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Analysis of delamination of retort pouch
release time：2019-03-14
Browse times：4806
The retort pouch is a flexible packaging product for packaging cooked foods. It is divided into a boiled (boiled) pouch (less than 100 ° C), a retort pouch (121-135 ° C) and a high temperature retort pouch (greater than 135 ° C) depending on the temperature resistance. After 30-40 minutes of high temperature sterilization, the shelf life of the contents of the food can be greatly extended, so the production of such bags is developing rapidly.
The delamination of the retort pouch refers to delamination after the food is cooked. Such problems have actually buried hidden dangers in the process of printing, compounding and post-processing. The problem arises after the cooking of the filled foods, which often causes great losses to the composite bag manufacturers.
When the delamination of the retort pouch is slight, it is generally characterized by a stripe on the force-receiving part or the ink layer of the packaging bag. It is easily peeled off after being picked up by hand or needle; in the case of heavy, it is naturally delaminated after being cooked. There are several reasons for delamination:
Reason one: insufficient temperature resistance of ink or adhesive
The ink or adhesive for the retort pouch is made of polyurethane resin, and the temperature resistance of the ink or the adhesive is mainly determined by the temperature resistance of the polyurethane resin. If the bonding strength is low or even delaminated due to ink or adhesive, the ink or adhesive manufacturer should technically change the chemical structure of the resin and add other substances to improve the ink or adhesive of the retort pouch. The bonding strength of the agent after high temperature cooking.
Reason 2: Improper use of ink or adhesive
1. When the retort pouch is produced, when the structure is BOPA/CPE or BOPA/CPP and other structures, the white ink is added with 3-5% of the original ink, and the mixture is evenly mixed and printed. When the full version of the white ink is laid, other color inks are used. No curing agent can be added; when no white ink is used, other color inks need to be added with 3-5% curing agent. This is because the white ink has a good screen effect and can prevent the penetration and fading of the color ink. As for the addition of the curing agent, it is advisable to use it according to the process results of the prior test, and after the process conditions are confirmed, it cannot be used less or less. If the amount is small, the crosslinking reaction between the curing agent and the resin is insufficient, and the adhesion strength and heat resistance of the ink layer are lowered; if the amount is too large, an excessive crosslinking reaction occurs, which affects the crystallization between molecules. Damage to the cohesive force of the adhesive layer, the ink layer will shrink, causing delamination.
2. The compounding post-treatment curing time is not enough. When the time is short, the resin crosslinking reaction is insufficient, the bonding strength is insufficient, and the temperature resistance is lowered.
3. The activity of the ink or adhesive is not enough, or because the water diffuses into the ink or the adhesive during the production process under high temperature and high humidity conditions, and the isocyanate in the partial curing agent is consumed, resulting in a proportional imbalance.
4, the substrate problem. First, the corona treatment of the film is not enough, or the long-term inventory is invalid, or it is not processed at all. The operator does not test before the machine is put on, so that the bonding strength is poor after printing or compounding and aging, and the food to be filled is cooked. Find. In addition, during the aging process, the high-temperature conditions for a long time accelerate the precipitation of the additives in the film, which also causes a decrease in the bonding strength.
5, the choice of adhesive type is not appropriate. The end use is to package liquids, such as mustard, kimchi, juice, yogurt and other foods, it is necessary to use anti-media type adhesives, can not use ordinary adhesives, otherwise, composite film cooking at 80 ° C or more will Layering does not meet the peel strength requirements when packaging. Therefore, when selecting an adhesive, it must be considered according to the structure of the composite membrane and its end use to ensure the overall quality of the product.
Solution
In order to prevent the occurrence of delamination of the retort pouch, the following work should be done:
1. The use of packaging bags is strictly controlled according to the process conditions during the cooking process. Pay attention to the stability of temperature and pressure. Because of the limited cooking conditions of the various materials of the composite membrane, the physical and chemical properties of the contents and the high temperature are limited. Changes in physical and chemical values that may occur may result in new substances that may penetrate into the composite film layer and cause a decrease in the performance of the package.
2, the composite bag manufacturer should strengthen the management work, do a good job in the detection and monitoring of process indicators, especially before the mass production and before the factory physical test. In the production process, it is necessary to check whether the surface treatment degree of the film meets the requirements before going to the machine. After compounding, pay attention to the curing temperature and time, and let the two-component adhesive fully cross-link the reaction. In addition, pay attention to the control under high temperature and high humidity conditions, do not add too much ink or adhesive at a time, to increase the number of hard work, if necessary, take certain protective measures. Ingredients and adhesives are formulated in strict accordance with the process ratio. According to the requirements of cooking conditions of food manufacturers, the products are tested and the conditions are simulated for final confirmation to prevent batch accidents.
