AN AEROSOL-FORMING SUBSTRATE

Abstract

An aerosol-forming substrate for an aerosol-generating system is provided, the aerosol-forming substrate including: one or more aerosol formers, the aerosol-forming substrate having an aerosol former content of greater than 30 percent by weight; hydroxypropylmethyl cellulose; and one or more cellulose based strengthening agents including cellulose powder, the aerosol-forming substrate having a cellulose powder content of between about 0.5 percent by weight and about 50 percent by weight.

Claims

1.-13. (canceled)

14. An aerosol-forming substrate for an aerosol-generating system, the aerosol-forming substrate comprising: one or more aerosol formers, wherein the aerosol-forming substrate has an aerosol former content of greater than 30 percent by weight; hydroxypropylmethyl cellulose; and one or more cellulose based strengthening agents comprising cellulose powder, wherein the aerosol-forming substrate has a cellulose powder content of between about 0.5 percent by weight and about 50 percent by weight.

15. The aerosol-forming substrate according to claim 14, wherein the aerosol-forming substrate has a hydroxypropylmethyl cellulose content of between about 0.5 percent by weight and about 50 percent by weight.

16. The aerosol-forming substrate according to claim 14, wherein the aerosol-forming substrate has a cellulose based strengthening agent content of greater than about 0.5 percent by weight.

17. The aerosol-forming substrate according to claim 16, wherein the aerosol-forming substrate has a cellulose based strengthening agent content of between about 0.5 percent by weight and about 50 percent by weight.

18. The aerosol-forming substrate according to claim 17, wherein the aerosol-forming substrate has a cellulose based strengthening agent content of between about 0.5 percent by weight and about 40 percent by weight.

19. The aerosol-forming substrate according to claim 14, wherein the one or more cellulose based strengthening agents comprises cellulose fibres.

20. The aerosol-forming substrate according to claim 19, wherein the aerosol-forming substrate has a cellulose fibres content of between about 0.5 percent by weight and about 50 percent by weight.

21. The aerosol-forming substrate according to claim 14, wherein the one or more cellulose based strengthening agents comprises microcrystalline cellulose.

22. The aerosol-forming substrate according to claim 21, wherein the aerosol-forming substrate has a microcrystalline cellulose content of between about 0.5 percent by weight and about 50 percent by weight.

23. The aerosol-forming substrate according to claim 14, wherein the aerosol-forming substrate comprises carboxymethyl cellulose.

24. The aerosol-forming substrate according to claim 23, wherein the aerosol-forming substrate has a carboxymethyl cellulose content of between about 0.5 percent by weight and about 20 percent by weight.

25. The aerosol-forming substrate according to claim 24, wherein the carboxymethyl cellulose comprises sodium carboxymethyl cellulose.

26. An aerosol-generating article comprising the aerosol-forming substrate according to claim 14.

Description

[0164] Specific embodiments will be further described, by way of example only, with reference to the accompanying drawings in which:

[0165] FIG. 1 illustrates an example of an aerosol-generating article containing the aerosol-forming substrate as described herein; and

[0166] FIG. 2 illustrates an example of an aerosol-generating system comprising an aerosol-generating device and the aerosol-generating article shown in FIG. 1.

[0167] Aerosol-generating systems for delivering an aerosol to a user typically comprise an atomiser configured to generate an inhalable aerosol from an aerosol-forming substrate. Some known aerosol-generating systems comprise a thermal atomiser such as an electric heater or an inductive heating device. The thermal atomiser is configured to heat and vaporise the aerosol-forming substrate to generate an aerosol. Typical aerosol-forming substrates for use in aerosol-generating systems are nicotine formulations, which may be liquid nicotine formulations comprising an aerosol former such as glycerine and/or propylene glycol.

[0168] Some aerosol-forming substrates have a low tensile strength. This means that such aerosol-forming substrates may break apart or deteriorate before the aerosol-generating article is used by a user, which is undesirable. Some aerosol-forming substrates have a tendency to melt, which may result in a crust forming on a part of the aerosol-generating article. A crust being formed on a part of the aerosol-generating article may reduce the level of nicotine that is delivered to a user. A crust being formed on a part of the aerosol-generating article may reduce the volume of aerosol that is generated by the aerosol-generating system.

