Note: Descriptions are shown in the official language in which they were submitted.
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PRnt~F..S!~lN(~ Cn~TlNll()ll!~l,Y-FXTR11nET~ TOBACCn-
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~n~TAININ~ ~ATFRIAL
The ~resent invention relates to the ProcessinR of continously-
extruded tohacco-contain~n~ material to enahle smokin~ articles to
be manufactured from such material.
One examDle of the formation of smokin~ articles hy extrusion
is described in ~.S. Patent Specification 4~51n~95n~ The smokinR
article described in that specification is tYPically sl~hstantially
cylindrical and is extruded under conditions such that the water in
the wet blend fed to the extruder die is converted to steam, therehy
foamin~ the article. The article is monolithic, that is, it is
extruded as a sin~le strand with a diameter of tYPicallY about ~mm
if the article is a ci~arette.
Another aDDroach is to extrude the wet blend out of a die
havinR a pluralitY of small apertures to form an extruded, coherent,
multistrand, tohacco-containinR, ~enerallv cvlindrica] smokinR
article comPrisin~ a plurality of co-extruded strands that extend
~enerally alonR the lonRitude of the smokin~ article and are
adhered to one another, preferably randomlv, so as to leave flow
passaRewavs between the strands alon~ the lon~itude of the smokin~
article. This approach is disclosed in a European patent
aPplication published under No.EP-A-016737~ on 8th January 1986.
The confi~uration of the strands and passa~eways of these foamed
areicles provide sufficient heat transfer area or sufficient
residence time or both for the hot Rases drawn towards the
proximal end of the smokin~ article by a smoker to cool and to exit
the proximal end at a temperature comfortable for the smoker.
These foamed, extruded tobacco materials are formed from
tobacco particles, binder, water, and optionally fillers or other
desired additives. They are Renerally hot, moist, soft, and
flexible thermoplastic-like materials as they exit the die. The
temperature of the extruded materials is tYpically in the ranRe from
4~-15n~C. Workin~ the tobacco-containin~ material at too hiRh a
temperature can result in overworkin~ or cookin~ of the material,
which de~rades the quality of the product. ~xtrudinR the materisl
at too low a temDerature will not foam the material at typical
~;~
:~S~3
2 --
extruder pressllres, resultin~ in too dense a product. The moisture
content, measl1red in terms of oven volatiles or ~V, is tYpicallY in
a ran~e from 15 to 5n%, dependin~ on the product formu]ation and
proce~ss conditions. This moisture content is above the tobacco
equllibrium content of about 1~-~5~. The terms "moisture content"
or OV refers to the liquid in which the tobacco and other materials
are mixed beFore extrusion. TYr)icallv, the liquid is water, but
orRanic or alcoholic liquids msv be used.
~ uch continuouslv formed foamed rod-like extruded materials are
too ho~, moist, and pliable to be formed directlY into smoki~R
articles at hi~h rates of speed bY, for examPle, passin~ the rods
into an automated smo~in~ article "maker" machine such as a ~ark 8
CiRarette Maker manufactured bv the Molins ~ompanY or the like.
These materials do not have enou~h structural inte~rity to be
wrapped and formed into smokin~ articles without further processin~.
The known methods of post extrusion ~rocessin~ of extruded
materials include dryin~ the extruded materials to reduce the OV to
about the equilibrium ~V of tohacco. DrYinR occurs commnonly by
allowinR the liquid used in the pre-extruded slurry, e.~., water or
other agents such as alcohols that aid in evaporation, to evaporate
in air at atmosPheric or reAuced pressures. In some cases suction
devices mav be used to remove the solvent before drYinR. In other
cases, the extruded materials are dried by infra-red heaters, steam,
or hot air, in a conventional dryinR oven.
The fore~oinR techniques are inadequate for commercial
utilization of continuouslY extruded materials, particularly
foamed extruded materials, because they require lon~ periods of
time to reduce the OV to the desired level. These techniques
require stora~e facilities or dryin~ ovens ~which can extend
hundreds of feet) to sufficientlv drv the material, each of which
are impractical and costly to maintain in a commercial operation.
With verv slow rates of dryin~ or low temperature dryin~, a foamed
structure can collapse under its own wei~ht, develop undesirable
flat spots a~ainst a supportinR structure, or otherwise result in
a product havin~ a non-uniform density. This adversely affects
the burn qualities and consumer acceptance of the smokinR article.
Attempts to heat raPidly the materials, particularly foamed rods,
I
il
reslllt in case hardeninR the outer portions o~ the extruded
materia], which in turn inhihits the interior section from drvin~
sufficientlY. ~ase hardenin~ can increase the drvin~ time by an
order of ma~nitude, e.~. from minutes to hours, or hours to davs.
nver-drvin~ the exterior to drY the interior can result in a brittle
product that crumbles when manipulated. Over-drvin~ also can lead
to a wrinkled or cracked Droduct or an undulv stiff ~roduct, each of
which is unaccentahle to the consumer.
