KR102154588B1 - A magnet of Nd-Fe-B system comprising organic binder - Google Patents

Abstract

The present invention is an Nd-based powder; Coupling agents; And an organic binder, wherein the organic binder relates to an Nd-based magnet, characterized in that the organic binder is based on methyl cellulose, which can minimize deterioration of magnetic properties of the magnetic powder and uses a thermoplastic resin having excellent moldability. While exhibiting excellent heat resistance, there is an effect of being able to easily manufacture a bonded magnet that can simplify the manufacturing process.

Description

Nd-based magnet including organic binder {A magnet of Nd-Fe-B system comprising organic binder}

The present invention relates to an Nd-based magnet including an organic binder, and more particularly, to an Nd-based magnet including an organic binder that can minimize magnetic properties of magnetic powder and has excellent formability.

In general, a permanent magnet is a material that retains a magnetic field in a material even when an external magnetic field is removed, and is essentially used in motors, generators, and electronic devices.

In particular, permanent magnets that have high added value and are applied to video recorders, computer disk drives and electric motors that are applied in various industries have a decisive influence on the quality and performance of the final product.

Conventionally, Alnico-based and Ferrite-based alloys have been mainly used as alloys for producing permanent magnets, but in recent years, as electronic, communication, and mechanical parts have been miniaturized and high-performance, neodymium-iron-boron (Nd-Fe) has excellent magnetic properties. -B)-based materials are widely used for magnets.

The neodymium-iron-boron (Nd-Fe-B)-based magnet was developed and commercialized by Sumitomo Special Metals in Japan in 1982, and is a powerful permanent magnet with the largest magnetic energy.

Meanwhile, domestic and overseas home appliance companies are contributing a lot to reducing the energy cost of consumers by developing energy-efficient products and putting them on the market. In particular, research and development for minimizing power consumption are being actively conducted with the increase in size of household refrigerators, kimchi refrigerators, and commercial refrigerators.

In particular, a fan motor of a brushless DC electric motor is used as a device to circulate the cool air contained in these products. In the case of such a fan motor for refrigerators, it is important to commercialize a high-efficiency refrigerator that can reduce the power consumption of the refrigerator to less than 2.5W. Is playing a role.

However, recent home appliance companies are actively conducting research and development to commercialize refrigerators with less than 2W power consumption, and for this reason, the importance of functions and core parts for BLDC fan motors is increasing.

As described above, a high-efficiency BLDC fan motor is applied as a cold air circulation motor applied to a refrigerator, and a bonded magnet in which a magnetic powder and an organic binder are mixed is applied as a core component.

Bond magnets currently being used and manufactured are solid-type bond magnets with ferrite as the main component, which has strong corrosion resistance and durability, but by using Nd-based rare earth magnetic powder, the reduction of power consumption due to miniaturization and high efficiency of the motor is realized. Therefore, it is essential to develop a bonded magnet containing rare earth magnetic powder with excellent magnetic properties in order to realize power consumption of 2 W or less.

However, in Korea, some companies have secured and produced the bonding technology of ferrite and organic binders in Korea, but there is no development of bond magnets in which rare-earth magnetic powder and organic binders are mixed, so they are entirely dependent on the products of TODA in Japan.

Korean Patent Publication 2001-0057613

An object to be solved by the present invention is to provide a rare earth bonded magnet for a BLDC fan motor based on an organic binder control technology of a highly anisotropic rare earth bonded magnet.

In addition, an object of the present invention is to optimize a magnetic circuit of a mold for making a high characteristic uniform magnetic flux and apply it to a refrigerator fan motor, thereby commercializing it in an energy-efficient refrigerator product capable of realizing power consumption of 2W or less.

Objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned will be clearly understood by those skilled in the art from the following description.

In order to solve the above-noted problems, the present invention includes an Nd-based powder; Coupling agents; And an organic binder, wherein the organic binder is a methyl cellulose-based magnet.

In addition, the present invention provides an Nd-based magnet, characterized in that the organic binder is 8 to 10% by mass compared to 100% by mass of the Nd-based magnet (bonded magnet).

