Barrier packaging: Automation specialist develops reliable PP/EVOH co-injection system

believes it may have made a major leap forward with two new technologies. Working with co-injection systems specialist Kortec (Ipswich, MA) on the first, the firms have developed an injection molding system and Q/A equipment allowing for high-volume molding of polypropylene containers with an EVOH barrier in which the barrier layer's consistency can be 100% verified in-line.

EVOH, a copolymer of ethylene and vinyl alcohol, is often used as a barrier material to prevent oxygen ingression and CO₂ egress.

The molding process developed by Waldorf and Kortec has been optimized for high volume packaging applications, for instance molding with a 32-or 64-cavity stack mold. Waldorf reports that multi-material injection of the retortable thin 3-layer structures (PP-EVOH-PP), plus tie layers, is repeatable and does not negatively affect cycle times.

Co-injection is not new, nor is it new with these materials, but Waldorf (Engen, Germany) claims its novelty is that processors now have the ability to prove that the EVOH barrier layer is consistent throughout the complete body of the container, using the company's newly developed Check´n Pack EVOH system. The in-line system provides 100% control of the complete EVOH layer, 100% inline extraction of rejects, and is a fully automated process and logistics system.

Standard inspection systems have troubles with EVOH, but Waldorf claims its system allows 360° rim, 360° side wall, bottom and injection point inspection. According to Kortec, which supplies the co-injection molding technology for the system, a shelf life of up to two years can be promised even for sensitive products such as fish, meat, fruit and pet food, aloof which commonly are retort or aseptically filled, and often in metal packaging. Switching to Check´n Pack leads to savings in production and logistics of typically 30-40%, claims Waldorf, compared with those metal containers. Plastic containers also of course offer more design options.

Waldorf also offers other barrier container solutions which it says are now ripe for market introduction. A second one from the company involves 3D in-line vacuum coating with various PVD or PECVD coatings developed by the company Cavonic (Stockach, Germany). These coating systems provide a low-cost option with solid barrier and similar hermetic property to glass, reports Waldorf, and can be integrated into established injection molding cells. "To date, laboratory tests have been successful, i.e. ready for the aseptic process, with the target of complete sterilization. Barrier against oxygen permeability currently achieves 99.15% after sterilization. In addition, the combination of thin-wall performance, superb barrier properties and low production costs make this technology—able to be adjusted to biodegradable polymers—a most attractive commercial proposition," says Wolfgang Czizegg, CEO at Waldorf.