JPS6071529A - Manufacture of spherical magnetite powder - Google Patents

Abstract

PURPOSE:To utilize all of Fe<2+> in a starting material and to obtain the titled powder having a uniform particle size and superior dispersibility by blowing a gas contg. O2 into an aqueous ferrous salt soln. contg. colloidal ferrous hydroxide at a prescribed temp., adding an alkali by an amount basing on the amount of residual Fe<2+>, and blowing a gas contg. O2 at said temp. CONSTITUTION:A reactive aqueous ferrous salt soln. contg. colloidal ferrous hydroxide is prepd. by adding 0.80-0.99 equiv. alkali hydroxide basing on the amount of Fe<2+> in an aqueous ferrous salt soln. to the ferrous salt soln. as a starting material. A gas contg. O2 is blown into the prepd. soln. under heating at 30-100 deg.C to form spherical magnetite particles from the colloidal ferrous hydroxide by oxidation. After finishing the reaction, 1.00 equiv. alkali hydroxide basing on the amount of the unreacted Fe<2+> is added, and oxidation is carried out under similar conditions. All of Fe<2+> in the ferrous salt soln. as a starting material is utilized, and spherical magnetite particles having a uniform particle size, superior dispersibility, high coloring power and superior productivity are obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing spherical magnetite particles using an aqueous ferrous salt solution. To obtain magnetite particle powder having a uniform particle size, excellent dispersibility, high coloring power, and a spherical shape with excellent productivity such as p-permeability and ease of crushing without leaving any Fe2+ particles. The purpose is to

Its main uses are black pigment powder for paints and material powder for magnetic toners for electrostatic copying.

Magnetite particles are widely used as black pigments, and from the viewpoint of improving work efficiency and improving the physical properties of paint films in the energy-saving era, improving the dispersibility of magnetite particles in a vehicle is important when manufacturing paints. It is increasingly requested.

In the production of paints, whether the pigment powder is well dispersed in the vehicle or not is an extremely important factor that not only affects the efficiency of the paint manufacturing process but also determines the various physical properties of the paint film.

This can be seen, for example, in the Journal of the Coloring Materials Association, Vol. 49, No. 1 (197
This is clear from the following statement on page 8 of (5th year).

``......The physical properties that a paint film should have are largely determined by the dispersibility of the pigment in the paint film if the pigments are the same. This does not seem to be an exaggeration. Theory teaches that if the dispersibility of the pigment in the coating film is good, the color tone will be clear and the basic properties of the pigment, such as coloring power and impregnation power, will also improve. In addition, the gloss, sharpness, mechanical properties, and air permeability of the coating film are improved, which improves the durability of the coating film. It can be understood that this is an extremely important factor that determines the various physical properties of the coating film.''On the other hand, electrostatic copying machines have spread rapidly in recent years, and along with this, research and development of magnetic toner, which is a developer, has been active. , there is a need to improve its characteristics.

For example, Japanese Patent Laid-Open No. 54-122129 describes the following.

[......Magnetic toner has a considerable amount of magnetic fine particles mixed in the toner binder, but magnetic fine particles generally have poor dispersibility in the toner binder resin, so there is no manufacturing variation. It is difficult to obtain a uniform toner, and insulating toner also causes a decrease in the electrical resistance of the toner. ”
Furthermore, in Japanese Patent Publication No. 53-21656, “...
...By uniformly distributing iron oxide throughout the developer particles, we obtain the appropriate magnetization required for visualization of electrostatic latent images.
It is stated that it is possible.

Conventionally, when producing magnetite particle powder by aerating oxygen-containing gas into a reaction aqueous solution containing ferrous hydroxide obtained by reacting a ferrous salt aqueous solution and an alkali, the production of magnetite particles is caused by the pH of the reaction aqueous solution. It is known that magnetite particles have various shapes.

