Excessive composite pressure of PUR hot melt adhesive laminating machine or uneven pressure at both ends of the composite roller will cause wrinkles on the surface of the composite film. After composite, the wrinkles will form an empty tunnel and affect the bonding fastness of the product.
(1) Increase the amount of glue applied. If the amount of glue is too small or part of the surface of the substrate is not coated with adhesive, it will cause the two substrates to be difficult to fit during lamination. We can choose an anilox roller with a deeper cell, or increase the pressure of the rubber roller and reduce the contact pressure between the doctor blade and the anilox roller to increase the amount of glue on the surface of the substrate. For some plastic film substrates, corona treatment can be performed before coating to make the surface fluffy, and then improve the ability of the substrate to absorb the adhesive and increase the amount of glue on the surface.
(2) If the appropriate drying temperature is too high or too low, it will affect the bonding fastness of the composite film. When the coated substrate is dry, the heating temperature is too high or after high-temperature cooking, the surface layer of the adhesive will be carbonized, and then the bonding ability of the adhesive will be damaged. If the drying temperature is too low, the manufacturer’s information will cause the adhesive to be incompletely cured, the adhesive’s viscosity is poor, and the composite is not strong. After a period of time, bubbles are easily formed in the composite film, which damages the composite quality of the product. Of course, we can choose the adhesive digital printer with good high temperature resistance and cooking resistance to adapt to higher temperature drying, such as the use of polyurethane adhesive.
(3) Appropriately add compound pressure. Excessive compound pressure on the compound machine or uneven pressure at both ends of the compound roller will cause wrinkles on the surface of the compound film. After compounding, the wrinkles will form an empty tunnel and affect the bonding fastness of the product. Appropriate addition of compound pressure is conducive to improving the bonding force of the compound. In addition, in order to improve the bonding effect of the composite film and the quality of dairy packaging, it is necessary to prevent foreign matter, dust and other debris from sticking to the adhesive or the composite surface of the substrate. Concluding remarks When operating, carefully observe various problems and failures in the production process, and use the above methods to eliminate the failures reasonably. When there are multiple problems or failures, it may not be possible to use a single method to co-ordinate. At this moment, we should avoid it.