Silicate-based blue pigment and method for producing same

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

Silicate-based blue pigment and its manufacturing method

[0001] This application claims priority to Japanese Patent Application No. 2023-187572, filed November 1, 2023, the contents of which are incorporated herein by reference.

[0002] Inorganic pigments are used as coloring materials for ceramics, glass, plastics, paints, etc. However, many of the 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 oldest known vivid blue pigment is cobalt blue (CI Pigment Blue 28: CoAl ２ O ４ 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 (YInMn blue, Y is yttrium, In is indium, and Mn is manganese). For example, in Non-Patent Document 1, the optimal composition of YIn ０．８ Mn ０．２ O ３ The blue pigment represented by is L ＊ (~34) and b ＊ In addition, Ba, a blue pigment made from inexpensive transition metal manganese, which has not been shown to be carcinogenic, has been reported. ３ (P １－ｘ Mn ｘ O ４ ) ２ On the other hand, in Non-Patent Document 3, Na obtained by solid-state reaction at 1300°C was reported. ２ Ca ６ Si ４ O １５ The single crystal structure of has been reported.

[0003] Andrew E. Smith, Matthew C. Comstock, M. A. Subramanian: Spectral properties of the UV absorbing and near-IR reflecting blue pigment, YIn1-xMnxO3, DYES AND PIGMENTS, Volume 133, 2016, Pages 214-221. LAHA, S. , SHARMA, R. , BHAT, S. V. et al. : Ba3(P1-xMnxO4)2: Blue / green inorganic materials based on tetrahedral Mn(V), Bull. Mater. Sci. , Volume 34, 2011, Pages 1257-1262. 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, Volume 110, 2016, pages 905-915.

[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. Meanwhile, there is a demand for blue pigments with better color tones than the blue pigment disclosed in Non-Patent Document 2. That is, there is a demand for blue pigments that are inexpensive, low-toxicity, have good color tones, and are durable at high temperatures. The present invention aims to provide a silicate-based blue pigment that is inexpensive, low-toxicity, exhibits a vivid blue color, and is durable at high temperatures, and a method for producing the same.

[0005] In order to solve these problems, the present inventors have ２ Ba ６ Si ４ O １５ , Na ２ Sr ６ Si ４ O１５ , Na ２ Ca ６ Si ４ O １５ By doping the silicon (Si) sites of silicates such as Na 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 has high-temperature durability. The embodiments of the present invention are as follows: [1] A silicate-based blue pigment in which Mn is doped into the Si sites of a silicate represented by the following formula (A), and the doping amount of Mn in the Si sites is 0.01 to 50% based on the total number of atoms including Si and Mn (100%). 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] A silicate-based blue pigment according to [1], represented by the following general formula (1): 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] The silicate blue pigment according to [1] or [2], which has a crystalline structure of silicate represented by formula (A). [4] The silicate blue pigment according to any one of [1] to [3], 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] A silicate-based blue pigment according to any one of [1] to [3], 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 a silicate blue pigment according to any one of [1] to [5], comprising: a mixing step of mixing a Na compound, an M compound, an oxide of Si, and a Mn compound; and a calcining step of calcining the mixture obtained in the mixing step. [7] A method for producing a silicate blue pigment according to [6], wherein the Na compound is at least one selected from the group consisting of NaCl and NaOH. [8] A method for producing a silicate blue pigment according to [6] or [7], wherein the Mn compound is an oxide of Mn. [9] A method for producing a silicate blue pigment according to any one of [6] to [8], 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] A method for producing a silicate blue pigment according to any one of [6] to [9], further comprising a washing step using water after the calcining step.

[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.

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

[0008] Preferred embodiments of the present invention will be described in detail below. (Silicate-based blue pigment (PA)) A silicate-based blue pigment (PA) according to one embodiment of the present invention (sometimes referred to as the silicate-based blue pigment of this embodiment) is a silicate represented by the following formula (A) (sometimes referred to as "silicate (A)") doped with Mn at the Si site. 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] Na ２ M ６ Si ４ O １５　　　 (A)

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

[0011] Doping of the Si site of the silicate (A) with Mn can be confirmed, for example, by X-ray diffraction (XRD). X-ray diffraction will be described in detail in the Examples. The amount of Mn doped in the silicate blue pigment (PA) of this embodiment can be determined by a known analytical method. In the present invention, this is a value calculated from the compounding ratio of the Si-derived raw material Si compound and the Mn-derived raw material Mn compound of the silicate blue pigment (PA) of this embodiment in the production method described below. The Si content and Mn content in the silicate blue pigment (PA) of this embodiment can also be measured by XRF analysis. The Si content relative to 100% by mass of the silicate blue pigment (PA) is calculated by the SiO ２ The Mn content is preferably 88.4 mass% or more and 99.998 mass% or less in terms of MnO, and the Mn content is preferably 0.002 mass% or more and 11.6 mass% or less in terms of MnO. When measuring by XRF analysis, an X-ray fluorescence analyzer (for example, Primus IV, manufactured by Rigaku Corporation) can be used as the measuring instrument.

