Silicate-based blue pigment and its manufacturing method

Abstract

The present invention provides: a silicate-based blue pigment which is inexpensive, low in toxicity, exhibits vivid blue color, and has high-temperature durability; and a method for producing the same. In a silicate-based blue pigment according to the present invention, Si sites of a silicate represented by formula (A) are doped by Mn, and the amount of Mn doped at the Si sites is 0.01-50% of a total atom number of 100%, including Si and Mn.　(A) Na2M6Si4O15 (In formula (A), M represents at least one selected from the group consisting of Ca, Sr, and Ba.)

Description

[Technical Field]

[0001] The present invention relates to a silicate-based blue pigment and a method for producing the same. This application claims priority based on Japanese Patent Application No. 2023-187572, filed on November 1, 2023, the contents of which are incorporated herein by reference. [Background technology]

[0002] Inorganic pigments are used as coloring materials for ceramics, glass, plastics, paints, etc. However, many existing inorganic pigments contain highly toxic metals, and it is therefore necessary to develop new, environmentally friendly pigments to replace these inorganic pigments. For example, the bright blue pigment that has been known for a long time is cobalt blue (CI Pigment Blue 28: CoAl2O4 spinel), but it is highly likely that it will be restricted in the future due to the carcinogenicity of cobalt compounds. A blue pigment with a similar concept is YInMn blue (Y stands for yttrium, In for indium, and Mn for manganese). For example, in Non-Patent Document 1, the optimal composition of YIn 0.8 Mn 0.2 The blue pigment represented by O3 is L in the CIE color system. * (~34) and b * A value of (~-39) has been reported. In addition, Ba3(P 1-x Mn x O4)2 (x≦0.25) has been reported (Non-Patent Document 2). On the other hand, in Non-Patent Document 3, Na2Ca6Si4O obtained by solid-state reaction at 1300 °C 15 The single crystal structure of has been reported. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Andrew E. Smith, Matthew C. Comstock, MA Subramanian: Spectral properties of the UV absorbing and near-IR reflecting blue pigment, YIn1-xMnxO3, DYES AND PIGMENTS, Volume 133, 2016, Pages 214-221. [Non-patent document 2] LAHA, S., SHARMA, R., BHAT, SV et al.: Ba3(P1-xMnxO4)2: Blue / green inorganic materials based on tetrahedral Mn(V), Bull. Mater. Sci.,Volume 34,2011, Pages 1257-1262. [Non-patent document 3] Volker Kahlenberg, Matthias Maier: MINERALOGY AND PETROLOGY, On the existence of a high-temperature polymorph of Na2Ca6Si4O15-implications for the phase equilibria in the system Na2O-CaO-SiO2, Volume110, 2016, pages 905-915. Summary of the Invention [Problem to be solved by the invention]

[0004] However, the YInMn blue disclosed in Non-Patent Document 1 is rarely used because indium is extremely expensive and there are concerns about its carcinogenicity. On the other hand, there is a demand for blue pigments with better color tones than the blue pigment disclosed in Non-Patent Document 2. In other words, there is a demand for blue pigments that are inexpensive, low-toxicity, have good color tones, and are durable at high temperatures. An object of the present invention is to provide a silicate-based blue pigment that is inexpensive, has low toxicity, exhibits a vivid blue color, and has high-temperature durability, and a method for producing the same. [Means for solving the problem]

[0005] In order to solve these problems, the present inventors have developed Na2Ba6Si4O 15 , Na2Sr6Si4O 15 , Na2Ca6Si4O 15 By doping the silicon (Si) sites of silicate systems such as these with inexpensive and low-toxicity manganese as a coloring ion, we have succeeded in synthesizing a new blue pigment that exhibits a vivid blue color and is durable at high temperatures. Embodiments of the present invention are presented below. [1] Mn is doped into the Si site of a silicate represented by the following formula (A), A silicate-based blue pigment in which the doping amount of Mn in the Si site is 0.01 to 50% based on the total number of atoms including Si and Mn (100%). Na2M6Si4O 15 (A) (In formula (A), M represents at least one selected from the group consisting of Ca, Sr, and Ba.) [2] The silicate-based blue pigment according to [1], which is represented by the following general formula (1): Na2M6(Si 1-x Mn x )4O 15 (1) (In formula (1), M represents at least one selected from the group consisting of Ca, Sr, and Ba, and x is 0.001 to 0.5.) [3] The silicate-based blue pigment according to [1] or [2], which has a crystalline structure of silicate represented by the formula (A). [4] A silicate blue pigment according to any one of [1] to [3], represented by the following formula (1a): Na2Ba6(Si 1-x Mn x )4O 15 (1a) (In formula (1a), x is 0.001 to 0.5.) [5] A silicate blue pigment according to any one of [1] to [3], represented by the following formula (1b): Na2Ca6(Si 1-x Mn x )4O 15 (1b) (In formula (1a), x is 0.001 to 0.3.) [6] A method for producing the silicate-based blue pigment according to any one of [1] to [5], a mixing step of mixing a Na compound, an M compound, an oxide of Si, and a Mn compound; a firing step of firing the mixture obtained in the mixing step; A method for producing a silicate-based blue pigment, comprising: [7] The method for producing a silicate-based blue pigment according to [6], wherein the Na compound is at least one selected from the group consisting of NaCl and NaOH. [8] The method for producing a silicate-based blue pigment according to [6] or [7], wherein the Mn compound is an oxide of Mn. [9] The method for producing a silicate-based blue pigment according to any one of [6] to [8], wherein the amount of the Na compound blended is 5 to 30 mass % in excess of the stoichiometric ratio represented by the general formula (A).

