Most parts of China have seen a sharp drop in temperatures of 10 or even 20 degrees. Such a sudden drop in temperature, for the temperature is very sensitive to the flexible packaging industry, will bring no small impact. So how can we avoid the problems that low temperature can cause in printing? Let's see how Giant packaging is made.
Effect on adhesive
Under normal circumstances, before the formal start of the dry compound process, the adhesive will be prepared to meet the requirements, but at this time, attention should be paid to the effect of temperature on the adhesive viscosity, the viscosity of the adhesive increases with the decrease of the ambient temperature. It can be seen that the viscosity of adhesives with the same working concentration increases in winter due to low temperature, such as 3s increase when 10℃ is compared with 25℃, which will directly lead to poor leveling property of adhesives and affect the final composite quality.
Giant packaging production department always pay attention to the weather conditions, three days before the cooling will be stored in the temperature adaptation of the adhesive production workshop, improve its leveling, to ensure production quality.
In addition, when the ambient temperature of acrylic acid and its modified water-based adhesives is too low (below 5℃) during storage and transportation in winter, the viscosity of water-based adhesives will become larger, and even the phenomenon of caking precipitation will occur, and finally can not be used normally.
Giant packaging attaches great importance to the storage and transportation conditions of water-based adhesive in winter, placed in the warehouse to avoid direct sunlight, moisture-proof and anti-freezing, in order to prevent failure.
Influence on rotary offset printing ink
For ink, if the room temperature and ink liquid temperature such as a large change, ink flow state will change, the tone will also change. At the same time, the low temperature weather on the highlight of the ink transfer rate will have a significant impact. Therefore, when printing high-grade products, in any case, the temperature and humidity of the printing workshop should be controlled. In addition, when using ink in winter, we will preheat in advance to reduce the temperature change of ink itself.
In addition, low temperature ink is too thick, viscosity is also large, but the giant packaging as far as possible without diluent or ink oil to adjust its viscosity. Because when the user needs to deploy ink, ink manufacturers output of the original ink can accommodate the total amount of various additives is limited, beyond the extreme limit, even if can be used, also weakened the basic performance of the ink, affecting the quality of printing.
Effect on the ripening process of composite membrane
The winding temperature of the composite film has a direct impact on the ripening effect of the composite film. If the winding temperature of the film in summer is 25℃, and the winding temperature of the film in winter is 0℃, then the film with a surface temperature of 50℃ should fully transfer the heat to the core of the film, and it will take longer time in winter than in summer. Of course, the maturing process of the composite film is also related to the winding diameter, the width of the film, the heat transfer of the material, the temperature uniformity of the curing chamber and other factors.
The influence of low winter temperature on the degree of maturation of the composite film is as follows: in severe cases, there will be impenetrable ripening phenomenon, that is, the peel strength of the surface and both sides of the film roll is good, but the strength of the composite film in the middle of the roll is very poor; When the situation is not too serious, the composite membrane of the core appears delamination phenomenon after boiling and steaming.
Therefore, in winter production, giant packaging attaches importance to the difference of the ripening effect of different parts of the same film roll, appropriately extend the ripening time, control the temperature of the cooling roller not too cold.
The bag may be damaged
Under low temperature environment in winter, the composite packaging bag with BOPP/CPP(CPP is a casting polypropylene film) structure becomes brittle and the sealing strength decreases after bag-making, and it is easy to break the top of the seal with steel rule and other tools, but all is normal in the test of peeling strength and other indicators. This is mainly because the cold resistance of casting polypropylene film is poor, and there is a certain brittleness when the ambient temperature is 10℃. If you do not adjust accordingly, when the temperature drops in winter, the phenomenon of sealing brittle is very common.
Considering the poor cold resistance of cast polypropylene film, Giant packaging chooses cast copolymer polypropylene film (CCPP). The cold resistance of CCPP films increases with the increase of ethylene content in the copolymer. Generally speaking, when the ethylene content is 5% ~ 7%, the casting polypropylene film can withstand the temperature of -10 ~ -5℃.
