Scheme for the production of polyethylene. Feedstock for polyethylene film

The first experience of ethylene polymerization at the end of the 19th century was received by a native of Russia - scientist Gustavson by carrying out this process with AlBr3 catalyst. For many years, polyethylene was produced in small quantities, but in 1938 the process industrial production mastered by the British. At that time, the polymerization method was not yet perfect.

1952 made a breakthrough in the process of industrial production. The German chemist Ziegler invented an effective version of ethylene polymerization under the action of metal-organic catalysts. However, the real technology for the production of polyethylene is based on this method.

Raw material

The starting material for production is ethene, the simplest representative of a number of alkenes. The simplicity of this production method is highly dependent on the presence of ethyl alcohol, which is used as a raw material. Modern industrial lines for polymer production are developed taking into account their work on oil and associated gases– readily available fractions of oil.

Such gases are released during pyrolysis or cracking of petroleum products at very high temperatures ah and contain impurities H2, CH4, C2H6 and other gases. Associated gas, in turn, contains such components as paraffin gases, therefore, when they are subjected to heat treatment, ethylene is obtained with a high yield.

High pressure polyethylene production technology

The process of obtaining PE proceeds according to a radical mechanism. When carrying out, various kinds of initiators are used to lower the activation threshold of the molecule. Examples of such are hydrogen peroxide, organic peroxides, O2, nitriles. The radical mechanism, in general, does not differ from conventional polymerization:

• Stage 1 - initiation;
• stage 2 - chain extension;
• Stage 3 - open circuit.

The chain is initiated by the release of free radicals upon thermal treatment of their source. Ethene reacts with the released radical, is endowed with a certain Eact, thereby increasing the number of monomer molecules around itself. Subsequently, the chain grows.

Process technology

There are two options for the polymerization process - either polyethylene is formed in bulk or in suspension. The first received and is a collection of processes.

Ethylene gas, which is a mixture and not a pure substance, first passes through a filtration path through a fabric filter that traps mechanical impurities. Further, the initiator is brought to the purified ethene in a cylinder, the volume of which is calculated based on the process conditions. The correction is made for the highest polymer yield.

After, the mixture is transported, filtered and subjected to compression in two stages. At the outlet of the reactor, almost pure polyethylene is obtained with an admixture of ethylene, which is eliminated by throttling the mixture in the receiver under low pressure.

Low pressure polyethylene production technology

The sources of raw materials for the production of this type of polyethylene are pure ethylene without impurities and a catalyst - aluminum triethylate and Ti tetrachloride. Al(C2H5)3 can be replaced by either diethylaluminum chloride or aluminum ethoxide dichloride. The catalyst is obtained in 2 stages.

Process technology

For this process of obtaining PE low pressure characterized by both periodicity and continuity. The process scheme also depends on the choice of technology, each of which is different in the design of equipment, the volume of reactors, the method of cleaning polyethylene from impurities, etc.

The most common polymer production scheme includes three continuous stages: raw material polymerization, product purification from catalyst residues and its drying. Apparatus for catalytic feeding release a five percent solution of the mixed catalyst into the measuring tank, after which it enters the tank, where it is mixed with an organic solvent to the required concentration of 0.2%. From the tank, the finished catalyst mixture is discharged into the reactor, where it is maintained at the required pressure.

Ethylene is fed into the reactor from below, where it subsequently mixes with the catalyst and forms a working mixture. For the production of polyethylene under reduced pressure, contamination of the product with residues of the catalyst mixture is typical, which change its color to brown. Purification of the main product is carried out by heating the mixture, resulting in the destruction of the catalyst, further separation of impurities and their direct filtration from polyethylene.

The moistened product is sent to the dryer drying chambers bunker, where it is completely cleaned on a nitrogen fluidized bed (T = 373 K). Dry powder is poured from the bunker to the pneumatic line, where it is sent for granulation. Dust with polyethylene particles, remaining after nitrogen purification, is sent to the same line.

In this article:

Plastic bags are used everywhere: in supermarkets and shops, for standard and gift packaging, for food storage and garbage disposal.

All applications plastic bags and do not list. Gone are the days when our compatriots preferred to use rag bags, and plastic bags were carefully folded and stored. Today, a plastic bag fulfills its main purpose - to be a disposable means for packaging and comfortable transportation of products. And this means that the demand for them will be stable and not prone to decline.

