KR20170053941A - Method for treating surface of sintered rare-earth magnet - Google Patents

Abstract

The present invention relates to a surface treatment method of a rare earth sintered magnet. The method for surface treatment of the rare-earth sintered magnet includes coating and curing a composition for forming a coating layer on the surface of the rare earth sintered magnet to form a coating layer. The composition for forming a coating layer includes a modified epoxy resin, a hardener, and an inorganic particle do.

Description

METHOD FOR TREATING SURFACE OF SINTERED RARE-EARTH MAGNET [0002]

The present invention relates to a surface treatment method of a rare earth sintered magnet. More particularly, the present invention relates to a surface treatment method of a rare-earth sintered magnet excellent in corrosion resistance and durability.

A neodymium magnet (Nd-Fe-B) sintered magnet represented by a rare earth sintered magnet is the most powerful permanent magnet existing today and has high magnetic properties and is widely used in various industrial fields such as a motor for a motor and a sensor part.

However, since such a neodymium (Nd-Fe-B) sintered magnet has high reactivity with oxygen, it is likely to be oxidized and corroded in the atmosphere, causing irregularities in magnet characteristics due to corrosion during use without surface treatment, (Nd-Fe-B) sintered magnet (permanent magnet) is subjected to surface treatment for the purpose of corrosion prevention.

Generally, the surface treatment applied to the rare earth sintered magnet is applied with a nickel-based metal plating, an epoxy resin coating, a water-soluble or oily zinc-aluminum composite coating coating method, and the like.

FIG. 1 (a) shows a conventional epoxy coated neodymium sintered magnet, and FIG. 1 (b) shows a cross section of the epoxy coated layer of the neodymium sintered magnet. Referring to FIGS. 1 (a) and 1 (b), in the case of the epoxy resin coating, a nickel (Ni) and copper (Cu) underlying plating layer is formed on the surface of a non- And then a secondary epoxy coating layer is formed to give a corrosion prevention function by air and moisture.

However, since the epoxy coating is poor in adhesion due to a nonuniform material surface, since nickel and copper plating are performed after plating, epoxy coating is performed thereon, so that plating and epoxy coating are carried out. A lot of attention is needed from the aspect of.

In addition, environmental problems arise due to the problem of the waste solution generated during the nickel and copper undercoating process. Therefore, an environment-friendly surface treatment method is required. In the case of epoxy resin coating, Surface treatment properties such as excellent corrosion resistance and adhesion to surface treatment are required for application of magnets.

BACKGROUND ART [0002] The background art relating to the present invention is disclosed in Korean Patent Publication No. 2007-0049245 (published on May, 10, 2007, entitled "Rare earth sintered magnet and method for producing rare earth sintered magnet").

An object of the present invention is to provide a surface treatment method of a rare-earth sintered magnet excellent in corrosion resistance and coating layer adhesion.

Another object of the present invention is to provide a surface treatment method of a rare-earth sintered magnet excellent in environmental friendliness and economical efficiency.

It is still another object of the present invention to provide a rare earth sintered magnet including a coating layer formed by the surface treatment method of the rare earth sintered magnet.

One aspect of the present invention relates to a method for surface treatment of a rare-earth sintered magnet. In one embodiment, the method for surface treatment of the rare earth sintered magnet includes coating and curing a composition for forming a coating layer on the surface of the rare earth sintered magnet to form a coating layer, wherein the composition for forming a coating layer includes a modified epoxy resin, Particles.

In one embodiment, the composition for forming a coating layer may include 100 parts by weight of a modified epoxy resin, 5 to 50 parts by weight of a curing agent, and 10 to 70 parts by weight of an inorganic particle.

In one embodiment, the composition for forming a coating layer may further comprise 1 to 50 parts by weight of a glycol compound and 5 to 350 parts by weight of a solvent based on 100 parts by weight of the modified epoxy resin.

In one embodiment, the composition for forming a coating layer may further comprise 1 to 30 parts by weight of an additive to 100 parts by weight of the modified epoxy resin.

In one embodiment, the additive may include at least one of a thickener, defoamer, and dispersant.

