Cigarette

The present invention relates to smoking articles such as cigarettes, and in particular to cigarettes which generate low amounts of visible sidestream smoke.

Popular smoking articles, such as cigarettes, have a substantially cylindrical rod shaped structure and include a charge of smokable material, such as shredded tobacco (e.g., cut filler), surrounded by a paper wrapper thereby forming a so-called "tobacco rod." It has become desirable to manufacture cigarettes having cylindrical filter elements aligned in an end-to-end relationship with the tobacco rod. Typically, filter elements are manufactured from fibrous materials such as cellulose acetate and plug wrap, and are attached to the tobacco rod using a circumscribing tipping material. It also has become desirable to perforate the tipping material and plug wrap, in order to provide for dilution of drawn mainstream smoke with ambient air.

Cigarettes are employed by the smoker by burning one end thereof. The smoker then receives mainstream smoke into his/her mouth by drawing on the opposite end (e.g., the filter end) of the cigarette. During the time that the cigarette is not being drawn upon by the smoker, it remains burning, and sidestream smoke is generated. Sidestream smoke is smoke which directly enters the atmosphere during the static burn period of a cigarette. Sidestream smoke diffuses into the atmosphere, and the characteristic visible nature thereof may be perceived negatively by certain individuals. Thus, certain cigarettes smokers have indicated a desire to decrease the levels of visible sidestream smoke generated by their cigarette.

Cigarette paper wrappers for the preparation of tobacco rods are set forth in U.S. Pat. Nos. 4,231,377 to Cline et al, 4,420,002 to Cline, 4,461,311 to Mathews et al, 4,450,847 to Owens, and 4,805,644 to Hampl, Jr. et al, as well as European Patent Application Nos. 338,156 and 338,159. The paper wrappers proposed in the foregoing patents have a propensity to provide cigarettes which generate relatively low levels of visible sidestream smoke. A cigarette which generates relatively low levels of visible sidestream smoke is set forth in European Patent Application No. 290,911. However, cigarette paper wrappers which are useful for manufacturing cigarettes which generate low amounts of visible sidestream smoke upon use, particularly those wrappers which include magnesium hydroxide as a filler component, often have the propensity to provide, upon use, an ash having flakey properties.

It would be desirable to provide a cigarette which incorporates a paper wrapper such that upon use (i) the cigarette generates low levels of visible sidestream smoke, (ii) the cigarette provides good flavor and smoking satisfaction to the smoker thereof, and (iii) the ash of the paper wrapper is fairly cohesive and not highly flakey.

The present invention relates to cigarettes having a rod of smokable material contained in a circumscribing paper wrapper. Such a rod is referred to herein as a "smokable rod." The paper wrapper includes a cellulosic base web and a water insoluble inorganic filler. The preferred cellulosic material is flax fibers, and the preferred inorganic filler is a mixture of calcium carbonate and magnesium hydroxide. The paper wrapper also includes at least one water soluble alkali metal salt. The total amount of water soluble alkali metal salt is sufficient to provide at least about 35 mg water soluble alkali metal ions per gram of dry base web. As used herein, the term "water soluble alkali metal ions" in reference to the incorporation of those ions within the paper wrapper means that those ions incorporated into the paper are provided into the paper in the form of water soluble salts. The alkali metal salt is such that the wrapping material includes a significantly greater level of potassium ions than sodium ions. Preferred wrapping materials have relatively high basis weights. Also preferred are wrapping papers having fairly low inherent permeabilities, which are electrostatically perforated so as to have relatively high net permeabilities.

Cigarettes of the present invention also include a filter element positioned adjacent one end of the smokable rod, and tipping material circumscribing the filter element and an adjacent region of the smokable rod. Cigarettes having low efficiency and moderate efficiency cellulose acetate filter tow items are particularly preferred. The cigarettes preferably are air diluted.

Preferred cigarettes of the present invention, when employed, yield low levels of visible sidestream smoke. In particular, cigarettes of the present invention, which incorporate paper wrappers for the smokable rod employing magnesium hydroxide filler, have improved ash properties over similar cigarettes which incorporate similar paper wrappers but having less than about 20 mg of alkali metal ions per gram of dry base web. An improved ash is an ash which is cohesive and exhibits good integrity, and which is not highly flakey. In addition, the paper wrappers of preferred cigarettes of the present invention can provide for sidestream and mainstream smoke which does not possess a significant off-aroma or off-taste.

