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Question and Answer

Safety and Handling of UV Coatings

by Staff

August-September, 2002
In large part, most of the processes that graphic finishers are involved with are “dry” processes. Foil stamping, embossing, die cutting, and even folding/gluing, except for the glue, do not facilitate special handling or create safety issues. However, this is not true with the UV coating process.

Many finishers today either have UV coating capabilities or have considered adding UV coating as an additional service. The big change (or challenge) for finishers who have or are considering adding UV is the safety and handling issues that go along with the process. InsideFinishing has explored a few of the issues regarding the safety and handling of UV coatings to help address some of the questions that are frequently asked.

What regulatory considerations exist with UV coatings?
Most UV/EB curing materials are not regulated by DOT as flammable or corrosive. Exceptions are styrene and BCEA, which have a high content of combustible and corrosive acrylic acid. With these exceptions, and unless diluted with flammable solvents, UV/EB curing materials generally are not “hazardous waste” (toxic, corrosive, flammable, or reactive) as defined under RCRA regulations. However, as with all chemicals, contaminated materials and wastes should be disposed of in accordance with federal and local requirements. In addition, UV/EB curing materials contain little to no VOC’s and typically contain no hazardous air pollutants (HAPS) as specified by the EPA. They are not typically specified in any federal or state Community Right-to-Know list as well.

Does the UV coating process create any byproducts which might cause concern?
The only byproduct of the UV lamp is ozone gas. It has a pungent sweet odor and is distinctive enough that concentrations well below the threshold limit value (TLV) of 0.1 ppm are still noticeable. At high enough concentrations, ozone gas and odors can cause headaches and fatigue. After repeated exposure at high concentrations, ozone can cause dryness of the upper respiratory tract, pulmonary irritation and possibly respiratory infections.

Simple steps can be taken to avoid any type of dangerous exposure to ozone gasses with spot collectors and proper ventilation adjacent to the UV curing unit, as well as with lamps to draw ozone away from the operators. The ozone can be effectively eliminated in the processing area by exhausting the air of the reactor’s cooling system to the exterior of the facility. This process is quite safe as the hot gas is very unstable and will rapidly break down to oxygen while passing through the ventilator ducting. One can also measure ozone levels within a facility with ozone gas detectors, test strips, or indicator badges. These products can be purchased by supply companies such as UV Process Supply.

What disposal issues must be considered with UV coatings?
Incineration is the most viable method used. Users should find a reputable, approved company to handle incineration. In a situation where a company uses both conventional solvent and UV-curable coatings in the same facility, both are disposed of in its solvent/paint waste stream. The solvent/paint waste is sent to a fractionation facility where the solvent is recovered and used as wash-up or cleaning solvent. The solids and still bottoms from the fractionation are sent to incineration.

It has been argued that UV coated paper is not recyclable. This is simply not true. Agitation of paperboard in water during the pulping process causes the cellulose fibers to fall apart and separation of the coatings to take place. UV varnishes produce larger fragments of hard resin than other coating types, thus a smaller proportion of this waste can currently be used in forming new board. However, such waste material can be used for “fillerboards” and “greyback” products produced by recycling industrial waste paper plants. It is also possible to install de-inking separation systems, which are able to “float off” inks and coating residues, and then skim these away from the pulp. Since it is possible to recycle UV coated boards, and since the technology exists to completely remove coating contamination from cellulose fibers, it can be argued, when viewed in the context with the substantially lower energy requirements and zero solvent emissions, that UV printing processes are more environmentally friendly than solvent or even water-based systems.

What type of protection should be worn when operating UV coating equipment?
UV equipment should be designed to shield the UV light from the operator; even bounce (reflected) light should be minimized or avoided all together. For safety purposes, it is recommended to wear safety glasses or other adequate eye protection when running UV/EB coating equipment. UV filtering safety glasses are available from companies like UV Process Supply, which provide UV filtering and should definitely be worn if optimum shielding cannot be attained. The use of contact lenses should be avoided when working with UV/EB curing materials as well.

Tests have shown that the best gloves to wear when working with UV coatings are made of nitrile or butyl rubber. They are both a more effective barrier to permeation than other materials. PVC gloves are okay in many applications if the contact is expected to be minimal and the gloves are disposed of immediately if contaminated. Tests have indicated that latex is not a recommended material when handling UV coatings.

If UV/EB materials are exposed to skin or clothing, the clothing should be immediately removed. It is recommended to wash the affected skin areas thoroughly with mild soap and water or with materials specially designed for that purpose. Never use abrasive cleaners or solvents. Solvents may increase the penetration of monomers into the skin. Continue to flush the skin with lukewarm water for 15 minutes to ensure the material is completely removed. As long as this is done immediately after exposure to the UV/EB material, little to no irritation should occur.

How should UV coatings be stored?
The most effective method to store UV chemicals is in black plastic containers that allow for oxygen to be in contact with the coating. Black is recommended because it preserves the chemicals by keeping them free of sunlight or other ambient light that could affect the stored materials. The presence of oxygen is also crucial as it acts as an inhibitor to polymerization reaction, and its presence in storage actually increases shelf life stability. UV coatings should be kept away from oxidizing agents, acids, alkalis, catalytic metals and polymerization initiators as well. It is recommended to check with the UV coating manufacturer for the proper temperature that the coatings should be stored at. Excessive heat and freezing of UV should be avoided. A full range of containers are available that are developed specifically for UV inks and coatings.

Although there are additional precautions that must be taken when utilizing UV coatings verses many other finishing processes, it does not have to be overwhelming if the right procedures are followed. Working with your UV coating supplier and machine supplier to create the right ventilation, disposal, and storage systems can make adding UV coating as an additional service a very profitable venture.

InsideFinishing would like to thank UV Process Supply, Inc. (800-621-1296) and RadTech International North America (240-497-1242) for their assistance with this article.