Multilayer co-extrusion composite film
The traditional multi-layer composite packaging film used in the production process of the adhesive, solvent volatile, easy to cause environmental pollution.With the increasing demand of environmental protection to reduce production waste and packaging waste, the manufacturing technology of multi-layer co-extrusion packaging materials has developed rapidly.
At present, PA, EVOH, PVDC, PE, EVA, PP and other multilayer combination of co-extrusion blow film, with its reasonable, economic, reliable performance and popular functional packaging film market.In particular, some asymmetric structure of multi-layer co-extrusion film, more with its excellent composite peeling strength, outstanding barrier, superior environmental and chemical resistance, cheap processing, suitable secondary processing, replace or simplify many of the dry composite as the main packaging film market.
The typical characteristics of multilayer co-extrusion composite films are shown in seven aspects:
(1) the stability of the barrier layer can be improved by replacing the monolayer polymer with the same polymer in the barrier layer.
(2) when it is confirmed that the set barrier thickness is enough to meet the barrier requirements, the one-layer polymer can be replaced by multiple layers of the same polymer in the barrier layer, which can reduce the cost of high value-added raw materials of the barrier film.
(3) replacing a single polymer with two different polymers in the barrier layer can significantly improve the barrier property of the film.For example, combining the EVOH layer with the PA layer can not only maintain the puncture resistance of PA, but also increase the strength of EVOH and improve the crack resistance of EVOH by sandwiched the EVOH layer in 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 in the outermost layer. In order to prevent the outer barrier film from being vulnerable to external damage and resulting in the reduction of barrier effect, the method of increasing the thickness of PA is usually adopted to make up for this, resulting in the increase of cost.
(4) the heat-sealing layer and the composite layer were divided into two groups. One group used the cheaper polymer to replace the higher-priced polymer to reduce the cost of the film while maintaining the strength of the film.The other group used functional polymers that met their functional requirements.Using the concept of multiple layers to make more economical composite films.For example, when comparing two one-kilogram films, the material cost of a five-layer film is about 19 per cent higher than that of a seven-layer film.
(5) the performance of PA co-extruded films under five layers can be improved by using more layers of co-extruded films.For example, an additional adhesive layer can be used to enhance the barrier properties of the film by increasing its water vapor barrier.Another advantage is that it can make the film softer and feel better.
(6) the stress buckling of PA co-extruded films under five layers can be improved by using more layers of co-extruded films.At the same time to meet the needs of bag - making and other secondary processing.
(7) set the dry composite film in addition to the inside printing other functions and integration, make the composite process simple, the composite structure tends to be flexible, the function tends to be diverse, the cost has a significant reduction, more safety, more in line with the requirements of health and environmental protection, social and economic benefits are more significant.
Therefore, the multilayer co-extrusion composite film can meet many more demanding packaging occasions, more in line with the needs of market development, will have a far-reaching impact on the technical progress and development of the packaging industry.
In China, multilayer co-extrusion barrier packaging film is widely used, so the multilayer co-extrusion technology will have a great application space in China.Multi-layer co-extrusion composite film has the same function as dry composite film, but also has stronger flexibility, superior environmental performance, can replace dry composite film or reduce the number of dry composite film, has become a development trend.
To develop the multi-layer co-extrusion plastic composite film blowing equipment, alternative dry compound, plastic film, vacuum aluminum plating thereof composite equipment in the production of special request flexible packaging composite materials, simplify the production process of packaging materials, save energy and reduce the workshop and the investment of human resources, reduce production cost, which saves resources and control pollution of the environment, reduce the occupational disease patients, to avoid dry compound adhesive and solvent residual harmful substances pollution packaging items, enhance competition of export commodities and foreign exchange earning ability, prompting to upgrade the level of packaging materials and technology of China.
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