US3291140A - Process for the purification of tobacco smoke - Google Patents

Description

United States Patent 3,291,140 PROCESS FOR THE PURIFICATION OF TOBACCO SMOKE Oliver W. Burke, Jr., 506 lntracoastal Drive, Fort Lauderdale, Fla, and Eldon E. Stahly, Pompano Beach, Fla; said Stahly assignor to said Burke N0 Drawing. Original application Aug. 13, 1963, Ser. No. 301,879. Divided and this application Aug. 7, 1964, Ser. No. 398,468

1 Claim. (Cl. 131-262) The present application is a division of application Serial No. 301,879 filed August 13, 1963 and has been filed pursuant to a requirement for restriction made in said application Serial No. 301,879, under 35 U.S.C. 121.

This invention relates to the improvement of tobacco smoke, filters, and cigarettes for the reduction of metal content, e.g., metal carbonyls, in the smoke. Strictly speaking, a metal carbonyl is a compound of metal and carbon monoxide, but in a broader sense the term metal carbonyl also includes the analogous metal nitrosyl carbonyls and the metal hydrocarbonyls, which are similar compounds in which one of the carbonyl groups has been replaced by a nitrosyl or a hydrocarbonyl group, and except where the context indicates to the contrary, the term is employed in said broader sense herein. Metals may also be present in the smoke in other forms, and the term metal content of the smoke has reference to the metal present therein whether in the form of gaseous metal carbonyl compounds or otherwise.

Objects of the invention, severally and interdependently, are to provide an improved cigarette having a substantially reduced content of metal in its smoke output as compared to conventional plain or filter-tipped cigarettes; to provide a process for the purification of tobacco smoke by removing metals therefrom by converting the same to non-volatile materials; to provide an improved cigarette smoke from which selected metals are substantially reduced or eliminated; to provide an improved method and cigarette, or cigarette filter, in which metals present in tobacco smoke in small amounts are converted to forms, e.g., non-volatile materials, in a manner which effectively prevents their leaving a cigarette in the smoke; and to provide an improved method and cigarette in which a ligand material is reacted with metals in the tobacco smoke and converts them into non-volatile compounds.

Other objects and advantages of the invention, and of preferred embodiments thereof, will be apparent from the following description and from the illustrative examples appended thereto.

The invention resides in the new and useful methods and products herein disclosed, and is more particularly defined in the appended claim.

GENERAL DESCRIPTION Conventional tobacco smoke, more particularly conventional cigarette smoke, contains substantial traces of metals, and especially of transition metals, e.g., nickel, cobalt and iron, and such materials are reported to be toxic and carcinogenic to animals.

Thus, it has been reported in a paper by the Drs. F. W. Sunderman (Sr. and Jr.), based on tests of six different brands of cigarettes, that nickel carbonyl containing from 0.4 to 0.6 microgram nickel per cigarette (corresponding Patented Dec. 13, 1066 ice to about 20% of the total nickel of the tobacco) passes through the butt and filter of conventional plain or filter cigarettes, reaching the smoker (Medical Science, page 617, May 25, 1961; American Journal of Clinical Pathology, 35, 203 (1961)). In studies with rats, small amounts of nickel carbonyl were found by the Drs. Sunderman to be carcinogenic. The nickel delivered in the smoke drawn from the butt ends of the cigarettes amounted to up to 8 micrograms nickel per pack of 20, or 23.5 micrograms nickel as nickel carbonyl per pack of 20 of unfiltered cigarettes; and up to 12 micrograms nickel or 35 micrograms of nickel as nickel carbonyl per pack of filtered cigarettes. On the basis of their studies cumulative exposure to these quantities of nickel was suggested by the Drs. Sunderman to be a possible cause of the so-called smokers pulmonary cancer. Based on the reported figures, a person who smokes a pack of cigarettes per day over a period of a year subjects himself to about one and one-half times the amount of nickel required to induce pulmonary cancer in rats, which are considered to be notably resistant to pulmonary cancer.

Aside from the nickel reported, it has been found that traces of volatile cobalt and iron are also present, apparently as carbonyls, in cigarette smoke. The cobalt is present in somewhat smaller amounts than the nickel, about 13 micrograms of cobalt passing the filters per pack of filter cigarettes; and the iron is present in at least about twice the amount of nickel in the smoke of some brands of cigarettes.

