JP3229948B2 - Manufacturing method of bonded magnet and bonded magnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a bonded magnet and a bonded magnet.

[0002]

2. Description of the Related Art Bonded magnets made from a composition comprising particles of an organic material, such as an organic polymer material, and magnetic material are well known. Typically, commercially available magnets of this type are made from a composition consisting of a mixture of a thermoplastic organic polymer and magnetic material particles. For example, a composition composed of a mixture of a thermoplastic organic polymer and magnetic material particles is molded in a plastic mold (eg, an injection molding machine, an extrusion molding machine). The composition may be formed by compression molding.

[0003] The composition is molded when the thermoplastic polymer is in a fluid state and then cooled and solidified. In addition, when the thermoplastic organic polymer is in a fluidized state, the composition can be exposed to a magnetic field to enhance the performance of the magnet in order to orient the magnetic particles in an easy direction of magnetization. The application of the magnetic field is continued until the organic polymer cools and solidifies. After complete cooling and solidification, the magnetic field is removed, as it is no longer necessary to maintain the orientation of the particles in the composition. The magnet molded in this way is taken out of the plastic molding machine.

[0004] The organic polymer in the composition used to make the bonded magnet is a polyolefin. For example, polyethylene and polypropylene, particularly preferred for such compositions are polyamides, one of which is nylon. Particularly preferred is nylon-6. For example, JP-A-59-94406 describes a composition comprising a synthetic resin and a magnetic powder surface-treated with a coupling agent. The magnetic powder is a ferrite or a rare earth cobalt intermetallic compound, and the synthetic resin is a polyamide such as polypropylene, polyvinyl chloride or nylon-6, nylon-11, nylon-12. Nylon-6, nylon-6.6
A composition using a polyamide such as
0-216524 and JP-A-61-5970.
No. 5 publication.

[0005] A magnet made of a composition having a property that it is hardly deformed even at a high temperature, which is made of an organic material,
It is obtained by using a composition comprising a crosslinkable organic material (for example, a thermosetting resin). In the production of a magnet made of such a composition, a composition obtained by adding a crosslinking agent that induces crosslinking of the organic material to the crosslinkable organic material as an additive and mixing them with magnetic material particles is used as a plastic molding method. Is formed at a temperature such that the organic material is in a fluid state, and then the organic material is cross-linked, resulting in a bonded magnet comprising solid organic resin cross-linked with magnetic material particles. When the organic material is in a fluid state, the composition may be exposed to a magnetic field in order to orient the easy magnetization direction of the magnetic material particles. By doing so, the magnetic properties of the magnet can be improved. In this case, the applied magnetic field is maintained at least until the cross-linking reaction exerts a sufficient effect so that the composition is solidified so that the oriented particles do not disturb even without the magnetic field. If the application of the magnetic field is removed while the organic material is still in a fluid state, the magnetic particles in the organic material will be out of alignment with adjacent ones repelling each other.

[0006] The following known materials are available for producing a bonded magnet made of a crosslinkable organic material. First, in JP-A-60-220905, an epoxy resin,
A method for producing a bonded magnet made from a composition comprising a rare earth magnet powder and a fatty acid ester as a lubricant is described. Next, JP-A-60-220906 describes a method for producing a bonded magnet made of a composition comprising an epoxy resin, a rare earth magnet powder and a fatty acid amide as a lubricant. As a third example, there is JP-A-60-206111. This patent describes as a special example a bonded magnet made from a composition comprising a bisphenol A novolak epoxy resin, a diluent and a magnetic powder of an Sm-Co intermetallic compound. As a fourth example, JP-A-60-183705 is cited. This patent relates to a method for producing a bonded magnet using a composition comprising a ferrite powder surface-treated with a surfactant and an unsaturated liquid polyester.

[0007]

However, magnets made from a composition in which the organic polymer material is a thermoplastic such as nylon or polyolefin have the following disadvantages. This is because polyolefins and nylons have relatively low glass transition temperatures. As a result, a magnet made of a composition composed of polyolefin or nylon is distorted or deformed. This phenomenon occurs especially when exposed to strong magnetic fields and as a result of repulsion forces acting between oriented magnetic particles in the magnet. These things
If this happens during use of the magnet, it will have a significant effect on the equipment on which the magnet is mounted. For example, nylon-6
The glass transition temperatures of nylon-11 and nylon-12 are 62.5 ° C, 46 ° C, and 37 ° C, respectively. Therefore, the use limit temperature of the magnet using such a resin is relatively low. It is believed that such low service temperature limit is lower than the temperature actually required. In addition, it is necessary to heat the organic polymer to a fluid state to form the composition. But its temperature is quite high,
It has an unfavorable effect on the performance of the magnetic particles during molding, for example oxidation. Further, if it is intended to obtain a bonded magnet having high magnetic performance, it is necessary to use a composition having a high filling ratio of magnetic particles. Since such compositions have a high viscosity at the time of molding, molding appears to be very difficult, if not impossible. In order to form such a composition, the organic polymer must be in a fluid state, which requires extremely high temperatures. However, doing so has an undesirable effect on the properties of the magnetic particles.

In general, since a crosslinkable resin has a high glass transition temperature, a bonded magnet using the same can be used at a higher temperature than a bonded magnet using a thermoplastic organic polymer.

However, magnets using such a crosslinkable resin also have the following disadvantages. First, magnetic materials, ferrite, rare earth elements, and transition metals are very expensive. Accordingly, defective or defective products during molding, or spools and runners in injection molding, which are usually discarded, and portions protruding in compression molding, etc., are particularly desired to be reused. However, once the organic material in the composition has been crosslinked, it cannot be reused using any plastic processing techniques. Therefore, the magnetic material contained in a defective product, a defective product, or a protruding portion is completely wasted. Further, in the production of a magnet using such a composition, the productivity is limited by the speed of crosslinking. The productivity further implies that the cross-linking reaction must proceed to such an extent that the composition does not collapse when the composition is removed from the mold in a mold of a molding machine such as a mold of an extrusion molding machine. It is also limited by necessity. When a magnetic field for orienting the easy magnetization direction of the magnetic particles is applied, the magnetic field must be continuously applied until the crosslinking reaction proceeds and the composition is sufficiently solidified. That is, it means that the oriented magnetic particles can maintain the orientation even when the application of the magnetic field is stopped. The crosslinking reaction has a finite time. It will take a few minutes for an effective amount of crosslinking to be obtained. Therefore, the productivity of this process is severely limited. And
It is both inconvenient and uneconomical to keep applying a magnetic field for such a long time.

