GB2159036A - Improvements relating to the manufacture of reconstituted tobacco - Google Patents

Abstract

A process for manufacturing reconstituted tobacco from tobacco stems and tobacco fines includes treating in a dry state the tobacco stems to reduce the stems to a fibrous form, mixing the fibrous tobacco stems with tobacco lamina fines, depositing the mixture on a moving mesh screen, whereon it is formed into a felt-like mat or sheet of generally uniform thickness and removing the reconstituted tobacco sheet from the mesh screen for further processing to produce a tobacco smoking article.

Description

SPECIFICATION Improvements relating to the manufacture of reconstituted tobacco This invention relates to the manufacture of reconstituted tobacco comprising tobacco stems and tobacco fines.

During the manufacture of tobacco products such as cigarettes, cigars and pipe tobacco, a portion of the tobacco is broken up and is therefore too small to be used in the tobacco product. The stems and veins are removed from the tobacco leaves purchased from the grower and thus also from byproducts in manufacture. It has been the general practice of tobacco product manufacturers to process the fines and stems, and mixtures thereof, into reconstituted tobacco which is produced generally in a sheet-like form. The reconstituted tobacco is mixed with the tobacco and thereafter cut and incorporated into the tobacco products.

The manufacture of reconstituted tobacco has been practised for many years. Most commercial processors involved in the manufacture of reconstituted tobacco adopt a series of steps which consist of mixing the tobacco materials with water and grinding the materials to a smaller particle size to form a slurry. The slurry is then cast on an endless band and heated to remove the water.

Binder material, such as Guar Gum, Methylcellulose or Sodium Carboxymethylcellulose, is added to the slurry to assist in forming a coherent sheet. Further, it is known to use the so-called "paper" process where the tobacco is extracted and the tobacco fibres are processed on conventional paper equipment wherein the fibres are formed into a sheet on conventional paper machines. The tobacco extract is concentrated and added back to the "paper" using a conventional sizing process. The sized reconstituted tobacco is then dried to remove excess water.

These conventional processes for manufacturing reconstitited tobacco treat the fine tobacco harshly.

These treatments tend to change the flavour characteristics of the starting tobacco and, depending on the temperature used in drying, drive off or change the natural tobacco characteristics.

These conventional processes for producing reconstituted tobacco also require large amounts of energy in the form of steam energy to remove the water used as the vehicle to cast the slurry.

It is an object of the present invention to provide a process for manufacturing reconstituted tobacco of tobacco stems and tobacco fines, which process is simple, requires comparatively low energy and manpower inputs, and minimises the treatment to which the tobacco materials are subjected and the reduction of taste and flavour characteristics.

The present invention provides a method of manufacturing reconstituted tobacco of tobacco stems and tobacco fines comprising treating stem parts of tobacco in essentially a dry form to reduce the stem to substantially fibrous form, mixing the fibrous stem with fine lamina tobacco, depositing the mixture of fibrous stem and fine lamina tobacco on a moving, continuous mesh belt to form a continuous non-woven felt sheet of fibrous stem and lamina particles on said belt, and removing said sheet from said belt in a form for use in the manufacture of tobacco smoking articles.

In order that the invention may be clearly understood and readily carried into effect, reference will now be made, by way of example, to the accompanying schematic drawings, wherein like numerals refer to like parts throughout, and in which: FIGURE 1 shows a system for carrying out the process of the present invention; FIGURE 2 shows an alternative advantageous embodiment of a stage of the system of Figure 1; FIGURE 3 shows a further advantageous embodiment of a stage of the system of Figure 1; and FIGURE 4 shows a yet further advantageous embodiment of a stage of the system of Figure 1.

The schematic of Figure 1 shows a system, generally denoted by the numeral 10, for carrying out the process of the present invention for manufacturing reconstituted tobacco.

The system 10 comprises a fibrillation stage 12, a mixing stage 14, and a reconstituted tobacco sheet forming stage 16.

Tobacco stems are fed from a source of tobacco stems 18 to the fibrillation stage 12 wherein the particle size of the stems is reduced to a size suitable for use in a smoking article. The fibrillation stage 12 can include, for example, a hammer mill or a disc refiner.

Tobacco fines are fed from a source of tobacco fines 20 to the mixing stage 14, and the fibrillated stems are fed from the fibrillation stage 12 to the mixing stage 14. The tobacco fines and fibrillated tobacco stems are thoroughly mixed together in the mixing stage 14to form a homogeneous mixture.

