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Methods for producing polyethylene. Low and high pressure polyethylene for packaging materials

Currently, the domestic polyethylene market is abstracted from the influence of the global industry, which is provoked by the rise in prices of imported raw materials and products. This created new conditions for activating one's own resources and capabilities. As experts point out, the Russian polyethylene production industry has all the necessary factors for successful independent development. In particular, this is ensured a large number strong manufacturers, annually supplying the market with more than 1.5 million tons of high-quality polyethylene.

Top three leaders in polyethylene production in Russia

Companies producing polyethylene polymer typically produce a wide range of products chemical industry, which ensures the integrated nature of production, significant cost savings and, as a result, a reduction in the cost of the final product. Best results in 2015 the following companies showed:

  • Kazanorgsintez;
  • Tomskneftekhim;
  • "Nizhnekamskneftekhim"

The leader of the Russian polyethylene market is PJSC Kazanorgsintez. At the end of 2015, the factories of this enterprise produced about 42% of the total volume of PE. In total, the company structure includes 7 plants that produce both low- and low-density polyethylene. high pressure, as well as a wide range of other polymers. Products are supplied to domestic Russian market and is actively exported.

The second position at the end of last year was taken by Tomskneftekhim LLC, an enterprise formed by PJSC SIBUR Holding, which is a leading integrated company in the Russian gas processing and petrochemical sector. In 2015, Tomskneftekhim produced 14.6% of the total volume of polyethylene produced in Russia. The main specialization of the company is the production of LDPE. The necessary raw materials are completely produced at our own production facilities.

Stable good results demonstrates PJSC Nizhnekamskneftekhim. Based on the results of 2015, this company produced 12.5 times the total volume of Russian polyethylene. The company is part of the TAIF group, of which industry leader Kazanorgsintez is also a part. At the production facilities of the Nizhnekamskneftekhim company, many types of polymers are produced, and the production of PE of various densities is one of priority areas work of the enterprise. One of the features of this company is its developed production infrastructure - already 40 years ago it organized a direct ethylene pipeline to Kazan, which had a length of 280 km.

A large volume of produced polyethylene is sold to the domestic market. Many companies are engaged in its implementation, in particular, Unitrade LLC, whose assortment includes polyethylene from large quantity domestic producers. These are not only leading companies, but also other influential players in this market niche.

Other major manufacturers

The following companies also produce significant volumes of polyethylene:

  • PJSC "Ufaorgsintez";
  • OJSC "Salavatnefteorgsintez";
  • JSC "Stavrolen";
  • JSC "Angarsk Plant"

The Bashkir company Ufaorgsintez is technologically integrated with the oil giant Bashneft. Specializes in the production of a wide range of products organic synthesis, including producing large volumes of polyethylene of various grades and densities. One of the areas of activity of the enterprise is the processing of associated gases from the petrochemical industry, from which raw materials are obtained for the production of polyethylene. This feature of the work allows PJSC Ufaorgsintez to optimize technologically complex process PE production.

OJSC Salavatnefteorgsintez is a full-fledged plant, which includes a large number of production units. Today the company is fully integrated into the structure of PJSC Gazprom. The range of manufactured products is varied; the plant produces not only various grades of polyethylene, but also fuel, paint and varnish products, fertilizers, etc.

A special feature of JSC Stavrolen is the fact that the company initially specialized in the production of polyethylene. In 1998, the company became part of the giant Lukoil-Neftekhim, which was followed by a large-scale re-equipment of production, Stavrolen received a stable supply of raw materials and significantly increased the volume of products produced. Today, the manufacturer's product range includes many grades of polyethylene of varying densities.

Located in Eastern Siberia JSC "Angarsk Plant" also specializes in the production of a large number of petrochemical products, among which polyethylene occupies a significant place. In particular, the company produces impressive volumes of various grades of LDPE. JSC Angarsk Plant is part of PJSC NK Rosneft, which ensures stable and large supplies of raw materials, established sales channels and economic stability.

As you can see, polyethylene production in Russia is carried out mainly by specialized companies that are part of the country's largest petrochemical holdings. This provides, on the one hand, a qualified approach to this knowledge-intensive industry, on the other hand, stable performance indicators and the opportunity to invest in the development of the domestic PE production sector.

