JPS59157841A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium which is produced by using a magnetic coating having an excellent packing property of magnetic powder and a long pot life and has excellent durability by using the magnetic coating contg. a specific trifunctional isocyanate compd. as a binder component. CONSTITUTION:An isocyanate compd. expressed by the formula [R is -COO(CH2)n or -(CH2)m and n is 1-10, m is 1-10] is combined with a binder resin such as a vinyl chloride/vinyl acetate copolymer, cellulosic resin, etc. to prepare a magnetic coating. The isocyanate compd. reacts with the active hydrogen of the other resin used in combination and is thus crosslinked to have the high binding power to the magnetic powder, by which a strong and tough magnetic layer is obtd. The isocyanate compd. is added within 5-80wt% by the total weight of the other binder resin. A recording medium having the magnetic layer which has uniform dispersibility of the magnetic powder and has excellent durability without dislodging, etc. of the magnetic powder is thus obtd.

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 having a magnetic layer that is compatible with the filling properties of magnetic powder and has excellent durability. .

Magnetic recording media are usually made by applying a magnetic paint consisting of magnetic powder, a binder component, an organic solvent, and other necessary components onto a substrate such as a polyester film, and drying the coating.
A material with excellent electrical properties and durability is required. Therefore, the binder component used has excellent dispersibility and filling properties of the magnetic powder, and can impart excellent electrical properties such as high sensitivity and high S/N ratio to the magnetic recording medium, as well as improve the wear resistance of the magnetic layer. Those that can improve durability and improve durability are retained.

For this reason, among various binder resins, vinyl chloride-vinyl acetate copolymers, cellulose resins, polyvinyl butyral resins, and polyurethane resins have been selected as having relatively good properties. It is possible to use a resin with excellent dispersibility of magnetic powder in combination with a low molecular weight incyanate compound obtained by reacting tolylene diisocyanate and trimethylolpurpane, such as Coronate L manufactured by Nippon Polyurethane Kogyo Co., Ltd. Although it is widely practiced,
This type of isocyanate compound has a high viscosity and strong reactivity, so magnetic paints that use this type of isocyanate compound in combination have a short pot life, and can also be obtained by using this type of isocyanate compound in combination as a binder component. These magnetic recording media have disadvantages, such as the fact that the filling of the magnetic powder in the magnetic layer is not sufficient, and the magnetic layer tends to become hard and brittle.

In view of the current situation, the inventors conducted various studies on binder components, and found that the general formula: CN-(CH2)n
-CH-NGO! -NGO (wherein R is -C00(CH2)m or -(CH
2) m, where n is an integer from 1 to 10/D, and m is an integer from 1 to 10; ) When used in combination with other commonly used binder resins such as vinyl chloride-vinyl acetate copolymers and cellulose resins, this type of isocyanate compound has a low viscosity. Because the reaction is slow, the pot life of the magnetic paint is improved, and the filling properties of the magnetic powder in the magnetic layer are further improved, and a larger amount can be used, resulting in a higher crosslinking density, which strengthens the strength of the magnetic layer. He discovered that it could be made even stronger, and came up with this invention.

The incyanate compound used in this invention is
General formula % Formula % (However, in the formula, R is -CC00(CH2) or -(CH
2) m, where n is an integer from 1 to 10, m is 1 to 1
It is an integer of 0. ) It has a very low viscosity and acts like a solvent when preparing magnetic paints, so the amount of organic solvent used can be reduced and the filling properties of the magnetic powder in the magnetic layer can be improved. do. In addition, compared to conventional isocyanate compounds such as Coronate L manufactured by Nippon Polyurethane Co., Ltd., the reaction with other binder resins containing active hydrogen used in combination is slower, resulting in a longer pot life for the magnetic paint and a lower viscosity. It can be used in large amounts, increasing the crosslinking density and further increasing the strength of the magnetic layer.

This type of isocyanate compound is usually produced by reacting triamine and phosgene, and is preferably n and m in the above general formula from 1 to 10. If n and m are too large, the crosslinking density will decrease. , the strength of the magnetic layer decreases. In addition, the viscosity increases and it cannot be used in large quantities.

Specific examples of such isocyane-1 compounds include:
Examples include 2-incyanate ethyl 2,6-life cyanate hexanoate, which is represented by the structural formula %, and 1,6,11-triisocyanate undecane, which is represented by the Mizozo formula %. A specific example of the product is T-100 manufactured by Toshisha Co., Ltd., for example.

