Coal tar pitch is a byproduct of the coking process that occurs when coal is heated and condensed during the production of coke. It is used in a variety of industrial applications, including the custom production of asphalt mixtures and as an additive to paints, waterproofing and other products. Beneficial and toxic properties derived from coal tar pitch have been recognized for over one hundred and fifty years, and the material has seen considerable development since its initial commercial applications.
Coal tar pitch is processed from hard coal into a viscous blackish liquid with a strong and unpleasant, but not necessarily poisonous, odor. Utilizing high temperatures, the gasification, liquefaction and fractional distillation of the coal produces coal tar pitch and other fractions
including crude benzene and aromatic hydrocarbons such as naphthalene as byproducts. The amount of each by-product produced varies in quanity and changes in quality, depending on the type and quality of coal used.
The chemical path of these by-products then leads to the development of the liquid that is known as coal tar pitch. The material is composed of phenols, carboxylic acids, quinolines, benzenoid compounds, aldehydes and carbon. As coal tar pitch is high in polynuclear aromatic compounds, it has been found to be a potential health hazard despite its use in many commercial and industrial applications.
The primary commercial application of coal tar pitch is in the manufacture of roofing materials. This use of coal tar pitch is supported by multiple factors, from its abundant availability and supply to its high adhesive properties and water resistance when applied to surfaces. Roofing with coal tar pitch often requires an application of the material that is heated to around 350 degrees Celsius, applied in thick layers and then left to cool. This creates a waterproof seal for the roofing surface, durable and able to last for many years with minimal upkeep.
A secondary use of coal tar pitch is in asphalt production, where the material is used to create a more durable, hardy and resistant coating for roads. Coal tar pitch ensures excellent waterproofing performance, and its superior adhesion capabilities when heated make it well suited to this application.
In addition to its essential uses, coal tar pitch has also been used in a variety of paint products. Coal tar pitch can be added to a range of paints, lacquers and other coatings, supplying excellent waterproofing capabilities, alkali resistance and an improved and smoother finish.
Despite its versatility and versatility, coal tar pitch has not come without its own challenges. Constant exposure to the by-product has been linked with a multitude of health and environmental concerns ranging from cancer and respiratory illness to soil and groundwater contamination. Although coal tar pitch has seen a fall in availability since the 1970s, its inherent characteristics have enabled it to maintain a prominent place in commercial, industrial and many other applications.
