Nano composite metal ion doped cobalt blue pigment for glass ink as well as preparation method and application of nano composite metal ion doped cobalt blue pigment

Abstract

The invention discloses a nano-composite metal ion doped cobalt blue pigment for glass ink as well as a preparation method and application thereof. The pigment is a nano-particle with a core-shell structure, wherein the core layer is a cobalt blue spinel phase doped with multi-element metal ions, the chemical general formula of the core layer is Co-x-y MxNyAl-z PzO, M and N are divalent metal ions, M is one or more of alkaline earth metal ions and zinc ions, and N is transition metal ions; p is a trivalent metal ion, and is one or more of a lanthanide rare earth ion and a first transition ion; and the shell layer is an amorphous silicon dioxide layer. The preparation method comprises the following steps: preparing a doped precursor by a coprecipitation method, performing high-temperature calcination to form a metal ion doped spinel core, coating a SiO shell layer by a sol-gel method, and performing medium-high-temperature heat treatment. The color development stability, the color saturation, the glossiness and the dispersity of the pigment are remarkably improved, and the pigment is adjustable in hue, bright in color and suitable for high-performance glass ink.

Description

Technical Field

[0001] This invention belongs to the field of inorganic nano-hybrid pigments, specifically relating to a high-stability, high-chromaticity cobalt blue pigment for glass decorative inks, and particularly a cobalt blue pigment modified by nanocomposite and multi-metal ion doping technology and its preparation method. Background Technology

[0002] Currently, the main blue inorganic pigments used for glass inkjet printing include Co-Al, Co-Si, and Co-Zn-Si. Co-Al cobalt blue (CoAl2O4) is a high-performance spinel-type blue inorganic pigment with advantages such as bright color, high temperature resistance, light resistance, weather resistance, and good chemical stability. It is widely used in glass, ceramics, paints and inks, engineering plastics, color television picture tubes, and high-transmittance automotive lighting. Glass ink is a suspension or emulsion containing a special glass pigment powder. In the glass decoration industry, especially for glass inks used in screen printing or inkjet printing, the performance requirements for pigments are extremely stringent. The pigments must not only maintain a stable crystal structure and color at high temperatures (usually above 800℃), but also possess extremely fine particle sizes (micrometers or submicrometers) and good dispersibility to adapt to the rheology and printing performance of the ink.

[0003] Traditional cobalt blue pigments have the following shortcomings in application and color development: (1) At high temperatures, especially in glass frit systems containing boron or phosphorus, Co²⁺ ions easily react with the glass phase, resulting in a grayish and darkened color, decreased saturation, and reduced vibrancy; (2) The hue of a single cobalt blue pigment tends towards purple, and its tinting strength is moderate to weak; (3) To achieve extremely fine particle size and obtain highly dispersible inks, the pigment usually needs to be ground later, but mechanical grinding easily damages the crystal structure and introduces lattice defects, which in turn affects its high-temperature stability and color development performance. The color of cobalt blue pigment is produced by the color-producing ions (Co²⁺ ions) in the crystal lattice. 2+ ) and coloring ions (Al 3+ and O 2- The hue and tinting intensity of cobalt blue pigment are achieved through a balance of chromatic hues, primarily depending on the Co content. 2+ The content of ions and the electronic state of d orbitals in different coordination fields. Existing research literature has adjusted the hue and stability of cobalt blue through ion doping (such as Zn²⁺, Mg²⁺, Cr³⁺, etc.), but single ion doping often sacrifices one property while improving another, making it difficult to improve the overall performance of cobalt blue pigments. Summary of the Invention

[0004] The purpose of this invention is to provide a nanocomposite metal ion-doped cobalt blue pigment for glass inks and its preparation method. This pigment achieves stable crystal structure at high temperatures, strong tinting strength, pure hue, adjustable hue, vibrant color, and easy dispersion through the dual effects of synergistic doping of multiple metal ions in the core and physical isolation by SiO2 coating on the outer shell. This makes the pigment more suitable for glass inks used in screen printing or inkjet printing.

[0005] This invention provides the following technical solution: A nanocomposite metal ion-doped cobalt blue pigment for glass ink is disclosed. This pigment consists of nanoparticles with a core-shell structure. The core layer is a cobalt blue spinel phase doped with multiple metal ions, with the general chemical formula: Co1-x-yMxNyAl2-zPzO4. Here, M and N are divalent metal ions, M being one or more of alkaline earth metal ions and zinc ions, and N being a transition metal ion. P is a trivalent metal ion, specifically one or more of lanthanide rare earth ions and first transition metal ions. x, y, and z represent molar doping amounts, with ranges of 0.02≤x≤0.20, 0.01≤y≤0.15, 0.01≤z≤0.15, and x+y≤0.35, respectively. The shell layer is an amorphous silica layer uniformly coating the surface of the core layer. By controlling the types and ratios of M and N, the blue-green hue of the pigment (from purplish-blue to sea blue) can be finely adjusted. Introducing P enhances lattice stability and finely tunes the yellow phase.

