Tobacco Smoke Filters

Abstract

Crimped celluclose acetate filter tow having dispersed therein at least one metal oxide selected from zinc oxide, ferric oxide and cuprous oxide, the tow being adapted to be activated by the application thereto of an organic activating agent to alter the characteristics of the individual filaments of the tow to make accessible the oxide dispersed in the two to hydrogen cyanide for removal thereof from the vapor phase of tobacco smoke. Representative of the organic activating agents are triethylene glycol, triacetin, polyethylene glycol, triethylene glycol diacetate, triethyl citrate, propylene glycol, and dimethoxyethyl phthalate. Also disclosed are tobacco smoke filters made from the tow.

Description

This invention relates to a new and improved tow useful in the manufacture of tobacco smoke filters and filters made therefrom.

More particularly the invention concerns crimped cellulose acetate filter tow having dispersed therein at least one metal oxide selected from zinc oxide, ferric oxide and cuprous oxide, the tow when activated by the application thereto of an organic activating agent is rendered reactive with hydrogen cyanide in the vapor phase of tobacco smoke.

The presence of ciliatoxic agents in tobacco and especially cigarette smoke has been demonstrated by numerous investigators whose test specimens ranged from protozoan to human cilia, the latter serving to clear the broncial tree of inhaled foreign matter. In every case, in vitro or in vivo, cigarette smoke was found to be toxic to the cilia. Kensler and Battista have reported that the vapor phase of cigarette smoke is responsible for the ciliatoxic properties of smoke. Walker and Kiefer found, in their study of smoke gases, that hydrogen cyanide was the most active ciliatoxic agent in cigarette smoke gases. Numerous other studies are reported in the literature concerning the toxicity of hydrogen cyanide. Consequently, much effort has been applied to the development of filters which would selectively remove this undesirable component from cigarette smoke.

In U.S. Pat. No. 3,251,365, Keith discloses a cigarette filter containing adsorbent granules impregnated with certain zinc and iron oxides which removes about 50 percent of the hydrogen cyanide in the smoke from cigarettes equipped with these filters. The adsorbent granules are essential in the operation of his invention since he states that the smooth and nonporous nature of the commonly used fibrous filtering materials, while effective in capturing tobacco smoke droplets, does not present a sufficient surface area to effectively adsorb gaseous molecules.

More recently, Horsewell and Tolman (U.S. Pat. No. 3,403,690) disclosed a cigarette filter containing an organozinc salt compound that is claimed to remove a substantial portion of the hydrogen cyanide from cigarette smoke. The organozinc salts are added as aqueous solutions. Application of a water solution to a conventional cellulose acetate filter tow destroys the crimp of the tow and therefore its effectiveness as a filter for tar and nicotine is decreased. Furthermore, since the salts are on the surface of the fibers within the filter, they may be transferred to the smoker's mouth or lungs via the smoke aerosol.

In considering the prior art I have found that U.S. Pat. No. 2,136,201 discloses cellulose ester textile yarns which have been delustered by means of incorporating therein certain pigments. Some of these pigments are titanium dioxide, zinc oxide, antimony oxide, barium sulfate, etc. However, there is no suggestion that any of the textile yarns disclosed in the patent would be useful in cigarette filters and particularly there is simply no suggestion by the inventors thereof that the additives did any more than deluster the yarn. U.S. Pat. No. 2,057,712 discloses that oxides, hydroxides or hydrated oxides of titanium, aluminum, zinc and tin which are precipitated from aqueous media in a gelatinous or flocculent form are useful to deluster cellulose acetate yarn and have the advantage of not unduly cutting or wearing away of guides on processing equipment.

I have discovered an improved cellulose acetate tow particularly adapted for making tobacco smoke filters that effectively adsorb hydrogen cyanide from tobacco smoke. The tow of this invention offers the advantage of making available the metal oxides to effect the removal of hydrogen cyanide from tobacco smoke without the risk of the oxides sifting out of the filter and into a smoker's mouth and lungs. Likewise, the use of the tow of this invention does not require that additive be sprayed, dusted, etc., on the tow by the plug manufacturer. In fact, no additional process steps are demanded of the plug maker and yet a superior filter is produced. The tow of this invention provides a simple and economical way to produce a tobacco smoke filter having the desirable property of removing hydrogen cyanide from tobacco smoke. The fabrication of the filter requires no extra labor or equipment since the metal oxides are present in the filaments of the tow as spun by the tow manufacturer.

