Post-treatment method of permanent yellow pigment crude product and obtained permanent yellow pigment

Abstract

The invention belongs to the technical field of pigment preparation, and particularly relates to a post-treatment method of a permanent yellow pigment crude product and the obtained permanent yellow pigment, and the post-treatment method comprises the following steps: S1, dispersing the permanent yellow pigment crude product in a pigment emulsifier to form a pigment emulsion; s2, the temperature of the pigment emulsion is controlled to be gradually reduced to reach or below the freezing point of the pigment emulsion, and frozen pigment emulsion is obtained; s3, crushing and ball-milling the frozen pigment emulsion by using an ultrasonic crusher to obtain pigment ice crystals, and transferring the pigment ice crystals into a freeze-drying chamber for freeze-drying treatment to obtain pigment crystals; and S4, adding the pigment crystals into the ethanol mixture of the cellulose nanocrystals to obtain the permanent yellow pigment. The coloring performance of the pigment can be remarkably improved by post-processing the permanent yellow pigment crude product, and compared with the prior art, the stability of the high coloring performance of the pigment is further improved by changing the mode that the pigment emulsion reaches the icing state.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of pigments, and particularly relates to a post-treatment method for crude permanent yellow pigments and the obtained permanent yellow pigments. Background Art

[0002] The coloring performance of organic pigments is mainly affected by three key factors: chemical structure, crystal morphology, and particle characteristics. For pigments with a fixed crystal structure, changes in particle size will significantly affect their stability and color performance. Specifically, as the particle size increases, the surface energy of the pigment decreases, the stability increases, and within a certain range, a stronger covering effect can be provided, but at the same time, some coloring intensity may be sacrificed. On the contrary, when the particles become finer, the transparency of the pigment will increase to some extent, but due to the increase in surface energy, the stability decreases, and agglomeration is more likely to occur during the drying process, thereby weakening the coloring ability.

[0003] Taking permanent red F2R as an example, this pigment is widely used in the coating industry. In order to achieve a high covering effect, it is usually necessary to accept a certain degree of reduction in coloring power. In plastic coloring applications, the degree of refinement of pigment particles is crucial; only by crushing the particles to a size close to that of aggregates can multiple performance indicators such as coloring intensity, hue purity, gloss, and covering power be effectively improved.

[0004] Permanent yellow (CIT Pigment Yellow 12, abbreviated as PY12) is an organic pigment belonging to the azo pigment class. In order to obtain high coloring power, the patent application CN118359944A discloses a preparation method for a permanent yellow pigment with high coloring power in an aqueous system, including the following steps: S1. Add the crude permanent yellow pigment to a container equipped with a pigment emulsifier, disperse the crude permanent yellow pigment in the pigment emulsifier, then seal the container, immerse the sealed container in a liquid nitrogen tank for quick freezing, and after the quick freezing is completed, obtain the frozen crude permanent yellow pigment; S2. Crush the frozen crude permanent yellow pigment with an ultrasonic crusher, ball-mill the crushed crude permanent yellow pigment to obtain permanent yellow pigment ice crystals, transfer the permanent yellow pigment ice crystals to a freeze-drying chamber, and sublime the frozen water to obtain permanent yellow pigment crystals. The finally prepared permanent yellow pigment with high coloring power in an aqueous system has a small particle size, good dispersibility, and high coloring power.

[0005] However, for the permanent yellow pigment treated by the above method, it is found during use that its high coloring performance is not stable, there are differences between batches, and the lightfast performance of the pigment is relatively poor. Summary of the Invention

[0006] The object of the present invention is to provide a post-treatment method for crude permanent yellow pigment and the obtained permanent yellow pigment, so as to solve the problems of unstable coloring performance and poor light fastness of permanent yellow pigment in the prior art.