[10] The method for producing a silicate blue pigment according to any one of [6] to [9], further comprising a washing step using water after the calcination step. [Effects of the Invention]

[0006] The present invention can provide a silicate-based blue pigment that is inexpensive, has low toxicity, exhibits a vivid blue color, and has high-temperature durability, and a method for producing the same. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 shows X-ray diffraction patterns of the silicate blue pigments (PA) of Examples 1 to 4 and Comparative Example 1. [Figure 2] FIG. 2 is a diagram showing the ultraviolet-visible reflectance spectra of the silicate-based blue pigments (PA) of Examples 1 to 4 and Comparative Example 1. [Figure 3] FIG. 3 is a diagram showing the L*a*b* color space spectra of the blue pigments of Example 1, Comparative Example 2, and Comparative Example 3. [Figure 4] FIG. 4 shows the X-ray diffraction patterns of the silicate-based blue pigments (PA) of Examples 5 to 8. [Figure 5] FIG. 5 is a diagram showing the results of a heat resistance test of the silicate blue pigment (PA) obtained in Example 1 in Example 9. [Figure 6] FIG. 6 shows X-ray diffraction patterns of the silicate blue pigments (PA) of Examples 10 to 12 and Comparative Example 4. [Figure 7] FIG. 7 is a diagram showing the ultraviolet-visible reflectance spectra of the silicate-based blue pigments (PA) of Examples 11 and 12 and Comparative Example 4. [Figure 8] FIG. 8 is a diagram showing X-ray diffraction patterns of the silicate blue pigments (PA) of Examples 13 to 19 and Comparative Example 5. [Figure 9] FIG. 9 is a diagram showing X-ray diffraction patterns of the silicate blue pigments (PA) of Examples 18 and 20 to 22 and Comparative Example 5. [Figure 10] FIG. 10 is a diagram showing the results of X-ray fluorescence analysis (XRF) of the silicate-based blue pigment (PA) of Example 18 in Example 23. [Figure 11] FIG. 11 is a diagram showing the ultraviolet-visible reflectance spectra of the silicate-based blue pigments (PA) of Examples 18, 20 to 22, and Comparative Example 5. DETAILED DESCRIPTION OF THE INVENTION

[0008] Preferred embodiments of the present invention will now be described in detail. (Silicate-based blue pigment (PA)) A silicate blue pigment (PA) according to one embodiment of the present invention (sometimes referred to as the silicate blue pigment of this embodiment) is obtained by doping Mn into the Si site of a silicate (sometimes referred to as "silicate (A)") represented by the following formula (A): In the Si site, the amount of Mn doped is 0.01% to 50% relative to the total number of atoms including Si and Mn (100%).

[0009] Na2M6Si4O 15 (A)

[0010] (In formula (A), M represents at least one selected from the group consisting of Ca, Sr, and Ba.)

[0011] Doping of Mn into the Si site of the silicate (A) can be confirmed by, for example, X-ray diffraction (XRD), which will be described in detail in the Examples. The amount of Mn doped in the silicate-based blue pigment (PA) of this embodiment can be determined using known analytical methods. In the present invention, this is a value calculated using the compounding ratio of the Si-derived raw material Si compound and the Mn-derived raw material Mn compound of the silicate-based blue pigment (PA) of this embodiment in the production method described below. The Si content and Mn content in the silicate-based blue pigment (PA) of this embodiment can also be measured by XRF analysis. The Si content, calculated as SiO2, is preferably 88.4% by mass or more and 99.998% by mass or less, and the Mn content, calculated as MnO, is preferably 0.002% by mass or more and 11.6% by mass or less, based on 100% by mass of the silicate-based blue pigment (PA). When measuring by XRF analysis, an X-ray fluorescence analyzer (for example, Primus IV manufactured by Rigaku Corporation) can be used as the measuring device.

[0012] In the silicate (A), M may be at least one selected from the group consisting of Ca, Sr, and Ba, is preferably at least one selected from the group consisting of Ca and Ba, and is particularly preferably Ba. That is, the silicate (A) is Na2Ba6Si4O 15As will be described later, Na2Ba6Si4O 15 When the Si site is doped with Mn, preferably in an amount of 0.01 to 30%, more preferably 0.01 to 20%, and even more preferably 0.05 to 20%, a good color tone as a blue pigment can be obtained.

