WO2012042199A1

WO2012042199A1 - Tobacco smoke filter

Info

Publication number: WO2012042199A1
Application number: PCT/GB2011/001398
Authority: WO
Inventors: Paul F. Clarke; Patrick G. Meredith
Original assignee: Filtrona International Limited
Priority date: 2010-09-29
Filing date: 2011-09-27
Publication date: 2012-04-05
Also published as: EP2621294B1; HUE045486T2; KR20130139266A; RU2013114719A; PL2621294T3; GB201016387D0; RU2603597C2; CN103281919A; KR101987886B1; LT2621294T; EP2621294A1; JP2013538580A; TW201216873A; CN103281919B; JP6462212B2; TWI589233B

Abstract

A tobacco smoke filter or filter element comprising: a longitudinally extending core of tobacco smoke filtering material including an additive spaced longitudinally from a first end of the core; a first wrapper around the core; and a second wrapper around the first wrapper; the first wrapper defining at least with (e.g. between itself and) the second wrapper at least one channel (e.g. 5 to 23 channels) extending longitudinally of the filter from at least one end thereof.

Description

TOBACCO SMOKE FILTER

The present invention relates to filters and filter elements for smoking articles such as cigarettes.

Cigarette filters containing particulate additives, notably activated carbon, are well known in the tobacco industry. The vast majority of such filters comprise a number of segments abutted longitudinally, in which the mouth end segment does not contain any particulate additives and so presents an acceptable end appearance, whilst one or more of the upstream segments comprise or contain particulate additives. It is known that such multi-segment filters are more complex and costly to produce than "single section" filters (which are formed from one (distinct) section of filtering material rather than two or more segments of filtering material), because of the requirement to make the various segments by separate processes and subsequently correctly arrange and abut the different segments to form the multi-segment filter rod; single section filters may be made e.g. by a single machine in a one-pass process.

The present applicant has previously developed 'monocarbon' filters - i.e. single section filters incorporating carbon that have at least one end free of particulate additive and which can be manufactured in a one-pass process. These are the 'Active Patch' (see GB 2261152) and the 'Smooth Core' (see WO 2006/059134) filters. These respectively feature particulate additive on either a portion of the inner face of the wrapper or in a centrally located pod. The applicant has also developed 'CPF' filters' (e.g. see GB 2133269). These feature an inner wrap that has embossed grooves over part of its length and have the advantage of providing enhanced filtration efficiency and/or lower pressure drop compared to standard cellulose acetate filters. In addition, they can provide a distinctive end appearance. Such filters can be used as a single section filter or as a segment within a multi-segment filter. In GB 2261152, it was proposed that features of the CPF filter could be combined with those of the Active Patch filter to create a single section CPF filter containing, e.g. carbon. Such filters can be termed 'APF/CPF'. However, a disadvantage of these filters is that they are prone to higher levels of carbon carry-over ('CCO') - that is, during manufacture stray carbon granules can be inadvertently transferred to the groove region of the inner wrap from which they can contaminate the appearance of the filter. It is difficult to remove said stray granules during filter manufacture. According to the present invention there is provided a (e.g. single section) tobacco smoke filter or filter element comprising: a longitudinally extending (e.g. single section) core of tobacco smoke filtering material including an additive (e.g. a particulate additive) spaced longitudinally from a first (downstream) end of the core; a first wrapper (e.g. of air- permeable material) around the core; and a second wrapper around the first wrapper; the first wrapper defining at least with (e.g. between itself and) the second wrapper at least one channel extending longitudinally of the filter from at least one end thereof. Preferably the first wrapper defines (at least with the second wrapper) at least one channel extending longitudinally from a first (downstream) end of the filter. Preferably the first wrapper defines at least with (e.g. between itself and) the second wrapper at least five channels (for example 5 to 23 channels, for example 9 to 20 channels), extending longitudinally of the filter from at least one end thereof. A filter or filter element of around 24-25 mm circumference may include, for example, 14 to 20 channels. A filter or filter element of around 16-17 mm circumference may include, for example, 9 to 14 channels.

