Introduction To Printing Process

Use dyes or pigments in spin Physical construction printing The process of texture. Printing can be divided into fabric printing, wool top printing and yarn printing, and mainly fabric printing. Top printing is used for making mixed color tweed; Yarn printing is used to weave colorful patterned fabrics with special styles. Textile printing has a long history. China has applied hollow block printing in the Warring States Period (see China's dyeing and finishing history). India had wood stencil printing in the 4th century BC. Continuous concave cylinder printing began in the 18th century (see cylinder printing). Screen printing is developed from hollow pattern, which is suitable for small batch and multi variety printing of easily deformed fabrics. In the 1960s, metal seamless rotary screen printing began to be applied, which provided conditions for continuous production, and its efficiency was higher than that of flat screen printing. In the late 1960s, the transfer printing method appeared. By using the sublimation characteristics of disperse dyes, the dye on the transfer paper can be transferred to synthetic fiber fabrics such as polyester through heating to print fine patterns. In the 1970s, a liquid jet printing method controlled by computer program was also developed, in which various colors of dye solution were intermittently sprayed from many combined nozzles to form color patterns, which were mainly used for carpet printing.

Process: Printed fabrics are artistic products, and the corresponding printing process is selected according to the designed patterns. Direct printing, resist printing and discharge printing are commonly used. Direct printing is to directly print dyes or pigments on white or light colored fabrics, and then obtain patterns after steaming. The process is simple and widely used. Anti dye printing is a kind of material printed on the fabric to prevent the dye from dyeing or developing, and then dyed or developed to obtain patterns on the dyed fabric. Discharge printing is a printing process in which dyed fabrics are printed with substances to eliminate dyeing dyes and patterns are obtained on dyed fabrics.

Dyes and pastes: Textile Before printing, it must be pretreated to make it have good wettability. The dyes used for printing are basically the same as those used for dyeing, and some patterns with small areas can be painted (pigment). In addition, there are special printing fast pigments, fast amine, fast sulfone and other dyes. Different kinds of dyes can be used to print various patterns on the same fabric. When printing, dye or pigment is mixed into color paste. After printing and drying, it is usually necessary to carry out steaming, color development or color fixation treatment, and then soaping and water washing to fully remove the paste, chemicals and floating color in the color paste.

The printing paste is composed of dyes (or pigments), moisture absorbents, cosolvents, etc. and the original paste. The function of printing paste is to make the color paste have certain viscosity and fluidity. It is made of hydrophilic polymer paste. The commonly used pastes are starch, starch degradation products (white dextrin and yellow dextrin), starch ether derivatives, sodium alginate (or ammonium), hydroxyethyl soap gum, dragon gum, cellulose ether, synthetic polymer electrolyte, etc. Emulsified paste made of water, fire oil and emulsifier is sometimes used as printing paste. The printing paste should have good stability to the chemicals in the color paste, not react with dyes, have certain adhesion to fibers and be easy to wash off from the fabric. The viscosity of printing paste depends on the nature of the original paste. When printing, if the viscosity of the color paste drops too much, it is difficult to print fine lines. If the viscosity is too large, it is difficult for the color paste to pass through the pores of the screen.

Steaming and its equipment: steaming is also called steam steaming. The fabric printed with color paste is dried and evaporated. The steam condenses on the fabric, causing the temperature of the fabric to rise, the fibers and pastes to swell, and the dyes to dissolve. Some dyes also undergo chemical reactions during the steaming process. Due to the existence of thickener, the dyeing process of printing dyes is more complex, and the steaming time is longer than that of pad dyeing.

There are three types of steaming equipment: ① Steamer box: hang the fabric on the support and push it into the box for steaming; ② Continuous steaming machine: hang the fabric on the roller in a ring shape, and slowly move forward for continuous steaming; ③ Various fast steaming machines. Steam box and suspension continuous steaming machine are suitable for silk fabrics, knitted fabrics and synthetic fabrics. The steam box is steamed under closed conditions, but cannot be produced continuously. The steaming conditions vary with the properties of dyes and fibers. When evaporating the printed fabric with vat dyes, the air in the steaming room should be removed. The polyester printed fabric with disperse dyes can be steamed at about 130 ℃ in a closed steamer, or heated at about 175 ℃ under normal pressure, or baked at about 200 ℃ Solid color 。