KR950006943B1 - Process for the preparation of magnetic paint - Google Patents

Abstract

The magnetic paint is composed of fine powders, such as ferromagnetic powder, an abrasive, an antistatic agent, and a binding resin solution and an organic solvent, is prepared by dispersing homogeneously the fine powders in the paint solution by contacting the magnetic paint to the horn of the ultrasonic generator which is installed around the sand grinder dispersing machine, ball mill or roll mill, and manufactured with PZT ceramic vibrator. The output of the ultrasonic generator is 5-10 kW per liter of paint, its frequency having the range of 1kHz-1MHz.

Description

Manufacturing method of magnetic paint

1 schematically shows the configuration of the ultrasonic dispersion device used in the present invention,

2 schematically shows the configuration of the main dispersion process using the ultrasonic dispersion apparatus for the practice of the present invention.

* Explanation of symbols for main parts of the drawings

1: Direction of magnetic paint 2: Conical horn

3: PZT Oscillator 4: Converter

5: nut 6: tube

7: stirring tank 8: ultrasonic dispersion device

9: sand grinder 10: pipe

11: pump

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a magnetic paint, and more particularly, to a method of dispersing and manufacturing a magnetic paint used for manufacturing a magnetic recording medium by using an ultrasonic generator.

The magnetic layer of the magnetic recording medium may, for example, disperse magnetic materials such as γ-Fe ₂ O ₃ , Co-γ-Fe ₂ O _3, or metal powder (Fe) together with a binder resin, a solvent and other additives in the case of a magnetic tape. To obtain a magnetic coating, which is applied onto a polyester film as a nonmagnetic support, oriented and dried, and then subjected to surface processing with a catenary ring.

Conventionally, sand grinders, such as those described in US Pat. No. 2,581,414, have been used mainly for the dispersion of magnetic powder, which is a dispersion medium in which a stirring disk inside a sand grinder is rotated at high speed and filled inside the sand grinder. As the rotational force is transmitted to the beads, collision or friction between the beads occurs, and the shear stresses generated between the beads act to disperse the magnetic paint. In addition to sand grinders, ball mills, roll mills, and the like are also used as dispersers for dispersing magnetic paints. These dispersers are also dispersed by shear force between bowls and rolls, respectively.

The composition of the process in the magnetic paint manufacturing method generally used is as follows. First, each powder and binder resin solution, etc. are kneaded in a kneader, and diluted with a solvent in a stirrer to make a suspension.

The paint in suspension is dispersed through a disperser such as a sand grinder, and the state up to this point is called a mill mix or primary dispersion. Once the mill mix is obtained, a binder resin solution such as polyurethane and other additives are mixed and stirred, and then dispersed in a sand grinder. This state is called let down or secondary dispersion. . The paint thus obtained is subjected to a filtration process, and then an isocyanate-based curing agent is added and the final filtration process is used to form a magnetic coating used for a magnetic tape.

As described above, in dispersing and manufacturing the magnetic paint, the dispersion state of the paint dispersed in the disperser such as the sand grinder is closely related to the dispersing force of the disperser itself. The dispersion state greatly varies depending on the size of the powder or the degree of wetness of the binder solution and the like to the magnetic powder. In the middle of flowing into the dispersing tank from the stirring tank, the paint passes through the tube. At this time, the coating is in a state before dispersing, so the distribution of the aggregated particles is uneven and the stability of the dispersed state is not good. There are problems such as re-agglomeration of paint or the like. This problem is the cause of poor dispersion of the paint in the disperser.

In addition, even in the case of the paint dispersed in the disperser, the thixotropy of the paint causes the paint with a strong shear stress between the beads in the disperser to be in a state where the stress is greatly reduced as it flows through the pipe, causing dispersion to occur during reaggregation The condition is bad.

Therefore, in providing the magnetic coating having good dispersibility, the dispersion treatment before and after the disperser is very important along with the dispersing force of the disperser itself.

The present invention has been made to solve the problems of the prior art as described above, by dispersing the magnetic coating by ultrasonic waves by introducing an ultrasonic generator before and after the disperser such as sand grinder to disperse the magnetic coating It aims to produce excellent magnetic paint.

In order to achieve the above object, the present invention in the manufacture of a magnetic powder consisting of fine powder components, such as ferromagnetic powder, abrasive, antistatic agent, binder resin solution and organic solvent, by installing the ultrasonic generator before and after the sand grinder disperser When the magnetic paint flows in contact with the horn of the ultrasonic generator, the output of the ultrasonic generator is 5 kW to 10 kW per liter of paint and the frequency is 1 kHz to 1 MHz to disperse the magnetic paint. It provides a manufacturing method.

The present invention also provides a method for producing a magnetic paint, characterized in that the frequency of the ultrasonic generator after the sand grinder is 0.1MHz ~ 1MHz.

When the output of the ultrasonic wave generated by the ultrasonic generator is less than 5kW, the dispersing effect is lowered, and if it is more than 10kW, the magnetic coating component may be damaged.

The frequency of the ultrasonic waves generated by the ultrasonic generator is based on the fact that the wavelength should be shorter than the aggregate size of the paint. It is preferable that the range of 1 kHz to 1 MHz is sufficient to obtain good dispersibility.

It is preferable that the ultrasonic frequency after the sand grinder is larger than the ultrasonic frequency before the sand grinder, and therefore the ultrasonic frequency after the sand grinder is preferably in the range of 0.1 MHz to 1 MHz.

Hereinafter, the present invention will be described in detail with reference to the drawings.

