RS11204A - CIGARETTE FILTER - Google Patents

Abstract

A cigarette filter that includes a multi-section filter that reduces the level of predetermined smoke ingredients. The filter (130) consists of a fibrous filter plug (132) located at the end of the cigarette which is placed in the mouth, a section (136) containing the selective absorbent material and a section (134) containing the general absorbent material. A selective absorbent material, such as a phenol-formaldehyde resin matrix, superficially reacts with mainly primary and secondary amino active groups, removing specific smoke constituents from tobacco smoke. General absorbent material, such as activated charcoal, can be absorbed through chemical compounds without a high degree of specificity. Structurally, the fibrous filter plug, the selective absorbent section and the general absorbent section are coaxially centered one after the other.

Description

CIGARETTE FILTER

REFERENCE TO RELATED PATENT APPLICATIONS

This patent application claims priority under US Provisional Patent Application Ser. No. 60/309,388, filed Aug. 1, 2001, which is incorporated herein by reference in its entirety, based on US Provisional Patent Application Ser. no. 60/309,435 filed on August 1, 2001, which is incorporated herein by reference in its entirety and US patent application ser. no. 10/011,841 filed on 30

October 2001.

ISTORT.TAT PRONALASAK

The present invention relates to a cigarette filter comprising a smoke constituent absorbing material which, when combined with a charcoal-based filter material, exhibits a synergistic reduction of smoke constituents.

Cigarettes comprise a tobacco stick or column which, when burned, produces a particle phase and a vapor phase. About 70 years ago, filters began to be attached to the end of the tobacco stick. Among other things, the filter removed various components of the smoke. Filters made of fibrous material, such as cellulose acetate fibers or paper, remove the particulate phase of tobacco smoke by mechanical means. However, fibrous materials are not effective in removing volatile compounds, such as aldehydes, hydrogen cyanide and sulfides, which are in the vapor phase. Typically, the absorbent is combined with a fibrous material to improve the removal of vapor phase components. For example, cigarette filters include activated carbon, porous minerals such as sepiolite, silica gel, cation exchange resins, and anion ion exchange resins.

Charcoal has a large specific surface area and is a relatively strong absorbing agent for the vapor phase constituents of tobacco smoke. When protected by a mixture of metal oxides, charcoal is particularly effective in removing acid gases.

Sepiolite has a large absorption surface with a strong tendency to absorb charged samples, but a significantly lower tendency to adsorb non-polar samples. Silica gels are generally considered as low retention absorbing agents for vapor phase constituents of tobacco smoke. easily silica-gel easily absorbs aldehydes and hydrogen cyanide, the ingredients are also easily removed from silica-gel. Cation ion exchange resins have been proposed for nicotine removal. Anion exchange resins have been proposed to remove smoke acids, but strong base anion exchangers have no effect on smoke vapor phase aldehydes. Weak base resins with anionic ion exchangers of a porous structure are suitable for removing smoke acids and aldehydes, but their effectiveness decreases during smoking, as well as with carbon and porous minerals.

Two or more absorbent materials may be used in combination with cigarette filters. For example, USA Patent 2,815,760 describes the use of ion exchange materials with materials that "chemically react with harmful, non-alkaline and non-acidic components of the smoke to form non-volatile compounds, thus retaining the latter on the filter". However, the above-mentioned additives did not provide satisfactory selective removal of such components in the smoke phase, such as aldehydes in the smoke, especially acetaldehyde and acrolein. USA Patent 4,300,577 describes the use of a low retention absorbing agent for vapor phase constituents mixed with a second component containing mainly primary amino active groups to remove vapor phase constituents, including aldehydes and hydrogen cyanide from tobacco smoke.

However, the filter of the '577 patent has not been shown to demonstrate adequate consumer acceptance or commercial feasibility.

OVERVIEW OF THE INVENTION

The present invention relates to a cigarette filter comprising a multi-section filter which reduces the level of predetermined smoke constituents. The fitter consists of a fibrous filter cap located at the mouth end of the cigarette, a section containing selective absorbent material, and a section containing general absorbent material.

The filter plug can be any filter plug known in the art, such as cellulose acetate fibers. The general absorbent material is selected from the group of relatively large surface area materials, such as activated charcoal, which can absorb a variety of chemical compounds without a great degree of specificity. Selective absorbent material is selected based on the specific components of the smoke that we want to remove. The selective absorbent material is selected from the group of surface-active resins, each resin consisting essentially of an inert element with a surface area greater than 35 m2 /gram. In a configuration of the present invention, the selective absorbent material has a matrix of phenol-formaldehyde resin which is surface-active mainly with primary and secondary amino active groups.

