Smoking articles with significantly reduced gas vapor phase smoking constituents

A smoking article having a tobacco rod, which is adapted to produce mainstream smoke, and a filter attached to said tobacco rod. A permeable wrapping paper circumscribes the tobacco rod and the filter. The filter has an upstream end portion and a downstream end portion, and includes a flow restricting segment of smoke impermeable material, which includes at least one open flow passage therethrough to deliver mainstream smoke, and a cavity downstream of the flow restricting segment. The smoking article also includes at least one ventilation zone upstream of the flow restricting segment.

BACKGROUND

Heretofore, cigarettes with high levels of ventilation have usually had unacceptably low levels of resistance to draw (RTD) unless some counter measure was in place to make-up the shortfall in RTD. In the past, high density cellulose acetate filter segments were used to address the shortfall. However such filtered segments tended to reduce tar delivery (FTC), with little or no effect upon gas phase constituents of mainstream tobacco smoke, such as carbon monoxide (CO) and nitrogen oxide (NO). This solution tended to worsen the CO to tar (FTC) ratios in lower delivery (FTC tar) cigarettes.

Ventilation has a desirable attribute in that, when operating alone, it will reduce both the particulate phase and the gas phase of mainstream smoke. Highly ventilated cigarettes however have drawbacks in RTD as previously discussed.

SUMMARY

Provided is a smoking article including a flow restriction device, a cavity and an upstream ventilation zone. Preferably, the ventilation zone is in communication with the cavity. In an embodiment, the smoking article can also include additional ventilation zones upstream and/or downstream of the flow restriction device.

In accordance with an embodiment, a smoking article comprises: a tobacco rod, which is adapted to produce mainstream smoke; a filter attached to said tobacco rod, the filter having an upstream end portion and a downstream end portion, the filter comprising: a flow restricting segment of smoke impermeable material, which includes at least one open flow passage therethrough to deliver mainstream smoke; and a cavity downstream of the flow restricting segment; a permeable wrapping paper, which circumscribes the tobacco rod and the filter; and at least one ventilation zone upstream of the flow restricting segment.

In accordance with a further embodiment, a smoking article comprises: a densely packed tobacco rod adapted to produce mainstream smoke; and a filter having an upstream end portion and a downstream end portion, said filter arranged to receive mainstream smoke at said upstream end portion, said filter comprising: a diffusion zone, which allows significant air inflow to dilute and transfer the smoke directly to the downstream portion of filter, the diffusion zone having a highly permeable cellulose acetate hollow tube and a high permeable wrapping paper; and a delivery zone, the delivery zone comprising a flow restriction element with a downstream cavity as a flow buffer for desirable draw resistance, wherein the flow restriction element includes a restriction establishing a substantial portion of a predetermined resistance to draw of said smoking article.

Described herein is a highly ventilated smoking article with desired amounts of resistance to draw and having provisions for facilitating high speed cigarette manufacturing on conventional cigarette making equipment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Since the 1960's there has been significant efforts to develop mechanical type filters, such as jet or impaction filters, which are constructed with at least one flow restriction filter element and substantial downstream air dilution, in an effort to reduce tar levels in mainstream smoke. The flow restriction filter element can be an impaction plate, a short polymer column with a number of holes along the axis, or simply a high density cellulose acetate plug with holes therein. Such mechanical filters rely heavily on the high flow-rate through the holes, which correlates strongly to high pressure drops before and after the flow restriction element.

However, there are drawbacks in current designs due to inconsistency and less redundancy of pressure drop and percentage air dilution, as the functioning of the filter unit is critically dependent on hole dimensions, wall thicknesses, number of holes, downstream air dilution, and total particulate matter (TPM) build-up during smoking.

