GB2160084A - Cigarette - Google Patents

Abstract

A cigarette comprises a tobacco rod wrapper made from sidestream smoke inhibiting material and a filter which decreases the CO:tar ratio of smoke drawn through the filter. Shredded stem material may be included in the tobacco rod to decrease the carbon monoxide further. <IMAGE>

Description

SPECIFICATION Cigarette The present invention relates to a hovel cigarette structure, and in particular to a smoke control system for a cigarette.

Cigarettes conventionally comprise a paper tube or wrapper housing a tobacco rod and a filter for removing smoke constituents. One of the common problems associated with cigarettes is the amount of sidestream smoke that is formed on static burning, for example, when the cigarette is idling and not being drawn upon by the smoker or is simply resting in an ashtray while burning. Visible sidestream smoke that is formed during static burning is comprised mainly of particulate matter and the smoke is irritating and objectionable to non-smokers in the vicinity of the idling cigarette.

A recent proposal, described in U.S. Patent No.4,231,377, provides a cigarette wrapper paper which minimizes the incidence of such visible sidestream smoke. As described in the aforementioned U.S. Patent, this result is achieved by incorporating into the wrapper at least 15% by weight of magnesium oxide (including magnesium hydroxide) in combination with at least 0.5% by weight of a chemical adjuvant which is an alkali metal acetate, carbonate, citrate, nitrate ortartrate.

While the incorporation of the combination of specific materials results in minimizing visible sidestream smoke, one unexpected additional result which occurs when such paper is used is an increase in the proportion of carbon monoxide which is formed on burning and hence is present in the smoke entering the smoker's mouth. The weight ratio of carbon monoxide to tar in cigarette smoke is one of the parameters of cigarette smoke for which voluntary guidelines exist and Canadian cigarette manufacturers usually attept to provide a CO:tar ratio of no more than about 1:1.

It has been found that, if a cigarette normally providing a CO:tar ratio of bout 1:1 is provided with a cigarette paper in accordance with U.S. Patent No.4,231,377, then the smoke from the resulting cigarette has a substantially increased CO:tar ratio.

In the present invention, a smoke conrol system is provided which utilizes the benefits of minimizing the incidence of visible sidestream smoke while also overcoming the problem of increased CO :tar ratio. In its broadest aspect, the present invention provides a cigarette having a visible sidestream smoke formationresistant wrapper of combustible paper containing a tobacco filler rod and a cigarette smoke filter attached to the rod which is constructed to decrease the CO:tar ratio of smoke entering the filter.

In accordance with the present invention, therefore, there is provided a cigarette, comprising: a tobacco filler rod enclosed within a combustible paper wrapper and having a tobacco smoke filter element attached at one end of the rod, the combustible paper wrapper being constructed of visible sidestream smoke-inhibiting material which coincidentally increases the carbon monoxide to tar ratio in tobacco smoke drawn through the cigarette, the filter element being constructed to decrease the carbon monoxide to tar ratio of tobacco smoke from the cigarette drawn therethrough.

The sidestream smoke formation-resistant paper used in the novel cigarette of this invention preferably is one containing the materials described in U.S. Patent No.4,231,377. Cigarette paper of the latter type is manufactured by and available from Ecusta Paper and film Group. any other sidestream smoke formation-resistant paper, however, may be used in the cigarettes of the invention. As noted earlier, such papers increase the CO:tar ratio of the cigarette smoke.

The other essential component of the smoke control system of the invention is the use of a cigarette smoke filter which is constructed to decrease the CO :tar ratio entering the filter. One manner of achieving this result is a cigarette smoke filter in which the centre portion of the filter is sealed off and is impermeable to the passage of smoke, so as to direct all the smoke entering the filter from the filler rod to the periphery of the filter, and in which a series of perforations is provided through the filter wall.

A filter of the latter type has previously been described in U.S. Patent No. 4,357,950 to achieve a decrease in CO:tar ratio in conventional cigarettes, for example from a ratio of about 1:1 to about 0.5:1 for conventional air-diluted cigarettes which deliver from 5 to 10 mg of tar. It is surprising, however, that it is possible to use such a filter to decrease the inordinately high CO:tar ratio of about 2:1 which results fom the use of the visible sidestream smoke-inhibiting wrapper to normal levels of about 1:1. Filters of the type described in U.S. Patent No. 4,357,950 are manufactured and sold by American Filtrona Corporation of Richmond, Virginia, U.S.A.

The deflection of all the smoke entering the filter from the filler rod into the periphery of the filter exposes the gases to the perforations in the filter wall, which causes selective venting of CO through the perforations, thereby decreasing the CO:tar ratio of the smoke. In addition, the perforations permit air to be blended with the smoke, rather than the conventional method in which the air passes down the peripheral region of the filter while the smoke passes down the central region of the filter.

