METHOD FOR PRODUCING A HOMOGENIZED TOBACCO MATERIAL, AND HOMOGENIZED TOBACCO MATERIAL

Abstract

The present invention relates to a method to produce a homogenized tobacco material for use in a heat-not-burn aerosol-generating article, comprising the steps of: —selecting a first target value for a first tobacco characteristic, said first tobacco characteristic being reducing sugars and the first target value being comprised between about (8) percent and about (18) percent in dry weight basis of a total amount of tobacco present within the homogenized tobacco material; —selecting a second target value of a second tobacco characteristic, wherein the second tobacco characteristic is one of total ammonia and total alkaloids; —blending graded tobacco types so as to form the tobacco blend, each graded tobacco type comprising a predetermined amount of the first and second tobacco characteristics, so that the first and second target values of said first and second tobacco characteristics are obtained in said blend within a predetermined tolerance range; —grinding said tobacco blend into a blended tobacco powder; —forming a slurry comprising the blended tobacco powder; and forming a web of homogenous tobacco web from the slurry.

Claims

1. Method for producing homogenized tobacco material for use in a heat-not-burn aerosol-generating article, comprising the steps of: selecting a first target value for a first tobacco characteristic, said first tobacco characteristic being reducing sugars and the first target value being comprised between about 8 percent and about 18 percent in dry weight basis of a total amount of tobacco present within the homogenized tobacco material; selecting a second target value of a second tobacco characteristic, wherein the second tobacco characteristic is one of total ammonia and total alkaloids; blending graded tobacco types so as to form the tobacco blend, each graded tobacco type comprising a predetermined amount of the first and second tobacco characteristics, so that the first and second target values of said first and second tobacco characteristics are obtained in said blend within a predetermined tolerance range; grinding said tobacco blend into a blended tobacco powder; forming a slurry comprising the blended tobacco powder; and forming a web of homogenous tobacco web from the slurry.

2. The method according to claim 1, wherein the second tobacco characteristic is total alkaloids and said second target value is comprised between about 1.5 percent and about 3.5 percent in dry weight basis of the total amount of tobacco present within the homogenized tobacco material.

3. The method according to claim 1, wherein the second tobacco characteristic is total ammonia and said second target value is below about 0.2 percent in dry weight basis of the total amount of tobacco present within the homogenized tobacco material.

4. The method according to claim 2, comprising the step of selecting a third target value for a third tobacco characteristic, wherein the third tobacco characteristic is total ammonia the third target value is below about 0.2 percent in dry weight basis of the total amount of tobacco present within the homogenized tobacco material.

5. The method according to claim 1, wherein the blended tobacco powder comprises between about 50 percent and about 100 percent of the total tobacco comprised within the homogenized tobacco material.

6. The method according to claim 1, wherein the step of blending graded tobacco types comprises blending at least about 30 percent of bright tobacco in dry weight basis of the total amount of tobacco included in the homogenized tobacco material.

7. The method according to claim 1, wherein the predetermined tolerance range for the first or second target value of the first or second tobacco characteristic is plus or minus about 10 percent the selected first or second target value, respectively.

8. The method according to claim 1, further comprising the steps of drying the homogeneous tobacco web.

9. The method according to claim 1, wherein the step of grinding said tobacco blend into a blended tobacco powder comprises the step of grinding said tobacco blend to a powder mean size of between about 0.03 millimeters and about 0.12 millimeters.

10. Homogenized tobacco material comprising powder from a blend of graded tobacco types, said tobacco blend comprising between about 50 percent and about 100 percent of the total amount of tobacco included in the homogenized tobacco material and wherein the graded tobacco types are blended such that the reducing sugars are in an amount comprised between about 8 percent and about 18 percent in dry weight basis of the total amount of tobacco present within the homogenized tobacco material.

11. Homogenized tobacco material according to claim 10, wherein the graded tobacco types are blended so that the total ammonia is in an amount below about 0.2 percent in dry weight basis of the total amount of tobacco present within the homogenized tobacco material.

12. Homogenized tobacco material according to claim 10, wherein the graded tobacco types are blended so that the total alkaloids are in an amount comprised between about 1.5 percent and 3.5 percent in dry weight basis of the total amount of the tobacco present within the homogenized tobacco material.

13. Homogenized tobacco material according to claim 10, wherein said tobacco blend comprises at least about 30 percent of bright tobacco in dry weight basis of the total amount of tobacco included in the homogenized tobacco material.

14. Homogenized tobacco material according to claim 10, wherein said tobacco blend comprises less than about 40 percent of dark tobacco in dry weight basis of the total amount of tobacco included in the homogenized tobacco material.

15. Homogenized tobacco material according to claim 10, wherein said tobacco blend comprises less than about 40 percent of aromatic tobacco in dry weight basis of the total amount of tobacco included in the homogenized tobacco material.

16. Homogenized tobacco material according to claim 10, wherein said tobacco blend comprises less than about 20 percent of filler tobacco in dry weight basis of the total amount of tobacco included in the homogenized tobacco material.

17. Homogenized tobacco material according to claim 10, comprising cellulose fibers in an amount between about 1 percent and about 3 percent in dry weight basis of the homogenized tobacco material.

