JP3398430B2 - Manufacturing method of magnetic particle powder for magnetic recording - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to a manufacturing method excellent magnetic particles in a suitable dispersion as a high-density recording magnetic particles.

[0002]

2. Description of the Related Art In recent years, as recording and reproducing equipment has become smaller and lighter, there has been a demand for higher performance and higher recording density for magnetic recording media such as magnetic tapes and magnetic disks.

In order to improve the performance and the recording density of the magnetic recording medium, it is necessary to improve the residual magnetic flux density Br. The residual magnetic flux density Br of the magnetic recording medium depends on the dispersibility of the magnetic particle powder in the vehicle, the orientation in the coating film, and the filling property.

Various attempts have been made to improve the dispersibility of magnetic particle powders, for example, JP-A-55-83207.
JP-A-57-56904, JP-A-58-
No. 161725, Japanese Patent Laid-Open No. 59-23505,
JP-A-60-217529, JP-A-61-639
21 and JP-A-62-89226, there is a method of modifying the particle surface by coating the particle surface of the magnetic particle powder with a Si compound or an Al compound.

Further, for example, Japanese Patent Laid-Open No. 63-161522.
As described in Japanese Patent Application Laid-Open No. 2004-242242, a coating made of a Si compound is formed on the surface of magnetic particle powder, a coating made of an Al compound is formed thereon, and a coating made of a Si compound is formed thereon. There is a method of making the magnetic powder.

Further, as a method of coating the particle surface of the magnetic particle powder with a compound other than the Si compound and the Al compound, for example, JP-A-58-60506 (Cu, Ag, A) is used.
l, Ti, Zr, Sn, V, Nb, Ta, Sb, Cr,
Method of coating Mo, W, Ni, etc.), JP-A-59-10
No. 3310 (Cu, Al, Ti, Zr, Sn, V,
Nb, Sb, Cr, Mo, W, Ni and the like), JP-A-63-303817 (Si, Al,
Ca, Ti, V, Mn, Ni, Zn, P, etc.), JP-A-2-280301 (Zn, Si, A)
1, Ga, Zr, Sb, Ti, V, Mg, Ba and the like) and the like.

[0007]

Magnetic particle powders having excellent dispersibility are currently most demanded, but it is said that particles having excellent dispersibility are obtained by any of the above-mentioned known methods. It's difficult.

The reason why particles having excellent dispersibility have not yet been obtained by the known method is, for example, "Magnetic paint from the viewpoint of researchers of magnetic recording materials" (powder powder metallurgy "No. 7").
Annual Ferrite Summer Seminar Lecture Summary "(1972)
In general, obtaining a high degree of dispersion is a very difficult problem even in the case of ordinary non-magnetic pigments. Makes the phenomenon even more complicated because of ...
As described above, the magnetic particle powder forms an aggregate due to the interaction due to magnetism, and therefore the surface is coated with the aggregate as it is.

Particularly, in the case of hexagonal ferrite particle powder having an easy axis of magnetization in the direction perpendicular to the plate surface, the particles are strongly aggregated by the interaction due to magnetism, and the aggregated particles are obtained only by mechanical treatment. It is difficult to separate into individual particles of.

Regarding the dispersibility of the magnetic particle powder,
For example, Techno System Co., Ltd., "Elucidation of Dispersion / Agglomeration and Applied Technology" (1992), p. 505, "... Magnetic powder in a system containing a polymer-solvent as a binding dispersant as a main component" , Prepare a magnetic paint that is stably dispersed.
Using it, a uniform coating thin film is formed on the substrate. Therefore, the performance as a recording medium is greatly influenced by the dispersion stability. "..."
It is how to disperse the magnetic particle powder in the polymer resin, and many studies have been made on improving the dispersibility for that purpose.

On the other hand, for the evaluation of dispersibility, for example,
As mentioned above, "Elucidation of Dispersion / Agglomeration and Applied Technology", pages 94 to 96, "... Many natural and synthetic polymers adsorb on the surface of colloidal particles to form a thick adsorption layer, so that the stability of dispersion system It has a great effect on the properties ..... Molecular weight of polymer (M)
And the saturated adsorption amount (As), the following relationship is generally established (Applicant: Note: Formula 1 below).

[Equation 1] Here, K ₁ and α are constants peculiar to the system, and particularly α is called a molecular weight-dependent parameter, and 0 to 1 depending on the structure of the adsorption layer.
Change. When α = 1, the polymer is adsorbed at the molecular end, and As is proportional to the molecular weight (M). In this system, the polymer forms the thickest forested adsorption layer on the particle surface, and therefore exhibits a strong steric repulsion effect, which more effectively contributes to the stability of the dispersion system. .. can be represented by a molecular weight-dependent parameter α (hereinafter referred to as α).

