US20110083687A1

US20110083687A1 - Cigarette filter to reduce smoke deliveries in later puffs

Info

Publication number: US20110083687A1
Application number: US12/577,039
Authority: US
Inventors: Raquel Olegario; San Li; Mike Braunshteyn; Roland W. Dwyer; Richard Jupe
Original assignee: Philip Morris USA Inc
Current assignee: Philip Morris USA Inc
Priority date: 2009-10-09
Filing date: 2009-10-09
Publication date: 2011-04-14
Also published as: WO2011042175A1

Abstract

A smoking article having a tobacco rod adapted to produce mainstream smoke, and a filter having an upstream end portion and a downstream end portion, and wherein the filter is arranged to receive mainstream smoke at the upstream end portion. The filter includes a first filter segment of low particulate efficiency at the upstream end portion; a channeled flow segment adjacent to the first filter segment, the channeled flow segment including a flow channel establishing a substantial portion of a predetermined resistance to draw of the smoking article; a mouthpiece filter segment of low particulate efficiency at the downstream end portion; and a tubular body segment at least partially defining a portion of a cavity between the mouthpiece filter and the channeled flow segment. Tipping paper attaches the filter with the tobacco rod and includes an air-admissible ventilation zone at a location along the tubular body segment.

Description

WORKING ENVIRONMENT

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 for the shortfall in RTD. In the past, high-density cellulose acetate filter segments were used to address the short fall. However such filtered segments tended to reduce tar delivery (FTC), with little or no effect upon gas phase components 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 filtered (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. However, highly ventilated cigarettes have drawbacks in resistance to draw (RTD) as previously discussed. It can be appreciated that with a flow restricting orifice in the cigarette filter, the mainstream smoke is forced to flow through the orifice. With the filter ventilation introduced downstream from this orifice, the ventilation level is dependent on the overall resistance to draw (RTD) upstream from the ventilation holes. For a given number of ventilation holes and size, the filter ventilation level increases as the upstream RTD increases. At a given filter efficiency, increased filter ventilation reduces the smoke tar delivery.
In a conventional filtered cigarette, per puff tar delivery increases as smoking progresses through the puff count. This is mainly due to the combination of reduced filtration from the tobacco rod, re-vaporization of tar build up on the tobacco rod from previous puff(s), and a decreased filter ventilation contribution as the puff (char line) progresses and the upstream RTD reduces. The tar delivery of the last puff could be twice as much as the first and/or second puffs. Reducing the degree of change from early to later puffs in principle would permit for a more consistent sensorial experience, and reducing the total tar delivery, without significantly affecting the overall smoking experience.
Accordingly, it would be desirable for a smoking article to address the phenomena of inconsistent smoke deliveries from puff to puff, since it is known that the delivered tar from earlier puffs is less than the delivery of the later puffs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a smoking article in accordance with one embodiment.

FIG. 2 is a cross-sectional view of the smoking article of FIG. 1 in accordance with another embodiment.

FIG. 3 is a cross-sectional view of a smoking article in accordance with another embodiment.

FIG. 4 is a cross-sectional view of the smoking article of FIG. 3, in accordance with a further embodiment.

FIG. 5 is a graph showing the puff by puff total particulate matter (TPM) deliveries of a conventional cellulose acetate (CA) filtered cigarette.

