NZ623277B2 - Composite heat source for a smoking article - Google Patents
Composite heat source for a smoking article Download PDFInfo
- Publication number
- NZ623277B2 NZ623277B2 NZ623277A NZ62327712A NZ623277B2 NZ 623277 B2 NZ623277 B2 NZ 623277B2 NZ 623277 A NZ623277 A NZ 623277A NZ 62327712 A NZ62327712 A NZ 62327712A NZ 623277 B2 NZ623277 B2 NZ 623277B2
- Authority
- NZ
- New Zealand
- Prior art keywords
- combustible
- composite heat
- ceramic matrix
- porous ceramic
- heat source
- Prior art date
Links
- 239000002131 composite material Substances 0.000 title claims abstract description 133
- 230000000391 smoking Effects 0.000 title claims abstract description 37
- 239000000919 ceramic Substances 0.000 claims abstract description 120
- 239000011159 matrix material Substances 0.000 claims abstract description 117
- 239000000446 fuel Substances 0.000 claims abstract description 85
- 239000002245 particle Substances 0.000 claims abstract description 45
- 239000011236 particulate material Substances 0.000 claims abstract description 7
- 229910000314 transition metal oxide Inorganic materials 0.000 claims abstract description 7
- 239000011148 porous material Substances 0.000 claims description 19
- OKTJSMMVPCPJKN-UHFFFAOYSA-N carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 16
- 239000000203 mixture Substances 0.000 claims description 12
- MCMNRKCIXSYSNV-UHFFFAOYSA-N ZrO2 Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims description 10
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 claims description 9
- 229910052799 carbon Inorganic materials 0.000 claims description 7
- 229910000460 iron oxide Inorganic materials 0.000 claims description 7
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 4
- 239000004411 aluminium Substances 0.000 claims description 3
- 229910052782 aluminium Inorganic materials 0.000 claims description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminum Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 3
- FYYHWMGAXLPEAU-UHFFFAOYSA-N magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims description 3
- 239000011777 magnesium Substances 0.000 claims description 3
- 229910052749 magnesium Inorganic materials 0.000 claims description 3
- 229910052751 metal Inorganic materials 0.000 claims description 3
- 239000002184 metal Substances 0.000 claims description 3
- 230000003647 oxidation Effects 0.000 claims description 3
- 238000007254 oxidation reaction Methods 0.000 claims description 3
- 150000001247 metal acetylides Chemical class 0.000 claims description 2
- 150000004767 nitrides Chemical class 0.000 claims description 2
- 229910052904 quartz Inorganic materials 0.000 claims description 2
- 239000010453 quartz Substances 0.000 claims description 2
- NUJOXMJBOLGQSY-UHFFFAOYSA-N Manganese dioxide Chemical compound O=[Mn]=O NUJOXMJBOLGQSY-UHFFFAOYSA-N 0.000 claims 1
- 229910000468 manganese oxide Inorganic materials 0.000 claims 1
- AMWRITDGCCNYAT-UHFFFAOYSA-L manganese(II,III) oxide Inorganic materials [Mn].O[Mn]=O.O[Mn]=O AMWRITDGCCNYAT-UHFFFAOYSA-L 0.000 claims 1
- 238000002485 combustion reaction Methods 0.000 description 47
- 239000000758 substrate Substances 0.000 description 26
- 239000007789 gas Substances 0.000 description 15
- 239000000463 material Substances 0.000 description 11
- UGFAIRIUMAVXCW-UHFFFAOYSA-N carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 8
- 229910002091 carbon monoxide Inorganic materials 0.000 description 8
- 239000001301 oxygen Substances 0.000 description 8
- MYMOFIZGZYHOMD-UHFFFAOYSA-N oxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 8
- 229910052760 oxygen Inorganic materials 0.000 description 8
- 239000000443 aerosol Substances 0.000 description 6
- 230000003197 catalytic Effects 0.000 description 6
- 238000000034 method Methods 0.000 description 6
- 239000007800 oxidant agent Substances 0.000 description 6
- 230000001590 oxidative Effects 0.000 description 6
- GEIAQOFPUVMAGM-UHFFFAOYSA-N oxozirconium Chemical compound [Zr]=O GEIAQOFPUVMAGM-UHFFFAOYSA-N 0.000 description 6
- 239000000654 additive Substances 0.000 description 5
- 239000003054 catalyst Substances 0.000 description 5
- 238000000354 decomposition reaction Methods 0.000 description 5
- 238000002156 mixing Methods 0.000 description 5
- 239000003610 charcoal Substances 0.000 description 4
- 235000019504 cigarettes Nutrition 0.000 description 4
- 150000001875 compounds Chemical class 0.000 description 4
- 238000009792 diffusion process Methods 0.000 description 4
- 238000001125 extrusion Methods 0.000 description 4
- -1 for example Chemical compound 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 238000007669 thermal treatment Methods 0.000 description 4
- 239000012298 atmosphere Substances 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 3
- 239000001569 carbon dioxide Substances 0.000 description 3
- 229910002092 carbon dioxide Inorganic materials 0.000 description 3
- 230000024881 catalytic activity Effects 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- 238000005755 formation reaction Methods 0.000 description 3
- 239000011121 hardwood Substances 0.000 description 3
- NSGJBNFQQJBZHT-UHFFFAOYSA-N iron(3+);manganese(2+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Mn+2].[Mn+2].[Fe+3].[Fe+3] NSGJBNFQQJBZHT-UHFFFAOYSA-N 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 239000000843 powder Substances 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 240000008962 Nicotiana tabacum Species 0.000 description 2
- 235000002637 Nicotiana tabacum Nutrition 0.000 description 2
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitrogen oxide Substances O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 2
- QEEAPRPFLLJWCF-UHFFFAOYSA-K Potassium citrate Chemical compound [K+].[K+].[K+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O QEEAPRPFLLJWCF-UHFFFAOYSA-K 0.000 description 2
- 238000007792 addition Methods 0.000 description 2
- 239000012300 argon atmosphere Substances 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 239000002285 corn oil Substances 0.000 description 2
- 235000005687 corn oil Nutrition 0.000 description 2
