US 3410282 A
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United States Patent 3,410,282 FILTER MEDIUM FOR REMOVING HYDROGEN CYANIDE FROM TOBACCO SMOKE Theodore Roosevelt Walker and John Edward Kiefer,
Kingsport, Tenn., assignors to Eastman Kodak Company, Rochester, N .Y., a corporation of New Jersey No Drawing. Filed Mar. 13, 1967, Ser. No. 622,470 6 Claims. (Cl. 131267) ABSTRACT OF THE DISCLOSURE Tobacco smoke filtering mediums containing at least one amine salt for selectivity removing hydrogen cyanide from tobacco smoke. The particular salts are produced by reacting a primary alkyl or hydroxyalkyl amine conta ning no more than 8 carbon atoms with a carboxylic acid.
It has been known for some time that tobacco smoke contains certain harmful components including hydrogen cyanide which, for obvious reasons, should be removed from tobacco smoke. It is well known, for example, that hydrogen cyanide is an extremely harmful ciliatoxic compound which contributes nothing beneficial to the pleasant taste or aroma of the smoke or to the smoker. It has therefore been the desire of the tobacco industry to provide an effective and practical tobacco smoke filter which is capable of selectively removing hydrogen cyanide from cigarette smoke without at the same time adversely affecting the pleasant taste and aroma found in the smoke.
The search for a suitable yet inexpensive filtermg medium which could be used with any tobacco product, and especially with cigarettes, led to the development of the so-called fibrous filter unit. These fibrous filters, and particularly those made of cellulose acetate tow, have been found to be very effective for removing solid particulate matter commonly referred to as tar from tobacco smoke. However, it is difiicult, if not impossible, to remove certain undesirable components, such as hydrogen cyanide, which is found in tobacco smoke by use of such filters.
It has been known that certain gas adsorbing additives in the form of finely divided particles can be dispersed within the fibrous filter for removing such undesirable gases. These particles of solid materials were generally placed on the surface of a fibrous material in either a dry or liquid state. Numerous solid adsorbing materials were tried with activated carbon and certain silica gels being the ones most often used.
However, there are certain limitations and disadvantages to using activated carbon in a cigarette filter for removing cigarette smoke vapors. Activated carbon does not remove cigarette smoke vapor selectively even though it has more afifinity for some vapor components than others. In general, the adsorption of vapors by carbon is dependent upon the boiling point of the. vapor being adsorbed, that is, the least volatile vapors will be more readily adsorbed and retained by activated carbon addltives as opposed to the more volatile vapors. Th1s IS a definite disadvantage since several of the least volatile vapors in cigarette smoke are those which give flavor and taste to the smoke and are neither deleterious nor harmful to the smoker. Therefore, the removal of these vapors Patented Nov. 12, 1968 ICC is highly undesirable and if permitted to occur can result in what has commonly been referred to as a carbon or dry taste.
The adsorption of vapors by carbon in a cigarette filter therefore is a physical phenomenon dependent upon temperature and pressure. Since the temperature of a cigarette filter increases as the burning zone of the cigarette approaches the filter during the smoking of a cigarette, the temperature of the carbon in the filter is raised causing the more volatile vapors adsorbed on the carbon to be eluted from the carbon. Thus, the carbon particles do not remove the more volatile vapors elfectively. In addition, as stated above, the less volatile gases which contribute to the taste and aroma of the smoke, and are generally neither deleterious or harmful, are also removed by carbon filters. Furthermore, since the removal of solid particulate matter commonly called tar is also of prime importance, cigarette filters containing activated carbon additives for the removal of vapors do not fulfill the requirement for the removal of solid particulate matter such as tar. Thus the problem of the tobacco industry; namely, how to economically produce a filter which is capable of selectively removing vapors such as hydrogen cyanide from the vapor phase of tobacco smoke, has todate remained unsolved.
