JPS61223069A - Magnetic paint - Google Patents

Abstract

PURPOSE:To provide a magnetic paint for magnetic recording medium, containing magnetic powder coated with 2-mercaptobenzothiazole, having excellent antioxidation property and capable of keeping the magnetic characteristics for a long period. CONSTITUTION:2-Mercaptobenzothiazole of formula is added to a composition composed of conventional ferromagnetic powder such as Fe-Co-Ni alloy, a binder, a dispersant, an abrasive, etc., and mixed with a kneader, etc., to coat the surface of the magnetic powder with 2-mercaptobenzothiazole. The objective magnetic paint is produced by using the surface-treated magnetic powder. The amount of 2-mercaptobenzothiazole is preferably 0.5-10pts.wt. based on the magnetic powder.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a magnetic paint. More specifically, the present invention relates to a magnetic coating material using ferromagnetic metal powder as a magnetic material, which can form a magnetic recording medium with an excellent anti-fouling effect.

[Prior Art] Coating-type magnetic recording media have been widely used, which are formed by applying a magnetic paint containing magnetic powder dispersed in a binder onto a support made of a non-magnetic material such as a polyester film. ing. Generally, γ-Fe2 is used as magnetic powder.
Oxide magnetic powder such as γ-Fe2O3 coated with O3 or Go has been used, but in recent years, ferromagnetic metal powder has been used instead of oxide magnetic powder, mainly for the purpose of improving recording density. Powders are increasingly used. This ferromagnetic metal powder has saturation magnetization (Bg) and coercive force (He)
is large, and a magnetic recording medium formed from a magnetic paint using this as a magnetic material has excellent magnetic properties. However, on the other hand, new drawbacks have arisen that have not been seen in magnetic recording media formed from conventional magnetic paints that use γ-Fe2O3-based oxides as magnetic materials.

In other words, in a magnetic recording medium using a ferromagnetic metal powder as a magnetic material, when exposed to high temperature and humidity, the ferromagnetic metal powder oxidizes, causing the magnetic layer formed by coating it on a support to deteriorate. A phenomenon in which magnetic properties deteriorate over time is observed.

In order to solve the above-mentioned problems, for example, the surface of ferromagnetic metal powder produced by reduction is gradually oxidized to form a thin oxide film on the particle surface, and the surface of ferromagnetic metal powder is coated with a metal that is difficult to oxidize. Various methods have been proposed, such as coating with organic substances such as silicone oil or higher fatty acids.1 Various methods have been proposed, such as adsorbing antioxidants on the surface of ferromagnetic metal powders, or dispersing antioxidants in binder resins. There is.

However, magnetic recording media formed from magnetic paints produced using these methods have not yet been fully satisfactory in terms of antioxidant effect.

[Problems to be solved by the invention] The present invention has been made in view of the above-mentioned problems,
An object of the present invention is to provide a magnetic coating material that can form a magnetic recording medium that has excellent oxidation resistance under high temperature and high humidity conditions and can suppress deterioration of magnetic properties over time.

[Means for Solving the Problems] The present invention achieves the above object by providing a magnetic paint for forming a magnetic recording medium containing magnetic powder surface-treated with 2-mercaptobenzothiazole represented by the following chemical formula. It is a magnetic paint characterized by being made of

[Embodiment 1 of the Invention The magnetic powder surface-treated with 2-mercaptobenzothiazole referred to in the present invention is as described below.

For the purpose of the present invention, it is preferable to use ferromagnetic powder as the magnetic powder.

The surface treatment of the magnetic powder with 2-mercaptobenzothiazole may be carried out using any method as long as it allows the 2-mercaptobenzothiazole and the magnetic powder to be brought into contact for a desired period of time.

Generally, 5M paints are made of magnetic powder and binder.

It is formed by applying a curing agent after thoroughly mixing and dispersing components such as a dispersant and abrasive, but the surface treatment of magnetic powder with 2-mercaptobenzothiazole may be performed at any stage of the production of magnetic paint. However, since it is practically impossible to perform surface treatment of the magnetic powder after applying the hardening agent, it is preferable to perform surface treatment of the magnetic powder with 2-mercaptobenzothiazole before applying the hardening agent.

In particular, for ease of production, 2-mercaptobenzothiazole is also added to the composition and mixed.

Preferably, the magnetic powder is surface-treated with 2-mercaptobenzothiazole at the same time as the composition is mixed; however, magnetic powder whose surface is previously surface-treated with 2-mercaptobenzothiazole before mixing the composition may also be used. good.

The simplest method for producing the magnetic paint of the present invention will be explained below.

First, 2-mercaptobenzothiazole and a conventionally known composition of magnetic powder, binder, dispersant, abrasive, etc., which is a raw material for a magnetic paint, are thoroughly mixed using a sand grinder, kneader, or the like. During this mixing, the surface of the magnetic powder is also simultaneously treated with 2-mercaptobenzothiazole.

