2. Research on chemical recycling of waste plastics
Although the waste plastics incineration, oilification, or co-concentration and recycling of energy technologies eliminates the need for sorting and cleaning of used plastics and can dispose of used plastics and household waste in large quantities, the one-off investment is relatively large, and the quality of the oil-derived products is low. The cost is high and the technology is still to be improved. The promotion and application are subject to certain restrictions. Therefore, most of the waste plastics are still recycled as raw material resources. Due to the aging of plastics during use, resulting in deterioration of performance, in order to meet application requirements, chemical (blend) modification is generally required to process into building materials, paints, coatings, and adhesives that have a wide range of applications and have high added value. Mixtures and so on.
2.1 paint, paint
Li Wanhai, Zhang Songbin, Wang Hong, etc. made use of waste foam to research and develop various kinds of coatings for different uses. Researched the method of using waste polystyrene foam to obtain coatings, discussed the formula selection and performance indicators of the coating.
2.2 Adhesives
Zhang Songbin, Li Wanhai, Wang Hong studied the method of making adhesive from waste polystyrene foam and discussed the formula selection and performance index of the adhesive.
2.3 Production of building materials
Zhang Zhimei, Liu Zhigang, Chen Qingyu, Yu Changhua, etc. discussed the technological methods and conditions for using waste plastics and fly ash to make construction tiles, and conducted density, water absorption, frost resistance, aging resistance and flexural strength of tiles. Detected.
Bao Yiwang, Su Shengshen, and Chen Zhicheng conducted research and discussion on how to recycle waste plastics that existed in urban solid waste. It is pointed out that the reuse of waste will form an emerging industry category, and the use of waste plastics for the preparation of building materials will be a cause for concern and have broad prospects for development.
2.4 Recycling chemical raw materials
Wang Haitao, Zhang Tiansheng, etc. use natural organic solvents to dispose the disused polystyrene foam after volume reduction, select the liquid precipitant to precipitate the polystyrene, and select another additive, which is a common liquid and can be precipitated. The agent is miscible so that the precipitant is separated from the solvent. Solvents, precipitants, and additives are all non-toxic and harmless, and will not cause secondary pollution. All three reagents can be recycled and the recovery rate is over 96%.
Zhang Congrong and An Linhong described the main recycling process of polyethylene terephthalate (PET), introduced several new polyester recycling technologies, and industrialized recycling practices of polyester recycling in the world, as well as the polyester recycling industry. The outlook was analyzed.
Qiu Ting, Ma Peisheng, Wang Jun, and Wang Jianing introduced the chemical recovery process and supercritical water properties of waste plastic under supercritical water in recent years, and used supercritical water to pyrolyze waste plastics (PE, PP, PS). And partial oxidation process to recover monomer, oil and gas.
Meng Linghui, Bai Yongping, Feng Liqun, Xing Yuqing et al. described the research progress of supercritical water in the recycling of waste plastics such as polyethylene terephthalate, polycarbonate, and polyethylene. Compared with traditional waste plastics processing methods, the use of special chemical and physical properties of supercritical water for the above-mentioned waste plastics can achieve high efficiency, high proportion of raw materials recovery, simple post-processing procedures, and no pollution. The advantages open up new ways for the recycling of waste plastics.
The new plastics company in Geneva, Switzerland, invented a method for processing unsorted household plastic waste into thermoplastics suitable for ordinary extruders, injection machines and calendering machines. This thermoplastic compound, called NPPOS, is a solid mixture of hybrid polymers and has a modulus of elasticity higher than low density polyethylene at a temperature of 0-85°C. Washed waste plastic is added to the hopper above the cylindrical barrel. A tilting impeller in the barrel is rotated by a 220-kw variable-speed motor. When the waste plastic melts due to friction between the impellers against the barrel wall, the load on the drive motor automatically increases. The thermoplastic compound is then crushed into micron-sized particles that are homogenized and discharged from the bottom of the barrel. Calculate the production cost by using unwashed household plastic as raw material (make pellets ready for use).
3. Pretreatment of recycling of waste plastics
3.1 Species identification and sorting
Chang Yuanliang and Zhang Hao introduced the composition characteristics and the method of identification of mixed waste plastics, and outlined the new progress in distinguishing mixed waste plastics identification technology for industrial applications.
