JP2658092B2 - Rubber magnet manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a rubber magnet. More specifically, the present invention relates to a method for producing a rubber magnet having excellent magnetic properties and workability.

[Conventional technology]

Conventionally, in order to improve the processability and flexibility of the sintered magnet, a ferrite-based magnetic powder represented by strontium ferrite (SrO · 6Fe ₂ O _3), barium ferrite _{(BaO · 6Fe 2 O 3)} , Known are rubber magnets used as a mixture with synthetic rubbers or natural rubbers such as NBR, ethylene-propylene copolymer rubber, chloroprene or plastic magnets used as a mixture with resins such as polyamide and polyvinyl chloride (Japanese Patent Application Laid-Open Sho 61-36342, 61
-67203-4, 60-53002, 59-170130
JP-A-59-82355, JP-A-50-37846, etc.).

However, although these rubber magnets or plastic magnets are excellent in workability and flexibility during molding, the magnets are weaker than sintered magnets, and therefore are not suitable for applications requiring high magnetic force. Could not be used.

[Problems to be solved by the invention]

Therefore, the present inventors have studied the use of rare-earth magnetic powder instead of ferrite-based magnetic powder as a method of increasing the magnetic force of a rubber magnet without impairing workability and flexibility during molding.

Since rare earth sintered magnets or magnetic powders have a higher magnetic force than ferrite-based magnetic powders, plastic magnets that are used by mixing them with resins such as polyamide and polyvinyl chloride are already known. Again, there are problems with workability and flexibility, and when rubber is used as a binder in order to obtain rubber elasticity, the fact is that production is not performed due to the problem of orientation of the magnetic material.

In order to obtain a rubber magnet having excellent workability, flexibility and rubber elasticity, and a magnetic force greater than that of a sintered ferrite magnet, the present inventors have prepared a method of mixing a specific rare earth magnetic powder with liquid silicone rubber as a binder thereof. It has been found that such a problem can be effectively solved by using the mixture as a mixture and applying a magnetic field to a cured product of the mixture.

[Means for solving the problem]

Therefore, the present invention relates to a method for producing a rubber magnet, which comprises producing 100 parts by weight of liquid silicone rubber and 1 part by weight.
This is performed by applying a magnetic field to a cured product of a mixture containing about 200 to 1800 parts by weight of a -5 type or 2-17 type rare earth magnetic powder.

The 1-5 type or 2-17 type as the rare earth magnetic powder indicates the ratio of the number of metal atoms in the alloy, and such a magnetic powder generally has a particle size of about 0.5 to 40 μm. SmCo ₅ , LaCo ₅ , PrCo ₅ , YCo ₅ , Sm ₂ Co ₁₇ , Sm ₂ Zr ₁₇ , S
etc. m ₂ Hf ₁₇ is illustrated, preferably SmCo ₅ and Sm ₂ Co ₁₇
Is used.

These magnetic powders are prepared by reducing a rare earth oxide with a reducing agent such as a lanthanum metal piece or a calcium metal piece into a rare earth metal, adding a metal such as cobalt, iron, or copper to the metal and melting it. It is obtained by heat-solutioning at a temperature of 1000 to 1200 ° C, then aging at about 400 to 900 ° C to produce an alloy, and then mechanically pulverizing to adjust the particle size of the powder.

The rare earth magnetic powder thus obtained can be used as it is, but in order to increase the interfacial adhesion with the liquid silicone rubber binder, the powder surface may be treated with a silane coupling agent before use. it can.

Examples of the silane coupling agent include γ-methacryloxypropyltrimethoxysilane, vinyltrichlorosilane, vinyltrimethoxysilane, vinyl ethoxysilane, γ-aminopropyltrimethoxysilane, γ-
Glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltriethoxysilane and the like are used.

The surface treatment of the magnetic material powder with these silane coupling agents is performed by adding about 0.1 to 10% by weight of the silane coupling agent to the magnetic material powder as it is or with water, methanol,
Using a mixing and dispersing machine such as a Henschel mixer or a ribbon mixer as a solution of about 5 to 40% such as ethanol, about 3%
After dispersing for 3030 minutes, heat treatment is performed at room temperature to about 80 ° C. for about 1 to 24 hours.

The liquid silicone rubber as a binder of the rare earth magnetic powder treated or not treated with the silane coupling agent is represented by the following general formula, wherein the clay is about 1 to 50.
Those having 0 poise (25 ° C.) are generally used.

Such a liquid silicone rubber is generally of a room temperature curing type and can be cured at room temperature. In this case, about 0.5 to 20% by weight, preferably about 1 to 10% by weight of a curing agent is used based on the liquid silicone rubber.

