EP4223149A1

EP4223149A1 - Tobacco sheet

Info

Publication number: EP4223149A1
Application number: EP21875858.9A
Authority: EP
Inventors: Keisuke HARUKI
Original assignee: Japan Tobacco Inc
Current assignee: Japan Tobacco Inc
Priority date: 2020-10-02
Filing date: 2021-10-01
Publication date: 2023-08-09
Also published as: JPWO2022071562A1; EP4223149A4; WO2022071562A1

Abstract

A tobacco sheet containing a tobacco material and a cellulose derivative having a degree of substitution of 0.65 or more.

Description

TECHNICAL FIELD

The present invention relates to a tobacco sheet.

BACKGROUND ART

There have been proposed numerous techniques concerning non-combustion smoking articles for inhaling a flavor component generated through heating of a tobacco sheet (Patent Literature (PTL) 1, for example).

CITATION LIST

PATENT LITERATURE

PTL 1: Japanese Patent No. 5292410

SUMMARY OF INVENTION

TECHNICAL PROBLEM

Conventional tobacco sheets used to generate dust or so-called detached shreds during or after use, thereby causing trouble in handling, such as adhesion to clothing. In view of this, the object of the present invention is to provide a tobacco sheet that reduces detached shreds.

SOLUTION TO PROBLEM

The present inventors have found that the above-mentioned problem can be resolved by using a specific binder. In other words, the object is attained by the present invention below.

(1) A tobacco sheet containing:
- a tobacco material; and
- a cellulose derivative having a degree of substitution of 0.65 or more.
(2) The sheet according to (1), where the degree of substitution is 0.7 or more.
(3) The sheet according to (2), where the degree of substitution is 0.8 or more.
(4) The sheet according to any of (1) to (3), where the cellulose derivative is a carboxyalkyl cellulose.
(5) The sheet according to any of (1) to (4), having an arithmetic average surface roughness Sa of 0.03 mm or less.
(6) The sheet according to any of (1) to (5), being a pressure-formed sheet.
(7) A method of producing the sheet according to any of (1) to (6), including:
- step 1 of preparing a mixture containing at least a tobacco material, the cellulose derivative, and a medium;
- step 2 of preparing a wet sheet by spreading the mixture on a substrate; and
- step 3 of drying the wet sheet.
(8) The method according to (7), where the step 1 includes kneading a tobacco material, the cellulose derivative, and a medium in a single-screw or a multi-screw kneader.
(9) The method according to (7) or (8), where the step 2 includes rolling the mixture using a roller or extruding the mixture from a die.
(10) The method according to (9), where the step 2 includes preparing a laminate sheet in which a wet sheet exists between two substrate films.
(11) A heat-not-burn smoking article including the tobacco sheet according to any of (1) to (6) or a material derived therefrom.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to provide a tobacco sheet that reduces detached shreds.

BRIEF DESCRIPTION OF DRAWINGS

Fig. 1 is a schematic view of exemplary tobacco segments using a tobacco sheet.
Fig. 2 is a schematic cross-sectional view of an exemplary heat-not-burn smoking system.
Fig. 3 is a schematic cross-sectional view of an exemplary heat-not-burn flavor inhaler article.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the present invention will be described in detail. In the present invention, the expression of "X to Y" includes the lower and the upper limits of X and Y.

1. Tobacco Sheet

A tobacco sheet is a sheet to be used for a smoking article and contains a tobacco material and, as a binder, a cellulose derivative having a degree of substitution of 0.65 or more.

(1) Binders

A binder is an adhesive for binding a tobacco material together or for binding a tobacco material and other components. In the present invention, a cellulose derivative having a degree of substitution of 0.65 or more is used as a binder. A cellulose derivative is cellulose in which -OH groups on glucopyranose residues are modified. Those having -OH groups modified into -OR groups (R is an organic group) are also referred to as cellulose ethers, those having -OH groups modified into -OX groups (X is a group derived from an acid) as cellulose esters, and those having at least one -OH group on glucopyranose residues replaced by an -OR group and at least one -OH group replaced by an -OX group as cellulose ether esters. Any of these cellulose derivatives can be used in the present invention.
The degree of substitution is the number of substituents per glucopyranose residue, in other words, the number of modified OH groups. The degree of substitution in the present invention is preferably 0.65 or more, more preferably 0.7 or more, and further preferably 0.8 or more. Moreover, the upper limit for the degree of substitution is preferably 3.0 or less, more preferably 2.0 or less, further preferably 1.6 or less, and particularly preferably 1.0 or less.
The degree of substitution is measured by a common method. For example, the degree of substitution is measured by a nitric acid/methanol method. The method includes 1) precisely weighing about 2.0 g of a sample, placing in a 300 mL Erlenmeyer flask with ground glass joint, adding 100 mL of nitric acid/methanol (solution of 1 g anhydrous methanol added with 100 mL GR-grade concentrated nitric acid), shaking for about 2 hours to convert the terminal acid groups from the salt form to the hydrogen form (from COONa to COOH, for example); 2) filtering the resulting sample through a glass filter 1G3, washing with 200 mL of 80% methanol, then drying at 105°C for 2 hours; 3) precisely weighing 1 to 1.5 g of the resulting bone-dry sample, placing in a 300 mL Erlenmeyer flask with ground glass joint, wetting with 150 mL of 80% methanol, adding 50 mL of 0.1 N NaOH, shaking at room temperature for 2 hours, back-titrating excess NaOH with 0.1 N sulfuric acid using phenolphthalein as an indicator; and 4) obtaining the degree of substitution according to the following formula.

