A Cigarette filter is part of a cigarette, as well as cigarette paper, capsules and adhesives. The filter may be made out of cellulose acetate fibre, paper or activated charcoal (either like a cavity filter or embedded in to the cellulose acetate). Macroporous phenol-formaldehyde resins and asbestos seemed to be found in cigarette filters The acetate and paper modify the particulate smoke phase by particle retention (filtration), and finely divided carbon modifies the gaseous phase (adsorption). Filters can reduce “tar” and nicotine smoke yields approximately 50%, which has a greater removal rate for other classes of compounds (e.g., phenols), but they are ineffective in filtering toxins such as deadly carbon monoxide. Most factory-made cigarettes come with a filter; those that roll their particular can buy them from your tobacconist.

Cellulose acetate is manufactured by esterifying bleached cotton or wood pulp with acetic acid. In the three cellulose hydroxy groups available for esterification, between two and three are esterified by managing the quantity of acid (a higher level 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 on demand, and additives colouring the cigarette could be included with cigarette filters. The five largest manufactures of filter tow are Hoechst-Celanese and Eastman Chemicals in the United States, 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 bring bonding the filters to the cigarettes.

Cellulose acetate is non-toxic, odorless, tasteless, and weakly flammable. It can be resistance against weak acids which is largely stable to mineral and fatty oils as well as petroleum. It can be biodegradable and the raw materials are a renewable natural polymer supposed to find application for other uses in the foreseeable future. Smoked cigarette butts contain 5-7 mg nicotine (about 25% in the total cigarette nicotine content), children ingesting >2 whole cigarettes, 6 cigarette butts or even a total of 0.5 mg/kg of nicotine should be admitted into a hospital. Cellulose acetate is hydrophilic and retains the water-soluble smoke constituents, which the majority are irritating (acids, alkali, aldehydes, and phenols), while letting through the lipophilic aromatic compounds.
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