NZ622007B2 - Smoking article comprising a combustible heat source with a rear barrier coating - Google Patents
Smoking article comprising a combustible heat source with a rear barrier coating Download PDFInfo
- Publication number
- NZ622007B2 NZ622007B2 NZ622007A NZ62200712A NZ622007B2 NZ 622007 B2 NZ622007 B2 NZ 622007B2 NZ 622007 A NZ622007 A NZ 622007A NZ 62200712 A NZ62200712 A NZ 62200712A NZ 622007 B2 NZ622007 B2 NZ 622007B2
- Authority
- NZ
- New Zealand
- Prior art keywords
- heat source
- combustible
- combustible heat
- barrier coating
- aerosol
- Prior art date
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- 239000011248 coating agent Substances 0.000 title claims abstract description 140
- 238000000576 coating method Methods 0.000 title claims abstract description 140
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- 235000009569 green tea Nutrition 0.000 description 1
- 239000005337 ground glass Substances 0.000 description 1
- 239000000665 guar gum Substances 0.000 description 1
- 229960002154 guar gum Drugs 0.000 description 1
- 235000010417 guar gum Nutrition 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium(0) Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 235000001050 hortel pimenta Nutrition 0.000 description 1
- 239000003906 humectant Substances 0.000 description 1
- DLINORNFHVEIFE-UHFFFAOYSA-N hydrogen peroxide;zinc Chemical compound [Zn].OO DLINORNFHVEIFE-UHFFFAOYSA-N 0.000 description 1
- 239000001863 hydroxypropyl cellulose Substances 0.000 description 1
- 235000010977 hydroxypropyl cellulose Nutrition 0.000 description 1
- 239000001866 hydroxypropyl methyl cellulose Substances 0.000 description 1
- 235000010979 hydroxypropyl methyl cellulose Nutrition 0.000 description 1
- 229920003088 hydroxypropyl methyl cellulose Polymers 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 238000001746 injection moulding Methods 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- ICIWUVCWSCSTAQ-UHFFFAOYSA-M iodate Chemical class [O-]I(=O)=O ICIWUVCWSCSTAQ-UHFFFAOYSA-M 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- VCJMYUPGQJHHFU-UHFFFAOYSA-N iron(3+);trinitrate Chemical compound [Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VCJMYUPGQJHHFU-UHFFFAOYSA-N 0.000 description 1
- 229960004995 magnesium peroxide Drugs 0.000 description 1
- 229910000529 magnetic ferrite Inorganic materials 0.000 description 1
- 230000005499 meniscus Effects 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
- 229910001092 metal group alloy Inorganic materials 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000003607 modifier Substances 0.000 description 1
- 150000002826 nitrites Chemical class 0.000 description 1
- 150000002828 nitro derivatives Chemical class 0.000 description 1
- 229910052813 nitrogen oxide Inorganic materials 0.000 description 1
- 150000001451 organic peroxides Chemical class 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000001590 oxidative Effects 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 235000006678 peppermint Nutrition 0.000 description 1
- 235000015132 peppermint Nutrition 0.000 description 1
- 235000007735 peppermint Nutrition 0.000 description 1
- LLYCMZGLHLKPPU-UHFFFAOYSA-M perbromate Chemical class [O-]Br(=O)(=O)=O LLYCMZGLHLKPPU-UHFFFAOYSA-M 0.000 description 1
- 150000002989 phenols Chemical class 0.000 description 1
- 235000021317 phosphate Nutrition 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 238000002459 porosimetry Methods 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 239000011591 potassium Substances 0.000 description 1
- 235000019396 potassium bromate Nutrition 0.000 description 1
- 229940094037 potassium bromate Drugs 0.000 description 1
- 159000000001 potassium salts Chemical class 0.000 description 1
- 235000019353 potassium silicate Nutrition 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000001812 pycnometry Methods 0.000 description 1
- 235000005227 red mallee Nutrition 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 235000002020 sage Nutrition 0.000 description 1
- 239000001296 salvia officinalis l. Substances 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Inorganic materials [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 description 1
- 238000007569 slipcasting Methods 0.000 description 1
- 229940080281 sodium chlorate Drugs 0.000 description 1
- 239000004317 sodium nitrate Substances 0.000 description 1
- 235000010344 sodium nitrate Nutrition 0.000 description 1
- 229910001488 sodium perchlorate Inorganic materials 0.000 description 1
- 235000010339 sodium tetraborate Nutrition 0.000 description 1
- 229910000144 sodium(I) superoxide Inorganic materials 0.000 description 1
- 235000019698 starch Nutrition 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 150000008163 sugars Chemical class 0.000 description 1
- 150000003462 sulfoxides Chemical class 0.000 description 1
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 1
- OUUQCZGPVNCOIJ-UHFFFAOYSA-M superoxide Chemical class [O-][O] OUUQCZGPVNCOIJ-UHFFFAOYSA-M 0.000 description 1
- 235000013616 tea Nutrition 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 230000001131 transforming Effects 0.000 description 1
- 229910052723 transition metal Inorganic materials 0.000 description 1
- 150000003624 transition metals Chemical class 0.000 description 1
- ILJSQTXMGCGYMG-UHFFFAOYSA-N triacetic acid Chemical compound CC(=O)CC(=O)CC(O)=O ILJSQTXMGCGYMG-UHFFFAOYSA-N 0.000 description 1
- WUUHFRRPHJEEKV-UHFFFAOYSA-N tripotassium borate Chemical compound [K+].[K+].[K+].[O-]B([O-])[O-] WUUHFRRPHJEEKV-UHFFFAOYSA-N 0.000 description 1
- BSVBQGMMJUBVOD-UHFFFAOYSA-N trisodium borate Chemical compound [Na+].[Na+].[Na+].[O-]B([O-])[O-] BSVBQGMMJUBVOD-UHFFFAOYSA-N 0.000 description 1
- 235000015112 vegetable and seed oil Nutrition 0.000 description 1
- 239000008158 vegetable oil Substances 0.000 description 1
- 235000001594 verbena Nutrition 0.000 description 1
- 235000002270 verbena Nutrition 0.000 description 1
- 235000007200 verbena Nutrition 0.000 description 1
- 235000007212 verbena Nutrition 0.000 description 1
- 239000003039 volatile agent Substances 0.000 description 1
- 239000010457 zeolite Substances 0.000 description 1
- QCWXUUIWCKQGHC-UHFFFAOYSA-N zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
- 229910000166 zirconium phosphate Inorganic materials 0.000 description 1
- LEHFSLREWWMLPU-UHFFFAOYSA-B zirconium(4+);tetraphosphate Chemical compound [Zr+4].[Zr+4].[Zr+4].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O LEHFSLREWWMLPU-UHFFFAOYSA-B 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
- 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
-
- A24F47/006—
Abstract
combustible heat source (4) with an airflow channel (16) and a non-metallic, non-combustible, gas-resistant barrier coating (14) for a tobacco heating e-cigarette is described. The barrier coating (14) prevents the migration of aerosol from the aerosol forming substrate (6) to the combustible heat source (4) and reduces the level of harmful or toxic smoke constituents. The barrier coating has an elemental metal or alloy content of less than 50 mole percent. source (4) and reduces the level of harmful or toxic smoke constituents. The barrier coating has an elemental metal or alloy content of less than 50 mole percent.
Description
SMOKING ARTICLE COMPRISING A COMBUSTIBLE HEAT SOURCE WITH A REAR BARRIER
COATING
The present invention relates to a smoking article comprising a combustible heat source
and an aerosol-forming substrate comprising at least one aerosol-former, wherein the substrate
is downstream of the combustible heat source, to a combustible heat source for use in such a
smoking article, and to a method of reducing the formation of certain harmful smoke
constituents during combustion of a combustible heat source in a smoking article.
A number of smoking articles in which tobacco is heated rather than combusted have
been proposed in the art. The aim of such smoking articles is to reduce known harmful smoke
constituents produced by the combustion and pyrolytic degradation of tobacco in conventional
cigarettes. Typically in such smoking articles, an aerosol is generated by the transfer of heat
from a combustible fuel element or heat source to an aerosol-forming substrate, which may be
located within, around or downstream of the fuel element. During smoking, volatile compounds
are released from the aerosol-forming substrate by heat transfer from the fuel element and
entrained in air drawn through the smoking article. As the released compounds cool they
condense to form an aerosol that is inhaled by the consumer.
