder) and a binding resin. More specifically, the surface of the base resin-bound magnet body is subjected to a phosphate treatment. The present invention relates to a resin-bonded magnet having a structure in which a resin film is formed on the outer peripheral surface and having excellent corrosion resistance against water or salt water, and a method for producing the same.

  Conventional permanent magnets used for small or high-performance motors, etc., are resin-bonded magnets made by mixing ferrite or rare-earth magnetic powder and a binding resin, or sintered by sintering magnetic powder. A magnet is used.

  In recent years, not only electronic equipment for automobiles, but also IT-related equipment, audio / video equipment, etc., have become lighter, thinner, and smaller, and motors using permanent magnets have become smaller and more precise. High performance and high durability are essential.

  Against this background, ferrite magnets and metal sintered magnets produced by the sintering method have a large shrinkage ratio in the sintering process, making it difficult to ensure the dimensional accuracy required for applications such as small motors. This leads to the problem that the processing process after the consequent is forced, the lead time of manufacturing becomes long, and the manufacturing cost rises rapidly.

  In addition, in ferrite magnets, there is a limit to the increase in the maximum energy product that governs the performance of permanent magnets, and there is a problem that it cannot follow the high performance of magnetic properties required for motors and the like.

  As described above, high dimensional accuracy can be achieved because the shrinkage ratio is extremely small in the process after molding into a predetermined shape, and high performance is achieved by molding with high pressure and densification. From the viewpoint that it can be achieved, resin-bonded magnets using a mixed material of rare-earth magnetic powders such as SmCo-based and NdFeB-based and binding resins have come to be used favorably.

  On the other hand, the rare earth-based magnetic powders described above are highly active because they contain rare earth metals, both in sintered magnets made by sintering and in resin-bonded magnets that are mixed with resins. There arises a problem that the magnetic properties are deteriorated due to the generation of rust and, consequently, alteration.

  As a method of suppressing the occurrence of rust in the resin-bonded magnet as described above and improving the corrosion resistance, it is roughly divided into a method of applying a corrosion-resistant treatment to the surface of the resin-bonded magnet body after molding, and a magnetic powder to be used in advance. There is a method of performing a corrosion resistance treatment. For example, Patent Document 1 below discloses a method in which phosphate is coated on the surface of a molded body formed by compression molding R-Fe-B magnetic powder and synthetic resin. Patent Document 2 below discloses a bonded magnet using magnet powder in which the surface of an iron-based magnetic powder containing a rare earth element is uniformly coated with a phosphate film having an average of 5 to 100 nm.

Japanese Patent Application Laid-Open No. 64-13707 Japanese Patent Laid-Open No. 2003-7521

  By the way, as motors incorporating permanent magnets are miniaturized and their applications are diversified, permanent magnets are required to have high levels of corrosion resistance as well as high performance. Conventionally, the corrosion resistance related to the moisture resistance test has been used as a quality test, but the field in which motors with permanent magnets are used has expanded from acoustic and communication equipment for fixed installation to in-vehicle use. In addition, the corrosion resistance test for salt water has been regarded as important, and the need for further improvement of the corrosion resistance has increased.

  However, the phosphating treatment disclosed in the above-mentioned Patent Document 1 can withstand a conventional moisture resistance test, but is insufficient for a corrosion resistance test against salt water, and causes problems such as generation of rust due to oxidation and hence deterioration of magnetic properties due to alteration. May occur.

As described above, the resin-bonded magnet having high magnetic characteristics is obtained by mixing a mixed material obtained by mixing rare earth magnetic powder and a binding resin with a high pressure (specifically, 784 to 980 Mpa (8 to 10 tf / cm ² ) or more). There is a need for compression molding. In this case, when a phosphate coating is applied to the magnetic powder, the above-mentioned Patent Document 2 causes a considerable amount of cracking or fracture of the rare earth magnetic powder during the compression molding process, resulting in a new active surface in the rare earth magnetic powder. Therefore, the corrosion resistance may be deteriorated.

  In view of the above-mentioned problems of the prior art, the present invention is not limited to the improvement of corrosion resistance to high temperature and high humidity, and is excellent in corrosion resistance to salt water, and has high magnetic characteristics with little generation of rust due to oxidation, and hence less deterioration of magnetic characteristics due to alteration. An object of the present invention is to provide a resin-bonded magnet and a method for producing the same.

  Other objects and novel features of the present invention will be clarified in embodiments described later.