DETAILED DESCRIPTION

In accordance with one embodiment, a channeled flow segment is designed such that during the process of smoking the cigarette, the resistance to flow of smoke through a channel within the segment increases as a result of tar accumulation or build-up within the channel. The increased resistance, as smoking progresses, causes the filter ventilation to increase and the delivered tar is decreased in the later puffs. In accordance with another embodiment, the increased resistance to draw (RTD) and filter ventilation during the later puffs can also be designed so that it is difficult to smoke the last few puffs (where tar per puff can be twice as much as the first few puffs) thereby reducing the total tar delivery without significantly impacting the overall smoking experience. In addition, depending on the size (inner diameter) and the length of the flow channel, a desired pressure drop across the segment can be achieved.
Referring to FIG. 1, a preferred embodiment provides a smoking article 10 comprising a tobacco rod 20 and a filter 30 connected with the tobacco rod 20 by an outer wrapper or tipping paper 28. Preferably, the filter 30 comprises a first filter segment 40 at an upstream portion 32 of the filter 30, a second or mouthpiece filter segment 50 at downstream end portion 34 of the filter 30, and a channeled flow segment 60 situated between the first and mouthpiece filter segments 40, 50. In accordance with a preferred embodiment, the first and mouthpiece filter segments 40, 50 are low particulate efficiency filter segments constructed from cellulose acetate tow.
As shown in FIG. 1, smoking articles 10 in the form of cigarettes typically include a generally cylindrical rod 20 of smokable material 22, contained in a circumscribing porous wrapping material or paper wrapper 24. The rod 20 is typically referred to as a “tobacco rod” and has a lit end or upstream end 12 and a downstream or filter end 14. The smokable material 22 is preferably a shredded tobacco or tobacco cut filler. However, any suitable smokable material 22 can be used.
The filter 30 is adjacent to the filter end 14 of the tobacco rod 20 such that the filter 30 and tobacco rod 20 are axially aligned in an end-to-end relationship, preferably abutting one another. The filter 30 preferably has a generally cylindrical shape, and the diameter thereof is essentially equal to the diameter of the tobacco rod 20. The ends (i.e., upstream end 16 and downstream end 18 (i.e., mouth end or buccal end) of the filter 30 are open to permit the passage of air and smoke therethrough.
The filter 30 is preferably attached to the tobacco rod 20 by an outer wrapper or tipping paper 28, which circumscribes both the entire length of the filter 30 and an adjacent region of the tobacco rod 20. The tipping paper 28 is typically a paper like product; however, any suitable material can be used.
As shown in FIG. 1, the channeled flow segment 60 is adjacent to the first filter segment 50. In accordance with a preferred embodiment, the channeled flow segment 60 including the flow channel 62 establishes a substantial portion of a predetermined resistance to draw of the smoking article 10. The flow channel 62 is preferably coaxially or concentrically positioned within the channeled flow segment 60. However, in an alternative embodiment, one or more flow channels 62 can be positioned on an outer periphery of the channeled flow segment 60. In accordance with a preferred embodiment, the channeled flow segment 60 and the flow channel 62 each have a length of about 1 mm to 15 mm. The flow channel 62 also preferably has a diameter of approximately .5 mm to 2 mm.
The channeled flow segment 60 may 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. In accordance with a preferred embodiment, the flow channel 62 is generally straight, having a relatively constant diameter such that the channel 62 extends in a continuous direction without bending from an upstream end to a downstream end of the channeled flow segment 60. Alternatively, the flow channel can be a spiral channel, or other suitable configuration.
In accordance with an embodiment, the flow channel 62 is at least in part defined by a cylindrical tubular member 48, which is constructed from a relatively heavy filter plug wrap or paper. The tubular member 48 preferably extends from an upstream end to a downstream end of the segment 60.
It can be appreciated that the channeled flow segment 60 is preferably sized to contribute sufficient pressure drop such that the smoking article 10 presents a resistance to draw of at least 50 mm water or greater, and more preferably in the range of 70-120 mm water. It can be appreciated that as the channeled flow segments 60 becomes clogged, the resistance to draw and/or flow through the flow channel 62 increases due to the tar build up. Preferably, the channeled flow segment 60 has a diameter of approximately 7.0 to 8.0 mm, and more preferably approximately 7.4 to 7.8 mm.
In accordance with one embodiment, a tubular body segment 64 at least partially defining a portion of a cavity 66 is situated between the mouthpiece filter 50 and the flow channel 62 of the channeled flow segment 60. The filter 30 can also include a second upstream tubular body portion (not shown) that spaces the channeled flow segment 60 a predetermined distance apart from the first filter segment 40.
The smoking article 10 also preferably includes a ventilating zone 70 comprised of a first row (and optionally second and possibly third rows) of ventilation holes or perforations 72, each of which extend through the tipping paper 28, the plug wrap 26 and the tubular body segment 64.
