Precursor for aerosol generating apparatus

Abstract

A solid aerosol precursor (6), where the solid aerosol precursor (6) comprises fine plant material particles and coarse plant material particles, the fine plant material particles having a first monomodal particle size distribution by number having a D50 particle size of from 40 to 70 µm, and the coarse plant material particles having a second monomodal particle size distribution by number having a D50 particle size of from 225 to 300 µm, where combining together the first monomodal particle size distribution and the second monomodal particle size distribution results in a bimodal particle size distribution. The consistency of the particle size, and flavour and structure of the solid aerosol precursor may be improved.

Description

FIELD

[0001] The present disclosure relates to a precursor for an aerosol generating apparatus, particularly to a solid aerosol precursor for a heat-not-burn consumable. The present disclosure also relates to: a method of preparing a solid aerosol precursor for a heat-not-burn consumable; a heat-not-burn consumable comprising such a solid aerosol precursor obtained and a use of such a solid aerosol precursor.BACKGROUND

[0002] A typical aerosol generating apparatus may comprise a power supply, an aerosol generating unit that is driven by the power supply, an aerosol precursor, which in use is aerosolised by the aerosol generating unit to generate an aerosol, and a delivery system for delivery of the aerosol to a user.

[0003] A drawback with known aerosol generating apparatuses is that, due to inconsistency of particle size of the solid components, the aerosol precursor may suffer from inconsistent texture and porosity. This in turn results in inconsistent user experience of the aerosol generating apparatus due to differences in flavour and pressure drop between products.

[0004] The present invention has been devised in light of the above considerations.SUMMARY

[0005] In a first aspect the present disclosure provides a solid aerosol precursor for a heat-not-burn (HNB) consumable.

[0006] In some examples, the solid aerosol precursor comprises fine plant material particles and coarse plant material particles. The fine plant material particles may have a first monomodal particle size distribution by number having a D50 particle size of from 40 to 70 µm, and the coarse plant material particles may have a second monomodal particle size distribution by number having a D50 particle size of from 225 to 300 µm such that combining together the first monomodal particle size distribution and the second monomodal particle size distribution results in a bimodal particle size distribution.

[0007] In other words, the solid aerosol precursor comprises plant material particles, a first portion of which are fine plant material particles and a second portion of which are coarse plant material particles. The fine plant material particles may have a first particle size distribution by number and the coarse plant material particles may have a second particle size distribution by number such that the first and second particle size distributions combine to give a total particle size distribution by number of the plant material particles. In some examples, the total particle size distribution may be bimodal with a first peak centred on the fine plant material particles and a second peak centred on the coarse plant material particles, the D50 particle size of the first particle size distribution being 40 to 70 µm and the D50 particle size of the second particle size distribution being 225 to 300 µm.

[0008] In this way, the flavour and the structure of the solid aerosol precursor may be improved. The fine plant material particles may provide the flavour of the precursor, whilst the coarse plant material particles may provide strength and structure to the precursor. An improvement in the consistency in the particle sizes may contribute to a more consistent precursor, and may contribute to improved appearance, porosity and / or injectability / extrudability of the precursor. Consequently, the user experience may be more consistent across products since there may be improved consistency of flavour delivery and pressure drop across the precursor between products.

[0009] As used herein, D-values define particle size distributions of subject particles. A particular D-value is used in combination with a respective size value and is the number of the particles of the distribution that have a particle size less than or equal to that size, expressed as a percentage of the total number of the particles of the distribution. For example, a D50 value of a given size indicates that the proportion by number of particles having a size less than or equal to this given size is 50%. Similarly, D10 indicates that the proportion by number of particles having a size less than or equal to the given size is 10%, and D90 indicates that the proportion by number of particles having a size less than or equal to the given size value is 90%.

[0010] As used herein, particle size values and particle size distributions are measured using sieve separation or differential screening performed according to the European Pharmacopoeia (Ph. Eur.) 2.9.38 (`Particle-size distribution estimation by analytical sieving'), the particle size values thus corresponding to respective sieve opening sizes. Such analysis may involve passing the plant material particles through a screen, or mesh covered screen. A particle size distribution may be determined using ISO 19430.

[0011] In some examples, the fine plant material particles have a D50 particle size of around 60 µm. In some examples, the fine plant material particles have a D50 particle size of up to about 70 µm, such as up to about 65 µm, or up to about 60 µm. In some examples, the fine plant material particles have a D50 particle size of 40 µm or more, such as 45 µm or more, such as 50 µm or more. In some examples, the D50 particle size of the fine plant material particles may be selected from a range with the upper and lower amounts selected from the values given above. In some examples, the fine plant material particles have a D50 particle size of 40 to 70 µm, such as 45 to 70 µm, such as 50 to 70 µm. In other examples, the fine plant material particles have a D50 particle size of 40 to 65 µm such as 40 to 60 µm.

[0012] In some examples, the coarse plant material particles have a D50 particle size of around 250 µm. In some examples, the coarse plant material particles have a D50 particle size of up to about 300 µm, such as up to about 280 µm, such as up to about 260 µm or up to about 250 µm. In some examples, the coarse plant material particles have a D50 particle size of 225 µm or more, such as 250 µm or more, such as 275 µm or more. In some examples, the D50 particle size of the coarse plant material particles may be selected from a range with the upper and lower amounts selected from the values given above. In some examples, the coarse plant material particles have a D50 particle size of 225 to 300 µm, such as 250 to 300 µm, such as 275 to 300 µm. In some examples, the coarse plant material particles have a D50 particle size of 225 to 280 µm, such as 225 to 260 µm, such as 225 to 250 µm.

[0013] In some examples, the fine plant material particles have a D10 particle size of around 30 µm. In some examples, the fine plant material particles have a D10 particle size of up to about 35 µm, such as up to about 33 µm, such as up to about 30 µm. In some examples, the fine plant material particles have a D10 particle size of 20 µm or more, such as 25 µm or more, such as 28 µm or more. In some examples, the D10 particle size of the fine plant material particles may be selected from a range with the upper and lower amounts selected from the values given above. In some examples, the fine plant material particles have a D10 particle size of 20 to 35 µm, such as 28 to 35 µm, such as 25 to 35 µm. In some examples, the fine plant material particles have a D10 particle size of 20 to 33 µm, such as 20 to 30 µm.

[0014] In some examples, the coarse plant material particles have a D10 particle size of around 200 µm. In some examples, the coarse plant material particles have a D10 particle size of up to about 220 µm, such as up to about 215 µm. In some examples, the coarse plant material particles have a D10 particle size of 100 µm or more, such as 110 µm or more, such as 150 µm. In some examples, the D10 particle size of the coarse plant material particles may be selected from a range with the upper and lower amounts selected from various given above. In some examples, the coarse plant material particles have a D10 particle size of 100 to 220 µm, such as 110 to 220 µm, such as 150 to 220 µm. In some examples, the coarse plant material particles have a D10 particle size of 100 to 215 µm, such as 100 to 200 µm.

