Patent Publication Number: US-2019174816-A1

Title: Smoking article having transparent wrapper

Description:
The present invention relates to a filter for a smoking article having a substantially transparent wrapper, and a method of manufacturing such filters. The present invention also relates to smoking articles incorporating such filters. 
     Filter cigarettes typically comprise a cylindrical rod of tobacco cut filler surrounded by a paper wrapper and a cylindrical filter axially aligned in an abutting end-to-end relationship with the wrapped tobacco rod. The cylindrical filter typically comprises a filtration material circumscribed by a paper plug wrap. Conventionally, the wrapped tobacco rod and the filter are joined by a band of tipping wrapper, normally formed of an opaque paper material that circumscribes the entire length of the filter and an adjacent portion of the wrapped tobacco rod. 
     A number of smoking articles in which an aerosol generating substrate, such as tobacco, is heated rather than combusted have also been proposed in the art. In heated smoking articles, the aerosol is generated by heating the aerosol generating substrate. Known heated smoking articles include, for example, smoking articles in which an aerosol is generated by electrical heating or by the transfer of heat from a combustible fuel element or heat source to an aerosol generating substrate. During smoking, volatile compounds are released from the aerosol generating substrate by heat transfer from the heat source and entrained in air drawn through the smoking article. As the released compounds cool they condense to form an aerosol that is inhaled by the consumer. Also known are smoking articles in which a nicotine-containing aerosol is generated from a tobacco material, tobacco extract, or other nicotine source, without combustion, and in some cases without heating, for example through a chemical reaction. 
     The wrappers of the smoking articles are typically provided such that opposed edges of each wrapper overlap with one another along a longitudinal overlapping region to form a seam. An adhesive, such as Polyvinyl alcohol (PVA) or a hot melt adhesive, is used to secure the opposed edges of each wrapper to one another along the seam. 
     It has previously been proposed to provide smoking articles having a wrapper which is at least partially transparent such that a consumer can observe at least a portion of the smoking article through the wrapper. For example, smoking articles have been provided with tipping wrappers formed from a transparent polymeric material. However, a transparent polymeric tipping wrapper provides a different surface feel compared to traditional paper tipping wrappers, which tends to be disliked by consumers. 
     As an alternative, it has also been proposed to provide smoking articles having an opaque tipping paper with a cut-out window so that a consumer can observe an underlying portion of the smoking article through the cut-out window. Where a plug wrap is provided between such tipping paper and the underlying filter, it has been necessary to use a plug wrap formed from a transparent material so that a user can see the underlying portion of the smoking article through the window and through the transparent plug wrap. 
     However, where the seam of the substantially transparent plug wrap is formed using an adhesive, such as PVA or a hot melt adhesive, the seam will not be transparent and consequently is visibly discernibly from the remainder of the plug wrap. This is particularly problematic where the substantially transparent plug wrap underlies a tipping paper with a cut-out window, since registration will be required to avoid the seam being placed under the window. 
     It would therefore be desirable to provide a smoking article having a substantially transparent wrapper that could appear transparent around the entire circumference of the smoking article. It would be further desirable to provide a smoking article having a substantially transparent wrapper underlying a cut out in a tipping paper window, without requiring registration between the substantially transparent wrapper and the tipping paper. 
     According to a first aspect of the present invention, there is provided a mouthpiece for a smoking article comprising: at least one mouthpiece element; a substantially transparent wrapper wrapped around the at least one mouthpiece element such that first and second opposed edges of the substantially transparent wrapper overlap with each other along a longitudinal overlapping region; and an agent disposed between the first and second opposed edges of substantially transparent in at least a portion of the longitudinal overlapping region; wherein the substantially transparent wrapper comprises an acetate ester of cellulose, and wherein the agent comprises an ester of glycerol. 
     Preferably, the ester of glycerol of the substantially transparent wrapper is triacetin (also known as glycerol triacetate). The ester of glycerol may be triethyl citrate, as an alternative or in addition to triacetin. 
     In contrast to prior art seam adhesives, the present inventors have found that a substantially transparent seam can be obtained by using an agent, or bonding agent, comprising an ester of glycerol and a substantially transparent wrapper comprising an acetate ester of cellulose. The ester of glycerol is a substantially transparent agent, and unlike conventional adhesives, interacts with the acetate ester of cellulose in the wrapper, to bond or otherwise weld the overlapping portions in the longitudinal overlapping region directly to one another. This can result in one of the overlapping edges seamlessly transitioning into the other overlapping edge in the overlapping region, rather than there being a distinct joint between the two overlapping edges, as would be the case with a conventional adhesive. Consequently, the overlapping region can have substantially the same appearance as the remainder of the wrapper, since it could in effect be considered to be a portion of the wrapper having the same or similar properties as the remainder of the wrapper, but being double the thickness of the remainder of the wrapper. 
