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Smoking article and smoking article filter

Smoking article and smoking article filter description/claims

This is a divisional application of U.S. Ser. No. 10/442,357 filed May 20, 2003 to which priority under 35 U.S.C. § 120 is claimed.

The present invention relates generally to improved filters useful for tobacco products, particularly cigarettes, and to novel cigarettes having such filters. More specifically, the invention relates to filters containing adsorbents which reduce one or more allegedly undesirable gas phase constituents normally found in mainstream tobacco cigarette smoke.

Typically, cigarettes are comprised of a paper-wrapped cylindrical rod of cut tobacco filler, alone or combined with other tobacco or non-tobacco substances, and a filter attached at the mouth or buccal end of the rod. On combustion, the smoke passing through the filter, commonly referred to as “mainstream” smoke, contains particulate matter, e.g. tar, and gas or volatile phase constituents. The gas phase of mainstream cigarette smoke contains certain components alleged to be harmful to a smoker, including carbon monoxide, hydrogen cyanide, aldehydes such as formaldehyde, acetaldehyde, acrolein, propionaldehyde and crotonaldehyde, as well as olefinic constituents such as 1,3 butadiene.

Most commercially available cigarettes have filters which are designed to reduce particulate matter but are ineffective to remove or reduce gas phase constituents of mainstream smoke. Such filters typically include one or more plugs of fiber “tow,” commonly cellulose acetate.

Filters have been designed for the removal of gas-phase constituents along with particulates. These filters usually incorporate an adsorbent material such as activated carbon (also known as “carbon,” “charcoal,” or “activated charcoal”) in a section of the filter. Granular carbon having high surface area is recognized as an effective adsorbent for removing components such as aldehydes from mainstream smoke.

A variety of approaches to incorporating activated carbon into cigarette filters have been employed. These approaches include carbon granules dispersed within a cellulose acetate tow, paper web or filter plug wrap, sometimes called “dalmation” filters. Another approach is to place a bed or charge of granular carbon into the cavity between two plugs of cellulose acetate tow in a so-called “plug-space-plug” or “triple filter” design. Examples of commercially available filters are Caviflex, Dualcoal, Recessed Dualcoal, Sel-X-4, and Triple Filter from Baumartner Fibertec (Switzerland); Active Acetate Dual, Active Charcoal Triple Solid, Active Myria White, Active Patch Mono, Adsorbent Coated Thread, Triple Granular, and V.P.A. Dual from Filtrona International Incorporated (Milton Keynes, U.K.).

The commercial acceptance of carbon filters, however, has been limited by the “off-taste” of the mainstream smoke characteristic of such filters. The smoke from carbon-filtered cigarettes is perceived as having a taste that has been described as unpleasant, astringent, bitter and drying. See “What's happening to Charcoal Filters?” Tobacco Reporter, Vol. 95, No. 3 (March 1968).

The art has attempted to address this problem by introducing various flavoring substances (“flavorants”) into the mainstream smoke to offset or cover up the carbon off-taste. However, the presence of flavorants tends to reduce the capacity of the adsorbent to remove the undesirable gas phase constituents. Flavorants applied as a coating to an adsorbent reduce its gas removal efficiency by decreasing the number of active sites for adsorption. It is known that flavorants in the tobacco or elsewhere in the cigarette package tend to vaporize and migrate to the activated carbon over time where they are adsorbed and thus deactivate the sites onto which they are adsorbed. For that reason, mentholated cigarettes having carbon filters require higher amounts of menthol to be added during manufacture to offset adsorption by the carbon.

Thus, there is a continuing need for a cigarette filter that significantly reduces the quantity of gas phase constituents in mainstream smoke without introducing unacceptable off-taste normally associated with the activity of gas phase adsorbents such as carbon. Further, there is a need for a carbon filter cigarette that tastes substantially like a non-carbon filter cigarette.

It is therefore an object of the present invention to provide filters for smoking articles, particularly tobacco cigarettes, that reduce quantities of one or more allegedly undesirable gas phase constituents normally found in mainstream smoke.

It is another object of the present invention to provide cigarettes having filters which utilize adsorbents, particularly activated carbon, to reduce gas phase constituents without introducing unacceptable off-taste such as normally results from use of such adsorbents.

It is a further object of the present invention to provide a carbon filter cigarette which tastes substantially like a non-carbon filter cigarette.

The foregoing and other objectives are achieved according to the invention by providing a filter containing a suitable amount of an adsorbent, preferably activated carbon, and an off-taste suppressant in association with the adsorbent. The adsorbent is capable of trapping and thereby reducing the amount of at least one allegedly undesirable gas phase constituent of mainstream smoke. The off-taste suppressant significantly reduces the characteristic off-taste stemming from the activity of the adsorbent. The composition and amount of off-taste suppressant applied to the adsorbent should be selected to maximize gas phase removal while at the same time minimizing, preferably substantially eliminating, off-taste stemming from adsorbent activity.

In a preferred embodiment of the invention, the smoking article is a tobacco cigarette having a filter that contains an activated carbon adsorbent for at least one gas-phase constituent of mainstream smoke, which has applied thereto a suitable amount of an off-taste suppressant selected from the group of molecules having B, X-B, AH-B, or AH-X-B moieties as defined by the “AH-B Theory” of sweetness discussed below in the Detailed Description of the Invention. These molecules include, but are not limited to, polyols, glycols, sugars, sugar-alcohols, oligosaccharides, polysaccharides, amino acids, amino acid derivatives, di- and tri-peptides, polypeptides, artificial sweeteners, and mixtures thereof. The off-taste suppressant preferably also includes an alkali metal or alkaline earth metal salt. The compositions and weight ranges for the off-taste suppressants applied to the adsorbent can be selected to maximize gas removal and reduction of off-taste, preferably without introducing additional foreign flavoring to the mainstream smoke so that the cigarette tastes substantially like filtered cigarette.

One example of a useful off-taste suppressant is a combination of fructose and mannitol, preferably in about a 50:50 ratio by weight. A more preferred off-taste suppressant is a combination of fructose, mannitol and sodium chloride in a ratio of about 46:46:8 by weight. It has been found that such a composition when applied to a bed of activated carbon in a range of about 2 to 40 percent by weight to the total weight of the carbon and off-taste suppressant, preferably in a range of about 5 to about 20-25 percent by weight, is particularly useful in achieving the objectives of the invention.

According to another aspect of the invention the filter may also include a chemisorbent for one or more of the allegedly undesirable gas phase constituents, preferably in admixture with the adsorbent. Preferred chemisorbents are amine derivatives of polystyrene. Admixtures of activated carbon and ion exchange resins such as polystyrene derivatives in a weight ratio of from about 25:75 to about 50:50 treated carbon to resin are particularly useful in the practice of the invention, although other ratios may be used.

The filters of the present invention are capable of reducing one or more of the allegedly undesirable volatile components of mainstream cigarette smoke including, but not limited to, aldehydes such as formaldehyde, acetaldehyde, acrolein, propionaldehyde and crotonaldehyde.

These and other aspects of the present invention will become apparent to those skilled in the art after a reading of the following detailed description of the invention, including the illustrative embodiments and examples.

• Provisional Patent
• Utility Patent

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