Iron oxyhydroxide powder

Abstract

To provide iron oxyhydroxide powder in which the content of nanoparticles is controlled.SOLUTION: Adding an alkali containing neither metallic carbonate nor metallic hydrogen carbonate to an aqueous solution containing Fe (II) to adjust the concentration of Fe (II) to 0. 10mol / L or more and 0. 35mol / L or less, and blowing an oxygen-containing gas at a flow of 0. 02L / min or more and 0. 13L / min or less with respect to Fe (II) 1. 00mol while maintaining the liquid temperature at 20 °C or higher and 35 °C or lower; Adding iron (II) so as to satisfy 7.0 ≤ (p + q) / p ≤ 12.0, where p is the amount of substance / mol of iron (III) in the obtained nuclei and q is the amount of substance / mol of iron (II) to be added; And blowing an oxygen-containing gas at flow rates of 0. 45mol / min or more and 0. 85mol / min or less in a first stage and 0. 10L / min or more and 0. 03L / min or less in a second stage with respect to iron (II) 1. 00mol while adjusting the concentration of iron (II) to 0. 01L / L or more and 0. 12L / L or less and maintaining the liquid temperature at 50 °C or higher and 80 °C or lower, thereby providing an iron oxyhydroxide powder in which the Dn50 of the short axis size is 100nm or more and or less and the proportion of particles having a short axis size of less than is 3.0 number% or less. 300nm 100nm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an iron oxyhydroxide powder. [Background technology]

[0002] Iron oxide has been used in a variety of applications. Its color-developing properties are typically used as a pigment in paints and cosmetics, its magnetic properties as an electronic material, and its wear resistance as a friction material. In recent years, iron oxide has been widely used in cosmetics and other applications where it may come into contact with the human body, as its harmful effects have not been confirmed. Iron oxide exhibits different properties depending on its oxidation state. Typical examples include black magnetite (Fe3O4), red hematite (α-Fe2O3), and yellow goethite. Iron oxides are also known to have various structures, including granular, plate-like, and needle-like. In particular, in the cosmetics industry, multiple colors must be mixed to achieve subtle shades, making each color essential.

[0003] The applicant has previously filed patent applications for various inventions relating to iron oxides, such as Patent Document 1 relating to black iron oxide and Patent Document 2 relating to iron oxide used in dark-colored cosmetics.

[0004] In recent years, growing health consciousness, particularly in Europe, has led to some opposition to the addition of nano-order substances to cosmetics. Although Christopher SJ Campbell et al. published experimental results showing that nano-order particles were not absorbed by healthy skin when applied to the skin (Christopher SJ Campbell et al., Journal of Controlled Release, Volume 162, Issue 1, 20 August 2012, pages 201-207), consumer concerns remain, and European regulatory authorities have already imposed restrictions on the amount and processing method of nano-order substances. For example, the acicular iron oxide particles described in the examples of Patent Document 3 are nano-order substances in terms of their minor axis diameter. Such powders are subject to regulations regarding nano-order substances, making it difficult to freely incorporate them into cosmetics. Furthermore, in reality, nano-order substances are sometimes avoided simply because they are nano-order substances.

[0005] Cosmetic pigments that are most affected by regulations targeting nano-order substances are iron oxide pigments composed of needle-shaped particles primarily composed of goethite, an iron oxyhydroxide used to achieve yellow. The particle size of a pigment has a significant effect on its color. Therefore, changing (increasing) the particle size of a pigment so that it is exempt from regulations targeting nano-order substances changes the color of the pigment, making it difficult to achieve the desired yellow color. What is needed is an iron oxide pigment with a controlled content of nano-order particles (nanoparticles) without significantly changing the color of the pigment. While research on large particles exceeding 1 μm in diameter and on fine particles, as exemplified by Patent Document 4, has progressed to date, research on iron oxyhydroxides with the above-mentioned characteristics has not progressed.

[0006] Regarding the goal of controlling particle size, previous experiments have shown that hydrothermal treatment improved the particle size distribution of iron oxyhydroxide (Non-Patent Document 1). However, no method for obtaining particles that satisfy the above conditions has been suggested. There is a need to provide an iron oxyhydroxide powder containing goethite as its main component with a controlled content of nanoparticles. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-000763 [Patent Document 2] Japanese Patent Publication No. 2022-177647 [Patent Document 3] Japanese Patent Application Publication No. 10-340447 [Patent Document 4] Japanese Patent Application Laid-Open No. 2007-254267 [Non-patent literature]

[0008] [Non-Patent Document 1] Takashi Asai et al., Journal of the Chemical Society of Japan, 1978 (5) P654-658 Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide an iron oxyhydroxide powder having a controlled content of nanoparticles. [Means for solving the problem]

[0010] To solve the above problem, the inventors have investigated the synthesis conditions of iron oxyhydroxide in more detail and have found that the minor axis diameter Dn 50 The present invention has been successful in obtaining an iron oxyhydroxide having a particle diameter of 100 nm or more and 300 nm or less, and a percentage of particles having a minor axis diameter of less than 100 nm of 3.0% or less by number. The present invention includes, but is not limited to, the following. (Aspect 1) Minor axis diameter Dn of particles constituting the powder 50 is 100 nm or more and 300 nm or less, and Among the particles constituting the powder, the proportion of particles having a minor axis diameter of less than 100 nm is 3.0% by number or less; The iron oxyhydroxide powder satisfies the above requirements and is mainly composed of iron oxyhydroxide particles whose crystalline phase is goethite. (Embodiment 2) The iron oxyhydroxide powder according to embodiment 1, wherein the powder is mainly composed of acicular particles. (Embodiment 3) BET specific surface area is 10.0 m 2 / g or less. (Embodiment 4) The iron oxyhydroxide powder according to any one of Embodiments 1 to 3, wherein, when the height of the diffraction line derived from the (1 0 1) plane of α-FeO(OH) appearing in the diffraction angle range of 20.75° to 21.75° in X-ray diffraction measurement is taken as 100.0, the height of the diffraction line derived from the (0 1 2) plane of hematite appearing in the diffraction angle range of 23.75° to 24.75° is 10.0 or less. (Embodiment 5) (1) A step of adding an alkali to an aqueous solution containing iron(II), wherein the alkali does not contain metal carbonate or metal bicarbonate, and the iron(II) concentration of the resulting product is adjusted to be 0.10 mol / L or more and 0.35 mol / L or less. (2) A step of generating nuclei by blowing an oxygen-containing gas into the product obtained in step (1) having an iron (II) concentration of 0.10 mol / L or more and 0.35 mol / L or less at a liquid temperature of 20°C or more and 35°C or less at a flow rate of 0.02 L / min or more and 0.13 L / min or less per 1.00 mol of iron (II); (3) When the amount of iron (III) per mole in the core from step (2) is p and the amount of iron (II) per mole to be added is q, p and q are expressed as in Equation 1: 7.00≦(p+q) / p≦12.00 (Equation 1) adding iron (II) to the cores from step (2) so as to satisfy the above condition, and adjusting the concentration of iron (II) in the resulting product to be 0.45 mol / L or more and 0.85 mol / L or less; (4) A step of growing nuclei by blowing an oxygen-containing gas into the product obtained in step (3) having an iron (II) concentration of 0.45 mol / L or more and 0.85 mol / L or less at a liquid temperature of 50°C or more and 80°C or less at a flow rate of 0.01 L / min or more and 0.08 L / min or less in the first stage and 0.03 L / min or more and 0.12 L / min or less in the second stage, per 1.00 mol of iron (II), wherein the flow rate in the second stage is greater than the flow rate in the first stage. 5. A method for producing the iron oxyhydroxide powder according to any one of Aspects 1 to 4, comprising: (Embodiment 6) (5) A production method according to embodiment 5, further comprising a step of hydrothermally treating the product obtained in step (4) in the presence of an alkali, wherein the temperature during the hydrothermal treatment is 160°C or higher and 230°C or lower, and wherein, where x is the alkali concentration / (mol / L) in the container during the hydrothermal treatment and y is the temperature rise rate / (°C / min), the relationship satisfies 0.50≦x×y≦5.00. (Embodiment 7) The production method according to embodiment 5, wherein the oxygen partial pressure of the oxygen-containing gas in steps (2) and (4) is 11.0 kPa or less. (Embodiment 8) A pigment containing the iron oxyhydroxide powder according to any one of Embodiments 1 to 4. (Aspect 9) A cosmetic comprising the iron oxyhydroxide powder according to any one of Aspects 1 to 4. [Effects of the Invention]

