KR920008223B1 - Magnetic medium manufacturing method - Google Patents

Abstract

The magnetic recording medium is prepared by coating a magnetic paint composed of magnetic material, grinding material and binder onto the non-magnetic substrate. The dispersing agent of formula R-NG-(CH2)n-COOM used for improving dispersion property of the magnetic paint has carboxyl or carboxylate as a hydrophilic end group and alkyl group containing amine as a lypophlic end group. In the formula, R is C6-12 alkyl, n is integer of 5 to 10, M is H, alkali metal salt or NH3. The magnetic recording material has a good adhesiveness and durability, and is used for magnetic tapes and magnetic disks.

Description

Method of manufacturing magnetic recording medium

The present invention relates to a method of manufacturing a magnetic recording medium having improved dispersibility.

Magnetic recording media such as audio and video tapes, magnetic disks, and magnetic cards have a magnetic coating made of a magnetic material, an abrasive, an antistatic agent, a lubricant, a binder, and the like on a nonmagnetic base film. The most important technique in preparing a magnetic paint is to uniformly disperse a magnetic substance, an abrasive, etc. in a binder, that is, to improve dispersibility. In the magnetic recording medium, why spraying is important is as follows. First, to improve the dispersibility of the magnetic material means to improve the orientation and filling properties of the magnetic material, and eventually to improve the angular ratio (Br / Bm) in the magnetic properties, to accurately record and reproduce the magnetic recording signal, and to obtain the S / N. Contributes to the improvement of the (Signal / Noise) ratio.

In addition, improving the dispersibility of the abrasive is known to directly reduce drop out and improve runability. Therefore, a lot of research and efforts to improve the dispersibility of the magnetic material and the abrasive in the magnetic paint, for example, using a surfactant such as lecithin, lauric acid, stearic acid is the most one way Known.

However, this method is not satisfactory in dispersing effect, and in some cases, there is a problem that the durability of the magnetic coating film is lowered. Therefore, the improvement has been sought. For example, (1) Uji diamine having 17 to 18 carbon atoms. (Japanese Patent No. 60-263319), (2) Copolymer containing carboxyl group (Japanese Patent No. 61-61225), or (3) Polyglycolic acid and polyglycoester (US Pat. No. 3,630,772) or (4) XnSi [OCH ₂ CH ₂ ) mo r] ₄ -n where n is 1,2,3, m is 0,1, X is an alkylamino group, a vinyl group And a method of introducing a methacryl group, an epoxy group, and R represents an alkyl group (Korean Patent Publication 81-1122).

However, in the method of (1), the square ratio is far below the required level of audio or video tape (0.8), and sometimes the used Uji is deposited as white powder in magnetic paint. In addition, the method of (2) has a limitation in that the temperature must be very high in order to disperse and is useful only when the binder is polyester-based. In the method of (3), the dispersion effect is generally similar to that of the conventionally used recipe, stearic acid and the like. In the case of (4), when the magnetic material is oxidized during the hydration reaction in which the magnetic material is immersed in water during the dispersion process, As a result, there is a drawback that the magnetic properties of the magnetic body are significantly reduced. Accordingly, the present inventors have overcome the above-mentioned problems as much as possible, and have proposed the present invention in which the angular ratio, the degree of orientation and the like improve the magnetic properties, the electronic properties such as the S / N ratio, the sensitivity, and the glossiness.

The inventors have focused on the fact that the surface of the magnetic body contains a hydrophilic group, while the binder resin is lipophilic. Therefore, as a result of exception examination of a substance having a hydrophilic end group on one side and a lipophilic end group on the other side, the hydrophilic end group has a carboxyl group or a carboxyl group, and the lipophilic end group has an amine-containing aliphatic compound. It has been found that the substance is effective for the purposes herein. More specifically, the present invention is characterized by employing a compound of the following general formula as a dispersant in forming a magnetic paint for producing a magnetic recording medium comprising a magnetic abrasive, an antistatic agent, a lubricant, a binder, and the like.

R-NH- (CH ₂ ) n-COON

Wherein R is an alkali group having 6 to 12 carbon atoms, n is an integer of 5 to 10, M is H or an alkali metal salt or NH ₃ .

As described above, the compound (hereinafter referred to as the 'original compound') exhibits excellent dispersing effect. As described above, a carboxyl group or a carboxyl base, which is a hydrophilic end group, is easily adsorbed onto the surface of a hydrophilic magnetic body, and an lipophilic amine-containing alkyl group is used as a binder. It is, of course, because it is well compatible with the nitro cellulose, polyether, vinyl copolymer, polyurethane and the like used.

