METHOD FOR THE PRODUCTION OF HOMOGENIZED TOBACCO MATERIAL

Abstract

The present invention relates to method for production of a slurry for homogenized tobacco material, said method comprising: —Selecting tobacco of one or more tobacco types; —Coarse grinding said tobacco; —Blending said tobacco of one or more tobacco types; and —Fine grinding said tobacco of one or more tobacco types.

Claims

1. A method for production of homogenized tobacco material, said method comprising: selecting tobacco of one or more tobacco types; coarse grinding the tobacco; blending the tobacco of one or more tobacco types; and fine grinding the tobacco of one or more tobacco types.

2. Method according to claim 1, wherein the step of fine grinding the tobacco comprises: fine grinding said tobacco up to a tobacco powder having a mean size between about 0.03 millimetres and about 0.12 millimetres.

3. Method according to claim 1 wherein the coarse grinding comprises: coarse grinding tobacco leaves to obtain tobacco particles of a mean size between about 0.25 millimetres and about 2.0 millimetres.

4. Method according to claim 1, wherein the step of coarse grinding is performed before the step of blending.

5. Method according to claim 1, wherein, before the step of coarse grinding, it comprises: shredding the tobacco leaves to obtain tobacco strips having a mean size between about 2 millimetres and about 100 millimetres.

6. Method according to claim 1, wherein the step of selecting tobacco of one or more tobacco types further comprises the step of selecting: at least about 30 percent of bright tobacco in dry weight basis of total amount of tobacco in the tobacco blend; between about 0 percent and about 40 percent of dark tobacco in dry weight basis of total amount of tobacco in the tobacco blend; and between about 0 percent and about 40 percent of aromatic tobacco in dry weight basis of total amount of tobacco in the tobacco blend.

7. Method according to claim 1, further comprising the step of: adding a binder to the blend of different tobacco types in an amount comprised between about 1 percent and about 5 percent in dry weight basis of the homogenized tobacco material.

8. Method according to claim 1, further comprising the step of: adding an aerosol-former to the blend of different tobacco types in an amount comprised between about 5 percent and about 30 percent in dry weight basis of the homogenized tobacco material.

9. Method according to claim 7, further comprising the step of: Mixing the binder and the aerosol-former before adding said binder and said aerosol-former to said blend of different tobacco types.

10. Method according to claim 1, wherein the tobacco blend is comprised in an amount between about 20 percent and about 93 percent in dry weight basis of the homogenized tobacco material.

11. Method according to claim 1, further comprising the step of: adding a cellulose pulp to the blend of tobacco powder in an amount between about 1 and about 3 percent in dry weight basis of the homogenized tobacco material.

12. Method according to claim 1, comprising: forming a slurry including said blend of tobacco powder; and casting a continuous web of the slurry.

13. Method according to claim 12, wherein the moisture of said web at casting is comprised between about 60 percent and 80 percent of the total weight of the web.

14. Method according to claim 12, further comprising the step of: drying the cast web; winding the cast web; wherein the moisture of said cast web at winding is between about 7 percent and about 15 percent of the total weight of the cast web.

15. Aerosol-generating article, comprising a portion of homogenized tobacco material realized according to claim 1.

16. Method according to claim 2 wherein the coarse grinding comprises: coarse grinding tobacco leaves to obtain tobacco particles of a mean size between about 0.25 millimetres and about 2.0 millimetres.

17. Method according to claim 7, further comprising the step of: adding an aerosol-former to the blend of different tobacco types in an amount comprised between about 5 percent and about 30 percent in dry weight basis of the homogenized tobacco material.

18. Method according to claim 8, further comprising the step of: Mixing the binder and the aerosol-former before adding said binder and said aerosol-former to said blend of different tobacco types.

19. Method according to claim 13, further comprising the step of: drying the cast web; winding the cast web; wherein the moisture of said cast web at winding is between about 7 percent and about 15 percent of the total weight of the cast web.

