White particles, production method therefor, ultraviolet-shielding agent including same, pigment, and cosmetic preparation

Abstract

White particles according to the present invention comprise amorphous silica derived from a phyllosilicate mineral and an aqua iron oligomer. This production method for the white particles includes preparing an aqueous raw-material dispersion containing a phyllosilicate mineral and an iron compound, regulating the pH of the aqueous raw-material dispersion to a value of -1 or larger but less than 0.3, and aging the aqueous raw-material dispersion while stirring.

Description

White particles, their manufacturing method, ultraviolet screening agent, pigment, and cosmetic using the same

[0001] The present invention relates to white particles, a method for producing the same, and an ultraviolet screening agent, a pigment, and a cosmetic composition using the same.

[0002] Titanium dioxide, which scatters ultraviolet rays, is used in cosmetics and paints. However, its photocatalytic activity can cause skin damage and decompose organic media, resulting in a deterioration of performance. For this reason, it is necessary to modify the surface of titanium dioxide with metals or other materials to suppress its photocatalytic activity.

[0003] Furthermore, because titanium oxide has a high refractive index, when it is mixed with an organic medium, the difference in refractive index can cause the coating to whiten, damaging the appearance of the underlying surface. Therefore, efforts are being made to reduce the refractive index by forming titanium oxide into nanoparticles or doping it with fluorine.

[0004] However, titanium dioxide may become unusable in the future due to the medical concerns mentioned above. Therefore, there is a need for a material that can scatter or absorb ultraviolet light as an alternative to titanium dioxide, without photocatalytic activity and with a small refractive index.

[0005] Iron oxide is ubiquitous on Earth and has excellent biocompatibility, and as such, research into its use as a substitute for expensive or toxic substances and materials is in full swing. Furthermore, iron oxide clusters and particles have a narrow energy gap (band gap) and absorb visible light, whereas molecular iron oxide has a wide energy gap and is known to absorb ultraviolet light. There have been reports on ultraviolet screening materials and photocatalysts using such molecular oxides (see, for example, Patent Document 1 and Non-Patent Documents 1 and 2).

[0006] Patent Document 1 and Non-Patent Document 1 report an ultraviolet screening material containing H-type magadiite encapsulating molecular iron oxide. By encapsulating iron oxide within the H-type magadiite layers, rather than between them, the iron oxide is stabilized and maintained in a molecular state without forming clusters or particles. This allows it to absorb ultraviolet rays and function as an ultraviolet screening material. However, further performance improvements are required for practical use.

[0007] Non-Patent Document 2 reports the synthesis of a material in which a dimer of an iron aquo complex (molecular iron oxide) is supported between the layers of montmorillonite, and reports that the material has high photocatalytic activity. However, this material has high photocatalytic activity and is colored due to the coexistence of iron oxides such as hematite, making it unsuitable for use as an ultraviolet screening material.

[0008] Japanese Patent Application Laid-Open No. 2022-033391

[0009] Hamza El-Hosainy et al., Materials Today Nano 19 (2022) 100227 Takano Shinichiro et al., Abstracts of the 66th Clay Science Symposium, P11

[0010] In view of the above, an object of the present invention is to provide white particles having low photocatalytic activity, a method for producing the same, and an ultraviolet screening agent, a pigment, and a cosmetic composition each using the same.

[0011] The white particles according to the present invention solve the above-mentioned problems by containing amorphous silica derived from a layered silicate mineral and an aqua iron oligomer formed by condensation of mononuclear aqua iron in which at least an oxygen-containing group is coordinated to the iron ion. The mononuclear aqua iron may have a hexacoordinated structure, and the aqua iron oligomer may be formed by condensation of the mononuclear aqua iron in the range of 3 to 100. The amorphous silica is a solid ２９ Q by Si-NMR spectrum ２ , Q ３ and Q ４ The peak area percentage (total 100%) indicates the state where Si has two hydroxyl groups (-OH). ２ The peak is 2.5% or more and 5.5% or less, and Q indicates a state in which Si has one hydroxyl group (—OH). ３ The peak is 31% or more and 55% or less, and Q indicates a state in which Si does not have a hydroxyl group (—OH). ４ The peak may be 40% or more and 65% or less. ２９ Q by Si-NMR spectrum ２ , Q ３ and Q ４ The peak area percentage (total 100%) indicates the state where Si has two hydroxyl groups (-OH).２ The peak is 2.8% or more and 5.2% or less, and Q indicates a state in which Si has one hydroxyl group (—OH). ３ The peak is 33% or more and 52% or less, and Q indicates a state in which Si does not have a hydroxyl group (—OH). ４ The peak may be 45% or more and 63% or less. The band gap may be in the range of 2.2 eV or more and 3.5 eV or less, and when dispersed in a solvent containing water, the maximum absorption wavelength may be in the wavelength range of 250 nm or more and 400 nm or less. The maximum absorption wavelength may be in the wavelength range of 300 nm or more and 400 nm or less. The molar extinction coefficient at the maximum absorption wavelength may be 2000 M －１ cm －１ Over 6000M －１ cm －１The mass ratio of the aqua iron oligomer to the amorphous silica may be in the range of 0.003 or more and 0.04 or less. The mass ratio of the aqua iron oligomer to the amorphous silica may be in the range of 0.004 or more and 0.03 or less. The amorphous silica may contain silicon (Si), iron (Fe), oxygen (O), hydrogen (H), and, if necessary, an M1 element (M1 is an alkali metal element), an M2 element (M2 is an alkaline earth metal element), and aluminum (Al), and may each satisfy the following in mass percentage: 0≦M1≦0.06 0≦M2≦2.1 0≦Al≦0.27 The above-mentioned white particles can be produced by the following methods: 30≦Si≦40 0<Fe≦10 55≦O≦68.5 1.5≦H≦3.0 0≦M1≦0.2 0≦M2≦2.5 0≦Al≦0.3 The Si, Fe, O, H, and, if necessary, the M1 element, the M2 element, and the Al can each satisfy the following mass percentages: 30≦Si≦35 0.3≦Fe≦1.7 60≦O≦66 1.5≦H≦3.0 0≦M1≦0.06 0≦M2≦2.1 0≦Al≦0.27 A method for producing the above-mentioned white particles according to the present invention includes preparing a raw material water dispersion containing a layered silicate mineral and an iron compound, adjusting the pH of the raw material water dispersion to a value of −1 or more and less than 0.3, and aging the raw material water dispersion while stirring, thereby solving the above-mentioned problem. The layered silicate mineral may be a 2:1 layered silicate mineral having a 2:1 layer structure. The iron compound may be selected from the group consisting of iron nitrate, iron sulfate, iron chloride, and hydrates thereof. In the raw water dispersion, the mass ratio of the iron compound to the layered silicate mineral may be 4 or more and 10 or less. In the aging with stirring, the raw water dispersion may be heated with stirring at a temperature range of 40°C to 60°C for 1 hour to 48 hours. In preparing the raw water dispersion, an inorganic base may be further added and then heated with stirring. The ultraviolet screening agent according to the present invention contains the white particles, thereby solving the above-mentioned problem. The pigment according to the present invention contains the white particles, thereby solving the above-mentioned problem.The cosmetic composition according to the present invention uses the above ultraviolet screening agent, thereby solving the above problems.

[0012] The white particles of the present invention comprise amorphous silica derived from a layered silicate mineral and an aqua iron oligomer formed by condensation of mononuclear aqua iron in which at least an oxygen-containing group is coordinated to the iron ion. The particles of the present invention function as a pigment because colored elements and impurity elements are removed from the layered silicate mineral by the above-described production method. Furthermore, photocatalytic activity is suppressed, and the particles efficiently absorb ultraviolet light, functioning as an ultraviolet screening agent. Such ultraviolet screening agents can be applied to various cosmetic compositions.

[0013] The method for producing white particles of the present invention includes preparing a raw material aqueous dispersion containing a layered silicate mineral and an iron compound, adjusting the pH of the raw material aqueous dispersion to be at least -1 and less than 0.3, and aging the raw material aqueous dispersion while stirring, and the white particles of the present invention are obtained by controlling the pH to a predetermined level and stirring and aging. As such, the production method of the present invention is advantageous for practical use because it does not require any special equipment or special techniques.

