US2956329A - Manufacture of filamentary tobacco smoke filter - Google Patents

Description

Oct. 18, 1960 FILTER WRAPPER G. P. TOUEY 2,956,329

MANUFACTURE OF FILAMENTARY TOBACCO SUOKE FILTER Filed Dec. 15, 1954 S I LICA GEL PARTICLES PIC-1.2.

GEORGE P. TOUEY VENTOR.

ATTORNEYS MANUFACTURE OF FILAMENTARY TOBACCO SMOKE FILTER George P. Touey, Kinsgport, Tenn., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey Filed Dec. 15, 1954, Ser. No. 475,578

3 Claims. (Cl. 28-72) The present invention relates to tobacco smoke filters. More particularly it is concerned with fibrous filters containing solid inorganic adsorbent for the selective removal of gaseous portions of the smoke.

Fibrous tobacco smoke filters of aligned filaments recently have been put to use on a commercial scale in cigarette filter tips for removal of elements deemed to be obnoxious in the tobacco smoke. Such filters and a method and apparatus suitable for preparing them are described in Crawford and Stevens U.S. Patent Nos.

2,794,239 and 2,794,480 patented June 4, 1957. Due,

to the particular internal physical structure of a preferred form of these filters in which synthetically spun crimped fibers which are coextensive in length with the filters and in which the fibers are in the aggregate in orientation parallel with the longitudinal axis of the filters have been found to be efiective in the removal of sizable quantities of solid and liquid components of the smoke without a disagreeable pressure drop through the filter. It is believed that a very limited amount of the gaseous phase of the smoke probably also is removed due to condensation and/or entrapment with the filtered tars and the like. For some purposes it is believed that it would be desirable to remove additional amounts of the gaseous components of the smoke, e.g. gaseous polar compounds. Substances which have been reported to be present in the gaseous phase in the main stream smoke of cigarette tobacco include CO, H 8, HCN, NH and low molecular weight aldehydes, ketones and hydrocarbons (Industrial and Engineering Chemistry, Vol.29, pages 11-19 and 7 7.1- 776, 1937).

2,956,329 Patented Oct. 18, 1960 Accordingly, it is an object of the present invention to prepare fibrous tobacco smoke filters containing activated silica gel as a solid particulate adsorbent for the removal of greater portions of the gaseous constituents of the smoke. Another object is to prepare a fibrous filter of the longitudinally aligned type carrying activated particulate adsorbent in such a way that there is no danger of the activated adsorbent leaving the filter. A further object is the preparation of a fibrous tobacco smoke filter having bonded particulate adsorbent whose activity is is not substantially reduced by the bonding agent.

I have discoveredthat'the objects of the invention may be accomplished by incorporation of activated silica gel in the material from which the fibers are spun. My invention therefore resides in a tobacco smoke filtering element adapted to remove gaseous components from tobacco smoke, said element comprising a mass of synthetically spun fibers, the fibers containing particles of finely divided activated silica gel adsorbent imbedded therein. My discovery includes the unexpected finding that in the filters made in accordance with the inven- The. use of a solid adsorbent such as activated silica gel has been discussed with regard to its potential for removal of various components of tobacco smoke. Wiggins (U.S. Patent 1,808,707 issued June 2, 1931) has suggested that the gel may be distributed over a carrier such as loose'fiber andformed into a capsule or cartridge. The efiectiveness of this method of addition of activated silica gel to filters of the type developedby Crawford and Stevens-"is extremely limited since there is little to prevent the gel from sifting out from the fibrous mass due to the fact that the fibers are in. substantial longitudinal alignment. Traube (U.S. Patent 1,826,331 issued'October 6, 1931) also has suggested the useof silica gel. of larger particle size, e.g. pills imbedded in a pad of wadding or. the like. This suggestion obviates loss of gel from the fibrous ,filter. However, the method is not easily adaptable to the processing problems in large scale filter production; furthermore, the eflectiveness of the adsorbent is reduced because of its smaller surface area; In U.S. Patent 2,325,- 386, issued July 27, 1943, Frank has shown a means for anchoring small grains of silica gel to the structural members of the filter body, using a rolled or folded web to which the grains are adhesively attached. This method is not suitable for use with the tow type of filter developed by Crawford and Stevens.

