JPH04144924A - Production of nonmagnetic black pigment powder - Google Patents

Abstract

PURPOSE:To improve dispersibility, workability, heat resistance and blackness by heating magnetite particles coated with Mn and Fe compound at a prescribed temperature to provide a hematite structure consisting essentially of iron in which Mn is subjected to solid solution. CONSTITUTION:An aqueous solution of iron (II) salt is reacted with an aqueous solution of alkali hydroxide of 1.01-1.3 equivalent weight based on Fe<2+> in the aqueous solution of iron (II) salt to afford a suspension containing an iron (II) hydroxide colloid. Oxygen-containing gas is introduced into the suspension while heating the suspension to 45-100 deg.C to prepare a suspension containing magnetite particles. Then Mn or Mn and Fe<2+> are added in a state of aqueous solution to the suspension and the mixture is heated and oxidized to apply a Mn compound, Fe compound, etc., to magnetite particle surface. Then the particles are filtered and burned at 750-1000 deg.C. Thereby particles consisting essentially of iron in which Mn is subjected to solid solution, having hematite structure and having 0.2-0.8mum diameter are obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for producing a non-magnetic black pigment powder consisting of particles having a hematite structure mainly composed of iron in which Ha is dissolved as a solid solution. .

The main uses of the black pigment particles according to the present invention are developing toners, paints, colorants for resins, and the like.

[Conventional technology]

The black pigment particle powder is widely used as a developing toner by cross-dispersing it in a resin and then molding it, and as a paint by mixing and dispersing it in a vehicle.

In recent years, there has been a strong demand for black pigment powder that is non-magnetic, safe, harmless, and has excellent workability and heat resistance from the viewpoint of improving work efficiency, health and safety, and improving properties in the energy-saving era. ing.

In order to improve workability, it is important that the pigment powder is non-magnetic, has an appropriate size, has excellent dispersibility, and is easy to handle.

Regarding heat resistance, the demand for developing toner, which has been increasing in recent years with the spread of copying equipment, is exposed to high temperatures of 150°C or more during the manufacturing process, so the black pigment powder used in developing toner is , it is necessary that the color is stable even at temperatures of 150° C. or higher.

Furthermore, in baking coating, in which the paint film is dried at high temperatures, curing is carried out at a temperature of 100 to 400°C, depending on the coating resin, so there is a need for pigments that do not change color even at high temperatures of 400°C.

Conventionally, magnetite particle powder and carbon black particle powder have been widely used as black pigment powder.

Further, examples of the non-magnetic black pigment powder made of a mixed oxide of iron and manganese include prior art disclosed in Japanese Patent Publication No. 17288/1982 and Japanese Patent Publication No. 30085/1983.

[Problem to be solved by the invention]

There is currently a demand for black pigment powder, which is non-magnetic, safe, harmless, and has excellent workability and heat resistance. Re-agglomeration occurred between the two, making dispersibility difficult and resulting in poor workability. In addition, since magnetite particles begin to change to maghemite at a temperature of 150° C. or higher, the color changes from black to brown and there is a problem in heat resistance.

Also, although carbon black has excellent heat resistance,
They are ultrafine particles of about 0.01-0.1 a- and are bulky powders that are difficult to handle and have poor workability. In addition, safety and hygiene issues such as carcinogenicity have also been pointed out.

On the other hand, in the technical means disclosed in Japanese Patent Publication No. 47-30085, in which an iron compound and a manganese compound are fired at 800 to 920°C to produce a mixed oxide with iron and manganese, the raw materials are dry mixed and fired. Therefore, it has a strong brown color and poor blackness.

In addition, the process shown in Japanese Patent Publication No. 43-17288 is carried out at a pi value of about 3.5 to 6.5, and manganese metal and (
or) A pigment mixture obtained by adding a manganese compound so as to be homogeneously distributed during the process, at 600-800°C.
In the technical means of firing with Fe, 0. It is said that the method of C) has been found to give a more complete black tone, but the blackness is still insufficient with the technical means.