In one embodiment, the coating layer may be formed by curing at a temperature of 190 ° C to 240 ° C.

In one embodiment, the coating layer may be formed to a thickness of 5 mu m to 30 mu m.

In one embodiment, the rare earth sintered magnet is pretreated, and the pretreatment includes degreasing the surface of the rare earth sintered magnet; Washing and degreasing the defatted rare-earth sintered magnet; Sanding the dried rare earth sintered magnet; And preheating the sandwiched rare earth sintered magnet.

Another aspect of the present invention relates to a rare earth sintered magnet including a coating layer formed by the surface treatment method of the rare earth sintered magnet. In one embodiment, the rare earth sintered magnet comprises a rare earth sintered magnet base material; And a coating layer formed on the surface of the rare earth sintered magnet base material, wherein the coating layer has a structure in which inorganic particles are dispersed in a continuous phase of a modified epoxy resin.

In one embodiment, the coating layer may be formed to a thickness of 5 mu m to 30 mu m.

In one embodiment, the coating layer may be formed by curing a composition for forming a coating layer comprising a modified epoxy resin, a curing agent, and an inorganic particle.

In one embodiment, the composition for forming a coating layer may include 100 parts by weight of a modified epoxy resin, 5 to 50 parts by weight of a curing agent, and 10 to 70 parts by weight of an inorganic particle.

In one embodiment, the composition for forming a coating layer may further comprise 1 to 50 parts by weight of a glycol compound and 5 to 350 parts by weight of a solvent based on 100 parts by weight of the modified epoxy resin.

When applying the surface treatment method of the rare-earth sintered magnet according to the present invention, it is possible to eliminate the step of forming the base plating layer, which is applied in forming a rare earth sintered magnet coating layer such as neodymium (NdFeB) Through the implementation, it is possible to prevent the quality problems that can occur during the assembly process, and the environmentally friendly and corrosion resistance can be excellent by applying the water-soluble epoxy coating.

Fig. 1 (a) shows a conventional epoxy-coated rare earth sintered magnet, and Fig. 1 (b) shows a cross section of the epoxy coating layer of the neodymium-based sintered magnet.
Fig. 2 shows a rare-earth sintered magnet according to one embodiment of the present invention.
3 (a) shows the result of a salt spray test on a rare-earth sintered magnet manufactured according to an embodiment of the present invention, and FIGS. 3 (b) to 3 (d) The results of the salt spray test on the rare earth sintered magnet are shown.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to be exemplary, self-explanatory, allowing for equivalent explanations of the present invention.

One aspect of the present invention relates to a method for surface treatment of a rare-earth sintered magnet. In one embodiment, the method includes coating and curing a composition for forming a coating layer on the surface of the rare earth sintered magnet of the rare earth sintered magnet to form a coating layer, wherein the composition for forming a coating layer includes a modified epoxy resin, a curing agent, do.

The rare earth sintered magnet may use a neodymium sintered magnet. In one embodiment, the neodymium sintered magnet may include neodymium (Nd), iron (Fe), and boron (B). In one embodiment, the neodymium sintered magnet may further comprise at least one rare earth metal selected from the group consisting of praseodymium (Pr), and dysprosium (Dy).

In one embodiment, a mixture containing Nd, Fe, and B is prepared, and the mixture is heated and melted in a vacuum high-frequency melting furnace to form an ingot. In one embodiment, the mixture may further comprise at least one rare earth metal of Pr and Dy. Next, the ingot is pulverized, the pulverized powder is shaped into a predetermined shape, sintered in a sintering furnace to produce a sintered body, and then the sintered body is heat-treated to manufacture a sintered magnet.

In one embodiment, the rare earth sintered magnet may have various shapes depending on the application. For example, in a rectangular parallelepiped shape.

In one embodiment, the rare earth sintered magnet may be pretreated. In one embodiment, the pretreatment comprises degreasing the surface of the rare earth sintered magnet; Washing and degreasing the defatted rare-earth sintered magnet; Sanding the dried rare earth sintered magnet; And preheating the sandwiched rare earth sintered magnet.

