Polyethylene is the cheapest non-polar synthetic polymer that belongs to the class of polyolefins. Polyethylene is a solid white substance with a grayish tint.

The first to study the polymerization of ethylene was the Russian chemist Butlerov in 1873. But an attempt to implement it was attempted in 1884 by the organic chemist Gustavson.

Polyethylene production technology + video on how to do it

All major companies in the petrochemical industry are involved in the production of polyethylene. The main raw material from which polyethylene is produced is ethylene. Production is carried out at low, medium and high pressure. As a rule, it is produced in granules that have a diameter of 2 to 5 millimeters, sometimes in powder form. Today there are four main methods for producing polyethylene. As a result, we get: polyethylene high pressure, polyethylene low pressure, medium pressure polyethylene, as well as linear high pressure polyethylene. Let's look at how MDV is produced.


HDPE is formed at high pressure by the polymerization of ethylene in an autoclave or tubular reactor. Polymerization in the reactor is carried out by a radical mechanism under the influence of oxygen, organic peroxides, such as lauryl, benzoyl or mixtures thereof. Ethylene is mixed with an initiator, then heated to 700 degrees and compressed by a compressor to 25 megapascals. After this, it enters the first part of the reactor, in which it is heated to 1800 degrees, and then into the second part of the reactor to carry out polymerization, which occurs at a temperature ranging from 190 to 300 degrees and a pressure from 130 to 250 megapascals. In total, ethylene is in the reactor for no more than 100 seconds. Its conversion rate is 25 percent. It depends on the type and quantity of initiator. The ethylene that has not reacted is removed from the resulting polyethylene, after which the product is cooled and packaged.

LDPE is produced in the form of both unpainted and colored granules. The production of low-density polyethylene is carried out using three main technologies. The first is polymerization, which occurs in suspension. The second is polymerization, which occurs in solution. Hexane serves as such a solution. The third is gas-phase polymerization. The most common method is solution polymerization. Polymerization in solution is carried out in a temperature range from 160 to 2500 degrees and pressure from 3.4 to 5.3 megapascals. Contact with the catalyst lasts approximately 10-15 minutes. Polyethylene is released from the solution as a result of solvent removal. First of all, in the evaporator, and then in the separator and in the vacuum chamber of the granulator. Granular polyethylene is steamed with water steam.


HDPE is produced in the form of both undyed and colored granules, and sometimes in powder form. The production of medium pressure polyethylene is carried out as a result of the polymerization of ethylene in solution. Medium pressure polyethylene is produced at a temperature of approximately 150 degrees, a pressure of no more than 4 megapascals, and also in the presence of a catalyst. PSD falls out of solution in the form of flakes. The product obtained in the manner described above has a weight-average molecular weight of no more than 400 thousand, and a degree of crystallinity of no more than 90 percent. The production of linear high-density polyethylene is carried out using chemical modification of LDPE. The process occurs at a temperature of 150 degrees and approximately 30-40 atmospheres. Linear low-density polyethylene is similar in structure to high-density polyethylene, but it has longer and more side branches. The production of linear polyethylene is carried out in two ways: the first is gas-phase polymerization, the second is liquid-phase polymerization. She is currently the most popular. As for the production of linear polyethylene by the second method, it is carried out in a liquefied bed reactor. Ethylene is fed into the reactor, and the polymer, in turn, is removed continuously. However, the level of the liquefied layer in the reactor is constantly maintained. The process occurs at a temperature of about one hundred degrees, pressure from 689 to 2068 kN/m2. The efficiency of this polymerization method in the liquid phase is lower than that of the gas phase.

Video how to do it:

It is worth noting that this method It also has its own advantages, namely: the installation size is much smaller than that of equipment for gas-phase polymerization, and the capital investment is much lower. Almost similar is the method in a reactor with a mixing device using Ziegler catalysts. This creates the maximum output. Not so long ago, technology began to be used for the production of linear polyethylene, which results in the use of metallocene catalysts. This technology makes it possible to obtain a higher molecular weight of the polymer, thereby increasing the strength of the product. LDPE, HDPE, PSD and LDPE differ from each other, both in their structure and properties, respectively, and they are used to solve various problems. In addition to the above methods of ethylene polymerization, there are others, but they are not widely used in industry.

