JPS59138312A - Manufacture of magnetic ferrous oxide powder containing cobalt - Google Patents

Abstract

PURPOSE:To improve magnetic characteristics such as square ratio and orientability by a method wherein at least one of metal compounds of Cs, Ni, Ce and the like is contained in magnetic ferrous oxide powder at the specific step of the manufacturing process of magnetic ferrous oxide powder containing cobalt. CONSTITUTION:Magnetic ferrous oxide powder is dispersed in an alkaline solution such as sodium hydroxide and a ferrous salt such as a ferrous sulfate is added. Then a cobalt salt such as cobalt sulfate is added to the solution. Or the magnetic ferrous oxide powder is dispersed in a solution containing a ferrous salt and an alkaline solution is added and then a cobalt salt is added. In this process, at least one of metal compounds of Cs, Ni, Ce and the like is contained in the magnetic ferrous oxide powder after the application of the compound which is applied at the former step and before the application of the compound which is applied at the latter step for the compound applied at the former step and at the time of its application for the compound applied at the latter step.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing cobalt-containing magnetic iron oxide powder that has excellent magnetic properties such as squareness and orientation when used as a magnetic tape.

Cobalt-containing magnetic iron oxide powder, which is made by coating magnetic iron oxide powder with a cobalt compound, has a high coercive force and is therefore widely used in magnetic recording fields such as video and audio. The demand for higher densities of media has led to a significant demand for further improvements in various performances.

When cobalt-containing magnetic iron oxide powder is kneaded with various binders to prepare magnetic paints, it is difficult to wet the binder, and due to its own magnetism, magnetic agglomeration of particles occurs, resulting in uniform dispersion in the binder. However, it had the disadvantage of <b>.

As a countermeasure to this problem, a method of loosening the agglomerates using mechanical dispersion means (JP-A-50-22297°, JP-A-55-15
7216. JP-A-56-10903) has been attempted. However, this method does not provide a fundamental solution since aggregation begins when the mechanical dispersion operation is stopped. %Zn# is a method for treating the surface of magnetic iron oxide powder with an inorganic compound.
A method of immersion in a solution of an inorganic salt such as C1l (Japanese Patent Application Laid-open No. 1983
-9671. Japanese Patent Publication No. 55-39656. JP-A-55-3
9654), CO ions, Mn ions, 'Fe (
#) A method of heating in the presence of ions and alkali at a temperature of 60°C or higher and lower than the boiling point (Japanese Patent Application Laid-Open No. 132799/1983)
is being attempted. Furthermore, there is a method of coating the particle surface of the magnetic powder with a surfactant that is compatible with an organic binder before preparing the magnetic paint (Japanese Patent Publication No. 53-19120. 1985-82354゜ JP-A-54-85397) and a method of adding a surfactant as a dispersant during the preparation of magnetic paint (
JP-A-55-151068, JP-A-55-15106
9) has been attempted.

Methods for coating the surface of particles with surfactant include immersion treatment in aqueous or non-aqueous systems, or direct spraying on the powder, but in this case, the coated surfactant is desorbed during crosstalk with the organic binder. However, even though dispersibility with vinyl acetate and vinyl chloride resins has been improved, there are problems with resin selectivity, such as poor effectiveness with urethane resins.

Furthermore, if a large amount of surfactant is added during the preparation of a magnetic coating material in order to improve the adhesion of the magnetic powder in the organic binder, there are disadvantages such as decreased strength of the tape, bleeding, and powder falling off.