The degreasing, washing and sanding may be carried out by a conventional method. In one embodiment, the degreasing may be to immerse the neodymium sintered magnet in an alkali degreasing agent for 3 to 8 minutes. In one embodiment, the degreased neodymium sintered magnet may be immersed in a water bath for 3 to 8 minutes, then taken out and dried at 130 ° C to 160 ° C for 40 to 60 minutes.

The sanding can sandwich the surface of the rare earth sintered magnet for 1 to 3 minutes using an aluminum oxide-based abrasive. The sintered rare earth sintered magnet may be preheated (maintained) at a temperature of 20 to 30 占 폚. As described above, when the sintered magnet is pretreated, workability is improved and corrosion resistance and adhesion of the coating layer can be further improved.

Next, the composition for forming a coating layer may be spray coated on the surface of the pre-treated rare earth sintered magnet and dried to form a coating layer.

Composition for forming coating layer

The composition for forming a coating layer includes a modified epoxy resin, a curing agent, and an inorganic particle. Hereinafter, the components of the composition for forming a coating layer will be described in detail.

Modified epoxy resin

The modified epoxy resin is included for the purpose of ensuring durability, corrosion resistance and coating adhesion of the present invention, and when the modified epoxy resin is included, adhesion to the coating layer and the surface of the sintered magnet can be excellent without undercoating.

In one embodiment, the modified epoxy resin may be a water-soluble modified epoxy resin. For example, at least one of a water-soluble acrylic-modified epoxy resin, a water-soluble polyglycol-modified epoxy resin and a water-soluble vinyl-modified epoxy ester resin. For example, a water-soluble acrylic-modified epoxy resin.

Hardener

The curing agent is contained in the modified epoxy resin and causes a curing reaction at about 150 ° C or higher to form the epoxy into a three-dimensional network structure. In one embodiment, the curing agent may include at least one of an amine-based curing agent, an acid anhydride-based curing agent, and a phenol-based curing agent.

In one embodiment, the amine curing agent includes hexamethylene diamine, octamethylene diamine, decamethylene diamine, bis (4-aminocyclohexyl) methane (bis (4-aminocyclohexyl) methane, 4,4'-diaminodiphenyl methane, m-phenylene diamine, and diamino diphenyl sulfone. In the present invention,

Examples of the acid anhydride-based curing agent include methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, 1,2,4,5-benzenetetracarboxylic anhydride, an anhydride, a benzophenone tetracarboxylic dianhydride, and a phthalic anhydride.

Examples of the phenolic curing agent include bisphenol A, bisphenol F, 4,4'-dihydroxydiphenyl methane, 4,4'-dihydroxydiphenyl methane, Dihydroxydiphenyl ether, 1,4-bis (4-hydroxyphenoxybenzene), 1,3-bis (4-hydroxyphenyl) (4-hydroxyphenyl) benzene), and 4,4'-dihydroxydiphenyl sulfide.

In one embodiment, the curing agent may be included in an amount of 5 to 50 parts by weight based on 100 parts by weight of the modified epoxy resin. When included in the above range, the corrosion resistance of the present invention can be prevented, the coating layer can be shrunk or the strength can be prevented from increasing excessively, and the modified epoxy resin can be easily cured and the physical strength of the coating layer can be improved. For example, 15 to 35 parts by weight.

Inorganic particle

The inorganic particles are included for the purpose of securing workability in the surface treatment of the rare-earth sintered magnet of the present invention, securing visibility, and preventing the problem of deterioration of sintered magnet quality due to incorporation of other speci fi c magnets in the process. The inorganic particles in one embodiment may include one or more of calcium carbonate (CaCO ₃₎ and titanium dioxide (TiO _2).

In one embodiment, the average size of the inorganic particles may be between 10 nm and 500 μm. In the present specification, the " size " is defined to mean the maximum length of the inorganic particles.

In one embodiment, the inorganic particles may be included in an amount of 10 to 70 parts by weight based on 100 parts by weight of the modified epoxy resin. When included in the above range, it is possible to prevent cracking and deterioration of physical properties of the coating layer of the present invention while preventing the problem of deterioration of sintered magnet quality due to incorporation of other speci fi c magnets in the process through securing visibility. For example, 30 to 55 parts by weight.

