DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0017] The cigarette filter of the present invention includes a multiple section filter which reduces the levels of predetermined smoke constituents. The filter consists of a fibrous filter plug located at the mouth-end of the cigarette, a section containing a selective adsorbent material, and a section containing a general adsorbent material.

[0018] As shown in FIG. 1 and as is known in the art, a typical filter-tipped cigarette 10 has a filter 30 attached to a tobacco rod 20. The tobacco rod 20 consists of a loose tobacco-containing mixture 22 wrapped in a cigarette paper 24, and the filter 30 includes a filter plug 32 wrapped in a plug wrap 34. A sheet of tipping paper 36 joins the filter 30 to the tobacco rod 20.

[0019] In the present invention, as shown in FIG. 2, a cigarette 110 has a multiple section filter 130 attached to the tobacco rod 20. The filter 130 includes a filter plug 132, a section containing a general adsorbent 134 and a section containing a selective adsorbent 136. The filter plug 132 is adjacent a first or mouth end 131 of the filter 130. The bed of the selective adsorbent 136 is adjacent a second or tobacco-rod end 137 of the filter 130. The bed of the general adsorbent 134 is positioned between the filter plug 132 and the selective adsorbent bed 136.

[0020] The filter plug 132 is made from a filamentary or fibrous material and provides a clean, neat appearance at the mouth end 131 of the cigarette. The filter plug 132 also retains a firmness at the mouth end 131 as the cigarette 110 is consumed. As is known in the art, the filter plug 132 can be made from a variety of materials, among the most common being cellulose, cellulose acetate tow, paper, cotton, polypropylene web, polypropylene tow, polyester web, polyester tow or combinations thereof. Optionally, a plasticizer may be included.

[0021] The general adsorbent section 134 includes a general adsorbent material 144 dispersed throughout a filter plug material 142, such as in a “dual-dalmatian” filter, known in the art. The general adsorbent material 144 is preferably selected from a group of relatively high surface area materials which are capable of adsorbing smoke constituents without a high degree of specificity. For example, the general adsorbent can be selected from activated charcoal, activated coconut carbon, activated coal-based carbon, zeolite, silica gel, meerschaum, aluminum oxide, or combining thereof, as well as a mineral-based charcoal made from semi-anthracite coal with a density about 50% greater than coconut-based charcoal (available from Calgon Carbon, Pittsburgh, Pa.), Ambersorb 572 or Ambersorb 563 (a carbonaceous resin derived from the pyrolysis of sulfonated styrene-divinylbenzene available from Rohm and Haas, 5000 Richmond Street, Philadelphia, Pa. 19137), other materials having similar particle sizes, surface area and binding affinities, or combinations thereof. To further enhance the efficacy of the general adsorbent, metal oxides or other metal-based complexes may be included in the general adsorbent section.

[0022] The selective adsorbent section 136 includes a selective adsorbent material 146 dispersed throughout a filter plug material 142, such as in a “dual-dalmatian” filter, known in the art. The selective adsorbent material 146 is preferably selected based on the material's 146 specificity for a predetermined class of chemical compounds. For example, the selective adsorbent 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 functional groups and binding affinities. The Duolite A7 has a phenol-formaldehyde rsin matrix and is surface-functionalized with primary and secondary amino groups, thereby enhancing the resin's specificity toward the aldehydes and hydrogen cyanide found in tobacco smoke.

[0023] Further, the selective adsorbent material 146 must be selected taking into consideration that the contact conditions between the tobacco smoke and the adsorbent 146 are dependent on a number of variables, including how strongly the smoker pulls the smoke through the filter as the cigarette is being smoked and how much of the tobacco rod has been consumed prior to each puff. Thus, it is advantageous that the selective adsorbent 146 have a surface area of greater than about 35 m²/g so that there is minimal diffusional resistance and the surface area functional sites are easily accessible. Materials with greater surface areas also demonstrate less noticeable performance decline if part of the surface is covered with a plasticizer, as might occur when the adsorbent 146 is dispersed in the filter plug 142.

[0024] When the cigarette is consumed, the tobacco smoke is puffed by the smoker through the filter 130. The smoke initially passes over the selective adsorbent section 136 where the targeted smoke constituents are adsorbed on the surface of the selective adsorbent material 146 and particulate matter in the smoke is retained by the filter plug material 142. The remaining smoke then passes over the general adsorbent section 134 where other constituents may be retained by the adsorbent material 144 and additional particulate matter is retained by the filter plug material 142. Finally, the remaining smoke then passes through the filter plug 132 where additional particulate matter can be removed. The filtered smoke is then delivered to the smoker.

