HK1234965A1 - Electronic vapour provision system - Google Patents

Description

FIELD OF THE INVENTION

The present disclosure relates to electronic vapour provision systems such as electronic nicotine delivery systems (e.g. e-cigarettes).

BACKGROUND TO THE INVENTION

Electronic vapour provision systems such as e-cigarettes generally contain a reservoir of liquid which is to be vaporised, typically nicotine. When a user inhales on the device, a heater is activated to vaporise a small amount of liquid, which is therefore inhaled by the user.

The use of e-cigarettes in the UK has grown rapidly, and it has been estimated that there are now over a million people using them in the UK.

During the operation of electronic vapour provision systems, the heater may heat the liquid to be vaporised to an extent that some undesirable impurities are formed by the heating. For example, the liquid may be heated to the extent that undesirable aldehyde compounds may be formed. Such compounds may impact on the taste of the inhaled vapour.

WO2011084907 relates to a tobacco smoking device comprises a porous mass of active particles adapted to enhance a tobacco smoke flowing over said active particles and binder particles. The active particles comprises about 1-99 % weight of the porous mass, and the binder particles comprises about 1-99 % weight of said porous mass. The active particles and said binder particles are bound together at randomly distributed points throughout the porous mass. The active particles have a greater particle size than the binder particles.

CN202233005 relates to a sanitary comfortable electronic cigarette which is formed by connecting an atomizer with a battery pipe, a battery is arranged in the battery pipe and is electrically connected with the atomizer, the atomizer comprises a cigarette holder pipe, an atomizing pipe, lampblack absorbing cotton, a fiber bushing, a heating sheet, an oil preventing device, a connecting ring, an insulating ring and an inner core; a filter tip made of soft fibers and tipping paper is wrapped on the outer surface of the cigarette holder pipe, a filter sheet is made of acetate fibers or activated carbon, the material quality of the heating sheet is a metal ceramic heating sheet, the fiber bushing is made of high temperature resistant material, the metal ceramic heating sheet is non-toxic and harmless to a human body at high temperature, heat-resisting insulating material is covered on the surface of the metal ceramic heating sheet, and chemical reaction between the metal ceramic heating sheet and lampblack can be avoided, thereby providing safe sanitary guarantees.

WO2013067511 relates to a method for forming a filter rod may include providing a bale of crimped tow band having about 10 denier per filament or greater and about 20,000 total denier or less, the crimped tow band comprising a plurality of cellulose acetate filaments; and placing the crimped tow band in an apparatus so as to form a filter rod.

CA2813575 relates to filters including porous masses that have an active particle and a binder particle, wherein the active particle comprises carbon and the porous mass has a carbon loading of at least about 6 mg/mm and an encapsulated pressure drop of about 20 mm of water or less per mm of porous mass.

R.Z. Behar et al "Identification of toxicants in cinnamon-flavored electronic cigarette refill fluids",TOXICOLOGY IN VITRO., vol. 28, no. 2, pages 198-208, relates to a study to determine if high cytotoxicity is a general feature of cinnamon-flavored EC refill fluids and to identify the toxicant(s) in Cinnamon Ceylon.

SUMMARY OF THE INVENTION

In one aspect, there is provided an electronic vapour provision system comprising:

• a vaporiser for vaporising liquid for inhalation by a user of the electronic vapour provision system;
• a power supply comprising a cell or battery for supplying power to the vaporiser; and
• a filter for filtering vaporised liquid prior to inhalation by the user of the electronic vapour provision system,
• wherein the filter can partially or completely remove from the vapour one or more aldehydes present in the vapour, wherein the filter has an amine functional group which reacts with aldehydes.

We have found that aldehydes, which are undesirable at least because of the taste which they may impart to the vapour, may be produced by the heating of the liquid to be vaporised. We have found that the aldehydes have a particular tendency to form in vapour provision systems, such as e-cigarettes, and this is especially the case towards the end of the use of the vapour provision system. Towards the end of the use of the system when the amount of liquid present in the device is low, the heater may contact a relatively small amount of liquid and heat the liquid to a temperature which is higher than the typical temperature during the majority of the operation of the device. This is a problem unique to electronic vapour provision systems containing a heating element. The provision of a filter that can partially or completely remove from the vapour one or more aldehydes present in the vapour, wherein the filter has an amine functional group which reacts with aldehydes, addresses this problem.

