US3411515A

US3411515A - Method of preparing a reconstituted tobacco sheet employing a pectin adhesive

Info

Publication number: US3411515A
Application number: US647278A
Authority: US
Inventors: John D Hind; Robert B Seligman
Original assignee: Philip Morris USA Inc
Current assignee: Philip Morris USA Inc
Priority date: 1967-04-28
Filing date: 1967-04-28
Publication date: 1968-11-19
Anticipated expiration: 1985-11-19

Description

United States Patent ABSTRACT OF THE DISCLOSURE This disclosure relates to a process for producing a binder composition for use in the manufacture of reconstituted tobacco. The binder is made from tobacco plant parts and involves the use of the naturally occurring tobacco pectins, which are obtained by a process in which an alkali metal phosphate is employed to treat the tobacco plant parts. The treatment involves the destruction of the alkaline earth metal cross-links of the tobacco pectins, the release of the resulting tobacco pectins by a washing action and the depositing of the released tobacco pectins 0n the treated plant parts.

This application is a division of application Ser. No. 557,903, which was filed on June 16, 1966, now Patent No. 3,253,541, and which, in turn, is a continuationin-part of application, Ser. No. 336,009, which was filed on January 6, 1964, now abandoned and which, in turn, is a continuation-in-part of application, Ser. No. 240,130 filed November 26, 1962, now forfeited, and application Ser. No. 169,995 filed January 16, 1962, now abandoned.

This invention relates generally to a method for the production of an adhesive tobacco composition in which the tobacco pectins within the tobacco itself serve as the binder.

During the production and processing of tobacco products, including aging, blending, sheet forming, cutting, drying, cooling, screening, shaping and packaging, considerable amounts of tobacco fines and tobacco dust are produced. It is known that such tobacco fines and dust can be combined with a binder to form a coherent sheet, which resembles leaf tobacco and which is commonly referred to as reconstituted tobacco. One method for making reconstituted tobacco of this general character is disclosed in United States Patent No. 2,734,510, wherein the tobacco fines and dust are applied to a binder made of carboxymethyl cellulose carboxymethyl hydroxethyl cellulose or a suitable salt thereof. The binder, in such compositions, ranges from about 5% to about 50% of the weight of the tobacco employed. United States Patent No.

2,708,175, describes a binder for reconstituted tobacco which consists of a plant gum, principally of galactomannan. United States Patent 2,592,554 to Frankenburg, describes, as binders for reconstituted tobacco, various water-soluble polysaccharides, such as alginic and pectinic acids and their sodium and potassium salts, derived from plants other than tobacco; for example derived from citrus "ice fruits. However, the addition of cellulosic binders further increases the amount of cellulosic material in the product and tends to create an acrid and bitter smoke, when the product is used to make cigarettes. The natural hydrophilic celloid gums such as guar gum, locust bean gum, algin and other commonly used materials, such as Irish moss, have additional disadvantages. These materials contain proteins and other materials not found in tobacco which add distinctive flavors of their own to tobacco products during smoking. Thus, Frankenburg, in describing the use of various water-soluble polysaccharides derived from plants other than tobacco, teaches that care should be exercised that they must be in a state of refinement. Frankenburg teaches that these materials should be free of extraneous matter containing compounds of nitrogen, particularly proteins, and compounds of sulfur, phosphorus and the halogens; i.e., compounds giving undesirable products of combustion or dry distillation. Such refining is often a very tedious and diflicult operation.

The present invention makes possible the production of improved reconstituted tobacco by a method which is simpler and more effective than the methods previously employed. The present method does not require refining of the binder and is, therefore, more easily and efficiently employed than other methods for making binders and for making reconstituted tobacco. The reconstituted tobacco which is obtained in accordance with the present invention need not contain any additional cellulose or proteinaceous material which is foreign to tobacco, since the binder which is employed may be derived solely from tobacco, and may be produced in such a manner that it contains no materials other than those which naturally occur in tobacco. Thus, reconstituted tobacco producd in accordance with the invention, can be so formulated as to be similar in physical properties and chemical composition to natural tobacco.

The term pectic substances 1 will mean those substances which are found in many plant products, and which con- 'sist essentially of partially methylated galacturonic acids joined in long chains.

The pectic substances found in tobacco plants contain acetyl groups and differ considerably from commercially available pectins found in other plants, including sugar beet pectins and citrus and fruit pectins. Tobacco protopectins are uniquely insoluble in hot water as compared with protopectins from many other sources and comprise mainly water-insoluble pectins (pr'otopectins) consisting of the calcium and magnesium salts of partially esterified and slightly acetylated polymers of galacturonic acid. The divalent calcium and/or magnesium atoms act as crosslinks between acid chains, thus making the polymers water-insoluble. As an illustration, the structure of the calcium salt of a polymer of galacturonic acid can be represented as follows:

cross-link COOCa OH OH +4 OH on 0000111"? oooon, Although pectins have long been known as constituents of plant tissue, it has been found extremely dii'ficult to separate pectins from the remainder of plant compositions cross-link CHsC O O 1 Unless otherwise specified, the term pectin-s will, for convenience, hereinafter be employed interchangeably with the term pectic substances.

and to obtain them as homogeneous compositions. The recovery of pectins from tobacco is even more diflicult than the recovery of pectins from other plants.

In accordance with the present invention, tobacco parts are bonded together by tobacco 'pectins which are speci- 5 ally prepared by a novel process which yields these pectins in a form in which they can be employed as binder materials. Our process for preparing tobacco pectins comprises first reacting tobacco parts, preferably in a form in which they present a large surface area, with an aqueous solution of a non-toxic reagent which is capable of reacting with and destroying the calcium and magnesium crosslinks in the pectinaceous substances which naturally occur in tobacco. After the calcium and magnesium crosslinks are destroyed, the tobacco pectins are liberated and made available for use as a binder. The tobacco pectins are then dissolved or dispersed in solution, or are at least sutficiently released from the interstices of the tobacco mass so that they form a coating on the surface thereof. Tobacco pectins which are dissolved or dispersed in the treating solutions, are thereafter precipitated or deposited from the solution, so that they become available for use as a binder material. In this Way, the tobacco parts can be bonded together by a binder material which is made of ingredients that are closely related to the naturally occurring ingredients of tobacco. The bonding can be accomplished without the need for the purification of the tobacco pectins, inasmuch as any materials which are present are closely related to the materials which are normally present in tobacco and, thus, do not add any undesired qualities to the tobacco.