[0014] Schematic diagram showing aqua iron oligomers. Figure showing a flow chart for producing white particles of the present invention. Figure showing the appearance of the sample of Example 3. Figure showing an SEM image of the sample of Example 3. Figure showing the particle size distribution by zeta potential of the sample of Example 3. Figure showing XRD patterns of the samples of Examples 1 to 7 and Examples 9 to 11. ２９ Figure showing Si MAS NMR spectrum Figure showing UV-vis diffuse reflectance spectra of samples of Examples 1 to 7 and Examples 9 to 11 Figure showing Tauc plots of samples of Examples 1 to 3 and Examples 9 to 11 Figure showing appearance of suspensions in which samples of Examples 1 to 3 are dispersed in aqueous acetic acid solution Figure showing UV-vis absorption spectra of suspensions in which samples of Examples 1 to 3 and Examples 9 to 11 are dispersed in aqueous acetic acid solution Figure showing appearance of suspensions in which sample of Example 2 is dispersed in sunflower oil Figure showing results of photocatalytic activity tests of samples of Examples 1 to 3 and Examples 9 to 11

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that like elements are designated by like numbers and their description will be omitted.

[0016] The white particles of the present invention and the method for producing the same will now be described. Fig. 1 is a schematic diagram showing an aqua iron oligomer.

[0017] The white particles of the present invention contain amorphous silica derived from a layered silicate mineral and an aqua iron oligomer formed by condensation of mononuclear aqua iron 100 in which at least an oxygen-containing group is coordinated to the iron ion.

[0018] Mononuclear Aqua Iron 100 contains trivalent iron ions (Fe ３＋ ) as a group containing at least oxygen, H ２ It is constituted by coordinate bonds of groups selected from the group consisting of O, hydroxyl groups (—OH groups), and O groups, forming a hexahedron with a coordinated structure.

[0019] Aqua iron oligomer refers to a molecule in which mononuclear Aqua iron 100 is condensed preferably in the range of 3 to 100, more preferably in the range of 3 to 70, even more preferably in the range of 3 to 40, and particularly preferably in the range of 3 to 12. By condensing mononuclear Aqua iron 100 in this range, high ultraviolet absorption ability can be exhibited.

[0020] Figure 1(A) shows an aqua-iron oligomer in which three mononuclear aqua-iron 100 molecules are condensed one-dimensionally by sharing a vertex; Figure 1(B) shows an aqua-iron oligomer in which three mononuclear aqua-iron 100 molecules are condensed one-dimensionally by sharing a vertex; and Figure 1(C) shows an aqua-iron oligomer in which four mononuclear aqua-iron 100 molecules are condensed two-dimensionally by sharing a vertex. However, the condensation form of the mononuclear aqua-iron 100 is not limited to these. The mononuclear aqua-iron 100 molecules can be condensed one-, two-, and / or three-dimensionally by sharing a vertex and / or a vertex. The presence of such aqua-iron oligomers and the condensation state of the aqua-iron oligomer can be confirmed by ultraviolet-visible absorption spectroscopy, X-ray absorption spectroscopy, or (if the condensation number is large) scanning transmission electron microscopy. Simply put, if the absorption edge of the ultraviolet-visible diffuse reflection spectrum is found at a wavelength of 480 nm or less, or the maximum absorption wavelength of the ultraviolet-visible absorption spectrum is found at a wavelength of 300 nm or more and 400 nm or less, it can be determined that the substance contains an aqua iron oligomer in which mononuclear aqua iron 100 is condensed within the above range.

[0021] In the white particles of the present invention, the aqua iron oligomers are stabilized within the voids (network) of the amorphous silica, which makes it difficult for substrates such as oxygen to access the aqua iron oligomers, thereby suppressing their photocatalytic activity.

[0022] The white particles of the present invention are particles whose object color is white and which are visually recognized as white, but the object color of the white particles of the present invention may be defined by the band gap and the maximum absorption wavelength.

[0023] The object color of a powder (particle) can be determined by its band gap; for example, it is known that red iron oxide (hematite) has a band gap of 2.2 eV, white titanium oxide (anatase) has a band gap of 3.2 eV, and pale yellow-white titanium oxide (rutile) has a band gap of 3.0 eV. Furthermore, the object color when molecules, clusters, or particles are dissolved or dispersed in a solvent can be determined by the maximum absorption wavelength in the absorption spectrum; for example, a white titanium oxide (rutile and anatase) dispersion exhibits a maximum absorption wavelength at 300 to 350 nm, and a red gold nanoparticle dispersion exhibits a maximum absorption wavelength around 550 nm.

[0024] From these findings, according to the white particles of the present invention, the band gap preferably satisfies the range of 2.2 eV or more and 3.5 eV or less, and the maximum absorption wavelength when the particles of the present invention are dispersed in a solvent containing the same water as that used for synthesis satisfies the range of 250 nm or more and 400 nm or less. This not only makes the particles visually white, but also allows them to be used as white pigments. The band gap more preferably satisfies the range of 2.4 eV or more and 3.5 eV or less. The maximum absorption wavelength more preferably satisfies the range of 300 nm or more and 400 nm or less. The maximum absorption wavelength may be in the range of 300 nm or more and 350 nm or less.

[0025] The object color of the white particles of the present invention can also be determined by the molar absorption coefficient. The molar absorption coefficient at the maximum absorption wavelength of the white particles of the present invention is preferably 2000 M. －１ cm －１ Over 6000M －１ cm －１ This value satisfies the following range: ３＋ ) molar extinction coefficient (2.5M －１ cm －１, wavelength 508 nm), which is 1000 times larger, and this makes the object color white.

[0026] In the white particles of the present invention, the amorphous silica is preferably a solid ２９ Q by Si-NMR spectrum ２ , Q ３ and Q ４ The peak area percentage (total 100%) indicates the state where Si has two hydroxyl groups (-OH). ２ The peak (chemical shift -80 ppm to -105 ppm) is 2.5% or more and 5.5% or less, and Q indicates a state in which Si has one hydroxyl group (-OH). ３ The peak (chemical shift -90 ppm to -115 ppm) is 31% or more and 55% or less, and Q indicates a state in which Si does not have a hydroxyl group (-OH). ４ The peak (chemical shift -95 ppm to -130 ppm) is satisfied by 40% or more and 65% or less, whereby the aqua iron oligomer is stabilized by the network structure of amorphous silica.

[0027] In the white particles of the present invention, the amorphous silica is more preferably a solid ２９ Q by Si-NMR spectrum ２ , Q ３ and Q ４ Q is the peak area percentage (total 100%) ２ The peak is 2.8% or more and 5.2% or less, and Q ３ The peak is 33% or more and 52% or less, and Q ４ The peak satisfies the range of 45% to 63%, whereby the aqua iron oligomer is further stabilized by the network structure of amorphous silica.

[0028] Furthermore, Q ２ , Q ３ and Q ４ Using the peak, the silanol group content can be determined using the following formula: Silanol group content (%) = [{(Q ２ ×2) + Q ３} / {(Q ２ +Q ３ +Q ４) × 4}] × 100 The silanol group content of the white particles of the present invention is preferably 9% or more and 20% or less, more preferably 10% or more and 18% or less, and even more preferably 12% or more and 15% or less. This allows the white particles of the present invention to have excellent ultraviolet absorption ability and suppress photocatalytic activity.

[0029] The white particles of the present invention preferably have a maximum absorption wavelength in the wavelength range of 250 nm or more and 400 nm or less, and exhibit excellent ultraviolet absorbing ability.

[0030] The white particles of the present invention more preferably have a maximum absorption wavelength in the wavelength range of 300 nm or more and 400 nm or less, and exhibit particularly excellent ultraviolet absorption ability. ２ (ultraviolet scattering ability of)

[0031] In the white particles of the present invention, the mass ratio of the aqua iron oligomer to the amorphous silica (aqua iron oligomer / amorphous silica) preferably satisfies the range of 0.003 to 0.04. Thus, the white particles of the present invention stabilize very small amounts of aqua iron oligomer within the amorphous silica network, thereby suppressing photocatalytic activity. The mass ratio of the aqua iron oligomer to the amorphous silica (aqua iron oligomer / amorphous silica) more preferably satisfies the range of 0.004 to 0.03, even more preferably satisfies the range of 0.006 to 0.27, and particularly preferably satisfies the range of 0.006 to 0.018. This allows the white particles of the present invention to further suppress the photocatalytic activity of the aqua iron oligomer.