[0169] For example, as discussed above, in an aerosol-generating system that includes an inductive heating device, the aerosol-generating article may include a susceptor that can be heated by an induction source. The heat from the susceptor then transfers to the aerosol-forming substrate. Components of the aerosol-forming substrate may then vaporise to produce an aerosol. However, if the susceptor becomes coated in an aerosol-forming substrate crust then the crust may reduce heat transfer from the heated susceptor to the aerosol-forming substrate. The reduction in heat transfer from the heated susceptor to the aerosol-forming substrate may reduce the level of nicotine delivered to a user. The reduction in heat transfer from the heated susceptor to the aerosol-forming substrate may reduce the volume of aerosol that is generated by the aerosol-generating system.

[0170] It is therefore desirable to provide an aerosol-forming substrate that has an increased tensile strength. It is also desirable to provide an aerosol-forming substrate that has a reduced tendency to melt, which may lower the effect of crusting of the aerosol-forming substrate on a component of an aerosol-generating article.

[0171] FIG. 1 illustrates an example of an aerosol-generating article 1000 containing an aerosol-forming substrate as described herein.

[0172] In the example of FIG. 1, the aerosol-generating article 1000 includes four elements: the aerosol-forming substrate 1020, a hollow cellulose acetate tube 1030, a spacer element 1040, and a mouthpiece filter 1050. The four elements 1020, 1030, 1040, 1050 are arranged sequentially and in a coaxial alignment. The four elements 1020, 1030, 1040, 1050 are assembled by a cigarette paper 1060 to form the aerosol-generating article 1000.

[0173] In the example of FIG. 1, the aerosol-generating article 1000 has a mouth-end 1012 and a distal end 1013. A user may insert the mouth-end 1012 into his or her mouth during use. The distal end 1013 is located at the opposite end of the aerosol-generating article 1000 to the mouth end 1012. The example of an aerosol-generating article 1000 illustrated in FIG. 1 is particularly suitable for use with an electrically-operated aerosol-generating device comprising a heater for heating the aerosol-generating substrate.

[0174] In one example, when assembled, the aerosol-generating article 1000 is about 45 millimetres in length and has an outer diameter of about 7.2 millimetres and an inner diameter of about 6.9 millimetres.

[0175] In the example of FIG. 1, the aerosol-forming substrate 1020 is provided in the form of a plug made by crimping a sheet of aerosol-forming substrate. A number of examples of aerosol-forming substrate 1020 are shown in Table 1 below. The sheet is gathered, crimped and wrapped in a filter paper (not shown) to form the plug.

[0176] An aerosol-generating article 1000 as illustrated in FIG. 1 is designed to engage with an aerosol-generating device in order to be consumed. Such an aerosol-generating device includes means for heating the aerosol-forming substrate 1020 to a sufficient temperature to form an aerosol. Typically, the aerosol-generating device may comprise a heating element that surrounds the aerosol-generating article 1000 adjacent to the aerosol-forming substrate 1020, or a heating element that is inserted into the aerosol-forming substrate 1020.

[0177] Once engaged with an aerosol-generating device, a user draws on the mouth-end 1012 of the smoking article 1000 and the aerosol-forming substrate 1020 is heated to a temperature of about 375 degrees Celsius. At this temperature, volatile compounds are evolved from the aerosol-forming substrate 1020. These compounds condense to form an aerosol. The aerosol is drawn through the filter 1050 and into the user's mouth.

[0178] FIG. 2 illustrates a portion of an electrically-operated aerosol-generating system 2000. The aerosol-generating system utilises a heating blade 2100 to heat an aerosol-generating substrate 1020 of an aerosol-generating article 1000. In the example of FIG. 2, the heating blade 2100 is mounted within an aerosol article receiving chamber of an electrically-operated aerosol-generating device 2010. The aerosol-generating device 2010 defines a plurality of air holes 2050 for allowing air to flow to the aerosol-generating article 1000. Air flow is indicated by the arrows in FIG. 2. The aerosol-generating device 2010 comprises a power supply and electronics, which are not illustrated in FIG. 2. The aerosol-generating article 1000 of FIG. 2 is as described in relation to FIG. 1.

Examples

[0179] Example formulations of an aerosol-forming substrate according to the invention (Examples A, B, C, D and E) are prepared having the compositions shown in Table 1.

