Retort pouch is a kind of composite plastic film bag that can be heated. It has the advantages of both canned containers and boiling water resistant plastic bags. Food can be left untouched in the pouch, after high temperature (generally 120~135℃) sterilization heating, take out can be eaten. Retort pouch is widely used, different specifications of the packaging bag for the selection of base material and raw materials are different.

1. Select the base material according to the cooking conditions and the characteristics of the content.

The film base material used for making high-temperature cooking bags is the basis for meeting cooking conditions, usually according to the cooking conditions of the high temperature retort pouch and the characteristics of the content to determine the selection of what substrate, what specifications, combination order, to use what type of ink and glue, etc... Commonly used film substrates are BOPET, B0PA, HDPE, RCPP, A L, co-extruded EVOH, co-extruded PVDC, co-extruded PE and so on.

2. According to the surface layer (or printing layer), barrier layer, heat sealing layer order to determine the packaging structure.

According to the surface layer (or printing layer), barrier layer, the order of the heat sealing layer can be combined with the structure of the composite packaging material, also there is a single layer of material to do both printing layer and barrier layer, so the pouch can be designed according to the need for two layers, three layers, four layers or more layers, such as BOPA//RCPP、BOPET//BOPA//RCPP、BOPET//A1//RCPP、BOPET//A1//BOPA//RCPP, etc. 

For the thickness of the base material usually choose is: BOPET12um, BOPA15um, AL7um or AL9um, RCPP50um RCPP70um RCPP80um RCPP100um, etc., for the barrier layer, usually choose BOPA and AL, according to the actual need to also choose BOPA25um and AL12um, large capacity and special requirements of the retort pouch selected RCPP thickness also has more than 100um. Liquid packaging bag in order to overcome the RCPP is not resistant to falling defects, additives are generally added in the film to enhance its anti-drop performance. Note that PP particles of block copolymerization type are used for high temperature resistant cooking CPP.

3. Choose appropriate materials and structures according to the form and nature of the contents.

Choose appropriate materials and structures according to the shape and nature of the contents, such as solid liquid or solid-liquid mixture, different material structures should be selected, Meat and seafood products with bones and thorns, greasy, spicy and other contents. 

Do not puncture the bag before and after high temperature cooking, as well as because of the physical and chemical properties of the contents, it may change at high temperatures to produce new substances, which may penetrate between the retort pouch layers and then cause the decline of the packaging performance of the retort pouch. Or because the acidity or alkalinity of the contents is different, also need to adjust the bag material structure and material specifications as required. For the barrier layer usually choose high barrier nylon film and AL, according to actual needs, BOPA15um, BOPA25um, BOPA30um can also be selected. 

Some retort pouches with special requirements will choose RCPP with thickness over 100um. However, RCPP has the defect of does not resist falling, additives are generally added in the film to enhance its anti-drop performance. Therefore, the structural design of high-temperature cooking packaging materials needs comprehensive consideration.

4. Standard for the selection of chemical materials for packaging materials for high temperature cooking.

High temperature resistance cooking ink should be a two-component reactive polyurethane as a binder ink, it has good printing fastness to adhesion, can withstand high temperature cooking after crosslinking curing reaction, and can form a very strong bond with the glue. At the same time, for a large area of spot color and white pattern, but also choose the supporting ink curing agent usually add 3%.

When choosing ink, special attention should be paid to distinguish: resistant to 100 below boiling ink and resistant to 121 above high temperature cooking ink, so as not to misuse. The glue should choose high temperature cooking level, usually considered to meet at least 121℃ cooking requirements, and must have good bonding fastness after compound high temperature resistance to medium and heat resistance, currently commonly used as two-component polyurethane glue. Ink is usually selected for high temperature cooking ink 135 degrees, glue selection is 135 degrees high temperature cooking glue with 60% solid content.

The above is about the choice and requirements of retort pouch base material in detail. In the choice of base material, we must consider the contents of the package is what kind of nature of goods, how much packaging capacity is, after packaging to undergo what kind of cooking and sterilization conditions, preserved in what kind of environment, how long shelf life requirements, etc. Different content requirements of cooking bag quality requirements are different, the combination of material structure, adhesives and ink selection is also different, production process control will be different.

Kolysen is specialized in laminating composite packaging bags and retort pouches for more than 20 years, experienced to provide you with the best service and quality. Please contact us if you have the demand for the retort pouch.