[0032] Furthermore, because the white particles of the present invention are based on amorphous silica, their refractive index is 1.4 or more and 1.5 or less, similar to that of silica. Therefore, when dispersed in an organic solvent, such as an oil such as silicone oil (refractive index 1.38 to 1.40) or sunflower oil (refractive index 1.47 to 1.48), or an ester such as isotridecyl isononanoate (refractive index 1.43 to 1.45), the particles become colorless and transparent. Because these are oils and organic solvents typically used in cosmetics, it is suggested that the white particles of the present invention are suitable for use in cosmetics.

[0033] The white particles of the present invention contain silicon (Si), iron (Fe), oxygen (O), and hydrogen (H), and, if necessary, further contain an M1 element (M1 is an alkali metal element), an M2 element (M2 is an alkaline earth metal element), and aluminum (Al). The mass percentages of Si, Fe, O, H, M1 element, M2 element, and Al preferably satisfy the following (total 100 mass%): 30≦Si≦40, 0<Fe≦10 (more preferably 0<Fe≦5, even more preferably 0<Fe≦2.5), 55≦O≦68.5, 1.5≦H≦3.0, 0≦M1≦0.2, 0≦M2≦2.5, and 0≦Al≦0.3. This allows the white particles of the present invention to have excellent ultraviolet absorption ability.

[0034] More preferably, Si, Fe, O, H, the M1 element, the M2 element, and Al satisfy the following mass percentages (total 100 mass%): 30≦Si≦35 0.3≦Fe≦1.7 60≦O≦66 1.5≦H≦3.0 0≦M1≦0.06 0≦M2≦2.1 0≦Al≦0.27 This provides the white particles of the present invention with even better ultraviolet absorption ability.

[0035] The white particles of the present invention contain amorphous silica derived from a layered silicate mineral, and therefore may contain an M1 element (M1 is an alkali metal element) and / or an M2 element (M2 is an alkaline earth metal element) that can be contained in a layered silicate mineral. However, by setting the mass percentages of the M1 element and the M2 element within the above ranges, the purity of the white color can be improved. Here, the M1 element is, for example, lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), etc., and the M2 element is, for example, calcium (Ca), strontium (Sr), barium (Ba), magnesium (Mg), beryllium (Be), etc.

[0036] The white particles of the present invention may be secondary particles having an average particle size of 2500 nm to 8500 nm, which are formed by agglomeration of primary particles having an average particle size of 200 nm to 1500 nm (preferably 200 nm to 500 nm). However, when the white particles of the present invention are used in pigments, ultraviolet screening agents, or cosmetics, for example, it is preferable to pulverize the secondary particles and use them as primary particles, as this provides excellent dispersibility. The average primary particle size and average secondary particle size of the white particles can be determined from the particle size distribution determined by zeta potential and particle size measurement (details will be described later in the Examples).

[0037] Next, a method for producing white particles of the present invention will be described. Fig. 2 is a diagram showing an example of a flow chart for producing white particles of the present invention.

[0038] The white particles of the present invention are produced by the following steps: Step S210: A raw water dispersion containing a layered silicate mineral and an iron compound is prepared. Step S220: The pH of the raw water dispersion is adjusted to -1 or more and less than 0.3. Step S230: The raw water dispersion is aged while being stirred.

[0039] According to the manufacturing method of the present invention, in step S220, the layered silicate mineral is subjected to acid treatment in a predetermined pH range, and thus SiO ２ By removing elements other than the iron compound, the layer structure is broken down to form amorphous silica with voids (networks). In step S230, mononuclear aqua iron derived from the iron compound condenses in the voids of the amorphous silica to form and stabilize aqua iron oligomers, thereby producing the white particles of the present invention.

[0040] Each step will be described in detail. In step S210, the layered silicate mineral is not particularly limited, and known layered silicate minerals can be used. The layered silicate mineral may be a naturally occurring mineral, a chemically modified naturally occurring mineral, or a synthetic mineral, but a synthetic layered silicate mineral is preferred because it contains fewer impurities.

[0041] Examples of layered silicate minerals include the serpentine-kaolin group having a 1:1 type crystal structure, which will be described later, the talc-pyrophyllite group having a 2:1 type crystal structure, the smectite group, the vermiculite group, the mica group, the brittle mica group, the chlorite group, and minerals in which these unit structural layers are alternately stacked (e.g., rectorite and corrensite).

[0042] Examples of layered silicate minerals in the serpentine-kaolin group include lizardite, berthelline, amesite, cronsteadite, nepoite, keryaite, freyponite, and brindleyite (trioctahedrons) in the serpentine subgroup, and kaolinite, di(ckite), nacrite, halloysite, and audinite (dioctahedrons) in the kaolin subgroup.

[0043] Examples of layered silicate minerals in the talc-pyrophyllite group include talc, willemsite, kerolite, and pimelite (trioctahedrons) in the talc subgroup, and pyrophyllite and ferripyrophyllite (dioctahedrons) in the pyrophyllite subgroup.

[0044] Examples of the smectite group layered silicate minerals include trioctahedral saponite, hectorite, sauconite, stevensite, and swinholdite, and dioctahedral montmorillonite, beidellite, nontronite, and volkonscoite.

[0045] Examples of layered silicate minerals of the vermiculite group include trioctahedral vermiculite, which has a trioctahedron structure, and dioctahedral vermiculite, which has a dioctahedron structure.

[0046] Examples of the layered silicate minerals of the mica group include biotite, phlogopite, iron mica, eastonite, siderophyllite, tetraferriferrite, lepidolite, and polylithionite (trioctahedron), as well as muscovite, celadonite, tobelite, illite, and paragonite (dioctahedron).

[0047] Examples of the layered silicate minerals of the brittle mica group include clintonite, xanthophyllite (trioctahedron), and margarite (dioctahedron).

[0048] Examples of layered silicate minerals of the chlorite group include trioctahedral clinochlore, chamosite, and nimite, dioctahedral donbassite, and di-trioctahedral cookeite and sudoite.

[0049] The crystal structure of layered silicate minerals generally consists of tetrahedral sheets and octahedral sheets, and the composite unit formed by combining "sheets" is a "layer." The tetrahedral sheets are generally composed of Si ４＋ Four O ２－ Three of the tetrahedrons surrounded by the Si are shared with neighboring tetrahedrons, and the remaining vertices are aligned in the same direction, forming a hexagonal network. ２ O ５ ] ２－ It is a phyllosilicate (layered silicate) with the following composition.

[0050] The octahedral sheet is generally made of Al ３＋ , Mg ２＋ , Fe ２＋ cations such as six (OH) － The octahedrons surrounded by Al share edges and spread out in a two-dimensional network. ２ (OH) ６ , or Mg ３ (OH) ６ It has the composition

[0051] When one tetrahedron sheet and one octahedron sheet are combined to form a composite layer, this is called a 1:1 layer, and layered silicate minerals having a crystalline structure formed by repeatedly stacking 1:1 layers are generally called kaolin minerals, and examples include kaolinite and halloysite.

[0052] A structure made up of three layers in which two tetrahedral sheets sandwich one octahedral sheet is called a 2:1 type structure (2:1 type layered silicate mineral), and examples of such layered silicate minerals include pyrophyllite, talc, smectite (sauconite, stevensite, beidellite, nontronite, hectorite, montmorillonite, saponite, etc.), sepiolite, vermiculite, mica (muscovite, paragonite, illite, phlogopite, biotite, etc.), and brittle mica (margarite, xanthophyllite, etc.).

[0053] As described above, layered silicate minerals are broadly classified into two types of layer structures: a two-layer structure (1:1 type) in which an octahedral sheet with aluminum, magnesium, or the like as a central metal is placed on top of a silica tetrahedral sheet, and a three-layer structure (2:1 type) in which an octahedral sheet with aluminum, magnesium, or the like as a central metal is sandwiched between silica tetrahedral sheets on both sides.