[0012] In the silicate (A), M may be at least one selected from the group consisting of Ca, Sr, and Ba, and is preferably at least one selected from the group consisting of Ca and Ba, and particularly preferably Ba. ２ Ba ６ Si ４ O １５ As will be described later, Na ２ Ba ６ Si ４ O １５ When the Si site of the above 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 this embodiment, the silicate-based blue pigment is obtained by doping the Si site of silicate (A) with Mn, and the doping amount of Mn is 0.01% to 50% based on 100% of the total number of atoms including Si and Mn. When the doping amount of Mn is within the above range, the resulting pigment exhibits a vivid blue color. The doping 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 Na ２ Ca ６ Si ４ O １５ In the case where the silicate (A) is Na, the doping amount of Mn is preferably 0.01 to 30%, more preferably 0.05 to 20%. ２ Ba ６ Si ４ O 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) may be Na ２ Ca ６ Si ４ O １５ , Na ２ Sr ６ Si ４ O １５ , Na ２ Ba ６ Si ４ O １５ The synthesis method, crystal structure, etc. of Na are described in detail in Non-Patent Document 3, which is incorporated herein by reference. ２ Ca ６ Si ４ O １５ , Na ２ Ba ６ Si ４ O １５ The crystal structure of ４ It is a monoclinic crystal with tetrahedral sites. ２ Sr ６ Si ４ O １５The crystal structure of has not been reported.

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

[0016] Na ２ M ６ (Si １－ｘ Mn ｘ ) ４ O １５　　　 (1)

[0017] (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.)

[0018] Specific examples of the silicate blue pigment (PA-1) of the present 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 both Ca and Ba.

[0019] Na ２ Ca ６ (Si １－ｘ Mn ｘ ) ４ O １５　　　 (1a)

[0020] Na ２ Sr ６ (Si １－ｘ Mn ｘ ) ４ O １５　　　 (1b)

[0021] Na ２ Ba ６ (Si １－ｘ Mn ｘ ) ４ O １５　　　 (1c)

[0022] Na ２ (Ca １―ｙ Ba ｙ )６ (Si １－ｘ Mn ｘ ) ４ O 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 in the above formula (1) 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-based blue pigment (PA-1) of this embodiment include the following silicate-based blue pigments: ２ Ca ６ (Si ０．９９ Mn ０．０１ ) ４ O １５ , its color: bright blue Na ２ Ca ６ (Si ０．９７ Mn ０．０３ ) ４ O １５ , its color: turquoise Na ２ Ca ６ (Si ０．０５ Mn ０．０５ ) ４ O １５ , its color: greenish blue Na ２ Ba ６ (Si ０．９９ Mn ０．０１ ) ４ O １５ , its color: bright blue Na ２ Ba ６ (Si ０．９５ Mn ０．０５ ) ４ O １５ , its color: Marine blue Na ２ Ba６ (Si ０．９０ Mn ０．１０ ) ４ O １５ , its color: turquoise

[0026] [Structure of Silicate-Based Blue Pigment (PA)] The silicate-based blue pigment (PA) of this embodiment is presumed to have a crystal structure (sometimes referred to as the "host crystal structure") similar to that of the matrix silicate (A). When the Si site of the silicate-based blue pigment (PA) of this embodiment is doped with a large amount of Mn, the crystal structure of the silicate-based blue pigment (PA) of this embodiment may be deformed from the matrix 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 element as or different from each site 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 the pigment with methyl methyl acrylate, an inorganic pigment having good color development and excellent heat resistance can be realized.

[0029] [Chromaticity of Silicate-Based Blue Pigment (PA)] The silicate-based blue pigment (PA) of the present embodiment has a chromaticity of L chromaticity 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 the present embodiment has a color similar to that of the CIE 1976 color scale 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 −50 or more.

[0031] The silicate-based blue pigment (PA) of the present embodiment has a color similar to that of the CIE 1976 color scale 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 −60 or more.

