Preparation method of cobalt blue pigment

Abstract

The invention discloses a cobalt blue pigment preparation method, which comprises: (1) adding a cobalt source, an aluminum source and a zinc source to water, dissolving, and carrying out mixing treatment under an ultrasonic condition to obtain a mixed suspension; (2) transferring the mixed suspension into a closed reaction kettle, adding a precipitant and polyvinylpyrrolidone, stirring and mixing at room temperature, adjusting the pH value to be alkaline, carrying out a co-precipitation reaction, and filtering to obtain a precursor precipitate; (3) carrying out ball milling treatment on the precursor precipitate, dispersing the precursor precipitate in water under an ultrasonic condition, adding silicate, heating, stirring and uniformly mixing, filtering, washing and drying at low temperature to obtain cobalt blue precursor powder; and (4) calcining the cobalt blue precursor powder in a protective atmosphere, and quenching with liquid nitrogen to obtain the cobalt blue pigment. The method is simple in process, environmentally friendly and free of solvent residues, the obtained cobalt blue pigment is small in particle size and good in dispersity and color retention performance, and heavy metal ions are not separated out.

Description

Technical Field

[0001] The present invention relates to the field of pigments, and specifically relates to a preparation method of cobalt blue pigment. Background Art

[0002] Cobalt blue pigment is a high-performance inorganic pigment with the chemical formula CoAl2O4. It belongs to the spinel-structured metal oxide mixed-phase pigment. Its appearance is a blue powder with a greenish tint, with distinct and saturated hues, having a unique red or green undertone, and strong covering power, suitable for scenarios with high transparency or high coverage requirements.

[0003] CN108516593A discloses a preparation method of cobalt blue pigment, which uses aluminum salt and cobalt salt as raw materials, adds urea and mineralizer for mixing, adjusts the pH of the mixed solution for coprecipitation, and then obtains cobalt blue pigment by means of high-temperature calcination. However, sintering phenomenon will occur during high-temperature calcination in this method, resulting in large particle size and dull color of the obtained pigment, affecting the performance of the pigment.

[0004] CN118546545A discloses a nano cobalt blue pigment, its preparation method and application. It uses a composite surfactant, n-hexanol, gasoline, and aluminum alkoxide to be mixed evenly to obtain an oil phase, dissolves magnesium salt and cobalt salt in water to obtain an aqueous phase, drops the aqueous phase into the oil phase, emulsifies to obtain a microemulsion, drops ammonia water, heats and stirs for hydrolysis reaction, centrifuges, washes, dries, and calcines to obtain nano cobalt blue particles, and then conducts multiple modifications in the presence of an organic solvent to obtain cobalt blue pigment. However, in multiple steps of this method, volatile organic solvents such as n-hexanol, ethanol, formic acid, and formaldehyde are used to dissolve and disperse pigment particles to avoid particle aggregation. However, the introduction of such organic solvents poses problems of environmental pollution and may cause residues of organic solvents in the pigment, which will surely lead to an increase in preparation cost.

[0005] Therefore, there is an urgent need to find a preparation method of cobalt blue pigment with simple process, environmental friendliness, green and environmental protection, no solvent residue, small particle size, good dispersibility and good color retention of the obtained cobalt blue pigment, and no precipitation of heavy metal ions. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the above-mentioned defects existing in the prior art and provide a preparation method of cobalt blue pigment with simple process, environmental friendliness, green and environmental protection, no solvent residue, small particle size, good dispersibility and good color retention of the obtained cobalt blue pigment, and no precipitation of heavy metal ions.