Preferably the ventilating zone 70 is located near or adjacent to the channeled flow segment 60 so that air drawn through the ventilation zone 70 is allowed to mix with the mainstream smoke from the flow channel 62 before arriving at the mouthpiece filter segment 50. The distance between the ventilating zone 70 and the mouthpiece filter segment 50 is preferably at least 5 mm and more preferably in the range of 5-12 mm. In accordance with a preferred embodiment, the holes or perforations 72 of the ventilating zone 70 achieve a ventilation level of the smoking article 10 of at least 25% and more preferably at least 50% to 90%.
During an initial puff or puffs, mainstream smoke is drawn from the lit end through the tobacco rod 20 to the downstream end of the filter 30, and drawn through the flow channel 62. Thus, by the time of subsequent puffs on the smoking article 10, the flow channel 62 is partially blocked. It can be appreciated that the resistance to draw (RTD) and the flow distribution of the flow channel 62 can be depend on several factors including the length of the filter 30 and the flow channel 62, the inner diameter of the flow channel 62, and the nature or type of filter materials within the first filter segment 40 and the mouthpiece segment 50.
The first filter segment 40 and the mouthpiece filter segment 50 are preferably a starch-based, polypropylene, or plasticized cellulose acetate tow, filter paper or other suitable material. The first filter segment 40 and the mouthpiece segment 50 can also be constructed from a gathered web (e.g., polypropylene web, polyester web, cellulosic web or starch-based web).
In accordance with a preferred embodiment, as the smoking progresses, tar gradually builds up inside and at the ends of the flow channel 62. Resistance to flow through the flow channel 62 increases due to the tar build up as shown in FIG. 2, and as a consequence the filter ventilation increases and the tar deliveries decreases in the later puffs. A more consistent puff-by-puff tar delivery is thus achieved attributable to the lowered delivery of the later puffs. In addition, the increased filter ventilation results in a decreased amount of tobacco burnt and smoke delivered.
In accordance with an embodiment, the increased resistance to draw (RTD) and filter ventilation during the later puffs can also be designed so that it is difficult to smoke the last few puffs. It is generally accepted that the first few puffs or earlier puffs are more important in terms of the smoking experience, and wherein the reduced tar deliveries in the last few puffs from this novel filter design can have overall tar reduction with minimum impact on the smoking experience. It can also be appreciated that the flow channel 62 can be fine tuned to control the tar build up, by adjusting or changing the size of the channel 62, including the length and diameter thereof, so that the resistance-to-draw (RTD) is acceptable and ventilation of the filter 30 achieves desired tar delivery from the smoking article 10.
In accordance with another embodiment, the flow channel 62 can include or be coated with a material 49 (FIG. 2) such as a sintered porous plastic. In accordance with an embodiment, the flow channel is filled with a sintered porous plastic. It can be appreciated that sintered porous plastics can allow “dry” air flow at a given resistance to draw (RTD). Alternatively, at another given resistance to draw (RTD), due to the capillary action of the sintered porous plastic materials, the resistance to draw (RTD) can increase when a “wet” stream is delivered in the flow channel 62.
In accordance with another embodiment, as shown in FIGS. 3 and 4, the flow channel 60 can be in the form of a thin plate 100 (0.2 mm to 2 mm in thickness) with at least one orifice (or flow passage) 110 with a diameter of 0.2 mm to 0.6 mm. The number of orifices 110 is not limited, but preferably the plate 100 has 2-8 orifices, and is mostly determined by the pressure drop introduced by this thin plate with orifices. The pressure drop is preferably in the range of 100 to 500 mm water drop. As the smoking progresses, smoke tar gradually builds up and partially blocks the orifices 110 which cause pressure drop increase. This pressure drop increase would force more air flowing through the filter ventilation holes 72, or ventilation level increases. The increased filter ventilation will reduce air flowing into the burning coal and reduce the smoke generated. In other words, the cigarette filter 30 will have lower ventilation in the earlier puffs and higher ventilation in later puffs. The net effect of gradual increase of ventilation as smoking processes is more smoke in the earlier puffs and less smoke in the latter puffs, resulting more consistent puff by puff smoke deliveries.
It is to be appreciated that in all embodiments, the filter 30 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 cavity 66 to provide desired firmness throughout length of the filter 30.
FIG. 5 shows puff by puff total particulate matter (TPM) (mg) deliveries of a conventional cellulose acetate filtered cigarette. In general, smoke tar tracks with smoke total particulate matter (TPM). As shown in FIG. 5, the average total particulate matter (TPM) of the first three puffs is 1.0 mg/puff, and the average of the last three puffs is 1.8 mg/puff. The total particulate matter (TPM) from the whole cigarette is 11.3 mg, with a total of 8 puffs. Accordingly, if the total particulate matter (TPM) from the last three or four puffs of the cigarette are kept at around 1.0 mg or so per puff, or similar to that of the first three puffs, as indicated by the dotted line in FIG. 5, the smoking articles 10 as shown in FIGS. 1-4 are able to deliver 8-9 mg total particulate matter (TPM) with a smoking experience similar to that of a 11 mg total particulate matter (TPM) product, at least for the first half of smoking.
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 many 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.