Structurally, the selective absorbent material may be located at the end of the tobacco stick, and the general absorbent material may be placed between the selective absorbent section and the filter cap. Alternatively, the general absorbent material can be placed at the end of the tobacco stick and the selective absorbent material between the general absorbent section and the filter cap. Previous data show that the earlier position produces a synergistic effect in reducing smoke constituents compared to the latter position. Further, the selective absorbent material and the general absorbent material may be dispersed in a common filter plug material, such as cellulose acetate, or the absorbent materials may be stacked as a layer or sections of thin layers within the filter plug material.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a perspective view of a cigarette with a top filter according to the prior invention;

Fig. 2 is a perspective view of a cigarette made in accordance with the present invention in which the absorbent materials are dispersed through the filter plug material and the general absorbent section is located between the filter plug and the selective absorbent section;

Figure 3 is a perspective view of a cigarette filter made in accordance with the present invention in which the absorbent materials are dispersed through the filter plug material and the selective absorbent section is located between the filter plug and the general absorbent section;

Figure 4 is a perspective view of a cigarette made in accordance with the present invention in which absorbent materials are stacked as layers within a segment of filter plug material;

Fig. 5 is a cross-sectional view of a configuration of the present invention in which a filter plug is placed between a general absorbent section and a selective absorbent section;

Figure 6 is a cross-sectional view of a configuration of the present invention with a filter plug at one end of a tobacco stick;

Figure 7 is a cross-sectional view of a configuration of the present invention with the absorbent materials sectioned along the length of the fibrous filter material; and

Figure 8 is a cross-sectional view of a configuration of the present invention where the filter plug section is omitted.

DETAILED DESCRIPTION OF THE PREFERRED CONFIGURATION OF THE INVENTION

The cigarette filter of the present invention comprises a multi-section filter that reduces levels of previously identified smoke constituents. The filter consists of a fibrous filter cap located at the mouth end of the cigarette, a section containing selective absorbent material and a section containing general absorbent material.

As shown in Figure 1 and as is known in the art, a typical filter tip cigarette 10 has a filter 30 attached to a tobacco stick 20. The tobacco stick 20 consists of a loose tobacco mixture 22 wrapped in a cigarette paper 24, and the filter 30 includes a filter plug 32 that is wrapped in a plug wrapper 34. A top paper layer 36 joins the filter. 30 for a 20 stick of tobacco.

In the present invention, as shown in Figure 2, the cigarette 110 has a multi-section filter 130 attached to the tobacco stick 20. The filter 130 includes a filter plug 132, a section containing a general absorbent material 134, and a section containing a selective absorbent material 136. The filter plug 132 is the first or end that is inserted into the mouth 131 of the filter 130. A layer of selective absorbent material 136 is second or at the end of the tobacco rod 137 of the filter 130. A layer of general absorbent material 134 is placed between the filter plug 132 and the selective absorbent layer 136.

The filter plug 132 is made of a fibrous material and provides a clean, tight appearance to the mouthpiece 131. The filter plug 132 also maintains strength at the mouthpiece 131 as the cigarette 110 is consumed. As known in the art, the filter plug 132 can be made of a variety of materials, the most common of which are cellulose, cellulose acetate fibers, paper, cotton, neoprene fabric, neoprene fibers, polyester fabric, polyester fibers, or a combination thereof. A plasticizer may optionally be included.

The general absorbent section 134 includes a general absorbent material 144 that is dispersed through the filter plug material 142, as in the "double dalmatian" filter known in the art. The general absorbent material 144 is selected from a group of relatively large surface area materials capable of absorbing smoke constituents without a great degree of specificity. For example, the general absorbent material can be selected from activated charcoal, activated coconut charcoal, activated charcoal, zeolite, silica gel, sepiolite, alumina, or a combination thereof, as well as mineral-based charcoal made from semi-anthracite charcoal with a density 50% greater than that of coconut charcoal (obtained from Calgon Carbon Pittsburgh, PA), Ambersorb 572, or Ambersorb 563. (coal tar pyrolyzed from sulfonated styrene-divinylbenzene available from Rohm and Haas, 5000 Richmond Street, Philadelphia, PA 19137), other materials having similar particle sizes, surface area, and bonding propensities, or a combination thereof. To further enhance the effectiveness of the general absorbent material, metal oxides or other metal-based compounds may be included in the general absorbent section.