In improving the performance of cobalt-containing magnetic iron oxide powder, the present inventors have previously found that the presence of ferrous compounds improves magnetic properties, for example, increases Hc, but at the same time reduces the stability of coercive force over time. Taking note of the fact that magnetic tapes made using this material deteriorate in squareness ratio, orientation, etc., a cobalt compound and a ferrous compound were coated on magnetic iron oxide powder in order to solve the above-mentioned drawbacks. As a result of repeated studies on the method, we found that by first coating a ml iron compound on magnetic iron oxide powder and then coating this with a cobalt compound in the first step, we were able to improve the stability of coercive force over time, squareness ratio, and orientation. The knowledge that the magnetic properties such as the magnetic field distribution and the reversal magnetic field distribution are significantly improved.
Patent Department H (Japanese Patent Application No. 57-215172). Therefore, as a result of further study on the above method, we found that either: ■ When the ferrous compound is deposited; ■ After the ferrous compound is deposited and before the cobalt compound is deposited; ■ When the cobalt compound is deposited. We have found that when a specific metal compound is incorporated into magnetic iron oxide powder at this stage, magnetic properties such as squareness ratio and orientation, which are indicators of dispersibility in an organic binder, are further improved. Also, in a method in which a cobalt compound is first applied to a magnetic iron oxide powder, and then a ferrous compound is applied to the powder, there is a method in which the cobalt compound is applied, and the first Before applying the iron compound,■
It is said that if a specific metal compound is included in the magnetic iron oxide powder at any stage during the deposition of the ferrous compound, the magnetic properties such as squareness ratio and orientation will be improved compared to when it is not included. The present invention was completed based on these findings. That is, the present invention provides magnetic iron oxide powder with
Cobalt-containing magnetism can be obtained by first depositing a ferrous compound and then depositing a cobalt compound thereon, or by first depositing a cobalt compound and then depositing a ferrous compound thereon. In the method of producing iron oxide powder, Cs
s Cu #Ag, Mg, Ca*Sr, BaeZn,
AA! ssc, 5iTi e Zr m Sn m
P#V, Nb*Sb#TamBi
#Cr,, Mo・* W t Mll, Fe
(1) When at least 1 of the Ni and α metal compounds are deposited in the first stage of the ferrous compounds and cobalt compounds, at the time of deposition, For those to be deposited, magnetic iron oxide is applied either after the deposition and before the subsequent compound is deposited, or for those to be deposited in the latter stage of both of the above compounds, at the time of deposition. This is a method for producing cobalt-containing magnetic iron oxide powder, the characteristic of which is to include it in the powder.

The magnetic iron oxide powder used in this issue is γ-p
Bertolide compound powder obtained by partially reducing e20g powder, Fe50+ powder, γ-Fezes in a reducing gas such as hydrogen, or these powders containing phosphorus, such as needles, which are precursors thereof. During the production of hydrated iron oxide (L, l:I, 1-Fe00H), phosphoric acids such as orthophosphoric acid, metaphosphoric acid, and boron-17 phosphoric acid, monononite acids, or alkali metal salts thereof, and ammonium are added to the mother liquor. A method of introducing water-soluble salts such as salt,
Acicular hydrated iron oxide or α-Fe20.
Examples include powders obtained by applying the above-mentioned IJ acids, phosphorous acids, or water-soluble salts thereof, and subjecting them to appropriate conventional heat treatment.

In the method of the present invention, magnetic iron oxide powder is first coated with a ferrous compound and then coated with a nicobalt compound, or alternatively, a magnetic iron oxide powder is first coated with a ferrous compound and then coated with a ferrous compound. A ferrous compound is applied to the object.Specifically, this method is as follows: 1) Magnetic iron oxide powder is dispersed in an alkaline aqueous solution, a ferrous salt is added to this, and a cobalt salt is added as a primary addition. Method: (1) Dispersing the powder in an aqueous solution containing a ferrous salt, adding an alkaline aqueous solution thereto, and then adding a cobalt salt; (2) Dispersing the powder in water or a weak alkaline aqueous solution; A method of adding an alkaline aqueous solution and a ferrous salt in parallel, and then adding a cobalt salt, or a method of simultaneously adding a cobalt salt and an alkaline aqueous solution; (2) A method of dispersing the powder in an aqueous solution containing a cobalt salt, adding an aqueous alkali solution thereto, and then adding a ferrous salt;
The above powder is dispersed in water or a weak alkali aqueous solution, into which an aqueous alkali solution and a cobalt salt are simultaneously added, and then a ferrous salt is added, or a ferrous salt and an aqueous alkali solution are simultaneously added. methods, etc. In addition, in these methods, an alkaline aqueous solution may be additionally added as necessary.