The portions of the filter not occupied by the sealing member are usually occupied by conventional cigarette smoke filter material, such as acetate tow material. The sealing member may take any desired shape and may be a hollow tube having a crimped end to prevent the passage of smoke therethrough.

Although the use of the special cigarette filler filter described above produces a substantial decrease in the CO:tar ratio of sidestream smoke-inhibited cigarette, further control of the chemistry of the smoke entering the smoker's mouth may be achieved by varying the components of the blend of tobacco in the filler rod.

Tobacco blends used in filler rods conventionally comprise shredded tobacco lamina material and processed stem material in varying proportions, usually from about 2 to about 50 weight % of processed stem material. The processed stem material conventionally employed is termed "cut rolled stem" or CRS and is formed by crushing moistened stems into sheet material and cutting the sheet material into shreds.

More recently, a novel form of processed stem material has been developed and is described in U.S.

Patent No. 4,386,617. This novel form of processed stem material is termed "shredded enhanced stem" or SES, is fibrous in character and has a lower burn rate and a higher filling power than CRS. SES is formed by mechanicallyfiberizing thoroughly soaked stem material at atmospheric pressure between counter-rotating fiberizing surfaces spaced apart about 0.05 to about 0.3 inches.

One important attribute of SES is that less CO per puff of cigarette is formed than in the case of CRS.

Substituting SES for all or part of the CRS conventionally employed in the tobacco blend at the same level of presence of processed stem material results in a decrease in the carbon monoxide present in the tobacco smoke, so that further control of the smoke chemistry is achieved thereby, enabling the CO:tar ratio to be further decreased.

Inclusion of SES in the tobacco blend in place of all or part of the CRS in addition to further decreasing the CO:tar ratio also improves the overall filling power of the blend, so that for the same firmness or cigarette, the weight of the blend may be decreased, permitting a further decrease in CO:tar ratio and further control of the smoke chemistry.

For a typical cigarette using the sidestream smoke-inhibiting paper producing a CO:tar ratio of smoke of about 2:1, the special filter is able to decrease the CO:tar ratio to about 1.3:1, substitution of SES for CRS in a typical blend is able to decrease the CO:tar ratio to about 1.1:1.

The invention is described further, by way of illustration, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a cigarette constructed in accordance with one embodiment of the invention, and Figure 2 is a graphical representation of the results of smoking tests conducted on cigarettes constructed in accordance with the invention and containing varying levels of processed stem material.

Referring to Figure 1 of the drawings, a filtered cigarette 10 in accordance with one embodiment of the invention comprises a tobacco rod 12 enclosed in a paper wrapper 14 of sidestream smoke formation inhibiting paper and a filter element 16. The filter element 16 includes a porous plug wrap 17 enclosing the elements of the filer 16, a paper overwrap 18 securing the tobacco rod 12 and the filter element 16 in end-to-end relationship in accordance with well known prior art techniques.

The paper overwrap 18 is provided with a plurality of air dilution perforations 20 arranged circumferentially arond the filter element 16 to permit ventilating air to be drawn through the filter element 16 with each draw or puff of the cigarette.

The filter element 16 includes an inner axially elongate member 22 formed from material impermeable to smoke, for example, polypropylene or polyethylene. The inner member 22 is hollow and crimped at one end to prevent passage of smoke through the central region of the filter element. The inner member 22 is generally centrally located in the filter element 16 and forces the smoke into an annular or peripheral region 24 of the filter.

The inner member 22 is supported in the filter element 16 by conventional filter tow material 26 which occupies the space not occupied by the inner member 22, including the annular region 24. The crimped end 28 of the inner member may be exposed at the end of the filter 18, as illustrated, or may be wholly enclosed by tow material 26 so as to be invisible.

The diameter of the inner member 22 to the overall diameter of the filter 18 determines the percentage of the total surface area of the filter 18 which is exposed to the smoke. by the use of an inner member 22 which has an outside diameter which corresponds to approximately 2/3rds the cross-sectional area of the filter 18, optimum results are obtained.

The invention is illustrated by the following Example: Example Smoking tests were carried out on a number of test cigarettes to determine the tar, nicotine and carbon monoxide in the smoke from the cigarettes. Test cigarettes were prepared using (1) a conventional production tobacco blend containing CRS and having standard filter and paper, (2) the same blend but with a wrapper of Ecusta TOD 01310 paper (a low sidestream smoke paper), (3) the same as (2) but with a 20mm Filtrona COD filter in place of the conventional filter, and (4) the same as (3) but at tobacco substitution levels of 0, 15, 30 and 45% both of SES and CRS. The smoke tests were performed on cigarettes having a weight t 25mg of a mean weight of 1120mg.

