U.S. patent number RE29,298 [Application Number 05/639,963] was granted by the patent office on 1977-07-12 for deposition of vaporized flavorant on tobacco.
This patent grant is currently assigned to Brown & Williamson Tobacco Corporation. Invention is credited to Jon F. Banks.
United States Patent |
RE29,298 |
Banks |
July 12, 1977 |
Deposition of vaporized flavorant on tobacco
Abstract
Tobacco is treated by introducing a tobacco flavorant vapor such
as menthol vapor into a conduit .[.an.]. .Iadd.and
.Iaddend.pneumatically conveying the vapor through the conduit.
.[.The air in the conduit being maintained at a temperature of from
about 75.degree. to 150.degree. F and above the vaporizing
temperature of the flavorant..]. Tobacco is injected into the
conduit at a point downstream from the vapor injection. The
flavorant vapor is uniformly deposited on the tobacco as it is
carried down the conduit. A predetermined level of flavorant is
maintained in the conduit through which the tobacco and flavorant
vapor are pneumatically conveyed. .Iadd.The air in the conduit is
maintained at a temperature of from about 75.degree. to 150.degree.
F, which temperature is sufficient to prevent condensation of the
vaporized flavorant in the conduit prior to adsorption of the
flavorant on the tobacco. .Iaddend.
Inventors: |
Banks; Jon F. (Louisville,
KY) |
Assignee: |
Brown & Williamson Tobacco
Corporation (Louisville, KY)
|
Family
ID: |
26898408 |
Appl.
No.: |
05/639,963 |
Filed: |
December 11, 1975 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
203206 |
Nov 30, 1971 |
03800806 |
Apr 2, 1974 |
|
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Current U.S.
Class: |
131/300 |
Current CPC
Class: |
A24B
15/30 (20130101) |
Current International
Class: |
A24B
15/00 (20060101); A24B 15/30 (20060101); A24B
015/04 () |
Field of
Search: |
;131/133,134,135,136,138,14R,144 ;126/374,348,343.5
;34/10,36,37,57 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2,156,357 |
|
Dec 1971 |
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DT |
|
128,092 |
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Jan 1973 |
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NO |
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1,049,908 |
|
Nov 1966 |
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UK |
|
135,805 |
|
Mar 1961 |
|
SU |
|
Primary Examiner: Michell; Robert W.
Assistant Examiner: Millin; V.
Attorney, Agent or Firm: Mason; William J.
Claims
I claim:
1. A method of treating tobacco comprising:
a. introducing by vapor injection a tobacco flavorant in heated
vapor form in the absence of a volatile or semi-volatile carrier
fluid, into a conduit having a heated air stream maintained at a
temperature within the range of from about 75.degree. to
150.degree. F, the temperature of said air stream being .[.above
the vaporizing temperature of the flavorant.]. .Iadd.maintained at
a level sufficient to prevent condensation of said vaporized
flavorant in said conduit prior to adsorption of said flavorant on
the tobacco.Iaddend., the vaporized flavorant being a material
selected from the group consisting of menthol, anethol,
benzyl.[.;.]. benzoate, cinnamaldehyde, coumarin, eugenol,
heliotropin, menthone, methyl salicylate, propylene glycol,
gamma-undecalactone and vanillin, a proportion of from .[.15.].
.Iadd.5 .Iaddend.to 30 milligrams per cubic foot of heated air to
form a uniform concentration of said vaporized flavorant in said
air stream;
b. injecting tobacco into said conduit and into said mixture of
said heated air and vaporized flavorant at a point downstream from
said vapor injection at the outlet side of a negative pressure
producing means;
c. keeping said tobacco and vaporized flavorant in said conduit in
contact for a period of time of .[.from.]. between 3 and 15 seconds
to permit uniform adsorption of said flavorant whereby a flavorant
level .[.of at least about 0.2 percent.]. on said tobacco is
obtained; and finally separating the flavored tobacco from said
conduit.
2. The invention in accordance with claim 1 wherein the vapor is
menthol vapor and the concentration of menthol vapor in said
conduit at said tobacco injection point is from .[.about 5.].
.Iadd.15 .Iaddend.to 30 milligrams per cubic foot .Iadd.of heated
air and said flavorant level of menthol obtained on said tobacco is
at least 0.2 percent by weight of tobacco.Iaddend..
