JPH0365172A - Improvement of smoking-product - Google Patents

Abstract

PURPOSE: To obtain a smoking product utilizing the advantage of a multilayer sheet and facilitating the usage of a multilayer sheet cover by providing a single sheet of paper forming the cover of a smoking product of at least two separate webs and combining one of the webs still at a wetting step before drying. CONSTITUTION: The mentioned webs consist of different materials (being the components of the mixture of a head box or a casing). Then at least two webs are combined when all the webs are at the wetting step of forming in advance of drying. In addition the cover is low in air permeability and desirably the permeability is not more than 10 coresta. In addition, it is desirable that two partially formed webs are combined and one of the webs is a substantially non-filled web with a low starting weight. As a result, the smoking product consisting of a cover with both of the rod of smoking material and the feature is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to smoking products, such as cigarettes, in which the smoking product employs a coating, the coating generally consisting of fibers of organic origin mixed with non-organic fillers and comprising: Often contains soluble chemical additives, binders and processing aids.

In the case of cigarettes, conventional coverings typically consist of wood and/or textile fibers mixed with non-organic fillers such as calcium carbide.

These materials undergo a refining process and can be mixed in various proportions to modify the properties of the coating to impart different properties to the cigarette, such as smoke rate, air permeability, ash quality, appearance and taste. Can be varied over a wide range.

Cigarette paper technology depends on paper parameters such as filler/fiber ratio and inherent air permeability and opacity (opac).
It has been well developed to establish relationships between properties such as lty). These relationships are well known, and indeed many of the relationships between the properties of papers and the performance of cigarettes made from these papers are well known.

It is recognized that conventionally formed cigarette paper is not a homogeneous mixture of filler and fibers in its cross section. The filler distribution tends to change from the -side to the other side, and this is due to the nature of the liquid removal process and filtration effect of the fibers. Conventional papers therefore usually have some degree of asymmetric fiber/filler mix, which is not extreme but has an important influence on their performance, especially with regard to ash formation.

These combinations, such as multiple or dual coatings, for example by using bulbs of different botanical origin and very high and very low filler contents to form papers with completely different properties separately. For example, products made by combining
This behavior is quite different from the single, substantially homogeneous mixing of identical components as achieved in conventional cigarette paper manufacturing.

It has already been proposed to use two substantially different coatings on cigarette smoking products.

U.S. Pat. No. 3,895,714 shows a technique that uses two thin sheets to form a hybrid wrapper, where the outer sheet is conventional cigarette paper and the inner paper in contact with the tobacco is heated to less than 440°C. It is a heat insulating resin film with a melting point. This specification is also presented as two sheets:
Alternatively, they have proposed manufacturing techniques by depositing a resin film as a composite with two sheets glued together or as a solution on a sheet of cigarette paper.

This patent proposes advantages of these systems, including the following advantages: These include changes in the cold distillation zone that affect the taste of the smoke, reduced tobacco consumption between puffs, and reduced sidestream smoke emissions.

US Pat. No. 3,633,589 proposes a hybrid covering consisting of two thin sheets, where both sheets are made of vegetable fibers, providing the advantages of US Pat. No. 3,395,714 without the disadvantages of resin films.

Although U.S. Pat. No. 38H589 does not suggest how to associate two thin sheets, the hybrid covering is described as an outer sheet of conventional cigarette paper and a glazed inner sheet that effectively blocks air. Indicates that it is formed from individually manufactured paper.

The present invention aims to take advantage of the advantages of multilayer sheets while at the same time overcoming the practical difficulties of using dual or multi-sheet coverings. Thus, without the manufacturing difficulties associated with either laminating sheets in an off-line process or attempting to make cigarettes while running two paper coverings simultaneously on a cigarette making machine. , it would be desirable to have the benefit of combining the properties of different paper coverings. Additionally, it would be desirable to avoid the disadvantages of laminating adhesives.

According to one aspect of the present invention, a covering for a smoking article is provided, the covering comprising a single sheet of paper formed from two or more separate webs, the web comprising: The combination is made while one is still in the wet stage of formation prior to drying.

