Smokable material and method for preparation of same

[57] ABSTRACT

The preparation of a smokable material in which a cellulosic material containing a metal salt in the form of the carbonate, oxalate pivalate or glycolate of calcium or magnesium or other alkaline earth metals and mixtures 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 270°-500°C for a time sufficient to effect a weight loss within the range of 40-75 percent 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 percent by weight and materials for strengthening and flexibilizing the cellulosic material prior to degradation, including a starch, sugar and dextrin and mixtures thereof, plus additives to improve color, taste, aroma and moisture retention characteristics.

Primary Examiner— Melvin D. Rein

Claims, No Drawings

3,861,402

SMOKABLE MATERIAL AND METHOD FOR PREPARATION OF SAME

This invention relates to a smokable material which can be used alone or in admixture 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 free 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.

Briefly described, in the manufacture of the improved smokable material of this invention, a cellulosic material is subjected to thermal treatment in the presence of alkaline earth metal salts until the cellulosic material experiences a weight loss, due to thermal degradation and the like, by an amount greater than 40 percent but preferably less than 75 percent, after which the thermally treated cellulosic material is processed through washing and compounding steps to a composition in form desirable for use as a smoking material, as will hereinafter be described in greater detail.

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, semicontinuous or batch operation. Instead of alphacellulose, the cellulosic material which may be employed in the practice of this invention includes wood pulp, paper pulp, straw, flax, bamboo, cotton, hemp, rice fibers, vegetable fibers, and the like, and mixtures thereof. Instead of a cellulosic material of the type described, use can be made of a cellulosic derivative such as cellulose ethers or esters, represented by methylcellulose, ethylcellulose, carboxymethylcellulose, or carbohydrate materials such as starch, gum, alginates 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. Instead 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 of 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 in2 vention, is formulated to contain an alkaline earth metal salt formed preferably of calcium and/or magnesium as the cation and 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 formation or during the formation of the fibrous sheet or strip, or it can be incorporated, 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 distribution 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, followed by treatment, as by one or more impregnations, with a dilute solution of oxalic acid which reacts with the calcium salt to form insoluble calcium oxalate in situ in the cellulosic material.

Instead, the calcium oxalate, calcium carbonate, magnesium oxalate, or magnesium 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 thereof. The metal salt can be incorporated in less intimate association with the cellulosic material, as by impregnation of the cellulosic material with an aqueous medium containing the calcium oxalate, calcium carbonate, magnesium oxalate or magmesium carbonate in suspension in a suitable concentration. When use is made of a cellulosic material other 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 percent by weight of the cellulosic material and preferably in an amount within the range of 15-25 percent. 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 an acid salt preferably in the form of a sulfate and/or chloride of an alkaline earth metal, preferably 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.

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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 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 functions 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 characteristics is achieved. The desired inhibitor 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, barium, aluminum, iron and the like.

The desired results are experienced when the chloride and/or sulfate are present in an amount corresponding to 2 percent 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 of 5-25 percent by weight and preferably in an amount within the range of 8-15 percent 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°-500°C and preferably at a temperature within the range of 325°-400°C, for a time sufficient to effect a weight loss of the cellulosic material in an amount of at least 40 percent but less than 75 percent, and preferably in an amount within the range of 50-60 percent. The time of exposure to degradation temperature will depend somewhat upon the form in which the cellulosic material is exposed and the temperature to which it is exposed. For example, when the cellulosic material 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 350°C will be sufficient. Less time is required at higher temperatures and more time at lower temperatures to achieve the corresponding amount of degradation and more time will be required the greater the thickness of the sheet or layer of cellulosic material exposed to the elevated temperature for thermal treatment.

When in the form of a sheet or strip, thermal treatment can be carried out as a continuous operation by passing the sheet continuously through a space maintained inert by the passage of nitrogen or other nonoxidizing 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 sufficient to achieve the desired degradation, as measured by weight loss of the cellulosic material. 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, although use can be made of other inert, nonoxidizing gas, such as carbon dioxide, helium and the like. The desired result can be achieved by heat treat4 ment 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 prevail to enable rapid heating of the cellulosic material to effect the desired thermal degradation in accordance with the practice of this invention. Instead, the non-oxidizing atmosphere can be provided by effecting thermal treatment of the cellulosic material in an enclosed space under vacuum conditions.

After themal 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 product. 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 subjected to subsequent processing steps for 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 of a synthetic film forming polymeric material in the form of a homopolymer (1) or copolymer (2) or vinyl carbonate derivative (3) or hydroxy (4), or ketone derivative thereof.

1“ II II 1 II II Ri R2 ΓΙΙ H Ί

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(1) (2) (3) (4) (5) in which Ri 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 combined with inert noncombustible 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 positions, 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.

