Modified ceramic pigments and dispersions and methods for their preparation

Abstract

The application belongs to the technical field of ceramic pigments, and relates to a modified praseodymium yellow pigment, a modified praseodymium yellow pigment dispersion liquid, a ceramic inkjet ink and a preparation method and application thereof. The application aims at the problems of complicated surface modification steps of inorganic pigments and difficult treatment of waste acid or waste alkali, and adopts a sol-gel method to prepare the praseodymium yellow pigment, and introduces an organic substituent trialkoxysilane as an organic silicon source, so as to improve the dispersion stability of the praseodymium yellow pigment in an organic solvent. In addition, by adjusting the feeding sequence of the sol-gel method, the organic substituent is grafted on the outside of the praseodymium yellow pigment particles, so that the dispersion stability of the praseodymium yellow pigment is improved, the color rendering performance is ensured, and the problems of color brilliance reduction or yellow degree deviation are avoided.

Description

Technical Field

[0001] This invention belongs to the field of ceramic pigment technology, and specifically relates to a modified praseodymium yellow pigment, a modified praseodymium yellow pigment dispersion, ceramic inkjet ink, and their preparation methods and applications. Background Technology

[0002] Ceramic inkjet printing technology is a ceramic decorative material technology developed with the support of modern computer technology. Compared with traditional ceramic decoration processes, it can achieve very high resolution, accurately reproduce complex patterns, subtle textures, and color transitions, and supports rapid design pattern changes. It is ideal for small-batch production or personalized customization needs, while eliminating the need for pre-production work such as plate making, shortening the production cycle and reducing costs. Therefore, ceramic inkjet printing technology has high market potential. The preparation of ceramic inkjet ink is the most critical part of the entire ceramic inkjet printing technology. Ceramic inkjet ink typically contains inorganic non-metallic pigments (colorants, glazes), binders, solvents, dispersants, surfactants, and other additives. Among these, inorganic non-metallic pigments are the most important component of the ink. According to the process standards of inkjet printing technology, the average particle size of inorganic non-metallic pigments is less than 200nm, with a narrow particle size distribution range, no particle aggregation, good dispersion stability, and minimal influence from solvents and other substances.

[0003] Currently, praseodymium yellow ceramic pigment (Pr-ZrSiO4) is the most widely used yellow pigment in ceramics. Praseodymium yellow ceramic pigment belongs to the zirconium-based pigment family and possesses excellent properties such as bright color, high temperature resistance, corrosion resistance, and strong tinting strength. It also exhibits excellent adaptability to glazes. In industrial production, the most common method for synthesizing praseodymium yellow pigment is the solid-state synthesis method, which uses SiO2, ZrO2, and Pr6O4. 11 It is prepared by high-temperature calcination of mineralizing agents under sealed conditions.

[0004] In the preparation of ceramic inkjet ink films, according to process standards, ceramic pigment particles are ultra-finely pulverized to the submicron level. Conventional yellow ceramic pigments such as vanadium zirconium yellow and nickel titanium yellow are difficult to develop color after high-intensity crushing. Only praseodymium yellow pigment has a certain hue after ultra-fine pulverization. Moreover, the structure of praseodymium yellow pigment is not destroyed under high temperature conditions, and it can maintain stable color development. Therefore, praseodymium yellow pigment is suitable for the preparation of ceramic inks.

[0005] However, the main component of praseodymium yellow pigment is zirconium silicate, with a theoretical chemical composition of 67.2 wt% ZrO2 and 32.8 wt% SiO2. Because both ZrO2 and SiO2 have hydroxyl groups on their surfaces, exhibiting high polarity, praseodymium yellow pigment is difficult to disperse in low-polarity organic solvents, easily leading to agglomeration and poor dispersion stability, making it difficult to meet the process standards of ceramic inkjet printing technology. A conventional method is to use coupling agents to surface-treat praseodymium yellow pigment, thereby improving pigment agglomeration and dispersion in low-polarity organic solvents. However, this method requires pretreatment with strong acids, strong oxidants, or strong alkalis to thoroughly expose the polar groups on the surface before modification with coupling agents. This results in a cumbersome process and the problem of difficult-to-treat waste acid or alkali, making it unsuitable for large-scale industrial processing of praseodymium yellow pigment. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the technical problem to be solved by this invention is to provide a modified praseodymium yellow pigment prepared by a sol-gel method, wherein the organosilicon source uses a combination of orthosilicate organic esters and organically substituted trialkoxysilanes. By adjusting the order of adding different organosilicon sources, the problem of praseodymium yellow pigment being difficult to disperse in low-polarity organic solvents is improved, while ensuring the color performance of praseodymium yellow pigment.

