GB2078087A - Smoking articles containing tobacco and method of making such - Google Patents

Abstract

A smoking article (15) comprises a coherent mass (9) of combustible tobacco-containing material having at least one passage extending through it between two spaced openings in the surface of the mass, the tobacco mass having such porosity as to support combustion when ignited and such density and porosity as to substantially occlude gas flow therethrough. The article preferably has at least one air-permeable plug (5, 6) of readily ignitable material blocking the passage at one or both ends. The tobacco-containing mass may include non-tobacco filler particles, such as carbon or clays, and the plug may contain a flavorant. The articles may be made by shaping a mixture of combustible tobacco material with a volatile liquid, for example a mixture of water and ethanol, under pressure into a discrete coherent mass, preferably by extrusion, forming a passage through the mass, and drying the mass to a porosity and density such as to substantially occlude gas flow therethrough but to support combustion when ignited. <IMAGE>

Description

SPECIFICATION Smoking articles and method of making such articles The present invention relates to smoking articles, particularly smoking articles having distinctive physical properties, and it further relates to a method of producing smoking articles so that such properties may be adjusted, thereby controlling their combustion behavior so as to achieve reduced tar delivery during smoking.

The quantity of combustion products produced by a burning bed of combustible material, such as tobacco or nontobacco smoking materials, is primarily dependent on certain physical properties of the burning material. The physical properties which influence the quantity of combustion products include the surface area of material available for combustion, the density and porosity of the material, the volume of air available for combustion, the velocity at which air is made available for combustion, the temperature at which the material combusts and the composition of the combustible material.

A primary cause of tar production during combustion in a conventional smoking article, such as a cigarette, cigar or pipe, is pyrolysis. Pyrolysis may be defined as the thermal evolution of tars and gases by heat produced from the combustion of a carbonaceous incandescent coal. As pyrolysis reduces smoking material to its carbonaceous skeleton, the carbonaceous remains, in turn, combust and provide heat for further pyrolysis of fresh material located adjacent to the combusting material.

Smoking materials used in conventional smoking articles are generally in the form of shredded tobacco leaf, shredded reconstituted tobacco sheet, tobacco stems and combinations thereof and, as a result, such materials present a relatively large surface area for pyrolysis. In smoking a conventional smoking article, moreover, gases drawn by a puff through the incandescent coal are heated. The heated gases pass through noncombusted tobacco adjacent to the coal and pyrolysis occurs. Thus, in conventional products pyrolysis occurs not only due to the heat of conduction and radiation from the coal, but also due to the heat transferred by such heated gases to noncombusted tobacco adjacent the coal.

The present invention provides tobaccocontaining smoking articles wherein control of combustion and pyrolysis processes is effected by adjusting properties, such as porosity, surface area and density of the tobacco-containing mass. By thus controlling the pyrolysis and combustion processes, gas phase and tar delivery by the articles of the present invention is concomitantly controlled.

Additionally, in conventional smoking articles of the above-mentioned type, substantial heat dissipation occurs in regions immediately adjacent the coal, thereby reducing the temperature of combustion gases as they progress down the article to the point where they no longer can be used to effect thermal release of flavorants downstream of the coal. It has been observed that such heat reduction is significantly less for the articles of the present invention, thereby permitting downstream thermal flavorant release.

This invention provides tobacco-containing smoking articles wherein tar delivery during combustion is controlled by adjusting the density, porosity, surface area and/or composition of the article. The smoking articles comprise a coherent mass of combustible tobacco material, having at least one through passage extending from a first opening in the surface of said mass to a second opening remote from the first, said tobacco mass being of a density and porosity such as to substantially occlude gas flow therethrough, while further being of a porosity sufficient to support combustion of said mass when ignited.

In making such articles, a combustible tobacco material in particulate form is mixed with one or more other ingredients including a liquid, the mixture being subjected to additional processing to produce a shaped coherent mass having a through passage therein. Shaping is effected by application of pressure to the mixture to form the coherent mass; subsequently the formed or shaped mass is dried.

The articles may be formed by extrusion of a homogeneous mixture of tobacco material containing both water and a volatile organic liquid which is compatible with the tobacco, said mixture having a solids content of 55 to 75 weight percent, and drying the resulting extrudate. The mixture for purposes of extrusion preferably contains comm inuted tobacco of a mesh size less than about 30 mesh. Nontobacco filler particles, as well as burn additives and/or flavorants, may be included in the tobacco mass.

In a further aspect of the invention, improved characteristics are realized by further processing of the dried coherent mass, such further processing including rewetting of the mass and subsequent redrying.

In a preferred embodiment, the smoking article of the invention has a passage extending axially through a mass of cylindrical shape, the crosssectional area of said passage most preferably being larger than that of the mass. It is also preferred to have an easily ignitabie air permeable plug disposed in passage blocking position in at least one end of the passage. An additional plug or plugs of the same or different material may be included, at least at the outlet end, and may optionally contain flavorants which are thermally released.

When provided in conjunction with the preferred extrusion process, it is preferable that the ignitable plug be extruded concurrently with the coherent mass.

FIGURE 1 depicts in section a smoking article in accordance with the present invention, having a conventional filter attached thereto by means of tipping paper.

FIGURE 1 b is an end view of the smoking article of FIGURE 1.

FIGURE 2 shows in section a smoking article similarto FIGURE1 having a plug position at both the mouth end and the ignition end of said article.

FIGURE 3 is a sectional view of an alternative embodiment of the invention in the form of a cigar like smoking article having thickened walls, and fitted with a mouthpiece.

FIGURE 4 is a sectional view through a still further embodiment in the form of a smoking article comprising a preformed body of smoking material having multiple channels therethrough, and disposed in the bowl of a pipe.

FIGURE 5 shows a smoking article similarto FIG URE 4, in which the entire pipe bowl is preformed from combustible material.

FIGURE 6 shows a flow diagram of steps involved in the manufacture of a smoking article in accordance with certain method aspects of the present invention.

FIGURE 7 shows in schematic fashion extrusion equipment for performing an extrusion step in accordance with a particular method of the invention.

FIGURE 8 shows a die head for the extrusion equipment of FIGURE 7.

In accordance with the present invention, tobacco-containing smoking articles formed from a coherent mass having at least one passage therethrough are provided. Delivery of tar and gas phase constituents is controlled by adjusting the density, surface area and porosity of the combustion portion of the mass. By decreasing the surface area and porosity of the mass available for combustion, while increasing its density, it is possible to minimize the tar delivery by the smoking articles of the invention.

More particularly, the smoking articles of the present invention can be produced from a coherent mass of combustible tobacco-containing material wherein the surface area of the mass available for the production of tar may be considerably lower than that of a conventional smoking product in current usage.

Moreover, the density of the mass in the instant smoking article may be significantly greater than that generally observed in conventional smoking products, while the porosity of the mass is substantially less. The resulting smoking article has substantially reduced tar and gas phase delivery relative to conventional smoking products.

By reducing porosity and surface area and increasing density of the material being burned, the smoking articles of the invention produce a reduced quantity of pyrolysis products per puff. Since the density, porosity and geometry of the smoking articles of the invention control the volume of air and the velocity at which it is drawn over and through a burning coal during a puff and inhibit access of heated gases to unburned tobacco material, control of the pyrolysis and combustion processes in the present smoking articles is possible. Furthermore, the temperature of the air passing through the passage of smoking articles of the invention can be maintained at a high enough level to effect thermal release of flavorants downstream of the burning coal thereby providing means for low tar, fully flavored smoke delivery.The present smoking articles are thus advantageous in that shape, density and porosity of the mass will lower tar delivery naturally without the addition of chemicals that alter combustion and in certain instances adversely affect the subjective qualities of the tobacco, while permitting distillation of flavorants.

In the practice of the invention, a combustible tobacco-containing material is formed into a coherent mass having at least one passage extending from a first opening in the surface of the mass to a second opening remote from the first. Both the density and porosity of the formed mass are such that puff induced air flow through the smoking article is preferentially through the passage; that is, the density and porosity of the mass are such that gas flow longitudinally through the mass itself is substantially occluded. Porosity, however, must be high enough to support combustion and preferably sufficlient to support static, nonpuff aided, combustion.

In a preferred embodiment of the invention, the mass is formed into a cylinder having at least one passage axially therethroug h. This passage permits the dense smoking material to be puffed, aids in the control of volume and velocity of air which passes through the coal, reduces the coal volume and serves as an air conduit whereby the smoke generated during combustion is diluted by air when drawn upon by the smoker. This obviates the necessity of highly diluted, ventilated filters frequently employed in conventional low delivery smoking articles.

