Study on Comprehensive Treatment of Plastic Packaging Wastes (1)

New materials are an important aspect of the technological revolution. Due to the development of plastics and their superior performance, plastic packaging has become more and more widespread. From the structural point of view, plastic packaging containers can be divided into boxes, barrels, bottles, bags and large containers; from the perspective of molding methods, they can be divided into injection, die-casting, hollow and vacuum-formed containers. Plastic packaging waste refers to the function of losing or completing the maintenance of the original value and use value of the contents, and becomes a plastic packaging container and material for discarding solid waste. Comprehensive treatment of plastic packaging waste refers to the disposal of plastic packaging waste (ie, Reducing the volume of plastic packaging waste that has been produced, etc.) and utilization (that is, by recycling, processing, etc., activities that are extracted from plastic packaging waste or converted into available resources and other raw materials).

First, the content of plastic packaging waste in urban life

Plastic packaging container When it loses or completes the function of maintaining the original value and use value of the contents, it becomes the same as other packaging wastes and becomes the solid waste to join the ranks of garbage. According to statistics, the United States produces 150 million tons of domestic garbage each year; in recent years, the amount of municipal solid waste in China has reached 150 million tons, taking Shanghai and Guangzhou as examples. Shanghai has already produced about 10,000 tons of municipal solid waste in Japan; Guangzhou has already produced more than 5,000 tons of municipal solid waste in Japan (see Table 1 and Table 2 for details), and about 1/3 to 1/2 of domestic garbage in these cities is Packaging waste, including plastic packaging discarded about 3 to 5%. For example, packaging waste in the United States accounted for about 33% of municipal solid waste, Japan accounted for about 40%, EU countries accounted for about 30% to 50%, and China accounted for about 30% to 40% (see Table 3, Table 4 and Table for details). 5).

Second, the status of plastic packaging waste pollution and harm

The annual output of plastics in the world has exceeded 100 million tons, of which about 30% is used for packaging. Most of these packages became solid waste after being used once. Because it is light, bulky, large in quantity, difficult to degrade, and can not be incinerated, it is mostly discarded at the edge of railways, inland waters, and streets of cities and towns. Over time, it has become a shocking "white pollution" belt, according to the investigation of related departments. It is understood that the total amount of waste plastics discharged into the environment in Shanghai is 290,000 tons per year, including 674 million disposable foaming tableware and 3,363 tons of weight; 12,000 tons of waste produced by Beijing and 360 tons of plastic waste; About 5,000 tons of garbage, 755 tons of plastic waste, white pollution, serious damage, the performance is as follows:

1 worsening environment

Some plastic products contain harmful substances such as PVC and acrylonitrile. When they burn, HCL is generated. HCL is one of the important causes of acid rain. In China, the acid rain area currently accounts for 30% of the country's land area, and acid rain in Central China's acid rain area has a frequency of more than 90%.
The use of chlorofluorocarbons (CFCs) and freons (which have been discontinued) in the production of foamed plastics will destroy the ozone layer in the atmosphere and cause excessive UV radiation, which will increase the greenhouse effect and damage the balance of the atmosphere.
Plastic waste not only causes long-term visual pollution, but long-term stacking refuse provides a breeding ground for rodents, mosquito ropes, and bacteria. Plastic waste also releases a variety of toxic chemical gases. It is conceivable that more and more hard-to-degrade white If no waste is taken, the rubbish will be the largest gas store on the planet.

2 Influence industrial and agricultural production

First of all it destroys the ecological balance of the soil and reduces crop production. China is a big country in the use of agricultural film, and its annual usage is as high as 800,000 to 900,000 tons. According to a special survey conducted by the agricultural sector, the country has residual activities in fields, soil, and river channels every year, hindering the absorption of water and root growth by plants, and deteriorating the quality of cultivated land and reducing crop production. According to the expert's test, when the residual plastic product per mu reaches 39kg, the output of various crops can be seen in Table 7.

3 Pollution Impact on Land Ecology

Many cities and towns in China use landfills to dispose of waste. Plastic waste is bulky and difficult to degrade. It not only consumes a lot of land resources, but also pollutes groundwater. Land that is buried in landfills cannot grow crops and trees and will cause large areas of land to be lost. If it is used for a long time, if mulches are not used for a long time, no effective measures will be taken. After 15 years, a lot of arable land will not receive the grain and will not receive it.
In recent years, the economic losses caused by environmental pollution and ecological destruction in China are as high as 200 billion yuan each year, among which ecological destruction is 100 billion yuan. Nearly 300 million mu of cultivated land is contaminated by "three wastes" and pesticides. Due to pollution, grain output is reduced by 25.6 billion jins.