[0015] In some examples, the fine plant material particles have a D90 particle size of around 90 µm. In some examples, the fine plant material particles have a D90 particle size of up to about 100 µm, such as up to 95 µm or up to 90 µm. In some examples, the fine plant material particles have a D90 particle size of 75 µm or more, such as 80 µm or more or 90 µm or more. In some examples, the D90 particle size of the fine plant material particles may be selected from a range with the upper and lower amounts selected from various given above. In some examples, the fine plant material particles have a D90 particle size of 80 to 95 µm, such as 85 to 95 µm.

[0016] In some examples, the coarse plant material particles have a D90 particle size of around 350 µm. In some examples, the coarse plant material particles have a D90 particle size up to about 400 µm, such as up to 380 µm or up to 370 µm. In some examples, the coarse plant material particles have a D90 particle size of 325 µm or more, such as 330 µm or more, or 335 µm or more. In some examples, the D90 particle size of the coarse plant material particles may be selected from a range with the upper and lower amounts selected from various given above. In some examples, the coarse plant material particles may have a D90 particle size of 325 to 400 µm, such as 330 to 400 µm.

[0017] In some examples, the difference between the D90 and D10 particle size of the fine plant material particles is less than 60 µm, such as less than 50 µm. In some examples, the difference between the D90 and D10 particle size of the coarse plant material particles is less than 150 µm, such as less than 100 µm, such as less than 60 µm.

[0018] In some examples, the spread of the particle size distribution of the fine plant material particles and / or the coarse plant material particles is 2 or less, such as 1.5 or less, such as 1 or less or 0.5 or less. The spread of the particle size distribution is defined by the relationship (D90-D10) / D50.

[0019] A narrow particle size distribution may reduce the inconsistency of particle size, particularly within the modes (i.e., within the fine plant material particles and within the coarse plant material particles). This may allow for improved properties of the precursor, for example more consistent pressure drop and flavour delivery between products, which may result in enhanced user experience. Additionally, more consistency in particle size may result in less variation in water content in the precursor, since the amount of water absorbed by the plant material particles may depend at least partially on the surface area to volume ratio of the particles. More consistent water content absorbed by the plant material particles may allow for other parts of the manufacturing process to be improved. For example, the drying time of the precursor may be more consistent between products. It may also allow water content of the final product to be more closely controlled, resulting in better shelf life and storage time of the products.

[0020] In particular, it has been found that providing a narrow particle size distribution of tea particles within the modes (i.e., within the fine tea particles and within the coarse tea particles) is beneficial for consistency in pressure drop and flavour delivery between products, provides less variation in water content in the precursor, more consistent drying time and better control of water content in the final product, resulting in better shelf life and storage time of the products.

[0021] In some examples, the plant material particles may comprise non-tobacco plant material particles. In some examples, non-tobacco plant material particles are particles substantially free of tobacco solids. In other words, the non-tobacco particles are derived from a plant material other than tobacco. The non-tobacco particles may comprise a non-tobacco plant material and a tobacco extract, such as nicotine.

[0022] In some examples, the non-tobacco plant material is tea, cotton, paper, maize, oat, tomato, barley, rye, sugarbeet, buckwheat, wheat, pea, potato, apple, cocoa, bamboo, citrus, cellulose or any combination thereof. In some examples, the non-tobacco plant material particles are tea particles, cotton particles, paper particles, maize fibres, oat fibres, tomato fibres, barley fibres, rye fibres, sugarbeet fibres, buck wheat fibres, wheat fibres, pea fibres, potato fibres, apple fibres, cocoa fibres, bamboo fibres, citrus fibres, cellulose particles or any combination thereof. In some examples, the plant material particles comprise a combination of non-tobacco plant material particles as described herein. That is, in some examples, the plant material particles comprise more than one type of non-tobacco plant material particles.

[0023] In some examples, the non-tobacco plant material is tea, cotton, wheat, bamboo, cellulose or any combination thereof. In some examples, the non-tobacco plant material is tea and another non-tobacco plant material as described herein. In some examples, the non-tobacco plant material particles are tea particles and another non-tobacco plant material particle as described herein. In some examples, the non-tobacco plant material is tea and / or cellulose. In some examples, the non-tobacco plant material is tea. In some examples the cellulose is microcrystalline cellulose. In some examples, the non-tobacco plant material particles are tea particles and cellulose particles.

[0024] In some examples, the solid aerosol precursor is substantially free of tobacco particles. In some examples, substantially free indicates that the solid aerosol precursor comprises no dry mass tobacco in accordance with regulatory standards. As used herein, dry mass tobacco may not encompass tobacco extract or tobacco essence (e.g., nicotine).

[0025] In some examples, the solid aerosol precursor comprises up to about 60 weight% (wt%) non-tobacco plant material particles relative to the total weight of the solid aerosol precursor. In some examples, the solid aerosol precursor comprises up to about 55 wt% non-tobacco plant material particles, or up to about 50 wt% non-tobacco plant material particles relative to the total weight of the solid aerosol precursor. In some examples, the solid aerosol precursor comprises about 40 wt% or more non-tobacco plant material particles, such as about 45 wt% or more non-tobacco plant material particles, such as about 50 wt% or more non-tobacco plant material particles relative to the total weight of the solid aerosol precursor.

[0026] In some examples, the solid aerosol precursor comprises an amount of non-tobacco plant material particles selected from a range with the upper and lower amounts selected from the values given above. In some examples, the solid aerosol precursor comprises 40 to 60 wt% non-tobacco plant material particles, such as 50 to 60 wt% non-tobacco plant material particles, such as 55 to 60 wt% non-tobacco plant material particles relative to the total weight of the solid aerosol precursor. In other examples, the solid aerosol precursor comprises 40 to 50 wt% non-tobacco plant material particles relative to the total weight of the solid aerosol precursor. In some examples, the solid aerosol precursor up to and including 60 wt% non-tobacco plant material particles relative to the total weight of the solid aerosol precursor.

[0027] In some examples, the plant material particles are tea particles. In some examples, the tea particles may comprise oolong tea. In other examples, the tea particles may comprise green tea. In some examples, the tea particles may comprise black tea. In some examples, the tea particles may comprise a mixture of two or three of oolong tea, green tea, and black tea.

[0028] In some examples, the coarse tea particles may comprise tea fibres.

[0029] In some examples, the solid aerosol precursor further comprises additional cellulose particles. That is, in some examples, the solid aerosol precursor comprises coarse plant material particles, fine plant material particles and cellulose particles. In some examples, the solid aerosol precursor comprises coarse tea particles, fine tea particles and cellulose particles.