[0006] Preferably, M is Ca 2+ Mg 2+ Zn 2+ Ba 2+ One or more of the following; N is Cu 2+ Mn 2+ Ni 2+ Fe 2+ One or more of them; P is Ce 3+ La 3+ Eu 3+ Cr 3+ Fe 3+ One or more of them.

[0007] Preferably, the shell layer accounts for 5-15% of the total mass of the core-shell structured nanoparticles.

[0008] Preferably, the core-shell composite nanoparticles have an average particle size of 50-600 nm and a specific surface area of ​​10-80 m²•g. -1 The thickness of the shell is 5-30 nm.

[0009] The preparation method of the glass ink using nanocomposite metal ion-doped cobalt blue pigment includes the following steps: (1) Weigh each metal soluble salt according to the stoichiometric ratio of the general chemical formula, prepare a mixed salt solution, and prepare a coprecipitation precursor by coprecipitation method; (2) After drying the coprecipitation precursor, it is calcined at high temperature in air atmosphere to form spinel nuclei doped with various ions. After cooling, it is ground to obtain cobalt blue pigment powder doped with various metal ions. (3) The obtained cobalt blue pigment powder is coated with a SiO2 shell layer by sol-gel method to obtain a cobalt blue pigment powder with a composite core-shell structure coated with an amorphous SiO2 layer. (4) The prepared composite cobalt blue pigment powder coated with SiO2 shell is heat-treated under medium and high temperature conditions to enhance the density and bonding force of the SiO2 shell. After cooling, the nano-composite metal ion doped cobalt blue pigment for glass ink is obtained.

[0010] Preferably, in step (1) preparation of the coprecipitation precursor: under stirring, the mixed salt solution and the precipitant are combined and added to the dispersant solution for coprecipitation reaction; after the reaction is completed, the metal ion-doped coprecipitation precursor is obtained by filtration, washing and drying.

[0011] Preferably, step (3) of coating SiO2 shell by sol-gel method: the prepared cobalt blue pigment powder is dispersed in a solvent and ultrasonically dispersed until a uniform suspension is formed; under heating conditions, an ethanol solution of tetraethyl orthosilicate (TEOS) is slowly added dropwise to the suspension while stirring, and ammonia water is added dropwise as a catalyst to control the hydrolysis and polycondensation reaction rate of TEOS; after the addition is completed, the reaction is continued under stirring to make SiO2 uniformly deposited on the surface of pigment particles; after the reaction is completed, the powder is centrifuged, washed and dried to obtain the composite cobalt blue pigment powder coated with SiO2 layer.

[0012] Preferably, the conditions for the coprecipitation reaction in step (1) are: pH value controlled at 8.5-10.0, temperature at 50-80℃, and time at 1.5-3.5h.

[0013] Preferably, the total metal ion concentration of the mixed salt solution in step (1) is 0.3-2.5 mol•L. -1 .

[0014] Preferably, the conditions for high-temperature calcination in step (2) are: temperature 800-1200℃, time 1-2.5h, and heating rate to calcination temperature of 5-8℃•min. -1 .

[0015] Preferably, the high temperature conditions in step (4) are heat treatment at 500-800℃ for 1-2.5h.

[0016] Preferably, the temperature of the hydrolysis-condensation reaction in step (3) is 50-80℃ and the time is 5-10h.

[0017] Preferably, the precipitant in step (1) is one or more of Na2CO3, NaHCO3, (NH4)2CO3, NH4HCO3, (NH4)2C2O4, NH3H2O, urea or NaOH solution; and the dispersant is one or more of polyethylene glycol, polyvinylpyrrolidone, polyacrylamide, and Triton X-100.

[0018] Preferably, the solvent in step (3) is a mixture of ethanol, isopropanol and water.

[0019] The present invention has the following advantages over the prior art: (1) This invention uses high temperature conditions to replace Co in the cobalt blue pigment lattice by introducing different metal ions for doping. 2+ Or Al 3+ The position of the ion effectively controls the hue of cobalt blue pigment, broadens the color system of cobalt blue pigment, and improves the chromatic saturation. This multi-ion synergistic design effectively reduces the cost of cobalt blue pigment while realizing the "customizability" of the color performance of cobalt blue pigment.