Α of the magnetic particle powder obtained so far
Was measured. As a result, the above-mentioned JP-A-55-83207, JP-A-57-56904 and JP-A-58-60.
506, JP-A-58-161725, JP-A-59-23505, and JP-A-60-21729.
JP, JP 61-63921 and JP 62.
When the particle surface of the magnetic particle powder is coated with a Si compound or an Al compound by a publicly known method such as JP-89226-A, α is about 0.40 to 0.45, and these coating treatments are not performed. Α of the magnetic particle powder is 0.28 to
It was found to be about 0.34.

The above-mentioned Japanese Patent Laid-Open No. 63-161522, Japanese Patent Laid-Open No. 58-60506, Japanese Patent Laid-Open No. 59-103310, Japanese Patent Laid-Open No. 63-303817.
In the case of Japanese Patent Laid-Open No. 2-280301 and Japanese Patent Laid-Open No. 2-280301,
α was about 0.40 to 0.45.

Further, when the magnetic tape is used, the mechanical strength may be lowered or a failure due to the friction coefficient may occur. For example, “Magnetic tape-friction wear of head running system” published by Engineering Information Center Publishing Department Factors and Countermeasures for Trouble -Comprehensive Technical Data- "(1987), page 169," ... Strength of magnetic layer surface (hardness to scratches) The higher the strength, the smaller the dropout increase with respect to the number of times of use. "..." on page 169 and "..." in the magnetic recording system, the magnetic tape runs while contacting with the head or a fixed guide. The magnitude of the friction coefficient of the contact portion between the magnetic tape and the device runs. It directly affects sex .... "

Generally, in order to improve the durability of the magnetic tape, an abrasive or a lubricant is added in the production of the magnetic tape.

Although adding an appropriate amount of an abrasive or a lubricant has the effect of improving durability, if the amount added is too large, the electromagnetic conversion characteristics of the magnetic tape may be impaired.
It can even make it less durable. Therefore, the amount of the abrasive or lubricant used is naturally limited.

The present inventor can improve the durability of the magnetic tape by modifying the particle surface of the magnetic particle powder, thereby reducing the amount of abrasive or lubricant used. I thought about it and worked on improvement.

Therefore, the present invention is more excellent in dispersibility,
It is a technical problem to provide a method for producing magnetic particle powder , which has a large magnetic recording medium and has excellent durability by improving mechanical strength and reducing a friction coefficient when used as a magnetic recording medium. To do.

[0019]

