Technology and equipment for polyethylene recycling. What is polyethylene waste, its processing and disposal

It is no longer possible to imagine modern world no plastic products. About a third of all plastic products today are made from polyethylene. Along with the obvious benefits of its use, actual problem the search remains effective ways processing and disposal of this polymer.

Polyethylene (accepted abbreviations - PET, PE) is a thermoplastic polymer that is widely used to create a huge number of products. Its use began in the 20th century: from the 30s it began to be used in the production of telephone cables, and from the 50s - as packaging in the food industry.

Today the list of PET products is huge:

packaging film, bags, garbage bags;
scotch;
all kinds of packaging: bottles, cans, boxes, cans, containers, flower pots, etc.;
pipes for sewerage and gas supply;
electrical insulation, thermal insulation;
storage devices, containers for liquid and solid chemicals;
different kinds fencing, etc.

Depending on the technology, in modern industry produce and use polyethylene different types and operational properties, for example:

high pressure or low density (abbr. - LDPE, LDPE - a more plastic type of polyethylene, used for the production of film and cable);
low pressure or high density (abbr. - HDPE, HDPE - has a more rigid and durable structure);
polyethylene terephthalate (abbr. - PET, PET, PETE - used only for the production of disposable goods), etc.

What is polyethylene of different densities, and what types of packaging are made from it?

Process of making plastic bags

Main types of polyethylene waste and where they come from

The popularity and mass consumption of PE lead to the fact that every day a huge number of used items made from it fall into the waste category:

Polyethylene products for household use. This includes packaging film, bags, bottles, vials and canisters. household chemicals, waste blisters from medicines and other items used by humans in Everyday life. All this is thrown out every day into regular garbage containers for solid waste (solid waste). household waste). According to various estimates, the share of polyethylene in solid waste is about ten percent of the total volume.
PE industrial waste. This, again, is packaging film, all kinds of bags, waste plastic containers from stores (for example, food boxes), pipes, worn cable braids, etc.
Technological defects at enterprises producing PE products. Its volume can reach up to ten percent of all produced raw materials.

Polyethylene products are cheap and convenient. The most significant “disadvantage” of any type of plastic is the long period of natural decomposition of waste.

According to preliminary estimates by ecologists, the decay period of a plastic film or bottle in wildlife is from one hundred to two hundred years. This makes quite real threat death of all living things under tons plastic waste in the near future.

Where can I take PET waste?

The bulk of household polyethylene waste ends up in ordinary garbage - solid waste containers located in the courtyards of residential buildings. A significant disadvantage of this disposal method is the severe contamination of PET with food debris, chemicals, dirt, liquids, etc. Further total weight The waste will need to be sorted, and the plastic itself will require additional cleaning.

Important! An excellent solution today is sorting household waste already at the moment of throwing it away, when plastic items are placed in specially designated storage areas.

Unfortunately, this method, which is very popular in European countries, takes root with difficulty in Russia:

Such containers are not yet available in every yard or even in every locality;
There is no working fine system for violating sorting rules, and as a result, even with such “distributors”, other types of waste often end up in the plastic bin.

You can donate PET waste:

To enterprises directly involved in processing PET waste, if they accept it themselves.
Recycling collection points operating in every city accept waste paper, scrap metal, plastic, etc. Payment for donating plastic will be a pittance, but in this way you will make your contribution to the cause of conservation environment.

What products are made from recycled polyethylene?

The raw materials obtained from the recycling of plastics are cheap and high-quality materials for the manufacture of a huge number of new useful products:

waste with a short shelf life - bottles, disposable containers and packaging - are successfully recycled into similar products;
Recycled granules serve as an additive to virgin polyethylene, for example, in the production of pressure pipes or large-volume containers;
blown bottles, canisters food products and household chemicals are used for the subsequent production of drainage pipes, wood-polymer composites (they are used to make picket fences, decking boards, garden parquet, etc.);
film waste from household waste, as well as used agricultural film, is usually processed into pellets for future injection molding products;
Multilayer films as well as cable waste can only be recycled as additives for other granules, etc.

Depending on the type of PE product, as well as the area where it was used, the methods and equipment used for its recycling.

Recycling of PET products

What does the production of polyethylene waste recycling consist of? The full cycle will include several main stages:

Recycling polyethylene at home

Today, the possibility of recycling polyethylene at home occupies many inquisitive minds. For example, there are already developed methods for independent safe combustion of PET containers, proposed by scientists working in the field of ecology.

But there is an alternative view: when plastic is burned or even melted, substances harmful to humans and nature are released into the atmosphere. Therefore, independent burning or recycling of polyethylene waste is prohibited; such work can only be carried out by special enterprises with the appropriate license.

PET recycling

Speaking about recycling, today we often mean plastic recycling processes, when recyclable materials are “ new life"and is used for remanufacturing products.

Sometimes recycling refers to an alternative to recycling - the physical destruction of plastic waste or its storage in landfills and landfills. Since burning plastic is prohibited, other, more environmentally friendly methods are used to destroy it.

