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. Color paste modulation
Stir the paste and dye thoroughly first, filter it, and then add the filtered processed tin. However, be careful not to stir the processed tin and dye at the same time, otherwise the dye will be difficult to dissolve, which will cause the screen to be blocked during printing. The appearance of color spots, plug spots and other phenomena occurs during modulation and pulling. When dyeing white paste or light-colored color drawing paste, add an appropriate amount of reactive blue. The processed tin must be fully stirred and filtered before use. The amount of processed tin must be controlled according to the pattern. If the amount is less, the pattern will be blurred. , the outline is unclear.
2. Control temperature
The temperature of the drying room of the printing machine , in general, it should not be higher than 100°C. It is better to dry at low temperature. If the drying temperature is too high, it will 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 highly 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 dyeing of polyester fabrics can be divided into alkali drawing and tin drawing, but processed tin is used in Polyester imitation silk fabric has good anti-discharge printing effect. Because processed tin is modified stannous chloride, it is insoluble in water and 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, and vinyl sulfone-based reactive black dye can be used to dye the background color. Print after drying, and use wet cover printing method after printing. Print 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. The dye 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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