Equipment for the production of film from recycled materials. Recycling of polyethylene into granules. How can you recycle material at home

Why is it important to recycle polyethylene and why is polyethylene interesting for a recycling business?

Polyethylene is the most widely used of all types of plastics. It can be harvested in large quantities at a relatively low cost, and therefore a recycling business can use economies of scale to reduce costs and increase profits.

How much polyethylene is consumed and what products are made from it?

In Russia, the annual consumption of polyethylene is 1.6-1.7 million tons, a significant part of which is spent on products with a short service life, feeding the waste stream.

What is polyethylene?

Polyethylene is a polymer, that is, a material consisting of very long molecules in which homogeneous groups of carbon and hydrogen atoms are connected in chains. Polyethylene has the simplest structure of all polymers. It has carbon atoms in the center of the chain, to which hydrogen atoms are attached.
The structure looks like this

In some places, instead of a hydrogen atom, a carbon atom is attached to the side of the chain, which also forms a chain or branch. Molecules can be branched to varying degrees, and the properties of the material strongly depend on this.

What raw material is polyethylene made from?

The very name of polyethylene suggests that it is a polymer of ethylene, that is, polymer chains consist of identical pieces, chemical formula of which C₂H₂ (ethylene). These constituents are called a monomer. In ethylene, each tetravalent carbon atom is bonded to two hydrogen atoms and to the adjacent carbon atom, with the last covalent bond double. Therefore, ethylene is also called an unsaturated compound. Compounds with a double bond in chemistry are called olefins, hence common name polyethylene and some other polymers - polyolefins.
So, polyethylene is obtained by joining chains (polymerization) of ethylene molecules.
At the same time, ethylene can be from different sources, depending on which raw material is more accessible to petrochemists in each specific region and in each specific case. The main groups of raw materials are naphtha (a derivative of oil refining), ethane isolated from natural gas or associated gas, and more and more now ethylene is being obtained from ethyl alcohol, which can be obtained from many types of vegetable raw materials, including on a commercial scale. ethanol from sugar cane is already being used.

What are the properties of polyethylene?

The industry produces many grades of polyethylene, but they all differ mainly in only two parameters. This is the size of the molecules and the degree of their branching. These parameters do not depend on the feedstock from which ethylene is obtained, but depend on the conditions of the polymerization process, pressure in the reactor, temperature, presence and type of catalyst.
They learned how to make the first polyethylene in the industry at high pressure, in which polymerization was initiated by free radicals. Such material is now called LDPE, it is characterized by high branching. That is, on each polymer chain there are many side branches, which in turn also have branches consisting of the same chains.
Later, with the help of catalysts, they learned to produce polyethylene at a lower pressure, it is called HDPE. Its molecules are much less branched.
To understand how the branching of molecules affects the properties of a polymer, imagine two panicles. One of them consists of smooth rods, without side branches. They are packed tightly and the panicle is so hard and strong. The other consists of rods with side branches. The density is already much less, and it is more pliable, flexible.
In the same way, HDPE, which is also called high-density polyethylene, and LDPE, called low-density polyethylene, differ. The first material is tougher, its strength is high. The second is plastic, products from it bend at lower loads.

Can LDPE be recycled into HDPE and vice versa?

No, it’s impossible, the structure and sizes of molecules are set during synthesis, that is, at the plant where the primary polymer was produced, it is little subject to changes during secondary processing. However, it is possible to add rigidity to the LDPE material by adding a more rigid HDPE or other material to it, and it is also possible to add plasticity to the HDPE material by adding LDPE accordingly. This is often done in the manufacture of products from recycled polymers. Mix different types.

What determines the rheological properties of polyethylene, the melt yield strength?

on the size of the molecules. The larger and longer the molecules in a polymer, the less fluid it is. The fluidity of a polymer is measured under load and at elevated temperature.

What types of polyethylene raw materials are available for recycling?

Industrial waste and consumer waste are available.
Industrial wastes differ, in most cases, in purity and are homogeneous, however, each source contains relatively few of them. a large number of. It is understandable, because production facilities are not designed to produce waste. Often recycled industrial waste is a relatively uncomplicated process and those who form them are increasingly using them themselves after minimal processing, such as crushing or granulating on a small, simplified granulator.
Large in volume, but complex in composition, consumer waste, that is, waste of products or packaging that were in use. Recycling of such waste is usually difficult, their processors must have a large amount of equipment, so economies of scale make enterprises for their processing relatively large. They collect waste from a variety of sources (garbage sorters and commercial sources).

What polyethylene consumer waste can be recycled?