[0030] In some examples, the cellulose particles have a D50 particle size of around 60 µm. In some examples, the cellulose particles have a D50 particle size of up to about 70 µm, such as up to about 65 µm, or up to about 60 µm. In some examples, the cellulose particles have a D50 particle size of 40 µm or more, such as 45 µm or more, such as 50 µm or more. In some examples, the D50 particle size of the cellulose particles may be selected from a range with the upper and lower amounts selected from the values given above. In some examples, the cellulose particles have a D50 particle size of 40 to 70 µm, such as 45 to 70 µm, such as 50 to 70 µm. In other examples, the cellulose particles have a D50 particle size of 40 to 65 µm such as 40 to 60 µm.

[0031] When the solid aerosol precursor comprises tea particles and additional cellulose particles, the solid aerosol precursor may comprise 20 to 25 wt% cellulose particles and 20 to 25 wt% tea particles relative to the total weight of the solid aerosol precursor. In some examples, the solid aerosol precursor comprises up to about 25 wt% cellulose particles, such as up to about 24 wt% cellulose particles, such as up to about 23 wt% cellulose particles relative to the total weight of the solid aerosol precursor. In some examples, the solid aerosol precursor comprises about 20 wt% or more cellulose particles, such as about 21 wt% or more, such as about 22 wt% or more relative to the total weight of the solid aerosol precursor. In some examples, the solid aerosol precursor comprises cellulose particles selected from a range with the upper and lower amounts selected from the values given above. In some examples, the solid aerosol precursor comprises up to about 25 wt% tea particles, such as up to about 24 wt% tea particles, such as up to about 23 wt% tea particles relative to the total weight of the solid aerosol precursor. In some examples, the solid aerosol precursor comprises about 20 wt% or more tea particles, such as about 21 wt% or more, such as about 22 wt% or more relative to the total weight of the solid aerosol precursor. In some examples, the solid aerosol precursor comprises an amount of tea particles selected from a range with the upper and lower amounts selected from the values given above.

[0032] In some examples, the amounts of plant material particles and additional cellulose particles in the solid aerosol precursor are equal. In other examples, the amounts of plant material particles and additional cellulose particles in the solid aerosol precursor are not equal. For example, the amounts tea particles and additional cellulose particles in the solid aerosol precursor may be equal. In other examples, the amounts of cellulose particles and tea particles in the solid aerosol precursor may not be equal.

[0033] In some examples, the solid aerosol precursor comprises a flavourant, such as tobacco extract or other plant extracts. The flavourant may provide flavour and / or odour to the solid aerosol precursor. In some examples, the solid aerosol precursor comprises a tobacco extract. In some examples, the solid aerosol precursor comprises other plant extracts such as fig, maple, or acer saccharum extract. In some examples, the solid aerosol precursor comprises up to about 40 weight (wt%) flavourant, such as up to about 35 wt% flavourant, such as up to about 30 wt% flavourant relative to the total weight of the solid aerosol precursor. In some examples, the solid aerosol precursor comprises about 20 wt% or more flavourant, such as about 25 wt% or more flavourant, such as about 30 wt% or more flavourant relative to the total weight of the solid aerosol precursor. In some examples, the solid aerosol precursor comprises an amount of flavourant selected from a range with the upper and lower amounts selected from the values given above. In some examples, the solid aerosol precursor comprises 20 to 40 wt% flavourant, such as 25 to 40 wt%, such as 30 to 40 wt%, such as 35 to 40 wt% relative to the total weight of the solid aerosol precursor. In some examples, the solid aerosol precursor comprises up to and including 40 wt% flavourant relative to the total weight of the solid aerosol precursor.

[0034] In some examples, the solid aerosol precursor comprises a humectant. In some examples, the humectant may comprise propylene glycol (PG) and / or glycerol (VG). In some examples, the amount of humectant present in the solid aerosol precursor is up to about 30 weight% (wt%), such as up to about 25 wt%, such as up to about 20 wt% relative to the total weight of the solid aerosol precursor. In some examples, the amount of humectant present in the solid aerosol precursor is about 20 wt% or more, such as about 25 wt% or more, such as about 30 wt% or more relative to the total weight of the solid aerosol precursor. In some examples, the solid aerosol precursor comprises an amount of humectant selected from a range with the upper and lower amounts selected from the values given above. In some examples, the amount of humectant present in the solid aerosol precursor is about 20 to 30 wt%, such as 25 to 30 wt%, such as up to and including 30 wt% relative to the total weight of the solid aerosol precursor.

[0035] In some examples, the solid aerosol precursor comprises a binding agent which may act as a thickening agent, or a thickening agent. In some examples, the binding and / or thickening agent is selected from one or more of microcrystalline cellulose (MCC), Konjac Mannan, carrageenan, starches such as corn starch, gelatine, pectin, gums such as guar or xanthan gum, or alginates. In some examples, the binding and / or thickening agent is Konjac Mannan. In some examples, the binding and / or thickening agent is a water-independent thickening agent. A water-independent binding and / or thickening agent may be a thickening agent which does not require water for activation. In some examples, the solid aerosol precursor comprises up to about 5 weight% (wt%) binding and / or thickening agent, such as up to about 4 wt% binding and / or thickening agent, such as up to about 3 wt% binding and / or thickening agent relative to the total weight of the solid aerosol precursor. In some examples, the solid aerosol precursor comprises about 1 wt% or more binding and / or thickening agent, such as about 2 wt% or more binding and / or thickening agent, such as about 3 wt% or more binding and / or thickening agent relative to the total weight of the solid aerosol precursor. In some examples, the solid aerosol precursor comprises an amount of binding and / or thickening agent selected from a range with the upper and lower amounts selected from the values given above. In some examples, the solid aerosol precursor comprises 1 to 5 wt% binding and / or thickening agent, such as 2 to 5%, such as 3 to 5% relative to the total weight of the solid aerosol precursor. In some examples, the solid aerosol precursor comprises up to and including 5 wt% binding and / or thickening agent relative to the total weight of the solid aerosol precursor.

[0036] In some examples, the solid aerosol precursor comprises a solvent. In some examples the solvent is aqueous. In some examples, the amount of solvent present in the solid aerosol precursor is up to about 75 weight% (wt%), such as up to about 60 wt%, such as up to about 50 wt% relative to the total weight of the solid aerosol precursor. In some examples, the amount of solvent present in the solid aerosol precursor is up to about 45 wt%, such as up to about 40 wt% relative to the total weight of the solid aerosol precursor. In some examples, the amount of solvent present in the solid aerosol precursor is about 5 wt% or more, such as 10 wt% or more, such as 20 wt% or more, such as 30 wt% or more relative to the total weight of the solid aerosol precursor. In some examples, the amount of solvent present in the solid aerosol precursor may be selected from a range with the upper and lower amounts selected from the values given above. In some examples, the amount of solvent present in the solid aerosol precursor is around 20 to 50 wt%, such as 20 to 45 wt%, such as 20 to 40 wt% relative to the total weight of the solid aerosol precursor. In some examples, the amount of solvent present in the solid aerosol precursor is around 25 to 50 wt%, such as 30 to 50 wt% relative to the total weight of the solid aerosol precursor.

