Abstract:
A cigarette filter that includes a multiple section filter which reduces the level 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. The selective adsorbent material, such as a phenol-formaldehyde resin matrix surface-functionalized with mainly primary and secondary amine functional groups, removes specific smoke constituents from the tobacco smoke. The general adsorbent material, such as activated charcoal, is preferably capable of adsorbing a range of chemical compounds without a high degree of specificity. Structurally, the fibrous filter plug, the selective adsorbent section, and the general adsorbent section are co-axially aligned in tandem.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS  
       [0001]    This application claims priority from U.S. Provisional Application Ser. No. 60/309,388, filed Aug. 1, 2001, which application is incorporated herein by reference in its entirety. 
     
    
     
       BACKGROUND  
         [0002]    The present invention relates to a cigarette filter that includes a smoke constituent adsorbent which, when combined with a carbon-based filtering material, demonstrates synergistic reductions in smoke vapor constituents.  
           [0003]    Cigarettes include tobacco rods or columns which, when burned, produce a particulate and a vapor phase. About 70 years ago, filters began to be attached to an end of the tobacco column. Among other things, the filter removed various smoke components. Filters made from filamentary or fibrous material, such as cellulose acetate tow or paper, remove the particulate phase of tobacco smoke by mechanical means. However, the fibrous materials are not effective at removing volatile constituents, such as aldehydes, hydrogen cyanide and sulfides, which are found in the vapor phase. Typically, an adsorbent or absorbent is combined with the fibrous material to improve removal of the vapor phase components. For example, cigarette filters have included activated carbon, porous minerals such as meerschaum, silica gel, cation-exchange resins and anion-exchange resins.  
           [0004]    Charcoal has a high specific surface area and is a relatively strong adsorbent for vapor-phase constituents of tobacco smoke. When coated with a mixture of metallic oxides, charcoal is particularly effective in removing acidic gases. Meerschaum has a large adsorption area with a strong adsorption affinity for charged species, but a considerably low adsorption affinity for non-polar species. Silica gels are generally regarded as weakly retentive adsorbents for vapor-phase constituents of tobacco smoke. Although silica gel readily adsorbs aldehydes and hydrogen cyanide, the constituents also readily desorb from the silica gel. Cation exchange resins have been proposed for nicotine removal. Anion exchange resins have been proposed for the removal of smoke acids, but strongly basic anion exchangers have no effect on smoke vapor phase aldehydes. Weakly basic anion-exchange resins of porous structure are suitable for the removal of smoke acids and aldehydes, but their efficiency diminishes during smoking, as does that of carbon and porous minerals.  
           [0005]    Two or more adsorbents can be used in combination in cigarette filters. For example, U.S. Pat. No. 2,815,760 describes the use of an ion exchange material with materials which “chemically react with the harmful, nonalkaline and nonacid components of the smoke to form non-volatile compounds, thus retaining the latter to the filter.” However, the aforesaid additives have not yielded satisfactory selective removal of such smoke phase components, as smoke aldehydes, particularly acetaldehyde and acrolein. U.S. Pat. No. 4,300,577 describes the use of a weakly retentive absorbent for vapor-phase constituents intermingled with a second component having mainly primary amino functional groups for the removal of vapor-phase constituents, including aldehydes and hydrogen cyanide from tobacco smoke. However, the filter of the &#39;577 patent has not been shown to demonstrate adequate consumer acceptance or commercial viability.  
         SUMMARY  
         [0006]    The present invention relates to a cigarette filter that includes a multiple section filter which reduces the level 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.  
           [0007]    The filter plug can be any filter plug known in the art, such as cellulose acetate tow. The general adsorbent material is preferably selected from a group of relatively high surface area materials, such as activated charcoal, which are capable of adsorbing a range of chemical compounds without a high degree of specificity. The selective adsorbent material is chosen based on the specific smoke constituents targeted for removal. Preferably, the selective adsorbent material is selected from a group of surface functionalized resins, wherein each resin consists of an essentially inert carrier with a surface area of greater than about 35 m 2 /g. In an embodiment of the present invention, the selective adsorbent material has a phenol-formaldehyde resin matrix surface-functionalized with mainly primary and secondary amine functional groups.  
           [0008]    Structurally, the selective adsorbent material may be adjacent to a tobacco rod and the general adsorbent material positioned between the selective adsorbent section and the filter plug. Alternatively, the general adsorbent material may be positioned adjacent to the tobacco rod and the selective adsorbent material between the general adsorbent section and the filter plug. Preliminary data indicates that the former orientation produces a synergistic effect in smoke constituent reductions relative to the latter orientation. Further, the selective adsorbent and general adsorbent may be interspersed in a traditional filter plug material, such as cellulose acetate, or the adsorbents may be packed as a bed or thin layer sections within filter plug material. 
       
