Many printers complained about the ink factory and complained about problems with their adhesives. In fact, many of these are caused by the use of cold water. Most of the regions in China are affected by the cold current. A lot of flexible packaging color printing plants in the northeast and northwest regions have appeared a strange kind of bubble: a composite film roll taken out of the maturation chamber, with a dozen outer layers. There are large bubbles in the circle, there are serious "tunnel." Some material structure is BOPP / milky white PE, polyethylene film is relatively soft, the shape of the formation of bubbles and the heat sealing layer polypropylene composite film is different, there are Material structure BOPP/CPP.
These air bubbles lead to a significant drop in the yield, which is unacceptable to the factory and requires urgent handling. During field trips, the composite membrane was found to have no air bubbles when it came off, but the common feature was low initial viscosity. The same process, except for the severe cold weather, was normal. After induction, it was discovered that no compounding machine with the above drawbacks had a second unwinding preheating roller system, which found the reason.
The basic reason is that the initial adhesive force is low, but the initial adhesive force of the glue is determined by the mountain process. We know that different types of rubber have different initial tack, and the molecular weight of the glue determines the level of initial tack. Therefore, polyurethane adhesives should be compared to the initial tack force at the same solid content, and can not take 50% of the solid content of the adhesive. 75% for comparison.
75% solids glue in the ordinary glue is the mainstream product, and reasonable: The process can get the required initial tack, and the compound heat roller has not set the proper temperature. However, if the second unwinding roll does not have a preheating roll, polyethylene and polypropylene film are only delivered from the warehouse when used, and some film roll temperatures are only about 1 degree. When the heat roll heat is compounded, it is taken away by a large amount of the second substrate. As the temperature of the middle section of the composite hot roller drops, the dried glue cannot be fully melted and the initial tack force is low. Although the initial tack force can be restored after being put into the curing room for a while, the outer layer can not be tightly fixed for several circles or even more than ten circles, resulting in white spots and bubbles.
There are two types of hot roller systems in domestic machines, one of which is electrically heated, but the temperature probes are placed on the edge of the hot roller rather than the composite film. Therefore, the measured temperature is not the hot roller center of our concern. Actual temperature. Another oil heating system simply puts the thermometer in a thermally conductive oil tank. The measured temperature is independent of the heat roller temperature.
Measured in some heating systems, the temperature display (tank temperature) of 70 degrees, the compound hot roller edge temperature of 50 degrees, hot roller 30 degrees, we can not be confused by the display temperature. The same heat roller has not set the temperature, and the temperature of the middle of the heat roller is different when the compounding machine operates at different speeds. Therefore, reducing the compounding speed can also solve the problem.
Completely solve the shortcomings of the low temperature of the heat roller can be installed in the second roll after the preheating roller or other preheating device, although it is time-consuming and cost-effective but the best. It is also a feasible method to increase the temperature of the compound heat roller. However, the maximum heating power of some heating system tanks is about 70 degrees, and the temperature is enough, but the heat roller is not transmitted. Consider increasing the flow of heat-conducting oil; The hot roll system preferably moves the temperature probe head in the middle of the heat roll to control the temperature of the heat roll portion of the heat roll.
The easiest way is to reduce the speed of recombination; if the temperature of the shop can be kept above 10 degrees, consider pre-storing the second composite substrate in the workshop.
Therefore, ink factory engineers must understand more about printing before they can make your customers more stable.
These air bubbles lead to a significant drop in the yield, which is unacceptable to the factory and requires urgent handling. During field trips, the composite membrane was found to have no air bubbles when it came off, but the common feature was low initial viscosity. The same process, except for the severe cold weather, was normal. After induction, it was discovered that no compounding machine with the above drawbacks had a second unwinding preheating roller system, which found the reason.
The basic reason is that the initial adhesive force is low, but the initial adhesive force of the glue is determined by the mountain process. We know that different types of rubber have different initial tack, and the molecular weight of the glue determines the level of initial tack. Therefore, polyurethane adhesives should be compared to the initial tack force at the same solid content, and can not take 50% of the solid content of the adhesive. 75% for comparison.
75% solids glue in the ordinary glue is the mainstream product, and reasonable: The process can get the required initial tack, and the compound heat roller has not set the proper temperature. However, if the second unwinding roll does not have a preheating roll, polyethylene and polypropylene film are only delivered from the warehouse when used, and some film roll temperatures are only about 1 degree. When the heat roll heat is compounded, it is taken away by a large amount of the second substrate. As the temperature of the middle section of the composite hot roller drops, the dried glue cannot be fully melted and the initial tack force is low. Although the initial tack force can be restored after being put into the curing room for a while, the outer layer can not be tightly fixed for several circles or even more than ten circles, resulting in white spots and bubbles.
There are two types of hot roller systems in domestic machines, one of which is electrically heated, but the temperature probes are placed on the edge of the hot roller rather than the composite film. Therefore, the measured temperature is not the hot roller center of our concern. Actual temperature. Another oil heating system simply puts the thermometer in a thermally conductive oil tank. The measured temperature is independent of the heat roller temperature.
Measured in some heating systems, the temperature display (tank temperature) of 70 degrees, the compound hot roller edge temperature of 50 degrees, hot roller 30 degrees, we can not be confused by the display temperature. The same heat roller has not set the temperature, and the temperature of the middle of the heat roller is different when the compounding machine operates at different speeds. Therefore, reducing the compounding speed can also solve the problem.
Completely solve the shortcomings of the low temperature of the heat roller can be installed in the second roll after the preheating roller or other preheating device, although it is time-consuming and cost-effective but the best. It is also a feasible method to increase the temperature of the compound heat roller. However, the maximum heating power of some heating system tanks is about 70 degrees, and the temperature is enough, but the heat roller is not transmitted. Consider increasing the flow of heat-conducting oil; The hot roll system preferably moves the temperature probe head in the middle of the heat roll to control the temperature of the heat roll portion of the heat roll.
The easiest way is to reduce the speed of recombination; if the temperature of the shop can be kept above 10 degrees, consider pre-storing the second composite substrate in the workshop.
Therefore, ink factory engineers must understand more about printing before they can make your customers more stable.
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