The above technical problems can be achieved by the present invention as follows. That is, the present invention, the pH value of the suspension was 10 or more by adding an alkaline aqueous solution to an aqueous suspension containing the magnetic particles, the magnetic particles in the suspension
The total amount of Al equivalent and SiO ₂ equivalent of the child is 0.01 to
5.0 wt% Al or Si or Al and Si and Z
An aqueous solution containing one or more selected from r, Ti, Hf, and Mo is added, and the pH value of this solution is adjusted to near neutral in 1 to 10 minutes while stirring to obtain Al or Si or After rapid precipitation of hydroxide ultrafine particles of Al and Si and one or more selected from Zr, Ti, Hf and Mo, the magnetic particles in the liquid are filtered out together with the hydroxide ultrafine particles to obtain magnetic properties. A mixture of particles and hydroxide ultrafine particles is obtained, and the mixture is washed with water and dried, and then the mixture is compacted and pulverized by an edge runner to form Al or Si or Al and Si on the surface of the magnetic particles. Ultrafine oxide particles or ultrafine hydroxide particles containing Zr, T
Method for producing magnetic particle powder for magnetic recording, which comprises fixing one or more oxide ultrafine particles or hydroxide ultrafine particles selected from i, Hf, and Mo to an aqueous suspension containing magnetic particles Alkaline aqueous solution is added to
The H value is set to 10 or more, and the suspension is added to the magnetic particles.
0.01 to 5.0 weight in total of Al and SiO ₂
% Al or Si or Al and Si and Zr, T
An aqueous solution containing one or more selected from i, Hf, and Mo is added, and the pH value of the solution is adjusted to 1 to 1 with stirring .
Adjust to near neutral in 10 minutes Al or Si or A
l and Si and one or more hydroxide ultrafine particles selected from Zr, Ti, Hf, and Mo are rapidly precipitated, and then the magnetic particles in the liquid are separated by filtration together with the hydroxide ultrafine particles to obtain magnetic properties. In a method for producing magnetic particle powder, which comprises obtaining a mixture of particles and hydroxide ultrafine particles, washing and drying the mixture, and then subjecting this mixture to compaction pulverization with an edge runner, the method comprising the magnetic particles The operation of adding an alkaline aqueous solution to the aqueous suspension to adjust the pH value of the suspension to 10 or more to the operation of consolidating and crushing the mixture with an edge runner is repeated at least twice or more to obtain the magnetic particles. Oxide ultrafine particles or ultrafine oxide hydroxide particles containing Al or Si or Al and Si and one or more kinds of oxidation selected from Zr, Ti, Hf and Mo on the particle surface A method for producing magnetic particle powder for magnetic recording, which comprises fixing ultrafine particles or hydroxide ultrafine particles, and adding an aqueous alkaline solution to an aqueous suspension containing magnetic particles to adjust the pH value of the suspension to 10 or more. And in the suspension
The total amount of Al equivalent and SiO ₂ equivalent to the magnetic particles
Add 0.01 to 5.0% by weight of Al or Si or an aqueous solution containing Al and Si and adjust the pH value of this solution to near neutral in 1 to 10 minutes while stirring to obtain Al or S.
After rapidly precipitating hydroxide ultrafine particles of i or Al and Si, the magnetic particles in the liquid are separated by filtration together with the hydroxide ultrafine particles to obtain a mixture of magnetic particles and hydroxide ultrafine particles. After washing and drying, the mixture is compacted and pulverized by an edge runner, and then the compacted and pulverized magnetic particles are used to prepare an aqueous suspension containing magnetic particles. The pH value of the suspension is adjusted to 10 or more by adding an aqueous solution, and
An aqueous solution containing one or more selected from r, Ti, Hf and Mo is added, and the pH value of this solution is adjusted with stirring.
Adjust to near neutral in 1-10 minutes, Zr, Ti, Hf,
A mixture of magnetic particles and hydroxide ultrafine particles obtained by rapidly precipitating one or more hydroxide ultrafine particles selected from Mo, and then filtering the magnetic particles in the liquid together with the hydroxide ultrafine particles. After washing and drying this mixture, the mixture is subjected to consolidation crushing treatment with an edge runner to form Al, Si or A on the particle surface of the magnetic particles.
and fixing ultrafine oxide particles or ultrafine hydroxide particles containing 1 and Si to one or more oxide ultrafine particles or ultrafine hydroxide particles selected from Zr, Ti, Hf and Mo. A method for producing magnetic particle powder for magnetic recording and an aqueous alkaline solution are added to an aqueous suspension containing magnetic particles to adjust the pH value of the suspension to 10 or more.
An aqueous solution containing one or more selected from r, Ti, Hf and Mo is added, and the pH value of this solution is adjusted with stirring.
Adjust to near neutral in 1-10 minutes, Zr, Ti, Hf,
A mixture of magnetic particles and hydroxide ultrafine particles obtained by rapidly precipitating one or more hydroxide ultrafine particles selected from Mo, and then filtering the magnetic particles in the liquid together with the hydroxide ultrafine particles. After washing and drying this mixture, the mixture is subjected to compaction crushing treatment with an edge runner, and then the magnetic particles subjected to the compaction pulverization treatment are used to prepare an aqueous suspension containing magnetic particles. the pH value of the suspension was 10 or more by adding an alkaline aqueous solution to the suspension, Al terms and in terms of SiO ₂ and relative to the magnetic particles in the suspension
Of 0.01 to 5.0% by weight of Al or Si or an aqueous solution containing Al and Si is added and stirred,
Adjust the pH value of this solution to near neutral in 1-10 minutes
l or Si or Al and Si hydroxide ultrafine particles are rapidly precipitated, and then the magnetic particles in the liquid are separated by filtration together with the hydroxide ultrafine particles to obtain a mixture of magnetic particles and hydroxide ultrafine particles. This mixture is washed with water and dried, and then the mixture is subjected to consolidation crushing treatment with an edge runner to obtain one or more oxide ultrafine particles selected from Zr, Ti, Hf, and Mo on the surface of the magnetic particles. A method for producing magnetic particle powder for magnetic recording, comprising fixing ultrafine hydroxide particles and ultrafine oxide particles or ultrafine oxide particles containing Al or Si or Al and Si.

Next, various conditions for carrying out the present invention will be described.

As the magnetic particle powder in the present invention, magnetic iron oxide particle powders such as maghemite particles, magnetite particles, and beltride compound particles which are intermediate oxides of maghemite and magnetite, and these magnetic iron oxide particles other than Fe can be used. Hexagonal ferrite particles such as particle powders containing different metals such as Co, or particle powders obtained by depositing Co on these magnetic iron oxide particles, metal magnetic particle powders containing iron as a main component, and plate-like Ba ferrite fine particles. Any of powder and the like can be used.

In the present invention, an alkaline aqueous solution is added to an aqueous suspension containing magnetic particles to adjust the pH value of the suspension to 10 or more, and then an aqueous solution containing Al, Si, Zr, Ti, Hf, Mo and the like. The reason for adding is to use the electrical repulsion between the magnetic particles in the aqueous suspension to sufficiently and uniformly mix them.

As the alkaline aqueous solution for adjusting the pH value to 10 or more, an aqueous solution of sodium hydroxide, potassium hydroxide, aqueous ammonia or the like can be used.

As the aqueous solution containing Al, an aqueous solution of alkali aluminate such as sodium aluminate and potassium aluminate, aluminum salt such as aluminum sulfate, aluminum chloride and aluminum nitrate can be used.

