Polyvinyl chloride

• PVC
• IUPAC: Poly (1- chloroethylene )

Amorphous thermoplastic

Fixed

Attention

Polyvinyl chloride is an amorphous thermoplastic. PVC (abbreviation) is hard and brittle, and is suitable only by the addition of plasticizers and stabilizers soft, malleable, and for technical applications. PVC is known for its use in flooring to window profiles, pipes, for cable insulation and sheathing and for records that are mentioned in the English language " vinyls".

• 5.1 Waste Prevention
• 5.2 reuse 5.2.1 Mechanical recycling
• 5.2.2 Feedstock recycling
• 5.2.3 downcycling

History

Henri Victor Regnault, the French chemist was 1835, the first to make the Giessen laboratory of Justus von Liebig vinyl chloride and noticed that they have on a prolonged exposure to sunlight, a white powder - polyvinyl chloride - was formed, but the importance of his discovery could not see.

1912 was the German chemist Fritz Klatte (together with Emil Zacharias and Adolf Rollett ) by Chemische Fabrik Griesheim-Elektron ( Griesheim near Frankfurt), later a production site of the company Hoechst, the order for which existing in large quantities of raw materials ethene ( ethylene ) to find new reaction products. He also sat for his experiments, as previously Regnault, glass jars with vinyl chloride and various additives to sunlight. His research led in 1912 to the synthesis of vinyl chloride from acetylene and hydrogen chloride. 1913 Klatte received the patent on the " polymerization of vinyl chloride and used as spare horn, as films, art threads and paints ."

He thus laid the foundation for the production of PVC, which initially allowed only the binding of chlorine and allowed as storage in large quantities. With the shortage of raw materials during and after the First World War, efforts were intensified to use PVC as raw material to replace expensive raw materials through low-cost materials. However, it was not until the late 1920s to more applications. In 1928 the large-scale expansion of production in the U.S. and 1930 in Rheinfelden (Baden) by BASF; In 1935, the I.G. Colors on PVC production.

In 1935 it achieved in Bitterfeld the plasticization of rigid PVC at temperatures of 160 degrees Celsius: the first products were sheets and pipes. The latter were laid in 1935 in Bitterfeld and Salzgitter. A product brand this time, which also colloquially the end of the name contained in the IG Farben still survived for a time, was the Igelit. After 1945, PVC was the most widely produced plastic in the world. In 1948, records were finally made ​​of PVC, which replaced the shellac final. Hence the present name vinyl disk.

One reason for today's use of polyvinyl chloride is safe to use a different substance and a resulting waste arising problem. With the flourishing of the chemical industry was the raw material sodium hydroxide, which is also used today for many processes and procedures, produced in ever increasing quantities. The main fields of application of sodium hydroxide are processing in the soap industry, the cellulose production and the extraction of aluminum from bauxite. The sodium hydroxide solution was obtained by means of electrolytic decomposition of common salt ( sodium chloride), left it remained chlorine and hydrogen. The evolution of chlorine chemistry is based on the cause of the easy accessibility of chlorinated paraffins and thus accessible range of substances derived therefrom and materials. This was favored by the fact that the resulting by electrolytic decomposition of sodium chloride in the manufacture of caustic soda to store large amounts of chlorine and were fed to a use. This was made possible by the industrial and commercial development of the thermoplastic material PVC.

Design and production

Polyvinyl chloride is by free-radical or ionic polymerization of the vinyl chloride monomer (chemical formula H2C = CHCl ) generated.

