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Causes of delamination of cooking bags

1. The heat and humidity resistance of the ink or glue is not enough. Whether the ink or glue used in the cooking bag is two-component or single-component, it is generally made of polyurethane resin. Humidity and heat resistance is determined. As far as the characteristics of the polyurethane resin itself are concerned, due to the strong polarity of the ester bond, urethane bond and other groups in the polyurethane resin, it is easily attacked by moisture under humid and hot conditions, hydrolysis occurs, and the polyurethane resin and the surface of the substrate The formed hydrogen bonds are easily damaged by damp heat, thereby reducing the bonding strength and even the adhesive layer falling off. Ink or glue manufacturers should technically improve the adhesion strength of cooking ink after high temperature cooking by changing the chemical structure of polyurethane resin and using additives. 2. The problems existing in the use and operation of ink or glue by flexible packaging manufacturers mainly include the following points: First, the amount of curing agent does not meet the requirements. According to the requirements, neither less nor more can be used. If the dosage is too small, the degree of cross-linking between the curing agent and the resin will be insufficient, and the adhesion strength, heat resistance and hydrolysis resistance of the ink layer will be reduced; If it is too large, excessive cross-linking will occur, affecting the crystallization and micro-phase separation between polymers, which may damage the cohesive strength of the adhesive layer, increase the internal stress, and excessively shrink the ink layer, causing delamination. Second, the curing time does not meet the requirements. If the time is short, the crosslinking is insufficient, and the temperature resistance and hydrolysis resistance of the ink layer are reduced. The third is that the ink or glue is not active enough, or there are too many expired and expired residues. If the ink or glue is not active enough before printing or compounding, the number of groups that can be used to connect the substrate is small, so the adhesion is not strong. 3. The compatibility between ink, glue and film is inconsistent. According to the adhesion theory, when the surface tension of the adhesive and the adherend are equal and the polarity is the same, the interfacial tension is the smallest and the adhesion strength is the highest. Therefore, the condition of the surface of the ink and glue after curing and film formation and the condition of the film surface may vary with the products of different manufacturers, because the groups on the various surfaces cannot be well attracted to form intermolecular forces or chemical reactions occur. Chemical bonds, even if they have a certain effect at low temperature to form adhesion, but at high temperature, the weak connection of surface groups may be damaged and delamination occurs. 4. The film problem is manifested in the following two aspects: First, the film treatment degree does not meet the requirements, or it is not treated at all. Operators often do not find this problem, so that the adhesion fastness is not high after printing, lamination, and aging, and this problem is only discovered after delamination after cooking. In production practice, I have found several such cases. Second, some additives in the film are rapidly released to the surface at high temperature, which may cause a decrease in adhesion. Such as opening agents, antistatic agents, slip agents, etc. added to plastic films. After the cooking delamination accident occurs in the cooking bag, the enterprise must first carefully identify which interface the delamination occurs, which two materials are related, and check whether the production process is operated according to the requirements. Find out the real cause of delamination. In order to prevent the delamination accident of the retort bag, the enterprise should do the following work: 1. When the food enterprise uses the retort bag, the temperature should be strictly controlled within the range guaranteed by the retort bag manufacturer because even if it exceeds a few degrees, it will be produced at this time. Various materials of the retort bag have often reached the limit that they can bear, and the excess of several degrees is very critical to whether the performance of the retort bag can be guaranteed. 2. Food companies should do a good job of confirming the performance of the retort bags before using them in batches. This confirmation is the process condition test for whether the retort bags can be used under specific process conditions. Because of the physical and chemical properties of the inner packaging, and new substances generated due to possible physical and chemical changes at high temperatures, it is possible that the retort bag layer may penetrate into the retort bag layer, causing the packaging performance of the retort bag to decrease, such as delamination. Even the vacuum within the retort pouch can cause stress differences between the layers of the retort pouch, which can lead to detachment of poorly adhered film layers. 3. Retort bag manufacturers should strengthen management, and do a good job in the detection and control of process indicators in each process, especially the last stage of the test of the contents of the retort bag before leaving the factory. 4. The retort bag manufacturer should do a good job in various packaging. The compatibility use test of printing materials has certain limitations and particularities in the scope of use of various products, and it is impossible to control or take care of all aspects of post-processing and further processing and use of various users. The processing and processing of downstream products and The use requirements of subsequent products may not be fully understood. Compatibility test should pay attention to the following points: First, it should be noted that the test should run through the whole production process, not only in the printing stage. The second is to pay attention to the high temperature resistance, and pay special attention to the problem of adhesion drop or delamination caused by the exudation of various additives in the film at high temperature. The third is to pay attention to the replacement of materials from different manufacturers, and even when using materials from the same manufacturer but different batches, the compatibility test must be done. 5. The production enterprises of packaging materials such as ink, glue and film should improve and stabilize the product quality in a solid way, and improve the temperature resistance of ink and glue. The actual temperature resistance must exceed the guaranteed temperature resistance to a certain extent. For example, the retort-resistant ink and glue produced by New Oriental Ink Group Co., Ltd. fully consider the possible temperature fluctuations in the actual application of food enterprises, and there are different The inks and glues with different grades and different temperature resistance requirements are sold, thus ensuring the temperature resistance of the retort pouch.

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