Described herein is a smoking article provides the benefit of a highly ventilated smoking article with desired amounts of resistance to draw, in which air dilution is positioned upstream (frontal) to a flow restriction element for improved consistency and redundancy of various smoking characteristics, such as percentage air dilution and total pressure drop. In general, the smoking article combines a mainstream smoke produced by a tobacco rod with a desirable level of air dilution in the cigarette rod or column which includes a highly permeable wrapping paper, which is optionally perforated, or in a perforated mixing chamber before access into a flow restriction filter element. The total combined volume through the flow restriction filter element is preferably significantly higher (i.e., in accordance with an embodiment, about a 3 fold increase for a typical ultra light smoke delivery without filtration, which combines about 25 percent mainstream smoke with about 75 percent air dilution), which results in an increased flow-rate and, therefore, an improved efficiency of the flow restriction filters.

In accordance with another embodiment, the increased total volume also provides for a flow restriction element to have larger holes for improved redundancy of pressure drop and machinability, since during the course of smoking, the total pressure drop is largely controlled by the size of the hole and/or length of the flow restriction column, independent of upstream air dilution.

In a preferred embodiment, the smoking article includes a flow restriction element and at least one ventilation zone upstream of the flow restriction element so as to provide about 20% to about 80% air to mainstream smoke. In an embodiment, the smoking article also includes at least one ventilation zone downstream of the flow restriction element.

In accordance with another embodiment, a smoking article is described herein that includes a combustion zone comprised of a short but densely packed tobacco rod, a diffusion zone which allows significant airflow, and a delivery zone comprised of at least one flow restriction element with a downstream cavity.

Referring now toFIG. 1, a preferred embodiment provides a smoking article10including a filter40adjacent to a tipped end14(i.e., downstream end) of a generally cylindrical rod20of smoking material21, contained in a circumscribing permeable outer wrapper or wrapping paper30. The filter40includes a flow restricting segment44of smoke impermeable material, which includes at least one open flow passage130therethrough to deliver mainstream smoke, and a cavity146downstream of the flow restricting segment44. The smoking article10also preferably includes at least one ventilation zone upstream of the flow restricting segment. In accordance with an embodiment, the at least one open flow passage130has a single hole having a diameter of about 0.6 mm.

Typically, the generally cylindrical rod20of smoking material21is referred to as a “tobacco rod” and has a lit end12and a tipped end14. The smoking material21(or tobacco filler) normally is employed so as to fill the tobacco rod at a packing density of about 100 mg/cm3to about 300 mg/cm3, and often about 150 mg/cm3to about 275 mg/cm3. The smoking material21is wrapped with a low permeability paper to form the cylindrical rod20. Tobaccos can have a processed form, such as processed tobacco stems (e.g., cut-rolled or cut-puffed stems), volume expanded tobacco (e.g., puffed tobacco, such as propane expanded tobacco and dry ice expanded tobacco), or reconstituted tobacco (e.g., reconstituted tobaccos manufactured using paper-making type or cast sheet type processes). Typically, tobacco materials for cigarette manufacture are used in a so-called “blended” form. For example, certain popular tobacco blends, commonly referred to as “American blends,” comprise mixtures of flue-cured tobacco, burley tobacco and Oriental tobacco, and in many cases, certain processed tobaccos, such as reconstituted tobacco and processed tobacco stems. It can be appreciated that the precise amount of each type of tobacco within a tobacco blend used varies from smoking article to smoking article. If desired, in addition to the aforementioned tobacco materials, the tobacco blend can further include other flavor components, including menthol.

The tobacco rod20is arranged such that the filter40and tobacco rod20are axially aligned in an end-to-end relationship, preferably abutting one another. The filter40has a generally cylindrical shape, and the diameter thereof is essentially equal to the diameter of the tobacco rod20. Preferably, the upstream end16and the buccal or downstream end18of the filter40are open to permit the passage of air and smoke therethrough.

The outer wrapper or wrapping paper30is preferably a highly permeably or porous wrapping material having permeability of at least 50 Coresta units (1 Coresta unit (Cu)=1 cm/kPa), and more preferably at least 100 Coresta units, and more preferably between about 100 Coresta units and about 200 Coresta units.

In an embodiment, the filter40includes an upstream filter segment42and a downstream filter segment46comprised of filtering material and a flow restricting segment44circumscribed by the wrapping material30. Preferably, the upstream filter segment42and the downstream filter segment46of filtering material are low particulate efficiency filter segments preferably constructed from less densely packed, large diameter fiber cellulose acetate tow of about 5.0 denier to about 15.0 denier per filament (dpf), such as 8 dpf, and about 10,000 to about 50,000 total denier (td), such as 35,000 td.