TABLE-US-00001 TABLE 1 Example A B C D E Hydroxypropylmethyl Cellulose 22.39 12.50 26.67 26.67 23.71 (% by weight) Cellulose Fibres (% by weight) 16.79 31.25 6.67 6.67 0 Microcrystalline Cellulose 0 0 0 6.67 0 (% by weight) Cellulose Powder (% by weight) 0 0 0 0 17.79 Sodium Carboxymethyl Cellulose 5.60 6.25 0 0 5.93 (% by weight) Agar (% by weight) 0 0 6.67 6.67 0 Nicotine (% by weight) 1.40 0 0 0 1.48 Glycerine (% by weight) 50.37 50.00 60.00 53.33 47.43 Lactic Acid (% by weight) 3.45 0 0 0 3.66

[0180] The aerosol-forming substrates of Examples A, B, C, D and E are prepared by: [0181] (1) mixing the components together with water using heat and agitation to form a slurry; [0182] (2) casting a layer of the slurry onto a plane surface to form a film having a thickness of about 210 micrometres; [0183] (3) leaving the film on the plane surface to solidify; and [0184] (3) drying the film by heating the film to about 140 degrees Celsius for about 8 minutes.

[0185] The aerosol-forming substrates obtained after drying are solid. In other words, the aerosol-forming substrates each have a stable size and shape and do not flow. The term stable is used herein to indicate that the aerosol-forming substrates substantially maintain their shape and mass when exposed to a variety of environmental conditions. As such, aerosol-forming substrates substantially do not release or absorb water when exposed to standard temperature and pressure while varying the relative humidity from about 10 percent to about 60 percent.

[0186] This is particularly advantageous as it ensures that aerosol-forming substrates in accordance with the present invention do not release a liquid phase during storage or transportation, for example, from the manufacturing facility to a point of sale.

[0187] In use in an aerosol-generating device, as described above, the aerosol-forming substrates of Examples A, B, C, D and E are heated to a temperature of between about 375 degrees Celsius. The nicotine and glycerine contained in the film evaporate. The nicotine and glycerine condense to form an inhalable aerosol. The aerosol can then be inhaled by a user. The aerosol-forming substrates shrink slightly and their volumes are reduced. However, the film remains solid and maintains its film form. The aerosol-forming substrates appear to harden slightly and to take on a darker, brownish colour.

[0188] The aerosol-forming substrate of Example A includes a combination of hydroxypropylmethyl cellulose and a cellulose based strengthening agent. In Example A, the cellulose based strengthening agent is cellulose fibres. The aerosol-forming substrate of Example A also includes sodium carboxymethyl cellulose, nicotine, glycerine and a carboxylic acid. In Example A, the carboxylic acid is lactic acid.

[0189] The aerosol-forming substrate of Example B includes a combination of hydroxypropylmethyl cellulose and a cellulose based strengthening agent. In Example B, the cellulose based strengthening agent is cellulose fibres. The aerosol-forming substrate of Example B contains more cellulose fibres than the aerosol-forming substrate of Example A. The aerosol-forming substrate of Example B also includes sodium carboxymethyl cellulose and glycerine.

[0190] The aerosol-forming substrate of Example C includes a combination of hydroxypropylmethyl cellulose and a cellulose based strengthening agent. In Example C, the cellulose based strengthening agent is cellulose fibres. The aerosol-forming substrate of Example C contains fewer cellulose fibres than the aerosol-forming substrate of Example A. The aerosol-forming substrate of Example C includes agar rather than sodium carboxymethyl cellulose. The aerosol-forming substrate of Example C also includes glycerine.

[0191] The aerosol-forming substrate of Example D includes a combination of hydroxypropylmethyl cellulose and two cellulose based strengthening agents. In Example D, the cellulose based strengthening agents are cellulose fibres and microcrystalline cellulose. The aerosol-forming substrate of Example D contains fewer cellulose fibres than the aerosol-forming substrate of Example A. The aerosol-forming substrate of Example D includes agar rather than sodium carboxymethyl cellulose. The aerosol-forming substrate of Example D also includes glycerine.

[0192] The aerosol-forming substrate of Example E includes a combination of hydroxypropylmethyl cellulose and a cellulose based strengthening agent. In Example E, the cellulose based strengthening agent is cellulose powder. The aerosol-forming substrate of Example E also includes sodium carboxymethyl cellulose, nicotine, glycerine and a carboxylic acid. In Example E, the carboxylic acid is lactic acid.

