Process for producing granules for being molded into ferrite, granules for being molded into ferrite, green body and sintered body

Abstract

A composition for producing granules for molding ferrite, which includes a ferrite slurry at least having raw ferrite powder; an ethylene-modified polyvinyl alcohol whose ethylene modified amount is from 4 to 10 mol %, average polymerization degree is from 500 to 1700, and average saponification degree is from 90.0 to 99.5 mol %; and water mixed therewith, ferrite granules produced from the composition, a ferrite green body produced from the granules and a ferrite sintered body produced from the green body are disclosed.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This is a continuation of application Ser. No. 10 / 132,242 filed Apr. 26, 2002; the above noted prior application is hereby incorporated by reference.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to a process for producing granules for molding ferrite capable of obtaining a ferrite green body excelling in molding properties, the granules for molding ferrite capable of obtaining a ferrite green body obtainable from the same, a ferrite green body and a ferrite sintered body. [0004] 2. Description of the Related Arts [0005] Ferrite has been widely utilized in various fields including electronic parts. The ferrite is obtainable by granulating raw ferrite powder together with a binder into ferrite granule to obtain a ferrite green body and sintering the resulting ferrite green body. [0006] Conventionally, various processes have been applied to produce a ferrite green body. Amongst them, a dr...

AI Technical Summary

Benefits of technology

The present invention provides ferrite granules that have excellent flowability, can be easily packed into a mold, and have good crushing properties at low pressure. The invention also provides a ferrite green body with high strength and a low water absorbency. The invention further provides a ferrite sintered body with low water absorbency and low magnet loss. The invention also includes a composition for producing ferrite granules that have good mold-releasing properties and a process for producing the same. The invention also provides ferrite granules that have been covered with hexitan higher aliphatic acid ester having a hydrophilicity / hydrophobicity ratio of 14 or less. The invention also provides a ferrite green body produced by dry-pressing ferrite granules of the invention. The invention also provides a ferrite sintered body with low water absorbency.

Problems solved by technology

However, these prior techniques, which can improve the strength of the ferrite green body, are disadvantageous in that the resulting ferrite granules are rigid, has a poor crushing property at a low pressure, and many boundary deficiencies remain in the resulting ferrite green body.

Consequently, these prior arts do not give any satisfactory effects in terms of strength and dielectric characteristics of the ferrite sintered body.

a. These techniques relate to improvement of ferrite slurry, the granulation process applicable to these techniques is restricted to a spray-drying granulation process using a spray dryer and, thus, these techniques are of low flexibility.

Also, the molded product produced by the use of such ferrite granules has insufficient dimensional accuracy.

Further, these ferrite granules are not suitable for producing a ferrite product having a complicated shape.

d. When being molded in a mold, the fine ferrite particles are stuck to the mold, causing sticking, which in some cases makes it impossible to continuously produce ferrite green bodies.

e. The resulting ferrite green body is poor in the mechanical strength and there is tendency that defective such as chipping or breaking will easily occur.

f. The dielectric characteristics of the resulting ferrite sintered body, particularly magnetic loss cannot be obtained in a sufficient manner.

g. The ferrite green body resulting from the granules only have a poor mold release property so that crack tends to occur in the interior of the ferrite green body due to the spring back

Images