[0037] In some examples, the amount of water (as the solvent) present in the solid aerosol precursor is up to about 75 weight% (wt%), such as up to about 60 wt%, such as up to about 50 wt% relative to the total weight of the solid aerosol precursor. In some examples, the amount of water present in the solid aerosol precursor is up to about 45 wt%, such as up to about 40 wt% relative to the total weight of the solid aerosol precursor. In some examples, the amount of water present in the solid aerosol precursor is about 5 wt% or more, such as 10 wt% or more, such as 15 wt% or more, such as 20 wt% or more, such as 30 wt% or more relative to the total weight of the solid aerosol precursor. In some examples, the amount of water present in the solid aerosol precursor may be selected from a range with the upper and lower amounts selected from the values given above. In some examples, the amount of water present in the solid aerosol precursor is around 20 to 50 wt%, such as 20 to 45 wt%, such as 20 to 40 wt% relative to the total weight of the solid aerosol precursor. In some examples, the amount of water present in the solid aerosol precursor is around 25 to 50 wt%, such as 30 to 50 wt% relative to the total weight of the solid aerosol precursor. In some examples, the amount of water present in the solid aerosol precursor is up to and including 20 wt% relative to the total weight of the solid aerosol precursor. In other examples, the amount of water present in the solid aerosol precursor is less than 10 wt% relative to the total weight of the solid aerosol precursor.

[0038] When the solvent content (for example, water content) is less than 10 wt% relative to the total weight of the solid aerosol precursor, this may require a higher amount of other wet ingredients in the solid aerosol precursor, such as an increased amount of humectant. A low solvent content may increase viscosity which is advantageous when the solid aerosol precursor is formed by extrusion.

[0039] In some examples, the solid aerosol precursor has a composition comprising binding agent, tea particles, humectant, tobacco extract, flavourants and solvent. In some examples, the solid aerosol precursor has a composition comprising cellulose, binding agent, tea particles, humectant, tobacco extract, flavourants and solvent. In some examples, the solid aerosol precursor has a composition comprising microcrystalline cellulose, Konjac Mannan, oolong and green tea particles, propylene glycol, glycerol, tobacco extract, flavourants and water.

[0040] In some examples, the solid aerosol precursor has a composition according to Table 1. Table 1Component Weight% (wt%) relative to the total weight of the solid aerosol precursor Cellulose20-25Konjac Mannan1-5Tea (oolong and green)20-25Glycerol18-30Propylene glycol0-5Tobacco extract10-25Flavourants10-15Solvent20-50

[0041] In this example, the tea component has the particle size distribution described herein.

[0042] In some examples, the solid aerosol precursor is formed or is formable by injection moulding. In this way, the solid aerosol precursor may be easily inserted into supports structures, such as card tubes, during manufacture of the heat-not-burn consumable.

[0043] In some examples, the solid aerosol precursor is formed or is formable by extrusion. Advantageously, extrusion may allow for a low or more consistent water content of the solid aerosol precursor, particularly at the point of manufacture. Extrusion may also result in better process control and may allow for continuous production. Continuous production may be beneficial as it may have the advantages of high speed and large-scale manufacturing. Material waste, costs and lead times may also be reduced. Further beneficially, extrusion may result in a solid aerosol precursor which can be portioned, cut, wrapped and assembled with minimal handling and increased automation.

[0044] In a second aspect the present disclosure provides a method of preparing a solid aerosol precursor for a heat-not-burn consumable.

[0045] In some examples, the method comprises the steps of: i) providing milled plant material; ii) separating fine plant material particles from the milled plant material, the fine plant material particles having a first monomodal particle size distribution having a D50 particle size of from 40 to 70 µm; iii) separating coarse plant material particles from the milled plant material, the coarse plant material particles having a second monomodal particle size distribution having a D50 particle size of from 225 to 300 µm ; and iv) combining the fine plant material particles and the coarse plant material particles to obtain a solid aerosol precursor.

[0046] In some examples, step i) comprises providing milled non-tobacco plant material, for example step i) may comprise providing milled tea leaves. In these examples, step ii) may comprise separating fine tea particles from the milled tea leaves and step iii) may comprise separating coarse tea particles from the milled tea leaves. In these examples, step iv) may comprise combining the fine tea particles and the coarse tea particles to obtain a solid aerosol precursor.

[0047] In some examples, separating the fine plant material particles and / or separating the coarse plant material particles comprises separating by sieve separation.

[0048] In some examples, sieve separation comprises the steps of: a) sieving milled plant material with a small pore screen such that a first passed fraction of plant material particles pass through the small pore screen and a first non-passed fraction of plant material particles do not pass through the small pore screen; b) sieving the first non-passed fraction of plant material particles with a large pore screen such that a second passed fraction of plant material particles pass through the large pore screen and a second non-passed fraction of plant material particles do not pass through the large pore screen; and c) collecting the second passed fraction of plant material particles with the desired particle size distribution.

[0049] In other examples, sieve separation comprises the steps of: a) sieving milled plant material with a large pore screen such that a first passed fraction of plant material particles pass through the large pore screen and a first non-passed fraction of plant material particles do not pass through the large pore screen; b) sieving the first passed fraction of plant material particles with a small pore screen such that a second passed fraction of plant material particles pass through the small pore screen and a second non-passed fraction of plant material particles do not pass through the small pore screen; and c) collecting the second non-passed fraction of plant material particles with the desired particle size distribution.

[0050] In this way, a fraction of plant material particles with a desired particle distribution may be obtained. A small pore screen, which in some examples may be a high mesh screen, may refer to a screen with finer holes than the large pore screen. A large pore screen, which in some examples may be a low mesh screen, may refer to a screen with larger holes than the small pore screen. In some examples, the above-mentioned method steps may be carried out for each mode (fine and coarse) of plant material particles in order to achieve fractions of plant material particles with the desired particle distributions. Sieve separation or differential screening of the plant material may allow for a narrower particle size distribution, such as less variation in the particle size, within each mode of plant material particle. A narrower particle size distribution within each mode of plant material particle may give more consistency in particle size. Greater consistency in particle size of the plant material particles may contribute to enhanced user experience, for example improved flavour deliver and more consistent pressure drop across the precursor during use.