[0007] The present invention adopts the following technical solutions: A post-treatment method for permanent yellow pigment, comprising the following steps: S1. Dispersing the crude permanent yellow pigment in a pigment emulsifier to form a pigment emulsion; S2. Controlling the temperature of the pigment emulsion to gradually decrease to reach the freezing point of the pigment emulsion and below, to obtain a frozen pigment emulsion; S3. Crushing and ball-milling the frozen pigment emulsion with an ultrasonic crusher to obtain pigment ice crystals, and transferring the permanent yellow pigment ice crystals to a freeze-drying chamber for freeze-drying treatment to obtain pigment crystals; S4. Adding the pigment crystals to an ethanol mixture of cellulose nanocrystals (CNCs) to obtain permanent yellow pigment.

[0008] For the permanent yellow pigment prepared by a conventional method, post-treatment can improve its coloring performance to a certain extent, as recorded in the prior art CN118359944A. However, for the permanent yellow pigment treated by the above method, it is found that the high coloring performance is not stable during use and there are differences between batches. But the real reason for this problem is not clear. Therefore, the inventor carefully analyzed the post-treatment steps and continuously tried to improve the treatment steps. At first, the liquid nitrogen quick-freezing was replaced with a cooling method, which was based on cost considerations. Since the cost of liquid nitrogen is high and the consumption is large, it was replaced with a cooling method. As a result, it was unexpectedly found that after replacing the freezing adjustment of the pigment emulsion, the stability of the coloring performance was greatly improved. Moreover, through experiments, it was further verified that by adopting a multi-stage and gradual cooling method, its stability was further improved.

[0009] Preferably, before performing step S2, the pigment emulsion is subjected to high-pressure homogenization treatment. In this solution, on the basis of the above solution, an additional step of high-pressure homogenization of the pigment emulsion is added. The pigment emulsion generates strong shear force and cavitation effect under high pressure, so that the pigment particles reach the nanoscale, which can improve the light fastness of the pigment on the basis of ensuring the stable high coloring performance of the pigment.

[0010] Preferably, in step S2, controlling the temperature of the pigment emulsion to gradually decrease to reach the freezing point of the pigment emulsion and below is achieved by a temperature gradient of more than three segments that gradually decreases to reach the freezing point of the pigment emulsion and below.

[0011] Preferably, in step S2, the temperature of the pigment emulsion is controlled to be a first temperature value, a second temperature value, and a third temperature value in sequence, and the temperature difference between the second temperature value and the third temperature value does not exceed 15°C.

[0012] Preferably, the cooling rate from the second temperature value to the third temperature value does not exceed 6°C / min.

[0013] Preferably, the cooling rate from the second temperature value to the third temperature value is 2°C / min to 3°C / min.

[0014] Preferably, in step S2, the temperature of the pigment emulsion is gradually reduced to reach 5°C to 10°C below the freezing point of the pigment emulsion.

[0015] The above further optimization of the cooling process in step S2 is beneficial to further improving the stability of the high coloring performance of the pigment.

[0016] Preferably, in step S2, the pigment emulsion is stirred at a speed of 120 - 160 rpm. Stirring at an appropriate speed can increase the mixing uniformity inside the solution and promote the freezing process.

[0017] Preferably, the pigment emulsifier is sodium stearate or cocamidopropyl betaine or sorbitan monooleate.

[0018] Preferably, the conditions for high-pressure homogenization treatment are: treatment for 5 min to 30 min under a pressure of 280 bar to 350 bar.

[0019] The present invention also provides a permanent yellow pigment, which is obtained by performing the above post-treatment method on the crude permanent yellow pigment.

[0020] By implementing the above technical solutions, the present invention has the following beneficial effects: 1. By performing post-treatment on the crude permanent yellow pigment, the present invention can significantly improve the coloring performance of the pigment. Compared with the prior art, by changing the way the pigment emulsion reaches the freezing state, the stability of the high coloring performance of the pigment is further improved.

