Apparatus and method for producing a cast sheet for a smoking article

Abstract

An apparatus for producing a cast sheet for a smoking article, comprises a continuous mixer (2) configured for mixing ingredients of a recipe and water to form a slurry mixture. The continuous mixer (2) delimits a mixing path (4) and has a plurality of inlets communicating with the mixing path (4) and configured to feed the ingredients and the water into the mixing path (4) and an outlet (28) located at an end of the mixing path (4) and configured to discharge the slurry mixture from the continuous mixer (2). The continuous mixer (2) is configured to mix the ingredients and the water while advancing the ingredients and water in the mixing path (4) towards the outlet (28). A casting box (32) is in fluid communication with the outlet (28) to receive the slurry mixture from the continuous mixer (2) and a surface is located under the casting box (32) and is configured to receive the slurry mixture from the casting box (32) to form a cast sheet (42).

Description

[0001] APPARATUS AND METHOD FOR PRODUCING A CAST SHEET FOR A SMOKING ARTICLE

[0002] The present disclosure relates to an apparatus and a method for producing a cast sheet for a smoking article. The present disclosure also relates to the cast sheet manufactured in said apparatus and / or through said method.

[0003] Cast sheets for smoking articles are known in the art and may be employed in the manufacturing of traditional smoking articles, which are ignited at one end causing them to smolder, and of aerosol-generating articles or heat-not-burn cigarettes, in which an aerosolgenerating substrate is heated rather than combusted. In the traditional smoking articles, the cast sheet may be a reconstituted tobacco leaf which may be used in tobacco blends in combination with other tobacco leaves. For instance, the reconstituted tobacco leaf may be shredded and mixed with other leaves to obtain a resulting tobacco blend intended to be ignited and smoked. In the aerosol-generating articles, the cast sheet may be a sheet of the abovementioned aerosol-generating substrate. For instance, the aerosol-generating substrate sheet is crimped, gathered, wrapped in a rod and cut in aerosol-generating substrate plugs intended to release volatile compounds by heat transfer from a heat source of an aerosol-generating system.

[0004] The cast sheet is prepared by casting a slurry with a high water content on a movable support. Currently, the slurry preparation takes place in batch mode. Current slurry preparation process is performed mixing different ingredients inside a slurry preparation tank at a certain mixing speed to achieve proper homogeneity. After the preparation, the slurry is transferred into a slurry storage tank, where it is stored for a maximum four hours before the following casting process.

[0005] For instance, W02016050471 and WO2017089589 disclose methods for the preparation of a tobacco based slurries and sheets. For instance, WO2022248378 and W02020074494 disclose methods for producing aerosol-forming substrates by preparing and casting slurries. US4325391 discloses a method and an apparatus for combining a liquid base web and dry comminuted tobacco to produce a homogeneous mix. US2023011797 discloses an apparatus for production of a sheet of material containing alkaloids used in aerosol-generating articles.

[0006] Preparation of reconstituted tobacco sheets by laminating slurries with a lower water content is also known. For instance, W02020058814A1 and WO2021181327A1 disclose methods for producing reconstituted tobacco wherein solid components of tobacco are comminuted to bring them to a particle size, the comminuted product thus obtained is mixed with water, at least one binding agent and at least one aerosol forming material until a mixture with a liquid content of about 35-40 percent, is obtained. The mixture is then subjected to a first lamination and to a series of further rolling passages to obtain a strip having a substantially constant thickness. The strip is then dried to bring its liquid content to about 8-15 percent.

[0007] It would be desirable to have an apparatus and a method for producing a cast sheet for a smoking article allowing to improve the quality of the cast sheets and therefore also the quality of the smoking articles comprising said cast sheets.

[0008] It would be desirable to have an apparatus and a method for producing a cast sheet for a smoking article allowing to improve the mechanical properties of the cast sheet, for instance the fracture force, and the uniformity of the mechanical properties in the cast sheet, thus improving the workability of said cast sheet and the homogeneity of the properties of the resulting smoking articles.

[0009] It would be also desirable to increase the productivity of the apparatuses and methods for producing a cast sheet for a smoking article.

[0010] It would be also desirable to have an apparatus and a method for producing a cast sheet for a smoking article which allow to reduce the waste and water consumption.

[0011] It would be also desirable to limit the complexity and the footprint of the apparatuses for producing a cast sheet for a smoking article.

[0012] It would be also desirable to increase the flexibility of the apparatuses for producing a cast sheet for a smoking article.

[0013] It would be also desirable to simplify the methods for producing a cast sheet for a smoking article.

[0014] The present disclosure relates to an apparatus for producing a cast sheet for a smoking article. The apparatus comprises: a continuous mixer configured for mixing ingredients of a recipe and water to form a slurry mixture. The continuous mixer may delimit a mixing path. The continuous mixer may have at least one inlet communicating with the mixing path, the at least one inlet being configured to feed the ingredients and the water into the mixing path, and an outlet located at an end of the mixing path, the outlet being configured to discharge the slurry mixture from the continuous mixer. The continuous mixer being configured to mix the ingredients and the water while advancing said ingredients and water in the mixing path towards the outlet. The apparatus may comprise a casting box in fluid communication with the outlet to receive the slurry mixture from the continuous mixer. The apparatus may comprise a surface located under the casting box and configured to receive the slurry mixture from said casting box and to form a cast sheet.

[0015] The present disclosure relates to a method for producing a cast sheet for a smoking article. The method comprises: feeding ingredients of a recipe and water through at least one inlet and into a mixing path of a continuous mixer; mixing the ingredients and the water while advancing said ingredients and water in the mixing path towards an outlet of the continuous mixer to form a slurry mixture and discharging the slurry mixture from the outlet. The method may also comprise: casting the slurry mixture coming from the outlet on a surface to form a cast sheet.

[0016] The method may be performed through the apparatus and / or the apparatus may be configured to perform the method.

[0017] The inventor found that the disclosed apparatus and method allow to manufacture a cast sheet provided with improved qualities compared to cast sheets obtained from slurries prepared by batch mode.

[0018] Indeed, the slurry preparation achieved through the disclosed apparatus and method (by continuously feeding the ingredients, continuously mixing said ingredients and continuously feeding the following casting box), prevents slurry degradation. In particular, the disclosed apparatus and method prevent enzymatic degradation of the slurry due to its aging during storage associated to preparation by batch mode.

[0019] The inventor found that the disclosed apparatus and method have an impact on the mechanical properties of the cast sheet. Indeed, the continuous mixing increases the mechanical strength of the cast sheet by reducing its aging time and improves the uniformity of the mechanical properties of the cast sheet.

[0020] The inventor found that disclosed apparatus and method allow to increase the productivity with respect to the known apparatuses and methods, since the storage time of the slurry is eliminated.

[0021] The inventor found that disclosed apparatus and method allow to eliminate at least the storage tank and thus to reduce the complexity and the footprint of the apparatuses for producing a cast sheet for a smoking article.

[0022] The inventor found that the adoption of the continuous mixer allows to improve the flexibility of the apparatus.

[0023] The inventor found that the method for producing a cast sheet for a smoking article results simplified and allows to reduce the waste and water consumption.

[0024] In some embodiments, the ingredients and the water are added at a same time into the continuous mixer. Since the water content of the slurry is high, the feeding order into the continuous mixer may not play an important role.

[0025] In some embodiments, the outlet of the continuous mixer is directly connected to the casting box. The apparatus may comprise a transfer duct connecting the outlet of the continuous mixer to the casting box. No buffer tank is located on the transfer duct between the outlet of the continuous mixer and the casting box. The inventor found that the direct connection of the outlet of the continuous mixer to the casting box allows to reduce the transfer time of the slurry from mixing to casting and to increase the fracture force of the cast sheet.