[0051] In some examples, the method comprises milling plant material to achieve a target particle size before carrying out sieve analysis. In some examples, the milling process is a quantitative milling process. In some examples, the quantitative milling process comprises setting a milling time and / or milling speed to achieve a target particle size. In some examples, the quantitative milling process comprises the use of a feedback system to achieve the target particle size. In some examples, the feedback system involves taking samples of the plant material during milling, determining the particle size of the plant material, and adjusting the milling time or milling speed in order to reach a target particle size. A quantitative milling process may provide more consistency in particle size compared with a qualitative milling process. Greater consistency in particle size of the plant material particles may contribute to enhanced user experience, for example improved flavour delivery and more consistent pressure drop across the precursor during use.

[0052] In some examples, the method may comprise a further milling step after collection of the second passed fraction of plant material particles. In some examples, optionally after further milling, the plant material particles may be subjected to steps a) to c) again in order to obtain a fraction of plant material particles with the desired particle size. That is, in some examples, steps a) to c) are repeated until a fraction of plant material particles with a desired particle size and / or particle distribution is achieved.

[0053] In some examples, milling the plant material and passing the resultant plant material particles through the relevant screen may be carried out in a continuous process. That is, milling and screening may be carried out by a single milling machine which comprises a screen. In some examples, the mill is a hammer mill or a ball mill. In other examples, milling and screening of the plant material and plant material particles are carried out separately.

[0054] In some examples, the heat-not-burn consumable prepared by the method of the second aspect may be the heat-not-burn consumable of the first aspect. That is, the considerations as described above in relation to the first aspect also apply to the second aspect.

[0055] In a third aspect the present disclosure provides a heat-not-burn consumable comprising a solid aerosol precursor of the first aspect or made by the method of the second aspect and a mouthpiece downstream of the solid aerosol precursor.

[0056] In a fourth aspect the present disclosure provides a use of a solid aerosol precursor of the first aspect or made by the method of the second aspect in increasing consistency of user experience with a heat-not-burn consumable.

[0057] The consistency of the user experience may be increased by one or more of the following. In some examples, the consistency of user experience may be increased by providing a more consistent pressure drop across the precursor during use. This may be achieved through the bimodal distribution of fine and course plant material particles providing more consistent porosity of the precursor. In some examples, the consistency of user experience may be increased by improving the consistency of flavour delivery as a result of the bimodal particle distribution. The fine plant material particles may provide the flavour to the solid aerosol precursor whilst the coarse particles may provide strength and / or structure. In some examples, the consistency of user experience may be increased through the control of the water content in the final precursor, which may result in better shelf life and storage time.

[0058] The preceding summary is provided for purposes of summarizing some examples to provide a basic understanding of aspects of the subject matter described herein. Accordingly, the above-described features should not be construed to narrow the scope or spirit of the subject matter described herein in any way. Moreover, the above and / or proceeding examples may be combined in any suitable combination to provide further examples, except where such a combination is clearly impermissible or expressly avoided. Other features, aspects, and advantages of the subject matter described herein will become apparent from the following text and the accompanying drawings.BRIEF DESCRIPTION OF THE FIGURES

[0059] Aspects, features and advantages of the present disclosure will become apparent from the following description of examples in reference to the appended drawings in which like numerals denote like elements. Fig. 1 is a block system diagram showing an example aerosol generating apparatus. Fig. 2 is a block system diagram showing an example implementation of the apparatus of Fig. 1, where the aerosol generating apparatus is configured to generate aerosol from a solid aerosol precursor. Fig. 3 is a schematic diagram showing an example implementation of the apparatus of Fig. 2. Fig. 4 is a graph illustrating the bimodal particle size distribution of the plant material particles of the solid aerosol precursor. Fig. 5 is a flow diagram representing some of the steps of a method of preparing a solid aerosol precursor for a consumable of the example apparatus of Fig. 2. DETAILED DESCRIPTION OF EMBODIMENTS

[0060] Before describing several examples implementing the present disclosure, it is to be understood that the present disclosure is not limited by specific construction details or process steps set forth in the following description and accompanying drawings. Rather, it will be apparent to those skilled in the art having the benefit of the present disclosure that the systems, apparatuses and / or methods described herein could be embodied differently and / or be practiced or carried out in various alternative ways.

[0061] Unless otherwise defined herein, scientific and technical terms used in connection with the presently disclosed inventive concept(s) shall have the meanings that are commonly understood by those of ordinary skill in the art, and known techniques and procedures may be performed according to conventional methods well known in the art and as described in various general and more specific references that may be cited and discussed in the present specification.

[0062] Any patents, published patent applications, and non-patent publications mentioned in the specification are hereby incorporated by reference in their entirety.

[0063] All examples implementing the present disclosure can be made and executed without undue experimentation in light of the present disclosure. While particular examples have been described, it will be apparent to those of skill in the art that variations may be applied to the systems, apparatus, and / or methods and in the steps or in the sequence of steps of the methods described herein without departing from the concept, spirit, and scope of the inventive concept(s). All such similar substitutions and modifications apparent to those skilled in the art are deemed to be within the spirit, scope, and concept of the inventive concept(s) as defined by the appended claims.

[0064] The use of the term "a" or "an" in the claims and / or the specification may mean "one," as well as "one or more," "at least one," and "one or more than one." As such, the terms "a," "an," and "the," as well as all singular terms, include plural referents unless the context clearly indicates otherwise. Likewise, plural terms shall include the singular unless otherwise required by context.

[0065] The use of the term "or" in the present disclosure (including the claims) is used to mean an inclusive "and / or" unless explicitly indicated to refer to alternatives only or unless the alternatives are mutually exclusive. For example, a condition "A or B" is satisfied by any of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

[0066] As used in this specification and claim(s), the words "comprising, "having," "including," or "containing" (and any forms thereof, such as "comprise" and "comprises," "have" and "has," "includes" and "include," or "contains" and "contain," respectively) are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

[0067] Unless otherwise explicitly stated as incompatible, or the physics or otherwise of the embodiments, examples, or claims prevent such a combination, the features of examples disclosed herein, and of the claims, may be integrated together in any suitable arrangement, especially ones where there is a beneficial effect in doing so. This is not limited to only any specified benefit, and instead may arise from an "ex post facto" benefit. This is to say that the combination of features is not limited by the described forms, particularly the form (e.g. numbering) of example(s), embodiment(s), or dependency of claim(s). Moreover, this also applies to the phrase "in one embodiment," "according to an embodiment," and the like, which are merely a stylistic form of wording and are not to be construed as limiting the following features to a separate embodiment to all other instances of the same or similar wording. This is to say, a reference to 'an,' 'one,' or 'some' embodiment(s) may be a reference to any one or more, and / or all embodiments, or combination(s) thereof, disclosed. Also, similarly, the reference to "the" embodiment may not be limited to the immediately preceding embodiment. Further, all references to one or more embodiments or examples are to be construed as non-limiting to the claims.

