Multilayer combustible heat source

Abstract

A multilayer combustible heat source for a smoking article is provided, including a combustible first layer including carbon; and a second layer in direct contact with the first layer, the second layer including carbon and at least one ignition aid, wherein the combustible first layer and the second layer are longitudinal concentric layers having a density of at least 0.6 g/cm.sup.3, and wherein the composition of the first layer is different from the composition of the second layer.

Claims

1. A multilayer combustible heat source for a smoking article, comprising: a combustible first layer comprising carbon; and a second layer in direct contact with the first layer, the second layer comprising carbon and at least one ignition aid, wherein the first layer and the second layer are longitudinal non-fibrous concentric layers, wherein the first layer and the second layer each have an apparent density of at least 0.6 g/cm.sup.3, wherein the second layer has an ignition aid content of at least 35 percent by dry weight, and wherein a composition of the first layer is different from a composition of the second layer.

2. The multilayer combustible heat source according to claim 1, wherein the first layer and the second layer have a density of between 0.6 g/cm.sup.3 and about 1.0 g/cm.sup.3.

3. The multilayer combustible heat source according to claim 1, wherein the apparent density of the first layer is different from the apparent density of the second layer, and wherein the difference in the apparent density of the first layer and the apparent density of the second layer is less than or equal to 0.2 g/cm.sup.3.

4. The multilayer combustible heat source according to claim 1, wherein the first layer further comprises at least one ignition aid, wherein the at least one ignition aid of the first layer does not include alkali metal salts of carboxylic acids.

5. The multilayer combustible heat source according to claim 4, wherein the ratio by dry weight of carbon to ignition aid in the first layer is different from the ratio by dry weight of carbon to ignition aid in the second layer.

6. The multilayer combustible heat source according to claim 5, wherein the ratio by dry weight of carbon to ignition aid in the first layer is greater than the ratio by dry weight of carbon to ignition aid in the second layer.

7. The multilayer combustible heat source according to claim 1, wherein the first layer is an outer layer and the second layer is an inner layer circumscribed by the first layer.

8. The multilayer combustible heat source according to claim 1, further comprising: a third layer disposed at an end of the first and the second layers, and comprising one or both of carbon and at least one ignition aid, wherein the at least one ignition aid of the third layer does not include alkali metal salts of carboxylic acids.

9. The multilayer combustible heat source according to claim 8, wherein the composition of the third layer is different from the composition of the first layer.

10. The multilayer combustible heat source according to claim 8, wherein the composition of the third layer is different from the composition of the second layer.

11. The multilayer combustible heat source according to claim 8, wherein the composition of the third layer is the same as the composition of the second layer.

12. A smoking article, comprising: a multilayer combustible heat source according to claim 1; and an aerosol-forming substrate downstream of the multilayer combustible heat source.

13. A multilayer combustible heat source for a smoking article, comprising: a combustible first layer comprising carbon; and a second layer in direct contact with the first layer, the second layer comprising carbon and at least one peroxide or superoxide that actively evolves oxygen at a temperature of less than 600° C., wherein the first layer and the second layer are longitudinal non-fibrous concentric layers, wherein the first layer and the second layer each have an apparent density of at least 0.6 g/cm.sup.3, wherein the second layer has a peroxide or superoxide content of at least 35 percent by dry weight, and wherein a composition of the first layer is different from a composition of the second layer.

14. The multilayer combustible heat source according to claim 1, wherein the second layer has a carbon content of less than or equal to 35 percent by dry weight.

Description

(1) The invention will be further described, by way of example only, with reference to the accompanying drawings in which:

(2) FIG. 1 is a perspective view of a multilayer combustible heat source according to a first embodiment of the invention;

(3) FIG. 2 is a perspective view of a multilayer combustible heat source according to a second embodiment of the invention;

(4) FIG. 3a shows a graph of the temperature of the aerosol-forming substrate of a smoking article according to the invention described in Example 1 during combustion of the multilayer combustible heat source thereof;

(5) FIG. 3b shows a graph of the absorbance at 320 nm of the aerosol generated by the smoking article according to the invention described in Example 1 as a function of puff number;

(6) FIG. 4a shows a graph of the temperature of the aerosol-forming substrate of a smoking article according to the invention described in Example 2 during combustion of the multilayer combustible heat source thereof; and

(7) FIG. 4b shows a graph of the absorbance at 320 nm of the aerosol generated by the smoking article according to the invention described in Example 2 as a function of puff number.

(8) The multilayer combustible heat source 2 according to the first embodiment of the invention shown in FIG. 1 is a substantially cylindrical, bilayer combustible heat source comprising a combustible first layer 4 and a second layer 6. As shown in FIG. 1, the second layer 6 is an annular longitudinal outer layer and the combustible first layer 4 is a substantially cylindrical longitudinal inner layer, which is circumscribed by the second layer 6. The inner diameter of the annular longitudinal outer second layer 6 is substantially equal to the diameter of the substantially cylindrical longitudinal inner combustible first layer 4.

(9) The multilayer combustible heat source 8 according to the second embodiment of the invention shown in FIG. 2 is a substantially cylindrical, trilayer combustible heat source comprising a combustible first layer 10, a second layer 12 and a third layer 14. As shown in FIG. 2, the combustible first layer 10 is an annular longitudinal outer layer, the second layer 12 is a substantially cylindrical longitudinal inner layer, which is circumscribed by the combustible first layer 10, and the third layer 14 is a substantially cylindrical transverse layer. The inner diameter of the annular longitudinal outer combustible first layer 10 is substantially equal to the diameter of the substantially cylindrical longitudinal inner second layer 12. The outer diameter of the annular longitudinal outer combustible first layer 10 is substantially equal to the diameter of the substantially cylindrical transverse third layer 14.

