US2976873A - Tobacco sheet - Google Patents

Description

United States Patent 'ronscco SHEET Andrew Eugene Carmellini, Mount Vernon, N.Y., and Eric Bell Hotelling, Westport, Conn., assignors to American Machine & Foundry Company, a corpora-. tion of New Jersey- N0 Drawing. Original application Apr. 6, 1959, Ser. No. 804,073, now Patent No. 2,949,117, dated Aug. 16, 1960. Divided and this application Feb. 16, 1960, Ser. No. 12,892

3 Claims. (Cl. 131-140) This invention relates to novel combination-s of plasticizers with water insoluble adhesives in tobacco products to impart new and useful properties.

Tobacco sheets composed of finely divided tobacco imbedded in an adhesive with flavoring agents and other additives are well known in the commercial production of smoking articles. For example, such sheets can be used to replace tobacco leaf as cigar binder on standard machines, or they can be shredded to form cigarette fillers. These applications do not require great pliability or extensibility of the sheets, and water soluble gums may be employed as adhesives in either case becausethe tobacco sheet material does not come in direct contact with the mouth of the smoker.

In order to overcome some of the drawbacks of water soluble gums, where wet strength is desirable, it has been proposed to employ water insoluble adhesives dissolved in organic solvents to form tobacco sheets. Such adhesives include water insoluble esters and ethers of cellulose, amylose and other carbohydrate materials which are non-toxic and have acceptable odors in the products of combustion. The wet tensile strengths of such sheets are generally very good without addition of any fibers. However, the pliability and particularly the elongation is uniformly poor when the sheets contain a substantial amount of tobacco (50% or more of the sheet weight). For this reason little or no commercial use has been made of water insoluble adhesives in tobacco sheets, although such sheets have been known in the laboratory, for many years. Efforts to plasticize tobacco sheets with many common types of plasticizers have been uniformly unsuccessful in imparting sufi'lcient elongation to make them usable on cigar machines as wrappers for cigars.

This invention embodies, in essence, new combinations of tobacco, water insoluble adhesives and certain types of plasticizers of highly. specific chemical structure, which can be formed into sheets useful as cigar wrappers and in other smoking articles. Such sheets have excellent elongation, pliability and tensile strength, either Wet or dry, and can be used on standard. cigar machines as a replacement for natural leaf cigar Wrappers. The invention also relates to the manufacture. and use of such sheets and of smoking articles containing them.

It is an object of the invention to. provide, plasticizers of highly specific chemical structure which will confer new and useful properties on tobacco sheetsmade with water insoluble. adhesives.

A further object of the invention is to prepare sheets from tobacco, plasticizer and a water insoluble adhesive which contain a high proportion of tobacco. and which also possess. desirable physical properties such as.elrniga-v tion. i i

A further object of the invention is to manufacture cigar wrappers from tobacco powder, plasticizer and a water insoluble adhesive which can befappliedcontinw ously'from a bobbin to cigars on standard cigar machines to produce a new type of cigar of good smoking quality and improved appearance.

. ing conditions.

,dio'ctyl phthalate, dibutyl sebacate, tricresyl phosphate,

ice

A further object of the invention is to produce cigars, cigarettes, cigarillos andother smoking products of improved taste andappearance and greater ease of manufacture by incorporating therein synthetic tobacco sheet as wrapper, binder or filler.

The foregoing and other objects of this invention will be apparent from the following description.

The new and useful sheet forming combinations of this invention are characterized by a tobacco content of at least about 50% for the sake of taste, odor and appearance. The tobacco is finely ground and suspended in a solution of a water insoluble adhesive dissolved in an organic liquid solvent. A plasticizer of the type to be described is added, together with any dyes, flavoring agents, ash improvers, mold inhibitors or other inert in gredients which it is desired to incorporate into the fin ished tobacco sheet. Enough solvent is employed to form a thick slurrytgenerally 2535% solids), which is extruded or cast to form a film of the desired thickness and sheet weight. The solvent is permitted to evaporate at,

ambient or slightly elevated temperatures, either at atmospheric pressure or under vacuum. Most economical operations require the recovery and recycle of the solvent bya solvent recovery unit.

