Silica resin filter for smoking articles

Abstract

A smoking article capable of delivering a regulated smoke composition to a smoker, includes a combustible filler wrapped in a combustible sheath and a filter unit designed to remove components from the smoke, disposed within the sheath. The filter unit includes a mass of porous silica or resin particles, where the porous silica or resin particles have an average particle size of from about 35 to about 400 &mgr;m and preferably an average porosity of from about 10 Å to about 1000 Å. The porous cigarette filter is self-compensating with respect to air ventilation.

Description

[0001] This application is a continuation-in-part of U.S. patent application Ser. No. 09/664,055, filed Sep. 18, 2000, which in turn is a continuation of U.S. patent application Ser. No. 08/995,217, filed Dec. 19, 1997, now U.S. Pat. No. 6,119,699. The entire disclosures of the above-referenced applications are incorporated herein in their entirety.

BACKGROUND OF THE INVENTION

[0002] 1. Field of Invention

[0003] The present invention relates to an improved filter, particularly a silica resin filter, for smoking articles such as cigarettes, cigars and the like. More particularly, the present invention relates to an improved silica resin filter that permits removal of desired degrees of smoke components without adversely affecting the pressure drop across the filter.

[0004] 2. Description of Related Art

[0005] The control of tar and nicotine in cigarette smoke is largely attributed to the use of filters that physically remove total particulate matter (TPM) from the mainstream smoke condensate. Thus, the grades of “full flavor,” “light,” and “ultralight” cigarettes are based on the effectiveness of their filters to eliminate the potential tar and nicotine as found in normal unfiltered cigarettes. This classification system relates to the Federal Trade Commission's (FTC) restrictions on the amount of “tar” the cigarettes may deliver to a smoker. A “full flavor” cigarette delivers 14 mg or more of tar; a “light” cigarette delivers between 8 and 14 mg of tar; and an “ultralight” cigarette delivers less than 7 mg of tar. The “ultralight” cigarette also has an air dilution filter tip to further reduce the tar in the mainstream smoke.

[0006] The latest technology is a “heat” cigarette, available from R. J. Reynolds under the trade designation ECLIPSE, which employs a carbon core in the cigarette. Unlike traditional cigarettes, this new cigarette does not burn at 800° C., but instead heats the tobacco to less than 300° C. This low temperature avoids combustion, which reduces tar formation and also the distillation of nicotine. The cigarette produces low levels of tar and nicotine in both the main and sidestream smoke. Toxicological and biological studies performed by Reynolds Tobacco Company have demonstrated that it is a safe smoking article. However, this cigarette does require some adjustment from the smoker. For example, it is more difficult to light this type of cigarette, and the different flavor requires some changes in personal preferences.

[0007] In addition, numerous filter elements are disclosed in the art to be useful in reducing the levels of tar delivered to a smoker. For example, numerous patents exist describing filter elements that employ baffles and orifices to reduce tar and nicotine. U.S. Pat. No. 3,777,765 to Yoshinga discloses a filter apparatus consisting of a chamber for depositing smoke condensates. The smoke micelles route through this chamber and then exit through another porous barrier disk to become the mainstream smoke. U.S. Pat. No. 3,650,278 to Cook describes an adjustable tar removing filter for cigarettes having an adjustable needle valve that the smoker adjusts to the desired level of taste. U.S. Pat. No. 3,472,238 to Blount et al. describes yet another cigarette holder device with a disposable tar collecting cartridge. U.S. Pat. No. 5,617,882 to Bushuev et al. describes a filter unit containing both organic and inorganic basalt fibers, which it claims provides better tar trapping effectiveness than conventional filters.

[0008] Further, examples of liquids for chemical reaction in a filter are known. U.S. Pat. No. 3,943,940 to Minami proposes a chemical process in the smoking filter to remove nicotine from the smoke. An aqueous solution of potassium permanganate (KMnO4) and chlorine is impregnated in the filter. Because the aqueous KMnO4 solution is unstable, chlorine is added as a stabilizer. It is not clear to what extent permanganate contributes to the oxidation of nicotine since the water barrier filter is also removing nicotine from the smoke.

[0009] The potential of activated silica resin as a smoke adsorbent is also suggested in the art. For example, the use of activated silica in cigarette filters is disclosed in U.S. Pat. Nos. 1,808,707, 1,826,331 and 2,325,386. However, all of these patents describe a loose distribution of the resin particles in the filter proper for removing smoke condensates, and the results are not dramatic. U.S. Pat. No. 2,956,329 to Touey describes the manufacturing of a filamentous acetate filter containing up to 35.5% of silica gel, and reports the effective removal of 34% of the acetaldehyde from the smoke stream. U.S. Pat. No. 2,968,305 and British Pat. No. 795,420 to Barnett disclose a chamber and smoke labyrinth construction in a cigarette filter element for the placement of silica granules. Further, U.S. Pat. Nos. 2,834,354 and 2,872,928 both suggest that by incorporating silica gel bearing either deoxycholate or partially polymerized furfural into the cigarette filter, it should be possible to remove heavy hydrocarbons such as benzopyrene from the smoke. However, in the article “Influence of Filter Additives on Smoke Composition,” Recent Advances in Tobacco Science, Vol. 8, No. 3 (1978) by M.L. Reynolds, it is discussed that the removal of polycyclic aromatic hydrocarbons (PAH) has been claimed in many patents, but has never been demonstrated to be successful.

[0010] Furthermore, both WO 00/25610 and WO 00/25611 disclose the use of functionalized silica gels for removal of specific smoke components, such as aldehydes. The references disclose that specific functional groups, such as 3-aminopropylsilyl groups, can be attached to silica gels for use in filter elements.

[0011] Additionally, the use of ion exchange resins in filter elements has been suggested in the art. For example U.S. Pat. No. 2,739,598 to Eirich describes the manufacture of a copolymer of methyl acrylate and vinyl pyrrolidone as both anion and cation exchanger by embedding the polymers in a paper pulp. The impregnated paper is used as a cigarette filter to remove those ionic species from smoke. U.S. Pat. Nos. 2,754,829 and 2,815,760 to Hess disclose the use of cationic exchangers, and U.S. Pat. No. 3,093,144 to van Bururen discloses the use of both anionic and cationic resins to remove nicotine from tobacco smoke.

[0012] U.S. Pat. No.4,700,723 to Yoshikawa and Shimamura also discloses a fibrous ion-exchange resin that can be incorporated into a cigarette filter. However, their approach is one dimensional. The gas chromatograms of the smoke condensate following the resin treatment appear to show only a quantitative reduction of tar and nicotine. There is no consideration of specificity and the disclosure does not address specific trapping of targeted components.

[0013] In U.S. Pat. Nos. 2,920,629 and 2,920,630 to Kinnavy, a special cotton filter that is impregnated with a waxy salt of trimethyloctadecylammonium chloride (or a class of long chain alkyl-quatemary ammonium chloride) and sodium stearate is disclosed as being useful as a cigarette filter. The input is roughly 1 gm per 2 gm of cotton. When this is used as a tobacco smoke filter, it drastically reduces both tar and nicotine. The high input of a waxy substance with cotton fiber apparently creates a sticky, fatty, and oily filter that obliterates the potential of the long chain hydrocarbon to be capable of specific interactions with smoke components. Instead, it is made into a sticky filter pad for the nonspecific removal of tar and nicotine. U.S. Pat. No. 3,033,212 to Touey and Kiefer discloses a similar intent of incorporating a waxy stearate into a cellulose filter to prevent smoke condensates from being dislodged from the cigarette filter after entrapment.

[0014] With the advent of ultra low tar cigarettes, there is a need to increase flavor and nicotine while decreasing tar. U.S. Pat. No. 5,524,647 to Brackmann discloses using the upper portion of the tobacco plant to provide a higher than normal flavor to tar ratio. In addition, a cylinder of microfine filter element is used to reduce tar and nicotine. This biological approach tends to increase flavor and nicotine relative to tar levels.

[0015] U.S. Pat. No. 5,465,739 to Perfetti et al. describe the incorporation of acids and bases into the filter elements to influence the nicotine content of tobacco in the mainstream smoke. Acid is used for removing more nicotine in the tobacco blends that have high nicotine content and base for those tobacco blends with low nicotine content. The intent is for normalizing the tobacco blends to achieve a consistent product.

[0016] Despite these and numerous other filter designs, typical conventional, commercial cigarette filters are of substantially the same design. Typically, the filter is cylindrical, about 24.6 mm in circumference and about 20 mm in length. The conventional filters are typically manufactured from acetate fiber that is about 20 &mgr;m in diameter and bundled together in a parallel array. The orientation of the fibers is in-line with the smoke flow, i.e., the fibers and fiber bundles are generally parallel with the smoke flow. Smoke particles are generally removed by this filter using three filtration mechanisms; these being diffusion capture by the fibers, direct interception of the particles, and impaction of particles on the fibers. The first mechanism depends on the Brownian motion of very small particles (about 0.1 to 1.0 &mgr;m), and is considered to be the most important filtration mechanism. The efficiency of this conventional filter is roughly 40%, meaning that about 40% of the tar and nicotine contained in the smoke stream is removed by the filter.

[0017] Further reduction or filtering of smoke particles can be achieved by controlling the fiber diameter, fiber distribution and packing in the filter, and filter length. In addition, there is more reliance on reconstituted tobacco and/or selection of tobacco, as discussed above, to produce less tar. However, until now the most dramatic changes in the design of low tar cigarettes are attributed to filter ventilation, where the smoke stream is mixed with air. In the ultra-ultra low tar cigarette, the ventilation is generally at about 60%, and thus the reduced tar delivered to the smoker is due primarily to the fact that there is less smoke.

[0018] The issues of quality control are by far less problematical than societal pressure to properly label such a cigarette. For example, the smoker's ability to tamper with air ventilation, such as by blocking the air vents, can dramatically change the performance of the filter. Likewise, the smoker's ability to tamper with conventional acetate filters, such as by poking needle-sized holes longitudinally through the filter, can also dramatically change the performance of the filter. Indeed, mandatory labeling for the tar and nicotine deliveries in cigarette may come under more stringent testing conditions, by the United States FTC as well as by regulatory agencies of other countries. These conditions may involve, for example, larger puff volume, shorter puff intervals, and testing for tar and nicotine without ventilation. Furthermore, tamper-resistant filter designs may be more desired and/or required, to ensure that the regulated amounts of tar and nicotine can not be readily defeated by the smoker.

SUMMARY OF THE INVENTION

[0019] There thus is clearly a need in the art for a more efficient cigarette filter, as well as for a filter that is more tamper-resistant.

[0020] For example, recently, increasing pressure to reduce cigarette tar has reached an all time high. The industry has responded by increasing the efficiency of filters to decrease tar and nicotine. Nevertheless, many smokers demand even further reductions in tar content, but without a coordinate reduction in the nicotine content, which is primarily responsible for the cigarette flavor. However, the ability of existing cigarette design technology to respond to that demand, while still providing a high, desirable flavor, is limited. Conventional methods generally achieve a coordinated reduction of tar and nicotine from the mainstream smoke. The resultant “ultralight” cigarette may thus not be as flavorful as desired. Consequently, a frustrated smoker may choose to smoke more cigarettes, or alter the filters in a number of ways. All of these known practices, however, defeat the intent of reducing the tar and nicotine in the cigarette smoke. There is thus also a need in the art for a filter that is less susceptible to smoker tampering.