FIG. 1 is a longitudinal sectional view of a cigarette of the present invention; and

FIG. 2 is a diagrammatic illustration of the type of wrapping material which can be employed to provide the smokable rod of a cigarette of the present invention.

One embodiment of a cigarette 10 of the present invention is shown in FIG. 1. The cigarette includes a generally cylindrical rod 15 of a charge or roll of smokable filler material 20 contained in circumscribing wrapping material 25. The rod 15 is conveniently referred to as a "smokable rod" or a "tobacco rod." The ends of the tobacco rod are open to expose the smokable filler material.

The cigarette 10 normally includes a filter element 30 or other suitable mouthpiece positioned adjacent one end of the tobacco rod 15 such that the filter element and tobacco rod are axially aligned in an end-to-end relationship, preferably abutting one another. Filter element 30 has a generally cylindrical shape, and the diameter thereof is essentially equal to the diameter of the tobacco rod. The ends of the filter element are open to permit the passage of air and smoke therethrough. The filter element 30 includes filter material 35 which is overwrapped along the longitudinally extending surface thereof with circumscribing plug wrap material 40. The filter element can have two or more filter segments, and/or flavor additives incorporated therein.

The filter element 30 is attached to the tobacco rod 15 by tipping material 45 which circumscribes both the entire length of the filter element and an adjacent region of the tobacco rod. The inner surface of the tipping material 45 is fixedly secured to the outer surface of the plug wrap 40 and the outer surface of the wrapping material 25 of the tobacco rod, using a suitable adhesive. A ventilated or air diluted smoking article is provided with an air dilution means, such as a series of perforations 50, each of which extend through the tipping material and plug wrap.

Referring to FIGS. 1 and 2, the wrapping material 25 has a width w (shown in FIG. 2) which is equal to the circumference of the cigarette plus the lap zone of the glue line which ultimately results during cigarette manufacture. The preferred wrapping material 25 includes a series of perforations 60 which extend in a linear fashion along the longitudinal length of thereof. Alternatively, other configurations such as a random perforation pattern can be provided. The size, number and relative positioning of the individual perforations 60 can vary depending upon the desired characteristics of the cigarette which has the wrapping material incorporated therein. The individual perforations are shown as enlarged in FIGS. 1 and 2.

Typically, the tobacco rod has a length which ranges from about 50 mm to about 85 mm, and a circumference of about 16 mm to about 28 mm. The tobacco rods and the resulting cigarettes can be manufactured in any known configuration using known cigarette making techniques and equipment.

Typically, the filter element has a length which ranges from about 20 mm to about 35 mm and a circumference of about 16 mm to about 28 mm. The filter material can be any suitable material such as cellulose acetate, polypropylene, tobacco material, or the like. Examples of suitable filter materials are cellulose acetate tow items having (i) about 3 denier per filament and about 35,000 total denier, and (ii) about 3.5 denier per filament and about 35,000 total denier. Such tow items conveniently provide filter elements exhibiting a removal efficiency of particulate matter from mainstream smoke of greater than about 40 weight percent. The plug wrap typically is a conventional paper plug wrap, and can be either air permeable or essentially air impermeable. However, if desired, a nonwrapped cellulose acetate filter element can be employed. Filter elements having two or more segments, and which are provided using known plug-tube-combining techniques, also can be employed. The various filter elements suitable for use in this invention can be manufactured using known cigarette filter making techniques and equipment.

Certain filter elements can provide minimal mainstream smoke removal efficiencies while maintaining the desirable draw characteristics of the cigarette. Such minimal smoke removal efficiencies are provided by the so-called "low efficiency" filters. Low efficiency filters have a minimal ability to remove mainstream smoke particulates. Generally, low efficiency filters provide about 40 weight percent mainstream smoke particulate removal efficiency or less. The low efficiency filter can be used in order that the relatively low "tar" yield is obtained primarily as a result of a relatively high level of filter ventilation or air dilution. Such cigarette configurations provide a means for reducing the yields of mainstream gaseous components. An example of a suitable material for providing a low efficiency filter element is a cellulose acetate tow item having about 8 denier per filament and about 40,000 total denier.

The filler material employed in the manufacture of the smokable rod can vary. The preferred filler material is an "American blend" of tobacco materials. For example, the filler can include a blend of flue-cured, Burley, Md., Oriental, reconstituted and volume expanded tobaccos. Other suitable blends are described in European Patent Application No. 290,911.

