A mile a minute

Almost 250 people from around the globe witnessed a new world record set in silicone coating when they attended the high speed symposium hosted by Maschinenfabrik Max Kroenert in Hamburg in September. A breathtaking 1,610m/min (one mile a minute) was set on a RECO 800 line during the event held in the Kroenert Technology Centre (KTC). Months of test runs preceded the event.

A group of partners including BASF, Dow Corning, Innovia, Nordson, Rohm and Haas, Siliconature and UPM, as well as Kroenert/BMB/Drytec actively participated in the symposium. The fact that competitors such as BASF/Rohm & Haas or Nordson/Kroenert were willing to come together marks a new approach in the breaking down of old barriers, said Kroenert.

Over two days the companies set out to prove that higher production speeds and better quality are possible when coating label materials, single-sided and double-sided covered adhesive tapes and self adhesive graphic foils using aqueous acrylate adhesives, thermal cross-linking silicones or UV curing hotmelts. "The result can be summed up as 'speed is not witchcraft' because it was proved that speed is a symbiosis of machine design, substrates and coating compounds," said Kroenert.

Exciting

Cost pressure is a constant issue for machine and substrate manufacturers. The market constantly demands higher production speeds and better quality. Manufacturers have come continuously closer to meeting these demands. However, end users require a balanced interaction between coating machines, runability of substrates and coating compounds. This is what the symposium in Hamburg set out to prove.

The excitement among the visitors was measurable as the machine operators inched the machine speed up towards the new world record, reported the company. Until recently, a speed of 1,000m/min was regarded as the maximum for silicone treatment and pressure sensitive adhesive coating with aqueous acrylate adhesives. Now the Kroenert RECO 8000, which has been in operation since November, 2004, with its record breaking 1,610m/min is the fastest production line of its kind in the world. Every second 33m² of silicone treated paper with a coated web width of 1,230mm was produced.

The six roll coating head is a central component, where the first five rollers are vertical and one roller is mounted horizontally. Rollers made of rubber and ceramics are used alternately; the final roller is made of steel.

Four demonstration runs were shown over the two days.

The first produced pressure sensitive adhesive coating for labels with Robond PS 7650, Rohm and Haas's water based acrylate adhesive. "It must have come as a surprise to many of the experts that right off the bat, the new adhesive made by Rohm and Haas could be used to produce an excellent quality with extremely low foam formation," said the company. In combination with BMB curtain coating technology (slot die process), production speeds of 800m/min (18g/m² dry) and 1,200m/min (12g/m² dry) were possible without the coating breaking. The product was dried with an 18m long drying channel, divided into six temperature control zones. This is a joint success for the producers of advanced material adhesives in developing a new adhesive bonding technology with a higher ratio of solids, and for Drytec in designing ever more efficient and powerful floating dryers, added Kroenert.

The second demonstration was the silicone treatment of UPM glassine HON 53 silicone paper (59g/m²) with Dow Corning Syl-Of Advantage series. It proved that production speeds of 1,200m/min (1.05g/m² coating weight) and 1,610m/min (1.25g/m² coating weight) are possible. Even a permanently focused observation could not detect silicone misting. A further aim of the run was to show reel changes at 1,200m/min. During automatic splicing a nozzle blows the cut-off material away from the new reel. The design of the knife and its cutting angle towards the web are crucial and high precision rollers synchronized with the web speed are essential to ensure that subsequent rollers are smoothly integrated in the process. Production of clear-on-clear label materials using BASF's UV curable acrylic hotmelt AC Resin 258 UV and Nordson curtain coating technology was next on the agenda. A PP film was laminated with a silicone treated PET film. Transparent and water insoluble labels are in large demand for cosmetics and household cleaners.

Two years ago Nordson and Kroenert agreed that new methods were required to meet future demands. They signed a co-operation agreement geared towards putting a new coating technology for clear-on-clear label production onto the market. They quickly took the technological step from a machine capable of running 200mm wide to a coating machine with a production width of 1,230mm. The 1,230 mm wide machine was initially demonstrated at 250m/min and then at 400m/min both at a coating weight of 20g/m². In combination with the applied special adhesive, the result was a fast, bubble-free coating.

Although a date for the market launch has not been announced, the partners are to meet soon to discuss an agreement.

The final run was a demonstration of pressure sensitive adhesive coating using BASF's water based, pressure sensitive adhesive Acronal V215. Here again participants were impressed to see a very stable bubble-free coating procedure, according to Kroenert. "Due to the very high solid content of the adhesive" (BASF supplied material with more than 60 per cent solids) "it would be possible to run faster than 1,200m/min on the machine. The existing drying tunnel is long enough to evaporate the water within the adhesive without any problem. There was no speed limitation in the coating system; this could also run faster."