- 238000007571 dilatometry Methods 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 238000010410 dusting Methods 0.000 description 2
- 238000000937 dynamic scanning calorimetry Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000002708 enhancing Effects 0.000 description 2
- 235000013312 flour Nutrition 0.000 description 2
- 238000001764 infiltration Methods 0.000 description 2
- 238000009413 insulation Methods 0.000 description 2
- 239000012299 nitrogen atmosphere Substances 0.000 description 2
- 239000001508 potassium citrate Substances 0.000 description 2
- 229960002635 potassium citrate Drugs 0.000 description 2
- 230000002028 premature Effects 0.000 description 2
- 238000005245 sintering Methods 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 230000035882 stress Effects 0.000 description 2
- 239000011791 tripotassium citrate Substances 0.000 description 2
- 235000015870 tripotassium citrate Nutrition 0.000 description 2
- 239000004108 vegetable carbon Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- TWHBEKGYWPPYQL-UHFFFAOYSA-N Aluminium carbide Chemical compound [C-4].[C-4].[C-4].[Al+3].[Al+3].[Al+3].[Al+3] TWHBEKGYWPPYQL-UHFFFAOYSA-N 0.000 description 1
- UIXRSLJINYRGFQ-UHFFFAOYSA-N Calcium carbide Chemical compound [Ca+2].[C-]#[C-] UIXRSLJINYRGFQ-UHFFFAOYSA-N 0.000 description 1
- 239000005997 Calcium carbide Substances 0.000 description 1
- 210000001736 Capillaries Anatomy 0.000 description 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate dianion Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- 240000009125 Myrtillocactus geometrizans Species 0.000 description 1
- 235000009781 Myrtillocactus geometrizans Nutrition 0.000 description 1
- 239000006057 Non-nutritive feed additive Substances 0.000 description 1
- 240000000450 Peltophorum pterocarpum Species 0.000 description 1
- VLTRZXGMWDSKGL-UHFFFAOYSA-M Perchlorate Chemical class [O-]Cl(=O)(=O)=O VLTRZXGMWDSKGL-UHFFFAOYSA-M 0.000 description 1
- 230000006399 behavior Effects 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- 150000001722 carbon compounds Chemical class 0.000 description 1
- 229910010293 ceramic material Inorganic materials 0.000 description 1
- XTEGARKTQYYJKE-UHFFFAOYSA-M chlorate Chemical class [O-]Cl(=O)=O XTEGARKTQYYJKE-UHFFFAOYSA-M 0.000 description 1
- 239000000567 combustion gas Substances 0.000 description 1
- 238000005056 compaction Methods 0.000 description 1
- 230000001186 cumulative Effects 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 230000020169 heat generation Effects 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 238000001746 injection moulding Methods 0.000 description 1
- 239000000314 lubricant Substances 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 1
- 229910052753 mercury Inorganic materials 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 150000002823 nitrates Chemical class 0.000 description 1
- 229910052813 nitrogen oxide Inorganic materials 0.000 description 1
- 238000002459 porosimetry Methods 0.000 description 1
- 230000001007 puffing Effects 0.000 description 1
- 238000004080 punching Methods 0.000 description 1
- 239000012266 salt solution Substances 0.000 description 1
- 238000007569 slipcasting Methods 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
Classifications
-
- A—HUMAN NECESSITIES
- A24—TOBACCO; CIGARS; CIGARETTES; SIMULATED SMOKING DEVICES; SMOKERS' REQUISITES
- A24B—MANUFACTURE OR PREPARATION OF TOBACCO FOR SMOKING OR CHEWING; TOBACCO; SNUFF
- A24B15/00—Chemical features or treatment of tobacco; Tobacco substitutes, e.g. in liquid form
- A24B15/10—Chemical features of tobacco products or tobacco substitutes
- A24B15/16—Chemical features of tobacco products or tobacco substitutes of tobacco substitutes
-
- A—HUMAN NECESSITIES
- A24—TOBACCO; CIGARS; CIGARETTES; SIMULATED SMOKING DEVICES; SMOKERS' REQUISITES
- A24B—MANUFACTURE OR PREPARATION OF TOBACCO FOR SMOKING OR CHEWING; TOBACCO; SNUFF
- A24B15/00—Chemical features or treatment of tobacco; Tobacco substitutes, e.g. in liquid form
- A24B15/10—Chemical features of tobacco products or tobacco substitutes
- A24B15/16—Chemical features of tobacco products or tobacco substitutes of tobacco substitutes
- A24B15/165—Chemical features of tobacco products or tobacco substitutes of tobacco substitutes comprising as heat source a carbon fuel or an oxidized or thermally degraded carbonaceous fuel, e.g. carbohydrates, cellulosic material
-
- A—HUMAN NECESSITIES
- A24—TOBACCO; CIGARS; CIGARETTES; SIMULATED SMOKING DEVICES; SMOKERS' REQUISITES
- A24D—CIGARS; CIGARETTES; TOBACCO SMOKE FILTERS; MOUTHPIECES FOR CIGARS OR CIGARETTES; MANUFACTURE OF TOBACCO SMOKE FILTERS OR MOUTHPIECES
- A24D1/00—Cigars; Cigarettes
- A24D1/22—Cigarettes with integrated combustible heat sources, e.g. with carbonaceous heat sources
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L5/00—Solid fuels
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E50/00—Technologies for the production of fuel of non-fossil origin
- Y02E50/30—Fuel from waste, e.g. synthetic alcohol or diesel
Abstract
composite heat source (6) for use in a smoking article comprises: a non-combustible porous ceramic matrix (16); and a particulate combustible fuel (18) embedded within the non-combustible porous ceramic matrix (16). The non-combustible porous ceramic matrix is formed from one or more particulate materials having a median D50 particle size at least five times less than the median D50 particle size of the particulate combustible fuel and wherein the volume fraction of the combustible fuel (18) embedded in the non-combustible porous ceramic matrix (16) is less than or equal to about 50% of the composite heat source (6). Preferably, the non-combustible porous ceramic matrix (16) comprises one or more transition metal oxides. aterials having a median D50 particle size at least five times less than the median D50 particle size of the particulate combustible fuel and wherein the volume fraction of the combustible fuel (18) embedded in the non-combustible porous ceramic matrix (16) is less than or equal to about 50% of the composite heat source (6). Preferably, the non-combustible porous ceramic matrix (16) comprises one or more transition metal oxides.