In one embodiment, the composition for forming a coating layer may further comprise a glycol compound and a solvent.

Glycol compound

The glycol compound may be further included as a water-soluble solvent for the purpose of controlling the viscosity of the modified epoxy resin to ensure mixing and workability. In one embodiment, the glycol compound is selected from the group consisting of ethylene glycol, propylene glycol, ethylene glycol monobutyl ether, propylene glycol monobutyl ether, diethylene glycol, dipropylene glycol, diethylene glycol monobutyl ether, and dipropylene glycol monobutyl ether, And diethylene glycol dibutyl ether.

In one embodiment, the glycol compound may be contained in an amount of 1 to 50 parts by weight based on 100 parts by weight of the modified epoxy resin. When the amount is within the above range, the viscosity of the modified epoxy resin can be easily controlled, and mixing and workability can be ensured. For example, 5 to 35 parts by weight.

menstruum

The solvent may further be included for the purpose of securing the mixing property and workability of the composition for forming a coating layer. In one embodiment, the solvent may comprise one or more of water and an organic solvent.

In one embodiment, the organic solvent may include at least one of a ketone solvent, an ester solvent, and an aprotic polar solvent.

The ketone-based solvent may include at least one of methyl ethyl ketone and methyl isobutyl ketone.

The ester-based solvent may include butyl acetate.

The aprotic polar solvent may include at least one of dimethyl sulfoxide, and N-methyl pyrrolidone.

In one embodiment, the solvent may be included in an amount of 5 to 350 parts by weight based on 100 parts by weight of the modified epoxy resin. When it is in the above range, the composition for forming a coating layer is excellent in compatibility, and mixing and workability can be excellent. For example, 50 to 350 parts by weight. As another example, 150 to 300 parts by weight may be included. As another example, 200 to 300 parts by weight may be included.

additive

In another embodiment of the present invention, the composition for forming a coating layer may further include an additive. In one embodiment, the additive may include at least one of a thickener, defoamer, and dispersant.

The thickener may include at least one of a urethane-based thickener and an acrylic thickener.

The defoaming agent may include at least one of an alcohol defoaming agent and a modified silicone defoaming agent.

The dispersant may include an acrylic dispersant.

In one embodiment, the additive may be included in an amount of 1 to 30 parts by weight based on 100 parts by weight of the modified epoxy resin. For example, 5 to 15 parts by weight.

In one embodiment, the composition for forming a coating layer may be charged into a spray container and sprayed at a pressure of 1 bar to 5 bar on the surface of the rare earth sintered magnet.

In one embodiment, the curing may be performed by curing the applied coating layer forming composition at a temperature of 190 ° C to 240 ° C for 40 to 60 minutes to form a coating layer. In one embodiment, the curing may be accomplished using one or more of thermal, ultraviolet, microwave, and infrared radiation, but is not limited thereto.

When forming the coating layer by curing under the above conditions, a coating layer having excellent adhesion with the sintered magnet and excellent durability can be formed.

In one embodiment, the coating layer may be formed to a thickness of 5 mu m to 30 mu m. The coating layer may have excellent adhesion and durability when formed into the above thickness. For example, 10 mu m to 20 mu m.

In one embodiment, when the rare earth sintered magnet is in the form of a rectangular parallelepiped, the composition for forming a coating layer containing the above-described components and content is applied to the sintered magnet at 4 to 5 surfaces at a pressure of 1 to 5 bar, , And cured at a temperature of 190 ° C to 240 ° C for 40 to 60 minutes to form a coating layer. The composition for forming a coating layer is applied to the remaining one or two surfaces of the sintered magnet at a pressure of 1 to 5 bar, After spray coating, the coating layer can be formed by secondary curing at a temperature of 190 ° C to 240 ° C for 40 to 60 minutes.

