EP4701454A1 - Wrapper with ph indicator for aerosol-generating article - Google Patents

Abstract

The invention relates to an aerosol-generating article comprising a mouthpiece portion and an aerosol forming substrate portion, and an outer wrapper configured to connect the mouthpiece portion and an aerosol forming substrate portion to form the aerosol-generating article, wherein at least a portion of the outer wrapper is provided with a halochromic portion. The invention relates to an aerosol-generating system comprising an aerosol-generating device and an aerosol-generating article of the invention. The invention further relates to a method of manufacturing an aerosol-generating article, comprising an outer wrapper that is provided with a halochromic portion.

Description

Philip Morris Products S.A.

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WRAPPER WITH PH INDICATOR FOR AEROSOL-GENERATING ARTICLE

The present invention relates to an aerosol-generating article comprising a moisture absorbing wrapper. The present invention also relates to an aerosol-generating system comprising the aerosol-generating article and a method of manufacturing the aerosolgenerating article.

One type of aerosol-generating system is an electrically operated aerosol-generating system. Known handheld electrically operated aerosol-generating systems typically comprise an aerosol-generating device comprising a battery, control electronics and an electric heater for heating an aerosol-generating article designed specifically for use with the aerosolgenerating device. The aerosol-generating article comprises an aerosol-forming substrate. In some examples, the aerosol-forming substrate is in the form of a plug, such as a tobacco plug, and the electric heater contained within the aerosol-generating device is inserted into the aerosol-forming substrate when the smoking article is inserted into the aerosol-generating device.

Typically, such aerosol-generating articles are made of a combination of multiple rodshaped elements, which may also be referred to as plugs. Each plug may be wrapped by a plug wrap. A stick wrap may be used to connect the individual rod-shaped elements and to form an elongated aerosol-generating article. A proximal end of the aerosol-generating article is intended to come into contact with the user’s lips. A distal end of the aerosol-generating article is intended to be inserted inside an aerosol-generating device and is intended to be heated for generating an inhalable aerosol. An aerosol-generating article may include at a distal end a substrate plug holding aerosol-forming substrate and a mouthpiece filter (MPF) at the proximal end. Other plugs may be provided between the substrate plug and the mouthpiece filter. Such plugs could be for instance a cardboard tube, cooling element made from polylactic acid (PLA) or a hollow acetate tube (HAT).

Electrically heated aerosol-generating articles are heated but not burned during consumption and are therefore also referred to as heat-not burn articles (HnB articles). HnB articles may not necessarily change their appearance during consumption such that a user may have a hard time distinguishing between used and unused HnB articles. This can be a problem when a consumer puts back a used aerosol-generating article in its original packaging together with other new (unused) aerosol-generating articles, as it could be the case when there is no bin nearby to dispose of the used/consumed aerosol-generating article.

It would be desirable to provide an aerosol-generating article that allows to easily distinguish a used from an unused aerosol-generating article. It would be particularly desirable to provide an aerosol-generating article having a front plug and a coated stick wrap, wherein a used aerosol-generating article can nevertheless be easily distinguished from an unused aerosol-generating article.

It would further be desirable to provide an aerosol-generating article that allows to permanently distinguish a used from an unused aerosol-generating article, and at least over a time period of several days.

According to an embodiment of the present invention there is provided an aerosolgenerating article comprising a mouthpiece portion, an aerosol forming substrate portion, and an outer wrapper configured to connect the mouthpiece portion and an aerosol forming substrate portion to form the aerosol-generating article. At least a portion of the outer wrapper is provided with a halochromic portion.

As used herein, the term “heated aerosol-generating article” refers to an aerosolgenerating article for producing an aerosol comprising an aerosol-generating substrate that is intended to be heated rather than combusted in order to release volatile compounds that can form an aerosol. Such articles are commonly referred to as “heat-not-burn” products.

As used herein, the term “aerosol-generating substrate” refers to a substrate capable of releasing upon heating volatile compounds, which can form an aerosol. The aerosol generated from aerosol-generating substrates of aerosol-generating articles described herein may be visible or invisible and may include vapours (for example, fine particles of substances, which are in a gaseous state, that are ordinarily liquid or solid at room temperature) as well as gases and liquid droplets of condensed vapours.

As used herein, the terms “rod” or “rod-shaped element” refer to a generally cylindrical element of substantially polygonal cross-section and preferably of circular, oval or elliptical cross-section. The term “article” will refer to an aerosol-generating article, unless otherwise stated.

As used herein, the term “longitudinal” refers to the direction corresponding to the main longitudinal axis of the aerosol-generating article, which extends between the upstream and downstream ends of the aerosol-generating article. During use, air is drawn through the aerosol-generating article in the longitudinal direction. The term “transverse” refers to the direction that is perpendicular to the longitudinal axis.

As used herein, the terms “upstream” and “downstream” describe the relative positions of elements, or portions of elements, of the aerosol-generating article in relation to the direction in which the aerosol is transported through the aerosol-generating article during use.

Aerosol-generating articles according to the present invention are suitable for use in an aerosol-generating system comprising an electrically heated aerosol-generating device having an internal heating element for heating the aerosol-generating substrate. For example, aerosol-generating articles according to the invention find particular application in aerosolgenerating systems comprising an electrically heated aerosol-generating device having an internal heater blade which is adapted to be inserted into the rod of aerosol-generating substrate. Aerosol-generating articles of this type are described in the prior art, for example, in European patent application EP-A-0 822 670.

As used herein, the term “aerosol-generating device” refers to a device comprising a heating element that interacts with the aerosol-generating substrate of the aerosol-generating article to generate an aerosol.

As used herein, the term “halochromic portion” or “halochromic material” refers to a portion or material which shows a visibly perceivable reaction under certain pH conditions and/or upon contact with an aqueous medium having a certain pH value. The visibly perceivable reaction of the halochromic portion may comprise a change of color.

