DE69008602T2 - Smoking articles. - Google Patents

Description

The subject matter of this application relates to cigarettes and similar smoking articles.

The use of humectants in the tobacco of smoking articles is explained in European Patent Application Publication No. 0 067 601. The use of expanded tobacco in smoking articles is also known. US Patent No. 4,310,006 describes a high expansion process using liquid carbon dioxide as an expansion agent. The tobacco is pretreated with humectants prior to expansion to lower the freezing point of the tobacco. However, typical levels of expanded tobacco in the tobacco blend of a smoking article are usually on the order of less than 30%, and typically less than 25% by weight of the tobacco in the smoking article, due to the lack of taste and flavour characteristics, even in markets where the weight of the cigarettes is of great importance.

It is an object of the present invention to provide a cigarette which has a low tar release but is sensorially acceptable to the smoker.

The present invention provides a smoking article comprising cut tobacco and a paper wrapper surrounding the tobacco, wherein 50% or more of the tobacco has been treated with a humectant to provide a humectant loading level of 6 to 15% by weight of the tobacco comprising expanded tobacco, wherein the packing density of the tobacco does not exceed 210 mg/cm3, and wherein, when the article is smoked under standard machine smoking conditions, the ratio of particulate material delivery on a water, nicotine and humectant free basis to nicotine delivery is not greater than 6:1. Suitably the humectant loading level of the tobacco does not exceed 12%. More suitably the loading level is in the range 7 to 10%, eg 9%.

The humectant is suitably one or more of the following substances: glycerine, propylene glycol, sorbitol and diethylene glycol.

Advantageously, the humectant is applied to the tobacco before the tobacco is subjected to an expansion process. The loading level of humectant in the tobacco before expansion may be in a range of about 5% to about 20% to result in a post-expansion level of 4% to 15%.

We have found that if the humectant is applied to the tobacco before rather than after the tobacco is subjected to the expansion process, a reduction in the length of the tobacco rod during the process is avoided. Other advantages of applying the humectant before expansion are the avoidance of an undesirably high equilibrium moisture content after expansion and the avoidance of a reduction in the filling capacity of the expanded tobacco.

Suitably, the humectant is applied to the tobacco by spraying, advantageously in aqueous solution. The humectant should be distributed over the tobacco with a significant degree of uniformity before the tobacco is subjected to the expansion process, this aim being assisted by rolling the tobacco and/or by allowing the tobacco to accumulate for a sufficient period of time after application of the humectant. or to stand in the crowd.

The tobacco of the smoking articles according to the present invention which is to be subjected to an expansion process is suitably pre-conditioned to a moisture content in a range of 22% to 30% and preferably to a moisture content in a range of 26% to 30%.

Tobacco of smoking articles according to the present invention which is subjected to an expansion process can be leaf and/or stem tobacco. The expanded tobacco advantageously comprises as leaf tobacco the product of a tobacco expansion process which is effective in achieving a high degree of expansion of the tobacco subjected to the process. High expansion processes are disclosed, for example, in the specification of United States Reissue Patent No. 30,693 and the specifications of United Kingdom Patent Nos. 1,570,270 and 2,160,408 A. By using a high expansion process, the tobacco expansion values expressed in fillability values increase from about typically 75%, and even up to 125% can be achieved. Tobacco which has undergone a high expansion process may have a bulk density of, for example, about 100 mg/cm³ to about 200 mg/cm³, and preferably not less than 150 mg/cm³, when measured using a Borgwaldt densimeter.

A minor proportion of the smoking material of smoking articles according to the present invention may take the form of reconstituted tobacco and/or tobacco substitute material. Preferably, however, the smokable material should be entirely natural cut tobacco. It is also preferable that all or a substantial proportion of the cut tobacco of smoking articles according to the present invention should be expanded tobacco and that all of the expanded tobacco has been treated with a humectant before being expanded. Suitably, at least 65% of the tobacco is treated expanded tobacco and more suitably 70% is treated expanded tobacco.

The weight of the smoking material in a cigarette according to the present invention is suitably in a range of 500 to 800 mg.

It can be observed that when measuring the PMWNF yield of a smoking article according to the present invention, the value obtained includes a proportion of the humectant. It may thus be of interest to express the yield of particulate matter on a water, nicotine and humectant free basis (PMWNHF). Preferably, the PMWNHF to nicotine delivery ratio of smoking articles according to the present invention is in the range of 6:1 and preferably in the range of about 5:1.

