EP4746723A1 - Apparatus and method for producing a sheet of aerosol-generating substrate for an aerosol-generating article - Google Patents

Abstract

An apparatus for producing a sheet of aerosol-generating substrate for an aerosol- generating article comprises: a dough mixer (5) configured for kneading a mixture with a recipe and water to form a dough (Do); rollers operatively placed downstream of the dough mixer (5) and configured to flatten the dough (Do) to form the sheet (10). The rollers comprise a couple of spreading rollers (28A, 28B) comprising: a first spreading roller (31) having a first rotation axis (X-X) and a first radial outer face; a second spreading roller (32) having a second rotation axis (Y-Y) and a second radial outer face. The first radial outer face faces the second radial outer face to delimit a passage (33) for the dough (Do). One of or both the first radial outer face and the second radial outer face has/have reliefs and recesses to spread the dough (Do) into a sheet provided with at least one uneven surface.

Description

APPARATUS AND METHOD FOR PRODUCING A SHEET OF AEROSOLGENERATING SUBSTRATE FOR AN AEROSOL-GENERATING ARTICLE

The present disclosure relates to an apparatus and a method for producing a sheet of aerosol-generating substrate for an aerosol-generating article. The present disclosure also relates to a process for manufacturing an aerosol-generating article component and to an aerosol-generating article.

Aerosol-generating articles or heat-not-burn cigarettes, in which an aerosolgenerating substrate is heated rather than combusted, are known in the art. The aerosolgenerating substrate is for instance a sheet of reconstituted tobacco, a tobacco-free herbaceous or plant-based sheet or a plastic fiber-based sheet or a biodegradable fiberbased sheet. The sheet is gathered and enclosed in a wrapping to form a rod of aerosol generating substrate.

Typically, in such heated aerosol-generating articles, an aerosol is generated by the transfer of heat from a heat source to a physically separate aerosol-generating substrate or material, which may be located in contact with, within, around, or downstream of the heat source. During use of the aerosol-generating article, volatile compounds are released from the aerosol-generating substrate by heat transfer from the heat source and are entrained in air drawn through the aerosol-generating article. As the released compounds cool, they condense to form an aerosol.

A sheet of aerosol-generating substrate may be prepared by rolling methods or casting methods, depending on the amount of water used in the process. If the amount of water is low in the starting mixture, the sheet is usually obtained by rolling steps, because the mixture is like pasta or dough. In order to flatten this dough material to a constant thickness, the dough is processed through multiple sequential rolling steps until the desired thickness of the material is obtained.

For instance, document W02020058814A1 discloses a method 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. A mixture forming unit forms a plurality of portions of the mixture. A first lamination unit 100 is configured to obtain, from the portions of said mixture, a continuous strip and a series of further rolling passages through lamination rollers allow to obtain a strip having a substantially constant thickness. The strip is then dried to bring its liquid content to about 8-15 percent. It would be desirable to have an apparatus and a method for manufacturing a sheet of aerosol-generating substrate allowing an accurate control of the thickness and quality of said sheet.

It would be desirable to have an apparatus and a method for manufacturing a sheet of aerosol-generating substrate, wherein the sheet of aerosol-generating substrate obtained has a desired uniform thickness.

It would be desirable to have an apparatus and a method for manufacturing a sheet of aerosol-generating substrate, wherein the sheet of aerosol-generating substrate obtained is free from defects and unevenness.

It would be desirable to have a method for manufacturing a sheet of aerosolgenerating substrate, wherein the sheet of aerosol-generating substrate obtained has a targeted thickness of less than a millimetre.

It would be also desirable to achieve the above features of the sheet of aerosolgenerating substrate through simple and reliable devices and processes.

It would be also desirable to achieve the above features of the sheet through devices not requiring continuous and accurate calibration of process parameters, like distance between lamination rollers, pressure applied to the material, speed which the material passes through the lamination rollers. Indeed, in the devices and methods of the prior art, a non-efficient calibration of these parameters or the uneven distribution of dough material across the width of the lamination rollers may produce defects, like holes, in the dough sheet.

The present disclosure relates to an apparatus for producing a sheet of aerosolgenerating substrate for an aerosol-generating article. The apparatus comprises rollers configured to flatten a dough to form the sheet. The apparatus may comprise a dough mixer configured for kneading a mixture with a recipe and water to form the dough. The rollers may be operatively placed downstream of the dough mixer. The apparatus may comprise a dryer operatively placed downstream of the rollers and configured to dry the sheet and obtaining a sheet of aerosol-generating substrate for an aerosol-generating article. The apparatus may also comprise a cooler placed downstream of the dryer to cool the sheet of aerosol-generating substrate. The rollers may comprise a couple of spreading rollers. The couple of spreading rollers may comprise a first spreading roller having a first rotation axis and a first radial outer face. The couple of spreading rollers may comprise a second spreading roller having a second rotation axis and a second radial outer face. The first rotation axis and the second rotation axis may be parallel to each other. The first radial outer face may face the second radial outer face to delimit a passage for the dough. At least one of the first radial outer face and the second radial outer face has reliefs and recesses to spread the dough into a sheet provided with at least one uneven surface.

The inventor found that the disclosed apparatus allows to obtain a sheet free from defects (like undesired holes) and unevenness and provided with the desired uniform thickness. Indeed, the radial outer face or faces provided with reliefs and recesses allow/s to distribute evenly the dough material across the width of the rollers, even if the dough has a high consistency.

The inventor found that the disclosed apparatus allows to manufacture sheets having targeted and controlled thickness, also of less than a millimetre.

The inventor found that the disclosed apparatus allows to manufacture the sheet as desired through a limited number of rollers.

The inventor also found that the disclosed apparatus allows to manufacture the sheet as desired without the need for an accurate calibration of process parameters, like distance between lamination rollers, pressure applied to the material, speed which the material passes through the lamination rollers.

The first radial outer face has a first maximum radius “R1” and the second radial outer face has a second maximum radius “R2”. A distance “d” between the first rotation axis and the second rotation axis may be greater than a sum of the first maximum radius “R1” and the second maximum radius “R2”. A minimum distance “B” of the passage is B = d - (R1 + R2). The minimum distance “B” may be measured in a plane containing the first rotation axis and the second rotation axis and along a direction perpendicular to the first rotation axis and the second rotation axis.

In some embodiments, both the first radial outer face and the second radial outer face have reliefs and recesses. In other embodiments, only one of the first radial outer face and the second radial outer face has reliefs and recesses.

In some embodiments, at the passage, the reliefs of the first spreading roller are spaced from the reliefs of the second spreading roller of the minimum distance “B”. Said minimum distance “B” may be between 1 mm and 10 mm, optionally, between 2 mm to 8 mm, optionally between 4 mm to 7 mm, optionally of 6 mm.

In some embodiments, the reliefs comprise blocks.

In some embodiments, the recesses comprise hollows delimited between said blocks.

In some embodiments, the reliefs comprise ridges.

In some embodiments, the recesses comprise grooves delimited between said ridges.

