JPS58159309A - Manufacture of metallic magnetic powder - Google Patents

Abstract

PURPOSE:To obtain powder having high bulk density and excellent packing property by a method wherein iron oxyhydroxide powder or iron oxide powder is suspended into water, a high molecular flocculant is added into water, iron oxyhydroxide powder or iron oxide powder is coagulated, and the powder is baked and reduced. CONSTITUTION:Iron oxyhydroxide powder or iron oxide powder is suspended into water, and the high molecular flocculant is added into the suspension and iron oxyhydroxide powder or iron oxide powder is coagulated. The powder is baked and reduced. Substances up to a high polymerization rate of several million molecular weight from a low one of not less than one thousand molecular weight are used as the high molecular flocculant, and sodium alginate, etc. are cited. The high molecular flocculant is used within a range of 0.1-2wt% to iron oxyhydroxide powder or iron oxide powder in the water suspension. alpha-FeOOH powder, alpha-Fe2O3 powder, gamma-Fe2O3 powder, Fe3O4 powder or powder corresponding to these intermediate type or the like is cited as iron oxyhydroxide powder and iron oxide powder, and powder having excellent needle property is used.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing metal magnetic powder, and an object thereof is to provide a method for producing metal magnetic powder that has a high bulk density and excellent filling properties.

Metal magnetic powder such as metallic iron powder is usually made by heating and reducing iron oxyhydroxide powder or iron oxide powder with hydrogen gas, etc., and has superior magnetic properties compared to conventional oxide-based magnetic powders. However, on the other hand, it is bulky, and when used as a magnetic recording medium by coating it on a base film together with a binder resin, there is a problem in that it lacks filling properties.

For this reason, attempts have been made to improve the filling properties by increasing the bulk density by pressing the metal magnetic powder obtained by thermal reduction using a press machine to reduce the bulk. There is a safety problem because the highly active gold magnetic powder is pressed after reduction, and it is difficult to improve filling properties.
I'm still not completely satisfied with it.

The inventors conducted various studies in view of the current situation, and found that iron oxyhydroxide powder or iron oxide powder was suspended in water in the process before thermal reduction, and a polymer flocculant was added to this suspension. In addition, if iron oxyhydroxide powder or #'i ferric oxide powder is aggregated, then fired and reduced, a metal magnetic powder with even higher bulk density and excellent filling properties can be obtained due to the aggregation effect of the polymer flocculant. The inventors have discovered that this can be obtained, and have come up with this invention. , 7 As the polymer flocculant used in this invention, any one having a low degree of polymerization with a molecular weight of 1000 or more to one with a high degree of polymerization having a molecular weight of several hundred blades is suitably used, and specific examples include For example, sodium alginate, water-soluble aniline resin base salt, starch, gelatin, sodium polyacrylate, maleic acid copolymer, polyacrylamide partially hydrolyzed salt, polyethylene amine, vinylpyridine copolymer salt, polyacrylamide, polyoxy Examples include ethylene. This type of polymer flocculant has an excellent flocculation effect by cross-linking adsorption of coarse particles, and when added to an aqueous suspension of iron oxyhydroxide powder or iron oxide powder, it can cross-adsorb these powder particles well. As a result of the iron oxyhydroxide powder or iron oxide powder being well agglomerated in this manner, when it is then fired and reduced, a metal magnetic powder with even higher bulk density and excellent filling properties can be obtained.

The amount of such a polymer flocculant to be used is 0.1% by weight relative to the iron oxyhydroxide powder or iron oxide powder in the aqueous suspension.If it is less than 10% by weight, the desired effect will not be obtained; 0.01 to 1 since increasing the amount may not have a negative effect on the magnetic properties of the metal magnetic powder obtained by subsequent reduction.
It is preferably used within a range of 0 weight, more preferably within a range of 0.1 to 2 weight.

As iron oxyhydroxide powder and iron oxide powder, α-F
eOOH powder, α-Fe20. Examples include powder, r-Fe203 powder, Fe, O, powder, and intermediate types thereof, and those with good acicularity are preferably used.

