Multilayer coextruded film
The traditional multilayer multi-layer packaging film volatilizes in the production process, which is easy to cause environmental pollution. With the increasing demand for environmental protection and the reduction of production waste and packaging waste, the manufacturing technology of multi-layer co-extruded packaging materials has developed rapidly.
At present, co-extrusion blown film composed of PA, EVOH, PVDC and PE, EVA, PP and other multilayers is popular in the functional packaging film market with its reasonable, economical and reliable performance. In particular, some multi-layer co-extruded films with asymmetric structure have excellent composite peel strength, outstanding barrier properties, superior environmental resistance and chemical resistance, low-cost processability, and suitable secondary processing properties. It replaces or simplifies the market for many packaging films based on dry compounding.
The typical characteristics of multi-layer co-extruded composite films are reflected in seven aspects:
(1) Replacing a single layer of polymer with multiple layers of the same polymer in the barrier layer improves the stability of the barrier layer.
(2) When it is confirmed that the thickness of the barrier layer is set to satisfy the barrier requirement, replacing the single-layer polymer with the same layer of the same polymer in the barrier layer can reduce the cost of the barrier-added high-value-added raw material.
(3) Replacing a single type of polymer with two different polymers in the barrier layer can significantly improve the barrier properties of the film. For example, combining the EVOH layer with the PA layer not only maintains the puncture resistance of the PA, but also increases the strength of the EVOH and improves the crack resistance of the EVOH by sandwiching the EVOH layer in the middle of the PE layer. For a five-layer structure, two different barrier layers should be used at the same time, one of which can only be on the outermost layer. In order to prevent the outer barrier film from being damaged by external force, the barrier effect is reduced. The method of thickness is compensated, resulting in an increase in cost.
(4) The heat seal layer and the composite layer are divided into two groups, one of which uses a less expensive polymer to replace the higher cost polymer to reduce the cost of the film while maintaining the strength of the film. The other group uses functional polymers that meet their functional requirements. Make a more economical composite film with a multi-layered concept. For example, comparing two two-kilogram films, the material cost of a five-layer film is about 19% higher than the material cost of a seven-layer film.
(5) The performance of a PA coextruded film of five or less layers can be improved by using a coextruded film having a larger number of layers. For example, the use of an additional adhesive layer can increase the barrier properties of the film by increasing the water vapor barrier of the film. Another advantage obtained at the same time is that the film can be made softer and feel better.
(6) The use of coextruded films with more layers can improve the stress warpage of PA coextruded films below five layers. At the same time, it satisfies the needs of secondary processing such as bag making.
(7) Integrating the functions of the dry composite film in addition to the inner printing, making the compounding process simple, the composite structure tends to be flexible, the functions tend to be diversified, the cost is significantly reduced, it is safer, and it is more hygienic and environmentally friendly. Requirements, social and economic benefits are more significant.
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