Method and apparatus for forming a rod for use in the manufacture of smoking articles

Abstract: The present invention relates to a method and an apparatus for forming a cylindrical rod and/or cylindrical segments (57) for use in the manufacture of smoking articles wherein a first web (50) of material is fed into a forming device (54) having a tapered outer cone and an inner cone which form an annular space by which said first web is gathered into a cylindrical shape, whereupon the cylindrical shaped first web is wrapped with a wrapping web (56) to form an endless rod. This endless rod may then be cut into a plurality of cylindrical segments (57) of predetermined length.

Description: The present invention relates to a method and an apparatus for forming a rod for use in the manufacture of smoking articles. More specifically, the invention relates to the manufacture of cylindrical segments for use in the manufacture of smoking articles having a fuel element, a physically separate aerosol generating means, and an improved mouthend piece which comprises a segment of non-woven thermoplastic fibers or filaments for delivering the aerosol produced to the user, and which, in preferred embodiments, includes a spacer member which separates the segment of thermoplastic material from the aerosol generating means. Still more spedifically, the present invention is directed to the manufacture of at least a portion of the mouthend piece of such smoking articles from a non-woven web of meltblown thermoplastic fibers. Smoking articles employing such an improved mouthend piece help reduce the temperature of the aerosol perceived by the user without interfering with delivery of the aerosol. Such articles produce an aerosol resembling tobacco smoke, but which contains no more than a minimal amount of incomplete combustion or pyrolysis products. US-A-3 860 011 discloses a method and an apparatus for forming rod-like segments for use as filter segments in the manufacture of conventional filter cigarettes. For preparing the filter segments an endless tubing of hollow plastic material is fed in axial direction into a hollow mandrel providing a longitudinal passageway for said tubing and having a conical shaped inlet. The mandrel extends in axial direction through a nozzle having an inner conical surface tapering in the travelling direction of said tubing and being coaxial with the mandrel. Behind the trailing edge of the inner conical surface, the nozzle provides for a cylindrical annular space between the mandrel and a cylinder of the nozzle, said cylinder circumscribing the mandrel and being coaxial therewith. Moreover, the nozzle is provided with an inlet for pressurized air fed into said cylindrical annular space. A stream of fibrous filter material being in the form of a tow of fibers is fed into the conical space between the mandrel and the inner conical surface of the nozzle, and when this stream of fibrous filter material reaches the cylidrical annular space of the nozzle the pressurized air causes the fibrous filter material to bloom. The stream of fibrous filter material is then caused to pass through a device for folding an endless web of plugwrap paper around said tow of fibrous filter material, whereupon the endless rod thus prepared is cut by a cutting knife into a plurality of cylindrical filter segments of predetermined length. It is an object of the present invention to provide a method and an apparatus for efficiently forming a cylindrical rod and/or cylindrical segments from web material for use in the manufacture of smoking articles, more particularly for use as a mouthend piece or part of a mouthend piece of smoking articles having a fuel element and a physically separate aerosol generating means. For achieving this object, according to the present invention the method and the apparatus according to claims 1 and 5, respectively, are proposed. The improved mouthend piece of a smoking article of the type defined above and prepared in accordance with the present invention comprises a non-woven web of thermoplastic fibers or filaments in the form of a low efficiency, heat dispersing mass of material in the form of a filter plug. The mouthend piece may also include a spacer member located between the thermoplastic mass and the aerosol generating means. It has been found that unlike conventional mouthend pieces, such as cellulose acetate tow, use of such improved mouthend piece reduces the aerosol temperature perceived by the user without interfering with delivery of desired amounts of the aerosol. Preferably, the smoking articles which employ the improved mouthend piece are of the cigarette type, which utilize a short, i.e., less than about 30 mm long, preferably carbonaceous, fuel element. Preferably, the aerosol generating means also is in a conductive heat exchange relationship with the fuel element. The mouthend piece of the present invention preferably comprises a cylindrical segment of a web of non-woven meltblown thermoplastic fibers