[0054] Further, they are subdivided according to the type of octahedron sheet, i.e., dioctahedron sheets (hereinafter simply referred to as "dioctahedrons") whose central metals are aluminum, iron (III), etc., and trioctahedron sheets (hereinafter simply referred to as "trioctahedrons") whose central metals are magnesium, lithium, nickel, iron (II), manganese, etc.

[0055] Examples of those having a 1:1 type layer structure include serpentine-based stones such as trioctahedral lizardite, amesite, and chrysotile, and kaolin-based stones such as dioctahedral kaolinite, dickite, and halloysite.

[0056] Among those having a 2:1 type layer structure, examples of dioctahedrons include pyrophyllite-montmorillonite, beidellite, dioctahedral vermiculite, illite, muscovite, paragonite, margarite, and donbasite.

[0057] Among those having a 2:1 type layer structure, trioctahedrons include talc, saponite, hectorite, sepiolite, trioctahedral vermiculite, phlogopite, biotite, lepidolite, clintonite, clinochlore, chamosite, and nimite.

[0058] Among these, the layer silicate mineral preferably has a 2:1 type layer structure, in that the resulting coating film has superior durability, and the layer silicate mineral is preferably a smectite group, in that white particles having superior effects of the present invention can be obtained.

[0059] In terms of obtaining white particles that exhibit the effects of the present invention, the layered silicate minerals are preferably minerals of the smectite group (sauconite, stevensite, beidellite, nontronite, hectorite, montmorillonite, saponite, etc.), vermiculite group, and swelling mica (swelling taeniolite, swelling tetrasilicic mica, swelling synthetic fluorine mica, etc.), with the smectite group being more preferred. Among these, those that do not contain coloring elements are preferred.

[0060] Commercially available layered silicate minerals can also be used, including "Kunipia," "Sumecton," "Polargel," "Hectabrite," "Laponite," "Lucentite," "Bentone," "NHT," and "Veegum."

[0061] The particle size (secondary particle size) of the layered silicate mineral is preferably in the range of 2500 nm or more and 10000 nm or less. The layered silicate mineral more preferably has a particle size in the range of 2500 nm or more and 8500 nm or less. The primary particle size of the layered silicate mineral is preferably in the range of 10 nm or more and 1000 nm or less, more preferably in the range of 10 nm or more and 100 nm or less. When the particle size of the layered silicate mineral is in this range, white particles having the above-mentioned particle size can be obtained.

[0062] The particle sizes (secondary particle size, primary particle size) of the layered silicate mineral are average values ​​determined by dynamic light scattering (DLS). It has been confirmed that these values ​​are consistent with observations under a microscope (e.g., a scanning electron microscope).

[0063] In step S210, the iron compound may be prepared using an iron compound selected from the group consisting of iron nitrate, iron sulfate, iron chloride, and hydrates thereof, which constitute the aqua iron oligomers in steps S220 and S230.

[0064] In step S210, the layered silicate mineral and the iron compound are preferably mixed so that the mass ratio of the iron compound to the layered silicate mineral is 4 or more and 10 or less. This allows the above-mentioned white particles to be obtained. The layered silicate mineral and the iron compound are more preferably mixed so that the mass ratio of the iron compound to the layered silicate mineral is 5 or more and 7 or less. This allows the above-mentioned white particles to be obtained with a good yield.

[0065] In step S210, the solvent for the raw material aqueous dispersion is water, and no organic solvent such as acetonitrile, as described in Non-Patent Document 2, is used, which is environmentally friendly. In step S210, when the entire raw material aqueous dispersion is taken as 100 mass%, the concentration of the layered silicate mineral preferably satisfies the range of 3 mass% to 20 mass% or less, more preferably 4 mass% to 10 mass%, and the concentration of the iron compound preferably satisfies the range of 5 mass% to 75 mass% or less, more preferably 20 mass% to 40 mass%. This results in the above-mentioned white particles.

[0066] In step S210, the raw water dispersion may be prepared by preparing an aqueous solution in which an iron compound has been dissolved and then adding the layered silicate mineral to the aqueous solution. In this case, the solution is easily prepared if the concentration of the iron compound dissolved therein is 0.4 M or more and 4.0 M or less.

[0067] In step S220, the pH of the raw material water dispersion from step S210 is adjusted to within the above range using an acid such as hydrochloric acid, sulfuric acid, or nitric acid. Within this range, interlayer cations and metal elements within the layers of the layered silicate mineral are eluted, making it impossible to maintain the layer structure and resulting in amorphous silica. The pH of the raw material water dispersion from step S210 is more preferably adjusted to between -1 and less than 0.29, and even more preferably between -0.15 and 0.28. This converts the layered silicate mineral into amorphous silica, allowing the above-mentioned white particles to be produced efficiently.

[0068] Furthermore, in step S220, by adjusting the pH to the above-mentioned level, the iron compound becomes mononuclear Aqua Iron 100 (FIG. 1).

[0069] In step S230, the mixture is stirred and aged, whereby the mononuclear aqua iron 100 condenses to form aqua iron oligomers, which are then immobilized within the voids of the amorphous silica. The stirring and aging can be performed, for example, using a magnetic stirrer. The stirring and aging time is, for example, in the range of 1 hour to 48 hours.

[0070] In step S230, the raw material water dispersion may be heated to promote condensation. Heating is preferably performed at a temperature in the range of 40° C. to 60° C. for 1 hour to 48 hours.

[0071] Drying may be performed following step S230. This allows the white particles to be obtained in powder form. Any drying method, such as freeze-drying, vacuum drying, heat drying, or spray drying, may be used. However, freeze-drying or vacuum drying is preferred from the viewpoint of the stability of the aqua iron oligomer in the white particles, with freeze-drying being particularly preferred. Freeze-drying is performed for, for example, one to four days. Furthermore, after step S230 (or after the drying described above), the white particles may be heated at 100 to 200°C. This heating promotes condensation of unreacted aqua iron and also forms chemical bonds (bonds formed by condensation between the terminal OH groups) between the aqua iron oligomer and the amorphous silica, thereby enhancing stability.

[0072] In another example of the method for producing white particles of the present invention, in step S210 of preparing the raw material water dispersion, an inorganic base may be further added, and the mixture may be stirred while heating after the addition of the inorganic base. Specifically, the inorganic base is added preferably so that the pH becomes 0.65 or more and 2 or less, more preferably so that the pH becomes 0.7 or more and 1.5 or less. After the inorganic base has been added, the raw material water dispersion is preferably heated with stirring at a temperature range of 15°C or more and 70°C or less for a period of 1 second to 24 hours. By adjusting the pH to the above range and then stirring and heating, the amount of aqua iron oligomer and the degree of condensation can be improved.

[0073] The timing of adding the inorganic base is not particularly limited. For example, the inorganic base may be added simultaneously with the layered silicate mineral or the iron compound, or the inorganic base may be added after preparing a raw material aqueous dispersion containing the layered silicate mineral and the iron compound.

[0074] The inorganic base is not particularly limited, and may be NaHCO ３ , NaOH, NH ３ , (NH ４ ) ２ CO ３ , KOH, LiOH, etc. These inorganic bases may be used as solutions by dissolving them in a solvent such as water.

[0075] Even when an inorganic base is added, as described above, when the entire raw water dispersion is taken as 100 mass%, the concentration of the layered silicate mineral in the raw water dispersion after the addition of the inorganic base preferably satisfies the range of 3 mass% to 20 mass% or less, more preferably 4 mass% to 10 mass% or less, and the concentration of the iron compound preferably satisfies the range of 5 mass% to 75 mass% or less, more preferably 20 mass% to 40 mass% or less.

[0076] When adding an inorganic base in step S210, it is preferable to previously pulverize the layered silicate mineral using a pulverizer such as a planetary ball mill before using it in the raw water dispersion. By pulverizing the layered silicate mineral using a pulverizer, the secondary particle size is reduced, making it easier to encapsulate aqua iron, thereby increasing the amount of oligomers included during silica gel conversion. It is preferable to pre-pulverize the layered silicate mineral regardless of whether or not an inorganic base is added in step S210. The pulverization using a pulverizer is preferably carried out until no significant change in secondary particle size is observed; for example, at a rotation speed of 200 to 600 rpm, for 30 minutes to 2 hours. Since no significant change in secondary particle size is observed after 1 hour, pulverization for about 1 hour is sufficient.