The amount of the compound containing Al added is 0.01 to 5.0% by weight in terms of Al based on the magnetic particle powder. If it is less than 0.01% by weight, the effect of the present invention cannot be obtained. When the amount exceeds 5.0% by weight, the desired effect of the present invention can be obtained, but the saturation magnetization is lowered due to the increase of the oxide ultrafine particles or hydroxide ultrafine particles containing Al that are not involved in magnetism, which is preferable. Absent. In consideration of the dispersibility and saturation magnetization of the magnetic particle powder, 0.05 to 3.
0% by weight is preferred.

As the aqueous solution containing Si, an aqueous solution of sodium silicate, potassium silicate, colloidal silica, No. 3 water glass or the like can be used.

The addition amount of the compound containing Si is 0.01 to 5.0% by weight in terms of SiO ₂ with respect to the magnetic particle powder.
Is. If it is less than 0.01% by weight, the effect of the present invention cannot be obtained. When the amount exceeds 5.0% by weight, the desired effect of the present invention can be obtained, but the saturation magnetization is reduced due to an increase in the amount of oxide-containing ultrafine particles or Si-containing oxide ultrafine particles not involved in magnetism. Absent. Considering the dispersibility and saturation magnetization of the magnetic particle powder,
2.0% by weight is preferred.

[0028] In the case of adding a mixed aqueous solution containing Al and Si in the present invention, with respect to magnetic granules element, 0.01 to 5.0 wt% in a total amount of Al in terms and in terms of SiO _2, preferably 0 0.1 to 3.0% by weight.

As the compounds such as Zr, Ti, Hf and Mo used in the present invention, water-soluble salts such as sulfate, chloride, nitrate and acetate of each element can be used.

The amount of each compound added is 0.01 to 5.0% by weight in terms of each element based on the magnetic particle powder.
If it is less than 0.01% by weight, the effect of the present invention cannot be obtained. Even when the amount exceeds 5.0% by weight, the effect of the present invention can be obtained, but the saturation magnetization is lowered due to an increase in the number of oxide ultrafine particles or hydroxide ultrafine particles not involved in magnetism, which is not preferable. Considering the dispersibility and saturation magnetization of the magnetic particle powder, 0.05 to 3.0% by weight is preferable.

Al, Si, Zr, Ti, Hf, Mo
The use of each of the above compounds as an aqueous solution is for sufficiently and uniformly mixing in a magnetic particle suspension having a pH value of 10 or more, but each compound is added as a crystalline salt,
It can also be sufficiently dissolved and mixed in the suspension.

In the present invention, an aqueous solution containing each of the above compounds is added to a magnetic particle suspension having a pH value of 10 or more, and the suspension is stirred to rapidly adjust the pH to near neutral (pH
By adjusting to 6.5-8.5), Al, Si,
Substantially all of Zr, Ti, Hf, Mo, etc. are rapidly precipitated as hydroxide ultrafine particles to obtain a mixture of magnetic particles and hydroxide ultrafine particles.

The time for rapid precipitation is in the range of 1 to 10 minutes. When it exceeds 10 minutes, the above-mentioned hydroxides may be formed in layers on the surface of the magnetic particles. Therefore, it is filtered off immediately after rapid precipitation. It may be less than 1 minute, but it takes about 1 minute to deposit the hydroxide ultrafine particles and sufficiently mix them.

As the acid for adjusting pH, sulfuric acid, hydrochloric acid, acetic acid, nitric acid, carbon dioxide gas or the like can be used.

The mixture of the magnetic particle powder and the ultrafine hydroxide particles may be filtered, washed with water and dried according to a conventional method.

As the edge runner used for the consolidation and crushing treatment in the present invention, "Sandmill" manufactured by Matsumoto Foundry Co., Ltd. or "Mix Mahler" manufactured by Shinto Kogyo Co., Ltd. can be used.

Edge runner line weight is 15-80kg
/ Cm, more preferably 30 to 60 kg / cm. If it is less than 15 kg / cm, the mechanochemical effect cannot be obtained because the shearing force due to grinding is too weak. 8
If it exceeds 0 kg / cm, the shearing force due to milling is too strong, and the particles themselves may be destroyed. The treatment time is 15 to 120 minutes, preferably 3
It is 0 to 60 minutes.

In the present invention, the operation until the mixture consisting of the magnetic particles and the hydroxide ultrafine particles is pulverized by the edge runner may be repeated at least twice, preferably 2 to 5 times. If the number of times exceeds 5, the effect can be obtained, but the effect tends to be saturated, and it is not industrial.

[0039]

In the present invention, Al or Si or an oxide or hydroxide containing Al and Si and Z are formed on the surface of the particles.
The α of the formula 1 is fixed to one or more oxides or hydroxides selected from r, Ti, Hf, and Mo.
Magnetic powder for magnetic recording comprising 50 or more magnetic particles, and when used as a magnetic tape, a magnetic recording medium having extremely excellent durability can be obtained.

