Egg Cartons: Molded Pulp Or Molded Polypropylene?

The big German trade shows usually open up one day (often Sundays) to boost traffic and allow consumers to cherry pick interesting items from demonstrations. So you might see people with an armful of hula hoops, assorted sizes of buckets, and various molded chickPack_F 160-  gifcuriosities.

One of the giveaways at the Fakuma show held in Friedrichshafen last October was an injection molded egg  carton—an application long dominated by molded pulp and polystyrene foam.

In one of its three exhibits, Ferromatik Milacron produced the egg cartons on an F 160-2F, the first multicomponent machine in its new modular F-Series. A 1+2-cavity mold by Udo Bodmer of Solution B (Hausach, Germany) was equipped with a main and a vertical injection unit.

In a first step, the vertical injection unit produces two separate parts that form the top of a container for six eggs. An in-mold label (IML) is applied. After the top is injected, the bottom of the container is molded by the main injection unit. The two top parts are arranged left and right from the bottom inside the mold and are joined to the base of the container with hinges that allow each half of the top to be opened individually.

It’s called chickPack and was developed by Bodmer.

The two-component part has an average wall thickness of 0.35 mm and is made from clarified polypropylene (PP) and has a weight of 19 grams. Cycle time is 2.8 seconds.

Thorsten Thümen, director of research & development at Ferromatik Milacron says that the advantages of the molded container include:

  • A “First Open” seal, showing that new packages have not been opened;
  • The plastic packaging is food safe, moisture resistant, odorless, and hygienic, keeping the porous egg shells safe from contaminants; and
  • The packages are 50% lighter and require 50% less space when stacked.

The economics are not clear. Certainly, a very sizable production run would be required to amortize the cost of the equipment and the mold. It’s also not clear that polypropylene would provide the same level of protection as plastic foam.


About Doug Smock

Former Chief Editor at Plastics World and Senior Technical Editor Design News
Consumer Goods, Design, Europe, In-Mold Decorating, Injection Molding, polypropylene, Two-Shot , ,

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