Recycling cellulose esters from the waste from cigarette manufacture

A process for recycling waste from the manufacture filtered cigarettes is disclosed herein. The process comprises the following steps: A waste stream from the manufacture of filtered cigarettes is provided. The waste stream includes tobacco, cellulose ester polymer, and paper. A substantial portion of the cellulose ester polymer is separated from this waste stream. This cellulose ester polymer is contacted with a sufficient volumne of fluid to extract contaminants therefrom. The fluid is under pressure and temperature conditions, such that the fluid is a supercritical or a near supercritical fluid.

FIELD OF THE INVENTION 
This invention is directed to recycling waste, particularly cellulose 
esters, generated during the manufacture of filtered cigarettes. 
BACKGROUND OF THE INVENTION 
Fibrous cellulose esters, particularly cellulose acetate, are the 
commercially preferred media for filtration of smoke from filtered 
cigarettes. This commercial application consumes worldwide several hundred 
million pounds of cellulose acetate fiber per year. During the production 
of these filtered cigarettes, a certain percentage of them will not be 
brought to market, due to damage of goods, variation from specifications, 
or other reasons. Those cigarettes which are not sold are typically 
subjected to a reclamation process wherein the tobacco-laden portion of 
the cigarette is mechanically broken from the filter, and the tobacco is 
removed by shaking within a screening device. An example of this process 
is given in U.S. Pat. No. 3,224,451, which is incorporated herein by 
reference. After reclamation of tobacco, several tens of millions of 
pounds of residual material, referred to as "ripper waste" in the 
industry, comprised of cellulose acetate (typically plasticized for 
example with glycerol triacetate), paper, residual tobacco, and often 
flavors and fragrances remain; this ripper waste is most generally 
disposed of as landfill, representing both a loss of natural resources and 
a burden on landfill capacity. 
The composition of "ripper waste" varies depending on the specifics of the 
cigarette products and the tobacco reclamation process employed. Typical 
composition ranges, by weight, of ripper waste are: a) cellulose acetate, 
40-55%; b) plasticizer, 1-12%; c) paper, 25-45%; d) residual tobacco, 
1-15%; e) adhesives, 2-3%; and f) flavors/fragrances, &lt;1%. Additional 
components for example charcoal, may be found in these waste streams, 
depending on the specific cigarette product. 
The physical/mechanical separations employed in reclaiming cigarette 
components have in the past either focused on sifting tobacco away from 
other components, as is the case in U.S. Pat. No. 3,224,451, or in the 
removal of cellulose acetate filter media from its paper liner, as in U.S. 
Pat. No. 4,261,790, which is incorporated herein by reference. Other 
approaches have included enzymatic degradation of the cellulose acetate to 
produce useful sugars, as in U.S. Pat. No. 4,298,013. 
Isolation of cellulose acetate from "ripper waste" is insufficient to 
provide a recycled product of high commercial utility. During the 
manufacture of cigarettes, the cellulose acetate is treated with a 
plasticizer which improves the mechanical performance of the finished 
filter. The cellulose acetate may also be treated with flavorants, for 
example, menthol, and the cellulose acetate will absorb some levels of 
nicotine and other substances from the tobacco. If the cellulose 
acetate/plasticizer/flavors mixture is dissolved in a typical cellulose 
ester solvent, and reformed into a product, these extraneous substances 
will change both the mechanical and the sensory properties of the 
cellulose acetate, thereby reducing the overall quality of products 
manufactured with these recycled materials. Extraction with conventional 
solvents, such as ethanol, can be used to remove the majority of 
undesirable contaminants from cellulose acetate. But, the extraction 
solvents then becomes an undesirable contaminant, and reduces the product 
quality. An additional difficulty introduced by use of such extraction 
solvent is that they can escape into the environment, necessitating costly 
preventative measures. 
Supercritical and near supercritical fluids have previously been described 
for the extraction of: removal of adhesives from cellulose (See, U.S. 
5,009,746); terpenes and oils from wood (See, U.S. Pat. No. 4,308,200); 
lignin from Kraft streams (See, U.S. Pat. No. 4,493,797); and removal of 
the natural oils from plant matter (See, U.S. Pat. No. 4,675,198). 
Commercial applications of this technique include: the decaffination of 
coffee and tea; extraction of hops flavors for beer manufacture; and 
denicotination of tobacco. Such commercial processes are well known to 
those skilled in the art and are described in reviews such as: McHugh and 
Krukonis, Supercritical Fluid Extraction: Principles and Practice, 
Butterworths; (1986); Eckerd et al., Environmental Science and Technology, 
Vol. 20, pp. 319-325, (1986); "Supercritical Fluids", Kirk-Othmer 
Encyclopedia of Chemical Technology 3rd, John Wiley & Son, New York, each 
of the foregoing are incorporated herein by reference. 