Preferably the webs are formed from different materials. (
The raw materials are components of the mixture in the headbox or container. ) Conveniently, the two or more webs are combined when all webs are in the wet stage of formation prior to drying.

In a preferred embodiment, the covering has a low air permeability, more preferably the permeability is 10 Corest.
a) The following. In another preferred embodiment, two partially formed webs are combined, one web being a substantially unfilled web having a low starting weight. Conveniently, the weight is less than or equal to 20 gmm, and one of the webs prevents or substantially reduces fouling;
Alternatively, one of the webs contains activated carbon.

Yet another desirable feature is that the other web is a filled web that gives the coating a conventional appearance, eg, the opacity of the coating is 60% or greater.

The filler of said other web may consist of an amount of calcium carbide (up to 50% by weight), or the filler of said other web may consist of an amount of a selected filler, e.g.
It will consist of Mg (OH) 2 , A I 20x, LiOH and high surface area Ca COs.

Although it is desirable that the total starting weight of the cladding be less than 50B-2, in other configurations the total starting weight of the cladding may be less than 35B-2.
It is less than H+-2.

In certain desirable configurations, the one or more webs contain a flame retardant, such as ammonium phosphate, or a first
or a combustion accelerator such as a soluble salt of a Group I metal,
It can be contained up to 10% by weight.

According to a second aspect of the invention, there is provided a smoking article consisting of a rod of smoking material and a covering having any of the above characteristics.

The term "duplex" as used herein is intended to encompass sheets consisting of two or more webs;
Here, at least one web is in a part-forming wet stage prior to drying when two or more webs are combined or laminated. Therefore, the adhesion between the two layers is
This is accomplished through fiber bonding inherent in the papermaking process. Additionally, this method of formation introduces interactions between two or more layers that can have a surprising effect on the air permeability of the finished duplex sheet.

Obviously, the component webs can be formed from different raw materials from separate headboxes or vessels in a multi-wire machine, or at least one web can be produced off-line and transferred to the wetting stage of the second paper machine. can be reintroduced as a completed sheet. In either method of manufacture, the objective is to use a fibrous structure to provide an integral sheet formed from two or more layers that can be used as a covering for a smoking product.

While conventional paper is also asymmetrical such that the ratio of fiber to filler changes from one side of the sheet to the other, duplex sheets offer a gradual progression of properties associated with a single wire sheet in traditional form. Instead of a change, it is possible to provide a sudden change from the - side to the other side.

Therefore, by using duplex sheets,
It becomes possible to provide a paper sheet having different properties on the - side and the other side.

As compared to the use of laminated materials or the use of two or more different sheets coated together to form a cladding,
The above-mentioned difficulties of lamination techniques and running more than one covering on a cigarette making machine are naturally avoided. Moreover, by utilizing a multi-wire machine in which different raw materials are provided for each wire to form a single sheet with different properties as described above across the cross-section, it is not suggested in the prior art that A synergistic effect is observed that affects the properties of the duplex web, which was not discovered. The inventors have discovered that air permeability due to paper's inherent porous structure is not a simple function of flow through the two components, but can be greatly reduced by the integrity of their surfaces. The same does not occur if two separate coatings are brought together after a wetting step following completion of the papermaking process.

Table 1 shows air permeability data obtained with the Gurley system on duplex papers and components. In these and subsequent tests,
The components, inner and top layers or webs, were obtained on the paper machine by sampling from each web without the two being combined. The sample was then final processed as a regular sheet.

The Gurley system of air permeability measurement is suitable for evaluating cigarette papers with low permeability relative to common commercial standards. The method involves measuring the time it takes to evacuate a fixed volume of air through a defined area of paper under a constant load of a weighted drop piston. This equipment is located at ν & Falton Street, Troy, York, 12181 New York.
Commercially available by L E Gurley. This test is described in ISO 8887-1976. Adjacent columns in the table do not correspond.