That is, this fact is based on the Powder and Powder Metallurgy Society of Japan's 1971 Autumn Conference Abstracts, page 112, lines 14-19. 40-44g106
1) was added, and the temperature was raised to 50°C and maintained for 5 hours to obtain fine particles. The pH was varied to change the shape of the particles. The pH is controlled by the amount of sodium hydroxide, and the pH is adjusted to the acidic side (Na
At OH40 to "g1036", we obtained pitahedral particles, at alkaline conditions (469% o, sl or higher) we obtained octahedral particles, and at near neutrality (Na11 (42 g103.)) we obtained polyhedral, nearly spherical particles. Description and Special Publication No. 44-6
68 Publication patent claims “...FQ
(OH), colloid-containing TIHL [1 or more aqueous solution is maintained at a temperature of 45°C or higher and 70°C or lower, and the oxidation reaction is carried out in a state where the precipitated particles present in the liquid are sufficiently moved by stirring. By this process, a precipitate consisting of black ferromagnetic particles (magnetite particles) having a granular or cubic (hexahedral) shape is produced.
It is clear from the statement "...".

The present inventor focused on the shape of magnetite particles, and in order to obtain magnetite particles with excellent dispersibility and high coloring power, it is necessary that the particles exhibit a spherical shape with low bulk density and oil absorption. Considering that, it was necessary to obtain magnetite particles exhibiting a spherical shape.

As mentioned above, it is known that spherical magnetite particles are produced in an aqueous solution near neutrality, but in this case, the entire amount of pi+ in the ferrous salt aqueous solution is converted into magnetite particles. Since conversion is difficult and unreacted xri+ remains, the yield is low, and unreacted Pe2+ causes waste water pollution, so countermeasures are needed.

In order to generate magnetite particles from the entire amount of ye''+ in the ferrous salt aqueous solution and increase the yield, the ferrous salt aqueous solution is reacted with an alkali equivalent of 1 equivalent or more to the ferrous salt aqueous solution. In this case, the alkaline reaction aqueous solution has a pH of about 11 or more, so the generated magnetite particles are hexahedral or octahedral particles with high bulk density and oil absorption.
The dispersibility and coloring power were poor.

In view of the above, the inventors of the present invention have proposed that the ferrous salt aqueous solution should have uniform particle size, excellent dispersibility, and high coloring power without leaving any unreacted Fe"+ in the ferrous salt aqueous solution. ,and,
In order to obtain magnetite particles with excellent productivity, the present invention was developed as a result of various studies.

That is, the present invention provides a ferrous salt aqueous solution containing a ferrous hydroxide colloid obtained by reacting a ferrous salt aqueous solution with an alkali equivalent to 0.80 to 0.9 g based on Fi+ in the ferrous salt aqueous solution. a first stage of generating spherical magnetite particles from the ferrous hydroxide colloid by passing an oxygen-containing gas while heating in a temperature range of 70°C to 100°C; After the completion of the reaction, 1.00 equivalents or more of alkali is added to the 1r e'' remaining after the reaction, and the second stage reaction is heated and oxidized under the same conditions. This is a method for producing magnetite particle powder.

The structure and effects of the present invention will be explained as follows.

First of all, the present inventor believes that in order to obtain magnetite particles having excellent dispersibility and high coloring power as a pigment, it is important to obtain magnetite particles exhibiting a spherical shape. I learned that it is necessary to be responsive.

Next, the present inventor discovered that unreacted Fe2 in the ferrous salt aqueous solution
In order to increase the yield by producing magnetite from the entire amount of Fe in the raw ferrous salt aqueous solution without leaving any + residue, and to obtain excellent productivity, the reaction must be on the alkaline side. I learned that.

Therefore, the present inventor developed a first stage in which a part of Fe2+ is precipitated from the raw material ferrous salt aqueous solution by adding an alkali, and then heated and oxidized to form magnetite, and unreacted FJ after the completion of the first stage reaction. If the reaction consists of two steps: adding 1.00 equivalents or more of alkali to precipitate, followed by heating and oxidation, no unreacted Fe2+ will remain in the ferrous salt aqueous solution. It is believed that spherical magnetite particles with uniform particle size, excellent dispersibility, high coloring power, and excellent productivity can be obtained from all the Fe2+ in the raw material ferrous salt aqueous solution. Various studies were conducted on the amount of precipitated Fe2+ in the first stage reaction, the relationship between the amount of precipitated Fe2+ and the unreacted FJ'' loss, the reaction temperature, and the shape of the product magnetite particles.