For example, WO-A2-2009/022232 discloses a smoking article comprising a
combustible heat source, an aerosol-forming 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-forming substrate. In the
smoking article of WO-A2-2009/022232, the surface of the aerosol-forming substrate is in direct
contact with the combustible heat source.
A number of previous attempts have been made to reduce the amount of carbon
monoxide produced during the combustion of carbonaceous heat sources for heatable smoking
articles, such as by using catalysts in the heat source to convert carbon monoxide produced
during combustion of the heat source to carbon dioxide. Other prior art documents, such as
US-A-5,040,551, disclose a method for reducing the amount of carbon monoxide produced in
the combustion of a carbonaceous fuel element by coating some or all of the exposed surfaces
of the carbonaceous fuel element with a thin, microporous layer of solid particulate matter which
is substantially non-combustible at temperatures in which the carbonaceous fuel combusts.
According to US-A-5,040,551, the microporous layer must be sufficiently thin, and therefore
permeable to air, so as not to unduly prevent the carbonaceous fuel from combusting. Like the
smoking article of WO-A2-2009/022232, the surface of the aerosol-forming substrate in
US-A-5,040,551 is in direct contact with the combustible heat source.
To facilitate aerosol formation, the aerosol-forming substrates of known heatable
smoking articles typically comprise a polyhydric alcohol such as glycerine or other known
aerosol-formers. During storage and smoking, aerosol-formers may migrate from the aerosol-
forming substrates of known heatable smoking articles to the combustible heat sources thereof.
This migration of the aerosol-formers can disadvantageously lead to their decomposition,
particularly during smoking of the heatable smoking articles. A number of previous attempts
have been made to inhibit migration of aerosol-formers from the aerosol-forming substrates of
heatable smoking articles to the combustible heat sources thereof (for example, in
US-A-4,714,082, EP-A2-0 337 507, EP-A2-0 337 508 and US-A-5,156,170). Generally, such
attempts have involved smoking articles in which the aerosol-forming substrate is enveloped
within a non-combustible capsule, such as a metallic cage, to reduce migration of aerosol-
formers from the aerosol-forming substrate to the combustible heat source during storage and
use, but in which the combustible heat source is still allowed to come into direct contact with
aerosol-formers from the aerosol-forming substrate during storage and use. Such prior art
designs disadvantageously allow for decomposition and combustion gases generated from the
combustible heat source to be directly drawn into the mainstream aerosol, make it difficult to
use known machinery and methods to produce the smoking article, and can hinder the ability of
the smoking article to attain a suitable temperature to provide a satisfactory aerosol during the
first few puffs by the consumer.
There remains a need for an improved heatable smoking article comprising a
combustible heat source and an aerosol-forming substrate comprising at least one aerosol-
former which may be assembled using known manufacturing equipment. There also further
remains a need for an improved heatable smoking article comprising a combustible heat
source and an aerosol-forming substrate comprising at least one aerosol-former in which
migration of the at least one aerosol-former from the aerosol-forming substrate to the
combustible heat source is substantially prevented or inhibited. Further, there still is a need to
reduce the level of harmful smoke constituents in the mainstream aerosol of a heatable smoking
article, like carbonyl compounds, such as formaldehyde, acetaldehyde, proprionaldehyde, and
phenolics.
According to an aspect of the invention there is provided a combustible heat source with
opposed front and rear faces for use in a smoking article, the combustible heat source
comprising: at least one airflow channel extending from the front face to the rear face of the
combustible heat source and a non-metallic, non-combustible, gas-resistant, first barrier coating
on substantially the entire rear face of the combustible heat source that allows gas to be drawn
through the at least one airflow channel, wherein the non-metallic, non-combustible, gas-
resistant, first barrier coating has an elemental metal or alloy content of less than 50 mole
percent.
The first barrier coating may have a thickness of at least about 10 microns.
The first barrier coating may be substantially impermeable to air.
The first barrier coating may comprise clay, glass, or alumina.
The combustible heat source may be a carbonaceous heat source.
The combustible heat source may comprise an ignition aid.
The ignition aid may be an oxidizing agent.
A gas-resistant, heat resistant, second barrier coating may be provided on the inner
surface of the at least one airflow channel.
The second barrier coating may be substantially impermeable to air.
According to another aspect of the invention, there is provided a smoking article
comprising: a combustible heat source according to the above aspect; and an aerosol-forming
substrate comprising at least one aerosol-former downstream of the combustible heat source.
The aerosol-forming substrate may comprise homogenised tobacco-based material.
The smoking article may further comprise 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-forming substrate.
The smoking article may further comprise an expansion chamber downstream of the
aerosol-forming substrate.
The smoking article may further comprise a mouthpiece downstream of the expansion
chamber.
Described herein is a smoking article for lowering the amount of carbon monoxide
produced during combustion of a combustible heat source in the smoking article.
Described herein is a smoking article for lowering the amount of certain harmful smoke
constituents, such as carbon monoxide, formaldehyde, acetaldehyde, proprionaldehyde and
phenolics, which are produced during combustion of a combustible heat source in the smoking
article.
Described herein is a combustible heat source for lowering the amount of certain
harmful smoke constituents, such as carbon monoxide, formaldehyde, acetaldehyde,
proprionaldehyde and phenolics, which are produced during combustion of the combustible
heat source in a smoking article.
Described herein is a method to reduce the formation of gas, selected from the group
consisting of carbon monoxide, formaldehyde, acetaldehyde, proprionaldehyde, phenolics and
mixtures thereof that is generated in mainstream aerosol during combustion of a combustible
heat source in a smoking article, comprising the step of forming a smoking article as described
herein.
As used herein, the terms ’upstream’ and ‘front’, and ‘downstream’ and ‘rear’, are used
to describe the relative positions of components, or portions of components, of combustible heat
sources and smoking articles according to the invention in relation to the direction of air drawn
through the combustible heat sources and smoking articles during use thereof.
As used herein, the term ‘coating’ is used to describe a layer of material that covers and
is adhered to the heat source.
As used herein, the term ‘non-metallic’ is used to describe a barrier coating that is not
formed primarily from an elemental metal or alloy, that is a barrier coating having an elemental
metal or alloy content of less than 50 mole percent.
As used herein, the term ‘non-combustible’ is used to describe a barrier coating that is
substantially non-combustible at temperatures reached by the combustible heat source during
combustion or ignition thereof.
As used herein, the term ‘gas-resistant’ is used to describe a barrier coating that is at
least substantially impermeable to gas. Preferably, the first barrier coating is at least
substantially impermeable to air.
As used herein, the term ‘aerosol-forming substrate’ is used to describe a substrate
capable of releasing upon heating volatile compounds, which can form an aerosol.
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.
The provision of a non-metallic, non-combustible, gas-resistant, first barrier coating on
substantially the entire rear face of the combustible heat source advantageously prevents or
inhibits migration of the at least one aerosol-former from the aerosol-forming substrate to the
combustible heat source during storage and use of smoking articles according to the invention.
Decomposition of the at least one aerosol-former during use of smoking articles according to
the invention is thus advantageously avoided or reduced.
The provision of a non-metallic, non-combustible, gas-resistant, first barrier coating on
substantially the entire rear face of the combustible heat source also advantageously may limit
or prevent migration of other volatile components of the aerosol-forming substrate from the
aerosol-forming substrate to the combustible heat source during storage and during use of
smoking articles according to the invention.
The non-metallic, non-combustible, gas-resistant, first barrier coating provided on the
rear face of the combustible heat source also advantageously prevents or inhibits combustion
and decomposition products formed during ignition and combustion of the combustible heat
source from entering air drawn through the smoking article during use thereof. As described
further below, this is particularly advantageous where the combustible heat source comprises
one or more additives to aid ignition or combustion of the combustible heat source or a
combination thereof.
The non-metallic, non-combustible, gas-resistant, first barrier coating provided on the
rear face of the combustible heat source also advantageously limits the temperature to which
the aerosol-forming substrate is exposed during ignition or combustion of the combustible heat
source, and so helps to avoid thermal degradation or combustion of the aerosol-forming
substrate during use of the smoking article. As described further below, this is also particularly
advantageous where the combustible heat source comprises one or more additives to aid
ignition of the combustible heat source.