[0013] In the silicate-based blue pigment of the present embodiment, the Si site of the silicate (A) is doped with Mn, and the doped amount of Mn is 0.01% to 50% based on the total number of atoms including Si and Mn (100%). When the doped amount of Mn is within this range, the resulting pigment exhibits a vivid blue color. The doped amount of Mn is more preferably 0.01 to 50%, even more preferably 0.025 to 40%, and particularly preferably 0.05 to 30%. In this embodiment, the silicate (A) is Na2Ca6Si4O 15 In this case, the doping amount of Mn is preferably 0.01 to 30%, and more preferably 0.05 to 20%. The silicate (A) is Na2Ba6Si4O 15 In this case, the doping amount of Mn is preferably 0.01 to 30%, more preferably 0.01 to 20%, and particularly preferably 0.05 to 20%.

[0014] [Silicate (A)] The silicate (A) is Na2Ca6Si4O 15 , Na2Sr6Si4O 15 , Na2Ba6Si4O 15 The synthesis method, crystal structure, etc. are described in detail in Non-Patent Document 3, which is incorporated herein by reference. Na2Ca6Si4O 15 , Na2Ba6Si4O 15 The crystal structure of Na2Sr6Si4O is monoclinic with SiO4 tetrahedral sites. 15 The crystal structure of has not been reported.

[0015] [Silicate-based blue pigment (PA-1)] The silicate blue pigment (PA) of this embodiment is preferably a silicate blue pigment (PA-1) represented by the following general formula (1).

[0016] Na2M6(Si 1-x Mn x )4O 15 (1)

[0017] (In formula (1), M represents at least one selected from the group consisting of Ca, Sr, and Ba, and x is 0.001 to 0.5.)

[0018] Specific examples of the silicate blue pigment (PA-1) of this embodiment include a silicate blue pigment (PA-1a) represented by the following formula (1a) in which M in formula (1) is Ca; a silicate blue pigment (PA-1b) represented by the following formula (1b) in which M in formula (1) is Sr; a silicate blue pigment (PA-1c) represented by the following formula (1c) in which M in formula (1) is Ba; and a silicate blue pigment (PA-1d) represented by the following formula (1d) in which M in formula (1) is Ca and Ba.

[0019] Na2Ca6(Si 1-x Mn x )4O 15 (1a)

[0020] Na2Sr6(Si 1-x Mn x )4O 15 (1b)

[0021] Na2Ba6(Si 1-x Mn x )4O 15 (1c)

[0022] Na2(Ca 1―y Ba y )6(Si 1-x Mn x )4O 15 (1d)

[0023] (In formulas (1a) to (1d), each x independently has the same meaning as in formula (1), and y is 0.1 to 5.9.)

[0024] Among these, the silicate blue pigment (PA-1) of this embodiment is preferably a silicate blue pigment (PA-1c) represented by the above formula (1c) in which M is Ba. In this case, x in the above formula (1c) is preferably 0.001 to 0.5, more preferably 0.002 to 0.3, and even more preferably 0.003 to 0.2. When x is within the above range, the resulting pigment exhibits a more vivid blue color.

[0025] Specific examples of the silicate blue pigment (PA-1) of this embodiment include the following silicate blue pigments. Na2Ca6(Si 0.99 Mn 0.01 )4O 15 , its color: bright blue Na2Ca6(Si 0.97 Mn 0.03 )4O 15 , its color: turquoise Na2Ca6(Si 0.05 Mn 0.05 )4O 15 , its color: greenish blue Na2Ba6(Si 0.99 Mn 0.01 )4O 15 , its color: bright blue Na2Ba6(Si 0.95 Mn 0.05 )4O 15 , its color: marine blue Na2Ba6(Si 0.90 Mn 0.10 )4O 15 , its color: turquoise

[0026] [Structure of silicate-based blue pigment (PA)] The silicate blue pigment (PA) of this embodiment is presumed to have a crystal structure (sometimes referred to as the "host crystal structure") similar to the crystals of the matrix silicate (A). If the silicate blue pigment (PA) of this embodiment has a large amount of Mn doped into the Si site, the crystal structure of the silicate blue pigment (PA) of this embodiment may be deformed from the host crystal structure. In the silicate-based blue pigment (PA) of this embodiment, the sodium (Na) site, barium (Ba) site, and oxygen (O) site other than the Si site may be the same or different elements as those at the sites of the matrix silicate (A), but are preferably the same or nearly the same. When Mn is doped at the Si site, some adjustment may be made to the oxygen (O) site, sodium (Na) site, etc. to maintain charge neutrality of the entire material.

[0027] Manganese (Mn) can exist in several oxidation states (divalent to heptavalent). Mn ions can be doped into the Si site of the silicate (A). In this embodiment, the Mn ions doped into the Si site are pentavalent (Mn 5+ ) is preferred.

[0028] In the silicate (A), manganese, particularly pentavalent manganese (Mn 5+ By doping with ), it is possible to realize an inorganic pigment with good color development and excellent heat resistance.

