HK1056298A - Tobacco reconstitution - Google Patents

Description

Tobacco homogenizing treatment

The present invention relates to tobacco homogenisation, and in particular to extrusion of homogenised tobacco strands. More particularly, the present invention relates to the treatment of reconstituted tobacco tow downstream of a tobacco homogenizing extruder.

Various proposals are known for making tobacco-based materials using granulated tobacco. According to these proposals, the particulate tobacco may be a tobacco powder which is a by-product of the manufacturing process of smoking articles such as cigarettes, or particulate tobacco obtained by grinding tobacco lamina or stem portions. The material made of granular material may be in the form of a sheet or plate, rod, wire or hollow cylinder. The production process of these materials is commonly referred to as the tobacco homogenisation process.

In the material resulting from the homogenisation process, the other ingredients preferably include water in addition to the tobacco; binders such as pectin, starch, pullulan and cellulose binders; a filler; a humectant; a swelling agent; a fortifier and a flavour agent.

One prior homogenisation process for the present applicant is described in british patent specifications nos. 2201081b and 2201080B. The process involves feeding a mixture of particulate tobacco, starch and binder, with water, to an extruder to form a sheeted extrudate, which is subjected to an expansion process by extrusion so that the cross-section of the extrudate is larger than the cross-section of the exit orifice of the extrusion die. It is desirable to blow or extrude the extrudate in sheet form to increase the machine direction dimension of the extrudate and to reduce its thickness.

Another procedure for homogenising tobacco is described in GB 2291778B.

One disadvantage of the homogenised tobacco process described in these patent specifications is that it can cause problems in the production of the sheet material. For example, the thickness, strength, and elasticity of the sheet material can be difficult to control, and if any of these parameters are not within tolerance, downstream processing (i.e., cutting) of the sheet material can be adversely affected.

Another disadvantage of the prior art reconstituted tobacco process is that once cooled, the resulting sheet product has an upper skin and a lower skin with a honeycomb structure between the upper and lower skins. So that the transverse surface of the article, i.e. the surface not constituted by the skin, is deteriorated. The article is therefore frangible. Thus adversely affecting or practically precluding pneumatic transport of the product.

In the extrusion of reconstituted tobacco tow disclosed in U.S. patent 4,632,131, a plurality of filaments are extruded from a die which includes a circular array of outlet orifices, and the strands are then bonded to one another to form a reconstituted tobacco rod having channels extending longitudinally thereof.

One disadvantage of this type of strand extrusion process of reconstituted tobacco is that it is difficult to achieve a strand extrusion from the exit orifice of the extrusion die that does not adhere to each other when it is desired to produce separate strands.

It is an object of the present invention to provide an improvement in the method of making extruded filamentary reconstituted tobacco.

It is another object of the present invention to provide an improvement in the process of processing extruded reconstituted tobacco filaments downstream of the exit orifice of an extruder.

It is another object of the present invention to provide improvements in filamentary reconstituted tobacco products.

It is a further object of the present invention to provide a reconstituted tobacco product of a size that facilitates the incorporation of the tobacco product into a smoking article, i.e., a cigarette.

The invention provides a method of treating an extruded reconstituted tobacco filament downstream of a die assembly through which the filament is extruded, wherein the filament is conveyed longitudinally of the filament away from the die by a pneumatic conveying means which effects blowing or extrusion of the filament such that the cross-sectional dimension of the filament is reduced.

The method may further include a cutting step in which the extruded filament is cut into a plurality of portions transversely spaced along its length. For example, the filaments may be cut at intervals in the range of about 10mm to 50 mm. The extruded filaments are preferably cut after the cross-sectional dimension of the filaments has been reduced. The cutting device used in the cutting step may be a rotary cutter.

In some instances the method may further comprise a cooling step in which cooling air is contacted with the extruded filaments to effect cooling of the filaments. The temperature of the extruded filaments at the cutting device is preferably low enough to ensure that the viscosity of the extrudate does not cause problems in the normal operation of the cutting device. The temperature of the extruded filaments during the cutting stage is about 20-60 deg.C, preferably about 30-50 deg.C.

