1. Material Preparation

• Selection of Substrates: Choose appropriate materials for the outer and inner layers of the composite bag according to the specific requirements of the product. For example, the outer layer may be made of a durable and tear-resistant material like nylon or polyester, while the inner layer could be a moisture-resistant material such as polyethylene or polypropylene. These materials provide protection and functionality to the contents of the bag.
• Adhesive Selection: Select the right composite adhesive based on the substrates used, the end use of the product, and the required quality standards. The adhesive should have good bonding strength, resistance to various substances (such as oils, flavors, and moisture), and meet safety and environmental requirements. Different types of adhesives, such as solvent-based adhesives, hot melt adhesives, or reactive adhesives, may be used depending on the specific application.

• 2. Printing

  • Design and Plate Making: Create the desired design or logo for the composite bag and transfer it onto a printing plate. This can be done using computer-aided design (CAD) software and then etching or engraving the design onto a metal or plastic plate. The quality of the plate affects the clarity and precision of the printed image.
  • Printing Process: Use a printing machine, such as a flexographic printer or a gravure printer, to apply the ink onto the surface of the substrate. The printing process requires careful control of parameters such as ink viscosity, printing pressure, and drying temperature to ensure good print quality and adhesion. Multiple colors can be printed in sequence to achieve the final desired design.

  • 3. Laminating

    • Dry Lamination: This is one of the most common methods. First, apply a layer of solvent-based adhesive evenly onto the first substrate. Then, pass the substrate through a laminating machine with a baking channel, which consists of evaporation, hardening, and odor exclusion zones. In the evaporation zone, the solvent in the adhesive evaporates and dries. Subsequently, the hot press rollers bond the first substrate with the second substrate (such as another plastic film, paper, or aluminum foil) under heat and pressure to form a composite film.
    • Wet Lamination: Coat one of the substrates with an adhesive and immediately combine it with another material through pressure rollers before the adhesive dries. The resulting composite is then dried in an oven to complete the lamination process. Wet lamination is relatively simple, requires less adhesive, and has a lower cost, but it may have limitations in terms of the types of substrates that can be used.
    • Extrusion Lamination: Heat and melt thermoplastic resin, which is then extruded through a die to form a molten film. Immediately after extrusion, this film is laminated with one or more other films or substrates and cooled to solidify, creating a multi-layer composite structure. Co-extrusion lamination involves using multiple extruders to simultaneously extrude different types of plastic resins, which are then combined in the die to form a laminated film with specific properties.

    • 4. Drying

      
      
      After the lamination process, the composite material, now in the form of a composite membrane, needs to be cured or dried. This step is crucial to ensure that the adhesive fully dries and hardens, resulting in a strong bond between the layers. The drying time and temperature depend on the type of adhesive used and the thickness of the composite material. It usually takes 24 to 48 hours or longer to allow the glue to dry completely and for the printing colors to set.
      
      

      5. Cutting

      
      
      The dried composite membrane is cut into the desired size and shape of the bags using cutting machines or dies. Precise cutting is essential to ensure uniformity and accuracy in the final product dimensions. The cutting process can be automated or done manually, depending on the production volume and requirements.

    • 6. Bag Making

      
      

      The cut pieces of the composite material are fed into a bag-making machine. The machine folds, seals, and shapes the material into the final bag form. Heat sealing is commonly used to create strong and reliable seals along the edges of the bag. The bag-making machine can be adjusted to produce different bag styles, such as stand-up pouches, flat bags, or zipper bags, according to customer requirements.

      
      

      7. Quality Inspection

      
      

      Conduct a thorough inspection of the finished bags to check for any defects or quality issues. Inspectors examine the printing quality, seal integrity, bag dimensions, and overall appearance of the bags. Any defective bags are removed from the production line to ensure that only high-quality products reach the customers.

      
      

      8. Packaging and Storage

      
      

      The inspected and approved bags are then packaged in appropriate quantities and stored in a clean and dry warehouse until they are ready to be shipped to customers. Proper packaging and storage conditions help protect the bags from damage, moisture, and other environmental factors.