Heatset and UV curing on coldset web offset presses

Leading newspapers and press manufacturers around the world are talking about semi-commercial printing on coldset webs, but what the September Ifra India conference and expo in Chennai demonstrated is that the Indian publishers are also at the leading edge of this transformation.

The most serious example of this of course were the presentations by K Balaji and the visit to Kasturi and Sons’ new plant in Maraimalai Nagar where two new Mitsubishi 4 x 1 presses were shown running with gas ovens and dryers and chill rolls. This implementation not only enhances the colour print on standard newsprint but also creates the flexibility of printing glazed or high brightness magazine substrates at high speeds with inline folding and stitching of other products on the same press.

Kasturi and Sons publishers of The Hindu newspaper have made a straightforward commitment to the what is being discussed at seminar after seminar around the world—how to keep the new presses productive by producing not just the newspaper in colour but also colour supplements and other magazine and commercial products. This is a path based on the proven technology of heatset printing on standard newsprint presses—something that has been practiced by newspapers in Japan on double width double circumference presses for almost 20 years and by Kasturi and Sons in India for a decade as well.

The group’s plant in Hyderabad at which the first Mitsubishi DiamondSpirit 4 x 1 with ovens and chillers were installed seemed to be a proving ground and pilot installation for the group. Thus heatset is the tried, tested and proven technology for semi-commercial printing on newspaper presses. However, UV curing is being used increasingly on smaller and slower presses as we recently saw on a Manugraph-DGM installation in the United States this August, and apparently being tried on faster and bigger presses in Europe.

Innocure
At the Ifra Chennai technical session on semi-commercial printing, Manfred Werfel of Ifra introduced the idea of UV curing and Thomas Litterst of Eltex gave a full (although hurried for lack of time) technical presentation of the Eltex Innocure solution using the example of its installation on a MAN Roland double width double circumference press in Vienna running at 70,000 cph.

Many of the visitors to the Ifra Expo in Vienna did in fact visit the installation but not always when it was running the Innocure system or printing semi-commercial products. With its innovative Innocure system, Eltex has succeeded in making impressive improvements in UV curing for printing and coating for high- speed web applications. According to Thomas Litterst’s presentation, the unwanted side effects in UV curing were primarily triggered by oxygen “dragged along” in the production process.

The inhibition effect of oxygen is compensated by an excess of photo initiators, which is not only expensive but also generates odor emissions as well as chemical compounds that are harmful to health. The Innocure system significantly reduces the oxygen on the surface, permitting a decrease in the expensive photo initiator share in UV inks, previously between 8 and 15 per cent to less than 2 per cent. This spells clear advantages for printing processes and results in brightly printed products, optimized costs and minimized odor emissions.

Innocure utilizes an electron and ion current to peel away the air boundary layer “touch-free”, replacing it with a layer of nitrogen. The nitrogen quantity required is only a fraction of the gas volume employed in conventional inert UV drying systems. A nitrogen infeed system especially adapted to the process and a special chamber design also allow higher web speeds during UV curing.

This system uses less energy by using laminar airflow to drive out the oxygen and putting a nitrogen or inert atmosphere next to the substrate creates optimal curing conditions with reduced thermal stress on the substrate. The Eltex Innocure system is a serious and comprehensive technical innovation that has attempted to overcome many of the shortcomings of earlier attempts at UV curing on large high-speed coldest presses. It is a sophisticated solution to many of the UV curing issues at high speed but UV curing on newspaper press is still relatively new. The technology may be more compelling in Europe or North America because of the environmental and energy issues concerning heatset printing with solvent based inks, and the ready availability and relatively low difference in price of UV inks. The Innocure system suggests the possibility of using inks with a reduced percentage of expensive photo initiators and hopefully this would also make the printed products more easily de-inkable and recyclable than previously.