The output of synthetic resin in the world has reached 200 million tons, and the disposal of large quantities of post-consumer plastics has become a hot spot for the protection of the earth today. At present, there are several ways to treat post-consumer plastics: 1 Landfill: 2 Incineration: 3 Composting; 4 Recycling; 5 Degradable plastics.
Recycling methods for plastic recycling include: melting regeneration, thermal cracking, energy recovery, recycling of chemical raw materials and other methods.
(1) Melt regeneration
Melt regeneration is a method of re-thermoplasticizing waste plastics. From the sources of waste plastics, this method can be divided into two categories: First, the recycling of clean waste plastics recovered from the scraps of resin factories and processing plants; and second, the recycling of various plastic products mixed after use. . The former said that simple regeneration, can produce better performance of plastic products; the latter said that the compound regeneration, generally can only prepare relatively poor performance of plastic products, and the recycling process is more complicated.
(2) Thermal cracking
The thermal cracking method is a method of burning burning oil and fuel gas by pyrolyzing the selected waste plastic.
(3) Energy recovery
Energy recovery is a method of using the heat generated when the waste plastic is burned.
(4) Recycling chemical raw materials
Some varieties of plastics, plus polyurethane can be obtained by hydrolysis of the synthesis of raw material monomers. This is a method of using chemical decomposition of waste plastics into chemical raw materials for recycling.
(5) Others
In addition to the recycling methods for waste plastics mentioned above, there are various methods for using waste plastics, such as mixing waste plastic polystyrene foam into the soil to improve the water retention, air permeability and drainage of the soil, or as a filler and cement. Mix to make light concrete, or add adhesive to press mat material.
Plastic recycling and plastic solid waste disposal
The use of petroleum and coal as raw materials to produce plastic instead of natural polymer materials has undergone a difficult process. An entire generation of outstanding chemists have devoted great efforts to achieving the excellent physical and chemical properties and durability of plastics currently available. Plastics, with its light weight, durability, aesthetics, and low cost, replaced a large number of traditional packaging materials and contributed to a revolution in the packaging industry. However, contrary to the expectations of the people, it is precisely these excellent properties of plastics that produce a lot of durable plastic waste. The large amount of discarded plastic packaging after use has become a major environmental hazard. The main reason is that these plastic wastes are difficult to handle and cannot be decomposed and turned into dust. In the existing municipal solid waste, the proportion of plastics has reached 15%-20%, and most of them are disposable plastic packaging products. The disposal of plastic waste is not only a problem in the plastics industry, but it has now become a widespread concern in the international community of public hazards.
In order to meet the needs of protecting the global environment, the world plastics processing industry has developed many new environmental protection technologies. In respect of saving resources, it is mainly to improve the endurance performance of products, extend the life span, and multi-functionalize the design of the products. In the aspect of resource reuse, it mainly deals with the efficient sorting of plastic waste, separation technology, and high-efficiency melt recycling technology. Chemical recycling technology, completely biodegradable materials, water-soluble materials, and edible films; in terms of reduction technology, the research mainly focuses on the technology of compression and volume reduction of waste plastics and the technology of film-packed containers, and on the premise of ensuring application performance, The thinning technology of products; the development of CFC substitutes is mainly focused on carbon dioxide foaming technology; on the research of substitutes, PVC and PVDC substitutes are mainly developed.
In the field of plastic solid waste disposal in cities, three methods are currently used for landfill, incineration and recycling. Because of different national conditions, different countries, the United States to landfill, Europe, Japan to burn mainly. With landfill treatment, the quality of plastics is generally light, and it is not easy to rot, which will cause the landfill to become a soft foundation and it is difficult to use it in the future. The use of incineration processing, due to the large heat of plastic, easy to damage the stove, plus the gas generated after burning will promote the global warming, and some plastics will also emit harmful gases in the burning and pollute the atmosphere. The use of recycling methods, due to man-hours, high recycling costs, and the lack of appropriate recycling channels, the world's recycling and reuse accounted for only about 15% of the total plastic consumption. However, due to limited world oil resources, from the perspective of saving the earth's resources, the recycling of plastics is of great significance. To this end, all countries in the world have invested a lot of manpower and material resources to develop various key technologies for the recycling of waste plastics, and have devoted themselves to the development of suitable applications for reducing the cost of recycling plastics.
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