Depending upon the desired characteristics and performance of the smoking article, the
non-metallic, non-combustible, gas-resistant, first barrier coating may have a low or high
thermal conductivity. In one example of the preferred embodiment, the non-metallic, non-
combustible, gas-resistant, first barrier coating may be formed from material having a bulk
thermal conductivity of between about 0.1 W per metre Kelvin (W/(m•K)) and about 200 W per
metre Kelvin (W/(m•K)) at 23°C and a relative humidity of 50% as measured using the modified
transient plane source (MTPS) method. In another example of the preferred embodiment, the
non-metallic, non-combustible, gas-resistant, first barrier coating may be formed from material
having a bulk thermal conductivity of between about 0.05 W per metre Kelvin (W/(m•K)) and
about 50 W per metre Kelvin (W/(m•K)) at 23°C and a relative humidity of 50% as measured
using the modified transient plane source (MTPS) method.
The thickness of the non-metallic, non-combustible, gas-resistant, first barrier coating
may be appropriately adjusted to achieve good smoking performance while avoiding or
minimizing one or both of the generation and intake of harmful volatile compounds from the
smoking article. In one example of the preferred embodiment, the non-metallic, non-
combustible, gas-resistant, first barrier coating may have a thickness of between about
microns and about 500 microns.
The non-metallic, non-combustible, gas-resistant, first barrier coating may be formed
from one or more suitable materials that are substantially thermally stable and non-combustible
at temperatures achieved by the combustible heat source during ignition and combustion.
Suitable materials are known in the art and include, but are not limited to, clays (such as for
example bentonite and kaolinite), glasses and other minerals, ceramic materials or
combinations thereof.
Preferred coating materials from which the non-combustible, gas-resistant, first barrier
coating may be formed include clays and glasses. More preferably, the non-metallic, non-
combustible, gas-resistant, first barrier coating may be formed from alumina (Al O ), resins, and
mineral glues. In one preferred embodiment of the invention, the non-metallic, non-
combustible, gas-resistant, first barrier coating is a clay coating comprising a 50/50 mixture of
bentonite and kaolinite. In another preferred embodiment of the invention, the non-metallic,
non-combustible, gas-resistant, first barrier coating is a glass coating, more preferably a
sintered glass coating.
Preferably, the non-metallic, non-combustible, gas-resistant, first barrier coating has a
thickness of at least about 10 microns. Due to the slight permeability of clays to gas, in
embodiments where the non-metallic, non-combustible, gas-resistant, first barrier coating is a
clay coating the non-metallic, non-combustible, gas-resistant, first barrier coating more
preferably has a thickness of at least about 50 microns, and most preferably of between about
50 microns and about 350 microns. In embodiments where the non-metallic, non-combustible,
gas-resistant, first barrier coating is formed from one or more materials that are more
impervious to gas, the non-metallic, non-combustible, gas-resistant, first barrier coating may be
thinner, and generally will preferably have a thickness of less than about 100 microns, and more
preferably about 20 microns. In embodiments where the non-metallic, non-combustible, gas-
resistant, first barrier coating is a glass coating, the non-metallic, non-combustible, gas-
resistant, first barrier coating preferably has a thickness under 200 microns. The thickness of
the non-metallic, non-combustible, gas-resistant, first barrier coating may be measured using a
microscope, a scanning electron microscope (SEM) or any other suitable measurement
methods known in the art.
The non-metallic, non-combustible, gas-resistant, first barrier coating may be applied to
cover and adhere to substantially the entire rear face of the combustible heat source by any
suitable methods known in the art including, but not limited to, spray-coating, vapour deposition,
dipping, material transfer (for example, brushing or gluing), electrostatic deposition or any
combination thereof.
The non-metallic, non-combustible, gas-resistant, first barrier coating, for example, may
be made by pre-forming a barrier in the approximate size and shape of the rear face of the
combustible heat source, and applying it to the rear face of the combustible heat source to
cover and adhere to substantially the entire rear face of the combustible heat source.
Alternatively, the non-metallic, non-combustible, gas-resistant, first barrier coating may be
formed, drilled or machined after it is applied to the rear face of the combustible heat source.
In a preferred embodiment, the non-metallic, non-combustible, gas-resistant, first barrier
coating is formed by applying a solution or suspension of one or more suitable coating materials
to the rear face of the combustible heat source. For example, the non-metallic, non-
combustible, gas-resistant, first barrier coating may be applied to substantially the entire rear
face of the combustible heat source by dipping the rear face of the combustible heat source in a
solution or suspension of one or more suitable coating materials or by brushing or spray-coating
a solution or suspension or electrostatically depositing a powder or powder mixture of one or
more suitable coating materials onto the rear face of the combustible heat source. The rear
face of the combustible heat source is preferably pre-treated with water glass before
electrostatic deposition. More preferably, the non-combustible, gas-resistant, first barrier
coating is applied by spray-coating.
The non-metallic, non-combustible, gas-resistant, first barrier coating may be formed
through a single application of a solution or suspension of one or more suitable coating
materials to the rear face of the combustible heat source. Alternatively, the non-metallic, non-
combustible, gas-resistant, first barrier coating may be formed through multiple applications of a
solution or suspension of one or more suitable coating materials to the rear face of the
combustible heat source. For example, the non-metallic, non-combustible, gas-resistant, first
barrier coating may be formed through one, two, three, four, five, six, seven or eight successive
applications of a solution or suspension of one or more suitable coating materials to the rear
face of the combustible heat source.
Preferably, the non-metallic, non-combustible, gas-resistant, first barrier coating is
formed through between one and ten applications of a solution or suspension of one or more
suitable coating materials to the rear face of the combustible heat source.
After application of the solution or suspension of one or more coating materials to the
rear face thereof, the combustible heat source may be dried to form the non-metallic, non-
combustible, gas-resistant, first barrier coating.
Where the non-metallic, non-combustible, gas-resistant, first barrier coating is formed
through multiple applications of a solution or suspension of one or more suitable coating
materials to the rear face thereof, the combustible heat source may need to be dried between
successive applications of the solution or suspension.
Alternatively or in addition to drying, after application of a solution or suspension of one
or more coating materials to the rear face of the combustible heat source, the one or more
coating materials on the combustible heat source may be sintered in order to form the non-
metallic, non-combustible, gas-resistant, first barrier coating. Sintering of the non-metallic,
non-combustible, gas-resistant, first barrier coating is particularly preferred where the barrier
coating is a glass or ceramic coating.
Preferably, the non-metallic, non-combustible, gas-resistant, first barrier coating is
sintered at a temperature of between about 500°C and about 900°C, and more preferably at
about 700°C.
Preferably, the combustible heat source is a carbonaceous heat source. As used
herein, the term ‘carbonaceous’ is used to describe a heat source comprising carbon.
Preferably, the combustible heat source is a carbon-based heat source. As used herein,
the term ‘carbon-based’ is used to describe a heat source comprising primarily carbon, that is a
heat source having a carbon content of at least 50 percent by dry weight. Preferably,
combustible carbon-based heat sources according to the invention have a carbon content of at
least about 60 percent by dry weight, more preferably of at least about 70 percent by dry weight,
most preferably of at least about 80 percent by dry weight.
The combustible carbonaceous heat sources may be formed from one or more suitable
carbon-containing materials.
If desired, one or more binders may be combined with the one or more carbon-
containing materials. Preferably, the one or more binders are organic binders. Suitable known
organic binders, include but are not limited to, gums (for example, guar gum), modified
celluloses and cellulose derivatives (for example, methyl cellulose, carboxymethyl cellulose,
hydroxypropyl cellulose and hydroxypropyl methylcellulose) flour, starches, sugars, vegetable
oils and combinations thereof.
In a particularly preferred embodiment of the invention, the combustible heat source is
formed from a mixture of carbon powder, modified cellulose, flour and sugar.
Instead of, or in addition to one or more binders, combustible heat sources according to
the invention may comprise one or more additives in order to improve the properties of the
combustible carbonaceous heat source. Suitable additives include, but are not limited to,
additives to promote consolidation of the combustible heat source (for example, sintering aids),
additives to promote ignition of the combustible heat source (for example, oxidisers such as
perchlorates, chlorates, nitrates, peroxides, permanganates, and/or zirconium), additives to
promote combustion of the combustible heat source (for example, potassium and potassium
salts, such as potassium citrate) and additives to promote decomposition of one or more gases
produced by combustion of the combustible heat source (for example catalysts, such as CuO,
Fe O and Al O ).
