The prevalent scare of Bis-Phenol A (BPA), originating from can liners and some plastic materials used for milk and food has spurred many efforts to find an alternative with better safety credentials. As far as can liners are concerned there are some plant derived natural materials suggested some years ago but due to poor receptivity by the can manufacturers these never found any practical application. Probably there could be a revival of interest in these coating materials under the present compelling circumstances. Can liners play a crucial role in preempting chemical reaction between the food constituents and the container wall, especially under high temperature and pressure conditions. Latest to arrive on the scene is made from CO2 by an innovative process by one of the companies in the US. Here are some details of the process covered under a patent.
"While many of the polyols are being aimed at the industrial sectors, the company identified at least one application that could mark a major breakthrough the food packaging industry as a replacement for bisphenol A (BPA) in can linings. "We believe our polyol technology may offer a replacement for epoxy in can linings," said Shepard. "The advantage is our polyols do not contain BPA. The applications include two- piece cans – such as soda and beer - and three-piece cans for food." The company said it had "just begun the food contact notification process" with the Food and Drug Administration (FDA). Rising consumer, scientific and political concern over the continued used of BPA in food contact materials on health grounds has triggered an intense search for alternatives. The North American Metal Packaging Alliance (NAMPA) said in May the canned food and drinks sectors were bowing to consumer pressure and seeking BPA replacers. Earlier this month, Heinz Australia said it would be phasing out BPA use in its baby foods and was actively trying to develop substitutes. The Novomer process uses a proprietary catalyst that enables the carbon dioxide to be inserted into an epoxide which forms a polymer, said Shepard. Using propylene oxide as an example, the chemical is placed into a reactor before the catalyst is added. The reactor is pressurised with CO2 – sourced from a gas or ethanol plant waste stream - which triggers the reaction. The reaction occurs at low temperatures and pressures so it requires much less energy than traditional petroleum based polymers, added Shepard. "The energy required is 40-60 per cent less than petro-based materials and the carbon footprint is 50-70 per cent less than competing materials."
Though BPA is yet to be banned officially in many countries, user pressure has already brought down its use in the production of resins and plastic materials very significantly. The most recent report implicates BPA in fertility related problems. Many large players in the food processing sector have already phased out use of BPA containing plastics from their packing line and more are expected to follow them any time from now. Probably the undue delay in coming to a conclusion regarding the safety of BPA by safety authorities is allowing some of the industry to use them without the consumer being aware of it. The new process to make BPS substitute through the Novomer process lend itself to easy use as both CO2 and Propylene Oxide are available at relatively low cost enhancing its viability considerably.