Patent Grant
9107455
A wide variety of materials have been suggested as additives in cigarette filters to selectively remove components of cigarette smoke. These materials include molecular sieves and particularly zeolite-type molecular sieves.
There is decided interest in a cigarette filter which can be tailored to selectively remove or reduce the concentration of various constituents of cigarette smoke while retaining desirable flavor components.
A filter cigarette is provided which contains a mesoporous silicate molecular sieve modified with aminoalkylsilyl groups. Also provided is a substantially cylindrical cigarette filter containing a mesoporous silicate molecular sieve modified with aminoalkylsilyl groups, a method of manufacturing the aforementioned filter cigarette, and a method of smoking a filter cigarette containing a mesoporous silicate molecular sieve modified with aminoalkylsilyl groups.
In one embodiment, a filter cigarette is prepared containing tobacco and a filter having a component comprising a mesoporous silicate molecular sieve modified with aminoalkylsilyl groups. The cigarette may be a traditional or non-traditional cigarette.
A further embodiment provides a method of manufacturing a filter cigarette which includes joining a filter containing a mesoporous silicate molecular sieve modified with aminoalkylsilyl groups to a tobacco rod with tipping paper.
In yet another embodiment, a cigarette filter is prepared containing a mesoporous silicate molecular sieve modified with aminoalkylsilyl groups. The modified molecular sieve may be incorporated in a filter component selected from filter paper, shaped paper insert, a plug, a space or a free-flow sleeve.
Another embodiment provides a method of smoking a filter cigarette. The cigarette is lit to form cigarette smoke which is drawn through the filter wherein the filter contains a mesoporous silicate molecular sieve modified with aminoalkylsilyl groups. The modified molecular sieve reacts with at least one constituent of the smoke to remove or reduce the concentration of the constituent without adversely affecting desirable flavor components in the cigarette smoke.
Filter cigarettes and filters are provided which contain a sorbent comprising a modified mesoporous silicate molecular sieve. At least some of the accessible hydroxyl groups associated with the tetrahedral framework of the molecular sieve are reacted with aminoalkyltrialkoxysilane reagents to provide the sieve with aminoalkylsilyl groups. These groups react with selected constituents present in mainstream cigarette smoke to remove or reduce the constituents.
The term “sorption” denotes filtration by adsorption and/or absorption and is intended to encompass interactions on the outer surface of a sorbent, as well as interactions within the pores and channels thereof. A “sorbent” is a substance that has the ability to condense or hold molecules of other substances on its surface and/or the ability to take up other substances, i.e., through penetration of the other substances into its inner structure or into its pores. The term “sorbent” as used herein refers to either an adsorbent, and absorbent, or a substance that can function as both an adsorbent and an absorbent.
The term “remove” as used herein refers to adsorption and/or absorption of at least some portion of a selected component of mainstream tobacco smoke.
The term “mainstream smoke” includes the mixture of gases which passes down a tobacco column and issues through the filter end, i.e., the amount of smoke issuing or drawn from the mouth end of a smoking article such as a cigarette during smoking. The mainstream smoke contains air that is drawn in through both the lit region of the smoking article, as well as through the paper wrapper.
The terms “aminoalkylsilyl” and “aminoalkyltrialkoxysilanes” are intended to include reagents where the alkyl group contains about 1 to 5 carbon atoms. These include reagents derived from alkylene polyamines such as N-[3-(trimethoxysilyl)propyl]-ethylenediamine and N′-[3-(trimethoxysilyl)propyl]-diethylenetriamine.
The term “mesoporous” generally refers to molecular sieve materials having pore sizes ranging from about 15 Å to about 300 Å.
Microporous and mesoporous molecular sieve materials admit molecules below a certain critical size into their extensive internal space, which makes them of considerable interest as heterogeneous catalysts and sorbents. Zeolites are by far the best-known class of molecular sieves. In comparison with microporous zeolites, mesoporous molecular sieve materials, developed in the past decade such as M41S and SBA-15, possess uniform size and shape of the pores over micrometer length scales. Their high thermal stability as well as the prospect of “tuning” the pore aperture, either by selecting a suitable template for their synthesis or by grafting various organic/inorganic functional groups via post-synthesis procedures, makes these materials potentially useful for many adsorption and catalytic applications. The ion-exchange, catalytic, and sorptive properties of aluminosilicate molecular sieves originate from acid sites which arise from the presence of accessible hydroxyl groups associated with tetrahedral framework aluminum in a silica matrix.
