ES2974759T3 - Sheet of a material containing alkaloids - Google Patents

Abstract

The present invention relates to a multilayer sheet of an alkaloid-containing material comprising: - a first layer comprising a substrate sheet including fibers having an average fiber length comprised between about 1 millimeter and about 5 millimeters, the first layer defining a first surface and a second surface; - a second layer comprising a mixture of: - a powder of the alkaloid-containing material, the powder having a size comprised between about 8 micrometers and about 200 micrometers; water; - a binder; - an aerosol former; the second layer being applied to the first surface of the substrate sheet, and wherein the binder is comprised in an amount comprised between about 0 percent and about 1 percent of the total weight of the multilayer sheet of alkaloid-containing material. (Automatic translation with Google Translate, no legal value)

Description

DESCRIPTION

Sheet of a material containing alkaloids

This invention relates to a sheet of an alkaloid-containing material, such as a multilayer sheet or a composite sheet.

In particular, the alkaloid-containing material may be a homogenized tobacco material, preferably used in an aerosol-generating article such as, for example, a cigarette or a “heat-not-burn” type tobacco-containing product.

Nowadays, in addition to tobacco leaves, homogenized tobacco material, such as molded tobacco or reconstituted tobacco, is also used in the production of tobacco products.

In a “heat-not-burn” aerosol-generating article, an aerosol-forming substrate is heated to a relatively low temperature to form an aerosol that prevents combustion of the tobacco material.

Homogenized tobacco material is produced by mixing different components, including tobacco dust, to form a tobacco slurry. In addition, the slurry commonly contains fibers, such as cellulosic fibers, in addition to those contained in the tobacco. This slurry is then stored in tanks before being sent, via a suitable delivery system, to a molding system where it enters a “mold box” to be melted on a moving steel conveyor belt and then dried in a dryer. US5449636 describes a multilayer sheet comprising tobacco. D2 CN108451001 describes a coated fibrous substrate sheet, coated on both sides. US3012914 describes a sheet of reconstituted tobacco with added reinforcing fibers, W02018/19782 describes a laminated tobacco product comprising a support sheet. US2018/310608 describes a reconstituted tobacco sheet comprising a lipid, reinforcing fibers and/or a reinforcing sheet.

There is a need for a process to obtain an alternative alkaloid-containing material that can be used for products that are heated, but not burned.

In one aspect, the invention relates to a multilayer sheet of an alkaloid-containing material comprising: a first layer comprising a substrate sheet including fibers having an average fiber length of between about 0.7 millimeters and about 50 millimeters. The first layer defines a first surface and a second surface. The multilayer sheet further comprises a second layer comprising a mixture of: a powder of the alkaloid-containing material, the powder having a size of between about 8 micrometers and about 200 micrometers; water; a binder; and an aerosol former. The second layer is applied to the first surface of the substrate sheet and wherein the binder is comprised in an amount of between about 0 percent and about 1 percent of the total weight of the multilayer sheet of alkaloid-containing material and comprising the aerosol former in an amount of between about 2.9 percent and about 8.5 percent of the total weight of the multilayer sheet of alkaloid-containing material.

The invention also relates to a sheet of an alkaloid-containing composite material comprising: a substrate sheet including fibers having an average fiber length of between about 0.7 millimeters and about 50 millimeters and defining a first surface and a second surface. The substrate sheet is impregnated with a mixture of: a powder of the alkaloid-containing material, the powder having a size of between about 8 micrometers and about 200 micrometers; water; a binder; and an aerosol former P wherein the binder is comprised in an amount of between about 0 percent and about 1 percent of the total weight of the sheet of an alkaloid-containing composite material and comprising the aerosol former in an amount of between about 2.9 percent and about 8.5 percent of the total weight of the sheet of an alkaloid-containing composite material.

A multilayer sheet or a sheet formed from composite material is provided. The multilayer sheet or the sheet formed from composite material has a relatively high tensile strength compared to the known molded sheet. The high tensile strength is provided by the substrate sheet having fibers that are relatively “long” compared to the fibers used in the molded sheet. In addition, the multilayer sheet or a sheet formed from composite material is relatively homogeneous. The slurry is applied to the substrate sheet including fibers to form a multilayer sheet or a sheet formed from composite material containing alkaloids. There is no need to add a large amount of fibers to the slurry to obtain a multilayer sheet or a sheet formed from composite material including alkaloids with a relatively high tensile strength because it is already provided by the substrate sheet. Thus, the suspension can be very homogeneous in composition, at least on its surfaces, and the resulting multilayer sheet or composite sheet obtained when the suspension is applied to the substrate sheet is also homogeneous. The suspension can form a layer on the substrate sheet. The suspension can impregnate the substrate sheet. Better control of the composition of the multilayer sheet or composite sheet can be achieved.

As used herein, the term “sheet” denotes a web having a width and length substantially greater than its thickness.

As used herein, the term “suspension” denotes a liquid-like, viscous or paste-like material which may comprise an emulsion of a different liquid-like, viscous or paste-like material. The suspension may contain a certain amount of solid-state particles, so long as the suspension still exhibits liquid-like, viscous or paste-like behavior.

The term “upstream” or “downstream” below refers to the direction of flow of the suspension.

As used herein, the term “movable support” denotes any means comprising a surface that is adapted to move in at least one longitudinal direction. The movable support may form a closed loop to provide uninterrupted conveying capability in one direction. However, the movable support may also move in an alternating manner. The movable support may include a conveyor belt. The movable support may be substantially planar. The movable support may exhibit a structured or unstructured surface. The movable support may comprise a flexible, movable web in the form of a sheet. The web may be made of a metallic material, including, but not limited to, steel, copper, iron alloys and copper alloys, or rubber.

“Substrate sheet including fibers” denotes a sheet used as a substrate for suspension and which is formed from a material including fibers. The material from which the sheet is formed may include any type of fibers, for example, cellulosic fibers. The sheet of material may be placed on top of a movable support or may be self-supporting.

An “alkaloid-containing material” is a material that contains one or more alkaloids. Alkaloids may include nicotine. Nicotine may be found, for example, in tobacco.

Alkaloids are a group of naturally occurring chemical compounds containing mainly basic nitrogen atoms. This group also includes some related compounds with neutral and even slightly acidic properties. Some synthetic compounds with a similar structure are also called alkaloids. In addition to carbon, hydrogen and nitrogen, alkaloids may also contain oxygen, sulfur and, more rarely, other elements such as chlorine, bromine and phosphorus.

Caffeine, nicotine, theobromine, atropine, tubocurarine are examples of alkaloids.

As used herein, the term “homogenized tobacco material” denotes a material that is formed by agglomeration of tobacco particles, containing the alkaloid nicotine. Thus, the alkaloid-containing material may be a homogenized tobacco material.

The most commonly used forms of homogenized tobacco material are the reconstituted tobacco sheet and the molded sheet. The process for forming sheets of homogenized tobacco material commonly comprises a step in which tobacco powder and a binder are mixed to form a slurry. The slurry is then used to create a tobacco sheet. For example, by molding a viscous slurry onto a moving metal belt to produce a so-called molded sheet. Alternatively, a slurry with low viscosity and high water content can be used to create reconstituted tobacco in a process resembling papermaking.

Tobacco sheet-like material may be referred to as reconstituted sheet-like material and formed by using particulate tobacco or a mixture of particulate tobacco, a humectant and an aqueous solvent to form the tobacco composition.

The homogenized tobacco sheet generally includes, in addition to tobacco, a binder such as guar. The homogenized tobacco sheet may further include an aerosol former, such as glycerin.

The term “aerosol-forming substrate” refers to a substrate capable of releasing volatile compounds that can form an aerosol. Typically, aerosol-forming substrates release volatile compounds upon heating. The aerosol-forming substrate may include the alkaloid-containing material containing volatile alkaloid aromatic compounds, which are released from the aerosol-forming substrate upon heating. The aerosol-forming substrate may include homogenized material.