which is gathered or folded into the shape of a conventional filter plug approximately 10 to 40 mm, preferably 15 to 35 mm, in length, together with a folded or gathered tobacco paper spacer member approximately 5 to 30 mm, preferably 5 to 15 mm, in length located between the non-woven web segment and the aerosol generating means. Conventional cigarette mouthend pieces normally consist of moderate to high efficiency filter materials, such as cellulose acetate tow. Such materials generally have fibers which are primarily oriented in the smoking direction which may result in air being channeled through a relatively small fraction of the filter. One notices, for example upon smoking filtered cigarettes, that only a portion of the filter appears discolored, evidencing the channeling of smoke in that portion of the filter. This channeling effect is often perceived by the user as a "hot spot" on the lips or tongue. It has been found that the improved mouthend piece formed in accordance with the present invention, and in particular the non-woven thermoplastic web component, acts as a heat sink and helps to reduce perceived hot spots by distributing the aerosol generated during smoking over a large surface area, preferably over substantially the entire surface area of the mouthend piece component(s). It is believed that distribution of the aerosol over a large surface area contributes to the perceived reduction in temperature by increasing the residence time of the aerosol in the mouthend piece, and in particular in the segment of non-woven thermoplastic material. Moreover, unlike conventional mouthend pieces which are generally used to filter out substantial amounts of various undesirable components of tobacco smoke, smoking articles employing the non-woven thermoplastic material as the mouthend piece prepared in accordance with the present invention provide such perceived temperature reductions without substantial reduction in the delivery of the aerosol components, e.g. glycerin, flavor components, and the like. In other words, the filter efficiency of such materials is substantially lower than that of conventional cigarette filter material such as cellulose acetate tow, which is important in maintaining desired delivery of the aerosol generated by the smoking articles of the type defined above and permitting the use of longer sections of material to provide increased residence and cooling of the aerosol. Preferred smoking articles of the type defined above and employing the improved mouthend piece prepared in accordance with the present invention are capable of delivering at least 0.6 mg of aerosol, measured as wet total particulate matter (WTPM), in the first 3 puffs, when smoked under FTC smoking conditions, which consist of 35 ml puffs of two seconds duration, separated by 58 seconds of smolder. More preferably, embodiments of the invention are capable of delivering 1.5 mg or more of aerosol in the first 3 puffs. Most preferably, embodiments of the invention are capable of delivering 3 mg or more of aerosol in the first 3 puffs when smoked under FTC smoking conditions. Moreover, preferred embodiments of the invention deliver an average of at least about 0.8 mg of WTPM per puff for at least about 6 puffs, preferably at least about 10 puffs, under FTC smoking conditions. Smoking articles which employ the improved mouthend piece, and a preferred embodiment of the inventive apparatus for manufacturing such a mouthend piece and/or a portion thereof are described in greater detail in the accompanying drawings and the detail description of the invention which follows. BRIEF DESCRIPTION OF THE DRAWING Figure 1 is a longitudinal view of one preferred smoking article employing the improved filter material prepared in accordance with the present invention. Figure 2 illustrates one preferred method for forming the non-woven, meltblown thermoplastic web useful in forming the mouthend piece in accordance with the present invention. Figure 3 schematically illustrates the inventive method and apparatus for forming the meltblown thermoplastic web into a cylindrical segment in the shape of a filter plug. Filter 3a illustrates a double cone system used to gather or fold material into the shape of a filter plug. Figure 4 illustrates the lip thermal temperature of a mouthend piece prepared in accordance with the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In accordance with a preferred embodiment of the present invention, there is prepared an improved mouthend piece for use in smoking articles. The mouthend piece is particularly suited for smoking articles having a combustible fuel element and a physically separate aerosol generating means such as those described in EP-A-174,645 as well as in EP-A-212,234. In general, the improved mouthend piece comprises a segment formed from a non-woven web of thermoplastic fibers or filaments and may also include a spacer member located between the segment of thermoplastic fibers and the aerosol generating