The tobacco-containing material employed to form the coherent mass may comprise high quality, highly flavorful tobacco, such as bright, burley, Oriental or mixtures thereof, preferably in comminuted form. Other tobacco materials, such as reconstituted tobaccos and prepyrolyzed tobaccos may also comprise all or part of the tobacco-containing materials.

In a particularly preferred embodiment, the smoking article is made in the form of a hollow cylinder.

Most preferably the wall thickness of the coherent mass is such that the cross-sectional surface area of the mass is less than the corresponding crosssectional area of the passage. In such a smoking article, it is desirable to provide at least one plug for insertion in passage blocking position. The plug may be positioned at the end or ends of the smoking article and/or may be disposed at intermediate positions in the passage. Such plugs may serve either to aid ignition or as baffles to prevent flash heating through the tube due to suction on ignition or in the event of relighting. Additionally, one or more of the plugs may contain flavorant materials. Plug material must be air permeable and, at least at one end, should be readily ignitiable. Plugs preferably consist of comminuted tobacco material prepared in a simi larmannertothe coherent mass.

Flavorant additions to the plugs (or for incorporation in the coherent mass) may be made during the preparation of either the tobacco-containing material, the plug material or both. Typical tobacco flavorants may be incorporated at any stage of processing, but it is generally convenient to do so during mixing.

Tobacco extracts may also be incorporated at this point as part of the liquid ingredient. Extracts of Burley tobacco prepared according to methods described in U.S. Patents 4,131,117 and 4,131,118 may be used. Other tobacco extracts or slurries prepared by processes which release the pectinaceous binder material contained therein may be employed similarly as part of the liquid ingredients in the production of the smoking articles. Descriptions of processes for releasing the natural tobacco pectins may be found in U.S. Patent 3,353,541 or 3,420,421 to Hind.

The smoking articles of the present invention do not require an outer wrapper of the type used in making conventional cigarettes. However, it will be appreciated that an outer wrapping of cigarette paper or the like, such as a coating material, or pigments incorporated directly in the smoking article, may be used to achieve the desired appearance.

In accordance with the method aspects of the present invention, tobacco articles are formed by first mixing a quantity of tobacco-containing material with water and with a volatile organic liquid to provide a tobacco mixture suitable for subsequent processing, i.e., shaping to provide a shaped mass in any one of a number of discrete forms. Generally the tobacco materials to be mixed will have a moisture content in the range of about 5 to 15% OV, and preferably 10% OV. As used herein, the term OV (oven volatiles) represents the moisture content of tobacco determined as percent oven volatiles. OV is determined by placing a weighed sample of tobacco in an air-circulating oven and maintaining the sample in the oven at a temperature of 100"C for a period of 3 hours after which the sample is again weighed.The difference in the two weight values, expressed as a percentage of the original weight, is defined as OV.

Prior to mixing, the tobacco may be comminuted to a desired particle size. Conventional means, such as a ball mill, a plate or disc-type colloidal mill or blendor, may be used to effect comminution. The time required to accomplish this will, of course, depend on the original size of tobacco components to be comminuted and to some extent on the type of tobacco used as well as the moisture content thereof.

Mixing of the tobacco with the liquid ingredients may be effected with conventional equipment. For example, conventional Hobart mixers equipped with a flat paddle or beater-type blade, ribbon-type mixers and the like or any other mixer that will effect homogenization or even distribution of liquid to tobacco is suitable.

In the mixing operation the addition of liquid ingredients to the tobacco particles may be simultaneous or the water may be added first followed by addition of the volatile agent. Mixing generally is accomplished at room temperature and generally is effected in a closed container to prevent premature volatilization of the organic liquid. The time necessark to achieve even distribution of the liquid and tobacco particles depends to a great extent on particle size as well as the type of liquid combination used. Generally 15 minutes to several hours is sufficlient to obtain the desired distribution of liquid.

Although it is usually desirable to prepare such mixture using both water and a volatile organic liquid in order to control porosity and density of the coherent mass, it is possible to use only water in preparing the mixture, especially in cases where forming of the mixture is done by means of extrusion under conditions which can be varied suffi cientlyto accomplish the desired results. Even so, one disadvantage is that the use of a sufficient quantity of water alone tends to make the density of the resulting mass too great as a practical matter. As noted elsewhere in greater detail, however, rewetting and redrying after forming the coherent mass ordinarily can be used to control its ultimate porosity as long as the starting mixture can be extruded or otherwise formed acceptably into the desired configuration.

The volatile organic liquid of the mixture serves to improve the density and porosity characteristics of the final smoking article, possibly due to rapid vaporization during drying. The organic liquids which may be employed are preferably those having a higher vapor pressure than water and include only those liquids which are compatible with tobacco products.

For purposes of this application, liquids are compatible with tobacco if they do not appreciably react with tobacco constituents and, in addition, will mix sufficiently with the tobacco material so as to avoid separation during the article forming operation.

Further, it is preferable to employ liquids which, when mixed with tobacco products, do not adversely affect the aromatic or subjective qualities thereof on smoking. Preferred liquids include those which may easily be removed by evaporation under relatively nondrastic heating or drying conditions and which upon evaporation leave no appreciable residue.

Among the suitable organic liquids are straight or branched-chain hydrocarbons of about 5 to 8 carbon atoms, such as the pentances, hexanes and heptanes. Straight or branched-chain alcohols selected from 1 to 8 carbon atoms and including methanol, ethanol, propanol, isopropanol, butanol and the like are also suitable for use. Moreover, the "Freon" liquids including trichloromonofluoromethane and dichlorodifluoromethane may be used. Selected ketones, e.g., methyl ethyl ketone, ethers, halohydrocarbons and the like, may be used in some instances. The selected liquid may be used alone or, in some instances, a combination of two or more agents may be used depending on the type of smoking article being produced.

The ratio of total water in the mixture to volatile organic liquid will depend to some extent on the type and mesh of tobacco and the specific liquid being used but generally will be in the range of about 6 parts water to 1 part organic liquid to about 1:1 ratio of each. Where less than -60 mesh tobacco is employed in accordance with the preferred forming practice discussed hereinbelow, a ratio of about 2 partswaterto 1 part organic liquid is preferred.

It may also be desirable to add filler materials to the aqueous tobacco mixture. Filler materials can include calcium carbonate, selected carbon materials, diatomaceous earth, attapulgite and the like. Up to about 40 to 50% of the solids in the mixture may comprise such fillers without requiring addition of binders. If desired, burn additives may also be added to the mixture to adjust burn properties.

While it is preferable to avoid adding an extraneous binder and to rely instead on natural binder substances of the tobacco, in order to achieve minimum tar delivery upon smoking, it will be recognized that the mechanical strength of such smoking articles may be increased through the use of additional binder materials provided that doing so is consistent with the delivery objectives of a particular product.

When all the desired ingredients have been added, and an homogeneous mixture is obtained, the thus prepared mixture is ready for further processing to produce smoking articles. By this further processing, the tobacco mixture is formed into a shaped article comprised of a coherent tobacco mass whose density and porosity are sufficient to occlude gas flow therethrough and whose density is sufficient to support combustion of the mass when ignited. The tobacco mass is further provided with at least one passage extending therethrough from a first opening on the mass surface to a second opening remote from the first opening. Providing of such passage as used herein means providing the same during the shaping operation or during operations subsequent thereto, or during both shaping and such subsequent operations.

In accordance with the invention, the article shaping operation includes pressure treatment of the mixture to transform the mixture into a coherent or self-supporting tobacco mass and subsequently drying of the mass. The pressure treatment will generally require application of pressure to the tobacco mixture in a confined space and, preferably, results in a coherent mass having the desired through passage. An alternate procedure would be to form the mass without the passage and to subsequently create the passage after the pressure treating operation, or after drying, by a material removal operation such as, for example, boring or driiling.

The pressure treatment can be effected by any one of a number of conventional techniques adapted to provide sufficient pressure to the tobacco mixture to cause release of the tobacco materiai's natural binding agents, thereby resulting in a cohesive mass. The pressure forming operation thus enables selfsupporting articles to be produced without the need to add extraneous binders to the tobacco mixture.