In accordance with an embodiment, the flow restricting segment44includes one or more flow restriction passages or holes130therethrough. The flow restricting segment44can include at least one flow restriction element45adjacent the first upstream filter plug46of a length of about 3 mm to about 10 mm, more preferably about 3 mm to about 7 mm in length.

Preferably, a cavity146within the filter40is defined at least in part by a tubular filter segment147, such as a cylindrical cellulosic tube and by the spaced apart relation of the downstream filter plug and the flow restrictor disc45.

The filter40attaches to the tobacco rod20by a tipping material50, which preferably circumscribes the filter40and an adjacent portion of the tobacco rod20. The tipping material50is typically a paper like product; however, any suitable material can be used. In accordance with an embodiment, the inner surface of the tipping material50is fixedly secured to the outer surface of the wrapping material30, using a suitable adhesive.

Upon lighting of the smoking article10, the mainstream smoke is generated by and drawn from the tobacco rod20and through the filter40. As used herein, the terms “upstream” and “downstream” describe relative positions between the filter40and other features in relation to the direction of mainstream smoke as it is drawn from the tobacco rod20and through the filter40.

In accordance with a preferred embodiment, the upstream and downstream (i.e., mouth end or buccal end) plugs42,46of filtering material are a starch-based, polypropylene, or plasticized cellulose acetate tow, filter paper or other suitable material. The upstream and the downstream plugs42,46of filtering material can alternatively have the form of a gathered web (e.g., polypropylene web, polyester web, cellulosic web or starch-based web). However, the filtering material can be carbon-on-tow (a cellulose acetate element mixed with an activated carbon material throughout), activated carbon, gas-vapor phase sorbents or any other suitable filtering material. In accordance with an embodiment, the upstream and the downstream plugs42,46of filtering material each have a generally cylindrical shape, and an outer diameter thereof that is essentially equal to the outer diameter of the tobacco rod20.

The filter40typically has an overall length of about 15 mm to about 40 mm in length for a smoking article10having an overall length of about 80 to about 160 mm. Each filter segment42,46of filtering material can have an equal length, or the upstream and downstream plugs42,46can have different lengths. It can also be appreciated that the length of the upstream and downstream plugs42,46of filtering material can vary depending on additional materials within the filtering material including activated carbons or other gas-vapor phase sorbent or additive materials.

The flow restriction element45establishes the flow restriction and is preferably sized to contribute sufficient pressure drop such that the smoking article10presents a resistance to draw of at least about 70 mm water or greater, and more preferably in the range of about 80 mm water to about 120 mm water. The flow restriction element45preferably has one or optionally, at least one or more flow restriction passages or holes130of a diameter of about 0.5 mm to about 0.9 mm and more preferably about 0.5 mm to 0.7 mm. Since the pressure drop of the flow restricting segment44depends on the open area, one or more flow restriction passages or holes130can also be used. In accordance with an embodiment, the flow restriction element45has a diameter of about 7.0 mm to about 8.0 mm, and more preferably a diameter of about 7.4 mm to about 7.8 mm.

In accordance with an embodiment, the flow restricting segment44may be constructed of paper, a plastic or a metal and more preferably made of a paper product or a biodegradable plastic or other suitable material having degradability properties.

The smoking article10also preferably includes at least one ventilation zone60, which provides air dilution to the smoking article10. In accordance with an embodiment, the wrapping material30is perforated with a first row (and optionally second and possibly a third row) or series of ventilation holes or perforations62, which extend through the wrapping material30to form a ventilation zone60. Alternatively, the outer wrapper or wrapping paper30can be a porous wrapping material or paper material having a permeability of less than 100 Coresta units with a row or series of ventilation holes or perforations62. Preferably, the holes or perforations62of the ventilation zone60achieve a ventilation level of the smoking article10of at least about 20% and more preferably at least about 50% to about 90% by volume.