Tobacco sheet may also be made by coating the tacky surface of a film of the non-tobacco ingredients or by coating a layer of tobacco particles with the adhesive preparation.

Nearly all common plasticizers fail to produce tobacco sheet with sufiicient elongation to be practical for use as cigar wrapper on a cigar machine under normal operat- Such customary plasticizers include tributyl borate, di-isooctyl adipate, didecyl azelate, polyethylene glycols, polypropylene glycols, glycerol, glycerol esters, ethylene glycol monoethyl ethers and esters, diethylene glycol monoethyl ethers and esters and their isomers and homologues.

The first class of effective plasticizers of this invention consists of polyesters prepared by condensing a lower polyethylene glycol or glycerol with an aliphatic acid glycol, pentaethylene glycol and mixtures of any of these compounds.

The aliphatic dicarboxylic acids which react with these glycols to yield active, polyester plasticizers, containing straight chains of six to ten carbon atoms, include adipic, pimelic, suberic, azelaic and sebacic acids, which may contain 011C101 more small alkyl substituents on the six to ten membered chain of carbon atoms, or mixtures of anyof these. In the practice of this invention the aliphatic dicarboxylic acid is condensed with less than twice the equivalent amount, but more than half the equivalent amount, of a lower polyethylene glycol by'customary chemical methods of esterification of form the active polyester plasticizers of the invention. It is preferable-to employ somewhat less than one molar equivalent of lower polyethylene glycol per mole of aliphatic dicarboxylic acid for best results.

The condensation can be carried out by any of the usual commercial or laboratory methods of esterification. One of the simplest procedures is to dissolve or suspend the reactants in benzene, add a few per cent of concentrated sulfuric. acid as catalyst, distill off the water formed in the reaction as an azeotrope with benzene and collect the water a trap for azeotr'opic removal of water with provision for the benzene to reflux into the reaction vessel. When evolution of water ceasesfgenerally after 3 four to eight hours at reflux temperature, the condensation is essentially complete. The polyester may conveniently be employed in the crude benzene solution after separation of the acid catalyst, or it may be further purified if desired.

Among the lower polyethylene glycols usable in this invention it is preferable to employ tetraethylene glycol. Polyesters derived from triethylene and lower glycols result in good elongation but reduce wet strength when incorporated into tobacco sheet, whereas polyesters produced from pentaethylene and higher glycols yield stiffer tobacco sheets with good wet strength but reduced pliability and extensibility. The best balance of properties is obtained with tetraethylene glycol in those applications which require both wet strength and good elongation, as in the case of tobacco sheet to be used for cigar wrapper. Modern cigar manufacturing machines require tobacco sheet with substantial elongation. Very satisfactorypolyester plasticizers are produced from tetraethylene glycol combined with somewhat more than an equivalent amount of an aliphatic dicarboxylic acid containing, for example, a straight chain of from six to ten carbon atoms.

. A particularly preferred embodiment of this invention is the use of polyesters prepared from tetraethylene glycol and a slight excess over the stoichiometric quantity of an aliphatic dicarboxylic acid containing a straight chain of eight carbon atoms. This chain may be unsubstituted as in the case of suberic acid, or it may contain one or more substituents of lower alkyl groups as in the case of Z-ethylsuberic acid. Although polyester plasticizers containing these acids impart the optimum physical properties to tobacco sheet, the acids are expensive and unavailable commercially in pure form. As a practical matter, therefore, these polyesters are generally synthesized from mixtures of cheap and commercially plentiful acids, and the composition of the acid mixture is adjusted to give an average chain length of close to eight carbon atoms. This results in some sacrifice of sheet quality, but the product is inexpensive and readily usable on standard cigar machines.