From the point of view of preserving the environment, it is highly effective, for example, the thermal decomposition of plastics during high temperatures in an oxygen-free environment.

However, a huge amount of plastic waste still ends up in city landfills.

Recycling PET waste is a promising direction in the economy, which is also supported by environmentalists. With the development of technology, recycling plastic waste becomes cheaper for the manufacturer, while at the same time making it possible to rid the planet of excess plastic, which is difficult to decompose in natural conditions. The environmental risks arising during the recycling process cannot be compared with the problems that humanity will face in the near future, since landfills every year it becomes more and more.

For some reason, many people have the opinion that polyethylene is only suitable for the manufacture of packaging products. Actually this is not true. Polyethylene is used in various spheres of human activity and is a universal material. Polyethylene can be recycled several times. A profitable activity is the purchase of polyethylene waste. Recyclables purchasing companies work closely with businesses. The population also actively participates in replenishing the raw material base.

The basis for all types of polyethylene is one chemical monomer. Nevertheless, finished products their qualities and properties are very different from each other. The reason lies in the fact that macromolecules have different geometric shapes and the ability to form crystals.

There are three types of polyethylene, which differ in the method of polymerization.

High pressure polyethylene is produced at a temperature of 180° C and a pressure of 1500-3000 atmospheres. This production method allows us to obtain a low-density product that is quite soft and elastic. High pressure polyethylenes contain branched macromolecules.

Medium pressure polyethylene is produced at a temperature of 120-150 °C and a pressure of 30-40 atmospheres. The process requires a diluent and metal oxide catalysts.

Low pressure polyethylene is produced by polymerization using an organic solvent. The temperature should be less than 80 ° C, and the pressure should be low, about 5 atmospheres. An organometallic complex is used as a catalyst. The processes involve an ionic mechanism.

Polyethylene, obtained using low or medium pressure, has a linear molecular structure, a high degree of crystallization, and is a rigid material. Polyethylene is a frost-resistant material and can be used at temperatures down to -60° C. There are brands that preserve beneficial features at even lower temperatures. A saturated hydrocarbon, it is not susceptible to the influence of aggressive environments and organic liquids.

In industry, polyethylenes are produced in the form of granules, sheets and blocks. Next, by casting method under very high pressure, the so-called extrusion - softened polymers are squeezed out through the nozzles of a spitz machine, and after further blowing, various products are made from the material.

Polyethylene is intended for the production of seamless pipes, electrical wire insulation and film, which is widely used for product packaging. Partitions and greenhouses for Agriculture, buckets, basins, bottles.

Polyethylene has dielectric properties, which determines its use as an insulating material for cables in television, radar, telephone lines communications. These are the reasons why it is so important to recycle polyethylene.

We all understand that waste is somehow recycled, but how is this done? Few people know. There are certain differences between the processing of industrial and household plastics, since polymers have different properties.

Similarly, secondary raw materials, that is, polyethylene, have their own properties, which often do not meet the requirements. This is comparable to the fact that polyethylene processing involves materials that differ in molecular structure. In addition, the plasticization process improves the quality of the processed material.

Recycling processes

Ordinary polyethylene, including the material used for packaging, has a long service life.

It must be remembered that when using industrial film, it is exposed to atmospheric factors:
temperature difference
Sun rays

the film may become covered with a layer of dust that is difficult to remove when thoroughly cleaning the film

As for the conditions, the processing of polyethylene is, in principle, no different from the processing of primary material. But the processing of polyethylene waste, in some cases, undergoes minor changes, so there are restrictions on the number of polyethylene processing cycles.

Our days IN modern times the most improved way to process polyethylene is to use intermediate material

to replace wooden materials. The recycling process itself requires special cleaning of the secondary product (for example, containers for fuels and lubricants). Most recycled PE has found its way into the production of canisters using blow molding. These canisters are made entirely from waste or with extrusion, primary granulate (in this case, a layer of secondary polymer creates a core between 2 layers of 1 polymer). The resulting products are used by quite a few companies to bottle a variety of detergents.

The second method is considered to be irrigation pipes. The diameter of these pipes reaches up to 630 mm. When performing injection molding, recycled polyethylene has a lower percentage. This technology is used for cladding panels, garbage containers, etc.

As for equipment, polyethylene processing has various types and brands. Many manufacturers produce equipment and successfully enter the Russian market.

Polyethylene recycling is one of the few recycling technologies that provides a solution environmental problem waste, and can bring good profits.

The problem of polyethylene pollution on the planet is becoming more serious every year. The use of this material is so widespread that it is found in almost every field. human life. Difficulties in disposal and long decomposition times threaten our planet. To solve the problem, technologies for processing and recycling the substance are being developed. This is a great way to get rid of the huge amount of garbage in landfills around large cities and build a profitable production on this basis. The introduction of this method on a global scale is a chance to defeat the environmental disaster.

Relevance of polyethylene recycling

Recycle this material not easy - the structure and composition of polyethylene provide resistance to various chemical factors, which is what makes it so popular. In terms of use, these qualities are exactly what you need. However, these same properties lead to the impact of waste on the environment.

