Filter capable of trapping carcinogens and toxic chemicals and manufacturing method thereof

Abstract

A filter has a urethane-based main chain having a repeat unit of the formula, R′—NH—COO—R—O—NHn, wherein the R group and the R′ group are an aliphatic chain and an aromatic group respectively. The R group, R′ group, and —NH— moiety in the repeat unit serve as reactive radicals for trapping cyanides, phenols, or polynuclear aromatic compounds, wherein the reactive radicals are revealed through an extraction process to remove a plurality of contaminants from the urethane-based main chain.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation application of U.S. application Ser. No. 10/250,058, filed Jun. 2, 2003.

The present application claims priority under 35 U.S.C. § 120 to U.S. patent application Ser. No. 09/252,334, filed Feb. 18, 1999 and now issued as U.S. Pat. No. 6,273,095, which in turns claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application Ser. No. 60/093,330, entitled SAFE CIGARETTE FILTER, filed Jul. 20, 1998.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for manufacturing a filter capable of removing cyanides and polynuclear aromatic compounds from cigarette smoke, and more specifically, to a method for manufacturing a filter capable of removing cyanides, phenols, and polynuclear aromatic compounds from air.

2. Description of the Prior Art

People begin smoking cigarettes for a variety of reasons. Smoking has been portrayed as being heroic, cool and as enhancing sexual appeal. For some people, smoking also serves to soothe tension, anxiety, or loneliness. However, as is commonly known, cigarette smoke contains the addictive compound nicotine. Addiction to nicotine makes it very difficult for smokers to stop smoking cigarettes, even though many realize that smoking will adversely affect their health.

The serious negative health effects of smoking are generally caused by chemicals in tobacco smoke other than nicotine. Among these are polynuclear aromatic compounds, which are carcinogens suspected to cause or contribute to a variety of cancers. The formation of polynuclear aromatic compounds in cigarette smoke is the result of incomplete combustion of the cigarette due to short burning resident time. Furthermore, polynuclear aromatic compounds harm not only smokers, but also the surrounding environment and people who inhale them as second-hand smoke. Furthermore, tobacco smoke also contains cyanides, a highly toxic compound which causes adverse health effects in smokers and those inhaling second-hand smoke.

The tobacco industry has attempted to alleviate the problems caused by polynuclear aromatics and cyanides by incorporating filters into cigarettes to remove these compounds when a smoker inhales. These filters are typically made of cellulose-based materials. The filters are effective in removing some of the toxic chemicals from tobacco smoke, but a substantial amount still passes through the filter. Consequently, there exists a need for improving filters for cigarettes and other tobacco products, which are more efficacious in removing toxic and carcinogenic chemicals from tobacco smoke. Moreover, to encourage use of such a filter, the filter should not interfere with those aspects of smoking which smokers desire, including the taste and nicotine content of the smoke.

SUMMARY OF THE INVENTION

It is therefore an objective of the present invention to provide a method for manufacturing a filter capable of removing cyanides, phenols, and polynuclear aromatic compounds from air.

It is another objective of the present invention to provide a method for manufacturing a filter capable of selectively removes polynuclear aromatic compounds and low molecular weight compound including mono-aromatic compounds and cyanides from tobacco smoke, while permitting most of the nicotine and flavor-enhancing molecules in the smoke to pass through. Because of this, people smoking tobacco products who use the filter of the present invention may enjoy the smoking experience, but with less exposure to the dangerous components of tobacco smoke.

According to the claimed invention, the filter comprises a urethane-based main chain having a repeat unit of the formula, R′—NH—COO—R—O—NH_n, wherein the R group and the R′ group are an aliphatic chain and an aromatic group respectively. The R group, R′ group, and —NH— moiety in the repeat unit are reactive radicals for trapping cyanides, phenols, or polynuclear aromatic compounds, wherein the reactive radicals is formed through an extraction process to remove a plurality of contaminants from the urethane-based main chain.