In a preferred embodiment, the ventilation zone60is located upstream of the flow restricting segment44. The ventilation zone60can be located along the tobacco rod20and/or along the filter40. The holes and/or perforations62can be formed using online laser perforation techniques, off-line, pre-perforated tipping paper, mechanical perforation, electrostatic perforation and other techniques. By locating the ventilation zone60upstream of the flow restricting segment44, percent air dilution and total pressure drop can be controlled. Also, since the ventilation zone60is upstream, the total smoke volume going through the flow restriction filter is increased so as to increase the flow-rate and improve the efficiency of the filter. During the course of smoking, the total pressure drop is largely controlled by the size of the hole in the flow restriction filter element and/or the length of the flow restriction filter element, independent of the upstream air dilution.

The filter40can also include a plurality of ventilation holes or perforations60on either the downstream and/or upstream side of the flow restricting segment44in addition to the upstream ventilation zone described above. In use, the filter40incorporating the at least one flow restriction element45into the cigarette or smoking article10, minimizes the ratio of total particulate matter (TPM) and tar yield by increasing the filtration efficiency for particulates (tar) with the increase of flow rate or puff volume. Specifically, the range of TPM or tar that the smoker is exposed to, by increasing puff volume, is reduced due to the reduction in smoking elasticity, i.e. reduction in Tar (mg/cigt)MDPH/Tar (mg/cigt)FTC.

Referring now toFIG. 2, in accordance with another embodiment provides a smoking article10comprising a tobacco rod20and filter40wrapped in a highly permeable wrapping material30. As shown inFIG. 2, the filter40includes an upstream cavity148, a flow restricting segment44, and a downstream cavity146, which is defined at least in part by a tubular filter segment147, and a downstream segment42of filtering material. The flow restricting segment44is preferably comprised of a flow restriction element45having one or more flow restricting passages or openings130therein.

In an embodiment, the upstream cavity within the filter40is defined at least in part by the tubular segment152and optionally, in part by the space enclosed by the tubular section of the flow restriction element45. Preferably, the upstream cavity148includes a ventilation zone60comprised of at least one row, and more preferably 2 to 4 rows of ventilation holes and/or perforations62. The tubular segment152is preferably constructed from a hollow acetate tube (HAT) and is preferably air permeable (low density) so that ventilation air may be drawn through ventilation holes62into the upstream cavity148during a puff. Other low density, low filtration materials can also be used to construct the tubular segment152.

In a preferred embodiment, the ventilation zone60comprises a plurality of ventilation holes62arranged in one or more circumferential rows, which extend through the tipping paper50and the highly permeable wrapping paper30, and optionally/partially into or through the tubular segment152. This arrangement facilitates the use of off-line laser perforation techniques to provide ventilation holes62. Other techniques may be used to create the ventilation zone60such as using on-line, laser perforation, mechanical pin perforation techniques, electrostatic perforation and other techniques. In accordance with an embodiment, the ventilation holes62in the tipping paper50allow atmospheric air to be drawn into the restricting ventilation zone40, through the tubular segment152, and into the upstream cavity148. When a hollow acetate tube forms at least part of the tubular segment152, in accordance with another embodiment, perforations need not be made in the upstream cavity148because the material is air permeable.

In accordance with an embodiment, it may be desirable to provide several ventilating zones60at locations in superposing relation to the one or more flow restriction passages or holes130provided in the flow restricting filter segment44so as to achieve the more elevated ventilation levels. Preferably, the ventilation zone60and the one or more flow restriction passages or holes130in the flow restricting filter segment44achieve a ventilation level of the smoking article of at least 25% and more preferably at least 50% to 90%.

Referring toFIG. 3, in accordance with a further embodiment, the smoking article10is comprised of a densely packed tobacco rod20and a filter40, which are wrapped in highly permeable wrapping paper30. The filter40preferably includes a diffusion zone or segment150comprised of an upstream cavity148comprised of a hollow tubular segment152, a flow restricting segment44, a downstream cavity146, and a downstream segment46of filtering material.

