CA1039491A - Smokable material and method for preparation of same - Google Patents

Abstract

A SMOKABLE MATERIAL AND METHOD
FOR PREPARATION OF SAME
Abstract of the Disclosure The preparation of a smokable material in which a cellulosic material containing a metal salt in the form of the carbonate or oxalate of calcium or magnesium and mix-tures thereof and a metal salt in the form of chloride or sulfate of the metal is subjected to thermal degradation in a non-oxidizing atmosphere at a temperature within the range of 275-500°C for a time sufficient to effect a weight loss within the range of 40-75% and which includes modifying the thermally degraded cellulosic material by the addition of a binder in an amount within the range of 0.5-10% by weight and materials for strengthening and fleibilizing the cellu-losic material prior to degradation, including a starch, sugar and dextrin and mixtures thereof, plus additives to improve color, taste, aroma and moisture retention charac-teristics.

Description

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This invention relates to a smokable material which can be used along or in admi~ture with conventional cured tobacco as a filler for smoking in cigars, cigarettes or pipes and it relates further to a method for the preparation of same.
It is an object of this invention to produce and to provide a method for producing a smokable material of the type described which is low in cost and formed of readily available materials; which can be produced in a simple and efficient manner, batchwise or in a continuous operation; which is low in tars and relatively ~ree of nicotine; which is low in polycyclics and carbonyls and is thus characterized by good taste and aroma; which can be mixed in wide proportions with cured tobacco without noticeable change in the smoking characteristics of the resulting product; which has strength, feel and mass integrity characteristic of conventionally cured tobacco to enable processing with conventional equipment and with conventional materials in the manufacture of cigars and cigarettes, and in which there is little if any deviation in the smoking characteristics, taste and aroma from conventional cured tobacco.
The invention provides a smokable material comprising the thermal reaction product, in a non-oxidizing atmosphere, of a cellulosic material containing 10-30% by weight of an alkaline earth metal sa]t of an organic carboxylic acid compound and 5-25% by weight of a compound selected from the group consisting of a metal chloride and a metal sulfate~ in which the cellulosic material is exposed to a temperature within the range of 275 500 C
for a time sufficient to effect a weight loss within the range of 40-75%, a flexibilizing and strengthening binder uniformly distributed in the thermally treated cellulosic material in an amount within the range of 0.5-10% by weight of the cellulosic material.
The invention also provides a method for producing a smokable material comprising expOsing a cellulosic material loaded with 10-30% by C

3949~
weight of an alkaline earth metal salt of an organic carboxylic acid compound and 5-25% by weight of a compound selected from the group consisting of a metal chloride and a metal sulfate, to a temperature within the range of 275-500 C, for a time sufficient to effect a weight loss within the range of 40-75% of the cellulosic material~ maintaining non-oxidizing conditions during normal treatment, treating the thermally degraded cellulosic material to incorporate a flexibilizing and strengthening agent in the form of a binder in an amount within the range of 0.5-10% by weight, and then processing the resulting thermally degraded cellulosic material to the form desired for use as a smoking material.

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In the preferred practice of this invention, use is made of a sheet or strip of cellulosic material, such as alpha-cellulose, in which the cellulosic fibers are interfelted in the form of a sheet or strip having sufficient mass integrity for processing through the various steps hereinafter described, as a continuous, semi-continuous or batch operation. Instead of alpha-cellulose, the cellulosic material which may be em-ployed in the practice of this invention includes wood pulp, paper pulp, straw, flax, bamboo, cotton, hemp, rice fibers, veg-etable fibers, and the like, and mixtures thereof. Instead ofa cellulosic material of the type described, use can be made of a cellulosic derivative such as cellulose ethers or esters, represented by methylcellulose, e-thylcellulose, carboxymethyl-cellulose, or carbohydrate materials such as starch, gum, al-ginates and the like, preferably reduced to fiber or sheet form,all of which are collectively hereinafter included within the term "cellulosic material".
When, as in the preferred practice of this invention, the cellulosic material is employed as a starting material in the form of a sheet or strip, it is desirable to make use of a sheet or strip having a thickness within the range of 5-10 mm and preferably within the range of 7-9 mm. ~nstead of making use of the cellulosic material in the form of sheets or strips, the raw material used in the manufacture of a smokable product f this invention can be provided in the form of fibers or other discrete particles.
The cellulosic material which is subjected to thermal treatment, in accordance with the practice of this invention, is formulated to contain an alkaline earth metal salt formed 3 preferably of calcium and/or magnesium as the cation and -~39~