The tobacco parts which can be employed in the present invention including tobacco leaves, stems and stalks, or a mixture of these, whether in sheet, flake, particulate or other form. Preferably, the parts are ground out or otherwise prepared in a form which presents a large surface area. The portions of the plant comprising the stems or midribs, and often referred to as tobacco petioles, are the preferred starting materials. Tobacco stalks contain lesser amounts of pectinaceous materials but can also be employed.

In the first step of the process of our invention, tobacco pectins are liberated from pectinaceous materials in tobacco by reacting the pectinaceous materials with a reagent which, under the conditions of the reaction, is reactive with the calcium (and/ or magnesium) contained in them to form a compound or product having a lower calcium ion, and, in the case of magnesium, magnesium ion, concentration 2 in the treating solution than the naturally occurring calcium (or magnesium) pectate. This reagant may, for convenience, be herein-after referred to as a cross-link destroying reagent.

The reaction may be generally represented by Equation I, which illustrates the reaction of one type of tobacco protopectin (a calcium salt of a polymer of galacturonic acid), wherein calcium cross-links are present with the reagent of the present invention. In the equation, R may be hydrogen, in which case the product is pectic acid, or R may be a monovalent inorganic cation, such as sodium, potassium or ammonium, in which case the product is a soluble pectate.

cross-link 1 CHaC O (1) C 0 C0 Treating re- Calcium Pectate By concentration we mean concentration or activity as set forth in Glasstone, Textbook of Physical Chemistry, 2nd

edition, page 954, D. V. N ostrancl Company, Inc.

CHaCOO OH I Product having lower cation coni H (5H centration than the calcium pectate in the treating solution. Pectate Acid or Soluble Pectate In one embodiment of this invention, the reagent, which can be, and preferably is, in aqueous solution, acts by forming a precipitate with the calcium or magnesium, in which case, it can be a water-soluble monovalent metal salt of the formula M X wherein M is a monovalent inorganic cation, n is an integer having a value of l, 2, or 3 and X is an anion which may be monovalent or polyvalent, such that the calcium salt of the formula Ca X is essentially insoluble in the treating solution and p and q are integers corresponding to the functionality of X. Monovalent cations which are effective include the alkali metals such as sodium, potassium and lithium, and also include such monovalent cations as ammonium, and substituted ammonium ions (NR where R=aryl or alkyl. The anion portion of the molecule may be CO POE, HPO4 P121304, and the like. For example, the compound MnX could be sodium carbonate, Na CO since sodium is a monovalent inorganic cation and calcium carbonate is essentially water insoluble. Additional representative examples of precipitating agents are the orthophosphates, metaphosphates and carbonates of sodium, potassium, lithium and ammonium. In the case of the orthophosphates, the anion portion of the molecule may be either PO.,=, HPO or H PO Specifically, for example, when ammonium orthophosphate is used, the precipitate is calcium and/ or magnesium ammonium phosphate. The pH of this reaction should be between about 5.8 and 10 and the temperature may be as high as 400 C. but should, preferably, be between about 25 C. and about C. for a period of from about 1 minute to about 24 hours. Preferred precipitating agents which may be employed are the alkali metal carbonates, for example, sodium carbonate and potassium carbonate. Particularly preferred precipitating agents which may be employed are the alkali metal phosphates and, most particularly, the alkali metal orthophosphates and the ammonium orthphosphates, such as the ammonium phosphates and ammonium orthophosphate, sodium orthophosphate, potassium orthophosphate, sodium dihydrogen orthophosphate, ammonium dihydrogen orthophosphate, potassium dihydrogen orthophosphate, diammonium monohydrogen orthophosphate, disodium monohydrogen orthophosphate and dipotassium monohydrogen orthophosphate.

In a second embodiment the cross-link destroying reagent acts by sequestering the calcium or magnesium, thereby removing the calcium or magnesium atoms by forming a complex therewith. Suitable reagents of this type include any sequestering agent which will form a complex or chelate with the calcium and/ or magnesium, thereby removing the calcium and/0r magnesium and making them unavailable for recross-linking wih the peetin. Illustrative of such sequestering agents are ethylenediaminetetraacetic acid and similar amino acids, alkali metal polymetaphosphates such as tetra-metaphosphates, hexametaphosphates and trimetaphosphates, pyrophosphates and tripolyphosphates, such as sodium hexametaphosphate, tetrasodium pyrophosphate and pentasodium tripolyphosphate. The mechanism which occurs when a sequestering agent is employed is the formation of a chelate; calcium and magnesium ions are no longer available to combine with the pectate ions in solution. Many naturally occurring amines and peptides are also effective as sequestering agents for calcium and/or magnesium. Representative examples include alanine, aspartic acid, glycine, glycyl glycine, glutamic acid, serine, tyrosine and OOCHs di-iodo-l-tyrosine. Amino acids that are elfective as chelating solubilizing agents include beta alanine, N,N-di acetic acid; amino barbituric acid, N,N-diacetic acid; 2- amino-benzoic acid, N,N-diacetic acid; beta-aminoethylphosphonic acid, N,N-diacetic acid; beta-aminoethylsulfinic acid, N,N-diacetic acid and ethylenediamine-tetraacetic acid. The pH of this reaction should, preferably, be between about 4 and about and the temperature should, preferably be between about 0 C. and about 145 C. for a period of from about 1 minute to about 24 hours.

A cross-link destroying reagent may also function partially as a precipitating reagent, in accordance with the first embodiment of this invention, and partially as a sequestering agent, in accordance with the second embodiment of this invention. Such a reagent, for example, is diammonium monohydrogen orthophosphate (DAP), which is a particularly preferred material, in accordance with the invention.