Aside from the carcinogenic aspects of metal carbonyls reported by the Drs. Sunderman, it has long been known that such metals are highly toxic and dangerous materials even in trace amounts. Thus Sax, Handbook of Dangerous Materials, published in 1951 by Reinhold Publishing Company, New York, prescribed a maximum allowable concentration of cobalt in the air as 0.4 part per million, and the Twenty-Second American Conference of Government Hygienists in April 1960 placed the maximal atmospheric concentration of nickel carbonyl for a working day at 1 part per billion (A.M.A. Arch. Environmental Health 1, 140444, year 1960). Iron carbonyl is also considered to be toxic, although less toxic than nickel and cobalt carbonyls. Accordingly, the cumulative toxicity effects of these three metals in tobacco smoke can be expected to be greater than that reported for nickel alone.

Likewise, aforesaid Drs. Sunderman in the above cited paper, demonstrated that cigars and pipe tobacco contain nickel in amounts similar to cigarette tobaccos, and similar amounts of nickel per gram of tobacco smoked can reach the smoker. Some pipe tobaccos contain 6 micrograms nickel per gram of tobacco, 6 micrograms cobalt per gram of tobacco and over 400 micrograms iron per gram of tobacco, of which over a microgram of each metal per gram of tobacco smoked can reach the smoker in conventional methods of smoking.

Hence it is evident that the quantities of transition metal present in the smoke from conventional plain and filter cigarettes and from cigars and pipe tobacco exceed the quantities deemed objectionable by the above authorities.

By the present invention such content of transition metal may be reduced in, or practically eliminated from, the tobacco smoke from such smoking articles, and this invention thus can serve as a safeguard to smokers against excessive exposure to such metals.

The new process for the treatment of tobacco smoke is based on the reduction of transition metal content of tobacco smoke by the formation of non-volatile complexes or low-volatility complexes or salts by combina tion of the metal carbonyl or other metal content of the tobacco smoke with a ligand, which for the purposes of this invention said ligand is an aromatic compound having a combination of at least one hydroxy radical and at least one other polar radical attached to the same aromatic nucleus, which compound acts as a complexing agent to form complexes of low volatility with transition metal content of tobacco smoke in the presence of other constituents of tobacco smoke, more particularly in the presence of moist carbon dioxide. The practice of the invention does not depend on the formation of exact empirical complexes since mixtures of such complexes may be formed with equal benefit for the process. Thus the ligands of this invention are principally aromatic compounds having one or more hydroxy (oxy) radicals attached to aromatic nuclei and such hydroxy groups in most of these ligands are in the ortho position to certain other groups which, with said hydroxy group of said compounds capable of forming relatively stable salts or complexes, or chelates of certain transition metal compounds, e.g., the carbonyls of nickel cobalt and iron.

Ligands hereof containing transition metal chelating groups and including thereamong at least one hydroxy group can be represented by the following Formula A:

[-fi-OH OX in which the position of the double bond may be shifted, as it is part of an aromatic ring, and in which X is selected from those other radicals which in combination with the ortho-hydroxy radical are capable of complexing certain transition metal compounds and such other radicals include:

TABLE A Markush Group of Radicals from which the Radical (x) in the Formula. A is selected Ligand Group Comprising both radical (X) and the hydroxy radical ortho thereto 1. Carbonyl [:0]

2. Carboxyl C=O] o-Hydroxy-carbonyl.

o-Hydroxy-amide. o-Hydroxy-N-mono substituted am es. oHydroxy-N-disubstituted amides.

o-Hydroxy-azomethine.

When the ligands hereof have chromophore and/or auxochromophore groups they are colored, for example, the mordant type dyes have metal complexing groups similar to those set forth in Table A above and therefore such mordant dyes in their unmordanted form may be employed as ligands for the purposes of this invention and the members of the mordant class of dyes are set forth throughout pages 1405-1616 of volume 1 (second edition, 1956) of the Colour Index (edited by The Society of Dyers and Colourists, and The American Association of Textile Chemists and Colorists).

Iron, nickel and cobalt or other transition metal compounds present in tobacco smoke will combine with unmordanted mordant dyes in the presence of other ingredients of tobacco smoke.

Thus mordant dyes in their unmetalized form (unmordanted form) and capable of complexing or combining with the transition metals of tobacco smoke are considered ligands for the purposes of this invention.

This invention comprises:

(1) the method of treating tobacco smoke which comprises reducing the content of transition metal therein by contacting said smoke with a ligand as herein described;

(2) a filter element for reducing the transition metal content of tobacco smoke, said filter element including a substance comprising a ligand as herein described;

(3) a new article of manufacture, a cigarette having exposed in the path of the tobacco smoke therein means for reducing the content of transition metal thereof, said means comprising a ligand; and in this invention the term ligand means a substance which contains at least two functional groups which are attached to two adjacent carbons of an aromatic moiety and one of said functional groups comprising a hydroxy group and the other of said functional groups being a group having atoms selected from the class consisting of oxygen, nitrogen and combinations of these atoms and said other group being selected from the class consisting of carbonyl, carboxyl, amide including N-mono-substituted and N-disubstituted amides, azomethine, azo, nitroso, oxazone, oxazine, lactone, oxy and combinations of such groups and said ligand being capable of removing transition metal compounds from tobacco smoke.