[0011] The iron oxyhydroxide powder of the present invention has a controlled nanoparticle content and can be added to cosmetics as a non-nano material. Furthermore, because the iron oxyhydroxide powder of the present invention has stable properties, including color, it can be used in a wide range of fields other than cosmetics.

[0012] While the names and definitions of nano-order substances vary by country and organization, the European standard (Commission Recommendation of 10.6.2022) defines powders with a number of particles with a minimum dimension of less than 100 nm as nanomaterials and subject to regulation. Therefore, by controlling the proportion of particles smaller than 100 nm in a powder to less than 50%, it is possible to obtain powders for cosmetics that comply with regulations. Regarding regulations in countries and regions outside of Europe, it is believed that compliance with the iron oxyhydroxide powder of the present invention can be determined by referring to the data described in this specification below. [Brief explanation of the drawings]

[0013] [Figure 1] 1 shows the results of X-ray diffraction measurement of the powder of Example 8. [Figure 2] 1 shows a transmission electron microscope photograph of the powder of Example 3. [Figure 3] 1 shows a transmission electron microscope photograph of the powder of Comparative Example 5. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention relates to an iron oxyhydroxide powder with a controlled content of nanoparticles. The following unit usage conforms to the document "Unit 2020: Amounts, Units, and Symbols Used in Chemistry" published by the Chemical Society of Japan.

[0015] [Iron oxyhydroxide] The iron oxyhydroxide powder of the present invention is primarily composed of iron oxyhydroxide particles whose crystalline phase is goethite. "Goethite" is a type of iron oxyhydroxide, also known as goethite or α-iron oxyhydroxide, and refers to a substance expressed as goethite in English and chemically as α-FeO(OH). "Containing iron oxyhydroxide particles whose crystalline phase is goethite as the main component" specifically means that 950 g / kg or more of the particles constituting the powder are iron oxyhydroxide particles whose crystalline phase is goethite. Preferably, this is 970 g / kg or more, and more preferably, 990 g / kg or more. Most preferably, substantially all of the particles constituting the powder are iron oxyhydroxide particles whose crystalline phase is goethite.

[0016] X-ray diffraction analysis can confirm that the powder of the present invention is primarily composed of iron oxyhydroxide particles with a goethite crystalline phase. Figure 1 shows the results of X-ray diffraction analysis of the powder of Example 8. As a guideline, X-ray diffraction analysis reveals a particularly large diffraction line originating from the (101) plane of α-FeO(OH) in the diffraction angle range of 20.75° to 21.75°. Furthermore, a diffraction line originating from the (301) plane is present in the range of 32.75° to 33.75°, and a diffraction line originating from the (111) plane is present in the range of 36.25° to 37.25°. Of these, the diffraction line originating from the (101) plane of α-FeO(OH) is the largest. When the height of this diffraction line is taken as 100.0, the height of the diffraction line from 32.75° to 33.75° is between 25.0 and 60.0°. The upper limit is preferably 50.0°. On the other hand, when goethite is not the main component because a certain amount of hematite is mixed in, the height of the diffraction line between 32.75° and 33.75° exceeds 60.0, where the height of the diffraction line originating from the (1 0 1) plane is taken as 100.

[0017] Since iron oxyhydroxide is a type of iron oxide in a broad sense, iron oxyhydroxide may be referred to simply as iron oxide in this specification. [Iron oxyhydroxide powder] The iron oxyhydroxide powder of the present invention has a number-based median minor axis diameter (hereinafter referred to as "Dn 50 In order not to be classified as a nanomaterial under the European standard, the minor axis diameter Dn 50The minor axis diameter Dn must be 100 nm or more. It is more preferably 105 nm or more, even more preferably 110 nm or more, even more preferably 120 nm or more, and most preferably 150 nm or more. 50 If Dn is 300 nm or less, the color of the powder tends to be yellow with a moderate hiding power. It is preferably 250 nm or less, more preferably 225 nm or less, and even more preferably 210 nm or less. 50 is calculated based on a microscopic photograph using the method described below.

[0018] The arithmetic mean value of the minor axis diameter of the particles constituting the iron oxyhydroxide powder of the present invention (hereinafter referred to as "Dn ave The thickness (hereinbelow referred to as "") is preferably 120 nm or more and 320 nm or less. The lower limit is more preferably 150 nm or more, and even more preferably 175 nm or more, and the upper limit is preferably 280 nm or less, and even more preferably 250 nm or less.

[0019] The iron oxyhydroxide powder of the present invention has a percentage of particles with a minor axis diameter of less than 100 nm of 3.0% by number or less, more preferably 2.9% by number or less, and even more preferably 2.4% by number or less. There is no particular lower limit, and it is most preferable that the powder contains no particles with a minor axis diameter of less than 100 nm. The percentage of particles with a minor axis diameter of less than 100 nm is calculated based on electron micrographs using the method described below.

[0020] The iron oxyhydroxide powder of the present invention preferably has a number-based standard deviation σ of minor axis diameter of 100 nm or less, more preferably 90 nm or less. The iron oxyhydroxide powder of the present invention is preferably composed primarily of particles having an acicular shape. Specifically, it is preferable that 850 g / kg or more of the particles constituting the powder are acicular particles. This is preferably 900 g / kg or more, and more preferably 950 g / kg or more. There is no particular upper limit, and it is preferable that all particles are acicular. However, in rare cases, the ends of acicular particles may crack, resulting in non-acicular fragments. "Acicular" refers to an elongated particle shape in which the width in the direction perpendicular to the major axis of the particle (minor axis diameter) is approximately constant throughout the entire length of the major axis. For example, shapes with a thick center, such as a spindle or rugby ball shape, or shapes with thick ends, such as a dumbbell shape, are not considered acicular.

[0021] The length of the major axis of the particles constituting the powder of the present invention is not particularly limited, and is, as a guideline, from the viewpoint of easily achieving the desired yellow color, from 2.0 to 10.0 times the minor axis diameter.

[0022] The iron oxyhydroxide powder of the present invention has a BET specific surface area of ​​10.0 m 2 / g or less. The BET specific surface area is preferably 10.0 m 2 If the BET specific surface area is less than 9.0 m / g, aggregation is less likely to occur and the powder is less likely to exhibit green color. 2 / g or less, and more preferably 7.5m 2 / g or less. The BET specific surface area is 3.5m 2 / g or more. The BET specific surface area is preferably 3.5 m 2 / g or more, the desired yellow color can be easily achieved. The lower limit of the BET specific surface area is preferably 4.0 m 2 / g or more, more preferably 4.2m 2 / g or more.

