Blow molded packaging processor Container Corp. of Canada (CCC; Richmond Hill, Ontario), has chosen Pro-fax X11540-81-3, a custom oriented polypropylene (OPP) experimental grade from LyondellBasell Industries (Rotterdam, the Netherlands; www.lyondellbasell.com) , for use in the commercial production of oriented PP (OPP) hot-fill jars and bottles. Significant new inroads in polymer, coating and injection stretch blow molding (ISBM) technology are making the commercialization possible.
Until now, blow molded PP applications generally have been limited to water bottles, pill vials and other containers where oxygen barrier properties were not critical. According to LyondellBassell, its new material could help OPP compete more readily with PET, glass and other materials in a broader spectrum of applications.
The launch of CCC's new packaging, called Enviroclear Barrier System, also is a result of CCC's partnerships with South Africa's Council for Scientific Industrial Research (CSIR), and an unidentified equipment manufacturer in China, which custom-built the ISBM equipment for CCC specifically to blow containers within the tighter processing window necessary for OPP. A dip/spray process developed by CSIR is used to coat the bottles; the coating improves the oxygen barrier on a 500 ml OPP bottle by approximately 140 times over an uncoated PP version, according to Lorie Struzik, technical program manager at LyondellBasell. That also gives the bottles about 10 times the barrier protection of an uncoated PET bottle. The bottles are said to be as clear as PET with no need for peroxide to enhance the OPP's melt flow.
Dave McKeeman, LyondellBasell's new business development manager for injection molding, explains, "Pro-fax X11540-81-3 is a 40 melt-flow, reactor-grade product optimized for adhesion of the oxygen barrier coating. This resin also contains no peroxide. What has typically been done in the past is to take a 12 melt flow base flake and visbreak it in a pelletizing extruder with peroxide to achieve a higher 35 melt flow so that parts could be produced more rapidly." Breaking the polymer chains resulted in a loss of stiffness; the new material avoids this problem. Also, its adhesion properties are such that the coating does not rub off when bottles bump against each other. "Additionally, the high melt flow allows you to injection mold preforms at a lower melt temperature which means less cooling time," McKeeman said. PET offers greater stiffness than PP but PP has a lower density, meaning processors can opt for slightly more PP and still lightweight packaging, compared to comparable PET bottles.
Various applications are currently being tested with commercialization expected towards the end of 2008.