The following types of polyethylene waste are available on the existing market of secondary raw materials in Russia:

1. Waste films from low-density polyethylene, including stretch films, collected by sorting from commercial sources - stores, are relatively clean, washing is not required to remove contamination, it is enough to filter the melt in an extruder and degassing.
2. Waste films collected from consumer waste require washing, as they are contaminated, among other things, with food waste.
3. Stretch - is assembled separately, it is most often a linear low-density polyethylene with additives.
4. Blown bottles for liquid products and goods - consist of HDPE, require washing and thorough degassing of the melt to remove product residues that are absorbed into the walls of the bottles. Abroad, milk bottles are usually collected separately, but this applies to those countries where a significant percentage of milk is packed in high-density polyethylene bottles.
5. Canisters may be different quality depending on what was in them before. As mentioned above, the processing of oil cans is difficult due to oil residues.
6. Multilayer films, most of which are polyethylene - the processing of such films presents technological difficulties, the description of which is beyond the scope of this article.
7. Waste cables - they often use cross-linked polyethylene, that is, one in which bridges between individual molecules were deliberately created. Its processing is difficult because the material does not flow at melting temperatures, but only softens. The percentage of gel there is very high.
8. Agricultural film - a film that has been used in agriculture. It can usually be severely damaged by photo-oxidative degradation.

There are two main processing methods, these are mechanical recycling, when the material is used as a polymer for the manufacture of products or other purposes, as well as thermo-chemical recycling, pyrolysis, which results in liquid and gaseous products of thermal degradation of the polymer. Next, we will talk about mechanical recycling.
What processes include the processing of polyethylene?
The main processes are sorting, grinding, washing, drying and agglomeration or granulation. Depending on the feedstock and productivity, the combination of these processes may be different, for example, grinding can be carried out both in one stage and in two stages. Also, if the raw materials are collected from relatively pure sources, then the washing and drying step can sometimes be omitted.

What equipment is used for processing?

​Polyethylene waste that has been in contact with products is washed contaminated on the washing lines. As a rule, the washing line includes the following elements:

- Equipment for grinding and shaping particles. Shredders or crushers. The former are preferred in most cases, as they are more durable when hit by hard objects such as stones or metals, but shredders are more expensive than crushers. In crushers, the rotor speed is higher, hitting a solid object can immediately disable the crusher, it will be required in special severe cases replacement of all knives. But crushers are often made with a pre-cleaning function, for this they are supplied with water. On high-capacity lines, both a shredder and a crusher are used, that is, grinding is organized in two stages, between which equipment for separating heavy particles is necessarily placed to protect the crusher.

- Equipment for separating heavy particles such as sand, stones, metals and plastics incompatible with polyethylene, such as polyethylene terephthalate, which sinks in ordinary water.
Two types of equipment are used to separate heavy particles: flotation tanks and hydrocyclones. The latter are almost exclusively in high-capacity lines, such as 2 tons per hour.

- Equipment for intensive washing of plastic. For this purpose, friction washers and (or) centrifuges are used.

Pressing equipment - usually centrifuges and screw presses. After mechanical pressing, the moisture content of the films can be from 6 to 12 percent. This may be too much for efficient further agglomeration, so mechanical drying is often not limited.

- Equipment for thermal drying - they, as a rule, organize the movement of plastic particles along with the flow of heated air in labyrinths (long pipes or channels) of various designs. Sometimes in the lines the final drying is not done and it is left for the stage of agglomeration or granulation.

The work of agglomerators and plastcompactors is based on mechanical heating of the material and then its clumping, compaction using various technological methods.

The operation of the granulator is based on heating the material with electric heaters to melting temperatures, mixing the resulting melt and purifying it by filtering, pumping out the gases formed during heating, and then forming granules by squeezing the melt through dies (matrices with holes) and cutting the resulting strands with one or another way. (water ring and strand granulators). The advantage of granulators over agglomerators and plast compactors is that they make it possible to obtain a more reliable product, since mechanical impurities that could remain after the washing line are filtered out on granulators and impurities of fats or other substances decomposing when heated can be removed by degassing the melt.

​More details about the equipment with examples of lines on the site http://moykaplastica.ru

What is polymer degradation?

Polymer molecules are inevitably damaged during recycling for three reasons. This is, firstly, a mechanical load, for example, in an extruder, when high blood pressure the material is mixed. Secondly, this is heat, which contributes to a more active movement of molecules and the bonds between atoms become not as strong as when normal temperatures. Thirdly, this is the action of atmospheric oxygen, which, being an active oxidizing agent, tends to oxidize the elements of the polymer chain, hydrogen and carbon. Thus, during recycling, polymer molecules change, some of them become shorter, torn apart. Every time a polymer chain breaks for one reason or another, a radical is formed, that is, an atom or a group of atoms whose valences are not closed, there is a vacancy on the external electron cloud. Such radicals are extremely active, they form compounds with neighboring molecules, while damage to the neighboring molecule forms a new radical, which in turn damages another chain. When the molecules are crosslinked by separate adhesions, the resulting structure is called a gel. The content of gels in secondary granules changes mechanical properties usually not the best
side.

Why are the properties of recycled polyethylene worse than those of primary?