As used herein, the term “aerosol-generating device” refers to a device configured to interact with an aerosol-forming substrate to generate aerosol. Preferably, the aerosol-generating device includes an aerosolizer, such as a heater.

The multilayer sheet or the sheet of a composite material containing alkaloids may be used as an aerosol-forming substrate for an aerosol-generating device. The sheet of alkaloid-containing material may include a sheet of homogenized tobacco.

The multilayer sheet or sheet of a composite material containing alkaloids is formed from a substrate sheet on which a suspension is applied.

The substrate sheet is provided including fibers. The substrate sheet defines a first surface and a second surface. On the first surface, the suspension is applied. The suspension may form a layer, such as the second layer, on the first surface of the substrate sheet. Furthermore, the suspension may essentially completely impregnate the substrate sheet. Furthermore, the suspension may partially impregnate the substrate sheet such that the substrate sheet is partially impregnated and partially covered by a second layer of material on the first surface.

The substrate sheet including fibers is typically a relatively “strong” sheet, the tensile strength of which is such that it can be transported between rollers, without the need for any additional substrate with which it must be in contact. The tensile strength of the substrate sheet is preferably between about 0.1 Newton/(millimeters)2 and about 1 Newton/(millimeters)2.

The substrate sheet can be made of different materials, natural or synthetic, including cellulose, hemp, kenaf, bamboo pulp, cotton, silk, wood or their combinations. The material selection is made in accordance with the expected mechanical properties for the final sheet that includes an alkaloid-containing material.

The fibers in the substrate sheet could be woven or nonwoven. If not woven, the fibers may be predominantly oriented in one direction. Alternatively, the fibers may be randomly oriented. If woven, various patterns could be used. The substrate sheet may include a mat of fibers. The fibers may be arranged, for example, randomly, flattened into a sheet, or woven into a fabric. The substrate sheet may include a binder to hold the fibers together. The binder may include methylcellulose.

Preferably, the substrate film is a braided film. A braided film is a film in which the fibres are intertwined. Not all fibres should be intertwined, but rather a fraction of them. A braided film allows for homogeneous and relatively high mechanical strength.

The content of fibers in the substrate sheet is preferably less than 50 grams/(meter)2.

The substrate sheet preferably includes cellulosic fibers. Cellulosic fibers that form the sheet are known in the art and include, but are not limited to: softwood fibers, hardwood fibers, jute fibers, flax fibers, tobacco fibers, and combinations thereof. In addition to defibration, the cellulosic fibers may be subjected to suitable processes such as refining, mechanical defibration, chemical defibration, bleaching, sulfate defibration, and combinations thereof. The cellulosic fibers may include materials from tobacco stems, culms, or other tobacco plant material. Preferably, the cellulosic fibers such as wood fibers comprise a low lignin content. Alternatively, fibers such as plant fibers may be used with or as an alternative to the above fibers, including hemp and bamboo.

The fiber-inclusive substrate sheet comprises fibers having an average fiber length ranging from about 0.7 millimeters to about 50 millimeters. More preferably, the fibers of the fiber-inclusive substrate sheet have an average fiber length ranging from about 1 millimeter to about 25 millimeters. More preferably, the fibers of the fiber-inclusive substrate sheet have an average fiber length ranging from about 1 millimeter to about 10 millimeters. More preferably, the fibers of the fiber-inclusive substrate sheet have an average fiber length ranging from about 1 millimeter to about 5 millimeters. Even more preferably, the fibers of the fiber-inclusive substrate sheet have an average fiber length ranging from about 1.2 millimeter to about 1.8 millimeters. Fibers having an average fiber length ranging from 1 millimeter to 5 millimeters are the preferred compromise between achieved tensile strength and sheet homogeneity.

The average length of fibers refers to their actual length (regardless of whether they are twisted or have bends) measured by MORFI COMPACT marketed by Techpap SAS. The average length is the mathematical average of the measured fiber length by MORFI COMPACT over a measurement of N fibers, where N > 5. The MORFI COMPACT is a fiber analyzer that measures the length of fibers following the fiber frame, thus measuring their actual developed length. Measured objects are considered fibers if their length is between 200 micrometers and 10000 micrometers and their width is between 5 micrometers and 75 micrometers. Fiber length is measured by adding deionized water to the fibers and using the Morfi software.

The substrate sheet defines a first surface and a second surface, one opposite the other. The first surface or the second surface may be an essentially flat surface. The first surface or the second surface may be horizontal, i.e. parallel to a horizontal plane, or inclined. The first surface or the second surface may also be essentially vertical.

The suspension applied to the first surface of the substrate sheet has the following composition.

The suspension includes particles of an alkaloid-containing material. The particles form a powder of an alkaloid-containing material. To obtain the powder, an alkaloid-containing material is ground into a powder. Preferably, the size of the ground particles of alkaloid-containing material is less than 200 micrometers, preferably less than 180 micrometers, preferably less than 160 micrometers, preferably less than 140 micrometers, preferably less than 120 micrometers, preferably less than 100 micrometers, preferably less than 80 micrometers, preferably less than 60 micrometers, preferably less than 40 micrometers.

Preferably, the size of the crushed particles of alkaloid-containing material has a size greater than 8 microns, preferably greater than 12 microns, preferably greater than 20 microns, preferably greater than 30 microns, preferably greater than 50 microns, preferably greater than 70 microns. Preferably, the step of crushing an alkaloid-containing material into a powder includes crushing the alkaloid-containing material into a powder having a size between about 8 microns and 200 microns. More preferably, the step of crushing an alkaloid-containing material into a powder includes crushing the alkaloid-containing material having a size between about 10 microns and 150 microns. Even more preferably, the step of grinding an alkaloid-containing material into a powder includes grinding the alkaloid-containing material having a size between about 15 microns and 120 microns.

By particle size of the alkaloid-containing material, we mean the Dv95 size. Each of the values listed above indicates the Dv95 of the particle size. The “v” in Dv95 means that a volume distribution is being considered. Using volume distributions introduces the concept of the equivalent sphere. An equivalent sphere is a sphere that is equal to the actual particle in the property being measured. Therefore, for light scattering methods, it is a sphere that would produce the same scattering intensities as the actual particle. This is essentially a sphere that has the same volume of the particle. Also, “95” in Dv95 means the diameter where ninety-five percent of the distribution has a smaller particle size and five percent has a larger particle size. Thus, the particle size is that size according to a volume distribution where 95 percent of the particles have a diameter (of the corresponding sphere having essentially the same volume as the particle) less than the indicated value. A particle size of 60 micrometers means that 95 percent of the particles have a diameter less than 60 micrometers, where the diameter is the diameter of the sphere having a volume corresponding to that of the particle.

The particle Dv95 size is measured by using a Horiba LA 950 or LA 960 particle size distribution analyzer. The HORIBA LA-960 particle size analyzer uses the laser diffraction method to measure size distributions. This technique uses first principles to calculate size by using scattered light off the particle (edge diffraction) and through the particle (secondary scattering refraction). The LA-960 incorporates Mie scattering theory.

Due to the fact that the suspension preferably contains no, or only a very small amount of, cellulosic fibres in addition to those already contained in the alkaloid-containing material, the powder size does not need to be “extremely small”. If fibres are present in the suspension, they act as a “glue” for the particles. In order to have a homogeneous sheet, therefore, the particles are kept small. In the invention, the suspension does not form a sheet by itself, but is applied to the substrate layer. There is no need for the suspension to create by itself a layer having a relatively high tensile strength. Therefore, the powder size can be larger than in the case of a suspension that is formed with added fibres.

The alkaloid-containing material powder may be, for example, a tobacco powder mixture. Preferably, the tobacco powder mixture contains the majority of the tobacco present in the suspension. Thus, the tobacco powder mixture is the source of the majority of the tobacco in the homogenized tobacco material. As such, the tobacco powder mixture defines the flavor of the final product, for example, an aerosol produced by heating the homogenized tobacco material.