The particulate additive is spaced (distanced) longitudinally from the first (downstream) end of the core such that it is not visible from the first (downstream or mouth) end of the core. In an example, the longitudinally extending core of tobacco smoke filtering material comprises a (e.g. single section) rod shaped core of tobacco smoke filtering material having fully enclosed (e.g. embedded) therewithin a (or at least one) pocket of additive (e.g. particulate additive). The rod shaped core of tobacco smoke filtering material may optionally have an additional wrapper (e.g. porous or non porous) engaged around the rod shaped core. The provision of the fully enclosed pocket of additive within the core of the tobacco smoke filtering material has the effect that the additive is longitudinally spaced (distanced) from the first (downstream) end of the core (because there is tobacco smoke filtering material between the pocket of additive and the first end of the core).

According to the present invention in one aspect there is provided a (e.g. single section) tobacco smoke filter or filter element comprising: a longitudinally extending (e.g. single section) core of tobacco smoke filtering material including an additive (e.g. a particulate additive) spaced longitudinally from a first (downstream) end of the core; a first wrapper (e.g. of air-permeable material) around the core; and a second wrapper around the first wrapper, the first wrapper defining at least with (e.g. between itself and) the second wrapper at least one channel extending longitudinally of the filter from one end thereof; wherein the longitudinally extending core of tobacco smoke filtering material comprises a rod shaped core of tobacco smoke filtering material having fully enclosed (e.g. embedded) therewithin a (or at least one) pocket of additive (e.g. particulate additive). Preferably the first wrapper defines at least with (e.g. between itself and) the second wrapper at least five channels (for example 5 to 23 channels, for example 9 to 20 channels), extending longitudinally of the filter from at least one end thereof. A filter or filter element of around 24-25 mm circumference may include, for example, 14 to 20 channels. A filter or filter element of around 16-17 mm circumference may include, for example, 9 to 14 channels.

Preferably the first wrapper is of air permeable material. In other words, preferably the first wrapper is an air permeable wrapper. The first wrapper may be, for example, air permeable filtering paper (e.g. corrugated air permeable filtering paper) or a wrapper of cellulose acetate (e.g. corrugated air permeable cellulose acetate).

Preferably the first wrapper is corrugate, thereby providing (defining) at least with (e.g. between itself and) the second wrapper channels extending longitudinally of the filter from at least one end thereof. The first wrapper may be corrugate, the corrugations providing (defining) [e.g. together with the second wrapper] 5 or more channels, for example 5 to 23 channels, for example 9 to 20 channels, extending longitudinally of the filter from at least one end thereof. A filter or filter element of around 24-25 mm circumference may include, for example, 14 to 20 channels (provided by the corrugations). A filter or filter element of around 16-17 mm circumference may include, for example, 9 to 14 channels (provided by the corrugations). Herein the term corrugate or corrugated includes the meaning shaped into folds including parallel and alternating ridges and grooves.

Preferably the corrugations in the first wrapper are embossed grooves (e.g. formed by embossing the material of the first wrapper). The first wrapper may, for example, be a sheet having a profiled (e.g. embossed, corrugated) surface, the sheet being wrapped around the core so that the profiled surface facing the second wrapper (i.e. facing radially outwards) forms channels with the second wrapper. It will be appreciated that the corrugate first wrapper will be wrapped around the core so the corrugations (and channels) are oriented longitudinally (e.g. substantially longitudinally) along the axial direction of the core. Each channel may be provided by a corrugation of the first wrapper, and is preferably closed or blocked at the end remote from the end of the filter from which the channel extends. Generally, the core surface conforms to the radially inward facing (profiled) surface of the first wrapper (i.e. the surface of the first wrapper which faces the core). In another example, the core surface does not conform to the radially inward facing (profiled) surface of the first wrapper; in this embodiment, the first wrapper may define longitudinally extending channels with the core as well as with the second wrapper. In another example the first wrapper is profiled on only one surface, the sheet being wrapped around the core so that the profiled surface faces the second wrapper (i.e. facing radially outwards) to form channels with the second wrapper, the enwrapped core surface conforming to the unprofiled corrugated inner surface of the first wrapper, leaving channels only between the first and second wrapper.

