CH659174A5 - FILTER ELEMENT AND TOBACCO SMOKE FILTER. - Google Patents

Description

The invention relates to a filter element and filter for tobacco smoke; its subject is a filter element for tobacco smoke having a core extending longitudinally and an envelope around this core, the envelope being preformed so as to define, externally to the latter, passages extending longitudinally at filter at / or towards at least one end of this filter, the casing further having a circumferential groove into which said passages open.

It also relates to a filter for tobacco smoke presen-5 as such an element comprising a nozzle material around the envelope; the tip material may extend longitudinally together with the element, or may be a cuff-wrap incorporating the element into a filter cigarette; the nozzle material may be air permeable or air impermeable and, firstly, in the case of a ventilation nozzle, it preferably performs ventilation directly in the circumferential groove.

The envelope will usually be corrugated longitudinally to form the exterior passages, although it may be otherwise configured (for example, with dimples) for this use.

The surface of the core may conform to the interior surface of the envelope, or the latter may also define internal passages between itself and the core, the latter extending in the same way from from the circumferential groove to / or towards at least one end of the element or of the filter; such internal passages will usually be closed by the outer circumferential groove.

The invention also relates to a process for manufacturing the filter element for tobacco smoke, a process in which a web extending longitudinally is produced, or a strip 2S of the envelope is stamped in spaced apart areas longitudinally, in order to form longitudinally extending channels on these zones, separated from other channels by an unstamped zone, and in that the material of the envelope is arranged around the core, by placing said channels outside , so that the unstamped zone of the envelope takes the form of a circumferential groove around the wrapped core, a groove into which the external longitudinal passages open. 4

The core of the element and of the filter according to the invention can be of any material from the whole range of materials used for cigarette filters, for example, made of staple fibers, agglomerated or not, or of tow filaments (cellulose acetate, polyolefin, etc.), crepe paper or a breathable foam material. The core may be of uniform structure and composition over its entire length, or have a composite site structure, comprising, for example, separate buffers of different properties (for example, pressure drop); the core can extend in whole or in part over the length of the element, and when it is formed from a composite of two or more pads, the adjacent pads can be in contact or at a distance from each other 45 others. The core may be unwrapped or have a perforated buffer envelope and / or a material by itself permeable to smoke; the core may also have an impermeable buffer envelope or an incorporated film (for example by hot melting or by means of a solvent). The core may still be waterproof or non-filtering.

When a waterproof envelope is used, this is advantageously a paper / thermoplastic polymer laminate, for example, a paper / thermoplastic / paper laminate, the plastic layer preferably being polyolefin, for example, polyethylene. Such a laminate has good embossing properties and retains its impermeability and its embossed configuration well. The envelope may also be permeable, for example, be formed from a permeable paper and / or perforated buffer envelope. The envelope is preferably fixed on the periphery of the core, by means of a lap and glued joint; it can also be fixed to the core by one or more longitudinal adhesive lines.

The tip material may be breathable; for ventilated filters, it may be permeable by its nature, but when it is a sleeve-cuff, connecting the element to a rod of 65 tobacco, one will more commonly use a substantially impermeable material provided with perforations in communication with the external passages, for example by the circumferential groove. The element may have an envelope made of a breathable material, this

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which gives a filter with a smooth external appearance, and around which the sleeve-cuff (or the annular end piece) engages, during the manufacture of the filter cigarette, but this is not usually necessary.

Used as part of a filtered cigarette, certain filters according to the invention can constitute, by means of passages between the envelope and the core, a certain derivation of the smoke around a part of the length of the soul, various controlled effects can thus be obtained, depending on the filter structure adopted; in such cases, of course, the core does not have a smoke-impermeable layer between itself and the impermeable envelope.

In the ventilated filters according to the invention, the external passages between the casing and the nozzle material can be opened only towards the buccal end of the filter, so that the ventilation air sucked inside these passages passes directly into the smoker's mouth, without first being mixed with the smoke. If, on the other hand, the external passages open only at the end of the filter in contact with the tobacco rod, the ventilation air sucked in these passages circulates upstream towards the tobacco rod, then downstream through the core of the filtered.

