GB2266833A

GB2266833A - Tobacco reconstitution

Info

Publication number: GB2266833A
Application number: GB9309476A
Authority: GB
Inventors: Phillip Michael Green; William David Lewis
Original assignee: British American Tobacco Co Ltd
Current assignee: British American Tobacco Investments Ltd
Priority date: 1992-05-15
Filing date: 1993-05-07
Publication date: 1993-11-17
Anticipated expiration: 2013-05-07
Also published as: IN181227B; CN1082364A; GB9309476D0; GB2266833B; CN1035658C; AR247977A1; GB9210473D0; HK104996A

Abstract

A tobacco sheet reconstitution process and draw down apparatus which comprises drawing down a sheet of tobacco- containing extrudate extruded from an extruder 2 the draw down is achieved by passing the extrudate around one or more draw down drums of a diameter within the range of 30-100cm, the extrudate is in contact with at least 50% of the circumferential surface of at least one draw down drum 10, 11; two draw down drums are used, the degree of contact of the extrudate with the circumference of the drum may be less than the contact with the first drum and is preferably at least 45% of the circumference of the second drum, water cooling and chilling means in the draw down drums assists in contraction of the extrudate, aiding the wrap around and friction contact of the extrudate with draw down drum(s). <IMAGE>

Description

"IMPROVEMENT8 RELATING TO TOBACCO RECONSTITUTION" The invention the subject of this application relates to tobacco reconstitution.

There have been many prior proposals for the production of tobacco based material utilising particulate tobacco. According to these proposals, the particulate tobacco may be derived from a waste product of smoking article manufacturing processes, cigarette manufacturing processes for example, or may be obtained by grinding tobacco leaf lamina or stem portions. The materials produced from the particulate material may take the form of flat webs or sheets, rods, filaments or hollow cylinders. Processes producing these materials are commonly referred to as tobacco reconstitution processes.

It has been proposed to operate tobacco reconstitution processes to produce materials which can be used as smoking articles. Thus if the material is produced as a rod of open cell structure, of 8mm diameter say, it has been suggested that the rod can be smoked as a smoking article having a likeness to a cigarette or a cigar. It has though more usually been proposed that the products of tobacco reconstitution processes should be utilised, after having been cut or shredded, as constituents of cut filler for conventional smoking articles. A further use for reconstituted tobacco materials, when in web or sheet form, is as smoking article wrapping materials.

Components additional to tobacco which have been proposed for inclusion in materials produced by reconstitution processes are water; binding agents, e.g.

pectin, starch, pullulan and cellulosic binders; fillers; humectants; expansion agents; reinforcing agents; and flavourants.

A prior proposed expansion process by the applicants was disclosed in UK Patent Specifications Nos. 2 201 081B and 2 201 080B. The process involved feeding a mixture of particulate tobacco, starch and binder, with the addition of water to an extruder to provide a sheet form extrudate, the extrusion being carried out under such conditions that the extrudate assumes a cross-section greater than that of the exit orifice of the extruder die. The description of these patent specifications are incorporated herein by reference.

Any extrudate to be processed according to the present invention should be comprised of materials which render the extrudate capable of being drawn down in the plastic phase thereof. The extrudate should exhibit a degree of plasticity and may also exhibit elasticity.

The tobacco mixture subjected to the expansion process described in the UK specifications above provides extrudate which exhibits properties which render it suitable to be processed according to the present invention in order to enable the draw down process.

It is an object of the present invention to provide a tobacco sheet reconstitution process which incorporates draw down of the extrudate, the draw down step being assisted by a high degree of contact between the surface of the draw down means and the extrudate. The contact between the extrudate and the draw down means may also be known herein as 'wrap-around'.

