Tobacco smoke filtering material

Disclosed are tobacco smoke filtering materials for selectively removing deleterious material from tobacco smoke without at the same time removing desirable smoke vapors which contribute to aroma and taste. The filtering materials comprise a fibrous article, the fibers of which have a coating on the surfaces thereof comprising a compound of the formula ##STR1## wherein R.sub.1 is the residue of a straight chain fatty acid having 8-22 carbon atoms and R.sub.2 is OH or ##STR2## wherein Ac is an acetyl group.

TECHNICAL FIELD 
This invention relates to a tobacco smoke filtering material for 
selectively removing deleterious materials from tobacco smoke without at 
the same time removing desirable smoke vapors which contribute to aroma 
and taste. More particularly, this invention concerns a novel cigarette 
filter tow and filters made therefrom, as well as the method for their 
manufacture, which will selectively remove nicotine from cigarette smoke. 
BACKGROUND ART 
The harmful physiological effects of certain constituents contained in 
tobacco smoke have long been recognized. It is well known, for example, 
that tobacco smoke contains certain solid tar constituents and 
health-affecting materials from tobacco smoke by either using various 
types of tobacco smoke filters attached to the smoking device, or 
incorporating certain preventive compounds into the tobacco being smoked. 
For certain types of tobacco, it is desirable to remove a higher percentage 
nicotine than tar (as defined by the Federal Trade Commission) to achieve 
a balance of taste, aroma, undesirable constituents, etc. Throughout the 
history of cigarette filtration, there has been a desire to selectively 
remove nicotine from tobacco smoke due to its toxicity. As of the present 
time, the use of a tobacco smoke filter element placed on the tip of the 
smoking device is the method or device most commonly used for removing 
these undesirable components from tobacco smoke. These filters, which 
normally consist of a bundle of cellulose acetate, convoluted crepe paper, 
cotton, or combinations of these products formed into a cylindrical plug, 
are designed to and do remove varying proportions of the liquid-solid 
particles passing through them, thereby greatly reducing the amount of 
undesirable materials reaching the smoker's mouth. This liquid-solid 
particle filtering action is accomplished by a combination of diffusional, 
impactive, and direct collision of the particles with the filter material. 
Upon collision the particles are retained in the filter by the surface 
attraction between the extremely small particles and the relatively large 
filter material. Thus, filters of this type are capable of removing 
varying percentages of tar and nicotine from cigarette smoke depending on 
the amounts of fibrous material compacted into them, their length, their 
resistance to draw, the surface characteristics of the fibers, and other 
factors. 
Most prior known fibrous filters show no selectivity for the removal of 
nicotine from the smoke of a cigarette, particularly when the tobacco 
involved is the conventional type used on domestic cigarettes. This type 
usually consists of a blend of bright, burley, and Turkish tobaccos with 
the bright ("flue cured") tobacco constituting the major portion of the 
blend. Filters of cotton, paper, or cellulose acetate fibers, when 
attached to such domestic cigarettes, always remove about the same 
percentage of nicotine from the smoke as they do tar. For example, if one 
of these filters removes 25% of the tar, it also removes about 25% of the 
nicotine; if it removes 40% of the tar, it also removes about 40% of the 
nicotine. Therefore, it can be said that these show no selectivity for 
removing nicotine over tar. 
It has been suggested that one way to make a fibrous filter of cellulose 
acetate, paper or cotton remove a higher percentage of nicotine than tar 
from cigarette smoke is to coat the fibers in the filter with acids and 
particularly with nontoxic, nonvolatile organic acids such as tannic acid, 
citric acid, glutaric acid and the like. However, such a technique leaves 
something to be desired from the standpoint of the taste of the filter. 
Also, in the case of filters of cellulose acetate fibers, the addition of 
an acid can cause hydrolytic degradation of the fibers on prolonged 
contact. As a result, acetic acid can be released from the filter giving 
it an objectionable odor and taste. 
U.S. Pat. Nos. 3,417,759 and 3,424,173 describe cigarette filter elements 
consisting of fibrous filters containing liquid additives (1,4 butanediol 
and 1,2,4 butanetriol respectively) that selectively remove nicotine from 
cigarette smoke. 
According the the present invention a convenient and effective method has 
been found by which a tobacco smoke filter can be constructed for the 
selective removal of nicotine from tobacco smoke. This method consists of 
coating or otherwise dispersing a particular coating compound on the 
filtering material from which the tobacco smoke filter element is formed. 
