Preparation method of high-strength, high-weatherability, easy-to-disperse nano-level pigment yellow 155 applied to inkjet colorant

Abstract

The application discloses a preparation method of high-strength, high-weather-resistance and easily-dispersed nano-level pigment yellow 155 applied to ink-jet colorant, and belongs to the technical field of organic pigments. In the coupling reaction stage, the coupling components include bisacetylacetoparaphenylenediamine and potassium p-sulfonate base bisethylaniline, wherein the amount of the potassium p-sulfonate base bisethylaniline is 2-5% of the mass of the bisacetylacetoparaphenylenediamine. The method specifically comprises the following six steps: diazotization reaction, coupling component preparation, coupling reaction, pressure filtration and washing, pigmentation and desolventization and drying. The single-function coupling component potassium p-sulfonate base bisethylaniline is introduced, the chain termination effect of which effectively controls the molecular weight and particle size of the pigment, and the sulfonic acid group provides excellent surface charge and dispersion stability. The method is simple in process, does not need long-time mechanical grinding, avoids crystal type damage and energy waste, is low in production cost, stable in product quality and suitable for industrial large-scale production.

Description

Technical Field

[0001] This invention relates to the field of organic pigment technology, specifically to a method for preparing a high-strength, high-weather-resistant, and easily dispersible nanoscale pigment yellow 155 for use in inkjet color pastes. Background Technology

[0002] Pigment Yellow 155 is an important diazo organic pigment, characterized by its bright color, strong tinting strength, excellent lightfastness (7-8 grade), and good heat resistance (up to 200℃). It is widely used in coatings, plastics, inks, and other fields. The traditional preparation method involves the diazotization of dimethyl 2-aminoterephthalate followed by a coupling reaction with diacetyl-p-phenylenediamine. This mature process ensures the stable production of products that meet industrial standards.

[0003] However, with the rapid development of inkjet technology in textile printing, packaging printing, advertising printing, ceramic decoration, and other fields, inkjet pigments have placed extremely stringent requirements on pigments. Firstly, there are particle size requirements. Inkjet printhead nozzles typically have a diameter of 20-50 micrometers, requiring the pigment particle size to be controlled at the nanometer level (D). 99 <200nm, D 50 The pigments must be <100nm in size and have a uniform particle size distribution to avoid clogging the nozzles. Traditional processes typically produce pigments with particle sizes between 0.5-3 micrometers, which is insufficient to meet these requirements. Secondly, dispersion stability is crucial; the pigment must remain stable in the dispersion medium for extended periods without sedimentation or flocculation. Traditional pigments, however, suffer from insufficient surface modification and poor dispersion stability. Thirdly, tinting strength is critical due to the extremely small droplet size, requiring pigments with exceptionally high tinting strength. Furthermore, inkjet pigments must possess excellent lightfastness and weather resistance to meet long-term usage requirements.

[0004] Currently, the main methods for preparing nanoscale organic pigments include mechanical grinding, recrystallization, and chemical synthesis. Mechanical grinding is energy-intensive and time-consuming, and it can damage the pigment's crystal structure, leading to decreased tinting strength, increased surface defects, and affecting dispersion stability. While recrystallization can yield particles with intact crystal structures, solvent recovery is difficult, costs are high, and yields are low, making it unsuitable for industrial production. Chemical synthesis (in-situ preparation) is the most ideal method, allowing control over particle size, crystal form, and surface properties from the source, eliminating the need for subsequent grinding. However, it is technically challenging and requires precise control of various factors during the synthesis process.

[0005] Therefore, there is an urgent need to develop a Pigment Yellow 155 product that simultaneously possesses nanoscale particle size, high coloring strength, easy dispersibility, and high weather resistance. Summary of the Invention

[0006] Based on the problems existing in the background technology, the present invention provides a method for preparing high-strength, high-weather-resistant, and easily dispersible nanoscale pigment yellow 155 for inkjet color paste. By introducing a specific monofunctional auxiliary coupling component, potassium sulfonate-based bis(ethylaniline), into the coupling reaction, precise control of particle size, crystal form, and surface properties is achieved, avoiding subsequent mechanical grinding, maintaining the integrity and excellent performance of pigment crystals, and significantly reducing production costs.

