Soot

Soot (from OHG Ruos, dark, dirt -colored) is a black, powdery solid, which is depending on the quality and use for 80 to 99.5 per cent of carbon.

Soot referred to colloquially both German industrial products as well as unwanted, harmful by-products of combustion processes. To distinguish the English term carbon black is used for the industrial raw material manufacture as usually used, sometimes even the older term carbon black. Carbon black is a modification of the carbon having a very high surface area and is mainly used as a filler and as a black pigment.

Properties

Two fundamental properties of Industrierußes determine the two main application areas: its reinforcing effect in rubber (natural and synthetic rubber ), and its color, which make it the most widely used black pigment. Moreover, within special applications, its thermal and electrical conductivity, and its resistance to UV radiation play a role. Depending on the application, carbon black has special property profiles that are specifically influenced by the nature of the production process and by varying the process parameters. Carbon black consists of tiny, generally spherical particles, which are also called primary particles. These usually have a size of 10 to 300 nanometers, which is less than a thousandth the diameter of a hair. These primary particles are chain-like, partially coalesced chunk-like aggregates. Many of these units group together to form the agglomerates. By varying the preparation conditions, both the size of the primary particles and their aggregation can be tailored. At these dimensions, it is not only the chemical composition alone, but also the size and shape of the particles, which determine the properties. Optical, electrical and magnetic properties, as well as hardness, toughness and melting point of nanomaterials to differ significantly from those of the macroscopic solid, it can be special properties of the soot reasons. The specific surface area of carbon black is about 10-1000 m2 / g

Production

Carbon black is an important industrial product which is produced by incomplete combustion or pyrolysis of hydrocarbons, in large quantities. In 2006, world's 8.1 million tons, in 2011, 10.8 million tons were produced.

Manufacturing process

Carbon black can be used in combustion soot, which is produced by incomplete combustion, and thermal black, which by thermal decomposition ( pyrolysis), subdivide.

Carbon black is distinguished by its manufacture or after its application. Industrial manufacturing processes include the acetylene, the Channelrußprozess, the Gasrußprozess, the Furnacerußprozess, the flame black and thermal black, with the furnace black with worldwide about 95 % is by far the most widely used method. Here Carbon black is produced by incomplete combustion of heavy fractions, most of the residues from FCC or steam crackers or from the distillation of coal tar. In this method, a hot gas from 1200 to 1800 ° C by combustion of oil or natural gas produced in a combustion chamber (English furnace ). In this hot gas is then a carbon black feedstock, mostly aromatic-rich coal-and petroleum-based carbon black oils injected. Incomplete combustion and thermal decomposition (pyrolysis ) of the carbon black raw material, the soot is formed here, the competing reactions of nucleation and growth in the reaction zone are controlled by process parameters such as oil loading and residence time so that the carbon black produced with the desired property profile. After a certain residence time of the process gas mixture is suddenly cooled by water injection (English quenching), and the carbon black is separated in bag filters. The systems are operated fully continuously in shifts.

Necessarily appropriate post-treatments of carbon black are carried out for many applications. For example, carbon blacks are produced for high color depth paints by subsequent oxidation of Basisruß. The oxidic groups give better wetting with binders and resins.

Füllstoffruß

Carbon black is used more than 90 percent as a filler in the rubber industry, mainly ( about 70 %) for car tires and about 20 % for technical rubber products such as conveyor belts, V-belts, hoses, damping elements. The automotive industry is by far the largest buyer of carbon black: For tires they consumed more than 7.8 million tons in 2011. For car tires, there are about 40 different Industrierußtypen that mediate each specific properties of the rubber. International practice is to classify Standardrußen by the U.S. ASTM standard. In the CIS countries the different GOST standard also is common. Industrial carbon with high surface area and appropriate amplification activity ( N1xx to N3xx according to the following table) are processed in the tread of the tire, to give her the necessary hardness and abrasion resistance. This group of carbon black is therefore also called Tread Blacks, Hard Blacks or active carbon black. The group of semi-active industrial carbon ( N5xx to N7xx ) is used for the side walls ( the carcass ) of the tire in order to adjust the requisite suspension and damping. So you make the rubber more elastic. You will also Carcass Blacks, called Soft Blacks or Halbaktivruße. Typically, the production equipment can be designed so that it can optimally produce either one or the other group. In addition to other raw materials and in particular of tire technology, even the property profiles of industrial carbon blacks used in tires determine its three main characteristics: These are rolling resistance, wet grip and abrasion.

Conductivity

The carbon black having small primary particles and have far branched aggregates, it allows an electrical conductivity in various applications. We therefore speak specifically of conductivity for this product qualities. Conductivity is used in the electrical industry and is used as raw material for engineering ceramics, as well as electrode material. A particular application is in the production of electrically conductive ink, which serve as a security feature for documents. With this black, conductive inks also interconnects are printed.