The halochromic portion of the outer wrapper may comprise a pH indicator. The halochromic portion may be configured to change its visual appearance upon contact with and in dependence of the pH value of an aqueous medium. The halochromic portion may be configured to be able to detect hydronium ions (HsO⁺) or hydrogen ions (H⁺) in the Arrhenius model.

The halochromic portion may be configured to change its visual appearance upon contact with saliva. The typical pH value of saliva may range from 6.2 to about 7.6. However, due to consumption of food or beverages, the pH value of saliva may even range from between 4 to 8.5. Thus, by contacting a halochromic material with saliva, a halochromic reaction, such as a color change, of the halochromic portion may occur.

As will be discussed in more detail below, the halochromic portion of the outer wrapper article may be configured in various ways. The change of the visual appearance may be visually perceivable by a user. By configuring the aerosol-generating article such that a halochromic portion of the outer wrapper changes its visual appearance upon a change in pH may enhance the overall user experience. A change in pH may be induced by saliva of a user’s lips contacting the halochromic portion. A contact of saliva and the halochromic portion may occur during use of the aerosol-generating article. Thus, a change of the visual appearance may be attributed to a user having used that specific aerosol-generating article. Accordingly, a user can readily distinguish between used and unused aerosol-generating articles.

This may be particularly advantageous when a consumer puts back a used aerosolgenerating article in its original packaging where also unused aerosol-generating articles are kept. This situation might occur when there is no thrash bin available to dispose the used aerosol-generating article. With the aerosol-generating articles as described herein, a user can readily tell the difference between used and unused aerosol-generating articles and may thereby avoid unpleasant and potentially harmful user experiences.

Further since users can differentiate between a used and an unused article, they might be more inclined to keep the unused aerosol-generating articles, rather than being tempted to think about littering and improper disposing of the used aerosol-generating articles.

The halochromic portion may be provided such that during normal use of the aerosolgenerating article, the halochromic portion comes into contact with a user’s lips. The halochromic portion may be provided such that during normal use of the aerosol-generating article, the halochromic portion comes into contact with a user’s saliva.

The halochromic portion may be provided adjacent a mouthpiece portion of the aerosolgenerating article. The halochromic portion may be provided at a mouthpiece portion of the aerosol-generating article. The halochromic portion may be provided around a mouthpiece portion of the aerosol-generating article.

The halochromic portion may extend around the entire circumference of the mouthpiece of an aerosol-generating article. The halochromic portion may extend around a part of the circumference of the mouthpiece of an aerosol-generating article.

The halochromic portion may extend over the full length of the mouthpiece of an aerosolgenerating article. The halochromic portion may extend over up to 70 percent of the full length of the mouthpiece of an aerosol-generating article. The halochromic portion may extend over up to 50 percent of the full length of the mouthpiece of an aerosol-generating article. The halochromic portion may extend over up to 30 percent of the full length of the mouthpiece of an aerosol-generating article.

By providing the halochromic portion at the mouthpiece of an aerosol-generating article the likelihood is increased that the halochromic portion comes into contact with the user’s lips and/or with the user’s saliva. This is particularly true for embodiments, in which the halochromic portion is configured to extend around a large apart or even the entire circumference of the mouthpiece of the aerosol-generating article.

The halochromic portion may also be configured to extend over the full length of the aerosol-generating article. The halochromic portion may extend over up to 50 percent of the full length of the aerosol-generating article. The halochromic portion may extend over up to 25 percent of the full length of the aerosol-generating article. The halochromic portion may extend over up to 20 percent of the full length of the aerosol-generating article. The halochromic portion may extend around the entire circumference of the aerosol-generating article. The halochromic portion may extend around a part of the circumference of the aerosol-generating article. The halochromic portion needs not necessarily be provided at the mouthpiece of an aerosol-generating article. Even if the halochromic portion is not provided at the mouthpiece, the halochromic portions may nevertheless come into contact with a user’s saliva, for example when users lick the aerosol-generating article with their tongue.

The halochromic portion may be selected from a material having an appropriate threshold pH to ensure that only upon contact with a pH outside the range threshold the halochromic portion undergoes a visual change. Selecting the halochromic portion to have an appropriate threshold pH may help to avoid erroneous activation of the halochromic portion. Such erroneous activation would lead to an erroneous marking of a used article when the article is actually still fresh.

Halochromic materials may be provided as chemical compounds in the form of solutions or slurries of organic acids, sugars, or amines combined with sugars.

The halochromic portion of the outer wrapper may be made from a halochromic paint, ink, glue, pigment, wax, or solution that can be applied to the outer wrapper during production. The halochromic portion may comprise one or more of: nano-particles, dyes, a chemical agent, and a combination thereof. A wide variety of materials are known with various pH profiles which will change visually when in contact with a solution, such as saliva.

The exposition of the halochromic portion to saliva, which may be seen as a solution having a pH value below a given threshold pH, may cause the pH indicator of the halochromic portion disposed on the outer surfaces of the article to react chemically and to change color. Prior to contact with saliva the indicators may be configured to remain invisible, and thus do not affect the appearance of the aerosol-generating article. Upon contact with saliva, the chemical reactions of the halochromic portion induce a color change. This color change can be recognized by a user. A user may thus, identify the respective article as a used article.

A wide variety of halochromic materials with various pH profiles are known to the skilled person. These halochromic materials may undergo a visual change at specific threshold pH values. The specific threshold pH values may depend on the specific halochromic material used. Different halochromic substances may exhibit different color changes. Different halochromic substances may exhibit different color changes and may change color at different threshold pH values.

The halochromic portion material may initially have any desired color. The initial color of the halochromic portion may be chosen as appropriate for any given aerosol-generating article. The halochromic portion may advantageously initially be transparent or white. The halochromic portion may be configured to appear initially with the same color as the outer wrapper of an article. By configuring the halochromic portion in this way, the halochromic portion may not be visually recognizable in an unused aerosol-generating article. The halochromic portion material may undergo a color change upon contact with a pH value below or above a given threshold pH value. The halochromic portion may be configured to become colored, become colorless, change its color, or display a marking or a message upon a change in pH value. The halochromic portion may be configured to have a gradual color change that becomes denser or more intense as the pH value increases or decreases. In any case, the halochromic portion is configured to undergo a visible color change that is recognizable by a user. The color change of the halochromic portion may depend on the pH value of the solution received thereon.