[0026] In some embodiments, the apparatus comprises a buffer tank placed between the outlet of the continuous mixer and the casting box. The apparatus may comprise a first transfer duct connecting the outlet of the continuous mixer to the buffer tank and a second transfer duct connecting the buffer tank to the casting box. The method may comprise: buffering the slurry mixture coming out of the outlet of the continuous mixer in a buffer tank before casting on the surface.

[0027] The inventor found that buffering allows to compensate possible flow rate changes at the output of the continuous mixer such to keep steady the flow rate of slurry mixture entering the casting box.

[0028] A pump may be placed between the outlet of the continuous mixer and the casting box for pumping the slurry mixture to the casting box. The pump may be operative between the buffer tank and the casting box. The pump may be placed on the second transfer duct.

[0029] The inventor found that the pump allows to feed the casting box continuously and to control the flow rate of the slurry mixture to the casting box.

[0030] In some embodiments, at least during steady-state operation, feeding, mixing and casting are carried out simultaneously.

[0031] In some embodiments, at least during steady-state operation, the slurry mixture advances in a continuous flow from the continuous mixer to the surface.

[0032] A holding time of the ingredients and the water and of the slurry mixture in the continuous mixer may be between 1 min and 20 min, optionally between 5 min and 15 min, optionally between 8 min and 10 min.

[0033] A transfer time of the slurry mixture from the outlet of the continuous mixer to the surface may be less than 40 min, optionally between 1 min 30 min, optionally between 1 min and 15 min.

[0034] The inventor found that the transfer time from the continuous mixer to the casting box is much lower than the transfer time of the known batch methods (in which the slurry mixture is stored for hours before casting) and this makes the cast sheet stronger. Indeed, faster is the transfer of the slurry mixture from the mixer to the casting box, higher are the mechanical properties of the cast sheet.

[0035] A continuous operation time of the apparatus may be some hours, optionally between 30 hours and 60 hours, optionally of 45 hours.

[0036] A flow rate of the slurry mixture coming out of the outlet of the continuous mixer may be between 80 Kg / h and 3000 kg / h, optionally between 1000 Kg / h and 2500 kg / h. The inventor found that the continuous operation time is very long and limited only by cleaning cycle requirements and / or maintenance requirements. Thus, the productivity of the apparatus is increased.

[0037] In some embodiments, a two-way valve is located at the outlet of the continuous mixer. The two-way valve may be connected to a drain. The two-way valve may be configured to feed the slurry mixture towards the casting box or to divert the slurry mixture towards the drain.

[0038] The inventor found that the two-way valve allows to discard off-spec portions of the slurry mixture directly after the continuous mixer without the risk of contaminating the slurry mixture transfer duct / s with off-spec product.

[0039] In some embodiments, the at least one inlet comprises a plurality of inlets. The at least one inlet may comprise a plurality of inlets for the ingredients and a water inlet. The plurality of inlets may be located at different positions along the continuous mixer or may be grouped at a single location on the continuous mixer.

[0040] The apparatus may comprise a plurality of ingredient tanks connected to the at least one inlet optionally to the plurality of inlets for the ingredients. A feed valve and / or a feed pump and / or a feed flowmeter may be placed between each ingredient tank and the at least one inlet.

[0041] According to some embodiments, the ingredients comprise: fibers, for instance cellulose fibers, a binder, for instance a derivative of cellulose such as carboxymethylcellulose (CMC) and hydroxypropylmethylcellulose (HPMC), and an aerosol forming agent, such as a polyhydric alcohol, for instance triethylene glycol or 1 ,3-butanediol or glycerine; optionally the ingredients further comprise nicotine and / or fumaric acid.

[0042] According to some embodiments, the ingredients comprise: tobacco powder or other nicotine containing materials, fibers, for instance cellulose fibers, an aerosol former, for instance glycerin, and a binder, for instance guar.

[0043] The aerosol former and the fibers may be stored in the ingredient tanks. The fibers may be stored as pulp (i.e. fibers and water) in one of the ingredient tanks.

[0044] A water tank or a water source may be operatively connected to the at least one inlet, optionally to the water inlet. The water may be stored in the water tank or may come from the water source. A water valve and / or a water pump and / or a water flowmeter may be placed between the water tank or the water source and the at least one inlet. A water content in the slurry mixture may be higher than 65 %, optionally between 70 % and 90 %.

[0045] A temperature of the ingredients when fed to the continuous mixer may be between 15°C and 35°C, optionally of 21 °C. A temperature of the slurry mixture at the outlet of the continuous mixer may be controlled by controlling a temperature of a body of the continuous mixer, optionally through a built-in jacket and supply of temperature-controlled water (hot / cold). The temperature of the slurry mixture at the outlet of the continuous mixer may be controlled by controlling a temperature of the water fed through the at least one inlet, optionally by increasing the temperature of the water up to 50 °C.

[0046] A temperature increase of the slurry mixture after mixing may be between 1 °C and 20°C, optionally between 3 °C and 4 °C.

[0047] A viscosity of the slurry mixture in the continuous mixer may be between 2000 cP and 4000 cP (measured at 35 °C and shear rate 100 Hz). Considering that the slurry mixture is fresh because the holding time may be no more than 20 minutes, the production may allow higher ranges of viscosity of the slurry mixture.

[0048] In some embodiments, the apparatus comprises a screw conveyor having an inlet provided with a hopper and an outlet connected to the at least one inlet of the continuous mixer. At least two tanks of the plurality of ingredient tanks may communicate with the hopper. The screw conveyor may be configured to disperse one ingredient from one of the two tanks in another ingredient from the other of the two tanks before feeding to the continuous mixer. The screw conveyor may comprise at least one screw and a motor connected to the screw to rotate said screw.

[0049] In some embodiments, one of the ingredients is dispersed on another of the ingredients before feeding to the continuous mixer. The dispersion may be carried out through the screw conveyor disclosed above. Said one of the ingredients and said another of the ingredients may be stored each in one of the two tanks disclosed above. For instance, the binder is dispersed on the tobacco powder or other nicotine containing materials.

[0050] The inventor found that the dispersion avoids the emergence of agglomerates in the slurry mixture during the mixing.

[0051] In some embodiments, the continuous mixer comprises at least one mixing tool located in the mixing path and configured to mix the ingredients and the water. The at least one mixing tool may also be configured to advance the ingredients and the water and the slurry mixture along the mixing path. Mixing may be performed through the at least one mixing tool.

[0052] The continuous mixer may comprise a main motor connected to the at least one mixing tool and configured to rotate the mixing tool. The at least one mixing tool may be configured to rotate about an axis parallel to the mixing path. In some embodiments, the mixing path and the axis are horizontal and the continuous mixer is a horizontal mixer. In some embodiments, the at least one mixing tool comprises at least two mixing tools rotating about parallel axes.

[0053] In some embodiments, the continuous mixer comprises a built-in jacket and a supply of temperature-controlled water (hot / cold) connected to the built-in jacket. The water temperature control may ensure that the slurry mixture temperature at the outlet of the mixer is matching a desired set point.

[0054] In some embodiments, a movable support is located downstream of the casting box and the surface located under the casting box is part of the movable support. The movable support may comprise a belt conveyor and said surface may be an upper branch of the belt conveyor.

[0055] Cooling devices may be configured to cool the movable support. In some embodiments, the cooling devices comprise a source of chilled water. The cooling devices may be placed and configured to cool the movable support at locations where said movable support does not support the cast sheet.

