JPS61223064A - Magnetic paint - Google Patents

Abstract

PURPOSE:To provide a magnetic paint for magnetic recording medium, containing a 2-thiouracil (derivative) as a dispersant, having excellent dispersibility of magnetic powder and capable of forming a magnetic recording medium having excellent magnetic properties. CONSTITUTION:A composition composed of a conventional magnetic powder such as Fe-Co-Ni alloy, a binder, an abrasive, etc., is added with preferably 0.5-10pts.wt. (based on the magnetic powder) of one or more dispersants selected from 2-thiouracil and its derivative of formula (R is H or 1-10C alkyl). The mixture is mixed thoroughly with a kneader, etc., transferred to a stirrer, and added with a curing agent, etc., to obtain the objective magnetic paint.

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 that has excellent dispersibility of magnetic powder and, as a result, can form a magnetic recording medium with excellent magnetic properties.

[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.

Powders of oxide magnetic substances such as γ-Fe2O3 and γ-Fe2O3 coated with Go are generally used as magnetic powders, but in recent years, magnetic paints have been used mainly for the purpose of increasing the density of magnetic recording media. The magnetic powder used is becoming finer. However, as the magnetic powder becomes finer, the cohesive force of the particles becomes stronger, and it is often difficult to achieve high dispersion of the magnetic powder using dispersants such as higher fatty acids used in conventional magnetic paints.

[Problems to be solved by the invention] The present invention has been made in view of the above-mentioned problems.
The object of the present invention is to provide a magnetic coating material that has excellent dispersibility and, as a result, can form a magnetic recording medium with excellent magnetic properties.

[Means for Solving the Problems] The present invention achieves the above object by using at least one of 2-thiouracil or its derivatives represented by the following general formula as a dispersant in a magnetic paint for forming a magnetic recording medium. This is a magnetic paint characterized by its use.

(However, R is H or an alkyl group having 1 to 10 carbon atoms.) [Embodiments of the invention] The magnetic paint using 2-thiouracil or a derivative thereof as a dispersant according to the present invention will be explained in detail below. do.

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

2-thiouracil or its derivative used as a dispersant is represented by the above general formula, and R in formula 1 is
2- is H or an alkyl group having 1 to 10 carbon atoms;
At least one of thiouracil or its derivatives is used.

Generally, magnetic paint consists of magnetic powder, binder, dispersant,
It is formed as a composition containing an abrasive etc. as a component, but
In the magnetic paint of the present invention using 2-thiouracil or a derivative thereof as a dispersant, conventionally known components other than the dispersant can be used. Furthermore, the composition of components other than these dispersants may be any conventionally used composition.

The dispersant may be added at any stage in the production of the magnetic paint, but from the point of view of improving the magnetic properties of the magnetic recording medium, the magnetic powder is prepared by mixing the magnetic powder and the dispersant in advance. After that, it is preferable to mix a binder, an abrasive, etc. to create a magnetic paint.

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

First, at least one of 2-thiouracil or its derivatives represented by the above general formula is added as a dispersant to a composition of conventionally known magnetic powder, binder, abrasive, etc., which is a raw material for a magnetic paint, and a sand grinder, kneader, etc.
Mix thoroughly.

What is the amount of 2-thiouracil or its derivative added?

Although it varies depending on the amount of the solvent etc. constituting the composition, it is preferably in the range of 0.5 to 10 parts by weight based on the 1m powder, and if it is less than 0.5 parts by weight, the effect as a dispersing agent is sufficient. In addition, if the amount exceeds 10 parts by weight, the magnetic property per unit volume of the magnetic layer of the magnetic recording medium formed from the manufactured magnetic coating material will decrease. This is not preferable because the amount of powder decreases and the magnetic properties deteriorate.

Next, this kneaded composition is transferred to a stirrer such as a paint agitator, a curing agent is added to the stirrer to obtain the desired composition, and the mixture is thoroughly stirred. Complete.

A magnetic paint using at least one of 2-thiouracil or its derivatives represented by the above general formula as a dispersant has excellent monodispersibility, and as a result provides a magnetic recording medium with excellent magnetic properties. The reason why this effect occurs is not necessarily clear, but the mercapto group (SH group) of 2-thiouracil or its derivatives forms a complex with the magnetic powder, and the hydroxyl group or alkoxy group is compatible with polymers such as binders. It is thought that this is because, as a result, 2-thiouracil or its derivatives act as a compatibilizer at the polymer-metal interface, giving the magnetic powder excellent coating properties.