[0023] The iron oxyhydroxide powder of the present invention preferably has a low content of iron oxides other than goethite, such as hematite and magnetite. When the content of these iron oxides is low, the desired yellow color is easily obtained. If the method for producing iron oxyhydroxide powder described below is properly carried out, other iron oxides such as hematite and magnetite will not be produced. However, if the temperature is not properly controlled, particularly in steps after step (4) (the growth step), red hematite may be produced, and if the amount of alkali added in step (2) is not properly controlled, black magnetite may be produced. The iron oxyhydroxide powder of the present invention preferably has a low content of hematite and magnetite. The content of hematite and magnetite can be confirmed by X-ray diffraction measurement.

[0024] Specifically, for hematite, when the height of the diffraction line derived from the (1 0 1) plane of goethite appearing in the diffraction angle range of 20.75° to 21.75° in X-ray diffraction measurement is taken as 100.0, the height of the diffraction line derived from the (0 1 2) plane of hematite appearing in the diffraction angle range of 23.75° to 24.75° is preferably 10.0 or less, more preferably 5.0 or less, and even more preferably 3.0 or less. There is no particular lower limit, and it is most desirable that no diffraction line be observed.

[0025] Furthermore, for magnetite, when the height of the diffraction line originating from the (101) plane of α-FeO(OH) is taken as 100.0, the height of the diffraction line originating from the (220) plane of magnetite appearing at a diffraction angle of 29.50° or more and 30.50° or less is preferably 5.0 or less, more preferably 3.0 or less, and even more preferably 2.0 or less. There is no particular lower limit, and it is most desirable that no diffraction line is observed.

[0026] The iron oxyhydroxide powder of the present invention preferably exhibits a yellow color. Specifically, when measured by the method described below, * a * b * The value of L * Value is 44.5 or more and 51.0 or less, a *Value is 6.0 or more and 12.0 or less, b * It is preferable that the value is 25.0 or more and 31.5 or less. This range includes not only yellow as defined by the JIS common color name, but also colors such as ochre and light brown. More preferably, L * The value is 45.0 or more and 49.5 or less, a * Value is 7.0 or more and 11.0 or less, b * The value is between 26.0 and 30.5.

[0027] When the iron oxyhydroxide powder of the present invention is used for applications in which it is dissolved in an oily dispersion medium, for example, the surface of the powder may be treated with a surface treatment agent to improve dispersibility. Examples of the surface treatment agent that can be used include silane coupling agents, silicone oils, and other known treatment agents.

[0028] [Method for producing iron oxyhydroxide powder] The iron oxyhydroxide powder of the present invention can be obtained by the following steps. (1) adding an alkali to an aqueous solution containing iron(II), wherein the alkali does not contain metal carbonates or metal bicarbonates, and the iron(II) concentration in the resulting product is adjusted to be 0.10 mol / L or more and 0.35 mol / L or less; (2) a step of generating nuclei by blowing an oxygen-containing gas into the product obtained in step (1) having an iron (II) concentration of 0.10 mol / L or more and 0.35 mol / L or less at a flow rate of 0.02 L / min or more and 0.13 L / min or less per 1.00 mol of iron (II) while maintaining the liquid temperature of the product at 20°C or more and 35°C or less (nucleation step); (3) When the amount of iron (III) per mole in the core from step (2) is p and the amount of iron (II) per mole to be added is q, p and q are expressed as in Equation 1: 7.00≦(p+q) / p≦12.00 (Equation 1) adding iron (II) to the cores from step (2) so as to satisfy the above condition, and adjusting the concentration of iron (II) in the resulting product to be 0.45 mol / L or more and 0.85 mol / L or less; (4) A process (growth process) in which, while maintaining the liquid temperature of the product obtained in step (3) having an iron (II) concentration of 0.45 mol / L or more and 0.85 mol / L or less at 50°C or more and 80°C or less, an oxygen-containing gas is blown in at a flow rate of 0.01 L / min or more and 0.08 L / min or less per 1.00 mol of iron (II) in the first stage and at a flow rate of 0.03 L / min or more and 0.12 L / min or less in the second stage to grow nuclei, the flow rate in the second stage being greater than the flow rate in the first stage.

[0029] In addition to the above, during the nucleation step and the growth step, a gas with a reduced oxygen partial pressure may be used as the oxygen-containing gas, preferably half or less of that of normal air. The iron oxide obtained through the growing step may be further subjected to a hydrothermal treatment, which will be described later. By these treatments, the proportion of particles having a minor axis diameter of less than 100 nm can be further reduced.

[0030] [Process (1)] When producing iron oxyhydroxide powder according to the present invention, an alkali is first added to an aqueous iron(II) solution and stirred. The alkali used is preferably aqueous ammonia or an alkali hydroxide. When an alkali containing a metal carbonate and / or a metal bicarbonate is used, the ends of the particles constituting the iron oxyhydroxide powder tend to become thinner, resulting in an increase in the number of particles that are considered to be fine particles. Therefore, the alkali used in step (1) does not contain any of these.

[0031] The alkali is preferably added in an amount approximately equal to the amount of iron in terms of the substance ratio. Preferably, the amount of alkali is 0.70 to 2.00 times the amount of iron (II) in terms of the substance ratio. If the amount of alkali added is 0.70 times or more the amount of iron (II), iron oxides other than goethite are unlikely to be produced, and if it is 2.00 times or less, the minor axis diameter Dn 50 The upper limit is more preferably 1.50 times or less.

[0032] The iron(II) concentration in the product obtained in step (1) is adjusted to 0.10 mol / L or more and 0.35 mol / L or less. If the iron(II) concentration is 0.10 mol / L or more, a sufficient yield can be ensured from an economical viewpoint, and if it is 0.35 mol / L or less, the oxidation rate can be kept low, allowing for the formation of uniform nuclei in the subsequent step (2). The lower limit is preferably 0.15 mol / L or more, and the upper limit is preferably 0.32 mol / L or less. The iron(II) concentration is evaluated by a method conforming to JIS K5109.

[0033] [Step (2): Nucleation step] After adding alkali in step (1), step (2) is performed to generate nuclei for the iron oxyhydroxide powder. To obtain nuclei with uniform particle size and oxidation rate, it is generally necessary to maintain a low oxidation rate in the nucleation step. However, if the oxidation takes too long, industrial production becomes unfeasible, and if the oxidation rate is too slow, the oxidation process becomes unstable, potentially resulting in unstable product properties. The inventors have discovered that by controlling the iron concentration, the flow rate of the oxygen-containing gas, and the temperature in step (2), it is possible to obtain an iron oxyhydroxide powder that achieves the characteristics of the present invention. To ensure uniform oxidation, it is preferable to use only an oxygen-containing gas in this step and in the growth step described below. It is preferable not to use an oxidizing agent other than the oxygen-containing gas.

[0034] The iron (II) concentration of the product from step (1) to be subjected to nucleation step (2) is set to 0.10 mol / L or more and 0.35 mol / L or less for the reasons explained in step (1).