In a third embodiment, the cross-link destroying reagent is an acid wash which forms the released but insoluble free pectic acid and soluble calcium and magnesium salts. Generally the acid wash will comprise an inorganic acid, such as hydrochloric acid, phosphoric acid, sulfuric acid or a similar acid, which will form soluble calcium and magnesium salts under the following conditions. Hydrochloric acid and sulfuric acid are particularly preferred. The acid may be employed as 0.25 N to 5.0 N solutions, but is preferably employed as 0.5 N to 1.0 N solutions. The exact dilution and amount to be employed will vary with the particular acid which is used, it only being necessary that sufficient acid be present to convert the calcium and magnesium present in the tobacco being treated to the calcium and magnesium salts of the acid. The acid treatment is preferably conducted at a temperature of from about l C. to about 50 C. The acid treatment comprises reacting the tobacco parts with the acid until the resulting mixture has a pH of from about 1.0 to about 2.5. Preferably, the pH is brought to from about 1.0 to about 1.7, the most desirable pH being between 1.15 and 1.55. This treatment will generally be conducted from about 10 minutes to 24 hours, depending in part on the size of the tobacco particles. The acid conditions which are necessary for this embodiment of the invention may be achieved by the use of ion exchange resins which may be used, with suitable recyle, to obtain the desired pH of the solution during treatment. The ion exchange resins may be used and regenerated in accordance with the usual practices for such resins.

Preferably, the mixture resulting from the acid treat-- ment is then washed with water. This water wash stepjis described treatment; thus, there should be at least 2 vol umes of water per volume of the mixture resulting from the acid treatment. The wash water is separated from the tobacco by any suitable means, for example, by conducting the wash in a centrifuge, filter press, Buchner funnel, or any other apparatus from which liquids can be substantially removed from solid materials.

In summary, in the first step of the first embodiment of this invention the treating agent #R attacks the calcium and/ or magnesium cross-links of tobacco protopectin and forms a precipitate which is a salt of calcium and/or magnesium, thus removing the calcium and/0r magnesium from the protopectin and from the solution. In the first step of the second embodiment, the treating agent Z=R is a sequestering agent which forms a chelate of the magnesium and/ or calcium from the tobacco protopectin and makes the calcium and/ or magnesium unavailable for recombining with the pectins. With certain reagents, such as DAP, the first step of the present process may comprise a combination of the mechanisms of the first embodiment of this invention and the mechanism of the second embodiment of this invention. In the first step of the third embodiment of this invention, the treating agent Z==R is an acid which attacks the calcium and/or magnesium cross-links of the tobacco protopectin and forms the soluble calcium and/ or magnesium salts, which are then washed away from contact with the pectins.

In the first step of each of the first two embodiments of the invention, the pectin which results is in condition for release from the tobacco cell structure, R in Equation I being a monovalent inorganic cation such as sodium. In the first step of the third embodiment, the insoluble pectic acid resulting from the acid treatment must be reacted with an alkaline material before it is in condition for release from the tobacco cell structure.

The acid treated pectins are placed in condition for release by bringing the mixture resulting from the acid treatment, and preferably, after the water wash described above, to :a pH of from about 5.0 to about 10.5 and, preferably, from about 6.3 to about 8.5, by the addition of an alkaline material. Suitable alkaline materials include ammonium hydroxide and alkali metal hydroxides, for example, sodium hydroxide, potassium hydroxide and lithium hydroxide, and alkali metal salts, such as sodium bicarbonate, sodium carbonate, sodium phosphate, and similar salts to convert the pectic acid to a soluble form. The alkaline material may be any water-soluble compound containing monovalent inorganic cation and capable of producing hydroxide ions when dissolved in water. The temperature of this step may be from about -1 C. to about 45 C., but is, preferably, from about 15 to about 35 C. The alkaline material is preferably in the form of solid particles or in the form of a solution having a concentration of from about 5 to about 50% Once the tobacco pectins have been liberated from the tobacco, by the removal of the calcium and magnesium cross-links, they should be released from the interstices of the tobacco. That is, they will be made available to the solution or suspension or, in certain instances, they will be merely deposited on the surface of the tobacco particles. Trhis comprises the second step of the process of the present invention. In embodiments 1 and 2 of the invention, this release or second step may be accomplished concurrently with the first step by reacting with the solution of the treating reagent. In embodiment 3, however, as indicated above, the insoluble pectic acid resulting from the treatment should be reacted with an alkaline material before it can be released. In such event, the release may be concurrent with the addition of the alkaline material due to a washing action. In any case, additional treating liquid or water may be used to effect the release through a washing action of the treated tobacco particles.

In accordance with the third step of our process, the liberated and separated tobacco pectins can next be precipitated or deposited in a relatively free form (as compared with the tobacco pectins as they were originally present in the tobacco), from the treating solution, for example, by being formed into the insoluble pectic acid or into an insoluble salt of pectic acid or by the action of a water-miscible solvent, such as acetone or ethyl alcohol to cause a water-soluble salt of pectic acid to go out of solution. In the case of tobacco pectin solutions such as solutions of sodium and potassium pectinates and/ or pectates, this can be accomplished by acidifying the solution until the pectins precipitate or by adding a gelation agent, such as an alcoholic solution, preferably having a pH of from about 1 to 9 and, preferably, from about 1 to 5. The pH of the alcoholic solution can be regulated by the addition of a mineral acid, such as HCl, to the alcohol. Although the preferred gelation agent is ethanol, any water-miscible organic solvent having up to about 10 carbOn atoms may be employed, for example, a ketone, such as acetone, or a diether, such as dioxane. Water-immiscible solvents such as ether, for example, ethyl ether. can

be used, if combined with a water-miscible solvent, such as acetone.

The tobacco pectins can be recovered by concentrating the solution or suspension in which they are present until they precipitate. This precipitate might also be characterized as an intractable mass, since the pectin solution, upon concentration, generally becomes progressively more viscous until it finally dries to leave a deposit in a glassy solid state.

While the tobacco pectins can be separated and purified before use as a binder in reconstituted tobacco sheets, they are preferably employed just as they are produced in situ, i.e., in combination with the treated tobacco plant parts from which they were obtained, the entire combination comprising the binder for reconstituted tobacco sheets or, under some circumstances, the entire combination comprising essentially the entire components of a reconstituted tobacco sheet. By using the entire mixture, no original tobacco flavors are lost, all of the tobacco is employed, and no expensive and time-consuming refining operations are required.

Although it is not necesary, the thixotropic properties of solutions containing soluble pectins can be adjusted in the preparation of a cured sheet by the addition of such materials as calcium chloride. If any complex or precipitate formed in the first step of this process is present with the soluble pectates, t-he thixotropic properties of the mixture can also be adjusted by adjusting the pH to precipitate calcium and magnesium pectates.