It has been reported that certain amines when applied to cigarette filters remove noxious gases from the smoke more selectively than carbon; however, there are several decided disadvantages to their use in filters. For example, amines are notorious for their offensive odors and this property alone eliminates most of them from consideration Another disconcerting property of amines is their strong basicity which causes skin irritation; therefore if they are to be used in cigarette filters, they must be prevented from entering the smoke stream. Amine filters also tend to impart an off-taste to the smoke which may be due to the imbalance caused by absorption of acids by the amine. Furthermore, they cannot be used as additives to cellulose acetate, the most widely used filter medium, because they degrade it.
According to this invention it has been found that the aforementioned difficulties of the prior art tobacco smoke filters can be substantially overcome by the use of an amine salt of a carboxylic acid dispersed on a carrier inserted into a stream of tobacco smoke and arranged to provide interstices for the passage of smoke therethrough, serves to selectively remove hydrogen cyanide from the smoke. These carboxylic acid salts are prepared by reacting primary or secondary alkyl and hydroxyalkylamines containing no more than 8 carbon atoms with an acid. Some amines which have been found particularly eifective are: ethylamine, dibutylamine, 2-amino-2-methyl-l-propanol, ethanolamine, and diethanolamine. The acids used in the preparation of the salts can be mono-, di-, tri-, and tetracarboxylic acids which include the following: carbonic, acetic, itaconic, lactic, succinic, citric, and pyromellitic acids.
As will be apparent, filters incorporating these amine salts of a carboxylic acid provide a means for selectively removing hydrogen cyanide from cigarette smoke vapors without the use of activated carbons, silica gel, molecular sieve or other materials commonly used for the physical adsorption of vapor. It has been found that such acid salts are capable of chemically reacting on contact with the hydrogen cyanide vapor to neutralize the vapor thereby assuring that cyanide is not later released or otherwise eluted from the filter due to the increase in temperature of the filter during the smoking of the cigarette. Furthermore, such means employed for selectively removing hydrogen cyanide from the vapor phase of tobacco smoke does so without decreasing the capacity of the filter for removing solid particulate matter such as tar from the tobacco smoke. Since the additive for the filter element is an odorless, nonvolatile, nonirritant which can be applied to such materials as cellulose acetate without subsequent degradation of the material, it can be used freely without fear of its affecting the taste of the tobacco smoke or entering the smoke stream.
The carboxylic acid salts of certain alkyl or hydroxyalkylamines may be applied by sifting, dusting, shaking, or from a plasticizer dispersion such as glyceryl triacetate. It may also be applied from any other suitable liquid by any convenient method such as by spraying or rolling on the carrier filter medium. Furthermore, more than one salt may be used as a mixture if desired. The fibrous media upon which the additives of this invention may be used is preferably a crimped continuous filament cellulose acetate tow, preferably of a denier per filament of about 1.620. However, it will be appreciated that such salts may be equally effectively employed upon filters which are made from other base materials such as paper, cotton, propylene and polyethylene fibers, or any other suitable material that can be formed into tobaco smoke filters.
The carboxylic acid salts of aliphatic amines may be applied to the paper, tow or other carrier materials in the amount of from about 10-150 mg. (milligrams) per filter, the preferred amount being about 20 to 60 mg. By uniform application to the surface of the fibrous media the salt is enabled to take advantage of the large surface area which provides the contact necesary for effective hydrogen cyanide removal.
It also has been found that it is possible to produce a fibrous filtering unit which is capable of selectively removing hydrogen cyanide from a gaseous medium by spinning the fibers of the filter from a dope of cellulose acetate which contains an additive of the water-soluble, organic salts. Since these organic salts are embedded in the cellulose acetate fibers as the fibers are being spun, the necessity of including additional processing steps, materials and equipment into the manufacturing operation is alleviated. The selected Water-soluble salts, if properly prepared, can be mixed with selective types of cellulose acetate dopes and spun to give a filament that readily neutralizes the hydrogen cyanide in tobacco smoke. It has been found, for example, rather unexpectedly that the salts are not masked by the acetate to a degree which would prevent their etfective removal of hydrogen cyanide when employed in tobacco smoke filters.