oxalate or carbonate as the anion, as represented by calcium carbonate, calcium oxalate, magnesium carbonate and magnesium oxalate, and mixtures thereof. The alkaline earth metal salt can be incorporated with the fibers during fiber fcrmation or during the ~ormation of the fibrous sheet or strip, or it can be i~corporated, as by impregnation, into the sheet or strip for uniform distribution after the sheet or strip has been formed. In the alternative, it can be introduced by formation of the salt in situ from the components thereof.
For example, when the salt is in the form of a calcium oxalate, the calcium oxalate can be incorporated in the desired amount in various ways. For most intimate and uniform distribu-tion with the cellulosic material, the calcium oxalate can be formed in situ in the cellulosic material by first treating the -cellulosic material to load the material with the desired amount of calcium carbonate, calcium oxide or other calcium salt, fol-lowed by treatment, as by one or more impregnations, with a dilute solution of oxalic acid which reacts with the calcium salt to ~rm insoluble calcium oxalate in situ in the cellu-

2~ losic material.
Instead, the calcium oxalate, calcium carbonate, mag-nesium oxalate, or magnesi~n carbonate, or other alkaline earth metal oxalate or carbonate can be introduced into the header or otherwise admixed with the cellulosic fibers for distribution with the pulp that is passed over the Fourdrinier screen in the manufacture of paper or strip thareof. The metal salt can be incorporated in less intimate association with the cellulosic material, as by impregnation of the cellulosic material with an aqueous mediurn containing the calcium oxalate, calcium car-