The smokable materials generally are employed in the form of cut filler as is common in conventional cigarette manufacture. For example, the smokable filler material can be employed in the form of shreds or strands cut into widths ranging from about 1/25 inch to about 1/60 inch, preferably from about 1/30 inch to about 1/40 inch. Generally, such pieces have lengths which range from about 0.25 inch to about 3 inches.

As used herein, "packing density" means the weight of the filler material which occupies a unit volume within the smokable rod. For articles of this invention, the packing density generally ranges from about 100 mg/cm.sup.3 to about 300 mg/cm.sup.3, more typically from about 150 mg/cm.sup.3 to about 275 mg/cm.sup.3.

Flavorants can be incorporated into the cigarettes. For example, the filler materials can be employed with casing or top dressing additives. See, for example, Leffingwell et al, Tobacco Flavoring for Smoking Products (1972). Flavorants such as menthol can be incorporated into the cigarette using techniques familiar to the skilled artisan. If desired, flavor additives such as organic acids can be incorporated into the cigarette as additives to the cut filler. In particular, levulinic acid, nicotine levulinate, or a mixture of levulinic acid and nicotine can be incorporated into the cigarette. For example, the levulinic acid, nicotine levulinate or levulinic acid/nicotine mixture can be added to the cut filler in amounts which typically range from about 1 to about 10 percent, based on the weight of the cut filler. See, U.S. Pat. No. 4,830,028 to Lawson et al.

Typically, the tipping material circumscribes the filter element and an adjacent region of the tobacco rod such that the tipping material extends about 3 mm to about 6 mm along the length of the tobacco rod. Typically, the tipping material is a conventional paper tipping material. The tipping material can have a porosity which can vary. For example, the tipping material can be essentially air impermeable, air permeable, or be treated (e.g., by mechanical or laser perforation techniques) so as to have a region of perforations, openings or vents thereby providing a means for providing air dilution to the cigarette. The total surface area of the perforations and the positioning of the perforations along the periphery of the cigarette can be varied in order to control the performance characteristics of the cigarette.

For certain cigarettes of the present invention, the air dilution means can be positioned along the length of the cigarette at a point along the filter which is at a maximum distance from the extreme mouthend thereof. The maximum distance is dictated by factors such as manufacturing constraints associated with the type of tipping employed and the cigarette manufacturing apparatus and process. For example, for a filter element having a 27 mm length, the maximum distance may range from about 23 mm to about 26 mm from the extreme mouthend of the filter element. The positioning of the air dilution vents a maximum distance from the extreme mouthend of certain cigarettes allows for providing a maximum ventilation level for a given "tar" yield and maximum cigarette pressure drop for a given filter element and tobacco rod combination.

As used herein, the term "air dilution" is the ratio (generally expressed as a percentage) of the volume of air drawn through the air dilution means to the total volume of air and smoke drawn through the cigarette and exiting the extreme mouthend portion of the cigarette. For air diluted or ventilated cigarettes of the present invention, the amount of air dilution can vary. Generally, the amount of air dilution for a cigarette is greater than about 10 percent, often greater than about 20 percent, and frequently greater than about 30 percent. Typically, for cigarettes of relatively small circumference (i.e., about 21 mm or less) the air dilution can be somewhat less than that of cigarettes of larger circumference. The upper limit of air dilution for a cigarette typically is less than about 75 percent, more frequently less than about 70 percent.

As used herein, the term "pressure drop" in referring to the cigarette is meant that difference between atmospheric pressure at the extreme mouthend point of the cigarette, as measured at a given flow rate through the cigarette. Typical pressure drop values for cigarettes of the present invention are greater than about 50 mm, more frequently greater than about 80 mm of water pressure drop at 17.5 ml/sec of air flow rate.

The preferred wrapping materials for the tobacco rod have relatively high basis weights. Typical basis weights for such wrapping materials are at least about 40 g/m.sup.2, often are greater than about 45 g/m.sup.2, and frequently are greater than about 50 g/m.sup.2. Typical basis weights do not exceed about 80 g/m.sup.2.