and FJ1 in the ferrous salt aqueous solution and the ferrous salt aqueous solution.
Oxygen-containing gas was added to the ferrous salt reaction aqueous solution containing ferrous salt colloid obtained by reacting 0.80 to 09 g equivalent of alkali to the ferrous salt reaction aqueous solution containing ferrous salt colloid, which was obtained by reacting an alkali equivalent to 0.80 to 0.09 g to A first stage in which spherical magnetite particles are produced from the ferrous hydroxide colloid by aeration, and a 1.
In the case of a two-stage reaction consisting of the first stage reaction in which 00 equivalents or more of alkali is added and the second stage of heating and oxidation under the same conditions, the spherical shape produced in the first stage reaction will be removed in the second stage reaction. Magnetite grows epitaxially on the surface of magnetite particles with a spherical shape, and does not produce hexahedral or octahedral magnetite particles, so the particle size distribution with a spherical shape is uniform.
It has been found that it is possible to obtain spherical magnetite particles having excellent dispersibility and high coloring power, and excellent productivity such as p-permeability and ease of crushing.

Next, various conditions for implementing the method of the present invention will be described.

Examples of the ferrous salt aqueous solution used in the present invention include a ferrous sulfate aqueous solution and a ferrous chloride aqueous solution.

Examples of the alkali used in the present invention include hydroxides and carbonates of alkali metals, such as sodium hydroxide and potassium hydroxide, magnesium hydroxide, and carbonates.

The amount of alkali used in the first stage reaction of the present invention is
The amount is 0.80 to 0.9 g equivalent to F♂1 in the ferrous salt aqueous solution.

If it is less than 0.080 equivalent or more than 0.9 g equivalent,
It is difficult to produce spherical magnetite particles.

The reaction temperature in the first stage reaction of the present invention is 70'C to 10
It is 06C.

If the temperature is 70° C. or lower, acicular goethite particles are mixed, and even if the temperature is 100° C. or higher, spherical magnetite particles are produced, but this is not suitable for industrial use.

The oxidation means is carried out by passing an oxygen-containing gas (for example, air) into the liquid.

The alkali shield used in the second stage reaction of the present invention has an equivalent amount of 1.00 or more relative to the remaining F82+ in the first stage reaction.

If the amount is 1.00 equivalent or less, the entire amount of Fe2+ will not precipitate. 1.
A preferable amount is 0.00 equivalent or more, taking into consideration industrial efficiency.

The reaction temperature of the second stage reaction in the present invention may be the same as that of the first stage reaction. Furthermore, the oxidation means may be the same.

The present invention configured as described above has the following effects.

That is, according to the present invention, unreacted F is contained in the ferrous salt aqueous solution.
The particle size was uniform from the entire amount of F♂1 without leaving e24°, and it had excellent dispersibility and high coloring power, and exhibited a spherical shape with excellent productivity such as p-permeability and ease of crushing. Magnetite particle powder can be used.

When the above-mentioned spherical magnetite particle powder is used in the production of paint, it is well dispersed in the vehicle, making it possible to improve coating film properties such as gloss, clarity, and durability. , work efficiency will also improve.

In addition, when the above-mentioned spherical magnetite particles are used in the production of magnetic toner, they have good dispersibility in resin, so they have appropriate magnetism and image quality with excellent image density. Obtainable.

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

In addition, the average particle diameter in the following examples and comparative examples is B
By the Ti:T method, the oil absorption amount and bulk density were J-5K51.
The coloring power was measured by the method described in 01, and the coloring power was measured by ffl using a colorimetric sample piece manufactured by Tokyo Juishoku Co., Ltd. using a colorimeter (To-5D).
It is indicated by the L value (lightness) obtained by coloring.

The lower the L value, the better the coloring power and the better the dispersibility. The test piece for color measurement was 0.5 g of magnetite particle powder, 1.5 g of titanium white, and 1.5 c of castor oil.
The paste was kneaded with a cQ Huber set of muller to form a paste, and 4.5 g of clear lacquer was added to the paste to form a paint, which was applied onto Miracoat paper using a 6ml applicator.

