Making the legally mandated transition from hydrochlorofluorocarbon blowing agents to chlorine-free HFC blowing agents was a good move for the ozone layer but a tough one economically for processors of extruded polystyrene (XPS) foam, who typically saw their production fall by about 30% due to process changes necessary to accommodate the new blowing agents. But a new die design from Extrusion Dies Industries LLC (EDI) is said to reduce the lengthy downtime needed for product changeovers to such an extent that it can help processors offset much of the loss in productivity caused by switching to non-ozone depleting blowing agents.
|EDI's new XPS foam board die allows for dimensional changes on the fly. Inset bolts just above and below the opening can be loosened to disengage the forming box from the die.|
As a signatory to the Montreal Protocol, the U.S. and other developed countries that signed the Protocol must incrementally decrease hydrochlorofluorocarbon (HCFC) consumption and production, culminating in a complete HCFC phaseout in 2030. The major milestones for developed countries are a reduction starting this year to at least 75% below baseline HCFC levels and a reduction in 2015 to at least 90% below baseline. In its bid to reach those goals, the U.S. Environmental Protection Agency banned the use and sale of virgin HCFC-22 and HCFC-142b for foam blowing purposes as of January 1, 2010.
According to EDI (Chippewa Falls, WI), its XPS foam board die technology makes it possible to accomplish a product changeover on the fly in 15 minutes. Putting that in perspective is Dennis Paradise, EDI's VP of sales and marketing, who says, "By comparison, a change in width or thickness with a conventional die system requires shutting down the production line for at least eight hours, followed by a two-hour startup phase in which no saleable board is produced-only scrap. The added uptime generated by our new system is sufficient to offset the lion's share of the output loss imposed by the switch to HFCs."
EDI is no newcomer to the market, having supplied dies to the XPS foam board industry for years, but its new die system comes with a different design that includes, among other improvements, a new type of forming box to facilitate dimensional changes on the fly. In most conventional die systems, the forming box and die lip constitute a single component. Changing the dimensions of the board requires stopping the production line, disassembling the lip/forming box, adjusting for new product dimensions, and reassembling the unit. The forming box in the new EDI system is separate from the die so changeovers can be made without stopping the production line.
Also new to this die is an adjustable full-manifold internal deckle inside the flow channel of the die. The deckle blades at either end of the manifold can be used to change flow-channel width by being moved farther into the channel or farther out. By coordinating the settings of the deckle blades and the forming box, it is possible to produce thicker board without changing width, again an easier adjustment in comparison with conventional die systems.
Another new component introduced to these dies is external edge restrictors that create the final side dimensions of the board as it emerges from the forming box and passes between the two top and bottom sizing plates that are typically used in foam board production. Restricting expansion at the edges results in less trim scrap and more lineal feet of board, says EDI. —[email protected]