A preferred preliminary step, in accordance with the present invention, comprises washing the tobacco plant parts, which are preferably ground or cut to a relatively small size, with cold water. This water wash serves to remove impurities which might otherwise hinder the subsequent treatments in accordance with the present invention. It is particularly desirable to employ such a cold water washing step when alkali metal carbonates are employed as the reagent in the first step. Generally, sufficient water should be used during such a water wash operation to cover all of the tobacco plant parts present. The temperature of the water may be between -l C. and 100 C., but is preferably about 20 C., and the water wash should generally continue for a period of from about /2 to 2 /2 hours. Agitation during the wash is desirable, but not necessary. After the water wash has been completed, the water can be removed from the tobacco parts by filtration, decantation or other suitable means.

As discussed above a particularly preferred embodiment of the present invention involves the use of an ammonium or alkali metal orthophosphate, such as diammoni'um monohydrogen orthophosp'hate (DAP), for the release of the tobacco pectins. The DAP will, generally, be added to the tobacco plant parts, which may, for example, be bright tobacco parts, burley tobacco parts, or a mixture of the same, in an aqueous solution. The concentration of the DAP in the aqueous solution is not critical, but will, generally, be in the range of 0.55.0% by weight. The DAP and water may be added separately to the tobacco. The amount of DAP should, preferably, comprise from about 0.01 to about 0.5 part, and, most preferably, from about 0.05 to 0.35 part (by weight) per part of tobacco being contacted. A humectant, such as glycerin or triethylene glycol, may be present, if desired, at about 0.5 to 1 part per part of DAP. The temperature during the DAP treatment of the tobacco may vary between room temperature and about 190 F. or higher, depending on the type of tobacco being treated. Under pressure, even higher temperatures may be employed. The pH of the mixture is, preferably, maintained at a value about 7.1 to 9.0, which may conveniently be accomplished by the addition to the solution of concentrated aqueous ammonia. By agitating or stirring such a mixture under the above-described conditions for from about 1 minute to about 1 day, and, preferably, from about 1 hour to about 5 hours, the tobacco pectins are liberated, released and deposited in the tobacco plant parts to form a binder composition. The resulting mixture may then be refined, for example, in a disk refiner, until substantially all the pulp (in excess of the water present), can be shaken through a screen of approximately 18 mesh to produce a binder composition which is ready for use in the manufacture of reconstituted tobacco sheets.

The term tobacco pectins as used throughout this specification means liberated tobacco pectins and comprehends pectins which have been freed or liberated from tobacco and are, therefore, not bound into the tobacco structure, as differentiated from the insoluble, naturallyoccurring protopectins which are found into a plant cell structure. The term includes the free pectinic or pectic acid, as well as soluble salts such as the sodium, potassium, ammonium, pectates and pectinates, and insoluble salts such as the calcium and magnesium pectates and pectinates depending on what method is employed to liberate and obtain them from the naturally occurring insoluble protopactins.

The tobacco pectins produced or liberated in situ or isolated by means of this invention can be used as the sole binder material for reconstituted tobacco, i.e., no other materials need be added to make the sheet. They can be sprayed, extruded or cast, thus facilitating application onto a moving belt carrying tobacco dust. Under proper conditions of formulation and processing, reconstituted tobacco made with the tobacco pectins produced by this invention exhibit excellent physical and aromatic properties. The ultimate tensile and wet strengths of the reconstituted tobacco are good. While no other materials need be added to the pectinaceous binder, other materials can be added, if desired. For example, organic acids and preservatives which may in themselves be of tobacco origin, may be added. Plasticizers, such as glycols and polyglycols, and humectants, such an glycerin, may also be added, if desired. In addition, the gel strength of the tobacco pectins can be regulated by partial precipitation to control such rheological properties as viscosity, fluidity and elasticity. Other additives or dispersants may be added in small amounts to regulate slurrying qualities, provided, however, that such substances are not added in large enough quantities to adversely affect the flavor or aroma of the final product. Furthermore, the tobacco pectins can be combined with water-soluble gums or water-dispersible gums commonly used as binders for tobacco sheets such as methyl cellulose, sodium carboxymethyl cellulose, guar gum, locust bean gum, or alginates, although it is preferred to minimize or eliminate such additions in order to obtain a product which most closely resembles natural tobacco.

The produce from treating the tobacco plant parts in accordance with the methods of the present invention may be cast directly and dried and cut into particulate material similar in physical form to ordinary smoking tobacco and so used, preferably mixed with tobacco leaf cut or shredded in the usual manner. The product may be cast in sheet form, in blocks or as threads or other shapes, as desired. An important use, however, of the prepared composite slurry or easily molded isolated pectinaceous mass is as a a binder for ground tobacco and for the making of corresponding tobacco products suitable for smoking. Sheet material of widely different prop erties may be formed by suitable variations in the manner of forming. One method and product comprises flowing the composite slurry onto a moving belt and applying a layer of dry ground or fragmented tobacco to the Wet adhesive surface. If desired, there may be first applied to the belt a layer of the tobacco, followed by a layer of the binder, and then a top layer of the tobacco. Various additives may be included with the ground tobacco such as flavorants, plasticizers and aromatic substances. The web is ultimately dried and then suitably moistened and rolled up. Such methods of forming continuous sheets are known generally in the art and the details need not be further described. Representative of this procedure is the apparatus and method disclosed in US. Patent 2,734,513.

Another method of forming a reconstituted tobacco product, with the slurry of the isolated tobacco pectins as a binder, comprises mixing ground tobacco thoroughly therewith into a mass of dough-like consistency and then casting the mass in sheet form onto a moving belt surface followed by drying and remoistening in accordance with the known procedures. Representative of this procedure is the apparatus and method disclosed in US. Patents 2,708,175 and 2,769,734. Obviously, the reconstituted tobacco may also be formed by molding or other suitable means.

A particularly preferred aspect of the present invention comprises employing, as a binder or directly, the mixture of tobacco and tobacco pectins which have been produced in situ, without any separation steps and without the necessity for any additional adhesive materials.

The following exmaples are illustrative:

Example 1 Tobacco stems parts) were covered with cold water and leached for /2 hour. The water was then decanted and discarded. A treating solution, made from 1 part of sodium carbonate dissolved in 60 parts of water, was added to the leached parts. This mixture was heated at its boiling point for 30 minute at atmospheric pressure and then for minutes at 20 p.s.i.g. In the course of this treatment, the tobacco pectins were dissolved from the tobacco parts. The entire wet mass (pulp mixture) was dried and ground in a Waring Blendor so that it would pass through a 50 mesh screen. The resultant material had gel-like properties and was thixotropic in nature.