    
    
     SUMMARY OF THE FIGURES  
       [0009]    [0009]FIG. 1 is a perspective view of a prior art filter-tipped cigarette;  
         [0010]    [0010]FIG. 2 is a perspective view of a filter for a cigarette made in accordance with the present invention wherein the adsorbents are dispersed throughout a filter plug material, and the general adsorbent section is positioned between the filter plug and the selective adsorbent section;  
         [0011]    [0011]FIG. 3 is a perspective view of a filter for a cigarette made in accordance with the present invention wherein the adsorbents are dispersed throughout a filter plug material, and the selective adsorbent section is positioned between the filter plug and the general adsorbent section; and  
         [0012]    [0012]FIG. 4 is a perspective view of a filter for a cigarette made in accordance with the present invention wherein the adsorbents are packed as beds within a segment of a filter plug material.  
         [0013]    [0013]FIG. 5 is a cross-sectional view of an embodiment of the present invention with the filter plug disposed between the general adsorbent section and the selective adsorbent section;  
         [0014]    [0014]FIG. 6 is a cross-sectional view of an embodiment of the present invention with the filter plug adjacent one end of a tobacco rod;  
         [0015]    [0015]FIG. 7 is a cross-sectional view of an embodiment of the present invention with the adsorbents being sectionalized in a single length of fibrous filter material; and, FIG. 8 is a cross-sectional view of an embodiment of the present invention absent a filter plug section. 
     
    
     DETAILED DESCRIPTION  
       [0016]    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.  
         [0017]    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 .  
         [0018]    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 .  
         [0019]    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.  
         [0020]    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, 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.  
         [0021]    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  may be an ion-exchange resin, such as Duolite A7 (a phenol-formaldehyde resin matrix and is surface-functionalized with primary and secondary amino groups available from Rohm and Haas, 5000 Richmond Street, Philadelphia, Pa. 19137), or a material having similar functional groups and binding affinities.  
         [0022]    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.  
         [0023]    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 .  
         [0024]    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 .  
         [0025]    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.  
         [0026]    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 .  
         [0027]    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.  
         [0028]    Example 1: 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.  
         [0029]    Example 2: 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.  
         [0030]    Example 3: 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.  
         [0031]    Example 4: 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.  
         [0032]    Example 5: 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.  
         [0033]    Example 6: 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.  
         [0034]    Example 7: 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.  
         [0035]    Example 8: 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.  
         [0036]    Example 9: 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.  
                                                                                                                         Average Vapor Phase Yields (μg/cig)            mg            Duolite/cigarette   40   20   60            Cigarettes       Prepared by            Example:   1   2   3   4   5   6       Filter Segment       Order   CA/GA/SA   CA/SA/GA   CA/GA/SA   CA/SA/GA   CA/GA/SA   CA/SA/GA                    Acetaldehyde   330.9   333.7   380.7   346.2   320.3   310.9       Isoprene   231.4   240.4   252.1   246.1   227.4   227.2       Acetone   144.1   163.5   156.0   160.5   148.0   151.4       Methanol   104.9   127.6   114.5   142.8   111.7   98.5       Acetonitrile   59.8   72.0   67.0   77.4   62.8   57.3       Acrolein   29.6   31.4   33.6   32.2   28.5   29.9       Methyl ethyl ketone   29.3   35.9   30.9   38.5   30.1   31.6       Formaldehyde   23.5   25.8   25.5   25.0   22.1   24.5       Propionaldehyde   25.7   27.4   29.3   28.5   25.3   25.0       1,3-Butadiene   25.5   25.9   27.5   25.5   25.8   25.0       Toluene   22.5   25.3   22.0   27.5   23.9   22.5       Benzene   20.6   23.6   21.6   24.1   21.1   21.4       Acrylonitrile   16.8   17.7   18.0   18.0   17.0   16.5       Furan   16.2   17.0   17.3   16.4   16.4   16.2       Hydrogen cyanide   15.1   16.4   20.7   19.6   13.6   14.8       Hydrogen sulfide   12.9   13.0   14.0   12.9   13.1   12.7       Propionitrile   12.9   15.0   13.5   15.9   13.6   12.8       2-Methylpropanal   6.4   6.7   7.0   7.0   6.6   6.4       Crotonaldehyde   5.1   5.9   5.5   6.3   5.3   5.0       Carbon disulfide   2.5   2.6   2.7   2.6   2.6   2.5       Styrene   2.0   1.8   2.2   1.9   2.1   1.7       Pyridine   1.9   1.9   1.9   1.8   1.9   1.8                          
 
         [0037]    Example 10: 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.  
                                                                                           Average Vapor Phase Yields (μg/cig)                mg Duolite/cigarette   40                Cigarettes Prepared by                Example:   7   8           Filter Segment Order   CA/GA/SA   CA/SA/GA                            Acetaldehyde   343.4   364.2           Isoprene   225.0   268.9           Acetone   138.6   162.3           Methanol   95.1   134.7           Acetonitrile   61.4   84.6           Acrolein   9.8   35.3           Methyl ethyl ketone   28.3   39.8           Propionaldehyde   26.4   30.2           1,3-Butadiene   25.4   27.7           Toluene   18.7   24.2           Benzene   21.3   27.3           Acrylonitrile   7.5   9.0           Furan   17.0   18.4           Hydrogen cyanide   16.7   19.5           Hydrogen sulfide   14.7   14.1           Propionitrile   15.7   20.3           2-Methylpropanal   13.0   14.8           Crotonaldehyde   3.3   5.1           Carbon disulfide   2.8   2.8           Styrene   1.8   2.1           Pyridine   1.3   1.4                                  
 
         [0038]    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.  
         [0039]    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.