As the curing agent, the following silane compounds are generally used (provided that R _{1 to} R ₃ are lower alkyl groups).

_{R 1 Si (OCOR 2) 3} CH 2 = CHSi (OCOR 1) 3 R 1 Si (O-N = CR 2 R 3) 3 CH 2 = SHSi (O-N = CR 2 R 3) 3 R 1 Si ( OR ₂ ) ₃ CH ₂ = CHSi (OR ₁ ) ₃ R ₁ R ₁ Si (NR ₃ -CO-R ₂ ) ₂ CH ₂ = SHSiR ₁ (NR ₃ -CO-R ₂ ) ₂ R ₁ Si (O-CR ₂ CHCH ₂ ) ₃ CH ₂ CHCHSi (O—CR ₂ OHOH ₂ ) ₃ More specifically, triacetylsilane, trimethoxymethylsilane, tri (methylethyloxime) methylsilane, trimethoxyvinylsilane, triethoxymethylsilane , Triethoxyvinylsilane, di (N-ethylacetyl) dimethylsilane, tris (2-ethylvinyloxy) methylsilane and the like.

In addition to these curing agents, curing catalysts such as chloroplatinic acid,
Rubber fillers such as silica and calcium carbonate, pigments and the like are appropriately added and used.

The above components are kneaded using a kneader or the like to form a mixture, in which case the rare earth magnetic powder is about 200 to 1800 parts by weight, preferably about 400 to 1000 parts by weight per 100 parts by weight of the liquid silicone rubber. Used in proportion. If the usage ratio of the rare earth magnetic powder is less than this, desired magnetic properties cannot be obtained for the rubber magnet, while if used in a higher ratio, the cured product becomes tattered and a desired molded product cannot be formed.

The mixture is cured and molded in an injection molding machine.At this time, a magnetic field of about 5 to 30 KOe is applied in a direction corresponding to the shape of the molded product such as the thickness direction of the mold, and the magnetic material in the rubber is removed by magnetism. Magnetization for orientation in the thickness direction or the like is performed, and if necessary, the rubber magnet removed from the mold is re-magnetized.

The reason why the magnetization is performed in the molding stage is as follows. That is, in the case of ferrite-based magnetic powder, it is possible to mechanically orient the magnetization axis by a roll, an extruder, or the like due to its characteristics. Can not. Therefore, it is necessary to adopt a method of magnetic field orientation before magnetization. However, rubber such as NBR or natural rubber has a large clay and cannot be magnetically oriented. Therefore, the rubber clay is reduced to a maximum of about 500 poise (25 ° C), and a magnetic force is applied during injection molding to enable magnetic field orientation. Further, since the rare earth magnetic powder is oxidized and deteriorated to deteriorate the magnetic force, liquid silicone rubber which can be cured in a short time even at around normal temperature is used.

〔The invention's effect〕

The rubber magnet according to the present invention has a maximum energy product (BH) ma
x indicates a value of about 2 to 6 MGOe, that is, has magnetic properties covering an intermediate region between the rare earth sintered magnet and the ferrite sintered magnet. Moreover, rubber elasticity, flexibility,
In terms of workability and the like, it has rubber properties equal to or higher than those of conventional ferrite rubber magnets.

Therefore, the rubber magnet of the present invention having such characteristics is a small PM type stepping motor, a brushless motor, a coreless motor, rotating devices such as an encoder, a micro horn, a headphone, a thin speaker,
Audio equipment such as cassette recorders, other sensors,
It can be used for relay devices, meters, ornaments, etc., or for seal products such as magnetic fluid seals, dust seals, and oil seals.

〔Example〕

 Next, the present invention will be described with reference to examples.

Example 1 100 parts (weight, same hereafter) of liquid silicone rubber (KE108, Shin-Etsu Chemical, viscosity 7 poise), 10 parts of trimethoxymethylsilane, 2 parts of chloroplatinic acid and SmCo ₅ (average particle size 5
480 parts were kneaded with a 3 kneader, injected into a mold of an injection molding machine, and cured by heating at 80 ° C. for 20 minutes.

At this time, a magnetic field of 20KOe is applied in the thickness direction of the mold,
Magnetization was performed by magnetizing the magnetic substance in the rubber in the thickness direction to obtain a rubber magnet sheet of 150 × 150 × 2 mm.

The magnetic properties of the obtained rubber magnet sheet were measured as the maximum energy product (BH) max using a BH curve tracer (manufactured by Nippon Electromagnetic Instruments), and JIS K-
Rubber properties (hardness, tensile strength and elongation) were measured by 6301, and the presence or absence of cracks was observed by a 90 ° bending test.

Comparative Example 1 In Example 1, the amount of SmCo ₅ used was changed to 80 parts.