[0056] Heating devices may be configured to heat the surface and the cast sheet supported by the surface to dry said cast sheet. The heating devices may comprise a source of steam and / or a source of hot air. The cast sheet may be dried, optionally through steam and / or hot air, optionally through the heating devices disclosed above.

[0057] In some embodiments the cooling devices are not adopted and the first drum is hot.

[0058] In some embodiments, the belt conveyor comprises a first drum, a second drum and a belt forming a closed loop around the first drum and the second drum. The first drum may be close to the casting box. A conveyor motor may be connected to at least one of the first drum and the second drum.

[0059] In some embodiments, the heating devices are configured to heat the upper branch and / or the first drum. In some embodiments, the cooling devices are configured to cool a lower branch of the belt conveyor and / or the first drum.

[0060] Casting the slurry mixture may be performed on the first drum. A temperature of the first drum may be kept constant, optionally between 45 °C and 65 °C, optionally of 55 °C. The first drum may be kept hot because the slurry mixture coming from the continuous mixer is fresh and no degradation occurs.

[0061] In some embodiments, the casting box comprises a casting blade adapted to cast the slurry mixture from the casting box on the surface.

[0062] In some embodiments, during a run-in time at the start of production, the outlet of the continuous mixer is closed to retain the slurry mixture inside while the ingredients are fed in a defined sequence. The inventor found that this ensures that no losses occur and that a first portion of the slurry mixture produced is already respecting the recipe.

[0063] In some embodiments, during the run-in time at the start of production, the outlet of the continuous mixer is opened to fill the buffer tank disclosed above, before start casting the slurry mixture on the surface.

[0064] In some embodiments, during a run-out time at the end of production, feeding of the ingredients is stopped in a defined sequence and the outlet of the continuous mixer is open while keep on mixing to discharge all the slurry mixture.

[0065] The inventor found that this ensures that all good product is discharged and no losses occur.

[0066] A control unit, optionally an electronic control unit, may be operatively connected to the continuous mixer. The control unit may be configured to monitor and control at least one working parameter of the continuous mixer. The working parameter of the continuous mixer may comprise a power consumption and / or a rotational speed and / or a temperature and / or a torque of the at least one mixing tool. The control unit may configured to control a temperature of the water fed through the at least one inlet, optionally by increasing the temperature of the water up to 50 °C, to adjust a temperature of the slurry mixture at the outlet of the continuous mixer. The control unit may be configured to monitor and control at least one working parameter of the screw conveyor. The control unit may be configured to monitor and control at least one working parameter of the feed valve and / or the feed pump and / or the water valve and / or the water pump. The control unit may configured to monitor and control at least one working parameter of the belt conveyor. The control unit may configured to monitor and control at least one working parameter of the heating devices. The control unit may configured to monitor and control at least one working parameter of the cooling devices.

[0067] Sensors may be connected to the control unit, wherein the control unit is configured to manage operation of the apparatus through the sensors. For instance, the sensors comprise flowmeters and / or pressure sensors and / or temperature sensors and / or weight sensors and / or speed sensors and / or torque sensors and / or viscometers. The off-spec portions of the slurry mixture may be detected through the viscometers.

[0068] The control unit may be configured to detect if the mixing process is stable and to detect variations of the at least one working parameter of the continuous mixer and to trigger alarms and / or to divert the slurry mixture towards the drain.

[0069] The control unit may be configured to detect variations of ingredients supply and / or slurry mixture output, optionally through the sensors, and to trigger alarms and / or to divert the slurry mixture towards the drain if said variations exceed tolerances. The control unit may be configured to detect interruptions of ingredients supply and / or output, optionally through the sensors, and to trigger alarms and / or to divert the slurry mixture towards the drain if said interruptions occur.

[0070] The present disclosure also relates to a cast sheet manufactured in the apparatus detailed above and / or through the method detailed above. The cast sheet may have a fracture force, in machine direction or cross direction, between 100 N / cm2and 500 N / cm2. The cast sheet may be an aerosol-generating substrate or may be a reconstituted tobacco leaf.

[0071] The present disclosure also relates to a smoking article comprising the cast sheet disclosed above wherein the smoking article may be a traditional smoking article or an aerosol-generating article.

[0072] The present disclosure also relates to a plant for manufacturing smoking articles comprising the apparatus of the present disclosure.

[0073] The present disclosure also relates to a process for manufacturing smoking articles comprising the method of the present disclosure. According to some embodiments, the cast sheet is gathered, wrapped in a rod and cut in aerosol-generating substrate plugs intended to release volatile compounds by heat transfer from a heat source of an aerosol-generating system. According to some embodiments, the cast sheet is shredded and mixed with other tobacco leaves to obtain a resulting tobacco blend intended to be ignited and smoked.

[0074] As used in the present description, the term “continuous mixer” means a device capable of mixing ingredients while transporting said ingredients from one or more inlets to an outlet. The continuous mixer receives a continuous input of ingredients through the one or more inlets and provides a continuous output through the outlet, as opposed to “batch mixer” which is loaded with given quantities of ingredients and, after mixing, must be stopped to discharge a given output.

[0075] As used in the present description, the term “smoking article” means both the traditional smoking articles which are ignited at one end causing them to smolder, like cigars and cigarettes, and the aerosol-generating articles or heat-not-burn cigarettes, in which an aerosol-generating substrate is heated rather than combusted.

[0076] As used in the present description, the term “slurry” means a watery mixture of insoluble matter with a water content so high (e.g. 65 percent - 90 percent) that cannot be kneaded or rolled out, as opposed to “dough” which is a mixture that is stiff enough to be kneaded or rolled out.

[0077] As used in the present description, the “holding time” is the average time a particle of the slurry mixture is inside the mixer during the continuous process. As used in the present description, the “transfer time” is the time that it takes to dose one particle of the slurry mixture from the outlet of the mixer to the casting box. It does not include the “holding time” in the mixer.

[0078] As used in the present description, the term “recipe” means a group of ingredients without any limitation concerning the order and the timing in which they are combined with each other and / or with water.

[0079] As used in the present description, the terms “upstream” and “downstream” are used to describe the relative positions of components, or portions of components, of the apparatus in relation to the direction in which a material or materials passes through the apparatus along a given path.

[0080] The invention is defined in the claims. However, below there is provided a non- exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of another example, embodiment, or aspect described herein.

[0081] EX1. An apparatus for producing a cast sheet for a smoking article, comprising: a continuous mixer configured for mixing ingredients of a recipe and water to form a slurry mixture; the continuous mixer delimiting a mixing path and having at least one inlet communicating with the mixing path, the at least one inlet being configured to feed the ingredients and the water into the mixing path, and an outlet located at an end of the mixing path, the outlet being configured to discharge the slurry mixture from the continuous mixer; the continuous mixer being configured to mix the ingredients and the water while advancing said ingredients and water in the mixing path towards the outlet; a casting box in fluid communication with the outlet to receive the slurry mixture from the continuous mixer; a surface located under the casting box and configured to receive the slurry mixture from said casting box and to form a cast sheet.

[0082] EX2. The apparatus according to EX1 , wherein the outlet of the continuous mixer is directly connected to the casting box.

[0083] EX3. The apparatus according to EX2, comprising a transfer duct connecting the outlet of the continuous mixer to the casting box and wherein no buffer tank is located on the transfer duct between the outlet of the continuous mixer and the casting box.

[0084] EX4. The apparatus according to EX1 , wherein the apparatus comprises a buffer tank placed between the outlet of the continuous mixer and the casting box.