That filters can be provided which remove aldehydes from the vapour of electronic vapour provision systems, wherein the filter has an amine functional group which reacts with aldehydes, was surprising at least because the airflow observed in such vapour provision systems is very different to that seen in systems where similar filters have previously been used, such as in combustible tobacco products. Furthermore, the number of puffs taken on a single electronic vapour provision system, such as an e-cigarette, can be as high as 250 or 300. In contrast the number of puffs taken on a single combustible cigarette is typically less than 10.

For ease of reference, these and further aspects of the present invention are now discussed under appropriate section headings. However, the teachings under each section are not necessarily limited to each particular section.

DETAILED DESCRIPTION

As described above, the present disclosure relates to an electronic vapour provision system, such as an e-cigarette. Throughout the following description the term "e-cigarette" is used; however, this term may be used interchangeably with electronic vapour provision system.

As discussed herein, the filter used in the present invention can partially or completely remove from the vapour one or more aldehydes present in the vapour. In one aspect, the filter partially or completely removes at least one aldehyde present in the vapour. In one aspect, the filter partially or completely removes at least two aldehydes present in the vapour. In one aspect, the filter partially or completely removes at least three aldehydes present in the vapour. In one aspect, the filter partially or completely removes each aldehyde present in the vapour.

As will be understood by one skilled in the art when aldehydes are formed in an electronic vapour provision system, some of the aldehydes are present in the particulate phase and some of the aldehydes are present in the vapour phase. The filter of the present invention acts to selectively remove aldehydes from the vapour phase and the purpose of the filter is not to remove aldehydes from the particulate phase. In the present specification (unless otherwise stated) all references to removal of aldehydes from the vapour phase refer only to the removal of aldehydes within that vapour phase and not the removal of any aldehydes within the particulate phase. It will be understood by one skilled in the art that the particulate phase may be carried by the vapour phase. References in the present specification to the removal of particular amounts of aldehyde from the vapour phase are based (unless otherwise stated) on the amount of aldehyde in the vapour phase and do not refer to or include the amount of aldehyde present in the particulate phase, irrespective of whether that particulate phase is carried by the vapour phase.

By the term "partially removes" it is meant that during an inhalation of vapour through the filter at least a portion of aldehyde is removed. In one aspect the term "partially removes" means at least 10 wt.% of aldehyde present in the vapour is removed from the vapour by the filter. In one aspect the term "partially removes" means at least 20 wt.% of aldehyde present in the vapour is removed from the vapour by the filter. In one aspect the term "partially removes" means at least 30 wt.% of aldehyde present in the vapour is removed from the vapour by the filter. In one aspect the term "partially removes" means at least 40 wt.% of aldehyde present in the vapour is removed from the vapour by the filter. In one aspect the term "partially removes" means at least 50 wt.% of aldehyde present in the vapour is removed from the vapour by the filter. In one aspect the term "partially removes" means at least 60 wt.% of aldehyde present in the vapour is removed from the vapour by the filter. In one aspect the term "partially removes" means at least 70 wt.% of aldehyde present in the vapour is removed from the vapour by the filter. In one aspect the term "partially removes" means at least 80 wt.% of aldehyde present in the vapour is removed from the vapour by the filter. In one aspect the term "partially removes" means at least 90 wt.% of aldehyde present in the vapour is removed from the vapour by the filter.

It is desirable that the filter of the present invention remains active over a significant number of uses. In particular it is desirable that the filter of the present invention remains active over the large number of inhalations which an e-cigarette is designed to provide. In one aspect after 30 inhalations of vapour have passed through the filter at least 30 wt.% of the one or more aldehydes present in the vapour are removed from the vapour by the filter. In one aspect after 30 inhalations of vapour have passed through the filter at least 40 wt.% of the one or more aldehydes present in the vapour are removed from the vapour by the filter. In one aspect after 30 inhalations of vapour have passed through the filter at least 50 wt.% of the one or more aldehydes present in the vapour are removed from the vapour by the filter. In one aspect after 30 inhalations of vapour have passed through the filter at least 60 wt.% of the one or more aldehydes present in the vapour are removed from the vapour by the filter.

In one aspect after 30 inhalations of vapour have passed through the filter at least 30 wt.% of formaldehyde present in the vapour is removed from the vapour by the filter. In one aspect after 30 inhalations of vapour have passed through the filter at least 40 wt.% of formaldehyde present in the vapour is removed from the vapour by the filter. In one aspect after 30 inhalations of vapour have passed through the filter at least 50 wt.% of formaldehyde present in the vapour is removed from the vapour by the filter. In one aspect after 30 inhalations of vapour have passed through the filter at least 60 wt.% of formaldehyde present in the vapour is removed from the vapour by the filter.