Degree of substitution = 0.162A/(1 - 0.058A)
A = 50 × F' - sulfuric acid volume (mL) × F/bone-dry sample weight (g) × 0.1
F: factor for sulfuric acid
F': factor for NaOH

In cellulose ethers, up to three R is present, and each R may be the same or different. Examples of R include C₁ to C₃ linear or branched alkyl groups, such as a methyl group, an ethyl group, and a propyl group; C₁ to C₃ linear or branched hydroxyalkyl groups, such as a hydroxymethyl group, a hydroxyethyl group, and a hydroxypropyl group; C₇ to C₂₀ arylalkyl groups, such as a benzyl group and a trityl group; cyanoalkyl groups, such as a cyanoethyl group; carboxyalkyl groups, such as a carboxymethyl group and a carboxyethyl group; and aminoalkyl groups, such as an aminoethyl group. Among these, R is preferably a carboxyalkyl group and more preferably a carboxymethyl group. The degree of substitution for cellulose ethers is also referred to as the degree of etherification.
In cellulose esters, up to three X is present, and each X may be the same or different. Examples of X include groups derived from C₀ to C₄ carboxylic acids, such as formic acid, acetic acid, propionic acid, and butyric acid; groups derived from C₆ to C₁₀ aromatic carboxylic acids, such as benzoic acid and phthalic acid; groups derived from sulfonic acids, such as p-toluenesulfonic acid; groups derived from inorganic acids, such as nitric acid, sulfuric acid, and phosphoric acid; and groups derived from xanthic acid. The degree of substitution for cellulose esters is also referred to as the degree of esterification.
Such a cellulose derivative having high hydrophilicity, when used as a binder, enhances the affinity with a tobacco material. Consequently, a tobacco sheet enhances the strength and is thus less likely to generate detached shreds during use.
Further, such a cellulose derivative is soluble in organic solvents, in particular, in ethanol. For this reason, when a mixture containing ethanol as a medium is used for producing a tobacco sheet as described hereinafter, it is possible to lower the viscosity of the mixture. Accordingly, such a mixture is more advantageous than a mixture containing water as a medium in the transport step, coating step, and so forth during the production. Furthermore, since ethanol is more volatile than water, it becomes possible, for example, to shorten the production time and reduce the energy costs during drying in the production method.
The amount of the cellulose derivative in a tobacco sheet is not particularly limited but is preferably 0.1 to 10 weight%, more preferably 1 to 5 weight%, and further preferably 2 to 4 weight% on dry weight basis (weight after removing water contained, the same applies hereinafter) relative to the dry weight of the tobacco sheet. When the amount of binder exceeds the upper limit or is less than the lower limit, the above-mentioned effects could not be exerted satisfactorily.
Hereinafter, concrete examples of cellulose derivatives will be described.
Cellulose Ethers: methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxymethyl ethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, benzyl cellulose, trityl cellulose, cyanoethyl cellulose, carboxymethyl cellulose, carboxyethyl cellulose, aminoethyl cellulose
Cellulose Esters: organic acid esters, such as cellulose acetate, cellulose formate, cellulose propionate, cellulose butyrate, cellulose benzoate, cellulose phthalate, tosyl cellulose, and cellulose nitrate; inorganic acid esters, such as cellulose sulfate, cellulose phosphate, and cellulose xanthate

(2) Tobacco Materials

Tobacco materials are materials derived from tobacco, and concrete examples include shreds of dry tobacco leaves and pulverized leaf tobacco. Pulverized leaf tobacco refers to particles obtained through pulverization of leaf tobacco. Such pulverized leaf tobacco may have the particle size D90 set to 20 to 1000 µm, for example, and preferably 50 to 500 µm. Pulverization may be performed using a common grinding mill as dry grinding or wet grinding. The resulting pulverized leaf tobacco is thus referred to as leaf tobacco particles as well. In the present invention, the average particle size is obtained by a laser diffraction/scattering method and is concretely measured using a laser diffraction particle size analyzer (LA-950 from Horiba, Ltd., for example). Further, the type of tobacco is not limited, and flue-cured, burley, oriental, and domestic may be used, and others such as Nicotiana tabacum varieties or Nicotiana rustica varieties, for example, may be used. The amount of tobacco material in a tobacco sheet is not particularly limited but is preferably 50 to 95 weight% and more preferably 60 to 90 weight% on dry weight basis.

(3) Aerosol Formers

A tobacco sheet may contain an aerosol former. An aerosol former is a material that generates an aerosol through vaporization upon heating and subsequent cooling or that generates an aerosol through atomization. A common aerosol former may be used, and examples include those having a boiling point above 100°C, such as polyhydric alcohols such as glycerol, propylene glycol (PG), and triethyl citrate (TEC), and triacetin. The amount of aerosol former in a tobacco sheet is preferably 1 to 40 weight% and more preferably 10 to 20 weight% on dry weight basis (weight after removing water contained, the same applies hereinafter). When the amount of aerosol former exceeds the upper limit, the production of tobacco sheets could become difficult. Meanwhile, when the amount is less than the lower limit, smoky feeling could deteriorate.

(4) Emulsifiers

A tobacco sheet may contain an emulsifier. An emulsifier enhances affinity between an aerosol former, which is lipophilic, and a tobacco material, which is hydrophilic. For this reason, the addition of an emulsifier is effective particularly when a lipophilic aerosol former is used. Any common emulsifier may be used, and examples include emulsifiers having HLB of 8 to 18. The amount of emulsifier is not particularly limited but is preferably 0.1 to 3 parts by weight and more preferably 1 to 2 parts by weight on dry weight basis relative to 100 parts by weight of a tobacco sheet.

