Smoking article with transparent wrapper

Abstract

A method of manufacturing a smoking article (10) comprises providing a mouthpiece (14) and an aerosol generating substrate (12) in axial alignment with the mouthpiece (14). The mouthpiece (14) includes one or more segments (16) and a substantially transparent wrapper (18) circumscribing at least a portion of the one or more segments (16). A sheet of paper material is provided and comprises a window in the paper material. The ratio of shrinkage of the substantially transparent wrapper (18) to shrinkage of the paper material at the time of manufacture of the smoking article is less than 3.5 when subjected to 15 percent relative humidity at 42 degrees Celsius for 3 hours. The sheet of paper material is wrapped around at least a portion of the transparent wrapper (18) so that an underlying mouthpiece segment can be viewed through the window and the substantially transparent wrapper (18).

Claims

1. A method of manufacturing a smoking article, the method comprising the steps of: providing a mouthpiece comprising one or more segments and a substantially transparent wrapper circumscribing at least a portion of the one or more segments, the substantially transparent wrapper being formed from a polymeric film comprising cellulose diacetate; providing an aerosol generating substrate in axial alignment with the mouthpiece; providing a sheet of paper material comprising a window in the paper material, wherein the ratio of shrinkage of the substantially transparent wrapper to shrinkage of the paper material at the time of manufacture of the smoking article is less than 3.5 when subjected to 15 percent relative humidity at 42 degrees Celsius for 3 hours; and wrapping the sheet of paper material around at least a portion of the transparent wrapper so that an underlying mouthpiece segment can be viewed through the window and the substantially transparent wrapper.

2. A method according to claim 1, wherein the step of wrapping the sheet of paper material around at least a portion of the transparent wrapper includes wrapping the sheet of paper material around a portion of the aerosol generating substrate to secure the mouthpiece to the aerosol generating substrate.

3. A method according to claim 1, wherein the ratio of shrinkage is less than 3.

4. A method according to claim 1, wherein the step of providing a mouthpiece includes providing a mouthpiece with a transparent wrapper with a shrinkage of less than 0.85 percent.

5. A method according to claim 2, wherein the ratio of shrinkage is less than 3.

6. A method according to claim 2, wherein the step of providing a mouthpiece includes providing a mouthpiece with a transparent wrapper with a shrinkage of less than 0.85 percent.

7. A smoking article comprising: a mouthpiece comprising one or more segments and a substantially transparent wrapper circumscribing at least a portion of the one or more segments, the substantially transparent wrapper being formed from a polymeric film comprising cellulose diacetate; an aerosol generating substrate in axial alignment with the mouthpiece; a paper wrapper circumscribing at least a portion of the mouthpiece and a portion of the aerosol generating substrate to secure the mouthpiece to the aerosol generating substrate; and a window in the paper wrapper so that an underlying mouthpiece segment can be viewed through the window and the substantially transparent wrapper; wherein the ratio of shrinkage of the substantially transparent wrapper to shrinkage of the paper wrapper at the time of manufacture of the smoking article is less than 3.5 when subjected to 15 percent relative humidity at 42 degrees Celsius for 3 hours.

8. A smoking article according to claim 7, wherein the ratio of shrinkage is less than 3.

9. A smoking article according to claim 7, wherein the shrinkage of the substantially transparent wrapper at the time of manufacture of the smoking article is less than 0.85 percent.

10. A smoking article according to claim 8, wherein the shrinkage of the substantially transparent wrapper at the time of manufacture of the smoking article is less than 0.85 percent.

11. A method comprising: assembling a substantially transparent wrapper and a paper wrapper about a mouthpiece segment of a smoking article, the substantially transparent wrapper being formed from a polymeric film comprising cellulose diacetate, wherein a window is provided in the paper wrapper so that the underlying mouthpiece segment can be viewed through the window and the substantially transparent wrapper, and wherein the ratio of shrinkage of the substantially transparent wrapper to shrinkage of the paper wrapper at the time of manufacture of the smoking article is less than 3.5 when subjected to 15 percent relative humidity at 42 degrees Celsius for 3 hours.

Description

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

(2) FIG. 1 shows a smoking article in accordance with the present invention;

(3) FIG. 2 shows the smoking article of FIG. 1 with the mouthpiece unwrapped; and

(4) FIG. 3 shows a diagram illustrating how to calculate the contact angle of a droplet.

(5) The filter cigarette 10 shown in FIGS. 1 and 2 comprises a wrapped rod 12 of tobacco cut filler which is attached at one end to an axially aligned filter 14 comprising a single filter segment 16. The single filter segment 16 is formed of cellulose acetate tow which has been wrapped with a substantially transparent wrapper in the form of substantially transparent plug wrap 18. The filter segment 16 incorporates particles of a cellulosic material (not shown) impregnated with a liquid flavourant, which are dispersed within the cellulose acetate tow. The wrapped tobacco rod 12 and the filter 14 are joined by an outer wrapper 20 formed of standard tipping paper, which circumscribes the entire length of the filter 14 and an adjacent portion of the tobacco rod 12. The outer wrapper 20 is secured to the substantially transparent plug wrap 18 at adhesive bond points (not shown) spaced around the circumference of the filter 14.