[0077] In this way, the white particles can be obtained in powder form, but depending on the application, the particle size of the white particles may be controlled by pulverization, classification, sieving, or the like.

[0078] Next, the uses of the white particles of the present invention will be described. The white particles of the present invention can be used as pigments because they have a white object color. That is, the white particles of the present invention have good color development, and because the aqua iron oligomer is stabilized within the amorphous silica, they do not deteriorate over a long period of time, making them suitable as pigments. Therefore, when used in paints, inks, and pigments, they can maintain good color development for a long period of time.

[0079] When the white particles of the present invention are used as a pigment, they may be dispersed in water or an organic solvent. Examples of such organic solvents include ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methylcyclohexanone, and diacetone alcohol; hydrocarbon-based solvents such as toluene, xylene, n-hexane, n-heptane, n-octane, cyclopentane, cyclohexane, methylcyclohexane, and dimethylcyclohexane; ester-based solvents such as methyl acetate, ethyl acetate, and n-propyl acetate; ether-based solvents such as tetrahydrofuran, dioxane, and diethyl ether; glycol ether-based solvents such as ethylene glycol monomethyl ether and ethylene glycol monoethyl ether; and alcohol-based solvents such as methanol, ethanol, n-propanol, isopropanol, ethylene glycol, and propylene glycol. If necessary, the white particles may further contain a polymerizable compound such as a monofunctional monomer, a polyfunctional monomer, a photocurable oligomer, or a photocurable polymer. This allows the particles to function as an inkjet ink.

[0080] The white particles of the present invention have excellent ultraviolet absorption capabilities and are therefore suitable as ultraviolet screening agents. Because the white particles of the present invention are based on amorphous silica, they have a small refractive index of 1.4 to 1.5. Therefore, even when blended with organic solvents or various resins, the refractive index difference can be reduced, resulting in transparency. Therefore, by applying the particles as a coating material (paint) to various products, the products can be effectively protected from ultraviolet degradation without impairing their appearance. Such coating materials may also contain the white particles of the present invention, water, organic solvents, and polymerizable compounds described above. Alternatively, by kneading the white particles of the present invention into resins such as acrylic resins (e.g., polymethyl methacrylate), polycaprolactone, polyvinyl alcohol resins, plasticized polyvinyl acetal resins, ethylene-vinyl acetate copolymer resins, ethylene-acrylic copolymer resins, and polyurethane resins, transparent plastics with excellent ultraviolet absorption capabilities can be produced.

[0081] When used as the above-mentioned pigment or ultraviolet screening agent, the composition may contain antioxidants, heat stabilizers, metal salts for adjusting adhesive strength, silicone oils for adjusting adhesive strength, silane coupling agents for adjusting adhesive strength, antiblocking agents, pigments, dyes, colorants, light diffusing agents, light diffusing particles, antistatic agents, plasticizers, organic solvents, additives for adjusting the polarity of the plasticizer or organic solvent, tackifiers, and the like, within the range that does not impair the effects of the present invention.

[0082] The ultraviolet screening agent of the present invention has low photocatalytic activity and is therefore applicable to various cosmetics, such as skin care cosmetics such as emulsions, lotions, and skin creams, makeup cosmetics such as powdery foundations, liquid foundations, blushes, and lipsticks, and hair cosmetics such as mousses, hair waxes, etc. The cosmetic of the present invention can be obtained by blending it with optional components described below as needed, and the blending ratio of the ultraviolet screening agent in the cosmetic can be set as desired depending on the ultraviolet absorption ability and the type of cosmetic, but is illustratively in the range of 3% by mass or more and 50% by mass or less.

[0083] The cosmetic of the present invention may contain, within the scope that does not impair the effects of the present invention, various resin powders such as polyester, polyethylene, polystyrene, polyurethane, acrylic resin, phenolic resin, fluororesin, divinylbenzene, styrene copolymer, or copolymer resin powder consisting of two or more of these, organic powders such as acetyl cellulose, polysaccharides, protein, etc., pigment powders such as Red No. 202 and Blue No. 1, metal soaps such as zinc stearate, magnesium stearate, zinc palmitate, dimethicone, methicone, cyclomethicone, polyether-modified silicone, fluorine-modified silicone, etc. The cosmetic composition may contain any of the following ingredients that are typically incorporated into cosmetics: silicon compounds such as silicone; ester oils such as trioctanoin and neopentyl glycol dicaprylate; mineral oils such as mineral oil, petrolatum and polybutene; waxes such as carnauba wax, candelilla wax and beeswax; natural ingredients such as jojoba oil, olive oil, aloe and safflower; vitamins or vitamin derivatives such as vitamin A, vitamin B and vitamin C; alcohols such as ethanol and polyhydric alcohols; surfactants, moisturizers, colorants, fragrances, preservatives, and other ingredients.

[0084] The present invention will now be described in detail using specific examples, but it should be noted that the present invention is not limited to these examples.

[0085] [Example 1] In Example 1, white particles were produced according to the method shown in Figure 2. Specifically, as shown in Table 1, 20 g of synthetic saponite (Sumecton SA, manufactured by Kunimine Industries Co., Ltd.) was used as a layered silicate mineral, and 129.28 g of iron nitrate nonahydrate (Fe(NO)) was used as an iron compound. ３ ・9H ２ 400 mL of a raw material water dispersion containing iron nitrate nonahydrate (manufactured by Nacalai Tesque, Inc.) was prepared (step S210 in FIG. 2 ). Specifically, 20 g of synthetic saponite was placed in a 500 mL flask, and 400 mL of an aqueous iron nitrate solution adjusted to 0.8 M was added thereto to prepare a raw material water dispersion. The concentration of the layered silicate mineral in the raw material water dispersion at this time was 5 mass %, and the concentration of iron nitrate nonahydrate was 32.3 mass %.

[0086] Next, the pH of the raw material water dispersion was adjusted to -0.13 with concentrated nitric acid (step S220 in FIG. 2). The raw material water dispersion was aged while being stirred (step S230 in FIG. 2). Stirring and aging were carried out at 50°C for 24 hours. The reaction product was centrifuged (rotation speed 3500 rpm, 20 minutes), and the solid was washed with pure water at least 10 times and dried under reduced pressure at room temperature for 3 days. The sample obtained in this manner is referred to as the sample of Example 1.

[0087] The appearance of the sample of Example 1 was observed, and the details were observed using a scanning electron microscope (SEM, Hitachi High-Tech Corporation, SU8230). The average particle size of the sample of Example 1 was calculated by zeta potential / particle size measurement (Otsuka Electronics Co., Ltd., ELSZ-2000). These results are shown in Table 3.

[0088] The amount of metal elements in the sample of Example 1 was measured using an inductively coupled plasma (ICP) optical emission spectrometer (Agilent 5800, manufactured by Agilent Technologies, Inc.). The amount of hydrogen in the sample was calculated by measuring the amount of water using a simultaneous differential thermal and thermogravimetric analyzer (TG / DTA6200, manufactured by Hitachi High-Tech Science Corporation). The amount of oxygen in the sample was calculated by subtracting all measured elements from 100. The X-ray diffraction pattern of the sample of Example 1 was measured using an X-ray diffractometer (MiniFlex 600, manufactured by Rigaku Corporation). These results are shown in FIG. 6 and Table 2.

[0089] For the sample of Example 1, solid ２９ The Si MAS NMR spectrum was measured using a nuclear magnetic resonance spectrometer (Varian, 600PS) equipped with a CP / MAS probe with a diameter of 6.0 mm. ２９ The measurement was performed using the MAS method under the following conditions: ２９ Si resonance frequency in MHz, ２９ The Si 90° pulse width was 5 μs, the MAS rotation speed was 7 kHz, the spectral width was 44.64 kHz, and the measurement temperature was room temperature. For each peak in the spectrum after Fourier transformation, calculations were performed using the center position, height, and half-width of the peak shape created by mixing Lorentzian and Gaussian waveforms as variable parameters. ２ (represents a state in which Si has two hydroxyl groups (—OH)), Q ３ (indicating a state in which Si has one hydroxyl group (—OH)), and Q ４ (indicating a state in which Si does not have a hydroxyl group (—OH)) ２ The content of Q ３ The content of and Q ４ The results are shown in FIG. 7 and Table 3.

