Treated Tobacco

Abstract

The invention provides an aerosol generating material (8) for a smoking article (5), comprising particulate porous material impregnated with a diluent (3), wherein said particulate porous material has a BET specific surface area of at least 1200 m2/g. The invention also provides an aerosol generating material (8) for a smoking article (5), comprising particulate calcium carbonate (1) carrying and/or impregnated with a diluent (3).

Description

The present invention relates to treated tobacco material. In particular, the present invention relates to tobacco that carries diluent and barrier material, products comprising the same and a method of producing the same.

It is known to include diluents in smoking articles such as cigarettes. Diluents are compounds that are vapourised during smoking and transfer to the mainstream smoke in aerosol form. They are generally selected such that they transfer to the smoke substantially intact. Other components of the smoke (tobacco-derived components in the case of tobacco-containing smoking articles) are therefore “diluted” by this means.

A cigarette can comprise a filter at the mouth end, a tobacco rod comprising smokable filler material, and cigarette paper wrapped around the rod. When diluent is present in the smokable filler material, this may be as a simple mixture with the other ingredients (particularly for diluents in solid form), or the diluent may be carried on one or more of the other ingredients (particularly if the diluent is in liquid form). If incorporated into the filler material as a simple mixture, this may present disadvantages during manufacturing, and the diluent may be easily dislodged from the finished product, especially if it is in fine powder form. Accordingly, it is preferred for the diluent to be held in intimate contact with another ingredient of the filler material.

It is known for the diluent to be provided in intimate contact with the tobacco itself. For instance, WO 2007/012980 and US 2006/283469 describe a tobacco-containing composition comprising added diluents, which may be administered by spraying, admixing or soaking of the tobacco.

It has been discovered that, although the diluent is vapourised during smoking in the course of performing its function, vapourisation of the diluent at lower temperatures can cause problems during storage of the cigarettes. Specifically, the diluent can migrate during storage and subsequently be lost to the atmosphere or interact with other parts of the product such as the cigarette paper. This may also lead to staining or marking of the cigarette paper, either by the diluent itself or by compounds released from the diluent interaction.

There is therefore a need in the art to avoid migration of the diluent during storage of a cigarette or other smoking article.

Accordingly, the present inventors have devised the invention defined in the claims.

FIG. 1 is a schematic illustration of a treated tobacco particle found in treated tobacco in accordance with one embodiment of the invention.

FIG. 2 is a schematic illustration of a treated tobacco particle found in treated tobacco in accordance with another embodiment of the invention.

FIG. 3 is a schematic illustration of another treated tobacco particle.

The tobacco used in the invention may be, for example, stem, lamina, dust, reconstituted tobacco or a mixture thereof. Suitable tobacco materials include the following tobacco types: Virginia or flue-cured tobacco, Burley tobacco, Oriental tobacco, or a blend of tobacco materials. The tobacco may be expanded, such as dry ice expanded tobacco (DIET), or processed by any other means such as extrusion. The stem tobacco may be pre-processed or unprocessed, and may be, for instance, solid stems, shredded dried stems or steam treated stems.

The diluent is at least one aerosol forming agent which may be, for instance, a polyol aerosol generator or a non-polyol aerosol generator, preferably a non-polyol aerosol generator. It may be a solid or liquid at room temperature, but preferably is a liquid at room temperature. Suitable polyols include sorbitol, glycerol, and glycols like propylene glycol or triethylene glycol. Suitable non-polyols include monohydric alcohols, high boiling point hydrocarbons, acids such as lactic acid, and esters such as diacetin, triacetin, triethyl citrate or isopropyl myristate. A combination of diluents may be used, in equal or differing proportions. Triacetin, triethyl citrate and isopropyl myristate are particularly preferred.

Application of the diluent to the tobacco is by any suitable method known to the skilled person, including washing, soaking, spraying or admixture.

The diluent may reside as a surface covering on the tobacco material, and/or at least some may be absorbed into the material. In the present invention, however, it is not essential for the diluent to be in any precise location on the tobacco.

There may be several factors influencing the stability and migration of diluents under ambient conditions. These factors may include hydrophobicity or hydrophilicity, viscosity, saturated vapour pressure at room temperature, boiling point, molecular structure (such as hydrogen bonding or Van der Waals forces) and the absorptive/adsorptive interaction between diluent and the tobacco. Some diluents will suffer from migration problems to a greater extent than others; for instance, it has been found that triacetin, isopropyl myristate and triethyl citrate particularly benefit from immobilisation as in the present invention.

Another relevant factor is the loading level of the diluent. For instance, if a diluent such as glycerol is included in a large amount, migration problems can still be significant.

The diluent loading level in the present invention may depend upon the specific diluent. Preferably, however, the treated tobacco of the invention carries at least 0.05 g diluent per g tobacco, more preferably at least 0.1 g diluent per g tobacco, more preferably at least 0.2 g diluent per g tobacco. In terms of the total weight of the treated tobacco, it preferably contains at least 5% by weight diluent, preferably at least 10%, 15%, 20% or 50%.

The barrier material is capable of inhibiting migration of the diluent during storage of the smoking article but allows release of the diluent during smoking of the smoking article. It may be one that melts, decomposes, reacts, degrades, swells or deforms to release the diluent at a temperature above room temperature but at or below the temperature reached inside a smoking article during smoking. For instance, the physical expansion occurring with vapourisation of sufficient levels of diluent may break down the structure of the barrier material. In embodiments of the invention, the barrier material releases substantial amounts of the diluent above 50° C., preferably above 60° C., 70° C., 80° C. or 90° C.

