Multi-layer co-extrusion technology directly uses more than one type of plastic particles (or plastic powder) as raw materials. Each plastic is melted and plasticized by one or more extruders and fed into a die (or through distribution). After the plastics supplied by the extruders are joined together, they are supplied to the inlet die, and then processed further to form a multi-layer composite film. Multi-layer co-extrusion technology is different from composite technology such as dry compounding. It does not need to first make plastic particles into film-like intermediate products. Multi-layer co-extrusion technology represents the direction of economic and environmental protection.
According to the survey, multi-layer co-extrusion technology is widely used in China's flexible packaging manufacturing enterprises, and has reached an application rate of 76.9%. At present, the multi-layer co-extrusion technology uses a different kind of plastic co-extrusion compound. Since the properties of the polar polymer compound and the non-polar polymer compound differ greatly, the properties can be complemented with each other, and a high-performance composite film can be obtained by complementarity between the properties of the materials in each layer. Extrusion techniques are commonly used in the production of high barrier composite films. China introduced single-layer blown film machines from Italy in the mid-1980s and three-layer co-extrusion blown film equipment from Barmag, Germany in the early 1990s, and introduced the world’s most advanced five, seven, and nine layers in the mid to late 1990s. Even twelve-story multi-layer co-extrusion equipment is growing faster and faster.
Based on the introduction of foreign equipment, Chinese enterprises have carried out digestion and absorption and technical cooperation, and further development and innovation. They have gradually been able to design and manufacture better domestically produced machinery by themselves, but there is still a large gap compared with the international advanced level. In the survey of flexible packaging factories, 16% of soft pack companies found that the level of application of the technology is consistent with that of foreign countries, while 42% of the companies have poor application of this technology, lagging behind foreign countries for more than 10 years. It is believed that with the development of multi-layer co-extrusion equipment and related processes, the development prospects of multi-layer co-extruded plastic composite films in China will become even broader.