[0007] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0008] Firstly, a modified praseodymium yellow pigment is prepared by a sol-gel method, the raw materials of which include: organosilicon source, zirconium source and praseodymium source;

[0009] The organosilicon source includes two combinations: an organic ester of orthosilicate and an organically substituted trialkoxysilane. The organic ester of orthosilicate is selected from any one or more of methyl orthosilicate, ethyl orthosilicate, propyl orthosilicate, and the oligomers corresponding to methyl orthosilicate, ethyl orthosilicate, and propyl orthosilicate.

[0010] The general structural formula of the orthosilicate ester oligomer is: R0 is any one or more of methyl, ethyl, and propyl; n is a positive integer greater than or equal to 1; preferably, 1 ≤ n ≤ 10; more preferably, 1 ≤ n ≤ 5;

[0011] Preferably, the orthosilicate organic ester oligomer is an orthosilicate oligomer.

[0012] The general structural formula of organically substituted trialkoxysilanes is:

[0013] Wherein, R1 is selected from any one of methyl, ethyl or isopropyl, and R2 is selected from a straight-chain, branched, cyclic alkyl or aromatic group with 1 to 12 carbon atoms, or a straight-chain, branched, cyclic alkyl or aromatic group with 1 to 12 carbon atoms substituted with alkenyl, amino, imino, hydroxyl, carboxyl, ether or epoxy groups.

[0014] Preferably, R2 is selected from straight-chain, branched, cyclic alkyl or aromatic groups with 1 to 8 carbon atoms, or straight-chain, branched, cyclic alkyl or aromatic groups with 1 to 8 carbon atoms substituted with alkenyl, amino, imino, hydroxyl, carboxyl, ether or epoxy groups.

[0015] Preferably, the organic substituent trialkoxysilane is selected from any one or more of methyltrimethoxysilane, methyltriethoxysilane, n-butyltrimethoxysilane, n-butyltriethoxysilane, tert-butyltrimethoxysilane, tert-butyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, n-octyltrimethoxysilane, n-octyltriethoxysilane, isooctyltrimethoxysilane, isooctyltriethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, anilinemethyltrimethoxysilane, and anilinemethyltriethoxysilane.

[0016] Zirconium source selected from Zr 4+ A salt solution of ions; preferably, the zirconium source is selected from any one of ZrCl4, Zr(SO4)2 or Zr(NO3)4; more preferably, the zirconium source is selected from Zr(NO3)4;

[0017] Praseodymium source is selected from Pr 3+ A salt solution of ions; preferably, the praseodymium source is selected from either PrCl3 or Pr(NO3)3; more preferably, the zirconium source is selected from Pr(NO3)3;

[0018] Preferably, the molar ratio of the organosilicon source, zirconium source, and praseodymium source is (1.1-1.8):1:(0.01-0.10);

[0019] More preferably, the molar ratio of the organosilicon source, zirconium source, and praseodymium source is (1.2-1.5):1:(0.03-0.06);

[0020] Preferably, the molar percentage of orthosilicate organic ester in the organosilicon source is 1-15%; more preferably, the molar percentage of orthosilicate organic ester in the organosilicon source is 5-15%.

[0021] The specific steps of the sol-gel method include: mixing organic ester of orthosilicate, zirconium source, praseodymium source, water and alcohol solvent, adjusting the pH of the system to 3-5, reacting for 1-4 hours before adjusting the pH of the system to 7-8, and then adding organic substituents, trialkoxysilane, and continuing the reaction at a constant temperature for 1-4 hours.

