US2780228A

US2780228A - Filters for tobacco smoke comprising cellulose esters and ethers

Info

Publication number: US2780228A
Application number: US413949A
Authority: US
Inventors: George P Touey
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1954-03-03
Filing date: 1954-03-03
Publication date: 1957-02-05
Anticipated expiration: 1974-02-05

Description

CELLULOSE ESTERS AND ETHERS Filed March 5, 1954 TOBACCO CIGARETTE WRAPPER GEORGE R TOUEY INVENTOR.

AT YURNEYS' l [Ir llllllvlv United States Patent FILTERS FOR TOBACCO SMOKE COMPRISING CELLULOSE ESTERS AND ETHER'S George P. Touey, Kingsport, Tenm, assignor =to :Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application March 3, 1954, Serial No, 413,949 7 Claims. (Cl. ISL-208) The present invention relates to tobacco smoke filters suitable for use in cigarettes, pipes, and cigarette and cigar holders. More particularly the invention is concerned with novel filtering material specifically adapted for more-extensive removal of nicotine and other alkaline ingredients from the smoke.

The prior art discloses a number of cellulosic tobacco smoke filtering materials including paper, cotton fibers, Woven cotton and the like. More recently the use of cellulose esters and the like :has been taught :by Berl in U. S. Patent No. 2,228,383, :by Cobb & Hargrave U. S. Patent application Serial No. 324,284 filed December 5, 1952, and by Crawford & Stevens in U. S. applications Serial No. 324,342, filed December 5, 1952 and Serial No. 374,168 filed August 14, I953.

I now have discovered that a filter of greatly improved efiiciency, particularly as respects removal of alkaline constituents, e. g. nicotine from the smoke may be obtained by employing a cellulose derivative having a plurality of radicals containing free acid groups, said radicals being chemically attached to the cellulose molecule. it is therefore an object of any invention to provide for the removal, during smoking, of all or the major portion of nicotine and other harmful ingredients of tobacco smoke. A second object is provision of a novel tobacco smoke filter capable of removing undesirable constituents from cigarette smoke both mechanically and chemically. Another object relates to the preparation of cigarette filters wholly or in part :from materials consisting of cellulose acid esters and cellulose acid ethers. Other objects Will be apparent from the accompanying specification and claims.

My invention may be broadly described as residing in an improved tobacco smoke filter having a mass of filtering-material providing a plurality of smoke passages therethrough, said material comprising at least a substantial amount of a substance which is a derivative of cellulose, said derivative having free acid groups chemically at tached to a cellulose residue through the oxygen atoms of the hydroxyl groups or oxygen atoms replacing these) of the cellulose. In accordance with the invention the cellulose derivative most advantageously is selected from the group consisting of those cellulose ethers and cellulose esters which have reactive free acid groups chemically attached to the cellulose.

The substances which I have found to be most advantageous maybe represented generally by the formula:

wherein Cell. represents the residue of a cellulose molemile, from which n hydroxyl groups have been removed, X is an ester or other residue containing at least one free organic or inorganic acid radical, and n is a number preferably amounting to at least lfor each 1 0 anhydroglucose units originally present in the cellulose molecule. Thus, stated in another Way, the novel smoke filters comprise derivatives of cellulose containing at least one free reactive acid group per ten anhydroglucose units of the cellulose and selected from the group consisting of (1) acid esters of cellulose and polybasic acids, and (2) acid ethers of cellulose and hydroxy acids.

2 The cellulose acid esters contemplated by the invention include:

1. Dicarboxylic acid-esters having one free-acid group, e. g. cellulose acid phthalate, cellulose acid succiuate, cellulose acid. maleate, and cellulose acid malonate. The compounds of this group may be represented by the 2. Trica'rboxylic acid esters including (a) those having one free acid group, e. g. cellulose acid citrate and cellulose acid carballylate represented by the formula and (b) those having two'freeacid groups, e. g. cellulose acid citrate :and cellulose acid 'carballylate represented by 3. Mineral acid esters, including (a) dibasic acid esters, e. .g. cellulose acid sulfate of the formula and ('11-) estersof tribasic acids, -e. g. cellulose monohydrogen phosphate and cellulose dihydrogen phosphate represented by the formulae 4. Mixed inorganic mineral and organic carboxylic acid esters, e. g. cellulose acetate phosphate, cellulose acetate sulfate and cellulose acetate phthalate.