Preferably, the pneumatic conveying means comprises a gaseous medium conveying means and conduit means, the gaseous medium conveying means being operable to cause a continuous flow of gaseous medium through the conduit means. The gaseous medium transport means may for example comprise air extraction means, which may be fan means. Preferably, the inlet end of the duct means is located adjacent the extrusion die so as to facilitate the transport of the filaments away from the die in the longitudinal direction of the filaments as they exit the die exit orifice by the continuous flow of gaseous medium through the duct means. The inlet end of the duct means is located at a distance from the extrusion die in the range of about 5-20mm, preferably in the range of about 10-15 mm. The filaments are preferably fed in the longitudinal direction initially perpendicular to the mould surface. And then may be transported in a generally horizontal or vertical plane.

The gaseous medium is usually air and will therefore only be described below in connection with air.

The velocity of the air flowing in the same direction as the direction of transport of the filaments is greater than the extrusion velocity, thus producing blowing or extrusion of the filaments to reduce their cross-sectional dimensions. The filaments downstream of the extrusion die are thus tensioned, blown or extruded with air. To enhance the blow molding or extrusion, the filaments may be further tensioned by drawing the filaments over a tensioning device. The tensioning device may be, for example, a driven roller.

The air velocity for effecting blowing or extrusion is from 60 to 180m/s, preferably at least 100 m/s. The required blow or extrusion speed is determined by the formulation and the throughput of the extruder. The air velocity can be varied by the air extraction device, the cross-sectional area of the conduit, or both. The conveying speed after blow moulding or extrusion may be from 30 to 60m/s, preferably at least 35m/s, more preferably from 40 to 60 m/s.

The configuration of the pneumatic conveying means and the air mass flow values are preferably selected to ensure that the filaments do not contact any interior surface of the catheter means when conveyed through the catheter means,

preferably, the extruded reconstituted tobacco tow has a cross-sectional shape similar to the cross-sectional shape of cut tobacco, particularly cut lamina tobacco. For this purpose, the cross-section of the extruded tobacco filaments should be rectangular or square. The extrudate expands as it exits the extrusion die. Thus, in the case of an extrudate which expands, in order to produce an extruded filament of rectangular or square cross-section, the die exit orifice will generally be square or rectangular in shape, with the four sides of the square or rectangle being concave. Using a suitable concavity with respect to extrudate expansion, a filament can be produced having a cross-sectional shape of a straight sided rectangle or square.

The cross-sectional dimensions of the filaments after blow molding or extrusion are about 0.7mm by about 1mm, preferably about 0.3mm by about 0.8 mm. The length of the wire after cutting may be about 10-50 mm. With the present invention, the advantageous result of a filament having a cross-sectional dimension that remains constant after blow molding or extrusion can be obtained.

The resulting filamentary reconstituted tobacco product is formed from lengths of filament, each comprising: a honeycomb interior; and an integral skin extending over at least four longitudinal sides of the filament when the filament is square or rectangular in cross-section. This construction makes the product strong and then pneumatically transportable without deterioration.

The product has a fill value of about 3.8-5.0mm³A suitable filling value of about 4.0 to 4.6 mm/mg³In terms of/mg. This represents a potential for a 10-20% increase in fill value over that of articles made by the process described in british patent specifications nos. 2201081b and 2201080B. The density of the article may be about 150-600mg/mm³Preferably less than about 400mg/mm³。

Typically, the reconstituted tobacco product made by the present invention forms part of a cigarette filler blend, the other tobacco components of which may be or include cut lamina and cut stem portions.

Preferably, a plurality of strands of reconstituted tobacco are extruded simultaneously. When extruding a plurality of filaments simultaneously, a die is used that includes a plurality of exit orifices. Preferably, the exit orifices of this extrusion die are arranged so that the filaments issuing therefrom are preferably in a side-by-side array in a horizontal direction. Preferably, none of the plurality of filaments contact each other. Thereby preventing the filaments from sticking to each other.

The invention also provides an extrusion die plate, which is provided with die holes, the die holes are square or rectangular, and four sides of the square or rectangular are concave.

The exit surface of the die is rectangular and the exit orifices thereof are arranged in a row on the surface. The outlet openings may also be arranged in two longitudinal rows above and below the surface, the outlet openings of the upper row being vertically offset from the outlet openings of the lower row. When extruding a plurality of filaments, the conduit of the pneumatic conveying device may have a rectangular cross-section, so that a plurality of filaments are conveyed side by side through the conduit. The number of holes in the die is selected according to the desired throughput of the extruder.

Preferably, the extrusion mixture includes particulate tobacco, starch, and a binder. Preferably, water is added to the mixture as it is in the barrel of the extruder.