In one aspect after 100 inhalations of vapour have passed through the filter at least 20 wt.% of formaldehyde present in the vapour is removed from the vapour by the filter. In one aspect after 100 inhalations of vapour have passed through the filter at least 30 wt.% of formaldehyde present in the vapour is removed from the vapour by the filter. In one aspect after 100 inhalations of vapour have passed through the filter at least 40 wt.% of formaldehyde present in the vapour is removed from the vapour by the filter. In one aspect after 100 inhalations of vapour have passed through the filter at least 50 wt.% of formaldehyde present in the vapour is removed from the vapour by the filter. In one aspect after 100 inhalations of vapour have passed through the filter at least 60 wt.% of formaldehyde present in the vapour is removed from the vapour by the filter.

In one aspect after 250 inhalations of vapour have passed through the filter at least 20 wt.% of formaldehyde present in the vapour is removed from the vapour by the filter. In one aspect after 250 inhalations of vapour have passed through the filter at least 30 wt.% of formaldehyde present in the vapour is removed from the vapour by the filter. In one aspect after 250 inhalations of vapour have passed through the filter at least 40 wt.% of formaldehyde present in the vapour is removed from the vapour by the filter. In one aspect after 250 inhalations of vapour have passed through the filter at least 50 wt.% of formaldehyde present in the vapour is removed from the vapour by the filter. In one aspect after 250 inhalations of vapour have passed through the filter at least 60 wt.% of formaldehyde present in the vapour is removed from the vapour by the filter.

In one aspect after 300 inhalations of vapour have passed through the filter at least 20 wt.% of formaldehyde present in the vapour is removed from the vapour by the filter. In one aspect after 300 inhalations of vapour have passed through the filter at least 30 wt.% of formaldehyde present in the vapour is removed from the vapour by the filter. In one aspect after 300 inhalations of vapour have passed through the filter at least 40 wt.% of formaldehyde present in the vapour is removed from the vapour by the filter. In one aspect after 300 inhalations of vapour have passed through the filter at least 50 wt.% of formaldehyde present in the vapour is removed from the vapour by the filter. In one aspect after 300 inhalations of vapour have passed through the filter at least 60 wt.% of formaldehyde present in the vapour is removed from the vapour by the filter.

The nature of the aldehydes to be removed from the vapour may depend on the liquid being vaporised. In one aspect the vapour contains and the filter can partially or completely remove from the vapour one or more aldehydes selected from acetaldehyde, acrolein, butyraldehyde, crotonaldehyde, formaldehyde and propionaldehyde. In one aspect the vapour contains and the filter can partially or completely remove from the vapour two or more aldehydes selected from acetaldehyde, acrolein, butyraldehyde, crotonaldehyde, formaldehyde and propionaldehyde. In one aspect the vapour contains and the filter can partially or completely remove from the vapour three or more aldehydes selected from acetaldehyde, acrolein, butyraldehyde, crotonaldehyde, formaldehyde and propionaldehyde. In one aspect the vapour contains and the filter can partially or completely remove from the vapour four or more aldehydes selected from acetaldehyde, acrolein, butyraldehyde, crotonaldehyde, formaldehyde and propionaldehyde. In one aspect the vapour contains and the filter can partially or completely remove from the vapour five or more aldehydes selected from acetaldehyde, acrolein, butyraldehyde, crotonaldehyde, formaldehyde and propionaldehyde. In one aspect the vapour contains and the filter can partially or completely remove from the vapour each of acetaldehyde, acrolein, butyraldehyde, crotonaldehyde, formaldehyde and propionaldehyde.

In one aspect the vapour contains and the filter can partially or completely remove from the vapour at least one or more aldehydes selected from acetaldehyde, acrolein and formaldehyde. In one aspect the vapour contains and the filter can partially or completely remove from the vapour two or more aldehydes selected from acetaldehyde, acrolein and formaldehyde. In one aspect the vapour contains and the filter can partially or completely remove from the vapour each of acetaldehyde, acrolein and formaldehyde.

