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April 1, 2007

4 Min Read
Product Focus: Film technology developments

MW04_pw_die_df.gifThe Bandera three-layer extrusion head for processing geomembranes has a 2300-mm-diameter die with spiral channels.Profile Booster cuts production of startup scrap and reduces time to production.

The ever-increasing problem of industrial and residential refuse and waste for many communities has helped open a new market for blown-film processors in many countries. To prevent pollution and ingress into ground water supplies, many landfill areas are relying on geomembranes to protect the earth’s surface. These thick, flexible, high-quality films need to provide puncture protection, withstand pressure, and exhibit high chemical resistance. Italian processing equipment maker Bandera has lines running in a number of countries producing carbon-black-filled high-density polyethylene (HDPE) web that often also includes plasticizers and mineral fillers. Very-low-density PE and polypropylene are also being processed for this purpose.Typical structure of a geomembrane is 1.5-3 mm thick and extruded in widths from 4-8m in an output range of 1200-1700 kg/hr. For better adhesion to the ground, processors can also emboss the extruded film. Most processors are opting for wider widths to reduce the number of welds needed. The three-layer co-extruded vertical bubble provides some biorientation of the film to give good tear resistance. This line features three extruders with screw diameters of 200/85/85 mm with screws featuring an L/D of 30:1. The three-layer extrusion head has a 2300-mm-diameter die with spiral channels and an internal bubble control. The two-section motorized bubble calibration basket is featured in the 25m high cooling tower. From German equipment maker Windmöller & Hölscher comes a technology that allows operators to work on ’Easy Street’. Much of the time of an operator of a blown-film line is spent making product changes as lots become shorter and customers more demanding. He needs to change the layer distribution, film thickness, and output, as well as adjust all components of the extrusion line such as the extruder, sizing cage, and haul-off to prepare for the new product run. Making life a little easier for the operator is Easy Change, a module that sets up and automatically adjusts Varex-brand blown-film lines to the product parameters of the new product being produced. This can be done on-the-fly in three minutes and is considerably faster than a manual changeover, generally a process that can take up to 14 minutes. Non-saleable production waste is therefore reduced to a minimum. Another new development, Profile Booster, a system previously only available for Filmex cast film systems, is now available for Varex blown-film lines. It makes gauge profile measurement and control faster, resulting in the time to production quality being reduced by as much as 60%. It can also be used to efficiently change thickness tolerances during production in short order and at a cost savings deriving from less scrap production. To produce barrier films, processing lines with two cast-film stations and an inline laminator from Austrian machinery maker SML are an interesting alternative to conventional co-extrusion through a feedblock. This manufacturer is offering such a unit made up of three sections: a cast-film line processing nylon (PA) lamination film; a cast-film line producing PE film; and a laminating station to join the PA/PE webs. The manufacturer says the biggest advantage of this line compared to a line with single-stage, multilayer feedblock extrusion is that all edge trim is recycled since in each section the edge trim is uncontaminated and can be fed back directly into the extruder. Layer-to-layer uniformity is said to be more precise since thickness gauges control the profile of the individual monolayers. Thickness ranges for the PA/PE film are from 80?300 µm. Main applications of these barrier films are for thermoformed food products packaging and vacuum bags. The Black Magic S4 winder (BMW S4), from U.S. processing equipment producer Davis-Standard for high-speed film production, is engineered to improve efficiencies for hand-wrap and stretch-film production. It offers integrated automatic core and roll handling, and capabilities for producing six-up rolls on a 25 sec/cycle, roll change to roll change. The manufacturer says that based on upstream capabilities and 80% line uptime, the Black Magic can produce up to 2700 roll sets or 16,588 rolls/24 hr. It has been designed to reduce the cost of offline equipment and labor with configurations that eliminate bleed trim and automation that can be customized to meet different production requirements. This four-spindle surface/ center winder has two center core shaft supports for 3m (10 ft) net width films. The continuous, dual-surface-driven lay-on rolls enable production of ’flat-tail’ film rolls. Davis-Standard, LLC, Pawcatuck, CT; +1 860-599-1010; www.bc-egan.com; Windmöller & Hölscher KG, Lengerich, Germany; +49 5481 14 3669; www.wuh-lengerich.de; SML, Lenzing, Austria; +43 7672 9120; www.sml.at; Luigi Bandera SpA, Busto Arsizio, Italy; +39 0331 398152; www.lbandera.com

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