JPH05299217A - Metal magnetic powder and magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the oxidation-resistant property of metal magnetic powder by a method wherein the surface of the metal magnetic powder is modified conjointly using a specific compound and phenylpropanoid, and the surface is bonded. CONSTITUTION:The surface of the title metal magnetic powder is modified at least using a kind of compound X indicated by the general formula A- (COOH)2, A- (CO)2O or A- (OH)2 (provided that A in the formula indicates a phenyl radical, a cyclohexyl radical or a naphthyl radical, and a substitute may be used), and also using at least a kind of pheylpropanoid. The title magnetic recording medium is provided with a magnetic layer 2, containing metal magnetic powder and a bonding agent, formed by coating on one surface of a non-magnetic supporting member 1, and a back coat formed on other surface of the supporting member 1 using non-magnetic powder and a bonding agent. Phthalic acid and 1,2 cyclohexanecarboxylic acid are enumerated as the compound X, and cinnamic acid, phenylacanine and the like are enumerated as phenylpropanoid. As a result, the oxidation-resistant property of the metal magnetic powder can be improved without deterioration of magnetic characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic metal powder (particularly, ferromagnetic metal fine particles used as a magnetic powder of a coating type magnetic recording medium), and a magnetic recording medium using the magnetic metal powder.

[0002]

2. Description of the Related Art Generally, a magnetic recording medium such as a magnetic tape is manufactured by applying a magnetic coating material composed of magnetic powder and a binder resin onto a non-magnetic support and drying it. In recent years, in the field of magnetic recording, particularly in video tape recorders and the like, higher recording density is required in order to achieve high image quality.

With this increase in density, iron or iron-based metal materials have come to be used in place of iron oxide-based materials conventionally used as magnetic powder for magnetic recording media.

In particular, Fe is the main component, and Co and Ni
Metal magnetic powders (metal magnetic powders) to which is added have been used for magnetic recording media. Recently, due to demands for higher recording density and higher frequency band, those metal magnetic powders having a smaller grain size, in other words, a larger specific surface area, have been selected and selected by the BET method. Specific surface area (SSA / BET value) is 50
It has been put to practical use even if it exceeds m ² / g.

However, as the SSA / BET value increases, the generation of oxidation (rust) on the powder surface has become a serious problem. That is, since rust is essentially non-magnetic, and its generation causes deterioration of the magnetic flux density Br and the coercive force Hc, the improvement of the oxidation resistance of the metal magnetic powder has become a real problem.

For the purpose of improving the oxidation resistance, it has been proposed to add another metal component to form an alloy or to coat the surface of the magnetic powder with a material having excellent oxidation resistance. All of these are accompanied by deterioration of the magnetic properties of the magnetic powder, and it cannot be said that satisfactory results have been obtained.

[0007]

OBJECT OF THE INVENTION It is an object of the present invention to provide a magnetic metal powder having excellent oxidation resistance and magnetic properties, and a magnetic recording medium using the same.

[0008]

That is, the present invention provides the following general formula: A- (COOH) ₂ , A- (CO) ₂ O or A- (OH) ₂ (wherein A is a phenyl group, cyclohexyl). Group or naphthyl group, which may have a substituent such as a methyl group) at least 1 in the compound X
And a metal magnetic powder surface-modified with at least one of phenylpropanoids.

The present invention also provides a magnetic recording medium in which a magnetic layer containing the above-mentioned metal magnetic powder and a binder is formed by coating on a non-magnetic support.

According to the present invention, the compound of the above general formula and the above phenylpropanoid (wherein the phenyl group has 3 carbon atoms)
Carbon skeleton C ₆ having a carbonyl group-containing hydrocarbon group bonded thereto
-C ₃ structure compound) is used together to modify the surface of the metal magnetic powder, and the metal magnetic powder is unexpectedly improved in oxidation resistance and at the same time has good magnetic properties. Turned out to be retained. It is considered that this is because a coating film composed of both the above compounds is sufficiently formed on the surface of the magnetic metal powder.

In this case, a hydroxyl group or the like contained in the molecules of both compounds and a surface of the metal magnetic powder (hydroxyl group which is a hydrophilic group) cause a dehydration reaction to form a film of the compound on the surface of the metal magnetic powder. It is presumed that this coating prevents the oxidation reaction of the surface of the metallic magnetic powder that occurs during storage of the magnetic magnetic powder, preparation of the magnetic coating material containing the magnetic magnetic powder, and storage of the magnetic recording medium. To be done.

