Use of recycled polymer in bfs technology. What is polymer waste, its processing and disposal. Major manufacturers of aggregates for polymer processing

25.11.2019

Provided by INVENTRA, a member of the CREON Group, which organized this event, which brought together leading representatives of the industry on February 17 in the Russian capital.

Polymer recycling, which is so developed in European countries, is still in its infancy in Russia: separate waste collection has not been established, there is no regulatory framework, there is no infrastructure, and there is no consciousness among the majority of the population. However, market players look to the future with optimism, pinning their hopes on the Year of Ecology, which was announced in the country in 2017 by presidential decree.

Third international conference "Polymer Recycling 2017", organized by INVENTRA, was held in Moscow on February 17. The partners of the event were Polymetrix, Uhde Inventa-Fischer, Starlinger Viscotec, MAAG Automatik, Erema and Moretto; support was provided by Nordson, DAK Americas and PETplanet. The information sponsor of the conference is the Polymer Materials magazine.

“Now the situation is not inspiring, but its improvement is a matter of time,” said the Managing Director of the CREON Group in his welcoming speech. Sergei Stolyarov. – With high prices for primary raw materials, the demand for recycled polymers and products from them will grow. At the same time, the appearance of domestic raw materials will shift the structure of primary consumption towards fibers and films. In this regard, the use of secondary polymers becomes especially promising.”

At the end of 2016, the global collection of PET for recycling amounted to 11.2 million tons, according to PCI consultant Wood Mackenzie Helen McGee. The main share fell on the countries of Asia - 55%, in Western Europe 17% of the world volume was collected, in the USA - 13%. According to the expert's forecast, by 2020 the collection of PET for recycling will exceed 14 million tons, and in percentage terms the collection level will reach 56% (now 53%). The main growth is expected at the expense of Asian countries, in particular, China.

At the moment, the highest level of collection is observed in China, it is 80%, and other Asian countries have reached approximately the same figure.

According to Ms. McGee, out of PET collected in 2016 (and this, we recall, 11.2 million tons), production losses amounted to 2.1 million tons, respectively, 9.1 million tons of flakes were obtained. The main direction of further processing is fibers and threads (66 %).

By 2025, 60% of household waste will be recycled in Europe, in 2030 this figure will grow to 65%. Such amendments are planned in the Waste Framework Directive, said Kaspars Fogelmanis, Chairman of the Board of Directors of Nordic Plast. Now the level of recycling is much lower - in Latvia, for example, it is only 21%, on average in Europe - 44%.

At the same time, the volume of plastic packaging produced in the Baltics is growing every year, the most common recyclable polymers are LDPE film, HDPE and PP.

In Russia, in 2016, the consumption of recycled PET (rePET) amounted to about 177 thousand tons, of which 90% fell to domestic collection. As reported Konstantin Rzaev, Chairman of the Board of Directors of EcoTechnologies Group, almost 100% of imports were PET flakes for the production of polyester fiber. The largest supplier countries are Ukraine (more than 60%), as well as Kazakhstan, Belarus, Azerbaijan, Lithuania and Tajikistan.

Konstantin Rzayev noted that last year the collection rate for the first time exceeded 25%, and this allows us to speak about the emergence in Russia of a full-fledged industry that is already of interest for investment. Today, the main consumer (62% of the total volume) and the price driver is still the recycled PET fiber segment. But changes in legislation and the trend towards the priority use of recycled materials as part of the sustainable development strategies of multinational manufacturing companies (MNCs) provide fertile ground for the development of another key segment of rePET consumption - bottle-to-bottle.

Over the past year, there were no new large-scale productions consuming rePET, but its use in the sheet segment is gradually growing.

However, already in 2017, it is expected to open new recycled PET fiber production facilities and expand existing ones, which, together with the ruble exchange rate, will be the main factor influencing the market balance and prices for rePET.

However, there are many other areas, still undeveloped, but quite promising, where recycled PET is also in demand. As the honorary president of ARPET said Victor Kernitsky, these are threads for furniture fabrics, car upholstery and various types of geosynthetics, foamed materials for heat and sound insulation, sorption materials for wastewater treatment, as well as bitumen reinforcing fibers for road construction.

According to the expert, there are many new processing technologies and applications, and the goal of state policy should not be to limit the use of PET, but to collect and rationally use its waste.

The topic was continued Lyubov Melanevskaya, Executive Director of the RusPEC Association, who spoke about the first results of the introduction of Extended Producer Responsibility (EPR) in Russia. It entered into force in 2016, its goal is to create a constant, solvent and growing demand for the recycling of product and packaging waste. After a year, it is already possible to draw some conclusions, the main of which is that there are a number of problems due to which the mechanism for the implementation of the RPR often simply does not work. As Ms. Melanevskaya said at the conference, there is a need to change and supplement the existing regulation. In particular, when declaring goods, including packaging, manufacturers encountered a discrepancy between the codes for the packaging of goods and the codes specified in the adopted regulatory acts, as a result of which many manufacturers and importers were unable to file declarations, because. did not find themselves in regulation. The solution was the rejection of codes and a proposal to switch to the identification of packaging by materials.