Table 1 30 000 3 23 375 4 7 760 000 25075 70 50 30 140 500 950 950 The interaction between the two surfaces is greater than the air permeability that would be achieved by a double coating of each component of the duplex paper. It has also been found that it guarantees a low level of transparency. Clearly this is a construction advantage when low air permeability is the objective, such as in the case of cigarettes where low sidestream smoke may be required.

Furthermore, it is observed that due to low tensile strength, low starting weight and poor appearance, the limitations normally imposed on the production of individual webs no longer apply. This is because duplex paper exhibits properties determined by a hybrid system and
This is because these are usually found to be superior to any of the individual components. As a result, it is possible to take into account duplex properties that would not be achievable as a double coating. Table 2 provides data regarding the tensile strength, starting weight and opacity of the duplex paper and its components. Opacity is determined by standard EEL machine (
B54432), where standard cigarette paper has an opacity of more than 60%.

Table 2 Tensile strength, starting weight and opacity data! Tensile strength Starting weight Opacity pull g
+111-' g l-'
%No dub top inside
dub crest in deb crest
Inside 1 195 95 B2 32.8 19
．． 1 13.5 71.8 60.4 20.22
211 31 79 37.4 24.1 13.
3 71.0 68.2 19.45 207 6
8 B9 38.3 23.7 14.8 78
．． 4 8B, 2 22.07 207 14 88
38! 1g, 9 17.4 89.4 B2
．． 2 18.89 311 42 114 47°7
29.8 18.1 77°8 72.4 21.
In some applications, duplex sheets are formed from two raw materials, one of which provides high impermeability properties and the other of which provides some of the properties of conventional cigarette paper, particularly those related to appearance.

Certain embodiments of the invention provide duplex paper for use in the manufacture of cigarettes, the paper being formed from two or more raw materials, one of which has a composition that provides high impermeability properties. However, others are suitable raw materials for producing tick-filled cigarette paper.

While there are many uses in smoking article coverings having unusual non-uniform cross-sectional properties, one particular benefit is that co-pending UK Application No. 8901579.8. The above application forms the basis of European Application No. 90300750.8.

In application no. 8901579.8, cigarette paper is required to form a self-extinguishing smoking product.

This is, of course, contrary to the usual conditions for traditional cigarettes, which are expected to smoke easily and maintain combustion between puffs. The purpose of this construction is to achieve low and negligible sidestream smoke emissions between puffs.

Although paper can be made to easily self-extinguish cigarettes, such paper can be made from Papi Rossi, which has the high fiber density and low opacity properties of non-permeable paper sheets.
rossl) type.

The highly non-permeable papers described above are not attractive for use in cigarettes because while they would accomplish the purpose described in the applicant's co-pending application, they It does not have an appearance that is acceptable to those who smoke it, and it also easily exhibits uneven burning and over-burning, resulting in the formation of scorch lines and staining during smoking.

To overcome this drawback, high opacity, low opacity paper can be coated with conventional cigarette paper. However, a disadvantage of this proposal is that the coating has to be made in a cigarette making machine or two coatings have to be laminated, which suffers from the disadvantages mentioned above.

Double coating is used commercially by Philip Morris in the USA under the brand Vlrginla Supersllms, but in this construction the starting weight of woven paper is 70 gmm2 compared to about 25 gmm2 for conventional paper. becomes. Therefore, in order to achieve a more conventional weight of paper, the two components of the double coating must have an extremely low starting weight, which also results in lower strength and therefore cannot be produced commercially as a single sheet. Otherwise, it will be difficult and in some cases impossible to use.

In one embodiment of the present invention, the above problems are overcome by forming a duplex paper, where the raw material for the high opacity and low opacity paper creates a partially formed web. This is combined with a partially formed web made from a more traditional cigarette paper stock. The above two partially formed webs are
They are combined before drying to form a duplex paper with different properties from one side of the sheet to the other.

By using the above duplex paper in the manufacture of cigarettes, a traditional appearance can be placed on the outside of the cigarette, with a lower opacity on the opposite side to the cigarette, thus without compromising the appearance and contaminating the cigarette. etc. without
Provide the necessary properties for the product.