[0007] This invention is implemented through the following technical solutions: The first aspect of this invention discloses a method for preparing high-strength, high-weather-resistant, and easily dispersible nanoscale pigment yellow 155 for inkjet color pastes. In the coupling reaction stage, the coupling components include diacetyl-p-phenylenediamine and potassium p-sulfonate diethylaniline.

[0008] Potassium sulfonate-based diethylaniline is a monofunctional coupling component, with only one end capable of reacting with diazonium salts. When participating in the coupling reaction, it acts as a chain terminator, effectively controlling the molecular weight of pigment molecules and preventing excessive polymerization to form large molecular aggregates. Simultaneously, the sulfonic acid groups in potassium sulfonate-based diethylaniline possess strong hydrophilicity, playing a role in crystal form regulation during pigment crystal nucleation and growth, guiding the formation of nanoscale fine crystals. The sulfonic acid groups can also be distributed on the surface of pigment particles, providing surface charge and hydrophilicity, endowing the pigment with inherent dispersibility.

[0009] Furthermore, the amount of potassium sulfonate diethylaniline used is 2-5% of the mass of diacetyl-p-phenylenediamine.

[0010] Furthermore, the preparation method of Pigment Yellow 155 specifically includes the following steps: (1) Diazotization reaction: Dimethyl 2-aminoterephthalate was reacted with sodium nitrite under acidic conditions to obtain a diazonium salt solution; (2) Preparation of coupling components: Add water to a dissolving tank, then add EDTA, diacetyl-p-phenylenediamine and potassium sulfonate diethylaniline, add alkali and dispersant, and slurry at room temperature to obtain a mixed coupling component solution; (3) Coupling reaction: Add water and acid to the coupling tank, add the mixed coupling component solution obtained in step (2), adjust the pH value to 5-6, and cool to 0-15℃; add the diazonium salt solution obtained in step (1) to carry out the coupling reaction and obtain the coupling product. (4) Filtration and washing: The coupling product is filtered by pressure and washed with water until neutral to obtain a wet filter cake; (5) Pigmentation: Add organic solvent and emulsifier to the pigmentation kettle, add the wet filter cake obtained in step (4), slurry at high speed, seal the reaction kettle, replace with nitrogen 1-3 times, raise the temperature and control the pressure to carry out pigmentation treatment; (6) Desolventizing and drying: The organic solvent is recovered by distillation. The substrate is cooled by pressure filtration, washed until neutral, and dried to obtain nano-sized pigment yellow 155.

[0011] Furthermore, in step (1), the acidic conditions are provided by hydrochloric acid with a concentration of 31%; the diazotization reaction is carried out at 0-10°C for 1-3 hours.

[0012] Furthermore, in step (2), the alkali solution is a 32% concentration liquid alkali, and the dispersant is OA-12.

[0013] Furthermore, in step (3), the acid is acetic acid with a concentration of 60%.

[0014] Furthermore, in step (3), the pH value is controlled at 4-4.5 with alkali solution during the coupling reaction; after the coupling reaction is completed, continue stirring for 0.3-2 hours, then heat to 85-90℃ and keep warm while stirring for 1-3 hours.

[0015] Furthermore, in step (5), the organic solvent is isobutanol, the emulsifier is emulsifier FM, the pigmentation treatment temperature is 120-125℃, the pressure inside the reactor is less than 0.5MPa, and the treatment time is 1-3 hours.

[0016] The second aspect of this invention discloses pigment yellow 155 prepared by the above preparation method.

[0017] The third aspect of this invention discloses the application of the pigment yellow 155 in inkjet inks.

