Retortable food package five-layer structure

Retortable food packages using EvOH as the oxygen barrier are multilayer structures which are formed by coextrusion. The number of different layers in a the structure can vary a representative five-layer structure is shown in Figure 3. Often one or more layers are added to reuse scrap and regrind in the package. There is a wide range of possible combinations of layer thicknesses which can be used in this type of structure. 

American Can s Omni retortable plastic can marks a major development in food packaging. The five layer can, used by Hormel, Del Monte, and Campbell Soup Company, consists of polyolefin structural layers, adhesive layers incorporating desiccants, and ethylene vinyl alcohol (EVOH) polymer as the barrier layer. 

It was found that before retort the OTR of the pure EVOH multilayer film was 0.40 cc/ (m -day) but the OTR of EVOH/MLS multilayer film was 1.10 cc/ (m -day). The WVTR of the EVOH/MLS was 57% lower than the pure EVOH film. Table 4 shows the OTR and WVTR data for the multilayer films. It was unexpected that the pure EVOH samples would have a lower OTR than the EVOH/MLS samples because the nanocomposites are supposed to create a toturous path which the molecules have to follow in order to permeate the material. After the retort the pure EVOH and EVOH/MLS multilayer films were tested with the Ox-Tran five times for consistency and accuracy, but failed the test all five times. A sample failure is when the OTR exceeds the upper limit of the sensor range which is 2000 cc/ (m -day), although there is some flexibility for the actual failure value. [14] EVOH is primarily used as an oxygen barrier since the OTR failed after retort it was not necessary to test the WVTR after retort. The OTR and WVTR of the multilayer films were not found to meet the military specifications. Although the transmission rates did not meet the military food packaging specifications further experimentation with different materials or a PP nanocomposite outer layer could lead to a structure which meets the required specifications. 

---

See also in sourсe #XX -- [ , ]

---