New foreign recycling process for waste plastics

At present, the global production of macromolecule polymer has reached 200 million tons, and its application has covered all aspects of the national economy and various aspects of people's lives. As a result, the amount of used high-molecular materials (mainly plastics) is increasing rapidly. Take the electronics-electric industry alone as an example. In the United States, there were 12 million computers that were abandoned in 2001. In California alone, there are now 6,000 computers that are discarded every day. In Europe, 6 million tons of waste electrical appliances are produced every year. The current phase-out of computers in China is estimated to be more than 5 million, and the annual phase-out of refrigerators, televisions and washing machines should be 3 to 4 million. Among the materials used to make these appliances, plastics account for a certain percentage. According to a rough estimate, the amount of plastic is about 4 kg for each computer produced. In 1997, 64 million home computers were sold globally, and nearly 260,000 tons of plastics were used. In Western Europe, the electronics used in the electronics industry in 2000 was 2.28 million tons, of which the flame-retardant plastic was 360,000 tons. Therefore, the recycling of waste plastics from many industries, such as electronics, electronics, and other industries, and recycling them as much as possible is an urgent task for protecting the environment. Otherwise, the disaster of waste plastics is bound to threaten the normal human survival. In view of this, many developed countries in the world (especially in Europe) have successively issued a number of proposals and regulations requiring manufacturers of manufactured products to recycle waste products, first of all electronic-electrical products. According to reports, in 1999, Western Europe recycled 32% of its waste plastic consumer goods. In the same year, the large waste electrical appliances collected in the Netherlands were 310,000 refrigerators, 30,000 washing machines, 1.72 million televisions, 55,000 refrigerators, 29,000 dishwashers, and about 0.7 million microwave ovens. At present, the European Commission is developing a schedule for the comprehensive recovery and reuse of used automotive components and electronic products.

It is worth mentioning in particular that the plastics in various waste products not only contain many kinds of additives, but also often combined with other materials, so the recovery and reuse of them is a very difficult problem, as they must first be Classify, separate, and screen, and treat with an appropriate process. Therefore, the above mentioned "recycling" does not mean "reusing." Judging from the current situation, the main methods for disposing of discarded electronic devices in various countries around the world are to discard, bury, incinerate (use energy), or ship to other countries. Still taking Europe as an example, only 11% of recycled plastic waste is actually recycled, 14% is shipped abroad, and 21% is burned. At the European Plastics Manufacturers Association (APME) recently held in Brussels, the plastic recycling process conference, experts believe that the European plastic recycling industry is in a difficult situation. However, several new processes for recovering plastics that are expected to be industrialized for the first time in Europe have brought hope for the recycling of plastics. This new process allows some of the used plastics to be reused instead of being simply burned as boiler fuel. The following are introduced separately.

Solvent recovery of PVC
Two newly developed solvent separation processes will be applied in Europe for the recovery of compounded PVC. The price of recycled PVC in this type of process is much lower than the price of new PVC.

Vinyloop process. This process was developed by Solvay SA and several other industry partners, and it was named "Vinyloop" process. The "Vinyloop" process has been used to recover short copper and rubber cords after copper removal. First, an electrostatic separator was used to separate the raw materials and the resulting PVC/rubber material, which was ground and sent to a dissolver, dissolved with methyl ethyl ketone (MEK), and the resulting solution was sent to a special filtration process to remove the undissolved Impurities and other contaminants. The filtrate was sent to a precipitator, and steam was blown into the solution to precipitate PVC into pellets. The solvent is then evaporated, condensed, and sent to the dissolver for recycling. The obtained PVC pellets are sent to the container, and then enter the air dryer to be dried and become a PVC with good dispersion. The density is similar to that of the new PVC, but the material is usually gray because of the color contained in the short cable material. All kinds of solvents are difficult to remove. However, because the temperature of each step of this process is not higher than 115°C, the properties of PVC are basically not deteriorated. The Vinyloop process is economically viable because recycled PVC pellets can be used directly without further granulation.