Description
COMPOSITE HEAT SOURCE FOR A SMOKING ARTICLE
The present invention relates to a heat source, for example a heat source suitable for
use in a smoking article. The present invention further relates to a smoking article comprising a
heat source according to the invention.
Smoking articles in which an aerosol is generated by the transfer of heat from a
combustible heat source to a physically separate aerosol-generating material are known in the
art. The aerosol-generating material may be located within, around or downstream of the heat
source. In use, the combustible heat source of the smoking article is lit and volatile compounds
are released from the aerosol-generating material by heat transfer from the combustible heat
source. The released volatile compounds are entrained in air and drawn through the smoking
article upon puffing. The formed aerosol is inhaled by the consumer.
It is desirable for a combustible heat source suitable for use in a smoking article to have
certain attributes to enable or enhance the smoking experience.
For example, the heat source should produce enough heat during combustion to allow
release of a flavoured aerosol from an aerosol-generating material, but still be sufficiently small
to fit within a smoking article that may be of a similar size as a conventional lit-end cigarette.
Furthermore, the heat source should be capable of burning with a limited amount of air
until the fuel in the heat source is expended and should also produce as little as possible or
substantially no carbon monoxide, nitrogen oxides or other potentially undesirable gases upon
combustion.
In addition, the ignition temperature of the heat source should be sufficiently low that the
heat source is readily ignitable under normal lighting conditions for a conventional lit-end
cigarette using, for example, a match or conventional cigarette lighter.
The heat source should also have an appropriate thermal conductivity. If too much heat
is conducted away from the burning zone of the heat source to other parts of the heat source
during combustion, combustion at the burning zone of the heat source will cease when the
temperature drops below the extinguishment temperature of the heat source. Therefore, a heat
source with too high a thermal conductivity may undesirably be difficult to ignite and, after
ignition, subject to premature self-extinguishment. The thermal conductivity of the heat source
should be at a level that, in use, allows effective heat transfer to the aerosol-generating material
without conducting too much heat to any means or structure by which it is fixed, mounted or
otherwise incorporated in the smoking article.
The heat source should also not disintegrate before or during use and should be able to
withstand small mechanical stresses that may occur as a result, for example, of a consumer
dropping the smoking article.
It would be desirable to provide a composite heat source suitable for use in smoking
articles that meets some or all of the above requirements.
It would further be desirable to provide a composite heat source capable of catalysing
the decomposition of one or more potentially undesirable gases produced during combustion
thereof.
It would also be desirable to provide a composite heat source capable of retaining
particulate matter produced during combustion thereof.
According to the present invention there is provided a composite heat source, suitable
for use in a smoking article, the composite heat source comprising: a porous non-combustible
ceramic matrix; and a particulate combustible fuel embedded within the non-combustible porous
ceramic matrix, wherein the non-combustible porous ceramic matrix is formed from one or more
particulate materials having a median D50 particle size at least five times less than the median
D50 particle size of the particulate combustible fuel and wherein the volume fraction of the
combustible fuel embedded in the non-combustible porous ceramic matrix is less than or equal
to about 50% of the composite heat source.
As used herein, the term ‘composite heat source’ (singular or plural) is used to denote a
heat source comprising at least two distinct components that in combination produce properties
not present in the at least two components individually. As described further below, the
functions of composite heat sources according to the present invention are advantageously
divided between the non-combustible porous ceramic matrix and the combustible fuel
embedded within the non-combustible porous ceramic matrix.
As used herein, the term ‘ceramic’ is used to denote any non-metallic solid which
remains solid when heated.
Advantageously, the particulate combustible fuel is completely embedded within the
non-combustible pourous ceramic matrix.
As used herein, the term ‘completely embedded’ is used to denote that the particles of
combustible fuel are completely surrounded by the non-combustible porous ceramic matrix.
That is, there is substantially no contact between particles of combustible fuel embedded within
the non-combustible porous ceramic matrix.
As used herein, the term ‘median D50 particle size” is used to denote the volume-basis
median value of the particle size distribution and is the value of the particle diameter at 50% in
the cumulative distribution.
The term ‘comprising’ as used in this specification and claims means ‘consisting at least
in part of’. When interpreting statements in this specification and claims which include the term
‘comprising’, other features besides the features prefaced by this term in each statement can
also be present. Related terms such as ‘comprise’ and ‘comprised’ are to be interpreted in a
similar manner.
Preferably, the non-combustible porous ceramic matrix is formed from one or more
particulate materials having a median D50 particle size at least ten times less than the median
D50 particle size of the particulate combustible fuel.
The strength of composite heat sources according to the invention is predominantly
controlled by the non-combustible porous ceramic matrix. Decoupling of the strength of
composite heat sources according to the present invention from the combustible fuel embedded
within the non-combustible porous ceramic matrix is advantageous, as the combustible fuel
undergoes large changes during combustion making it difficult to control its mechanical
behaviour.
The particles of combustible fuel in composite heat sources according to the present
invention have substantially no contact with each other and are embedded within individual
cavities within the non-combustible porous ceramic matrix. During combustion, the particles of
combustible fuel undergo changes within these individual cavities, but the structure of the non-
combustible porous ceramic matrix advantageously remains substantially unchanged.
Completely embedding the particulate fuel within the non-combustible porous ceramic
matrix in accordance with the present invention advantageously avoids a number of significant
drawbacks in combustion properties associated with prior art heat sources comprising a non-
combustible porous ceramic matrix and a particulate combustible fuel in which the particles of
combustible fuel are in contact with each other.