[0007] The technical solution adopted by the present invention to solve its technical problem is as follows: A preparation method of cobalt blue pigment, comprising the following steps: (1) Dissolve the cobalt source, aluminum source, and zinc source in water, and then mix and process them under ultrasonic conditions to obtain a mixed suspension; the mass ratio of the cobalt source, aluminum source, and zinc source is 1.3 - 2.3:3 - 5:1. In the method of the present invention, Zn is introduced by adding a zinc source 2+ for doping modification to improve the blue light reflectivity of the pigment, thereby optimizing the optical properties of the pigment and enhancing the ability of the cobalt blue pigment to maintain its color without fading. At the dosage described, the optical and color retention properties are better; (2) Transfer the mixed suspension obtained in step (1) to a closed reaction kettle, add a precipitant and polyvinylpyrrolidone, stir and mix at room temperature, then adjust the pH value to alkaline for coprecipitation reaction, and filter to obtain a precursor precipitate; (3) After ball-milling the precursor precipitate obtained in step (2), disperse it in water under ultrasonic conditions, add silicate, heat and stir to mix evenly, filter and wash, and dry at low temperature to obtain cobalt blue precursor powder; the addition amount of the silicate is equivalent to 12 - 15% of the total mass of the cobalt source, aluminum source, and zinc source. In the method of the present invention, surface modification is carried out by adding silicate, coating on the precursor precipitate to form a core-shell structure. Under the action of electrostatic repulsion between particles, the agglomeration tendency is overcome. While improving the dispersibility, it also plays a role in encapsulating heavy metal ions to prevent their precipitation; (4) Calcinate the cobalt blue precursor powder obtained in step (3) under a protective atmosphere and rapidly cool it with liquid nitrogen to obtain cobalt blue pigment; the calcination is divided into three stages: low-temperature calcination, medium-temperature calcination, and high-temperature calcination; the low-temperature calcination is to increase the temperature to 300 - 600 °C at a rate of 5 - 10 °C / min and hold for 2 - 4 h; the medium-temperature calcination is to increase the temperature to 600 - 800 °C at a rate of 10 - 15 °C / min and hold for 1 - 3 h; the high-temperature calcination is to increase the temperature to 800 - 1100 °C at a rate of 15 - 20 °C / min and hold for 1 - 4 h. In the method of the present invention, the calcination quality can be improved by the segmented temperature control technology to ensure the purity and color stability of the cobalt blue pigment: by means of low-temperature calcination, the impurity removal time is extended; by means of medium-temperature calcination, the initial melting temperature of the silicate is controlled, so that the pigment particles and the silicate are initially combined in a vitrified state; finally, high-temperature calcination is used to promote the uniform coating of the glass phase on the pigment particles, thereby achieving the purpose of preventing the dissolution of cobalt ions and solving the problem of reducing the application safety of cobalt blue pigment due to the dissolution of cobalt ions. In addition, the segmented calcination uses a stepped temperature increase, which can reduce the microcracks caused by thermal stress, improve the density of the vitrified layer, and further improve the effect of preventing the dissolution of heavy metals, overcoming the problem of poor color fastness and poor quality of cobalt blue pigment caused by uneven color rendering when using cobalt blue pigment due to the dissolution of heavy metals.

[0008] Preferably, in step (1), the dosage of water is equivalent to 2 - 4 times the total mass of the cobalt source, aluminum source, and zinc source.

[0009] Preferably, in step (1), the power of the ultrasound is 100 - 200 W. The method of the present invention utilizes the shock wave generated when the cavitation bubbles collapse under the action of ultrasonic cavitation. Under the ultrasonic conditions, the cobalt source, aluminum source, and zinc source are fully dispersed, and the mixing effect is better.

[0010] Preferably, in step (1), the time for the mixing treatment is 30 - 40 min.

[0011] Preferably, in step (1), the cobalt source includes cobalt nitrate, etc. When using hydrates, the dosage is converted based on cobalt nitrate.

[0012] Preferably, in step (1), the aluminum source includes aluminum nitrate, etc. When using hydrates, the dosage is converted based on aluminum nitrate.

[0013] Preferably, in step (1), the zinc source includes zinc nitrate, etc. When using hydrates, the dosage is converted based on zinc nitrate.

[0014] Preferably, in step (2), the mass ratio of the precipitating agent to polyvinylpyrrolidone is 1:0.5 - 1.5. In the method of the present invention, the precipitating agent plays a role in promoting the precipitation reaction. The precipitating agent and sodium hydroxide react with the cobalt source and aluminum source to form a cobalt blue pigment precursor precipitate.

[0015] Preferably, in step (2), the addition amount of polyvinylpyrrolidone is equivalent to 1 - 3% of the total mass of the cobalt source, aluminum source, and zinc source. The method of the present invention improves the dispersibility of the coprecipitation system by adding polyvinylpyrrolidone to avoid agglomeration phenomena, which is beneficial to obtaining a nanoscale precursor precipitate.

[0016] Preferably, in step (2), the precipitating agent includes Na2CO3 and / or urea, etc.

[0017] Preferably, in step (2), the rotation speed of the stirring and mixing is 500 - 600 r / min, and the time is 20 - 30 min.

[0018] Preferably, in step (2), the pH value is adjusted to 8 - 10.

[0019] Preferably, in step (2), the pH value is adjusted with a sodium hydroxide solution having a concentration of 1 - 3 mol / L.

[0020] Preferably, in step (2), the temperature of the coprecipitation reaction is 150 - 210 °C, the pressure is 2 - 4 MPa, and the time is 6 - 12 h.

[0021] Preferably, in step (3), the rotation speed of the ball milling treatment is 60 - 80 r / min, and the time is 2 - 4 h. By optimizing the ball milling conditions, the particle size of the pigment particles is refined in the present invention method, so that the obtained cobalt blue pigment has a small particle size, no particle feeling, uniform quality, no color difference and good dispersibility. The ball milling treatment is carried out in a ball mill.

[0022] Preferably, in step (3), the diameter of the grinding balls used in the ball milling treatment is 20 - 40 mm, and the grinding balls are equivalent to 40 - 50% of the mass of the precursor precipitate. By optimizing the ball milling conditions, the particle size of the pigment particles is refined.

[0023] Preferably, in step (3), the power of the ultrasonic wave is 100 - 200 W.

[0024] Preferably, in step (3), the amount of water used is 1.5 - 2.0 times the mass of the precursor precipitate.

[0025] Preferably, in step (3), the silicate includes sodium silicate, etc.

[0026] Preferably, in step (3), the temperature of the heating and stirring is 80 - 100 °C, the stirring speed is 200 - 600 r / min, and the time is 1 - 2 h. The purpose of heating and stirring in the present invention method is to promote the reaction between the silicate and the precursor precipitate to improve the homogenization effect.

[0027] Preferably, in step (3), the temperature of the low-temperature drying is 50 - 80 °C, and the time is 10 - 15 h. By the low-temperature drying treatment at 50 - 80 °C in the present invention method, the discoloration and performance degradation of the pigment are avoided.

[0028] Preferably, in step (4), the protective atmosphere includes one or more of nitrogen, argon, helium, etc.

[0029] Preferably, in step (4), the calcined material is taken out and placed in a container, and liquid nitrogen is introduced for rapid cooling treatment. The present invention method is based on the rapid cooling treatment after calcination with liquid nitrogen to slow down the oxidation process and improve the quality of the cobalt blue pigment.

[0030] The beneficial effects of the present invention method are as follows: (1) The present invention method uses cobalt source, aluminum source and zinc source, and carries out alkali leaching coprecipitation under the dispersion of polyvinylpyrrolidone, combined with ball milling + ultrasonic dispersion to obtain cobalt blue precursor powder with good dispersibility and small particle size. Then, the calcination quality is improved by means of segmented temperature control technology to ensure the purity and color stability of the cobalt blue pigment. The whole preparation process does not need to introduce organic solvents such as n-hexanol and ethanol, has no solvent residue, and the obtained cobalt blue pigment has stable performance; (2) The present invention method improves the quality of the cobalt blue pigment by introducing Zn 2+Doping modification is carried out to improve the blue light reflectivity of the pigment, thereby optimizing the optical properties of the pigment and enhancing the ability of the cobalt blue pigment to maintain its color without fading; polyvinylpyrrolidone is introduced to improve the dispersibility of the coprecipitation system to avoid agglomeration and facilitate the obtaining of nanoscale precursor precipitates; silicate is introduced in combination for surface modification, and coating is carried out on the precursor precipitate to form a core-shell structure. Under the action of electrostatic repulsion between particles, the agglomeration tendency is overcome. While improving the dispersibility, it also plays a role in encapsulating heavy metal ions to prevent their precipitation. Detailed implementation mode

[0031] The present invention will be further described below with reference to the embodiments.

