Asbestos - Ishiwata

Also called asbestos. A flexible and strong fibrous mineral. In the strictest sense, it is a serpentine type of chrysotile asbestos, but in industry, asbestos is a general term for various fibrous silicate minerals, most of which are amphibole and can be classified into the following four types: chrysotile H ₂ Mg ₃ Si ₂ O ₃ , blue asbestos NaFe(SiO ₃ ) ₂ ･FeSiO ₃ , amphibole Ca(MgFe) ₃ (SiO ₃ ) ₄ , orthobole (Fe, Mg)SiO ₃ . Of these, blue asbestos with a low iron content is called amosite. There is also synthetic asbestos, which is synthesized by hydrothermal reaction or melting. Chrysotile asbestos produced in the Quebec region of Canada is the most famous and has excellent properties. Asbestos strands are 0.01-1 μm in diameter and are twisted together to form thin fibers measuring 0.5-1 mm. Asbestos has a wide range of uses due to its properties of heat resistance, acid and alkali resistance, tensile strength, and thermal and electrical insulation, and until the 1980s, around 300,000 tons were imported to Japan annually. High-quality asbestos was made into textile products such as thread, tape, and cloth, and was used for fireproofing, fire-resistant insulation, electrolytic melting membranes, high-temperature packing, etc. Lower-quality asbestos was mixed with cement to make various asbestos-cement products. It was also mixed with synthetic resin or rubber and used as brake linings or clutch facings. The health problems associated with asbestos began to become apparent in Japan in 1988. A relationship between the inhalation of asbestos and the incidence of lung cancer and mesothelioma was pointed out, and in 2005 the Ordinance on the Prevention of Asbestos-Related Hazards was enacted, and production of asbestos has essentially been discontinued.

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

アスベストともいう．柔軟で強靭な繊維質の鉱物．狭義には，蛇紋石系の温石綿であるが，工業的には，各種の繊維状ケイ酸塩鉱物を総称して石綿とよび，その大部分は角せん石質で，次の4種類に分類できる．温石綿H₂Mg₃Si₂O₃，青石綿NaFe(SiO₃)₂･FeSiO₃，角せん石綿Ca(MgFe)₃(SiO₃)₄，直せん石綿(Fe，Mg)SiO₃．このうち，青石綿で鉄分の少ないものをアモサイトという．また，水熱反応あるいは溶融法で合成される合成石綿もある．カナダのケベック地方に産出する温石綿はもっとも有名で，性質もすぐれている．石綿は，1本の直径が0.01～1 μm であり，それがより合わさって0.5～1 mm の細い繊維となる．耐熱性，耐酸・耐アルカリ性，抗張性，熱および電気絶縁性などの性質を備えているために広い用途があり，1980年代までは日本には毎年30万t 程度輸入され，良質なものは糸あるいはテープ，布などの紡織品となり，防火材，耐火保温材，電解用融膜，高温用パッキングなどに使用された．低級なものはセメントと混合して各種の石綿セメント製品となった．また，合成樹脂またはゴムに混入して，ブレーキライニングあるいはクラッチフェーシングとして利用されていた．石綿は，1988年になって国内で健康障害の問題があることが顕在化した．石綿の吸入と肺がん・中皮腫の発生率との関係が指摘され，2005年に石綿障害予防規則が施行され，原則的に製造中止になっている．

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