While pressure treatments such as molding can be used to implement the invention, a preferable treating technique is extrusion. In general, extrusion conditions will depend upon the type of extruder used (ram, screw, etc.), the particular composition of the tobacco mixture and the desired shape, density and porosity conditions for the resultant extrudate.

Conventional screw extruders or higher pressure producing ram extruders may be employed, with the die heads of these extruders preferably having the desired shape of the smoking articles to be produced. These extruders may be operated at selected pressures and with selected cooling of one or more sections of the extruder barrel to promote production of the desired extrudate. An extruder found suitable is a Wayne plastics extruder equipped with a 1:1 screw adapted to rotate at 1 to 120 rpms.Such an extruder, due to its 1:1 screw, does a minimum amount of work on the tobacco mixture, while providing pressure sufficientto release the natural binding agents of the tobacco and thereby result in a cohesive product With screw extruders of this type, extrudate pressures at the end of the extruder barrel (i.e., melt pressures) of up to 2500 psig are useable, with pressures of up to 1200 psig being preferable.

Extrudate temperatures at such barrel end (i.e., melt temperatures) of less than about 40"C also are useable and can be developed by maintaining the screw barrel temperature in the range of about 20 to 25"C.

Preferable tobacco mixture conditions for extrusion are a tobacco particle size of below about 30 mesh and a tobacco content sufficient to produce a mixture having a solids content in the range of about 55 to 75 weight percent solids, and preferably about 60 to 70 percent solids.

As above indicated, the shape of the desired smoking articles controls the extruder die head construction. Preferable smoking articles are of hollow cylindrical shape and, more preferably, are cylindrical tubes having a wall thickness such that the crosssectional area of the mass is less than the corresponding cross-sectional area of the passage. Die heads having a suitably adapted annular extrusion passage are thus employed to achieve this construction. A particular extruder for realizing hollow cylinders is the aforementioned Wayne extruder. Thus, for example, thin-walled tobacco tubes having a high density and low porosity and which burn with coal temperatures in the range of 585"C to 785"C may be produced with suitably modified extruders of thins type.Additionally, when using such extruders it is customary to introduce air flow into the inner part of the formed tube to prevent collapse thereof.

Forming part of the article pressure treating operation may be a severing or separating operation which results in the production of individual coherent masses corresponding to individual smoking articles. Such an operation is necessary if pressure treatment is not itself on an individual article basis.

In the case of the above-described preferred extrusion practice, wherein the extrudate will typically be a single cohesive continuous length mass exiting from the extruder die, it is desirable to perform a cutting operation at the die exit, thereby to form individual units of length corresponding to that of the desired smoking articles. Where articles of preselected length are desired, the cutting operation is synchronized with the rate of extrudate output to provide the required length.

The aforesaid operation of providing individual units also may be effected subsequent to the drying of the extrudate if severing of the dried extrudate is found to be a more acceptable practice.

Drying the resultant pressure-formed coherent mass may be accomplished either by simple evaporation at ambient environment, e.g., room temperature, or by application of heat. Typically, at a room temperature of from about 70 to 75"F, typical drying times might range from about 12 to 24 hours. Heat application might be at a temperature of about 100 C. This can be done by conventional heating means such as a Freas oven (forced air oven) over a period of time from about 15 minutes to 1 hour.

Heating can also be accomplished more rapidly by microwave application in which case the time of application will depend upon the power used. At power levels about 150 watts, drying times of about 2 minutes have been found acceptable. Such rapid drying may be employed to enhance the static burn properties of the resultant smoking article.

Following the drying operation, the dried articles may be further processed as by affixing the articles to suitable mouthpieces which may or may not include filters to result in the completed smoking article construction.

While the method of the invention as described above has been found to provide suitable smoking articles, a further aspect of the invention is to provide further processing of the pressure-formed coherent mass subsequent to the initial drying operation. Such further processing enables changing of the porosity of the dried mass, whereby improved combustion characteristics of the resultant smoking product result. This further processing comprises rewetting the dried mass and subsequent redrying.

Rewetting may be carried out by spraying or immersion of the dried mass. Suitable rewetting has been carried out by immersing the mass in a bath of liquid, preferably water, for a time sufficient to obtain the desired change in porosity. In general, rewetting conditions will depend upon initial porosity, tobacco particle size and the type of organic fluid used. Suitable rewetting conditions to realize desired porosity changes can be determined through empirical procedures. Subsequent redrying after the rewetting is preferably carried out in accordance with the initial drying procedure discussed hereinabove.

In a further aspect of the method of the invention, the method is further modified to allow for disposition of a readily ignitable air permeable plug in the through passage of the pressure-formed coherent mass. Other plugs may be placed at one or more positions along the passage and in blocking relation thereto. In a preferred practice of the present invention wherein cylindrical tubular smoking articles are formed, it is desirable to situate such plugs at opposite ends of the tubular passage.

Usually only one or two such plugs will be needed, especially at one end for lighting the smoking article.

Consequently, the typical embodiments have a hollow passageway that is largely unrestricted. It will be appreciated, however, that such passageway may be filled partly or wholly with an innocuous filler material which either is non-combustible or does not contribute excessively to the production of tar upon smoking. Plug material maytakevariousforms and may contain flavorants releaseable upon heating. Plug material preferably comprises comminuted tobacco prepared in the same manner as the coherent mass forming the smoking article. Plugs can, therefore, be formed using a procedure analogous to that outlined above for making the coherent mass, with pressure treatment modified as may be necessark to produce plugs of the desired configuration and suitable for insertion in the coherent mass in passage blocking relation.Air permeability for the plugs may be realized either through the inherent porosity of the plug material or by through orifices provided in the plug during or after plug formation.

While plugs might be formed independently of the coherent mass and inserted in the mass subsequent to its formation or subsequent to drying, in a preferred practice the plugs are formed and situated in the mass passage simultaneously or concurrently with mass formation. In yet a further preferred practice, this is accomplished in the preferred extrusion procedure by co-extruding the plug with the mass in suitably timed relationship so as to obtain plugs of desired size at desired passage blocking positions and in intimate contact with the inner mass wall.

The smoking article of the present invention can be made in various forms particularly those which are conveniently extruded, although other article shaping methods can be employed to that end. With reference now to FIGURE 1,the smoking article 10 comprises an elongated coherent mass 9 shaped in this embodiment as a tubular rod having a through passage 2 extending end to end thereof. While the tubular mass 9 serves in and of itself as a smoking article, it is possible (see FIGURE 2) to fit a filter3 at the smoking end and join same to the mass 9 with a tipping paper 4 in conventional manner. As seen in FIGURE 1 b, the passage 2 and the mass 9 have circular configuration but it will be appreciated that other sectional geometrics could be employed, for example, hexagonal, etc.The mass 9 may correspond generally in length and circumference to that of conventional sized cigarette tobacco cylinders. Depending upon the particular delivery characteristics to be produced with the article upon smoking of same, the cross-sectional area of the mass relative to the passage will be varied.

The smoking article 15 shown in FIGURE 2 is fitted at the ignition end with a passage blocking plug 5 of air permeable combustible material. In addition to functioning as an ignition device, the plug 5 functions to prevent flash heating through the passage when lighting the smoking article. Additional plugs, for example, the plug 6 shown adjacent the filter com ponent 3 can be provided and may serve to embody flavorant materials in the smoking article. If desired, plugs could also be disposed at one or more locations intermediate the ends of the smoking article to serve as either flavorant carriers or ignition means, or both.

In accordance with the present invention, the smoking article can be provided in the familiar shapes of other types of smoking articles, as for example, in the fashion and approximate dimensions of a cigar 16 as shown in FIGURE 3. In such article 16, the walls 7 of the tubular mass will be of greater thickness relative to the size of the article and as compared with the FIGURE 2 smoking article. In addition to ignition and flavorant plugs 5 and 6, the article can be fitted with a mouthpiece 17, which in turn itself can serve to embody flavor releasing elements or filter means 8.

FIGURES 4 and 5 illustrate the manner of providing a smoking article either for utilization in a conventional smoking pipe or as a pipe shaped component as such. The smoking article 30 shown in FIG URE 4 is formed as a realtivelytruncated mass 19 shaped and sized for reception in the bowl of pipe 18, with the mass being provided with one or more through passages 2 extending from top to bottom thereof. FIGURE 5 shows the manner in which a coherent mass 20 is shaped in the form of a smoking pipe bowl and, like the FIGURE 4 mass, has one or more passages 2 and is fitted with a side opening as at 21 for reception of a pipe stem 28 having a filter 40 as does pipe 18.