[0090] The ultraviolet-visible (UV-vis) spectrum (diffuse reflection type) of the sample of Example 1 was measured using an ultraviolet-visible spectrophotometer (V-770, manufactured by JASCO Corporation). The results are shown in FIGS.

[0091] A suspension was prepared by dispersing the sample of Example 1 at a concentration of 0.3 wt% in an aqueous acetic acid solution (acetic acid concentration: 5 vol%), and the suspension was observed and the UV-vis absorption spectrum was measured. A suspension was prepared by dispersing the sample of Example 1 at a concentration of 2 wt% in sunflower oil, and the results are shown in Figures 10 to 12.

[0092] A photocatalytic activity test was carried out on the sample of Example 1. The photocatalytic activity test was carried out by irradiating the above-mentioned suspension dispersed in an aqueous acetic acid solution with simulated sunlight (100 mW / cm ２ ) for 90 minutes. ２ ) was quantified by gas chromatography. The results are shown in Figure 13.

[0093] [Examples 2 to 6] Examples 2 to 6 were the same as Example 1, except that the raw material aqueous dispersions were adjusted to different pH values ​​as shown in Table 1. The samples obtained in this manner are referred to as samples of Examples 2 to 6, respectively. The properties and characteristics of the samples of Examples 2 to 6 were evaluated in the same manner as Example 1. The results are described below.

[0094] Example 7 Example 7 was the same as Example 1 except that no iron compound was used, as shown in Table 1. The sample thus obtained was referred to as the sample of Example 7 and was evaluated in the same manner as in Example 1. The results are described below.

[0095] Example 8 was the same as Example 3, except that freeze-drying was performed instead of drying under reduced pressure. The freeze-drying was performed by drying a sample that had been frozen in liquid nitrogen in advance at 200 Pa for 3 days. The sample obtained in this manner is referred to as the sample of Example 8.

[0096] Example 9 In Example 9, first, 10 g of the same synthetic saponite as in Example 1 was pulverized (rotation speed: 400 rpm, 60 minutes) in a planetary ball mill (LP-1, manufactured by Ito Seisakusho Co., Ltd.). The average secondary particle diameter of the synthetic saponite before pulverization was 7336 nm, and the average secondary particle diameter of the synthetic saponite after pulverization was 4366 nm. The average secondary particle diameter of the synthetic saponite was a value determined from the particle size distribution determined by dynamic light scattering (DLS).

[0097] 20 g of crushed synthetic saponite and 129.28 g of iron nitrate nonahydrate (Fe(NO) ３ ・9H２ 400 mL of a raw material water dispersion containing iron nitrate nonahydrate (product of Nacalai Tesque, Inc.) was prepared in the same manner as in Example 1 (step S210 in FIG. 2 ). Specifically, 20 g of synthetic saponite was placed in a 500 mL flask, and 400 mL of an aqueous iron nitrate solution adjusted to 0.8 M was added thereto to prepare a raw material water dispersion. The concentration of the layered silicate mineral in the raw material water dispersion at this time was 5 mass %, and the concentration of iron nitrate nonahydrate was 32.3 mass %.

[0098] Then, NH as an inorganic base was added to a raw material water dispersion containing synthetic saponite and iron nitrate nonahydrate. ３ was added, and the mixture was stirred for 8 hours while heating at 50°C. ３ was added to the raw material water dispersion as an aqueous solution with a concentration of 28-30% by mass (8 mL). The pH of the raw material water dispersion after the addition of the inorganic base is as shown in Table 1. The pH before the addition of the inorganic base was 0.7.

[0099] Next, similarly to Example 1, a raw material water dispersion was prepared with concentrated nitric acid until the pH reached that shown in Table 1 (step S220 in FIG. 2 ), and the raw material water dispersion was aged while stirring (step S230 in FIG. 2 ). After that, the procedure was the same as in Example 1, except that freeze-drying was performed instead of vacuum drying. The freeze-drying was performed by drying a sample previously frozen with liquid nitrogen at 200 Pa for 3 days.

[0100] [Example 10] In Example 10, NaHCO was used as an inorganic base. ３ The procedure was the same as in Example 9, except that NaHCO ３ was added in an amount of 32 mL in a 0.08M aqueous solution.

[0101] Example 11 was the same as Example 9, except that NaOH was added as an inorganic base. Note that 16 mL of NaOH was added as a 1.5 M aqueous solution.

[0102]

[0103] The above results will be summarized as follows: Figure 3 is a diagram showing the appearance of the sample of Example 3.

[0104] As shown in grayscale in Figure 3, the powder of Example 3 was white. Although not shown, the powders of Examples 1, 2, and 8 to 11 were also white. From this, it can be seen that the samples of Examples 1 to 3 and 8 to 11 are all white powders and can be used as pigments utilizing their white color. On the other hand, the powders of Examples 4 to 6 were orange to red. This suggests that the samples of Examples 1 to 3 and 8 to 11 do not contain ordinary iron oxide (nano)particles that exhibit red, etc. (or contain only trace amounts that do not impair the white color).

[0105] Figure 4 shows an SEM image of the sample of Example 3. Figure 5 shows the particle size distribution of the sample of Example 3 according to the zeta potential.

[0106] According to Figures 4(A) and (B), the sample of Example 3 was composed of agglomerated particles (secondary particles) of plate-like particles (primary particles) with a size of 100 to 500 nm. The average particle sizes of the primary particles and secondary particles determined using the particle size distribution obtained from the zeta potential and particle size measurements in Figure 5 were 284 nm and 6600 nm, respectively. The average primary particle size is the average value (number average) of the normal distribution in the small size region of the particle size distribution, and the average secondary particle size is the average value (number average) of the normal distribution in the large size region of the particle size distribution. Although not shown, the samples of other examples were also composed of agglomerates of plate-like particles. As shown in Table 3, the primary average particle sizes of the samples of Examples 1 to 3 and Example 9 were in the range of 200 nm to 1500 nm. Note that primary particles were absent in Examples 10 and 11. The secondary average particle sizes of the samples of Examples 1 to 3 and Example 9 to 11 were in the range of 2500 nm to 8500 nm. The primary average particle size and secondary average particle size were consistent with the values ​​observed by SEM.

[0107]

[0108] Focusing on the results of the samples of Examples 1 to 3 and Examples 8 to 11 in Table 2, it was found that by adjusting the pH to less than 0.3 by acid treatment in step S220, the Na, Mg, and Al contained in the raw synthetic saponite (SSA) were almost completely eluted. From this, it was confirmed that the samples of Examples 1 to 3 and Examples 8 to 11 contain silicon (Si), iron (Fe), oxygen (O), hydrogen (H), and, as necessary, M1 element (M1 is an alkali metal element), M2 (M2 is an alkaline earth metal element), and aluminum (Al), and satisfy the following mass percentages: 30≦Si≦40, 0<Fe≦10, 55≦O≦68.5, 1.5≦H≦3, 0≦M1≦0.2, 0≦M2≦2.5, and 0≦Al≦0.3.

[0109] FIG. 6 shows XRD patterns of the samples of Examples 1 to 7 and Examples 9 to 11.

[0110] Figure 6 also shows the XRD pattern of the synthetic saponite (SSA) used as the raw material. As shown in Figure 6, the samples of Examples 4, 5, and 6 exhibited diffraction peaks (001, 020, 130, 220, etc.) derived from the raw synthetic saponite (SSA), indicating a layered structure. The diffraction peaks derived from these raw materials disappeared in the sample of Example 7, instead exhibiting a broad peak near 23°. According to the introduction by T. Linssen et al., J. Phys. Chem. B 2002, 106, 4470-4476, it is known that acid treatment of layered silicate minerals results in the elution of interlayer cations and metal elements within the layers, resulting in the formation of amorphous silica. Therefore, the sample of Example 7 is amorphous silica, which is consistent with the results in Table 2. In the samples of Examples 1 to 3, the diffraction peaks derived from the raw materials disappeared and a broad peak characteristic of amorphous substances was exhibited around 23°, similar to the sample of Example 7. This suggests that the samples of Examples 1 to 3 and Examples 9 to 11 also contain amorphous silica.

