US2755207A - Cigarette paper - Google Patents

Description

United States Patent CIGARETTE PAPER Walter G. Frankenburg, Millersville, Pa., assignor to General Cigar Co., Inc., New York, N. Y., a corporation of New York No Drawing. Application December 4, 1953,, Serial No. 396,326

9 Claims. (Cl. 131-45) This invention relates to an improved cigarette paper.

In recent years, the cigarette industry has given considerable attention to undesirable components in cigarette smoke and efforts to minimize or overcome the objectionable characteristics of cigarette smoke have resulted in two widespread trends in cigarette manufacture, namely, the addition of filter elements in cigarettes and the production of extra-long or king-size cigarettes. The theory is that the material in the filter element or in the additional length of a king-size cigarette absorbs some of the undesirable components of the cigarette smoke as it is drawn through the cigarette by the smoker so that these components are removed or filtered .out from the smoke reaching the smokers mouth. These trends have increased the cost of cigarettes without providing completely satisfactory elimination of the troublesome components of cigarette smoke.

Tests with cigarette paper alone have revealed that when cigarette paper burns slowly as in a cigarette, the smoke evolved by the burning paper is distinctly acrid and irritating to the nose and throat. These findings are unexpected because, theoretically, burning paper, which is essentially cellulosic material, yields only carbon dioxide and water vapor which are inert and not obnoxious. Apparently, what actually happens is that the portion .of the celiulosic material contiguous to the glowing and burning portion of the cigarette paper .undergoes thermal decomposition with generation of acidic gaseous materials that diffuse away and thus escape combustion.

The principal objectof this invention is to provide an improved cigarette paper that on burning yields a smoke substantially free of obnoxious components.

A further important object is to provide cigarette paper with modified burning characteristics so that the generation of disagreeable gases during combustion is substantially eliminated.

Other features of the invention will be apparent in the description which follows.

In accordance with this invention, cigarette paper which is essentially cellulosic material in fiber form has intimately associated therewith a finely divided, mineral-type, siliceous catalyst which being incombustible and refractory remains substantially unchanged during combustion of the cigarette paper and functions like a catalyst in modifying the combustion of the paper so that the resultant combustion gases and vapors are substantially free of the undesirable components formed when cigarette paper is burned in the absence of the siliceous catalyst.

Typical suitable siliceous catalysts are acid-treated clays, heat-treated montrnorillonite, and natural and synthetic silicates containing some hydrogen atoms which are relatively mobile. Inasmuch as these siliceous'materials survive the combustion of the cigarette paper as particulate solids while exerting a favorable influence on the burning of the cellulosic content of the cigarette paper, I believe that they act as catalysts in the sense that the usual aldehydic or acidic or hydrocarbon-type products 2,755,207 Patented July 17, 1956 2 of combustion are not at all formed or, if formed, are promptly further oxidized to the harmless form of carbon dioxide and water vapor so that the smoker observes no foreign taste or odor.

Tests with various siliceous catalysts have revealed a striking parallelism between their effectiveness for the purposes of this invention "and their effectiveness as petroleum cracking catalysts. In short, there is a Well defined trend indicating that a siliceous catalyst which is good for cracking hydrocarbons is good for avoiding the development of objectionable smoke components in cigarette paper. In fact, I have prepared distinctly superior cigarette paper which on burning is free of obnoxious gaseous products by incorporating therein siliceous catalysts selected merely on the basis that they were known to be successful cracking catalysts of the petroleum refining industry. This surprising discoverymay indicate that the pyrogenic decomposition products of the cellulosic material in cigarette paper are similar, or identical with, hydrocarbons and that the function of the siliceous catalyst consists in cracking these hydrocarbons into smaller molecular units which are then readily and completely oxidized to carbon dioxide and water vapor.

it is today generally accepted that a certain acidic nature is essential for the effectiveness of catalysts for cracking of high molecular hydrocarbons to lower molecular fragments. This property also seems to be a prerequisite for the efficiency of the siliceous catalysts used pursuant to my invention for the improvement of the smoke developed in burning cigarette paper. A class of catalysts with the proper acidic nature which can be used is that of solid particles containing silica and such amounts of ditficultly reducible metal oxides that the molecular ratio of silica to the other oxides exceeds appreciably the value of 1. As all these combinations of silica with other oxides, such as for instance, alumina, zirconia, titania, chromium oxide, magnesium oxide and others, contain small amounts of water, it is quite likely that the solid phase comprises a kind of complex acid in which some hydrogen atoms are in a rather mobile state especially at the surface of the solid particles. This view and experimental support for it have been pre- Sented by R. C. 'Hansford in a paper entitled, A mechanism of catalytic cracking, "Ind. and Eng. Chem., 39, 849 1947). The specific catalyst mentioned in this paper was composed of approximately 12% alumina and 88% silica (on dry basis). In another paper entitled, Montmorillonite cracking catalyst, Ind. and Eng. Chem., 41 148 5 (1949), Alexander G-renall has demonstrated the presence of hydrogen ion in Filtrol clay catalysts.

Silica gels which have been impregnated, even with as little as 1% alumina, have been shown to be efficient cracking catalysts by Pitzer in Advancing Fronts in Chemistry, vol. 1, page 33, 1945, "Rhein'hold Publishing Corp. Another cracking catalyst has been described by OKelly et al. in ind. and Eng. Chem, 39, 154 (1947), as being prepared by the co-precipitation of the hydrous oxides of silicon and aluminum in a weight ratio of 9:1 of silica to alumina. A tri-component cracking catalyst consisting of silica, alumina and zirconia has been described by Thomas et al. in J. Am. Chem. Soc., 66, 1694 (1944).