tion, silica gel is still of a highly active nature and is sufiiciently exposed to the gaseous phase of the smoke to be capable of removing therefrom undesirable gaseous components. It is also an unexpected finding that in a preferred embodiment of the invention wherein a plasticizer is employed to promote surface solvation bonds between fibers, the gel activity is not destroyed by the plas-' ticizer. In other words, under the conditions of the invention the adsorbent still has adsorbtive afiinity for polar components of the smoke despite the fact that the gel particles are firmly and permanently imbedded in and bound to the fibers and despite the fact that the fibers originally may have contained large amounts of solvents and subsequently may have been sprayed with a plasticizer. The acetone dope from which cellulose acetate fibers are spun is not stificned or coagulated by the addition of activated silica gel powders of a nature suitable for the invention.

The spinning of the fibers may be accomplished by methods well known in the art. The invention contemplates the use of any of a large number of known plastic masses suitable for formation of synthetic fibers by extrusion, e.g. dry spinning or wet spinning. Among those fibers with which the invention is operative are regenerated cellulose, polyamides, polyesters, proteins,

polyvinyl resins, acrylic resins and the like. In its most advantageous form the invention comprises a filter of cellulose acetate fibers.

With respect to acetate, the dopes, i.e. spinning solutions, may be formed as known in the art and in ways such as are discussed in Schneider U.S. Patent 2,280,933, issued April 28, 1928, British Patents 539,327 and 474,879, and Ladisch U.S. Patent 2,571,457 issued October 16, 1951.

Once the fiber is formed it can be put through any of the usual processes which convert it into a filter tip. Thus, for example, a large number of the filaments can be collected together in the form of a continuous tow which, in turn, can be fed into a cigarette making machine by procedures which are known to the art, e.g.

Any of the commercially available activated silica gels of fine particle size may be employed to obtain the advantage of the present invention. Although the fineness of the activated gel powder 'selected'is somewhat dependent on the diameter of the holes in the spinnerette Various concentrations of activated gel may be em-- ployed within the range of 1% e to 60%, preferably about to 40% by weight 'of the fiber. size and cross-sectional shape may be employed and, of

course, the particle size of the activated gel will be to some extent determined 'by the fiber size if the fibers are to have small diameters and gel particles of larger size are to be employed. Obviously, it will be advantageous in general to form a uniform dispersion of the activated gel in the fiber-forming material. This is ordinarily accomplished by suspending the activated gel in the form of a fine powder in the plastic mass of a spinning dope or composition, e.g. the solution of a polymeric substance capable of being spun into a fiber by the commonly known textile spinning techniques. The mass is then either wet or dry spun through spinnerettes and the spun fibers collected in the conventional manner. Thus, the activated gel becomes an integral part of the fiber and shows no tendency to separate from the fiber. Fibers of about 3 to about 100 denier can be employed, the denier determination being made to include the weight of the silica gel particles. Normally fibers of 5 to 30 denier will be employed, particularly in the production of filters from cn'mped continuous filament tow.

In the preparation of filters of this type a number of spun filaments, for instance 5000 to 100,000, are brought together to form a tow which is supplied with e.g. 2-9 crimps per inch in a crimping machine. The tow is subsequently conditioned and then cigaretted, i.e. condensed, shaped, wrapped with paper and cut to lengths as desired. The conditioning of the tow takes place by means of the successive steps of filament separation and creation of an adhesive attitude among the separated filaments. In the case of cellulose acetate, the latter step is achieved by the use of a plasticizer such as dimethoxyethyl phthalate which is sprayed onto the separated fibers. Under the proper conditions the plasticizer puts surface portions of the fibers into solution which results in surface portions of the fiber flowing into and coalescing with like areas of contiguous fibers whereby to form bonds known as surface solvation bonds. Filament separation may be best accomplished by first opening the tow through the use of tensioning means such as disclosed in the aforementioned Crawford and Stevens applications, in Jackson U.S. Patent Application Serial No. 403,131, filed January 11, 1954, and in Smith U.S. Patent Application Serial No. 416,010, filed March 15, 1954, and now U.S. Patent No. 2,790,208 granted April 30, 1957. Filament separation may be accomplished by other means serving to promote blooming of the tow and breaking up compact smaller bundles of filaments which exist within the larger tow bundle. A second and final phase of filament separation, i.e. tow banding, may be accomplished by any of several .means such as by directing jets of air onto the tow in a manner as described, in the Cnawford and Stevens patents, and for example, in Jackson pending U.S. Patent application Serial No. 356,983, filed May 25, 1953, now U.S. Patent No. 2,737,688.

