US3470883A - Tobacco smoke filters - Google Patents

Description

@L T, B969 T. H. SHEPHERD Erm, ,470,333

TOBACCO SMOKE FILTERS Filed Aug. 29, 1968 l J in? Y United States Patent O 3,470,883 TOBACCO SMOKE FILTERS Thomas H. Shepherd, Hopewell, and Francis E. Gould,

Princeton, NJ., assgnors to National Patent Development Corporation, New York, N.Y., a corporation of Delaware Continuation-in-part of applications Ser. No. 567,856, July 26, 1966, and Ser. No. 654,044, July 5, 1967. This application Aug. 29, 1968, Ser. No. 756,128

Int. Cl. A24d I/06 U.S. Cl. 131-10 8 Claims ABSTRACT F THE DISCLOSURE Tobacco smoke filters are prepared from a porous, hydrophilic acrylate or methacrylate polymer having a pore volume of at least 60%. The pores are conveniently formed by polymerizing in aqueous medium and freeze drying or by polymerizing with or without water utilizing a foaming agent to form a hard, friable foam.

The present application is a continuationinpart of application Ser. No. 654,044, filed July 5, 1967, and application Ser. No. 567,856, filed July 26, 1966.

The present invention relates to tobacco smoke filters and more particularly to the removal from tobacco smoke tars which may contain undesirable components such as carcinogenic substances therein.

Carcinogenesis, the causing of cancerous growth in living tissue, is a complex process. Many factors are involved; some related to the host and others to the agent. Some agents by themselves cause irreversible alterations in cells which may lead to the production of cancer; others promote the carcinogenic process. The former are called initiators; the latter, promoters.

It has been determined that the pyrolysis of many organic materials can lead to the formation of components which are carcinogenic. The more injurious of these are high boiling point polynuclear hydrocarbons. For example, researchers in seeking to identify the active substance in high-boiling fractions of coal tar distillates of established carcinogenicity to mice, discovered that dibenzo (a,h) anthracene prepared by synthesis is carcinogenic. Later other researchers isolated the coal tar constituent responsible for the characteristic fiuorescence and identified it as benzo (a) pyrene. The latter is one of the most potent of all the carcinogens now known. The smoke produced by the combustion of tobacco is very complex; cigarette smoke, for example, is a heterogeneous mixture of gases, uncondensed vapors, and liquid particulate material. One important factor determining the composition of the smoke is the temperature in the burning zone. While air is being drawn through a cigarette, the temperature of the burning zone may reach approximately 884 C. and when the cigarette is burned in the absence of air being drawn therethrough, the temperature is approximately 835 C. At these temperatures, extensive pyrolytic reactions occur in the tobacco adjacent to the burning zone. Some of the many constituents of tobacco are stable enough to distill unchanged, but many others suffer extensive reactions involving oxidation, dehydrogenation, cracking, rearrangement, and condensation. It is thus not surprising that some 500 different compounds have been identified in the smoke.

It has been determined that most of the carcinogenic compounds identified in cigarette smoke are not present in the native tobacco leaf but are formed by pyrolysis at the high burning temperature of cigarettes. Furthermore, it has been postulated that some polycyclic hydrocarbons, though very weak, and inactive in and of themselves as carcinogenic substances, are capable of initiating malignant growth under the influence of a promoter. -Products such as phenols, fatty acid esters, and free fatty acids, which are abundant in tobacco smoke, are reported to have a potentiating effect and have been termed or called cocarcinogens.

Many efforts have been made in the past to reduce the yield of specific substances, e.g., nicotine and tars in tobacco smoke. For many years it was believed that the nicotine content of tobacco was especially objectionable. The use of filters, therefore, has enjoyed widespread acceptance, both by the tobacco industry and the consumer.

In addition to the presently known filters, other methods suggested for neutralizing obnoxious gaseous products resulting from the combustion of tobacco include interposing an intermediary layer consisting of a metal salt between a paper wrapper and the tobacco roll. It has also been proposed that tobacco be impregnated with dior-tri-valent metal salts of an alcohol or an organic acid in the presence of a halogenated solvent. However, all of these proposed methods have failed to remove carcinogenic material with any degree of success.