[0032] The raw materials or chemical reagents used in the examples and comparative examples of the present invention are all obtained through conventional commercial channels unless otherwise specified.

[0033] Example 1 (1) After dissolving 15 g of cobalt nitrate, 45 g of aluminum nitrate and 10 g of zinc nitrate in 180 mL of water, under the ultrasonic condition with an ultrasonic power of 100 W, the mixture is treated for 40 min to obtain a mixed suspension; Zn is introduced by adding a zinc source 2+ Doping modification is carried out to improve the blue light reflectivity of the pigment, thereby optimizing the optical properties of the pigment and enhancing the ability of the cobalt blue pigment to maintain its color without fading; by using the shock wave generated when the cavitation bubbles collapse under ultrasonic cavitation, under the ultrasonic condition, the cobalt source, aluminum source and zinc source are fully dispersed and the mixing effect is better; (2) Transfer the mixed suspension obtained in step (1) to a closed reaction kettle, add 2 g of Na2CO3 and 1 g of polyvinylpyrrolidone, stir and mix at room temperature and a rotation speed of 500 r / min for 30 min, then adjust the pH value to 8 with a 1 mol / L sodium hydroxide solution, and carry out a coprecipitation reaction at 150 °C and a pressure of 2 MPa for 12 h, and filter to obtain a precursor precipitate; The precipitating agent plays a role in promoting the precipitation reaction. The precipitating agent and sodium hydroxide react with the cobalt source and aluminum source to form a cobalt blue pigment precursor precipitate; by adding polyvinylpyrrolidone to improve the dispersibility of the coprecipitation system to avoid agglomeration, which is beneficial to obtaining nanoscale precursor precipitates; (3) Place the precursor precipitate obtained in step (2) in a ball mill. Under the conditions of a rotation speed of 60 r / min, a grinding ball diameter of 20 mm, and the mass of the grinding balls being 40% of the mass of the precursor precipitate, perform ball milling for 4 h. Then, under ultrasonic conditions with an ultrasonic power of 100 W, disperse it in water with a mass 1.5 times that of the precursor precipitate, add 9 g of sodium silicate, and heat and stir to mix evenly for 2 h at 80 °C and a stirring speed of 200 r / min. Filter and wash, and then perform low-temperature drying at 50 °C for 15 h to obtain cobalt blue precursor powder; By optimizing the ball milling conditions, the particle size of the pigment particles is refined, resulting in cobalt blue pigment with small particle size, no particle feeling, uniform quality, no color difference, and good dispersibility; by adding sodium silicate for surface modification, coating is carried out on the precursor precipitate to form a core-shell structure. Under the action of electrostatic repulsion between particles, the agglomeration tendency is overcome. While improving the dispersibility, it also plays a role in encapsulating heavy metal ions to prevent their precipitation; the purpose of heating and stirring is to promote the reaction between silicate and the precursor precipitate to improve the homogenization effect; through low-temperature drying treatment, the discoloration and performance degradation of the pigment are avoided; (4) Calcine the cobalt blue precursor powder obtained in step (3) under a nitrogen atmosphere, which is divided into three stages: low-temperature calcination, medium-temperature calcination, and high-temperature calcination. The low-temperature calcination is to heat up to 400 °C at a rate of 5 °C / min and hold for 4 h. The medium-temperature calcination is to heat up to 600 °C at a rate of 10 °C / min and hold for 3 h. The high-temperature calcination is to heat up to 900 °C at a rate of 15 °C / min and hold for 4 h. Then, take out the calcined material and place it in a container, and introduce liquid nitrogen for rapid cooling treatment to obtain 1# cobalt blue pigment; The quality of calcination can be improved through segmented temperature control technology to ensure the purity and color stability of cobalt blue pigment: by means of low-temperature calcination, the impurity removal time is extended; by means of medium-temperature calcination, the initial melting temperature of sodium silicate is controlled, enabling the preliminary vitrification combination of pigment particles and sodium silicate; finally, high-temperature calcination is used to promote the uniform encapsulation of pigment particles by the glass phase, thereby achieving the purpose of preventing the dissolution of cobalt ions and solving the problem of reducing the application safety of cobalt blue pigment due to the dissolution of cobalt ions. In addition, the segmented calcination uses a stepped heating method, which can reduce the microcracks caused by thermal stress, improve the density of the vitrification layer, and further improve the effect of preventing the dissolution of heavy metals, overcoming the problem of poor color fastness and poor quality of cobalt blue pigment caused by the uneven color depth of cobalt blue pigment during use due to the dissolution of heavy metals; based on liquid nitrogen for rapid cooling treatment after calcination to slow down the oxidation process and improve the quality of cobalt blue pigment.