The ridges and the grooves may extend from a first axial end to a second axial end of the first spreading roller and/or of the second spreading roller. The ridges and the grooves may cover all or part of the first radial outer face of the first spreading roller and/or of second radial outer face the second spreading roller. The first radial outer face and /or the second radial outer face have/has a corrugated or wavy shape.

In some embodiments, the ridges and the grooves are parallel with respect to the respective first rotation axis or second rotation axis.

In some embodiments, the ridges and the grooves are skew with respect to the respective first rotation axis or second rotation axis.

In some embodiments, the ridges and the grooves extend around the respective first rotation axis or second rotation axis.

The ridges and the grooves may lie in planes perpendicular to the respective first rotation axis or second rotation axis.

The ridges and the grooves may be circular.

In a cross section including the respective first rotation axis or second rotation axis, the ridges may have a rectangular outline or a triangular outline or an arched outline.

In a cross section including the respective first rotation axis or second rotation axis, a top of ridges may be flat or rounded or edged.

In a cross section including the respective first rotation axis or second rotation axis, the grooves may have a rectangular outline or a triangular outline or an arched outline.

In a cross section including the respective first rotation axis or second rotation axis, a bottom of grooves may be flat or rounded or edged.

In some embodiments, tops of the ridges of the first radial outer face and tops of the ridges of the second radial outer face are facing each other.

A pitch “C” of the ridges may be between 4 mm to 50 mm, optionally between 15 mm to 30 mm, optionally between 17 mm to 25 mm, optionally of 20 mm.

In some embodiments, the recesses further comprise a plurality of gaps crossing the ridges and the grooves. The gaps may extend partially or fully along a length of the respective first spreading roller or second spreading roller. The gaps may be parallel or skew with respect to the respective first rotation axis or second rotation axis.

A radial distance “A” between a bottom of the recesses or grooves and a top of the reliefs or ridges may be between 5 mm to 40 mm, optionally between 10 mm to 25 mm, optionally between 10 mm to 20 mm, optionally of 15 mm.

A radial depth of the gaps may be equal to or less than the radial distance “A”, optionally half of the radial distance “A”.

An axial length “L” of the first spreading roller and of the second spreading roller may be between 1000 mm and 2100 mm.

A diameter “D” of the first spreading roller and of the second spreading roller may be between 100 mm and 600 mm, optionally of 400 mm. In some embodiments, the first spreading roller and the second spreading roller of the couple of spreading rollers have a same geometry. In other embodiments, the first spreading roller and the second spreading roller of the couple of spreading rollers may have different geometries.

In some embodiments, the first spreading roller and the second spreading roller of the couple of spreading rollers have a same size. In other embodiments, the first spreading roller and the second spreading roller of the couple of spreading rollers may have different sizes.

In some embodiments, the reliefs and recesses of the first radial outer face and of the second radial outer face have a same shape. In other embodiments, the reliefs and recesses of the first radial outer face and of the second radial outer face may have different shapes.

In some embodiments, the rollers comprise a plurality of couples of spreading rollers positioned one after the other.

In some embodiments, a radial distance “A” between a bottom of the recesses or grooves and a top of the reliefs or ridges of a couple of spreading rollers placed upstream is greater than a radial distance “A” between a bottom of the recesses or grooves and a top of the reliefs or ridges of a couple of spreading rollers placed downstream.

In some embodiments, a pitch “C” of the ridges of a couple of spreading rollers placed upstream is greater than a pitch “C” of the ridges of a couple of spreading rollers placed downstream.

In some embodiments, a minimum distance “B” of the passage, measured in a plane containing the first rotation axis and the second rotation axis and along a direction perpendicular to the first rotation axis and the second rotation axis, of a couple of spreading rollers placed upstream is greater than a minimum distance “B” of the passage of a couple of spreading rollers placed downstream.

In some embodiments, the rollers further comprise at least one couple of flattening rollers placed downstream of the spreading rollers, optionally a plurality of couples of flattening rollers placed one after the other. The flattening rollers may have flat radial outer faces, i.e. straight parallel surfaces without any corrugation delimiting a respective passage there between.

The inventor found that the spreading rollers allows to spread the dough before the following flattening steps to ensure a steady input for the first couple of flattening rollers and obtain an unbroken sheet. If more than one couple of flattening rollers is provided, gradually reduce the thickness until reaching the target. While flattening the dough sheet, the width of the sheet may increase. In between the rollers there may be conveyor belts that forward the product.

Each flattening roller may be equipped with a scraper cleaning the roller surface from potential residues.

The present disclosure also relates to a method for producing a sheet of aerosolgenerating substrate for an aerosol-generating article.

The method may be implemented through an apparatus for producing a sheet of aerosol-generating substrate for an aerosol-generating article.

The apparatus comprises rollers configured to flatten a dough to form the sheet. The apparatus may comprise a dough mixer configured for kneading a mixture with a recipe and water to form the dough. The rollers may be operatively placed downstream of the dough mixer. The apparatus may comprise a dryer operatively placed downstream of the rollers and configured to dry the sheet and obtaining a sheet of aerosol-generating substrate for an aerosol-generating article. The apparatus may also comprise a cooler placed downstream of the dryer to cool the sheet of aerosol-generating substrate. The rollers may comprise a couple of spreading rollers.

The method may comprise: mixing a recipe with water to form a mixture, the recipe comprising as ingredients vegetable and/or alkaloid particles, a binder and an aerosol forming agent.

The method may comprise: kneading the mixture in a dough mixer to form a dough. The dough mixer may be the dough mixer of the apparatus.

The method comprises: flattening the dough through rollers to form a sheet. The rollers may be the rollers of the apparatus.

In some embodiments, the method comprises: drying the sheet in a dryer to obtain a sheet of aerosol-generating substrate for an aerosol-generating article. The dryer may be the dryer of the apparatus.

Flattening comprises: passing the dough through a couple of spreading rollers rotating in opposite directions, to spread the dough into a sheet provided with at least one uneven surface.

The couple of spreading rollers may comprise a first spreading roller having a first rotation axis and a first radial outer face. The couple of spreading rollers may comprise a second spreading roller having a second rotation axis and a second radial outer face. The first rotation axis and the second rotation axis may be parallel to each other. The first radial outer face may face the second radial outer face to delimit a passage for the dough. At least one of the first radial outer face and the second radial outer face has reliefs and recesses to spread the dough into a sheet provided with at least one uneven surface.

The first radial outer face has a first maximum radius “R1” and the second radial outer face has a second maximum radius “R2”. A distance “d” between the first rotation axis and the second rotation axis may be greater than a sum of the first maximum radius “R1” and the second maximum radius “R2”. A minimum distance “B” of the passage is B = d - (R1 + R2). The minimum distance “B” may be measured in a plane containing the first rotation axis and the second rotation axis and along a direction perpendicular to the first rotation axis and the second rotation axis.

In some embodiments, both the first radial outer face and the second radial outer face have reliefs and recesses. In other embodiments, only one of the first radial outer face and the second radial outer face has reliefs and recesses.