The amount of alkaloid-containing material powder in the suspension is preferably between about 40 percent and about 70 percent of the total mass of the suspension, i.e., of the mass of the suspension including water. Preferably, the alkaloid-containing material is in powder form. More preferably, the amount of alkaloid-containing material in the suspension is preferably between about 40 percent and about 50 percent of the total mass of the suspension, i.e., of the mass of the suspension including water.

A binder is preferably added to the suspension, to improve the tensile properties of the multilayer sheet or the sheet of a composite material.

The amount of binder present in the suspension may comprise between about 0 percent and about 1 percent of the total mass of the suspension, i.e., of the mass of the suspension that includes water. More preferably, the amount of binder present in the suspension is between about 0 percent and about 0.5 percent of the total weight of the suspension. The amount of binder may depend on the desired characteristics of the sheet of alkaloid-containing material. If it is desired that the suspension be largely absorbed by the substrate sheet, then less binder may be used to enhance absorption. If a coating of suspension on the substrate sheet is preferred, a greater amount of binder may be used. The amount of binder may vary the viscosity of the suspension. A greater amount of binder may lead to a higher viscosity of the suspension.

The binder used in the suspension may be any of the gums or pectins described herein. The binder can ensure that the alkaloid powder remains essentially dispersed throughout the sheet of alkaloid-containing material. Although any binder may be employed, preferred binders are natural pectins, such as fruit, citrus or tobacco pectins; guar gums, such as hydroxyethyl guar and hydroxypropyl guar; locust bean gums, such as hydroxyethyl and hydroxypropyl locust bean gum; alginate; starch, such as modified or derivatized starches; celluloses, such as methyl, ethyl, ethylhydroxymethyl and carboxymethyl cellulose; tamarind gum; dextran; pulalon; konjac flour; xanthan gum and the like. Particularly preferred binder for use in the present invention is guar.

If the suspension is impregnated into the substrate film, the amount of binder differs depending on which part of the film is considered, for example, it is maximum on the surface where the suspension has been deposited. Therefore, the maximum value is between 0 percent and 1 percent.

An aerosol former is preferably added to the suspension to promote aerosol formation.

Suitable aerosol formers for inclusion in the suspension for the alkaloid-containing sheet material are known in the art and include, but are not limited to: monohydric alcohols such as menthol; polyhydric alcohols such as triethylene glycol, 1,3-butanediol, and glycerin; esters of polyhydric alcohols such as glycerol mono-, di-, or triacetate; and aliphatic esters of mono-, di-, or polycarboxylic acids such as dimethyl dodecanedioate and dimethyl tetradecanedioate.

Examples of preferred aerosol formers are glycerin and propylene glycol.

The suspension may have an aerosol former content of between about 1 percent and about 5 percent of the total mass of the suspension, i.e., of the mass of the suspension that includes water. Preferably, it is between 1 and 3 percent of the total mass of the suspension corresponding to an aerosol former amount of between about 2.9 percent and about 8.5 percent on a dry weight basis of the suspension.

Water is also preferably present in the suspension, to achieve a certain viscosity and moisture for applying the suspension to a substrate sheet. The amount of water is preferably between about 30 percent and 55 percent of the total mass of the suspension, i.e., of the mass of the suspension that includes water. More preferably, the amount of water is between about 45 percent and about 55 percent of the total mass of the suspension, i.e., of the mass of the suspension that includes water.

The alkaloid-containing material, preferably in powder form, may contain cellulose. However, preferably, no cellulosic fibers are added to the suspension, i.e., in addition to the fibers already contained in the alkaloid-containing material, no further fibers are added to the suspension. Therefore, the amount of fibers added (i.e., in addition to those already contained in the alkaloid-containing material) to the suspension is preferably less than 0.5 percent of the total mass of the suspension, i.e., of the mass of the suspension including water. More preferably, the added fibers are present in an amount less than about 0.1 percent of the total mass of the suspension.

The suspension is formed at a given location. The suspension can then be stored. The suspension can, for example, be stored and formed at the same location, for example in the same storage tank, or at two different locations, for example in two different storage tanks. The storage tank used is preferably known in the field. Furthermore, the suspension can be formed or stored in a single storage tank, or in a plurality of storage tanks. Preferably, in the storage tank, a mixer is present for homogenizing the suspension.

Preferably, the suspension is applied to the first surface of the substrate sheet. Upon application, the suspension may form a suspension strip on the substrate sheet that includes fibers.

The suspension need not be applied to the entire first surface. The suspension may be applied only to a portion of the first surface, for example, to a central portion of the first surface.

The suspension that comes into contact with the substrate sheet may be completely absorbed or adsorbed by the substrate sheet. The suspension may form a layer, called a second layer, on the first surface of the substrate sheet. The suspension may be partially absorbed or adsorbed by the substrate sheet and partially coat the first surface of the substrate sheet.

Preferably, the application of the suspension may form a second layer on the substrate sheet. Essentially, a suspension coating layer is formed on the first surface of the substrate sheet.

The application of the suspension can impregnate the substrate sheet with the suspension.

The suspension may be minimally, partially, or mostly absorbed or adsorbed by the substrate sheet. The absorption or adsorption of the suspension depends on the composition of the substrate sheet or the composition of the suspension, or on both the compositions of the substrate sheet and the suspension. For example, the absorption or adsorption of the suspension depends on the amount of water or binder contained in the suspension. If the suspension is only minimally or partially absorbed by the substrate sheet, the second layer is formed on the surface of the substrate sheet where the suspension is applied and a multilayer sheet is formed.

If a sorption process takes place, where the substrate film absorbs or adsorbs the suspension, the substrate film is impregnated by the suspension. The suspension can be completely absorbed by the substrate film. The suspension can also form a coating layer and impregnate the substrate film.

Sorption is a physical and chemical process by which one substance binds to another. Specific cases of sorption are: absorption, where the incorporation of a substance in one state into another in a different state takes place, such as a liquid suspension that is absorbed by a sheet of solid substrate; or adsorption, where the physical adhesion or binding of ions and molecules on the surface of another phase takes place.

The resulting sheet formed by the substrate sheet and the suspension applied to the first surface may have a different composition in a cross section taken perpendicular to the first surface of the substrate sheet. At the second surface, the lower concentration of suspension may be present. At the first surface, the higher concentration of suspension may be present. Between the first surface and the second surface, a combination of the substrate sheet material and the suspension may be present in different concentrations.

The suspension may be applied to both the first and second surfaces. The composition of the sheet of alkaloid-containing material may be symmetrical. The concentration of fibers per unit volume of the sheet of alkaloid-containing material may be highest in the center of the sheet of alkaloid-containing material and lowest at the first surface and the second surface.

The combination of the substrate sheet and the suspension provided on its first surface forms a multilayer sheet of alkaloid-containing material or a sheet of an alkaloid-containing composite material.

In addition to the substrate sheet and the suspension, other elements may be combined to form the multilayer sheet of alkaloid-containing material or the composite sheet containing alkaloids. The substrate sheet itself may be a multilayer sheet. The substrate sheet may include a flavor sheet, a sheet of alkaloid-containing material (e.g., nicotine), and others.

The formation of a multilayer sheet of alkaloid-containing material or an alkaloid-containing composite sheet by supplying slurry onto an already formed substrate sheet including fibers allows for essentially no added fibers to be used in the slurry, or a very limited amount of added fibers. Fibers are commonly added into the slurry of a prior art molded sheet to increase the tensile strength of the sheet by acting as a reinforcing agent.

However, the presence of a substrate sheet onto which the suspension is supplied provides sufficient tensile strength to the resulting sheet of alkaloid-containing material. The addition of cellulosic fibres to the suspension can be avoided.