The spinning solution or dope from which the filaments containing the organic salt are spun can be produced in any one of several manners. In its broadest aspect, this can be accomplished by adding directly to the cellulose acetate solution one or more of the carboxylic acid salts selected from the groups that are prepared from primary or secondary alkyl and hydroxyalkylamines which contain no more than 8 carbon atoms which are reacted with a suitable acid. More specifically, these salts are added to an acetone solution of cellulose acetone solution of cellulose acetate in the amount of from about to 30 percent based on weight of the cellulose acetate. After the carboxylic acid salts have been added to the acetone solution of cellulose acetate, the mix is uniformly dispersed. The spinning solution containing the carboxylic acid salt is now ready to be spun into filaments on a conventional spinning machine after which it can be formed into a tobacco smoke filter by any suitable manner.
The subject mater which is regarded as the invention is clearly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, as to its organization and operation, together with the further objects and advantages thereof will best be understood by reference to the following examples which are preferred embodiments of our invention.
EXAMPLE I With methanol as sol-vent, a solution of ethanol ammonium citrate was prepared by adding a ratio of three moles ethanolamine to one mole of citric acid. The solution was added to commercial creped-paper filters and after evaporation of the methanol, the 10 mm. filters each contained 60 mg. of the salt.
They were attached to king size cigarettes and the cigaretes smoked by an automatic smoking device which removed particulate matter from the smoke by means of a Cambridge filter. By a colorimetric test the smoke vapors were shown to contain 76% less HCN than vapors from an unfiltered cigarette smoked in the same manner.
In addition ciliatoxicity of the vapor phase of smoke from these filtered cigaretes was determined by the method which was described by Spears, Tryfiates, and Schultz at the 18th Tobacco Chemists Research Conference (1964) [see Science, 153, No. 3741, 1248 (1966)]. This method uses clam gill cilia as the test specimen. This test showed that the filter reduced ciliastasis of the gas phase of smoke by 80%.
EXAMPLE II An aqueous solution of dibutylamine was titrated to neutrality with 5% aqueous acetic acid. The resulting salt solution was pipetted onto 10 mm. cellulose acetate filters such that each filter contained 60 mg. of the salt. When the filters were dry they were tested as in Example I. The elfect of this filter on the ciliatoxicity of tobacco smoke and its ability to remove HCN is shown in Table 1.
EXAMPLE III Diethanol ammonium carbonate was prepared by adding 50 mg. diethanolamine in CH OH to a 20 mm. cellulose acetate filter and passing CO through the filter for twenty minutes. The filters were attached to cigarettes and tested as in Example I with the results being given in Table 1.
EXAMPLE IV Seven hundred grams (3 /3 moles) of citric acid was added slowly with mechanical stirring to a solution of ml. water in 1051 g. (10 moles) diethanolamine. An ice bath kept the temperature from rising above 50 C. The pH of this preparation was 7.3 measured as a 5% aqueous solution. Since diethanol ammonium citrate is a liquid, it was rolled onto cellulose acetate tow by a method'developed for the application of plasticizers. The effect of this filter on the ciliatoxicity of tobacco smoke and its ability to remove HCN is shown in Table 1.
EXAMPLE V Diethanol ammonium acetate, ethyl ammonium itaconate, 1,1-dimethyl ethanol ammonium malonate, ethyl ammonium pyromellitate and diethyl ammonium lactate were prepared as in Example I in a ratio of one amino group per carboxyi group. Crimped cellulose acetate tow was spread out to a length of approximately 15 in. The tow was sprayed with a 50-50 w./w.% aqueous solution of the salt and dried. The tow was then sprayed with triacetin, compacted, wrapped with a paper tape to form a rod and allowed to stand until firm. The triacetin cures the tow making a rigid rod and leaving the salt evenly distributed throughout the tow. After the rod became firm it was cut to a 20 mm. length and attached to a cigarette for testing as in Example I with the results being given in Table 1.