Thus volatile metal compounds in the cigarette smoke by the present invention are converted to non-volatile complexes by contacting the smoke with one or more ligand aromatic ortho-hydroxy compounds as above defined.

The complexes are formed by passing the smoke containing the metal compounds into contact with one or more of said ligands or over or through a filter material acting as a carrier body for the ligand material, and preferably comprising fibrous material, for example, cellulose ester tow, e.g., cellulose acetate tow prepared with the ligand thereon and/or therein, or wholly or partly coated with the ligand or with material such as activated carbon carrying the same.

To remove the transition metal compounds at least in part from tobacco smoke the ligands hereof are interposed in the path of said tobacco smoke as for example by depositing 0.01 to 10% preferably 0.5 to 5% by weight of such ligand material on the filter or other material located in the path of the tobacco smoke.

In the practice of the invention for example in making tobacco smoke filters one or more of the ligands or com plex-forming compounds or components with or without a solvent or plasticizer are preferably dispersed on solid adsorbents; for example, the liquid or complex-forming components may be vaporized onto an adsorbent material, or a solution of a ligand may be applied to adsorbent material such as carbon, e.g., activated carbon, silica, pumice, vermiculite, clay, asbestos, polyesters, polystyrene, and cellulosic materials, e.g. cotton, cellulose, cellulose acetate, cellulose acetate-butyrate, cellulose propionate, tobacco, and other absorbing materials having a high surface area per unit weight or per unit volume.

The ligand material of the present invention may be incorporated in or with the smoke-permeable bases, carriers or filters which themselves may embody various adhesives, adsorbents and surface area augmenting materials, and such incorporation of ligand material also may be made during the manufacture of the filter material or filters and thus such ligand materials can be incorporated with the materials and during the processes as disclosed, for example, in US. patents as follows:

Number: Issued 2,215,620 9-24-40 2,228,383 1-14-41 2,770,241 11-13-56 2,916,777 12-15-59 2,917,054 12-15-59 2,928,399 3-15-60 2,928,400 3-15-60 2,940,456 6-14-60 2,948,282 8-9-60 3,033,212 5-8-62 3,033,698 5-8-62 3,038,478 6-12-62 3,038,780 6-12-62 The invention as above disclosed will be more fully understood by reference to the following examples of materials which may be employed as ligands for the practice of this invention and which examples are to be taken as illustrative and not restrictive of the invention.

1. The o-hydroxy-carbonyl ligand-The ligands of this group embrace the structure,

and include the following sub groups of ligands:

1 (a). The aromatic hydroxyl-ketone ligands-This group of o-hydroxy-carbonyl ligands having the formula (1) HO OH Alizarine Yellow C ((11, No. 57000) (II) HO OH Allzariue Yellow A (CI, :No. 57005) The C1. numbers as used herein refer to compounds heretofore employed as dyes or dye intermediates and such C.I. numbers in the above cited Colour Index 2nd Edition (1957). Where, in the Colour Index. the Cl.

number cited refers to a metalated dye, e.g., with copper, chromium, cobalt, nickel or iron, it is to be understood that as a ligand hereof the compound should be in unmetalated form in reference to these metals.

1(b). The naphthaquinone ligands.The o-hydroxycarbonyl ligands of this group have one of the formulae OH E) OH R R R! or RZGR1 wherein R and R are radicals selected from the group consisting of -NHC H -O-C H OH, --SO H and hydrogen radicals.

Usable as ligands of this group are compounds heretofore employed as naphthaquinone dyes and designated by the CI. numbers: 57010, 57015, 57020, 57025 and 57030.

1(a). The anthraquinone ligands.-This group of ohydroxy-carbonyl ligands have the formula *Including the isomer with N in starred position,

wherein R and R are selected from the radicals consisting of --0H, -SO H, NO COOH, -NH and hydrogen.

Usable as ligands of this group are compounds heretofore employed as anthraquinone dyes and designated by the Cl. numbers:

and the like.

1 (d). The anthrahydroxy phthalein ligands.-This group of o-hydroxy-carbonyl ligands is represented by compounds heretofore employed as anthrahydroxyphthalein dyes and designated by the Cl. numbers 45505 and 45510, and the like.

2. The hydroxycarboxyl ligands.-The ligands of this group embrace the structure il-OH /C(|J=O and include the following subgroups of ligands.