In the future, according to RusPEC, it is necessary to adopt a single end-to-end terminology for all elements of the RPR and determine unambiguous, understandable and transparent conditions for concluding contracts with waste management operators. On the whole, the association supports the law on EPR as necessary and positive for the industry.

When introducing and popularizing PET recycling in the country, the availability of modern technologies (as a rule, they are provided by foreign companies) is of great importance. Thus, Polymetrix offers modern solutions for the recycling of PET, in particular, the SSP technology for recycling into food bottled polyethylene terephthalate. Now there are 21 such lines in the world, said Danil Polyakov, regional sales manager. The technology involves the processing of bottles into pellets for food containers. The first step is washing, when paper fibers and surface contaminants are completely removed, as well as labels and glue. Next, the bottles are crushed into flakes, which are sorted by color. Then comes the removal of impurities (wood, metal, rubber, colored flakes) to a level of less than 20 ppm.

According to Mr. Polyakov, various granules can be obtained in the process of extrusion: cylindrical or spherical, amorphous or crystallized.

Viscotec offers its customers the technology to convert PET bottles into sheets, says company representative Gerhard Osberger. For example, the viscoSTAR and deCON solid phase polycondensation reactors are designed to purify and increase the viscosity of PET pellets and flakes. They are used after the granulator, before the production extrusion equipment or as a stand-alone unit.

The ViscoSHEET line is capable of producing tape made from 100% recycled PET and fully food grade.

Erema representative Christoph Wioss spoke about the in-line production of food plastic bottles from PET flakes. The VACUREMA® inline system allows you to process flakes directly into finished thermoforming sheet, bottle preform, finished packaging tape or monofilament.

Summing up the results of the conference, its participants identified the main factors hindering the development of polymer recycling in Russia. The main one they called the lack of regulatory documents:

“Nevertheless, there is another factor that we cannot ignore, and that is public consciousness,” says the director of the conference. Rafael Grigoryan. “Unfortunately, our mentality today is such that the separate collection of waste is perceived more as pampering than as the norm. And no matter what progress we see in other areas, it is necessary first of all to change the thinking of our fellow citizens. Without this, even the most modern infrastructure will be useless.”

These were the results of the industry conference “Polymer Recycling 2017”. A detailed list can be found in our calendar.

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Products made of polymers are an integral part of our daily lives today, however, along with the growth in the production of such products, it is only natural that the amount of solid waste is also increasing.

Today, polymer waste makes up about twelve percent of all household waste, and their number is constantly growing. And it is natural that the recycling of polymers today is one of the most pressing problems, because without it, humanity can literally drown in mountains of garbage.

The recycling of polymers today is not only a problem, but also a very promising line of business, since it is possible to obtain many useful substances from seemingly waste raw materials - household waste. In addition, this waste recycling technology (MSW) is a much safer method of recycling polymer waste than traditional incineration, which causes significant environmental damage.

Polymer processing technology

So what is polymer recycling?

To convert polymer waste into raw materials suitable for further processing into products, it is necessary to pre-process it. The choice of pre-treatment method primarily depends on the degree of contamination of the waste and the source of their formation. So, homogeneous production wastes are usually processed right at the place of their formation, since in this case little pre-treatment is required - just grinding and granulation.

However, waste in the form of obsolete products requires much more thorough preparation. So, the pre-treatment of polymer waste usually includes the following steps:

Rough sorting and identification for mixed waste.
Waste shredding.
Separation of mixed waste.
Waste washing.
Drying.
Granulation.

Pre-sorting provides for a rough separation of polymer waste according to various criteria: type of plastic, color, shape and dimensions. Pre-sorting is usually carried out manually on conveyor belts or tables. Also, the technology of polymer processing implies that various foreign inclusions are removed from the waste during sorting.

Polymer wastes that have become obsolete and have ended up at the waste processing plant, in which the content of foreign impurities does not exceed 5%, are sent to the sorting unit, where random foreign inclusions are removed from them. Waste that has been sorted is crushed in knife crushers until a loose mass is obtained, the particle size of which is 2 ... 9 mm.

Grinding is one of the most important stages in the preparation of waste for processing, since the degree of grinding determines the flowability, particle size and bulk density of the resulting product. And the regulation of the degree of grinding allows you to improve the quality of the material due to the averaging of its technological characteristics. This also simplifies the processing of polymers.

A very promising method of grinding polymer waste is cryogenic, thanks to which it is possible to obtain powders from polymer waste with a degree of dispersion from 0.5 to 2 mm. The use of this technology has a number of advantages over traditional mechanical grinding, since it allows to achieve a reduction in the mixing time and a better distribution of the components in the mixture.

The separation of mixed plastic waste by type is carried out in the following ways:

Flotation.
Separation in heavy media.
Aeroseparation.
Electroseparation.
Chemical methods.
Deep cooling methods.

The most common of these today is the flotation method, in which the separation of plastics is carried out by adding various surfactants to the water, due to which the hydrophilic properties of the polymers are selectively changed.

In some cases, a fairly effective way to separate polymers is to dissolve them in a common solvent. Processing the resulting solution with steam, PVC, a mixture of polyolefins and PS are isolated, and the purity of the products is not less than 96%.

It is these two methods that are economically more expedient of all those listed above.