5. Mixed esters of monoand polybasic acids, e. g. cellulose acetate phthalate.

The cellulose acid ethers contemplated by the invention include:

(l) carboxyalkyl cellulose others, e. g. carboxymethyl cellulose and carbo'xyethyl cellulose as represented by the formula .(2) alkyl sulfonicacid ethers, e. g. sulfoethyl cellulose,

represented by the formula '|7Z Thefilters of the invention may be made in accordance with any of the methods or any of the forms described in the prior art wherein a foraminous, pervious or porous mass is formed from fibers, powder, flake, sponge or the like. Fibrous filters containing the novel filtrants and prepared by the methods described in the Cobb & Hargrave and Crawford & Stevens pending U. S. patent applications referred to above have proved most advantageous, especially when the filters are composed of fibers or filaments synthetically spun from the novel filtering substances and converted into rod-like masses of substantially longitudinally aligned crimped filaments coextensive with the masses. The novel substances of the invention also may be used in admixture with cotton asbestos or the like and may be carried on porous supporting material as coatings thereon. It is contemplated that the invention will give improved action by the combination of mechanical removal of undesirable ingredients by means of impingement, absorption, adsorption and/or condensation and the like, as taught by the prior art, and also by the chemical combination of the free acid groups with alkaline material existing as impurity in the smoke.

In fibrous form, the acid cellulose derivatives of this invention are, as indicated above, ideally suited for the preparation of filter tips for cigarettes. A simple method consists in preparing a small wad of the fibers approximately 11 mm. in length and with a thickness equal to that of a cigarette. This wad is then inserted in the end of the cigarette by procedures known to the art. In the case of the soluble cellulose acid esters and ethers this wad can be prepared from spun filaments either directly or in the form of a sliver or tow. Thus, for example, cellulose acetate phthalate can be spun from an acetone solution, and the fibers converted to a tow from which the filter wad is prepared.

ln powder or flake form, the acid cellulose derivatives are more suitable for the preparation of filters for pipes or cigarette holders. For such purposes the filter material is usually held in a suitable compartment within the pipe stem or cigarette holder.

The number of acid groups on the residue of a cellulose molecule does not seem to be highly critical although it seems preferable to have at least one acid group per three units of anhydroglucose. However, substantial amounts of nicotine can be removed with acid cellulose derivatives containing as low as one acid group for every ten anhydroglucose units originally existing in the cellulose molecule. Where other filtering substances are mixed with the free acid derivative in one filter unit, it may be necessary to employ a derivative containing a higher percentage of free acid groups. In any event,

While the preferred concentration of reactive free acid be noted that the preparation of dicarboxylic acid esters of cellulose'is discussed in Heusers Cellulose Chemistry (page 289), and the preparation of cellulose acid citrate is disclosed in my copending U. S. patent application S. N. 355,416, filed May 15, 1953. Preparation of cellulose phosphates is reported by Iergens et al., Textile Research Journal, 18, 42-44 (1948). Procedures for making cellulose acid esters are also described in U. S. Patent 2,505,561. U. S. Patent 2,093,462 discloses methods for the preparation of cellulose acetate acid phthalate and cellulose acid succinate. The preparation of cellulose acid phosphate is disclosed in my copending U. S. patent application S. N. 264,677, and the preparation of sulfoethyl cellulose is described in my copending U. S. patent application S. N. 253,957, filed October 30, 1951.

Carboxymethyl cellulose may be prepared from alkali cellulose and chloroacetic acid in accordance with a reaction which may be represented as follows:

ClOHzCOOH (NaOH) HCl CelL-O CHQC ONa GelL-O CHzCO OH Coll.ONa

CH2=CHCN Cell.0 Na

(NaOH) Cell.-O CH2CHzCN H01 Cell.0 CHzCHzCOONa Gen-00111011200 on Sulfoethylcellulose (cellulose ethane sulfonic acid) is a representative example of an alkyl sulfonic acid ether of cellulose. It can be prepared by etherifying cellulose with Z-chloroethane sodium sulfonate.

ClCH CHzSOaNfl Ccll.ONa

(NaOH) HCl ll.OCHgCHzSOsNa CGll.--OCHHCH1SO3H One embodiment of the invention is illustrated in the accompanying drawing which is a partially cut-away view of a cigarette equipped with a filter comprising a rod-like mass of crimped, longitudinally aligned fibers spun from cellulosic material having reactive free acid groups.