In principle, the Vinyloop process can be used to treat a variety of PVC waste, such as cable coatings and insulation, floors, etc., and recycled PVC can still be used for its original purpose. However, short wire materials cannot be mixed with the crushed floor materials because various lead stabilizers in PVC short wire materials are compatible with each other. Various tin stabilizers in PVC flooring are also compatible, but lead Stabilizer and tin stabilizer were mixed and used recycled brown to show brown color.

A medium-sized pilot plant established in Brussels based on the Vinloop process has been operating since 1999. The first industrial-scale plant of its kind in the world was also started in March 2001 in Ferrara, Italy. The plant costs US$7.2 million. The annual disposal of waste PVC is 10,000 tons, and the cost of recycling PVC is 0.3USD/kg. France is planning to establish a second plant of the same size to recover PVC from Vinyloop, which is scheduled to operate in 2004. It is used to recover PVC and PET fibers from a single PVC coated canvas. This canvas is used for billing and truck covers. With the outdoor flag, PVC recovered from this waste material should be able to be used for flooring or other industrial equipment. According to reports, 10 manufacturers around the world are discussing the construction of this PVC recycling line, but are waiting for the results of the Ferrara plant in Italy. However, from the economic point of view, the scale of this production line should be at least 10,000 tons per year to be profitable.

Delphi Process <br> The second new solvent-based PVC recycling process is used to recover PVC from the entire automotive panel. The process was jointly developed by Wuppertal and Delphi automakers in Germany and Wuppertal University. Three years ago, it was industrialized for Wiefek GmbH, an automotive parts recycler based in Nohfelden-Fisen, Germany. Using this process to recycle PVC costs less than 20% of the new PVC price. The process uses esters and ketones as solvents, but the amount of solvent is much less than the Vinyloop process. The solvent does not completely dissolve the waste PVC, but merely softens it, making it easy to separate from the copper wire, and the resulting copper wire can be used to pay for the recycling process. Wiefek has invented a process that uses centrifugation to separate plastics and solvents, and has patented it. Because this process recycles cables with PVC jackets or insulation layers, the cables are not chopped, so the recycling process is dust-free and does not require filtering and separation of metals. Wiefek's recycling PVC production line established according to this process can recycle 225 tons of reusable PVC each year, and the production line can also recover some other materials. For example, Wiefek has successfully developed a solvent-based method for automotive grilles. New processes for recycling ABS and ABS/acrylic resins from luminaires and certain metal-containing plastic parts.

Centrifugal Separation Process <br> Europe has newly developed a process for separating and recovering mixed plastics using both thermal and rotary processes (eg, certain automotive parts). This process was also successfully studied by German Delphi and Wuppertal Universities. When this process is used to recover plastics, the entire part is placed in the basket of the centrifuge, then heated with hot nitrogen (no oxygen in nitrogen to avoid degradation when the plastic is heated). The heating temperature should be strictly controlled, and the up-down fluctuation should be less than ±3°C, so that the low-melting plastic softens and the high-melting plastic does not melt, so the molten plastic flows from the centrifuge, and the undissolved plastic stays in the centrifuge, so that the two are separated and recovered.

Only kilograms of discontinuity tests were performed in this process. The energy consumed is about 6kWh/kg nylon, which is about 1/5 of the energy needed to produce the new nylon (30kWh/kg). Dephi has also used this technology to recycle PP from automotive interior trim materials (nylon fabrics with PP liners). In the recycling process, the nylon fabric contained in this part does not melt, only the PP melts, and after the melt is separated, the nylon fabric stays in the centrifuge. This method can also be used to separate the PC from the metallized coating of the CD. The metal is then left in the centrifuge and the resulting PC is fairly pure and can be reused. Because this separation process only involves the heating and separation of plastics, it does not involve chemical reactions, nor does it require the use of chemicals such as solvents, so no toxic chemicals that need to be disposed of are produced in the process.