The second class of eifective plasticizers of this invention consists of phenolic compounds or bisphenols which contain one or more substituents selected from the class consisting of hydroxymethyl, dialkylaminomethyl, cyclic aminomethyl or alkyl in positions ortho and para to the phenolic hydroxyl group. These phenolic compounds or bisphenols are produced by known methods from phenol, a bisphenol or a substituted phenol or bisphenol having not more than one substituent group in the positions ortho and para to the phenolic hydroxyl groups. The simplest method for introducing hydroxymethyl groups into the remaining unsubstituted ortho and para positions is to treat the starting phenol, bisphenol or substituted phenol with formaldehyde in the present of sodium hydroxide by methods well known in the literature. The simplest method for introducing dialkylaminomethyl groups into the remaining unsubstituted ortho and para positions is to treat the starting phenol, bisphenol or substituted phenol with a mixture of stoichiometric quantities of formaldehyde and a dialkylamine. This synthesis is also well known in the literature as the Mannich Reaction.

Either class of efiiective plasticizer of this invention, or mixtures of them, can be incorporated into tobacco sheet in the manner described above to produce the beneficial plasticizing effect necessary to make cigar wrapper which can be fed automatically from a bobbin to a cigar machine. Generally, flavoring and coloring materials, humectant and other inert ingredients such as ash improvers are incorporated into cigar wrapper sheet. Cigars prepared from tobacco sheet wrapper of this invention are light in color, smooth in texture, uniform in quality, inexpensive and do not dissolve or disintegrate in the mouth when wet with saliva. The same type of tobacco plasticizers of this invention to which other ingredients may be added if desired.

The choice of the water insoluble adhesive to be employed in preparing the tobacco sheets of this invention is subject to certain limitations. The material must be nearly tasteless and completely non-toxic in the concentrations used, must possess good burn odor, must be virtually insoluble in water but soluble in whatever organic solvent is chosen for the process to form a viscous solution which can be cast or extruded, and for economic considerations should be inexpensive and readily available. These limitations practically indicate the choice of the ester or ether derivatives of carbohydrate high polymers such as cellulose, amylose and starches. Such materials, which are in widespread use, include cellulose esters, particularly cellulose acetate, the mixed esters such as cellulose acetate propionate and cellulose acetate butyrate and cellulose ethers such as methylcellulose and ethylcellulose. The molecular weight and degree of sub stitution of the cellulose or other carbohydrate derivative must be in the proper range to produce the solubility and viscosity characteristics mentioned above. Within these limitations the particular adhesive chosen will depend upon the specific flavor, burn odor and texture which the formulator wishes to impart to the finished smoking article.

The solvent chosen for the manufacture of tobacco sheet of this invention must be one that will dissolve the adhesive, evaporates easily and is cheap and easily reooverable. Highspeed elevated temperature drying is desirable. Among the common solvents it is preferable to employ acetone, but methanol, ethanol, isopropyl alcohol, benzene, toluene, chloroform and methyl butynol or mixtures of any of these can be used with particular adhesives which dissolve in the solvent chosen.

. This invention is more particularly described by the following examples.

Example 1 This example illustrates a preferred form of the invention.

' A plasticizer solution was prepared from 365 grams of commercial adipic acid (2.5 moles), 282 grams of technical azelaic acid (1.5 moles) and 582 grams of tetraethylene glycol (3.0 moles) dissolved in approximately 2.5 liters of benzene. The reactants and solvent were placed in a five liter, five-neck, round bottom flask equipped with a motor stirrer, thermometer well, addition funnel, heating mantle, two reflux condensers and two modified Dean-Stark traps for collection of water. The solution was treated with 20 ml. of concentrated sulfuric acid as catalyst and refluxed with continuous stirring for 3.5 hours, after which time no more water was evolved. After cooling the benzene solution of crude polyester plasticizer was separated from the lower acid layer. The plasticizer content, determined by drying a sample to constant weight, was 37%. a

This plasticizer was incorporated into tobacco shee by the following procedure. Sixty grams of ball-milled, dry ground tobacco, all of which had passed through a l70-mesh screen, were suspended in a Waring Blendor in 350 ml. of acetone containing 30 grams of commercial cellulose acetate in solution. To this suspension was grams of polyesterplasticizer, t0 PIQ I Ce a-solids couassesses t f} bou .1 1% hr eishthick; s aw. h n. s nt s eets t a} s in kn te lfi-WQPQQ Qt.- about 6 mils. The; solventwas; permitted; to evaporate, at room. e p a n mo n e c p ssur n r ndom samples of the sheets were removed; for testing. The sheet tensile strength was; over 330-grarnsper inch. After soaking in water for 45 seconds the tensile strength. was still. over 270 grams per inch; (82% wetgst-reugth) and the elongation was between 35 and; 40%.; 7

