US3258014A - Method of making a tobacco sheet - Google Patents

Description

United States Patent 1 Claim. (Cl. 131-140) This application is a division of application Serial No. 103,216, filed April 17, 1961, now Patent No. 3,118,452.

This invention relates to a method of making reconstituted tobacco sheet products and more particularly to a method for making an improved selfsustaining tobacco sheet from tobacco dust or dispersion including tobacco substitutes and to the product produced thereby. Tobacco sheet material of this type is suitable for cigar wrapper or binder, as filler for cigarettes and cigars, for pipe and chewing tobacco, as well as for other uses to which natural leaf tobacco may be applied.

In procedures for the formation of tobacco sheet by casting a tobacco dispersion into films and evaporating the liquid phase therefrom, various formulations have been proposed. Generally, in present procedures for making tobacco sheet, the tobacco, either as dust or finely ground particles is applied onto a moist substrate or suspended in a liquid vehicle as a slurry. The slurry is then cast on a sheet-forming belt, the tobacco layer is dried to form a self-sustaining sheet, and the sheet is then removed from the supporting endless steel belt. In the process of removal of the dried sheet, it has generally been necessary to remoisten the tobacco sheet substantially before it is released from the forming belt. Attempts to remove the tobacco web in the absence of rewetting have been generally unsuccessful. In such cases, the tobacco sheet has been damaged substantially, excessive wear of the doctor knife occurs and the whole operation is delayed. The extent of rewetting of the tobacco web to effect good release has required remoistening to water content of at least 20% and generall in excess of 25%. After the tobacco sheet is wetted to facilitate removal, it is subsequently necessary to redry the tobacco sheet to a commercially acceptable moisture content. In general, commercially employed tobacco has a moisture content of the following order:

Cigarette tobacco, in finished cigarettes, from about 9% to about 15%, preferably about ll%14%.

Cigar tobacco, in finished cigars, from about 10% to about 18%, preferably about 13%17%.

Cigar filler, about 15%30%.

Manufactured cigar binder, about 18%-22%.

Cigar wrapper, about %50%.

In connection with the relatively high moisture content in cigar wrapper sheet, it is important to note that tobacco cannot be stored at these high moisture levels because of mold and other deterioration of the tobacco. Therefore, even these tobaccos are preferably produced so as to have a storage and shipping moisture of between about 10% and about 14%.

The advantages of a tobacco composition, which incorporates in the formulation a release agent, include easy removal of the formed sheet at a desired moisture level from the sheet-forming surface without remoistening and drying, greater uniformity in sheet appearance and savings on doctor knife wear. Another advantage is retention of desirable flavors and aromas which would otherwise be lost due to their entrainment with the liquid being vaporized as co-distillates, steam distillates or azeotropes.

It is an object of this invention to provide a self- 3,25%,fili Patented June 28, 1966 supporting tobacco sheet composition which permits ready removal of the tobacco sheet from the sheet-forming endless belt.

It is a more specific object of this invention to provide a method of forming a self-supporting tobacco sheet material which incorporates a compound which greatly facilitates removal of the dried Web from the sheetforming surface without the necessity of rewetting the web.

A further object of the invention resides in the provision of a class of belt-release agents for tobacco sheet which are wholly compatible with sheet formable tobacco compositions and which have no deleterious effect upon the use of the tobacco product.

Other objects and advantages of the invention will become apparent as the more detailed description of the invention progresses.

According to the invention, I have discovered that, by incorporating in tobacco sheet-forming compositions, a small amount of phosphatide which comprises preferably a derivative of lecithin, a wholly unexpected and advantageous property is imparted to the dried tobacco sheet. I have found that when from about 0.1% to about 16% by weight of the phosphatide, based on the weight of tobacco, is incorporated in the sheet-formable tobacco slurry composition, the resulting sheet may be dried to the moisture content desired for the marketable sheet while still permitting uniform release of the sheet tobacco from the endless web-forming belt. Preferably from about 0.2% to about 2% by weight of the phosphatide produces the desired effect.