In addition to their obvious functions, packages have become a means of effective mobile advertising - after all, almost every large company, boutique or supermarket has a branded package with the company's logo, a list of services and contact details that are distributed as a gift. And the client is pleased, and there is never too much advertising.

Analysis of the demand for products (plastic bags) and the sales market

According to statistics, there are enough unfilled niches in the market of domestic production, because 20% of polyethylene products continue to come from foreign manufacturers. At the same time, the main competitors of domestic entrepreneurs are Turkish and Chinese-made bags, which are distinguished by an extremely low price and appropriate quality. Torn handles, not completely soldered seams, falling out bottoms - just a small list of "charms" from buying such products. But for our consumer, the price has always been a decisive factor, so there is such competition, especially in the border regions.

However, this only applies to direct wholesale sales finished products. It is much more profitable to work on order, concluding contracts for the supply of packaging material and ready-made packages for various trade, manufacturing, construction and agricultural enterprises. This is where the “company image” rule comes into play: no self-respecting company will offer the buyer a product in low-quality packaging.

Polyethylene products are in demand in any region. Moreover, even if a large plant is already operating in your city, medium and small businesses will freely find their niche by studying the offers of competitors. There are many types of plastic bags: banana bags, T-shirt bags, garbage bags, gift bags, promotional packaging with a logo, single-layer, multi-layer, various sizes, colors and shapes. The task of the entrepreneur is to find products with the highest demand, or to occupy a niche not covered by other manufacturers.

Choosing a strategy and legal registration of a business

Opening the production of plastic bags, you can go in two ways:

• full-cycle production (from film production to the production of packages of any configuration);
• partial production (from the purchase of finished film, applying images, cutting into forms with subsequent soldering).

Consider the full cycle as more perspective view business. Although such an enterprise will require more capital investments, marketing opportunities, the diversity of products and, accordingly, profitability will be much higher. In addition, such an enterprise can thus become a supplier of finished film for part-time production.

Possibilities of using the finished film:

• universal packaging material,
• building waterproofing,
• material for greenhouses, greenhouses and other needs of the agricultural sector,
• protection against pollution during construction or repair work.

Optimal organizational form for the production of polyethylene products - entity on a simplified taxation system.

When registering an enterprise, you must specify the following OKVED codes:

• 25.2 - Manufacture of plastic products
• 25.22 - Manufacture of plastic products for packaging
• 51.47 — Wholesale other non-food consumer goods.

To start the workshop, you will need a certificate for production, permits obtained from the local administration, sanitary-epidemiological and environmental services, energy supervision, and fire protection. The production of film for plastic bags must comply with GOST 10354-82 (food film certification is required to be confirmed every 3 months). But in order to obtain such a certificate, you must run production line(of course, after obtaining all permits for production), and provide the received samples for an expert opinion.

Plastic bag production facility

The production of plastic film is an environmentally harmful production, so there are a number of specific requirements for choosing a room:

• the production workshop or mini-factory should be located in an industrial or suburban non-residential area;
• the presence of supply and exhaust ventilation, heating and humidity control in the workshop and in the warehouse;
• three-phase electrical connection, grounding of batteries; - ceiling height of at least 8 m (extrusion machine height ~ 6 m), interior decoration of walls, floor, ceiling - from non-combustible materials;
• placement of production equipment in the shop premises must comply with GOST 12.3.002-74;
• the presence of a fire-fighting system, the possibility of safe evacuation in case of fire;
• the organization of workplaces must comply with the requirements of GOSTs 12.2.061-81 and 12.3.002-74, as well as ergonomic characteristics in accordance with GOSTs 12.2.033-78, 12.2.032-78.

To accommodate a complex of production equipment, a room of 300 square meters will be needed, which will be divided into three parts: a production workshop (180 m 2), a warehouse for raw materials and finished products (80 m 2), an office and an exhibition hall (40 m).

Equipment for the production of plastic bags

For the production of polyethylene film with the subsequent formation of bags, it is planned to purchase a production line consisting of the following equipment:

1) extruder– converter of raw material granules into a film (300-550 mm wide, 0.009-0.10 mm thick), by bottom-up blowing method. Productivity - 40 kg / hour;

2) Flexo printing machine– for printing drawings, logos and other images;

3) Plastic Clip Making Machine for Packaging;

4)Bag Making Multifunctional Machine, with a built-in punching press, equipped with a servo drive, a photosensor, a conveyor, thermal needles, and allowing the production of packages of various modifications, incl. T-shirt, banana, double-bottom bags, trash bags, food packaging with a plastic clip, etc.

