EB ink curing and drying principle

Various kinds of technologies in the printing industry emerge one after another, among which the fastest growing one is the energy curing technology. It means that the ink or coating material is fixed or hardened on the substrate under irradiation energy, so as to obtain a dry print. UV light and accelerated high energy electron beam (EB) are two energy forms of energy curing technology. Correspondingly, inks cured with UV light and EB energy, respectively, are called UV inks and EB inks. Due to the good drying effect and small pollution, the use cost has also been significantly reduced in recent years, so it is increasingly favored by printing manufacturers.

This article will focus on some of the issues related to EB curing inks.

EB ink curing principle

The drying of the ink film after the printing of common ink is that the binder (solvent, grease) in the ink is absorbed and volatilized by the substrate, and the solid material (color, resin, wax, desiccant, etc.) remains on the surface of the substrate. A thin layer of ink. General ink drying and energy curing ink fixation, the difference lies in the ink / coating coating chemical composition is different, followed by whether the printing shop needs to be equipped with energy curing device device.

Process of Drying Principle of EB Ink and General Ink

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 radicals react with C=C double bonds to form a growth chain; finally, the growth chain and the rest of the paint or ink The components react 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 negative reactions such as molecular degradation and molecular ion rearrangement. The EB-cured coating thus produced greater branching and higher crosslink density.

EB curing requires dedicated curing equipment. 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.

The curing time of the first EB ink is very short, and it usually takes only 1/10 second to completely dry the surface of the substrate. For conventional thermosetting inks and sheet-fed offset inks, the drying time may take several minutes or even several minutes. It takes days to dry thoroughly, so the use of energy-curable inks to print offset printing jobs has a short delivery time, which is comparable to flexo and gravure, and greatly improves the production efficiency of offset printing.

The EB energy required for the second cure ranged from 150 to 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 also can cure the adhesive between paper and other substrate internal coatings and opaque substrates (such as aluminum foil).

The third EB cures 100% cure of coatings, inks, and adhesives, especially in areas where curing must be 100%, such as food packaging.

The third print, printed with energy-curable ink, is very resistant. Due to the cross-linking reaction of the chemical substances in the ink, a macromolecular network polymer is formed, and the ink surface has strong chemical resistance and friction resistance.

The solid content of the fourth EB ink after curing is close to 100%, and usually does not contain VOC (organic volatiles). This strongly demonstrates that the EB ink system is more environmentally friendly than the ordinary ink system. If the chemical composition of EB ink is appropriate, the odor of common inks dried by many oxidized conjunctivas is much smaller, and the printed surface is clean and free of dirt.

Fifth, with the development of technology, EB-curable inks for humans have been developed. What is the value of soda swell?

The sixth energy consumption is low, EB curing energy consumption is 5% of UV curing, and 1% of conventional thermal curing. Easy to operate, easy to control, high accuracy and repeatability, no environmental pollution.

Development of EB curing technology and application 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 presses using EB inks require special roller, fountain solution, and cleaning agents because the surface energy of the EB Gondola is different from conventional inks.

In the early 1970s, the Ford Company of America applied the 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 EB 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 continuous efforts of the R&D personnel, this issue has now been resolved. EB curing technology has been widely used in sheet folding cartons, sheetfed commercial printing and other fields.

Today, high-quality EB curing technology has become the best choice for flexible 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 CI (central impression cylinder) label flexographic printing machine. During the printing process, the ink achieves wet-to-wet imprint without having to dry after each color is printed. With EB technology, it is only necessary to use an EB curing system 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 a “single layer” film instead of the traditional double layer base to multilayer structure, 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 the wax and lubricant in common ink will hinder the wetting of EB lacquer.

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 time from printing, storage, glazing to packing and transportation, enabling the entire process of printing, glazing, packing and transportation to be completed within one day, truly meeting the high timeliness of today's times. Sex and requirements.

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 is dense at the end and the printed product has a beautiful appearance with a strong gloss and three-dimensionality.

(5) Reduce the cleaning time of the printing press. Even if the EB ink in the ink fountain is stored for one night, the skinning and hardening phenomenon will not occur and waste will be reduced.

(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. Therefore, the geometry of the cured product is limited; an important characteristic of EB ink is that it has good resistance, but this becomes a factor for deinking and hindering recycling in the recycling of waste prints. Therefore, it also has a New research must be done.

In short, the application of EB curing technology in the packaging and printing industry is promising. In order to make the EB curing process more convenient and economical, it is necessary to actively develop a low-cost, compact EB curing device, 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 will have greater development in the future due to its features of low pollution, low energy consumption, and high product quality.