Production

Originally Carbidverfahren for producing vinyl chloride (VCM = vinyl chloride monomer ) is used. This is obtained from calcium carbide by the reaction of acetylene with water. The acetylene, in turn, is reacted with hydrochloric acid (HCl) to vinyl chloride. This process plays no role in Europe, but rather it is in China, the more dominant manufacturing process. Today ethene is produced from crude oil. Chlorine is produced on a large scale, especially in the chlor-alkali electrolysis of saline. The chlorine is added to the ethylene in the first step, and there is 1,2-dichloroethane. In a second step is cleaved HCl therefrom, VCM produced. Under pressure, and the addition of initiators, and other additives, VCM is polymerized in an autoclave for PVC. Essentially are known three different polymerization. The historically oldest method is emulsion polymerization ( first time 1929). The initiators (for example peroxides, and other peroxy compounds ) are water soluble in this case. This gives the so-called E-PVC. If the VCM dispersed by vigorous stirring in the water and is the initiator ( for example, organic peroxides, azobisisobutyronitrile [ AIBN ] ) soluble in the monomer, one speaks of the suspension, which leads to S- PVC. If no water is used during the polymerization, one speaks of block or bulk PVC, also called M- PVC. Here, the initiator in the vinyl chloride monomer is dissolved.

Today, PVC is after application in soft PVC (PVC -P / P = plasticized ) divided and rigid PVC (PVC -U / U = unplasticized ). Made of hard - PVC pipes and profiles, made ​​for example for windows, further pharmaceutical films. Soft PVC contains up to 40 % plasticizer; Rigid PVC basically contains no plasticizer. PVC -P plays a major role in cable applications. However, it is also used in floor coverings, hoses, shoe soles, roof waterproofing, " rubber " gloves its application.

PVC is a thermoplastic material that is usually processed in the temperature range of 160 to 200 degrees Celsius. The intrinsically brittle and rigid PVC is adjusted with additives primarily stabilizers, plasticizers, impact modifiers to the wide variety of applications. The additives improve the physical properties such as temperature, light and weather resistance, toughness and elasticity, impact resistance, gloss and serve to improve the processability. At the PVC additives used high demands are made: you need to achieve the lowest possible concentration in a high effect, which may not be affected by the different manufacturing processes for plastic molding. They must ensure a good workability and impart the molded part during its lifetime, the desired properties. They should be and from a consumer point of view safe to use.

The addition of heat stabilizers is necessary when processing takes place at temperatures between 160 ° C and 200 ° C. At these temperatures, otherwise the process starts decomposition with elimination of hydrogen chloride HCl. If the PVC is exposed to elevated temperatures during further processing ( for example, by hot plate welding at 260 ° C), the additive package must be adjusted accordingly.

The addition of plasticizers gives the plastic by nature hard material properties such as resilience and softness. As plasticizers, especially phthalic acid esters are used. Less important are adipic acid esters and phosphoric esters. The plasticizer embed themselves in the thermoplastic processing between the molecular chains of PVC and thereby loosen the structure. This storage is a physical distention of the structure, so that despite the low volatility of migration and gas disposal is made. This results depending on the application to a surface adsorbed layer or for the migration of the plasticizer into adjacent materials or through the airspace in neighboring substances. Migrating plasticizers based on dioctyl phthalate (DOP). Products and other sources that migrate more slowly due to significantly lower vapor pressures, are significantly more expensive, but are increasingly used at least in Europe.

Through so-called impact modifier properties are improved as the notched impact strength. Such modifiers are usually made ​​of special acrylate or chlorinated polyethylene. Thanks Modifiers also the processing of PVC is improved, a faster plasticization of PVC is achieved.

Dry blends are special blends with PVC powder.

Economy

With the rebound in construction industry after the global financial crisis, the PVC demand will continue to grow strongly. The average growth rate of the past eight years, from 3.3% per annum is expected to be exceeded in the future. For the global PVC market is expected to annual sales of more than $ 65 billion in 2019. It is also expected that consumption will increase annually in the coming years by an average of 3.9%. Mostly window are exported with PVC frame. Frequently PVC is used for pipes in cable channels and membrane roofs, and flooring. In 2001, services provided in Germany 150,000 employees in 5,000 companies a turnover of 20 billion euros, which is about a quarter of the entire plastics industry.