(5) Cellulose other than Tobacco

A tobacco sheet may contain cellulose other than tobacco. Examples of cellulose other than tobacco include cellulose fibers and cellulose powder but does not include any cellulose derivative as a binder. A tobacco sheet containing cellulose fibers exhibits high strength. Exemplary such fibers include pulp fibers. Pulp fibers are aggregates of cellulose fibers taken from plants, such as wood, and are typically used as raw materials for paper. Exemplary pulp fibers include recycled pulp, chemical pup, and mechanical pulp.
The amount of such fibers in a tobacco sheet is preferably 1 to 20 weight% and more preferably 5 to 10 weight% on dry weight basis in view of mechanical strength and so forth. Nevertheless, a tobacco sheet, when does not contain such fibers, can reduce odd taste. Accordingly, a tobacco sheet does not contain such fibers in an embodiment. In this case, it is possible to enhance the strength by adjusting the amount of binder.

(6) Flavors

A tobacco sheet may contain a flavor. A flavor is a substance that provides aroma or taste. Such a flavor may be a natural flavor or a synthetic flavor. One flavor or a mixture of a plurality of flavors may be used. Any flavor commonly used for smoking articles may be used, and concrete examples will be described hereinafter. A flavor may be incorporated into a sheet for a smoking article in an amount such that the smoking article can provide preferable aroma or taste. For example, the amount in a tobacco sheet is preferably 1 to 30 weight% and more preferably 2 to 20 weight%.
From a viewpoint of imparting satisfactorily perceived flavor, exemplary flavors include, but are not particularly limited to, acetanisole, acetophenone, acetylpyrazine, 2-acetylthiazole, alfalfa extract, amyl alcohol, amyl butyrate, trans-anethole, star anise oil, apple juice, Peru balsam oil, beeswax absolute, benzaldehyde, benzoin resinoid, benzyl alcohol, benzyl benzoate, benzyl phenylacetate, benzyl propionate, 2,3-butanedione, 2-butanol, butyl butyrate, butyric acid, caramel, cardamom oil, carob absolute, β-carotene, carrot juice, L-carvone, β-caryophyllene, cassia bark oil, cedarwood oil, celery seed oil, chamomile oil, cinnamaldehyde, cinnamic acid, cinnamyl alcohol, cinnamyl cinnamate, citronella oil, DL-citronellol, clary sage extract, cocoa, coffee, cognac oil, coriander oil, cuminaldehyde, davana oil, δ-decalactone, γ-decalactone, decanoic acid, dill oil, 3,4-dimethyl-1,2-cyclopentanedione, 4,5-dimethyl-3-hydroxy-2,5-dihydrofuran-2-one, 3,7-dimethyl-6-octenoic acid, 2,3-dimethylpyrazine, 2,5-dimethylpyrazine, 2,6-dimethylpyrazine, ethyl 2-methylbutyrate, ethyl acetate, ethyl butyrate, ethyl hexanoate, ethyl isovalerate, ethyl lactate, ethyl laurate, ethyl levulinate, ethyl maltol, ethyl octanoate, ethyl oleate, ethyl palmitate, ethyl phenylacetate, ethyl propionate, ethyl stearate, ethyl valerate, ethyl vanillin, ethyl vanillin glucoside, 2-ethyl-3,(5 or 6)-dimethylpyrazine, 5-ethyl-3-hydroxy-4-methyl-2(5H)-furanone, 2-ethyl-3-methylpyrazine, eucalyptol, fenugreek absolute, genet absolute, gentian root infusion, geraniol, geranyl acetate, grape juice, guaiacol, guava extract, γ-heptalactone, γ-hexalactone, hexanoic acid, cis-3-hexen-1-ol, hexyl acetate, hexyl alcohol, hexyl phenylacetate, honey, 4-hydroxy-3-pentenoic acid γ-lactone, 4-hydroxy-4-(3-hydroxy-1-butenyl)-3,5,5-trimethyl-2-cyclohexen-1-one, 4-(p-hydroxyphenyl)-2-butanone, 4-hydroxyundecanoic acid sodium salt, immortelle absolute, β-ionone, isoamyl acetate, isoamyl butyrate, isoamyl phenylacetate, isobutyl acetate, isobutyl phenylacetate, jasmine absolute, kola nuttincture, labdanum oil, terpeneless lemon oil, licorice extract, linalool, linalyl acetate, lovage root oil, maltol, maple syrup, menthol, menthone, L-menthyl acetate, p-methoxybenzaldehyde, methyl 2-pyrrolyl ketone, methyl anthranilate, methyl phenylacetate, methyl salicylate, 4'-methylacetophenone, methyl cyclopentenolone, 3-methylvaleric acid, mimosa absolute, molasses, myristic acid, nerol, nerolidol, γ-nonalactone, nutmeg oil, δ-octalactone, octanal, octanoic acid, orange flower oil, orange oil, oris root oil, palmitic acid, ω-pentadecalactone, peppermint oil, petitgrain Paraguay oil, phenethyl alcohol, phenethyl phenylacetate, phenylacetic acid, piperonal, plum extract, propenylguaethol, propyl acetate, 3-propylidenephthalide, prune juice, pyruvic acid, raisin extract, rose oil, rum, sage oil, sandalwood oil, spearmint oil, styrax absolute, marigold oil, tea distillate, α-terpineol, terpinyl acetate, 5,6,7,8-tetrahydroquinoxaline, 1,5,5,9-tetramethyl-13-oxatricyclo[8.3.0.0.(4.9)]tridecane, 2,3,5,6-tetramethylpyrazine, thyme oil, tomato extract, 2-tridecanone, triethyl citrate, 4-(2,6,6-trimethylcyclohex-1-enyl)but-2-en-4-one, 2,6,6-trimethylcyclohex-2-ene-1,4-dione, 4-(2,6,6-trimethylcyclohexa-1,3-dienyl)but-2-en-4-one, 2,3,5-trimethylpyrazine, γ-undecalactone, γ-valerolactone, vanilla extract, vanillin, veratraldehyde, violet leaf absolute, N-ethyl-p-menthane-3-carboxamide (WS-3), ethyl 2-(p-menthane-3-carboxamido)acetate (WS-5), sugars (sucrose, fructose, and so forth), cocoa powder, carob powder, coriander powder, licorice powder, orange peel powder, rose hip powder, chamomile flower powder, lemon verbena powder, peppermint powder, leaf powder, spearmint powder, black tea powder, natural plant flavors (jasmine oil, lemon oil, vetiver oil, lovage oil, for example), esters (menthyl acetate, isoamyl propionate, for example), and alcohols (phenethyl alcohol, cis-6-nonen-1-ol, for example). These flavors may be used alone or in combination of two or more.