[0018] The beneficial effects of this invention are: First, the method of this invention can directly prepare nanoscale pigment yellow 155, with a product particle size D. 50 Controlled within 50-100nm, D 99 With a particle size of less than 200 nm and a uniform, narrow distribution, the product fully meets the stringent requirements of inkjet pigments for pigment particle size, avoiding nozzle clogging issues. While achieving nanoscale particle size, the product's tinting strength is not reduced but increased, exceeding that of conventional pigment Yellow 155 by 10-15% and approximately 20% higher than nanoscale products prepared by mechanical grinding, thus meeting the high tinting strength requirements of inkjet pigments. By introducing sulfonic acid groups into the pigment molecular structure, the product exhibits excellent dispersibility, forming stable dispersion systems in both aqueous and solvent-based dispersion media. Its dispersion stability is significantly superior to traditional products, and the prepared inkjet pigments do not exhibit sedimentation or flocculation during long-term storage.

[0019] Secondly, the method of this invention is simple in process, eliminating the need for lengthy mechanical grinding, thus avoiding problems such as crystal structure damage, decreased coloring power, and increased energy consumption caused by grinding, and significantly reducing production costs. Because nano-sizing and surface modification are achieved during the synthesis stage, the stability and consistency between product batches are greatly improved, and color difference is controlled within a very small range. The raw materials of this invention are readily available, and the process parameters are easy to control, making it suitable for large-scale industrial production and possessing good economic benefits and market promotion value. Detailed Implementation

[0020] The technical solution of the present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

[0021] Example 1: This example describes the preparation of a high-strength, high-weather-resistant, and easily dispersible nano-scale pigment yellow 155 for inkjet color pastes. The specific steps include: (1) Diazotization reaction: Add 500 kg of water and 235 kg of hydrochloric acid (31% concentration) to the diazo tank and stir until homogeneous. Add 0.5 kg of EDTA (99% purity) through the feed port and stir until dissolved. Add 209 kg of dimethyl 2-aminoterephthalate (99% purity) under continuous stirring and slurry for 1.5 hours to ensure full dispersion. Add 200 kg of crushed ice and an appropriate amount of water to lower the temperature to 0-5℃ and stabilize it within this temperature range. Dissolve 70 kg of sodium nitrite (98% purity) in water to prepare a 25% aqueous solution. Under the condition of maintaining the temperature at 0-5℃, slowly add the sodium nitrite solution through a high-level metering tank, controlling the addition rate to ensure the reaction temperature does not exceed 5℃, and the addition time is about 30 minutes. After the addition is completed, continue stirring and reacting for 2 hours. The resulting diazonium salt solution is kept at a low temperature in the diazo tank for later use.

[0022] (2) Preparation of coupling components: Add 800 kg of water and 0.5 kg of EDTA (99% purity) to the dissolving tank and stir until the EDTA is completely dissolved. Then add 140.6 kg of diacetyl-p-phenylenediamine (99% purity) and 4.4 kg of potassium p-sulfonate diethylaniline (99% purity). Add 250 kg of liquid alkali (32% concentration) to the dissolving tank through the high-level liquid tank and stir continuously during the addition. Add 3 kg of dispersant OA-12 and continue stirring. Under normal temperature conditions, turn on high-speed stirring at 220 rpm and slurry for 0.6 hours to obtain the mixed coupling component solution.

[0023] (3) Coupling reaction: Add 700 kg of water and 100 kg of acetic acid (60% concentration) to the coupling tank and stir to mix. Then, use the liquid level difference to transfer the mixed coupling component solution into the coupling tank, and perform acid precipitation for 1 hour. Adjust the pH value to 5.5, and add crushed ice to lower the temperature to about 5℃. After the temperature stabilizes, transfer the diazo solution from the diazo tank into the coupling tank using the liquid level difference. The coupling reaction takes about 2.5 hours. Add 32% liquid alkali to control the pH at 4.2. After stirring for 1 hour, introduce steam to heat the temperature to 90℃, and continue stirring and keeping warm for 2 hours to obtain the coupling product.