2(a). The substituted phenyl-o-hydroxycarbonyl ligands represented by the formula wherein R R and R are similar radicals to those set forth under 1(a) heretofore.

7 2 (b). The substituted naphthyl-o-hydroxycarbonyl ligands represented by the formula I wherein R R and R are similar radicals to those set forth under 1(a) heretofore.

Examples of these -o-hydroxycarboxyl ligands include:

2(a). The azo-o-hydroxycarboxyl ligands.--The ligands of this group include the mon-oazo, disazo and trisazo compounds with the lower molecular weight compounds usually being preferred for such can bind a greater quantity of metal based on the weight of the compound. These compounds, if desired, may be applied to the filter material as a sodium salt, as for example:

COONa C.I. Mordant Yellow 18 0.1. No. 13990) and may then be acidified at least in part to yield the free o-hydnoxycarboxylic acid COOH 2(c-1). The monoazo o-hydroxycarboxy ligands include ligands represented by the formulae:

wherein R R and R are similar radicals to those set forth under 1(a) heretofore.

Usable as ligands of this group are compounds heretofore used as dyes and designated by the Cl. Nos.:

2(c-2). The disazo-o-hydroxy-carboxyl ligands.-'Ilhe ligands of this group are similar in structure to the m0noazo compounds set [forth under 2(c-1) heretofore except such are disazo compounds having two azo groups and because of their higher molecular weight are less preferred.

2(c-3). The trisazo and polyazo-o-hydroxy-carboxyl ligands.-'l"he ligands in this group are similar in structure to the monoazo compounds set forth under 2(0-1) heretofore except that these compounds have three azo groups and therefore because of their higher molecular weight are less preferred.

2(d). The triarylmethane-o-hydroxy-carboxyl ligands.Ligands of this group include the triphenyl-rnethane o-hydroxy-carboxyl ligands such as the compounds heretofore used as dyes designated by the Cl. numbers:

The compounds heretofore used in the phth'alein dyes designated by C1. numbers 45445, 45450 and 45455 may also be employed as ligands in the present invention.

3. The o-hydroxy-amide ligands.This class comprises the ligands represented by one of the formulae:

in which R and R are radicals selected from the C to C hydrocarbon radicals.

4. The o-hydroxy-azomethine ligands.-This group of o-hydroxy-azomethine ligands have the common radical represented by the formula in which R is a hydrocarbon or substituted hydrocarbon radical and include ligands represented by the following formula including the hydroxy-oximes, hydroxy-aldimines, hydroxy-ketimines and such compounds as the following wherein R and R are similar radicals to those set forth under 1(a) heretofore.

5. The o-hydroxy-azo ligands.Tl1e o-hydroxy-azo ligand can embrace the structure CN=N- and include the following subgroups of ligands:

(a-1). Monoazo and disazo ligand compounds having the o-hydroXy-azo group including such structures as represented by the following:

OH R I R1 and similar disazo compounds in which R and R are radicals selected from the radicals set forth under 1(a), 6mg. -CH3, "-NO2, C1, SO3H, 'NH2, CONH or hydrogen radical etc.

5 (b). The 0,0-dihydr0xy-az0 ligands.These ligands embrace the structure and include compounds heretofore employed as :rnonoazo, disazo and polyazo dyes. They have the structural forwherein R R and R are similar radicals to those set forth under 1(a) heretofore.

Examples of the ligands of this group are the o,o-dihydroxy-azo ligand compounds, which compounds have heretofore been employed as dyes designated by the Cl. numbers:

10 Among the above examples of ligands are also included dihydroXy-azo ligands which have a nitrogen containing ring, e.g., a pyrazole ring or a quinoline ring such as the following:

I GEEK-(300E, COOR and -CONH2) OH HO 1 R1 1 N=Nm R N 2 and the like.

6. The o-hydroxy-m'troso ligands.Ligands having the o-hydr-oXy-nitroso roup embraced !by the following strucinclude compounds such as:

l-nitroso-Z-naphthoL6-sulfonic acid 1-nitroso-2-naphtho1-4-sulfonic acid l-nitr-oso-Z-naphthol 2-nitroso-1-naphthol Chromotropic acid dioxime Nitnosochromotnopic acid 2,4-dinitroso-3,5-dihydroxy-toh1ene 2,4-dinitroso-1,3-dihydroXy benzene o-Nitrosocresol Z-nitroso-1-naphthol-4-sulfionic acid 4-nitrosoresorcino1 Nitroso-R-salt p-Nitroso-thy-mol 7. The o-hydroxy-oxazo ne ligands.--Ligands having the ortho-hydroXy-oxazone group are exemplified by compounds heretofore used as dyes and designated by the Cl. numbers 51405, 51410.