The marking of the aerosol-generating element may have any suitable form that can be easily perceived and understood by a user. The marking may comprise a word, a graphical element or a symbol, which may be useful to convey information to the user. The marking may be a printed marking. The marking may include the terms “used”, “empty”, “dispose” or similar. A symbol may include an “X” (capital X), a “I” (exclamation mark), an attention sign or any other symbol suitable for warning or alerting a user. The marking may comprise one or more lines or dots. The marking may comprise a pattern of lines or dots.

The halochromic portion may be configured to undergo a reversible or an irreversible color change upon a change in pH value. The halochromic portion may be configured to comprise a combination of reversible and irreversible halochromic materials, which lead to both reversible and irreversible visual changes.

A halochromic portion configured to undergo an irreversible color change may be advantageous. An irreversible visual change of the halochromic portion may allow to suitably convey to the user the information that an aerosol-generating article has been used. Therefore, an irreversible visual change may be advantageous for ensuring that the user is informed of a used article after they have consumed a given article.

The change of color of the halochromic portion of the outer wrapper may be irreversible at least at when considering a time scale at which a user can be reasonably expected to carry with himself an used aerosol-generating article. In order to qualify as an irreversible change of color, the change shall be lasting for at least 10 days, for at least 5 days or for at least 3 days. The change of color of the halochromic portion of the outer wrapper may last at least 24 hours.

The halochromic portion may comprise a single halochromic material with a specific threshold pH and a corresponding visual change. The halochromic portion may comprise a plurality of different halochromic materials, wherein each of the different halochromic materials may comprise a different threshold pH and/or visual change to each other. The halochromic portion may also comprise color-forming agents blended together with the one or more halochromic materials to obtain any desired color changing effect. The halochromic portion may comprise one or more of the following halochromic materials as pH indicators (The approximate operable range at which the respective pH indicator changes from substantially colorless to colored or from a first color to a second color are given in parentheses. As indicated, some of the halochromic material have plural operational ranges): Alizarin (5.6-7.2; 11.0-12.4); Alizarin Red S (4.3-6.3); Benzopurpurine 4B (2.2-4.2); 4,4'-bis(2-amino-1-nathylazo)-2,2'-stilbenedisulfonic acid (3.0-4.0); 4,4'-bis(4-amino- 1-nathylazo)-2,2'-stilbenedisulfonic acid (8.0-9.0); Brilliant Yellow (6.6-8.0); Bromocresol Green (3.8-5.4); Bromocresol Purple (5.4-6.8); Bromophenol Blue (3.0-4.6); Bromothymol Blue (6.0-7.0); Chlorophenol Red (5.2-8.8); Congo Red (3.0-5.2); o-cresolphthalein (7.8-9.8); Cresol Red (0.0-1.0; 7.0-8.8); p-dimethylaminoazobenzene (2.8-4.4); 4-(4-dimethylamino-1-naylazo)- 3-methoxybenzenesulfonic acid (3.5-4.8); 2-(p-dimethylaminophenylazo)pyridine (0.2-1.8; 4.4-

5.6); N, N-dimethyl-p-(m-tolylazo)analine (2.6-4.8); 2,4-dinitroenol (2.0-4.7); 2-(2,4- dinitroenylazo)-1-nathol-3,6-disulfonic acid, disodium salt (6.0-7.0); 6,8-dinitro-2,4- (1 H)quinazolinedione (6.4-8.0); 4-(p-exthoxyphenylazo)-m-phenylene-diamine monohydrochloride (2.2-5.8); ethyl bis(2,4-dimethylphenyl)ethanoate (8.4-9.6); Ethyl Orange (3.2-4.8); Ethyl Red (4.0-5.8); Metacresol Purple (1 .2-2.8; 7.4-9.0); Methyl Orange (3.2-4.4); Methyl Red (4.8-6.0); p-naphtholbenzein (8.2-10.0); Neutral Red (6.8-8.0)1 o-nitrophenol (5.4-

6.6); m-nitrophenol (6.8-8.6); phenolphthalein (8.2-9.8); Phenol Red (6.6-8.0); 4-phenylazo-1- naphthylamine (4.0-5.6): Propyl Red (4.8-6.6); Resazurin (3.8-6.4); Resorcin Blue (4.4-6.2); tetrabromophenolphthalein ethyl ester, potassium salt (3.0-4.2); and Thymol Blue (1.2-2.8; 8.0-

9.6).

The halochromic portion may also comprise one or more of the following halochromic materials as pH indicators, which change their color under basic conditions: Phthalein-type pH dyes such as o-cresolphthalein, phenolphthalein, and thymolphthalein, phenol-type dyes such as m-nitrophenol and p-nitrophenol, cyanine, and bis-(2,4-dinitro-phenyl)acetic acid ethyl ester.

The halochromic portion may also comprise one or more of the following halochromic materials as pH indicators, which change their color under acidic conditions: phthalide-type color-forming dyes such as diarylphthalide dyes and indolylphthalide dyes, fluoran dyes, leuco dyes such as acylleucoazine dyes and leucoauramine dyes, spiropyrane dyes, rhodaminelactam dyes, triarylmethane dyes, and chromene dyes.

Suitable color change dyes that are colored under acidic conditions are commercially available under the PERGASCRI PT® trade name (Ciba-Geigy Corporation, Greensboro, N.C.) and under the COPIKEM® trade name (Hilton Davis Company, Cincinnati, Ohio). Preferred color change dyes include crystal violet lactone, malachite green lactone, PERGASCRI PT® red I-6B (a bis-indolyl phthalide dye), PERGASCRI PT® black I-2R (a diamino fluoran dye), PERGASCRIPT® I-2G (a xanthene dye), COPIKEM® 1 Blue CVL, Vermilion-DCF (Hodogaya Chemical (USA) Inc.), Red-DCF (Hodogaya Chemical (USA) Inc.), and Orange-DCF (Hodogaya Chemical (USA) Inc.).