means. The preferred means for making such thermoplastic webs is by meltblowing such as is described in U.S. Patent No. 3,849,241 to Buntin et al. issued 19 November 1974, the disclosure of which is incorporated herein by reference. FIG. 2 illustrates conventional meltblowing. Extruder 41 driven by motor 42 receives thermoplastic polymer pellets 44 from hopper 43. The extruder is heated as necessary to bring the polymer to the desired viscosity as it enters die 45. As the extruded polymer exits die 45, normally vertically downward, it is contacted from opposing sides by hot air from conduits 46. As needed, die 45 may be heated electrically or by other means using conduits 47. Fibers 48 are carried by the air stream onto collecting surface 49 forming mat 50. The collecting surface 49 may comprise rotating drum 51 driven about axis 52 as shown or may be a belt, screen or other collecting device as will be apparent to those skilled in this art. The thermoplastic web may be formed into a cylindrical or other appropriate shape by conventional filter plug making techniques such as ordinary plugmakers used to make cellulose acetate tow. FIG. 3 illustrates one means for forming the webs into a filter plug. As shown schematically in FIG. 3, a roll 53 of thermoplastic fiber web 50 is unwound and drawn into a pre-forming tapered cone system 54 that "gathers" or "folds" the flat web 50 into a cylindrical shape suitable for passage into the filter plugmaker. This formed cylinder 55 receives a wrapping of paper web 56 (so called plug wrap) and the combination is cut into desired lengths 57 using blade 58. Prior to entering the garniture, a continuous bead of adhesive is applied to one edge of the plugwrap via an applicator. As these components pass through the garniture, the formed web is further compressed into a cylindrical cross-sectional rod while at the same time being enveloped by the plugwrap 56. As the adhesive bead contacts the overlapped section of wrapped rod, it is sealed by means of a sealing bar. This endless filter rod is then cut into lengths 57 by means of cuter 58. While not essential for making acceptable filter plugs, the thermoplastic webs lend themselves to pre-treatment prior to being formed into a rod. Two such treatments, illustrated in Fig. 3, may include a pair of grooved rolls 59 used for crimping and a liquid applicator 60 used for surface treating the material with, for example, glycerin or other humectants. The cone system 54 is further illustrated in Figure 3A. This system comprises a cone 54b within a cone 54a as the preforming apparatus. The thermoplastic web material is fed into the annular space 54c between the cones in a substantially tension-free state, such that at the entry point, the web material wraps around the radial portion of the inner cone. The cones can be moved in relation to each other by means not being illustrated in order to achieve the desired uniformity and firmness of the filter plug. While most thermoplastic polymers may be used in preparing the web material used to make the segment of thermoplastic fibers, the preferred thermoplastic polymers are polyolefins such as isotactic polypropylene, and polyesters such as poly (butylene terephthalate). Due to the nature of the meltblown thermoforming process, various additives (e.g., calcium carbonate) can be easily incorporated internally in the polymer melt or blown onto the molten polymer surface as it is extruded in order to change the structure of the meltblown web and thus its performance in a filter element. Also, meltblown webs, after formation, are easily subject to known post treatments with auxiliary agents in dry or liquid form to provide certain organoleptic and/or medicinal attributes. The basis weight of such webs may vary depending on a number of factors including the process used to forn the web material as well as the particular thermoplastic polymer used. For preferred meltblown polypropylene materials, the basis weight is preferably in the range of from about 0.5 oz/yd 2 to 1.0 oz/yd 2 . The grab tensile strengths of such webs may also vary but generally are in the range of from about 0.1 pound to about 3.0 pounds in the cross machine direction (CD) and at least about 0.1 pound in the machine direction (MD). Preferred ranges are from about 0.7 to about 2.4 pounds in the machine direction and from about 0.5 to about 2.3 pounds in the cross machine direction. Preferred webs will also have a grab tensile strength providing a ratio of MD to CD in the range of about 1:1 to 4:1 and preferably in the range of 1:1 to 2:1. The grab tensile strength of such materials is determined generally in accordance with the Method 5100-Federal Test Methods Standard No. 191A using an Instron Model 1122 Testing Instrument available from Instron Corporation. These strengths generally depend on a number of factors including the web's machine direction to cross machine direction fiber orientation, degree of fiber to fiber fusion and fiber width