Specifically, α of the magnetic particle powder composed of hexagonal ferrite particles is about 0.50 to 0.70, Co
Α of the magnetic particle powder composed of adhered magnetic iron oxide particles is 0.
It is about 55 to 0.70, and α of the magnetic particle powder composed of magnetic iron oxide particles of maghemite particles, magnetite particles, and beltride compound particles that are intermediate oxides of maghemite and magnetite is about 0.55 to 0.70. Is.

The inventor of the present invention was previously described in JP-A-55-83207.
JP-A-57-56904, JP-A-58-
No. 161725, Japanese Patent Laid-Open No. 59-23505,
JP-A-60-217529, JP-A-61-639
The reason why α of the magnetic particle powder coated by the known method described in JP-A No. 21 and JP-A-62-89226 is as low as about 0.40 to 0.45 is S.
In order to coat the particle surface of the magnetic particles with the i compound or the Al compound, the hydroxide of the compound was deposited over a relatively long time and uniformly coated. We suspected that the number of polymer adsorption points on the surface of magnetic particles was small.

Further, for example, JP-A-63-161522.
Japanese Patent Laid-Open No. 58-60506, Japanese Patent Laid-Open No. 59-103310, Japanese Patent Laid-Open No. 63-3038.
In the case of JP-A No. 17 and JP-A No. 2-280301, α of the coated magnetic particle powder is 0.40 to 0.4.
The reason for the low value of about 5 is that in order to coat the surface of the magnetic particles with a Si compound, an Al compound or one or more compounds selected from Zr, Ti, Hf and Mo, the hydroxylation of the compound is performed. Since the substance was deposited over a relatively long period of time and uniformly coated, it was considered that the number of adsorption points of the polymer on the particle surface of the magnetic particles was small when dispersed in the polymer resin.

Therefore, a method for increasing the thickness of the adsorption layer of the polymer by increasing the adsorption points of the polymer on the surface of the magnetic particles as much as possible was examined.

To this end, Al or Si or Al
And Si oxide ultrafine particles or hydroxide ultrafine particles and Z
It is considered that one or more kinds of oxide ultrafine particles or hydroxide ultrafine particles selected from r, Ti, Hf, and Mo should be adsorbed on the surface of the magnetic particles as much as possible and chemically. It was

Therefore, Al or Si or Al and Si hydroxide ultrafine particles and Z are suspended in a suspension containing magnetic particles.
Rarely deposited and mixed with one or more kinds of hydroxide ultrafine particles selected from r, Ti, Hf, and Mo, and the mixture is subjected to a consolidating treatment to cause the mechanochemical effect on the surface of the magnetic particles. Al or Si or Al and Si oxide ultrafine particles or hydroxide ultrafine particles and Z
Since one or more kinds of oxide ultrafine particles or hydroxide ultrafine particles selected from r, Ti, Hf, and Mo could be fixed, α of the magnetic particle powder is increased to 0.50 or more. I was able to. This is considered to be the result of increasing the number of polymer adsorption points on the particle surface.

On the particle surface of the magnetic particles, Al or Si or ultrafine oxide particles of Al and Si or ultrafine hydroxide particles and one or more oxide ultrafine particles selected from Zr, Ti, Hf and Mo, or When a magnetic recording medium obtained by coating and drying a magnetic particle powder obtained by fixing ultrafine hydroxide particles on a non-magnetic support together with a binder resin, etc., a binder resin is used. Not only does it have better compatibility with and improved dispersibility, but it can also improve the mechanical strength (scratch characteristics) of the coating film obtained by applying the coating composition and curing it, and further reduce the friction coefficient. As a result, extremely excellent running durability could be obtained.

This shows that a magnetic recording medium having extremely excellent practicality can be obtained. As described above, the present inventors can improve the durability of the magnetic tape by modifying the particle surface of the magnetic particle powder, thereby reducing the use of abrasives and lubricants. It is the result of efforts to improve it by thinking that it can be done, and we investigated the relationship between the durability of magnetic particle powder and magnetic tape,
This is a result of finding that the particle surface of the magnetic particle powder has a great influence on the durability of the magnetic tape.

The reason for this is that the nature of the surface of the magnetic particles exposed on the outermost surface of the magnetic tape when used as a magnetic recording medium affects the scratch and friction characteristics of the magnetic tape. On the surface of the magnetic particles of Al, Si, or ultrafine particles of oxides or hydroxides of Al and Si, and ultrafine particles of one or more oxides selected from Zr, Ti, Hf, and Mo or ultrafine particles of hydroxide. The presence of ultra-fine particles improves abrasion resistance due to sliding with the magnetic head, and since it also functions as a solid lubricant, it can also reduce the friction coefficient, resulting in extremely excellent running performance. I think that we were able to obtain durability.