In the slurry where fibres are added, a relatively high amount of water may be required, because water is needed for the defibrementation of the fibres. Furthermore, due to the high amount of water present in the slurry, a high amount of energy is needed to dry the slurry and form a sheet of the alkaloid-containing material. In this “high water content” process, the steel conveyor belt on which the slurry is cast can also play an important role: any imperfections in the conveyor belt can be transferred to the cast sheet, so a high-quality belt is often required. Removing the added fibres from the slurry allows the amount of water needed to homogenise the slurry to be reduced. A certain amount of water may still be needed for good homogenisation. This relatively “dense” slurry is suitable for application to the substrate sheet including the fibres.

Less drying time or less drying power is required to dry the multilayer sheet of alkaloid-containing material or the alkaloid-containing composite sheet according to the invention. Preferably, the substrate sheet is already dry when it is wound onto a reel. The substrate sheet can be moistened, for example, by spraying water on it, before it comes into contact with the suspension. The moistening is done to facilitate the penetration of the suspension into the substrate sheet. The resulting multilayer sheet of alkaloid-containing material or the alkaloid-containing composite sheet is only “partially wet” and the drying time or the amount of energy required for drying is comparatively low. Less “intense” drying allows for better control over the taste of the aerosol that is produced by the multilayer sheet of alkaloid-containing material or the alkaloid-containing composite sheet when used as an aerosol-forming substrate. During drying, alkaloids, flavours or other volatiles may evaporate and their concentration may be reduced in the multilayer sheet of alkaloid-containing material or a composite sheet containing alkaloids. Minimising drying when alkaloids are present helps to control aerosol characteristics.

The fact that a fibre-containing substrate sheet is provided allows for a multi-layer sheet of alkaloid-containing material or an alkaloid-containing composite sheet having sufficient tensile strength, given by the fibres, to allow robust processing in downstream manufacturing stages. The length or configuration of the fibres is not limited by the constraint of having a homogeneous alkaloid-containing material. The tensile strength is provided by the substrate sheet, while the spray characteristics are imparted by the suspension applied to the substrate sheet. Both the tensile strength and the spray characteristics can be independently optimised.

Preferably, the first layer is partially impregnated with the second layer. In the multilayer film, there may not be a “sharp” transition between the first layer and the second layer. The suspension forming the second layer may be partially absorbed by the second layer. Depending on the composition of the substrate film or the composition of the suspension, or both compositions of the substrate film and the suspension, for example, depending on the amount of water or binder contained in the suspension, the suspension may be minimally, partially, or mostly absorbed by the substrate film. If the suspension is only minimally or partially absorbed by the substrate film, a suspension layer, the second layer, is formed on the surface of the substrate film where the suspension is applied. A suspension coating layer may then be formed on the surface of the substrate film. On the other hand, if a sorption process takes place, where the suspension is absorbed or adsorbed by the substrate film, the substrate film is impregnated by the suspension. The suspension can be completely absorbed by the substrate film. The suspension can also form a second coating layer or impregnate the substrate film.

Preferably, the multilayer sheet of alkaloid-containing material comprises a third layer, the third layer comprising a mixture of: a powder of the alkaloid-containing material, the powder having a size between about 8 microns and about 200 microns; water; a binder; an aerosol former; the third layer being applied to the second surface of the substrate sheet. The multilayer sheet may be symmetrical, with a second layer and a third layer being applied to both the first surface and the second surface of the substrate sheet. The second layer may be identical to the second layer. The multilayer sheet may be asymmetrical, where the second layer is different from the third layer. For example, the thickness of the second layer may be different from the thickness of the third layer.

Preferably, the multilayer sheet of alkaloid-containing material or the sheet of an alkaloid-containing composite material comprises the powder of the alkaloid-containing material in an amount between about 40 percent and about 80 percent of the total weight of the multilayer sheet of alkaloid-containing material or the sheet of an alkaloid-containing composite material. The multilayer sheet of alkaloid-containing material or the sheet of an alkaloid-containing composite material contains a high level of alkaloid-containing material. This amount is obtained for a “dry” sheet, that is, for a sheet having a water content between about 7 percent and about 15 percent.

In the present invention, the suspension is preferably formed by the tobacco lamina and stem of different types of tobacco, which are appropriately mixed together. Preferably, more than one type of tobacco is mixed together. For example, at least two different types of tobacco are mixed together. The term “type of tobacco” is understood to mean one of the different varieties of tobacco. With respect to the present invention, these different types of tobacco are distinguished into three main groups: blond tobacco, dark tobacco and aromatic tobacco. The distinction between these three groups is based on the curing process to which the tobacco is subjected before it is further processed into a tobacco product.

Blond tobaccos are tobaccos with generally large, light-colored leaves. Throughout the description, the term "blond tobacco" is used for tobaccos that have been flue-cured. Examples of blond tobaccos are Chinese flue-cured, Brazilian flue-cured, American flue-cured such as Virginia tobacco, Indian flue-cured, Tanzanian flue-cured or other African flue-cured. Blond tobacco is characterized by a high sugar to nitrogen ratio. From a sensory perspective, blond tobacco is a type of tobacco that, after curing, is associated with a spicy and light sensation. In accordance with the invention, blond tobaccos are tobaccos with a reduced sugar content of between about 2.5 percent and about 20 percent on a dry leaf weight basis and a total ammonia content of less than about 0.12 percent on a dry leaf weight basis. Reduced sugars comprise, for example, glucose or fructose. Total ammonia includes, for example, ammonia and ammonium salts.

Dark tobaccos are tobaccos with generally large, dark-colored leaves. Throughout the description, the term “dark tobacco” is used for tobaccos that have been air-cured. Additionally, dark tobaccos may be fermented. Tobaccos that are used primarily for chewing, snuff, cigars, and pipe blends are also included in this category. From a sensory perspective, dark tobacco is a type of tobacco that, after curing, is associated with a smoky, dark cigar-like sensation. Dark tobacco is characterized by a low sugar to nitrogen ratio. Examples of dark tobacco are Malawi Burley or other African Burley, Dark Cured Brazilian Galpao, Indonesian Kasturi sun-cured or air-cured. In accordance with the invention, dark tobaccos are tobaccos having a reduced sugars content of less than about 5 percent on a dry leaf weight basis and a total ammonia content of up to about 0.5 percent on a dry leaf weight basis.

Aromatic tobaccos are tobaccos that often have small, light-coloured leaves. Throughout the description, the term “aromatic tobacco” is used for other tobaccos that have a high aromatic content, for example a high content of essential oils. From a sensory perspective, aromatic tobacco is a type of tobacco that, after curing, is associated with a spicy and aromatic sensation. Examples of aromatic tobaccos are Greek Oriental, Turkish Oriental, semi-oriental tobacco, but also open-air cured, American Burley, such as Perique, Rustica, American Burley or Meriland.

Additionally, a blend may comprise so-called filler tobaccos. Filler tobacco is not a specific type of tobacco, but rather includes types of tobacco that are primarily used to complement the other types of tobacco used in the blend and do not provide a specific characteristic aroma direction to the final product. Examples of filler tobaccos are the stems, main vein or culms of other types of tobacco. A specific example may be the flue-cured stems of the bottom cane of the Brazilian flue-curing.

Within each tobacco type, tobacco leaves are further classified, for example with respect to origin, position in the plant, colour, surface texture, size and shape. These and other characteristics of the tobacco leaves are used to form a tobacco blend. A tobacco blend is a mixture of tobaccos belonging to the same or different types so that the tobacco blend has a specific agglomeration characteristic. This characteristic may be, for example, a unique flavour or a specific aerosol composition when heated or burned. A blend comprises specific tobacco types and classifications with a given ratio of one to the other.

Different grades within the same tobacco type may be cross-blended to reduce variability of each component of the blend. In accordance with the invention, the different grades of tobacco are selected to make a desired blend having specific predetermined characteristics. For example, the blend may have a target value of reducing sugars, total ammonia and total alkaloids on a dry weight basis of the homogenized tobacco material. Total alkaloids are for example nicotine and minor alkaloids including nornicotine, anatabine, anabasine and myosmine.

