JP2005109421A - Method for manufacturing corrosion-resistant rare earth based permanent magnet, corrosion-resistant rare earth based permanent magnet, dip spin coating method of work, and coating film forming method of work - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stable and easy manufacturing method of a rare earth based permanent magnet which has a zinc particulate variance corrosion-resistant coat on a surface, the corrosion-resistant rare earth based permanent magnet which is manufactured by the method, a dip spin coating method suitable for coating film formation to thin works of various profiles, and a coating film forming method of the work. <P>SOLUTION: In the manufacturing method of the corrosion-resistant rare earth based permanent magnet, basin system treatment liquid whose pH is 6-8 and viscosity is at most 1,000 cP and which contains hydrolysis polymerized reactant of an alkyl silicate and zinc particulate whose mean particle diameter is 1-50 μm is spread on a surface of the rare earth based permanent magnet. After that, thermal treatment is performed at 250-400°C, and zinc particulate variance corrosion-resistant coat is formed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a stable and simple method for producing a rare earth permanent magnet having a zinc fine particle dispersed corrosion resistant coating on its surface, a corrosion resistant rare earth permanent magnet thus produced, and dip spin coating suitable for forming a coating film on thin workpieces of various shapes. The present invention relates to a method and a method for forming a coating film on a workpiece.

Rare earth permanent magnets such as R—Fe—B permanent magnets represented by Nd—Fe—B permanent magnets and R—Fe—N permanent magnets represented by Sm—Fe—N permanent magnets are In particular, R-Fe-B based permanent magnets are used in various fields today because they use abundant and inexpensive materials and have high magnetic properties.
However, since rare earth permanent magnets contain a highly reactive rare earth element: R, they are easily oxidatively corroded in the atmosphere. When used without any surface treatment, a slight amount of acid, alkali, moisture, etc. Corrosion proceeds from the surface due to the presence of rust, and rust is generated, resulting in deterioration and variation in magnet characteristics. Furthermore, when a magnet in which rust is generated is incorporated in an apparatus such as a magnetic circuit, the rust may be scattered to contaminate peripheral components.
There are many methods for imparting corrosion resistance to a rare earth permanent magnet. One of them is a method of forming a corrosion resistant coating using a silicon compound as a starting material on the surface of a rare earth permanent magnet. In recent years, various studies have been conducted for the purpose of further improving the performance of such corrosion-resistant coatings.
For example, in Patent Document 1 below, a method of forming a zinc fine particle-dispersed corrosion-resistant coating by applying a treatment liquid composed of an alkali silicate aqueous solution in which zinc fine particles are dispersed to the surface of a rare earth-based permanent magnet and then performing a heat treatment. Has been proposed. This method is based on the corrosion resistance of the coating using alkali silicate as a starting material and the sacrificial corrosion protection of fine zinc particles that are potentially base, and can provide high corrosion resistance to rare earth permanent magnets. Be expected. However, in this method, in order to uniformly disperse the zinc fine particles in the treatment liquid for forming the zinc fine particle-dispersed corrosion-resistant coating, the treatment liquid must be made alkaline. When applied to the surface of the permanent magnet, a metal hydroxide constituting the magnet is generated on the surface of the magnet, and the surface of the magnet is covered with a layer made of such a metal hydroxide. The problem is that it is difficult to form a zinc fine particle-dispersed corrosion-resistant film with excellent adhesion, the problem that a film using alkali silicate as a starting material is inferior in flexibility, and cracking tends to occur, and the waste liquid treatment is troublesome. There are problems.
In Patent Document 2 below, inorganic fine particle dispersion is achieved by applying a treatment liquid containing a silicon organic compound and inorganic fine particles having an average particle diameter of 1 nm to 100 nm to the surface of a rare earth permanent magnet, followed by heat treatment. A method for forming a corrosion-resistant coating has been proposed. This method is for forming a thin and dense corrosion-resistant film using a silicon organic compound as a starting material on the surface of a rare earth permanent magnet, and dispersing inorganic fine particles having a specific average particle diameter in the film component. Thus, the internal stress in the coating film generation process is relaxed and physical defects such as cracks are prevented from occurring. This method is also expected as a method capable of imparting high corrosion resistance to rare earth permanent magnets. However, considering that it is difficult to uniformly disperse nanometer-order inorganic fine particles in water, in the preparation of the treatment liquid, a slight amount of water is mainly added to an organic solvent such as a lower alcohol. Therefore, it is necessary to hydrolyze and polymerize the silicon organic compound under acidic conditions to form a sol liquid and to disperse the inorganic fine particles. Therefore, since the prepared treatment liquid is acidic, the treatment liquid is made of a rare earth permanent magnet. Problems such as magnet corrosion when applied to the surface, volatilization of organic solvent due to volatilization of the processing liquid composition, adverse effects on the environment, and cumbersome waste liquid processing There is.
Japanese Patent Laid-Open No. 2000-182813 JP 2001-143949 A

  Accordingly, the present invention provides a stable and simple method for producing a rare earth permanent magnet having a zinc fine particle dispersed corrosion resistant coating on its surface, a corrosion resistant rare earth permanent magnet thus produced, and a dip spin suitable for coating on thin workpieces of various shapes. It aims at providing the coating method and the coating-film formation method of a workpiece | work.

