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Development direction of PET protective film biaxial stretching

In recent years, China's two-way stretching production line has developed rapidly. There are nearly a hundred double-drawing production lines for various plastic film sizes, but most of them have been imported from abroad. Foreign film double-drawing production line suppliers include Brückner, DMT, DORNIER, MITSUBIHI, etc. At present, domestic film double-drawing production lines are also on the rise. There are also several companies that can independently design and manufacture film double-drawing production lines, but there is still a certain gap between the scale of the production line and the technical level.

Analyzing the current film market, the development direction of film double-drawing production lines in the future has the following characteristics:

  (1) Development towards thin film and thick film

For BOPET film, most of the specifications produced by domestic double-stretch production lines are in the range of 8-75μ, and the capacity in this thickness range has far exceeded supply. However, there is considerable room for development of thick films below 4μ or 150-300μ, especially the application scope of thick films is expanding. For example, the protective screen films of liquid crystal displays and plasma display devices require a large amount of PET thick films, which is worth attention. Solar films and explosion-proof films are also increasingly used in automobiles and buildings, and the market is extremely broad. In addition, in order to develop differentiated PET products for many manufacturers, small double-pull test lines with a width of about 2 meters are also very popular, because large lines are wasteful and risky for new product development tests.

(2) Development towards multilayer coextrusion

 In order to improve the comprehensive performance of the film, the double-drawing production line now mostly adopts the structure of A / B / A, A / B / C or even more layers. Multi-layer co-extrusion can produce multi-functional films that meet different purposes, such as heat-sealing films, high-resistance films, and anti-ultraviolet radiation films.

(3) Design of special film double-drawing production line

  Heat shrinkable films are widely used in convenience foods, beverage markets, electronics, household goods, shrink labels, etc., and only require large horizontal shrinkage, which requires corresponding changes in the design of the stretching equipment to meet High lateral shrinkage requirements.

  (4) PET film straight-drawing production line

PET resin is a PET slice product sold by direct esterification of PTA and EG, post-polycondensation casting, underwater pelletizing, air-drying, and packaging. After the film manufacturer purchases PET chips (including masterbatch chips), they need to be mixed, crystallized and dried, heated and melted, extruded, melt measured, filtered, ... casted, and finally stretched into a bidirectional film. However, if the PET resin production device is connected to the PET film double-drawing production line, the outlet of the polyester polycondensation kettle is directly connected to the die, casting device, MDO, TDO and other processes of the double-drawing production line through the melt pipe. Membrane can save the processes of crystallization drying, melt extrusion, melt filtration, etc. This not only saves equipment and plant investment, saves energy, reduces production and operation costs, but also improves film quality, and reduces secondary heating and oxidative degradation of PET chips. Both are the advantages of the straight pull method. For this reason, designing a double-drawing production line adapted to the direct-drawing film formation is also a development direction of PET film bidirectional stretching.