Biaxially oriented polypropylene film (BOPP) has the advantages of light weight, transparency, non toxicity, moisture resistance, and water resistance. It has good thermal stability, chemical stability, and electrical properties, and is therefore widely used in packaging of food, candy, cigarettes, tea, medicine, juice, milk, textiles, as well as in the production of electrical appliances and adhesive tapes. In recent years, the production of BOPs has adopted a new seven layer co extrusion technology, which enables BOPs to be evenly distributed inside the central gas barrier layer containing propylene butadiene copolymer, effectively blocking the entry of corrosive substances such as oxygen, carbon dioxide, water vapor, etc., greatly increasing the anti-corrosion ability of the packaged materials and extending the storage period of the items. Therefore, people have given this BOPP film with gas barrier layer the title of “Packaging Queen”.
- Main raw materials
BOPP film is mainly made of isotactic PP as the main raw material, and is made with additive masterbatch with a mass fraction of 3% to 5% according to different products and applications. The raw material should be selected as sea film P homopolymer and should have the following characteristics: ① The melt flow rate should be 1.5-4.0g/0min; ② The isotropy is 5% to 98%; ③ Moisture content<0.03%; ④ Ash content<0.2 × 10-3. Additives are auxiliary components in film making, and are generally selected as erucamide lubricants, ethylenediamine antistatic agents, and anti freezing agents containing silica particles to improve the surface properties of the product. - Main equipment and basic process flow
The equipment is mainly manufactured by professional companies specializing in BOPP automatic production lines. Companies that can provide complete BOPP equipment technology include Mitsubishi Heavy Industries and Toshiba; Cellier, France; Bruckner, Lenzing, and Marsali from Germany, among others. Among these competitive technologies, Mitsubishi Heavy Industries and Bruckner have more advanced technologies. Mitsubishi Heavy Industries’ technology is characterized by Shenlian twin-screw extrusion and multi roll cooling forming; Bruckner is known for its multi machine co extrusion, dual cylinder filtration, large roller water bath cooling, and rational use of additives. Mitsubishi Heavy Industries’ twin-screw co extrusion has good plasticization, uniform and stable pressure, small transverse shrinkage of thick sheets, and good thickness tolerance. However, the multi roll cooling process conditions are narrow and slow, which limits large-scale high-speed production. Bruckner’s multi machine co extrusion uses different combinations of extruders and matching die heads to produce optical films and multi-layer films; Adopting a dual cylinder filtration device, the filter can be replaced while producing; The use of large rollers for internal cooling and water dissolution allows the molten material to quickly pass through the crystallization temperature zone and rapidly cool to room temperature, which is beneficial for high-speed and large-scale production; By using additives to adjust the formula, the product has high variability and good film performance.
The production of BOPP film follows the following basic process flow
PP → extrusion → filtration → die forming → rapid cooling casting → thickness measurement → longitudinal stretching → transverse stretching → edge cutting → film thickness measurement → corona treatment → winding aging treatment → slitting and packaging.