Oxygen appears to be the main culprit for the reduction in properties. During destruction, it not only creates radicals, as described above, but it can also be incorporated into the material, replacing hydrogen and carbon atoms, and oxidize polyethylene. The presence of oxygen atoms in a material changes its properties. Initially, polyethylene is non-polar. This means that it only contains hydrogen and carbon atoms, which have a non-polar bond between them, because their electronegativity is quite close. That is, they are connected through a common cloud of electrons, which is more or less in the middle ( in simple terms, is actually more difficult). But as soon as an oxygen atom appears nearby, the second most electronegative element after fluorine, then immediately oxygen affects all the bonds that are nearby. It polarizes them to some extent. Attracts electrons to itself. This reduces their strength under mechanical action, reduces the resistance of neighboring bonds to other oxygen atoms, which also tend to snatch and oxidize something from the polymer molecule.
Hence, important practical knowledge is that the more polyethylene is oxidized (destructed), the faster it oxidizes further and its properties fall even faster. This explains more unsuccessful than successful experiments to improve the properties of recycled plastic by adding unspoiled primary. The secondary, if it has already destroyed, then quickly poisons the primary with its influence, and this is precisely because of oxygen and its magnetic activity in relation to electrons in molecules.

For example, following a link to an article by Swedish researcher Michael Hamskog (whom I have worked with before), the article concluded that blending virgin polyolefin with recycled polyolefin was inefficient and adding additives was more effective. which will be discussed below.
https://www.sciencedirect.com/scienc...41391005003629

How does the MFR of polyethylene change during recycling?

So the MFI can change both up and down, depending on which process develops more strongly, shortening or crosslinking, and this, in turn, depends on the processing conditions. Most often, there is a shortening of the molecules, that is, an increase in fluidity.

How to reduce polymer degradation during recycling?

In order to slow down the degradation, special substances are added to the polymer that can take on the resulting radicals and do not allow the process to develop according to a chain scenario, when damage to one polymer chain leads to damage to neighboring ones.
Unfortunately, these substances are consumable. That is, over time, their action weakens and they are already working out. Sometimes, in order to restore the dose of stabilizers, they are added to the polymer during recycling. For example, such a composition as Ricyclestab.
In order to minimize degradation, in general, it is necessary to minimize the mechanical and thermal loads on the polymer during recycling, that is, do not overheat it above what is necessary, do not use excessive mixing under pressure in the extruder.

How do polymer contaminants affect the properties of the recycled material?

When recycling end-of-life waste, contamination is always a major concern. They are acquired from contact with other substances, including the substance that was packaged in polyethylene packaging. Contaminants are either surface or internal.
So oil canisters contain some residual amount of these oils in the form of surface contaminants, but part of the oil is dissolved in the walls of the canister and during recycling, even if the material is well washed, an odor may appear, the properties of the secondary polymer may change due to plasticization of polyethylene with oil (partial dissolving oil in polyethylene).
This is typical not only for such pronounced substances as butter and detergents, but also for ordinary milk. Bottles made of HDPE, which previously contained milk, even after washing, contain in their walls a certain amount of lactic acid, which has dissolved in polyethylene. Odor may occur during processing.
Other contaminants such as sand or earth, pieces of paper also reduce the mechanical properties of the polymer and must be removed.
To remove surface contaminants, washers are used, in which the material is thoroughly washed with water in combination with some mechanical efforts (friction washers), and dry cleaning installations, for example, manufactured by MAS, can also be used, but the latter do not cope well with sticky contaminants even in cases where there are sticky ingredients.

How to recycle cross-linked polyethylene?

Cross-linked polyethylene is one in which links (bridges) are additionally made between individual macromolecules. This is usually done for those products that are used in elevated temperatures e.g. for electrical insulation. Such polyethylene can withstand somewhat higher than the melting point. So, for example, the cable insulation will not drain, but will only soften. In fact, cross-linked polyethylene is no longer a thermoplastic plastic. It does not melt, as it should, but softens, so it is impossible to process it in the usual ways.
There are two possible approaches to the processing of cross-linked polyethylene. First, it can be processed by thermal methods, such as pyrolysis, to produce liquid and gaseous products.
Secondly. Theoretically, cross-linked polyethylene can be ground to a particle size of less than 0.5 mm and used as an additive in conventional polyethylene products. The author worked on this idea for a long time and was already planning to test it in practice, but somehow his hands did not reach. The difficulty is that cross-linked polyethylene grinds very poorly, so it was not possible to obtain powder from it at a very low price. The estimated price was up to 10 rubles per kilogram. Second, it is unclear how cross-linked polyethylene will affect Melt Yield Strength. Apparently, it will reduce the MFR, but this needs to be checked.

Probably, the great potential for the processing of cross-linked polyethylene lies in the development of new methods for its grinding. For example, if you use the natural cold in the Siberian part of the country, then you can probably get a more productive grinding process in conventional mills than it was before. At a sufficiently low cost, this material could compete in the filler market, because it has the same density as polyethylene, that is, there will be no increase in the density of granules or products and it is likely to lesser degree will affect the properties of the polymer than when compared with mineral fillers. If you are interested in equipment for grinding cross-linked polyethylene, write to the contacts below.