[0068] The present disclosure may be better understood in view of the following explanations, wherein the terms used that are separated by "or" may be used interchangeably: As used herein, an "aerosol generating apparatus" (or "electronic(e)-cigarette") may be an apparatus configured to deliver an aerosol to a user for inhalation by the user. The apparatus may additionally / alternatively be referred to as a "smoking substitute apparatus", if it is intended to be used instead of a conventional combustible smoking article. As used herein a combustible "smoking article" may refer to a cigarette, cigar, pipe or other article, that produces smoke (an aerosol comprising solid particulates and gas) via heating above the thermal decomposition temperature (typically by combustion and / or pyrolysis). An aerosol generated by the apparatus may comprise an aerosol with particle sizes of 0.2 - 7 microns, or less than 10 microns, or less than 7 microns. This particle size may be achieved by control of one or more of: heater temperature; cooling rate as the vapour condenses to an aerosol; flow properties including turbulence and velocity. The generation of aerosol by the aerosol generating apparatus may be controlled by an input device. The input device may be configured to be user-activated, and may for example include or take the form of an actuator (e.g. actuation button) and / or an airflow sensor.

[0069] Each occurrence of the aerosol generating apparatus being caused to generate aerosol for a period of time (which may be variable) may be referred to as an "activation" of the aerosol generating apparatus. The aerosol generating apparatus may be arranged to allow an amount of aerosol delivered to a user to be varied per activation (as opposed to delivering a fixed dose of aerosol), e.g. by activating an aerosol generating unit of the apparatus for a variable amount of time, e.g. based on the strength / duration of a draw of a user through a flow path of the apparatus (to replicate an effect of smoking a conventional combustible smoking article).

[0070] The aerosol generating apparatus may be portable. As used herein, the term "portable" may refer to the apparatus being for use when held by a user.

[0071] As used herein, an "aerosol" may include a suspension of precursor, including as one or more of: solid particles; liquid droplets; gas. Said suspension may be in a gas including air. An aerosol herein may generally refer to / include a vapour. An aerosol may include one or more components of the precursor.

[0072] As used herein, a "precursor" may include one or more of a: liquid; solid; gel; loose leaf material; other substance. The precursor may be processed by an aerosol generating unit of an aerosol generating apparatus to generate an aerosol. The precursor may include one or more of: an active component; a carrier; a flavouring. The active component may include one or more of nicotine; caffeine; a cannabidiol oil; a non-pharmaceutical formulation, e.g. a formulation which is not for treatment of a disease or physiological malfunction of the human body. The active component may be carried by the carrier, which may be a liquid, including propylene glycol and / or glycerine. The term "flavouring" may refer to a component that provides a taste and / or a smell to the user. The flavouring may include one or more of: Ethylvanillin (vanilla); menthol, Isoamyl acetate (banana oil); or other. The precursor may include a substrate, e.g. reconstituted tobacco to carry one or more of the active component; a carrier; a flavouring.

[0073] As used herein, a "storage portion" may be a portion of the apparatus adapted to store the precursor. It may be implemented as a carrier for solid material.

[0074] As used herein, a "flow path" may refer to a path or enclosed passageway through an aerosol generating apparatus, e.g. for delivery of an aerosol to a user. The flow path may be arranged to receive aerosol from an aerosol generating unit. When referring to the flow path, upstream and downstream may be defined in respect of a direction of flow in the flow path, e.g. with an outlet being downstream of an inlet.

[0075] As used herein, a "delivery system" may be a system operative to deliver an aerosol to a user. The delivery system may include a mouthpiece and a flow path.

[0076] As used herein, a "flow" may refer to a flow in a flow path. A flow may include aerosol generated from the precursor. The flow may include air, which may be induced into the flow path via a puff by a user.

[0077] As used herein, a "puff" (or "inhale" or "draw") by a user may refer to expansion of lungs and / or oral cavity of a user to create a pressure reduction that induces flow through the flow path.

[0078] As used herein, an "aerosol generating unit" may refer to a device configured to generate an aerosol from a precursor. The aerosol generating unit may include a unit to generate a vapour directly from the precursor (e.g. a heating system or other system) or an aerosol directly from the precursor (e.g. an atomiser including an ultrasonic system, a flow expansion system operative to carry droplets of the precursor in the flow without using electrical energy or other system). A plurality of aerosol generating units to generate a plurality of aerosols (for example, from a plurality of different aerosol precursors) may be present in an aerosol generating apparatus.

[0079] As used herein, a "heating system" may refer to an arrangement of at least one heating element, which is operable to aerosolise a precursor once heated. The at least one heating element may be electrically resistive to produce heat from the flow of electrical current therethrough. The at least one heating element may be arranged as a susceptor to produce heat when penetrated by an alternating magnetic field. The heating system may be configured to heat a precursor to below 300 or 350 degrees C, including without combustion.

[0080] As used herein, a "consumable" may refer to a unit that includes a precursor. The consumable may include an aerosol generating unit, e.g. it may be arranged as a cartomizer. The consumable may include a mouthpiece. The consumable may include an information carrying medium. With liquid or gel implementations of the precursor, e.g. an e-liquid, the consumable may be referred to as a "capsule" or a "pod" or an "e-liquid consumable". The capsule / pod may include a storage portion, e.g. a reservoir or tank, for storage of the precursor. With solid material implementations of the precursor, e.g. tobacco or reconstituted tobacco formulation, the consumable may be referred to as a "stick" or "package" or "heat-not-burn consumable". In a heat-not-burn consumable, the mouthpiece may be implemented as a filter and the consumable may be arranged to carry the precursor. The consumable may be implemented as a dosage or pre-portioned amount of material, including a loose-leaf product.

[0081] As used herein, an "information carrying medium" may include one or more arrangements for storage of information on any suitable medium. Examples include: a computer readable medium; a Radio Frequency Identification (RFID) transponder; codes encoding information, such as optical (e.g. a bar code or QR code) or mechanically read codes (e.g. a configuration of the absence or presents of cutouts to encode a bit, through which pins or a reader may be inserted).

[0082] As used herein "heat-not-burn" (or "HNB" or "heated precursor") may refer to the heating of a precursor, typically tobacco, without combustion, or without substantial combustion (i.e. localised combustion may be experienced of limited portions of the precursor, including of less than 5% of the total volume).

[0083] As used herein "solid" refers to a state of matter. It may distinguish from liquid forms such as slurries or solutions, and gaseous forms. Semi-solid forms, such as gels or pastes, may be encompassed by "solid".