Thus, the present invention may provide a single section filter with a 'pod', or fully enclosed pocket of particulate additive axially located centrally (e.g. as described in WO 2006/059134), and a corrugated inner wrap that is embossed with grooves over part of its length, which form channels (with the second wrapper). In this way, the manufacturing cost and complexity associated with particulate-bearing multi-segment filters and the CCO disadvantages of APF/CPF single section filters can be avoided. Furthermore, it enables great flexibility in filter design. By controlling such parameters as the size and location of the central pod (pocket) and the length and location of the grooved portion of the first (inner) wrapper, it is possible to channel the smoke through the filter in such a way that the filtration performance, taste experience and end appearance can be varied. For example, when a central pod of activated carbon granules is used, smoke can be directed away from the pod if the channels ("fluted region") occupy a similar longitudinal region of the filter to the pod therefore creating less of a 'carbon taste' to the smoker. Conversely, smoke can be preferentially directed through the pod if the channels (fluted region) occupy a different longitudinal region of the filter to the pod, therefore creating more 'carbon taste' for the smoker (if the pod includes carbon) or other taste (if the pod includes other flavouring agent). In addition, the filter enables higher tar retention (at the same pressure drop) or lower pressure drop (at the same tar retention) than conventional 'Smooth Core' filters.

The longitudinally extending core (e.g. single section longitudinally extending core) of tobacco smoke filtering material may have fully enclosed (e.g. embedded) therewithin a single pocket of additive (e.g. particulate additive) close to the second end (e.g. the upstream tobacco end in a filter cigarette) and remote from the first end (e.g. the downstream or buccal or mouth end), or close to (but spaced longitudinally from) to the first end and remote from the second end. The longitudinally extending core of tobacco smoke filtering material may have fully enclosed (e.g. embedded) therewithin a single pocket of additive (e.g. particulate additive) positioned equidistantly between the second end of the core (e.g. the tobacco end) and the first end of the core (e.g. the mouth end). The single longitudinally extending core of tobacco smoke filtering material may have fully enclosed therewithin one or more (e.g. two, three, four) separate pockets of additive (e.g. particulate additive). The fully enclosed (e.g. embedded) pocket(s) of additive may taper towards one or both ends - e.g. may be of a generally ellipsoidal configuration. If there is more than one pocket of additive, these may have even longitudinal spacing. Other pocket dispositions are possible - e.g. relatively close longitudinal spacing alternating with longer spacing - it being possible to achieve this by appropriate adjustment of the manufacturing process. The longitudinally extending core of tobacco smoke filtering material comprising a rod shaped core of tobacco smoke filtering material having fully enclosed (e.g. embedded) therewithin a (or at least one) pocket of additive (e.g. particulate additive) may be manufactured, for example, by the methods and apparatus disclosed in WO 2006/059134.

The filtering material may be for example any of those materials (usually filamentary, fibrous, web or extruded) conventionally employed for tobacco smoke filter manufacture. The filtering material may be natural or synthetic filamentary tow, e.g. of cotton or plastics such as polyethylene or polypropylene, or cellulose acetate filamentary tow. It may be, for example, natural or synthetic staple fibres, cotton wool, web material such as paper (usually creped) and synthetic non-wovens, and extruded material (e.g. starch, synthetic foams).

The additive may be a particulate additive. The particulate additive may any particulate additive suitable for use in a tobacco smoke filter - e.g. activated carbon, zeolite, ion exchange resin (e.g. a weakly basic anion exchange resin), sepiolite, silica gel, alumina, molecular sieves, carbonaceous polymer resins and diatomaceous earths. The particulate additive may be a mixture of two, or more, materials. The additive may include a smoke modifying agent (for example a flavourant). This may be any smoke modifying agent (e.g. flavourant) known or suitable for use in a smoking article such as a cigarette, for example flavourant such as menthol, spearmint, clove oil etc. The flavourant may be any flavouring agent known for use in tobacco smoke filters or filter elements. For example, the flavouring agent may be menthol, spearmint, peppermint, nutmeg, cinnamon, clove, lemon, chocolate, peach, strawberry, vanilla etc. A preferred smoke modifying agent (flavourant) is menthol. For example, the additive may be sepiolite granules to which menthol flavourant has been applied. If the longitudinally extending core of tobacco smoke filtering includes fully enclosed (e.g. embedded) pocket(s) of additive embedded therein, the additive may be a particulate additive such as activated carbon (see above), which is for example enclosed within the filtering material as a discrete pocket or pod of particles of particulate additive which is substantially separate from, and fully enclosed within, the filtering material. In another example, the fully enclosed (e.g. embedded) pocket(s) of additive may be a frangible capsule or capsules, or one or a plurality of frangible microcapsules. The capsule(s) or microcapsule(s) may contain a variety of media - e.g. a smoke modifying agent such as a flavourant (such as those flavourants disclosed above) and/or a liquid, solid or other material e.g. to aid smoke filtration. The use of capsules or microcapsules is well known in the art. The weight of the additive (e.g. a particulate additive of around 0.5 g/cm³ density) fully enclosed within the longitudinally extending core of tobacco smoke filtering material may, for example, be between 10 and 65 mg, for example 20 and 50mg, for example between 25 and 40mg, per filter, for a filter of 20 to 30mm length. The weight of the first additive may, for example, be between 40 and 65 mg per filter, for a filter of 20 to 30mm length (e.g. if a high loading is required). The weight of the first additive may, for example, be between 10 and 40 mg per filter, for a filter of 20 to 30mm length (e.g. if a lower loading is required).