When the surface treatment method of the rare earth sintered magnet as described above is applied, it is possible to remove the base plating layer forming process applied in forming the rare earth sintered magnet coating layer such as neodymium (NdFeB) It is possible to reduce the cost by 10%, prevent environmental pollution caused by wastewater which is a byproduct of the plating process, prevent quality problems that may occur during the assembly process by implementing various colors, It can be excellent in environmental friendliness and corrosion resistance.

Another aspect of the present invention relates to a rare earth sintered magnet including a coating layer formed by the surface treatment method of the rare earth sintered magnet. Fig. 2 shows a rare-earth sintered magnet according to one embodiment of the present invention. Referring to FIG. 2, the rare earth sintered magnet 100 includes a rare earth sintered magnet base material 10; And a coating layer (20) formed on the surface of the rare earth sintered magnet base material (10). The coating layer (20) has a structure in which inorganic particles are dispersed in a continuous phase of a modified epoxy resin.

The continuous phase of the modified epoxy resin is formed by curing a modified epoxy resin and may have a three-dimensional network structure. In one embodiment, the inorganic particles may be dispersed and dispersed in the continuous phase.

In one embodiment, the coating layer 20 may be formed to a thickness of 5 [mu] m to 30 [mu] m. The coating layer 20 may have excellent adhesion and durability when formed into the above thickness. For example, 10 mu m to 20 mu m. In one embodiment, the coating layer 20 may be formed by curing a composition for forming a coating layer comprising the aforementioned modified epoxy resin, a curing agent, and inorganic particles.

In one embodiment, the composition for forming a coating layer may include 100 parts by weight of a modified epoxy resin, 5 to 50 parts by weight of a curing agent, and 10 to 70 parts by weight of an inorganic particle. In one embodiment, the composition for forming a coating layer comprises a modified epoxy resin 100 1 to 50 parts by weight of the glycol compound and 5 to 350 parts by weight of the solvent.

In one embodiment, the composition for forming a coating layer may further comprise 1 to 30 parts by weight of an additive to 100 parts by weight of the modified epoxy resin.

Hereinafter, the structure and operation of the present invention will be described in more detail with reference to preferred embodiments of the present invention. It is to be understood, however, that the same is by way of illustration and example only and is not to be construed in a limiting sense.

The contents not described here are sufficiently technically inferior to those skilled in the art, and a description thereof will be omitted.

Example  And Comparative Example

Example

A neodymium (Nd-Fe-B) sintered magnet base material having a rectangular parallelepiped shape was immersed in an alkaline degreasing agent for 5 minutes using a rare earth sintered magnet to degrease the surface of the sintered magnet, and the degreased rare earth sintered magnet was immersed in a water bath for 5 minutes And then dried at a temperature of 140 ° C to 160 ° C for 55 to 65 minutes. The dried sintered magnet is sandwiched for 1 minute using an aluminum oxide abrasive, and then preheated and maintained at a temperature of 20 ° C to 30 ° C Respectively.

100 parts by weight of a modified epoxy resin (acrylic modified epoxy resin), 5 parts by weight of an amine curing agent, 46 parts by weight of inorganic particles (including calcium carbonate and TiO ₂ ), 10 to 50 parts by weight of a glycol compound, And 14 parts by weight of an additive (acrylic dispersant) were mixed to prepare a composition for forming a coating layer, sprayed (sprayed) to 4 to 5 surfaces of the surface of the pre-treated rectangular solid sintered magnet base material at a pressure of 3 bar, And cured at a temperature of 230 캜 for 45 to 55 minutes to form a coating layer having a structure in which inorganic particles are dispersed in the continuous phase of the modified epoxy resin.

Next, the composition for forming a coating layer is sprayed (applied) to the remaining one or two surfaces of the sintered magnet at a pressure of 3 bar and cured at a temperature of 210 ° C to 230 ° C for 45 to 55 minutes to form a coating layer, A coating layer having a thickness of 15 탆 was formed.

Comparative Example  One

A nickel (Ni) -copper (Cu) underlying plating layer was formed on the surface of the neodymium sintered magnet, and the surface of the nickel plating layer was coated with a conventional epoxy resin and cured to form a coating layer.

Comparative Example  2

A zinc (Zn) - aluminum (Al) composite coating layer was formed on the surface of the neodymium sintered magnet.

