VERSATILE Bobst presents the new Rotosil line for silicon application on paper and other flexible supports, destined for the production of self-adhesive labels and release liners.

Analysis of the demand trends and technical evolution of the (growing) market of labeling and liners; the major host-enterprises who shared their thoughts and strategies, including Gascogne Laminates, the owner of the spreader that was presented, and Dow Corning, a supplier of silicon products; the Rotosil brand machine by Bobst for silicon application on paper and other flexible supports, shown in operation during the open house… all this helped make the event organized last July by Bobst Italia at its facility in San Giorgio Monferrato a substantial one. At center stage was the new line for silicon application, which evidences the investments which the Swiss group has made in special machinery, as well as the knowhow developed by Bobst Italia over the course of more than 50 years in the sectors of self-adhesive labels, adhesive tapes and pre-/post-metalization processes.

Precise, flexible, modular
Versatility is one of the most standout features of the new Rotosil by Bobst, a high profile concern both in terms of performance quality and in terms of the ergonomics, reliability and eco-sustainability of the solutions it adopts. A fundamental contribution is made in this sense by the trolley spreading unit, which enables employing different technologies and adjusting the machine’s configuration at any moment in order to satisfy new market requirements. In fact, Rotosil has the capacity for integrating other equipment types that meet specific production requirements, such as, for example, rotogravure printing units or in line cutting.

The unit in question can be configured with 5 rollers for solventless silicon spreading or as a rotogravure spreading unit for applying water or solvent based silicon; in that case 2 trolley’s suffice for up to five different silicon application techniques.
The 5 roller element’s design, in particular, was developed in such a way as to guarantee excellent precision and uniform spreading, in addition to task repeatability even when applying products with a low net weight.
Worth pointing out, moreover, is that the spreading unit is completely closed and equipped with air expulsion and suction systems in order to cut back fumes emissions, while the main controls are located externally, guaranteeing maximum operator safety.

Elements that make the difference
Rotosil reaches 1000 m/min and is made up of modules designed to guarantee the robustness and reliability of the machine and process repeatability in all application types, even at maximum speed. Equipped with automatic shaftless heads, this spreader incorporates a few elements of particular interest.

For optimized drying – The ventilation and drying section is impressive. All parts that make up the system have been designed by Bobst Italia technicians based on decades of experience, with the primary objective of guaranteeing the same level of drying throughout the width of the web, in addition to other decisive advantages in terms of the installation’s functioning and efficiency. Each section of the tunnel is equipped with a system for feeding air from above and below, with independent pressure control, enabling different parameters according to production requirements. Furthermore, the individual variable recycling system for each section of the tunnel optimizes energy consumption.

Ergonomics and safety – Rigorously applied throughout the entire line, from the early design phases, the ergonomics and safety criteria stand out especially because of the accessibility of the various parts, which facilitates maintenance operations and the web insertion, and because of the tunnel’s electronic shaft control opening/closure system with no manual transmission. All the safety solutions adopted have been approved by a certified risk assessment agency.

Correct humidification – When working with paper supports, correct humidification is essential in order to prevent the formation of defects or ruptures in the web. The system installed on the Rotosil includes one or more vapor humidifiers and is based on Bobst technology, featuring individually adjustable sections in order to dispense the most suitable flow of vapor, guaranteeing uniform humidity throughout the web width.
Also, this solution enables optimize overall consumption of energy, resulting in costs reduction.           

Partners in adhesives
Bobst has recently conducted a series of tests on its fold ‘n glue machines with the water-based adhesives of various suppliers, in order to identify the products capable of guaranteeing the most precise application, even at high speeds, and corresponding savings in materials. Those of H.B. Fuller proved to be the best, and a partnership agreement has been signed by the two concerns. Their common objective is the continuous development of adhesives that minimize the quantities used, cleaning times, refuse and maintenance, while at the same time optimizing production yield. The tests developed by the Swiss multinational employed wheel and nozzle adhesive applicators. In the first case, Fuller’s Swift®tak 5490 effectively supported processes at 700 meters/min, with minimal spray and no debris accumulation in the storage containers. After testing the machine proved higher performing, with less stops for cleaning and a reduction in waste materials. In the nozzle applications, on the other hand, H.B. Fuller’s Swift®tak 5580 was used, whose optimal balance between fluidity and hardening times presents particular flexibility. Also in this case, the results proved excellent, with a particularly low rate of defective pieces, waste and unscheduled stops.