In some embodiments, at the passage, the reliefs of the first spreading roller are spaced from the reliefs of the second spreading roller of the minimum distance “B”. Said minimum distance “B” may be between 1 mm and 10 mm, optionally, between 2 mm to 8 mm, optionally between 4 mm to 7 mm, optionally of 6 mm.

In some embodiments, the reliefs comprise blocks.

In some embodiments, the recesses comprise hollows delimited between said blocks.

In some embodiments, the reliefs comprise ridges.

In some embodiments, the recesses comprise grooves delimited between said ridges.

The ridges and the grooves may extend from a first axial end to a second axial end of the first spreading roller and/or of the second spreading roller. The ridges and the grooves may cover all or part of the first radial outer face of the first spreading roller and/or of second radial outer face the second spreading roller.

In some embodiments, the ridges and the grooves are parallel with respect to the respective first rotation axis or second rotation axis.

In some embodiments, the ridges and the grooves are skew with respect to the respective first rotation axis or second rotation axis.

In some embodiments, the ridges and the grooves extend around the respective first rotation axis or second rotation axis.

The ridges and the grooves may lie in planes perpendicular to the respective first rotation axis or second rotation axis.

The ridges and the grooves may be circular.

In a cross section including the respective first rotation axis or second rotation axis, the ridges may have a rectangular outline or a triangular outline or an arched outline. In a cross section including the respective first rotation axis or second rotation axis, a top of ridges may be flat or rounded or edged.

In a cross section including the respective first rotation axis or second rotation axis, the grooves may have a rectangular outline or a triangular outline or an arched outline.

In a cross section including the respective first rotation axis or second rotation axis, a bottom of grooves may be flat or rounded or edged.

In some embodiments, tops of the ridges of the first radial outer face and tops of the ridges of the second radial outer face are facing each other.

A pitch “C” of the ridges may be between 4 mm to 50 mm, optionally between 15 mm to 30 mm, optionally between 17 mm to 25 mm, optionally of 20 mm.

In some embodiments, the recesses further comprise a plurality of gaps crossing the ridges and the grooves. The gaps may extend partially or fully along a length of the respective first spreading roller or second spreading roller. The gaps may be parallel or skew with respect to the respective first rotation axis or second rotation axis.

A radial distance “A” between a bottom of the recesses or grooves and a top of the reliefs or ridges may be between 5 mm to 40 mm, optionally between 10 mm to 25 mm, optionally between 10 mm to 20 mm, optionally of 15 mm.

A radial depth of the gaps may be equal to or less than the radial distance “A”, optionally half of the radial distance “A”.

An axial length “L” of the first spreading roller and of the second spreading roller may be between 1000 mm and 2100 mm.

A diameter “D” of the first spreading roller and of the second spreading roller may be between 100 mm and 600 mm, optionally of 400 mm.

In some embodiments, the first spreading roller and the second spreading roller of the couple of spreading rollers have a same geometry. In other embodiments, the first spreading roller and the second spreading roller of the couple of spreading rollers may have different geometries.

In some embodiments, the first spreading roller and the second spreading roller of the couple of spreading rollers have a same size. In other embodiments, the first spreading roller and the second spreading roller of the couple of spreading rollers may have different sizes.

In some embodiments, the reliefs and recesses of the first radial outer face and of the second radial outer face have a same shape. In other embodiments, the reliefs and recesses of the first radial outer face and of the second radial outer face may have different shapes. In some embodiments, the rollers comprise a plurality of couples of spreading rollers positioned one after the other.

In some embodiments, a radial distance “A” between a bottom of the recesses or grooves and a top of the reliefs or ridges of a couple of spreading rollers placed upstream is greater than a radial distance “A” between a bottom of the recesses or grooves and a top of the reliefs or ridges of a couple of spreading rollers placed downstream.

In some embodiments, a pitch “C” of the ridges of a couple of spreading rollers placed upstream is greater than a pitch “C” of the ridges of a couple of spreading rollers placed downstream.

In some embodiments, a minimum distance “B” of the passage, measured in a plane containing the first rotation axis and the second rotation axis and along a direction perpendicular to the first rotation axis and the second rotation axis, of a couple of spreading rollers placed upstream is greater than a minimum distance “B” of the passage of a couple of spreading rollers placed downstream.

In some embodiments, the rollers further comprise at least one couple of flattening rollers placed downstream of the spreading rollers, optionally a plurality of couples of flattening rollers placed done after the other. The flattening rollers may have flat radial outer faces.

The sheet provided with at least one uneven surface may have protrusions and recesses of similar outline to a cross section of the passage.

In some embodiments, flattening further comprises: passing the sheet provided with at least one uneven surface between the at least one couple of flattening rollers. The flattening rollers may be the flattening rollers of the apparatus.

A maximum thickness of the sheet provided with at least one uneven surface may be 10 to 100 times a final thickness of the sheet downstream of the flattening rollers.

The final thickness of the sheet may be between 150 pm and 300 pm, optionally between 170 pm and 290 pm.

In some embodiments, flattening comprises: passing the dough through a plurality of couples of spreading rollers. The plurality of couples of spreading rollers may be the plurality of couples of spreading rollers of the apparatus.

In some embodiments, flattening comprises: passing the dough through a plurality of couples of flattening rollers. The plurality of couples of flattening rollers may be the plurality of couples of flattening rollers of the apparatus.

In some embodiments, a pressure applied by the couple of spreading rollers on the dough is between 20 N/mm to 150 N/mm, optionally between 40 N/mm to 80 N/mm across the width of the sheet. A consistency of the dough may be up to 14 Nm at 25° measured with a Farinograph instrument. A consistency of the dough may be above 14 Nm at 25° measured with a Farinograph instrument, for instance up to 20 Nm.

The inventor found that, if the consistency of the dough is low (below 14 Nm), it is advisable to choose spreading rollers with a bigger pitch C and shorter radial distance A.

The inventor found that, if the material consistency is high (i.e. above 14 Nm), more than one couple of spreading rollers can be applied starting from a roller with higher radial distance “A” and bigger pitch “C” and ending with a couple of spreading rollers with lower radial distance “A” and lower pitch “C”.

The inventor found that, when the sheet is of such high consistency, spreading of the dough through the spreading rollers before its further flattening allows to produce the sheet of the desired thickness and without defects.

Depending on the features of the dough, the number of the coupled of spreading and flattening rollers, the distance between the rollers of each couple, the shape of the rollers, the pressure on the material and the speed of the material entering the rollers may be determined.

A temperature of the couple of spreading rollers may be the room temperature or a temperature between - 50 °C and + 50 °C, optionally between - 20 °C and + 20 °C, with respect to the room temperature.

An amount of water in the dough may be 7% to 60%, optionally 15% to 50%, optionally 27% to 35%, in 100% of dough.

According to some embodiments, the method comprises: winding the sheet of aerosol-generating substrate in a master bobbin and then cutting the master bobbin in small bobbins.

According to some other embodiments, the method comprises: slitting the sheet of aerosol-generating substrate in a plurality of tapes and winding each tape in a small bobbin.