EXAMPLE 1

(10) Smoking articles according to the invention are assembled by hand using bilayer combustible heat sources according to the first embodiment of the invention shown in FIG. 1 having the composition shown in Table 1. The smoking articles are assembled with the bilayer combustible heat source adjacent to and abutting the aerosol-forming substrate.

(11) For the purposes of comparison, smoking articles of the same construction and dimensions are assembled by hand using monolayer combustible heat sources having the composition shown in Table 1.

(12) TABLE-US-00001 TABLE 1 Monolayer Bilayer combustible combustible heat source heat source Comparative Example 1 Example A Combustible First Layer Length (mm) 13 13 Diameter (mm) 4.8 6.3 Carbon (% by dry weight) 65 45 Carboxymethyl cellulose (% by dry 5 5 weight) Calcium peroxide (% by dry weight) 30 50 Second Layer Length (mm) 13 — Inner Diameter (mm) 4.8 — Outer Diameter (mm) 6.3 — Carbon (% by dry weight) 45 — Carboxymethyl cellulose (% by dry 5 — weight) Calcium peroxide (% by dry weight) 50 —

(13) The temperature of the aerosol-forming substrate of the smoking articles during combustion of the combustible heat sources is measured using a thermocouple attached to the surface of the smoking articles at a position 2 mm downstream of the combustible heat source. The results are shown in FIG. 3a.

(14) The absorbance of the aerosol generated during each puff of the smoking articles is measured using a UV-Visible optical spectrometer with an optical cell set up to record data in the Near UV region at 320 nm. The results, which are indicative of the density of the aerosol generated, are shown in FIG. 3b.

(15) To generate the profiles shown in FIGS. 3a and 3b, the combustible heat sources of the smoking articles are ignited using a conventional yellow flame lighter. Puffs of 55 ml (puff volume) are then taken in 2 seconds (puff duration) every 30 seconds (puff frequency) using a smoking machine.

(16) As shown in FIG. 3a, during early puffs the temperature of the aerosol-forming substrate of the smoking article according to the invention comprising the bilayer combustible heat source according to the invention is similar to the temperature of the aerosol-forming substrate smoking article comprising a monolayer heat source having the same composition as the second layer of the bilayer combustible heat source according to the invention.

(17) As also shown in FIG. 3a, during later puffs the temperature of the aerosol-forming substrate of the smoking article according to the invention comprising the bilayer combustible heat source according to the invention is significantly greater than the temperature of the smoking article comprising a monolayer heat source having the same composition as the second layer of the bilayer combustible heat source according to the invention.

EXAMPLES 2 AND 3

(18) Smoking articles according to invention are assembled by hand using trilayer combustible heat sources according to the second embodiment of the invention shown in FIG. 2 having the compositions shown in Table 2. The smoking articles are assembled with the third layer of the bilayer combustible heat source adjacent to and abutting the aerosol-forming substrate.

(19) The temperature of the aerosol-forming substrate of the smoking articles during combustion of the trilayer combustible heat sources is measured using a thermocouple attached to the surface of the smoking articles at a position 2 mm downstream of the trilayer combustible heat source. The results are shown in FIG. 4a.

(20) The absorbance of the aerosol generated during each puff of the smoking articles is measured using a UV-Visible optical spectrometer with an optical cell set up to record data in the Near UV region at 320 nm. The results, which are indicative of the density of the aerosol generated, are shown in FIG. 4b.

(21) To generate the profiles shown in FIGS. 4a and 4b, the trilayer combustible heat sources of the smoking articles are ignited using a conventional yellow flame lighter. Puffs of 55 ml (puff volume) are then taken in 2 seconds (puff duration) every 30 seconds (puff frequency) using a smoking machine.

(22) As shown in FIG. 4a, the temperature of the aerosol-forming substrate of the smoking articles according to the invention comprising trilayer combustible heat sources according to the invention is substantially constant during both early puffs and later puffs.

(23) TABLE-US-00002 TABLE 2 Trilayer combustible heat sources Example 2 Example 3 Combustible First Layer Length (mm) 10 10 Inner Diameter (mm) 4 4 Outer Diameter (mm) 7.8 7.8 Carbon (% by dry weight) 65 65 Carboxymethyl cellulose (% by dry 5 5 weight) Calcium peroxide (% by dry weight) 30 30 Second Layer Length (mm) 10 10 Diameter (mm) 4 4 Carbon (% by dry weight) 45 45 Carboxymethyl cellulose (% by dry 5 5 weight) Calcium peroxide (% by dry weight) 50 50 Third Layer Length (mm) 3 3 Diameter (mm) 7.8 7.8 Carbon (% by dry weight) 45 15 Graphite (% by dry weight) — 20 Carboxymethyl cellulose (% by dry 5 5 weight) Calcium peroxide (% by dry weight) 50 60

(24) The embodiments and examples described above illustrate but do not limit the invention. Other embodiments of the invention may be made without departing from the spirit and scope thereof, and it is to be understood that the specific embodiments and examples described herein are not limiting.

(25) In particular, while the invention has been illustrated above by reference to embodiments and examples describing bilayer and trilayer combustible heat sources, it will be appreciated that multilayer combustible heat sources according to the invention comprising four or more layers may also be produced.