When employed in the present specification, phosphatides will be understood to include, in addition to lecithin and derivatives of lecithin, other phosphatides that have chemical structural features similar to those present in lecithin.

For the purpose of this disclosure, the term lecithin is taken in the context of commercially available lecithin. Pure lecithin consists of glycerol combined with two fatty acid radicals, phosphoric acid and choline. Hence, there are many lecithins or phosphatidylcholines depending on the nature and disposition of the fatty acid groups. Normally, such derivatives of lecithin are very complex mixtures. Commercial lecithin is a mixture of phosphatides, including true lecithin and cephalin together with other components such as carbohydrates, glycerides, oils, and steroids, that occur with the phosphatides. Thus an approximate composition of soybean lecithin would include:

Constituent: Percent Phosphatidylcholine 21 Phosphatidylethanolamine 8 Phosphoinositides, lipositol, etc. 20 Phosphatides, others 11 Soybean oil 33 Sterols, tocopherols, etc. 2 Carbohydrates, free 5 Total According to the invention, modified commercial lecithins which have increased water solubility are the preferable phosphatides.

Included among the phosphatides which may be employed are those having the formula:

HzO-OR wherein R R and R are substituents selected from the group consisting of (a) hydrogen, (b) fatty acyl radicals, (c) chemically modified fatty acyl radicals, ((1) phosphate radicals, and (e) phosphate ester radicals; at least one of said substituents is a phosphate ester radical and at least one a chemically modified fatty acyl radical. Phosphate radicals include salts thereof as well as phosphate radicals combined to form an ester with an alcohol.

In the above formula where any one of R R or R is a hydrogen atom, the compound will be called a phosphomonoglyceride. Where any two of R R or R are fatty acyl radicals, the compounds will be called phosphodiglycerides. The fatty acyl radicals contemplated according to the invention are those derived from fatty acids having a carbon chain length from about 12 to about 24 carbon atoms and including in the structure either saturated or unsaturated linkages i.e. including saturated phosphoglycerides as well as unsaturated phosphoglycerides. The unsaturated phosphoglycerides may be a mixture of monodiand triglycerides fatty acid linkages and may also be in combination with the saturated glycerides.

Where R R or R is a phosphate radical, the compound is referred to as a phosphatidic acid. Esters derived from the phosphatidic acid are referred to as phosphatides. The phosphatide is a true lecithin when the alcohol moiety is choline. When the alcohol is an inositol, it is an inositide; and when the alcohol is aminoethanol, the phosphatide is a cephalin. Other minor alcohol compounds, including carbohydrates, sterols, etc., also contribute to the phosphatide composition. Commercial lecithin is a complex mixture of phosphoglycerides plus glyceride oils and carbohydrates, among which is an inositol, and refers to the complex mixture described above.

A preferred group of chemically modified lecithins are those having less than 50% of the double bonds, or unsaturated linkages, combined with acyl groups and preferably from 225% are so combined with sulfate, including sulfonate; phosphate groups including phosphate ester groups; or nitrate groups, e.g. SO OSO H, OPO H -O -P(OH) -NO Preferably 15- of the double bonds are chemically combined with substituents of this kind. The reaction product may subsequently be treated to form derivatives of salts of potassium, sodium, ammonium, barium and the like. In a strict sense, the nitratealecithin derivative, does not form a salt but a neutral derivative of the lecithinate.

The compositions of matter which have general utility in this disclosure may be broadly divided into weakly oxidized commercial lecithins and into ester derivatives thereof, and oxyalkylated lecithins. These three derivedlecithin groups are more water soluble than the parent lecithin mixture. It will be recognized that these derived lecithins are extremely complex products. For example, the weakly oxidized commercial lecithin, which is a hydroxylated lecithin, prepared by the methods in US. Patent 2,445,948 or 2,791,594, is a mixture of dihydroxylated, epoxylated and hydroxy acetoxylated lecithins, cephalins, inositides and triglycerides. The sulfates or phosphates of such mixtures may be prepared, for example, according to U.S. Patent No. 2,791,594. These derived products are even more complex. In view of the complexity of the derived phosphatides, they are generally conveniently defined by describing their methods of preparation.