The selective absorbent section 136 includes a selective absorbent material 146 that is dispersed through the filter plug material 142, as in the "double dalmatian" filter known in the art. The selective absorbent material 146 is selected based on the specificity of the material 146 for a predetermined class of chemical compounds. For example, the selective absorbent material 146 may be an ion exchange resin, such as Duolite A7 (available from Rohm and Haas, 5000 Richmond Street Philadelphia, PA 19137), or a material having similar active groups and binding propensities. Duolite A7 has a phenol-formaldehyde resin matrix and is surface-active with primary and secondary amino groups, which increases the specificity of the resin to aldehydes and hydrogen cyanide found in tobacco smoke.

Further, the selective absorbent material 146 should be selected taking into account the fact that the contact conditions between the tobacco smoke and the absorbent material 146 depend on a number of variables, including how hard the smoker draws smoke through the filter while smoking the cigarette and how much tobacco stick is consumed before each puff of smoke. It is therefore advantageous if the selective absorbent material 146 has a surface area greater than 35 m<2>/g so that there is minimal diffusion resistance and the surface active sites are easily accessible. Materials with a larger surface area also exhibit a less noticeable drop in performance if a portion of the surface area is covered with plasticizer, as may occur when the absorbent material 146 is sprayed into the filter plug 142 .

When the cigarette is consumed, the smoker inhales the tobacco smoke through the filter 130. The smoke initially passes through the selective absorbent section 136 where the desired constituents of the smoke are absorbed on the surface of the selective absorbent material 146 and the particles in the smoke are retained by the filter plug material 142. The remaining smoke then passes through the general absorbent section 134 where other substances can be retained by the absorbent material 144 and additional particles are retained by the material filter plug 142. Finally, the remaining smoke then passes through the filter plug

cap 132 where additional particles can be removed. The filtered smoke is then led to the smoker.

In a first example configuration of the present invention, as shown in Figure 2, the multi-section filter 110 is made to have a filter plug 132 made of cellulose acetate fibers about 7 mm in length, and has a general absorbent section 134 consisting of 40 mg of activated coconut charcoal 144 dispersed through the cellulose acetate fibers 142 which are cut to give a section 134 of about 10 mm long, the cellulose acetate fibers being plasticized, and having a selective absorbent section 136 consisting of 40 mg of Duolite A7 dispersed through the cellulose acetate fibers 142 which are cut to give a section 136 about 10 mm long, while the cellulose acetate fibers are plasticized. When the tobacco stick burns under a normal draw/rest cycle, analysis of the tobacco vapor present at the mouth end 131 of the cigarette 110 shows statistically significant reductions in the levels of hydrogen cyanide, furan, propionaldehyde, acetone, methyl ethyl ketone/butyraldehyde, hydrogen sulfide, 1,3-butadiene, 2-methyl propanal, isoprene, styrene, pyridine, toluene, and benzene. compared to cigarettes using similar resin-only filters. When the tobacco stick is burned under a normal draw/rest cycle, analysis of the smoke vapors present at the mouth end 131 of the cigarette 110 shows statistically significant reductions in the levels of pyridine, hydrogen cyanide, hydrogen sulfide, styrene, 2-methylpropanal, benzene, propionaldehyde, furan, isoprene, 1,3-butadiene, crotonaldehyde, acetone, acrylonitrile, acetaldehyde, toluene, carbon disulfide, methyl ethyl ketone/butyraldehyde, propionaldehyde, acetonitrile and methanol compared to cigarettes using only charcoal filters.

As shown in Figure 2, the multi-section filter 130 has a filter plug 132 at the mouth end 131, a selective absorbent section 136 at the end of the tobacco stick 137, and a general absorbent section 134 located between the filter plug 132 and the selective absorbent section 136.

In an alternative configuration as shown in Figure 3, the cigarette 210 has a multi-section filter 230 in which a filter plug 132 is disposed at the mouthpiece end 131, a general absorbent section 134 located at the end of the tobacco rod 137, and a selective absorbent section 136 sandwiched between the filter plug 132 and the general absorbent section. 134. In this configuration, during normal smoke entrainment, the smoke first passes through the general absorbent section 134, then through the selective absorbent section 136, and finally through the filter plug 132.