[0022] The alcohol solvent is selected from any one or more of methanol, ethanol, n-propanol, and isopropanol;

[0023] Preferably, hydrochloric acid, sulfuric acid, or nitric acid is used to adjust the pH of the system to 3-5; more preferably, nitric acid is used to adjust the pH of the system to 3-5.

[0024] Preferably, sodium hydroxide or ammonia is used to adjust the pH of the system to 7-8; more preferably, ammonia is used to adjust the pH of the system to 7-8.

[0025] Preferably, after the heat preservation reaction is completed, the product is allowed to stand and age.

[0026] Preferably, the aging time is 12 to 36 hours;

[0027] Preferably, the temperature during the aging process is controlled at 40–60°C;

[0028] Preferably, after aging, the modified praseodymium yellow pigment is obtained by drying.

[0029] Preferably, the drying includes vacuum drying or spray drying; further, the temperature of the vacuum drying is 70–100°C.

[0030] Secondly, a praseodymium yellow pigment dispersion comprises: the modified praseodymium yellow pigment described above, an organic solvent, and a dispersant.

[0031] The organic solvent is selected from n-alkanes, isoalkanes, cycloalkanes, aromatic hydrocarbons or petroleum fractions with 6 to 20 carbon atoms, wherein the petroleum fraction is a mixture of n-alkanes, isoalkanes, cycloalkanes and aromatic hydrocarbons.

[0032] Preferably, the organic solvent is selected from petroleum fractions; more preferably, the organic solvent is selected from 200# solvent oil;

[0033] Preferably, the dispersant is selected from wetting and dispersing agents; more preferably, the dispersant is selected from DISPER BYK-2200 dispersant.

[0034] Thirdly, the preparation method of the above-mentioned praseodymium yellow pigment dispersion includes: dispersing the above-mentioned modified praseodymium yellow pigment in an organic solvent.

[0035] Preferably, the dispersion process includes heating the mixture to 40–60°C;

[0036] Preferably, the dispersion process includes: ultrasonic-assisted dispersion of the mixture for 10 to 60 minutes.

[0037] Fourthly, a ceramic inkjet ink comprising the praseodymium yellow pigment dispersion described above.

[0038] Fifthly, the above-mentioned praseodymium yellow pigment dispersion is used as a colorant in ceramic inkjet printing.

[0039] The beneficial effects of this invention are as follows: by preparing praseodymium yellow pigment by sol-gel method, it is more convenient to adjust the type and amount of organosilicon source participating in the reaction. In addition to conventional orthosilicate organic esters, organosilicon sources also introduce organic substituents, such as trialkoxysilanes, thereby increasing the compatibility of modified praseodymium yellow pigment with organic solvents and improving the dispersion stability of modified praseodymium yellow pigment in organic solvents.

[0040] In addition, by adjusting the feeding sequence of the sol-gel method, the organic ester of orthosilicate reacts first with the zirconium source and praseodymium source, and then the organic substituent trialkoxysilane is added to continue the hydrolysis-condensation reaction. This prevents the steric hindrance effect of the organic substituent from hindering the early reaction. Thus, the organic substituent is grafted onto the outside of the praseodymium yellow pigment particles, which improves the dispersion stability of the modified praseodymium yellow pigment while ensuring its color performance, avoiding problems such as decreased color brightness or yellowness deviation. Attached Figure Description

[0041] Figure 1 The ATR-IR spectrophotometric results are for the praseodymium yellow pigment prepared in Example 3 and Comparative Example 1, and the raw material tert-butyltrimethoxysilane.

[0042] Figure 2 This is a transmission electron microscope (TEM) image of the praseodymium yellow pigment dispersion prepared in Example 3. Detailed Implementation

[0043] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0044] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0045] Unless otherwise specified, the experimental conditions used in the examples are generally in accordance with conventional conditions in the art or the conditions recommended by the reagent company. Unless otherwise specified, the materials and reagents used in the examples can be purchased commercially.