FIGURE 6 illustrates schematically a preferred embodiment of the invention wherein tobacco is comminuted, mixed with water and a volatile organic liquid and then subjected to a pressure treatment, preferably extrusion, to produce a coherent tobacco mass. The tobacco mass is dried at room temperature or by application of heat. Further processing of the coherent tobacco mass to alter the porosity thereof is achieved by a rewetting step followed by a drying step.

FIGURE 7 shows schematically extrusion equipment for providing the aforesaid co-extrusion of a tubular coherent mass and plugs in accordance with the method of the invention, the die head construction being shown in greater detail in FIGURE 8. Turning to FIGURE 7, a tobacco mixture as abovedescribed for forming the coherent mass or body of the smoking article is supplied to an automatic hopper feeder 71. The hopper 71 applies a continuous force to the tobacco mixture via a rotating blade which extends into a material receiving port of a screw extruder 72 driven by a drive 73. The tobacco mixture is force fed to the extruder 72 and the extrudate developed in the extruder is forced into a common die head 74 where it is formed into a tubular coherent mass 100 at the die head exit.Air also is supplied to the die head 74 from a source 75 and is conveyed by a line 76 to the die head exit interiorly of the tubular mass 100 to prevent collapse thereof as the mass is being formed.

Plug material of similar composition to the mass material is supplied to a hopper feeder 81 having a construction analogous to that of hopper feeder 71.

The plug material is fed by hopper 81 to a plug screw extruder 82 which is driven by a drive 83. Extrudate passes from the extruder 82 through the valve 84 into the common die head 74 where it is made available interiorly of and joined to the inner wall of the tubular mass 100.

Control synchronization circuit 91 effects control of the continued pressure applied to the plug extrudate in passing to the head 74. This control is synchronized with the issuance of the tube 100. Circuit 91 maintains the valve 84 closed and the drive 83 stopped for a predetermined period of time corresponding to the delivery of a preselected length of tube.

After such time the valve 84 is opened and the drive 83 restarted, causing pressure to be applied to the plug extrudate and, as a result, common delivery of plug and tube. This condition lasts for a second predetermined period of time corresponding to the common delivery of a preselected length of tube and plug, after which the vale is again closed and the drive 83 is again stopped. Repeated control of the valve 84 and drive 83 thus results in the tube 100 being continuously extruded with plugs 101 of determined length being disposed at determined space positions therein and in passage blocking relationship thereto. For slow speed operation of extruder, valve 84 may be omitted, and at high speed, drive 83 may be omitted.

Contro synchronization circuit 91 also controls the direction of rotation of the blades of the hoppers 81 and 71. This direction is changed periodically by the circuit 91 to ensure proper delivery of tobacco mixture to the respective screw extruders.

Also shown in FIGURE 7 is a cutting assembly 92 at the die head exit which also is synchronously operated by the control circuit 91 to cut the tube 100 into individual coherent mass units. Such cutting operation can be synchronized to occur immediately before disposition of a plug 101, whereby each unit will contain a single plug at the forward passage thereof. Preferably, however, the cutting assembly is controlled to effect cutting so that uhits are produced having plugs at both ends. This is realized by controlling the plug extruder operation to issue plug material of desired length and by correspondingly controlling the cutting assembly to sever the tube 100 at positions along the length of each extruded plug.

FIGURE 8 illustrates the common die head 74 of FIGURE 7 in greater detail. As illustrated die head 74 includes an outer casing or support assembly 110 comprised of a central hollow cylindrical body 111 to whose opposite ends are attached by screws (not shown) support rings 112 and 113. A central recessed section 114 of the body 111 cooperates with a facing central recessed section 115 of the ring 112 to support a first hollow mandrel 116. Inner conical surface 117 of mandrel 116 extends to a shortcylindrical guide surface 118, the lattersurface 118terminating at the end of mandrel 116 to define an exit orifice 119.

Afurther hollow mandrel 121 is supported by ring 113 and by a hollow retainer element 122 held betwees the latter ring and body 111. The mandrel 121 extends the length of the assembly 110 and the mandrel outer surface 123 is spaced from the repsective inner surfaces 128 and 117 of body 111 and mandrel 116. These surfaces (123, 128, 117) define an annular passage 124 for receipt of the tubular mass extrudate from the extruder73. Surface 123 is tapered inwardly in the region of the surface 117, both surfaces cooperating to provide an exit annular passage 125 of radial expanse corresponding to the thickness of the tubular mass to be formed and of outer diameter commensurate with the guide surface 118.

A central bore 126 extends the length of mandrel 121 and receives plug extrudate from the extruder 82.

Bore 126 at the end of mandrel 121 is of expanse substantially equal to that of the inner diameter of the exit passage 125, whereby plug extrudate of such expanse is delivered to the end of the exit passage. Air line 76 passes through the bore 126 and delivers air to the region adjacent the passage 125 and the exit port 119 to prevent collapse of the tube 100 as it is being extruded.

In operation, pressure applied to the tubular mass extrudate via the extruder 73 forces the extrudate into the passage 124 and thence to the exit annular passage 125. The extrudate departs the passage 125 as the thin walled tubular coherent mass 100, the latter mass being guided by cylindrical surface 118 to exit port 119. With no pressure applied to the plug extrudate by the extruder 82, the tubular mass 100 exits without plug material and passes through a constriction ring 127 attached to the mandrel 116.

Upon pressure being applied to the plug extrudate by the extruder 82, the extrudate is forced through the central bore 126 and supplied to the end of the annular passage 125 where it is received interiorly of an in contact with the inner wall of the simultane ously formed tubular mass 100. As pressure con tinges to be applied to the plug extrudate, the plug extrudate and the tubular mass together pass through exit port 119 into the central orifice 129 of the ring 127. The latter orifice tapers inwardly and thereafter outwardly, the inward taper ending at a radial expanse which is less than the outer diameter of the tubular mass. Upon reaching the end of the inward taper, the forward end of the tubular mass is inwardly constricted forcing its wall into cohesive engagement with the forward end of the plug extrudate.At this time, the pressure applied to the plug extrudate terminates, and the tubular mass which continues to be extruded and is now joined to the plug extrudate breaks from the plug extrudate a plug 101 which continues to move with the tube through the orifice 129. The portion of the tube coextensive with the plug is thereupon continuously constricted over further incremental areas, thereby cohesively joining the plug to the tube wall over the entire plug length. In this way the tube and plug are joined without excessive drag being placed on the tubular mass, whereby thickening of the tube wall is prevented during the joining operation.

It should be noted that cohesive joining of the plug 101 and the tubular mass 100 can be effected in other ways such as, for example, by expanding the plug by known methods so it cohesively joins to the mass wall.

As noted above, air-permeability of the plugs 101 can be brought about in the plug forming operation and it is contemplated that the die head of FIGURE 8 can be modified to provide through orifices in the plugs as they are being extruded. This can be accomplished by the placement of spaced thin solids rods 131 in the bore 126, such rods extending from a point in the bore to beyond the annular passage 125.

These rods might be held by a ring 133 which can be placed between sections of the mandrel 121, thereby placing the rods in their desired position in the bore 126.

Density of the rods formed in the hereinbelow examples was determined according to the following formula:

Density(g/cc) = OD |B6OD) 2 ~ (iDX 21 2 rod length -1 lv2 2 - 7 rod weight wherein OD is the outer diameter of the rod in centimeters, ID is the inner diameter of the rod in centimeters and the length and weight of the rod are in centimeters and grams respectively.

Pressure drop (AP) was measured by blocking an open extruded tube at one end while inserting the other end in a pressure drop instrument (P.D.I.). The AP recorded is inversely proportional to the air flow through the walls of the tube.

The following examples are illustrative of the invention.

Example 1 Bright tobacco having an approximate moisture content of 11.6% OV was ground in a Fritsch Pulverisette grinder. The ground tobacco was pas sed through a 60-mesh screen to remove coarse par ticles and the fraction having a sieve size of 60 or smaller (-60 mesh) was selected for further proces sing.

To 224.9 g of the -60 mesh tobacco having a moisture content of 11.06% OV, was added 48.0 ml of 95% ethanol and 47.1 g water. This mixture was stirred for approximately 20 minutes in a hobart mixer (Model N-50) equipped with a conventional "B"-flat beater blade.