In addition, the present invention is the methyl cellulose (Methyl Cellulose)-based organic binder, carboxyl methyl cellulose (CMC), methyl cellulose (MC (Methyl Cellulose)), hydroxy propylene methyl cellulose (HPMC (Hydroxy Propylene Methyl Cellose)) of It provides an Nd-based magnet, characterized in that at least any one.

In addition, the present invention further comprises a lubricant, the Nd-based magnet, the lubricant is paraffin wax (Paraffine wax), Aluminum stearate, Butyl stearate, Lithium stearate, Magnesium stearate, Sodium stearate, Steric acid, Zinc stearte, Oleic acid , It provides an Nd-based magnet, characterized in that at least one selected from the group consisting of polyglycols.

In addition, the present invention provides an Nd-based magnet, characterized in that the coupling agent is N-(beta-aminoethyl)-gamma-aminopropylmethyldimethoxysilane or 3-methacryloxypropyltrimethoxysilane.

According to the present invention as described above, it is possible to minimize deterioration of magnetic properties of magnetic powder, exhibit excellent heat resistance while using a thermoplastic resin having excellent moldability, and facilitate bonding magnets that can simplify the manufacturing process. There is an effect that can be manufactured.

In addition, according to the present invention, for mechanical and magnetic properties while achieving simplification and cost reduction, an Nd-based magnet (bonded magnet) having characteristics equal to or higher than that of a bonded magnet manufactured by adding a commercial organic binder is provided. Can provide.

1 is a schematic flowchart illustrating a method of manufacturing an Nd-based magnet (bonded magnet) according to the present invention.
2 is a SEM photograph showing an Nd-based magnet (bonded magnet) according to the present invention.
3 is a SEM photograph showing particles of Nd ₂ Fe ₁₄ B powder according to the present invention.
4 is a diagram showing specifications of the extruder according to the present invention and conditions of an extrusion process.
5 is a real photograph showing a specimen manufactured through an extruder, and FIG. 6 is a photograph showing a microstructure of a specimen according to an extrusion temperature.
7 is a view showing the change in density according to the extrusion temperature of the specimen according to the present invention, Figure 8 is a view showing the change in strength according to the extrusion temperature of the specimen according to the present invention.
9 is a diagram showing a change in density according to the content of the organic binder.
10 is a measurement value of the magnetic properties of a specimen to which 9% by mass of an organic binder is added.
11 is an SEM photograph showing the microstructure of a specimen to which 9% by mass of an organic binder is added.
12 is a view showing the time required according to the manufacturing method of the Nd-based magnet including the organic binder according to the present invention.

Advantages and features of the present invention, and a method of achieving them will become apparent with reference to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in a variety of different forms, and only these embodiments make the disclosure of the present invention complete, and common knowledge in the technical field to which the present invention pertains. It is provided to completely inform the scope of the invention to those who have it, and the invention is only defined by the scope of the claims.

With reference to the accompanying drawings below will be described in detail for the implementation of the present invention. Regardless of the drawings, the same reference numerals refer to the same elements, and "and/or" includes each and all combinations of one or more of the mentioned items.

Although the first, second, and the like are used to describe various components, it goes without saying that these components are not limited by these terms. These terms are only used to distinguish one component from another component. Therefore, it goes without saying that the first component mentioned below may be the second component within the technical idea of the present invention.

The terms used in the present specification are for describing exemplary embodiments and are not intended to limit the present invention. In this specification, the singular form also includes the plural form unless specifically stated in the phrase. As used in the specification, “comprises” and/or “comprising” do not exclude the presence or addition of one or more other elements other than the mentioned elements.

Unless otherwise defined, all terms (including technical and scientific terms) used in the present specification may be used as meanings that can be commonly understood by those of ordinary skill in the art to which the present invention belongs. In addition, terms defined in a commonly used dictionary are not interpreted ideally or excessively unless explicitly defined specifically.

Spatially relative terms "below", "beneath", "lower", "above", "upper", etc., as shown in the figure It can be used to easily describe the correlation between a component and other components. Spatially relative terms should be understood as terms including different directions of components during use or operation in addition to the directions shown in the drawings. For example, if a component shown in a drawing is turned over, a component described as "below" or "beneath" of another component will be placed "above" the other component. I can. Accordingly, the exemplary term “below” may include both directions below and above. Components may be oriented in other directions, and thus spatially relative terms may be interpreted according to the orientation.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Rare-earth bonded magnets are magnets with complex characteristics in which rare-earth metal magnetic powder and organic binder are fused, and are manufactured by injection and extrusion molding by uniformly mixing metal powder with certain performance, organic binder, and other organic additives at a certain ratio. It is made of a kind of fusion material.