In accordance with the present invent;on a method of processin~
continuouslv-extruded tobacco-containin~ material wherein the
extruded material comin~ from the extrusion die is drled by exposure
to microwave ener~v is characterized in that the 0~ level of the
extruded material is reduced by the microwave dryin~ to a level at
or below the eaullibrillm n-~ level and the extruded material is
subsequentlv cooled so that the surface temDerature is decreased
substantially below the bulk temperature, therebv providin~ the
extruded material with a structure adequately ri~id and stable
dimensionallv for formin~ into smokin~ articles.
The present invention is directed to drvin~ and coolin~
extruded tobacco-containin~ smokin~ materials rapidly, under
conditions that will enable the extruded material to be passed
directlv from the extruder die to aPParatus for formin~ the
smokin~ material into the desired product. The invention
apPlies to both foamed and unfoamed tobacco-containin~ extruded
material.
The extruded material is first dried to volatize the water or
other liquid Present in the extruded material and thereby reduce the
moisture content to a level at about or preferably below the equil-
ibrium OV level of the tobacco-containin~ product. Dryin~ also can
initiate or continue a foamin~ operation, when used, by volatizin~,
~assifyin~, or decomposin~ any a~ent present used to foam the
extruded material. Foamin~ is a result of the moisture, other
foamin~ a~ent, or ~as within the extrùdate chan~in~ from a super-
heated liquid or comPressed ~as to a ~as at essentially atmospheric
.
4-
pressure either as the extruded material leaves thehigh-pressure environment behind the die inside the
extruder and enters the atmospheric environment just
downstream of the die openings, or after extrusion,
by passing the material through a drying chamber for
heating the material so that it foams. The resulting
dried material is a hot and pliable thermoplastic
material which may be tacky on contact.
After drying, the material is immediately
cooled to lower the temperature of the extruded
material. Two temperature definitions used herein
are (1) surface temperature, :i.e., the temperature
detected at the surface of the extruded material;
and (2) bulk temperature, i.e., the average tempera-
ture of a selected quantity of the tobacco material
mass after equilibration in a calorimeter. Cooling
the dried extruded material requires reducing the
bulk temperature at least somewhat and the surface
temperature substantially to give the extruded
material an adequately rigid structure, to substan-
tially minimize the tackiness of the surface, and to
dimensionally fix or se~ the extruded material for
subsequent forming by the maker apparatus.
The temperature to which the e~truded
material must be cooled to obtain an adequately rigid
structure is a function of the specific ingredients
of the thermoplastic tobacco-containing mass and the
rate of cooling, and will generally be between about
-196C and 85C for the surface temperature, and
between about 20C and 90C for the bulk temperature.
In general, the more cooling achieved, the firmer
and better the resulting product. Limits on cooling
are principally equipment limitations, the heat
capacity of the cooling medium applied and how good
an insula~or t~e ex~r~ded material is. ~he dried
~S~3
and cooled mass will likely continue to change dimen-
sions very slightly as it equilibrates with ambient
or other controlled conditions.
Preferably, cooling reduces the bulX tem-
perature to about, and the surface temperature suf-
ficiently below, the glass tran~ition temperature of
the material to provide a case hardened periphery
that is semi-rigid for easy handling by automatic
maker machines. Unlike the prior art methods, such
a case hardening does not interfere with drying the
interior of the material or the equilibration of the
finished smoking product to the desired conditions
because the material is about equilibrated (except
thermally) before it becomes case hardened.
Further, cooling the material below the
volatization temperatures for the flavor generating
components also may prevent certain flavors, both
natural in tobacco and added, from volatizing during
a long cooling down period. This enhances the sub-
jective characteristics of the finished article.
~ith foamed materials, the surface and bulk tempera-
tures are preferably lowered to below the flash point
of the particular foaming agent used, thereby halting
any foaming action caused by drying or residual heat
stored in the extruded material during the drying
step.
The cooled, dried material may then be fed
directly into apparatus for producing the desired
smoking article. In one embodiment, the tobacco-
containing material could be extruded as a sheet
which is dried, cooled, and cut up for use as tobacco
filler like conventional tobacco leaf or reconsti-
tuted tobacco. Alternately, and preferably, the
material could be extruded in a rod-like shape hav-
ing a cylindrical, cross section and passed directly
from the cooling apparatus into the garniture of a
commercially available maker. Optionally, the
~;~52~.3
(
material may be wrapped with cigarette or cigar
wrapper or coated with a formulation capable of
forming an outer sheath using coextrusion or post
extrusion techniques, before being fed to the maker.
A primary advantage of the present inven-
tion is the ability to process the hot pliable
extruded material into a material that can be formed
into a smoking article on a continuous basis.
In one embodiment, the tobacco containing
material includes particles of tobacco mixed in a
medium such as water to form a slurry which
is extruded, and microwave energy is used to dry the
extruded material substantially uniformly throughout
the material as it passes through an appropriately
dimensioned microwave cavity. The cavity dimensions
and microwave frequency are preselected to obtain
the required depth of penetration for the given cross
sectional area and configuration of the material to
excite and volatize the medium and thereby
dry the extruded material. The energy level pr~pa-
gated into the cavity is selected based on the rate
of advance of the extruded material, the exposure
time and OV ~or amount of medium) in the
extruded material as it enters the drying cavity and
the desired OV as it exits the cavity. Optionally,
vents may be provided in or adjacent to the microwave
drying cavity to exhaust the steam or other vaporized
materials generated by the drying action. Thus, the
extruded material is dried uniformly, with the vapors
generated from the interior portions replenishing
the moisture vaporized from the surface regions to
give the material a substantially uniform density
while reducing the overall OV level to the desired
level without case hardening or embrittling the
extruded material.