The starch is present in the tobacco/starch/binder mixture in an amount of about 5% to about 35% by weight, preferably about 10% to about 20% by weight. The starch is present in the mixture in an amount of more than twice, preferably more than three times or more than three times the weight of the binder. The binder is present in the mixture in an amount of not more than 10% by weight, preferably not more than 5% by weight.

The starch may be, for example, corn starch. The starch or a portion thereof may be a modified starch.

The binder may comprise a cellulosic binder. The cellulosic binder material used in the practice of the present invention may be hydroxypropyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose and ethyl cellulose. Other binders that can be used in the practice of the present invention include gums such as xanthan gum, guar gum and carob gum. Suitable adhesives known to those of ordinary skill in the art may also be used. The binder of the mixture may consist of two or more binder materials.

The present invention also makes it possible to use a less expensive binder of inferior quality, as compared to the high quality binders typically required in reconstituted tobacco products as described in GB 2201080. The present invention can also use a smaller amount of high quality adhesive. The invention allows the use of a lesser quantity and/or quantity of binder, since the particulate filamentary reconstituted tobacco product obtained according to the invention comprises a cellular interior and, when the particles are square or rectangular in cross-section, an integral skin extending over at least four longitudinal sides of the particles. This is in contrast to the sheet-like reconstituted tobacco product of GB 2201080 which comprises only an upper and a lower skin with a honeycomb structure therebetween.

Furthermore, as described above, the increase in filling value obtained with the product produced according to the invention allows the content of binder in the formulation to be reduced while maintaining a filling value comparable to that of the product described in GB 2201080B.

In addition to tobacco, starch and binder, sugar may be added to the extruder. If added, the sugar may comprise a sugar or sugars such as fructose, glucose or sucrose. Suitable levels of sugar in the tobacco/starch/binder mixture are not more than about 5% by weight, but may be as high as about 10%.

The total amount of water in the extruder was as follows: if an extrudate drying step is not used, the moisture content of the filaments after blowing or extrusion is about 5% to 20% by weight (on a moisture basis). "Total water amount" refers to the sum of the moisture in the "dry" ingredients of the tobacco/starch/binder mixture and the added water. Water may be added to one or more of the ingredients of the mixture before the ingredients are fed into the extruder and/or injected from an orifice in the barrel of the extruder. One convenient way is to mix the ingredients of the mixture and feed the mixture into the extruder in a dry state and then inject water into the barrel of the extruder.

Humectants and/or plasticizers such as glycerin or propylene glycol can be fed into the extruder and/or injected into the extruder barrel along with the ingredients of the mixture. The plasticizer may be present at a moisture content of about 1% to 10% by weight.

Filaments having optimum properties are obtained by ensuring that the material fed into the extruder is treated adiabatically or near adiabatically within the extruder. Another important point is that the temperature profile through the barrel of the extruder is operated until the extrusion die so that the temperature of the tobacco portion in the various materials in the extruder does not reach temperatures harmful to the tobacco, with a suitable range of about 80-180℃.

The treatment is preferably carried out under conditions such that the extrudate expands once it exits the die by flashing of the water therein to steam. The cross section of the extrudate increases, creating a honeycomb internal structure.

It will be readily apparent to those skilled in the art of tobacco homogenisation that the flavourant may be fed into the extruder. Such fragrances may be natural or artificial flavourants or plant extracts.

The particulate tobacco used in the process of the invention may be taken from the stem and/or lamina parts of tobacco leaves, such as tobacco powder. The particulate tobacco preferably has a particle size of less than about 500 μm, and more preferably less than about 370 μm. The particle size is generally determined by the minimum size of the orifice.

For a fuller understanding and appreciation of the invention, reference is made to the accompanying illustrative drawings, in which:

FIG. 1 shows an apparatus for carrying out the method of the invention;

FIG. 2 shows another apparatus for carrying out the method of the present invention; and

fig. 3 shows the front face of the extrusion die and its exit orifice.

Like parts in the various drawings are indicated with like reference numerals as much as possible.