For example, blond tobacco may comprise grade A tobacco, grade B tobacco, and grade C tobacco. Grade A blond tobacco has slightly different chemical characteristics than grade B and grade C blond tobacco. Aromatic tobacco may include grade D tobacco and grade E tobacco, where grade D aromatic tobacco has slightly different chemical characteristics than grade E aromatic tobacco. A possible target value for the tobacco blend, for better exemplification, may be for example a reduced sugar content of about 10 percent on a dry weight basis of the total tobacco blend. To achieve the selected target value, 70 percent blond tobacco and 30 percent aromatic tobacco may be selected to form the tobacco blend. 70 percent of the blond tobacco is selected from A grade tobacco, B grade tobacco and C grade tobacco, while 30 percent of the aromatic tobacco is selected from D grade tobacco and E grade tobacco. The amounts of A, B, C, D, E grade tobacco included in the blend depend on the chemical composition of each of the A, B, C, D, E grade tobacco to meet the target value of the tobacco blend.

The various types of tobacco have different chemical characteristics. More than 300 chemical constituents are believed to be present in tobacco leaves. Within the same type of tobacco, different classifications may also have differences in chemical composition. Chemical constituents of tobacco can be influenced by genetics, farming practice, soil type and nutrients, climatic conditions, plant disease, cane position, harvesting and curing procedures.

Preferably, the multilayer sheet of alkaloid-containing material or the sheet of an alkaloid-containing composite material comprises water in an amount between about 7 percent and about 15 percent of the total weight of the multilayer sheet of alkaloid-containing material or the sheet of an alkaloid-containing composite material.

Preferably, the multilayer sheet of alkaloid-containing material or the sheet of an alkaloid-containing composite material comprises the binder in an amount of between about 0 percent and about 1 percent of the total weight of the multilayer sheet of alkaloid-containing material or the sheet of an alkaloid-containing composite material. More preferably, the amount of binder present in the suspension is between about 0 percent and about 0.5 percent of the total mass of the suspension. The amount of binder may depend on the desired characteristics of the multilayer sheet of alkaloid-containing material or the sheet of alkaloid-containing composite material. If it is desired that the suspension be largely absorbed by the substrate sheet, then less binder may be used to enhance absorption. If a suspension layer is preferred in the substrate sheet, a greater amount of binder may be used. The amount of binder may vary the viscosity of the suspension. A higher amount of binder can lead to a higher viscosity of the suspension.

The multilayer sheet of alkaloid-containing material or the sheet of an alkaloid-containing composite material comprises the aerosol former in an amount of between about 2.9 percent and about 8.5 percent of the total weight of the multilayer sheet of alkaloid-containing material or the sheet of an alkaloid-containing composite material.

The multilayer sheet of alkaloid-containing material or the sheet of an alkaloid-containing composite material comprises fibers other than fibers of the alkaloid-containing material in an amount of between about 2 percent and about 5 percent of the total weight of the multilayer sheet of alkaloid-containing material or the sheet of an alkaloid-containing composite material. The fibers are concentrated in the substrate sheet, very few fibers (other than those contained in the alkaloid-containing material) are present in the second layer.

The multilayer sheet of alkaloid-containing material or the sheet of alkaloid-containing composite material has a thickness between about 150 micrometers and about 400 micrometers, more preferably the thickness of the sheet is between about 180 micrometers and about 300 micrometers, even more preferably between about 180 micrometers and 250 micrometers.

Preferably, the substrate sheet has a thickness between 175 microns and about 250 microns. The thickness of the substrate sheet is preferably selected such that the final thickness, when the slurry is applied to one or both surfaces, is the preferred thickness for further processing of the sheet, such as crimping and gathering into a bar.

The multilayer sheet of alkaloid-containing material or the sheet of an alkaloid-containing composite material preferably has a width of between about 100 millimetres and about 2500 millimetres. The width of the multilayer sheet of alkaloid-containing material or the sheet of an alkaloid-containing composite material is chosen depending on the size of the coil to be obtained. Preferably, after the multilayer sheet of alkaloid-containing material or the sheet of an alkaloid-containing composite material is formed, it is dried. Preferably, after drying, the multilayer sheet of alkaloid-containing material or the sheet of an alkaloid-containing composite material is wound into a coil. The coil could be a “master coil” which is then cut into smaller coils, or already a coil used for further processing of the sheet of alkaloid-containing material.

Preferably, the powder of the alkaloid-containing material comprises tobacco dust. Preferably, the powder is a mixture of tobacco dust.

Preferably, the fiber-inclusive substrate sheet comprises cellulosic fibers. More preferably, the fiber-inclusive substrate sheet comprises fibers derived from hemp, kenaf, bamboo, wood, cotton, or silk.

The invention may also relate to an aerosol-generating article, comprising a portion of the multilayer sheet of alkaloid-containing material or the sheet of the alkaloid-containing composite material according to the invention. Aerosol-forming articles according to the present invention may encompass articles in which the alkaloid-containing material is heated to form an aerosol, rather than being burned.

Aerosol-forming articles according to the invention may be complete aerosol-forming articles, assembled aerosol-forming articles, or components of aerosol-forming articles that are combined with one or more other components to provide an assembled article for producing an aerosol, such as, for example, the consumable part of a heated smoking device.

An aerosol-forming article may be an article that generates an aerosol that is directly inhalable into the user's lungs through the user's mouth. An aerosol-forming article may resemble a conventional smoking article, such as a cigarette, and may comprise tobacco. An aerosol-forming article may be disposable. Alternatively, an aerosol-forming article may be partially reusable and comprise a refillable or replaceable aerosol-forming substrate.

In preferred embodiments the aerosol-forming article may be substantially cylindrical in shape. The aerosol-forming article may be substantially elongated. The aerosol-forming article may have a length and circumference substantially perpendicular to the length. The aerosol-forming article may have an overall length between about about 30 millimeters and about about 100 millimeters. The aerosol-forming article may have an outer diameter between about about 5 millimeters and about about 12 millimeters.

In all aspects of the invention, preferably the sheet including an alkaloid-containing material is a homogenized tobacco sheet, wherein the alkaloid-containing material is nicotine-containing tobacco.

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

- Figure 1 shows a flow chart of a method for producing a sheet of homogenized tobacco material in accordance with the invention;

- Figure 2 shows an enlarged view of one of the steps of the method in Figure 1;

- Figure 3 shows a schematic perspective view of a first embodiment of an apparatus for the production of a sheet of an alkaloid-containing material according to the invention;

- Figure 4 shows a schematic sectional side view of a second embodiment of an apparatus for producing a sheet of an alkaloid-containing material according to the invention;

- Figure 5 shows a schematic sectional side view of a third embodiment of an apparatus for producing a sheet of an alkaloid-containing material according to the invention;

- Figure 6 shows a schematic sectional side view of a fourth embodiment of an apparatus for producing a sheet of an alkaloid-containing material according to the invention;

- Figure 7 shows a graph depicting the composition of a cross section of a sheet of homogenized tobacco produced with the method of the invention;

- Figure 8 shows a schematic representation of a side view of a multilayer sheet according to the invention; and

- Figure 9 shows a schematic representation of a side view of a composite sheet according to the invention.

Referring initially to Figure 1, the method for producing a sheet of alkaloid-containing material 200 is shown. In the embodiments shown, the sheet of alkaloid-containing material 200 is a sheet of homogenized tobacco and the alkaloid-containing material is tobacco.

The first step of the method of the invention is the selection of tobacco types and tobacco classifications to be used in the tobacco blend to produce the homogenized tobacco material. Tobacco types and tobacco classifications used in the present method are for example blond tobacco, dark tobacco, aromatic tobacco and filler tobacco.

The selected tobacco types and tobacco classifications intended to be used for the production of the homogenized tobacco material are subjected to processing in accordance with the following steps of the method of the invention.