The ferrous salts used in this ζ include ferrous sulfate and ferrous nitrate.
Ferrous salts of mineral acids such as iron and ferrous chloride are preferred, and ferrous sulfate is preferred industrially, and cobalt salts include inorganic or organic acid salts of cobalt, such as cobalt sulfate,
Examples include cobalt chloride and cobalt acetate, with cobalt sulfate being industrially preferred. As alkali metals, alkaline earth metal hydroxides, oxides, or carbonates are used, such as sodium hydroxide, potassium hydroxide, sodium oxide, and calcium carbonate. Sodium hydroxide and IJium hydroxide are preferred.

Examples of ferrous compounds or cobalt compounds formed by salts and alkalis include water hydroxides, water oxides, and water oxyhydroxides. The amount of the former is 0.5 to 30% by weight as Fe, preferably 1 to 20% by weight as Fe, and the latter is 0.1 to 20% by weight as Co, based on the appearance amount of the commercial magnetic iron oxide powder. %, preferably 0.5 to 10%.

In the deposition of the ferrous compound and cobalt compound in the method of the present invention, the suspension slurry concentration of the magnetic iron oxide powder is usually 20 to 200 g/13, preferably 50 to 150 g/13.
/7), the deposition reaction temperature is usually below the boiling point, preferably below 50°C, and the atmosphere during deposition is usually non-oxidizing so that the ferrous compound is not substantially oxidized. . In order to make the atmosphere non-oxidizing, for example, the reaction vessel is replaced with an inert gas.1 The inert gas is bubbled into the solution in the reaction vessel. The addition time of raw materials during deposition varies depending on the deposition method, molar concentration of OH groups, deposition reaction temperature, etc. The time period is preferably 1 to 2 hours.
The OH group concentration in the solution after the iron compound or cobalt compound has been deposited (concentration of free O and I groups above the neutralization equivalent) is usually 0 to 3 mol/l, preferably 0.5 to 2 mol/l. It is l.

The magnetic iron oxide powder that has been coated with both compounds is usually aged at a temperature below the boiling point, for example below 50°C, in a non-oxidizing atmosphere, but if desired, aging at 50 to 90°C improves the magnetic properties. It can also have a positive impact on money.

Aging time is usually 01 to 10 hours.

In the method of the present invention, if desired, heat treatment may be performed in a non-oxidizing atmosphere between the steps of depositing the ferrous compound and the cobalt compound, so that the deposition of the solid compound is completed and the slurry is aged. This is usually followed by heat treatment. As a method for these heat treatments, for example,
A method of wet heat treatment at 00°C. ■Filter the adhered slurry, wash it with water, disperse the wet cake in water again to make a slurry, and put this slurry in an autoclave to a temperature of 100 to 250°C.
1. A method of wet heat treatment at a temperature of 60 to 200 °C, preferably 200 °C, 2) A method of drying the wet cake at a temperature of 30 to 200 °C, 2) A method of drying the wet cake at a temperature of 30 to 200 °C; 10 dried items
Examples include a dry heat treatment method at 0 to 300°C, preferably 100 to 200°C.

In the method of the present invention, (1) among the ferrous compounds and cobalt compounds to be deposited in the previous step, (1)
For the compound to be M+ applied in the first stage of both of the above compounds, before applying M+ to the compound in the latter stage; In this step, the above-mentioned specific metal compound is incorporated into the magnetic iron oxide powder. Specifically, in the above-mentioned specific methods for depositing cobalt compounds and ferrous compounds ■ to ■, when depositing the ferrous compounds of ■deposition methods ■ to ■, a specific metal compound is used. Co-existence method or deposition method When depositing the cobalt compound of ■~■, method of coexisting a specific metal compound, @deposition method of depositing the ferrous compound of ■~■
A method of applying a heat treatment after ripening, and then applying a specific metal compound to this product, or a method of applying a cobalt compound according to method ① to ① and aging, then applying a heat treatment to this product, and applying a specific metal compound to this product. Deposition method, θDeposition method When depositing a cobalt compound according to ■~■, a method in which all of the specific metal compounds coexist, or when depositing a ferrous compound according to deposition methods ■~■, a specific metal compound Examples include ways to coexist. At least one of the methods (1) to (theta) above may be employed, but two or three methods are preferably combined. Specific metal compounds mentioned here include water-use hydroxides, water-use oxides, hydrated oxyhydroxides, etc., and the content of this specific metal compound is determined based on the total iron content of the magnetic iron oxide powder. Usually o, oi to 2% by weight, preferably 0.05
~5% by weight.

