METHOD FOR THE PRODUCTION OF HOMOGENIZED TOBACCO MATERIAL

Abstract

The present invention relates to a method of preparation of a slurry for the production of a homogenized tobacco material, said method comprising: —suspending a binder in an aerosol-former to form a suspension; —creating a cellulose pulp from cellulose fibers and water; —providing a tobacco powder blend; and —combining said suspension of binder in aerosol-former, said cellulose pulp and said tobacco powder blend to form said slurry.

Claims

1. Method of production of a homogenized tobacco material, said method comprising: suspending a binder in an aerosol-former to form a suspension; creating a cellulose pulp from cellulose fibers and water; providing a tobacco powder blend; and combining the suspension of binder in aerosol-former, the cellulose pulp and the tobacco powder blend to form a slurry.

2. Method according to claim 1, further comprising the step of: Adding water to the slurry formed by the suspension of binder in aerosol-former, the cellulose pulp and the tobacco powder blend.

3. Method according to claim 1, wherein the step of forming a pulp with cellulose fibers and water comprises: Forming a concentrated pulp wherein the cellulose fibers in the concentrated pulp are in an amount comprised between about 3 percent and 5 percent of the total weight of the pulp.

4. Method according to claim 1, wherein the step of combining the suspension of binder in aerosol-former, the cellulose pulp and the tobacco powder blend to form the slurry comprises the step of: Combining the suspension of binder in an aerosol-former, the cellulose pulp and the tobacco powder blend in such a proportion that the binder is in an amount comprised between about 1 percent and about 5 percent in dry weight basis of the slurry.

5. Method according to claim 1, wherein the step of combining said suspension of binder in aerosol-former, the cellulose pulp and the tobacco powder blend to form the slurry comprises: Combining the suspension of binder in aerosol-former, the cellulose pulp and the tobacco powder blend in such a proportion that the aerosol-former is in an amount comprised between about 5 percent and about 30 percent in dry weight basis of the slurry.

6. Method according to claim 1, further comprising: Combining the suspension of binder in aerosol-former, the cellulose pulp and the tobacco powder blend to form the slurry in a tank; and Cooling the tank in order to keep a temperature of the slurry between about 15 degrees Celsius and about 40 degrees Celsius.

7. Method according to claim 1, further comprising: Combining the suspension of binder in aerosol-former, the cellulose pulp and the tobacco powder blend to form the slurry in a tank; and Mixing the slurry.

8. Method according to claim 7, wherein the slurry mixing is performed in a tank defining a central region and an outer mantel, the mixing being performed by means of a spiral mixer adapted to remove slurry from the outer mantel and to direct it towards said central region or to remove slurry from the central region and to direct it towards the outer mantel, so as to uniformly mix the slurry.

9. Method according to claim 1, wherein the step of forming a pulp with cellulose fibers and water comprises: reducing the fiber length of the cellulose fibers by means of grinding in order to obtain a mean fiber length of the cellulose fibers comprised between about 0.2 millimetres and about 4 millimetres.

10. Method according to claim 1, wherein the step of forming a pulp with cellulose fibers and water comprises: At least partially fibrillating the cellulose fibers.

11. Method according to claim 1, wherein the step of mixing binder and aerosol-former to form a suspension comprises: Adding a first amount of binder to a first amount of aerosol-former; Mixing the first amount of binder and the first amount of aerosol-former; and Adding a second amount of aerosol-former.

12. Method according to claim 1, further comprising one or more of the following steps: Monitoring a viscosity of the slurry; Monitoring a temperature of the slurry; or Monitoring moisture of the slurry.

13. Method according to claim 1, comprising: Casting the slurry so as to form a continuous homogenized tobacco web; and Drying the homogenized tobacco web.

14. Method according to claim 13, wherein, before the casting step, the moisture of the slurry is comprised between about 60 percent and about 80 percent of the total weight of the slurry.

15. Homogenized tobacco material comprising: a binder in an amount comprised between about 1 percent and 5 percent in dry weight basis of said homogenized tobacco material; an aerosol-former in an amount comprised between about 5 percent and about 30 percent in dry weight basis of said homogenized tobacco material; a grinded tobacco blend in an amount comprised between about 20 percent and about 93 percent in dry weight basis of said homogenized tobacco material; and cellulose fibres added to cellulose fibres present in the grinded tobacco blend, the added cellulose fibres being in an amount comprised between about 1 percent and about 3 percent in dry weight basis of said homogenized tobacco material, said cellulose fibers comprising fibers from one or more of wood, flax, temp or tobacco.

