KR100355156B1 - Black magnetite powder manufacturing method - Google Patents

Abstract

The present invention relates to a method for producing black magnetite powder suitable for producing fine powder of black magnetite by spray roasting method.

The method for producing a black magnetite powder according to the present invention includes spraying and roasting an iron chloride mixed solution into a roasting furnace maintaining a temperature range of 600 to 900 ° C. in a carbon dioxide atmosphere containing 0 to 0.5 vol% of oxygen. Is done.

Therefore, according to the present invention, the manufacturing process is simpler than the conventional solid-state method, and the manufacturing time is short, and the toner has excellent electrical and magnetic properties of 70 to 95 emu / g and coercive force of 120 to 160 Oe while the saturation magnetization of the particles is short. It is effective to provide a method for producing a magnetic powder for solvents and black pigments in a high yield of 70% or more yield.

Description

Black magnetite powder manufacturing method

The present invention relates to a method for producing black magnetite powder. More specifically, the present invention relates to a method for producing black magnetite powder suitable for producing fine powder of black magnetite by spray roasting.

Magnetite-based powder is a ferromagnetic material having magnetic properties. It is used as a charge control and black auxiliary agent in magnetic toners used as a developer for copiers, laser beam printers, and facsimiles operated by the principle of electrophotographic process. It is widely used for pigments, such as paint using the black color, and cosmetics.

Commercial methods for producing magnetite powders are known as wet methods and solid phase methods.

In the wet method, iron is dissolved in hydrochloric acid or sulfuric acid, and an alkali solution is added to the solution to precipitate and precipitate with ferrous hydroxide (Fe (OH) ₂ ), and the precipitate is recovered and vented with an oxidizing gas at a temperature of 70 to 100 ° C. To produce magnetite. However, this wet method has advantages in that magnetite powder having a spinel single phase crystal structure, uniform shape and good magnetic properties can be manufactured, but the manufacturing process is complicated and waste water treatment facilities are required. There is a disadvantage that the manufacturing cost is high for such reasons.

The solid state method uses hematite (a small amount of metal) -Fe ₂ O ₃ ) is a method of producing a coarse magnetite powder by reducing the powder with a reducing gas such as hydrogen for a long time in a high temperature heat treatment furnace, and then grinding it by a ball mill to produce a magnetite powder. This solid-phase method has been used for the production of red iron oxide from the past, and the iron oxide (hematite) produced by hot spray roasting of ferrous chloride waste liquid produced when the steel industry is pickled with hydrochloric acid in the air Compared with the wet method, the process of sedimentation and separation can be omitted, and the pickling waste can be recycled, which has a great advantage in terms of cost reduction. However, since the main phase is hematite, the high temperature is required to change the structure to the magnetite phase. There is a disadvantage that the reduction treatment and grinding treatment of the inevitable.

Accordingly, the present invention has been completed as a result of constant efforts to develop a method for producing black magnetite powder easily and simply and inexpensively using a salt iron solution.

An object of the present invention is to provide a production method for producing black magnetite powder easily, simply and inexpensively using a conventional roasting furnace.

Figure 1 is a schematic diagram showing the configuration of the roasting furnace for the production of black magnetite powder according to the present invention.

※ Explanation of code for main part of drawing

11: raw material supply tank 12: atmosphere gas supply source

13: roasting furnace 14: nozzle

15 Separator 16: Product Recovery Container

17: scrubber

The method for producing a black magnetite powder according to the present invention includes spraying and roasting an iron chloride mixed solution into a roasting furnace maintaining a temperature range of 600 to 900 ° C. in a carbon dioxide atmosphere containing 0 to 0.5 vol% of oxygen. Is done.

The mixed ferric chloride solution sprayed and roasted into the roasting furnace may be a mixture of ferrous chloride solution and ferric chloride solution.

The ferric chloride mixed solution may be a mixture of 20 to 80% by volume ferrous chloride solution and 80 to 20% by volume ferric chloride solution.

Hereinafter, the present invention will be described in detail with reference to specific examples.

The method for producing the black magnetite powder according to the present invention includes spraying and roasting the mixed iron chloride aqueous solution into a roasting furnace which maintains a temperature range of 600 to 900 ° C in an atmosphere of carbon dioxide containing 0 to 0.5% by volume of oxygen. Characterized in that made.

The roasting furnace may have a structure as shown in FIG. 1, and a method of manufacturing the black magnetite powder according to the present invention will be described as follows based on the roasting furnace 13 shown in this drawing.

