Physically Foamed HIPS Is New Factor in Rigid Packaging

Relief for escalating costs of packaging materials and an opportunity to address sustainability goals are two factors that have helped attract global attention to a new physical foaming technology for HIPS packaging. First introduced at the K 2010 show in Germany last fall, this liquid-CO₂ foaming technology suitable for existing single-screw extrusion lines first came to commercialization at an Australian customer within the past month.

Dubbed CO₂RE (pronounced “core”) Foaming  Technology, this patented technique comes from Styron LLC, whose U.S. offices are in Midland, Mich. (Styron plans to change its name to Trinseo and recently moved its global operating center to Berwin, Pa.) It produces HIPS sheet with a foamed core and solid surface, suitable for deep-draw thermoforming into rigid packaging with walls as thin as 0.3 to 1.5 mm (0.01 to 0.06 in.). Overall density reductions can be 13% to 20%, though one licensee has achieved 24%. Thus, it does not compete with much lower-density PS foam sheet used in meat trays and clamshell packs, which is produced on specialized tandem extrusion lines with annular dies. By contrast, CO₂RE foaming technology can be used on existing conventional single-screw sheet extrusion lines with flat dies at a modest conversion cost, Styron says. Liquid CO₂ reportedly offers cost and performance advantages over chemical blowing agents. Initial targets for the technology are dairy packaging and disposable foodservice items like plates and cups.

 

GLOBAL INTEREST

According to John Case, Styron’s global marketing manager for packaging and consumer goods, CO₂RE technology has attracted considerable interest over the past year in Europe, Asia/Pacific, South Africa, and Latin America. “We have lots of orders for samples and many customers are in various stages of process validation,” says Case. The company (styron.com) is currently assessing plans for introducing CO₂RE in North America.

The first CO₂RE licensee to bring actual products to market is REMA Industries in Australia. It introduced the technology with its Biorene foodservice products that contain an organic additive to make them biodegradable. REMA reportedly will implement CO₂RE foaming technology to convert all its products from solid to foamed HIPS.

Another licensee, Intraplas in Portugal, is in the final stages of commissioning its first CO₂RE line for form/fill/seal dairy packaging. Other packaging firms who made testimonials about the potential added value of CO₂RE foaming technology on Styron’s website are Promens in Sweden and Fernholz in Germany, along with packaging distributor Toyota Tsusho of Japan.

Styron works with customers to validate the CO₂RE process for specific applications at a demonstration facility in Terneuzen, The Netherlands. Styron describes the necessary equipment modifications as low cost—meaning 2 to 8 Euros per metric ton of annual output, depending on extruder size, as compared with material cost savings of 250 to 400 Euros/m.t.

Hardware modifications include a new screw, designed by Styron to provide good mixing of the CO₂ with the PS melt. The blowing agent can be introduced through a vent port in the barrel. Additional extras are the liquid-CO₂ storage and pumping system. Very little additional floorspace is required, Case notes. Styron reports that addition of liquid CO₂ to the melt can enable higher output if the downstream system can handle it.

Foaming does produce some texture on the surface of products, but Case says this is perceived as an advantage by some customers. Alternatives to achieve a glossy surface are sleeve or in-mold labeling or coextrusion with a solid PS cap layer.