Here, organic substances and other organic additives are collectively referred to as organic binders. When the bonded magnet is manufactured, if the metal powder is anisotropic, it can be oriented in a magnetic field to manufacture a highly anisotropic bonded magnet.

Although these rare earth bonded magnets are being commercialized in many industrial fields besides BLDC motors, the current situation in Korea relies entirely on Japanese imports. This is because rare earth metal magnetic powder has been researched and developed in universities, research institutes, and companies, but there is no research on organic binders, which are the core components of bonded magnets.

Although this is a factor that determines the properties of the bonded magnet, which is the final product, since the organic binder was determined and manufactured through literature or experience, the magnetic properties of the bonded magnet were very low, and many problems occurred in mechanical properties and durability. It is imported and used by TODA.

In addition, since Japan does not sell only organic binders, but sells products in the form of a mixture of magnetic powder and organic binders, high-priced compounds are purchased and used in Korea, where there is no technology for organic binders.

Despite this necessity, in Korea, in preparation for the price increase of rare earth magnetic powders and rare earth materials and resource weaponization in China, only rare earth parts and rare earth reduction technologies are being used, which are essential powders for the maximum characteristics of rare earth magnets. There is no research on organic binders for forming rare earth powder magnets for controlling orientation / suppressing powder degradation / improving moldability.

As described above, if the import of organic binders for rare earth powders and technological lag continues, in the situation where the patent rights for the powder manufacturing technology are released, the result of having to waste more foreign currency on imports without securing the organic binder control technology. Therefore, it is necessary to develop organic binders for rare earth bonded magnets.

Existing imported products are manufactured by adding an organic binder with polyamide 12 resin applied to the rare earth Nd-based magnetic powder.

Since polyamide resins have extremely low melt viscosity, their viscosity changes sensitively to temperature changes during molding. Therefore, special attention is required for molding a uniform product. In addition, due to its strong hygroscopicity, special care is required when handling, since there is a difference in characteristics in a humid environment and a dry environment.

On the other hand, the methyl cellulose-based organic binder according to the present invention is a resin that can compensate for these problems because the variation in viscosity according to temperature change during molding is small and the change in properties according to hygroscopicity does not occur.

In addition, since it has excellent flowability in the molten state, it is advantageous for dispersion between magnetic powders, and since it has excellent adhesion, an additional material for improving adhesion is not required, thereby simplifying the manufacturing process and reducing cost.

1 is a schematic flowchart illustrating a method of manufacturing an Nd-based magnet (bonded magnet) according to the present invention.

Referring to FIG. 1, by mixing an Nd-based powder and a coupling agent, a first Nd-based compound powder is prepared, and the first Nd-based compound powder and an organic binder are mixed. Through the second Nd-based compound powder thus formed, an Nd-based magnet (bond magnet) according to the present invention may be manufactured.

At this time, in the present invention, a methyl cellulose based organic binder is used as the organic binder.

That is, the Nd-based magnet (bonded magnet) according to the present invention includes an Nd-based powder; Coupling agents; And an organic binder, wherein the organic binder is a methyl cellulose system.

On the other hand, as will be described later, the Nd-based magnet (bond magnet) according to the present invention may further include a lubricant, which will be described later.

2 is a SEM photograph showing an Nd-based magnet (bonded magnet) according to the present invention.

Referring to FIG. 2, it can be seen that the microstructure of the fracture surface of the Nd-based magnet (bonded magnet) includes an organic binder (A) and a magnetic powder (B).

Hereinafter, the Nd-based magnet (bonded magnet) according to the present invention will be described in more detail.

In general, in the case of an anisotropic bonded magnet, the role of an organic binder is important in order to favor powder orientation during magnetic field molding.

Among rare earth permanent magnets, organic binders included in bonded magnets are added to benefit moldability and physical properties with polymers and resins as main components.