The invention herein disclosed may be employed in the various known procedures for producing sheet tobacco from a slurry of finely ground tobacco including the procedures disclosed in U.S. Patents 2,734,509, 2,734,510 and 2,734,513, wherein reconstituted finely divided tobacco materials are converted into sheet or strip material which can be used in the same manner as natural leaf tobacco in making products such as cigarettes, cigars, pipe tobacco and the like. According to the procedure described in these patents, a reconstituted tobacco sheet is formed by depositing a dilute aqueous solution which pref rably contains a surface active agent (and which may optionally contain tobacco therein) to which finely ground tobacco in dry form is then applied. The phosphatide of the invention is preferably incorporated in the web-wetting aqueous solution. An adhesive film followed by a second layer of dry ground tobacco may then be applied to form a composite web. The tobacco dust adheres to the water solution on the belt and forms an integral part of the sheet of reconstituted tobacco material produced. Particularly advantageous results are obtainable using the present invention with the above referred to dust-on procedure for tobacco sheet production.

In preparing tobacco sheet material using a tobacco slurry, the following illustrative general procedure may be followed.

Finely divided tobacco is mingled with an adhesive formation to form a slurry or a suspension and the phosphatide is blended therein. The viscosity of the slurry is controlled by the relative amount of water, tobacco and adhesive used. To promote the mingling of tobacco particles, the release agent and film-forming agent, the mixture is agitated thoroughly until all the particles are completely wetted. Mixing may conveniently be done in a high shear mixer or a ball mill. In a ball mill, the relation of ball size and volume of the mixing chamber will depend upon several factors such as viscosity, particle size of tobacco and proportion of adhesive material solids to tobacco.

Alternatively, the tobacco particles and dry adhesive may be mixed together and added to a slurry of suitable fibrous material such as tobacco or paper pulp containing the phosphatide belt release agent. The product of either method may be applied to a continuous, substantially impervious belt using known techniques such as by casting, reverse roll coating, spraying or other conventional filmforming procedures to form a continuous film which is then dried and removed in a continuous sheet. The viscous slurry can also be shaped and formed into a sheet by suitable means such as by calendering or extrusion.

Drying the wet material is a part of the sheet-forming operation and is necessary in some cases to achieve substantial water resistance. The moisture content of the sheet, according to the invention, can be adjusted by suitable control of the drying means so that the finished dried sheet contains the requisite moisture for its end use or for optimum storage composition without rewetting to moistures heretofore necessary for uniform release from the sheet-forming surface.

The invention is further illustrated by the following examples. Parts expressed in the examples are parts by weight unless otherwise stated.

EXAMPLE 1 A slurry was prepared having the composition described below in which the quantities shown are in parts by weight on a bone-dry basis.

Adhesive (0.5/05 guar gum/ethyl hydroxyethyl cel- -Potassiurn salt of the phosphate derivative of hvdroxvlated leclthin, available commercially as Alcolee HO-etiO from American Lecithin C0.

3 Based on Water in the total to S0nds 10% bacco slurry. Slurry ab;fitl;);it(l:li5dg:4O part diatomaceous ash whitener and These ingredients were formed into a slurry by dissolving the gum into the pulp suspension and adding the other ingredients with enough water to bring the solids concentration to approximately 10%. The slurry was formed into a film by casting it onto an endless steel belt.

The tobacco slurry film was dried, adjusted to 14% moisture and doctored from the belt with no difficulty. The sheets had the physical properties set forth in Table I.

Runs parallel to 20 and 2b, in which the belt release agent was omitted, required rewetting of the belt to a moisture content of about 28% in each run before doctoring of the tobacco sheet from the steel belt with com- T able I 5 parable case, was possible.