The mixing stage 14 should be capable of not only mixing the fines and stems together, but also of preventing clumping of the mixture. Towards this end, an air mixing device has been found to be advantageous for the mixing stage 14. The air mixing device utilises an air stream to tumble and, thereby, mix the tobacco fines and fibrillated stems and break up clumps of material.

The homogeneous mixture of fines and fibrillated stems is then transferred to the sheet forming stage 16 for forming a mat of the mixture. As shown, the sheet forming stage 16 comprises a reticulated endless belt conveyor 22. The mixture of fines and fibrillated stems is fed to a preselected area on the top flight of the belt conveyor 22 in an air stream passing through a duct 24 communicating at one end with the mixing stage 14 and at the other end with the preselected area on the top flight of the belt conveyor 22. An air moving means 26, such as a blower, can be associated with the air duct 24 to generate the air stream through the duct 24 from the mixing stage 14 to the preselected area of the top flight of the belt conveyor 22. An air plenum chamber 28 is located beneath and open to the top flight of the belt conveyor 22 at the preselected area.

A suction fan 30 is operatively associated with the plenum chamber 28 to create an air flow downwardly through the preselected area of the belt conveyor top flight into the plenum chamber 28 as indicated by the flow arrows "A". Preferably, the air duct 24 directs the mixture of fines and fibrillated stems generally downwardly onto the preselected area of the belt conveyor top flight. As the mixture is deposited on the preselected area of the moving conveyor belt top flight, the air flow moving downwardly through the preselected area produces a relatively even distribution of the tobacco mixture, thus forming a tobacco sheet 32 of generally uniform thickness on the belt conveyor top flight.

The tobacco sheet forming stage 16 can also include tobacco binder application means 34, such as spray nozzles, for directing a tobacco binder material onto the tobacco sheet 32 moving from the preselected area of the belt conveyor top flight Further, drying means 36 is provided downstream, relative to the direction of travel of the belt conveyor top flight, of the binder application means 34 to aid in the rapid drying of the binder in the tobacco sheet 32 moving with the belt conveyor top flight. As illustrated, the drying means 36 includes a hood 38 located over the belt conveyor top flight by a distance adequate to allow the tobacco sheet 32 to pass therebeneath. An air flow, indicated by flow arrows "B", upwardly through the tobacco sheet 32 and into the hood 38 can be created by air moving means 40, such as a fan, in association with the hood 38.

As an additional option feature of the apparatus 10, calender rolls 42 can be provided along the path of the tobacco sheet 32 to further compress the tobacco sheet 32 to further reduce its thickness.

With reference to Figure 2, it is contemplated that the binder material can be added to the tobacco fines and fibrillated tobacco stems being mixed in the mixing stage 14. This can be accomplished by supplying the binder from a source of binder 134, thus eliminating the binder application means 34 at the belt conveyor 22.

Figure 3 illustrates a somewhat modified arrangement of the fibrillation stage 12 and mixing stage 14 of the apparatus 10. It is contemplated, as shown, that tobacco stems and tobacco fines can both be fed to the fibrillation stage 12 which would function not only to fibrillate the tobacco stems but also function as a pre-mixer of the stems and fines.

The pre-mixture of fibrillated stems and fines would then be conveyed to the mixing stage 14 for more thorough mixing and for breaking up any clumps which may have formed in the mixture.

Figure 4 illustrates another modification of the apparatus 10. In this embodiment, the tobacco fines are fed from the source of fines 20 to a treatment station 44. In the treatment station 44 the tobacco fines are treated to release pectin material which will function as a tobacco mixture binder. Towards this end, in the treating station 44 the tobacco fines can be mixed with diammonium phosphate or pectic enzymes. The treated tobacco fines are then transferred to a puiping station 46 wherein the treated fines are shredded. The shredded, treated tobacco fines are then fed from the pulping station 46 to the mixing stage 14 wherein they are throughly mixed with the fibrillated tobacco stems from the fibrillation stage 12 to form a homogeneous mixture to be supplied to the tobacco sheet forming stage 16 for processing as hereinabove described.

It is further contemplated that non-tobacco extenders such as cellulose fibre and inorganic materials such as alumina can be added to the reconstituted tobacco in orderto: (1) increase the volume of the reconstituted tobacco sheet without the need of using more tobacco components and (2) modify the combustibility of the reconstituted tobacco sheet. The non-tobacco extenders can be incorporated into the tobacco components at virtually any step in the process in the process. For example, the non-tobacco extenders can be added to the tobacco stems in the fibrillation stage 12, at the mixing stage 14, or at the sheet forming stage 16.