To this material was added 2 parts of glycerin, to serve as a humectant. The pH of the resulting mixture was adjusted to 6 by the addition of a solution of 10% hydrochloric acid. One gram of sodium carboxymethyl cellulose (CMC) was added to the mixture, giving a proportion of about 1 part of CMC to 10 parts of total solids in the mixture. Since it was desired to use this mixture as a sprayed tobacco binder, the CMC was employed in order to adjust the spraying qualities. The mixture of (a) treated tobacco plant parts, including the liberated tobacco pectins, (b) the sodium carboxymethyl cellulose and (c) the glycerin had a viscosity which was suitable for spray application of the mixture as a binding material for reconstitutedtobacco. This material was sprayed on top of an undercoating of tobacco dust, of an 80 mesh size, which had been dusted on a wet belt. Another coat of the tobacco dust was laid on top of the binder. In general an apparatus similar to that described in US. Patent 2,734,513 was employed. As in said patent, the reconstituted sheet was dried and was then humidified to the desired moisture content. The control in Table I was made in a conventional manner, using a relatively large amount of CMC in proportion to the pulped washed tobacco stems. The test data as observed are recorded in Table I.

1 Part CMC per parts of total tobacco solids in the slurry (including tobacco peer-ins) 2 The percentage of moisture contained in the entire sheet -(wet basis).

3 The breaking strength of a 10 cm. test strip which is 1 inch wide; an average of 10 strips.

4 One fold; test strip creased by application of a 400 gram weight for 30 seconds.

5 The percent elongation, at breakage, on the Instron Test Machine.

6 Free (fiameless) burning rate of a single test strip, in air.

The reconstituted tobacco sheets made pursuant to this example were shredded and made into cigarettes. The test cigarettes, as well as control cigarettes made from standdard reconstituted tobacco sheet, were submitted to a smoking panel for subjective testing. The panel found that the smoke of the cigarettes made by the method of this invention was significantly less harsh than the smoke obtained from the control cigarettes. A pleasing vanillin odor was found to be transmitted into the aerosol phase of the smoke from the test cigarettes made employing reconstituted tobacco made by the present invention.

Example 2 Fifty grams by weight of burley tobacco stems were thoroughly washed in about 5 liters of cold water for three hours. The washed tobacco stems were then mixed with 500 grams of water having dissolved therein 5 grams of sodium carbonate. The resultant mixture, containing about 8% solids, was steamed under atmospheric pressure for 30 minutes and under a pressure of 20 p.s.i.g. for an additional 20 minutes. At the end of this time, the mixture was allowed to cool and the liquid was separated from the solid materials. The solid materials were treated in a cider press to recover as much as possible of the remaining liquid. The liquid was added to a previously prepared coagulant bath which consisted of ethanol and hydrochloric acid, in an amount to adjust the pH of the coagulant to about 1.0. The resulting mixture (which had a pH of about 3.0) was alternately stirred and allowed to settle for a period of two hours. At the end of this time the mixture was strained through a cloth sieve and the filtrate was discarded leaving a solid, gel-like mass, consisting essentially of pectinaceous materials combined with approximately 10 parts of liquor. The yield of pectinaceous materials was 15%, based upon the dry weight of the starting tobacco plant parts. The mass was observed to be thixotropic, soluble in water at a pH of about 6 and soluble in a sodium carbonate solution.

The tobacco pectins thus isolated were quite impure and had a color characteristic of tobacco. The solid mass was then redissolved in a sodium carbonate solution and the resultant solution was poured into an acidified ethanol bath similar to the coagulant bath used earlier. The recoagulated solid was obtained :by filtration and dried in an oven at 105 C. The dried tobacco pectins were in the form of an opaque, substantially colorless sheet. When the sheet was pulverized, a white powder was obtained having a distinct and pleasing odor similar to vanillin.

Ten grams of the dried to'bacco pectins prepared above were swelled in ml. of cold water. The mixture was then added to a slurry consisting of 8.5 grams of refined kraft pulp dispersed in 200 ml. of water. The resultant mixture was homogenized in a Waring Blendor. Four grams of glycerin were then added to the mixture to serve as a humectant. The resulting mixture was cast into a binder film, using a Gardiner casting knife set to pro duce a sheet having a wet thickness of 50 mils. The physical properties of this sheet, after drying, were tested and were found comparable to the properties of conventional binder films. The physical test data are given in Table II. The control material was made by mixing pulp, which had been refined with NaOH, with sodium carboxymaterial cellulose (CMC) and a humectant, as is shown in Table II.

1 CMC (sodium carboxymethyl cellulose) and pulp, as prepared by known methods and containing about 33% CMC.

2 Work coelficient is proportional to the product of the tensile strength and the elongation.

1 1 Example 3 One hundred grams of burley tobacco stems were covered with distilled Water, leached for 30 minutes and then drained. The washed stems were then mixed with a solution containing 10 grams of diammonium monohydrogen orthophosphate in 600 ml. of water. The resultant slurry was heated for 1 hour at a temperature of from 90 to 100 C. The pH of the reaction mixture, after completion of the reaction, was about 7. The entire reaction mixture was homogenized in a Waring Blendor. The solids content was determined to be by weight.

Two grams of glycerin, to serve as a humectant, were blended with 200 grams of the above reaction mixture. A film of 50 mil wet-thickness was cast from this mixture. The extruded film was found to have the property of being able to slide off a surface even when newly cast. After the film was partially dried, it was found that it could be peeled off a plate by hand, while still partially wet and then hung up to dry like wet cloth. This property provides definite advantages in the manufacture of tobacco products.

Physical tests were carried out on the dried film thus prepared and were also carried out on a control film made by using conventionally pulped tobacco plant parts with sodium carboxymethyl cellulose (CMC) as the binder. A film of binder as made in this example was burned and was found to give a pleasant aromatic smoke. The test data was given in Table III.

Basis Weight, gins/ft 2 Moisture, percent Tensile Coefficicnt 2 Instron Tensile, p.s.i. Elongation, percent 15.1 4.1. Work Coefficient, gm. cm./sq. ins. 31.0 51.0.

