Tobacco treatment and product therefrom

United States Patent Office

3,020,179

Patented Feb. 6, 1962

3,020,179 TOBACCO TREATMENT AND PRODUCT

THEREFROM

Earl II. Hess, Lancaster, Pa., assignor to General Cigar Co., Inc., New York, N.Y., a corporation of New York

No Drawing. Filed Dec. 29,1959, Ser. No. 862,451 24 Claims. (Cl. 131—17)

This invention relates to the manufacture of coherent , tobacco products suitable for smoking and more particularly to such tobacco products formed in part of comminuted tobacco and in part of comminuted tobacco which has been treated to develop a cohesive property sufficient to hold the first-mentioned part of comminuted tobacco in a coherent form.

Several processes have been developed for converting tobacco leaves, trimmings and stems into continuous tobacco sheets that may be utilized in the manufacture of cigars and cigarettes. These prior processes have generally been predicated upon the use of extraneous binding agents which serve to hold the particles of comminuted tobacco together in a coherent form. In spite of the commercial success of some of these processes, the tobacco industry has long sought a process which would avoid the use of an extraneous binding agent. Several ' attempts have been made to produce tobacco sheets with* out the addition of an extraneous binding agent but none ΐ; appears to have been adopted for commercial operation.

E For instance, U.S. Patent 2,433,877 proposes a. process in which all of the tobacco to be converted into a sheet * is ground in water for a very long period of time so that the tobacco is largely reduced to colloidal particles. According to the patent, the prolonged wet grinding of tobacco yields an aqueous colloidal suspension of tobacco which may be spread as a coating on a support and the coating then dried to a coherent sheet. While the patent alleges that the aroma and smoke taste of the tobacco remain unaltered by the prolonged wet grinding, other workers in the tobacco industry have found that tobacco invariably undergoes changes when subjected to extensive wet grinding. Moreover, U.S. Patent 2,485,670 sets forth an additional proposal as an improvement of the process disclosed in U.S. Patent 2,433,877. The improvement patent states that its chief object is the production of improved sheets. Experience has revealed that tobacco sheets made solely by prolonged wet grinding of the tobacco not only have inferior aroma and smoking properr ties as compared with leaf tobacco but also have poor L physical properties, making such sheets unsatisfactory for f use in the commercial manufacture of cigars and cigaf rettes. The improvement patent proposes to increase the Ί tensile strength of a tobacco sheet made by wet grinding tobacco by subjecting the aqueous colloidal tobacco suspension to heating at a water vapor temperature of 250° F. under a pressure of 15 pounds per square inch. This heating step, which lasts from 3 to 6 hours, precedes the spreading and drying of the tobacco suspension to form a sheet. The alleged improvement of tensile strength of the sheet resulting from this interposed step of heating the tobacco suspension to a temperature of 250° F., has not been sufficient to bring the proposal into commercial production. In any event, even though there may be some increase in tensile strength, the heating step certainly does not bring back the losses in aroma and in smoking properties arising when tobacco is converted into a sheet by extensive wet grinding of the tobacco.

A primary object of this invention is to convert comminuted tobacco into a coherent tobacco product without reliance on extraneous binding agents and without subjecting all of the tobacco to the inherent changes resulting from extensive wet grinding of tobacco.

Another important object is to process a portion of the tobacco to develop therein a cohesive property sufficient to hold another portion of finely divided tobacco in a coherent form.

These and other objects and advantages of the inven5 tion will be apparent from the description which follows.

In accordance with this invention, a quantity of tobacco is placed in water and heated while in water in a sealed zone to attain a steam pressure of at least 90 pounds per square inch absolute (p.s.i.a.) and thereby de10 velop a cohesive property in the treated tobacco. This treatment of tobacco at an elevated steam pressure is of limited duration and should not exceed a steam pressure of 300 p.s.i.a. to achieve desirable results. In general, a heating period of 5 to 50 minutes is satisfactory. It is 15 usually preferred to maintain the tobacco in water heated to a steam pressure in the range of 110 to 140 p.s.i.a. for a period in the range of 10 to 30 minutes. The resulting aqueous slurry of treated tobacco has sufficient cohesive property that another quantity of finely divided tobacco, 20 which has been neither ground nor boiled in water, may be combined with the slurry and the composite dried to a coherent tobacco product. In spite of the incorporation of a substantial quantity of tobacco that has been simply dry-ground, the tobacco sheet or like coherent 25 product has all of the tensile strength requisite for use of the product in cigar, cigarette and pipe tobacco manufacturing operations in addition to fine aroma and smoking properties stemming principally from the quantity of tobacco that has not been treated or altered.