[0020] (2) By designing multi-metal ion synergistic doping, the present invention optimizes the lattice energy state of spinel and improves the intrinsic stability of the lattice at high temperature; the outer amorphous SiO2 shell can physically isolate the pigment nucleus from the direct contact with the glass melt at high temperature, significantly suppressing the migration effect of Co²⁺. Under this dual protection, the color stability of the pigment in the glass ink sintering process is qualitatively improved.

[0021] (3) The pigment of the present invention has nanoscale particles and a smooth SiO2 shell surface, which reduces hard agglomeration and van der Waals forces between particles, so that the pigment can be well dispersed in organic solvents or water-based systems. It can achieve the fineness and stability required for ink without strong grinding, avoids crystal damage caused by excessive grinding, and greatly improves the ink applicability of pigment powder.

[0022] (4) The present invention adopts a combination of coprecipitation and sol-gel method. By controlling the precipitation, calcination and TEOS hydrolysis conditions, the core composition, particle size and shell thickness can be precisely controlled. The method has controllable conditions, mature process route and is easy to scale up for industrial production. Attached Figure Description

[0023] Figure 1 These are transmission electron microscope (TEM) images of the nano-composite cobalt blue pigment (P1) prepared in Example 1 of the present invention at different magnifications.

[0024] Figure 2 These are scanning electron microscope (SEM) images of the nano-composite cobalt blue pigment (P1) prepared in Example 1 of the present invention at different magnifications.

[0025] Figure 3 The XRD patterns are those of the metal ion-doped cobalt blue pigment (C1) prepared in Example 1 of the present invention and the pure cobalt blue pigment (D1) prepared in Comparative Example 1. Detailed Implementation

[0026] The present invention will be further described below through specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0027] Example 1 1. Preparation of doped precursor (Co0.7Zn0.2Cu0.1Al1.9Cr0) by co-precipitation method. 05 Fe0. 05 O4) Weigh out Co(NO3)2·6H2O, Zn(NO3)2·6H2O, Cu(NO3)2·6H2O, Al(NO3)3·9H2O, Cr(NO3)3·9H2O, and Fe(NO3)3·6H2O, and prepare a 1.0 mol•L solution according to the molar ratio of Co:Zn:Cu:Al:Cr:Fe = 0.7:0.2:0.1:1.9:0.05:0.05. -1 A mixed aqueous solution. With stirring, 1.5 mol•L -1 A (NH4)2C2O4 solution was slowly added dropwise to the above mixed solution, and then the mixture was added to a 1.5 wt% polyvinylpyrrolidone solution, controlling the pH at 9.5 and the temperature at 65℃. The reaction was carried out with stirring for 2.5 h, followed by filtration, washing, and drying at 105℃ for 4 h. The precursor was then placed in a programmable temperature-controlled muffle furnace and heated at 5℃•min under an air atmosphere. -1 The mixture was heated to 1100℃ and calcined for 2.5 hours. After natural cooling, it was ground to obtain metal ion-doped cobalt blue powder pigment (C1).

[0028] 2. Sol-gel method for coating SiO2 shell 15g of the above-mentioned powdered pigment C1 was weighed and dispersed in 300mL of a mixed solvent of ethanol:isopropanol:water (volume ratio 1:1:1), and ultrasonically dispersed for 60min until a uniform suspension was formed. Under a 65℃ water bath, an ethanol solution of tetraethyl orthosilicate (TEOS) (a mixture of 7.5mL TEOS and 75mL ethanol, equivalent to a theoretical SiO2 shell coating of approximately 8.0wt%) was slowly added dropwise to the suspension while stirring. Simultaneously, an ethanol solution of ammonia (a mixture of 7.5mL ammonia and 75mL ethanol) was added dropwise as a catalyst to control the hydrolysis and condensation of TEOS. After the addition was complete, the reaction was continued at the same temperature and with stirring for 8.0h to allow SiO2 to be uniformly deposited on the surface of the pigment particles. After the reaction was completed, the pigment was centrifuged, washed, and dried (90℃) to obtain a composite core-shell structured cobalt blue pigment coated with an amorphous SiO2 layer.

[0029] 3. Medium and high temperature heat treatment The dried composite cobalt blue pigment was heat-treated at 700℃ for 2.5 h to obtain the final product P1. TEM showed that its average particle size was about 300 nm and the SiO2 shell thickness was about 20 nm.