According to the present invention, the method for manufacturing a filter capable of removing cyanides, phenols, or polynuclear aromatic compounds from air is provided. Firstly, a polyurethane material including a urethane-based main chain having a repeat unit of the formula, R′—NH—COO—R—O—NH_n, with a plurality of contaminants absorbed around the urethane-based main chain is provided. Then, an extraction is performed to remove the contaminants from the urethane-based main chain so as to form a plurality of reactive radicals for trapping cyanides, phenols, or polynuclear aromatic compounds.

In one aspect of the present invention, the polyurethane filter comprises a tubular body with a proximal and a distal end. The tubular body is formed out of middle-density cellular polyurethane foam. The foam is pre-treated to increase the number of available reactive radicals for absorbing polynuclear aromatic compounds, pernicious mono-aromatic compounds, and cyanides. When used with a cigarette having a conventional filter, the polyurethane foam filter having an uncompressed volume of about 2 cubic centimeters absorbs about 60% of the polynuclear aromatic compounds and cyanide contained in cigarette smoke which contact the filter, but permits about 75% of the contacting nicotine in the smoke to pass through.

In another embodiment, a polyurethane foam filter of the present invention is substantially substituted for a conventional cigarette filter and is incorporated into the body of the cigarette as part of the manufacturing process. In this embodiment, a polyurethane foam filter, which prior to incorporation into the cigarette has an uncompressed volume of about 2-cubic centimeters, absorbs at least 74% of the polynuclear aromatic hydrocarbons contacting the filter in the cigarette, but permits about 75% of the nicotine contacting the filter to pass through. In another embodiment, a similarly sized polyurethane foam filter of the present invention is completely substituted for a conventional cigarette filter and absorbs at least 90% of the polynuclear aromatic hydrocarbons which pass through the filter.

In another aspect of the present invention, there is provided an improved filter for removing carcinogenic and toxic compounds from tobacco smoke. The invention comprises a pre-treated polyurethane foam body which absorbs 30-45% of contacting total polynuclear aromatic compounds per cubic centimeter of uncompressed polyurethane foam material forming the filter, but which permits more than 88% of the contacting nicotine to pass through unabsorbed per cubic centimeter of polyurethane foam material. The improved filter having these properties may be incorporated into a cigarette body, a cigar or a pipe body.

In another aspect of the present invention, there is provided a pre-treated polyurethane foam filter which absorbs in aggregate 60%-90% of 2-methylnaphthalene, acenaphthylene, acenaphthene, dibenzofuran, fluorene, phenantherne, anthracene, carbazole, fluoranthene, pyrene, benzo(a)anthracene and chrysene in tobacco smoke passing through the filter per 2 cubic centimeters of uncompressed foam used to make the filter.

In another aspect of the present invention, there is provided a method of making a safer cigarette. The method comprises providing a middle-density cellular polyurethane foam (PUF), which may then be formed into a cylindrical body to form a filter. The PUF filter is then pre-treated by cleaning to increase reactive radicals for adsorbing the polynuclear aromatic compound and cyanide. Alternately, the pre-treating step may occur before PUF filter is shaped into the cylindrical body. The cylindrical body is incorporated into a cigarette as a filter such that when the cigarette is lit, smoke will pass through the PUF filter prior to being inhaled by a smoker.

These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a cigarette incorporating the filter of the present invention into the body of the cigarette.

FIG. 2 illustrates extracted polyurethane foam having reactive radicals for trapping cyanides and phenols via hydrogen bonds.

FIG. 3 is a cross-sectional view of a filter of the present invention incorporated into a cigarette holder that may be attached and detached from cigarettes.

FIG. 4 illustrates the comparison of polynuclear aromatic emissions (in ng) of cigarette smoke from a filterless cigarette, a conventional cigarette with a filter, and a cigarette with a PUF filter.

FIG. 5 is analytical results of experiment 1.

FIG. 6 is analytical results of experiment 2.

FIG. 7 is analytical results of experiment 4.

