1. The tension of the substrate The dry compounding process is to apply adhesive to one of the two different rolls of base material, and then press the heated roller to form a composite. Therefore, the tension between the two different base materials and the tension of the composite product is Important. Generally speaking, the tension of the two substrates during compounding is not suitable. One of them is too large and the other is too small. Since the film rolls are tight during compounding, it seems that there is nothing to see. After compounding, the original tension A substrate that is too large must shrink, and its shrinkage is obviously larger than that of a substrate with a small tension, which causes relative displacement and wrinkles. Therefore, once cooled after compounding, BOPP shrinks, wrinkles occur, aluminum foil bulges, and a series of "tunnels" appear laterally. Of course, this example uses a more extreme example. In fact, another composite substrate, such as vacuum aluminized film, or PE and CPP film, as long as the unwinding tension of the two substrates is not well matched, this will happen. The solution is: First, adjust the unwinding tension of the two substrates to make them adapt to each other. Dry-type laminating machines are often equipped with unwinding tension adjusting devices composed of magnetic powder brakes, which are specially used for this phenomenon. The second is to appropriately reduce the temperature of the drying tunnel. Since the substrate with large deformation is dried through the drying tunnel, the higher the temperature, the greater the elongation of the film. The larger the deformation, the greater the shrinkage after cooling. Of course, this method must consider the amount of residual solvent, the lower the temperature, the better. However, low viscosity adhesives tend to have small molecular weights and low cohesion. It is necessary to wait for it to cure and crosslink to form a macromolecular structure to achieve the ideal adhesion. The initial tack force at the time of compounding is very small, and the tack force is insufficient. Therefore, when a substrate shrinks, there will be a relative displacement between the two different substrates, that is, wrinkles and "tunnels." Therefore, choosing an adhesive with high solids content, low viscosity, and high initial adhesion is the preferred method to solve this problem. Generally speaking, plastic / plastic composite and plastic / aluminum composite, no matter whether the composite is mainly printed with large area or blank without printing, the glue amount of 2.0 ～ 5.0 /? Is necessary. Not too low. Too low, it seems to save costs, the actual combination is not strong, but instead give up their previous efforts. Of course, it is not necessary to apply too much glue. In a certain range, the fastness is proportional to the amount of glue, but after a certain degree, it is not proportional. The winding tension is too small, the winding is not tight, and the compound has a slack phenomenon, which provides the possibility of shrinking the substrate to be shrunk. This phenomenon is most obvious at the two ends of the composite product, and the middle part is often strong, but the exposed parts of the two ends are wrinkled due to uneven shrinkage. The solution is simple. Rewind as tightly as possible. The rewinding tension should be greater. The reel should be tightly compacted without slack. Even if there is some uneven tension and insufficient initial adhesion, the tightly pressed film roll is less likely to shrink. When the adhesive is cross-linked and cured during curing, the initial adhesion is greatly improved and the relative displacement between the composite substrates The living conditions are lost, so that wrinkles will not appear. Igrow's desks and chairs can be raised and lowered at will to accompany children's growth. The height of the tables and chairs can be adjusted freely to meet the height requirements of all age groups. Selected environmentally friendly plates, fresh companionship, healthy growth, high quality and safe use, create a healthy learning environment for children,
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Take the compounding of BOPP and aluminum foil as an example. After BOPP is glued, it is heated in the drying tunnel. If the unwinding tension is large, it will be pulled tightly and then heated, it will inevitably elongate and deform. But the tension of aluminum foil cannot be as large as BOPP, and the elongation is small.
2. The adhesive strength of the adhesive â‘ Select the applicable adhesive. The solid content of the commonly used polyurethane adhesive main agent is 35% or 50%, and the solid content of the curing agent is 75%. In order to adapt to the high-speed dry compound process, most of them now adopt the method of high solid content and low viscosity.
â‘¡Appropriate coating amount. One of the factors that affect the coating amount is the anilox roller used for gluing. The thickness of the anilox roller line number and the depth of the mesh hole directly affect the amount of adhesive that it can carry. The second is the preparation of glue and the control of glue concentration. Each glue supplier should have detailed preparation ratio and method introduction. The third is to pay attention to the hardness, pressure, angle and pressure of the rubber roller.
3. Rewinding tension after compounding
