At present , the vast majority of domestic cooking bags are manufactured using the dry compound method, and some are manufactured using the solvent-free compound method or the co-extrusion compound method.Here we will only talk about the dry compound manufacturing process.
1. Material selection
The selection of materials should be determined according to the end use of the cooking bag , including the nature of the packaging, weight, cooking sterilization temperature and time, food shelf life, etc. Because of different end uses, the requirements for the quality of the cooking bag are different, the combination of material structure, adhesive The quality requirements of the agent and ink are different, and the cost is also different.
2. Determine process parameters
In the specific operation , the operator must strictly follow the process parameters of the process sheet, including the number of glue rollers and the depth of the mesh hole, the amount of glue, the concentration of glue, the temperature of each heating section of the drying tunnel, the amount of air blowing and the exhaust air The amount of the volume, the starting speed, as well as the control of the unwinding tension, the drying tunnel tension, the winding tension, the surface temperature and the composite pressure of the composite steel roller, etc. Among them, the amount of glue (generally 4 ~ 5g / m2) and residual The amount of solvent (the national standard is less than 10g / m2. The internal control of the enterprise is preferably less than 3mg / m2. It is the key to the internal quality of the cooking bag and must be taken seriously.
3. complex
When performing compounding operations; some adhesive suppliers require the first two layers (pet / al or opa / al). After compounding, they should be placed in a curing room at 50 ～ 55 ℃ for 4 ～ 12 hours, and then proceeded. The third layer (pet / al / cpp or pet / al / opa) is compounded. However, there are also many adhesives that can directly compound two, three or even four layers of materials and then cure them.
4. Ripening
It is generally required to keep at 50 ～ 55 ℃ for more than 48 hours, preferably 72 hours, but some adhesives are required to be placed for 5-7 days. It is also necessary to maintain the ventilation and flow of the curing room to maintain the same temperature at all points in the room. The air should also be properly replaced, and the residual solvent released during aging should be discharged to the outside and then replenished; strive for fresh air, which will help reduce the amount of residual solvent and odor of the composite membrane.
5. Inspection bag
After the composite film is cured , the compound fastness and the amount of residual solvent between the layers must be detected first, and then the bag can be taken out after reaching the requirements. Most of the cooking bags using composite film materials are made into flat bags or stand-up bags by three-side sealing. It is rarely made into a back seal bag. The heat seal strength of composite films with different structures, different combinations and different layers is different, between 45-80n / 15mm. The cooking bag uses cpp film or hdpe film as the heat seal layer , The melting point is higher than ldpb. Therefore, the temperature of the heat sealing knife should be much higher, most of which are stored at 180-230 ℃. When heat sealing the bag, the smaller the number of composite layers and the smaller the thickness of the composite film, the lower the temperature of the heat sealing knife; The higher the number, the greater the thickness or the composite film containing aluminum foil, the higher the temperature of the heat sealing knife. In addition, some bag making machines can be heated by the upper knife and the lower knife, and some bag making machines can only be heated by the upper knife. For a large number of composite layers and a large thickness of the film, it is more ideal to heat the upper and lower knives. It is particularly important to note that when the hot knife is pressed down, the pressure on the inside of the bag must not be large, and the pressure on the outside should be small. It is good to adjust the pressure on the inside of the bag to be slightly less than the pressure on the outside, so that the original shape of the film will not be damaged when the two inner films are welded under pressure, and the sealing strength is guaranteed.
Ningbo XISXI E-commerce Co., Ltd , https://www.petspetscleaning.com