FIG. 8 is a summary of percentage of total polynuclear aromatics absorbed by a PUF filter.

DETAILED DESCRIPTION

Referring to FIG. 1, there is shown a cigarette 10 incorporating a polyurethane foam (PUF) filter 35 of the present invention. Although illustrated and described in the context of a tobacco cigarette, it should be understood by those of skill in the art that the filter of the present invention might be readily incorporated in a mask or other filtering device that is applied to filter out pollutants or poisonous gas from air. Moreover, although the filter of the present invention is described as having a tubular or cylindrical shape, it should be appreciated by those of skill in the art that the filters of the present invention may take other shapes, including square, rectangular, spherical, and the like.

As shown in FIG. 1, the cigarette 10 comprises a cylindrical body 12 formed from a paper product, which is wrapped around tobacco 20. The cigarette 10 has a distal end 14 and a proximal end 16. In this respect, the cigarette 10 may be any conventional cigarette known to those of skill in the art, such as those made and sold today by the tobacco industry. The cigarette 10 may also incorporate a conventional filter 25 near the proximal end 16 thereof. The conventional filter 25 is used in cigarettes sold today, such as cellulose-based filters, but may be reduced in size when used in conjunction with the PUF filter 35 of the present invention, as described below.

Polyurethane foam (PUF) has been used by United States Environmental Protection Agency to trap polynuclear aromatic compounds, polychlorinated biphenyls, dioxins/furans, and the like, from air with reasonably high efficiency. These compounds have an affinity for polyurethane, and tend to be absorbed onto the surface of polyurethane. However, the polyurethane foam cannot efficiently absorb low molecular weight compounds, including cyanides, phenols, and aromatic compounds with a single aromatic ring. Accordingly, the present invention makes the polyurethane foam be pre-treated to form the PUF filter 35 capable of effectively removing not only the polynuclear aromatic compounds but also the low molecular weight compounds from cigarette smoke or air.

As shown in FIG. 1, the PUF filter 35 is incorporated at a proximal end 16 by being wrapped with a paper product. Preferably, the cigarette 10 also incorporates a portion of the conventional filter 25, and the PUF filter 35 is positioned proximal to the conventional filter 25 at the proximal end 16. When this two-filter combination is used, the conventional filter 25 will function to protect the PUF filter 35 from burning when the tobacco is completely combusted. In this respect, it is preferred that the conventional filter 25 have a diameter approximately that of the cigarette body 12, and a length of from about 1 mm to about 4 mm, and more preferably from about 2 mm to about 3 mm. As stated above, the conventional filter 25 may be made of cellulose-based materials. However, other types of materials known to those of skill in the art may be used in place of the conventional filter 25 to protect the PUF filter 35, provided that the materials are compatible with polyurethane foams. Moreover, in some embodiments, it may be desirable to eliminate the conventional filter 25, and use only the PUF filter 35 at the proximal end 16 of the cigarette 10.

As described above, the PUF filter 35 is formed from the polyurethane foam, which has extensive cellular structure and is preferably selected from middle-density polyurethane foam having a density of from about 0.01 to about 0.05 grams per milliliter. More preferably, the polyurethane foam used will have a density of from about 0.02 to about 0.04 grams per milliliter. However, it should be understood by those of skill in the art that any polyurethane foam with a cellular structure and appropriate density that permits cigarette smoke to pass through may be used with the present invention, provided that it conforms to the teachings herein. One kind of polyurethane foam found suitable for use in the present invention may be purchased from San Antonio Foam Fabricator, Product No. NA-85. This foam has a cellular structure and a density of 0.0302 grams per milliliter. Additionally, the PUF filter 35 could also be formed from polyurethane fibers, which could achieve the goal of filtering out low molecular weight compounds, as well as polyurethane foams.

