Acetate fiber - Acetate fiber

A man-made fiber made of cellulose acetate, an acetate ester of cellulose. According to the Quality Labeling Act, this refers to a fiber made of cellulose acetate with an acetylation rate of 45.0% or more. However, fibers made of cellulose acetate with an acetylation rate of 59.5% or more may be called "triacetate fiber." The acetate esterification reaction of cellulose is generally carried out in anhydrous conditions, producing triacetate (primary acetate) in which all three OH groups in the glucose unit are acetylated. Since triacetate is insoluble in acetone, in order to make it soluble in acetone, the acetyl groups are partially hydrolyzed (called saponification or aging) to produce secondary acetate (usually called acetate or diacetate) in which an average of 2.5 OH groups per glucose unit are acetylated. For the acetylation mentioned above, acetic anhydride is used as the main acetylation agent, sulfuric acid is used as the catalyst, and acetic acid is mainly used as the diluent (for 100 parts of cellulose, 240-300 parts of acetic anhydride, 7-15 parts of sulfuric acid, and 400-800 parts of acetic acid). Ordinary acetate fibers are made by dissolving flakes of secondary acetate in acetone and dry spinning them. Triacetate fibers are usually made by dissolving the complete acetate in a mixture of dichloromethane (85-90% by weight) and methanol or ethanol (10-15% by weight) and dry spinning them. Acetate fibers are lustrous, flexible, and have a good texture. Short acetate fibers are used in cigarette filters. Triacetate fibers have low hygroscopicity and their thermal behavior is similar to that of hydrophobic synthetic fibers.

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

セルロースの酢酸エステルである酢酸セルロースからなる人造繊維．品質表示法によれば酢化度45.0％ 以上の酢酸セルロースからなる繊維をいう．ただし，酢化度が59.5％ 以上の酢酸セルロースからなる繊維の場合は“トリアセテート繊維”とよんでもよいとされている．セルロースの酢酸エステル化反応は，一般に無水状態で行われ，グルコース単位の三つのOH基が全部アセチル化されたトリアセテート(第一次アセテート)を生成する．トリアセテートはアセトンに不溶のため，これに可溶にするため，アセチル基を部分的に加水分解(けん化，熟成という)させ，グルコース単位当たり，平均2.5個のOH基がアセチル化された第二次アセテート(普通，アセテート，ジアセテートともいう)として用いられる．前述の酢化には無水酢酸を酢化主剤，硫酸を触媒，希釈剤には酢酸がおもに用いられる(セルロース100部に対し，無水酢酸240～300部，硫酸7～15部，酢酸400～800部)．通常のアセテート繊維は第二次アセテートよりなるフレークをアセトンに溶解し，乾式紡糸する．トリアセテート繊維は完全酢化物をジクロロメタン(85～90重量％)とメタノールまたはエタノール(10～15重量％)の混合溶剤に溶かし，乾式紡糸をするのが普通である．アセテート繊維は光沢があり柔軟で，風合いがよい．また，短いものはタバコフィルターに用いる．トリアセテート繊維は吸湿性が少なく，熱的挙動は疎水性の合成繊維に似ている．

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