Accordingly, it is an object of the present invention to provide a tobacco filter element vwhich enhances removal of tars containing some carcinogens from gas streams wherein they are formed during pyrolysis of certain organic materials in the tobacco.

Another object of this invention is to provide a process for producing such filter elements.

Still another object of the invention is to provide a tobacco filter element which enhances removal of carcinogens formed during combustion of said tobacco.

A further object of the invention is to prepare a porous hydrophilic polymer.

Still further objects and the entire scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

It has now been found that these objects can be attained by preparing a porous, hydrophilic acrylate or methacrylate polymer. The polymer has a high surface area and a pore volume preferably in the range of 60 to The surface area is usually between 10 and 300 meters2/gram.

The pores are preferably formed by freeze drying the polymer which has been formed in the presence of water. The freeze drying is usually done at -5 to -30\ C. Lower temperatures can be used but the process is slower. The drying or desiccation is preferably done in a vacuum of less than l mm. Hg, e.g. 0.001 mm. although a vacuum of up to about 4.5 rnm. can be used. The desiccation product is then disintegrated to provide granules having a high specific surface area.

The particles generally are from l0 mesh to 200 mesh, preferably 40 to 100 mesh (U.S. Standard Sieve).

In place of freeze drying a concentrated electrolyte can be put into the polymer, e.g. sodium chloride or ammonium bicarbonate, to pull the water out. The freeze drying or concentrated electrolyte procedure is employed to avoid shrinkage of the polymer to the non-porous type as it dries.

Alternatively the porous product or sponge can be prepared by polymerizing the acrylate or methacrylate in the presence of a blowing agent which will decompose at the temperature of polymerization. The blo-wing agent procedure can be used whether the polymerization is carried out without a solvent 0r whether water is employed. When the porous polymer is formed with the aid of a blowing agent preferably 0.5 to 5% of blowing agent is used based on the Weight of the polymerizable monomer although up to of foaming agent can be used. The foamed polymer can be extruded to produce rods of a predetermined diameter as a filter of the foam can be disintegrated into granules as set forth above.

The tobacco filter of the present invention can be employed in cigarettes, cigars, pipes or other smoking implements. The filter can be the sole filter or other filters can be employed such as activated carbon, plasticized cellulose acetate fibers, corrugated paper, polyethylene particles or fibers, etc.

The filtering elements of the present invention are also useful as non-migratory humectant carriers when presaturated with a polyhydric alcohol, e.g. glycerine, propylene glycol, ethylene glycol, polypropylene glycol, sorbitol, mannitol, corn syrup. There can be l to 90% of the polyhydric based on the total weight of the filtering element.

The hydrophilic polymer filtering element can be impregnated with a flavor, e.g. menthol, peppermint, or natural or artificial tobacco flavor for slow release of the flavor imparting compound to the smoke.

Examples of suitable blowing or foaming agents include sodium bicarbonate, sodium bicarbonate-citric acid (e.g. 4:3), potassium bicarbonate, azobisisobutyronitrile, N,N dimethyl N,N' dinitrosoterephthalamide, p,p' oxybis (benzenesulfonyl hydrazide), urea-biuret (1:2), diazoaminobenzene, 1,6-di-n-decyl azobisformamide, diphenyl 4,4'di(sulfonylazide) p,p'oxybis (N-nitroso N methyl benzenesulfonamide), tetramethylene dinitroso dimethyl urethane, benzene sulfonic acid hydrazide, -naphthalene sulfonic acid hydrazide, diphenyl sulfone-3,3'disulfonyl hydrazide, benzene sulfonic acid N-phenyl hydrazide, sodium bicarbonate-melamine (e.g. 95:5).

Unless otherwise indicated all proportions are by weight.

The hydrophilic monomer employed is preferably a hydroxy lower alkyl acrylate or methacrylate or a hydroxy lower alkoxy lower alkyl acrylate or methacrylate, e.g. 2hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, diethylene glycol monomethacrylate, diethylene glycol monoacrylate, 2hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, dipropylene glycol monomethacrylate. Acrylamide, methylol acrylamide, methacrylamide, methylol methacrylamide and diacetone acrylamide are useful but less preferred hydrophilic monomers.

The most preferred monomer is 2-hydroxyethyl methacrylate and the next most preferred monomer is 2-hydroxyethyl acrylate.