Therefore, the present invention is non-magnetic, safe and harmless,
In addition, the technical object is to obtain a pigment powder with good blackness and excellent workability and heat resistance.

[Means to solve problems]

The present inventor has arrived at the present invention as a result of various studies regarding the above-mentioned technical problems.

That is, the present invention provides ferrous hydroxide obtained by reacting an aqueous ferrous salt solution with an aqueous alkali hydroxide solution in an amount of 1.01 to 1.3 equivalents to Fe2+ in the aqueous ferrous salt solution. Magnetite particles are produced by oxidizing the ferrous hydroxide colloid to produce magnetite particles through a magnetite production reaction in which a suspension containing a colloid is heated to a temperature range of 45 to 100°C and oxygen-containing gas is passed through it. A suspension containing Mn is added to the suspension containing magnetite particles.
Or, after adding Mn and Fe2' in the state of an aqueous solution to make Mn exist in an amount of 18 to 32 atomic % based on the total Fe in the solution,
The surface of the magnetite particles is coated with the Mn compound or the Mn compound and the Fe compound by heating and oxidizing the suspension under the same conditions as the magnetite production reaction, and then the Mn compound or the Mn compound and the Fe compound are coated. The obtained magnetite particles are separated by P, washed with water, dried, and then heated and fired in a temperature range of 750 to 1000°C to obtain a hematite structure with an average diameter of 0.25°C, which has a hematite structure mainly composed of iron in which Mn is solidly dissolved. A method for producing a non-magnetic black pigment powder comprising obtaining granular particles of 2 to 0.8 μm, an aqueous ferrous salt solution, and 0.80 to 0.99 equivalent of water to Fe2+ in the aqueous ferrous salt solution A suspension containing a ferrous hydroxide colloid obtained by reacting it with an aqueous alkali oxide solution is heated to a temperature range of 45 to 100°C while passing an oxygen-containing gas through a magnetite production reaction. A suspension containing magnetite particles is obtained by oxidizing iron colloid to generate magnetite particles, and an aqueous solution of an Mn compound of 18 to 32 at % based on the total Fe in the liquid is added to the suspension containing the magnetite particles. After adding an aqueous alkali hydroxide solution in an amount exceeding 1.00 equivalents to the Mn compound and the remaining pel*, the surface of the magnetite particles is heated and oxidized under the same conditions as the magnetite production reaction to convert the magnetite particle surface into a Mn compound. Then, the magnetite particles coated with the Mn compound and Fe compound are separated, washed with water, dried, and then heated and fired in a temperature range of 750 to 1000°C to solidify Mn. This is a method for producing a non-magnetic black pigment powder, which consists of obtaining spherical particles having an average particle diameter of 0.2 to 0.8 μm and having a hematite structure containing dissolved iron as a main component.

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

The ferrous salt aqueous solution in the present invention includes ferrous sulfate,
Ferric chloride or the like can be used.

As the aqueous solution of the Mn compound in the present invention, manganese sulfate, manganese chloride, etc. can be used, and in order to uniformly coat the surface of the magnetite particles, it is preferable to add it in the form of an aqueous solution.

As the aqueous alkali hydroxide solution in the present invention, sodium hydroxide, potassium hydroxide, etc. can be used.

As a manufacturing method for producing granular magnetite particles from which the granular nonmagnetic black pigment powder of the present invention is obtained, for example, the technical means disclosed in Japanese Patent Publication No. 44-668 can be used.

The amount of alkali hydroxide aqueous solution is the amount of Fa in ferrous salt aqueous solution.
It is 1.01 to 1.3 equivalents to 2+. When the amount is less than 1.01 equivalent, it is difficult to control the alkali addition ratio, and in some cases, the equivalent ratio may be less than 1.0, and it is also difficult to control the particle size, etc. 1
．． If the amount exceeds 3 equivalents, acicular goethite particles will be mixed.