An object of the present invention is to have excellent magnetic performance,
It is an object of the present invention to provide a bond magnet having good moldability, and a bond magnet having high productivity and economy.

[0011]

This and other objects are achieved by the present invention which is defined below as (1) to (20).

(1) The magnetic material particles and a crosslinkable organic material are mixed, and further kneaded using a twin roll mill under a high shearing force and at a temperature at which the organic material softens. A step of obtaining a composition having a content of 50% by weight or more, a step of melt-molding the composition, and a step of cross-linking the organic material in the obtained molded body. A method for producing a bonded magnet, wherein the method is performed so as to pass through a gap of the twin roll mill.

(2) The method for producing a bonded magnet according to the above (1), wherein the average particle diameter of the magnetic material particles is 0.5 to 200 μm.

(3) The composition contains a polymer material that can be dissolved or dispersed in the organic material when the organic material is in a fluid state or a liquid state.
Or the manufacturing method of the bonded magnet as described in (2).

(4) The method for producing a bonded magnet according to the above (1) or (2), wherein the composition contains a polymer material having a functional group having an affinity for the magnetic material particles.

(5) The method according to any one of (1) to (4), wherein the kneading is performed at a temperature at which the organic material softens.

[0017]

(6) The method for manufacturing a bonded magnet according to any one of the above (1) to (5), wherein the organic material is a solid at a temperature of 25 ° C.

(7) The method according to any one of (1) to (6), wherein the organic material is a thermosetting resin.

(8) The method for manufacturing a bonded magnet according to the above (7), wherein the thermosetting resin is an epoxy resin.

(9) The method for producing a bonded magnet according to any one of the above (1) to (8), wherein the content of the magnetic material particles in the composition is 80% by weight or more.

(10) The method for manufacturing a bonded magnet according to any one of the above (1) to (9), wherein the magnetic material particles are made of an intermetallic compound containing a rare earth metal and a transition metal.

(11) The method according to (10), wherein the transition metal is Co and the rare earth metal is Sm.

(12) The magnetic material particles are Nd-Fe
-The method for producing a bonded magnet according to the above (10), comprising a B-based intermetallic compound.

(13) The method for producing a bonded magnet according to any one of the above (1) to (12), wherein the composition contains an additive having a function of causing or accelerating the crosslinking of the organic material. .

(14) The method for producing a bonded magnet according to the above (13), wherein the content of the additive in the composition is 0.01 to 2% by weight.

(15) The molding of the composition is carried out by extrusion molding, injection molding or compression molding.
The method for producing a bonded magnet according to any one of (14) to (14).

(16) The method for producing a bonded magnet according to any one of the above (1) to (15), wherein the crosslinking of the organic material is performed so that the shape of the molded body is maintained.

(17) Before crosslinking the organic material,
The method for producing a bonded magnet according to any one of the above (1) to (16), wherein demagnetization is performed.

(18) A bonded magnet manufactured by the method for manufacturing a bonded magnet according to any one of (1) to (17).

(19) The magnetic energy product (BH) max is 4.
The bonded magnet according to the above (18), which is not less than 3MGOe.

In the present invention, the magnetic material particles and the crosslinkable organic material are mixed and kneaded to obtain a composition, and the composition is molded into a desired shape, and then the organic material in the molded article is formed. Is used to produce a bonded magnet.

The organic material in the composition (compound) used in the present invention is preferably in a solid state and can be applied by a melt molding method. Generally, an organic material is solid at around room temperature (about 25 ° C.), but has a predetermined melting point. Therefore, at a high temperature, it is in a fluid state, and melt molding is possible. The organic material or composition can be melt molded by a plastic molding machine (eg, an injection molding machine, an extrusion molding machine, a compression molding machine).

The organic material in the composition may be a solid monomer material or a solid polymer material.
The composition may consist of a mixture of two or more monomer materials, a mixture of two or more polymer materials, or a mixture of one or more monomer materials and one or more polymer materials.

When the organic material in the composition is a monomeric material, the monomeric material must have a sufficiently high molecular weight in order for the composition to be solid near room temperature. The monomer material preferably contains ethylenically unsaturated groups, and more preferably contains two or more such groups. This is because such a group assists the crosslinking reaction.

Examples of suitable organic monomer materials include 1,
3-diallylurea,

[0037]

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9-vinylcarbazole,

[0039]

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Pentaerythritol tetramethacrylate,

[0041]

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3,9-divinyl-2,4,8,10-tetraoxaspiro- (5,5) -undecane,

[0043]

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Adduct of 4,4'-diphenylmethane diisocyanate with hydroxyethyl methacrylate,

[0045]

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And the like.

Examples of organic polymer materials which are solid and to which the melt molding method can be applied include ethylenically unsaturated polyester resins and epoxy resins.

Suitable epoxy resins include epoxidized bisphenol A. The structural formula is shown below.

[0049]

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[0050] Epoxidized phenol formaldehyde novolak is also promising. The structural formula is shown below.

[0051]

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In the above two structural formulas,

[0053]

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Is as follows.

The epoxy resin usually contains a curing agent having a plurality of hydroxy groups. Examples of suitable curing agents include phenol formaldehyde novolak,

[0056]

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There is a

The composition crosslinks the organic material in the composition,
Alternatively, an additive which promotes crosslinking of the organic material can be contained, and it is better to contain it. However,
Of course, the crosslinking reaction can proceed without the additive. Particularly when the organic material contains ethylenically unsaturated groups (eg, when it is a polyester resin or an acrylic material), suitable materials for such additives include peroxides and, for example, azo-bis- Radical initiators such as azo compounds such as isobutyronitrile are included. If the organic material is an epoxy resin, it may contain an additive that catalytically promotes the reaction between the epoxy resin and the curing agent.