[0021] Moreover, because the delivery of tar and nicotine is highly dependent on the manner of smoking, issues of cigarette labeling and testing (may have to be raised) with manufacturers by the United States FTC and similar governing bodies in other countries. Clearly, there is a need for a new approach to control tar and nicotine in the mainstream smoke.

[0022] These and other needs are met by the invention disclosed herein. The invention represents a drastic departure from conventional cigarette filter design and engineering, and provides a filter capable of selectively removing tar, or virtually any other component, without coordinately removing other components, such as nicotine, below desired levels.

[0023] The present invention also provides a filter design that is less susceptible to smoker tampering, and can thus provide the designated filtering level despite user attempts to influence that level.

[0024] In particular, the present invention provides a smoking article capable of delivering a regulated smoke composition to a smoker, comprising:

[0025] a) a combustible filler wrapped in a combustible sheath; and

[0026] b) a filter unit designed to remove specific targeted components from said smoke disposed within said sheath, said filter unit comprising a mass of porous silica or resin particles,

[0027] wherein said porous silica or resin particles have an average particle size of from about 35 to about 400 &mgr;m.

[0028] The present invention also provides a filter cartridge for targeted components from cigarette smoke, comprising a hollow sleeve packed with porous silica or resin particles, wherein said porous silica or resin particles have an average particle size of from about 35 to about 400 &mgr;m.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIGS. 1A-1C depict chromatograms of the mainstream vapor-phase smoke of various cigarettes collected in a methanol trap: FIG. 1A is smoke from a cigarette treated with a combination of resins consisting of 50 mg silica (100&mgr;m and 60 Å), 100 mg C-18 resin (100 &mgr;m and 60 Å) 100 mg of C-18 resin (200 &mgr;m and 60 Å) and 100 mg 3-aminopropyl resin (200 &mgr;m and 60 Å); FIG. 1C is the ECLIPSE regular flavor and FIG. 1B is the control Marlboro with the acetate filter removed.

[0030] FIGS. 2A-2C show chromatograms of the mainstream vapor-phase smoke collected in methanol trap for cigarettes treated with various resin combinations of C-18, amino, and silica resins. From top to bottom:

[0031] FIG. 2A is the Control of FIG. 1B diluted 1:4;

[0032] FIG. 2B is Resin 50/300 consisting of 50 mg 3-aminopropyl resin (100 &mgr;m and 60 Å) and 300 mg of C-18 resin (200 &mgr;m and 60 Å); and

[0033] FIG. 2C is 150 mg of C-18 resin (100 &mgr;m and 60 Å).

[0034] FIG. 3 illustrates the utility of the affinity C-1 resin in delivering menthol in the mainstream smoke.

[0035] FIG. 4 illustrates the percent reduction of tar and nicotine as a function of mg resin input for a low porosity filter.

[0036] FIG. 5 illustrates the percent reduction of tar and nicotine as a function of mg resin input for a high porosity filter.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0037] The present invention represents a new approach in the control of tar and nicotine in cigarette smoke. Although the separation of molecules according to affinity is a well-known chemical principle, the selective separation and removal of cigarette smoke constituents on a solid phase resin has not previously been effectively accomplished. Cigarette smoke condensate is both aqueous and organic, and is amenable to the characteristics of gas and liquid chromatography. However, it differs from traditional chromatography because the parameters have more constraints. For example, the puff composition, unlike the carrier gas or mobile phase of traditional chromatography, is not homogenous. Further, the time of flight of the smoke composition over the resin surface with each puff is very short. The total number of puffs per cigarette is also limited. Additionally, the binding affinity of the smoke components to the resin may involve complex interactions. In the first puff, the resin surface is unoccupied and therefore smoke components possessing both weak and strong interactions may have equal probability of landing on available binding sites. As smoking is continued, potential sites gradually disappear, and stronger binding molecules generated by each new puff begin to compete with all other existing molecules on the resin. The competition favors those that are specific and with high affinity and therefore the weaker binding components begin to be displaced by stronger binding molecules.

[0038] The present invention embodies the control of tar and nicotine via the incorporation of one or more resins with diverse functional groups that regulate the composition of the mainstream smoke as it exits the cigarette. In particular, the invention provides an improved use of silica, in the form of functionalized silica resins having a high capacity bonded phase for the selective removal of specific classes of tar components to achieve a desired balance in a cigarette that is still full of aroma and flavor, yet offers slightly more nicotine than unwanted tar to satisfy a smoker. Additionally, the present invention alleviates concerns that smokers can defeat the beneficial attributes of reduced tar by the manner in which they smoke. Because the affinity binding of the targeted smoke component to the resin is practically irreversible, the present invention generates a mainstream smoke that is true to the intended label. The smoker can no longer change the manner of smoking to effect the composition of the mainstream smoke.

[0039] The present invention thus has multifaceted attributes, including the ability of resins with distinctive characteristics to be designed to bring about adsorption of only that population of tar components with such specificity. As a result, nicotine and tar can be regulated independently through the use of high capacity bonded phase silica resins. In contrast, such independent regulation of nicotine and tar has not been possible in the art. For example, a silica resin functionalized with a broad spectrum bonded phase, such as an eighteen carbon (C-18) aliphatic hydrocarbon, a catch-all resin, is uniquely suited for the removal of aliphatics and hydrocarbons from smoke, yet allows some polar flavor components to be delivered to the smoker. The C-18 bonded silica filter provides a reduction of the volatile and semi-volatile smoke components equal to the standard of clean smoke generated by the no burn cigarette known as ECLIPSE, while maintaining an acceptable level of nicotine. The process is simple, safe, and efficacious. Since no chemical is added to the tobacco rod, no new chemical species are generated.

[0040] Additionally, the present invention provides cigarettes capable of delivering an artificial flavor, e.g., menthol, into the smoke by incorporating the flavoring into the resin particles such that they are removed in a “reverse mode” by smoke constituents exhibiting greater affinity for the functional groups on the resin particles. Consequently, the new generation of cigarettes with desired advantages can even deliver menthol flavor continuously with every puff, and even to the last puff.

[0041] The present invention provides a novel application of the principles of affinity chromatography in the design of cigarette filtration media to permit the planning and development of filter elements that selectively remove a class of targeted components of the smoke. The filter elements are comprised of functionalized resin particles wherein the ligands exhibit the desired specific affinities for the targeted component molecules. Useful resin particles include materials that are rigid, chemically stable, nontoxic and with very large resin surface areas that can be derivitized to permit the design and construction of useful functional groups. Suitable resins and resin-like materials include, but are not limited to, polymeric materials such as methacrylate, methyl methacrylate, ethylmethacrylate, styrene, styrene divinylbenzene, and the like; silica materials such as silica, magnesium silicate, ceramic, porous glass, and the like; and mixtures or composites thereof, such as composite resins of silica and polymeric materials; and the like. However, silica is generally preferred because of its rigidity and its avoidance of swelling and shrinking over a broad range of humidity conditions. Thus, although much of the detailed discussion of the invention below focuses on the use of silica, silica being preferred as the solid support in embodiments of the invention, it will be understood that the invention is not limited to the use of silica.

[0042] The resin particles preferably have a particle size of from about 35 to 400 microns, and are preferably spherical or irregularly shaped and of high porosity. Non-porous resins are generally not preferred because they create draw resistance and have reduced available surface area for the bonding of ligands.

[0043] The performance of the affinity resin is dependent upon its size, porosity and functional group capacity, which can be varied to maximize the efficiency or the specificity of the resulting filter. The efficiency of an affinity resin is measured by its ability to remove tar and nicotine from the smoke condensate. In general, the smaller the resin particle, the more efficient the resin is. Spherical or irregular particulates create a resin filter column wherein the beads are stacking and overlapping. The interbead spacing of 40-60 &mgr;m resin is only ˜20-30 &mgr;m. This narrow and convoluted passage-way ensures the collision and adsorption of smoke micelles. Consequently, particles of such size provide a resin filter that is generally nonspecific, but which is highly efficient in removing tar and nicotine from the smoke condensate. However, the particle size and porosity is preferably selected so as not to increase pressure drop, which increases draw resistance during smoking.

[0044] In general, specificity varies directly as the parameters of resin particle size, pore size, and resin capacity. The most selective resin therefore would generally have a large particle size (e.g., about 200 &mgr;m) a high porosity (e.g., about 1000 Å) and a high ligand loading capacity (e.g., at least about 1 milliequivalence per gram of resin). However, such a resin may be too fragile due to the thin walls created by the large pores in the particles. Accordingly, it is generally preferred that the selected resin be spherical or irregular particles having an average diameter of from about 35 to 400 microns, more preferably from 75 to 200 microns, and an average pore size ranging from about 60 to 1000 angstroms, more preferably from about 300 to 1000 angstroms. Additionally, the shape and size of the resin particles should be selected so as to enhance the interbead spacing to allow free flow of the smoke micelles.

[0045] To achieve a balance of efficiency and specificity, a preferred embodiment of the resin filter may employ a multicomponent resin cartridge. The first resin cartridge component preferably comprises a column from about 2-4 millimeters of a fine resin having an average particle diameter of from about 50 to 70 mm with a high porosity of from about 300 to 1000 Å to result in the gross reduction of tar and nicotine. The first component cartridge is preferably followed by a second component cartridge comprising a column of from about 5 to 10 millimeters in length of a relatively large bead resin have an average particle diameter of from about 150 to 200 &mgr;m, with large pore size of at least about 300 Å and a high capacity loading of functionality for specificity.

[0046] Alternatively, it is envisioned that a honey combed, filigree-like, or even fibrous construction of nonparticulate materials bearing functional groups may be used as a substitute. The ultimate criteria is to achieve high capacity of ligand bonding of at least about 0.6 millimoles per gram of material.

[0047] The ligand attached to the resin beads are preferably selected to preferentially bond with the molecules targeted for removal from the smoke stream. According to embodiments of the present invention, the ligand can be attached to the resin beads according to any of the various methods that are known in the art. For example, the ligand (R) can be attached directly to the resin beads, such as by direct bonding to silicon atoms in a silica resin. This bonding can thus be denoted as Si—R bonding. In other embodiments, the ligand (R) can be attached to the resin beads through a suitable linking atom such as oxygen, such as by forming a bond between an alcohol group in the ligand and a surface hydroxyl group of the silica resin. This bonding can thus be denoted as Si—OR bonding. In still other embodiments, the ligand (R) can be to the resin beads through a suitable linking group such as by treatment with an organosilane. This bonding can thus be denoted as Si—O—Si—R bonding.