In order to achieve the above object, a resin-bonded magnet according to the first aspect of the present invention is provided with Zn ₃ (PO ₄ ) on the surface of a resin-bonded magnet body obtained by mixing rare earth magnetic powder and a binding resin. ) ₂ · 4H ₂ O and / or Zn ₂ M (PO ₄ ) ₂ · 4H ₂ O (where M is an essential component of Mn and includes one of Ni and Fe), and a resin thereon It is characterized in that a film is formed.

  The resin-bonded magnet according to the invention of claim 2 is characterized in that, in claim 1, the resin film has an average film thickness of 1 to 10 μm.

  A resin-bonded magnet according to a third aspect of the present invention is characterized in that, in the first or second aspect, the resin film has a multilayer structure.

  The resin-bonded magnet according to the invention of claim 4 is the resin-bonded magnet according to claim 1, 2 or 3, wherein the rare earth-based magnetic powder is 95 parts by weight or more with respect to 100 parts by weight of the resin-bonded magnet body. It is a feature.

  According to a fifth aspect of the present invention, there is provided a method for producing a resin-bonded magnet, wherein the surface of a resin-bonded magnet body formed by mixing a rare earth-based magnetic powder and a binding resin is made of zinc phosphate and / or manganese phosphate. It is characterized in that a phosphate treatment is performed using a phosphate, and a resin film is formed on the surface of the resin-bonded magnet body after the phosphate treatment.

  The method for producing a resin-bonded magnet according to the invention of claim 6 is characterized in that, in claim 5, etching is performed with a weak alkali before the phosphate treatment.

  The resin-bonded magnet according to the invention of claim 7 is the resin-bonded magnet according to claim 5 or 6, wherein the resin-bonded magnet body after the phosphate treatment is repeatedly immersed in a resin solution a plurality of times to form the resin film. It is characterized by doing.

The resin-bonded magnet according to the present invention has Zn ₃ (PO ₄ ) ₂ .4H ₂ O and / or Zn ₂ M on the surface of a resin-bonded magnet body obtained by mixing rare earth-based magnetic powder and a binding resin. (PO ₄ ) ₂ · 4H ₂ O (where M is an essential component of Mn and contains one of Ni and Fe), and a resin film is formed on it. Moreover, it is possible to improve the corrosion resistance, particularly the salt water resistance.

  Further, the method for producing a resin-bonded magnet according to the present invention includes the step of subjecting the surface of a resin-bonded magnet body formed by mixing rare earth-based magnetic powder and a binding resin to a phosphate treatment, and the resin after the phosphate treatment. By forming a resin film on the surface of the combined magnet body, it does not stop improving corrosion resistance against high temperatures and high humidity, it has excellent corrosion resistance against salt water, rust generation due to oxidation, and less deterioration of magnetic properties due to alteration, and high performance Can realize high quality products.

  Hereinafter, as the best mode for carrying out the present invention, embodiments of a resin-bonded magnet and a manufacturing method thereof will be described with reference to the drawings.

  FIG. 1 is an embodiment of the present invention, and is a process diagram showing a manufacturing process of a resin-bonded magnet.

  First, in the mixing step 1, a rare earth magnetic powder and a thermosetting resin as a binding resin are mixed. As the rare earth magnetic powder (rare earth magnet powder), SmCo type or NdFeB type is preferable from the viewpoint of magnetic properties, and the average particle size of the magnetic powder is in the range of 10 to 200 μm and the maximum particle size is 500 μm or less. is necessary. On the other hand, the binding resin to be used is a thermosetting resin, for example, an epoxy resin or a phenol resin is preferable. Furthermore, when the mixed material of the rare earth magnetic powder and the binding resin is 100 parts by weight, in order to obtain high performance magnetic characteristics, the rare earth magnetic powder is 95 parts by weight (that is, 95% by weight) or more. It is preferable to do.

In the compression molding process 2, the mixed material of the rare earth magnetic powder and the binding resin produced in the mixing process 1 is compression molded. For this compression molding, a normal compression molding machine may be used, and a magnetic field molding machine may be used as necessary. In this case, in order to obtain high-performance magnetic characteristics, it is preferable to compression-mold the mixed material at a high pressure (784 to 980 Mpa (8 to 10 tf / cm ² or more)). In addition, in order to cure the binding resin of the thermosetting resin, a heat curing process is performed at 100 to 200 ° C. after the compression molding.

  In the weak alkali etching step 3, the surface of the resin-bonded magnet body formed in the compression molding step 2 is etched with a weak alkali (soak the magnet body in a weak alkaline solution). This is because the surface of the resin-bonded magnet body is etched (the surface is roughened so that the metal of the magnetic powder is exposed) at the time of phosphating, which is the next step. Is required.

