EB curing is a form of radiation curing. It is a process in which an electron beam is used as a radiation source to induce the rapid conversion of a specially formulated 100% reactive liquid to a solid. The principle is: First, high-energy electrons interact with paint or ink molecules to decompose them into free radicals; then. The free radical reacts with the C=C double bond to form a growing chain; finally, the growing chain reacts with the rest of the coating or ink to crosslink the cured coating and increase the crosslink density. Due to the high electron energy of the irradiation, the above reaction is often accompanied by molecular degradation. Molecular ion rearrangements and other negative reactions. The EB-cured coating thus produced greater branching and higher crosslink density.
EB curing requires dedicated curing equipment. Figure 1 shows the structure of the curing device body - electron curtain accelerator. The working principle is that after electrons are emitted from a group of linear cathode plates, they are accelerated by a vertical uniform electric field and a curtain electron beam is obtained under the accelerator irradiation box. Since the irradiated product is close to the electric field, its accelerating voltage is not high (below 500 kV), but the power is high due to the large output current. The linear cathode gun is far more compact than the scanning device, and it is easier to install on the production line and also easier to shield.
EB curing technology features
As a new type of curing technology, EB curing has unique advantages over traditional curing techniques.
(1) The EB energy required for curing ranges from 150-300 keV. It reaches the surface of the cured material at a speed close to the speed of light and is not only limited by the color of the coating, but it also cures the adhesive between paper and other substrate internal coatings and opaque substrates such as aluminum foil.
(2) EB curing can make paint. Ink and adhesive 100% cure, especially for areas where curing must be 100%, such as food packaging.
(3) High productivity and finished product rate create conditions for large-scale production.
(4) Low energy consumption, 5% of EB curing energy is 5% for UV curing, and 1% for traditional thermal curing.
(5) Simple operation, easy control, high accuracy and repeatability, no environmental pollution.
Application of EB curing technology in printing
At present, EB curing technology is mainly used in printing flexo printing, offset printing and coating.
EB inks are special inks that are cured using electron beam energy. Printing machines that use EB inks require special rollers, fountain solutions, and cleaning agents because the surface energy of EB inks is different from conventional inks.
In the early 1970s, Ford Motor Company of the United States applied EB curing technology to automotive parts and instrument coatings for the first time, which created a precedent for the application of EB curing technology in industrial production. During the same period, Album used EB-cured inks and coatings on packaging materials.
Early printing curing techniques were limited to the printing or glazing of web materials. This is because on a sheet-fed press, the gripper bar interferes with X-ray shielding produced by the electron beam device. On a web press, the EB curing device is located at the end of the press and is easily affixed to the top of the web without support. Through the constant efforts of the R&D personnel, this problem has been solved at present. EB curing technology has been widely used in the fields of sheet-fed folding cartons, sheet-fed commercial printing, and other fields.
Today, high-quality EB curing technology has become the best choice for flexographic printing. This is not only because it meets the requirements of environmental protection, but also because of its excellent printing quality and the continuous decline in the price of EB curing equipment (EB curing equipment has dropped from the original more than one million US dollars to about 200,000 US dollars today, and also There is a further decline.) The biggest breakthrough in EB ink application is its application on the mouth (central impression cylinder) label flexographic printing machine. During the printing process, the ink achieves a wet-to-wet imprint without drying after each color is printed. Using field technology, only one set of EB curing system can be used to instantly and thoroughly dry the substrate, that is, a “dryer†replaces multiple sets of drying devices in traditional printing.
In label printing, EB coating has also been widely used. The main difference between EB Varnish and EB Ink is that the former does not contain pigments. In UV glazing, two-layer coating is often performed in order to obtain a good gloss. The first glazing unit coats the substrates with substrates of water quality. This coating isolates offset inks and UV varnish to prevent chemical reactions and to print both graphic and non-graphic components on the prints. Micro concave and convex filled; the second coating unit coated with UV varnish, so that the printing products get a better printing effect. In the middle, up to 3 hot air blowers need to be equipped to achieve thorough drying of printed products. EB curing has the outstanding advantage of being able to cure thicker layers. EB coating uses “single-layer†film instead of traditional double-layer or even multi-layer structures, which greatly saves materials and greatly reduces production costs. According to statistics, only coating the process, the use of EB coating can reduce production costs by about 10%. In this field, the most effective progress is the successful development of Sun Bean, a product with low solubility. It is allowed to come in direct contact with food and can be used as an internal coating for food packaging. Today, this product has been widely used, such as coating in film paper packaging, multi-layer cloth bags, food boxes and the like. When applying EB, it is also necessary to pay attention to the compatibility with ordinary printing inks, because waxes and lubricants in ordinary inks will hinder the wetness of EB lacquers.
With EB curing, the coating layer, which originally required several minutes or even several days to completely dry, can be dried instantaneously, streamlining operations can be realized, and the production efficiency can be greatly improved. The application of EB curing technology has greatly shortened the printing and storage. From the time of glazing to packing and transportation, the entire process of printing, glazing, and shipping can be completed in one day, which truly meets the requirements of high timeliness in today's times.
Application Prospect of EB Curing Technology in Printing Field
EB ink (varnish) has many advantages, making EB curing technology show strong vitality in the future development.
(1) It contains no volatile substance VOC, has no odor or only a small odor, reduces the harm to the health of workers, and has no environmental pollution.
(2) Good resistance, since the chemical substances in the ink form a polymer three-dimensional network polymer through cross-linking reaction, the ink film has good chemical resistance and friction resistance.
(3) The curing time is short, generally only 0.1 seconds can be completely dry, compared with the traditional printing takes several minutes or even several days to completely dry, compared to greatly improve the production efficiency, is conducive to the scale of production.
(4) The pigment concentration is high, the printed product has a beautiful appearance, and has a strong glossiness and three-dimensionality.
(5) Reduce the cleaning time of the printing press. The printing ink in ink fountain will not appear crusting and hardening even if it is stored for one night, which reduces waste.
(6) There is no strong heat that causes the substrate to deform when cured.
Of course, as a new developing curing technology, EB curing technology also has some shortcomings. For example, in recent years, although EB curing equipment has been greatly reduced in price, its one-time investment in equipment is still relatively large; the price of EB ink is still higher than the price of ordinary ink; EB curing is only suitable for flat coating curing. Thus, the geometry of the cured product is limited; an important feature of EB ink is that it has good resistance, but this becomes difficult to remove ink when the waste print is recycled. One of the factors that hinders recycling, so new research must also be done on the recycling of printed materials.
In short, the application of EB curing technology in the packaging and printing industry is promising. In order to make the field curing process more convenient and economical, it is necessary to actively develop low-cost, compact EB curing equipment, and improve the transmission device so that the product can be rotated and cured, so that the radiation curing can be applied to various shapes of products. It can be asserted that EB curing technology by virtue of its low pollution. Low energy consumption. The characteristics of high quality will have greater development in the future.