In accordance with one embodiment, the tobacco rod20has a packing density of 10% to 200% higher than a regular tobacco rod. The length22of the tobacco rod20is preferably 2/10 to 8/10 of the length of a regular tobacco rod. In accordance with an embodiment, the densely packed tobacco rod20provides for a slower burning tobacco rod20as compared to a regular or commercially available tobacco rod. In accordance with an embodiment, the tobacco rod20has a length of about 25 to 35 mm and more preferably about 30 mm for a smoking article10having an overall length of about 80 to 90 mm and more preferably about 84 mm.

The diffusion zone or segment150is preferably comprised of a media which allows significant air inflow to dilute and transfer the smoke directly to the downstream portion of filter40. In accordance with an embodiment, the diffusion zone150includes a highly permeable cellulose acetate hollow tubular segment152, which is surrounded by a highly permeable wrapping material30with varying permeability, and which may optionally include additional ventilation60in the form of at least one row of perforations62.

The filter40also includes a flow restricting segment44, which includes at least one flow restriction element45with a downstream cavity146as a flow buffer for a desirable draw resistance (i.e., pressure drop) without significant filtration effect to the tar in the mainstream smoke. In an alternative embodiment, low efficiency filters, such as whistle-through cellulose acetate filter or a recess filter, can be placed adjacent to the flow restriction element45to achieve optimized flow control.

In accordance with an embodiment, the filter40includes a flow restriction element45in the form of an annular disk132that defines at least one or more flow restriction passages or holes130(or flow restriction) of reduced diameter. In accordance with an embodiment, the hole130preferably has a diameter of about 0.5 mm to about 2.5 mm and more preferably about 0.5 mm to 2.0 mm, and a length of about 0.5 mm to 20 mm, and more preferably about 5 mm to 15 mm.

The downstream cavity146is preferably formed with a downstream tubular body portion147that spaces the flow restriction element45a predetermined distance apart from the downstream segment46of filtering material, preferably about 1 mm to about 6 mm, and more preferably about 1 mm to 3 mm. Preferably, the distance between the ventilation zone60and the downstream segment46of filtering material is at least 5 mm, and more preferably in the range of about 5 mm to about 12 mm.

For example, the flow restriction element45can be formed of a polymer column including a single, centered hole130having a diameter of about 1.0 mm. A highly permeable cellulose acetate hollow tubular segment152can be positioned adjacent to and upstream of the flow restriction element45to provide sufficient air inflow. The total pressure drop is largely controlled by the length of the polymer column and the diameter of the single, centered hole.

Referring toFIG. 4, in accordance with a further embodiment, the flow restriction element45is a polymer column47with a centered bypass passage or hole130preferably having a diameter of about 0.5 mm to about 2.0 mm and a length of about 1.0 mm to about 20.0 mm and more preferably about 5.0 mm to about 10.0 mm, or a high density/low permeability cellulose acetate column with a central bypass passage or hole130preferably having a diameter of about 0.5 mm to about 2.0 mm and a length of about 1.0 mm to about 20.0 mm and more preferably about 5.0 mm to about 10.0 mm.

It is to be appreciated that in all embodiments, the filter may be constructed from simple combining techniques typically used in the industry for manufacturing cigarettes at high speeds. Additionally each embodiment includes support about the cavity146so as to provide desired firmness throughout length of the filter40.

In accordance with an embodiment, the diffusion zone150includes a highly permeable cellulose acetate hollow tubular segment152, which is surrounded by a highly permeable wrapping material30with varying permeability, and which may optionally include additional ventilation60in the form of at least one row, and more preferably at least two or three rows of ventilation holes or perforations62.

In accordance with an embodiment, the ventilation60in combination with tobacco rod20and filter40with a highly permeable wrapping paper30provides the necessary amount of resistance to draw while maintaining the desired degree of high ventilation throughout the smoking article10. The later attribute is achieved by placement of the ventilation zone60upstream of the flow restricting segment44. Furthermore, placing the ventilation in zone60in spaced apart relation to the mouthpiece or downstream plug48of filtering material assures mixing of air drawn into the filter40through the ventilating zone60with mainstream smoke drawn from the tobacco rod20.

