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Causes and solutions of common problems in composite food bags

At present, some common problems of compound food bags in my country are discussed in detail by many industry experts in many publications and technical exchange meetings, and colleagues in the industry have benefited a lot. Below, YLTpacking will analyze the causes and solutions of common problems of composite food bags for you one by one. Reasons for wrinkling on the surface of composite food bags, excessive solvent residue, poor opening, low composite strength and other problems and solutions. Causes of wrinkling on the surface of the bag The wrinkling on the surface of the bag usually occurs at the ink, which is divided into wrinkling after curing, wrinkling after heat sealing, wrinkling after heat sealing for a period of time, and wrinkling after boiling and cooking. Many reasons will not be repeated here, only to remind everyone to pay attention to the consumption of ink on curing agent. Due to the popularity of benzene-free and ketone-free inks and integrated inks, this problem occurs in many flexible packaging companies. The reason is that the connection of such inks is usually polyurethane system, and there are also alcohols in the solvent combination, which is easy to consume glue. of the curing agent, resulting in the glue not drying. If the glue does not dry, there will be a problem of wrinkling on the surface of the bag. The phenomenon is different but the degree of glue dryness is different, and the root cause is still the same. Solution: It is best to add a hardener to the printing ink, and the specific amount can be communicated with the ink manufacturer. If no hardener is added during printing, some more hardener can also be added when compounding. According to past experience, the added amount should be no less than 20%. However, in the recent work, it was found that the printing film of some inks was added with 50% more curing agent and the glue was still not dry. Therefore, flexible packaging companies must test to verify these two materials when switching to ink and glue. matching. Excessive Solvent Residue Solvent residual problem has been paid enough attention in food packaging, and there are many reasons for its occurrence. Only the factors of equipment are discussed here. Most of the solvent remains. The problem is that the drying temperature, air speed and air pressure of the drying tunnel of the printing machine and the compound machine are improperly adjusted. High temperature, low wind speed and positive pressure formed by the wind direction of the drying tunnel will cause the solvent residue to be high. Solution: First, ensure that the outlet of the sealing mouth in the drying tunnel has a sufficient wind speed, and then adjust the inlet and outlet of the drying tunnel to a negative pressure state, that is, the airflow at the entrance and exit of the drying tunnel flows into the drying tunnel. Special attention should be paid to the fact that the indoor air vents of many factories and the air vents that come with the equipment (such as the air vents above the gluing unit of the laminating machine and the air vents between the printing units) are also connected to the main exhaust duct. , which requires a large flow of exhaust fans to form a negative pressure in the wind direction of the drying tunnel. When adjusting, these exhaust openings can be additionally installed with pipes and equipped with separate exhaust fans, or these exhaust openings can be blocked. In addition, the drying temperature of the printing machine and the temperature of the first stage of the composite machine should not be too high, so as to avoid the problem of excessive solvent residue caused by false drying. The secondary return air of the drying tunnel should not be used as much as possible, especially the compound machine

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