Obviously, for products of optimum smoking quality, the quantity of untreated tobacco should be as large as is consistent with the attainment of adequate tensile strength. From the economic point of view, it is naturally also desirable to treat a minimum quantity of to35 bacco in water at the elevated steam pressure range required in the process of this invention. Experience, has shown that generally the quantity of untreated tobacco cannot exceed 75 % of all the tobacco used in making a sheet or like coherent product. The proportion of treated 40 to untreated tobacco will vary in each case depending upon the tobacco used and the selected conditions for treating a portion of the tobacco as well as the desired tensile strength of the product in relation to subsequent utilization such as in the manufacture of cigars , and cig45 arettes. However, to ensure satisfactory smoking quality, the tobacco sheet or similar coherent tobacco product should be made of tobacco of which not less than 25% by weight has not been subjected to wet-grinding or cook-, ing in boiling water. In most instances, tobacco prod50 ucts with desirable physical properties made pursuant to this invention have between 50 .and 70% by weight of the total tobacco content in an essentially unaltered state.

The quantity of tobacco which is subjected to treatment in water heated to an elevated steam pressure may 55 initially be a finely divided state or, if large tobacco fragments are placed in water for treatment, the resulting aqueous suspension may be processed to convert the suspension into a creamy pulp. Preferably, the aqueous tobacco suspension, after the heat treatment, is homog60 enized, whether or not the treated tobacco was initially in a finely divided form.

While homogenization may be performed with any known means, such as a Waring Blendor, a device which subjects the aqueous suspension to intensive shearing is 65 particularly advantageous. Accordingly, a valve-type homogenizer operating at a pressure of the order of at least 2000 pounds per square inch gauge (p.s.i.g.) is preferred for converting the aqueous suspension into a uniform homogenized pulp. The valve-type homogenizer 70 may optionally be operated at pressures up to 5000 p.s.i.g; and higher but in the usual case there is no technical·or* economic justification for operating at pressures bevond

3,020,179

5000 p.s.i.g. Where the tobacco subjected to the heat treatment is initially in the form of large fragments or coarse particles, say particles retained on a 20-mesh screen, it is advisable to pass the aqueous tobacco suspension, after heat treatment through a wet grinder, such as a wet hammer mill or a Rietz disintegrator having a high-speed rotor within a stator, in order to obtain a creamy pulp that may be spread evenly in subsequent operations involved in making a tobacco sheet or similar coherent product. As previously mentioned, the creamy pulp obtained by wet-grinding the aqueous tobacco suspension that has been heated may also preferably be homogenized by passage through a valve-type homogenizer.

The creamy pulp of tobacco which has been heated to an elevated steam pressure, with or without homogenization, serves as the aqueous binding agent for a further quantity of finely divided tobacco that has been exposed to neither grinding nor boiling in water. This further quantity of tobacco is advantageously dry-ground to particles of which more than 99% by weight pass through a 100-mesh screen and more than 25% by weight pass through a 200-mesh screen. U.S. Patent 2,897,103 to A. M. Gottscho discloses that tobacco sheets of notably high tensile strength are obtained when the amount of tobacco particles passing through a 200-mesh screen is increased to more than 86% and preferably more than 95 % of the total weight of the powdered tobacco. Accordingly, very fine tobacco powder'is favored in making the coherent tobacco products of this invention.

Where the finely divided tobacco added to the aqueous binding agent of this invention constitutes on the order of 50% or more by weight of the total tobacco content of the tobacco sheet or similar coherent product made therefrom, it is advantageous to increase product tensile strength by mixing only part of the finely divided tobacco with the aqueous binding agent and moderately homogenizing this incomplete mixture, say by passing it 1 to 3 times through a valve-type homogenizer. The remaining finely divided tobacco, which is desirably not less than about 25% by weight of the total tobacco content, is subsequently combined with the homogenized incomplete mixture to produce a continuous sheet or similar coherent form of tobacco.

