nitcd States Patet- 2,897,103 Patented July 28, 1959 Alfred M. Gottscho, Lancaster, Pa., assignor to General Cigar Co., Inc., New York, N.Y., a corporation of New ork N Drawing. Application August 5, 1957 Serial No. 676,391
12 Claims. (Cl. 131-17) This invention relates to tobacco products suitable for smoking, and more particularly to tobacco products formed of comminuted tobacco and a binding agent forthe tobacco particles.
U.S. Patents 2,592,553 of W. G. Frankenburg and P. W. Garbo and 2,592,554 of W. G. Frankenburg, both issued April 15, 1952, described the production of tobacco sheets by mixing tobacco particles with an aqueous solution of a water-soluble binding agent, like methyl cellulose or sodium alginate, to form a paste which is spread as a thin layer and then dried. As disclosed in US. Patent 2,797,689 of W. G. Frankenburg, issued July 2, 1957, such tobacco products may also be made of comminuted tobacco and water-insoluble binding agents. The commercial success of converting tobacco into continuous sheets is attributable to improved smoking qualities resulting from the disintegration of tobacco veins and stems and from the intimate blending of several tobaccos. However, in the utilization of these tobacco sheets, for instance, as binders in cigars, some dilficulty has been encountered because of tearing and rupturing. Research has recently been directed to improving the strength of tobacco sheets without adding any new component.
It has now been discovered that a narrow range of fine particle sizes materially increases the tensile strength of tobacco sheets produced from such finely divided to bacco and a binding agent. The criticalness of particle size of the comminuted tobacco long escaped attention because it was not anticipated that very small amounts of somewhat coarser particles could appreciably lower the tensile strength of the tobacco sheet produced therefrom. Thus, US. Patent 2,706,695 of W. G. Frankenburg issued April 19, 1955, disclosed in Example 3 a tobacco sheet made of ground tobacco having a screen analysis of 2.8% by weight retained on a SO-mesh screen and 82% passing through ZOO-mesh. In spite of the comparatively fine powder used in the aforesaid patent, the tensile strength obtained with a tobacco sheet made of ground tobacco containing as much as 2.8% by weight of particles coarser than 80-mesh falls far short of the tensile strengths now attainable pursuant to this invention. Unexpectedly high tensile strengths are obtained when tobacco is dry ground to a powder having a screen analysis of more than 99% by weight through a 100-mesh screen and more than 86% through ZOO-mesh. Preferably, more than 95% by weight of the tobacco powder should pass through a ZOO-mesh screen. Studies have shown that the predominant part, usually at least 70 by weight, of the particles which pass through the ZOO-mesh screen should have maximum dimensions in the range of 40 to 65 microns for optimum results.
The surprisingly disproportionate decrease of tensile strength of tobacco sheets resulting from the presence of a very small amount of tobacco particles coarser than 100-mesh is illustrated by a series of tests made with a German cigar tobacco. This tobacco was dry ground to obtain three batches of tobacco powder of the following screen analyses:
Batch A B C Percent Percent Percent 011 100-mesh... 1. 6 0. 0 0.0 011 200-mesh 18.4 11. 7 1.8 On 325mesh 79. 7 86.0 94. 1 Thru 325-mesh O. 3 2. 3 4. 1
Batch A was ground in a Gruendler pulverizer (hammertype mill with horizontal shaft), batch B was first passed through the Gruendler pulverizer and then through a Mikro-Bud grinder. (hammer-type mill with vertical shaft), and batch C was twice ground in a Shutz-ONeill pulverizer (mill with beater plates having fixed hammers).' t
Each batch of ground German tobacco was converted to a tobacco sheet using the same procedure and formulation in each instance. For each 100 weight parts of tobacco powder, there were used 14.7 parts of methyl cel lulose (400 centipoise grade), 22.8 parts of triethylene glycol, 6.3 parts of diatomaceous-earth, 6.3 parts of finely powdered siliceous catalyst, and sufiicientwater to form a 2.5% by weight solution of the methyl cellulose.
