Chemical and physical properties:
Rigid PVC is one of the most widely used plastic materials.PVC is actually a polymerization of vinyl, the material is a non-crystalline material.PVC materials are often added to the actual use of stabilizers, lubricants, auxiliary processing agents, Color, impact resistance and other additives are often added to PVC materials in practice. It has non-flammability, high strength, weather resistance and excellent geometric stability. PVC is highly resistant to oxidizing agents, reducing agents and strong acids. However, it can be corroded by concentrated oxidizing acids such as concentrated sulfuric acid and concentrated nitric acid and is also not suitable for contact with aromatic hydrocarbons and chlorinated hydrocarbons.
PVC in the processing of melting temperature is a rubber fender marine airbags very important process parameters, if this parameter is not appropriate will lead to material decomposition problems. PVC marine airbags flow characteristics are quite poor, its process range is very narrow. Especially large molecular weight PVC material is more difficult to process (this material usually need to add lubricants to improve the flow characteristics), so usually use small molecular weight PVC material. Shrinkage of PVC is quite low, generally 0.2~0.6%.
Injection Molding Conditions
Drying: Usually no drying is required.
Melting Temperature:185~205℃ Mold Temperature:20~50℃
Injection Pressure:up to 1500bar Holding Pressure:up to 1000bar Injection Speed:in order to avoid degradation of the material, the rubber fenders should be injected with a considerable speed of the marine fenders and marine airbags.
Runners and gates: All conventional gates can be used. If processing smaller parts, it is best to use a needle tip gate or dive gate; for thicker parts, it is best to use a fan gate. The minimum diameter of the needle tip gate or dive gate should be 1mm; the thickness of the fan gate should not be less than 1mm.
Typical use: PVC is rich in raw materials (petroleum, limestone, coke, salt and natural gas), the manufacturing process is mature, inexpensive, versatile and other salient features, please modify and add the content of the body, has now become the second largest in the world, second only to polyethylene resin, the general-purpose resin, accounting for the world's synthetic resin. It is now the second largest general-purpose resin in the world after polyethylene resin, accounting for 29% of the world's total consumption of synthetic resins. Polyvinyl chloride is easy to process, can be molded, laminated, injection molding, extrusion, calendering, blow molding hollow and other ways to process. Polyvinyl chloride is mainly used for the production of artificial leather, film, wire sheathing and other plastic soft products, marine fenders, water supply pipes, household piping, housing wall panels, commercial machinery shells, electronic packaging, marine airbags The A1, medical equipment, speedboat fenders, but also the production of plates, windows and doors and valves, such as plastic hard products.
PVC can be divided into soft PVC and hard PVC, of which hard PVC accounted for about 2/3 of the market, soft PVC accounted for 1/3. Soft PVC is generally used for marine fender boards, ceilings, and the surface of the leather, but because of the soft PVC contains softeners (which is the difference between soft and hard PVC), easy to become brittle, not easy to save, so its scope of use by the rubber fender limitations. Hard PVC does not contain softener, so good flexibility, easy to mold, marine fender, not easy to brittle, non-toxic non-polluting, long preservation time, so it has a lot of development and application value. Below are referred to as PVC. Soft PVC is mostly used to make vacuum blister film, used for all kinds of panel surface packaging, so it is also known as decorative film, adhesive film, used in building materials, packaging, medicine and many other industries. The building materials industry accounted for the largest proportion of 60%, followed by the packaging industry, there are a number of other small-scale application of the industry.
Simply put, an aqueous solution of salt undergoes chemical decomposition under the action of an electric current. This process produces chlorine, caustic soda and hydrogen gas. Refining or cracking oil or gasoline produces ethylene. When chlorine and ethylene are mixed, vinyl dichloride is produced; vinyl dichloride can be converted to produce chlorinated vinyl, which is the basic component of polyvinyl chloride. The polymerization process links the chlorinated vinyl molecules together to form the rubber fender PVC chain. The PVC produced in this way is a white powder. It cannot be used alone, but can be mixed with other components to produce many products.
Vinyl chloride was first synthesized in 1835 in the laboratory of Justus von Liebig. Polyvinyl chloride was synthesized by Baumann in 1872. But it wasn't until the 1920s that rubber fenders were produced commercially in the United States as the first commercial product of polyvinyl chloride for marine airbags, and it wasn't until the next 20 years that large-scale production began in Europe.