Such iron oxyhydroxide powder and iron oxide powder may be used by suspending them in water once they have been dried, but oxyhydroxide powder produced by mixing an aqueous iron salt solution and an aqueous alkali solution may be used. A suspension of iron powder may be used as it is, and a polymer flocculant is usually added to this suspension by adding a polymer flocculant prepared by dissolving a predetermined amount of the polymer flocculant in a predetermined amount of water. This is carried out by adding an aqueous solution and then stirring to collect iron oxyhydroxide powder or i'i iron ferrite powder.

After the iron oxyhydroxide powder or iron oxide powder has been agglomerated with a polymer flocculant, calcination is performed at a temperature within the range of 500 to 1000°C, and this calcination produces iron oxyhydroxide powder or iron oxide powder. The polymer flocculant used to flocculate is burned away.

After such firing, the iron oxyhydroxide powder or the iron monoxide powder is heated to a temperature of 300 to 600 in a reducing gas atmosphere such as hydrogen gas.
The metal magnetic powder is reduced by heating at a temperature of .degree. C., and a metal magnetic powder with high bulk density and excellent filling properties is obtained.

Next, embodiments of the invention will be described.

Example 1 in aqueous sodium hydroxide solution 201 with a concentration of 5 mol/l
While stirring at room temperature, an aqueous solution 201 of ferrous sulfate (Fe50.-7H20) having a concentration of 0.719 mol/l was added and reacted to obtain a greenish milky white precipitate of ferrous hydroxide. The P)l of this suspension was 12 or more. Next, air was blown into the precipitate suspension at a rate of 301/min while maintaining the precipitate suspension at 60° C., and the mixture was stirred for 8 hours to obtain a suspension of α-FeOOH powder. The particle diameter (long axis) of the obtained α-Felon powder was 0.5 μ, and the axial ratio (long axis/short axis) was 8.

The PIF of the suspension after the reaction was completed was 113.6.

Next, an aqueous solution of polyacrylamide partial hydrolyzate (molecular weight 1 million, anion-modified 5 molar beak) 39 dissolved in water 31 was added to the suspension of this strongly alkaline α-Fe00H powder, and 0.5 After stirring for a period of time, the EG was washed with water, dried, and aggregated with polyacrylamide partial hydrolyzate.
The obtained Fe0OH powder was then dried at 100°C and then calcined at 900°C for 2 hours to obtain α-F e20
．． A powder was obtained. This α-Fe20. The powder was reduced in an electric furnace at 500° C. for 8 hours in a hydrogen flow of 17 j/min, and after the reduction, it was immersed in toluene and then taken out to obtain metallic iron powder of about 0.8 rf. The average particle diameter of the obtained metallic iron powder (
The length of the long axis) was 0.35 s, and the axial ratio (long axis/short axis) was 7.

Comparative Example In the example, addition and stirring of the polyacrylic acid partially hydrolyzed aqueous solution was omitted, and approximately
, 5sIIf metallic iron powder was obtained. The average particle diameter (long axis) of the obtained metallic iron powder was 0.35 μ, and the axial ratio (long axis/short axis) was 7.

The bulk densities of the metal iron magnetic powders obtained in Examples and Comparative Examples were measured. The bulk density was measured by measuring the weight of the metallic iron powder per constant volume.

The table below shows the results.

As is clear from the table above, the metallic iron powder obtained by the present invention (Example) has a higher bulk density than the metallic iron powder obtained by the conventional method (Comparative Example) k, and from this, the present invention It can be seen that according to the manufacturing method described above, a metal magnetic powder having a high bulk density and excellent filling properties can be obtained.

Claims (1)

[Claims] 1. Suspend iron oxyhydroxide powder or Fi iron oxide powder in water, add a polymer flocculant to this suspension to flocculate the iron oxyhydroxide powder or iron oxide powder, and then calcinate and reduce. A method for producing metal magnetic powder characterized by