The method includes an additional step 101 in which the selected tobacco is placed at rest. This step may comprise checking the integrity of the tobacco, such as the classification and quantity, which may be verified for example by a bar code reader for product tracking and traceability. After harvesting and curing, the tobacco leaf is given a classification, which describes for example the position of the stem, the quality, and the color.

Furthermore, the resting step 101 may further include, in the case where the tobacco is being sent to manufacturing facilities for the production of homogenized tobacco material, unpacking or opening the tobacco boxes. The unpacked tobacco is then preferably fed to a weighing station for weighing.

Furthermore, the step of resting the tobacco 101 may include cutting the packages, if necessary, since the tobacco leaves are typically compressed into packages in shipping boxes for shipment.

The following steps are performed for each type of tobacco, as detailed below. These steps may be performed subsequently by sorting so that only one production line is required. Alternatively, the different types of tobacco may be processed on separate lines. This may be advantageous when the processing steps for some types of tobacco are different. For example, in conventional primary tobacco processes, blond and dark tobaccos are at least partially processed in separate processes, since dark tobacco often receives an additional coating. However, in accordance with the present invention, preferably no coating is added to the blended tobacco powder prior to the formation of the homogenized tobacco web.

Furthermore, the method may include a step of shredding the tobacco leaves 102. The shredding step 102 may be a single shredding step or a double shredding step, where the tobacco is first coarsely shredded and then finely shredded.

Preferably, after the grinding step 102, a step of removing non-tobacco material from the dust (not shown in Figure 1) is performed. This removal step may be performed prior to grinding. Removing non-tobacco material may be easier prior to grinding because non-tobacco material may be easier to recognize and remove than after grinding.

Preferably, after the grinding stage 102, the tobacco particles are transported, for example by pneumatic transfer, to a mixing stage 103.

In the mixing stage 103, all the coarsely ground tobacco particles of different tobacco types selected for the tobacco blend are mixed. The mixing stage 103 is thus a single stage for all the selected tobacco types. This means that after the mixing stage only a single process line is needed for all the different tobacco types. In Figure 2, the mixing of four coarsely ground tobacco particles of four different tobacco types selected for a tobacco blend is shown, respectively schematically indicated by boxes 1, 2, 3 and 4.

In the mixing step 103, the mixing of the various types of particulate tobacco is preferably carried out. A step of measuring and controlling one or more of the properties of the tobacco mixture is preferably carried out.

Alternatively, steps 102 are performed after the mixing step 103, where the various types of tobacco are mixed together to form the desired mixture. If performed after the mixing step, the process may be faster.

It should be understood that each type of tobacco should be a sub-blend in itself, in other words, the “blond type of tobacco” could be, for example, a blend of Virginia tobacco and flue-cured Brazilian tobacco of different classifications.

The tobacco powder obtained in this way can be used immediately to form the tobacco suspension. Alternatively, a further storage step of the tobacco powder can be inserted, for example in suitable containers (not shown).

From the fine mixing step 103, the tobacco dust is used in a subsequent slurry preparation step 104. The slurry preparation step 104 preferably comprises adding together an aerosol former, a binder, and the ground tobacco dust into a slurry mixing tank. More preferably, this step further includes processing the slurry with a high shear mixer to ensure uniformity and homogeneity of the slurry.

Preferably, the slurry preparation step 104 further includes a water addition step, where water is added to the slurry to obtain the desired viscosity and moisture.

The composition of the suspension after stage 104 is as follows:

Water: 30% - 55%

Tobacco dust: 40% - 70%

Binders: 0% -1%

Aerosol former: 1% - 5%

Added fibers: less than 0.5%

To form the homogenized tobacco sheet 200, preferably the slurry formed in accordance with step 104 is molded in a molding or applying step 105. Preferably, this molding step 105 includes transporting the slurry to a molding station and applying the slurry to a substrate sheet 11 (shown in Figures 3 - 6).

The homogenized molded sheet 200 is then dried in a drying step 106 comprising uniformly and gently drying the molded web. Preferably the drying step comprises monitoring the temperature of the molded sheet in each drying zone to ensure a gentle drying profile in each drying zone.

Referring now to Figures 3, a first embodiment of an apparatus for producing a homogenized tobacco sheet 200 in accordance with the present invention is shown and indicated by reference numeral 10.

Preferably, the apparatus 10 is adapted for producing a plurality of sheets of homogenized tobacco material 200.

The apparatus 10 for producing a sheet of homogenized tobacco material includes an extruder 5, a tank 6 which is positioned at an outlet 20 of the extruder 5 and a movable drum 7 which is located below the tank 6.

The extruder 5 comprises an inlet 21 into which the suspension 22 (indicated by an arrow in Figure 3) is introduced to form the sheet of homogenized tobacco material, a screw 23 for extruding the suspension 22, and the outlet 20. The suspension 22 is pushed by the screw 23 from the inlet 21 to the outlet 20 (see again the arrows 22 in Figure 3). The screw 23 pushing the suspension 22 can be rotated by a motor 24, which is schematically represented in Figure 3 as a rectangle.

The suspension 22 reaches the extruder 5 from a separate storage tank or silo, not shown in the accompanying drawings. The suspension 22 comprises tobacco dust, water, a binder and an aerosol former. Preferably the binder is guar. Preferably the aerosol former is glycerin. Preferably no further fibres are added to the suspension. The suspension is formed as described in step 104.

From the extruder 5, the suspension 22 reaches the tank 6. From the above composition, approximately 5 percent of the water is removed from the suspension by the extrusion process.

The tank 6 comprises a plurality of outlets all indicated at 30. The tank 6 may have any geometric shape, and in the embodiment shown is essentially a basin. The tank 6 includes side walls 32 and also further includes a bottom wall 33. A mixer 34 (indicated by an arrow in Figure 3) may be present within the tank 6 for agitating and mixing the slurry 22.

Furthermore, a sensor 50 is present in the tank 6 for measuring the level of the suspension 22. Preferably, a feedback is present between the sensor 50 and the extruder 5 so that the suspension is maintained in the tank 6 at an essentially constant level.

Below the outlet 30, the movable drum 7 is located. The movable drum 7 is adapted to rotate about its axis 77 in a direction of rotation 8 indicated by an arrow in Figure 3. The movable drum 7 defines an external cylindrical surface 41.

Furthermore, the apparatus 10 includes a plurality of reels 9 (a single reel is shown in Figure 3). Each reel 9 of the plurality is made of reels of a substrate sheet 11, for example, a sheet of cellulosic fibers. The reel is unwound and the free portion of the sheet 11 unwound from the reel 9 is positioned in contact with the movable drum 7. The substrate sheet 11 includes first and second surfaces 12, 13, one opposite the other. The second surface 13 is preferably in contact with the cylindrical surface 41 of the movable drum 7. The first surface 12 faces at least one of the plurality of outlets 30. Rotation of the movable drum 7 causes a movement of the plurality of substrate sheets 11 along a common transport direction, which is indicated by arrow 14 in Figure 3. The reels 9 are therefore continuously unwound by rotation of the drum 7.

Each substrate sheet 11 of the plurality is in contact with the surface 41 of the movable drum 7 and, downstream of the drum 7 along the transport direction, is independent, i.e. the first and second surfaces 12, 13 are not supported by any element. An additional drum or roller (not visible in the drawing) can also pull the plurality of sheets 11 in the transport direction 14.

From the outlets 30, the suspension 22 is supplied to the plurality of substrate sheets 11. Preferably, each outlet 30 of the plurality of outlets supplies suspension 22 to a single substrate sheet 11 of the plurality of sheets. The suspension is supplied from the outlets 30 by gravity or by applying pressure, for example by means of a pump (not shown in the drawings). Preferably, the pump comprises a flow rate control (not visible in the drawing) for controlling the amount of suspension supplied to the substrate sheet 11.