A wide variety of natural or synthetic binders are suitable for use in the present invention provided that they are not inimical to the flavour of the tobacco. Specific examples of such suitable binders include natural vegetable gums such as, for example, gum arabic, gum tragacanth, guar gum, locust bean gum, etc. Other suitable gums include carbohydrate gums from animal sources, such as glycogen, deacetylated chitin and the like, marine plant gums such as algins, carageenans, and agar.

Preferred binders which are particularly advantageous in the method of the present invention include treated cellulosic gums, such as cellulose ethers, cellulose esters and mixtures thereof. Specific examples of such binders include methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, methyl hydroxyethyl cellulose, ethylhydroxyethyl cellulose, cellulose acetate, hydroxyethyl cellulose, sodium carboxymethyl cellulose etc.

Specific examples of forming smoking tobacco material according to the process of the present invention are as follows.

EXAMPLE 1 A 50/50 mixture of flue-cured tobacco and Burley tobacco stems having approximately 12 percent moisture content by weight is passed through a double disc refiner two produce a shredded product of highly fibrillated fibres. Twenty grams of this mixture is mixed with thirty grams of cigarette tobacco waste fines, five grams of flue-cured lamina fines of -14 mesh and five grams of Burley lamina fines of -14 mesh, ail of which fines have a 12 percent moisture content by weight. The tobacco fines and fibrillated tobacco stem mixture is tumbled to evenly distribute the fibrillated stems throughout the mixture and to separate the intertwined bundles or clumps of stem fibres to form a homonogeneous mixture. The homogeneous mixture is conveyed in an air stream to, and impacted on, a 170 U.S. wire mesh screen under which a vacuum of 21 inches of Hg is applied. The homogeneous mixture is thereby evenly distributed on the screen to a thickness of approximately 20 mls to form a sheet or mat of interlaced fibrillated stem fibres and tobacco fines.

Twenty ml of a 5 percent solution of NaCMC Grade 7LF supplied by Hercules Chemical Co. is then sprayed on the sheet as a binder. The sheet is next dried in a forced draught oven at 1 OO"C. After the sheet of reconstituted tobacco is dried, it is mixed with regular strip tobacco and cut and formed into cigarettes.

EXAMPLE 2 A reconstituted tobacco sheet is prepared on a mesh screen as in Example 1. The tobacco sheet is removed from the screen and passed through a pair of calender rolls to reduce the sheet thickness from 20 mls to 10 mls. After passing from the calender rolls, the tobacco sheet of reduced thickness is dried in a forced draught oven at 100 C. The dried sheet of reconstituted tobacco is then mixed with tobacco stems, cut, and formed into a cigarette.

EXAMPLE 3 Fifty grams of Pectic enzyme is dissolved in 300 grams of water. This solution is sprayed on 500 grams of flue-cured stems to raise the total moisture content of the stems to about 60 percent by weight.

The enzyme treated stems are then maintained at about 25 C for about from 24to 48 hours to allow the pectic enzyme to break down the pectin contained in the stems. The pectins are the "glue" which hold the fibres of the stems together. After the stems are treated for a sufficient length of time to break down and loosen the fibres, the stems are passed through a double disc refiner to produce fibrillated, individual fibres. Next, 100 grams offluecured lamina fines are added to the 500 grams of fibrillated treated stems, and mixed together to uniformly distribute fibrillated stems and lamina fines and form a homogeneous mixture. This homogeneous mixture is then conveyed in an air stream to, and impacted on, a mesh screen which has a vacuum chamber therebeneath.The vacuum created by the vacuum chamber beneath the homogeneous mixture and the force of impact of the tobacco mixture as it is blown on the screen cause the homogeneous mixture to form into a felt-like sheet or mat of intertwined fibrillated tobacco stems with tobacco fines uniformly dispersed therethrough. The pectins liberated by the action of the pectin enzymes on the tobacco stems function as a "glue" to bond the intertwined, fibrillated tobacco stems and tobacco fines together to form a reconstituted tobacco leaf on the mesh screen. The sheet of reconstituted tobacco is removed from the mesh screen and subjected to heated air at 100" C for a sufficient time to reduce the moisture content to about 12 percent by weight.The reconstituted tobacco sheet is then passed through cutters to produce discreet particles which are added to cut leaf tobacco and formed into a cigarette.