8. The o-hydroxy-oxazine ligands Ligands having the orfho-hydroxy oxazine group 1 1 include compounds heretofore used in dyes and identified by the Cl. numbers 51025, 51030, 51040, 51045, 51050, 51060, 51065 and 51070.

9. The hydroxy-lactone ligands.Ligands of this class have both the hydroxy group and a laotone group and as such ligands may be employed compounds heretofore used as dyes and identified by the Cl. numbers 55000, 55005 and 55010.

Among the compounds included in subclasses 1 through 9 above are the mordant dyes and for the purposes of the present invention the mordant dyes are inconporated in the cigarette filters in essentially unmordanted form, and thus are present in a form capable of combining with and extracting from tobacco smoke the transition metal content thereof.

By the term unmordanted is meant the mordant dyestutf is essentially free of metal ions which mordant or insolubilize the dyestufl, e.g., is essentially tree of aluminum, iron, manganese, chromium, nickel, cobalt, copper, zinc, calcium, lead and other metals including the transition metals of sub-groups 1V, V and VI of the Periodic Table. For purposes hereof the mordant dyestuff is sometimes employed in the form of a water soluble salt, e.g., an alkali metal, ammonia or amine salt.

10. The o-dihydroxy ligands.The ligands of this group have at least one aromatic radical with two hydroxy groups in ortho position to one another and such ligands embrace the following structure:

Included among the compounds of this class is pyrogallol, catechol and the alkyl substituted catechols, pyrocatechol, methyl pyrocatechol, the 1,2,3-trihydroxybenzene, the 1,2,4-trihydroxybenzene, the tetrahydroxyabenzenes, hexahydroxy-benzene, similar compounds of the naphthalene series gallic acid, m-di gallic acid, the tan-nic acids, the tannins protocatechuic acid, 1,2-dihydroxybenzene-3,5- disulfonic acid, 9-methyl-2,3,7-trihydroxy-6-flurone, and the dyestuffs having such structure as for example HO OH pyrocatechol vlolet EXAMPLES In the following examples wherein coating procedures are not otherwise described, filters were prepared as follows: The manufacturers filters were removed from Brand A filter cigarettes and 0.5 ml. of an aqueous and/or alcoholic solution of the ligand was added dropwise to the filters. The individual filters average 0.125 g. in weight. The proportions of water and alcohol in the solution were adjusted for ligand solubility considerations. Where the ligand was a dyestutf and the acid form of the dye was desired the major portion of the solvent mixture used was alcohol, and the required amount of hydrochloric acid was added thereto to convert the commercial sodium or ammonium salt of the dye to its acid form. The inorganic salts present in most commercial dyes were removed by dissolving the dye in a solvent e.g., alcohol and filtering or the insoluble salts were allowed to settle out and only the soluble organic dye material was added to the cigarette filters. When the salt of the dye was desired as the coating agent the alcohol was diluted with water, thus increasing the dye salt solubility. The amount of dye present in the 0.5 ml. of solution was varied to give from 1% to 10% as desired. The filters were observed to be substantially uniformly colored by the 0.5 ml. of dye solution, and were dried at 50 C., atmospheric moisture equilibrated at room temperature and about 70% humidity, and each filter was employed for filtering the smoke of one Brand A cigarette from which the manufacturer's filters had been removed.v A sample for analysis consisted of 60 smoked filters.

An alternate procedure was to use the dyed filter as a back-up filter for smoking Brand A filter cigarettes. In this procedure a direct comparison of effectiveness of the transition metal absorptions by conventional filters and the filters of this invention is possible.

The analysis of the tobaccos of the Brands A, B, C and D employed in these tests showed the following range of metal contents.

Brand A: Micrograms per cigarette Iron 353 to 1150 Nickel 1.06to 10.0 Cobalt 0.7 to 1.8

Brand B:

Iron 288to 352 Nickel 0.4 to 6.2 Cobalt 0.75 to 0.9

Brand C:

Iron 440to 600 Nickel 2.8 to 3.4 Cobalt 0.8 to 1.9

Brand D:

Iron 310to 460 Nickel 0.8 to 5.2 Cobalt 1.4 to 1.8

Since such variations occur in the metal content of the same brand of cigarettes it is apparent that the smoke will vary widely in metal content and each lot of cigarettes must have control tests run with conventional filters for comparison with the ligand treated filters of this invention.