3. The invention in accordance with claim 1 including the steps of
separating the .[.menthol-treated.]. .Iadd.flavorant-treated
.Iaddend.tobacco from said air stream, thereafter, recycling said
separated air stream to said conduit.
4. A method of treating tobacco comprising:
a. introducing by vapor injection menthol in heated vapor form in
the absence of a volatile or semi-volatile carrier fluid into a
conduit having a heated air stream maintained at a temperature
within the range of from .[.about.]. 75.degree. to 150.degree. F,
the temperature of said air stream being .[.above the vaporizing
temperature of said menthol.]. .Iadd.maintained at a level
sufficient to prevent condensation of said vaporized flavorant in
said conduit prior to adsorption of said menthol on the
tobacco.Iaddend., a vaporized menthol being in the proportion of
from between 15 to 30 milligrams per cubic foot of heated air to
form a uniform concentration of said menthol in said air
stream;
b. injecting tobacco into said conduit and into said mixture of
said heated air and vaporized menthol at a point downstream from
said vapor injection at the outlet side of a negative pressure
producing means;
c. keeping said tobacco and vaporized menthol in said conduit in
contact for a period of time of .[.from.]. between 3 and 15 seconds
to permit uniform adsorption of said menthol at a menthol level of
at least .[.about.]. 0.2 percent on said tobacco; and finally
separating the flavored tobacco from said conduit.
5. The invention in accordance with claim 4 including the steps of
separating the menthol-treated tobacco from said air stream and
thereafter recycling said air stream to said conduit.
6. The method in accordance with claim 4 in which the temperature
of .[.the pneumatic.]. .Iadd.said heated air .Iaddend.stream is
between 100.degree. and 115.degree. F.
Description
BACKGROUND OF THE INVENTION
The invention relates to a method for treating tobacco with
volatilizable flavorants. In particular, it relates to a method for
uniformly depositing menthol vapor on tobacco.
In the past the application of flavorants, including menthol, to
tobacco has often been a rather haphazard operation. In general,
menthol has been applied to tobacco by first forming a dilute
menthol solution and thereafter spraying the solution onto tobacco.
It is well known that during spraying operations, tobacco is
contacted only by discrete spray droplets of menthol solution. Such
droplets are not uniformly distributed over the surface of the
tobacco with the result that conventional spraying operations do
not, for the most part, provide uniform deposition of menthol. Only
through subsequent blending and menthol transferring operations can
uniform deposition be obtained.
In an attempt to remedy the aforesaid deficiencies it has been
proposed to feed tobacco into a conduit where it is mixed with an
air stream. The tobacco-air mixture is combined with an
alcohol-menthol mixture which is sprayed onto the tobacco. This
method, disclosed in U.S. Pat. No. 3,548,838, has various defects.
The patent teaches that a menthol solution must be formed,
preferably employing an alcohol solvent. The use of alcohol as a
solvent for menthol is expensive and hazardous. As illustrated in
the patent, it is necessary to vent the tobacco mentholating system
to prevent the formation of an explosive concentration of alcohol
vapors. The venting procedure permits a substantial loss of menthol
from the system. Further, it may be necessary to permit the tobacco
to stand after contact with the menthol-alcohol solution for at
least 4 hours prior to use.
An additional defect of the above patent and indeed, of the prior
art menthol spraying procedures, lies in the failure to control the
level of menthol application during a continuous processing
operation. In any direct contact spray system it is necessary to
maintain matched flows of both tobacco and menthol solution. When
any variations occur in either flow, off target levels for menthol
application occur. No convenient method has been proposed to
immediately monitoring the application of menthol on tobacco and of
rapidly compensating for any variation therein. This is basically
an inherent defect in the prior art processes, since spray droplets
require time to spread over the surface of the tobacco. There is no
convenient way of rapidly monitoring and adjusting for variations
in levels of menthol application and other flavorants via the spray
process.
The tobacco industry has long desired to apply menthol vapor
directly to tobacco in a continuous application process. However,
the industry has not been able to overcome the problems associated
with such a process. In fact, U.S. Pat. No. 3,548,838 warns that it
is impractical to mix menthol directly with tobacco since it is too
difficult to control the very minor quantities which it is desired
to use. The patent further teaches that adsorption of menthol on
cut blend tobacco in a closed air recirculation system is not
feasible, since, in order to provide an acceptable contentration of
menthol vapor in the system, it has allegedly proven necessary to
operate at extremely high temperatures, well in excess of
200.degree. F. Such high temperatures are not conducive to tobacco
processing.
