A method for improving the dispersion stability of pigments by nonionic surfactants

Abstract

A method for improving the dispersion stability of pigments by nonionic surfactants, characterized by adopting the following process: (1) preparing an acetic acid solution with a mass concentration of 2%, mixing it with ethanol in a volume ratio of 5:3, adding chitosan to make the chitosan concentration 12.5 g / L, and ultrasonically dissolving it; (2) adding citral to ethanol to make the citral concentration 37.5 g / L, and stirring and dissolving it continuously; (3) mixing the above two solutions in a volume ratio of 4:1, stirring at 50°C for 6 hours to react, filtering the reaction solution after completion, dialyzing the filtrate for 72 hours and freeze-drying to obtain modified chitosan; (4) adding nonionic surfactant AEO-9 and organic pigment into water, wherein the mass concentration of AEO-9 is 0.8%, and the mass concentration of organic pigment is 4%, ultrasonically dispersing it for 50 minutes, and then adding the above prepared modified chitosan, wherein the mass concentration of chitosan is 0.4%. The modified chitosan of the present invention can significantly improve the performance of pigment dispersion at room temperature, frozen (-18°C), high temperature (80°C), acidic (10mmol / L CH 3 COOH), alkaline (1mmol / L NaOH), electrolyte (5mmol / L MgCl 2 ) conditions.

Description

Technical Field

[0001] The invention relates to a method for improving the dispersion stability of a nonionic surfactant on a pigment by utilizing modified chitosan, and belongs to the technical field of textile printing and dyeing. Background Art

[0002] Organic pigments are widely used as colorants in industry due to their high light stability, weather resistance, color intensity and gloss. Generally, in order to fully exert the properties of organic pigments, they need to be properly dispersed. Since pigment particles are prone to aggregation, the preparation of stable and uniform pigment dispersions has always been the focus of researchers.

[0003] Surfactant is the most commonly used pigment surface modification substance. It is an amphiphilic small molecule that can significantly reduce the surface tension of water, change the surface or interface state of the system, and can quickly reduce the size of pigment particles under conditions such as crushing, grinding, and ultrasound. It relies on electrostatic repulsion and steric hindrance to maintain the dispersion stability of pigment particles. Studies have shown that anionic, cationic and non-ionic surfactants with suitable structures can be used to disperse pigments under certain conditions. Among them, non-ionic surfactants do not ionize in water, and the dispersion properties of pigments are less affected by acids, alkalis and electrolytes, and have received widespread attention and application. However, non-ionic surfactants have a small molecular weight. Although they adsorb quickly on the pigment surface, they cannot produce enough adsorption sites for pigment particles, resulting in a weak binding force between the two, and the dispersion stability of the pigment needs to be further improved.

[0004] Chitosan is a product of the natural polysaccharide chitin with some acetyl groups removed. It has multiple functions such as biodegradation, biocompatibility, non-toxicity, and antibacterial properties. It is widely used in textiles, food additives, agriculture, etc. Appropriate modification can further expand its application areas. Summary of the invention

[0005] The invention obtains modified chitosan by reacting citral with chitosan, so that the modified chitosan can be effectively combined with the surface of the organic pigment, thereby enhancing the dispersion stability of the nonionic surfactant on the pigment.

[0006] The present invention comprises the following processes:

[0007] (1) Prepare a 2% acetic acid solution, mix it with ethanol in a volume ratio of 5:3, add chitosan to a concentration of 12.5 g / L, and dissolve it by ultrasonication;

[0008] (2) Add citral to ethanol to make the citral concentration 37.5 g / L, and stir continuously to dissolve;

[0009] (3) The two solutions were mixed at a volume ratio of 4:1, and stirred at 50°C for 6 h for reaction. After completion, the reaction solution was filtered, and the filtrate was dialyzed for 72 h and freeze-dried to obtain modified chitosan;

[0010] (4) Add nonionic surfactant AEO-9 and organic pigment into water, wherein the mass concentration of AEO-9 is 0.8% and the mass concentration of organic pigment is 4%, and ultrasonically disperse for 50 minutes. Then, add the modified chitosan prepared above, and its mass concentration is 0.4%.

[0011] Prepare an acetic acid solution with a mass concentration of 2%, mix it with ethanol, and the volume ratio of the two is 5:3 to prepare a solvent system that can dissolve chitosan. Add commercial chitosan with a viscosity of less than 200mPa·s and dissolve it by ultrasonication. Add citral to ethanol and stir it to dissolve it continuously so that it can react with chitosan. The above two solutions are mixed at a volume ratio of 4:1 and stirred at 50°C for 6 hours. During this process, the citral molecules and chitosan molecules react and connect with each other. After completion, filter, dialyze the filtrate for 72 hours and freeze-dry to obtain modified chitosan. Add nonionic surfactant AEO-9 and organic pigment to water, where the mass concentration of AEO-9 is 0.8% and the mass concentration of organic pigment is 4%, ultrasonically disperse for 50 minutes, and then add the modified chitosan prepared above, whose mass concentration is 0.4%. The modified chitosan can combine with the pigment and modify its surface, thereby enhancing the dispersion stability of the nonionic surfactant AEO-9 on the pigment. Implementation

[0012] The present invention is described below by way of examples and comparative examples.