Most often, a manufacturing business involves a large investment of initial capital. In addition, for a person unfamiliar with the technological process, mastering a new business can be quite difficult. The production of polyethylene can easily be considered a pleasant exception from general rules. For a successful start, there is no need to spend a lot of money at once, because the business quickly pays for itself and begins to generate a stable profit. But before we set up the production of polyethylene, let’s study its features, varieties, application possibilities and try to draw up a small business plan.

What is polyethylene?

This is the name of a synthetic polymer material based on ethylene, an organic colorless gas with a faint odor. It is the most productive material in the world. Such well-known products as ethyl alcohol, styrene, ethylbenzene, acetic acid, vinyl chloride and many others are synthesized from it.

Polyethylene is produced in the form of transparent or colored granules of various shapes. Their size is usually from three to five millimeters. The production of polyethylene granules involves the polymerization of ethylene gas under high and low pressure conditions, as well as using additional conditions. The main enterprises engaged in the production of polymer materials are located in Russia, Uzbekistan, Belarus, and South Korea.

Thanks to special properties The following grades of polyethylene are distinguished:

  • HDPE – high density;
  • LDPE – low density;
  • LLDPE – linear;
  • mLLDPE, MPE – metallocene linear;
  • MDPE – medium density;
  • HMWPE, VHMWPE – high molecular weight;
  • UHMWPE – ultra-high molecular weight;
  • EPE – foaming;
  • PEC – chlorinated.

There are also many materials that belong to the category of copolymers. Let's analyze several types that are most often found in industrial processing.

Low density polyethylene

The material has a plastic and soft structure. The production of high-density polyethylene (HDPE) involves the polymerization of ethylene in a tubular reactor or autoclave. The process takes place at a temperature of about 750 o C under a pressure of 1.5–3 kgf/cm2. The result is low-density granulate. The resulting raw materials are sent for the production of polyethylene packaging in contact with dry and bulk substances. Bags made from this material can withstand up to four kilograms of weight.

High Density Polymer

The production of low-density polyethylene (HDPE) involves a polymerization process using catalyst systems. The result is hard granules with high level density – 0.960 g/cm3. They are suitable for release cling film. Commercial granulate is produced colored and colorless. Sometimes the finished product is in the form of a powder.

What does foaming polyethylene look like?

This is the name given to a synthetic material that has a closed-porous structure. The production of foamed polyethylene is based on the strong heating of raw materials and subsequent whipping with gas (butane, freon and others). In practice, polyethylene foam is widely used as an excellent universal-purpose heat insulator.

What is cross-linked polyethylene?

The production of especially durable granulates is based on the use of ultra-high pressure. As a result of the process, strong adhesion of the molecules of the original substance occurs. The modified polymer is distinguished by high technical characteristics:

  • Resistant to high temperatures. The material softens only at temperatures above 150 o C, melts at 200 o C, and ignites only when it reaches 400 o C.
  • Increased degree of rigidity and tensile strength.
  • Preservation of basic characteristics under sudden changes in environmental conditions, as well as under the influence of chemical or biological destroyers.
  • High vapor and waterproofing properties.

Cross-linked polyethylene is actively used in the production of pressure pipes for cold and hot water supply. In addition, it is used in the manufacture of elements of heating systems and special building materials.

Where does a business start?

A polyethylene production plant may include several technological lines for the production of various products: polymer films, bags, caps, containers, pipes, bottle caps and much more. You should not organize several directions at once. It makes more sense to enter the polymer market as a manufacturer of polyethylene film and bags. Having established stable operation, you can gradually expand the range of products.

Practical experience shows that polyethylene production in Russia is guaranteed to provide a profitability level of at least 15%. Before starting a business, you need to take care of the registration permitting documents. You will have to visit the city administration, energy supervision, sanitary and epidemiological station, fire department, environmental service. If you work closely on these issues, you can completely meet the deadline of a month or a month and a half. Overhead costs will be only 15–20 thousand rubles.

The issue of processing residues

Before you start organizing the production of polyethylene products, think carefully about the issue of waste disposal. Under no circumstances should plastic scraps be buried in the ground or burned. First of all, it does a lot of harm. environment. And secondly, such actions face serious punishment.