[0032] By satisfying the above conditions, a more suitable color tone, more specifically, a vivid blue color, can be exhibited. ＊ squared and b ＊ The square root of the sum of the squares of ＊ ) and is an index of vividness. ＊ , b ＊ Even if the blue 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, Na in Example 1 described later２ Ba ６ (Si ０．９９５ Mn ０．００５ ) ４ O １５ The silicate-based blue pigment is L ＊ (brightness) = 65.2, a ＊ (Red-green axis) = -17.8, b ＊ The chromaticity coordinates (yellow-blue axis) = -27.1, and the resulting color is a pure, vivid, deep blue color. ２ Ba ６ (Si ０．９９ Mn ０．０１ ) ４ O １５ The silicate-based blue pigment is L ＊ (brightness) = 60.6, a ＊ (Red-green axis) = -19.3, b ＊ It has chromaticity coordinates of (yellow-blue axis) = -21.9, and exhibits a pure and vivid blue color.

[0035] [Thermal Stability of Silicate-Based Blue Pigment (PA)] The silicate-based blue pigment (PA) of the present embodiment has excellent thermal stability, and specifically, it is preferable that the following conditions are 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, even when the silicate blue pigment (PA) of the present embodiment is subjected to heat treatment at particularly high temperatures, such as for coloring pottery, it can preferably maintain an excellent color tone even after the heat treatment.

[0038] The form of the silicate blue pigment (PA) of the present embodiment is not particularly limited, but is preferably in a particulate form 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] When the silicate blue pigment (PA) of this embodiment is in the form of particles, the average particle size thereof 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, another inorganic or organic material 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 component of the silicate blue pigment (PA), and preferably contains the component of the silicate blue pigment (PA-1) represented by formula (1). Furthermore, the silicate blue pigment (PA) may 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 entire 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] 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 the silicate blue pigment (PA) of the present embodiment together with coloring materials of other colors in a predetermined pattern to a substrate, or the silicate blue pigment (PA) may be mixed with other coloring materials to express a color tone different from that 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 suitably 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, ceramics, and other ceramic colorants.

[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 therefore is also favorably used as a colorant for various inks, for example, inkjet inks.

[0051] (Method for Producing Silicate 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 firing step of firing 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 blue pigment (PA) according to this embodiment can be suitably produced by a method including a mixing step of mixing a Na compound, an M compound, an oxide of Si, and a Mn compound as raw materials to obtain a mixture, and a firing step of reacting the mixture obtained in the mixing step to synthesize the target product. It is also possible to use a microwave heating method or a method called water-assisted solid-state reaction, in which the firing step is carried out at a relatively low temperature in the presence of a small amount of water.

[0052] <Mixing Step> In the mixing step, raw materials, ie, an Na compound, an M compound, an oxide of Si, and an Mn compound, are mixed together 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] Na compounds include NaCl, Na ２ CO ３ 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 the M compound include MCO ３ , MO, etc., and MCO ３ For example, the Ca compound is preferably CaCO ３ , CaO, etc., and CaCO ３ As the Sr compound, SrCO３ , SrO, etc., and SrCO ３ The Ba compound is preferably BaCO ３ , BaO, etc., and BaCO ３ As the Mn compound, MnO ２ , MnCO ３ In this embodiment, Mn oxide, i.e., MnO ２ is preferred.

[0055] Examples of oxides of Si include SiO ２ Among these, amorphous silica is preferred.

[0056] The raw materials for the silicate blue pigment (PA) of this embodiment may be in any shape, but are preferably in particulate form, which allows multiple raw materials to be mixed appropriately 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 materials for the silicate-based 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. Furthermore, the solid-phase reaction in the firing step can proceed more favorably, improving the productivity of the inorganic pigment. In this step, the raw materials are typically first weighed and mixed according to the stoichiometric ratio. For example, when producing the silicate-based blue pigment (PA) of this embodiment, the stoichiometric ratio refers to the ratio of the blending amounts of the raw materials theoretically calculated from the formula (A) above and the doping amount of Mn. On the other hand, when producing the silicate-based blue pigment (PA-1), the ratio refers to the ratio of the blending amounts of the raw materials theoretically calculated from the general formula (1) above.