Additionally, the interaction between the two components as a monolithic duplex sheet increases tensile strength and creates an opportunity for producing low starting weight sheets, which
As a single paper, it has characteristics that would not be acceptable for manufacturing reasons. The development of paper manufacturing is 32gmm2
We produce duplex cigarette paper with a weight of
It consists of a 15gn+-2 dense, low transmissive, low opaque layer and a highly transmissive, high opaque chalk fill layer.

Data for this paper are given in Table 3. Traditional cigarette paper manufacturing methods would not produce paper with the same properties as this duplex sheet. Furthermore, a reduction in starting weight is possible with this system, while still maintaining acceptable appearance, strength, etc.

Table 3 Pull g ■12 No Deb 1 Inside 4 32, OL8.2 14.8 31.3 16, 2 15.3 30.8 18.0 14.0 % Gurley % Top Deb 1 Inside Dubu Ring 27.
9 1390 (1184 (1888193000114)
708881 2105018780 865026781 Furthermore, the duplex paper manufacturing experiment shows that the 2
It is shown to reduce the thickness compared to the sum of the thicknesses of the two layers, thus further promoting the integrity of the forming process. Table 4 shows thickness data for duplex construction.

Table 4 1 49
88 223 57
49 258
65 46
It will be appreciated that there are many other applications for duplex paper in cigarette manufacturing. Unusual properties needed in the coating would be achievable without penalty to appearance or handling in cigarette products. These non-membrane properties can be provided by the inner surface of the duplex covering while maintaining the desired appearance on the outer surface.

The properties of the paper can be engineered to improve taste, burn rate, sidestream smoke emissions, ignitability, etc., or even to achieve altered appearance.

The above structure provides the opportunity to include paper additives or fillers with beneficial effects, such as an improvement over the ideas contained in the patent literature. For example, the outer surface contains a disproportionately high level of calcium carbide of normal or enhanced specific surface area, as suggested in British patent no.
Provides intensity and pollution control, where the structure has sidestream smoke reduction as its objective.

Another example is achieved by replacing calcium carbide on the outer surface with an alternative filler, which when used as a single sheet performs sidestream smoke reduction and adds to these in duplex products. Selected from a list of those that confer benefits: strength, control of air permeability, resistance to fouling, and promotion of reduction of sidestream smoke. Suggested fillers include magnesium hydroxide (US Patent No. 4,281,377 and British Patent No. 21L8986B).
), aluminum hydroxide, calcium hydroxide or lithium hydroxide (U.S. Pat. No. 4,721,120)
, gamma alumina (US Pat. No. 4,108,151) or those contained in British Patent No. 2,191,930, but this list is by no means exhaustive.

Other cladding improvements are found, for example, in U.S. Pat.
Suggested in the literature to improve taste and reduce smoke emissions, as in No. A similar objective can be achieved with a duplex cladding in which the outer surface provides a conventional appearance while the inner surface contains a suitable ratio of activated carbon. The resulting cladding can even be designed to provide a suitable combustion source that meets the requirements of one of the embodiments described in co-pending British Patent Application No. 8901579.6.

The above system can also be designed with a low absorbent inner surface as a solution to the formation of yellow spots during storage of cigarettes, without the need for double coating, as proposed by at least one commercial paper product. becomes.

Duplex coatings for cigars can also be formed by replacing the binders and coatings currently used in the manufacture of the majority of cigars.

The advantage of duplex construction is that it provides a range of combinations of two surfaces that are not achievable with conventional papermaking coverings so that the desired appearance, burn characteristics and taste can be achieved.

The duplex paper described herein is formed from raw materials manufactured according to recognized papermaking techniques;
It can contain, separately or in selected mixtures, textile fibers (eg flax or hemp), hardwood fibers, soft water fibers and other fibers (eg esparto).

The invention will now be described by means of some examples.

