Smoking article with improved extinguishing characteristics

Description

[0001] The invention relates to a smoking article with improved extinguishing characteristics (reduced or lower ignition propensity or ignition proclivity) and to a method of manufacturing such a smoking article.

[0002] Product regulations in many countries specify that cigarettes have to fulfil certain safety standards regarding their ignition propensity. The ignition propensity of cigarettes can be measured by a standardized test method. Usually, the test defined in ASTM E 2187-04 is performed (ASTM: "American Standard for Testing and Materials"; ASTM E 2187: "Standard Test Method for Measuring the Ignition Strength of Cigarettes"; the extension "-04" refers to 2004 as the year of the last revision). According to ASTM E 2187-04, a sample of 40 cigarettes is tested under well-defined conditions, and the fraction of these cigarettes which burn their full length is called "the test result". A safety standard specifies which test result is acceptable. For example, in Canada and some U.S. states, the acceptable test result is 25%, i.e. at least 75% of the cigarettes have to extinguish before burning their full length in order to comply with the safety standard.

[0003] The most common way to reduce the ignition propensity of cigarettes is to enhance the extinguishing characteristics by using a paper wrapper comprising spaced bands of lower porosity, which extend along the circumference of the wrapper. By these means, oxygen supply is reduced when the burning cone of the cigarette reaches a respective band, and the cigarette extinguishes when smoldering on a substrate, as described in ASTM E 2187-04. Common methods to produce such banded cigarette papers are described in EP 1 234 514 A2.

[0004] A general disadvantage of using low-porosity bands on wrapper papers is a reduced rod ventilation caused by the reduced porosity in these bands, resulting in changes of CO/NFDPM ratios to often undesired levels (CO: carbon monoxide, NFDPM: nicotin-free dry particulate matter).

[0005] The use of inorganic salts as burn retardants is commonly known, including some applications for tobacco products. Inorganic salts as such, however, have not been used for reducing ignition propensity, which is probably based on the assumption that a certain oxygen deficit is necessary to make cigarettes self-extinguish in the ASTM test cited above and that this can only be achieved by reducing the wrapper porosity to a level lower than 10 CU to 15 CU (CU: Coresta unit, permeability as measured in the tobacco industry, see CORESTA Recommend Method No. 40). In EP 1 234 514 A2, for example, ammonium phosphate is used as a burn retardant, but only in combination with additional substances, as e.g. alginates, which provide for a low porosity.

[0006] The object of the invention is to provide a smoking article with reduced ignition propensity, which does not exhibit the disadvantage of a significantly reduced rod ventilation.

[0007] This object is achieved by a smoking article having the features of claim 1. Claim 10 relates to a method of manufacturing such an article. Claims 19 and 20 relate to a paper for rolling cigarettes and to a paper tube for making cigarettes, respectively, which have a reduced ignition propensity. Advantageous embodiments of the invention emerge from the dependent claims.

[0008] The smoking article according to the invention comprises a tobacco rod and a wrapper. The wrapper includes at least one zone treated with an inorganic salt providing reduced ignition propensity. This zone can comprise the total wrapper. In advantageous embodiments of the invention, however, the wrapper includes at least one discrete zone treated with the inorganic salt, wherein the total surface area of the discrete zones is smaller than the total surface area of the wrapper; i.e. in addition to any areas of the wrapper being covered by, e.g., a tipping paper of a filter, there are exposed areas of the wrapper which are not treated with the inorganic salt.

[0009] Surprisingly, it was found that the application of inorganic salts is able to reduce the ignition propensity of the smoking article without reducing the porosity of the wrapper to levels as commonly required for this purpose. Thus, the invention does not rely on the main effect of a reduced porosity in the zones treated with the inorganic salt.

[0010] In advantageous embodiments of the invention, the porosity of the wrapper in the treated zones is larger than 10 CU, preferably larger than 12 CU or than 15 CU. Porosities in this range permit access of sufficient oxygen to the tobacco rod in order to minimise carbon monoxide formation and provide for sufficient diffusion.

[0011] The inorganic salt can comprise, e.g., magnesium chloride, aluminium sulfate, alum, sodium tetraborate, hydrated magnesium chloride, hydrated aluminium sulfate, hydrated alum, hydrated sodium tetraborate, sodium chloride, or mixtures thereof. In the discrete zones of the wrapper, the specific amount of the organic salt can be in the range of from 0.2 mg/cm² to 20 mg/cm² or in the range of from 0.5 mg/cm² to 5 mg/cm². Moreover, any interval limits in the range of from 0.2 mg/cm² to 20 mg/cm² are explicitly disclosed herewith. Such inorganic salts are less expensive than porosity-reducing agents like alginates.