[0035] An oxygen-containing gas is blown into an aqueous solution containing iron(II) at the above concentration at a flow rate of 0.02 L / min to 0.13 L / min per 1.00 mol of iron(II). If the flow rate of the oxygen-containing gas is 0.02 L / min or more per 1.00 mol of iron(II), oxidation proceeds stably, while if the flow rate is 0.13 L / min or less, uniform goethite particles are easily obtained after completion of the subsequent step (4). The lower limit is preferably 0.03 L / min or more per 1.00 mol of iron(II), and the upper limit is preferably 0.12 L / min or less.

[0036] The liquid temperature while blowing in the oxygen-containing gas is maintained at 20° C. or higher and 35° C. or lower. If the liquid temperature is 20° C. or higher, oxidation proceeds stably, and if the liquid temperature is 35° C. or lower, uniform goethite particles are easily obtained. The lower limit is preferably 22° C. or higher, and the upper limit is preferably 30° C. or lower.

[0037] It is preferable to adjust the oxidation time so that the oxidation rate of iron(II) is approximately 50 mol%, specifically, in the range of 48 mol% to 52 mol%, at the end of the oxygen-containing gas blowing in step (2). If the oxidation rate is lower than this, the oxidation rate of the iron oxyhydroxide obtained after the end of the subsequent step (4) is likely to vary, while if the oxidation rate is higher than this, fine particles are likely to be produced. The oxidation time in the nucleation step (2) (hereinafter referred to as "oxidation time 1") is not limited to this, but is generally between 10 hours and 250 hours.

[0038] [Process (3)] In the subsequent step (3), iron (II) is added to the nuclei from step (2). As the iron (II) added in step (3), an aqueous solution of iron sulfate is preferably used. In step (3), the amount of iron (III) per mole in the nuclei from the nucleation step (2) is p, and the amount of iron (II) per mole added in step (3) is q, as determined by the following formula (1): 7.00≦(p+q) / p≦12.00 (Equation 1) Iron(II) is added so as to satisfy the above. When (p+q) / p is 12.00 or less, the powder color does not become too whitish. When (p+q) / p is 7.00 or more, the powder color does not become too black and the proportion of small particles is prevented from increasing. The lower limit of the above ratio is preferably 7.50 or more, and the upper limit is preferably 11.00 or less, more preferably 10.50 or less. The amount of iron(III) is evaluated according to a method in accordance with JIS K5109.

[0039] Step (3) may be carried out after filtering and washing the product obtained in step (2) to obtain solid nuclei, and then placing the nuclei in a tank separate from that used in step (2). Step (3) may also be carried out continuously in the same tank as step (2) for nucleation. Any embodiment may be used as long as the iron mass ratio (p+q) / p can be controlled.

[0040] The iron(II) concentration in the product obtained in step (3) is adjusted to 0.45 mol / L or more and 0.85 mol / L or less. The lower limit is preferably 0.50 mol / L or more, more preferably 0.55 mol / L, and the upper limit is preferably 0.80 mol / L or less.

[0041] [Process (4): Growth process] Following step (3), the particle growth step (4) is performed. In the growth step (4), the iron concentration, the flow rate of the oxygen-containing gas, and the liquid temperature are all controlled for the same reasons as in the nucleation step (2). Furthermore, in the growth step (4), the flow rate of the oxygen-containing gas is increased once oxidation has progressed to a certain extent. That is, oxidation is performed by changing the flow rate of the oxygen-containing substrate in two stages, with a higher flow rate in the second stage than in the first stage. If oxidation is performed with a high flow rate of the oxygen-containing gas from the beginning, it is difficult to obtain powder with a narrow particle size distribution. The flow rate may be changed in three or more stages. In this case, the flow rates in the second and subsequent stages are set to be higher than the flow rate in the first stage. The flow rate in the first stage does not necessarily have to be higher than the flow rate in the nucleation step.

[0042] The iron(II) concentration of the product from step (3) subjected to growth step (4) is 0.45 mol / L or more and 0.85 mol / L or less, with the lower limit preferably being 0.50 mol / L or more, more preferably 0.55 mol / L, and the upper limit preferably being 0.80 mol / L or less.

[0043] In step (4), the flow rate of the oxygen-containing gas is preferably switched between the first and second stages when the viscosity in the tank increases. For example, but not limited to, the second oxidation stage may be initiated when the viscosity in the tank increases and uniform stirring in the tank becomes difficult under the conditions of the first oxidation stage. While this depends on the size and shape of the tank, the first oxidation stage (hereinafter referred to as "oxidation time 2") is preferably between 6.5 and 10.0 times the second oxidation stage (hereinafter referred to as "oxidation time 3"). A ripening period or similar is not particularly required between the first and second oxidation stages, and the flow rate switching operation is not particularly limited as long as the flow rate of the oxygen-containing gas can be controlled. The stirring conditions may be changed at any time as long as they do not interfere with the flow rate switching operation.

[0044] The flow rate of the oxygen-containing gas in step (4) is 0.01 L / min or more and 0.08 L / min or less per 1.00 mol of iron(II) in the first oxidation stage. The lower limit is more preferably 0.02 L / min or more, and the upper limit is more preferably 0.07 L / min or less. In the second oxidation stage, the flow rate is 0.03 L / min or more and 0.12 L / min or less per 1.00 mol of iron(II). The lower limit is more preferably 0.04 L / min or more, and the upper limit is more preferably 0.11 L / min or less. The flow rates in the first and second stages are set so that the flow rate in the second stage is greater than the flow rate in the first stage.

[0045] When the flow rate of the oxygen-containing gas in both the first and second steps is within the above range, the same advantages as those described in step (2) can be obtained. On the other hand, when the flow rate of the oxygen-containing gas is below the lower limit of the above range, the combined oxidation time for steps 2 and 3 takes 20 days or more, which is not industrially realistic.

[0046] In step (4), the liquid temperature during the blowing of the oxygen-containing gas is kept at 50° C. or higher and 80° C. or lower. The lower limit is more preferably 60° C. or higher, and the upper limit is more preferably 75° C. or lower.

[0047] In the growth step (4), the target oxidation rate of iron (II) is 100 mol %. The oxygen-containing gas used in steps (2) and (4) may be air as is, or a gas with a lower oxygen partial pressure than air, typically by simultaneously blowing nitrogen with air, may be used. Assuming the oxygen partial pressure of air is 21.3 kPa, the oxygen partial pressure of the oxygen-containing gas when blowing in an equal amount of nitrogen as air is 10.6 kPa, while the oxygen partial pressure of the oxygen-containing gas when blowing in twice the amount of nitrogen as air is 7.1 kPa. In steps (2) and (4), the desired iron oxyhydroxide can be obtained using ordinary air as the oxygen-containing substrate. However, from the viewpoint of slowly proceeding with oxidation, the oxygen partial pressure of the oxygen-containing gas is preferably 11.0 kPa or less, and more preferably 10.6 kPa or less. Because oxygen oxidizes iron(II) after dissolving in water, reducing the oxygen partial pressure has a different effect than simply reducing the flow rate. While there is no particular lower limit for the oxygen partial pressure, a value of 1.0 kPa or more is preferred to ensure reliable oxidation.

[0048] When blowing in the oxygen-containing gas, a bubbling mechanism that is normally provided in reaction tanks in chemical plants may be used. When using a bubbling mechanism, it is preferable to use a mechanism that generates so-called millibubbles with a diameter of several millimeters or centimeters. If the oxygen-containing gas is blown in as nanobubbles or microbubbles, the oxygen-containing gas may remain in the tank, increasing the number of nuclei and potentially resulting in an excessively small particle size of the powder obtained in the end. Therefore, it is not preferable to use nanobubbles or microbubbles.