Moreover, the multi-section filter 230 is substantially identical to the filter 130 (FIG. 2) of the first example configuration except that the absorbent section 134 is located at the end of the tobacco rod 20 and the selective absorbent section 136 is sandwiched between the filter plug 132 and the general absorbent section 134. When the tobacco rod is burned under a normal smoke draw/rest cycle, the analysis of tobacco vapor present in the mouth end 131 of cigarette 210 (Figure 3) shows statistically significant reductions in the levels of propionaldehyde, acetone, methyl ethyl ketone/butyraldehyde, crotonaldehyde, hydrogen sulfide, 2-methyl propanal, pyridine, acrolein, toluene, acetaldehyde, acrylonitrile, methanol, and benzene compared to cigarettes using similar resin-only filters. When a tobacco stick

burned under a normal draw/rest cycle, analysis of tobacco vapor present in the mouth end of 131 cigarettes 210 shows statistically significant reductions in levels of pyridine, hydrogen cyanide, benzene, propionitrile, crotonaldehyde, acrylonitrile, acetaldehyde, toluene, carbon disulfide, methyl ethyl ketone/butyraldehyde, propionaldehyde, acetonitrile, and methanol compared to filter-only cigarettes from charcoal.

As shown in the following configuration in Figure 4, in the multi-section filter 330 of the cigarette 310, the absorbent materials 144, 146 are stacked within the filter cap material as sections of thin layers of the general absorbent material 344 and the selective absorbent material 346. In this configuration, the layered absorbent materials are exposed to less plasticizer than the fibrous dispersed absorbent materials and they retain a larger surface area for interaction with the ingredients of the smoke. Furthermore, as shown in FIG. 7 , the multi-section filter 630 for the cigarette 610 includes a general absorbent material 344 and a selective absorbent material 346 dispersed in separate sections within a single length of the fibrous filter material 342 .

An advantage of the configuration 110 of Figure 2 is that the smoke passes through the selective absorbent material 146 before passing through the general absorbent material 144. This allows the selective absorbent material 146 to remove some specific smoke constituents before the general absorbent material 144 is exposed to the smoke, allowing the general absorbent material 144 to be more effective in removing the remaining smoke constituents. Thus there is a synergistic effect observed for absorbents in cellulose acetate / general absorbents / position of specific absorbents compared to cellulose acetate / specific absorbents / position of general absorbents.

As shown in Figures 5 and 6 , in the multi-section filter 430 and 530 of cigarettes 410 and 510 , the filter plug 132 is placed between the general absorbent section 134 and the selective absorbent section 136 in Figure 5 and is located at the end of the tobacco stick 20 in Figure 6 In Figure 5 the selective absorbent section 136 is located at the end of the mouthpiece filter 430, and in Figure 6, the general absorbent section 134 is located at the end of the mouthpiece filter 530. Furthermore, as shown in FIG. 8 , the multi-section filter 730 of the cigarette 710 includes only the general absorbent section 134 and the selective absorbent section 136 .

The following examples present the configurations that can be prepared in accordance with the present invention and the smoke constituent removal performance based on these configurations. The configurations shown here are provided by way of example only and are not intended to be limiting in this area.

Example 1: A multi-section filter cigarette 110 130 is prepared as shown in Figure 2 wherein the filter plug 132 is made of cellulose acetate fibers and has a thickness of 7 mm; general absorbent section 134 consists of about 40 mg of activated coconut charcoal 144 dispersed through plasticizer-treated cellulose acetate fibers 142 cut to form a section 134 of about 10 mm length, and selective absorbent section 136 consists of about 40 mg of Duolite A7 dispersed through cellulose acetate fibers 142 which were treated with plasticizer and were cut to give a section 136 with a length of about 10 mm. The filter is attached to a tobacco rod having a length of about 56.5 mm and containing about 617 mg of a characteristic non-menthol cigarette blend wrapped in 50 Coresta cigarette paper with about 1.8% citrate. A cigarette releases about 10.3

mg of tar per cigarette.

Example 2: A multi-section filter cigarette 210 230 is prepared with a section arrangement as shown in Figure 3, wherein the filter plug 132, general absorbent section 134, and selective absorbent section 136 are substantially identical to the filter plug 132, general absorbent section 134, and selective absorbent section 136 of Example 1. The filter is attached to a tobacco rod having a length of about 56.5 mm and containing about 617 mg of a characteristic non-menthol cigarette blend wrapped in 50 Coresta cigarette paper with about 1.8% citrate. A cigarette releases about 10.0 mg of tar per cigarette.