The cost of the production line with delivery, setup, staff training and signal launch is 3,840,000 rubles.

In addition to machine tools, it is planned to purchase office, exhibition and storage equipment (racks, boxes, boxes, tables, stands) for placing raw materials, finished products and equipping workplaces for staff. The cost of additional equipment for the workshop is 60,000 rubles.

Raw materials for the production of polyethylene bags

Polyethylene film is made from first grade or recycled polymer granules.

Two types of raw materials are used:

• HDPE (low pressure polyethylene, GOST 16338-85), for contact with loose and dry products;
• LDPE (high pressure polyethylene, GOST 16337-77), designed for food packaging).

South Korean granulate is recognized as the cheapest raw material (~ $ 380 per ton), but there are many other types of domestic or foreign production, with a price range from $ 420 to $ 750 per ton. To produce a color film, special dyes are added to the raw material ($ 15-50 per 1 kg).

At production of garbage bags or other types of non-food film, you can also use secondary granulate, which is much cheaper, because it is made from polyethylene waste, but the quality of such raw materials is correspondingly low.

Technology for the production of plastic bags

1. Polymer granules are loaded into extruder hopper from where the feed auger picks them up. Here, the temperature is maintained from 180 0 C to 240 0 C, and as they move, the granules are heated, melting into a homogeneous mass. As a result of extrusion, a polyethylene film is formed in the form of a pipe (sleeve). One extruder makes it possible to produce a film of various thicknesses and widths by special adjustment.

2. The polyethylene "pipe" is gradually cooled, then rolled out with rollers.

3. The sleeve is cut with an automatic knife so that two identical strips of the desired width are obtained.

4. The winder winds the film into rolls (cuts are packed separately for recycling). When the width of the roll reaches the set size, the roll is moved away by the operator and the next one starts to be wound. And so on until the end of the produced film.

5. Drawing a picture. The paint is diluted with alcohol and constantly mixed so as not to lose viscosity.

6. With the help of a dispenser, the dye goes to special ink rollers, which print the pattern. After printing, the film is rewound into rolls.

7. The finished roll enters the bag making machine, where a template for future bags is formed, the bottom fold is highlighted.

8. The stamping press makes holes for the handles (cuts out the “shirt”, cuts off the top to attach the plastic fastener - it all depends on the template).

9. The welding surface connects the edges, sealing with heating up to 180 0 С. Finished packages are formed into packs of 100 pieces.

10. Quality control. Checking seams and fasteners.

Business plan for the production of plastic bags

The cost of manufacturing plastic bags is calculated individually for each order, since in addition to the price of the used granulate, it depends on a number of additional factors:

• size, shape, package design,
• film density,
• the presence of a reinforced handle and bottom folds,
• color printing (the number of shades used, the area of ​​the pattern, the presence of complex combinations, one-sided, two-sided printing, etc.).

To calculate the payback of a business project, let's take the production of white opaque bags with a die-cut handle, 40 cm wide, 60 cm high and 16 microns thick side fold.

The cost of such a package made from HDPE granules is 0.13 kopecks, and the wholesale price is 0.70 kopecks. Considering that the production capacity allows to produce about 70 pieces / minute, then with one-shift work and 22 working days, the profit will be: 60 minutes * 8 hours * 22 rubles / day * 70 pieces (0.70 - 0.13 rubles) \u003d 421 344 rubles / month.

Expenditure part:

• rent of a production workshop (300 m 2 * 150 rubles / m 2) = 45,000 rubles / month,
• electricity - 8,000 rubles / month,
• heating (for 6 months of the heating season, divided in equal parts for all months of the year),
• water and others public Utilities- 12,000 rubles / month,
• staff salary (6 people: director, accountant, technologist, 3 workers) - 128,000 rubles / month.,
• income tax (15% of profit minus expenses) - 34,252 rubles per month.

Total expenses: 227,252 rubles / month.

Net profit: 421 344 – 227 252 = 194,092 rubles/month.

