JPS5836931A - Manufacture of magnetic iron oxide fine powder for use in magnetic recording - Google Patents

Abstract

PURPOSE:To obtain a magnetic iron oxide fin powder for magnetic recording small in drop of coercive force, good in dispersibility and filling performance, and superior in magnetic tape characteristics, by compaction grinding said iron oxide in presence phosphoric ester. CONSTITUTION:Powdery magnetic iron oxide of gamma-Fe2O3, magnetic, or the like is immersed in a phosphoric ester, especially its aq. liquid, or its nonaq. liquid. This treated liquid is filtered and the obtained iron oxide contg. the phosphoric ester is dried and compaction grinded with an edge runner type grinder to obtain an intended magnetic iron oxide powder for magnetic recording. For this phosphoric ester, for example, polyoxyethylene nonylphenyl ether phosphate is used. This is added to the iron oxide by 0.1-6pts.wt. per 1pt.wt. iron oxide.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing magnetic iron oxide fine powder for magnetic recording.

Magnetic recording media such as magnetic tapes are usually round, made by dispersing magnetic powder such as magnetic iron oxide in a binder resin and coating a good magnetic paint on a polymer base, but in recent years magnetic recording has become more advanced. As magnetic particles become more magnetic, there is an increasing demand for increasing the filling rate of magnetic powder in the coating film. Coupled with this, there is a strong demand for magnetic powders used in these applications to have good dispersibility in magnetic paint systems and to have greater filling properties.

On the other hand, magnetic powder used for magnetic recording is generally produced by precipitating acicular hydrated ferric oxide through a wet reaction between an iron salt solution and an alkali, and heating and dehydrating this precipitate to produce hematite (-
-F@1on), then heat-treated in a reducing atmosphere to produce magnetite (F@104), or further heat-treated in an oxidizing atmosphere to form a magnetite (F@104).
-F@mOs) K L, or their intermediates, the bertolide series (F@OX 1.33<X
<' 1.5) Powdered magnetic iron oxide is used, but particles of these O magnetic iron oxide particles whose surfaces have been modified with cobalt or other metals are used. . However, these magnetic powders tend to generate coarse particles due to sintering between particles and entanglement of particles due to their acicular nature during the heat treatment process in the dehydration, reduction, and oxidation steps described above, and are susceptible to loose particles in magnetic paint systems. Dispersibility, filling properties, magnetic properties, etc. are impaired. Although various proposals have been made for these improvements, there are still many problems that need to be solved.

The present invention relates to a method for solving the above-mentioned problems, and provides a method for producing magnetic iron oxide fine powder for magnetic recording, which comprises compacting and crushing powdered magnetic iron oxide in the presence of a phosphate compound. be.

In the method of the present invention, since the powdered magnetic iron oxide can be efficiently pulverized, the acicularity of the magnetic iron oxide particles is less likely to be impaired, and the magnetic iron oxide fine powder does not substantially contain coarse particles. (average particle diameter of major axis 0.1 to Q, 8 tones) can be easily obtained. This material has extremely good dispersibility in various magnetic recording media systems such as magnetic paints, and is extremely useful for improving filling properties and magnetic properties.

In order to carry out the consolidation and crushing process in the method of the present invention, it is desirable to use a type of crusher that is capable of consolidation and has a relatively small impact force, such as an edge runner, ring roller mill, rod-built type, etc. can.

In the method of the present invention, various phosphoric acid ester compounds can be used, but polyoxyalkylene alkyl ether-based or Hiropolyoxyalkylene diaryl ether-based phosphoric ester compounds are particularly desirable; for example, those having 4 to 4 carbon atoms. By adding 1 to 30 moles of ethylene oxide to alcohols and alkylphenols having 24 alkyl groups, alkenyl groups, or alkylaryl groups, the following compounds can be prepared. In addition, phosphorus IN = c Sulfur compound '11111, monoester, diester, or a mixture thereof may be used, and the alkali metal salt, alkaline earth metal salt, ammonium salt, or amine salt of these esters may be used. etc.

In the method of the present invention, in order to make the phosphate ester compound present in the compaction grinding of powdered magnetic iron oxide, it may be added directly at the time of crushing, or the powder may be added directly to an aqueous or non-aqueous solution containing the phosphate ester compound. A more desirable result may be obtained if powdered magnetic iron oxide is immersed and mixed in advance with wet crushing or crushing as required. The object of the present invention can be achieved by adding the phosphoric acid ester compound in an amount of 0.1 to 6%, preferably 0.5 to 4%, based on the weight of the powdered magnetic iron oxide. If the amount added is too small than the above range, the desired effect will not be obtained, and if the amount added is too much than the above range, not only will it not be advantageous in terms of cost reduction, but smooth grinding operation will not be possible and
, the strength of the magnetic coating may be impaired.