Next, the crushed waste polymers are fed into the washing machine for cleaning. Washing is carried out in several steps using special detergent mixtures. The polymer mass squeezed out in a centrifuge with a moisture content of 10 to 15% is fed for final dehydration to a drying plant, where it is dried to a moisture content of 0.2%.

After that, the mass enters the granulator, where the material is compacted, thereby facilitating its further processing and averaging the characteristics of secondary raw materials. The end result of granulation is a material that can be processed by standard polymer processing equipment.

So, it is clear that the processing of polymer waste is quite a difficult task, and requires certain equipment. What kind of polymer recycling equipment is used today?

Washing lines for polymer waste.
Crushers of polymers.
Recycling extruders.
Belt conveyors.
Shredders.
Agglomerators.
Granulation lines, granulators.
Sieve substitutes.
Mixers and dispensers.

If you have all the equipment necessary for polymer processing, then you can get down to business and make sure from your own experience that today waste recycling (MSW) is not only a concern for the planet's ecology, but also an excellent investment, since the profitability of this business is very high.

In the modern world, the problem of recycling polymer waste is considered quite relevant. Every year, millions of tons of this type of product are collected at landfills. And only a small part of polymers is recycled. As a result of its implementation, high-quality raw materials are obtained, suitable for the production of new products.

What is a polymer product?

Every year, the production of polymeric materials increases by approximately 5%. This popularity is due to their many positive properties.

This product is mainly used as packaging. It increases the service life of the products that are inside the package. Also polymers have excellent appearance and long service life.

Modern industry produces the following types of products of this type:

polyethylene and materials made on its basis - 34%;
PET - 20%;
paper with lamination - 17%;
PVC - 14%;
polypropylene - 7%;
polystyrene - 8%.

What products are recyclable?

Not all polymers are recycled.

Thermoplastic synthetic materials, which are able to change their shape when exposed to high temperatures, are most often used for recycling.

Therefore, for this purpose, the following types of waste are collected and prepared in a special way:

materials that remain in the plastic production process. Most often, these are all kinds of segments. Products of this type are of high quality, since there are no impurities in their composition. They are delivered to processing plants already sorted, which greatly simplifies the preparatory stage of work. Up to 90% of all industrial waste is usually recycled;
polymers obtained after consumption. They are also called household waste. These are bags, disposable tableware, plastic bottles, window profiles and many other products. A feature of these materials is their contamination. For the processing of polymers of this type, a lot of effort and resources should be expended for sorting and cleaning waste.

What is the main problem of polymer waste recycling?

At the moment, only a small part of all existing waste is recycled. The development of this area is slow, despite its relevance. This is related to the following:

the state does not provide all the necessary regulatory and technical standards that could ensure the high quality of recyclables. That is why there are no powerful industries that supply the market with recycled waste with optimal characteristics;
since modern technologies are not used to carry out the processing process, huge financial resources are needed to maintain it;
due to the lack of government support, the level of waste collection among the population and small businesses is low;
the received secondary raw materials do not have sufficient competitiveness;
there is no campaigning among the population that would encourage them to separate waste disposal. Most people do not understand that the use of recyclable materials allows you to limit the consumption of other resources - oil, gas.

How is the collection of recyclable materials for recycling?

Recycling of polymers occurs after all stages of preparation of raw materials have been completed:

Special points are being opened that are engaged in the collection and primary sorting of the products received. They cooperate both with the population and with industrial enterprises of various types.
Collection of polymers at landfills for household waste. Usually this is done by special companies.
Raw materials enter the secondary market after preliminary sorting at special waste processing points.
Processing companies purchase recyclable materials from large industrial complexes. Such materials are less polluted and are not subject to such thorough preparation for processing.
A small part of recyclables is also collected through a special program that involves separate waste collection.

How are polymers processed?

After collection and primary sorting, the processing of polymer waste occurs in the following way:

Grinding of raw materials. It is one of the important stages in the preparation of polymers for further processing. The degree of grinding of materials determines the quality characteristics of products that will be manufactured in the future. To carry out this stage of work, modern plants use a cryogenic method of processing. It allows to obtain a powder with a degree of dispersion from 0.5 to 2 mm from polymer products.
Separation of plastics by type. To carry out this operation, the flotation method is most often used. It involves the addition of special surfactants to the water, which are able to act on certain types of polymers and change their hydrophilic properties. The dissolution of raw materials with special substances is also very effective. Subsequently, it is treated with steam, which allows you to select the necessary products. There are other methods for the separation of polymers (aero- and electroseparation, chemical method, deep freezing), but they are less popular.
Washing. The resulting raw materials are washed in several stages using special means.
Drying. Materials are previously disposed of water in centrifuges. The final drying takes place in special machines. The result is a product with a moisture content of 0.2%.
Granulation. The prepared material enters a special installation, where it is compacted as much as possible. The result is a product that is suitable for the production of polymer products of any type.

Recycling plastic bottles

Standard list of equipment for a waste processing plant

Recycling of waste polymers is carried out using the following equipment:

line for washing, where the purification of raw materials occurs with minimal labor;
extruder - used to give the plastic mass the desired shape by punching;
belt conveyors - to move raw materials in the right direction;
shredders - designed for primary crushing of materials. They are able to work with almost any raw material;
crushers - are actively used for more thorough grinding of raw materials after using a shredder;
mixers and dispensers;
agglomerators - necessary for the processing of thin polymer films;
granulators - used to compact recycled raw materials;
dryers;
refrigerators;
sinks;
press and others.