Polyethylene takes about 300 years to decompose. Another dangerous factor is that when decomposed, polyethylene objects can release hazardous substances into the biosphere. chemical elements that pollute the air, soil, groundwater. These actions add up to environmental and public health impacts.

If this material has such amazing properties and is stored for several hundred years, the question arises, why not take advantage of these qualities of the waste. Modern technology allows for the recycling of polyethylene waste at such a level that the material becomes again suitable for use. This is both a way to save on new materials and a solution to the problem of environmental pollution.

For the smooth and constant functioning of the processing system, it is necessary to collect raw materials and have the necessary equipment. Subsequent recycling will give the waste a new life as everyday household items.

The number of enterprises involved in processing polyethylene waste naturally increases every year - this is facilitated by the relevance and demand for this service. The cheapness of the starting material and the wide possibilities for producing goods for which the demand does not fall are the key advantages of such a business.

Important point. The use of products made from recycled polyethylene must be stated on the product packaging, while the quality of the recycled product is inferior to virgin polyethylene. This fact should be considered.

How does the raw material processing process take place?

Waste is processed in several successive steps:

collection of raw materials;
sorting;
primary processing;
grinding;
centrifuge processing;
effect of temperature;
use of material for the production of products.

Collecting raw materials and sorting them is the beginning of the process. At this stage, waste is divided into categories that correspond to the type of raw material. Sorting can be done manually or using mechanized devices.

Sorted waste must be cleaned of contaminants and parts made of foreign material. Raw materials are cleaned in special washing machines. Some raw material collectors carry out their own this procedure, increasing its price.

Grinding of purified and prepared raw materials is carried out in special machines using crushing. Next step processing - centrifugation. This removes moisture and impurities from the material. After grinding, heat treatment of the material follows.

The raw materials are ready for recycling and the production of items from them.

Necessary equipment for polyethylene processing

For a complete and high-quality recycling process, the following equipment is used:

washing machine;
waste shredding machine;
centrifuge;
installation for heat treatment;
agglomerator - to reduce the volume of raw materials;
granulator;
extruder - to form homogeneous raw materials using temperature.

Automation of the process is carried out using a conveyor - this speeds up the process and allows you to control it step by step.

Using an agglomerator is one of the ways to increase the efficiency and economy of processing. The output is a commercial product - an agglomerate.

See the video for the operating principle of the agglomerator for polyethylene processing:

Using an extruder makes it possible to obtain low-density polyethylene, which is resistant to physical and chemical factors.

Extruders are also used to process raw materials (agglomerate) into a homogeneous melt and give it a certain shape.

Polyethylene is the most widely used polymer material in the world with a share of about 39% of global thermoplastics production. The closest competitor, polypropylene, occupies only 24%. In this article we will look at the most common methods of processing polyethylene and their technological features.

Recycling of virgin polyethylene

Primary is called polyethylene, synthesized in production by polymerization of ethylene. Most often, this granular raw material is milky-white in color (if the brand has not been dyed). Here are the most common ways to process polyethylene:

Extrusion. More than 70% of polyethylene in Russia is processed using the extrusion method, as it is very versatile. The essence of the method is to supply the polymer melt to the extruder head under pressure. In this case, the head may have different shape, and, passing through it, the polymer takes on the required shape. First of all, PE of “pipe” and “film” grades is processed in this way for the production of corresponding products. In addition, cable insulation and PE sheets of various thicknesses are produced using the extrusion method.
Rotational formation. The method is used for the manufacture of various hollow PE containers: from small food containers to large containers with a volume of up to 10 thousand liters. The essence of the method is to load the required amount of polyethylene granules of a grade applicable for rotational molding into special form, which simultaneously heats up and rotates in several axes. As a result, a melt is formed inside, which evenly covers the walls of the mold and allows you to obtain a product with different wall thicknesses.
Injection molding. The technology is suitable for the manufacture of products for various purposes, most often from HDPE grades. The essence of the method is to supply melted polyethylene into a mold of the desired geometry under pressure. Injection grades are characterized by increased melt fluidity, which allows the polymer to accurately replicate the shape of the mold and achieve the correct geometry of the finished product.

Recycling of recycled polyethylene

Considering Negative influence PE waste on the environment, the issue of processing waste raw materials and their reuse is very relevant. Almost any PE waste goes through the following algorithm:

Sorting. The polymer is separated from other waste on semi-automatic lines: part of the work is done by people manually, partly the mechanical mixture of waste is sorted by machines.
Washing and cleaning. In order for polyethylene to be recycled, it must be as clean as possible from impurities, for which it is washed under streams of water and steam.
Grinding in crushers and filtration using a centrifuge. The material is finally cleaned of foreign impurities.
Another wash and dry. After the crushed mixture is dried again, the secondary raw materials can be considered ready for further processing.

For recycled materials, the most commonly used method is extrusion and injection molding. At the same time, not all types of products can be made from recycled PE, since the technological properties of the material after such processing still significantly deteriorate.