[0111] FIG. 7 shows the results of the samples of Examples 1 to 3, 7, and 9 to 11. ２９ FIG. 1 shows a Si MAS NMR spectrum.

[0112] Figure 7 also shows the NMR spectrum of synthetic saponite (SSA) used as a raw material. The NMR spectrum of SSA showed peaks of Si(0Al), Si(1Al), and Si(2Al) derived from layered silicate minerals (tetrahedral sheets containing Al). The sample of Example 7 did not show these peaks, but showed Q derived from amorphous silica. ２ , Q ３ and Q ４ This also indicated that the sample of Example 7 was amorphous silica.

[0113] Similarly to the sample of Example 7, the samples of Examples 1 to 3 and Examples 9 to 11 also did not exhibit peaks of Si(0Al), Si(1Al), and Si(2Al) derived from layered silicate minerals, and Q derived from amorphous silica. ２ , Q ３ and Q ４ The Q of the samples in Examples 1 to 3 was 0.015 and 0.025. ２ ~Q ４ As shown in Table 3, the peak area ratio of Q ２ , Q ３ , Q ４ Q is the area percentage of the peak ２ The peak is 3% and Q ３ The peak is 45% or more and 52% or less, and Q ４ The peak was 45% or more and 50% or less. The silanol group contents of the samples of Examples 1 to 3 were 13.25%, 12.75%, and 14.5%, respectively.

[0114] Furthermore, like the sample of Example 7, the samples of Examples 9 to 11 did not exhibit peaks of Si(0Al), Si(1Al), and Si(2Al) derived from layered silicate minerals, but Q derived from amorphous silica. ２ , Q ３ and Q ４ The Q of the samples of Examples 9 to 11 was 0.015 and 0.016, respectively. ２ ~Q ４ As shown in Table 3, the peak area ratio of Q ２ , Q ３ , Q ４ Q is the area percentage of the peak ２The peak is 4% or more and 5% or less, and Q ３ The peak is 34% or more and 37% or less, and Q ４ The peak was 58% or more and 62% or less. The silanol group contents of the samples of Examples 9 to 11 were 11.75%, 10.5%, and 11.75%, respectively.

[0115]

[0116] Fig. 8 is a diagram showing UV-vis diffuse reflectance spectra of the samples of Examples 1 to 6 and Examples 9 to 11. Fig. 9 is a diagram showing Tauc plots of the samples of Examples 1 to 3 and Examples 9 to 11.

[0117] The diffuse reflectance spectra in Figure 8 are all spectra of powder samples. Figure 8 also shows the diffuse reflectance spectra of titanium oxide (MT-100tv, manufactured by Teika Corporation), which is a commercial ultraviolet scattering material, hematite (manufactured by Aldrich), synthetic saponite (SSA) used as a raw material, and the sample of Example 2 in Figure 6 of Patent Document 1. The Tauc plot in Figure 9 was created from the diffuse reflectance spectra in Figure 8.

[0118] The spectra of the samples of Examples 4 to 6 showed an absorption peak at wavelengths of 500 nm to 600 nm, indicating the coexistence of iron oxides such as hematite, which is consistent with the orange to red color of the samples of Examples 4 to 6.

[0119] On the other hand, according to the spectra of the samples of Examples 1 to 3 and Examples 9 to 11, the absorption rise (absorption edge) was at a wavelength of 480 nm or less. According to the Tauc plot of FIG. 9, the band gaps (energy gaps) of the samples of Examples 1 to 3 and Examples 9 to 11 were 3.4 to 2.4 eV, which was equivalent to the band gap of titanium oxide (3 to 3.2 eV). This is consistent with the white color of the samples of Examples 1 to 3 and Examples 9 to 11. Note that the sample of Example 9 was slightly yellowish white, but was white enough to be used without problems in cosmetics, etc. The band gap was determined from the Tauc plot obtained from the diffuse reflectance spectrum of FIG. 8.

[0120] As described above, the spectra of the samples of Examples 1 to 3 and Examples 9 to 11 showed an absorption rise at wavelengths of 480 nm or less, with the absorbance reaching an upper limit at a wavelength of around 300 nm. It is noteworthy that this absorption rise and absorbance (K-M function) were similar to those of commercially available titanium oxide. This suggests that the samples of Examples 1 to 3 and Examples 9 to 11 have UV scattering or UV absorption capabilities equivalent to titanium oxide and function as ultraviolet screening agents.

[0121] The spectrum of the sample in Example 2 of Patent Document 1 showed a maximum absorption peak near 300 nm, but no absorption edge at wavelengths shorter than 480 nm. This suggests that the samples in Examples 1 to 3 and 9 to 11 contain oligomers with a higher condensation number than the molecular oxide contained in the sample in Example 2 of Patent Document 1, i.e., aqua iron oligomers. These results indicate that the samples in Examples 1 to 3 and 9 to 11 are white particles containing amorphous silica derived from layered silicate minerals and aqua iron oligomers. Considering the elemental analysis results in Table 2, the mass ratio of aqua iron oligomer to amorphous silica was found to be in the range of 0.004 to 0.03. The mass ratio of aqua iron oligomer to amorphous silica can be calculated by dividing the mass percent of Fe by the mass percent of Si converted to SiO2 (Fe / (Si × 60.08 / 28.09)).

[0122] Fig. 10 is a diagram showing the appearance of suspensions in which the samples of Examples 1 to 3 are dispersed in an acetic acid aqueous solution, and Fig. 11 is a diagram showing UV-vis absorption spectra of suspensions in which the samples of Examples 1 to 3 and Examples 9 to 11 are dispersed in an acetic acid aqueous solution.

[0123] 10 and 11 also show the appearance and spectrum of a suspension in which synthetic saponite (SSA), used as the raw material, and titanium oxide (MT-100tv, manufactured by Teika Corporation), a commercial ultraviolet scattering agent, are dispersed in an aqueous acetic acid solution.

[0124] Although the samples of Examples 1 to 3 had absorbance comparable to that of commercially available titanium oxide, as shown in Figures 10 and 11, the suspensions of the samples of Examples 1 to 3 were much more transparent than the suspensions of titanium oxide. The samples of Examples 9 to 11 also had absorbance comparable to that of commercially available titanium oxide, but the suspensions of the samples of Examples 9 to 11 were much more transparent than the suspensions of titanium oxide. This is because the refractive index of the amorphous silica in the samples of Examples 1 to 3 and Examples 9 to 11 (1.4 to 1.5) was closer to the refractive index of an aqueous acetic acid solution (1.3) than the refractive index of titanium oxide (2.5 to 2.7). Furthermore, the samples of Examples 9 to 11 tended to have higher absorbance than the samples of Examples 1 to 3, particularly in the range of 300 nm to 400 nm. This is thought to be due to the fact that the addition of an inorganic base to the raw material aqueous dispersion improved the degree of condensation of the aqua-iron oligomer in the samples of Examples 9 to 11.

[0125] 11, the molar absorption coefficients were calculated using the absorbance at a wavelength of 324 nm (maximum absorption wavelength) for the suspensions of the samples of Examples 1 to 3 and 9 to 11, and the titanium oxide suspension, with an optical path length (cell length of the spectroscopic cell) of 1 cm. The molar concentrations (as iron) of the suspensions of Examples 1 to 3 and 9 to 11 were 0.00020 M, 0.00031 M, 0.00063 M, 0.00079 M, 0.00066 M, and 0.00057 M, respectively. The molar concentration (as titanium oxide) of the titanium oxide suspension was 0.033 M.

[0126] The molar extinction coefficients of the samples of Examples 1 to 3 and Examples 9 to 11 were 5224 M －１ cm －１ , 3645M －１ cm －１ , 2038M －１ cm －１ , 2453M －１ cm －１ , 2422M －１ cm －１ , 2359M －１ cm －１ The molar absorption coefficient of titanium oxide was 49 M －１ cm －１ It was.

