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April 1, 2008

4 Min Read
Compression molded multilayer closures? Here they come

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Sacmi’s Luca Nanetti during the Nova-Pack conference in February; Sacmi is betting processors will consider compression molding as an alternative to injection molding, and not just for simple one-piece closures.

Following its announcement at last October’s K Show that it would offer a machine for molding PET preforms, compression molding machine manufacturer Sacmi Imola now has a larger market in its sights, and will tackle it with a major partner.

Announced in mid-February at the Nova-Pack packaging conference in Florida, Sacmi Imola (Imola, Italy) and Aisapack (Vouvry, Switzerland) said they will introduce a compression molding system for processing multilayer closures that improve a package’s gas barrier. Sacmi will manufacture the machines, with the multilayer technology helped along by Aisapack, which is a leading manufacturer of machines to process plastic tubes, such as those containing toothpaste or personal-care creams.

Aisapack’s Hugues-Vincent Ray, managing director, told MPW at the Nova-Pack conference that the technology used will be similar to the Bacomex technology already perfected by Aisapack for processing tubes with a barrier layer. One of the first of these tube lines will be delivered soon to a Polish processor, he said. Aisapack realized that, if it could do multilayer tubes incorporating ethylene vinyl alcohol (EVOH) barrier layers, then the technology would also work for compression molding, he recalled, as the processes (tube forming and compression molding) are quite similar. Aisapack approached Sacmi and the two firms went from there.

Luca Nanetti, marketing manager, containers and closures, for Sacmi, says the trick to the process is Sacmi’s ability to ensure effective dosing of the multilayer pellets into its compression molds. “Our added value comes from the way we handle the dose,” he said. For multilayer parts the dosing needs to be handled somewhat differently than with monolayer closures, he says, to ensure the materials are oriented properly. Unlike injection molding’s need for a more complicated mold and second barrel to handle multiple materials, compression molding the multilayer closures will cost essentially the same as monolayer closures, he says, with the only added cost being the EVOH (or other) barrier material. The doses are coextruded, cut, placed in a mold and then compressed; no modification of the compression molding process is necessary. Compared to a polyethylene terephthalate (PET) bottle capped with a standard monolayer closure, the gas barrier factor is improved four-fold when the bottle is capped with a Becomax closure, he says, oxygen being kept out of the bottle and carbon dioxide being kept inside.

Commercial soon, and retrofits possible

Nanetti says machines for commercial processing of such closures will be available soon, and that existing Sacmi compression molding machinery for closure processing can be retrofitted for the multilayer closures. He reckons the first multilayer compression molded closures will have either a PE/tie layer/EVOH/tie/PE or a PP/tie/EVOH/tie/PP structure. Compared to injection molding, he says compression molding offers processors a number of advantages, among them a 40% reduction in energy use, according to Sacmi. Cycle times are exceptionally low—2.4 seconds for 2g closures on Sacmi’s 48-cavity CCM48S unit. He says consistency is also more readily achieved. Also, he noted that beverage makers could welcome knowing that polyethylene (or PP), and not a coating or liner material, is in contact with their beverages. Sacmi is marketing the systems initially to bottlers of energy drinks, nectars and juices, and beer.

Only last year Sacmi introduced another competitor to injection molding machinery, its compression molding equipment for PET preform molding. The PAM (Preform Advanced Molding) unit Sacmi developed is a 48-cavity prototype able to run at 27,000 preforms/hr, producing a 23g CSD preform with 28PCO neck finish. In comparison to injection molding of preforms, with preforms cooled and then dropped onto a conveyor for later orientation, preforms exit a compression molding machine already oriented, for ease of in-line quality control and, possibly, inline stretch blowmolding.

Nanetti said the firm also is heavily involved, with potential customers, in the development of systems for processing of standard thin-walled packaging, the sort of application over which custom injection molders and thermoformers compete.

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