How to start a polyethylene recycling project?

From establishing contacts. First of all, we need contacts with waste sorting stations and other sources of recycled polyethylene, then contacts with manufacturers of plastic products who are ready to consider proposals for the use of recycled polyethylene.
When there is an understanding of the available volume of raw materials and possible sales, you can begin to select equipment and, together with suppliers, design a production line for processing.
​
Information about advanced level processing equipment:

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​ For questions about the sale of polyethylene waste, films, bags, substandard products, call
​ +7 916 103 1486
or write mail.ru

In life modern man polyethylene is used everywhere. Almost every home has a variety of packages. The better the raw material, the more difficult it is to dispose of and the longer the period of its decomposition. processed into new products. This is what is discussed in the article.

Disposal

The widespread use of polyethylene has led to environmental problem- accumulation of waste in landfills. It is estimated that these products account for 8-10%. The material does not rot, it is resistant to acids and alkalis, it almost does not dissolve, it takes many years to decompose, and at the same time, dangerous substances that pollute soil and water bodies.

Polyethylene does not burn completely, forming toxic dioxins that are harmful to all living things: poisons accumulate in the body, which causes dermatitis, ulcers, and mutations. Pyrolysis from this raw material has not been widely used - it is economically beneficial with a large amount of raw materials (over 20 thousand tons per year).

The best option is to hand over polyethylene. Recycling allows you to use this opportunity to save resources, reduce the cost of products, reduce costs.

Waste types

Polyethylene waste differs in shape, composition, location, contamination, level of preparation for secondary use. They are divided into several groups:

1. Technological marriage (2-10%) - practically does not differ from standard products. It is used as a returnable raw material or low-grade commercial products.
2. Waste industrial use- films, containers, containers, pipelines, cable sheaths, non-working products.
3. Part of the waste in landfills - films, bags, bottles, household items.
4. According to the level of preservation: slight destruction and partial loss of the desired characteristics.

Polyethylene waste is mixed with the rest of the waste. There are 2 directions for polyethylene recycling - separation of homogeneous products and processing in a mixture of waste.

Recycling

Reception of polyethylene waste is carried out by specialized companies. From the type of product, they determine what the technological cycle of processing will be. It usually includes sorting, cleaning, fractionating, grinding, crushing, agglomeration, granulation and product formation.

Large fragments are cut with circular saws or band saws. Jaw or rotary crushers, hydro grinders, devices cooled by liquefied carbon dioxide are suitable for small products.

Cleaning of contaminants is carried out in places of washing and on washing lines with the function of solvent recovery. From thermoplastics, polyethylene is extracted using the screening method with separation or flotation. To reduce the volume, degassing, cleaning products are sintered. Agglomerate is used as marketable products or used for granulation to create superior secondary granules.

Recycled polyethylene has a high melt viscosity. Its granulation is carried out at high temperatures in apparatuses equipped with rotary-knife grinding crushers and melt pumps. These granulators are needed for recycling, degassing and modification of waste.

Features of work

During the processing of packages, several stages are carried out. The first cycle has practically no effect on the decrease in consumer characteristics of new products. But with each stage, the raw material acquires negative characteristics, which is why it can be used for special materials. Waste is used to make new products. The processing technology is as follows:

1. There is a collection of raw materials: films, bottles, garbage. Sorting is done manually or mechanically. If the waste is divided into waste paper, glass, paper, PET, then it will be possible to reduce the amount of garbage for disposal.
2. Raw material goes to washing devices. The stage is required to eliminate dirt, foreign objects. If the products are handed over to the receiving points, then the quality is checked in order to assign a price.
3. Raw materials are crushed by crushers.
4. If it contains moisture or impurities, then processing is carried out in a centrifuge.
5. The material is sent to a drying chamber for heat treatment.
6. The work is finished and the material can be reused. They make universal products - polyethylene films, bags, packaging containers, pipes.

What comes from waste?

The collection of polyethylene waste allows you to obtain various products. Mixtures with a large amount of foreign inclusions are processed by casting or intrusion at low pressure. This low-cost option allows you to get lightly loaded products for decorative street fencing.

Reception of polyethylene waste with a short period of use (containers, films, bottles for single use) is carried out for processing into products of this type. If the materials have a crushed structure, then large products with low strength are obtained from them.

Now the sphere for the manufacture of composites from secondary polymers and fillers has been developed: crumb rubber. They are used in the production of containers, finishing tiles, furniture, decorative elements for cars.

The secondary granule is used as an additive to polyethylene in the manufacture of standard products or as a binder in composites for the production of pressure pipes, large containers. This raw material is used to create containers and packaging for non-food items, building films, pipelines. This area, although complex, is actively developing.

Outcome

Recycling will reduce the amount of garbage in city landfills. Polyethylene and plates practically do not decompose. But on their basis, new products are obtained that are useful in various fields human life.

