JPS5829605B2 - Kiyoji Seifun Matsuno Seiho - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to ferromagnetic iron oxide, and particularly to ferromagnetic iron oxide, which exhibits stability against pressure and heating, changes in coercive force over time, small coercive force distribution, large coercive force, and good performance when used as a magnetic tape. The present invention relates to a method for producing a ferromagnetic material with improved SP ratio and erase characteristics.

In particular, the present invention is applicable to Japanese Patent Publication No. 36-5515, Japanese Patent Publication No. 37-Sho
4825, Japanese Patent Publication No. 49-49475, etc., in which ferrite is precipitated on acicular particles, and JP-A-49-108599 and JP-A-50-37667, which have the same purpose.
No., JP-A No. 50=37668, CO in the midst of remission
The present invention relates to an improvement in a method for improving coercive force by precipitation of a compound containing.

Co
Compared to magnetic materials in which particles are dispersed uniformly within particles, it is superior in terms of stability against heating and stability over time such as SP ratio.

Furthermore, since the manufacturing process is simple, this method is suitable for industrial products.

However, the coercive force remains saturated even when the amount of Co added is increased, and it is extremely difficult to increase the coercive force to 500 to 6,000 e or more, which is not necessarily sufficient for use in high recording density magnetic tapes.

The present invention relates to an improved reaction method that provides good stability and high coercive force through the reaction in the aqueous solution.

The present invention improves the timing and amount of alkali addition in the method for precipitating Co-containing compounds in an acid solution. and + Adding an aqueous solution containing other cations and an alkaline solution to a method for producing ferromagnetic iron oxide containing a metal provided by these ions, the above alkaline solution and co+2 ions or co+2 ions This is a method for producing ferromagnetic powder, which is characterized in that an aqueous solution containing other cations is added alternately in at least two portions, and finally the alkaline vinegar solution is added.

The ferromagnetic iron oxide used in the present invention is maghemite (
γ-Fe2O3), magnetite (Fe304), bertholed iron oxide (iron oxide with intermediate oxidation degree between maghemite and magnetite, FeOx1,33 <x< 1.50
), partially oxidized metal iron, etc. are used.

These ferromagnetic iron oxides have an acicular ratio of about 2/1 to 20/1.
Preferably 4/1 to 12/1. The average length of particles is 0.3~
1.5 μm, preferably 0.4 to 1 μm is used.

These maghemite and magnetite are usually about 250 ~
It has a coercive force (He) of about 4500e, and the beltlide iron oxide obtained by oxidizing or reducing He is F
It has a high coercive force of about 300e around e01.36.

The aqueous solution containing co+2 ions or co+2 ions and other cations is an aqueous solution in which hydroxyl salts of these metals are dissolved, and as other cations, +2 is Cr+3. Cr+6. Mn, Fe+2゜Fe+
3, Ni+2. Ions such as zn+2 are used and incorporated into the above-mentioned ferromagnetic iron oxide by the method of the present invention.

Hydroxylic cobalt salts are compounds that supply CO+2 ions in water, and include compounds such as inorganic salts, inorganic acid salts, organic acid salts, and complex salts of cobalt. Specifically, cobalt chloride, cobalt sulfate, cobalt nitrate, Examples include cobalt hexamine chloride, cobalt hexamine nitrate, cobalt hexamine sulfate, cobalt acopentamine chloride, and ammonium cobalt sulfate.

Among these, chlorides and nitrates are often used.

The amount of the hydroxyl cobalt salt added is about 0.5 to 10 atomicφ, preferably 0.8 to 5 atomic%, based on the Fe element of the ferromagnetic iron oxide.

, co+2 ions and other cations, water-soluble cobalt salts and other cations, ie, Ch+3. C
r 9Mn+2. Fe+2°+6 Ni+2. As mentioned above, the total amount of hydrometallurgical metal salts such as Zn 1,22 is about 0.5 to 10% relative to the element of ferromagnetic iron oxide Fe.
About atomic%, preferably 0.8 to 5 atoms
It is sufficient to add co+2 ions so that icφ is obtained, and the amount of co+2 ions is 1/3 or more of the above a tomi cφ, and the amount of other cations is 2/3 or less of the above atomiσ.

Hydroacidic chromium salts are compounds that supply Cr+3 or Cr+6 ions in water, specifically chromium chloride, chromium sulfate, chromium potassium sulfate, chromium ammonium sulfate, chromium nitrate, ammonium chromate, sodium chromate, chromium Potassium acid etc.

