JPS59172130A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having excellent durability and heat resistance by adding copper oleate into a magnetic coatig contg. an isocyanate compd. and applying the coating on a magnetic body thereby forming a magnetic layer. CONSTITUTION:A magnetic coating contg. copper oleate, isocyanate compd. and magnetic powder is coated on a base body. When the copper oleate is added into the magnetic coating contg. the isocyanate compd., the cross-linking reaction between the isocyanate compd. and a binder resin such as a vinyl chloride resin, polyester resin or the like having active hydrogen is much accelerated and the network cross-linking is quickly effected, by which the strength of the magnetic layer is improved and the wear resistance and heat resistance thereof are improved. A trifunctional low mol.wt. isocyanate compd. or the like is preferable as the isocyanate compd., and if the other binder resin having active hydrogen is used in combination with isocyanate compd., the sgrength of the magnetic layer is improved by cross-linking. If the copper oleate is used in combination in this stage, the crosslinking reaction is much accelerated and therefore the strength of the magnetic layer is improved and the wear resistance of the magnetic layer and heat resistance are much improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium, and an object thereof is to provide a magnetic recording medium with excellent durability and heat resistance.

In general, magnetic recording media, which are made by coating a magnetic paint consisting of magnetic powder, a binder component, an organic solvent, and other necessary components on a substrate such as a polyester film, come into violent sliding contact with magnetic heads, etc. during recording and playback. The magnetic layer is easily abraded, so a material with excellent durability and little abrasion is required.

In order to meet these demands, various improvements have been made to binder components. For example, by adding a curing accelerator such as sodium oleate or potassium oleate to a magnetic paint containing an isocyanate compound,
By strengthening the strength of the magnetic layer through the action of this hardening accelerator, the wear resistance of the magnetic layer is improved.

However, by adding sodium oleate or potassium oleate to the magnetic paint, the crosslinking reaction between the isocyanate compound and other binder components containing active hydrogen is promoted, and the strength of the magnetic layer is improved. However, the wear resistance and heat resistance are still not fully satisfactory.

The inventors conducted various studies in view of the current situation, and found that when copper oleate is added to a magnetic paint containing an isocyanate compound and this is applied onto a substrate to form a magnetic layer, copper oleate Since the curing accelerating effect is superior to that of conventional sodium oleate or potassium oleate, the crosslinking reaction of the isocyanate compound is rapidly promoted, the strength of the magnetic layer is sufficiently strengthened, and the wear resistance and heat resistance of the magnetic layer are improved. They have found that this can be sufficiently improved and have come up with this invention.

The copper oleate used in this invention has a much better effect of promoting the crosslinking reaction between the isocyanate compound and other binder components containing active hydrogen than the conventional sodium oleate or potassium oleate. When this type of copper oleate is added to a magnetic paint containing an isocyanate compound, the active hydrogen of the isocyanate compound and vinyl chloride resin, polyester resin, polyurethane resin, polyvinyl acecool resin, cellulose resin, etc. The crosslinking reaction with the binder resin having the above properties is further promoted, and these are quickly crosslinked into a network, thereby strengthening the strength of the magnetic layer and improving its abrasion resistance and heat resistance. In addition, this type of copper oleate has good compatibility with commonly used binder resins, so it is well mixed into the magnetic coating material, and the above-mentioned crosslinking reaction promoting effect is sufficiently exerted. This effect is due to the fact that copper oleate is 0% of the total amount of binder components.
．． Copper oleate is exhibited by adding 1% by weight or more, and the effect becomes more pronounced as the amount added increases, but if it exceeds 10% by weight, there is a risk of bleed-out on the surface of the magnetic layer and deterioration of electromagnetic conversion characteristics. The amount used is preferably within the range of 0.1 to 10% by weight based on the total amount of binder components.

