Reconstituted Tobacco

Abstract

A process for manufacturing a reconstituted tobacco composition wherein a foamed slurry is created from tobacco, a foaming agent or adhesive and ethylhydroxyethyl cellulose having an ethoxyl D.S. of 1.2 to 1.6 and a hydroxyethyl M.S. of 0.5 to 1.2. The foamed slurry is shaped while maintaining the temperature thereof below the gelatin temperature of the ethylhydroxyethyl cellulose and dried to form a shaped sheet or rod of predetermined moisture content. The foaming agent employed may be a synthetic or natural gum or water dispersible protein.

Description

This invention relates to improved smoking products made from foamed tobacco slurries. More particularly this invention relates to the use of a particular grade of ethylhydroxyethyl cellulose as a foam-stabilizing agent in foamed reconstituted tobacco compositions and to the novel and beneficial properties that result therefrom.

In U.S. Pat. No. 3,364,935, U.S. Pat. No. 3,404,690, U.S. Pat. No. 3,404,691 and U.S. Pat. No. 3,410,279, Moshy and Germino described inventions to produce a foamed tobacco slurry which, when cast or otherwise formed into a desired shape and suitably treated will provide a smoking article with an open cellular structure. The Moshy and Germino inventions involve processes for combining a foaming agent, a foam-stabilizng agent and tobacco, at least one element of said mixture being adhesive, creating a tobacco foam slurry from said mixture, forming said slurry into a predetermined shape and drying said shaped slurry to a preselected moisture content to produce a stable foamed product in which tobacco particles are spaced from each other by a gaseous media. During the process of pumping and shaping the foamed tobacco slurry, the work done on this slurry can cause some degree of foam breaking and collapse. Furthermore, during the process of drying the shaped foamed tobacco slurry, further foam disruption and collapse can occur. Although the practice of the Moshy and Germino patents does result in foamed tobacco products, the lack of optimum foam stabilization characteristics using the foam-stabilizing ingredients specified makes the production of foamed tobacco products with exact density characteristics difficult to obtain and control. Since the uniformity of weight, firmness and draw of smoking articles produced by this process depends on control of the ultimate foam density characteristics, it is apparent to those involved in research in this area that a significantly more stable foamed tobacco slurry is required to provide the degree of foam density control during transfer, shaping and drying which is necessary for a commercially acceptable process and product.

Accordingly, it is an object of this invention to provide an improved foamed reconstituted tobacco product and an improved process for making same.

It is a further object of this invention to provide foamed reconstituted tobacco products which can be made to exacting density specifications, and a process for accomplishing same.

It is still a further object of this invention to provide reconstituted tobacco products which, because they are made by a process which results in reproducibility of product density, will exhibit commercially acceptable reproducibility of product weight, compressibility and pressure drop ("draw") as well.

It is another objective of this invention to provide foamed tobacco products with readily controllable product densities which are achieved through the usage of a small percentage of a particular grade of a particular water-soluble cellulosic derivative as the foam stabilizing agent.

Additional objectives will become apparent from the description of the invention which follows:

It should be understood throughout the discussion that this invention contemplates manufacture of foamed reconstituted tobacco compositions in the shape of sheet, rods, cylinders, plugs, shreds and the range of forms associated with the production of hundreds of different shapes of cigars. In the case of foamed reconstituted tobacco sheet, this sheet may be made at the thickness of the ultimate smoking article, and the smoking article may be cut from such sheet. As an alternative, the foamed reconstituted sheet may be manufactured thinner than the desired smoking article, and this thinner sheet chopped or shredded and used as filler in cigars, cigarettes or pipes.

According to the present invention, when a particular grade of ethylhydroxyethyl cellulose, that with an ethoxyl degree of substitution (D.S.) of 1.2 to 1.6 and a hydroxyethyl molar substitution of 0.5 to 1.2 is incorporated as a foam stabilizing agent in a reconstituted tobacco slurry of the type described by Moshy and Germino at a level of at least 0.3 percent, the superior stability of the foamed tobacco slurry during the manufacturing operations results, as described above.

The purpose of the following three paragraphs is to explain the use herein and in the prior art of the terms "degree of substitution" (D.S.) and "molar substitution" (M.S.).