The manufacturing method of the corrosion-resistant rare earth-based permanent magnet of the present invention made in view of the above points contains, as described in claim 1, an alkyl silicate hydrolysis polymerization reaction product and zinc fine particles having an average particle diameter of 1 μm to 50 μm. It is characterized in that after applying an aqueous treatment liquid having a pH of 6 to 8 and a viscosity of 1000 cP or less to the surface of the rare earth permanent magnet, a heat treatment is performed at 250 ° C. to 400 ° C. to form a zinc fine particle dispersed corrosion resistant coating. To do.
The manufacturing method according to claim 2 is characterized in that, in the manufacturing method according to claim 1, the zinc fine particles are scaly.
The manufacturing method according to claim 3 is the manufacturing method according to claim 1 or 2, wherein the total blending ratio of the alkyl silicate as the starting material and the zinc fine particles in the aqueous treatment liquid is 40 wt% to 90 wt% (alkyl Silicate is SiO ₂ equivalent).
The production method according to claim 4 is the production method according to any one of claims 1 to 3, wherein the mixing ratio of the alkyl silicate as the starting material in the aqueous treatment liquid and the zinc fine particles is 1: 1 to 1: 19 (weight ratio: alkyl silicate is SiO ₂ equivalent).
The manufacturing method according to claim 5 is characterized in that in the manufacturing method according to any one of claims 1 to 4, an organic dispersant is added to the aqueous treatment liquid.
The manufacturing method according to claim 6 is characterized in that, in the manufacturing method according to any one of claims 1 to 5, the thickness of the zinc fine particle-dispersed corrosion-resistant film is 1 μm to 50 μm.
The manufacturing method according to claim 7 is characterized in that in the manufacturing method according to any one of claims 1 to 6, other inorganic fine particles are further dispersed in the zinc fine particle-dispersed corrosion-resistant coating.
The manufacturing method according to claim 8 is characterized in that, in the manufacturing method according to any one of claims 1 to 7, the aqueous treatment liquid is applied to the surface of the rare earth permanent magnet by a dip spin coating method. To do.
The manufacturing method according to claim 9 is characterized in that in the manufacturing method according to claim 8, the viscosity is 300 cP to 600 cP and an aqueous processing solution is used.
The manufacturing method according to claim 10 is the manufacturing method according to claim 8 or 9, wherein a plurality of rare earth-based permanent magnets are provided on a substantially outer peripheral end portion of a rotating pedestal that is rotatable about a central axis in the vertical direction. Immerse the rotating pedestal holding the magnet and the rare earth-based permanent magnet in the aqueous treatment liquid tank so that the rare earth-based permanent magnet is dipped in the aqueous treatment liquid, then remove it from the solution and rotate the rotating pedestal. It is characterized in that dip spin coating is performed by centrifuging off an aqueous treatment liquid adhering to the rare earth permanent magnet.
The manufacturing method according to claim 11 is characterized in that, in the manufacturing method according to claim 10, a plurality of rare earth-based permanent magnets are held in a substantially annular shape on a substantially outer peripheral end portion of the rotating pedestal.
The manufacturing method according to claim 12 is the manufacturing method according to claim 10 or 11, wherein the rare earth permanent magnet is a thin magnet.
A manufacturing method according to a thirteenth aspect is characterized in that, in the manufacturing method according to the twelfth aspect, the thin magnet is held such that the widest surface thereof is substantially parallel to the radial direction of the rotating pedestal.
The manufacturing method according to claim 14 is the manufacturing method according to claim 13, wherein the plurality of thin magnets are widest in a state where the individual magnets are separated from each other when mounted on the substantially outer peripheral end portion of the rotating base. It is characterized by using a coating jig that can be set in a substantially annular shape so that the surface is substantially parallel to the radial direction of the rotating pedestal.
The manufacturing method according to claim 15 is characterized in that, in the manufacturing method according to claim 12, the thin magnet has any one of a flat plate shape, a ring shape, and a bow shape.
The manufacturing method according to claim 16 is the manufacturing method according to claim 14, wherein after the dip spin coating is performed, the coating jig with the thin magnet set is removed from the rotating pedestal and painted at an arbitrary place. The thin magnet as set in the jig is heat-treated.
In addition, the rare earth permanent magnet of the present invention has a corrosion-resistant coating film on which zinc fine particles having an average particle size of 1 μm to 50 μm are dispersed in a coating component using alkylsilicate as a starting material, as described in claim 17. It is characterized by.
The rare earth permanent magnet according to claim 18 is the rare earth permanent magnet according to claim 17, characterized in that the content of zinc fine particles in the corrosion-resistant coating is 50 wt% to 95 wt%.
The rare earth permanent magnet according to claim 19 is the rare earth permanent magnet according to claim 17 or 18, characterized in that zinc diffuses from the surface of the magnet body to the inside.
A rare earth permanent magnet according to claim 20 is the rare earth permanent magnet according to any one of claims 17 to 19, which is manufactured by the manufacturing method according to claim 1.
The workpiece dip spin coating method of the present invention, as described in claim 21, holds a plurality of workpieces on a substantially outer peripheral end of a rotating pedestal that is rotatable about a vertical central axis as a rotation axis, It is characterized by immersing the rotating pedestal holding the work in the paint tank, immersing the paint on the work, removing it from the liquid, rotating the rotating pedestal, and centrifugally shaking off the extra paint on the work. To do.
In addition, the method for forming a coating film on a workpiece according to the present invention has a plurality of workpieces when the workpiece is mounted on a substantially outer peripheral end of a rotatable pedestal that is rotatable about a vertical central axis as a rotation axis. Using a coating jig that can be set in a substantially annular shape with individual workpieces separated, the workpiece is dipped in the coating by immersing the rotating pedestal with the coating jig on which the workpiece is set in the coating tank. After that, remove from the liquid, rotate the rotating pedestal, centrifuge off any paint that has adhered to the workpiece, remove the coating jig with the workpiece set from the rotating pedestal, and place it on the coating jig at any place It is characterized in that the workpiece as it is is dried after desired.

  According to the present invention, a stable and simple method for producing a rare earth-based permanent magnet having a zinc fine particle-dispersed corrosion-resistant coating on its surface, a corrosion-resistant rare earth-based permanent magnet thus produced, and a dip suitable for forming a coating film on thin workpieces of various shapes. A spin coating method and a method for forming a coating film on a workpiece are provided.

  In the present invention, the zinc fine particle-dispersed corrosion-resistant coating film is formed from an aqueous treatment liquid having a pH of 6 to 8 and a viscosity of 1000 cP or less, which contains alkyl silicate hydrolysis polymerization reaction product and zinc fine particles having an average particle diameter of 1 μm to 50 μm. It is formed by applying heat treatment at 250 ° C. to 400 ° C. after coating on the surface of the system permanent magnet. The zinc fine particle-dispersed corrosion-resistant coating formed in this way imparts high corrosion resistance to the rare earth-based permanent magnet, and has excellent adhesion due to the diffusion of zinc from the surface of the magnet body.

Here, as the alkyl silicate, one represented by the general formula: Si _n O _(n-1) (OR) _{(2n + 2)} is used. In the formula, R is an alkyl group, and examples thereof include lower alkyl groups having 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group and a butyl group. An ethyl group (ethyl silicate) excellent in handleability is preferred. Further, n is an integer of 1 or more, but n is preferably an integer of 10 or less in order to form a dense film.

  In addition, zinc fine particles having an average particle diameter of 1 μm to 50 μm are used. This is because if the average particle size is smaller than 1 μm, the zinc fine particles may cause secondary aggregation in the aqueous processing solution, whereas if the average particle size is larger than 50 μm, the zinc fine particles settle in the aqueous processing solution. This is because, in any case, it may be difficult to prepare an aqueous treatment liquid in which zinc fine particles having excellent storage stability are uniformly dispersed. The average particle size of the zinc fine particles is desirably 2 μm to 30 μm, and more desirably 5 μm to 20 μm. The zinc fine particles may have any shape. However, in order to prevent pinholes from being generated as much as possible in the zinc fine particle-dispersed corrosion-resistant coating, it is advantageous that the zinc fine particles are densely stacked and filled in the coating components. In order to diffuse zinc from the magnet body surface to the inside, it is advantageous that the contact area of the zinc fine particles with the magnet body is wide. Therefore, from this viewpoint, the zinc fine particles are preferably scaly. When the zinc fine particles are scaly, the average particle size of the zinc fine particles means an average major axis.

The total blending ratio of the alkyl silicate as the starting material and the zinc fine particles in the aqueous processing liquid is preferably 40% by weight to 90% by weight (the alkyl silicate is converted to SiO ₂ ), and 60% by weight to 80% by weight. It is more desirable. If the total blending ratio is less than 40% by weight, the number of production steps may be increased more than necessary to obtain a zinc fine particle-dispersed corrosion-resistant film having a film thickness that exhibits sufficient characteristics. This is because exceeding the weight percentage may affect the storage stability of the aqueous treatment liquid.

The mixing ratio of the alkyl silicate as the starting material in the aqueous treatment liquid and the zinc fine particles is 1: 1 to 1 so that the zinc fine particle content of the formed zinc fine particle-dispersed corrosion-resistant coating is 50 wt% to 95 wt%. : 19 (weight ratio: alkyl silicate calculated as SiO ₂₎ is preferably set to be 1: 3 to 1: it is more desirable to be 10. If the zinc fine particle content of the formed zinc fine particle-dispersed corrosion resistant coating is less than 50% by weight, the effect of dispersing the zinc fine particles in the coating component may not be sufficiently exerted, whereas if more than 95% by weight, This is because the original characteristics as a corrosion-resistant film using alkyl silicate as a starting material may not be sufficiently exhibited.