Example 3: Cigarettes were prepared as in Example 1, except that about 20 mg of Duolite A7 was used in the selective absorbent section 136 instead of 40 mg. A cigarette releases about 10.2 mg of tar per cigarette.

Example 4: Cigarettes were prepared as in Example 2 except that about 20 mg of Duolite A7 was used in the selective absorbent section 136 instead of 40 mg. A cigarette releases about 10.9 mg of tar per cigarette.

Example 5: Cigarettes were prepared as in Example 1 except that about 60 mg of Duolite A7 was used in the selective absorbent section 136 instead of 40 mg. A cigarette releases about 10.0 mg of tar per cigarette.

Example 6: Cigarettes were prepared as in Example 2 except that about 60 mg of Duolite A7 was used in the selective absorbent section 136 instead of 40 mg. A cigarette releases about 10.3 mg of tar per cigarette.

Example 7: Cigarettes were prepared as in Example 1 except that about 69 mg of mineral based charcoal made from semi-anthracite charcoal was used in the general absorbent section 136 instead of 40 mg of activated coconut charcoal. A cigarette releases about 10.1 mg of tar per cigarette.

Example 8: Cigarettes were prepared as in Example 2 except that about 69 mg of mineral based charcoal made from semi-anthracite charcoal was used in the general absorbent section 136 instead of 40 mg of activated coconut charcoal. A cigarette releases about 10.2 mg of tar per cigarette.

Example 9: The shown cigarettes of Examples 1 to 6 are smoked to a stem length of about 4 mm from the tip using a Borgwalt RM-20 smoking machine. Following the procedures outlined by the FTC, the smoke constituents present at the filter end of each cigarette are passed through a Cambridge filter pad, the vapor phase is collected in a bag and analyzed by GC/MS. The data is normalized to about 10 mg of tar per cigarette.

The mean value of the vapor phase gives the result ((_ig/cig)

Example 10: The shown cigarettes of Examples 7 and 8 are smoked to a stem length of about 4 mm from the tip using a Borgwalt RM-20 smoking machine. Following the procedures outlined by the FTC, the smoke constituents present at the filter end of each cigarette are passed through a Cambridge filter pad, the vapor phase is collected in a bag and analyzed by GC/MS. The data is normalized to about 10 mg of tar per cigarette.

The mean value of the vapor phase gives the result ((Lig/cig)

From a manufacturing standpoint, there are some advantages to dispersing the selective absorbent material 146 and the general absorbent material 144 throughout the filter fibers 142. When the absorbent materials 144, 146 are dispersed within the fibers 142, the absorbent materials are easier to handle than when they are in the form of loose particles.

However, when the absorbent materials 144, 146 are dispersed within the fibers 142, there is a risk that the plasticizer used on the fibers 142 will affect the surface of the absorbent materials 142, 146, thereby reducing their absorption capacity. Thus, as shown in FIG. 4 , absorbent materials 144 , 146 may be stacked within filter plug material 142 as thin layered sections of general absorbent material 344 and selective absorbent material 346 .

Since layered absorbent materials would not be exposed to the same amount of plasticizer as fiber dispersed absorbent materials, the absorbent materials would retain much more surface area for interaction with smoke constituents.

Based on the above, one of ordinary skill in the art of the invention should be able to devise variations of the features of the invention. For example, the filter plug, general absorbent section, and selective general absorbent may vary in length and diameter with respect to any of the dimensions specified herein and with respect to each other. Furthermore, the optimal values of the dimensions of the sections can be determined for a certain mixture of tobacco or for certain dimensions of a tobacco stick. It is believed that these

and other variations fall within the meaning and scope of the attached requirements.

Claims (31)