[0024] (4) Pressure filtration and washing: The coupling product is pressure filtered and washed with water until neutral to obtain a wet filter cake.

[0025] (5) Pigmentation: Add 400 kg of isobutanol (99% purity) to the pigmentation reactor. After starting the stirrer, add the wet filter cake in batches, followed by 5 kg of emulsifier FM. Close the feed port, turn on the high-speed stirring system, set the speed to 350-400 rpm, and slurry for 2 hours to ensure the materials are fully mixed and dispersed into a uniform slurry. After slurrying, seal the reactor, open the nitrogen valve, and purge the reactor with nitrogen for 10 minutes each time, repeating twice to reduce the oxygen content in the reactor to below 1%. Raise the temperature to 122℃, control the reactor pressure to be less than 0.5 MPa, and maintain the temperature within the range of 120-125℃ for 2 hours of pigmentation reaction.

[0026] (6) Desolventizing and drying: After pigmentation, isobutanol is recovered by distillation, the distillate is cooled to 80°C by adding water, pressure filtration, washing, and drying to obtain nano-sized pigment yellow 155 product.

[0027] Example 2: This example is prepared according to the method of Example 1, except that in step two, the preparation stage of the coupling component, 142.1 kg of diacetylacetyl-p-phenylenediamine with a purity of 99% and 2.9 kg of potassium p-sulfonate diethylaniline with a purity of 99% are accurately weighed. The amount of other raw materials, process conditions and operation steps are exactly the same as in Example 1.

[0028] Example 3: This example is prepared according to the method of Example 1, except that in step two, the preparation stage of the coupling component, 138.1 kg of diacetyl-p-phenylenediamine with a purity of 99% and 6.9 kg of potassium p-sulfonate diethylaniline with a purity of 99% are accurately weighed. The amount of other raw materials, process conditions and operation steps are exactly the same as in Example 1.

[0029] Comparative Example 1: This comparative example was produced according to the traditional Pigment Yellow 155 preparation process, without the addition of the auxiliary coupling component, potassium sulfonate diethylaniline. In step two, during the preparation of the coupling component, only 145 kg of diacetyl-p-phenylenediamine was used as the coupling component, without the addition of potassium sulfonate diethylaniline; other operations were the same as in Example 1.

[0030] Comparative Example 2: Using conventional Pigment Yellow 155 prepared in Comparative Example 1 as raw material, nanoscale products were prepared by mechanical grinding. 200 kg of conventional Pigment Yellow 155, 20 kg of dispersant, 5 kg of wetting agent, and 775 kg of deionized water were mixed and ground in a sand mill. The grinding media consisted of zirconia beads with a diameter of 0.6-0.8 mm and a filling rate of 80%. The mill speed was set to 2800 rpm, and grinding was performed in a circulating manner. Particle size was measured hourly. When D... 99 Grinding is stopped when the particle size is less than 200 nm. The entire grinding process lasts approximately 18 hours and consumes a significant amount of energy. After grinding, the nanoscale pigment product is obtained through pressure filtration, washing, and drying.

[0031] Experimental example: Performance tests were conducted on the pigment yellow 155 prepared in Examples 1-3 and Comparative Examples 1-2.

[0032] 1. Particle size distribution: The particle size distribution was determined using a Malvern Mastersizer 3000 laser particle size analyzer. The sample was dispersed in deionized water (containing 0.1% dispersant), sonicated for 10 minutes, and the light occlusion was controlled at 10-20%. Each sample was tested 3 times, and the average value was taken.

[0033] 2. Tinting strength: Weigh 0.1g of pigment and 1.0g of titanium dioxide, draw 1mL of ink oil with a syringe, and grind three times on a three-roll mill, 50 revolutions each time. Scrape a sample of the ground ink and measure its tinting strength with a colorimeter, using the tinting strength of the conventional pigment yellow 155 in Comparative Example 1 (100) as a reference.