Example 1 A suspension-solution was prepared by stirring 1 gram of the red compound 2,4-dibenzene-azoresorcinol, with a mixture of 60 g. benzene and 15 g. isopropanol. Cellulose acetate tow (5.024 g.) was immersed in the resultant suspension-solution for 18 hours and then, with 50 g. of absorbed liquid, was placed in a 70 C. air stream for 2 hours. The tow was equilibrated with the atmospheric moisture until a constant weight was reached and the coated tow contained 10% of the red compound. The tow was divided into 20 portions weighing 0280:0005 g. and each portion was employed as a back-up filter for smoking two Brand A filter cigarettes. The back-up filter was prepared by fitting the tow snugly into a ID. glass tube which served as a cigarette holder for the cigarettes. The amounts of iron and cobalt absorbed per cigarette smoked were as follows for the manufacturers filter and the back-up filter:

Manufacturer's Back-Up Filter Transition Metals Filter (inicrograms/ (m crograms/ cigarette) clgarette) 011 15. 0 36. 7 Cobalt None 0. 02

Example 2 the thirty used back-up filters showed absorption of 38.8 micrograms of iron per cigarette smoked while the manufacturers filter showed absorption of 2 micrograms of iron per cigarette smoked. The structure of this dye material is as follows:

l CH

Example 3 Five grams of Cl. Mordant Yellow (CI. 18710) was dissolved in 400 grams warm water as in Example 1 and 7.734 g. of cellulose acetate tow was immersed in the solution for 5 minutes, squeezed, immersed in acid, squeezed dry, and dried at 70 C. The equilibrated sample contained 2.5% of the dye ligand material. Sixty Brand A filter cigarettes were smoked in pairs as in Example 2 using a 0.258i0.005 g. portion of the dyed tow as a back-up filter. Analysis of the used back-up filters showed absorption of 17.6 micrograms of iron, 0.30 microgram of nickel and 0.43 microgram of cobalt per cigarette smoked vs. 3.2, 0.17 and 0.18 micrograms of iron, nickel and cobalt absorbed respectively by the manufacturers filter per cigarette smoked. The structure of the dye ligand material of this example is:

Example 4 Example 2 was repeated using the dye C.I. Mordant Blue 1 (CI. 43830) with 8.3 grams of tow. The wet material was immersed in dilute hydrochloric acid solution and dried. The coated tow was used as back-up in smoking sixty Brand A filter cigarettes which Were smoked in pairs using a 0.277 g. (i0.005 g.) portion of the dyed tow as back-up filter for each pair of cigarettes. Analysis of thirty used back-up filters showed absorption of 0.76 microgram of nickel per cigarette smoked vs. 0.17 microgram nickel absorbed per cigarette for the manufacturers filters.

The structure of this dye ligand material is:

COOH

Example 5 Example 4 was repeated but omitting the acid treatment, thus allowing the Cl. Mordant Blue 1 ligand dye to remain as the sodium salt of the structure shown in Example 4 (the treated tow absorbed 4% dry). Smoking of 60 Brand A filter Cigarettes in pairs was conducted using a 0.262 g. ($0.005 g.) portion of the tow as backup filter for each pair of cigarettes. Analysis of the used back-up filters showed absorption of 20.0 micrograms iron, 1.8 micrograms nickel and 0.43 microgram of cobalt per cigarette smoked in comparison with 3.2, 0.17 and 0.18 micrograms of iron, cobalt and nickel per cigarette respectively absorbed by the manufacturers filter during smoking.

Example 6 0 OH H -SO Na Example 7 Example 2 was repeated using 7.55 g. cellulose acetate tow containing about 2.5% total acidified Tartrazine dye C.I. Food Yellow 4 (CI. 19140) contents. Smoking was conducted with sixty Brand A filter cigarettes as in Example 2, but using the presently prepared ligand-coated cellulose acetate as back-up filter. Analysis of the filter material after use showed absorption of 64.5 micrograms of iron per cigarette smoked in comparison with 0.75 microgram absorbed by the manufacturers filter per cigarette smoked. The structure of this ligand dye is as 1 COOH Example 8 FD & C Yellow No. 6 (CI. 15985) was used to coat cellulose acetate filters of Brand A filter cigarette. The aqueous solution of the commercial dye (5 g. in 400 ml. water) coated the tow with the sodium salt and the wet tow was immersed in 1% hydrochloric acid solution to convert it to the free acid form:

The final dried and equilibrated tow showed about 1.3% dye had been absorbed. Each filter was used to filter the smoke of a Brand A cigarette. Likewise 300 non-dyed filters were used as a control in substantially identical smoking tests. Analyses of sixty ligand treated filters showed the following absorptions of iron and nickel per cigarette smoked in comparison with the manufacturers filters:

Non-dyed Manu- Dyed Manu- Transition Metal facturers Filters iacturer's Filters (microgram/cigarette) (micrograms/cigarette) Iron .1 1. 0 3. 7 Nickel 0. 16 0. 27