There are many kinds of such organic binders, and when selecting an organic binder, the bonding force is large, the mechanical strength is excellent, the water absorption is low, the dimensional stability is good, the shrinkage rate at the time of solidification is small, the dimensional accuracy of the bonded magnet to be manufactured is excellent, and the thermal stability is good. And the like.

At this time, organic binders can be classified according to their thermal characteristics, and thermosetting organic binders include epoxy resin, phenol resin, urethane resin, and melamine resin, and thermoplastic resins include nylon (polyamide) resin, polypropylene resin, polyethylene resin, poly Vinyl chloride resin and the like. These plastic resins have good fluidity during processing and have excellent thermal stability and mechanical performance.

Epoxy resins are commonly used as organic binders for bonded magnets using a compression molding process. The epoxy resin is a generic term for a compound having an oxygen-interposed structure.

In other words, it is a chemical unit of the constituting molecule, which must have an epoxy bond, and is mainly made by polymerizing epichlorohydrin and bisphenol A. Unlike general thermosetting resins, curing does not occur by heating or pressing alone, and a polymer having a three-dimensional network structure is formed at room temperature and high temperature by a curing agent such as amine, acid anhydride, metal salt, Lewis acid.

At this time, the epoxy resin generally has excellent electrical and mechanical properties of the cured product after curing, and has a low weight change rate during curing, enabling precise molding. In addition, after curing, the cured product has no twist or deformation, so it is excellent in durability, and if the curing agent is not mixed, curing does not occur.

However, unlike conventional thermosetting resins, since curing occurs only when a curing agent is mixed, there is a disadvantage of having to mix, and a difference in curing speed depending on external temperature is large.

Accordingly, in the present invention, the organic binder is characterized in that a methyl cellulose (Methyl Cellulose)-based organic binder is used, and the methyl cellulose (Methyl Cellulose)-based organic binder is carboxyl methyl cellulose (CMC), methyl cellulose ( MC (Methyl Cellulose)) or hydroxy propylene methyl cellulose (HPMC (Hydroxy Propylene Methyl Cellose)).

First, the molecular formula of the carboxyl methyl cellulose (CMC) is (C6H10O5)n, and there are 3 OH groups per 1 glocose in the cellulose, and the formula is (C6H7O2(OH)3)n. The chemical bonding structure is shown in the following structural formula 1.

[Structural Formula 1]

The manufacturing method of the carboxyl methyl cellulose (CMC) is etherified by reacting monocrole sodium acetate on alkaline cellulose. Since the carboxymethyl group is a Na salt in which cellulose and ether are bonded, it becomes a water-soluble polymer having ionizing properties. The degree of D and S substitution (average number of OH groups reacted to the substituent per unit of no water glycous) is at most 3 in any derivative. As D and S increase, water solubility increases. The good uniformity of D and S is an aqueous solution that is close to Newton's characteristics with small thixotropy. In general, CMC has D,S of 0.5-1.2, and has wettability. Solubility becomes an aqueous solution by swelling in water, but it is soluble in hydrophilic solvents such as methanol, ethanol, and acetone. It can be mixed with other water-soluble polymer solutions, i.e., tracanth rubber, sodium alkynate, MC, etc.

At this time, various grades with a viscosity of 2% in aqueous solution and between 50 cps-105 cps are commercially available, and their characteristics are well soluble in water, colorless and transparent, viscosity can be adjusted, and are compatible with other materials. ) Has sex. Thixotrophic, dispersible, stable, chemically stable, makes a film, and is non-toxic.

Also, it is not spoiled and is easy to decompose. When the form of Na salt for ceramic is not desirable, use ammonium salt. The standard is 30-35% volatile matter, 6.0-6.5 PH (in 1% aqueous solution), and 280-400 cps viscosity (1%, 25℃). While the ash contains 5-10% Na salt, there are also less than 0.3-0.2%. . As a ceramic binder, it is used as a paint binder for insulators and fluorescent lamps.

Next, the methyl cellulose (MC (Methyl Cellulose)) is an environmentally friendly material and is made of cellulose obtained from wood or cotton as a raw material.