[0034] 3. Lightfastness: Tested according to ISO 105-B02 standard method. The pigment was prepared into a standard depth coating and aged using a xenon lamp aging chamber (irradiance 550W / m²). 2 After being exposed to sunlight for 500 hours at a temperature of 45±5℃ and a relative humidity of 50±10%, the samples were compared with a blue wool standard sample for grading.

[0035] 4. Heat resistance: Tested according to GB / T 5211.12 standard. Treat the pigment at a constant temperature of 200℃ for 2 hours, observe the color change, and evaluate the heat resistance level (1-5).

[0036] 5. Dispersion stability: Measured using a Malvern Zetasizer Nano ZS potential analyzer. The pigment was dispersed in deionized water at a concentration of 0.1%, and the pH was adjusted to 7.0. The Zeta potential value was measured at 25℃, and each sample was tested three times and the average value was taken.

[0037] The test results are shown in Table 1.

[0038] Table 1. Performance test results of Pigment Yellow 155 prepared in Examples 1-3 and Comparative Examples 1-2 As can be seen from the data in Table 1, Examples 1-3 prepared by the method of the present invention have significant technical advantages compared with the comparative examples.

[0039] The D50 values ​​of Examples 1-3 were 75 nm, 82 nm, and 68 nm, respectively, and the D99 values ​​were all less than 180 nm, meeting the nanoscale requirements and fully satisfying the stringent requirements for pigment particle size in inkjet inks (D99 < 200 nm). In contrast, Comparative Example 1, prepared using conventional methods, produced Pigment Yellow 155 particles that were micron-sized and unsuitable for inkjet inks. Although Comparative Example 2 achieved nanoscale size (D50 = 95 nm) through prolonged mechanical grinding (18 hours), the production cycle was long and energy consumption was high. In Examples 1-3, the particle size decreased with increasing amounts of potassium sulfonate-based diethylaniline. This is because potassium sulfonate-based diethylaniline, as a monofunctional coupling component, acts as a chain terminator, effectively controlling the molecular weight and crystal size of the pigment molecules.

[0040] The tinting strength of Examples 1-3 was increased by 15%, 12%, and 18% respectively compared to Comparative Example 1. This significant improvement is mainly attributed to two factors: first, the increased specific surface area due to the nanoscale particle size enhances the interaction between pigment and light per unit mass; second, the method of this invention directly prepares nanoparticles through chemical synthesis, maintaining the integrity and regularity of the pigment crystals and avoiding crystal structure damage caused by mechanical grinding. Although Comparative Example 2 also achieved a nanoscale particle size, its tinting strength decreased to 95%, precisely because the mechanical grinding process damaged the crystal structure, generating numerous surface defects and leading to a decline in optical performance.

[0041] Examples 1-3 all achieved a lightfastness rating of 7-8, consistent with Comparative Example 1, demonstrating that the method of this invention maintains the inherent excellent lightfastness of Pigment Yellow 155 while achieving nano-sizing. This is because the lightfastness of pigments is mainly determined by their molecular structure, and the introduced potassium sulfonate diethylaniline content is very small (2-5%), not affecting the molecular structure of the pigment matrix. Comparative Example 2's lightfastness dropped to 6-7, further demonstrating the destructive effect of mechanical grinding on the crystal structure. Examples 1-3 were consistent with Comparative Example 1; the introduction of a small amount of potassium sulfonate diethylaniline did not affect the thermal stability of the pigment matrix. Comparative Example 2's heat resistance dropped to 4, still at a good level, but significantly lower than the examples. This is consistent with the lightfastness test results; the increase in surface defects not only reduces light stability but also affects thermal stability.

