Filter materials

Details Filter materials Filter materials

1997-02-21

1998-04-14

Millin, Vincent

Tobacco

Smoke separator or treater

131345, A24D 310

Patent

active

057381194

DESCRIPTION:

BRIEF SUMMARY
This invention relates to filter body materials in cigarette filters.
Fibre-containing filters for cigarettes are well known. In one known form of construction, the filter body consists of a tow of continuous filaments, commonly cellulose acetate (acetate) filaments, arranged parallel to the long axis of the cigarette. In another known form of construction, the filter body consists of pleated or fluted paper compressed into a cylinder. Such forms of construction contain a single filter element and may be called `mono` filters. Another known form of construction is the so-called `dual` filter which contains two filter elements, for example a paper filter towards the interior and a tow filter towards the exterior of the cigarette. A further known form of construction is the so-called `triple` filter, which resembles a dual filter except that a quantity of activated carbon or other material is interposed between the two filter elements hereinbefore mentioned.
Paper filters are known to be generally more efficient than tow filters at removing tar from tobacco smoke. High tar removal efficiency is particularly desirable in view of the trend towards low-tar cigarettes. Paper filters absorb moisture from the tobacco smoke as the cigarette is smoked, with the result that they become soggy and easy to compress, and offer increased resistance to the passage of smoke through the filter. The external end of a cigarette filter generally becomes stained as the cigarette is smoked. It is known that acetate filters generally exhibit a light tan, uniform staining, whereas paper filters generally exhibit a darker, mottled staining, the latter effect being visually undesirable. Mono paper filters are generally less expensive to manufacture than acetate tow filters even though the manufacturing process is more complex, because paper is a cheaper material than acetate. Dual filters are generally more expensive to manufacture than either mono paper or tow filters because the manufacturing process is more complex, and triple filters are more expensive still. It is an object of the present invention to provide a cigarette filter with high tar removal efficiency which overcomes at least some of the disadvantages associated with those conventional paper filters which comprise paper in the filter body.
The present invention provides a cigarette filter characterised in that the body of the filter comprises a hydroentangled fabric which comprises lyocell staple fibres. The present invention further provides a cigarette incorporating such a filter.
Lyocell fibres are known materials, and their manufacture is described for example in U.S. Pat. No. 4,246,221. They are readily biodegradable. They are available commercially from Courtaulds plc. They are made by dissolving cellulose in a solvent and extruding the solution so formed through a spinnerette into a coagulating bath which serves to precipitate the cellulose and wash the solvent from the fibre. This process may be called solvent-spinning, and lyocell fibres may also be called solvent-spun cellulose fibres. The cellulose is usually woodpulp. The solvent may be a tertiary amine N-oxide, preferably N-methylmorpholine N-oxide, and in general contains a small proportion of water. If the solvent is a tertiary amine N-oxide, the coagulating bath is preferably an aqueous bath. Fabrics which consist essentially of lyocell fibres may be called lyocell fabrics. The solvent-spinning process is to be distinguished from other known processes for the manufacture of cellulose fibres which rely on the formation and decomposition of a chemical derivative of cellulose, for example the viscose process.
Hydroentangling is a process for forming a fabric by mechanically wrapping and knotting fibres in a web about each other through the use of high velocity jets or curtains of water. The web may in general comprise one or more layers of parallelised staple fibres, for example carded webs. When two or more layers are used, the layers may be arranged so that the fibres lie essentially parallel to each othe

REFERENCES:
patent: 3485706 (1969-12-01), Evans
patent: 4416698 (1983-11-01), McCorsley, III

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