If the composition contains additives which serve to initiate or promote the crosslinking reaction, the combination of organic materials and additives must be carefully chosen.

The molding step in the production method of the present invention can be performed at a temperature at which the organic material is in a fluid state (or softened state). Crosslinking, if any, when the organic material is in a fluid state at elevated temperatures is preferably kept to a minimum and not at least in an amount that prevents re-use of the composition. And when the composition contains additives for crosslinking, the additives should be selected to be active so as not to cause undesired amounts of crosslinking at the molding temperature. The additives selected will, of course, depend on the organic material in the composition, and in particular on the temperature at which the composition is molded during the molding process. Indeed, additives that are suitable for one organic material may not be at all suitable for different organic materials that can be melt formed only at higher temperatures. This is because at higher temperatures unacceptably high amounts of crosslinking reactions occur during melt molding. A preferable combination of the organic material and the additive should be selected after thoroughly examining the behavior of the organic material during melt molding and the thermal decomposition characteristics of the additive. However, a suitable combination of additives and organic materials is, for example, 3,9-divinyl-2,4,8,10-tetraoxaspiro- (5,5) -undecane having a melting point of 42 ° C. and about 70 ° C. ° C
Combination with azo-bis-isobutyronitrile which decomposes into radicals at the above temperature, and melts at 65 ° C. 9
-Combinations of vinyl carbazole and azo-bis-dicyclohexanecarbonitrile which decompose into radicals above about 90 ° C.

The term “magnetic material” means a material that can be magnetized or magnetized. Thus, the magnetic material need not itself be magnetized. It is sufficient that the composition is magnetized by application of a magnetic field when the composition is manufactured. There are no special restrictions on the size of the magnetic material particles,
The particle size is desirably in the range of 0.5 to 200 μm.

Suitable examples of the magnetic material include ferrite materials such as barium ferrite (Ba _0.6 Fe ₂ O ₃ ) and strontium ferrite (Sr _0.6 Fe ₂ O ₃ ). Another example is an intermetallic compound of a rare earth metal and a transition metal, which can be used in the present invention and can provide a bonded magnet having high magnetic performance. Rare earth metals as raw materials for such magnetic materials are Sm, Ce, La, Y, Nd, P
r, Gd, etc., and suitable transition metals are Fe, C
o, Ni, Zr, Hf, Cu, and Ti. The intermetallic compound is generally approximately RCo ₅ or R ₂ Co
It is represented by the general formula ₁₇ . Here, R is at least one rare earth metal. One example of a rare earth metal forming an intermetallic compound is Sm. As an example of an intermetallic compound, a compound generally represented by a composition formula of SmCo ₅ and Sm ₂ Co ₁₇ is known. These composition formulas are not exact chemical formulas of rare earth-transition metal intermetallic compounds. This is because elements other than Sm and Co can also exist in the composition formula. Incidentally, Japanese Patent Application Laid-Open No. 60-22 / 1985
No. 7408 _discloses Sm (Co _0.672 Cu _0.08 Fe
_0.22 Zr _0.028 ) A rare earth-transition metal intermetallic compound having a composition formula of _5.3 is described. JP-A-60-2209
No. 05 describes a rare earth-transition metal intermetallic compound having the following composition formula.

That is, Sm (Co _0.672 Cu _0.08 Fe
_0.22 Zr _0.028 ) _8.35 , Sm _0.75 Y _0.25 Co _0.65 Cu
_0.05 Fe _0.28 Zr _0.02 ) _7.8 , Sm _0.81 Ce _0.19 (Co
_0.61 Cu _0.06 Fe _0.31 Zr _{0.02) 7.6.}

As another example of the magnetic material, Nd—Fe—B
There is an intermetallic compound based on at least one rare earth metal and at least one transition metal. As an example, JP-A-60-220905 also discloses that N
d (Fe _0.905 B _0.095 ) _5.67 is described. Still other examples include the following intermetallic compounds. That is, Sm (Co _0.67 Cu _0.08 Fe _0.22 Zr
_0.03 ) _7.6 , Sm (Co _0.74 Cu _0.10 Fe _0.15 T
i _0.01 ) _7.2 , Sm (Co _0.69 Cu _0.10 Fe _0.20 Hf
_0.01 ) _7.0 , Ce (Co _0.69 Cu _0.12 Fe _0.18 Z
_{r 0.01) 6.0, Sm 0.5 Pr} 0.5 Co 5, Sm 0.5 Nd 0.4 C
e _0.1 (Co _0.67 Cu _0.08 Fe _0.22 Zr _0.03 ) _8.35 and Nd ₁₄ Fe ₈₁ B ₅ .

The composition is, of course, one or more organic materials,
It may include one or more magnetic material particles and, if necessary, one or more additives that assist in crosslinking the organic material.

The proportions of organic material, additives, if any, which cause or promote crosslinking, and magnetic material particles in the composition may sometimes vary widely. Generally speaking, the ratio of the magnetic material is preferably as high as possible within the range that can be melt-molded in plastic molding. This is because the higher the value, the better the magnetic performance of the bonded magnet made from the composition. Generally, the proportion of magnetic material in the composition will have to be at least 50% by weight. Preferably 8
0% by weight or more. A more preferred composition range of the magnetic material is 80 to 98% by weight, particularly 80 to 95% by weight.

The amount of the organic material in the composition is determined in consideration of whether it can be melt-molded by a plastic molding machine. And generally, at least 2% by weight of the organic material must be included in the composition. The optimum range of the content of the organic material is 5 to 20% by weight.