In addition, the reaction temperature is in the temperature range of 45 to 100"C. If the temperature is lower than 45℃, there is a risk that acicular goethite particles will be mixed in, and if it exceeds 100℃, granular magnetite particles will not be formed. However, it is not economical.

The amount of Mn that coats the particle surface of the granular magnetite particles in the present invention with a Mn compound or a Mn compound and an Fe compound is 18 to 32 at % based on the total Fe in the suspension. If Mn is less than 18 atomic % or more than 32 atomic %, a non-magnetic pigment powder can be obtained, but the brown color becomes strong, which is undesirable.
Obtained at 2 atomic %. More preferably, it is 20 to 25 atom %.

In addition, the reason why Fe'' is added to Mn is to make it easier to coat the particle surface of the magnetite particles with Mn, and the amount of Fe'' added is less than 25 at % based on the total Fe in the suspension. Although non-magnetic black pigment powder can be obtained even when the content exceeds 25 atomic %, the degree of blackness is slightly inferior.

In addition, it is desirable to use the same ferrous salt aqueous solution used to generate the magnetite particles as the Fe'' compound to be added, and an alkali hydroxide aqueous solution may be additionally added during the coating treatment. Furthermore, the conditions such as the treatment temperature for coating may be the same as the conditions for producing magnetite particles.

As a manufacturing method for producing spherical magnetite particles from which the non-magnetic black pigment powder of spherical particles can be obtained in the present invention, for example, the technical means disclosed in Japanese Patent Publication No. 08 of 1988 can be used. .

The amount of alkali hydroxide aqueous solution is Fe in ferrous salt aqueous solution.
It is 0.80 to 0.99 equivalent to 2+. 0.80
If the amount is less than equivalent or exceeds 0.99 equivalent, it is difficult to produce spherical magnetite particles, and
The reaction temperature is in the temperature range of 45-100°C, and 45°C
If the temperature is less than 100° C., there is a risk that acicular goethite particles will be present, and even if the temperature exceeds 100° C., spherical magnetite particles can be produced, but this is not economical.

The amount of Mn added to the spherical magnetite particles in the present invention is also 18 to 32 at % based on the total Fe in the suspension. The reason for this is the same as in the case of the granular magnetite particles described above.

Further, the amount of the aqueous alkali hydroxide solution added to coat the Mn compound and the Fe compound is more than 1.00 equivalents, but less than 1.00 equivalents, based on the Mn compound to be added and the remaining Fe. In this case, Mn and Pe'' do not precipitate in their entirety, making it impossible to coat them uniformly.

When the amount exceeds 1.00 equivalents, the amount is determined in consideration of economic efficiency, and is preferably 1.01 to 1.3 equivalents.

In addition, it is desirable to use the same alkali hydroxide aqueous solution as the alkali hydroxide aqueous solution used to generate the magnetite particles, and the conditions such as the treatment temperature for coating may be the same as the conditions for generating the magnetite particles. .

The oxidation means for the reaction in both methods of producing magnetite particles of the present invention can be carried out by bubbling an oxygen-containing gas (for example, air) into the reaction suspension, and in a reactor equipped with a stirring function. It is preferable to do so.

The particle diameter of the nonmagnetic black pigment powder obtained in the present invention is 0.2 to 0.8 μm in average diameter. If the diameter is less than 0.2 μm, magnetite particles with a particle diameter of less than 0.15 μm are required, and when firing magnetite particles less than 0.15 μm, the reaction activity becomes high, so a non-magnetic black pigment is used. It becomes difficult to control the particle size of the powder. If it exceeds 0.8 μm, the particles become too large and the coloring power decreases, which is undesirable. Therefore, it is desirable that the particle diameter of the magnetite particles is less than 0.5 μm.

Therefore, the particle diameter of the magnetite particles obtained by both methods of producing magnetite particles in the present invention is preferably 0.15 to 0.5a-, and 0°15 to 0.5a.
Mn compound or Mn is added to magnetite particles with a particle size of μm.
By coating the compound and the Pe compound and heating and baking, the particle size becomes slightly larger, and a black pigment powder having the above particle size is obtained.