Drylongtenslle i 680 Breaking length refers to the maximum length of 21W iransvefseltenslle 1 1 jeh film, which when freely suspended, will support itself.

et ong. tensie strengt gm. in., wi t Wet transverse tensile strength, gm./in., width 90 EXAMPLES 3 AND 4 Elongation at break, dry, percent 6 Following the procedure described in U.S. Patent 511694t gIIL/ftz 2,734,513, a tobacco sheet product is prepared by apply In a comparative run in which the belt release agent, mg dust to a surface Wetted Yvlth belt Water i.e. the lecithin derivative was omitted, it was necessary cogltammg b release agent then appiymg tobacco dust to remoisten the Web to 2225% moisture before comr t g g and a second layer tobacco.dust

parable release of the tobacco sheet from the steel belt m t F or Flrst surface was molstened K? 3 was possible solution of release agent and a surfactant of composition EXAMPLE 2 as shown in Table II. Thereafter, tobacco dust is deposited, upon which a thin layer of suitable film of sodium The Procedure of f PP 1 Was repeated 115mg h carboxymethyl cellulose is applied; and a further applicaformulations and obtammg the results set forth in i f tobacco dust is applied to the exposed Surface Table of the sodium carboxymethyl cellulose film. The product,

Table II which is then dried, consists of a central thin layer of a film-forming material having substantially permanently Example 2a 2b adhered thereto, on both of its surfaces, substantial quantities of tobacco dust.

Adhesivc, 1 1.0 1.0 The composition and properties of Examples 3 and 4 $3 5,335,153 5 are provided in Table III. The procedure of Examples 'Iobae c o. H 06.58 6.0 3 and 4 was repeated but without the addition of the g;, ff :32 release agent to the belt water. The release, from the %elt itelea e tgept 8.8 sheet-forming surface, is poor. Belt release at moisture g figgglggfi, git g i ggfi t jj: 1 2 290 levels below 27% is difficult. Below this moisture content Elongation (percent) 5.4 6.1 (of 27%) the tobacco sheet does not release readily and it causes excessive doctor knife wear, necessitating knife ig fi/ua loeugbegngu ilmet yggguulosc. changes every 15 minutes. Further, the scraping action a ?3; i ;fi; 53 reeness of the doctor knife causes structural damage to the sheet Melamine-formaldehyde resin. e t g Includes about 0.35 part pigments, 0.40 part diatomaceous ash resultmg m lowered t nslle properues and poor app ar Whitener and about 0.04 fungicide. ance- 2 gsuloinated lecithin prepared according to Example 1 0i U.S. Patent Th b lt release agent may b d alone b t preferred Hydl'0Xy1ated lecithin prepared according to Example 7 of U.S. esults a P Q when the halt 11618336 agent 15 used Patent 2,791,594- 4 in combination with a surfactant. Su1table surfactants for Each of these formulations resulted in tobacco sheets this P p Well kflowll aft, include Such as ihfi which are readily doctored from the steel Web-forming g chain fatty acld amldes, yl sulfates, lkyl aryl belt at moisture contents below 15%. sulfonates, polyoxyethylene derivatives and the like.

Table III Exarrmlt 3 4 Parts Parts Formula:

Tobacco 8 Tobacco Dust 8 Tobacco Dust mesh, U.S. (-50 mesh, U.S. Standard Screen). Standard Screen). Gum l NaCMC Medium Viscosity. Pulp B 1 Bright Stems 1 Bright Stems Unwashed. Unwashed. Additives:

(A) Base Web 0.3 Glycerine 0.3 Glycerine. (B) Belt Water 1.5 .AlcolecHO-410. 0.4 Alcolcc H0410.

0.1 Antaron ITO-34.

Application:

Base Web Solids (percent) 7. 40 Base Web Viscosity (eentipoises) 6, 200 Base Web (gmJftfi) 2.3 Underdust plus Base Web (gmJftfi) 6.86 Sheet (full) m rm) {g 5:5 Belt Speed, t'.p.m 20. 3 Line Moisture, percent B 15. Life of Doctor Knife (Hours) 6. 3 Sheet Properties:

Equil. Moisture, percent 12.8 Long. Dry Tensile, g./in. width 285 Trans. Dry Tensile, g./in. width 232 Moisture content of sample at time of test,

percent 11.7 15.2 Comments Test stopped, belt water consumed.

