What are reclosable bags?
is a kind of pressed and sealed packaging bag. Clear plastic resealable bags
are made using two or more layers of plastic film with characteristics bonded by a high-speed laminating machine. Reclosable bags
are also known as resealable poly bags, reclosable poly bags, reclosable plastic bags, zipper closure bags, and bone bags.Reclosable poly bags
are suitable for vacuum packaging or general packaging of food, electronic products, chemical, pharmaceutical, tea, precision instruments, and cutting-edge national defense products.
The raw materials of resealable poly bags
are OPP, PE, POF, PPE, PP, laminated film, and so on. Its process is divided into side seal bag, bottom seal bag, middle seal bag, and three side seal. If you want to achieve these processes, you need to use four different kinds of machines.
Types of reclosable bags
Reclosable zipper bags
|BOPP / LLDPE |
|Instant noodles, snacks, frozen snacks, powder packaging, etc.
|Instant noodles, cookies, candy, and all kinds of light food.
|All kinds of dry food, fried food, potato chips.
|All kinds of food, rice snacks, snacks, tea.
|Steaming, food containing wine, fragrant food.
|Powder packaging, soy sauce, liquid, shampoo.
Heat sealing failure of reclosable bags
Resealable poly bags
Failure A: The type, thickness, and quality of the heat seal material have the most direct impact on the strength of the heat seal.
On the market, the commonly used heat-sealing materials for general composite packaging are CEP, LPPE, CPP, OPP, EVA, hot melt adhesive and some other ionic resin coextruded or co-blended modified films. The thickness of heat-sealing layer material generally fluctuates between 20-80μm. In special cases, there are also up to 100-200μm of the same heat-sealing material, its heat-sealing strength increases with the increase in the thickness of the heat seal. For example, the heat-sealing strength of steaming bags generally requires up to 40-50 Newton, therefore, its heat-sealing thickness should be 60-80μm or more. The heat-sealing bag-making process involves the temperature and the temperature control of how much the temperature instrument is to display. In the heat sealing composite bag processing, the more precise the temperature gauge requirements the better, the error range and the set value is preferably not greater than ± 5 ℃. Heat sealing temperature has the most direct impact on the strength of the heat seal, the melting temperature of various materials, directly determines the minimum heat-sealing temperature of the composite bag.
The difference between boiling and steaming reclosable bags
Boiling sterilization is divided into low-temperature boiling packaging, boiling conditions are generally controlled at 100 degrees sterilization for 30 minutes, there are boiling conditions controlled at 85 degrees sterilization for 15 minutes, called pasteurization; low-temperature boiling packaging, boiling conditions can be controlled at 100 degrees ~ 120 degrees range of a specific temperature value sterilization 30 minutes; medium-temperature boiling packaging, boiling conditions can be controlled at 121 degrees sterilization 45 minutes; high-temperature sterilization packaging, steaming conditions is to control the temperature to 135 degrees sterilization 15 minutes; ultra-high-temperature packaging sterilization, sterilization conditions are in the microwave heating oven sterilization 3 to 5 minutes.
Boiled and steamed packaging structure is also different, boiled packaging structure, the usual NY/CPE, PET/CPE, NY/CPP, PET/CPP, PET/PET/CPP, etc.; while the usual structure of steamed packaging is NY/CPP, PET/CPP, NY/NY/CPP, PET/PET/CPP, PET/AL/CPP PET/AL/NY/CPP, etc.
Failure B: To achieve the desired heat seal strength, heat seal pressure is essential.
For light packaging bags, heat sealing pressure should be at least 2kg/cm2, and with the increase of the total thickness of the composite film and the corresponding increase. If the heat-sealing pressure is not enough, it is difficult to achieve a real fusion between the two layers of film, resulting in poor local heat sealing or difficulty to eliminate the bubbles in the middle of the weld, resulting in false welding. However, the heat-sealing pressure is not as large as possible, but should not damage the weld edge, because at higher heat-sealing temperature, the heat-sealing material of the weld edge is already in a semi-molten state, and too much pressure is easy to squeeze away part of the heat-sealing material and make the weld edge form a semi-cut-off state. The weld is brittle and the strength of the heat seal is reduced. So, the regulation of pressure is very critical.