1 Based on total solution.

2 Kg. per gm. of basis weight.

3 KgJin. for a cm. test strip.

4 Work coefficient is proportional to the product of the tensile strength and the elongation.

Examples 4-10 In each of these examples, burley tobacco stems were covered with distilled water, leached for 30 minutes, and drained. One hundred grams of stems were treated with the agent indicated in Table IV. The agent was dissolved in 600 ml. of distilled water in an amount sufiicient to make up a 10% (by weight) solution. The leached tobacco stems were placed in said solution and heated in a steam bath for 1 hour at a temperature of from 90 to 100 C. (Except for the example in which Versene was employed. That example was conducted at room temperature.) A five ml. aliquot was taken from the resulting mixture and mixed with mls. of ethyl alcohol in a graduated cylinder whereby a precipitate of tobacco pectins was obtained. The amount of precipitate in the graduated cylinder was observed. Each of these precipitates of tobacco pectins was suitable for use in the preparation of a reconstituted tobacco sheet in accordance with the methods taught by the present invention. The results obtained in these experiments are presented in Table IV below:

TABLE IV Volume of coagulated Reagent: tobacco pectins Pentasodium tripolyphosphate 15 Sodium hexametaphosphate 5 Diammonium monohydrogen orthophosphate (DAP) 15 Trisodium orthophosphate 15 Disodium monohydrogen orthophosphate 15 Dihydrogen monosodiurn orthophosphate 5 Versene (tetrasodium salt of ethylenediaminetetraacetic acid) 15 1 2 Example 1 1 One hundred grams of burley tobacco stems were covered with distilled water, leached for 30 minutes and drained. A solution of 10 grams of Versene (tetrasodium salt of ethylenediamine-tetraacetic acid) in 600 ml. of water was added to the stems and the mixture was made basic with aqueous sodium hydroxide. The resulting mixture was then heated for 1 hour at room temperature. The entire mixture (a pulp) was homogenized in a Waring blendor and the solids content was determined to be 5% by weight. A 200 gram portion of the pulp, thus prepared, was combined with 2 grams of glycerin as a humectant, and then cast into a film of 50 mils thickness by the use of a Gardiner casting knife. The resultant sheet was found to have satisfactory physical properties and, upon burning, exhibited a very pleasing aroma.

Example 12 Green bright tobacco leaves were soaked in isopropanol to remove sugars and chlorophyll. The midrib was stripped out of the leaves leaving the web. One thousand grams of the web (82 grams on a solids basis) were placed in a porcelain bucket and covered with boiling distilled water containing 9.3 grams of diammonium monohydrogen orthophosphate (DAP). The DAP was added on the basis of 10 grams of DAP per grams of stems (which contained 12% moisture, :by weight). The resulting mixture was boiled at low heat for one hour. The juice was then first expressed from the mixture by hand. Solids, for example cellulose and sand, were then further separated from the juice by centrifuging. The clear juice from both operations was then mixed with 70% ethanol to form a gel, which was then squeezed out in cheese cloth. The gel was transferred to a Biichner funnel where it was washed first with acetone and then with ethyl ether. Finally, the gel was placed in a vacuum desiccator and dried. The gel was suitable for use in the preparation of a reconstituted tobacco in accordance with the teachings of the present invention.

Example 13 Burley tobacco stalks were separated into cortical tissue, woody tissues, and pith. A sample of each was steam cooked with 10% sodium carbonate for 30 minutes at atmospheric pressure and for 20 minutes at 20 p.s.i.g. After this cooking, the woody tissues was still hard and could not be pulped in a Waring Blendor. The cortical tissue and pith were soft and pulpable. Each of these latter two preparations were suitable for use in the preparation of reconstituted tobacco.

Example 14 Coarse ground bright stem tobacco fines (30 grams) were washed thoroughly in cold water, and then placed in a boiling aqueous solution of 3 grams of diammonium monohydrogen orthophosphate and coked for 5 minutes. The mixture was then placed in a Waring Blendor. After a very short period in the blendor, the mixture was converted to a viscous, fine, impalpable slurry; wherein the tobacco stem particles had been completely separated to units of cellular size. This impalpable mass was suitable for use as a binder in reconstituted tobacco. When remixed with some of the cold water washings removed in the first step, the impalpable mass immediately became viscous and eventually jelled to a soft mass.

For further comparison, a similar sample of coarse ground stem fines (30 grams), was disparsed in boiling water and cooked for about 30 minutes with three grams of diammonium monohydrogen orthophosphate. The pH of this mixture was brought to a value of 7.1 by the addition to the mixture of 30% aqueous ammonia. The granules of tobacco could then be refined to a palpable pulp, similar to the soft mass produced in the experiment described in the first part of this example.

13 Example Burley tobacco stems /2 pound) were covered with distilled water, allowed to stand several hours and the water decanted. This step was repeated several times and finally the stems were covered with distilled water containing 50 ml. of concentrated HCl and left overnight at 24 C.

After standing overnight the acidic water was decanted and the stems washed repeatedly free of HCl until the wash water gave no precipitate when treated with silver nitrate solution. The stems were then covered with distilled water containing 15 grams of sodium carbonate and left overnight at 24 C. The pH of the sample, the following morning, was 8.8. The stems were swollen and soft and were easily disintegrated with the fingers and the mixture could be homogenized and employed, as a binder in reconstituted tobacco.

Example 16 The apparatus employed in this experiment was large scale equipment, comprising a 200 gallon conical bottom, open top, stainless steel tank, fitted with a Cowles high shear mixer.

One hundred and forty-eight gallons of water were placed in the tank and heated to a temperature of 207 F. One hundred and twenty-eight pounds of bright tobacco (milled to pass a 6 mesh per inch sieve) stems were added, while operating the Cowles mixer at a low speed. Almost immediately after the addition of the tobacco, nine and one-quarter pounds of diammonium monohydrogen orthophosphate (technical grade) were added to the mixture. Ammonia (assaying 28%, by weight NH Was added to adjust the pH to 7.1. The mixing speed was increased to 1700 rpm. After a period of 3 minutes the temperature of the mixture was 194 F. Most of the particles in the mixture were soft enough to be smeared by hand and the mixture had a jelly-like consistency. The mixing was continued for 1 hour to obtain the highest possible state of disintegration, although a 15 minute period appeared to be sufiicient for this purpose.

