JP4972975B2 - Rare earth magnet and manufacturing method thereof - Google Patents

Description

  The present invention relates to a rare earth magnet, and more particularly to a rare earth magnet having a protective layer on the surface and a method for producing the same.

  Conventionally, as a rare earth magnet containing a rare earth element, a sintered magnet obtained by sintering magnetic powder and a bonded magnet formed by mixing magnetic powder and a binder resin are known. Since these rare earth magnets contain a rare earth element which is relatively easily oxidized as a main component, rust is likely to occur, and the corrosion resistance tends to be relatively low. For this reason, deterioration of the performance as a magnet was remarkable at the time of manufacture and use.

  In order to solve such problems, a protective layer having corrosion resistance is formed on the surface of the magnet body by electrodeposition coating, or a protective layer having corrosion resistance is applied by applying a sol solution and heat-treating at 200 ° C. or higher. It is formed to improve the corrosion resistance of the magnet. However, the former electrodeposition coating is difficult to apply to a bonded magnet containing a binder resin, and the latter heat treatment has the disadvantage that the magnet body deteriorates due to high temperatures, etc. There was a tendency that it was difficult to reliably obtain rare earth magnets having sufficiently excellent corrosion resistance.

Therefore, as a method for forming a protective layer different from the above, a method for forming a chemical conversion film by performing chemical conversion treatment on the surface is known. For example, Patent Document 1 below discloses a resin-bonded magnet (bonded magnet) having a protective layer made of phosphate formed on the surface thereof.
Japanese Patent Application Laid-Open No. 64-13707

  According to the chemical conversion treatment described above, the protective layer can be formed under mild conditions, and thus the protective layer can be reliably formed regardless of the type of the magnet body. However, in recent years, rare earth magnets have come to be applied to various uses such as automotive electronic devices (motors, etc.) and audio / video equipment, and can be used reliably under various conditions. Is required.

  The above-mentioned conventional rare earth magnet on which a protective layer made of phosphate is formed has sufficient corrosion resistance under normal use conditions, for example, severe conditions such as being exposed to high temperature and high humidity for a long time. Then, rust tends to occur. For this reason, the further improvement of corrosion resistance, especially the improvement of rust prevention performance was calculated | required.

  Then, this invention is made | formed based on such a situation, and it aims at providing the rare earth magnet which has the antirust performance outstanding compared with the former, and its manufacturing method.

  In order to achieve the above object, the present inventors have conducted intensive research. As a result, the above-described protective layer made of phosphate is not necessarily in a sufficiently dense state, and is partially partially thin or It has been found that there are many cases with minute pinholes. In such a protective layer, it has been difficult to sufficiently prevent moisture from entering under severe conditions such as high temperature and high humidity. For this reason, moisture adheres to the magnet body and rust is easily generated. Accordingly, as a result of further research based on such knowledge, the present inventors have formed a protective layer in which a specific substance adheres to a layer made of phosphate, so that moisture as described above can be formed. As a result, the inventors have found that the intrusion of water can be sufficiently suppressed, and have completed the present invention.

That is, the rare earth magnet of the present invention includes a bonded magnet body that includes a rare earth element and further includes a binder resin, and a protective layer formed on the surface of the bonded magnet body. And a spectrum containing a peak derived from an organic acid containing a hydrophobic structure when analyzed by Fourier transform infrared spectroscopy (FT-IR). It is characterized by that.

  The protective layer in the rare earth magnet having the above-described structure includes a phosphate derived from an organic acid in the FT-IR analysis, and further includes an organic acid attached to the layer containing the phosphate metal salt. It is a thing. The rare earth magnet provided with such a protective layer is composed of a metal phosphate, and can exhibit excellent rust prevention performance as compared with the conventional rare earth magnet provided with a protective layer to which no organic acid or the like is attached. It will be a thing.

  Although this factor is not yet clear, the present inventors presume as follows. That is, in the protective layer having the above configuration, even when the layer mainly composed of the metal phosphate has a partially thin region or a minute pinhole, these portions are organic Since it is covered with an acid, it is considered that water can be prevented from adhering to the magnet body by sufficiently suppressing the intrusion of moisture. In particular, many organic acids have a hydrophobic structure in the molecule, and are considered to be excellent in performance for preventing the adhesion of moisture as described above. However, the action is not limited to these.

