JP3597893B2 - Iron oxide ultrafine particles and method for producing the same - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a method for producing iron oxide composed of ultrafine particles, and a black pigment produced by the method.
Iron oxide composed of ultrafine particles is extremely stable under various environmental conditions, does not discolor, and is a substance harmless to the human body. Therefore, it is useful as a pigment for cosmetics and the like.
[0002]
[Prior art]
In Japan, black iron oxides such as titanium pigments and iron pigments have been used as black pigments for cosmetics such as eye lines and eye shadows, but titanium pigments have poor elongation when used as cosmetics. In addition, in the United States, there is a problem that it cannot be manufactured as an export product due to the fact that it is not licensed as a cosmetic pigment, and black iron oxide by the conventional manufacturing method is a harmless substance applied to the human body However, depending on the conditions of the atmosphere, it lacks stability and may turn reddish brown, making it difficult to produce the same color as a pigment, and also has a problem with discoloration at the stage of use as a cosmetic. there were.
[0003]
The method of producing ultra-fine particles by creating high-temperature plasma involves introducing the target substance into a plasma flame together with a carrier gas, evaporating it at high temperature, and precipitating the target substance in the cooling process to form ultra-fine particles. In the case where the ultrafine particles are to be made of an oxide, the carrier gas is oxygen, and a raw material that generates an oxide by oxidation is introduced into the carrier gas, or the cooling atmosphere is oxygen, It is often performed to generate ultrafine oxide particles by advancing an oxidation reaction in the process.
[0004]
Such a method is also possible to obtain ultra-fine particles of iron oxide, but ultra-fine particles of iron oxide obtained by such a method, even if initially brown, are left brown in the air over time if left in the air. And the discoloration increased, and it was not possible to obtain ultrafine iron oxide as a pigment having a stable color tone. Furthermore, black iron oxide ultrafine particles having a stable color tone could not be obtained.
[0005]
[Problems to be solved by the invention]
Therefore, there is a need for the development of iron oxide as a new black pigment that is stable under the conditions of production and use, is harmless to the human body, and can be used as a pigment for cosmetics. An object of the present invention is to produce the iron oxide ultrafine particles as the black pigment.
[0006]
[Means for Solving the Problems]
In order to solve this problem, the inventors of the present invention have conducted intensive research and have found that iron oxide ultrafine particles obtained by converting iron into a plasma in the gas phase in the presence of water vapor have a particle size as the ultrafine particles and a stable black iron oxide. As a result, the present inventors have found that the material is an excellent material as a black pigment, and completed the present invention.
[0007]
That is, the present invention relates to ultrafine iron oxide particles that convert a gas flow in which iron powder is supported on a carrier gas in the presence of high-temperature steam into plasma to vaporize and evaporate the iron powder, and cool the plasma to precipitate the generated iron oxide. And a method for producing the same.
[0008]
Furthermore, the present invention relates to a black pigment produced by the above method.
In this method, an RF plasma method is preferably used for converting a gas flow in which a carrier gas carries iron powder into plasma.
[0009]
Although the method of the present invention is required to be performed in the presence of high-temperature steam, when the gas flow for supporting the iron powder on the carrier gas by the RF plasma method is turned into plasma, the steam is directly introduced into the plasma torch. However, if water vapor is introduced directly into the plasma torch, energy for dissociation of water molecules is consumed and the plasma flame becomes unstable, so hydrogen is mixed with the carrier gas and introduced into the plasma torch. Then, oxygen is introduced into the plasma torch in a state surrounding the carrier gas together with the carrier gas as a sheath gas, and a plasma flame is formed by the action of a high-frequency electric field formed by the high-frequency coil. Preferably, steam is generated.
[0010]
Conversely, the carrier gas is mixed with oxygen and introduced into the plasma torch, and hydrogen is introduced as a sheath gas into the plasma torch in a state surrounding the carrier gas together with the carrier gas to form a high-frequency coil formed by the high-frequency coil. It is also possible to form a plasma flame by the action of an electric field, resulting in the generation of high-temperature steam in the plasma flame.
[0011]
As described above, by using a high-power plasma torch instead of introducing oxygen and hydrogen into the plasma torch, it is a matter of course that steam may be directly introduced into the plasma torch.