3 bonate, magnesium oxalate or magnesium carbonate in suspension 1S~3~49~
in a suitable concentration. When use is made of a cellulosic materialother than in sheet form, the alkaline earth metal salt can be admixed with the cellulosic material in the form of a dry powder or aqueous suspension, and then sheeted or dried for subsequent thermal treatment in the manner hereinafter described.
The desired results are achieved when such alkaline earth metal ; salts are present in an amount within the range of 10-30% by weight of the cellulosic material and preferably in an amount within the range of 15-25%.
Instead of calcium and magnesium oxalate or carbonate, use can be made of salts formed of calcium barium, magnesium, strontium, or the like alkaline earth metals as the cation and anions such as the pivalate~ glycolate and the like polyhydroxy organic compounds.
Thermal degradation of the cellulosic material is benefitted greatly from the standpoint of uniformity and character of the degradation by the presence in the cellulosic material of the metal chloride or metal sulphate, preferably of calcium and/or magnesium.
In the preferred practice of this invention~ the chloride and/or sulfate is provided on the cellulosic material subsequent to sheet formation or incorporation of the carbonate and/or oxalate, so that the chloride and/or sulfate will remain concentrated at the surface of the cellulosic material during the subsequent thermal treatment.
Application of the alkaline earth metal sulfate and/or chloride can be made from solution in aqueous medium as by spraying onto the dried cellulosic material prior to thermal treatment, or by immersion of the dried sheet in the aqueous _ ~ _ ~399~9~L
solution, or by mixing the desired amount of solution with the cellulosic material, depending somewhat upon the form of the cellulosic material which is to be subjected to the thermal treatment.
It is believed that the sulfate and/or chloride func tions as an inhibitor to control the character of the thermal degradation of the cellulosic material whereby a thermally treated product having optimum strength and smoking character-istics is achieved. The desired inhibitvr effect can be secured with chlorides and/or sulfates of other metal cations, such as of metals of the Groups I, II, III and IV of the periodic table including sodium, potassium, barium9 aluminum, iron and the like.
The desired results are experienced when the chloride and/or sulfate are present in an amount corresponding to 2% by weight of the cellulosic material but for best results it is desirable to make use of such chloride and/or sulfate in an amount within the range o~ 5-25% by weight and preferably in an amount within the range of 8-15% by weight of the cellulosic material~
Thermal treatment of the described cellulosic material is carried out in a non-oxidizing, preferably inert, atmosphere ~ at a temperature within the range of 275-500C and preferably at ; a temperature within the range of 325-400C9 for a time suffi-cient to effect a weight loss of the cellulosic material in an amount of at least 40% but less than 75%, and preferably in an amount within the range of 50-60%. The time of exposure to de-gradation temperature will depend somewhat upon the form in which the cellulosic material is exposed and the temperature to 3 which it is exposed. For example, when the cellulosic material ~L~399~91 is in the form of a sheet or strip having a thickness within the range of 7-9 mils, exposure for from 4-5 minutes at 350C
will be sufficient. Less time is required at higher tempera-tures and more time at lower temperatures to achieve the cor-responding amount of degradation and more time will be requiredthe greater the thickness of the sheet or layer of cellulosic material exposed to the elevated temperature for thermal treat-ment.
when in the form of a sheet or strip, thermal treat-1~ ment can be carried out as a continuous operation by passingthe sheet continuously through a space maintained inert by the passage of nitrogen or other non-oxidizing gas therethrough and which is heated to the desired temperature, with the rate of travel coordinated with the length of the heated space to provide for the time of exposure to elevated temperature suffi-cient to achieve the desired degradation, as measured by weight loss of the cellulosic mcterial. when in a form other than an endless sheet or strip, the cellulosic material can be subjected to thermal treatment in a batch operation, or in a continuous operation when supported on a suitable surface for continuous passage through the space heated to the desired temperature.
As the inert atmosphere in which thermal treatment is carried out, it is preferred to make use of nitrogen gas, al-though use can be made of other inert, non~oxidizing gas, such as carbon dioxide, helium and the like. The desired result can be achieved by haat treatment of the cellulosic material, at the desired temperature, in an enclosed chamber wherein the oxygen originally present in the air entrapped within the chamber is quickly reduced to a level wherein non-oxidizing conditions pre-3 vail to enable rapid heating of the cellulosic material to 1~3~4~
effect the desired thermal degradation in accordance with the practice of this invention. Instead, the non-oxidizing atmos-phere can be provided by effecting thermal treatment of the celluiosic material in an enclosed space under vacuum conditions.
After thermal degradation it is desirable to subject the cellulosic material to a water wash for removal of water soluble components which remain in the thermally treated prod-uct. The desired wash can be effected by flowing a stream of water, preferably warm water, over the endless sheet or strip as it issues from the heat treatment step. Instead, it can be washed by immersion in a water bath, with or without agitation, for a time sufficient to effect the desired cleansing action.
If a water wash is employed, the treated cellulosic material is dried before being sub~ected to subsequent processing steps for ~5 incorporating various additives with the thermally degraded cellulosic material prior to processing to the form desired for use as a smokable product.
Marked increase in the strength and flexibility of the thermally degraded cellulosic material can be achieved by the addition of an organic binder component. For this purpose, use is preferably made o~ a synthetic film forming polymeric mater-ial in the form of a homopolymer (1) or copolymer (2) or vinyl carbonate derivative (3) or hydroxy (4), or ketone (5) deriva-tive thereof.
H H

