(1) According to the sterilization time temperature, the two-component polyurethane adhesive meeting the cooking requirements was selected. The internal quality of the adhesive, first of all, is the percentage content of the curing agent. Generally, the percentage content of the curing agent shall be less than 2% of the original specification, otherwise the viscosity of the prepared glue will be greatly reduced. Secondly, the proportion of the curing agent shall be too large. If it is too large, it is easy to cause embrittlement tear of the composite film. If the activity of ink glue is enough, there is too much expired residue, the number of groups that can be used to connect the substrate is small, so the adhesion is strong. The water activity of expired ink glue is good, which will lead to the poor adhesion of the boiling bag. Pay attention to use expired ink glue.
(2) The corona treatment intensity shall reach (pa-52dny, pet-48dny, PE, rcpp-40dny), the glue application amount shall reach 4.5-5g/m2 (refers to the dry glue amount) according to GB / t10004-2008. The thermal seal film that has been placed for too long is available, the phenomenon of delamination may occur.
(3) The additives (auxiliaries) of printing heat sealing materials are too much, which make the composite layer degrade peel off easily. The inner film of cooking bag shall have stable heat shrinkage rate, good temperature resistance oil resistance, so as to prevent the oil content permeating into the rubber layer, resulting in the separation of composite film. The smooth dosage of the thermal seal film is too high (above 500 ppm), which will also cause low degree of peeling.
(4) The cross-linking of different adhesives is different. In order to ensure the complete cross-linking of glue, different curing processes should be adopted according to different brands of glue different uses. Appropriate curing time temperature to ensure the composite quality. If the ripening conditions do meet the requirements, the ripening time is too short, the peeling fastness will decrease after sterilization. If the curing time is short, the crosslinking is enough, the temperature hydrolysis resistance of ink layer are reduced. The basic ripening time of the cooking bag is 60 hours, but sometimes it needs to be adjusted according to the size of the cooking bag the size of the oil ink surface. If the curing time is enough, the high temperature resistance hydrolysis resistance of the ink layer will be reduced, so the curing time of the high temperature resistant cooking bag is generally 72 hours.
(5) According to the adhesion theory, when the surface tension of the adhesive the adherend is equal the same, the interfacial tension is small the adhesion strength is high. Therefore, the conditions of the surface film surface after the ink glue solidify into film may vary with the products of different manufacturers. Because the groups on various surfaces can attract well to form intermolecular force chemical reaction to form chemical bond, even if they have certain effect at low temperature to form adhesion, but at high temperature, the surface groups are weakly connected Delamination may occur due to damage. There is a problem in the ratio of curing agent of cooking glue. The ratio of curing agent is the higher the cooking bag is, the more it meets the standard, more it will lead to ink delamination, less it will affect the adhesion hydrolysis resistance of ink layer. The peeling force of the composite membrane was tested. In particular, the intensity of sampling inspection at the beginning near the end of each volume can be larger, various quality accidents are easy to occur at this stage.
(6) Use 80-90 wire / inch glue coated wire roller. In this way, it can ensure that there is a higher glue amount under the appropriate viscosity of the glue liquid. If there is a return to the use of uniform roller to ensure uniform coating. Before compounding, it is necessary to check the cleanness of the cot whether the anilox roll is blocked to ensure a good coating state. The oven should be well ventilated the environment should be clean.
(7) Environmental factors are very important. Make workshop production records. Generally, humidity in the air is more than 80%, which is very unfavorable for printing compounding. It is recommended to use production.
(8) When using cooking bags, food enterprises should strictly control the temperature within the range guaranteed by the cooking bag manufacturers. That is to say, when 121 ℃, the actual sterilization temperature is 125 ℃. Because even if it is more than a few degrees, but at this time, all kinds of materials used to make cooking bags are often up to the limit that they can bear, which is very important to ensure the performance of cooking bags.
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