Japan's Oichi Eiji Festival and Chen Yang introduced dry and wet sorting methods for waste plastics. The equipment, process parameters and results of the sorting of PVC plastics from mixed plastics using an air shaker are described in more detail.
3.2 Smash
Li Hui, Ma Zhengxian et al. conducted a theoretical analysis of the basic characteristics of plastics and the fracture mechanism and mechanical behavior of plastic comminution. Through the analysis of the mechanical properties of the polymer and the study of mechanical impact crushing mechanism, the high-density polyethylene was crushed and tested. The feasibility and economics of the mechanical crushing of polyethylene at room temperature were proved. The polyethylene was crushed at room temperature. Provides a new method.
Liu Yuan and Wang Qi introduced the application of solid phase shear comminution technology in the field of post-consumer reprocessing of polymer waste materials, and related equipment and reprocessed material properties. The solid phase shear comminution technology was used in polymer disposal. Various chemical effects in the reprocessing process.
4. Recycling waste plastics is a long way to go
Relevant departments of China's plastics industry have paid great attention to the recycling of plastic waste. As early as July 1975, the former Ministry of Light Industry held the “National Exchange Experience of Waste Plastics Recycling and Utilization†held in Shanghai. The meeting pointed out that recycling of waste plastics is not an expedient one. It is a long-term job. In September 1978, the former Ministry of Light Industry organized an on-site inspection of waste plastic recycling technology and equipment. Since the reform and opening up, China's plastics processing industry has developed rapidly. In more than 20 years, the output of plastic products has increased from about IMt in 1980 to the current 20 Mt. The introduction and development of waste plastic recycling machinery and equipment has also attracted great attention. Currently, China itself has been able to develop polyethylene, polypropylene waste film recycling production equipment, plastic crusher, recycling granulation unit (including exhaust extrusion Granulation), pelletizing equipment, etc. The amount of plastic waste that can be recycled every year is calculated at 10% and will reach 2Mt. The production of such a large amount of plastic waste has brought great pressure on environmental protection. If it can be handled well, it will have enormous economic and social benefits, and it will be of great significance to the healthy development of China's plastics industry.
At present, there are about 2 to 3 Mt of plastic waste that can be recycled in society every year in China. With the rapid increase in the use of plastics in daily necessities and packaging, the content of plastic waste in urban waste is increasing (about 8%). The cost of recycling waste plastics for recycling, cleaning, and separation processing is increased, and the amount of remanufactured products is low. Therefore, the recycling department is reluctant to recycle, and most of the municipal waste is landfilled, which not only occupies land, but also causes secondary pollution. Pollution. At present, the level of cleaning and separation technologies for waste plastics in China is relatively low, and the development of remanufactured products is also a low-grade product, and the economic benefits cannot be high. The comprehensive utilization of plastic waste is a systematic project that involves issues such as policies and regulations. It is closely related to the society. It is an urgent task to carry out research on the use of plastic waste.
In a word, in the past more than 20 years, the research and development of plastic waste recycling shows that the disposal of plastic waste is not simply a technical problem. It requires the establishment of a treatment system for the entire society, and the establishment of a scientific and rational resource recovery technology system. It also requires the government. And the attention of the production department, the mutual cooperation of various links, and the development of relevant laws and regulations to ensure.
In order to protect the environment, the "Law of the People's Republic of China on the Prevention and Control of Environmental Pollution Caused by Solid Waste" has been implemented since April 1, 1996. The main principle to follow is to reduce, recycle, and harmless solid waste pollution prevention so that solid waste is not produced or produced. The solid waste produced is recycled and recycled as much as possible during the production process. Use or as another production raw material; Solid waste that cannot be used temporarily through various treatment and disposal methods is completely free of polluted ground; the generation, discharge, storage, transportation, treatment, and disposal of solid waste Process control. At the same time, according to the type of solid waste and the degree of harm to the environment, the implementation of classification management.
In short, the development of the plastics industry today centers around the center of "plastics and the environment." We believe that the research on the recycling and utilization of plastic waste will promote the scientific and technological advancement of the plastics industry. It will become a cause of environmental protection, improvement of resource utilization and the benefit of mankind.