Failure C: The heat-sealing time is mainly determined by the speed of the bag-making machine.
If the speed is fast, the heat-sealing time is short; if the speed is slow, the heat-sealing time is long. Heat sealing time is also a key factor in the strength and appearance of the weld seam. Under the same heat-sealing temperature and pressure, the heat-sealing time is longer, the heat-sealing layer is more fully fused and more firmly bonded; however, the heat-sealing time is too long, which will easily cause the weld seam to wrinkle and deform, affecting the flatness and appearance. If the weld after heat sealing is not cooled well, it will not only affect the apparent flatness of the weld doubt but also have some influence on the heat-sealing strength. The cooling process is to set the shape of the weld just after molten heat sealing by using a lower temperature under certain pressure. Therefore, insufficient pressure, poor cooling, and circulation, insufficient circulation, too high-water temperature, or untimely cooling will result in poor cooling and reduced heat-sealing strength.
Failure D: The more the number of heat sealing, the higher the heat-sealing strength. The number of longitudinal heat sealing depends on the ratio of the effective length of the longitudinal welding rod and bag length.
The number of transverse heat-sealing times is determined by the number of groups of transverse heat-sealing devices on the machine. Good heat sealing requires the number of heat sealing to be at least two times or more. For the composite film of the same structure and thickness, the higher the peel degree between composite layers, the greater the heat sealing strength; for products with low composite peel strength, the weld damage is often the first interlayer peel of the composite film at the weld seam, resulting in the inner heat sealing layer to independently bear the damage tension, while the surface layer material loses its complementary role, resulting in the heat sealing strength of the weld seam is greatly reduced; if the peel degree between composite layers is strong, the peel of the layer at the weld edge will not occur If the interlayer peel is strong, the peeling of the layer at the edge of the weld will not occur, and the actual heat seal strength measured is much better; when the inner layer of the heat seal is PE or OPP, the heat seal strength is much better than the same thickness of BOPP.
Failure E: The effect of the contents of the reclosable bags.
Some products are powdered and tend to stain the seal when filling. For example, when LDPE material is used as the inner layer material, it is found that the seal is easy to break. This is because the heat-sealing property of LDPE for inclusions is not very good, then it is necessary to replace the inner layer film material or increase the thickness of the material can improve the heat-sealing strength.
Failure F: The effect of composite additives.
In the process of compounding polyethylene film, polyethylene has the phenomenon of precipitation after extrusion by hot press rollers - a layer of white like crushed powder white. This phenomenon is the polyethylene in the production process, adding a certain amount of lubricant, is some low melting point wax, easy to precipitate out to the film surface. This layer of low melting point wax precipitation after the most direct harm greatly weakened the composite strength, but also greatly weakened the heat-sealing strength, especially in the sealing position, resulting in the easy opening, leaving the layer.
The solutions are as follows.
a. Re-pre-treating the polyethylene to achieve the desired surface tension.
b. Select a suitable adhesive to enhance the fastness of the compound.
c. Reduce the maturation temperature and try not to make the material precipitate, to increase the fastness of the compound and heat seal strength.
Failure G: Flexible packaging composite bag heat sealing after delamination and printing ink layer and corona surface is good or bad.
In the actual production process, to achieve the true reproduction of color, the printing and surface printing ink are inevitably mixed printing. From the theoretical analysis, the printing and surface printing ink is not affinity, if the printing film ink layer using the mixed use of the table, the inevitable ink layer between the fastness is not good, easy to delamination, in the heat seal welding seam is also easy to cause delamination phenomenon, heat seal strength thus becoming poor.
The solution is to avoid the mixing of surface printing ink and printing ink, to improve the heat seal strength and reduce the phenomenon of delamination.
How to buy reclosable bags?
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