Profitability calculation:

Initial investment (3,930,000 rubles):

• purchase of equipment - 3,840,000 rubles,
• additional equipment - 60,000 rubles,
• costs for documenting production (opening law firm, obtaining the necessary permits and certification of products) - 30,000 rubles.

With an estimated profit of 194,092 rubles / month, the initial investment will pay off in 1 year and 9 months.

It should be borne in mind that the calculations were based on one of the simplest options for finished products, and everything depends on demand and sales opportunities in your region. For example, the sale price of color packages of the same parameters will be 15% higher, with one central one-color image - by 34% (with an increase in cost by 5 and 10%, respectively). In addition, the company can accept orders for the manufacture of LDPE or HDPE packages according to individual layouts, and the profitability of such projects is much higher.

Products made of polyethylene (PE), along with other polymeric materials, are widely used in the world as an excellent substitute for such traditional materials as metals, wood, glass, natural fibers, textile industry and other industries. Polypropylene pipes are rapidly replacing metal pipes in public utilities and industry. In this regard, the world production of polypropylene is growing at a very fast pace.
Polyethylene of various grades (LLDPE, LDPE, HDPE) continues to hold a leading position among large-capacity plastics. In 2012, the world production of polymers amounted to 211 million tons, with 38% or 80 million tons. accounted for PE of various brands. It is expected that in 2015 the world production of PE will reach 105 million tons.
Figure 1. The ratio of different types of polymers in world production, 2012

PE can be considered the most popular polymeric material, primarily due to its comparative simplicity, reliability, and relatively low cost of its manufacture. So for the production of 1 ton of PE in all modern technologies no more than 1.005 - 1.015 tons of ethylene and 400-800 kWh of electricity are required. In most areas where plastics are used, there is no need to use other materials. For the same reason, the second most popular material is polypropylene (25%).
Polypropylene and polyethylene together can be called the most "universal" plastics. According to their characteristics, both of them are not leaders. In terms of optical properties, all other materials leave behind polycarbonates, in terms of mechanical characteristics - polyamides, in terms of electrical insulating properties - PVC, and PET is ideal for blow molding products. Not being an ideal material in all respects, PE in all areas shows a moderate second or third result. , which gives it the ability to be used for all purposes, and the combination of these properties with a much lower price makes PE the most popular polymer material in the world.
PE was first obtained in 1873; its father can be considered the great Russian chemist Alexander Mikhailovich Butlerov, who was the first to study the polymerization reactions of alkenes. Another father can be considered his successor, the Russian chemist Gavrila Gavrilovich Gustevson, who continued to study polymerization reactions. In the West, the German chemist Hans von Pechmann, who obtained PE in a more advanced way in 1899, is considered to be the discoverer of polyethylene, then it was commonly called "polymethylene".
Like many similar discoveries, PE was far ahead of its time, so it was undeservedly forgotten for more than 30 years. This can be understood, no one at the beginning of the century could have imagined that an incomprehensible jelly-like substance would make a real technological revolution, seriously weakening the position of traditional materials.
The first industrial technology for the production of PE was in 1935 the gas-phase technology of the English company ICI (Imperial Chemical Industries) ). After that, the first PE production plants began to appear in Europe and the USA. Initially, the main purpose of this polyethylene was the production of wires, due to the good electrical insulating properties of polyethylene. The new polyethylene insulated wires replaced rubber wires and were in widespread use until they were replaced by PVC wires. However, time itself contributed to the real triumph of PE. The post-war years were characterized by an unprecedented growth in the purchasing power of citizens, an increased demand for food and light industry goods. The first supermarkets appeared. It was then that the plastic bag began to gain immense popularity around the world.
It is noteworthy that one of the two PE production units operating at OJSC Kazanorgsintez is the unit of the English company ICI , sample 1935, it works to the present, being the oldest installation operating in Russia.
To understand the differences in production technologies, it is important to understand the specific composition of the polyethylene products produced. A clear distinction is made between high-pressure and low-density polyethylene and low-pressure and high-density polyethylene.
High density polyethylene LDPE/ LDPE
High pressure polyethylene (LDPE) aka low density polyethylene (LDPE), in the English name LDPE (Low-Density PE) is obtained at a high temperature of 200-260 0 C and a pressure of 150-300 MPa in the presence of a polymerization initiator (oxygen or, more often, organic peroxide). Ego density lies in the range of 0.9 - 0.93 g / cm 3.
Low pressure polyethylene HDPE/ HDPE
Low pressure polyethylene (HDPE) aka high density polyethylene (HDPE), in the English name HDPE (High-Density PE) is obtained at a temperature of 120-1500C, a pressure below 0.1-2 MPa in the presence of a Ziegler-Natta catalyst (mixture TiCl 4 and AlCl 3 ).
table one . Comparative indicators of different types of polyethylene.