Claims

1. A smoking article comprising:

a tobacco rod adapted to produce mainstream smoke;

a filter having an upstream end portion and a downstream end portion, the filter arranged to receive mainstream smoke at the upstream end portion, the filter comprising:

a first filter segment of low particulate efficiency at the upstream end portion;

a channeled flow segment at a location downstream of the first filter segment, the channeled flow segment including a flow channel establishing a substantial portion of a predetermined resistance to draw of the smoking article;

a mouthpiece filter segment of low particulate efficiency at the downstream end portion; and

a tubular body segment at least partially defining a portion of a cavity between the mouthpiece filter and the flow channel of the channeled flow segment; and

tipping paper attaching the filter with the tobacco rod and including an air-admissible ventilation zone at a location along the tubular body segment.

2. The smoking article of claim 1, wherein the channeled flow segment is spaced from the mouthpiece filter segment by a distance sufficient to reduce impaction of a mainstream smoke component upon an upstream end portion of the mouthpiece filter.

3. The smoking article of claim 1, wherein the air-admissible ventilation zone comprises a row of perforations extending through the tipping paper and the tubular body segment.

4. The smoking article of claim 1, wherein the ventilation zone is spaced from the mouthpiece filter segment by a distance sufficient to promote mixing of air drawn through the ventilation zone and mainstream smoke drawn from the tobacco rod.

5. The smoking article of claim 1, wherein at least one of the first filter segment and the mouthpiece filter segments comprises cellulose acetate tow of low resistance to draw.

6. The smoking article of claim 1, wherein the flow channel is coaxially positioned within the channeled flow segment.

7. The smoking article of claim 1, wherein the flow channel is in an outer periphery of the channeled flow segment.

8. The smoking article of claim 1, wherein the flow channel has a relatively constant diameter extending from an upstream end to a downstream end of the channeled flow segment.

9. The smoking article of claim 1, wherein the flow channel is a spiral channel.

10. The smoking article of claim 1, wherein the flow channel includes a sintered porous plastic.

11. The smoking article of claim 1, wherein the channel flow segment is a a plate having at least one orifice.

12. The smoking article of claim 11, wherein the plate has a thickness of less than 2 mm and the at least one orifice has a diameter of 0.2 mm to 0.6 mm.

13. A filter having an upstream end portion and a downstream end portion and arranged to receive mainstream smoke at the upstream end portion, the filter comprising:

a tubular body segment at least partially defining a portion of a cavity between the mouthpiece filter and the flow channel of the channeled flow segment.

14. The filter of claim 13, wherein the channeled flow segment is spaced from the mouthpiece filter segment by a distance sufficient to reduce impaction of a mainstream smoke component upon an upstream end portion of the mouthpiece filter.

15. The filter of claim 13, wherein at least one of the first filter segment and the mouthpiece filter segments comprises cellulose acetate tow of low resistance to draw.

16. The filter of claim 13, wherein the flow channel is coaxially positioned within the channeled flow segment.

17. The filter of claim 13, wherein the flow channel is in an outer periphery of the channeled flow segment.

18. The filter of claim 13, wherein the flow channel has a relatively constant diameter extending from an upstream end to a downstream end of the channeled flow segment.

19. The filter of claim 13, wherein the flow channel is a spiral channel.

20. The filter of claim 13, wherein the flow channel includes a sintered porous plastic.

21. A method of reducing total FTC tar delivery of a smoking article by drawing mainstream smoke during each puff through an upstream, channeled filter segment and a downstream filter portion having a ventilation zone, said upstream channeled filter segment accumulating tar as smoking progresses through a puff count such that delivered FTC tar is decreased in the later puffs of the puff counts when compared to a conventional cigarette.