The easiest and cheapest way is to hand over the polymer residues to a plastics processing plant. But it is worth keeping in mind that such a plant may not be in your locality. If the production of recycled polyethylene is planned, then it is best to launch the production of garbage bags. To do this, you will have to incur additional costs for the purchase of a production line. But in the end, the costs will be recouped by the quick sale of popular goods that are in steady demand among the population.

Purchase of capital equipment

The choice of production lines today is quite large. As an example, consider the list of machines and units that will be required for the production of film with the further formation of packages for household use from it.

Necessary equipment for polyethylene production:

  • Extruder (extrusion unit)– a machine for converting raw granules into film by blowing from bottom to top. The width of the sleeve must correspond to the size of the produced bags (300–550 mm). The unit also includes a device for folding seams.
  • Bag making machine– a machine for cutting film or sleeves into pieces of a certain length. The device also seals the workpiece on one side, forming the finished product.
  • Die-cutting press with a set of molds for the production of T-shirt bags or bags with a slotted handle.
  • Machine for making plastic clips for packaging.
  • Flexograph is a machine for applying printed images to the sleeve of a bag.

If you don’t have a lot of start-up capital, then at first you can completely do without a printing device. It would be wiser to turn to specialized printing centers for drawing services.

To process production waste, you will need to purchase a special crushing apparatus. The approximate cost of a production line with delivery and setup of machines is 1.5–2 million rubles.

Additional equipment items

The production of polyethylene also requires the purchase of warehouse equipment (racks, tables, stands, boxes, etc.) for storing raw materials and finished products. Don't forget about office equipment. Additional equipment can increase the total cost by 50–60 thousand rubles.

Production workshops require the installation of a high-quality, powerful ventilation unit and fire protection system. Special requirements are imposed on warehouse premises: the primary raw material for the production of polyethylene (granulate) tends to absorb fumes and gases. Failure to comply with the rules for storing raw materials can lead to deterioration in the quality of manufactured products.

Necessary raw materials

The main synthetic material for the production of polyethylene products is polymer granules. They have dimensions of 3–5 mm and are available in the form of a ball, cube, cylinder or small crumbs. The second source of raw materials is recycling of waste or process residues.

Receiving the film

Polyethylene production technology includes several stages that need to be completed in order to obtain bright and convenient bags from the raw material.

  • Polymer granules are loaded into the hopper compartment of the extruder. From here they are picked up using a feed auger. The container maintains a constant temperature in the range from 180 to 240 degrees. During the movement, the granules, heating up greatly, are melted into a homogeneous mass. The resulting mixture is pressed through the forming hole, resulting in a polyethylene film in the form of a sleeve (or pipe). Automatic adjustment of the extruder allows you to produce a finished web of a given thickness and width.
  • The resulting sleeve is gradually cooled and rolled out by rollers.
  • An automatic knife cuts the fabric into two strips of equal width.
  • The finished sleeve enters the winder, which twists the film into rolls. The scraps are packaged separately and are subsequently recycled.

Drawing

If necessary, color images are printed using flexography.

  • The special paint is diluted with alcohol and stirred constantly. This is necessary so that the solution does not lose the desired viscosity.
  • The dispenser directs certain portions of the dye to the rollers, which make an impression on the film. After applying the pattern, the polyethylene is again wound into a roll.

Formation of packages

The next stage allows you to create the base for the bags.

  • The roll with the printed image is placed in a bag-making machine. By using special devices a “pattern” of the future bag is cut out of the film and a bottom fold is formed.
  • Passing polyethylene blanks through a stamping press, holes are made for the handles. Guillotine cuts off top part bag to further secure the plastic handles, or cut out a T-shirt.
  • A welding knife joins the edges of the bag at a temperature of 180 degrees, resulting in a whole product.

The final process is checking the quality of seams and fasteners.

Conclusion

As we were able to see, the production of polyethylene is a rather complex chemical process that can only be done by large specialized industrial enterprises. And the technology for processing finished granules seems to be a fairly simple matter that does not require in-depth knowledge. Having started your business by installing a production line, you can fully return the money spent in 2-3 years.