There are three hydroxyl groups in each anhydroglucose unit in the cellulose molecule. D.S. is the average number of hydroxyl groups substituted in the cellulose per anhydroglucose unit. M.S. is the average number of moles of reactant combined with the cellulose per anhydroglucose unit. For the alkyl, carboxyalkyl, or acyl derivatives of cellulose, the D.S. and M.S. are the same. For the hydroxyalkyl derivatives of cellulose, the M.S. is generally greater than the D.S. The reason for this is that each time a hydroxyalkyl group is introduced into the cellulose molecule, an additional hydroxyl group is formed with itself is capable of hydroxyalklation. As a result of this, side chains of considerable length may form on the cellulose molecule. The M.S./D.S. ratio represents the average length of these side chains. Thus, from the foregoing, it will be seen that the total D.S. of a cellulose derivative can be no higher than 3, whereas the M.S. may be considerably higher than 3, depending on the extent to which side chains are formed.

With a mixed ether such as ethylhydroxyethyl cellulose, the ethoxyl content is reported as D.S. since, as noted above, the D.S. and M.S. must be the same for this constituent. The hydroxyethyl substituent, on the other hand, is reported as M.S. since addition to side chains is possible in this case.

The two most widely used methods for determining M.S. are the Zeisel-Morgan method and the terminal methyl method. The Zeisel-Morgan method is reported beginning at page 500, vol. 18, 1946, of "Industrial and Engineering Chemistry, Analytical Edition." The terminal methyl method is reported by Lemieux and Purves beginning at page 485, vol. 25B, 1947, of "Canadian Journal of Research". Some are of the opinion that perhaps the latter method is more accurate. However, all those skilled in the art realize that it is quite difficult to obtain a high degree of accuracy in determining M.S. at high M.S. levels, and that the accuracy of neither of these methods is as high as desired. However, the D.S. and M.S. values specified herein were determined by the most accurate methods known and, at the substitution levels of the ethylhydroxyethyl cellulose of choice, are quite satisfactory. The ethoxyl D.S. was determined by the terminal methyl method and the hydroxyethyl M.S. was determined by the Ziesel-Morgan method.

Other grades of ethylhydroxyethyl cellulose are referred to in the prior art. The use of the normal commercial grade of ethylhydroxyethyl cellulose as the adhesive in reconstituted tobacco compositions is reported by Rosenberg and Schmidt in U.S. Pat. No. 3,042,552 (July 3, 1962 ). The ethoxyl content of this material is listed by Rosenberg and Schmidt as 17 -18 percent (D.S. =0.8 ), and the hydroxyethyl content at about 17.3 percent (M.S. =0.9 ). The ethylhydroxyethyl cellulose used by Rosenberg and Schmidt is different in composition than that of the present invention, which involves an ethoxyl degree of substitution of 1.2 to 1.6 and a hydroxyethyl molar substitution of 0.5 to 1.2 . The differences are even greater than one might anticipate from the substitution differentials, and are in fact differences in kind, not just in degree. The normal ethylhydroxyethyl cellulose (EHEC) used by Rosenberg and Schmidt will dissolve in water at temperatures up to about 60.degree. C. The EHEC of this invention will not dissolve in water if the temperature is over 25.degree. C. and, for complete solubilization, the temperature should be below 15.degree. C. The Rosenberg and Schmidt EHEC will gel or precipitate from aqueous solution when the temperature is raised to 55.degree. -70.degree. C., depending on the exact substitution; the EHEC of the present invention will gel or precipitate from aqueous solution when the temperature is raised to about 32.degree.-38.degree. C. The Rosenberg and Schmidt EHEC is insoluble in methanol or ethanol or 95 percent isopropanol; the EHEC of the present invention is completely soluble in these solvents. In spite of the fact that both materials are ethylhydroxyethyl celluloses, the difference in substitution between the two grades have resulted in physical and chemical properties for the two grades of gum that are as different from each other as one would expect from adhesives of entirely different classes.

The properties contributed to foam stabilization by the incorporation of the EHEC of the present invention are also radically different from those which are obtained using other carbohydrate, protein or synthetic gums at similar levels in the formulation, or even at substantially higher levels. Furthermore, the foam stabilization properties are radially different from those which are obtained with any other cellulose ether and even from other grades of ethylhydroxyethyl cellulose with different levels of substitution.

It should be noted that Moshy and Germino employed, as foaming agents, adhesives such a animal gums, such as glycogen, plant gums and derivatives, such as cellulose ethers, cellulose esters, startches, starch ethers, starch esters, amylose, amylopectin and their ester and ether derivatives, locust bean gum, guar gum, gum arabic and related seed gums and plant exudate gums, marine plant gums, such as algins, carrageenans, laminarins and agar, and microbial gums such as the dextrans, phosphomannans such as USDA B-1459 and B-1428, and the gluconic acid microbial-containing gums such as the USDA Y-1409 gums, and water-dispersible protein classes such as animal proteins such as hydrolyzed keratins, egg albumin, and vegetable proteins such as gluten and synthetic gums such as polyvinyl alcohol, polyoxyethylene and polyacrylamide.