[0030] Example 2 Change the type of dopant ion, according to Co 0.7 Mg 0.2 Ni 0.1 Al 1.9 Cr 0.05 Ce 0.05 Core layer powder (C2) was prepared using the same O4 formulation. The coating steps were the same as in Example 1, except that the amount of TEOS was adjusted to achieve a theoretical SiO2 coating amount of 8 wt%. The product P2 was obtained by heat treatment at 700°C for 2.5 h.

[0031] Example 3 Change the type of dopant ion, according to Co 0.7 Ca 0.2 Mn 0.1 Al 1.9 Cr 0.05 La 0.05 Core layer powder (C3) was prepared using the same O4 formulation. The coating steps were the same as in Example 1, except that the amount of TEOS was adjusted to achieve a theoretical SiO2 coating amount of 8 wt%. The product P3 was obtained by heat treatment at 700°C for 2.5 h.

[0032] Example 4 Change the type of dopant ion, according to Co 0.7 Ba 0.2 Fe 0.1 Al 1.9 Cr 0.05 Eu 0.05Core layer powder (C4) was prepared using the same O4 formulation. The coating steps were the same as in Example 1, except that the amount of TEOS was adjusted to achieve a theoretical SiO2 coating amount of 8 wt%. The product P4 was obtained by heat treatment at 700°C for 2.5 h.

[0033] Comparative Example 1 To prepare pure cobalt blue (CoAl2O4) pigment, a precursor was prepared by co-precipitation method with a Co:Al ratio of 1:2. The precursor was calcined at 1100℃ for 2.5 h, and then ground after natural cooling to obtain cobalt blue pigment D1 without other metal ions.

[0034] Comparative Example 2 The cobalt blue pigment D1 obtained in Comparative Example 1 was coated according to the steps in Example 1, with the amount of TEOS adjusted to achieve a theoretical SiO2 coating amount of 8wt%. The product D2 was obtained by heat treatment at 700°C for 2.5 hours.

[0035] Comparative Example 3 Cobalt blue powder pigment C1 was prepared using the same formulation and process as in Example 1, but without SiO2 coating and subsequent heat treatment, and was directly used as pigment D3.

[0036] Pigment color development performance test The pigments from Examples 1, 2, 3, and 4, and Comparative Examples 1, 2, and 3 were mixed with low-melting-point glass powder (mainly composed of PbO-P2O5-SiO2) in the same proportion (15 wt%), and organic carriers (diethylene glycol butyl ether acetate, sorbitan monooleate, and ethyl cellulose) were added to prepare glass inks. These inks were then screen-printed onto flat glass and placed in a programmable temperature-controlled muffle furnace at 5 °C / min in an air atmosphere. -1 The temperature was raised to 650℃ and sintered for 15 minutes. The color (CIE Lab system) and gloss of the sintered coating were tested, and the uniformity of pigment color development was observed. The results are shown in Table 1 below: Table 1

[0037] Table data explanation: The larger the negative values ​​of a and b, the purer and deeper the blue; the larger the color saturation C* value, the more vibrant the color.

[0038] The color development performance test results of the prepared pigments in the table above show that the nanocomposite pigments P1, P2, P3, and P4 prepared by the technology of this invention have a more vivid and pure blue color (larger negative values ​​for a* and b*), a significantly higher color saturation (C*) than the comparative examples, and higher gloss, indicating that the pigments have better stability and lower reactivity in glass glazes. Comparative Example 1 (pure cobalt blue) has a grayish color and is not vivid enough, with low color saturation; Comparative Example 2 is a composite pigment of pure cobalt blue pigment (undoped) coated with a SiO2 shell, with a dark color and low color saturation and gloss; Although the color development performance of Comparative Example 3 (doped but uncoated) is better than that of pure cobalt blue (D1), it is inferior to the doped and coated composite pigments of this invention in terms of color saturation, gloss, and uniformity, which fully demonstrates that the SiO2 shell plays a key role in protecting the doped core and preventing the migration effect of color-producing ions Co²⁺ at high temperatures.

[0039] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Those skilled in the art can make various additions, improvements, or extensions without departing from the scope of the present invention. The scope of protection of the present invention is determined by the appended claims.