Example 1 This example shows the applicant's co-pending UK patent application No. 8.
No. 901579.8, for which duplex cigarette paper was developed to provide control over free smoldering and achieve reduced sidestream smoke emissions. (The definition of sidestream smoke is given in Application No. 8901579.8.) The paper is first treated to provide rapid self-extinguishing and later treated with a combustion promoter for reasons explained in the co-pending application. Improved.

The low porosity conditions that affect the shape and propagation of the cigarette coal reduce consumption of tobacco between puffs while capturing the condensable vapor phase that normally waves out from behind the coal as sidestream "smoke". Thus dictated by the requirement to reduce the production of side stream emissions. First, this requirement was met by a dual coating in which the inner coating provided low porosity and high density, but was translucent and did not burn uniformly. The outer coating was regular cigarette paper and provided good appearance and uniform burn.

The idea of lightweight duplex paper was pursued as a solution to the problems of manufacturing double-coated cigarettes, the desire for low weight paper, and the lack of results and aversion to adhesive lamination and coating.

Examples of the cited co-pending application No. 8901579.8 and the duplex paper primarily used are as shown in the specification below.

Table 5 Duplex used in co-pending application No. 8901579.8 37 Top 2540% pine, 20% birch 40%
Inside Eucalyptus 1270% Pine, 30% Birch Calcium Carbide, % 22 (Top Layer) Air Permeability, Gurley 385000 Sample Code 05g9987 Cigarettes
It was made of expanded tobacco blend with a density of 143 Kgmm' and was combined with the combustion element described in the co-pending application. These were compared to commercial cigarettes in a smoking test to establish mainstream and sidestream total particulate (TPM) emissions.

As a result, Table 6 was obtained.

Table 6 Type Number of smoke intake Mainstream Sidestream Open TPM
TPM dry density Vantage x 8.3 11.4
1.3Excel SD O,51,
90,09 (RJR-USA) 42 n 30 10 10 nm
bassy x 9.0 9.4
2.32 234M1ld SD O
,40,90,12(ITL-υK) n 24 7 g test x 13.8 8.6 0.55 143
Sample SD 1.0 0.8 0.05n
29 9 9 These results demonstrate a substantial reduction in sidestream production rates in the test cigarettes compared to a commercially available low sidestream product (Vantage) available from RJ Reynolds in the USA and a typical low tar in the UK. shows. The above results also show that the number of puffs obtained from cigarettes of equal or lower density and therefore lower weight is significantly increased. (These cigarettes had similar circumference and tobacco length.) Additionally, the appearance of the cigarette paper matched the commercial brand;
There were no yellow spots or smoke stains observed prior to smoking.

The ash properties are improved compared to conventional low air permeability papers, and another improvement is the addition of ash-controlling additives, e.g.
observed with the use of potassium citrate supplied at levels up to %.

Example 2 Early attempts at making duplex cigarette paper formed a relatively high permeability chalk-free inner layer and a low permeability chalk-filled top layer. The pulp used was a mixture of eucalyptus and flax. Two samples were formed to demonstrate different levels of permeability of the chalk packed bed. The paper details are shown in Table 7 below and the fibers in both webs of both samples are 50% flax and 50%
Made of eucalyptus.

Table 7 Duplex paper 0189969^ and B starting weight, g
-20189969A 0189989B Duplex 43.8 42.3 Top
24.8 25.8 #
17.3 17.3 Air Permeability, Coresta Unit Duplex 108 Top 5929 Internal 9494 Calcium Carbide, % Top Layer 3436 Opacity, % (Dup) 84.8 84.
5 Coresta permeability is a standard measurement used in the tobacco industry for the air permeability of cigarette paper. The apparatus includes a sample clamp that exposes the sample at 201 to a constant pressure of IK Pascals and provides a means to measure the flow rate through the sample. The result is 11/sl
Calculated in units of n/cm”/KPa.

Cigarette samples were tested for mainstream and sidestream smoking with specifications consistent with UK low tar commercial cigarettes, i.e.
591■Tobacco rod, 25■Filter, 24.9mm
Circumference, 210 kgmm' open cured tobacco density, and 45% tip ventilation (Ventllatlon).