The elements according to the invention are manufactured in an appropriate manner, first by forming the core (in order to constitute a continuous rod or of discontinuous finished length), then by embossing the envelope in the required configuration, the embossed or corrugated envelope then being applied around the core and fixed to it. A tip material can be subsequently applied around the envelope; this tip material may be the sleeve-cuff which is used to connect the filter and the tobacco rod to one another, during the formation of cigarettes filtered according to the conventional method.

Normally, the core will be brought in the form of a continuous rod which will then be continuously wrapped in the corrugated envelope, the continuous composite thus obtained being subsequently cut transversely into finished lengths. An envelope of a permeable or air-impermeable material can be, if desired, applied continuously around the composite formed by the core and the corrugated envelope, before cutting into finite lengths. For the manufacture of filter cigarettes, double lengths of such products are placed with wrapped tobacco rods, in contact with one and the other end, a sleeve-cuff or an annular end-piece being applied so as to connect between they tobacco stems and filter rods interposed, and the resulting combination is cut through double lengths to produce individual filter cigarettes. The continuous filter rod initially produced is usually cut into units of length constituting a multiple even (for example sixfold), to then be sent to the manufacturer of filter cigarettes, which then cuts these multiple lengths into double lengths, for the purpose of use in the production of filter cigarettes, as described above. It should be noted that in the case of individual filter lengths according to the invention, where the first and the other passages extend from only one end of the filter and end near the other end , so that the two filter ends are different, the initial rods, of lengths forming an even multiple, coming from the filter manufacturer and from which individual lengths are definitively formed, can have identical ends; for example, the length rod forming a multiple even could have passages extending from the two ends, or closed at both ends, depending on whether, in the final filter cigarette, the passages will be open, respectively, to the tobacco end, or mouth end. Such filter rods of lengths forming an even multiple are also part of the present invention.

Although the core of the filters and filter elements according to the invention may be of a composite structure, as mentioned previously, for example, composed of pads in mutual contact or at a distance between them longitudinally, the corrugated envelope is usually extends over the entire length of the filter or filter element, to give it a completely coherent and unitary structure.

It is possible to use as core, or in the core of filters and elements according to the invention, a pad with high pressure drop, of low retention, of coarse agglomerated fibers, or of stamped and condensed sheets of plastic, metallic (for example aluminum) or other sheets.

In filter cigarettes employing elements according to the invention, there may be ventilation through the mouthpiece material directly into the circumferential groove and, therefore,

in all exterior passages; for example ventilation perforations can be provided in the end-piece material, on a circumferential annular zone coinciding with the circumferential groove.

Different configurations of the filter element according to the invention are possible; for example, the circumferential groove may be disposed in the middle of the envelope, the exterior (and, optionally, interior) passages extending from this groove, in opposite directions, towards the two ends of the element; or alternatively, the circumferential groove may be situated towards one end of the element where the envelope is circumferentially wavy, or shaped to close the circumferential groove from this end, the external (and, optionally, internal) passages extending from the circumferential groove to the other end of the element; according to another variant, the circumferential groove is at one end of the envelope, open at this end, with the external (and, optionally, internal) passages extending from this groove towards the other end; according to other embodiments, a plurality of circumferential grooves is provided at a distance between: they along the envelope, for example, at the opposite ends * thereof. The envelope to be used in the production of this type of element according to the invention can simply be profiled, in a normal manner, so as to form the required undulations, while each zone which must constitute a circumferential groove remains smooth and not profiled. ; when the corrugated envelope is applied around the core, it has been found that said smooth non-profiled zones naturally adopt the conformation of the circumferential grooves.

This characteristic of a filter element provided with a core having a longitudinally corrugated envelope, forming an outer circumferential groove into which the outer channels of the corrugations open, as well as the method of forming this structure by application around the core, of a pre-corrugated envelope and comprising parts remaining smooth, as described above, are generally useful and applicable, whatever the nature of the core, the nature of the corrugated envelope (for example, waterproof or permeable and / or perforated), and regardless of the nature of the tip material used with this envelope. In addition, said envelope could, instead of being corrugated, be shaped in another way (for example provided with dimples), so as to form said external channels.

