JPS627606B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a binder used for magnetic recording media such as audio tapes, video tapes, magnetic cards, and magnetic sheets. Conventional magnetic recording media are made of ferromagnetic powder such as gamma iron oxide or chromium dioxide on a support such as polyethylene terephthalate, cellulose triacetate, polycarbonate, or polypropylene, and are coated with vinyl chloride-vinyl acetate copolymer, polybutyl acrylate, or acrylic. Ferromagnetic powder is manufactured by coating and laminating a binder such as butyl acid-acrylonitrile copolymer, but ferromagnetic powder is highly polar and has the disadvantage of poor wetting with the binder and poor dispersibility. Therefore, dispersants such as higher fatty acids, metal soaps, higher alcohols, polyethylene oxide, and lecithin are added. However, even if the above-mentioned dispersant is added, it is not dispersed sufficiently uniformly, creating voids between particles.
It has drawbacks such as low residual magnetic flux density, squareness ratio, S/N ratio, etc., and also has drawbacks such as blooming of the above-mentioned dispersant. The object of the present invention is to have compatibility with ferromagnetic powder that does not have the above-mentioned drawbacks, has a wide dynamic range, has a high S/N ratio, and is suitable for producing a magnetic recording medium that does not cause blooming. The object of the present invention is to provide a binder that can uniformly disperse magnetic powder because of its excellent properties. The gist of the invention is 2-acidophosphoxyethyl acrylate, 2-acidophosphoxyethyl methacrylate, acidphosphoxypropyl alklate, acidphosphoxypropyl methacrylate, 3-chloro-2-acidophosphoxypropyl acrylate and 3-chloro-2
- at least one phosphoric acid ester of alkylene glycol acrylate or alkylene glycol methacrylate of acid phosphoxypropyl methacrylate, and at least one of acrylate, methacrylate, acrylic acid, methacrylic acid, vinyl acetate, styrene, acrylonitrile and vinyl chloride; The phosphoric acid ester of alkylene glycol acrylate or alkylene glycol methacrylate used in the present invention is present in a binder for magnetic recording media which contains as a main component a copolymer with a type of copolymerizable monomer. For example, it can be obtained by hydrolyzing a reaction product of alkylene glycol acrylate or alkylene glycol methacrylate and anhydrous phosphorus pentoxide. Specifically, the phosphoric acid esters include 2-acidophosphoxyethyl acrylate, 2-acidophosphoxyethyl methacrylate, acidphosphoxypropyl acrylate, acidphosphoxypropyl methacrylate, and 3-chloro-
At least one of 2-acidophosphoxypropyl acrylate and 3-chloro-2-acidophosphoxypropyl methacrylate is used. The monomer copolymerizable with the phosphoric acid ester used in the present invention is a monomer having ethylenic unsaturation, such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isobutyl acrylate, t- Butyl acrylate, amyl acrylate, hexyl acrylate, cyclohexyl acrylate, heptyl acrylate, octyl acrylate, nonyl acrylate, decyl acrylate, dodecyl acrylate, tetradecyl acrylate, hexadecyl acrylate, stearyl acrylate,
β-hydroxyethyl acrylate, diethylene glycol acrylate, polyethylene glycol acrylate, β-hydroxypropyl acrylate, glycidyl acrylate, diethylaminoethyl acrylate, 7-amino-3,7-dimethyloctyl acrylate, dimethylaminoethyl acrylate, 2-cyanoethyl acrylate, β- Acrylates such as ethoxyethyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, amyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, heptyl methacrylate, octyl methacrylate, nonyl methacrylate, decyl methacrylate, dodecyl methacrylate , tetradecyl methacrylate, stearyl methacrylate,
At least one of methacrylates such as β-hydroxyethyl methacrylate, β-hydroxypropyl methacrylate, diethylene glycol methacrylate, polyethylene glycol methacrylate, and glycidyl methacrylate, acrylic acid, methacrylic acid, vinyl acetate, styrene, acrylonitrile, and vinyl chloride is used. , acrylate or methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate and butyl methacrylate are preferably used. In the present invention, the phosphoric acid ester and the monomer are copolymerized to form a binder for magnetic recording media, but the copolymerization method is not particularly limited; for example, solution polymerization, Any known method such as emulsion polymerization may be employed. The copolymerization ratio is also not particularly limited, but if the amount of the phosphoric acid ester is too small, the dispersibility of the ferromagnetic material will decrease, and if it is too large, gelation may occur during the reaction.