Therefore, this invention provides tobacco smoke filters which remove a 
higher percentage of nicotine than tar from tobacco smoke. Also, this 
invention provides additives for a tobacco smoke filter which impart to 
the filter an improved capacity for removing nicotine from tobacco smoke. 
DESCRIPTION OF THE INVENTION 
According to the present invention, there is provided a tobacco smoke 
filter adapted to remove certain undesirable components from tobacco 
smoke. The filter comprises a bundle of continuous filaments having a 
coating on the surfaces thereof comprising a compound of the formula 
##STR3## 
wherein R.sub.1 is the residue of a straight chain fatty acid having 8-22 
carbon atoms and R.sub.2 is OH or 
##STR4## 
wherein Ac is an acetyl group, said compound having an iodine value of 
about 20-40, and being present in an amount of about 1-10% based on the 
weight of said filaments. 
Where R.sub.2 is OH, the compound is a monoglyceride and where R.sub.2 is 
the indicated structural group, the compound is diacetyl tartaric acid 
ester of monoglycerides. 
Conventional tobacco smoke filter material may be used such as fibrous 
products of cotton, paper, regenerated cellulose, cellulose acetate, 
polyolefins or any other suitable fibrous carrier medium having large 
surface areas that can be coated. However, the preferred carrier for these 
are the surface of cellulose acetate fibers in the form of crimped tow. 
These fibrous filter products are commonly formed into a bundle of about 
4000 to 35,000 filaments of a denier of about 16 to about 1 and having 
about 4-40 crimps per inch formed into a cylindrical rod, wrapped with a 
covering such as paper, cut into individual cigarette filters and 
subsequently joined to the cigarette. 
Coating compounds defined structurally above include partially saturated 
monoglycerides and diacetyl tartaric acid esters of partially saturated 
monoglycerides. The partially saturated monoglycerides have iodine values 
of about 20-40, preferably about 25-35. Such monoglycerides are prepared 
in a conventional manner by the glycerolysis of oils or fats which contain 
mixtures of partially saturated straight chain fatty acids having 8-22 
carbon atoms. Common oils and fats include lard, tallow, cottonseed oil, 
palm oil, soybean oil, peanut oil, corn oil, sunflower oil and the like. 
Edible beef tallow is preferred because it contains acids having the 
preferred degree of saturation or iodine value. 
The term "monoglyceride" as used herein is intended to include blends which 
contain quantities of diglycerides and triglycerides. Normally, 
monoglycerides will contain up to about 40% diglycerides and 
triglycerides, but it is preferred that blends contain at least 90% 
monoglycerides. 
The diacetyl tartaric acid esters of monoglycerides may be prepared in 
conventional manner by reacting diacetyl tartaric acid anhydride with 
monoglycerides. Diacetyl tartaric acid anhydride may be prepared in 
conventional manner by reacting acetic anhydride with tartaric acid. Such 
reactions and techniques are well known in the art. See, for example, U.S. 
Pat. No. 2,938,027. 
Commercially available coating compounds described structurally above 
include Myverol 18-30 emulsifier (monoglyceride) and Myvatem 30 dispersing 
aid (diacetyl tartaric acid anhydride ester of monoglyceride), both 
marketed by Eastman Chemical Products, Incorporated. Myverol 18-30 
emulsifier is a monoglyceride prepared by glycerolysis of tallow. Myvatem 
30 dispersing aid is the diacetyl tartaric acid ester of monoglycerides 
which have been prepared by glycerolysis of tallow. Both have iodine 
values of about 30. 
The coating compound may be applied to the filter material by conventional 
means. It may be applied as a solution, emulsion, melt, etc. Application 
from a solution is preferred. The coating compound may be applied by 
brush, roller, spraying, or any means known in the art. 
The amount of additive needed to selectively remove the nicotine from the 
effluent stream of tobacco smoke has been found to be between 1 and 10% by 
weight of the filter material. Amounts greater than 10% tend to make the 
filter plug wrap "greasy" and interfere with the adhesives used to bond 
paper wrap on the filter. 
As will be appreciated, the addition of the distilled monoglyceride 
derivatives to a filter does not preclude the possibility that other 
liquid additives can be added to it for other purposes. For example, in 
the case of filters made from a crimped tow of cellulose acetate fibers it 
is highly desirable that this material be treated with certain high 
boiling plasticizers prior to the final rod formation to impart rigidity 
to the filter rod. Thus, it is common to use such room temperature bonding 
agents as glycerol triacetate or polyethylene glycol diacetates for this 
purpose. In such a case, this additive can be incorporated in the 
plasticizer and heated to 35.degree. C. and applied by conventional filter 
making equipment to the filter. The additive has little or no effect on 
the bonding properties of the plasticizer.