As shown in fig. 1, the apparatus 1 comprises a twin screw extruder 2 (manufactured by APV Baker, of Peterborough, u.k. model number MPF 50-15) comprising a die 3 and a barrel 4. The extrusion die 3 is mounted on the outlet end of the barrel 4 of the extruder 2. Above the extrusion die 3 there is a steam suction device 5 for removing steam from the die 3 during the extrusion process. The apparatus 1 further comprises pneumatic conveying means comprising a gaseous medium (i.e. air) duct means 6 extending from a position adjacent to the extrusion die 3 and gaseous medium conveying means 8. As can be seen from fig. 1 and 2, the duct means 6 comprises an arcuate inlet portion 6' at its upstream end. The cross-section of the duct means 6 is rectangular. The major dimension of this cross-section is perpendicular to the plane of the drawing of fig. 1. The gaseous medium conveying means 8 comprise suction means provided by a suction fan. A cool air inlet 9 communicates with the duct means 6 at the lower end thereof, the air inlet 9 being adapted to draw cool air into the duct means 6. The duct means 6 includes a cutting means 10, i.e. a rotary cutter, for cutting the extruded reconstituted tobacco filaments 7 into filamentary reconstituted tobacco product particles 12. A particle/air separator 11 is housed within the duct means 6 to separate air flowing within the duct means 6 from the filamentary reconstituted tobacco product particles 12 and any other particulate matter entrained within the duct means 6. The filamentary tobacco products 12 are fed to a feeding device 14 through an air lock 13, i.e. a rotary air lock, which feeding device 14 feeds the filamentary tobacco products 12 to a hopper (not shown).

Fig. 2 shows a further apparatus which may be an alternative to the apparatus of fig. 1, wherein the duct means 6 is positioned such that the filament 7 is conveyed away from the die 3 in a substantially horizontal plane in the longitudinal direction of the filament 7. In comparison with the apparatus 1 of fig. 1, the catheter means 6 is positioned such that the wire 7 is transported in a substantially vertical plane over at least a part of the catheter means 6. The apparatus of figure 2 is otherwise similar to that of figure 1 except that the apparatus 1 of figure 2 includes a storage container 15 into which container 15 the cut articles 12 are pneumatically conveyed during operation of the apparatus 1.

Fig. 3 is a view of the front face 3' of the mold 3. As shown in fig. 3, the die 3 has a plurality of outlet holes 16, 16'. Fig. 3 shows only a small number of outlet openings 16, 16'. In practice, however, there are a total of about 100 outlet holes 16, 16' in the die 3. Thus simultaneously extruding a plurality of strands of reconstituted tobacco 7. All outlet holes 16, 16' of the die 3 are square or rectangular, the sides of the square and rectangle being concave. Once the extrudate exits the die 3, the use of appropriate concavity with respect to the degree of expansion of the extrudate results in filaments 7 having a cross-sectional shape of straight sided squares and rectangles. The exit orifices 16, 16' of the die 3 are arranged so that the filaments 7 issuing therefrom are juxtaposed in a horizontal array. The plurality of filaments 7 do not contact each other. The die 3 is rectangular and the outlet openings 16, 16 'are arranged in two longitudinal rows above and below the surface 3'. As shown in fig. 3, the apertures of the upper row 16 are vertically offset from the apertures of the lower row 16'.

In operation of the apparatus of figure 1 or figure 2, a dry mixture of 80% granulated tobacco powder, 15% starch and 5% cellulosic binder is fed into extruder 2 at a rate of about 145 kg/hr. A feeder device (not shown) of the extruder 2 feeds the mixture via a feed pipe (not shown) into the inlet end of the barrel 4 of the extruder 2. A pump (not shown) injects water drawn from a water tank (not shown) into the drum 4 at a rate of about 21 kg/hour. Likewise, glycerol drawn from another tank (not shown) is injected into the drum 4 at a rate of about 5 kg/hour. For example, the total amount of water in the wet mixture in the drum 4 is 16% by weight of the wet mixture.

The drum 4 has heating means (not shown) to maintain a desired temperature profile along the drum 4. The barrel temperature increases from say 40c at the entrance end to 95 c at the exit end.

The pressure in the extruder is maintained at a sufficiently high value to ensure that the water therein remains liquid. Pressures of 500psig (3,400kPa or 34.5Bar) to 2000psig (13,600kPa or 137.8Bar) can thus be used, for example 1000psig (6,800kPa or 68.9Ba r) to 1500psig (102,000kPa or 103.4 Bar).

At these temperatures and pressures, the starch fed into the extruder 3 is caused to gelatinize.

As the extruded filaments 7 exit the plurality of exit orifices 16, 16', the water therein flashes off to steam causing the cross-sectional shape of each filament to change due to expansion such that the cross-sectional shape of each filament 7 changes to a straight sided square or rectangle when the shape of each exit orifice is as shown in fig. 3.