In a preferred embodim~.~t, two spaced apart
microwave c~vities may be used in tandem to dry the
~5~ 3
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material passing therethrough. Using two cavities
permits venting the vapors between the cavities as
well as the input and outputs to the drying section,
and permits more precise control over the energy
level applied to dry the material. Further, the
spacing between the cavities can be adjusted to per-
mit the material to equilibrate somewhat between
microwave exposures. Also, the orientation of the
microwave cavities can be selected, for example, to
be oriented in parallel, or with one cavity rotated
about the axis of the extruded material relative to
the other cavity to better average the microwave
energy and modal power distribution within the ex-
truded material. Thus, using two or more microwave
cavities permits drying the material more evenly
with somewhat greater control than would be possible
with a single microwave drying chamber.
Following the drying step, the extruded
material is cooled. In one embodiment, the extruded
material is passed through a cooling cavity flushed
with refrigerated air, preferably exchanged contin-
uously. Ambient air also may be included in the
airflow. Refrigerated air, when used, may be gen-
erated by, for example, a conventional air condi-
tioning system, passing ambient air over cooling
coils chilled to about 4~, dry ice, or the like.
The temperature of the refrigerated air is selected
in view of the rate of speed of the extruded material
and total exposure time in the cooling chamber to
reduce the surface and bulX temperatures of the ex-
truded material sufficiently to fix dimensionally
the material for subsequent handling. Thus, the
material must be cooled to be adequately rigid for
feeding directly to a wrapper and maker apparatus to
make smoking articles.
The extruded material ~ay be advanced
through the cooling chamber by rneans that will permit
~P~520f~3~3
cooling of the extruded material, preferably by a
perforated supporting belt or opposing belts per-
mitting continuously exchanged refrigerated (and
optionally ambient) air to contact the hot extruded
material. Alternately, an air cushion could be used
to support the extruded material as it passes thro~lgh
the cooling chamber. Other conventional conveyance
means also could be used.
In another embodiment, the cooling step
could be conducted by passing the extruded material
through a tunnel having a plurality of air jets so
that air exiting the jets at high velocity impinges
on the surface of the extruded material. The high
velocity air acts to remove the solvent or water and
cool the extruded material sufficiently.
In another embodiment, the cooling step
could be conducted by contacting the hot extruded
material with a cooled member, such as one or more
cooled rollers, a continuously advanced cooled belt,
or cooled particulates. In yet another embodiment,
cooling could be achieved by contacting or spraying
the hot extruded material with a li~uid, such as
water or alcohol, nitrogen, or a solid, such as dry
ice particles, that will vaporize on contact (sub-
stantially without being absorbed) and thereby cool
the material. In yet another embodiment, cooling
could be achieved by passing the material through a
cryogenic chamber that contains, for example, liquid
nitrogen. In any case, the contacting temperature
or quantity of cooling material applied is selected
in view of the overall residence time to provide the
desired uniform cooling. Any of the foregoing methods
could be used singly or in combination, as necessary
to cool rapidly the exterior surface temperature of
the extruded material to provide a structure that is
sufficiently stiff to pass the prod~t through a
cigarette type maker device. Fllrther, the cooling
~5~3
g
chamber could be at least partially evacuated to aid
in cooling.
DETAILED DESCRIPTION OF THE DRAWING
The Figure is a schematic view of an embod-
iment of the tobacco processing apparatus of this
invention.
DETAILED DESCRIPTION OF T~E INVENTION
Referring to the Figure, an illustrative
embodiment o~ the tobacco processing apparatus of
the present invention is shown. ~he apparatus of
the present invention includes drying cavity 2, and
cooling chamber 3, placed in tandem, downstream of
extruder 1 and the output of extruder barrel 13, and
upstream from smoking article forming device 4.
Finely divided tobacco materials are input to input
port 12 of extruder 1 at a controlled rate, from
supply 7. Binder materials also are input to input
port 12 of extruder 1 at a controlled rate. Water,
from water supply 11, is input to extruder barrel 13
as necessary to maintain the desired moisture content
in the mixing cha~'oer. In other embodiments, the
materials are mixed in a different order and fed to
different input ports as discussed elsewhere herein
in connection with prehydration mixing techniques.
A means for advancing extruded material 20 through
drying cavity 2 and cooling chamber 3 is provided.
The advancing means is preferably adjusted to advance
extruded material 20 at the selected rate of extru- ¦
sion with substantially no relative movement between
extruded material 20 and the contacting or support-
ing member o~ the advancing means. Alternately there
may be some relative movement where constant tension
on or compression of ~he extruded material is
desirable.