Properties

Resistant to conc. and dilute alkalis, oils, aliph. hydrocarbons Decomposition by oxidizing mineral acids

The addition of plasticizers, the hardness and toughness of PVC can vary good. It can be dyed. PVC absorbs little water, it is resistant to acids, alkalis, ethanol, oil and gasoline. Attacked is PVC of acetone, ether, benzene, chloroform, and concentrated hydrochloric acid. Rigid PVC can be good, soft PVC handle poorly machined. At temperatures of 120 ° C to 150 ° C, it can be deformed without cutting. Connections can be made with adhesives ( solvent-based adhesives, two-component adhesives) or by welding (various manual and automated welding processes ).

PVC burns with a yellow, sooty flame strong and goes without any additional external flame quickly. Due to the high chlorine content, PVC is flame resistant, in contrast to other engineering plastics such as polyethylene or polypropylene. For fires of PVC plastics can arise and hydrogen chloride, dioxins and aromatics.

PVC is a good insulator. The formation of dipoles and their constant realignment of the AC electric field results in comparison to most other insulators to high loss tangents. Because of the high strength of the cable sheath and the good insulation PVC low voltage cables for laying under plaster or in the open air are very well suited. The maximum allowable concentration for PVC is 1.5 mg · m- third

Use

PVC is mainly used as a raw material for window profiles, pipes, flooring and roofing construction sheeting. Tubes sit down due to the smooth inner surface less, window profiles are low-maintenance and weather resistant, they can be produced in various colors and decorations. PVC is used for fire-resistant cable jacket. PVC films have various applications, eg for water cores of waterbeds and as artificial leather.

PVC is often used as insulating material for electric cables, as an electric switch box and the insertion tube for cables. Credit cards and the like, as phone cards, are usually made of PVC. PVC foam found in fiber composite technology use as sandwich material. Application areas are sport boats, rotor blades for wind turbines and the wagon. Foamed PVC in sheet form ( FOREX ® ) is used as a carrier material for advertising media, such as ausgeplottete logos, images and graphics, especially because of the light weight and ease of processing. Special preparations are used in art installations and events. Highly plasticized PVC films are offered as anti -slip materials.

In some applications, other plastics such as polypropylene (PP ) and polyethylene (PE ) can be used with the advantage that the exhaling of soft PVC (typical plastic smell) and harmful substances eliminated. Also the PVC attributed to acid, oil and seawater resistance are often not required. Some environmental organizations recommend restricting PVC for a few special applications.

Environmental aspects, disposal and recycling

The recycling code of polyvinyl chloride is 03

The advantage of PVC, namely its durability, also comes into play, when it is supposed to rot. Sunlight it does not degrade the mechanical properties are not impaired. Water ( also salty sea water) and air can to not destroy pvc little.

Therefore, PVC is mainly used for long-life products such as window frames or sewage pipes. So go out about 80 percent of the PVC produced in Germany in the production of building components ( 50 percent in window, 13 percent in tubes, 15 percent in roofing sheets ). Therefore, the disposal problem is not quite compare with that of other types of plastic in " disposable products ". The withdrawal of PVC products is easier, violations are more easily traceable.

In the recycling process, a distinction between a material and a raw material recycling method.

Basically, there are the following approaches to solve the waste problem of PVC:

Waste prevention

Solutions that exist for other types of plastic (biodegradable packaging), come for PVC naturally not considered.

Reuse

For other types of plastic, it is possible to use the product almost unchanged again. Example: deposit bottle. This is drunk, returned, cleaned and then reused for its original purpose by being refilled and sold again.

Case of PVC, however, this is difficult. Although there may be for PVC building products such as pipes and windows nationwide take-back systems for the plastics processing industry. However, the products will be used again only in the rarest of cases - mostly they are recycled.

Mechanical recycling

Thermoplastics can be, once formed into a workpiece, meltdown again and shape into a new product. However, the sequence of heat treatments leads to a progressive degradation of the material ( down-cycling ).