16. Aerosol-generating device including a portion of said homogenized tobacco material realized according to the method according to claim 15.

17. Aerosol-generating device including a portion of said homogenized tobacco material realized according to the method of claim 1.

Description

[0084] Specific embodiments will be further described, by way of example only, with reference to the accompanying drawings in which:

[0085] FIG. 1 is a flow diagram of an embodiment of the method of preparation of a slurry for the production of a homogenized tobacco material;

[0086] FIG. 2 is a schematic view of an apparatus for the production of a suspension of binder in aerosol-former;

[0087] FIG. 3 is a schematic view of an apparatus for the production of cellulose pulp;

[0088] FIG. 4 is a schematic view of an apparatus for the preparation of slurry; and

[0089] FIG. 5 is a schematic view of an apparatus for casting and drying a homogenized tobacco sheet.

[0090] With reference to FIG. 1, a method to realize a slurry for the production of a homogenized tobacco material according to the invention is schematically depicted.

[0091] The method of realize the slurry includes a step of preparing a cellulose pulp 100. The pulp preparation step 100 preferably comprises mixing water 1 and cellulose fibers 2 in a concentrated form, optionally storing the pulp so obtained and then diluting the pulp before forming the slurry. The cellulose fibers, for example in boards or bags, are loaded in a pulper and then liquefied with water. The resulting water-cellulose solution may be stored at different densities, however preferably the pulp which is the result of the step 100 is “concentrate”. Preferably, “concentrate” means that between about 3 and about 5 percent of cellulose fibers are included in the water/cellulose pulp. Preferred cellulose fibers are soft wood fibers. Preferably, the total amount of cellulose fibers in the slurry in dry weight, in addition to the cellulose fibres present in the tobacco blend added to the slurry, is between about 1 percent and about 3 percent, preferably, between about 1.2 percent and about 2.4 percent in dry weight of the homogenized tobacco material.

[0092] Preferably, the step of mixing of water and cellulose fibers lasts between about 20 and about 60 minutes, advantageously at a temperature comprised between about 15 degrees Celsius and about 40 degrees Celsius.

[0093] The storage time, if storage of the pulp is performed, may preferably vary between about 0.1 and about 7 days.

[0094] Advantageously, water dilution takes place after the step of storing of the concentrated pulp. Water is added to the concentrated pulp in such an amount that the cellulose fibers are less than about 1 percent of the total weight of the pulp. For example, a dilution of a factor comprised between about 3 and about 20 can take place. Further, an additional step of mixing may take place, which comprises mixing the concentrated pulp and the added water. The additional mixing step preferably lasts between about 120 minutes and about 180 minutes at a temperature between about 15 degrees Celsius and about 40 degrees Celsius, more preferably, at a temperature of between about 18 degrees Celsius and about 25 degrees Celsius.

[0095] Preferably, after the step of pulp preparation 100, an optional step of fibers' fibrillation is performed (not depicted in FIG. 1).

[0096] An apparatus 200 to perform the method step 100 of the pulp formation is depicted in FIG. 2. FIG. 2 schematically depicts a cellulose fibre feeding and preparation line 200 comprising a feeding system 201, preferably adapted to handle cellulose fibres 2 in bulk form, such as board/sheets or fluffed fibers, and a pulper 202. The feeding system 201 is adapted to direct the cellulose fibres to the pulper 202, which is in turn adapted to disperse the received fibres uniformly.

[0097] The pulper 202 includes a temperature control unit 201a so that the temperature in the pulper is kept within a given temperature interval, and a rotational speed control unit 201b, so that the speed of an impeller (not shown) present in the pulper 202 is controlled and kept preferably comprised between about 5 rpm and about 35 rpm.

[0098] The cellulose fibre feeding and preparation line 200 further comprises a water line 204 adapted to introduce water in the pulper 202. A flow rate controller 205 to control the flow rate of water introduced in pulper 202 is preferably added in the water line 204.

[0099] The cellulose fibre feeding and preparation line 200 may also further comprise a fibre refiner system 203 to treat and fibrillate fibres, so that long fibres and nested fibres are removed, and a uniform fibre distribution is obtained.

