The evolution continues for gas vapor barrier coatings for rigid plastics packaging, with some of the front-runners among systems suppliers now bringing their second-generation products to market. But multilayer solutions have the upper hand, and challenges remain to coatings’ wider adoption.
Barrier coatings or layers for rigid packaging are not new, with, for example, Sidel (Le Havre, France) offering its Actis plasma coating system since 1999. However, developments have continued, and the need for some sort of gas vapor barrier is only going to increase globally as those regions which place the highest demands on plastic packaging—in the hot and humid climates in South America and India, for instance—also are among the ones seeing better-than-average GDP growth. One result: more consumers with more money available for more impulse purchasing of products, such as the single-serve beverages that so often come in barrier packaging.
What’s more, these barrier systems, to date primarily for improving gas barrier performance of polyethylene terephthalate (PET) packaging, now are being tested for more materials, including polypropylene (PP) and polylactic acid (PLA).
Brian Furey, projects manager for two-stage PET blowmolded packaging at processor Graham Packaging Europe, said that the SurShot multilayer barrier co-injection technology developed by Graham and machine/moldmaker Husky (Bolton, ON) is, from April 2007, the first and as yet only multilayer barrier technology for PET packaging that has been endorsed for recyclability by Petcore, a European nonprofit pushing for PET recycling. Petcore tests established that SurBond-E barrier material developed by Graham, and based on ethylene vinyl alcohol (EVOH), could be effectively separated from PET during recycling. A Petcore endorsement isn’t legally necessary to introduce a barrier technology, but it has become the de facto standard for whether a technology adversely affects recycling.
Speaking at the PETnology conference in Munich in late March, Furey said SurShot could include up to 40% post-consumer recyclate (PCR). This year Graham hopes to be able to secure enough PCR supply so that interested beverage bottling customers can be assured of a steady, and high-volume, supply of preforms or bottles with the full regrind content.
Furey says Graham has about 70 SurShot systems in operation, and has licensed an additional 15 to other processors. Output has increased: he notes the first 144-cavity, bimaterial, five-layer (PET/SurBond/PET/SurBond/PET) SurShot system was shipped in January 2007 in the U.S., and work now is on a 144-cavity, bimaterial, three-layer system.
Plasma coatings remain a tough sell
Compared to SurShot’s success, the demand for plasma coating systems has been considerably more measured. Arne Anderson, product manager for the Plasmax plasma coating technology owned by stretch blowmolding machine manufacturer SIG Corpoplast (Hamburg, Germany), says commercial use of Plasmax is as yet limited to two plasma coating units at Hokkai Can in Japan, one used by Rexam in the Czech Republic, one in Switzerland at juice bottler Eckes-Granini, and one at Ball in the U.S. (this used to date mainly for small wine bottles). Plasmax coats up to 12,000 bottles per hour (bph) with a silicon dioxide plasma, so PET bottles retain their transparency. Work is ongoing on a larger unit able to treat 26,000 bph, with field testing on that to start in late 2008, he says. SIG also offers to rent its Plasmax systems for projects requiring coating. Corpoplast placed its first Plasmax unit (at Eckes-Granini) in 2003.
At Sidel, the first Actis 48 coating unit was recently installed and is running 24/7 at almost 95% efficiency at an as-yet unidentified customer, according to Sven Muregard, business manager coating systems. Muregard says new Actis units are a technological leap ahead of the original models. For one, the first systems, which could coat up to 12,000 bph, required a 30-minute break for maintenance (replacing gas injectors) and cleaning every 12 hours; now this takes only five minutes every 48 hours and is fully automated.
At stretch blowmolding machine maker Sipa (Vittorio Veneto, Italy), Marco Leonardi, packaging development manager, says Sipa’s SmartCoat system differs in many respects from the Plasmax and Actis offerings. SmartCoat is an external organic polymer (not a plasma) coating with two layers—the first for gas barrier, the second to protect the barrier layer from scuffing. The coatings are applied in a simple dip process suitable for any size/shape bottle, with the extent of the barrier dependant on the speed of the dipping line (lower speeds for a higher barrier). The systems requires about a 30-minute changeover time between bottle size changes, as long as the bottle neck is the same; a different neck will require about four hours of downtime. Actis requires about one-and-half to two hours and Plasmax about the same. SmartCoat’s water-based coating is then “flashed off” in an IR and air oven. Maintenance is recommended once a month. Sipa won’t yet reveal the name of the coating supplier.
Bottle-to-bottle recycling is not affected at all with Plasmax and SmartCoat, according to Corpoplast and Sipa, respectively. Sidel’s Muregard allows that for bottle-to-bottle recycling, Actis-coated bottles shouldn’t exceed more than 50% of total input to a transparent bottle waste stream; Actis-treated bottles can be added in any amount when recycling brown PET bottles. Officials at none of the four firms above would discuss cost/bottle for their barriers.
Cost and concerns about recyclability have hampered greater use of coated and multilayer barrier bottles, and challenges to their future continue to flourish. Muregard noted at the PETnology event that the transition from cans to PET bottles for carbonated soft drinks in North America is taking much longer than many market experts had predicted.
Tackling the cost issue is Husky, which, in conjunction with Nano Scale Surface Systems Inc., has begun marketing systems for molding plastic medical disposables with an internal barrier coating of silicon dioxide. The transparent coating provides a barrier against gas transfer and prevents any chemical reaction between fluids and the plastic. The systems are expected to help processors replace glass medical packaging, including test tubes and blood vials.
The coating system uses radio frequency (RF) energy to generate plasma in place of microwaves, the conventional approach. RF energy results in lower costs and simplified operation for coating the inside of plastic containers, according to Nano Scale (Alameda, CA); the new barrier process is expected to cost less than $6/1000 bottles. The firms claim the system has proven effective at improving the barrier of PET bottles, polypropylene bottles, and injection molded items like medical disposables.
Monolayer gas vapor barrier solutions have been introduced in the last few years as well, from PET suppliers including Invista, Eastman, M&G, and Novapet. These are understood to be lower-cost solutions compared to coatings or multilayer technologies, but concerns about the materials’ effects on the recycling stream have hindered their use. In March 2007 colorants supplier Holland Colours (Apeldoorn, Netherlands), with a large PET packaging customer base, became exclusive agent for sales and service of ValOR barrier compounds for Europe, the Middle East, and Africa. ValOR compounds, PET based and suitable for monolayer or multilayer packaging, were developed and are marketed by coatings supplier Valspar (Pittsburgh, PA; more on ValOR in August 2006 MPW, p. 18).
New PP grades compete
In late May polyolefins supplier Basell (Hoofddorp, Netherlands) announced market introduction of its Stretchene polypropylene, said to offer much better rigidity, transparency, impact strength, and processability compared to standard PP. Basell markets the material as a direct competitor to PET in single- and two-stage stretch blowmolding. One Stretchene grade, RP1685, has a heat deflection temperature of 109C, suitable for hot-fill applications; the second grade, RP1903, is said to improve of the transparency of standard PP.