(6) The outer wrapper 20 comprises a circular cut-out portion 22 having a diameter of approximately 5 mm which is positioned approximately 5 mm from the rod end of the outer wrapper 20. The underlying substantially transparent plug wrap 18 is exposed through the cut-out portion 22 in the outer wrapper 20 and an area of the filter including the cellulosic granules is therefore visible through the cut-out portion 22.

(7) The substantially transparent plug wrap 18 is formed from a cellulose diacetate film which exhibits shrinkage of approximately 0.2 percent when subjected to 15 percent humidity at 42 degrees Celsius for 3 hours. The low shrinkage minimises relative shrinkage between the substantially transparent plug wrap 18 and the outer wrapper 20, which typically exhibits shrinkage of approximately 0.26 percent under the same conditions. Accordingly, the outer wrapper 20 does not wrinkle when the cigarette 10 is subject to dry conditions, such as during storage.

(8) Test Procedures

(9) Contact Angle Test

(10) As shown in FIG. 3, the contact angle, theta (8), can be calculated by measuring the base of droplet (a) and the height of the droplet (h) to characterise the droplet shape. Using standard triangle geometry, the contact angle theta (8) can be calculated according to Equation 2 below:
[in degrees]=2arctan(2h/a)(2)

(11) A skilled person will have no difficulty in providing suitable means for making accurate measurements of the base of droplet (a) and the height of the droplet (h). For example, a high-resolution digital photograph can be taken of the droplet on the substrate and the base of droplet (a) and the height of the droplet (h) measured using appropriate computer software.

(12) The base of droplet (a) and the height of the droplet (h) should be measured around 1 second after the droplet has been placed on the substrate. A suitable droplet volume is 4 microlitres and a suitable droplet composition is demineralised water.

(13) Shrinkage Test 1

(14) Preferably, the test is performed on samples of material obtained from the production facility prior to their use in forming a mouthpiece or a smoking article.

(15) Ten sheets or strips of the material to be tested are measured along their longest dimension under normal atmospheric conditions (60 percent relative humidity at 22 degrees Celsius) and the lengths are recorded. A skilled person will readily understand that the lengths of the samples can be measured using any suitable length measuring device, such as a ruler. Any sample size can be used, although greater lengths will reduce the experimental error. As a compromise between reducing error and providing a practical sample size, sheets or strips having a length corresponding to A4 are appropriate for the test. The length of A4 is typically around 297 millimetres.

(16) The sample sheet or strips are then stored under dry conditions (15 percent relative humidity at 42 degrees Celsius) for 3 hours. During the exposure to the dry conditions, the samples are placed on a shelf having a plurality of projections which support the samples in a raised position above the main body of the shelf. The projections help reduce the amount of shelf surface contacting the samples during exposure to the dry conditions, thereby ensuring a more uniform exposure.

(17) After the 3 hour exposure to the dry conditions, the samples are then re-measured along the same dimension as was measured prior to exposure to the dry conditions and the new lengths recorded. The shrinkage for each sample can then be calculated using Equation 1 above. The shrinkage value for the material being tested is taken to be the number average of the shrinkage values obtained for the ten samples.

(18) To accurately determine the shrinkage of a particular material, Shrinkage Test 1 should be used. However, as set out below, a second shrinkage test (Shrinkage Test 2) can be used to provide a general indication of the shrinkage levels of the materials when they have already been formed on a mouthpiece. The results of Shrinkage Test 2 may vary depending on the construction of the mouthpiece segment underlying the materials at the point of measurement. Accordingly, Shrinkage Test 2 should be used for no more than general guidance of whether the material exhibits certain shrinkage properties.

(19) Shrinkage Test 2

(20) The tests should be conducted on sample mouthpieces which are substantially the same as those used at the time of manufacture. Preferably, the test is performed on samples obtained from the production facility prior to their use in forming a smoking article. However, where such samples are not available, samples may be obtained from an already manufactured smoking article. In this case, the samples should be obtained prior to the mouthpieces being exposed to environmental conditions which may affect the test results, such as the dry conditions used in the test.

(21) Three mouthpieces each comprising at least one segment and a substantially transparent wrapper are used for the test. The test can be used to indicate the presence of shrinkage of the substantially transparent wrapper.

(22) Under normal atmospheric conditions (60 percent relative humidity at 22 degrees Celsius) the diameter of each mouthpiece is measured at three separate points along the length of the mouthpiece. The mouthpiece is marked (with a pen, for example) to provide a reference for each measurement point so that subsequent measurements can be made across the same diameter. A skilled person will have no difficulty in providing suitable means for making accurate diameter measurements. For example, a high-resolution digital photograph can be taken of the end of each mouthpiece and the diameter measured using appropriate computer software.

(23) The sample mouthpieces are then stored under dry conditions (15 percent relative humidity at 42 degrees Celsius) for 3 hours. During the exposure to the dry conditions, the samples are placed on a shelf having a plurality of projections which support the sample in a raised position above the main body of the shelf. The projections help reduce the amount of shelf surface contacting the sample during exposure to the dry conditions, thereby ensuring a more uniform exposure.

