JPH0554370A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve durability and electromagnetic conversion characteristics by treating the surfaces of powder components, such as magnetic powder, forming a magnetic layer with a specific polyether compd. CONSTITUTION:This magnetic recording medium is constituted by providing the magnetic layer formed by dispersing the powder components, such as magnetic powder, into a binder on a nonmagnetic base. At least the surfaces of the magnetic powder in the powder components of such magnetic layer are treated with the polyether having 1000 to 5000 number average mol.wt. and an acid chloride group at both terminals of the molecule. The dispersibility of the powder components including the magnetic powder is improved in this way and the excellent electromagnetic conversion characteristics are exhibited.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium having good dispersibility of powder components such as magnetic powder, excellent electromagnetic conversion characteristics and excellent durability.

[0002]

2. Description of the Related Art In a magnetic coating material used for a magnetic recording medium such as a video tape or a floppy disk, improvement of dispersibility of powder components including magnetic powder is
It is an important factor for improving the durability of magnetic recording media and obtaining excellent electromagnetic conversion characteristics such as high reproduction output and high C / N ratio. Studies have been conducted from various points of view to improve the dispersibility of such powder components. For example, a method of treating the surface of the powder component with a binder in advance, a method of treating the surface of the powder component with a silane coupling agent or a titanium coupling agent, a method of adding a dispersant such as a phosphate ester or lecithin, and the like have been tried. However, none of these methods is satisfactory in improving the dispersibility of powder components such as magnetic powder, and a magnetic recording medium having excellent durability and electromagnetic conversion characteristics has not been provided yet. ..

[0003]

[Means for Solving the Problems] As a result of intensive studies to solve the above problems, the present inventors have found that the number average molecular weight is 1,000 to
By treating the surface of the powder component such as magnetic powder forming the magnetic layer with a polyether compound having an acid chloride group at both ends of 5000, the dispersibility of the powder component is improved, and the durability and electromagnetic conversion characteristics are improved. It was found that an excellent magnetic recording medium can be obtained, and the present invention has been completed.

That is, the present invention provides a magnetic recording medium having a magnetic layer in which a powder component such as magnetic powder is dispersed in a binder on a non-magnetic support, and at least the magnetic powder is contained in the powder component in the magnetic layer. The present invention provides a magnetic recording medium characterized in that the surface thereof is treated with a polyether compound having a number average molecular weight of 1000 to 5000 and having acid chloride groups at both ends of the molecule.

Number average molecular weight 1000 to 50 used in the present invention
For example, a polyether compound having acid chloride groups at both terminals of 00 is, for example, a glycol polymer (polyethylene glycol, polypropylene glycol, polybutylene glycol, etc.) and a dibasic acid (adipic acid, isophthalic acid, etc.).
Obtained by reacting with chloride. This reaction is represented by the following formula.

[0006]

[Chemical 1]

As the polyether compound, as shown in the following formula, a compound obtained by reacting a diamine having a polyether skeleton and amino terminals at both ends with a dibasic acid chloride as described above is used. It can also be used. still,
The diamine used in this reaction is commercially available and is easily available.

[0008]

[Chemical 2]

The number average molecular weight of the polyether compound according to the present invention is in the range of 1000 to 5000, and the molecular weight is
If it is less than 1,000, the dispersing effect itself is poor, and if the molecular weight exceeds 5,000, the reactivity with the functional groups on the powder surface may be lowered, and as a result, the function as a dispersant is lowered.

Examples of the powder component treated with the above polyether compound include magnetic powder, carbon black, alumina used as an abrasive, chromium oxide, and the like. Of these powder components, at least the magnetic powder needs to be treated. That is, of the powder components used in the magnetic paint,
Since the magnetic powder is the largest in quantity, treating it is advantageous in terms of the effect of improving dispersibility.

The amount of the polyether compound according to the present invention to be used is 5 to 50 parts by weight, preferably 10 to 30 parts by weight, based on 100 parts by weight of the total amount of powder components. The surface treatment is performed by heating and stirring in an organic solvent such as toluene or tetrahydrofuran. However, when the polyether compound is liquid, it can be treated without an organic solvent. Also,
The powders other than the magnetic powder may be treated in the same manner, and some powders may be treated by a method utilizing the reaction with the functional group (hydroxyl group, carboxyl group, carbonyl group, etc.) on the surface.

The magnetic powder that can be used in the magnetic recording medium of the present invention is acicular fine γ-Fe ₂ O ₃ , Fe ₃ O ₄ , Cr.
O ₂ -like metal oxides, Co-deposited γ-Fe ₂ O ₃ , Co-doped γ-Fe ₂ O ₃ processed γ-Fe ₂ O ₃ , iron-based metal magnetism Powder (usually called metal powder), microplate-like barium ferrite and some of its Fe atoms are T
Magnetic powder substituted with i, Co, Zn, V, Nb, etc., Co, Fe-Co,
Examples include ultrafine powders of metals such as Fe-Ni or alloys.

As the binder used in the magnetic recording medium of the present invention, polyurethane resin, polyester, polyvinyl chloride, vinyl chloride / vinyl acetate copolymer, polyacrylonitrile, nitrile rubber, epoxy resin, alkyd resin, polyamide, poly Acrylic ester, polymethacrylic acid ester, polyvinyl acetate, polyvinyl butyral, vinylidene chloride, vinylidene chloride copolymer, nitrification cotton, maleic acid modified vinyl chloride / vinyl acetate copolymer,
Examples include various resins such as ethyl cellulose. These may be used alone or in combination of two or more. The amount of the binder compounded is generally 15 to 60 parts by weight based on 100 parts by weight of the magnetic powder.