(7) Characteristics and Forms of Tobacco Sheet

1) Thickness

The thickness of a tobacco sheet is not limited but is preferably 20 to 2000 µm, more preferably 100 to 1500 µm, and further preferably 100 to 1000 µm in an embodiment.

2) Strength

A tobacco sheet has a tensile stress of preferably 1.7 N/mm or more, more preferably 2 N/mm or more, and further preferably 3 N/mm or more.

3) Arithmetic Average Surface Roughness Sa

A tobacco sheet has an arithmetic average surface roughness Sa of preferably 0.3 mm or less. Sa is an indicator of surface roughness, and a tobacco sheet of the present invention, when having Sa in this range, reduces detached shreds from the surface. In view of this, the upper limit for Sa is more preferably 0.02 mm or less. Sa is measured by a common method and is preferably measured using a microscope (VK-X 100 from Keyence Corporation, for example) through the following procedure of:

1) setting the focus position of the lowest portion in a sheet;
2) setting the focus position of the highest portion in the sheet;
3) dividing the section obtained in 1) and 2) and imaging therethrough while gradually shifting the focus;
4) measuring a height from the difference between the focus position of each portion and the focus position of the lowest portion; and
5) calculating the roughness from the height data at each position (by automatic calculation using measuring apparatus software, as necessary) to calculate the arithmetic average surface roughness Sa.

(8) Tobacco Segment

A tobacco segment used for a smoking article can be produced from a tobacco sheet. The tobacco segment includes, in an embodiment, a tubular wrapper and a tobacco sheet spirally rolled and packed within the wrapper (see Fig. 1 (A)). In the figure, 20A is a tobacco segment, 1 is a tobacco sheet, and 22 is a wrapper, which is typically paper. The tobacco segment preferably has a rod shape, and the length may be set to about 15 to 80 mm and the diameter to about 5 to 10 mm. Further, the tobacco segment 20A in Fig. 1 (A) may also be cut to have an aspect ratio (length/diameter) of about 0.5 to 1.2 (see Fig. 1 (B)).
The tobacco segment 20A includes, in another embodiment, a tubular wrapper 22 and a tobacco sheet 1 folded and packed within the wrapper. The ridges formed through folding extend almost parallel to the longitudinal direction of the segment (see Fig. 1 (C)). The tobacco segment 20A preferably has a rod shape, and the length may be set to about 15 to 80 mm and the diameter to about 5 to 10 mm. In this embodiment, the tobacco sheet 1 has preferably been processed in advance by surface creasing, such as pleating or crimping.
The tobacco segment 20A includes, in another embodiment, a tubular wrapper 22 and a cut piece 1c of a tobacco sheet, which is packed within the wrapper (see Fig. 1 (D)). The tobacco segment 20A preferably has a rod shape, and the length may be set to about 15 to 80 mm and the diameter to about 5 to 10 mm. The size of a cut piece is not limited, but the length of the longest side may be set to about 2 to 20 mm and the width to about 0.5 to 1.5 mm, for example.
The tobacco segment 20A includes, in another embodiment, a tubular wrapper 22 and strand-type shreds packed within the wrapper (see Fig. 1 (E)). Such strand-type shreds are packed with the longitudinal direction almost parallel to the longitudinal direction of the wrapper 22. The width of a strand-type shred may be set to about 0.5 to 1.5 mm.
The tobacco segment 20A includes, in another embodiment, a tubular wrapper 22 and tobacco shred filler randomly packed within the wrapper. Tobacco shreds are shredded products and thus differ from strand-type shreds.

2. Production Method

A tobacco sheet can be produced by any method but is preferably produced by a method including the following steps of:

step 1 of preparing a mixture containing at least a tobacco material, the cellulose derivative, and a medium;
step 2 of preparing a wet sheet by spreading the mixture on a substrate; and
step 3 of drying the wet sheet.

(1) Step 1

In this step, a tobacco material, a cellulose derivative as a binder, and a medium are mixed. An aerosol former, an emulsifier, or a flavor may also be added as necessary. The amounts of the respective components to be added are adjusted to attain the above-mentioned amounts. The medium preferably primarily contains, for example, water or a water-soluble organic solvent having a boiling point below 100°C, such as ethanol, and is more preferably water or ethanol. The method for mixing is not limited, and a common apparatus, such as a mixer or a kneader, may be used therefor. The solid concentration of a mixture obtained through mixing is not limited and is appropriately adjusted to be suitable for step 2. For example, the upper limit for the solid concentration is preferably 98 weight% or less, 90 weight% or less, or 80 weight% or less. Meanwhile, the lower limit is preferably 10 weight% or more, 20 weight% or more, 30 weight% or more, 40 weight% or more, or 50 weight% or more.