The PUF filter 35 may vary in size and dimension as desired by the cigarette manufacturer. Preferably, the PUF filter 35 has approximately the same diameter as the cigarette in which it is incorporated and a length similar to conventional filters used today for cigarettes. This length may average from about 1 to 2.5 centimeters. Furthermore, because the beneficial effects of the present invention result from the polyurethane foam absorbing the harmful compounds, providing a larger polyurethane foam filter will tend to increase the total percentage of these compounds absorbed. As described in more detail below, the polyurethane foam formed into the filter having a volume of two cubic centimeters has been shown to successfully absorb about 75% of the polynuclear aromatic compounds passing through it.

As mentioned above, the present invention makes the polyurethane foam be pre-treated to form the PUF filter 35 capable of effectively trapping not only the polynuclear aromatic compounds but also the low molecular weight compounds, including cyanides, phenols, and aromatic compounds with a single aromatic ring. One method that has been shown useful to achieve this is Soxhlet extraction, which cleans the polyurethane foam and therefore increases the number of reactive radicals for trapping cyanides, phenols, and polynuclear aromatic compounds. In the Soxhlet extraction, a solvent containing 6% ether in hexane is evaporated from a solvent reservoir. The solvent vapor is then condensed into a chamber containing the polyurethane foam to be treated. The polyurethane foam in the chamber is gradually immersed in the condensed solvent until it is totally immersed. Most of the contaminants on or in the polyurethane foam will be extracted into the solvent. The solvent in the chamber is then siphoned through a tube down to the solvent reservoir at the bottom. The solvent evaporated out of the solvent reservoir is always pure and free from contaminants from the polyurethane foam. Therefore, only contaminant-free solvent is condensed into the chamber and all contaminants from the polyurethane foam accumulate in the reservoir. The solvent in the chamber is siphoned approximately once every hour for 16 hours. After the Soxhlet extraction, excess solvent is removed from the polyurethane foam by blowing it to dryness in nitrogen.

Before the polyurethane foam is pre-treated, the polyurethane foam originally comprises a urethane-based main chain and a plurality of contaminants absorbed by the urethane-based main chain. Usually, the urethane-based main chain has a repeat unit of the formula: R′—NH—COO—R—O—NH_n, wherein the R group is an aliphatic chain, such as n-octyl, and the R′ group is an aromatic group, such as tolyl. In addition, the contaminants absorbed by the urethane-based main chain include phenols, such as 6-tert-butyl-2,4-dimethylphenol and butylated methyl phenol, tinuvin, monomers, dimers, oligomers, 4,4,5,6-tetramethyltetrahydro-1,3-oxazin-2-thione, and so on. Furthermore, it is observed that the NH moieties of the urethane-based main chain are originally occupied by 6-tert-butyl-2,4-dimethylphenol, butylated methyl phenol and another unknown phenol, while the R group and the R′ group are originally absorbed by tinuvin, monomers, dimers, oligomers, and 4,4,5,6-tetramethyltetrahydro-1,3-oxazin-2-thione.

It should be noticed that after the polyurethane foam is extracted by use of the Soxhlet extraction, those unwanted contaminants are removed from the polyurethane foam, thus forming the urethane-based main chain having a plurality of reactive radicals, wherein each radical has at least one unpaired electron and is highly reactive. Referring to FIG. 2, FIG. 2 illustrates extracted polyurethane form having reactive radicals for trapping cyanides and phenols via hydrogen bonds. As shown in FIG. 2, the urethane-based main chain of the polyurethane foam is formed after the polyurethane foam is pre-treated by the Soxhlet extraction. Additionally, as shown in FIG. 2, the nitrogen atom of the NH moiety has a lone pair electron that can absorb a hydrogen atom of cyanides or phenols due to hydrogen bonds, so that the NH moieties are reactive radicals for trapping cyanides and phenols. Furthermore, after the removal of the contaminants, the R group and the R′ group are available for absorbing polynuclear aromatic compounds via van der Waals attraction that is molecular attracting force between neutral and non-polar organic portions. Therefore, the R group and the R′ group are also reactive radicals for absorbing polynuclear aromatic compounds. As a result, the polyurethane foam that is pre-treated by the Soxhlet extraction can trap not only polynuclear aromatic compounds but also the low molecular weight compounds, including cyanides, phenols, and aromatic compounds with a single aromatic ring. However, most of the nicotine, which is a substituted pyridine, and some small volatile molecules contributing to the smoke's flavor in the smoke still can pass the pre-treated polyurethane foam, so that a pleasant sensation of a smoker may not be decreased.