The viscosity of the mixture was found to be 10,400 cps. and its'solids content was found to be 8.05% by weight.

This mixture was then employed as a binder, being pumped through a filter to storage tanks and subsequently sprayed on tobacco by the method and equipment described in U.S. Patent 2,734,513. It was applied at the rate of 3 grams per square foot to form a reconstituted tobacco sheet having the following physical properties:

Weight of all the ingredients, including tobacco pulp essentially free of moisture. T Computed by an integrator attached to the Instron Tensile ester.

Example 17 Burley tobacco stems were washed in cold water whereby, from about 75 to 80% of the natural content of water-soluble substances were removed in the wash water. Thef stems were then dried and ground and used to make a binder as follows:

One hundred parts of water were brought to a temperature of 195 C., and to this were added: 7.00 parts by weight (dry basis) of the washed burley stems, 1.05 parts diammonium phosphate, and 0.70 part of glycerin, as a humectant.

Concentrated aqueous ammonia was then added to bring the pH of the mixture to a value of at least 7.1 but no higher than 9.0.

The mixture was then stirred for one hour and subsequently refined in a disk type refiner until better than 99% of the pump (in excess water) could be shaken through an 18 mesh sieve.

The resulting material was then employed as a binder for tobacco plant parts to form reconstituted tobacco sheet in a manner similar to that described in Example 16.

Example 18 Burley tobacco stems were washed in cold water whereby, from about 75 to of the natural content of water-soluble substances were removed in the wash water. The stems were then used directly in the wet condition to make a binder as follows:

One hundred parts of water were brought to a temperature of C., and to this were added: 7.00 parts by weight (dry basis) of the washed burley stems, 1.05 parts diammonium phosphate, and 0.70 part of a glycerin, as a humeclant.

The resulting material was then employed 'as a binder for tobacco plant parts to form a reconstituted tobacco sheet in a manner similar to that described in Example 16.

Example 19 Burley tobacco stems were washed in cold water whereby, from about 75 to 80% of the natural content of water-soluble substances were removed in the wash water. The stems were then dried and ground and used to make a binder as follows:

One hundred parts ofwater were brought to a temperature of C., and to this were added: 7.00 parts by weight (dry basis) of the washed burley stems, 1.05 parts diammonium phosphate, and 0.70 part of triethylene glycol (TEG), as a humectant.

The mixture was then stirred for one hour and subsequently refined in a disk type refiner until better than 99% of the pulp (in excess water) could be shaken through an 18 mesh sieve.

The resulting material was then employed as a binder for tobacco plant parts to form a reconstituted tobacco sheet in a manner similar to that described in Example 16.

Example 20 Burley tobacco stems were washed in cold water whereby, from about 75 to 80% of the natural content of water-soluble substances were removed in the wash Water. The stems were then used directly in the wet con dition to make a binder as follows:

One hundred parts of water were brought to a tem perature of 195 C., and to this were added: 7.00 parts by weight (dry basis) of the washed burley stems, 1.05 parts diammonium phosphate, and 0.70 part of triethylene glycol (TEG), as a humectant.

The resulting material was then employed as a binder for tobacco plant parts to form a reconstituted tobacco ilgeet in a manner similar to that described in Example Example 21 Bright tobacco stems were washed in cold water whereby, from about 75 to 80% of the natural content of water-soluble substances were removed in the wash water. The stems were then dried and ground and used to make a binder as follows:

One hundred parts of water were brought to a temperature of 100 C., and to this were added: 7.00 parts by weight (dry basis) of the washed bright (flue cured) stems, 1.05 parts diammonium phosphate, and 0.70 part of glycerin, as a humectant.

Concentrated aqueous ammonia was then added to bring the pH of the mixture to a value of at least 8.0 but no higher than 8.5.

The mixture was then stirred for four hours and subsequently refined in a disk type refiner until better than 99% of the pulp (in excess water) could be shaken through an 18 mesh sieve.

Example 22 Bright tobacco stems were washed in cold water whereby, from about 75 to 80% of the natural content of water-soluble substances were removed in the wash water. The stems were then used directly in the wet condition to make a binder as follows:

Example 23 Bright tobacco stems were washed in cold water whereby, from about 75 to 80% of the natural content of water-soluble substances were removed in the wash water. The stems were then dried and ground and used to make a binder as follows:

One hundred parts of water were brought to a temperature of 100 C., and to this were added: 7.00 parts by Weight (dry basis) of the washed bright (flue cured) stems, 1.05 parts diammonium phosphate, and 0.70 part of triethylene glycol (TEG), as a humectant.

Example 24 Bright tobacco stems were washed in cold water whereby, from about 75 to 80% of the natural content of water-soluble substances were removed in the wash water. The stems were then used directly in the wet condition to make a binder as follows:

One hundred parts of water were brought to a tem- 16 perature of C., and to this were added: 7.00 parts by weight (dry basis) of the washed bright (flue cured) stems, 1.05 parts diammonium phosphate, and 0.70 part of triethylene glycol (TEG), as a humectant.

Example 25 In the acid wash treatment of tobacco parts for removal of alkaline earth minerals of the tobacco pectin, it is necessary to use quite large volumes of water if it is desired to reduce the soluble anion content of the product to a very low level. In this case, the use of a cation exchange resin in a closed loop system with the tobacco parts can make it possible to conduct the process with limited amounts of water and acid.

The use of a resin (such as Dowex 50 W) in this way does not at all alter the principles of this form of treatment since the resin merely serves as a convenient reservoir of acidity, continuously reconditioning efliuent from the stems for reuse in the extraction.

In the following example, the use of a cation exchange resin permits the treatment of stems with a small fraction of their natural nitrate ion content. Hydrochloric acid is used at intervals to regenerate the resin, but never directly contacts the tobacco.

The apparatus used for ion-exchange extraction of calcium from tobacco stems consisted of a 20 inch diameter washing column fitted with a 20 mesh screen to support the charge of stems and a 6 inch diameter Pyrex column filled with 13 pounds of Dowex 50 W-8 acidform ion exchange resin beads. The valves and piping permitted a pump to be used either for recycling waters from the stem charge through the column or for separately regenerating the resin with hydrochloric acid solution.