One of the promising areas entrepreneurial activity currently is the processing of polyethylene. This type of business is attractive due to the fact that its products are in high demand in many industries, construction, and growing crops. Before investing in a polyethylene processing business, you should carefully familiarize yourself with all the subtleties and nuances of the process, as well as the requirements for the production itself.

Our business valuation:

Starting investment - 1,500,000 rubles.

Market saturation is low.

The complexity of starting a business is 7/10.

Who is the product for?

The start of any business, as a rule, is carried out with a preliminary study of demand, and indeed the demand for that final product or service, which will be the main activity.

So, polyethylene processing - who will be the main consumer of the goods produced by your enterprise? If you are planning to set up the production of polyethylene granules, then the main customers will also be processing plants for the production of the following products:

• and containers for food and household purposes;
• as a container - consumer and for packaging any type of product in industrial scale;
• Decor elements for equipping the interior and exterior of an apartment and a house, a garden, a kitchen garden, a pool;
• insulating materials for construction;
• For the production of finishing tiles;
• Pipes for organizing irrigation, water supply, heating;
• Purifying drainage systems;
• Materials for equipping storm systems.

So, as you can see from this list, having established the production of polyethylene granules (and it is produced in the form of such small units), you will be a desirable supplier of raw materials for many small workshops and large enterprises.

Of course, in this case, do not forget that for buyers, important indicators will be the quality of your products, your ability to deliver in the required volume and within a clearly defined time frame, as well as the fact that the cost is at the level of existing competitors, and at first and even lower.

What types of products will be at the exit from the shop?

Polyethylene recycling technology, first of all, involves the use of already used material as a raw material - practically your main focus is the so-called recycling of polyethylene waste. It is often referred to as garbage recycling, as a result of which, through transformations, cleaning and changing the physical state, a product comes out that can become the basis for the production of a large number of useful things.

The polyethylene processing technology, which will need to be applied at the opening of production, allows the production of the following types of products:

Features of production technology

Consider how the recycling process is carried out. First of all, I would like to immediately note that the processing of polyethylene waste into granules at the output has a product that is identical in property to those materials that are made from chemical components. In addition, when organizing such a business, it is also important that when processing recycled materials, you can count on various subsidies from the state, the allocation of funds for opening, as well as especially favorable conditions for paying taxes.

So, the recycling of polyethylene consists of the following main operations:

1. Collection of waste for polyethylene and acceptance of raw materials for production. in the best way in this case, it will be on your own to organize a collection point for polyethylene waste, of course, if you have sufficient funds for that.
2. Sorting of received raw materials. It is aimed at separating it from garbage and impurities, as well as separating it according to the degree of recyclability.

In the process of sorting, they are divided into types of waste according to the following criteria:

• By size. Most large species raw materials are sent for cutting with the help of circular saws or special band saws;
• By composition - separately distribute bags, plastic film waste, bottles, trays, etc.;
• Recycling where possible – in practice, 2 to 10% of the collected raw materials are subject to disposal due to the impossibility of being used for industrial purposes;
• By pollution. Basically, all collected raw materials are pre-washed, but excessively dirty ones undergo such an operation twice.

Basically, the process of sorting raw materials is done manually - existing on this moment polyethylene processing equipment does not allow fully mechanizing this process. In connection with this circumstance, it will be necessary to hire workers to carry out such a process. It is very important to carefully sort the raw materials, since getting into the total mass of other substances can significantly change the initial qualities of the polyethylene produced by your plant. As a result, upon its acquisition and the further production cycle, the finished product may turn out to be Bad quality and re-appeal to you is unlikely to take place.

1. Grinding to the required particle size. Crushers or shredders are used as equipment for such processing;
2. Washing of crushed raw materials on washing machines. With a large output finished products use installed washing lines, in which automatic loading into the apparatus, washing itself, partial drying and transportation for the next stage. Washing of raw materials is also milestone the entire recycling process, since the remaining impurities can degrade the resulting primary polyethylene granules - they will be of poor quality, cloudy and foamy.
3. processing in a centrifuge. Under the action of centrifugal force in such equipment, particles are directly separated for production from the remaining elements of dirt and impurities, as well as excess moisture, which is superfluous during the passage of the following technological processing operations.
4. Placement of washed and dried raw materials in agglomerators for polyethylene processing. In these devices, due to the action of high temperatures, the raw materials are melted and sintered. The resulting semi-finished product significantly increases the productivity of the machines that follow along the technological chain and facilitates the passage of the main operation of raw material granulation. In the event that a polyethylene processing line is installed in your workshop, then the best option will choose the one in which the plastcompactor is installed, which performs an operation similar to the agglomerator, but provides a higher quality of the processed product.
5. Direct granulation process. At the output after such an operation, a secondary polyethylene granule is obtained. The very process of its formation is as follows: the material is transported by means of a screw to the granulator, where a heating cycle is carried out, mechanically cleaned from impurities. The resulting mass, which, as a result of exposure to temperatures, heats up to 200 degrees, falls on the molding hole. The hole has thin slots - spinnerets through which thin streams of hot polymer are formed. At the exit, these streams are rapidly cooled, hardened and cut by a mechanical device using sharp knives. Further cooling with water or a jet of air takes place.
6. Secondary polyethylene granules are packaged in bags according to a predetermined weight. Such a process can be carried out manually, but it will be much more productive to purchase a special apparatus, which, moreover, ensures the accuracy of measurements and simultaneously performs the sealing operation.

