The recycling of plastic packaging is the most active way to promote the recycling of materials, that is, there is no longer a processing process, but it is directly reused 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 packing boxes, plastic barrels and other large containers for transportation and packaging, are hard, smooth, clean and easy to clean. They are still intact after being used once or even many times, and can be reused with a little trimming, cleaning and disinfection. The treatment process of recycling technology is generally as follows: sorting → selection (discarded after use, basically pollution-free, scratch-free, transparent and smooth) → water washing → acid washing → alkali washing → disinfection → water washing → sodium bisulfite soaking → water washing → distilled water washing → drying at 50℃ → reuse.

In order to reuse bottled containers for many times, we must pay attention to the development of sterilization and washing technology and refilling technology. For example, Sweden and other countries have adopted advanced sterilization and washing technology, which can reuse PET bottles for 20 times, and a largest dairy factory can reuse polycarbonate plastic bottles for 75 times. In recent years, Germany attaches great importance to the development of enzyme-killing washing technology, and polycarbonate bottles and cans can be recycled up to 100 times; The United States has vigorously developed concentrated washing products and refilling technology, and the refilling of fabric washing products has reached 40%.

2. Mechanical treatment and modification and regeneration of plastic packaging materials

Mechanical treatment and reuse include direct regeneration and improved regeneration. As for direct regeneration, the process is relatively simple and easy to operate, so it is widely used. However, due to the aging in use and recycling, the mechanical properties of recycled products are lower than those of new resin products, so they are generally used in low-grade plastic products, such as agriculture, industry and construction industries.

(1) Direct recovery. Direct recycling mainly refers to the process that waste plastics are directly plasticized after pretreatment and crushing, and then molded or granulated. In some cases, it is necessary to add a certain amount of new resin or appropriate additives (such as antioxidants, lubricants, stabilizers, plasticizers, colorants, etc.). ) to make recycled plastic products. The existing technology and equipment can be adopted, which is economical and efficient. The general process of direct recovery is:

Pretreatment (sorting, cleaning, defoaming, etc. ) → crushing → washing and stirring → mixing and homogenizing → plasticizing → granulation or replica molding.

(2) transformation and recycling. The purpose of modification and regeneration is to improve the basic mechanical properties of recycled materials to meet the needs of the quality 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 multicomponent polymers are prepared by a mixing process. Usually involves activation.

The filling modification of inorganic particles, toughening modification of waste plastics, fiber reinforcement modification of waste plastics, alloying of recycled plastics, etc., are mainly to forcibly add various active inorganic fillers, elastomers or reinforcing fibers in the process of * * * mixed plasticization to enhance the mechanical properties and toughness of plastics or make thermoplastic glass fiber reinforced plastics.

② chemical modification. That is, the properties of materials are changed by chemical crosslinking and grafting blocks. In recent years, a new method has been developed, which considers both chemical and physical modification. Its technological process and characteristics are as follows: in a specific screw extruder, all components are modified by physical mixing and chemical grafting at the same time, and the two components are further mixed after modification, and then granulated or directly molded at a specific temperature. This is a comprehensive system integrating grafting, crosslinking and * * * mixing. This technical method can not only shorten the time and production cycle of the improvement process, but also make the production continuous and obtain more effective modification effect.

It should be noted that at present, inorganic powder modified plastic material, as a brand-new environmental protection material, has appeared as a new material that can effectively control white pollution, and has been accepted by producers, consumers and regulators.

3. Chemical degradation and regeneration of plastic packaging materials

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

This regeneration method has the following advantages: first, the chemical raw materials produced by decomposition are as good as new raw materials in quality, and can be used equally with new materials to realize recycling; Secondly, it has considerable treatment potential and can really control the white pollution caused by plastics. Therefore, this method has high economic and social benefits and 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 has attracted great attention at home and abroad. According to the different products, thermal cracking can be divided into oiling process, gasification process and carbonization process.

4. Recovery of heat energy through incineration and landfill.

(1) incineration. Incineration method is to use the mixture of mixed plastics and other unrecoverable garbage as fuel, burn it in an incinerator, and then make full use of the heat generated by combustion. The biggest feature of this method is to convert what really becomes waste into energy, and at the same time, it has obvious volume reduction effect. The residue after combustion has small volume, high density, small occupation area during landfill, convenience and stability, and is easy to disintegrate and dissolve in soil.

However, the incineration method has the following disadvantages: large one-time investment and high cost in incineration equipment construction; If incinerated indiscriminately, some plastics will inevitably produce harmful substances of secondary pollution, such as SO2, HC 1, HCN, etc. Heavy metals and harmful substances remain in the remaining ashes, which will do harm to the ecological environment and human health.

(2) Landfill method. Landfill is a passive and simple treatment method, that is, the waste packaging plastics are buried in the wasteland or concave land in the suburbs, so that they will die out on their own. But it takes hundreds of years for ordinary plastics to decompose and disappear, so this treatment method is economical and simple, but it is the least ideal for reducing environmental load.