During combustion, new pore channels with large diameters may be formed in such prior
art heat sources as a result of the combustion of the connected particles of combustible fuel.
As a result, hot particles of combustible fuel may disadvantageously escape from such prior art
heat sources through the newly formed channels.
Furthermore, the mechanical integrity of such prior art heat sources may
disadvantageously decrease to a critical level during combustion due to the formation of weak
zones as a result of the combustion of the connected particles of combustible fuel.
Preferably, the non-combustible porous ceramic matrix has a compressive strength of
greater than or equal to about 10 megapascals (MPa) as measured in a standard mechanical
testing device by pushing the front and rear face of the sample with constant strain rate and
measuring the force, when the sample is destroyed. This enables composite heat sources
according to the present invention to withstand small mechanical stresses and preventing
disintegration of the composite heat sources before and during use.
The pores within the non-combustible porous ceramic matrix of composite heat sources
according to the present invention control the combustion kinetics of the composite heat
sources.
Preferably, the non-combustible porous ceramic matrix has substantially continuous pore
channels. Use of a non-combustible porous ceramic matrix having substantially continuous
pore channels in composite heat sources according to the present invention advantageously
enables oxygen to flow through the substantially continuous pore channels to the combustible
fuel embedded within the non-combustible porous ceramic matrix. In addition, it
advantageously allows carbon monoxide or carbon dioxide produced during combustion of the
combustible fuel to flow out of composite heat sources according to the present invention
through the substantially continuous pore channels.
In preferred embodiments of the present invention, the non-combustible porous ceramic
matrix has pores that are sufficiently small to retain any particulate material produced during
combustion of the fuel embedded within the non-combustible porous ceramic matrix.
Preferably, the non-combustible porous ceramic matrix has pores with diameters of
between about 0.01 microns ( μm) and about 10 microns ( μm) as measured by mercury
porosimetry.
The conductivity of composite heat sources according to the invention is predominantly
controlled by the non-combustible porous ceramic matrix. The use of a ceramic material with
low thermal conductivity advantageously enables composite heat sources according to the
present invention having moderate thermal conductivity to be produced, even when the thermal
conductivity of the combustible fuel embedded within the non-combustible porous ceramic
matrix is much higher.
Preferably, the non-combustible porous ceramic matrix has a thermal diffusivity of less
-6 2
than or equal to about 1 x 10 square metres per second (m /s) as measured using the laser
flash method. More preferably, the non-combustible porous ceramic matrix has a thermal
-6 2 -6 2
diffusivity of between about 0.4 10 m /s and about 1 10 m /s as measured using the laser
flash method. Use of a non-combustible porous ceramic matrix having a thermal diffusivity of
-6 2
less than or equal to about 1 x 10 m /s in composite heat sources according to the present
invention advantageously enables the combustible fuel embedded within the non-combustible
porous ceramic matrix to be ignited using a match, lighter or other suitable ignition means within
about 10 seconds.
In preferred embodiments of the present invention, the non-combustible porous ceramic
matrix does not undergo significant volumetric changes during combustion of the combustible
fuel embedded within the non-combustible porous ceramic matrix.
Preferably, the coefficient of thermal expansion of the non-combustible porous ceramic
matrix is greater than the coefficient of thermal expansion of the combustible fuel embedded
within the non-combustible porous ceramic matrix.
Preferably, the non-combustible porous ceramic matrix undergoes a volumetric change
of less than or equal to about 5 percent as measured by dilatometry during combustion of the
combustible fuel embedded within the non-combustible porous ceramic matrix. More
preferably, the non-combustible porous ceramic matrix undergoes a volumetric change of less
than or equal to about 1 percent as measured by non-contact dilatometry during combustion of
the combustible fuel embedded within the non-combustible porous ceramic matrix.
Materials suitable for use in the non-combustible porous ceramic matrix of composite
heat sources according to the present invention are known in the art and are commercially
available from various suppliers.
Preferably, the non-combustible porous ceramic matrix comprises one or more oxides.
Preferably, the non-combustible porous ceramic matrix comprises at least one transition metal
oxide, more preferably at least one transition metal oxide with a high catalytic activity for the
conversion of carbon monoxide to carbon dioxide. Suitable transition metal oxides are known in
the art and include, but are not limited to, iron oxide, manganese oxide and mixtures thereof.
Alternatively or in addition, the non-combustible porous ceramic matrix may comprise
one or more oxides of low thermal conductivity. Suitable oxides of low thermal conductivity
include, but are not limited to, zirconia, quartz, amorphous silica and mixtures thereof.
Non-combustible porous ceramic matrices having low thermal diffusivity for use in
composite heat sources according to the invention may be formed from one or more particulate
materials, such as, for example, zirconia (ZrO ) and iron oxide (Fe O ).
2 2 3
The strength of the non-combustible porous ceramic matrix may be provided by a
binder, a consolidation treatment, or a combination thereof. Methods for consolidation
treatment are known in the art. The consolidation treatment may involve a thermal process
where contacts between particles of the non-combustible ceramic matrix are formed, for
example by surface diffusion. Thermal treatment may involve gradual or stepwise heating to a
desired maximum temperature, for example of up to about 750°C and subsequent cooling.
Heating, cooling or advantageously both heating and cooling are advantageously performed
under an inert gas atmosphere, such as an argon or nitrogen atmosphere. Alternatively, the
consolidation treatment may be a process like that described in DE-A-10 2004 055 900.
The consolidation treatment advantageously preserves sufficient pores within the non-
combustible porous ceramic matrix for gas flow to and from the combustible fuel embedded
within the non-combustible porous ceramic matrix.
The consolidation treatment should also preserve sufficient thermal resistance between
adjacent particles of the non-combustible porous ceramic matrix to enable the combustible fuel
embedded within the non-combustible porous ceramic matrix to be ignited using a match, lighter
or other suitable ignition means within about 10 seconds.
Preferably, composite heat sources according to the present invention comprise at least
one catalyst for the decomposition of a gas produced during combustion of the combustible fuel
embedded within the non-combustible porous ceramic matrix.