[0049] After the growth step (4) is completed, the iron oxyhydroxide is removed from the reaction tank, filtered, washed, and then dried. The washing method is not particularly limited. Since acids and alkalis are attached to the surface of the particles at the stage when they are removed from the reaction tank, any washing method capable of removing these components may be used. It is preferable that the drying temperature is not too high, and as a guideline, it is 120°C or less. If a hydrothermal treatment is subsequently performed in the step (5) described below, the slurry may be subjected to the hydrothermal treatment without drying. Furthermore, the powder obtained after drying may be subjected to treatments such as classification and surface treatment.

[0050] [Step (5): Hydrothermal treatment] Step (4) may be followed by step (5) of hydrothermal treatment. By performing the hydrothermal treatment, the proportion of particles smaller than 100 nm can be further reduced. However, as will be described later, if the temperature and alkali concentration are not properly controlled during the hydrothermal treatment, hematite may be generated. Therefore, it is preferable to properly control the alkali concentration and temperature during the hydrothermal treatment.

[0051] In the hydrothermal treatment of step (5), the product of the growth step (4) is made into a slurry, an alkali is added, and the slurry is heated to a predetermined temperature under pressure using a pressure vessel such as an autoclave and maintained for a certain period of time. The type of alkali used in step (5) is not particularly limited, but a typical example is an aqueous sodium hydroxide solution.

[0052] In step (5), the heating temperature in the pressure vessel is preferably 160°C or higher and 230°C or lower. Furthermore, when the alkali concentration in the vessel (mol / L) is x and the temperature increase rate (°C / min) is y, it is preferable to adjust the temperature so that the relationship 0.50≦x×y≦5.00 is satisfied. When x×y is 0.50 or higher, the effect of reducing fine particles is enhanced, and when x×y is 5.00 or lower, hematite is less likely to form. The lower limit is preferably 0.75 or higher, more preferably 0.90 or higher, and the upper limit is preferably 4.50 or lower, more preferably 4.00 or lower, and even more preferably 3.50 or lower.

[0053] The reasons for this are unclear, but are thought to be as follows: If the temperature of the hydrothermal treatment is too high, hematite may be formed. Furthermore, if the viscosity of the reaction system is high due to a high alkali concentration, or if the heating rate is high, uneven heat and pressure are likely to occur, leading to localized hematite formation and uneven heat and pressure, which can lead to the product having an uneven shape. On the other hand, in order for particles to dissolve during hydrothermal treatment, the temperature must rise at a certain rate. If the temperature of the hydrothermal treatment is too low or the alkali concentration is low, the hydrothermal treatment will not be effective enough. It is thought that small particles are more likely to remain undissolved, especially when the alkali concentration and heating rate are both low.

[0054] After the temperature rise is complete, it is preferable to hold the temperature for 1.0 to 6.0 hours, then cool and remove the mixture. If the holding time is 1.0 hour or longer, a large proportion of fine particles will disappear, while if it is 6.0 hours or shorter, redissolution is unlikely to proceed, so the effect of the hydrothermal treatment is less likely to be impaired. The slurry obtained after step (5) is filtered, washed, and dried in the same manner as described in step (4).

[0055] The iron oxyhydroxide powder of the present invention may be subjected to additional washing and purification after production within the scope of common sense for each application. It is desirable to perform necessary purification taking into consideration the allowable impurity content, cost, and other factors.

[0056] The uses of the iron oxyhydroxide powder of the present invention are not limited. Typically, the powder's color can be utilized as a pigment to be added to cosmetics, food colorings, paints, and the like. In particular, its use in cosmetics is preferred, taking advantage of its harmlessness to the human body and its non-nanomaterial properties. Additionally, its adsorption properties can be utilized for catalysts and adsorbents, and its wear resistance can be utilized for friction materials. It is also believed possible to further oxidize the iron oxyhydroxide powder of the present invention to obtain hematite particles with a low nanoparticle content.

[0057] The iron oxyhydroxide powder of the present invention may have at least a portion of its particle surface coated with an inorganic coating, such as a hydrous oxide or oxide of a metal such as aluminum, silicon, zinc, titanium, zirconium, iron, cerium, or tin, depending on the intended application. Metal salts other than those mentioned above may also be used as the inorganic coating. Furthermore, at least a portion of the particle surface may be coated with an organic coating to modify the surface, typically by hydrophobic treatment. Examples of organic coatings include silicone compounds such as dimethylpolysiloxane and methylhydrogenpolysiloxane; silane-, aluminum-, titanium-, or zirconium-based coupling agents; fluorine compounds such as perfluoroalkyl phosphate compounds; hydrocarbons; lecithin; amino acids; polyethylene; wax; and metallic soaps. These treatments may be combined, and the order of the treatments is not particularly limited.

[0058] When the iron oxyhydroxide of the present invention is used in cosmetics, the nanoparticle content is controlled, making it possible to obtain cosmetic compositions that do not fall under the current European nanomaterial regulations. If regulations regarding the content of fine particles exist in other countries or regions, it is possible to appropriately determine whether the composition complies with the relevant regulations, for example, by referring to the data in the examples described below.

[0059] The iron oxyhydroxide powder of the present invention can be used as a pigment to achieve a yellow color. As used herein, "pigment" refers to a powder that is insoluble in water or organic solvents and is used for coloring. For example, the powder of the present invention can be used as a food colorant or a pigment to be added to paints, taking advantage of its color. When used as a pigment, the color can be adjusted by combining it with other coloring materials. The iron oxyhydroxide powder of the present invention has the advantage that it tends to achieve a uniform color and is less likely to produce uneven color when used as a pigment.

[0060] The iron oxyhydroxide powder of the present invention is particularly preferably used as a pigment for cosmetics. It may be used alone or in combination with other coloring materials. By mixing the iron oxyhydroxide powder of the present invention with coloring materials of other colors, such as red or black, it is possible to achieve colors similar to various human skin tones, and it is expected to be used in skin cosmetics. The type of coloring material to be used in combination is not particularly limited, but it is generally considered best to use it in combination with a pigment having similar properties.

[0061] The content of the iron oxyhydroxide powder of the present invention in a cosmetic composition can be set arbitrarily depending on the required properties of the cosmetic composition. For example, but not limited to, it can be 5 g / kg or more and 200 g / kg or less. Generally, a powder content of 5 g / kg or more in a cosmetic composition can achieve a desired color, and a powder content of 200 g / kg or less is considered to achieve a non-powdery feel, taking into account other coloring materials. The upper limit is preferably 150 g / kg or less, and even more preferably 120 g / kg or less, and the lower limit is preferably 7 g / kg or more, and even more preferably 10 g / kg or more.