[0085] EX5. The apparatus according to EX4, comprising a first transfer duct connecting the outlet of the continuous mixer to the buffer tank and a second transfer duct connecting the buffer tank to the casting box. EX6. The apparatus according to any of EX1 to EX5, comprising a pump placed between the outlet of the continuous mixer and the casting box for pumping the slurry mixture to the casting box.

[0086] EX7. The apparatus according to EX6 when according to EX4 or EX5, wherein the pump is operative between the buffer tank and the casting box.

[0087] EX8. The apparatus according to EX7 when EX6 is according to EX5, wherein the pump is placed on the second transfer duct.

[0088] EX9. The apparatus according to any of EX1 to EX8, comprising a two-way valve located at the outlet of the continuous mixer; optionally wherein the two-way valve is connected to a drain.

[0089] EX10. The apparatus according to EX9, wherein the two-way valve is configured to feed the slurry mixture towards the casting box or to divert the slurry mixture towards the drain.

[0090] EX11. The apparatus according to any of EX1 to EX10, wherein the at least one inlet comprises a plurality of inlets, optionally a plurality of inlets for the ingredients and a water inlet.

[0091] EX12. The apparatus according to EX11 , wherein the plurality of inlets are located at different positions along the continuous mixer or grouped at a single location on the continuous mixer.

[0092] EX13. The apparatus according to any of EX1 to EX12, comprising a plurality of ingredient tanks connected to the at least one inlet, optionally to a plurality of inlets for the ingredients.

[0093] EX14. The apparatus according to any of EX13, wherein a feed valve and / or a feed pump and / or a feed flowmeter is / are placed between each ingredient tank and the at least one inlet.

[0094] EX15. The apparatus according to any of EX1 to EX14, comprising a water tank or a water source operatively connected to the at least one inlet, optionally to a water inlet.

[0095] EX16. The apparatus according to EX15, wherein a water valve and / or a water pump and / or a water flowmeter is / are placed between the water tank or the water source and the at least one inlet.

[0096] EX17. The apparatus according to any of EX1 to EX16, comprising a screw conveyor having an inlet provided with a hopper and an outlet connected to the at least one inlet of the continuous mixer.

[0097] EX18. The apparatus according to EX17 when according to EX13, wherein at least two tanks of the plurality of ingredient tanks communicates with the hopper. EX19. The apparatus according to EX18, wherein the screw conveyor is configured to disperse one ingredient from one of the two tanks in another ingredient from the other of the two tanks before feeding to the continuous mixer.

[0098] EX20. The apparatus according to any of EX17 to EX19, wherein the screw conveyor comprises at least one screw and a motor connected to the screw to rotate said screw.

[0099] EX21. The apparatus according to any of EX1 to EX20, wherein the continuous mixer comprises at least one mixing tool located in the mixing path and configured to mix the ingredients and the water and to advance the ingredients and the water and the slurry mixture along the mixing path; optionally the continuous mixer comprises a built-in jacket and a supply of temperature-controlled water (hot / cold) connected to the built-in jacket.

[0100] EX22. The apparatus according to EX21 , wherein the continuous mixer comprises a main motor connected to the at least one mixing tool and configured to rotate the mixing tool.

[0101] EX23. The apparatus according to EX21 or EX22, wherein the at least one mixing tool is configured to rotate about an axis parallel to the mixing path; optionally wherein the mixing path and the axis are horizontal and the continuous mixer is a horizontal mixer.

[0102] EX24. The apparatus according to any of EX21 to EX23, wherein the at least one mixing tool comprises at least two mixing tools rotating about parallel axes.

[0103] EX25. The apparatus according to any of EX1 to EX24, comprising a movable support located downstream of the casting box; wherein the surface located under the casting box is part of the movable support.

[0104] EX26. The apparatus according to EX25, wherein the movable support comprises a belt conveyor and said surface is an upper branch of the belt conveyor.

[0105] EX27. The apparatus according to EX25 or EX26, comprising cooling devices configured to cool the movable support; optionally the cooling devices comprise a source of chilled water.

[0106] EX28. The apparatus according to EX27, wherein the cooling devices are placed and configured to cool the movable support at locations where said movable support does not support the cast sheet.

[0107] EX29. The apparatus according to any of EX1 to EX28, comprising heating devices configured to heat the surface and the cast sheet supported by the surface to dry said cast sheet; optionally the heating devices comprise a source of steam and / or a source of hot air.

[0108] EX30. The apparatus according to EX26 and EX27 and EX29, wherein the belt conveyor comprises a first drum, a second drum and a belt forming a closed loop around the first drum and the second drum; wherein the first drum is close to the casting box; wherein a conveyor motor is connected to at least one of the first drum and the second drum.

[0109] EX31. The apparatus according to EX30, wherein the heating devices are configured to heat the upper branch and / or the first drum.

[0110] EX32. The apparatus according to EX30 or EX31 , wherein the cooling devices are configured to cool a lower branch of the belt conveyor and / or the first drum.

[0111] EX33. The apparatus according to any of EX1 to EX32, wherein the casting box comprises a casting blade adapted to cast the slurry mixture from the casting box on the surface.

[0112] EX34. The apparatus according to any of EX1 to EX33, comprising a control unit, optionally an electronic control unit, operatively connected to the continuous mixer.

[0113] EX35. The apparatus according to EX34, wherein the control unit is configured to monitor and control at least one working parameter of the continuous mixer; optionally the control unit is configured to control a temperature of the water fed through the at least one inlet, optionally by increasing the temperature of the water up to 50 °C, to adjust a temperature of the slurry mixture at the outlet of the continuous mixer.

[0114] EX36. The apparatus according to EX35 when EX34 is according to any of EX21 to EX24, wherein the working parameter of the continuous mixer comprises a power consumption and / or a rotational speed and / or a temperature and / or a torque of the at least one mixing tool.

[0115] EX37. The apparatus according to EX35 when EX34 is according to any of EX17 to EX20, wherein the control unit is configured to monitor and control at least one working parameter of the screw conveyor.

[0116] EX38. The apparatus according to EX35 when EX34 is according to EX14 and / or EX16, wherein the control unit is configured to monitor and control at least one working parameter of the feed valve and / or the feed pump and / or the water valve and / or the water pump.

[0117] EX39. The apparatus according to EX35 when EX34 is according to any of EX30 to EX32, wherein the control unit is configured to monitor and control at least one working parameter of the belt conveyor and / or at least one working parameter of the heating devices and / or at least one working parameter of the cooling devices.

[0118] EX40. The apparatus according to any of EX35 to EX39, comprising sensors connected to the control unit, wherein the control unit is configured to manage operation of the apparatus through the sensors; optionally wherein the sensors comprise flowmeters and / or pressure sensors and / or temperature sensors and / or weight sensors and / or speed sensors and / or torque sensors and / or viscometers. EX41 . The apparatus according to any of EX35 to EX40, wherein the control unit is configured to detect variations of the at least one working parameter of the continuous mixer and to trigger alarms and / or to divert the slurry mixture towards the drain of EX9 or EX10; optionally, the control unit is configured to: detect variations of ingredients supply and / or slurry output, optionally through the sensors of EX40, and to trigger alarms and / or to divert the slurry mixture towards the drain if said variations exceed tolerances; or detect interruptions of ingredients supply and / or output, optionally through the sensors of EX40, and to trigger alarms and / or to divert the slurry mixture towards the drain if said interruptions occur.

[0119] EX42. A method for producing a cast sheet for a smoking article, comprising: feeding ingredients of a recipe and water through at least one inlet and into a mixing path of a continuous mixer; optionally the ingredients and the water are added at a same time into the continuous mixer; mixing the ingredients and the water while advancing said ingredients and water in the mixing path towards an outlet of the continuous mixer to form a slurry mixture and discharging the slurry mixture from the outlet; casting the slurry mixture coming from the outlet on a surface to form a cast sheet.

