A Cigarette filter is part of the cigarette, in addition to cigarette paper, capsules and adhesives. The filter could be made from cellulose acetate fibre, paper or activated charcoal (either as being a cavity filter or embedded in the cellulose acetate). Macroporous phenol-formaldehyde resins and asbestos are also employed in cigarette filters The acetate and paper customize the particulate smoke phase by particle retention (filtration), and finely divided carbon modifies the gaseous phase (adsorption). Filters can help to eliminate “tar” and nicotine smoke yields approximately 50%, with a greater removal rate for other classes of compounds (e.g., phenols), but they are ineffective in filtering toxins like carbon monoxide. Most factory-made cigarettes have a filter; those that roll their own can get them from your tobacconist.
Cellulose acetate is created by esterifying bleached cotton or wood pulp with acetic acid. From the three cellulose hydroxy groups available for esterification, between two and three are esterified by controlling the level of acid (amount of substitution (DS) 2.35-2.55). The ester is spun into fibers and formed into bundles called filter tow. Flavors (menthol), sweeteners, softeners (triacetin), flame retardants (sodium tungstate), breakable capsules releasing flavors at will, and additives colouring the cigarette smoke could possibly be included with cigarette filters. The 5 largest manufactures of filter tow are Hoechst-Celanese and Eastman Chemicals in the usa, Rhodia Acetow in Germany, Daicel in Japan, and Courtaulds in the United Kingdom.
Starch glues or emulsion-based adhesives can be used for gluing cigarette seams. Hot-melt and emulsion-based adhesives can be used for filter seams. Emulsion-based adhesives can be used for bonding filters towards the cigarettes.
Cellulose acetate is non-toxic, odorless, tasteless, and weakly flammable. It can be resistance against weak acids and is also largely stable to mineral and fatty oils along with petroleum. It can be biodegradable as well as the raw materials are a renewable natural polymer expected to find application for other uses in the future. Smoked cigarette butts contain 5-7 mg nicotine (about 25% from the total cigarette nicotine content), children ingesting >2 whole cigarettes, 6 cigarette butts or even a total of 0.5 mg/kg of nicotine needs to be admitted to some hospital. Cellulose acetate is hydrophilic and retains the water-soluble smoke constituents, which many are irritating (acids, alkali, aldehydes, and phenols), while letting through the lipophilic aromatic compounds.
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