The present invention provides a tobacco reconstitution process, wherein a sheet of tobaccocontaining extrudate is extruded from an extruder die, the extrudate in the plastic phase thereof is drawn down to reduce the thickness thereof, the draw down being assisted by passing the extrudate around one or more draw down means, the extrudate being in contact with the surface of at least one of said one or more draw down means over at least 50% of the surface thereof to provide a high degree of contact of the extrudate with the draw down means.

Preferably the draw down means comprises one or more draw down drums. Suitably the surface of the drums is flat and smooth in order to prevent the collection of small particles of tobacco extrudate material in depressions in the surface of the draw down drum(s), such as might occur with a drum or drums having a knurled surface.

Preferably the draw down means comprises a first large diameter draw down drum. The first draw down drum is suitably paired with a second large diameter draw down drum. Advantageously the first and second draw down drums are driven by common drive means at a common linear speed.

Suitably the linear speed is within the range of 10lOOm/min and is advantageously about 30m/min.

Advantageously, there is a high degree of wrap-around of the extrudate about the cylindrical draw down means.

Advantageously the extrudate passes from the exit of the extruder die to the first draw down drum over a smaller diameter roller, which roller may suitably be free-running.

Preferably the draw down means is provided with water chilling and circulating means. Suitably the size of the first and second draw down drums is determined by the requisite degree of cooling of the extrudate which is required. The smaller the size of the draw down drums, the greater the degree of wrap-around which is likely to be required.

The present invention further provides a tobacco reconstitution draw down apparatus comprising an extruder, an extruder die, draw down means comprising one or more large diameter draw down drums arranged to provide a high degree of contact of the surface area of said drums by the extrudate extruded through said extruder die, when wrapped around said drum(s), wherein the degree of contact by the extrudate with at least one of the draw down drums is at least 50% of the circumference of said drum.

Preferably the extrudate is in contact with the surface of the first draw down drum over at least 55% to about 90% of the circumference of the draw down drum.

More preferably at least 60% of the drum circumference is contacted by the extrudate and more preferably at least 65%, and even more preferably at least 70% of the drum circumference is contacted by the extrudate. The extrudate is also preferably in contact with the surface of the second draw down drum over at least 45% to about 90% of the circumference of the drum. The degree of contact with the surface of one of the draw down drums may be less than the degree of contact with the other draw down drum, especially if the degree of contact of the extrudate with the surface of the other draw down drum is high, say greater than 75%.

The contact with the surface of the drums as used herein refers to the contact with respect to the circumference of the drum in axial cross-section. In other words, the contact with the surface of the draw down drum or drums is an indication of the wrap-around of the extrudate about the draw down drum(s).

Preferably the size of the draw down drums is within the range of 30cm - 90cm diameter.

In order that the present may be easily understood and readily carried into effect, reference will now be made to the accompanying diagrammatic drawing which shows a tobacco reconstitution draw down apparatus according to the present invention.

The drawing shows tobacco reconstitution draw down apparatus 1 comprising an extruder 2, such as a twin-screw extruder. The extruder 2 comprises an extruder barrel 3 and an extruder die 4. Tobacco in fine particulate form, starch and cellulosic binder in a formulation such as described in UK Patent Specification No. 2 201 081B is fed from in-feed bin 5 directly to the extruder barrel 3.

Water is fed from a water source 6 through a feed line 7 to the extruder barrel 3. Water may be present in the extruder in an amount such that water is present in the range of 5% to 20% by weight (wet basis) of the cut extrudate, without an extrudate drying step being utilised. Optionally, humectants, plasticisers and/or sugar may also be fed to the extruder barrel 3 from a source 6' through a feed line 7' or the in-feed bin 5.

The barrel 3 is provided with heating means (not shown) by the operation of which a desired temperature profile can be maintained along the barrel 3. The barrel temperature is suitably within the range of 259C at the inlet end and 1350C at the outlet end. The barrel temperature may, for example, be maintained at 400C at the inlet end increasing to 950C at the outlet end.