In the present invention, the temperature range for heating and firing the magnetite particles coated with the Mn compound or the Mn compound and Fe compound is 750 to 1000°C. If it is less than 750'C, the blackness will be insufficient, and if it exceeds 1000'C, the particles will become too large and no coloring power will be produced.

Incidentally, the atmosphere for heating and baking is air.

The purpose of heating and firing in air is to oxidize magnetite and transform it into hematite.

In the present invention, St, AI, P, B,...
Cu, Zn.

Metal compounds such as Cr, Co, Sn, Cd, V, Mo, etc. may be added before or during the reaction in both production methods, and Mn compounds or Mn compounds and Fe compounds may be coated after the reaction is completed. The object of the present invention is not impaired even if the surface of the magnetite particles is coated with the metal compound to form or maintain the particle shape.

[For production]

In the present invention, magnetite particles coated with a Mn compound or a Mn compound and an Fe compound are coated with 750-1000
By heating and firing in the temperature range of ℃, magnetite is oxidized and changed to hematite, and the coated Mn
Since the compound is diffused and solid-solved inside the particles to form particles having a hematite structure mainly composed of iron in which Mn is solid-dissolved, a non-magnetic black pigment powder with good blackness can be obtained.

The reason for this is not clear, but it is thought that the coating of the particle surface with a Mn compound causes Mn to dissolve in solid solution in the hematite structure in an exquisite balance, resulting in an improvement in blackness.

In the nonmagnetic black pigment powder obtained in the present invention, both magnetite particles obtained in the reaction step have uniform particle sizes, and are then coated with a Mn compound or a Mn compound and an Fe compound and then fired. Therefore, uniform particle size is maintained.

In addition, by heating and baking the granular magnetite particles in the present invention and compacting them, the granular particles become rounded particles.

In addition, since it has a hematite structure and is non-magnetic,
Since the particles no longer aggregate with each other due to magnetism, it has excellent dispersibility and workability.

Furthermore, since it is obtained by firing at a high temperature in the temperature range of 750 to 1000°C, it is a black pigment powder that has excellent heat resistance and does not change color even when heated when used for paints or toners.

It should be noted that the non-magnetic black pigment powder obtained by the present invention has an excellent blackness, which means that the Vi value is 21.0, according to the values obtained by embellishing the Hunter's Lab space color value, a0 value, and Bi value. 0~0, all values are 1.0~o, b"
Since the values are within the range of -0.7 to -1.7, it can be said that the pigment powder has good blackness.

〔Example〕

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

In addition, the average diameter of particles in the following Examples and Comparative Examples is shown as the average value of numerical values measured from electron micrographs.

The magnetization value was measured in a powder state in a magnetic field of 10 KOe.

In addition, the vi value (brightness), a0 value, and b The value, a0 value, and b3 value are each shown as a colorimetric value.

The sample piece for measurement was prepared by kneading 0.5 g of non-magnetic black pigment particles, 1 part of castor oil, and 1 part of Occ into a paste using a two-bar type muller, and adding 4.5 parts of clear lacquer to this paste.
Add and knead to make a paint, and apply 6m1 onto cast coated paper.
It was obtained by applying it using a 1 applicator.

Example I Pe5o a containing 1.35 mol/I!
Aqueous solution 19.911 was mixed with 22.09f of a 2°758N NaOH aqueous solution prepared in advance in a reactor equipped with a stirrer.
In addition to fi, it corresponds to 1.08 equivalents with respect to the amount of Fe''.

), Fe(OR) at pH 13 or higher and temperature 85°C
An aqueous ferrous salt solution containing z was produced.

The above ferrous iron aqueous solution containing Fe (OH) z was heated to a temperature of 90°C.
Magnetite particles were generated by blowing air at 1002/min for 150 minutes at 'C.

Next, Mn'' is added to the above magnetite-containing suspension.

