Discharge printing is also called engraving. It refers to the printing process of printing on the dyed fabric with the color paste that can eliminate the "ground color" to produce white or colorful patterns. When printing, the ground color fabric is printed with a color paste that can destroy the ground color, and after drying, it is printed with a color dye containing a discharge agent or a discharge-resistant agent at the same time. In post-processing, the ground color dye in the printing area is destroyed and decolorized, forming a white pattern on the color ground or a colored pattern formed by dyeing with the color dye, which is also called color discharge or color discharge. Because the patterns of discharge printing are more detailed and lifelike, the patterns are rich in layers, the color contrast is strong, the outline is clear, and the color is full, so people pay more and more attention. It uses reducing agents and oxidizing agents to destroy the background color of colored fabrics to obtain partial achromatic or colored patterns.
Due to the different fabrics, the chemical discharge agent used is also different. Discharge printing can be used for both piece cloth and finished garments.
1. The color paste preparation paste and dyes are mixed thoroughly, filtered, and then the filtered processed tin is added. But be careful not to mix the processed tin and the dye at the same time, otherwise, the dye will be difficult to melt, which will cause the blocking of the network, the color dots, the clogging dots, etc. during printing. When preparing the discharge white paste or the light color paste discharge, To add an appropriate amount of reactive blue, the processed tin must be fully stirred and filtered before use; master the amount of processed tin according to the pattern, if the amount is small, the pattern will be blurred and the outline will be unclear.
2. Control the temperature of the open type rotary screen printing machine drying room. Generally, it should not be higher than 100°C. Low-temperature drying is appropriate. The drying temperature is too high to reduce the discharge effect of processed tin. The bottom dyeing should not exceed 120°C, and the bottom rolling and bottom scraping drying should not exceed 100°C. Low-temperature drying is appropriate, and the drying process should not be stopped in the middle of the drying process. Processing tin is more corrosive to the screen and equipment. Under normal circumstances, when producing 5000 meters, be sure to check the screen to prevent hourglasses and uneven lines.
Open type rotary screen printing machine squeegee pressure adjustment should be uniform, and the pattern should be printed well. Discharge pastes generally use white dextrin or synthetic dragon gum. The de-paste is worse than sodium alginate, so it is best to use a rope-type washing machine and strengthen the reduction and cleaning to make the cloth surface refreshing, the color is pure, and the pattern is clear. . Polyester fabric anti-discharge can be divided into alkali pull-out and tin pull-out, but the effect of anti-discharge printing on polyester imitation silk fabrics with processed tin 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, thereby improving the quality of printing. Discharge-resistant printing on cotton fabrics: the base color can be dyed with dischargeable reactive dyes, and the base color can be dyed with vinylsulfone-based reactive black dyes. After drying, the printing is done, and after printing, the base color (black) is covered by wet mask printing ). The base color (black) is dyed by the pad-baking process, and the dye is not easy to fix.
Overprint on the unfixed black background, drying, steaming, and promoting simultaneous color development, the black background is easy to change into black and red. Discharge dyeing and printing of silk and wool textiles: the ground color can be dyed with acid dyes and reactive dyes with an azo structure, and the ground color of polyester and acetate textiles can be dyed with disperse dyes with an azo structure. The discharge agent is usually strong. Reducing agent, commonly used stannous oxide, discharge printing is mainly used for deep ground color printing with good printing effect.