Comparative Example  3

A nickel (Ni) -copper (Cu) plating layer was formed on the surface of the neodymium sintered magnet.

Test Example : Salt spray test

The salt spray test is a typical test method for evaluating the corrosion resistance. It is a method of evaluating the corrosion resistance by spraying a test piece with KS M 8115 (sodium chloride reagent) and measuring the area or weight with time. The neodymium (rare earth) sintered magnets of the above Examples and Comparative Examples 1 to 3 were subjected to a salt water spray test, and the surface of the neodymium sintered magnet after 96 hours had passed was observed.

FIG. 2 (a) shows the results of a salt spray test on a sintered magnet produced according to an embodiment of the present invention, FIG. 2 (b) shows a salt spray test result of Comparative Example 1, FIG. 2 (d) shows the results of the salt spray test for Comparative Example 3, and FIG. 2 (d)

Referring to FIGS. 2 (a) to 2 (d), the neodymium sintered magnets of Examples and Comparative Examples 1 to 3 of the present invention were tested on the surface of the neodymium sintered magnet even after 96 hours from the salt spray test It is possible to eliminate the base plating coating process while ensuring the corrosion resistance equivalent to that of the conventional epoxy resin when the rare earth sintered magnet is surface-treated by applying the composition for forming a coating layer according to the present invention, It is possible to minimize the amount of wastewater discharged from the plating process and to be environmentally friendly.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

10: Rare earth sintered magnet base material 20: Coating layer
100: Rare earth sintered magnet

Claims (13)

Applying and curing a composition for forming a coating layer on the surface of the rare earth sintered magnet to form a coating layer,
Wherein the composition for forming a coating layer comprises a modified epoxy resin, a curing agent, and inorganic particles.
The method for surface treatment of a rare-earth sintered magnet according to claim 1, wherein the composition for forming a coating layer comprises 100 parts by weight of a modified epoxy resin, 5 to 50 parts by weight of a curing agent, and 10 to 70 parts by weight of an inorganic particle.
[3] The method of claim 2, wherein the composition for forming a coating layer further comprises 1 to 50 parts by weight of a glycol compound and 5 to 350 parts by weight of a solvent based on 100 parts by weight of the modified epoxy resin.
The method of claim 2, wherein the composition for forming a coating layer further comprises 1 to 30 parts by weight of an additive to 100 parts by weight of the modified epoxy resin.
5. The method according to claim 4, wherein the additive comprises at least one of a thickener, a defoaming agent, and a dispersant.
The method of claim 1, wherein the coating layer is formed by curing at a temperature of 190 ° C to 240 ° C.
The method for surface treatment of a rare-earth sintered magnet according to claim 1, wherein the coating layer is formed to a thickness of 5 탆 to 30 탆.
The magnetron of claim 1, wherein the rare-earth sintered magnet is pretreated,
The pre-
Degreasing the surface of the rare earth sintered magnet;
Washing and degreasing the defatted rare-earth sintered magnet;
Sanding the dried rare earth sintered magnet; And
And preheating the sand-sintered rare-earth sintered magnet.
Rare earth sintered magnet base material; And
And a coating layer formed on the surface of the rare earth sintered magnet base material,
Wherein the coating layer has a structure in which inorganic particles are dispersed in a continuous phase of a modified epoxy resin.
The rare-earth sintered magnet according to claim 9, wherein the coating layer is formed to a thickness of 5 탆 to 30 탆.
The rare earth sintered magnet according to claim 9, wherein the coating layer is formed by curing a composition for forming a coating layer comprising a modified epoxy resin, a curing agent and inorganic particles.
The rare earth sintered magnet according to claim 11, wherein the composition for forming a coating layer comprises 100 parts by weight of a modified epoxy resin, 5 to 50 parts by weight of a curing agent, and 10 to 70 parts by weight of an inorganic particle.
The rare earth sintered magnet according to claim 11, wherein the composition for forming a coating layer further comprises 1 to 50 parts by weight of a glycol compound and 5 to 350 parts by weight of a solvent based on 100 parts by weight of the modified epoxy resin.

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