Embodiments of the invention will now be described by way of example, with reference to the accompanying drawing, in which the same numerical references designate the same elements, and in which:

- Figure 1 is a longitudinal sectional view of a filter and a filter cigarette according to the invention;

- Figures 2 and 3 are sectional views, respectively, along II-II and III-III of Figure 1;

- Figure 4 is a perspective view of the filter element according to the invention, used in the filter of Figure 1;

- Figures 5 and 13 are views similar to Figure 1 of other filters and other filter cigarettes according to the invention;

- Figures 6 and 11 are perspective views of the filter elements according to the invention, used in the filters respectively, of Figures 5 and 13;

- Figure 7 is a view similar to Figure 6, of another filter element according to the invention;

- Figures 8 to 10 and Figure 12 are schematic views,

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in longitudinal section, rods of multiple lengths according to the invention.

In the embodiments of FIGS. 1 to 7, the filter element or the rod comprises a filter core 4 (which incorporates a plain buffer envelope 1, permeable or impermeable to smoke), housed in an impermeable envelope 2 smoke, provided with longitudinal corrugations 3 forming longitudinal passages 5 between the envelope and the core and external longitudinal passages 6; in the elements of Figures 1 to 7, the impermeable envelope also forms a circumferential groove 8 communicating with said outer grooves 6 which extend from said groove, as shown, towards one end of the filter. A ventilation envelope-cuff 12 surrounds the filter element, in use, and connects it to a tobacco rod envelope 10, this envelope-cuff having an annular zone of perforations 14 opening into said circumferential groove.

In the embodiment of Figures 1 to 4, internal and external passages extend longitudinally from the circumferential groove towards the two ends of the filter rod. In the embodiment of FIGS. 5 and 6, the impermeable casing at the end of the filter coming into contact with the tobacco rod has circumferential undulations 20 closing the circumferential groove and the external channels from the tobacco rod , the circumferential groove being directly adjacent to the circumferential undulations, and the longitudinal undulations of the envelope extending from this groove towards the buccal end of the filter. In the element of Figure 7, which can be incorporated into a filter cigarette, in the same manner as shown in Figures 1 and 5, the circumferential groove 8 is open at one end of the element, the channels 5 and 6 extending from this groove to the opposite end.

As indicated previously, during the formation of the filter elements shown, the initially planar envelope 2 is first stamped so as to form series of corrugations 3 (FIGS. 1 to 4 and FIG. 7), or 3 and 20 (Figures 5 and 6), spaces remaining smooth and not stamped being formed between them. When the pre-corrugated envelope is engaged around the core 4, the unstamped portions of the envelope are naturally deformed to provide the circumferential groove 8 into which the channels 6 open.

As previously described, a filter element according to the invention, such as one of those illustrated, will initially be produced in a continuous length from which rods of lengths forming an even multiple (i.e. each rod is an even multiple of the final individual element) are cut, the length rods are then subdivided into elements of double lengths and then, during the production of filter cigarettes, into final elements of single lengths. Examples of rods of sixfold lengths according to the invention, which can be further subdivided into individual elements in accordance with the invention, are shown schematically in Figures 8 to 10. Figure 8 illustrates a rod of sixfold length from which simple elements, as in figure 4, can be produced by cutting in the middle of the corrugated sections longitudinally inwards. An identical rod, of multiple length, but of suitably different relative dimensions of the corrugated and circumferentially grooved zones, can be cut in the middle of the grooves, to provide individual elements of the kind of that represented in FIG. 7. FIG. 9 illustrates a six-length rod which can be cut in the middle of the circumferentially wavy zones and in the middle of the longitudinally inwardly wavy zones, to provide individual elements of the type shown in Figure 6. Figure 10 illustrates a six-length rod which can be cut through the circumferentially corrugated areas 20, to provide individual elements according to the invention (not shown), having circumferential corrugations at one end, the longitudinal corrugations extending towards the other end.

Although in all the previous embodiments, the filter rod 4 incorporates a smooth buffer envelope 1, the latter is not always necessarily present and, when it exists, it can be permeable or impermeable to smoke. The dual individual elements and the rods of multiple lengths shown in FIGS. 4 and 7 to 10 can be provided, during a phase of the filter manufacturing process, with a smooth, air-permeable buffer envelope. The wrapped elements or the filters can then be incorporated into filter cigarettes, by means of a ventilation sleeve-cuff, as shown in FIGS. 1 and 5 or by means of an annular end-piece.