The accessible hydroxyl groups of mesoporous silicate molecular sieves can be reacted with aminoalkyltrialkoxy silane reagents to provide the molecular sieves with aminoalkylsilyl groups such as 3-aminopropylsilyl groups. This chemical modification provides modified mesoporous silicate molecular sieves with the capability of selectively removing constituents of cigarette smoke by reaction of the constituents with the aminoalkylsilyl groups. It is believed that the primary amine group at the terminal (exposed or free) end of the aminopropylsilyl group readily reacts with aldehydes and ketones. The primary amine reacts with the aldehyde to form an imine and/or other covalently bonded derivatives of the aldehyde. The imine group or other covalently bonded derivative of the aldehyde remains anchored to the modified molecular sieve and thus, the formation of such derivatives serves to effectively remove the aldehydes and ketones and their reaction products from cigarette smoke. The primary amine group also may react with hydrogen cyanide through an acid-base reaction thus reducing the levels of this compound in the cigarette smoke.
Suitable mesoporous silicate molecular sieve materials include SBA-15, MCM-41, MCM-48 and the like. These materials generally have pore sizes in the range of about 15 Δ to about 300 Δ.
Suitable reagents which may be employed to provide aminoalkylsilyl groups on the molecular sieves include aminoalkyltrialkoxy silanes such as 3-aminopropyltriethoxy silane and 3-aminopropyltrimethoxy silane. Other reagents which can be used to incorporate aminoalkylsilyl groups into the molecular sieves include alkylene polyamine derivatives such as N-[3-(trimethoxysilyl)propyl)-ethylenediamine or N′-[3-(trimethoxysilyl)propyl]-diethylenetriamine. In this case, the modified molecular sieve would contain aminoethylaminopropylsilyl or aminoethylaminoethylaminopropylsilyl groups.
The modified molecular sieve can be prepared by admixing the molecular sieve in powder or particulate form or as a slurry with the reagent such as 3-aminopropyltriethoxysilane (APS) in a solvent such as aqueous ethanol solvent. Other solvents, such as toluene, can also be used. The mixture is heated for several hours to allow the 3-aminopropyltriethoxysilane to react with and chemically bond to the molecular sieve. The reaction mixture is then decanted to obtain a reaction product. The reaction product is subsequently rinsed with a solvent, and dried in an oven at an elevated temperature such as around 100° C., or above. Although the rinsing and drying steps are optional, the drying step is preferred.
The modified molecular sieve is preferably prepared by an incipient-wetness impregnation technique conducted at elevated temperatures. The mesoporous molecular sieve is impregnated with the reagent in dry toluene via incipient-wetness impregnation at an elevated temperature.
The modified mesoporous silicate molecular sieve can be incorporated into the cigarette filter by various manufacturing techniques. In one embodiment, the modified molecular sieve is incorporated into or onto a support such as paper (e.g., tipping paper) located along a filter portion of a cigarette. As will be recognized by persons skilled in the art, such paper can be used, for example, as a wrapper or a liner in the filter portion of the cigarette. The modified molecular sieve can also be loaded onto a support such as lightly or tight folded paper inserted into a hollow portion of the cigarette filter. The support is preferably in the form of a sheet material such as crepe paper, filter paper, or tipping paper. However, other suitable support materials such as organic or inorganic cigarette compatible materials can also be used.
The modified molecular sieve can be incorporated into the filter paper in a number of ways. For example, it can be mixed with water to form a slurry. The slurry can then be coated onto pre-formed filter paper and allowed to dry. The filter paper can then be incorporated into the filter portion of a cigarette in the manner shown in
Alternatively and more preferably, the modified molecular sieve is added to the filter paper during the paper-making process. For example, it can be mixed with bulk cellulose to form a cellulose pulp mixture. The mixture can be then formed into filter paper according to methods known in the art.