Other methods suitable to pre-treat the polyurethane foam and therefore increase its reactive radicals for trapping polynuclear aromatic compound and toxic compound may include extraction using solvents other than 6% ether in hexane, such as methylene chloride, hexane, light hydrocarbon based solvents, and mixtures of the foregoing. Furthermore, supercritical fluid extraction, steam distillation, hot solvent extraction and any other suitable organic extraction technique may also be used.

Referring to FIG. 3, there is shown as an alternative embodiment of the PUF filter of the present invention, where the PUF filter is incorporated into a cigarette holder 50 which can be removably attached to a conventional cigarette 100. As shown in FIG. 3, the cigarette 100 comprises a tubular body composed of a paper product wrapped around tobacco 120. A conventional filter 125 may be incorporated into the tubular body at a proximal end 116, but this is not required. The cigarette holder 50 has a generally tubular body 55, which extends from a distal end 54 to a proximal end 56, and as shown in FIG. 3, tapers to a smaller diameter beginning at a point 58 to form a smaller diameter mouthpiece opening 65 at the proximal end 56. The cigarette holder 50 may take a variety of other forms, as may be aesthetically pleasing or to provide ergonomic benefits. Furthermore, the holder 50 may be formed from any of the variety of materials known to those of skill in the art to be useful for manufacture of cigarette holders, such as metals and plastics. The holder 50 may also vary in length, diameter and appearance, as desired by its manufacturer to provide for desired aesthetic and ergonomic properties.

For purposes of the present invention, the holder 50 merely provides structure to encompass a polyurethane foam filter and provide an airway channel so that cigarette smoke inhaled by a smoker must pass through the polyurethane foam filter. For the holder 50, such an airway channel is defined by a lumen 60, which extends from the proximal end 56 to the distal end 54.

The lumen 60 has a larger inner diameter at the distal end 54, and is proportioned to receive the proximal end of a conventional cigarette. Preferably, the lumen 60 is dimensioned to snugly fit over a conventional cigarette, such that a cigarette inserted into the lumen 60 will be held firmly in place, but may be removed with minimal effort by a person. Incorporated into the lumen 60 is a polyurethane foam (PUF) filter 35 of the present invention. Preferably, the PUF filter 35 has been pre-treated to increase the number of reactive radicals for absorbing polynuclear aromatic compounds and cyanides, as described above. The PUF filter 35 should have a diameter to fill the entirely of the lumen 60, such that any cigarette smoke which passes through the lumen 60 to the mouthpiece opening 65 must pass through the PUF filter 35. This may be accomplished by forming the PUF filter 35 to have an uncompressed diameter slightly greater than that of the lumen 60, and then slightly compressing the PUF filter 35 so that it fits snugly in the lumen 60.

In this manner, polynuclear aromatic compounds, cyanides, and mono-aromatic compounds which contact and bond to the reactive radicals in PUF filter 35 will be removed from cigarette smoke as they pass through the PUF filter 35. Because these compounds are removed from the smoke prior to being inhaled by a smoker, they should not adversely affect the smoker's health, and should not adversely affect bystander's health through second-hand smoke. However, as described previously, most of the nicotine and flavor-enhancing molecules present in the smoke will pass through the PUF filter 35 to mouthpiece opening 65. Thus a pleasant sensation of a smoker may not be decreased.

The selective absorption properties of the polyurethane foam of the present invention are demonstrated in the following experimental examples.