O i~

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in which Rl and R2 may each be hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec butyl, pentyl, isopentyl, hexyl, nonyl, decyl or other alkyl group or mixtures of such hydrogen and alkyl groups.
Such polymers of vinylene carbonate and derivatives thereof form water insoluble plastic films or coatings and can therefore function admirably as a binder or film former in the preparation of reconstituted smokable products when com-bined with inert non-combustible fillers and/or combustible materials of the types previously described. The polymer (1) which consists of repeating l,3-dioxolane~2-one ring system, in which the repeating units are coupled at the C4 and C5 pOS i-tions, respectively, is capable of clean combustion to carbon dioxide and water, since all carbon atoms in the ring system are bonded to oxygen atoms. The linear polycarbonates should also burn in an analogous manner to yield very little if any chemical irritants and carcinogens.
I Polyvinylene carbonate can be produced by homopoly-merization of vinylene carbonate by the process described by M.
20 S. ~ewman and R. W. Addor, J. Am. Chem. Soc., 75, 1263 (1953)o The polymethylol derivative can be produced by hydrolysis of polyvinylene carbonate, as described by unruh and Smith, J.
org. Chem., 23~ 625 (1958) and the corresponding ketone should be produced by conventional oxidation of the polymethylol.
~inylene carbonate or derivatives thereof, copoly-merized with olefins, such as acrylic acid, alkyl acrylates such as methyl acrylate or methyl methacrylate, or maleic acid or anhydride can be used as the film former or binder in the same manner as the polyvinylene carbonate, since such copolymers 3 should also combust with the production of very little, if any, ~394~1 noxious combustion products in the smoke.
Treatment of the thermally degraded cellulosic mater-ial with polyvinylene carbonate or other polyalkylene carbon-ate of the type described provides a very strong and flexible sheet which burns cleanly without introducing undesirable odor or taste. The thermally degraded sheet treated with the binder component is relatively water resistant thereby to militate against leaching of water soluble additives. As will herein-after be described, the polyvinylene carbonate ser~es as a vehicle for imparting the desired tobacco color to the ultimate smokable material formed in accordance with the practice of this invention and improves the stability of the smokable mater-ial during storage and helps maintain a desirable moisture balance therein.
Instead of a polyalkylene copol~mer of the type de-scribed, the binder component may comprise a cellulose deriva-tive such as methylcellulose or carboxymethylcellulose and preferably a cellulose derivative of the type described from which the sodium has been removed, as by ion exchange, to ~ provide the free acid of the corresponding cellulose deriva-tive which is no longer water soluble and, like the polyalkyl-ene carbonates, imparts a desirable degree of water resistance to the smokable thermally degraded cellulosic material.
As the binder, use can also be made of a natural resin 2~ or gum, such as gum tragacanth~ guar gum, terpene resins and the like, which impart strength and flexibility to the degraded fibrous structure without giving off undesirable taste, odor, polycyclics, tars or nicotine during smoking of the product.
Improvement in strength, flexibility and water resist-3 ance is observed when the binder or polymeric component is ~3~99L9~
present in an amount of at least 0~5% by weight of the cellu-losic material but it is undesirable to make use of an amount greater than 10% by weight. In the preferred practice of the invention, the smokable thermally degraded cellulosic material is treated to incorporate one or more of the described binder components in an amount within the range of 1-10% by weight.
The binder component can be applied as a coating onto the thermally degraded cellulosic material from solvent solu-tion or a~ueous dispersion. For example, when use is made of a polyalkylene carbonate, application onto the sheet can be ef-fected by spraying from a solution in acetone to wet both sides of the sheet until the desired amount of polymeric material has been incorporated. when use is made of carboxymethyl cellulose, methyl cellulose, or other water soluble gum or resin, applica-tion can be made from water solution while the water insolublefree acid of the cellulose derivative can be applied from solu-tion in suitable solvents or from an aqueous dispersion. The degraded cellulosic material can be sprayed with the binder component when in sheet or other form or else combined with the degraded cellulosic material for admixture therewith in suit-able mixing equipment for uniform distribution.
The dried cellulosic material is now in condition for processing to the forms desired for use as a smokable material.
When in the form of a sheet or strip, the processed cellulosic material can be slitted into thin strips for twisting or inter-twisting with other strips to form strands which can be cut to lengths suitable for use in filling machines for the fabrica-tion of cigars, cigarettes or as a pipe tobacco substitute.
Such strips can be intertwisted one with another to form a fil-3 ler composed entirely of the synthesized smokable material or ~3949~
they can be intertwisted wi-th strands of natural tobacco for admixture therewith in various proportions to produce a smok-able material.
when in the form of discrete particles, the cellu~-losic material can be agglomerated into pellets or plugs cutto the desired shape and size for use in the filler. As pre-viously described, such discrete particles can be blended in various proportions with cured natural tobacco to form a mix-ture which has the appearance, aroma and taste and which burns like natural tobacco when fabricated into a smoking product.
Having described the basic concepts of this invention, exemplification will now be made by way of the following ex-amples which are given by way of illustration, but not by way of limitation.
Example 1 A sheet formed of paper pulp having a thickness of 8 mils and containing 20% by weight calcium carbonate, incorpor-ated into the pulp slurry for separation with the fibers on the screen for uniform distribution with the fibers during fabrica-tion of the paper sheet, is spray coated with a 5% aqueoussolution of calcium chloride in an amount to dampen the paper - and incorporate about 5% by weight calcium chloride.
The sheet is advanced through a dryer and then through an oven heated to a temperature of 350C and maintained inert by circulation of nitrogen gas therethrough. The sheet is ad-vanced through the oven at a rate for exposure of 4-5 minutes at the elevated temperature. under these conditions, the cellu-losic material experiences a weight loss of 50-55% by weight while still remaining in sheet form having strong mass integri-3 ty.