The humectant in the mainstream smoke of cigarettes according to the present invention, measured under standard machine smoking conditions, preferably constitutes not less than 15%, and more preferably not less than 20% of the mainstream PMWNF. Even more preferably, the mainstream smoke humectant constitutes about 25% of the mainstream PMWNF. Suitably, the mainstream smoke humectant may also be in the range of 24 to 26%, e.g. 24%.

A burn retardant may be used in smoking articles according to the present invention. The burn retardant may be, for example, magnesium chloride, sodium chloride, ammonium sulfate, ammonium lactate or mixtures thereof applied to the smoking material.

In order to facilitate understanding of the present invention, corresponding examples will now be described.

EXAMPLE I

A cut tobacco blend containing 20% water-treated ribs, 40% Burley tobacco leaves and 40% hot-air-dried tobacco leaves was added with glycerine at a loading value of 10% and magnesium chloride at a loading level of 1%. The mixture was pre-treated or conditioned to a moisture content of 25%, after which the mixture was subjected to a high expansion process. The glycerine loading of the expanded tobacco was approximately 6%.

Using the expanded tobacco thus obtained, cigarettes with a circumference of 24.75 mm were produced. Each cigarette contained a 64-minute long tobacco rod consisting of 100% expanded tobacco and a wrapper made of commercially available standard cigarette paper. The packing density of tobacco in the tobacco rods was approximately 145 mg/cm3. A 20-mm long cellulose acetate filter was attached to each tobacco rod through a filter tipping paper. The cigarettes were provided with ventilation holes on the filters by laser beams to provide a ventilation rate of 55%.

These cigarettes were smoked under standard (Coresta) smoking machine conditions, whereby a 35 cc puff of 2 seconds duration is taken every minute; it was found that the following major smoke component yields resulted:

Component Yield (mg)

TPM5.88

Nicotine 0.63

PMWNF 4.37

Glycerine 1.35

PMWNHF 3.02

It is thus observed that the PMWNHF to nicotine ratio was 4.8. It can also be observed that the glycerol yield represented 31% of the PMWNF yield.

It was found that when smoked under Coresta smoking machine conditions, a commercially available cigarette, Benson & Hedges Ultra (trade mark), of the same yield, ie 5.57 mg TPM, had a mainstream glycerine yield of 0.44 mg which represents 9.4% of the PMWNF yield. The PMWNHF to nikontine ratio of the Ultra Cigarette was 9.9.

In sensory smoking tests, it was found that the cigarettes according to the present invention described above had taste characteristics that were superior to those of the Ultra cigarettes.

EXAMPLE II

A cut tobacco blend contained 25% Burley leaf, 40% hot air dried leaf, 25% water treated ribs and 10% sun dried Oriental leaf. Glycerine was added to this blend at a loading level of 10% and magnesium chloride at a loading level of 1%. The blend was then subjected to a high expansion process. The glycerine loading level on the expanded tobacco was 8%.

Using the tobacco thus obtained, cigarettes were prepared which were of the same format as the cigarettes according to the invention of Example I. When smoked under standard smoking machine conditions, the mainstream smoke component yields were determined as follows: Component Delivery (mg) TPM Nicotine PMWNF Glycerine PMWNHF

Thus, the PMWNHF to nicotine ratio was 6.1, and the humectant represented 33% of the PMWNF.

Claims (8)

1. A smokable article comprising a tobacco rod, the tobacco rod comprising cut tobacco and a paper wrapper surrounding the tobacco, 50% or more of the tobacco having been treated with a humectant to provide a loading level of said humectant of from 6% to 15% by weight of the tobacco, the tobacco comprising expanded tobacco, the packing density of the tobacco rod not exceeding 210 mg/cc, and when the article is smoked under standard machine smoking conditions, the ratio of particulate matter delivery on a water, nicotine and humectant free basis to nicotine delivery is not more than 6:1. 2. A smoking article according to claim 1, wherein the loading value is not less than 7%. 3. A smoking article according to claim 1 or 2, wherein the loading value does not exceed 12%. 4. A smoking article according to claim 3, wherein the loading value does not exceed 10%. 5. A smoking article according to any preceding claim, wherein the humectant is one or more of the following substances: glycerol, propylene glycol, sorbitol and diethylene glycol. 6. A smoking article according to any preceding claim, wherein the bulk density of the tobacco which has been expanded is from about 100 mg/cc to about 200 mg/cc. 7. A smoking article according to any preceding claim, wherein the expanded tobacco of the rod comprises at least 65% of the total tobacco of the rod. 8. A smoking article according to claim 7, wherein the expanded tobacco has been treated with humectant prior to expansion.