2 3 2 3
Such additives may be incorporated in the combustible heat source prior to or after
application of the non-metallic, non-combustible, gas-resistant, first barrier coating to the rear
surface thereof.
In a particularly preferred embodiment, the combustible heat source is a cylindrical
combustible heat source comprising carbon and at least one ignition aid, the cylindrical
combustible heat source having an upstream end face and an opposed downstream end face,
wherein at least part of the cylindrical combustible heat source between the upstream end face
and the downstream end face is wrapped in a combustion resistant wrapper and wherein upon
ignition of the upstream end face of the cylindrical combustible heat source the downstream end
face of the cylindrical combustible heat source increases in temperature to a first temperature
and wherein during subsequent combustion of the cylindrical combustible heat source the
downstream end face of the cylindrical combustible heat source maintains a second
temperature lower than the first temperature. As used herein, the term ‘ignition aid’ is used to
denote a material that releases one or both of energy and oxygen during ignition of the
combustible heat source, where the rate of release of one or both of energy and oxygen by the
material is not ambient oxygen diffusion limited. In other words, the rate of release of one or
both of energy and oxygen by the material during ignition of the combustible heat source is
largely independent of the rate at which ambient oxygen can reach the material. As used
herein, the term ‘ignition aid’ also is used to describe an elemental metal that releases energy
during ignition of the combustible heat source, wherein the ignition temperature of the elemental
metal is below about 500°C and the heat of combustion of the elemental metal is at least about
kJ/g..
As used herein, the term ‘ignition aid’ does not include alkali metal salts of carboxylic
acids (such as alkali metal citrate salts, alkali metal acetate salts and alkali metal succinate
salts), alkali metal halide salts (such as alkali metal chloride salts), alkali metal carbonate salts
or alkali metal phosphate salts, which are believed to modify carbon combustion.
In use the release of one or both of energy and oxygen by the at least one ignition aid
during ignition of the combustible heat source results in a boost in temperature of the
combustible heat source upon ignition thereof. This is reflected in an increase in temperature of
the combustible heat source. In use in a smoking article according to the invention, this
advantageously ensures that sufficient heat is available to be transferred from the combustible
heat source to the aerosol-forming substrate of the smoking article and so facilitates production
of an acceptable aerosol during early puffs thereof.
Examples of suitable oxidizing agents include, but are not limited to: nitrates such as, for
example, potassium nitrate, calcium nitrate, strontium nitrate, sodium nitrate, barium nitrate,
lithium nitrate, aluminium nitrate and iron nitrate; nitrites; other organic and inorganic nitro
compounds; chlorates such as, for example, sodium chlorate and potassium chlorate;
perchlorates such as, for example, sodium perchlorate; chlorites; bromates such as, for
example, sodium bromate and potassium bromate; perbromates; bromites; borates such as, for
example, sodium borate and potassium borate; ferrates such as, for example, barium ferrate;
ferrites; manganates such as, for example, potassium manganate; permanganates such as, for
example, potassium permanganate; organic peroxides such as, for example, benzoyl peroxide
and acetone peroxide; inorganic peroxides such as, for example, hydrogen peroxide, strontium
peroxide, magnesium peroxide, calcium peroxide, barium peroxide, zinc peroxide and lithium
peroxide; superoxides such as, for example, potassium superoxide and sodium superoxide;
carbonates; iodates; periodates; iodites; sulphates; sulfites; other sulfoxides; phosphates;
phospinates; phosphites; and phosphanites.
While advantageously improving the ignition and combustion properties of the
combustible heat source, the inclusion of ignition and combustion additives can give rise to
undesirable decomposition and reaction products during use of the smoking article. For
example, decomposition of nitrates included in the combustible heat source to aid ignition
thereof can result in the formation of nitrogen oxides. The non-metallic, non-combustible, gas-
resistant, first barrier coating provided on the rear face of the combustible heat source
advantageously prevents or inhibits such decomposition and reaction products from entering air
drawn through the smoking article during use thereof.
In addition, the inclusion of oxidisers, such as nitrates or other additives to aid ignition
can result in generation of hot gases and high temperatures in the combustible heat source
during ignition of the combustible heat source. By acting as a heat sink and barrier to the hot
gases, the non-metallic, non-combustible, gas-resistant, first barrier coating provided on the
rear face of the combustible heat source advantageously limits the temperature to which the
aerosol-forming substrate is exposed, and so helps to avoid thermal degradation or combustion
of the aerosol-forming substrate during ignition of the combustible heat source.
To form the combustible carbonaceous heat sources, one or more carbon-containing
materials is preferably mixed with the one or more binders and other additives, where included,
and pre-formed into a desired shape. The mixture of one or more carbon containing materials,
one or more binders and other additives may be pre-formed into a desired shape using any
suitable known ceramic forming methods such as, for example, slip casting, extrusion, injection
moulding and die compaction. Preferably, the mixture is pre-formed into a desired shape by
extrusion.
Preferably, the mixture of one or more carbon-containing materials, one or more binders
and other additives is pre-formed into an elongate rod. However, it will be appreciated that the
mixture of one or more carbon-containing materials, one or more binders and other additives
may be pre-formed into other desired shapes.
After formation, the elongate rod or other desired shape is preferably dried to reduce its
moisture content and then pyrolysed in a non-oxidizing atmosphere at a temperature sufficient
to carbonise the one or more binders, where present, and substantially eliminate any volatiles in
the elongate rod or other shape. Preferably, the elongate rod or other desired shape is
pyrolysed in a nitrogen atmosphere at a temperature of between about 700°C and about 900°C.
In one embodiment, at least one metal nitrate salt is incorporated in the combustible
heat source by including at least one metal nitrate precursor in the mixture of one or more
carbon containing materials, one or more binders and other additives. The at least one metal
nitrate precursor is then subsequently converted in-situ into at least one metal nitrate salt by
treating the pyrolysed pre-formed cylindrical rod or other shape with an aqueous solution of
nitric acid. In one embodiment, the combustible heat source comprises at least one metal
nitrate salt having a thermal decomposition temperature of less than about 600°C, more
preferably of less than about 400°C. Preferably, the at least one metal nitrate salt has a
decomposition temperature of between about 150°C and about 600°C, more preferably of
between about 200°C and about 400°C.
In preferred embodiments of the invention, exposure of the combustible heat source to a
conventional yellow flame lighter or other ignition means should cause the at least one metal
nitrate salt to decompose and release oxygen and energy. This decomposition causes an initial
boost in the temperature of the combustible heat source and also aids in the ignition of the
combustible heat source. Following decomposition of the at least one metal nitrate salt, the
combustible heat source preferably continues to combust at a lower temperature.
The inclusion of at least one metal nitrate salt advantageously results in ignition of the
combustible heat source being initiated internally, and not only at a point on the surface thereof.
Preferably, the at least one metal nitrate salt is distributed substantially homogeneously
throughout the combustible heat source. Preferably, the at least one metal nitrate salt is
present in the combustible heat source in an amount of between about 20 percent by dry weight
and about 50 percent by dry weight of the combustible heat source.
In another embodiment of the invention, the combustible heat source comprises at least
one peroxide or superoxide that actively evolves oxygen at a temperature of less than about
600°C, more preferably at a temperature of less than about 400°C.
Preferably, the at least one peroxide or superoxide actively evolves oxygen at a
temperature of between about 150°C and about 600°C, more preferably at a temperature of
between about 200°C and about 400°C, most preferably at a temperature of about 350°C.
In use, exposure of the combustible heat source to a conventional yellow flame lighter or
other ignition means should cause the at least one peroxide or superoxide to decompose and
release oxygen. This causes an initial boost in the temperature of the combustible heat source
and also aids in the ignition of the combustible heat source. Following decomposition of the at
least one peroxide or superoxide, the combustible heat source preferably continues to combust
at a lower temperature.
The inclusion of at least one peroxide or superoxide advantageously results in ignition of
the combustible heat source being initiated internally, and not only at a point on the surface
thereof. Preferably, the at least one peroxide or superoxide is distributed substantially
homogeneously throughout the combustible heat source.
The combustible heat source preferably has a porosity of between about 20 percent and
about 80 percent, more preferably of between about 20 percent and 60 percent. Where the
combustible heat source comprises at least one metal nitrate salt, this advantageously allows
oxygen to diffuse into the mass of the combustible heat source at a rate sufficient to sustain
combustion as the at least one metal nitrate salt decomposes and combustion proceeds. Even
more preferably, the combustible heat source has a porosity of between about 50 percent and
about 70 percent, more preferably of between about 50 percent and about 60 percent as
measured by, for example, mercury porosimetry or helium pycnometry. The required porosity
may be readily achieved during production of combustible heat sources according to the
invention using conventional methods and technology.