Cellulose is an insoluble natural polymer with 30-65% crystallinity due to hydrogen bonding between molecules. Cellulose, which is insoluble in water, is transformed into a water-soluble polymer called cellulose ether through etherification. Using various ether groups, the gelation rate, water absorption amount, viscosity, etc. are changed to reach dozens of types of MC, PMC, HMC, and the like, and the chemical bonding structure is shown in the following Structural Formula 2.

[Structural Formula 2]

In addition, the methyl cellulose (MC (Methyl Cellulose)) is a white, tasteless, odorless, stable powder that is soluble in cold water. It contains 27-32% of a methoxy group (-OCH3) in the molecule. Those in this range are best soluble in water. There are several grades depending on the viscosity range of the aqueous solution. According to the catalog it can be classified according to the viscosity at 20°C of a 2% solution of MC with 27-32% methoxy groups. MC is a transparent aqueous solution, has stability, does not decompose by acid alkali, and does not precipitate due to substitution with heavy metals and alkaline earth metals.

In addition, the methyl cellulose (MC (Methyl Cellulose)) creates a transparent and strong film, has plasticity, and has a high tensile strength and elongation. It has strong adhesion and bonding power. Table 1 shows a comparison of the adhesive strength with other binders. In addition, it has dispersion, emulsification, protective colloidality, and viscosity, and has a hydrophilic group and a lipophilic group in the structure, so it can be called a kind of surfactant in a sense. Therefore, the surface tension of the aqueous solution and the interfacial tension between the liquids are reduced.

[Table 1]

Next, hydroxy propylene methyl cellulose (HPMC (Hydroxy Propylene Methyl Cellose)) was substituted with a hydroxy propoxy group (-OC3H6OH) instead of a methoxy group (-OCH3), which increased the thermal gelation temperature and has hydrophilicity, The chemical bond structure is shown in the following Structural Formula 3.

[Structural Formula 3]

On the other hand, as described above, the Nd-based magnet (bonded magnet) according to the present invention, Nd-based powder; Coupling agents; And an organic binder.

In general, metal ferromagnetic powder belongs to hydrophilicity due to good wettability of water, but the main component resin of organic binder is a polymer material and belongs to lipophilicity. If the surface of the magnetic metal powder granules is modified lipophilically, the affinity between the magnetic powder and the organic binder can be increased. To this end, it is necessary to add a coupling agent when manufacturing a bonded magnet.

The lipophilic functional group in the coupling agent binds to the organic binder and the hydrophobic functional group binds to and interacts with the magnetic powder, thereby increasing the affinity between the organic binder and the magnetic powder granules. In addition to these roles, it is advantageous during magnetic field molding by increasing the fluidity and rotational properties of magnetic powder, reducing oxidation of powder, and contributing to the improvement of the strength and thermal stability of bonded magnets.

The coupling agent mainly used for bonded magnets is a compound composed of organic matter and silicon, and has two or more different reactors, one that chemically bonds with inorganic materials in the molecule and one that chemically bonds with organic materials. By acting as an intermediary for combining organic and inorganic materials that are quite difficult to combine from such a reactor, it is used for improving the mechanical strength and physical properties of the final composite material, thereby realizing high functionality and high quality of the material.

At this time, there are various types of functional groups of organic substances constituting the coupling agent, such as vinyl, epoxy, meta-hydroxy, amino, mercapto, acryloxy, isocyanate, and styryl, and epoxy functional groups are most widely used.

More specifically, the coupling agent according to the present invention may contain various functional groups to improve the bonding strength between different materials, for example, vinyl, epoxy, styryl, methacryloxy ( methacryloxy), acrylicoxy (acryloxy), amino (amino), chloropropyl (chloropropyl), mercapto (mercapto), sulfido (sulfido), may contain a functional group selected from the group consisting of isocyanato (isocyanato) .

Meanwhile, the Nd-based magnet (bonded magnet) according to the present invention may further include a lubricant.

It lowers the friction between the mold and the molded product for smooth topography of the extruded product, plays a role of releasing the mold and the molded body during demoulding, and uses a lubricant for the purpose of improving the life of the mold by preventing abrasion or oxidation corrosion of the mold. Oil-type, a solvent, is widely used.