[0084] As used herein "slurry" refers to a suspension of solid particles in liquid. It may distinguish from a solution, which has dissolved solute rather than suspended particles.

[0085] As used herein "water-independent binding and / or thickening agent" may refer to a binding and / or thickening agent which does not require water for activation. That is, the presence of water may not be required for the binding and / or thickening agent to increase the viscosity.

[0086] Referring to Fig. 1, an example aerosol generating apparatus 1 includes a power supply 2, for supply of electrical energy. The apparatus 1 includes an aerosol generating unit 4 that is driven by the power supply 2. The power supply 2 may include an electric power supply in the form of a battery and / or an electrical connection to an external power source. The apparatus 1 includes a precursor 6, which in use is aerosolised by the aerosol generating unit 4 to generate an aerosol. The apparatus 2 includes a delivery system 8 for delivery of the aerosol to a user.

[0087] Electrical circuitry (not shown in figure 1) may be implemented to control the interoperability of the power supply 4 and aerosol generating unit 6.

[0088] In variant examples, which are not illustrated, the power supply 2 may be omitted since, e.g. an aerosol generating unit implemented as an atomiser with flow expansion may not require a power supply.

[0089] Fig. 2 shows an implementation of the apparatus 1 of Fig. 1, where the aerosol generating apparatus 1 is configured to generate aerosol by a-heat not-burn process.

[0090] In this example, the apparatus 1 includes a device body 50 and a consumable 70.

[0091] In this example, the body 50 includes the power supply 4 and a heating system 52. The heating system 54 includes at least one heating element 54. The body may additionally include any one or more of electrical circuitry 56, a memory 58, a wireless interface 60, one or more other components 62.

[0092] The electrical circuitry 56 may include a processing resource for controlling one or more operations of the body 50, e.g. based on instructions stored in the memory 58.

[0093] The wireless interface 60 may be configured to communicate wirelessly with an external (e.g. mobile) device, e.g. via Bluetooth.

[0094] The other component(s) 62 may include an actuator, one or more user interface devices configured to convey information to a user and / or a charging port, for example (see e.g. Fig. 3).

[0095] The body 50 is configured to engage with the consumable 70 such that the at least one heating element 54 of the heating system 52 penetrates into the solid aerosol precursor 6 of the consumable. In use, a user may activate the aerosol generating apparatus 1 to cause the heating system 52 of the body 50 to cause the at least one heating element 54 to heat the solid aerosol precursor 6 of the consumable (without combusting it) by conductive heat transfer, to generate an aerosol which is inhaled by the user.

[0096] Fig. 3 shows an example implementation of the aerosol generating device 1 of Fig. 2.

[0097] As depicted in Fig. 3, the consumable 70 is implemented as a stick, which is engaged with the body 50 by inserting the stick into an aperture at a top end 53 of the body 50, which causes the at least one heating element 54 of the heating system 52 to penetrate into the solid aerosol precursor 6.

[0098] The consumable 70 includes the solid aerosol precursor 6 proximal to the body 50, and a filter distal to the body 50. The filter serves as the mouthpiece of the consumable 70 and thus the apparatus 1 as a whole. The solid aerosol precursor 6 may be a reconstituted tobacco formulation. The solid aerosol precursor typically comprises fine plant material particles and coarse plant material particles. For example, the solid aerosol precursor may include cellulose particles (20-25 wt.%), Konjac Mannan (1-5 wt.%), Tea (oolong and green, at 20-25 wt.%), glycerol (18-30 wt.%), Propylene glycol (0-5 wt.%), Tobacco extract (10-25 wt.%), Flavourants (10-15 wt.%) and Solvent (20-50 wt.%).

[0099] In this example, the at least one heating element 54 is a rod-shaped element with a circular transverse profile. Other heating element shapes are possible, e.g. the at least one heating element may be blade-shaped (with a rectangular transverse profile) or tube-shaped (e.g. with a hollow transverse profile).

[0100] In this example, the body 50 includes a cap 51. In use the cap 51 is engaged at a top end 53 of the body 50. Although not apparent from Fig. 5, the cap 51 is moveable relative to the body 50. In particular, the cap 51 is slidable and can slide along a longitudinal axis of the body 50.

[0101] The body 50 also includes an actuator 55 on an outer surface of the body 50. In this example, the actuator 55 has the form of a button.

[0102] The body 50 also includes a user interface device configured to convey information to a user. Here, the user interface device is implemented as a plurality of lights 57, which may e.g. be configured to illuminate when the apparatus 1 is activated and / or to indicate a charging state of the power supply 4. Other user interface devices are possible, e.g. to convey information haptically or audibly to a user. The body may also include an airflow sensor which detects airflow in the aerosol generating apparatus 1 (e.g. caused by a user inhaling through the consumable 70). This may be used to count puffs, for example.

[0103] In this example, the consumable 70 includes a flow path which transmits aerosol generated by the at least one heating element 54 to the mouthpiece of the consumable.

[0104] In this example, the aerosol generating unit 4 is provided by the above-described heating system 52 and the delivery system 8 is provided by the above-described flow path and mouthpiece of the consumable 70.

[0105] Fig. 4 is a graph illustrating the bimodal particle size distribution of the plant material particles of solid aerosol precursor for the example consumable of the apparatus of Fig. 2. In this example, the plant material particles are tea particles.

[0106] The bimodal particle size distribution results from combining a fraction of fine plant material particles having a first monomodal particle size distribution 401 with a fraction of coarse plant material particles having a second particle size distribution 402. The D50 particle size of the first monomodal particle distribution is 40 to 70 µm. The D50 particle size of the second monomodal particle distribution is 225 to 300 µm.

[0107] In this way, the flavour and the structure of the solid aerosol precursor may be improved. The fine plant material particles may provide the flavour of the precursor, whilst the coarse plant material particles may provide strength and structure to the precursor. An improvement in the consistency in the particle sizes may contribute to a more consistent precursor, and may contribute to improved appearance, porosity and / or injectability / extrudability of the precursor. Consequently, the user experience may be more consistent across products since there may be improved consistency of flavour delivery and pressure drop across the precursor between products.

[0108] Fig. 5 is a flow diagram representing some of the steps of a method of preparing a solid aerosol precursor for the example consumable of the apparatus of Fig. 2. In this example, the plant material particles of the solid aerosol precursor are tea particles.

[0109] In step 501, fine tea particles are separated from a first portion of milled tea leaves by sieve separation. The fine tea particles have a first monomodal particle size distribution by number. The D50 particle size of the first monomodal particle distribution is 40 to 70 µm. The first portion of milled tea leaves are obtained from a quantitative milling process, in which a milling time and / or milling speed is set to allow for a target particle size to be achieved. The quantitative milling process may also comprise a feedback system to achieve the target particle size. Typical feedback systems are known to the skilled person, but may involve taking samples of the tea leaves during milling, determining the particle size of the tea leaves and adjusting the milling time or milling speed.