--.1 o--
` The advancing means may comprise one or
~'! more conveyor belts operating at the same linear
speed. The conveyor may be a supporting belt, a
single belt that is folded about to envelope the
extruded material, or opposing belts configured to
retain and advance the material. Following the
cooling section, puller means 5 may be used to feed
and advance the leading edge of extruded material 20
into extruded material receiving funnel 14 attached
to the inp~t of conventional smoking article maker
device 4. Puller 5 may be disengaged once the
extruded material is advancing directly into maker
device 4.
The method of the invention comprises dry-
ing the wet and pliable extruded tobacco-containing
material in drying means 2 to about or below the
ambient or other controlled level of moisture for
the tobacco-containing material, cooling the dried
extruded material in cooling means 3 to lower the
surface temperature of the extruded material below
the bulk temperature to form the tobacco containing
material into an adequately rigid material that can
be wrapped and severed cleanly into smoking articles.
The surface temperature is typically lowered to
between about -196~C and 85C and the bulk temperature
lowered to between about 20C and 90C. Cooling
provide~ ~he surface that extends about the periphery
of the extruded material with a case hardened semi-
rigid structure so that it can be thereafter formed
into smoking articles by maker device 4.
In one embodiment, the method of the inven-
tion includes mixing ~ogether finely divided tobacco
materials, binder materials, water (or other solvent)
and other desired additives in extruder 1 to create ~
a thoroughly mixed slurry, extruding the slurry out
the die at the end of the mixing chamber or barrel 13
of extruder I to f~rm a cohosive extruded material,
preferably having a rod-like configuration, drying
the extruded material in drying ca~ity 2, cooling
the extruded material in cooling chamber 3, and
advancing the extruded material into maker device 4
for forming the desired smoking articles of, for
example, substantially uniform dimensions.
In the preferred embodiment, the method of
the present invention is adaptable for use in form-
ing foamed extruded smoking articles comprising
(a) from about 5 to about 98 wt.% of tobacco parti-
cles having a particle size of up to about 5 mesh,
(b) from 0 to about 60 wt.~ of a filler having a
particle size of up to about 350 ~, (c) from 0 to
about 1.0 wt.% of a residual foaming agent, ~d) from
about 2 to about 40 wt.% of a binder selected from
the groups of (1) cellulosic binders consisting of
hydroxypropyl cellulose, carboxymethyl cellulose and
its sodium, potassium, and ammonium salts, cross-
linked carboxymethyl cellulose and its sodium,
potassium, and ammonium salts, hydroxyethyl cellulose,
ethyl hydroxyethyl cellulose, hydroxypropyl methyl
cellulose, methyl cellulose, ethyl cellulose, and
mixtures thereof; or (2) natural binders, modified
natural binders, and synthetic binders consisting of
pectin and its ammonium, sodium, and potassium salts,~
starch, guar, chitin, chitosan, and derivatives
thereof, hemicellulose, xanthan, curdlan, a s~lt of
xanthamonas gum, carageenan, alginic acid and its
ammonium, sodium, and potassium salts, chitosan and
its water soluble salts, oxycellulose, polyvinyl
maleic acid polymer and its ammonium, sodium, and
potassium salts, micro-crystalline cellulose, dex-
tran, dextrin, malto-dextrin, fibrous cellulose, and
mixtures thereof; os (3) a mixture of cellulosic,
natural, mod.ified natural, or synthetic binders, all the
preceding ingredients being measured on a dry weight basis, and
(e) from about 5 to about 20 wt.& water, the article
~s~
-12
having a density within the range of from about 0.05
to about l.5 g/cc.
The tobacco used herein may be any type of
tobacco and will generally be comminuted tobacco
selected from the group consisting of bright, burley,
oriental, and mixtures thereof, comminuted reconsti-
tuted tobacco, comminuted st~ems, tobacco dust or
fines, and mixtures thereof. The tobacco may have
been previously subjected to a stiffening or expan-
sion process to increase its filling power. When
tobacco particle sizes greater than 35 mesh are
employed, it may be necessary to add a polyfunctional
acid, such as citric or phosphoric acid and their
ammonium, sodium, and potassium salts, during forma-
tion of the wet blend in order to achieve ~he desired
appearance and foaming of the extruded article. The
polyfunctional acid or its salts is added in an amount
such that the smoking article contains from about
O.l to about 15 wt.% thereof, preferably from about
2 to about lO wt.%. A typical binder combination is
5 wt.% hydroxypropyl cellulose, 2.5 wt.% carboxymethyl
cellulose, and 2.5 wt.% starch. Another typical
combination is 1 wt.% hydroxypropyl cellulose, 4 wt.%
hydroxypropyl guar and 5 wt.% starch.
The article may also include as a filler
any particulate material having a particle size of
up to about 350 ~m that is comp-atible with the other
components of the blend. The filler is preferably
selected from the group consisting of calcium
carbonate, magnesium carbonate, calcium oxide, mag- i
nesium oxide, calcium hydroxide, magnesium hydroxide, .
metallic aluminum, alumina, hydrated alumina, clay,
diatomaceous earth, silica, and mixtures thereof and ,!
preferably is calcium carbonate. -
The dried or equilibrated smoking article
contains from about 5 to about 2~ OV, preferably
from .bout B to about 1~ wt . %.