[0120] EX43. The method according to EX42, wherein said method is performed through the apparatus according to any of EX1 to EX41.

[0121] EX44. The method according to EX42 or EX43, wherein, at least during steadystate operation, feeding, mixing and casting are carried out simultaneously.

[0122] EX45. The method according to any of EX42 to EX44, wherein, at least during steady-state operation, the slurry mixture advances in a continuous flow from the continuous mixer to the surface.

[0123] EX46. The method according to any of EX42 to EX45, wherein a holding time of the ingredients and the water and of the slurry mixture in the continuous mixer is between 1 min and 20 min, optionally between 5 min and 15 min, optionally between 8 min and 10 min.

[0124] EX47. The method according to any of EX42 to EX46, wherein a flow rate of the slurry mixture coming out of the outlet of the continuous mixer is between 80 Kg / h and 3000 kg / h, optionally between 1000 Kg / h and 2500 kg / h.

[0125] EX48. The method according to any of EX42 to EX47, wherein mixing is performed through the at least one mixing tool according to any of EX21 to EX24.

[0126] EX49. The method according to any of EX42 to EX48, wherein a continuous operation time of the apparatus is some hours, optionally between 30 hours and 60 hours, optionally of 45 hours. EX50. The method according to any of EX42 to EX49, wherein a transfer time of the slurry mixture from the outlet of the continuous mixer to the surface is less than 40 min, optionally between 1 min - 30 min, optionally between 1 min and 15 min.

[0127] EX51 . The method according to any of EX42 to EX50, further comprising: buffering the slurry mixture coming out of the outlet of the continuous mixer in a buffer tank before casting on the surface; optionally in the buffer tank according to EX4 or EX5 or EX7.

[0128] EX52. The method according to any of EX42 to EX51 , further comprising: drying the cast sheet, optionally through steam and / or hot air, optionally through the heating devices according to EX29 or EX31.

[0129] EX53. The method according to any of EX42 to EX52, further comprising: dispersing one of the ingredients on another of the ingredients before feeding to the continuous mixer; optionally through the screw conveyor according to EX17, EX19, EX20 or EX37; optionally wherein said one of the ingredients and said another of the ingredients are stored each in one of the two tanks of EX18.

[0130] EX54. The method according to any of EX42 to EX53, wherein the water is stored in the water tank or comes from the water source according to EX15 or EX16.

[0131] EX55. The method according to any of EX42 to EX54, wherein a water content in the slurry mixture is higher than 65 %, optionally between 70 % and 90 %.

[0132] EX56. The method according to any of EX42 to EX55, wherein the ingredients comprise: fibers, for instance cellulose fibers, a binder, for instance a derivative of cellulose such as carboxymethylcellulose (CMC) and hydroxypropylmethylcellulose (HPMC), and an aerosol forming agent, such as a polyhydric alcohol, for instance triethylene glycol or 1 ,3- butanediol or glycerine; optionally the ingredients further comprise nicotine and / or fumaric acid.

[0133] EX57. The method according to any of EX42 to EX55, wherein the ingredients comprise: tobacco powder or other nicotine containing materials, fibers, for instance cellulose fibers, an aerosol former, for instance glycerin, and a binder, for instance guar.

[0134] EX58. The method according to EX57, wherein the binder is dispersed according to EX53 on the tobacco powder or other nicotine containing materials.

[0135] EX59. The method according to EX56 or EX58, wherein the aerosol former and the fibers are stored in the ingredient tanks according to EX13 or EX14.

[0136] EX60. The method according to EX59, wherein the fibers are stored as pulp (i.e. fibers and water) in one of the ingredient tanks.

[0137] EX61 . The method according to any of EX42 to EX60, wherein a temperature of the ingredients when fed to the continuous mixer is between 15°C and 35°C, optionally of 21°C. EX62. The method according to any of EX42 to EX61 , wherein a temperature of the slurry mixture at the outlet of the continuous mixer is controlled by controlling a temperature of a body of the continuous mixer, optionally through a built-in jacket and supply of temperature-controlled water (hot / cold), or by controlling a temperature of the water fed through the at least one inlet, optionally by increasing the temperature of the water up to 50 °C.

[0138] EX63. The method according to any of EX62, wherein a temperature increase of the slurry mixture after mixing is between 1 °C and 20°C, optionally between 3 °C and 4 °C.

[0139] EX64. The method according to any of EX42 to EX63, wherein casting the slurry mixture is performed on the first drum of EX30, wherein a temperature of the first drum is kept constant, optionally between 45 °C and 65 °C, optionally of 55 °C.

[0140] EX65. The method according to any of EX42 to EX64, wherein, during a run-in time at the start of production, the outlet of the continuous mixer is closed to retain the slurry mixture inside while the ingredients are fed in a defined sequence.

[0141] EX66. The method according to EX65, wherein, during the run-in time at the start of production, the outlet of the continuous mixer is opened to fill the buffer tank of any of EX4, EX5, EX6 before start casting the slurry mixture on the surface.

[0142] EX67. The method according to any of EX42 to EX66, wherein, during a run-out time at the end of production, feeding of the ingredients is stopped in a defined sequence and the outlet of the continuous mixer is open while keep on mixing to discharge all the slurry mixture.

[0143] EX68. The method according to any of EX42 to EX67, wherein a viscosity of the slurry mixture in the continuous mixer is between 2000 cP and 4000 cP (measured at 35 °C and shear rate 100 Hz).

[0144] EX69. The apparatus of EX1 to EX41 which is configured to perform the method according to any of EX42 to EX68.

[0145] EX70. A cast sheet manufactured in the apparatus according to any of EX1 to EX41 and / or through the method according to any of EX42 to EX68.

[0146] EX71. The cast sheet according to EX70, wherein said cast sheet has a fracture force, in machine direction or cross direction, between 100 N / cm2and 500 N / cm2.

[0147] EX72. The cast sheet according to EX70, wherein the cast sheet is an aerosolgenerating substrate.

[0148] EX73. The cast sheet according to EX70 or EX71 , wherein the cast sheet is a reconstituted tobacco leaf.

[0149] EX74. A smoking article comprising a cast sheet according to any of EX70 to EX73, wherein the smoking article is a traditional smoking article or an aerosol-generating article. EX75. A plant for manufacturing smoking articles comprising the apparatus of any of EX1 to EX41.

[0150] EX76. A process for manufacturing smoking articles comprising the method of any of EX42 to EX68.

[0151] EX77. The process of EX76, wherein the cast sheet is gathered, wrapped in a rod and cut in aerosol-generating substrate plugs intended to release volatile compounds by heat transfer from a heat source of an aerosol-generating system.

[0152] EX78. The process of EX76, wherein the cast sheet is shredded and mixed with other tobacco leaves to obtain a resulting tobacco blend intended to be ignited and smoked.

[0153] Examples will now be further described with reference to the figures in which:

[0154] Figure 1 shows schematically an apparatus for producing a cast sheet for a smoking article;

[0155] Figure 2 shows a variant embodiment of the apparatus of Figure 1 ;

[0156] Figures 3 and 4 show mechanical properties of cast sheets manufactured through the apparatus of Figure 1 or 2.

