JPH0689368B2 - Method for producing metal magnetic powder for magnetic recording - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for producing a metal magnetic powder suitable for magnetic recording having improved oxidation resistance stability.

(Technical background of the invention and its problems) In recent years, magnetic recording media such as magnetic tapes, magnetic disks, magnetic sheets, and magnetic cards for audio, video, and computers have been miniaturized due to high recording capacity. , The trend toward higher performance is becoming stronger. Combined with this, in recent years, as magnetic powder for magnetic recording media, iron-based metal magnetic powder of iron or iron-based alloys (hereinafter metal Magnetic powder) is attracting attention and
Along with the demand for higher S / N ratio and higher output, a magnetic metal powder having a fine particle size has been particularly desired.

By the way, such a metal magnetic powder has a strong surface activity, and as a result of oxidation over time, the magnetic characteristics are likely to be greatly impaired with it, and so-called deterioration of oxidation resistance is unavoidable, or even worse. In such a case, if the oxidation reaction in the air rapidly progresses, various troubles such as spontaneous ignition and combustion may be unavoidable in terms of handling operation and process control.

Various proposals have already been made to improve these problems. For example, the metallic magnetic powder immediately after being produced by reduction is slowly oxidized to form a thin iron oxide film, or an inorganic substance such as chromium, silicon, or aluminum is adhered to the metallic magnetic powder, and further, mineral oil silane is used. Attempts have been made to attach various organic substances such as coupling agents and organic phosphates to the metallic magnetic powder. However, even by these conventional methods, the oxidation resistance is not sufficiently stabilized, or while the oxidation resistance is brought about, on the other hand, the excellent magnetic properties of the metal magnetic powder are liable to be significantly impaired. The problem of remains.

(Object of the Invention) The present invention is to provide an industrially advantageous method for producing a metal magnetic powder suitable for magnetic recording, which is capable of solving the above-mentioned problems and has excellent oxidation resistance stability.

(Structure of the Invention) As a result of various investigations to solve the above-mentioned problems, the inventors of the present invention have performed various studies, and as a result, by applying a specific polyamine compound to a metal magnetic powder in a non-oxidizing atmosphere,
A dense and stable coating can be formed by a relatively small amount of treatment, and the oxidation resistance is good without substantially impairing the original magnetic properties of the metallic magnetic powder, and handling and dispersion in magnetic recording media are excellent. The present invention has been completed based on the finding that a metallic magnetic powder can be obtained. That is, the present invention is inert to the metal magnetic powder, and wet or dip the metal magnetic powder in a non-oxidizing atmosphere using a solvent capable of dissolving the polyalkyleneamine condensate represented by the following general formula, Then, a method for producing a metal magnetic powder for magnetic recording with improved oxidation stability, which is characterized by evaporating a solvent, is represented by the general formula R ₁ CONH (R ₂ NR ₃ ) _n R ₂ NHR ₃ (where, R ₁ is an alkyl or alkenyl group having 7 to 21 carbon atoms, R ₂ is C ₂ H ₄ or C ₃ H ₆ , R ₃ is H or OCR ₁ , n
Is an integer of 1 or more.) The metallic magnetic powder used as the object to be treated in the present invention is iron-based metal powder of various iron-based alloys mainly composed of iron or iron produced by various methods. And is typically in the shape of needle crystals and has an average particle size (major axis length)
Is 0.15 to 0.5μ, axial ratio is 2 to 20 and specific surface area (Sg) is 20 to 80m
² / g, coercive force (Hc) 500 to 2,000 (Oe), saturation magnetization (σ
s) 100 to 220 emu / g, but in addition to the above-mentioned needle crystal shape, various shapes such as spindle shape, rice grain shape, spherical shape, rod shape, flat plate shape, dice shape, Sg, Hc, σs etc. It may be in the above range.