Example 9 Chrome Fast Black FWX or Cl. Mordant Black 5 (Cl. No. 26695) was employed as in Example 8 to dye filters taken from Brand A filter cigarettes. About 8% of total dye material was found absorbed by the dried dyed tow. The smoking test conducted as in Example 8 showed the following metal absorptions in comparison with the controls:

Non dyed Manu- Dyed Manu- Transition Metal facturers Filters facturers Filters (microgram/eigarette) (micrograms/cigarette) Iron 1. 9.6 Niekel- 0.16 0.49 Cobalt 0. 0. 22

The structure of this ligand dye is as follows:

NaOOCIE (OH) HCI) NaO S Example Non-dyed Manu- Dyed Manu- Transition Metal Iaeturers Filters faeturers Filters (m erogram/cigarette) (micrograms/cigarette) None 71. 8 0.01 0.20 None 0. 09

The structure of the dye used in this example is as follows:

N=N N =N OzN H N- NH, SO Na Example 11 This example is similar to Example 8 except that Superchrome Brilliant Violet NR or Cl. Mordant Violet 1 (Cl. No. 43565) was employed without acidification. The filters contained 8.5% dye material. In an identical smoking test as used in Example 8 the following absorptions of metals were obtained:

Example 12 This example was made similar to Example 7 but Tartrazine (FD & C Yellow No. 5) was used without 16 acidification as the dye material. About 2% dye materials were absorbed by the filter in dyeing. Analyses of filters after smoking showed the following data:

Non-dyed Manu- Dyed Manu- Transition Metal Iacturers Filter lacturers Filter (rnierograrn/cigarette) (micrograms/cigarette) The structure of the dye of this example was:

('ZOONa Acidification of the dye ligand improves the ability of the filter for absorption of metals from the smoke.

Example 13 The cellulose acetate tow (7.540 g.) was coated with 8.5% salicylic acid from a mixture of 5 g. salicylic acid, 112.5 g. isopropanol and 225 g. water. The coated tow was divided into thirty portions each weighing 0.269 :0.005 g., and each portion was used as filter to smoke two Brand C cigarettes. Likewise a control smoking test with an equivalent amount of uncoated tow as filter material was smoked for comparison. Analyses of the filters from these two tests show absorption in micrograms of metals absorbed from the smoke per cigarette as follows:

Uneoated Tow Ligand Coated Tow Transition Metal (micrograms/cigarette) (micrograms/cigarette) Iron 14.3 106.4

Example 14 In this example the ligand material was gallic acid. Gallic acid coated cellulose acetate tow was prepared containing about 4.3% gallic acid. The coating solution consisted of 5 g. gallic acid, 200 g. isopropanol and 50 g. Water, the amount of tow used was 17.295 g., drying time was 15 hours C. and atmospheric moisture equilibration time was 29 hours. Smoking tests were conducted with 30 portions of the coated tow each portion weighing 0.260 g.i0.005 g.; each portion was used as a filter for smoking two Brand D non-filter cigarettes. Similar smokin tests with uncoated tow were also carried out. Analyses of the filters with and acid solution in water to prepare a filter material containing 19.2% tannic acid. The volume of solution was 130 ml., the weight of cotton was 20.450 g., the immersion time was five minutes, the wet weight was grams, the drying time was 15 hours 70 C., and the atmospheric moisture equilibration time was 8.5 hours. Thirty portions of this ligand coated cotton were weighed out 0.308-* -0.005 g. and each portion was employed as a back-up filter for smoking two Brand A filter cigarettes. The combined back-up filters and the manufacturers filters from smoking sixty cigarettes were analyzed for iron, nickel and cobalt. The following micrograms of metals were found to have been absorbed per cigarette smoked.

Sixty filters were removed from Brand A filter cigarettes, and were coated by adding to each filter 0.5 ml. of a filtered solution of 5 g. of PD & C Red No. 4 dye in a mixture of 100 ml. water, 100 ml. isopropanol and 1.5 ml. 37% hydrochloric acid. After drying and equilibrating the filters were found to contain about 12% dye. The structure may be represented by the following formula:

Sixty Brand A cigarettes without the manufacturers filters were smoked using as filter one of the above coated filters. After use in smoking, the filters were combined and analyzed for iron. The results showed that 17.25 micrograms of iron had been absorbed. per cigarette smoked. In an identical smoking test using the manufacturers filters only 8.6 micrograms of iron were absorbed per cigarette smoked.