When the substrate sheet 11 is supplied with suspension 22, it becomes a homogenized tobacco sheet 200. The suspension may be absorbed by the substrate sheet 11 partially or completely. The majority of the suspension may coat the substrate sheet 11, in particular the first surface 12.

Furthermore, the second surface 13 can be supplied with the suspension 22.

Each outlet 30 preferably ends with a nozzle 38 where the outlet 30 is present.

Furthermore, additional sensors (not shown) are preferably disposed on the substrate sheet 200 downstream of the outlets 30 to measure the weight per square centimeter and thickness of the homogenized tobacco sheets 200. The sensor may be, for example, a nucleonic measuring head. Additional sensors, not shown in the drawings, are preferably also present, such as a sensor to locate and determine the positions of defects in the homogenized tobacco sheet. A sensor may be added to determine the moisture of the sheets 200. A sensor may be present to measure a thickness of the sheet. A sensor may be added to verify the alignment of the sheets to prevent misaligned and jammed sheets in the event that more than a single sheet is formed.

The operation of the apparatus 10 for forming the plurality of homogenized tobacco sheets 200 is as follows. The slurry 22, which is preferably formed by mixing and blending tobacco dust, water and other ingredients, preferably with no or low added fiber content, as described in step 104, is transferred from a storage tank (not shown) by use of, for example, in-line mixers (also not shown) to the extruder 5. The slurry is reduced in water content in the extruder 5 and extruded into tank 6. In tank 6, the slurry reaches outlets 30, with or without the need for the pump. The nozzle 38 supplies suspension to the substrate sheet 11 including fibers which are positioned in contact with the movable drum 7. The movements of the drum 7 cause the substrate sheets 11 to move along the transport direction 14. Each nozzle 38 deposits suspension on a different substrate sheet 11. Thus, a plurality of homogenized tobacco sheets 200 are formed.

The thickness of the sheets 200 and the grammage controlled by the nucleonic calibrator immediately after supplying the suspension are preferably monitored continuously and controlled by feedback through the use of the suspension measuring device.

In Figure 4, a second embodiment of an apparatus 110 for producing the homogenized tobacco sheet 200 is shown. The apparatus 110 comprises a molding flask 42 containing slurry 22 and a substrate sheet 11, wherein a molding roll 45 - associated with the molding flask 42 - molds the slurry 22 contained in the molding flask 42 onto the substrate sheet 11 to form the molding sheet 200 of homogenized tobacco material. The slurry 22 is prepared as in step 104 described above.

The substrate sheet 11 is wound around the moving rollers (only roller 52 is shown) and positioned above the molding box 42. The substrate sheet 11 defines a first surface 12 and a second surface 13 and is moved by the moving rollers 52 in a transport direction 14 indicated by an arrow in Figure 4.

The molding box 42 comprises side walls including a first wall 43 and a second opposite wall 44. The molding box 42 is generally defined by four side walls, i.e., the first wall 43 and the second opposite wall 44 and a third wall and a fourth opposite wall (not shown in the figures), connecting the first wall 43 and the second opposite wall 44.

Furthermore, the molding box 42 includes a bottom wall 46. It also includes an opening 47, in this case coinciding with an upper part of the molding box. The opening 47 is positioned close to the substrate sheet 11.

The incoming suspension 22 is introduced into the molding box 42 from an inlet (not visible), in particular the end of a pipe, for example, connected to one of the side walls of the molding box.

The suspension 22 from the intermediate tanks (not shown in the drawings) is transferred to the moulding flask 42 normally by means of a pump (not shown in the drawings). Preferably, the pump comprises a flow rate control (not visible in the drawing) to control the quantity of suspension 22 introduced into the moulding flask 42. The pump is advantageously designed to ensure that suspension transfer times are kept to the necessary minimum.

The amount of suspension 22 in the molding box 42 has a predetermined level, which is preferably kept essentially constant or within a given range. In order to keep the amount of suspension 22 essentially at the same level, the pump controls the flow of suspension 22 into the molding box 42.

The molding roll 45 is associated with the molding box 42 for molding the suspension. The molding roll 45 has a dominant dimension which is its longitudinal width. The molding roll defines a first rotating axis 48 (indicated by a cross in Figure 4) corresponding to its longitudinal direction. Preferably, the first rotating axis 48 is horizontal and most preferably perpendicular to the molding direction 17.

The moulding roller 45 is preferably rotatably connected to the moulding box 42 via its ends to two opposite side walls. Furthermore, the moulding roller 45 partially projects out of the opening 47 and faces the substrate film 11 (see in detail Figure 4).

Between the molding roller 45 and the substrate sheet 11a there may be a space whose dimensions determine - among others - the thickness of the molded web 200 of homogenized tobacco material.

The slurry 22 is molded onto the substrate sheet 11 by the molding roll 45, which creates a continuous sheet 200 of homogenized tobacco material. The slurry is molded onto the first surface 12 of the substrate sheet 11 that faces the roll 45.

The thickness of the sheet may be further controlled by the lamination rolls 52, 53. The movable roll 52 may be part of a pair of lamination rolls 52, 53 having a gap therebetween where the sheet 200 is inserted. The lamination rolls 52, 53 are used to facilitate absorption and wetting of the cellulosic fibers of the substrate sheet 11 and to achieve control of the final thickness of the sheet 11.

The molded sheet 200 is driven by the movable rollers 52 along the transport direction 14 and enters a heating unit (not shown in the figures), where it is progressively heated and homogeneously dried.

The operation of the apparatus 110 for forming the homogenized tobacco sheets 200 is as follows. The slurry 22, which is preferably formed by mixing and blending tobacco dust, water and other ingredients, preferably with no or low added fiber content, as described in step 104, is transferred from a storage tank (not shown) by use of, for example, in-line mixers (also not shown) to the molding box 42. The molding roll 45 supplies slurry to the fiber containing substrate sheet 11 by rotating as the substrate sheet 11 moves along the conveying direction 14. Thus, a layer of slurry is deposited on the first surface 12 of the substrate sheet 11 forming a homogenized tobacco sheet 200.

The thickness of the sheets 200 and the grammage controlled by the nucleonic calibrator immediately after the supply of the suspension are preferably monitored continuously and controlled by feedback through the use of a suspension measuring device.

In Figure 5, a third embodiment of an apparatus 120 for producing homogenized tobacco sheet 200 is shown. The apparatus 120 is similar to the apparatus 110 of Figure 4, so only the differences between the two apparatuses will be outlined.

In addition to the molding roller 45, the apparatus 120 comprises, in the molding flask 42, also a second roller, the transfer roller 49. The transfer roller 49 is located below the molding roller 45. The transfer roller 49 preferably has a diameter larger than a diameter of the molding roller 45. Preferably, the transfer roller 49 is cylindrical and defines a second rotational axis 51 (indicated with a cross in Figure 5) parallel to the first rotational axis 48. The transfer roller 49 is rotatably attached to two opposite side walls of the molding flask 42, preferably by means of its longitudinal ends. Furthermore, the transfer roller 49 is preferably located inside the molding flask 42 in its entirety and is immersed by the suspension 22 at least in part. The direction of rotation of the transfer roller 49 is opposite to the direction of rotation of the molding roller 45.

A gap is formed between the molding roller 49 and the molding roller 45.

The transfer roller 49 is therefore in contact with the suspension and transfers it to the molding roller 45 which applies the suspension to the substrate sheet 11 as detailed with reference to the apparatus 110.

In the operation of the apparatus 120, the suspension 22 is supplied to the moulding flask 42 at the inlet. The suspension reaches a given level. The transfer roller 49 is partially in contact with the suspension 22 in the moulding flask when it reaches the given level and, due to its rotation, covers its outer surface with a layer of suspension 22, so that there is a suspension coating on the transfer roller 49. This suspension coating on the transfer roller 49 is transferred to the moulding roller 45. The suspension is then transferred to the moulding roller 45 due to the contact between the suspension layer on the transfer roller 49 and the surface of the moulding roller 45, and a suspension coating layer is formed on the surface of the moulding roller 45 before its final transfer to the substrate sheet 11.