[0042] Zeta potential is an important indicator for evaluating the stability of a dispersion system. Generally, when the absolute value of the Zeta potential is greater than 30 mV, the electrostatic repulsion between particles is sufficient to overcome van der Waals forces, and the dispersion system is stable. The absolute values ​​of the Zeta potentials in Examples 1-3 are all greater than 30 mV, indicating that the dispersion system is very stable. This is because the sulfonic acid groups in the introduced potassium p-sulfonate diethylaniline molecule ionize in the aqueous medium, generating strong negative charges. These negative charges are distributed on the particle surface, providing a strong electrostatic stabilizing effect. In contrast, the Zeta potential of Comparative Example 1 is only -15 mV, belonging to the critically unstable region. This is because the conventional pigment yellow 155 molecule does not contain strong ionizing groups, resulting in a weak surface charge. After mechanical grinding, the Zeta potential of Comparative Example 2 increased to -28 mV. This may be due to the increased specific surface area caused by grinding and fragmentation, exposing more surface groups. However, since no new strong ionizing groups were introduced, its Zeta potential remains below the stability threshold of 30 mV, and its dispersion stability is inferior to that of Examples 1-3.

[0043] Finally, it should be noted that the above embodiments are merely illustrative of several implementations of the present invention and are not intended to limit the scope of the invention. For those skilled in the art, any modifications, equivalent substitutions, or improvements made without departing from the concept of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing a high-strength, high-weather-resistant, and easily dispersible nano-scale pigment yellow 155 for inkjet color paste, characterized in that, During the coupling reaction stage, the coupling components include diacetylacetyl-p-phenylenediamine and potassium p-sulfonate diethylaniline.

2. The preparation method according to claim 1, characterized in that, The amount of potassium sulfonate diethylaniline used is 2-5% of the mass of diacetyl-p-phenylenediamine.

3. The preparation method according to claim 1, characterized in that, Specifically, the following steps are included: (1) Diazotization reaction: Dimethyl 2-aminoterephthalate was reacted with sodium nitrite under acidic conditions to obtain a diazonium salt solution; (2) Preparation of coupling components: Add water to a dissolving tank, then add EDTA, diacetyl-p-phenylenediamine and potassium sulfonate diethylaniline, add alkali and dispersant, and slurry at room temperature to obtain a mixed coupling component solution; (3) Coupling reaction: Add water and acid to the coupling tank, add the mixed coupling component solution obtained in step (2), adjust the pH value to 5-6, and cool to 0-15℃; add the diazonium salt solution obtained in step (1) to carry out the coupling reaction and obtain the coupling product. (4) Filtration and washing: The coupling product is filtered by pressure and washed with water until neutral to obtain a wet filter cake; (5) Pigmentation: Add organic solvent and emulsifier to the pigmentation kettle, add the wet filter cake obtained in step (4), slurry at high speed, seal the reaction kettle, replace with nitrogen 1-3 times, raise the temperature and control the pressure to carry out pigmentation treatment; (6) Desolventizing and drying: The organic solvent is recovered by distillation. The substrate is cooled by pressure filtration, washed until neutral, and dried to obtain nano-sized pigment yellow 155.

4. The preparation method according to claim 3, characterized in that, In step (1), the acidic conditions are provided by hydrochloric acid with a concentration of 31%; the diazotization reaction is carried out at 0-10°C for 1-3 hours.

5. The preparation method according to claim 3, characterized in that, In step (2), the alkali solution is a 32% liquid alkali solution and the dispersant is OA-12.

6. The preparation method according to claim 3, characterized in that, In step (3), the acid is acetic acid with a concentration of 60%.

7. The preparation method according to claim 3, characterized in that, In step (3), the pH value is controlled at 4-4.5 with alkali solution during the coupling reaction; after the coupling reaction is completed, continue stirring for 0.3-2 hours, then heat to 85-90℃ and keep warm while stirring for 1-3 hours.

8. The preparation method according to claim 3, characterized in that, In step (5), the organic solvent is isobutanol, the emulsifier is emulsifier FM, the pigmentation treatment temperature is 120-125℃, the pressure inside the reactor is less than 0.5MPa, and the treatment time is 1-3 hours.

9. A pigment yellow 155 prepared by the preparation method according to any one of claims 1-8.

10. The application of Pigment Yellow 155 according to claim 9 in inkjet inks.

Images