In order to incorporate a specific metal compound at >lx into the above method, it can be carried out by neutralizing the specific metal salt with an acid or alkali) or hydrolyzing it; in these cases, sura IJ
It goes without saying that it is preferable to stir well and keep the object to be well dispersed. Further, the temperature of the slurry, the concentration of the alkaline earth metal salt (PH%), the addition rate, etc. may be adjusted as appropriate depending on the method of containing the slurry.

In the method of incorporating a specific metal compound in the method of the present invention, the above-described heat treatment may or may not be performed after incorporating the specific metal compound. In these heat treatments, it is necessary to take care to prevent specific planned compounds, ferrous compounds, and cobalt compounds from diffusing inside the particles of magnetic iron oxide.

The cobalt-containing magnetic iron oxide powder containing all of the specific metal compounds produced by the method of the present invention has improved magnetic properties, and magnetic tapes made using this iron oxide powder have better magnetic properties such as squareness and orientation. The characteristics are improved.

The reason why magnetic properties such as squareness ratio and orientation, which are indicators of dispersibility in an organic binder, are improved by the method of the present invention is not necessarily clear. In particular, it is presumed that magnetic aggregation in the organic binder becomes less likely to occur, and (1) the affinity between the magnetic iron oxide powder wood and the organic binder increases, resulting in better wetting.

The invention will be understood in more detail from the following examples and comparative examples.

Examples 1-9 Coercive force He p 3990 e h P as starting material
Using r-Fe20st- containing i0.63%, the γ
-Fe, 03100g was dispersed in total water 11 to form a slurry, and while blowing N2 gas into the liquid at room temperature (30°C), a predetermined amount of 10 mol Δ NaOH aqueous solution shown in Table 1 below was added, and then 0. Add a 90 mol/l ferrous sulfate aqueous solution 168g or a mixed solution of this and a predetermined amount of a metal salt shown below, stir, and then add a predetermined amount of 168 g as shown below.
A 0 mol 4 NaOH aqueous solution was added, or a predetermined amount of a metal salt as shown below was further added. Next, 70 ml of a 0.85 mol 4 cobalt sulfate aqueous solution or this solution and a predetermined amount of the metal salt shown below were added and stirred at room temperature (30° C.) for 5 hours. This slurry'fr was filtered, washed with water, and the resulting wet cake was placed in an autoclave with water in a separate container.
After purging with nitrogen and gas, the reactor was sealed and heat-treated at 130° C. for 6 hours in the presence of steam.

After the treatment, it was dried at 120° C. in N2 gas to obtain desired cobalt-containing magnetic iron oxide powders (A) to (I).

Comparative Example 1 A cobalt-containing magnetic iron oxide powder (J) was obtained in the same manner as in Examples 1 to 9, except that a specific metal salt was added.

For the above samples (4) to (J) in Table 1, add the coercive force to the side of the coercive force basin in the usual manner, and record the results in Table 2 (2). A blend was prepared and kneaded in a ball mill to produce a magnetic paint.

