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Pretreatment technology for improving the quality of recycled plastic products
Source:      Date:2018-04-20

The rapid development of China's plastics industry, its annual output has exceeded 20 million tons, ranking second in the world, becoming a veritable plastic power. The rapid development of the plastics industry has brought convenience to people's production and life, but it has also brought about negative effects - "white pollution." According to statistics, between 70% and 80% of the total plastic in plastics will be converted into waste plastic within 10 years, and 50% of the plastic will be converted into waste plastic within two years.
Because these waste plastics have a macromolecular structure, they are not easy to decompose and rot, and they are scattered in the natural world for a long time, causing environmental pollution and affecting human health. “It is imperative. Compared with the rapid development of the domestic plastics industry, the recycling of domestic waste plastics And utilization is lagging far behind international standards.It is reported that the recycling rate of waste plastics in the United States is more than 35%, the average recycling rate in Europe is more than 45%, and the plastic recycling rates in Germany and Sakamoto are as high as 60%, while the recycling rate in China Only 25%, about 14 million tons of waste plastics are not recycled and used every year, directly causing resource wastage of 28 billion yuan.
At present, the main methods of disposing of waste plastics include incineration, landfilling, and recycling. However, incineration produces a large amount of toxic gases, causing secondary pollution. Landfills will occupy a large space. After the landfill, residual plastic debris in the soil will affect the soil. Breathability, so that crops production, so the trend of waste plastic processing technology is recycling. The recycling route is mainly divided into two types. The type is to regenerate the plastic into the same variety of raw materials or into a fund project: Hunan Science and Technology Major Project (2006SK1002; Guangdong Provincial Ministry of Education, Production, Research and Integration Key Project (2009A090100016 Renewable Resources and Circular Economy Flooring) Leather, wallpaper.
Foaming material: 2,1% monomer; the other is to make it into other raw materials and energy sources that can be comprehensively utilized. Recycling waste plastics into new plastic products and processing plastic raw materials is an effective way of recycling, but at present there are problems such as low recovery rate and low product quality. Research on sorting, crushing and cleaning pretreatment technologies for waste plastics was conducted to investigate the feasibility of different sorts of waste plastic sorting combined with re-election and manual sorting; through the key technologies of crushing and cleaning integration, the particle size of broken materials was investigated. The influence of vinyl chloride content (vcM content) on the physicochemical properties of recycled plastics has led to the discussion of advanced and feasible waste plastics pretreatment schemes to improve the recycling rate of used plastics and the quality of products.
According to the production process, the purchased raw materials are divided into two major categories according to the appearance color: white broken material, ash broken material. The types of waste plastics contained in the two major types of raw materials are as follows: white broken material: small tube material, large tube material, Secondary pipe material, primary sheet material, general white sheet material.
Ash crushing materials: fine ash sheet material, blue tube material, primary ash sheet material, switch material, curtain material, blue mixed material.
Shoe and sole material: 5.2% cable material = 7% film: 丨 2% artificial leather □ thin 睽 □ cable material waste PVC plastic soft component ratio grain size / mm PVC waste physical properties impact on crusher selection curve can be seen, application 3 The crushing waste of the crusher produced a cumulative sieving rate of 35% to 100%, which increased with the increase of the particle size (0.11.0mm). The waste material after crushing with the cutting crusher is 0.10.4mm in size, and the cumulative screening rate increases linearly with the increase of grain size from 45?0%; and the disk vibratory crusher accumulates at the grain size of 0.21.0mm. The sieving rate tends to be more stable as the particle size increases. The particle size distribution of the waste particles corresponding to the disc vibratory crusher and the range of the accumulated cumulative screening rate are the widest, indicating that the disc vibratory crusher has the best crushing effect on the test waste sample.
2.2.2 The effect of particle size of different grades of the PVC crushing material on the ratio of the sifting rate to the cumulative sieve rate of each type of waste (white powder as a sample).
Granular/mm tube material Large tube material One-stage material White film material As can be seen from Table 5, the level of VCM content of grade sheet material and general white film material is not significantly changed with the grain size, and small tube material and large tube material The content of VCM decreased significantly with the increase of particle size, and all had significant changes.
The content of VCM in the wastes of the same size fraction and low-grain size fraction (矣0.8mm) decreased in turn, while in the high-grain size fraction (>0.8mm), the content of VCM was generally higher than that of the tube material.
From the results of the analysis of the VCM content of the four different types of waste materials, the content of chemical components contained in the same type of waste at different particle sizes has changed significantly. The reason why this occurs is only attributed to the waste itself. The non-uniformity of the distribution of the material components and the non-uniformity of the distribution of the material components when the sample is broken to different particle sizes.
2.3 Cleaning experiments Under normal conditions, following the above steps for high-quality cleaning, the contents of various impurities in the waste plastics are controlled at about 10-5, which ensures the quality of plastic products. The number of impurity particles in the PVC profile products obtained by the experiment was 12/900cm2, exceeding the requirement of the national standard GB5761-1993 for the corresponding SG3 model superior products of 16/900cm2. Moreover, the entire system was based on the principle of water saving, achieving a water cycle utilization rate of more than 90%.
3 conclusions
(1 disc vibratory crusher has the best adaptability to waste crushing; taking into account the physical properties of different grades of waste PVC raw materials, the white material in the recycling waste is the best for small tubes, followed by large tubes, and once for 1 sheet. In addition, the common white material is poor; the chemical composition content of the same kind of waste material at different particle sizes has a significant change, so it can be based on the physical properties of raw materials and chemical composition analysis experiments of different grades and different grades. As a result, different formula ratios were adjusted for different grades of waste PVC as the raw material production process, in order to achieve the desired objectives of optimizing the process parameters, saving production costs, and obtaining high-quality plastic products.
(2 Cleaning process The pre-washing, cleaning and rinsing cleaning system for waste plastics has been developed, which can effectively reduce the content of various impurities in waste plastics, and significantly increase the reuse rate of water, and has good environmental protection benefits and great promotion value.