[0021] 2. The present invention further performs high-pressure homogenization treatment on the pigment emulsion before the pigment emulsion freezes, which can further improve the stability of the high coloring performance, and at the same time, also improves the light fastness of the permanent yellow pigment. Detailed Embodiments

[0022] The present invention will be further described in detail below with reference to specific embodiments.

[0023] This specific embodiment is only an interpretation of the present invention and does not limit the present invention. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as it is within the scope of the claims of the present invention, it is protected by the patent law.

[0024] The crude pigment fast yellow used in the following examples and comparative examples was prepared by the following method: Add 200 kg of water, 16.3 kg of 3,3'-dichlorobenzidine hydrochloride, and 16 kg of 35% hydrochloric acid to the diazotization reactor. Cool down to 4 °C, add 28.4 kg of 25% sodium nitrite solution, react for 30 min, decolorize with activated carbon, and filter to obtain the diazonium salt for standby.

[0025] Mix 29.91 g of 2,5-dimethoxy-4-chloroacetoacetanilide with 500 kg of water and 10 kg of 40% sodium hydroxide, add 50 kg of sodium acetate, and dropwise add 85 kg of formic acid. Couple with the diazonium salt at 10 °C, continue stirring for 30 - 60 min, heat up to 90 - 95 °C and maintain for 30 - 60 min. Filter and dry to obtain the crude product of pigment fast yellow. Of course, the post-treatment method of the present invention is also applicable to the crude pigment fast yellow obtained by other methods.

[0026] Example 1 This example provides a post-treatment method for pigment fast yellow, including the following steps: S1. Disperse the crude pigment fast yellow in an aqueous solution of sodium stearate (the mass-volume ratio of the crude pigment fast yellow to the aqueous solution of sodium stearate is 1:3) to form a pigment emulsion; S2. Control the temperature of the pigment emulsion to decrease in three stages until it reaches below the freezing point of the pigment emulsion (the first stage is maintained at 10 °C for 30 min, cooled at a rate of 2 °C / min to the second stage of 3 °C and maintained for 30 min, cooled at a rate of 2 °C / min to the third stage of -5 °C). During this period, stir the pigment emulsion at a speed of 150 rpm until the pigment emulsion is completely frozen; S3. Crush and ball-mill the frozen pigment emulsion with an ultrasonic crusher (frequency 40 kHz, process for 10 s, interval 10 s, total processing time 20 min) to obtain pigment ice crystals, transfer the pigment fast yellow ice crystals to the freeze-drying chamber, and perform freeze-drying treatment (temperature maintained at -22 °C, pressure reduced to 10 -2 mbar) to obtain pigment crystals; S4. Wet the cellulose nanocrystals (CNCs) with ethanol to obtain a cellulose nanocrystals (CNCs) colloid, and add the pigment fast yellow crystals to the cellulose nanocrystals (CNCs) colloid to obtain the pigment fast yellow.

[0027] Example 2 This example provides a post-treatment method for permanent yellow pigment, including the following steps: S1. Form an emulsion of sorbitan monooleate with hot water, and disperse the crude permanent yellow pigment in the sorbitan monooleate emulsion (the mass-volume ratio of the crude permanent yellow pigment to the sorbitan monooleate emulsion is 1:4) to form a pigment emulsion; S2. Control the temperature of the pigment emulsion to decrease in three stages until it reaches below the freezing point of the pigment emulsion (the first stage is maintained at 10 °C for 30 min, the cooling rate is 5 °C / min to the second stage of 0 °C and maintained for 30 min, and the cooling rate is 5 °C / min to the third stage of -10 °C). During this period, stir the pigment emulsion at a speed of 150 rpm until the pigment emulsion is completely frozen; S3. Crush and ball-mill the frozen pigment emulsion with an ultrasonic crusher (frequency 40 kHz, process for 10 s, interval for 10 s, total processing time 20 min) to obtain pigment ice crystals. Transfer the permanent yellow pigment ice crystals to a freeze-drying chamber for freeze-drying treatment (temperature maintained at -22 °C, pressure reduced to 10 -2 mbar) to obtain pigment crystals; S4. Wet the cellulose nanocrystals (CNCs) with ethanol to obtain a cellulose nanocrystals (CNCs) colloid, and add the permanent yellow pigment crystals to the cellulose nanocrystals (CNCs) colloid to obtain the permanent yellow pigment.