  In the rare earth magnet of the present invention, the magnet body is preferably a bonded magnet body further containing a binder resin. A rare earth magnet (bonded magnet) having a bonded magnet body is difficult to be electrodeposited as described above, and it is difficult to perform high-temperature heat treatment because the binder resin is easily decomposed by heat. On the other hand, since the protective layer comprising the phosphoric acid metal salt and adhering the organic acid in the present invention can be formed without performing the above-described treatment, it is extremely effective when such a bonded magnet element is used. It becomes.

  The method for producing a rare earth magnet according to the present invention is suitable for producing a rare earth magnet having the above-described configuration, and is a method for producing a rare earth magnet in which a protective layer is formed on the surface of a magnet element body containing a rare earth element. A chemical conversion treatment layer is formed by attaching a solution containing a metal and phosphoric acid to the magnet body, and a solution containing an organic acid is attached on the surface of the chemical conversion treatment layer. And

  In such a rare earth magnet manufacturing method, since a so-called chemical conversion treatment is performed on a magnet body and a solution containing an organic acid is attached to a solution containing a metal and phosphoric acid, the magnet body is attached. The protective layer can be formed without performing a high temperature treatment or the like that deteriorates the temperature. In addition, since a solution containing an organic acid is attached on the surface of the chemical conversion treatment layer, even if this chemical conversion treatment layer has a partially thin region or pinhole, these The part can be covered with an organic acid. The protective layer thus formed can sufficiently prevent external moisture such as moisture from entering, and can significantly reduce the adhesion of water to the magnet body. As a result, the obtained rare earth magnet has excellent rust prevention performance.

  In the method for producing a rare earth magnet of the present invention, the magnet body is preferably a bonded magnet body further including a binder resin. As described above, since the manufacturing method of the present invention does not require high-temperature treatment or the like, the protective layer can be reliably formed even when such a bonded magnet body is used.

  Furthermore, as an organic acid, what has a benzene ring is preferable. Since the benzene ring has a highly hydrophobic structure, the use of an organic acid having a benzene ring can more effectively reduce the adhesion of moisture to the magnet body.

  More specifically, alkyl naphthalene sulfonic acid is preferable as the organic acid. Such a compound can exhibit particularly excellent hydrophobicity in the protective layer. Therefore, the rare earth magnet provided with such a protective layer is further excellent in rust prevention performance.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the bonded magnet which has the antirust performance outstanding compared with the past, and its manufacturing method.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same element through all the figures, and the overlapping description is abbreviate | omitted.

First, the structure of the rare earth magnet of this embodiment will be described with reference to FIGS.
FIG. 1 is a perspective view showing a rare earth magnet of the present embodiment. FIG. 2 is a diagram schematically showing a cross-sectional structure along the II-II direction of the rare earth magnet shown in FIG. As shown in the drawing, the rare earth magnet 1 has a configuration including a magnet body 3 and a protective layer 5 formed to cover the surface of the magnet body 3. Hereinafter, as a rare earth magnet, a bonded magnet will be described as an example.

  The magnet body 3 is a so-called bonded magnet body including a magnetic powder containing a rare earth element and a binder resin, and the magnetic powder is in a state of being bound by the binder resin. The magnetic powder containing the rare earth element is not particularly limited as long as it is normally used as a raw material for the rare earth magnet, and examples include those containing rare earth elements such as Sm and Nd. More specifically, Sm—Co based magnetic powder, Nd—Fe—B based magnetic powder, Sm—Fe—N based magnetic powder and the like can be mentioned.

Among the magnetic powders described above, as the magnetic powder, Sm—Co based magnetic powder represented by SmCo ₅ or Sm ₂ Co ₁₇ or Nd—Fe—B based magnetic powder represented by Nd ₂ Fe ₁₄ B is used. preferable. These magnetic powders can exhibit excellent magnetic properties when the bonded magnet 1 is formed. The magnetic powder has an average particle size (major axis) of 10 to 200 μm, and a maximum particle size of 500 μm or less is particularly preferable because good magnetic properties can be obtained.

  As the binder resin, a thermosetting resin or a thermoplastic resin capable of binding magnetic powders can be used. Examples of such binder resins include thermosetting resins such as epoxy resins and phenol resins, styrene-based, olefin-based, urethane-based, polyester-based, and polyamide-based elastomers, ionomers, ethylene-propylene copolymers (EPM), and ethylene. -Thermoplastic resins such as ethyl acrylate copolymer. Especially, a thermosetting resin is preferable and an epoxy resin or a phenol resin is more preferable.

