Pencil pitch

Asphalt, cut back Cut-backs Bitumen Pencil pitch Pitch prill Road asphalt Road asphalt or tar liquids Tars, liquid, 3.2, 3.3 Tars, liquid, including road asphalt and oils, bitumens and cut backs, 3 

Bituminous materials are dark brown or black, semi-solid or liquid, thermoplastic mixtures of hydrocarbons derived from natural or synthetic processes in which hydrocarbon mixtures have lost their volatile components leaving a denser residue. Natural bitumens come from exposed and weathered petroleum and rock deposits. Synthetic bitumens come from the residue remaining after the distillation of petroleum, coal tar, and other organic materials like wood and peat. The complexity of the high molecular weight hydrocarbon oils and resins bitumens contain make complete chemical characterization impossible. The terms bitumen, tar (8007-45-2), pitch (61789-60-4), and asphalt (8052-42-4) apply to any of these substances, although pitch and tar also describe the sticky resins that exude from various trees. 

Petroleum asphalt is used extensively as a binder in concrete road paving, hence road asphalt. Mixed with asphalt, coal tar pitch makes exceptional road surfaces that resist oils, are non-skid, adhere excellently to stone, and provide weathered hard surfaces. Cutback asphalt is asphalt dissolved in and made less viscous by a solvent (usually a petroleum distillate) allowing easier application in road repair and waterproofing. Road oil is very fluid asphalt used as a dust suppressant. 

Prills are small globules of material that are often of high purity either separated from inferior pieces or manufactured into granules, pellets, or cylinders by dropping the melted material from a height or other means. Pitch prills are spherical, granular, or cylindrical products pencil pitch) made from bitumens. 

Bitumens contain many chemicals of unknown toxicity and all will bum when heated to a sufficiently high temperature. Flammable solvents are widely added to bitumens to decrease their viscosity and improve handling. Bitumens may also be transported at sufficiently high temperatures to evolve these solvents and other flammable constituents in ignitable concentrations. 

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PAH have very low vapor pressure at room temperature. These substances, however, may deposit on the dusts in the air. PAH may be produced during pyrolysis of organic materials. These compounds can contaminate the air near coke ovens, as well as during loading and unloading of pencil pitch. 

Pencil pitch, see also Solid Bulk Materials,... 

Pitch prill, prilled coal tar, and pencil pitch are combustible solids and dust irritants. 

Pencil pitch, see Bituminous Products, p.32 Petroleum Coke, see also Petroleum, p.l83 Pitch prill, see Bituminous Products, p.32 Prilled coal tar, see Coal, p.44... 

Pitch. Pitch used to be stored in solid form at the tar distillery in open bays, from which it was removed by small explosive charges. Loading of the lump pitch by mechanical shovel created a dust ha2ard both at the tar installation and at the customer s, where the lumps had to be ground before use. In the 1990s, pitch is stored in tanks heated by superheated steam or circulating hot-oil coils and transported in fiquid form in insulated rad, road tankers, or ships. When transport as a hot fiquid is not feasible, not acceptable by the customer, or for small amounts, the pitch is converted into a dust-free particulate form, ie, short rods termed pencils, pastilles, or flakes. 

The risk of skin cancer by contact with pitch dust has in more recent years been reduced by the transport and handling of pitch as a Hquid or as dust-free flakes or pencils. Nevertheless, in handling coal-tar products, certain precautions should be taken. These have become obligatory in tar distilleries and plants using pitch or creosote. 

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