It is the process of transferring the dyestuff, which has the property of sublimation (i.e. evaporation with the effect of heat) transferred to the paper, to the fabric with the effect of heat and pressure.
Sublimable disperse dyestuffs are printed on paper with a specially configured cylinder printing machine, rotary printing machine or offset printing machine. After checking the paper for errors, it is combined with the printed side of the textile surface to be printed and passed through a cylinder heated to 20 - 30°C (for PES) for 210-215 seconds. In the meantime, the pattern is transferred to the fabric. It is a great advantage that no post-processing is required after the printing process. Handle hardening may occur due to the high transfer temperature. Attitude hardening may be different according to the fiber type. Today, it is generally printed on polyester or cellulose polyester blends. Cellulose ratio should be very low.
In the printing of transfer printing papers, the dyestuff should be selected considering the vapor pressure, diffusion coefficient (transient of substances from very dense environment to less dense environment), sublimation temperature (170-230°C), molecular weight (400). Printing of papers with printing paste prepared with dispersion dyestuffs; It is carried out according to the roll, rotation or film-druck printing method.
Transfer printing paper is used only once. The paper is brought face to face with the fabric between the heated drum and the blanket and transfers the dyestuff on it to the fabric with the effect of heat and pressure. If the paper is to be printed with solvent-based pastes, its absorption ability should be low, and if it is to be printed with aqueous pastes, its absorption ability should be high. Depending on the absorption ability, the dyestuff shows different efficiency.
When the absorbency is high, the dyestuff will pass to the back surface of the paper and the dyestuff yield will decrease. The paper should have little but sufficient absorbency. A binder is used if most of the printing paste is to remain on the paper. In transfer printing, the printer or its intermediary orders the printed paper from one of the companies that produce these very special papers. This paper is printed in accordance with the pattern created by the designer. The printer either prints special patterns in large batches or uses ready-made patterned papers.
Factors affecting the transition of dyestuff from paper to fabric;
1-The structure of the dyestuff,
2-The structure of the product,
The temperature accuracy should be ±1°. A small change in the dyestuff molecule leads to a change of up to 50% in dyestuff uptake. The pressure residence time affects the result obtained. There was a balance between the dyestuff and the textile product. If the water is not well adjusted, the dyestuff that passes from the paper to the fiber passes from the fiber to the paper again.
Transfer printing papers must be resistant to high temperatures and pressure. Printing of transfer printing paper is a printing method based on rotogravure (prints that result in the meeting of a copper canvas and a diamond-tipped brush), flexographic (it is a printing method based on the transfer of inked images on the printed areas high on the surface of the printing plate onto the printing material with the effect of pressure.), lithographic (Stone printing system oil It is based on the principle of obtaining printing and non-printing areas on the same surface, based on the fact that water and water do not mix with each other.), can be made as stencil and digital printing. Transfer printing papers should have sufficient strength to prevent tearing in high-speed printing and should show sufficient strength after being exposed to temperatures of 30°C and above for 200 seconds or longer in the transfer step. It is recommended that the weight of the papers be 55-80 g/m². Paper is produced from pulp by mechanical means. It can be obtained from pulp formed by mechanical grinding, crushing or chemical substances.
Permeability is an important property because of the degree to which printing ink or other surface treatments penetrate the paper. However, since high permeability will increase the transmission of ink and solvents during transfer, it causes a decrease in the clarity of the print patterns and a low transfer effect on the fabric.
There are binders, solvents, plasticizers and other additives in the structure of transfer printing inks. Binders fix the dyestuff on the printing material. Solvents dissolve the resins and also reduce the printing viscosity of the ink and ensure the transfer of the ink onto the printing material.