The filter or filter element may include at least one channel extending longitudinally of the filter from a first (downstream) end thereof, and at least one channel extending longitudinally of the filter from the second (upstream), each channel extending only part of the core length.

The (or one or more) channels may extend longitudinally from the first (downstream) end of the filter to the second (upstream) end of the filter. However, it is preferred that at least one portion of the filter or filter element includes no longitudinally extending channels along its length (i.e. that the channel(s) does not extend longitudinally from the first (downstream) end of the filter to the second (upstream) end of the filter).

The filter or filter element may include up to 23 channels, preferably between 14 and 20 channels, extending longitudinally from one (or both) ends of the filter or filter element (for a filter/element of around 25mm circumference). The filter or filter element may include 5 or more channels, for example 5 to 23 channels, preferably 14 to 20 channels (for example 9-14 channels or 14-20 channels), extending longitudinally from one (or both) ends of the filter or filter element. The total cross-sectional area of these channels may amount to between 2 and 12%, preferably at least 4%, more preferably between 4 and 8%, of the overall cross-sectional area of the filter or filter element. Thus, careful control over the number and/or depth of the channels (e.g. by controlled embossing of the first wrapper) can give improved filtering performance. This may be achieved by increasing the depth of the corrugations in the first wrapper, preferably with increase in surface area of the corrugations available to smoke, and optionally along with increase in the corrugation pitch - that is, widening of the corrugations with reduction in their number. For example, a filter according to the invention may have 15 channels at one or both ends of the filter which are about 0.45mm deep and at a pitch of about 1.5mm; another filter may have 0.32mm deep channels, the number of channels (at each or either end) being 23, at a pitch of 1.05mm. The area of the corrugated wrap available for smoke filtration in these examples is generally a little less than the total corrugated surface area, since the crest of corrugations will generally be against the outer wrapper and hence not effective to filter. A filter or filter element of around 24-25 mm circumference may include, for example, 14 to 20 channels. A filter or filter element of around 16-17 mm circumference may include, for example, 9 to 14 channels.

The tobacco smoke filter may be of length 15 to 40 mm, e.g. 17 to 35 mm, e.g. 20 to 30 mm. The tobacco smoke filter may be of circumference 14 to 28 mm, for example 16 to 26 mm, for example 16 to 17 mm or 24 to 25 mm.

Preferably, the length of each channel is 2mm or greater, preferably between

2.5mm and 23mm, more preferably between 3mm and 15mm, more preferably between 3.5mm and 9mm. The channel or channels extending from one end (upstream or downstream) may be a different length to those extending from the other end (if present), or they may be the same length. The channels may be between 7 and 8mm long. The channels may be between 3 and 4mm long, for example 3.75mm long. In one example, channels extend from one end (upstream or downstream) only and are between 7 and 8mm long. In another example channels extend from both upstream and downstream ends and are between 3 and 4mm long (at each end).

The channels will preferably be of substantially uniform depth over their longitudinal extent, although there may be variation, for example where a channel approaches a closed end.