[0034] Example 2 (1) Add 28 g of cobalt nitrate, 68 g of aluminum nitrate, and 12 g of zinc nitrate to 250 mL of water and dissolve. Then, under ultrasonic conditions with an ultrasonic power of 150 W, perform mixing treatment for 35 min to obtain a mixed suspension; (2) Transfer the mixed suspension obtained in step (1) to a closed reactor, add 3 g of urea and 3 g of polyvinylpyrrolidone, stir and mix for 20 min at room temperature and a rotation speed of 600 r / min, then adjust the pH value to 10 with a 3 mol / L sodium hydroxide solution, and carry out a coprecipitation reaction at 210 °C and a pressure of 4 MPa for 6 h, followed by filtration to obtain a precursor precipitate; (3) Place the precursor precipitate obtained in step (2) in a ball mill, carry out ball milling for 3 h at a rotation speed of 70 r / min, a ball diameter of 30 mm, and with the mass of the grinding balls being 45% of the mass of the precursor precipitate. Then, disperse it in water with a mass 1.5 times that of the precursor precipitate under ultrasonic conditions with an ultrasonic power of 150 W, add 13 g of sodium silicate, heat and stir to mix evenly at 90 °C and a stirring speed of 400 r / min for 1.5 h, followed by filtration and washing, and low-temperature drying at 70 °C for 12 h to obtain cobalt blue precursor powder; (4) Follow the steps of Example 1, step (4) to obtain 2# cobalt blue pigment.

[0035] Example 3 (1) Add 17 g of cobalt nitrate, 43 g of aluminum nitrate, and 9 g of zinc nitrate to 240 mL of water and dissolve. Then, under ultrasonic conditions with an ultrasonic power of 200 W, carry out a mixing treatment for 30 min to obtain a mixed suspension; (2) Transfer the mixed suspension obtained in step (1) to a closed reactor, add 3 g of Na2CO3 and 1.6 g of polyvinylpyrrolidone, stir and mix for 25 min at room temperature and a rotation speed of 550 r / min, then adjust the pH value to 9 with a 2 mol / L sodium hydroxide solution, and carry out a coprecipitation reaction at 180 °C and a pressure of 3 MPa for 8 h, followed by filtration to obtain a precursor precipitate; (3) The amount of sodium silicate used is 9 g, and the rest is the same as in step (3) of Example 2; (4) Calcinate the cobalt blue precursor powder obtained in step (3) under an argon atmosphere, which is divided into three stages: low-temperature calcination, medium-temperature calcination, and high-temperature calcination. The low-temperature calcination is to increase the temperature to 500 °C at a rate of 10 °C / min and hold for 2 h. The medium-temperature calcination is to increase the temperature to 700 °C at a rate of 15 °C / min and hold for 1 h. The high-temperature calcination is to increase the temperature to 1100 °C at a rate of 20 °C / min and hold for 2 h. Then, take out the calcined material and place it in a container, and carry out a rapid cooling treatment by introducing liquid nitrogen to obtain 3# cobalt blue pigment.