Among these, it is preferable to use cr-H-+- salt.

Hydroxylic manganese salts are compounds that supply Mn+2 ions in water, and include manganese inorganic salts, inorganic acid salts, organic acid salts, complex salts, etc. Specifically, manganese chloride, manganese sulfate, nitric acid Manganese etc. are used.

A swimsuitable iron salt is a compound that supplies Fe+2 ions and Fe+3 ions in water. Specifically, ferrous sulfate, ferrous chloride, chromium ammonium sulfate, etc. are used as Fe++ ions, and as Fe""Ft+ ions. is ferric chloride,
Ferric sulfate and the like are used.

Hydroacidic nickel salts are compounds that supply Ni +2 ions in water, and include compounds such as nickel inorganic salts, inorganic acid salts, organic acid salts, and complex salts. Specifically, nickel chloride, nickel sulfate, nickel nitrate, hexamine nickel chloride,
Nickel ammonium chloride or the like is used.

Hydroxic zinc salts are compounds that supply Zn+2 ions in water, and there are compounds such as inorganic salts, inorganic acid salts, organic acid salts, and complex salts of zinc. Specifically, chloride raw salts, zinc sulfate, zinc nitrate, etc. is used.

The alkalis used in the present invention include alkali hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide; alkali carbonates such as sodium carbonate and potassium carbonate; ammonium hydroxide, aqueous ammonia; monoethanolamine, and P-phenylene. These include aliphatic or aromatic amines such as diamines, p, and mixtures thereof.

These alkaline substances are used after being dissolved in water.

The total amount of alkali addition is co+2 ions, or co+2
After neutralizing the ions and other cations, the (O
H-) It is desirable that the concentration is 0.5 N or more, and 0.
．． If it is less than 5N, the effect of increasing coercive force (He) is small.

Addition of alkaline liquid to CO+2 ion or co+2
ions and other cations, namely Ch+3. Cr+6
Ion, Fe+2°+2 Fe+3. Ni+2. It is stated in the specification of the earlier application that the coercive force increases when the aqueous solution containing ions such as zn+2 is added twice before and after the addition step, but the present invention further advances this, The aqueous solution containing the ions is added in at least two portions, and the alkaline vinegar solution is added in at least three portions before and after the addition step.

That is, by repeatedly adding this alkaline vinegar solution and an aqueous solution containing the ions described above, ferromagnetic iron oxide containing the ions having a higher coercive force than the conventional method can be obtained.

To explain the process of the present invention explained above in more detail, first, the starting material, ferromagnetic iron oxide, is sufficiently dispersed in water, and j=-
Then, a first alkali is added, and a first co+2 ion or an aqueous solution containing co+2 ions and other cations is added.

The reaction solution is preferably stirred during this step.

Stirring is performed using a styler, ultrasonic waves, or the like.

Next, prior to the second alkali addition, stirring is continued for 30 minutes or more to homogenize and ripen the precipitate, and then press the button.

At this time, it is possible to further increase the coercive force by adding VCF e +3 salt or the like, and to improve the coercive force distribution and lower the erasure level by adding Mn+2 salt or the like.

Next, the second aqueous solution containing the above-mentioned I, Ion is added, and the alkaline fermentation solution is added third time.

This process is further repeated if necessary.

After addition of each vinegar solution, it is necessary to thoroughly stir the suspension to make it homogeneous, and stirring is usually carried out for 30 to 60 minutes.

The fact that uniform deposition is achieved by carrying out the multi-step precipitation reaction in this way is useful for narrowing the distribution of the coercive force of the high coercive force of the present invention.

Although it is usually advantageous in terms of workability to heat the suspension after all the reaction liquids have been added, the suspension may be heated from the beginning.

The heating range is preferably from 8°0C to 150°C, and from 90°C to 150°C.
It is most desirable to react in a boiling state at 105°C.

If the temperature is below this, it will take a long time to increase the coercive force, which is industrially disadvantageous, and if it is above 105°C, the advantage of being able to carry out the process in a reaction vessel at normal pressure will be lost.

However, by using an autoclave, it is possible to process at high temperatures up to about 150'C.

Next, in order to remove excess alkali in the reaction solution, the p
After washing with water until H becomes 9.5 or less, preferably 8.5 or less, dehydration is performed by flow filtration, centrifugation, etc., and the remainder is dried at a temperature of about 40 to 20°C.