The amount of the additive that causes or promotes crosslinking is
Depending on the nature of the additives and the nature of the organic material, at least to some extent, generally 0.01 to 5% by weight of the composition will be sufficient. When the organic material contains an ethylenically unsaturated group such as a polyester resin or an acrylic material, and the additive is a radical initiator, the amount of the additive in the composition is generally 0.1%. It is preferably from 0.01 to 2% by weight. Even when the organic material is an epoxy resin, the amount of the additive is generally preferably 0.01 to 2% by weight. The greater the amount of additive, the faster the organic material crosslinks.

Each component in the composition is kneaded by appropriate methods and conditions. For example, when each component is in the form of fine particles, it may be kneaded with an appropriate device for kneading the fine particle material. An example of a preferred method of producing a particularly uniform composition of the organic material and the magnetic material particles is to knead the composition under a large shear force, for example, at a temperature at which the organic material softens.
In this case, kneading can be performed using a twin-roll mill (such as a twin-screw open roll), and the mixture is repeatedly passed through the gap of the roll mill. The temperature during kneading depends on the type of organic material, the amount added, and the like, but is preferably from 60 to 100 ° C., as shown in each example described later.

If necessary, finally, additives which cause or promote crosslinking may be added to the mixture in the roll mill. This method is a very convenient way to mix the additives into the composition if the additives are liquid. When the additives are mixed, the effect appears in a relatively short time,
Although slight, crosslinking of the organic material occurs during kneading. For this reason, the additives are preferably added at the end of the kneading. Performing the above kneading sufficiently is preferable for improving the magnetic performance of the obtained magnet.

[0071] Alternatively, the components of the composition may be mixed in the presence of a liquid diluent. The liquid diluent is removed once the mixing role has been completed. Liquid diluents help to homogeneously mix the ingredients in the composition and are later removed from the composition. For example, when the boiling point of the diluent is low, it is removed by evaporation.

Even when the organic material in the composition is a monomeric material, or even when it is a polymeric material, kneading the components in the composition under high shear and melt-molding subsequent to kneading involves the use of an organic material. Can be carried out smoothly by incorporating a small amount of a polymer material which can be dissolved or dispersed in an organic material in a fluid state or a liquid state into the composition. The inclusion of a small amount of such a polymer material promotes (advantages) molding of a composition which contains a high content of magnetic material particles and can be melt-molded by a plastic molding machine.

As a specific example of the present invention, a composition comprising the following components is mentioned.

(1) Crosslinkable organic materials, especially those which can be melt-molded.

(2) Magnetic material particles.

(3) A polymer material that can be dissolved or dispersed in an organic material when the organic material is in a fluid state or a liquid state.

And, if necessary, (4) an additive which causes or promotes the crosslinking of the organic material for forming the crosslinking material.

The polymer material is generally a copolymer containing a functional group having an affinity for the magnetic particles. The addition of the polymer material improves the wettability between the magnetic particles and the organic material,
It contributes to improving the quality and characteristics of permanent magnets. Suitable as such polymers are copolymers of polyvinyl butyral and polyvinyl alcohol, copolymers of polyvinyl chloride and polyvinyl acetate and polyvinyl alcohol, copolymers of polyvinyl acetate and polycrotonic acid, copolymers of polyvinylidene chloride and polyacrylonitrile. is there. Preferably, the composition contains no more than 5% by weight of such polymeric material, especially 0.5 to 5% by weight. The composition may also include one or more such polymeric materials.

The composition can be melt-molded and molded with an appropriate plastic molding machine such as an extrusion molding machine, an injection molding machine or a compression molding machine.

When the present invention is carried out by extrusion, the composition is first introduced into an extruder. The composition is then heated to bring the organic material into a fluid state, extruded using a suitable mold, and cooled near the exit of the mold to solidify the organic material. Then, the molded product is taken out of the mold. When producing an anisotropic magnet, a magnetic field is applied to the composition in the mold of the extruder when the organic material is in a fluid state. As a result, the magnetic material particles are oriented in the direction of the magnetic field. The magnetic field is applied by an electromagnet placed close to the extruder mold. The molding temperature must not be too high during the molding process. It is important that the time during which the organic material is in a fluidized state is relatively short so that the crosslinking reaction is suppressed as small as possible. This is because by doing so, it is possible to reuse defective products and waste products in molding.

The molding step according to the present invention and the optional optional magnetic field orientation step can also be performed on an injection molding machine having a suitable mold when the organic material in the composition is in a fluid state. It can be carried out. If desired, the electromagnet is mounted in close proximity to the mold and serves to orient the magnetic material particles in their easy direction. Once molded, it is cooled and removed from the mold.

The composition can also be formed by compression molding. In this case, the kneaded composition is charged into an appropriate mold and compression-molded in the mold. At this time, the composition can be heated to bring the organic material into a fluid state, and then the composition is cooled in a mold. Also in the case of such compression molding, it is desirable that an electromagnet is mounted close to the mold in order to orient the magnetic material particles in the direction of easy magnetization. When the molding step is performed in a magnetic field, the application of the magnetic field is performed to orient the magnetic material particles in the direction of easy magnetization.However, even when cooling the molded product, the magnetic field is applied to maintain the orientation of the magnetic particles. Need to be continuously applied. The application of a magnetic field must be continued until the organic material in the composition has solidified sufficiently to maintain the orientation of the magnetic particles without the aid of a magnetic field. The organic material in the molded composition is crosslinked to obtain a crosslinked resin. When isotropic magnetic material particles such as Nd-Fe-B-based magnets are used, they can be formed without a magnetic field.

The molded article formed as described above crosslinks the organic material contained therein. The crosslinking of the organic material is performed by heating the molded body at, for example, 120 to 200 ° C. for a predetermined time. However, when heated, the organic material is in a fluid state, so that the molded composition (molded body)
Must be maintained. It is believed that the shape of the compact can be maintained by placing the compact in a suitable mold during the crosslinking of the organic material. Alternatively, the cross-linking reaction of the organic material may be performed when the organic material is in a solid state (for example, at the time of molding at room temperature, or after cooling and taking out after heat molding). By doing so, the shape of the molded body is maintained.