[0046] Example 1

[0047] Pr6O 11 A 0.1 mol / L Pr(NO3)3 solution was prepared by dissolving Pr(NO3)3 in concentrated HNO3. Tetraethyl orthosilicate and methyltrimethoxysilane were separately dissolved in anhydrous ethanol to prepare 50 wt% solutions. Zr(NO3)4·5H2O was prepared to prepare a 0.1 mol / L Zr(NO3)4 solution. The molar ratio of methyltrimethoxysilane, tetraethyl orthosilicate, Zr(NO3)4 and Pr(NO3)3 was 0.15:1.25:1:0.05. First, tetraethyl orthosilicate, Zr(NO3)4, and Pr(NO3)3 were added to a flask in the above proportions. The pH of the mixture was adjusted to 3.5 using nitric acid, and the mixture was heated to 70°C and stirred for 1 hour. Then, the pH of the mixture was adjusted to 7-8 using ammonia. The prescribed amount of methyltrimethoxysilane was added, and the mixture was kept at 70°C for 1.5 hours to obtain a sol. The sol was aged at 50°C for 24 hours and then dried under vacuum at 90°C to obtain a yellow powder.

[0048] Example 2

[0049] Pr6O 11A 0.1 mol / L Pr(NO3)3 solution was prepared by dissolving Pr(NO3)3 in concentrated HNO3. Tetraethyl orthosilicate and aniline methyltriethoxysilane were separately dissolved in anhydrous ethanol to prepare 50 wt% solutions. Zr(NO3)4·5H2O was prepared to prepare a 0.1 mol / L Zr(NO3)4 solution. The molar ratio of aniline methyltriethoxysilane, tetraethyl orthosilicate, Zr(NO3)4, and Pr(NO3)3 was 0.18:1.22:1:0.04. First, tetraethyl orthosilicate, Zr(NO3)4, and Pr(NO3)3 were added to a flask in the above proportions. The pH of the mixture was adjusted to 3.5 using nitric acid, and the mixture was heated to 70°C and stirred for 1 hour. Then, the pH of the mixture was adjusted to 7-8 using ammonia. The formulated amount of aniline methyltriethoxysilane was added, and the mixture was kept at 70°C for 1.5 hours to obtain a sol. The sol was aged at 50°C for 24 hours and then dried under vacuum at 80°C to obtain a yellow powder.

[0050] Example 3

[0051] Pr6O 11 A 0.1 mol / L Pr(NO3)3 solution was prepared by dissolving Pr(NO3)3 in concentrated HNO3. Tetraethyl orthosilicate and tert-butyltrimethoxysilane were separately dissolved in anhydrous ethanol to prepare 50 wt% solutions. Zr(NO3)4·5H2O was prepared to prepare a 0.1 mol / L Zr(NO3)4 solution. The molar ratio of tert-butyltrimethoxysilane, tetraethyl orthosilicate, Zr(NO3)4 and Pr(NO3)3 was 0.15:1.25:1:0.03. First, tetraethyl orthosilicate, Zr(NO3)4, and Pr(NO3)3 were added to a flask in the above proportions. The pH of the mixture was adjusted to 3.5 using nitric acid, and the mixture was heated to 70°C and stirred for 1 hour. Then, the pH of the mixture was adjusted to 7-8 using ammonia. The formulated amount of tert-butyltrimethoxysilane was added, and the mixture was kept at 70°C for 1.5 hours to obtain a sol. The sol was aged at 50°C for 24 hours and then dried under vacuum at 80°C to obtain a yellow powder.

[0052] Example 4

[0053] Pr6O 11A 0.1 mol / L Pr(NO3)3 solution was prepared by dissolving Pr(NO3)3 in concentrated HNO3. Tetraethyl orthosilicate, tetraethyl orthosilicate oligomer with an average degree of polymerization of 4 (JH-T40, Jianghan New Materials), and phenyltriethoxysilane were each dissolved in anhydrous ethanol to prepare 50 wt% solutions. A 0.1 mol / L Zr(NO3)4 solution was prepared by preparing Zr(NO3)4·5H2O. The molar ratio of phenyltriethoxysilane, tetraethyl orthosilicate, JH-T40, Zr(NO3)4, and Pr(NO3)3 was 0.15:1.10:0.15:1:0.05. First, tetraethyl orthosilicate, JH-T40, Zr(NO3)4 and Pr(NO3)3 were added to a flask in the above proportions. The pH of the mixture was adjusted to 3.5 with nitric acid, and the mixture was heated to 70°C and stirred for 1 hour. Then, the pH of the mixture was adjusted to 7-8 with ammonia. The formulated amount of phenyltriethoxysilane was added and the mixture was kept at 70°C for 2 hours to obtain a sol. The sol was aged at 50°C for 24 hours and then dried under vacuum at 80°C to obtain a yellow powder.