  The reason why the pH of the aqueous treatment liquid applied to the surface of the rare earth permanent magnet is defined as 6 to 8 is that if the pH is smaller than 6, the corrosion of the rare earth permanent magnet may be caused as described in Patent Document 2 above. On the other hand, if the pH is higher than 8, there is a possibility that a zinc fine particle dispersed corrosion-resistant film having excellent adhesion as described in Patent Document 1 may not be formed.

  The reason why the viscosity of the aqueous treatment liquid applied to the surface of the rare earth permanent magnet is defined as 1000 cP or less is that when the viscosity of the aqueous treatment liquid exceeds 1000 cP, it is difficult to form a zinc fine particle-dispersed corrosion-resistant film having a uniform film thickness. Because there is a risk of becoming.

  Preparation of an aqueous processing solution with excellent homogeneity can be achieved, for example, by using an aqueous solution obtained by subjecting an alkyl silicate to a hydrolysis polymerization reaction under acidic conditions (about pH 3 to 4) or basic conditions (about pH 10 to 12). After adding 1 μm to 50 μm of zinc fine particles, it is preferable to adjust the pH to 6 to 8 and maintain or adjust the viscosity to 100 cP or less (viscosity is more preferably 50 cP or less, and further preferably 25 cP or less). When the alkyl silicate is subjected to a hydrolysis polymerization reaction under acidic conditions, the pH may be adjusted using, for example, sodium hydroxide. When alkyl silicate is subjected to a hydrolysis polymerization reaction under basic conditions, the pH may be adjusted using, for example, hydrochloric acid.

  The reason why the alkyl silicate is hydrolytically polymerized at the stage of preparation of the aqueous treatment liquid is to make the formed film dense. The hydrolysis polymerization reaction of the alkyl silicate is not necessarily required to carry out the hydrolysis polymerization reaction for all of the alkyl silicate to be used, and may be an embodiment in which a part of the alkyl silicate is subjected to the hydrolysis polymerization reaction. The degree of the hydrolysis polymerization reaction can be adjusted by the amount of acid or base added or the amount of water as a medium used for causing the hydrolysis polymerization reaction. If the degree of hydrolysis polymerization reaction of the alkyl silicate is high, the viscosity of the aqueous solution may exceed 100 cP. Even if the viscosity exceeds 100 cP, it is possible to reduce the viscosity by adding warm water, but in order to ensure better homogeneity of the aqueous treatment liquid, hydrolysis is required. If the viscosity of the aqueous solution is likely to exceed 100 cP during the polymerization reaction, it is desirable that the viscosity does not exceed 100 cP by appropriately adding water. For example, when it is desired to make the surface tension of the aqueous treatment liquid appropriate for the purpose of facilitating the formation of a film having a desired film thickness, for example, a cellulose-based thickener (hydroxyethylcellulose) is added to the aqueous treatment liquid. , Methyl cellulose, methyl hydroxypropyl cellulose, water-soluble cellulose ether exemplified by ethyl hydroxyethyl cellulose, methyl ethyl cellulose, etc.) can be added to adjust the viscosity. When it is desired to increase the viscosity of the aqueous processing solution to 100 cP or more for the purpose of increasing the thickness of the coating film to be formed, the viscosity is increased by adding a thickener to the prepared aqueous processing solution. It is desirable.

  When adding the zinc fine particles to the aqueous solution obtained by subjecting the alkyl silicate to hydrolysis polymerization reaction, it is desirable to use an organic dispersant so that the zinc fine particles are uniformly dispersed in the aqueous treatment liquid. The organic dispersant is added to the aqueous treatment liquid by, for example, introducing zinc fine particles into water added with the organic dispersant to prepare a zinc fine particle dispersed aqueous medium in which the zinc fine particles are uniformly dispersed. What is necessary is just to mix by mixing the aqueous medium and the aqueous solution which hydrolyzed the alkyl silicate. In addition, as an organic dispersion medium, anionic dispersion medium (aliphatic polyvalent carboxylic acid, polyether polyester carboxylate, high molecular weight polyester acid polyamine salt, high molecular weight polycarboxylic acid long chain amine salt, etc.), nonionic Dispersion media (carboxylates such as polyoxyethylene alkyl ethers and sorbitan esters, sulfonates, and ammonium salts), polymer dispersion media (carboxylates, sulfonates, and ammonium salts of water-soluble epoxies, styrene-acrylic) Acid copolymers, glues, etc.) are preferably used from the viewpoint of affinity with zinc fine particles and cost.

  In addition, in order to form the viscosity of the aqueous processing liquid applied to the surface of the rare earth-based permanent magnet without repeating the number of manufacturing steps more than necessary, the zinc fine particle-dispersed corrosion-resistant coating film having a film thickness that exhibits sufficient characteristics is formed. It is desirable that it is 5 cP or more.

  When applying the aqueous treatment liquid to the surface of the rare earth permanent magnet, a dip coating method, a spray method, a spin coating method, a dip spin coating method, or the like can be employed. In order to improve the adhesion with the zinc fine particle-dispersed corrosion-resistant coating formed on the surface of the rare earth-based permanent magnet, the magnet may be subjected to sandblasting or pickling before applying the aqueous processing solution. .

  Application of the aqueous treatment liquid to the surface of the rare earth permanent magnet is preferably performed by a dip spin coating method in order to form a more uniform aqueous treatment liquid coating. In particular, a plurality of rare earth-based permanent magnets are held on a substantially outer peripheral end of a rotating pedestal that can be rotated with a central axis in the vertical direction as a rotation axis, and the rotating pedestal holding the rare earth-based permanent magnets is After dip-coating the aqueous treatment liquid onto the rare earth permanent magnet by immersing in It is desirable to perform the coating.

  As a method of forming a thin coating film with a film thickness of, for example, about 10 μm on the surface of a thin work, after the work is immersed in the paint tank, the paint is immersed in the work, and then removed from the liquid and rotated at a high speed for extra work A dip spin coating method by shaking off the paint adhering to the surface may be employed. As a dip spin coating method for a thin workpiece known so far, for example, there is a method proposed as a method for applying a protective film on an optical disk in Japanese Patent Application Laid-Open No. 7-201088. In this method, a plurality of substrates are set on a horizontal main axis vertically at regular intervals, and the material other than the center part of the substrate is immersed in a protective film material while rotating at low speed around the main axis, and then the material is applied. This is because the material is shaken off by pulling it up and finally rotating at high speed. In Japanese Patent Laid-Open No. 3-86271, a vertical line passing through the center of gravity including the hanger and the object to be coated is rotated while the application surface (plane) of the object to be coated is held almost horizontally using the hanger. There has been proposed a dip spin coating method characterized by including a step of rotating the shaft as a shaft and centrifugally shaking off the paint. Japanese Patent Laid-Open No. 2000-164556 uses a wafer carrier in which a pair of holding members having a plurality of grooves are opposed to each other on the side having the grooves, and the periphery of the wafer is held by the opposed grooves. There has been proposed a method in which the liquid on a plurality of wafers held on a carrier by rotating the substrate so that the groove is directed substantially in the direction of rotational acceleration is centrifugally spun off and dried.