Polyvinyl chloride has the advantages of flame retardant (flame retardant value of 40 or more), high chemical resistance (resistant to concentrated hydrochloric acid, concentration of 90% of sulfuric acid, concentration of 60% of nitric acid and concentration of 20% of sodium hydroxide), mechanical strength and good electrical insulation. But its heat resistance is poor, softening point of 80 ℃, at 130 ℃ began to decomposition and discoloration, and precipitation of HCI.[edit this paragraph] PVC characteristics and molding characteristics Specific gravity: 1.38 g / cm3, molding shrinkage: 0.6-1.5%, molding temperature: 160-190 ℃.
Features: mechanical properties, excellent electrical properties, acid and alkali resistance, chemical stability, but the softening point is low. Suitable for the production of sheet, wire and cable insulation, PVC, seals and so on.
Molding characteristics:
1. Amorphous material, small moisture absorption, poor fluidity. In order to improve the fluidity, to prevent the occurrence of air bubbles, the plastic can be pre-dried. The mold casting system should be thick and short, the gate cross-section should be large, there should be no dead ends. The mold should be cooled and the surface should be chrome plated.
2. Due to its corrosive and fluid characteristics, it is best to use special equipment and molds. All products must be added with different kinds and quantities of additives according to the needs.
3. It is very easy to decompose, and is more likely to decompose in contact with steel and copper at a temperature of 200 degrees Celsius. It is easy to decompose when it comes in contact with steel and copper at 200 degrees Celsius, and when it decomposes, corrosive and irritating gases will be released. Irritating gases are emitted during decomposition. Molding temperature range is small.
4. Screw injection machine nozzle, the aperture should be large, to prevent dead-end stagnant material. Good without inserts, such as inserts should be preheated.
What is the pollution of PVC?
PVC pollution causes:
PVC some toxic additives and plasticizers, may leak or gasification; some additives will interfere with the biological endocrine (affecting reproductive function), some can increase the risk of cancer; incineration of PVC waste will produce carcinogenic dioxins and pollution of the atmosphere.
Conventional PVC materials, such as wires and cables, are a serious source of pollution. In the manufacture, use and disposal, will produce a large number of dioxin, chlorohydrogen acid, lead and other harmful substances; PVC material combustion will occur in a very large smoke, and produce harmful HCL gas; and most of the PVC material contains Pb (lead), Cd (cadmium), etc. (used as cable stabilizers), a variety of harmful heavy metals, which will cause certain hazards to human health; incineration or landfill, it will cause Pollution of soil and water.
Since the disposable medical device products are mostly used in medical grade polyvinyl chloride (PVC) or polycarbonate (PC), and the thermal decomposition of PVC processing process has a strong corrosive effect on the steel, marine fenders, PC is a high degree of hardness, viscosity, and thus the plasticizing part of the parts and components of the material requirements must be able to corrosion-resistant, anti-abrasion and have a high degree of polished performance. Most of the current medical injection molding machine barrel screw with hard chrome plating method or stainless steel as the material to produce machine screw to achieve the above special requirements. In addition, in order to prevent the thermal decomposition of PVC processing gas, the requirements of the surface of the moving fixed template for aluminum plating, but also on the periphery of the plate gold for aluminum plating or stainless steel plate production of plate gold, plate gold seams using non-toxic silicone sealing to prevent the plastic processing of gas to the outside (plastic processing of gas can be centralized through a special device and then after purification and treatment can be discharged into the atmosphere) (The gases generated during plastic processing can be collected centrally by special equipment and then purified before being discharged into the atmosphere).
Hazards of DEHP, a common additive in PVC: Because DEHP (di-phthalate) is easily atomized, other vinyl products, including automobile interiors, shower curtains, or floor coverings, release toxic gases into the atmosphere, and DEHP dissolves readily in oily liquids. There are also concerns about marine fenders and the safety of children chewing on these soft plastic toys with additives leaking out. Some studies suggest that this additive may complicate health issues, but further research is needed. According to some medical studies, PVC plasticizers may cause chronic diseases such as scleroderma, cholangiocarcinoma, angiosarcoma, brain cancer and acrosteolysis. In 2004, a team of Swedish and Danish academics found that the phthalates DEHP and BBzP, which are commonly used in PVC, were associated with a number of health problems. A team of Swedish and Danish academics in 2004 found that the phthalates DEHP and BBzP, commonly used in PVC, were strongly associated with allergies in children.