The halochromic portion may comprise a plurality of pH indicators that change colors at different pH ranges. The halochromic portion may show a variety of different colors depending on the detected pH value. For example, the halochromic portion may be configured to change its color in dependence of the pH value according to the following color scheme: Red, pH 2.0, very strong acid; Orange, pH 4.0, strongly acid; Yellow, pH 6.0, weakly acid; Green, pH 8.0, weekly alkaline; Blue, pH 10.0, strongly alkaline. With such a color change spectrum, when the halochromic portion comes into contact with saliva a first color change may appear from a first color to a second color. When the halochromic portion is fully saturated, a further color change from the second color to a third color may appear.

The halochromic portion may comprise a single pH indicator material. A single pH indicator material may have one or more threshold pH values. A particularly suitable pH indicator material may be litmus. Litmus is a pH indicator material, which turns red at any pH value less than 5.0 and which turns blue at any pH value greater than 8.0. Thus, either color change may be perceived as an indication that the article has been used. In addition, this pH indicator material enables a user to determine whether their saliva is acidic or basic. The change in color may comprise also a variation in color shades (i.e. , a change from light blue to dark blue or a change from pink to red) and need not, but may, comprise a complete change between colors (i.e., a change from red to blue).

Suitable color-forming or color-changing agents may include leuco dyes, liquid crystalbased inks, color developers, and melt materials. The change in color can be brought about in such systems by contacting the leuco dye with a color activator/developer which can induce proton transfer to the leuco dye and thereby cause the leuco dye to adopt its colored form, but similar color changes from substantially colorless to colored can also result from electron transfer and/or proton transfer reactions. A leuco dye is a dye that can switch between two chemical forms. In one of these chemical forms the leuco dye may be colorless. In the other chemical form the leuco dye may have a specific color.

Reversible transformations between the different chemical forms of a leuco dye may be caused by changes in the pH value. Irreversible transformations may involve reduction or oxidation reactions. The colorless form of a leuco dye may be referred to as the leuco form. From a structural standpoint, the change from substantially colorless to colored is often induced by cleaving a lactone ring to form a more highly conjugated species that absorbs in the visible range. As described above, the aerosol-generating article may comprise an outer wrapper and at least a portion of the outer wrapper is provided with the halochromic portion. The halochromic material of the halochromic portion may be applied to the surface of the outer wrapper by one or more of the following techniques: spraying, micro-capsules application, stamping, printing, silk screen printing, intaglio, letterpress, lithographic, stencil, flexogray, and coater printing methods. The appropriate application technique may be chosen depending on the halochromic material and depending on the wrapping material used. The halochromic material may be provided in the form of a halochromic ink. The halochromic ink can be deposited on the wrapper material using conventional printing techniques.

The halochromic material may be mixed with the glue to obtain pH sensitive glue. Such pH sensitive glue may be used to form a glue seal on the outer wrapper of the aerosolgenerating article.

The halochromic material may be provided in the form of a pH sensitive wax. Such pH sensitive wax may be applied to any desired portion of the outer wrapper of the aerosolgenerating article, as described above.

The outer wrapper may be a paper wrapper. The outer wrapper may be formed from conventional paper used in manufacture of aerosol-generating articles. The outer wrapper may also be referred to as tipping paper. The tipping paper is used to connect the mouthpiece portion to the remainder of the aerosol-generating article.

The outer wrapper may be formed from a paper sheet material having a thickness of less than 100 micrometers. The outer wrapper may be formed from a paper sheet material having a thickness of less than 65 micrometers, of less than 60 micrometers, of less than 55 micrometers, of less than 50 micrometers, of less than 45 micrometers, of less than 40 micrometers or of less than 35 micrometers.

The grammage of the paper sheet material from which the outer wrapper is formed may amount to less than 65 grams per squaremeter, to less than 60 grams per squaremeter, to less than 55 grams per squaremeter, to less than 50 grams per squaremeter, to less than 45 grams per squaremeter, to less than 40 grams per squaremeter, to less than 35 grams per squaremeter, to less than 30 grams per squaremeter, to less than 25 grams per squaremeter or to less than 20 grams per squaremeter.

The outer wrapper may be formed from a paper sheet material having a suitable porosity.

The air permeability of the paper sheet material used for the hydrochromic portion of the stick wrap may be above 30 corresta units (CU) at an applied pressure difference of 1 kilopascal (kPa). A non-perforated outer wrapper may exhibit a Filtrona Pressure Drop of between about 14.1 and 24.2 millimeters of water. In this respect the term “Filtrona Pressure Drop” is defined as the number of millimeters of water passing through a layer of tipping paper in response to a flow rate of 17.5 cubic centimeters per second.

The paper material used for forming the outer wrapper may itself be a pH sensitive paper that changes its color upon a change of the pH value.

The chemical reactions leading to the color change of the halochromic material are substantially independent of the material of the paper wrapper. However, the surface properties of the paper wrapper may affect the chemical reactions.

An aerosol-generating article may comprise a plurality of elements, including the rod of aerosol-generating substrate.

Aerosol-generating articles commonly may comprise a hollow acetate tube directly adjacent to the aerosol-generating substrate. The rod of aerosol-generating substrate may be formed of an aerosol-forming material, which may comprise homogenised tobacco material.

As used herein, the term “homogenised tobacco material” encompasses any tobacco material formed by the agglomeration of particles of tobacco material. Sheets or webs of homogenised tobacco material are formed by agglomerating particulate tobacco obtained by grinding or otherwise powdering of one or both of tobacco leaf lamina and tobacco leaf stems. In addition, homogenised tobacco material may comprise a minor quantity of one or more of tobacco dust, tobacco fines, and other particulate tobacco by-products formed during the treating, handling and shipping of tobacco. The sheets of homogenised tobacco material may be produced by casting, extrusion, paper making processes or any other suitable processes known in the art.