What is the value of waste in the relevant market?

After analyzing prices on the market, it is clear that the cost of waste stored in landfills is 3-6 times lower than the price of recyclable materials (7-10 times relative to primary raw materials). If we analyze pricing using the example of a polyethylene film, we can understand the following:

the price of polygon material from intermediary companies is 5 rubles per 1 kg;
after washing and sorting, the cost of the film rises to 12 rubles/kg;
raw materials in the form of agglomerate or granules have an even greater cost - 25-35 rubles / kg;
the price of primary polyethylene varies from 37 to 49 rubles/kg.

Such a big difference in prices is not observed for all products. For example, it is almost imperceptible with PVC, polypropylene, polystyrene and ABS plastic. In the case of PET, the cost of landfill raw materials differs from secondary products by only 2-3 times. This is due to the peculiarities of its processing, as a result of which flakes are obtained due to grinding.

Where is the recycled material sold?

Waste recycling companies most often send the resulting product for sale. If such factories have their own equipment, they can be engaged in the production of polymers from the raw materials obtained. But it's not always cost effective.

Manufactured plastic products are most often of the same type, which makes it difficult to sell them in large quantities.

Most often, such companies are engaged in the production of sewer pipes, building materials or some car parts. There is a great demand for this type of product in the market.

Third-party recycling of polymer-type waste is also very popular. This service consists in the fact that the interested company gives its waste to the plant, which, after recycling, returns the finished recyclable material to it. The owner of polymer waste pays about 8-10 rubles/kg for their processing, which is considered a very good deal.

The recycling of polymers is an industry that is extremely poorly developed in our country. The traditional and most common way for Russia to dispose of polymer waste is its burial and storage in landfills. While processing plants are in full swing in developed countries, we are drowning in our own waste.

Polymer wastes are different types of end-of-life products and materials made from synthetic polymers. The production of the latter is carried out at industrial enterprises, while from simple substances (monomers) various polymeric (high molecular weight) products are obtained through polymerization and polycondensation reactions.

Undoubtedly, products made of polymers have a lot of advantages associated with the properties of the material and the economic feasibility of its use. However, synthetic high-molecular compounds are extremely difficult to biodegrade, which negatively affects the environment.

Waste polymers in large quantities are formed in the manufacture of plastics and products from them. Industrial polymer waste includes, for example, parts of plastic pipes, residues remaining during the production of plastic (PVC) windows, etc.

A large share is made up of household polymer waste. This broad group consists of:

plastic bottles;
polyethylene packaging;
polymer film;
cases of different types of equipment (household, garden, etc.);
plastic boxes and other plastic containers;
window profiles, etc.

The share of household polymer waste from the total volume of this type of waste is over 60%.

Disposal

Utilization of polymers includes various methods that differ not only in the technological process, but also in the degree of environmental safety and profitability. We list the main methods.

Burial. Until now, this method of waste disposal is the most popular. Assumes the use of large land areas. Plastic waste is not amenable to biodegradation, because of this, more and more areas are required for disposal. The implementation of this method has an extremely negative impact on the state of the environment.

Burning. It does not require sorting of raw materials and does not involve vast territories. However, in the process of burning polymers, toxic gases are released into the atmosphere, which make their significant “contribution” to the formation of the greenhouse effect and the formation of ozone holes. To minimize such phenomena, expensive types of equipment for cleaning combustion products can be introduced, but in this case, incineration is likely to be unprofitable.

Pyrolysis. The process of decomposition of polymer compounds is carried out under conditions of high temperature and lack of oxygen. The result of plastic pyrolysis are gaseous, liquid and solid products. The former are used, for example, for heating. The resulting liquid components can be used in the production of heat transfer fluids, while solid components can be used in enterprises producing protective lubricants, emulsions, impregnating compositions, etc.

Pyrolysis of polymeric materials provides fuel and raw materials for various industries. For more information, we recommend reading a detailed article on the topic.

Cleavage of polymers to obtain products with a lower molecular weight. The process of decomposition of polymer molecules is carried out at high temperatures and pressures, as well as in the presence of various compounds: water and catalysts (hydrolysis), glycols, methyl alcohol (methanolysis), etc.

Recycling of polymers. The most modern and rational way, implemented in a number of developed countries. The technology and processing of polymer waste involves the use of different methods.

Interesting fact! The benefits of recycling plastic waste are clear. Example: the price of 1 ton of pressed PET bottles is $100, cleaned and crushed is $300, plastic granules are $1000, threads used by the textile industry are $2500/t.

Recycling

The operation of most polymer waste recycling plants is based on the same principle. Let's consider the steps of the process in more detail.

Note! Not all types of polymers are suitable for. The enterprises process thermoplastic synthetic materials, among which the most common are polyethylene, PP, PVC, PS and ABS plastic.