The pressure within the extruder must be maintained at a high enough value to ensure that water therein remains in the liquid phase. A pressure range of 500 psig (3400 kPa) to 2000 psig (13600 kPa) has been found to be suitable.

At these temperatures and pressures the starch in the tobacco formulation is caused to gelatinise within the extruder 2.

At the outlet end of the barrel 3 there is mounted an extruder die 4, which die has an exit orifice of horizontal slit formation. As the extrudate 8 issues from the die 4, some water in the extrudate 8 flashes off to steam, as a result of which the cross-section of the extrudate 8 becomes greater than the cross-section of the exit orifice of the die 4. There is thus imparted to the extrudate 8 a substantially closed cell interior structure. It is to be noted that the cellular structure of the extrudate may also be open cell. Whatever the cellular structure the extrudate should exhibit plasticity.

The temperature at the extruder die 4 has typically been found to be about 1300C.

The sheet form extrudate is then passed over a freerunning small diameter roller 9 and around two larger diameter draw down drums 10 and 11 of draw down unit 12.

The draw down drums 10, 11 have a diameter of about 60cm and are driven at a common linear speed of about 30m/min.

Drum 10 is driven in a clockwise direction and drum 11 is driven in an anti-clockwise direction as viewing the accompanying drawing. The surface of each drum 10 and 11 is smooth, the drum surface being stainless steel.

Chilled water, either alone or with other cooling additives such as glycol, is circulated through the rollers 10 and 11 from a pumping unit (not shown). The surface temperature of the chilled drums 10 and 11 is kept within the range of 00C-110C and is usually less than about 80C.

The drums 10 and 11 are arranged on parallel longitudinal axes. Their longitudinal axes are preferably horizontal. Drum 11 is located above drum 10, the location of drum 11 being such that the extrudate 8, when passed from drum 10 to drum 11, is in contact with at least 60% of the circumference of drum 10 to give a high degree of wrap-around of the extrudate 8 about drum 10.

The contact with the circumference of drum 10 may be 70% or even 75%. The extrudate 8 passes from drum 11 to the infeed belt 13 of a feed conveyor 14. The feed conveyor 14 is positioned with respect to drum 11 at such an angle that the extrudate 8 is in contact with at least 45% of the circumference of drum 11. The degree of wrap-around of the extrudate 8 about drum 11 may be greater than 50%, or greater than 55% of the circumference of drum 11.

It has been found that, provided the degree of wraparound of the cooling drum(s) is sufficient to achieve the requisite cooling of the extrudate 8 and the extrudate 8 itself is capable of exhibiting plasticity, as contraction and stretching of the extrudate 8 occurs, the extrudate 8 will wrap around the smooth draw down drums 10, 11 and will be driven by the frictional contact between the surface of the drums 10, 11 and the extrudate 8. Thus the need for nip rollers to feed the extrudate away from the exit of the extruder die 4 can be negated. Crushing forces exerted by the use of such nip rollers are also avoided, thus the cellular structure of the extrudate can be maintained.

Surprisingly, the extrudate 8 may be driven successfully away from the exit orifice of the extruder die 4, without the need for the surface of the drums to be provided with means for temporarily securing the extrudate 8 to the surface thereof. Such securing means may be, for example, a knurled drum surface. A disadvantage with such an arrangement is that particles of tobacco material can become lodged in the surface of the knurled drum, making the drums difficult to clean. The removal of excess moisture from the surface of such drums is also made more difficult. The trapped material will also deteriorate.

Particles which attach to the reconstituted sheet can significantly affect the taste characteristics of the extruded tobacco material when utilised in smoking articles, such as cigarettes. Furthermore, when it is important to maintain a particular sheet thickness, the possibility of material from the drum surface adhering to the extrudate 8 is highly undesirable. Such adhered material can contaminate the cutters at the cutting stage.