[0012]
In any case, the condition required in this method is that, in an oxidizing atmosphere in which high-temperature steam is present, a gas flow in which iron powder is supported on a carrier gas is converted into plasma to vaporize metallic iron, and the plasma is cooled to reduce FeO or FeO. The purpose is to obtain iron oxide ultrafine particles having a chemical composition of Fe ₃ O ₄ . The ultrafine particles obtained in this way are substantially spherical and have a particle size of about 0.01 μm to 0.1 μm.
[0013]
The ultrafine iron oxide particles thus obtained are extremely excellent as a black pigment because of their particle diameter. The black pigment itself consists of iron oxide and is used in environmental conditions, such as oxidizing or reducing conditions, acidic or alkaline conditions, or in dry conditions. It is a substance that is stable under various conditions, such as whether it is a condition or a wet condition, or a low temperature condition or a high temperature condition, and is also harmless when applied to the human body. It is especially useful as a pigment for cosmetics. And when this pigment is used as a pigment for the manufacture of eye lines and eyeshadow, it has no discoloration and is extremely fine, so it is extremely excellent in elongation and covering power, and it is harmless to the human body. It has.
[0014]
The iron oxide ultrafine particles are produced, for example, using an apparatus shown in FIG.
That is, this apparatus is composed of a raw material iron powder supply device shown in FIG. 1A, a plasma torch shown in B, a cooling double tube shown in C, a chamber shown in D, and an ultrafine particle recovery device shown in E. Become.
[0015]
In the raw material iron powder supply device A, the raw material iron powder is sent out from the hopper 10, and the raw material iron powder is carried by the argon gas supplied from the carrier gas supply port 11 and introduced into the plasma torch B from the raw material iron supply pipe. You.
[0016]
The plasma torch B is mainly composed of a quartz tube 1, a high-frequency oscillation coil 2 is attached outside the quartz tube 1, and a cooling jacket 3 is provided outside the quartz tube 1. At the upper part of the plasma torch are provided gas outlets 4, 5, 6 whose ejection directions are tangential, axial and radial. The gas outlets 7, 8 and 9 supply oxygen gas, A mixed gas of an argon gas and a hydrogen gas and an oxygen gas are supplied. The mixed gas of argon gas and hydrogen gas serves as a plasma gas, and the oxygen gas serves as a sheath gas. The mixed gas serves to cover the plasma gas and stabilize the plasma.
[0017]
The cooling double tube C is composed of an inner tube of a quartz tube and an outer tube that covers the inner tube, and cooling water circulates between both tubes to cool the quartz tube.
[0018]
The chamber D includes a stainless steel inner cylinder and a stainless steel outer cylinder, and cooling water circulates between the two cylinders to cool the inner cylinder. The raw iron powder evaporated and vaporized by the plasma torch B reacts with water vapor and oxygen generated and existing in the plasma gas, and is cooled in the cooling double tube and the chamber to generate iron oxide ultrafine particles.
[0019]
It is essential that the generation zone of the iron oxide ultrafine particles is a steam atmosphere, and thereby, the iron oxide ultrafine particles are stable. This water vapor atmosphere can be formed by directly introducing water vapor into this production zone, or by using oxygen gas and hydrogen gas as the sheath gas and carrier gas and reacting them as described above.
[0020]
The ultra-fine particle collecting device E has a trap 15 connected to a decompression line 16, and the generated ultra-fine particles are captured and collected here.
[0021]
The thus-produced ultrafine iron oxide particles have an average particle diameter of 0.01 μm to 0.1 μm, preferably 0.05 μm or less, and have a chemical composition of FeO.Fe ₃ O ₄ Can be indicated by Since it is obtained by rapidly cooling iron oxide from a molten state through a gas phase plasma state, its surface is extremely smooth as shown in FIG. Is considered to be stable.
[0022]
The ultrafine iron oxide produced by this method is considered to be a mixture of FeO.Fe ₃ O ₄ as described above. For example, it is sufficiently stable not only in the air but also in water, and the particle shape is spherical. It has the same function as iron oxide fine particle powder conventionally used as a black pigment. Accordingly, the iron oxide ultrafine particles are useful as black pigments for cosmetics.
[0023]
Next, the present invention will be described in more detail with reference to examples. However, these examples are merely for describing the present invention and should not be construed as limiting the present invention to the examples.