[0029] [Color of silicate-based blue pigment (PA)] The silicate-based blue pigment (PA) of this embodiment is a blue pigment having a color of L 100% of the CIE 1976 color scale specified in JIS Z8518. * a * b * In the chromaticity coordinates specified in the color system, L * The lightness (brightness) is preferably 40 or more, more preferably 45 or more, and even more preferably 50 or more. * may be 70 or less.

[0030] The silicate-based blue pigment (PA) of this embodiment has a color scale of CIE1976 L, as specified in JIS Z8518. * a * b * In the chromaticity coordinates specified in the color system, a * is preferably -5 or less, more preferably -10 or less, and even more preferably -15 or less. * may be greater than or equal to -50.

[0031] The silicate-based blue pigment (PA) of this embodiment has a color scale of CIE1976 L, as specified in JIS Z8518. * a * b * In the chromaticity coordinates specified in the color system, b * is preferably 0 or less, more preferably -10 or less, and even more preferably -20 or less. * may be greater than or equal to -60.

[0032] By satisfying the above conditions, a more suitable color tone, more specifically, a vivid blue color, can be exhibited. In general, a * squared and b * The square root of the sum of the squares of * ) and is an index of vividness. * , b * Even if the blue color falls within the range of C * The larger the value, the more vivid the blue color. * In addition to L * The larger the value, the more vivid the color and the brighter the blue.

[0033] By satisfying the above conditions, a more suitable color tone, more specifically, a vivid blue color, can be exhibited.

[0034] For example, Na2Ba6(Si 0.995 Mn 0.005 )4O 15The silicate-based blue pigments of L * (brightness)=65.2,a * (red-green axis)=-17.8, b * It has a chromaticity coordinate of (yellow-blue axis) = -27.1, and exhibits a pure, vivid, deep blue color. Na2Ba6(Si 0.99 Mn 0.01 )4O 15 The silicate-based blue pigments of L * (brightness)=60.6, a * (red-green axis)=-19.3, b * It has a chromaticity coordinate of (yellow-blue axis) = -21.9, and exhibits a pure and vivid blue color.

[0035] [Thermal stability of silicate-based blue pigments (PA)] The silicate blue pigment (PA) of this embodiment has excellent thermal stability, and specifically, it is preferable that the following conditions be satisfied.

[0036] That is, when the silicate-based blue pigment (PA) of this embodiment is heated at 300 to 600°C for 6 hours, the decrease in reflectance at a wavelength of 450 nm in the ultraviolet-visible reflectance spectrum is preferably 10% or less, and more preferably 5% or less.

[0037] As a result, the silicate-based blue pigment (PA) of this embodiment can preferably maintain its excellent color tone even after heat treatment, particularly at high temperatures, such as for coloring pottery.

[0038] The form of the silicate blue pigment (PA) of this embodiment is not particularly limited, but is preferably particulate from the viewpoint of suitable use in preparing compositions containing inorganic pigments, such as various paints and inks.

[0039] Examples of the shape of the particles include substantially spherical, polyhedral, spindle-shaped, irregular, plate-like, and needle-like shapes. From the viewpoints of the fluidity of the inorganic pigment itself, the fluidity when the inorganic pigment is incorporated into compositions such as various paints and inks, and the stability of the hue of the inorganic pigment, the shape of the particles is preferably a shape other than plate-like or needle-like.

[0040] Furthermore, when the silicate blue pigment (PA) of this embodiment is in the form of particles, the average particle size is preferably 0.1 μm or more and 50 μm or less, and more preferably 0.2 μm or more and 20 μm or less.

[0041] The silicate blue pigment (PA) of this embodiment may be surface-treated using, for example, other inorganic or organic materials by a known treatment method to make it more dispersible. When the surface-treated silicate blue pigment (PA) of this embodiment is applied to compositions containing inorganic pigments, such as various paints and inks, the dispersion stability of the inorganic pigment can be improved.

[0042] In the present invention, the average particle size refers to the average particle size on a volume basis unless otherwise specified. The average particle size can be determined, for example, by measurement using a particle size distribution analyzer.

[0043] The silicate blue pigment (PA) of this embodiment may contain any of the components of the silicate blue pigment (PA), and preferably contains the component of the silicate blue pigment (PA-1) represented by formula (1). It may also contain other components in addition to the components. Examples of such components include unreacted raw materials, decomposition products of the silicate blue pigment (PA), and unavoidable impurities.

[0044] When other components are contained, the content of the other components is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 2% by mass or less, based on the total silicate-based blue pigment (PA) of this embodiment.

[0045] The silicate blue pigment (PA) of this embodiment exhibits a vivid blue color and can be used to color various members.

[0046] Furthermore, the silicate blue pigment (PA) of this embodiment can also be suitably used as a raw material for various paints and inks.

[0047] The silicate blue pigment (PA) of this embodiment may be mixed with various resins and glasses and used to produce a molded article.

[0048] The silicate blue pigment (PA) of the present embodiment may be used in combination with other coloring materials. For example, a color image may be formed by applying it to a substrate in a predetermined pattern together with coloring materials of other colors, or it may be mixed with other coloring materials to express a color tone different from the color tone of the silicate blue pigment (PA) of the present embodiment alone.