Advantageously, the combustible carbonaceous heat sources have an apparent density
of between about 0.6 g/cm and about 1 g/cm .
Preferably, the combustible heat source has a mass of between about 300 mg and
about 500 mg, more preferably of between about 400 mg and about 450 mg.
Preferably, the combustible heat source has a length of between about 7 mm and about
17 mm, more preferably of between about 11 mm and about 15 mm, most preferably of about
11 mm.
As used herein, the term ‘length’ denotes the dimension in the longitudinal direction of
the combustible heat source.
Preferably, the combustible heat source has a diameter of between about 5 mm and
about 9 mm, more preferably of between about 7 mm and about 8 mm.
Preferably, the combustible heat source is of substantially uniform diameter. However,
the combustible heat source may alternatively be tapered so that the diameter of the rear
portion of the combustible heat source is greater than the diameter of the front portion thereof.
Particularly preferred are combustible heat sources that are substantially cylindrical. The
combustible heat source may, for example, be a cylinder or tapered cylinder of substantially
circular cross-section or a cylinder or tapered cylinder of substantially elliptical cross-section.
The combustible heat source comprises at least one airflow channel, preferably passing
through an inner portion of the combustible heat source and extending along the entire length of
the combustible heat source. Alternatively or in addition, the combustible heat source may
comprise at least one airflow channel extending along the external periphery of the combustible
heat source. Combustible heat sources according to one preferred embodiment of the invention
comprise one, two or three airflow channels. Most preferably, a single airflow channel is
provided through combustible heat sources according to the invention. In particularly preferred
embodiments of the invention, the combustible heat source comprises a single substantially
central or axial airflow channel. The diameter of the single airflow channel is preferably
between about 1.5 mm and about 3 mm. The non-metallic, non-combustible, gas-resistant,
first barrier coating, which covers substantially the entire rear face of the combustible heat
source, allows gas to be drawn through at least one of the airflow channel of the combustible
heat source from the upstream end face of the smoking article.
The inner surface of the at least one airflow channel of the combustible heat source may
be partially or entirely coated with a second barrier coating. Preferably, the second barrier
coating covers substantially the entire inner surface of all airflow channels of the combustible
heat source.
Preferably, the second barrier coating comprises a layer of solid particulate matter that is
gas-resistant. More preferably, the second barrier coating is at least substantially impermeable
to air. Advantageously, the gas-resistant second barrier coating is of low thermal conductivity.
The second barrier coating may be formed from one or more suitable materials that are
substantially thermally stable and non-combustible at temperatures achieved by the
combustible heat source during ignition and combustion. Suitable materials are known in the
art and include, but are not limited to, for example: clays; metal oxides, such as iron oxide,
alumina, titania, silica, silica-alumina, zirconia and ceria; zeolites; zirconium phosphate; and
other ceramic materials or combinations thereof. Preferred coating materials from which the
second barrier coating may be formed include clays, glass, aluminium, iron oxide and
combinations thereof. If desired, catalytic ingredients, such as ingredients that promote the
oxidation of carbon monoxide to carbon dioxide, may be incorporated in the second barrier
coating. Suitable catalytic ingredients include, but are not limited to, for example, platinum,
palladium, transition metals and their oxides.
The second barrier coating may be formed from the same or different material or
materials as the non-combustible, gas-resistant, first barrier coating.
Preferably, the second barrier coating has a thickness of between about 30 microns and
about 200 microns, more preferably of between about 30 microns and about 100 microns.
The second barrier coating may be applied to the inner surface of the at least one airflow
channel of the combustible heat source by any suitable method, such as the methods described
in US-A-5,040,551. For example, the inner surface of each airflow channel may be sprayed,
wetted or painted with a solution or a suspension of the second barrier coating. Alternatively,
the second barrier coating may be provided by insertion of a liner into one or more airflow
channels. For example, a gas-resistant hollow tube may be inserted into each airflow channel.
In a preferred embodiment, the second barrier coating is applied to the inner surface of
the at least one airflow channel of the combustible heat source by the process described in
WO-A2-2009/074870 as the combustible heat source is extruded.
Optionally, the combustible heat source may comprise one or more, preferably up to and
including six, longitudinal grooves that extend along part of or all of the periphery of the
combustible heat source. If desired, the combustible heat source may comprise at least one
airflow channel and one or more longitudinal grooves.
Combustible heat sources with opposed front and rear faces according to the invention
having a non-metallic, non-combustible, gas-resistant, first barrier coating provided on
substantially the entire rear face thereof are particularly suited for use in smoking articles of the
type disclosed in WO-A-2009/022232. However, it will be appreciated that combustible heat
sources according to the invention may also be used in smoking articles having different
constructions and compositions.
Preferably, the combustible heat source and the aerosol-forming substrate abut one
another.
Preferably, smoking articles according to the invention further comprise 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-forming substrate. The heat-conducting element is
preferably combustion resistant and oxygen restricting.
Suitable heat-conducting elements for use in the invention include, but are not limited to:
metal foil wrappers such as, for example, aluminium foil wrappers, steel wrappers, iron foil
wrappers and copper foil wrappers; and metal alloy foil wrappers.
Preferably, the rear portion of the combustible heat source surrounded by the heat-
conducting element is between about 2 mm and about 8 mm in length, more preferably between
about 3 mm and about 5 mm in length.
Preferably, the front portion of the combustible heat source not surrounded by the heat-
conducting element is between about 5 mm and about 15 mm in length, more preferably
between about 6 mm and about 8 mm in length.
Preferably, the aerosol-forming substrate extends at least about 3 mm downstream
beyond the heat-conducting element.
Preferably, the aerosol-forming substrate has a length of between about 5 mm and about
mm, more preferably of between about 8 mm and about 12 mm. Preferably, the front portion
of the aerosol-forming substrate surrounded by the heat-conducting element is between about 2
mm and about 10 mm in length, more preferably between about 3 mm and about 8 mm in
length, most preferably between about 4 mm and about 6 mm in length. Preferably, the rear
portion of the aerosol-forming substrate not surrounded by the heat-conducting element is
between about 3 mm and about 10 mm in length. In other words, the aerosol-forming substrate
preferably extends between about 3 mm and about 10 mm downstream beyond the heat-
conducting element. More preferably, the aerosol-forming substrate extends at least about 4
mm downstream beyond the heat-conducting element.
Preferably, aerosol-forming substrates of smoking articles according to the invention
comprise at least one aerosol-former and a material capable of emitting volatile compounds in
response to heating. The aerosols generated from aerosol-forming substrates of smoking
articles according to the invention may be visible or invisible and may include vapours (for
example, fine particles of substances, which are in a gaseous state, that are ordinarily liquid or
solid at room temperature) as well as gases and liquid droplets of condensed vapours.
The at least one aerosol-former may be any suitable known compound or mixture of
compounds that, in use, facilitates formation of a dense and stable aerosol and that is
substantially resistant to thermal degradation at the operating temperature of the smoking
article. Suitable aerosol-formers are well known in the art and include, for example, polyhydric
alcohols, esters of polyhydric alcohols, such as glycerol mono-, di- or triacetate, and aliphatic
esters of mono-, di- or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl
tetradecanedioate. Preferred aerosol formers for use in the smoking articles according to the
invention are polyhydric alcohols or mixtures thereof, such as triethylene glycol, 1,3-butanediol
and, most preferred, glycerine.
Preferably, the material capable of emitting volatile compounds in response to heating is
a charge of plant-based material, more preferably a charge of homogenised plant-based
material. For example, the aerosol-forming substrate may comprise one or more materials
derived from plants including, but not limited to: tobacco; tea, for example green tea;
peppermint; laurel; eucalyptus; basil; sage; verbena; and tarragon. The plant based-material
may comprise additives including, but not limited to, humectants, flavourants, binders and
mixtures thereof. Preferably, the plant-based material consists essentially of tobacco material,
most preferably homogenised tobacco material.
