A new method for recycling the hottest waste plast

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New methods of waste plastic recycling

nowadays, the continuous improvement of environmental protection laws and regulations, customers' environmental protection requirements for products, and manufacturers' demand for the continuous recycling of plastic raw materials and waste materials have all promoted the waste plastic recycling industry and the use of relevant equipment. Some foreign companies have achieved success in recycling waste plastics. Generally speaking, waste recycling can be divided into mechanical recycling, chemical recycling and raw material recycling. The mechanical recovery method is to directly recover the discarded materials and make them into plastic particles, and then send the reconstituted rubber particles back to the plastic manufacturing process to make new products. The first step is to collect plastic waste discarded by consumers from waste bins. Through the central collection system, the consumed water bottles, detergent bottles and other household waste are collected, and then sent to the material recovery center together with other recyclable waste. The waste is separated from other materials by machines or hands, and then all kinds of miscellaneous plastic waste are sorted out. After being roughly classified, it is packed separately according to the type and transported to the plastic recycling plant

most local reconstitutors reconstitute transparent and colored pet, as well as primary or colored HDPE. After receiving the specified plastic bales from material recycling, the reconstitutor will send these compacted bales to the shredder to break them up into a string of scattered recyclable materials, and then send them to the special vibrating screen. Fine garbage and dust will fall into the garbage bin through the sieve. This is the first step to remove impurities. After that, the screened recyclable plastics enter the grinding and cleaning process. First, cut the material into small pieces to make the labels and other container attachments fall off. This is beneficial to the cleaning work later. After shredding, add water to soften the fragments and remove impurities, and then send the fragments to the cleaning machine. Some cleaning machines use warm water and detergent; Others use room temperature water, which is heated by mechanical movement during cleaning. This cleaning process removes residues, dust and stickers

then use a flotation cylinder to separate plastics with different densities from impurities. HDPE plastic has a lower density than water, so it floats on the water surface. Dust and dense plastic (such as PET) sink at the bottom of the cylinder and are removed later. Clean debris floating out after separation shall be dried with hot air, and then the film and label shall be separated by air flow sorter. After the plastic fragments enter the sorter, an air flow is blown down, and the lighter film fragments will be blown away, while the heavier plastic fragments will continue to fall down. Finally, the plastic fragments are melted, filtered, and then extruded into small particles. At the beginning, the plastic fragments were poured into the big bucket to improve the communication mechanism between government and enterprises, so as to reduce the quality difference, and then the fragments were sent to the extruder. Inside the machine is a heated cylinder with a screw conveyor. After melting in the extruder, the debris flows through the filtration at the end of the machine. The unmelted impurity particles cannot pass through the eyes, while the pure melt is squeezed through the plate full of holes and becomes a noodle shape. During the cooling period of these plastic strips, they can be quickly cut and made into small particles. Chemical recycling refers to the removal of polycondensation or addition polymerization by depolymerization to make the polymer return to monomer. Plastics that can be recycled in this way include polyester (such as PET plastic for water bottles), polyamide (such as nylon for carpets), and polyurethane (such as foam plastic for car seats created by Burt Rutan in 1982)

for long-chain polymers, chemical methods and heat can be used to break the chain. If the purpose of depolymerization is to reduce the chemicals that originally made the polymer, this process is called raw material or monomer manufacturing. After the polymer is decomposed into various chemicals, the chemicals used as raw materials can be recycled, or various chemicals can be used as fuels; One part can also be used as raw material and the other as fuel. Although raw material recycling includes chemical recycling, it refers to the depolymerization of polyolefins and substituted polyolefins by heat to turn them into various smaller olefin intermediates. This kind of intermediate is not very different from gasoline or lubricating oil. In some cases, heat can be used to depolymerize the addition polymer and directly change it back to monomer, with a high recovery rate. For example, polystyrene is changed back to styrene, and polymethyl methacrylate is changed back to methyl methacrylate

at present, there are many industrial polymerization methods that can be recycled from plastics to synthesize monomers or raw materials. There are still some methods under development. The depolymerization process of recovering monomer raw materials must be very effective. In other words, there should be a high monomer recovery rate and a small amount of waste. Some plastics are particularly suitable for thermal depolymerization due to their unique chemical properties. Pet, some polyamides and polyurethane can be effectively depolymerized, and the synthetic chemicals produced can be used to make new plastics, which is no different from the original polymers

pet plastic bottles are the most common cases of sheet metal damage. In addition to the above situation, there are also containers in the process of transportation, especially in developed countries, whose use is considerable. Japan is one example. In 1997, the production of PET plastic bottles in Japan reached nearly 220000 tons, but only one tenth of them will be recycled. As environmental protection has become a global focus, recycling campaigns have become a post-processing process that various industries must consider, prompting governments of various countries to implement waste recycling plans. The Japanese government and enterprises are also very responsive, followed by an increase in the demand for PET plastic bottle recycling equipment. More and more people in tomengro, Japan, began to seek cars with energy conservation and emission reduction, excellent effects, longer life and higher "appearance". Up went with the trend, introduced machines that automatically screen plastic bottles after consumption from Austria, and purchased shredders that disassemble plastic bottle bundles from the United States. Tom's automatic plastic bottle screening machine is from the criterion of binder company, which can distinguish eight kinds of materials, such as pet, PVC, PE, PP, PS, PA, ABS, etc. Whether the plastic bottle is labeled or deformed, it can classify plastic bottles at a rate of 5 to 7 per second. The recycled PET pellets are made into clothes by Tom

recycled plastics in China

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