Although the waste plastics incineration, oilification, or co-concentration and recycling of energy technologies eliminates the need for sorting and cleaning of used plastics and can dispose of used plastics and household waste in large quantities, the one-off investment is relatively large, and the quality of the oil-derived products is low. The cost is high and the technology is still to be improved. The promotion and application are subject to certain restrictions. Therefore, most of the waste plastics are still recycled as raw material resources. Due to the aging of plastics during use, resulting in deterioration of performance, in order to meet application requirements, chemical (blend) modification is generally required to process into building materials, paints, coatings, and adhesives that have a wide range of applications and have high added value. Mixtures and so on.
2.1 paint, paint
Li Wanhai, Zhang Songbin, Wang Hong, etc. made use of waste foam to research and develop various kinds of coatings for different uses. Researched the method of using waste polystyrene foam to obtain coatings, discussed the formula selection and performance indicators of the coating.
2.2 Adhesives
Zhang Songbin, Li Wanhai, Wang Hong studied the method of making adhesive from waste polystyrene foam and discussed the formula selection and performance index of the adhesive.
2.3 Production of building materials
Zhang Zhimei, Liu Zhigang, Chen Qingyu, Yu Changhua, etc. discussed the technological methods and conditions for using waste plastics and fly ash to make construction tiles, and conducted density, water absorption, frost resistance, aging resistance and flexural strength of tiles. Detected.
Bao Yiwang, Su Shengshen, and Chen Zhicheng conducted research and discussion on how to recycle waste plastics that existed in urban solid waste. It is pointed out that the reuse of waste will form an emerging industry category, and the use of waste plastics for the preparation of building materials will be a cause for concern and have broad prospects for development.
2.4 Recycling chemical raw materials
Wang Haitao, Zhang Tiansheng, etc. use natural organic solvents to dispose the disused polystyrene foam after volume reduction, select the liquid precipitant to precipitate the polystyrene, and select another additive, which is a common liquid and can be precipitated. The agent is miscible so that the precipitant is separated from the solvent. Solvents, precipitants, and additives are all non-toxic and harmless, and will not cause secondary pollution. All three reagents can be recycled and the recovery rate is over 96%.
Zhang Congrong and An Linhong described the main recycling process of polyethylene terephthalate (PET), introduced several new polyester recycling technologies, and industrialized recycling practices of polyester recycling in the world, as well as the polyester recycling industry. The outlook was analyzed.
Qiu Ting, Ma Peisheng, Wang Jun, and Wang Jianing introduced the chemical recovery process and supercritical water properties of waste plastic under supercritical water in recent years, and used supercritical water to pyrolyze waste plastics (PE, PP, PS). And partial oxidation process to recover monomer, oil and gas.
Meng Linghui, Bai Yongping, Feng Liqun, Xing Yuqing et al. described the research progress of supercritical water in the recycling of waste plastics such as polyethylene terephthalate, polycarbonate, and polyethylene. Compared with traditional waste plastics processing methods, the use of special chemical and physical properties of supercritical water for the above-mentioned waste plastics can achieve high efficiency, high proportion of raw materials recovery, simple post-processing procedures, and no pollution. The advantages open up new ways for the recycling of waste plastics.
The new plastics company in Geneva, Switzerland, invented a method for processing unsorted household plastic waste into thermoplastics suitable for ordinary extruders, injection machines and calendering machines. This thermoplastic compound, called NPPOS, is a solid mixture of hybrid polymers and has a modulus of elasticity higher than low density polyethylene at a temperature of 0-85°C. Washed waste plastic is added to the hopper above the cylindrical barrel. A tilting impeller in the barrel is rotated by a 220-kw variable-speed motor. When the waste plastic melts due to friction between the impellers against the barrel wall, the load on the drive motor automatically increases. The thermoplastic compound is then crushed into micron-sized particles that are homogenized and discharged from the bottom of the barrel. Calculate the production cost by using unwashed household plastic as raw material (make pellets ready for use).
3. Pretreatment of recycling of waste plastics
3.1 Species identification and sorting
Chang Yuanliang and Zhang Hao introduced the composition characteristics and the method of identification of mixed waste plastics, and outlined the new progress in distinguishing mixed waste plastics identification technology for industrial applications.