[0025] In a first example embodiment of the present invention, as shown in FIG. 2, the multiple section filter 110 is made having a filter plug 132 made of cellulose acetate tow and being about 7 mm in length, and having a general adsorbent section 134 consisting of 40 mg of activated coconut charcoal 144 dispersed throughout cellulose acetate tow 142 cut to deliver a section 134 about 10 mm in length wherein the cellulose acetate tow is treated with a plasticizer, and having a selective adsorbent section 136 consisting of 40 mg of Duolite A7 dispersed throughout cellulose acetate tow 142 cut to deliver a section 136 about 10 mm in length wherein the cellulose acetate tow is treated with a plasticizer. When the tobacco rod is burned with a normal puff/rest cycle, analysis of the smoke vapor exiting 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-methylpropanal, isoprene, styrene, pyridine, toluene and benzene as compared to cigarettes using similar resin-only filters. When the tobacco rod is burned with a normal puff/rest cycle, analysis of the smoke vapor exiting 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 as compared to cigarettes using charcoal-only filters.

[0026] As shown in FIG. 2, the multiple section filter 130 has the filter plug 132 adjacent the mouth end 131, the selective adsorbent section 136 adjacent the tobacco-rod end 137, and the general adsorbent section 134 positioned between the filter plug 132 and the selective adsorbent section 136.

[0027] In an alternative embodiment, such as shown in FIG. 3, a cigarette 210 has a multiple section filter 230 wherein the filter plug 132 is positioned at the mouth end 131, the general adsorbent section 134 is adjacent the tobacco-rod end 137, and the selective adsorbent section 136 is sandwiched between the filter plug 132 and the general adsorbent section 134. In this embodiment, during a normal puff, the smoke first passes through the general adsorbent section 134, then through the selective adsorbent section 136, and finally through the filter plug 132. Moreover, the multiple section filter 230 is essentially identical to the filter 130 (FIG. 2) of the first example embodiment except that the general adsorbent section 134 is adjacent to the tobacco rod 20 and the selective adsorbent section 136 is sandwiched between the filter plug 132 and the general adsorbent section 134. When the tobacco rod is burned with a normal puff/rest cycle, analysis of the smoke vapor exiting at the mouth end 131 of the cigarette 210 (FIG. 3) shows statistically significant reductions in the levels of propionaldehyde, acetone, methyl ethyl ketone/butyraldehyde, crotonaldehyde, hydrogen sulfide, 2-methylpropanal, pyridine, acrolein, toluene, acetaldehyde, acrylonitrile, methanol and benzene as compared to cigarettes using similar resin-only filters. When the tobacco rod is burned with a normal puff/rest cycle, analysis of the smoke vapor exiting at the mouth end 131 of the cigarette 210 shows statistically significant reductions in the levels of pyridine, hydrogen cyanide, benzene, propionitrile, crotonaldehyde, acetone, acrylonitrile, acetaldehyde, toluene, carbon disulfide, methyl ethyl ketone/butyraldehyde, propionaldehyde, acetonitrile, and methanol as compared to cigarettes using charcoal-only filters.

[0028] As shown in another embodiment in FIG. 4, in a multiple section filter 330 of a cigarette 310, the absorbents 144, 146 are packed within the filter plug material as thin layer sections of general absorbent 344 and selective absorbent 346. In this embodiment, the layer packed absorbents are exposed to less plasticizer than the tow-dispersed absorbents and retain more surface area for interacting with smoke constituents. Moreover, as shown in FIG. 7, a multi-section filter 630 for a cigarette 610 includes the general adsorbent 344 and the selective adsorbent 346 dispersed in separate sections within a single length of fibrous filter material 342.

[0029] An advantage of the embodiment 110 of FIG. 2 is that the smoke passes over the selective adsorbent material 146 before passing over the general adsorbent 144. This allows the selective adsorbent 146 to remove some specific smoke constituents before the general adsorbent 144 is exposed to the smoke, thereby allowing the general adsorbent 144 to be more effective in removing the remaining smoke constituents. Thus, there is a synergistic effect observed for the adsorbents in the cellulose acetate/general adsorbent/specific adsorbent orientation as compared to the cellulose acetate/specific adsorbent/general adsorbent orientation.

[0030] As shown in FIGS. 5 and 6, in a multiple section filter 430 and 530 of cigarettes 410 and 510, respectively, the filter plug 132 is disposed between the general adsorbent section 134 and the selective adsorbent section 136 in FIG. 5 and is adjacent one end of the tobacco rod 20 in FIG. 6. In FIG. 5 the selective adsorbent section 136 is at the mouth end of the filter 430 and in FIG. 6 the general adsorbent section 134 is at the mouth end of the filter 530. Moreover, as shown in FIG. 8, a multiple section filter 730 of a cigarette 710 includes only a general absorbent section 134 and a selective absorbent section 136.

[0031] The following examples are representative of the embodiments which can be prepared in accordance with the present invention and the smoke constituent removal performance of those embodiments. The embodiments presented are intended for example purposes only and are not intended to be limiting in scope.

