Tobacco filter and production thereof

(74) Agent: Cabinet Michel Nony,

29, rue Cambacérès, 75008 Paris.

The present invention relates to filters. Although the products of the present invention are generally used as filters whether, for example, for the smoke of tobacco, cigarettes, cigars, pipes or the like, filters for cigarettes are of particular commercial importance, and the description mainly refers to cigarette filters.

While filtration efficiency is an important property for cigarette filters, a trade-off must frequently be made to achieve a commercially acceptable combination of other properties, including pressure drop, taste, hardness, appearance. and the cost. For example a cellulose acetate filter may have a relatively low filtration efficiency which could be increased by increasing the density of the filter material or the length of the filter element, but only at the cost of commercially excessive pressure drop. unacceptable.

Air dilution has become a common method to compensate for the relatively low filtration efficiency of cigarette filters with a commercially acceptable pressure drop. This technique uses ventilation air to dilute the smoke stream and thereby the tar and other unwanted constituents of tobacco smoke drawn into the mouth. Ventilation air can enter through perforations in the paper forming the end joining the filter to the tobacco column of the cigarette, and if the filter is wrapped with wrapping paper, wrapping paper is used. permeable.

Air dilution is an economical process for reducing the tar level at will, and also allows the reduction of unwanted components in the gas phase such as CO and NO. A disadvantage of dilution by air is the loss of taste, especially of low-tar cigarettes, a commercially satisfactory taste can be obtained in some cases by flavor enrichment of cigarette tobacco, but it is appears that this is not possible at levels below 5 mg tar.

Since tobacco filters tobacco smoke, filters have been proposed containing tobacco to improve the taste of filtered smoke. These earlier filters used tobacco either as fine particles or granules, dispersed in a bound matrix of the main filter material (e.g. as in the patents

US Nos. 2,948,282 and 3,353,543) or in the form of a separate short column made of loose filaments of tobacco similar to that of the main tobacco column of the cigarette and separated from it by a disc of quenching (eg, as in US Pat. Nos. 3,288,145 and 4,091,821) or by other filter materials (eg, as in US Pat. No. 3,858,587). These arrangements have been found to be too cumbersome and / or too expensive for large scale production, or ineffective to achieve commercially acceptable taste with very low tar levels, particularly with air dilution.

The present invention relates to a smoke filter comprising a coherent sheet of reconstituted tobacco, gathered into an axially elongated filter, the sheet having at least one face provided with grooves, the latter extending longitudinally with respect to the filter; these grooves have a large surface in contact with the smoke which is enriched in flavor by extracting the tobacco flavor from the leaf. The leaf can be made from a mixture of strong tobacco and / or flavor enriched, to achieve the desired taste.

In preferred filters according to the invention, an axially elongated member of fibrous filter material, such as cellulose acetate tow, is coaxial with the member of reconstituted tobacco; one of the elements is formed into a bar-like core, enveloped by the other. Although the reconstituted tobacco element can be either of these coaxial portions it is preferably the core portion. In either case, the element of fibrous filter material may have a greater suction resistance than that of the reconstituted tobacco element, whereby the smoke is mainly directed through the latter to optimize the tobacco aroma enrichment of the smoke.

Filters according to the invention can be quickly and easily manufactured by a continuous automated process, in which the piece of reconstituted tobacco is produced from a continuous web of coherent sheet of reconstituted tobacco. The web which continuously advances longitudinally can first of all be continuously stamped to form therein grooves extending longitudinally, then gathered in a compact manner into an axially elongated shape the longitudinal axis of which extends longitudinally with respect to the grooves. The advancing stamped compact web can then be made to pass continuously through a limited heated area where heated steam or gas is introduced into the compact, stamped web to bond it into a continuous self-sustaining body, which is then preferably cooled to substantially room temperature.

For the production of a coaxial part filter as described above, the filtering fibrous material part can be made from a tow of bonded continuous filaments, for example cellulose acetate. Preferably, the filamentous tow is continuously fed in tubular form in peripheral juxtaposition with a continuous body of advancing reconstituted tobacco, formed as described above, both of which are then passed through a heated confined area where the steam or heated gas is introduced into the fibrous filter material to bind it into a dimensionally stable self-supporting tube enveloping the reconstituted tobacco core. In an alternative embodiment, the process is reversed, that is, a continuous bar of fibrous filter material is first produced and then wrapped with a tubular body of reconstituted tobacco. In either case, the resulting continuously advancing dual element filter bar is then preferably cooled to substantially room temperature.

In all cases the continuously advancing bar, comprising the stamped, gathered sheet of reconstituted tobacco, is cut transversely into appropriate defined lengths.

The filters of the present invention can be used with dilution by air or ventilation and then can, even at low tar levels, provide filtered tobacco smoke of commercially acceptable taste when smoke and ventilation air passing. through them come into contact with a large surface of reconstituted tobacco and, therefore, are substantially enriched with tobacco flavor. The ventilated filters of the invention also allow good removal of CO and, therefore, give a good tar / CO ratio in the filtered smoke. .