B Pulp Freeness cc. Schopper-Riegler Frecness.

b Potassium salt of the phosphate derivate of hydroxylatcd lecithin. Commercially available from American Lecithin Co.

v Manufactured by Antara Chemicals Div. of General Aniline 00., a complex fatty amido emulsifier with 40% minimum activity, surfactant.

' Run terminated-doctor knife still in usable condition. a Moisture content of the tobacco sheet at the time it is doctorcd from the sheet forming line.

7 The sodium carboxymethyl cellulose (NaCMC) filmforming gum emlployed has a degree of substitution of between 0.50.8 carboxyrnethyl group per anhydroglucose unitand a 2% viscosity in water of 400-1000 cps. at 25 C.

EXAMPLE 5 Dry Longitudinal Breaking Length, it .t 2, 560 2, 380 2, 710 Dry Transverse Breaking Length, it a 814 945 1, 270 Elongation 5.0 6.5 7. Percent moisture needed to effect doctor g... 16 14 Where the belt release agent is omitted, a moisture content of greater than 22% was necessary to obtain comparable release property.

In forming tobacco sheet, the film-forming agent is known to be an important structural ingredient of the sheet. Accordingly, if the film-forming agent is weak or discontinuous, the sheet will crumble and distintegrate when handled in tobacco machinery. The film-forming agent should be easy to handle, should be chemically stable, should be in a convenient form, and should require little special treatment to prepare it for final use. When tobacco sheet material is fed from continuous rolls into automatic cigar making equipment, for example, its crimping and setting properties may be important. Tobacco sheet material made according to this invention produces desirable crimping and setting properties and conforms very satisfactorily when used in automatic cigar making machines and other machinery for fabricating tobacco moking articles.

Any of the various adhesive film-forming agents which are known and have been used in the art may be employed. In the finished tobacco sheet, the adhesive formulation may be between 0.5% and up to 100% of the weight of the tobacco but a preferred range is between 1% and 20%. The adhesive film-forming agent or binder is preferably selected to impart to the finished dry tobacco sheet material, a high degree of moisture resistance.

The preferred film-forming agents are polysaccharides, or water-soluble cellulose ethers or combinations thereof. For example, galactomannans as guar or locust bean gun which are commercially available may be used; mixtures of locust bean gum and ethyl hydroxyethyl cellulose; locust bean gum and carboxymethyl cellulose; locust bean gum and methyl cellulose; guar and ethyl hydroxyethyl cellulose or water-soluble salts of carboxymethyl cellulose and carboxymethylhydroxyethyl cellulose and the like are suitable. When the adhesive film-forming agent is provided in the form of dry powder, particle sizes used in this invention are preferably similar in size to the tobacco particles, although they may be smaller. For example, sodium carboxymethyl cellulose is a desirable film-forming material since the dried acidified form of carboxymethyl cellulose is substantially initially waterresistant. In addition to the other film-forming materials such as viscose, the polyuronides, and the like when properly formulated, are other polysaccharides which can be used.

A cross-linking agent, such as glyoxal, dimethylol urea, melamine-formaldehyde resins or a dialdehyde polysaccharide as disclosed in US. Patent 2,887,414 may be added to improve further the water resistance of the film-forming agent. If desired, a humectant uch as glycerine or triethylene glycol may be added to the film-forming surface. When a humectant is used, it has been found that the quantity thereof required to maintain a given degree of pliability in the final sheet varies as the ratio of fibers, tobacco and other additives, to film-forming agent, is changed. It is preferred to use a minor quantity of humectant to prevent excessive brittleness in the final film.

Natural gums have the disadvantage of not producing a coherent sheet or film when used as the sole adhesive with the rapid drying of the slurry required to maintain commercial operation. As a result, cracks form in the film during the drying operation so that small islands are formed on the belt and after drying small pieces flake off the web detracting from the uniformity desired. Drying cracks can be minimized by reducing the drying rate, but in so doing an uneconomical operation may result.