Indicator	LDPE	PESD	HDPE
The total number of CH 3 groups per 1000 carbon atoms:	21,6	5	1,5
The number of end groups CH 3 per 1000 carbon atoms:	4,5	2	1,5
Ethyl branches	14,4	1	1
Total number of double bonds per 1000 carbons	0,4—0,6	0,4—0,7	1,1-1,5
including:
vinyl double bonds (R-CH=CH 2),%	17	43	87
vinylidene double bonds , %	71	32	7
trans-vinylene double bonds (R-CH=CH-R"), %	12	25	6
Degree of crystallinity, %	50-65	75-85	80-90
Density, g/cm³	0,9-0,93	0,93-0,94	0,94-0,96

Sometimes medium-density polyethylene (MDPE) is also distinguished, but it is usually referred to as HDPE, because. these products have the same density and weight, and the pressure during the polymerization process at the so-called low and medium pressures is most often the same. Often, especially often in foreign literature, it is customary to single out various high-pressure PE linear products separately, as is done in Figure 1, but in general it will not be a mistake to consider them together with other LDPE products.
In OAO NIITEKHIM, it has historically been the practice to consider the production of PE as the sum of the production of LDPE and HDPE, attributing LLDPE to LDPE. This approach is logical, convenient and fully justified. In the same way, Rosstat also divides production, separating ethylene polymerization products with a density of at least 0.94 (meaning HDPE) and ethylene polymerization products with a density of less than 0.94 g / cm 3 (LDPE).
The main difference between LDPE and HDPE is density. In this case, it is necessary to clearly understand that a copolymer is almost always used. Butene-1, Hexene-1, octene-1 or others. Pure homopolymer is very different from the modern polyethylenes we are used to and has very limited applications due to its very high density and low fluidity.
There are other more special types of polyethylene. So allocate linear low density PE- LLDPE or LLDPE , which is mainly used for the production of containers and packaging.
Bimodal PEthis is polyethylene, which is synthesized according to the two-reactor cascade technology, i.e. there are two large fractions with different molecular weights - low molecular weight is responsible for fluidity, high molecular weight - for physical and mechanical characteristics.
Cross-linked PE(PE-X or XLPE, PE-S) - an ethylene polymer with cross-linked molecules (PE - PolyEthylene, X - Cross-linked). The stitching is a three-dimensional mesh due to the formation of cross-links. Metallocene PE is an ethylene polymer obtained using catalysts with single center polymerization. Usually denoted mLLDPE , mMDPE or mHDPE .
The most important copolymer of ethylene is sevilen, in foreign periodicals, the name EVA is accepted - ethylene vinyl acetate.
Figure 2. The structure of consumption of LDPE, HDPE, sevilen, as well as the total consumption of PE by sectors in Russia in 2014Figure 2 shows the ratio of HDPE, LDPE and the most important of the ethylene copolymers - savilene in the structure of consumption in Russia. The figure shows that the main sectors of PE consumption in 2014 were manufacturers of containers and packaging, films, pipes, household and household products, which accounted for more than 86% of the total volume of PE consumed.
Wherein, different types PE is in different demand in consumption sectors. So, for example, the PE pipe sector is fully represented only by HDPE. HDPE is used for the production of pipes grades PE-100, PE-100+.
The reverse picture is seen in the case of film production. If only 6% of HDPE is used for film production, then the share of LDPE is already 43%, which makes high pressure and low density polyethylene the most suitable for this consumption sector. The same applies to the production of PE sheets, as well as the production of cables. In the production of containers and packaging, HDPE and high-pressure products are represented almost equally (30 and 28%). 13% of HDPE goes to the production of household and household products, while LDPE goes to about 18% for this purpose.
Ethylene and vinyl acetate nozzle - sevilen represented not as massively as HDPE and LDPE, its share in general production PE is only 0.65%. At the same time, twice as much savilen comes to Russian market through import. Sevilen goes to the production of household and household products - 42%, containers and packaging - 32%, film 15% and cable 6%.
Among the main licensors of polyolefin production technologies, there has long been a trend towards consolidation and globalization of manufacturers. The number of participants in the technology market is declining, in the end, only the largest players have the opportunity to develop their own technology. The main production technology licensors are presented in Table 2.
table 2. Technology licensors and main technologies for the production of PE.

Name	Owner	Type of polymerization	Products
UNIPOL PE	UnionCarbide	gas phase	LLDPE, HDPE
INNOVENE	BP Chemicals	gas phase	LLDPE, HDPE
Innovene G	BP Chem.	gas phase	LLDPE, HDPE
EXXPOL	ExxonMobil	gas phase	LLDPE, HDPE
COMPACT (Stamylex)	DSM	Solution	LLDPE, HDPE
SPHERILENE	Basell	Gas phase, cascade	LLDPE, HDPE
HOSTALEN	Basell	Gas phase, cascade	HDPE
LUPOTECH T	Basell	in mass	LDPE, sevilen
ENERGX	Eastman Chemical	gas phase	LLDPE, HDPE
SCLAIRTECH	NOVA Chemicals	gas phase	LLDPE, HDPE
BORSTAR PE	Borealis	Suspension, cascading	LLDPE, HDPE
PHILLIPS	Phillips	Suspension	LLDPE, HDPE
CX	Mitsui Chemicals	Gas phase, cascade	HDPE

The leading players in the global market in terms of existing capacities in the world are Dow and Carbide, whose Unipol technology is the most popular technology in the world. Another equally popular technology is Innovene, owned by BP . A merger between Dow and UnionCarbide in 2000 brought Dow's control of UnionCarbide's 50 percent stake in Univation.
All production technologies can be divided according to the principle of operation of the polyethylene synthesis reactor. Technologies Unipol , Innovene , Exxpol , Spherilene , Hostalen , Sclairtech and CX (Mitsui ) are based on the gas-phase polymerization reaction of ethylene and a copolymer. The reaction takes place at 70-110 0 C, pressure 15-30 bar in the presence of Ziegler-Natta catalysts.
Hostalen Technologies - Basell and CX - MitsuiChemicals a second cascade polymerization reactor is also provided. This realizes the possibility of obtaining bimodal high-density PE by mixing two large fractions with different molecular weights - low molecular weight, which is responsible for fluidity, and high molecular weight, for physical and mechanical characteristics. The gas-phase synthesis of polyethylene is characterized by low capital and operating costs and allows the production of both LDPE and HDPE in a wide range. That is why gas-phase technologies are the most popular in Russia and in the world.
DSM offers a technology for producing PE using solution synthesis. It produces LLDPE using proprietary COMPACT Solution technology (Stamylex) in combination with Ziegler catalysts. COMPACT technology - a highly flexible polymer production process High Quality. Synthesis in solution is carried out at a temperature of 150-300 0 and a pressure of 30-130 bar in the presence of Ziegler-Natta catalysts or a metallocene catalyst. Octene is used as a solvent. In the case of using a second liquid-phase reactor, it is also possible to obtain a bimodal PE. The technology is characterized by higher capital and operating costs compared to gas-phase synthesis. Among major manufacturers linear polyethylene COMPACT technology is used by LG Chemicals, Hyundai Petrochemical Co.
BorstarPE - Borealis and Philips offer a technology for producing low-density PE in an isobutane suspension, while the reaction occurs at 85-100 0 C, a pressure of 4.2, after which the resulting mixture is separated and degassed at 80-85 0 C. A special loop is used in this case ( slurryloop )reactor. It is possible to use a cascade scheme for obtaining bimodal PE, using a second reactor.
Figure 3. Types of PE production plants. Reactor principles in schemes.

It can be seen from Figures 3 and 4 that there is no universal method for obtaining all types of PE. Each method of obtaining PE covers only part of the production of polyethylene. The widest range of products can be obtained in the gas phase reactor, Unipol, Innovene, Exxpol, Spherilene, Hostalen, Sclairtech and CX (Mitsui), but each of these technologies, in turn, also has its own limitations. Most complete list Unipol/UnipolII technology can offer products, but even this technology has significant limitations, mainly for high density PE products with a low flow index. Such products are used for the manufacture of blow molded HDPE products, films and pipes, in these cases bimodal PE is required, for the production of which, in turn, a cascade reactor is used, consisting of two consecutive reactors with different polymerization conditions.

Figure 4. Principles of production and types of products.

Figure 5. Correspondence of production methods and types of manufactured PE products.

The cascade reactor can be implemented for both gas phase (Spherilene and Hostalen, both Basell) and slurry (Philips) polymerization processes. However, dual reactor plants are much more capital expensive and more difficult to maintain.
High-density polyethylene grades intended for extrusion molding require a high flow index. Such products are used for pipes made of polyethylene. So the numbers in the most famous pipe grades PE 60, PE 80, PE 100, PE 100+ correspond to their flow index.

Most often manufacturing business associated with great investment initial capital. In addition, for a person unfamiliar with technological process, mastering a new business can be quite difficult. The production of polyethylene can be safely attributed to pleasant exceptions from general rules. For a successful start, there is no need to spend a lot of money at once, because the business quickly pays off and begins to bring a stable profit. But before setting up the production of polyethylene, we will 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 mild 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. various shapes. Their size is usually from three to five millimeters. The production of polyethylene granules consists in the process of polymerization of ethylene gas under high and low pressure conditions, as well as using additional conditions. Major manufacturing companies polymer materials, are located in Russia, Uzbekistan, Belarus, South Korea.

Due to the 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 common in industrial processing.

Low density polyethylene

The material has a plastic and soft structure. The production of high pressure polyethylene (LDPE) involves the polymerization of ethylene in a tubular reactor or autoclave. The process takes place at a temperature of about 750 ° C under a pressure of 1.5–3 kgf / cm 2. The result is a low density granulate. The resulting raw material is sent to the production of packaging made of polyethylene 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) consists in a polymerization process using catalyst systems. As a result, rigid granules with a high density level of 0.960 g/cm 3 are obtained. They are suitable for the production of food film. Commodity 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 of a synthetic material having a closed porous structure. The production of foamed polyethylene is based on the strong heating of the raw material and subsequent whipping with gas (butane, freon, and others). In practice, polyethylene foam is widely used as an excellent heat insulator for universal purposes.

What is cross-linked polyethylene?

The production of extra strong granules is based on the use of ultra-high pressure. As a result of the process, there is a strong adhesion of the molecules of the original substance. 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 lights up only when it reaches 400 o C.
• Increased stiffness and tensile strength.
• Preservation of the main features with a sharp change in environmental conditions, as well as under the influence of chemical or biological destroyers.
• High steam 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 heating systems and special building materials.

How to start a business

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

Practical experience shows that the production of polyethylene in Russia is guaranteed to provide a profitability level of at least 15%. Before launching an enterprise, you need to take care of the design permits. You will have to visit the city administration, energy supervision, sanitary and epidemiological station, fire brigade, environmental service. If you deal with these issues closely, then you can completely meet the deadline of a month and a half. Overhead costs will be only 15-20 thousand rubles.

Recycling issue

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, it does a lot of damage. environment. And secondly, such actions face serious punishment.

The easiest and cheapest way is to take polymer residues to a plastics processing plant. But it should be borne 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 arrange the production of garbage bags. To do this, you will have to make additional costs for the purchase of a technological line. But in the end, the costs will pay off with a quick implementation. popular products that are in constant demand among the population.

Procurement of the main 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 household packages from it.

Necessary equipment for the production of polyethylene:

• Extruder (extrusion unit)– a machine for converting raw granules into a film by blowing from the bottom up. The width of the sleeve must correspond to the dimensions of the packages produced (300–550 mm). The set of the unit also includes a device for folding seams.
• bag making machine- a machine for cutting a film or sleeve into blanks of a certain length. The device also seals the workpiece on one side, forming the finished product.
• Punch 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 - a machine for applying printed images on the sleeve of the package.

If start-up capital not very much, then at first you can completely do without a printing device. It would be wiser to apply for a drawing service at specialized printing centers.

For the processing of production waste, it will be necessary to purchase a special apparatus for crushing. The approximate cost of the production line with the delivery and setup of machines is 1.5–2 million rubles.

Additional items of equipment

The production of polyethylene also requires the purchase of storage equipment (racks, tables, stands, boxes, etc.) for storing raw materials and finished products. Do not forget about the equipment of offices. Optional equipment can increase the total amount of expenses by 50-60 thousand rubles.