A suitable method for realizing the crosslinking includes electron beam irradiation. In this case, the crosslinking of the organic material in the shaped body will be affected by the presence or absence of the above-mentioned crosslinking-promoting or promoting additives. Crosslinking can also be performed by irradiating a molded article (molding composition) with γ-rays. For example, it can be cross-linked by gamma rays obtained from a Co ⁶⁰ source. Similarly, crosslinking is affected by the presence or absence of additives that cause or promote crosslinking. Crosslinking may be performed after the molded article is taken out of a molding die such as a plastic molding machine. By doing so, the utilization efficiency of a molding machine or the like can be increased, and the molding step can be shortened.

The shape of the molded article can be maintained by partially cross-linking when the organic material in the composition is solid. For example, the organic material on the outer surface of the molded body can be cross-linked by electron beam irradiation or gamma ray irradiation even if the organic material is solid. And when the compact is heated to a high temperature to complete crosslinking, this outer surface is solid and helps to maintain the shape of the compact.

When the magnetic material particles in the compact are already in the oriented state, it is very convenient to effect crosslinking when the composition is in the solid state. If the organic material is brought into a fluidized state before or during crosslinking, for example, by heating, adjacent magnetic particles repel each other and disturb the orientation, thereby deteriorating the performance of the bonded magnet.

Even when the cross-linking of the organic material in the molded body is performed in a solid state, a cross-linking reaction by heating is also performed.
Therefore, the crosslinking reaction in the solid state must not be softened by the subsequent crosslinking by heating, and the magnetic material particles must be sufficiently conducted to maintain the oriented state.

Prior to the crosslinking reaction of the molded article, the magnetic material particles oriented in the direction of easy magnetization may be demagnetized by an appropriate method. Demagnetization by an alternating magnetic field is considered as an example. It is not necessary to completely demagnetize the magnetic material particles, but it is desirable to demagnetize it to some extent. The term "to a certain degree" means that the organic material slightly shows a state close to flow at the time of crosslinking, but even at this time, there is only a slight repulsion between the magnetic material particles. When cross-linking is performed at a temperature at which the organic material slightly shows a state close to fluidity, the magnetic material particles are not magnetized even under such fluidity, so that there is no repulsion between adjacent particles and the orientation state is maintained. It is surprising to be drowned.

The magnetic material particles that have been demagnetized after the completion of the crosslinking reaction of the organic material are re-magnetized.

[0090]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail based on embodiments. However, the term “parts” hereinafter means parts by weight.

Example 1 The following components were uniformly mixed to some extent to form a mixture.

Magnetic particles: Sm (Co _0.672 Fe _0.22 Cu
_0.08 Zr _0.028 ) 91.47 parts of _8.35 powder Organic material: 4.13 parts of oligomerized and epoxidized bisphenol A powder 2.2 phenol formaldehyde novolak powder
9 parts 0.33 parts of epoxidized phenol formaldehyde novolak powder Polymer material: Copolymer powder of vinyl butyral and vinyl alcohol (trade name: Pioloform BN18, Wecker)
Chemie GmbH) 1.26 parts Silica powder (Aerosil OX50) 0.2 parts Calcium stearate 0.17 parts Bleached monton wax 0.17 parts 3- (3,4-dichlorophenyl) -1, 0.05 part of 1-dimethyl urea was then charged into a twin-roll mill at a temperature of 90 ° C. and kneaded by repeatedly passing through the gap of the mill to form a plastic sheet containing magnetic particles. Sheeting was assisted by the presence of the organic polymer in the composition. The sheet is twin roll milled to 8
Rolled to a thickness of 0.7 mm at a temperature of 0 ° C., further placed in a mold and pressed at a temperature of 110 ° C.
mm. The sheet was further divided into six small sheets of the same size.

One of the small sheets was placed in a mold located between the poles of a 23.5 kG electromagnet, rapidly heated to 140 ° C., and then rapidly cooled to room temperature. At 140 ° C., the organic material in the composition melts and the magnetic particles are oriented under an applied magnetic field. Even if the molded product is crosslinked, the degree of the crosslinking is very small, so that a part of the sheet can be remelted and used. Further, the sheet was placed between poles of an electromagnet, and an alternating magnetic field was applied to demagnetize the magnetic particles.

The sheet was then heated in a mold at a temperature of 170 ° C. for 30 minutes for crosslinking of the organic material. Finally, the sheet was magnetized with a magnetic field of 23.5 kG between the poles of the electromagnet. The magnetic energy product (BH) max of the sheet-like bonded magnet thus obtained was 4.5 MGOe.

(Example 2) One of the small sheets obtained in Example 1 was magnetically oriented as in Example 1, and subsequently demagnetized to obtain a demagnetized sheet. The organic material in the sheet is uncrosslinked, but the magnetic particles are in an oriented state.

Next, the sheet was precisely machined to the required shape. The parts cut off by machining can be reused because the organic material in them is not crosslinked. A varnish was sprayed on the sheet. The varnish solidifies into a film and withstands temperatures of 170 ° C. The sheet is further heated to 170 ° C.
For 30 minutes to crosslink the organic material in the sheet. The shape of the sheet remained. 2 between poles of electromagnet
As a result of applying a magnetic field of 3.5 kG to magnetize and measure, the magnetic energy product (BH) max of the bonded magnet is 4.3 M
It was found to be GOe.

Example 3 The following components were uniformly mixed to some extent to form a mixture.