In another embodiment, the modified molecular sieve is incorporated into the fibrous material of the cigarette filter portion itself. Such filter materials include, but are not limited to, fibrous filter materials including paper, cellulose, acetate fibers, and polypropylene fibers. This embodiment is illustrated in
Various techniques can be used to apply the modified molecular sieve to filter fibers or other substrate supports. For example, the modified molecular sieve can be added to the filter fibers before they are formed into a filter cartridge, e.g., a tip for a cigarette, or added to the filter fibers, for example, in the form of a dry powder or a slurry by methods known in the art. If applied in the form of a slurry, the fibers are allowed to dry before they are formed into a filter cartridge.
In another embodiment, the modified molecular sieve is employed in a hollow portion of a cigarette filter. For example, some cigarette filters have a plug/space/plug configuration in which the plugs comprise a fibrous filter material and the space is simply a void between the two filter plugs. That void can be filled with the modified molecular sieve. An example of this embodiment is shown in
In another embodiment, the modified molecular sieve may be employed in a filter portion of a cigarette for use with a smoking device as described in U.S. Pat. No. 5,692,525, the entire content of which is hereby incorporated by reference.
In such a cigarette, the modified molecular sieve can be incorporated in various ways such as by being loaded onto paper or other substrate material which is fitted into the passageway of the tubular free-flow filter element 102 therein. It may also be deployed as a liner or a plug in the interior of the tubular free-flow filter element 102. Alternatively, the modified molecular sieve can be incorporated into the fibrous wall portions of the tubular free-flow filter element 102 itself. For instance, the tubular free-flow filter element or sleeve 102 can be made of suitable materials such as polypropylene or cellulose acetate fibers and the modified molecular sieve can be mixed with such fibers prior to or as part of the sleeve forming process.
In another embodiment, the modified molecular sieve can be incorporated into the mouthpiece filter plug 104 instead of in the element 102. However, as in previously described embodiments, the modified molecular sieve may be incorporated into more than one component of a filter portion such as by being incorporated into the mouthpiece filter plug 104 and into the tubular free-flow filter element 102.
The filter portion 62 of
The amount of modified molecular sieve which can be employed in the cigarette filter by way of incorporation on a suitable support such as filter paper and/or filter fibers, depends on the amount of selected substituents such as aldehydes in the tobacco smoke and the amount of aldehydes desired to be removed. As an example, the filter paper and the filter fibers may contain from 10% to 50% by weight of the modified molecular sieve.
Mesoporous SBA-15 was modified with aminopropyl functional groups via incipient-wetness impregnation with (3-aminopropyl)triethoxysilane (0.017-0.267μ) at 100EC in dry toluene.
Characterization by powder x-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption, thermogravimetric analysis (TGA), Fourier-transform infrared (FTIR), electron energy loss (EELS), and 1H, 13C, and 29Si magnetic-angle-spinning (MAS) NMR spectroscopy with or without 1H cross polarization (CP) was carried out to investigate the pore structure of the modified material and the chemical nature and thermal stability of incorporated organic moieties. The results revealed that the channels of the SBA-15 material are essentially lined with abundant silanol groups, which serve as the sites for the incorporation of aminopropyl groups. The loading of the aminopropyl groups by impregnation is quantitatively controllable and reaches a maximum molar percentage of about 11% with respect to silicon, which indicates a percentage of the silicon present as silanol groups. The incorporated aminopropyl groups are chemically bonded to surface silicon associated with the silanol groups of the SBA-15 material and thermally stable up to 550° C. The modified materials still possess high surface area and defined mesoporous structure with decreased pore dimensions due to occupation of the incorporated aminopropyl groups. This indicates a uniform distribution of aminopropyl groups on the internal surface of the SBA-15 material.
This Example shows that aminoalkyl functional groups can be successfully incorporated into the channels of mesoporous silicate molecular sieves by a more efficient incipient-wetness impregnation technique while preserving the well-defined mesoporous structure of the parent molecular sieve.
While the invention has been described with reference to preferred embodiments, it is to be understood that variations and modifications may be resorted to as will be apparent to those skilled in the art. Such variations and modifications are to be considered within the purview and scope of the present invention.
This application claims priority under 35 U.S.C. §119 to U.S. Provisional Application No. 60/523,671 entitled CIGARETTE FILTER, filed Nov. 21, 2003, the entire content of which is hereby incorporated by reference.
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