In one aspect the vapour contains and the filter can partially or completely remove from the vapour at least formaldehyde. In one aspect the vapour contains and the filter can partially or completely remove from the vapour at least acetaldehyde. In one aspect the vapour contains and the filter can partially or completely remove from the vapour at least acrolein. In one aspect the vapour contains and the filter can partially or completely remove from the vapour at least acetaldehyde and formaldehyde. In one aspect the vapour contains and the filter can partially or completely remove from the vapour at least acrolein and formaldehyde.

A "key" aldehyde to be removed from vapour is formaldehyde. In one aspect the vapour contains and the filter can partially or completely remove from the vapour at least formaldehyde. In one aspect the vapour contains formaldehyde and the filter can remove from the vapour at least 10 wt.% of the formaldehyde present in the vapour. In one aspect the vapour contains formaldehyde and the filter can remove from the vapour at least at least 20 wt.% of the formaldehyde present in the vapour. In one aspect the vapour contains formaldehyde and the filter can remove from the vapour at least at least 30 wt.% of the formaldehyde present in the vapour. In one aspect the vapour contains formaldehyde and the filter can remove from the vapour at least at least 40 wt.% of the formaldehyde present in the vapour. In one aspect the vapour contains formaldehyde and the filter can remove from the vapour at least at least 50 wt.% of the formaldehyde present in the vapour. In one aspect the vapour contains formaldehyde and the filter can remove from the vapour at least at least 60 wt.% of the formaldehyde present in the vapour. In one aspect the vapour contains formaldehyde and the filter can remove from the vapour at least at least 70 wt.% of the formaldehyde present in the vapour. In one aspect the vapour contains formaldehyde and the filter can remove from the vapour at least at least 80 wt.% of the formaldehyde present in the vapour. In one aspect the vapour contains formaldehyde and the filter can remove from the vapour at least at least 90 wt.% of the formaldehyde present in the vapour.

The filter can partially or completely remove from the vapour one or more aldehydes present in the vapour. As will be understood by one skilled in the art the effectiveness of the filter will depend on the extent to which it has already filtered aldehyde from the vapour. The removal may be achieved by any known mechanism by which a filter material may remove a constituent from a vapour. Typically the filter adsorbs the one or more aldehydes or the filter reacts with one or more aldehydes. In one aspect, the filter adsorbs the one or more aldehydes. As will be understood by one skilled in the art, in this context, adsorption is the adhesion to a surface of the filter material aldehyde present in the vapour. In one aspect, the filter reacts with one or more aldehydes. In the process known as chemisorption, a bond will be formed between aldehyde and the material of the filter. The filter is provided with an amine functional group. When an amine functional group reacts with an aldehyde it forms an imine.

In one aspect, the filter physically adsorbs the one or more aldehydes. In this aspect, the filter may be selected from any suitable adsorbent materials. In this aspect, preferably the filter comprises or is activated carbon (AC).

In one aspect, the filter is a resin having polyamine groups bonded to a cross-linked polystyrene matrix. Preferably the reactive filter material is an ion exchange resin.

Ion exchange resins are highly ionic, covalently cross-linked, insoluble polyelectrolytes. They are often supplied as porous beads or granules, their high surface area:volume ratio maximising the rate of ion exchange and the total ion exchange capacity. They can be precisely engineered to have a particular porosity and surface chemistry (i.e. surface functional groups for ion exchange), these features facilitating selective and effective ion exchange. They can be fabricated by cross-linking polymer molecules. In some cases, they can be made by cross-linking polystyrene using the cross-linking agent, divinylbenzene.

The composition of the present invention may comprise any ion exchange resin as long as it is suitable for incorporating into an e-cigarette. In some embodiments, the ion exchange resin may comprise ion exchange resin beads. In these embodiments, the beads may have any suitable size (i.e. diameter) and any suitable size distribution. In some embodiments, the beads may have a mean diameter of from about 20 to about 1200 µm, from about 100 to about 1100 µm, from about 200 to about 1000 µm, from about 300 to about 900 µm, from about 400 to about 800 µm, from about 500 to about 700 µm, or about 600 µm.

In some embodiments, the ion exchange resin may comprise porous ion exchange resin beads. In these embodiments, the beads may have any suitable porosity. The porosity of the beads may be precisely engineered by controlling the conditions used in resin synthesis, such as the concentration of the cross-linking agent. The porosity of the beads can affect the surface area:volume ratio of the resin. The ion exchange resin may have any suitable surface area:volume ratio, although in some embodiments it may be beneficial to maximise the surface area:volume ratio in order to maximise the rate of, and capacity for, ion exchange.