[0048] Preferably, in embodiments of the present invention, the functional group is attached to the resin beads, particularly in the case where the resin beads are silica beads, by linkage through a linking group formed by treatment with an organosilane. This method is generally preferred because it provides more stable bonding of the functional groups to the resin beads. Where organosilanes are used, the organosilane can be any organosilane or derivative thereof that is known in the art. For example, preferred organosilanes have the general formula RnSiX4n where n is an integer representing the number of organo groups and X is a reactive group such as halogen, methoxy, ethoxy and the like. Thus, the bonding of a functional group R can be monomeric, dimeric or trimeric, depending on the corresponding reactive group X. Although not limited thereto, a very broad range of organosilanes are commercially available and can be used in the present invention, including epoxy, vinyl, sulfydryl, alkylamine, alkylchloro, alcoholic, carbonyl, phenylsilane, nitrile, alkyl, etc. organosilanes. In addition, the range of available organosilanes is constantly increasing, and it is envisioned that any of the later-developed organosilanes can also be used in the present invention with only routine experimentation. Furthermore, although the detailed examples set forth herein and below are only directed to a limited number of bonded phase syntheses, the chemistry of solid phase technology is well developed in the art, and is directly applicable to the present invention. Accordingly, one of ordinary skill in the art will be readily able to practice and modify the present invention. Such modifications are also within the contemplated scope of the invention.

[0049] Although the specific functional groups utilized may vary widely depending upon the targeted smoke component, selection of suitable functional groups are well within the purview of one skilled in the art based upon fundamental chemical principles. Furthermore, the practice of smoke affinity chemistry, like the parent affinity chromatographic field, is largely empirical. Once a specific functional (R) group is identified, successful use and design of the affinity resin may take some logical considerations and routine experimentation. However, with regard to the generally desired reductions of tar, preferred functional groups that exhibit greater affinity for tar than for nicotine have been found to contain hydrocarbon groups of the general formula R1—(CH2)n— where n is an integer from 1 to 40; and R1 represents hydrogen, hydroxy, amine, amide, cyano, nitrate, nitro, thio, sulfide, sulfone, sulfoxide, I, Br, Cl, F or an alkyl or aryl organic substituent containing from about 1 to about 40 carbon atoms, more preferably from about 8 to about 18 carbon atoms, which may be straight or branched, saturated or unsaturated and optionally substituted with one or more substituents selected from O, N, S, or halides. For example, R1 may be an alkyl group such as an alkane, alkene, alkyne, acid, alcohol, aldehyde, ester, ether, or ketone; or an aryl group such as a benzyl, naphthyl, anthryl, biphenyl, phenolic or heterocyclic group.

[0050] In addition, the functionality provided by the functional group at the end of the chain may be selected to provide any desired degree. For example, the functionality can be single, several or clustered and bundled. Likewise, the spacer arm, which generally separates the functionality of the functional group from the support material (resin beads) can be selected to provide either a small separation or a large separation. Many bifunctional reagents are known for the elongation and propagation of the spacer arm and include, for example, but are not limited to reagents such as succinic anhydride or glutaric anhydride, bromoacetylbromide, ethylene-diamine, dihydrazide, diaazonium coupling, periodate coupling to vicinal hydroxyl, and the like. Other reagents are well known in the art and are described in the literature. In addition, as desired, the spacer can be made hydrophilic by incorporating hydroxyl (OH) groups. The spacer can be straight chained or branched structure.

[0051] Particularly useful functional groups have been found to be straight chain, aliphatic hydrocarbons of from 3 to 18 carbon atoms in length, with C-18 hydrocarbons, having been discovered to exhibit selectivity for a broad range of volatile organic smoke constituents in preference to nicotine. Additionally, aromatic functional groups such as benzene, naphthene and anthracene may be particularly useful in selectively removing volatile aromatic PAH components through chemical bonding known as &pgr;-&pgr; interaction.

[0052] In the practice of the invention, cigarette filters are formed of the functionalized particles by encasing a desired volume of the particles behind the tobacco rod of a conventional cigarette. The encasement may be formed in part by the cigarette filter paper overwrap, or the resin particles may be encased in a separate vapor permeable membrane to form a cartridge that may be affixed to the end of the cigarette, or included within the paper shell. The resin filter cartridges may be used alone or in conjunction with conventional acetate filters. In such embodiments the resin filters may be conveniently located between the tobacco rod and the conventional acetate filter element. Additionally, multiple resin filter cartridges may be serially connected to the tobacco rod and used to effectuate the desired selective removal of targeted molecules. In this manner, filter cartridges containing particles of varying functionality, size, porosity, etc. can be connected serially to remove specified amounts of targeted components. Furthermore, particles having different functionalities, size, porosity, etc. can be combined into a single filter cartridge as desired.

[0053] Accordingly, the preferred smoking article of the invention has incorporated therein at least about 15 mg of functionalized 35-200 &mgr;m silica gel particles right behind the tobacco rod and placed uniformly before the final monoacetate filter. The synthesis of the functionalized resin is illustrated below in Example 1, however, modifications necessary for the attachment of other functional groups will be readily apparent to the skilled artisan. The smoking article may be any brand of commercially available cigarettes, either filtered or unfiltered.

[0054] According to the present invention, the filter formed using porous silica or resin particles may be placed in any suitable location in relation to the tobacco material or rod. For example, in the simplest structure, the filter of the present invention is placed adjacent to or attached to the tobacco, and no additional filter materials are used. In modifications of this structure, a conventional or other filter unit may be included, either between the tobacco and the filter of the present invention, and/or on an opposite side of the filter of the present invention in relation to the tobacco material. In addition, other materials such as glass wool or the like, or even an air space, can be located between the tobacco and one or more filter units, as is known in the art. Other modification and alterations, conventional in the art, will be readily apparent to one of ordinary skill in the art and are contemplated by the present invention.

[0055] According to the present invention, improved filtering results can be provided either by functionalized silica resins, or even by proper selection of a non-functionalized silica resin. The present invention thus allows for the provision of filters for smoking articles, such as cigarettes, that can be either specific or non-specific as to the components that are filtered. For example, a non-specific filter can be obtained that coordinately reduces both tar and nicotine, or a specific filter can be obtained that specifically reduces one or more components of the smoke stream in preference to other components.

[0056] In terms of specificity, it has been found that silica resins can generally be classified into two classes —specific silica resins and non-specific silica resins. Generally, it has been found that silica resins having an average particle size of from about 35 or about 40 &mgr;m to about 60 or about 80 &mgr;m are nonspecific, whereas silica resins having an average particle size of from about 80 or about 100 &mgr;m to about 200 or about 400 &mgr;m are specific. Generally speaking, silica resins having an average particle size less than about 35 &mgr;m are unsuitable for the present invention, because the small particle sizes generally can not be functionalized to provide the targeted smoke component removal, while silica resins having an average particle size greater than about 400 &mgr;m are unsuitable for the present invention, because the large particle sizes generally provide a filter that is too open to effectively trap the desired smoke components. Of course, it will be apparent that average particle sizes of less than about 35 &mgr;m or greater than about 400 &mgr;m if the above problems are compensated for.

[0057] That the small-sized silicas are generally non-specific in their filtering performance is exemplified in FIG. 4. FIG. 4 provides the results of an experiment performed using a silica resin having an average particle size in the range of 40 to 50 &mgr;m, with an average pore size of 60Å. The experiment is described in detail in Example 4, below. The % reduction of tar and nicotine are plotted as a function of mg resin input. The parallel reduction of tar and nicotine are clearly indicated, which shows that tar and nicotine are coordinately (non-specifically) removed by the silica resin. However, the curve also quickly reaches a plateau as the amount of silica used increases. This is due to an increased pressure drop attributed to the fine particle size of silica.

[0058] According to embodiments of the present invention, any silica resin can be used, either with or without functional groups. Thus, for example, in terms of particle size, a suitable silica resin can be used that has a small average particle size of from about 10 to about 35 &mgr;m, an intermediate average particle size of from about 35 or about 40 to about 120 or about 150 &mgr;m, preferably from about 50 or about 60 to about 120 or about 150 &mgr;m, or a larger average particle size of from about 120 or about 150 to about 400 or about 1000 &mgr;m, preferably from about 120 or about 140 to about 200 or about 300 &mgr;m.

[0059] A particular attribute of silica resins that is important in the filters of the present invention, is the pore size of the silica resins. Porosity is a unique property of the silica resins that can be selected and exploited to obtain any of a wide range of filtering results. The importance of porosity can be realized by comparing the smoke or air volume in a confined space when solid resin particles are replaced by porous resin particles. In a nonporous (solid) packed resin column, the total volume for air or smoke to elute is the void volume, or the inter-bead volume. For perfectly spherical particles, this volume equals (computed as total column volume—total packed bead volume) 33% of the total column volume. However, the void volume for a column using porous material is equal to the inter-bead volume, plus the volume provided by the pores. In such columns, the void volume can be drastically increased as compared to a column using non-porous material.

[0060] For example, when the resin is treated thermally and hydrothermally, more pores develop. The intra-bead is gouged to provide open channels. Depending on the severity of treatment, the pores can be micropores having an average pore size (or diameter) of less than about 10 Å in size, mesopores having an average pore size (or diameter) of greater than about 10 Å but less than about 50Å, or macropores having an average pore size (or diameter) of from greater than about 50 Å to about 1000 Å or more. As will be apparent to those of ordinary skill in the art, the pores can be created by other methods, and the pore size can be varied by various methods.

[0061] In embodiments, the resin particles preferably have an average pore size of at least about 60 Å or greater, and preferably at least about 300Å or greater, but preferably no greater than about 1000 Å. For example, suitable average pore sizes can be in the range of from about 60 Å to about 300 Å, or from about 300 Å to about 1000 Å. In addition, proper selection of the desired support can also provide much higher average pore sizes. For example, in the case of porous glass, the average pore sizes can be as high as 2000 to 3000 Å or more.

[0062] Furthermore, as is generally known in the art, the pores themselves can be formed to have different shapes, and to thereby provide different results. The pore shapes are generally of three types: cylindrical pores, inkbottle pores having a narrow neck and wide body, and slit shaped pores with parallel plates. Any of these or other pore shapes can be utilized in the silica resins of the present invention.

[0063] As described above, the void volume of a packed column of resin, in this case the packed column being a filter, can be increased by selecting a particular size silica having a particular pore size. For example, the following resin porosity table shows that, for a resin of a particular particle size, the hollow space can be increased from about 33% (where solid particles are used) to about 80% (where highly porous particles are used. The increased void space can be provided by thinning out the bead-shell and/or increasing the pore size. Presumably, this permits more smoke flow through the filter resin, as the smoke can flow both around the resin particles as well as through the resin particle. However, this table is only a theoretical consideration and in reality the actual pore volume may be lesser due to the fact that some pores are blind-ended and may not lead to another open pore. Of course, it will be appreciated that the values presented in the porosity table will vary with different resin materials and particularly with different sized resins. 1 POROSITY TABLE Hollow Space Pore Size Pore Volume Surface Area (void volume + Å ml/g m2/g pore volume) Non-porous 0 N/D 33%  23 0.43 800 50%  60 0.75 480 67%  150 1.15 300 76%  500 ≅1.15 160 76% 1000 ≅1.2 75-80 80% N/D = not determined

[0064] However, the porosity table demonstrates that the void volume, and thus the flow of smoke through the filter, can be increased by adjusting the pore volume of the material. Thus, for example, as the particle size becomes smaller, or the weight loading of the resin in the filter increases, the pore volume can be increased to counteract an otherwise increasing pressure drop across the filter. In embodiments, it is preferred that the theoretical void volume (or hollow space) be at least about 45% of the total volume, and preferably at least about 50% of the total volume. In other embodiments, the theoretical void volume is at least about 60% of the total volume, and preferably at least about 65% of the total volume. In general, a high void volume is preferred because this allows for more trapping of smoke components.