[0062] When preparing a cosmetic composition containing the iron oxyhydroxide powder of the present invention, various components used in ordinary cosmetics, such as inorganic pigments and organic pigments, can be used in combination as needed. Examples of inorganic pigments that can be used in combination include titanium oxide, zinc oxide, red iron oxide, black iron oxide, brown iron oxide, ultramarine, Prussian blue, cerium oxide, talc, muscovite, synthetic mica, phlogopite, biotite, synthetic fluorphlogopite, titanium mica, micaceous iron oxide, sericite, zeolite, kaolin, bentonite, clay, silicic acid, silicic acid anhydride, magnesium silicate, aluminum silicate, calcium silicate, barium sulfate, magnesium sulfate, calcium sulfate, calcium carbonate, magnesium carbonate, boron nitride, bismuth oxychloride, alumina, zirconium oxide, magnesium oxide, chromium oxide, calamine, hydroxyapatite, and complexes thereof. Examples of organic pigments that can be used in combination include silicone powder, silicone elastic powder, polyurethane powder, cellulose powder, nylon powder, urethane powder, silk powder, polymethyl methacrylate (PMMA) powder, starch, polyethylene powder, polystyrene powder, carbon black, tar dyes, natural dyes, metal soaps such as zinc stearate, and complexes thereof.

[0063] In addition to the above-mentioned components, cosmetic compositions containing the iron oxyhydroxide powder of the present invention may contain other components depending on the purpose, within quantitative and qualitative ranges that do not impair the effects of the present invention. For example, oily components, pigments, pH adjusters, moisturizers, thickeners, surfactants, dispersants, stabilizers, colorants, preservatives, antioxidants, sequestering agents, astringents, anti-inflammatory agents, UV absorbers, fragrances, etc. may be appropriately blended within ranges that do not impair the effects of the present invention.

[0064] Cosmetic compositions containing the iron oxyhydroxide powder of the present invention can be produced by known methods. The cosmetic formulation may be in any form, such as powder, solid powder, cream, emulsion, lotion, oily liquid, oily solid, or paste. For example, the cosmetic composition may be used in the form of makeup base, foundation, concealer, face powder, control color, sunscreen cosmetics, lipstick, lip balm, eye shadow, eyeliner, mascara, blush, nail polish, body powder, perfume powder, baby powder, or other makeup cosmetics, skin care cosmetics, or hair care cosmetics.

[0065] In addition to its use as a pigment, the iron oxyhydroxide powder of the present invention can also be used as an adsorbent for organic compounds generated in factories and other places. When used to remove organic compounds, its coloration has the advantage of making it possible to quickly detect any abnormalities in the adsorption system. Other applications include catalysts, friction materials, and electrical and electronic materials.

[0066] The powder obtained by the present invention can also be used as a raw material for obtaining other iron oxide powders. A typical example is a method of obtaining hematite by further oxidation. By adjusting the oxidation conditions, it is possible to obtain hematite particles with a small nanoparticle content. However, the manufacturing method described in this specification is a method optimized solely for the purpose of obtaining iron oxyhydroxide.

[0067] Before describing the examples, the test methods used in the present invention will be described. [Evaluation method] [Number-based median of minor axis diameter Dn 50 Measurement and calculation of The particles were measured using a JEOL JEM-1400plus transmission electron microscope. The observation magnification was 30,000 times (10,000 times the observation magnification of the transmission electron microscope × 3 times the print). The minor axis diameters of approximately 300 acicular particles in the observation field were analyzed using a Carl Zeiss Particle Size Analyzer TGZ-3, and a cumulative curve of the minor axis diameters was created. The minor axis diameters corresponding to 50% of the number of particles were defined as Dn. 50 The above analysis device does not directly display the minor axis diameter of each particle, but rather digitally classifies each particle into one of approximately 40 categories based on the minor axis diameter, and the final result is the number of particles that fall into each category. Dn 50 When calculating the value, the median value of each division was used as the minor axis diameter of the particles in that division.

[0068] [Percentage of particles with minor axis diameter less than 100 nm] The aforementioned number-based median of minor axis diameter Dn 50 Each particle was observed in the same manner as in the measurement of (1), and the minor axis diameter of the particles was analyzed using the same analytical device. In this case, for the divisions spanning 100 nm, the proportion of particles less than 100 nm was calculated by approximating that the particles were evenly distributed within the division. For example, if there were six particles in the division with a minor axis diameter of 95 nm to 110 nm, it was assumed that there were two particles between 95 nm and 100 nm and four particles between 100 nm and 110 nm, and the number of particles less than 100 nm was counted as two. For the minor axis diameters obtained above, the number of particles less than 100 nm was divided by the number of particles observed to calculate the proportion of particles with a minor axis diameter less than 100 nm.

[0069] [Number-based arithmetic mean value of minor axis diameter Dn ave , number-based standard deviation of minor axis diameter σ] Based on the above observation results, the arithmetic mean value Dn ave and the standard deviation σ were calculated. [BET specific surface area] Measurement was carried out by the BET single-point method using a Gemini VII 2390 manufactured by Micromeritics Instrument Corporation.

[0070] [X-ray diffraction measurement] The Rigaku RINT-TTRIII X-ray diffractometer was used, and the target was copper (Cu), the tube voltage was 50 kV, the tube current was 300 mA, the divergence slit was set to automatic mode, the vertical divergence slit was 10 mm, the scattering slit was 1 / 2°, the receiving slit was 0.15 mm, and the scanning speed was 5.00° / min. The scanning was performed over a 2θ range of 10° to 90°. The presence of diffraction lines from the (1 0 1) plane of goethite appearing in the range of 20.75° to 21.75°, diffraction lines originating from the (3 0 1) plane appearing in the range of 32.75° to 33.75°, and diffraction lines originating from the (1 1 1) plane appearing in the range of 36.25° to 37.25° was confirmed, and when these were confirmed and the height of the diffraction line from the (1 0 1) plane of goethite was taken as 100.0, the crystalline phase was determined to be goethite if the height of the diffraction line appearing in the range of 32.75° to 33.75° was 25.0 or more and 60.0 or less. Furthermore, when the height of the diffraction line of the (1 0 1) plane of the above-mentioned goethite was taken as 100.0, the height ratios of the diffraction line derived from hematite appearing in the range of 23.75° to 24.75° and the diffraction line derived from magnetite appearing in the range of 29.50° to 30.50° were calculated, and these height ratios were designated as the "hematite peak height" and the "magnetite peak height," respectively. In this case, when the presence of the diffraction line derived from hematite or the diffraction line derived from magnetite could not be confirmed, the height ratios were not calculated and the result was displayed as "not observed."

[0071] [L * value, a * value, b * value] 834 g / kg of alkyd resin (Alkidia® 4250 manufactured by DIC Corporation), 156 g / kg of mineral spirits manufactured by Sigma-Aldrich Corporation, and 10 g / kg of butan-2-one oxime were mixed to form Solvent 1. 0.5 g of iron oxyhydroxide powder was placed on the bottom plate of a Huber-Muller (manufactured by Toyo Seiki Seisakusho Co., Ltd.), 1 mL of Solvent 1 was added dropwise, and the mixture was kneaded under a load of 667 N until a uniform paste was formed. 2 mL of Solvent 1 was then added and mixed. The resulting slurry was applied to a test paper, allowed to stand for 30 minutes, and then baked in air at 130°C for 30 minutes. The L of the baked coating was measured using a color tester. * value, a * value, and b * The values ​​were measured. [Example]

[0072] The present invention will be described in more detail with reference to the following examples and comparative examples, which are provided for illustrative purposes only and are not intended to limit the scope of the invention. In the stirring operations described in the examples and comparative examples, the rotation speed is appropriately adjusted to ensure that the entire liquid is mixed uniformly and that droplets do not scatter, taking into consideration properties related to the behavior of the liquid during stirring, such as the liquid volume, viscosity, and shape of the container. Furthermore, in cases where the same effect can be obtained using any company's general commercially available product, such as hydrochloric acid, the names of the manufacturer and distributor are omitted.