  In the phosphate treatment step 4, the surface of the resin-bonded magnet body that has been subjected to the treatment in the weak alkali etching step 3 is immersed in a phosphate solution to perform the phosphate treatment. Examples of the phosphate include manganese phosphate, zinc phosphate, iron phosphate, and sodium phosphate, with manganese phosphate and zinc phosphate being particularly preferred. The hot water temperature of the phosphate solution is preferably room temperature to 100 ° C., and the time for immersing the resin-bonded magnet body in the phosphate solution is preferably 5 minutes or more.

  In the drying step 5, the resin-bonded magnet body after the phosphate treatment in the phosphate treatment step 4 is dried. After drying, a phosphate coating is formed on the surface of the resin-bonded magnet body (particularly, the portion where the magnetic powder is exposed on the surface is coated).

  In the resin coating process 6, a resin is applied to the outer periphery of the phosphate coating formed on the surface of the resin-bonded magnet body after the drying process in the drying process 5. As the type of resin to be coated, a phenol-based thermosetting resin having good heat resistance is preferable. The type of resin may be the same as or different from the type of binding resin used in the resin-bonded magnet body.

  The resin coating is performed by a dipping method, and the resin-bonded magnet body after the phosphate treatment is dipped in the resin solution a plurality of times, and the average thickness of the resin coating film is 1 to 10 μm (more preferably 2 to 2 μm). 5 μm) is preferable. When the average film thickness exceeds 10 μm, the relative ratio of the resin-bonded magnet body (molded body) is lowered, and the magnetic properties are lowered. Further, if the average film thickness is to be less than 1 μm, there is a possibility that a part where a film is not partially formed may occur, which is not preferable.

  When immersed in the resin solution, it is difficult to cover the entire surface of the resin-bonded magnet body all at once, and a coating film of the resin is formed on the surface of the resin-bonded magnet body. If there is no part, the corrosion resistance is deteriorated, and rust is generated due to oxidation, and as a result, magnetic properties are deteriorated due to alteration. By immersing the resin solution in the resin solution a plurality of times, it is possible to form a multi-layered coating film so that the entire surface of the resin-bonded magnet body can be fully covered.

  In addition to the dipping method, the spraying method and the electrodeposition method can be cited as a method for coating the resin. However, the spray method and the electrodeposition method tend to form a very thick film with a large amount of coating at a time. Therefore, it is possible to form a uniform thin resin coating film by performing the treatment a plurality of times by the dipping method.

  In the drying step 7, a thermosetting resin coating film applied to the surface of the resin-bonded magnet body is heated and dried and cured at 100 to 200 ° C. After heat drying, a cured film of the thermosetting resin is formed on the surface of the resin-bonded magnet body.

In the embodiment of the present invention, when the phosphate treatment and the resin coating are taken together, (1) Zn ₃ (PO ₄ ) ₂ · 4H ₂ O and / or ( 2) It is preferable to form Zn ₂ M (PO ₄ ) ₂ .4H ₂ O (where M is an essential component of Mn and includes one of Ni and Fe). Furthermore, it is preferred that the phases (1) and (2) are present in a ratio of 65:35 to 90:10. These phases can be formed by zinc phosphate processing among phosphates. More specifically, it can be formed by treating with zinc manganese phosphate.

  According to this embodiment, the following effects can be obtained.

(1) Even when exposed to high temperatures and high humidity, it is possible to realize a resin-bonded magnet that prevents the occurrence of rust due to oxidation and that does not cause deterioration of magnetic properties due to alteration.

(2) Not only the improvement of corrosion resistance against high temperature and high humidity, but also high corrosion resistance against salt water, high performance with less rust due to oxidation, and less deterioration of magnetic properties due to alteration, can be realized. It is.

  The manufacturing method of the resin-bonded magnet body according to the present invention will be described in detail in Examples. First, an NdFeB magnet powder having an average particle size of 50 μm is selected as a rare earth magnetic powder (rare earth magnet powder), an epoxy resin is selected as a binding resin, and the weight blending ratio of the magnetic powder and the binding resin is 97: 3. A mixed material was prepared.

Next, 980 Mpa (10 tf / cm ² ) was applied as a molding pressure by a molding machine to produce a cylindrical sample having an outer diameter (diameter) of 4 mm and a height of 8 mm.

A film was formed on the surface of the sample by a zinc manganese phosphate treatment. In this case, the ratio of Zn ₃ (PO ₄ ) ₂ .4H ₂ O to Zn ₂ M (PO ₄ ) ₂ .4H ₂ O (where M is an essential component of Mn and includes one of Ni and Fe). Was 3: 1.