[0065] In embodiments of the present invention, a filter can thus be provided that enables high levels of removal of smoke components such as nicotine and tar, without the need for filter ventilation (compensation) and without an undesirably high pressure drop across the filter. For example, the filter of the present invention can achieve a nicotine and tar removal of 40% or more or even 50% or more, with an acceptable pressure drop. In embodiments, removal of tar and nicotine can be increased to 60% or more or 70% or more, or even as high as 80% or more. These removal rates are significantly higher than can or has been achieved with conventional filters.

[0066] In fact, according to the present invention, the filter preferably has an acceptable pressure drop across the filter.

[0067] The unexpected high efficiency result obtained by the present invention is attributable to the unconventional placement of the fine and porous resin. As is known in the art, filter media placed perpendicular to the smoke stream flow tends to impede smoke flow, increase pressure drop across the filter, and decrease the smoking enjoyment. According to the present invention, the resins are seated perpendicular to the smoke flow. However, based on the resin particle size and/or porosity selection, the otherwise impeded smoke flow can be counteracted, while still providing a significant filtering effect. The filtration mechanisms of importance in the present invention are thus believed to be collision and direct interception of smoke particles by the silica resin. Furthermore, the packing of the resin beads is relentlessly overlapping, which helps to assure the collision by nearly all smoke particles with resin particles. Furthermore, silica is also an excellent adsorbent and the combined physical and chemical properties of the filter compound to provide the observed efficiency.

[0068] In fact, the placement of a conventional acetate filter right behind the resin filter of the present invention has little or no effect on the tar and nicotine recovered on the conventional Cambridge filter. This is because the resin filter of the present invention is so efficient that those smoke particles having escaped or passed through the resin filter will no longer be retained by a less efficient (conventional) filter.

[0069] Another concern in the cigarette field is the reliability of the cigarette filters, particularly in terms of their ability to perform to specification in the face of intentional or accidental tampering. As described above, the smoker's ability to tamper with air ventilation used in ultra low cigarettes, such as by blocking the air vents, can dramatically change the performance of the filter by eliminating the ventilation and increasing the amount of tar and nicotine delivered by the cigarette. Likewise, the smoker's ability to tamper with conventional acetate filters, such as by poking needle-sized holes longitudinally through the filter, can also dramatically change the performance of the filter by allowing more tar and nicotine to pass through the filter. Thus, in response to societal pressures and possible government regulation, it is desired that cigarette filters be tamper resistant.

[0070] In fact, as shown by Example 8 below, when a monoacetate filter is pierced several times by a needle, an otherwise filtered, full flavored regular cigarette is effectively transformed into an unfiltered cigarette. The tar and nicotine content delivered to the smoker (and thus not captured by the filter) increase dramatically.

[0071] However, the filters of the present invention are substantially tamper resistant. For example, the filters of the present invention utilizing resin particles, whether functionalized or not, are resistant to tampering by poking small holes through the filter. Due to their nature as packed particles in the filter, even if the resin filter is pierced, the beads reconstitute back to the original configuration when the piercing item is withdrawn, and the filter is not affected by the act of tampering.

[0072] The filters of the present invention are thus more amenable to more stringent regulatory testing and labeling. First, the filters are less susceptible to tampering by the smoker. Accordingly, their is a higher guarantee that the regulated amount of tar and nicotine delivered by the cigarette can not be increased. Second, the filters are more uniform and predictable in terms of the filtering effect provided; i.e., the filtering capacity of the filter is more predictable. Accordingly, their will be less fluctuation from cigarette to cigarette or batch to batch, based on variation in the filter or tobacco materials.

[0073] The non-specific silica use as described above in cigarettes, either as the sole filter or in combination with all or part of a conventional filter, is unprecedented. Although silica has been used in cigarettes for decades, it's use has never been in the manner of the present invention. That is, silica had previously been used either as very fine particles incorporated into the conventional filamentous filter, or as larger particles (such as of 400-1000 &mgr;m) as a filter segment to augment the conventional acetate filter.

[0074] In contrast to the prior use of silica, the present invention is based on rational considerations of particle size, pore size, pressure drop and placement of the resin in the filter to efficiently reduce tar and nicotine. This new and innovative use of silica resin, particularly in the preferred particle size range of 50-120 &mgr;m—a resin size class that is largely ignored by the cigarette industry—is thus provided by the present invention.

[0075] Still further, the present invention provides the combination use of a silica resin filter, preferably with non-functionalized silica particles, with the chemically modified silica of larger particle size to arrive at a reduced risk smoke. The strategy is to efficiently remove tar and nicotine in bulk to a desired level with the non-specific smaller sized silica particles, then combine it with a specific resin cartridge to specifically and preferentially remove other unwanted tar components such as aldehydes, ketones, phenols, PAHs etc. The end result of this combination filter assembly is a smoke profile similar to that of a “burning” ECLIPSE brand cigarette, although provided by an otherwise conventional cigarette construction.

[0076] The following examples are illustrative of the present invention. The specific ingredients and processing parameters are presented as being typical, and various modifications can be derived in view of the disclosures as presented within the scope of the invention. Example 1 describes the basic strategies in the resin design. Examples 2-4, describe the solid phase affinity chemistry. The initial challenge to differentiate between nicotine and tar is borne out by the observation that nicotine is not retained by the reverse phase column. A specificity index is used to quantitate the differentiation and also to compare data between different groups of experiments. The resin experiments are recorded in the history of the mainstream smoke components in its passage through the compartments of resin, monoacetate filter and then collected onto a Cambridge filter pad. By studying the inter-reltionship of the compartments, the molecular anatomy and the intricacies as well as the dynamics of the affinity smoke chemistry unfold. Additional confirmation of selectivity can be found in the Examples of amino and phenyl resins. The subtleties of selectivity are often difficult to recognize. This is due to the complexities in molecular recognition. Often it involves many functionalities and each contribute only a small percentage to the overall selectivity. The examples given are designed to provide the tools necessary to solve these intricate problems. Capacity and particle size parameters that enhance selectivity are discussed in Example 4. Example 5 validates the puff affinity technology by creating low or ultralow tar cigarette that burns rather than heats the tobacco and achieves a clean vapor phase composition which is comparable to the industry standard of ECLIPSE. Additionally, menthol cigarettes have been a commercial favorite, and Example 6 demonstrates the reverse mode of affinity resin utility for delivering this flavor.

EXAMPLE 1

[0077] Silica is a very desirable solid phase sorbent and comes in various sizes and shapes. It can be either porous or nonporous, spherical or irregular, and with particle sizes that range from the very fine of 5 &mgr;m to the bead size of 1200 &mgr;m. Porous silica resin is the preferred material for the synthesis of a universal affinity precursor resin that possesses amino functionality. The arm of the precursor resin contains a 3 amino-propyl group, which may be lengthened by reacting with various acyl-chlorides. For example, reaction with acetyl-chloride yields a resin containing a 5 carbon chain length functional group. In addition, more carbon chains may be extended to the amino arm by using fatty acids of different chain lengths.

[0078] The synthesis of the precursor resin began with selecting activated and porous silica resins with a mean diameter of either 50 &mgr;m, 100 &mgr;m or 200 &mgr;m. The fines of the resins were progressively removed by sedimentation and decantation in water and the resins were finally washed in methanol. The resins were dried in a vacuum oven overnight at 100° C. These resins were then used to make the following functionalized resins as follows:

[0079] 3-amino-propyl resin: 20 gm of the washed and defined resins were treated with 10 ml of 3-aminopropyltriethoxysilane in 100 ml of toluene. The resins were refluxed overnight to allow maximum incorporation of the propyl-amino group. The following day, the solvents were decanted and the resins were washed with 100 ml of toluene followed by three washes of methanol in a sintered disk funnel. The resins were thoroughly dried in a vacuum oven, and the capacity of the resin was determined by acid base titration. For the 200 &mgr;m resin, it was about 0.8 millimoles per gm; for the 60-120 &mgr;m resin, it was about 0.6 millimoles and the 40-60 &mgr;m resin was about 0.5 millimoles. These levels are at least about 10 times more than the capacity of resins typically used for High Pressure Liquid Chromatography (HPLC) applications, and they approach that of the ion-exchanger for deionizing water. In addition, the resin amino groups may be visualized by staining with ninhydrin and their lack of staining for the following resins.

[0080] C-1 resin: 2 gm of the washed and defined resins was treated with approximately 3 ml of chlorotrimethylsilane in 20 ml of toluene and refluxed for 2 hours. Following reaction, the C-1 resin was washed with toluene and followed by three washes with methanol and then dried.

[0081] C5 or C7 resin: Acetyl chloride or succinyl chloride was synthesized by reacting 5 ml of 2 M thionyl chloride in 10 ml of toluene with acetic acid or succinic acid. The acid chlorides were further purified by distillation. 2 gm of the 3-amino-propyl resin was then incubated overnight with the fresh acetyl chloride or succinyl chloride in pyridine. The next day, the resin was washed with methanol and dried.

[0082] Phenyl resin: Benzoyl chloride was synthesized by refluxing 5 ml of 2 M thionyl chloride in 10 ml of toluene with benzoic acid for 30 minutes. The residual thionyl chloride and toluene were removed by distillation. 2 gm of the 3-amino-propyl resin was then incubated at room temperature overnight with the fresh benzoyl chloride in pyridine. The next day, the resin was washed with methanol and dried.

[0083] C18 resin: Pentadecanoyl chloride was synthesized by reacting 10 ml of 2 M thionyl chloride in 10 ml of toluene with 1.5 gm pentadecanoic acid. After 40 minutes of refluxing, the remaining thionyl chloride and toluene were removed by distillation. 4 gm of the 3-amino-propyl resin was then incubated overnight with the freshly prepared pentadecanoyl chloride in pyridine. The next day, the resin was twice washed with methylene chloride and then three times more with methanol and dried.