In the present invention, as the polyalkylene polyamine condensate, higher fatty acids such as capric acid, caprylic acid, lauric acid, myristic acid, palmitic acid, oleic acid,
Stearic acid, coconut fatty acid, beef fatty acid, erucic acid, 12-
Dehydration condensation of hydroxamic stearic acid, isostearic acid, isopalmitic acid, etc. with polyalkylene polyamines such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, aminoethylaminopropylamine, triethylenetetraaminopropylamine From the effect and economical efficiency, one obtained by reacting 1 to 2 mol of oleic acid, stearic acid or palmitic acid with 1 mol of triethylenetetramine, tetraethylenepentamine or pentaethylenehexamine and dehydration-condensing is obtained. preferable. Specific examples thereof include (1) C ₉ H
₁₉ CONH (C ₂ H ₄ NH) ₃ C ₂ H ₄ NH ₂ , (2) C ₉ H ₁₉ CONH (C ₂ H ₄ NH) ₃ C ₂
H ₄ NHOCH ₁₉ C ₉ , (3) C ₁₁ H ₂₃ CONH (C ₂ H ₄ NH) ₃ C ₂ H ₄ NH ₂ ,
(4) C ₁₁ H ₂₃ CONH (C ₂ H ₄ NH) ₃ C ₂ H ₄ NHOCH ₂₃ C ₁₁ , (5) C ₁₇
H ₃₃ CONH (C ₂ H ₄ NH) ₂ C ₂ H ₄ NH ₂ , (6) C ₁₇ H ₃₃ CONH (C ₂ H ₄ NH) ₂
C ₂ H ₄ NH ₂ , (7) C ₁₇ H ₃₃ CONH (C ₂ H ₄ NH) ₃ , C ₂ H ₄ NHOCrl ₃₃ C
₁₇ , (8) C ₁₇ H ₃₃ CONH (C ₂ H ₄ NH) ₄ C ₂ H ₄ NH ₂ , (9) C ₁₇ H ₃₃
CONH (C ₃ H ₆ NH) ₃ C ₃ H ₆ NH ₂ , (10) C ₁₇ H ₃₅ CONHC ₂ H ₄ N (COC ₁₇ H
₃₅ ) C ₂ H ₄ NHC ₂ H ₄ NHOCC ₁₇ H ₃₅ , (11) C ₁₅ H ₃₁ CONH (C ₂ H ₄ NH) ₂
C ₂ H ₄ NH _2, and the like _{(12) C 17 H 35 CONH} (C 2 H 4 NH) 4 C 2 H 4 NHOCC 17 H 35.

These compounds may be used alone or as a mixture of two or more kinds.

In the present invention, in order to coat the metal magnetic powder with the coating treatment agent comprising the polyalkylene polyamine condensate, the treatment agent is dissolved in an appropriate solvent and the solution is used to wet or dip the metal magnetic powder. And then the solvent is evaporated. The suitable solvent, which is inert to the metal magnetic powder and capable of dissolving a part or all of the treating agent,
For example, benzene, toluene, xylene, kerosene, pyridine, acetonitrile, methyl ethyl ketone, methyl butyl ketone, cyclohexanone, ethyl acetate, methanol, ethanol, butanol, water and the like can be mentioned. It is also possible to mix two or more species. In addition, the above-mentioned wetting or immersing is carried out in a non-oxidizing atmosphere, for example, in a nitrogen gas, hydrogen gas, helium or argon gas atmosphere, or in a vacuum to prevent oxidation during the treatment. The wet or dipping treatment is usually performed at room temperature, but may be performed under heating if necessary. The processing time is usually about 10 to 300 minutes. Next, in order to evaporate only the solvent while leaving the polyalkylene polyamine condensate on the surface of the metal powder, it may be carried out by simply air drying, but it is usually carried out under heating or under reduced pressure.
In the case of heat evaporation, it is usually 50 to 220 ° C., although it cannot be generally determined depending on the type of solvent.

It is preferable to evaporate the solvent in a non-oxidizing atmosphere as much as possible. The deposition amount of the treatment agent comprising the polyalkylene polyamine condensate is
It is 0.1 to 20%, preferably 0.5 to 10%, based on the weight of the metal magnetic powder. If the deposition amount is less than the above range, the desired effect cannot be obtained, and if it is more than the above range, magnetic properties such as saturation magnetization are likely to be impaired, and further bleeding phenomenon occurs. It is not preferable because it deteriorates the performance of the magnetic coating film. Incidentally, prior to the deposition treatment of the polyalkylenepolyamine condensate, the metal magnetic powder may be subjected in advance to a treatment for producing an oxide coating, a nitride coating, an inorganic coating and the like.

The present invention will be further described with reference to examples.