[0193] The effect of the components of the above Examples A, B, C and D, including the effect of the cellulose based strengthening agents, will now be shown by comparison to an example of a comparative aerosol-forming substrate. The comparative aerosol-forming substrate includes 25.53 percent by weight hydroxypropylmethyl cellulose, 6.38 percent by weight agar, and 63.81 percent by weight glycerine.

[0194] Table 2 shows a comparison of tensile strength between the five example formulations of the aerosol-forming substrate (Examples A, B, C and D), and the comparative example.

[0195] The tensile strength of the example formulations and the comparative formulation is measured by using the conventional method of stretching a given size of a test specimen of each formulation at a constant rate of elongation until it ruptures. A tensile strength testing instrument is attached to the test specimen, which provides a measure of the fracture force when the formulation ruptures. The tensile strength of a test specimen is derived from the fracture force at rupture divided by the width of the specimen.

TABLE-US-00002 TABLE 2 Comparative Example Example A B C D Tensile Strength (N/m) 421 677 1580 830 1199

[0196] As shown in Table 2, the aerosol-forming substrate of Example A provides an increase in tensile strength of 256 N/m compared to the comparative example. This is a 61% increase in tensile strength.

[0197] The aerosol-forming substrate of Example B provides an increase in tensile strength of 1159 N/m compared to the comparative example. This is a 275% increase in tensile strength.

[0198] The aerosol-forming substrate of Example C provides an increase in tensile strength of 409 N/m compared to the comparative example. This is a 97% increase in tensile strength.

[0199] The aerosol-forming substrate of Example D provides an increase in tensile strength of 778 N/m compared to the comparative example. This is a 185% increase in tensile strength.

[0200] Accordingly, the aerosol-forming substrates of Examples A, B, C and D all show large increases in tensile strength compared to the comparative example. The present inventors have found that this increase in the tensile strength of the aerosol-forming substrate may provide a number of advantages, particularly relating to the subsequent processing steps of manufacturing an aerosol-generating article that contains the aerosol-forming substrate.

[0201] For example, after an aerosol-forming substrate is made, it is typically rolled onto a bobbin. An increase in the tensile strength of the aerosol-forming substrate may reduce breakage of the aerosol-forming substrate due to tension when it is transferred to the bobbin.

[0202] The subsequent manufacturing step usually involves unwinding the aerosol-forming substrate from the bobbin, and then crimping the aerosol-forming substrate using crimping rollers. An increase in the tensile strength of the aerosol-forming substrate may reduce breakage during the crimping process.

[0203] Reduced breakage of the aerosol-forming substrate during subsequent processing steps may reduce wastage of aerosol-forming substrate during the process of manufacturing an aerosol-generating article containing the aerosol-forming substrate. In addition, if the aerosol-forming substrate breaks during the processing steps then there may be loss of manufacturing time and so increased tensile strength of the aerosol-forming substrate may improve manufacturing time.

[0204] Although the aerosol-forming substrates of Examples C and D exhibit a high increase in tensile strength, Examples C and D may cause crusting on a part of an aerosol-generating article containing the aerosol-forming substrate because they contain agar. The present inventors believe that the agar melts when it is heated (for example by an aerosol-generating device). The melted agar can form agglomerate and form around the part of the aerosol-generating article. After the aerosol-generating article stops being heated, the melted agar may then cool and solidify as a crust. This is particularly a problem with an aerosol-generating article containing a susceptor because it has been found that crusting on the susceptor reduces heat transfer from the susceptor to the aerosol-forming substrate, which may reduce the level of nicotine and the volume of aerosol delivered to a user.

[0205] The aerosol-forming substrates of Examples A and B do not contain agar. Instead, the aerosol-forming substrates of Examples A and B contain sodium carboxymethyl cellulose. The present inventors have found that an aerosol-forming substrate containing a carboxymethyl cellulose instead of agar has reduced crusting. Indeed, in some examples, the present inventors have found that using a carboxymethyl cellulose instead of agar may completely eliminate the problem of crusting. Reducing and eliminating crusting, particularly crusting on a susceptor, may lead to an increased level of nicotine being delivered to a user, and an increased volume of aerosol being generated from the aerosol-forming substrate.