In accordance with an embodiment, the flow restricting segment44includes a flow restricting element45(or orifice or flow regulator) comprised of a high-density capillary (cellulose acetate) tube having a 1 mm inner diameter and an 8 mm outer diameter, which has shown to provide about 47 or about 87 mm H2O pressure drop at a length of 5 mm or 10 mm, respectively.

FIG. 5is a side view of a smoking article10in accordance with an embodiment. As shown inFIG. 5, the smoking article10includes a densely packed tobacco rod20, an upstream cavity148formed with a hollow tubular segment152, an upstream segment of filtering material42, flow restricting segment44in the form of a flow restricting element45(or orifice or flow regulator), a downstream cavity146adjacent to the flow restricting segment44, and a downstream segment of filtering material46. In accordance with an embodiment, the downstream cavity146is defined at least in part by a tubular filter segment147.

In accordance with an embodiment, the smoking article10has an overall length of about 84 mm comprising of a tobacco rod20of about 30 mm in length, a hollow tubular segment152of about 30 mm in length, an upstream segment of filtering material42of about 5 mm in length, a flow restricting element45of about 5 mm in length, a cavity146adjacent to the flow restricting element45of about 5 mm in length, and a downstream segment of filtering material46of about 9 mm in length. The smoking article10is preferably wrapped in a highly permeable wrapping material or paper30, which extends from the lit end12of the tobacco rod20to the mouth or buccal end18of the filter40. The wrapping material or paper30preferably has a length of about 84 mm. In addition, the tipping material or paper50on the mouth or buccal portion of the smoking article10preferably has a length of about 27 mm.

FIGS. 6 and 7are charts showing the smoke chemistry for commercially available cigarettes and a series of smoking articles as shown inFIG. 5.

FIGS. 8(a) and8(b) are graphs showing “Per TPM Light Gas Delivery” versus “TPM Delivery” for commercially available cigarettes and a smoking article as shown inFIG. 5, respectively.

FIG. 9is a graph showing Dilution (%) and RTD (mm H2O) versus TPM Delivery Rate (mg) for a series of smoking articles as shown inFIG. 5.

FIGS. 10(a) and10(b) are graphs showing Total Pressure Drop and Percentage Dilution versus Length of Rod for a series of smoking articles as shown inFIG. 5.

FIG. 11is a side view of a smoking article10in accordance with an embodiment as shown inFIG. 5, and wherein the Pressure Drop (RTD) through each section (Ri, ri), Flowrate through each section (Fi, fi) and Total Flow (F) parameters for various sections are shown. In accordance with an embodiment, the correlations of constant and variables are as follows:

Total flowrate at the outlet of the mouth-end CA filter:
F=35 cc per 2 seconds(cc/2s)(FTC, 17.5 cc/s); 45 cc/2s; 55 cc/2s−
The Only Input

Therefore, the smoke delivery rate S and ventilation V:
S=F1/F; V=(f1+f2+f3)/F

Pressure drop to the inlet of the CA hollow tube:
R1′=R1

Pressure drop through and at the outlet of the CA hollow tube:
R2′=R2+R1′×r1/(R1′+r1)
R3′=R3+R2′×r2/(R2′+r2)
R4′=R4+R3′×r3/(R3′+r3)
R=R4′+R5+R6+R7

Correlation of pressure drop and flowrate:
(ri,fi);(Ri,Fi)i=1˜7 of each section

FIGS. 12-17are side views of smoking articles10showing the design specification on the tobacco rod20(i.e., combustion zone), hollow tubular segment152(i.e., distribution zone) and the upstream segment of filtering material42, the flow restricting element45, the cavity146adjacent to the flow restricting element45, and the downstream segment of filtering material46(i.e., delivery zone) in accordance with various embodiments.

It will be understood that the foregoing description is of the preferred embodiments, and is, therefore, merely representative of the article and methods of manufacturing the same. It can be appreciated that variations and modifications of the different embodiments in light of the above teachings will be readily apparent to those skilled in the art. Accordingly, the exemplary embodiments, as well as alternative embodiments, may be made without departing from the spirit and scope of the articles and methods as set forth in the attached claims.