Bidirectional polypropylene film (BOPP) has the advantages of light weight, transparent, non-toxic, moisture-proof, water resistance, with good thermal stability, chemical stability and electrical properties, so in food, candy, cigarettes, tea, medicine, juice, milk, textiles and other packaging, as well as electrical appliances, viscose tape production has been very widely used. In recent years, the BOP production adopts the new technology of seven-layer co-extrusion, which makes the BOP evenly distributed in the central gas blocking layer of the propylene – butadiene copolymer, effectively blocking the entry of oxygen, carbon dioxide, water vapor and other putrid substances, greatly increasing the anti-corrosion ability of the packaged material and extending the storage period of the item. Therefore, people give this BOPP film containing an air barrier layer “packaging queen” reputation.
- Main raw materials
BOPP film is based on isometric PP as the main raw material, according to different products and uses, with a mass fraction of 3% ~ 5% of the additive masterbatch made. The raw material should be sea film P homopolymer, and should have the following characteristics :① melt flow speed of 1.5-4.0g/0min; The isometric degree is 5% ~ 98%; ③ Moisture content < 0.03%; ④ Ash content < 0.2×10-3. Additives are auxiliary components of film making, and erucic acid amide lubricant, ethylenediamine antistatic agent and anti-freezing agent containing silicon oxide particles are generally selected to improve the surface properties of products. - Main equipment and basic process flow
The equipment is mainly manufactured by specialized companies of BOPP automatic production line. Companies that can provide complete BOPP equipment technology are: Japan’s MT-SUBISHI and TOSHIBA; CELLIER, France; German BRUCKNER, LENZING and MARSALI, etc. Among these competitive technologies, Mitsubishi Heavy Industries and Bruckner are the most advanced. Mitsubishi Heavy Industries technology, Shenlian twin screw extrusion, multi-roll cooling molding features; Bruckner is known for multi-machine co-extrusion, double-cylinder filter large roller water bath chilling, and rational use of additives. Mitsubishi Heavy Industry’s twin screw joint extrusion, plasticization is good, the pressure is uniform and stable, the thick sheet is reduced horizontally, the thick sheet tolerance is good, but the multi-roll cooling process conditions are narrow, the cooling is slow, and the large-scale high-speed production is limited. Bruckner’s multi-machine co-extrusion, using different extrusion units and matching die heads, can produce light film and multilayer film; The double cylinder filter device can replace the filter while producing. The use of large roller internal cooling and water dissolution, so that the molten material can quickly pass through the crystallization temperature zone and sudden cooling to room temperature, is conducive to high-speed large-scale production; Using additives to adjust the formula, the product variability is large, the film performance is good. - The production of BOPP film is carried out according to the following basic process flow
PP→ extrusion → filtration → die molding → quench casting → thickness measurement → longitudinal stretching → transverse stretching → Edge cutting → thickness measurement → corona treatment → winding aging treatment → slitting packaging.
