When producing composite film in daily production, it is necessary to composite various materials together through composite processing technology based on the material structure and customer needs. The common composite processing techniques mainly include: dry composite, extrusion composite, solvent-free composite, wet composite, mixed composite, etc. The following will mainly introduce the concepts and characteristics of dry composite, extrusion composite, and solvent-free composite processing processes.
1、 Dry composite
Dry compounding refers to a method of bonding adhesive in a dry state. It is a process of coating Adhesive on a substrate, drying the solvent in Adhesive through drying, melting the Adhesive under heating, bonding another substrate with it, cooling, curing, and producing composite materials with excellent performance.
2、 Extrusion composite
Extrusion lamination, also known as casting lamination, is one of the main production methods for composite soft packaging. It involves melting thermoplastic plastics such as polyethylene and polypropylene in an extrusion lamination machine, uniformly flowing out in a thin film form from the flat machine head, continuously coating on the substrate, pressing and cooling with a roller, and making a composite film with two or more layers.
Extrusion lamination has the advantages of fast production speed, simple production process, clean production environment, high production efficiency, simple operation, low cost, no solvent residue, no Carcinogen residue, etc. It is an economical and environmentally friendly composite film production method and plays an important role in plastic flexible packaging.
Advantages and disadvantages of composite film extrusion composite and dry composite:
1. Dry lamination is suitable for the production of composite films with a wide variety and small production volume; And extrusion composite is most suitable for large-scale continuous production.
2. High cost of dry composite production; The production cost of extrusion composite is relatively low.
3. Dry lamination uses adhesives, and the coating amount is large, which is prone to residual solvents. To fully meet hygiene requirements, it is difficult to control the process; Extrusion composite basically does not use or only uses water-based primer (with a small amount of coating), there is no solvent residue, and the hygiene performance is good.
4. The thickness uniformity of dry composite films depends on the quality of the selected substrate and cannot be adjusted; The extrusion composite must adjust the film thickness uniformity and average thickness.
5. When combining different products, the dry composite process technology does not change much, and the extrusion composite process needs to be adjusted frequently, which requires higher requirements for process engineers.
3、 Solventless composite
The solvent-free composite process is an advanced green composite process. It does not have the problem of exhaust emissions, does not require large and complex heating and blowing, exhaust gas exhaust devices, simple equipment, reduced energy consumption, simple process flow, and small equipment footprint. In solvent free composite, the adhesive used does not require the use of organic solvents, and the amount of adhesive applied per square meter only needs 1-2 grams. However, the difficulty lies in the very small amount of coating.
The main characteristics of solvent-free composite of composite roll films:
1. There is no solvent residue in the composite packaging material, which particularly meets the hygiene requirements of modern food and drug packaging.
2. There is no emission of volatile solvents during production, and there is no pollution to the atmospheric environment. The production environment is excellent.
3. Due to not using the usual drying system, energy consumption can be significantly reduced.
4. The production cost is relatively low, and the total cost of gluing is somewhat reduced compared to the existing process.
5. Fast machine speed, small footprint, and no risk of fire and explosion.