1.68mol/j! Mn5O, aqueous solution containing 57!
(The amount of Mn corresponds to 25 atomic % with respect to the total Fe.) and Fe" 1.344m.

Fe3O4 aqueous solution 51 containing l/l (Fe' amount corresponds to 20 atomic % with respect to the total Fe of magnetite particle generation.

) and 6.05N NaOH aqueous solution 5j! (This corresponds to 1.14 equivalents for the amount of Mn and the amount of added Fe.) and 100 f/min at a ptl of 13 or more and a temperature of 90°C.
fi air was aerated for 40 minutes to produce magnetite particles covering the Mn compound and the Fe compound.

The generated particles were separated into a furnace, washed with water, dried, and crushed to obtain a black particle powder using a conventional method.

Next, put the obtained black particle powder into a porcelain Lupo,
It was fired in air at 800°C for 2 hours in an electric furnace to obtain black particle powder.

The obtained black particle powder was examined using an electron microscope (X20.
As shown in 0OO), the particles have an average diameter of 0.5 μm, and the Mr+ content is 14.5e as a result of fluorescent X-ray analysis.
+t%, and its color has a lightness L1 of 18.89 and a
The 0 value was 0.60 and the b0 value was -1.54.

Furthermore, as shown in the X-ray diffraction diagram of FIG. 2, a hematite peak was observed.

Magnetism is a magnetization value of 0°6 when an external magnetic field of 10 koe is applied.
It was 9 esu/g, which was approximately the same level as hematite.

Furthermore, 10 g of the above black pigment powder was heated in air at 500°C for 60 min.
A heat-resistant treatment test was conducted by heat-treating for a minute. The color of the heat-treated product was 19.53 in lightness, 0.44 in AS value, and -1.70 in B'' value, showing almost no discoloration compared to before heat treatment, indicating that it has excellent heat resistance. It was done.

Example 2 20 ffi of Fe5Oa aqueous solution containing 1.5 mol/Il of Fe"" was added to 201 of 2,64N NaOH aqueous solution prepared in advance in a reactor equipped with a stirrer (Fe
This corresponds to 0.88 equivalent to 2+. ), pH 6,9
, an aqueous ferrous salt solution containing Fe(OR)z was produced at a temperature of 90°C.

A ferrous aqueous solution containing Fe (OR) t was heated to a temperature of 90°C.
100 per minute at ℃! Air was passed through the tube for 120 minutes to produce a ferrous salt aqueous solution containing magnetite particles.

Next, 1.2 mol/j! of Mn"" was added to the suspension containing the magnetite particles and residual Fe2+. MnS containing
O4 aqueous solution 54! (The amount of Mn corresponds to 20 atomic % with respect to the total Fe.

) and a 4.64N NaOH aqueous solution 54ICMn (corresponding to 1.21 equivalents for the amount of residual Fe)) were added, and at a pH of 13 or higher and a temperature of 90°C, 1001 air per minute was aerated for 40 minutes to form a Mn compound. Magnetite particles coated with Fe compound and Fe compound were produced.

The generated particles were separated into a furnace, washed with water, dried, and crushed to obtain a brown powder by a conventional method.

Subsequently, the obtained brown powder particles were placed in a porcelain crucible and fired in air at 800° C. for 2 hours in an electric furnace to obtain black particle powders.

The obtained black particle powder was examined using an electron microscope (X20.
000), it is a spherical particle with an average diameter of 0.5 μm, and the Mn content is 12.3 wt as a result of fluorescent X-ray analysis.
%, and its color had a brightness value of 19.74, an a0 value of 0.86, and a b'' value of -1.32.

Furthermore, as shown in the X-ray diffraction diagram of FIG. 4, a hematite peak was observed.

Magnetism is a magnetization value of 0°5 when an external magnetic field of 10 kOe is applied.
It was 1 esu/g, which was approximately the same level as hematite.