[0100] Preferably, the mean fibre length of the cellulose fibres after the refining step is between about 0.2 millimetres and about 4 millimetres.

[0101] The mean size is considered to be the mean length. Each length of the fibre is calculated following the framework of the fibre, therefore it is the real developed length of the fibre. The mean fibre length is calculated per number of fibres, for example it may be calculated on 5.000 fibers.

[0102] Measured objects are considered as fibres if their length and width are comprised within: [0103] 200 μm<length<10.000 μm [0104] 5 μm<width<75 μm

[0105] In order to calculate the mean fibre length, the MorFi Compact fibre analyzer on fibers produced by Tech Pap SAS can be used.

[0106] The analysis is performed for example putting the fibres in a solution, so as to form an aqueous fibrous suspension. Preferably, deionized water is used and no mechanical mixing is applied during sample preparation. Mixing is performed by the fibre analyzer. Preferably, measurements are performed on fibres which have stayed at least 24 hours at about 22 degrees Celsius and about 50 percent relative humidity.

[0107] Downstream the fibre refiner system 203, the cellulose fibre feeding and preparation line 200 may comprise a cellulose buffer tank 207 connected to the fibre refiner system 203 to store the high consistency fibre solution coming out of the system 203.

[0108] At the end of cellulose fibre feeding and preparation line 200, a cellulose dilution tank 208 in which pulp is diluted is preferably present and connected to cellulose buffer tank 207. The cellulose dilution tank 208 is adapted to batch out cellulose fibres of right consistency for subsequent slurry mixing. Water for dilution is introduced in tank 208 via a second water line 210.

[0109] Referring back to FIG. 1, the method to realize the slurry according to the invention also includes a step of suspension preparation 101. The suspension preparation step 101 preferably comprises mixing an aerosol-former 3 and a binder 4 in order to form a suspension. Preferably, the aerosol-former 3 comprises glycerol and the binder 4 comprises guar. The suspension step 101 of binder in aerosol-former includes the steps of loading the aerosol-former and the binder in a container and mixing the two. Preferably, the resulting suspension is then stored before being introduced in the slurry. Preferably, the glycerol is added to the guar in two steps, a first amount of glycerol is mixed with guar and a second amount of glycerol is then injected in the transport pipes, so that glycerol is used to clean the processing line, avoiding hard-to-clean points within the line.

[0110] A slurry preparation line 300 adapted to perform the suspension step 101 of binder in aerosol-former of the invention is depicted in FIG. 3.

[0111] The slurry preparation line 300 includes an aerosol-former, such as glycerol, bulk tank 301 and a pipe transfer system 302 having a mass flow control system 303 adapted to transfer the aerosol-former 3 from the tank 301 and to control its flow rate. Further, the slurry preparation line 300 comprises a binder handling station 304 and a pneumatic transport and dosing system 305 to transport and weight the binder 4 received at the station 304.

[0112] Aerosol-former and binder from tank 301 and handling station 304 are transported to a mixing tank, or more than a mixing tank, 306, part of the slurry preparation line 300, designed to mix binder and aerosol-former uniformly.

[0113] All tanks and transfer pipes for cellulose fiber, guar and glycerol are preferably designed to be as optimally short as possible to reduce transfer time, minimize waste, avoid cross contamination and facilitate ease of cleaning. Further, preferably, the transfer pipes for cellulose fiber, guar and glycerol are as straight as possible, to allow a swift and uninterrupted flow. In particular for the suspension of binder in the aerosol-former, turns in the transfer pipe could otherwise result in areas of low flow rate or even standstill, which in turn can be areas where gelling can occur and with that potentially blockages within the transfer pipes. As mentioned before, those blockages can lead to the need for cleaning and standstill of the entire manufacturing process.

[0114] Further, the method of the invention includes a step of a tobacco powder blend formation 102. Tobacco has been blended and grinded in a blending and grinding line, not depicted in the drawing, in order to obtain a tobacco powder blend preferably to a mean size between about 0.03 millimetres and about 0.12 millimetres.

[0115] The method to form a slurry according to the invention further comprises a step of slurry formation 103, where the suspension 5 of the binder in the aerosol-former obtained in step 101, the pulp 6 obtained in step 100 and a tobacco powder 7 obtained in step 102 are combined together.