[0036] Example 4 (1) Add 20 g of cobalt nitrate, 48 g of aluminum nitrate, and 12 g of zinc nitrate to 200 mL of water and dissolve. Then, under ultrasonic conditions with an ultrasonic power of 200 W, carry out a mixing treatment for 40 min to obtain a mixed suspension; (2) The dosage of urea was 2 g, and the dosage of polyvinylpyrrolidone was 2.4 g. The remaining steps were the same as those in step (2) of Example 2; (3) The precursor precipitate obtained in step (2) was placed in a ball mill. Under the conditions that the rotation speed was 80 r / min, the diameter of the grinding balls was 40 mm, and the mass of the grinding balls was 50% of the mass of the precursor precipitate, after ball milling for 2 h, under the ultrasonic condition with an ultrasonic power of 200 W, it was dispersed in water with a mass 2.0 times that of the precursor precipitate, and 12 g of sodium silicate was added. At 100 °C and a stirring speed of 600 r / min, it was heated and stirred evenly for 1 h, filtered and washed, and then dried at a low temperature of 80 °C for 10 h to obtain cobalt blue precursor powder; (4) The same steps as in step (4) of Example 3 were followed to obtain 4# cobalt blue pigment.

[0037] Comparative Example 1 The difference between this comparative example and Example 2 was only that: in step (1), no zinc source was added, and in step (4), 5# cobalt blue pigment was finally obtained. The remaining steps were the same as those in Example 2.

[0038] Comparative Example 2 The difference between this comparative example and Example 2 was only that: in step (2), no polyvinylpyrrolidone was added, and in step (4), 6# cobalt blue pigment was finally obtained. The remaining steps were the same as those in Example 2.

[0039] Comparative Example 3 The difference between this comparative example and Example 2 was only that: in step (3), no sodium silicate was added, and in step (4), 7# cobalt blue pigment was finally obtained. The remaining steps were the same as those in Example 2.

[0040] Comparative Example 4 The difference between this comparative example and Example 2 was only that: in step (4), it was directly calcined at a high temperature of 1100 °C for 5 h, and in step (4), 8# cobalt blue pigment was finally obtained. The remaining steps were the same as those in Example 2.

[0041] A commercially available cobalt blue pigment was used as the control group (labeled as 0#), and the cobalt blue pigments obtained in Examples 1 - 4 and Comparative Examples 1 - 4 of the present invention (labeled as 1# - 8#) were subjected to light fastness tests on the cobalt blue pigments based on the standard of GB / T2115 - 2015 to evaluate color changes; based on the method of EPA3060A, dissolution solutions of 0# - 8# pigments were prepared respectively, and whether cobalt ions were dissolved in the dissolution solutions was determined by diphenylcarbazide spectrophotometry; the average particle size of the cobalt blue pigments was determined based on the microscopy method; the results are shown in Table 1.

[0042] Table 1 Performance comparison table of 0# - 8# cobalt blue pigments obtained from the control group, Examples 1 - 4 and Comparative Examples 1 - 4 of the present invention

[0043] Note: In the table, level 1 indicates severe color fading, while level 8 indicates good color retention.

[0044] As can be seen from Table 1, by comparing Example 2 of the present invention with Comparative Examples 1 to 4, it can be known that the method of the present invention can optimize the optical properties of the pigment by introducing Zn 2+ for doping modification; and by introducing polyvinylpyrrolidone and sodium silicate for synergistic cooperation, a pigment product with small particle size and good dispersibility can be prepared; in addition, since sodium silicate was not introduced for surface modification in Comparative Example 3, heavy metal ion dissolution was detected during the dissolution test of the obtained cobalt blue pigment (7#), and the pigment particle size was significantly larger than that of Example 2, indicating that sodium silicate has a positive dual effect in improving the dispersibility of the pigment and encapsulating heavy metal ions to prevent their dissolution; since stepwise calcination was not carried out in Comparative Example 4, a small amount of heavy metal ion dissolution was measured in the cobalt blue pigment, and the pigment particle size increased significantly. The reason is that during direct high-temperature calcination, the glass phase cannot evenly encapsulate the pigment particles well, affecting the effect of preventing heavy metal dissolution. In addition, direct high-temperature calcination will also enhance the interaction between pigment molecules, resulting in molecular aggregation and affecting dispersibility, while the stepwise calcination system designed by the present invention can well avoid the foregoing situation.