The completed filters of the invention may have a second wrapper which is air permeable (which may be of inherently permeable material and/or perforate) around the first (e.g. corrugated) wrapper. This permeable outer wrapper may be the tipping overwrap by which the filter is incorporated in a filter cigarette, such overwrap being applied only at the cigarette manufacturing stage. In this case the filter rod is initially produced with the first wrapper exposed, and the invention includes such rods (see below) as well as the completed filters with the outer wrapper attached. Thus, according to the present invention in a further aspect there is provided a (e.g. single section) tobacco smoke filter or filter element comprising: a longitudinally extending core of tobacco smoke filtering material including an additive (e.g. a particulate additive) spaced longitudinally from a first (downstream) end of the core; and a first wrapper (e.g. of air-permeable material) around the core; the first wrapper being corrugate, the corrugations (on its radially outer face) defining at least one channel extending longitudinally of the filter from one end thereof; wherein the longitudinally extending core of tobacco smoke filtering material comprises a rod shaped core of tobacco smoke filtering material having fully enclosed (e.g. embedded) therewithin a (or at least one) pocket of additive (e.g. particulate additive). The filters can also be used in conjunction with a second wrapper which is air- impermeable, e.g. tipping overwrap.

The (or each) portion of the filter which includes longitudinal channels (e.g. the or each portion where the first wrapper is corrugated, e.g. embossed with corrugations) may be referred to herein as a flute or fluted portion. The (or each) part or portion of the filter which does not include longitudinal channels (over the filter cross section) (e.g. the or each portion where the first wrapper is plain - e.g. not embossed/not corrugated) is referred to herein as a bar or bar portion. In one example a filter according to the invention includes a 3mm flute portion at each end and a single central bar portion as the remaining full length of the filter. Such a configuration has a further advantage that the amount of filtering material in the core (e.g. cellulose acetate tow) may be reduced because the pressure drop (PD/mm) of bar is higher than that of flute. This configuration may also give a more desirable end appearance.

In a further example of the invention, the tobacco smoke filter further comprises at least one channel (e.g. defined by the first wrapper and the second wrapper) which extends longitudinally of the filter and which extends only part of the core length but which does not extend from either the upstream or downstream ends of the filter. In this example of the invention, the tobacco smoke includes one or more longitudinal channels (a fluted portions) at one or both of the upstream and downstream end of the filter; and a further longitudinal channel or channels within the filter (a further fluted portion). In such an example, there is more than one portion or section of the filter having no longitudinal channels (more than one bar portion). The filter may have additional fluted and/or bar areas.

In a filter cigarette according to the invention, a filter of the invention (or a filter which includes a filter element of the invention) is joined to a wrapped tobacco rod with one (the second, upstream) end of the filter towards the tobacco. The filter may, for example, be joined to the wrapped tobacco rod by ring tipping [which engages around just the adjacent ends of the (wrapped) filter and rod to leave much of the filter wrap exposed] or, more preferably, by a full tipping overwrap (which engages around the full filter length and the adjacent end of the tobacco rod).

Any filter or filter cigarette according to the invention may be unventilated, or may be ventilated by methods well known in the art, e.g. by use of a pre-perforated or air- permeable wrapper(s) (plugwrap), and/or laser perforation of wrapper(s) (plugwrap) and tipping overwrap. A ventilating full tipping overwrap may likewise be inherently air- permeable or provided with ventilation holes, and in ventilated products where both filter plugwrap and tipping overwrap are present ventilation through the overwrap will usually be in register with that through the plugwrap. Ventilation holes through a filter plugwrap, or through a tipping overwrap, or through both simultaneously, may be made by laser perforation during filter or filter cigarette production. Where ventilation in a filter or filter cigarette according to the invention is localised longitudinally of the product, this localisation is preferably to one or two regions selected from upstream of, downstream of, and in register with the or a pocket of additive, depending upon the ventilation and filtering performances required. Ventilation upstream of and/or in register with a pocket of first additive is frequently preferred. There may be ventilation between portions (or pockets or patches) of second additive when two or more are present.

According to the invention in a further aspect there is provided a multiple rod comprising a plurality (e.g. 2, 4, 6 etc.) of filters (or filter elements) as described above and/or herein integrally joined end-to-end in a mirror image relationship.