The invention is further illustrated in the following examples.

Example 1.-Preparati0n of cellulose acetate acid phthalate filter tips A sample of cellulose acetate acid phthalate containing an average of l phthalyl group 0 ebormooom and two acetyl groups for each anhydroglucose unit was dissolved in acetone and spun into filaments of about 16 denier. The filaments were cut into short fibers of approximately inch in length and packed into cigarette paper tubes obtained by the removal of the tobacco from standard brand cigarettes. The rods thus formed were cut into lengths of /2 inch thus producing filter tips. Ten of these tips were then sealed to the ends of ten cigarettes of a standard brand. The filter tipped cigarettes were smoked on a smoking machine similar in operation and design to the one described by I. A. Bradford, W. R. Horton, and H. R. Hanmer, Industrial and Engineering Chem., 28, 836-9, 1936; Figure 2. As a control run, ten cigarettes of the same brand were also smoked on the smoking machine. All cigarettes were smoked to a mark representing 70% of the total length of the cigarette and the smoke was collected in a mixture of chloroform and 5% aqueous sulfuric acid. After the completion of the smoking procedure the chloroform-sulfuric acid mixture of each run was separated. The sulfuric acid layers were analyzed for nicotine according to the silicotungstic acid procedure described in Methods of Analysis, Association of Official Agricultural Chemists, 7th ed., pp. 69-70 (1950). The chloroform layers were analyzed for dissolved solids or tars by evaporating ofi the chloroform and drying the residues at C. until constant weights were obtained. The amounts of nicotine and tar found in the smoke from the filtered and unfiltered cigarettes are given in the table below.

mg. Tars mg.

Nicotine 10 cigarettesno filters 158 20 10 cigarettes-filter tips added 100 5 Example 2.Preparati0n of cellulose acid succinate filter tips A fibrous cellulose acid succinate was prepared by allowing 10 grams of cotton linters to react with 50 grams of succinic anhydride in ml. of pyridine at 65 C.

for 48 hours and precipitating the dope which formed in dilute aqueous HCl. This washed and dried acid ester containing approximately 50% succinyl was cut, packed into cigarette paper tubes, and converted to cigarette filter tips in the manner described in Example 1. These filter tips were then sealed to the ends of ten cigarettes of a standard brand and smoked on the smoking machine (Example 1). As a control ten cigarettes of the same brand but without filter tips were also smoked on the smoking machine. The amounts of nicotine and tar found in the smoke from the filtered and unfiltered cigarettes are given in the table below.

Example 3.Preparati0n of cellulose acid citrate filter tips A ZO-gram sample of long-fibered cotton was soaked for 20 minutes in a 35% aqueous solution of citric acid, pressed to a weight corresponding to 1 part cotton and 1 part citric acid, and dried for hours at 105 C. The washed and dried product was a cellulose acid citrate with a free carboxyl content of 11%. This fibrous material was converted into a cotton cord or sliver and wrapped in cigarette paper to form paper rods of the cellulose acid citrate. Finally, the rods were cut into V2 lengths and used as filter tips for cigarettes in the manner described in Example 1. The smoke collected from ten cigarettes containing the cellulose acid citrate tips gave a test showing that over 70% of the nicotine had been removed by the filter.

Example 4.--Preparati0n of cellulose acid phosphate filter tips A ZO-gram sample of cotton linters was immersed in a solution containing 15 grams of 85% phosphoric acid, 25 grams of urea, and 35 grams of water. The ureaphospl'rate impregnated linters were pressed to a weight corresponding to 1 part cellulose and three parts solution and heated at 150 C. for forty minutes. The heated product was washed free of reagents with water and finally treated with dilute HCl to convert the cellulose phosphate salt into its corresponding cellulose acid phosphate. This product, when dry, was a fibrous material similar in appearance to cotton linters. It was packed into cigarette paper in the manner described in the pre ceding examples and cut into filter tips of la lengths. Analysis of the smoke obtained from ten cigarettes containing the cellulose acid phosphate filter tips indicated that 90% of the nicotine in the main stream had been removed by the filter.

Example 5 .Preparation of carboxymethylcellulose filter tips Twenty grams of cotton linters was rapidly stirred in 4.00 ml. of isopropyl alcohol while 60 grams of 35% NaOH was slowly added. After the addition of the alkali, twenty grams of sodium chloroacetate was added and the mixture was rapidly stirred and heated to 60 C.