The present invention will now be described in more detail only by way of example with reference to the accompanying drawing in which:

Figure I is an enlarged perspective view of a cigarette having a filter according to the invention, Figure 2 is a schematic representation of a process and a production line for the production of this filter, Figure 3 is a fragmentary top view of a cohesive sheet web of reconstituted tobacco after passing through the stamping station and before entering the forming station of the production line shown in Figure 2, Figure 4 is a view, in elevation, end, enlarged, of the filter of the cigarette of figure 1, figures 5 and 6 are enlarged views, in elevation, end, similar to figure 4 showing other filters according to 1¹ invention, Figure 7 is a fragmentary sectional view, enlarged, of part of the production line of Figure 2, Figure 8 is a fragmentary sectional view, enlarged, of another part of the production line of Figure 2, and Figure 9 is an enlarged end elevational view similar to Figure 4 showing yet another filter according to the invention.

In Figure 1, a cigarette filter 10 comprises a column 12 of cigarette tobacco and a filter 14 according to the present invention. Tobacco column 12 and filter 14 are secured end-to-end by an outer shell of conventional end paper 16 having peripheral perforations 18 for air dilution.

The filter 14 is composed of three coaxial elements. elongated (Figure 4) a bar-shaped core member 20 which is peripherally wrapped by a tubular intermediate member 22, in turn peripherally wrapped by an outer wrapping member 24, consisting of a paper end wrapper tube , breathable, conventional. Each of the elements 20, 22 and 24 is of constant cross section along the entire length and is in close contact with the element or elements contiguous thereto, to at least substantially prevent the axial passage of smoke and gas. ventilation air between them.

The core element 20 of the filter 14 is a cohesive sheet of reconstituted tobacco which has been embossed uniformly with grooves extending parallel, longitudinally, and then compactly gathered and bonded onto itself into a self-supporting bar. -maintained dimensionally stable, whose longitudinal axis extends parallel to the stamped grooves. Although the bar can be quickly shaped into any desired geometric pattern it is shown in Figure 4 as being of circular cross section.

The reconstituted tobacco leaf suitable for use in the present invention is a commercially available material made from tobacco waste products, such as dust, debris, short pieces and husks of tobacco created during the years. primary and secondary process of turning tobacco into cigarettes. Various methods of making reconstituted tobacco leaves are commercially practiced, including the method using the paste form in which the particles of tobacco waste and any additives other than tobacco are suspended in water to form a paste. thick which is cast and dried on a moving stainless steel belt to form a cohesive sheet of reconstituted tobacco. The reconstituted tobacco leaf produced by any of the known techniques is suitable for use in the present invention.

The intermediate element 22 of the filter 14 is made of a fibrous filter material and has a higher suction resistance than that of the core element 20 so that the smoke passing through the filter is directed mainly through the filter element. reconstituted tobacco. Such member 22 may be formed from a continuous tow of cellulose acetate filaments bonded together into a dimensionally stable, self-sustaining, smoke permeable body defining sinuous paths for the passage of smoke through it. Other fibrous filter materials can be used, for example, filamentary tow of polyethylene or polypropylene, or nonwoven fabric fibers of the type described in US Patents Nos. 2,297,041 and 3,552,400.

End aspects of the final filter 14 different from that of Figure 4 can be achieved by proper shaping of the core 20 during manufacture of the filter. Examples of such variants are shown in Figures 5 and 6, in which the parts corresponding to those of Figure 4 have been given the same reference numerals as in Figure 4 followed by the letters a and respectively b.

Figures 2, 3, 7 and 8 show a method according to the invention in which a continuous web 30 of reconstituted tobacco leaf from a supply roll 32 is first passed through a pair of stamping rollers 34 peripherally provided with grooves, to form a web 30a (figure

3) Uniformly stamped with a series of parallel grooves 36 extending longitudinally. Stamping increases the volume and surface area of ​​the sheet and facilitates further processing. The stamped web is brought to pass through a funnel 38 (FIG. 7) in which it is gathered in a bar whose longitudinal axis extends parallel to the grooves 36.

The gathered web is then caused to pass through the passage 42 of a hot bonding head 40. An inlet 44 leads into the passage 42 for the admission of water vapor or other hot steam or gas, for example from the air, inside. The head 40 preferably contains heating elements (not shown) to maintain it at 200-235 ° C. The steam or hot gas (eg at 260-290 ° C) is preferably directed into passage 42 countercurrent to the web of reconstituted tobacco (eg at an angle of approximately 45 ° to the ground. passage 42) and exits through the mouth of passage 42. Passage 42 has a desired size and cross-sectional shape for the core member to be produced. When it passes through the confined zone defined by passage 42, the gathered web is subjected to the treatment of steam or hot gas and is thermally bonded in a self-supporting bar 30b of desired cross-sectional shape, for example circular (figure 4), triangular (figure 5) or rectangular (figure 6).