  When the dip spin coating method is employed for a large number of thin workpieces, it is desirable that uniform coating can be performed without causing variations in film thickness for all workpieces without being limited by the shape of the workpiece. However, in view of this point, any of the methods described in the above patent documents has more or less disadvantages. Specifically, the method described in Japanese Patent Application Laid-Open No. 7-201088 has a drawback that it can be applied only to a ring-shaped workpiece because the workpiece must be held at its center. In this method, the horizontal spindle is brought into contact with the inner peripheral surface of the ring-shaped workpiece, and the workpiece itself is rotated by the frictional force generated between the two. Therefore, the frictional force generated between the workpiece and the spindle varies. In such a case, since the rotation speed of the workpieces varies, there is a possibility that uniform coating cannot be applied to all the workpieces, and it is difficult to rotate the workpieces at a high speed. In the case of coating a workpiece with an excess of the above, there is a drawback that the extra adhered paint may not be sufficiently shaken off. Further, the method described in Japanese Patent Application Laid-Open No. 3-86271 has a drawback in that since the plane of the workpiece is held almost horizontally, there is a possibility that a difference in the coating amount of the paint may occur between the upper surface and the lower surface. Further, in the method described in Japanese Patent Application Laid-Open No. 2000-164556, since one plane of the workpiece is held facing the rotation axis, the rotation speed varies depending on the holding position. On the other hand, there is a drawback that uniform coating may not be possible.

  However, according to the dip spin coating method proposed in the present invention, a uniform coating film can be formed even on a large number of thin workpieces without causing variations in film thickness.

  Hereinafter, the dip spin coating method proposed in the present invention will be described with reference to the drawings as necessary. However, the dip spin coating method proposed in the present invention is not construed as being limited to the following description. . The dip spin coating method proposed in the present invention can be applied to the painting of workpieces of any shape without being restricted by the shape of the workpiece, but is particularly suitable for the painting of thin workpieces such as flat plates, rings and bows. Therefore, in the following description, the case where the method of the present invention is applied to the coating of a flat workpiece and a ring workpiece is taken as an example.

  FIG. 1 is a schematic process diagram of an example of the dip spin coating method proposed in the present invention. The process will be described in order. (A) First, a plurality of flat workpieces X are individually placed on the substantially outer peripheral end of a rotating base 2 that can be rotated with the central axis 1 in the vertical direction as a rotation axis. It is held in a substantially annular shape so that the widest surface (plane) is substantially parallel to the radial direction. (B) Next, the paint tank 4 is lifted by the air cylinder 3 and the rotary base 2 holding the work X is immersed in the paint tank 4 to dip the paint on the work X. (C) Next, the paint tank 4 is lowered by the air cylinder 3 and the rotary base 2 is taken out of the liquid. (D) Finally, the rotating pedestal 2 is rotated by the motor 5 about the central axis 1 as the rotation axis (preferably, the rotation direction is reversed at least once), and the paint adhered to the plane of the workpiece X is centrifuged. Shake off. According to this method, even if the paint has a relatively high viscosity (for example, a viscosity exceeding 200 cP), by adjusting the size of the rotary base 2 or controlling the rotation speed, the work X Since the adhesion amount of the paint to the flat surface can be freely adjusted, the film thickness of the coating film to be formed can also be freely adjusted.

  The pedestal surface of the rotary pedestal 2 is preferably mesh-shaped so as not to cause paint accumulation.

  FIG. 2A shows an example of a state in which a plurality of flat workpieces X are held on a substantially annular end so that their respective planes are substantially parallel to the radial direction on the substantially outer peripheral end of the rotating base 2. It is a general | schematic fragmentary perspective view. FIG. 2B is a view of the rotary base 2 holding the workpiece X as viewed from above. The workpiece X is placed on two holding members 11 (preferably rod-like ones having a semicircular cross section) laid on the rotary base 2. As shown in FIG. 1, the workpiece X may be placed directly on the rotary base 2, but by adopting such a placement method, the placement trace generated on the lower surface of the workpiece X is minimized. (See FIG. 2C).

  The individual flat workpieces X are held in a state of being separated by spacers 12 provided in the vertical direction with respect to the holding member 11. The spacer 12 also has a function of preventing the workpiece X from overturning. The interval between the adjacent spacers 12 and the spacers 12 is desirably wider than the thickness of the workpiece X. This is because if the spacer 12 is always in contact with both surfaces of the workpiece X, the contact mark becomes remarkable. The cross section of the spacer 12 is preferably circular. This is because the contact trace generated on the plane of the workpiece X can be minimized by rotating the rotary base 2.

  In the step (d), when the rotating base 2 is rotated by the motor 5 with the central axis 1 as the rotation axis, and the paint adhered excessively to the plane of the flat workpiece X is spun off, the workpiece X is moved in the radial direction by centrifugal force. However, the centrifugal pop-out restricting bar 13 fixed to the rotary base 2 and arranged in the horizontal direction by an unillustrated configuration abuts against the outer side surface of the work X and causes the work X to jump out in the radial direction. Has the function of regulating. Further, the spacer 14 provided in the direction of the rotation axis with respect to the centrifugal protrusion regulating rod 13 has a function of regulating the movement of the workpiece X during centrifugal swing-off.

  FIG. 3A shows an example of a state in which a plurality of ring-shaped workpieces Y are held on a substantially annular end so that their individual planes are substantially parallel to a radial direction on a substantially outer peripheral end portion of the rotary base 2. It is a general | schematic fragmentary perspective view. The workpiece Y is suspended and held by the ring portion on a horizontal suspension member 15 fixed to the rotary base 2 with a configuration not shown. The horizontal hanging member 15 is preferably a rod-shaped member having a circular cross section. Further, it is desirable that the portion of the horizontal hanging member 15 on which the workpiece Y is hung is cut out, for example, in a V shape (see FIG. 3B). With the horizontal hanging member 15 having such a configuration, the hanging trace generated in the ring portion of the workpiece Y can be minimized.

  When performing dip spin coating on a plurality of thin workpieces, as shown in FIGS. 1 to 3, each thin workpiece may be directly held on a rotating pedestal. When mounted on the outer peripheral edge, a plurality of thin workpieces can be set in a substantially annular shape so that the widest surface of the thin workpieces is substantially parallel to the radial direction of the rotating pedestal with the individual workpieces separated. A painting jig may be used.

  FIG. 4 shows that when mounted on the substantially outer peripheral end of the rotating pedestal, a plurality of flat workpieces are substantially parallel to the radial direction of the rotating pedestal in a state where the individual workpieces are separated from each other. It is a schematic perspective view of an example of the coating jig which can be set cyclically | annularly. The coating jig Z includes two pieces arranged in parallel in the horizontal direction for holding a plurality of flat workpieces X so that the planes are substantially parallel to the vertical direction with the individual workpieces separated. When the holding rod 21 with the spacer 22 and the jig on which the workpiece X is set are mounted on the substantially outer peripheral end of the rotating base and the rotating base is rotated, the rotating rod is brought into contact with the outer side surface of the rotating base X and centrifuged. It has at least a centrifugal pop-out restricting bar 23 with a spacer 24 arranged in parallel in the horizontal direction to restrict the pop-out of the workpiece X in the radial direction by force. A jig is placed above the holding bar 21. When the workpiece X is turned upside down, the planes of the plurality of workpieces X are substantially parallel to each other with the workpieces separated from each other, and the upper portion of the workpiece X has a space with the holding rod 21. To holding rod 21 for holding Are row arrangement, two, further comprising a spacer 26 with the rod-shaped member 25. The holding bar 21 for holding the workpiece X in the upper stage functions as a bar-like member 25 when the jig is turned upside down.

  FIG. 5 is a schematic front view (a) and a DD sectional view (b) of a coating jig Z on which a plurality of thin workpieces X are set.