[0012] In advantageous embodiments of the invention, there are discrete zones treated with the salt(s) arranged as bands (rings) extending along the circumference of the smoking article and having a width, measured along the tobacco rod axis, of from 2 mm to 12 mm or from 2 mm to 8 mm or preferably of 6 mm. Generally, the provision of the inorganic salts in the bands is sufficient for achieving reduced ignition propensity such that it is not required to treat the whole wrapper material with the inorganic salt, which results, e.g., in cost reduction and the possibility of an even higher porosity in the wrapper areas between the discrete zones. Preferably, the wrapper comprises at least two such bands which are separated by at least 1 mm or at least 5 mm and preferably by at least 10 mm.

[0013] In advantageous embodiments of the invention, the smoking article comprises a filter, and the smoking article can be designed as a cigarette, wherein the wrapper is a cigarette paper (which includes the possibility of manufacturing the wrapper from reconstituted tobacco).

[0014] Other embodiments of the invention relate to a paper for rolling cigarettes (RYO cigarettes; RYO: "Roll Your Own"), as well as to a paper tube (preferably a paper tube including a filter at one of its ends) for making cigarettes (MYO cigarettes; MYO: "Make Your Own") by filling the paper tube with tobacco. In these cases, the rolling paper and the paper tube comprise, with respect to reduced ignition propensity, the features of the wrapper of a smoking article explained so far.

[0015] There are several ways of manufacturing a smoking article according to the invention, in particular of applying the inorganic salts to the wrapper. These methods can be applied to a paper for rolling cigarettes or to a paper tube for making cigarettes in an analogue way.

[0016] In advantageous embodiments, the inorganic salt is applied to the wrapper by means of a solution or suspension. To improve the solubility of the inorganic salt, such solution can be heated. Preferably, the solvent or the suspension agent comprise water.

[0017] The inorganic salt can be applied to the wrapper by, e.g., printing techniques like gravure printing or inkjet printing, but also techniques like spraying or sizing. Printing techniques are very precise and can even be used online, e.g., in a cigarette making process after wrapping a continuous tobacco rod with the wrapper material.

[0018] For example, the inorganic salt can be applied to the wrapper by sizing in a papermaking process for providing the material of the wrapper. Whereas, usually, sizing is applied to the overall surface of the paper produced in a papermaking process, it is also possible to size zones of the paper only.

[0019] In another possibility, the inorganic salt is applied to the wrapper immediately after a papermaking process during the cutting step of a mother reel into bobbins containing wrapper material, as usually performed in the cigarette paper industry in order to provide wrapper material suitable for use in a cigarette making machine.

[0020] When a bobbin containing ordinary wrapper material is provided, the inorganic salt can be applied to the wrapper material during a rewinding step of such bobbin. This step is performed offline, i.e. not during the usual operating steps of a cigarette making machine.

[0021] It is also possible to apply the inorganic salt to the wrapper during a cigarette making process, i.e. online, either before wrapping a continuous tobacco rod with the wrapper material or after wrapping a continuous tobacco rod with the wrapper material. For such applications, gravure printing and inkjet printing, which apply a solution or suspension of the inorganic salt as "ink", are particularly suitable.

[0022] In the following, the invention is described in more detail by means of several embodiments, which are not considered as exclusive.

Example A

[0023] In a pilot test, cigarette papers were homogeneously treated with inorganic salts, and the porosity of the respective cigarette paper was measured before the treatment and after the treatment. The porosity measurements were performed according to CORESTA Recommended Method No. 40. 1 CU ("CORESTA unit") is the air flow (in cm³/min) through an area of the cigarette paper of 1 cm² when the pressure difference across the cigarette paper is 1 kPa. The following table shows the initial porosity ("base porosity") of the cigarette paper, the salt and its amount applied as well as the porosity after the salt treatment ("remaining porosity").

Base porosity	Salt	Amount	Remaining porosity
35 CU	Magnesium chloride (hydrate)	1.2 mg/cm2	16 CU
35 CU	Aluminium sulfate (hydrate)	3.0 mg/cm2	11 CU
35 CU	Sodium chloride	4.0 mg/cm2	64 CU
50 CU	Aluminium sulfate (hydrate)	3.0 mg/cm2	18 CU

[0024] It is evident that the remaining porosity is larger than 10 CU in all cases and significantly larger than 10 CU in most of the cases.

Example B

[0025] In another test, a commercial cigarette comprising a cigarette paper with a base porosity of 35 CU was homogeneously treated with an aqueous solution of sodium chloride until a weight of 4.0 mg sodium chloride per cm² was achieved.

[0026] The test result according to ASTM E 2187-04 (see above) for cigarettes treated in this way was 35%.

