Transfer printing technology basic knowledge and application methods

The pigments or dyes are printed on paper, rubber or other carriers and then transferred onto the goods to be printed. Transfer printing is called transfer printing. In the narrow sense, transfer printing refers to pad printing technology using needle textiles as a carrier. Transfer printing is mainly applied to polyester fiber products. With the improvement of transfer printing, it has also been widely used in nylon, acrylonitrile, cotton, hemp and wool fabrics.

Transfer printing wet, dry, steam, vacuum, heat and other forms. The transfer printing method can accurately reproduce the pattern and facilitate the mechanized production, and the process is simple. In particular, the post-printing treatment process is simpler than the traditional printing and dyeing, and the printing touch is the same as the printing and dyeing, and therefore, there is a great potential to gradually replace the old printing. However, most printing and dyeing plants in China still use traditional printing and dyeing methods, and only a few production units use transfer printing for production.

At present, a wide range of hot-melt resins are used in addition to polyester, polyamides, vinyl acetate copolymers, and polyurethanes. The main component of the polyester hot melt adhesive is a polyester resin, and the polyester resin is a polybasic acid. It is derived from the esterification of polyols. Polyamide hot melt adhesive has strong adhesive force, toughness, low temperature resistance and nylon fabric affinity, and is suitable for preparing nylon transfer printing paper. Ethylene-vinyl acetate copolymer has a low melting point and strong adhesion. It is suitable for the production of transfer printing paper after adding printing ink. Polyurethane hot melt adhesives are mainly used for leather and poly vinyl plastic bonding. Transfer Printing Because of the different fabrics to be printed, it is best to use suitable hot melt adhesive inks.

First, the characteristics of transfer printing method

(1) The transfer printing pattern has the characteristics of vivid patterns, detailed patterns, clear layers, and strong three-dimensional impression. Transfer printing can print natural scenery and artistic patterns.
(2) The transfer printing equipment has the characteristics of simple structure, small footprint, low investment and high economic efficiency. Because the equipment is tension-free, it is suitable for all kinds of printing. In addition, after transfer printing, it can be packaged and shipped without post-processing.
(3) There is no environmental pollution problem in transfer printing. Due to the dry processing, there is no need for water washing, steaming, drying, etc., so no exhaust gas and waste water are discharged.
(4) Transfer printing has the advantages of high production efficiency, labor saving and easy operation.

Second, transfer printing mechanism

Transfer printing is mostly used for polyester fabrics. It is through the high temperature (200 °C or so) so that the dye sublimation of the dye into the gas phase condensed polyester surface, and then infiltrated into the amorphous fiber in the amorphous area, after cooling in the fiber fixation method.

Third, the requirements of dye transfer printing

For disperse dyes used in transfer printing, the sublimation temperature should be lower than the melting point of fiber macromolecules and the principle of not damaging the strength of fabrics. The processing temperature suitable for polyester fibers is 180--210°C. In this temperature range, dyes with sublimation have a molecular weight of 230-270. There are generally three types of disperse dyes having a molecular weight in this range.

Fast-dyeing disperse dyes: When the temperature is around 180°C, the hair color can be sublimated, the temperature can be increased, the color can change, and the edge can be osmotic.

Good disperse dyes: The color can be sublimated in the temperature range of 180--210°C. The hair color curve is flat. The effect of temperature on dyeing is not great. It is a suitable disperse dye for transfer printing.

Late-Staining Disperse Dyes: Under 180--210°C, dyes can not sublimate and color well. If you increase the temperature, you can get a good hair color. These dyes have a strong dependence on temperature when dyed.

Based on the above conditions, the dyes suitable for transfer printing should meet the following conditions:

(1) The dyestuff for transfer printing must be fully sublimated below 210°C, fixed on the fiber, and can obtain good washing fastness and ironing fastness.
(2) The transfer printing dye can be fully sublimated and transformed into gas-phase dye macromolecules when heated, condensed on the fabric surface, and can diffuse into the fiber interior.
(3) The dyestuffs used for transfer printing have a low affinity for transfer papers and have a high affinity for fabrics.
(4) Transfer printing dyes should have a bright, bright color.

Fourth, the color ink printing transfer paper

Most of the transfer printing of transfer printing paper uses printing and screen printing processes and equipment. The composition of the color ink includes a dye, a carrier, and a binder. The preparation of the color ink is to mix the above three components and pour it into a colloid mill or a three-roll mill to grind the dye so that the dye is evenly distributed in the color ink.

(A) The role of the carrier of the carrier is to distribute the dye evenly in the color ink and transfer the dye from the printing apparatus to the transfer paper. Carriers should have low-cost, non-toxic, non-combustible properties. According to this requirement, the water is the most suitable. However, the transfer paper is composed of cellulose. When water is used as a carrier, the fibers will expand, causing fine pattern deformation, and due to slow water evaporation, high speed production is difficult. For example, when using organic solvents, the paper can be printed with fine patterns and have a suitable volatility, which is beneficial to the advantages of higher speed production. However, there are disadvantages of high cost and flammability. Use strict attention when using. Oil vehicle, such as high boiling point oil, can also be used. However, high boiling point oils cause the dye to diffuse deeper into the transfer paper, which affects the transfer of the dye onto the fabric.

(b) Adhesives Adhesives are substances that control the viscosity of color inks. If the amount of the binder is too small, the viscosity of the color ink cannot be guaranteed, resulting in poor transfer of the printing paper, and excessive use of the binder, so that the transfer speed of the dye from the transfer paper to the fabric is slowed down, which results in residue on the transfer paper. Too much dye. According to the use of carrier, the binder should be selected separately. When water is used as a vehicle, the commonly used synthetic alonine or carboxymethyl cellulose is a binding agent: ethyl cellulose can be used as a binder when an organic solvent or oil is used as a vehicle.

Fifth, transfer printing on the transfer paper requirements

When transferring printing printing transfer paper, the use of transfer paper should have the following characteristics:

(1) Have sufficient strength;
(2) The affinity for color ink should be small, but the transfer paper should have good coverage on the ink;
(3) The transfer paper should not be deformed, brittle, or yellow during the printing process.
(4) The transfer paper should have proper moisture absorption. Poor hygroscopicity will cause color inks to pick up; excessive hygroscopicity will cause deformation of the transfer paper. Therefore, it is necessary to strictly control the filler when producing transfer paper. It is appropriate to use the semi-filler in the paper industry.

According to the above requirements, the transfer paper should meet the following standards:

Hygroscopicity 40--100g/m2
Tear strength about 100kg/5x20cm
Breathability 500---2000l/min
Weight 60--70g/m2
Ph value 4.5--5.5
Dirt does not exist

The transfer paper is preferably made from softwood pulp. Among them, chemical pulp and mechanical pulp production are equally good. This will ensure that the paper will not be brittle and yellow when it is processed at high temperatures.

Sixth, printing paper printing method

The printing of floral paper is a process in which a pattern is printed on a transfer paper by a method in which the color ink is printed and screen printed. At present, transfer printing papers are mostly printed by printing methods. There are four types of printing methods for gravure printing: gravure printing, letterpress printing, lithographic printing, and screen printing. Printing paper is printed using the printing method, which is the most widely used for gravure printing. The screen printing method is suitable for the printing of small-lot, multi-variety transfer printing paper, and can be made in the printing and dyeing plant. It has the characteristics of low cost, fast speed, rich color, and easy operation. However, due to the use of water-soluble ink in the screen printing method, the three-dimensional pattern and the sharpness of the outline on the floral paper are not good, and the pattern is coarse, and the characteristics of the transfer printing pattern cannot be exhibited.

Source: Textile Forum