The isocyanate compound is not particularly limited as long as it has an isocyanate group; for example, 2.4
--Diisocyanate compounds such as tolylene diisocyanate, m-phenylene diisocyanate-1, 1,5-naphthalene diisocyanate, and trifunctional diisocyanate compounds usually obtained by reacting 1 mol of triol with 3 mol of diisocyanate. Molecular weight isocyanate compounds are preferably used, and these isocyanes! - When the compound and other binder resins containing active hydrogen are used together, they crosslink and strengthen the strength of the magnetic layer, but at this time, when the above-mentioned copper oleate is used together, the crosslinking reaction is further accelerated. As a result, the strength of the magnetic layer is further strengthened, and the wear resistance and heat resistance of the magnetic layer are further improved. Specific examples of trifunctional low molecular weight isocyanate compounds include:
For example, Coronate manufactured by Nippon Polyurekun Industries, Ltd., Takenate D102 manufactured by Narita Pharmaceutical Industries, Ltd., Desmodur manufactured by Bayer, and Lisbon N manufactured by Dainippon Ink and Chemicals.
Examples include X.

As the binder resin used in combination with the isocyanate compound, those normally used in manufacturing magnetic recording media are suitably used, including vinyl chloride resin, cellulose resin, polyurethane resin, and polyvinyl acecool. Binder resins having active hydrogen, such as polyester-based resins and polyester-based resins, are preferably used.

Magnetic powders include γ-Fe203 powder, Fe3O4 powder, Co-containing T Fe2O3 powder, CO-containing Fe3O
4 powder, CrO2 powder, Fe powder, CO powder, Fe
- Various conventionally known magnetic powders such as metal powders such as Ni powders are widely used.

Further, as the organic solvent, methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, toluene, ethyl acetate, tetrahydrofuran, dimethyl formamide, etc. are used singly or in combination of two or more.

In addition, various additives commonly used in magnetic paints,
For example, dispersants, lubricants, abrasives, antistatic agents, and the like may be optionally added.

Next, embodiments of the invention will be described.

Example I Co-containing 7Fe203 powder 80 parts by weight VAGH (
Vinyl chloride manufactured by U, C, C, Co., Ltd. 10〃Ru-vinyl acetate-
(Vinyl alcohol copolymer) Bandesox T-5201 (Large 8 Urethane elastomer manufactured by Nippon Ink Co., Ltd.) Coronate Shiku Nippon Polyurethane 2 Trifunctional low molecular weight isocyanate compound manufactured by Nippon Ink Co., Ltd.) Copper oleate 1.0〃Methyl isobutyl ketone 50 〃toluene
50 This composition was mixed and dispersed in a ball mill for 72 hours to prepare a magnetic paint, and this magnetic paint was coated on a polyester base film with a thickness of 12μ to a coating thickness of 5μ.
It was applied so that Next, after calendering, the tape was cut into a predetermined width to make a magnetic tape.

Examples 2 to 4 Magnetic tapes were produced in the same manner as in Example 1, except that the amount of copper oleate used in the composition of the magnetic paint in Example 1 was changed as shown in Table 1 below.

Table 1 Comparative Example 1 A magnetic tape was produced in the same manner as in Example 1 except that the same amount of sodium oleate was used in place of copper oleate in the composition of the magnetic paint in Example 1.

Regarding the magnetic tapes obtained in each example and comparative example,
Tested for heat resistance and abrasion resistance. The heat resistance test was performed by cutting the obtained magnetic tape into a length of 1.5 m, applying a load of 1 kg, wrapping it around a glass tube with a diameter of 36 mm, and placing it in a constant temperature bath at 60°C and 80% RH for 48 hours. After storing the tape for an additional 24 hours at room temperature, the tape was unwound from the glass tube and the degree of adhesion between the tape layers was observed. The score was rated as (○) if it could not be loosened, (△) if it was slightly loosened, and (×) if it could not be loosened at all.

In addition, the abrasion resistance test was conducted by loading each magnetic tape into a tape recorder and running it at a running speed of approximately 4.8 c + n/36 c.
This was done by measuring the output fluctuation after running the vehicle twice.

Table 2 below shows the results.

As is clear from the upper table of Table 2, the magnetic tapes obtained in Examples 1 to 4 all had better heat resistance and smaller output fluctuations than the magnetic tape obtained in Comparative Example 1. Therefore, the magnetic recording medium obtained by the present invention has excellent durability and heat resistance.

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Claims (1)

[Claims] 1. A magnetic recording medium obtained by coating a substrate with a magnetic paint containing copper oleate, an isocyanate compound, and magnetic powder.