  In the magnet body 3, the magnetic powder and the binder resin are preferably blended in a mixing ratio as shown below. That is, the magnet body 3 preferably contains 95 parts by mass or more of magnetic powder with respect to 100 parts by mass in total of the magnetic powder and the binder resin. When the blending amount of the magnetic powder is less than 95 parts by mass, the magnetic properties of the bond magnet 1 tend to be deteriorated. However, from the viewpoint of sufficiently binding the magnetic powder, it is preferable that at least 1.5 parts by mass of a binder resin is included.

  In addition to the magnetic powder and binder resin described above, the magnet body 3 may contain various metal soaps such as zinc stearate, coupling agents such as titanate and silane.

  The protective layer 5 is a layer containing a metal phosphate formed on the surface of the magnet body 3 and has a function of reducing the influence of outside air (oxygen, moisture, etc.) on the magnet body 3. . Such a protective layer 5 is preferably composed mainly of a chemical conversion film formed by subjecting the magnet body 3 to chemical conversion treatment as will be described later. Examples of such a metal phosphate include zinc phosphate, manganese phosphate, iron phosphate, zinc calcium phosphate, and the like.

Of these, the protective layer 5 is more preferably a layer containing zinc phosphate. Such a protective layer 5 can impart excellent corrosion resistance to the rare earth magnet 1. Examples of zinc phosphate include compounds represented by Zn ₃ (PO ₄ ) ₂ .4H ₂ O, but the protective layer 5 contains a composition containing phosphorus and zinc different from this chemical composition. It may be.

  Moreover, the protective layer 5 is a thing by which the spectrum containing the peak derived from an organic acid is obtained, when analyzing by a Fourier-transform infrared spectroscopy. That is, the protective layer 5 is mainly composed of a metal phosphate and an organic acid attached thereto. In the protective layer 5, the organic acid is preferably attached to the surface of the metal phosphate layer formed so as to cover the magnet body 3. In particular, when the layer made of a metal phosphate has partially thin regions or pinholes, the organic acid is preferably attached so as to cover these regions. When pinholes are formed as in the latter case, the organic acid may directly adhere to the magnet body 3 and constitute a part of the protective layer 5. The protective layer 5 only needs to be formed at least in a desired region, and does not necessarily cover the entire surface of the magnet body 3.

Here, “organic acid” refers to an organic compound having a functional group capable of expressing acidity. As the functional group capable of expressing this acidity, carboxyl group (—COOH), sulfo group (—SO ₃ H), sulfino group (—SO ₂ H), phenolic hydroxyl group (—Ar—OH; Ar is aromatic Group) and the like.

  In addition to the above functional group, the organic acid in the present embodiment is preferably a compound having a hydrophobic structure (hereinafter referred to as “hydrophobic structure”). According to the organic acid containing this hydrophobic structure, the permeation | transmission of the water | moisture content of the protective layer 5 can be reduced effectively, and the rust prevention performance of the rare earth magnet 1 can be improved favorably. Examples of the hydrophobic structure in the organic acid include a structure containing a benzene ring and a linear or branched hydrocarbon structure having 4 or more carbon atoms.

  Especially, as a hydrophobic structure, the structure containing a benzene ring is preferable, the structure containing two or more benzene rings is more preferable, and the structure (for example, naphthalene structure) formed by condensing two or more benzene rings is more preferable. For example, examples of the organic acid containing a benzene ring as a hydrophobic structure include phenylphosphonic acid and alkylnaphthalenesulfonic acid.

As described above, when the protective layer 5 is analyzed by FT-IR, a spectrum including a peak derived from an organic acid is obtained. Here, the peak derived from an organic acid, different from each other depending on the structure of the organic acid used, for example, in the case of alkyl naphthalene sulfonic acid as described above, 1170Cm ^{-1 around, 1370~1380cm -1, 3030~3050cm} -1 ( A spectrum having a characteristic peak in the vicinity of the aromatic absorption) is obtained.

  Next, a method for manufacturing the bonded magnet 1 having the above-described configuration will be described.