     Accordingly, according to a second aspect of the present invention, there is provided a mouthpiece for a smoking article comprising: at least one mouthpiece element; and substantially transparent sheath circumscribing the at least one mouthpiece element, wherein the substantially transparent sheath comprises an acetate ester of cellulose, and wherein the substantially transparent sheath comprises a longitudinally extending portion formed from the interaction of the acetate ester of cellulose with an ester of glycerol. Put another way, there is provided a mouthpiece for a smoking article comprising: at least one mouthpiece element; and substantially transparent sheath circumscribing the at least one mouthpiece element, wherein the substantially transparent sheath comprises an acetate ester of cellulose, and wherein the substantially transparent sheath comprises a longitudinally extending portion having a thickness of about two times the thickness of the remainder of the substantially transparent sheath, as measured in a radial direction of the mouthpiece. 
     This contrasts with a conventional adhesive, which simply creates a joint between the two overlapping portions. Consequently, the resultant overlapping region can appear as a continuation of the regions of the wrapper either side of the overlapping region, except that the resultant overlapping region is about two times as thick as the regions of the wrapper either side of the overlapping region. The term “substantially transparent” is used herein to describe a material which allows at least a sufficient proportion of incident light to pass through it so that it is possible to see through the material. In the present invention, the substantially transparent wrapper allows sufficient light to pass through it such that an underlying mouthpiece segment is visible through the wrapper. The transparency of the substantially transparent wrapper may be evaluated in accordance with ASTM D1003-13. 
     The substantially transparent wrapper may be completely transparent. Alternatively, the substantially transparent wrapper may have a lower level of transparency whilst still transmitting sufficient light so that the underlying mouthpiece segment is visible through the substantially transparent wrapper. In some cases, the substantially transparent wrapper may be tinted or coloured. 
     Preferably, the acetate ester of cellulose is selected from the group of cellulose acetate, cellulose diacetate and cellulose triacetate. Particularly preferably, the acetate ester of cellulose is cellulose diacetate. 
     The substantially transparent wrapper may be composed of additional compounds in addition to the acetate ester of cellulose. However, preferably, the substantially transparent wrapper consists essentially of an acetate ester of cellulose. This can help to ensure that sufficient acetate ester of cellulose is present at the surface of the substantially transparent wrapper and therefore able to react with the ester of glycerol. 
     The substantially transparent wrapper may comprise one or more layers, with at least one layer comprising an acetate ester of cellulose. In some preferred embodiments, the substantially transparent wrapper comprises a polymeric layer, such as a layer of polyvinyl alcohol, disposed between two layers comprising an acetate ester of cellulose, such as cellulose diacetate. 
     Preferably, the agent is provided in the form of a line extending along the overlapping region. Preferably, the line has a width of from about 0.1 millimetres to about 5 millimetres, more preferably of from about 0.5 millimetres to about 3 millimetres, even more preferably of from about 1 millimetres to about 2.5 millimetres. 
     Preferably, the agent is provided in an amount of from about 0.5 milligrams to about 1.5 milligrams. 
     The mouthpiece of smoking articles in accordance with the present invention may comprise a filter including one or more segments of filtration material. For example, the mouthpiece may comprise a single segment of filtration material, or the mouthpiece may comprise a multi-segment filter including two or more segments of filtration material. Where two or more filter segments are provided, the filter segments may be of the same construction and materials as each other. Preferably, however, the filter segments have a different construction, and/or contain different filtration material to each other. 
     In embodiments in which the mouthpiece comprises two or more segments of filtration material, at least two segments of filtration material may be spaced apart to form a cavity therebetween. The cavity may be at least partially filled with a flavourant material. 
     In any of the embodiments in which the mouthpiece comprises one or more segments of filtration material, at least one of the filter segments may include a flavourant material. This may be in addition to any flavourant material provided in a cavity when present. 
     In some embodiments, the flavourant material is particulate flavourant material. Suitable particulate flavourant materials include particles of a sorbent or cellulosic material impregnated with a liquid flavourant. In some preferred embodiments, the particulate flavourant material may comprise particles of plant leaf, as described in EP-A-1,958,523. For example, flavourant material may include leaf from tobacco, green tea, peppermint, spearmint, laurel,  eucalyptus , basil, sage,  verbena  and tarragon. In addition, portions of mint plants may also be used. The term ‘mint’ refers to plants that belong to the genus  Mentha . The plant material may alternatively be in the form of a seed, root, bark and/or flower, such as those typically used as spices. 
