Improvements relating to smoking articles

Abstract: A cigarette, the smoking material rod of which comprises a proportion of expanded tobacco, yet which provides an acceptable mainstream smoke temperature over the whole smoking process. When cigarettes containing expanded tobacco also comprise a low sidestream wrapper, such cigarettes provide substantial CO to PMWNF parity and smoker acceptable mechanics.

Description: The invention the subject of this application relates to cigarettes and similar smoking articles, smoking material of which comprises expanded tobacco. It has been observed that when the cut tobacco filler of a cigarette includes a proportion of expanded tobacco, DIET-expanded tobacco for example, a smoker of the cigarette is likely to perceive that the mainstream smoke is hotter over the last few puffs than during the prior puffs. An object of the subject invention is the provision of a smoking article, the smoking material of which comprises expanded tobacco, but which smoking article nevertheless provides to the smoker acceptable mainstream smoke over the whole of the smoking process. It has also been observed that when smoking articles having a low density smoking material rod are wrapped with wrappers which, when wrapped around conventional density smoking material rods, effect a reduction in sidestream smoke constituents, the ratio of carbon monoxide (CO) to particulate matter, water and nicotine free (PMWNF), of the mainstream smoke is greater than one, i.e. there is little parity in CO and PMWNF. Efforts to reduce the CO to PMWNF ratio using a lower pressure drop cellulose acetate filter results in a more acceptable CO to PMWNF ratio but with poor smoking article mechanics, which mechanics are unacceptable to the smoker. It is a further object of the subject invention to provide a smoking article which has acceptable smoke mechanics and a substantially matched CO to PMWNF ratio. The present invention provides a smoking article comprising a material rod and filter means disposed at one end of said rod, said rod comprising smoking material, and a paper wrapper circumscribing said smoking material, said rod and said filter means being interattached by a tipping wrapper, the density of said smoking material in said rod being in the range of about 100 mg cm -3 to about 260 mg cm -3 , the smoking material comprising at least 20% expanded tobacco, and said paper wrapper being a sidestream reducing wrapper having an inherent permeability of not more than about 20 Coresta Units, characterised in that said filter means comprises first and second longitudinally aligned bodies of filtration material, the first body being a polyolefin material of low filtration efficiency, the second body being a cellulose acetate material, the first body having a pressure drop greater than that of the second body, and ventilation means operable to provide the smoking article with a ventilation level of at least 50%, the ventilation means being located downstream of said first body, and said paper wrapper comprising a total filler content of 20% or less, a proportion at least of the filler being a filler effective for visible sidestream reduction, and the weight of the wrapper being about 30 grams per square metre or more. Preferably, the smoking material comprises at least 30% by weight of expanded tobacco, and, more preferably, at least 40% by weight of expanded tobacco. In smoking articles according to the present invention smoking material not being expanded tobacco preferably comprises leaf tobacco, suitably in conventional cut filler form. The leaf tobacco may be lamina and/or stem tobacco. Smoking material not being expanded tobacco may comprise a reconstituted tobacco or a tobacco substitute. The expanded tobacco may be lamina and/or stem tobacco. The expanded tobacco is advantageously a lamina tobacco the product of a tobacco expansion process which is effective to provide a high degree of expansion in tobacco subjected to the process. High expansion processes are disclosed, for example, in the specification of United States Reissue Patent No. 30 693 and in United Kingdom Patent Specifications Nos. 1570270 and 2160408A. By the use of high expansion processes, tobacco expansion values, in terms of filling value increase, of from about, typically, 75% and even up to about 125% may be obtained. Tobacco which has been subjected to a high expansion process may have a bulk density of, for example, from about 100 mg cm -3 to about 175 mg cm -3 , as measured using a Borgwaldt Densimeter. Preferably, the first body of filtration material comprises polyolefin, polypropylene or polyethylene, for example. Preferably, the ventilation means is located at or downstream of the first body of filtration material. Suitably, the level of ventilation is high, say 40% or more and even more suitably, at least 50% or more. Suitably, the paper wrappers of smoking material rods of smoking articles in accordance with the subject invention comprise a sidestream reducing agent. There may be utilised, for example, a wrapper paper comprising a total filler content of 20 per cent by weight, or less, a proportion at least of the filler being