Rubber or plastic magnet and magnetic powder for making the same

Claim 2

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° 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 1.00μ and about 1.50μ measured with a Fisher Sub-Sieve Sizer and having a compressed density in the range of about 3.30 g/cm 3 and about 3.55 g/cm 3 when compressed under a pressure of 1 ton/cm 2 ; and (d) annealing said fine powder at an elevated temperature.

Claim 3

A process according to claim 1 wherein said ferrite is barium ferrite.

Claim 4

A process according to claim 1 wherein said coarse particles are pulverized in a ball mill.

Claim 5

A process according to claim 1 wherein said coarse particles are pulverized in a vibration mill.

Claim 6

A process according to claim 1 wherein said alcohol is selected from the group consisting of methanol, ethanol, propanol, ispropanol, mixtures thereof, and ethanol denatured with methanol.

Claim 7

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° 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 1.00μ and 1.50μ measured with a Fisher Sub-Sieve Sizer having a compressed density in the range of about 3.30 g/cm 3 and about 3.55 g/cm 3 when compressed under a pressure of 1 ton/cm 2 ; and (d) annealing said fine powder at an elevated temperature.

Claim 8

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° 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 1.00μ and 1.50μ measured with a Fisher Sub-Sieve Sizer having a compressed density in the range of about 3.30 g/cm 3 and about 3.55 g/cm 3 when compressed under a pressure of 1 ton/cm 2 ; and (d) annealing said fine powder at an elevated temperature.

Claim 9

A magnetic powder according to claim 6 wherein said ferrite is barium ferrite.

Claim 10

A magnetic powder according to claim 6 wherein said powder is comprised predominantly of single crystal particles.

Claim 11

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° 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 1.00μ and about 1.50μ measured with a Fisher Sub-Sieve Sizer and having a compressed density in the range of about 3.30 g/cm 3 and about 3.55 g/cm 3 when compressed under a pressure of 1 ton/cm 2 ; and (d) annealing said fine powder at an elevated temperature.

Claim 12

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° 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 1.00μ and about 1.50μ measured with a Fisher Sub-Sieve Sizer and having a compressed density in the range of about 3.30 g/cm 3 and about 3.55 g/cm 3 when compressed under a pressure of 1 ton/cm 2 ; and (d) annealing said fine powder at an elevated temperature.

Claim 13

A magnet according to claim 9 wherein said ferrite is barium ferrite.

Claim 14

A magnet according to claim 9 wherein said plastic matrix is selected from the group consisting of thermoplastic materials and thermosetting materials.