Optimized sheet extrusion

When it comes to recycling, the thermoformers have gotten the process down, with most using the trim back into the extrusion of new sheet. Demand for recycled-content sheet material to meet green requirements for many packaging products continues to increase, but there are a few challenges when it comes to meeting that demand.

Larry Koster of Burcham International Corp., a supplier of PET resin to the sheet industry, noted at the recent SPE Thermoforming Conference in Milwaukee, WI that “it’s hard to make any money in RPET [recycled PET], as the recovery rate for bottles is low—way below what recyclers need.” Another problem for U.S.-based PET recyclers is that about half of the PET “is exported to China” only to come back as other products.

“If I could get my way about one thing—if I were a reseller, which I’m not—I wouldn’t allow bales of [recyclate] to be exported,” noted Koster. “We have the capacity to recycle all PET bales in the U.S. What’s your objective? If you want a recycling industry in the U.S., you have to support it.”

With California being one of the largest collectors of PET bottles (some estimates put it at 80 million to 100 million lb), that should be good news for the recently announced PET recycling plant being established in Riverside, CA. As we reported at PlasticsToday.com, the plant, owned by CarbonLite Industries, will have the capacity to handle 100 million lb of PET in its 220,000-ft² facility when it comes online in mid-2011. That should handle California’s PET recyclate pretty nicely, so long as CarbonLite is willing to outbid the Chinese for the material, said a number of people at the Thermoforming Conference.

Shouldn’t recyclate be cheaper?
With that said, the next challenge is getting RPET at competitive prices. Currently, most RPET costs as much or more than virgin PET.

Sheet and rollstock producer Spartech Corp. (Atlanta, GA) could always use more recyclate for its sustainable packaging materials. “We always like to buy more recycled materials,” said Jeffrey Best, commercial development manager for Spartech. “While there’s a good availability of recyclate, there are different grades, and it’s the high-clarity, high-purity materials that are in high demand.”

Extruded from recyclate, Spartech’s EnviroSeal XP30 and XP35 PET rollstock is designed to reduce a processor’s energy costs and reduce the sheet’s environmental impact. “These materials are designed specifically to allow more recycled materials to be used back into the recycling stream,” explained Best. “Formers can RF and heat-seal this material to compete against PVC.”

Octal Inc. (Oman) promoted its DPET (direct-to-sheet PET) material at the Thermoforming Conference. The company exports its sheet globally and is promoting the use of this virgin material as a sustainable material because the DPET process skips the energy-intensive drying, pelletizing, and extrusion of the material.

“We’re doing things no one else is doing that make DPET’s carbon footprint and sustainability benefits equal to or better than those of RPET,” said an Octal spokesperson. “With DPET’s precise gauge control, ease of forming, and lower carbon footprint, customers see the potential to downgauge, increase throughput, and improve sustainability. They can use less material, which helps everyone’s sustainability efforts and bottom line.”

Hop Industries Corp. (Lyndhurst, NJ), a supplier of thin-gauge rigid PVC, has no problem getting recycled amorphous PET for its 80,000-ft² facility; it sources the material from an overseas supplier. However, said Frank Aversa, a sales rep for the extruder, the costs associated with bringing the recyclate from Taiwan prompted the company to plan to bring an extrusion line into a facility in Warton, TX so that it can recycle PET. Currently, that facility is producing rigid PVC.

Bill and Brenda Mechar of Integrated Packaging Films (IPF) Inc. said their company has problems with sourcing a supply of clean recycled PET. “We get a lot of postconsumer resin [PCR] so cleanliness of the material is an issue; consistency is spotty,” said Brenda Mechar. “Materials that have already been compounded such as postindustrial materials have better consistency.”

The Mechars, whose facility is in Ontario, Canada, said that while they’ve always been able to meet their RPET demand, customers don’t want to pay the higher prices for that material. “A good, clean product costs more now than—or at least as much as—virgin material. But if the end customer wants it, they’ll pay more for it,” said Brenda Mechar.

Stan Yachera, product engineer for Multi-Plastics Extrusions Inc. (Columbus, OH), agreed with the Mechars. “There’s plenty of postconsumer supply of PET, but the quality is not there,” he said. “Postindustrial is better quality, but to get a truly ‘green’ product, people want postconsumer. We’ve had trouble getting a good, clean source, but it is getting better.”

Yachera notes that for recycled flake, the price is close to virgin PET. Pricing for pellets is higher than for virgin material. “Will the market bear the higher price? We’ll see. It’s end-user driven,” he added.

Tips of the trade: Using your sheet die to make every pellet count
Courtesy of sheet extrusion die manufacturer Extrusion Dies Industries LLC (EDI; Chippewa Falls, WI) comes these “tips of the trade,” a fast list of the ways in which die systems can be designed to increase production uptime, speed up job changeovers or maintenance, reduce scrap, or in some other way boost the efficiency of the entire production line.

The list is mostly generic, although EDI allows that some of the technologies involved are more or less unique to the company. The first two involve systems just being introduced, while the others have been around a good while but are often overlooked by processors. Most involve purchase of a new die rather than refurbishment of 
an existing die.

1. The enhanced responsiveness of automated gauge profiling systems on dies can help processors of light-gauge sheet to increase productivity, reduce scrap, and save plastic.

2. New-generation adjustable coextrusion feedblocks can increase uptime in sheet production by eliminating the need to disassemble the feedblock to modify product thickness.

3. Layer multiplier technology enhances properties by creating dozens or even hundreds of microlayers within a structure without increasing thickness or raw material content.

4. Single-point adjusting systems for rapid changes in sheet thickness increase uptime by eliminating the need to adjust the flexible lip of the die or install an alternate lower lip.

5. Tungsten carbide coating on dies enables sheet manufacturers to gain several more days of production time annually because, in comparison with standard chrome plating, the coating is substantially more resistant to micro-fractures during initial sharpening, abrasion during normal use and cleaning, and corrosion.

6. Depending on design, the manifolds or flow channels of sheet dies can be engineered to reduce scrap and downtime by minimizing thermal degradation of sensitive polymers, reducing the differential die body deflection that causes product deformation, or optimizing the interface between layers in a coextrusion.

7. Motorized deckles speed changes in product width.

8. “Split-and-clean” systems make it possible to carry out cleaning and maintenance without taking the die offline.

9. Specialized die rework services can clean, repair, resurface, and even upgrade dies, extending their working life, reducing downtime, and increasing productivity. —Clare Goldsberry