The isocyanate compound of the present invention can be used with other binder resins having active hydrogen, such as vinyl chloride-vinyl acetate copolymers such as vinyl chloride-vinyl acetate-vinyl alcohol copolymers, cellulose resins, and polyvinyl butyral. It is used in combination with resins, etc. with good compatibility, and the trifunctional isocyanate group in the incyanate compound reacts with the active hydrogen of the other binder resin used in combination to form a crosslinking bond, strengthening the strength of the magnetic layer and making it even tougher. A magnetic layer is obtained. The amount used is preferably within the range of 5 to 80% by weight based on the total amount of other binder resins used in combination; if it is too small, the desired effect cannot be obtained, and if it exceeds 80% by weight, There is a risk that the crosslinking density will become too high, making the magnetic layer hard and brittle.

Examples of the magnetic powder used in this invention include r-F
e203 powder, Fe > 04 powder, CO containing r-F
In addition to e203 powder, Co-containing Fe3O4 powder, CrO□ powder, various conventionally known magnetic powders such as metal powders such as Fe powder, Co powder, and Fe-Ni powder are widely included.

Examples of organic solvents include ketone solvents such as cyclohexanone, methyl ethyl ketone, and methyl isobutyl ketone; esters such as ethyl acetate and butyl acetate;
, aromatic hydrocarbon solvents such as alcohol, xylene, toluene, alcohol solvents such as isopropyl alcohol, acid amide thread solvents such as dimethylformamide, sulfoxide solvents such as dimethyl sulfoxide, ether solvents such as tetrahydrofuran and dioxane, etc. A solvent suitable for dissolving the binder component used may be used alone or in combination of two or more without particular limitation.

In addition, each rod additive commonly used in magnetic paint,
For example, dispersants, lubricants, abrasives, antistatic agents, and the like may be optionally added.

Next, embodiments of the invention will be described.

Example 1 Using an isocyanate compound represented by the structural formula %, 80 parts by weight of Co-containing rFe2O3 magnetic powder VAGH (
Manufactured by U, C, C, USA, vinyl octide-vinyl acetate-
Vinyl alcohol copolymer) Polyethylene glycol #600 8 (Polyether polyol manufactured by Gyudon Kagaku Co., Ltd.) Isocyanate compound 4 Stearic acid 0.5 Methyl isobutyl ketone 100 Toluene 10
This composition was mixed and dispersed in a ball mill for 72 hours to prepare a magnetic paint. This magnetic paint was applied onto a 15 μm thick polyester film to a dry thickness of approximately 4 μm, dried, surface treated, and then cut to a predetermined width to produce a magnetic tape. .

Example 2 In the composition of the magnetic paint in Example 1, VA G
8 parts by weight of nitrocellulose H1/2 (manufactured by Chokasei Co., Ltd., nitrocellulose) was used in place of H8 weight ft m, and Crisbon 720 was used in place of polyethylene glycol #600.
9 (Manufactured by Dainippon Ink Co., Ltd., polyurethane elastomer)
A magnetic tape was produced in the same manner as in the example except that 8 parts by weight was used.

Comparative Example 1 In the composition of the magnetic paint in Example 1, the isocyanate compound used in Example 1 was replaced with Coronet) L(
A magnetic tape was prepared in the same manner as in Example 1, except that the same amount of trifunctional low molecular weight isocyanate compound (manufactured by Nippon Polyurethane Industries, Ltd.) was used.

Ratio I biting example 2 In the composition of the magnetic paint in Example 2, in place of the incyanate compound used in Example 2, coronae) L(
A magnetic tape was prepared in the same manner as in Example 2, except that the same amount of trifunctional low molecular weight incyanate compound (manufactured by Nippon Polyurethane Kogyo Co., Ltd.) was used.

When the magnetic paint obtained in each Example and each Comparative Example was left to stand, the one obtained in each Comparative Example gelled in 2 to 3 days, but the one obtained in each Example was left to stand for 3 weeks. There was no abnormality. This shows that the magnetic paint according to the present invention has a longer pot life.

In addition, the squareness of the magnetic tapes obtained in each example and each comparative example was measured, and each magnetic tape was loaded into a tape recorder and run repeatedly at a running speed of 3.35 m/sec, 100 times. The number of dropouts per unit time after the test was measured.

The table below shows the results.

As is clear from the above table, the magnetic tapes obtained by the present invention (Examples 1 and 2) have a square shape and less dropouts than the conventional magnetic tapes (Comparative Examples 1 and 2). This shows that the magnetic recording medium obtained by the present invention is inferior in filling properties of magnetic powder and superior in durability.

Claims (1)

[Claims] 1. As a binder component, the general formula % (wherein R is -CC00(CH2) or -(CH
2) m, where n is an integer from 1 to 10, m is 1 to 1
It is an integer of 0. ) A magnetic recording medium having a magnetic layer containing an isocyanate compound represented by