     In some embodiments, the flavourant material is provided in a capsule which is adapted to release at least a portion of a fluid when the capsule is subjected to external force, such as squeezing, by the consumer. 
     The mouthpiece may also include a particulate material that does not comprise a flavourant, such as beads or granules of a cellulosic material or an adsorbent. This may be in addition to or as an alternative to the particulate flavourant materials described above. Suitable adsorbents include activated carbon, carbon beads, active aluminium, zeolites, sepiolites, molecular sieves and silica gel. 
     Where the mouthpiece includes one or more segments of filtration material, the filtration material is preferably a plug of fibrous filtration material, such as cellulose acetate tow or paper. A filter plasticiser may be applied to the fibrous filtration material in a conventional manner, by spraying it onto the separated fibres, preferably before applying any particulate material to the filtration material. The mouthpiece may include a variety of different types of filter segments or combinations of filter segments, including those described above as well as other types of filter segments that would be known to the skilled person, such as segments including restrictors and segments that are used for adjusting the resistance to draw (RTD). 
     Where the filter comprises a single segment, the substantially transparent wrapper may be a plug wrap surrounding the filter material. Where the filter comprises two or more segments, any or all of the segments may each be individually wrapped in a segment plug wrap. The segments of the filter may then be subsequently attached to one another in a conventional manner using a substantially transparent wrapper, which forms a combining plug wrap. In this case, at least one of the segment plug wraps is preferably transparent in addition to the combining plug wrap being transparent, and in some cases these transparent wrappers are formed from the same material. 
     As noted above, the present invention advantageously enables the overlapping region to have a transparency that is close to or the same as that of the remainder of the substantially transparent wrapper. Accordingly, preferably, the transparency level of overlapping region of the substantially transparent wrapper is within 10 percent, more preferably 5 percent of the transparency level of the remainder of the substantially transparent wrapper. The transparency level may be evaluated in accordance with ASTM D1003-13. 
     The thickness of the substantially transparent wrapper is preferably about 10 micrometers or more. The thickness of the substantially transparent wrapper is preferably about 200 micrometers or less, more preferably about 100 micrometers or less. More preferably, the thickness of the substantially transparent wrapper is between about 25 micrometers and about 75 micrometers. The basis weight of the substantially transparent wrapper is preferably at least about 15 grams per square meter (gsm). More preferably, the basis weight of the substantially transparent wrapper is between about 20 gsm and about 130 gsm. 
     Preferably, the mouthpiece further comprises a paper wrapper circumscribing at least a portion of the substantially transparent wrapper. 
     A window may be provided in the paper wrapper such that an underlying mouthpiece segment can be viewed through the window and the substantially transparent wrapper. This allows a consumer to view a portion of the mouthpiece underlying the substantially transparent wrapper. The paper wrapper may include a single window or multiple windows as desired. Where the paper wrapper includes multiple windows, they may be identical windows or they may have different sizes or shapes to accommodate different mouthpiece designs. 
     The window may be provided by forming a cut-out in the paper wrapper. Alternatively, the paper wrapper may be formed from a composite material having a band of transparent material which circumscribes at least a portion of the mouthpiece to form a window. As a further alternative, the paper wrapper can comprise two bands of paper material which are spaced apart along the length of the mouthpiece to define a gap, the gap forming the window. 
     In embodiments in which the paper wrapper includes a window, the window may extend around the entire circumference of the mouthpiece. However, preferably, the window extends around only a portion of the circumference of the mouthpiece. In some embodiments, the mouthpiece preferably includes a high basis weight transparent plug wrap underlying the paper wrapper and extending across the window to prevent the mouthpiece from collapsing or breaking at the window during use. For example, the basis weight of the substantially transparent plug wrap can be at least 60 gsm, preferably around 80 gsm. 
     In those embodiments in which the mouthpiece includes a cavity, the window preferably overlies at least a portion of the cavity so that a consumer can observe the cavity through the window and the substantially transparent layer. 
     Alternatively, or in addition, the paper wrapper may include a window which overlies at least a portion of a filter segment which includes a particulate material so that a consumer can observe the particulate material through the window and the substantially transparent layer. Where the paper wrapper also includes a window overlying a cavity within the mouthpiece, these may be the same window extending over both portions of the mouthpiece or they may be different windows. 
