Transfer printing is divided into heat transfer and cold transfer, both of which are paper printing. Generally speaking, the flower shape is printed on the transfer paper first, and then the paper and the material to be printed are printed and transferred through the machine.

Heat transfer printing is a new printing process developed in the 1960s. Compared with the traditional process, this process saves 2/5 of the time, 1/3 of the workshop and manpower, 4/5 of the water, and 2/3 of the defective rate. Its advantages include accurate color registration, clear and delicate patterns, and strong flexibility. It can be produced in large quantities or small quantities (compared with the traditional process), and can also print hand-painted, photographic, traditional Chinese painting and other artistic styles, And partial printing.

Further subdivision, heat transfer printing in the clothing industry can be divided into hot melt transfer printing and heat sublimation transfer printing. Hot melt transfer printing is commonly used for all cotton products, with the disadvantage of poor hand feel and permeability. Thermal sublimation transfer printing is often used for polyester transfer printing, but the disadvantage is that the cost of plate making is high. Thermal sublimation transfer printing can be divided into offset printing, gravure printing, silk screen printing and data printing according to different printing methods.

Thermal sublimation transfer printing is a common method. Using the sublimation characteristics of disperse dyes, disperse dyes with molecular weight of 250~400 and particle diameter of 0.2~2 μ m are used to make ink with water-soluble carriers (such as sodium alginate) or alcohol soluble carriers (such as ethyl cellulose) and oil soluble resins. The ink is processed on a transfer printing machine at 200~230 ° C for 20~30 seconds, so that the disperse dyes are transferred to polyester and other synthetic fibers and fixed.

At present, the heat transfer printing process has three disadvantages:

First, because natural fibers and other hydrophilic fibers have no affinity with the dyes used for heat transfer printing, they can only be printed on polyester fabrics at present. The tension of heat transfer printing machines is large, and they are not suitable for printing fabrics that are easily deformed under tension, such as cotton knits, elastic fabrics, etc., which limits the scope of application;

Second, using paper as the base material of heat transfer printing does not fundamentally solve the environmental problem. Water consumption and pollution caused by paper making and waste paper recycling are still very serious;

Third, the cost of plate making is expensive. The cost of each set of plate (including the plate base) is 3000~5000 yuan, which can not meet the development needs of personalization, small batch and multiple varieties (digital direct jet printing is a good solution to this problem).

The principle of cold transfer printing is to use dyes with good solubility and stability (reactive dyes, acid dyes, etc.) to make color paste, adjust the surface tension between the color paste and the paper, print the image clearly on the paper coated with release agent, and dry and roll. After that, the fabric to be printed (after pretreatment, no softener, smoothing agent and other water repellent additives can be added) shall be dipped into the printing pretreatment solution, and then aligned with the transfer printing paper. After fitting, the fabric will enter the transfer printing roller. The pretreatment solution on the fabric will dissolve the color paste on the transfer printing paper. Under certain pressure conditions, because the affinity of dyes to the fabric is greater than that to the transfer paper, the dyes transfer and enter the fabric pores. Therefore, cold transfer printing is also called wet transfer printing. Finally, separate the paper and cloth, dry the fabric in the oven, and send it to the steaming machine for steaming and color development within the specified time.

Cold transfer printing has significant advantages in the printing of natural fiber fabrics such as cotton, wool and silk; The color is diversified, especially for the patterns that need gradual change in light colors; High color saturation, strong and prominent; High uniformity; The production process is short and economical; Low defective rate; Compared with heat transfer printing, it is more environmentally friendly.