JPS5837610B2 - magnetic recording medium - Google Patents

Description

Detailed Description of the Invention The present invention relates to a magnetic recording medium such as a magnetic tape, and its object is to provide a magnetic layer in which the binder component is mainly vinyl chloride-vinyl propionate copolymer or this and urethane elastomer. The objective is to improve the heat resistance of

The inventors found that the use of vinyl chloride-vinyl propionate copolymer as a binder in the magnetic layer improves the dispersibility and wear resistance of magnetic powder compared to the conventionally widely used vinyl chloride-vinyl acetate copolymer. It was also found that adding urethane elastane to the above copolymer further improves the abrasion resistance.

However, this type of copolymer has poor heat resistance and tends to increase the wear loss of magnetic powder due to thermal deterioration.As a result of further research, it was found that a low molecular weight epoxy resin was added to the above copolymer or to the urethane elastomer. It was found that heat resistance was improved by adding it, and this invention was made.

The vinyl chloride-vinyl propionate copolymer of this invention has better affinity with magnetic powder than conventional vinyl chloride-vinyl acetate copolymers, and is relatively flexible, which improves the dispersibility of the magnetic powder and the magnetic layer. Improves wear resistance.

A specific example of the copolymer is Ryuron QA manufactured by Toyo Soda Co., Ltd.
-431,! J Yuron QA-433, Ryuron QJ
-L Ryuron QS-4301 Ryuron Q8
530 and the like.

The urethane elastomer that can be used in combination with the above copolymer is a high molecular weight urethane resin that does not have free isocyanate groups, and this type of urethane resin has good compatibility with the copolymer and plays a role as a plasticizer for the copolymer. As a result, the flexibility of the magnetic layer is made more appropriate, thereby further improving wear resistance.

Specific examples of urethane elastomers include Nipporan 82304 manufactured by Nippon Polyurethane Industries, Paraprene 22S,
Examples include Estan 5702, Estan 5715, and Estan 5711 manufactured by Goodrich Chemical Company, USA.

The proportion used is usually 5 to 50% by weight based on the total amount with the copolymer.
The amount is preferably 10 to 30% by weight; if too much is used, the dispersibility characteristic of the copolymer will be impaired.

The low molecular weight epoxy resin used in this invention is a generally liquid epoxy resin with a molecular weight of about IOOO or less, preferably about 300 to 500. When this epoxy resin is used in combination with the copolymer, it plays a role as a stabilizer for the copolymer. This suppresses thermal deterioration over time, thereby improving the heat resistance of the magnetic layer.

The proportion used is usually 10% by weight or less, preferably 2 to 5% by weight, based on the total amount of the binder.

Specific examples of epoxy resins include Epicoat #828 manufactured by Shell Petrochemical Co., Ltd. and Evicron #8 manufactured by Dainippon Ink Industry Co., Ltd.
50, etc.

Examples of magnetic powder applicable to this invention include r-F
e203 powder, Fe304 powder, Co-containing γF e 2
03 powder, Co-containing Fe304 powder, Cr
A wide variety of conventionally known powders are included, such as O2 powder.

The magnetic recording medium of the present invention can be produced according to a conventional method. For example, in the case of a magnetic tape, a base film such as a polyester film, a magnetic powder, a vinyl chloride-vinyl propionate copolymer, or a urethane elastomer and the like are used. A binder with the addition of low molecular weight epoxy resin,
A magnetic paint consisting of a required organic solvent and other additives may be applied by any means such as spraying or roll coating, and then dried.

Next, the present invention will be specifically explained with reference to examples.

In addition, in the following, parts indicate parts by weight.

Example row 1 400 parts of γ-Fe203 powder, 38 parts of granular α-F0203, 8 parts of carbon black, 2 parts of zinc stearate, vinyl chloride-vinyl propionate copolymer (Luron QA
-431, supra), 100 parts of low molecular weight epoxy resin (Epicote #828, supra), 4 parts of liquid paraffin, and I of toluene, methyl ketone, and tetrahydrone
:A mixture consisting of 770 parts of a 1:1 mixed solvent was stirred and dispersed in a ball mill for about 70 hours to prepare a magnetic coating material.

This magnetic paint is applied to a polyester film having a thickness of 21 μm to a dry thickness of 5 to 6 μm and dried.

Next, the surface of the magnetic layer was calendered and mirror-finished, and then
It is cut to a specified width to make magnetic tape for video.

Example 2 In place of 100 parts of the vinyl chloride-vinyl propionate copolymer of Example WIJx, 80 parts of the above copolymer and urethane elastomer (manufactured by Nippon Polyurethane Kogyo Co., Ltd., Nitsuporan #2) were used.
Example 1 except that a mixed resin with 20 parts of 304) was used.
I made magnetic video tape in exactly the same way.

A video magnetic tape was made in the same manner as in Example 1 for the reference column except that 3 parts of the low molecular weight epoxy resin was not used.

Comparative Example A video was produced in exactly the same manner as in Example 1, except that 100 parts of vinyl chloride-vinyl acetate copolymer was used in place of 100 parts of vinyl chloride-vinyl propionate copolymer and 3 parts of low molecular weight epoxy resin in Example 1. created magnetic tape for

The S/N ratio of each of the above magnetic tapes and the results of the abrasion resistance test are shown in Table 1 below.

However, in the abrasion resistance test, a certain length of magnetic tape is connected in a loop, and the wear loss after running for 1 hour in sliding contact with a magnetic head at a running speed of 380 ml seconds is calculated as an index, with the comparison example being 100. It is expressed as

Further, the results of heat resistance tests of Examples 1 and 2 and Reference Examples are shown in Table 2 below.

However, in the heat resistance test, after using a Weather-O-meter (equivalent to outdoor exposure for one year), a test similar to the above-mentioned abrasion resistance test was conducted to measure the wear loss, and the reference example was taken as 100 and expressed as an index.

As is clear from Tables 1 and 2 above, the magnetic tape of the present invention (Execution F!I1, 2) is different from the conventional magnetic tape (comparative example) using vinyl chloride-vinyl acetate copolymer.
It can be seen that not only the dispersibility and abrasion resistance of the magnetic powder are better than that of the magnetic powder, but also the heat resistance is improved compared to the one that does not use a low molecular weight epoxy resin (reference row).

Claims (1)

[Claims] 1. A magnetic recording medium in which the binder of the magnetic layer is mainly composed of pinychloride-vinyl propionate copolymer or a urethane elastomer and a low molecular weight epoxy resin.