[0116] Preferably, the step of slurry formation 103 comprises first a step of introduction in a tank of the suspension of binder in aerosol-former 5 and of the cellulose pulp 6. Afterwards, the tobacco powder 7 is introduced as well. Preferably, the suspension 5, the pulp 6 and the tobacco powder 7 are suitably dosed in order to control the amount of each of them introduced in the tank. The slurry is prepared according to specific proportion among its ingredients. Preferably also water 8 is added.

[0117] Preferably, the step of slurry formation 103 further comprises a mixing step, where all the slurry ingredients are mixed together for a fixed amount of time. In a further step of the method according to the invention, the slurry is then transferred to a following casting step 104 and drying step 105.

[0118] An apparatus 400 for the slurry formation adapted to realize step 103 of the method of the invention is schematically depicted in FIG. 4. Apparatus 400 includes a mixing tank 401 where cellulose pulp 6 and suspension 5 of binder in aerosol-former are introduced. Further, tobacco powder 7 from the blending and grinding line is fine-ground and dosed into the mixing tank 401 in specified quantity to prepare the slurry.

[0119] For example, the tobacco powder 7 may be contained in a tobacco fine powder buffer storage silo to ensure continuous upstream powder operation and meeting demand of slurry mixing process. Tobacco powder is transferred to the mixing tank 401 preferably by means of a pneumatic transfer system (not shown).

[0120] The apparatus 400 further comprises preferably a powder dosing system (also not shown) to dose required amount of the slurry's ingredients. For example, the tobacco powder may be weighed by a scale (not shown) or weighing belt (not shown) for precise dosing. The mixing tank 401 is specially designed to mix the dry and liquid ingredients to form a homogenous slurry. The slurry mixing tank preferably comprises a cooler (not shown), such as water jacket wall to allow water cooling on the external walls of the mixing tank 401. The slurry mixing tank 401 is further equipped with one or more sensors (not shown) such as level sensor, a temperature probe and sampling port for control and monitoring purpose. Mixing tank 401 has an impeller 402 adapted to ensure uniform mixing of the slurry, in particular adapted to transfer slurry form the external walls of the tank to the internal part of the tank or vice-versa. The speed of the impeller can be preferably controlled by means of a dedicated controlling unit. Mixing tank 401 also includes a water line for the introduction of water 8 at a controlled flow rate.

[0121] Preferably, mixing tank 401 includes two separated tanks, one downstream to the other in the flow of slurry, one tank for preparing the slurry and the second tank with slurry for transfer to provide continuous slurry supply to a slurry casting station.

[0122] The method of the invention to produce a homogenized tobacco web includes further a casting step 104 in which the slurry prepared in step 103 is cast in a continuous tobacco web onto a support. The casting step 104 includes transferring the slurry from the mixing tank 401 to a casting box. Then, the casting step 104 includes casting, preferably by means of a casting blade, the slurry onto a support, such as a steel conveyor. Further, in order to obtain a final homogenized tobacco web for the use in an aerosol-formed article, the method of the invention includes a drying step 105 in which the cast web of homogenized tobacco material is preferably dried. The drying step 105 includes drying the cast web, by means of steam and heated air. Preferably the drying with steam is performed on the side of the cast web in contact with the support, while the drying with heated air is performed on the free side of the cast web.

[0123] An apparatus for performing the step of casting 104 and drying 105 is schematically depicted in FIG. 5. The casting and drying apparatus 500 includes a slurry transfer system 501, such as a pump, preferably having a flow control, and a casting box 502 to which the slurry is transferred by the pump. Preferably, casting box 502 is equipped with level control 503 and a casting blade 504 for the casting of the slurry into a continuous web of homogenized tobacco material. Casting box 502 may also comprise a density control device 505 to control the density of the cast web.

[0124] A support, such as a stainless steel belt conveyor 506, receives the slurry cast by the casting blade 504.

[0125] Casting and drying apparatus 500 also includes a drying station 508 to dry the cast web of slurry. Drying station 508 comprises a steam heating 509 and top air drying 510.

[0126] Preferably, at the end of the casting step 104 and of the drying step 105, the homogenized tobacco web is removed from the support 506. Doctoring of the cast web after the drying station 508 at the right moisture content is preferably performed.

[0127] Preferably, the cast tobacco web is transported through a secondary drying process to remove further moisture content of the web to reach target moisture.

[0128] After the drying step 105, the cast web is preferably wound in one or more bobbins in a winding step 106, 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).