The tobacco mixture having a solids content of 64.5% by weight was then extruded to form tubes having a wall thickness of 0.5 mm. A Wayne Plastics 1" extruder with 1:1 compression ratio screw, 3 zone automatic heat, and 3 zone automatic fan cooling, straight tubing die having an 8 mm outer diameter (OD) and 7 mm inner diameter (ID) and 3 HP variable speed (0 to 60 rpm) drive was employed to effect extrusion. Zones 1 through 3 were maintained at room temperature. The maximum die head pressure was 1.500 psig. Although these extrusion conditions were favorable for small runs, for longer, continuous runs it was necessary to cool the barrel to prevent skin formation on the rod.

Some of the extruded tobacco tubes were dried in an Apollo Microwave oven for 5 minutes at maximum power. After drying, the tubes were ignited and maintained a static burn.

Extruded tubes were also allowed to dry at room temperature overnight. These tubes were then cut into 85 mm lengths having an average measured weight of 12.70 mg/mtm and calculated density of 1.078 g/cc. Four of these tubes were allowed to static burn, and the average burn rate was determined and found to be 4.8 mm/minute. Other room temperature dried tubes were smoked automatically under controlled laboratory conditions. TPM and tar delivery were measured using standard analytical techniques of the tobacco industry. The average TPM/puff was 0.35 mg and the average tar/puff was 0.28 mg.

Example 2 677.7 g of bright tobacco (-60 mesh) having a moisture content of 11.56% OV was combined with 144 ml 95% ethanol and 138 g water. The mixture was stirred in a Hobart mixer for 30 minutes, covered and left at ambient temperature for 1.5 hours. The percent solids prior to extrusion was 65.82%.

The equipment and conditions for extrusion were the same as those of Example 1. The die pressure during the collection of samples was approximately 500 psig, and the maximum melt temperature of the extrudate at the die head was 1 10"F. The extruded tubes had an outer diameter of 8 mm and an inner diameter of 7 mm and a wall thickness of 0.5 mm.

The tubes were allowed to dry overnight at room temperature. Representative samples were cut to 85 mm lengths, having an average weight of 12.64 mg/mm. The calculated density was 1.073 g/cc. The static burn was determined as in Example 1 and found to be 3.52 mm/min. TPM and tar delivery/puff, also determined as in Example 1, were found to be 0.26 mg and 0.16 mg respectively.

In addition, the smoke from the third puff of four tobacco tubes was collected and their gas phase constituents measured using gas chromatography techniques. The average gas concentrations of the third puff of the four samples was as follows: O2 - 9.61 mg/tube third puff CO - 0.07 mg/tube third puff CO2 - 1.11 mg/tube third puff Finally, average pressure drop (AP) of five representative 85 mm tubes was found to be 1.56 inches of H2O.

Example 3 564.7 g bright tobacco (-60 mesh) having a moisture content of 11.5% OV was combined with 120 ml of 95% ethanol and 115.3 g water in the same manner as described in Example 2. The mixture was stirred for 25 minutes and thereafter was allowed to stand covered overnight. Priorto extrusion, the mixture had a solids content of 65.05%.

The die of the extruder was modified to extrude a tobacco tube having an outer diameter of 8 mm and an inner diameter of 5 mm. Employing the equipment of Example 1,the extrusion conditions were as follows: Extrusion Conditions

PSIG Head Time Pressure Melt TOF minutes 0 75 5 minutes 550 85 10 minutes 450 98 15 minutes 375 105 20 minutes 375 106 25 minutes 375 109 30 minutes 375 110 34 minutes 350 112 The extruded tubes were dried overnight at room temperature.Representative examples of tubes extruded between the time interval of 6 to 10 minutes were coded A and additional tubes extruded between approximately 23 and 28 minutes were coded B.

Representative tobacco tubes were analyzed and the results are tabulated in Table 1 below.

Table 1

Inches Units mg/mm g/cc of H2O mm/minute mg mg mg mm Rod AP for Static Burn TPM Tar Third Wall Example Weight Density 85 mm Rate ----- ----- PuffCO Thickness Puff Puff 3A 31.69 1.035 0.60 1.91 0.36 0.28 0.16 1.5 3B 32.51 1.061 4.65 1.21 0.22 0.18 0.09 1.5 Example 4 443.21 g burley tobacco (-60 mesh) having a moisture content of 9.75% OV was stirred in a Hobart mixer with 96 ml of 95% ethanol and 100.8 g water for approximately 25 minutes. The mixture had a solids content of 64.5% prior to extrusion.

Burley tobacco tubes having an outer diameter of 8 mm and an inner diameter of 6.5 mm were extruded using the Wayne plastics extruder perviously described and under the same conditions as in Example 2 with the exception that the gearing on the extruder was changed to increase the range of rotation of the screw from 0 to 120 rpm. During extrusion at 120 rpm, the maximum head pressure was 2500 psig and the maximum melttemperaturewas 151"F.

Tobacco tubes were successfully extruded. See also Example 11.

Example 5 440.8 g of Oriental tobacco (-60 mesh) having a moisture content of 9.25% OV was combined with 96 ml 95% ethanol and 103.2 g water. The mixture was stirred for 25 minutes and extruded using the same extrusion conditions and equipment as in Example 4. The maximum head pressure was 600 to 700 psig and maximum melt temperature was 110 F. The tobacco tubes exiting the extruder die were found to be slightly sticky and were more flexible than either bright or burley tobaccos. With regard to static burn, see Example 11.

Example 6 A blended tobacco tube was prepared using the following ingredients: 220.1 g bright tobacco at 9.12% OV, 110.8 g burley tobacco at 9.75% OV, 110.8 g Oriental tobacco at 9.25% OV, 96.0 ml 95% ethanol and 102.0 g water. All starting tobacco materials were -60 mesh.

The dry tobacco materials were blended in the Hobart mixer and the alcohol and water were added.

After 25 minutes of mixing, the material was extruded as previously described in Example 4. The maximum head pressure was 950 psig and the maximum melttemperaturewas 112"F.

The blended extruded tobacco tubes exiting the die appeared to be more flexible than a tube of all bright tobacco but less flexible than a tube of all burley or all Oriental tobacco.

Example 7 An all bright tobacco tube was extruded using the same procedure and die as in Example 4. The ingre dients employed were 440.1 g bright tobacco (-60 mesh) at 9.12% OV, 96.0 ml 95% ethanol and 103.9 g water.

During extrusion, the maximum head pressure reached 1400 psig and the maximum melt temperature was 116"F.

Example 8 The following tobacco constituents were blended in a Hobart mixer: 220.1 g brighttobacco (-60 mesh) at 9.12% OV 110.9 g burley tobacco (-60 mesh) at 9.75% OV 110.2 g Oriental tobacco (60 mesh) at 9.25% OV To the tobacco mixture was added in an alternating manner 102.9 g water and 26.0 ml of a cigarette flavorant solution in 70 ml of ethanol. After all the solutions were added, the total mixture was stirred for an additional 25 minutes.

The tobacco mixture having a total solids content of 64.5% was then extruded using the Wayne Plastics 1" extruder. Zones 1 through 3 there maintained at room temperature during extrusion. The maximum head pressure was 950 psig and the maximum melt temperature was 1270F. The extruded tubes, having an outer diameter of 8 mm and an inner diameter of 6.5 mm, appeared to be very pliable as they exited the die. See also Example 11, especially Table 3.

Example 9 In a manner similar to Example 8, the following ingredients were combined and mixed in a Hobart mixer: 220.1 g bright tobacco (-60 mesh) at 9.12% OV 110.8 g burley tobacco (-60 mesh) at 9.75% OV 110.2 g Oriental tobacco (-60 mesh) at 9.25% OV 10.0 g mixed sugar solution 96.0 ml 95% ethanol 92.9water The water and ethanol were mixed and added to the tobacco materials in an alternating manner with the sugar solution. Mixing continued for 25 minutes after all ingredients were added. The percent solids was 64.5%.

Tobacco tubes were extruded in the same manner as that of Example 8. During extrusion, the maximum head pressure was 900 psig and the maximum melt temperature was 126"F.

The extruded tubes were dried in an oven at 10000 overnight. Sampletubes lighted immediately after removal from the oven would maintain a static burn.

Tubes which had been dried in the oven and then equilibrated in ambient air at room temperature would also static burn, although some tended to go out and required relighting.

