The trend of ink curing and drying (2)

Common ink drying and curing equipment

Ink drying is often compound drying, so what drying equipment, how to set the parameters, so that the best drying efficiency while saving energy is the printer's most concern.

Infrared drying equipment

(1) Light source. For ink drying, the effect of medium-wave infrared is best. There are three kinds of infrared light sources.

The first is the heating wire radiation source, and the common is the non-enclosed resistance wire jacket quartz lamp. The heat radiation intensity of the lamp tube cannot be controlled with the distribution of light wavelength, the efficiency is low, the price is low, and the service life is about 2000-3000 hours.

The second type of light source is to place the resistance wire inside the closed quartz tube, and fill different gases in the tube to change the wavelength distribution characteristics of the radiation light, and at the same time, the filament is isolated from the oxygen in the air, and the radiation efficiency is high. Most of the imported printing presses nowadays are equipped with such light sources and have a lifetime of 5,000 to 10,000 hours. However, a large part of their radiation energy is still distributed in the visible light and near-infrared rays. Medium-wave infrared light is not very abundant.

The third type is electrothermal semiconductor light tubes. The outer shape of the ceramic tube is coated with a red or gray matt semiconductor material, and the inner wall of the tube is wound with a resistance wire. Electric heating induces radiative emission of the semiconductor material. When the lamp ignites, the light is dark red or black. By selecting the semiconductor material, the wavelength distribution of the radiant energy can be changed, and the radiation efficiency is extremely high.

(2) Infrared lamp reflector. At present, there are two kinds, one is a gold-plated reflector, coated with a metal film 180 ° around the lamp tube, the metal film reflects infrared efficiency up to 90%; the other is the aluminum plate or aluminum plate pressed oval or figure eight Reflector, as shown in Figure 2, the closer the lamp is to the lampshade, the higher the reflection efficiency and the highest reflectivity of 85%.

(3) Heat dissipation of infrared lamps. The heat dissipation of the surface of the infrared lamp can be blown, and the air volume does not affect the infrared power output of the lamp. Since only about 1% of the energy radiated by the infrared lamp is absorbed by paper and ink, and the rest of the energy is completely converted into heat, causing the temperature around the machine to rise, it needs to be exhausted to the outdoors or recycled.

(4) Scope of application. Infrared lamps are used for drying infrared inks. The drying efficiency of non-dedicated infrared inks is very low and does not even work for some inks. Infrared penetrating power can dry the upper and lower layers of the ink film at the same time, accelerating the ink penetration, and promoting the oxidized conjunctiva, especially for the application of thick ink layer printing and drying of coating oil. For the lower solvent content offset, letterpress, screen printing, ink printing, flexographic printing inks and water-based gloss oil drying effect is very good.

2. Hot air drying equipment

(1) Heat source. There are three types of heat sources that generate hot air: electric air ducts, such as stainless steel, quartz glass, and ceramic-coated hot air ducts; high-temperature oil pipes, high-temperature oil heating air through pipes to generate hot air; high-temperature steam pipes that produce high-temperature steam through boilers to generate hot air .

(2) Hot air device. The air around the heat source is heated by the fan and blown to the surface of the ink. The adjustment of the direction of the hot air and the angle of operation of the paper can improve the efficiency of hot air drying.

The higher the speed of the hot air relative to the paper, the more favorable it is to reduce the vapor pressure on the surface of the paper and increase the volatilization rate of the solvent; the wind direction is adjusted so that the wind direction will have an additive effect on the running speed of the paper, which is more conducive to drying. The speed of the hot air duct must not be lower than the required speed. Otherwise, poor heat dissipation on the surface of the duct will burn the lamp. The wind speed should not be too high, because some energy will be lost during the air circulation process. The optimum drying effect can be achieved only by properly selecting the fan pressure and air volume.

(3) Scope of application. It is suitable for the drying of plastic gravure and flexo printing inks and solvent-based varnish, and it also accelerates the drying of water-based inks and varnish.

3.UV curing equipment

(1) Light source. Commonly used high-pressure mercury lamps and metal halide lamps, high-pressure mercury lamps are mercury atoms excited to form a continuous spectrum, adjust the mercury content of the lamp, so that the radiation wavelength in the curing section 254 ~ 420nm, more abundant ultraviolet light. Metal Halide Lamps are metal halides such as antimony and iron added to mercury lamps. They excite them under mercury excitation conditions to generate radiation. Different metals can be added in an appropriate amount according to the difference in the absorption spectrum of ink, so that UV lamps can absorb more ink. Light waves improve curing efficiency.

The content of impurities in the metal halide tube is extremely small, and the purity of the electrode material is high. Therefore, the manufacturing process is complicated, the difficulty is high, and the price is high. At present, domestic production of high-quality, high-power metal halogen lamps is not yet available. The current market is the United States Fusion, Germany IST, Japan's research Qi company's products. The lamp life of the power density 160W/cm can reach 2000 hours and the lamp head is not dark, still can reach 50% emissivity after 4000 hours.

(2) Cold UV light source. When the UV lamp is ignited, its internal temperature should reach 600-1000°C. If the temperature in the lamp is too low or the light is too high, the light will go out. Therefore, the “cold light source” does not actually exist, but the lamp cooling system can be used.

(3) Microwave UV lamps. This is Fusion's new product, the lamp length of 6 inches, no metal electrodes at both ends, relying on the microwave to stimulate the lamp absorbs high-speed movement of the material molecules generate heat, and then excite mercury, metal halides and other substances glow. Aluminum is a good material for reflecting microwaves. A microwave source emits microwaves to an elliptical aluminum lamp shade, and focuses on an infinite lamp tube to excite mercury or a metal halide to emit light.