Causes of Inaccurate Printing and Poor Heat Sealing Strength of Aluminum Foil Bags
January 21, 2023
1, Aluminum foil vacuum bag color registration is not allowedReasons: The main reason is that the diameter of the gravure cylinder is deviated; the image and text are deformed due to improper plate loading; the spacing between the shafts and the teeth is uneven, the gap is too large or small, or the phenomenon of the top teeth causes inaccurate overprinting; the tension of the film unwinding reel Unbalanced control or uneven thickness of gravure printing film, ruffles; uneven pressure at both ends of the printing plate cylinder and impression cylinder or inconsistent pressure between the printing plates during multi-color overprinting.Inaccurate overprinting of gravure printing is the main quality problem, which can be caused by many reasons. Practical experience shows that the main reason is the mechanical equipment, because the mechanical equipment has not paid attention to maintenance during the long-term survival and operation, and the wear or obstruction of the mechanical structure parts will cause the overprint to be inaccurate. This requires regular inspection and adjustment of various equipment; control of the plate-making process to minimize plate errors; selection of qualified film raw materials; timely elimination of misregistration caused by other printing accidents.
2, aluminum foil bag heat sealing strength is poor
1) Influence of aluminum foil bag heat sealing materialDifferent types of heat-sealing materials have different heat-sealing strengths, such asPP,PE/EVAThe heat-sealing strength is inconsistent; products of the same film with different polymerization methods have different heat-sealing strength; the thickness and uniformity of the material will also affect the heat-sealing strength; different processing methods of the heat-sealing layer, such as blow molding, cast film, etc., Both affect the heat seal strength. If the storage time of the film is too long, the precipitates will increase, and the heat sealing strength will be poor after corona treatment; the hygroscopic material will absorb moisture, the heat cover will delaminate, and the peel strength will decrease.
2) Influence of processing technology of aluminum foil vacuum bag composite filmThe temperature resistance of the printing ink is poor or the additives in the ink are not suitable. Under the high temperature of bag making, the printing layer will delaminate and the heat sealing strength will decrease. The heat sealing edge should be designed as no pattern as possible. Adhesive selection is also very important in the lamination process. Whether the adhesive ratio, viscosity and other parameters are reasonable or not will affect the sealing strength. In the extrusion compounding or coating process, the processing temperature is high, and the surface oxidation degree of the material is large, which is not conducive to heat sealing.
3) Influence of bag making processAfter heat sealing, the cooling of the edge banding is not enough, the shape is not enough, the internal stress cannot be eliminated, and the strength and appearance are affected. It should be checked in time and the cooling water circulation system should be strengthened. The more times of heat sealing, the higher the heat sealing strength. The number of longitudinal heat seals depends on the ratio of the effective length of the longitudinal welding knife to the bag length; the number of transverse heat seals is determined by the number of combinations of the machine’s transverse heat seal devices. Good heat sealing requires at least two times of heat sealing.
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