Production Process of Packaging Film, Stretch Film, and Easy-Peel Materials

The packaging film is produced using the extrusion compounding process. Extrusion compounding is to pass two or more different resins through two or more extruders to melt and plasticize the various resins respectively, and then extrude them through a molding die under the rotation and extrusion of the screw. The sheet or tubular film embryo is stretched to the required size using a blowing method or a salivating roller and then cooled and shaped by wind or water to form a film.

Plastic films are distinguished by production process:

Cast film

Cast film refers to the resin that is melted and plasticized by an extruder, extruded through the T-shaped slit die, so that the melt is tightly attached to the cooling roller, and is made through processes such as stretching, trimming, and winding. membrane.

Casting process characteristics and applications

The process of coextruded film production by casting method is the same as that of downblowing method, and the cooling rate is controlled by the temperature of the cooling roller. The materials produced are also highly transparent and are the most commonly used stretch film materials for thermoformed packaging.

Blown film

Inflated film is a film in which plastic resin is melted and plasticized by a single or multiple extruders, extruded into a tubular film embryo through a ring die, inflated to the required size using compressed air and cooled and shaped . In the plastic inflation molding process, it is divided into top blown film and bottom blown film according to its different cooling processes.

Features and applications of upward blowing process:

The upward blowing process uses air as the cooling medium, and the overall cooling rate is relatively low. Since the crystallization of polymer materials is relatively complete during the slow cooling process, the materials produced by the up-blowing process have a higher haze due to the larger size of the crystallized spherulites, which are prone to diffuse reflection and scattering of light, as shown in the following: The transparency is relatively poor (compared to casting and down-blowing processes). Suitable for producing colored stretch films that do not require high stretch effects

The down-blowing process uses filtered and sterilized cooling water as the cooling medium. Since water has a specific heat capacity much higher than that of air, the cooling efficiency of the film produced by the down-blowing method is much higher than that of the up-blowing method. The fast cooling rate leads to a low crystallization rate and The size of the crystal grains is small and has little effect on light transmission, so the film produced by the down-blowing method has excellent transparency. The most commonly used packaging areas for down-blown coextruded films are thermoforming materials.

Basic introduction to printed composite films

Printed composite film refers to a multi-layer structure film formed by combining various plastics with paper, metal or other materials through printing and compounding process technology. Printed composite films generally consist of printed base materials, laminating adhesives, barrier materials, heat sealing materials, printing and protective coatings, etc. The commonly used printed composite film structure is: surface layer/printing ink/adhesive layer 1/middle barrier layer/adhesive layer 2/inner heat sealing layer.

Common material combinations for composite packaging films:

Printing layer: BOPA, BOPP, BOPET, etc.

Adhesive layer: Adhesive, PE, EAA, etc.

Barrier layer: AL, EVOH, PVDC, etc.

Heat sealing layer: PE, PP, EVA, etc.