Before winding in the master bobbin or before slitting, the sheet of aerosol-generating substrate may be cooled. Cooling may be performed in the cooler of the apparatus.

According to some embodiments, vegetables and/or alkaloids are grinded to obtain the vegetable and/or alkaloid particles, before mixing. Grinding may be performed in a grinder of the apparatus placed upstream of the dough mixer.

According to some embodiments, after kneading and before flattening, the dough is calendered to form a thick sheet.

The present disclosure also relates to a process for manufacturing an aerosolgenerating article component. The process may comprise: manufacturing a sheet of aerosol-generating substrate for an aerosol-generating article using the apparatus for producing a sheet of aerosolgenerating substrate for an aerosol-generating article above disclosed and/or through the method for producing a sheet of aerosol-generating substrate for an aerosol-generating article above disclosed.

The process may comprise: gathering the sheet of aerosol-generating substrate and wrapping the gathered sheet of aerosol-generating substrate in a wrapper to form a continuous rod.

The process may comprise: cutting the continuous rod into a plurality of aerosolgenerating article components each having a rod shape, wherein each aerosol-generating article component comprises a gathered sheet formed from a cut portion of the sheet of aerosol-generating substrate.

The present disclosure also relates to an aerosol-generating article made according to the process above disclosed.

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.

As used in the present description, the term “dough” means a mixture that is stiff enough to be kneaded or rolled out, as opposed to a “slurry” which is a watery mixture of insoluble matter with a water content so high (e.g. 70 percent - 80 percent) that cannot be kneaded or rolled out.

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.

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.

EX1. An apparatus for producing a sheet of aerosol-generating substrate for an aerosol-generating article, the apparatus comprising: a dough mixer configured for kneading a mixture with a recipe and water to form a dough; rollers operatively placed downstream of the dough mixer and configured to flatten the dough to form the sheet; an optional dryer operatively placed downstream of the rollers and configured to dry the sheet and obtaining a sheet of aerosol-generating substrate for an aerosol-generating article; an optional cooler placed downstream of the dryer to cool the sheet of aerosolgenerating substrate; wherein the rollers comprise a couple of spreading rollers, comprising: a first spreading roller having a first rotation axis and a first radial outer face; a second spreading roller having a second rotation axis and a second radial outer face; the first rotation axis and the second rotation axis being parallel to each other and the first radial outer face faces the second radial outer face to delimit a passage for the dough; wherein at least one of the first radial outer face and the second radial outer face has reliefs and recesses to spread the dough into a sheet provided with at least one uneven surface.

EX2. The apparatus according to EX1 , wherein the first radial outer face has a first maximum radius “R1” and the second radial outer face has a second maximum radius “R2”; wherein a distance “d” between the first rotation axis and the second rotation axis is greater than a sum of the first maximum radius “R1” and the second maximum radius “R2”.

EX3. The apparatus according to EX2, wherein a minimum distance “B” of the passage, measured in a plane containing the first rotation axis and the second rotation axis and along a direction perpendicular to the first rotation axis and the second rotation axis, is: B = d - (R1 + R2).

EX4. The apparatus according to any of EX1 to EX3, wherein, both the first radial outer face and the second radial outer face have reliefs and recesses.

EX5. The apparatus according to EX4, wherein, at the passage, the reliefs of the first spreading roller are spaced from the reliefs of the second spreading roller of the minimum distance “B”.

EX6. The apparatus according to EX3 or according to EX4 or EX5 when EX4 is according to EX3, wherein the minimum distance “B” is between 1 mm and 10 mm, optionally, between 2 mm to 8 mm, optionally between 4 mm to 7 mm, optionally of 6 mm.

EX7. The apparatus according to any of EX1 to EX6, wherein the reliefs comprise blocks and the recesses comprise hollows delimited between said blocks.

EX8. The apparatus according to any of EX1 to EX7, wherein the reliefs comprise ridges and the recesses comprise grooves delimited between said ridges. EX9. The apparatus according to EX8, wherein the ridges and the grooves extend from a first axial end to a second axial end of the first spreading roller and/or of the second spreading roller.

EX10. The apparatus according to EX8 or EX9, wherein the ridges and the grooves are parallel with respect to the respective first rotation axis or second rotation axis.

EX11 . The apparatus according to EX8 or EX9 or EX10, wherein the ridges and the grooves are skew with respect to the respective first rotation axis or second rotation axis.

EX12. The apparatus according to any of EX8 to EX11 , wherein the ridges and the grooves extend around the respective first rotation axis or second rotation axis.

EX13. The apparatus according to EX12, wherein, in a cross section including the respective first rotation axis or second rotation axis, the ridges have a rectangular outline or a triangular outline or an arched outline.

EX14. The apparatus according to EX12 or EX13, wherein, in a cross section including the respective first rotation axis or second rotation axis, a top of ridges is flat or rounded or edged.

EX15. The apparatus according to any of EX12 to EX14, wherein, in a cross section including the respective first rotation axis or second rotation axis, the grooves have a rectangular outline or a triangular outline or an arched outline.

EX16. The apparatus according to any of EX12 to EX15, wherein, in a cross section including the respective first rotation axis or second rotation axis, a bottom of grooves is flat or rounded or edged.

EX17. The apparatus according to any of EX12 to EX16, wherein the ridges and the grooves lie in planes perpendicular to the respective first rotation axis or second rotation axis.

EX18. The apparatus according to any of EX12 to EX17, wherein the ridges and the grooves are circular.

EX19. The apparatus according EX18 when EX8 is according to EX4 or EX5, wherein tops of the ridges of the first radial outer face and tops of the ridges of the second radial outer face are facing each other.

EX20. The apparatus according to any of EX8 to EX19, wherein a pitch “C” of the ridges is between 4 mm to 50 mm, optionally between 15 mm to 30 mm, optionally between 17 mm to 25 mm, optionally of 20 mm.

EX21. The apparatus according to any of EX8 to EX20, wherein the recesses further comprise a plurality of gaps crossing the ridges and the grooves.

EX22. The apparatus according to EX21 , wherein the gaps extend partially or fully along a length of the respective first spreading roller or second spreading roller. EX23. The apparatus according to EX22, wherein the gaps are parallel or skew with respect to the respective first rotation axis or second rotation axis.

EX24. The apparatus according to any of EX1 to EX23, wherein a radial distance “A” between a bottom of the recesses or grooves and a top of the reliefs or ridges is between 5 mm to 40 mm, optionally between 10 mm to 25 mm, optionally between 10 mm to 20 mm, optionally of 15 mm.

EX25. The apparatus according to EX22, EX23 or EX24, wherein a radial depth of the gaps is equal to or less than the radial distance “A”, optionally half of the radial distance A.

EX26. The apparatus according to any of EX1 to EX25, wherein an axial length “L” of the first spreading roller and of the second spreading roller is between 1000 mm and 2100 mm.

EX27. The apparatus according to any of EX1 to EX26, wherein a diameter “D” of the first spreading roller and of the second spreading roller is between 100 mm and 600 mm, optionally of 400 mm.