About 100 simultaneously extruded filaments 7 exit die 3 at a total mass flow rate of about 157 kg/hr, and the linear velocity of each extruded filament 7 is about 1 m/s. The vapour suction means 5 removes the flash vapour.

The filaments 7 emerging from the holes 16, 16' are guided into the duct means 6 and are transported in the duct means 6 away from the die 3 in the longitudinal direction of the filaments 7. Once inside the duct means 6, the filaments 7 are introduced into a continuous flow of air flowing inside the duct means 6. The filaments 7 are thus pneumatically conveyed in the duct means 6. The air flow in the duct means 6 is caused by an extraction fan 8. When a plurality of wires 7 are transported in the rectangular catheter device 6, the wires do not touch each other. Thereby avoiding the filaments 7 from sticking to each other.

The filaments 7 are blown or extruded to reduce their cross-sectional dimensions. To this end, the air flow rate in the duct means 6 is greater than the extrusion speed, this speed difference being such that the air exerts a drawing force on each wire 7. The filaments 7 downstream of the extrusion die 3 are thus tensioned by the air and are thus blown or extruded. For example, an effective air flow rate to tension, blow or extrude the filament 7 is about 60-180m/s when the extrusion speed is about 1 m/s. This flow rate of the air stream is provided at least at the beginning of the duct means 6 in order to perform blowing or extrusion of the filaments 7 issuing from the outlet orifices 16, 16' of the die 3. The filaments 7 are blown or extruded until the desired cross-sectional size of the filaments 7 is obtained. The flow rate of the gas stream in the duct means 6 downstream of the initial blow or extrusion section of the duct means is at least 35m/s and may be in the range of about 50-60 m/s. To reduce the flow rate of the gas stream, the cross-sectional area downstream of the blow or extrusion section of the duct means 6 can be made larger than the cross-sectional area of the blow or extrusion section. A downstream air flow rate of, say, 35m/s can convey the filaments 7 without blowing or extruding the filaments. The cross-sectional dimensions of the filaments 7 remain unchanged after the blowing or extrusion step. The transport speed of the filaments 7 after blowing or extrusion is, for example, about 2 m/s.

The strands 7 are transversely cut at about 30mm intervals along the length of the strands 7 with a cutting device 10 to produce a product 12 of filamentary reconstituted tobacco particles. This cutting step is carried out after the cross-sectional dimensions of the wire 7 have been reduced. The granular product 12 is then pneumatically conveyed at about 20 m/s to an air lock 13 (fig. 1) or directly to a storage container 15 (fig. 2). The hopper feed device 14 may be located downstream of the air lock 13. An air/particle separator 11 separates the particles of the product 12 and the conveying air.

The method may further comprise an enhanced cooling step, whereby cooling air is brought into contact with the extruded filaments 7, thereby cooling the filaments. Cooling air enters the duct means 6 from a cooling air inlet 9. Multiple cooling air inlets may be used if desired. The cross-sectional area of the holes of the cooling air inlet may be the same as the holes of the inlet portion 6' of the duct means 6. Preferably, the sum of the cross-sectional areas of the inlet 9 and the inlet section 6 'is equal to the cross-sectional area of the chute of the duct means 6 extending immediately downstream of the inlet section 6'. Preferably, the air flow in the cooling air inlet 9 is adjustable; for example, a position adjustable baffle (not shown) may be provided in the cooling air inlet 9, the baffle being used to control the flow rate of the air stream in the inlet 9. The temperature of the filaments 7 at the cutting device 10 should be low enough to ensure that the extrudate does not stick to the cutting device 10. The temperature of the filaments 7 at the cutting device 10 should be 30-50 deg.c.

For example, the inlet 9 and the inlet portion 6' of the duct means 6 each have a cross-sectional area of about 10-20cm²The cross-sectional area of the duct means 6 in said blow-moulded or extruded part thereof is about 20-40cm²The cross-sectional area of the catheter device 6 at the cutting device 10 is about 250-400cm²。

The cross-sectional dimension of each filament 7 after blowing or extrusion is for example about 0.7mm x 1 mm. Each filamentary tobacco product 12 particle (i.e. the portion of the filament 7 after cutting) is for example about 30mm long. The resulting filamentary reconstituted tobacco product 12 is formed from particles, each particle 12 being formed from a length of filamentary material 7 and thereby comprising a cellular interior and, when the particle is square or rectangular in cross-section, an integral skin extending over at least four longitudinal sides of the particle.