EXAMPLE 4 A mixture of tobacco stem fibres and tobacco is prepared as in Example 1. To this mixture is added 20 grams of cellulose fibres prepared in a similar manner as tobacco stems.

The resulting blend of tobacco and cellulose is then tumbled together to distribute the cellulose fibres uniformly. The mixture is then formed to a reconstituted tobacco in the same manner as in Example 1.

EXAMPLE 5 A portion of the mixture as per Example 4 is mixed with an additional 20 grams alumina trihydrate (Al2O3.3H2O) and that mixture is formed into an extended tobacco as per Example 1.

EXAMPLE 6 A reconstituted tobacco is prepared and formed as per Example 1. After the binder has been added, calcium carbonate (CaCO3) is dusted on top. The sheet is then dried and removed from the screen as per Example 1.

EXAMPLE 7 A reconstituted tobacco mat is formed on a mesh screen as per Example 1 but at only 1/2 the thickness. After the binder has been added, a second mixture prepared as per Example 5 is blown on top in a similar manner as per Example 1 to form a laminated sheet. The laminated sheet is then dried and removed from the screen as per Example 1.

The foregoing detailed description is given primarily for clearness of understanding and no unnecessary limitations are to be understood therefrom for modifications will become obvious to those skilled in the art upon reading this disclosure and may be made without departing from the spirit of the invention and scope of the appended claims.

Claims (19)

1. A method of manufacturing reconstituted tobacco of tobacco stems and tobacco fines comprising treating stem parts of tobacco in essentially a dry form to reduce the stem to substantially fibrous form, mixing the fibrous stem with fine lamina tobacco, depositing the mixture of fibrous stem and fine lamina tobacco on a moving, continuous mesh belt, to form a continuous nonwoven felt sheet of fibrous stem and lamina particles on said belt, and removing said sheet from said belt in a form for use in the manufacture of tobacco smoking articles.

2. A method according to Claim 1, wherein a binder material is added to the mixture of fibrous stem and fine lamina tobacco.

3. A method according to Claim 2, wherein the binder material comprises treated cellulosic gum.

4. A method according to Claim 3, wherein the treated cellulosic gum is selected from the group consisting of cellulose ethers, cellulose esters and mixtures thereof.

5. A method according to Claim 4, wherein the binder material is selected from the group consisting of methyl cellulose, ethyl cellulose, hyd roxypropyl cellulose, methyl hydroxyethyl cellulose, ethylhydroxyethyl cellulose, cellulose acetate, hydroxyethyl cellulose and sodium carboxymethyl cellulose.

6. A method according to Claim 2, wherein the binder comprises a natural vegetable gum.

7. A method according to Claim 6, wherein the natural vegetable gum is selected from the group consisting of gum arabic, gum tragacanth, guar gum, locust bean gum and mixtures thereof.

8. A method according to Claim 2, wherein the binder comprises carbohydrate gums.

9. A method according to Claim 8, wherein the carbohydrate gum is selected from a group consisting of glycogen, deacetylated chitin and mixtures thereof.

10. A method according to Claim 2, wherein the binder comprises a marine plant gum.

11. A method according to Claim 10, wherein the marine plant gum is selected from the group consisting of algins, carageenans, agar and mixtures thereof.

12. A method according to any one ofthe preceding claims, wherein the non-woven felt sheet of fibrous stem and lamina material is passed through calender rolls before being removed from said continuous mesh belt.

13. A method according to Claim 1, wherein the tobacco stem material is treated with a suitable chemical or enzyme to liberate natural pectin material before treatment to produce fiberised tobacco stem material.

14. A method according to any one of the preceding claims, wherein the moisture of said stem is from about 10% to about 60% before the treatment thereof to reduce said stem to substantially fibrous form.

15. A method according to any one of the preceding claims, comprising the further step of adding a non-tobacco extender material to the stem parts.

16. A method according to any one of the preceding claims, comprising the further step of adding a non-tobacco extender material to the fine lamina tobacco.

17. A method according to any one of Claims 1 to 14, comprising the further step of adding a nontobacco extender material to the mixture of fibrous stem and fine lamina tobacco prior to depositing said mixture on said mesh belt.

18. A method according to any one of Claims 1 to 14, comprising the further step of adding a nontobacco extender material to the non-woven felt sheet of fibrous stem and lamina particles.

19. A method of manufacturing reconstituted tobacco of tobacco stems and tobacco fines substantially as hereinabove described with reference to Figure 1, or as modified with reference to Figure 2,3 or 4 of the drawings hereof.