In order to control the quality of high-temperature cooking bags , we must pay attention to the operation of the three processes of printing, compounding and bag making. During the production process, each control item must be inspected according to the requirements. This is a basic measure to verify whether the quality meets the standard. Therefore, from the raw material to the finished product, the inspection must be strictly carried out, especially the high-temperature cooking test to verify the function of the bag careless.
1. Printing process
1. Before printing, BOPA nylon composite film can be placed in a space with a temperature of 35 degrees in the curing room for 2 hours for preheating. Relative humidity should be controlled in the printing workshop. When the relative humidity exceeds 75 %, we recommend not to print. When printing, we should pay attention to the gradient of drying temperature, otherwise it will affect the drying and overprinting accuracy of BOPA .
2. According to the characteristics of the printing material and the structure of the composite film, select the appropriate ink. For example, choose BOPA nylon as the printing layer. In the case of cooking, the pigments of individual colors may penetrate on the BOPA . The same applies to only the printing layer and heat seal. In the two-layer cooking bag, the ink may also penetrate on the RCPP , which brings the risk of contamination of the contents. Therefore, it is recommended to pay attention to the selection of retort-resistant inks, and select the use of penetration-resistant inks to further reduce the risk.
3. For spot colors and white inks that need to be used on a large area, add 3% of the ink curing agent. The amount of addition must be determined according to the technical information provided by the ink manufacturer, not too much or too little. This place has been weighed with sophisticated electronic scales. The remaining ink recovered in the ink tray, no matter how long it is stored, can no longer be used for printing high-temperature cooking products. It is recommended that it can be digested and used on other products as soon as possible after use. ( Only when there are not enough orders for high-temperature cooking products. )
4. Minimize the amount of solvent residue in the printing material, and the ink fastness is good. It is necessary to select standard production process parameters, such as oven temperature, air volume and machine speed. For large-area inks with added ink curing agents, the oven The temperature is 10 ~ 15 ℃ higher than other inks .
5. The printed BOPA film must be wrapped tightly with a composite film with AL foil or a composite aluminum-plated film to prevent moisture shrinkage and performance changes.
6. The printing material added with ink curing agent should be rewinded once, and the storage time should not exceed three days, that is, the printing layer should be compounded at least within three days.
2. Compound process
1. The use of high-temperature cooking glue must be in accordance with the manufacturer's instructions, such as mixing ratio, curing temperature and time, etc. The purity of the ethyl acetate solvent used for dilution must reach more than 99% .
2. The thickness of each layer of material must be uniform, and the thickness deviation should not exceed 7% . In addition to the mechanical performance parameters of AL foil products, the surface of AL foil should be dry, and the cleanliness must reach the A level standard, that is, use distilled water When inspecting, all must be able to be infiltrated, and the number of pinholes should be as small as possible. In order to enhance the compound fastness, the BOPA compounded in the middle should be a double-sided corona, and the corona value should not be less than 50 dyne.
3. Glue coating should be uniform. According to the characteristics of different manufacturers and different types of glue, the dry base volume should generally be 3.5 ~ 4.8g / m2. When the minimum coating volume standard is reached, apply the left, center and right positions. The cloth deviation should not exceed 0.3g / m2 as a reference. The curing agent should be added as required. If the humidity in the dry workshop exceeds 75% , the amount of curing agent should be appropriately increased. Generally, it should be increased by 5% ~ 10% on the original basis. If the product printing pattern has more yellow , White and other light-colored areas, the coating amount during production should be increased by about 0.3g / m2 than the dark pattern design to prevent obvious spots after cooking.
4. Determine the proper processing parameters of the machine, especially the temperature of the three-section oven is 5 ~ 10 ℃ higher than the production of ordinary products , the temperature of the composite heating roller is 70 ~ 80 ℃ , and the composite pressure is increased by 0.1 ~ 0.2MPa compared with the common products of the same specifications. According to the machine performance, the speed is controlled below 120m / min . The selection of the initial tension and taper of the winding is determined according to the type and specifications of the material, with a moderate degree of winding tightness and no wrinkle of the film.
5. When curing, different types of glue should be made according to the manufacturer's use requirements. The temperature and time must not deviate too much. The temperature deviation should be within 5 ℃ . The time deviation should not exceed 4 hours. take.
6. The matured material must be cooled normally at room temperature for more than 12 hours before it can be cut into bags.
7. The selection of compound high-temperature cooking glue must be well matched with ink and film. If it is not matched properly, there will be a phenomenon of delamination after high-temperature cooking, so a sample test must be done before mass production.
8. According to the characteristics of the glue, each compound layer can be cured for 12 to 24 hours . After the last layer is completed, the final curing can be completed according to the curing time required by the glue. It is also possible to enter the curing room after the multi-layer one-time compounding is completed, and complete the final curing according to the curing time required by the glue. The advantages of layering and aging are stable quality, reducing the effect of compound wrinkling, and you can also check whether the appearance of compound AL products has white spots; the benefits of one-time completion are high production efficiency and easy management, but there are wrinkles Hidden quality. Our suggestion is that after segmentation and compounding, the quality will be relatively high.
3. Bag making process
1. Before batch bag making, sample test is done to determine the processing parameters, including the temperature, pressure and machine speed of each section of heat sealing knife, and these parameters can ensure that the heat sealing strength before and after cooking can reach the standard. Load the same volume of content in a high-temperature cooking tester to do media resistance test to determine the conformity of the material structure.
2. Ensure that the roll film before bag making has been sufficiently cooled, and the compound strength between the layers, the residual solvent of the roll film, etc. have reached the standard after testing, and the first inspection item has been confirmed.
3. The width of the heat sealing edge is not less than 5mm when making bags . In addition, in order to ensure that the heat sealing area is flat and beautiful, the cooling mold must ensure a sufficiently low temperature, generally below 25 ℃ . Fully check the circulation of cooling water.
4. The evaluation of the suitability of the roll film in the bag making process should be sufficient to ensure that the film is smooth during each production, the heat sealing condition is good, and the quality of the bag is stable. In particular, RCPP as a heat-sealable layer is likely to cause poor bag opening. It is necessary to prevent the bag from collapsing due to poor opening. To do prior to production control the friction coefficient, it is recommended 0.15 - 0.18COF within range.
5. Due to the particularity of high-temperature cooking materials and processes, the sampling ratio of high-temperature cooking products in the bag-making process should be appropriately increased so that the quality abnormality in the process can be detected early. The cooking test should be done once per production shift. To be correct, simulate the customer's use conditions, that is, to enclose the content of the same capacity and the same nature, according to the customer's sterilization conditions (mainly cooking temperature, time, pressure, such as the condition parameters of 121 ℃ , 40min , 0.2 ~ 0.24MPa ) Carry out the test of high temperature cooking resistance.
6. Choose the appropriate packaging quantity according to the size and weight of the bag, pay attention to protection and prevent mechanical damage to the bag.
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