In preparing hydroxyalkyl mono acrylates and methacrylates a small amount of the diacrylate or dimethacrylate is also formed. Ordinarily this need not be removed since it aids in forming cross linked hydrophilic polymers. The preferred polymers of the invention are cross linked although uncross linked hydrophilic acrylates and methacrylates can also be employed.

When cross linked polymers are prepared the cross linking agent can be present in an amount of 0.05 to of the total monomers, usually not over 10% and preferably not over 2%. The most preferred range of cross linking agent is 0.1 to 0.2% of the total monomers. Typical examples of cross linking agents include ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,2-butylene dimethacrylate, 1,3-butylene dimethacrylate, 1,4-butylene dimethacrylate, propylene `glycol diacrylate, propylene glycol diacrylate, diethylene glycol dimethacrylate, dipropylene glycol dimethacrylate, diethylene glycol diacrylate, dipropylene glycol diacrylate, divinyl benzene, divinyl toluene, diallyl tartrate, allyl pyruvate, allyl malate, divinyl tartrate, triallyl melamine, N,N'methylene bis acrylamide, glycerine trimethacrylate, diallyl maleate, divinyl ether, diallyl mono ethylene glycol citrate, ethylene glycol vinyl allyl citrate, allyl vinyl maleate, diallyl itaconate, ethylene glycol diester of itaconic acid, divinyl sulfone, hexahydro-1,3,5-triacryltriazine, triallyl phosphite,

diallyl ester of benzene phosphonic acid, polyester maleic anhydride with triethylene glycol, polyallyl glucose, e.g. triallyl glucose, polyallyl sucrose, e.g. pentaallyl sucrose, sucrose diacrylate, glucose dimethacrylate, pentaerythritol tetraacrylate, sorbitol dimethacrylate, di allyl aconitate, divinyl citraconate, diallyl fumarate.

It is also frequently desirable to copolymerize t0 99% of the acrylate or methacrylate with 15 to 1% of an ethylenically unsaturated mono or polycarboxylic acid or partial ester of an ethylenically unsaturated polycarboxylic acid. The free acid groups for example bind in the form of salt, metals present in the tobacco being smoked. Typical examples of such acids include acrylic acid, methacrylic acid, itaconic acid, aconitic acid, cinnamic acid, crotonic acid, citraconic acid, measaconic acid, maleic acid and fumarie acid. Less preferably there can also be used partial esters of polybasic acids such as mono 2hydroxy propyl itaconate, mono 2-hydroxyethyl itaconate, mono 2- hydroxyethyl citraconate, mono-2-hydroxypropyl aconitate, mono 2-hydroxyethyl maleate, mono-2-hydroxypropyl fumarate, monomethyl itaconate, monoethyl itaconate, mono Methyl Cellosolve ester of itaconic acid (Methyl Cellosolve is the monomethyl ether of diethylene glycol), mono Methyl Cellosolve ester of maleic acid.

As catalysts for carrying out the polymerization there is employed free radical catalyst in the range of 0.05 to 1% of the polymerizable hydroxyalkyl ester, for example, the preferred amount of catalyst is 0.1 to 0.2% of the monomer. Typical catalysts include t-butyl peroctoate, benzoyl peroxide, isopropyl percarbonate, methylethylketone peroxide, cumene hydroperoxide and dicumylperoxide. Irradiation, e.g., by ultra violet light or gamma rays, also can be employed to catalyze the lpolymerization. Polymerization can be done at 20 to 150 C., usually 40 to 90 C.

Typical examples of suitable cross linked hydrophilic polymers are those prepared in Wichterle Patent 2,976,- 576, Examples l, 2, 3 and 4 followed by freeze drying, e.g. at 10 C. in place of molding and the polymers prepared in Wichterle Patent 3,220,960, e.g. Examples III, V, VI, VII and IX with the modification that the polymers are freeze dried, e.g. at 5 C. to form porous products having large surface areas. While the formation of micro pores as in Wichterle Patent 2,976,576 Example 3 is adequate for liquid filtration it does not give a Satisfactory cigarette filter. Instead procedures such as those set forth supra must be resorted to.