(2) Step 2

In this step, a wet sheet is prepared by spreading the mixture on a substrate. The substrate is not limited, and examples include inorganic substrates, such as a glass sheet; metal substrates, such as an aluminum sheet; organic substrates, such as a PET film and fluoropolymer films; and fiber substrates, such as a nonwoven fabric. The method for spreading the mixture on a substrate is not limited, and examples include a rolling process using a roller, an extrusion process from a die, and a casting process as described hereinafter.

(3) Drying Step

In this step, the wet sheet is dried. The drying can be performed by a common method. For example, the wet sheet may be dried with air at room temperature or may be dried by heating. The heating temperature is also not limited and may be set to 60°C to 150°C, for example. A tobacco sheet is obtained by releasing the dry sheet from the substrate.
Hereinafter, preferable embodiments of the method of producing a tobacco sheet of the present invention will be described.

[Rolling Process]

1) Step 1

1-1) Pulverization

A raw material (classified leaf tobacco, for example) is coarsely crushed, followed by fine grinding using a grinding mill (ACM-5 from Hosokawa Micron Corporation, for example). The particle size (D90) after fine grinding is preferably 50 to 800 µm. The particle size is measured using a laser diffraction particle size analyzer, such as Mastersizer (from Malvern Panalytical Ltd.).

1-2) Preparation of Wet Powder

The pulverized tobacco raw material (tobacco particles, for example) is added with a binder and, as necessary, additives, such as a flavor and a lipid, and mixed. Since the mixing is preferably dry blending, a mixer is preferably used as a mixing apparatus. Subsequently, the resulting dry blend is added with water or another medium and, as necessary, glycerol or another aerosol former and mixed using a mixer to prepare wet powder (powder in the wet state). The amount of medium in the wet powder can be set to 20 to 80 weight% and preferably 20 to 40 weight% or may be set to 20 to 50 weight% since rolling is performed in step 2. The solid concentration of wet powder is preferably 50 to 90 weight%.

1-3) Kneading

The wet powder is kneaded using a single-screw or a multi-screw kneader (DG-1 from Dalton Corporation, for example). The kneading is preferably performed until the medium permeates through the entire powder. For example, kneading is preferably performed until a mixture becomes uniform in color under visual observation.

2) Step 2 (Rolling)

The mixture after kneading is sandwiched between two substrate films and rolled into a predetermined thickness (over 100 µm) by passing through a pair of rollers using a calendaring machine (from Yuri Roll Machine Co., Ltd., for example), thereby obtaining a laminate in which a wet sheet exists between two substrate films. Such rolling using rollers may be performed a plurality of times. The substrate films are preferably non-adhesive films, such as fluoropolymer films, and concrete examples include Teflon^™ films.

3) Step 3

Either substrate film of the laminate is released. The resulting laminate is dried using a circulation dryer. The drying temperature is preferably 50°C to 100°C, and the drying time may be set to 1 to 2 minutes. Subsequently, a tobacco sheet is obtained by releasing the other substrate film and further drying under the above-mentioned conditions. By performing drying like this, it is possible to avoid attachment of the tobacco sheet to other substrates.
A tobacco sheet obtained through this process is also referred to as "laminate sheet." Such a laminate sheet is preferable since the sheet exhibits surface smoothness and can suppress generation of detached shreds when comes into contact with other members. Further, this method is suitable for the production of a sheet of 300 µm or less.

[ExtrusionProcess]

1) Step 1

Step 1 of this process is as described for the rolling process. A wet powder (powder in the wet state) is prepared. When extrusion is performed in step 2, the amount of medium in the wet powder may be selected within the range of 20 to 80 weight% and is preferably 20 to 40 weight%.

2) Step 2

In this step, the wet powder is extruded from a die provided with a predetermined gap to form a wet sheet on a substrate. A common extruder can be used for extrusion.

3) Step 3

In this step, the wet sheet is dried to obtain a tobacco sheet. The drying conditions are as described for the rolling process. A tobacco sheet obtained by this process is also referred to as "extruded sheet." Such an extruded sheet is preferable since the sheet exhibits surface smoothness and can suppress generation of detached shreds when comes into contact with other members. This method is suitable for the production of a sheet of 200 µm or more.
Herein, a sheet formed as above under applied pressure is referred to as "pressure-formed sheet," and such "pressure-formed sheets" encompass a "laminate sheet" and an "extruded sheet." A laminate sheet is a sheet obtained by rolling a mixture once or more using a roller into a target thickness, followed by drying to a target water content. An extruded sheet is a sheet obtained by extruding a mixture from a T die or the like at a target thickness, followed by drying to a target water content. A pressure-formed sheet may be produced by rolling and extrusion in combination. For example, a mixture may be formed into a sheet through extrusion, further followed by rolling.

[Casting Process]

1) Step 1

Step 1 of this process can be performed by any method. For example, a mixture can be prepared by mixing, using a mixer or the like, a tobacco raw material having a desirable particle size, a cellulose derivative, a medium, and, as necessary, additives. A mixture obtained in this step has a solid concentration of preferably about 3 to 15 weight% and is thus referred to as slurry as well.

2) Step 2

In this step, the slurry is cast on a substrate to form a wet sheet. Such casting can be performed as known commonly.

3) Step 3

In this step, the wet sheet is dried to obtain a tobacco sheet. The drying conditions are as described for the rolling process. A tobacco sheet obtained by this process is also referred to as "cast sheet."