  Furthermore, on the outer peripheral surface of the coating formed by the zinc-manganese phosphate treatment, the number of immersions in the phenol resin solution was changed to 4, 2, and 1 to obtain coating films with average film thicknesses of 3 μm, 2 μm, and 1 μm, respectively. Three types of samples A, B, and C were prepared.

  In addition, in order to investigate the effect of forming a coating with zinc manganese phosphate on the surface of the sample, a sample with a coating with sodium phosphate treatment and a sample without any phosphate treatment were prepared. Two types of samples D and E were prepared, which were immersed in the resin solution four times to form a coating film having an average thickness of 3 μm.

  Table 1 below shows the state of rust generation after the samples A to E were left at a constant temperature of 60 ° C. and a relative humidity of 90% for 120 hours in a constant humidity bath or left in a 1% solution of NaCl for 24 hours. Is the result of visual observation.

From Table 1, rust after high-temperature and high-humidity test and salt water immersion test by forming a coating film of phenol resin with an average thickness of 2 μm or more on the outer peripheral surface after the resin-bonded magnet body was treated with zinc manganese phosphate It can be seen that the occurrence of this can be prevented.

  FIG. 2 (A) shows a sample of a conventional product in which a phenol resin coating film having an average thickness of 3 μm is formed on the surface of the resin-bonded magnet body without performing phosphate treatment, and the surface of the resin-bonded magnet body. Surface after the high temperature and high humidity test shown in Table 1 was performed on samples of the present invention in which a phenolic resin coating film having an average thickness of 3 μm was formed by applying zinc manganese phosphate treatment to the outer peripheral surface many times. It is the result of taking a picture of the state. As far as the above-mentioned high-temperature and high-humidity test conditions are concerned, no rust was observed on the surface of the resin-bonded magnet in both the conventional sample and the sample of the present invention.

  Further, FIG. 2 (B) is a result of taking a photograph of the surface state after the salt water immersion test shown in Table 1 was performed on the sample of the conventional product and the sample of the present invention shown in FIG. 2 (A). In the conventional sample, rust was observed on the surface of the resin-bonded magnet. In the sample of the present invention, no rust was observed.

  Although the embodiments and examples of the present invention have been described above, it is obvious to those skilled in the art that the present invention is not limited thereto and various modifications and changes can be made within the scope of the claims. I will.

  According to the resin-bonded magnet and the manufacturing method thereof according to the present invention, the corrosion resistance to water and salt water of a resin-bonded magnet using a rare earth-based magnetic powder having high magnetic performance, such as having a large maximum energy product, can be improved. Applications of in-vehicle devices such as small motors, plungers, and other actuators can be achieved.

It is an embodiment of the present invention and is a block diagram showing a manufacturing process of a resin-bonded magnet. The results of taking a photograph of the surface of the resin-bonded magnet after the high temperature and high humidity test and after the salt water immersion test are shown. (B) is a photograph of the conventional product and the product of the present invention after the salt water immersion test.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mixing process 2 Compression molding process 3 Weak alkali etching process 4 Phosphate treatment process 5 Drying process 6 Resin coating process 7 Drying process

Claims (7)

Zn ₃ (PO ₄ ) ₂ .4H ₂ O and / or Zn ₂ M (PO ₄ ) ₂ .4H ₂ O (on the surface of a resin-bonded magnet body obtained by mixing rare earth magnetic powder and a binding resin. Here, M is a resin-bonded magnet characterized in that Mn is essential and includes one of Ni and Fe), and a resin film is formed thereon.   The resin-bonded magnet according to claim 1, wherein the resin film has an average film thickness of 1 to 10 μm.   The resin-bonded magnet according to claim 1 or 2, wherein the resin coating has a multilayer structure.   The resin-bonded magnet according to claim 1, 2, or 3, wherein the rare earth-based magnetic powder is 95 parts by weight or more with respect to 100 parts by weight of the resin-bonded magnet body.   The surface of a resin-bonded magnet body formed by mixing rare earth-based magnetic powder and a binding resin is subjected to a phosphate treatment using a zinc phosphate-based and / or manganese phosphate-based phosphate, and after the phosphate treatment, A method for producing a resin-bonded magnet, comprising forming a resin film on a surface of a resin-bonded magnet body.   The method for producing a resin-bonded magnet according to claim 5, wherein etching is performed with a weak alkali before the phosphating treatment.   The method for producing a resin-bonded magnet according to claim 5 or 6, wherein the resin-bonded magnet body after the phosphate treatment is repeatedly immersed in a resin solution a plurality of times to form the resin film.