Printing pigments or dyes on paper, rubber, or other carriers, and then printing onto the goods to be printed is called transfer printing, but in the narrow sense, transfer printing refers to pad printing technology that uses needle textiles as a carrier. Transfer printing is mainly used on polyester fiber products. With the improvement of transfer printing, it is also widely used on nylon, acrylonitrile, cotton, hemp and wool fabrics. Transfer printing wet method, dry method, steam method, vacuum method, thermal method and other forms. The transfer printing method can accurately reproduce the pattern, which is convenient for mechanized production, and the process is simple. In particular, the post-printing process is simpler than traditional printing and dyeing and the printing feel is the same as printing and dyeing, so it is likely to gradually replace the old printing method. However, most printing and dyeing factories in China still use traditional printing and dyeing methods, and only a few production units use transfer printing for production. At present, in addition to polyester, the widely used hot-melt resins include polyamide, vinyl acetate copolymer and polyurethane. The main component of polyester hot melt adhesive is polyester resin, which is polybasic acid. It is obtained by lipidation with polyol. Polyamide hot melt adhesive has strong adhesion, toughness, low temperature resistance and good affinity with nylon fabric, 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 adhesive is mainly used for the bonding of leather and PVC plastic. Due to the different fabrics to be printed, it is best to use suitable hot melt adhesive ink.
1. Features of transfer printing method
(1) The transfer printing pattern has the characteristics of realistic flower pattern, detailed pattern, clear layer and strong three-dimensional sense. Transfer printing can print natural landscapes 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 processing, it is suitable for various thickness printing. In addition, after the transfer printing, no post-processing can be packaged and shipped.
(3) There is no environmental pollution problem in transfer printing. Due to dry processing, there is no need for washing, steaming, drying and other processes, so there is no exhaust gas and waste water.
(4) Transfer printing has the advantages of high production efficiency, labor saving and easy operation.
2. Transfer printing mechanism Transfer printing is mostly used for polyester fabrics. It is a printing method that makes the dye sublime to the polyester surface by heating at high temperature (about 200 ℃), and then penetrates into the amorphous area of ​​the fiber macromolecule, and then is fixed in the fiber after cooling.
3. The requirements of transfer printing on dyes The disperse dyes used in transfer printing should have a sublimation temperature lower than the melting point of the fiber macromolecules and not damage the fabric strength. The processing temperature for polyester is 180-210 ℃. In this temperature range, the molecular weight of the dye sublimation varieties are between 230-270. There are generally three types of disperse dyes with molecular weights in this range. Quick-disperse disperse dyes: The temperature can be sublimated to develop hair color at about 180 ℃, and the color will change when the temperature is increased, and the edges will seep.
Good disperse dye: temperature can sublimate and develop color in the range of 180-210 ℃. Hair color curve is flat. The temperature has little effect on dyeing, and it is a suitable disperse dye for transfer printing. Late dye disperse dyes: the dyes cannot sublimate and develop well at 180-210 ℃. If the temperature is increased, good color development can be obtained. These dyes are strongly temperature-dependent when dyeing. According to the above situation, the dyes suitable for transfer printing should meet the following conditions:
(1) The dye for transfer printing must be fully sublimed and fixed on the fiber below 210 ℃, and can obtain good washing fastness and ironing fastness.
(2) The dye for transfer printing can be fully sublimated and transformed into a gas phase dye macromolecule after being heated, condensed on the surface of the fabric, and can diffuse into the fiber.
(3) The affinity of dyes for transfer printing to transfer paper is small, and the affinity to fabric is large.
(4) The dyes for transfer printing should have bright and bright colors.
Fourth, the printing of transfer paper color ink transfer printing with transfer paper printing, most of the printing and screen printing process and equipment. The composition of colored ink includes dyes, vehicles, adhesives, etc. The preparation of color ink is to mix the above three components and pour into a colloid mill or a three-roller abrasive machine to grind, so that the dye is evenly distributed in the color ink.
(1) Carrier The role of the carrier is to distribute the dye evenly in the color ink and transfer the dye from the printing equipment to the substance on the transfer paper. The vehicle should be inexpensive, non-toxic, and non-flammable. According to this requirement, water is the most suitable. However, the transfer paper is composed of cellulose. When water is used as the vehicle, the fibers will swell, causing deformation of the fine patterns, and due to the slow evaporation of water, high-speed production is difficult. If the organic solvent type vehicle is selected, although the deformation of the paper is small, the color ink can be printed with fine patterns, and has a suitable volatility, which is advantageous for higher speed production. But it has the disadvantages of higher cost and easy burning. Be careful when using it. Oil vehicles, such as high-boiling oils, can also be used. However, the high boiling point oil will cause the dye to diffuse deep into the transfer paper, thereby affecting the amount of dye transferred from the transfer paper to the fabric.
(2) Adhesive Adhesive refers to a substance that controls the viscosity of color ink. If the amount of binder is too small, the viscosity of the color ink cannot be guaranteed, which results in poor printing transfer paper. If the amount of binder is too large, the transfer speed of dye from the transfer paper to the fabric is slowed, which causes residue on the transfer paper Has too much dye. Depending on the vehicle used, the binder should be selected separately. When water is used as the vehicle, commonly used synthetic agar gum or carboxymethyl cellulose is used as the binder: when using organic solvents or oils as the vehicle, ethyl cellulose can be used as the binder.
V. Requirements of transfer printing on transfer paper
Transfer printing When printing transfer paper, the transfer paper used should have the following characteristics:
(1) Have sufficient strength;
(2) The affinity for the color ink should be small, but the transfer paper should have a good coverage of the ink;
(3) The transfer paper should not be deformed, brittle and yellowed during the printing process.
(4) The transfer paper should have proper hygroscopicity. Too bad hygroscopicity will cause color ink to match; too much hygroscopicity will also cause deformation of the transfer paper. Therefore, the production of transfer paper should strictly control the filler. It is more appropriate to use semi-fillers in the paper industry.
According to the above requirements, the transfer paper should meet the following standards:
Hygroscopicity 40--100g /?
Tear strength about 100kg / 5x20cm
Breathability 500 --- 2000l / min
Weight 60--70g /?
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 are better than half. This can ensure that the floral paper does not become brittle and yellow when treated at high temperature.
6. Printing method of floral paper
The printing of flower paper is the process of printing the pattern on the transfer paper by printing the color ink through printing and screen printing. At present, transfer printing paper is mostly printed by printing method. The printing methods of flower paper include gravure printing method, letterpress printing method, lithographic printing method and screen printing method. The printing method is used to print the flower paper, and the gravure printing is the most extensive. The screen printing method is suitable for the printing of small batches and multiple varieties of transfer printing floral paper, and can also make homemade floral paper in printing and dyeing factories. It has the characteristics of low cost, fast speed, high color density and easy operation. However, since the screen printing method uses water-soluble ink, the three-dimensional impression of the pattern on the floral paper and the clarity of the outline are not good, and the pattern is relatively thick, and the characteristics of transferring the printed pattern cannot be exerted.
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