1. A multi-section cigarette filter comprising: a) a selective absorbent section comprising a selective absorbent material having a preference for a predetermined class of chemical compounds dispersed through the fibrous material; and b) a general absorbent section comprising a general absorbent material, which has a large surface area and is able to absorb smoke constituents without a high degree of specificity; said selective absorbing section and general absorbing section are axially centered one behind the other. 2. The cigarette filter of claim 1 wherein said selective absorbent material is an ion exchange resin. 3. The cigarette filter of claim 2 wherein said selective absorbent material has a surface area sufficient to ensure that the surface active sites are readily accessible to smoke constituents. 4. The cigarette filter of Claim 2 wherein said ion exchange resin has a phenol-formaldehyde resin matrix and is surface-active with primary and secondary amino groups. 5. The cigarette filter of claim 2 wherein said selective absorbent section comprises a selective absorbent material dispersed throughout the fibrous material. 6. The cigarette filter of claim 2 wherein said selective absorbent section comprises a closely packed layer of said selective absorbent material. 7. The cigarette filter of claim 1, wherein the general absorbent material is selected from the group consisting of activated charcoal, coconut activated carbon, activated carbon, zeolite, silica gel, sepiolite, aluminum oxide, charcoal made from semi-anthracite coal, carbon resin obtained by pyrolysis of sulfonic styrene-divinylbenzene, or a combination thereof. 8. The cigarette filter of claim 7 wherein said general absorbent section comprises said general absorbent material dispersed throughout the fibrous material. 9. The cigarette filter of claim 7 wherein the general absorbent section comprises a closely packed layer of said range of absorbent material. 10. The cigarette filter of claim 7 wherein the general absorbent section further comprises a metal oxide or other metal-based compounds. 11. A cigarette filter according to claim 1 comprising a fibrous filter plug wherein said filter plug is made of cellulose, cellulose acetate fibers, paper, cotton, neoprene fabric, neoprene fibers, polyester fabric, polyester fibers or a combination thereof; said fibrous filter plug is coaxially centered with said selective absorbent section and said general absorbent section. 12. The cigarette filter of claim 11 wherein said filter plug further comprises a plasticizer, a liquid additive, a flavoring agent, or a combination thereof. 13. The cigarette filter of claim 11 wherein said joint is located between said fibrous filter plug and said selective absorbent section. 14. The cigarette filter of claim 11 wherein the selective absorbent section is located between said fibrous filter plug and said general absorbent section. 15. The cigarette filter of claim 11, said fibrous filter plug is positioned between said selective absorbent section and said general absorbent section. 16. The cigarette filter of claim 1 comprising a plug jacket surrounding said general absorbent section and said selective absorbent section. 17. The cigarette filter of claim 1, said selective absorbent material having a surface area greater than about 35 m2 / g. 18. A multi-section cigarette filter comprising: a) a fibrous filter plug selected from the group consisting of cellulose, cellulose acetate fibers, paper, cotton, neoprene fabric, neoprene fibers, polyester fabric, polyester fibers, or combinations thereof; b) a selective absorbing section comprising a resin with ion exchangers, having a surface area sufficient to ensure that the surface active sites are easily accessible to the smoke constituents; and c) a general absorbent section comprising a general absorbent material selected from the group consisting of activated charcoal, activated coconut charcoal, activated charcoal, zeolite, silica gel, sepiolite, aluminum oxide, charcoal made from semi-anthracite coal, carbon resin obtained by pyrolysis of sulphonic styrene-divinylbenzene or their combination; said fibrous filter plug, said selective absorption section and said general absorption section are axially centered one behind the other. 19. The cigarette filter of claim 18 wherein said ion exchange resin has a phenol-formaldehyde resin matrix and is surface active with primary and secondary amino groups. 20. The cigarette filter of claim 18 wherein said selective absorbent section comprises said ion exchange resin dispersed throughout the fibrous material. 21. The cigarette filter of claim 18 wherein said selective absorbent section comprises a tightly packed layer of said ion exchange resin. 22. The cigarette filter of claim 18 wherein said general absorbent section comprises said general absorbent material dispersed throughout the fibrous material. 23. The cigarette filter of claim 22 wherein said general absorbent section further comprises an additive selected from a metal oxide or other metal-based compound. 24. The cigarette filter of claim 18 wherein said general absorbent section comprises a closely packed layer of said general absorbent material. 25. The cigarette filter of claim 24 wherein said general absorbent section further comprises an additive selected from metal oxides or metal-based compounds. 26. The cigarette filter of claim 18, wherein said filter plug is made of cellulose acetate fibers. 27. The cigarette filter of claim 18 wherein said filter plug further comprises a plasticizer, a liquid additive, a flavoring agent, or a combination thereof. 28. The cigarette filter of claim 18 wherein said general absorbent section is located between said fibrous filter plug and said selective absorbent section. 29. The cigarette filter of claim 18 wherein said selective absorbent section is located between said fibrous filter plug and said general absorbent section. 30. The cigarette filter of claim 18, said fibrous filter plug being located between said selective absorbent section and said general absorbent section. 31. The cigarette filter of claim 18, said selective absorbent material having a surface area greater than 35 m<2>/g.