JPS6070514A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium contg. well dispersed ferromagnetic powder and having high durability by using a specified copolymer and a specified monomer as the components of a binder. CONSTITUTION:A vinyl chloride-acrylic ester copolymer and an acrylic acid monomer are used as the components of a binder for a magnetic layer. Magnetic powder is kneaded with the binder components, a dispersant, a lubricant and a solvent by means of a ball mill, urethane resin and an isocyanate compound are further added, and they are kneaded to prepare a magnetic coating material. By this method a magnetic recording medium contg. well dispersed magnetic powder and having superior durability is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium in which ferromagnetic powder is highly dispersible and durable.

In general, magnetic recording media such as audio tapes and video tapes are obtained by coating a magnetic paint consisting of a ferromagnetic powder and a binder on a non-magnetic support such as polyethylene terephthalate. In such coating type magnetic recording media.

High dispersion of magnetic powder is extremely important to obtain excellent electromagnetic conversion characteristics. Various attempts have been made to achieve high dispersion of magnetic powder, and typical examples include examining and modifying the binder resin, and adding surfactants. In particular, as binder resins, many resins have been developed that are excellent in dispersibility of magnetic powder and in various physical properties after curing. Namely, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl propionate copolymer, vinyl chloride-acrylic acid ester copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, polyvinyl butyral, acrylonitrile- Butadiene copolymer, epoxy resin.

Examples include phenoxy resin and urethane resin.

Also, as an attempt to further improve dispersibility.

Various methods of blending and using these resins have been investigated, but a fully satisfactory combination has not yet been obtained.

In view of the current situation, the present inventors investigated the combination of various binders, and found that when a vinyl chloride-acrylic acid ester copolymer and an acrylic acid monomer were used as the binder, excellent dispersibility and durability were achieved. We have found that it is possible to obtain sexual characteristics7.

The vinyl chloride-acrylic ester copolymer used in the present invention has an acrylic ester component content of 0 to 6.
It is preferable that the acrylic acid ester moiety is expressed by the general formula % (%) and has an average molecular weight of 40 and ODD or less. Furthermore, the acrylic acid monomer is a compound having the following structure.

■　CH2=　CHCOOR,.

■ (CH,, = C)TCOOR,),, C/R'
\R5 ■ (CH,, = CHCOORII) 3CR7 or less Specific examples include 2-ethylhexyl aqueous IJ'J-)
, 2-hydroxypropyl acrylate), 2,2-dimethylpropane-1,3-diacrylate, and trimethylolpropane triac IJ 17-1.

Next, an example will be described.

Example 1 Magnetic powder γ-Fe2O3...Bun, A, 8-part dispersant
Lentin River/Yama... 2 parts Lubricant Stearic acid...Yama/O 5 parts After kneading the above composition in a ball mill for 20 hours, add 18 parts of urethane resin and 9 parts of Coronet C-3041 (Isonoanate compound manufactured by Nippon Polyurethane Co., Ltd.) was added and kneaded for an additional 4 hours to obtain a magnetic paint. This was applied onto a polyethylene terephthalate thin film so that the thickness after drying would be 6 μm, and then subjected to magnetic field orientation treatment using opposed orientation magnets (1,000 gauss), and after drying, it was used as a sample.

Example 2 A sample was obtained in the same manner as in Example 1, except that 4 parts of 2-ethylhexyl acrylate in Example 1 was replaced with 4 parts of trimethylolpropane triac IJ rate.

Comparative Example 1 Magnetic powder r-Fe2O 3 songs + 80 songs Binder Vinyl chloride-(2-hydroxypropyl acrylate) copolymer (vinyl chloride component content 80%, average molecular weight 30,000)...
... 12 parts Dispersant Shi/Chin ... Song 2 parts Shishi F base - Lubricant Stearic acid 0.5 parts After mixing the above composition in a ball mill for 20 hours, further urethane Add 18 parts of resin and 9 parts of Coronate C-3041 (inonoaate compound manufactured by Nippon Polyurethane Co., Ltd.),
After further kneading for 4 hours, magnetic coating O-1 was obtained. After coating this on a polyethylene terephthalate f+17 film so that the thickness after drying becomes 6prn, facing orientation magnets (1
, 000 gauss) to perform magnetic field orientation treatment,
After drying, it was used as a sample.

Comparative Example 2 Magnetic powder γ-F e 203 80 parts Binder Vinyl chloride-vinyl acetate-vinyl alcohol copolymer (the content of each component of vinyl chloride and vinyl acetate is 91
Person in charge and 3, average molecular weight 26,0OQI...
・12 parts Dispersant 7 parts 2 parts Lubricant Stearic acid 0.5 parts Mix the above composition in a ball mill for 20 hours, then add urethane. 18 parts of resin and 9 parts of Coronate C-3041 (incyanate compound manufactured by Nippon Polyurethane Co., Ltd.) were added and kneaded for an additional 4 hours to obtain a magnetic paint. After coating this on a polyethylene terephthalate thin film so that the thickness after drying would be 6 μm, a facing orientation magnet (1, DQO Gauss
) was used for magnetic field orientation treatment, and after drying it was used as a sample.

The squareness ratio in the longitudinal direction measured for each of these samples and the results of the durability test are shown in the table. The visual evaluation was made after running for 3 hours at a running speed of 68 Gin while making sliding contact with the throat.

As is clear from this table, according to the present invention, a magnetic recording medium with excellent dispersibility and durability can be obtained.

Procedural amendment (voluntary) Showa H, Melo month 2? Mr. Kazuo Wakasugi, Commissioner of the Japan Patent Office 1, Indication of the case, Patent Application No. 177086 of 1982, 2, Title of the invention: Magnetic recording medium 3, Person making the amendment 5, Detailed explanation of the invention in the specification to be amended 6 , Contents of correction 1) "18 copies" on page 4, line 15 is corrected to "l'-10 copies".

2) Correct "4 copies" on page 4, line 16 to "2 copies."

3) Correct "4 copies" on page 5, line 11 to "2 copies."

4) Correct "4 copies" on page 5, line 12 to "2 copies."

(Lee, :1-'

Claims (2)

[Claims] (1) A magnetic recording medium characterized in that the binder component of the magnetic layer is a vinyl chloride-acrylic acid ester copolymer and an acrylic acid monomer. (2) A magnetic recording medium characterized in that the binder component of the magnetic layer is a vinyl chloride-acrylic acid ester copolymer, an acrylic acid monomer, a urethane resin, and an incyanate compound.