Stock material or miscellaneous articles – Composite – Of inorganic material
Patent
1983-09-09
1985-12-03
Barr, Josephine L.
Stock material or miscellaneous articles
Composite
Of inorganic material
428695, 428900, 427 44, 360134, 360135, 360136, 252 6254, 252519, G11B 570
Patent
active
045566119
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a magnetic recording medium and, more particularly, to a magnetic recording medium having a superior durability.
BACKGROUND ART
In order to enhance the durability of a magnetic recording medium, there has been employed a method, for example, of providing an improved binding of magnetic powder to a binder using a binder having a high compatibility with the magnetic powder, thus improving dispersibility and packing properties to decrease the rubbing-off of the powder. In this method, it has been proposed that there be employed as a binder a polymer which is modified by the polymerization of its copolymeric ingredients highly compatible with the magnetic powder, thereby improving the binding property of the binder to the magnetic powder. This method, however, requires that all the copolymeric ingredients are capable of being polymerized. Even if this requirement is met, a binder containing a desired amount of copolymeric ingredients cannot be produced or a block copolymer is produced in the absence of a proper relative polymerzation ratio, so that conditions of manufacture are significantly limited. This method is accordingly less valuable and less practical in industrial applications.
DISCLOSURE OF INVENTION
The object of this invention is to provide a magnetic recording medium having a superior durability by using a binder containing a modified polymer.
The modified polymer used in this invention can be obtained by modifying a polymer conventionally used as a binder for magnetic recording media by graft-polymerizing a nitrogen-containing polymerizable unsaturated compound onto the polymer by the irradiation of radiation.
That is, such a modified polymer can be obtained by first irradiating the polymer to be graft-polymerized with a radiation such as gamma rays, electron beams or the like, to generate organic free radicals and then graft-polymerizing the nitrogen-containing polymerizable unsaturated compound to the free radical to modify the polymer. The modified polymer can be also obtained by using a mixture of a polymer usually used as a binder for magnetic recording media and a nitrogen-containing polymerizable unsaturated compound and irradiating the mixture with radiation to perform the graft-polymerization.
Any polymer which can generate free radicals upon being irradiated with radiation and is not degraded by the radiation may be used as the polymer to be modified by the graft polymerization of a nitrogen-containing polymerizable unsaturated compound to the polymer. It is to be noted that, since any organic material without exception can produce free radicals if a radiation having a high penetrating power is used, and since a polymer likely to be degraded by such radiation can produce enough free radicals to react with the nitrogen-containing polimerizable monomer even if the radiation is applied at a small dose under conditions which control degradation, the applicable range of the foregoing method is very broad.
It is preferred that the polymer to which the aforesaid method can be applied has a molecular weight ranging from about 10,000 to about 100,000. Such a polymer may be enumerated by, for example, a vinyl chloride-vinyl acetate copolymer, a vinyl chloride-vinyl propionate copolymer, a vinyl chloride-vinyl acetate-vinyl alcohol copolymer, a vinyl chloride-vinyl propionate-vinyl alcohol copolymer, a vinyl chloride-vinyl acetate-maleic acid copolymer, a vinyl chloride-vinylidene chloride copolymer, a vinyl chloride-acrylonitrile copolymer, an acrylic ester-acrylonitrile copolymer, an acrylic ester-vinylidnene chloride copolymer, a methacrylic ester-vinylidene chloride copolymer, a methacrylic ester-styrene copolymer, a thermoplastic resin, a phenoxy resin, polyvinyl fluoride, a vinylidene chloride-acrylonitrile copolymer, a butadiene-acrylonitrile copolymer, an acrylonitrile-butadiene-acrylic acid copolymer, an acrylonitrile-butadiene-methacrylic acid copolymer, polyvinyl butyral, a cellulose derivative, a styrene-butadiene copolymer, a polyester
REFERENCES:
patent: 4396660 (1983-08-01), Hata et al.
patent: 4410584 (1983-10-01), Toba et al.
patent: 4415630 (1983-11-01), Kubota et al.
Barr Josephine L.
Sony Corporation
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