  First, an alloy having a desired composition for forming a magnetic material containing a rare earth element is manufactured by a process such as a casting method, a melt spinning method, or a strip casting method. The obtained alloy is coarsely pulverized using a coarse pulverizer such as a jaw crusher, brown mill, stamp mill, etc., and then the above-mentioned magnetic powder has a suitable particle size by a fine pulverizer such as a jet mill or an attritor. Thus, the powder is pulverized to obtain a magnetic powder.

The obtained magnetic powder is mixed with a binder resin, a curing agent, and the like, and then charged into a kneader such as a pressure kneader and kneaded. Next, the kneaded product is compression-molded by a compression molding machine or the like. At this time, magnetization may be performed simultaneously by performing compression molding in a magnetic field. Magnetization may be performed separately after compression molding. From the viewpoint of obtaining the magnet body 3 having excellent magnetic properties, it is preferable to perform compression molding at a high pressure of about 784 to 980 MPa and about 8 to 10 t / cm ² .

  Then, when a thermosetting resin is used as the binder resin, the magnet body 3 is obtained by curing the binder resin by heating the obtained molded body at about 100 to 250 ° C. after compression molding. When a thermoplastic resin is used as the binder resin, such thermosetting does not have to be performed.

  Subsequently, the magnet body 3 is washed by spraying a solvent such as ethanol onto the magnet body 3 to remove excess magnetic powder and oil adhering to the surface of the magnet body 3. The solvent is not particularly limited as long as it has a sufficient cleaning function and does not affect the binder resin or the like in the magnet body 3, and a solvent other than ethanol may be used. Moreover, it may replace with washing | cleaning by solvent spraying, and may perform ultrasonic cleaning, and may use these together. After washing, the solvent and the like attached to the surface of the magnet body 3 is removed by natural drying or heat drying.

  And the surface adjustment process for performing the below-mentioned chemical conversion treatment favorably with respect to the magnet body 3 after washing | cleaning is performed. Specifically, for example, the magnet body 3 is immersed in a solution containing colloidal particles of titanium salt such as titanium phosphate, so that the colloid particles are attached to the surface of the magnet body 3. Thereby, the part to which this colloidal particle adhered becomes an active point, and subsequent chemical conversion treatment comes to be performed favorably. For the purpose of attaching the colloidal particles to the inside of the magnet body 3, the above-described immersion may be performed under reduced pressure.

  Next, the surface of the magnet body 3 is subjected to a chemical conversion treatment by attaching a solution containing a metal and phosphoric acid (chemical conversion solution) to the magnet body 3 to form a chemical conversion treatment layer containing a metal phosphate. To do. The chemical conversion treatment liquid is preferably attached by, for example, immersing the magnet body 3 in the treatment liquid.

  Examples of the chemical conversion treatment liquid include an aqueous solution containing a metal raw material compound constituting phosphoric acid metal salt and phosphoric acid, and may optionally contain an oxidizing agent for promoting chemical conversion treatment. A metal salt is mentioned as a metal raw material compound. Examples of the oxidizing agent include sodium nitrite and sodium sulfite.

More specifically, as the chemical conversion treatment liquid, for example, when forming the protective layer 5 containing zinc phosphate, first zinc phosphate (Zn (H ₂ PO ₄ ) ₂ ), nickel (Ni), manganese ( Mn), fluoride ion (F ⁻ ), nitrate ion (NO ₃ ⁻ ) and the like are included. Further, zinc phosphate - when forming a protective layer 5 containing calcium, first zinc phosphate _{(Zn (H 2 PO 4)} 2), the chemical conversion treatment liquid is exemplified with calcium nitrate (Ca _{(NO 3) 2)} it can. Furthermore, the case of forming the protective layer 5 containing manganese phosphate, first manganese phosphate _{(Mn (H 2 PO 4)} 2), chemical conversion treatment solution containing iron (Fe), and the like. Furthermore, when forming the protective layer 5 containing iron phosphate, a chemical conversion treatment solution containing sodium dihydrogen phosphate (NaH ₂ PO ₄ ), ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ), or the like can be used. .

Such a chemical conversion treatment solution contains ions such as phosphate ions (PO ₄ ³⁻ ) and metal ions. In the magnet body 3 to which the chemical conversion treatment liquid has adhered, the metal (for example, Fe) in the constituent material of the element body 3 is dissolved in the chemical conversion treatment liquid by reacting with phosphoric acid. Then, on the surface where this dissolution has occurred, metal ions and phosphate ions react to produce zinc phosphate. Such a reaction occurs on the surface of the magnet body 3 in a region where the magnetic powder is not covered with the binder resin.