[0054] Example 5

[0055] Pr6O 11 A 0.1 mol / L Pr(NO3)3 solution was prepared by dissolving Pr(NO3)3 in concentrated HNO3. Tetraethyl orthosilicate, tetraethyl orthosilicate oligomer with an average degree of polymerization of 4 (JH-T40, Jianghan New Materials), and n-octyltriethoxysilane were each dissolved in anhydrous ethanol to prepare 50 wt% solutions. A 0.1 mol / L Zr(NO3)4 solution was prepared by preparing Zr(NO3)4·5H2O. The molar ratio of n-octyltriethoxysilane, tetraethyl orthosilicate, JH-T40, Zr(NO3)4, and Pr(NO3)3 was 0.13:1.10:0.12:1:0.04. First, tetraethyl orthosilicate, JH-T40, Zr(NO3)4, and Pr(NO3)3 were added to a flask in the above proportions. The pH of the mixture was adjusted to 3.5 using nitric acid, and the mixture was heated to 70°C and stirred for 1 hour. Then, the pH of the mixture was adjusted to 7-8 using ammonia. Next, the prescribed amount of n-octyltriethoxysilane was added, and the mixture was kept at 70°C for 2.5 hours to obtain a sol. The sol was then aged at 50°C for 24 hours and then dried under vacuum at 90°C to obtain a yellow powder.

[0056] Example 6

[0057] Pr6O 11A 0.1 mol / L Pr(NO3)3 solution was prepared by dissolving Pr(NO3)3 in concentrated HNO3. Methyl orthosilicate, tetraethyl orthosilicate oligomer with an average degree of polymerization of 4 (JH-T40, Jianghan New Materials), and 3-aminopropyltrimethoxysilane were each dissolved in anhydrous ethanol to prepare 50 wt% solutions. Zr(NO3)4·5H2O was prepared to prepare a 0.1 mol / L Zr(NO3)4 solution. The molar ratio of 3-aminopropyltrimethoxysilane, methyl orthosilicate, JH-T40, Zr(NO3)4, and Pr(NO3)3 was 0.15:1.15:0.05:1:0.06. First, methyl orthosilicate, JH-T40, Zr(NO3)4 and Pr(NO3)3 were added to a flask in the above proportions. The pH of the mixture was adjusted to 3.5 with nitric acid, and the mixture was heated to 60°C and stirred for 1 hour. Then, the pH of the mixture was adjusted to 7-8 with ammonia. The prescribed amount of 3-aminopropyltrimethoxysilane was added, and the mixture was kept at 60°C for 1.5 hours to obtain a sol. The sol was aged at 50°C for 24 hours and then dried under vacuum at 90°C to obtain a yellow powder.

[0058] Example 7

[0059] Pr6O 11 A 0.1 mol / L Pr(NO3)3 solution was prepared by dissolving Pr(NO3)3 in concentrated HNO3. Methyl orthosilicate and γ-(2,3-epoxypropoxy)propyltrimethoxysilane were separately dissolved in anhydrous ethanol to prepare 50 wt% solutions. Zr(NO3)4·5H2O was prepared to prepare a 0.1 mol / L Zr(NO3)4 solution. The molar ratio of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, methyl orthosilicate, Zr(NO3)4 and Pr(NO3)3 was 0.15:1.35:1:0.05. First, methyl orthosilicate, Zr(NO3)4, and Pr(NO3)3 were added to a flask in the above proportions. The pH of the mixture was adjusted to 3.5 using nitric acid, and the mixture was heated to 60°C and stirred for 1 hour. Then, the pH of the mixture was adjusted to 7-8 using ammonia. The prescribed amount of γ-(2,3-epoxypropoxy)propyltrimethoxysilane was added, and the mixture was kept at 60°C for 2 hours to obtain a sol. The sol was then aged at 50°C for 24 hours and then dried under vacuum at 80°C to obtain a yellow powder.