On the other hand, since the mixture of the magnetic particles and the ultrafine hydroxide particles is present by interaction with each other, filtration, washing with water and drying can be carried out as usual, and workability is particularly deteriorated. There is no such thing.

Incidentally, when a dispersant is added to the iron oxide magnetic powder slurry disclosed in JP-A-55-157216 to give a mechanical shearing force, and JP-A-2-188.
In the case of dry mixing in which the silane coupling agent disclosed in Japanese Patent No. 429 is added, the effect of the present invention cannot be obtained.

[0051]

The present invention will be described below with reference to Examples and Comparative Examples.

[0052] Evaluation of the dispersion of the present invention, the number 1 α
The value of α is determined by the binder (M
= 15000, 28000, 42000) , the saturated adsorption amount (As) of each binder to the magnetic particle powder is measured by a conventional method, and the obtained As and M are plotted in a logarithmic table to obtain a straight line. The relationship was obtained, and the value of α was calculated from the slope of the straight line.

Al, Si, Z coated with magnetic particle powder
The amount of each element of compounds such as r, Ti, Hf, and Mo was measured by fluorescent X-ray analysis.

The magnetic characteristics of the magnetic particle powder are obtained by using an "oscillating sample magnetometer VSM-3S-15" (manufactured by Toei Industry Co., Ltd.) in an external magnetic field of 10 KOe (however, when magnetic iron oxide particles are used). Is a value measured under 5 KOe), and the various characteristics of the magnetic tape have an external magnetic field of 10 KOe (however, 5 when Co-deposited magnetic iron oxide particles and magnetic iron oxide particles are used).
It is the result measured under KOe).

The surface gloss of the coating film is measured by a gloss meter.
Incident angle of 45 with "UGV-5D" (manufactured by Suga Test Instruments Co., Ltd.)
It is a value measured in °, and the value when the standard plate gloss is 86.3% is shown in%.

The surface roughness Ra is "Surfcom-57".
5A "(manufactured by Tokyo Seimitsu Co., Ltd.) was used to measure the center line average roughness of the coating film.

The friction coefficient of the coating film is "autograph"
(Manufactured by Shimadzu Corporation) was used to determine the friction coefficient between the coated surface and the base film from the relationship between tensile stress and load. The lower the friction coefficient, the better the coating is.

The running durability is "Media Durab".
“Ility Tester MDT-3000” (St
Einberg Associates), load 200 gw, relative speed between head and tape 16
The evaluation was made by the actual moving time at m / s. The longer the actual movable time, the better the running durability.

The scratch characteristics were evaluated by visually observing the surface of the tape after running with a microscope and visually checking for scratches.
The grade was evaluated. A: No scratches B: Some scratches C: Scratches D: Severe scratches

<Surface Treatment of Magnetic Particle Powder> Examples 1-8, Comparative Examples 1-6;

Example 1 The particle size was 0.05 μm, the plate ratio was 5.0, and the coercive force was 7
Using 36 Oe Co and Ti substitutional plate-like Ba ferrite particles, 6 kg of the particles were mixed with water and stirred,
PH value of 11.4 with 0.1 mol / l NaOH aqueous solution
Was added until. After stirring and mixing the mixed suspension, a 0.5 mol / l sodium aluminate aqueous solution 222
0 ml (corresponding to 0.5 wt% in terms of Al with respect to the magnetic particle powder) was added and stirred and mixed. Next, the pH of the suspension was adjusted to 7.0 by adding 0.1 mol / l HCl aqueous solution while stirring. The time required at that time was 5 minutes. Immediately, it was separated by filtration, washed with water and dried to obtain a magnetic particle powder. 5 kg of magnetic particle powder obtained
Was put into an edge runner "MPUV-2 type" (manufactured by Matsumoto Foundry Iron Works Co., Ltd.) and subjected to consolidation crushing for 60 minutes with a line load of 30 kg / cm. The obtained magnetic particle powder had a particle diameter of 0.05 μm, a plate ratio of 5.0, and a coercive force of 73.
8Oe and α were 0.57.

Further, 4.5 kg of the obtained magnetic particle powder was again mixed with water and stirred, and then a 0.1 mol NaOH aqueous solution was added to adjust the pH to 10.5. Then 0.5mo
2470 ml of 1 / l zirconium sulfate aqueous solution (corresponding to 2.50 wt% in terms of Zr with respect to magnetic particle powder)
Was added and stirred and mixed to obtain a suspension. Then, the suspension was adjusted to pH 7.0 with 0.1 mol / l HCl aqueous solution while stirring. The time required at that time is 5
It was a minute. Immediately, it was separated by filtration, washed with water and dried to obtain a magnetic particle powder. 4 kg of the obtained magnetic particle powder was put into an edge runner "MPUV-2 type" (manufactured by Matsumoto Foundry Iron Works Co., Ltd.) and compacted and pulverized for 60 minutes at a linear load of 60 kg / cm. The particle size of the obtained magnetic particle powder is 0.
05μm, plate ratio is 5.0, coercive force is 748O
e and α were 0.64.