In some embodiments, the ion exchange resin may have a BET surface area of about 10 - 300 m²/g. In some embodiments, the ion exchange resin may have a BET surface area of from about 15 to about 250 m²/g, from about 20 to about 200 m²/g, from about 25 to about 150 m²/g, from about 30 to about 100 m²/g, from about 35 to about 80 m²/g, from about 40 to about 60 m²/g, from about 45 to about 55 m²/g, or about 50 m²/g.

In some embodiments, the ion exchange resin may have a mass density of from about 0.1 to about 1 g/cm. In some embodiments, the ion exchange resin may have a mass density of from about 0.1 to about 0.9 g/cm, from about 0.2 to about 0.8 g/cm, from about 0.3 to about 0.7 g/cm, from about 0.4 to about 0.6 g/cm, or about 0.5 g/cm.

In some embodiments, the ion exchange resin may have a total exchange capacity of from about 0.5 to about 20 meq/cm³. In some embodiments, it may be beneficial to maximise the total exchange capacity to maximise the number of ions that can be adsorbed from vapour. In some embodiments, the resin may have a total exchange capacity of from about 0.1 to about 18 meq/cm³, from about 0.5 to about 15 meq/cm³, or from about 0.7 to about 10 meq/cm³. In some embodiments, the total exchange capacity of the resin is from about 0.5 to about 2 meq/cm³.

The filter may be present in any suitable amount to provide the required extent of filtration. In some embodiments, the filter is present in an amount of from 10 to 100 mg, such as in an amount of from 20 to 80 mg, such as in an amount of from 30 to 70 mg, such as in an amount of from 30 to 50 mg, such as in an amount of from 40 to 70 mg, such as in an amount of from 50 to 70 mg. In some embodiments, the ion exchange resin is present in an amount of from 10 to 100 mg, such as in an amount of from 20 to 80 mg, such as in an amount of from 30 to 70 mg, such as in an amount of from 30 to 50 mg, such as in an amount of from 40 to 70 mg, such as in an amount of from 50 to 70 mg.

In some embodiments, the ion exchange resin may comprise one type of functional group. In other embodiments, it may comprise two or more types of functional group. Having one type of functional group may make the resin more selective in ion exchange, and result in a smaller range of ionic species being adsorbed. Having two or more functional groups may make the resin less selective in ion exchange, and result in a greater range of ionic species being adsorbed.

The functional groups of the resin may be anionic, cationic, and/or neutral. In some embodiments, they may be suitable for removing one or more compounds from vapour. In some embodiments, they may be suitable for removing one or more compounds from vapour which are undesirable for human inhalation. They are of course suitable for removing aldehydes, such as formaldehyde, acrolein and acetaldehyde from vapour.

In some embodiments, the composition of the invention comprises a Diaion® CR20 ion exchange resin. In some embodiments, the composition of the invention comprises a XORBEX ion exchange resin. The surface chemistries and porosities of these resins make them highly effective for the selective adsorption of compounds from vapour.

It may be beneficial for the composition of the invention to comprise a Diaion® CR20 resin. Diaion® CR20 resin is a resin having polyamine groups bonded to a cross-linked polystyrene matrix. Diaion® CR20 resins have previously been used in combustible tobacco products, such as cigarettes, because they can selectively and effectively remove compounds by ion exchange. They have amine functional groups with a high affinity for aldehydes and cyanides. They can thus selectively remove constituents that are undesirable for human inhalation, such as formaldehyde, acrolein and acetaldehyde.

We have found that the use of filter formed from a resin having polyamine groups bonded to a cross-linked polystyrene matrix, such as Diaion® CR20 resin, is particularly advantageous because of the large number of uses over which aldehydes are adsorbed and in particular the large number of uses over which formaldehyde is adsorbed. The longevity of such resins particularly in respect of formaldehyde is extremely useful in the field of e-cigarettes and no suggestion of such advantages can be found in the prior art.

In embodiments wherein the composition of the invention comprises a Diaion® CR20 resin, the Diaion® CR20 resin may have any suitable properties. In some embodiments, the Diaion® CR20 resin may comprise beads with a mean diameter of from about 500 to about 700 µm, a density of from about 0.4 to about 0.6 g/cm, and a total exchange capacity of from about 0.5 to about 2 meq/cm³. In some embodiments, the Diaion® CR20 resin may comprise beads with a mean diameter of about 600 µm, a density of about 0.5 g/cm, and a total exchange capacity of about 1 meq/cm³.