The biggest problem when a new material recovery, however, is the separation of the individual plastics. If you mix different polymers in one material, this usually leads to a strong loss of quality and significantly poorer mechanical properties. To facilitate the separation, one in 1988 to one recycling code. The recycling is not unmixed waste, such as household waste, but still is very difficult. The usual separation methods are very labor intensive and require a high use of water and energy, so turn here both the cost -benefit analysis as well as the ecological balance negative.

The mechanical recycling is therefore currently used almost exclusively where large amounts of unmixed material are available. For example, foam polystyrene packaging collected in Germany, which are re- utilization as a soil conditioner in agriculture or in the production of foam polystyrene concrete or bricks. The recycling rate for foam polystyrene was about 70 percent in 2000.

Also there is a return system for PVC; are collected primarily floor coverings, roof sheeting, window profiles and PVC pipes. Other areas of application for the plant material recycling are, for example, the recycling of vehicles or beverage bottles, or in countries in the second or third world, where collecting unmixed plastic waste contributes to income. So from the secondary raw materials once products such as window profiles, pipes, flowers and beverage boxes, new films, window frames or watering cans.

The biggest problem with the reprocessing put metal contaminations cable waste, in which the copper has been removed, are still heavily contaminated and must be cleaned in order to get back into a real circuit and to attain the quality of a virgin material.

Feedstock recycling

By pyrolysis plastics can be returned to the respective monomers or other petrochemical recoverable materials such as methanol or syngas split. The availability of unmixed material but is also a prerequisite for the recovery of the monomers. Examples are the hamburger method, which is currently operated by BP and is used both for the production of monomers and petrochemical raw materials, as well as developed by Walter Michaeli and other methods of degradative extrusion, which is capable of mixed plastic waste into feedstock usable gases, convert waxes and oils. These processes are naturally mainly used for recycling of mixed plastics that would can be separated only with great effort.

Downcycling

Downcycling is a form of recycling, with which the original material quality is not achieved by a recycling. From a previously high-quality product, a poor-quality product can be produced by a down-cycling just yet. An example of such an inferior end product is the Bakenfuß ( the holder, be plugged into the red and white road barriers ).

Disposal

As landfill is defined as the storage in a landfill. By the year 1989 we deposited about 70 percent of the waste deposit. (Hard PVC shall not pass away, and also harms neither water nor air, but it just takes so at the dump a lot of space. ) Furthermore it can be taken any forecast, whether the hard PVC can not be but eventually attacked by microorganisms or chemical processes. From the ingredients of soft PVC but one can assume with great certainty that these contaminate the leachate and thus the environment due to their plasticizer content.

Energy recovery

A relatively simple method to dispose PVC and other plastic waste, the combustion. From the combustion process, energy can be extracted ( hence the name). So can be the same from the disposal of rubbish a profit.

However, the energy recovery also has disadvantages. If PVC burned itself corrosive, gaseous hydrogen chloride, which forms with water or humidity is hydrochloric acid. In waste incineration plants, this is neutralized with lime in the Ablüftungsanlagen. At these temperatures, caused by the burning plastics highly toxic dioxins.

Combustion is incomplete and sooty. The resulting smoke and soot contains polycondensated aromatics such as benzo [a ] pyrene, pyrene and chrysene, which have a highly toxic and carcinogenic. Another danger comes from heavy metal containing stabilizers such as Bleidistearat.

For this reason, elaborate filtering techniques are applied to the harmful emissions to filter waste incineration plants. Thus, the production of energy are offset by very high expenditure on environmental protection.

Evaluation of disposal routes

According to EU regulations the following waste hierarchy, which underlies all legislation and policies relating to waste prevention and management as a priority order based is:

Considering that waste prevention and reuse only to a certain degree are always realistic, recycling therefore plays an important role.

