UV curable hotmelt is finding application for labels, reports IST Metz's Rolf Müller
Self adhesive specialist Herma is setting its sights towards using innovative technology, particularly for extremely demanding applications. With its UV curable acrylate adhesive, it is believed to be the first manufacturer to use this new high tech PSA technology in adhesive and label production. Since the adhesive can be used universally, it is especially suitable for labelling carton board, synthetic materials, lacquered metal, glass and PE containers.
Hazardous goods containers for the chemical industry may be just as easily labelled using this adhesive as can pharmaceutical ampoules or food packages.
Label applications will be more and more demanding due to the world wide usage of labelled goods. The surfaces requiring labelling are very diverse, for instance plastics materials, lacquered metal, carton board, stainless steel or glass. Not only are these surfaces different, but also external influences may vary widely. Many goods are exposed to climatic change during transport – they may be affected by hot and cold temperatures, by seawater or by the high humidity of a tropical climate. To compound matters, the labels have to remain in place during the complete lifetime of the goods. This could be up to five years.
The adhesive combines ecology with innovative technology. Herma has developed a new ecologically based UV cured acrylate adhesive, which it uses in its label production for the chemical, pharmaceutical and food industries. The UV adhesive is said to have many advantages over the previous types based on solvents, standard hotmelts and dispersions. Thanks to its 100 per cent solid content, the use of solvents is no longer necessary, which reduces both the quantity to be transported and energy consumption. The technology is based on curing extremely stable polyacrylates with the help of UV energy – in contrast to the previous heat activated types.
As the range of 250 to 260nm is responsible for curing the adhesive, non doped mercury (Hg) lamps are advantageous. It is absolutely necessary to know the exact UV energy dose, because the adhesive properties depend upon a certain degree of curing.
For converting the material, it is important to know that printing transparent films like PE, PP or PET with UV cured inks will not influence adhesive properties, that is there is no post-curing effect. The photo-initiator is already polymerized in the base polymer. This technology prevents a migration of the photo-initiator from the adhesive to the surface of the labelled goods. The raw material therefore meets FDA regulation 21 CFR 175.105.
The UV cured acrylic polymer is also said to exhibit excellent die cutting properties. In addition, the adhesive shows an extremely high resistance to heat and water and very good ageing properties, since it does not tend to become brittle or show any fading.
The acrylate adhesive may be used together with almost all Herma label materials. Herma PE laser, a material that is suitable for outdoor use, was specially developed for laser printers. It is also the first PE film that may be printed with laser technology. Extreme flexibility and weather resistance are characteristics of the white, impregnated Printex L, a special paper that is coated on one side. And Herma PETP, a white, semi transparent polyester film, meets the demands of weather resistance.
The good characteristics of both adhesive and film are claimed to guarantee perfect printing results in all xerographical printing processes. Depending on applications, the labels are available in rolls for thermo transfer printers, in endless reproduction folded sheets for matrix printers or in sheets for laser printers. With the new UV adhesive, these materials are claimed to represent “the near perfect solution” for labelling chemical drums, automobile spare parts and electric or electronic components. The labels are available in all sizes.
Tel: +49 7022 600237. www.ist-uv.com
Tel: +49 0711 / 7702 0. www.herma.com