Waste plastic is a popular term, which does not refer to waste, old and useless plastic products.Most plastic products, especially a large number of disposable products, have no significant change in the performance of their plastic materials after use, so they can be recycled and reprocessed into plastic products with appropriate methods for reuse.
The more formal term for waste plastics is post consumer plastic waste, which refers to waste plastic products after consumption or use.Plastics also produce waste products and wastes in the process of synthesis, molding, processing and circulation. These plastic wastes are also called pre consumer plastic wastes. Although they also belong to the scope of waste plastics, they are relatively small, easy to recycle and have a large recycling value. Generally, manufacturers will recycle by themselves and directly use the recycled products in production.Therefore, we usually refer to waste plastics after consumptionPlastic waste。Unless otherwise specified, the waste recycling website mentioned[1]It also refers to post consumer plastic waste.
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In our daily life and various fields of agricultural production, plastic products are ubiquitous. When the life or use purpose of these products is reached, they will be discarded and become waste plastics.Of course, the sources of waste plastics are not limited to thisWaste recycling websiteAs mentioned earlier, waste materials or waste products will be generated in every link of plastic synthesis, molding, distribution and consumption.Its specific sources mainly include the following aspects.[2]
Produced in resin production
The waste generated in resin production is reported in the following three aspects:
① The adhesive materials (commonly known as "Guoba") scraped off the inner wall of the reactor during polymerization and unqualified reactants.
② Cleaning waste of extruder and unqualified mixing materials during mixing.
③ Falling materials (throwing materials) and slag falling materials during transportation and storage.
The amount of waste depends on the complexity of polymerization reaction, the number of manufacturing processes, production equipment and operation proficiency.In the production of various resins, polyethylene produces the least waste,polyvinyl chlorideThe largest amount of waste is generated.
Generated during forming process
stayThermoplasticThe various forming processes of our company will produce different quantities of waste products, substandard products and leftovers.For example, six layers of cold materials in injection molding, gate cold solids, cleaning waste, waste edge, etc;Machine cleaning waste, trimming material and cutting material on the final product in extrusion molding;The blank wearing mouth on the blow molding machine in the blow molding process, the cold solid and cleaning waste in the equipment and the flash of the hollow container, etc. (the waste rate of the blank wearing mouth can reach 40% when producing the bottle with handle);Waste materials, trimming materials and waste products falling from the mixer and calender during calendering;Overflow, edge seam material and waste products taken out from mold parting county in rotational molding processing.
The amount of waste generated in the forming process depends on the processing technology, molds and equipment.Generally speaking, the recycling rate of this kind of waste is relatively high.Their varieties are clear, the amount of filler is clear, the pollution is small, the performance is close to the original material, the pre-treatment workload is small, and they are usually only used for crushing treatment, which can be added into the new material as the recycled material, and have little impact on the performance and quality of the products.
Thermosetting plasticsWaste products and waste materials will also be produced during the molding process. If the waste products have been cross-linked, it is very difficult to recycle these waste products.
Generated during mixing and regeneration processing
The waste generated in the mixing and recycling process only accounts for a small part of all waste plastics. They are the waste removed during the cleaning of the mixing equipment and the defective products produced under abnormal operation, most of which are recyclable waste plastics.
Produced during secondary processing
The secondary processing is usually to transfer the plastic semi-finished products purchased from the molding factory to finished products through transfer printing (the process of transferring the toner image formed on the drum surface to the paper is called transfer printing), sealing, thermoforming, mechanical processing, etc. The waste generated here is often more difficult to deal with than the waste generated by the molding factory, such as after printingIt is very difficult and costly to take out the printing layer and electroplating layer of waste products after electroplating and other treatment, while the value of recycled materials obtained by direct crushing or granulation is much lower.It is easy to recycle the waste edges and particles generated by thermal forming and mechanical cutting, and the value of recycled waste is also high.
Generated after consumption
This kind of waste plastics has a wide range of sources and complex use conditions, and can only be recycled after treatment.Such wastes include:
(1) Bags and barrels used in the chemical industry.
(2) Container and rayon in textile industry.
(3) Packaging materials, foam shock pads, etc. in the household appliance industry.
(4) Building materials and pipes in the construction industry.
(5) Shrink film and stretch film in the canning industry.
(6) Turnover boxes and egg trays in food processing.
(7) Plastic film, greenhouse film, fertilizer bag, etc. in agriculture.
(8) Fishing nets, floating balls, etc.
(9) Bumpers, fuel tanks, battery boxes, etc. removed from scrapped vehicles.
This kind of waste plastic is also post consumer plastic. Due to its large quantity and difficulty in recycling, it has posed a serious threat to the environment and will be the focus of future recycling work, so it is classified separately.Waste plastics account for% 2~% 4 of China's urban domestic waste, most of which are disposable packaging materials. They are basically polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyethylene terephthalate (PET), etc.Among these waste plastics, polyolefin (PO) accounts for% 70.
There are many kinds of waste plastic products in domestic garbage, including various packaging products, such as bottles, films, cans;Daily products, such as barrels, basins, cups, plates, etc;Toy accessories, entertainment supplies, clothing and shoes, strapping ropes, packing belts, woven bags, health care supplies, etc.
Waste plastic is directly crushed into powder or granule, which can still distinguish what kind of material it is, such as injection molding, wire drawing, film, etc.However, the recycled raw meal means that it is impossible to accurately distinguish something after being recycled for many times. It can only be graded according to the number of cycles. The least beginning is special grade, first grade and second grade.