If the ferromagnetic iron oxide used as the starting material is magnetite, the above process may be used; however, if the ferromagnetic iron oxide used as the starting material is magnetite (Fear) or berthride iron oxide, the final step of drying is performed using N2.
2 or in an inert gas such as a rare gas such as He, Net Ar+Kr, Xe, or Rn.

This is because magnetite and beltride iron oxide may oxidize when dried in the air due to heating.

Through the above steps, ferromagnetic iron oxide containing Co or C
A 7'6ffl magnetic iron oxide containing at least one metal selected from O, Cry Mn, and Fe y Nis Zn is obtained.

When the obtained ferromagnetic iron oxide is magnetite or bertholed iron oxide, it is also possible to obtain a ferromagnetic iron oxide whose degree of oxidation is adjusted by further treatment in an oxidizing atmosphere.

The effect of the present invention is to increase the saturation value of coercive force with respect to the amount of co+2 ions added by dividing an aqueous solution of ions contained in iron oxide and an alkaline vinegar solution several times and performing a multi-stage precipitation reaction.

The disadvantage of the conventional method is that the increase in coercive force is saturated with a relatively small amount of Co.

Furthermore, by carrying out a multi-stage precipitation reaction, Cr+3. Cr+
6°Mn+2. Fo+2. Fo+3. Ni+2. It has also been found that it is possible to adjust the amount of the third added cation such as zn12.

According to the conventional method of adding alkali all at once, as the reaction continues, red coloring indicating the presence of CO+2 ions may be observed in the supernatant liquid, and this coloring is removed by adding alkali from the second time onwards. In addition, as shown in Example IK below, the tendency for the coercive force to increase with heating time continues for a longer time, and the multi-stage precipitation reaction by the divided addition method of the present invention increases the coercive force with respect to the amount of Co added. It has been confirmed that the saturation value increases.

These facts are considered to be related to the precipitation of co+2 ions in the reaction solution due to the partial addition of alkali and the form of fermentation and decomposition in the reaction solution.

In the method of the present invention explained above, the conventional method after drying (
Japanese Patent Publication No. 47-27719, Japanese Patent Publication No. 49-119196
No. 1, U.S. Pat. No. 3,725,126, etc.).
Although it is possible to obtain a ferromagnetic iron oxide having a high coercive force without the need for heat treatment (approximately 200 to 500'C), it is also possible to further increase the coercive force by carrying out this heat treatment.

The ferromagnetic iron oxide obtained by the method of the present invention is used for various devices, but especially when used for magnetic recording media, it can be manufactured with good properties.

When manufacturing a magnetic recording medium, by a conventionally known method,
The ferromagnetic iron oxide obtained by the method of the present invention is mixed and dispersed with a binder and a fabric additive, and if necessary, additives such as a dispersant, a lubricant, an abrasive, an antistatic agent, etc. are mixed, It is applied onto a non-magnetic support or a non-magnetic support having a punctured layer, and dried while being oriented in a magnetic field.

The obtained magnetic recording medium is slit, cut, punched, etc. as necessary to form tapes, sheets, disks, cards, etc.
Use the drum.

Example 1 200 g of Bertolide iron oxide (FeOx, x=1.4
5: Fe+3/Fe+2=9/1: Average particle length: 0.5μmyμmization: 8/L Coercive force (He): 3
98Qe was dispersed in 2 tons of water.

While stirring, 100 mt of alkaline hydroxide solution was added, stirring was continued for 30 minutes, and then 100 mt of co+
2) An aqueous solution containing D ions was added and stirring continued for 30 minutes.

Alkaline hydroxide solution Sodium hydroxide 240g (water 6゜Omt Co+2 ion-containing water solution Cobalt sulfate (CoSO4・7H20) 20g water
soom, /.

This operation of adding the alkaline hydroxide solution and the Co+2 ion-containing aqueous solution was repeated 4 times, and finally 11C100m, 1 of the alkali hydroxide solution was added, the temperature was raised, and the water was boiled for 4 hours (approximately 100℃).
) was processed.

After thoroughly washing with water, it was separated and dried.

This sample was designated as AI, and a vibrating sample magnetometer (VSM-II) was used.
The magnetic properties were measured using an external magnetic field of 5 KOe using a type I (manufactured by Toei Kogyo).