The mixed iron chloride solution to be sprayed and roasted is introduced into the roasting furnace 13 from the raw material supply tank 11 via a nozzle 14 located at the lower end of the roasting furnace 13. At this time, the roasting furnace 13 is also filled with carbon dioxide containing oxygen supplied from the atmosphere gas supply source 12 connected thereto, the temperature is maintained in the temperature range of 600 to 900 ℃ for proper oxidation. Oxygen content in the carbon dioxide containing oxygen may occupy 0 to 0.5% by volume relative to the total volume of the atmosphere gas. This content is an optimum oxygen content for oxidizing the iron chloride mixed solution as a raw material to magnetite, and is the content obtained by the inventors' experiment repeatedly. Even if the oxygen content exceeds 0.5% by volume, there may be a problem that the desired oxidation may not occur. Since the temperature in the roasting furnace 13 provides calories for the iron oxide to be formed quickly, the setting of the roasting temperature is very important for this reason. As a result of the experiment, the optimum roasting temperature is preferably within the range of 600 to 900 ° C, more preferably within the range of 650 to 850 ° C. When the roasting temperature is lower than 600 ℃, a large amount of unreacted iron chloride is present at the time of roasting, which is combined with water to become corrosive, so that the roasting temperature to maintain a temperature higher than 600 ℃ as possible to avoid the presence of unreacted iron chloride It is desirable to. On the other hand, if it exceeds 900 ℃, despite the change in the method such as atmosphere control or composition, the amount of iron oxide on the hematite phase is increased thermodynamically there may be a problem that also lowers the yield of the magnetite powder. In addition, control of the roasting atmosphere in the roasting furnace 13 is one of the most important factors in the production of the magnetite powder, and it is important that the oxygen does not come into contact with the reactants alone, that is, the mixed solution of iron chloride. In order to avoid the direct reaction of the mixed iron chloride solution and oxygen, the reaction was conventionally performed under an inert atmosphere using nitrogen or argon gas. However, in the present invention, a small amount of oxygen, that is, 0 to 0.5% by volume of oxygen based on the total volume of the atmospheric gas, The atmosphere in the roasting furnace 13 was created using the containing carbon dioxide gas. When the oxygen content is more than 0.6% by volume, the fraction of hematite phase is sharply increased, which may cause a problem of lowering the yield of magnetite powder. In addition to carbon dioxide in the atmosphere gas, the presence of less than 10% by volume of carbon monoxide was found to have little effect on the reaction or yield of the magnetite powder produced.

The mixed iron chloride solution injected into the roasting furnace 13 filled with the atmosphere gas made of carbon dioxide containing oxygen is oxidized in a microdroplet state by the nozzle 14 to be a powder of water vapor and iron chloride (FeCl ₂ ), The iron chloride powder is further oxidized with water vapor to form iron oxide powder and gaseous hydrochloric acid (HCl). The iron oxide powder is a black magnetite powder to be obtained in the present invention. After the reaction, the product mixture exits from the roasting furnace 13 and flows into the separator 15 to be separated into a waste gas including a solid magnetite powder and a gaseous hydrochloric acid gas. Recovered, the gaseous waste gas is introduced into the scrubber 17 to remove the fine dust and the like, it is possible to be released into the atmosphere through the appropriate post-treatment, such as neutralization, or may be introduced into the other processes required. As the separator 15, a commercially available separator 15 capable of separating solid components from gas components, such as a cyclone separator, may be used. Also, a scrubber 17 and a post treatment may be extremely easily understood by those skilled in the art. As the present invention, description thereof will be omitted. In particular, the scrubber 17 is known enough to be commercially available and can be easily understood by those skilled in the art, and the post-treatment of the waste gas is also appropriately discharged by neutralization or the like according to the composition or content of the waste gas. It can be easily understood by those skilled in the art that it can have the necessary requirements.

The most important condition of the formation of the single phase of the magnetite powder in the resulting iron oxide powder phase is the composition of the mixed iron chloride aqueous solution sprayed and roasted into the roasting furnace 13. The ferric chloride mixed solution may be a mixture of ferrous chloride solution and ferric chloride solution. At this time, when the composition ratio of ferric chloride in the iron component in the solution is within the range of 10 to 90 mol%, preferably within the range of 30 to 70 mol%, it is experimentally found that the single phase of the magnetite powder is best formed. lost. If the amount of ferric chloride in the solution of the iron content is less than 20 mol% there may be a problem that the yield of the magnetite powder is reduced due to a rapid increase in the rate of formation of the Weston (FeO) phase during spraying, roasting, whereas 80 If it is more than mole%, gamma iron oxide ( -Fe ₂ O ₃ ) may be a problem that the yield of the magnetite powder is also reduced due to the rapid increase in the production rate.