The magnetic metal particles (ferromagnetic metal particles) used in the magnetic recording medium according to the present invention include Fe, Co and Ni.
Ferromagnetic metal materials such as Fe-Co, Fe-Ni, Fe
-Co-Ni, Co-Ni, Fe-Mn-Zn, Fe-
Ni-Zn, Fe-Co-Ni-Cr, Fe-Co-N
i-P, Fe-Co-B, Fe-Co-Cr-B, Fe
Ferromagnetic metal fine particles made of various ferromagnetic alloy materials containing Fe, Co, and Ni as main components, such as -Co-V. Furthermore, for the purpose of improving these various characteristics, Al, S
An element such as i, Ti, Cr, Mn, Cu, Zn, Mg, or P may be added.

Although the specific surface area of these ferromagnetic metal fine particles is arbitrary, it is highly effective when applied to a specific surface area of 25 m ² / g or more, further 30 m ² / g or more, especially 40 m ² / g or more. ..

Examples of the compound X used for such surface modification of the metallic magnetic powder are as follows. The compound X may be used alone or in combination of two or more.

[0015]

[Chemical formula 1] Phthalic acid:

[0016]

Embedded image 1,2-cyclohexanedicarboxylic acid:

[0017]

Embedded image 2,3-naphthalenedicarboxylic acid:

[0018]

Embedded image Phthalic anhydride:

[0019]

Embedded image 1,2-cyclohexanedicarboxylic acid anhydride:

[0020]

Embedded image 2,3-naphthalenedicarboxylic acid anhydride:

[0021]

[Chemical 7] Catechol:

[0022]

Embedded image 1,2-dihydroxycyclohexane:

[0023]

Embedded image 2,3-dihydroxynaphthalene:

Further, as the phenylpropanoid for surface-modifying the metal magnetic powder together with the compound X, the following can be used. The phenylpropanoids may be used alone or in combination of two or more.

[0025]

[Chemical formula 10] cinnamic acid:

[0026]

[Chemical formula 11] Phenylalanine:

[0027]

[Image Omitted] o-coumaric acid:

[0028]

[Chemical 13] cinnamic aldehyde:

[0029]

Embedded image Phenylpyruvic acid:

In the present invention, the amount of the compound X and phenylpropanoid deposited on the metal magnetic powder is preferably 0.03 to 30 parts by weight, and 0.1 to 10 parts by weight, per 100 parts by weight of the metal magnetic powder. Is more preferable. If it exceeds this range, the effect does not change even if the adherend compound is present in excess, and the excess is wasted.
If it is deposited excessively, the physical properties of the magnetic coating film of the magnetic recording medium may be adversely affected. On the other hand, if the amount is less than the above range (that is, less than 0.03 part by weight), the effect is insufficient and it becomes difficult to obtain sufficient stability over time.

To modify the surface of the metal magnetic powder with the above compound X and phenylpropanoid, for example, the following (1) to
It can depend on the process of (5).

(1) Compound X and phenylpropanoid are added to alcohol such as ethyl alcohol to prepare a solution. (2) Dilute the solution of (1) by adding a solvent such as acetone. (3) Add metal magnetic powder to the solution of (2) and stir in an airtight mixer. (4) The slurry obtained in (3) is treated with a centrifugal dehydrator to remove the solvent and excess compound X and phenylpropanoid. (5) The cake thus obtained is roughly crushed and dried.

The surface-modified metal magnetic powder for a magnetic recording medium of the present invention can be made into a magnetic coating material together with a binder (binder), an organic solvent and various additives, and this magnetic coating material is applied on a non-magnetic support. A magnetic recording medium can be produced by applying the composition to a magnetic layer to form a magnetic layer. In this case, a binder or organic solvent,
As the various additives, any of those used in ordinary magnetic recording media can be used, and the compounding ratio and the like are set according to the case of ordinary magnetic recording media.

As the above-mentioned binder that can be used, a modified or non-modified vinyl chloride resin, polyurethane resin or polyester resin can be used or mixed, and further, a fibrin resin, a phenoxy resin or a specific method of use. You may use together the thermoplastic resin, thermosetting resin, reaction type resin, electron beam irradiation hardening type resin etc. which have. The group to be introduced for the above modification, -SO ₃ M that attained a dispersibility improvement of the magnetic _{powder, -OSO 3 M, -COOM, -PO} (OM ') may be ₂ or the like (M is Na Alkali metal atom such as, M'is the same alkali metal atom or alkyl group).

As usable fibrin resin, cellulose ether, cellulose inorganic acid ester, cellulose organic acid ester, etc. can be used. Phenoxy resin has advantages such as high mechanical strength, excellent dimensional stability, good heat resistance, water resistance, chemical resistance, and good adhesiveness.

Further, it is preferable to add a curing agent to such a binder in order to further improve the durability. As this curing agent, a polyfunctional isocyanate can be used, and particularly tolylene diisocyanate (T
The DI) system is preferred. The addition amount of the curing agent is preferably 5 to 30% by weight based on the total amount of the binder.

