コールタール 化学特性,用途語,生産方法
種類
コールタールは、各種鉄鋼製品の防蝕剤、木材の防腐剤、研究開発用試薬製品として販売されています。
防錆防食材としては16 kg、2.5 kgなどの容量で提供されている製品です。研究開発用製品としては100 mL、500 mLなどの容量があります。
また、コールタールは蒸留法により分留されてタール分留品としても販売されています。主なものとその用途は次の通りです。
- ピッチ: 電極用バインダー
- クレオソート油: 防腐剤、塗料
- ナフタリン: 染料、顔料
- タール酸: 樹脂原料、顔料
性質
図2. コールタールの主成分
コールタールの主成分は多環芳香族炭化水素です。主な化合物と含有率は下記の通りです。
- ナフタレン: 5%–15%
- ベンゼン: 0.3%–1%
- フェノール: 0.5%–1.5%
- ベンゾ[a]ピレン: 1%–3%
- フェナントレン: 3%–8%
外観は茶褐色あるいは黒色で、粘性の高い液体です。ナフタレン様の特異臭を呈します。比重は1.18-1.23です。 水に微溶であり、ほとんどがベンゼン、ニトロベンゼンに溶解します。
また、一部のアルコール等や苛性ソーダ溶液にも部分的に可溶です。
解説
タール（油状物質），有機物の熱分解によって生成する褐色から黒色の粘稠(ねんちゅう)性油状物質の総称。木(もく)タール、石油ピッチなどがあるが、狭義には石炭の乾留で得られるコールタールをさす。タールの組成・性状は原料により異なるが、多環縮合芳香族化合物を基本とし、これに少量の硫黄(いおう)、窒素、酸素、灰分などを含む。防腐剤、塗料などに用いられるが、もっとも重要なのは芳香族系化学原料としての用途で、石炭化学工業はコールタールから、有用な化学物質を得ることを出発点として発展した。
用途
コールタール=タール製品原料、防錆塗料、漁網染料、油煙、燃料
説明
Coal tar is a complex hydrocarbon mixture produced by
thermal destruction (pyrolysis) of coal, typically a dark
viscous liquid or semisolid with a smoky or naphthenic odor.
The composition of coal tar will be influenced by the process
used for pyrolytic distillation as well as by the original
composition of the coal; however all coal tars will be
comprised of a variable mixture of organic compounds
including benzene, toluene, xylenes, cumenes, coumarone,
indene, benzofuran, naphthalene, acenaphthene, methylnaphthalenes,
fluorine, phenol, cresols, pyridine, picolines,
phenanthracene, carbazole, quinolines, fluoranthene, and
pyrene. The number of specific chemical constituents is in the
thousands. Coal tar creosotes and coal tar distillates, oily
liquids generally lighter in color and of lower viscosity than
coal tar, are fractions produced by additional distillation of
crude coal tar. Coal tar pitch is a highly viscous dark semisolid
byproduct of coal pyrolysis. Coal tar volatiles are the vapors
produced from heated coal tar or coal tar pitch, containing
lower molecular weight (smaller ring number) polycyclic
aromatic hydrocarbons (PAHs).
Coal tar is noteworthy as one of the first – if not the
first – chemical substances documented to cause cancer
through occupational exposures. In the eighteenth century,
Sir Percival Pott, a British surgeon, noticed a higher incidence
of cancers in chimney sweeps chronically exposed to
soot and coal tar. He then demonstrated excess cancers
occurring in laboratory animals when coal tar is applied to
the ears and skin. In the early twentieth century, polycyclic
aromatic compounds isolated from coal tar were identified
as chemical carcinogens.
化学的特性
Coal tars are by-products of the destructive distillation (carbonization) of coal to produce coke or gas. The composition and properties of a coal tar depend primarily on the temperature of the carbonization and to a lesser extent on the nature (source) of the coal used as feedstock. In general, coal tars are complex combinations of hydrocarbons, phenols, and heterocyclic oxygen, sulfur, and nitrogen compounds. Over 400 compounds have been identified in coal tars, and as many as 10,000 may actually be present. The PAH content of coal tars increases with increasing carbonization temperature. Coal tars typically are black or almost-black viscous liquids or semisolids with a characteristic naphthalene-like odor (ATSDR 2002). They are slightly soluble in water, partially soluble in acetone, carbon disulfide, chloroform, diethyl ether, ethanol, methanol, petroleum ether, and sodium hydroxide, and soluble in benzene and nitrobenzene. Lowtemperature coal tars (formed at temperatures below 700°C) are black, viscous liquids that are denser than water and contain a lower percentage (40% to 50%) of aromatic compounds than high-temperature coal tars (IARC 1985). Coal tars are highly flammable and corrosive, and toxic gases may be released when they burn. Their vapors can form explosive mixtures with air (HSDB 2009).