Magnetic particles: 18 used in Example 1
7 parts Organic material: 18.7 parts powder of adduct of 4,4'-diphenylmethane diisocyanate and hydroxyethyl methacrylate Polymer material: powder of copolymer of vinyl butyral and vinyl alcohol (trade name: Pioloform BN 18, Wecker)
3.1 parts of polymer material (manufactured by Chemie GmbH) The mixture was then worked in a twin-roll mill at a temperature of 80 ° C., repeatedly kneaded through the gaps of the mill and formed into plastic sheets containing magnetic particles. The presence of the organic polymer in the composition aided in the production of the sheet. Here, 0.2 part of 1,1′-azo-bis- (cyclohexanecarbonitrile) as a radical initiator was added, and the mixture was further kneaded for 1 minute. Thereafter, the plastic sheet was removed from the mill and cooled to room temperature. Next, it is rolled to a thickness of 0.7 mm at a temperature of 60 ° C. using a twin-roll mill, and further placed in a mold at a temperature of 80 ° C. to a thickness of 0.7 mm.
Pressed to a thickness of 5 mm. The sheet was divided into five small sheets of the same size.

One of the small sheets was sandwiched between poles of an electromagnet of 23.5 kG, the temperature was rapidly increased to 100 ° C., and then rapidly cooled to room temperature. At 100 ° C., the organic material in the composition melts, so that the magnetic particles can be oriented in the presence of a magnetic field. The cooled sheet could be reused. This indicates that even though some cross-linking has occurred, it has not occurred to prevent sheet reuse.

Next, the sheet was irradiated with γ-rays of Co ⁶⁰ at room temperature in order to crosslink the organic material in a solid state. The irradiation was performed for a time sufficient to crosslink a resin having a glass transition temperature of 60 ° C. After that, the sheet is
Heated to a temperature of ° C. At this temperature, the sheet softens slightly, but not so much that it deforms or disturbs the orientation of the magnetic particles. Heating at 120 ° C. lasted 5 minutes and crosslinking proceeded further. The sheet then had a glass transition temperature of 100 ° C. The magnetic energy product (BH) max of the sheet-like bonded magnet thus obtained
Was 5.0 MGOe.

Example 4 Another small sheet obtained in Example 3 was subjected to the same orientation treatment under a magnetic field as in Example 3. After cooling to room temperature, the magnet was demagnetized by a damping magnetic field between the poles of the electromagnet. Further, in order to partially cross-link the resin, particularly the resin on the surface of the sheet, 170 k
The electron beam was irradiated at a dose of 1 Mrad accelerated at a potential of V. The sheet was then heated at a temperature of 120 ° C. for 5 minutes for further crosslinking. The sheet was then magnetized as in Example 1. When the magnetic energy product (BH) max of the sheet-like bonded magnet was measured, it was found to be 4.5 MGOe. This indicates that even if the organic material is softened by heating to 120 ° C., particularly inside the sheet, the orientation of the magnetic particles is not disturbed because it is demagnetized.

Comparative Example 1 A bonded magnet was manufactured in the same manner as in Example 1 except that the mixture was used without kneading.

Although the resulting bonded magnet retains its shape, it has low mechanical strength (brittle), vibration,
When subjected to an impact, defects such as cracks and chips occurred, and it was not usable as a bonded magnet.

Comparative Example 2 Production of a bonded magnet was attempted in the same manner as in Example 3 except that the mixture was used without kneading.

The organic material was crosslinked under the same conditions as in Example 3,
After that, when it was taken out of the mold, it was partially collapsed and could not be used as a bonded magnet.

Example 5 The following components constituting the composition were mixed to obtain a powder mixture having a certain degree of uniformity.

Magnetic particles: Nd ₁₄ Fe ₈₁ B ₅ 93.30
Part Organic material: 4.13 parts of oligomerized and epoxidized bisphenol A powder 2.2 parts of phenol formaldehyde novolak powder
9 parts 0.33 parts of epoxidized phenol formaldehyde novolak powder Polymer material: Copolymer powder of vinyl butyral and vinyl alcohol (trade name: Pioloform BN 18, Wecker)
Chemie GmbH) 1.26 parts of polymer material 0.2 parts of silica powder (Aerosil OX50) 0.17 parts of calcium stearate 0.17 parts of bleached monton wax 0.17 parts 3- (3,4-dichlorophenyl)- Next, the mixture was charged into a twin-roll mill at a temperature of 90 ° C. and kneaded by repeatedly passing through the gap of the mill to form a plastic sheet containing magnetic particles. Sheeting was assisted by the presence of the organic polymer in the composition. The sheet was placed in a twin roll mill at 80 ° C. for 0.7
mm, and the sheet was placed in a mold and pressed at a temperature of 110 ° C. to reduce the thickness to 0.5 mm.

The sheet was placed in a mold, rapidly heated to 140 ° C., and then rapidly cooled to room temperature. It was found that a portion of the sheet could be re-melted. This indicates that little cross-linking is not enough to prevent sheet reuse. Thereafter, 170 μm in the mold to crosslink the organic material in the sheet.
Heated at a temperature of ° C for 30 minutes. The magnetic energy product (BH) ma of the sheet-like bonded magnet thus obtained
x was 5.5 MGOe.

(Examples 6 to 9) As Examples 6 to 9, four types of compositions as shown in Table 1 (the ratio of each component was expressed by weight%
Are mixed by hand so as to form an appropriately uniform mixture, and each mixture is separately charged into a twin-roll mill, repeatedly passed through the gap of the mill, and kneaded. The kneading temperature of the composition was 95 ° C. in Examples 6 and 7, and 100 ° C. in Examples 8 and 9. Each composition was formed into a sheet and removed from the mill.

Next, each composition was pulverized into granules, charged into a screw type extruder, passed through a cylindrical mold, and extruded. The barrel temperature of the extruder was 120 ° C., the mold temperature was 130 ° C., and the extrusion speed was 1 mm / sec. 15kOe for mold during molding
Was applied to orient the magnetic particles of the composition. The ambient temperature at the tip of the mold is the temperature at which the molded composition solidifies. The molded cylindrical composition is
The outer diameter was 30 mm and the inner diameter was 26 mm. After demagnetizing the magnetic particles in the molded article by the method described in Example 1,
The resin was heated at a temperature of 200 ° C. for 30 minutes for crosslinking.