Acetylene black (English acetylene black) is used as an additive in the manufacture of cathodes for zinc -carbon batteries. The addition of acetylene black increases the conductivity of the electrochemically active manganese dioxide ( manganese dioxide ) and allowed better absorption of electrolyte solution in the cathode.

Lampblack

Carbon black (in particular as UV protection ) used as a black pigment (C.I. Pigment Black 7), for printing inks, inks, paints for coloration of plastics. Even in specialties such as mascara, grave soil, decorative paper and fibers, it serves as a black pigment.

Carbon blacks are nanoparticulate carbon blacks are losing by their fineness brown tone. Their use is in particular in the production of black inks of different printing processes. Since the printed layers are very thin and partially transparent, a special grade of carbon black is required. For a sufficient color depth ( black tone ) of cheaper grades of carbon black, especially in newspaper printing inks, is often embellished with blue pigments.

Carbon blacks for high color depth paints are produced by subsequent oxidation of the Basisrußes. The oxidic groups provide better compatibility with the binders and resins.

Ecology and Toxicology

Carbon black is used as wide, that it occurs everywhere, but always embedded in the respective matrix of the application system. He passes through abrasion, for example, of tires or newsprint colors in the environment. Basic damage effects are possible firstly because of the chemistry of the production process and, secondly, in the capacity as fine or nano material. In the preparation containing PAH ( polycyclic aromatic hydrocarbons ), and therefore highly carcinogenic raw material in an inorganic pigment is converted. This raises the question of whether residual traces of the starting material may remain on the carbon black produced. This is the case, depending on the process conditions of manufacture. The hazard potential is limited by the fact that these residues due to the high surface activity (van der Waals forces) of Industrierußes are strongly adsorbed. The current toxicological evaluation of carbon black can be found at the International Agency for Research on Cancer ( IARC). After that, "Carbon black is Possibly carcinogenic to humans (Group 2B) ". Short-term exposure to high concentrations of carbon black dust may cause irritation by mechanical impairment of the upper respiratory tract. Carbon black is possibly carcinogenic to humans as viewed and classified as a Group 2B carcinogen, because there are plenty of meaningful studies with animals, but no studies with humans. The main statements of carcinogenicity in animal studies stem from studies in rats, two of Chronic inhalation and two for direct instillation into the trachea. These studies showed significantly higher incidence of lung cancer in the rats studied. Another inhalation study, this time on mice showed no increase in lung cancer. Epidemiological data, there are three different cohorts of production workers. Two studies, one from UK and one from Germany ( production plant Kalscheuren near Cologne), with more than 1,000 workers each in each investigated group showed an increased mortality from lung cancer. Another study of over 5,000 black workers from the United States did not show this increased mortality.

History

The production of carbon blacks as a black pigment for inks and inks goes back to the early civilizations of mankind. The industrial application begins with the discovery of the amplifier effect in natural rubber around the year 1900, which was an essential prerequisite for the much improved characteristics of tires and thus for the recovery of the automotive industry. The first larger plants were built as channel black plants in the oil fields in the U.S. to utilize a portion of the natural gas occurring in oil extraction. The yields were low (2 %), which did not matter because of the surplus of natural gas. However, the strong increase in demand in the tire industry saw in the 20s and 30s in the United States for the development of Furnacerußverfahrens, the yield achieved depending on product feature from 50 to 70 %. The development of technologically furnace blacks in about four shafts: a first generation of products differed mainly in the size of the primary particles and hence the specific surface area ( N110, N220, N990 ... ), then in a second generation and the Aggregierungsverhalten, thus, the degree of intergrowth of the primary particles, the so-called structure varies. In the 70s and 80s began, for example, via the residence directly influence performance properties of the rubber. Finally, in the 90s, other fillers came on the market, the silica - silane system in the patented Michelin green tires, with the rolling resistance and therefore the fuel consumption has been reduced. In response, the nanostructured industrial carbon have been developed as the fourth generation of innovation Reifenrußen.

In Germany, the gas black process was developed in parallel with the furnace black American. In 1932, Degussa is the largest German production plant in Cologne. Under the National Socialists was carbon black, a key raw material war and was produced in newly established joint venture between Degussa and tire manufacturers after the gas black (for example, in 1936 founding of the German Gasrußwerke GmbH & Co. KG in Dortmund).

Unwanted soot

Carbon black also occurs in combustion processes as a product and also contains undesirable oily products of incomplete combustion. Such soot ( soot English ) trigger has the potential to cancer in animal experiments. When incomplete combustion produces polycyclic aromatic hydrocarbons ( PAHs) that determine the risk of developing cancer. In old heating systems soot sat on cooling as a product of incomplete combustion from and caused (not as the sole cause ) the sooting of chimneys. The harmful effects of soot fell repeatedly in the media spotlight; an example is the discussion of the diesel soot load in automotive exhaust gases. See also: soot