     In smoking articles according to the present invention, the mouthpiece may abut the aerosol-generating substrate, or the mouthpiece may not abut the aerosol-generating substrate. For example, the mouthpiece may be spaced apart from the aerosol-generating substrate so as to define a gap or a cavity therebetween. Alternatively, an intervening material may be positioned between the mouthpiece and the aerosol-generating substrate. 
     Smoking articles in accordance with the present invention may be filter cigarettes or other smoking articles in which tobacco material is combusted to form smoke. For example, the aerosol-generating substrate may comprise a tobacco rod and the mouthpiece may comprise a filter, as described above. The paper wrapper may comprise a tipping wrapper. 
     Alternatively, smoking articles according to the present invention may be articles in which an aerosol-generating substance, such as tobacco, is heated to form an aerosol rather than combusted. In one type of heated smoking article, an aerosol generating substance is heated by one or more electrical heating elements to produce an aerosol. In another type of heated smoking article, an aerosol is produced by the transfer of heat from a combustible or chemical heat source to a physically separate aerosol generating substrate, which may be located within, around or downstream of the heat source. The present invention further encompasses smoking articles in which a nicotine-containing aerosol is generated from a tobacco material, tobacco extract, or other nicotine source, without combustion, and in some cases without heating, for example through a chemical reaction. 
     According to a fourth aspect of the invention there is provided a method of forming a mouthpiece for a smoking article, the method comprising: providing at least one mouthpiece element; providing a substantially transparent wrapper comprising an acetate ester of cellulose, the substantially transparent wrapper having first and second opposed edges; disposing an agent adjacent to the first opposed edge of the substantially transparent wrapper, the agent comprising an ester of glycerol; wrapping the substantially transparent around the at least one mouthpiece element such that the first and second opposed edges of the substantially transparent wrapper overlap with each other along a longitudinal overlapping region; wherein the ester of glycerol of the agent reacts with the acetate ester of cellulose to secure the opposed edges to one another. 
     Preferably, the method further comprises the step of heating the substantially transparent wrapper, heating the agent comprising an ester of glycerol, or heating both the substantially transparent wrapper and the agent comprising an ester of glycerol to a temperature of at least 25 degrees Celsius, more preferably at least 50 degrees Celsius, even more preferably at least 70 degrees Celsius. Alternatively or additionally, preferably, the method further comprises the step of heating the substantially transparent wrapper, heating the agent comprising an ester of glycerol, or heating both the substantially transparent wrapper and the agent comprising an ester of glycerol to a temperature of 140 degrees Celsius or less, more preferably 100 degrees Celsius or less, even more preferably 80 degrees Celsius or less. 
     Such elevated temperatures can help to enhance or speed up the interaction between the agent and the substantially transparent wrapper, without greatly risking damaging the agent or the substantially transparent wrapper. 
     Preferably the method further comprises the step of applying a compressive force to the longitudinal overlapping region. Where the method involves the step of heating the substantially transparent wrapper, heating the agent comprising an ester of glycerol, or heating both the substantially transparent wrapper and the agent comprising an ester of glycerol, preferably the element that provides the heat is the same element as that which provides the compressive force to the longitudinal overlapping region. 
     It will be appreciated that features described above in respect of the first aspect of the invention are equally applicable and preferable for the second aspect of the invention. 
    
    
     
       The invention will now be further described, by way of example only, with reference to the accompanying drawings in which: 
         FIG. 1  shows a smoking article in accordance with the present invention; 
         FIG. 2  shows the smoking article of  FIG. 1  with the mouthpiece unwrapped; and 
         FIG. 3  shows a cross sectional view of the overlapping region of the substantially transparent wrapper of  FIG. 1 . 
     
    
    
     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 . 
     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 . 
     The substantially transparent plug wrap  18  is formed from a cellulose diacetate film. A first portion  19  of the substantially transparent plug wrap  18  is provided with an agent comprising triacetin. The first portion  19  is adjacent to a first edge of the plug wrap  18 , which is configured to be wrapped around the filter segment  16 , such that the first edge overlaps with a second opposed edge of the substantially transparent wrapper along a longitudinal overlapping region. When overlapped the agent reacts with the cellulose diacetate in the overlapping portions of the plug wrap  18  to secure them together. 
     As can be seen from  FIG. 3 , the resultant overlapping portion  30  has a thickness  37  of about two times the thickness  35  of the remainder of the wrapper  34 . The agent  32  therefore results in an effectively seamless transition of the film from one overlapping piece to the other. In the  FIG. 3  arrangement, the agent  32  has not been provided across the entire width of the overlapping region  30 . Consequently, the tips  38 ,  39  of the two overlapping edges are not secured to their corresponding portions of overlapping wrapper.