The results of the smoking tests for samples (1), (2) and (3) are set forth in the following Table I: TABLE I Sample ID. Sample No. COlTarRatio Conventional (1) 1.2:1 With low sidestream paper (2) 1.9:1 With paper and COD filter (3) 1.3:1 The results of this Table show the marked increase in CO/tar ratio which results from the use of the low sidestream smoke and the significant decrease which is subsequently obtained using the COD filter.

As the substitution of processed stem for shredded lamina blend increased in the sample (4) cigarettes, the tar and nicotine content of the cigarette smoke declined.

No significant difference was observed in the nicotine content of the smoke between SES and CRS at the same substitution levels, decreasing from about 1.6mg at 0% substitution to about 0.9 mg at 45% substitution. However, the tar content of the smoke was significantly less in he case of SES as compared with CRS at the same levels of substitution and the difference became greater with increasing substitution levels.

For CRS, the tar declined from about 17mg at 0% substitution to 12mg at 45% substitution and, for SES, the tar declined to about 9mg at 45% substitution.

In the case of carbon monoxide, increasing levels of CRS increased somewhat the CO content of the smoke from about 14mg at 0% substitution to about 16mg at 45% substitution while increasing levels of SES cause a significant and decreasing CO content of the smoke to about 8mg at 45% substitution. The CO and tar results for the blends were combined and expressed as the ratio of CO/tar in the smoke. These results were plotted graphically and appear as Figure 2.

As may be seen in Figure 2, at SES substitutions of 0 to 45 wt.%, the CO/tar ratio is fairly constant at approximately 0.9 while for CRS over the same levels of substitution, the CO/tar ratio increased, substantially so at higher levels. At a 26% substitution level (approximating the weight ratio of stem to lamina in whole leaf) SES exhibited a 18% decrease in CO:tar ratio when compared with CRS, which would have the effect with sample (3) (see Table I) of decreasing the CO:tar ratio to about 1.1 :1.

In summary of this disclosure, the present invention provides a novel cigarette structure having a smoke conrol system which inhibits sidestream smoke formation while controlling the CO:tar ratio of the smoke.

Modifications are possible within the scope of this invention.

Claims (10)

1. A cigarette, comprising a tobacco filler rod enclosed within a combustible paper wrapper and having a tobacco smoke filter element attached at one end of the rod, the combustible paper wrapper being constructed of visible sidestream smoke-inhibiting material which coincidentally increases the carbon monoxide to tar ratio in tobacco smoke drawn through the cigarette, the filter element being constructed to decrease the carbon monoxide to tar ratio of tobacco smoke from the cigarette drawn therethrough.

2. A cigarette as claimed in claim 1, in which the visible sidestream smoke inhibition is achieved by the presence in the paper wrapper of at least 15 wt.% magnesium oxide and at least 0.5 wt.% of a chemical adjuvant salt selected from the group consisting of alkali metal acetates, carbonates, citrates, nitrates and ta rtrates.

3. A cigarette as claimed in claim 2, in which the paper wrapper contains at least 35% magnesium oxide and at least 2.0% adjuvant salt.

4. A cigarette as claimed in any one of claims 1 to 3, in which the filter element comrises an axially-elongate outer member having an axial passage therein, the outer member consisting essentially of a tobacco smoke filtering material, sealing means sealing off the passage to substantially prevent the axial movement of smoke through the passage and for directing the smoke entering the smoke receiving end of the filter element to pass through the filtering material of the outer member, and wrapping means for retaining smoke within the filtering material of the outer member and disposed on the outer surface of the outer member, the wrapping means including a plurality of perforations for admitting ambient air into the filter material of the outer member so that smoke being drawn through the filter material is admixed with air.

5. A cigarette as claimed in any one of claims 1 to 4, in which the tobacco filler rod includes a carbon monoxide-decreasing proportion of sredded tobacco stem material.

6. A cigarette substantially as hereinbefore described and as illustrated in Figure 1 of the accompanying drawings.

7. A cigarette as claimed in claim 1 substantially as herein before described with reference to the Example.

8. A method of controlling the smoke produced by a burning cigarette filter rod, which comprises wrapping the cigarette rod in a combustible paper wrapper which inhibits the production of visible sidestream smoke during burning of the cigarette and which coincidentally increases the carbon monoxide to tar ratio in tobacco smoke drawn through the cigarette, and attaching to the cigarette rod a tobacco smoke filter element which is constructed to decrease the carbon monoxide to tar ratio of tobacco smoke drawn therethrough from the burning filler rod.

9. A method of controlling the smoke produced by a burning cigarette filter rod, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

10. A method as claimed in claim 8 substantially as hereinbefore described with reference to the Example.