EX28. The apparatus according to any of EX1 to EX27, wherein the first spreading roller and the second spreading roller of the couple of spreading rollers have a same geometry.

EX29. The apparatus according to any of EX1 to EX28, wherein the first spreading roller and the second spreading roller of the couple of spreading rollers have a same size.

EX30. The apparatus according to any of EX1 to EX29, wherein the reliefs and recesses of the first radial outer face and of the second radial outer face have a same shape.

EX31. The apparatus according to any of EX1 to EX30, wherein the rollers comprise a plurality of couples of spreading rollers positioned one after the other.

EX32. The apparatus according to EX31 , wherein a radial distance “A” between a bottom of the recesses or grooves and a top of the reliefs or ridges of a couple of spreading rollers placed upstream is greater than a radial distance “A” between a bottom of the recesses or grooves and a top of the reliefs or ridges of a couple of spreading rollers placed downstream.

EX33. The apparatus according to EX31 or EX32, wherein a pitch “C” of the ridges of a couple of spreading rollers placed upstream is greater than a pitch “C” of the ridges of a couple of spreading rollers placed downstream.

EX34. The apparatus according to EX31 or EX32 or EX33, wherein a minimum distance “B” of the passage, measured in a plane containing the first rotation axis and the second rotation axis and along a direction perpendicular to the first rotation axis and the second rotation axis, of a couple of spreading rollers placed upstream is greater than a minimum distance “B” of the passage of a couple of spreading rollers placed downstream.

EX35. The apparatus according to any of EX1 to EX34, wherein the rollers further comprise at least one couple of flattening rollers placed downstream of the spreading rollers, optionally a plurality of couples of flattening rollers placed done after the other.

EX36. The apparatus according to EX35, wherein the flattening rollers have flat radial outer faces.

EX37. A method for producing a sheet of aerosol-generating substrate for an aerosol-generating article through the apparatus of any of EX1 to EX36.

EX38. The method according to EX37, comprising: mixing a recipe with water to form a mixture, the recipe comprising as ingredients vegetable and/or alkaloid particles, a binder and an aerosol forming agent; kneading the mixture in the dough mixer to form a dough; flattening the dough through the rollers to form a sheet; optionally drying the sheet in the dryer to obtain a sheet of aerosol-generating substrate for an aerosol-generating article; wherein flattening comprises: passing the dough through the couple of spreading rollers rotating in opposite directions, to spread the dough into a sheet provided with at least one uneven surface.

EX39. The method according to EX38, wherein the sheet provided with at least one uneven surface has protrusions and recesses of similar outline to a cross section of the passage.

EX40. The method according to EX38 or EX40, wherein flattening further comprises: passing the sheet provided with at least one uneven surface between the at least one couple of flattening rollers.

EX41. The method according to EX40, wherein a maximum thickness of the sheet provided with at least one uneven surface is 10 to 100 times a final thickness of the sheet downstream of the flattening rollers.

EX42. The method according to EX41 , wherein the final thickness is between 150 pm and 300 pm, optionally between 170 pm and 290 pm.

EX43. The method according to any of EX38 to EX42, wherein flattening comprises: passing the dough through a plurality of couples of spreading rollers.

EX44. The method according to any of EX38 to EX43, wherein flattening comprises: passing the dough through a plurality of couples of flattening rollers. EX45. The method according to any of EX38 to EX44, wherein a pressure applied by the couple of spreading rollers on the dough is between 20 N/mm to 150 N/mm, optionally between 40 N/mm to 80 N/mm across the width of the sheet.

EX46. The method according to any of EX38 to EX45, wherein a consistency of the dough is up to 14 Nm at 25° measured with a Farinograph instrument; optionally the consistency of the dough is above 14 Nm at 25° measured with a Farinograph instrument, optionally up to 20 Nm.

EX47. The method according to any of EX38 to EX46, wherein a temperature of the couple of spreading rollers is the room temperature.

EX48. The method according to any of EX38 to EX47, wherein a temperature between - 50 °C and + 50 °C, optionally between - 20 °C and + 20 °C, with respect to a room temperature.

EX49. The method according to any of EX38 to EX48, wherein an amount of water in the dough is 7% to 60%, optionally 15% to 50%, optionally 27% to 35%, in 100% of dough.

EX50. The method according to any of EX38 to EX50, further comprising: winding the sheet of aerosol-generating substrate in a master bobbin and then cutting the master bobbin in small bobbins.

EX51. The method according to any of EX38 to EX50, further comprising: slitting the sheet of aerosol-generating substrate in a plurality of tapes and winding each tape in a small bobbin.

EX52. The method according to EX50 or to EX51 , further comprising: cooling the sheet of aerosol-generating substrate before winding in the master bobbin or before slitting.

EX53. The method according to any of EX38 to EX52, comprising: grinding vegetables and/or alkaloids to obtain the vegetable and/or alkaloid particles, before mixing.

EX54. The method according to any of EX38 to EX53, wherein after kneading and before flattening, the dough is calendered to form a thick sheet.

EX55. A process for manufacturing an aerosol-generating article component, comprising: manufacturing a sheet of aerosol-generating substrate for an aerosol-generating article using the apparatus according to any of EX1 to EX36 or through the method according to any of EX37 to EX54; gathering the sheet of aerosol-generating substrate and wrapping the gathered sheet of aerosol-generating substrate in a wrapper to form a continuous rod; cutting the continuous rod into a plurality of aerosol-generating article components each having a rod shape, each aerosol-generating article component comprising a gathered sheet formed from a cut portion of the sheet of aerosol-generating substrate.

EX56. An aerosol-generating article comprising at least one aerosol-generating article component made according to the process of EX55.

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

Figure 1 shows schematically an apparatus for producing a sheet of aerosolgenerating substrate for an aerosol-generating article according to the invention;

Figure 2 shows schematically an apparatus for making a rod of aerosol-generating substrate;

Figures 3 and 4 show a longitudinal section and a cross section of an aerosolgenerating article component made with the rod of Figure 2;

Figure 5 shows a couple of rollers of the apparatus of Figure 1 ;

Figures 6 to 14 show variants of the rollers of Figure 5;

Figure 15 is an embodiment of a roller assembly of Figure 1 ;

Figures 16 and 17 are 3D views of the sheet of aerosol-generating substrate in respective intermediate working steps carried out through the rollers of Figure 15.

The apparatus 1 shown in Figure 1 is a schematic example of an apparatus configured for producing a sheet of aerosol-generating substrate for an aerosol-generating article according to the invention.

The apparatus 1 comprises a grinder 2 configured to grind vegetable and/or alkaloid into particles “T”. For instance, the vegetable and/or alkaloid are tobacco strips and the grinder 2 is a tobacco mill adapted to coarse grind the tobacco strips to tobacco particles having a size of 70 - 550 pm, with no particles greater than 325 pm.