Example 10 The following ingredients were combined and mixed in a Hobart mixer: 286.1 g bright tobacco (-60 mesh) at 9.12% OV 110.8 g burley tobacco (-60 mesh) at 9.75% OV 44.1 g Oriental tobacco (-60 mesh) at 9.25% OV 10.0 g mixed sugar solution 13.0 ml flavorant solution (humectant and flavorants) 92.2 ml 95% ethanol 106.4 g water The materials were blended for approximately 25 minutes following addition of all ingredients. The percent solids was 64.5%. Extrusion of tobacco tubes having an 8 mm outer diameter and 6.5 mm inner diameter was conducted under the conditions described in Example 8. The maximum head pressure noted was 700 psig and the maximum melt temperature was 1260F.

Selected representative tubes were dried overnight in an oven at 100 C. The dried tubes successfully burned. Tubes that had been dried and equilibrated at ambient room temperature would also static burn. It was noted on burning that a distinctive cigar aroma was produced by the tobacco tube.

Example ii Representative extruded tubes from Examples 4 through 7 were dried in an oven at 1000C overnight.

One-half of the tubes were lit immediately after removal from the oven to determine whether a static burn could be maintained. The remaining half were equilibrated in ambient air at room temperature overnight and then tested for static burn. The results are set forth in Table 2.

Table2

Example Dried Dried and Equiiibrnted 4 Burned Burned 5 No Static Burn No Static Burn 6 Burned Burned 7 Burned Burned As to the second item in Table 2, however, when the extruded tubes of Example 5 (and a comparison specimen from Example 8) were subjected to the water treatment described below, it was found that substantially improved combustion properties were obtained.

Extruded tubes were cut to a length of 100 mm and were then submerged in water so that a length of 50 mm per tu be became wet. The tubes were dried in a microwave oven and conventional cellulose acetate filters were attached to the untreated end of each tube. The static burn rate and length of tube which burned were determined. The results are tabulated below in Table 3.

Table3

Time Submerged Static Burn Sample Seconds Rate Length Burned Example 5 30 no burn Example 5 45 no burn Example5 60 0.75 10 mm Example 5 90 1.81 50 mm Example 8 30 2.58 50 mm Example 13 433.1 g of bright tobacco (-60 mesh) having 7.46% OV was combined with 96 g of 95% methanol and 110.9 g water. The material was mixed in a Hobart mixer for 25 minutes at room temperature.

The tobacco mixture, having approximately 62.5% solids, was extruded using a Wayne plastic extruder equipped with an 8 mm outer diameter and 7 mm inner diameter tubing die. Extrusion conditions were same as those employed in Example 4. The pressure in the extruder increased to 1,200 psi as the first tubes were collected and when the extrusion was terminated 17 minutes later, the pressure was recorded at 1,000 psi.

The hollow, extruded tubes were dried overnight at room temperature. The outer walls of the tubes appeared to be very smooth and dense. Attempts to static burn the tubes were unsuccessful.

Extruded tubes, 100 mm in length, prepared as above were immersed in waterto a depth of 50 mm for varying periods of time. The tubes were thereupon dried in a microwave oven for 2 minutes. The pressure drop of each tube was determined priorto and afterwatertreatment and redrying. The results are shown in Table 4.See also Example 19 Table4

Pressure Drop -- Inches of H20 Time Submerged Seconds Before After 5 60.99 60.54 10 60.50 57.71 15 60.62 52.07 20 60.57 16.48 25 60.71 10.21 30 60.05 5.70 The results indicate that rewetting and redrying significantly modify the tube wall thereby decreasing the pressure drop.

Example 14 In a mannersimilarto Example 13, the following materials were combined and mixed in the Hobart mixer to form a mixture having 62.5% solids which was extruded using the Wayne plastics extruder: 324.8 g bright tobacco (-60 mesh) at 7.65% OV 72.0 g 95% n-propyl alcohol 83.2 g water The initial material that exited the extruder appeared to be quite dry. Extrusion continued for approximately 15 minutes; production of tubing was slower than normally observed. The extruded hollow tubes were dried overnight at room temperature. The tubes, when ignited, would static burn.

Example 15 In a manner similar to Example 13, the following ingredients were combined and mixed to form a mixture having 62.5% solids which was extruded using the Wayne plastics extruder: 324.8 g bright tobacco (-60 mesh) at 7.64% OV 72.0 g 95% isopropyl alcohol 83.0 g water The pressure in the extruder rose to 1,300 psi during extrusion. The extruded hollow tubes had good mechanical properties. After drying overnight at room temperature, the tubes were tested for static burn. The tubes would not maintain static burn under normal testing conditions. However, see Example 19 with regard to subsequent treatment.

Example 16 In a mannersimilarto Example 13, the following materials were combined, mixed 25 minutes and then extruded: 324.8 g bright tobacco (-60 mesh) at 7.64% OV 72.0 g 95% tert-butyl alcohol 83.2 9 water During extrusion the pressure varied between 1100 and 1475 psig. The hollow tubes extruded appeared to have poor mechanical properties when wet. The solvent tended to evaporate rapidly on exiting the die and the tubes turned lighter in color as the solvent evaporated. After drying overnight, the extruded tubes were tested for static burn. After burning for approximately 2 minutes, the tube went out. However, see Example 19 with regard to subse quent treatment.

Example 17 Using the procedure of Example 13, the following materials were combined and mixed to form a 62.5% solid mixture which was extruded: 324.8 g bright tobacco (-60 mesh) at 7.64% OV 72.0 g 95% methylene chloride 83.2 g water During extrusion the pressure rose to about 1,500 psi. The mechanical properties of the extruded hollow tubes were excellent. The tubes exhibit a high degree of plasticity and could be stretched without rupturing. Lengths greater than 1 meter could be extruded successfully. The dried tubes would not maintain static burn. However, see Example 19 with regard to subsequent treatment.

Example 18 Using the procedure of Example 13, the following materials were combined and mixed to form a mixture having 62.5% solids which was extruded: 332.2 g bright tobacco (-60 mesh) at 9.7% OV 34.2 g methylene chloride 36.0 g ethanol 77.0water On extrusion, the tubes exhibited some plasticity; however, it was not as great as observed when methylene chloride was used as the major solvent.

Static burn was achieved by subsequent treatment as noted in the following example.

Example 19 Representative tubes prepared in Examples 13, 15, 16,17 and 18 were cutto a length of 100 mm. The tubes were immersed in water for 30 seconds in such a manner that 50 mm of each tube came in contact with the water. The tubes were dried for 2 minutes in CEM Corporation Model AVC-MP microwave oven at maximum power. Conventional cellulose acetate filters were attached to the untreated end of each tube after drying. The tubes were secured by the filter end and the water treated end was ignited. The static burn rate was based on the time required to burn the 50 mm water treated portion of the tube. The results are tabulated below in Table 5. TableS

Example Solvent and Tobacco Static Burn Rate mmlmin.

13 Methyl Alcohol 1.85 15 Isopropyl Alcohol 3.64 16 Tert-Butyl Alcohol 2.13 17 Methylene Chloride 18 Methylene Chloride-Ethanol 2.42 'The tube immersed for 30 seconds would not static burn.

After immersion for 45 seconds, the tube burned for 8 minutes 5 seconds and went out. After relighting the tube burned for an additional 6 minutes 35 seconds. Total length burned was 10 mm.

The results indicatethatwhen dried extruded tobacco tubes are subjected to a water treatment, the tube wall is modified in such a manner that combustion properties of the tube are improved.

Example 20 The following ingredients were combined and mixed in a Hobart mixer for approximately 25 minutes: 154.05 g bright tobacco (-60 mesh) at 9.15% OV 61.53 g PCB * carbon (-40 +60 mesh) at 2.48% OV 48.0 ml 95% ethanol 56.4 gwater * PCB = Pittsburgh Coal Carbon -40 +60 mesh The tobacco-carbon mixture having 64.5% solids was dark but appeared to have the same consistency as previous mixtures used.

Using extrusion conditions from Example 8, tobacco-carbon tubes were produced wherein the outer diameter was 8 mm and the inner diameterwas 6.5 mm. During extrusion the maximum head pressure was 2000 psig and the maximum melt temperature was 1 060F.

After drying overnight, the tobacco-carbon tubes would maintain a static burn.

Example 21 Tobacco-carbon tubes wherein carbon represented approximately 40% of the total solids in the formulation were prepared using the following ingredients: 206.7 g brighttobacco (-60 mesh) at 9.12% OV 130.3 g PCB carbon (-60+140 mesh) 75.1 ml 95% ethanol 88.7 g water (64.5% solids) Tobacco-carbon tubes were extruded wherein the outer diaterwas 8 mm and the inner diameter was 5 mm. The Wayne plastics extruder was modified to include a low restriction spider to improve flow properties.