The invention is illustrated in the accompanying drawings in which Fig. 1 represents a photomicrograph of the interior (in side elevation) of a mass of synthetically spun fibers pre-- pared in accordance with the invention,

Fibers of various 4 Fig. 2 is a view of a cigarette having attached thereto a tip prepared from a filtering material of the invention,

Fig. 3 is a photomicrograph in greater magnification of several of the individual filaments of Fig. 1 in crosssection showing the silica particles embedded in the filaments, large numbers of the particles having areas exposed at the filament surfaces, and

Fig. 4 is a photomicrograph in greater magnification of several of the individual filaments of Fig. l in side elevation, showing exposed areas of silica particles at the filament surfaces.

The invention is further illustrated in the following I examples:

. parts of acetone.

Example I A cellulose acetate spinning dope was prepared by dissolving 30 parts of cellulose acetate (39.3% acetyl) in 67 To this dope 3 parts of activated silica gel powder capable of passing through a 325-mesh screen was added. After the activated gel powder was uniformly dispersed throughout the dope, the combinationwas dry spun in the conventional manner into a 95-denier tow of 19 filaments. The spun tow was heated in a forced air dryer for 3 hours at 212 F. to remove residual solvent and stored for two days at 75 F. and relative humidity.

Five 0.2-gram samples of the tow were wadded into the form of a plug. Each of the five wads or plugs was placed in a paper tube 20 mm. in length and 8 mm. in diameter. These tubes were then attached to the ends of 5 standard brand, king size cigarettes. The cigarettes were smoked to a total butt length of 35 mm. on a smoking machine similar in design and operation to the smoking machine described by J. A. Harlan and H. R. Hanmer in Industrial and Engineering Chemistry, vol. 28, pp. 836-839 (1936). The smoke which passed through the filtered cigarettes was collected and analyzed for acetaldehyde.

Five 0.2-gram samples of a 95-denier tow of '19 fila-' ments containing no silica gel were also wadded and placed in paper tubes and attached to the same brand of' cigarettes in a similar manner. These filtered cigarettes were also smoked on the smoking machine and the smoke which passed through their filters was collected and analyzed for acetaldehyde content.

Five of the unfiltered cigarettes were smoked on the smoking machine and the collected smoke was analyzed Results were as follows:

Mg. CHaCHO found in the smoke Smoke collected from the 5 unfiltered cigarettes (50 mm. of the cigarette smoked) 9.8 Smoke collected from the five filtered cigarettes, filter of cellulose acetate (50 mm. of the cigarette smoked) Smoke collected from the five filtered cigarettes, filter of cellulose acetate containing 9% activated silica gel (50 mm. of the cigarette smoked 8.0

for acetaldehyde.

The unfiltered cigarettes had'a pressure drop (resistance to air flow) rating of 20%. The filtered cigarettes had an average pressure drop rating of 25%.

The values listed above indicate that the filter of cellulose acetate fibers containing no silica gel removed only a trace (2%) of acetaldehyde while the cellulose acetate fibers containing 9% activated gel removed 18% of the acetaldehyde. I

7 Example 2 1 A cellulose acetate spinningdope was prepared by dissolving 30 parts of cellulose acetate (39.3% acetyl) in 61 parts of acetone. To this dope 9 parts of activated silica gel powder capable of passing through a 325-mesh screen were added. After the activated gel powder was uniwas dry spun in the conventional manner to form a 88- denier tow of filaments, each filament having a cross section in the shape of a Y. The spun tow was heated in a forced air dryer for 3 hours at 212 F. and stored for two days at 75 F. and 45% relative humidity.

Five 0.2-gram samples of the tow were wadded and placed in paper tubes as in Example 1. These tubes were attached to the ends of 5 standard brand, king size cigarettes and the cigarettes were smoked on the machine to a total butt length of,35 mm. The smoke which passed through the filtered cigarettes was collected and analyzed for acetaldehyde.

