JPH10251561A - Preparation of magnetic coating and production of magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium of excellent quality and the production process for the magnetic coating that gives the above-stated magnetic recording medium. SOLUTION: In this production process for the magnetic coating, the materials for the magnetic coating are mixed with dispersing machines as kneader, roll mill, ball mill, sand mill or the like and the resultant mixture after completion of dispersion is irradiated with ultrasonic waves to effect homogeneous dispersion. The irradiation with ultrasonic waves can be repeated several times. The more repetition, the more improvement in the degree of dispersion and mixing. There is no particular limitation in the frequency of the ultrasonic waves, but 15kHz-20kHz are preferably employed. The materials for magnetic coating are mixed and dispersed and the mixture for the magnetic coating after completion of dispersion is irradiated with ultrasonic waves to disperse the mixture homogeneously. Then, the resultant homogeneously dispersed magnetic coating 3 is applied immediately after irradiation of the ultrasonic waves onto the nonmagnetic supporter to produce the objective magnetic recording medium. Thus, the magnetic recording medium having the high characteristics with the level the same as that of the produce produced by the high-pressure homogenizer can be produced by using a usual homogenizer. Thus, the time for washing and maintenance is saved and the operability and productivity of this process are improved than those of the conventional technology.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a magnetic paint and a method for producing a magnetic recording medium.

[0002]

2. Description of the Related Art For example, when a magnetic tape is manufactured, a magnetic powder or the like is uniformly dispersed in a binder solution and used as a magnetic paint. In order to mix and disperse such magnetic powder, a disperser such as a kneader, a roll mill, a ball mill, or a sand mill is generally used. Since the magnetic powder is a fine particle, it is easy for the particles to aggregate to form an aggregate, and the dispersibility is usually poor. For this reason, a method is used in which a magnetic powder, a dispersant or a binder is mixed and dispersed by a dispersing machine, and the mixture is subdivided into a shape close to the primary particles, and the binder is adsorbed on the magnetic powder, thereby producing a coating which is hardly aggregated and has a stable dispersion. Have been.

[0003]

However, when the prepared magnetic paint is stored with stirring (stirring storage), the re-agglomeration of the paint proceeds gradually, so that a filter or a high-speed rotary mixer or the like is used. Shear is constantly applied to minimize the generation of re-agglomerates. When a paint containing the above-mentioned aggregates and the like is applied to a substrate, fine defects on the surface of the magnetic layer due to the above-mentioned aggregates and the like cause a serious problem in quality.

In order to cope with such a problem, for example, a method in which a coating material subjected to a dispersion treatment by a high-pressure homogenizer is immediately applied to a substrate is adopted. However, the high-pressure homogenizer has many sliding parts due to its structure, and it takes time to clean when changing paint types, and it is necessary to replace parts by disassembly and cleaning and wear, which increases the attendant time on maintenance. I have.

At present, there is no effective means for solving such a problem. The present invention has been made to solve the above problems, and an object of the present invention is to provide a magnetic recording medium having excellent quality and to provide a method for producing a magnetic paint from which the recording medium can be obtained. That is. Another object of the present invention is to provide a method for preparing a magnetic paint which does not require much time for cleaning and maintenance of the homogenizer for a magnetic paint.

[0006]

The above object of the present invention is attained by the following constitution. That is, this is a method for producing a magnetic coating material in which a magnetic coating material is mixed, and the mixture for the magnetic coating material whose dispersion has been completed is irradiated with ultrasonic waves to be uniformly dispersed. The ultrasonic irradiation may be performed in one or more stages. The greater the number of stages, the better the degree of dispersion and mixing.

The frequency of the ultrasonic wave is not particularly limited, but is preferably 15 kHz to 20 kHz in consideration of the balance between heat generation, energy density and the number of shearing times. In the present invention, the magnetic coating material obtained by mixing the magnetic coating material and irradiating ultrasonic waves to the mixture for the magnetic coating material whose dispersion has been completed is uniformly dispersed by a non-magnetic support immediately after the ultrasonic irradiation. A method for manufacturing a magnetic recording medium to be applied on a body is also included.
In this way, a magnetic recording medium having characteristics comparable to that of a high-pressure homogenizer can be obtained with a normal homogenizer, and cleaning and maintenance of the homogenizer does not take much time, and the workability and productivity of manufacturing a magnetic recording medium are reduced to those of the prior art. It improves compared to.

