Cigarette with adsorbent at tip end thereof

The present invention relates a cigarette with an adsorbent material at the tip end thereof, and more particularly to selective filtration of cigarette smoke by providing a zone or plug of porous adsorbent material at the lighting tip end of the cigarette.

The concentration of mainstream smoke constituents changes on a puff-by-puff basis starting with the lighting puff and progressing down the tobacco rod. It is desirable to selectively reduce certain compounds which occur at significantly higher concentrations in the first one or two puffs of a cigarette.

Accordingly, it is an object of the present invention to reduce the level of volatile smoke constituents in mainstream cigarette smoke.

Another object of the invention is the adsorption of volatile smoke constituents close to the burning coal of a cigarette where such constituents are formed.

In accordance with the present invention, a cigarette comprises a tobacco rod and an adjoining filter, such as a cellulose acetate tow. A zone or plug of porous adsorbent material is positioned in the tobacco rod a short distance from the lighting end thereof. The amount of adsorbent material is sufficient for effective removal of volatile smoke constituents while allowing the cigarette to burn continuously. The adsorbent material traps volatile smoke constituents in close proximity to the burning coal during the first puffs of the cigarette. As the cigarette continues to burn, the burning coal consumes the adsorbent material, and the adsorbed smoke constituents are thereby effectively removed without releasing them back into the mainstream smoke.

The zone or plug of porous adsorbent material may be activated carbon, and one or more spaced apart zones or plugs may be utilized. The activated carbon material may comprise a zone of carbon granules or a carbon plug in the form of a wafer. Preferably, the zones or plugs of absorbent material are spaced approximately 4 to 8 mm from the lighting end of the cigarette.

Novel features and advantages of the present invention in addition to those mentioned above will become apparent to persons of ordinary skill in the art from a reading of the following detailed description in conjunction with the accompanying drawings wherein similar reference characters refer to similar parts and in which:

FIG. 1 is a side elevational view of cigarette with a zone or plug of adsorbent material at the tip end of the cigarette, according to the present invention, with portions broken away to illustrate interior details; and

FIG. 2 is a side elevational view of another cigarette with several spaced apart zones or plugs of adsorbent material at the tip end of the cigarette, according to the present invention, with portions broken away to illustrate interior details.

Referring in more particularity to the drawings, FIG. 1 illustrates a cigarette 10 comprising a tobacco rod 12 and an adjoining filter 14 . As shown, the filter is a cellulose acetate tow although alternative filter arrangements may also be utilized, if desired. Cigarette 10 includes a zone or plug of porous adsorbent material 16 at the lighting end 18 of the tobacco rod. The porous adsorbent material may be activated carbon, either in the form of granules or carbon wafers and the material may be positioned a short distance from the lighting end 18 , preferably about 4 to 8 mm.

The amount of adsorbent material 16 (about 20 to 50 mg, preferably 25 to 40 mg) is sufficient for the effective removal of volatile smoke constituents while allowing the cigarette 10 to burn continuously. The adsorbent material 16 traps volatile smoke constituents in close proximity to the burning coal in the first few puffs of the cigarette. As the cigarette 10 continues to burn, the burning coal consumes the adsorbent material to thereby effectively remove the adsorbed smoke constituents without releasing them back into the mainstream smoke. Following the consumption of the adsorbent material in the tobacco rod, cigarette 10 is unchanged from a cigarette of conventional design.

FIG. 2 shows an alternate cigarette 10 A comprising a tobacco rod 12 with an adjoining filter 14 . Cigarette 10 A includes two spaced apart zones or plugs of porous adsorbent material 16 A at the lighting end 18 of tobacco rod 12 . The porous adsorbent material 16 A may be activated carbon, either carbon granules or carbon wafers, and the material may be positioned a short distance from the lighting end 18 , preferably about 4 to 8 mm. Also the spacing between the plugs or zones of porous adsorbent material 16 A may be about 4 to 8 mm. Each plug or zone 16 A may comprise 20 to 50 mg of activated carbon, preferably about 25 to 40 mg. Otherwise cigarette 10 A is the same as cigarette 10 and functions in the same manner as cigarette 10 , as explained above.

Adding the adsorbent material 16 , 16 A to the tobacco rod in a discrete zone or plug provides for the adsorption of the volatile smoke constituents close to the burning coal where they are formed. Being heated due to the closeness of the hot coal, the adsorbent material is also more effective at adsorption of gases. After adsorption of the volatiles during the first two puffs, the adsorbent material is consumed with the surrounding tobacco through normal cigarette burning as the cigarette coal progresses through the adsorbent zones or plugs.

Another advantage is that the filter design and construction are unaffected. Also, following consumption of the adsorbent material, the cigarette is the same as a conventional cigarette, and there is a lower impact on smoke flavor when compared to a cigarette design that incorporates the adsorbent material in the filter.

The adsorbent zone or plug can also be used to affect the cigarette burn rate so the cigarette would self extinguish if not puffed thereby producing a cigarette of reduced ignition propensity.

Also, some aldehydes and dienes are produced in disproportionally high amounts in the first puff (lighting puff). By placing the adsorbent material so that it removes these compounds from the first few puffs after which the adsorbent is consumed, the overall subjectives of the cigarette are only minimally affected. At the same time, the total deliveries of target compounds such as 1, 3-butadiene and formaldehyde are significantly reduced.

After passing through the adsorption zone, the tobacco smoke and hot gases still sweep across the remaining tobacco rod where its flavors are added to the smoke. In a conventional carbon-filtered cigarette this would not be possible.

Experimental data is attached showing the effectiveness of cigarettes 10 , 10 A in adsorbing reducing volatile constituents from tobacco smoke.

The following test data in Table 1 compares a control cigarette (IR4F) with cigarettes A through D each of which comprises a tobacco rod 12 and cellulose acetate filter 14 . The individual readings comprise percentages of the total smoke constituents delivered for each of cigarette puffs 1 - 8 . Reduced amounts occur during the first few puffs of cigarettes B, C and D, each of which is an embodiment of the present invention. Cigarette A is not an embodiment of the present invention and simply comprises carbon granules dispersed amongst the tobacco over 4 mm from the lighting end. As indicated, the removal percentages with cigarette A are not as good as cigarettes B, C and D.