EXPERIMENTAL EXAMPLES

A set of cylindrical PUF filters was cut from a sheet of NA-85 polyurethane foam. Each cylindrical PUF filter had an outside diameter (O.D.) of about 1 cm and a height of 1 inch (2.54 cm), and therefore in an uncompressed state had a volume of about 2 cubic centimeters. The PUF filters were then pre-treated to increase reactive radicals for absorbing polynuclear aromatic and cyanide by Soxhlet extraction as described above with 6% ether in hexane for 16 hours. The PUF filters were then blown to dryness using nitrogen until all of the solvent was removed.

One of the PUF filters was slightly compressed and then inserted into clean 6.7 inch long and 0.8 cm inside diameter(I.D.)glass tubing with 1.8 cm tapered end. The filter end of a Dorall Full Flavor Premium™ cigarette was inserted into the other end of the glass tubing. Because the O.D. of PUF filter was slightly larger than the I.D. of the glass tubing, the PUF filter fit snugly in the tubing and all tobacco smoke passing through the glass tubing passed through the PUF filter. Teflon tape was wrapped around the filter end of the cigarette and glass tubing to seal them together. All of the Dorall cigarettes used in the study were from the same package.

The glass tubing was then connected horizontally to an inlet of a 100 mL impinger manufactured by Ace Glassware. The impinger used in this study was designed to trap polynuclear aromatics, cyanide and tar passing through the PUF filter.

All the trapped polynuclear aromatics, cyanide and tar in the impinger would have been inhaled by a smoker if the cigarette had been smoked. The outlet of the impinger was connected to a hand-pump (Mityvac #OB61, Neward Enterprises, Cucamonga, Calif.). Each press of the hand-pump pumped approximately 30-40 mL of air through the cigarette to simulate an inhalation by an average smoker. The impinger was then immersed in liquid argon and the cigarette was lit. Continuous pumping was then applied to the hand pump to suck the air through the cigarette. Cigarette smoke went through the PUF filter, impinger, and hand-pump before venting into a fume hood. The hand-pump was continuously pumped by hand until the cigarette had 4 mm of length left. The approximate sampling time was one minute.

After sampling, the impinger was filled with 70 mL of methylene chloride to dissolve the tar collected and left overnight. Afterwards, the methylene chloride was poured into a vial. The impinger was then rinsed with methylene chloride to capture any tar remaining in the impinger, and the rinse was poured into the same vial. The methylene chloride solution was concentracted down to 20 mL prior to gas chromatography and mass spectroscopy (GC/MS) analysis. A 4 mL sample of the methylene chloride solution was blown down with nitrogen to remove all methylene chloride and the residue or tar was weighed to five decimal places. The tar was weighed twice: one at five minutes after the first weighing and the second in the next day. The average of the tar weights is reported in FIG. 5.

The PUF filter used in the experiment was removed from the glass tubing. The PUF filter was then Soxhlet extracted using methylene chloride and the extract was concentrated to 5 mL before GC/MS analysis. One milliliter of the extract was used to measure the weight of tar by the method mentioned above.

This experiment was repeated as described above, except that in the second experiment the cigarette was completely burned. The conventional cigarette filter burned slightly before end of the sampling.

The same procedure as the first experiment was performed four more times with the following changes to the protocol:

Experiment 3 was with a conventional filtered cigarette and without a PUF filter,

Experiment 4 was with a partially filtered cigarette and a PUF filter,

Experiment 5 was with an unfiltered cigarette and without a PUF filter,

Experiment 6 was with a PUF filter, but without a cigarette (laboratory blank).

In Experiment 4, 75% of the regular cigarette filter was removed and replaced with a PUF filter without tearing the paper holding the cigarette filter. The remaining 25% of the regular cigarette filter segregated the cigarette from PUF filter to prevent burning of the PUF filter during this experiment.

RESULTS

No compounds were detected in the laboratory blank in either the impinger and PUF filter (Experiment 6).