An autoclave conveniently provides the sealed zone requisite for heating an aqueous suspension of tobacco in accordance with this invention. Advantageously, the autoclave is equipped with a moderate speed stirrer, i.e., a stirrer having a speed in the approximate range of 500 to 1500 revolutions per minute. With a stirrer autoclave, the comminution of the tobacco to be treated therein may be minimized to the extent that even physically tough tobacco stems previously cut to coarse pieces of about % to Va inch in length may be used. The benefit of cooking coarse particles of tobacco in the autoclave appears to lie in fiber preservation. Tobacco fiber fragments which survive the process of converting comminuted tobacco into a continuous sheet improve both the tensile strength and flexibility of that sheet. Where the tobacco entering the autoclave is in the form of coarse particles, it is usually necessary to homogenize the aqueous slurry of treated tobacco· to a smooth pulp which may be spread evenly in the sheet-forming operation. Use of a valve-type homogenizer operating at an elevated pressure of the order of at least 2000 p.s.i.g. is favored since homogenization is thereby achieved without complete fiber destruction or disappearance.

Where there is an opportunity to keep tobacco stems separated from tobacco laminae and both materials are to be used in making a product of this invention, it is preferred to treat the stems in the autoclave and to prepare from the laminae the finely divided tobacco which is, ultimately combined with the treated portion of the tobacco. In this manner, the components of tobacco stems which ordinarily contribute a certain harshness to the smoke of cigars and cigarettes are apparently altered because togacco stems treated in accordance with this invention have been found by smoking experts to give a blander smoke than that from the same tobacco stems without treatment. At the same time, by withholding at least a substantial portion of the tobacco laminae from the treatment in the autoclave, the final product has the benefit of the fine aroma and smoke taste components of tobacco laminae.

Some tobaccos tend to darken when treated in the autoclave so that the ultimate sheet or like tobacco product is darker than desired. It has been found that this darkening can be substantially eliminated by the use of hydrogen peroxide which may be introduced into the process of this invention at any convenient stage after the aqueous suspension of tobacco has been treated in the autoclave. Thus, a 3% aqueous solution of hydrogen peroxide may be sprayed on a tobacco sheet made by the process of this invention to lighten the color thereof. However, it is usually preferable to admix concentrated hydrogen peroxide (30% strength) directly with the creamy or homogenized pulp of treated tobacco before the casting or like forming operation. The quantity of hydrogen peroxide consumed will naturally vary with the darkening propensity of the tobacco used and the degree of lightening to be achieved. Simple trials with varying amounts of hydrogen peroxide will indicate the optimum proportion in each case. Generally, 10 to 50 cubic centimeters of concentrated hydrogen peroxide (30% strength) for each 100 grams of total tobacco content of the casting pulp will give a tobacco sheet of good color.

It is significant that the effectiveness of the process of this invention lies within a comparatively narrow temperature range. Examination of a steam table shows that the operative steam pressure range of 90 to 300 p.s.i.a. corresponds to the temperature range of about 320 to 417° F. Of course, the preferred pressure range of 110 to 140 p.s.i.a. embraces only an 18° F. variation, i.e., from 335 to 353° F.

As known in the tobacco art, humectants and plasticizers such as glycerol, sorbitol and various glycols are used in tobacco smoking products to avoid excessive drying and embrittlement of the tobacco prior to smoking. Humectants and plasticizers are desirably incorporated in the products of this invention at any point in the process, after part of the tobacco has been treated in the autoclave. Humectants and plasticizers in an amount usually not exceeding about 10% by weight and frequently not exceeding about 5% by weight of the total tobacco content are conveniently added to the homogenized pulp of treated tobacco when the powdered tobacco is also combined therewith. Humectants and plasticizers may be even added to the final product of the invention by applying such materials, usually in aqueous solution, as a coating or spray on the final product.

The composite of treated tobacco pulp and dry-ground tobacco may be converted to a continuous tobacco sheet on a stainless steel conveyor belt equipped with a film applicator such as a reverse roll coater and with, dry hoods, all as shown in U.S. Patent 2,747,583. In making tobacco sheets pursuant to this invention, it has been found particularly advantageous to heat the film or coating applied on the top side of the stainless steel belt by condensing steam on the bottom side. Such technique is illustrated in U.S. Patent 2,155,453. In this way, a very high drying speed is attained without impairment of the final product.