Example 1 25 g of α-FeOOH acicular powder (average major axis length 0.2 μ, axial ratio 12)
Was heated in a muffle furnace at 750 ° C. for 2 hours to obtain α-Fe ₂ O ₃ . Thereafter, the obtained α-Fe ₂ O ₃ was heated and reduced in a tubular furnace in a hydrogen gas stream at 400 ° C. for 8 hours to be metallic iron powder (average major axis length 0.15 μ, axial ratio 12, specific surface area (BET Law) 55m ² / g, H
c1610 Oe, σs145emu / g). Next, as a deposition treatment agent, 10 g of the metallic iron powder was introduced into 100 ml of a solution prepared by dissolving 0.5 g of the polyalkylene polyamine condensate of the exemplified compound (7) in toluene while blowing nitrogen gas, and stirred for 2 hours. Immersion treatment was carried out at room temperature (25 ° C.), followed by filtration and drying at 120 ° C. in a nitrogen gas atmosphere to evaporate the solvent and deposit the polyalkylene polyamine condensate on the surface of the metallic iron powder. (Sample A) Example 2 A treatment was performed in the same manner as in Example 1 except that 0.5 g of the polyalkylenepolyamine condensate of the above-exemplified compound (6) was used as the deposition treatment agent in Example 1. .
(Sample B) Example 3 In Example 1, in addition to using 0.5 g of a polyalkylene polyamine condensate composed of a mixture (1: 1) of the above-exemplified compounds (6) and (7) as an adherend treatment agent. Was processed in the same manner as in the case of the same example. (Sample C) Example 4 A treatment was carried out in the same manner as in Example 1 except that 0.5 g of the polyalkylenepolyamine condensate of the above-exemplified compound (8) was used as the deposition treatment agent in Example 1.
(Sample D) Example 5 The same procedure as in Example 1 was carried out except that 0.5 g of the polyalkylenepolyamine condensate of the above-exemplified compound (5) was used as the deposition treatment agent in Example 1. (Sample E) Example 6 In Example 1, 0.5 g of a polyalkylene polyamine condensate composed of a mixture (1: 0: 5) of the above-exemplified compounds (3) and (4) was used as an adhesion treatment agent. Other than
The same process as in the case of the same example was performed. (Sample F) Example 7 In addition to using in Example 1 0.5 g of a polyalkylene polyamide condensate composed of a mixture (1: 0.5) of the above-exemplified compounds (1) and (2) as an adherend treatment agent. Is
The same process as in the case of the same example was performed. (Sample G) Comparative Example 1 In Example 1, the same treatment as in the case of the same example was performed except that the adherend treatment agent was not used. (Sample H) Comparative Example 2 The same process as in Example 1 was performed except that 0.5 g of γ-glycidoxypropyltrimethoxylane was used as the adherend treatment agent in Comparative Example 2. (Sample I) Comparative Example 3 In Example 1, a polyoxyethylene tridecyl ether phosphate-based phosphate ester was used as an adhesion treatment agent.
The procedure was the same as in the same example except that 5 g was used. (Sample J) Table 1 shows the results of measuring the following characteristics of each sample obtained in Examples 1 to 7 and Comparative Examples 1 to 3.

Powder characteristics: Coercive force (Hc), saturation magnetization (σ
s), squareness ratio (Rs) = σr / σs (σs (σr: remanent magnetization)
Was measured.

The rate of change with time Δσs of the saturation magnetization was measured after the sample powder was left for 14 days at 60 ° C and 80% relative humidity.
(%) Was obtained and used as an index of oxidation resistance stability.

Sheet characteristics: Sample powder is dispersed in a binder consisting mainly of vinyl chloride-vinyl acetate copolymer resin to prepare a magnetic paint (PVC 35%), which is applied on a polyester film by a conventional method and oriented to form a magnetic recording medium (coating). A film thickness of 8 μ) was prepared. The coercive force (Hc), residual magnetic flux density (Br) and squareness ratio (SQ) of this recording medium were measured by conventional methods.

As is clear from the results in Table 1, the metal magnetic powder obtained according to the present invention has greatly improved oxidation resistance stability, good dispersibility in a resin binder, and a high dispersibility. It is very desirable for a magnetic recording medium suitable for increasing the recording density.

(Effect of the invention) The metal magnetic powder coated with the polyalkylene polyamine condensate obtained by the method of the present invention has significantly improved oxidation resistance stability, and therefore can retain excellent magnetic properties for a long period of time. It is excellent in storage stability per se, very favorable in handling operation and process control, and has good dispersibility in the medium, which is extremely suitable for producing a high output, high recording density magnetic recording medium. It is something. Further, according to the method of the present invention, the performance such as the oxidation resistance can be industrially advantageously imparted by a relatively simple means without impairing the magnetic properties.

Claims (1)

[Claims] 1. A magnetic magnetic powder is wetted or dipped in a non-oxidizing atmosphere using a solvent which is inert to the magnetic metal powder and in which a polyalkylene polyamine condensate represented by the following general formula is dissolved, and then the solvent is used. A method for producing a metal magnetic powder for magnetic recording with improved oxidation resistance, characterized by evaporating a general formula R ₁ CONH (R ₂ NR ₃ ) _n R ₂ NHR ₃ (wherein R ₁ is carbon An alkyl group or an alkenyl group of the numbers 7 to 21, R ₂ is C ₂ H ₄ or C ₃ H ₆ , R ₃ is H or OCR ₁ , and n is an integer of 1 or more)