In operation, fifty pounds of stems were placed in the washing column and rinsed with cold water until they were nearly free of water-soluble material. Then, the effluent waters were diverted through the ion exchange bed, returning by gravity to the top of stem charge. When the aqueous extract from one pound of burley stems was added to the recycling waters, a pH of between 1.5 and 2.0 was soon attained. During the treatment, the waters flowing from the resin column were monitored for their calcium content. (An appreciable precipitate from 50 ml. of resin efliuent treated with ammonium oxolate and made basic with ammonia indicated that the resin was saturated with calcium and needed to be regenerated with hydrochloric acid.) After sixteen hours of operation, and one regeneration of the ion exchange resin, the treatment was considered complete. A subsequent analysis showed that the calcium content of the stems had been reduced to less than one-sixth of the starting value of 4.5% CaO. The stems were rinsed twice with cold distilled water, pressed lightly, and redried in a tobacco processing oven to a final moisture content of about 4%, and ground to pass a 40 mesh screen. When a small sample of this powder was stirred with a little cold ammonia, it dispersed immediately, forming a stilt paste.

Example 26 Twenty grams of tobacco fines were washed in 1 liter of distilled water to get rid of the tobacco solubles. The

17 fines were then admixed with l N hydrochloric acid until the mixture had a pH of 1.35. The pH was checked on a Beckman pH machine and the curves were also plotted against a titration of distilled water.

After titration, the acid was washed off the fines with three 400 ml. portions of distilled water. The fines were redisbursed in 400 ml. of distilled water and sodium bicarbonate was added to bring the pH to 7. The slurry was cast at a thickness of 30-50 mils and dried to form a sheet and the resulting sheet was used as the adhesive binder in sandwich type reconstituted tobacco sheet.

Example 27 Twenty grams of tobacco fines were washed in 1 liter of distilled water to :get rid of the tobacco solubles. The fines were then admixed with 1 N hydrochloric acid until the mixture had a pH of 1.35. The pH was checked on a Beckman pH machine, and the curves were also plotted against a titration of distilled water.

After titration, the acid was washed off the fines with a 400 ml. portion of distilled water. The fines were redisbursed in 400 ml. of distilled water and sodiumbicarbonate was added to bring the pH to 7. The slurry thickened to a viscous mass, which is evidence that the pectin had been solubilized. The slurry was cast at a thickness of 3050 mils and dried to form a sheet and the resulting sheet was used as the adhesive binder in sandwich type reconstituted tobacco sheet.

Examples 28-30 In each of these three examples, gms. of tobacco fines were washed in 1 liter of distilled water to get rid of the tobacco solubles. The fines were then admixed with l N hydrochloric acid until the mixture had a pH of 1.35. The pH was checked on a Beckman pH machine and the curves were also plotted against the titration of distilled water.

After titration, the acid was washed off the fines with three 100 ml. portions of distilled water. The fines were redisb-ursed in 400 ml. of distilled water and a neutralization agent, .as indicated in Table V, was added to bring the pH to the value shown in Table V. The slurry in each case thickened to a viscous mass which is evidence that the pectin had been solubilized. The slurry was cast at a thickness of -50 mils and dried to form sheets. The binders formed in this way were tested to determine their physical properties. These properties are shown in Table V below. The binder was used as the adhesive in a sandwich type reconstituted tobacco sheet.

TABLE V.-PROPERTIES OF BINDER FILM MADE BY ACID WASH PROCESS 1 Cone. NHlOH. 2 15% KOH. 3 15% NaOH.

In the table the terms have the following meanings:

1. Integrator Count is proportional to the area under the stress-strain curve recorded by an Instron Test Machine.

2. Percent Moisture=The percentage of moisture contained in the entire sheet (wet basis).

3. Percent Elongation=The percentage elongation, at breakage, on an Instron Test Machine.

4. Tensile, kg./in.=The breaking strength of a 10 cm. test strip which is 1 inch wide; an average of 10 strips.

5. Tensile Coefiicient=Kg. per gm. of basis weight.

6. Work Coefiicient, gim. cm./sq. in.=Work coefficient is proportional to the product of the tensile strength and the elongation.

Example 31 The following ingredients were mixed into 900 parts of hot water and heated for 3 hours at 90 C., maintaining a pH of 7.0 by adding small amounts of aqueous ammonia.

Parts:

87.9 mixed manufacturing byproducts and scrap tobacco 5.0 diammonium ortho phosphate (DAP) 5.0 glycerin 2:0 corn syrup 0.14 potassium sorbate The slurry was then refined in a one gallon capacity Waring Blendor for 5 minutes. With this amount of refining, the fibrous portion of the composition was seen to be well dispersed and thoroughly interlocked when examined in a droplet at a 1:9 dilution. This examination was facilitated by the addition of a small amount of Congo red dye.

The composition was cast on stainless steel panels with an eight inch angle knife set for wet film thicknesses of 0.020 to 0.045 inch, and dried on a steam table.

The wet strength of the films was determined on a Scott Serigraph IP-2 using 1 inch width strips. The center of each strip was wet with distilled water on both sides and allowed to become thoroughly wet through (30 seconds or one minute) before actuating the tensile mechanism. These films showed the extraordinarily high wet film strength of 140 grams at a film weight of 9.5 grams per square foot. A high wet strength is highly desirable in the preparation of cigarette filler, and assures that the subsequent manufacturing performance of this material will exceed that of the finest grades of leaf tobacco. Such strength is uniquely obtainable in the presence of the liberated form of pectin described in this disclosure.

We claim:

1. A process for producing reconstituted tobacco sheet material which comprises contacting comrninutedtobacco plant parts with a treating solution containing a reagent selected from the group consisting of sodium and potassium orthophosphate in a concentration of 5 to 50% and at a temperature of to C. so as to destroy the alkaline earth metal cross-links which hold the pectinaceous material and thus occasioning release of the pectins by formation of a precipitate comprising an insoluble calcium or magnesium salt and finally casting the tobacco and in situ formed pectins to form a reconstituted sheet, the pectins serving as a binder for the treated tobacco parts in the final sheet.

References Cited UNITED STATES PATENTS 1,634,879 7/ 1927 Nanji et al.

3,012,915 12/1961 Howard 13117 3,120,233 2/ 19'64 Battista et al 13l,143 X 3,121,433 2/1964 Plunkett et al. 131--140 MELVIN D. REIN, Primary Examiner.

SAMUEL KOREN, Assistant Examiner.