These materials, although foamable with Moshy and Germino compositions, were quite unstable and required the addition of a foam-stabilizing agent initially or after foaming, or the use of a blowing agent, in order to provide any measure of foam stability. The foam-stabilizng agents of the Moshy patents were ionic and nonionic surfactants consisting of the salts of the sulfate esters of the alkylphenoxypolyoxyethylene ethanol, the salts of sulfate compounds of the type N-methyl-N-oleoyl taurine, sorbitan esters such a sorbitan monostearate (Span 60 ) or the monooleate (Span 80 ), ethylene oxide-sorbitol condensation products, and lecithin and lecithin derivitives. Such materials in addition to that fact that they do not provide the desired degree of foam stability for optimum process control, also contribute off-aromas on combustion, even when used at low levels.

Based on the Moshy and Germino disclosures of the foam instability when any one of their many foaming agent-adhesives are incorporated in tobacco slurries at generally high levels to provide the proper adhesive qualities, it was quite unexpected and novel to find that the EHEC of this invention, a cellulose ether, should function as an exceptional foam-stabilizing agent when used at low concentrations in the product of only 0.3 to 2.5 percent. It is also interesting to note that the closest material to the EHEC of this invention, the EHEC of the Rosenberg and Schmidt patent, does not provide such foam stability when employed in otherwise identical formulations. The uniqueness of the EHEC of this invention indicates that the problem of tobacco foam stabilization to both mechanical work and heat energy is most complex and, as yet, without theoretical prediction or explanation.

It should be noted that the foam stabilization characteristic associated with the use of the particular EHEC of this invention is due to the degree of substitution of the ethoxyl and hydroxyethyl substituents, with no significant effect of the viscoity of the gum on this property. Differences in product strength are also not obtained when different molecular weights or viscosities of this EHEC are employed, since at the low usage concentrations involved in tobacco foam stabilization, the EHEC does not function as an adhesive to any measurable extent.

In the practice of this invention, any of the processing modifications employed in the four Moshy and Germino patents may be employed, with ethylhydroxyethyl cellulose with an ethoxyl D.S. of 1.2 to 1.6 and a hydroxyethyl molar substitution of 0.5 to 1.2 being used at a concentration of 0.3 to 2.5 percent of the composition (Dry basis) in place of the foam stabilizing agents employed by Moshy and Germino. Accordingly, the stabilized tobacco foam may be prepared by: (a) foaming the foaming agent, then adding tobacco and the foam-stabilizing agent (the EHEC of this invention); (b) foaming the foam stabilizing agent (the EHEC of this invention), then adding tobacco and the foaming agent; (c) foaming a foaming agent, foam stabilizing agent (the EHEC of this invention) mixture, then adding tobacco; (d) foaming a mixture of foaming agent, foam-stabilizing agent (the EHEC of this invention) and tobacco; (e) foaming a mixture of foaming agent and tobacco, then adding foam-stabilizing agent (the EHEC of this invention); (f) foaming a mixture of foam-stabilizing agent (the EHEC of this invention) and tobacco, then adding foaming agent.

It should be noted that if tobacco is treated in a manner such that its adhesive properties are fully developed, such as in Light and Osborne U.S. Pat. No. 661,762, then addition of one of the adhesive foaming agent types referred to by Moshy and Germino is not necessary. Accordingly, (f) above, for example, would involve only foaming a mixture of foam-stabiling agent (the EHEC of this invention) and tobacco, shaping and drying to a preselected moisture content.

Optional additives in the formulations of this invention include humectants or plasticizers, ash whiteners, fungicides, fibers for reinforcement and cross-linking or insolubilizing agents for resistance to water. Use of such additives, of course, depends on the particular properties required in the final smoking article.

In working with the dispersions and foamed dispersions containing the EHEC of this invention as the foam-stabilizing agent, it must be remembered that this material has a low thermal gelation temperature. Care must be taken at each step of the tobacco slurry preparation, foaming, transfer and shaping, to insure that the thermal gelation temperature is not approached, other gelatin or precipitation will occur and the foam stabilization property will be lost.

The following examples are provided as further illustrations of the inventive concept, and should not be construed as limitations on the invention.