  It is desirable that the holding rod 21 and the rod-like member 25 have a circular cross section. This is because the placement trace generated on the lower surface of the thin workpiece X can be minimized. Moreover, it is desirable that the centrifugal protrusion regulating rod 23 also has a circular cross section. This is because the contact trace generated on the outer side surface of the thin workpiece X can be minimized. In addition, the spacer 22, the spacer 24, and the spacer 26 are preferably circular in cross section. This is because the contact trace generated on the flat surface of the thin workpiece X can be minimized. Note that two holding rods 21 and rod-like members 25 are not necessarily required, and may be one.

  The coating jig Z shown in FIG. 4 is used as follows, for example. FIG. 6 is a schematic partial plan view of an example of a state in which a coating jig Z on which a plurality of flat workpieces X are set is mounted on a substantially outer peripheral end portion of the rotating base 2 by a publicly known removable mounting means. It is. In accordance with the schematic process diagram shown in FIG. 1, the paint tank 4 is lifted by the air cylinder 2, and the rotating base 2 equipped with the coating jig Z on which the work X is set is immersed in the paint tank 4 to apply the paint to the work X. Apply dip coating. Next, the paint tank 4 is lowered by the air cylinder 3 and the rotary base 2 is taken out of the liquid. Finally, the rotating pedestal 2 is rotated by the motor 5 with the central axis 1 as the rotation axis, and the paint adhering excessively to the plane of the workpiece X is spun off to complete the dip spin coating. After an arbitrary time has elapsed, the coating jig Z with the workpiece X still set is removed from the rotating base 2, and the workpiece X that has been set on the coating jig Z at an arbitrary place is optionally dried (naturally dried or heated). dry. Thereafter, the coating jig Z on which the workpiece X is set is turned upside down and mounted again on the rotating pedestal 2, and dip spin coating is performed again in the same process as described above. In this way, the position of the placement trace and the contact trace generated on the workpiece X changes between the first coating and the second coating, so that the second coating causes the workpiece X in the first coating. Since the coating is also performed on the placement trace and the contact trace, the workpiece X can be more uniformly painted. Thereafter, the coating jig Z with the workpiece X still set is removed from the rotary base 2, and the workpiece X with the workpiece X set on the coating jig Z is dried at any place as desired (natural drying or heat drying). For example, uniform coating can be efficiently formed without causing variations in film thickness even for a large amount of workpieces.

  In addition, when apply | coating to the surface of the rare earth-type permanent magnet of an aqueous processing liquid by the dip spin coating method, a more uniform coating-film formation can be performed by using the aqueous processing liquid with a viscosity of 300 cP-600 cP. As described above, it is desirable that the aqueous treatment liquid having such a viscosity has a viscosity increased by adding a cellulose-based thickener or the like to the aqueous treatment liquid once prepared (the thickener is It is desirable to add such that it is contained in the aqueous treatment liquid in an amount of 1 to 2% by weight.

  Heat treatment of the rare earth permanent magnet having a coating film of the aqueous treatment liquid formed on the surface is performed at 250 ° C to 400 ° C. When heat treatment is performed under such temperature conditions, a part of the zinc fine particles contained in the aqueous processing solution is appropriately diffused from the surface of the magnet body to the inside during the film formation process, so that zinc having excellent adhesion can be obtained. A fine particle dispersed corrosion resistant coating is formed. If the temperature of the heat treatment is lower than 250 ° C., not only the diffusion of zinc will not occur sufficiently, but also water will not sufficiently evaporate and remain on the surface of the rare earth permanent magnet. On the other hand, if the temperature is higher than 400 ° C., zinc diffusion may occur more than necessary, which may adversely affect the magnet characteristics. The heat treatment time is preferably, for example, 10 minutes to 120 minutes. Note that a rare earth-based permanent magnet coated with an aqueous treatment liquid is temporarily dried at 100 ° C. to 170 ° C. and then heat-treated to form a more uniform zinc fine particle-dispersed corrosion resistant coating.

  The zinc fine particle-dispersed corrosion resistant coating is preferably formed to have a thickness of 1 μm to 50 μm, and more preferably 5 μm to 15 μm. If the film thickness is less than 1 μm, the characteristics as a zinc fine particle-dispersed corrosion-resistant film may not be sufficiently exhibited. On the other hand, if the film thickness exceeds 50 μm, a sufficient effective volume of the rare earth permanent magnet can be secured. Because there is a risk of disappearing.

Note that other inorganic fine particles may be further dispersed in the zinc fine particle-dispersed corrosion-resistant coating. Examples of the inorganic fine particles include fine particles of a potential base metal like zinc such as aluminum, tin, manganese, magnesium, titanium and nickel. For example, by dispersing aluminum fine particles together with zinc fine particles, generation of white rust (basic zinc carbonate) due to corrosion of zinc fine particles can be effectively prevented. In addition, in order to further reduce pinholes that can occur in the coating and to further improve the corrosion resistance of the coating, fine particles of oxide such as Al ₂ O ₃ , TiO ₂ , SiO ₂ and mica are dispersed in the coating along with zinc fine particles. Also good. When other inorganic fine particles are dispersed together with the zinc fine particles, the total content of the zinc fine particles and the other inorganic fine particles in the formed corrosion-resistant coating is desirably 95% by weight or less.

Examples of rare earth permanent magnets include R—Fe—B permanent magnets typified by Nd—Fe—B permanent magnets and R—Fe—N permanent magnets typified by Sm—Fe—N permanent magnets. A known rare earth permanent magnet can be used. Among these, R-Fe-B permanent magnets are desirable in that they have particularly high magnetic properties and are excellent in mass productivity and economy. The rare earth permanent magnet may be a sintered magnet or a bonded magnet.
The rare earth element (R) in the rare earth based permanent magnet is at least one of Nd, Pr, Dy, Ho, Tb, Sm, or La, Ce, Gd, Er, Eu, Tm, Yb, Lu, Y. Among them, those containing at least one kind are desirable.
Usually, one type of R is sufficient, but in practice, a mixture of two or more types (such as misch metal and didymium) may be used for reasons of convenience.
Furthermore, by adding at least one of Al, Ti, V, Cr, Mn, Bi, Nb, Ta, Mo, W, Sb, Ge, Sn, Zr, Ni, Si, Zn, Hf, and Ga, It becomes possible to improve the squareness of the coercive force and the demagnetization curve, improve the manufacturability, and reduce the price. Further, by replacing part of Fe with Co, the temperature characteristics can be improved without impairing the magnetic characteristics of the obtained magnet.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is limited to this and is not interpreted.

Example 1:
As a starting material, electrolytic iron, ferroboron, and Nd as R are blended into the required magnet composition, and after melt casting, finely pulverized by mechanical pulverization and then finely pulverized to obtain a fine powder having a particle size of 3 μm to 10 μm After being molded in a magnetic field of 10 kOe and sintered in an argon atmosphere at 1100 ° C. for 1 hour, the obtained sintered body was subjected to aging treatment at 600 ° C. for 2 hours. The following experiment was conducted using a plate-like sintered magnet test piece having a size of 36 mm × 32 mm × 3 mm cut out from a magnet body having a composition of 15Nd-7B-78Fe.