As also indicated above, while the embodiments of FIGS. 1 to 10 use a filter core 4 and an impermeable casing 2 forming two interior and exterior passages 15 and 6, one or more of these characteristics can be eliminated or modified. For example, the core can conform to the envelope, without leaving interior passages 5; the core can be permeable or impermeable and with a high, low or zero filtering power; in addition, the casing 2 can be made of a permeable or waterproof material, and perforated or non-perforated. The preceding explanations, relating to rods of lengths forming a multiple even, also apply to these modified embodiments. In addition, these elements can be used with either a permeable or waterproof envelope-cuff. As another variant, the envelope 2 is not necessarily corrugated longitudinally, but may have a completely different configuration (for example, with dimples), so as to form the outer channels extending from the groove 8 at one end. , or towards one end of the element.

According to a particular type of variant according to the invention., The core 30 can be of low permeability (or even of zero permeability), said passages and the circumferential groove constituting, outside the core, a path which extends from one end to the other of the core and which has a pressure drop, the perforations 14 being closed, less than that of the core. During use, at least most of the smoke is thus constrained or caused to flow through the passages and the circumferential groove, rather than through the core, so that there is little or no mechanical smoke filtration; adequate tar and CO reduction can, however, be achieved by providing for high (e.g. 50% more) levels of air dilution 40 through the vent material to the peripheral smoke path, preferably directly in the circumferential groove; however, due to the flow-blocking core and the relatively restricted smoke flow path around the core, this high degree of air dilution can be achieved by maintaining acceptable high pressure drops for the filter and the filter cigarette. These means therefore make it possible to obtain a cigarette filter in which most or substantially all of its tar reduction, etc., is carried out by dilution with air rather than by mechanical retention, the filter retaining resistance to acceptable print in use; this represents a clear progress compared to conventional filter structures, where high air dilution and low mechanical retention inevitably lead to filters or filter cigarettes with a pressure drop that are too low to be acceptable. Filters of the type 55 described, in accordance with the invention, can also provide a significantly lower CO / tar ratio (for example 0.5 or less) than that which can be obtained with conventional filters (generally of the order of 1 'unit) with the same pressure drop and tar retention, with closed filter. The pressure drops, tar retentions, etc., with the perforations 14 closed, are those measured by preventing dilution by air.

Referring again to the drawing, a filter element, a filter and a filter cigarette according to the invention may be as shown in the various forms of Figures 1 to 4. In this case, the filter element , as shown in Figure 4, has a core 4 of very low permeability, in material of the "Transorb" type (dense rod, with reduced draft, in agglomerated cellulose acetate filaments), provided with a buffer envelope 1 (for example, paper or

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in plastic film), the envelope 2 being impermeable (for example, a paper / thermoplastic / paper laminate, as previously described) and supplying, via the two series of passages 6 and the interposed circumferential groove 8, a peripheral longitudinal flow path, pressure drop, in closed filter, 5 lower than that of the core. The properties of “Transorb” rods and their production methods (which allow the initial creping of the filaments to be eliminated) are described in United Kingdom patent No. 970,817 to which reference may be made for more details.

In the filter and the corresponding filter cigarette, according to the invention (Figures 1 to 3), the element is surrounded by a ventilation nozzle material 12 providing a high degree of dilution (for example 50 % more) in the peripheral smoke flow path, in this case, by means of a ring of ventilation perforations 14 corresponding to the circumferential groove 3; the end piece 12 15 is here made of a material which is impermeable by air, but it could be made of a permeable material, with or without perforations 14. In a similar embodiment, the “Transorb” core wrapped 4.1 is replaced by an extruded waterproof rod made of closed cell plastic foam. 20

The element shown in FIG. 7 can also have the same components as those which have just been described, with a closed cell foam core or “Transorb” wrapped, and an impermeable envelope 2 constituting, through 6 and 8, a peripheral path of smoke flow, pressure drop, in closed filter, lower than that of the core; this element will be incorporated into a high air dilution filter and into a filter cigarette, as described in connection with FIGS. 1 to 3. The components of the multiple-length rod represented in FIG. 8 may also be like those which have just been described for FIGS. 4 and 7. 30