[0060] Comparative Example 1

[0061] Pr6O 11A 0.1 mol / L Pr(NO3)3 solution was prepared by dissolving Pr(NO3)3 in concentrated HNO3. A 50 wt% solution was prepared by dissolving tetraethyl orthosilicate and tetraethyl orthosilicate oligomer (JH-T40, Jianghan New Materials) with an average degree of polymerization of 4 in anhydrous ethanol. A 0.1 mol / L Zr(NO3)4 solution was prepared by dissolving Zr(NO3)4·5H2O. The molar ratio of tetraethyl orthosilicate, JH-T40, Zr(NO3)4 and Pr(NO3)3 was 1.15:0.15:1:0.05. First, tetraethyl orthosilicate, JH-T40, Zr(NO3)4 and Pr(NO3)3 were added to a flask in the above proportions. The pH of the mixture was adjusted to 3.5 with nitric acid, and the mixture was heated to 70°C and stirred for 1 hour. Then, the pH of the mixture was adjusted to 7-8 with ammonia. After reacting at 70°C for 1.5 hours, a sol was obtained. The sol was aged at 50°C for 24 hours and then dried under vacuum at 80°C to obtain a yellow powder.

[0062] Comparative Example 2

[0063] Pr6O 11 A 0.1 mol / L Pr(NO3)3 solution was prepared by dissolving Pr(NO3)3 in concentrated HNO3. Tetraethyl orthosilicate and methyltrimethoxysilane were separately dissolved in anhydrous ethanol to prepare 50 wt% solutions. Zr(NO3)4·5H2O was prepared to prepare a 0.1 mol / L Zr(NO3)4 solution. The molar ratio of methyltrimethoxysilane, tetraethyl orthosilicate, Zr(NO3)4 and Pr(NO3)3 was 0.15:1.25:1:0.05. Methyltrimethoxysilane, tetraethyl orthosilicate, Zr(NO3)4, and Pr(NO3)3 were added to a flask in the above proportions. The pH of the mixture was adjusted to 3.5 with nitric acid, and the mixture was heated to 70°C and stirred for 1 hour. The pH of the mixture was then adjusted to 7-8 with ammonia. The mixture was kept at 70°C for 2 hours to obtain a sol. The sol was aged at 50°C for 24 hours and then dried under vacuum at 90°C to obtain a yellow powder.

[0064] Preparation and testing of dispersions

[0065] Infrared spectral structural characterization: The ATR-infrared spectra of the praseodymium yellow pigment prepared in Example 3 and Comparative Example 1, as well as tert-butyltrimethoxysilane, were compared and tested. The results are as follows: Figure 1 As shown.

[0066] 10g of DISPER BYK-2200 (BYK) was dissolved and dispersed evenly in 100mL of 200# solvent oil. Then, 150g of the yellow powder from Examples 1-7 and Comparative Examples 1-2 was weighed and added to the solvent oil. The mixture was then transferred to an ultrasonic cleaner and heated to 40°C. After ultrasonic-assisted dispersion for 30min, a dispersion of praseodymium yellow pigment was obtained.

[0067] Average particle size test of dispersion: The average particle size of the praseodymium yellow pigment dispersions prepared in Examples 1-7 and Comparative Examples 1-2 was tested using a Mastersizer 3000 laser diffractometer.

[0068] Transmission electron microscopy (TEM) testing of the dispersion: 5 μL of the praseodymium yellow pigment dispersion prepared in Example 3 was dropped onto a TEM test grid. The morphology of the praseodymium yellow pigment particles in the dispersion was observed using a JEM-1230 transmission electron microscope at 120 kV. The results are as follows: Figure 2 As shown.