EXAMPLE 2

[0084] Chromatography of nicotine on C8 or C4 HPLC column under reverse phase condition showed that it was eluted in the void volume and was not retained by the column. This is due to the fact that nicotine is positively charged in an aqueous pH environment and does not bind to a resin that is specific for aliphatic carbon interaction. This fact makes it plausible to test if the nicotine present in the smoke condensate also behaves in the same manner. More specifically, the test may be conducted with C5 or C7 resins as manufactured under Example 1 in a “cigarette column.” The resins used had an average particle size of 100 &mgr;m and a pore size of 60 angstroms. Table 1 shows the results of the experiments. The resins were placed between the filter and the tobacco rod of a conventional cigarette, and the cigarette was tested on a smoking machine. The control and resin treated cigarettes were smoked under standard FTC conditions. The puffing regimen consisted of 35±0.5 ml puff volume, a puff duration of 2 seconds and a puff frequency of 1 puff per 60 seconds. In measuring the semivolatiles of the cold trap experiments, the cigarettes were smoked to 12 mm from the overwrap. Smoke collection onto the Cambridge filter pad were extracted with 2-propanol. The determination of nicotine and propylene glycol was by capillary gas chromatography employing a HP5890 GC equipped with a 30 meter megabore carbowax column and flame ionization detector (FID). The semivolatiles were collected in a dry ice in isopropanol cold trap at −70° C. and determined on a 30 meter DB624 capillary column equipped with a precolumn and also by FID detection. In the resin treated cigarette, the monoacetate filter was dislodged and removed from a commercial cigarette. The resins were weighed and placed right behind the tobacco rod from the open butt end of the cigarette. To insure even placement of the resin, the cigarette was kept in a vertical position, gently tapped, and a new and intact monoacetate filter reinserted. This experiment examined specific interactions between the smoke condensate and the resin. Therefore, the nonspecific trapping of smoke condensate was reduced in part by removing all the fines in the resins. The values of tar, nicotine, and propylene glycol, were all derived from the Cambridge filters.

[0085] Initially, the reduction of nicotine was compared to that of tar, however, any change in nicotine as a ratio to tar is insensitive because tar is at least ten times larger. In addition, tar is a poorly defined complex entity and its determination is not highly quantitative. The comparison should be to a specific indicator component of the tar such that both chemicals can be accurately determined. Propylene glycol is a suitable indicator since it is also a major component of the tar. However, it is chemically distinct from nicotine; that of a glycol versus an alkaloid. Both chemicals are slightly polar and yet both are soluble in organic solvents. In Table 1, the relative retention of nicotine by the two resins is compared to propylene glycol. In the control cigarette there is a basal ratio of nicotine to tar and it is 2.16. If the resin removes more propylene glycol than nicotine, this ratio will also increase proportionately. Therefore, by expressing the ratio of increase due to resin as a percentage of the control, a normalized quantitative comparison is achieved. This is defined as the specificity index. 2 TABLE 1 SPECIFICITY INDEX % of Control - Tar Nicotine Propylene Glycol Ratio Specificity mg mg mg Nic/PG Index Control 12.54 0.8405 0.388 2.16 100% Succinyl C 7-30 mg 9.31 0.6062 0.200 3.03 140% C 7-45 mg 7.80 0.5057 0.181 2.79 129% C 7-45 mg 7.24 0.4220 0.162 2.60 120% C 7-60 mg 6.13 0.4022 0.105 3.83 177% Acetyl C 5-30 mg 8.10 0.5406 0.215 2.51 116% C 5-45 mg 7.42 0.4409 0.138 3.19 147% C 5-45 mg 6.69 0.4068 0.100 4.07 188%

[0086] The data of Table 1, as expected, does not appear to differentiate between C7 and C5 resins. The percent increase of nicotine to propylene glycol as a percentage of the control ratio reaches a high of approximately 180%. This indicates that the smoke condensate to resin interaction is akin to the HPLC column. Nicotine is subtly excluded from binding to the functional groups of C5 and C7 present on the “cigarette column.”

EXAMPLE 3

[0087] In the present example, the nonspecific entrapment of the smoke condensate was further reduced by using a more open resin with a bead size of 200 &mgr;m. In Table 2, the distributions of nicotine in the three compartments of the Cambridge filter, cigarette acetate filter and the recovered resin are shown. 3 TABLE 2 DISTRIBUTION OF NICOTINE Nicotine Nicotine from from Acetate Nicotine Total Nicotine Cambridge Cigarette from Recovered Resin Type Filter Pad Fiber Resin in mg Control 0.9167 0.6918 n/a 1.64 Silica - 50 mg 0.8148 0.4386 0.1195 1.37 Silica - 150 mg 0.7765 0.3383 0.2584 1.37 Amino - 50 mg 0.8913 0.4766 0.1059 1.47 Amino - 150 mg 0.8521 0.3768 0.3498 1.58 C 5 - 50 mg 0.9090 0.5246 0.1012 1.54 C 5 - 150 mg 0.8324 0.4316 0.3031 1.57 Phenyl - 50 mg 0.8888 0.4844 0.0658 1.44 Phenyl - 150 mg 0.9148 0.4541 0.2669 1.64

[0088] As shown in Table 2, due to the large bead size of the resins, nicotine on the Cambridge filters did not diminish greatly even when the resin input was 150 mg. The total nicotine recovered in each experiment is the sum total of all three compartments. The upper limit (1.64 mg) is shown in the control experiment.

[0089] In all the resin experiments, the total nicotine recovered approaches this value except for silica. This is due, in part, to incomplete resins' recovery, but is largely due to inadequate extraction of nicotine from the silica by the isopropanol.

[0090] The recovery result of nicotine from the monoacetate fiber filter is most interesting. This conventional filter is a passive diffusion and capture device permitting certain population of smoke micelles to pass. The resin column at the level of 150 mg input is 0.5 cm long segregating the tobacco rod from the acetate filter. Since the resin column precedes the acetate filter, it has the first right to take up smoke micelles which would have been available to the monoacetate filter. The resins are 200 &mgr;m, with 60 Å pore size, and a theoretically calculated 92 &mgr;m inter-bead spacing. Statistically the resin would favor the uptake of the larger size micelle population. The removal of this population of smoke condensate reflects the observed lower recovery of nicotine in all the acetate filters of the resin treated cigarettes than the control. The decrease actually is quite significant and ranges from a low of 35% to a high of 51%. This creates an apparent paradox because nicotine content of the Cambridge filter fraction is almost unaffected as compared to the control.

[0091] Accordingly, at the resin level, it must be replenishing the nicotine flight to the Cambridge filter with reprocessed micelles that are able to escape the acetate filter entrapment. Specifically, the resin is apparently behaving as a dynamic exchanger and functioning like an HPLC column in chromatographing nicotine with the mobile phase as the smoke condensate. This example illustrates the multidimensional physical-chemical dynamics of the filtration process of the invention in contrast to convention physical entrapment technologies.

[0092] Table 3 illustrates the comparative selectivity of the functional groups in the porous resin (200 &mgr;m and 60 Å). It shows the differential retention by the resins of propylene glycol and not for nicotine. 4 TABLE 3 DIFFERENTIAL REMOVAL OF PROPYLENE GLYCOL AND NICOTINE BY RESIN % Control % Reduction Resin Propylene Propylene Type Nicotine Glycol Tar Nicotine Glycol Tar Silica - 88.9 55.4 89.5 11.1 44.6 10.5 50 mg Silica - 84.7 41.4 83.2 15.3 58.6 16.8 150 mg Amino - 97.2 63.4 97.2 2.8 36.6 2.8 50 mg Amino - 93.0 39.4 87.4 7.0 60.6 12.6 150 mg C 5-50 99.2 80.2 102.8 0.8 19.8 −2.8 mg C 5-150 90.8 51.9 92.3 9.2 48.1 7.7 mg Phenyl- 96.9 64.2 92.3 3.1 35.8 7.7 50 mg Phenyl - 99.8 54.3 92.3 0.2 45.7 7.7 150 mg

[0093] Table 3 again demonstrates the differential removal of nicotine and propylene glycol in this very porous resin. The low percentage nicotine reduction makes it easy to contrast the over 50% reduction of propylene glycol. The carbon backbone of propylene glycol is C3, and this apparently accounts for its retention by the C5 resin. The phenyl ring as a rigid planar structure viewed from its side, is actually four carbons long. Together with the amino-propyl arm, the phenyl resin may actually behave like a C7 resin. This also accounts for its selectivity towards the propylene glycol. The 3-amino-propyl resin appears to have a two fold interaction with propylene glycol. The first is the propyl group of the resin with the propylene backbone. Then the resin amino group can hydrogen bond with the glycol-OH. Amino HPLC column is selective for carbohydrates and involves hydrogen bonding between N—H and the cis glycol O—H of carbohydrates. The duality of interactions suggests that the amino resin may show a slight advantage towards propylene glycol in comparison to the C5 and phenyl-resin. Table 4 summarizes the results of the specificity index comparisons. 5 TABLE 4 AMINO RESIN SELECTIVITY Particle Nicotine/Propylene Specificity Index Size Resin Glycol Ratio % of Control 200 &mgr;m Control 0.977 100% 200 &mgr;m C 5 - 50 mg 1.208 124% C 5 - 150 mg 1.711 175% 200 &mgr;m Phenyl - 50 mg 1.476 151% Phenyl - 150 mg 1.797 184% 200 &mgr;m Amino - 50 mg 1.498 153% Amino - 150 mg 2.30 235%  50 &mgr;m Control 1.87 100%  50 &mgr;m Amino - 20 mg 2.69 144% Amino - 40 mg 3.60 193% Amino - 60 mg 3.87 207% Amino - 80 mg 3.72 199% Amino - 100 mg 4.44 237%

[0094] Table 4 shows the comparison of specificity index for amino resins of two particle sizes to that of C5 and Phenyl resins. The nicotine and propylene glycol are both extracted from the Cambridge filter pads. Additional comparison data seen in Table 6 firmly establish higher selectivity of the amino resin towards propylene glycol.

[0095] Finally, the selectivity of the phenyl resin was investigated by comparing the volatile and semi-volatile major aromatic components of the cold trap collected smoke condensate such as benzene, toluene and phenol. The semivolatiles in the cigarette smoke were collected in cold traps (−76° C.) and analyzed by DB624 capillary column with FID detection in a gas chromatograph. Table 5 summarizes the comparisons and demonstrates the selectivity of the phenyl resin towards both benzene and toluene. It also illustrates the selectivity of the amino resin for phenol.

[0096] Phenol or hydroxy-benzene is weakly acidic in an aqueous laden smoke condensate and therefore may form ionic interaction with the weak basic amino resin. This explains the selectivity seen in Table 5 of phenol by the amino resin. 6 TABLE 5 PHENYL - RESIN SELECTIVITY Benzene Toluene Phenol % % % Resin Type Reduction Reduction Reduction Amino - 150 mg 43% 70% 78% Amino - 150 mg 43% 52% 74% Phenyl - 150 mg 68% 88% 64% Phenyl - 150 mg 53% 79% 59% C 5 - 150 mg 51% 76% 56% Silica - 150 mg 38% 56% 60%

[0097] All of the above data documents that “Affinity Smoke Chemistry” is valid and that the smoke components obey the principles governing the reverse phase column chromatography. This finding presents unique opportunities for the removal, or at least a reduction in, the level of all unwanted deleterious smoke components from the mainstream smoke of a cigarette.

