Transfer printing refers to the printing process in which dyes are transferred to fabrics via transfer paper. According to the sublimation characteristics of some disperse dyes, the disperse dyes sublimated at 150℃～230℃ are selected, mixed with the slurry to make "color ink", and then according to different design pattern requirements, the "color ink" is printed to Transfer paper, and then close the transfer paper printed with patterns and fabrics. Under the control of certain temperature, pressure and time, the dye transfers from the printed paper to the fabric, and enters the interior of the fabric through diffusion. The purpose of coloring.
There are several methods for transfer printing, such as sublimation method, migration method, melting method and ink layer peeling method. Among them, sublimation transfer printing is the most mature.
This is the most commonly used method. Using the sublimation characteristics of disperse dyes, disperse dyes with a molecular weight of 250-400 and a particle diameter of 0.2-2 microns are used together with water-soluble carriers (such as sodium alginate) or alcohol-soluble carriers ( For example, ethyl cellulose) and oil-soluble resin are used to make inks, which are processed on a transfer printing machine at 200°C to 230°C for 20 to 30 seconds to transfer and fix the disperse dyes to synthetic fibers such as polyester.
The sublimation method generally undergoes three processes: before the transfer process occurs, all the dyes are in the printed film on the paper, the dye concentration in the printed fabric and the air gap is zero, and the size of the air gap depends on the structure of the fabric and the yarn count. And transfer pressure. In the transfer process, when the paper reaches the transfer temperature, the dye starts to volatilize or sublime, and a concentration volatilization is formed between the paper and the fiber. When the printed fabric reaches the transfer temperature, the dye adsorption starts on the fiber surface until it reaches a certain saturation. value. Since the dye transfer from paper to fiber is continuous, its adsorption rate depends on the rate at which the dye diffuses into the fiber. In order to enable the dye to diffuse directionally, a vacuum is often drawn on the underside of the dyed material to achieve directional diffusion and transfer of the dye. After the transfer process, after the dyed material is colored, the dye content on the paper decreases, and part of the remaining dye migrates to the inside of the paper. The amount of residual dye depends on the vapor pressure of the dye, the affinity of the dye to the slurry or transfer paper, and the printing film thickness of. The sublimation method generally does not require wet treatment, which can save energy and reduce the load of sewage treatment.
The dye in the ink layer of the transfer paper is selected according to the nature of the fiber. The fabric is first subjected to padding treatment with a mixture of fixing aids and pastes, and then in the wet state by hot-pressing migration, so that the dye is transferred from the transfer printing paper to the fabric and fixed, and finally steamed and washed Isotonic treatment. When the dye is transferred, a greater pressure is required between the fabric and the transfer paper.
The ink layer of the transfer paper is based on dyes and waxes. The ink layer is embedded in the fabric by melting and pressing, so that part of the ink is transferred to the fiber, and then the corresponding post-treatment is performed according to the nature of the dye. When using the melting method, a greater pressure is required, and the transfer rate of the dye increases with the increase of the pressure.
Ink layer peeling method
Using the ink that can produce strong adhesion to the fiber when exposed to heat, the entire ink layer can be transferred from the transfer paper to the fabric under a small pressure, and then the corresponding fixing treatment can be done according to the nature of the dye.
In addition to being suitable for synthetic fiber fabrics, transfer printing can also be used for printing on pure natural fiber and blended fabrics. It has the following advantages: short process flow, the finished product after printing, no need for post-processing such as steaming, washing, etc.; simple equipment, small investment, small footprint, low energy consumption; fine patterns, rich and clear layers, and artistic High and three-dimensional, it is not as good as the general method of printing, and can print photography and painting style patterns; the printing is bright in color, and the tar in the dye is left on the transfer paper during the sublimation process, which will not pollute the fabric; High rate, multi-color patterns can be printed at one time during transfer without the need for matching flowers; strong flexibility, customers can print out in a short time after selecting the pattern. In addition to printing the head pattern, it can also be used on clothes Transfer printing on the finished product, such as partial printing on the collar, cuffs, and pockets of the jacket.
Transfer printing also has its shortcomings. For example, 80% of transfer printing is used for polyester fabrics, 10% is used for polyester blended fabrics, and 10% is used for fabrics such as acrylic, nylon and acetate fibers. Natural fiber fabrics have not yet been mass-produced. The scope of use is subject to certain restrictions. In addition, a large amount of paper needs to be consumed. In addition to transfer paper, backing paper is also needed. Therefore, the area of paper consumed is twice that of printed fabric, and the disposal of leftover paper is also a problem. In addition, the production efficiency of transfer printing is low. The output of a transfer printing machine is 3 to 4 meters per minute, and the higher one is only about 8 meters per minute, which is only suitable for small batches and multiple varieties.