From the grinder 2, the vegetable and/or alkaloid particles “T” are transported, for example by means of a pneumatic transport, to a powder mixing silo 3 schematically shown in Figure 1. In the powder mixing silo 3, other powders, such as cellulose fibers “F”, can be introduced and mixed to form a first premix “PM1”.

The apparatus 1 further comprises a container 4, in which a wet mixture is formed by loading an aerosol forming agent “G”, like glycerine, a binder “M”, such as carboxymethylcellulose (CMC), and then water “W”, to mix them and forming a second premix “PM2”.

The first premix “PM1” and the second premix “PM2” are fed to a dough mixer 5 operatively located downstream of the powder mixing silo 3 and of the container 4.

In the dough mixer 5, the first premix “PM1” and the second premix “PM2” form a mixture which is kneaded to form a dough “Do” through kneading elements 6. The dough “Do” is therefore made by mixing the recipe and water in the dough mixer 5, wherein the recipe comprises the vegetable and/or alkaloid particles “T”, the aerosol forming agent “G”, the cellulose fibers “F” and the binder “M”.

The following Table 1 contains examples of ingredients of the recipe.

Table 1

An amount of total process water used may be 7-60%, more preferably 15-50%, most preferably 27-35%, in 100% of dough.

The dough “Do” is then calendered through a dough-sheeter or calendaring rollers 7, which may be part of the dough mixer 5, to shape the dough “Do” like a thick sheet 8. For instance, a thickness of the thick sheet is between 2 mm and 20 mm.

A consistency of the dough may be up to 14 Nm at 25° measured with a Farinograph instrument. The consistency may be also above 14 Nm at 25° measured with a Farinograph instrument, for instance up to 20 Nm.

Downstream of the dough mixer 5, the apparatus 1 comprises flattening rollers assembly 9 which is configured to flatten the thick sheet 8 to form a flattened thin sheet 10.

A dryer 11 is operatively placed downstream of the flattening rollers assembly 9 and is configured to dry the flattened thin sheet 10 and obtaining a sheet 12 of aerosolgenerating substrate for an aerosol-generating article. The dryer 11 may comprise a casing delimiting a chamber 13 and a belt conveyor 14, for instance a mesh belt, moving through the chamber 13 while supporting the thin sheet 10. Heating devices, not shown, are configured to heat and dry the thin sheet 10 moving through the chamber 13.

The flattened sheet 10 is dried down to a liquid content of 5.8 - 11.2 percent on wet weight basis, for instance to 8.5 percent on wet weight basis.

Downstream of the dryer 11 , longitudinal edges of the sheet 12 are trimmed though a trimming device 15. A winder operatively placed downstream of the dryer 11 and of the trimming device 15 is configured to wind the sheet 12 of aerosol-generating substrate on a core 16 to form a master bobbin 17. The master bobbin 17 is slit in a plurality of small bobbins 19 so that each small bobbin 19 comprises a tape 20 of aerosol-generating substrate winded on a respective portion of the core 16 (Figure 2). In a different embodiment, not shown in the drawings, the apparatus 1 comprise an inline slitter operatively placed downstream of the dryer 11 and configured to divide the sheet of aerosol-generating substrate 12 in a plurality of tapes 20. A plurality of small winders are employed for winding each tape 20 on a respective small bobbin 19.

A cooler 18 may be placed between the dryer 11 and the winder or winders so that the sheet 12 of aerosol-generating substrate is cooled prior to be winded (figure 1).

The sheet 12 of aerosol-generating substrate of the small bobbins 19 is employed in the manufacturing of aerosol-generating article components and of an aerosol-generating article.

Each tape 20 of aerosol-generating substrate may be, for instance, gathered and wrapped to form a respective continuous rod 21 through an apparatus 22 for manufacturing aerosol-generating article components, shown in Figure 2.

The apparatus 22 for manufacturing aerosol-generating article components comprises a reel holder 23 carrying the smaller bobbin 19 formed by the tape 20 of aerosolgenerating substrate for an aerosol-generating article component. The tape 20 of aerosolgenerating substrate, previously manufactured, is unwound from the bobbin 19 and fed along a feeding path in a feeding direction “V”.

Downstream of the reel holder 23, the apparatus 1 comprises two rotating cylindrical crimping rollers 24 between which the tape 20 is pressed. These crimping rollers 24 have matching textured ridge-and-trough patterns on their outside surfaces that crimp the tape 20 through transversal stretching of substrate’s fibers. This crimping process is helpful for folding and gathering the tape 20 of aerosol-generating substrate into rod pieces that will fit into the aerosol generating articles. Indeed, the term “crimped tape” denotes a tape 20 having a plurality of substantially parallel ridges or corrugations which are substantially parallel to the cylindrical axis of the rod piece. This facilitates folding and gathering of the crimped tape 20 of aerosol-generating substrate to form the aerosol-generating article component.

Figure 2 shows schematically a folding device 25 placed downstream of the two rotating cylindrical rollers 24 and configured to move the tape 20 from a flat configuration (upstream of the folding device 24) to a gathered rod-shaped configuration (downstream of the folding device 25) and to wrap the wrapper 26 (shown in figures 3 and 4) around the gathered tape 20 to obtain the continuous rod 21. The folding device 24 may be shaped like a tapered funnel. The continuous rod 21 is then cut in a plurality of aerosol-generating article components 27. Each aerosol-generating article component 27 has a rod shape and comprises a gathered tape formed from a cut portion of the tape 20 of aerosol-generating substrate (Figures 3 and 4). The roller assembly 9 comprises a first couple 28A of spreading rollers placed just downstream of the dough mixer 5. A second couple 28B of spreading rollers follows the first couple 28A of spreading rollers and is followed by a first couple 29A of flattening rollers and a second couple 29B of flattening rollers.

The first couple of spreading rollers 28A is shown in Figure 5 and comprises a first spreading roller 31 and a second spreading roller 32. The first spreading roller 31 is configured to rotate about a first rotation axis “X-X” and has a first radial outer face. The second spreading roller 32 is configured to rotate about a second rotation axis “Y-Y” and has a second radial outer face.

As shown in Figure 5, the first rotation axis “X-X” and the second rotation axis “Y-Y” are parallel to each other and the first radial outer face faces the second radial outer face to delimit a passage 33 for the dough “Do”.

As shown in Figures 1 and 15, the first rotation axis “X-X” and the second rotation axis “Y-Y” are perpendicular to an advancement direction “P” of the sheet of aerosol-generating substrate downstream of the first couple of spreading rollers 28A.

The first spreading roller 31 and the second spreading roller 32 of the example embodiment of Figure 5 are identical to each other, meaning that they both have a same geometry and sizes. Therefore, only the first spreading roller 31 will be described in details.

The first radial outer face of the first spreading roller 31 comprises a plurality of ridges 34 and a plurality of grooves 35 delimited between said ridges 34. The ridges 34 and the grooves 35 extend from a first axial end to a second axial end of the first spreading roller 31 . The ridges 34 and the grooves 35 extend around the first rotation axis “X-X” and lie in planes perpendicular to the first rotation axis “X-X”. In other words, the ridges 34 and the grooves 35 are circular and coaxial to the first rotation axis “X-X”.