The non-combustible porous ceramic matrix may comprise a catalyst for the
decomposition of a gas produced by combustion of the combustible fuel. For example, as
previously described above, the non-combustible porous ceramic matrix may comprise one or
more transition metal oxides with a high catalytic activity for the conversion of carbon monoxide
to carbon dioxide such as, for example, iron oxide or manganese oxide.
In such embodiments of the present invention, in use, as gas molecules produced during
combustion of the combustible fuel flow out of the composite heat source through the pores in
the non-combustible porous ceramic matrix, they have multiple contacts with the walls of the
pore channels. The use in composite heat sources according to the present invention of a non-
combustible porous ceramic matrix having catalytic activity can thereby advantageously help to
ensure efficient removal of any potentially undesirable gases produced during combustion of the
combustible fuel.
Alternatively or in addition, composite heat sources according to the present invention
may comprise at least one catalyst embedded within the non-combustible porous ceramic
matrix for the decomposition of a gas produced during combustion of the combustible fuel
embedded within the non-combustible porous ceramic matrix.
Alternatively or in addition, at least a portion of the surface of the non-combustible
porous ceramic matrix may be coated with a layer of a catalyst for the decomposition of a gas
produced during combustion of the combustible fuel embedded within the non-combustible
porous ceramic matrix.
The thermal conductivity, structure and dimensions of composite heat sources according
to the present invention and the thermal contact between composite heat sources according to
the present invention and any means or structure by which the composite heat sources are
fixed, mounted or otherwise incorporated in a smoking article should be adjusted so that in use
the surface temperature of the composite heat sources remain within the temperature range for
optimum operation of any catalysts incorporated therein.
In use, composite heat sources according to the present invention preferably reach
operational temperature within a period of about 30 seconds or less after ignition of the
combustible fuel embedded in the non-combustible porous ceramic matrix.
To reduce the time taken to reach operational temperature, composite heat sources
according to the present invention may further comprise one or more oxidants embedded within
the non-combustible porous ceramic matrix that provide additional oxygen during ignition of the
combustible fuel embedded within the non-combustible porous ceramic matrix. Suitable
oxidants include, but are not limited to, nitrates, chlorates, perchlorates, permanganates and
mixtures thereof.
The one or more oxidants may be distributed substantially evenly throughout the non-
combustible porous ceramic matrix.
Alternatively, a mixture of the one or more oxidants and combustible fuel may be
localised in a channel or other portion of the composite heat source that acts as a ‘fuse’ upon
ignition of the composite heat source. For example, where the non-combustible porous ceramic
matrix comprises at least one airflow passageway, a mixture of the one or more oxidants and
combustible fuel may be localised in the at least one airflow passageway.
Composite heat sources according to the present invention for use in smoking articles
are preferably capable of generating heat for about 10 minutes upon combustion of the
combustible fuel embedded within the non-combustible porous ceramic matrix.
The non-combustible porous ceramic matrix may comprise one or more airflow
passageways for one or both of gas exchange and heat exchange.
Preferably, composite heat sources according to the present invention have a maximum
combustion temperature of between about 400°C and about 800°C.
In use, the combustion kinetics of composite heat sources according to the present
invention are controlled by the flow of oxygen to the combustible fuel embedded within the non-
combustible porous ceramic matrix. In preferred embodiments of the present invention, the
time controlling mechanism is the rate of diffusion of oxygen molecules through the pore
channels in the non-combustible porous ceramic matrix.
The rate of diffusion of oxygen molecules through the pore channels in the non-
combustible porous ceramic matrix increases slightly with increasing temperature. Therefore, to
obtain a stable combustion temperature between about 400°C and about 800°C, composite
heat sources according to the present invention may include an additional mechanism to limit
the rate of combustion of the combustible fuel embedded within the non-combustible porous
ceramic matrix at high temperatures.
In certain embodiments of the present invention, the additional rate limiting mechanism
may be a counter flow of gas molecules that is produced at high temperatures. For example, in
embodiments of the present invention in which the combustible fuel embedded within the non-
combustible porous ceramic matrix comprises carbon, the production of carbon monoxide due
to combustion of the carbon increases at high temperature. Each molecule of oxygen flowing
through the pore channels to the combustible fuel embedded within the non-combustible porous
ceramic matrix results in the production of two molecules of carbon monoxide, which then have
to flow out of the composite heat source through the pore channels. The diffusion of further
oxygen molecules into the non-combustible porous ceramic matrix is retarded by the counter
flow of carbon monoxide molecules out of the non-combustible porous ceramic matrix.
Alternatively or in addition, a counter flow of gas molecules may be produced at high
temperatures by the release of gas from an additional component included in the non-
combustible porous ceramic matrix. For example, a carbonate or a hydrate that thermally
decomposes at an appropriately high temperature may be included in the non-combustible
porous ceramic matrix.
In other embodiments of the present invention, the additional rate limiting mechanism
may alternatively be a thermally activated change in porosity of the non-combustible porous
ceramic matrix of the composite heat source. For example, sintering of a non-combustible
porous amorphous ceramic matrix may reduce the size of the pores of the non-combustible
porous amorphous ceramic matrix during combustion.
In yet further embodiments of the present invention, the redistribution of a melt formed
during combustion of the combustible fuel embedded within the non-combustible porous
ceramic matrix of the composite heat source may be used to control the combustion kinetics
thereof. For example, the composite heat source may comprise a combustible fuel having a low
melting point (such as, for example, aluminium or magnesium), which in use is soaked into the
pore channels of the non-combustible porous ceramic matrix by capillary forces, thereby
changing the reactivity of the non-combustible porous ceramic matrix and the cross section of
the pore channels.
Preferably, the combustible fuel embedded within the porous ceramic matrix has an
oxidation enthalpy of greater than or equal to 40 x 10 joules per cubic metre (J/m³) as
measured by dynamic scanning calorimetry (DSC).