The ferric chloride mixed solution may be a mixture of 20 to 80% by volume ferrous chloride solution and 80 to 20% by volume ferric chloride solution.

The injection amount of the mixed iron chloride solution into the roasting furnace 13 may be affected by the internal volume of the roasting furnace 13, the reaction rate, the viscosity of the aqueous solution, and the like, but this is known to those skilled in the art, that is, the composition of the atmosphere gas. And, if only the temperature of the roasting furnace 13 and the conditions of the mixed iron chloride aqueous solution is the same, it can be understood that it can be found experimentally suitable operating conditions according to the volume of the roasting furnace 13 to be used.

Hereinafter, preferred embodiments and comparative examples of the present invention will be described.

The following examples are intended to illustrate the invention and should not be understood as limiting the scope of the invention.

Example 1

Ferric chloride (FeCl ₂ ) and ferric chloride (FeCl ₃ ) were dissolved in pure water at a mixing ratio of 50: 50 in a molar ratio to prepare an iron chloride mixed solution so that the iron content was 100 g / liter. The product was sprayed and roasted in a 125 mm diameter quartz tube maintained at a constant temperature of 700 ° C. Atmospheric gas in the furnace was pure carbon dioxide, that is, carbon dioxide containing no oxygen at a rate of 25liter / min, and the iron chloride mixed solution was also blown at a rate of 25liter / min and roasted. It is shown in Table 1 below.

Example 2

The atmosphere gas in the roasting furnace 13 was carried out in the same manner as in Example 1 except that the mixture of carbon dioxide and oxygen in a volume ratio of 99.8 / 0.2 was used, and the results are shown in Table 1 below.

Example 3

The atmosphere gas in the roasting furnace 13 was carried out in the same manner as in Example 1 except that the mixture of carbon dioxide and oxygen was mixed at a volume ratio of 99.6 / 0.4, and the results are shown in Table 1 below.

Comparative Example 1

The atmosphere gas in the roasting furnace 13 was carried out in the same manner as in Example 1 except for using a mixture of carbon dioxide and oxygen in a volume ratio of 99.4 / 0.6, and the results are shown in Table 1 below.

Comparative Example 2

The atmosphere gas in the roasting furnace 13 was carried out in the same manner as in Example 1 except that the mixture of carbon dioxide and oxygen in a volume ratio of 99.0 / 1.0 was used, and the results are shown in Table 1 below.

Comparative Example 3

The atmosphere gas in the roasting furnace 13 was carried out in the same manner as in Example 1 except that the mixture of carbon dioxide and oxygen in a volume ratio of 95.0 / 5.0 was used, and the results are shown in Table 1 below.

Item Atmospheric gas fraction (% by volume) Powder structure Volume fraction on magnetite (%) Magnetic characteristics (H _ex = 5000 Oe) carbon dioxide Oxygen Saturation Magnetization (emu / g) Coercive force (Oe) Example 1 100.0 0 Fe ₃ O ₄ 100 95 120 Example 2 99.8 0.2 Fe ₃ O ₄ + Fe ₂ O ₃ ≥99 93 125 Example 3 99.6 0.4 Fe ₃ O ₄ + Fe ₂ O ₃ ≥70 72 140 Comparative Example 1 99.4 0.6 Fe ₃ O ₄ + Fe ₂ O ₃ ≤20 15 170 Comparative Example 2 99.0 1.0 Fe ₂ O ₃ -0 - - Comparative Example 3 95.0 5.0 Fe ₂ O ₃ -0 - -

Therefore, according to the present invention, the iron chloride solution, which can be used as a pickling waste liquid, is maintained as a starting material at a constant temperature, and spray roasted into the spray furnace 13 under carbon dioxide atmosphere gas containing less than 0.5% by volume of oxygen. The black magnetite powder can be prepared, especially the manufacturing process is simpler than the conventional solid phase method, and the manufacturing time is short, but the saturation magnetization of particles is 70-95 emu / g, and the coercivity is 120-160 Oe. There is an effect of providing a method for producing a magnetite powder for a toner and a black pigment having a characteristic in a high yield of 70% or more yield.

Although the present invention has been described in detail only with respect to the described embodiments, it will be apparent to those skilled in the art that various modifications and variations are possible within the technical scope of the present invention, and such modifications and modifications are within the scope of the appended claims.

Claims (3)

A mixed aqueous solution containing 20 to 80% by volume of ferrous chloride solution and 80 to 20% by volume of ferric chloride solution is maintained at a temperature range of 600 to 900 ° C. in a carbon dioxide atmosphere containing 0 to 0.5% by volume of oxygen. Method for producing a black magnetite powder, characterized in that made by spraying into a roasting furnace to be roasted. delete delete