(1) Cobalt-containing magnetic iron oxide powder 24 parts by weight (
2) Polyurethane resin 5" (3)
Vinyl chloride-vinyl acetate copolymer 1.2 (4) Dispersant 0.5 (5) Mixed solvent (Toluene AEK = 1/1) 69.5 Next, apply each magnetic paint to a polyester film using the usual method. A magnetic tape having a magnetic coating film of approximately 9 μm was prepared by coating, orienting and drying the magnetic tape. For each tape, the coercive force (He), saturation magnetic flux density (
Bm), squareness ratio (B r / B m), orientation (OR
) are shown in Table 2.

・Table 2 Examples 10 to 12 Same as those used in Examples 1 to 9) -Feze31
Disperse in 110 g of water to make a slurry and keep it at room temperature (30 g
0.85 while blowing N2 gas into the liquid at
70 ml of cobalt sulfate aqueous solution of mol/It or a mixed solution of this and a prescribed amount of metal salt shown in Table 3 below was added and stirred, and further a prescribed amount of 10 mol/liter of N
An aOH aqueous solution was added and stirred, or a predetermined amount of metal salt shown below was further added. Next, 168 d of a 0.90 molar ferrous sulfate aqueous solution or this solution and a predetermined amount of the metal salt shown below were added and stirred at room temperature (30° C.) for 5 hours. This slurry was filtered and washed with water, and the resulting wet cake was placed in an autoclave with water in a separate container, purged with N2 gas, sealed, and heat-treated in the presence of steam at 130°C for 6 hours. . After treatment, dry at 120°C in N2 gas,
The desired cobalt-containing magnetic iron oxide powders (1) to (M) were obtained.

Comparative Example 2 A cobalt-containing magnetic iron oxide powder was obtained in the same manner as in Examples 10 to 12, except that no specific metal salt was added.

Table 3 The coercive forces of the above samples (1) to (7) were measured using the usual method, and the results are shown in Table 4.For samples (K)-/(N), By the same method as above,
Coercive force (He), saturation magnetic flux density (Bm), squareness ratio (Br
/Bm) and orientation (OR) are shown in Table 4.

Table 4 Procedural Amendment (Voluntary) February 4, 1981 Commissioner of the Patent Office Kazuo Wakasugi Tonodo 2 O/
2.RO 1. Indication of case: Patent application 2, filed on January 28, 1988. Title of invention: Process for producing cobalt-containing magnetic iron oxide powder 3. Person making the amendment. Relationship with the case: Patent applicant 5: Amendment. Contents (1) In the specification, page t52, line 15, "adjustment" is replaced by "preparation"
I am corrected.

(2) Ibid., page 2, lines 16 and 17, "There is still magnetic cohesion between the particles due to their own magnetism.""Agglomerationoccurs," he corrected.

(3) Same, page 12, line 18, ``After being applied and aged, heat treatment is applied'' is corrected to ``after being applied.''

(4) Same, page 12, line 19, "Method of depositing" is corrected to "Method of depositing and then depositing a cobalt compound in step 1."

(5) In the same article, page 12, line 20 and page 13, line 1, ``After being applied and aged, heat treatment is applied'' is corrected to ``after being applied.''

(6) Same, page 13, line 2, "Method of depositing" is corrected to "Method of depositing and then depositing a ferrous compound."

Claims (1)

[Scope of Claims] A magnetic iron oxide powder is first coated with a ferrous compound and then a cobalt compound is coated thereon, or alternatively, a cobalt compound is first coated and then a first iron compound is coated on the powder. In a method for producing cobalt-containing magnetic iron oxide powder by depositing an iron compound, Cs, Cu #Ag #Mg
#Ca, Sr, Ba# Zn a A7 #
Sc, Si * Ti t Zr e Sn jP
m V # Nb* Sb * Ta, Bi#
Cr, IVlo. W # Mn # Fe(II) m A method for producing a cobalt-containing magnetic iron oxide powder, which comprises incorporating at least one of the metal compounds of Ni and Ce into the magnetic iron oxide powder in any of the following steps. . (2) For those of the above-mentioned compounds that break in the first stage, at the time of adhesion. 2. For those of the above compounds to be deposited in the first stage, after that and before the second stage compound is deposited. 3. For those of the above-mentioned compounds that will be deposited later, at the time of deposition.