Recycling and regeneration of the hottest plastic

Recycling and recycling of plastic packaging materials

Plastic packaging materials have been rapidly developed and widely used in the field of packaging materials since the 1970s because of their light weight, high strength, convenient and cheap plastic recycling granulator, which reprocesses the waste plastics from ordinary life and generates the plastic raw materials needed by enterprises again. However, due to serious environmental pollution, the degradability of plastic packaging materials and the possibility and ways of recycling should be fully considered in the use and ecological design of plastic packaging materials. The government should also take measures to promote the research and development of degradable plastics, so as to promote the development of circular economy. 1、 "White pollution" has become a public nuisance

at present, China has occupied the position of the world's largest plastic country, and is rapidly moving towards the world's largest plastic country. According to relevant data, in 2003, China produced more than 13 million tons of synthetic resin for plastics, imported more than 13 million tons of synthetic resin recorded by the customs, and also imported more than 3 million tons of waste leftovers. As raw materials for plastics, the apparent consumption of synthetic resin has exceeded 30million tons. Together with the fillers and additives used, the total output of plastic products is second only to the United States, and far exceeds Germany, Japan, France, Italy and other countries. At present, the "white pollution" caused by plastic packaging has brought adverse effects on China's economic development and ecological environment

because ordinary plastics and their additives and additives are high molecular materials with stable chemical structure and performance, they generally cannot degrade by themselves and are not easy to be eroded by bacteria. Plastic packaging materials do not decay and decompose after being discarded, which will form permanent garbage that will not decay for hundreds of years. In particular, the waste of disposable plastic packaging materials is large, scattered and messy, which is difficult to collect. Some of these garbage are discarded randomly and scattered on the ground, polluting the city appearance and environmental landscape; Some of them are buried with garbage and remain in the soil, destroying the permeability of the soil, reducing the water storage capacity of the soil, affecting the absorption of water and nutrients by crops, resulting in crop production reduction; Pouring into rivers, lakes and seas will pollute water bodies and cause a large number of deaths of aquatic organisms. If burned indiscriminately, some plastics will release toxic gases after burning, destroy the ozone layer, form acid rain and destroy the ecological balance

in order to solve the problem of "white pollution", the government, enterprises and the majority of scientific and technological workers have done a lot of work. There are some who advocate using less, restricting and banning; Advocating and formulating local regulations to enforce the implementation of degradable plastics; It is also proposed to use economic means (taxes and charges) to guide consumption. Unfortunately, many measures have little effect. Restrictions and bans make people feel inconvenient; Charges will increase the burden on citizens

facts have proved that modern society is inseparable from plastics. It is better to dredge than to intercept and block. Use materials with better performance and price ratio, and use technologies and methods that are more in line with the characteristics of the times to develop degradable plastics, and increase the recycling and reuse of plastic waste, Is to solve the "white pollution" "The way out.

Second, the recycling and treatment methods of plastic waste

at present, there are many recycling and treatment methods of plastic packaging material waste, the first is recycling, the second is to recover raw materials or burn for energy, and the third is to implement landfill.

1. Recycling and reuse of plastic packaging

recycling and reuse of plastic packaging is the most active way to promote the recycling of materials, that is, there is no processing and treatment Process, but directly reuse after cleaning. This is a recycling technology, which is an important means to effectively save raw material resources and energy and reduce the amount of packaging waste

many plastic packaging containers, such as pallets, turnover boxes, large packaging boxes, plastic barrels and other large hard, smooth, clean and easy to clean containers used for transportation packaging, are still intact after one use or even multiple uses, and can be reused with only a little trimming, cleaning and disinfection. The treatment process of its reuse technology is generally:

classification → selection (those discarded just after use, basically free of pollution, scratches, transparency and smoothness) → water washing → acid pickling → alkaline washing → disinfection → water washing → sodium bisulfite soaking → water washing → distilled water washing → drying at 50 ℃ → reuse

in order to make the bottled containers can be reused for many times, we must pay attention to the development of sterilization washing technology and refilling technology. For example, due to the adoption of advanced sterilization and washing technology in Sweden and other countries, polyester (PET) bottles can be reused for 20 times, and polycarbonate resin plastic bottles can be reused for 75 times by one of the largest dairy factories; Germany has paid attention to the development of enzyme killing washing technology in recent years. Polycarbonate bottles and cans are recycled and reused up to 100 times. 1. Machine part; The United States has vigorously developed concentrated washing products and refilling technology, and the refilling of its fabric washing products has reached 40%

2. Mechanical treatment and modified regeneration of plastic packaging materials

mechanical treatment and reuse include direct regeneration and modified regeneration. As a direct regeneration, the process is relatively simple, easy to operate, so it is widely used. However, due to the aging of products in the process of use and regeneration processing, the mechanical properties of recycled products are lower than new resin products, so they are generally used for low-grade plastic products, such as agricultural, industrial, construction, etc