[0013] Example 1

[0014] (1) Prepare a 2% acetic acid solution, mix it with ethanol in a volume ratio of 5:3, add chitosan to a concentration of 12.5 g / L, and dissolve it by ultrasonication;

[0015] (2) Add citral to ethanol to make the citral concentration 37.5 g / L, and stir continuously to dissolve;

[0016] (3) The two solutions were mixed at a volume ratio of 4:1, and stirred at 50°C for 6 h for reaction. After completion, the reaction solution was filtered, and the filtrate was dialyzed for 72 h and freeze-dried to obtain modified chitosan;

[0017] (4) Add nonionic surfactant AEO-9 and organic pigment into water, wherein the mass concentration of AEO-9 is 0.8% and the mass concentration of organic pigment is 4%, and ultrasonically disperse for 50 minutes. Then, add the modified chitosan prepared above, and its mass concentration is 0.4%.

[0018] Comparative Example 1

[0019] The same AEO-9 and organic pigment as in Example 1 were added into water, wherein the mass concentration of AEO-9 was 0.8% and the mass concentration of organic pigment was 4%, and ultrasonic dispersion was performed for 50 minutes.

[0020] Comparative Example 2

[0021] The same AEO-9 and organic pigment as in Example 1 were added into water, wherein the mass concentration of AEO-9 was 0.8% and the mass concentration of organic pigment was 4%, and ultrasonically dispersed for 50 minutes, and then unmodified chitosan was added, and its mass concentration was 0.4%.

[0022] The stability values ​​(R) of the pigment dispersions obtained in the examples and comparative examples were measured by spectrophotometry at room temperature, freezing (-18°C), high temperature (80°C), acidity (10mmol / L CH3COOH), alkalinity (1mmol / L NaOH), electrolyte (5mmol / L MgCl2), etc. Specific test method: The pigment dispersion was allowed to stand for 48 hours under the above-mentioned different conditions, the supernatant was diluted, and its absorbance at the maximum absorption wavelength was measured by a spectrophotometer. The absorbance values ​​before and after standing were named "b" and "a", respectively. The R value was calculated by the following formula: R=a / b×100%. The larger the R value, the more stable the pigment dispersion.

[0023] After testing, the stability R values ​​of the pigment dispersion obtained in Example 1 at room temperature, freezing (-18°C), high temperature (80°C), acidic (10mmol / L CH3COOH), alkaline (1mmol / L NaOH), and electrolyte (5mmol / L MgCl2) were 93.11%, 96.61%, 95.97%, 78.83%, 94.51%, and 80.28%, respectively; the stability R values ​​of the pigment dispersion obtained in Comparative Example 1 at room temperature, freezing (-18°C), high temperature (80°C), acidic (10mmol / L CH3COOH), alkaline (1mmol / L NaOH), and electrolyte (5mmol / LMgCl2) were 83.2%, 43.14%, 90.95%, 0.6%, 81.69%, and 5.56%, respectively; the stability R values ​​of the pigment dispersion obtained in Comparative Example 2 at room temperature, freezing (-18°C), high temperature (80°C), acidic (10mmol / L The stability R values ​​under the conditions of CH3COOH), alkaline (1mmol / LNaOH), and electrolyte (5mmol / L MgCl2) are 9.43%, 28.03%, 0.73%, 8.67%, 43.17%, and 6.68%, respectively. It can be seen that Example 1 can significantly improve the dispersion stability of the pigment dispersion under different conditions by using the modified chitosan described in the present invention.

Claims

1. A method for improving the dispersion stability of pigments by nonionic surfactants, characterized in that The following processes are used: (1) Prepare a 2% acetic acid solution, mix it with ethanol in a volume ratio of 5:3, add chitosan to make the chitosan concentration 12.5 g / L, and dissolve it by ultrasonication; (2) Add citral to ethanol to make the citral concentration 37.5 g / L, and stir continuously to dissolve; (3) The above two solutions were mixed in a volume ratio of 4:1, and stirred at 50°C for 6 h for reaction. After completion, the reaction solution was filtered, and the filtrate was dialyzed for 72 h and freeze-dried to obtain modified chitosan; (4) Add nonionic surfactant AEO-9 and organic pigment into water, wherein the mass concentration of AEO-9 is 0.8% and the mass concentration of organic pigment is 4%, and ultrasonically disperse for 50 minutes. Then, add the modified chitosan prepared above, and its mass concentration is 0.4%.

2. The method according to claim 1, characterized in that The chitosan used is commercially available chitosan with a viscosity lower than 200 mPa•s.