~z,5~ 3
.: . ,~
The smoking article comprises a porous
structure that permits static burning and the passage
of smoke (gas/aerosol) through the article to the
smoker. The density of the article is related to
the porous structure and the open cellular structure
created in a single strand extruded product, or the
voids created between the strands in a multistranded
extruded product, and an article having a density
within the specified range and having either type of
air passageway provides good burn rate and trans-
mission of smoke to the smoXer.
The smoking articles may also include from
about 0.001 to about 1 wt.% of an alcohol in which
the cellulosic binder is soluble. That alcohol is
selected from the group consisting of ethanol,
methanol, isopropanol, n-propanol, and mixtures
thereof. The alcohol present in the smoking article
may result from adding alcohol during the formation
of the article to lower the moisture content of the
extrudate at the die or may be residual alcohol as a
result of adding flavor casings.
The smoXing article may also contain from
about 0.1 to about 40 wt.%, preferably from about
0.5 to about 20 wt.%, of a cross-linking or stiffen-
ing agent. The stiffening age~t which is preferably
added prior to extrusion and then cross-linked during
extrusion is selected from the group consisting of
alginic acid, carboxymethyl chitin, pectinic acid,
chitosan, carboxymethyl chitosan, water soluble salts
thereof, malto-dextrins and mixtures thereof. From
abGut 0.1 to about 10.0 wt.% of a water soluble salt
of calcium, magnesium, and/or aluminum may also be
used.
The smoking articles are preferably extruded
and formed ,as generally cylindrical, coherent, single
or multistrand articles having a diameter of from
about 2 to about 35 mm, preferably from about 4 to
- ~4 -
a~out 2~ mm. Alternate cross-sectional confi~urAtions may be made
with an aPpronriate die, for exam~le, ova~, star~shAned,
cv]indr~cal, and the li~e, or shaped a~propriatelv in an
additional post-extrusion ~rocess. A ~ost-extrusion fiizin~ die
also mav he used. These rods are tv~icall~ made in conventional
ci~arette or ci~ar len~ths and mav be wra~Ped with ci~arette
paper, a ci~ar wrapDer, or a co-extruded shell of combustible
material or the like. The articles mav he thus marketed as non-
filtered "ci~arettes" or as "ci~ars". A conventional filter mav
he ~oined to the "ci~arette" bv ti~Din~ paPer to form a filtered
smokin~ article.
~7arious flavorants and/or humectants that are commonly
emploved in the manufacure of smokin~ articles may be added
prior to extrusion or maY he subsequentlY added ~o the extruded
article, for example, after the coolin~ step. An examPle of
addin~ flavorants to a smokin~ material prior to hein~ fed to a
maker apparatus which is applicable to the present invention is
found in European patent application ~o. ~53n5139.9, published on
2~th Fehruarv 19~6 under No. 0172654. Other known methods also may
be used, as known to those of skill in the art.
~hese tohacco containin~ articles are PreferablY made by mixin~
or blendin~ to~ether the tobacco particles with hinder, filler,
foamin~ a~ent, cross-linkin~ or stiffenin~ a~ent, and any other
desired in~redient with water or other liquid to form a wet blend,
and extrudin~ the wet blend throu~h a selected die in accordance
with one of the followin~ extrusion conditions such that (1) as the
wet blend is extruded the moisture or other foamin~ a~ent in the
blend is converted to steam or other ~aseous Product so as to foam
the extruded material 5
15-
as it exits the die of the extruder; or (2) the wet
blend is extruded to form a plurality of strands
which are processed in a drying chamber under condi-
tions that cause the moisture or other foaming agent
in the extruded material to be converted to Steam or
other gaseous product, thereby foaming the material.
'~hen multistranded extrudates are formed, each strand
must be foamed and randomly adhered to neighboring
strands along their length, either by the foaming
action or by the application of an adhesive in post
extrusion processing.
Mixing may be carried out in any conven-
tional mixing device and the resulting mixture is to
be a wet blend containing frorn about 15 to about
50 wt.% of water.
As indicated in the Figure, the extruded
material may be formed by (a) dry blending tobacco
particles with binder~ filler, foaming agent, cross-
linking or stiffening agent, and any other desired
ingredient; (b) admixing this dry blend with water
to form a wet blend; and (c) extruding the wet blend
through a die having one or a plurality of holes
in accordance with one of the extrusion conditi~ns
set forth above so as to foam the extruded material
as it exits the die.
Alternately, the extruded material may be
formed by (1) dry blending tobacco particles with
filler, foaming agent, cross-linking or stiffening
agent, an~ any other desired ingredient, (2) prehy-
drating the binder material with water or similar
solvent to activate the adhesive character of the
binder, (3) admixing the dry blend and the prehydrated
binder to form a wet blend, and ~4) extruding the wet
blend through a die under any of the extrusion condi-
tions set forth above, preferably so as to substan-
tially foam the extruded material as it exits the
die.