a filler, magnesium oxide and/or hydroxide for instance, which is effective for visible sidestream reduction, the weight of the paper being about 30 grams per square metre or more. Advantageously, the inherent permeability, i.e. that due to viscous flow, of paper wrappers of smoking material rods of smoking articles in accordance with the subject invention is not more than about 20 Coresta units and is more advantageously not more than about 10 Coresta units. In addition, the paper wrappers of smoking material rods of smoking articles in accordance with the subject invention may comprise a burn retardant. As used herein the term "burn retardant" means a substance the inclusion of which in or on a paper wrapper of a smoking material rod effects a reduction in the smoulder rate of the smoking material rod. The term "burn retardant" can refer to the use of two or more such substances, as well as to the use of a single such substance. Suitable burn retardants will be known to those skilled in the art. Reference is directed to those substances mentioned in our co-pending U.K. Patent Application No. 8820498.7. Suitable water soluble and water insoluble substances and their respective loading levels are described therein. The filter means may further comprise a ventilated tubular mouthpiece element. In order that the subject invention may be clearly understood and readily carried into effect, reference will now be made, by way of example, to the diagrammatic drawing hereof, which shows, in axial section, a smoking article comprising a cigarette. The cigarette shown in the drawing, which cigarette is generally designated by reference numeral 1, comprises a cigarette rod 2 and a dual filter 3, which filter 3 is interattached with the rod 2 by means of a tipping wrapper 4. The cigarette rod 2 comprises a cut tobacco filler 5, 40% of the weight of which filler 5 is accounted for by DIET-expanded tobacco. The density of filler 5 in cigarette rod 2 is 200 mg cm -3 . The cigarette rod 2 further comprises a cigarette paper wrapper 6 comprising as filler 4.9% by weight chalk and 10.5% by weight magnesium oxide. The wrapper 6 has a basis weight of 36.6 g m -2 and an air permeability of 7.0 Coresta units. The wrapper 6 includes no burn additive. The filter 3 comprises a plug 7 of polyethylene, in abutment with the cigarette rod 2, and a plug 8 of cellulose acetate in abutment with the plug 7. The plugs 7 and 8 are interattached by a circumscribing porous plugwrap 9. The filter 3 was supplied by Filtrona Limited under the designation "Ratio Filter". The tipping wrapper 4 comprises a ring of ventilation perforations 10 so located that during the smoking of the cigarette 1 ventilation air enters the plug 8 through the peripheral surface thereof. Cigarette 1 provides an acceptably cool mainstream smoke throughout the smoking process and suffers less from hot collapse. In order to assess the CO to PMWNF ratio for cigarettes according to the subject invention the following test cigarettes were prepared. EXAMPLE 1 Cigarettes A according to the invention of a circumference of 24.75 mm and having a 59 mm long smoking material rod and 25 mm long filter body were produced. The tobacco rod density was 190 mg cm -3 , the expanded tobacco being 40% of DIET tobacco. The rod was wrapped in a paper having a basis weight of 37.5 g m -2 and comprising 11.5% magnesium oxide, 4.3% calcium carbonate and 4.6% sodium acetate. The paper had an inherent permeability of 5.0 Coresta units, but was electrostatically perforated to a total permeability of 55 Coresta units. The filler body comprised an 8 mm long polyethylene filter element having a pressure drop of 175 mm WG and 17 mm long cellulose acetate filter element having a pressure drop of 40 mm WG. The Cigarettes A were ventilated to a level of 71-72%. The unbound pressure drop was 96 mm WG. Control Cigarettes, Cigarettes B, of the same format were wrapped in a wrapper having a permeability of 50 Coresta units and a basis weight of 29 g m -2 . The paper comprised 21% chalk and 2% mixed sodium citrate and potassium citrate. The filter body comprised a 25 mm long cellulose acetate element. The density of the tobacco rod was 246 g cm -3 . The cigarettes were ventilated to a level of 57% and had an unbound pressure drop of 100 min WG. Cigarettes A and B were smoked under standard machine smoking conditions, i.e. a 35 cm 3 puff of 2 seconds duration every minute, to a cigarette tobacco rod butt length of 8 mm and measurements of the mainstream and sidestream smoke component yields were taken. These are outlined in Table 1 below. CIGARETTES PMWNF (mg/cig) TNA (mg/cig) CO (mg/cig) PN CO/PMWNF A (MAINSTREAM) 4.0 0.3 3.7 9.3 0.93 A (SIDESTREAM) 13.1 2.2 40 8.3 - B (MAINSTREAM) 4.3 0.3 4.7 8.6 1.09 B (SIDESTREAM) 25.8 3.5 51 7.8 - EXAMPLE 2 Cigarettes C were produced. (The cigarettes in this example do not contain all the features of claim 1.) The cigarettes were of a circumference of 24.75 mm and had a tobacco rod length of 64 mm and 20 mm long filter body comprising a 6 mm long polyethylene filter element and a 14 mm long cellulose acetate element. The filter pressure drop was 136 mm WG. The density of the