[0157] The apparatus 1 comprises a continuous mixer 2 configured for mixing ingredients of a recipe and water to form a slurry mixture. The continuous mixer 2 comprises a casing 3 shaped like a barrel and delimiting internally a mixing path 4. The mixing path 4 is horizontal and the continuous mixer 2 is a horizontal mixer. A mixing tool 5 is lodged in the mixing path

[0158] 4 and supported by the casing 3, for instance through bearings, not shown. The mixing tool

[0159] 5 of Figure 1 is shaped like a shaft extending along an axis “X-X” parallel to the mixing path 4. The shaft of the mixing tool 5 is provided with mixing elements, like reliefs or blades not shown in details, and is connected to a main motor 6 configured to rotate the shaft about the respective axis “X-X”. The mixing tool 5 is configured to mix ingredients and water and to advance the ingredients and the water and the slurry mixture along the mixing path 4.

[0160] A plurality of inlets are fashioned through the casing 3 and communicate with the mixing path 4 to feed ingredients and water into the mixing path 4. In the example embodiment of Figure 1 , the apparatus 1 has a first inlet 7, a second inlet 8, a third inlet 9 and a fourth inlet 10. The first inlet 7 is close to a first end of the casing 3 and to the main motor 6. The second inlet 8, third inlet 9 and fourth inlet 10 are placed one after the other along the axis “X-X”.

[0161] The first inlet 7 is connected to a screw conveyor 11. The screw conveyor 11 comprises a housing 12 accommodating a screw 13 rotated by a respective motor 14. The housing 12 has an inlet 15 located at one end of the screw 13 and an outlet 16 located at an opposite end of the screw 13. The outlet 16 of the screw conveyor 11 communicates with the first inlet 7 of the continuous mixer 2 through a piping. A hopper 17 is positioned at the inlet 15. A first ingredient tank 18 and a second ingredient tank 19, provided each with a feed pump 20, a feed valve 21 and a feed flowmeter, not shown, are located above the hopper 17 and communicates with an intake 22 of the hopper 17.

[0162] According to this example embodiment, the first ingredient tank 18 stores a binder, for instance guar, and the second ingredient tank 19 stores tobacco powder or a powder of another nicotine containing material. Manufacturing of the tobacco powder may be of the known type, for instance: selection of tobacco types and tobacco grades, checking tobacco integrity, shredding of tobacco leaves, coarse grinding of tobacco leaves, blending of the different tobacco types, fine grinding.

[0163] The guar and the tobacco powder are fed to the hopper 17 and then to the inlet 15 of the screw conveyor 11. Therefore, the guar is going to be dosed above the tobacco powder that is being conveyed through the screw conveyor. The screw conveyor 11 disperses the guar on the tobacco powder while moving these ingredients towards the outlet 16 of the screw conveyor 11 and towards the first inlet 7 of the continuous mixer 2.

[0164] The second inlet 8 of the continuous mixer 2 is connected to a third ingredient tank 23 storing an aerosol former, for instance glycerin, through a respective feed pump 20, feed valve 21 and a feed flowmeter, not shown. The third inlet 9 of the continuous mixer 2 is connected to a fourth ingredient tank 24 storing pulp (i.e. premix of fibers, for instance cellulose fibers, and water) through a respective feed pump 20, feed valve 21 and a feed flowmeter, not shown. The cellulose pulp may be prepared through known steps. For instance, cellulose fibers and water are mixed in a concentrated form (total amount in the cellulose fibers in the pulp is between about 3 percent and 5 percent of the total pulp weight before dilution). A storage time of the concentrated pulp, if storage of the pulp is performed, may vary between 0.1 day and 7 days. The concentrated pulp is then diluted; water is added to the concentrated pulp in such an amount that the cellulose fibers may be less than about 1 percent of the total weight of the pulp. Further, an additional step of mixing may take place. After the step of pulp preparation 107, an optional step of fibers’ fibrillation may be performed

[0165] The fifth inlet 10 of the continuous mixer 2 is connected to a fifth water tank 25 storing water or may be connected to a water source, for instance a water supply network, through a water pump 26, water valve 27 and a water flowmeter, not shown. The ingredients may be dosed relative to the tobacco powder which is the master material flow.

[0166] An outlet 28 of the mixing path 4 is located at a second end of the casing 3, i.e. at an end of the mixing path 4 and at a distal end of the mixing tool 5. The outlet 28 is coupled to a two-way valve 29. The two-way valve 29 is configured to discharge the slurry mixture through the outlet 28 or to divert the slurry mixture towards an auxiliary outlet 30 connected to a drain 31.

[0167] The continuous mixer 2 is configured to mix the ingredients and the water while advancing the mixing ingredients and water in the mixing path 4 and towards the outlet 28, thus forming the slurry mixture.

[0168] A casting box 32 is in fluid communication with the outlet 28 to receive the slurry mixture from the continuous mixer 2 and a belt conveyor 33 is located under the casting box 32. The belt conveyor comprises a first drum 34, a second drum 35 and a belt 36 forming a closed loop around the first drum 34 and the second drum 36. A conveyor motor 37 is connected to the first drum 34 to move an upper branch 38 of the belt 36 along a conveying direction “F”.

[0169] The casting box 32 has a top opening 39 and a bottom opening 40. The bottom opening 40 is close to and faces a portion of the upper branch 38 of the belt 36 located at the first drum 34. The casting box 32 comprises a casting blade 41 delimiting a slot together with the upper branch 38 of the belt 36. The casting blade 41 is an element having one edge that is intended to come into contact with the slurry mixture. Said edge may have a sharp and knife-like shape or a rectangular or a rounded shape. The belt 36 is a movable support and the upper branch of the belt 36 is a movable surface located under the casting box 32 moving along the conveying direction “F” and configured to receive the slurry mixture from said casting box 32 and to form a cast sheet 42.

[0170] The slurry mixture is transferred from the outlet 28 of the continuous mixer 2 to the casting box 32 through a first transfer duct 43 connecting the outlet 28 to a buffer tank 44 and a second transfer duct 45 connecting the buffer tank 44 to the casting box 32. A terminal opening 46 of the second transfer duct 45 provided with a terminal opening valve 46a is located just above the top opening 39 of the casting box 32. A pump 47 is operative on the second transfer duct 45 for pumping the slurry mixture to the casting box 32.

[0171] The apparatus 1 further comprises heating devices configured to heat the upper branch 38 of the belt 36 and the cast sheet 42 supported by the upper branch 38 and to dry the cast sheet 42. In the example embodiment of Figure 1 , the heating devices comprise a source of steam 48 placed below the upper branch 38 and configured to increase or maintain a temperature of the belt 36. The heating devices comprise another source of steam 49 placed above the upper branch 38 and above the cast sheet 42 to dry the cast sheet 42. The heating devices comprises a further source of steam 50 connected to the first drum 34 to increase or maintain a temperature of the first drum 34.

[0172] The apparatus 1 shown in Figure 1 further comprises cooling devices, for instance a source of chilled water 51 , operative on the first drum 34 and on a lower branch of the belt 36 to cool these elements. In the depicted embodiment of Figure 1 , the source of chilled water 51 is coupled to a part of the lower branch of the belt 36. The another source of steam 49, the further source of steam 50 and the source of chilled water 51 may be controlled to adjust the temperatures of the first drum 34 and of the belt 36. For instance, a temperature of the first drum 34 is kept constant, optionally between 45 °C and 65 °C, optionally of 55 °C.

[0173] The casing 3 of the continuous mixer 2 is also provided with a built-in jacket 52 connected to a supply 53 of temperature-controlled water (hot / cold).