Claims

1. A nanocomposite metal ion-doped cobalt blue pigment for glass ink, characterized in that, The pigment is a core-shell structured nanoparticle; the core layer is a cobalt blue spinel phase doped with multiple metal ions, with the general chemical formula: Co1-x-yMxNyAl2-zPzO4, where M and N are both divalent metal ions, M is one or more of alkaline earth metal ions and zinc ions, and N is a transition metal ion; P is a trivalent metal ion, and is one or more of lanthanide rare earth ions and first transition metal ions; x, y, and z are molar doping amounts, with the ranges being: 0.02≤x≤0.20, 0.01≤y≤0.15, 0.01≤z≤0.15, and x+y≤0.35, respectively; the shell layer is an amorphous silicon dioxide layer uniformly coated on the surface of the core layer.

2. The nanocomposite metal ion-doped cobalt blue pigment for glass ink according to claim 1, characterized in that, M is Ca 2+ Mg 2+ Zn 2+ Ba 2+ One or more of the following; N is Cu 2+ Mn 2+ Ni 2+ Fe 2+ One or more of them; P is Ce 3+ La 3+ Eu 3+ Cr 3+ Fe 3+ One or more of them.

3. The nanocomposite metal ion-doped cobalt blue pigment for glass ink according to claim 1 or 2, characterized in that, The shell layer accounts for 5-15% of the total mass of the core-shell structured nanoparticles.

4. The nanocomposite metal ion-doped cobalt blue pigment for glass ink according to claim 1, characterized in that, The nanoparticles of the core-shell composite structure have an average particle size of 50-600 nm and a specific surface area of ​​30-70 m²•g. -1 The thickness of the shell is 5-30 nm.

5. The method for preparing nanocomposite metal ion-doped cobalt blue pigment for glass ink according to any one of claims 1-4, characterized in that, Includes the following steps: (1) Weigh each metal soluble salt according to the stoichiometric ratio of the general chemical formula, prepare a mixed salt solution, and prepare a coprecipitation precursor by coprecipitation method; (2) After drying the coprecipitation precursor, it is calcined at high temperature in air atmosphere to form spinel nuclei doped with various ions. After cooling, it is ground to obtain cobalt blue pigment powder doped with various metal ions. (3) The obtained cobalt blue pigment powder is coated with a SiO2 shell layer by sol-gel method to obtain a cobalt blue pigment powder with a composite core-shell structure coated with an amorphous SiO2 layer. (4) The prepared composite cobalt blue pigment powder coated with SiO2 shell is heat-treated under medium and high temperature conditions and cooled to obtain the nano-composite metal ion doped cobalt blue pigment for glass ink.

6. The preparation method according to claim 5, characterized in that, Step (1) Preparation of coprecipitation precursor: Under stirring, the mixed salt solution and precipitant are combined and added to the dispersant solution for coprecipitation reaction; after the reaction is completed, the metal ion-doped coprecipitation precursor is obtained by filtration, washing and drying. Step (3) Sol-gel method for coating SiO2 shell: The prepared cobalt blue pigment powder is dispersed in a solvent and ultrasonically dispersed until a uniform suspension is formed; under heating conditions, an ethanol solution of TEOS is slowly added dropwise to the suspension while stirring, and ammonia water is added dropwise as a catalyst to control the hydrolysis and condensation reaction rate of TEOS; after the addition is completed, the reaction is continued under stirring to make SiO2 uniformly deposited on the surface of the pigment particles; after the reaction is completed, the powder is separated by centrifugation, washed and dried to obtain the composite cobalt blue pigment powder coated with SiO2 layer.

7. The preparation method according to claim 6, characterized in that, The conditions for the coprecipitation reaction in step (1) are: pH value of 8.5-10.0, temperature of 50-80℃, and time of 1.5-3.5h.

8. The preparation method according to claim 5, 6, or 7, characterized in that, The total metal ion concentration of the mixed salt solution in step (1) is 0.3-2.5 mol•L. -1 The conditions for high-temperature calcination in step (2) are: temperature 800-1200℃, time 1-2.5h, and heating rate to the calcination temperature of 5-8℃•min. -1 The high-temperature conditions described in step (4) are heat treatment at 500-800℃ for 1-2.5h.

9. The preparation method according to claim 6 or 7, characterized in that, The precipitant in step (1) is one or more of Na2CO3, NaHCO3, (NH4)2CO3, NH4HCO3, (NH4)2C2O4, NH3H2O, urea, or NaOH solution; the dispersant is one or more of polyethylene glycol, polyvinylpyrrolidone, polyacrylamide, or Triton X-100; the hydrolysis-condensation reaction in step (3) is carried out at a temperature of 50-80℃ for 5-10 hours; the solvent in step (3) is a mixture of ethanol, isopropanol, and water.

10. The application of the nanocomposite metal ion-doped cobalt blue pigment in glass ink according to any one of claims 1-4.

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