In another particular type of variant, the core is made of a filtering material, the envelope 2 is permeable to smoke, and the peripheral path, formed by the circumferential groove and the longitudinal passages communicating with it, ends at proximity of at least one end of the element. Such an element can be used with a nozzle material, with ventilation or without ventilation and, in use, the smoke is forced or caused to circulate at

through the envelope, between the core and the peripheral flow path. Such an element can, for example, be as represented in FIG. 6, with its version in multiple lengths, represented in FIG. 9, the core 4 being a porous filter rod in tow of creped filaments agglomerated of cellulose acetate , the cover envelope 1 being (for example highly) permeable or entirely omitted, and the envelope 2 being (for example highly) permeable. However, in other cases, the core 4 will not have a smooth cylindrical surface, but will conform to the inner corrugated face of the envelope 2, so that there will be no internal channels 5; this is easily obtained in practice by wrapping the rod 4 of the core which has just been produced in a preconfigured envelope 2, while the agglomerated tow of the core is still "lively" and untreated, the envelope printing then its profile in the surface of the soul. A filter and a corresponding filter cigarette, in accordance with the invention, may be as shown in FIG. 5, except that the ventilation perforations 14 are preferably not present in the waterproof tip material 12 and that , as previously mentioned, the buffer envelope 1 (which, if it exists, is permeable and preferably highly permeable) can be omitted. In the latter case, the core 4 may conform to the internal profile of the casing 2 and, therefore, fill the passage 5. Figures 11, 12 and 13 illustrate, respectively, such a filter element, an element to multiple lengths and a filter and a filter cigarette according to the invention, where the filter core 4 has no buffer envelope and is shaped according to the profile of the envelope 2 which, in use, is surrounded by a tip material 13 without ventilation. The element shown is preferably used in an orientation opposite to that shown in FIG. 13, that is to say with the passages 6 in the direction of the tobacco rod and the circumferential undulations 20 at the buccal end and, in fact, it is the filter cigarette which would be obtained by the conventional method described above, from elements of double length cut from the rod of FIG. 12 (on the internal section wavy longitudinally). Rods of sixfold length for the filters according to Figure 13 (or 5) would normally look like that of Figure 12 (or 9), but with the circumferential corrugations 20 located at each end.

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Claims (14)

659,174 1. Filter element for tobacco smoke, characterized in that it has a longitudinally extending core and an envelope around this core, the envelope being preformed so as to define, outside thereof, passages s 'extending longitudinally of the filter to / or towards at least one end of this element, the casing further having a circumferential groove into which said passages open. 2. Filter element according to claim 1, characterized in that the circumferential groove and the passages form a peripheral flow path, from one end to the other of the core, and having a pressure drop, as a filter closed, inferior to the soul. 2 3. Filter element according to claim 1, characterized in that the core is a permeable filtering core, and in that the envelope is a permeable envelope through which the smoke can pass in the direction of the soul or from of it. 4. Smoke filter, characterized in that it comprises an element according to claim 1, 2 or 3 and has a nozzle material around the envelope. 5. Filter according to claim 4, characterized in that the tip material is breathable and / or perforated. 6. Filter according to claim 5, characterized in that the nozzle material ensures, during use, the entry of outside air, laterally, in the circumferential groove. 7. Filter according to claims 3 and 4, characterized in that the tip material is not ventilated. 8. A method of manufacturing a filter element for tobacco smoke according to claim 1, characterized in that a web extending longitudinally is produced, a strip of the envelope is stamped in spaced apart areas longitudinally, in order to forming longitudinally extending channels on these zones, separated from other channels by an unstamped zone, and in that the material of the envelope is arranged around the core, by placing said channels outside, so that the unstamped zone of the envelope takes the form of a circumferential groove around the wrapped core, a groove into which the outer longitudinal passages open. 9: Process according to claim 8, characterized in that the core is formed in the form of a continuous rod, in that this core is continuously wrapped in the envelope, then the element obtained is cut into length sections finished. 10. The method of claim 9, characterized in that after having placed the envelope it is surrounded by a tip material and then proceeds to cut the element into sections of finished length. 11. Filter cigarette, comprising a filter according to one of claims 4 to 7. 12. Filter cigarette according to claim 11, characterized in that the tip material comprises a sleeve-cuff connecting the filter to the tobacco rod. 13. Rod comprising several unitary elements according to one of claims 1 to 3, these elements being joined end to end, the rod being intended to be sectioned into individual elements. 14. Rod comprising several unit filters according to one of claims 4 to 7, these filters being joined end to end, the rod being intended to be sectioned into individual filters.