3. Smoking Articles

Exemplary smoking articles include flavor inhaler articles, in which a user tastes a flavor through inhalation, and smokeless tobacco (smokeless smoking articles), in which a user places the product directly in the nasal or oral cavity to taste a flavor. Flavor inhaler articles are broadly divided into non-combustion smoking articles and combustion-type smoking articles represented by conventional cigarettes. A tobacco sheet of the present invention is suitable for flavor inhaler articles.
Exemplary combustion-type flavor inhaler articles include cigarettes, pipes, kiseru or Japanese smoking pipes, cigars, and cigarillos.
A heat-not-burn flavor inhaler article may be heated by a heating device separate from the article or may be heated by a heating device integrated with the article. In the former flavor inhaler article (separate-type), a heat-not-burn flavor inhaler article and a heating device are also collectively referred to as "heat-not-burn smoking system." Hereinafter, an exemplary heat-not-burn smoking system will be described with reference to Figs. 2 and 3.
Fig. 2 is a schematic cross-sectional view of an exemplary heat-not-burn smoking system and illustrates the state before inserting a heater 12 into a tobacco segment 20A of a heat-not-burn flavor inhaler article 20. During use, the heater 12 is inserted into the tobacco segment 20A. Fig. 3 is a cross-sectional view of a heat-not-burn flavor inhaler article 20.
As illustrated in Fig. 2, the heat-not-bum smoking system includes a heat-not-burn flavor inhaler article 20 and a heating device 10 for heating the tobacco segment 20A from the inside. However, the heat-not-bum smoking system is not limited to the structure in Fig. 2.
The heating device 10 illustrated in Fig. 2 includes a body 11 and a heater 12. Although not illustrated, the body 11 may include a battery unit and a control unit. The heater 12 may be an electric resistance heater and is inserted into the tobacco segment 20A to heat the tobacco segment 20A.
A tobacco sheet of the present invention is highly effective when the tobacco segment 20A is heated from the inside as illustrated in Fig. 2. Such a heating mode has conventionally tended to generate detached shreds due to direct contact between a tobacco sheet and a heater. Meanwhile, a tobacco sheet of the present invention is less likely to generate detached shreds even in this case. For this reason, a tobacco sheet of the present invention is further effective in an internal heating mode. However, the embodiment of the heat-not-burn flavor inhaler article 20 is not limited to this. In another embodiment, the tobacco segment 20A is heated from the outside.
The heating temperature by the heating device 10 is not particularly limited but is preferably 400°C or lower, more preferably 50°C to 400°C, and further preferably 150°C to 350°C. Herein, the heating temperature means the temperature of the heater 12 in the heating device 10.
As illustrated in Fig. 3, the heat-not-burn flavor inhaler article 20 (hereinafter, simply referred to as "flavor inhaler article 20") has a cylindrical shape. The flavor inhaler article 20 has a circumferential length of preferably 16 mm to 27 mm, more preferably 20 mm to 26 mm, and further preferably 21 mm to 25 mm. The entire length (length in the horizontal direction) of the flavor inhaler article 20 is not particularly limited but is preferably 40 mm to 90 mm, more preferably 50 mm to 75 mm, and further preferably 50 mm to 60 mm.
The flavor inhaler article 20 comprises a tobacco segment 20A, a filter section 20C that forms a mouthpiece, and a connection section 20B that connects the tobacco segment 20A and the filter section 20C.
The tobacco segment 20A is cylindrical. The entire length (length in the axial direction) is, for example, preferably 5 to 100 mm, more preferably 10 to 50 mm, and further preferably 10 to 25 mm. The cross-sectional shape of the tobacco segment 20A is not particularly limited but may be circular, elliptic, or polygonal, for example.
The tobacco segment 20A includes a tobacco sheet or a material derived therefrom 21 and a wrapper 22 wrapped therearound. The wrapper 22 may be a tobacco sheet 1 of the present invention.
The filter section 20C is cylindrical. The filter section 20C includes a rod-shaped first segment 25 filled with cellulose acetate fibers and a rod-shaped second segment 26 similarly filled with cellulose acetate fibers. The first segment 25 is positioned on the side of the tobacco segment 20A. The first segment 25 may have a hollow portion. The second segment 26 is positioned on the mouth side. The second segment 26 is solid. The first segment 25 comprises a first filling layer (cellulose acetate fibers) 25a and an inner plug wrapper 25b wrapped around the first filling layer 25a. The second segment 26 comprises a second filling layer (cellulose acetate fibers) 26a and an inner plug wrapper 26b wrapped around the second filling layer 26a. The first segment 25 and the second segment 26 are joined by an outer plug wrapper 27. The outer plug wrapper 27 is bonded to the first segment 25 and the second segment 26 using a vinyl acetate emulsion adhesive, for example.
The length of the filter section 20C may be set to 10 to 30 mm, for example, the length of the connection section 20B to 10 to 30 mm, for example, the length of the first segment 25 to 5 to 15 mm, for example, and the length of the second segment 26 to 5 to 15 mm, for example. The lengths of these individual segments are examples and may be changed appropriately depending on production feasibility, required quality, the length of the tobacco segment 20A, and so forth.
For example, the first segment 25 (center hole segment) comprises a first filling layer 25a having one or more hollow portions and an inner plug wrapper 25b that covers the first filling layer 25a. The first segment 25 acts to enhance the strength of the second segment 26. The first filling layer 25a of the first segment 25 is, for example, cellulose acetate fibers packed at high density. The cellulose acetate fibers are, for example, added with 6 to 20 mass%, based on the mass of cellulose acetate, of a plasticizer including triacetin and hardened. The hollow portion of the first segment 25 has an inner diameter of ø1.0 to ø5.0 mm, for example.
The first filling layer 25a of the first segment 25 may be formed, for example, at a relatively high filling density of fibers or at a filling density of fibers comparable to the second filling layer 26a of the second segment 26 described hereinafter. Consequently, air and an aerosol flow only through the hollow portion and hardly flow within the first filling layer 25a during inhalation. For example, when it is desirable to suppress reduction in aerosol components through filtration in the second segment 26, it is also possible to shorten the second segment 26 and extend the first segment 25 by the corresponding length.
Replacing the shortened second segment 26 by the first segment 25 is effective for increasing the amount of aerosol components to be delivered. Since the first filling layer 25a of the first segment 25 is a fiber filling layer, the touch from the outside during use does not cause any discomfort to a user.
The second segment 26 comprises a second filling layer 26a and an inner plug wrapper 26b that covers the second filling layer 26a. The second segment 26 (filter segment) is filled with cellulose acetate fibers at common density and thus exhibits typical filtration performance of aerosol components.
The first segment 25 and the second segment 26 may be different in filtration performance of an aerosol (mainstream smoke) released from the tobacco segment 20A. Further, at least either of the first segment 25 and the second segment 26 may contain a flavor. The structure of the filter section 20C is optional and may be a structure having a plurality of segments as mentioned above or a structure of a single segment. In the case in which the filter section 20C is formed from one segment, the filter section 20C may comprise either the first segment or the second segment.
The connection section 20B is cylindrical. The connection section 20B includes a cylindrically formed paper tube 23 of cardboard, for example. The connection section 20B may be filled with a cooling member for cooling an aerosol.
Exemplary cooling members include a polymer sheet of poly lactic acid, for example, and such a sheet may be folded and packed therein. Further, a support may be provided between the tobacco segment 20A and the connection section 20B for suppressing the displacement of the tobacco segment 20A. Such a support may be formed of a common material, such as a center hole filter like the first segment 25.
A wrapper 28 is cylindrically wrapped around the tobacco segment 20A, the connection section 20B, and the filter section 20C to join these components integrally. On either side (inner side) of the wrapper 28, almost the whole surface or the whole surface excluding near a ventilation hole portion 24 is coated with a vinyl acetate emulsion adhesive. A plurality of ventilation hole portions 24 are formed by laser processing from the outside after the tobacco segment 20A, the connection section 20B, and the filter section 20C are integrated by the wrapper 28.
The ventilation hole portion 24 includes two or more penetrating holes in the thickness direction of the connection section 20B. Two or more penetrating holes are formed in radial arrangement when viewed from the extension of the central axis of the flavor inhaler article 20. The ventilation hole portion 24 is provided on the connection section 20B in this embodiment but may be provided on the filter section 20C. Moreover, two or more penetrating holes of the ventilation hole portion 24 are provided aligning in one row or on one ring at certain intervals in this embodiment but may be provided aligning in two rows or on two rings at certain intervals. Further, the ventilation hole portion 24 in one or two rows may be provided aligning discontinuously or irregularly. When a user inhales with the mouthpiece in the mouth, external air is taken into mainstream smoke through the ventilation hole portion 24. Nevertheless, the ventilation hole portion 24 need not necessarily be provided.