Example 1 An aqueous ferrous sulfate solution 201 containing Fe2 + 1.5 mo was prepared in advance in a reactor with 2,64
-N in NaOH aqueous solution 201 (0 for Fe2+)
．． This corresponds to 88 equivalents. ), pH 6,9, temperature 90°C
At we(oH).

A ferrous salt aqueous solution containing ferrous salt was produced.

The above ferrous salt aqueous solution containing Fe(OH)2 was heated to a temperature of 9°.
A ferrous salt aqueous solution containing magnetite particles was produced by blowing air at 100 l/min for 240 minutes at C.

Next, 3.78-N NaOH aqueous solution 21 was added to the ferrous salt aqueous solution containing the magnetite particles (for Fe2+).

This corresponds to 1.05 equivalents. ), pH 11.8, temperature 90° C., and 201 air per minute was passed through for 60 minutes to generate magnetite particles.

The produced particles were washed with water, separated from P, dried, and crushed by a conventional method.

As is clear from the electron micrograph (x20,000) shown in FIG. 1, the obtained magnetite particles had a spherical shape and were uniform in particle size.

In addition, this spherical magnetite particle powder has an average particle diameter of 0.18 μm, an L value of 35.8, and an oil absorption amount of 19jItAO.
o9 and bulk density of 0.549/q, it was sold as a product with extremely good productivity.

Examples 2 to 8 Same as Example 1 except that the type and concentration of the ferrous salt aqueous solution; the type and concentration of the extraction alkali, the amount used in the first stage and the reaction temperature were varied. Then, magnetite particle powder was obtained.

Table 1 shows the main manufacturing conditions and the properties of the produced magnetite particles.

As a result of electron microscopic observation, the magnetite particles obtained in Examples 2 to 8 all had a spherical shape,
Moreover, the particle size was uniform.

An electron micrograph (X2000[+) of the magnetite particles obtained in Example 4 is shown in FIG.

Comparative Example 1 A ferrous sulfate aqueous solution 20J17 containing 1.5 mol/1 of ferrous sulfate was prepared in advance in a reactor.
In addition to 45-N NaOH aqueous solution 204 (corresponding to 1.15 equivalents to he2+), an aqueous solution containing Fe(OH)2 was produced at T)H12,8 and a temperature of 90°C.

A magnetite particle powder was produced by blowing air at a rate of 100 l/min for 220 minutes at a temperature of 90° C. into the Fe(OH) 2 -containing aqueous solution.

As is clear from the electron micrograph (X20000) shown in FIG. 3, the obtained magnetite particles were hexahedral particles.

In addition, this magnetite particle powder exhibiting a hexahedral shape has an average particle diameter of 0.17 μm, a value of 40.1, and an oil absorption amount of ゛.
・・29w1A o o q and bulk density 0.259/
c te attuta.

Comparative Example 2 2 ol of ferrous sulfate aqueous solution containing P□e” 1.5 m Ol,/1 was prepared in advance in a reactor.
In addition to 92-N NaOH aqueous solution 201 (corresponding to 0.64 equivalent to Fe2+), 7) H4,8, temperature 9
A ferrous salt aqueous solution containing Fe(OH)2 was produced at 0°C.

The temperature of the ferrous salt aqueous solution containing Fe(OH)2 is 90°.
Magnetite particle powder was produced by blowing 1001 air per minute at C for 190 minutes.

The obtained magnetite particles were irregularly shaped particles, as is clear from the electron micrograph (x20000) shown in FIG.

In addition, this irregularly shaped magnetite particle powder has an average particle diameter of 0.19 μm, an l value of 390, and an oil absorption in ”V* 0.
0g and bulk density 0.349/c.