(1) direct recycling. Direct regeneration mainly refers to the process of directly plasticizing waste plastics after pretreatment and crushing, and then molding or granulating. In some cases, a certain amount of new resin or appropriate additives (such as antioxidant, lubricant, stabilizer, plasticizer, colorant, etc.) need to be added to make recycled plastic products. It can adopt existing technology and equipment, which is both economical and efficient. The general process of direct recycling is:

pretreatment (sorting, cleaning, defoaming, etc.) → crushing → washing and mixing → mixing and homogenization → plasticization → granulation or remanufacture molding

(2) modified recycling. The purpose of modified regeneration is to improve the basic mechanical properties of recycled materials to meet the quality needs of recycled special products. There are many methods of modification, which can be divided into two categories:

① physical modification. That is, composite materials and copolymers are prepared by mixing process. It usually includes the filling and modification of activated inorganic particles, the toughening and modification of waste plastics, the fiber reinforcement and modification of waste plastics, and the alloying of recycled plastics. It is mainly to forcibly add various activated inorganic fillers, elastomers or reinforcing fibers in the process of blending and plasticization to enhance the mechanical properties and toughness of plastics, or make thermoplastic FRP, etc

② chemical modification. That is to change the properties of materials by means of chemical crosslinking, grafting block and so on. In recent years, a new method of chemical and physical modification has been developed. Its technological process and characteristics are that in a specific screw extruder, multi-component materials are physically blended and chemically grafted at the same time, and the blending is further strengthened after the modification of the two, and then granulated or directly molded at a specific temperature. This is a comprehensive system integrating grafting, crosslinking and blending. This technical method can not only shorten the time and production cycle of the improvement process, make the production continuous, but also obtain more effective modification effect

it should be noted that at present, inorganic powder modified plastic materials, as a new environmentally friendly material, have emerged as a new material that can effectively control white pollution and is accepted by producers, consumers and regulators

inorganic powder modified plastic materials have remarkable economy, functionality and environmental protection. The huge price difference between inorganic powder materials and synthetic resins has significantly reduced the raw material cost of modified plastics, and the rational use of inorganic powder can improve some aspects of the properties of matrix plastics or be endowed with new functions. The plastic filled with inorganic powder is easy to be absorbed by the environment after use. Using less synthetic resin is to save oil resources. Using 20 ~ 30% inorganic minerals in plastic materials is a social evaluation of the experimental results, which mainly adopts three methods; 1 is to record the time when cracks begin to appear in the sample during the test process; 2. Grade the crack of the sample; 3. It is a significant contribution that the bidding price of enterprises taking photos of the samples after the experiment is even lower than the material price itself. According to actual calculation, if inorganic powder is used in the 3million tons of packaging plastic bags produced nationwide, at least 700000 tons of synthetic resin can be saved, which means that a large petrochemical enterprise with an investment of more than 10 billion yuan will be built less, which is also in line with the quantitative reduction principle of controlling "white pollution". On the other hand, replacing the synthetic resin made of petroleum with inorganic minerals that come from nature and can return to nature harmlessly is itself a contribution to environmental protection

in terms of waste and recycling, the water and carbon dioxide in the soil have little effect on the buried polymer materials, but they have a rapid erosion effect on the inorganic mineral powder in the plastic products. The products have a certain water solubility, leaving micropores after separating from the plastic products, which can greatly increase the oxygen contact area of the plastic products and is conducive to the aging and disintegration of the products. After the plastic is landfilled, inorganic minerals such as calcium carbonate, dolomite and talc will not bring harm to the ecological environment when they return to nature

it is understood that some enterprises have made remarkable achievements in the production of inorganic powder modified plastic environment-friendly materials. For example, the Linda (LD) brand photodegradable polyethylene film products (bags) produced by Shanghai Linda Plastic Chemical Co., Ltd. have won the China Environmental Labeling Product Certification because they meet the technical requirements of environmental labeling products issued by the State Environmental Protection Administration; Hunan Kexun environmental protection plastic Co., Ltd. has also made solid steps in the industrialization and market entry of inorganic powder modified plastics

3. chemical degradation and regeneration of plastic packaging materials

the basic principle of chemical degradation and regeneration is to thoroughly decompose the macromolecular chain of the original resin polymer of waste plastic products to make it return to the low molecular state. Some components are their monomers, while others are basic organic raw materials, small molecules, compounds, fuels and other high-value chemical products with different degrees of polymerization. This recycling method can be said to make the use of natural resources truly form a closed cycle

this method of regeneration has the following advantages: first, the quality of the chemical raw materials generated by decomposition is equal to that of the new raw materials, which can be used equally with the new raw materials, achieving the reuse; Second, it has considerable processing potential, which can truly control the white pollution formed by plastics. Therefore, this method has higher economic and social benefits, which is an inevitable development trend. It can be divided into depolymerization, hydrolysis and alcoholysis, thermal cracking, Hydrogenolysis and gasification. Among them, hydrolysis is a convenient and economical means of plastic recycling; Thermal cracking is also a promising technology, which is attached great importance at home and abroad. Thermal cracking can be divided into oiling process, gasification process and carbonization process according to the different products

4. Heat recovery by incineration and landfill treatment

(1) incineration. Incineration method is to use the mixture of mixed plastics and other garbage that cannot be recycled as fuel, put it into an incinerator for incineration, and then make full use of the heat generated by combustion. The biggest feature of this method is to transform what really becomes waste