Printing pigments or dyes on paper, rubber or other carriers, and then pad printing onto the product to be printed is called transfer Printing, but in a narrow sense, transfer printing refers to t...
Printing pigments or dyes on paper, rubber or other carriers, and then pad printing onto the product to be printed is called transfer Printing, but in a narrow sense, transfer printing refers to the pad printing technology that uses needle textiles as carriers. Transfer printing is mainly used on polyester fiber products. With the improvement of transfer printing technology, it is also widely used on nylon, acrylic, cotton, linen, and wool fabrics.
Transfer printing can be divided into wet method, dry method, steam method, vacuum method, thermal method, etc. form. The transfer printing method can accurately reproduce patterns, facilitate mechanized production, and has a simple process. In particular, the post-printing process is simpler than traditional printing and dyeing and the printing feel is the same as printing and dyeing. Therefore, it has the potential to gradually replace the old printing method. However, most printing and dyeing factories in my country still use traditional printing and dyeing methods, and only a few production units use transfer printing for production.
In addition to polyester, the widely used hot-melt resins currently include polyamide, vinyl acetate copolymer and polyurethane. The main component of polyester hot melt adhesive is polyester resin, which is a polybasic acid. Obtained by lipidation with polyols. Polyamide hot melt adhesive has strong adhesion, toughness, low temperature resistance and excellent affinity with nylon fabrics. It is suitable for preparing nylon transfer printing paper. Ethylene-vinyl acetate copolymer has a low melting point and strong adhesion. After adding printing ink, it is suitable for producing transfer printing paper. Polyurethane hot melt adhesive is mainly used for gluing leather and polyhydrethylene plastic. For transfer printing, since the fabrics to be printed are different, it is best to use suitable hot melt adhesive ink.
1. Characteristics of transfer printing method
(1) Transfer printing patterns have the characteristics of realistic patterns, delicate patterns, clear layers, and strong three-dimensional effect. Transfer printing can print natural scenery and artistic patterns.
(2) Transfer printing equipment has the characteristics of simple structure, small area, low investment and high economic efficiency. Since the equipment is tension-free processing, it is suitable for printing of various thicknesses. In addition, no need to After post-processing, it can be packaged and shipped to the factory.
(3) Transfer printing does not have environmental pollution problems. Due to dry processing, there is no need for washing, steaming, drying and other processes, so there is no waste gas and waste water discharge.
(4) Transfer printing has the advantages of high production efficiency, labor saving and easy operation.
2. Transfer printing mechanism
Transfer printing is mostly used on polyester fabrics. It is a printing method that uses high temperature (about 200°C) to heat the dye to sublimate into a gas phase and condense on the polyester surface, and then penetrate into the amorphous area of the fiber macromolecules, and is fixed inside the fiber after cooling.
3. Requirements for dyes for transfer printing
The sublimation temperature of disperse dyes used in transfer printing should be lower than the melting point of fiber macromolecules and not damage the strength of the fabric. The suitable processing temperature for polyester is 180-210°C. Within this temperature range, the molecular weights of dye sublimation species are all between 230–270. There are generally three types of disperse dyes with molecular weights in this range.
Fast-dying disperse dyes: The temperature can be sublimated at about 180°C. If the temperature increases again, the color will change, and the edges will bleed.
Good disperse dyes: the temperature can be sublimated within the range of 180–210℃ . Hair color curve is flat. The temperature during dyeing has little effect, so it is a suitable disperse dye for transfer printing.
Late dyeing disperse dyes: in 180–2At 10°C, it is impossible for dyes to sublimate and develop color well. If the temperature is raised, good hair color can be obtained. This type of dye has a strong dependence on temperature when dyeing.
Based on the above situation, dyes suitable for transfer printing should meet the following conditions:
(1) The dye for transfer printing must be fully sublimated and fixed on the fiber below 210°C, and can obtain good washing fastness and ironing fastness.
(2) Transfer printing After being heated, the dye can fully sublimate and transform into gas-phase dye macromolecules, which condense on the surface of the fabric and can diffuse into the fiber.
(3) The dye used for transfer printing has a small affinity to the transfer paper and has a low affinity to the fabric. Be more friendly.
(4) The dye for transfer printing should have a bright and bright color.
Four. Color ink for printing transfer paper
Most of the printing of transfer paper for transfer printing uses printing and screen printing processes and equipment. The composition of the color ink includes dyes, carriers, adhesives, etc. The preparation of the color ink is the above The three ingredients are mixed and then poured into a colloid mill or three-roller grinder to grind the dye evenly in the color ink
(1) Vehicle The function of the vehicle is to evenly distribute the dye in the color ink and transfer the dye from the printing equipment to the transfer paper. According to this requirement, the vehicle should be cheap, non-toxic and non-flammable. Water is suitable. However, the transfer paper is composed of cellulose. When water is used as the color carrier, the fiber will swell, causing the deformation of the fine pattern. Moreover, due to the slow evaporation of water, it is difficult to produce the color at high speed if using organic solvents. When taking the dose, although It has the advantages of small deformation of paper, the color ink can print fine patterns, and has suitable volatility, which is conducive to higher speed production. However, it has the disadvantages of higher cost and easy burning. It can also be used with strict caution. Oil-based color carriers, such as high-boiling point oil, will cause the dye to diffuse deep into the transfer paper, thus affecting the amount of dye on the transfer paper transferred to the fabric.
(2) Binder Binder refers to the substance that controls the viscosity of the color ink. If the amount of binder is too small, the viscosity of the color ink cannot be guaranteed, resulting in poor printing transfer paper effect. If the amount of binder is too large, the dye transfer speed from the transfer paper to the fabric will be reduced. Slow down, which results in too much dye remaining on the transfer paper. Press. Depending on the vehicle used, the binder should be selected separately. When water is used as the vehicle, commonly used synthetic dragon glue or carboxymethyl cellulose is used as the binder: when organic solvents or oils are used as the vehicle, it can be used. Ethylcellulose is the binder.
5. Transfer printing requirements for transfer paper
When printing transfer paper for transfer printing, the transfer paper used should have the following characteristics:
（1） It must be strong enough;
(2) The affinity for the color ink should be small, but the transfer paper should have good coverage of the ink;
（3） The transfer paper should not deform, become brittle or yellow during the printing process.
(4) The transfer paper should have appropriate hygroscopicity. Too little hygroscopicity will cause mismatching of color and ink; too much hygroscopicity will cause deformation of the transfer paper. Therefore, the filler must be strictly controlled when producing transfer paper. It is more suitable to use semi-fillers from the papermaking 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
Transfer paper is best made of softwood pulp. It is better to have half chemical pulp and half mechanical pulp. This can ensure that the flower paper will not become brittle and brittle when treated at high temperatures. Turn yellow.
Six. Seal of floral paper Preparation method
The printing of floral paper is a process in which colored ink is printed on transfer paper through printing and screen printing methods. At present, transfer printing paper is mostly printed by printing method. The printing method of floral paper There are four printing methods: gravure printing, letterpress printing, lithography and screen printing. The printing method is used to print decals, with gravure printing being the most widely used. Batch and various varieties of transfer printing paper can be printed at the printing and dyeing factory. It has the characteristics of low cost, fast speed, rich color and easy operation. However, the screen printing method uses water-soluble ink. The three-dimensional effect and outline clarity of the pattern on the flower paper are not good, and the pattern is thick, which cannot bring out the characteristics of the transfer printing pattern.
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