The raw material for the production of polyethylene films are polyethylene granules obtained by polymerization of ethylene. To produce high- and low-density polyethylene, two technologies are used, which involve going through the process at different conditions polymerization. HDPE and LDPE are produced at different temperatures and pressure. As a result, materials acquire different physical and chemical properties.

A little about production technology

Granules obtained under high pressure (1000-3000 kg/cm 2) have a lower intrinsic density of 0.925 g/cm 3. The film obtained in this way has a more “oily” feel to the touch. It is relatively transparent and stretches well without tearing. The material is characterized by shorter polymer chains. It is less crystalline and melts at temperatures above 100 C. These characteristics relate to high-density polyethylene, which is often referred to as LDPE.

Low-density polyethylene or HDPE polymerizes at a pressure of 1-5 kg/cm 2 and reaches a density of 0.945 g/cm 3 . This type of polyethylene film is more crystalline, the polymer chains in it are longer, and less transparent. Melting HDPE film requires more than heat- from 120C, so the energy costs for its production are higher. But during operation, this type of polyethylene film can withstand higher temperatures.

Popular facts

It is very easy to distinguish LDPE from HDPE by eye: a polyethylene film made from a low-pressure material always “rusts” when crushed. Domestic abbreviations are different from foreign ones. LDPE corresponds to LDPE (Low Density PolyEthylene), and HDPE corresponds to HDPE (High Density PolyEthylene). This is due to the fact that in Russia the pressure during the polymerization of polyethylene is taken as the basis for the classification, and beyond its borders - the density of the granules used. A material made at high pressure has a low density, and at low pressure, on the contrary, it has a high density.

Where do we most often see products made from polyethylene film? Of course in stores. Remember the rustling matte packaging bags and T-shirt bags and know that they are made of high-density low-density polyethylene. While smooth packaging bags and bags with welded and die-cut handles are made of low-density high-density polyethylene. Products made from LDPE have a more aesthetic appearance and allow you to apply bright, colorful designs to your surface.

In conclusion, it is worth saying that currently polyethylene has become the most in mass form polymer material used in the packaging industry. He was invented first, but still its popularity in packaging remains one of the highest.


The production of polymer film is accompanied by dangerous emissions into the atmosphere and is classified as harmful. And when organizing it, special requirements should be taken into account.

Primary requirements

The company should be located in industrial zone. The room must be heated and have a forced ventilation system. Water supply is mandatory, its consumption may increase when using special processing devices.

For uninterrupted operation of the line, you will need a three-phase electrical connection (380 V) and grounding of all elements of the circuit. A system is required fire safety and evacuation plan. The placement of equipment and organization of workplaces must comply with standards GOST.

Workshop characteristics

The total area of ​​the workshop should be not less than 300 square meters , and the ceiling height is at least 8 m. Non-combustible materials must be used for interior decoration.

The room should be divided into 3 compartments:

  • manufacturing facility;
  • warehouses that must be steam- and waterproofed;
  • showroom.

Equipment for the production of polyethylene film

When setting up polyethylene production, it is necessary to purchase(in dollars):

  • Extruder 60000-300000
  • Flexo printing machine 30000-50000
  • Special machine for making packaging clips 20000-40000
  • Multifunctional bag making machine 8000-10000

How can you cut costs?

Buying a used line will help you save up to 50% on your investment. In this case, the dollar costs would be as follows:

  • Extruder 6000-8000
  • Flexo printing machine 3000-6000
  • Machine for making plastic clips for packaging 10000-20000
  • Bag making machine 4000

Which equipment to choose - used or new?

The new equipment has a number of advantages:

  • manufacturer's warranty;
  • durability;
  • implementation in the future.

But its main drawback is the high price that a novice businessman is not willing to pay. In this case, purchasing used equipment is the best option.

But the selection of such a line must be entrusted to an experienced specialist so as not to buy heavily worn or low-quality equipment.

Raw materials for the production of polyethylene film

Produced from polymer granules using 2 types of polyethylene with different pressures:

  • high (LDPE) for packaging and storage of food products;
  • low (HDPE) for bulk goods.

It is most profitable to buy South Korean granulate, the cost of a ton of the substance is 340 euros. But you can also use domestic raw materials; their price ranges from 420-750 dollars. To further reduce the cost of production, you can switch to secondary granulate.