Special requirements for the premises

A polyethylene processing plant, due to the fact that it is associated with some particularly harmful conditions and increased production hazards, should be located exclusively in industrial areas. In addition to this requirement, the production premises are subject to the following:

• Availability of an entrance to the zone of unloading of raw materials and shipment of finished products;
• The area of ​​production premises should start from a size of 100 square meters;
• It is obligatory to have a sewerage system, a connected system of hot and cold water;
• The room must be equipped good system ventilation;
• It is desirable that the entire building be divided into such four main zones: the receipt and storage of raw materials, primary processing (sorting), main processing - a workshop in which the semi-finished product is affected by pressure and high temperature, area for storage of raw materials and shipment of finished products.

Necessary personnel for the organization of production

The main workers that will be needed to start the full operation of the workshop and the sale of finished products are as follows:

• Head of the enterprise;
• Accountant. In the event that production volumes are not too large, then it is possible to combine the functions of an accountant and a manager in one person;
• Production technologist;
• Workers for maintenance of technological lines - from 3 people;
• Ancillary workers performing operations for unloading raw materials, sorting them, storing finished products and loading them into vehicles for further shipment to suppliers.

Estimated Costs and Expected Benefits

What amount will need to be invested in the organization of a polyethylene processing plant in order to open a competitive production that will provide you with income for a long period of time?

The main costs, in this case, will be the purchase of equipment, which will cost from 800 thousand rubles and the initial supply of raw materials, in an amount not less than 100 thousand rubles. In general, the total amount of funds that will be needed for the opening will be from 1.2 million rubles.

The level of profitability of such enterprises is on average 15% and allows you to recoup investments in a period of one to two years. With sufficient effort and high professionalism of employees, you will be able to further expand production by organizing a workshop for the production of any kind of products from the obtained secondary granulate, thus increasing the amount of potential profit.

The annual consumption of polyethylene in Russia is about 1.7 million tons.

A significant proportion of the polymer goes to the manufacture goods with a limited service life, which are sources of waste.

Consequently, from year to year the issue of utilization of this raw material is becoming more acute.

Polyethylene is of great interest to the recycling business for several reasons:

• this niche is relatively free;
• a large amount of waste means affordable raw materials and scalability of production;
• low cost will ensure the demand for secondary products.

Polyethylene is a polymerization product of ethylene (C 2 H 4), an unsaturated gaseous hydrocarbon, the first in the olefin series.

The compound is almost never found in nature., and in industry it is obtained by cracking high-molecular components of oil, dehydrogenation of ethane, and dehydration of ethyl alcohol.

The polymerization process is the destruction of one of the bonds in the H 2 C \u003d CH 2 molecule and the connection of the monomer -H 2 C-CH 2 - into a non-cyclic chain. The process is influenced by temperature, pressure and the type of catalyst used.

On an industrial scale, four types of polyethylene are synthesized, differing in structure and properties:

1. LDPE(polyethylene high pressure) is a transparent and elastic material with low tensile strength. The molecule of a substance has a large number of side branches that do not allow the creation of a crystalline structure. At a temperature of 103 - 110 °C, the polymer passes into a liquid state and has a high fluidity. LDPE is used for the production of packaging materials: films, containers and bags.
2. HDPE(low-pressure polyethylene) – stronger and tougher than LDPE. Polymer threads have a linear structure with a small number of branches, due to which at room temperature about 80% of the substance is in a crystalline state. The melting point is 125 - 132 °C. HDPE is resistant to most chemicals. They make from it trash bags, containers for oils, acids, solvents, non-pressure pipes.
3. PSD(medium pressure polyethylene) – mixture of HDPE and PSD. The material combines the advantages of both types of polymers and is used in the production of films, bags, blown thick-walled containers.
4. LPLD(linear high pressure polyethylene) – elastic and soft material with high resistance to tears, punctures and other types of destruction. Due to their colorability, most of these polymers are used in the production of stretch films, laminates and laminates.

IN last years Another type of polyethylene is widely used in Russia - PEX, or cross-linked polyethylene. It is obtained from HDPE.

Under the influence of reagents or ionizing radiation, abstraction of hydrogen atoms from polymer chains, and free bonds in carbon immediately interact with each other.

The result is a three-dimensional network with a pronounced crystalline structure.

The material has a high melting point and has a "shape memory".

They make from it:

• water pipes;
• cable insulation;
• heat shrink materials.

Recycling technologies

In Russia, two technologies for processing polyethylene are most widely used: the production of secondary granules and pyrolysis.

The first involves the return of the polymer to production, and the second is the production of energetically valuable gases and liquids that can be used as heating oil, as well as in the production of other types of organic compounds.