distribution. The Frazier porosity of such webs may also range generally from about 100 cu.ft./sq.ft./min. to about 1000 cu ft./sq.ft./min. and, preferably in the range of from about 150 cu.ft./sq.ft./min. to about 1000 cu.ft./sq.ft./min. (for a 5-ply sample). The Frazier porosity tests on such materials are determined using a Frazier air permeability tester available from Frazier Precision Instrument Company. These porosity measurements reflect the air permeability of the web. The procedure conforms to Method 5450, Federal Test Methods Standard No. 191A except that the specimen size used is 8 inches by 8 inches, and a 5-ply sample is measured with 20 mm air nozzle. Frazier units are expressed in cubic feet of air per square foot of specimen per minute. The percent open area of such webs generally will be from about 10 percent to 60 percent with a preferred range of from about 14 percent to 52 percent. The percent open area is a measure of the web's openness and may be measured using a Quantimet Model 970 image analyzer available from Cambridge Instruments. This property is significant in determining the filtration characteristics of cylinders made from webs in accordance with the present invention. A particularly preferred web material useful for forming the improved filter plug in accordance with the present inventionis an experimental meltblown polypropylene material obtained from Kimberly-Clark Corporation designated PP-100-F. This particular material has a Frazier permeability of about 600, Grab Tensile Strength of about 1.3 pounds (MD) and 0.7 pounds (CD), and a basis weight of about 0.75 oz/yd 2 . This material also has incorporated therein glycerin in an amount of about 2% by weight to facilitate formation of the material into a cylinder. The amount of glycerin, or other humectant, used may vary between about 0.5 and 8%, preferably between about 1 and 4%, and most preferably between about 1.5 and 2.5%. Such materials are described in greater detail in United States Application Serial No. 003,980 filed on January 16, 1987, the disclosure of which is hereby incorporated by reference. From a performance and/or aesthetic standpoint the filter firmness of the thermoplastic segments employed in accordance with the present invention may vary broadly without substantially interfering with delivery of aerosol to the user. However, it is desirable to have a segment which feels and has the firmness of a cigarette which employs conventional cellulose acetate filters. While there are a number of ways of evaluating the firmness of a filter material, firmness results for segments of thermoplastic fibers prepared from Kimberly-Clark Corporation's PP-100-F were obtained by placing a filter plug under a 19 mm diameter platen. The platen was brought into contact with the filter and an initial uncompressed diameter reading taken. In this condition an actual force of some 27 grams was exerted on the filter. The platen was then loaded with an additional 100 grams of weight. After about 10 seconds under this loading, a second reading was taken. The firmness was reported as a percentage and was calculated by multiplying the ratio of the second reading to the first reading by 100. In general, the range of filter firmnesses will be from about 94 percent to about 99 percent with a preferred range of from about 96 percent to about 98 percent. The overall pressure drop of articles employing the improved mouthend piece prepared in accordance with the present invention is preferably similar to or less than that of conventional cigarettes. The pressure drop of the mouthend piece itself will vary in accordance with the pressure drop of the front end piece of the smoking article. For preferred smoking articles, the pressure drop will generally be less than that of conventional mouthend pieces, normally in the range of about 0.1 to 6.0 cm water/cm filter length, preferably in the range of from about 0.5 to about 4.5 cm water/cm filter length, and most preferably in the range of from about 0.7 to about 1.5 cm water/cm filter length. Filter pressure drop is the pressure drop in centimeters of water when 1050 cm 3 /min. of air is passed through a filter plug. These pressure drops may be normalized to unit length of filter plug by dividing by the actual filter length. Filter efficiency per unit length of the segment of non-woven thermoplastic fibers prepared in accordance with the present invention will in general be substantially less than that of a conventional cellulose acetate filter. Preferably, the filter efficiency of such materials will be less than that of low efficiency cellulose acetate tow filters made from an 8.0/40K material obtained from Celanese Corporation. As noted above, the mouthend piece prepared in accordance with the present invention helps to reduce the temperature of the aerosol perceived by the user by, for example, distributing the aerosol generated during smoking over a larger surface area. Use of low efficiency materials in accordance with