Frequently Asked Questions

How does E-Beam Drying Work? E-beam drying makes use of the ability of electrons to interact with the atoms and molecules of materials in ways which cause the material properties to change. Special solventless inks and coatings are formulated so that the interaction between the electrons and the inks/coatings produce favorable functional and aesthetics properties in the dried product. A simplified way to visualize the "drying" process is to imagine the inks/coatings to be mixtures of atoms and molecules which are not tightly connected to each other in the "wet" state. When these "wet" products are passed through an E-beam dryer, the beam's electrons transfer energy into the atoms and molecules, causing them to break apart and then join to other atoms and molecules. By this process, individual molecules become linked together and form a large bound molecular structure containing all of the "loose" atoms and molecules of the "wet" product. This connecting of molecules is the mechanism producing favorable properties of the dry inks/coatings.

How is the Electron Beam Produced? The BroadBeam dryer creates an electron beam much as the beam is produced in conventional electron tubes used for high power radars or radio and television wave transmission. The electrons originate from tungsten filaments which are electrically heated. After the electrons are emitted from the filaments, they are accelerated to high velocities by the force exerted on them by a high voltage electric field. All of this takes place in a stainless steel vacuum chamber. The accelerated electrons have so much energy that they are able to pass through thin metallic foils which are used as "E-beam windows" to separate the vacuum chamber from atmospheric pressure. The window foils are often made from 0.006 inch thick titanium. Outside the vacuum chamber the electrons hit the printed web as it passes through the BroadBeam dryer. The actual region where the interaction occurs is kept filled with nitrogen gas, because the oxygen in normal air inhibits the favorable joining of molecules.

What are the Benefits? The numerous benefits associated with the use of E-beam drying include:

• High Speed. The entire process is completed in the time that it takes for the web to pass through the electron beam. For example, a web running at 1,000 fpm passes through the BroadBeam in 0.04 seconds. BroadBeam dryers are powerful enough to dry at the highest speeds of the new generation of presses, 1600 fpm (500 mpm). At these speeds, the entire process is completed in 0.024 seconds.
• Minimal Space in Line. The dryer length can be very short because the drying occurs so fast. Overall in-line length of the BroadBeam processor is less than seven feet.
• No Solvents, No VOC's. Solvents are not used in the "wet" inks/coatings. Unlike conventional heat set inks, the process does not require the removal of solvents in order to create a dry product. In other words, all of the chemicals in the "wet" product remain locked into the "dry" product. This is the reason that no VOC's are produced, and no incinerators or other devices are needed to treat pollution.
• High Electrical Efficiency. The process for creating the electron beam is highly efficient as is the interaction of the beam with the inks and coatings. The electrical energy is carried directly into the inks and coatings by the electrons, in contrast to heat set dryers in which a large volume of air must be heated and must in turn heat the product. Electron beam dryers can be as much as 100 times more efficient than thermal dryers. This high efficiency contributes to the favorable cost comparison to heat set printing. (Ref. 1)
• Negligible Web Heating. Because the electrical energy goes directly into the inks and coatings, and the web doesn't dwell in a hot gas, the temperature rise of the web is typically less than a few degrees Fahrenheit. The small amount of heating is an important factor when printing on paper or paperboard because remoisturizing is not needed, and also enables printing and drying on heat sensitive substrates such as plastic film or foam.
• Functional and Aesthetic Characteristics. High gloss, scuff resistance, depth of color, and strong bond to paperboard are some of the best known properties of E-beam cured inks and coatings. Not as well known is the way in which these features relate to recyclability of the finished product. A recent study by the Beloit Corporation, funded by RadTech International North America, showed that de-inking and recycling fiber in E-beam products is actually easier, and better final results are obtained, than with water-based inks and coatings. (Ref. 2)

References:

1. W.T. Newcomb, T.J. Menezes "A Comparison of E-beam UV and Thermal Drying for Web Offset Printing", RadTech '92, Boston, April 26-30, 1992

2. D. Kom, "Recyclability of EB/UV Coated Paper", RadTech '92, Boston, April 26-30, 1992.

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