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Upon issuance from the thermal treating oven, the thermally degraded sheet is washed with warm water as by pass-ing beneath rollers submerged in a warm water bath, followed by drying in an air circulating oven.
Thereafter, the processed sheet is spray coated on both sides with a 10% solution in acetone of polyvinylene carbonate to deposit 2% by weight of resin solids, based upon the weight of the degraded cellulosic material. After drying, the sheet is cut into strips, twisted into strands, and cut into pellets suitable for use in filling machines for preparing cigars, cigarettes, or for use as pipe tobacco.
By way of modification, the strips can be inter-twisted with strips of tobacco in an amount to make up 20-50%
by weight of the resulting intertwisted smokable material.
Example 2 The procedure of Example 1 is followed except that the paper pulp is replaced by alpha-cellulose containing 10% by weight calcium carbonate and 15% by weight calcium oxalate.

Example 3 The procedure of Example 1 is followed except that instead of the polyvinylene carbonate, use is made of a corres-ponding amount of carboxyethyl cellulose, methylcellulose, or free acid derivative thereof.
By way of modification, an improved smokable material is produced when, prior to thermal treatment to effect control-led degradation of the cellulosic material and preferably be-fore introduction of the chloride or sulfate of the alkaline earth metal, the cellulosic material is modified by the incor-poration of starch, sugar or a dextrin, and preferably a mix-3 ture thereof. Such materials can be employed in rather wide ~L~3949~l proportions such as 1-20% by weight and preferably 10-15% by weight of starch, 10-30% and preferably 15-25% by weight sugar or other sucrose or dextrose, and 20-400~ and preferably 20-30%
by weight of dextrin. SUCh components or mixtures thereof in the amounts described can be incorporated by spray or brush coating the cellulosic sheet with an aqueous solution of the componen~ or by admixture with the cellulosic material from an aqueous solution or dispersion, for uniform distribution with the cellulosic material. After the incorporation of the starch, sugar and/or dextrin, the cellulosic material is dried before being sub~ected to thermal treatment.
Example 4 The procedure of Example 1 is followed except that prior to coating with the calcium chloride, the cellulosic sheet is first coated by brushing to wet each side of the sheet with an aqueous medium containing 2% by weight starch, 3% by weight cane sugar and 4% by weight dextrin. Application is made in amount to provide about 12% b~ weight starch, 18% by weight sugar and 24% by weight dextrin based upon the weight of the cellulosic material. The material is dried and then treated with the solution of calcium chloride as described in Example L
The resultin~ thermally degraded product is char-acterized by improved strength by comparison with cellulosic material thermally degraded under the same conditions but with-out the added sugar, starch and dextrin.
Various other additives can be incorporated with the thermally degraded cellulosic material of this invention to provide desirable improvements in processing characteristics and to improve color, taste, feel and aroma~
3 Addition can be made of a humectant to keep the 945~
smoking material moist and pliable and to enhance the packing characteristics as well as the burning characteristics of the product. For this purpose, use can be made of a polyhydric ; alcohol, such as glycerol or a glycol, represented by ethylene glycol, propylene glycol and the like, inositol, butane diol and the like hygroscopic materials and mixtures thereof~ These materials can be applied by spraying from water solution onto the sheet or particulates, or by admixture with the treated cellulosic or carbohydrate material. Addition is made in amounts up to 10% by weight and preferably within the range of 1~4% by weight, when added.
The glow and ashing characteristics of the smoking material can be improved by the addition of water soluble alkali metal salts, such as sodium or potassium salts of low molecular weight hydroxy acids, such as oxalic, citric, maleic, pivalic and the like organic acids, or carbonates, bicarbonates or phos-phates, such as potassium citrate, sodium citrate, potassium bicarbonate, potassium maleate and dihydrogen sodium phosphate, - and mixtures thereof. In addition, the hydroxy acids, such as oxalic, citric, maleic and pivalic and the like organic acids may be used. Such mineralizing agents or ashing ingredients, when employed, may be incorporated in amounts up to 30% by weight of the smokable material and preferably in an amount within the range of 1-10% by weight.
Modification of the thermally degraded cellulosic material by the incorporation of an alkaline earth metal (calcium, magnesium, barium, strontium, etc.) salt of a chlor-ide or sulphate enhances the burning characteristics of the re-sulting smokable material by control and uniformity o~ burning 3 rate. Such alkaline earth metal sulphates or chlorides can be incorporated from solution or dispersion, as by spraying to wet the cellulosic material or by admixture of the salts with the cellulosic material in solution, dispersion or dry powder form.
Improved burning characteristics and control is experienced when the alkaline earth metal sulphate and/or chloride is present in an amount up to 10% by weight but it is preferred, when present, to make use of an amount within the range of 0.5-5% by weight of the cellulosic material.
From the standpoint o~ appearance, it is desirable for the smoking material to have a dark brownish color, corre-sponding to that of rich cured tobacco. The dark gray material resulting from the thermal treatment of this invention is not readily colored by conventional dyestuffs unless employed in un-desirable enormous amounts. It has been found that novel use, as a coloring material, can be made of triquinonyl C606.8H20, which produces a strong orange to brown color with calcium or magnesium present in the cellulosic or carbohydrate product thereby to provide a non-leachable color that is effective to convert the thermally treated product to a rich brown color.
Flavor and aroma can be improved by the addition of flavoring agents, such as nicotine, menthol, chlorogenic, caf-feic and quinic acids, essential oils, tobacco extracts and the like.