Accordingly, there exists a long felt need for a process for
uniformly applying menthol and other flavorants directly to tobacco
without employing sprayed, dilute solutions, free of the side
effects and deficiencies of the prior art.
SUMMARY OF THE INVENTION
It is, therefore, a primary object of this invention to provide a
process for uniformly treating tobacco with flavorant vapors, such
as menthol vapor.
It is another object of the invention to provide a process for the
vapor mentholation of tobacco in the absence of a carrier fluid for
the menthol.
It is an additional object of the invention to employ menthol vapor
to treat tobacco at temperatures compatible with tobacco
processing.
The above and other objects are attained in a method for treating
tobacco comprising introducing a tobacco flavorant in vapor form
into a conduit at a predetermined concentration, wherein said
conduit has a pneumatic stream therein; injecting tobacco into said
conduit at a point downstream from said vapor injection; permitting
said tobacco and vapor to remain in contact to permit uniform
adsorption of said flavorant on said tobacco; and maintaining said
predetermined concentration of said vapor in at least that portion
of said conduit wherein said tobacco and said vapor are in
contact.
It has been discovered that flavorant and, particularly, menthol,
application is unexpectedly enhanced by exposing tobacco to a
pneumatic stream containing a controlled, predetermined
concentration of flavorant vapor. Flavorant concentration may be
maintained in the stream by sampling the pneumatic stream in the
conduit in the region of contact between the tobacco and flavorant
vapor and simultaneously metering into the system, flavorant vapor
in proportions sufficient to replace the flavorant adsorbed by the
tobacco.
The invention will be illustrated in greater detail in the
accompanying drawing in which a system suitable for the performance
of the invention is illustrated.
DESCRIPTION OF PREFERRED EMBODIMENTS
Although applicable to other volatizable flavorants the following
discussion is primarily directed toward the vapor deposition of
menthol on tobacco. Among the factors to be considered in the vapor
deposition of menthol on tobacco are the following: concentration
of menthol vapor in the process; contact time of menthol vapor with
tobacco; temperature of the air stream in the pneumatic conduit;
velocity of air in the conduit; tobacco feed rate and temperature
of the tobacco, with the first three factors being of major
importance. In general, the level of menthol on tobacco in
conventional mentholated cigarettes is from about 0.2 to 0.5
percent by weight of tobacco. This level may be achieved by the
present invention during a single pass of tobacco through the
pneumatic system disclosed herein.
During mentholation of tobacco it is preferred to maintain menthol
vapor concentration in the system from about 5 to 30 milligrams per
cubic foot (mgm/ft.sup.3) and, more preferably, from 15 to 30
mgm/ft.sup.3. For best results the concentration of menthol vapor
is from 20 to 28 milligrams per cubic foot. When the menthol
concentration is maintained significantly below about 5 milligrams
per cubic foot, it becomes necessary to employ an unacceptably long
contact time with tobacco and/or an unduly elevated pneumatic
stream temperature. Where concentrations of over about 30
milligrams per cubic foot are employed, the system becomes
unnecessarily wasteful of menthol and, in general, requires
unacceptably high temperatures to overcome the tendency of the
menthol vapor to condense on the walls of the system.
In order to maintain the desired concentration of menthol vapor in
the system it is preferred to employ an air temperature in the
system from about 75.degree. to 150.degree. F. Temperatures below
the lower value tend to induce condensation of menthol vapor within
the system. Operating with air temperature above about 150.degree.
F tends to warm the tobacco to an undesirable level and create
ultimate processing problems.
For best results it is particularly preferred to employ an air
temperature from about 100.degree. to 130.degree. F and especially
from 100.degree. to 115.degree. F. Above about 100.degree. F there
is a marked increase in the amount of menthol vapor adsorbed by the
tobacco. By operating at temperatures no greater than about
115.degree. F. the heating requirements for the system can be
reduced with a corresponding savings in fuel consumption and
insulation requirement.
In order to achieve a mentholation level of from about 0.2 to 0.5
percent by weight of tobacco during a single pass of tobacco
through the system, it is preferable to achieve a contact time of
tobacco and menthol vapor of about 3 to 15 seconds, preferably
about 5 to 12 seconds. The tobacco-vapor contact time of 3 to 15
seconds is particularly advantageous where the concentration of
menthol in the process is from 5 to 30 milligrams per cubic foot
and the air temperature is from 75.degree. to 150.degree. F.