Processing technology

On the way to obtain raw materials from polymer waste for different areas of production, the following is carried out:

Preliminary. Polymers are roughly classified according to the type of plastic, its color, shape and dimensions. Usually this stage of processing is carried out manually. Foreign components are removed from the polymer mass.
Grinding. An extremely important stage. The degree of grinding determines the characteristics of the resulting products. Knife crushers crush polymers into a loose mass with a particle size of 0.2-0.9 cm. An innovative method is the cryogenic grinding method, which ensures the production of polymer chips with a diameter of only 0.05-0.2 cm.
Separation of a mixture of polymers. Various methods are used here, the most popular of which is flotation: surfactants are added to water with a plastic mixture, which change the hydrophilic properties of polymeric materials.
Washing and drying. The crushed mass is washed with special detergents in industrial washing machines. With the help of a centrifuge, the primary drying of the raw material is carried out, bringing its moisture content up to 10-15%. Final drying (up to 0.2% moisture) is carried out in a dryer.
Granulation. The prepared raw material is compacted in the granulator, which facilitates the subsequent processing of the material and ensures the averaging of its characteristics. The final product is granules suitable for the production of new products and materials.

Equipment

The complex of equipment for processing polymers (into granules) consists of:

washing lines;
crushers;
extruders;
belt conveyors;
shredders;
agglomerators and granulators;
mixers and dispensers.

All these types of equipment can be purchased separately. It is also possible to purchase a complete line for the processing of polymer waste into granules.

Additional Information! In the Republic of Tatarstan, Zelenodolsk Plant - ERA operates today, processing polymers into materials for the production of children's toys and furniture.

Where to send for recycling

Reception of polymers is carried out in special points, which are in all major cities. Also, to hand over plastic waste, you can directly contact specialized companies (their addresses are easy to find on the Internet). "Suppliers" of polymers can be both individuals and organizations, and for the delivery of recyclable materials it is possible to get a good amount of money. Among other things, in our country, separate waste collection is beginning to be practiced, which implies that plastic products should be thrown into a special container marked accordingly.

About how the process of obtaining granules from plastic waste is carried out at one of the enterprises, and the importance of processing polymeric materials is discussed in this video.

Recycling of polymers is not a "hackneyed topic" in our country. This is a free business niche, the opening of which will not only have a positive impact on the state of the environment, but will also bring profit to the businessman. Plastic recycling is considered a profitable business, but government support is needed to successfully launch it.

During the operation of products made of polymers, wastes appear.

Used polymers under the influence of temperature, environment, air oxygen, various radiation, moisture, depending on the duration of these influences, change their properties. Significant volumes of polymer materials that have been used for a long time and are thrown into landfills pollute the environment, so the problem of recycling polymer waste is extremely relevant. At the same time, these wastes are good raw materials with appropriate adjustment of the compositions for the manufacture of products for various purposes.

Used polymeric building materials include polymeric films used for covering greenhouses, for packaging building materials and products; barn flooring: rolled and tiled polymeric materials for floors, finishing materials for walls and ceilings; heat and sound insulating polymeric materials; containers, pipes, cables, molded and profile products, etc.

In the process of collection and disposal of secondary polymeric raw materials, various methods for identifying polymers are used. Among the many methods, the following are the most common:

· IR-spectroscopy (comparison of the spectra of known polymers with recyclable ones);

Ultrasound (US). It is based on the attenuation of US. Index is determined HL the ratio of the attenuation of the sound wave to the frequency. The ultrasonic device is connected to a computer and installed on the technological line of waste disposal. For example, index HL LDPE 2.003 10 6 sec with a deviation of 1.0%, and HL PA-66 - 0.465 10 6 sec with a deviation of ± 1.5%;

· X-rays;

laser pyrolysis spectroscopy.

The separation of mixed (domestic) waste thermoplastics by type is carried out by the following main methods: flotation, separation in liquid media, aero separation, electro separation, chemical methods and deep cooling methods. The most widely used method is the flotation method, which allows the separation of mixtures of industrial thermoplastics such as PE, PP, PS and PVC. Separation of plastics is carried out by adding surfactants to water, which selectively change their hydrophilic properties. In some cases, an effective way to separate polymers may be to dissolve them in a common solvent or in a mixture of solvents. By treating the solution with steam, PVC, PS and a mixture of polyolefins are isolated; purity of products - not less than 96%. Flotation and separation methods in heavy media are the most efficient and cost-effective of all those listed above.

Recycling of used polyolefins

Waste of agricultural PE film, fertilizer bags, pipes for various purposes, out of service, waste from other sources, as well as mixed waste are to be disposed of with their subsequent use. For this, special extrusion plants are used for their processing. When polymer waste is received for processing, the melt flow rate must be at least 0.1 g/10 min.

Before starting processing, a rough separation of waste is carried out, taking into account their distinctive features. After that, the material is subjected to mechanical grinding, which can be either at normal (room) temperature or in a cryogenic method (in an environment of refrigerants, for example, liquid nitrogen). Shredded waste is fed into the washing machine for washing, which is carried out in several stages with special washing mixtures. The mass squeezed out in a centrifuge with a moisture content of 10–15% is fed for final dehydration to a dryer, to a residual moisture content of 0.2%, and then to an extruder. The polymer melt is fed by the extruder screw through the filter into the strand head. The cassette or rewind filter is used to clean the polymer melt from various impurities. The purified melt is pressed through the strand holes of the head, at the exit of which the strands are cut with knives into granules of a certain size, which then fall into the cooling chamber. Passing through a special installation, the granules are dehydrated, dried and packed into bags. If it is necessary to process thin PO films, then an agglomerator is used instead of an extruder.