[0049] In particular, the silicate blue pigment (PA) of this embodiment has excellent heat resistance (high-temperature stability) and color durability, and can maintain a predetermined color tone for a long period of time. Therefore, it is particularly suitable for use in heated environments, such as for coloring pottery and ceramics, and as a colorant for other ceramics.

[0050] Furthermore, the silicate blue pigment (PA) of the present embodiment is resistant to fading, and can maintain its vivid color tone favorably for a long period of time, and is therefore also favorably used as a colorant for various inks, for example, inkjet inks.

[0051] (Method for manufacturing silicate-based blue pigment (PA)) A method for producing a silicate blue pigment (PA) according to one embodiment of the present invention (sometimes referred to as the "method for producing a silicate blue pigment (PA) according to this embodiment" or the "production method according to this embodiment") is a method for producing the silicate blue pigment (PA) according to this embodiment, preferably the silicate blue pigment (PA-1) represented by general formula (1) above. The production method according to this embodiment includes a mixing step of mixing a Na compound, an M compound, an oxide of Si, and a Mn compound to obtain a mixture, and a calcination step of calcining the mixture obtained in the mixing step. The M has the same meaning as M in formula (A) and general formula (1) above. The silicate-based blue pigment (PA) of this embodiment can be suitably produced by a method including a mixing step of mixing raw materials, i.e., a Na compound, an M compound, an oxide of Si, and an Mn compound, to obtain a mixture, and a calcination step of reacting the mixture obtained in the mixing step to synthesize the target product. The calcination step can also be performed using microwave heating or a method called water-assisted solid-state reaction, in which the calcination step is performed at a relatively low temperature in the presence of a small amount of added water.

[0052] <Mixing process> In the mixing step, a Na compound, an M compound, an oxide of Si, and a Mn compound are mixed as raw materials to obtain a mixture.

[0053] As the Na compound, M compound, and Mn compound, for example, at least one of a metal carbonate and a metal oxide can be used.

[0054] Examples of the Na compound include NaCl, Na2CO3, NaOH, etc. In this embodiment, from the viewpoint of reactivity, it is preferable to use at least one selected from the group consisting of NaCl and NaOH, and it is more preferable to use NaCl. Examples of M compounds include MCO3, MO, etc., with MCO3 being preferred. For example, examples of Ca compounds include CaCO3, CaO, etc., with CaCO3 being preferred. Examples of Sr compounds include SrCO3, SrO, etc., with SrCO3 being preferred. Examples of Ba compounds include BaCO3, BaO, etc., with BaCO3 being preferred. Examples of Mn compounds include MnO2 and MnCO3, but in this embodiment, an oxide of Mn, namely MnO2, is preferred.

[0055] The oxide of Si includes SiO2, and amorphous silica is preferred.

[0056] The raw materials for the silicate-based blue pigment (PA) of this embodiment may be in any shape, but are preferably particulate, which allows for favorable mixing of multiple raw materials and more effectively prevents unintended compositional variations and unintended residual unreacted raw materials in the inorganic pigment produced.

[0057] The average particle size of the raw material of the silicate blue pigment (PA) of this embodiment is preferably 0.1 μm or more and 50 μm or less. This makes it easier to handle the raw materials and more effectively prevents the problems described above from occurring. In addition, the solid-phase reaction in the firing step can be more effectively promoted, thereby improving the productivity of the inorganic pigment. In this step, the raw materials are usually first weighed out according to the stoichiometric ratio and mixed together. The stoichiometric ratio is, for example, the ratio of the amounts of raw materials theoretically calculated from the formula (A) and the amount of Mn doped when producing the silicate blue pigment (PA) of this embodiment, whereas, for example, the ratio is the ratio of the amounts of raw materials theoretically calculated from the general formula (1) when producing the silicate blue pigment (PA-1).

[0058] The mixing method may be a general method using a mortar, a ball mill, or the like. The mixing method may be dry mixing or wet mixing (more specifically, wet mixing using a highly volatile solvent such as alcohol or acetone), with wet mixing being preferred. In wet mixing, it is more preferable to use a highly volatile solvent such as alcohol or acetone. Wet mixing makes it easier for the raw material powder to clump together, and can more effectively prevent the powder from scattering.

[0059] In the mixing step of the manufacturing method of this embodiment, if necessary, the Na compound can be blended in an amount in excess of the stoichiometric ratio. By adding the Na compound in an amount in excess of the stoichiometric ratio, the excess acts as a flux component, promoting the growth of the target crystal and improving the homogeneity of the target product. Specifically, when the amount of Na compounds according to the stoichiometric ratio is 100 parts by mass, the total amount of Na compounds to be blended may be within the range of 101 to 150 parts by mass. That is, when the amount of Na compounds according to the stoichiometric ratio is 100 parts by mass, the total amount of Na compounds to be blended may be 102 parts by mass or more (referred to as a 2% excess by mass) or more, 105 parts by mass or more (referred to as a 5% excess by mass) or more, 110 parts by mass (referred to as a 10% excess by mass) or more, 120 parts by mass (referred to as a 20% excess by mass) or more, 130 parts by mass or more (referred to as a 30% excess by mass) or more, or 150 parts by mass or less (referred to as a 50% excess by mass) or less, 140 parts by mass (referred to as a 40% excess by mass) or less, or 130 parts by mass (referred to as a 30% excess by mass) or less.