20. Aerosol-generating article, comprising a portion of homogenized tobacco material realized according to claim 14.

Description

[0052] The invention will be further described, by way of example only, with reference to the accompanying drawings in which:

[0053] FIG. 1 shows a flow diagram of a method to produce slurry for homogenized tobacco material according to the invention;

[0054] FIG. 2 shows a block diagram of a variant of the method of FIG. 1;

[0055] FIG. 3 shows a block diagram of a method for production of a homogenized tobacco material according to the invention;

[0056] FIG. 4 shows an enlarged view of one of the steps of the method of FIG. 1, 2 or 3;

[0057] FIG. 5 shows a schematic view of an apparatus for performing the method of FIGS. 1 and 2; and

[0058] FIG. 6 shows a schematic view of an apparatus for performing the method of FIG. 3.

[0059] With initial reference to FIG. 1, a method for the production of slurry according to the present invention is represented. The first step of the method of the invention is the selection 100 of the tobacco types and tobacco grades to be used in the tobacco blend for producing the homogenized tobacco material. Tobacco types and tobacco grades used in the present method are for example bright tobacco, dark tobacco, aromatic tobacco and filler tobacco.

[0060] Only the selected tobacco types and tobacco grades intended to be used for the production of the homogenized tobacco material undergo the processing according to following steps of the method of the invention.

[0061] The method includes a further step 101 in which the selected tobacco is laid down. This step may comprise checking the tobacco integrity, such as grade and quantity, which can be for example verified by a bar code reader for product tracking and traceability. After harvesting and curing, the leaf of tobacco is given a grade, which describes for example the stalk position, quality, and colour.

[0062] Further, the lay down step 101 might also include, in case the tobacco is shipped to the manufacturing premises for the production of the homogenized tobacco material, de-boxing or case opening of the tobacco boxes. The de-boxed tobacco is then preferably fed to a weighing station in order to weight the same.

[0063] Moreover, the tobacco lay down step 101 may include bale slicing, if needed, as the tobacco leaves are normally compressed into bales in shipping boxes for shipping.

[0064] The following steps are performed for each tobacco type, as detailed below. These steps may be performed subsequently per grade such that only one production line is required. Alternatively, the different tobacco types may be processed in separate lines. This may be advantageous where the processing steps for some of the tobacco types are different. For example, in conventional primary tobacco processes bright tobaccos and dark tobaccos are processed at least partially in separate processes, as the dark tobacco often receives an additional casing. However, according to the present invention, preferably, no casing is added to the blended tobacco powder before formation of the homogenized tobacco web.

[0065] Further, the method of the invention includes a step 102 of coarse grinding of the tobacco leaves.

[0066] According to a variant of the method of the invention, after the tobacco lay down step 101 and before the tobacco coarse grinding step 102, a further shredding step 103 is performed, as depicted in FIG. 2. In the shredding step 103 the tobacco is shredded into strips having a mean size comprised between about 2 millimetres and about 100 millimetres.

[0067] Preferably, after the shredding step 103, a step of removal of non-tobacco material from the strips is performed (not depicted in FIGS. 1 and 2).

[0068] Subsequently, the shredded tobacco is transported towards the coarse grinding step 102. The flow rate of tobacco into a mill to coarse grind the strips of tobacco leaf is preferably controlled and measured.

[0069] In the coarse grinding step 102, the tobacco strips are reduced to a mean particle size of between about 0.25 millimetres and about 2 millimetres. At this stage, the tobacco particles are still with their cells substantially intact and the resulting particles do not pose relevant transport issues.

[0070] The method of the invention may include an optional step 104, depicted in FIG. 2, which includes packing and shipping the coarse grinded tobacco. This step 104 is performed in case the coarse grinding step 102 and the subsequent step of the method of the invention are performed in different manufacturing facilities.

[0071] Preferably, after the coarse grinding step 102, the tobacco particles are transported, for example by pneumatic transfer, to a blending step 105. Alternatively, the step of blending 105 could be performed before the step of coarse grinding 102, or where present, before the step of shredding 103, or, alternatively, between the step of shredding 103 and the step of coarse grinding 102.