[0028] Example 3 This example provides a post-treatment method for permanent yellow pigment, including the following steps: S1. Disperse the crude permanent yellow pigment in an aqueous solution of sodium stearate (the mass-volume ratio of the crude permanent yellow pigment to the aqueous solution of sodium stearate is 1:3) to form a pigment emulsion; S2. Control the temperature of the pigment emulsion to decrease in three stages until it reaches below the freezing point of the pigment emulsion (the first stage is maintained at 10 °C for 30 min, the cooling rate is 3 °C / min to the second stage of 3 °C and maintained for 30 min, and the cooling rate is 3 °C / min to the third stage of -5 °C). During this period, stir the pigment emulsion at a speed of 150 rpm until the pigment emulsion is completely frozen; S3. Crush and ball-mill the frozen pigment emulsion with an ultrasonic crusher (frequency 40 kHz, process for 10 s, interval for 10 s, total processing time 20 min) to obtain pigment ice crystals. Transfer the permanent yellow pigment ice crystals to a freeze-drying chamber for freeze-drying treatment (temperature maintained at -22 °C, pressure reduced to 10 -2 mbar) to obtain pigment crystals; S4. Wet the cellulose nanocrystals (CNCs) with ethanol to obtain a cellulose nanocrystals (CNCs) colloid, and add the permanent yellow pigment crystals to the cellulose nanocrystals (CNCs) colloid to obtain the permanent yellow pigment.

[0029] Example 4 This example provides a post-treatment method for the permanent yellow pigment, including the following steps: S1. Disperse the crude permanent yellow pigment in an aqueous solution of sodium stearate (the mass-volume ratio of the crude permanent yellow pigment to the aqueous solution of sodium stearate is 1:3) to form a pigment emulsion; S2. Control the temperature of the pigment emulsion to decrease in three stages until it reaches below the freezing point of the pigment emulsion (the first stage is maintained at 10 °C for 30 min, and the temperature is decreased to the second stage at a rate of 3 °C / min and maintained at 3 °C for 30 min, and then decreased to the third stage at a rate of 3 °C / min to -5 °C). During this period, stir the pigment emulsion at a speed of 120 rpm until the pigment emulsion is completely frozen; S3. Crush and ball-mill the frozen pigment emulsion with an ultrasonic crusher (frequency 40 kHz, process for 10 s, interval 10 s, total processing time 20 min) to obtain pigment ice crystals, and transfer the permanent yellow pigment ice crystals to a freeze-drying chamber for freeze-drying treatment (the temperature is maintained at -22 °C, and the pressure is reduced to 10 -2 mbar) to obtain pigment crystals; S4. Wet the cellulose nanocrystals (CNCs) with ethanol to obtain a cellulose nanocrystals (CNCs) colloid, and add the permanent yellow pigment crystals to the cellulose nanocrystals (CNCs) colloid to obtain the permanent yellow pigment.

[0030] Example 5 The difference from Example 1 is that during the process of step S2, no stirring operation is carried out.

[0031] Example 6 The difference from Example 1 is that the operation of step S2 is different. In this example, S2. Control the temperature of the pigment emulsion to decrease in three stages until it reaches below the freezing point of the pigment emulsion (the first stage is maintained at 20 °C for 30 min, and the temperature is decreased to the second stage at a rate of 2 °C / min and maintained at 10 °C for 30 min, and then decreased to the third stage at a rate of 2 °C / min to -10 °C). During this period, stir the pigment emulsion at a speed of 150 rpm until the pigment emulsion is completely frozen.