3o

Claims (44)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A smokable material comprising the thermal reaction product, in a non-oxidizing atmosphere, of a cellulosic material containing 10-30% by weight of an alkaline earth metal salt of an organic carboxylic acid compound and 5-25% by weight of a compound selected from the group consisting of a metal chloride and a metal sulfate, in which the cellulosic material is exposed to a temperature within the range of 275°-500°C for a time sufficient to effect a weight loss within the range of 40-75%, a flexibilizing and strengthening binder uniformly distributed in the thermally treated cellulosic material in an amount within the range of 0.5-10% by weight of the cellulosic material.

2. A smokable material according to claim 1 in which the cellulosic material has been exposed to the thermal reaction temperature for a time sufficient to effect a weight loss within the range of 50-60%.

3. A smokable material according to claim 1 or 2 in which the alkaline earth metal salt of a carboxylic acid compound is a carbonate and/or oxalate of the alkaline earth metal present in an amount within the range of 15-20% by weight.

4. A smokable material according to claim 1 in which the alkaline earth metal salt of an organic carboxylic acid compound is selected from the group consisting of the oxalate and carbonate of calcium and magnesium.

5. A smokable material according to claim 1 in which the metal chloride or metal sulfate is present in an amount within the range of 8-15%
by weight.

6. A smokable material according to claim 1 in which the metal chloride and sulfate is selected from the group consisting of calcium chloride, magnesium chloride, calcium sulfate and magnesium sulfate.

7. A smokable material according to claim 1 in which the flexibilizing and strengthening binder is present in an amount within the range of 1-10% by weight.

8. A smokable material according to claim 7 in which the binder is a polyalkylene carbonate.

9. A smokable material according to claim 7 in which the binder is polyvinylene carbonate.

10. A smokable material according to claim 7 in which the binder is a cellulose derivative or a free acid thereof.

11. A smokable material according to claim 10 in which the cellulosic material subjected to thermal treatment has added thereto a compound selected from the group consisting of starch, sugar and dextrin, and mixtures thereof.

12. A smokable material according to claim 11 in which the starch, when present, is present in an amount within the range of 10-15% by weight, the sugar, when present, is present within the range of 15-20% by weight, and the dextrin, when present, is present in an amount within the range of 20-25% by weight.

13. A smokable material according to claim 1 which includes a humectant in an amount up to 10% by weight.

14. A smokable material according to claim 13 in which the humectant is a compound selected from the group consisting of glycerol, glycol, and a polyhydric alcohol.

15. A smokable material according to claim 11 which includes a coloring agent in combination with the thermally reacted cellulosic material for con-verting the product to a rich brown color.

16. A smokable material according to claim 15 in which the coloring agent comprises the reaction product of a calcium ion with triquinonyl.

17. A smokable material according to claim 1 which includes an organic amine in an amount sufficient to adjust the pH to at least 8.

18. A smokable material according to claim 1 in which the burning rate of the cellulosic material is controlled by the presence of an alkaline earth metal salt of an anion selected from the group consisting of sulfate and chloride.

19. A smokable material according to claim 18 in which the burning rate controlling alkaline earth metal salt is present in an amount within the range of 0.5% to 5% by weight.

20. A smokable material according to claim 1 which includes a metal citrate in an amount within the range of 1-10% by weight of the smokable material to improve the glow characteristics during burning.