While the supercritical extraction of natural products from cellulose is 
described U.S. Pat. No. 5,009,746, it does not describe the removal of 
polymeric additives and impurities from cellulose acetate. Those familiar 
with the chemistry, binding properties, and solution properties of both 
cellulose acetate and cellulose will recognize that these two structural 
polymers share few common properties, and, therefore, must therefore be 
treated as different materials. See, "Cellulose" and "Cellulose Acetate" 
Kirk-Othmer Encyclopedia of Chemical Technology 3rd, John Wiley & Sons, 
New York, both of which are incorporated here in by reference. 
SUMMARY OF THE INVENTION 
A process for recycling waste from the manufacture of filtered cigarettes 
is disclosed herein. The process comprises the following steps: A waste 
stream from the manufacture of filtered cigarettes is provided. The waste 
stream includes tobacco, cellulose ester polymer, and paper. A substantial 
portion of the cellulose ester polymer is separated from this waste 
stream. The cellulose ester polymer is contacted with a sufficient volume 
of fluid to extract contaminants therefrom. The fluid is under pressure 
and temperature conditions, such that the fluid is a supercritical or a 
near supercritical fluid.

DETAILED DESCRIPTION OF THE INVENTION 
The present invention, which is directed to a process for recycling the 
waste from the manufacture of filtered cigarettes, is set forth in greater 
detail below. 
The waste stream from the manufacture of filtered cigarettes comprises 
generally tobacco, paper, and cellulose ester filter material This waste 
stream maybe "ripper waste" as discussed above, or maybe the entire broken 
filtered cigarettes (the differences between the latter and the former 
being that the latter would have a greater tobacco content). The cellulose 
ester filter material typically comprises a fibrous form of cellulose 
acetate, which is referred to in the industry as "TOW" and various 
"contaminants" discussed below. 
The cellulose ester filter material or polymer generally comprises 
cellulose acetate (acetyl value of about 40.3%), but may also include 
other conventionally known or commercially available cellulose esters. The 
cellulose acetate filters are typically "contaminated" with plasticizers, 
adhesives, and flavors/fragrances during the manufacture of both the 
filter tips and the filtered cigarettes. Exemplary plasticizers include, 
but are not limited to, triacetin (also known as glycerol triacetate), 
trimethylene glycol diacetate (also known as TEGDA), and mixtures thereof. 
Exemplary adhesives include, but are not limited to, polyvinyl acetate 
(PVA), ethylene vinyl acetate (EVA), cellulose acetate, and mixtures 
thereof. The flavors/fragrances may be absorbed by the filter material 
from the tobacco, for example, nicotine, or may be added, for example, 
menthol. Prior to recycling the "contaminated" ester polymer with "virgin" 
cellulose ester polymer, the contaminants must be removed or significantly 
reduced. 
Preferably, before the contaminants are removed from cellulose ester 
polymer, the cellulose ester polymer is removed from the waste stream. The 
weight content of tobacco in the cellulose ester polymer, after the 
separation, should be less than about 1% by weight. Optimally, the weight 
content of tobacco in the cellulose ester polymer should be less than 
about 0.1% by weight. 
Any conventional means maybe used for separating the cellulose ester 
polymer from the waste stream. Exemplary methods include: manually 
separating tobacco and paper from the cellulose ester polymer; screening 
or sifting paper and tobacco from the cellulose ester polymer; and 
cycloning or elutriating the paper and tobacco from cellulose ester 
polymer. Elutriation by air is the preferred method for separating the 
cellulose ester polymer from the waste stream. 
Optionally, the waste stream, either before or after the foregoing 
separation, maybe subjected to any conventional particle size reduction 
process. These particle size reduction process facilitate separation, as 
well as, the extraction, as is known to those of ordinary skill in the 
art. Such processes include, but are not limited to, grinding, chopping, 
milling, and pelletizing. 
The contaminants are cleansed from the cellulose ester polymer by 
contacting the polymer with a sufficient volume of fluid to extract the 
contaminants therefrom. The fluid is under pressure and temperature 
conditions, so that the fluid is a supercritical or a near supercritical 
fluid. 