In preferred embodiments, the rod comprises one or more sheets of a homogenised tobacco material that have been gathered to form a plug and circumscribed by an outer wrapper. As used herein with reference to the invention, the term “sheet” describes a laminar element having a width and length substantially greater than the thickness thereof. As used herein with reference to the invention, the term “gathered” describes a sheet that is convoluted, folded, or otherwise compressed or constricted substantially transversely to the longitudinal axis of the aerosol-generating article.

Sheets of homogenised tobacco material for use in the invention may have a tobacco content of at least about 40 percent by weight on a dry weight basis, more preferably of at least about 50 percent by weight on a dry weight basis more preferably at least about 70 percent by weight on a dry weight basis and most preferably at least about 90 percent by weight on a dry weight basis.

Preferably, the sheets of homogenised tobacco material comprise an aerosol former. The sheets of homogenised tobacco material may comprise a single aerosol former. Alternatively, the sheets of homogenised tobacco material may comprise a combination of two or more aerosol formers.

Suitable aerosol-formers are known in the art and include, but are not limited to: monohydric alcohols like menthol, polyhydric alcohols, such as triethylene glycol, 1 ,3- butanediol and glycerine; esters of polyhydric alcohols, such as glycerol mono-, di- or triacetate; and aliphatic esters of mono-, di- or polycarboxylic acids, such as dimethyl dodecanedioate, dimethyl tetradecanedioate, erythritol, 1 ,3-butylene glycol, tetraethylene glycol, triethyl citrate, propylene carbonate, Ethyl laurate, triacetin, meso-erythritol, a diacetin mixture, a diethyl suberate, triethyl citrate, benzyl benzoate, benzyl phenyl acetate, ethyl vanillate, tributyrin, lauryl acetate, lauric acid, myristic acid, and propylene glycol.

Preferably, the sheets of homogenised tobacco material have an aerosol former content of greater than 5 percent on a dry weight basis. The sheets of homogenised tobacco material may have an aerosol former content of between approximately 5 percent and approximately 30 percent on a dry weight basis. In a preferred embodiment, the sheets of homogenised tobacco material have an aerosol former content of approximately 20 percent on a dry weight basis.

Sheets of homogenised tobacco material for use in the invention may comprise one or more intrinsic binders, that is tobacco endogenous binders, one or more extrinsic binders, that is tobacco exogenous binders, or a combination thereof to help agglomerate the particulate tobacco. Alternatively, or in addition, sheets of homogenised tobacco material for use in the aerosolgenerating substrate may comprise other additives including, but not limited to, tobacco and nontobacco fibres, aerosol-formers, humectants, plasticisers, flavourants, fillers, aqueous and nonaqueous solvents and combinations thereof.

Suitable extrinsic binders for inclusion in sheets of homogenised tobacco material for use in the invention are known in the art and include, but are not limited to: gums such as, for example, guar gum, xanthan gum, arabic gum and locust bean gum; cellulosic binders such as, for example, hydroxypropyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose and ethyl cellulose; polysaccharides such as, for example, starches, organic acids, such as alginic acid, conjugate base salts of organic acids, such as sodium-alginate, agar and pectins, and combinations thereof.

Suitable non-tobacco fibres for inclusion in sheets of homogenised tobacco material for use in the aerosol-generating substrate are known in the art and include, but are not limited to: cellulose fibers, soft-wood fibres, hard-wood fibres, jute fibres and combinations thereof. Prior to inclusion in sheets of homogenised tobacco material for use in the aerosol-generating substrate, non-tobacco fibres may be treated by suitable processes known in the art including, but not limited to: mechanical pulping, refining, chemical pulping, bleaching, sulfate pulping, and combinations thereof.

Sheets of homogenised tobacco for use in the invention preferably have a width of between about 70 mm and about 250 mm, for example between about 120 mm and about 160 mm. Preferably, the thickness of the sheets of homogenised tobacco material is between about 50 micrometres and about 300 micrometres, more preferably between about 150 micrometres and about 250 micrometres.

Sheets of homogenised tobacco for use in the aerosol-generating article of the present invention may be made by methods known in the art, for example the methods disclosed in international patent application WO-A-2012/164009 A2.

In a preferred embodiment, sheets of homogenised tobacco material for use in the aerosol-generating article are formed from a slurry comprising particulate tobacco, guar gum, cellulose fibres and glycerine by a casting process.

As an alternative to the use of a gathered sheet of homogenised tobacco material, as described above, the aerosol-generating substrate may be formed of a plurality of strips or shreds of a sheet of homogenised tobacco material. For example, the aerosol-generating substrate may be formed of a plurality of shreds of homogenised tobacco material that are aligned in the longitudinal direction and have been brought together and wrapped to form a rod of aerosol-forming substrate.

The shreds of homogenised tobacco material preferably have a length of between about 10 millimetres and about 20 millimetres, more preferably between about 12 millimetres and about 18 millimetres, more preferably between about 14 millimetres and about 16 millimetres, more preferably about 15 millimetres. Alternatively, or in addition, the shreds of homogenised tobacco material preferably have a width of between about 0.4 millimetres and about 0.8 millimetres.

Preferably, the density of the sheet of homogenised tobacco material from which the shreds are formed is between about 500 and about 1500 milligrams per cubic centimetre, more preferably between about 800 and about 1200 milligrams per cubic centimetre, more preferably between about 900 and about 1100 milligrams per cubic centimetre, and most preferably between about 900 and about 970 milligrams per cubic centimetre.

Preferably, the bulk density of the shreds of homogenised tobacco material within the aerosol-generating substrate is between about 0.4 grams per cubic centimetre and about 0.8 grams per cubic centimetre, preferably between about 0.5 grams per cubic centimetre and about 0.7 grams per cubic centimetre and most preferably between about 0.65 grams per cubic centimetre and about 0.67 grams per cubic centimetre. As described above, the homogenised tobacco material may be formed by the casting of a slurry. Alternatively, the homogenised tobacco material may be formed by another suitable method, such as for example, an extrusion method.