In press molding, injection molding, and vibration injection molding, when the sliding action between ceramic raw material particles is poor, the molding density does not increase. If the finish of the raw material is not good, the small crystal density is bad.

Therefore, in order to improve the lubrication of the raw material particles, it is necessary to activate the binder. Since most of the aqueous viscosity agents are materials with a high coefficient of friction, if a material having lubricity is mixed with an aqueous aid as a binder and molded, the deformation is small and the density is large. To give more lubricity, a substance with a hydrocarbon chain is required.

For example, the longer the hydrocarbon, the better the lubricity, and the longer the hydrocarbon, the better the lubricity. The structure of this hydrophilic group also affects the coefficient of friction, and lubrication is well performed in the order of amide group (-NH2), amide group (-CONH2), and carboxyl (-COOH). Then there is an alcohol group (-OH).

These lubricants have both internal lubricity and external lubricity, and structurally high internal lubricity includes fatty alcohol, dicarboxylic acid ester, fatty acid ester, fatty acid, fatty acid salt, fatty acid amide, and both properties. What I have is Hector Wax OP (Partially Golded Ester Wax), Hector Wax E (Ester Wax), and Hector Wax S (San Wax).

In addition, liquid paraffin and paraffin wax are those with high external lubricity, and polyethylene wax (molecular weight of about 9,000 as high density and 2,000 molecular weight as low density) is excessively active.

More specifically, the lubricant according to the present invention may use paraffin wax, Aluminum stearate, Butyl stearate, Lithium stearate, Magnesium stearate, Sodium stearate, Steric acid, Zinc stearte, Oleic acid, Polyglycols, etc., but, In the present invention, the type of lubricant is not limited.

Hereinafter, the Nd-based powder according to the present invention will be described.

First, the Nd-based powder according to the present invention may be an Nd-Fe-B-based magnetic powder.

3 is a SEM photograph showing particles of Nd ₂ Fe ₁₄ B powder according to the present invention.

Referring to FIG. 3, the Nd ₂ Fe ₁₄ B powder according to the present invention has been subjected to HDDR treatment, as shown in the SEM photo confirmed at 1000 times magnification (left of FIG. 3) and 30000 times magnification (right of FIG. 3). , It can be confirmed that the powder particles of about 100 μm are agglomerated to form a shape, and since the gaps between the powder particles and the particles are spherical, the density must be supplemented by filling the space between the particles and the particles with an organic binder and coupling agent.

At this time, in the present invention, it is preferable that the particle size of the NdFeB-based magnetic powder is 50 to 100 μm, and oxidation may occur when the particle size of the NdFeB-based magnetic powder is less than 50 μm, and when it exceeds 100 μm, during injection Since the flowability becomes non-uniform, a decrease in the molding density may occur, and the particle size of the NdFeB-based magnetic powder in the present invention is preferably 50 to 100 μm.

Table 2 corresponds to a qualitative analysis of the HDDR-treated Nd ₂ Fe ₁₄ B powder. However, in the present invention, the type of the NdFeB-based magnetic powder is not limited, and since the NdFeB-based magnetic powder is a matter that is apparent in the art, a detailed description will be omitted below.

[Table 2]

Hereinafter, a preferred experimental example according to the present invention will be described, but the present invention is not limited to the following experimental examples.

As described above, the Nd-based magnet (bonded magnet) according to the present invention includes an Nd-based powder; Coupling agents; And an organic binder, wherein the organic binder is a methyl cellulose system.

Table 3 below is a table showing commonly used coupling agents.

[Table 3]

As shown in Table 3, most commonly used silane-based coupling agents are used, and in the present invention, A1120 and A174 coupling agents of Table 3 were used.

Table 4 below is a table showing the properties of the A1120 and A174 coupling agents.

[Table 4]

When a coupling agent is added in the mixing process with magnetic powder, it is expected to improve physical and electronic properties such as a decrease in shear viscosity and an increase in the applied magnetic field versus residual magnetic flux density.

In addition, when the powder filling is increased, the residual magnetic flux density is slowed due to the increase in the orientation friction force, and the filling rate for the powder has an effect on the difference in the coercive force.

According to the results of Table 4, as the coupling agent is added, the powder filling degree is improved to effectively accelerate the density increase, and the magnetic property value is expected to increase due to the increase in orientation due to the increase in the distance between the powders.