A. Water is added to ethyl silicate 40 (a colorless transparent liquid containing 40% by weight of ethyl silicate in terms of SiO ₂ ), and the pH is adjusted to 3 with 1N hydrochloric acid to cause hydrolytic polymerization reaction of ethyl silicate. ethyl silicate 20% by weight (SiO ₂ equivalent) aqueous solution containing prepared. A zinc fine particle-dispersed aqueous medium prepared by adding this aqueous solution, an organic dispersant (trade name Solsperse S20000: manufactured by Avicia) and scaly zinc fine particles having an average major axis of 20 μm (approximately 20 μm × 20 μm × 1 μm) to water. Mix, mix well and adjust the pH to 7 with 1N sodium hydroxide. The total blending ratio of ethyl silicate and zinc fine particles as the starting material is 70% by weight (ethyl silicate is equivalent to SiO ₂ ). An aqueous processing solution having a mixing ratio of ethyl silicate, zinc fine particles and organic dispersant of 9.9: 90: 0.1 (weight ratio: ethyl silicate converted to SiO ₂ ) and a viscosity of 15 cP was obtained.
B. The test piece which was ultrasonically cleaned with ethanol (degreasing treatment) and then naturally dried for 15 minutes was immersed in the aqueous processing solution. The test piece taken out from the aqueous processing solution is stored in a centrifugal dryer, and after removing the excess aqueous processing solution adhering to the surface of the test piece by shaking off at 300 rpm for 30 seconds, the atmosphere is 100 ° C. for 5 minutes. It was temporarily dried inside. The test piece obtained by temporarily drying the aqueous treatment liquid applied to the surface in this manner was again immersed in the aqueous treatment liquid. After removing the excess aqueous treatment liquid adhering to the surface of the test piece taken out from the aqueous treatment liquid in the same manner as described above, the test piece with the aqueous treatment liquid coating film formed on the surface was 320 ° C. × A heat treatment was performed in the air for 10 minutes to form a zinc fine particle-dispersed corrosion-resistant film having a zinc fine particle content of 90% by weight on the surface of the test piece. The film thickness of the formed zinc fine particle-dispersed corrosion-resistant film was about 10 μm (from cross-sectional observation).
C. A corrosion resistance test was carried out by spraying 5% salt water at 35 ° C. for 500 hours on 10 test pieces having zinc fine particle dispersed corrosion resistance coatings produced on the surface. However, the appearance change (rusting) occurred after the test. There was nothing I did.

Example 2:
An aqueous solution having a pH of 3 containing 20% by weight (converted to SiO ₂ ) of ethyl silicate as a starting material prepared in the same manner as in Example 1, an organic dispersant (trade name Solsperse S20000: manufactured by Avicia) and an average major axis A zinc / aluminum fine particle dispersed aqueous medium prepared by adding 20 μm scale-like zinc fine particles (approximately 20 μm × 20 μm × 1 μm) and granular aluminum fine particles having an average particle diameter of 3 μm to water is mixed and stirred well to give 1N water. The pH is adjusted to 7 with sodium oxide, and the total blending ratio of ethyl silicate, zinc fine particles and aluminum fine particles as a starting material is 70% by weight (ethyl silicate is converted to SiO ₂ ), and ethyl silicate and zinc fine particles as starting materials The mixing ratio of the aluminum fine particles and the organic dispersant is 9.9: 60: 30: 0.1 (weight ratio: ethyl chloride). Kate viscosity is calculated as SiO ₂₎ to obtain a water-based treatment liquid 13CP. Using this aqueous treatment liquid, a zinc / aluminum fine particle-dispersed corrosion-resistant film having a zinc fine particle content of 60% by weight and an aluminum fine particle content of 30% by weight on the surface of a test piece similar to that of Example 1 was used. Formed. The film thickness of the formed zinc / aluminum fine particle-dispersed corrosion-resistant film was about 10 μm (from cross-sectional observation). A corrosion resistance test similar to that of Example 1 was performed on 10 test pieces having zinc / aluminum fine particle-dispersed corrosion resistant coatings on the surface thus produced, but none of the specimens had changed in appearance (rusting) after the test. It was.

Example 3:
An aqueous solution having a pH of 3 containing 20% by weight (converted to SiO ₂ ) of ethyl silicate as a starting material prepared in the same manner as in Example 1, an organic dispersant (trade name Solsperse S20000: manufactured by Avicia) and an average major axis Zinc / aluminum / tin fine particle dispersion prepared by adding 20 μm scaly zinc fine particles (approximately 20 μm × 20 μm × 1 μm), granular aluminum fine particles having an average particle diameter of 3 μm and granular tin fine particles having an average particle diameter of 3 μm to water. The aqueous medium was mixed, stirred well, adjusted to pH 7 with 1N sodium hydroxide, and the total blending ratio of ethyl silicate, zinc fine particles, aluminum fine particles and tin fine particles as a starting material was 70% by weight (ethyl silicate is SiO 2 ₂ terms), ethyl silicate and zinc particles and fine aluminum particles and tin particles and organic dispersant as the starting material If the ratio is 9.9: 55: 25: 10: 0.1 (weight ratio: ethyl silicate calculated as SiO ₂₎ Viscosity is to obtain an aqueous treating solution of 18 cP. Using this aqueous processing solution, on the surface of the same test piece as in Example 1, as in Example 1, the zinc fine particle content was 55% by weight, the aluminum fine particle content was 25% by weight, and the tin fine particle content was 10% by weight. % Zinc / aluminum / tin fine particle dispersed corrosion-resistant film was formed. The film thickness of the formed zinc / aluminum / tin fine particle-dispersed corrosion-resistant film was about 10 μm (from cross-sectional observation). The same corrosion resistance test as in Example 1 was performed on 10 test pieces having zinc, aluminum, and tin fine particle dispersed corrosion resistance coatings produced on the surface, but the appearance change (rusting) occurred after the test. There was no.

Comparative Example 1:
A. An aqueous sodium silicate solution having a SiO ₂ / Na ₂ O value of 4.0 and a pH of 12 was prepared. A zinc fine particle-dispersed aqueous medium prepared by adding this aqueous solution, an organic dispersant (trade name Solsperse S20000: manufactured by Avicia) and scaly zinc fine particles having an average major axis of 20 μm (approximately 20 μm × 20 μm × 1 μm) to water. Mixing and stirring well, the total blending ratio of alkali sodium silicate and zinc fine particles as starting material is 70 wt% (alkali sodium silicate is SiO ₂ equivalent), alkali sodium silicate and zinc fine particles as starting material and organic dispersion mixing ratio of agent, 9.9: 90: 0.1 (weight ratio: sodium alkaline silicate is in terms of SiO ₂₎ to obtain a processing solution is.
B. A test piece similar to Example 1 that had been subjected to ultrasonic cleaning (degreasing treatment) with ethanol and then naturally dried for 15 minutes was immersed in the treatment solution. The test piece taken out from the treatment liquid is stored in a centrifugal dryer, and after removing the excess treatment liquid adhering to the surface of the test piece by shaking off at 300 rpm for 30 seconds, it is placed in the atmosphere at 100 ° C. for 5 minutes. And temporarily dried. The test piece obtained by temporarily drying the treatment liquid applied to the surface in this manner was again immersed in the treatment liquid. After removing the excess treatment liquid adhering to the surface of the test piece taken out from the treatment liquid in the same manner as described above, the atmosphere is 150 ° C. for 30 minutes with respect to the test piece having a coating film of the treatment liquid formed on the surface. A heat treatment was performed inside to form a zinc fine particle-dispersed corrosion-resistant film having a zinc fine particle content of 90% by weight on the surface of the test piece. The film thickness of the formed zinc fine particle-dispersed corrosion-resistant film was about 10 μm (from cross-sectional observation).
C. When the corrosion resistance test of spraying 5% salt water at 35 ° C. for 500 hours was performed on 10 test pieces having zinc fine particle-dispersed corrosion resistance coatings thus produced on the surface, the appearance change (rusting) after 200 hours. There were 7 things that came.