[Brief explanation of the drawing]

Figures 1 to 4 are all electron micrographs (X20000
), and FIGS. 1 and 2 show the spherical magnetite particles obtained in Example 1 and Example 4, respectively, and FIG.
4 shows hexahedral magnetite particles obtained in Comparative Example 1, and FIG. 4 shows irregularly shaped magnetite particles obtained in Comparative Example 2. Patent Applicant Toda Kogyo Co., Ltd. Representative Matsui Gobe Figure 1 (X 200oo) Figure 2 Figure 3 (X2oooo) Figure 4 Procedures Practitioner Ho Seisho (spontaneous) December 24, 1981 1 Case Indication 1988 Patent Application No. 181290 2. Name of the invention: Process for producing spherical magnetite particles 3. Amendment 4. B. Section ``1.1''Claims'' in the specification and ``Part 5, Contents of the amendment.'' (1) The statement in "Claims column J" on page 1 of the specification is corrected as shown in the attached sheet. (2) "And" in line 6N, third line of the specification has been replaced with "is larger,"
I will correct it. (3) In the specification section, from the top line of page 6 to the first line of page 7, "hexahedral or octahedral particles with high bulk density and oil absorption" are replaced with "
Since it is a hexahedral or octahedral particle, the bulk density is small and the oil absorption is high.'' (4) "Hydroxide" will be inserted next to "equivalent" on page 7, line 10 of the specification. (5) On page 7, line 16 of the specification, ``Hydroxide'' will be inserted next to J above. (6) Insert "Type of alkali" after "Relationship," on the third line of No. 6N of the specification. (7) "Hydroxide" will be inserted next to "equivalent" on page 9, line 11 of the specification. (8) "Hydroxide" will be inserted after "more than" on page 9, line 17 of the specification. (9) In the specification, page 1O, lines 14 to 19, "In the present invention...carbonates, etc." was changed to "The alkali hydroxides used in the present invention include sodium hydroxide, potassium hydroxide, etc." hydroxides of alkaline earth metals such as alkaline metal hydrides, magnesium hydroxide, calcium hydroxide, etc.''. (10) In the first line of page 11 of the specification, after “use”, “
We will insert hydroxide. (11) "Hydroxylation" will be inserted next to "Used" on page 11, line 14 of the specification. (12) "Hydroxylation" will be inserted next to "Type," on page 15, line 3 of the specification. (13) In "Table 1" on page 18 of the specification, "alkali" in the second line has been corrected to "alkali hydroxide." Claims (1) A hydroxide 1 obtained by reacting a ferrous salt aqueous solution with an alkali in an amount of 0.80 to 0.9 g equivalent to 0.80 to 0.9 g of Fe in the ferrous salt aqueous solution. Spherical magnetite particles are generated from the ferrous hydroxide colloid by passing oxygen-containing gas through the ferrous salt reaction aqueous solution containing iron colloid while heating it in a temperature range of 30°C to 100°C. From the two-step reaction, the first step is to add 1.00 equivalents or more of water M alkali to the residual Fe 2 ゛ after the first step reaction, and the second step is to heat and oxidize under the same conditions as the first step reaction. A method for producing magnetite particle powder exhibiting a spherical shape characterized by the following: Procedures (Spontaneous writing by Hosho) December 27, 1980 1, ¥ > Display 1981 Patent Application No. 181290 2, Invention Name of method for producing spherical magnetite particles 3, person making the amendment Column 5 of "Detailed Description of the Invention" in the specification, contents of the amendment (1) "Becomes" on page 6, line 19 of the specification We will correct ``to become'' to ``to become''. that's all

Claims (1)

[Claims] 1. Ferrous salt aqueous solution and F+32 in the ferrous salt aqueous solution
A ferrous salt reaction aqueous solution containing ferrous hydroxide colloid obtained by reacting 0.80 to 0.9 g equivalent of alkali per 100 ml was heated in a temperature range of 70 ° C to 100 ° C. A first stage in which spherical magnetite particles are produced from the ferrous hydroxide colloid by passing an oxygen-containing gas through the ferrous hydroxide colloid, and an alkali in an amount of 1.00 equivalent or more based on the remaining Fi+ after the first stage reaction is completed. A method for producing magnetite particle powder exhibiting a spherical shape, characterized by comprising a two-step reaction of adding and heating the first step and a second step of heating and oxidizing under the same conditions.