For unplasticized polyvinyl chloride (U-PVC), due to the absence of plasticizers, there is no DEHP leakage, but the process will usually be added to the stabilizers, most of the lead salt stabilizers, lead is a kind of toxic substances, in the use of the process there will be leakage, harmful to human health, also can not be ignored. Currently there are non-lead salt stabilizers, but the cost is high, has not been popularized. [Edit paragraph] China's PVC market development In recent years, China's polyvinyl chloride (PVC) development speed is amazing, new construction, expansion projects have been launched, rapid expansion of production capacity, production increased significantly. 1997-2006, China's PVC production capacity, production average annual growth rate of up to 22.2% and 20.0% respectively.
In 2006, the national cumulative output of PVC resin was 8,238,583.86 tons; in 2007, the national cumulative output of PVC resin reached 9,716,783.63 tons; January-May 2008, the national cumulative output of PVC resin was 4,028,666.03 tons.
2008-2012, marine fenders, the global market demand for polyvinyl chloride (PVC) is expected to an average annual rate of 4% of the rapid growth of marine airbags, especially rubber fenders some developing countries, the market demand will show a rapid growth trend. China's demand for PVC resin rubber airbags will maintain rapid growth, especially in building materials, in recent years is in a period of rapid growth. With the increasing pace of internationalization of the Chinese market, polyvinyl chloride resin packaging materials and tubes in the cement, fertilizers, food, food, beverages, pharmaceuticals, detergents, cosmetics and other fields will have a broad space for development, its demand for the corresponding substantial growth; in addition, automotive, communications, transportation demand for polyvinyl chloride resin rubber airbags is a high-speed growth in the field of polyvinyl chloride resin industry in China is still a greater development! Space. [Edit paragraph] PVC futures PVC futures Polyvinyl Chloride (Polyvinyl Chloride, referred to as PVC), is China's first, the world's second largest general-purpose synthetic resin materials, due to the excellent flame retardant, abrasion resistance, chemical corrosion resistance, comprehensive mechanical, product transparency, electrical insulation and easier to process and so on, PVC has become the most widely used plastics. Has become one of the most widely used plastic varieties, in industry, construction, agriculture, daily life, packaging, electricity, utilities and other fields are widely used, and polyethylene (PE), polypropylene (PP), polystyrene (PS) and ABS are collectively referred to as the five major general-purpose resins.
I, PVC Introduction
PVC is a non-toxic, odorless white powder. Its chemical stability is very high, with good plasticity. In addition to a few organic solvents, at room temperature can withstand any concentration of hydrochloric acid, 90% of the following sulfuric acid, 50 ~ 60% of nitric acid and 20% of the following caustic soda, for the salts are also quite stable; PVC's thermal stability and light resistance is poor in 140 ℃ or more can begin to decompose and release hydrogen chloride (HCl) gas, resulting in the discoloration of PVC PVC's electrical insulation is excellent, marine fenders, and generally do not Burning, in the flame can burn and release HCl, but away from the flame that is self-extinguishing, is a "self-extinguishing", "flame retardant" material. Based on the above characteristics, PVC is mainly used in the production of profiles, profiles, pipes and fittings, plates, sheets, cable sheaths, rigid or flexible tubes, blood transfusion equipment and film and other fields.
Second, the classification of polyvinyl chloride
Based on different applications, PVC can be divided into: general-purpose PVC resin, high polymerization PVC resin, cross-linked PVC resin. General-purpose PVC resin is formed by vinyl chloride monomer polymerization under the action of the initiator; high degree of polymerization of PVC resin refers to the vinyl chloride monomer polymerization system by adding a chain growth agent polymerization of resins; crosslinked PVC resin is a vinyl chloride monomer polymerization system by adding a cross-linking agent containing bis- and poly-alkenes polymerization of resins. General-purpose polyvinyl chloride because of the simple preparation method, wide range of applications, in the spot market circulation of the vast majority of general-purpose polyvinyl chloride resin, while the high degree of polymerization and crosslinked PVC resin is generally in the special field of application more.
Based on the method of obtaining vinyl chloride monomer to distinguish, can be divided into calcium carbide method, ethylene method and imported (EDC, VCM) monomer method (customarily referred to as ethylene and imported monomer method collectively referred to as ethylene method). At present, the world's most for the ethylene method of PVC, and China is mainly to the calcium carbide method of PVC-based.