Most desirable wrapping materials for the tobacco rod have relatively low inherent permeabilities and relatively high net permeabilities. By the term "inherent permeability" is meant the air flow porosity of the wrapping material itself. Typically, wrapping materials having low inherent permeabilities have porosities which are less than about 25 CORESTA units, preferably less than about 20 CORESTA units, and more preferably about 15 CORESTA units or less. By the term "net permeability" is meant the air flow porosity of the wrapping material as used in manufacturing the tobacco rod. Typically, the air permeability is provided to the wrapping material using micro laser, mechanical or electrostatic perforation techniques. During micro laser and electrostatic perforation operations, it is most desirable that care be taken to maintain the desired color and opacity of the paper. For example, it is most desirable to minimize or avoid an unsightly "browning" or singeing of the paper.

The wrapping materials preferably are processed in order to have relatively high net permeabilities (e.g., net permeabilities above about 50 CORESTA units). For example, wrapping materials having low inherent permeabilities can be perforated using conventional electrostatic perforating techniques (e.g., to provide individual perforations comparable in size to conventional electrostatically provided perforations) to obtain a wrapping material having a porosity of from about 50 to about 225 CORESTA units, preferably from about 80 to about 180 CORESTA units, more preferably from about 90 to about 120 CORESTA units.

The sizes of the individual perforations which provide for the high net permeabilities to the cigarette paper wrap generally are such that the perforations are larger than the pores which are present in the naturally occurring paper wrap (i.e., which provide the inherent permeability to the paper). For aesthetics purposes, the individual perforations preferably are small enough to not be unsightly. For example, the perforations are not particularly noticeable, and in most instances are barely visible to the naked eye.

Typical wrapping materials are paper wrapping materials which contain about 55 to about 75, preferably about 60 to about 70 weight percent cellulosic material; and about 25 to about 45, preferably about 30 to about 40 weight percent inorganic filler. Often, desirable paper wrapping materials contain more than about 15 percent by weight of magnesium hydroxide filler. Preferred paper wrapping materials which contain from about 15 to about 35 percent, more preferably about 20 to about 30 percent, by weight of magnesium hydroxide. Examples of suitable materials are described in U.S. Pat. No. 4,450,847 to Owens. See, also, European Patent Application Nos. 338,156 and 338,159. The preferred wrapping materials also contain other inorganic fillers, such as calcium carbonate. Preferred paper wrapping materials contain about 5 to about 25 percent, more preferably about 10 to about 20 percent, by weight of calcium carbonate. The preferred papers also contain flax fibers, wood pulp, or other cellulosic material to provide a cellulosic base web.

The cigarette paper wrap includes at least one water soluble alkali metal salt. Examples of water soluble alkali metal salts include potassium acetate, potassium nitrate, potassium citrate, potassium chloride, potassium succinate, potassium propionate, potassium formates and the like, as well as mixtures thereof. It is preferable that at least a portion of the alkali metal be provided in the form of a salt exhibiting a very low hygroscopic character. An example of such a salt is potassium chloride.

The manner in which the water soluble alkali metal salt is incorporated into the paper wrap can vary. The salt can be incorporated into the paper during the manufacturing process. Alternatively, the salt can be incorporated into the paper using size press techniques, painting techniques, or the like. Such techniques will be apparent to the skilled artisan. It is highly preferred that the salt be incorporated into the paper in an essentially uniform manner throughout the paper. The various water soluble salts can be incorporated into the paper simultaneously, or at different processing stages during or after paper manufacture.

The amount of water soluble alkali metal salt incorporated into the paper wrap is such that the amount of that salt provides at least about 35 mg water soluble alkali metal ions per gram of dry base web. The amount of water soluble alkali metal salts incorporated into the paper wrap normally is such that those salts provide at least about 40 mg, and frequently at least about 45 mg, water soluble alkali metal ions per gram of dry base web. The amount of water soluble alkali metal salts incorporated into the paper wrap normally is such that those salts provide less than about 90 mg, and frequently less than about 80 mg, water soluble alkali metal ions per gram of dry base web.

The level of potassium ions within the paper wrapping material is significantly greater than the level of sodium ions within the paper. In particular, the weight ratio of potassium ions to sodium ions within the paper is greater than about 100:1, preferably greater than about 150:1, more preferably greater than about 200:1.

Examples of suitable paper wrapping materials are available as Ecusta Experimental Paper Nos. TOD 4982 and TOD 5024 from Ecusta Corp.

Cigarettes of this invention generally deliver FTC "tar" in the range from about 2 to about 14 mg/cigarette. Typical FTC "tar" to FTC carbon monoxide ratios are less than about 1.6, frequently less than about 1.2.