The invention will be understood best in connection with the drawings wherein:

FIGURE 1 is a perspective View of a cigarette having a lter according to the invention;

FIGURE 2 is a sectional view taken along the line 2&-2 0f FIGURE l FIGURE 3 is a sectional view taken along the line 3 of FIGURE 2; and

FIGURE 4 is a sectional view of a smoking pipe filter according to the invention.

Referring more specifically to the drawings there is provided a cigarette designated generically at 2 comprising tobacco 4, foamed, hydrophilic acrylate or methacrylate filter 6 and cellulose acetate fibers 8 encased in an overall outer paper wrapper 10. The particles of -filter 6 have a mesh size of -40 to 100 mesh and a surface area of about 200 m.2/g.

FIGURE 4 shows a smoking pipe filter 12 containing foamed hydrophilic acrylate or methacrylate particles 14 encased in cartridge 16. The cartridge has screens (not shown) at both ends, the openings in the screen are of smaller size, e.g. 325 mesh, than the particles of the highly porous acrylate or methacrylate, -40 to 100 mesh.

All mesh sizes unless otherwise indicated are U.S. Standard Sieve mesh sizes.

Example 1 100 grams of Z-hydroxyethyl methacrylate were mixed with 0.15 gram of tertiary butyl peroctoate. 0.2 gram of ethylene glycol dimethacrylate was added along with 1 gram of sodium bicarbonate. The mixture was heated to 70 C. and the resulting polymer was disintegrated into pellet size particles (30 mesh) by grinding and shearing. The pellets had 60% void space therein. The pellets were employed as a tobacco smoke filter in a cigarette.

ExampleZ The procedure of Example 1 was repeated but the pellets were mixed in a 50-50 mixture of glycerine and water for 8 hours to provide a non-migratory humectant action and dried. The resulting pellets were employed as a tobacco smoke filter in a cigarette.

Example 3 The process of Example 2 was repeated with the exception that tobacco avor was added to the glycerinewater mixture to impart a tobacco avor to the filtered smoke to replace the avor lost by filtration of the tars and other combustion products which normally impart the tobacco avor upon inhalation. i

Example 4 In another embodiment a alcoholic solution of menthol based on the hydrophilic polymer was employed as a flavoring agent along with the tobacco flavor in Example 3. The alcoholic solutions may be employed so as to result in an amount ranging from 1 to 90% by weight of the hydrophilic polymer. The alcoholic solution normally is saturated with menthol. The 10% alcoholic solution is preferred, particularly if glycerine is employed as the humectant.

Example 5 90 grams of 2-hydroxyethyl methacrylate, 10 grams of itaconic acid, 2 grams of t-butyl peroctoate, 1.5 grams of sodium bicarbonate were heated to 85 C. for 6 hours and the resulting porous, foamed, polymer used as a cigarette filter.

Example 6 A solution was prepared consisting of 30 grams of 2- hydroxyethyl mehtacrylate, 0.3 gram of ethylene glycol dimethacrylate, 0.15 gram of ammonium persulfate, 0.1 gram of sodium bisulfite and 70 grams of water. The solution was then poured into a 200 ml. beaker and placed in a closed chamber at a temperature of 50 C. under a carbon dioxide atmosphere. Polymerization occurred Within 30 minutes to form a white, opaque, spongy, cylindrical mass. (The polymer precipitates as a foam.) This mass was frozen at 5 C. and subjected to a vacuum of 1 mm. Hg absolute to remove the water from the solid phase. The dried, rigid, friable mass was then crushed to provide granules having a high specific surface area, i.e. 50 HL2/g., a pore volume of 70% and a particle size of l-40 mesh to 100 mesh. The product was employed as a cigarette iilter.

Example 7 The procedure of Example 6 was repeated omitting the ethylene glycol dimethacrylate to produce an uncross linked hydrophilic polymer which also was useful as a cigarette filter.

Example 8 pire volume of 80% and was employed as a cigarette fi ter.

Example 9 Granules prepared in accordance with Example 6 were screened to provide a fraction with a 40 mesh particle size. Cigarette filters were prepared by removing one half of the cellulose filter of a conventional cigarette and filling the void with the prepared granules. Cigarettes prepared in this Ymanner were compared with control cigarettes of conventional construction.