Preferably, the aerosol-generating substrate comprises a rod of the homogenised tobacco material circumscribed by a wrapper, wherein the wrapper is provided around and in contact with the homogenised tobacco material. The wrapper may be formed from any suitable sheet material that is capable of being wrapped around homogenised tobacco material to form an aerosol-forming substrate. The wrapper may be porous or non-porous. Preferably, the wrapper is a paper wrapper but the wrapper may alternatively be non-paper.

The rod of aerosol-forming substrate preferably has an external diameter that is approximately equal to the external diameter of the aerosol-generating article.

Preferably, the rod of aerosol-generating substrate has an external diameter of at least 5 millimetres. The rod of aerosol-generating substrate may have an external diameter of between about 5 millimetres and about 12 millimetres, for example of between about 5 millimetres and about 10 millimetres or of between about 6 millimetres and about 8 millimetres. In a preferred embodiment, the rod of aerosol-generating substrate has an external diameter of 7.2 millimetres, to within 10 percent.

The rod of aerosol-generating substrate may have a length of between about 7 millimetres and about 15 mm. In one embodiment, the rod of aerosol-generating substrate may have a length of about 10 millimetres. In a preferred embodiment, the rod of aerosol- forming substrate has a length of about 12 millimetres.

Preferably, the rod of aerosol-generating substrate has a substantially uniform crosssection along the length of the rod. Particularly preferably, the rod of aerosol-generating substrate has a substantially circular cross-section.

The aerosol-generating articles according to the invention preferably comprise one or more elements in addition to the rod of aerosol-forming substrate. For example, aerosolgenerating articles may further comprise at least one of: a mouthpiece, an aerosol-cooling element and a support element such as a hollow acetate tube. For example, in one preferred embodiment, an aerosol-generating article comprises, in linear sequential arrangement, a rod of aerosol-generating substrate as described above, a support element located immediately downstream of the aerosol-generating substrate, an aerosol-cooling element located downstream of the support element, and a stick wrap circumscribing the rod, the support element and the aerosol-cooling element.

Aerosol-generating systems according to the present invention comprise an aerosolgenerating article as described in detail above in combination with an aerosol-generating device which is adapted to receive the upstream end of the aerosol-generating article during a user experience. The aerosol-generating device comprises a heating element which is configured to heat the aerosol-generating substrate in order to generate an aerosol during use. Preferably, the heating element is adapted to penetrate the aerosol-generating substrate when the aerosol-generating article is inserted into the aerosol-generating device. For example, the heating element is preferably in the form of a heater blade.

The heater element may also be an external heating element that surrounds the aerosolgenerating article during use.

The heating element may be a resistive heating element or an inductive heating element.

The heating element is controlled during use to operate with a defined operating temperature range, below a maximum operating temperature. The thermal indicator of the aerosol-generating article is adapted such that the threshold temperature will not be reached during normal use of the aerosol-generating article in the aerosol-generating device with the heating element operating below the maximum operating temperature. This ensures that when the aerosol-generating article and aerosol-generating device are used together, the thermal indicator will not be activated during normal use.

Preferably, the aerosol-generating device additionally comprises a housing, an electrical power supply connected to the heating element and a control element configured to control the supply of power from the power supply to the heating element.

Suitable aerosol-generating devices for use in the aerosol-generating system of the present invention are described in WO-A-2013/098405.

The invention also relates to an aerosol-generating system comprising an aerosolgenerating device as described herein and an aerosol-generating article.

The aerosol-generating article may be configured as described above.

The invention also relates to a method of manufacturing an aerosol-generating article. The method comprises the steps of providing at least a mouthpiece portion and an aerosolforming substrate portion, providing an outer wrapper, and connecting the mouthpiece portion and the aerosol-forming substrate portion by wrapping them with the outer wrapper to form the aerosol-generating article. The outer wrapper is provided with a halochromic portion.

Providing the outer wrapper with a halochromic portion may be obtained in plural ways. The halochromic portion may be obtained by applying a halochromic solution comprising a pH indicator to a paper wrapper. The halochromic material may be applied or affixed onto the surface of the paper wrapper, in the form of paint, ink, dye, or another layer of material having halochromic material applied thereon. A halochromic solution may be applied using different methods such as spraying, micro-capsules application, stamping, and printing. Suitable printing methods include silk screen printing, intaglio, letterpress, lithographic, stencil, flexogray, and coater printing methods. The halochromic material may also be applied to a paper wrapper by methods of the evaporation drying type, penetration drying type, emulsion type, or oxidation polymerization type. The halochromic material may also be provided in the from of a thermosetting resin, a photocurable resin, or printing ink. Application of the halochromic material may also comprise the use of a mold.

Applying the halochromic solution to the paper may comprise applying a leuco dye by printing or stamping the ink on to a paper wrapper. The halochromic material may be based on liquid crystal concepts. In this case, the material may need to be encapsulated and then applied to the paper wrapper.

The wrapper material may be formed from pH-indicating sensor paper. The halochromic material may be integral to the pH-indicating sensor paper. The halochromic material may further be integral to at least any other component, layer, or portion of the outer wrapper. The halochromic material may be incorporated into the wrapper material during paper manufacture. The halochromic material may be soaked into the paper structure during paper manufacture. In this way the halochromic material may form a part of the paper material, rather than being applied after paper manufacture to the surface of the paper wrapper.

Below, there is provided a non-exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of another example, embodiment, or aspect described herein.

Example Ex 1 : An aerosol-generating article comprising: a mouthpiece portion and an aerosol forming substrate portion, and an outer wrapper configured to connect the mouthpiece portion and an aerosol forming substrate portion to form the aerosol-generating article, wherein at least a portion of the outer wrapper is provided with a halochromic portion.

Example Ex 2: An aerosol-generating article according example 1 , wherein the halochromic portion comprises a pH indicator.