Suitable combustible fuels for use in composite heat sources according to the present
invention include, but are not limited to, carbon (such as, for example, charcoal (including
hardwood charcoal powder) or carbon black), low atomic weight metals (such as, for example,
aluminium or magnesium), carbides (such as, for example, aluminium carbide (Al C ) and
calcium carbide (CaC )), nitrides and mixtures thereof. Combustible fuels suitable for use in
composite heat sources according to the present invention are commercially available.
Preferably, the volume fraction of the combustible fuel embedded in the non-combustible
porous ceramic matrix is greater than or equal to about 20% of the composite heat source.
Preferred combustible fuels for use in composite heat sources according to the present
invention essentially consist of one or more carbon compounds.
The ignitability of composite heat sources according to the present invention is
controlled by the particle size and surface activity of the combustible fuel. Typically, particulate
combustible fuels having small particle sizes are easier to ignite. However, it is more difficult to
incorporate a high volume fraction of particulate combustible fuels having small particle sizes
within the non-combustible porous ceramic matrix. To address this challenge, composite heat
sources according to the present invention may comprise mixtures of particulate combustible
fuels having particles of different size.
Where composite heat sources according to the present invention comprise two or more
particulate combustible fuels having different median D50 particle sizes, the non-combustible
porous ceramic matrix is formed from one or more particulate materials having a median D50
particle size at least five times less than the median D50 particle size of the particulate
combustible fuel present in the greatest amount by weight.
Preferably, composite heat sources according to the present invention comprise one or
more particulate combustible fuels having a particle size of between about 1 micron (µm) and
about 200 microns (µm).
The combustible fuel may comprise one or more additives for reducing the ignition
temperature of the combustible fuel.
Alternatively or in addition, the combustible fuel may comprise one or more additives for
reducing the emission of potentially undesirable gases from the combustible fuel during
combustion thereof.
In use, the combustible fuel embedded within the non-combustible porous ceramic
matrix of composite heat sources according to the invention delivers the required heat of
combustion.
In addition to the combustible fuel, part of the non-combustible porous ceramic matrix
may also contribute to heat generation. For example, the non-combustible porous ceramic
matrix of composite heat sources according to the present invention may comprise one or more
oxides in a reduced state (such as, for example, Fe O ), which support ignition of the composite
heat sources through exothermic oxidation.
Composite heat sources according to the present invention may have any desired
shape. Advantageously, the shape of composite heat sources according to the present
invention is designed to provide a desired available surface area taking into account, for
example, manufacturing considerations and performance requirements.
Preferably, composite heat sources according to the present invention are substantially
cylindrical.
Preferably, composite heat sources according to the present invention are of
substantially circular transverse cross section.
Composite heat sources according to the present invention may be produced using
suitable known ceramic forming methods such as, for example, slip casting, extrusion, injection
molding and die compaction. Co-extrusion and other suitable known techniques may also be
employed where, for example, concentration gradients in the composite heat source are
desired. Composite heat sources according to the present invention may be prepared from
larger compacts by punching or cutting procedures.
The particulate combustible fuel may be embedded in the non-combustible porous
ceramic matrix by mixing one or more particulate combustible fuels with a suitable amount of
one or more particulate raw materials for forming the non-combustible porous ceramic matrix
having a suitable relative particle size.
To avoid or reduce the formation of agglomerates, the particles of the one or more
particulate combustible fuels are preferably not attracted to one another.
Alternatively or in addition, to avoid or reduce the formation of agglomerates, the
particles of the one or more particulate raw materials for forming the non-combustible porous
ceramic matrix are preferably not attracted to one another.
Preferably, the particles of the one or more particulate combustible fuels are attracted to
the particles of the one or more particulate raw materials for forming the non-combustible
porous ceramic matrix.
Organic binders may be used during the forming process. Other additives may also be
included to, for example, facilitate processing (processing aids), such as, for example,
lubricants, promote consolidation (sintering aids), combustion or removal of potentially
undesirable combustion gases. Such additives and their utility are known in the art.
Where consolidation of composite heat sources according to the present invention is
performed by a thermal treatment, the furnace atmosphere should be adapted to the
requirements of the composite heat source. Typically, inert or reducing atmospheres should be
used to prevent premature combustion of the combustible fuel embedded within the porous
ceramic matrix.
During thermal treatment, phase changes may be used to enhance the activity of some
of the components of composite heat sources according to the present invention or to improve
other properties thereof.
For example, composite heat sources according to the invention may include Fe O ,
which is reduced to form Fe O , which has a very low combustion temperature, or FeO, which
has a low thermal conductivity. Such phase changes may be controlled by controlling the
furnace atmosphere (oxygen partial pressure) and the time temperature cycle in the furnace.
Additives that do not tolerate any of the previous process steps may be introduced into
composite heat sources according to the invention by an additional infiltration step. For
example, oxidants that would decompose during a thermal treatment may be added to
composite heat sources according to the present invention by infiltration from salt solutions and
subsequent drying of the composite heat sources.
Where composite heat sources according to the present invention comprise carbon as a
combustible fuel, the carbon concentration near the surface of the composite heat sources may
be advantageously reduced by a final treatment to reduce carbon monoxide emissions during
combustion. For example, the outer surface of the composite heat sources may be quickly
heated by a flame or other suitable method in order to burn the carbon locally without igniting
the composite heat sources.
According to the present invention there is also provided a smoking article comprising: a
composite heat source according to the invention; and an aerosol-generating substrate.
As used herein, the term ’aerosol-generating substrate’ denotes a substrate capable of
releasing volatile compounds upon heating to generate an aerosol.
The composite heat source and aerosol-generating substrate of smoking articles
according to the present invention may abut one another. Alternatively, the composite heat
source and the aerosol-generating substrate of smoking articles according to the present
invention may be separated by suitable means (such as, for example thermal insulation or an
air gap) to prevent ignition of the aerosol-generating substrate during combustion of the
combustible fuel embedded within the non-combustible porous ceramic matrix of the composite
heat source.