[0008]

Embodiments of the present invention will be described below. It goes without saying that the present invention is not limited to the following examples. The sample was prepared by kneading raw materials having the following composition, and diluting the resulting paste to 43% by weight with a mixed solvent of methyl ethyl ketone, toluene and cyclohexanone for 2 hours using a disperser (stirring device). Thereafter, the mixture was dispersed in a sand mill for 1 hour, passed through a filter and filtered to obtain a final product. Thereafter, before application, 2 parts by weight of a curing agent such as isocyanate and 1 part by weight of a lubricant such as myristic acid were added.

Iron oxide magnetic powder 100 parts by weight PVC copolymer 11 parts by weight Polyurethane resin 4 parts by weight Phenoxy resin 3 parts by weight Silane coupling agent 2 parts by weight Alumina (0.5 μm) 2 parts by weight Carbon (0.06 μm) 1 part by weight Misty phosphoric acid 1 part by weight Methyl ethyl ketone Appropriate amount Toluene Appropriate amount Cyclohexanone Appropriate amount The magnetic paint prepared by the above composition and the above-mentioned method is applied to a 12 μm thick base film at a thickness of 6 μm by a coating apparatus via the apparatus shown in FIG. went.

An embodiment will be described below with reference to FIG. After the magnetic paint 3 in the stirring tank 2 having the paint stirring blades 1 is passed through the ultrasonic homogenizer 5 by the liquid feed pump 4,
The coating was performed on the base film by the coating device 6. In addition,
In this case, the ultrasonic homogenizer has one or two stages, but multiple stages can be connected in order to adjust to the desired dispersion, and the number of stages is not limited.

Example 1 One stage of ultrasonic homogenizer treatment, a frequency of 15 KHz
And the treatment flow rate of the paint was set between 0.2 and 1.2 liter / min. Example 2 One stage of ultrasonic homogenizer treatment, frequency 20 KHz
And the treatment flow rate of the paint was set between 0.2 and 2.0 liter / min. Example 3 Two steps of ultrasonic homogenizer treatment and a frequency of 20 KH
z, the processing flow rate of the paint was 2.0 liter / min.

The results of Examples 1, 2, and 3 and the characteristics of the treated product using only the high-pressure homogenizer are shown in Comparative Example 1, and the characteristics without the homogenizer treatment are also shown in Table 1. The squareness ratio R
For s, sample vibration magnetometer (VSM Toei Kogyo)
It measured using. The glossiness is an index of the dispersibility of the magnetic layer, and was measured by a gloss meter at an incident angle of 45 °.

[0013]

[Table 1] From this result, 0.5 liter / mi at 15 KHz.
At a processing flow rate of 1.4 liter / min or less at n and 20 KHz, characteristics equivalent to or higher than high pressure type can be obtained. In addition, although there are restrictions on the flow rate and characteristics, it is possible to adjust to a desired value by increasing the number of processing stages from the results of the third embodiment, and an alternative is possible.

[0014]

According to the present invention, a magnetic recording medium having characteristics equal to or higher than that of a high-pressure homogenizer can be obtained by optimizing the conditions in the ultrasonic homogenizer treatment. In addition, the time required for cleaning and maintenance of the homogenizer can be reduced, thereby improving workability and productivity.

[Brief description of the drawings]

FIG. 1 is a system diagram of a step of applying a magnetic paint.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Paint stirring blade 2 Stirring tank 3 Magnetic paint 4 Liquid feed pump 5 Ultrasonic homogenizer 6 Coating device

Claims (4)

[Claims] 1. A method for producing a magnetic paint, comprising mixing a magnetic paint material and uniformly irradiating the mixture for magnetic paint after dispersion with ultrasonic waves. 2. The method for producing a magnetic paint according to claim 1, wherein the irradiation of the ultrasonic wave is performed in one or more steps. 3. The method for producing a magnetic paint according to claim 1, wherein the irradiation of the ultrasonic wave is performed in one or more steps. 4. A magnetic paint obtained by mixing a magnetic paint material and uniformly dispersing the mixture for magnetic paint after the dispersion by irradiating an ultrasonic wave to the non-magnetic support immediately after the ultrasonic irradiation. A method for producing a magnetic recording medium, wherein the method is applied on the magnetic recording medium.