Japan's Oichi Eiji Festival and Chen Yang introduced dry and wet sorting methods for waste plastics. The equipment, process parameters and results of the sorting of PVC plastics from mixed plastics using an air shaker are described in more detail.
3.2 Smash
Li Hui, Ma Zhengxian et al. conducted a theoretical analysis of the basic characteristics of plastics and the fracture mechanism and mechanical behavior of plastic comminution. Through the analysis of the mechanical properties of the polymer and the study of mechanical impact crushing mechanism, the high-density polyethylene was crushed and tested. The feasibility and economics of the mechanical crushing of polyethylene at room temperature were proved. The polyethylene was crushed at room temperature. Provides a new method.
Liu Yuan and Wang Qi introduced the application of solid phase shear comminution technology in the field of post-consumer reprocessing of polymer waste materials, and related equipment and reprocessed material properties. The solid phase shear comminution technology was used in polymer disposal. Various chemical effects in the reprocessing process.
4. Recycling waste plastics is a long way to go
Relevant departments of China's plastics industry have paid great attention to the recycling of plastic waste. As early as July 1975, the former Ministry of Light Industry held the “National Exchange Experience of Waste Plastics Recycling and Utilization†held in Shanghai. The meeting pointed out that recycling of waste plastics is not an expedient one. It is a long-term job. In September 1978, the former Ministry of Light Industry organized an on-site inspection of waste plastic recycling technology and equipment. Since the reform and opening up, China's plastics processing industry has developed rapidly. In more than 20 years, the output of plastic products has increased from about IMt in 1980 to the current 20 Mt. The introduction and development of waste plastic recycling machinery and equipment has also attracted great attention. Currently, China itself has been able to develop polyethylene, polypropylene waste film recycling production equipment, plastic crusher, recycling granulation unit (including exhaust extrusion Granulation), pelletizing equipment, etc. The amount of plastic waste that can be recycled every year is calculated at 10% and will reach 2Mt. The production of such a large amount of plastic waste has brought great pressure on environmental protection. If it can be handled well, it will have enormous economic and social benefits, and it will be of great significance to the healthy development of China's plastics industry.
At present, there are about 2 to 3 Mt of plastic waste that can be recycled in society every year in China. With the rapid increase in the use of plastics in daily necessities and packaging, the content of plastic waste in urban waste is increasing (about 8%). The cost of recycling waste plastics for recycling, cleaning, and separation processing is increased, and the amount of remanufactured products is low. Therefore, the recycling department is reluctant to recycle, and most of the municipal waste is landfilled, which not only occupies land, but also causes secondary pollution. Pollution. At present, the level of cleaning and separation technologies for waste plastics in China is relatively low, and the development of remanufactured products is also a low-grade product, and the economic benefits cannot be high. The comprehensive utilization of plastic waste is a systematic project that involves issues such as policies and regulations. It is closely related to the society. It is an urgent task to carry out research on the use of plastic waste.
In a word, in the past more than 20 years, the research and development of plastic waste recycling shows that the disposal of plastic waste is not simply a technical problem. It requires the establishment of a treatment system for the entire society, and the establishment of a scientific and rational resource recovery technology system. It also requires the government. And the attention of the production department, the mutual cooperation of various links, and the development of relevant laws and regulations to ensure.
In order to protect the environment, the "Law of the People's Republic of China on the Prevention and Control of Environmental Pollution Caused by Solid Waste" has been implemented since April 1, 1996. The main principle to follow is to reduce, recycle, and harmless solid waste pollution prevention so that solid waste is not produced or produced. The solid waste produced is recycled and recycled as much as possible during the production process. Use or as another production raw material; Solid waste that cannot be used temporarily through various treatment and disposal methods is completely free of polluted ground; the generation, discharge, storage, transportation, treatment, and disposal of solid waste Process control. At the same time, according to the type of solid waste and the degree of harm to the environment, the implementation of classification management.
In short, the development of the plastics industry today centers around the center of "plastics and the environment." We believe that the research on the recycling and utilization of plastic waste will promote the scientific and technological advancement of the plastics industry. It will become a cause of environmental protection, improvement of resource utilization and the benefit of mankind.
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