The molding roller 45 rotates around the axis 48 and the suspension layer touches the substrate film 11. This causes a transfer of the suspension from the molding roller 45 to the substrate film, where the suspension coating forms the molded web 200.

The web is then preferably dried and wound onto reels for storage (not shown in the figures). These reels are then unwound and used to create the tobacco component of aerosol-generating articles.

In Figure 6, a fourth embodiment of an apparatus 130 for producing the homogenized tobacco sheet 200 is shown. The apparatus 130 is similar to the apparatus 120 of Figure 5, so only the differences between the two will be outlined.

The apparatus 130 includes, in addition to the configuration shown with reference to the apparatus 120, a counter-pressure roller 56 which is located above the molding roller 45. A space is formed between the molding roller 45 and the counter-pressure roller. In the space, the substrate sheet 11 is positioned. The suspension 22 molded by the molding roller 45 reaches the substrate sheet and is pressed between the molding roller 45 and the counter-pressure roller 56. The molding roller 45 and the counter-pressure roller 56 press the first and second surfaces 12, 13 of the substrate sheet 11, respectively.

The amount of suspension exiting the moulding box 42 could then be controlled by adjusting the distance between the two rollers 45 and 49 (moulding roller and transfer roller). The amount of suspension applied onto the substrate sheet 11 could further be adjusted by controlling the pressure exerted on the sheet by the moulding roller 46 and the counter-pressure roller 56.

Acting on the pressure exerted on the sheet helps to have good control over the deposition of the suspension on the substrate sheet 11.

The operation of the apparatus 130 is the same as that of the apparatus 120, to which compression by the counter-pressure roller 56 is added.

As shown in Figure 7, a graph is shown with respect to the concentration of various components of the homogenized tobacco sheet 200. The solid curve represents the concentration of the suspension in the sheet, while the dashed curve represents the concentration of the substrate forming material. The abscissa of the graph represents the position on the substrate sheet 11, from the first surface 12 of the substrate sheet to the second surface 13 of the substrate sheet. In the event that the suspension 22 is placed on a surface, such as the first surface 12, of the substrate sheet 11, the suspension will have a decreasing concentration (in percent of the mass of the tobacco sheet reported to the total mass of a unit volume) going from the first surface 12 to the second surface 13 across the thickness of the substrate sheet.

Such decreasing concentration could vary according to the suspension recipe, the size distribution of the tobacco particles and the nature of the fiber substrate 11.

For example, in the area of the first surface 12 where the slurry is applied, the slurry content could go from about 70-80 percent (in percent of the mass of the reported tobacco compound to the total mass of a unit volume) to about 25-20 percent on the second surface 13. The fiber substrate may go from about 30-20 percent on the first surface 12, to about 75-80 percent on the area of the second surface 13.

The shapes of the curves in Figure 7 are only schematic.

This configuration of the homogenized tobacco sheet 200 can be obtained by using any of the apparatuses 10, 110, 120 and 130 of Figures 3 - 6.

The homogenized tobacco sheet 200 may be a multilayer sheet or a sheet of a composite material, depending on the absorption of suspension into the substrate sheet. Figure 8 shows a multilayer sheet 200 where the suspension 22 is coated onto the substrate sheet 13, forming a second layer 201. In Figure 9, the suspension 22 is essentially all absorbed by the substrate sheet 13, and a composite sheet 200 is formed.

Claims (13)

1. A multilayer sheet of alkaloid-containing material (200) comprising: - a first layer comprising a substrate sheet (11) including fibers having an average fiber length comprised between about 1 millimeter and about 5 millimeters, the first layer defining a first surface (12) and a second surface (13); - a second layer (201) comprising a mixture of: ■ a powder of the alkaloid-containing material, the powder having a size between about 8 micrometers and about 200 micrometers; ■ water; ■ a binder; ■ an aerosol former; the second layer (201) is applied to the first surface (12) of the substrate sheet (11), and wherein the binder is comprised in an amount between about 0 percent and about 1 percent of the total weight of the multilayer sheet of alkaloid-containing material (200) and comprising the aerosol former in an amount between about 2.9 percent and about 8.5 percent of the total weight of the multilayer sheet of alkaloid-containing material (200). 2. The multilayer sheet of alkaloid-containing material (200) according to claim 1, wherein the first layer is partially impregnated with the second layer (201). 3. The multilayer sheet of alkaloid-containing material (200) according to claim 1 or 2, comprising a third layer, the third layer comprising a mixture of: ■ a powder of the alkaloid-containing material, the powder having a size between about 8 micrometers and about 200 micrometers; • water; • a binder; • an aerosol former; The third layer is applied to the second surface (13) of the substrate sheet (11). 4. A sheet of a composite material containing alkaloids (200) comprising: a. a substrate sheet (11) including fibers having a nominal average fiber length of between about 1 millimeter and about 5 millimeters and defining a first surface (12) and a second surface (13); b. The substrate sheet (11) is impregnated with a mixture of: i. a powder of the alkaloid-containing material, the powder having a size between about 8 microns and about 200 microns; ii. water; iii. a binder; iv. an aerosol former; wherein the binder is comprised in an amount between about 0 percent and about 1 percent of the total weight of the sheet of an alkaloid-containing composite material (200) and comprising the aerosol former in an amount between about 2.9 percent and about 8.5 percent of the total weight of the sheet of an alkaloid-containing composite material (200). 5. The multilayer sheet of alkaloid-containing material (200) or the sheet of an alkaloid-containing composite material (200) according to any preceding claim, comprising the powder of the alkaloid-containing material in an amount between about 40 percent and about 80 percent of the total weight of the multilayer sheet of alkaloid-containing material (200) or the sheet of an alkaloid-containing composite material. 6. The multilayer sheet of alkaloid-containing material (200) or the sheet of an alkaloid-containing composite material (200) according to any preceding claim, comprising water in an amount between about 7 percent and about 15 percent of the total weight of the multilayer sheet of alkaloid-containing material (200) or the sheet of an alkaloid-containing composite material (200). 7. The multilayer sheet of alkaloid-containing material (200) or the sheet of an alkaloid-containing composite material (200) according to any preceding claim, comprising fibers other than fibers of the alkaloid-containing material in an amount between about 2 percent and about 5 percent of the total weight of the multilayer sheet of alkaloid-containing material (200) or the sheet of an alkaloid-containing composite material (200). 8. The multilayer sheet of alkaloid-containing material (200) or the sheet of an alkaloid-containing composite material (200) according to any preceding claim, wherein the multilayer sheet of alkaloid-containing material or the sheet of an alkaloid-containing composite material (200) has a thickness between about 150 micrometers and about 400 micrometers. 9. The multilayer sheet of alkaloid-containing material (200) or the sheet of an alkaloid-containing composite material (200) according to any preceding claim, wherein the multilayer sheet of alkaloid-containing material or the sheet of an alkaloid-containing composite material (200) has a width between about 0.1 meters and about 2.0 meters. 10. The multilayer sheet of alkaloid-containing material (200) or the sheet of a composite material containing alkaloids (200) according to any preceding claim, wherein the powder of the alkaloid-containing material comprises tobacco dust. 11. The multilayer sheet of alkaloid-containing material (200) or the sheet of an alkaloid-containing composite material (200) according to any preceding claim, wherein the fiber-including substrate sheet (11) comprises cellulosic fibers. 12. The multilayer sheet of alkaloid-containing material (200) or the sheet of an alkaloid-containing composite material (200) according to any preceding claim, wherein the substrate sheet (11) including fibers comprises fibers derived from hemp, kenaf, bamboo, wood, cotton or silk. 13. The aerosol-generating article, comprising a portion of the multilayer sheet of alkaloid-containing material (200) or the sheet of the alkaloid-containing composite material (200) according to any one of claims 1 to 12.