It has been found that the tobacco feed rate may be varied within
relatively broad limits with little effect on the amount of menthol
adsorbed. This feature is desirable in the process since it can be
very difficult to control the feed rate of cut tobacco through a
pneumatic conduit.
Usually, the air velocity within the pneumatic conduit can vary
within wide ranges. As the air velocity increases, the tobacco
velocity is increased, thereby decreasing the retention time of
tobacco in the system. However, this factor can be counter balanced
by elevating the level of menthol in the pneumatic stream.
Of course, it will be obvious to those skilled in the art that the
tobacco mentholation level can be reduced or increased to achieve a
particular purpose by varying the aforesaid and other parameters.
Under certain circumstances it may be desirable to operate beyond
one or more of the preferred ranges. In any event, the invention
may be carried out by introducing a predetermined concentration of
vaporized menthol into a pneumatic conduit, injecting tobacco into
the conduit downstream from the menthol vapor injection point,
permitting the tobacco and menthol vapor to remain in contact and
maintaining the concentration of menthol vapor at least in the
vapor-tobacco contacting portion of the system.
Turning now to the drawing, the process is carried out in a
pneumatic system. Molten menthol is fed into a vaporizing apparatus
10 to provide a supply of menthol vapor. The molten menthol is
vaporized at temperatures no greater than about 500.degree. F in
order to avoid decomposition products. The supply of molten menthol
(not shown) is supplied to the vaporizer by means of pump 12.
For best results menthol vapor is introduced into the system in an
area of negative or reduced pressure. Employing a reduced pressure
zone to withdraw menthol vapors from the vaporizing means greatly
contributes to the efficiency of the process. For the
aforementioned reasons, it is preferred that the menthol vapor is
introduced into the system at the negative pressure or intake side
16 of blower 14.
In order to introduce menthol vapor at the positive or outlet side
15 of blower 14 it is necessry to augment the menthol vapor with a
volatile or semi-volatile carrier fluid, such as water. The carrier
fluid, upon vaporization, serves to increase the total volume of
vapors in vaporizing means 10, thus forcing the menthol into the
system. Of course, the use of a volatile or semi-volatile fluid
creates additional problems and requires subsequent removal of the
fluid carrier.
Air is delivered to conduit 18 from blower 14. Cut blended tobacco
is injected into the conduit downstream from the menthol vapor
introduction point 17. Conventional tobacco conveying apparatus
(not shown) is employed for this purpose. Tobacco may be drawn from
a storage bin, delivered to a metering conveyor and thereafter
conveyed into a hopper or loading chute. The tobacco is fed into a
standard rotary air lock 20 which injects tobacco into the air
stream in conduit 18.
The tobacco is carried along and dispersed by the air stream
through the conduit. As the tobacco is injected into conduit 18, it
is contacted with the pneumatically conveyed menthol vapors. The
concentration of menthol vapor at this point is preferably from
5-30 mgm/ft.sup.3. The tobacco-menthol vapor pneumatic stream 21 is
carried into a conventional tangential separator from which the
tobacco is removed by a rotary air lock 24 and collected in a
storage bin (not shown).
The air stream, carrying unadsorbed menthol vapor recycles through
conduit 26 to air heaters 28 where it is heated to the control
temperature. The air stream then passes through conduit 30 to
intake port 31 of blower 14.
In order to maintain proper control of the menthol concentration in
conduit 18 a closed loop control system 32 is provided. The level
of menthol vapor in conduit 18 is accurately and rapidly determined
by a gas chromatograph, a total hydrocarbon analyzer, or other
conventional analyzing means. The output 34 of the analyzer
controls metering pump 12 which delivers molten menthol to the
vaporization chamber. The accurate monitoring and control of the
menthol vapor concentration is a key factor in the present
process.
The process previously described is applicable to tobacco
flavorants which can be vaporized without decomposition. Suitable
flavorants include anethol, benzyl benzoate, cinnamaldehyde,
coumarin, eugenol, heliotropin, menthone, methyl salicylate,
propylene glycol, gamma-undecalactone and vanillin and the
like.
Numerous advantages are achieved by the present process. More
uniform control of the deposition of menthol on tobacco is achieved
by vapor deposition than is achieved by spray deposition. In the
present process each tobacco particle is exposed to direct contact
with menthol molecules, while in the liquid spray systems
conventionally employed, droplets strike tobacco at specific
contact points and must migrate through the tobacco to achieve
uniformity. In the preferred embodiments of the present invention
no menthol carrier is employed. Obviating such a carrier represents
a substantial economic benefit. Further, problems in venting
dangerous volatile carriers are eliminated.