The European Commission recommends " the use of recycled PVC should be encouraged in the production of certain construction, because this allows the recycling of post-consumer PVC. [ ..] So would avoid that PVC waste is landfilled or incinerated and thus carbon dioxide and cadmium are emitted into the environment. "

Sustainability, Vinyl 2010 and VinylPlus

Annually publishes the non-profit counseling organization " The Natural Step " (TNS ) a report on the progress of the sustainability programs of the industry during the previous year. It describes five sustainability demands that have been developed on the basis of the framework of TNS. The European PVC industry has subsequently adopted a commitment to sustainable development in March 2000; in the "Vinyl 2010" mentioned undertaking is the industry mainly to recycle a certain percentage of PVC. In June 2011, a further initiative as "Vinyl Plus" was launched to meet all five required points:

• TNS sustainability challenge for PVC No. 1 deals with the final intrinsic energy and CO2 volumes. The ultimate goal is the attainment of the CO2 neutrality.

• Controlled, closed loops are the target of TNS sustainability challenge No. 2 Different companies support the " Recovinyl " initiative. This new product lines are developed, which consist largely of post-industrial, reclaimed PVC waste from end-users. Recovinyl provides financial incentives ( " Incentives " ) to promote the collection of PVC waste from the construction and demolition industry. His goal is to ensure a constant supply of post-consumer PVC waste for recycling in Europe. Recovinyl cooperates with various partners, consumers, municipalities, recyclers, businesses in general and waste management company in particular, and with the European Commission and national state governments. Since 2005, the recycled quantities are constantly rising. The waste registration in 2008 yielded 12,365 PVC supply inputs; 198,000 tons a registered PVC waste were collected and recycled.

• The emission of POPs throughout the life cycle of a PVC product is the focus of the 3rd TNS sustainability challenge for PVC. It tries to fugitive emissions of potentially persistent substances to minimize in the production of PVC, for example, by a tendency for the formation of dioxins rubber seals are replaced with titanium seals.

• Looking at the use of additives that contribute not only by their properties in terms of direct toxicity to full sustainability of PVC products, so you get to the fourth TNS sustainability challenge for PVC. The additives determine not only the use, but throughout the entire life cycle of the product and beyond during recycling the potential for sustainability. In cooperation with strategic suppliers of raw materials whose processes and products are assessed and looked for improvements.

• The obligation to raise awareness for sustainable development across the PVC industry is underpinned in the 5th TNS sustainability challenge. There are approximately initiated training courses to accelerate the development in the PVC industry towards sustainability.

Health hazards

As the first workers in the PVC production to deformations of the Fingerendgliedmaßen diseased or severe liver damage or even liver cancer ( Hämangioendothelsarkom ) showed, the work was improved in the production and processing of PVC. The "VC 's disease " has been recognized by the professional associations as an occupational disease. The starting material for PVC, vinyl chloride may cause cancer in humans and causes genetic mutations. Other starting materials of PVC production are questionable.

Soft PVC is physiologically questionable by the plasticizer contained depending on the application. For toys, the use of plasticized PVC is problematic, although it is used because of its low price and features. Despite the low vapor pressure plasticizer may access through saliva, skin contact or the airways in the infant's body. The phthalate are partially damaging the liver and kidneys and are suspected to be carcinogenic. This resulted in several studies in which there were clear traces in the blood. Phthalate ( DEHP) was classified as fruit and toxic effects by an EU working group in 2000. Soft PVC with phthalate was banned in the EU in 1999 for small children's toys.

" The human body takes PVC plasticizer at higher levels than previously thought. Particularly at risk are children. The widely used plasticizer phthalates are considered highly hazardous to health because they interfere with the hormone balance and impair reproduction or development "

In food packaging soft PVC is problematic, if not prevents the migration into the food by barrier layers. For fatty foods soft PVC should be avoided as plasticizers are well absorbed by fat.

Determination

In an internal sample the gases smell of hydrogen chloride. When burning copper, the flame turns green (see Beilstein test ). Both for such a focal sample and for the Beilstein test should ( outside the examination laboratories) only very small quantities are used as a health risk, organochlorine compounds.