[0073] [Manufacturing Example 1] An aqueous solution of iron(II) sulfate containing 170 g of iron(II) was added to the reaction vessel, and nitrogen gas was bubbled in at a flow rate of 1.00 L / min. Thereafter, when oxygen was not being bubbled in, nitrogen gas bubbled in continuously to prevent spontaneous oxidation of iron(II). Ammonia water containing 52.4 g of ammonia (NH3 equivalent) was added, and the mixture was stirred for 10 min. While continuing to stir, tap water was added, and the vessel was heated with a heater to adjust the iron(II) concentration in the reaction vessel to 0.30 mol / L and the liquid temperature to 25°C. The mass of ammonia was 1.01 times the mass of iron(II).

[0074] While maintaining the liquid temperature constant and stirring, air was blown in at a flow rate of 0.32 L / min to oxidize (nucleation step). 31.3 hours after the start of air blowing, the oxidation rate reached 50 mol%, so the air blowing was stopped. In other words, oxidation time 1 was 31.3 hours. After the end of air blowing, the mixture was promptly filtered and washed to obtain powder (nuclei). The air flow rate at this time was 0.11 L / min per 1.00 mol of iron(II).

[0075] To 65.7 g of the resulting powder, an aqueous solution of iron(II) sulfate containing 486 g of iron(II) was added and stirred while nitrogen gas was blown in. At this time, the amount of iron(III) in the powder (nuclei) per mole was p, and the amount of iron(II) in the added iron sulfate solution per mole was q, resulting in a ratio of (p + q) / p of 8.40 (mol / mol). While continuing stirring, tap water was added and the vessel was heated with a heater to adjust the iron(II) concentration in the reaction vessel to 0.80 mol / L and the liquid temperature to 65°C. While maintaining the liquid temperature constant, air was blown in at 0.50 L / min while stirring for 100.0 h. At this stage, the viscosity in the vessel increased, so the flow rate was changed to 0.70 L / min and the mixture was blown in for an additional 12.5 h (growth step). At this stage, the oxidation rate reached 100 mol%, so the oxidation was terminated. That is, oxidation time 2 was 100.0 h and oxidation time 3 was 12.5 h. The air flow rate in the growth step was 0.06 L / min in the first stage and 0.08 L / min in the second stage relative to 1.00 mol of iron (II).

[0076] The cross-sectional area of ​​each reactor is 260 cm 2 A roughly cylindrical shape was used. The slurry in the reaction tank was filtered and washed to obtain powder 1.

[0077] [Manufacturing Example 2] Powder 2 was obtained in the same manner as in Production Example 1, except that a gas mixture of equal amounts of air and nitrogen was used instead of air in the nucleation step and growth step. Oxidation time 1 was 69.4 hours, oxidation time 2 was 250.0 hours, and oxidation time 3 was 29.1 hours.

[0078] [Manufacturing Example 3] Powder 3 was obtained in the same manner as in Production Example 1, except that the air flow rate was halved to 0.16 L / min in the nucleation step, halved to 0.24 L / min in the first stage of the growth step, and halved to 0.36 L / min in the second stage. Oxidation time 1 was 52.1 hours, oxidation time 2 was 181.8 hours, and oxidation time 3 was 23.6 hours. The air flow rate per mole of iron(II) was 0.05 L / min in the nucleation step, 0.03 L / min in the first stage of the growth step, and 0.04 L / min in the second stage.

[0079] [Manufacturing Example 4] Powder 4 was obtained in the same manner as in Production Example 2, except that an aqueous sodium hydroxide solution containing 123.2 g of sodium hydroxide was used instead of ammonia water, and the gas flow rate in the nucleation step was 0.16 L / min, the flow rate in the first stage of the growth step was 0.24 L / min, and the flow rate in the second stage was 0.36 L / min. Oxidation time 1 was 97.7 h, oxidation time 2 was 333.3 h, and oxidation time 3 was 40.3 h. The gas flow rate per mole of iron(II) was 0.05 L / min in the nucleation step, 0.03 L / min in the first stage of the growth step, and 0.04 L / min in the second stage.

[0080] [Manufacturing Example 5] Powder 5 was obtained in the same manner as in Production Example 1, except that the air flow rate in the nucleation step was 0.61 L / min, the air flow rate in the first stage of the growth step was 0.91 L / min, and the air flow rate in the second stage was 1.26 L / min. Oxidation time 1 was 16.9 hours, oxidation time 2 was 55.6 hours, and oxidation time 3 was 7.6 hours. The air flow rate per mole of iron(II) was 0.20 L / min in the nucleation step, 0.10 L / min in the first stage of the growth step, and 0.14 L / min in the second stage.

[0081] [Manufacturing Example 6] Powder 6 was obtained in the same manner as in Production Example 1, except that an aqueous iron(II) sulfate solution containing 381 g of iron(II) was used and the air flow rate in the first stage of the growth process was 0.38 L / min and the air flow rate in the second stage was 0.56 L / min. Oxidation time 2 was 98.5 h and oxidation time 3 was 12.6 h. Furthermore, (p + q) / p was 6.80 (mol / mol). The air flow rate per 1 mol of iron(II) was the same as in Production Example 1.

[0082] [Example 1] 50 g of Powder 1 was weighed and dispersed in water, after which sodium hydroxide was added and stirred. The resulting slurry (sodium hydroxide concentration: 0.33 mol / L, Powder 1 concentration: 115 g / L) was placed in a jacketed autoclave (NU-4 model, manufactured by Nitto Koatsu Corporation) and heated to 170°C at a rate of 1.6°C / min and held there for 4.0 hours. After the holding period, the mixture was cooled over 6.0 hours, and the product was recovered, filtered, and washed. The resulting iron oxyhydroxide powder was designated as Iron Oxide A.

[0083] Minor axis diameter Dn of iron oxide A 50 is 174 nm, Dn ave The standard deviation of the minor axis diameter σ was 81 nm, the percentage of particles with a minor axis diameter of less than 100 nm was 2.1% by number, and the BET specific surface area was 6.6 m 2 / g, the crystalline phase is goethite, no peaks of hematite or magnetite are observed, and the color evaluated by the above-mentioned method is L * The value is 46.0, a * Value 10.5, b * The value was 29.2.

[0084] [Example 2] Iron oxide B was obtained in the same manner as in Example 1, except that powder 2 was used instead of powder 1, the sodium hydroxide concentration was adjusted to 1.00 mol / L, and the temperature was raised to 200°C at a rate of 2.6°C / min. The properties of iron oxide B are shown in Table 3.

[0085] [Example 3] Iron oxide C was obtained in the same manner as in Example 1, except that powder 3 was used instead of powder 1, the sodium hydroxide concentration was adjusted to 2.00 mol / L, and the temperature was increased to 190°C at a rate of 0.8°C / min. The properties of iron oxide C are shown in Table 3.

[0086] [Example 4] Iron oxide D was obtained in the same manner as in Example 2, except that powder 4 was used instead of powder 2. The properties of iron oxide D are shown in Table 3.

[0087] [Example 5] Iron oxide E was obtained in the same manner as in Example 3, except that powder 2 was used and the temperature rise rate was set to 1.4°C / min. The properties of iron oxide E are shown in Table 3.

[0088] [Example 6] Iron oxide F was obtained in the same manner as in Example 3, except that powder 1 was used and the temperature rise rate was set to 0.4°C / min. The properties of iron oxide F are shown in Table 3.