Preferred cigarettes of the present invention produce less visible sidestream smoke than conventional cigarettes of comparable configuration when evaluated using the method described by Baker at col. 3, lines 38-49 of U.S. Pat. No. 4,624,268. The reduction in visible sidestream smoke of cigarettes of the present invention is such that sidestream smoke emitted by cigarettes of the present invention frequently can be as much as about 50 percent of that of conventional cigarettes of comparable FTC "tar" delivery and configuration. By the term "configuration" in referring to a cigarette is meant the circumference, tobacco rod length and filter element length. Cigarettes of the present invention also generate relatively low levels of sidestream "tar" when evaluated using the technique described by Proctor et al, Analyst, Vol. 113, p. 1509 (1988).

The following examples are provided in order to further illustrate the invention but should not be construed as limiting the scope thereof. Unless otherwise noted, all parts and percentages are by weight.

Cigarettes having lengths of about 99 mm and circumferences of about 24.85 mm have tobacco rod lengths of about 68 mm and filter element lengths of about 31 mm. The tobacco rod includes a charge of tobacco cut filler contained in a circumscribing cigarette paper wrap. The filler material employed in providing the tobacco rod is in the form of strands cut at about 32 cuts per inch. The filler material includes a blend of about 29 percent flue-cured tobacco, about 14 percent of a mixture of volume expanded flue-cured and Burley tobacco cut filler, about 25 percent reconstituted tobacco material, about 17 percent Oriental tobaccos, and about 15 percent Burley tobacco.

The paper wrap is available as Ecusta Experimental No. TOD 4982 by Ecusta Corp. The paper wrap is a heavy weight sheet, low visible sidestream paper. The base sheet contains about 15 percent calcium carbonate, about 25 percent magnesium hydroxide and about 60 percent flax fiber. The paper has an inherent permeability of 10 to 12 CORESTA units and a basis weight of about 48 g/m.sup.2. The paper includes about 58 mg potassium ions per gram of dry base sheet. The paper has potassium chloride incorporated therein from an aqueous solution using a size press. The magnesium hydroxide filler of the paper is precipitated by contacting potassium hydroxide with magnesium acetate. The ratio of potassium ions to sodium ions in the paper is about 193:1. The paper is electrostatically perforated in order to yield a net permeability of 100 to 130 CORESTA units. The general perforation pattern is shown in FIG. 2. The individual perforations each have a size comparable to conventional electrostatic perforations in conventional cigarette wrap, and are positioned with about 1 to about 10 perforations/mm essentially linearly in the longitudinal direction such that the lines of perforations are positioned about 1 mm to about 3 mm apart.

The filter element is manufactured using conventional cigarette filter making technology from a moderate efficiency cellulose acetate tow item (3 denier per filament, 35,000 total denier) and circumscribing air impermeable paper plug wrap. Such a filter element provides for greater than 40 percent removal efficiency of particulate matter from the mainstream tobacco smoke of the cigarette.

The tobacco rod and filter element have similar circumferences, are aligned in an abutting, end-to-end relationship, and are secured together using tipping paper. The tipping paper is adhesively secured to the filter element and the adjacent portion of the tobacco rod. The tipping material circumscribes the length of the filter element and about 4 mm of the length of the tobacco rod. Cigarettes so described are manufactured using a Hauni Protos Cigarette Maker from Hauni-Werke Korber & Co. KG. A ring of laser perforations, thus providing air permeability, extends around the periphery of the cigarette about 13 mm from the extreme mouthend thereof. The perforations so provided yield cigarettes with about 30 percent air dilution.

The cigarette weighs about 1.15 g and the filler material within the rod has a packing density of about 240 mg/cm.sup.3.

The cigarette is smoked and delivers a rich tobacco flavor as well as an acceptable draft resistance. The mainstream smoke is not harsh and the cigarette yields desirable smoking satisfaction. Also, the cigarette yields low amounts of visible sidestream smoke.

Cigarettes are provided using the techniques and materials substantially as described in Example 1. However, the cigarettes have lengths of about 84 mm (i.e., tobacco rod lengths of about 57 mm and filter element lengths of about 27 mm). The filter element is manufactured from a cellulose acetate tow item (3.5 denier per filament, 35,000 total denier). The cigarette weighs about 0.95 g and the filler material within the rod has a packing density of about 230 mg/cm.sup.3.