Thermomechanical - production of granules

Thermomechanical recycling is the production of granules from polyethylene waste. Technology does not allow converting HDPE to HDPE and vice versa.

The structure and molecular weight of the polymer are set during its synthesis and remain unchanged.

However, to give the secondary material the required technological properties - rigidity, plasticity or fluidity when heated - LDPE is added to HDPE and vice versa.

The production of granules from polyethylene waste is carried out according to the following algorithm:

1. Collection and sorting. The degree of readiness for processing depends on the size, composition, degree of preservation and contamination of raw materials. Waste is sorted mechanically and manually.
2. Grinding. On high-performance lines, crushing to the desired fraction is carried out in two stages: using shredders and crushers. Between them, a hydrocyclone or flotation bath is installed to separate solid and heavy particles.
3. flushing. Generally, industrial and commercial waste is cleaner than household waste and in some cases is not washed. Milk containers, on the other hand, may require double rinsing.
4. Drying. The crushed and washed raw materials enter the centrifuge, where excess moisture is removed from it, and then into the thermal drying chamber.
5. Agglomeration. The process proceeds under pressure and at elevated temperature, is a partial melting and sintering of polyethylene into pellets.
6. Granulation. In the granulator, the polymer is heated to the melting point, purified from solid and liquid impurities, and degassed. The mixture is also mixed and its composition is averaged. Mass under pressure passes through the holes - molding dies. The jets of melt are cooled by water and compressed air, after which they are cut into a finished granule.

In modern lines for the processing of LDPE and HDPE, plastic compactors are used instead of agglomerators.

In the devices, the raw material is pressed by rollers through dies with holes of given diameters, and heating occurs due to the action of friction forces.

Plastcompactors work with wet raw materials. This eliminates the need for a second drying stage. With properly configured technological process raw materials are not completely melted, which positively affects the quality of the secondary granule.

The processing of polyethylene is accompanied by a partial destruction of polymer chains.

Under the action of temperature, the bonds in them weaken and can be broken with active stirring.

In addition, the polymer is oxidized by atmospheric oxygen.

As a result, the chains are shortened and the mechanical properties of the granulate are reduced.

To reduce degradation, experts recommend setting up the processing process so that the raw materials are subjected to minimal thermal and mechanical stress. It is also possible to slow down the destruction of the polymer with the help of special stabilizer additives that bind free radicals.

Thermochemical - pyrolysis

Multilayer films, including those with metallization, cross-linked polyethylene and waste with a strong degree of degradation processing into a secondary pellet in commercial plants is difficult. They are subjected to thermal decomposition in pyrolysis plants.

Polyethylene pyrolysis products are of high quality and environmental safety, since the raw materials do not contain sulfur, phosphorus, and nitrogen compounds.

Thermal decomposition occurs in three stages:

1. Splitting of lateral branches.
2. Cracking of the main carbon chain.
3. Decomposition of carbon residues.

Most researchers believe that the mechanism of pyrolysis is a random chain reaction.

The products of the first two stages are:

• combustible gases;
• heavy waxes;
• resins.

At the third stage heavy hydrocarbon fractions are decomposed into lighter ones.

A large proportion of gaseous products belongs to the olefin series (ethylene, propylene, etc.). Also in the composition of the products there are cyclic compounds - benzene, toluene.

Some processes produce hydrogen and methane. In addition to gaseous products resulting from the pyrolysis of polyethylene receive liquid and condensable fractions rich in aliphatic hydrocarbons.

The decomposition process and the composition of its products depend on the degree of branching of polyethylene, its average molecular weight, temperature and type of reactor, catalyst used.

used in industrial processing installations give 40 - 70% of gas and 30 - 60% of pyrolysis oils.

Under laboratory conditions in a continuous reactor with an aluminosilicate catalyst 80% of the gasoline fraction was obtained(C 5 -C 12). The proportion of gases generally increases with increasing temperature in the reactor.

Features of processing cross-linked polyethylene

The largest sources of cross-linked polyethylene are waste cable insulation and plumbing pressure pipes.

In addition to pyrolysis decomposition, it is processed using the following technologies:

1. Powdering and use as a filler in the production of LDPE and HDPE granules.
2. hot cutting with partial oxidation. Crushing at elevated temperatures leads to rupture of carbon bonds between the chains and an increase in the fluidity of the material.
3. Hydrolysis and alcoholysis. Water and alcohol can break the crosslink. The resulting product does not differ from the synthesized polyethylene.
4. Ultrasonic processing. The energy of high-frequency pulses allows destroy the three-dimensional structure PEX and leave the main polymer chains unchanged.

The use of cross-linked polyethylene processing waste can be found in the production of pipes for cable ducts, low-voltage insulation and many household products.

The use of secondary granules in the production of finished products

If you follow the processing technology, use high-quality equipment and be responsible for the sorting process, the secondary granule is practically not inferior in quality to the primary one.

In the manufacture of the final product, it can partially or completely replace the synthesized polyethylene.