The extruder may be any extruder that can provide a range of flow rates. The throughput may be up to 300 kg/h and a suitable extruder to provide this throughput is Buhler DNDG 62. Increasing the throughput of the extruder requires a corresponding increase in the gas medium conveying device, for example to a power of about 75 to 100kW for a throughput of about 300 kg/h of suction fan. A throughput of about 150 kg/h requires the use of an extraction fan of about 45 kW.

In another configuration of the invention the pneumatic conveying means may additionally comprise air injection means. The gas jet means is preferably located adjacent the barrel of the extruder so as to facilitate the transport of the filaments in the duct means longitudinally thereof away from the die under the action of the continuous flow of gaseous medium provided by the gas jet means as they exit the die orifice.

Alternatively, the pneumatic conveying means may also comprise a jet of compressed air. In this alternative configuration of the invention, compressed air may be obtained from a controlled pulsed or continuous stream of compressed air jets so as to convey the wire in its longitudinal direction as it exits the die orifice. The compressed air provided can separate the filaments from each other and transport the filaments side by side. The compressed air jets are preferably arranged with respect to the barrel of the extruder so that the compressed air is tangential to the direction of flow of the filaments. The compressed air jets may also be arranged to deliver air through the die plate with at least one die orifice. The orifices are preferably not orifices for extruding filaments.

In another configuration of the invention using compressed air jets, the pneumatic conveying means may or may not include conduit means.

The jet of compressed air may be arranged to break the filaments into segments of controlled size and to convey the segments of filaments away from the die orifice.

In these configurations of the invention using compressed air, the air pressure is about 1 to 200bar, preferably about 5 to 10 bar.

Claims (46)

1. A method of handling an extruded reconstituted tobacco filament downstream of a die means through which said filament is extruded, wherein said filament is conveyed away from said die in the longitudinal direction of said filament by pneumatic conveying means which blow or extrude said filament such that the cross-sectional dimension of said filament is reduced.

2. The method of claim 1 wherein said extruded filament is cut transversely into a plurality of filament segments at spaced intervals along its length.

3. The method of claim 2 wherein said filament segments are cut at intervals of about 10mm to about 50 mm.

4. A method as claimed in claim 2 or 3, wherein said extruded filament is cut after the cross-sectional dimension of said extruded filament has been reduced.

5. A method according to any one of claims 2 to 4, wherein the cutting means used in the cutting step is a rotary cutter.

6. A method according to any preceding claim, wherein cooling air is brought into contact with the extruded filaments to cool the filaments.

7. The method of claim 6 wherein said extruded filament is cut at a temperature of about 20 ℃ to about 60 ℃.

8. The method of claim 7, wherein said temperature is about 30 ℃ to about 50 ℃.

9. A method according to any preceding claim, wherein said pneumatic conveying means comprises gaseous medium conveying means and conduit means, said gaseous medium conveying means causing a continuous flow of gaseous medium through said conduit means.

10. A method according to any preceding claim, wherein the transport in the longitudinal direction of the filaments is initially perpendicular to the mould surface of the mould means.

11. The method of claim 10, wherein after the transport perpendicular to the mold surface, the transport is in a horizontal or vertical plane.

12. A method according to any preceding claim, wherein the filaments are blown or extruded with the velocity of the gaseous medium in the same direction as the direction of transport of the filaments being greater than the extrusion speed.

13. The method of claim 12, wherein said velocity of said gaseous medium is from 60 to 180 m/s.

14. The method of claim 13, wherein said velocity is at least 100 m/s.

15. A method according to any one of claims 11 to 13, wherein to enhance blowing or extrusion of said filament, said filament is further tensioned by drawing said filament over tensioning means.

16. The method of claim 14, wherein said tensioning means is a driven roller.

17. A method according to any preceding claim, wherein the delivery rate of the filaments after blowing or extrusion is from 30 to 60 m/s.

18. The method of claim 17, wherein said conveying speed is at least 35 m/s.

19. The method of claim 18, wherein said conveying speed is 40-60 m/s.

20. The method of any one of claims 9 to 19, wherein the configuration of the pneumatic conveying means and the mass air flow valve are selected such that said filaments are not in contact with the inner surface of said conduit means when conveyed therein.