[0060] In this embodiment, the amount of the Na compound is preferably 5 to 30% by mass in excess of the stoichiometric ratio represented by the general formula (A), more preferably 6% to 20% by mass in excess, and particularly preferably 10% to 20% by mass in excess. By setting the amount of the Na compound within this range, handling is improved when removing the target product from the container after the firing step.

[0061] When the Na compound is blended in an amount in excess of the amount according to the above stoichiometric ratio, the Na compound is preferably NaCl or NaOH, and more preferably NaCl. When a Na compound is blended in an amount exceeding the amount according to the stoichiometric ratio, in the following examples (where the Na compound is NaCl), no residual Cl was observed in the final product from the X-ray diffraction pattern or X-ray fluorescence analysis (XRF) results, and so it is presumed that the Na compound acts as a flux. Also, in some examples, it was observed that the target product was hardly obtained in samples with an excess amount of NaCl of 0 mass % (samples in which the Na compound was blended in an amount according to the stoichiometric ratio), and so it is thought that molten NaCl affects the diffusion rate.

[0062] <Firing process> In the firing step, the mixture obtained in the mixing step is fired.

[0063] The atmosphere in the firing step is not particularly limited. For example, the firing step may be performed in air or in an inert gas atmosphere.

[0064] The heating temperature in the firing step is preferably 800°C or higher and 1500°C or lower. The heating time in the firing step is preferably 5 hours or more and 24 hours or less.

[0065] <Forming process> The manufacturing method of this embodiment may further include a molding step of molding the mixture of raw material powders into pellets after the mixing step and before the firing step. By molding the mixture of raw material powders into pellets, a dense fired product is obtained in the firing step, and an inorganic pigment with excellent properties is obtained. Furthermore, molding into pellets and firing the product also increases raw material efficiency. The molding pressure in the mixing step is preferably 5 MPa or more and 20 MPa or less.

[0066] <Cleaning process> The production method of this embodiment may further include a washing step using an acid, alkali, water, or an organic solvent after the firing step. By carrying out the washing step, by-product ion components and salts can be removed or agglomerated particles can be broken down, and the silicate-based blue pigment of the present invention can be suitably used to improve the hiding power or dispersibility when used in a paint.

[0067] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these. [Example]

[0068] The present embodiment will be further described below with reference to examples, but the present invention is not limited thereto. (raw materials) NaCl powder: Product name: Sodium chloride (I), 99.9%, manufactured by Kojundo Chemical Co., Ltd. Na2CO3 powder: Product name: Sodium carbonate, 99.8%, manufactured by Kanto Chemical Co., Ltd. BaCO3 powder: Product name: Barium carbonate, 4N, manufactured by Kanto Chemical Co., Ltd. SrCO3 powder: Product name: Strontium carbonate, 4N, manufactured by Kanto Chemical Co., Ltd. CaCO3 powder: Product name: Calcium carbonate, 4N, manufactured by Kanto Chemical Co., Ltd. SiO2 powder: Product name: Silicon dioxide, 99.9%, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. MnO2 powder: Trade name: Manganese (IV) oxide, 99.5%, manufactured by Wako Pure Chemical Industries, Ltd.

[0069] (Evaluation method) [XRD] Measurement equipment: Powder X-ray diffractometer MX-Labo (manufactured by Mac Science) Measurement conditions: X-ray: Cu / 40kV / 25mA Divergence slit: 1° Scattering slit: 1° Receiving slit: 0.15 nm Detector: Scintillation counter Scan speed: 0.02° / sec Scanning range: 10~50°

[0070] [UV-Visible Reflectance Spectrum] Measuring device: Ultraviolet-visible spectrophotometer (UV-vis spectrometer) V-630DS (manufactured by JASCO Corporation) Measurement conditions: An integrating sphere unit (ISV-722, manufactured by JASCO Corporation) was attached for the measurements. Barium sulfate was used for baseline measurements. Then, 30 mg of inorganic pigment was packed into the window (φ5 mm) of a trace powder cell (PSH-003, manufactured by JASCO Corporation) to achieve a filling rate of 50% or more. The spectral reflectance of diffuse reflected light, including specular reflected light, was measured in the wavelength range of 300 to 800 nm.

[0071] [XRF] Measurement equipment: Fluorescence spectrophotometer (JASCO Corporation, FP-6500 model) Measurement conditions were: excitation bandwidth: 10 nm, emission bandwidth: 10 nm, and fluorescence spectrophotometric measurement was performed in vacuum mode.