Components

In production, a secondary granule of HDPE, LDPE, LPVD, as well as mixed compositions is used.

As additives can be used:

• PEX powder;
• polypropylene;
• rubbers and other elastomers.

Technological processes

Production includes the following processes:

1. Extrusion. The technology consists in forcing the melt through the forming head, which sets the cross section of the finished product. This method is used to obtain window profiles, films, pipes, and other products of measured and random lengths.
2. Injection molding. The technology consists in pouring the melt into a mold with subsequent cooling and allows to obtain serial piece products. Equipment - injection molding machine - is capable of pouring hollow, foamed and reinforced products of complex configuration.

What products can be obtained from recycled materials?

The table shows which products and additives are created from different types recycled polyethylene:

How can the material be recycled at home?

Unfortunately, recycling polyethylene at home with zero investment is not possible.

However, there are offers of Russian and foreign manufacturers on the market. mini equipment, which can be installed in the garage or in the country.

To start need not be organized immediately. full cycle processing. Many enterprises buy crushed polyethylene of various grades.

There are resources that promote homemade polymer processing equipment. Dave Hakkens - author of the PreciousPlastic project - on his website provides drawings of such devices and gives video tutorials. Its technologies and recycling equipment allow you to create finished products at home.

Related videos

For more information on bag recycling, see this video:

Conclusion

Polyethylene recycling is a tempting niche to start your own business. But it is worth considering that the payback of industrial equipment, declared by manufacturers, is 1.5 - 2 years. In practice, this is only possible in conditions of "ideal" raw materials and well-established sales.

Before deciding to open, it is worth calculating all costs based on real conditions.

In contact with

The neglect of polyethylene waste is dangerous for the ecological situation. Processing polyethylene into granules allows you to give it new life, because many useful goods can be made from this raw material.

Limit the production of packaging products made of polyethylene in modern world quite difficult, but competent waste management solves the problem. Polyethylene raw materials are highly recyclable, modern technology recycling is environmentally friendly and does not require significant costs of natural resources.

Why is it important to recycle waste instead of throwing it in landfills?

1. In natural natural environment polyethylene decomposes for more than 300 years, releasing toxic substances into the soil and water.
2. Recycling allows you to use raw materials rationally, produce from recycled polyethylene necessary goods cheaper, save resources.
3. Recycling practically does not affect the quality of the material, secondary polyethylene is almost the same in properties as the primary one.

Stages of processing

1. Collection of raw materials.
2. Sorting, separation from household waste.
3. Cleaning - polyethylene must be washed from contaminants in special washing machines.
4. Grinding - in special crushers, the material is crushed.
5. Processing in a centrifuge relieves raw materials of residual impurities and excess moisture.
6. Drying - polyethylene undergoes heat treatment in special drying chambers.
7. Agglomeration - on special equipment under temperature and pressure, as well as using catalysts, raw materials are melted and sintered into granules.

Polyethylene granulation

1. Bulk material enters the granulator, several heating cycles clean it from impurities (garbage, metal, water, air inclusions).
2. At a temperature of 200°C, the molten polyethylene mass is passed through the forming holes (dies), from where the molten polymer flows out in thin streams.
3. Raw materials are cut with knives and cooled with cold water.
4. Collection of the product in the storage hopper and packaging in containers.

Necessary equipment

The line for recycling polyethylene waste includes:

• washing machine;
• crusher;
• drying plant;
• centrifuge;
• agglomerator;
• granulator;
• extruder.

For automatic supply of raw materials to the line, a conveyor or pneumatic conveyor is used. Processing of polyethylene into granules takes place directly in the agglomerator. With the help of special machines, finished products are formed. Granulation equipment is not always part of the production line.

Granular polyethylene can be of different quality, it is divided into 3 grades:

• Higher - made from unpainted packaging films, according to the characteristics of such granules are universal, suitable for the production of cast products and secondary film;
• 1st - the physical characteristics are similar to the highest grade, the basis for the production of granules is taken from packaging material painted in light colors;
• 2nd - made from sorted dark-colored raw materials (black, gray), then produced from recycled granules Construction Materials and household goods.

Application

From recycled polyethylene you can get:

1. New bottles for bottling drinks.
2. Disposable container.
3. Packaging films and bags.

Recycled polyethylene can become the basis for the production of building materials:

• finishing and decorative tiles;
• heat and waterproofing;
• sanitary communications (pressure pipes, drainage systems);
• decorative fences and pool accessories.

The use of pellets for the production of useful goods can be much wider. The technology is constantly being improved, specialists are looking for new areas of application for recycled polyethylene.

Recycling polyethylene waste into pellets is very profitable. Residents of large cities, by handing over raw materials to special collection points, can help improve the environmental situation. As a result, production receives inexpensive raw materials, which allows producing quality goods at more affordable prices. In the recycling process, the main difficulty is to establish a regular collection and delivery of raw materials to the site. A civilized way of waste disposal helps relieve public landfills and improve the quality of life for people in megacities.