In a cross section including the first rotation axis “X-X”, the ridges 34 have a triangular outline with a rounded top and the grooves 35 present the shape of the ridges 34 with a rounded bottom. Therefore, the first radial outer face has a corrugated or wavy shape.

The first spreading roller 31 has an axial length “L”, measured parallel to the first rotation axis “X-X”, and a diameter “D”, measured on top of the ridges 34. For instance, the axial length “L” is 1600 mm and the diameter “D” is 400 mm. According to other embodiments, the axial length “L” may be between 1000 mm and 2100 mm and the diameter “D” may be between 100 mm and 600 mm.

As shown in Figure 5, a pitch “C” of the ridges 34, meaning an axial distance between two consecutive ridges 34, may be 20 mm. A radial distance “A” between a bottom of the grooves 35 and a top of the ridges 34, i.e. a height of the ridges 34, may be 20 mm. According to embodiments of the invention, the pitch “C” may be between 4 mm to 50 mm, optionally between 15 mm to 30 mm, optionally between 17 mm to 25 mm. The radial distance “A” may be between 5 mm to 40 mm, optionally between 10 mm to 25 mm, optionally between 10 mm to 20 mm, optionally of 15 mm.

The first spreading roller 31 and the second spreading roller 32 are arranged such that the tops of the ridges 34 of the first radial outer face and the tops of the ridges 34 of the second radial outer face are facing each other, i.e. the ridges 34 of the first spreading roller 31 and ridges 34 of the second spreading roller 32 are aligned along directions perpendicular to the first rotation axis “X-X” and second rotation axis “Y-Y”.

Given that the first radial outer face has a first maximum radius “R1”, the second radial outer face has a second maximum radius “R2” and given a distance “d” between the first rotation axis “X-X” and the second rotation axis “Y-Y”, a minimum distance “B” of the passage 33, measured in a plane containing the first rotation axis “X-X” and the second rotation axis “Y-Y” and along a direction perpendicular to the first rotation axis “X-X” and the second rotation axis “Y-Y”, is B = d - (R1 + R2).

Said minimum distance “B” is the distance between the tops of the ridges 34 of the first radial outer face and tops of the ridges 34 of the second radial outer face (Figure 5).

For instance, the minimum distance “B” is 5 mm. According to embodiments of the invention, the minimum distance is between 1 mm and 10 mm, optionally, between 2 mm to 8 mm, optionally between 4 mm to 7 mm, optionally of 6 mm.

The first spreading roller 31 and the second spreading roller 32 are rotated, by an actuator or motor, in opposite directions to advance the dough though the passage 33. When the dough “Do” from the dough mixer 5 is fed through the passage 33 of the first couple of spreading roller 28A, it fills the grooves 35, spreads all along the passage 33 and it is shaped into a first intermediate sheet 8’ provided with uneven surfaces, i.e. the faces of the first intermediate sheet 8’ comprise respective ridges and grooves as depicted in Figure 16.

The second couple 28B of spreading rollers is similar to the first couple 28A of spreading rollers, i.e. the first radial outer face and the second radial outer face of the first spreading roller 31 and the second spreading roller 32 of the second couple 28B of spreading rollers have a corrugated or wavy shape.

Anyway, the radial distance “A”, the pitch “C” and the minimum distance “B” of the second couple of spreading rollers 28B are smaller than the radial distance “A”, the pitch “C” and the minimum distance “B” of the first couple of spreading roller 28A. For instance, the radial distance “A” is 10 mm, the pitch “C” is 10 mm and the minimum distance “B” is 3 mm. A second intermediate sheet 8” exiting the passage 33 of the second couple of spreading rollers 28B is thinner than the first intermediate sheet 8’ and the respective ridges and grooves are smaller than the ridges and grooves of the first intermediate sheet 8’, as depicted in Figure 17.

The first couple 29A of flattening rollers comprises a first flattening roller 36 and a second flattening roller 37 with parallel rotation axis and delimiting a respective passage. The second couple 29B of flattening rollers comprises a first flattening roller 36 and a second flattening roller 37 with parallel rotation axis and delimiting a respective passage. A radial outer face of the first flattening roller 36 and the second flattening roller 37 of both the first and second couple 29A, 29B is flat, i.e. is not provided with reliefs and recesses.

A distance between the first flattening roller 36 and the second flattening roller 37 of the first couple 29A is greater than a distance between the first flattening roller 36 and the second flattening roller 37 of the second couple 29B. Therefore, the second intermediate sheet 8” is flattened and smoothed by the first couple 29A of flattening rollers into a third intermediate sheet 8”’ having smooth surfaces. Finally, the second couple 29B of flattening rollers further reduce the thickness of the sheet to generate the thin sheet 10 (Figure 15). The distance between the rollers of the second couple 29B is equal to the desired thickness of the sheet.

For instance, a maximum thickness of the first intermediate sheet 8’ is 10 mm and a final thickness of the thin sheet 10 is 200 pm. The maximum thickness of the first intermediate sheet 8’ is therefore 50 times the final thickness of the thin sheet 10. Generally speaking, a maximum thickness of the sheet provided with at least one uneven surface is 10 to 100 times a final thickness of the sheet downstream of the flattening rollers. The final thickness may be between 150 pm and 300 pm, optionally between 170 pm and 290 pm.

A temperature of the first and/or second couple of spreading rollers 28A, 28B may be the room temperature or may be between - 50 °C and + 50 °C, optionally between - 20 °C and + 20 °C, with respect to a room temperature. A pressure applied by the first and/or second couple of spreading rollers 28A, 28B on the dough may be between 20 N/mm to 150 N/mm, optionally between 40 N/mm to 80 N/mm across the width of the sheet.

The shape of the first radial outer face and second radial outer face disclosed above is preferred but not exclusive. Further possible geometries of the first spreading roller 31 are depicted in Figures 6 to 14. In particular, reliefs and recesses of the first radial outer face and of the second radial outer face may be other than the grooves 35 and ridges 34 disclosed so far. The same geometries may apply to the second spreading roller 32.

Figure 6 shows ridges 34 with a rectangular outline and a flat top and grooves 35 with an arched outline. Figure 7 shows ridges 34 with an arched outline and grooves 35 having a flat bottom.

Figure 8 shows ridges 34 and grooves 35 provided with a triangular outline. The ridges have an edged top. The grooves have an edged bottom.

Figure 9 shows a corrugated or wavy shape, like the one of Figure 5, wherein the top of the ridges 34 and the bottom of the grooves 5 have a curvature radius greater than the one of Figure 5.

Figure 10 shows ridges 34 and grooves 35 both provided with a rectangular outline with flat tops and bottoms.

The first spreading roller 31 of Figures 11A and 11 B differs from the one Figure 10 because of the gaps 38 which crosses the ridges 34 and the grooves 35. The gaps 38 extend fully along a length of the first spreading roller 31 and are parallel with respect to the first rotation axis “X-X”. A radial depth of the gaps 38 may be equal to or less than the radial distance “A”. For instance, the radial depth of the gaps 38 is half of the radial distance “A”.