The amount of 2-mercaptobenzothiazole added varies depending on the amount of the solvent and the like constituting the composition, but is usually 0.5 to 1G parts by weight based on the magnetic powder.

If the amount is less than 0.5 parts by weight, the surface treatment of the magnetic powder cannot be performed sufficiently, and the object of the present invention cannot be fully achieved. If it exceeds 10 parts by weight, the produced magnetic paint The magnetic layer of a magnetic recording medium formed from
This is not suitable because the magnetic properties of the recording medium deteriorate.

The well-mixed composition containing the 2-mercaptobenzothiazole-surface-treated magnetic powder is then transferred to a stirrer, into which the curing agent is also added. By thoroughly stirring this curing agent and the composition using a stirrer, the production of the magnetic paint of the present invention containing magnetic powder surface-treated with 2-mercaptobenzothiazole is completed.

The device recording medium is composed of a magnetic paint using magnetic powder surface-treated with 2-mercaptobenzothiazole.
Less likely to be oxidized. Therefore, its magnetic properties are also less likely to deteriorate. Although the reason why such an effect occurs is not necessarily clear, it is thought that 2-mercaptobenzothiazole and the magnetic particles interact to form a complex, and as a result, the surface of the magnetic particles is protected.

[Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

[Example 1] *Parts → parts by weight Ferromagnetic metal powder (Fe-Go-old alloy.

Long axis 0.25M, axial ratio 8) 100! Vinyl chloride-vinyl acetate-vinyl alcohol copolymer (polymerization molar ratio 9
1:3:8) 15 parts polyurethane elastomer 10 parts α-AJ203 (abrasive material)
5 parts lecithin (dispersing agent)
1 part methyl ethyl ketone 12
0 parts Toluene 120 parts 2-mercaptobenzothiazole 2 parts The above composition was mixed and dispersed using a sand grinder.

Next, the mixed composition was transferred to a stirrer, 5 parts of a polyisocyanate crosslinking agent having the following chemical formula % was added thereto, and the mixture was sufficiently stirred using a stirrer to produce a magnetic paint.

〔Example? ]

Ferromagnetic metal powder (Fe-Go-Xi gold alloy major axis 0.25
u, axial ratio 8) 100 parts 2-mercaptobenzothiazole 5 parts ethyl alcohol
500 parts of the mixture having the above composition were mixed for 3 hours using a stirrer.

The ferromagnetic powder was then dried to form a 2-mercaptobenzothiazole surface treated ferromagnetic metal powder after removing the solution by filtration.

Next, a magnetic paint was produced in the same manner as in Example 1 with the following composition.

Ferromagnetic metal powder subjected to the above treatment 100 parts Vinyl chloride-vinyl acetate-vinyl alcohol copolymer (polymerization molar ratio 91:3:8) 15 parts Polyurethane elastomer 10 parts α-M20s (abrasive)
5 parts lecithin (dispersing agent)
1 part methyl ethyl ketone
120 parts top Luenoluene 12 (1
[Comparative example] 2-mercaptobenzothiazole was not used)
A magnetic paint was produced in the same manner as in Example 1.

[Application example]

The magnetic paints produced in Example 1.2 and Comparative Example were each applied onto a 1G-thick polyester film, and a magnetic field was applied in a predetermined direction (in this case, the thickness direction of the film) to perform a magnetic orientation treatment. provided.

Next, after a drying process, a magnetic layer with a thickness of about 3JIIm was formed on the polyester film by calendering to smooth the surface.Next, after being left at 50°C for 24 hours, A magnetic tape was prepared by cutting the tape into pieces (0.8 cm wide).

The initial residual magnetic flux density, squareness ratio, and coercive force of the magnetic tape thus prepared were measured. The results are shown in Table 1.
Further, each magnetic tape was left under conditions of 80° C. and 80% RH, and changes in residual magnetic flux density over time were measured. The results are shown in Figure 1.

As is clear from Table 1 and Figure 1, the magnetic tape formed from the magnetic paint containing the ferromagnetic metal powder treated with 2-mercaptobenzothiazole has no deterioration in its initial magnetic properties, and Even with the passage of time, the decrease in residual magnetic flux density is extremely small compared to magnetic tapes made from conventional magnetic paints.Thus, the magnetic paints of the present invention form magnetic tapes with excellent antioxidant properties. It is clear that it can be done.

Table 1 [Effects of the Invention] As explained above, by forming a magnetic recording medium using the magnetic paint of the present invention containing magnetic powder surface-treated with 2-mercaptobenzothiazole, it has an excellent antioxidant effect. As a result, it has become possible to form a magnetic recording medium whose magnetic properties do not deteriorate over time.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing changes over time in the residual magnetic flux density of magnetic tapes formed using the magnetic paints manufactured in Examples and Comparative Examples.

Claims (1)

[Claims] (1) A magnetic paint for forming a magnetic recording medium, characterized in that it contains a magnetic powder surface-treated with 2-mercaptobenzothiazole represented by the following chemical formula. ▲Contains mathematical formulas, chemical formulas, tables, etc.▼