Cracking catalysts can be prepared by using natural clays as a starting material. Many clays contain silica and alumina in a ratio which corresponds to the postulate that the number of moles of silica exceed appreciably the number of moles of alumina or other oxide. However, some of these clays contain, instead of mobile hydrogen atoms combined with excess silica, other atoms, such as alkali and alkaline earth atoms. Such clays can be activated by removing part or all of the alkali and alkaline earth atoms and replacing them with hydrogen atoms by treatment with acid. Other clays, which already in their original composition have a potential acidic nature by having the proper ratio of silica to alumina or other oxides, can be activated by heat treatment (cf. Alexander Grenall l. c.).

All of the aforementioned natural and synthetic cracking catalysts are effective siliceous catalysts for the purposes of this invention. To recapitulate, my siliceous catalyst is a combination of a major weight proportion of silica and a minor weight proportion of one or more difficulty reducible metal oxides; this combination may be effected synthetically or it may be derived from natural materials like clays through activation by heat and/or acid treatment.

The finely powdered siliceous catalyst can be incorporated in the cigarette paper in various ways and at ditfercnt stages of the manufacture of the paper. For instance, since the powdered siliceous catalyst used in this invention is insoluble, it may be dispersed in the aqueous pulp of cellulosic fibers from which the paper is made or it may be added while the cigarette paper is being formed from the pulp. Alternatively, the catalyst may be applied to the surface of the cigarette paper; calendering or a small amount of adhesive such as methyl cellulose may be used to improve the adhesion of the powdered catalyst deposited on the paper. In any event, the siliceous catalyst is brought into close and uniform association with the fibrous cellulosic content of the cigarette paper so that the latter may subsequently be burned without evolving unpleasant combustion products.

The quantity of siliceous catalyst used in cigarette paper in accordance with this invention depends upon the efiicacy or activity of the chosen siliceous catalyst. in general. the addition of the siliceous catalyst falls in the approximate range of 20% to 60% based on the weight of cellulosic material in the cigarette paper. Preferably. siliceous catalysts, like good hydrocarbon cracking catalysts, are usually employed in the proportion of about 45% to 55% based on the weight of cellulosic material.

In an illustrative embodiment of the invention, the fibrous ccllulosic pulp for a conventional cigarette paper is uniformly admixed with a finely powdered siliceous catalyst (passing through a ZOO-mesh sieve) which is a silica gel containing about 11% by weight of alumina (ground Sovabead catalyst of Socony-Vacuum Company). The quantity of catalyst used corresponds to approximately 50% by weight of the dried cellulosic material in the pulp. The fibrous pulp containing the admixed siliceous catalyst is then formed into cigarette paper in the usual manner. Tests in which the catalystcontaining paper is burned slowly reveal that the gaseous products of combustion are mild and not disagreeable whereas identical tests with cigarette paper made from the same pulp without the addition of the siliceous catalyst yield combustion gases that are distinctly obnoxious and irritating to the nose and throat.

This application is a continuation-in-part of my copending application Serial No. 105,660, filed July 19, 1949, now matured as U. S. Patent No. 2,706,695, issued April 19, 1955, which discloses the use of the same siliceous catalysts, herein discussed, in smoking products made with water-soluble cellulose derivatives such as methyl cellulose and the sodium salt of carboxymethyl cellulose.

Those skilled in the art will visualize many other modifications and variations of the invention set forth hereinabove without departing from its spirit and scope. Accordingly, the claims should not be interpreted in any restrictive sense other than that imposed by the limitations recited within the claims.

What is claimed is:

1. An improved cigarette paper comprising substantially purified cellulosic material and a hydrocarboncracking, activated siliceous catalyst in powdered form in intimate association with said cellulosic material.

2. The cigarette paper of claim 1 wherein the weight of the activated siliceous catalyst is in the range of about 20 to of the weight of the cellulosic material.

3. The cigarette paper of claim 1 wherein the activated siliceous catalyst is an acid-treated clay.

4. The cigarette paper of claim 1 wherein the activated siliceous catalyst is a synthetic catalyst comprising a major weight proportion of silica and a minor weight proportion of at least one ditficultly reducible metal oxide.

5. The cigarette paper of claim 4 wherein the synthetic catalyst has been prepared by the co-precipitation of the hydrous oxides of silicon and aluminum in a weight ratio of 9:1 of silica to alumina.

6. An improved cigarette paper comprising a major weight proportion of substantially purified cellulosic material and a minor weight proportion of a hydrocarboncracking, activated siliceous catalyst in powdered form uniformly dispersed in said cellulosic material.

7. The cigarette paper of claim 6 wherein the activated siliceous catalyst is an acid-treated clay.

8. The cigarette paper of claim 6 wherein the activated siliceous catalyst is heat-treated montmorillonite.

9. The cigarette paper of claim 6 wherein the activated siliceous catalyst comprises a major weight proportion of silica gel impregnated with a minor weight proportion of alumina.

References Cited in the file of this patent UNITED STATES PATENTS 1,614,660 Darlington et al. Jan. 18, 1927 2,007,407 Sadtler July 9, 1935 2,460,285 Hale Feb. 1, 1949 2,466,051 Shakbaker et al Apr. 5, 1949 FOREIGN PATENTS 1,218 Denmark Aug. 10, 1897

Claims (1)

1. AN IMPROVED CIGARETTE PAPER COMPRISING SUBSTANTIALLY PURIFIED CELLULOSIC MATERIAL AND A HYDROCARBONCRACKING, ACTIVATED SILICEOUS CATALYST IN POWDERED FORM IN INTIMATE ASSOCIATION WITH SAID CELLULOSIC MATERIAL.