Example Ex 3: An aerosol-generating article according to the preceding example, wherein the halochromic portion is configured to change its visual appearance upon contact with and in dependence of the pH value of an aqueous medium.

Example Ex 4: An aerosol-generating article according to any one of the preceding examples, wherein the halochromic portion is configured to change its visual appearance upon contact with saliva.

Example Ex 5: An aerosol-generating article according to any one of the preceding examples, wherein the halochromic portion extends circumferentially at least partially around the aerosol-generating article.

Example Ex 6: An aerosol-generating article according to any one of the preceding examples, wherein the halochromic material is located adjacent to and/or around the mouthpiece, preferably wherein the halochromic material extends around the entire circumference of the mouthpiece of the aerosol-generating article.

Example Ex 7: An aerosol-generating article according to any one of the preceding examples, wherein the halochromic material is located around the mouthpiece and extends around the entire circumference of the mouthpiece of an aerosol-generating article.

Example Ex 8: An aerosol-generating article according to any one of the preceding examples, wherein the halochromic portion is configured to be able to detect hydronium ions (HsO⁺) or hydrogen ions (H⁺) in the Arrhenius model.

Example Ex 9: An aerosol-generating article according to any one of the preceding examples, wherein the halochromic portion comprises one or more of: nano-particles, dyes, a chemical agent, and a combination thereof.

Example Ex 10: An aerosol-generating article according to any one of the preceding examples, wherein the halochromic portion is made of a halochromic paint, ink, glue, pigment, wax, or a solution that can be applied to the outer wrapper during production.

Example Ex 11 : An aerosol-generating article according to the preceding example, wherein the halochromic material comprises one or more of a leuco dye, a liquid crystal-based ink, a color developer, and a melt material.

Example Ex 12: An aerosol-generating article according to any one of the preceding examples, wherein the halochromic material is applied to the surface of the outer wrapper by one or more of: spraying, micro-capsules application, stamping, printing, silk screen printing, intaglio, letterpress, lithographic, stencil, flexogray, and coater printing methods.

Example Ex 13: An aerosol-generating article according to any one of the preceding examples, wherein the halochromic portion of the outer wrapper is configured to initially be transparent or to have the same (or a similar) color as the outer wrapper, and wherein the halochromic portion of the outer wrapper is configured to change its color upon detection of a change in pH value.

Example Ex 14: An aerosol-generating article according to any one of the preceding examples, wherein a color change of the halochromic portion depends on the pH value of the solution received thereon.

Example Ex 15: An aerosol-generating article according to any one of the preceding examples, wherein the halochromic portion comprises a single halochromic material with a specific threshold pH and a corresponding visual change.

Example Ex 16: An aerosol-generating article according to example 15, wherein the halochromic material comprises a single pH indicator dye, such as litmus, which assumes a first color below a first pH threshold and which assumes a second color above a second pH threshold. Example Ex 17: An aerosol-generating article according to any one of the preceding examples, wherein the halochromic portion comprises a plurality of different halochromic materials, wherein each of the different halochromic materials comprises a different threshold pH and/or visual change to each other.

Example Ex 18: An aerosol-generating article according to any one of the preceding claims, wherein the halochromic portion comprises a leuco dye and a color activator/developer, configured to induce proton and/or electron transfer to the leuco dye upon contact and in dependence of the pH value of an aqueous medium.

Example Ex 19: An aerosol-generating article according to any one of the preceding examples, wherein the halochromic portion extends longitudinally along at least part of the length of the aerosol-generating article.

Example Ex 20: An aerosol-generating article according to any one of the preceding examples, wherein the halochromic portion has the same length as the mouthpiece or wherein the length of the halochromic portion is at least 75% of the length of the mouthpiece or wherein the length of the halochromic portion is at least 50% of the length of the mouthpiece.

Example Ex 21 : An aerosol-generating article according to any one of the preceding examples, wherein the change of color of the halochromic portion is irreversible.

Example Ex 22: An aerosol-generating system comprising: an aerosol-generating device; and an aerosol-generating article according to any preceding example.

Example Ex 23: A method of manufacturing an aerosol-generating article, comprising: providing at least a mouthpiece portion and an aerosol-forming substrate portion, providing an outer wrapper, and connecting the mouthpiece portion and the aerosol-forming substrate portion by wrapping them with the outer wrapper to form the aerosol-generating article, wherein the outer wrapper is provided with a halochromic portion.

Features described in relation to one embodiment may equally be applied to other embodiments of the invention.

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

Fig. 1 shows a schematic view of an aerosol-generating article;

Fig. 2 shows an aerosol-generating article with halochromic portion before and after use;

Fig. 3 shows an aerosol-generating article with a halochromic portion comprising a text portion; and Fig. 4 shows an aerosol-generating article with a halochromic portion comprising a graphical element.

Fig. 1 shows an aerosol-generating article 10 in a cross-sectional view. The aerosolgenerating article 10 comprises a mouthpiece 12 located at a proximal end of the article 10. The article 10 further comprises a PLA (poly lactic acid) plug 14, a hollow acetate tube 16, and an aerosol-forming substrate portion 18 comprising an aerosol-forming substrate, for example, a gathered sheet of homogenized tobacco. At the distal end of the article 10 there is provided a front plug 20. The article is circumscribed by an outer wrapper 22. A central axis 24 extends centrally along a longitudinal direction of the aerosol-generating article 10.

Outside air drawn into the aerosol-generating article 10 by the user, enters mainly through the front plug 20 at the distal or upstream end of the aerosol-generating article 10. The outside air is guided through the aerosol-forming substrate and mixes with vapours and other volatiles created upon heating of the aerosol-forming substrate to form an aerosol. Heated air and aerosol is then guided onwards through the further elements of the aerosol-generating article 10 and exits the aerosol-generating article 10 at the proximal or downstream end through the mouthpiece 12. All elements form an internal airflow path through the aerosolgenerating article 10.