Drying of waste is carried out by various methods, using shelf, belt, bucket, fluidized bed, vortex and other dryers, the productivity of which reaches 500 kg/h. Due to the low density, the film floats, and the dirt settles on the bottom.

Dehydration and drying of the film is carried out on a vibrating screen and in a vortex separator, its residual moisture content is not more than 0.1%. For ease of transportation and subsequent processing into products, the film is granulated. During the granulation process, the material is compacted, its further processing is facilitated, the characteristics of secondary raw materials are averaged, resulting in a material that can be processed on standard equipment.

For plasticization of crushed and purified polyolefin waste, single-screw extruders with a screw length (25–33) are used. D, equipped with a continuous filter for melt purification and having a degassing zone, allowing to obtain granules without pores and inclusions. When processing contaminated and mixed waste, disk extruders of a special design are used, with short multi-thread worms (3.5–5) long D having a cylindrical nozzle in the extrusion zone. The material melts in a short period of time, and fast homogenization of the melt is ensured. By changing the gap between the cone nozzle and the shell, you can adjust the shear force and friction force, while changing the mode of melting and homogenization of processing. The extruder is equipped with a degassing unit.

Granules are produced mainly in two ways: head granulation and underwater granulation. The choice of granulation method depends on the properties of the thermoplastic being processed and, in particular, on the viscosity of its melt and adhesion to the metal. During granulation on the head, the polymer melt is squeezed out through a hole in the form of strands, which are cut off by knives sliding along the spinneret plate. The resulting granules with a size of 4–5 mm (in length and diameter) are discarded with a knife from the head into the cooling chamber, and then fed into the moisture extraction device.

When using equipment with a large unit capacity, underwater granulation is used. With this method, the polymer melt is extruded in the form of strands through the holes of the die plate on the die. After passing through a cooling bath with water, the strands enter the cutting device, where they are cut into pellets by rotating cutters.

The temperature of the cooling water entering the bath along the countercurrent of the strands is maintained within 40–60 °C, and the amount of water is 20–40 m 3 per 1 ton of granulate.

Depending on the size of the extruder (the size of the screw diameter and its length), the productivity varies depending on the rheological characteristics of the polymer. The number of outlet holes in the head can be in the range of 20–300.

From the granulate, packages for household chemicals, hangers, construction parts, pallets for transporting goods, exhaust pipes, lining of drainage channels, non-pressure pipes for melioration and other products are obtained, which are characterized by reduced durability compared to products obtained from virgin polymer. Studies of the mechanism of degradation processes occurring during the operation and processing of polyolefins, their quantitative description allow us to conclude that the products obtained from recycled materials must have reproducible physical, mechanical and technological indicators.

More acceptable is the addition of secondary raw materials to the primary in an amount of 20–30%, as well as the introduction of plasticizers, stabilizers, fillers up to 40–50% into the polymer composition. Chemical modification of recycled polymers, as well as the creation of highly filled recycled polymer materials, allows even wider use of used polyolefins.

Modification of recycled polyolefins

Modification methods of secondary polyolefin raw materials can be divided into chemical (crosslinking, introduction of various additives, mainly of organic origin, treatment with organosilicon liquids, etc.) and physical and mechanical (filling with mineral and organic fillers).

For example, the maximum content of the gel fraction (up to 80%) and the highest physical and mechanical properties of cross-linked HLDPE are achieved with the introduction of 2–2.5% dicumyl peroxide on rollers at 130°C for 10 min. The relative elongation at break of such a material is 210%, the melt flow rate is 0.1–0.3 g/10 min. The degree of crosslinking decreases with an increase in temperature and an increase in the duration of rolling as a result of a competing degradation process. This allows you to adjust the degree of crosslinking, physical, mechanical and technological characteristics of the modified material. A method has been developed for molding products from HLDPE by introducing dicumyl peroxide directly in the process of processing, and prototypes of pipes and molded products containing 70–80% of the gel fraction have been obtained.

The introduction of wax and elastomer (up to 5 parts by mass) significantly improves the processability of VPE, increases the physical and mechanical properties (especially elongation at break and crack resistance - by 10% and from 1 to 320 hours, respectively) and reduces their spread, which indicates an increase in the homogeneity of the material.

Modification of HLDPE with maleic anhydride in a disk extruder also leads to an increase in its strength, heat resistance, adhesiveness and resistance to photoaging. In this case, the modifying effect is achieved at a lower concentration of the modifier and a shorter duration of the process than with the introduction of elastomer. A promising way to improve the quality of polymer materials from recycled polyolefins is thermomechanical treatment with organosilicon compounds. This method allows to obtain products from recycled materials with increased strength, elasticity and resistance to aging.

The modification mechanism consists in the formation of chemical bonds between the siloxane groups of the organosilicon liquid and unsaturated bonds and oxygen-containing groups of secondary polyolefins.

The technological process for obtaining a modified material includes the following stages: sorting, crushing and washing of waste; waste treatment with organosilicon liquid at 90±10 °C for 4–6 hours; drying of modified waste by centrifugation; regranulation of modified waste.

