The physical recycling process of PET plastic bottles is relatively simple, mainly involving drying and pelletizing of the cleaned PET plastic bottle waste. The physical treatment of PET plastic bottles is closely related to the sorting process. There are mainly two physical recycling methods: one is to cut the waste PET plastic bottles into pieces, separate HDPE, aluminum, paper and adhesives from PET, and then wash, dry and pelletize the PET pieces; the other is to first mechanically separate non-PET impurities such as bottle caps, bottoms and labels from the waste PET plastic bottles, and then wash, crush and pelletize them. Regenerated PET must not contain PVC impurities, otherwise it will affect the color of PET. When the amount of PVC mixed in is small, it can be separated manually on the conveyor belt. Under the action of torsion, PVC and PET plastic bottles have different melting points at the stressed part. The crushed PET and PVC fragments are passed through a conveyor belt equipped with a heater and temperature control. PVC melts and adheres to the conveyor belt, thus separating from PET. The labels on beverage bottles can be removed after the bottles are crushed by a combined separation device of a blower and a cyclone separator. A separation device with a suction tower can also be used. The crushed PET fragments are added vertically from the top of the separation tower, and the fragments and the ascending air flow form a counter-current. The labels are removed due to the difference in specific gravity between PET and label fragments, and PET comes out from the bottom of the separator. To ensure the efficiency of label separation, two or more separation devices can be used in production. The washing of PET fragments is very important. Hot water at 80-100℃ is often used to soften or dissolve the EVA adhesive or other types of adhesives used to attach labels and bottoms. To prevent the detached adhesives from re-adhering to the PET fragments, additives such as alkali, emulsifiers or other special chemicals are added to the water. The composition and content of the cleaning solution are usually determined by the factory based on the source of the waste bottles and the characteristics of the adhesives. The cleaning solution can be filtered to remove impurities and reheated for recycling. The washing can be carried out in a special cleaning tank equipped with a stirrer. To ensure the washing effect, a two-stage washing process can be adopted. The PET fragments are usually dehydrated by a centrifugal dehydrator to reduce the moisture content to 2%, and then dried by a belt or tube dryer to reduce the moisture content to 0.5%. The high-quality PET plastic bottle recycling system successfully developed by the German Krones company can process up to 15,000 tons of PET beverage bottles per year. The processed PET raw materials can be directly made into other PET containers, significantly reducing production costs. The PET plastic bottle recycling system uses a chemical coating removal technology, using caustic soda as the chemical coating removal agent to remove contaminants adhering to the surface of PET plastic bottles, enabling the recycling of any type of PET plastic bottles. The recycled products treated by this technology can not only be directly mixed to make bottle preforms, but also meet the requirements of purity and quality due to their low acetaldehyde and yellow pigment content. They are particularly suitable for packaging in the food and beverage industry and have a cost 20%-30% lower than that of new materials.