The barrier material may be, for example, a polysaccharide or cellulosic barrier material, a gelatin, a gum, a gel or a mixture thereof. Suitable polysaccharides include an alginate, dextran, maltodextrin, cyclodextrin and pectin. Suitable cellulosic materials include methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, and cellulose ethers. Suitable gums include gum Arabic, gum ghatti, gum tragacanth, Karaya, locust bean, acacia, guar, quince seed and xanthan gums. Suitable gels include agar, agarose, carrageenans, furoidan and furcellaran.

In a preferred embodiment of the invention, the barrier material comprises a polysaccharide. An alginate is especially preferred, due to its encapsulation properties. The alginate may be, for instance, a salt of alginic acid, an esterified alginate or glyceryl alginate. Salts of alginic acid include ammonium alginate, triethanolamine alginate, and group I or II metal ion alginates like sodium, potassium, calcium and magnesium alginate. Esterified alginates include propylene glycol alginate and glyceryl alginate.

In an embodiment, the barrier material is sodium alginate and/or calcium alginate. Calcium alginate provides a greater inhibition of migration of the diluent at ambient temperature than sodium alginate, but also may release the diluent at a higher temperature than the latter.

The barrier material is applied to the tobacco prior to or simultaneously with the diluent. In an embodiment, the barrier material is applied to the tobacco after the diluent has been applied. Preferably, the diluent is in intimate contact with the tobacco.

Application of the barrier material is by any suitable method known to the skilled person or described herein, which does not cause complete loss of the diluent in the process. Preferably, substantially no diluent is lost due to the step of applying the barrier material. In an embodiment, the method of the invention involves spraying of the barrier material or a precursor thereto.

For instance, the tobacco can be sprayed with an aqueous sodium alginate solution and dried to form a water-soluble film on the surface. Calcium ions from the tobacco itself can at least partially gel the sodium alginate to calcium alginate. Calcium ions can be added to the tobacco prior to alginate treatment to enhance this effect. Alternatively, the tobacco can be sprayed with sodium alginate and then treated with a source of calcium ions to form a water-insoluble film or gel covering of calcium alginate.

In the resulting product of the invention, the diluent is surrounded by the barrier material and its migration is hindered under ambient conditions. A schematic illustration of a treated tobacco particle found in one embodiment of the invention is given in FIG. 1. In this embodiment, the treated tobacco particle (1) is a tobacco particle (2) containing diluent (3) in a first coating and optionally also in its cellular structure. “Pores” (5) or air gaps between the tobacco fibres are shown; whilst diluent (3) is shown coating a pore, it may completely fill the pore. The barrier material (4) forms an external coating around the tobacco particle. In practice, the boundary between the barrier material layer and the diluent layer may not necessarily be a sharp one, but the barrier material will be substantially found external to the diluent.

Another treated tobacco particle (10) of the invention is shown in FIG. 2, in which the barrier material and diluent have been applied to the tobacco together and reside inside the cellular structure and/or as a coating layer (31) on the surface of the particle. In an embodiment, a further coating of barrier material (4) is then applied to provide an additional barrier to migration.

In an embodiment, the invention excludes treated tobacco in which the diluent has been pre-encapsulated with the barrier material before application to the tobacco. This is illustrated by tobacco particle (100) in FIG. 3, in which the diluent (3) has been pre-encapsulated with the barrier material (4) before application to the tobacco (2), and so is not in intimate contact with the tobacco.

In the invention, the treated tobacco contains as much barrier material as is required to perform its function. This will be dependent upon the type of tobacco used. For example, when shredded dried stem is used, the treated tobacco may contain 1-10% by weight of the barrier material, optionally 3-8% by weight, optionally 4-6% by weight. As will be appreciated by those skilled in the art, the amount of barrier material by weight of expanded tobacco will be greater than with, for instance, shredded dried stem.

The treated tobacco can be incorporated into a smoking article by conventional means. It may be the sole tobacco used in the smoking article or may be combined or blended with other tobacco materials. As used herein, the term “smoking article” includes smokeable products such as cigarettes, cigars and cigarillos. The term also includes so-called “heat-not-burn” products, which produce smoke or a smoke-like aerosol. The smoking article may be provided with a filter for the particulate and gaseous flow drawn by the smoker. Preferably, the smoking article is a cigarette.

Claims

1. Treated tobacco for a smoking article, wherein the tobacco carries diluent and barrier material, wherein the diluent has been applied to the tobacco prior to or simultaneously with the barrier material, wherein the barrier material is substantially found external to the diluent.

2. Treated tobacco as claimed in claim 1, wherein the diluent is in intimate contact with the tobacco.

3. Treated tobacco as claimed in claim 1, wherein the barrier material comprises an alginate.

4. Treated tobacco as claimed in claim 1, containing 1-10% by weight barrier material.

5. Treated tobacco as claimed in claim 1, containing at least 0.05 g diluent per 100 g tobacco.

6. Treated tobacco as claimed in claim 1, containing at least 5% by weight diluent.

7. Treated tobacco as claimed in claim 1, wherein the diluent is triacetin.

8. A smoking article containing a filter and treated tobacco wherein the tobacco carries diluent and barrier material, wherein the diluent has been applied to the tobacco prior to or simultaneously with the barrier material, wherein the barrier material is substantially found external to the diluent.

9. A method of producing treated tobacco for a smoking article, comprising treating tobacco with a diluent prior to or simultaneously with treating the tobacco with a barrier material, wherein the barrier material is substantially found external to the diluent.

10. The method as claimed in claim 9, wherein the diluent is applied to the tobacco prior to application of the barrier material.

11. The method as claimed in claim 9, wherein the diluent is sprayed onto the tobacco.

12. The method as claimed in claim 9, wherein the barrier material is sprayed onto the tobacco.

13. Treated tobacco as claimed in claim 1, wherein the diluent is trielthyl citrate.

14. Treated tobacco as claimed in claim 1, wherein the diluent is isopropyl myristate.