Example 4:
2 wt% of an epoxy resin is added to an alloy powder having an average major axis of 150 μm having a composition of Nd: 12 atomic%, Fe: 77 atomic%, B: 6 atomic%, and Co: 5 atomic% prepared by a rapid cooling alloy method and kneaded. After compression molding at a pressure of 686 N / mm ² and curing at 150 ° C. for 1 hour, a ring-shaped bonded magnet test piece having an outer diameter of 30 mm × inner diameter of 28 mm × length of 4 mm was used as in Example 1. Thus, a zinc fine particle-dispersed corrosion-resistant film having a zinc fine particle content of 90% by weight was formed on the surface of the test piece. The film thickness of the formed zinc fine particle-dispersed corrosion-resistant film was about 10 μm (from cross-sectional observation). Moreover, cross-sectional observation of the surface vicinity of the test piece which has a zinc fine particle dispersion | distribution corrosion-resistant film on the surface was performed using EPMA (electron beam microanalyzer: Shimadzu Corporation EPM810). The secondary electron image is shown in FIG. 7, the zinc X-ray image is shown in FIG. 8, and the iron X-ray image is shown in FIG. 7 to 9, it was found that zinc was diffused from the surface of the test piece main body to the inside. In addition, the deterioration of the magnetic properties of the test piece main body due to the diffusion of zinc was not recognized. A corrosion resistance test was carried out by spraying 5% salt water at 35 ° C. for 500 hours on 10 test pieces having zinc fine particle dispersed corrosion resistance coatings produced on the surface. However, the appearance change (rusting) occurred after the test. There was nothing I did.

Example 5:
Hydroxyethyl cellulose as a thickener was added to the aqueous treatment liquid prepared in Example 1 so that its concentration was 1% by weight, and the viscosity was adjusted to 450 cP. A number of test pieces similar to Example 1 that had been ultrasonically cleaned (degreased) with ethanol and dried for 15 minutes were set on the coating jig shown in FIG. 4, and the coating jig on which the test pieces were set 6 was mounted on the substantially outer peripheral end of the rotating pedestal, and dip spin coating using the above-described treatment liquid was performed as shown in FIG. 1 (centrifugal shaking off at 300 rpm for 30 seconds). Thereafter, the coating jig with the test piece set is removed from the rotating pedestal, and temporarily dried in the atmosphere at 130 ° C. for 10 minutes while the test piece is set on the coating jig. A heat treatment was performed in the air at 350 ° C. for 30 minutes on the test piece on which the coating film was formed. Next, turn the coating jig with the test piece set upside down and mount it again on the rotating pedestal, and perform dip spin coating, temporary drying and heat treatment in the same process as above, to the surface of the test piece. A zinc fine particle-dispersed corrosion-resistant film having a zinc fine particle content of 90% by weight was formed. The film thickness of the formed zinc fine particle-dispersed corrosion-resistant film was 10 μm (from cross-sectional observation). A corrosion resistance test similar to that of Example 1 was performed on 10 test pieces having zinc fine particle dispersed corrosion resistance coatings thus produced on the surface, but none of the specimens had changed in appearance (rusting) after the test.

Example 6:
Hydroxyethyl cellulose as a thickener was added to the aqueous treatment liquid prepared in Example 2 so that its concentration was 1% by weight, and the viscosity was adjusted to 440 cP. Using this treatment solution, the surface of a test piece similar to Example 1 that had been ultrasonically cleaned (degreased) with ethanol and dried for 15 minutes had the same zinc fine particle content as in Example 5. A zinc / aluminum fine particle-dispersed corrosion-resistant film having an aluminum fine particle content of 60% by weight and 30% by weight was formed. The thickness of the formed zinc / aluminum fine particle-dispersed corrosion-resistant film was 10 μm (from cross-sectional observation). A corrosion resistance test similar to that of Example 1 was performed on 10 test pieces having zinc / aluminum fine particle-dispersed corrosion resistant coatings on the surface thus produced, but none of the specimens had changed in appearance (rusting) after the test. It was.

Example 7:
Hydroxyethyl cellulose as a thickener was added to the aqueous treatment liquid prepared in Example 3 so that its concentration was 1% by weight, and the viscosity was adjusted to 460 cP. Using this treatment solution, the surface of a test piece similar to Example 1 that had been ultrasonically cleaned (degreased) with ethanol and dried for 15 minutes had the same zinc fine particle content as in Example 5. A zinc / aluminum / tin fine particle-dispersed corrosion-resistant film having an aluminum fine particle content of 55% by weight and an aluminum fine particle content of 25% by weight and a tin fine particle content of 10% by weight was formed. The film thickness of the formed zinc / aluminum / tin fine particle-dispersed corrosion-resistant film was 10 μm (from cross-sectional observation). The same corrosion resistance test as in Example 1 was performed on 10 test pieces having zinc, aluminum, and tin fine particle dispersed corrosion resistance coatings produced on the surface, but the appearance change (rusting) occurred after the test. There was no.

Example 8:
An aqueous solution having a pH of 3 containing 20% by weight (converted to SiO ₂ ) of ethyl silicate as a starting material prepared in the same manner as in Example 1, an organic dispersant (trade name Solsperse S20000: manufactured by Avicia) and an average major axis 20 μm scaly zinc fine particles (approximately 20 μm × 20 μm × 1 μm in size), granular aluminum fine particles having an average particle diameter of 3 μm, granular tin fine particles having an average particle diameter of 3 μm, and alumina fine particles having an average particle diameter of 1 μm are added to water. The prepared zinc / aluminum / tin / alumina fine particle dispersed aqueous medium is mixed, stirred well and adjusted to pH 7 with 1N sodium hydroxide, and ethyl silicate, zinc fine particles, aluminum fine particles, tin fine particles and alumina as starting materials. The total blending ratio of fine particles is 70% by weight (ethyl silicate is SiO ₂ equivalent), and ethyl silicate as a starting material The blending ratio of the fine particles, zinc fine particles, aluminum fine particles, tin fine particles, alumina fine particles, and the organic dispersant is 9.9: 55: 25: 8: 2: 0.1 (weight ratio: ethyl silicate is converted to SiO ₂ ). An aqueous treatment liquid having a viscosity of 16 cP was obtained. To this aqueous processing solution, hydroxyethyl cellulose as a thickener was added so that its concentration was 1% by weight, and the viscosity was adjusted to 465 cP. Using this treatment solution, the surface of a test piece similar to Example 1 that had been ultrasonically cleaned (degreased) with ethanol and dried for 15 minutes had the same zinc fine particle content as in Example 5. A zinc / aluminum / tin / alumina fine particle-dispersed corrosion resistant coating having 55% by weight, aluminum fine particle content of 25% by weight, tin fine particle content of 8% by weight and alumina fine particle content of 2% by weight was formed. The film thickness of the formed zinc / aluminum / tin / alumina fine particle-dispersed corrosion-resistant film was 10 μm (from cross-sectional observation). The same corrosion resistance test as in Example 1 was performed on 10 test pieces having zinc, aluminum, tin, and alumina fine particle dispersed corrosion resistant coatings on the surface, but the appearance change (rusting) occurred after the test. There was nothing I did.