Smoking articles according to the invention preferably further comprise an expansion
chamber downstream of the aerosol-forming substrate. The inclusion of an expansion chamber
advantageously allows further cooling of the aerosol generated by heat transfer from the
combustible heat source to the aerosol-forming substrate. The expansion chamber also
advantageously allows the overall length of smoking articles according to the invention to be
adjusted to a desired value, for example to a length similar to that of conventional cigarettes,
through an appropriate choice of the length of the expansion chamber. Preferably, the
expansion chamber is an elongate hollow tube.
Smoking articles according to the invention may also further comprise a mouthpiece
downstream of the aerosol-forming substrate and, where present, downstream of the expansion
chamber. The mouthpiece may, for example, comprise a filter made of cellulose acetate, paper
or other suitable known filtration materials. Preferably, the mouthpiece is of low filtration
efficiency, more preferably of very low filtration efficiency. Alternatively or in addition, the
mouthpiece may comprise one or more segments comprising absorbents, adsorbents,
flavourants, and other aerosol modifiers and additives which are used in filters for conventional
cigarettes, or combinations thereof.
Smoking articles according to the invention may be assembled using known methods
and machinery.
The invention will be further described, by way of example only, with reference to the
accompanying drawing in which:
Figure 1 shows a schematic longitudinal cross-section of a smoking article according to
a preferred embodiment of the invention; and
Figure 2 shows a graph of the temperature of the aerosol-forming substrate of a smoking
article according to the first embodiment of the invention during combustion of the combustible
heat source thereof.
The smoking article 2 shown in Figure 1 comprises a combustible carbonaceous heat
source 4 according to the invention, an aerosol-forming substrate 6, an elongate expansion
chamber 8 and a mouthpiece 10 in abutting coaxial alignment. The combustible carbonaceous
heat source 4, aerosol-forming substrate 6, elongate expansion chamber 8 and mouthpiece 10
are overwrapped in an outer wrapper of cigarette paper 12 of low air permeability.
As shown in Figure 1, a non-metallic, non-combustible, gas-resistant, first barrier
coating 14 is provided on substantially the entire rear face of the combustible carbonaceous
heat source 4.
The combustible carbonaceous heat source 4 comprises a central airflow channel 16
that extends longitudinally through the combustible carbonaceous heat source 4 and the non-
metallic, non-combustible, gas-resistant, first barrier coating 14. A gas-resistant, heat resistant,
second barrier coating (not shown) is provided on the inner surface of the central airflow
channel 16.
The aerosol-forming substrate 6 is located immediately downstream of the combustible
carbonaceous heat source 4 and comprises a cylindrical plug of tobacco material 18 comprising
glycerine as aerosol former and circumscribed by filter plug wrap 20.
A heat-conducting element 22 consisting of a tube of aluminium foil surrounds and is in
contact with a rear portion 4b of the combustible carbonaceous heat source 4 and an abutting
front portion 6a of the aerosol-forming substrate 6. As shown in Figure 1, a rear portion of the
aerosol-forming substrate 6 is not surrounded by the heat-conducting element 22.
The elongate expansion chamber 8 is located downstream of the aerosol-forming
substrate 6 and comprises a cylindrical open-ended tube of cardboard 24. The mouthpiece 10
of the smoking article 2 is located downstream of the expansion chamber 8 and comprises a
cylindrical plug of cellulose acetate tow 26 of very low filtration efficiency circumscribed by filter
plug wrap 28. The mouthpiece 10 may be circumscribed by tipping paper (not shown).
In use, the consumer ignites the combustible carbonaceous heat source 4 and then
draws air through the central airflow channel 16 downstream towards the mouthpiece 10. The
front portion 6a of the aerosol-forming substrate 6 is heated primarily by conduction through the
abutting non-combusting rear portion 4b of the combustible carbonaceous heat source 4 and
the heat-conducting element 22. The drawn air is heated as it passes through the central
airflow channel 16 of the combustible carbonaceous heat source 4 and then heats the aerosol-
forming substrate 6 by convection. The heating of the aerosol-forming substrate 6 releases
volatile and semi-volatile compounds and glycerine from the aerosol-forming substrate 18,
which are entrained in the heated drawn air as it flows through the aerosol-forming substrate 18.
The heated air and entrained compounds pass downstream through the expansion chamber 8,
cool and condense to form an aerosol that passes through the mouthpiece 10 into the mouth of
the consumer (at about ambient temperature).
To assemble the smoking article 2, a rectangular piece of the heat-conducting element
22 is glued to cigarette paper 12. The combustible carbonaceous heat source 4, the plug of the
aerosol-forming substrate 6 and the expansion chamber 8 are suitably aligned and positioned
on the cigarette paper 12 with the attached heat-conducting element 22. The cigarette paper 12
with the attached heat-conducting element 22 is wrapped around the rear portion 4b of the
combustible carbonaceous heat source 4, the aerosol-forming substrate 6 and the expansion
chamber 8 and glued. The mouthpiece 10 is attached to the open end of the expansion
chamber using known filter combining technology.
Smoking articles according to the preferred embodiment of the invention shown in
Figure 1 having the dimensions shown in Table 1 were assembled using combustible
carbonaceous heat sources produced in accordance with Example 1 and 6 below.
EXAMPLE 1- Preparation of combustible heat source
Combustible cylindrical carbonaceous heat sources according to the invention may be
prepared as described in WO2009/074870 A2 or any other prior art that is known to persons of
ordinary skill in the art. An aqueous slurry, as described in WO2009/074870 A2, is preferably
extruded through a die having a central die orifice of circular cross-section to make the
combustible heat source. Preferably, the die orifice has a diameter of 8.7 mm so as to form
cylindrical rods, preferably having a length of between about 20 cm and about 22 cm and a
diameter of between about 9.1 cm and about 9.2 mm. A single longitudinal airflow channel may
be formed in the cylindrical rods by a mandrel mounted centrally in the die orifice. The mandrel
preferably has a circular cross-section with an outer diameter of approximately 2 mm or
approximately 3.5 mm. Alternatively, three airflow channels may be formed in the cylindrical
rods using three mandrels of circular cross-section with an outer diameter of approximately 2
mm mounted at regular angles in the die orifice. During extrusion of the cylindrical rods, a clay-
based coating slurry (made using clay, such as natural green clay) may be pumped through a
feed passageway extending through the centre of the mandrel or mandrels to form a thin
second barrier coating of about 150 microns to about 300 microns on the inner surface of the
airflow channel or channels. The cylindrical rods may be dried at a temperature of about 20°C
to about 25°C under about 40% to about 50% relative humidity for between approximately 12
hours to approximately 72 hours and then pyrolysed in a nitrogen atmosphere at about 750°C
for approximately 240 minutes. After pyrolysis, the cylindrical rods can be cut and shaped to a
defined diameter using a grinding machine to form individual combustible-carbonaceous heat
sources. The rods after cutting and shaping preferably have a length of about 11 mm, a
diameter of about 7.8 mm and a dry mass of about 400 mg. Individual combustible
carbonaceous heat sources may be subsequently dried at about 130°C for approximately
1 hour.
Smoking article
Overall length (mm) 70
Diameter (mm) 7.9
Porous carbonaceous heat source
Length (mm) 11
Diameter (mm) 7.8
Diameter of airflow channel (mm) 1.85-3.50
Thickness of first barrier coating (microns) 0-500
Thickness of second barrier coating (microns) 0-300
Aerosol-forming substrate
Length (mm) 10
Diameter (mm) 7.8
Density (g/cm ) 0.8
Aerosol former Glycerine
Amount of aerosol former 20% by dry wt. of tobacco
Expansion chamber
Length (mm) 42
Diameter (mm) 7.8
Mouthpiece
Length (mm) 7
Diameter (mm) 7.8
Heat-conducting element
Length (mm) 9
Diameter (mm) 7.8
Thickness of aluminium foil (microns) 20
Length of the rear portion of the combustible carbonaceous heat
Length of the front portion of the aerosol-forming substrate (mm) 5
Length of the rear portion of the aerosol-forming substrate (mm) 5
Table 1
EXAMPLE 2 – Coating of combustible heat source with bentonite/kaolinite
A non-metallic, non-combustible, gas-resistant, first barrier coating of bentonite/kaolinite
may be provided on the rear face of a combustible carbonaceous heat source prepared as
described in Example 1 by dipping, brushing or spray coating. Dipping involves inserting the
rear face of the combustible carbonaceous heat source into a concentrated bentonite/kaolinite
solution. Preferably, the bentonite/kaolinite solution for dipping contains 3.8% bentonite, 12.5%
kaolinite and 83.7 % H O [m/m]. The rear face of the combustible carbonaceous heat source is
preferably dipped into the bentonite/kaolinite solution for about 1 second and the meniscus
allowed to disappear as the result of penetration of the solution into the carbon pores at the
surface of the rear face of the combustible carbonaceous heat source. Brushing involves
dipping a brush into a concentrated bentonite/kaolinite solution and applying the concentrated
bentonite/kaolinite solution on the brush to the surface of the rear face of the combustible
carbonaceous heat source until covered. The bentonite/kaolinite solution for brushing
preferably contains 3.8% bentonite, 12.5% kaolinite and 83.7 % H2O [m/m].