[0069] Dispersion stability test: 150 mL of the dispersed samples from Examples 1-7 and Comparative Examples 1-2 were added to 250 mL stoppered graduated cylinders, placed on a test tube rack, and their stability and dispersibility were observed. After standing for 30 min, the position of pigment sedimentation in the system was recorded. The formula for calculating the dispersion stability W is as follows:

[0070] W = (H - h) / H × 100%

[0071] In the formula: h is the sedimentation volume (mL), H is the total volume of the dispersion (mL), and W is the dispersion stability (%). The lower the sedimentation height, the higher the corresponding dispersion stability W.

[0072] Colorimetric testing: The L*a*b* values ​​of the dispersion samples prepared in Examples 1-7 and Comparative Examples 1-2 were tested using a spectrophotometer. L* represents lightness, with the lightness axis ranging from pure black (0) to pure white (100). a* represents red (+) to green (–), with redness values ​​a* gradually increasing from 0 to +99.9 and greenness values ​​a* gradually increasing from 0 to –99.9. b* represents yellow (+) to blue (–), with yellowness values ​​b* gradually increasing from 0 to 99.9 and blueness values ​​b* gradually increasing from 0 to –99.9. Therefore, a higher lightness value L* indicates a more vibrant color in the sample, and a higher yellowness value b* indicates a higher degree of yellowness in the sample. The yellow colorimetric effect of the praseodymium yellow pigment dispersion can be comprehensively evaluated using both the lightness value L* and the yellowness value b*.

[0073] The test results are listed in Table 1.

[0074] Table 1

[0075]

[0076] Analysis of the results in Table 1 shows that Examples 1-7 and Comparative Examples 1-2 all used the sol-gel method to prepare praseodymium yellow pigment and praseodymium yellow pigment dispersions. In Examples 1-7, different types of organic substituents (trialkoxysilanes) were added during the sol-gel preparation process to change the surface of the praseodymium yellow pigment from polar to nonpolar. By introducing alkyl groups onto the surface of the praseodymium yellow pigment particles, its dispersion stability in nonpolar solvents was improved. On the other hand, the preparation method of first hydrolyzing organic orthosilicate, Zr(NO3)4, and Pr(NO3)3, and then adding organic substituents (trialkoxysilanes) for condensation reaction, can improve dispersion stability while ensuring the color performance of praseodymium yellow pigment, avoiding problems such as decreased color brightness or yellowness deviation.

[0077] Comparative Example 1 did not use organic substituents trialkoxysilane. Instead, it used tetraethyl orthosilicate, Zr(NO3)4, and Pr(NO3)3 as raw materials to prepare praseodymium yellow pigment via a sol-gel reaction. The final praseodymium yellow pigment had a strong surface polarity and was difficult to disperse stably in non-polar solvents.

[0078] In Comparative Example 2, tetraethyl orthosilicate, an organically substituted trialkoxysilane, Zr(NO3)4, and Pr(NO3)3 were simultaneously added to the reaction. The organically substituted trialkoxysilane contained organic alkyl segments, which had poor compatibility with other inorganic raw materials, leading to incomplete reaction and affecting the color development ability of the praseodymium yellow pigment. Compared with Examples 1-7, the praseodymium yellow pigment dispersion prepared in Comparative Example 2 showed a decrease in both the brightness value L* and the yellowness value b* in the corresponding chromaticity parameters. Furthermore, the simultaneous addition method used in Comparative Example 2 also affected the dispersion stability of the praseodymium yellow pigment. Without the alkyl segments being introduced to the surface of the praseodymium yellow pigment, it was difficult to improve its compatibility with organic solvents, thus reducing the dispersion stability of the praseodymium yellow pigment prepared in Comparative Example 2.