21. A tobacco thread made by the method of any one of claims 1 to 20, wherein said tobacco thread has a rectangular or square cross-section.

22. A tobacco filament made by the process of any of claims 2 to 21, wherein said filament has a cross-sectional dimension of about 0.7mm x 1mm after blow molding or extrusion.

23. A tobacco filament according to claim 22, wherein said dimensions are about 0.3mm x 0.8 mm.

24. An extrusion die plate comprising a die orifice, said die orifice being generally square or rectangular in shape, the four sides of the square or rectangle being concave.

25. An extrusion die plate according to claim 24 wherein said die orifices are arranged such that the extruded filaments exit the die plate in a side-by-side array.

26. An extrusion die plate according to claim 23 or 24, wherein the exit face of said die plate is rectangular and the exit orifices thereof are arranged in a single row on said face.

27. An extrusion die plate according to claim 23 or 24, wherein said die plate outlet face is rectangular and the outlet orifices therein are arranged in two longitudinal rows, the outlet orifices of the upper row being vertically offset from the outlet orifices of the lower row.

28. An extruded reconstituted tobacco filament, wherein said filament has a substantially rectangular or square cross-section.

29. An extruded reconstituted tobacco filament according to claim 23, comprising a cellular interior and an integral skin extending over at least four sides of said filament.

30. An extruded reconstituted tobacco filament according to claim 28 or 29, wherein the cross-sectional dimension of said filament is about 0.7mm x 1 mm.

31. An extruded reconstituted tobacco filament according to claim 30, wherein said dimensions are about 0.3mm x 0.8 mm.

32. A filamentary reconstituted tobacco product consisting of a length of filament, comprising: a cellular interior, and, when the filament is square or rectangular in cross-section, an integral skin extending over at least four longitudinal sides of the filament.

33. The filamentary reconstituted tobacco product according to claim 32, wherein said product has a fill value of about 3.8-5.0mm³/mg。

34. The filamentary reconstituted tobacco product according to claim 33, wherein said fill value is from about 4.0 mm to about 4.6mm³/mg。

35. A filamentary reconstituted tobacco product according to any one of claims 32 to 34 having a density of about 150-600mg/mm³。

36. The filamentary reconstituted tobacco product according to claim 35, wherein said density is less than about400mg/mm³。

37. A method according to any one of claims 1 to 20, when used with an extrusion die plate according to any one of claims 24 to 27, wherein the concavity of the holes of the die plate is such that the resulting filament has a square or rectangular cross-section with four straight sides.

38. A method according to any one of claims 1 to 20 or claim 37, wherein a plurality of the strands of reconstituted tobacco are extruded simultaneously using a die comprising a plurality of outlet orifices.

39. A method according to claim 37 or 38, wherein the exit orifices of the die are arranged so that the filaments emerge from the die in a side-by-side array.

40. A pneumatic conveying apparatus for extruded filamentary tobacco, comprising in combination gaseous medium conveying means for causing a continuous flow of gaseous medium in duct means and duct means for forming a plurality of filaments from an extruder comprising a die plate, wherein the inlet end of said duct means is located adjacent said die plate such that as said filaments emerge from the die openings, said filaments are readily conveyed away from said die plate in the longitudinal direction of said filaments by the action of said continuous flow of gaseous medium in said duct means; a plurality of filaments may be conveyed side-by-side in the conduit, the conveying means blowing or extruding the filaments such that the cross-sectional dimension of the filaments is reduced.

41. The pneumatic conveying apparatus for extruded reconstituted tobacco as claimed in claim 40, wherein said inlet end of said duct means is spaced from said extrusion die by a distance in the range of about 5mm to about 20 mm.

42. The pneumatic conveying apparatus for extruded reconstituted tobacco as claimed in claim 41, wherein said inlet end of said duct means is spaced from said extrusion die by a distance in the range of about 10mm to about 15 mm.

43. An extruded reconstituted tobacco delivery apparatus according to any of claims 40 to 42, wherein said side-by-side arrangements are arranged horizontally.

44. An extruded reconstituted tobacco delivery device according to any of claims 40 to 43, wherein said duct means is rectangular in cross-section so that a plurality of strands can be delivered side by side in said duct.

45. An extruded reconstituted tobacco delivery device according to any of claims 40 to 44, wherein said die plate is a die plate according to claims 24 to 27.

46. A smoking article comprising a filamentary reconstituted tobacco product according to any one of claims 32 to 36.