the present invention, however, also permits longer segments of the non-woven thermoplastic fibers to be used without interfering with desired aerosol delivery. This increases the residence time of the aerosol in the mouthend piece which also helps to reduce the temperature of the aerosol as perceived by the user. The length of the segment of non-woven thermoplastic fibers used in the mouthend piece may vary broadly depending on a number of factors including the desired reduction in temperature of the aerosol as perceived by the user. For preferred smoking articles employing the mouthend piece prepared in accordance with the present invention, the thermoplastic segment will generally be between about 10 mm and 40 mm in length, and preferably between about 15 mm and 35 mm in length, and most preferably about 30 mm in length. The spacer member preferably used may be prepared from a number of materials including conventional cigarette filter materials, such as cellulose acetate tow, and materials such as tobacco, tobacco-containing paper, and a segment of conventional filter materials surrounding a tube. The preferred material used to construct the spacer member is tobacco-containing paper. The preferred tobacco-containing paper comprises a web of reconstituted tobacco material obtained from Kimberly Clark Corporation as P144-185-GAPF Reconstituted Tobacco Sheet. The material includes about 60 percent tobacco principally in the form of flue-cured/burley tobacco stems and 35 percent soft wood pulp (based on dry weight of the material). The moisture content of the sheet-like material preferably is between about 11 and 14 percent. The material has a dry tensile strength of about 1,600 to about 3,300 gm/inch, and a dry basis weight of about 38 to about 44 g/sq. meter. The material is manufactured using a conventional papermaking-type process including the addition of about 2 percent glycerin or other humectant, about 1.8 percent potassium carbonate, about 0.1 percent flavorants and about 1 percent of a commercial sizing agent. The sizing agent is commercially available as Aquapel 360XC Reactive Size from Hercules Corp., Wilmington, Delaware. The tobacco paper may be formed into a plug by conventional plug making techniques. However, for smoking articles employing the mouthend piece prepared in accordance with the present invention, it preferably is formed by the inventive double cone system used to form the segment of non-woven thermoplastic fibers. The length of the spacer member will, in general, vary inversely with the length of the segment of non-woven thermoplastic fibers. For preferred smoking articles employing the mouthend piece prepared in accordance with the present invention, it is generally between about 5 and 30 mm in length, preferably between about about 5 and 15 mm in length, and most preferably about 10 mm in length. A cigarette-type smoking article using a mouthend piece prepared in accordance with the present invention is set forth in Figure 1 accompanying this specification. Referring to Figure 1 there is illustrated a cigarette-type smoking article having a small carbonaceous fuel element 10 with a plurality of passageways 11 therethrough, preferably about thirteen arranged as shown in Figure 1A. This fuel element is formed from an extruded mixture of carbon (preferably from carbonized paper), sodium carboxymethyl cellulose (SCMC) binder, K 2 CO 3 , and water, as described in the above referenced patent applications. The periphery 8 of fuel element 10 is encircled by a resilient jacket of insulating fibers 16, such as glass fibers. A metallic capsule 12 overlaps a portion of the mouthend of the fuel element 10 and encloses the physically separate aerosol generating means which contains a substrate material 14 which carries one or more aerosol forming materials. The substrate may be in particulate form, in the form of a rod, or in other forms as detailed in the above referenced patent applications. Capsule 12 is circumscribed by a jacket of tobacco 18. Two slit-like passageways 20 are provided at the mouth end of the capsule in the center of the crimped tube. At the mouth end of tobacco jacket 18 is a mouthend piece 22, preferably comprising a cylindrical segment of a spacer member 24 and a segment of non-woven thermoplastic fibers 26 through which the aerosol passes to the user. The article, or portions thereof, is overwrapped with one or more layers of cigarette papers 30 - 36. Upon lighting the aforesaid embodiment, the fuel element burns, generating the heat used to volatilize the tobacco flavor material and any additional aerosol forming substance or substances in the aerosol generating means. Because the preferred fuel element is relatively short, the hot, burning fire cone is always close to the aerosol generating means which maximizes heat transfer to the aerosol generating means, and resultant production of aerosol, especially when the preferred heat conducting member is used. Because of the small size and