In addition, manufacturers of packaging materials such as inks, adhesives and films pay attention to the control of process parameters, ensure the stability of product quality, ensure the temperature resistance of materials used in retort bags, and understand the use of users and downstream users as much as possible. Claim.
The delamination of the retort pouch refers to delamination after the food is cooked. Such problems have actually buried hidden dangers in the process of printing, compounding and post-processing. The problem arises after the cooking of the filled foods, which often causes great losses to the composite bag manufacturers.
When the delamination of the retort pouch is slight, it is generally characterized by a stripe on the force-receiving part or the ink layer of the packaging bag. It is easily peeled off after being picked up by hand or needle; in the case of heavy, it is naturally delaminated after being cooked. There are several reasons for delamination:
Reason one: insufficient temperature resistance of ink or adhesive
The ink or adhesive for the retort pouch is made of polyurethane resin, and the temperature resistance of the ink or the adhesive is mainly determined by the temperature resistance of the polyurethane resin. If the bonding strength is low or even delaminated due to ink or adhesive, the ink or adhesive manufacturer should technically change the chemical structure of the resin and add other substances to improve the ink or adhesive of the retort pouch. The bonding strength of the agent after high temperature cooking.
Reason 2: Improper use of ink or adhesive
1. When the retort pouch is produced, when the structure is BOPA/CPE or BOPA/CPP and other structures, the white ink is added with 3-5% of the original ink, and the mixture is evenly mixed and printed. When the full version of the white ink is laid, other color inks are used. No curing agent can be added; when no white ink is used, other color inks need to be added with 3-5% curing agent. This is because the white ink has a good screen effect and can prevent the penetration and fading of the color ink. As for the addition of the curing agent, it is advisable to use it according to the process results of the prior test, and after the process conditions are confirmed, it cannot be used less or less. If the amount is small, the crosslinking reaction between the curing agent and the resin is insufficient, and the adhesion strength and heat resistance of the ink layer are lowered; if the amount is too large, an excessive crosslinking reaction occurs, which affects the crystallization between molecules. Damage to the cohesive force of the adhesive layer, the ink layer will shrink, causing delamination.
2. The compounding post-treatment curing time is not enough. When the time is short, the resin crosslinking reaction is insufficient, the bonding strength is insufficient, and the temperature resistance is lowered.
3. The activity of the ink or adhesive is not enough, or because the water diffuses into the ink or the adhesive during the production process under high temperature and high humidity conditions, and the isocyanate in the partial curing agent is consumed, resulting in a proportional imbalance.
4, the substrate problem. First, the corona treatment of the film is not enough, or the long-term inventory is invalid, or it is not processed at all. The operator does not test before the machine is put on, so that the bonding strength is poor after printing or compounding and aging, and the food to be filled is cooked. Find. In addition, during the aging process, the high-temperature conditions for a long time accelerate the precipitation of the additives in the film, which also causes a decrease in the bonding strength.
5, the choice of adhesive type is not appropriate. The end use is to package liquids, such as mustard, kimchi, juice, yogurt and other foods, it is necessary to use anti-media type adhesives, can not use ordinary adhesives, otherwise, composite film cooking at 80 ° C or more will Layering does not meet the peel strength requirements when packaging. Therefore, when selecting an adhesive, it must be considered according to the structure of the composite membrane and its end use to ensure the overall quality of the product.
Solution
In order to prevent the occurrence of delamination of the retort pouch, the following work should be done:
1. The use of packaging bags is strictly controlled according to the process conditions during the cooking process. Pay attention to the stability of temperature and pressure. Because of the limited cooking conditions of the various materials of the composite membrane, the physical and chemical properties of the contents and the high temperature are limited. Changes in physical and chemical values that may occur may result in new substances that may penetrate into the composite film layer and cause a decrease in the performance of the package.
2, the composite bag manufacturer should strengthen the management work, do a good job in the detection and monitoring of process indicators, especially before the mass production and before the factory physical test. In the production process, it is necessary to check whether the surface treatment degree of the film meets the requirements before going to the machine. After compounding, pay attention to the curing temperature and time, and let the two-component adhesive fully cross-link the reaction. In addition, pay attention to the control under high temperature and high humidity conditions, do not add too much ink or adhesive at a time, to increase the number of hard work, if necessary, take certain protective measures. Ingredients and adhesives are formulated in strict accordance with the process ratio. According to the requirements of cooking conditions of food manufacturers, the products are tested and the conditions are simulated for final confirmation to prevent batch accidents.
In addition, manufacturers of packaging materials such as inks, adhesives and films pay attention to the control of process parameters, ensure the stability of product quality, ensure the temperature resistance of materials used in retort bags, and understand the use of users and downstream users as much as possible. Claim.