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, a transfer printing method was introduced. By using the sublimation property of the disperse dye, the dye on the transfer paper was transferred to a synthetic fiber fabric such as polyester by heating, and a fine pattern was printed. In the 1970s, a liquid-jet printing method controlled by an electronic computer program was also developed, in which a plurality of combined ejection openings intermittently ejected various coloring liquids to form a color pattern, which was mainly used for carpet printing.
Printed fabrics are artistic products, and the corresponding printing process is selected according to the design pattern. Commonly used are direct printing, anti-dye printing and discharge printing. The direct printing is to directly print the dye or pigment on the white or light-colored fabric, and then obtain the pattern by steaming and the like, and the process flow is short and the application is the most widely used. Anti-dye printing is a substance printed on a fabric to prevent dyeing or coloring, and then dyed or developed to obtain a pattern on the dyed fabric. The discharge printing is a printing process in which a dyed dye is printed on a dyed fabric to obtain a pattern on the dyed fabric.
Dyes and pastes
The fabric must be pretreated prior to printing to provide good wettability. The dye used for the printing is basically the same as the dyeing, and some of the smaller patterns can be used for the coating (pigment). In addition, there are dyes such as fast pigments, fast amines, and fast sulfonates for printing. Different types of dyes can be used to print various patterns on the same fabric. The dye or pigment is adjusted to a color paste during printing. After printing and drying, it is usually steamed, developed or fixed, and then soaped and washed to remove the paste, chemicals and floating color in the paste.
The printing paste is composed of a dye (or pigment), a moisture absorbent, a cosolvent, and the like, and the original paste. The function of the original paste is to make the paste have a certain viscosity and fluidity. It is prepared from a hydrophilic polymer paste. Commonly used pastes are starch, starch degradation products (white dextrin and yellow dextrin), starch ether derivatives, sodium alginate (or ammonium), hydroxyethyl Acacia gum, long gum, cellulose ether, synthetic polymer electrolyte, and the like. Emulsified paste made of water, kerosene and emulsifier is sometimes used as a printing paste. The printed original paste should have good stability to the chemicals in the color paste, does not interact with the dye, has a certain adhesion to the fibers and is easily washed away from the fabric. The viscosity of the printing paste depends on the nature of the original paste. If the viscosity of the color paste drops too much during printing, it is difficult to print fine lines. If the viscosity is too large, the color paste will not easily pass through the fine holes of the screen.
Steaming and its equipment
Steaming is also known as steaming. The printed fabric is dried and then steamed. The steam condenses on the fabric, causing the temperature of the fabric to rise, the fibers and paste to swell, the dye to dissolve and the dye to be dyed. Some dyes also undergo a chemical reaction during the steaming process. Printing dyes Due to the presence of paste, the dyeing process is more complicated, and the steaming time is longer than the steaming time of padding.
There are three types of steaming equipment:
1 steaming box: the fabric is hung on the bracket and pushed into the box for steaming;
2 continuous steaming machine: the fabric is hung on the roller in a ring shape, slowly advancing, continuous steaming ;
3 various fast steaming machines. Steamer and pendant continuous steamer for silk fabrics, knits and fiber-forming fabric. The steamer is steamed under closed conditions, but cannot be continuously produced. The steaming conditions vary with the dye and fiber properties. When the printed fabric of the vat dye is steamed, the air in the vaporization chamber should be driven off. The polyester printed fabric of disperse dye can be steamed in a sealed steamer at about 130 °C, or under normal pressure with superheated steam of about 175 °C, or can be baked at 200 °C.