~S~ 3
16
; ~his procedure is used in conjunction with a
twin screw positive mass displacement extruder having
multiple feed ports (not shown). Step ~2) prehydra-
tion is performed by adding the binder materials to a
first feed port of the extruder and by adding the
water or similar solvent to a second feed port a
distance downstream of the first feed port so that as
a charge of binder is inserted, it is processed,
sheared, and homogenized as it progresses down the
extrusion barrels. Then it is admixed with the water
as it passes the second port, prehydrating the binder
as the materials are displacecl down the extruder
barrel. Step (1), dry blending the tobacco, filler,
and other materials occurs in a conventional mixing
device and is added in a blended state to the extruder
barrel by a third feed port, a distance downstream of
the second port. Thus the prehydrated binder material
from step (2~ is admixed with the tobacco and other
materials from step (1) in a continuous feed process.
Because some extruder and mixing apparatus cannot
generate the forces necessary to process and extrude
the smoking article in accordance with the preferred
procedure, it may be advantageous to dry blend with
the binder a small amount of tobacco particles,
preferably an amount less than 5 wt.% of the tobacco,
a small amount of filler, or other added component,
and then prehydrate the blended binder and tobacco
or other components. The resultant wet blend will
have a lower viscosity than if no tobacco or other
component were present and may be more easily pro-
cessed without significantly raising the moisture
content of the mass.
Also, because the viscous prehydrated binder
can become very sticky and adhere to the mixing equip-
ment, it is advantageous to dry bler.d with the binder
a small amount of tobacco partic]eC~ filler material,
or both. The amount of tobacco added is preferably
~52~.~3
i -17-
less than about 5 wt. % o~ the tobacco. The dry blend
is then prehydrated, resulting in a wet blend that has
a reduced tendency to stick to the processing equip-
ment and is relatively easier to process unifor~ly, as
the material progresses from one step to the next.
Alternately, a portion of the binder may
be dry blended with the tobacco and the balance of
the binder prehydrated. Because of the relative
surplus of water or similar solvent (later taken up
by the dry blended tobacco and binder), the viscosity
will be lower and the mass easier to handle. Although
having a somewhat higher OV content than without
cross mixing tobacco and binder in steps (1~ and
~2), the more efficient activation of the binder
results in a dryer and stronger extrudate than that
made without prehydrating the binder.
Optionally, a foaming agent may be added
to the mixture, preferably selected from the group
consisting of air, nitrogen, carbon dioxide, nitrous
oxide, ammonium carbonate, aml~onium carbamate, '~
ammonium and/or sodium or potassium bicarbonate, an
azide, a hydrazide, pentane, hexane, heptane, a halo- j
genated fluorocarbon, pyrrole, acetone, ethanol, a
peroxide, and azodicarbonamide. Some of these foaming
agents may require the addition of an acid or a base
for decomposition, and the use of a foam stabili~er
and/or a suitable surfactant such as licorice, yucca
or yucca extracts, sodium lauryl sulfate, etc.
Extruder 1 may be any conventional extruder
having input apertures for materials, mixing chamber
or barrel 13 for thoroughly mixing the tobacco slurry
ingredients and a die output. Typical extruders
include, for example, Wenger Model X-20 single screw
cooXer/extruder, a Manley collet-type extruder, or
twin screw extruders such as those made by Werner v
and Pfleiderer, C. L. Simon, and ~a~.er Perkins (Models
MPF-50D and MPF-50L).
~'
- lR -
~ he ~n~redients of the selected tohacco containin~ s]urry
are mixed to~ether in accordance with anv DroceAure and
extruded as a cohesive mass, DreferablY as a foamed product. The
extruded material, foamed or not, is moist and Dliahle, tYPicallv
hav~n~ an 0~' content in the ran~e of 17-2R~, dependin~ on the
processin~ conditions useA. Particular methods, alternate
formulations, and additional details re~ardin~ foamed, extruded
materials are discussed in l~.S, Patent No.4 51n 950 and
Furopean Specification EP-A-n16737n.
The preferred foamed extruded material foams as it exits the
die, ~ivin~ off lar~e quantities of steam, which may have a sli~ht
coolin~ effect on the extruded material, but the bulk
temperature will be tvPicallv at about, and probably iust below,
the flash Point of the liquid used. These hot, moist materials
exhibit little or no ri~iAitv and have tacky surfaces. Thev
deform easilv and cannot be wrapped or maniPulated into smo~in~
articles.
In accordance with the present invention, these extruded
materials are immediately passed throu~h dryin~ chamber 2 to
lower the moisture content to at or below the equilibrium
moisture content level. Microwave dryin~ is preferred because: tl~
it dries the material fast and uniformlv; (2) it can cause anv
foamin~ a~ent or residual foamin~ a~ent present to volatize to foam,
or additionallv or more comDletelv foam, the Product~ (3) it rapidlv
dries the material without adversely affectin~ t~he foamed
structure once all the foamin~ is complete: (4) it can be used
to dry materials extruded at hi~h rates of speed, for example,
6n-25n meters per minute, in a short period of time usin~
equipment occuDyin~ little floor sPace, e.~. 3 meters: and (5) it
is more ener~v efficient than prior art dryin~ ovens because the
ener~y required to dry the material is
~.5;~3
--19 -
applied directly to the material at the necessary
energy density and is not wasted in having to also
heat long chambers or large volumes of air.