Since the solubility in solvents decreases, the amount of the phosphoric acid ester in the copolymer is preferably 0.01 to 10% by weight, more preferably 0.5 to 5.5% by weight. The method of using the binder for magnetic recording media of the present invention is not particularly limited, and may be used in the same manner as conventionally known binders, for example, by dissolving it in a solvent such as toluene, methyl ethyl ketone, or methyl isobutyl ketone. Next, a magnetic recording medium is obtained by adding and dispersing a ferromagnetic material such as gamma iron oxide or chromium dioxide, and coating the mixture onto a support such as polyethylene terephthalate or cellulose triacetate and drying it. It goes without saying that the binder of the present invention may be used in combination with conventionally used binders. The structure of the binder for magnetic recording media of the present invention is as described above, and since the copolymer contains a specific phosphoric acid ester of alkylene glycol acrylate or alkylene glycol methacrylate, it can be wetted with a ferromagnetic material. (affinity) is very good, so it has excellent dispersibility. Therefore, when ferromagnetic powder is dispersed and applied to a support, the ferromagnetic powder is uniformly dispersed and coated at high density without creating any gaps between particles, resulting in a wide dynamic range and a high S/N ratio. A great magnetic recording medium can be obtained. Furthermore, since the binder of the present invention has good leakage with the ferromagnetic material, there is no need to add dispersants such as higher fatty acids or metal soaps, so there is no problem such as blooming. Therefore, the binder of the present invention is suitably used as a binder for magnetic recording media such as audio tapes, video tapes, computer tapes, magnetic cards, magnetic sheets, and magnetic disks. Next, embodiments of the present invention will be described. Note that simply "parts" means "parts by weight." Example 1 Methyl methacrylate 75 parts Butyl acrylate 20 parts 2-Acid phosphoxyethyl methacrylate
5 parts Azobisisobutyronitrile 0.6 parts Toluene 75 parts Methyl isobutyl ketone 75 parts While replacing the mixture with the above composition with nitrogen, 80 parts
A copolymer solution was obtained by reacting at ℃ for 8 hours. The obtained copolymer solution was dried to obtain a dry product of the copolymer, 1 part and 2.5 parts of the dry product were dissolved in methyl isobutyl ketone, and γ-iron oxide 10 was added to the obtained solution.
24 hours later, the adsorption amount and sedimentation volume were measured. The results are shown in Table 1. Copolymer solution 50 parts γ-iron oxide 47 parts Toluene 47.5 parts Methyl isobutyl ketone 47.5 parts Next, the mixture having the above composition was mixed with a ball mill for 15 parts.
The mixture was mixed and dispersed for a period of time to obtain a magnetic paint, which was coated onto a polyethylene terephthalate film having a thickness of 25 μm to a thickness of 6 μm after drying, and dried to obtain a magnetic film. The squareness ratio of the magnetic film was measured and shown in Table 1. Examples 2 and 3, Comparative Examples 1 to 2 The compositions shown in Table 2 were polymerized in the same manner as in Example 1, and the adsorption amount and sedimentation were determined in the same manner as in Example 1. The volume was measured and the results are shown in Table 1. A magnetic coating material was obtained in the same manner as in Example 1, and then a magnetic film was obtained, and the squareness ratio was measured, and the results are shown in Table 1. Furthermore, comparative example 2
The magnetic paint gelled.

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Claims (1)

[Scope of Claims] 1 2-Acidphosphoxyethyl acrylate, 2-Acidphosphoxyethyl methacrylate, Acidphosphoxypropyl acrylate, Acidphosphoxypropyl methacrylate, 3-Chloro-2-Acidphosphoxypropyl Phosphate ester of at least one alkylene glycol acrylate or alkylene glycol methacrylate among acrylate and 3-chloro-2-acidophosphoxypropyl methacrylate, acrylate, methacrylate, acrylic acid, methacrylic acid, vinyl acetate, styrene, acrylonitrile A binder for a magnetic recording medium, which contains as a main component a copolymer with at least one copolymerizable monomer of vinyl chloride. 2. The binder according to claim 1, wherein the content of the phosphoric acid ester of alkylene glycol acrylate or alkylene glycol methacrylate in the copolymer is 0.01 to 10% by weight.