21. A smokable material according to claim 1 which includes a hydroxy acid or salt thereof to improve the ashing characteristics of the smokable material.

22. A smokable material according to claim 21 in which the hydroxy acid is selected from the group consisting of oxalic acid, citric acid, maleic acid and pivalic acid.

23. A smokable material according to claim 21 in which the ashing ingredient is present in an amount within the range of 1-10% by weight of the smokable material.

24. A method for producing a smokable material comprising exposing a cellulosic material loaded with 10-30% by weight of an alkaline earth metal salt of an organic carboxylic acid compound and 5-25% by weight of a compound selected from the group consisting of a metal chloride and a metal sulfate, to a temperature within the range of 275-500°C, for a time sufficient to effect a weight loss within the range of 40-75% of the cellulosic material, maintaining non-oxidizing conditions during normal treatment, treating the thermally degraded cellulosic material to incorporate a flexibilizing and strengthening agent in the form of a binder in an amount within the range of 0.5-10% by weight, and then processing the re-sulting thermally degraded cellulosic material to the form desired for use as a smoking material.

25. The method according to claim 24 in which the cellulosic material is subjected to thermal treatment for a time sufficient to effect a weight loss within the range of 50-60%.

26. The method according to claim 25 in which the alkaline earth metal compound is selected from the group consisting of the carbonate and oxalate of calcium and magnesium and mixtures thereof.

27. The method according to claim 26 in which the alkaline earth metal compound is present in an amount within the range of 15-25% by weight of the cellulosic material.

28. The method according to claim 25 in which the metal chloride or sulfate is selected from the group consisting of calcium chloride, calcium sulfate, magnesium chloride and magnesium sulfate.

29. The method according to claim 28 in which the metal chloride or sulfate is present in an amount within the range of 8-15% by weight.

30. The method according to claim 24 in which the flexibilizing and strengthening agent is present in an amount within the range of 1-10% by weight.

31. The method according to claim 30 in which the flexibilizing and strengthening agent is a binder selected from the group consisting of a polyalkylene carbonate, a cellulose ethyl or ester,or carboxymethyl cellulose, or a free acid derivative thereof.

32. The method according to claim 28 in which the metal sulfate or chloride is incorporated in the cellulosic material by wetting the cellulosic material with a solution or dispersion of the sulfate or chloride in a suit-able liquid diluent and then drying the treated product before subjecting the treated cellulosic material to thermal degradation.

33. The method according to claim 24 which includes the step of treating the cellulosic material prior to degradation with a solution or dispersion containing a compound selected from the group consisting of starch, sugar, and dextrin, and mixtures thereof.

34. The method according to claim 33 in which the starch is incorporated in an amount within the range of 10-20% by weight, the sugar is incorporated in an amount within the range of 15-25% by weight, and the dextrin is incor-porated in an amount within the range of 20-30% by weight.

35. The method according to claim 24 which includes the step of washing the thermally degraded cellulosic material with water following the thermal reaction step.

36. The method according to claim 24 which includes the step of adding a humectant to the thermally degraded cellulosic material in an amount up to 10% by weight.

37. The method according to claim 24 which includes the step of adding an amine to the thermally degraded cellulosic material in an amount to raise the pH to at least 8.

38. The method according to claim 24 which includes the step of adding a coloring agent to the thermally degraded cellulosic material to impart a brown color thereto.

39. The method according to claim 24 which includes the step of mixing a cured natural tobacco with the thermally degraded cellulosic material to form the smokable material.

40. The method according to claim 24 which includes the step of adding an alkaline earth metal salt of an anion selected from the group consisting of sulfate and chloride to control the burning rate of the cellulosic material.

41. The method according to claim 40 in which the alkaline earth metal salt for controlling the burning rate is present in an amount within the range of 0.5-5% by weight.

42. The method according to claim 24 which includes the step of adding to the thermally degraded cellulosic material a metal citrate in an amount within the range of 1-10% by weight to improve the glow characteristics during burning of the cellulosic material.

43. The method according to claim 24 which includes the step of adding to the thermally degraded cellulosic material a hydroxy acid or salt thereof in an amount within the range of 1-10% by weight of the cellulosic material to improve the ashing characteristics of the smokable material.

44. The method according to claim 43 in which the hydroxy acid is selected from the group consisting of oxalic acid, citric acid, maleic acid and pivalic acid.