The present invention will now be illustrated with reference to the following Examples and the attached drawings in which FIGURE 1 schematically illustrates a filter according to an embodiment of the invention; FIGURE 2 schematically illustrates a filter according to a second embodiment of the invention; and FIGURE 3 schematically illustrates a filter according to a further embodiment of the invention.

Examples

Figures 1 , 2 and 3 show examples of 'Smooth Core' CPF filters.

Figure 1 shows a single section tobacco smoke filter 1 of 27mm length and 24.5mm circumference comprising a longitudinal extending core 2 of tobacco smoke filtering material in the form of a rod shaped core of cellulose acetate filtering material having fully enclosed (e.g. embedded) therewithin a "pod" or pocket 3 of additive in the form of particles 4 of activated carbon in the central portion of the core and filter. The core (pod filter element) 2 may, for example, be formed by the method disclosed in WO 2006/059134. Immediately surrounding the core 2 is a first wrapper 5 of air-permeable filtering paper (or corrugated cellulose acetate) which is corrugated longitudinally (i.e. so the corrugations or grooves run in the axial direction of the filter) over all of its length apart from a non- corrugated circumferential portion 6 in the central portion or section of the filter 1 (i.e. the section of the wrapper which surrounds the part of the core 2 which includes the embedded pocket or pod). The core surface conforms to the corrugations in first wrapper 5. Immediately surrounding the first wrapper 5 and forming (defining) channels 9a, 9b with the corrugations in first wrapper 5 is an uncorrugated second wrapper 10 of air-permeable paper. The core and the wrappers 5 and 10 extend over the entire length of the filter 1. The inclusion of a non-corrugated circumferential portion 6 of wrapper 5 in the central portion of the filter means that there are no channels in this portion and that the channels 9a, 9b do not run the full length of the filter. Thus, filter 1 has a set of 15 channels 9a of length 7.5mm, formed at the first, or downstream, end 11 of the filter (formed between the corrugated portion of first wrapper 5 and the uncorrugated second wrapper 10 of air- permeable paper), and a second set of 15 channels 9b of length 7.5mm at the second or upstream end 13 of the filter (formed between the corrugations in the first wrapper 5 and the uncorrugated second wrapper 10) at the second end; these corrugations form fluted portions or flutes at each end 1 1 , 13 of the filter 1. In the centre of the filter the uncorrugated area of wrapper 5 in the circumferential portion 6 forms an uncorrugated or non-fluted bar portion (bar) of length 12mm in the centre of the filter. This bar portion blocks the end of each channel opposite the end of the filter from which it extends. This bar portion of the filter includes no longitudinally extending channels over the cross section of the filter 1 along the full length of the bar portion. Formation of the corrugate first wrapper (e.g. by embossing), application of the corrugate first wrapper around the core, and application of the second wrapper may be by well known methods - for example those described in GB2133269. It will be appreciated that the process of applying the first wrapper is synchronised with, and is in registration with, the process of forming and positioning the pod in the central section of the filter core.

Filter 1 may be attached to a cigarette by ring-tipping or by a full tipping overwrap, for example, such methods are well known in the art. It will be appreciated that other materials that are well known in the art may be used to form core 2, and wrappers 5, 10. Thus the filter includes embossed (corrugated) channels 9a, 9b (i.e. is 'fluted') at either end, giving a distinctive appearance to both ends of the filter; and has a central portion 6 (i.e. a 'bar') that is not embossed. A pocket of activated carbon granules is located within the body of filter, approximately located within the region defined by the bar. In use, with the filter attached at end 13 to a cigarette (not shown), some of the smoke enters directly into the core 2 and passes to the end 11 of the filter 1 , being filtered by contact with the filaments which form the core, and coming into contact with activated carbon in the pocket. Smoke, along with diluting air drawn in through permeable wrapper 10, also enters the channels 9b up to the non-corrugated portion (bar) 6 and the diluted smoke then enters the core 2 after passing through the corrugated wrapper 5 and passes out of the filter at the end 11 ; this smoke is thus filtered both by wrapper 5 and by core 2. It will be understood that filters according to the invention may also be used with non- ventilating wrappers, in which case there will be no diluting air drawn into the filter through the wrapper.