[0072] In the blending step 105, all the coarse grinded tobacco particles of the different tobacco types selected for the tobacco blend are blended. The blending step 105 therefore is a single step for all the selected tobacco types. This means that after the step of blending there is only need for a single process line for all of the different tobacco types.

[0073] In the blending step 105, preferably mixing of the various tobacco types in particles is performed. Preferably, a step of measuring and controlling one or more of the properties of the tobacco blend is performed. According to the invention, the flow of tobacco may be controlled such that the desired blend according to a pre-set target value or pre-set target values is obtained. For example, it may be desirable that the blend includes bright tobacco 1 at least for about 30 percent in dry weight basis of the total tobacco in the blend, and that dark tobacco 2 and aromatic tobacco 3 are comprised in a percentage between about 0 percent and about 40 percent in dry weight basis of the total tobacco in the blend, for example about 35 percent. More preferably, also filler tobacco 4 is introduced in a percentage between about 0 percent and about 20 percent in dry weight basis of the total tobacco in the blend. The flow rate of the different tobacco types is therefore controlled so that these ratios of the various tobacco types is obtained. Alternatively, where the coarse grinding step 102 is done subsequently for the different tobacco leaves used, the weighing step at the beginning of the step 102 determines the amount of tobacco used per tobacco type and grade instead of controlling its flow rate.

[0074] In FIG. 4, the introduction of the various tobacco types during the blending step 105 is shown.

[0075] It is to be understood that each tobacco type could be itself a sub-blend, in other words, the “bright tobacco type” could be for example a blend of Virginia tobacco and Brazil flue-cured tobacco of different grades.

[0076] After the blending step 105, a fine grinding step 106, to a tobacco powder mean size of between about 0.03 millimetres and about 0.12 millimetres is performed. This fine grinding step 106 reduces the size of the tobacco down to a powder size suitable for the slurry preparation. After this fine grinding step 106, the cells of the tobacco are at least partially destroyed and the tobacco powder may become sticky.

[0077] The so obtained tobacco powder can be immediately used to form the tobacco slurry. Alternatively, a further step of storage of the tobacco powder, for example in suitable containers, may be inserted (not shown).

[0078] With reference to FIG. 3, a method of the invention for a manufacture of a homogenized tobacco web is shown. From step 106 of fine grinding, the tobacco powder is used in a subsequent slurry preparation step 107. Prior to or during the slurry preparation step 107, the method of the invention includes two further steps: a pulp preparation step 108 where cellulose fibres 5 and water 6 are pulped to uniformly disperse and refine the fibres in water, and a suspension preparation step 109, where an aerosol-former 7 and a binder 8 are premixed. Preferably the aerosol-former 7 includes glycerol and the binder 8 includes guar. Advantageously, the suspension preparation step 109 includes premixing guar and glycerol without the introduction of water.

[0079] The slurry preparation step 107 preferably comprises transferring the premix solution of the aerosol-former and the binder to a slurry mixing tank and transferring the pulp to the slurry mixing tank. Further, the slurry preparation step comprises dosing the tobacco powder blend into the slurry mixing tank with pulp, and the guar-glycerol suspension. More preferably, this step also includes processing the slurry with a high shear mixer to ensure uniformity and homogeneity of the slurry.

[0080] Preferably, the slurry preparation step 107 also includes a step of water addition, where water is added to the slurry to obtain the desired viscosity and moisture.

[0081] In order to form the homogenized tobacco web, preferably the slurry formed according to step 107 is cast in a casting step 110. Preferably, this casting step 110 includes transporting the slurry to a casting station and casting the slurry into web having a homogenous and uniform film thickness on a support. Preferably, during casting, the cast web thickness, moisture and density are controlled immediately after casting and more preferably are also continuously monitored and feedback-controlled using slurry measuring devices during the whole process.

[0082] The homogenized cast web is then dried in a drying step 111 comprising a uniform and gentle drying of the cast web, for example in an endless, stainless steel belt dryer. The endless, stainless steel belt dryer may comprise individually controllable zones. Preferably the drying step comprises monitoring the cast leaf temperature at each drying zone to ensure a gentle drying profile at each drying zone and heating the support where the homogenized cast web is formed. Preferably, the drying profile is a so called TLC drying profile.