Technology for the production of polyethylene film

The resulting layer is cooled, rolled out with a roller and cut into equal parts using an automatic machine.

The design is applied using rollers, to which paint is supplied through a special dispenser.

The finished fabric enters the bag-making machine, where a product template is formed. The press makes holes for the handles, and a special machine seals the edges. Next comes packaging of products and quality control.

Recruitment

For productive work, it is enough to hire 6 people: a director, an accountant, a technologist and 3 workers.

Film production technology is quite simple, servicing the machines is easy. Therefore, the production of polyethylene can be entrusted to beginners, having previously taught them everything.

Enterprise profitability

The initial investment will be about $38,000. for the purchase of used equipment and paperwork. And the monthly expenses in dollars will be as follows:

  • rental premises 600;
  • heating, electricity 200;
  • utilities 160;
  • employee salary 2700;
  • taxes 450.

total amount will be 3810 dollars.

The production capacity of the line allows the production of 70 bags in 60 seconds. What if the wholesale price of the product is 0.01 dollars? will allow you to receive a monthly income of $6,000.

And the net profit will be about $2,200. Taking into account the initial investment, the enterprise should pay for itself in 1.5 years.

Polyethylene production is very But the calculations presented were based on ideal conditions demand.

In reality, profits will depend on sales opportunities and inflation.




Ethylene. Ethylene is a chemical compound described by the formula C2H4, a colorless gas with a faint odor. It is the simplest alkene (olefin). Contains a double bond and therefore belongs to unsaturated compounds and is highly reactive. Ethylene practically does not occur in nature. It is formed in small quantities in the tissues of plants and animals as an intermediate metabolic product. Plays an extremely important role in industry, the most produced organic compound in the world.

Currently, the main source of ethylene production is the pyrolysis of gaseous and liquid saturated hydrocarbons: ethane, propane and straight distilled gasoline.

Properties of ethylene:

Chemical formula H2C=CH2

Molecular weight 28.05

State - gaseous

Melting point 103.8 K (-169.2°C)

Boiling point 169.3 K (-103.7 ° C)

Density at normal conditions 1.26 kg/m 3

Density of liquid ethylene at 163.2 K (-109.8 ° C) - 610 kg/m 3

Flammability temperature 728 K (455°C)

Ethylene purity. For polymerization, ethylene must be thoroughly purified from impurities. Impurities in ethylene are divided into two main groups - inert and active. An inert impurity present in a noticeable amount, for example 5-10%, reduces the ethylene concentration by a significant amount, given the low compressibility of ethylene.

Active impurities in ethylene, such as vinyl-type compounds, usually copolymerize with ethylene, change the properties of the resulting polymer and affect the rate of polymerization.

Depending on the impurity content technical specifications It is planned to produce three grades of liquefied ethylene: A, B and C. Ethylene grades A and B are used for the production of polyethylene and ethylene oxide. Ethylene grade B - for the production of other organic products. Liquefied ethylene must comply with the requirements and standards.

Catalysts (initiators). Molecular oxygen and organic peroxides are mainly used as catalysts for the polymerization of ethylene. Of the peroxides in industry, the most widely used are di-tert-butyl peroxide, tert-butyl perbenzoate, etc. The effect of the initiator depends on the degree and rate of its decomposition at a given temperature and on the ability of the resulting radicals to react with the monomer.

Another factor characterizing the initiator is the content of active oxygen, i.e. theoretical percentage of active oxygen in pure peroxide.

In dry form, peroxides are explosive; their solutions in organic solvents are more stable and less explosive. Storage of initiators must be carried out under certain temperature conditions.

The main properties of the most common peroxide initiators are described below.

Di-tert-butyl peroxide (C8H18O2)

Application temperature 513-553 K (240-280°C)

Molecular weight 146.2

Liquid, density 793 kg/m 3

Boiling point at 0.1 MPa - 463 K (190°C)

Peroxide is insoluble in water, soluble in most organic solvents

Storage temperature 298 K (20°C).

Tert-butyl perbenzoate (C11H14O3)

Application temperature 453-513 K (180-240°C)

Molecular weight 194

Liquid, density at 293 K (20°C) - 1040 kg/m 3

Boiling point at 0.1 MPa - 397 K (124°C)

Storage temperature 293 K (20°C).