The measurement results in the above Examples and Comparative Examples are shown in Table 1 below.

Table 1 Item Example 1 Comparative Example 1 (BH) max (MGOe) 4.2 0.6 Hardness [JIS A] (point) 62 48 Tensile strength (Kgf / cm ² ) 30 40 Elongation (%) 40 90 Flexural test From the results, it can be seen from the results that, in Example 1, the (BH) max was large and the rubber properties were good, while that of Comparative Example 1 was (BH) max.
H) It can be seen that the value of max is equal to or less than the conventional ferrite rubber magnet.

Comparative Example 2 In Example 1, the used amount of chloroplatinic acid was changed to 1 part, and the used amount of SmCo ₅ was changed to 2000 parts. The heat-cured product was tattered and could not be formed into a sheet.

Example 2 100 parts of liquid silicone rubber (KE16, viscosity 200 poise), 8 parts of trimethoxyvinylsilane, 0.9 part of chloroplatinic acid and Sm ₂ Co ₁₇ (average particle diameter 16 μm, powder surface treated with vinyltriethoxysilane) 3) 850 copies
The mixture was kneaded with a kneader, injected into a mold of an injection molding machine, and cured by heating at 60 ° C. for 60 minutes.

At this time, a magnetic field of 15KOe is applied in the thickness direction of the mold,
It was magnetically aligned. After that, take out the rubber magnet sheet (150 × 150 × 2mm) from the mold, and again 22K in the thickness direction
A magnetic field of Oe was applied to perform magnetization.

The same measurement as in Example 1 was performed on this rubber magnet sheet.

Comparative Example 3 In Example 2, the amount of Sm ₂ Co ₁₇ used was changed to 160 parts.

The measurement results in the above Example 2 and Comparative Example 3 are as follows:
It is shown in Table 2 below.

Table 2 Item Example 2 Comparative Example 3 (BH) max (MGOe) 5.9 1.3 Hardness [JIS A] (point) 86 63 Tensile strength (Kgf / cm ² ) 35 42 Elongation (%) 30 85 In bending test From the results, it can be seen from the results that the material of Example 2 has a large (BH) max and good rubber properties, while the material of Comparative Example 3 has (BH) max.
H) It can be seen that the value of max is comparable to that of conventional ferrite rubber magnets.

Comparative Example 4 In Example 2, the amount of Sm ₂ Co ₁₇ used was changed to 2000 parts.

The heat-cured product was tattered and could not be formed into a sheet.

Example 3 100 parts of liquid silicone rubber (KE1091, product of the company, viscosity 170 poise), 7 parts of triethoxyvinylsilane, 0.5 part of chloroplatinic acid and Sm ₂ Co ₁₇ (average particle diameter 12 μm, powder surface is γ)
-Glycidoxypropyltrimethoxysilane-treated) (720 parts) was kneaded with a 3 kneader, injected into a mold of an injection molding machine, and cured by heating at 60 ° C for 2 hours.

At this time, apply a magnetic field of 10KOe in the thickness direction of the mold,
It was magnetically aligned. After that, take out the rubber magnet sheet (150 × 150 × 2mm) from the mold, and again in the thickness direction 20K
A magnetic field of Oe was applied to perform magnetization.

The same measurement as in Example 1 was performed on this rubber magnet sheet.

In Comparative Example 5-6 Example 3, Sm ₂ instead of Co _17, both with an average particle diameter of 5 [mu] m, the powder surface γ- glycidoxypropyltrimethoxysilane treated SrO · 6Fe ₂ O ₃ ( The same amount of Comparative Example 5) or BaO.6Fe ₂ O ₃ (Comparative Example 6) was used.

The measurement results in Example 3 and Comparative Examples 5 to 6 are shown in Table 3 below.

From these results, it can be seen that, in Example 3, the (BH) max was large and the rubber properties were good, but in Comparative Examples 5 to 6, not only the value of (BH) max was small, but also that of the ferrite magnetic powder. It can be seen that elongation is small due to poor dispersibility in rubber, and a crack consisting of minute cracks is generated by bending.

Claims (4)

(57) [Claims] (1) 100 parts by weight of a liquid silicone rubber and 1-
A method for producing a rubber magnet, wherein a magnetic field is applied to a cured product of a mixture containing 200 to 1800 parts by weight of a type 5 or 2-17 type rare earth magnetic powder. 2. The method according to claim 1, wherein the rare earth magnetic powder is SmCo ₅ or Sm ₂ Co ₁₇ . 3. The method for producing a rubber magnet according to claim 1, wherein a rare earth magnetic powder surface-treated with a silane coupling agent is used. 4. The method for producing a rubber magnet according to claim 1, wherein a magnetic field of 5 to 30 KOe is applied.