[0110] In step 502, coarse tea particles are separated from second portion of milled tea leaves by sieve separation. The coarse tea particles have a second monomodal particle size distribution by number. The D50 particle size of the second monomodal particle distribution is 225 to 300 µm. The second portion of milled tea leaves are obtained from a quantitative milling process, in which a milling time and / or milling speed is set to allow for a target particle size to be achieved. The quantitative milling process may also comprise a feedback system to achieve the target particle size. Typical feedback systems are known to the skilled person, but may involve taking samples of the tea leaves during milling, determining the particle size of the tea leaves and adjusting the milling time or milling speed.

[0111] In some examples, step 502 may proceed step 501. In some examples, steps 501 and 502 may occur simultaneously.

[0112] Sieve separation of the fine tea particles and / or the coarse tea particles from the first and / or second portion of milled tea leaves comprises sieving milled tea leaves through a small pore screen, collecting and passing the first non-passed fraction of tea particles through a large pore screen and collecting the second passed fraction of tea particles with the desired particle distribution. The desired particle distribution is the first or second monomodal particle distribution referred to above. In this way, a fraction of tea particles with a desired particle distribution may be obtained. Additionally, sieve separation achieves a narrower particle size distribution within each mode of tea particle, with greater consistency in particle size of tea particles contributing to an enhanced user experience. Optionally, additional milling of tea leaves and repetition of the sieve separation steps may be carried out. This is beneficial as it allows for an even narrower particle size distribution within each mode to be achieved.

[0113] In step 503, the fine tea particles and the coarse tea particles obtained in steps 501 and 502 are combined. This creates a total particle size distribution by number of tea particles, where the total particle size distribution is a bimodal distribution. In this way, the flavour and the structure of the solid aerosol precursor may be improved. The fine tea particles may provide the flavour of the precursor, whilst the coarse tea particles may provide strength and structure to the precursor. An improvement in the consistency in the particle sizes may contribute to a more consistent precursor, and may contribute to improved appearance, porosity and / or injectability / extrudability of the precursor. Consequently, the user experience may be more consistent across products since there may be improved consistency of flavour delivery and pressure drop across the precursor between products.

Claims

1. A solid aerosol precursor for a heat-not-burn consumable, wherein the solid aerosol precursor comprises fine plant material particles and coarse plant material particles, the fine plant material particles having a first monomodal particle size distribution by number having a D50 particle size of from 40 to 70 µm, and the coarse plant material particles having a second monomodal particle size distribution by number having a D50 particle size of from 225 to 300 µm, wherein combining together the first monomodal particle size distribution and the second monomodal particle size distribution results in a bimodal particle size distribution.

2. The solid aerosol precursor according to claim 1, wherein the plant material particles are non-tobacco plant material particles, such as tea particles.

3. The solid aerosol precursor according to claim 1 or 2, wherein: the fine plant material particles have a D10 particle size of 20 to 35 µm, such as around 30 µm, and / or the coarse plant material particles have a D10 particle size of 100 to 220 µm, such as around 200 µm; and / or the fine plant material particles have a D90 particle size of 70 to 105 µm, such as around 90 µm, and / or the coarse plant material particles have a D90 particle size of 300 to 400 µm, such as around 350 µm.

4. The solid aerosol precursor according to any one of claims 1 to 3, wherein the difference between D90 and D10 particle sizes of the fine plant material particles is less than 60 µm, and / or wherein the difference between D90 and D10 particle sizes of the coarse plant material particles is less than 150 µm.

5. The solid aerosol precursor according to any one of claims 1 to 4, wherein the spread of the particle size distribution of the fine plant material particles and / or the coarse plant material particles is 2 or less, such as 1 or less, the spread being equal to (D90-D10) / D50.

6. The solid aerosol precursor according to any one of claims 1 to 5, wherein the fine plant material particles have a D50 particle size of around 60 µm, and / or wherein the coarse plant material particles have a D50 particle size of around 250 µm.

7. The solid aerosol precursor according to any one of claims 1 to 6, wherein the solid aerosol precursor further comprises cellulose particles.

8. The solid aerosol precursor according to any one of claims 1 to 7, wherein the solid aerosol precursor further comprises at least one of the following: tobacco extract, a humectant, a binding agent, and / or a thickening agent.

9. The solid aerosol precursor according to any one of claims 1 to 8, wherein the solid aerosol precursor is formed or is formable by injection moulding.

10. The solid aerosol precursor according to any one of claims 1 to 9, wherein the solid aerosol precursor is formed or formable by extrusion.

11. A method of preparing a solid aerosol precursor according to any one of claims 1 to 10, wherein the method comprises the steps of: i) providing milled plant material; ii) separating fine plant material particles from the milled plant material, the fine plant material particles having a first monomodal particle size distribution by number having a D50 particle size of from 40 to 70 µm; iii) separating coarse plant material particles from the milled plant material, the coarse plant material particles having a second monomodal particle size distribution by number having a D50 particle size of from 225 to 300 µm; and iv) combining the fine plant material particles and the coarse plant material particles to obtain a solid aerosol precursor.

12. The method according to claim 11, wherein separating the fine plant material particles and / or separating the coarse plant material particles comprises separating by sieve separation.

13. The method of claim 12, wherein the sieve separation comprises the steps of: a) sieving milled plant material with a small pore screen such that a first passed fraction of plant material particles pass through the small pore screen and a first non-passed fraction of plant material particles do not pass through the small pore screen; b) sieving the first non-passed fraction of plant material particles with a large pore screen such that a second passed fraction of plant material particles pass through the large pore screen and a second non-passed fraction of plant material particles do not pass through the large pore screen; and c) collecting the second passed fraction of plant material particles with the desired particle size distribution; or a) sieving milled plant material with a large pore screen such that a first passed fraction of plant material particles pass through the large pore screen and a first non-passed fraction of plant material particles do not pass through the large pore screen; b) sieving the first passed fraction of plant material particles with a small pore screen such that a second passed fraction of plant material particles pass through the small pore screen and a second non-passed fraction of plant material particles do not pass through the small pore screen; and c) collecting the second non-passed fraction of plant material particles with the desired particle size distribution.

14. A heat-not-burn consumable comprising the solid aerosol precursor according to any of claims 1 to 10 or made by a method according to any of claims 11 to 13 and a mouthpiece downstream of the solid aerosol precursor.

15. Use of a solid aerosol precursor according to any of claims 1 to 10 or made by the method according to any of claims 11 to 13 in increasing consistency of user experience with a heat-not-burn consumable.

Images