The unexpected result obtained by this invention is not fully understood. Although the metal oxides are dispersed within the fiber, the fiber can be activated by certain organic activating agents. One possible explanation is that the activating agent increases the permeability of the cellulose acetate matrix for hydrogen cyanide, thus the hydrogen cyanide molecules can penetrate the surface of the fiber and make contact with the metal oxide. I have found that about 4 percent of the oxide based on the weight of the tow is necessary to result in appreciable adsorption of hydrogen cyanide and that more than about 15 percent does not add any appreciable adsorption characteristic to the activated tow. Further, greater amounts tend to create problems in the spinning of the tow.

Generally, the tow of this invention is made by incorporating into a spinning solution a finely ground zinc oxide, ferric oxide or cuprous oxide ranging in size up to about one micron and in the amount of about 4 percent or more, by weight of the tow, the spinning solution comprising cellulose acetate and a solvent such as acetone. Methods for dispersing particles such as these oxides in spinning solutions are well known. The spinning solution is forced through a spinneret and pulled into a fiber by the conventional techniques for manufacturing cellulose acetate fibers. The denier per filament may range from about 1.5 denier per filament to about 16 denier per filament and the crimps per inch may range from about 7 to about 20. The fibers are bundled together and crimped in a manner similar to that described in U.S. Pat. No. 2,747,233. The tows have physical properties and appearances similar to those of conventional cellulose acetate tows used in the manufacture of cigarette filters. The surface of the fibers are virtually identical in appearance to convention cellulose acetate fibers.

As a preferred embodiment of this invention I provide crimped cellulose acetate filter tow made up of a multitude of continuous filaments, the tow being characterized in that the individual filaments thereof have dispersed therein about 4 percent or more, by weight of the tow, of discrete particles of a metal oxide selected from zinc oxide, ferric oxide and cuprous oxide, the metal oxide ranging in size up to about 1 micron, said tow being adapted to be activated by the application thereto of an organic activating agent to alter characteristics of the individual filaments of said tow to make accessible said metal oxides to hydrogen cyanide for removal thereof from the vapor phase of tobacco smoke. The tow ranges from 1.5 to 16 denier per filament and is provided with 7 to 20 crimps per inch. Representative of organic activating agents which are useful as activators in this invention are triethylene glycol, triacetin, polyethylene glycol, triethylene glycol diacetate, diethyl citrate, propylene glycol and di(methoxyethyl) phthalate.

I provide a process for producing cellulose acetate filter tow having improved characteristics comprising opening cellulose acetate tow which has dispersed in the filter tow about 4 percent or more by weight of the tow, of discrete particles of at least one metal oxide selected from zinc oxide, ferric oxide and cuprous oxide, the particles ranging in size up to about 1 micron; and applying an organic activating agent to said tow to activate said tow by altering characteristics of the individual filaments to make accessable said metal oxides to hydrogen cyanide for removal thereof from the vapor phase of tobacco smoke.

A process for producing tobacco smoke filters of this invention having improved affinity for hydrogen cyanide in tobacco smoke, comprises opening cellulose acetate tow which has dispersed in the filaments thereof about 4 percent or more, by weight of the tow, of discrete particles of at least one metal oxide selected from zinc oxide, ferric oxide and cuprous oxide, the particles ranging in size up to about 1 micron, applying an organic activating agent to said tow to activate said tow by altering characteristics of the individual filaments to make accessable said metal oxides to hydrogen cyanide for removal thereof from the vapor phase of tobacco smoke, and forming said filaments into a filter plug.

A further embodiment of this invention is a tobacco smoke filter comprising a filter plug of crimped cellulose acetate filament, said filaments having dispersed therein about 4 percent or more by weight of the tow of discrete particles of a compound selected from zinc oxide, ferric oxide or cuprous oxide, said filaments having been activated with an organic activating agent to alter the characteristics of said cellulose acetate filaments to make accessable the metal oxides to hydrogen cyanide for removal thereof from the vapor phase of tobacco smoke.

A still further embodiment of this invention is a shaped article comprising cellulose acetate fiber having dispersed therein a compound selected from zinc oxide, ferric oxide or cuprous oxide, the article having been activated by subjecting it to plasticizing action of an organic activating agent to impart thereto an affinity for hydrogen cyanide found in the vapor phase of tobacco smoke.

Another process for manufacturing cellulose acetate tow for tobacco smoke filter comprises dispersing in cellulose acetate dope about b 4 percent or more, by weight of the tow, of a compound selected from zinc oxide, ferric oxide or cuprous oxide, spinning filaments from said cellulose acetate dope, forming said filaments into a tow, and treating said filaments with an organic activating agent to activate the filaments to render them capable of adsorbing hydrogen cyanide from tobacco smoke.