After a reaction time of 2 hours at 60 C. the linters were removed by filtration and washed in sufficient dilute aqueous HCl to convert the sodium salt of the carboxymethylcellulose to the free acid. This product was a white fibrous product similar in appearance to cotton linters. It had a carboxyl content of 14.5%

The free acid carboxymethylcellulose was tightly packed into cigarette paper in the form of rods and the rods were cut into cigarette filter tips of approximately b-inch lengths. These tips were placed on 10 standard brand cigarettes and the 10 cigarettes were smoked on the smoking machine. Analyses of the smoke collected 6 from the l0 cigarettes and the smoke collected from 10 cigarettes of the same brand without the filter tip indicated that 65% of the nicotine in the main stream smoke was trapped by the filter.

Example 6.Preparati0n of sulfoethyl cellulose filter tips A sample of cotton linters was etherified with 2-chloroethane sodium sulfonate giving a cellulose ethane sodium sulfonate with an average degree of substitution of one ethane sulfonate group for every three anhydroglucose units in the cellulose. This fibrous material was converted to the free acid by treatment with dilute HCl and dried. This product removed over 75% of the nicotine from the main stream smoke of a standard brand cigarette.

The term polybasic acids as used herein is intended to include dibasic acids and any acid having more than one acid radical. As respects the esters and ethers of polybasic acids other than dibasic acids, it should be noted that the invention encompasses, in addition to the compounds covered by the formulae given herein, also those esters and ethers having a free-acid containing radical linked to a plurality of cellulose molecule residues, e. g.

I claim:

1. A tobacco smoke filter comprising a structurally unitary, elongated, rod-like mass of coextensive, crimped fibers of an ester of cellulose and a polybasic acid, the fibers of the mass being in substantial parallelism with the longitudinal axis thereof, said ester having at least one free, reactive acid group per ten anhydroglucose units of the cellulose.

2. A tobacco smoke filter as defined in claim 1 wherein the ester of cellulose contains at least one reactive free acid group for every three anhydroglucose unit in the cellulosic portion of the ester molecule.

3. A tobacco smoke filter as defined in claim 2 wherein the ester is a dicarboxylic organic acid ester of cellulose having one reactive free acid group in the residue of each acid molecule.

4. A tobacco smoke filter as defined in claim 3 wherein the ester is cellulose acid phthalate.

5. A tobacco smoke filter as defined in claim 2 wherein the ester is a tricarboxylic acid ester of cellulose.

6. A tobacco smoke filter as defined in claim 5 wherein the two of the three acid groups of the tricarboxylic acid remain free.

7. A tobacco smoke filter as defined in claim 2 wherein the mass comprises a segment of a crimped continuous filament tow, the filaments of the mass being substantially longitudinally aligned, and having a denier within the range of 1 to 16.

References Cited in the file of this patent UNITED STATES PATENTS 2,228,383 Berl Jan. 14, 1941 2,394,887 Berl Feb. 12, 1946 2,592,553 Frankenburg et al Apr. 15, 1952 FOREIGN PATENTS 177,706 Austria Feb. 25, 1954 250,360 Switzerland June 1, 1948 665,278 Great Britain Jan. 23, 1952 695,046 Great Britain Aug. 5, 1953 OTHER REFERENCES Hofipauir and Guthrie: Ion Exchange Characteristics of Chemically Modified Cotton Fabrics, pages 617-620 of vol. 20, (September 1950) issue of Textile Research Journal.

Davidson and Nevelle: Pages T59-T60 of volume 39 (1948) of the Journal of the Textile Institute.

Claims

1. A TOBACCO SMOKE FILTER COMPRISING A STRUCTURALLY UNITARY, ELONGATED, ROD-LIKE MASS OF COEXTENSIVE, CRIMPED FIBERS OF AN ESTER OF CELLULOSE AND A POLYBASIC ACID, THE FIBERS OF THE MASS BEING IN SUBSTANTIAL PARALLELISM WITH THE LONGITUDINAL AXIS THEREOF, SAID ESTER HAVING AT LEAST ONE FREE, REACTIVE ACID GROUP PER TEN ANHYDRGLUCOSE UNITS OF THE CELLULOSE.