[0058] The mixing method may be a general method using a mortar, a ball mill, or the like. Furthermore, 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 amount according to 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, for example, when the amount of Na compound according to the stoichiometric ratio is 100 parts by mass, the total amount of Na compound blended may be in the range of 101 parts by mass to 150 parts by mass. That is, when the amount of Na compounds according to the above stoichiometric ratio is 100 parts by mass, the total amount of Na compounds to be blended may be 102 parts by mass (referred to as an excess of 2% by mass) or more, 105 parts by mass (referred to as an excess of 5% by mass) or more, 110 parts by mass (referred to as an excess of 10% by mass) or more, 120 parts by mass (referred to as an excess of 20% by mass) or more, 130 parts by mass (referred to as an excess of 30% by mass) or more, and may be 150 parts by mass (referred to as an excess of 50% by mass) or less, 140 parts by mass (referred to as an excess of 40% by mass) or less, or 130 parts by mass (referred to as an excess of 30% 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% by mass or more and 20% by mass or less, and particularly preferably 10% by mass or more and 20% by mass or less. By setting the amount of the Na compound within this range, handling properties are improved when removing the target product from the container after the firing step.

[0061] When the Na compound is blended in an amount exceeding the stoichiometric ratio, the Na compound is preferably NaCl or NaOH, and more preferably NaCl. When the Na compound is blended in an amount exceeding the stoichiometric ratio, in the following examples (where the Na compound is NaCl), no residual Cl was observed in the final product based on the X-ray diffraction pattern or X-ray fluorescence analysis (XRF) results, suggesting that the Na compound acts as a flux. Furthermore, in some examples, samples with 0% excess NaCl (samples blended in the stoichiometric ratio) were observed to yield almost no target product, suggesting that molten NaCl affects the diffusion rate.

[0062] <Firing Step> 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 more and 1500° C. or less. The heating time in the firing step is preferably 5 hours or more and 24 hours or less.

[0065] <Forming Step> The manufacturing method of this embodiment may further include a forming step of forming the mixture of raw material powders into pellets after the mixing step and before the firing step. By forming 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, forming into pellets and firing the product also increases raw material efficiency. The forming pressure in the mixing step is preferably 5 MPa or more and 20 MPa or less.

[0066] <Washing Step> 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 disintegrated, 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.

[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: Trade name: Sodium chloride (I), 99.9%, manufactured by Kojundo Chemical Co., Ltd. ２ CO ３ Powder: Product name: Sodium carbonate, 99.8%, manufactured by Kanto Chemical Co., Ltd. BaCO ３ Powder: Product name: Barium carbonate, 4N, manufactured by Kanto Chemical Co., Ltd. SrCO ３ Powder: Product name: Strontium carbonate, 4N, manufactured by Kanto Chemical Co., Ltd. CaCO ３ Powder: Product name: Calcium carbonate, 4N, manufactured by Kanto Chemical Co., Ltd. SiO ２ Powder: Trade name: Silicon dioxide, 99.9%, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. MnO ２ Powder: Trade name: Manganese (IV) oxide, 99.5%, manufactured by Wako Pure Chemical Industries, Ltd.

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

[0070] [Ultraviolet-Visible Reflection Spectrum] Measurement 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 measurement. Formed barium sulfate was used for baseline measurement. Then, 30 mg of inorganic pigment was packed into the window (φ5 mm) of a trace powder cell (PSH-003, manufactured by JASCO Corporation) so that the packing rate was 50% or more, and the spectral reflectance of diffuse reflected light, including specular reflected light, was measured in the wavelength range of 300 to 800 nm.

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

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

[0073] [Heat Resistance Test] Measuring device: Colorimeter CR-300 (manufactured by Konica Minolta) Measuring conditions: Each inorganic pigment was compression molded and pelletized into a sample. Each sample was heated at 300°C, 600°C, and 1000°C, respectively, to measure the color temperature according to the above CIE L ＊ a ＊ b ＊ The same evaluation was carried out.

[0074] (Example 1) NaCl powder, BaCO ３ powder, SiO ２ powder, and MnO ２ Prepare powders, NaCl powder, BaCO ３ powder, SiO ２ powder, and MnO ２ The powder was mixed with the composition shown in Table 1 [Na ２ Ba ６ (Si ０．９９５Mn ０．００５ ) ４ O １５ The weights were weighed out according to the stoichiometric ratio so that the weight of the components was 1:1.

[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 [Na ２ Ba ６ (Si ０．９９５ Mn ０．００５ ) ４ O １５ A silicate-based blue pigment represented by the formula:

[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 ＊ The positive direction was yellow, and the negative direction was blue. The result was a vivid blue color. The results are shown in Table 1 and Figures 1 to 3.

[0079] (Examples 2 to 4, Comparative Example 1) Silicate-based blue pigments were produced using the compositions shown in Table 1 in the same manner as in Example 1. They were evaluated in the same manner as in Example 1. The results are shown in Table 1 and Figures 1 to 3.