Cigars prepared on a cigar machine; with tobacco. sheet as wrapper were very satisfactory in,tast e and appearance. I

Example 2 To illustrate the effect of changing the proportions of the reactants, three polyesters were prepared from varying amounts of tetraethylene' glycol andtechnical azelaic acid by the procedure of Example 1. In the first case a 33% molar excess of tetraethylene glycol was employed; in the second case stoichiometric amounts of glycol and acid were charged; and in the third case the acid was present in 33% molar excess. The three poly esters were incorporated into tobacco sheets which were otherwise identical, composed of about 60% tobacco, 20% ethylcellulose (a commercial product described as having a medium ethoxy content and a viscosity of 100 cps. measured in solution under standard conditions) and 20% plasticizer. The solvent was acetone plus a small amount of benzene added with the plasticizer. The physical properties of the sheets, all cast with an 8-mil knife, appear in the following table;

Sheet Properties Plastl eizer Elongation, Wet

Elongatlon,

Wot

Strength Dry Percent Percent Percent 11 1 (Excess glycol) I 2 (Equimolar amounts 3 (Excess acid) It is evident from these datathat an: excess of carboxylic acid produces the best elongation in the sheet at the expense of a slight drop in wet strength.

Example 3 Elongation, Dry

Elongation, Wet

Carbon Wet Dlcarboxylic Acid Atoms Strength Percent Percent Percent Succinic 89 Glutaric- Adipie-.-

Pimelic. Suberic Azelaic Sebaole It is apparent that only the dicarboxylic acids having a straight chain of 6 to carbon atoms produce tobacco sheets with sufficient elongation to be usable on cigar machines, and the optimum properties are observed when the chain length is about eight carbon atoms.

Example 4 glycol (average; molecular weight about-400) and glycerol. In the. case of glycerol only a stoichiometric amount of; azelaic acid'was employed for condensation. Each lasticiZer wasincorporated into tobacco sheet with the forrnulationof; Example 2, and the physical properties of the resulting sheets were measured. The results appear in the following table:

Wet Elonga- Elonga- Polyol .Strength tion, tlon, Dry et 5 Percent Percent Percent Ethylene glycol 55 25 28 DiethyleneglycoL 56-' 23 27 Triethyleneglycol... 60 20 27" Tetraethylene glycol. 75 25 i 32. Polyethylene glycol 4 90 10 13 Glycerol 53 25 24 Example 5 vA plasticizer was prepared from 265 grams. (1.36 moles) of tetraethylene glycol and 367' grams (1.82 moles) of a commercial mixture of isomeric ten-carbon dicarboxylic acids containing Z-ethylsuberic acid as the principal isomer, using the procedure of Example 1. A tobacco sheet was prepared from 15 grams (29%) of ethylcellulose (medium ethoxy-IOO cps.), 7.5 grams (14% of this polyester (in benzene'solution) and 30 grams (57%) of tobacco suspended in 145 ml. of acetone. The sheet was cast with a six-mil knife and dried at room temperature. Tensile strength of the dry sheet was 320 grams per inch and tensile strength of the wet sheet was, 227 grams per. inch; elongation, 22%.- dryand 41%.

wet.

Cigars wrapped on a cigar machine with this sheet had good taste, color and appearance.

Example 6 I To illustrate the use of adhesives derived from starch, b co; h st was st w d f m 5, grams of amylose triacetate dissolved in 110 ml. of methyl butynol, 7.5 grams (13%) of the polyester plasticizer of Example 1, 5.0 grams (9%) of hnmectant (triethylene glycol) and 30 grams (52%) of tobacco with 0.3 gram of a commercial flavoring agent. The sheet strength was 407 grams per inch wet and 340 grams per inch dry (83% wet strength); elongation, 35% dry and 42% wet.

Cigars wrapped on a cigar machine with this sheet were light in color and had good taste and appearance.