In the present invention, the compound of the present application is preferably added in the range of 2 to 10 parts by weight based on 100 parts by weight of the magnetic body. This is because, if it is less than 2 parts by weight, of course, there is no dispersing effect. If it exceeds 10 parts by weight, the durability of the binder is lowered.

And when the dispersion proceeds, it is better if the preliminary dispersion in the temperature range of 30 to 70 ℃.

Hereinafter, the present invention will be described in more detail with reference to the following examples, which of course do not limit the present invention.

Example 1

1 part by weight of 1-chloro-pentylcarboxylic acid is added to 1 part by weight of normal-heptylamine, followed by reaction at 110 ° C. to obtain the present compound. 4 parts of nitrocellulose, 15 parts of polyurethane, 15 parts of toluene, and 20 parts of cyclohexa based on a sieve (Co-r-Fe ₂ O ₃ ) and 100 parts by weight of the magnetic body in a high-speed stirrer with an internal volume of 12 liters Then, 60 parts of methyl ethyl ketone, 3 parts of alumina, 4 parts of carbon black, 3 parts of silicone oil, 3 parts of the present compound were added and preliminarily dispersed at 50 ° C. for 10 hours, followed by further dispersion for 36 hours in infertility.

The magnetic coating thus obtained was applied on a polyethylene terephthalate film having a thickness of 15 mu m at a thickness of 5 mu m, then oriented with a permanent magnet, joined with a heated calender to smooth the applied surface. Physical properties of the resulting magnetic tape were measured by dividing them into magnetic properties, electronic properties, and glossiness, and the results are shown in Tables together with those of other examples and comparative examples.

The physical properties were measured by the following means.

* Coercivity, Square Ratio-VSM (manufactured by Japan's Dongyoung Industry Co., Ltd.)

* Orientation-SAM

* Video S / N and Sensitivity-Noise Meter (Shiba Corporation)

* Glossiness-Glossimeter (Hunter)

Example 2

As in Example 1, except for the present compound. In Example 2, 3 parts of a substance (C ₇ H ₁₅ NHC ₅ H ₁₀ COONa) obtained by reacting the compound of Example 1 with an aqueous NaOH solution at 50 ° C. was added to 100 parts by weight of a magnetic substance as in Example 1. .

Comparative Example 1

In the same manner as in Example 1, 3 parts of lecithin was added instead of the present compound.

Comparative Example 2

The procedure was carried out in the same manner as in Example 1, but 3 parts of polyglycol phosphoric acid was used instead of the compound of the present application.

Comparative Example 3

It carried out similarly to Example 1, but added 3 parts of mixed type Uji diamine (Aspazol # 20 by a Japanese fat and oil company) instead of the compound of this application.

[Comparative Example 4]

100 parts of Co-r-Fe ₂ O ₃ was suspended in 190 parts of water in a stirrer of Example 1, stirred for 2 hours, 3 parts of r-aminoclotritriethoxy silane were added, and then stirred at a high speed for another 3 hours, Only the magnetic material was extracted and dried, followed by the composition (except the original compound) and conditions of Example 1, but again 2 parts of r-aminopropyl triethoxy silane was added as a dispersant.

TABLE 1

* ×: Electronic characteristic analysis dances due to poor magnetic characteristics

Claims (3)

In a method of manufacturing a magnetic recording medium by applying a magnetic paint composed of a magnetic material, an abrasive, a binder, or the like on a nonmagnetic support, the magnetic paint has a carboxyl group or a carboxyl group as a hydrophilic end group on one side and a lipophilic horse on the other side. A method for producing a magnetic recording medium comprising using a dispersant of the following general formula having an amine antimu alkyl group as a short term. R-NH- (CH ₂ ) n-COOM (In the above, R is an alkyl group of 6 to 12 carbon atoms, n is an integer of 5 to 10, M is H or an alkali metal salt or NH _3. ) The method of manufacturing a magnetic recording medium according to claim 1, wherein the dispersing agent is a compound represented by C ₇ H ₁₅ NHC ₅ H ₁₀ COOH, or an alkali metal salt thereof. The method of manufacturing a magnetic recording medium according to claim 1 or 2, wherein the dispersant is added in an amount of 2 to 10 parts by weight based on 100 parts by weight of the magnetic material.