[0032] Example 7 The difference from Example 1 lies in the operation of step S2. In this example, S2. Control the temperature of the pigment emulsion to decrease in three stages until it reaches below the freezing point of the pigment emulsion (the first stage is maintained at 20°C for 30 min, and the temperature is decreased at a rate of 2°C / min to the second stage of 10°C and maintained for 30 min, and then decreased at a rate of 2°C / min to the third stage of -8°C). During this period, stir the pigment emulsion at a speed of 150 rpm until the pigment emulsion is completely frozen.

[0033] Example 8 The difference from Example 1 is that the pigment emulsion is subjected to high-pressure homogenization treatment between steps S1 and S2 under the conditions of: pressure of 280 bar and treatment for 20 min.

[0034] Example 9 The difference from Example 1 is that the pigment emulsion is subjected to high-pressure homogenization treatment between steps S1 and S2 under the conditions of: pressure of 300 bar and treatment for 10 min.

[0035] Example 10 The difference from Example 5 lies in the operation of step S2. In this example, S2. Control the temperature of the pigment emulsion to decrease in two stages until it reaches below the freezing point of the pigment emulsion (the first stage is maintained at 10°C for 30 min, and the temperature is decreased at a rate of 2°C / min to the second stage of -5°C). During this period, stir the pigment emulsion at a speed of 150 rpm until the pigment emulsion is completely frozen.

[0036] Example 11 The difference from Example 5 lies in the operation of step S2. In this example, S2. Control the temperature of the pigment emulsion to decrease in two stages until it reaches below the freezing point of the pigment emulsion (the first stage is maintained at 10°C for 30 min, and the temperature is decreased at a rate of 10°C / min to the second stage of -5°C). During this period, stir the pigment emulsion at a speed of 150 rpm until the pigment emulsion is completely frozen.

[0037] Comparative Example 1 The difference from Example 1 lies in the operation of step S2. In this comparative example, S2. Control the temperature of the pigment emulsion to directly decrease to -5°C. During this period, stir the pigment emulsion at a speed of 150 rpm until the pigment emulsion is completely frozen.

[0038] Comparative Example 2 The difference from Example 1 lies in the operation of step S2. In this comparative example, S2. Control the temperature of the pigment emulsion to -5°C. During this period, do not stir the pigment emulsion until the pigment emulsion is completely frozen.

[0039] Comparative Example 3 The difference from Example 1 lies in the operation of step S2. In this comparative example, in S2, the container filled with the pigment emulsion is placed in liquid nitrogen, and the pigment emulsion is quickly frozen to obtain a frozen pigment emulsion.

[0040] Using the crude pigment of permanent yellow obtained in the same batch, the post-treatment of the crude pigment of permanent yellow is carried out by the methods of the above-mentioned examples and comparative examples, and each method is repeated 5 times. The relevant properties of the permanent yellow pigment obtained after post-treatment are detected.

[0041] The test objects and methods are as follows: Relative tinting strength: GB / T 13451.2 - 1992.

[0042] Tinting strength deviation (STDEVP).

[0043] See Table 1 for the test results.

[0044] Table 1 Test results of each example and comparative example It can be seen from the results shown in the above table that the tinting strength deviation of the pigment corresponding to the comparative example is larger than that of the example, and the tinting strength stability is poorer. Specifically, compared with Example 1, in Comparative Example 1, the temperature was not decreased in stages, but directly decreased to -5°C, and the results showed that the tinting strength was generally lower, and the tinting strength deviation also increased significantly. Compared with Example 1, in Comparative Example 2, the temperature was directly decreased to -5°C without stirring, and the tinting strength and its stability of the obtained pigment were equivalent to those of Comparative Example 1. In Comparative Example 3, the pigment emulsion was quickly frozen directly using liquid ammonia, and the obtained pigment had a worse tinting strength and a worse tinting strength stability. It shows that the cooling method of the pigment emulsion has a great influence on the tinting strength and its stability of the pigment.