Claims

1. A method for preparing cobalt blue pigment, characterized in that, It includes the following steps: (1) After adding a cobalt source, an aluminum source, and a zinc source into water and dissolving them, perform a mixing treatment under ultrasonic conditions to obtain a mixed suspension; the mass ratio of the cobalt source, aluminum source, and zinc source is 1.3 - 2.3:3 - 5:1; (2) Transfer the mixed suspension obtained in step (1) to a closed reaction kettle, add a precipitant and polyvinylpyrrolidone, stir and mix at room temperature, then adjust the pH value to alkaline, carry out a coprecipitation reaction, and filter to obtain a precursor precipitate; (3) After performing ball milling treatment on the precursor precipitate obtained in step (2), disperse it in water under ultrasonic conditions, add silicate, heat and stir to mix evenly, filter and wash, and dry at a low temperature to obtain cobalt blue precursor powder; the addition amount of the silicate is equivalent to 12 - 15% of the total mass of the cobalt source, aluminum source, and zinc source; (4) Calcinate the cobalt blue precursor powder obtained in step (3) under a protective atmosphere and rapidly cool it with liquid nitrogen to obtain cobalt blue pigment; the calcination is divided into three stages: low-temperature calcination, medium-temperature calcination, and high-temperature calcination; the low-temperature calcination is to increase the temperature to 300 - 600°C at a rate of 5 - 10°C / min and hold for 2 - 4 h; the medium-temperature calcination is to increase the temperature to 600 - 800°C at a rate of 10 - 15°C / min and hold for 1 - 3 h; the high-temperature calcination is to increase the temperature to 800 - 1100°C at a rate of 15 - 20°C / min and hold for 1 - 4 h.

2. The preparation method of the cobalt blue pigment according to claim 1, characterized in that In step (1), the amount of water used is equivalent to 2 - 4 times the total mass of the cobalt source, aluminum source, and zinc source; the power of the ultrasonic wave is 100 - 200 W; the time of the mixing treatment is 30 - 40 min; the cobalt source includes cobalt nitrate; the aluminum source includes aluminum nitrate; the zinc source includes zinc nitrate.

3. The preparation method of the cobalt blue pigment according to claim 1 or 2, characterized in that, In step (2), the mass ratio of the precipitant to polyvinylpyrrolidone is 1:0.5 - 1.5; the addition amount of polyvinylpyrrolidone is equivalent to 1 - 3% of the total mass of the cobalt source, aluminum source, and zinc source; the precipitant includes Na2CO3 and / or urea.

4. The preparation method of the cobalt blue pigment according to claim 3, wherein, In step (2), the rotation speed of the stirring and mixing is 500 - 600 r / min, and the time is 20 - 30 min; adjust the pH value to 8 - 10; use a sodium hydroxide solution with a concentration of 1 - 3 mol / L to adjust the pH value; the temperature of the coprecipitation reaction is 150 - 210°C, the pressure is 2 - 4 MPa, and the time is 6 - 12 h.

5. The preparation method of the cobalt blue pigment according to claim 1 or 2, characterized in that, In step (3), the rotation speed of the ball milling treatment is 60 - 80 r / min, and the time is 2 - 4 h; the diameter of the grinding balls used in the ball milling treatment is 20 - 40 mm, and the grinding balls are equivalent to 40 - 50% of the mass of the precursor precipitate; the power of the ultrasonic wave is 100 - 200 W; the amount of water used is equivalent to 1.5 - 2.0 times the mass of the precursor precipitate; the silicate includes sodium silicate.

6. The preparation method of the cobalt blue pigment according to claim 5, wherein, In step (3), the temperature of the heating and stirring is 80 - 100°C, the stirring speed is 200 - 600 r / min, and the time is 1 - 2 h; the temperature of the low-temperature drying is 50 - 80°C, and the time is 10 - 15 h.

7. The method for preparing cobalt blue pigment according to claim 1 or 2, characterized in that, In step (4), the protective atmosphere includes one or more of nitrogen, argon, or helium.

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