Industrial tubular polymerization reactors are series-connected pipe-in-pipe heat exchangers. The reactor tubes have a variable diameter (50 – 70 mm). The individual links of the “tubular” are connected by massive hollow slabs. Pipes and rolls are equipped with jackets connected in series to each other. Superheated water with a temperature of 190 - 230 0 C is used as a coolant for heating ethylene and removing excess heat, which enters the jacket of a tubular reactor in a countercurrent to ethylene and to the flow of the reaction mass. Application high temperatures necessary to prevent the formation of a polymer film on the pipe walls. To maintain constant temperature regime in the reactor and to ensure effective heat removal, additional ethylene and initiator are introduced into various zones along the length of the reactor. A multi-zone reactor is more productive than a single-zone reactor. A single-zone reactor at a maximum reaction temperature (300 0 C) provides 15–17% ethylene conversion in one pass. A two-zone reactor achieves 21–24% conversion at the same temperature. In a three-zone reactor, the conversion degree increases to 26 - 30%. The productivity of a four-zone device increases slightly compared to a three-zone one.

To obtain constant indicators of the properties of polyethylene, it is necessary to maintain the temperature in the reactor at the same level in zones.

The performance of the reactor depends on its size, so they are currently used with different pipe lengths and diameters. For high-power reactors, the pipe length reaches 1000 m or more.

The technological process for the production of high-density polyethylene in a tubular reactor consists of the following stages:

· mixing fresh ethylene with return gas and oxygen,

· two-stage gas compression,

· polymerization of ethylene in the condensed phase (ethylene density 400 – 500 kg/m 3),

· separation of high-density polyethylene and unreacted ethylene entering recycling,

· granulation of polyethylene.

For coloring, stabilization and filling, high-density polyethylene is injected with appropriate additives, after which it is melted and granulated.

In Fig. 1. A schematic diagram of the production of high-density polyethylene in a tubular reactor using a continuous method is presented.

From the gas separation shop, fresh ethylene at a pressure of 0.8 - 1.1 MPa enters the collector 1 and then into the mixer 2 , in which there is no pressure with return ethylene. Next, oxygen is introduced into the flow and the mixture enters a three-stage compressor of the first stage 3 , where it compresses to 25 MPa. After each compression stage, ethylene is cooled in refrigerators, separated from the lubricant in separators, and then enters the mixer 4 , in which it is mixed with return high-pressure ethylene from the separator 7 . The mixture is then sent to a two-stage compressor 5 the second cascade, where it is compressed to 245 MPa. After the first stage of compression, ethylene is cooled in a refrigerator, cleared of lubricant in separators, and after the second stage at a temperature of about 70 0 C without cooling, it enters a tubular reactor through three inlets 6 for polymerization.

Ethylene. Ethylene -- chemical compound, described by the formula C2H4, is 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 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. From peroxides in industry greatest application found 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).

Most often, a manufacturing business involves a large investment of initial capital. Moreover, for a person unfamiliar with 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 ethanol, styrene, ethylbenzene, acetic acid, vinyl chloride and many others.

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

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

  • HDPE – high density;
  • LDPE – low density;
  • LLDPE – linear;
  • mLLDPE, MPE – linear metallocene;
  • 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 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 molecules occurs starting material. 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 is more expedient to enter the polymer market as a manufacturer polyethylene film and packages. 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 an enterprise, you need to take care of obtaining permits. 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, for similar actions faces 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 establish production 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. Approximate cost technological line with delivery and setup of machines - 1.5–2 million rubles.

Additional equipment items

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

Production workshops need to be equipped with 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 measure 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 setup 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 then sent for recycling.

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. Using special devices, a “pattern” of the future bag is cut out of the film and a bottom fold is formed.
  • By 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 have seen, polyethylene production is quite complex. chemical process, which is only possible for large specialized industrial enterprises. And the technology for processing finished granules seems quite simple matter, which does not require in-depth knowledge. Having started your business by installing some production line, you can fully return the money spent in 2-3 years.