On the other hand, in the present invention, the organic binder is preferably 8 to 10% by mass compared to 100% by mass of the Nd-based magnet (bonded magnet).

In the present invention, a compound compounding ratio experiment was performed to produce a final injection bonded magnet.

This is done through the extrusion process, and in order to confirm the quantitative ratio of the organic binder to the magnetic powder mixed in the compound, the detailed conditions of the extrusion process were determined. In particular, the characteristics according to the temperature conditions around 200℃ are the most important. In the invention, Max. The temperature was 225 ℃, 230 ℃, 235 ℃, 240 ℃ four temperatures, 5 ℃ step by step to conduct the experiment. Detailed specifications of the extruder and conditions of the extrusion process are shown in Fig. 4, and the mixing ratio of raw materials and the temperature conditions of the extrusion process are shown in Table 5 below.

[Table 5]

FIG. 5 is a real photograph showing a specimen manufactured through an extruder, and FIG. 6 is a photograph showing a microstructure of a specimen according to an extrusion temperature.

Through the above experiment, detailed temperature conditions of the extruder for the development of the injection bonded magnet were established, and the density and tensile strength of the extruded specimen were measured according to the manufacturing conditions.

7 shows the density change according to the extrusion temperature of the specimen according to the present invention, Figure 8 shows the strength change according to the extrusion temperature of the specimen according to the present invention.

Referring to FIGS. 7 and 8, most of the density was 4.8 g/cc, and the strength was 15.5 to 18.95 kgf. As shown in Fig. 7, there is almost no change in density, which is judged to be more dominant in the mixing ratio of magnetic powder and puller than the factor of injection temperature, and the cross-sectional fracture strength is the higher the temperature, the more the flowability of the organic binder is. Because it is good, the mechanical strength for dispersibility is high, but at a temperature of 240°C or higher, resin deterioration occurs in which carbon of the organic binder is volatilized, and accordingly, its properties are judged to be deteriorated.

On the other hand, in the present invention, the organic binder is preferably 8 to 10% by mass compared to 100% by mass of the Nd-based magnet (bonded magnet).

More specifically, when the content of the organic binder is included as 8% by mass relative to 100% by mass of the Nd-based magnet (bond magnet), and 9% by mass relative to 100% by mass of the Nd-based magnet (bonded magnet), the organic When the content of the binder was included as 10% by mass compared to 100% by mass of the Nd-based magnet (bonded magnet) (MC-U003), the experiment was conducted.

At this time, the coupling agent was included in an amount of 0.3% by mass compared to 100% by mass of the Nd-based magnet (bonded magnet).

Under these conditions, the binder of MC-U002 and the binder of MC-U003 were used, and the binder of MC-U002 and the binder of MC-U003 had a certain difference in the glass transition temperature and melting start temperature.

That is, as shown in Table 6 below, in the case of MC-U002, a glass transition temperature appears at a temperature of 133.84°C, and in the case of an MC-U003 binder, a glass transition temperature of 130.21°C appears and curing begins at 120.97°C.

[Table 6]

9 shows the density change according to the content of the organic binder.

Referring to FIG. 9, it was confirmed that the specimen to which the MC-U003 organic binder was added has a higher density than the MC-U002 organic binder specimen. Since the melt viscosity value of MC-U003 is higher than the melt viscosity value of MC-U002, it is judged that the density value is high due to excellent fluidity according to the process in the magnetic powder.

In addition, the change in density decreases as the content of the organic binder increases compared to the magnetic powder is considered to be because the mass of the manufactured magnet decreases as the content of the organic binder increases.

In addition, the higher the content of the organic binder, the smaller the content of the magnetic powder, so the magnetic properties are expected to deteriorate. Therefore, it is necessary to maintain the properties of the density that determines the mechanical properties and secure the magnetic properties. As can be seen, the content of 9% by mass is judged to be the most suitable.

10 is a measurement value of the magnetic properties of a specimen to which 9% by mass of an organic binder is added.

As shown in FIG. 10, it can be seen that the average maximum magnetic energy value of 12 MGOe appears as a value measured twice for each of three specimens manufactured under the same conditions.