  The temperature of the chemical conversion treatment solution during the chemical conversion treatment is preferably 40 to 90 ° C, more preferably 50 to 80 ° C, and particularly preferably 65 to 75 ° C. When the temperature condition of the chemical conversion treatment is less than 50 ° C., the solubility of each component in the chemical conversion treatment liquid is lowered, and the protective layer 5 having sufficient characteristics tends to be hardly obtained.

  Further, when the chemical conversion treatment is performed by immersing the magnet body 3 in the chemical conversion treatment solution, the chemical conversion treatment time (that is, the immersion time) is preferably about 5 to 30 minutes, preferably about 10 to 20 minutes. It is more preferable. When the chemical conversion treatment time is less than 5 minutes, the protective layer 5 having a sufficient thickness tends not to be formed. On the other hand, if it exceeds 30 minutes, the cost increases as the time required for the chemical conversion treatment increases, and components of the chemical conversion treatment liquid evaporate during the treatment, and the concentration thereof fluctuates. It tends to be difficult.

  After the chemical conversion treatment described above, the magnet body is appropriately washed with ion exchanged water to remove excess chemical conversion treatment liquid and moisture adhering to the surface, and then dried at 85 ° C. for about 30 minutes. Remove ion-exchanged water and dry.

  Then, an organic acid is made to adhere with respect to the magnet body in which the chemical conversion treatment layer was formed. In this way, the protective layer 5 is formed on the surface of the magnet body 3 by adhering the organic acid to the chemical conversion treatment layer mainly composed of a metal phosphate, and the rare earth magnet 1 is obtained. Examples of the organic acid include those described above.

  The organic acid can be attached by, for example, preparing a solution containing the organic acid and immersing the magnet body 3 after the chemical conversion treatment in this solution. The solvent used in this solution is not particularly limited as long as it can dissolve or disperse the organic acid, and examples thereof include alcohol solvents such as isopropyl alcohol. When magnet body 3 is immersed in a solution containing an organic acid, the temperature of the solution is preferably about 0 to 40 ° C. The immersion time is preferably about 30 to 180 seconds.

  Thereafter, the obtained rare earth magnet 1 is naturally dried for about 1 hour to remove the solvent adhering to the surface, and the treatment is completed. Thus, the rare earth magnet 1 having the structure shown in FIGS. 1 and 2 can be obtained.

  The rare earth magnet 1 configured as described above includes a protective layer 5 on the surface of the magnet body 3, in which an organic acid is attached to a layer mainly made of a metal phosphate formed by chemical conversion treatment. Yes. In this protective layer 5, even if the layer made of the metal phosphate has a region where the thickness is partially insufficient, a minute pinhole, or the like, these portions are organic materials including a hydrophobic structure. Covered with acid. For this reason, the protective layer 5 is extremely difficult to transmit moisture and the like. In the rare earth magnet 1 having such a protective layer 5 on the surface, moisture such as external moisture passes through the protective layer 5 and the magnet element. Less sticking to the body 3. As a result, the rare earth magnet 1 having the above-described configuration is extremely difficult to generate rust even when exposed to high temperature and high humidity conditions.

  In addition, the rare earth magnet and the manufacturing method thereof according to the present invention are not necessarily limited to the above-described embodiment, and can be appropriately changed without departing from the gist thereof. For example, in the said embodiment, although the example which the organic acid adhered to the layer (chemical conversion treatment layer) which consists of a metal phosphate as the protective layer 5 was given, this chemical conversion treatment layer was combined with the organic acid or organic Instead of the acid, a compound obtained by changing the organic acid by reaction or the like may be attached. As long as such a compound retains a characteristic structure of the original organic acid, the protective layer 5 gives a spectrum including “a peak derived from the organic acid” by analysis by FT-IR. .

  In the above embodiment, the chemical conversion treatment liquid and the organic acid are attached to the magnet element body 3 by immersing the magnet element body 3 in the chemical conversion treatment liquid and the solution containing the organic acid. For example, these solutions may be applied or sprayed to adhere to the magnet body 3. Furthermore, in the above description, the bonded magnet element is exemplified as the magnet element 3, but in the present invention, a sintered magnet formed by sintering magnetic powder in addition to the bonded magnet is applied as the magnet element. May be.

EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these Examples.
[Manufacture of bonded magnets]

Example 1
An alloy containing 72 wt% Fe, 19 wt% Nd and 7 wt% B was prepared and pulverized to obtain a magnetic powder. Next, the obtained magnetic powder was mixed with an epoxy resin as a binder resin, and then compression molded at a pressure of 980 MPa, and further heat-treated at 150 ° C. to cure the binder resin to obtain a magnet body. Next, the obtained magnet body was washed with ethanol and dried, and then immersed in a solution containing titanium phosphate under reduced pressure to perform surface conditioning treatment.

Then, after the surface of the magnet body is immersed in titanium phosphate for surface conditioning treatment, the magnet body is converted into a chemical conversion treatment solution containing 1600 ppm PO ₄ ³⁻ , 700 ppm NO ₃ ⁻ , and 7000 ppm Zn. A chemical conversion treatment was performed by dipping to form a chemical conversion treatment layer made of zinc phosphate on the surface of the magnet body. In this example, the chemical conversion treatment was performed under the conditions of a chemical conversion treatment solution temperature of 70 ° C. and a treatment time of 10 minutes.

  Subsequently, the magnet body on which the chemical conversion treatment layer was formed was naturally dried for about 1 hour, and then the magnet body was put into an isopropyl alcohol solution (concentration: 10% by mass) of phenylphosphonic acid which is a solution containing an organic acid. After being immersed at 25 ° C. for 1 minute, it was naturally dried for about 1 hour to obtain a rare earth magnet of Example 1 having a protective layer on the surface of the magnet body.

(Example 2)
The solution of Example 2 was the same as Example 1 except that instead of the isopropyl alcohol solution of phenylphosphonic acid, an isopropyl alcohol solution of naphthalene sulfonic acid (concentration: 5% by mass) was used as the solution containing the organic acid. A rare earth magnet was obtained.

(Example 3)
Example 1 was carried out in the same manner as in Example 1 except that an isopropyl alcohol solution of dinonylnaphthalenesulfonic acid (concentration: 5% by mass) was used as the solution containing the organic acid instead of the isopropyl alcohol solution of phenylphosphonic acid. 3 rare earth magnets were obtained.

(Comparative Example 1)
A rare earth magnet of Comparative Example 1 was obtained in the same manner as in Example 1 except that the treatment with the solution containing the organic acid was not performed.

(Comparative Example 2)
A rare earth magnet of Comparative Example 2 was obtained in the same manner as in Example 1 except that the chemical conversion treatment was not performed.

(Comparative Example 3)
A rare earth magnet of Comparative Example 3 was obtained in the same manner as in Example 2 except that the chemical conversion treatment was not performed.

(Comparative Example 4)
A rare earth magnet of Comparative Example 4 was obtained in the same manner as in Example 3 except that the chemical conversion treatment was not performed.
[Evaluation of rust prevention performance]

Ten rare earth magnet samples of Examples 1 to 3 and Comparative Examples 1 to 4 were produced, and these were left in a high temperature and high humidity environment of 60 ° C. and 95% RH for 500 hours. Then, the surface of all the samples was observed with the microscope (20 times), and the presence or absence of rust generation was confirmed. Then, among the 10 samples corresponding to each example or comparative example, the number of samples in which no rust was observed (hereinafter referred to as “non-defective product”) was counted. Based on this result, the ratio (non-defective product rate (%)) at which good products were obtained with the bonded magnets of the examples and comparative examples was calculated. The obtained results are shown in Table 1.

From Table 1, it was confirmed that the rare earth magnets of Examples 1 to 3 having a protective layer in which an organic acid was adhered to the chemical conversion treatment layer were extremely unlikely to generate rust even when exposed to a high temperature and high humidity environment. On the other hand, although the rare earth magnet of Comparative Example 1 having a protective layer composed of only the chemical conversion treatment layer obtained a certain yield rate, rust was easily generated as compared with the rare earth magnet of the Example. Further, it was found that the rare earth magnets of Comparative Examples 2 to 4 in which the chemical conversion treatment layer was not formed have a non-defective rate of 0% and are very likely to generate rust.
[Protective layer analysis]

The protective layer in the rare earth magnets of Examples 1 to 3 was observed by Fourier transform micro-infrared spectroscopy (reflection method, μ-FT-IR; Nexus 670, Continu μm manufactured by Thermo Electron). As a result, from the protective layer in the rare-earth magnet of Example ^1, 1440cm ^-1, 750cm ^-1, the spectrum having characteristic peaks at 690 cm ^-1 was obtained. These peaks are derived from phenylphosphonic acid, which is an organic acid.