Examples 2-8, Comparative Examples 1-6 Types of magnetic particle powders, types of compounds to be added and addition amounts,
Magnetic particle powders were obtained in the same manner as in Example 1 except that the time required for addition / stirring, the linear load and time for consolidation treatment and the number of treatments were variously changed.

Tables 1 to 4 show the main production conditions and various characteristics of the obtained magnetic particle powder in each example.

[0065]

[Table 1]

[0066]

[Table 2]

[0067]

[Table 3]

[0068]

[Table 4]

<Production of magnetic tape> Reference Examples 1 to 14

Reference Example 1 Using the magnetic particle powder obtained in Example 1, first, the magnetic particle powder was mixed with a binder resin and a solvent, and the solid content was 76% by weight using a plastomill for 30 minutes. Kneaded
Thereafter, a predetermined amount of the kneaded product was taken out, added to a glass bottle together with an abrasive, carbon black, glass beads and a solvent, and mixed and dispersed for 6 hours with a paint conditioner.

Then, a lubricant and a curing agent were added, and the mixture was further mixed and dispersed for 15 minutes. The composition of the obtained magnetic paint was as follows. Magnetic particle powder 100 parts by weight Vinyl chloride-vinyl acetate copolymer resin having sodium sulfonate group 10 parts by weight Polyurethane resin having sodium sulfonate group 10 parts by weight Abrasive 10 parts by weight Carbon black 3 parts by weight Lubricant 2.5 parts by weight Parts curing agent 5 parts by weight cyclohexanone 52.5 parts by weight methyl ethyl ketone 130.5 parts by weight toluene 78.3 parts by weight

The obtained magnetic paint was applied on a polyethylene terephthalate film having a thickness of 14 μm to a thickness of 15 μm using an applicator, then oriented in a magnetic field of 5 KOe and dried to obtain a sheet sample piece. It was The obtained sheet sample piece was subjected to calendering treatment, followed by curing reaction at 60 ° C. for 24 hours and slitting into a 0.5 inch width to obtain a magnetic tape. The obtained magnetic tape had an Hc of 795 Oe, a squareness ratio of 0.83, and a gloss of 185.
%, Surface roughness Ra is 6.0 nm, friction coefficient is 0.28,
The running durability time was 20.7 minutes, and the scratch resistance was A.

Reference Examples 2 to 14 Magnetic tapes were obtained in the same manner as in Reference Example 1 except that the kind of the obtained magnetic particle powder was changed variously.

Tables 5 and 6 show various characteristics in each reference example.

[0075]

[Table 5]

[0076]

[Table 6]

[0077]

INDUSTRIAL APPLICABILITY The magnetic particle powder according to the present invention is suitable for high density recording because it has excellent dispersibility as shown in the above-mentioned Examples.

When a magnetic recording medium is prepared by using the magnetic particle powder according to the present invention, the mechanical strength (scratch characteristics) is improved and the friction coefficient can be reduced, so that the running durability is extremely excellent. Can be obtained.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Norio Sugita               4-1-2 Funairinami Naka-ku, Hiroshima City, Hiroshima Prefecture               Toda Industry Co., Ltd. Creative Center

Claims (4)