11 is an SEM photograph showing the microstructure of a specimen to which 9% by mass of an organic binder is added.

As shown in FIG. 11, in the 100-fold magnification photograph of the specimen prepared by adding an organic binder of 9% by mass, it can be seen that the binder is distributed on the powder surface as a whole, but the size of the distributed binder particles is uneven. I can confirm.

It can be considered that this is because the binder is in a solid state when it is mixed, so that the efficiency in dispersibility is poor.

In addition, in the 1000x magnification photo, the binder is located in the gap between the powders, and fine powders are attached to the surface of the binder, indicating that the powder fell off when cutting the specimen and was acting as a binder between the powders.

12 is a view showing the time required according to the manufacturing method of the Nd-based magnet including the organic binder according to the present invention.

Referring to FIG. 12, in the case of "A", a basic method of mixing a binder after mixing a coupling agent takes 80 minutes when using a thermoplastic resin to prepare a specimen.

In the case of "B", the coupling agent and the binder are each dissolved and mixed with the magnetic powder at one time, and in the case of "C", the binder is mixed with the diluted coupling agent solution and mixed with the magnetic powder.

The "C" method is a process that reduces two steps to one, and takes 70 minutes, which is less than 80 minutes. Compared to the existing method, the multi method has the effect of reducing 25 minutes.

In order to check whether the specimens manufactured in this manner have the same characteristics as those manufactured in the basic A-way method, the density of the specimens prepared in A, B, and C was measured.

Table 7 is a table showing the density of the specimen according to the manufacturing method of the Nd-based magnet.

[Table 7]

Referring to Table 7, it was confirmed that the density of the specimen according to the manufacturing method has a slight difference in value, but has an excellent density of 4.8 g/cc or more. This simplifies the blending process and thereby secures the effect of reducing the manufacturing cost.

However, in the case of the specimen manufactured by the method of "C", the density value tends to be lowered, and therefore, in the present invention, it can be said that it is most preferable to manufacture it by the method of "B".

As described above, the Nd-based magnet (bonded magnet) according to the present invention includes an Nd-based powder; Coupling agents; And an organic binder, wherein the organic binder is a methyl cellulose system.

Therefore, according to the present invention, it is possible to minimize the decrease in magnetic properties of the magnetic powder, exhibit excellent heat resistance while using a thermoplastic resin having excellent moldability, and easily manufacture a bonded magnet that can simplify the manufacturing process. It can have an effect.

In addition, according to the present invention, for mechanical and magnetic properties while achieving simplification and cost reduction, an Nd-based magnet (bonded magnet) having characteristics equal to or higher than that of a bonded magnet manufactured by adding a commercial organic binder is provided. Can provide.

Although the embodiments of the present invention have been described with reference to the above and the accompanying drawings, those of ordinary skill in the art to which the present invention pertains can be implemented in other specific forms without changing the technical spirit or essential features. You can understand that there is. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not limiting.

Claims (5)

In the Nd-based magnet,
The Nd-based magnet,
Nd-based powder;
Coupling agents; And
Including organic binders,
The organic binder is characterized in that the methyl cellulose (Methyl Cellulose) system,
The organic binder is characterized in that 8 to 10% by mass compared to 100% by mass of the Nd-based magnet (bonded magnet),
The Nd-based magnet,
A material formed by mixing the Nd-based powder and the coupling agent to prepare a first Nd-based compound powder, and mixing the first Nd-based compound powder and the organic binder. Through 2Nd-based compound powder, to prepare the Nd-based magnet,
Nd-based magnet, characterized in that the particle size of the Nd-based magnetic powder is 50 ~ 100㎛. delete The method of claim 1,
The methyl cellulose (Methyl Cellulose)-based organic binder is at least one of carboxyl methyl cellulose (CMC), methyl cellulose (MC (Methyl Cellulose)), and hydroxy propylene methyl cellulose (HPMC (Hydroxy Propylene Methyl Cellose)). Nd-based magnet characterized by. delete The method of claim 1,
The coupling agent N-(beta-aminoethyl)-gamma-aminopropylmethyldimethoxysilane or 3-methacryloxypropyltrimethoxysilane Nd-based magnet, characterized in that.

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