The extrudate 8 passes from the downstream end of the infeed belt 13 between slitters 15 to form longitudinal strips of reconstituted sheet material. The slit sheet material then passes between a multi-bladed, rotatably driven cylinder 16, whereby the slit sheet material is severed to provide discrete filaments of a length of 40mm, for example. The slitters 15 have a distance of about 0.7mm between each knife blade. The thickness of the sheet of reconstituted tobacco material is of the order of imam.

The discrete filaments are deposited on a conveyor 17 and conveyed to a skip 18. This conveying step allows the product to cool to substantially ambient temperature.

The filaments may be fed during a further processing stage to the chimney of a cigarette making machine as particulate tobacco filler material.

The moisture content of the extrudate 8 as the extrudate 8 enters the cutters if often about 14%, and more often about 12%.

It has been found that, where the ambient temperature effects even further cooling of the extrudate and loss of moisture, at low sheet moisture contents, i.e. less than 10%, the sheet does not run effectively around the cooled draw down drums. This is due to the loss of plasticity of the extrudate.

Claims

1. A tobacco reconstitution process, wherein a sheet of tobacco-containing extrudate is extruded from an extruder die, the extrudate in the plastic phase thereof is drawn down to reduce the thickness thereof, the draw down being assisted by passing the extrudate around one or more draw down means, the extrudate being in contact with the surface of at least one of said one or more draw down means over at least 50% of the surface thereof to provide a high degree of contact of the extrudate with the draw down means.

2. A tobacco reconstitution process according to Claim 1, wherein said draw down means comprises one or more draw down drums.

3. A tobacco reconstitution process according to Claim 1 or 2, wherein the surface of said one or more drums is flat and smooth.

4. A tobacco reconstitution process according to Claim 1, 2 or 3, wherein said draw down means comprises a first large diameter draw down drum.

5. A tobacco reconstitution process according to Claim 4, wherein said first draw down drum is paired with a second large diameter draw down drum.

6. A tobacco reconstitution process according to Claim 5, wherein said first and second large diameter draw down drums are driven by common drive means at a substantially common linear speed.

7. A tobacco reconstitution process according to Claim 6, wherein said substantially common linear speed is within the range of 10-lOOm/min.

8. A tobacco reconstitution process according to Claim 7, wherein said linear speed is about 30m/min.

9. A tobacco reconstitution process according to any one of the preceding claims, wherein said draw down means further comprises water chilling and circulating means.

10. A tobacco reconstitution process according to any one of the preceding claims, wherein the extrudate is in contact with the surface of the first large diameter draw down drum over at least 55% to about 90% of the circumference of said drum.

11. A tobacco reconstitution process according to Claim 10, wherein at least 60% of the drum circumference is -contacted by said extrudate.

12. A tobacco reconstitution process according to Claim 10 or Claim 11, wherein at least 65% of the drum circumference is in contact with said drum circumference.

13. A tobacco reconstitution process according to any one of Claims 5 to 12, wherein the extrudate is in contact with the surface of the second large diameter draw down drum over at least 45% to about 90% of the circumference of the drum.

14. A tobacco reconstitution process according to any one of Claims 4 and 5 to 13, wherein the size of said first and second large diameter draw down drums is within the range of 30-90 cm diameter.

15. Tobacco reconstitution draw down apparatus comprising an extruder, an extruder die, draw down means comprising one or more large diameter draw down drums arranged to provide a high degree of contact of the surface area of said drums by the extrudate extruded through said extruder die, when wrapped around said drum(s), wherein the degree of contact by the extrudate with at least one of the draw down drums is at least 50% of the circumference of said drum.

16. Tobacco reconstitution draw down apparatus according to Claim 15, wherein a second draw down drum is arranged so that the degree of contact by the extrudate with said second draw down drum is at least 45% of the circumference of said drum.

17. A tobacco reconstitution process substantially as described hereinabove with reference to the accompanying diagrammatic drawing hereof.

18. Tobacco reconstitution draw down apparatus substantially as hereinabove described with reference to the accompanying diagrammatic drawing hereof.