Technological enlightenment

Commercial products that are made using UV and EB radiation-curing technology are diverse. CDs and DVDs, magazines, credit cards, shopping bags, labels, computer keyboards, cars, hardwood and vinyl tile flooring, food packaging, optical fibres, dental fillings, glassware, pipes and metal sheets are examples. Manufacturers are increasingly using UV and EB technology for coatings, ink, adhesive and composite applications. Converting Today spoke with David Helsby, president of Radtech Europe, the association for UV and EB curing and drying.

When the converting industry refers to curing, it is typically describing the use of ultraviolet (UV), electron beam (EB) or visible light to polymerise a combination of monomers and oligomers onto a substrate. The UV and EB material may be formulated into an ink, coating, adhesive or other product. This process is also known as radiation-curing technology because UV and EB are radiant energy sources. The energy sources for UV or visible-light curing are medium-pressure mercury lamps, pulsed-xenon lamps, LEDs or lasers. EB processing, unlike photons of light, which tend to be absorbed mainly at the surface of materials, has the ability to penetrate through matter.

With definitions out of the way, Radtech Europe promotes UV and EB radiation-curing technology by providing an organised and collaborative platform to serve the industry, which encourages interaction and exchange among its members and other UV and EB technology users. The association identifies, researches and acts on issues relevant to the UV and EB industry, such as the harmonisation of standards and procedures for safety and optimal output of products, and the R&D of radiation-curing technology. It operates at European and international levels with public and private bodies, which are of technical, ecological, economic and social interest to its members.

David Helsby, president of RadTech Europe, explains: "UV and EB technology is already used in a wide variety of industrial segments. RadTech Europe envisions UV and EB technology gaining broader acceptance by authorities and increased implementation throughout the European industry. The Association is confident that UV and EB radiation-curing technology will be recognised as one of the leading technologies for VOC reduction and economic development in the future."

An average person would have come into contact with an object cured using either UV or EB processing several times in a day, simply by reaching for a box of cereal, grabbing a CD or DVD, reading a magazine, buying something with a credit card, typing on a keyboard or driving a car.

UV and EB radiation-curing technology refers to a specific way in which coatings, inks, adhesives, composites and other materials may be cured, rather than using traditional methods, which use more energy and create harmful emissions. The UV light spectrum in a lamp and the focused electrons in an electron beam interact with specially formulated chemistries to cure materials quicker, with less energy and at lower cost.

The advantages of UV and EB are well-documented, particularly when used with manufactured products that require fast processing or on substrates that are sensitive to heat. In addition, UV and EB radiation-curing technology is considered environmentally responsible since most of the solvents in traditional processes may be eliminated, due to the special capabilities of UV and EB curing.

Advantages of UV and EB technology

Helsby says that the two leading reasons why companies switch to UV and EB radiation-curing technology are energy savings and improved productivity. "Since most systems are solvent-free and require less than a second of exposure, the productivity gains can be tremendous compared with conventional coating techniques. Web-line speeds of 1,000ft a minute are common, and the product is immediately ready for testing and shipment. While other processes might still be in the coating or drying process, UV or EB ensures a faster throughput with a low incidence of error and a big gain in productivity."

UV and EB radiation-curing technology is suited for sensitive substrates, as most systems do not contain any water or solvent. In addition, the process provides total control of the curing temperature, which makes it ideal on heat-sensitive substrates. Legislation and consumer choices influence manufacturers as to what substrates they use, which has caused categorical shift towards these sensitive substrates being used more frequently.

Compositions are typically solvent-free, which makes them environmentally friendly. Emissions and flammability are not a concern, light-cure systems are compatible with many application techniques and require minimum space, and UV lamps can usually be installed on existing production lines.

Migration regulation

Helsby says: "It is notable that although some of today's advanced packaging structures may effectively act as a barrier against migration, only two materials - glass and metal - are regarded as absolute barriers. The permeation of possible contaminants through the packaging substrate, including ink migration, may therefore be possible."

Ink migration brings the possibility of set off, which refers to ink transferring from the printed side of packaging or printed labels to the surface which makes contact with the packaging's contents. Concern over people's exposure to chemicals is at the heart of RadTech Europe's consumer-safety agenda.

The association is engaged with the packaging print supply chain, from the suppliers of raw ink materials to the end-user, brand-owners and retailers. There is ongoing progress in increasing the performance of UV inks for food packaging to ensure suitability for use. Brand-owners, such as Nestlé, have instituted their own company-specific food-packaging production standards.

Food safety has brought about regulatory initiatives across Europe, providing a framework for the use of inks in food packaging. RadTech Europe and other leading technical associations are all actively addressing these concerns with EU authorities.

There is currently no specific EU legislation concerning printing inks in food-packaging applications. However, regulation (EC) No1935/2004 ensures that the materials used in the production and packaging of food, which in their finished state are intended to or may make contact with foodstuffs, must not transfer any components to the packed foodstuff in quantities which could endanger human health or bring about change in the composition or deterioration of organoleptic properties.

Additionally, the Swiss ordinance on materials and articles in contact with food is often used as an industry standard. It lists permissible substances as any components that are subject to specific migration limits. Germany is also developing its own ordinance.

Radtech Europe members are using their expertise to help establish the highest possible migration limits for key raw materials. The association, in conjunction with EuPIA and the CEFIC UVEB Sector Group, has been developing REACH dossiers and compiling migration data for submission under the Swiss and German ordinances. As a result, GPOTA and TMPEOTA have higher migration limits when working on other substances, including a number of commodity photoinitiators.