EXAMPLES

[Example 1]

Tobacco leaves were pulverized to attain D90 of 50 to 800 µm using a grinding mill (ACM-5 from Hosokawa Micron Corporation), thereby obtaining leaf tobacco particles. The D90 was measured using Mastersizer (from Malvern Panalytical Ltd.). The leaf tobacco particles and carboxymethyl cellulose (Sunrose F30MC from Nippon Paper Industries Co., Ltd.) as a binder were dry-blended using a mixer. Subsequently, the resulting dry blend was added with glycerol as an aerosol former and water as a medium and mixed using a mixer to prepare wet powder. The composition of the respective components is as follows.

[Table 1]

Table 1 Composition

	Pulverized tobacco leaves	Glycerol	Binder	Water
Feed weight proportion [WB weight%]	65	11	2	22
Water content of each component [wt%]	10	13	5.4	100
Feed weight proportion [DB weight%]	83	14	3	-
Weight in wet powder [g]	180.7	31.54	6.2	61.5
Weight proportion in wet powder [WB weight%]	64.5	11.3	2.2	22.0

WB: wet-based
DB: dry-based

In Table 1, "weight in wet powder" represents the dry weight for the pulverized tobacco leaves, glycerol, and the binder and represents for water the total amount of the feed weight and the weight of water contained in the pulverized tobacco leaves, glycerol, and the binder.
The wet powder was kneaded six times at room temperature using a kneader (DG-1 from Dalton Corporation) to yield a mixture. The die has a T-shape (T die), and the screw rotation speed was set to 38.5 rpm.
The wet powder was sandwiched between two Teflon^™ films (Nitoflon^® No. 900UL from Nitto Denko Corporation) and rolled at four stages using a calendaring machine (from Yuri Roll Machine Co., Ltd.) to attain a predetermined thickness (over 100 µm), thereby preparing a 105 µm-thick laminate having a layered structure of film/wet sheet/film. The roll gaps for the first to the fourth stages were respectively set to 650 µm, 330 µm, 180 µm, and 5 µm. The roll gap for the fourth stage is smaller than the thickness of the finally obtained sheet. This is because the sheet released from the pressure between the rollers expanded near the final thickness.
The laminate, after releasing one Teflon^™ film therefrom, was dried at 80°C for 1 to 2 minutes using a circulation dryer. Subsequently, a wet sheet after releasing the other film was dried under the same conditions to produce a tobacco sheet of the present invention.

[Examples 2 to 5]

Each tobacco sheet was produced and evaluated in the same manner as Example 1 except for using, as a binder, carboxymethyl cellulose shown in Table 2 (all from Nippon Paper Industries Co., Ltd.).