After application of a non-metallic, non-combustible, gas-resistant, first barrier coating by
dipping or brushing, the combustible carbonaceous heat source may be dried in an oven at
about 130°C for approximately 30 minutes and placed in a desiccator under about 5% relative
humidity overnight.
Spray-coating involves a suspension solution, preferably containing 3.6% bentonite,
18.0% kaolinite and 78.4% H O [m/m] and having a viscosity of around 50 mPa·s at a shear
rate of about 100 s as measured with a rheometer (Physica MCR 300, coaxial cylinder
arrangement). Spray-coat may be done with a Sata MiniJet 3000 spray gun using spray
nozzles of 0.5 mm, 0.8 mm or 1 mm on a SMC E-MY2B linear actuator at a velocity of about 10
mm/s to about 100 mm/s. The following spray parameters may be used: distance sample-pistol
cm; sample velocity 10 mm/s; spray nozzle 0.5 mm; spray jet flat and spray pressure 2.5 bar.
In a single spray-coating event, a coating thickness of about 11 microns is typically obtained.
Spraying is repeated preferably three times. Between each spray-coating, the combustible
carbonaceous heat source is dried at room temperature for about 10 minutes. After application
of the non-metallic, non-combustible, gas-resistant, first barrier coating, the combustible
carbonaceous heat source is preferably pyrolysed at about 700°C for approximately 1 hour.
EXAMPLE 3- Coating of combustible heat source with sintered glass
A non-metallic, non-combustible, gas-resistant, first barrier coating of glass may be
provided on the rear face of a combustible carbonaceous heat-source prepared as described in
Example 1 by spray-coating. Spray-coating with glass may be performed with a suspension of
ground glass using a fine powder. For example, a spray-coating suspension containing either
37.5% glass powder (3µm), 2.5% methylcellulose and 60% water with a viscosity of 120 mPa·s,
or 37.5% glass powder (3µm), 3.0% bentonite powder, and 59.5% water with a viscosity of 60 to
100 mPa·s, may be used. Glass powder having the compositions and physical properties
corresponding to Glass 1, 2, 3 and 4 in Table 2 can be used.
Spray-coating may be done with a Sata MiniJet 3000 spray gun using spray nozzles of
0.5 mm, 0.8 mm or 1 mm on a SMC E-MY2B linear actuator at a velocity of about 10 mm/s to
about 100 mm/s. Spraying is preferably repeated several times. After the spraying is
completed, the combustible carbonaceous heat source is preferably pyrolysed at about 700°C
for approximately 1 hour.
Glass 1 Glass 2 Glass 3 Glass 4
SiO 70 70 65 60
Na O 20 15 20 20
K O 5
CaO 10 8 10 10
MgO 4 5 5
Al O 3
T (°C) 517 539 512 465
-6 -1
Α (10 K ) 10.9 9.3 10.2 12.1
-300
KI-value 30 21 35 40
Table 2: Composition of glasses in weight percent, transformation temperature Tg, coefficient of
thermal expansion A and KI-value calculated from composition
-300
EXAMPLE 4- Methods for measuring smoke compounds
Conditions for smoking
Conditions for smoking and smoking machine specifications are set out in ISO Standard
3308 (ISO 3308:2000). Atmosphere for conditioning and testing are set out in ISO Standard
3402. Phenols are trapped using Cambridge filter pads. Quantitative determination of
carbonyls in aerosols, including formaldehyde, acrolein, acetaldehyde and propionaldehyde, is
done by UPLC-MSMS. Quantitative measurement of phenolics such as catechol, hydroquinone
and phenol is done by LC-fluorescence. Carbon monoxide in the smoke is trapped using gas
sampling bags and measured using a non-dispersive infra-red analyzer as set out in ISO
Standard 8454 (ISO 8454:2007).
Smoking regimes
Cigarettes tested under a Health Canada smoking regime are smoked over 12 puffs with
a puff volume of 55 ml, puff duration of 2 seconds and a puff interval of 30 seconds. Cigarettes
tested under an intense smoking regime are smoked over 20 puffs with a puff volume of 80 ml,
a puff duration of 3.5 seconds and puff interval of 23 seconds.
EXAMPLE 5- High temperature protection and reduction of carbon monoxide by back
coating
Smoking articles according to the preferred embodiment of the invention shown in Figure
1 having a total length 70 mm were made by hand. The smoking articles comprised a
combustible cylindrical carbonaceous heat source with a single longitudinal airflow channel
having an outer diameter of 1.85 mm and a non-metallic, non-combustible, gas-resistant, first
barrier coating of clay, made essentially as described in A2 and Example 1.
The aerosol-forming substrate of the smoking articles was 10 mm in length and comprised
approximately 60% by weight flue-cured tobacco, approximately 10% by weight oriental tobacco
and approximately 20% by weight sun-cured tobacco. The heat conducting element of the
smoking articles was 9 mm in length, of which 4 mm covered the rear portion of the combustible
heat source and 5 mm covered the adjacent front portion of the aerosol-forming substrate.
Except as noted in the foregoing description in this Example, the properties of the smoking
articles conformed to those listed in Table 1 above. Smoking articles of the same construction,
but without a non-metallic, non-combustible, gas-resistant, first barrier coating, were also made
by hand for comparison.
The temperature was measured in the aerosol-forming substrate during lighting of the
combustible heat source of a smoking article comprising a combustible heat source with a non-
metallic, non-combustible, gas-resistant, first barrier coating of clay and a smoking article
comprising a combustible heat source without a non-metallic, non-combustible, gas-resistant,
first barrier coating. To measure the temperature, a thermocouple was inserted into the
aerosol-forming substrate of the smoking articles as disclosed in patent application WO-A2-
2009/022232. The results are summarised in Figure 2 and show that during the first few
seconds of ignition of the combustible heat source, the temperature in the aerosol-forming
substrate was much lower for the smoking article comprising a combustible heat source with a
non-metallic, non-combustible, gas-resistant, first barrier coating of clay (shown by a dotted line
in Figure 2) compared to the smoking article comprising a combustible heat source without a
non-metallic, non-combustible, gas-resistant, first barrier coating (shown by a solid line in
Figure 2). The total carbon monoxide delivery of the smoking articles was also was measured
under a Health Canada smoking regime. The measured total carbon monoxide delivery for the
smoking article comprising a combustible heat source without a non-metallic, non-combustible,
gas-resistant, first barrier coating of clay was 1.47 μg. The measured total carbon monoxide
delivery for the smoking article comprising a combustible heat source with a non-metallic, non-
combustible, gas-resistant, first barrier coating of clay was only 0.97 μg. Provision of a non-
metallic, non-combustible, gas-resistant, first barrier coating of clay on the rear face of the
combustible heat source thus resulted in approximately a 35% reduction in total carbon
monoxide delivery.
EXAMPLE 6- Preparation of combustible heat source with ignition aid
A carbonaceous combustible heat source comprising an ignition aid may be prepared by
mixing 525 g of carbon powder, 225 g of calcium carbonate (CaCO ), 51.75 g of potassium
citrate, 84 g of modified cellulose, 276 g of flour, 141.75 g of sugar and 21 g of corn oil with 579
g of deionised water to form an aqueous slurry, essentially as disclosed in WO2009/074870 A2.
The aqueous slurry may then be extruded through a die having a central die orifice of circular
cross-section with a diameter of about 8.7 mm to form cylindrical rods having a length of
between about 20 cm and about 22 cm and a diameter of between about 9.1 mm and about 9.2
mm. A single longitudinal airflow channel may be formed in the cylindrical rods by a mandrel
mounted centrally in the die orifice. The mandrel preferably has a circular cross-section with an
outer diameter of approximately 2 mm or approximately 3.5 mm. Alternatively, three airflow
channels may be formed in the cylindrical rods using three mandrels of circular cross-section
with an outer diameter of approximately 2 mm mounted at regular angles in the die orifice.