Based on the polymerization method of vinyl chloride monomer, polyvinyl chloride and the acquisition of suspension method, emulsion method, body method and solution method. Suspension method with its simple production process, easy to control and large-scale production, marine fenders, product suitability, is the main mode of production of PVC, from the world, the suspension method of PVC production accounted for about 80% of the total. The body method does not use water and dispersant, polymerization after treatment is simple, high product purity, but there are polymerization process mixing and heat transfer problems, high production costs, belongs to the elimination of class technology, its production capacity of less than 10% of the total, China is only Yibin, Sichuan, Tianyuan using the body method of production of PVC. emulsion method of polymerization of water as a dispersing medium, the resulting particles are finer, thermal stability and electrical insulation is not good, suitable for Paste resin production, mainly used in the manufacture of artificial leather, impregnated gloves, screens, paddy boots, tool handles, wallpaper, flooring rolls, battery separators and toys, etc., China's PVC paste resin production is less than 4% of the total output of PVC. Solution polymerization is only used to produce coatings or specialty products. In the United States, using a variety of polymerization methods to produce the proportion of resin is: suspension 87.8%, emulsion and micro-suspension method 6.4%, 4.4% of the body polymerization method, solution method 1.4%. In China, more than 90% of the PVC is prepared using the suspension method of production.
Three, PVC marine airbags production process and cost analysis
1. Production process
PVC production there are two main preparation process, one is the calcium carbide method, the main raw materials for production is calcium carbide, coal and raw salt; the second is the ethylene method, the main raw material is oil. PVC production in the international market is mainly ethylene-based method, while the domestic coal-rich, oil-poor, less gas resource endowment constraints, it is mainly calcium carbide-based method, as of December 2007, calcium carbide accounted for more than 70% of China's total PVC production capacity.
It is worth noting that, in the calcium carbide method of preparation of PVC, the original salt electrolysis of hydrogen chloride for the production of PVC, the remaining part of the sodium used in the production of caustic soda, so, chlorine, alkali in fact exist *** raw relationship, chlor-alkali balance rubber airbags is the whole process of the development of the marine airbags industry has to consider the important factors.
2. Cost analysis
From the perspective of production costs, the two processes in different economic development cycle, the cost difference. Usually, in the international macroeconomic development stage, due to high oil prices, ethylene production costs are higher, calcium carbide method cost advantage is obvious; and once the international economy into recession, oil prices will be running at a low level, calcium carbide method due to high energy consumption, coal, electricity, oil and transportation prices have support, the cost advantage disappears. Since 2003, the international oil prices have risen sharply, so that the ethylene method of PVC cost increases, while the production of calcium carbide method is less affected by this, leading to a new round of domestic calcium carbide method of PVC production plant construction boom, so that the calcium carbide method of PVC production capacity to expand dramatically on the ethylene method of PVC production has formed a great challenge to the ethylene method of production of PVC, many of the ethylene method of enterprises in the edge of the loss. But with the continuous downward adjustment of crude oil prices after May 2008, the cost advantage of the ethylene method is obvious, calcium carbide method producers run at a small profit, or even unsustainable.
The cost of the calcium carbide method consists mainly of calcium carbide costs, hydrogen chloride costs and utility costs. National standards: the production of 1 ton of PVC consumption of calcium carbide 1.45 ~ 1.5 tons, (generally calculated at 1.45, but the actual production process will generally consume more than this ratio, only a small number of standards can be achieved), the consumption of hydrogen chloride gas 0.75 ~ 0.85 tons (generally calculated at 0.76), per ton of electricity consumption of about 450 ~ 500kw - h, and other items of expenditure, such as packaging costs, Other expenses, such as packaging, initiator, dispersant, water, management personnel costs, etc. vary according to the different manufacturers and production scale. Generally speaking, the cost of calcium carbide method is distributed as follows: 65-70% for calcium carbide, 15% for HCl, 6% for electricity and 6% for other manufacturing costs. Calcium carbide method of a significant feature of marine airbags for the higher consumption of electricity, not only in the production of PVC to consume electricity, coke from the preparation of calcium carbide also consume a lot of electricity, such as the production of 1 ton of calcium carbide requires the consumption of about 3,450 kw - h of electricity, 0.6 tons of coke and 0.9 tons of limestone.