Fig. 2 illustrates an aerosol-generating article 10 wherein for the sake of simplicity only the mouthpiece 12 on the proximal end and the remaining part of the aerosol-generating article 10 at the distal end are shown. The article 10 at the left-hand side is unused. At the mouthpiece 12 there is provided a halochromic portion 30 that cannot be visually recognized at the unused aerosol-generating article 10. The halochromic portion comprises a pH indicator. In this case the pH indicator comprises Phenol Red. Phenol Red exhibits a gradual transition from light yellow to orange to red over the pH range from 6.8 to 8.2.

The article 10 at the right-hand side has been used and was brought into contact with a user’s lips during use. Upon contact with the user’s lips, an amount of the user’s saliva is brought into contact with the halochromic portion 30 provided at the mouthpiece 12 of the aerosol-generating article 10. The pH value of the user’s saliva was in the range of between 6.5 to 7.0. For this reason, the pH indicator of the halochromic portion 30 undergoes a visual change and changes its color from a light yellow color to a light orange color. The halochromic portion 30 is provided in the form of two stripes on the at the outer wrapper 22 of the mouthpiece 12. Therefore, two light orange stripes appear at the mouthpiece 12 of the used aerosol-generating article 10. In this way, the user can distinguish between used and unused aerosol-generating articles 10. Fig. 3 also illustrates an aerosol-generating article 10 that is similar to the aerosolgenerating article 10 of Fig. 2. At the mouthpiece 12 there is provided a halochromic portion 30 that cannot be visually recognized at the unused aerosol-generating article 10. Upon use, the article 10 is brought into contact with a user’s lips and the halochromic portion 30 provided at the mouthpiece 12 of the aerosol-generating article 10 becomes recognizable. In this case the halochromic portion 30 comprises two portions 32, 34. The text portion 32 is configured to form the word element “used”. Thus, in this embodiment the user can actually read from the article 10 that the article 10 has been used. In addition, in the embodiment of Fig. 3, the halochromic portion 30 comprises a progressive portion 34, which is indicative of how long the aerosol-generating article 10 has been used. The length of the use may be indicative of the level of depletion of the aerosol-generating article 10. The progressive marking 34 is an arrow symbol comprising four segments. The first and the second segment is already visible. The further segments are not yet visible and are only indicated by the dotted lines. Thus, the user can derive from this progressive marking 34 that the aerosol-generating article 10 is already depleted by 50 percent.

Fig. 4 depicts an aerosol-generating article 10 comprising a plurality of rod-shaped elements 12, 14, 16, 18, 20 that are connected to each other by an outer wrapper 22. The outer wrapper 22 is made from conventional cigarette paper. The aerosol-generating article 10 comprises five elements, a front plug 20, a sensorial media plug 18, a hollow acetate tube 16, a PLA filter 14, and a mouthpiece 12.

When the article 10 is still unused, no specific marking can be seen. However, after use, when the halochromic portion 30 of the outer wrapper 22 is contacted with the user’s saliva, the halochromic portion 30 changes its color and a marking appears. In this case, the halochromic portion 30 is provided in the form of a graphical icon. The icon shows a red triangle with an exclamation mark. With the appearance of the graphical icon, the user is informed that this article 10 has already been used. Accordingly, the user can now clearly and easily distinguish between used and unused aerosol-generating articles 10.

Claims

1. An aerosol-generating article comprising: a mouthpiece portion and an aerosol forming substrate portion, and an outer wrapper configured to connect the mouthpiece portion and an aerosol forming substrate portion to form the aerosol-generating article, wherein at least a portion of the outer wrapper is provided with a halochromic portion.

2. An aerosol-generating article according to any one of the preceding claims, wherein the halochromic portion comprises a pH indicator.

3. An aerosol-generating article according to the preceding claim, wherein the halochromic portion is configured to change its visual appearance upon contact with and in dependence of the pH value of an aqueous medium.

4. An aerosol-generating article according to any one of the preceding claims, wherein the halochromic portion is configured to change its visual appearance upon contact with saliva.

5. An aerosol-generating article according to any one of the preceding claims, wherein the halochromic material is located adjacent to and/or around the mouthpiece, preferably wherein the halochromic material extends around the entire circumference of the mouthpiece of the aerosol-generating article.

6. An aerosol-generating article according to any one of the preceding claims, wherein the halochromic portion comprises one or more of: nano-particles, dyes, a chemical agent, and a combination thereof.

7. An aerosol-generating article according to any one of the preceding claims, wherein the halochromic portion is made of a halochromic paint, ink, glue, pigment, wax, or a solution that can be applied to the outer wrapper paper during production.

8. An aerosol-generating article according to the preceding claim, wherein the halochromic material comprises one or more of a leuco dye, a liquid crystal-based ink, a color developer, and a melt material.

9. An aerosol-generating article according to any one of the preceding claims, wherein the halochromic portion comprises a single halochromic material with a specific threshold pH and a corresponding visual change.

10. An aerosol-generating article according to claim 9, wherein the halochromic material comprises a single pH indicator dye, such as litmus, which assumes a first color below a first pH threshold and which assumes a second color above a second pH threshold.

11. An aerosol-generating article according to any one of the preceding claims, wherein the halochromic portion comprises a plurality of different halochromic materials, wherein each of the different halochromic materials comprises a different threshold pH and/or visual change to each other.

12. An aerosol-generating article according to any one of the preceding claims, wherein the halochromic portion comprises a leuco dye and a color activator/developer, configured to induce proton and/or electron transfer to the leuco dye upon contact and in dependence of the pH value of an aqueous medium.

13. An aerosol-generating article according to any one of the preceding claims, wherein the change of color of the halochromic portion is irreversible.

14. An aerosol-generating system comprising: an aerosol-generating device; and an aerosol-generating article according to any preceding claim.

15. A method of manufacturing an aerosol-generating article, comprising: providing at least a mouthpiece portion and an aerosol-forming substrate portion, and providing an outer wrapper, connecting the mouthpiece portion and the aerosol-forming substrate portion by wrapping them with the outer wrapper to form the aerosol-generating article, wherein the outer wrapper is provided with a halochromic portion.