[0072] [CIE L * a * b * ] Measurement device: Colorimeter CR-300 (Konica Minolta) Measurement conditions: Each inorganic pigment was compression molded and pelletized to prepare a sample. Each sample was heated at 300°C, 600°C, and 1000°C, respectively, and the above CIE L * a * b * The same evaluation was carried out.

[0073] [Heat resistance test] Measurement device: Colorimeter CR-300 (Konica Minolta) Measurement conditions: Each inorganic pigment was compression molded and pelletized to prepare a sample. Each sample was heated at 300°C, 600°C, and 1000°C, respectively, and the above CIE L * a * b * The same evaluation was carried out.

[0074] Example 1 As raw materials, NaCl powder, BaCO3 powder, SiO2 powder, and MnO2 powder were prepared, and the NaCl powder, BaCO3 powder, SiO2 powder, and MnO2 powder were mixed in the composition ratio shown in Table 1 [Na2Ba6(Si 0.995 Mn 0.005 )4O 15 The components were weighed out according to the stoichiometric ratio so that:

[0075] Next, the powder raw materials were mixed in an agate mortar using acetone as a solvent, and the mixture was then dried to obtain a raw material mixture.

[0076] The mixture of raw materials was fired in air at 900°C for 6 hours.

[0077] In this way, the formula [Na2Ba6(Si 0.995 Mn 0.005 )4O 15 A silicate-based blue pigment represented by the formula: was produced.

[0078] The obtained silicate-based blue pigment was subjected to powder X-ray diffraction measurement, diffuse reflectance spectrum measurement, and chromaticity measurement using the above-mentioned measurement methods. * a * b * Expressed in color system, L * (lightness), a * (positive direction: red, negative direction: green), b * (Positive direction: yellow, negative direction: blue) was evaluated. It shows a vivid blue color. The results are shown in Table 1 and Figures 1 to 3.

[0079] (Examples 2 to 4, Comparative Example 1) A silicate-based blue pigment was produced using the composition shown in Table 1 in the same manner as in Example 1. The evaluation was carried out in the same manner as in Example 1. The results are shown in Table 1 and Figures 1 to 3.

[0080] Example 5 A silicate-based blue pigment was produced in the same manner as in Example 2, except that CaCO powder was used instead of BaCO powder, and NaCl powder was weighed out in a 20% excess by mass (i.e., when the stoichiometric ratio mass was 100 parts by mass, 120 parts by mass of NaCl powder was weighed out). Powder X-ray diffraction measurement and color saturation measurement were carried out in the same manner as in Example 1. The results are shown in Table 1 and FIG.

[0081] Examples 6 to 8 A silicate-based blue pigment was produced using the composition shown in Table 1 in the same manner as in Example 5. Powder X-ray diffraction measurement and color saturation measurement were carried out in the same manner as in Example 5. The results are shown in Table 1 and Figure 4.

[0082] Example 9 Using the silicate-based blue pigment obtained in Example 1, the diffuse reflectance spectrum was measured under the following treatment conditions, and a heat resistance test was carried out. Temperature conditions: 300℃ / 600℃ / 900℃ Baking time: 6 hours The results are shown in Figure 5. In Figure 5, "Sample," "300°C," "600°C," and "900°C" represent the diffuse reflectance spectra before heat treatment, after treatment at 300°C, after treatment at 600°C, and after treatment at 900°C, respectively.

[0083] [Table 1]

[0084] (Comparative Example 2) "Inorganic pigment CoAl2O4 L * a * b * Color Space Measurement The inorganic pigment CoAl2O4 obtained by the method described in Non-Patent Document A1 below was subjected to L * a * b * The color space was measured and the results are shown in Table 1.

[0085] [Non-patent document A1] Simeen Sattar, J. Chem. Educ. 96, 1124-1128, (2019).

[0086] (Comparative Example 3) "Inorganic pigment YIn 0.95 Mn 0.05 O3 L * a * b * Color Space Measurement Inorganic pigment YIn obtained by the method described in Non-Patent Document A2 below 0.95 Mn 0.05 O3 was added to L in the same manner as in Example 1. * a * b * The color space was measured and the results are shown in Table 1.

[0087] [Non-patent document A2] Andrew E. Smith et al., DYES PIGMENT, 133, 214-221, (2016).

[0088] Example 10 A silicate-based blue pigment was produced in the same manner as in Example 1, except that the composition ratio shown in Table 2 was used and SrCO3 powder was added instead of BaCO3 powder. Powder X-ray diffraction measurement and color saturation measurement were carried out in the same manner as in Example 1. The results are shown in Table 2 and FIGS.

[0089] (Examples 11 and 12, Comparative Example 4) A silicate-based blue pigment was produced in the same manner as in Example 5, except that the composition ratio shown in Table 2 was used and SrCO3 powder was added instead of BaCO3 powder. Powder X-ray diffraction measurement and color saturation measurement were carried out in the same manner as in Example 1. The results are shown in Table 2 and FIGS.

[0090] [Table 2]

[0091] Example 13 A silicate-based blue pigment was produced in the same manner as in Example 1, except that the composition ratio shown in Table 3 was used and CaCO3 powder was blended in place of BaCO3 powder. Powder X-ray diffraction measurement and color saturation measurement were carried out in the same manner as in Example 1. The results are shown in Table 3 and FIG.