The cigarettes were conditioned for 24 hours at 75 F. and 60% relative humidity. Smoking was done in a room conditioned to 75i2 F. and 60i2% R.H. The smoking system consisted of the cigarette, a tared Cambridge iilter assembly and a smoking machine that produces a 35 ml. puf of 2-second duration at a rate of one puff per minute. All cigarettes were smoked to the predetermined butt length of 33 mm. Five cigarettes were smoked through each Cambridge filter and the results calculated and reported in terms of one cigarette.

Moisture was determined by GLC. This determination was made according to the procedure described in a paper entitled Determination of Moisture in Total Particulate Matter by Schultz and Spears in Tobacco Science, vol. X, pp. 75-76 (1966).

As soon as the filter assembly had been weighed, it was opened and the filter placed in a dry 30 ml. serum bottle. The inner face of the filter holder was then wiped with one-fourth of a Cambridge filter pad and this added to the serum bottle. Ten ml. of dry dioxane-isopropanol (100:1) was measured from an automatic burette into the serum bottle and the stopper inserted. The bottle was shaken for 20 minutes on a Wrist-Action shaker.

A sample of 10 microliters was Withdrawn with a Hamilton syringe through the rubber serum cap and subjected to gas chromatography in an Aerograph -P3 gas chromatograph. The moisture content of the particulate matter was read from a calibration curve made by adding known amounts of Water to the solvent mixture. Filters conditioned at 75 F. and 60% R.H. were run and the average value of the moisture content subtracted from the amounts found in the used filters to get the net moisture content.

The balance of the solution for GLC moisture, plus the filter pad was transferred to a Kjeldahl ask and the nicotine determined by the usual procedure of double distilling and reading in the ultraviolet in a spectrophotometer.

The results of the tests are indicated below in Table I.

TABLE I.CONTROL Total particulate Run matter Moisture Nicotine Tar Average 39. 3 7. 5 1. 50 30. 3

Average number of puffs 7.9.

POLYME RIC FILTE R Total particulate Run matter Moisture Nicotine Tar Average 11. 0 1. 2 0. 20 9. 6

Average number of puffs 8.2.

It can be seen from Table I that the lter element of the present invention is eiective in removing tar and nicotine from tobacco smoke.

Example 10 The procedure of Example 6 was repeated but there was included in the aqueous mixture 0.4 gram of sodium bicarbonate and 0.3 gram of citric acid to aid in forming the foamed product.

What is claimed is:

1. A tobacco smoke iilter comprising a substantially cylindrical charge of a hydrophilic particulate polymeric compound, said particulate lter material being highly porous and having a high surface area and being selected from the group consisting of polymers of hydroxy lower alkyl acrylates, hydroxy lower alkyl methacrylates, hydroxy lower alkoxy lower alkyl acrylates and hydroxy lower alkoxy lower alkyl methacrylates, wherein the highly porous, high surface area characteristics are produced by foaming or freeze drying the polymer mix.

2. A cigarette having a wrapped charge of tobacco and containing the iilter, of claim 1.

3. A cigarette according to claim 2 wherein the polymeric lter particle pores have a pore volume of 60-90% 4. A cigarette according to claim 2 wherein the polymeric compound filter particles have a surface area of 10 to 300 meters2/grams.

5. A cigarette according to claim 2 wherein the polymeric compound of the lter is a cross linked solvent insoluble acrylate or methacrylate, the cross linking agent being present in an amount not over 20% of the polymer.

6. A cigarette according to claim 2 wherein the acrylate or methacrylate comprises a polymer of a member of the group consisting of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate and hydroxypropyl methacrylate.

7. A cigarette according to claim 6 wherein the polymer is a polymer of Z-hydroxyethyl methacrylate.

8. The lter of claim 1 wherein the porous hydrophilic acrylate or methacrylate polymer is produced by polymerizing said acrylate or methacrylate in an aqueous medium to produce a solid polymer, then freezing the polymer below 0 C. and subjecting the frozen polymer to a vacuum to dry the polymer and thereby form the pores.

References Cited UNITED STATES PATENTS 2,739,598 3/ 195 6 Eirich. 2,933,460 4/1960 Richter et al 131-269 X 3,366,582 1/1968 Adams et al 131-269 X MELVIN D. REIN, Primary Examiner U.S. C1. X.R. 131-269; 260-2.5

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