Thus, the example of Figure 1 is a single section filter with a 'pod' or fully enclosed pocket of particulate additive axially located centrally (e.g. as described in WO 2006/059 34) and an inner wrap that is embossed with grooves (channels) over part of its length. The filter avoids both the manufacturing cost and complexity associated with particulate-bearing multi-segment filters (because it is a single section filter), and the CCO disadvantages of APF/CPF single section filters (because the activated carbon is located within the pod or pocket and not on the wrapper). The Figure 1 example also illustrates that by controlling such parameters as the size and location of the central pod (pocket) and the length and location of the grooved portion of the inner wrap, it is possible to channel the smoke through the filter in such a way that the filtration performance, taste experience and end appearance can be varied. As discussed above, smoke is preferentially channelled through the carbon pod because the fluted region occupies a different longitudinal region of the filter to the pod, therefore creating more 'carbon taste' for the smoker. In addition, the filter enables higher tar retention (at the same pressure drop) or lower pressure drop (at the same tar retention) than conventional 'Smooth Core' filters. It will be appreciated that smoke can be channelled away from the pod by providing a different arrangement in which the fluted region occupies a similar longitudinal region of the filter to the pod therefore creating less of a 'carbon taste' to the smoker (see e.g. Figure 3).

Figure 2 shows a further embodiment, with a single fluted region facing the mouth end of the filter 31 (right hand side of the diagram) thereby presenting a distinctive mouth end appearance. Figure 2 shows a single section tobacco smoke filter 21 of 27mm length and 24.5mm circumference comprising a longitudinal extending core 22 of tobacco smoke filtering material in the form of a rod shaped core of cellulose acetate filtering material having fully enclosed (e.g. embedded) therewithin a "pod" or pocket 23 of additive in the form of particles 24 of activated carbon located towards the second or upstream end 33 of the filter. Immediately surrounding the core 22 is a first wrapper 25 of air-permeable filtering paper which is corrugated longitudinally over all of its length apart from a circumferential non corrugated portion 26 towards the second or upstream end 33 of the filter (i.e. the section of the wrapper which surrounds the part of the core 2 which includes the embedded pocket or pod). As with the Figure 1 embodiment, in the example of Figure 2 the core surface conforms to the corrugations in first wrapper 25. Immediately surrounding the first wrapper 25 and forming (defining) channels 29a with the corrugations in first wrapper 25 is an uncorrugated second wrapper 30 of air-permeable paper. The core and the wrappers 25 and 30 extend over the entire length of the filter 1. The inclusion of an uncorrugated circumferential portion 26 of wrapper 25 in the upstream portion of the filter means that there are no channels in this portion and that the channels 29a do not run the full length of the filter. Thus, filter 21 has a set of channels 29a (e.g. 15 channels 29a) of length 15 mm, formed at the first, or downstream, end 31 of the filter, formed between the corrugated portion of first wrapper 25 and the uncorrugated second wrapper 30 of air- permeable paper. These channels (corrugations) form fluted portions or flutes at downstream or mouth end 31 of the filter 1 , providing distinctive end appearance at this end, with a bar region at the other end. The pocket of activated carbon granules is located approximately under the bar region, towards the tobacco end of the filter.

Figure 3 shows a further embodiment, with a single fluted region facing the tobacco end of the filter 53 (left hand side of the diagram) thereby presenting a conventional mouth end appearance. The carbon pod is also located towards the tobacco end of the filter, approximately concurrent with the fluted region. Figure 3 shows a tobacco smoke filter 41 of 27mm length and 24.5mm circumference comprising a longitudinal extending core 42 of tobacco smoke filtering material in the form of a rod shaped core of cellulose acetate filtering material having fully enclosed (e.g. embedded) therewithin a "pod" or pocket 43 of additive in the form of particles 44 of activated carbon located towards the second or upstream end 53 of the filter. Immediately surrounding the core 42 is a first wrapper 45 of air-permeable filtering paper which is corrugated longitudinally over all of its length apart from a circumferential non corrugated portion 46 towards the first or downstream end of the filter (i.e. the section of the wrapper which does not surround the part of the core 42 which includes the embedded pocket or pod). The core surface conforms to the corrugations in first wrapper 45. Immediately surrounding the first wrapper 45 and forming (defining) channels 49b with the corrugations in first wrapper 45 is an uncorrugated second wrapper 50 of air-permeable paper. The core and the wrappers 45 and 50 extend over the entire length of the filter 41. The inclusion of an uncorrugated circumferential portion 46 of wrapper 45 in the downstream portion of the filter means that there are no channels in this portion and that the channels 49b do not run the full length of the filter. Thus, filter 21 has a set of channels 49b (e.g. 15 channels 49b) of length 10 mm, formed at the second, or upstream, end 51 of the filter, formed between the corrugated portion of first wrapper 45 and the uncorrugated second wrapper 50 of air-permeable paper. These channels (corrugations) form fluted portions or flutes at upstream end 51 of the filter 41 , with a bar region at the other (mouth) end.