4 Harm to human health, many species of plants and animals are on the verge of extinction

"White pollution" worsens the environment. The acid rain it causes, and the hollowness of the ozone layer will destroy the human immune system, increasing the chance of carcinogenesis and the incidence of intrinsic guinea pigs. A variety of poisonous chemical gases released by plastic waste will cause people to lose weight, liver dysfunction, nerve damage, and cancer induction. The free units of polystyrene products will be released after being released into the body and will harm health. Nai’s climate change, rapid population growth, and new-born diseases have the most serious effects of pollutants and chemical pollution.

Third, the sorting technology of plastic packaging waste

Plastic packaging waste can be separated from other garbage by artificial or mechanical (gravity method), and then visual identification, combustion identification, specific gravity identification, solvent separation, wind screening, electrostatic separation, cryogenic grinding and other methods.

1Intuitive identification and sorting technology

For a small amount of waste plastics, the following methods can be used to classify them: first, remove metal, glass, wire rope, and other contaminated and heavily polluted waste plastic; second, remove agricultural film, packaging film, foam plastic, and plastic bottle box. The classification is based on the color shade of the product. The base 4 uses the simple methods of visual inspection, feel, specific gravity, and combustion to classify commonly used plastics such as PVC, polystyrene, and polypropylene.

2  density sorting technology

Each section of plastic has a different density. Different types of plastics are placed in a specific solution, and plastics are classified and identified by the floating plastics in the solution. Because plastics have non-wetting properties, surfactants are commonly used for pretreatment, and are then wetted before being divided. selected. Commonly used identification plastic solutions are water, saturated salt solution, alcohol solution and calcium chloride solution.

3solution sorting technology

The use of various plastics in organic solutions depends on the difference in solubility to achieve waste plastic sorting. The method is to add waste plastic chips to a specific solution, control different temperatures, and selectively dissolve and sort various plastics. The technology has low solvent loss, the recovered polymer can be reused after being heated and granulated, and its performance is good.

4 Wind Power Screening Technology

When the amount of waste is large and there is a lot of debris, wind screening technology can be used. In this method, the crushed waste plastic is put into the re-screening chamber from above, air is injected from the horizontal direction, and the weight of the plastic is used and the resistance to air is different.

5 electrostatic separation technology

Electrostatic separation technology stems from the dry separation method, which is characterized by separation and density-independent, granular material with a diameter of 8mm or less, its size and shape does not affect the separation, and low energy consumption, large processing volume. Recycling of plastic packaging waste Plastic packaging discards have great environmental and social hazards. Therefore, it is particularly important to recycle them. Generally, the following methods can be taken: one is to manufacture building materials, and the other is to make general supplies. Produce chemical products; its four cracked gas, oil and monomer; and its fourth incineration with other garbage, heat recovery (steam, hot gas and power generation).

1Recycling of used PVC

Polyvinyl chloride accounts for more than 30% of China's plastic products. The recycling of waste PVC is mainly to directly recover or supplement appropriate new materials, and to re-manufacture various products. When these recycled materials are poorly-organized and cannot be used as other products, they can still be used for infrastructure and water conservancy products ( Tubes, slots, strips, plates, etc.).

1 Direct reuse of recycled PVC recycled recycled products should be based on different types of additives added to meet the requirements. The formula is shown in Table 8.
The composition of polyvinyl chloride is more complex. In addition to resins, there are certain plasticizers, stabilizers, lubricants, pigments and other auxiliary materials. In the process of using these additives, due to the effects of light and heat, there will be different degrees of volatilization and loss. In the process of replication, it is necessary to make appropriate supplements to make the PVC plastic after the duplication of the waste plastics to maintain good physics Institutional performance.

2 As a bitumen and plastic grease, the waste polyethylene plastic reacts with the coal tar in the reaction. In the presence of the catalyst, the less concentrated components such as naphthoquinone in the coal tar are easily reacted with the bonded polyvinyl chloride molecules. Cross-linking occurs to form a two-dimensional network structure, so that the softening point of the modified tar pitch is improved. Its performance is better than that of general-purpose petroleum bitumen felt, tar bituminous felt and tar bituminous felt, especially low-temperature-resistant and flexible, and is particularly suitable for construction use in northern areas. Its specific operation is to add asphalt in the enamel reaction kettle to 150-200r/min. Electric stirring, and heating to 150 ~ 170 °C reaction with 3h, then add the filler, stir for a moment that was called modified tar pitch.
Basic formula: 100 parts of tar, 12-15 parts of waste PVC, 29-32 parts of plasticizer, 30-50 parts of filler