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Dry lamination is the process of using dry lamination equipment to bond two or more films together to form a composite flexible package . In plastic composite flexible packaging, dry lamination is one of the most commonly used production methods. Due to its wide selection of substrate surfaces, high composite strength, convenient printing and fast production speed, it occupies an important position in the packaging industry .
  But in dry composite products , bubbles often appear, which not only affects the appearance of the product, but also affects the oxygen barrier, breathability and peel strength of the composite film. This problem has long plagued flexible packaging manufacturers. There are many reasons for bubbles, including production environment, film materials, adhesives, coating, drying process, compounding, curing, etc. It can be said that there are factors that cause bubbles in almost every link in production.
 Here we mainly introduce the influence of the production environment on air bubbles.
  When the ambient temperature is too high, the two-component adhesive is prone to turbidity, viscosity, and poor coating performance, resulting in composite flexible packaging bubbles. The low temperature leads to poor dispersion of the adhesive, poor wetting and adhesion to the film, and also causes bubbles. Generally, the workshop temperature should be controlled at 18 ～ 25 ℃.
  If the ambient humidity is too high (more than 70%), condensation will occur at the anilox roller and rubber roller. The reaction of moisture with the curing agent will generate carbon dioxide, which will eventually cause bubbles. In addition, the plastic film is easy to absorb moisture in the air, especially the plastic film with high hygroscopicity, such as nylon and cellophane, etc., resulting in the formation of bubbles after compounding. The relative humidity must be maintained at 60% to 70%.
The air contains a lot of particles such as dust and impurities. These particles may be adsorbed on the plastic film, or fall on the coating roller, composite roller, and glue. Therefore, we must keep the workshop clean and hygienic, reduce the floating dust in the air, and clean the drying tunnel frequently, and try to keep the workshop in a good sealed state.
Of course, in addition to the production environment, there are many reasons for the generation of bubbles in the composite flexible packaging, which must be analyzed in accordance with the specific situation.
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