Samples of the tobacco sheets produced from the three batches of ground German tobacco were subjected Iunder the same conditions to. tensile strength tests. The sheet made of batch. A tobacco powder had a tensile strength of grams per square millimeter, that of batch B 145 grams per square millimeter and that of, batch C 190 grams per square millimeter. Accordingly, by eliminating only 1.6% by weight of tobacco particles coarser than -mesh and decreasing the amount of tobacco powder coarserthan ZOO-mesh from 18.4% to 11.7% by weight, the tensile strength of the tobacco sheet was increased about 60%. In the case of batch C tobacco powder, the sheet showed an improvement in tensile strength of over 100% when compared with the sheet made of batch A tobacco powder.
In another series of tests, three batches of a blend of American cigar tobaccos were dry ground in the Mikro- Bud pulverizer to different degrees of particles fineness as shown by the following screen analyses:
In batch F, approximately 80% by weight of the tobacco particles finer than ZOO-mesh had maximum dimensions in the range of 40 to 65 microns.
Following the same procedure and formulation, each batch of ground cigar tobacco was converted to a tobacco sheet. Each 100 weight parts of tobacco powder were combined with 14.7 parts of methyl cellulose (4000 centipoise grade), 22.8 parts of triethylene glycol, 6.3 parts of diatomaceous earth, 6.3 parts of finely powdered siliceous catalyst, and sufficient water to form a 2% by weight solution of the methyl cellulose. The resulting pasty mixture was spread in a thin layer and dried to a coherent tobacco sheet.
Tensile strength tests under the same conditions were performed on samples of the tobacco sheets produced from the three "batches of ground cigar tobacco. The sheet made of batch D tobacco powder had a tensile strength of 90 grams per square millimeter, that of batch E grams per square millimeter and that of batch F grams per square millimeter. In spite of the batch F powders were increased nearly 40% and 85%.
This series of tests illustrates that, if tobacco sheets of high tensile strength are to be produced, it is not sulficient to grind the tobacco so that substantially all of the particles pass through a IOO-mesh screen, but that it is also necessary to grind the tobacco so that more than 86% by weight of the particles will pass through a 200- mesh screen. When at least 70% by weight of the particles finer than 200-mesh have maximum dimensions in the range of 40 to 65 microns, an optimum tensile strength is obtained.
What is claimed is:
1. In tobacco smoking products in which particles of dry ground tobacco are held together in a coherent form 'by a binding agent, the improvement of tobacco dry ground to particles of which more than 99% by Weight pass through a lOO-rnesh screen and more than 86% by weightpass through a ZOO-mesh screen to yield increased tensile strength in said coherent form.
2. The tobacco smoking products of claim 1 wherein the binding agent is methyl cellulose.
3. The tobacco smoking products of claim 1 wherein at least 70% by weight of the particles passing through a ZOO-mesh screen have maximum dimensions in the range of 40 to 65 microns.
4. The tobacco smoking products of claim 3 wherein the binding agent is a Water-soluble cellulose derivative.
5. In the process of converting tobacco into a continuous and coherent form by comminuting tobacco and adhering the resulting particles of tobacco to one another with a binding agent, the improvement of grinding dry tobacco to particles more than 99% by weight of which pass through a IOO-mesh screen and more than 86% by weight of which pass through a ZOO-mesh screen in order to increase the tensile strength of the continuous and coherent form resulting from the adhesion of said particles to one another with a binding agent.
6. The process of claim 5 wherein the binding agent is methyl cellulose.
7. The process of claim 5 wherein the grinding of dry tobacco to particles more than 86% by weight of which pass through a ZOO-mesh screen yields particles with maximum dimensions in the range of to microns in an amount at least by weight of the particles passing through a ZOO-mesh screen.
8. The process of claim 5 wherein the grinding of dry tobacco is effected in a hammer-type mill.
9. The process of converting tobacco into a continuous sheet of improved tensile strength, which comprises dry grinding tobacco to particles more than 99% by weight of which pass through a lOO-mesh screen and more than by weight of which pass through a 200- mesh screen, admixing said particles With an aqueous solution of a binding agent, spreading the resulting admixture of said particles and said solution as a continuous film and drying said film to yield a continuous sheet of improved tensile strength.
10. The process of claim 9 wherein at least 70% by weight of the particles which pass through a ZOO-mesh screen have maximum dimensions in the range of 40 to 65 microns;
11. The process of of tobacco is effected in a 12. The process of claim is methyl cellulose.
claim 10 wherein the dry grinding hammer-type mill.
10 wherein the binding agent References Cited in the file of this patent