The tow can be boxed, baled, or packaged by any of the methods now used for conventional cellulose acetate filter tow. When nonactivated textile tows made by this method are formed into cigarette filters they exhibit the same properties as filters made from conventional cellulose acetate tow in that they remove a substantial portion of the tars and nicotine from cigarette smoke, by are not effective for adsorbing gases such as hydrogen cyanide. However, after the tow is treated with an activating solvent, it adsorbs hydrogen cyanide readily.

This invention will be further illustrated by the following examples of preferred embodiments, although it will be understood that these examples are included merely for purposes of illustration and are not intended to limit the scope of the invention.

EXAMPLE 1

Twelve parts of zinc oxide particles (Horse Head Kadox-15) were dispersed in a spinning solution consisting of 88 parts of cellulose acetate and 400 parts of acetone. The dispersion was spun into fibers using a conventional spinning cabinet. The fibers were 3.3 denier per filament and had an average tensile strength of 1.14 grams per denier. The fibers were white and had the appearance of conventional cellulose acetate fibers. Examination of the fibers with a light microscope and with a scanning electron microscope did not reveal the presence of any particles on the surface of the fibers. Fifteen thousand fibers were bundled together and passed through a filter tow crimper. The fibers in the crimped tow were separated by combing, then pulled together into a plastic cylinder which has an internal circumference of 22 mm. The cylinder was cut into 20-mm. segments or filters and divided into two equal samples of five filters each. One sample was designated control filters and the other set was designated activated filters. Diethylether, as a carrier, containing 15 mg. of triethylene glycol and 15 mg. of triacetin was added to each filter designated activated. The diethylether was removed by evaporation, then both types of filters were attached to 85-mm. cigarettes. A 20-mm. segment of tobacco was removed from each of the cigarettes so that their total length was 85 mm. The cigarettes were smoked with an automatic smoking device and the amount of hydrogen cyanide delivered by each cigarette was determined spectrophotometrically. The results were as follows:

Hydrogen Cyanide Type Filter Cigarette Found, .mu.g./Cigarette __________________________________________________________________________ Cigarette without filter 227 Cigarette with unactivated filter 204 Cigarette with activated filter 106 __________________________________________________________________________

EXAMPLE 2

Eight parts of zinc oxide particles (Horse Head Kadox-15) were dispersed in a spinning solution consisting of 92 parts of cellulose acetate and 400 parts of acetone. The dispersion was spun into fibers using a conventional spinning cabinet. The fibers were 3.3 denier per filament and had an average tensile strength 1.16 grams per denier. Fifteen thousand fibers were bundled together and passed through a filter tow crimper. The tow was spread to a band width of 12 inches and sprayed with a solution of 1:1 triacetin:triethyleneglycol until the tow contained 21 percent of the solution. It was then pulled into a plastic tube and cured overnight. The plastic tube was cut into 20-mm. lengths. Control filters were made by the same procedure except that no zinc oxide was added to the spinning solution. Both sets of filters were attached to cigarettes and tested as in example 1. The cigarettes containing the control filters delivered 161 .mu.g. of hydrogen cyanide per cigarette compared to only 89 .mu.g. of hydrogen cyanide for the cigarettes with the zinc oxide filters. Cigarettes without filters delivered 200 .mu.g. of hydrogen cyanide.

EXAMPLE 3

Ten parts of ferric oxide particles were dispersed in a spinning solution consisting of 90 parts of cellulose acetate and 400 parts of acetone. The dispersion was spun into fibers of 5 denier per filament. Nine thousand fibers are bundled together and crimped by conventional techniques. The crimped tow was bonded, treated with 11 percent triethylene glycol diacetate, and recompacted into a cord and drawn through a device that seals it with a thin paper wrapper into the form of a continuous rod having a circumference of 24.8 mm. As the rod exited from the machine it was cut into 120 mm. lengths. After curing for 2 hours the rods were cut into six equal segments which were attached to 85-mm. cigarettes; 20-mm. segments of tobacco were removed from each of the cigarettes so that the total length of each cigarette was 85 mm. The cigarettes containing the filter deliver 81 .mu.g. of hydrogen cyanide compared to 231 .mu.g. for 85-mm. nonfilter cigarettes.

EXAMPLE 4

Twelve parts of cuprous oxide particles were dispersed in a spinning solution consisting of 88 parts of cellulose acetate and 400 parts of acetone. The dispersion was spun into fibers of 3 denier per filament. Fifteen thousand fibers are bundled together and crimped by conventional techniques. The crimped tow was treated with 15 percent of a mixture of 1:1 triethyl citrate:tetraethylene glycol then made into cigarette filters by the procedure outline in example 3. Cigarettes equipped with these filters deliver 72 .mu.g. of hydrogen cyanide compared to 231 .mu.g. for 85-mm. nonfilter cigarettes.