18. Homogenized tobacco material according to claim 10, comprising a binder in an amount between about 1 percent and about 5 percent in dry weight basis of the homogenized tobacco material.

19. Homogenized tobacco material according to claim 10, comprising an aerosol-former in an amount between about 5 percent and about 30 percent in dry weight basis of the homogenized tobacco material.

20. An aerosol-generating article including a portion of the homogenized tobacco material according to claim 10.

21. A batch of aerosol-generating articles according to claim 20, wherein the first or the second target value of the first or the second tobacco characteristic, respectively, is within a predetermined tolerance range, and the tolerance range is equal to the first or second target value plus or minus about 10 percent of the selected first or second target value, respectively.

22. An aerosol-generating article including a portion of the homogenized tobacco material realized according to the method of claim 1.

23. A batch of aerosol-generating articles according to claim 22, wherein the first or the second target value of the first or the second tobacco characteristic, respectively, is within a predetermined tolerance range, and the tolerance range is equal to the first or second target value plus or minus about 10 percent of the selected first or second target value, respectively.

Description

[0059] Specific embodiments will be further described, by way of example only, with reference to the accompanying drawings in which:

[0060] FIG. 1 shows a flow diagram of a method to produce slurry for homogenized tobacco material according to the invention;

[0061] FIG. 2 shows a block diagram of a variant of the method of FIG. 1;

[0062] FIG. 3 shows a block diagram of a method for production of a homogenized tobacco material according to the invention;

[0063] FIG. 4 shows an enlarged view of one of the steps of the method of FIG. 1, 2 or 3;

[0064] FIG. 5 shows an enlarged view of one of the steps of the method of FIG. 1, 2 or 3;

[0065] FIG. 6 shows a schematic view of an apparatus for performing the method of FIGS. 1 and 2; and

[0066] FIG. 7 shows a schematic view of an apparatus for performing the method of FIG. 3.

[0067] 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.

[0068] Only the selected tobacco types and tobacco grades intended to be used in the production of the homogenized tobacco material undergo the processing according to following steps of the method of the invention.

[0069] 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 the stalk position, quality, and colour.

[0070] The tobacco types are either examined in order to obtain the value of some tobacco characteristics of the various tobacco types, or the tobacco characteristics have been already analyzed, for example reported or written down in a bar-code or sticker. These tobacco characteristics include reducing sugars and one of total ammonia or total alkaloids.

[0071] The analysis or retrieval of the value of these characteristics is performed for every grade within each tobacco type. For example, the flue-cured tobacco may include a type or grade having a reducing sugars content equal to about 22 percent in dry weight basis and an Ontario flue-cured tobacco having a reducing sugars content of about 18 percent in dry weight basis. The graded tobacco types are used in a tobacco blend 9 formed in a further step of the method of the invention. For the blend, a plurality of target values of tobacco characteristics is set. A target value for the reduced sugar within a range of about 8 percent and about 18 percent in dry weight basis of the total amount of tobacco is selected. Further, preferably a target value for the total ammonia below about 0.2 percent in dry weight basis of the total amount of tobacco is selected. Preferably, also a target value for the total alkaloids comprised between about 1.5 percent and about 3.5 percent in dry weight basis of the total amount of tobacco is selected. Reduced sugar, total alkaloids and total ammonia can be measured directly in the tobacco leaves, so that the percentage of the various types of tobacco to be present in the tobacco blend 9 can be chosen in order to obtain the selected target values.

[0072] 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.

[0073] Moreover, the tobacco lay down step 101 may include bale slicing, if needed, as the tobacco leaves are normally transported in bales when boxed and shipped.

[0074] The tobacco bales are separated depending on the tobacco type. For example there may be a processing line for each tobacco type. Therefore, 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.

[0075] Further, the method of the invention includes a step 102 of coarse grinding of the tobacco leaves.

[0076] 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 1 millimetre and about 100 millimetres.

[0077] 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).

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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 this ratio 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.

[0084] As shown in FIG. 5, the blend is so prepared that the target values for the reducing sugars 10 and at least for one of the target values for total alkaloids 11 and total ammonia 12 are met. Preferably all three target values are selected, so that the resulting blend has a value of reduced sugar, of total ammonia and total alkaloids at about the selected target values. The first, second and third target values are obtained in the process of the invention within a predetermined tolerance range, said predetermined tolerance range being preferably plus or minus 10 percent the first, second, and third target values, respectively.

[0085] In FIG. 4, the introduction of the various tobacco types during the blending step 105 is shown. These tobacco types are introduced in such ratios that the above mentioned target values are obtained in the resulting blend.

[0086] 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.

[0087] 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.

[0088] 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).

[0089] With now 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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 in a small bobbin forming process. The smaller bobbins may then be used for the production of an aerosol-generating article (not shown).

[0096] The method of production of a slurry for the homogenized tobacco material according to FIG. 1 or 2 is performed using an apparatus for the production of a slurry 200 depicted schematically in FIG. 6. 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.

[0097] In FIG. 6 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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 transporting 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.

[0102] The slurry which has been prepared using the tobacco powder above described in steps 100-109 of the method of the invention is preferably also cast in a casting station 300 as depicted in FIG. 7.

[0103] 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 knife 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.