The first spreading roller 31 of Figures 12A and 12B differs from the one Figures 11 A and 11 B because the gaps 38 are skew with respect to the respective first rotation axis “X- X”.

The grooves 35 and gaps 38 of Figures 11 A, 11 B, 12A, 12B delimit blocks 39 on the first outer surface.

Figure 13 shows ridges 34 and grooves 35 lying in planes which are skew with respect to planes perpendicular to the first rotation axis “X-X”.

The grooves 34 of Figure 14 are crossed and lie in planes which are skew with respect to planes perpendicular to the first rotation axis “X-X”, thus delimiting a plurality of diamond shaped blocks 39.

In other embodiments, not shown in the appended drawings, the ridges 34 and the grooves 35 do not extend around the respective first rotation axis “X-X” or second rotation axis “Y-Y” and may be parallel or skew with respect to the respective first rotation axis “X- X” or second rotation axis “Y-Y”.

In other embodiments, not shown in the appended drawings, the first radial outer face and/or the second radial outer face may comprise blocks and hollows, delimited by the blocks, of different shapes and sizes.

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

1. Method for producing a sheet of aerosol-generating substrate for an aerosolgenerating article through an apparatus for producing a sheet of aerosol-generating substrate for an aerosol-generating article; wherein the apparatus (1) comprises: a dough mixer (5) configured for kneading a mixture with a recipe and water to form a dough (Do); rollers operatively placed downstream of the dough mixer (5) and configured to flatten the dough (Do) to form the sheet (10); wherein the rollers comprise a couple of spreading rollers (28A, 28B) comprising: a first spreading roller (31) having a first rotation axis (X-X) and a first radial outer face; a second spreading roller (32) having a second rotation axis (Y-Y) and a second radial outer face; the first rotation axis (X-X) and the second rotation axis (Y-Y) being parallel to each other and the first radial outer face faces the second radial outer face to delimit a passage (33) for the dough (Do); wherein at least one of the first radial outer face and the second radial outer face has reliefs and recesses to spread the dough (Do) into a sheet provided with at least one uneven surface; wherein the rollers further comprise at least one couple of flattening rollers (29A, 29B) with flat radial outer faces placed downstream of the spreading rollers (28A, 28B); wherein the method comprises: mixing the recipe with water to form the mixture, the recipe comprising as ingredients vegetable and/or alkaloid particles, a binder and an aerosol forming agent; kneading the mixture in the dough mixer (5) to form a dough (Do); flattening the dough through the rollers to form a sheet; wherein flattening comprises: passing the dough (Do) through the couple of spreading rollers (28A, 28B) rotating in opposite directions, to spread the dough (Do) into a sheet provided with at least one uneven surface; passing the sheet provided with the at least one uneven surface between the at least one couple of flattening rollers (29A, 29B); wherein a maximum thickness of the sheet provided with at least one uneven surface is 10 to 100 times a final thickness of the sheet downstream of the flattening rollers (29A, 29B). 2. The method of claim 1 , wherein the final thickness is between 150 pm and 300 pm, optionally between 170 pm and 290 pm.

3. The method of claim 1 or 2, wherein a pressure applied by the couple of spreading rollers (28A, 28B) on the dough is between 20 N/mm to 150 N/mm, optionally between 40 N/mm to 80 N/mm across the width of the sheet.

4. The method of any of claims 1 to 3, wherein a consistency of the dough (Do) is up to 14 Nm at 25° measured with a Farinograph instrument.

5. The method of any of claims 1 to 4, wherein an amount of water in the dough (Do) is 7% to 60%, optionally 15% to 50%, optionally 27% to 35%, in 100% of dough.

6. The method of any of claims 1 to 5, wherein the first radial outer face has a first maximum radius (R1) and the second radial outer face has a second maximum radius (R2); wherein a distance (d) between the first rotation axis (X-X) and the second rotation axis (Y- Y) is greater than a sum of the first maximum radius (R1) and the second maximum radius (R2); a minimum distance (B) of the passage (33), measured in a plane containing the first rotation axis (X-X) and the second rotation axis (Y-Y) and along a direction perpendicular to the first rotation axis (X-X) and the second rotation axis (Y-Y), being: B = d - (R1 + R2).

7. The method of claim 6, wherein, both the first radial outer face and the second radial outer face have reliefs and recesses and, at the passage (33), the reliefs of the first spreading roller (31) are spaced from the reliefs of the second spreading roller (32) of the minimum distance (B).

8. The method of claim 6 or 7, wherein the minimum distance (B) is between 1 mm and 10 mm, optionally, between 2 mm to 8 mm, optionally between 4 mm to 7 mm, optionally of 6 mm.

9. The method of any of claims 1 to 8, wherein the reliefs comprise ridges (34) and the recesses comprise grooves (35) delimited between said ridges (34); wherein the ridges (34) and the grooves (35) extend around the respective the first rotation axis (X-X) or second rotation axis (Y-Y).

10. The method of claim 9, wherein, in a cross section including the respective first rotation axis (X-X) or second rotation axis (Y-Y), the ridges (34) have a rectangular outline or a triangular outline or an arched outline; wherein, in a cross section including the respective first rotation axis (X-X) or second rotation axis (Y-Y), the grooves (35) have a rectangular outline or a triangular outline or an arched outline.

11 . The method of any of claims 9 to 10, wherein the ridges (34) and the grooves (35) lie in planes perpendicular to the respective the first rotation axis (X-X) or second rotation axis (Y-Y); wherein tops of the ridges (34) of the first radial outer face and tops of the ridges

(34) of the second radial outer face are facing each other.

12. The method of any of claims 9 to 11 , wherein a pitch (C) of the ridges (34) is between 4 mm to 50 mm, optionally between 15 mm to 30 mm, optionally between 17 mm to 25 mm.

13. The method of any of claims 9 to 12, wherein a radial distance (A) between a bottom of the grooves (35) and a top of the ridges (34) is between 5 mm to 40 mm, optionally between 10 mm to 25 mm, optionally between 10 mm to 20 mm, optionally of 15 mm.

14. The method of any of claims 9 to 13, wherein the recesses further comprise a plurality of gaps (38) crossing the ridges (34) and the grooves (35) and the gaps (38) extend partially or fully along a length of the respective first spreading roller (31) or second spreading roller (32).

15. The method of claim 13 when claim 13 depends on claim 12 and claim 9 depends on any of claims 6, 7 or 8, wherein the rollers comprise a plurality of couples of spreading rollers (28A, 28B) positioned one after the other; wherein the radial distance (A) between a bottom of the grooves (35) and a top of the ridges (34), the minimum distance (B) of the passage (33) and the pitch (C) of the ridges (34) of a couple of spreading rollers (28A) placed upstream are greater than the radial distance (A) between a bottom of the grooves

(35) and a top of the ridges (35), the minimum distance (B) of the passage (33) and the pitch (C) of the ridges (34) of a couple of spreading rollers (28B) placed downstream.