[0092] (Examples 14 to 19) A silicate-based blue pigment was produced in the same manner as in Example 13, except that the amount of NaCl powder added was adjusted to the amount shown in Table 3. Powder X-ray diffraction measurement and color saturation measurement were carried out in the same manner as in Example 1. The results are shown in Table 3 and Figure 8. In Example 18, diffuse reflectance spectrum measurement was carried out in the same manner as in Example 1. The results are shown in Figure 11.

[0093] Examples 20 to 22 A silicate-based blue pigment was produced in the same manner as in Example 18, except that the composition ratios shown in Table 3 were used. Powder X-ray diffraction measurement, color chromaticity measurement, and diffuse reflectance spectrum measurement were carried out in the same manner as in Example 1. The results are shown in Table 3, and Figs.

[0094] (Comparative Example 5) The composition ratio is Na2Ca6Si4O 15 A silicate-based blue pigment was produced in the same manner as in Example 18, except that: Powder X-ray diffraction measurement and diffuse reflectance spectrum measurement were carried out in the same manner as in Example 1. The results are shown in Figures 9 and 11.

[0095] Example 23 X-ray fluorescence analysis (XRF) was performed using the silicate-based blue pigment obtained in Example 18. The results are shown in FIG.

[0096] [Table 3]

[0097] (Consideration) From the results shown in Table 1 and Figures 1 to 5, when M=Ba, the target substance was obtained as the main phase in all samples with Mn content, and Na2Ba6(Si 0.995 Mn 0.005 )4O 15 The sample showed the most vivid blue coloration, and no significant difference was observed between the sample synthesized using excess NaCl.

[0098] From the results in Table 2 and Figures 6 and 7, when M = Sr, Sr2SiO4 was obtained as the product.

[0099] From the results of Table 3 and Figures 8 to 11, when M=Ca, the target substance was obtained as a mixed phase in all samples with Mn content, and Na2Ca6(Si 0.99 Mn 0.1 )4O 15 showed the most vivid blue coloration.

[0100] L in Figure 3 * a * b * The color space results showed that the sample exhibited a blue coloration. The sample was confirmed to be a vivid blue compared to Comparative Example 2, and a greenish blue compared to Comparative Example 3.

[0101] The results of the heat resistance test shown in Figure 5 confirmed high heat resistance up to 600°C.

[0102] From the results of the NaCl-flux amount (excess NaCl) in Figure 8 and the XRF results in Figure 10, it was confirmed that the NaCl-flux amount (excess NaCl) was 20 wt%, which resulted in few impurities and a vivid blue color. Furthermore, since the XRF measurement results showed no Cl peak in the sample after water washing, it is believed that the Cl in the NaCl-flux (excess NaCl) was not incorporated into the crystals.

Claims

1. Mn is doped into the Si site of a silicate represented by the following formula (A): The silicate-based blue pigment has a doping amount of Mn of 0.01 to 50% based on 100% of the total number of atoms including Si and Mn at the Si site. Na ２ M ６ Si ４ O １５ (A) (In formula (A), M represents at least one selected from the group consisting of Ca, Sr, and Ba.)

2. 2. The silicate-based blue pigment according to claim 1, which is represented by the following general formula (1): Na ２ M ６ (Si １－ｘ Mn ｘ ) ４ O １５ (1) (In formula (1), M represents at least one element selected from the group consisting of Ca, Sr, and Ba, and x is 0.001 to 0.5.)

3. 2. The silicate-based blue pigment according to claim 1, having a silicate crystal structure represented by formula (A).

4. 2. The silicate-based blue pigment according to claim 1, which is represented by the following formula (1a): Na ２ Ba ６ (Si １－ｘ Mn ｘ ) ４ O １５ (1a) (In formula (1a), x is 0.001 to 0.5.)

5. 2. The silicate-based blue pigment according to claim 1, which is represented by the following formula (1b): Na ２ Ca ６ (Si １－ｘ Mn ｘ ) ４ O １５ (1b) (In formula (1a), x is 0.001 to 0.3.)

6. A method for producing the silicate-based blue pigment according to any one of claims 1 to 5, comprising the steps of: a mixing step of mixing a Na compound, an M compound, an oxide of Si, and a Mn compound; a firing step of firing the mixture obtained in the mixing step; A method for producing a silicate-based blue pigment, comprising:

7. 7. The method for producing a silicate blue pigment according to claim 6, wherein the Na compound is at least one selected from the group consisting of NaCl and NaOH.

8. The method for producing a silicate blue pigment according to claim 6, wherein the Mn compound is an oxide of Mn.

9. 7. The method for producing a silicate blue pigment according to claim 6, wherein the amount of the Na compound blended is 5 to 30% by mass in excess of the stoichiometric ratio represented by general formula (A).

10. The method for producing a silicate blue pigment according to claim 6, further comprising a washing step using water after the calcination step.

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