EXAMPLE 1

[0032] A cigarette 110 with a multiple section filter 130 is prepared as shown in FIG. 2 wherein a filter plug 132 is made of cellulose acetate tow and is about 7 mm in length, a general adsorbent section 134 consists of about 40 mg of activated coconut charcoal 144 dispersed throughout plasticizer-treated cellulose acetate tow 142 cut to deliver a section 134 about 10 mm in length, and a selective adsorbent section 136 consists of about 40 mg of Duolite A7 dispersed throughout plasticizer-treated cellulose acetate tow 142 cut to deliver a section 136 about 10 mm in length. The filter is attached to a tobacco rod having a length of about 56.5 mm and containing about 617 mg of a typical non-menthol cigarette blend wrapped in a 50 Coresta cigarette paper with about 1.8% citrate. The cigarette delivers about 10.3 mg tar per cigarette.

EXAMPLE 2

[0033] A cigarette 210 with a multiple section filter 230 is prepared with the section orientations as shown in FIG. 3 wherein the filter plug 132, the general adsorbent section 134, and the selective adsorbent section 136 are essentially identical to the filter plug 132, the general adsorbent section 134, and the selective adsorbent 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 typical non-menthol cigarette blend wrapped in a 50 Coresta cigarette paper with about 1.8% citrate. The cigarette delivers about 10.0 mg tar per cigarette.

EXAMPLE 3

[0034] Cigarettes are prepared as in Example 1 except that about 20 mg Duolite A7 is used in the selective adsorbent section 136 instead of 40 mg. The cigarette delivers about 10.2 mg tar per cigarette.

EXAMPLE 4

[0035] Cigarettes are prepared as in Example 2 except that about 20 mg Duolite A7 is used in the selective adsorbent section 136 instead of 40 mg. The cigarette delivers about 10.9 mg tar per cigarette.

EXAMPLE 5

[0036] Cigarettes are prepared as in Example 1 except that about 60 mg Duolite A7 is used in the selective adsorbent section 136 instead of 40 mg. The cigarette delivers about 10.0 mg tar per cigarette.

EXAMPLE 6

[0037] Cigarettes are prepared as in Example 2 except that about 60 mg Duolite A7 is used in the selective adsorbent section 136 instead of 40 mg. The cigarette delivers about 10.3 mg tar per cigarette.

EXAMPLE 7

[0038] Cigarettes are prepared as in Example 1 except that about 69 mg of a mineral-based charcoal made from semi-anthracite coal is used in the general adsorbent section 136 instead of 40 mg of activated coconut charcoal. The cigarette delivers about 10.1 mg tar per cigarette.

EXAMPLE 8

[0039] Cigarettes are prepared as in Example 2 except that about 69 mg of a mineral-based charcoal made from semi-anthracite coal is used in the general adsorbent section 136 instead of 40 mg of activated coconut charcoal. The cigarette delivers about 10.2 mg tar per cigarette.

EXAMPLE 9

[0040] Representative cigarettes of Examples 1-6 are smoked to a butt length of about 4 mm from the tipping using a Borgwalt RM-20 smoking machine. Following the procedures set forth by the FTC, smoke constituents exiting 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 tar per cigarette. 1

EXAMPLE 10

[0041] Representative cigarettes of Examples 7 and 8 are smoked to a butt length of about 4 mm from the tipping using a Borgwalt RM-20 smoking machine. Following the procedures set forth by the FTC, smoke constituents exiting 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 tar per cigarette. 2

[0042] From a production perspective, there are some advantages to dispersing the selective adsorbent material 146 and the general adsorbent material 144 throughout the filter tow 142. Specifically, when the adsorbents 144, 146 are dispersed within the tow 142, the adsorbents are easier to handle than they are as loose particles. However, when the adsorbents 144, 146 are dispersed within the tow 142, there is a risk that any plasticizer which is used on the tow 142 will affect the surface of the adsorbents 144, 146, thereby reducing the adsorption capacity. Thus, as shown in FIG. 4, the adsorbents 144, 146 may be packed within the filter plug material 142 as thin layer sections of general adsorbent 344 and selective adsorbent 346. Because the layer packed adsorbents would not be exposed to the same level of plasticizer as the tow-dispersed adsorbents, the adsorbents would retain more available surface area for interacting with smoke constituents.

[0043] From a reading of the above, one with ordinary skill in the art should be able to devise variations to the inventive features. For example, the filter plug, the general adsorbent section, and the selective adsorbent section may vary in length and diameter, relative to any dimensions specified herein and relative to each other. Further, the various section dimensions may be optimized for a particular tobacco blend or for particular tobacco rod dimensions. These and other variations are believed to fall within the spirit and scope of the attached claims.