Discharge printing is also called carving printing. It refers to a printing process that produces white or colored patterns by printing color paste that can eliminate the “ground color” on dyed fabrics. When printing, first print on the ground color fabric with a color paste that can destroy the ground color. After drying, print with floral dyes containing a discharge agent or a discharge-resistant agent. During post-processing, the ground color dyes in the printing area are destroyed and faded, forming white patterns on the color ground or colored patterns caused by dyeing with floral dyes, also known as color discharge or color discharge. Because the patterns of discharge printing are more detailed and realistic, with rich patterns, strong color contrast, clear outlines and full color, it has attracted more and more people’s attention. It uses reducing agents and oxidizing agents to destroy the background color of colored fabrics to obtain partially achromatic or colored patterns. Due to different fabrics, the chemical discharge agents used are also different. Discharge printing can be used on both pieces of fabric and finished garments.
1. Preparation of color paste
Stir the paste and dye thoroughly before filtering, and then add the filtered processing tin. However, be careful not to stir the processed tin and the dye at the same time, otherwise the dye will be difficult to dissolve, which will cause screen blocking, color spots, plug spots, etc. during printing. When preparing white discharge paste or light color discharge paste, To add an appropriate amount of active blue, the processed tin must be fully stirred and filtered before use; the amount of processed tin should be controlled according to the pattern. If the amount is too small, the pattern will be blurred and the outline will be unclear.
2. Control the temperature
The temperature of the drying room of the printing machine should generally not be higher than 100°C. Low-temperature drying is appropriate. If the drying temperature is too high, in order to reduce the dye discharge effect of processed tin . The dyeing temperature should not exceed 120°C, and the padding and scraping drying should not exceed 100°C. Low-temperature drying is appropriate, and the machine should not be stopped midway during the drying process. Processing tin is very corrosive to the screen and equipment. Under normal circumstances, the production is 5,000 meters long. Be sure to check the screen to prevent sand leaks, uneven lines, etc. The pressure of the printing machine scraper should be adjusted evenly, and the connecting pattern should be laid out properly. The dye discharge paste generally uses white dextrin or synthetic dragon glue, and its depasting properties are worse than sodium alginate. Therefore, it is best to use a rope-type water washing machine and strengthen reduction cleaning to make the cloth surface fresh, pure in color and clear in pattern. .
Anti-discharge printing of polyester fabrics can be divided into alkali drawing and tin drawing, but the anti-discharge printing effect of processed tin on polyester imitation silk fabrics is good. Because processed tin is modified stannous chloride, it is difficult to dissolve in water and is not easily oxidized by air, which increases the stability of the color paste and thus improves the quality of printing.
Anti-discharge printing of cotton fabrics: Dischargeable reactive dyes can be used to dye the background color, vinyl sulfone-based reactive black dye can be used to dye the background color, and then printed after drying. After printing, the wet cover printing method can be used to overprint. Background color (black). The base color (black) is dyed using the pad-and-bake process, and the dye is not easy to fix. Overprint on the unfixed black background, dry, steam, and promote simultaneous color development. The black background can easily transform into black with red phase.
Discharge printing of silk and wool textiles: The ground color can be dyed with acid dyes and reactive dyes with azo structure. The ground color of polyester and acetate textiles can be dyed with disperse dyes with azo structure. Discharge dyeing The agent is usually a strong reducing agent, and stannous oxide is commonly used. Discharge printing is mainly used for dark ground color printing, and the printing effect is good.
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