[Comparative Example 1]

A tobacco sheet was produced and evaluated in the same manner as Example 1 except for using, as a binder, carboxymethyl cellulose shown in Table 2 (from Nippon Paper Industries Co., Ltd.). The results are shown in Table 3. In the table, "physical properties of finished sheet" is for sheets produced through drying as described above and thus represent the physical properties of the sheets that are not dried to the bone-dry state.

[Table 2]

Table 2 Sheet Composition and Physical Properties

	Binder	Binder physical properties		Physical properties of finished sheet
	Binder	Degree of substitution [mol/C6]	Viscosity** [mPas]	Basis weight [g-WB/m²]	Thickness [g-WB/m²]	Density [g-WB/mL]
Comp. Ex. 1	F20LC 3%	0.62	250	163	133	1.23
Ex. 1	F30MC 3%	0.72	350	165	134	1.23
Ex. 2	F20HC 3%	0.89	250	149	120	1.24
Ex. 3	A04SH 3%	1.30 or more*	60	217	177	1.23
Ex. 4	A20SH 3%	1.30 or more*	250	228	191	1.19

* manufacturer nominal value
** manufacturer nominal value (viscosity of OD 1% aqueous solution)

[Table 3]

Table 3 Sheet Physical Properties

		Sa (mm)	Tensile strength (N/mm)	Solidification properties after heating (N)	Volume of detached shreds (mm³)
Ex.	1	-	1.8	29	9.5
Ex.	2	0.015	3.4	39	5
Comp. Ex.	1	0.035	1.3	16	15

Hereinafter, the evaluation methods will be described.

[Volume of Detached Shreds]

An internal-heating non-combustion smoking system illustrated in Fig. 2 was prepared. The tobacco sheet produced in each example was cut into shreds. The shreds were packed within a wrapper 22 of 12 mm in length and 7 mm in diameter at 70 volume% to prepare a tobacco segment 20A. The system was subjected to a smoking test (14 puffs, CIR conditions, constant heating at 350°C) using a smoking machine. After the smoking test, the shreds were removed gently from the tobacco segment 20A. Subsequently, new shreds were packed within the wrapper 22 again at 70 volume%, and the system was subjected to the second smoking test. The smoking test was repeated in the same manner 20 times in total, and the total volume of detached shreds remained within the wrapper 22 was measured.

[Surface Roughness]

The surface roughness was measured using a microscope (VK-X 100 from Keyence Corporation) through the following procedure of:

1) setting the focus position of the lowest portion in a sheet;
2) setting the focus position of the highest portion in the sheet;
3) dividing the section obtained in 1) and 2) and imaging therethrough while gradually shifting the focus;
4) measuring a height from the difference between the focus position of each portion and the focus position of the lowest portion; and
5) calculating the roughness from the height data at each position (by automatic calculation using measuring apparatus software) to calculate the arithmetic average surface roughness Sa.

[Solidification Properties after Heating]

An internal-heating non-combustion smoking system was prepared under the conditions described in the "Volume of Detached Shreds" section and was subjected to a smoking test once under the same conditions. After the test, the tobacco segment 20A was taken from the system and compressed in the radial direction at a constant speed by placing a jig at a position 6 mm from the tip in the longitudinal direction. The solidification properties after heating were evaluated by obtaining a load (N) when the jig reached the 3.5 mm position. As the load value is higher, shreds tend to stick together after heating and are thus less likely to generate detached shreds.

[Tensile Strength]

The obtained sheet was cut into 15 mm in width × 180 mm in length, and the tensile strength was assessed as tensile stress by measuring using a tensile strength tester (Strograph E-S from Toyo Seiki Seisaku-sho, Ltd.) under conditions of load range: 25 and speed range: 50.

[Degree of Substitution]

The degree of substitution was obtained by the foregoing measuring method.

REFERENCE SIGNS LIST

1: Tobacco sheet
1c: Cut piece of tobacco sheet

10: Heating device
11: Body
12: Heater

20: Heat-not-burn flavor inhaler article
20A: Tobacco segment
20B: Connection section
20C: Filter section

21: Tobacco sheet or material derived therefrom
22: Wrapper
23: Paper tube
24: Ventilation hole portion
25: First segment
25a: First filling layer
25b: Inner plug wrapper
26: Second segment
26a: Second filling layer
26b: Inner plug wrapper
27: Outer plug wrapper
28: Wrapper

Claims

A tobacco sheet comprising:
a tobacco material; and

a cellulose derivative having a degree of substitution of 0.65 or more.
The sheet according to Claim 1, wherein the degree of substitution is 0.7 or more.
The sheet according to Claim 2, wherein the degree of substitution is 0.8 or more.
The sheet according to any of Claims 1 to 3, wherein the cellulose derivative is a carboxyalkyl cellulose.
The sheet according to any of Claims 1 to 4, having an arithmetic average surface roughness Sa of 0.03 mm or less.
The sheet according to any of Claims 1 to 5, being a pressure-formed sheet.
A method of producing the sheet according to any of Claims 1 to 6, comprising:
step 1 of preparing a mixture containing at least a tobacco material, the cellulose derivative, and a medium;

step 2 of preparing a wet sheet by spreading the mixture on a substrate; and

step 3 of drying the wet sheet.
The method according to Claim 7, wherein the step 1 includes kneading a tobacco material, the cellulose derivative, and a medium in a single-screw or a multi-screw kneader.
The method according to Claim 7 or 8, wherein the step 2 includes rolling the mixture using a roller or extruding the mixture from a die.
The method according to Claim 9, wherein the step 2 includes preparing a laminate sheet in which a wet sheet exists between two substrate films.
A heat-not-burn smoking article comprising the tobacco sheet according to any of Claims 1 to 6 or a material derived therefrom.