EXAMPLE 4

[0098] The main constraint of smoke chromatography is the flow rate of the puff passing through the resin column. Total flow under the FTC condition is 35 ml per 2 seconds; thus the flow rate is 1.05 liters per minute. The linear velocity of the flow over a 0.5 cm resin column is 2.1 liters/cm/min. This flow rate hitherto is very foreign to any conditions of chromatography, and the resin needs some special treatment to increase the probability of successful encounters between the smoke components and the functional groups. One parameter that directly relates to specificity is the density of functional groups on the resin. When smoke components are accelerating at such a high velocity, the abundance of functional groups may encourage more frequent collision, meandering, probing and testing to result in only high affinity binding. Density of functional group loading in the resin is noted as its capacity. Table 6 examines the resin capacity as a function of the specificity index for nicotine and propylene glycol. 7 TABLE 6 SPECIFICITY AS A FUNCTION OF CAPACITY Approx. Capacity Specificity Index Particle milliequivalent (% of Control Size per Gm resin Resin Type Ratio Nic/PG) Control 100% Fiber Low  40 mg Glass Fiber, C-5 110%  60 mg, Glass Fiber, C-5 100%  50 &mgr;m ˜0.1 meq  75 mg, Bead C-18 122% 100 mg, Bead C-18 130% 100 mg, Bead C-18 124%  60 &mgr;m  0.5 meq 100 mg Bead, NH2 183% 130 mg, Bead, NH2 197% 100 mg, Bead C-5 168% 130 mg, Bead C-5 164% 100 &mgr;m  0.6 meq  50 mg, Bead NH2 203%  50 mg, Bead NH2 195%  45 mg, Bead C-5 147%  45 mg, Bead C-5 188% 200 &mgr;m  0.8 meq  50 mg, Bead NH2 153% 150 mg, Bead NH2 235%  50 mg, Bead C-5 124% 150 mg, Bead C-5 175%  40 &mgr;m  1.0 meq  60 mg, Bead NH2 207%  80 mg, Bead NH2 199% 100 mg, Bead NH2 237%

[0099] As Table 6 illustrates, the higher the capacity, the better the specificity. At the low end when glass fibers are derivitized, the capacity is too low to measure and its specificity index is not very different from the control. The specificity factor increases dramatically when the capacity reaches 0.5 to 0.6 milliequivalent per gram resin. At 0.8 meq./gm to 1.0 meq/gm resin, it is at the maximum value. The selectivity of the amino resin follows the same trend when compared to resin capacity. Indeed the difference in specificity index between the amino and C-5 resins at the lower capacity of 0.5 meq is 20%, however, at 0.8 meq, the specificity indexes of the two resins now differ by 50%. This is consistent with the supposition that the higher the capacity, the easier it is to attain specificity.

[0100] The chromatography of smoke components on the resin is limited in time and space. Even at the optimum, the first and the last puff are less specific. When the smoke micelles of the first puff reach the resin surface, there is no competition and all components regardless of affinity can occupy a site on the resin. The last puff is equivalent to the final mobile phase load to the resin column with no additional washing. Each cigarette smoked according to the FTC method has a total of six to seven puffs. When the efficiency of the resin column is at its best, there is still roughly a minimum of 2/7 puffs or 30% error. Experimentally, this was investigated by extracting the resin after a smoking session and studying the specificity of binding for the intended design of the column. Table 7 examines the bound nicotine and propylene glycol (p.g.) on the amino resins. 8 TABLE 7 PARTICLE SIZE VS SELECTIVITY Approx. &mgr;g/mg resin Ratio Particle Size Nicotine Propylene Glycol Nic/PG  60 &mgr;m  30 mg 14.52 12.52 1.16  40 mg 14.99 14.48 1.04  50 mg 12.99 10.18 1.27  60 mg 12.01 9.22 1.30  80 mg 9.31 6.53 1.43 100 mg 7.24 4.55 1.59 100 &mgr;m  70 mg 5.50 8.83 0.62 100 mg 4.89 7.15 0.68 130 mg 3.47 4.89 0.71 200 &mgr;m  50 mg* 2.12 6.24 0.34 150 mg* 2.33 4.81 0.48 *Assuming total recovery

[0101] As Table 7 illustrates, the resin design selects propylene glycol and excludes nicotine. The ratio of nicotine to propylene glycol equal to 0.34 is found in the last row of the table in the 50 mg resin experiment. This ratio indicates high selectivity for propylene glycol and it approaches the theoretical error limit as previously discussed. Ultimately, the superiority of the resin is only recognized for its outcome at the level of the Cambridge filter. In Table 6, the specificity index of this 200 &mgr;m, 50 mg resin is 153%. To put this into perspective, the 50 mg resin column faces the most stringent of puffing competition and therefore those molecules that survive the test are very specific. However, because of the length and volume of the resin column, its overall performance is at a disadvantage. When the resin column is increased to 150 mg, the ratio of bound nicotine/p.g. (Table 7) drops to 0.48. However, there is an overwhelming increase in column performance as measured by the specificity index of 235% (Table 6).

[0102] The ratio of nicotine/propylene glycol data of Table 7 classifies the resins as a function to particle size roughly into two classes; the 60 &mgr;m resins are not specific while the 100 and 200 &mgr;m resin columns are more specific. This correlation to particle size can be explained in terms of nonspecific entrapment by the small particle size resins which act like a physical filter. Whereas, with the large particles, the molecules are free to collide, explore, and thus results in specific binding.

EXAMPLE 5

[0103] A practical application of the affinity smoke chemistry is to test a C-18 resin of high porosity and particle size of 100-200 &mgr;m. The C-18 resin is the most popular reverse phase media in HPLC chromatography because the long aliphatic side-chain has the broadest selectivity. It is a “catch-all” resin. Conversely, many polar flavor molecules of alcohol and aldehyde and some flavor molecules including nicotine show weak interactions with the C-18 resin. Again the resins were placed behind the tobacco rod in tandem and kept in place by a thin layer of glass wool. A hollow acetate filter of 0.5 cm in length was removed from an Eclipse cigarette and used to support the glass wool which indirectly prevented the resin from shifting. Similarly, two hollow acetate filters were used to support the control cigarette as it was tested in the smoking machine. FIGS. 1A-1C shows the comparative GC evaluations of the vapor-phase smoke collected in methanol traps of: the resin treated cigarettes, the control cigarettes and the full flavored Eclipse cigarettes. FIG. 1B, the control chromatogram illustrates many volatile and semivolatile smoke components. A total of about 100 vapor phase smoke components of a burning cigarette have been described in the monograph of “Chemical and Biological Studies On New Cigarette Prototypes That Heat Instead of Burn Tobacco” (R. J. Reynolds Tobacco Company, 1988). Several components in the chromatogram have been assigned identity and these are: benzene at 7.43 mins, internal standard (I.S.) methyl-cyclohexane at 9.48 mins., toluene at 12.76 mins., propylene glycol at 17.2 mins., phenol at 28.8 mins., glycerol at 30.3 mins., quinoline (I.S.) at 36.0 mins. and nicotine at 39.32 mins. The ECLIPSE vapor phase chromatogram (FIG. 1C) in comparison to the unfiltered control cigarette is very simple. The most prominent species are: nicotine, glycerol, toluene, and benzene. However, many other smoke components between toluene and glycerol are clearly visible. Also observed are the volatiles that appear at the beginning of the chromatogram, before the benzene peak at 7.4 minutes. At the end of the chromatogram between 45-57 minutes a large number of low level components are indicated. The simple and clean vapor phase chromatogram of ECLIPSE is therefore a standard for purity of cigarette smoke.

[0104] In FIG. 1A, the vapor phase chromatogram of the C-18 puff affinity resin treated cigarette is shown. The resin composition consists of: 50 mg silica (100 &mgr;m and 60 Å), 100 mg C-18 resin (100 &mgr;m and 60 Å) 100 mg C-18 resin (200 &mgr;m and 60 Å) and 100 mg 3 aminopropyl resin (200 &mgr;m and 60 Å), and thus contains silica, C-18 and amino functionalities. From visual examination of the chromatogram, it is readily apparent that the resin treated vapor phase is also relatively simple and clean. In particular, the multitude of semivolatiles and volatiles appearing between the I.S. (methyl-cyclohexane) and glycerol as seen in the control chromatogram are all absent, except for propylene glycol and a trace of toluene and phenol. The resins also have significantly decreased the highly retentive components which are eluted after 54 minutes. There are a few volatile species including benzene at the beginning of the chromatogram. At room temperature these components are very volatile and a small amount may even come off the resin during the smoking session and be retained in the cold trap. In contrast, there is a significant amount of nicotine still present in the smoke even after passage through such a broad spectrum specificity resin.

[0105] FIG. 2B shows the vapor phase chromatogram of the combination resin consisting of: 50 mg 3 aminopropyl resin (100 &mgr;m and 60 Å) and 300 mg of C-18 resin (100 &mgr;m and 60 Å). The total areas of all the vapor phase components were summed and compared to the total integrated areas of the control (FIG. 1B). The relative areas of the resin treated smoke components were 19.7% of the control integrated areas. Therefore, the control methanol trap vapor phase content was diluted 1:4 and then subjected to GC analysis. The resultant chromatogram (FIG. 2A) is compared to the resin treated GC vapor phase chromatogram. The diluted control serves as a barometer in determining the efficiency of removal of any smoke component by the C-18 resin. The resin vapor phase profile should resemble the 1:4 diluted control chromatogram, if all smoke components is removed proportionately and non-specifically. Obviously, this is not the case, as the following smoke components of known identity illustrate. The most prominent component is nicotine and it is enhanced by two fold; the resin treated nicotine content is 0.4 mg whereas the 1:4 diluted control is 0.2 mg. Glycerol is even removed less by the C-18 resin and it is four and half times more than the diluted control. By contrast, the removal of toluene and propylene glycol are nearly complete. They are respectively: 7.6% and 22.7% that of the 1:4 diluted control. Benzene is relatively neutral, in that the resin treated content is 75% of the diluted control. Phenol in the resin treated is 51% that of the diluted control. These quantitative comparison results illustrate that the C-18 and the amino resins are actively removing smoke components on the basis of structural and chemical characteristics. By design, nicotine and other flavor smoke components that possess a positive charge, or which are very polar, are deferentially less removed by the resins. Hence, many of the tobacco specific alkolides such as nornicotine, anatabine, and anabasin will also be differentiated by the C-18 resin. Their exact locations have not been assigned, however, they should reside near quinolin and nicotine. Indeed, several candidate species are clearly visible between 32-46 minutes which like nicotine appear to be significantly less removed than the 1:4 diluted control. As revealed in FIG. 3, the flavor components of menthol and vanillin are eluted in this region of the chromatogram. In provisional taste tests by a knowledgeable smoker, the resin treated cigarette is still flavorful.

[0106] The chromatograms of FIGS. 1A and IC further illustrate that the C-18 resin vapor phase is comparable both in simplicity and in the total amount of components to that of the Eclipse. This experiment affirms the uniqueness of the affinity resin technology. The implication is that the cigarette smoke is also safe. This is not surprising since both PAH and nitrosoamines are highly retentive on the C-18 resin in HPLC chromatography. The total tar of the resin treated cigarette as evaluated by spectrophotometry is also decidedly low, only at about 3.5-4.0 mg. The nicotine content is between 0.3-0.4 mg which is about 3-4 times more than the full flavored Eclipse of 0.1 mg.