In addition to the solid-phase modification method, a method for modifying VPE in solution is proposed, which makes it possible to obtain an VLDPE powder with a particle size of not more than 20 μm. This powder can be used for processing into products by rotational molding and for coating by electrostatic spraying.

Filled polymer materials based on recycled polyethylene raw materials

Of great scientific and practical interest is the creation of filled polymeric materials based on recycled polyethylene raw materials. The use of polymeric materials from recycled materials containing up to 30% filler will make it possible to release up to 40% of primary raw materials and send it to the production of products that cannot be obtained from secondary raw materials (pressure pipes, packaging films, reusable transport containers, etc.).

To obtain filled polymeric materials from recycled materials, it is possible to use dispersed and reinforcing fillers of mineral and organic origin, as well as fillers that can be obtained from polymer waste (crushed thermoset waste and rubber crumb). Almost all thermoplastic waste can be filled, as well as mixed waste, which for this purpose is also preferable from an economic point of view.

For example, the expediency of using lignin is associated with the presence of phenolic compounds in it, which contribute to the stabilization of WPE during operation; mica - with the production of products with low creep, increased heat and weather resistance, and also characterized by low wear of processing equipment and low cost. Kaolin, limestone, oil shale ash, coal spheres and iron are used as cheap inert fillers.

With the introduction of finely dispersed phosphogypsum granulated in polyethylene wax into WPE, compositions with increased elongation at break were obtained. This effect can be explained by the plasticizing effect of polyethylene wax. Thus, the tensile strength of VPE filled with phosphogypsum is 25% higher than that of VPE, and the tensile modulus is 250% higher. The reinforcing effect when mica is introduced into the HPE is associated with the features of the crystalline structure of the filler, a high characteristic ratio (the ratio of the flake diameter to the thickness), and the use of crushed, powdery WPE allows you to preserve the structure of the flakes with minimal destruction.

Among polyolefins, along with polyethylene, significant volumes fall on the production of products from polypropylene (PP). The increased strength properties of PP in comparison with polyethylene and its resistance to the environment indicate the relevance of its recycling. The secondary PP contains a number of impurities, such as Ca, Fe, Ti, Zn, which contribute to the crystal formation nuclei and the creation of a crystalline structure, which leads to an increase in the rigidity of the polymer and high values of both the initial elastic modulus and the quasi-equilibrium modulus. To assess the mechanical performance of polymers, the method of relaxation stresses at various temperatures is used. Secondary PP under the same conditions (in the temperature range of 293–393 K) withstands much higher mechanical stresses without destruction than the primary one, which makes it possible to use it for the manufacture of rigid structures.

Recycling of used polystyrene

Used polystyrene plastics can be used in the following areas: recycling of technological waste of high impact polystyrene (HIPS) and acrylonitrile butadiene styrene (ABS) - plastic by injection molding, extrusion and pressing; disposal of used products, EPS waste, mixed waste, disposal of heavily polluted industrial waste.

Significant volumes of polystyrene (PS) fall on foamed materials and products made from them, the density of which is in the range of 15–50 kg/m 3 . These materials are used to make mold matrices for packaging, cable insulation, boxes for packing vegetables, fruits and fish, insulation for refrigerators, refrigerators, pallets for fast food restaurants, formwork, heat and sound insulation boards for insulating buildings and structures, etc. In addition, when transporting used such products, transportation costs are sharply reduced due to the low bulk density of foamed PS waste.

One of the main methods of recycling foamed polystyrene waste is a mechanical recycling method. For agglomeration, specially designed machines are used, and for extrusion, twin-screw extruders with degassing zones are used.

The consumer point is the main location for the mechanical recycling of used EPS products waste. Contaminated foamed PS waste is subject to inspection and sorted. At the same time, impurities are removed in the form of paper, metal, other polymers and various inclusions. The polymer is crushed, washed and dried. The polymer is dehydrated by centrifugation. The final grinding is carried out in a drum, and from it the waste enters a special extruder, in which the polymer prepared for processing is compressed and melted at a temperature of about 205–210 °C. For additional purification of the polymer melt, a filter is installed, which operates on the principle of rewinding the filter material or a cassette type. The filtered polymer melt enters the degassing zone, where the screw has a deeper thread compared to the compression zone. Next, the polymer melt enters the strand head, the strands are cooled, dried and granulated. In the process of mechanical regeneration of PS waste, processes of destruction and structuring occur, so it is important that the material is subjected to minimal shear stress (a function of screw geometry, speed and melt viscosity) and a short residence time under thermomechanical load. The reduction of destructive processes is carried out due to the halogenation of the material, as well as the introduction of various additives into the polymer.

The mechanical recycling of expanded polystyrene is regulated based on the area of application of the recycled polymer, for example, for insulation, cardboard, cladding, etc.

There is a method for depolymerization of polystyrene waste. To do this, PS or foamed PS waste is crushed, loaded into a sealed vessel, heated to the decomposition temperature, and the released secondary styrene is cooled in a refrigerator and the monomer thus obtained is collected in a sealed vessel. The method requires complete sealing of the process and significant energy consumption.

Recycling of used polyvinyl chloride (PVC)

Recycling of recycled PVC involves the processing of used films, fittings, pipes, profiles (including window frames), containers, bottles, plates, roll materials, cable insulation, etc.