As shown in FIG. 2, by attaching the ultrasonic dispersion device 8 before and after the sand grinder 9, the dispersion state of the paint flowing into the disperser is made uniform and dispersion by the sand grinder through the pretreatment dispersion by the ultrasonic wave is performed. It is easy to improve dispersibility. In addition, by applying ultrasonic dispersion to the paint dispersed in the sand grinder to prevent re-agglomeration of the dispersed paint to improve the dispersion stability.

As can be seen in Figure 1, the configuration of the ultrasonic generator is a combination of the PZT armature 3 and the horn (2), in the magnetic paint dispersion process of the magnetic paint flows through the tube (6) The upper surface of the horn is in contact with the tube 6 at right angles to the traveling direction. Such an ultrasonic dispersion device is installed between the sand grinder 9 and between each stirring tank 7.

The PZT vibrator used in the ultrasonic generator is formed of a solid solution by mixing lead zirconate (PbZrO ₃ ) and lead titanate (PbTiO ₃ ). The exact name is lead zircon titanate, but it is generally called PZT according to a commonly used trade name.

By attaching the ultrasonic dispersing device before and after the sand grinder as shown in FIG. 2, the dispersibility of the paint is improved by pretreatment dispersion by ultrasonic waves, and the dispersion stability is improved by dispersing ultrasonically on the dispersed coating material. Paints can be produced.

The following describes the preferred examples of the present invention and comparative examples that can demonstrate the effects of the present invention.

Example 1

[Composition of Magnetic Paint]

Primary Mill Mix Usage (parts by weight)

Magnetic component (Co-γ-Fe ₂ O ₃ , coercive force 650 Oe) 100

Carbon black 5

Alumina (α-Al ₂ O ₃ ) 5

Vinyl Chloride-Vinyl Acetate Copolymer Resin 14

Cyclohexanone 50

Methyl ethyl ketone 60

Toluene 60

Secondary (Let down) usage amount

Polyurethane Resin 8

Normal Butyl Stearate 2

Stearic acid 3

Cyclohexanone 30

Methyl Ethyl Ketone 40

Toluene 50

Polyisocyanate 7

Magnetic coating having the composition was dispersed and prepared under the following dispersing conditions. In order to disperse the mixture of the components, an ultrasonic disperser was attached before and after the sand grinder during the first and second dispersions. The sand grinder's main speed is 10 m / sec, and the output and frequency of the ultrasonic disperser are 6 kW and 20 kHz for each liter of paint before dispersion in the first dispersion, 8 kW and 0.2 MHz after dispersion, and 8 kW and 0.2 MHz for the second dispersion. The magnetic coating was dispersed. The flow rate of the magnetic paint was 1 liter per minute. As a dispersion medium used in the sand grinder, zirconia beads having a particle diameter of 1.0 to 1.5 mm were used. The PZT oscillator used in the ultrasonic disperser was PSZ-4 of Clevite Corp., USA, and the shape of the horn was conical.

The magnetic coating obtained by the above dispersion conditions was applied, oriented and dried on a polyester film and subjected to surface treatment by calendaring. After calendering, the magnetic layer was cured and slitted at 52 ° C. and 20% RH, and then the magnetic tape was prepared.

Example 2

A magnetic tape was manufactured in the same manner as in Example 1, except that the conditions before dispersing in the first dispersion of the ultrasonic disperser in Example 1 were changed to 8 kW and 0.1 MHz instead of 6 kW and 20 kHz. After the evaluation of the properties are shown in Table 1 below.

Comparative Example 1

Except for dispersing the magnetic paint using only a sand grinder in the Example 1 without using an ultrasonic disperser, the magnetic tape was produced in the same manner as in Example 1 to evaluate the characteristics Table 1 shows.

TABLE 1

Characteristics of Magnetic Tape

1) Measured at the incidence and reflection angle of 60 degrees (length direction) by U type glossmeter manufactured by Toyoseiki, Japan.

2) Based on Ra measured by a non-contact three-dimensional surface roughness meter manufactured by Wyko, USA.

3) Based on JHS's VHS standard tape.

4) Based on JHS's VHS standard tape.

5) Measured by VSM of Toei, Japan.

6) Measured by Toei Co., Ltd. VSM, the larger the square ratio, the better the orientation, and the greater the output and the better the dispersibility.

7) Measured by VEI of Toei, Japan. The larger the SFD value, the larger the particle size, and the less dispersed. The smaller the value, the better the dispersion.

As can be seen in Table 1, by manufacturing the magnetic coating according to the present invention by using the ultrasonic dispersing apparatus before and after the disperser such as sand grinder, dispersibility and dispersion stability of the magnetic coating can be significantly improved. . Therefore, when the magnetic paint prepared by the magnetic paint production method of the present invention is used for the production of a magnetic tape or the like, a product having excellent general characteristics can be obtained.

Claims (3)

In the manufacture of magnetic coatings consisting of fine powder components such as ferromagnetic powders, abrasives and antistatic agents, binder resin solutions and organic solvents, an ultrasonic generator is installed before and after the sand grinder disperser, and the magnetic paint contacts the horn of the ultrasonic generator. When the flow of the ultrasonic wave generator, the output of the ultrasonic coating device per liter paint 5kW ~ 10kW, the frequency is 1kHz ~ 1MHz to produce a magnetic coating, characterized in that the magnetic coating is dispersed. The method of claim 1, wherein the frequency of the ultrasonic generator after the sand grinder is 0.1 MHz to 1 MHz. The method of claim 1 wherein a bowl mill or a roll mill is used in place of the sand grinder disperser.