In most instances, the layer of aqueous binding agent and powdered tobacco applied on the conveyor belt is dried to an adherent film; that is more readily removable from the belt after reordering, i.e., conditioning with moisture. U.S. Patent 2,747,583 demonstrates reordering of the adherent film with a fine water mist from a spray nozzle which may desirably be enclosed by^; a humidifica3,020,179 tion chamber as illustrated in U.S. Patent 2,867,220. Alternatively, a spongy roller, maintained continuously wet with water, may be disposed in rotating contact with the conveyor belt so that the dry tobacco film is moistened as it passes under the roller. As previously indicated, humectants and plasticizers like glycerol may be admixed with the water used in recording the tobacco film.

.The reordered tobacco film is then removed or peeled from the conveyor belt and wound up as a roll of continuous. tobacco sheet as shown in U.S. Patent 2,747,583. Often, a doctor blade is used to facilitate parting of the tobacco sheet from the surface of the belt. Where the tobacco sheet is ultimately shredded for use in the manufacture of cigarettes or pipe tobacco, the sheet may be cut into pieces, such as squares with sides measuring 2 or 3 inches, as it is removed from the conveyor belt so that these pieces which are collected in suitable bins may subsequently be easily blended, prior to shredding, with tobacco leaves going into the cigarettes or pipe tobacco.

For a better understanding of the invention and its scope, illustrative embodiments are presented hereinbelow in detail. In the examples, proportions are given in parts by weight unless otherwise specified.

Example 1

Tobacco rejects from cigarette manufacturing operations were collected in three fractions, namely, 25 parts of Burley tobacco stems, 30 parts of winnowings (slivers or small particles of cut tobacco vein and rib), and 45 parts of short (small particles broken from tobacco leaves during processing).

The Burley stems, flaked between differential calender rolls and cut to pieces approximately 14 inch in length, and the winnowings were admixed with 695 parts of water. The aqueous tobacco suspension was heated in a sealed autoclave provided with a stirrer operating at 800 revolutions per minute. The heating was controlled to raise the temperature of the water in the autoclave rapidly to develop a steam pressure therein of 115 p.s.i.a. The contents of the autoclave were maintained at that steam pressure for 20 minutes and then cooled and depressurized.

The thus treated aqueous tobacco suspension was passed twice through a valve-type homogenizer operating at a pressure of about 3000 p.s.i.g.

The tobacco shorts were dry-ground to a powder completely passing through an 80-mesh screen and this tobacco powder (45 parts) was blended with the homogenized pulp of treated tobacco.

One-half of the blend was spread on a stainless steel belt heated from the underside by steam at a gauge pressure of less than an inch of water. A gated hopper was used to cast the blend of homogenized pulp and tobacco powder on the steel belt. The wet coating on the belt was dried to a continuous tobacco sheet and rehumidified with a fine water mist to facilitate further handling of the sheet. The rehumidified tobacco sheet was removed from the steel belt with the aid of a doctor blade and was cut into squares measuring 3 inches on each side. The tobacco sheet was about 0.004 inch in thickness and had satisfactory tensile strength and flexibility even though no plasticizer had been used in making the sheet. The color, however, was distinctly darker than that of the original tobacco rejects.

To the other half of the blend of homogenized pulp and tobacco powder were added 20 parts of hydrogen peroxide (30% strength) and 15 minutes later this half of the blend was cast, dried, rehumidified and removed as a tobacco sheet from the stainless steel belt in the same manner described for the first half of the blend. This tobacco sheet was appreciably lighter in color than that of the first sheet; this color was not materially different from that of the original tobacco rejects. While hydrogen peroxide had been beneficial in maintaining the original color of the tobacco used in making the sheet, it was noted that the ten6 site strength and flexibility of the sheet had remained substantially unchanged.

Each of the two tobacco sheets was blended with leaf tobacco and converted into cigarettes by the conventional manufacturing technique. Cigarettes made with a tobacco blend containing 12% by weight of the shredded tobacco sheet were submitted to a panel of smoking experts. The cigarettes containing the first tobacco sheet as well as those containing the second sheet (treated with hydrogen peroxide) were given very favorable ratings in smoking qualities; some experts preferred both experimental cigarettes over the standard cigarettes made with the same leaf tobacco but free of either tobacco sheet because the smoke of the standard cigarettes was not as mild as that from either experimental cigarette.