burning characteristics of the fuel element, the fuel element usually begins to burn over substantially all of its exposed length within a few puffs. Thus, that portion of the fuel element adjacent to the aerosol generator becomes hot quickly, which significantly increases heat transfer to the aerosol generator, especially during the early and middle puffs. Because the preferred fuel element is so short, there is never a long section of nonburning fuel to act as a heat sink, as was common in previous thermal aerosol articles. Because the aerosol forming substances are physically separate from the fuel element, they are exposed to substantially lower temperatures than are generated by the burning fuel, thereby minimizing the possibility of thermal degradation. In preferred embodiments, the short carbonaceous fuel element, heat conducting member and insulating means cooperate with the aerosol generator to provide a system which is capable of producing substantial quantities of aerosol on virtually every puff. The close proximity of the fire cone to the aerosol generator after a few puffs, together with the insulating means, results in high heat delivery both during puffing and during the relatively long period of smolder between puffs. Such smoking articles produce an aerosol resembling tobacco smoke without any undesirable off-taste due to scorching or thermal decomposition of the aerosol forming material. Such smoking articles were smoked under so-called human conditions which consist of 50 ml puff volumes of 2 second duration, separated by 28 seconds of smolder, for at least about six puffs. As can be seen from Figure 4 the lip thermal temperature as measured by a Cyclops portable Radiation Thermometer at about 4 mm in from the end of the mouthend piece was less than or equal to body temperature. In other words, such articles produced aerosol without the undesirable "hotness" perceived by users of similar articles not employing the improved mouthend piece, prepared in accordance with the present invention.

Claims: A method for forming a rod (57) for use in the manufacture of smoking articles, said method comprising the steps of feeding a stream of a first material (50) into and through a forming device (54) having an annular inner conical surface tapering in the travelling direction of said first material (50), forming the stream of said first material (50) into the shape of a cylinder (55), and wrapping said cylinder (55) with a wrapping web (56) to form said rod (57), characterized in that said first material is provided in the form of a first web (50), that said first web (50) is fed into a conical annular space (54c) provided between said inner conical surface and an outer conical surface of an inner cone (54b) positioned within said inner conical surface and tapering in the travelling direction of said first web (50), whereby said first web (50) is folded into a cylindrical shape (55), whereupon the cylindrical shaped first web (55) is wrapped with said wrapping web (56). The method of claim 1, further including the step of cutting the rod into a plurality of cylindrical segments (57) of predetermined length. The method of claim 1 or 2, wherein the first material of the first web (50) is a non-woven material. The method of one or several of claims 1 to 3, wherein for the first web (50) a first material is used which comprises meltblown thermoplastic fibers and/or filaments. An apparatus for manufacturing rods (57) for use in the manufacture of smoking articles, the apparatus including first means (59) for providing a stream of a first material (50), a forming device (54) having an annular inner conical surface tapering in the travelling direction of said first material (50) for forming said first material into the shape of a cylinder (55), and wrapping means for providing said cylinder (55) with a wrapping web (56) to form said rod (57), characterized in that said first means (59) is in the form of feed means for feeding said first material (50) in the form of a first web into said forming device (54), and that said forming device (54) has an inner cone (54b) with an outer conical surface positioned within said inner conical surface and tapering in the travelling direction of said first web (50) thereby providing a conical annular space (54c) for receiving said first web (50) and for folding the same into the shape of said cylinder (55). The apparatus of claim 5, further including means (58) for subdividing said rod into a plurality of cylindrical segments (57) of predetermined length. The apparatus of claim 5 or 6, further including means for moving the outer conical surface (54a) and the inner conical surface (54b) in relation to each other.

Inventors: MARRITT CLIFFORD RUSSELL, NELSON JOHN LARKIN, PRYOR JAMES WILLARD, MARRITT, CLIFFORD RUSSELL, NELSON, JOHN LARKIN, PRYOR, JAMES WILLARD
Applicants: REYNOLDS TOBACCO CO R, R.J. REYNOLDS TOBACCO COMPANY
Application year: 1988
Main classification: A24D3
IPC codes: A24D3, A24F47