In certain embodiments of the present invention, the composite heat source is axially
aligned with the aerosol-generating substrate, which is located downstream of the composite
heat source. For example, composite heat sources according to the invention may be used in
heated smoking articles of the type disclosed in WO-A-2009/022232, which comprise a
combustible heat source, an aerosol-generating substrate downstream of the combustible heat
source, and a heat-conducting element around and in contact with a rear portion of the
combustible heat source and an adjacent front portion of the aerosol-generating substrate.
However, it will be appreciated that composite heat sources according to the invention may also
be used in smoking articles having other constructions.
As used herein, the terms ‘upstream’ and ‘downstream’ are used to describe the relative
positions of components, or portions of components, of smoking articles according to the
present invention in relation to the direction of air drawn through the smoking articles during use
thereof.
In alternative embodiments of the present invention, the composite heat source is
surrounded by the aerosol-generating substrate.
In alternative embodiments of the present invention, the aerosol-generating substrate is
surrounded by the composite heat source. For example, smoking articles according to the
present invention may comprise a hollow substantially cylindrical composite heat source that
circumscribes the aerosol-generating substrate.
Smoking articles according to the present invention may further comprise an expansion
chamber downstream of the composite heat source and aerosol generating substrate.
Smoking articles according to the invention may further comprise a mouthpiece
downstream of the composite heat source, aerosol-generating substrate and, where present,
expansion chamber.
The aerosol-generating substrate of smoking articles according to the present invention
may include any material capable of releasing volatile compounds when contacted by hot gases
flowing through the composite heat source. Preferably, the aerosol-generating substrate
comprises tobacco.
The invention will be further described, by way of example only, with reference to the
accompanying drawings in which:
Figure 1 shows a schematic longitudinal cross-sectional view of a smoking article
according to a first embodiment of the present invention;
Figure 2 shows a schematic longitudinal cross-sectional view of a smoking article
according to a second embodiment of the present invention; and
Figure 3 shows a schematic longitudinal cross-sectional view of a composite heat source
according to a first embodiment of the present invention;
Figure 4 shows a schematic longitudinal cross-sectional view of a composite heat
source according to a second embodiment of the present invention;
Figure 5a shows a composite heat source according to the present invention prepared in
accordance with Example 1;
Figure 5a shows a composite heat source according to the present invention prepared in
accordance with Example 2.
The smoking articles according to the first and second embodiments of the present
invention shown in Figures 1 and 2, respectively, have several components in common; these
components have been given the same reference numerals throughout.
Each smoking article generally comprises an elongate cylindrical rod 2, which is
attached at one end to an axially aligned cylindrical filter 4. The elongate cylindrical rod 2
includes a cylindrical composite heat source 6 and an aerosol-generating substrate 8, which are
overwrapped in an outer wrapper of cigarette paper (not shown). The composite heat source 6
is made as described in Composite Heat Sources: Example 1 or Composite Heat Sources:
Example 2, below.
In the smoking article according to the first embodiment of the present invention shown
in Figure 1, the composite heat source 6 and the aerosol-generating substrate 8 are axially
aligned. As shown in Figure 1, the composite heat source 6 is located at the end of the rod 2
distant from the filter 4 and the aerosol-generating substrate 8 is located downstream of the
composite heat source 6 at the end of the rod 2 adjacent the filter 4.
In the smoking article according to the second embodiment of the present invention
shown in Figure 2, the composite heat source 6 is located within and surrounded by the
aerosol-generating substrate 8.
In a third embodiment of the present invention, which is not shown in the drawings, the
composite heat source 6 is a hollow cylindrical tube and the aerosol-generating substrate 8 is
located within and surrounded by the composite heat source 6.
In all three embodiments, thermal insulation or an air gap 10 is provided between the
composite heat source 6 and the aerosol-generating substrate 8 in order to prevent ignition of
the aerosol-generating substrate 8 during combustion of the combustible fuel embedded within
the non-combustible porous ceramic matrix of the composite heat source 6.
In use, the consumer ignites the combustible fuel embedded within the non-combustible
porous ceramic matrix of the composite heat source 6 and then draws air downstream through
the rod 2 of the smoking article towards the filter 4 thereof. As it passes through the rod 2, the
drawn air is heated by the composite heat source 6 and the heated air flows through the
aerosol-generating substrate 8, releasing flavoured vapours from, for example, shredded
tobacco cut filler in the aerosol-generating substrate 8. As the flavoured vapours released from
the aerosol-generating substrate 8 pass downstream through the rod 2 they condense to form
an aerosol that passes through the filter 4 into the mouth of the consumer.
Composite heat sources according to first and second embodiments of the present
invention, for use in the smoking articles shown in Figures 1 and 2, are shown in Figures 3 and
4, respectively. The composite heat sources shown in Figures 3 and 4 have several
components in common; these components have been given the same reference numerals
throughout.
Each composite heat source is a cylinder of substantially circular transverse cross
section and generally comprises a non-combustible porous ceramic matrix 16 and a plurality of
particles of combustible fuel 18 embedded within the non-combustible porous ceramic matrix
The composite heat source according to the first embodiment of the invention shown in
Figure 3 further comprises an outer insulating layer 20, which circumscribes the non-
combustible porous ceramic matrix 16 and may be formed of the same or different material as
the non-combustible porous ceramic matrix 16.
The composite heat source according to the second embodiment of the invention shown
in Figure 4 comprises a central cylindrical airflow passageway 22 that extends axially through
the non-combustible porous ceramic matrix 16. As shown in Figure 4, a layer of catalytic
material 24 (such as, for example, iron oxide or manganese oxide) is disposed between the
inner surface of the non-combustible porous ceramic matrix 16 and the airflow passageway 22.
It will be appreciated that in alternative embodiments of the present invention, not shown
in the drawings, the outer insulating layer 20 and layer of catalytic material 24 shown in Figures
3 and 4, respectively, may be omitted.
It will also be appreciated that in further embodiments of the present invention, not
shown in the drawings, composite heat sources according to the present invention may
comprise both an outer insulating layer and a layer of catalytic material.
