Co-extruded flexible packaging production process

The co-extruded flexible packaging material is composed of multiple layers of plastic sheets or films and is produced by a one-step method using a flat extrusion or inflation process using two or more plastic resins. When designing a co-extrusion process, in order to prevent the mixing between the layers, the rheology of the polymer should be carefully considered, especially the flow pattern and the melt viscosity after the co-extrusion of the mold and the single-layer material are the same. .

There are many materials that are co-extruded together and if the stickiness between the two polymers is insufficient, the overall adhesive effect of the final product will be affected. That is, layers and layers may be separated under stress. In this case, a third material, the adhesive layer, is added, which is essentially a thermoplastic adhesive.

By tightly bonding the two materials, the adhesive layer maintains the integrity of the multilayer material. The adhesive layer must also be melted in a dedicated extruder and fed into the mold as a separately added layer. Therefore, many coextruded materials are three-layer structures, two are plastics, and the third is an adhesive layer as the first two material bonding materials. Coextruded films that are more than four layers in structure are also common.

For example, if EVOH is contained as an impermeable layer, it must be sandwiched between two polymers to prevent moisture penetration, so that the adhesive layer should be at least a five-layer structure. Although the resin melt from a single extruder can supply two or more layers of a co-extruded film structure, each new type of resin in the structure must have a dedicated extruder.

Coextruded films or sheets are widely used in the packaging industry. For example, there is a pallet elastic packaging film with different adhesion properties on the inner and outer surfaces; a snack food made of a co-extruded film of brown polyethylene with light-irradiation in the inner layer and white polyethylene on the inner and outer layers. Bags and so on.

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