[0107] Similar results were obtained with different combination resins incorporating several large and small particle sizes resins of 100-200 &mgr;m. The capacity of the 100 &mgr;m and 200 &mgr;m resins were both 0.8 milli-equivalents of C-18 loading per gm of silica. The pressure drops of these resins were measured and shown in Table 8. 9 TABLE 8 PRESSURE DROP MEASUREMENTS Filter or Particle Size Porosity Nicotine/Tar Pressure Drop Resin &mgr;m Å mg mm H2O IR4F filter N/A N/A 1.3/20   89 removed IR4F + 25 mm N/A N/A 0.83/10.8 163 filter Large Resins  300 mg 200-400 60  0.8/14.6 200  120 mg 690-200 60  200 mg 150-230 150 1.15/17.1 146  150 mg 150-230 150 0.99/15   Medium Resins 50.2 mg  90-130 1000 0.96/15   150  101 mg  90-130 1000 207   60 mg 35-70 1000 140   40 mg 35-70 500 0.5/7.9 150

[0108] The low tar delivery of the resin treated cigarette is not a result of non-specific physical trapping or to a high pressure drop. The 1:4 dilution of control smoke experiment clearly shows that it is due to differential binding. Further, the potential of this technology to produce different marketable cleaner cigarettes is illustrated in FIGS. 2A-2C. As FIG. 2C shows, a 150 mg of 100 &mgr;m C-18 resin treated cigarette produces a vapor phase GC chromatogram comparable to that of the diluted control, differing primarily in that the nicotine content is almost doubled at 0.8 mg and the tar content is 14 mg. This is equivalent to a full flavored low tar cigarette, except that it has a much cleaner vapor phase smoke. For the 50/300 resin treated cigarette (FIG. 2B), the nicotine content is 0.4 mg. It is equivalent to an ultra low tar cigarette with a higher than normal nicotine and flavor content. These experiments demonstrate the range of cigarette products that can be manufactured by simply adjusting the amount of C-18 resins in the filter.

EXAMPLE 6

[0109] The displacement of nicotine by other strong binding smoke components in the puff affinity resin has been illustrated in many of the above experiments. These results suggest that extrinsic flavor can be delivered by a flavor cartridge to the smoker. The flavor can be delivered in large doses or made to release slowly. In the experiment, 50 mg of C-1 resin was loaded by melting 4.2 mg of menthol and 9.6 mg of vanillin in-situ. The resins were carefully placed behind the tobacco rod of a Marlboro cigarette as in the above experiments. The flavor cartridge immediately transformed the full flavored cigarette into a menthol cigarette. FIG. 3 shows the mainstream smoke GC chromatogram of the smoke trapped on a Cambridge filter and extracted by 2-propanol. The menthol delivered is 1.19 mg or 28.2% of the input, however, only a small percentage of vanillin is delivered. This shows the selectivity of the resin binding towards vanillin and not menthol. For vanillin delivery, another bonded phase resin would have to be selected or empirically determined. The menthol delivered by the affinity technology is a controlled release. The flavor is released in each puff; from the first to the last puff. In the monoacetate loaded menthol, the flavor is chronically released because there is no chemical binding. The delivery is most abundant in the first puff and then quickly diminishes with every puff such that in the last few puffs, there is no menthol.

[0110] In a limited number of experiments, the loading and delivery of menthol has been further investigated. By melting the menthol in-situ on a smaller cartridge of 30 mg, the percentage delivery was increased to 34.4%. When the menthol was loaded in alcohol and dried by vacuum evaporation, only 4% of the loaded menthol was found on the Cambridge filter. This indicated that most of the menthol was not available for the smoke micelles to displace. Presumably, the menthol must have been lodged in the interior of the resin where the pores of 0.6 &mgr;m were limited in accessibility to the smoke micelles of 0.1-1.0 &mgr;m. This further suggests that all the affinity experiments thus far are a surface phenomenon. A resin with much larger pores, such as a 5 &mgr;m pore size may be used by making available additional interior resin surface.

[0111] A low tar menthol cigarette can also be manufactured by adding the menthol cartridge to the C-18 affinity resin. When the flavor cartridge preceded the C-18 affinity resin cartridge, most of the menthol was removed by the C-18 resin. By placing the flavor cartridge (30 mg C-1 resin) behind the C-18 affinity resin, 18.25% of the menthol now become available. The decrease of menthol delivery from 34.4% to 18.25% may reflect the importance of moisture when the resins were located next to the tobacco rod versus far away from it.

EXAMPLE 7

[0112] The relationship of particle size and porosity to the efficiency of tar and nicotine removal by a silica resin filter according to the present invention is studied. The data is depicted in Tables 8 and 9. In Table 8, the composite data illustrates that the large silica resins are similar in draw resistance and tar and nicotine retention as a 20-25 mm conventional monoacetate filter. The relative dimension of the inter-bead space of 100 &mgr;m (200 &mgr;m resin) and that the tobacco smoke particles 0.1-1 &mgr;m makes the filter less effective in tar/nicotine removal and even if the filter length is increased to 2 cm (300 mg silica). When the particle size is decreased to about 100 &mgr;m as in medium resins, the inter-bead space is proportionately decreased and concomitantly the removal of tar and nicotine. There is a direct relationship between resin input, tar and nicotine removal, and pressure drop, in that the longer the filter column, the higher the pressure drop, the better the efficiency of tar and nicotine removal. This relationship also holds true for the fine resins of Table 9. Indeed, particle size is perhaps the most important parameter relative to pressure drop and tar and nicotine removal.

[0113] The role of particle size in the constitution of this new filter according to the present invention is more difficult to assess. Clearly, particle and pore size and shape differ from different sources of silica, and these two parameters affect the manner in which smoke micelles make their passage through the hollow inter and intra resin spaces. Accordingly, in this Example, silica from the same manufacturer is used in order to eliminate this order of variability that might confuse the outcome of the investigation. Two batches of silica: 35-70 &mgr;m, 1000 Å; and 35-70 &mgr;m, 500 Å are used for porosity comparisons. The 35-70 &mgr;m, 1000 Å silica is further selected by passage through a 55 &mgr;m screen to obtain the 55-70 &mgr;m 1000 Å resin and for particle size comparisons. Different loadings of the resin particles are used in a packed column to simulate a smoking cigarette, as described above. The results are presented in the following Table 9. 10 TABLE 9 PARTICLE SIZE AND POROSITY COMPARISONS Resin Pressure Drop Puffs per % reduction % Reduction (mg) (mm of H2O) cigarette Nicotine Tar Marlboro 56 minus filter Marlboro 112 Plus filter 1000 Å, 55-70 &mgr;m   0 56 7.5 0 0  20 7.5 13.29 18.67  30 7.5 24.58 28.00  40 83 7.5 46.52 44.66  50 90 7.5 57.11 58.52  60 98 7.5 72.15 71.59  500 Å 35-70 &mgr;m   0 56 7.5 0.00 0.00  15.35 7.0 25.85 27.95  22.81 7.5 43.80 37.90  30 110 7.5 52.80 49.85  40 128 8.0 61.70 60.45 1000 Å 35-70 &mgr;m   0 56 7.5 0.00 0.00  15.49 7.5 17.05 18.37  27.59 7.5 40.31 42.33  41.37 95 7.5 55.04 51.77  50.71 105 7.5 68.22 70.05

[0114] The data for the 55-70 &mgr;m, 1000 Å silica resin is plotted in FIG. 5. In FIG. 5, the reduction of tar and nicotine are generally parallel and, for all practical purposes, linear. The minor deviation at low resin input is believed to be due to silica shifting during testing. The linearity also points to the fact that resin porosity has overcome the pressure drop created by fine resins.

[0115] As shown in this Example, at 60 mg input, both tar and nicotine are reduced by an astounding 72%. To put this into perspective, 60mg of silica is only about a 3-4 mm thick filter. This filter is highly efficient, far beyond the efficiency provided by currently available cigarette filters. The data further suggests that between about 40% and about 80% reduction (a reduction range that is not easily attainable with the conventional filter) can be readily achieved by the present invention. Furthermore, the data shows that this nonspecific filter of the present invention is easily scaleable to any desired tar and nicotine content and removal amount.

[0116] The linearity of the reduction curve shown in FIG. 5 suggests that the reduction response and resin input are predictable. Hence, for a batch of resin to be used for a given blend of tobacco, the testing results of tar and nicotine should remain very similar. The fact that little or no air ventilation (compensation) is required, indicates that this filter is more equipped to address present and future potential regulatory issues of labeling and testing under more stringent conditions.

[0117] The tabulated data for the other two resins further amplify the above conclusions with respect to resin input, linearity and filter efficiency. The three sets of data firmly establish this unusual and unexpected characteristic of the highly porous silica resin ideally suited as a cigarette filter. The data in Table 9 can further be analyzed with respect to particle size. The efficiency of tar and nicotine removal is clearly determined by particle size. The smaller particle size filter: 35-70 &mgr;m, 1000 Å, is more efficient than the larger particle size filter: 55-70 &mgr;m, 1000 Å. Specifically, at the 50 mg input of the smaller particle filter (35-70 &mgr;m, 1000 Å), the percent reduction is equal to the 60mg input of the larger particle filter (55-70 &mgr;m, 1000 Å). This relationship appears to hold true for all other levels of resin input.

[0118] The porosity comparisons between the 500 Å and 1000 Å of same particle size resins 35-70 &mgr;m are also shown in Table 9. The efficiency of tar and nicotine removal appears to be more related to particle size than to porosity. More experiments with other resin sizes would likely confirm this point. However, the pressure drop experiment clearly shows that the larger the pore, the less the pressure drop. For example, the 50.7 mg input of the larger pore resin 1000 Å, the pressure drop is similar to the 30 mg input of the smaller pore resin 500 Å. This relationship is also followed at other levels of resin input.

[0119] Accordingly, porosity extends the working range of the new cigarette filter of the present invention and allows the filter to work efficiently at a particle size that was previously deemed impossible. This porous silica filter is estimated to be 5-10 times more efficient than the conventional monoacetate filter. The porous cigarette filter is thus self-compensating with respect to air ventilation.

EXAMPLE 8

[0120] There is a strong demand world-wide to reduce tar and nicotine contents in cigarettes. For example, in the developing countries the demand for ultra low tar and nicotine cigarettes is at the highest point. Even in Japan, the so-called 1 mg tar cigarette has captured a significant percent of the market. To achieve this level of tar delivery, heavy ventilation (compensation) has previously been necessary. A problem with compensation, however, is that air is compressible and highly variable. Accordingly, cigarette manufacturers are often finding it difficult to meet the stringent requirement of ±0.5 mg of the target. The dilution variation at 8mg/35% dilution would have to be manufactured in a dilution range of 31-39% (±8% range) in order to meet the ±0.5 mg tar variation constraint. At the 3 mg target tar level, the dilution range is increased to ±15%. Hence, the variation at 1 mg tar level to maintain the ±0.5 mg tar become infinitely more difficult.