FIG. 4 shows a table comparing the polynuclear aromatics and tar trapped in the impinger while (1) using the cigarette with only a conventional cigarette filter; (2) using a partially filtered cigarette with only a PUF filter; and (3) using the cigarette without any filter. As shown in FIG. 4, the PUF filter of the present invention is significantly better than regular cigarette filters in removing toxic polynuclear aromatics such as 2-methylnaphthalene, acenaphthylene, acenaphthene, dibenzofuran, fluorene, phenanthrene, anthracene, carbazole, fluoranthene, pyrene, benzo(a)anthracene and chrysene. This is demonstrated from comparing the weight of polynuclear aromatic compounds found in the impinger when a conventional filter was used to those found when the PUF filter was used. However, the nicotine and cotinine (oxidation product of nicotine) emissions from the cigarette with PUF filter are roughly the same as a cigarette with the regular cigarette filter.

The percentage of polynuclear aromatics and tar removed in the other experiments using the PUF filter are listed in FIG. 5 to FIG. 7 and summarized in FIG. 8. In those experiments where a 2 cubic centimeter PUF filter is used in conjunction with a regular cigarette filter, the PUF filter of the present invention removed about 60% of polynuclear aromatic compounds in cigarette smoke which contacted it, or 30% per cubic centimeter of uncompressed foam material. Furthermore, the PUF filter permitted about 75% of the nicotine in cigarette smoke which contacted the PUF filter to pass through. In those embodiments in which about 75% of the regular filter of a cigarette was replaced with the PUF filter, the PUF filter removed about 74% of polynuclear aromatic compounds contacting it, or about 37% per cubic centimeter of uncompressed foam material, but still permitted about 75% of the nicotine in cigarette smoke to pass through.

As noted above, a PUF cylindrical body having a volume of 2 cubic centimeters in its uncompressed state was slightly compressed and inserted into the experimental apparatus to function as a filter. In Experiment 4, this PUF filter removed 74% of the polynuclear aromatic compounds when used without a complete regular filter (75% of the regular filter removed), compared to only 60% when a complete regular filter was used as in Experiment 1. This may be due to the fact that there are significant amounts of glycerol triacetate embedded in most regular cigarette filters. It was observed that the amount of glycerol triacetate found in each experiment was approximately the same as that of nicotine. The glycerol triacetate emitted during these experiments may be trapped by the PUF filters. The trapped glycerol triacetate would occupy many of the reactive radicals on the PUF filter, which would be otherwise available for polynuclear aromatics. Therefore, with a complete regular cigarette filter, the efficacy of the PUF filter trapping polynuclear aromatics was reduced, compared to when used with only a partial (25%) regular cigarette filter. In view of these results, it is expected that the percentage of polynuclear aromatic compounds absorbed by the PUF filter would increase from 74% to about 80-90% per 2 cubic centimeters of uncompressed PUF starting material, if the PUF filter is used without any conventional cigarette filter, or if the amount of glycerol triacetate in regular cigarette filter is reduced.

Three more experiments were performed to determine the efficiency of PUF filters in removing cyanide from cigarette smoke. These experiments were performed in the same manner as the first experiment. However, instead of 70 mL of methylene chloride to dissolve tar trapped in the impinger by liquid argon, 37 mL of 0.25 N sodium hydroxide was added to impinger to rinse and convert trapped inorganic cyanide compounds to cyanide anion, which was then analyzed by ion chromatography. For a cigarette with conventional filter but without PUF filter, 660 micrograms of total cyanide were found in the 37 mL impinger rinsing solution. This was from the smoke that would have been inhaled by the smoker if the cigarette had been smoked. However, for a cigarette with both regular filter and PUF filter, 250 micrograms of total cyanide were found in the 37 mL impinger rinsing solution. For a blank, an unlit cigarette with regular filter but without PUF filter was used. For the blank, cyanide was not found at the detection limit of 3.7 micrograms in the 37 mL impinger rinsing solution. These experiments indicate that approximate 62% of totalcyanide in cigarette smoke passing through the PUF filter was removed by a PUF filter of the present invention.