Further, from the protective layer in the rare-earth magnet of Example ^{2, 1170cm -1,} the spectrum is obtained having characteristic peaks at 1376cm ^-1 and 3050 cm ^-1, from the protective layer in the rare-earth magnet of Example 3, 1170Cm Spectra with characteristic peaks at ^-1 and 3050 cm ^-1 were obtained. These peaks are peaks derived from naphthalenesulfonic acid and dinonylnaphthalenesulfonic acid, respectively.

  Furthermore, the protective layers of Examples 1 to 3 were observed with an X-ray microanalyzer (EPMA-WDS; JEOL JXA-8800RL). As a result, in the protective layer for the rare earth magnet of Example 1, it was confirmed that many phosphorus atoms derived from phenylphosphonic acid were present in the depressions of the chemical conversion treatment layer made of zinc phosphate. Further, in the protective layers of the rare earth magnets of Examples 2 and 3, there are many sulfur atoms derived from naphthalene sulfonic acid or dinonyl naphthalene sulfonic acid, respectively, in the depressions of the chemical conversion treatment layer made of zinc phosphate. Was confirmed.

  From the above results, it was confirmed that the organic acid adhered to the protective layer in the rare earth magnets of Examples 1 to 3. Since this organic acid was present in a large amount in the depressions in the chemical conversion treatment layer, it was found that the organic acid was particularly attached to cover the thin region and pinhole in the chemical conversion treatment layer. .

It is a perspective view which shows the bonded magnet of this embodiment. It is a figure which shows typically the cross-sectional structure which follows the II-II direction of the bonded magnet shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Bond magnet, 3 ... Magnet base body, 5 ... Protective layer.

Claims (9)

A bond magnet body including a rare earth element and further including a binder resin, and a protective layer formed on the surface of the bond magnet body,
The protective layer consists of an organic acid comprising a hydrophobic structure attached to the layers and the surface of the phosphoric acid metal salt, when analyzed by Fourier transform infrared spectroscopy, a peak derived from the organic acid containing the hydrophobic structural A spectrum containing
Rare earth magnet characterized by that. The protective layer, when analyzed by Fourier transform infrared spectroscopy, 1170Cm around ^-1, in which spectrum is obtained having a peak near 1370～1380Cm ^-1, and 3030～3050Cm ^-1, and wherein the The rare earth magnet according to claim 1.   The rare earth magnet according to claim 1, wherein the organic acid is naphthalene sulfonic acid or dinonyl naphthalene sulfonic acid. The rare earth magnet according to any one of claims 1 to 3, wherein the protective layer has more sulfur atoms in the recessed portion of the metal phosphate layer than in other portions. . A method for producing a rare earth magnet comprising forming a protective layer on the surface of a bonded magnet body containing a rare earth element and further containing a binder resin,
A step of attaching a solution containing metal and phosphoric acid to the bonded magnet body to form a chemical conversion treatment layer composed of a metal phosphate layer;
Attaching an organic acid containing a hydrophobic structure on the surface of the chemical conversion treatment layer;
A method for producing a rare earth magnet, comprising:   The method for producing a rare earth magnet according to claim 5, wherein the organic acid has a benzene ring.   7. The method for producing a rare earth magnet according to claim 5, wherein the organic acid is an alkyl naphthalene sulfonic acid. In the step of attaching the organic acid, the organic acid is attached on the surface of the chemical conversion treatment layer using a solution containing the organic acid, and the temperature of the solution is set to 0 to 40 ° C. The method for producing a rare earth magnet according to any one of claims 5 to 7. In the step of attaching the organic acid, the organic acid is attached on the surface of the chemical conversion treatment layer by immersing the bond magnet body in which the chemical conversion treatment layer is formed in a solution containing the organic acid, and The method for producing a rare earth magnet according to any one of claims 5 to 8, wherein the immersion time is 30 to 180 seconds.

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