[0121] In the United States, Carlton® cigarette is an ultra-ultra low tar cigarette and Marlboro® ultra-light is a low tar cigarette. In Table 10 below, the 55-70 &mgr;m, 1000 Å silica is used as a filter and compared to the two control cigarettes. The cigarettes are either tested after the pack is opened or are conditioned overnight at 25° C. and 60% RH (relative humidity). The testing is performed according to U.S. Federal Trade Commission (FTC) standards, with either a one minute per puff or ½ minute per puff frequency and with the standard puff volume of 35±0.5 ml. 11 TABLE 10 CARLTON AND MARLBORO CIGARETTE EQUIPPED WITH A SILICA FILTER (55-70 &mgr;m, 1000 Å) Puff Frequency TPM Cigarette and Filter (puffs/min.) (mg) Carlton Ultra-Ultra Low Control Filter 1 2.1 Control Filter 1 1.81 Control Filter 2 3.44 Control (60% RH) 2 3.74 60 mg Silica 1 1.75 60 mg Silica 2 2.14 60.09 mg Silica (60% RH) 1 0.74 60.36 mg Silica (60% RH) 1 1.0 60.34 mg Silica (60% RH) 2 1.44 Marlboro Ultra-Light Control Filter 1 8.89 Control Filter 1 6.97 50 mg Silica 1 6.52 45.1 mg Silica 1 8.0

[0122] Table 10 illustrates the use of porous silica resin 55-70 &mgr;m, 1000 Å in the two low tar cigarettes. The data shows that the flexibility of resin input readily mimics and replaces the regular filters. The pressure drop in the silica filters of the present invention is decidedly and significantly lower than for conventional filters due to the self-compensation and the ventilation holes already present in the filter paper. The Example also demonstrates that with certain degrees of air ventilation, a 25 mg tar cigarette can easily and reliably be reduced to a 1 mg cigarette. This extends the range of tar and nicotine reduction from 80% to more than 95%. Brand cigarettes can easily be converted to using silica filters with the added advantage of the use of affinity resins for the removal of specific tar components. It further illustrates how the resin filter offers brand extension on all the existing cigarettes products.

EXAMPLE 9

[0123] Effects of tampering on a conventional acetate filter and a resin filter according to the present invention are compared. Similar cigarettes are burned using different filter cartridges, as follows:

[0124] (1) an unaltered acetate filter (control);

[0125] (2) an acetate filter similar to the control, but pierced several times by a needle;

[0126] (3) a combination filter incorporating (a) a first filter segment containing 80 mg silica (40 &mgr;m, 60 Å) and (b) a second, 1 cm long acetate filter segment; the first filter segment (a) is placed between the tobacco and the second filter segment; and

[0127] (4) a combination filter similar to the filter (3), but needle pierced several times with no regard whether the piercing is through the entire assembly.

[0128] Each cigarette is smoked according to the FTC method, as described in Example 4 above. Experimentally, this was investigated by extracting the Cambridge filters after a smoking session and quantitating the content of nicotine, tar and propylene glycol. Table 11 examines the bound nicotine and propylene glycol (p.g.) on the Cambridge filters. 12 TABLE 11 EFFECTS OF TAMPERING ON FILTER DESIGNS Propylene Nicotine Glycol Tar Control 1.096 mg 0.535 mg 15.3 mg Pierced Control  1.37 mg 0.828 mg 23.5 mg 80 mg Silica + 1 cm  0.07 mg  0.06 mg  1.1 mg Acetate Filter 80 mg Silica + 0.066 mg 0.054 mg  1.3 mg 1 cm Pierced Acetate Filter

[0129] This Example demonstrates that when a conventional monoacetate filter is pierced several times by a needle, an otherwise filtered, full flavored regular cigarette (control) is effectively transformed into an unfiltered cigarette. The tar and nicotine content now increases from 15.3 mg to 23.5 mg and from 1.1 mg to 1.37 mg, respectively. Although only several small piercings are made, the piercings defeat the filtering effect of the acetate filter. By contrast, the effectiveness of a resin-filtered cigarette is little changed or there is no effect on piercing the monoacetate filter. Even if the resin filter is pierced, the beads reconstitute back to the original configuration and are not affected by the act of tampering.

[0130] The examples provided above are illustrative of the present invention and numerous modifications will be apparent to the skilled artisan. Accordingly, the present invention is not intended to be limited by the foregoing examples, but rather, is defined by the claims which follow and their equivalents.

Claims

1. A smoking article capable of delivering a regulated smoke composition to a smoker, comprising:

a) a combustible filler wrapped in a combustible sheath; and

b) a filter unit designed to remove components from said smoke disposed within said sheath, said filter unit comprising a mass of porous silica or resin particles,

wherein said porous silica or resin particles have an average particle size of from about 35 to about 400 &mgr;m.

2. The smoking article of claim 1, wherein the filter unit is adjacent said combustible filler.

3. The smoking article of claim 1, wherein the porous silica or resin particles have chemically bonded to their surfaces functional groups that exhibit preferential affinity for said components and that reversibly bind said components to elute components having a lower affinity than a previously bound component.

4. The smoking article of claim 3, wherein the functional groups are bonded to the porous silica or resin particles by one of (i) direct bonding to surface atoms of the silica or resin particles, (ii) ester bonded to surface hydroxyl groups of the silica or resin particles, and (iii) bonded to the silica or resin particles by treatment of the silica or resin particles with an organosilane.

5. The smoking article of claim 3, wherein the functional groups have the general formula:

R1(CH2)n—

wherein:

n is an integer from 1 to 40; and

R1 is hydrogen, hydroxy, amine, amide, cyano, nitrile, nitro, thio, sulfide, sulfone, sulfoxide, I, Br, Cl, F, or an alkyl or aryl group of from 1 to 40 carbon atoms which may be straight or branched, saturated or unsaturated and is optionally substituted with one or more atoms selected from the group consisting of O, N, S, I, Br, Cl and F.

6. The smoking article of claim 1, wherein the porous silica or resin particles have an average particle size of from about 40 to about 200 &mgr;m.

7. The smoking article of claim 1, wherein the porous silica or resin particles have an average particle size of from about 35 to about 80 &mgr;m.

8. The smoking article of claim 1, wherein said porous silica or resin particles have an average porosity of from about 10 Å to about 1000 Å.

9. The smoking article of claim 1, wherein the porous silica or resin particles have an average porosity of from about 50 Å to about 1000 Å.

10. The smoking article of claim 1, wherein the porous silica or resin particles have an average porosity of from about 60 Å to about 1000 Å.

11. The smoking article of claim 1, wherein the porous silica or resin particles have an average porosity of from about 150 Å to about 500 Å.

12. The smoking article of claim 1, wherein the porous silica or resin particles are selected from the group consisting of polymeric materials, silica based materials, composites of polymeric materials and silica based materials, and mixtures thereof.

13. The smoking article of claim 1, wherein the porous silica or resin particles are selected from the group consisting of methacrylate, methyl methacrylate, ethylmethacrylate, styrene, styrene divinylbenzene, silica, magnesium silicate, ceramic, porous glass, and composite resins of silica and polymeric materials.

14. The smoking article of claim 1, wherein the porous silica or resin particles are porous silica beads.

15. The smoking article of claim 1, wherein the porous silica or resin particles form a packed column having a hollow space of at least 45%.

16. The smoking article of claim 1, wherein the porous silica or resin particles form a packed column having a hollow space of at least 67%.

17. The smoking article of claim 1, wherein the filter unit has an efficiency of about 50% or more.

18. The smoking article of claim 1, wherein piercing the filter unit with a needle does not substantially affect filtering activity of the filter.

19. The smoking article of claim 1, wherein the filter unit consists essentially of said mass of porous silica or resin particles.

20. A filter cartridge for removal of components from cigarette smoke, comprising a hollow sleeve packed with porous silica or resin particles, wherein said porous silica or resin particles have an average particle size of from about 35 to about 400 &mgr;m.

21. The filter cartridge of claim 20, wherein the porous silica or resin particles have chemically bonded to their surfaces functional groups that exhibit preferential affinity for said components and that reversibly bind said components to elute components having a lower affinity than a previously bound component.

22 The filter cartridge of claim 21, wherein the functional groups are bonded to the porous silica or resin particles by one of (i) direct bonding to surface atoms of the silica or resin particles, (ii) ester bonded to surface hydroxyl groups of the silica or resin particles, and (iii) bonded to the silica or resin particles by treatment of the silica or resin particles with an organosilane.

23. The filter cartridge of claim 21, wherein the functional groups have the general formula:

R1(CH2)n—

wherein:

n is an integer from 1 to 40; and

R1 is hydrogen, hydroxy, amine, amide, cyano, nitrile, nitro, thio, sulfide, sulfone, sulfoxide, I, Br, Cl, F, or an alkyl or aryl group of from 1 to 40 carbon atoms which may be straight or branched, saturated or unsaturated and is optionally substituted with one or more atoms selected from the group consisting of O, N, S, I, Br, Cl and F.

24. The filter cartridge of claim 20, wherein the porous silica or resin particles have an average particle size of from about 40 to about 200 &mgr;m.

25. The filter cartridge of claim 20, wherein the porous silica or resin particles have an average particle size of from about 35 to about 80 &mgr;m.

26. The filter cartridge of claim 20, wherein the porous silica or resin particles have an average porosity of from about 10 Å to about 1000 Å.

27. The filter cartridge of claim 20, wherein the porous silica or resin particles have an average porosity of from about 50 Å to about 1000 Å.

28. The filter cartridge of claim 20, wherein the porous silica or resin particles have an average porosity of from about 60 Å to about 1000 Å.

29. The filter cartridge of claim 20, wherein the porous silica or resin particles have an average porosity of from about 150 Å to about 500 Å.

30. The filter cartridge of claim 20, wherein the porous silica or resin particles are selected from the group consisting of polymeric materials, silica based materials, composites of polymeric materials and silica based materials, and mixtures thereof.

31. The filter cartridge of claim 20, wherein the porous silica or resin particles are selected from the group consisting of methacrylate, methyl methacrylate, ethylmethacrylate, styrene, styrene divinylbenzene, silica, magnesium silicate, ceramic, porous glass, and composite resins of silica and polymeric materials.

32. The filter cartridge of claim 20, wherein the porous silica or resin particles are porous silica beads.

33. The filter cartridge of claim 20, wherein the porous silica or resin particles form a packed column having a hollow space of at least 45%.

34. The filter cartridge of claim 20, wherein the filter cartridge has an efficiency of about 50% or more.

35. The filter cartridge of claim 20, wherein the porous silica or resin particles form a packed column having a hollow space of at least 67%.

36. The filter cartridge of claim 20, wherein piercing the filter unit with a needle does not substantially affect filtering activity of the filter.

37. The filter cartridge of claim 20, wherein the filter cartridge consists essentially of said hollow sleeve packed with said porous silica or resin particles.