[0127] According to Yaoya Shusaku et al., Clay Science, Vol. 33, No. 2, pp. 92-101 (1993), the molar absorption coefficient of iron is known to be smaller than that of titanium oxide, but the molar absorption coefficients of the samples in Examples 1 to 3 and 9 to 11 are about 100 times larger than that of titanium oxide. Thus, despite containing only small amounts of iron, such as 1% by mass, the samples in Examples 1 to 3 and 9 to 11 exhibit a light absorption peak in the wavelength region shorter than 350 nm, equivalent to that of titanium oxide, in a suspension with the same mass % concentration as titanium oxide. From this, it can be said that the samples in Examples 1 to 3 and 9 to 11 have a white object color.

[0128] FIG. 12 shows the appearance of a suspension of the sample of Example 2 dispersed in sunflower oil.

[0129] Figure 12 also shows the appearance of a suspension in which titanium oxide (MT-100tv, manufactured by Teika Corporation), a commercial UV scattering agent, was dispersed in sunflower oil. Comparing Example 2 in Figure 10 with Example 2 in Figure 12, the suspension dispersed in sunflower oil (Example 2 in Figure 12) was much more transparent than the suspension dispersed in an aqueous acetic acid solution (Example 2 in Figure 10). This is because the refractive index of sunflower oil (1.5) is closer to the refractive index of amorphous silica (1.4 to 1.5) than the refractive index of an aqueous acetic acid solution (1.3).

[0130] The samples of Example 3 and Example 8 were dispersed in water (ultrapure water) at a concentration of 5 wt % to prepare suspensions, and after stirring the suspensions at room temperature for 3 days, the iron dissolved in the water was measured by ICP atomic emission spectrometry. The sample of Example 8 showed almost no iron elution compared to the sample of Example 3. This suggests that the sample of Example 8 is chemically more stable than the sample of Example 3 and that freeze-drying is preferable.

[0131] FIG. 13 is a diagram showing the results of the photocatalytic activity test of the samples of Examples 1 to 3 and Examples 9 to 11.

[0132] Figure 13 also shows the results of photocatalytic activity tests on the raw material synthetic saponite (SSA), titanium dioxide (MT-100tv, manufactured by Teika Corporation), a commercial UV scattering agent, and titanium dioxide (P25), a benchmark for commercial photocatalysts.

[0133] According to FIG. 13, the photocatalytic activity of the samples of Examples 1 to 3 and Examples 9 to 11 was considerably lower than that of the benchmark P25, and was about 50% of that of titanium oxide, a commercially available UV scattering agent with suppressed photocatalytic activity. Referring to Patent Document 1 and Non-Patent Document 1, in the samples of Examples 1 to 3 and Examples 9 to 11, the aqua iron oligomer, which exhibits photocatalytic activity equal to or greater than that of P25, is encapsulated in the amorphous silica network, making it difficult for the substrate acetic acid and oxygen to access, which is thought to have further suppressed the photocatalytic activity. In the samples of Examples 1 to 3 and Examples 9 to 11, the photocatalytic activity was mainly suppressed by silica fragments (SiO ４ We believe that aqua iron oligomers exist stably surrounded by a number of connected tetrahedra (including sheets).

[0134] The white particles of the present invention are applicable to pigments, UV screening agents, and cosmetics using the same. Furthermore, by utilizing the property of becoming transparent when dispersed in an organic phase, they can also be used as UV-absorbing transparent coatings (paints) for color-sensitive products such as mobility aids.

[0135] 100 Mononuclear Aqua Iron

Claims

1. White particles comprising amorphous silica derived from a layered silicate mineral and an aqua iron oligomer formed by condensation of mononuclear aqua iron in which at least a group containing oxygen is coordinated to iron ions.

2. The white particles according to claim 1, wherein the mononuclear aqua iron has a 6 - coordinate structure, and the aqua iron oligomer is formed by condensation of the mononuclear aqua iron in the range of 3 or more and 100 or less.

3. The amorphous silica is a solid ２９ Q by Si-NMR spectrum ２ , Q ３ and Q ４ The peak area percentage (total 100%) indicates the state where Si has two hydroxyl groups (-OH). ２ The peak is 2.5% or more and 5.5% or less, and Q indicates a state in which Si has one hydroxyl group (—OH). ３ The peak is 31% or more and 55% or less, and Q indicates a state in which Si does not have a hydroxyl group (—OH). ４ The white particles according to claim 1 , wherein the peak satisfies 40% or more and 65% or less.

4. The amorphous silica is a solid ２９ Q by Si-NMR spectrum ２ , Q ３ and Q ４ The peak area percentage (total 100%) indicates that the Q showing the state where Si has two hydroxyl groups (-OH) is ２ The peak is 2.8% or more and 5.2% or less, and the Q showing the state where Si has one hydroxyl group (-OH) is ３ The peak is 33% or more and 52% or less, and the Q showing the state where Si has no hydroxyl group (-OH) is ４ The white particles according to claim 3, wherein the peak satisfies 45% or more and 63% or less.

5. The white particles according to claim 1, wherein the band gap satisfies the range of 2.2 eV or more and 3.5 eV or less, and has a maximum absorption wavelength in the wavelength range of 250 nm or more and 400 nm or less when dispersed in a solvent containing water.

6. The white particles according to claim 5, having a maximum absorption wavelength in the wavelength range of 300 nm or more and 400 nm or less.

7. The molar absorption coefficient at the maximum absorption wavelength is 2000 M. －１ cm －１ Over 6000M －１ cm －１ The white particles according to claim 1 , which satisfy the following ranges:

8. The white particles according to claim 1, wherein the mass ratio of the aqua iron oligomer to the amorphous silica satisfies the range of 0.003 or more and 0.04 or less.

9. The white particles according to claim 8, wherein the mass ratio of the aqua iron oligomer to the amorphous silica satisfies the range of 0.006 or more and 0.027 or less.

10. The white particles according to claim 1, containing silicon (Si), iron (Fe), oxygen (O), hydrogen (H), and optionally an M1 element (M1 is an alkali metal element), an M2 element (M2 is an alkaline earth metal element), and aluminum (Al), and satisfying the following in mass percentages respectively: 30 ≦ Si ≦ 40, 0 < Fe ≦ 10, 55 ≦ O ≦ 68.5, 1.5 ≦ H ≦ 3.0, 0 ≦ M1 ≦ 0.2, 0 ≦ M2 ≦ 2.5, 0 ≦ Al ≦ 0.3 11. The white particles according to claim 10, wherein the Si, the Fe, the O, the H, the M1 element, the M2 element, and the Al satisfy the following in mass percentages respectively: 30 ≦ Si ≦ 35, 0.3 ≦ Fe ≦ 1.7, 60 ≦ O ≦ 66, 1.5 ≦ H ≦ 3.0, 0 ≦ M1 ≦ 0.06, 0 ≦ M2 ≦ 2.1, 0 ≦ Al ≦ 0.27 12. A method for producing the white particles according to any one of claims 1 to 11, comprising preparing a raw material aqueous dispersion containing a layered silicate mineral and an iron compound, adjusting the pH of the raw material aqueous dispersion to - 1 or more and less than 0.3, and aging while stirring the raw material aqueous dispersion.

13. The method according to claim 12, wherein the layered silicate mineral is a 2:1 type layered silicate mineral having a 2:1 type layer structure.

14. The method according to claim 12, wherein the iron compound is selected from the group consisting of iron nitrate, iron sulfate, iron chloride, and hydrates thereof.

15. The method according to claim 12, wherein in the raw material aqueous dispersion, the mass ratio of the iron compound to the layered silicate mineral satisfies 4 or more and 10 or less.

16. The method according to claim 12, wherein in the aging with stirring, the raw material aqueous dispersion is heated with stirring in a temperature range of 40°C or higher and 60°C or lower for 1 hour or more and 48 hours or less.

17. The method according to claim 13, wherein in preparing the raw material aqueous dispersion, an inorganic base is further added and then heated with stirring.

18. An ultraviolet light shielding agent containing the white particles according to any one of claims 1 to 11.

19. A pigment containing the white particles according to any one of claims 1 to 11.

20. A cosmetic using the ultraviolet light shielding agent according to claim 18.

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