[0083] At the conclusion of the web drying step 111, a monitoring step (not shown) is executed to measure the moisture content and number of defects present in the dried web.

[0084] The homogenized tobacco web that has been dried to a target moisture content is then preferably wound up in a winding step 111, for example to form a single master bobbin. This master bobbin may be then used to perform the production of smaller bobbins by slitting and small bobbin forming process. The smaller bobbin may then be used for the production of an aerosol-generating article (not shown).

[0085] The method of production of a slurry for the homogenized tobacco material according to FIG. 1 or 2 is performed using an apparatus 200 for the production of a slurry depicted schematically in FIG. 5. The apparatus 200 includes a tobacco receiving station 201, where accumulating, de-stacking, weighing and inspecting the different tobacco types takes place. Optionally, in case the tobacco has been shipped into cartons, in the receiving station 201 removal of cartons containing the tobacco is performed. The tobacco receiving station 201 also optionally comprises a tobacco bale splitting unit.

[0086] In FIG. 5 only a production line for one type of tobacco is shown, but the same equipment may be present for each tobacco type used in the homogenised tobacco material web according to the invention, depending on when the step of blending is performed. Further the tobacco is introduced in a shredder 202 for the shredding step 103. Shredder 202 can be for example a pin shredder. The shredder 202 is preferably adapted to handle all sizes of bales, to loosen tobacco strips and shred strips into smaller pieces. The shreds of tobacco in each production line are transported, for example by means of pneumatic transport 203, to a mill 204 for the coarse grinding step 102. Preferably a control is made during the transport so as to reject foreign material in the tobacco shreds. For example, along the pneumatic transport of shredded tobacco, a string removal conveyor system, heavy particle separator and metal detector may be present, all indicated with 205 in the appended drawing.

[0087] Mill 204 is adapted to coarse grind the tobacco strips up to a size of between about 0.25 millimetres and about 2 millimetres. The rotor speed of the mill can be controlled and changed on the basis of the tobacco shreds flow rate.

[0088] Preferably, a buffer silo 206 for uniform mass flow control, is located after the coarse grinder mill 204. Furthermore, preferably mill 204 is equipped with spark detectors and safety shut down system 207 for safety reasons.

[0089] From the mill 204, the tobacco particles are transported, for example by means of a pneumatic transport 208, to a blender 210. Blender 210 preferably includes a silo in which an appropriate valve control system is present. In the blender, all tobacco particles of all the different types of tobacco which have been selected for the predetermined blend are introduced. In the blender 210, the tobacco particles are mixed to a uniform blend. From the blender 210, the blend of tobacco particles is transported to a fine grinding station 211.

[0090] Fine grinding station 211 is for example an impact classifying mill with suitable designed ancillary equipment to produce fine tobacco powder to the right specifications, that is, to a tobacco powder between about 0.03 millimetres and about 0.12 millimetres. After the fine grinding station 211, a pneumatic transfer line 212 is adapted to transport the fine tobacco powder to a buffer powder silo 213 for continuous feed to a downstream slurry batch mixing tank where the slurry preparation process takes place.

[0091] The slurry which has been prepared using the tobacco powder above described in steps 106, 107 and 108 of the method of the invention is preferably also cast in a casting station 300 as depicted in FIG. 6.

[0092] Slurry from a buffer tank (not shown) is transferred by means of suitable pump with precision flow rate control measurement to the casting station 300. Casting station 300 comprises preferably the following sections. A precision slurry casting box and blade assembly 301 where slurry is cast onto a support 303, such as a stainless steel belt with the required uniformity and thickness for proper web formation, receives the slurry from the pump. A main dryer 302, having drying zones or sections is provided to dry the cast tobacco web. Preferably, the individual drying zones have steam heating on the bottom side of the support with heated air above the support and adjustable exhaust air control. Within the main dryer 302 the homogenized tobacco web is dried to desired final moisture on the support 303.