EB to boost flexo

3 August 2006



Sun Chemical, Comexi and ESI partnership advances ‘wet on wet’ printing, Mike Taylor reports


Sun Chemical has introduced a process using patented energy curable ink technology to improve flexo print quality and efficiency for flexible packaging. The company has linked with US based electron beam (EB) systems specialist Energy Sciences Inc (ESI) and Spanish press manufacturer Comexi in the “technological breakthrough” that involves printing “wet on wet” with a colour-independent tack sequence on the CI drum of a conventional flexible packaging press. According to Sun, it will provide “product-safe, high quality package printing that can be executed in less time and with less waste”.

The worldwide commercial launch of the WetFlex flexo printing process was staged at a recent open house in Comexi’s Girona facility. Converting Today joined more than 500 customers from over 20 countries to witness an impressive live demonstration of the innovative technology in which Sun’s UniQure inks were wet trapped through a CI press then cured instantly by an in-line EB system.

Bob Greenslade, product manager, energy curing products, for Sun Chemical Europe, stated: “We have maintained the good qualities of UV flexo and developed a mechanism for wet trapping of inks through the press. WetFlex is a truly new energy curable flexo print process.” Felipe Mellado, corporate vice president, marketing and technology, added: “This event marks a significant breakthrough for WetFlex, which we first introduced at drupa in 2004.”

By eliminating the need for interstation drying, the new process is said to provide higher quality products at a lower cost. Minimal dot gain for high quality print graphics is claimed and, for food applications, the UniQure ink system “virtually eliminates” taint and odour, the company states. High colour strength is said to offer significantly better mileage than conventional flexo inks, while the cured print has “inherent resistance properties that allow it to be used in the home and garden products market”.

In bulk form, the UniQure product is said to have the low viscosity associated with flexo printing. Once printed into a thin film, the ink phase changes to give a high tack surface, similar to offset. This allows the next layer to trap effectively without drying. The effect is independent of colour sequence, and the printed ink is said to have very stable properties - dots and solids retain structure, even when not dried.

As no heat is required for drying the inks, WetFlex is also said to be ideal for thin films and shrink sleeve applications. “Colour blind,” it offers excellent cure of both white and dark colours. Another benefit is that the inks do not contain VOCs.

To date, EB curing has only made strong penetration in the packaging market for carton printing. But the latest generation of EB equipment is said to offer lower costs and improved reliability. ESI market manager Brian Sullivan said: “EB is less expensive than ever and provides better quality at less cost for flexible packaging”.

The Comexi machine used to demonstrate WetFlex is an FW 1508 “hybrid EB” gearless CI flexo press incorporating an EZCure EB curing system from ESI. It also features a new high speed ink delivery system with a doctor chamber said to have enhanced inflow considerably and reduced ink consumption from 4.5 to 2.2g/m2. The press is said to be capable of printing WetFlex or solvent inks with rapid change-over. “Long term, we could have a dedicated machine, without drying units,” Comexi’s Peter Saey told Converting Today. “The hybrid is just a starting point.” Retrofit packages can also be developed for existing CI presses.

In the impressive demo at Girona, the press ran a seven colour, 1,040mm width job on 25 micron white OPPalyte BOPP at 300m/min. Using high resolution 60 line/cm screen DuPont plates and a Praxair anilox, it featured a three colour surface printed trap to highlight the capabilities of the new process.

WetFlex is suitable for wide web flexo printing, and the low viscosity, “easy handling” UniQure inks are said to be ideal for colour process work on a broad range of flexible packaging substrates. High gloss and good scratch, chemical and product resistance properties are claimed.

According to Sun, the inks do not dry until curing, reducing press downtime and start-up costs. They can be washed up and cleaned with water, and are easier to store.

Dr Volker Linzer, Sun’s energy curable packaging inks manager, noted: “You can use a much finer anilox roller, needing only 60 per cent of the ink you would for solvent or water based. The process also eliminates solvent recovery and incineration costs, and overhead thermal dryers - you can have a smaller footprint press.”

In summary, Bob O’Boyle NAI product marketing manager WetFlex, boasted: The print quality can compete with short run gravure on process work. WetFlex is a long term investment for cost savings.”


Related Articles
Fischer & Krecke delivers first WetFlex press

Contacts

Sun Chemical
Tel: +44 (0)1689 894168
Comexi
Tel: +34 972 477 744 209
ESI
Tel: +1 978 694 9000





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WetFlex demonstration run at Comexi WetFlex demonstration run at Comexi


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