In smoking tests, these cigarettes were found to smoke freely without the assistance of a smoke source.

These are 35III for 2 seconds every minute.
Approximately 8 mg of textile machine particles (TPM) were produced from 10 puffs with a standard smoking resin using a puff volume.

Sidestream smoke emissions are described in co-pending patent application No. 8901579.
．． It was measured as an aerosol density indicator and as TPM collected on the filter pad according to the method described in No. 8.

Table 8 Conventional low tar cigarettes 0189989A 0189989B
Mainstream TPM, Ilg cig-' 9.4 7
．． 8 9.2 Smoking 9.0 10
．． 3 10.1-carbon oxide mg clg-' 14.4
18.0 Sidestream TPM, mg cig-' 2.32 1.
3 1.4 Visible side stream 5.7 2.
7 2.8 Indicator (average value) A reduction in sidestream smoke of more than 40% is obtained with this construction, while the paper maintains a good appearance and also maintains free smoldering without the use of combustion-promoting additives. did it.

Example 3 In this example, Applicants demonstrated a means of achieving an alternative coating for free-smoldering low sidestream cigarettes that improves on the reduction in sidestream smoke emissions obtained in Example 2. In the summary, the applicant states that the applicant's co-pending patent application No. 890
No. 1579.8 product specifications and knowledge gained in the development of the paper were utilized.

Additionally, by applying a combustion promoter (known for industrial clay pots) to paper, it was possible to produce a free-smoldering (self-maintaining coal) low sidestream cigarette with typical British cigarette dimensions, appearance and mainstream smoke emission. .

Duplex paper samples were selected based on previous test data and treated with potassium citrate solution to achieve the levels shown in Table 9 below. Treatment was carried out by surface contact between the top of the duplex paper and the liquid container, followed by subsequent drying and re-rolling.

The above process is reproducible through conventional on-line cigarette paper machines, with soluble additive feeding functions such as size presses and other soluble additives selected from the range of cigarette paper additives known in the prior art. − becomes.

Additive levels were checked after dispensing and cigarettes were made with each treated paper for mainstream and sidestream smoke emission measurements. Details of the cigarette paper are shown in Table 9.

Table 9 Starting weight, g m -2 Duplex 37.1 Top layer 25.4 Inner layer 14.5 Fibers Top layer 43/17/40% (pine/birch/eucalyptus) Inner layer 70730% (pine/birch) Air Permeability, Gurley Duplex 240.000 Top Layer 4 Inner Layer 1480 Calcium Carbide, % Top Layer 23.2 Opacity, % (Dup) 74 Tensile Strength, gs-' (Dup) 37.8 26.4 tt, a 40/20/40% 70730% 27.800 0 33.5 0 68 Cigarette dimensions are typical of British commercial brands;
The tobacco density was reduced to 110 kgmm', using cut tobacco that was expanded by at least 75% of its bulk volume using commercially available tobacco expansion processes. The precise level of expansion or blending of expanded and unexpanded tobacco is a decision to achieve an acceptable balance of cigarette pull resistance, tobacco rod stiffness, and burn rate.

The above cigarette structure is 59mm tobacco rod, 25cm
■Filter, 24.8-■circumference, 110 kg+e-' open dry density, 50% chip ventilation, and 100% high expansion cut tobacco blend.

Smoking tests were performed according to standard procedures for assessment of mainstream emissions. Sidestream measurements are the "visible indicators" described in co-pending application no. 8901579.6 filed by the applicant.
The method was limited to the evaluation of aerosol density. The following data were obtained.

Table 1O Conventional low tar cigarette 03899788 09899923 Mainstream TPM, s+g elg-' 9.4 10
．． 2 8.8 Smoke 9.0 7
．． 0 B,8-carbon oxide Bclg-' 13.0
11.9 Static combustion time s sv-' 12 11.9
10.3 Sidestream visible indicator 5.7 0.5 0.5
(Average Values) These results demonstrate a very large improvement in side stream reduction compared to previous examples, and also have good visual and combustion properties, with virtually no unsightly fouling. A distant relative due to a missing piece of paper. Furthermore, these products are freely smokable without the need for additional fuel sources and allow for a substantial reduction in tobacco weight.

