Thermal Sublimation Transfer Technology of Fabrics
The method of printing fabric with heat sublimation transfer paper is also called vapor phase heat transfer printing. The basic production method of transfer printing is to make inks from suitable dyes, then print them into flower paper, and then overlap them with fabrics under heating, pressure or decompression. The dyes on paper are sublimated into vapor phase and transferred to fabrics.
1. Thermal Sublimation Transfer Ink
Thermal Sublimation Transfer Printing Ink
Dyes for thermal sublimation transfer printing can be selected according to the following conditions:
The molecular weight of dyes should not exceed 350.
There is an intermolecular force between dye gas and fibers, and it can diffuse into the fibers.
Thermal sublimation temperature of dyes below 200 C is suitable.
The color fastness of the dyes transferred to the fibers meets the wearing requirements.
The colour and lustre of the fibers are bright.
Dyes have no affinity with base paper.
The commonly used transfer printing dyes are anthraquinone dyes, azo dyes, cationic dyes and so on.
The commonly used resins are low viscosity ethyl cellulose, ethyl hydroxyethyl cellulose (EHEC), long oil modified alkyd resins, etc. The commonly used solvents are turpentine, terpineol, high boiling point alkanol, aromatic alkanes, fibrinolytic agents, and a small number of other additives. The main requirements of the binder are low affinity with dyes, easy release of dye gas, suitable printing adaptability, preservation and heat transfer adaptability.
2. heat transfer paper
Base paper for flower paper abroad is made of Dutch products, all of which are made of coniferous wood pulp. Chemical loading accounts for 50% and mechanical loading accounts for 50%. This kind of paper does not yellowish or crisp at high temperature.
Sulfite softwood chemical pulp paper is also used. The paper with filler has good heat resistance. The filler formula is as follows (for reference only).
In addition, the transfer effect can be increased by adding coatings on the base paper, such as silicone, polyvinyl acid and other substances.
3. printing methods
There are four common printing methods: gravure, embossing, lithography and screen printing.
4. transfer printing equipment
Generally, it can be divided into two categories. Two are: one is intermittent, commonly known as lithographic; the other is continuous, mainly hot roll. There are two types: one is pressure type, the other is vacuum transfer printing, which is the so-called vacuum transfer printing with air pumping. Vacuum transfer printing is most suitable for deformed fabrics, fuzzed fabrics and heat-resistant fabrics, such as acrylic bulky fabrics, artificial fur and so on. Decompression transfer printing can also make some non-sublimation-resistant disperse dyes available, thus expanding the choice of dyes; on the other hand, it can also increase the color yield and transfer speed.
5. transfer printing process
Pressure type transfer printing and embossing process. Taking polyester as an example, the most suitable technological conditions should be 20-30 s at 205 C. However, the effect is not good at 170-180 C and 10s. The ring dyeing effect can only be achieved at 180-190 C and 15-10s. If the temperature is 230-240 and above 40s, the hand feel is rough and hard, and if the temperature is 240 and above 45s, it is close to melting. Fabric fibers have different types and transfer conditions.
In addition to temperature and time, the pressure of transfer printing is also a very important condition. If the pressure is too low, the gap between the fabric and the pattern paper is large, and the yarn is circular, so that the gas molecules of dye collide with the air and escape, resulting in poor effect, while the dye is easy to penetrate, the lines are thick and the pattern is blurred. If the pressure is increased, the yarn can become flat, the gap between the fabric and the pattern paper is small and the transfer coloring effect is good, the pattern is clear and the lines are smooth and fine. However, excessive pressure will cause deformation, fuzzing and changes in the shape of heavy fabrics, and produce aurora, resulting in rough handle and color surface defects.