-Five 0.2-gram samples of an 88-denier tow of 10 filaments containing no silica gel were also wadded, placed in paper tubes, and attached to the same brand of cigar- The filtered cigarettes had an average pressure drop rating of 23% a a a The values listed above indicate that the filter of cellulose acetate fibers containing no silica gel removed less than 2% of the acetaldehyde from the smoke stream while the filter of cellulose acetate fibers containing 23% activated gel removed 29% of the acetaldehyde from the smoke stream.

Example 3 A cellulose acetate spinning dope was prepared by dissolving 30 parts of cellulose acetate (39.3% acetyl) in 65.5 parts of acetone. To this dope 4.5 parts of activated silica gel powder, 1 to 6 microns in particle size, were added. After the powder was dispersed throughout the dope the combination-was dry spun in the conventional manner to form a ISO-denier tow of 30 filaments. The spun tow was heated in a forced air dryer for 3 hours at 212 F. and stored for two days at 75 F. and 45% relative humidity. A control tow containing no silica gel was prepared in a similar manner.

Five 0.2-gram tow samples of both the control tow and the tow containing 13% activated gel powder were attached to standard cigarettes as in the previous examples. These filtered cigarettes were smoked on the smoking machine and the collected smoke which had passed through the filters was analyzed for acetaldehyde content. Results were as follows.

Mg. of CHsCHO found in the smoke Smoke collected from the 5 filtered cigarettes, filter of cellulose acetate (50 mm. of the cigarette smoked) 9.5 Smoke collected from the 5 filtered cigarettes, filter of cellulose acetate containing 13% activated silica gel (50 mm. of the cigarette smoked) 7.5

Example 4 A cellulose acetate spinning dope was prepared by dissolving 30 parts of cellulose acetate (39.3% acetyl) in 61 parts of acetone. To this dope 9 parts of activated silica gel powder (l-5 microns particle size) were added.

After the powder was uniformly dispersedthroughout the dope the combination was dry spun in the conventional manner into a tow of 15,000 filaments, 8 denier per filament. The spun tow was heated for 6 hours at 180 F. and stored for two days at 75 F. and 45% relative humidity.

The tow ofcellulose acetate containing 23% of activated silica gel powder was fed into a cigarette filter plug "making -machine which conditioned and paper wrapped"it"and cut it into filter rods 66 mm. in length and 7.5mm. in diameter. These plugs were then cut into 13-mm. filter tip lengths and attached to the endsv of 5 standard brand king size cigarettes and the cigarettes were smoked'on the smoking machine to total butt lengths. of 35 mm. The smoke which passed through the filtered cigarettes was collected and analyzed for acetaldehyde.

A tow of 15,000 filaments of 8 denier per filament cellulose acetate without silica gel was also prepared in a similar manner. This tow was converted into filter tips of 13 mm. length and 7.5 mm. diameter in the manner described above. These control filter tips were attached tothe ends of 5 standard brand king size cigarettes and the cigarettes were smoked on the smoking machine to total butt lengths of 35 mm. The smoke which passed through the filtered cigarettes was collected and analyzed for acetaldehyde content.

Mg, of CHaCHO found in the smoke (1) Smoke from 5 filtered cigarettes, filter of cellulose acetate (2) Smoke from 5 filtered cigarettes, filter of cellulose acetate containing 23% activated silica gel..- 7.4 (3) Smoke from 5 unfiltered cigarettes 9.8

Both filtered cigarettes had a pressure drop which was approximately 15% higher than that of an unfiltered king size cigarette.

The values listed above indicate that the filter of A cellulose acetate spinning dope was prepared by dissolving 30 parts of cellulose acetate (39.3% acetyl) in parts of acetone. To this dope, 17 parts of activated silica gel powder (1-5 microns particle size) were added. After the powder was dispersed throughout the dope the combination was dry spun in the conventional manner into a tow of 10,000 filaments of 20 denier per filament. The spun tow was heated for 6 hours at F. and stored for two days at 75 F. and 45% relative humidity.