EXAMPLE 5

Four parts of zinc oxide particles (Horse Head Kadox-15) were dispersed in a spinning solution consisting of 96 parts of cellulose acetate and 400 parts of acetone. The dispersion was spun into fibers using a conventional spinning cabinet. The fibers were 3.3 denier per filament and had an average tensile strength of 1.16 grams per denier. Fifteen thousand fibers were bundled together and passed through a filter tow crimper. The tow was spread to a band width of 12 inches and sprayed with a solution of 1:1 triacetin:triethyleneglycol until the tow contained 21 percent of the solution. It was then pulled into a plastic tube and cured overnight. The plastic tube was cut into 20-mm lengths. Control filters were made by the same procedure except that no zinc oxide was added to the spinning solution. Both sets of filters were attached to cigarettes and tested as in example 1. The cigarettes containing the control filters delivered 161 .mu.g. of hydrogen cyanide per cigarette compared to only 116 .parallel.g. of hydrogen cyanide for the cigarettes with the zinc oxide filters. Cigarettes without filters delivered 200 .mu.g. of hydrogen cyanide.

EXAMPLE 6

Filters were prepared as in example 1 except that the activating solution contained 10 mg. of propylene glycol and 20 mg. of triacetin. Cigarettes equipped with these filters deliver 110 .mu.g. of hydrogen cyanide.

EXAMPLE 7

Filters were prepared as in example 1 except that the activating solution contained 15 mg. of polyethylene glycol (molecular weight of 600) and 15 mg. of triacetin. Cigarettes equipped with these filters deliver 95 .mu.g. of hydrogen cyanide.

EXAMPLE 8

Filters were prepared as in example 1 except that the activating solution contained 20 mg. of dimethoxyethyle phthalate and 10 mg. of triethylene glycol. Cigarettes equipped with these filters deliver 98 .mu.g. of hydrogen cyanide.

EXAMPLE 9

Filters were prepared as in example 1 except that the activating solution contained 15 mg. of triacetin. Cigarettes equipped with these filters deliver 118 .mu.g. of hydrogen cyanide.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

Claims

I claim:

1. Crimped cellulose acetate tow adapted to be cut up into filter plugs, said tow being made up of a multitude of continuous filaments, the tow being characterized in that the individual filaments thereof are spun from a cellulose acetate solution having dispersed therein about 4 percent or more, by weight of the tow, of discrete particles of a metal oxide selected from zinc oxide, ferric oxide and cuprous oxide, the metal oxide particles ranging in size up to about 1 micron, said tow activated by the application thereto of an organic activating agent solvent selected from the group consisting of triethylene glycol, triacetin, polyethylene glycol, triethylene glycol diacetate, triethyl citrate, propylene glycol and dimethoxyethyl phthalate to alter characteristics of the individual filaments in such manner that they are permeable to hydrogen cyanide and the action of the exposed metal oxides in removing this gas from the vapor phase of the tobacco smoke is facilitated.

2. Crimped cellulose acetate filter tow of claim 1 in which the denier/filament ranges from 1.5 to 16 and the crimps per inch range from 7 to 20.

3. Tobacco smoke filter comprising a filter plug of crimped cellulose acetate filaments, said filaments being spun from a solution of cellulose acetate having dispersed therein about 4 percent or more, by weight of discrete particles, of a compound selected from zinc oxide, ferric oxide or cuprous oxide, said filaments having been activated with an organic activating agent selected from the group consisting of triethylene glycol, triactin, polyethylene glycol, triethylene glycol diacrtate triethyl citrate, propylene glycol and dimethoxyethyl phthalate to alter characteristics of said acetate cellulose acetate filaments in such manner that the permeability to hydrogen cyanide of the filaments is increased and the removal of this gas from the vapor phase of the tobacco smoke by exposure to the contained metal oxide, is facilitated. said tow being made up of a multitude of continuous filaments, the tow being characterized in that the individual filaments thereof are spun from a cellulose acetate solution having dispersed therein about 4 percent or more, by weight of the tow, of discrete particles of a metal oxide selected from zinc oxide, ferric oxide and cuprous oxide, the metal oxide particles ranging in size up to about 1 micron, said tow activated by the application thereto of an organic activating agent solvent selected from the group consisting of triethylene glycol, triacetin, polyethylene glycol, triethylene glycol diacetate, triethl citrate, propylene glycol and dimethoxyethyl phthalate to alter characteristics of the individual filaments in such manner that they are permeable to hydrogen cyanide and the action of the exposed metal oxides in removing this gas from the vapor phase of the tobacco smoke is facilitated.