The retort pouch gradually replaces some iron cans and glass jars by virtue of its light weight, small volume, fast heat conduction, short sterilization time, and good color and flavor of the contents, but it is subject to bag making, sterilization, etc. due to its many properties of packaging materials. The impact of the process is large and there is a potential risk of breaking the bag.
Reason one: the substrate problem
The retort pouch is heated together with the product, which determines that the surface material of the retort pouch has very good stability after cooking, especially the dimensional stability after retort cooling. If the thermal stability of the substrate is not good, it is easy to appear. After the cooking is cooled and shrunk, the separation layer causes the bag to break.
The retort pouch is generally made of high temperature resistant PET, NY, AL, RCPP and other substrates. Pay attention to the shelf life of various substrates, especially pay attention to the shelf life of RCPP, because RCPP is used as the inner layer material for high temperature cooking. The performance of the bag plays a central role. If the quality of the RCPP is relatively poor or has passed the shelf life, there will be a large amount of brittleness and rupture when the pressure is resisted after the cooking is cooled.
Reason 2: The impact of the bag making process
The temperature, pressure and machine speed of the heat sealing knife are the three major factors of the bag making process. To make a bag with good sealing, a reasonable match between the three is required. Heat sealing is the result of the combination of heat and force. On the one hand, in the molten state, the sealing surface, the macromolecules diffuse, penetrate, and entangle each other to achieve sealing and sealing; on the other hand, the polymer molecules in the molten state are heated by means of heat. The pressure of the sealing tool makes the upper and lower layers of the film merge into one another, and can maintain a certain strength after cooling and setting.
Due to the high requirements of the use environment, it is generally required that the retort pouch has a strong heat-sealing strength, which requires a reasonable setting of temperature and pressure in combination with the structure of the retort pouch and the inner layer material, especially when making the self-standing pouch. The point seal at the junction with the bag body, because under the cooking conditions, as the material shrinks, the intersection position will become the focus of moisture and hot gas attack. The number of heat seals greatly affects the heat seal strength. The number of transverse seals and longitudinal seals can be reasonably set during bag making to ensure good heat seal strength of each seal.