[0080] Example 5 BaCO ３ Instead of powder, use CaCO ３ A silicate-based blue pigment was produced in the same manner as in Example 2, except that the powders were blended and the NaCl powder was weighed out in a 20% excess by mass (i.e., when the mass of the stoichiometric ratio was 100 parts by mass, 120 parts by mass of NaCl powder was weighed out). Powder X-ray diffraction measurement and chromaticity measurement were carried out in the same manner as in Example 1. The results are shown in Table 1 and FIG. 4.

[0081] (Examples 6 to 8) Silicate-based blue pigments were produced using the compositions 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 FIG.

[0082] Example 9 Using the silicate-based blue pigment obtained in Example 1, a heat resistance test was conducted by measuring the diffuse reflectance spectrum under the following treatment conditions: Temperature conditions: 300°C / 600°C / 900°C 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]

[0084] (Comparative Example 2) "Inorganic pigment CoAl ２ O ４ L ＊ a ＊ b ＊ Measurement of color space" Inorganic pigment CoAl obtained by the method of Non-Patent Document A1 below ２ O ４ In the same manner as in Example 1, ＊ 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 O ３ L ＊ a ＊ b ＊ Measurement of color space" Inorganic pigment YIn obtained by the method of Non-Patent Document A2 below ０．９５ Mn ０．０５ O ３ 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) The composition ratio shown in Table 2 was used, and further, BaCO ３ SrCO instead of powder ３ A silicate-based blue pigment was produced in the same manner as in Example 1, except that the powder was blended. 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 Figures 6 and 7.

[0089] (Examples 11 and 12, Comparative Example 4) The composition ratios shown in Table 2 were used, and further, BaCO ３ SrCO instead of powder ３ A silicate-based blue pigment was produced in the same manner as in Example 5, except that the powder was blended. 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 Figures 6 and 7.

[0090]

[0091] Example 13: BaCO ３ CaCO instead of powder ３ A silicate-based blue pigment was produced in the same manner as in Example 1, except that the powder was blended. 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. 8.

[0092] Examples 14 to 19 Silicate-based blue pigments were produced in the same manner as in Example 13, except that the amount of NaCl powder blended was adjusted to the amount shown in Table 3. Powder X-ray diffraction measurement and chromaticity measurement were carried out in the same manner as in Example 1. The results are shown in Table 3 and FIG. 8. In Example 18, diffuse reflectance spectrum measurement was carried out in the same manner as in Example 1. The results are shown in FIG. 11.

[0093] Examples 20 to 22 Silicate-based blue pigments were 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, 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. 9 and 11.

[0094] (Comparative Example 5) Composition ratio: Na ２ Ca ６ Si ４ O １５ A silicate-based blue pigment was produced in the same manner as in Example 18, except that the above-mentioned conditions were changed. 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 Figs. 9 and 11.

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

[0096]

[0097] (Discussion) From the results 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 Na ２ Ba ６ (Si ０．９９５ Mn ０．００５ ) ４ O １５ The sample showed the most vivid blue coloration, and no significant difference was observed between the sample synthesized using an excess amount of NaCl.

[0098] From the results in Table 2 and Figures 6 and 7, when M = Sr, the product is Sr ２ SiO ４ was obtained.

[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 Na ２ Ca ６ (Si ０．９９ Mn ０．１ ) ４ O 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 FIG. 5 confirmed high heat resistance up to 600°C.

[0102] From the results of the NaCl-flux amount (excess amount of NaCl) in Figure 8 and the XRF results in Figure 10, it was confirmed that the NaCl-flux amount (excess amount of 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 Cl from the NaCl-flux (excess amount of NaCl) was not incorporated into the crystals.

Claims

1. A blue silicate pigment in which Mn is doped into the Si site of a silicate represented by the following formula (A), and 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%). ２ M ６ S ４ O 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 claim 1, which is represented by the following general formula (1): Na ２ M ６ (Si １－ｘ Mn ｘ ) ４ O １５　　　 (In formula (1), M represents at least one selected from the group consisting of Ca, Sr, and Ba. x is 0.001 to 0.5.) 3. The silicate-based blue pigment according to claim 1, having a silicate crystal structure represented by formula (A).

4. The silicate-based blue pigment according to claim 1, 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. The silicate-based blue pigment according to claim 1, 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 a silicate-based blue pigment according to any one of claims 1 to 5, comprising: a mixing step of mixing a Na compound, an M compound, an oxide of Si and a Mn compound; and a firing step of firing the mixture obtained in the mixing step.

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

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

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

Images