[0045] Meanwhile, through the comparison between each embodiment, it can be seen that different process conditions also affect the coloring power and its stability of the pigment. Specifically, compared with Embodiment 1, in Embodiment 5, the stirring operation is not carried out during the cooling process. The results show that the deviation of the coloring power increases and the coloring power stability of the pigment decreases. In Embodiments 6 and 7, compared with Embodiment 1, the temperature difference from the second stage to the third stage is relatively large, reaching 20°C and 18°C respectively. The results show that the deviation of the coloring power increases and the coloring power stability of the pigment decreases. This shows that the temperature difference from the second stage to the third stage has an obvious influence on the coloring power stability of the pigment. In Embodiments 8 and 9, compared with Embodiment 1, the pigment emulsion is subjected to high-pressure homogenization treatment between Steps S1 and S2. The results show that the coloring power stability of the pigment has been significantly improved and the coloring power has also been enhanced. In Embodiments 10 and 11, although the temperature is also reduced in stages, divided into two stages of temperature reduction, the results show that although the coloring power stability has been improved to some extent, it is not particularly significant, and the stability is poor compared with the three-stage temperature reduction.

Claims

1. A post-processing method for permanent yellow pigment, characterized in that: The steps include: S1. dispersing the crude permanent yellow pigment in a pigment emulsifier to form a pigment emulsion; S2. controlling the temperature of the pigment emulsion to gradually decrease to the freezing point of the pigment emulsion or below, to obtain a frozen pigment emulsion; S3. The frozen pigment emulsion is crushed and ball-milled with an ultrasonic pulverizer to obtain pigment ice crystals, and the permanent yellow pigment ice crystals are transferred to a freeze-drying chamber for freeze-drying to obtain pigment crystals; S4. Adding the pigment crystals into an ethanol mixture of cellulose nanocrystals to obtain a permanent yellow pigment.

2. The post-processing method of a permanent yellow pigment according to claim 1, characterized in that: Before performing step S2, the pigment emulsion is subjected to high pressure homogenization treatment.

3. The post-processing method of a permanent yellow pigment according to claim 1, characterized in that: In step S2, the temperature of the pigment emulsion is controlled to gradually decrease to the freezing point of the pigment emulsion or below, and the temperature is reached to the freezing point of the pigment emulsion or below through more than three gradually decreasing temperature gradients.

4. The post-processing method of a permanent yellow pigment according to claim 3, characterized in that: In step S2, the temperature of the pigment emulsion is controlled to be a first temperature value, a second temperature value and a third temperature value in sequence, and the temperature difference between the second temperature value and the third temperature value does not exceed 15°C.

5. The post-processing method of a permanent yellow pigment according to claim 4, characterized in that: The cooling rate from the second temperature value to the third temperature value does not exceed 6°C / min.

6. The post-processing method of a permanent yellow pigment according to claim 4, characterized in that: The cooling rate from the second temperature value to the third temperature value is 2° C. / min to 3° C. / min.

7. The post-processing method of a permanent yellow pigment according to claim 1, characterized in that: In step S2, the pigment emulsion is stirred at a rotation speed of 120-160 rpm.

8. The post-processing method of a permanent yellow pigment according to claim 1, characterized in that: The pigment emulsifier is sodium stearate or cocamidopropyl betaine or sorbitan monooleate.

9. The post-processing method of a permanent yellow pigment according to claim 2, characterized in that: The conditions of high pressure homogenization treatment are: treatment at a pressure of 280 bar to 350 bar for 5 min to 30 min.

10. A permanent yellow pigment, characterized in that: The permanent yellow pigment is obtained by subjecting a crude product of the permanent yellow pigment to a post-treatment method according to any one of claims 1 to 9.

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