The following examples illustrate a preferred embodiment of the
present invention and are not limitative of scope:
Example I
Tobacco was treated with menthol vapor in an apparatus similar to
that illustrated in the drawing and described hereinabove. A
heating tape was wrapped around the portion of the recycle line 26
immediately upstream of intake end 31 of the blower 14. The menthol
concentration of the system was maintained at 22 milligrams per
cubic foot. The temperature of air stream was maintained at
110.degree. F. In a single run through the system the tobacco
remained in contact with the menthol vapor for 3.1 seconds. The
treated tobacco was analyzed for menthol. The results indicated
that a menthol level of 0.35 percent by weight was achieved.
During treatment the concentration of menthol vapor was monitored
employing a gas chromatograph. A peristoltic pump was operated in
conjunction with the chromatograph to control the supply of molten
menthol delivered to the vaporizer.
The efficiency of the present process is entirely unexpected in
light of the prior art, particularly U.S. Pat. No. 3,548,838 which
teaches that it is impractical to mix menthol directly with tobacco
owing, in part, to the difficulty in controlling the minor
quantities in use and, also, to the alleged need for employing
temperatures well in excess of 200.degree. F.
Example II
In order to determine the effect of varying the concentration of
menthol vapor in the process, tobacco was mentholated according to
the procedure set forth in Example I. The air temperature was
110.degree. F. Cut tobacco was contacted with menthol vapor in the
conduit of the system for 21/2 seconds. Molten menthol was pumped
into the vaporizer at the rate of 2.0 cubic centimeters per minute.
The following table illustrates the weight percent of menthol
deposited on cut tobacco as the concentration of menthol vapor in
the apparatus was varied:
Menthol Analysis ______________________________________ Menthol
Concentration Menthol on Tobacco Sample milligrams/cu.ft Weight
Percent ______________________________________ 1 9 0.24 2 12 0.24 3
18 0.34 4 21 0.34 5 25 0.34 6 27 0.32 7 33 0.32 8 37 0.31
______________________________________
The results obtained illustrate the enhanced deposition effects
obtained when the menthol concentration is controlled within a
range from about 15 to 30 milligrams per cubic foot and
particularly 20 to 28 mgm/ft.sup.3.
Example III
In order to illustrate the effect of air temperature on the
process, tobacco was mentholated in accordance with the procedure
set forth in Example I. The rates at which menthol and tobacco were
fed into the process remained constant. The system temperature was
controlled at points between 80.degree. and 115.degree. F.
From about 80.degree. to 100.degree. F the quantity of menthol
deposited on tobacco remained substantially constant. However, at
temperatures above 100.degree. F there was a marked increase in the
amount of menthol adsorbed by tobacco. It was observed that at
temperatures above about 100.degree. F there was no significant
condensation of menthol on the system walls. It is postulated that
maintaining a constant menthol feed while eliminating menthol
condensation effectively increases the amount of menthol vapor in
the pneumatic stream. The enhanced menthol application obtained is
considered to be a combined effect of increasing temperature and,
correspondingly, menthol concentration.
Example IV
Tobacco is treated with the following flavorants according to the
procedure set forth in Example I: anethol; benzyl benzoate;
cinnamaldehyde; coumarin; eugenol; heliotropin; menthone, methyl
salicylate, propylene glycol; gamma-undecalactone and vanillin. The
flavorants are deposited on tobacco in amounts sufficient to yield
acceptable flavor.
The preferred levels of application of flavorant on tobacco is as
follows for each of the flavorants employed -- the levels of
application are expressed in weight percent of tobacco:
______________________________________ Flavorant Level of
Application ______________________________________ anethol
0.0005-0.02 benzyl benzoate 0.0005-0.01 cinnamaldehyde 0.0002-0.005
coumarin 0.0005-0.005 eugenol 0.0005-0.01 heliotropin 0.0005-0.015
menthone 0.01-0.05 methylsalicylate 0.0005-0.01 propylene glycol
0.01-2.0 .gamma.-undecalactone 0.0002-0.005 vanillan 0.0002-0.005
______________________________________
For reasons of economy there is a practical limit to the amount of
additive which is usually applied by vapor deposition. The upper
limit is proportional to the vapor pressure of the specific
additive.
* * * * *