Furthermore, 10 g of the above black pigment powder was heated in air at 500°C for 60 min.
A heat-resistant treatment test was conducted by heat-treating for a minute. The color of the heat treated product is brightness 20.45, a11 value 0.71, b0
The value was -1.49, and almost no discoloration was observed compared to before heat treatment, indicating excellent heat resistance.

Examples 3 to 5, Comparative Examples 1 to 5 Type and amount of ferrous salt aqueous solution for magnetite production reaction, type and amount of alkali hydroxide aqueous solution, oxidation reaction time, coating treatment with Mn compound or Mn compound and Fe compound Example 1 except that the type and amount of the Mn salt aqueous solution and the addition timing, the type and amount of the added ferrous salt aqueous solution, the type and amount of the additionally added alkali hydroxide aqueous solution, and the heating and calcination temperature were varied.
A black pigment powder was obtained in the same manner as above.

The main manufacturing conditions and characteristics at this time are shown in Tables 1 to 3.

〔Effect of the invention〕

As shown in the above examples, the black pigment powder according to the present invention is non-magnetic, safe and harmless, and consists of particles having a hematite structure mainly composed of iron in which Mn is solidly dissolved. Since it is a black particle powder, it has excellent dispersibility, workability, and heat resistance, and also has good blackness, making it suitable as a coloring material for developing toners and paint resins.

[Brief explanation of drawings]

1 and 3 are electron micrographs (X 20
, 000). 2 and 4 are X-ray diffraction patterns of the black pigment powders obtained in Example 1 and Example 2.

Claims (1)

[Claims] 1. Ferrous salt aqueous solution and Fe^2^ in the ferrous salt aqueous solution
A suspension containing ferrous hydroxide colloid obtained by reacting an aqueous alkali hydroxide solution of 1.01 to 1.3 equivalents with respect to + is heated to a temperature range of 45 to 100°C while being heated with oxygen. A suspension containing magnetite particles is obtained by oxidizing the ferrous hydroxide colloid to produce magnetite particles through a magnetite production reaction in which the containing gas is aerated, and Mn or Mn is added to the suspension containing magnetite particles.
and Fe^2^+ in the form of an aqueous solution to reduce the total F in the solution.
After making Mn exist in an amount of 18 to 32 atomic % based on e, the suspension is heated and oxidized under the same conditions as the magnetite production reaction to coat the surface of the magnetite particles with a Mn compound or a Mn compound and a Fe compound. Then, the magnetite particles coated with the Mn compound or the Mn compound and Fe compound are filtered, washed with water, and dried.
By heating and firing at a temperature range of 750 to 1000°C, granular particles with an average diameter of 0.2 to 0.8 μm and having a hematite structure mainly composed of iron in which Mn is dissolved are obtained. Method for producing non-magnetic black pigment powder. 2. Ferrous salt aqueous solution and Fe^2^ in the ferrous salt aqueous solution
A suspension containing a ferrous hydroxide colloid obtained by reacting an aqueous alkali hydroxide solution of 0.80 to 0.99 equivalents to + is heated to a temperature range of 45 to 100°C while being heated with oxygen. A suspension containing magnetite particles is obtained by oxidizing the ferrous hydroxide colloid to produce magnetite particles through a magnetite production reaction in which the containing gas is aerated, and the total F in the liquid is added to the suspension containing magnetite particles.
After adding an aqueous solution of a Mn compound of 18 to 32 atom % to e and an aqueous alkali hydroxide solution in an amount exceeding 1.00 equivalents to the Mn compound and residual Fe^2^+, the magnetite production reaction is carried out. The surfaces of the magnetite particles are coated with a Mn compound and an Fe compound by heating and oxidizing under the same conditions as above, and then the magnetite particles coated with the Mn compound and Fe compound are filtered, washed with water, and dried. By heating and firing in a temperature range of ~1000°C, the average particle size is 0.2 to 0.8μ, which has a hematite structure mainly composed of iron in which Mn is dissolved.
A method for producing a non-magnetic black pigment powder, characterized by obtaining spherical particles of m.