Composite Heat Sources: Example 1
Composite heat sources according to the present invention are prepared by mixing
236 g of iron oxide (Fe O ) having a median D50 particle size of 0.140 µm commercially
available from Alfa Aesar of Massachusetts, USA, 52 g of NORIT A Special E153 powdered
activated carbon having a median D50 particle size of 4 µm commercially available from Norit
Nederland BV of Amersfoort, The Netherlands, 104 g of hardwood charcoal powder having a
median D50 particle size of 45 µm commercially available from Holzkohlewerk Lüneburg of
Hamburg, Germany and 190 g of zirconia (ZrO ) having a median D50 particle size of 0.6 µm
commercially available from Wilhelm Priem GmbH & Co. KG of Bielefeld Germany in a
planetary mixer. Mixing is carried out with the addition of 125 g of flour, 64 g of sugar, 14 g of
corn oil and 24 g of potassium citrate. Water is slowly added to the mixture to obtain an
extrudable paste.
The paste is then extruded through a die using a laboratory screw extruder to form
cylindrical rods of circular cross-section having a length of about 30 cm and a diameter of about
7.8 mm. Three longitudinal airflow passageways having a diameter of about 1.66 mm are
formed in the cylindrical rods by mandrels of circular cross-section mounted in the die orifice.
After extrusion, the cylindrical rods are dried on grooved plates. After drying, the
cylindrical rods are cut into pieces having a length of about 10 cm. The pieces are heated in a
furnace in an argon atmosphere from room temperature up to 100°C over a period of 1.3 hours
and then from 100°C to 700°C over a period of 2 hours. After a dwell period of 0.3 hours at
700°C, the furnace was cooled to room temperature.
The individual composite heat sources formed can be ignited using a yellow flame lighter
and are found to combust for a period of 12 minutes with a maximum combustion temperature
of 780°C.
After combustion, the composite heat sources are mechanically robust and, for example,
cannot be fractured with fingers. Dusting is low. After combustion, the composite heat sources
can be handled without major caution.
Composite Heat Sources: Example 2
Composite heat sources according the present invention are prepared by mixing 236 g
of iron oxide (Fe O ) having a median D50 particle size of 0.140 µm commercially available
from Alfa Aesar of Massachusetts, USA, 52 g of NORIT A Special E153 powdered activated
carbon having a median D50 particle size of 4 µm commercially available from Norit Nederland
BV of Amersfoort, The Netherlands, 104 g of hardwood charcoal powder having a median D50
particle size of 45 µm commercially available from Holzkohlewerk Lüneburg of Hamburg,
Germany and 190 g of zirconia (ZrO ) having a median D50 particle size of 0.6 µm
commercially available from Wilhelm Priem GmbH & Co. KG of Bielefeld Germany in a
planetary mixer. Mixing is carried out with the addition of 125 g of flour, 64 g of sugar, 14 g of
corn oil and 24 g of potassium citrate. Water is slowly added to the mixture to obtain an
extrudable paste.
The paste is then extruded through a die using a laboratory screw extruder to form
cylindrical rods of circular cross-section having a length of about 30 cm and a diameter of about
7.8 mm. Three longitudinal airflow passageways having a diameter of about 1.66 mm are
formed in the cylindrical rods by mandrels of circular cross-section mounted in the die orifice.
After extrusion, the cylindrical rods are dried on grooved plates. After drying, the
cylindrical rods are cut into pieces having a length of about 10 cm. The pieces are heated in a
furnace in a nitrogen atmosphere from room temperature up to 100°C over a period of 1.3 hours
and then from 100°C to 680°C over a period of 1.9 hours. After a dwell period of 0.2 hours at
680°C, the furnace is cooled to room temperature.
The individual composite heat sources formed can be ignited using a blue flame lighter
and are found to combust for a period of 12 minutes with a maximum combustion temperature
of 800°C.
The composite heat sources are mechanically robust before and after combustion and,
for example, cannot be fractured with fingers. Dusting is minimal.
Claims (9)
1. A composite heat source for a smoking article comprising: a non-combustible porous ceramic matrix; and 5 a particulate combustible fuel embedded within the non-combustible porous ceramic matrix, wherein the non-combustible porous ceramic matrix is formed from one or more particulate materials having a median D50 particle size at least five times less than the median D50 particle size of the particulate combustible fuel and wherein the volume fraction of the 10 combustible fuel embedded in the non-combustible porous ceramic matrix is less than or equal to about 50% of the composite heat source.
2. A composite heat source according to claim 1 wherein the non-combustible porous ceramic matrix comprises one or more oxides.
3. A composite heat source according to claim 2 wherein the non-combustible porous ceramic matrix comprises one or more transition metal oxides.
4. A composite heat source according to claim 2 or 3 wherein the non-combustible porous 20 ceramic matrix comprises one or more oxides selected from the group consisting of: iron oxide; manganese oxide; zirconia; quartz; and amorphous silica.
5. A composite heat source according to claim 1, 2 or 3 wherein the non-combustible porous ceramic matrix has pores with diameters of between about 0.01 µm and about 10 µm.
6. A composite heat source according to any one of claims 1 to 5 wherein the non- combustible porous ceramic matrix has a thermal diffusivity of less than or equal to about 1 x -6 2 10 m /s. 30
7. A composite heat sourc according to any one of claims 1 to 6 wherein the combustible fuel has an oxidation enthalpy of greater than or equal to about 40 x 10 J/m³.
8. A composite heat source according to any preceding claim wherein the combustible fuel comprises carbon, aluminium, magnesium, one or more metal carbides, one or more metal 35 nitrides or a combination thereof.
9. A composite heat source according to any preceding claim further comprising at least
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP11196058.9 | 2011-12-29 | ||
EP11196058 | 2011-12-29 | ||
PCT/EP2012/077033 WO2013098380A1 (en) | 2011-12-29 | 2012-12-28 | Composite heat source for a smoking article |
Publications (2)
Publication Number | Publication Date |
---|---|
NZ623277A NZ623277A (en) | 2016-02-26 |
NZ623277B2 true NZ623277B2 (en) | 2016-05-27 |
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