The extruder conditions were as follows: Zonel - 100"F Zone2 - 150"F Zone3 - 2000F Die - 250"F Screw speed 120 rpm During extrusion the head pressure built up to about 600 psig and this was followed by rapid extrusion of tube product As the pressure dropped, tube production ceased; however, with pressure build up, product was again extruded.

Samples of extruded tubes were dried overnight and tested for static burn. All samples maintained a static burn.

Example 22 The following ingredients were combined and mixed in a Hobart mixer: 154.0 g brighttobacco (-60 mesh) at 9.12% OV 60.0 g calcium carbonate at 0.06% OV (-50 mesh) 48.0 ml 95% ethanol 57.9 g water (64.5% solids) After mixing for 25 minutes, tobacco tubes were extruded using the conditions described in Example 8. The maximum head pressure reached 1000 psig during extrusion. The extruded tubes appeared to have a diameter slightly largerthan 8 mm. This may be due to expansion caused by the carbonate salt.

Example 23 Bright tobacco, 222.3 g, -60 mesh at 10.09% OV, was combined with 84.8 g of water and mixed in a Hobart mixer for 1 hour and 20 minutes. Fifty g of ammonium carbonate at 20% OV was added and the mixture was stirred for 10 minutes.

The material was extruded using the Wayne plastic extruder under the following conditions: Zone 1 - 30"C Zone2 - 50"C Zone3 - 70"C Die - 1000C Feed cooling water on Straight tubing die (8 mm outer diameter, 7 mm inner diameter) No die head pressure was observed; the die temperature was reduced to 90"C during extrusion.

A representative example of the extruded tubes, cut to a 85 mm length, was equilibrated overnightto 60 RH in a humidity cabinet. On ignition with a gas flame, the hollow tube maintained a static burn for over 6 minutes. a 20 mm section of the tube had a burn rate of 0.185 mm/second.

Example 24 200.2 9 bright tobacco (-40 +60 mesh) at 10.0% OV and 150.0 g tobacco slurry containing diammonium phosphate and having 18.0% solids content (the slurry being of a type prepared according to U.S. Patent 3,353,541) were blended in a Hobart mixer for2 hours to give a mixture having approximately 59.12% solids.

The material, which tended to form small balls, was successfully extruded using the Wayne plastics extruder. All three zones and the die were initially at room temperature and no cooling was used during extrusion. Screw speed was between 30 to 60 rpm; head pressure was 700 psig.

Extrusion was stopped and the die temperature was raised to 100 C. Additional tubes having 8 mm outer diameter and 7 mm inner diameterwere successfully extruded.

Upon ignition with a gas flame, a sample of the latter tubes static burned for approximately 3 minutes, 20 seconds.

Example 25 222.3 g of bright tobacco (-40 mesh) having a moisture content of 10.05% OV was combined with 111.0 g water. The mixture was stirred in a Hobart mixer for 1.5 hours.

The tobacco mixture having a solids content of 60% by weight was then fed into the hopper of the extruder described in Example 1 and an attempt was made to extrude 8 mm O.D. x 7 mm I.D. hollowtobaccotubes.

The initial temperatures controller settings were as follows: Zone 1 - 30"C Zone2 - 50"C Zone3 - 70"C Die - 100"C Hopper cooling water on robacco tubes were extruded under these conditions. Steam was noted to exit the die during extrusion. The temperature of Zone 3 was then raised to 100 C. Tobacco tubes were extruded under these conditions and more steam was noted to exit the die than at the 70 C setting.

The temperature of the die was then raised to 140"C. Tobacco tubes were extruded under these conditions. Steam was noted to exit the die and the exterior surface of the extruded tubes was more irregular (not smooth) than under previous conditions. None of the samples extruded under the above extrusion conditions would maintain static burning, suggesting the need for post-treatment or other means for controlling porosity.

Example 26 112.5 g of brighttobacco (-40 +60 mesh) having a moisture content of 11.06% OV was combined with 61.33 g water and 17.0 g 95% ethanol.

The mixture was stirred in a Hobart mixer for 1.25 hours. 112.5 g of brighttobacco (-20+40 mesh) having a moisture content of 11.06% OV was then added to the mixture and stirred for an additional 15 minutes. The tobacco mixture having a solids content of 65.9% by weight was then fed into the extruder hopper in an attempt to extrude 8 mm O.D. x 7 mm I.D. hollow tobacco tubes.

The extrudertemperature controls were set as follows: Zone 1 - ambient Zone 2 - ambient Zone 3 - ambient Die - off Hopper cooling water off Ambient temperature settings were obtained by positioning the controller setting to such a position that the controller supplied neither heat nor cooling. The temperature was 21 0C.

Hollow tobacco tubes were extruded, placed on paper towels and allowed to dry in room air overnight. The tubes would maintain static burn when dried.

Example 27 1092.2 g of brighttobacco (-60 mesh) having a moisture content of 8.44% was combined with 268.3 g water and 189.9 g 95% ethanol. The mixture was stirred in a Hobart mixer for 35 minutes.

The tobacco mixture having a solids content of 64.5% by weight was then divided into two parts. Approximately 3/4 of the mixture was fed into a Wayne Machine and Die Company table top extruder with a 1-inch barrel. The extruder was supplied with four automatic temperature controls, three zones on the barrel and one on the die, water cooled hopper feed, cooling fans mounted on the barrel, a 1:1 extrusion screw, and a 0 to 10,000 psi Gentron No. GT-90 pressure gauge. One-fourth of the mixture was placed in the hopper feeder of a Wayne plastics extruder Model No. 2417. The model No. 2417 extruder was modified to take a 1 inch water cooled barrel, a 1 inch 1:1 extrusion screw, and an automatic hopper feeder. It was mated to the extruder referred to above via a modified Wayne Machine & Die Company cross-head die.

The Model No. 2417 extruder was then operated in such a manner as to sequentially extrude the tobacco mixture into the open passage of coextruded hollow tobacco tubes which were being extruded by the extruder described above.

The sequential extrusion of the tobacco mixture into the 8 mm O.D. x 7 mm l.D. tubes resulted in a succession of plugs, approximately 5 mm in length, located at approximately 70 mm intervals along the longitudinal axis of the hollow tubes. The extrusion conditions of the hollow tubes were as follows: Zone 1 - 50 C Zone2 - 70 C Zone3 - 90"C Die - 200"C Hopper cooling water on Used cross-head die and coextrusion Some samples from this extrusion were placed in a CEM Model AVC-MP microwave oven and dried at 1/2 power for five minutes.

The samples so dried would maintain static burn.

Additional samples of extrudate were allowed to air dry on a paper towel overnight. These samples were then cut into smokable lengths by cutting the tube samples at the midpoint of each plug resulting in samples 75 mm in length with tobacco plugs of 2.5 mm thickness, located at each end. Several small holes were then drilled longitudinally through the plugged ends of the samples using number 80 and number 69 drill bits to enable the samples to be puffed on by a smoker. Cellulose acetate filters approximately 20 mm in length were then attached to one end of the samples with cellophane tape.

These samples would not maintain static burn. The samples were then dipped into water for 2 seconds and allowed to dry in room air overnight. After drying, the samples would maintain static burn and could be smoked.

Example 28 372.2 g of brighttobacco (-60 mesh) having a moisture content of 8.44% OV was combined with 81.67 g water, 57.4 g 95% ethanol and 3.03 g tert butyl - p - menthanecarboxamide. The mixture was stirred in a Hobart mixer for 25 minutes.

The tobacco mixture having a solids content of 64.5% by weight was then divided into two parts and extruded under similar conditions as described in Example 27.

Plugged tube samples extruded in this manner were dried in a microwave for five minutes at one-half power (181.4 watts). These samples would maintain static burn.

Smokable samples were produced from air dried extrudate by the same procedure used in Example 27. These samples would not maintain static burn but would burn sufficiently so that they could be lit and smoked in a normal man ner. A menthanol-like cooling was detected when these samples were smoked.

Example 29 338.8 g of brighttobacco (-60 mesh) having a moisture content of 11.46% OV was combined with 69.2 g water and 56.8 g 95% ethanol. The mixture was stirred in a Hobart mixer for 35 minutes.