In order to eliminate the crack formation, thermogelling gums from the class of water-soluble cellulose ethers e.g. methyl cellulose, ethyl hydroxyethyl cellulose are used in conjunction with the natural gums to form a suitable adhesive film-forming material. The gums function by gelling the film before significant evaporation of water takes place. The gel is firm enough so that stresses induced by shrinkage are resisted and crack do not occur. Although the gums are effective for this phenomenon, they have shortcomings which include high price relative to the natural gums, difficulty in forming solutions and poorer reaction with the cross-linking reagents used to impart wet strength to the tobacco sheet. For these reasons, it is most desirable to eliminate or at least reduce the quantity of thermogelling gum required.

The finely divided or fragmented tobacco used in conjunction with the invention may be prepared by grinding or by otherwise comminuting tobacco leaf and stems. Fines which are residues from handling of tobacco and would otherwise constitute waste may be used advantageously. Tobacco sheet using entirely dry ground tobacco is preferred but the invention is not limited to thi form. Tobacco which is entirely dry ground is tobacco which has not undergone comminution in the presence of excess liquid, such as a wet milling. Satisfactory tobacco sheets can be made from finely divided tobacco which will pass through a 20 mesh screen and will be mostly retained by a 325 mesh screen. A preferred particle size range is between 60 and 250 mesh. Tobacco sheet formed from small tobacco particles appear to burn more evenly than large particles.

The composition of the finished sheet is such that it has a tensile strength superior to that of natural tobacco leaf. Of course, the strength and sheet thickness may be adjusted for particular applications. A preferred sheet thickness range is between .002" and .011". Tensile strength may be, for example, at 12% sheet moisture about 400 grams per inch of width of material .003" thick. The sheet is self-supporting and composed so that it is coherent even after immersion in water. In characterizing properties of the wetted Web, its tensile strength is preferably such that one foot of width of the sheet material has a strength of at least about 400 grams.

Some inorganic fillers which may be used in powder form, for example, with tobacco sheet material are kaolin and fullers earth. Among suitable organic fillers are various cellulosic preparations known in the art such as paper pulp. Fillers may range from 2% to 15% or more by weight of the finished sheet. Various food dyes may also be used in manufacturing the tobacco sheets and foils to produce a desired color in the tobacco.

The tobacco sheet of this invention has many useful applications, and smoking articles such as cigars, cigarettes, pipe tobacco as well as chewing tobacco made in whole or in part from this sheet material, are within the contemplation of the invention. The sheet material may be fed from rolls to automatic machines, for example,

cigar machines, for use as binder or wrapper. The sheet may also be shredded for filler in pipes, cigarettes, and cigars. It may be mixed with shredded whole tobacco or used alone. It may also serve as an outside wrapper for cigars or cigarettes and has the advantage of uniformity in appearance and in physical properties as well as uniformly blended flavor.

While the invention has been described in its preferred embodiment, it will be understood that the invention is not limited to the specific details set out for purposes of illustration and that those skilled in the art may make various changes in these details Within the scope of the claim without departing from the spirit of the invention.

I claim:

In a method of forming a tobacco sheet from finely divided tobacco by moistening a web-forming belt surface with water containing a surfactant, depositing the finely divided tobacco on said moistened surface, applying on said tobacco an adherent film-forming composition, and thereafter applying on said composition a second deposit of finely divided tobacco, the improvement which comprises adding to said belt Water from about 0.05% to about 10% of a phosphatide of the formula H- 0R H29] OR References Cited by the Examiner UNITED STATES PATENTS 2,475,128 7/1949 Cresswell 18-47 2,496,976 2/1950 Barney 264--2l3 2,566,982 9/1951 Clemens 26421 3 2,734,509 2/1956 Jurgensen 13117 2,734,510 2/1956 Hungerford et al. 13ll7 OTHER REFERENCES Classification Bulletin No. 459 of the United States Patent Office.

SAMUEL KOREN, Primary Examiner.

FRANCIS R. CHAPPELL, Examiner.

MELVIN D. REIN, Assistant Examiner.