In some embodiments the filter is or comprises an ion exchange resin has one or more of the following properties: a mean bead diameter of from about 20 to about 1200 µm; a BET surface area of from about 10 to about 300 m²/g; a mass density of from about 0.1 to about 1 g/cm³; and a total exchange capacity of from about 0.5 to about 2 meq/cm³.

The invention will now be described with reference to the following non-limiting example.

Example

The aim of the current study was to investigate a filter material that could still exhibit some filtration efficiency when used for multiple inhalations. Synthetic AC beads (Blucher GmbH) which have been found to be an exceptionally efficient filter and CR20 (Mitsubishi Chemical Company) which is selective and highly efficient for aldehydes (and especially formaldehyde), were chosen as the adsorbents of choice [Branton et al., Adsorption Sci. & Technology, 29, 117-138 (2011), Branton et al., Chem.Central. 5:15 (2011)].

EXPERIMENTAL

Activated Carbon was supplied by Blucher GmbH. CR20 was supplied by Mitsubishi Chemical Company. Material characteristics are shown in Table 1. Table 1 - Filter Additive Characteristics

Particle shape	Spherical	Spherical
Mean Particle size (mm)	0.40	0.60
0.37	0.64
1660 (micro/meso/macroporous)	44 (macroporous)
0.94	0.08
Surface chemistry	-	Amine functionality

Table 1 - Filter Additive Characteristics

*From nitrogen adsorption at 77 K

A predetermined weight of additive (60-150 mg) was weighed into a filter. Each use was six puffs, equivalent to smoking one tobacco cigarette.

Selected aldehydes were measured using real time Time of Flight Mass Spectrometry (TOF-MS) (acetaldehyde, 1,3-butadiene, acetone, isoprene, MEK, benzene, toluene) and HPLC (acetaldehyde, acetone, acrolein, butyraldehyde, crotonaldehyde, formaldehyde, MEK, propionaldehyde). Aldehyde yields were measured from the whole aerosol (vapour+particulate phases). It is known that 70% of formaldehyde is present in the vapour phase, selective filtration of formaldehyde (or any compound) in the particulate phase is extremely unlikely and thus a selective reduction of 70% is the maximum likely. By contrast, other aldehydes such as acetaldehyde are essentially exclusively in the vapour phase and thus a 100% selective removal is theoretically possible.

AC samples were also evaluated using a Rubotherm InfraSorp (Fraunhoffer Institute, Dresden, Germany) which enables material (both fresh and previously contacted with aldehydes) to be screened for their adsorption characteristics.

n-Butane was used as the test adsorbate gas. The sample size required was only 200mg and 20 samples could be screened in 2 hours.

RESULTS AND DISCUSSION

Figures 1(i) to (v) shows the effect on filtration efficiency as a function of usage using 60mg and 150mg of Activated Carbon beads in the filter by TOF-MS and HPLC analytical procedures and 60mg CR20 by HPLC.

Despite the different analytical methods used for the measurement of aldehydes, it is clear from the figures that there was good agreement between the two techniques. Filtration efficiencies differ for different aldehydes, i.e. each aldehydes has a different breakthrough profile. For example, re-using AC 8 times results in the filtration efficiency falling :

• 80→20% for acetone & 90→40% for crotonaldehyde using 60mg of AC and
• 90→60% for acetone & 90→70% for crotonaldehyde using 150mg of AC.

CR20 is an excellent filter for formaldehyde. Even using only 60 mg in the filter, the filtration efficiency does not significantly fall over 5 uses (30 puffs).

By measuring the heat of adsorption (using n-butane) it was found that there was a trend with the filtration performance of a filter material.

Figure 2 shows the thermal response of AC that was used 5 times (using 150 mg in the filter) and 'fresh' AC upon exposure to n-butane gas.

The greater the peak area above the y-axis, the stronger the adsorption (greater heat loss). This implies a greater available surface area and thus greater filtration efficiency. The greater the peak area below the y-axis, the stronger the desorption (greater heat rise) and thus the pores are partially filled suggesting a lower available surface area and lower filtration efficiency (and also higher odour from desorption of volatile species).