During extrusion of the cylindrical rods, a green clay-based coating slurry may be pumped
through a feed passageway extending through the centre of the mandrel to form a thin second
barrier coating having a thickness of between about 150 microns and about 300 microns on the
inner surface of the single longitudinal airflow channel. The cylindrical rods are preferably dried
at between about 20°C and about 25°C under about 40% to about 50% relative humidity for
between approximately 12 hours and approximately 72 hours and then pyrolysed in a nitrogen
atmosphere at about 750°C for approximately 240 minutes. After pyrolysis, the cylindrical rods
may be cut and shaped to a defined diameter using a grinding machine to form individual
combustible-carbonaceous heat sources having a length of about 11 mm, a diameter of about
7.8 mm, and a dry mass of about 400 mg. The individual combustible carbonaceous heat
sources may then be dried at about 130°C for approximately 1 hour and then placed in an
aqueous solution of nitric acid having a concentration of 38 percent by weight and saturated
with potassium nitrate (KNO). After approximately 5 minutes, individual combustible
carbonaceous heat sources are preferably removed from the solution and dried at about 130°C
for approximately 1 hour. After drying the individual combustible carbonaceous heat sources
may be placed once again in an aqueous solution of nitric acid having a concentration of 38
percent by weight and saturated with potassium nitrate (KNO ). After approximately 5 minutes,
the individual combustible carbonaceous heat sources may be removed from the solution and
dried at about 130°C for approximately 1 hour, followed by drying at about 160°C for
approximately 1 hour and finally drying at about 200°C for approximately 1 hour.
EXAMPLE 7- Smoke compounds from smoking articles with combustible heat-sources
with a non-combustible, gas-resistant, first barrier coating of clay or glass
Combustible cylindrical carbonaceous heat sources comprising an ignition aid prepared
as described in Example 6 with a single longitudinal airflow channel having a diameter of 1.85
mm and a bentonite/kaolinite second barrier coating, were provided with a non-metallic, non-
combustible, gas-resistant, first barrier coating of clay as described in Example 2. Additionally,
combustible cylindrical carbonaceous heat sources comprising an ignition aid as described in
Example 6 with a single longitudinal airflow channel having a diameter of 1.85 mm and a glass
second barrier coating, were provided with a non-metallic, non-combustible, gas-resistant, first
barrier coating of sintered glass as described in Example 3. In both cases, the length of the
combustible cylindrical carbonaceous heat sources was 11 mm. The non-metallic, non-
combustible, gas-resistant, first barrier coating of clay preferably has a thickness of between
about 50 microns or about 100 microns and the non-metallic, non-combustible, gas-resistant,
first barrier coating of glass preferably has a thickness of about 20 microns, about 50 microns or
about 100 microns. Smoking articles according to the preferred embodiment of the invention
shown in Figure 1 having a total length of 70 mm comprising the aforementioned combustible
cylindrical carbonaceous heat sources were assembled by hand. The aerosol-forming
substrate of the smoking articles was 10 mm in length and comprised approximately 60% by
weight flue-cured tobacco, approximately 10% by weight oriental tobacco and approximately
% by weight sun-cured tobacco. The heat conducting element of the smoking articles was 9
mm in length, of which 4 mm covered the rear portion of the combustible heat source and 5 mm
covered the adjacent front portion of the aerosol-forming substrate. Except as noted in the
foregoing description in this Example, the properties of the smoking articles conformed to those
listed in Table 1 above. Smoking articles of the same construction, but without a non-metallic,
non-combustible, gas-resistant, first barrier coating, were also made by hand for comparison.
The resulting smoking articles were smoked as described in Example 5 under a Health
Canada smoking regime. Before smoking, the combustible heat sources of the smoking articles
were lit using a regular yellow flame lighter. The formaldehyde, acetaldehyde, acrolein and
propionaldehyde in the mainstream aerosol of the smoking articles was measured as described
in Example 5. The results are summarised in Table 3 below and show that carbonyls, such as
acetaldehyde and especially formaldehyde, are significantly reduced in the mainstream
aerosols of smoking articles comprising a combustible heat source with a non-metallic, non-
combustible, gas-resistant, first barrier coating compared to the mainstream aerosols of
smoking articles comprising a combustible heat source without a non-metallic, non-
combustible, gas-resistant, first barrier coating.
Example 5 above demonstrates the reduction of carbon monoxide by one embodiment
of the invention. As can be seen from Example 7, providing a non-metallic, non-combustible,
gas-resistant, first barrier coating on substantially the entire rear face of the combustible heat
source according to the invention also surprisingly results in significantly reduced formation of
carbonyl compounds, such as formaldehyde, acetaldehyde, proprionaldehyde and phenolics, in
the mainstream aerosol. The Examples described above illustrate but do not limit the invention.
Other embodiments of this invention may be made without departing from the spirit and scope
thereof, and it is to be understood that the specific Examples and embodiments described
herein are not limiting.
Non-combustible, gas-resistant,
(a) None (b) Clay (c) Glass
first barrier coating
Thickness (microns) 50 100 20 50 100
formaldehyde 22.19 18.2 17.6 14.87 12.99 14.56
acetaldehyde 102.83 103.9 89.4 75.11 69.56 86.89
acrolein 7.09 7.7 7.1 6.22 4.29 5.41
propionaldehyde 5.09 4.9 7.7 4.50 3.64 4.78
Table 3: Amount of carbonyls (micrograms per sample) measured in mainstream aerosol under
Health Canada smoking regime for smoking articles comprising a combustible carbonaceous
heat source (a) without a non-metallic, non-combustible, gas-resistant, first barrier coating, (b)
with a non-metallic, non-combustible, gas-resistant, first barrier coating of clay and (c) with a
non-metallic, non-combustible, gas-resistant, first barrier coating of sintered glass.
Claims (15)
1. A combustible heat source with opposed front and rear faces for use in a smoking article, the combustible heat source comprising: 5 at least one airflow channel extending from the front face to the rear face of the combustible heat source and a non-metallic, non-combustible, gas-resistant, first barrier coating on substantially the entire rear face of the combustible heat source that allows gas to be drawn through the at least one airflow channel, 10 wherein the non-metallic, non-combustible, gas-resistant, first barrier coating has an elemental metal or alloy content of less than 50 mole percent.
2. A combustible heat source according to claim 1 wherein the first barrier coating has a thickness of at least 10 microns.
3. A combustible heat source according to claim 1 or 2 wherein the first barrier coating comprises clay, glass, or alumina.
4. A combustible heat source according to any one of claims 1 to 3 wherein the combustible 20 heat source is a carbonaceous heat source.
5. A combustible heat source according to claim any preceding claim wherein the combustible heat source comprises an ignition aid. 25
6. A combustible heat source according to claim 5 wherein the ignition aid is an oxidizing agent.
7. A combustible heat source according to any preceding claim wherein a gas-resistant, heat resistant, second barrier coating is provided on the inner surface of the at least one airflow 30 channel.
8. A smoking article comprising: a combustible heat source according to any one of claims 1 to 7; and an aerosol-forming substrate comprising at least one aerosol former downstream of the 35 combustible heat source.
9. A smoking article according to claim 8 wherein the aerosol-forming substrate comprises homogenised tobacco-based material.
10. A smoking article according to claim 8 or 9 further comprising: 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-forming substrate.
11. A smoking article according to any one of claims 8 to 10 further comprising: an expansion chamber downstream of the aerosol-forming substrate.
12. A smoking article according to claim 11 further comprising: 10 a mouthpiece downstream of the expansion chamber.
13. A smoking article substantially as herein described with reference to any embodiment shown in the accompanying figures. 15
14. A smoking article according to claim 8, substantially as herein described with reference to any embodiment disclosed.
15. A combustible heat source according to claim 1, substantially as herein described with reference to any embodiment disclosed.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP11250893 | 2011-11-15 | ||
EP11250893.2 | 2011-11-15 | ||
PCT/EP2012/072557 WO2013072336A1 (en) | 2011-11-15 | 2012-11-14 | Smoking article comprising a combustible heat source with a rear barrier coating |
Publications (2)
Publication Number | Publication Date |
---|---|
NZ622007A NZ622007A (en) | 2016-05-27 |
NZ622007B2 true NZ622007B2 (en) | 2016-08-30 |
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