The tobacco mixture having a solds content of 64.5% was fed into the extruder referred to in Example 26 and 8 mm O.D. x 7 mm l.D. hollow tobacco tubes were extruded under similar conditions as described in Example 26.

Samples of the extrudate were placed on paper towels and allowed to dry in room air overnight.

Some samples collected during the time interval of 5.5 to 7.0 minutes of extrusion were selected for analysis. The results of the analysis were as follows: Sample weight 12.96 mgimm Wall density (calculated) 1.100 g/cc AP (85 mm) 3.94 inches H20 Static burn rate 23.46 mm/min TPM/puff .16 mg Tar/puff .10 mg Third puff CO delivery .03 mg Example 30 451.8 g of brighttobacco having a moisture content of 11.46% OV was combined with 92.2 g water and 75.7 9 95% ethanol. The mixture was stirred in a Hobart mixer for 25 minutes.

The tobacco mixture having a solids content of 64.5% by weight was then fed into the Wayne Machine and Die Company table top extruder referred to in Example 27. The die of the extruder was modified to extrude 8 mm O.D. x 6 mm l.D. hollow tubes. The extrusion conditions were the same as Example 26.

The extruded tobacco tubes were placed on papertowelsto dry overnight in room air.

Extrudate samples collected during the time interval of 5.5 to 7.5 minutes of extrusion were selected for analysis. The results of the analysis were as follows: Sample weight 19.87 mg/mm Wall density .904 g/cc AP (85 mm) 6.77 inches H2O Static burn rate 31.20 mm/min TPM/puff .21 mg Tar/puff .17 mg Third puff CO delivery .06 mg

Claims (53)

1. A smoking article characterised by a coherent mass of combustible tobacco-containing material having at least one passage extendingthrough it between an opening in the surface of the mass and a second opening spaced from the first, the said tobacco mass having such porosity as to support combustion when ignited and such density and porosity as to substantially occlude gas flow through the mass itself.

2. A smoking article according to claim 1, characterised by an air-permeable plug of readily ignitable material blocking the said passage at one end.

3. A smoking article according to claim 2, characterised by at least one additional air-permeable plug blocking the passage at a position spaced from the first plug.

4. A smoking article according to claim 3, characterised in that the additional plug is at the other end of the passage.

5. A moking article according to any of claims 1 to 4, characterised by a passage extending axially through a cylindrically shaped mass.

6. A smoking article according to claim 5, characterised in that the cross-sectional area of the passage is greater than the corresponding area of the mass.

7. A smoking article according to any of claims 1 to 6, characterised in that the tobacco-containing material comprises extruded comminuted tobacco.

8. A smoking article according to claim 7, characterised inthatthecomminutedtobacco is less than 30 mesh (0.6 mm).

9. Asmoking article according to any of claims 1 to 8, characterised in that the tobacco-containing material further comprises non-tobacco filler particles.

10. Asmoking article according to claim 9, characterised in that the filter particles are selected from carbon, calcium carbonate diatomaceous earth and attapulgite.

11. A smoking article according to any of claims 1 to 10 characterised in that the tobacco-containing material further comprises a burn additive.

12. A smoking article according to any of claims 2 to 11, characterised in that at least one plug blocking the said passage contains a flavorant.

13. A method of producing smoking articles, characterised by shaping a mixture of combustible tobacco material with at least one volatile liquid under pressure into a discrete coherent mass; forming a passage through the mass; and drying the mass, the mixture composition, the shaping pressure and the drying conditions being controlled to confer on the mass a porosity and density such as to substantially occlude gas flow thereth rough but to support combustion when ignited.

14. A method according to claim 13, characterised in that the through passage is formed during shaping of the mass.

15. A method according to claim 13, characterised in that the through passage is formed subse quest to shaping of the mass.

16. A method according to any of claims 13 to 15, characterised in that the tobacco mixture has a solids content of 55 to 75 weight percent, preferably 60 to 70 percent solids.

17. A method according to any of claims 13 to 16, characterised in that the tobacco material is comminuted.

18. A method according to claim 17, character ised in that the tobacco material has a mesh size of less than 30 mesh (0.6 mm), preferably less than 60 mesh (0.25 mm).

19. A method according to any of claims 13 to 18, characterised in that the mixture additionally contains a non-binder material.

20. A method according to any of claims 13 to 19 characterised in that the said liquids comprise water and a volatile organic liquid.

21. A method according to claim 20 characterised in that the organic liquid is a low molecular weight alcohol compatible with tobacco, for example ethanol.

22. A method according to claim 20 or 21 characterised in that the ratio of organic liquid to water is between 1:6 and 1:1, and preferably between 1:2 and 1:1.

23. A method according to any of claims 13 to 22 characterised in thatthe tobacco material and other ingredients are mixed together until a substantially homogenous mixture is obtained.

24. A method according to claim 23 characterised in that mixing is carried out for 15 minutes to several hours.

25. A method according to claim 23 or 24 characterised in that the tobacco material and otheringre- dients are mixed in a closed environment to prevent volatilization of the organic liquid.

26. A method according to any of claims 23 or 25 characterised in that the tobacco material is comminuted prior to mixing.

27. A method according to any of claims 13 to 26 characterized in that the said mixture is shaped into a coherent mass by extrusion.

28. A method according to claim 27 characterised in that extrusion is carried out with minimum working of the tobacco mixture but under sufficient pressureto release the natural binding agents contained in the tobacco material.

29. A method according to claim 27 or 28 characterised in that the tobacco mixture is forced fed to the extrusion mechanism.

30. A method according to any of claims 27 to 30 characterised in that extrusion is carried out by screw extrusion, preferably with an extruder having a 1:1 screw.

31. A method according to claim 30 characterised in that the extrusion of the tobacco mixture is at a melt pressure equal or less than 17.25 Pa (2500 psi), preferably equal to or less than 8-25Pa (1200 psi).

32. A method according to claim 31 characterised in that the said tobacco mixture during extrusion is at or below a melt temperature of 40"C.

33. A method according to claim 27 characterised in that the extrusion is carried out by ram extrusion.

34. A method according to any of claims 27 to 33 characterised in that the extrusion produces a substantially cylindrically shaped mass.

35. A method according to claim 34 characterised in that a passage is formed along the axis of the cylindrically shaped mass, preferably defined by an inner surface of the shaped mass.

36. A method according to claim 35 characterised in that the extruded cross-sectional area of the mass normal to its axis is less than the crosssectional area of the passage normal to the same axis.

37. A method according to any of claims 13 to 36 characterised in that one or more porous readily ignitable plugs is or are inserted into the passage of the shaped mass.

38. A method according to claim 37 characterised in that a plug is inserted by extruding plug material into the passage.

39. A method according to claim 38 characterised in that the tobacco mixture and the plug material are extruded concurrently.

40. A method according to claim 39 characterised in that the extrusion of the plug material is intermittent.

41. A method according to claim 40 characterised in that the said mass is cut transverse to the said axis at positioned at which the plug material is located in the passage.

42. A method according to claim 41 characterised in that the cut passes through the plug material.

43. A method according to claim 41 or 42 characterised in that cutting occurs concurrently with the extrusion of the tobacco mixture and, is preferably synchronized therewith.

44. A method according to any of claims 39 to 43 characterised in that force is applied to the wall of the extruded tobacco mixture to cohesively join the tobacco mixture to the extruded plug material.

45. A method according to any of claims 39 to 43 characterised in that the plug material is allowed to expand and cohesively join itself to the wall of the extruded tobacco mixture.

46. A method according to any of claims 13 to 45 characterised in that drying is effected by subjecting the shaped mass to heat.

47. A method according to claim 46 characterised in that drying is effected by hot air, preferably at a temperature of about 100 C for a period of 15 minutes to 1 hour.

48. A method according to claim 46 characterised in that drying is effected by subjecting the shaped mass to microwave energy.

49. A method according to any of claims 13 to 45 characterised that the drying is effected by exposing the shaped mass to ambient atmosphere, preferably at a temperature within the range of 21 to 240C (70 to 75"F) for a period of 12 to 24 hours.

50. A method according to any of claims 13 to 49 characterised in that the dried mass is rewetted and redried.

51. A method according to claim 50 characterised in that rewetting is carried out for a period sufficient to adjust the porosity of the mass to a desired value after redrying.

52. Asmoking article substantially as described with reference to any one of Figs. 1 to 5 herein.

53. A method of producing smoking articles substantially as described with reference to any of the drawings.