The peak areas (weight normalised) for adsorption and desorption and the ratio of desorption to adsorption are shown in Table 2 for AC. Table 2 - Adsorption-Desorption Peak Areas for AC

AC	Adsorption peak area (arb units)	Desorption peak area (arb units)	Desorption:Adsorption ratio
Fresh	13.6	0	0
Used once	6.4	-1.2	-0.2
Used twice	3.8	-2.4	-0.6
Used 3 times	2.3	-5.6	-2.4
Used 5 times	1.5	-9.4	-6.5

As can be seen from Table 2, the adsorption peak area falls with increasing number of uses, whilst the desorption peak increases.

Purging with dry air at room temperature was investigated to see if the AC surface area could be regenerated.

There is a significant loss in the AC adsorption capacity (for butane) of ca 90% after 5 reuses.

The percentage of adsorption sites for butane on AC before and after purging are summarised below.

Fresh	used once	used 2 times	used 3 times	used 5 times
100%	46→83%	27→55%	16→48%	11→35%

The above shows that after one use, the number of available adsorption sites fell to 46%. By purging with dry air at room temperature, the number of available adsorption sites could be increased to 83% (it is extremely difficult to desorp the volatile species from the smallest of pores without using heat and a vacuum and so a 100% regeneration in practise would be unlikely).

After two uses, the number of available adsorption sites fell to 27%. By purging with dry air at room temperature, the number of available adsorption sites could be increased to 55% and so on.

CONCLUSIONS

Activated Carbon (60-150mg) can be reused at least 5 times whilst maintaining some enhanced filtration. CR20 (60mg) can be reused at least 5 times without a significant drop in formaldehyde filtration efficiency. The AC activity can be (partially) regenerated via purging with dry air. Various modifications and variations of the present invention will be apparent to those skilled in the art without departing from the scope the present claims. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention which are obvious to those skilled in chemistry or related fields are intended to be within the scope of the following claims. The invention is strictly defined by the claims.

Claims (13)

1. An electronic vapour provision system comprising:

   a vaporiser for vaporising liquid for inhalation by a user of the electronic vapour provision system;

   a power supply comprising a cell or battery for supplying power to the vaporiser; and

   a filter for filtering vaporised liquid prior to inhalation by the user of the electronic vapour provision system,

   wherein the filter can partially or completely remove from the vapour one or more aldehydes present in the vapour, wherein the filter has an amine functional group which reacts with aldehydes.
2. An electronic vapour provision system according to claim 1 wherein the filter is an ion exchange resin.
3. An electronic vapour provision system according to claim 1 or 2 wherein the filter is a resin having polyamine groups bonded to a cross-linked polystyrene matrix.
4. An electronic vapour provision system according to any one of claims 1 to 3 wherein the filter can partially or completely remove from the vapour each aldehyde present in the vapour.
5. An electronic vapour provision system according to any one of claims 1 to 4 wherein the filter can partially or completely remove from the vapour one or more aldehydes selected from acetaldehyde, acrolein, butyraldehyde, crotonaldehyde, formaldehyde and propionaldehyde.
6. An electronic vapour provision system according to any one of claims 1 to 5 wherein the filter can partially or completely remove from the vapour at least formaldehyde.
7. An electronic vapour provision system according to any one of claims 1 to 6 wherein the filter can partially or completely remove from the vapour each of acetaldehyde, acrolein, butyraldehyde, crotonaldehyde, formaldehyde and propionaldehyde.
8. An electronic vapour provision system according to any one of claims 1 to 7 wherein at least 30% of the one or more aldehydes present in the vapour are removed from the vapour by the filter.
9. An electronic vapour provision system according to any one of claims 1 to 7 wherein at least 50% of the one or more aldehydes present in the vapour are removed from the vapour by the filter.
10. An electronic vapour provision system according to any one of claims 1 to 7 wherein after 30 inhalations of vapour have passed through the filter at least 40% of the one or more aldehydes present in the vapour are removed from the vapour by the filter.
11. An electronic vapour provision system according to any one of claims 1 to 7 wherein after 30 inhalations of vapour have passed through the filter at least 40% of formaldehyde present in the vapour is removed from the vapour by the filter.
12. An electronic vapour provision system according to any one of claims 1 to 7 wherein after 100 inhalations of vapour have passed through the filter at least 40% of formaldehyde present in the vapour is removed from the vapour by the filter.
13. An electronic vapour provision system according to any one of claims 1 to 7 wherein after 250 inhalations of vapour have passed through the filter at least 40% of formaldehyde present in the vapour is removed from the vapour by the filter.