Example 2

Sixty-seven parts of stems and 33 parts of cuttings of Connecticut shade-grown tobacco were comminuted in 1400 parts of water and the aqueous tobacco dispersion was heated in a sealed autoclave while being stirred. The contents of the autoclave were maintained at a steam pressure of 140 p.s.i.a. for 20 minutes. The thus treated aqueous tobacco dispersion was cooled and transferred to a Waring Blender homogenizer wherein it was homogenized for 10 minutes.

A blend of Pennsylvania and Wisconsin cigar tobaccos was dry-ground to a powder completely passing through a 100-mesh screen and 100 parts of this tobacco powder were admixed with the aqueous homogenized pulp of treated tobacco.

As in Example 1, the composite pulp was cast, dried, rehumidified and removed as a tobacco sheet from the stainless steel belt. However, instead of cutting this tobacco sheet into squares, it was slit into ribbons approximately 3 inches wide and each ribbon was wound on a spool adapted for use on a cigar-making machine provided with a device for feeding this ribbon automatically as the cigar binder.

Cigars made with binders of the tobacco sheet were adjudged by smoking experts to be as fine in smoking qualities as the same cigars made with leaf tobacco instead of the tobacco sheet. Again, some smokers commented favorably on the mildness of the smoke from the cigars made with this tobacco sheet as a binder.

Example 3

One hundred and twenty-five parts of Burley stems, flaked and cut as in Example 1, were mixed with 1400 parts of water and heated rapidly in an autoclave to generate a steam pressure of 280 p.s.i.a., which pressure was maintained for 7 minutes. The autoclave was cooled and the contents were transferred to a Waring Blendor homogenizer for a 5-minute treatment.

An amount of the resultant homogenized pulp equivalent to 50 parts of Burley stems was mixed with 92.5 parts of cigarette tobacco shorts, dry-ground as in Example 1, and about 800 parts of additional water to allow good mixing. Mixing with a high-speed stirrer was allowed to proceed for 15 minutes after which the aqueous tobacco blend was cast and dried to a tobacco sheet. This product had mechanical and smoking properties suitable for its use as cigarette or pipe filler although its color was dark.

The remaining portion of homogenized pulp equivalent to 75 parts of Burley stems was blended with 139 parts of ground cigarette tobacco shorts and 1200 parts of additional water in the same manner just described. After the 15-minute stirring period, 75 parts of hydrogen peroxide (30% strength) were added with hand stirring to the aqueous tobacco blend. Ten minutes after adding the hydrogen peroxide, the aqueous tobacco blend was cast and dried to a tobacco sheet of lighter color than that of the previous sheet. Again, this product had mechanical properties suitable for its -used, as cigarette or pipe filter.

3,020,179 β

The smoking aroma of this tobacco sheet was superior to that of the same tobacco sheet made without the use of hydrogen peroxide.

Example 4

One hundred and twenty-five parts of winnowings, rolled and then passed once through a hammermill having a screen with ’/i-inch openings, were mixed with 1400 parts of water and the mixture was heated rapidly in an autoclave to generate a steam pressure of 100 p.s.i.a. This steam pressure was maintained for 40 minutes after which time the autoclave was cooled. The tobacco slurry was then treated for 5 minutes in a Waring Blendor homogenizer.

A portion of the homogenized tobacco pulp equivalent to 50 parts of winnowings was admixed with 21.5 parts of dry-ground tobacco shorts and 500 parts of water with stirring for 15 minutes. The aqueous tobacco blend was then converted to a tobacco sheet in the usual manner. This product had a dark color and physical properties making it suitable for shredding to provide 10% by weight of a cigarette filler.

The remaining 75 parts of homogenized tobacco winnowings were also blended with dry-ground tobacco shorts and water in the same proportions just used. After the 15-minute stirring operation, 36 parts of hydrogen peroxide (30% strength) were added and 10 minutes later the aqueous blend was cast and dried to a light-colored tobacco sheet having physical properties comparable to those of the same tobacco sheet prepared without the use of hydrogen peroxide. It was found that the use of hydrogen peroxide gave a tobacco sheet of better smoking aroma.

Many variations and modifications of the invention hereinabove disclosed will be visualized by those skilled in the art without departing from its spirit and scope. Accordingly, the claims should not be interpereted in any restrictive sense other than that imposed by the limitations recited within the claims.