Incorporation of barrier packaging materials for thermoformed and form-fill-seal extended shelf-life food packaging applications is typically achieved through the use of a multi-layer coextrusion process or an extrusion lamination process. At ICPG, we are capable of developing and producing a wide range of structures from monolayer extruded sheet and rollstock, to multilayer symmetric or asymmetric coextruded structures in rollstock form. Our state-of-the-art coextrusion line is designed to process precision material structures suitable for a vast range of market applications in the food (processed, baby food, dairy-cheese, yogurt, coffee, etc.) and medical (wound care, surgical kits, etc.) industries where protection from external elements and extended shelf-life performance are required.
Incorporation of barrier materials into extruded rollstock structures can be achieved through two primary methods:
Coextrusion:
Coextrusion is the process in which two or more plastic materials (with similar or dissimilar characteristics and behavior) are extruded as one. In a standard monolayer sheet extrusion process, one material is fed and extruded through a die. The coextrusion process involves multiple extruders and multiple materials (depending on the structure), and the molten material is channeled through the melt pipes to create a laminar flow for the coextrusion feed block and die technology to weld the extrudates into a one-piece structure. When multiple material layers are combined, the end result yields in a multi-layer structure deriving distinct properties from each material used in the structure. During the extrusion of these plastics materials, the required cooling is achieved by feeding the material through the cooling rolls, also known as the stack rolls or chill rolls. These rolls deliver the required cooling in addition to determining the sheet thickness and the surface texture using specialty surface finish rolls like matte, sand matte, hair cell, etc.
Although new and advanced compounded materials are enhancing the properties of traditional plastic materials, coextrusion continues to expand material capabilities for food packaging applications, offering added benefits through the combination of materials in terms of extended shelf-life, cost control and increased structural properties.
Extrusion Lamination:
Extrusion lamination is the process of applying a multilayer coextruded lamination film to a desired substrate such as paper, plastics, ceramic, metal, etc. via heat, pressure or a combination of both. Laminates are very thin extruded film structures that are produced using multiple layers of materials to achieve improved strength, stability, appearance and other enhanced properties. Use of laminates could be used to improve mechanical, barrier or chemical properties, or to enhance the appearance of the substrate it is laminated to. Depending on the required property enhancement, a lamination method is selected to weld the lamination structure and the substrate together such as dry lamination, wet lamination, thermal lamination, etc. Regardless of the lamination method used, in all cases the webs are combined at a lamination nip i.e. typically two rolls pressed against each other under a controlled temperature, pressure and gap. Since the web is combined using just the heat and pressure from the stack/chill roll, it is important that the lamination web has low thermal properties (low melting point) so that the preheating caused from the stack roll and pressure will thermally laminate and create a strong bond soon after it exits the stack roll and pull roll system.
ICPG offers extrusion thermal laminated materials using PE, PP, PS, the base substrate and desired lamination film web for enhanced properties such as oxygen barrier, UV barrier, and decorative films. Depending the end-use application either of process can be used to create an effective barrier packaging material with enhanced barrier and other desired properties.
Benefits of Coextrusion vs. Extrusion Lamination:
Some of the benefits to using coextrusion vs. lamination in barrier packaging applications includes high productivity, consistent quality, cost savings, and sustainability:
| Coextrusion | Extrusion Lamination |
|
High output rate with exceptional bond and material properties. |
Moderate output rate for effective bond strength. |
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Complex equipment requiring continued maintenance. |
Less equipment to maintain if added on line as extrusion thermal lamination process. |
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Longer setup time. |
Setup time is short and easy. |
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High capital investment for equipment, materials and storage. |
Lower capital investment and more diverse range of lamination equipment and film options. |
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Shorter lead time as material is readily available in stock. |
Longer lead time as lamination films is custom and outsourced. |
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Ideal process for cost effective products as reprocessed/recycled material can be easily integrated back in the system. |
Less energy consumption compared to multiple extrusion system with coextrusion process, but materials cannot be re-integrated into structure. |
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Rollstock specifications limited to equipment capabilities for gauge, width, and materials. |
Lamination film can be outsourced in varying gauge, width and materials based on application. |
Theoretically, the coextrusion process is the most cost effective and ideal method to process and produce a barrier packaging material. But it is important to understand the end-use application, processing method (thermoforming, lamination, in mold labelling), volume, etc. to justify the cost, quality and output rate for coextrusion vs. lamination.
For more information on barrier packaging materials and processes for extended shelf-life food packaging applications, download our free Guide to Barrier Materials and Processes:
