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What is PVC?

polyvinyl chloride

The full name is PVC, and the main component is PVC, which is bright in color, corrosion-resistant and durable. Because some toxic auxiliary materials such as plasticizer and antioxidant are added in the manufacturing process to enhance its heat resistance, toughness and ductility, its products are generally not stored in food and medicine. It is a kind of synthetic material which is deeply loved, quite popular and widely used in the world today. Its global usage ranks second among all kinds of synthetic materials. According to statistics, in a short period of 1995, the output of PVC in Europe was about 5 million tons, while its consumption was 5.3 million tons. In Germany, the average output and consumption of PVC is1400,000 tons. The production and application of PVC in the world is growing at a rate of 4%. In recent years, the growth of PVC in Southeast Asia is particularly remarkable, which is attributed to the urgent demand for infrastructure construction in Southeast Asian countries. Among the materials that can be used to make three-dimensional surface films, PVC is the most suitable material.

PVC (polyvinyl chloride) has a simple structural formula CH2=CHCl.

Chemical and physical properties:

Rigid PVC is one of the most widely used plastic materials. PVC is actually a vinyl polymer, and its material is an amorphous material. In practical use, stabilizers, lubricants, processing AIDS, pigments, impact agents and other additives are often added to PVC materials. It is nonflammable, high strength, weatherability and excellent geometric stability. PVC has strong resistance to oxidants, reductants and strong acids. However, it can be corroded by concentrated oxidizing acids such as concentrated sulfuric acid and concentrated nitric acid, and is not suitable for contact with aromatic hydrocarbons and chlorinated hydrocarbons.

The melting temperature of PVC during processing is a very important technological parameter. If this parameter is not suitable, it will lead to the problem of material decomposition. PVC has poor fluidity and narrow processing range. In particular, PVC materials with large molecular weight are more difficult to process (this material usually needs to add lubricants to improve its flow characteristics), so PVC materials with small molecular weight are usually used. The shrinkage of PVC is quite low, generally 0.2~0.6%.

Technological conditions of injection mold

Drying treatment: drying treatment is usually not needed.

Melting temperature: 185~205℃ Mold temperature: 20~50℃

Injection pressure: up to 1500bar holding pressure: up to 1000bar injection speed: In order to avoid material degradation, it is generally necessary to use a considerable injection speed.

Runner and gate: All conventional gates can be used. If machining smaller parts, it is best to use needle gate or submerged gate; For thicker parts, it is best to use fan gate. The minimum diameter of needle gate or submerged gate should be1mm; The thickness of the sector gate should not be less than 1 mm.

Typical uses: PVC has the outstanding characteristics of rich raw materials (oil, limestone, coke, salt and natural gas), mature manufacturing technology, low price and wide application. Now it has become the second largest general resin in the world, accounting for 29% of the total consumption of synthetic resin in the world. PVC is easy to process, and can be processed by molding, laminating, injection molding, extrusion, calendering and blow molding. PVC is mainly used to produce artificial leather, film, wire sheath and other plastic soft products, water supply pipes, household pipes, house wall panels, commercial machine shells, electronic product packaging, medical devices, speedboat fenders, and plastic hard products such as plates, doors and windows, valves, etc.

PVC can be divided into soft PVC and hard PVC. Among them, hard PVC accounts for about 2/3 of the market and soft PVC accounts for 1/3. Soft PVC is generally used for floors, ceilings and leather surfaces, but its application is limited because it contains softener (which is also the difference between soft PVC and hard PVC), which is easy to become brittle and difficult to store. Rigid PVC contains no softener, so it is flexible and easy to form, not fragile, non-toxic and pollution-free, and has long storage time, which is of great development and application value. Hereinafter referred to as PVC. Soft PVC is mostly used to make vacuum plastic film, which is used for surface packaging of various panels, so it is also called decorative film and adhesive film, and is used in building materials, packaging, medicine and other industries. Among them, the building materials industry accounts for the largest proportion, accounting for 60%, followed by the packaging industry and several other small-scale application industries.

Simply put, the aqueous solution of salt is chemically decomposed under the action of electric current. This process produces chlorine, caustic soda and hydrogen. Refining and cracking petroleum or gasoline can produce ethylene. When chlorine and ethylene are mixed, dichloroethylene will be produced; Dichloroethylene can be converted into chloroethylene, which is the basic component of PVC. During the polymerization process, chlorinated vinyl molecules are linked together to form PVC chains. The PVC produced in this way is white powder. It cannot be used alone, but it can be mixed with other ingredients to make many products.

In 1835, vinyl chloride was synthesized for the first time in Justus von Liebig laboratory. And PVC was synthesized by Bowman in 1872. But it was not until the 1920s that the first commercial product of PVC was produced in the United States, and it was not until the next 20 years that mass production began in Europe.

PVC has the advantages of flame retardant (flame retardant value above 40), high chemical resistance (concentrated hydrochloric acid, 90% sulfuric acid, 60% nitric acid and 20% sodium hydroxide), good mechanical strength and good electrical insulation. However, its heat resistance is poor, its softening point is 80℃, and it begins to decompose and change color at 130℃, and HCI is precipitated.

[Edit this paragraph] Characteristics and molding characteristics of ]PVC

Specific gravity: 1.38g/cm3, molding shrinkage: 0.6- 1.5%, molding temperature: 160- 190℃.

Features: excellent mechanical and electrical properties, strong acid and alkali resistance, good chemical stability, but low softening point. Suitable for manufacturing thin plates, wire and cable insulation layers, seals, etc.

Molding characteristics:

1. Amorphous substances have low hygroscopicity and poor fluidity. In order to improve fluidity and prevent bubbles, plastics can be dried in advance. The gating system of the mold should be thick and short, the gate section should be large, and there should be no dead angle. The mold should be cooled and the surface should be chrome plated.

2. Because of its corrosiveness and fluidity, it is best to use special equipment and molds. All products must be added with different kinds and quantities of additives as required.

3. Very easy to decompose, it is easier to decompose when contacting steel and copper at 200 degrees, and corrosive and irritating gases escape during decomposition. The molding temperature range is small.

4. When using the nozzle of the screw injection machine, the aperture should be large to prevent the dead angle from being delayed. If there is an insert, preheat it.

What is the pollution of PVC?

Causes of PVC pollution:

Some toxic additives and plasticizers in PVC may seep or evaporate; Some additives will interfere with biological endocrine (affect reproductive function), and some will increase the risk of cancer; Burning PVC garbage will produce carcinogenic dioxins and pollute the atmosphere.

Traditional PVC materials, such as wires and cables, are quite serious pollution sources. A large number of harmful substances, such as dioxins, hydrochloric acid and lead, will be produced in the process of manufacture, use and treatment. When PVC material is burned, it will produce a lot of smoke and harmful HCL gas; Moreover, PVC materials mostly contain harmful heavy metals such as Pb (lead) and Cd (cadmium) (used as cable stabilizers), which will do some harm to human health. After burning or burying, it will pollute the soil and water.

Medical-grade polyvinyl chloride (PVC) or polycarbonate (PC) are mostly used in disposable medical devices. The thermal decomposition products in the processing of PVC have strong corrosiveness to steel, while PC has high hardness and viscosity, so the parts and components of plasticized parts must have high corrosion resistance, wear resistance and polishing performance. At present, most medical injection molding machines use hard chromium or stainless steel plating on the barrel screw to make a simple screw to meet the above special requirements. In addition, in order to prevent the gas generated by thermal decomposition during PVC processing, it is required to aluminize the surfaces of the movable template and the fixed template, and at the same time, aluminize the surrounding metal sheets or make metal sheets with stainless steel plates, and seal the flat seams of the metal sheets with non-toxic silica gel to prevent the gas generated during plastic processing from being emitted to the outside (the gas generated during plastic processing can be collected by special equipment, purified and discharged into the atmosphere).

Harm of DEHP, a common additive for PVC: DEHP (phthalate) is easy to atomize, and other vinyl products, including automobile interiors, shower curtains or floor materials, also release toxic gases into the atmosphere, and DEHP is also easy to dissolve into oily liquid. In addition, people have begun to pay attention to the safety of additives oozing out when children chew these soft plastic toys. Some studies show that this additive may complicate health problems, but further research is needed. According to some medical research, PVC plasticizer may cause chronic diseases, such as scleroderma, cholangiocarcinoma, angiosarcoma, brain cancer and acroosteoporosis. In 2004, a research team composed of Swedish and Danish scholars found that DEHP and BBzP commonly used in PVC have a strong correlation with children's allergies.

For unplasticized polyvinyl chloride (U-PVC), there is no DEHP exudation because there is no plasticizer, but stabilizers are usually added during processing. At present, most of them are lead salt stabilizers. Lead is a toxic substance, which will seep out during use and endanger human health. At present, there are non-lead salt stabilizers, but the cost is high and they are not popularized.

[Edit this paragraph] Development of PVC market in China

In recent years, the development of PVC in China is amazing, and new and expanded projects have been launched one after another, with the rapid expansion of production capacity and a substantial increase in output. From 65438 to 0997 to 2006, the average annual growth rate of PVC production capacity and output in China was as high as 22.2% and 20.0% respectively.

In 2006, the cumulative output of PVC resin in China was 8238583.86 tons; In 2007, the cumulative output of PVC resin in China reached 97 16783.63 tons; From June to May, 2008, the national cumulative output of PVC resin was 4,028,666.03 tons.

In 2008-20 12, the global market demand for polyvinyl chloride (PVC) is expected to increase by 4% annually, especially in some developing countries. The demand for PVC resin in China will also maintain rapid growth, especially for building materials, which is in a period of rapid growth in recent years. With the internationalization of China market, PVC resin packaging materials and pipes will have broad development space in the fields of cement, fertilizer, grain, food, beverage, medicine, detergent, cosmetics and so on, and their demand will also increase greatly accordingly; In addition, the demand for PVC resin in automobile, communication, transportation and other fields is also growing at a high speed, and China's PVC resin industry still has great room for development.

[Edit this paragraph] PVC futures

Polyvinyl chloride (PVC) is the largest synthetic resin material in China and the second largest in the world. At present, PVC has become one of the most widely used plastic varieties because of its excellent flame retardancy, wear resistance, chemical corrosion resistance, comprehensive mechanical properties, product transparency, electrical insulation and processability. Widely used in industry, construction, agriculture, daily life, packaging, electricity, public utilities and other fields. Together with polyethylene (PE), polypropylene (PP), polystyrene (PS) and ABS, they are called five general resins.

I. Introduction of PVC

PVC is a nontoxic and odorless white powder. High chemical stability and good plasticity. Except for a few organic solvents, it can resist any concentration of hydrochloric acid, sulfuric acid below 90%, nitric acid below 50-60% and caustic soda below 20% at room temperature, and it is also quite stable to salts. PVC has poor thermal stability and light resistance. Hydrogen chloride (HCl) gas can be decomposed and released above 140℃, resulting in discoloration of PVC. PVC has excellent electrical insulation and generally does not burn. It can burn on a flame and release HCl, but it will extinguish itself when it leaves the flame. It is a "self-extinguishing" and "flame retardant" substance. Based on the above characteristics, PVC is mainly used to produce profiles, profiles, pipes and fittings, plates, sheets, cable sheaths, hard pipes or hoses, blood transfusion equipment and films.

Second, the classification of PVC

According to the different application scope, PVC can be divided into: universal PVC resin, high polymerization degree PVC resin and crosslinked PVC resin. Universal PVC resin is polymerized by vinyl chloride monomer under the action of initiator; High polymerization degree PVC resin refers to the resin polymerized by adding chain extender into vinyl chloride monomer polymerization system; Crosslinked PVC resin is a resin polymerized by adding a crosslinking agent containing diene and polyene into the polymerization system of vinyl chloride monomer. Because of its simple preparation method and wide application, general PVC resins are mostly circulated in the spot market, while high polymerization degree and cross-linked PVC resins are generally used in special fields.

According to the methods of obtaining vinyl chloride monomer, it can be divided into calcium carbide method, ethylene method and imported (EDC, VCM) monomer method (ethylene method and imported monomer method are collectively referred to as ethylene method). At present, most PVC in the world is made of ethylene, while PVC in China is mainly made of calcium carbide.

According to the polymerization methods of vinyl chloride monomer, PVC can be divided into suspension method, emulsion method, bulk method and solution method. Suspension method is the main production method of PVC because of its simple production process, easy control and large-scale production and strong product adaptability. Worldwide, the production of suspension PVC accounts for about 80% of the total. The bulk method does not use water and dispersant, and the post-polymerization treatment is simple and the product purity is high. However, there are stirring and heat transfer problems in the polymerization process, and the production cost is high. It belongs to the elimination process, and the production capacity is less than 65,438+00% of the total. At present, only Sichuan Yibin Tianyuan uses bulk method to produce PVC in China. When water is used as dispersion medium in emulsion polymerization, the particles are fine, the thermal stability and electrical insulation are not good, and it is suitable for producing paste resin. It is mainly used to make artificial leather, impregnated gloves, screens, rice boots, tool handles, wallpaper, floor coils, battery diaphragms and toys. The output of PVC paste resin in China is less than 4% of the total output of PVC. Solution polymerization is only used to produce coatings or special products. In the United States, the ratio of resin produced by various polymerization methods is: suspension method 87.8%, emulsion and micro-suspension method 6.4%, bulk polymerization method 4.4%, solution method 1.4%. In China, more than 90% of PVC is produced by suspension method.

Third, the production process and cost analysis of PVC

1. production process

There are two main preparation processes for PVC production. One is calcium carbide method, the main raw materials are calcium carbide, coal and raw salt. The second method is ethylene method, and the main raw material is petroleum. In the international market, the production of PVC is mainly based on ethylene method, while China is limited by the resource endowment of rich coal, poor oil and little gas, mainly based on calcium carbide method. By the end of 65438+February 2007, the calcium carbide process accounted for more than 70% of the total PVC production capacity in China.

It is worth noting that in the preparation of PVC by calcium carbide method, hydrogen chloride after electrolysis of raw salt is used to produce PVC, and the remaining sodium is used to produce caustic soda. Therefore, there is actually a * * relationship between chlor-alkali, and chlor-alkali balance is also an important factor that has to be considered in the development of the whole industry.

2. Cost analysis

From the perspective of production cost, the cost of the two processes is quite different in different economic development cycles. Usually, in the high-speed development stage of international macro-economy, due to the high oil price and the high production cost of ethylene method, the cost advantage of calcium carbide method is obvious; Once the international economy enters recession, oil prices will run at a low level, and the cost advantage of calcium carbide method will disappear because of its high energy consumption and the support of coal, electricity and oil transportation. Since 2003, the international oil price has risen sharply, which has increased the cost of PVC by ethylene method, but the production by calcium carbide method has been less affected by this, which has led to a new upsurge in the construction of domestic PVC production facilities by calcium carbide method, greatly expanding the production capacity of PVC by calcium carbide method, posing a great challenge to PVC production by ethylene method, and many ethylene enterprises are on the verge of losses. However, with the continuous downward adjustment of crude oil price after May 2008, the cost advantage of ethylene process is obvious, and calcium carbide process manufacturers are running at a low profit, even unsustainable.

The cost of calcium carbide method is mainly composed of calcium carbide cost, hydrogen chloride cost and public works. According to national standards, the production of 1 ton of PVC consumes 1.45 ~ 1.5 ton of calcium carbide (generally calculated as 1.45, but the consumption in actual production will be higher than this ratio, and only a few of them can meet the standard), and the consumption of hydrogen chloride gas per ton is 0.75 ~ 0.85 ton (generally H, there are other project costs, such as packaging costs, initiators, dispersants, water charges, management personnel costs, etc. This varies by manufacturer and production scale. Generally speaking, the cost distribution ratio of calcium carbide method is about: calcium carbide accounts for 65 ~ 70%, hydrogen chloride accounts for 15%, electricity accounts for 6%, and other manufacturing expenses account for 6%. A remarkable feature of calcium carbide method is high power consumption, which not only consumes electricity to produce PVC, but also consumes a lot of electricity to prepare calcium carbide from coke. For example, the production of 1 ton calcium carbide requires about 3450 kw. Electricity, 0.6 tons of coke and 0.9 tons of limestone.

The main factors of ethylene process cost are ethylene consumption, chlorine consumption, power consumption, processing AIDS, management labor costs and so on. The ethylene process consumes 0.5 tons of ethylene and 0.65 tons of chlorine per ton of PVC produced/kloc-0, accounting for about 60% of the cost. The cost of ethylene accounts for the main part of raw material cost, and the price of ethylene has a great influence on the cost of PVC. Although the energy consumption of ethylene method is lower than that of calcium carbide method, its equipment investment is huge, so the depreciation of equipment accounts for a large proportion of the cost. The equipment investment is fixed, so the price change of ethylene and vinyl chloride is the main factor of the price change of PVC resin.

Iv. main uses and industrial chain of PVC

1.PVC profile

Profile and profile are the largest areas of PVC consumption in China, accounting for about 25% of the total PVC consumption. They are mainly used to make doors and windows and energy-saving materials. At present, their applications are still increasing in a large number throughout the country. In developed countries, the market share of plastic doors and windows is also the highest, such as 50% in Germany, 56% in France and 45% in the United States.

2. PVC pipes

Among many PVC products, PVC pipe is the second largest consumption field, accounting for about 20% of its consumption. In China, PVC pipes have developed earlier than PE pipes and PP pipes, with many varieties, excellent performance and wide application range, and occupy an important position in the market.

3. PVC film

The consumption of PVC in the field of PVC film ranks third, accounting for about 10%. After PVC and additives are mixed and plasticized, they are made into transparent or colored films with specified thickness by a three-roll or four-roll calender, and processed into calendered films by this method. You can also cut heat-sealed packaging bags, raincoats, tablecloths, curtains, inflatable toys, etc. Wide transparent film can be used in greenhouses, plastic greenhouses and plastic films. Biaxially stretched film can be used for shrink packaging because of its thermal shrinkage.

4.PVC hardwood and board

Stabilizers, lubricants and fillers are added to PVC. After mixing, hard pipes, special-shaped pipes and corrugated pipes with various diameters can be extruded by an extruder to be used as sewer pipes, drinking water pipes, wire sleeves or stair handrails. By overlapping and hot-pressing calendered sheets, hard plates of various thicknesses can be manufactured. The plate can be cut into the required shape, and then welded with hot air and PVC covered electrode into various chemical corrosion-resistant storage tanks, air ducts and containers.

5.PVC ordinary textiles

The extruder can be used to extrude hoses, cables, wires, etc. Plastic sandals, soles, slippers, toys, auto parts, etc. can be made by injection molding machine with various molds.

6.PVC packaging materials

PVC products are mainly used for packaging various containers, films and hard sheets. PVC containers mainly produce mineral water, beverages and cosmetic bottles, and are also used for packaging refined oil. PVC film can be used for extrusion with other polymers to produce low-cost laminated products and transparent products with good barrier properties. PVC film can also be used for stretching or heat shrinking packaging, and used for packaging mattresses, fabrics, toys and industrial products.

7.PVC wallboard and floor

PVC wallboard is mainly used to replace aluminum wallboard. PVC floor tiles not only contain part of PVC resin, but also contain recycled materials, adhesives, fillers and other components, which are mainly used for hard floors in airport terminals and other places.

8. PVC consumer goods

Luggage is a traditional product made of PVC. PVC is used to make all kinds of imitation leather, used in bags and sporting goods, such as basketball, football and rugby. It can also be used to make uniform belts and special protective equipment. PVC fabrics for clothing are generally water-absorbent fabrics (uncoated), such as ponchos, baby pants, imitation leather jackets and various rain boots. PVC is used in many sports and entertainment products, such as toys, records and sporting goods. At present, PVC toys have increased greatly, which has advantages because of its low production cost and easy molding.

PVC futures contract

Trading variety

polyvinyl chloride

Trading unit

5 tons/hand

Quotation unit

Yuan (RMB)/ton

Minimum variable price

5 yuan/ton

Price limit range

4% of the settlement price of the previous trading day

Contract month

1, 2, 3, 4, 5, 6, 7, 8, 9, 10,1,65438+ February.

trading hour

Every Monday to Friday from 9: 00 am to 1 1: 30, and from 13: 30 pm to 15: 00 pm.

last trading day

The 10 trading day of the contract month

end delivery date

The second trading day after the last trading day

Intersecting lamp set

The quality standard conforms to SG5 first-class product and first-class product specified in Suspension General PVC Resin (GB/T 576 1-2006).

place of delivery

Dalian commodity exchange appointed delivery warehouse

Minimum trading margin

5% of the contract value

transaction cost

No more than 6 yuan/hand

Mode of delivery

Actual delivery

Event code

Listed exchange

Dalian commodity exchange

Pvc delivery standard

The standard PVC product is SG5-type first-class product, and its quality standard conforms to the national standard "Suspension Universal PVC Resin (GB/T 576 1-2006)". Superior products are allowed to be delivered as substitutes, and there is no grade premium between superior products and first-class products.

For PVC with brands recommended by manufacturers recommended by the Exchange, the consignor can provide the materials specified in the Management Measures for Standard Warehouse Receipts of Dalian Commodity Exchange 1 No.2 Soybean, Corn, Linear Low Density Polyethylene and PVC, which can be exempted from inspection after being examined and approved by the delivery warehouse. The list of enterprise qualifications and recommended brands of recommended manufacturers shall be determined and published by the Exchange.

PVC designated delivery warehouses are divided into benchmark delivery warehouses and non-benchmark delivery warehouses, which are located in Guangdong, Shanghai, Zhejiang, Jiangsu and other places. The Exchange may adjust the designated delivery warehouse as appropriate. The list of designated delivery warehouses and discounts shall be determined and published by the Exchange.

Ex-factory PVC products should be packed by the original manufacturer or its approved packaging, and the packaging bag should be marked with trademark, product name, product standard number, net weight, manufacturer's name and address, and product model.

The packaging materials are kraft paper bags lined with plastic film bags, polypropylene woven bags or composite bags of kraft paper and polypropylene woven bags, which should ensure that the products are not damaged, polluted or leaked during normal storage and transportation. The net weight of each bag is 25±0.2kg, and there are 40 bags per ton without overflow.

The price of PVC packaging is included in the contract price of PVC.