Depending on the composition of the composition, which may consist of vinyl plastic or plastic compound and the purpose of secondary PVC, recycling methods may be different.

For recycling, PVC product waste is washed, dried, crushed and separated from various inclusions, incl. metals. If products are made from compositions based on plasticized PVC, cryogenic grinding is most often used. If the products are made of rigid PVC, then mechanical crushing is used.

The pneumatic method is used to separate the polymer from the metal (wires, cables). The separated plasticized PVC can be processed by extrusion or injection molding. The magnetic separation method can be used to remove metallic and mineral inclusions. To separate the aluminum foil from the thermoplastic, heating in water at 95–100 °C is used.

Separation of labels from unusable containers is carried out by immersion in liquid nitrogen or oxygen at a temperature of about -50 ° C, which makes the labels or adhesive brittle and then allows them to be easily shredded and separated from a homogeneous material, such as paper. For the processing of artificial leather (IR) waste, PVC-based linoleums, a method for the dry preparation of plastic waste using a compactor is proposed. It includes a number of technological operations: grinding, separation of textile fibers, plasticization, homogenization, compaction and granulation, where additives can also be introduced.

Cable waste with PVC insulation enters the crusher and is fed by a conveyor to the loading hopper of the cryogenic mine, which is a sealed container with a special transport screw. Liquid nitrogen is supplied to the mine. The cooled crushed waste is unloaded to the grinding machine, and from there it enters the metal separation device, where the brittle polymer is deposited and passed through the electrostatic corona of the separator drum and copper is extracted there.

Significant volumes of used PVC bottles require different methods of their disposal. Noteworthy is the method of separating PVC from various impurities according to the density of the calcium nitrate solution in the bath.

The mechanical process of recycling PVC bottles provides for the main stages of the process of processing waste of secondary thermoplastics, but in some cases it has its own distinctive features.

During the operation of various buildings and structures, significant volumes of metal-plastic window frames based on PVC compositions that were in use are formed. Recycled PVC frames with a frame, which were in use, contain approximately 30% wt. PVC and 70% wt. glass, metal, wood and rubber. On average, a window frame contains about 18 kg of PVC. The incoming frames are unloaded into a container 2.5 m wide and 6.0 m long. Then they are pressed on a horizontal press and turned into sections up to an average of 1.3–1.5 m long, after which the material is additionally pressed using a roller and fed to chopper in which the rotor rotates at an adjustable speed. A large mixture of PVC, metal, glass, rubber and wood is fed to the conveyor, and then to the magnetic separator, where the metal is separated, and then the material enters the rotating metal separation drum. This mixture is classified into particle sizes<4 мм, 4–15 мм, 15–45 мм, >45 mm.

Fractions (>45 mm) larger than usual are returned for re-crushing. A fraction of 15–45 mm in size is sent to a metal separator, and then to a rubber separator, which is a rotating drum with rubber insulation.

After removing the metal and rubber, this coarse fraction is sent back for grinding for further size reduction.

The resulting mixture with a particle size of 4-15 mm, consisting of PVC, glass, fine residue and wood waste from the silo is fed through a separator to a drum sieve. Here, the material is again divided into two fractions with particle sizes: 4–8 and 8–15 mm.

Two separate processing lines are used for each particle size range, for a total of four processing lines. The separation of wood and glass takes place in each of these processing lines. The wood is separated by using inclined vibrating air sieves. Wood, which is lighter than other materials, is transported downward by the airflow, while heavier particles (PVC, glass) are transported upward. Glass separation is carried out in a similar manner on subsequent screens where the lighter particles (ie PVC) are transported downwards while the heavy particles (ie glass) are transported upwards. After the removal of wood and glass, PVC fractions from all four processing lines are combined. Metal particles are detected and removed electronically.

Purified polyvinyl chloride enters the workshop, where it is moistened and granulated to a size of 3–6 mm, after which the granules are dried with hot air to a certain moisture content. Polyvinyl chloride is divided into four fractions with a particle size of 3, 4, 5 and 6 mm. Any oversized granules (i.e. > 6 mm) are returned to the area for regrinding. Rubber particles are separated from PVC on vibrating sieves.

The final step is an optoelectronic color sorting process that separates the white PVC particles from the colored ones. This is done for fractions of each size. Since the amount of colored PVC is small compared to white PVC, white PVC fractions are sized and stored in separate bins while the colored PVC streams are mixed and stored in one bin.

The process has some special features that make the operations environmentally friendly. Air pollution does not occur as the grinding and air separation is equipped with a dust extraction system that collects dust, paper and foil in the air stream and feeds them to the microfilter trap. The grinder and drum sieve are insulated to reduce the occurrence of noise.

During wet grinding and washing of PVC from contaminants, water is supplied for re-cleaning.

Recycled PVC is used in the production of new co-extrusion window profiles. In order to obtain the high surface quality required for co-extrusion profiled window frames, the inner surface of the frames is made from recycled PVC and the outer surface from virgin PVC. The new frames contain 80% recycled PVC by weight and are comparable in mechanical and performance properties to frames made from 100% virgin PVC.

The main methods for recycling PVC plastic waste include injection molding, extrusion, calendering, and pressing.

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