[0079] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of them. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention. Although the specific embodiments of the present invention have been described above, they are not intended to limit the protection scope of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A modified praseodymium yellow pigment, characterized in that, Modified praseodymium yellow pigment was prepared by the sol-gel method, and its raw materials included: organosilicon source, zirconium source and praseodymium source; Zirconium source selected from Zr 4+ Salt solutions of ions; Praseodymium source is selected from Pr 3+ Salt solutions of ions; The organosilicon source includes two combinations: organic esters of orthosilicate and organically substituted trialkoxysilanes. The organic esters of orthosilicate are selected from any one or more of methyl orthosilicate, ethyl orthosilicate, propyl orthosilicate, and their corresponding oligomers. The general structural formula of organic silicate oligomers is: R0 is any one or more of methyl, ethyl, and propyl; n is a positive integer greater than or equal to 1; The general structural formula of organically substituted trialkoxysilanes is: R1 is selected from any one of methyl, ethyl or isopropyl, and R2 is selected from straight-chain, branched, cyclic alkyl or aromatic groups with 1 to 12 carbon atoms, or straight-chain, branched, cyclic alkyl or aromatic groups with 1 to 12 carbon atoms substituted with alkenyl, amino, imino, hydroxyl, carboxyl, ether or epoxy groups. The molar ratio of the organosilicon source, zirconium source, and praseodymium source is (1.1-1.8):1:(0.01-0.10); The molar percentage of orthosilicate organic ester in the organosilicon source is 1-15%; The specific steps of the sol-gel method include: mixing the organic ester of orthosilicate, the zirconium source, the praseodymium source, water and an alcohol solvent; first, adjusting the pH of the system to 3-5 and reacting for 1-4 hours; then adjusting the pH of the system to 7-8, adding the organic substituent trialkoxysilane and continuing the reaction for 1-4 hours; and then allowing it to stand for aging and drying to obtain the modified praseodymium yellow pigment. The alcohol solvent is selected from any one or more of methanol, ethanol, n-propanol, and isopropanol.

2. The modified praseodymium yellow pigment according to claim 1, characterized in that, The R2 is selected from straight-chain, branched, cyclic alkyl, or aromatic groups with 1 to 8 carbon atoms, or straight-chain, branched, cyclic alkyl, or aromatic groups with 1 to 8 carbon atoms substituted with alkenyl, amino, imino, hydroxyl, carboxyl, ether, or epoxy groups.

3. The modified praseodymium yellow pigment according to claim 1, characterized in that, The organic substituent trialkoxysilane is selected from any one or more of methyltrimethoxysilane, methyltriethoxysilane, n-butyltrimethoxysilane, n-butyltriethoxysilane, tert-butyltrimethoxysilane, tert-butyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, n-octyltrimethoxysilane, n-octyltriethoxysilane, isooctyltrimethoxysilane, isooctyltriethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, anilinemethyltrimethoxysilane, and anilinemethyltriethoxysilane.

4. The modified praseodymium yellow pigment according to claim 1, characterized in that, Use hydrochloric acid, sulfuric acid, or nitric acid to adjust the pH of the system to 3-5.

5. The modified praseodymium yellow pigment according to claim 1, characterized in that, Use sodium hydroxide or ammonia to adjust the pH of the system to 7-8.

6. The modified praseodymium yellow pigment according to claim 1, characterized in that, The aging time is 12-36 hours.

7. The modified praseodymium yellow pigment according to claim 1, characterized in that, The temperature during the aging process is controlled at 40~60℃.

8. The modified praseodymium yellow pigment according to claim 1, characterized in that, The drying process includes vacuum drying or spray drying.

9. A praseodymium yellow pigment dispersion, characterized in that, The praseodymium yellow pigment dispersion comprises the modified praseodymium yellow pigment as described in any one of claims 1-8, an organic solvent, and a dispersant; The organic solvent is selected from n-alkanes, isoalkanes, cycloalkanes, aromatic hydrocarbons, or petroleum fractions with 6 to 20 carbon atoms, wherein the petroleum fractions are mixtures of n-alkanes, isoalkanes, cycloalkanes, and aromatic hydrocarbons.

10. A method for preparing the praseodymium yellow pigment dispersion as described in claim 9, characterized in that, The modified praseodymium yellow pigment according to any one of claims 1-8 is obtained by dispersing it in an organic solvent containing a dispersant.

11. A ceramic inkjet ink comprising the praseodymium yellow pigment dispersion of claim 9.

12. The application of the praseodymium yellow pigment dispersion as described in claim 9 as a colorant in ceramic inkjet printing.

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