The following examples are submitted for a better understanding of the 
invention. 
Tobacco smoke filters are prepared on a production-type filter making 
machine equipped with a brush applicator of the type commonly used to 
apply plasticizer to cellulose acetate tow. The brush applicator is fitted 
with electric heaters to maintain the applicated solution at 50.degree. C. 
The plasticizer mixtures shown in Table I are applied to crimped 3.0 
denier per filament 35,000 total denier cellulose acetate filter tow and 
converted to cigarette filter rods. All the finished filter rods contain 
8% glycerol triacetate and either 1%, 2%, or 3% of the additives depending 
on which plasticizer-additive mixture is used. The filter rods are cut 
into 21 mm tips and attached to 63 mm tobacco columns from domestic filter 
cigarettes. The assembled cigaretes are conditioned for 48 hours at 60% 
relative humidity (72.degree. F.) before being smoke tested. 
The cigarettes are smoke tested in accordance with the procedure described 
in the Federal Trade Commission's Report of Tar, Nicotine, and Carbon 
Monoxide Content of the Smoke of 187 Varieties of Cigarettes (April, 
1981). The nicotine content of the smoke is measured by the gas 
chromatographic procedure described by Mumpower and Kiefer in Tobacco 
Science XI, 144-147 (1967). Additional cigarettes are smoked and the 
cambridge filter pads (collected smoke) are slurried in water for 
subsequent pH measurements. The percent tar and nicotine removed by the 
filters is calculated using the following formulas: 
##EQU1## 
A summary of test data is shown in Table 2. The test data shows that the 
filter with 2 and 3% of the additives removes significantly higher amounts 
of nicotine than tar from the test cigarettes without a measurable effect 
on the smoke pH. Smoke pH should not change appreciably due to the filter. 
The control cigarettes contain only triacetin on the filters. 
TABLE 1 
______________________________________ 
Plasticizer-Additive Mixtures 
______________________________________ 
1. 88% Glycerol triacetate 
12% Myvatem 30 dispersing 
agent 
2. 80% Glycerol triacetate 
20% Myvatem 30 dispersing 
agent 
3. 70% Glycerol triacetate 
30% Myvatem 30 dispersing 
agent 
4. 88% Glycerol triacetate 
12% Myverol 18-30 emulsifier 
5. 80% Glycerol triacetate 
20% Myverol 18-30 emulsifier 
6. 70% Glycerol triacetate 
30% Myverol 18-30 emulsifier 
7. 100% Glycerol triacetate 
______________________________________ 
.sup.1 The mixtures are not miscible at room temperature, however, when 
heated above 35.degree. C. all samples were miscible. 
TABLE 2 
______________________________________ 
Summary of Test Data 
Tar Nico- 
Additive.sup.1 
(T) tine (N) % T % N N/T pH 
______________________________________ 
Available from 
30.1 2.02 .0670 
5.95 
unfiltered 
cigarettes 
3% Myverol 18-30 
16.9 1.00 44 50 .0593 
6.2 
emulsifier 
2% Myverol 18-30 
17.2 1.09 43 46 .0636 
6.2 
emulsifier 
1% Myverol 18-30 
17.3 1.23 42 39 .0696 
6.2 
emulsifier 
Control filter 
17.4 1.21 42 40 .0696 
6.2 
cigarette with- 
out additive 
3% Myvatem 30 
17.8 1.11 41 45 .0621 
6.3 
dispersing agent 
2% Myvatem 30 
17.4 1.18 42 42 .0677 
6.2 
dispersing agent 
1% Myvatem 30 
17.5 1.27 42 37 .0726 
6.1 
dispersing agent 
______________________________________ 
.sup.1 All filters are 3.0 D/F 35,000 T.D. tow containing 8% triacetin an 
indicated amount of additive. 
The iodine values specified herein are measured in accordance with AOCS 
Official Method Cd 125 (rev. April 1956). Official and Tentative Methods 
of the American Oil Chemists Society, 2nd ed., additions and revisions 
1947 through 1963, inclusive. 
Unless otherwise specified, all parts, percentages, ratios, etc., are on a 
weight basis. 
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.