Example 7 To illustrate the use of the second type of plasticizer of this invention, a tobacco sheet was prepared according to the formulation of Example 2 except that the plasticizer was technical 2,4,6-tris-(dimethylaminomethyl) phenol. When cast with an 8-mil knife and allowed to air dry, the sheets weighed 3.9 grams per square foot; tensile strength, 312 grams per inch dry and 290 grams per inch wet; elongation, 40% dry and 37% wet.

This material made a satisfactory filler for cigarettes and also smoked well in a pipe.

Example 8 To illustrate the effect of varying the polyethylene night, diluted with 500 ml. of water, and extracted four 7 times with benzene. The benzene was stripped ofi under reduced pressureto leave the crude Mannich base plasticizer, 2,4,6-tris-(morpholinomethyl) phenol. l

A tobacco sheet was prepared with grams of this plasticizer dissolved in ml. of benzene, 15 grams (25%) of ethylcellulose (medium ethoxy100 cps.) dissolved in 170 ml. of acetone and 30 grams of tobacco. A film of the non-tobacco material was'formed and thereafter coated with tobacco dust. When the non-tobacco film was cast with a six-mil knife, the sheet tensile strength was 250 grams per inch dry and 200 grams per inch wet (80% wet strength); elongation, 29% dry and wet.

Example 9 'Three plasticizers were prepared from 4,4'-iso-' Plasticizer A B C- Sheet Weight, gJtt 3. 7 3.9 8. 8 Tensile Strength, dry, g [in 325 468' 515 Tensile Strength, wet, g. in 202 340 861 Elongation, dry, percent" 45 45 45 Elongation, wet, percent 6O 50 It is apparent that a higher degree of substitution on the aromatic nucleus results in increased tensile strength, both wet and dry, at little sacrifice in elongation.

Example 10 The reaction product of phenol and formaldehyde, 2,4,6-trimethylolphenol, is available commercially as a solution in water of partially resinified material. A tobacco sheet was prepared with 7.5 grams (11.5%) of this technical product as a plasticizer, 15 grams (23%) of ethylcellulose (medium ethoxy cps.), 42.5 gra 1 ns- (65.5%) of tobacco,; ml. of acetone and 35 ml. of When cast with an eight-mil knife, this sheet appearance, dark color and good taste.

ter comprising in combination the steps of forming a vis-' cous adhesive paste in a liquid organic solvent from a water insoluble adhesive and a material selected from they group consisting of polyesters, aminomethyl phenols and hydroxymethyl phenols, combining said paste with finely divided tobacco and thereafter evaporating said solvent.

2. A method of making a tobacco sheet comprising in combination the steps of providing a viscous paste in a liquid organic solvent from a water insoluble adhesive and a material selected from the group consisting of polyesters, aminomethyl phenols and hydroxymethyl phenols, mixing said paste with finely divided tobacco to form a tobacco slurry, forming said slurry into a thin film and thereafter evaporating said. solvent to form a tobacco sheet. 3. A method of making a tobacco sheet comprising in combination the steps of providing a viscous adhesive paste in liquid organic solvent from a water insoluble adhesive and a material selected from the group consisting of polyesters, aminomethyl phenols and hydroxymethyl phenols, contacting a layer of tobacco particles with a" layer of adhesive and thereafter evaporating said solvent to form a tobacco sheet.

No references cited.

Claims (1)

1. 2. A METHOD OF MAKING A TOBACCO SHEET COMPRISING IN COMBINATION THE STEPS OF PROVIDING A VISCOUS PASTE IN A LIQUID ORGANIC SOLVENT FROM A WATER INSOLUBLE ADHESIVE AND A MATERIAL SELECTED FROM THE GROUP CONSISTING OF POLYESTERS, AMINOMETHYL PHENOLS AND HYDROXYMETHYL PHENOLS, MIXING SAID PASTE WITH FINELY DIVIDED TOBACCO TO FORM A TOBACCO SLURRY, FORMING SAID SLURRY INTO A THIN FILM AND THEREAFTER EVAPORATING SAID SOLVENT TO FORM A TOBACCO SHEET.