Claims (1)

Claims: 1. A coating for a smoking product, said coating comprising a single paper sheet formed from two or more separate webs, at least one web formed prior to drying. a coating with which said web is combined while still in the wetting stage of said web. 2. The coating according to claim 1, wherein the two or more webs are formed from different raw materials. 3. The two or more webs are combined when all webs are still in the wet stage of formation prior to drying.
Or the covering according to 2. 4. The covering according to any one of claims 1 to 3, wherein the covering has low air permeability. 5. The covering according to claim 4, wherein the permeability is 10 Coresta or less. 6. A covering according to any one of claims 1 to 5, wherein two partially formed webs are combined. 7. The coating of claim 6, wherein one web is a substantially unfilled web having a low starting weight. 8. The coated body according to claim 7, wherein the weight is 20 gm^-^2 or less. 9. A covering according to any of claims 6 to 8, wherein one of the webs prevents or substantially reduces the formation of stains during smoking and yellow spots during storage. 10. The coated body according to any one of claims 6 to 9, wherein the one web contains activated carbon. 11. A covering according to any of claims 7 to 10, wherein the other web is a filled web giving the covering a conventional appearance. 12. The coating according to claim 11, wherein the opacity of the coating is 60% or more. 13. The coating according to claim 11 or 12, wherein the filler of the other web comprises a predetermined amount of calcium carbide. 14. The coating of claim 13, wherein said web comprises up to 50% by weight calcium carbide. 15. A coating according to any of claims 11 to 14, wherein the filler of the other web comprises a predetermined amount of a selected filler such as Mg(OH)_2, Al_2O_3, LiOH and high surface area CaCO_3. 16. A coated body according to any one of claims 1 to 15, wherein the total starting weight of the coated body is less than 50 gm^-^2. 17. The coating of claim 16, wherein the total starting weight of the coating is less than 40 gm^-^2. 18. The coating of claim 17, wherein the total starting weight of the coating is less than 35 gm^-^2. 19. The coating according to any one of claims 1 to 18, wherein one or more of the webs contains a flame retardant and/or a flame promoter. 20. The coated body according to claim 19, wherein the flame retardant is ammonium phosphate. 21. Claim 19 or 2, wherein the combustion promoter is less than 10% by weight of a soluble salt of a Group I or Group II metal.
The covering according to 0. 22. A smoking product comprising a rod of smoking material and a covering according to any of claims 1 to 21. 23. The smoking product of claim 22, wherein a filter is provided, said filter being ventilated or non-ventilated. 24. The rod of smoking material contains 0 to 100% expanded tobacco, the open dry density of the smoking material in the product is 80 to 260 kgm^-^3, and the circumference of the rod is 10 to 30 mm. , the length of the above rod is 2
24. A smoking product according to claim 22 or 23, which is between 5 and 100 mm. 25. The smoking article is configured to extinguish the smoking material during puffing, and a combustion source is incorporated into the smoking article to reignite the smoking material during puffing, thus causing combustion of the smoking material. 24. A smoking product according to claim 22 or 23, wherein the smoking material is coated within the covering. 26. The permeability of the covering is about 10 Coresta and the starting weight is about 43 gm^-^2, the tobacco rod is 59 mm long, has a circumference of 24.9 mm, and has a tobacco density of 210 Kgm. ^-^ There are 3, and 2 again
24. A smoking product according to claim 22 or 23, wherein a filter is provided having a length of 5 mm and providing 45% ventilation. 27. The air permeability of the covering is 27,600 Gurley seconds or more, the starting weight is about 37 gm^-^2, and the tobacco has a density of 110 Kgm^- when 100% expanded.
^3, and the length of the above rod is 59mm, 24.8
22. mm, and is provided with a filter having a length of 25 mm and providing 50% ventilation, said covering also containing up to 10% by weight of potassium citrate. or the smoking product described in 23.