(57) [Claims] 1. A by adding an aqueous alkali solution to an aqueous suspension containing the magnetic particles the pH value of the suspension was 10 or more, Al terms and in terms of SiO ₂ and relative to the magnetic particles in the suspension
Of 0.01 to 5.0% by weight of Al or Si or Al and Si, and an aqueous solution containing Si and one or more selected from Zr, Ti, Hf, and Mo are added, while stirring. The pH value of the liquid is adjusted to near neutral in 1 to 10 minutes, and Al or Si or Al and Si and Zr, Ti, H
After rapid precipitation of one or more hydroxide ultrafine particles selected from f and Mo, the magnetic particles in the liquid are separated by filtration together with the hydroxide ultrafine particles to obtain magnetic particles and hydroxide ultrafine particles. After washing and drying the mixture, the mixture is subjected to compaction crushing treatment with an edge runner to form Al or Si or oxide ultrafine particles or hydroxide containing Al and Si on the surface of the magnetic particles. A method for producing magnetic particle powder for magnetic recording, which comprises fixing ultrafine particles of an object and ultrafine particles of an oxide or ultrafine particles of one or more kinds selected from Zr, Ti, Hf and Mo. 2. An alkaline aqueous solution is added to an aqueous suspension containing magnetic particles to adjust the pH value of the suspension to 10 or more, and the suspension is subjected to Al conversion and SiO ₂ conversion for the magnetic particles.
Of 0.01 to 5.0% by weight of Al or Si or Al and Si, and an aqueous solution containing Si and one or more selected from Zr, Ti, Hf, and Mo are added, while stirring. The pH value of the liquid is adjusted to near neutral in 1 to 10 minutes, and Al or Si or Al and Si and Zr, Ti, H
After rapid precipitation of one or more hydroxide ultrafine particles selected from f and Mo, the magnetic particles in the liquid are separated by filtration together with the hydroxide ultrafine particles to obtain magnetic particles and hydroxide ultrafine particles. After obtaining a mixture consisting of, washing and drying the mixture,
In a method for producing magnetic particle powder, which comprises subjecting this mixture to compaction pulverization with an edge runner, an aqueous alkaline solution is added to an aqueous suspension containing the magnetic particles to adjust the pH value of the suspension to 10 or more. By repeating at least two times from the operation to the operation of consolidating and crushing the mixture with an edge runner, Al or Si or oxide ultrafine particles or hydroxide ultrafine particles containing Al and Si is added to the surface of the magnetic particles. Zr, Ti, H
A method for producing magnetic particle powder for magnetic recording, comprising fixing one or more oxide ultrafine particles or hydroxide ultrafine particles selected from f and Mo. 3. A pH value of the suspension is adjusted to 10 or more by adding an alkaline aqueous solution to an aqueous suspension containing magnetic particles, and the suspension is subjected to Al conversion and SiO ₂ conversion for the magnetic particles.
Of 0.01 to 5.0% by weight of Al or Si or an aqueous solution containing Al and Si is added and stirred,
Adjust the pH value of this solution to near neutral in 1-10 minutes
l or Si or Al and Si and hydroxide ultrafine particles of Si are rapidly precipitated, and then the magnetic particles in the liquid are separated by filtration together with the hydroxide ultrafine particles to obtain a mixture of magnetic particles and hydroxide ultrafine particles. After washing and drying this mixture, the mixture is compacted and pulverized by an edge runner, and then the compacted and pulverized magnetic particles are used to prepare an aqueous suspension containing magnetic particles. The pH value of the suspension is adjusted to 10 or more by adding an alkaline aqueous solution to the suspension, and one or two selected from Zr, Ti, Hf, and Mo is added to the suspension.
An aqueous solution containing at least one species is added and the pH value of this solution is adjusted to near neutral in 1 to 10 minutes with stirring to adjust Zr, T
After rapid precipitation of one or more hydroxide ultrafine particles selected from i, Hf and Mo, the magnetic particles in the liquid are separated by filtration together with the hydroxide ultrafine particles to obtain magnetic particles and hydroxide ultrafine particles. A mixture of and is obtained, and the mixture is washed with water and dried, and then the mixture is compacted and pulverized by an edge runner to form Al or Si on the surface of the magnetic particles.
Alternatively, selected from ultrafine oxide particles or ultrafine hydroxide particles containing Al and Si and Zr, Ti, Hf, or Mo 1
A method for producing magnetic particle powder for magnetic recording, which comprises fixing one kind or two or more kinds of oxide ultrafine particles or hydroxide ultrafine particles. 4. A pH value of the suspension is adjusted to 10 or more by adding an aqueous alkaline solution to an aqueous suspension containing magnetic particles, and the suspension is made of one selected from Zr, Ti, Hf, and Mo, or An aqueous solution containing two or more kinds is added, and while stirring, the pH value of this solution is adjusted to near neutral in 1 to 10 minutes, and Zr, T
After rapid precipitation of one or more hydroxide ultrafine particles selected from i, Hf and Mo, the magnetic particles in the liquid are separated by filtration together with the hydroxide ultrafine particles to obtain magnetic particles and hydroxide ultrafine particles. After obtaining a mixture consisting of, and washing and drying this mixture, the mixture is subjected to consolidation crushing with an edge runner, then using the magnetic particles subjected to the consolidation pulverization, an aqueous suspension containing magnetic particles. An alkaline aqueous solution was added to this suspension to adjust the pH value of the suspension to 10 or more, and the suspension was converted into Al and Si for the magnetic particles.
Add 0.01 to 5.0 wt% of Al or Si or an aqueous solution containing Al and Si in a total amount calculated as O ₂ and, while stirring, adjust the pH value of this liquid to near neutral in 1 to 10 minutes. A mixture of magnetic particles and hydroxide ultrafine particles obtained by controlling the rapid precipitation of Al or Si or hydroxide ultrafine particles of Al and Si, and then filtering the magnetic particles in the liquid together with the hydroxide ultrafine particles. After washing this mixture with water and drying it, the mixture is subjected to consolidation crushing treatment with an edge runner to obtain Zr, Ti, H on the surface of the magnetic particles.
f, one or more kinds of oxide ultrafine particles or hydroxide ultrafine particles selected from Mo and Al or Si or Al
A method for producing magnetic particle powder for magnetic recording, which comprises fixing ultrafine particles of oxide or ultrafine particles of hydroxide containing Si.