[0024]
Example 1 Production of Ultrafine Iron Oxide Particles Ultrafine iron oxide particles were produced using the apparatus shown in FIG. The plasma torch is composed of a quartz tube 1 having an inner diameter of 55 mm, a coil 2 for high-frequency oscillation outside thereof, and a jacket tube 3 for cooling, and radial and axial gas outlets 4 provided on the upper portion of the plasma torch and 5 to 90 L / min in total of argon gas and 10 L / min of hydrogen gas as plasma gas, and 3 L / min of oxygen gas as sheath gas from gas jet port 6 in tangential direction. And a power of 20 kW was introduced into the high-frequency oscillation coil to form a plasma in the plasma torch. The raw iron powder supply port 12 provided on the upper part of the plasma torch is supplied with 4 g / min of raw iron powder having an average particle diameter of 50 μm and supported by 10 liter / min of argon gas introduced from the carrier gas supply port 11 by plasma. Introduced into the torch.
[0025]
Iron formed in the plasma torch and heated and evaporated by the plasma gas reacts with high-temperature steam generated by the plasma to generate a precursor of iron oxide ultrafine particles.
[0026]
The lower part of the plasma torch is connected to a cooling double tube, which comprises a quartz inner tube having an inner diameter of 120 mm and a length of 200 mm and a cooling outer tube outside the inner tube. Here, the plasma gas is cooled and ultrafine iron oxide particles are generated.
[0027]
This cooling double pipe is connected to a chamber, and this chamber is composed of a stainless steel inner pipe having an inner diameter of 400 mm and a length of 500 mm and an outer pipe covering the inner pipe, and cooling water circulates between the inner pipe and the outer pipe. Then, the flow of the gas carrying the formed ultrafine iron oxide particles is cooled.
[0028]
The iron oxide ultrafine particles thus obtained are recovered and separated by an ultrafine particle recovery device comprising a filter connected to a pressure reducing line, and are taken out. The resulting iron oxide ultrafine particles was analyzed and found to be those having a chemical composition represented by the formula FeO · Fe ₃ O _4. The obtained iron oxide ultrafine particles were black ultrafine particles having an average particle size of 0.01 to 0.05 μm. The scanning electron micrograph of the iron oxide ultrafine particles is as shown in FIG. From this photograph, it can be seen that the iron oxide ultrafine particles are particles having a smooth surface.
[0029]
Even when the iron oxide ultrafine particles were allowed to stand in water for 12 months, they did not turn brown and remained black. Also, there was no change when left in the air at room temperature.
[0030]
Comparative Example 1
Using the same apparatus as in Example 1, argon was introduced into the plasma torch in a total amount of 50 to 100 L / min from the gas ejection port to form plasma, and oxygen gas was changed as the sheath gas at 0 to 10 L / min. In a plasma torch, and iron powder was introduced into the formed plasma at a rate of 4 g / min to make it ultrafine. The generated ultrafine iron particles were cooled in a cooling chamber and collected by a filter. The average particle size of the obtained ultrafine particles was 0.01 to 0.05 μm.
When oxygen was set to 0 (anoxic), the produced product was ultrafine iron particles, but when removed from the apparatus, the color changed to reddish brown. This is because Fe ₂ O ₃ was generated. When the oxygen was gradually increased, the generated ultrafine particles became reddish brown, indicating that ultrafine particles of Fe and Fe ₂ O ₃ were generated.
[0031]
Comparative Example 2 When FeO.Fe ₃ O ₄ (black iron oxide) was used as a raw material, black iron oxide was introduced into an argon plasma gas to obtain ultrafine particles. As in the case of iron powder, when oxygen is used, the product is reddish brown, and the product is a mixture of iron and iron oxide and has a composition of Fe and Fe ₂ O ₃ . That is, in plasma, the black iron oxide becomes a mixture of Fe and Fe ₂ O _{3 under} the ultrafine particle condition.
[Brief description of the drawings]
FIG. 1 shows an apparatus for producing ultrafine iron oxide particles used in Example 1.
FIG. 2 shows a scanning electron micrograph of the ultrafine iron oxide particles obtained in the present invention.

Claims (3)

A method for producing ultrafine iron oxide particles in which a gas flow in which iron powder is carried on a carrier gas in the presence of high-temperature steam is turned into plasma to vaporize and evaporate the iron powder, and cools the plasma to precipitate iron oxide produced. The method according to claim 1, wherein the high-temperature steam is generated by plasma-forming a gas stream in which iron powder is supported on a carrier gas in the presence of oxygen and hydrogen. 2. The method according to claim 1, wherein the plasma conversion is performed by an RF plasma method.

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