JPS59172126A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having excellent durability and heat resistance by adding cobalt octenate into a magnetic coating contg. an isocyanate compd. and applying the coating on a magnetic body thereby forming a magnetic layer. CONSTITUTION:A magnetic coating contg. cobalt octenate, isocyanate compd. and magnetic powder is coated on a base body. When the cobalt octenate 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 hydrogen activity is much accelerated and the network crosslinking and bonding are 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, the strength of the magnetic layer is improved by crosslinking and bonding. If the cobalt octenate 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 to heat resistance is 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, a curing accelerator such as zinc octenoate is added to a magnetic paint containing an isocyanate compound, and this curing accelerator is improved. The wear resistance of the magnetic layer is improved by strengthening the strength of the magnetic layer.

However, by adding this zinc octenoate 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, but it is still not sufficient. , 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 cobalt octenoate is added to a magnetic paint containing an isocyanate compound and coated on a substrate to form a magnetic layer, cobalt octenoate Since the curing accelerating effect is superior to that of conventional zinc octate, the crosslinking reaction of the isocyanate compound is rapidly promoted, the strength of the magnetic layer is sufficiently strengthened, and the abrasion resistance and heat resistance of the magnetic layer are sufficiently improved. This discovery led to the creation of this invention.

The cobalt octenoate used in this invention has a much superior effect of promoting the crosslinking reaction between isocyanate compounds and other binder components containing active hydrogen, compared to conventional zinc octenoate. When acid cobalt is added to a magnetic paint containing an isocyanate compound, the isocyanate compound and a binder containing active hydrogen such as vinyl chloride resin, polyester resin, polyurethane resin, polyvinyl acecool resin, cellulose resin, etc. The crosslinking reaction with the resin 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 cobalt octenoate 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. Such an effect is exhibited by adding 0.1% by weight or more of cobalt octenoate to the total amount of the binder components, and the effect becomes more pronounced as the amount added increases, but if it exceeds 10% by weight, the surface of the magnetic layer Since there is a risk that the electromagnetic conversion characteristics may deteriorate due to bleed-out, the amount of cobalt octenoate used is preferably within the range of 0.1 to 10% by weight based on the total amount of the 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 lylene diisocyanate, m-phenylene diisocyanate, and 1,5-naphthalene diisocyanate, and trifunctional low molecular weight isocyanate compounds usually obtained by reacting 1 mol of triol with 3 mol of diisocyanate are suitable. When these isocyanate compounds and other binder resins containing active hydrogen are used in combination, they are crosslinked and the strength of the magnetic layer is strengthened. When used in combination, the crosslinking reaction is further promoted, thereby further strengthening the strength of the magnetic layer and further improving the abrasion resistance and heat resistance of the magnetic layer. Specific examples of the trifunctional low molecular weight isocyanate compound include Coronate L1 (manufactured by Nippon Polyurethane Industries, Ltd.), Takena D102 (manufactured by Takeda Pharmaceutical Co., Ltd.), Desmodur (manufactured by Bayer), and Lisbon NX (manufactured by Dainippon Ink & Chemicals).
Examples include.

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.

Examples of magnetic powder include 7-Fe2O3 powder, Fe3O4 powder, Co-containing -Fe203 powder, Co-containing pe3Q4
powder, CrO2 powder, Fe powder, co powder, Fe-
Various conventionally known magnetic powders such as metal powders such as Ni powder are widely used.

Further, as the organic solvent, methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, toluene, ethyl acetate, tetrahydrofuran, dimethylformamide, etc. are used alone 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 Fe203 powder 80 parts by weight VAGH
(U, C, C, vinyl chloride 10 - vinyl acetate-vinyl alcohol copolymer manufactured by Nippon Ink Co., Ltd.) Bandex T-5201 (large 8 urethane elastomer manufactured by Nippon Ink Co., Ltd.) Coronate Nippon Polyurethane 2 manufactured by Nippon Ink Co., Ltd., 3 Functional low molecular weight isocyanate compound) Cobalt octenoate 1. o Methyl isobutyl ketone 5o Toluene
5o# A magnetic paint was prepared by mixing and dispersing this composition in a ball mill for 72 hours.
It was applied onto a polyester base film having a coating thickness of 5 μm. Next, the tape was calendered and cut into a predetermined width to produce a magnetic tape.

Examples 2 to 4 Magnetic tapes were produced in the same manner as in Example 1, except that the amount of cobalt octenoate 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 zinc octenoate was used in place of cobalt octenoate 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 carried out 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 heating it for 60 minutes.
After storing it in a constant temperature bath at 80% RH for 48 hours and leaving it at room temperature for 24 hours, the tape was unwound from the glass tube and the degree of adhesion between the tape layers was observed, and no adhesion was observed. The case was evaluated as (◎), the case that it was rarely observed as (O), the case that it was observed slightly (△), and the case that it could not be disentangled as (x).

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 about 4.8 cm/see for 600 minutes.
This was done by measuring the output fluctuation after running the vehicle twice.

0 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. It can be seen from this that the magnetic recording medium obtained by this invention has excellent durability and heat resistance.

Patent applicant: Hitachi Maxell, Ltd.

Claims (1)

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