What are the process flow of paper- plastic composite bags?

1. Substrate pretreatment
‌Paper selection‌
A three-layer composite structure is used, the core layer is high-strength kraft paper, and the outer layer is selected according to the needs of 120-200g/m² bleached or natural wood pulp paper.

‌Polymer film matching‌
Matched with 12-25μm thick LDPE or BOPP film as a barrier layer, the melt index is controlled in the range of 2-8g/10min to meet the heat sealing performance.

2. Composite process
Paper-plastic composite is mainly achieved by the following methods:
Dry composite‌
Coat substrate (such as plastic film) with polyurethane adhesive (coating amount 2.5-3.5g/m²), and heat-press composite with paper after aging at 40-45℃.
‌Wet composite‌
Use water-based acrylic adhesive to complete the bonding of paper and plastic film in a wet state, and then dry and solidify (composite roller pressure 0.3-0.5MPa).
‌Hot-melt lamination‌
Use hot-melt adhesive to directly heat and coat, omitting the solvent drying process, suitable for fast production scenarios.