EXAMPLE 1

A tobacco slurry is prepared by adding, with mild agitation, 0.2 parts (dry basis) of a 3.0 percent dispersion of refined sulfite pulp to one part (dry basis) of a 2 percent aqueous dispersion of methylcellulose with a viscosity of 15,000 c.p.s. The pulp dispersion and the methylcellulose dispersion are each at about 5.degree. C. before mixing, and 10.degree. C. or less after the mild agitation. To this mixture is added, with mild agitation, 0.03 parts (dry basis) of a 2 percent solution of ethylhydroxyethyl cellulose with an ethoxyl D.S. of 1.2 a hydroxyethyl M.S. of 0.5, a viscosity of 15,000 c.p.s. and at a temperature of 5.degree. C. Also, a 20 percent aqueous dispersion of minus 80 mesh Bright tobacco leaf is added, and the completed slurry is mixed for 15 minutes, to produce a uniform dispersion at a temperature of 16.degree. C. The tobacco slurry is foamed to a density of 0.55 grams/cc., using Hobart mixer with a wire whip, and the resultant foamed slurry is cast on a moving stainless steel belt at a thickness such that the tobacco slurry film after drying, will weigh 6 grams per square foot. The foamed tobacco sheet product is 24 mils thick, as compared to a conventional nonfoamed product of the same formulation which would be only 6 -7 mils thick at 6 grams per square foot . It may be shredded and used as a cigarette filler.

EXAMPLE 2

A 6 percent solids dispersion of refined burley stem pulp is prepared to a Schopper-Riegler freeness of minus 300 cc. using the stem pulp preparative procedure described by Light and Osborne in U.S. Pat. Ser. No. 661,762. To 6 parts (dry basis) of this tobacco stem pulp is added, with agitation, 4 parts (dry basis) of a 20 percent dispersion of minus 120 mesh Wisconsin leaf dust and 0.25 parts of a 2 percent aqueous dispersion of ethylhydroxyethyl cellulose with an ethoxyl D.S. of 1.6, a hydroxyethyl M.S. of 1.2 and a viscosity of 300 c.p.s. Mild agitation is continued until a uniform dispersion is obtained, with care being taken to prevent the slurry temperature from rising above 20.degree. C. The resultant tobacco slurry is foamed to a density of 0.60 grams per cc. and may be cast and dried in sheet form as in Example 1, or extruded or molded to product, after drying, a porous self-supporting rod or other core shapes suitable for wrapping as a cigar.

Claims

What is claimed is:

1. The process of manufacturing a smokable product comprising creating a foamed slurry from a foaming agent or adhesive, tobacco particles, water and 0.3 percent to 2.5 percent, by weight of the nonsolvent ingredients, of ethylhydroxyethyl cellulose with an ethoxyl D.S. of 1.2 to 1.6 and a hydroxyethyl M.S. of 0.5 to 1.2, shaping said foamed slurry while maintaining the temperature thereof below the gelation temperature of said ethylhydroxyethyl cellulose and subsequently drying said slurry to a shaped sheet or rod form of a predetermined moisture content.

2. The process of manufacturing a smokable product comprising creating a foamed slurry from tobacco particles, water, 0.3 percent to 2.5 percent by weight of nonsolvent ingredients of ethylhydroxyethyl cellulose with an ethoxyl D.S. of 1.2 to 1.6 and a hydroxyethyl M.S. of 0.5 to 1.2 and a foaming agent in amounts between 3 percent and 15 percent by weight of the nonsolvent ingredients and selected from natural or synthetic hydrophylic gums in which the natural gums are selected from carbohydrate classes including the animal gums such as glycogen, plant gums and their derivatives, such as cellulose ethers, cellulose esters, starches, starch ethers, starch esters, amylose, amylopectin and their ester and ether derivatives, locust bean gum, guar gum, gum arabic and related seed gums and plant exudate gums, marine plant gums, such as algins, carrageenans laminarins and agar, and microbial gums such as the dextrans, phosphomannans such as the USDA B-1459 and B-1428, and the gluconic acid microbial containing gums such as the USDA Y-1409 gums, and protein classes including water dispersible proteins such as animal proteins such as hydrolyzed keratins, egg albumin, and vegetable proteins such as gluten, and the synthetic gums are selected from the group consisting of polyvinyl alcohol, polyoxyethylene and polyacrylamide shaping said foamed slurry while maintaining the temperature thereof below the gelation temperature of said ethylhydroxyethyl cellulose and subsequently drying said slurry to a shaped sheet or rod form of a predetermined moisture content.