Example 17 A solution of ligand material was prepared by dissolving 5 g. Alizarin Red S (C.I. 58005) in a mixture of 200 ml. isopropanol and 50 ml. water containing 0.56 g. of hydrogen chloride, and filtering to remove inorganic salts. Sixty filters were removed from Brand B cigarettes and were impregnated with the filtered Alizarin solution by adding 0.5 ml. of said solution to each of the sixty filters. The dried and equilibrated filters were found to contain about 6% of the ligand material represented by the following formula:

This is the acid form of the ligand material of Example 6.

Sixty of the Brand B cigarettes, from which manufacturers filters had been removed, were smoked using one of the coated filters above prepared for each cigarette. The combined filters after smoking were analyzed for nickel and were found to have absorbed 0.64 micrograms of nickel per cigarette smoked. Simultaneously a control smoking test was made with 60 Brand B cigarettes with the manufacturers filters. The combined manufacturers filters after use showed absorption of 0.0 microgram of nickel from the smoke, thus demonstrating the eifectiveness of the ligand material.

Example 18 Sixty filters removed from Brand A cigarettes were coated as in Example 16 using for each filter 0.5 ml. of a filtered solution prepared by dispersion of 5 g. Indigotine (FC & D Blue No. 2, Cl. 73015) in a mixture of ml. water, ml. isopropanol and 2 ml. concentrated HCl. The dried equilibrated filters contained about 3.6% of the dye represented by the following structure:

0 0 II II C 0 H035 so n /C=C N \N Sixty Brand A cigarettes were smoked as in Example 16 using one of these above coated filters in place of the manufacturers filters. The filters were found by analysis to have absorbed 28.9 micrograms of iron per cigarette smoked. This is to be compared with 8.6 micrograms of iron absorbed per cigarette by the manufacturers filter.

Example 19 In a smoking test as in Example 16 with sixty Brand A cigarettes (with manufacturers filters removed) the filters absorbed 0.4 microgram nickel per cigarette smoked vs. none for the control.

Example 20 Five grams of polygalacturonic acid was dissolved in 400 g. water at 80 C. and 7.507 g. of cellulose acetate tow was immersed therein for ten minutes. The dried coated tow after equilibration with the moisture in the laboratory air showed a 13.5% content of the polygalacturonic acid. The coated tow was divided into thirty portions, each weighing 028910.005 g. and each portion was used to filter the smoke of two Brand D non-filter cigarettes. The combined filters after smoking showed absorption of 9.2 micrograms of iron per cigarette smoked. In a control test 300 Brand D cigarettes were smoked using cellulose acetate tow filters made by the manufacturer of Brand D cigarettes and these commercial filters, in the absence of the ligand, removed only 2 micrograms of iron per cigarette.

The effectiveness of the ligands hereof in removing trace metals from tobacco smoke can be improved in most instances when such ligands are combined with a suitable plasticizer. By the term suitable plasticizer is meant a plasticizer in which the ligand is soluble or at least partially soluble.

The plasticizers for the ligands hereof may contain alcohol, ether, ester groups or combinations of such groups and examples of such include the following: Triacetin (glyceryl triacetate), glycerine, glyceryl mono-oleate, glyceryl mono-ricinoleate, 2-butoxyethanol, butoxyethyl laurate, diethylene glycol, diethylene glycol mono-ricinoleate, olive oil, butyl oleate and for additional plasticizers see Table 15.3 (pages 904-927) of The Technology of Solvents and Plasticizers by Arthur K. Doolittle, published 1954 by John Wiley & Sons, Inc., New York, New York.

While there have been described herein what are at present considered preferred embodiments of the invention, it will be obvious to those skilled in the art that modifications and changes may be made without departing from the essence of the invention. It is therefore to be understood that the exemplary embodiments are illustrative and not restrictive to the invention, the scope of which is defined in the appended claim, and that all modifications that come within the meaning and range of equivalency of the claim are intended to be included therein.

We claim:

A process for the purification of tobacco smoke from a smoking article by the removal of volatile metal compounds therefrom, which comprises passing said smoke through a filter into the mouth of the user down stream therefrom, said filter comprising a ligand compound which is an orthohydroxy aromatic compound containing transition metal chelating groups selected from the groups consisting of o-hydroxy-nitroso, o-hydroxy-oxazone, and ohydroxy-oxazine groups.

References Cited by the Examiner OTHER REFERENCES Chaberek and Martell: (Text) Organic Sequestering Agents, published by John Wiley & Sons, Inc. NY. (1959), pp. 2 to 5 and pp. 329 and 330 especially cited. Copy in the US. Patent Ofiice Scientific Library.

ALDRICH F. MEDBERY, Acting Primary Examiner.

MELVIN D. REIN, SAMUEL KOREN, Examiners.