Rubber or plastic magnet and magnetic powder for making the same
AssigneeTDK Electronics Co., Ltd.
InventorsTakeo Tada, Katsuji Honda, Masami Oguriyama
Life of this patent
Estimating the term…
Abstract
A rubber or plastic magnet of high magnetic properties is produced by incorporating a magnetoplumbite type magnetic powder into a rubber or thermoplastic or thermosetting matrix at a high concentration with a high degree of orientation of the magnetic particles. Such high concentration and orientation can be obtained by using a magnetoplumbite type magnetic powder having a compressed density in the range between 3.30 g/cm.sup.3 and about 3.55 g/cm.sup.3 and an average particle size of about 1.00 and 1.50.mu., said particles being prepared by dry crushing process from coarse sintered particles and having predominantly single crystal structure.
Claims11
A process of producing a magnetic powder for use in a plastic or rubber magnet wherein said powder is filled in a plastic or rubber matrix and magnetically oriented comprising:
- (a) firing a starting composition capable of forming when fired a ferrite selected from the group consisting of barium ferrite, strontium ferrite and lead plumbite ferrite at a temperature above 1200.degree. C. to produce a sintered body of magnetic material;
- (b) coarse-crushing said sintered body to obtain coarse particles;
- (c) pulverizing said coarse particles together with about 0.1% by weight of about 10% by weight based on the weight of said coarse particles of a lower alcohol having three or less carbon atoms until a fine powder is obtained, said fine powder having an average particle size in the range between about 1.00.mu. and about 1.50.mu. measured with a Fisher Sub-Sieve Sizer and having a compressed density in the range of about 3.30 g/cm.sup.3 and about 3.55 g/cm.sup.3 when compressed under a pressure of 1 ton/cm.sup.2 ;
- and
- (d) annealing said fine powder at an elevated temperature.
A magnetic powder for use in a plastic or rubber magnet wherein said powder is filled in a plastic or rubber matrix and magnetically oriented, said powder being made according to the following steps:
- (a) firing a starting composition capable of forming when fired a ferrite selected from the group consisting of barium ferrite, strontium ferrite and lead plumbite ferrite at a temperature above 1200.degree. C. to produce a sintered body of magnetic material;
- (b) coarse-crushing said sintered body to obtain coarse particles;
- (c) pulverizing said coarse particles together with about 0.1% by weight to about 10% by weight based on the weight of said coarse particles of a lower alcohol having three or less carbon atoms until a fine powder is obtained, said fine powder having an average particle size in the range between 1.00.mu. and 1.50.mu. measured with a Fisher Sub-Sieve Sizer having a compressed density in the range of about 3.30 g/cm.sup.3 and about 3.55 g/cm.sup.3 when compressed under a pressure of 1 ton/cm.sup.2 ;
- and
- (d) annealing said fine powder at an elevated temperature.
A plastic or rubber magnet comprising a magnetic powder uniformly dispersed in a plastic or rubber matrix, said powder being magnetically or mechanically oriented in said matrix, said powder being made according to the following steps:
- (a) firing a starting composition capable of forming when fired a ferrite selected from the group consisting of barium ferrite, strontium ferrite and lead plumbite ferrite at a temperature above 1200.degree. C. to produce a sintered body of magnetic material;
- (b) coarse-crushing said sintered body to obtain coarse particles;
- (c) pulverizing said coarse particles together with about 0.1% by weight to about 10% by weight based on the weight of said coarse particles of a lower alcohol having three or less carbon atoms until a fine powder is obtained, said fine powder having an average particle size in the range between about 1.00.mu. and about 1.50.mu. measured with a Fisher Sub-Sieve Sizer and having a compressed density in the range of about 3.30 g/cm.sup.3 and about 3.55 g/cm.sup.3 when compressed under a pressure of 1 ton/cm.sup.2 ;
- and
- (d) annealing said fine powder at an elevated temperature.
Dependencies are inferred from the claim text.