LAYER UPON LAYER
I f you have happened upon a blown film equipment manufacturer recently, you have probably heard them boasting about the number of layers they can offer on their lines. Although the fundamental techno...
July 1, 2008 by Umair Abdul, Assistant Editor
If you have happened upon a blown film equipment manufacturer recently, you have probably heard them boasting about the number of layers they can offer on their lines. Although the fundamental technologies haven’t changed, most of the major players in the blown film field are either developing or currently offer 9-, 10-, or 11-layer blown film lines.
“Co-extrusion has been around for 40 years; what’s different is the quantity of layers that are being offered to clients,” noted Paul Waller, president of consulting firm Plastics Touchpoint Group. “And the reason for that is that there is a trend towards barrier structures.”
Traditionally, in sectors like food and pharmaceutical where barrier properties are essential, a smaller number of layers doesn’t do the trick. Waller uses the example of bacon wrap made with polyethylene (PE) and nylon, where a 3-layer structure wouldn’t work. The other option is to use a lamination process to achieve the necessary barrier structure.
“And that requires two machines, and it’s much more expensive,” he continued.
Which is where these new 9-, 10-and 11-layer lines come into the picture.
BREAKING THE BARRIER
A few months ago, Brampton Engineering announced that it had shipped an 11-layer blown-film line, a world first, the company claimed. The company’s SCD multilayer streamlined co-extrusion die became the first successfully commercial 7-layer die, and BE has since shipped dozens of 7-to 11-layer systems.
“BE was the first one to go into market with 8, 9, 10 and now 11 layers,” said Adolfo Edgar, marketing manager for Brampton Engineering Inc. “The idea is that you can do the same structure better, or you could do the same structure cheaper.”
In addition to eliminating the need for lamination, blown film experts note that multi-layer co-extrusion can help processors reduce their raw material costs.
“You can reduce the overall cost of that structure by 25 per cent, so there is an economic driving force that pushes you towards the layers,” said Waller.
For instance, processors can utilize a thinner film of their more expensive material without affecting the quality and properties of their final product.
“Co-extrusion can also give some savings on materials because people want to use additives with the multilayer structures, and these additives are very expensive,” added Felix Guberman, director of research and development at Macro Engineering and Technology Ltd. The company is currently making a 9-layer line at its Mississauga, Ont. plant after finishing a 7-layer line with an encapsulated layer, which allows for the production of a 9-layer film structure.
Industry experts note that one of the key factors that has allowed suppliers to offer more layers has been the evolution of blown film technology.
“There’s been a learning curve…there have been developments in die technology and also in extruder screw designs that feed the resin to the die,” said BE’s Edgar.
Additionally, suppliers are more confident in offering this level of sophistication because they can produce very complex multi-layer lines with better quality products. For instance, there is less variation in thickness, less frequency of imperfections, and fewer problems with interfacial instabilities.
“The big improvement is that die technology is much better because we are using more and more sophisticated simulation processes to optimize the processing windows before we cut the steel,” said Waller.
ON THE CUTTING EDGE
Brampton’s 11-layer line featured a unique extruder design to avoid a constricted die-extruder arrangement.
“From a production standpoint, it’s not a very good idea to have a cramped, hot section,” said Edgar. “We more or less kept a 9-layer configuration, and in a couple of those positions we piggybacked the extruders.”
BE’s SCD die allows the extruders to have different centre line heights, making the piggybacking of extruders possible.
Woodbridge, Ont.-based Alpha Marathon Film Extrusion Technologies Inc. has already delivered several 5-and 7-layer lines and is currently building a 10-layer fully automatic project to be shipped later this year. According to the company, the 10-layer line will feature a number of cutting edge technologies such as Gearless Direct Drive for all extruders, Alpha Dual Spiral Stacked co-extrusion die, Triton cool air ring with manual film gauge compensation mechanism, Advanced Water Ring and Accurate Layflat Controller, Horizontal Film Oscillator, and fully automatic winding with in-line sitters.
“The reason for Alpha Marathon to do this R&D and then design and build such a line is mainly based on our customers’ and the market demands, and to create a purely custom-made turnkey system to support the trendy market’s needs,” explained company president Domenic Marzano. CPL
Alpha Marathon Film Extrusion Technologies Inc. (Woodbridge, Ont.); www.alphamarathon.com; 905-265-2055 Brampton Engineering (Brampton, Ont.); www.be-ca.com; 905-793-3000
Macro Engineering and Technology Inc. (Mississauga, Ont.); www.macroeng.com; 905-507-9000
Plastics Touchpoint Group, Inc. (Thornhill, Ont.); www.plasticstouchpoint.com; 905-738-9742