In the preferred embodiment, where the
extruded material is about 12 mm upon exiting the
die (B mm in final diameter), two substantially iden-
tical microwave energy sources and cavities are used,
for example Model 56F, manufactured by Cober. These
models each have a power capacity of about 6kw and
operated at 245~ MHz. The microwave cavity dimensions
also are the same being about 127 mm x ~2.55 mm x
146.05 mm, having the input and output apertures of
both cavities in axial alignment and a distance of
about 990.6 mm separates the output and input walls
of the two adjacent cavities. Equivalent models or
a single microwave unit having the equivalent total
power capacity may be used in the alternative. For
other configurations of extruded materials, e.g.,
sheets, greater power may be required to dry ade-
quately the extruded material, as may be determined
empirically.
Other known frequencies capable of exciting
the resonant frequency of the molecules of the mois-
ture or other 1 iquid or foaming agent in the extruded
material for volatizing those molecules could be
used. Vent means 25 is provided to exhaust the mois-
ture, liqui~ or other foaming agent volatized during
drying, and foaming, if any, to thereby facilitate
drying. Endless conveyor 17, comprising a nonconduc-
tive material that does not appreciably interfere
with the passage of microwaves energy therethrough,
e.g., polyester, nylon, etc., may be u~ed to support
the extruded material as it passes through the drying
cavity.
Cooling chamber 3 may comprise air condi-
tioner 15, air fan 16 and conveyor belt 6. Air
conditioner 15 may be any conventional air conditioner
~,5~3
capable of providing refrigerated air such as, for
example, a Comfort Aire, 3 ton unit, manufactured by
Heat Controller Inc., Jackson, Michigan. Air fan 16
is designed to distribute the refrigerated air at a
selected flow rate along and preferably perpendicular
to the path extruded material 20 follows as it
advances across endless conveyor belt 6. Conveyor
belt 6 which is preferably perforated. The distribu-
tion of refrigerated air may be relatively uniform
or it may be graduated so that there is more or cooler
air at one location along cooling chamber 3 than
another. In an alternate embodiment, the direction
of cool air flow may be incident or parallel to the
extruded material. Air fan 16 and air conditioner
15 may be incorporated into a single unit.
In an alternate embodiment, cooling chamber
3 may be an air impinging tunnel such as an Air Miser
manufactured by Huestis Machine Csrporation, Bristol,
Rhode Island. Such a device could be used to impinge
air at high velocity on the surface o the extruded
material, through a plurality of air jets, to dry
the extruded mater~al. Other cooling means could be
used such as cryogenic baths, cold contacting me~bers
and other techniques for removing heat from the
extruded material.
In the preferred embodiment, the drying
and cooling are coordinated so that the resulting
product has an OV content below the eguilibrium OV
content. This permits wrapping the extruded material
with a conventional wrapper while it is in a more
dry condition so that when the extruded material
equilibrates, the extruded material will absorb some
moisture and expand slightly and tighten against the
wrapper. This will substantially prevent the wrapper
from f~lling o~f the smoking article, e.g., in low
humidity environments, and give the product the look
i
!
~2
-21-
and feel of a conventional cut tobacco-filler smoking
article.
The present invention is particularly adapt-
able to preserving tobacco flavors and characteristics
originally present in the tobacco that heretofore
have been lost due to volatilization during extrusion
and heating. The flavors are preserved by cooling
the extruded material rapidly after drying and thereby
reducing the tem~erature below the volatization tem-
perature of the flavors. This minimizes the volatil-
ization of the flavors that previously were lost.
Further, flavors or other additives that would not
or do not survive the extrusion, foaming and drying
conditions and temperatures can be added to the ex-
truded material immediately after the cooling step,
without significant loss due to volatization. These
additives can be metered onto the passing extruded
material in an efficient manner by conventional
equipment.
Foamed products create a thermal barrier
that so~ewhat inhibits cooling the interior of the
extruded material. By cooling the exterior rapidly,
a thermal gradient is created across the cross sec-
tion. Thus, by maintaining the exterior relatively
cooler than the interior, the natural flavors of the
original tobacco and the additives and flavors in or
added to at least the substantially cooler periphery
of the extruded material may be preserved. The loss
of flavors fro~ the relatively interior extruded
material i5 therefore less significant and can be
compensated for accordingly.
Maker device 4 may be any commercially
usable cigarette manufacturing device modified appro-
priately by removing the hopper, such as Mark 8 or a
Mark 9 Cigarette Maker manufactured by the Molins
Company, or an equivalent Rauni model. Other smoking
article forming devices (not shown) could include
~.
-2~-
apparatus such as grinders, slitters, shredders or
the like used for processing the dried and cooled
extruded material, preparatory for use in forming
typical smoking products, e.g , pipe, smokeless,
cigarette or cigar tobacco. In the preferred embod-
iment, the extruded material is fed directly from
cooling chamber 3 into the garniture of a Mark 8
Cigarette Maker which was modified by removing the
chimney section and replacing it with funnel 14 dis-
posed for receiving the extruded material in either
a single or multi-stranded rod-like form, before or
after the rod liXe material is wrapped conventionally,
if at all, and fed into the garniture. After the
garniture, the rod is severed by the cut off knife
into substantially uniform lengths appropriate for
formation into smoking articles and removed by the
revolving take off wheel for subsequent handling in
accordance with conventional cigarette-type smoking
article forming methods and apparatus.
