Already displacing the material in items like baby- and portable water bottles, Eastman's Tritan copolyester has staked out another polycarbonate (PC) conversion: reusable 3- and 5-gal water bottles for the home/office delivery (HOD) market. Officially launched by industrial packaging supplier Greif Packaging, a subsidiary of Greif Inc. (Delaware, OH), in January, the bottle's development began about a year prior, according Rick Volker, Greif sales and marketing manager.

"Our project to find a resin that was Bisphenol-A (BPA) free began over a year ago," Volker said in response to questions from PlasticsToday. "During that time we investigated a number of resins from around the world, with one of our goals being to identify a resin system that would allow us to produce a bottle with the same dimensions, design elements, and features as our current PC bottle. The copolyester resin that we chose came as close as possible to meeting that goal."

The new bottles required a new Tritan grade from Eastman, according to Dante Rutstrom, VP and general manager of Eastman's Specialty Plastics Business. "As [Eastman] goes after new market spaces, what we'll find is the polymer needs to be tweaked or adjusted—that's where 5-gallon was," Rutstrom said.

To be viable in the extrusion blowmolding (EBM) process used to make some HOD water bottles, Eastman determined a material with higher branching, and thereby greater melt strength, would be needed. The result was Tritan WX500. While EBM is the dominant process to create the large water bottles in the U.S., the two-stage injection stretch blowmolding (ISBM) process, where a preform is injection molded and then reheated and stretched on a second machine, is more prevalent elsewhere. The new Tritan material is suitable for both, but the company is also developing ISBM-specific grades.

Greif's Volker said the company used as much of its current tooling and equipment as it could to better ensure product consistency, but as it was working with a new resin system, some of the manufacturing parameters differed from those for PC. In addition to consistent look and feel, Eastman and Greif said Tritan's ability to endure the harsh cleaning environment applied to make the bottles suitable for reuse was also key. At this point, Volker said Greif hasn't made a wholesale switch from PC to Tritan. "We made the decision to offer a BPA-free water bottle as an alternative because our customers were asking for it," Volker said.