[0111]

[Table 1]

For comparison, as Comparative Examples 3, 4 and 5, three types of compositions as shown in Table 2 (the ratio of each component is shown by weight%) were mixed so as to form an appropriately uniform mixture. Combine and put separately in a twin roll mill, 250 ° C
Kneading was performed at a temperature of (Comparative Examples 3 and 4) or 260 ° C. (Comparative Example 5). The mixture was taken out of the mill, the barrel temperature was 240 ° C., the mold temperature was 220 ° C., and the extrusion speed was 0.5 m.
Extrusion was performed at m / sec by passing through a cylindrical mold of a screw type extrusion molding machine. A radial magnetic field of 15 kOe is applied to the mold, and the ambient temperature at the tip of the mold is a temperature at which the molded composition solidifies. The molded cylindrical composition had an outer diameter of 30 mm and an inner diameter of 26 mm.

[0113]

[Table 2]

Incidentally, as Comparative Example 6, magnetic particles: 95.
A composition consisting of 6% by weight, nylon-12 powder: 4.3% by weight, and zinc stearate: 0.1% by weight was kneaded with a twin-roll mill, but could not be mixed satisfactorily and was extruded satisfactorily. Could not be molded.

Table 3 shows the magnetic performance of the cylindrical magnets obtained in Examples 6 to 9 and Comparative Examples 3 to 5. Comparative Example 6
No magnetic performance was measured due to poor molding.

[0116]

[Table 3]

As shown in Examples 6 to 9 and Comparative Examples 3 to 5, when the content is not more than 95% by weight,
Extrusion molding is possible in the present invention even with a composition containing more than 2 magnetic particles. On the other hand, a composition comprising a thermoplastic resin and more than 95% by weight of magnetic particles cannot be favorably molded. Furthermore, the composition of the present invention has excellent magnetic performance because the magnetic particles are easily oriented during molding and exhibit a higher degree of orientation.

Examples 10 to 13 As Examples 10 to 13, the particle diameter was 1 to 200 μm and the composition was Nd ₁₄ (Fe
Four types of cylindrical bonded magnets were manufactured in the same manner as in Examples 6 to 9 except that magnetic particles of _0.95 Co _0.05 ) _80.5 B _5.5 were used.

The difference is that the kneading temperature is 95 ° C. and the extrusion speed is 2 mm / sec.

Table 4 shows the components of each composition in% by weight.

[0121]

[Table 4]

As Comparative Example 7, a composition comprising 90.4% by weight of magnetic particles, 9.5% by weight of nylon-12 powder and 0.1% by weight of zinc stearate used in Examples 10 to 13 Was used to produce cylindrical magnets in the same manner as in Comparative Examples 3 to 5. The kneading temperature was 250 ° C, the barrel temperature of the extruder was 230 ° C, the mold temperature was 205 ° C, and the extrusion speed was 1 mm / sec.

As Comparative Example 8, a composition containing at least 92% by weight of magnetic particles was kneaded with a twin roll mill, but could not be satisfactorily mixed and could not be satisfactorily extruded. Therefore, the measurement of the magnetic performance was not performed.

Table 5 shows the magnetic performance of the obtained cylindrical magnet.

[0125]

[Table 5]

As apparent from Table 5, Examples 10 to 13 in which the composition containing the organic material having crosslinkability was kneaded and used.
Has high magnetic performance even when the magnetic particles are isotropic. The lower magnetic performance of the bonded magnet of Comparative Example 7 made from a composition containing a thermoplastic polymer, ie, nylon-12, than that of Examples 10 to 13 is due to the high molding temperature required for the production of the magnet. Then, the magnetic particles oxidize,
It is probably due to deterioration.

Example 14 The composition used in Example 7 was kneaded with a twin roll mill and extruded in the same manner as in Examples 6 and 7, to obtain a cylindrical material having an outer diameter of 16 mm and an inner diameter of 14 mm. A magnet was manufactured and it was cut to a length of 15 mm. Other conditions were the same as in Examples 6 and 7.

As Comparative Example 9, the composition used in Comparative Example 4 was charged into a twin-roll mill and kneaded at a temperature of 250 ° C. Remove the composition formed into a sheet from the mill,
It was pulverized into fine particles and put into an injection molding machine. While applying a radial magnetic field of 6 kOe to the mold of the injection molding machine, a cylindrical magnet having a length of 15 mm, an outer diameter and an inner diameter of 16 mm and 14 mm, respectively, was injection-molded.

Table 6 shows the magnetic performance of the obtained magnet.

[0130]

[Table 6]

As is clear from Table 6, the bonded magnet of Comparative Example 9 has only the same characteristics as the conventional isotropic magnet. The reason seems to be that it is difficult to apply a magnetic field sufficient to orient the particles when the composition is in the mold of the injection molding machine. In contrast, Example 1
The fourth bonded magnet of the present invention has high magnetic performance.

(Examples 15 to 18) As Examples 15 to 18, four kinds of compositions were prepared using an outer diameter of 33 mm and an inner diameter of 32.
mm (Examples 15 and 17) or 31.6 mm
Extrusion molding into a cylindrical shape (Examples 16 and 18),
It was cut to a length of 8 mm.

The compositions in Examples 15 and 16 are the same as those used in Example 6, and are the same as in Examples 17 and 18.
Is the same as that used in Example 10.
The conditions for kneading, molding and crosslinking in Examples 15 and 16 are the same as in Example 6, and the conditions for kneading, molding and crosslinking in Examples 17 and 18 are the same as in Example 10.

As Comparative Examples 10 to 13, four types of compositions were prepared using an outer diameter of 33 mm, a length of 8 mm, and an inner diameter of 32 mm.
(Comparative Examples 10 and 12) or a cylindrical shape of 31.6 mm (Comparative Examples 11 and 13) was attempted.

The compositions in Comparative Examples 10 and 11 were the same as those used in Comparative Example 3 and Comparative Examples 12 and 13
Is the same as that used in Comparative Example 7. The kneading conditions in Comparative Examples 10 and 11 are the same as in Comparative Example 3, and the kneading conditions in Comparative Examples 12 and 13 are the same as in Comparative Example 7. Each composition was removed from the twin roll mill, pulverized, and injected into an injection molding machine at a temperature of 295 ° C. Molding was performed at a mold temperature of 90 ° C. by applying a radial magnetic field of 15 kOe.