The coercive force is shown in Table 2 below. Example 2 Example IJI - Co-containing ferromagnetic iron oxide ( Samples 2, 3, 4.5 and 6) were obtained.

Actual coercive force of samples A2-6! II! It was measured in the same manner as Jl and is shown in Table 2 below.

From the above results, it is confirmed that the Co-containing ferromagnetic iron oxide produced by the multi-stage precipitation reaction of the present invention has a higher coercive force than that produced by the conventional method. Example 3 200ml1Vc of the co+2 ion-containing aqueous solution of Example 1
10.4 ji manganese sulfate (MnSO4H20)
was dissolved to prepare a water-vinegar solution A containing Co+2 and M n +'' ions.

This aqueous liquid containing co+2 and ※※Mn+2 ion-containing aqueous liquid Example 1
Ferromagnetic iron oxide containing Co and Mn was produced in the same manner as described above.

Let it be sample A7. Comparative Example 2 As a water solution containing CO+2 and Mn+2 ions, a water solution with the following composition was used, and Co and Mn were added in the same manner as in Example 3 at the times and amounts shown in Table 4 below. Ferromagnetic iron oxide was produced.

Let it be sample A8.

■Tate @ Water solution containing co+2 and Mn+2 ions Cobalt sulfate (CoSO4・7H20) 20g Manganese sulfate (MnS04・H2O) 10.4g Water
The magnetic properties of these samples/I67 and A8 were measured in the same manner as in Example 1, and the results shown in Table 5 below were obtained.

From these results, it was confirmed that even when using the split precipitation method of the present invention, better properties can be obtained when Mn is added in the latter half of the addition step.

The Mn contained in iron oxide in Samples 7 and 1 was thought to be effective in improving the erasing characteristics of magnetic tapes when they were manufactured, and the process for Sample A7 was better than that for Sample A8. It was confirmed that the decrease in coercive force was small, and it was possible to control the magnitude of coercive force by adjusting the timing of addition of cations.

Example 4 (Hereinafter, all parts indicate parts by weight) The erasing characteristics as a magnetic tape were determined by the uniformity of the coercive force of the ferromagnetic powder, C
This property is largely dependent on the uniform deposition of ob and other metals onto the ferromagnetic powder and is discussed below.

Co-containing ferromagnetic iron oxides of samples A1 to 6, and sample A7,
The following composition was thoroughly kneaded using a ball mill to 300 parts each of the eight Co- and Mn-containing ferromagnetic iron oxides.

Vinyl chloride/vinyl acetate 40 parts (87:13
) Copolymer epoxy resin 30 parts silicone oil (
dimethylpolysiloxane) 5 parts toluene sulfo/acid ethylamide 7 parts ethyl acetate
250 parts methyl ethyl keto 7
250 parts of this composition [20 parts Dismodur L-75 (trade name, manufactured by Bayer AG, polyisocyanate compound, 75 wt. % ethyl acetate solution), mixed and dispersed uniformly to obtain a magnetic paint.

This paint was applied onto a polyethylene terephthalate film (thickness, 25 μm) to a dry thickness of 10 μm, oriented in a magnetic field at 10,000 e, dried, and slit to obtain a magnetic tape.

Erasure rate was recorded at standard input level +10dB, DN-3
42R-1 (DENONo, manufactured by Nippon Comvia) and an erase current of 0.5 AK.

The results are shown in Table 6.

These results show that the magnetic tape produced by the split precipitation method of the present invention exhibits a better erasing rate compared to conventional tapes, and when it contains Co and Mn, it shows an even better erasing rate. was confirmed.

The present invention is characterized in that a high coercive force can be obtained without requiring heat treatment at a high temperature of 300 to 500°C, but if necessary, the coercive force can be adjusted by adding this heat treatment. .

Because it is deposited multiple times, selected ions are deposited in layers, so it can also be used to control the diffusion of ions between adjacent layers to bring about new physical properties. It seems possible.

Claims (1)

[Claims] 1. Co+2 ions c are added to a suspension containing ferromagnetic iron oxide.
In a method for producing ferromagnetic iron oxide containing metals provided by these ions by adding an aqueous solution containing o+2 ions and other cations, and an azure alkaline solution, the alkaline vinegar solution and co+2 ions or Co ”:
1. A method for producing ferromagnetic powder, which comprises adding an aqueous solution containing ions and other cations alternately in at least two portions, and finally adding the alkaline solution.