Polyvinylene carbonate can be produced by homopolymerization of vinylene carbonate by the process described by M. S. Newman and R. W. Addor, J. Am. Chem. Soc. 75, 1263 (1953). 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.

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Vinylene carbonate or derivatives thereof, copolymerized 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 should also combust with the production of very little, if any, noxious combustion products in the smoke.

Treatment of the thermally degraded cellulosic material with polyvinylene carbonate or other polyalkylene carbonate, of the type described provides a very strong and flexible sheet which burns cleanly without introducing undesirable ordor 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 hereinafter be described, the polyvinylene carbonate serves 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 material during storage and helps maintain a desirable moisture balance therein.

Instead of a polyalkylene copolymer of the type described, the binder component may comprise a cellulose derivative 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 derivative which is no longer water soluble and, like the polyalkylene 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 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 resistance is observed when the binder or polymeric component is present in an amount of at least 0.5 percent by weight of the cellulosic material but it is undesirable to make use of an amount greater than 10 percent 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 percent by weight.

The binder component can be applied as a coating onto the thermally degraded cellulosic material from solvent solution or aqueous dispersion. For example, when use is made of a polyalkylene carbonate, application onto the sheet can be effected 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, application can be made from water solution while the water insoluble free acid of the cellulose derivative can be applied from solution 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 suitable 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 intertwisting with other strips to form strands which can be cut to lengths suitable for use in filling machines for the fabrication of cigars, cigarettes or as a pipe tobacco substitute. Such strips can be intertwisted one with another to form a filler composed entirely of the synthesized smokable material or they can be intertwisted with strands of natural tobacco for admixture therewith in various proportions to produce a smokable material.

When in the form of discrete particles, the cellulosic material can be agglomerated into pellets or plugs cut to the desired shape and size for use in the filler. As previously described, such discrete particles can be blended in various proportions with cured natural tobacco to form a mixture 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 examples 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 percent by weight calcium carbonate, incorporated into the pulp slurry for separation with the fibers on the screen for uniform distribution with the fibers during fabrication of the paper sheet, is spray coated with a 5 percent aqueous solution of calcium chloride in an amount to dampen the paper and incorporate about 5 percent by weight calcium chloride.

The sheet is advanced through a dryer and then through an oven heated to a temperature of 350°C and maintained inert by circulation of nitrogen gas therethrough. The sheet is advanced through the oven at a rate for exposure of 4-5 minutes at the elevated temperature. Under these conditions, the cellulosic material experiences a weight loss of 50-55 percent by weight while still remaining in sheet form having strong mass integrity.

Upon issuance from the thermal treating oven, the thermally degraded sheet is washed with warm water as by passing 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 percent solution in acetone of polyvinylene carbonate to deposit 2 percent 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 intertwisted with strips of tobacco in an amount to make up 20-50 percent 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 percent by weight calcium oxalate.

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EXAMPLE 3

The procedure of Example 1 is followed except that instead of the polyvinylene carbonate, use is made of a corresponding 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 controlled degradation of the cellulosic material and preferably before introduction of the chloride or sulfate of the alkaline earth metal, the cellulosic material is modified by the incorporation of starch, sugar or a dextrin, and preferably a mixture thereof. Such materials can be employed in rather wide proportions such as 1-20 percent by weight and preferably 10-15 percent by weight of starch, 10-30 percent and preferably 15-25 percent by weight sugar or other sucrose or dextrose, and 20-40 percent and preferably 20-30 percent 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 components 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 subjected 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 percent by weight starch, 3 percent by weight cane sugar and 4 percent by weight dextrin. Application is made in amount to provide about 12 percent by weight starch, 18 percent by weight sugar and 24 percent 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 1.

The resulting thermally degraded product is characterized by improved strength by comparison with cellulosic material thermally degraded under the same conditions but without 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.

Addition can be made of a humectant to keep the 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 percent by weight and preferably within the range of 1-4 percent 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 car8 bonates, bicarbonates or phosphates, 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 percent by weight of the smokable material and preferably in an amount within the range of 1-10 percent 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 chloride or sulphate enhances the burning characteristics of the resulting smokable material by control and uniformity of burning 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 percent by weight but it is preferred, when present, to make use of an amount within the range of 0.5-5 percent by weight of the cellulosic material.

From the standpoint of appearance, it is desirable for the smoking material to having a dark brownish color, corresponding 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 undesirable enormous amounts. It has been found that novel use, as a coloring material, can be made of triquinonyl C₆O₆.8H₂O, 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, caffeic and guinic acids, essential oils, tobacco extracts and the like.

It will be understood that changes may be made in the details of formulation and operation without departing from the spirit of the invention, especially as defined in the following claims.