[0174] An electronic control unit 54 (schematically illustrated in Figure 1) is configured to run, monitor and control the apparatus 1. The electronic control unit 54 is operatively connected to: the main motor 6, the motor 14, the conveyor motor 37, the feed pumps 20, the feed valves 21 , the water pump 26, the water valve 27, the two-way valve 29, the pump 47, the source of steam 48, the another source of steam 49, the further source of steam 50, the source of chilled water 51 , the supply 53 of temperature-controlled water.

[0175] Sensors, not shown in Figure 1 , are also connected to the control unit 54 and the control unit 54 is configured to manage operation of the apparatus 1 and to control working parameters of said apparatus 1 also through signals received from said sensors. The sensors comprise the feed flowmeters cited above and / or pressure sensors and / or temperature sensors and / or weight sensors and / or speed sensors and / or torque sensors and / or viscometers.

[0176] The electronic control unit 54 is configured to monitor and control working parameter of the feed valves 21 and the feed pumps 20 and of the water valve 27 and the water pump 26. The electronic control unit 54 is configured to monitor and control flows of the binder from the first ingredient tank 18 and of the tobacco powder from the second ingredient tank 19. The control unit 54 is configured to monitor and control a rotational speed of the screw 13 of the screw conveyor 11. The control unit 54 is configured to monitor and control flows of the aerosol former from the third ingredient tank 23, of the pulp from the fourth ingredient tank 24 and of the water from the fifth water tank 25. A temperature of the ingredients when fed to the continuous mixer 2 is controlled to be between 15°C and 35°C, optionally of 21°C. A water flow is controlled so that a water content in the slurry mixture is higher than 65 %, optionally between 70 % and 90 %.

[0177] The electronic control unit 54 is configured to monitor and control a rotational speed, a torque, a power consumption and a temperature of the mixing tool 5 and a flow and / or temperature of the supply 53 of temperature-controlled water. A temperature increase of the slurry mixture after mixing is between 1 °C and 20°C, optionally between 3 °C and 4 °C. A viscosity of the slurry mixture in the continuous mixer is between 2000 cP and 4000 cP (measured at 35 °C and shear rate 100 Hz).

[0178] The electronic control unit 54 is configured to monitor and control the two-way valve 29 and the pump 47.

[0179] The electronic control unit 54 is configured to monitor and control a speed of the conveyor motor 37. The control unit 54 is configured to monitor and control a flow and / or temperature of the steam from the source of steam 48, the further source of steam 49, the further source of steam 50. The control unit 54 is configured to monitor and control a flow and / or temperature of the chilled water from the source of chilled water 51.

[0180] The electronic control unit 54 is also configured to detect variations or interruptions of ingredients supply and / or slurry mixture output and to trigger alarms and / or to divert the slurry mixture towards the drain 31 if said variations exceed tolerances or if said interruptions occur.

[0181] According to a method for producing a cast sheet for a smoking article performed by the apparatus 1 , the binder, the tobacco powder, the aerosol former, the pulp (ingredients of a recipe) and the water are fed in controlled manner (through the electronic control unit 54) to the continuous mixer 2. These ingredients and the water are mixed by the mixing tool 5 and move towards the outlet 28 while the temperature of the slurry mixture may be controlled through the temperature-controlled water in the built-in jacket 52 or by controlling a temperature of the water fed through the water inlet, for instance by increasing the temperature of the water fed through the water inlet up to 50 °C.

[0182] During a run-in time at the start of production, the ingredients and the water are fed in a defined sequence while the outlet 28 of the continuous mixer 2 is closed to retain the slurry mixture inside.

[0183] Off-spec portions of the slurry mixture are detected through the viscometers and the two-way valve 29 is controlled to divert said off-spec portions to the drain 31 .

[0184] Then, during the run-in time, the outlet 28 is opened to fill the buffer tank 44 while the terminal opening valve 46a is closed. The slurry mixture is forwarded to the buffer tank 44, where it is accumulated before starting the conveyor motor 37 and the heating devices configured to dry the slurry mixture. This may be helpful to allow filling up of the casting box 32 in a short time, for instance running the pump 47 in over-speed mode, in order to reach a defined fill level in the casting box 32 and stable hydraulic conditions.

[0185] The terminal opening valve 46a is then opened and continuous casting begins.

[0186] During steady-state operation, feeding, mixing and casting are carried out simultaneously, the ingredients and the water are added at a same time into the continuous mixer 2 and the slurry mixture advances in a continuous flow from the continuous mixer 2 to the belt 36 of the belt conveyor 33. The buffer tank 44 allows to compensate possible flow rate changes at the output 28 of the continuous mixer 2 such to keep steady the flow rate of slurry mixture entering the casting box 32.

[0187] During steady-state operation, the ingredients, water and slurry mixture travels inside the mixing path 4 from the first inlet 7, second inlet 8, third inlet 9 and fourth inlet 10 to the outlet 28 for a holding time that is between 1 min and 20 min, optionally between 5 min and 15 min, optionally between 8 min and 10 min.

[0188] During steady-state operation and once flowed out of the outlet 28, a transfer time of the slurry mixture from said outlet 28 to the belt 36 of the belt conveyor 33 (flowing through the first transfer duct 43, the buffer tank 44 and the second transfer duct 45) is less than 40 min, optionally between 1 min 30 min, optionally between 1 min and 15 min. The pump 47 allows to feed the casting box 32 continuously and to control the flow rate of the slurry mixture to the casting box 32.

[0189] During steady-state operation, a continuous operation time of the apparatus 1 is some hours, optionally between 30 hours and 60 hours, optionally of 45 hours, and a flow rate of the slurry mixture coming out of the outlet 28 of the continuous mixer 2 is between 80 Kg / h and 3000 kg / h, optionally between 1000 Kg / h and 2500 kg / h.

[0190] During a run-out time, at the end of the continuous operation time, feeding of the ingredients is stopped in a defined sequence and the outlet 28 of the continuous mixer 2 is kept open while keep on mixing in order to discharge all the slurry mixture.

[0191] Figure 2 schematically shows a variant embodiment of the apparatus 1. In Figures 1 and 2, the same reference numbers show the same elements. The belt conveyor 33 is shown partially.

[0192] Differently from the apparatus 1 of Figure 1 , the apparatus of Figure 2 comprises only four ingredient tanks (the second ingredient tank 19 for tobacco powder is not present) and lacks the screw conveyor 11 and the buffer tank 44. The feed pumps 20 and the feed valves 21 , the water pump 26 and the water valve 27 are not shown.

[0193] The first ingredient tank 18 stores the binder, for instance carboxymethylcellulose (CMC) and hydroxypropylmethylcellulose (HPMC), the third ingredient tank 23 stores the aerosol former, such as a polyhydric alcohol, the fourth ingredient tank 24 stores the pulp (i.e. premix of fibers, for instance cellulose fibers, and water) and the fifth water tank 25 stores water. The plurality of inlets are grouped in a single inlet 55 on the continuous mixer 2.

[0194] No buffer tank is located on the transfer duct 43 between the outlet 28 of the continuous mixer 2 and the casting box 32. The continuous mixer 2 is the same as the one of Figure 1. In other embodiments, not shown, the continuous mixer 2 may comprise two or more mixing tools 5 rotating about parallel axes.

[0195] The heating devices and cooling devices, not shown in Figure 2, may be the same as the devices disclosed in Figure 1. In other embodiments, not shown, the heating devices comprise a source of hot air instead of steam.

[0196] The cast sheet may have a fracture force, in machine direction or cross direction, between 100 N / cm2and 500 N / cm2.

[0197] The cast sheet 42 obtained at the end of the drying step (downstream of the heating devices) is then winded in a bobbin and then slit in small bobbins or first slit in tapes and the each tape is rolled in a respective small bobbin.