Production shops need to equip a high-quality powerful ventilation system and a fire-fighting system. Special requirements are imposed on warehouses: the primary raw material for the production of polyethylene (granulate) tends to absorb vapors and gases. Failure to comply with the rules for storing raw material can lead to deterioration in the quality of manufactured products.

Required 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 the recycling of waste or residues of the technological process.

Getting the film

The technology for the production of polyethylene includes several stages that must be passed in order to obtain bright and convenient bags from the raw material.

• Polymer granules are loaded into the bunker compartment of the extruder. From here they are taken with the help of a feeding auger. The tank maintains a constant temperature in the range from 180 to 240 degrees. In the process of movement, the granules, being strongly heated, 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 canvas of a given thickness and width.
• The resulting sleeve is gradually cooled and subjected to rolling rollers.
• The automatic cutter cuts the web into two strips of the same width.
• The finished sleeve enters the winder, which twists the film into rolls. The scraps are packaged separately and then recycled.

drawing

If necessary, a color image is printed using flexography.

• A special paint is diluted with alcohol and constantly mixed. 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 drawing the pattern, the polyethylene is again wound into a roll.

Packet formation

The next step allows you to create the basis for the bags.

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

The final process is to check the quality of the seams and fasteners.

Conclusion

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

Polyethylene is the cheapest non-polar synthetic polymer, which belongs to the class of polyolefins. Polyethylene is a white solid 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 made in 1884 by the organic chemist Gustavson.

Polyethylene production technology + video how they do it

Everyone is engaged in the production of polyethylene large companies petrochemical industry. The main raw material from which polyethylene is obtained is ethylene. Production is carried out at low, medium and high pressures. As a rule, it is produced in granules, which have a diameter of 2 to 5 millimeters, sometimes in the form of a powder. To date, four main methods for the production of polyethylene are known. As a result, we obtain: high-pressure polyethylene, low-pressure polyethylene, medium-pressure polyethylene, as well as linear high-pressure polyethylene. Let's look at how the production of MPE is carried out.

High pressure polyethylene is formed at high pressure as a result of the polymerization of ethylene in an autoclave or in a tubular reactor. Polymerization in the reactor is carried out by a radical mechanism under the influence of oxygen, organic peroxides, they are 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 that, 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 for polymerization, which occurs at a temperature in the range from 190 to 300 degrees and a pressure of 130 to 250 megapascals. In total, ethylene is in the reactor for no more than 100 seconds. The degree of its conversion is 25 percent. It depends on the type and quantity of the 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 undyed and colored granules. The production of low-density polyethylene is carried out according to three main technologies. The first is polymerization, which occurs in suspension. The second is polymerization occurring in solution. This solution is hexane. The third is gas-phase polymerization. The most common method is polymerization in solution. Solution polymerization is carried out in the temperature range from 160 to 2500 degrees and pressure from 3.4 to 5.3 megapascals. Contact with the catalyst is carried out for about 10-15 minutes. Polyethylene is separated from the solution by removing the solvent. 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 vapor.

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 ethylene polymerization in solution. Medium pressure polyethylene is obtained at a temperature of approximately 150 degrees, a pressure of not more than 4 megapascals, and also in the presence of a catalyst. PSD from the solution precipitates in the form of flakes. The product obtained as described above has a weight average molecular weight of not more than 400 thousand, a degree of crystallinity of not more than 90 percent. The production of linear high-pressure polyethylene is carried out using the chemical modification of LDPE. The process takes place at a temperature of 150 degrees and approximately 30-40 atmospheres. Linear low density polyethylene is similar in structure to high density polyethylene, however, it differs in longer and more numerous 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 fluidized bed reactor. Ethylene is fed into the reactor, while the polymer is in turn withdrawn continuously. However, the level of the liquefied bed is constantly maintained in the reactor. The process takes place at a temperature of about one hundred degrees, pressure from 689 to 2068 kN/m2. The efficiency of this method of polymerization in the liquid phase is lower than that of the gas phase.

Video how to do it:

It is worth noting that this method also has its advantages, namely: the size of the installation is much smaller than that of equipment for gas-phase polymerization, and much lower capital investment. Practically similar is the method in the reactor with a stirrer using Ziegler catalysts. This results in maximum output. Not so long ago, for the production of linear polyethylene, technology began to be used, as a result of which metallocene catalysts are used. 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 have not received distribution in industry.