In the magnetic recording medium of the present invention,
Furthermore, if necessary, a dispersant such as lecithin, a lubricant such as stearic acid, an antistatic agent such as carbon black, and a rust preventive may be added. As the dispersant, the lubricant, the antistatic agent and the rust preventive, any conventionally known material can be used, and the dispersant, the lubricant, the antistatic agent and the rust preventive are not limited.

The non-magnetic support usable in the present invention includes polyethylene terephthalate and polyethylene-
Polyesters such as 2,6-naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate,
Examples include plastics such as polyamide and polycarbonate. Further, metals such as Cu, Al and Zn, glass, boron nitride, ceramics such as Si carbide and the like can also be used.

An intermediate layer or an undercoat layer may be provided on the surface of the non-magnetic support in order to improve the adhesiveness of the magnetic layer.

Further, on the surface of the non-magnetic support opposite to the magnetic layer, a non-magnetic powder (eg silica, carbon black) and a binder (similar to those mentioned above) are used to improve the running property of the medium. Back coat layer consisting of
It can be provided in a thickness of 0.4 to 0.8 μm.

FIG. 1 shows an example (magnetic tape for video) of the magnetic recording medium of the present invention. That is, a magnetic layer 2 containing magnetic powder, a binder and the like is provided on one surface of the non-magnetic support 1. Further, the other surface may have a back coat layer 3 mainly composed of a non-magnetic powder and a binder as indicated by a chain line.

[0042]

EXAMPLES The present invention will be described below with reference to specific examples, but the present invention is not limited to the following examples.

Metallic magnetic powder: The metallic magnetic powder used was a commercially available one (Fe-based) and was as shown in Table 1 below.

Compound X: Compound X used is cis-
It was 1,2-cyclohexanedicarboxylic acid and 2,3-dihydroxynaphthalene.

Phenylpropanoid: The phenylpropanoid used was cinnamic acid.

Then, the surface of the metal magnetic powder was modified by the following procedure. (1) Compound X (0.3 kg) and phenylpropanoid (0.3 kg) were added to ethyl alcohol (8 kg) to give a solution. (2) 40 kg of acetone was added to the solution of (1) to dilute it. (3) 10 kg of metal magnetic powder was added to the solution of (2), and the mixture was stirred in an airtight mixer for 24 hours. (4) The solvent and excess compound X and phenylpropanoids were removed from the slurry of (3) by a centrifuge. (5) The cake thus obtained was roughly crushed and dried.

The magnetic properties of the metal magnetic powder surface-modified in this way are shown in Table 3 below. The magnetic characteristics are V.
S. M. (Sample vibration type measurement method). In addition, surface-modified ones have a slight saturation magnetization σs [Am ² /
Although a decrease in [kg] is observed, this is due to the addition of non-magnetic organic substances and does not hinder practical use.

Next, the surface-modified magnetic powder was treated at 60 ° C./90
After being stored in an environment of% RH for 1 week, magnetic properties were measured. It is shown in Table 4 below. From this table, Examples 1 and 2
In comparison with Comparative Examples 1, 2, 3, and 4, it is clear that the deterioration of the saturation magnetization σs due to the oxidation is small.

Further, using this surface-modified metal magnetic powder, a magnetic tape was prepared by the following procedure. First, the surface-modified metal magnetic powder was kneaded with a binder and the like in the composition shown in Table 2 below, filtered, coated on a 11 μm-thick polyester film to a dry thickness of 3.5 μm, and dried to form a magnetic tape. obtain. The magnetic characteristics of this tape are shown in FIG. S.
M. The results measured in Table 5 are shown in Table 5 below.

Next, the magnetic tape thus obtained is treated at 60 ° C.
The magnetic properties were measured after storage for 1 week in an environment of / 90% RH. It is shown in Table 6 below. From this table, Example 1,
It can be seen that in Comparative Example 1, the deterioration of the saturation magnetic flux density Bm [mT] due to the oxidation is small compared to Comparative Examples 1, 2, 3, and 4.

[0051]

[0052]

[0053]

[0054]

[0055]

[0056]

[0057]

As described above, the present invention uses the metal magnetic powder surface-modified with the compound X and phenylpropanoid. Therefore, the oxidation resistance of the metal magnetic powder is improved,
The magnetic characteristics can be stabilized without deteriorating.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing one structural example of a magnetic recording medium to which the present invention is applied.

[Explanation of symbols]

 1 ... Non-magnetic support 2 ... Magnetic layer 3 ... Back coat layer

Claims (2)

[Claims] 1. The following general formula: A- (COOH) ₂ , A- (CO) ₂ O or A- (OH) ₂ (In the general formula, A is a phenyl group, a cyclohexyl group or a naphthyl group. And optionally have a substituent), the metal magnetic powder surface-modified with at least one kind of the compound X represented by (4) and at least one kind of the phenylpropanoid. 2. A magnetic recording medium having a magnetic layer containing the magnetic metal powder according to claim 1 and a binder formed on a non-magnetic support by coating.