A supercritical fluid exists at or above its "triple point". The triple 
point is the temperature and pressure at which the solid, liquid, and 
vapor (gas) of a substance are in equilibrium with one another. A 
supercritical fluid possesses approximately the penetration properties of 
a gas simultaneously with the solvent properties of a liquid. Accordingly, 
supercritical fluid extraction has the benefit of high penetrability and 
good solvation. Exemplary fluids included, but are not limited to, carbon 
dioxide and propane. Other fluids are listed in the "Supercritical Fluids" 
section of Kirk-Othmer, Ibid., at Table 2, which is incorporated herein by 
reference. The preferred fluid is carbon dioxide which has a triple point 
at 30.degree. C. and 72.9 atmospheres (about 1072 psig). 
In the preferred embodiment, cellulose ester polymer is contacted with 
carbon dioxide within the pressure ranges of about 1400 psia to about 
10,000 psia and within the temperature range of about 20.degree. C. to 
about 80.degree. C. 
The supercritical or near supercritical fluid extracts the contaminants 
from the cellulose ester polymer. This remaining cellulose ester polymer 
is of sufficiently good quality that it can be resolvated and used as 
"virgin" polymer or with "virgin" polymer. However, if necessary, this 
recycled polymer could be subjected to further separation if residual 
tobacco or paper remain. The contaminants which are held in the fluid are 
released when the fluid is expanded. The contaminants are then collected 
and disposed of. The expanded fluid may be compressed and then recycled 
back into the process. 
Without limiting the foregoing invention, in any manner, it is further 
illustrated by way of the following examples. 
EXAMPLE 1 
This example illustrates the separation of the waste stream, i.e. "ripper 
waste" from a cigarette manufacturing operation. The waste stream 
comprised, in major components, tobacco, paper and filter tips (fibrous 
cellulose acetate). A total of 295 pounds of this waste was separated into 
its three major components. The final weight of each component stream is 
as follows: 66.5 pounds-- tobacco; 65 pounds--paper; and 163.5 
pounds--filter tips. 
The separation was accomplished by means of air elutriation. A commercially 
available elutriator, Sterling Model 1608EL from Sterling Blower Company 
of Lynchburg, VA, was used. It was operated with air at 5000 feet per 
minute. 
295 pounds of waste product was introduced into the elutriator for a first 
pass of separation. At the end of this pass, a mixture of 61 
pounds--tobacco and 48 pounds--paper was removed from the remaining mass. 
The mixture of tobacco and paper was separated into its components by use 
of a conventional shaker screen device, as is well known. 
The remaining mass was reintroduced into the elutriator for a second pass. 
At the end of this pass, a mixture of 5 pounds --tobacco and 10 
pounds--paper was removed and farther resolved into components by the 
shaker screen method noted above. 
The remaining mass from the second pass was reintroduced into the 
elutriator for a third pass. At the end of this pass, a mixture of 0.5 
pounds tobacco and 7 pounds paper was removed and separated as before. The 
remaining mass, which weighted 163.5 pounds, consisted primarily of filter 
tips, but included trace amounts of tobacco and paper as was apparent by 
visual inspection. 
EXAMPLE 2 
The waste product with tobacco and paper removed, for example in the manner 
set forth in Example 1, consisted substantially of filter tips from 
cigarettes. The contaminants in this material were removed via an 
extraction technique using supercritical carbon dioxide. 
The filter tip waste, prior to extraction, was analyzed to quantify 
contaminant levels. Using conventional gas chromatography techniques, the 
amount of plasticizer (glycerol triacetate) was measured at 7.59% by 
weight. Using industry acceptable techniques, the samples were observed to 
possess a strong tobacco odor and taste. 
The range of conditions for the extractions are set forth in Table 1. 
Additionally, a weight ratio of carbon dioxide:cellulose acetate of 120:1 
was utilized. 
TABLE 1 
______________________________________ 
Weight of Sample 
Weight 
Serial 
Temperature 
Pressure Loaded Fraction 
No. (.degree.C.) 
(psia) (gms) Extracted 
______________________________________ 
A-1 45 2000 2.4136 0.08734 
A-2 3000 2.2810 0.09698 
A-3 4000 2.6014 0.09349 
B-1 80 2000 2.5298 0.08546 
B-2 3000 2.4800 0.08952 
B-3 4000 2.5826 0.09820 
B-4 4000 1.2654 0.09278 
B-5 4500 1.2916 0.10514 
C-1 80 1500 2.2852 0.04551 
C-2 3000 2.3222 0.08888 
C-3 4000 2.3908 0.10013 
______________________________________ 
After extraction, samples, when analyzed by the foregoing techniques, 
showed no trace of the plasticizer (detection limit of the instrument was 
0.0001%) and no trace of the odor nor the taste.