The main factors in the cost of ethylene method are ethylene consumption, chlorine consumption, electricity consumption, processing aids, management labor costs. Ethylene method to produce 1 ton of PVC to consume 0.5 tons of ethylene, 0.65 tons of chlorine consumption, both account for about 60% of the cost. In the cost of raw materials in the cost of ethylene accounted for the main part of the rubber fender, ethylene prices have a greater impact on the cost of polyvinyl chloride. Although the ethylene method of energy consumption is lower than the calcium carbide method, but its equipment investment is very huge, marine? Fender, so the depreciation of equipment in the cost of a larger proportion. And equipment investment is fixed, so ethylene, vinyl chloride price changes is the main factor in the price change of PVC resin.
Four, the main uses of polyvinyl chloride and industrial chain
1. PVC profiles
Profiles, profiles is the largest area of consumption of PVC in China, accounting for about 25% of the total consumption of PVC, mainly used for the production of windows and doors and energy-saving materials, and its application is still a relatively large amount of growth in the country. In developed countries, the market share of plastic doors and windows is also high, such as Germany for 50%, France for 56%, the United States for 45%.
2. Polyvinyl chloride pipe
In many polyvinyl chloride products, polyvinyl chloride pipe is its second largest consumption area, accounting for about 20% of its consumption. In China, PVC pipe than PE pipe and PP pipe development early, marine fenders, more varieties, excellent performance, wide range of uses, in the market occupies an important position.
3. PVC film
PVC film in the field of PVC consumption ranks third, accounting for about 10% or so. PVC and additives mixed, plasticized, the use of three-roller or four-roller calender to make the required thickness of transparent or color film, film processing in this way, become calendered film. Rubber airbags can be cut and heat-laminated into bags, raincoats, tablecloths, curtains, inflatable toys and so on. The wide transparent film can be used for greenhouses, plastic greenhouses and ship fenders. The bi-directionally stretched film can be used for shrink wrapping due to its heat-shrinkage property.
4. PVC hard materials and plates
PVC in the addition of stabilizers, lubricants and fillers, after mixing, with the extruder can be extruded in a variety of calibers of the hard pipe, profiled pipe, corrugated pipe, used as downpipes, drinking water pipes, wire casing or stair handrails. The calendered sheet can be overlapped and hot pressed to make various thicknesses of rigid sheet. Sheet can be cut into the required shape, and then use PVC welding rod with hot air welding into a variety of chemical corrosion-resistant tanks, ducts and containers.
5. PVC general soft goods
The use of extruders can be extruded into hoses, cables, wires, etc.; the use of injection molding machines with a variety of molds, can be made into plastic sandals, soles, slippers, toys, auto parts, etc..
6. Polyvinyl chloride packaging materials
Polyvinyl chloride products used for packaging is mainly a variety of containers, film and rigid sheet. PVC containers are mainly produced for mineral water, beverages, cosmetic bottles, but also for the packaging of refined oils. PVC film can be used with other polymers **** extrusion production of low-cost laminated products, as well as transparent products with good barrier properties. PVC film is also used in stretch or heat shrink packaging for mattresses, cloth, toys and industrial goods.
7. Polyvinyl chloride siding and marine fenders
Polyvinyl chloride siding is mainly used to replace aluminum siding. Polyvinyl chloride floor tiles in addition to a portion of the polyvinyl chloride resin, the remaining components are recycled materials, adhesives, fillers and other components, mainly used in airport terminal floors and other places in the hard ground.
8. Polyvinyl chloride consumer goods
Luggage bags are made of polyvinyl chloride processing from the traditional products of marine airbags, polyvinyl chloride is used to produce a variety of imitation leather, used for luggage bags, marine fenders, sports products, which is the new article 1.html, such as basketball, soccer and rugby. It is also used to make uniforms and belts for specialized protective equipment. PVC fabric rubber fenders for apparel are generally absorbent fabrics (without coating), marine fenders, such as ponchos, baby pants, imitation leather jackets and a variety of rain boots. Polyvinyl chloride is used in many sports and recreational products, such as toys, records and sporting goods, PVC toys at present a large growth rate, due to the low cost of production of PVC toys and sporting goods, rubber fenders Die, easy to mold and have the advantage.