The non-magnetic support used in the magnetic recording medium of the present invention includes polyesters such as polyethylene terephthalate and polyethylene naphthalate; polyolefins such as polyethylene and polypropylene; cellulose derivatives such as cellulose triacetate and cellulose diacetate; polycarbonates; Polyvinyl chloride; polyimide; plastic such as aromatic polyamide; metal such as Al and Cu; paper and the like. The form may be any of film, tape, sheet, disk, card, drum and the like. The surface of the support may be treated with corona discharge, radiation, ultraviolet rays or the like, or may be precoated with a suitable resin.

In the magnetic layer of the magnetic recording medium of the present invention, in addition to the above-mentioned components, a dispersant, a lubricant, an abrasive, a rust preventive, a fungicide and the like are added as additives usually used in this field. May be. Further, a curing agent such as a polyisocyanate compound may be used to adjust the hardness of the magnetic layer.

[0016]

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Parts and% in the examples are based on weight unless otherwise specified.

Example 1 Synthesis of Polyether Compound A flask equipped with a dropping funnel, a reflux condenser and a nitrogen introducing tube was charged with 1 mol of polypropylene glycol having a number average molecular weight of 2000, and 2 mol of adipic acid chloride was dropped from the dropping funnel. While stirring at 50 ° C. for 3 hours, a desired polyether compound having acid chloride groups at both ends was obtained (number average molecular weight: about 2292). Hereinafter, this polyether compound was used as a treating agent. Treatment of magnetic powder In a flask, 20 parts of the polyether compound obtained above and triethylamine as a dehydrochlorinating agent were added to 100 parts of metal powder (major axis diameter 0.2μ, axial ratio 10, coercive force 1450 Oe).
Add 0.1 parts and 100 parts of toluene as solvent, and add 1 part at 50 ℃.
Stir for 0 hours. Then, 900 parts of tetrahydrofuran was added, and this was centrifuged at 10,000 ppm to take out a precipitate, and the precipitate was washed with tetrahydrofuran to obtain a surface-treated magnetic powder. Preparation of magnetic paint ・ 100 parts of treated magnetic powder obtained above ・ Polyurethane resin 9 ・ Vinyl chloride / vinyl acetate resin 13 ・ Carbon black (average particle size 17 nm) 8 ・ Alumina (average particle size 0.2 μ) 2 ・ Palmitin Acid 1.25 ・ Stearic acid butyl ester 0.75 Ingredients shown above and solvent (methyl ethyl ketone / toluene / cyclohexanone = 2/2/3 weight ratio mixed solvent)
To a solid content of approximately 35%, and mix with a disper to 90
Minutes, and then kneaded for 4 hours with a Glen Mill, and further 4 parts of a curing agent (trade name Coronate L manufactured by Nippon Polyurethane Industry Co., Ltd.) was added to obtain a magnetic coating material. Production of tape and measurement of its physical properties The above magnetic paint was applied on a polyethylene terephthalate film with a thickness of 10μ to a dry film thickness of 2.5μ,
After the magnetic field orientation, it was naturally dried and the gloss (light reflectance) of this product was measured. The results are shown in Table 1. Further, the naturally dried product was calendered, kept at 60 ° C. for about 48 hours, and slit into a predetermined width to obtain a magnetic tape. The gloss and squareness of this magnetic tape were measured. The results are shown in Table 1.
Shown in.

Comparative Example 1 In Example 1, a magnetic tape was prepared in the same manner as in Example 1 except that the magnetic powder not treated with the polyether compound was used, and the same evaluation was performed. The results are shown in Table 1.

Comparative Example 2 In Example 1, the magnetic powder was treated with 20 parts of phosphoric acid ester (sesquiphosphoric acid ester containing nonylphenyl group to which ethylene oxide was added) instead of the polyether compound. A magnetic tape was prepared in the same manner as in Example 1 and evaluated in the same manner. The results are shown in Table 1.

[0020]

[Table 1]

Example 2 Instead of adipic acid chloride used in the synthesis of the polyether compound of Example 1, isophthalic acid chloride was used to synthesize the polyether compound.
A magnetic tape was prepared in the same manner as above, and the same evaluation was performed. As a result, almost the same measured values as in Example 1 were obtained.

Example 3 To 100 parts of all powder components (magnetic powder + carbon black + alumina) used in the preparation of the magnetic paint in Example 1, 20 parts of the polyether compound synthesized in Example 1 were used. A magnetic tape was produced in the same manner as in Example 1 except that the powder component of Example 1 was treated, and the same evaluation was performed. As a result, a value improved by about 10% from the numerical value of Example 1 was obtained.

Claims (1)

[Claims] 1. A magnetic recording medium having a magnetic layer in which a powder component such as magnetic powder is dispersed in a binder on a non-magnetic support, wherein at least the surface of the magnetic powder in the powder component in the magnetic layer is A magnetic recording medium characterized by being treated with a polyether compound having a number average molecular weight of 1,000 to 5,000 and having acid chloride groups at both ends of the molecule.