Technical Points About Discharge Printing Various Fabrics

- Nov 28, 2020-

Also known as engraving, it refers to the printing process of printing color paste that can eliminate the "ground color" on the dyed fabric to produce white or colorful patterns.

When printing

Firstly, print the color paste containing the destructible ground color on the ground color fabric, and then use the color dye which contains the discharge agent or the discharge-resistant agent at the same time after drying.

When post-processing

The ground color dye in the printing place is destroyed and decolorized, forming a white pattern on the color ground or a colored pattern formed by dyeing with the color dye, also known as 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 different fabrics, the chemical discharge agent used is also different.

Discharge printing can be used for both piece cloth and finished garments


Color paste modulation

Stir the paste and dye thoroughly, and then add filtered processed tin after filtering.

But pay attention:

1. It is not possible to stir the processed tin and dye at the same time, otherwise the dye will be difficult to melt, which will cause blockage, color spots, plugging spots and other phenomena during printing;

2. When preparing the discharge dyeing white paste or the light color paste, the appropriate amount of reactive blue must be added, and the processed tin must be fully stirred and filtered before use;

3. Master the amount of tin processed according to the pattern. If the amount is less, the pattern will be blurred and the outline will be unclear.


temperature control

The temperature of the drying room of the printing machine should not be higher than 100°C under normal circumstances, and low temperature drying is appropriate.

Too high drying temperature will reduce the discharge effect of processed tin.

Dyeing should not exceed 120°C, bottom-rolling and bottom-scraping drying should not exceed 100°C, low-temperature drying is appropriate, and the drying process should not be stopped during the drying process.

Processing tin is more corrosive to the screen and equipment. Under normal circumstances, when producing 5,000 meters, you must check the screen to prevent hourglasses and uneven lines.

The pressure adjustment of the squeegee of the printing machine should be even, and the pattern should be printed well. Discharge paste generally uses white dextrin or synthetic dragon gum, which has poorer de-paste than sodium alginate. Therefore, it is best to use a rope-type washing machine and strengthen the reduction and cleaning to make the cloth surface fresh, pure in color and clear in shape. .

Discharge resistant polyester fabric

It can be divided into alkaline drawing and tin drawing, but the effect of anti-discharge printing on polyester imitation silk fabric 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.

Anti-discharge of cotton cloth

The base color can be dyed with dischargeable reactive dyes, and the base color can be dyed with vinylsulfone-based reactive black dye. After drying, printing, and after printing, use wet mask printing to cover the base color (black). 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 of silk 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 a strong reducing agent, and stannous oxide is commonly used. Dye printing is mainly used for deep ground color printing with good printing effect.

Points to note for discharge printing:

(1) The paste selected for discharge printing must have a certain degree of acid resistance, resistance to additives, good storage stability and easy de-paste. And it requires good permeability, uniform printing and clear outline; after the fabric is printed with discharge paste, it should be fully dried to prevent color buildup.

(2) The fabric after printing should not be left for a long time and should be steamed in time. If one steaming is insufficient, it can be steamed once again to effectively improve the discharge effect.

(3) Discharge printing dyes should be used as far as possible to choose dyes with better white discharge effect. If necessary, some dyes with moderate white discharge effect can be selected to adjust the shade. Dyes with poor white discharge effect should not be used.

(4) Discharge printing fabrics should be fully washed and soaped after steaming to improve the printing effect of discharge printing. This is an important factor affecting the whiteness of discharge dyeing.

(5) When designing the original manuscript, it is necessary to consider the characteristics of discharge printing and design the pattern. Generally speaking, the suitable pattern for discharge printing includes large-area deep color printing, fine white flowers and some complicated patterns.