[0089] [Example 7] Iron oxide G was obtained in the same manner as in Example 6, except that the sodium hydroxide concentration was set to 3.00 mol / L. The properties of iron oxide G are shown in Table 3.

[0090] [Example 8] Iron oxide H was obtained in the same manner as in Example 7, except that powder 4 was used. The properties of iron oxide H are shown in Table 3.

[0091] [Example 9] Iron oxide I was obtained in the same manner as in Example 7, except that powder 2 was used. The properties of iron oxide I are shown in Table 3.

[0092] [Example 10] Iron oxide J was obtained in the same manner as in Example 6, except that the sodium hydroxide concentration was 1.00 mol / L. The properties of iron oxide J are shown in Table 3.

[0093] [Example 11] Powder 4 was used as is without hydrothermal treatment to produce potassium iron oxide. The properties of potassium iron oxide are shown in Table 3.

[0094] [Example 12] Iron oxide L was obtained in the same manner as in Example 5, except that the temperature was increased to 150°C at a rate of 0.8°C / min.

[0095] [Example 13] Powder 2 was used as is without hydrothermal treatment to produce iron oxide M. The properties of iron oxide M are shown in Table 3.

[0096] [Comparative Example 1] Iron oxide N was obtained in the same manner as in Example 1, except that powder 5 was used, the sodium hydroxide concentration was 1.00 mol / L, and the temperature was increased to 190°C at a rate of 2.6°C / min. The properties of iron oxide N are shown in Table 3.

[0097] Comparative Example 2 Iron oxide O was obtained in the same manner as in Comparative Example 1, except that the sodium hydroxide concentration was 2.00 mol / L. The crystalline phases were goethite and hematite. The properties of the iron oxide O are shown in Table 3.

[0098] Comparative Example 3 Powder 5 was used as is without hydrothermal treatment to obtain iron oxide P. The properties of iron oxide P are shown in Table 3.

[0099] Comparative Example 4 Powder 6 was used as is without hydrothermal treatment to produce iron oxide Q. The properties of iron oxide Q are shown in Table 3.

[0100] [Table 1]

[0101] [Table 2]

[0102] [Table 3]

[0103] As shown in the results of the Examples and Comparative Examples, the iron oxyhydroxide powder subjected to the nucleation step and growth step under the conditions described in this specification exhibited Dn 50 The ratio of particles with a minor axis diameter of less than 100 nm was 3.0% by number or less. All particles had little variation in particle size and were yellow powders.

[0104] Furthermore, it was found that powders subjected to hydrothermal treatment under the conditions described in this specification tend to have a smaller proportion of particles with a minor axis diameter of less than 100 nm. The obtained iron oxyhydroxide powder can be used in cosmetics as a non-nano material.

[0105] [Prescription example 1] Powder foundation using the iron oxyhydroxide powder of the present invention Components 1 to 6 were mixed uniformly using a coffee mill (FJM-703, manufactured by Fukai Kogyo Co., Ltd.), and then component 7 was added and mixed again. After mixing, the mixture was filled into a mold and compression molded to obtain the desired powder foundation.

[0106] Ingredients Mixing ratio (g / kg) 1. Iron Oxide A 15 2. Red iron oxide pigment 4 3. Black iron oxide pigment 1 4. Mica (Topy Industries PDM-10S) 480 5. Talc (Asada Flour Milling Co., Ltd. JA-46R) 300 6. Titanium Oxide KR-380 100% manufactured by Titanium Industries Co., Ltd. 7. Oil {Crodalan SWL (manufactured by Croda), Phytosqualane (manufactured by Iwase Cosfa Co., Ltd.), Tri(caprylic / capric)glyceryl (manufactured by Nisshin Oillio Group, Ltd.), Trioctanoin (manufactured by Nisshin Oillio Group, Ltd.), and KF-56 (manufactured by Shin-Etsu Chemical Co., Ltd.) in a 4:4:3:3:6 ratio} 100 The light beige powder foundation obtained had an even color, a smooth feel, and was easy to remove after use.

Claims

1. The minor axis diameter Dn of the particles constituting the powder ５０ is 100 nm or more and 300 nm or less, and Among the particles constituting the powder, the proportion of particles having a minor axis diameter of less than 100 nm is 3.0% by number or less; and the iron oxyhydroxide powder is mainly composed of iron oxyhydroxide particles whose crystalline phase is goethite (α-FeO(OH)).

2. 2. The iron oxyhydroxide powder of claim 1, wherein the powder is composed mainly of acicular particles.

3. BET specific surface area is 10.0 m ２ 3. The iron oxyhydroxide powder according to claim 1, wherein the iron oxyhydroxide powder has a molecular weight of 1 / g or less.

4. When the height of the diffraction line derived from the (1 0 1) plane of α-FeO(OH) appearing in the range of diffraction angles of 20.75° to 21.75° in X-ray diffraction measurement is taken as 100.0, hematite (α-Fe ２ O ３ 3. The iron oxyhydroxide powder according to claim 1, wherein the height of the diffraction line derived from the (0 1 2) plane of the iron oxyhydroxide powder is 10.0 or less.

5. (1) A step of adding an alkali to an aqueous solution containing iron (II), wherein the alkali does not contain metal carbonate or metal bicarbonate, and the concentration of iron (II) in the resulting product is adjusted to be 0.10 mol / L or more and 0.35 mol / L or less. (2) a step of generating nuclei by blowing an oxygen-containing gas into the product obtained in step (1) having an iron (II) concentration of 0.10 mol / L or more and 0.35 mol / L or less at a liquid temperature of 20°C or more and 35°C or less at a flow rate of 0.02 L / min or more and 0.13 L / min or less per 1.00 mol of iron (II); (3) When the molar amount / mol of iron (III) in the core from step (2) is p and the molar amount / mol of iron (II) to be added is q, p and q are expressed by the formula 1: 7.00≦(p+q) / p≦12.00 (Formula 1) adding iron (II) to the cores from step (2) so as to satisfy the above condition, and adjusting the concentration of iron (II) in the resulting product to be 0.45 mol / L or more and 0.85 mol / L or less; (4) A step of growing nuclei by blowing an oxygen-containing gas at a flow rate of 0.01 L / min to 0.08 L / min in the first stage and 0.03 L / min to 0.12 L / min in the second stage relative to 1.00 mol of iron (II), while maintaining the liquid temperature of the product obtained in step (3) having an iron (II) concentration of 0.45 mol / L to 0.85 mol / L at a temperature of 50°C to 80°C, wherein the flow rate in the second stage is greater than the flow rate in the first stage. The method for producing the iron oxyhydroxide powder according to claim 1 or 2, comprising:

6. (5) The production method according to claim 5, further comprising a step of hydrothermally treating the product obtained in step (4) in the presence of an alkali, wherein the temperature during the hydrothermal treatment is 160°C or higher and 230°C or lower, and wherein, when the alkali concentration / (mol / L) in the container during the hydrothermal treatment is x and the temperature rise rate / (°C / min) is y, the relationship 0.50≦x×y≦5.00 is satisfied.

7. 6. The method according to claim 5, wherein the oxygen partial pressure of the oxygen-containing gas in steps (2) and (4) is 11.0 kPa or less.

8. A pigment containing the iron oxyhydroxide powder according to claim 1 or 2.

9. A cosmetic comprising the iron oxyhydroxide powder according to claim 1 or 2.

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