The tow of cellulose acetate containing 35.5% of activated silica gel powder was fed into a cigarette filter plug making machine which conditioned and paper wrapped it and cut it into filter rods 66 mm. in length and 7.5 mm. in diameter. These plugs were then cut into 13-mm. filter tip lengths and attached to the ends of 5 standard brand king size cigarettes and the cigarettes were smoked on the smoking machine to total butt lengths of 35 mm. The smoke which passed through the filtered cigarettes was collected and analyzed for acetaldehyde.

A tow of 10,000 filaments of 20 denier per filament cellulose acetate without silica gel was also prepared in a similar manner. This tow was converted into filter tips of 13 mm. length and 7.5 mm. diameter in the man ner described above. These control filter tips were attached to the ends of 5 standard brand king size cigarettes and the cigarettes were smoked on the smoking machine to total butt lengths of 35 mm. The smoke which passed through the filtered cigarettes was collecte and analyzed for acetaldehyde. V

.Mg. of CHBCHO found in the smoke (1): Smoke from filtered cigarettes of cellulose acetate r (2) Smoke from 5 filtered cigarettes, -filters-of .cellulose acetate containing 35.5% activated silica gel powder Both filtered cigarettes had a pressure drop which was approximately 12% higher than that of an unfiltered king.

size cigarette. Y

The values listed above indicate that the filter of cellulose acetate containing no silica gel removed 1% of the acetaldehyde from the smoke while the filter of cellulose acetate fibers containing 35.5% silica gel,.based on the total weight of the fibers, removed 34% of the acetaldehyde from the smoke stream.

I claim:

1. A method for the preparation of a filamentary tobacco smoke filter capable of removing gaseous components from smoke comprising the steps of incorporating about 313% by weight of finely divided silica gel of a particle size of mostly less than 30 microns in diameter in an acetone solution of cellulose acetate and thereby providing a material suitable forformation of synthetic filaments, spinning 5,000 to 100,000 filaments of not greater than 20 denier per filament from the silica gelcontaining material, forming the filaments into a continuous tow of substantially parallel filaments, crimping the formed tow, heating and storing'the crimped tow to provide a relatively uniform filament bundle and compacting the tow into the form of a tobacco smoke filter element with a diameter approximating'that of a cigarette.

2. The method for preparing a filamentary tobacco smoke filter capable of removing gaseous components from the smoke which comprises the steps of incorporating from 1-60% by weight of a finely divided absorbent of particle size mostly less than 30 microns in a solution of cellulose acetate and thereby providing a solution suitable for the formation of synthetic filaments, spinning 5.5, (3) Smoke from 5 unfiltered cigarettes 9.8

8 filaments of not greater than 20 denier per filament for the cellulose acetate solution, forming the filaments into a continuous tow of substantially parallel filaments, crimping the formed tow, heating andstoring the crimped tow for providing a uniform filament bundle and compacting the tow into the-form of a tobacco smoke filter element with a diameter approximating that of a cigarette.

3. A method for the manufacture of a filamentary tobacco smoke filter which comprises incorporating finely divided activated silica gel of a particle size of mostly less than 30 microns in diameter into a solution of cellulose acetate adapted for spinning into filaments, said silica gel being incorporated in an amount to provide filaments containing 10-40% by weight of the filaments of said silica gel, spinning the solution into filaments of not greater than 20 denier per filament, then forming several thousand of said filaments into a bundle of continuous, substantially parallel filaments crimping the filament bundle, heating and storing the crimped filament bundle to provide a relatively uniform filter bundle and compacting the filament bundle into the form of a tobacco smoke filter element with a diameter approximating that of a cigarette.

References Cited in the file of this patent UNITED STATES PATENTS 1,629,241 1,985,840 Sadtler Dec. 25, 1934 2,042,702 Dreyfus June 2, 1936 2,160,839 Dreyfus et al. June 6, 1939 2,215,620 Skumburdis Sept. 24, 1940 2,520,502 Haux Aug. 29, 1950 2,688,380 MacHenry Sept. 7, 1954 2,707,308 Taylor et al. May 3, 1955 2,763,267 Miiller Sept. 18, 1956 2,780,228 Touey Feb. 5, 1957 2,819,173 Dithmar Jan. 7, 1958 FOREIGN PATENTS 666,035 Germany Oct. 8, 1938 665,278 Great Britain Jan. 23, 1952 Ubbelohde May 17, 1927

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