(24) After the 3 hour exposure to the dry conditions, the samples are then re-measured along the same diameters as measured previously, and the new diameters of the wrapper are recorded. The shrinkage of each wrapper for each sample can then be calculated using Equation 1 above, and the average shrinkage calculated to provide a shrinkage value for each wrapper material.

EXAMPLES

Example 1

(25) Four different transparent films were tested using Shrinkage Test 1. The four sample films were: biaxially oriented polypropylene film, uncoated cellulose film, cellulose film with a 1.2 gram per square metre (gsm) nitrocellulose lacquer moisture barrier coating on one side, and cellulose diacetate film. The biaxially oriented polypropylene film sample and the uncoated cellulose film sample were each approximately A4 size. The cellulose film coated with nitrocellulose lacquer and the cellulose diacetate film sample were narrower strips which each had a length equivalent to A4 size. The tipping paper samples were narrower strips which had a length equivalent to A4 size. The results of the test are shown below:

(26) TABLE-US-00001 Mean Shrinkage (%) [Calculated Using Material Equation 1] Standard tipping paper (white appearance) 0.26 Standard tipping paper (cork appearance) 0.21 Uncoated cellulose film 0.91 Biaxially oriented polypropylene film 0.3 Cellulose film with nitrocellulose 0.68 lacquer coating on one side Cellulose diacetate film 0.2

(27) As can be seen from the table above, biaxially oriented polypropylene film, cellulose film coated on one side with nitrocellulose lacquer and cellulose diacetate film all show a significantly lower level of shrinkage compared to uncoated cellulose film, which has been used previously to form transparent plug wraps in smoking articles. The shrinkage of the biaxially oriented polypropylene film and the cellulose diacetate film is comparable to the shrinkage of the standard tipping papers. It is expected that providing a nitrocellulose lacquer on both sides of a cellulose film would further reduce shrinkage of the film compared to uncoated cellulose film.

Example 2

(28) Based on the results from Example 1, a plurality of test mouthpieces were constructed using a single segment filter having a standard paper plug wrap.

(29) A number of these test mouthpieces were overwrapped with a cellulose diacetate film (mouthpiece B), whilst another number of these mouthpieces were overwrapped with an uncoated cellulose film (mouthpiece A). The remainder of the test mouthpieces were left without any overwrapping material (mouthpiece C).

(30) The shrinkage of the different mouthpieces was measured using Shrinkage Test 2 and the results are shown below:

(31) TABLE-US-00002 Mouthpiece Mean Shrinkage (%) A - Overwrapped with Cellulose film 1.3 B - Overwrapped with Cellulose diacetate film 0.2 C - Without any overwrapping material 0.4
As a further general comparison, a number of cigarettes having a single segment filter with a standard paper plug wrap overwrapped by standard tipping paper (white appearance or cork appearance) were constructed. The shrinkage of the mouthpieces of these cigarettes was measured using Shrinkage Test 2 and the results are shown below:

(32) TABLE-US-00003 Mouthpiece Mean Shrinkage (%) Conventional paper plug wrap overwrapped with 0.24 standard tipping paper (white appearance) Conventional paper plug wrap overwrapped with 0.24 standard tipping paper (cork appearance)

(33) It can be seen that using cellulose diacetate film as the plug wrap material in a mouthpiece results in a percentage shrinkage similar to that of a mouthpiece having conventional plug wrap paper overwrapped with standard tipping paper. On the other hand, it is apparent that using a cellulose film as the plug wrap material in a mouthpiece results in a percentage shrinkage significantly higher than that of a mouthpiece having conventional paper plug wrap overwrapped with standard tipping paper. The inventors have recognised that such significant relative shrinkage can cause wrinkling of the tipping paper when the mouthpiece is exposed to dry storage conditions.

(34) Based on the results of Example 2, a number of test smoking articles were constructed using a filter with a cellulose diacetate film plug wrap circumscribed by standard tipping paper (smoking articles B). For comparison, a number of test smoking articles were constructed using a filter with an uncoated cellulose film plug wrap and standard tipping paper (smoking articles A).

(35) Smoking articles A and B were left for 3 hours in 15 percent relative humidity at 42 degrees Celsius. After such exposure, wrinkling of the tipping paper in smoking articles A was visually perceivable to the naked eye, whereas no wrinkling of the tipping paper in smoking articles B was visually perceivable to the naked eye.

(36) Therefore, to avoid undesirable wrinkling when using standard tipping paper (shrinkage of 0.26 percent), the inventors have found that the transparent plug wrap should have a shrinkage of about 0.85 percent or less. At these shrinkage values, the ratio of shrinkage of the transparent plug wrap to shrinkage of the tipping paper is 3.27 (that is, 0.85 divided by 0.26). Therefore, allowing for minor variations in the shrinkage of standard tipping paper, the ratio of shrinkage of the substantially transparent wrapper to the shrinkage of the paper wrapper in smoking articles manufactured according to the present invention should be less than about 3.5.