Puller apparatus 5 may be a pinch roll
feed type puller or a pair of opposing endless
advancing belts designed and operated for use in
start up conditions for feedin~ the leading edge of
the extruded material into funnel 14. Puller 5
operates to maintain slight tension on the extruded f
material across cooling chamber 3 during start up.
Once the extruded rod has been fed into funnel 14,
and i~to the garniture so that the garniture pulls
on ~he rod, puller 5 is typically disengaged and the
opposing beltQ separated to prevent damaging the 1
extruded material by exerting forces on the material ~i,
as the material advances. Commercially available
pullers are available from Versa Machinery Division,
Foster & Allen Inc., Sommerville, New Jersey, e.g.,
Model CM22.
The driven apparatus, conveyor belt 17,
conveyor belt 6, puller 5, maker ùevice 4, and
extruder 1 may all be synchronized by a tachometer
(not shown) or equivalent timing means to the drying
capacity of microwave cavity 2. The drying capacity
can be adjusted for the desired process conditions
and the desired extruded material moisture character-
istics, primarily by changing the power level of
microwave energy propagated into the microwave cavi-
ties. Additional cooling means may be required at
higher rates of speed when large amounts of microwave
energy are used to dry the material. Thus, for the
given rate of advance of the extruded material, and
the related residence time of the extruded material
in the microwave heating cavity, the desired OV level
can be achieved. For example, drying extruded
material having about an 8.0 + .1 mm diameter and
advancing at about 182 meters per minute from 20% OV
to less than 6% OV can be achieved using a total of
about 10 kw of power distributed between the two
microwave cavities. Using 9kw of power resulted in
an OV content of about 8%.
The method of this invention further con-
templates performing the foregoing operations using
the described apparatus at high rates of speed so
that the tobacco slurry ingredients can be continu-
ously mixed, extruded, dried, cooled, and formed
into smoking articles continuously in a single work
station area on the factory floor. The foamed ex-
truded material of the preferred embodiment can be
produced at rates from zero to in excess of about
200 meters per minutes in a rod of about 8 mm in
diameter. These rates are well within the capacity
of conventional cigarette maker devices.
EXAMPLE
To illustrate further the present invention,
the following representative example is presented.
,: -2a-
`! The. formulation of min~te,
finely divided tobacco particles, binder materials,
and water were fed to their respective input ports
of a Baker Perkins Model MPF-50L twin screw extruder.
The tobacco was fed at a rate of about .82 kg/min of
tobacco dust. The binder mixture was 1% klucel, 4%
hydroxypropyl guar, and 5% starch, premixed to form
a blend that was fed at a rate of .09 kg/min. The
tobacco and binder were mixed together and added to
a common port of the extruder mixing barrel. Water
was added downstream at a rate sufficient to maintain
about 20-23% OV in the mixing barrel of the extruder.
The OV content of the extruded material as it exited
the die was measured to be about 17.2%. The bulk
temperature was about 130C and the surface tempera-
ture was about 95C. The extruded material was passed
through twin microwave cavities at a speed of about
124 meters per minute. The drying cavity included a
first and second microwave cavity with the first
cavity and second cavities set at a co~ined power
level of 7kw. The OV content of th~ extruded ~aterial
as it exited the drying cavity was at about 10.9%.
The surface temperature of the extruded material was
61.7C and the bulk temperature was 91.7C. The
dried extruded material possessed little or no
rigidity and could not be continuously processed for
wrapping or feeding into the maker.
The extruded material was then passed
through a cooling section that was about 4.6 meters
long. Refrigerated air chilled to 15.5C was gener-
ated and blown perpendicular to the extruded material
at a velocity of 104 meters per minute. The extruded
material was cooled to a surface temperature of about
46.7C and a bulk temperature of 85DC. The OV content
dropped to 9.9%. At this point, the extruded mate-
rial possessed sufficient rigidity ~o be cut and
wrapped using the modified Mark 8 maker. The bulk
~5~ 3
-25-
temperature of the resulting wrapped cigarette rods
of dried and cooled extruded material was about 57DC.
In the course of experimentation, it was
discovered that the total microwave energy absorbed
by the extruded material was more important than
whether the two microwave cavities produced the same
energy level, or which unit provided more power.
For example, substantially the same results were
found when the first unit produced 3kw and the second
unit produced 4kw, as when the first unit produced
4kw and the second unit produced 3kw. Similar re-
sults were found with the power divided into 2kw in
one unit and 5kw in the other unit. It was also
discovered that for every additional kilowatt of
microwave energy absorbed, the OV content would be
lowered by about 1.2%. Lowering the power similarly
resulted in a higher OV content. Typical extrusion
rates for the preferred tobacco-containing materials
include from 270 to 455 meter/min. These materials
can be dried to desired moisture levels of bet~een
about 8% and 14% by using from about 5 kw to lO k~,
distributed between the two microwave cavities.
Cooling the extruded materials using refrigerated
air cooled to temperatures in the range of from abo~t
1C to 16C and blown across the material at veloci-
ties of from about 50 to 150 meter/min was sufficient
to cool the dried extruded material for wrapping and
forming.