Comparative Example 2:
Hydroxyethyl cellulose as a thickener was added to the treatment solution prepared in Comparative Example 1 so that its concentration was 1% by weight, and the viscosity was adjusted to 420 cP. Using this treatment liquid, the ultrasonic drying (degreasing treatment) with ethanol was followed by drying for 15 minutes, and then the temporary drying conditions and heat treatment conditions were the same as in Comparative Example 1 on the surface of the same test piece as in Example 1. Except that, a zinc fine particle-dispersed corrosion-resistant film having a zinc fine particle content of 90% by weight was formed in the same manner as in Example 5. The film thickness of the formed zinc fine particle-dispersed corrosion-resistant film was 10 μm (from cross-sectional observation). When the same corrosion resistance test as in Example 1 was performed on 10 test pieces having the zinc fine particle-dispersed corrosion-resistant coating thus produced on the surface, 6 specimens that had changed in appearance (rusting) after 200 hours had elapsed. There were.

  The present invention relates to a stable and simple method for producing a rare earth permanent magnet having a zinc fine particle dispersed corrosion resistant coating on its surface, a corrosion resistant rare earth permanent magnet thus produced, and dip spin coating suitable for forming a coating film on thin workpieces of various shapes. The present invention has industrial applicability in that a method and a method for forming a coating film on a workpiece can be provided.

The schematic process drawing of an example of the dip spin coating method of the workpiece | work of this invention. Schematic of an example of the state which hold | maintained the several flat plate-shaped workpiece | work on the substantially outer periphery edge part of the rotation base of this invention. Schematic of an example of the state which hold | maintained several ring-shaped workpiece | work on the substantially outer periphery edge part of the rotation base of this invention. The schematic perspective view of an example of the painting jig of the present invention. The schematic diagram of the painting jig which set up a plurality of flat works of the present invention. The schematic of an example of the state which mounted | wore the substantially outer peripheral edge part of the rotation base with the coating jig which set the some flat plate-shaped workpiece of this invention. The EPMA secondary electron image in Example 4. Same as above, zinc X-ray image. Same as above, iron X-ray image.

Explanation of symbols

1 Central axis (rotary axis)
DESCRIPTION OF SYMBOLS 2 Rotation base 3 Air cylinder 4 Paint tank 5 Motor 11 Holding member 12 Spacer 13 Centrifugal protrusion control bar 14 Spacer 15 Horizontal suspension member 21 Holding bar 22 Spacer 23 Centrifugal protrusion control bar 24 Spacer 25 Bar-shaped member 26 Spacer X Thin work (flat plate) Work)
Y Thin workpiece (ring-shaped workpiece)
Z painting jig

Claims (22)

  After applying an aqueous treatment liquid having a pH of 6 to 8 and a viscosity of 1000 cP or less containing an alkyl silicate hydrolysis polymerization reaction product and zinc fine particles having an average particle diameter of 1 μm to 50 μm to the surface of the rare earth permanent magnet, 250 A method for producing a corrosion-resistant rare earth-based permanent magnet, characterized in that a zinc fine particle-dispersed corrosion-resistant coating film is obtained by performing a heat treatment at from 400C to 400C.   2. The production method according to claim 1, wherein the zinc fine particles are scaly. The process according to claim 1 or 2, wherein the total blending ratio of alkyl silicate and zinc particles as the starting material in the aqueous treating solution is 40 wt% to 90 wt% (alkyl silicate calculated as SiO ₂₎ is . 4. The mixing ratio of alkyl silicate as a starting material and zinc fine particles in an aqueous processing solution is 1: 1 to 1:19 (weight ratio: alkyl silicate is converted to SiO ₂ ). The manufacturing method of crab.   The manufacturing method according to any one of claims 1 to 4, wherein an organic dispersant is added to the aqueous processing solution.   The manufacturing method according to any one of claims 1 to 5, wherein the zinc fine particle-dispersed corrosion-resistant film has a thickness of 1 µm to 50 µm.   7. The production method according to claim 1, wherein other inorganic fine particles are further dispersed in the zinc fine particle-dispersed corrosion-resistant coating.   The manufacturing method according to any one of claims 1 to 7, wherein the aqueous treatment liquid is applied to the surface of the rare earth permanent magnet by a dip spin coating method.   The production method according to claim 8, wherein the treatment is performed using an aqueous treatment liquid having a viscosity of 300 cP to 600 cP.   A plurality of rare earth-based permanent magnets are held on a substantially outer peripheral end of a rotatable pedestal that can be rotated about a vertical central axis as a rotation axis, and the rotating pedestal holding the rare earth-based permanent magnets is immersed in an aqueous treatment liquid tank After dip-coating the aqueous treatment liquid on the rare earth permanent magnet, remove it from the liquid, rotate the rotating pedestal, and spin off the aqueous treatment liquid adhering to the rare earth permanent magnet. The manufacturing method according to claim 8, wherein the manufacturing method is performed.   The manufacturing method according to claim 10, wherein the plurality of rare earth-based permanent magnets are held in a substantially annular shape on a substantially outer peripheral end portion of the rotating pedestal.   The method according to claim 10 or 11, wherein the rare earth permanent magnet is a thin magnet.   13. The manufacturing method according to claim 12, wherein the thin magnet is held such that the widest surface thereof is substantially parallel to the radial direction of the rotating base.   When mounted on the outer peripheral edge of the rotating pedestal, a plurality of thin magnets are set in an annular shape so that the widest surface of the thin magnets is substantially parallel to the radial direction of the rotating pedestal when the individual magnets are separated. The manufacturing method according to claim 13, wherein the manufacturing method is performed using a coating jig that can be used.   13. The manufacturing method according to claim 12, wherein the thin magnet has a flat plate shape, a ring shape, or a bow shape.   After performing the dip spin coating, the coating jig with the thin magnet set is removed from the rotating base, and the thin magnet with the coating jig set at an arbitrary place is heat-treated. 14. The production method according to 14.   A rare earth-based permanent magnet having a corrosion-resistant film in which zinc fine particles having an average particle diameter of 1 to 50 μm are dispersed in a film component using an alkyl silicate as a starting material.   18. The rare earth-based permanent magnet according to claim 17, wherein the content of zinc fine particles in the corrosion-resistant coating is 50% by weight to 95% by weight.   The rare earth-based permanent magnet according to claim 17 or 18, wherein zinc is diffused from the surface of the magnet body into the interior.   The rare earth-based permanent magnet according to any one of claims 17 to 19, which is manufactured by the manufacturing method according to claim 1.   A plurality of workpieces are held on the substantially outer peripheral end of a rotatable pedestal that can rotate about the vertical central axis as a rotation axis, and the rotating pedestal holding the workpieces is immersed in the paint tank to immerse the paint in the workpiece. A dip spin coating method for workpieces characterized in that after coating is taken out of the liquid, the rotating pedestal is rotated, and the extra paint on the workpiece is spun off. A coating jig that can set a plurality of workpieces in a substantially annular shape with the individual workpieces separated when mounted on a substantially outer peripheral end of a rotatable pedestal that can rotate about a vertical central axis as a rotation axis. Used, after the paint is immersed in the paint tank by immersing the rotating pedestal with the coating jig on which the work is set in the paint tank, the paint is removed from the liquid, and the rotating pedestal is rotated and the paint adheres to the work. The coating jig with the workpiece still set is removed from the rotating base, and the workpiece with the workpiece set on the coating jig is dried at any place as desired. Coating film forming method.

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