In Comparative Examples 10, 12 and 12, the composition did not flow satisfactorily and could not be filled in the mold. Therefore, the measurement of the magnetic performance was not performed.

Table 7 shows the magnetic performance of the obtained cylindrical magnet.

[0138]

[Table 7]

The magnetic performance of the bonded magnet of Comparative Example 11 was comparable to that of the conventional isotropic magnet, while the magnetic properties of Examples 15 to
All of the eighteen bonded magnets of the present invention have sufficiently high magnetic performance.

(Example 19) The composition used in Example 7 was manufactured in the same manner as in Example 7, except that the extrusion speed was 1.2 mm / sec.
m, a cylindrical bonded magnet in which magnetic particles having an inner diameter of 14 mm were radially oriented was manufactured and cut into a length of 4 mm. Other conditions were the same as in Example 7. 4mm
Length magnets were produced at a rate of 18 pieces / min.

As Comparative Example 14, the same composition as in Comparative Example 9 was injection-molded under the same conditions as in Comparative Example 9 to produce a magnet having a length of 4 mm, an outer diameter of 16 mm, and an inner diameter of 14 mm. The minimum molding cycle time is 20 seconds, so that only 3 parts / min can be produced when molding one by one.

[0142]

According to the present invention, by using a composition containing a crosslinkable organic material and kneaded under the desired conditions as described above, regardless of whether the magnet is anisotropic magnet or anisotropic magnet, Also, regardless of the type and composition of the magnetic material and the molding method, a bonded magnet having improved magnetic performance and excellent moldability is provided.

In particular, since the organic material is melted and cross-linked to such an extent that it can be re-melted and retain the shape after molding, the time of the molding step is significantly longer than when molding is performed while the organic material is sufficiently cross-linked. Can be shortened.

Further, since the molded body immediately after the molding step is crosslinked to such an extent that the organic material can be re-melted, it can be used for moldings, spools, runners, burrs and the like, which have become defective in the molding process. An unnecessary portion that cannot be reused can be reused as a raw material, and an excellent effect that productivity can be improved is exhibited.

The present invention can further provide an extremely flexible manufacturing method capable of manufacturing a magnet having a simple or complex shape. For example, a considerably long bonded magnet (for example, a long cylindrical magnet) can be manufactured by a method such as extrusion.

The magnet manufactured according to the present invention can be applied to many uses. For example, motors, televisions, printers, and suction devices (eg, suction devices at doors).

Continued on the front page (73) Patent holder 590000341 Imperial Chemical Industries plc Imperial Chemical Industries plc 1P3JF, Millbank, Imperial Chemical House London, England UK (72) Inventor James Hugue Rastertric Cheshire Runcorn the Heath, UK (no address) (72) Inventor Tatsuya Shimoda 3-5-5 Yamato, Suwa City, Nagano Prefecture Inside Seiko Epson Corporation ( 72) Inventor Masaaki Sakata 3-5-5 Yamato, Suwa-shi, Nagano Seiko Epson Corporation (56) References JP-A-61-27605 (JP, A) JP-A-60-202723 (JP, A)

Claims (19)

(57) [Claims] 1. A magnetic material particle and a crosslinkable organic material are mixed, and further kneaded using a twin roll mill under a high shearing force and at a temperature at which the organic material softens, so that the content of the magnetic material particle is reduced. A step of obtaining a composition that is 50% by weight or more; a step of melt-molding the composition; and a step of cross-linking the organic material in the obtained molded body. A method for producing a bonded magnet, wherein the method is performed so as to pass through a gap of a twin roll mill. 2. The magnetic material particles having an average particle size of 0.5 to 0.5.
The method for producing a bonded magnet according to claim 1, wherein the thickness is 200 μm. 3. The bonded magnet according to claim 1, wherein the composition includes a polymer material that can be dissolved or dispersed in the organic material when the organic material is in a fluid state or a liquid state. Production method. 4. The method according to claim 1, wherein the composition includes a polymer material having a functional group having an affinity for the magnetic material particles. 5. The method for producing a bonded magnet according to claim 1, wherein the kneading is performed under conditions that minimize a crosslinking reaction of the organic material. 6. The method for producing a bonded magnet according to claim 1, wherein the organic material is a solid at a temperature of 25 ° C. 7. The method according to claim 1, wherein the organic material is a thermosetting resin. 8. The method according to claim 7, wherein the thermosetting resin is an epoxy resin. 9. The method according to claim 1, wherein the content of the magnetic material particles in the composition is 80% by weight or more. 10. The method for manufacturing a bonded magnet according to claim 1, wherein the magnetic material particles are made of an intermetallic compound containing a rare earth metal and a transition metal. 11. The method according to claim 10, wherein the transition metal is Co, and the rare earth metal is Sm. 12. The magnetic material particles may be Nd—Fe—B.
The method for manufacturing a bonded magnet according to claim 10, wherein the bonded magnet is composed of a systemic intermetallic compound. 13. The method for producing a bonded magnet according to claim 1, wherein the composition contains an additive having a function of causing crosslinking of the organic material or promoting crosslinking. 14. The method according to claim 13, wherein the content of the additive in the composition is 0.01 to 2% by weight. 15. The molding of the composition may be extrusion molding,
The method for producing a bonded magnet according to any one of claims 1 to 14, wherein the method is performed by injection molding or compression molding. 16. The method for manufacturing a bonded magnet according to claim 1, wherein the crosslinking of the organic material is performed so that the shape of the molded body is maintained. 17. The method for manufacturing a bonded magnet according to claim 1, wherein demagnetization is performed before crosslinking the organic material. 18. A bonded magnet manufactured by the method for manufacturing a bonded magnet according to claim 1. Description: 19. The magnetic energy product (BH) max is 4.3M
19. The bonded magnet according to claim 18, which is not less than GOe.