tobacco rod was 195 mg cm -3 and comprised 13% by weight of tobacco expanded by the G13 process. The cigarettes were wrapped in a paper designated Paper C having a basis of weight of 25.4 g m -2 , and a permeability of 3 Coresta units. The paper also comprised 0.5% mono ammonium phosphate and 20.4% calcium carbonate. Cigarettes D and E were produced having the same format. The filter body of each of these cigarettes comprised cellulose acetate. The filter pressure drop of each of these cigarettes was 50 mm WG and 70 mm WG respectively. The tobacco rod density of each of these cigarettes was 197 mg cm -3 and 201 mg cm -3 respectively. The cigarettes D and E were wrapped in the same paper as Cigarettes C, i.e. Paper C. When these cigarettes were smoked under standard machine smoking conditions to a tobacco rod butt length of 10 mm, the mainstream smoke deliveries were measured. Details thereof and of the level of ventilation of each cigarette are outlined in Table 2. PARAMETER CIGARETTE C D E % Ventilation 50 50 45 PMWNF (mg/cig) 18.0 14.4 14.2 TNA (mg/cig) 1.71 1.5 1.45 CO (mg/cig) 14.7 12.3 14.4 Puff Number 10.3 11.0 10.7 CO to PMWNF ratio 0.82 0.85 1.01 It was found to be difficult to measure a quantitative temperature difference between control cigarettes and cigarettes C. Tharefore, in order to provide a qualitative assessment of the perceived decrease in the hot sensation associated with cigarettes containing expanded tobacco, a subjective smoke panel test was carried out using Cigarettes C and D described above, details of which smoke panel test are outlined below. Ten panellists were asked to comment, using a scale of 0 to 5 for increasing temperature, on the temperature of each cigarette smoked at three pre-determined locations along the tobacco rod length in a duplicated, paired comparison test. The paired comparison test comprises ten pairs of coded cigarettes. Each pair of cigarettes is smoked together and, in this case, a rating of the perceived temperature at the same pre-determined location for each cigarette is given by the smoker. Thus, twenty cigarettes are smoked. The entire test is duplicated, so that, in total, forty cigarettes are smoked. The significance of any difference is assessed using the Wilcoxon matched pairs, signed-ranks test. The results are presented below in Table 3 along with a brief conclusion. Length from Overtip CIGARETTES C D Score Mean values Significance 43 mm 1.26 1.28 NS 23 mm 1.94 2.23 3 mm 2.94 3.71 The test indicates that there is a significant perceived difference in temperature of the smoke at a 99% confidence level at a location 3 mm from the overtip, i.e. the Cigarettes C have a cooler smoke in the last few puffs.

Claims: A smoking article (1) comprising a material rod (2) and filter means (3) disposed at one end of said rod (2), said rod (2) comprising smoking material (5), and a paper wrapper (6) circumscribing said smoking material (5), said rod (2) and said filter means (3) being interattached by a tipping wrapper (4), the density of said smoking material (5) in said rod (2) being in a range of about 100 mg cm -3 to about 260 mg cm -3 , the smoking material (5) comprising at least 20% expanded tobacco, and said paper wrapper (6) being a sidestream reducing wrapper having an inherent permeability of not more than about 20 Coresta Units, characterised in that said filter means (3) comprises first (7) and second (8) longitudinally aligned bodies of filtration material, the first body (7) being a polyolefin material of low filtration efficiency, the second body (8) being a cellulose acetate material, the first body (7) having a pressure drop greater than that of the second body (8), and ventilation means (10) operable to provide the smoking article with a ventilation level of at least 50%, the ventilation means (10) being located downstream of said first body (7), and said paper wrapper (6) comprising a total filler content of 20% or less, a proportion at least of the filler being a filler effective for visible sidestream reduction, and the weight of the wrapper (6) being about 30 grams per square metre or more. A smoking article according to Claim 1, wherein said first body (7) of polyolefin material comprises polyethylene material. A smoking article according to Claim 2, wherein said first body (7) of polyolefin material comprises polypropylene material. A smoking article according to Claim 1, 2 or 3, wherein the ventilation means (10) is located whereby ventilation air enters said second body (8) through the periphery thereof. A smoking article according to any one of Claims 1 to 4, wherein said first body (7) abuts the downstream end of the smoking material rod (5) and said second body (8) abuts the downstream end of said first body (7). A smoking article according to any one of the preceding claims, wherein the filler effective for visible sidestream reduction is magnesium oxide and/or hydroxide.

Inventors: CASE PAUL DAVID, STEPHENSON ALAN GEORGE, CASE, PAUL DAVID, STEPHENSON, ALAN GEORGE
Applicants: BRITISH AMERICAN TOBACCO CO, BRITISH AMERICAN TOBACCO (INVESTMENTS) LIMITED
Application year: 1990
Main classification: A24D1
IPC codes: A24D3, A24D1, A24B3