Claims

1. A tobacco smoke filter or filter element comprising: a longitudinally extending core of tobacco smoke filtering material including an additive spaced longitudinally from a first end of the core; a first wrapper around the core; and a second wrapper around the first wrapper; the first wrapper defining at least with (e.g. between itself and) the second wrapper at least one channel extending longitudinally of the filter from at least one end thereof.

2. A filter or filter element according to claim 1 wherein the longitudinally extending core of tobacco smoke filtering material comprises a rod shaped core of tobacco smoke filtering material having fully enclosed therewithin at least one pocket of additive.

3. A tobacco smoke filter or fWter element comprising: a longitudinally extending core of tobacco smoke filtering material including an additive spaced longitudinally from a first end of the core; a first wrapper around the core; and a second wrapper around the first wrapper, the first wrapper defining at least with the second wrapper at least one channel extending longitudinally of the filter from one end thereof; wherein the longitudinally extending core of tobacco smoke filtering material comprises a rod shaped core of tobacco smoke filtering material having fully enclosed therewithin at least one pocket of additive.

4. A filter or filter element according to any preceding claim wherein the filter or filter element is a single section filter or filter element.

5. A filter or filter element according to any preceding claim wherein the first wrapper is of air-permeable material.

6. A filter or filter element according to any preceding claim wherein the first wrapper is corrugate, the corrugations defining 5 or more (e.g. 9 to 20) channels extending longitudinally of the filter from at least one end thereof.

7. A filter or filter element according to any preceding claim wherein the filtering material is one or more of natural or synthetic filamentary tow, e.g. cotton or plastics such as polyethylene or polypropylene, cellulose acetate filamentary tow, natural or synthetic staple fibres, cotton wool, a web material such as paper (e.g. creped paper), synthetic non- woven material, or extruded material (e.g. starch, synthetic foams).

8. A filter or filter element according to any preceding claim wherein the additive is a particulate additive.

9. A filter or filter element according to claim 8 wherein the particulate additive is activated carbon, zeolite, ion exchange resin (e.g. a weakly basic anion exchange resin), sepiolite, silica gel, alumina, molecular sieve, carbonaceous polymer resin, a diatomaceous earth, or a mixture of two, or more, of these additives.

10. A filter or filter element according to any of claims 1 to 7 wherein the additive in the fully enclosed pocket(s) of additive is a frangible capsule or capsules, or one or a plurality of frangible microcapsules.

11. A filter or filter element according to any preceding claim which includes a flavourant.

12. A tobacco smoke filter or filter element comprising: a longitudinally extending core of tobacco smoke filtering material including an additive spaced longitudinally from a first end of the core; and a first wrapper around the core; the first wrapper being corrugate with the corrugations defining at least one channel extending longitudinally of the filter from one end thereof; wherein the longitudinally extending core of tobacco smoke filtering material comprises a rod shaped core of tobacco smoke filtering material having fully enclosed therewithin at least one pocket of additive.

13. A tobacco smoke filter or filter element according to claim 12 wherein the first wrapper is corrugate with the corrugations defining 5 or more (e.g. 9 to 20) channels extending longitudinally of the filter from one end thereof.

14. A tobacco smoke filter substantially as hereinbefore described with reference to any of the attached drawings.

15. A filter cigarette comprising a filter according to any preceding claim joined to a wrapped tobacco rod with the second end of the core towards the tobacco.

16. A multiple rod comprising a plurality (e.g. 2, 4, 6 etc.) of filters (or filter elements) according to any of claims 1 to 14 integrally joined end-to-end in a mirror image relationship.