Example C

[0027] The outer side ("felt side") of a commercial cigarette paper (base porosity 35 CU) was sprayed with an aqueous solution of magnesium chloride to form treated discrete zones in band form of 6 mm width with a distance (gap width) of 20 mm on the paper. The concentration of the solution and the amount of spraying were adjusted so that a weight of 1.2 mg magnesium chloride per cm² was achieved. In other embodiments, the inner side ("wire side") or both sides of the cigarette paper could be sprayed with the solution.

[0028] Conventional American Blend cigarettes were produced with the treated paper and tested according to ASTM E 2187-04. The test result was 13%.

Example D

[0029] A warm (50°C), saturated solution of aluminium sulfate was applied to the cigarette paper (porosity 50 CU) of a conventional cigarette during the cigarette making process using a gravure printing device. The gravure depth was adjusted so that a weight of 3 mg aluminium sulfate per cm² was achieved in the printed areas. The salt was applied in band-shaped discrete zones having a width of 6 mm each and a respective distance (width of untreated zones) of 20 mm.

[0030] According to ASTM E 2187-04, the test result was 20%.

Claims

1. Smoking article, comprising a tobacco rod and a wrapper, wherein the wrapper includes at least one zone treated with an inorganic salt providing reduced ignition propensity.

2. Smoking article according to claim 1, characterized in that the porosity of the wrapper in the treated zone(s) is larger than 10 CU, preferably larger than 12 CU or 15 CU.

3. Smoking article according to claim 1 or 2, characterized in that the inorganic salt comprises at least one substance selected from the group consisting of magnesium chloride, aluminium sulfate, alum, sodium tetraborate, hydrated magnesium chloride, hydrated aluminium sulfate, hydrated alum, hydrated sodium tetraborate, sodium chloride.

4. Smoking article according to anyone of claims 1 to 3, characterized in that the specific amount of the inorganic salt in the treated zone(s) of the wrapper is in the range of from 0.2 mg/cm² to 20 mg/cm², preferably in the range of from 0.5 mg/cm² to 5 mg/cm².

5. Smoking article according to anyone of claims 1 to 4, characterized in that the wrapper includes at least one discrete zone treated with the inorganic salt, wherein the total surface area of the discrete zones is smaller than the total surface area of the wrapper.

6. Smoking article according to claim 5, characterized in that the discrete zones are arranged as bands extending along the circumference of the smoking article and having a width, measured along the tobacco rod axis, of from 2 mm to 12 mm, preferably of from 2 mm to 8 mm, most preferred of 6 mm.

7. Smoking article according to claim 6, characterized in that the wrapper comprises at least two discrete zones, two neighboring discrete zones being separated by at least 1 mm, preferably by at least 10 mm.

8. Smoking article according to anyone of claims 1 to 7, characterized in that it comprises a filter.

9. Smoking article according to anyone of claims 1 to 8, characterized in that it is a cigarette, the wrapper being a cigarette paper.

10. Method of manufacturing a smoking article according to anyone of claims 1 to 9, which includes a step being characterized in that the inorganic salt is applied to the wrapper by means of a solution or a suspension.

11. Method according to claim 10, characterized in that the solution is heated to improve the solubility of the inorganic salt.

12. Method according to claim 10 or 11, characterized in that the solvent or suspension agent, respectively, comprises water.

13. Method according to anyone of claims 10 to 12, characterized in that the inorganic salt is applied to the wrapper by one of the following techniques: gravure printing, inkjet printing, spraying, sizing.

14. Method according to anyone of claims 10 to 13, characterized in that the inorganic salt is applied to the wrapper by sizing in a papermaking process for providing the material of the wrapper.

15. Method according to anyone of claims 10 to 13, characterized in that the inorganic salt is applied to the wrapper, immediately after a papermaking process for providing the material of the wrapper, during cutting of a mother reel into bobbins containing wrapper material.

16. Method according to anyone of claims 10 to 13, characterized in that the inorganic salt is applied to the wrapper during an offline rewinding step of a bobbin containing wrapper material.

17. Method according to anyone of claims 10 to 13, characterized in that the inorganic salt is applied to the wrapper online in a cigarette making process, before wrapping a continuous tobacco rod with the wrapper material.

18. Method according to anyone of claims 10 to 13, characterized in that the inorganic salt is applied to the wrapper online in a cigarette making process, after wrapping a continuous tobacco rod with the wrapper material.

19. Paper for rolling cigarettes, characterized by the features of the wrapper of a smoking article according to anyone of claims 1 to 9.

20. Paper tube, preferably including a filter, for making cigarettes by filling the paper tube with tobacco, characterized by the features of the wrapper of a smoking article according to anyone of claims 1 to 9.