The powdered magnetic iron oxide used in the method of the present invention includes:
Examples include r-Fe, O, magnetite, bertholed iron oxide, and those modified with metal compounds such as cobalt.

Next, the present invention will be explained with reference to Examples and Comparative Examples.

Example 1 Ferrous sulfate #i[K] was added with a sodium hydroxide solution and precipitated from the reaction mother liquor by air oxidation, and the iron was dehydrated by heating, and then reduced and reoxidized to form r-F・mow E. Obtain powdered iron oxide. This powdered magnetic iron oxide is converted into polyoxyethylene nonylphenyl ether phosphate ester CW.
Add 94 ethylene (R) to a water moat, stir thoroughly, and leave to cool. This product was dried, and powdered magnetic iron oxide 20# containing a nonaphosphate compound was compacted and ground for 60 minutes using Edge Runner (Natsukusumara M8G-05ml, manufactured by Shinto Kogyo) to form a circle.

Example 2 The same procedure as in Example 1 was carried out except that the compaction crushing was carried out at 20# for 40 minutes.

Example 3 In Example 1, the amount of phosphoric acid ester compound added was changed to 2
The same procedure as in the same example was carried out except that the weight was increased and the circle was changed.

Example 4 Rehabilitation of polyoxyethylene/tridecyl ether as the phosphoric acid ester compound in Example 1 Comparative Example 1 The same procedure as in Example I was carried out except that the phosphoric acid ester compound was not added.

Comparative Example 2 In Example 1, before adding the sulphur/acid ester compound,
The procedure was repeated in the same manner as in the same example except that 9 was crushed into powdered magnetic iron oxide 20 using an edge runner for 60 minutes in a pressure machine and that the phosphoric acid ester compound was not compacted and pulverized after the addition of the phosphate ester compound.

Comparative Example 3 In Example 1, before adding the phosphate ester compound, powdered magnetic iron oxide 20 and 9 were pulverized for 150 minutes using an edge runner, and after adding the phosphoric ester compound, the powder was crushed! ! The same procedure as in the same example was carried out except that pulverization was not performed.

Comparative Example 4 The same example as in Example 1, except that 6 kg of powdered magnetic iron oxide was compressed and pulverized for 60 minutes with an edge runner before adding the phosphate ester compound, and that the phosphoric ester compound was not compressed and crushed after the addition of the phosphate ester compound. I did the same thing.

Comparative Example 5 In Example 1, the powdered magnetic iron oxide 20# was crushed in a pressure device with an edge runner for 30 minutes before the addition of the phosphate ester compound, and the pressure after addition of the phosphate ester compound was 1! F
The same procedure as in the same example was carried out except that the pulverization was carried out for 30 minutes.

The results of measuring the magnetic properties of these O11 crushed products are shown in 1!1.

As is clear from the results in Table 1, the method of the present invention can efficiently crush powdered magnetic iron oxide, so there is little decrease in coercive force (He'') due to loss of acicularity, and dispersion The properties and filling properties are excellent, and the residual magnetic flux density (B
Table 1 is industrially advantageous for easily producing magnetic iron oxide fine powder that has excellent magnetic tape properties such as r ), squareness ratio (Br78m = saturation magnetic flux density), and degree of orientation. In, the He (coercive force) of the powder is determined by the respective r -F@,
0. were measured using the usual method.

M9, He%Br (residual magnetic flux density) of magnetic tape, B
r/8m (squareness ratio) and orientation f (OR) are determined by preparing a compound according to the following formulation procedure for each of the above r -1i'@10m, and kneading it in a l-ru to produce a magnetic paint. Next, each magnetic coating material is coated on a polyester film in a conventional manner, oriented and dried to produce a magnetic recording medium having a magnetic coating film approximately 7 tones thick. Measured by the method of circle.

(1) ' -F@1031i) end xoO
Weight 11 (2) Soy lecithin 1.6 parts by weight (3) Surfactant 4 parts by weight (4)
Vinegar vinyl chloride copolymer resin illαS parts by weight (5) Dioctyl phthalate Parts by weight (6) Methyl ethyl ketone 84 parts by weight (7) Toluene
93 parts by weight As used herein, "weight" means % by weight.

Claims (1)

[Claims] A method for producing magnetic iron oxide fine powder for magnetic recording, which comprises ortho-pulverizing powdered magnetic iron oxide in the presence of a phosphate ester compound.