Manufacturing Process of High Temperature Retort Bags At present, most of the world's retort pouches are made by dry compounding method, and few of them can be manufactured by solventless compounding method or coextrusion compounding method. The quality of the dry composite is higher than that of the solventless composite, and the arrangement of the materials is also reasonable and extensive than the coextrusion compounding, and the use is also more assured. In China, at present, 100% of retort pouches are manufactured by dry compounding method, so only the dry composite manufacturing process is mentioned here.
The first is the selection of materials. According to the end use of the retort pouch to determine which substrates to use, how to combine, which ink and adhesive to use. The so-called end use refers to the nature of the food to be packaged in the bag, and the weight of the package. How high the temperature is to be applied after packaging (121 ° C, 128 packs, so that the package has a reasonable price/performance ratio, so it is important to understand the end use. The second is to determine the process parameters. After determining the substrate and auxiliary materials You can place an order for the workshop to produce. As the technical management and operation personnel of the workshop production, you must go to the department and prepare the materials in strict accordance with the requirements of the craft sheet. Do not make mistakes.
Then, in the specific operation, the process parameters of the process sheet should be followed, including the number of lines of the rubberizing roller and the depth of the dot, the concentration of the operating glue, the temperature of each heating section of the drying tunnel, and the amount of exhaust air of the blasting quantum port. The speed of the booting speed, as well as the unwinding tension, the drying tunnel tension, the control of the winding tension, the surface temperature of the composite steel roll and the composite pressure. In the above process parameters, the amount of sizing required (generally 4~5g/m2) and the amount of residual solvent (national standard is less than 10mg/m2, the internal control of the enterprise is preferably less than 3mg/m2), which is the inside of the retort pouch. The key to quality must be taken seriously.
Third: In the specific compound operation, some adhesive suppliers require that the second layer (PET/AL or OPA/AL) be restored after the first time. It should be placed in the ripening room at 50~55 °C. After 4h or 12h, the second layer of the third layer (PET/AL/CPP or PET/AL/OPA) is compounded. Every time there is a good compounding, there must be this process, but there are also many glues that can be used in one go. After all the layers, three layers and even four layers have been restored, they are placed in a curing chamber of 50-55 ° C to allow it to mature. This latter adhesive is advantageous for production management and labor productivity.
The fourth is ripening. Regarding the temperature of ripening and the time of curing, it is generally required to maintain at 50 to 55 ° C for more than 48 hours, preferably 72 hours, but some adhesives are required to be placed for 15 to 7 days. This must be done according to the requirements of various crystal brand product specifications. The temperature of the curing chamber is too low and the curing time is too short. The temperature in the curing chamber should be maintained in the same way by ventilation, and the indoor air should be properly replaced. The residual solvent released during curing should be discharged to the outside to replenish clean fresh air. This is beneficial to the fresh air. Reducing the residual solvent amount and heterogeneity of the composite is beneficial to improve product quality.
The fifth is to detect bag making. After the composite is matured, the composite fastness and residual solvent amount between the layers should be detected first. After the data meets the requirements, it can be taken out and taken to make the bag. The composite film is used as an empty bag for the retort pouch, and most of the three-side seals are used to make a flat bag or a stand-up pouch, and the shape of the middle seam (back seal) bag is rarely formed. The composite film with different structures, different combinations and different layers has different heat seal strengths and can be between 45 and 80 N/15 mm. For composite membranes with different structural combinations and different layers, the process parameters of heat-sealed bags should also be different. The process parameters of heat-sealed bags are mainly temperature, pressure and time. They have complementary and interdependent relationships. Among them, temperature plays a leading role, and pressure and time are auxiliary. We know that the retort pouch is made of CPP film or HDPE film as the heat sealable layer. Their melting point is higher than that of LDPE, so the temperature of the hot knife is much higher than that of the LDPE film, and most of them are selected between 180~230 °C. If the temperature is too low, the pressure will be too large, and the length of the pressurization will be longer, and the CPP will not be able to reach the degree of melting and self-adhesive. Only when the suitable temperature is selected, after a certain contact pressure and contact time, the heat sealing can be completed. The purpose of the bag. When heat-sealing the bag, the composite layer with less composite layer and thinner thickness, the lower the temperature of the hot knife, the more layers, the thicker the thickness, or the composite film containing aluminum foil, the temperature of the hot knife should be The higher. The hot knife on the bag making machine has two or three rows in terms of longitudinal distribution, and there are several in each row. The temperature must be the same for each and every point. Otherwise, the sealing strength of the bag will be inconsistent, some high and some low. We must strictly control and observe and check frequently. When heat sealing the bag, the pressure of the hot knife can not be too small or too large. Too small, the fastness is not enough, too much, and it may damage the original thickness of the inner film of CPP or HDPE, so that the total thickness of the inner film of the second layer of the heat-sealed welded part is smaller than the sum of the original two layers, resulting in The sealing power is reduced. In particular, it is necessary to remind that when the hot knife is pressed down, the pressure on the side of the bag should not be large, and the pressure on the outside side is small. It is better to adjust the pressure on the side of the inner side of the bag to be slightly smaller, so that when the inner film of the two layers is not welded, the thickness on the inner side is reduced, the original shape of the film is destroyed, and the sealing strength is ensured. For different composite membranes, it is best to use the heat seal tester to detect the best three parameters of temperature, time and pressure, and then use them as the basis of the workshop operation, and make some adjustments to make a good The bag is gone. In order to make the bag not only to be strong, but also to be flat and beautiful, after the hot sealing, the cooling knife should be used to cool and shape with a cold knife to avoid wrinkles and ripples. The so-called cold knife is an air-core copper square tube that is cooled by tap water. When using it, it is necessary to let cold tap water flow in. The hot water after heat exchange flows out, so that the knife maintains a lower temperature, if there is no circulation. The tap water is used for heat exchange. After a long time, the water temperature in the pipe will increase, and the cooling setting effect is not good. Therefore, the operator should pay attention to the inspection, don't forget to use the cooling water, and do not let the pipe block. Second, the product standards and project testing of high temperature retort pouches China's high temperature retort pouch product standards, the first is GB10004-1988 "polyester (PET) aluminum foil (AL) polypropylene (CPP) composite film bag", the standard; The material structure is only three layers of PE / AL / CPP, and the cooking conditions are limited to 121 ° C · 40 min. After ten years, it was revised to G810004-1998 "Retort-resistant composite film and bag". The material structure of the product has been expanded, including PET/CPP, PA/CPP two-layer transparent type and PET/AL/CPP, PA. The /AL/CPP three-layer opaque type and the PET/PA/CPP three-layer transparent type, as well as the PET/AL/PA/CPP four-layer opaque type. In terms of physical and mechanical properties of the product, the three items of the medium resistance, the peeling force after cooking and the heat sealing strength after cooking are added, and the original oil resistance project is eliminated, highlighting the practical use of the product for high temperature cooking. Sex. After being revised again in 2002, the high-temperature retort pouch was included in the standard of "Composite film for packaging, bag general rule". This latest standard was approved in Guiyang at the end of December 2002, and the draft was officially confirmed. The text, but has not yet been enacted.
Elevator Ceiling,Best Elevator Ceiling,Elevator Ceiling Panels,Elevator Ceiling Design
MAURER TECHNOLOGIES CO., LTD. , https://www.maurer-elevator.com