TABLE 1 Mg. Filter Inhibition of HCN Filter Additive Additive Medium Cilia Fre- Removal quency percent percent Ethanol ammonium citrate 62 Paper 5 76 Dibutyl ammonium acetate 60 Cellulose acetate. 0 85 Diethanol ammonium carbonate 74 d 8 89 Diethanol ammonium citrate 78 3 82 Ethyl ammonium itaconate 65 10 82 1,1-dimethyl ethanol ammonium malonat 71 12 79 Ethyl ammonium pyromellitate 78 8 85 Diethanol ammonium acetate 68 4 90 Diethyl ammonium lactate 65 8 80 None 0 Paper 62 0 Do 0 Cellulose acetate 58 0 Dom. 0 one 65 0 Carbon 113 Cellulose acetate 35 55 From the foregoing description and illustrative eX- 15 being produced by reacting an amine selected from the amples it is apparent the inventive concept of incorporating certain amine salts of organic acids with the fibrous carrier media of a tobacco smoke filter offers numerous de-toxicating advantages over those filters previously used in the tobacco industry. For example, a filter so produced is a highly selective one which is capable of removing substantial amounts of the solid particulate matter, such as tar, found in tobacco smoke as the smoke moves through the interstices of the filter, while at the same time selectively removing hydrogen cyanide from the vapor phase of the tobacco smoke by neutralizing or reducing it to a solid by-product which cannot later be eluted from the filter. Furthermore, the fact that the salt particles may also be embedded within the cellulose filaments of the filter eliminates sifting out and companion problems that have been heretofore present in filters containing solid additives. Furthermore, these amine salts may be incorporated in any of the known filter fibrous media used in the making of tobacco smoke filters such as, for example, cellulose acetate or paper. Thus, the hereinabove described method for the selective removal of hydrogen cyanide from the vaporous phase of tobacco smoke has been found to be both surprising and effective in its ability to remove this highly undesirable component from tobacco smoke and still provide the tobacco smoke with a taste and aroma most desirable for the ultimate smoker.
What is claimed and desired to be secured by the United States Letters Patent is:
1. A tobacco smoke filter element adapted for selective removal of deleterious and noxious materials from tobacco smoke which comprises a carrier medium having as an additive thereon at least one amine salt, said salt group consisting of primary alkyl amines and hydroxyalkyl amines containing no more than 8 carbon atoms with a carboxylic acid.
2. A tobacco smoke filter according to claim 1 in which the carboxylic acid is an acid selected from the group consisting of mono-, di-, tri-, or tetracarboxylic acids.
3. A tobacco smoke filter of claim 1 wherein the amine is selected from the group consisting of ethylamine, 2- amino 2 methyl 1 propanol, ethanolamine, and diethanolamine.
4. A tobacco smoke filter of claim 2 wherein the carboxylic acid is selected from the group consisting of carbonic, acetic, lactic, malonic, itaconic, succinic, citric, and pyromellitic acids.
5. The tobacco smoke filter element of claim 1 wherein the filter element contains from about 10-150 mg. of
, said salt per filter element.
6. The tobacco smoke filter element of claim 1 wherein the carrier medium is selected from the group consisting of paper, cotton, cellulose acetate, polypropylene and polyethylene.
References Cited UNITED STATES PATENTS 2,920,416 1/1960 Kinnavy 131-266 X 2,956,329 10/1960 Touey 131-266 X 2,968,306 1/1961 Touey et al 131266 3,127,901 4/ 1964 Whitefield et al 131267 3,144,024 8/1964 Eichwald et al. 131-267 3,246,655 4/1966 Spears et al 131--266 X SAMUEL KOREN, Primary Examiner.
DENNIS J. DONOHUE, Assistant Examiner.