[0198] The cast sheet 42 manufactured through the apparatus 1 and through the method of the present disclosure may be an aerosol-generating substrate employed to make aerosol-generating articles or may be a reconstituted tobacco leaf employed to make traditional smoking articles or also aerosol-generating articles. For instance, the cast sheet 42 is crimped, gathered, wrapped in a rod and cut in aerosol-generating substrate plugs intended to release volatile compounds by heat transfer from a heat source of an aerosolgenerating system. For instance, the cast sheet 42 is shredded and mixed with other tobacco leaves to obtain a resulting tobacco blend intended to be ignited and smoked in a traditional smoking article.

[0199] Figures 3 and 4 show comparative results of cast sheets obtained through the apparatus 1 and through the method of the present disclosure (continuous mixing) and of cast sheets obtained through traditional batch mixing. Figure 3 and Figure 4 show the mechanical properties of the cast sheet 42 as function of a position over a length of a bobbin of said cast sheet 42. Figure 3 shows fracture strain in machine direction, i.e. the direction that the sheet moves through the machine. Figure 4 shows fracture force in cross direction. “L1 0” refers to a first portion of the bobbin, cast at the beginning of the process, while “L1 9” is the final portion. The total size of each bobbin was 200 m and every sampling point was taken approximately every 20 m.

[0200] Figure 3 shows the fracture strain (elongation to break) in machine direction for different points of the bobbins. Lines C, D, E, F, G relate to runs with the continuous mixing mode of the present disclosure while lines A and B relates to batch mixing modes. The fracture strain of the slurry mixture obtained through continuous mixing mode is higher than the fracture strain of the slurry mixture obtained through batch mode (Table 1 below).

[0201] Table 1

[0202] Figure 4 shows the fracture force in cross direction for different points of the bobbins. Lines C, D, E, F relate to runs with the continuous mixing mode of the present disclosure while lines A and B relates to batch mixing modes. The fracture force of the slurry mixture obtained through continuous mixing mode is higher than the fracture force of the slurry mixture obtained through batch mode (Table 2 below).

[0203] Table 2

[0204] For the runs with batch modes (lines C, D, E, F, G), a clear decrease in mechanical properties occurs as we approach the end of the bobbin. This goes in line with the fact that, in batch mode, the slurry mixture at the end of the process is already partially degraded (aged). For the continuous mode, on the other hand, the mechanical properties are quite stable (lines A and B).

[0205] Furthermore, the cast sheet 42 manufactured through the continuous mixing of the present disclosure appears visually more uniform than the cast sheet obtained through the batch mode.

[0206] For the purpose of the present description and of the appended claims, except where otherwise indicated, all numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified in all instances by the term "about". Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein. In this context, therefore, a number A is understood as A ± 5 percent of A. Within this context, a number A may be considered to include numerical values that are within general standard error for the measurement of the property that the number A modifies. The number A, in some instances as used in the appended claims, may deviate by the percentages enumerated above provided that the amount by which A deviates does not materially affect the basic and novel characteristic(s) of the claimed invention. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.

Claims

CLAIMS1. Apparatus for producing a cast sheet for a smoking article, comprising: a continuous mixer (2) configured for mixing ingredients of a recipe and water to form a slurry mixture; the continuous mixer (2) delimiting a mixing path (4) and having at least one inlet communicating with the mixing path (4), the at least one inlet being configured to feed the ingredients and the water into the mixing path (4), and an outlet (28) located at an end of the mixing path (4), the outlet (28) being configured to discharge the slurry mixture from the continuous mixer (2); the continuous mixer (2) being configured to mix the ingredients and the water while advancing said ingredients and water in the mixing path (4) towards the outlet (28); wherein the continuous mixer (2) comprises at least one mixing tool (5) located in the mixing path (4) and configured to mix the ingredients and the water and to advance the ingredients and the water and the slurry mixture along the mixing path (4); wherein the at least one mixing tool (5) is configured to rotate about an axis (X-X) parallel to the mixing path (4); wherein the at least one inlet comprises a plurality of inlets for the ingredients and a water inlet; wherein the mixing path (4) and the axis (X-X) are horizontal and the continuous mixer (2) is a horizontal mixer; a casting box (32) in fluid communication with the outlet (28) to receive the slurry mixture from the continuous mixer (2); a surface located under the casting box (32) and configured to receive the slurry mixture from said casting box (32) and to form a cast sheet (42).

2. The apparatus of claim 1 , wherein the outlet (28) of the continuous mixer (2) is directly connected to the casting box (32) or the apparatus (1) comprises a buffer tank (44) placed between the outlet (28) of the continuous mixer (2) and the casting box (32).

3. The apparatus of claim 2, comprising a pump (47) placed between the outlet (28) of the continuous mixer (2) and the casting box (32) for pumping the slurry mixture to the casting box (32), optionally wherein the pump (47) is operative between the buffer tank (44) and the casting box (32).

4. The apparatus of any of claims 1 to 3, comprising a plurality of ingredient tanks connected to the plurality of inlets for the ingredients and a water tank (25) or a water source operatively connected to the water inlet.

5. The apparatus of any of claims 1 to 4, wherein the at least one mixing tool (5) comprises at least two mixing tools rotating about parallel axes.

6. The apparatus of any of claims 1 to 5, wherein the plurality of inlets are located at different positions along the continuous mixer (2) or grouped at a single location on the continuous mixer (2).

7. The apparatus of any of claims 1 to 6, comprising a two-way valve (30) located at the outlet (28) of the continuous mixer (2); the two-way valve (30) being configured to feed the slurry mixture towards the casting box (32) or to divert the slurry mixture towards a drain (31).

8. The apparatus of any of claims 1 to 7, comprising a screw conveyor (11) having an inlet (15) provided with a hopper (17) and an outlet (16) connected to the at least one inlet of the continuous mixer (2); wherein at least two tanks of a plurality of ingredient tanks communicates with the hopper (17).

9. The apparatus of any of claims 1 to 8, comprising a control unit (54) operatively connected to the continuous mixer (2), wherein the control unit (54) is configured to monitor and control at least one working parameter of the continuous mixer (2), optionally a power consumption and / or a rotational speed and / or a temperature and / or a torque of the at least one mixing tool (5).

10. Method for producing a cast sheet for a smoking article performed through the apparatus of any of claims 1 to 9, the method comprising: feeding ingredients of a recipe and water through the at least one inlet and into the mixing path (4) of the continuous mixer (2); mixing the ingredients and the water while advancing said ingredients and water in the mixing path (4) towards the outlet (28) of the continuous mixer (2) to form a slurry mixture and discharging the slurry mixture from the outlet (28); casting the slurry mixture coming from the outlet (28) on the surface to form a cast sheet (42); wherein a holding time of the ingredients and the water and of the slurry mixture in the continuous mixer (2) is between 1 min and 20 min.

11. The method of claim 10, wherein, at least during steady-state operation, feeding, mixing and casting are carried out simultaneously.

12. The method of claim 10 or 11 , wherein, at least during steady-state operation, the slurry mixture advances in a continuous flow from the continuous mixer (2) to the surface.

13. The method of any of claims 10 to 12, wherein the holding time is between5 min and 15 min, optionally between 8 min and 10 min.

14. The method of any of claims 10 to 13, wherein a flow rate of the slurry mixture coming out of the outlet (28) of the continuous mixer (2) is between 80 Kg / h and 3000 kg / h, optionally between 1000 Kg / h and 2500 kg / h.

15. The method of any of claims 10 to 14, wherein a continuous operation time of the apparatus (1) is some hours, optionally between 30 hours and 60 hours, optionally of 45 hours.

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