Coal-tar pitches are shiny, dark-brown to black residues produced during the distillation of coal tars. They contain various PAHs, their methyl and polymethyl derivatives, and heteronuclear compounds (IARC 1985).
使用
Coal tars and coal-tar pitches have many uses in industry and in consumer products. Coal tars are used primarily for the production of refined chemicals and coal-tar products, such as creosote, coal-tar pitch, and crude naphthalene and anthracene oils from the distillation of crude coal tar. Coal tar has been used as a fuel in open-hearth furnaces and blast furnaces in the steel industry, as a binder and filler in surface-coating formulations, and as a modifier for epoxy-resin surface coatings. U.S. Pharmacopeia–grade coal tar is approved for use in denatured alcohol (IARC 1985). Coal-tar preparations have been used for many years to treat various skin conditions, such as eczema, psoriasis, seborrheic dermatitis, and dandruff. Both prescription and nonprescription preparations are available and include cleansing bars, creams, gels, lotions, ointments, shampoos, and other topical solutions and suspensions (DermNet NZ 2010). Coal tar is also registered as an active ingredient in pesticides with the U.S. Environmental Protection Agency (EPA 2003).
Coal-tar pitches are used primarily as the binder for aluminumsmelting electrodes (IARC 1984). They are also used in roofing materials, to impregnate and strengthen refractory brick (for lining industrial furnaces), and in surface coatings, such as pipe-coating enamels and black varnishes used as protective coatings for industrial steelwork and as antifouling paints for boats. Hard pitch is used as a binder for foundry cores. Coke-oven pitch is used to produce pitch coke, which is used as the carbon component of electrodes, carbon brushes, and carbon and graphite articles. Distillation fractions and residues from high-temperature coal tars are used for road paving and construction and in the production of naphthalene, recovery of benzene, production of anthracene paste, briquetting of smokeless solid fuel, impregnation of electrodes and fibers, and manufacture of electrodes and graphite (IARC 1985).
使用用途
コールタールの主な使用用途は、タール分留製品原料、防錆塗料、漁網染料、油煙、燃料です。かつては枕木や木電柱などの木材の防腐剤や、トタン屋根の塗料として広く用いられていましたが、近年では建材の移り変わりやコンクリート製の普及により、使用されることが少なくなっています。炭素電極の支持材にも使用されていました。
また、コールタール製剤には角質溶解・形成作用、止痒作用があるため、かつては医療にも用いられていた物質です。特に、皮膚疾患の1種である乾癬では、かつてはコールタールを外用するゲッケルマン療法が行われていました。しかし、後述する発癌性が指摘されてからは行われなくなってきています。
安全性プロファイル
A human and experimental skin
irritant. A flammable liquid. When heated to
SYNS: ANTHMCITE PARTICLES 0 COAL FACINGS 0
COAL, GROUND BITUMINOUS (DOq 0 COAL-MILLED
0 COAL SLAG-MILLED SEA COAL
decomposition it emits acrid smoke and
irritating fumes.
発がん性
Coal tars and coal-tar pitches are known to be human carcinogensbased on sufficient evidence of carcinogenicity from studies in humans.
環境運命予測
Due to the variability in composition, it is not possible to
describe all potential mechanisms of toxicity for coal tar. The
reader is recommended to review additional references for
individual constituents found in the Table of Contents. It is
likely that acidity of some constituents, such as phenols, and
the defatting potential of some hydrocarbons, contribute to the
irritancy of coal tar. Phototoxicity of PAHs is likely to be a main
cause of contact irritation.
The carcinogenicity of PAH constituents is believed to lie in
their potential for their reactive metabolites to be bound to
macromolecules such as DNA. The mechanism of therapeutic value as a topical agent in the treatment of skin diseases is
unknown but is thought to involve decreased epidermal
proliferation.
コールタール 上流と下流の製品情報
原材料
準備製品