[Example J Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples. In the following description, "v%J" and "1 part" representing the composition are based on weight unless otherwise specified.

[Example 1] Ferromagnetic metal powder (Fe-Co-old alloy.

Long axis 0.25g, axial ratio 8) 100 parts vinyl chloride-vinyl acetate-vinyl alcohol copolymer (polymerization molar ratio 8)
t:3:6, average degree of polymerization 280)
15 parts polyurethane elastomer
lO part α-Aj203 (abrasive material)
5 parts methyl ethyl ketone 1
20 parts toluene 120
Part 2 - Thiouracil (dispersant; however, R-H) 2 parts The above composition was mixed and dispersed using a sand grinder.

Next, the mixed composition was transferred to a stirrer.

Five parts of a polyisocyanate crosslinking agent having the chemical formula shown below was added thereto, and the mixture was sufficiently stirred with a stirrer to produce a magnetic paint.

[Example 2] A magnetic coating material was produced in the same manner as in Example 1, except that a 2-thiouracil derivative of tho-C4H9 was used in place of 2-thiouracil (R-)1) used in Example 1.

[Example 3] Rm-c8Htt instead of 2-thiouracil in Example 1
A magnetic coating material was produced in the same manner as in Example 1 except for using the 2-thiouracil derivative.

[Example 4] Ferromagnetic metal powder (Fe-Co-old alloy.

Long diameter: 0.25 μs, axial ratio: 8) 100 parts Methyl ethyl ketone 500 parts 2-thiouracil derivative of Example 3 5 parts The mixture having the above composition was mixed with a stirrer for 3 hours.

Next, after removing the solution by filtration, the ferromagnetic powder was dried to form a ferromagnetic metal powder to which a 2-thiouracil derivative as a dispersant had been adsorbed in advance.

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, average degree of polymerization 280)
15 parts polyurethane elastomer 10 parts α-M20sC abrasive)
5 parts methyl ethyl ketone
120 parts toluene 12
0 parts [Comparative Example] A magnetic paint was produced in the same manner as in Example 1, except that 2 parts of lecithin was used instead of 2-thiouracil as a dispersant.

[Application example]

The magnetic paints produced in Example 1.2.3.4 and Comparative Example were each applied onto a 10-thick polyester film, and a magnetic field was applied in a predetermined direction (in this case, the thickness direction of the film) to create a magnetic field. Next, after a drying process, a calender treatment was performed to smooth the surface to form a magnetic layer with a thickness of about 3 mm on the polyester film.
next.

After leaving it at 50℃ for 24 hours, the specified width (in this case, 0
．． A magnetic tape was prepared by cutting the tape into pieces (8 cts width).

The magnetic properties of the magnetic tape thus prepared were determined by measuring the residual magnetic flux density and squareness ratio, and the dispersibility of the magnetic paint used for each was evaluated. Results first
In addition, the glossiness of each magnetic tape as shown in the table was determined, and the coating film characteristics of the magnetic paint used for each were evaluated. That is, the results are shown in Table 1, showing that the higher the gloss, the less the stickiness of the magnetic layer, the smoother the surface, and the better the coating properties.

As is clear from Table 1, the magnetic tape produced from the magnetic paint of the present invention using 2-thiouracil or its derivative as a dispersant has excellent magnetic properties and gloss. Among them, a magnetic tape manufactured using magnetic powder (Example 4) prepared by pre-mixing 2-thiouracil or its derivative as a dispersant with magnetic powder had extremely excellent magnetic properties. From the results of 0 or more, it is clear that the magnetic paint of the present invention has excellent dispersibility and can form a magnetic recording medium with superior magnetic properties compared to conventional magnetic paints.

Relative value when the value of the Trout Comparative Example in Table 1 is taken as 100 [Effects of the Invention] As explained above, by forming a magnetic recording medium using the magnetic paint of the present invention, it has excellent dispersibility and results. As a result, it has become possible to create a magnetic recording medium with excellent magnetic properties.

Claims (1)

[Claims] (1) A magnetic paint for forming a magnetic recording medium, characterized in that at least one of 2-thiouracil or its derivatives represented by the following general formula is used as a dispersant. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (However, R is H or an alkyl group having 1 to 10 carbon atoms.)