The bar 30b is then preferably passed through a cooling head 46 where it is cooled by injecting air or the like to a temperature close to room temperature to enhance its dimensional stability. The bar 30b then passes through an elongated pulling device 48, the longitudinal passage of which has substantially the size and cross-sectional shape of the bar 30b and maintains it in that size and shape for a period sufficient to ensure the maintenance. of its dimensional stability in subsequent processing.

The bar 30b emerging from the traction device 48 is caused to pass (FIG. 8) through a tube 50 which passes through an air supply device 52 and a conventional stuffing nozzle 54. Before entering the tube 50, the bar 30b bar 30b can receive the application of a coating of plasticizer, for example, triacetin to ensure its safe contact with the enveloping tube subsequently formed of fibrous filter material. This plasticizer can be flavor enhanced to the taste desired for the finished filters.

The air supply device 52 has a passage 56 receiving a tube 50 and an air inlet 58 leading into the passage 56, through the wall of the tube 50 to direct the pressurized air downstream into the tube. â approximately 18 ° from the axis of the tube to provide a stream of air converging with the bar 30b. This creates suction at the inlet of tube 50, pulling the bar inside. A continuous filamentary tow 60, for example a cellulose acetate tow, having a large number of bondable plasticized filaments activated by steam or hot gas, is continuously fed into the stuffing nozzle 54 funnel. peripherally around the tube 50, and is thus gathered in a tubular form around the outer surface of the tube 50. The gathered tow emerging from the stuffing nozzle 54 is brought into peripheral juxtaposition with the bar 30b emerging from the tube 50. The bar 30b and its enveloping gangue of tow are then drawn continuously through the thermal connection head 62. and a cooling head 64 through accessory 66 (Figure 2). The thermal bonding head 62 (Figure 8) is similar to the head 40, having a longitudinal passage 68 and an inlet 70 leading therein to admit steam or hot gas, such as air into the passage 68. The passage 68 has a larger cross-sectional dimension than the passage 42 of the head 40, to receive the composite bar passing therethrough. During its passage through the passage 68, the outer filamentary tow part of the composite bar is subjected to a treatment of steam or hot gas in the confined zone defined by the passage and is thermally bonded in a filter tube, 60a, self-supporting, enveloping the reconstituted tobacco core 30b which is protected against softening by the air stream flowing along its outer surface from the air device 52. When passing through the cooling head. dissement 64, the tube 60a is cooled by injected air or the like to substantially room temperature to enhance its dimensional stability.

The accessory abandoning composite bar 66 is passed through another cooling head 72 and wrapped with a conventional air permeable end wrap paper 40 74 in an attachment 76 to form the completed filter bar. who

2452257 is then cut transversely by cutting means 78 in suitable lengths 14.

Alternative filters with respect to those described above as well as other methods are possible according to the invention. Thus, in another embodiment, the element of fibrous filter material can be removed and the reconstituted tobacco core element expanded to occupy the total space within the casing. In some embodiments, the air permeable end wrap can be eliminated and the filter can be directly wrapped with the end paper 16, resulting in maximum, uniform air dilution without the variations. found in porous end caps.

Yet another filter according to the invention is shown in Figure 9. This filter 114 has a bar-shaped core member 120 of fibrous filter material enveloped by a tube 122 of reconstituted tobacco; the tube 122, made of a gathered sheet provided with longitudinal grooves, of reconstituted tobacco, as for the core of the filter of FIG. 4, has, for its part, an outer shell 124 of conventional end permeable to air. The filters illustrated in Fig. 9 can be made by modification of the process of Fig. 2. This can comprise a first forming of a continuous bar of fibrous filter material, by passing a filamentous continuous tow, linkable, longitudinally through a confined area where steam or hot gas is injected into the collected tow to bind it into a dimensionally stable, self-supporting bar. Then a continuous web of a coherent sheet of reconstituted tobacco, embossed uniformly with a series of parallel grooves extending longitudinally, can then be assembled into a tubular configuration in peripheral juxtaposition with the preformed bar of fibrous filter material and the resulting composite bar can then be passed through a confined area where hot vapor or gas is introduced into the gathered web for the bond into a dimensionally stable, self-supporting tube enveloping the fibrous filter bar.

In another variant according to the invention, at least one coherent sheet of reconstituted tobacco provided with longitudinal grooves and at least one coherent sheet (optionally provided with similar grooves) of fibrous filter material such as cellulose acetate, are compactly assembled and linked into a single multi-layered bar. A composite member of this type can be produced, by a method according to Figure 2 modified, by simultaneously passing the continuous webs of coherent sheet material in a layered arrangement through the stamping rolls 34, the funnel 38. , the thermal connection head 40 and the cooling head 46.

When the smoke passes primarily through the reconstituted tobacco element, which is initially dark in appearance, the soiling of the fibrous filter material found in conventional filters is less noticeable and the appearance of the tip. of the filter can be about the same before as after the passage of the smoke.

Although the filters according to the invention are particularly useful in connection with air dilution, they may also have the advantage of providing filtered, flavor enriched tobacco smoke in conventional filter cigarettes without air dilution. 'air.