Because the PUF filter used in this study are made from medium density polyurethane foam, the pressure drop across the PUF filter is much lower than regular cigarette filter. Most smokers familiar with a conventional cigarette filter may not be familiar with a filter which has a low pressure drop. Consequently, they may inhale larger quantities of smoke at the beginning. Therefore, smokers may either be informed of the lower pressure drop, or use a PUF filter as an additional filter after the regular cigarette filter. In the latter way, the PUF filter may be inserted in a cigarette holder and then a cigarette with regular filter is inserted into the cigarette holder before smoking.

Although this invention has been described in terms of certain preferred embodiments, other embodiments will be apparent to those of ordinary skill in the art in view of the disclosure herein are also within the scope of this invention. Accordingly, the scope of the invention is intended to be defined only by reference to the appended claims.

Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.

Claims

1. A filter comprising a urethane-based main chain having a repeat unit of the formula, R′—NH—COO—R—O—NHn, the R group and the R′ group being an aliphatic chain and an aromatic group respectively, wherein the R group, R′ group, and —NH— moiety in the repeat unit of the urethane-based main chain are reactive radicals for trapping cyanides, phenols, or polynuclear aromatic compounds.

2. The filter of claim 1, wherein the nitrogen atom of the reactive radical —NH— moiety in the repeat unit, R′—NH—COO—R—O—NHn, has a lone pair electron for binding the phenols and the cyanides via hydrogen bonds.

3. The filter of claim 1, wherein the reactive radicals R group and R′ group absorb the polynuclear aromatic compounds via van der Waals attraction.

4. The filter of claim 1, wherein the reactive radical R group comprises n-octyl.

5. The filter of claim 1, wherein the reactive radical R′ group comprises tolyl.

6. The filter of claim 1, wherein the reactive radicals are formed through an extraction process to remove a plurality of contaminants originally bonded with the reactive radicals in the repeat unit of the urethane-based main chain.

7. The filter of claim 6, wherein the urethane-based main chain having the contaminants bonded with the reactive radicals in the repeat unit before the extraction process is a polyurethane foam or a polyurethane fiber.

8. The filter of claim 7, wherein the polyurethane foam or polyurethane fiber has a density of between about 0.01 g/ml to about 0.05 g/ml.

9. The filter of claim 6, wherein the reactive radical —NH— moiety is originally occupied by the contaminants comprising phenols before the extraction process.

10. The filter of claim 9, wherein the phenols comprise 6-tert-butyl-2,4-dimethylphenol and butylated methyl phenol.

11. The filter of claim 6, wherein the reactive radicals R group and the R′ group are originally occupied by the contaminants comprising tinuvin, monomers, dimers, oligomers, and 4,4,5,6-tetramethyltetrahydro-1,3-oxazin-2-thione before the extraction process.

12. The filter of claim 6, wherein the extraction is a Soxhlet extraction.

13. The filter of claim 12, wherein the Soxhlet extraction uses a solvent containing 6% ether in hexane to extract the contaminants from the polyurethane material for revealing the urethane-based main chain.

14. The filter of claim 12, wherein the Soxhlet extraction uses a solvent comprising methylene chloride, hexane, light hydrocarbon based solvents, or mixtures of the foregoing to extract the contaminants from the polyurethane material for revealing the urethane-based main chain.

15. The filter of claim 6, wherein the extraction is a supercritical fluid extraction, a steam distillation, a hot solvent extraction, or an organic extraction.

16. The filter of claim 6, the filter is further formed through drying the urethane-based main chain after the extraction process.

17. The filter of claim 1, wherein the polynuclear aromatic compounds comprise 2-methylnaphthalene, acenaphthylene, acenaphthene, dibenzofuran, fluorene, phenanthrene, anthracene, carbazole, fluoranthene, pyrene, benzo(a)anthracene, and chrysene.